JPS6142088B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to fuel control for diesel engines. Conventionally, among fuel injection devices used particularly for large diesel engines, the so-called BOSCH type injection device has the schematic structure shown in FIG. 1, and the present invention relates to a control method for this injection device and improvements to the device. It is something.

The fuel injection system is installed independently in each cylinder of the engine, and consists of a constant stroke relief hole type injection pump A shown on the left side of Figure 1, an automatic injection valve with a closing nozzle B shown on the right side, and a pipe connecting them. It is composed of a combination of roads. In the fuel injection pump A, a plunger 1 within a cylinder 16 moves up and down in conjunction with a cam 14 driven by an engine crank (not shown). That is, the lowest position of the cam 14 is the bottom dead center of the pump cam, and as the cam rotates, the roller 15 is pushed up and the plunger 1 moves up and down accordingly. When the plunger descends, fuel is sucked into the plunger upper chamber 21 from the fuel suction pipe 6, which is previously opened in the cylinder 16. From the moment the plunger upper end closes the suction hole 24 during the upward stroke of the plunger 1, the fuel oil in the plunger upper chamber 21 is compressed, pushing up the suction valve 4 against the reaction force of the spring 5, and the fuel oil flows into the injection tube. 7. The fuel oil that has flowed into the pipe line 7 flows to the automatic injection valve B with a closing nozzle and is introduced into the valve chamber 22. When the pressure inside the valve chamber 22 overcomes the spring 13, the valve 10 is lifted and fuel oil flows into the nozzle 1.
2 is injected into the engine. The top dead center of the engine piston (not shown) does not coincide with the fuel injection start timing, and the cam 14 is moved toward the camshaft 1 so as to have an advance angle.
It is set to 8. Let this angle be α. That is, the advance angle α refers to the phase difference in crank angle between the engine piston top dead center and the preceding fuel injection start timing.

The amount of fuel injected from the nozzle 12 into the engine as the plunger 1 in the fuel injection pump rises is controlled by the diagonal groove 2 located below the plunger.
This is done by draining the fuel oil in the upper chamber 21 from the vertical groove 3 after it has passed through the oil drain hole 25. That is, the amount of fuel injected into the engine is determined by the rotation angle of the plunger 1, which is influenced by the position of the oblique groove 2. The means for changing the rotation angle of the plunger 1 is to rotate the plunger 1 via a rack and pinion 8 using a governor 9 or the like.

The advance angle α has a large effect on the fuel consumption rate of the engine, and its optimum value varies greatly depending on the operating conditions of the engine and the quality of the fuel oil. When the quality of fuel oil changes, or for marine engines driven by variable pitch propellