JPH0513979Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to a multi-fuel valve injection system.

[Conventional technology]

FIG. 7 shows the basic configuration of a diesel engine fuel injection system. In FIG. 7a, high pressure is generated by a fuel pump 1001, which passes through an injection pipe 1002 and is injected in the form of a mist from a fuel valve 1003. Some modern engines have one fuel pump equipped with two or more fuel valves. FIG. 7b shows an arrangement with three fuel valves. Here, the specific structure, operation, drawbacks, etc. of the injection system will be explained using FIG. 8 using these three systems as examples.

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 discharge valve seat, 08 is a discharge valve, 09 is a discharge valve suction back collar, 10 is a discharge valve spring, 11 is a discharge valve presser, and 12 is a controller rack. Further, 101 is a fuel valve main body, 102 is a nozzle tip, and 103 is a cap nut that fastens the nozzle tip 102 to the fuel valve main body 101. 104 is an oil passage in the fuel valve, 105 is an oil passage in the nozzle tip, 10
6 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
112 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, talking about the action 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 fuel becomes high pressure and is discharged. The valve 08 is pushed open, and the oil 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. As a result, the pressure in the system gradually decreases, and the pressure in the oil reservoir 106 also decreases, and the spring force overcomes the hydraulic pressure, closing the needle valve and ending the injection. Normally, the pressure at the end of injection is about 40% lower than the pressure at the beginning of injection.
In addition, when the pressure at the end of discharge decreases, 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 are not transmitted back and forth between the fuel valve and the pump. This remaining pressure wave may cause the needle valve 107 to reopen, causing re-injection from the nozzle hole, or creating a cavity in the pipe or oil reservoir. This double injection phenomenon is usually called secondary injection. Figure 9 shows the injection pressure and movement of the needle valve.

[Problem that the invention attempts 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. Furthermore, since the secondary injection is also a low-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, FIG. 10 shows constant injection pressure lines when the horizontal axis is the engine speed N and the vertical axis is the average effective pressure Pme. At low rotation speeds and low loads, the injection pressure becomes low, which also leads to deterioration of combustion as described above.

In view of the current situation, the applicant for utility model registration has filed a patent application for a multi-fuel valve injection device that eliminates the drawbacks of the prior art described above in Japanese Patent Application No. 59-248653.

[Means for solving problems]

The purpose of this invention is to focus on the above points, to simultaneously complete injection at high pressure without secondary injection or cavity formation,
To provide an injection device capable of improving so-called "cutting of injection" and further increasing injection pressure and maintaining good combustion by closing a part of a fuel valve in a low load and low rotation range. Its feature is that it is a diesel engine fuel injection device that is branched from a jerk-type fuel pump and has multiple fuel valves in one cylinder. A check valve that is opened at the time of discharge, a check valve that is opened by pressure on the discharge side at the end of discharge, and a needle valve of the fuel valve that is provided in each of the fuel valves and receives hydraulic pressure separate from the injection system. The microcomputer comprises a piston to press, a solenoid valve to open and close hydraulic pipes leading to the piston, and a microcomputer to control opening and closing of the solenoid valve based on engine speed, crank rotation angle, engine load, etc. 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 some fuel valves to reduce the engine load. In a multi-fuel valve injection device that controls to intermittently stop the injection of each fuel valve according to the timing of the injection, and to periodically and sequentially replace the fuel valves that stop the injection, a pressure detector is installed in the fuel supply chamber of the fuel valve. The present invention is configured such that the end of injection of the fuel valve is detected by the pressure detector.

[Effect]

In this case, the injection can be completed with high pressure in the latter half of the injection, the pressure is absorbed on the pump side, there is no problem with secondary injection or cavitation, and the injection pressure is increased by closing part of the fuel valve. Maintains good combustion.

In the embodiment of the invention of Japanese Patent Application No. 59-248653, the end of injection of each fuel valve is detected using a rack position detector attached to the control rack of the fuel pump, so the control is used to determine the end of injection. There is a risk of mechanical errors such as backlash and plunger wear, but in this invention, the pressure in the oil supply chamber is detected using a pressure detector such as a piezoelectric element, so injection control with even higher precision can be performed. I can do it.

〔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 the 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. 1
1 is a ball valve or check valve, 12 is a spring, and 13 is a spring receiver having an oil passage. 14 is orifice, 1
5 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 adjustment screw, 113
is rock nut. 114 is a piston guide, and 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, 304 is a solenoid valve, 305 is a relief pipe, 30
6, 307 is a hydraulic pipe, 308 is a pressure accumulator, 309 is a pump, and 310 is an oil tank.

401 is a trigger signal generator, and 402 is a rotation speed pulse generator.

501 is a deflector, and 502 is a piezoelectric element (AE sensor).

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

First, I will explain how a microcomputer works.

As a calculation function, the load is calculated based on the rotation speed from the rotation speed pulse, the determination of the end of pump discharge from the piezoelectric element signal, and the difference from the trigger signal.

The memory section includes a map for changing the delay trigger generation timing according to the rotation speed and load, and the number of activated fuel valves with the rotation speed on the horizontal axis and the load on the vertical axis.
An example of the operation map is shown in Figure 2.

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 solenoid valve mounting hardware 302, which is maintained at a constant pressure by the action of 08, 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 delayed trigger signal from a microcomputer.

We will discuss the operation of the injection system, but here we will discuss the 7th function.
Taking the three fuel valves shown in FIG. 2 as an example, explanation will be given in sequence according to the operation map shown in FIG.

First, the operation in the three-fuel valve operating range A, that is, at high loads, will be described.

A fuel chamber 06 in the fuel pump 01 is filled with fuel by a fuel supply pump (not shown), which 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 drain 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 internal oil passage 104, nozzle tip internal oil passage 1
05 and is led to the oil reservoir 106. 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
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 is applied to 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, which further increases the pressure 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, oil sump part 1
The pressure at 06 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. 3 shows the jetting 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.

Next, the action in the two-fuel valve operating range B will be described.

In FIG. 4, in the first cycle, the fuel valve c,
Next, b, then c, etc., the timing at which the hydraulic pressure is applied is set so that the fuel valve that does not inject changes in each cycle (this is, of course, determined by the rotational speed input to the microcomputer and the discharge (The load is calculated from the end signal and the trigger signal, and the system operates accordingly.) At this time, the area of the nozzle hole is reduced to two-thirds of that of the conventional one, resulting in high-pressure injection. Furthermore, as mentioned above, hydraulic pressure is applied to the other two fuel valves in the latter half of the injection to complete the injection at high pressure.

Next, the load and rotational speed further decrease, and in the 1-fuel valve operating range C, as shown in FIG. 5, the no-injection state continues for two cycles, and then a trigger signal is issued to inject once. That is, in the first cycle in the figure, the fuel valves injecting are fuel valves a, then c,
Only one of the three fuel valves injects fuel as shown in b, a, and so on. However, the fuel valves that are activated alternate. At this time, the nozzle hole area is reduced to 1/3 of the conventional size, making it possible to achieve high-pressure injection even at low load rotation speeds.

FIG. 6 briefly describes the calculation flow within the microcomputer. The rotation speed is calculated using the rotation speed pulse, the end of ejection is determined based on the signal from the piezoelectric element (AE sensor), and the load is calculated from the difference with the trigger signal. These rotational speeds and loads are compared on a rotational speed-load map stored as a storage device, and a delay trigger signal is thereby issued to the electromagnetic valve controller corresponding to each fuel valve.

[Effect of idea]

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 (2) By eliminating poorly atomized spray and completing injection quickly, good combustion in the engine can be ensured, leading to improved performance. (2) Secondary injection or durability that adversely affects engine performance Since cavitation, which causes a decrease in performance, does not occur, a highly reliable engine injection system can be provided.

Furthermore, in a partial load range, by completely closing some of the plurality of fuel valves, the nozzle hole area is narrowed and high-pressure injection can be realized, and the fuel valves that are stopped are not the same every cycle but are alternated. (3) It is possible to improve combustion and performance under partial load, and (4) problems such as deterioration of the fuel valve or carbon blockage, which are concerns due to stoppages, can be eliminated by alternating stoppages, and high fuel efficiency can be achieved. Reliability can be maintained.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an embodiment of the device according to the present invention, Fig. 2 is an explanatory diagram showing an operation map for changing the number of actuated fuel valves, and Fig. 3 is an explanatory diagram showing the piston oil pressure and needle valve of the device of Fig. 1. lift, nozzle pressure, pump pressure,
Diagram showing piezoelectric element signal and static discharge start, 4th
The figure is a line diagram showing the oil pressure, nozzle pressure, and needle valve lift of each valve in the 2-fuel valve operating range. Figure 5 is a line showing the oil pressure, nozzle pressure, and needle valve lift of each valve in the 1-fuel valve operating range. Figure 6 is a diagram showing the calculation flow of the microcomputer, Figure 7a is an explanatory diagram showing a conventional fuel injection system with one fuel pump and one fuel valve per cylinder, Figure 7b is also 1
FIG. 8 is an explanatory diagram showing a conventional fuel injection system, and FIG. 9 is an explanatory diagram showing the pump pressure, nozzle pressure, and Diagram showing needle valve lift, 1st
Figure 0 is a diagram showing equal injection pressure lines. 01...Fuel pump body, 06...Refueling chamber, 0
8, 11... Check valve, 101... Fuel valve body, 1
07... Needle valve, 115... Piston, 303,3
04... Solenoid valve.

Claims (1)

[Scope of utility model registration request] A fuel injection device for a diesel engine having a plurality of fuel valves in one cylinder branched from a jerk-type fuel pump, the check valve being provided in the fuel pump and opened when fuel is discharged, and the discharge valve. A check valve that is opened by the pressure on the discharge side at the end of the process,
A piston installed in each of the above fuel valves that receives hydraulic pressure separate from the injection system to press the needle valve of the fuel valve, a solenoid valve that opens and closes the hydraulic pipes leading to the above piston, and engine speed and crank rotation. a microcomputer that controls the opening and closing of the electromagnetic valve based on the engine angle and engine load, and the microcomputer supplies hydraulic pressure to the piston of the fuel valve at the end of injection of each fuel valve to operate the fuel valve. Closed,
When the engine is under partial load, hydraulic pressure is supplied to the pistons of some fuel valves, injection of each fuel valve is intermittently stopped depending on the engine load, and the fuel valves that stop injection are periodically alternated in sequence. In the multi-fuel valve injection device, a pressure detector is attached to the fuel supply chamber of the fuel valve, and the end of injection of the fuel valve is detected by the pressure detector. Valve injection device.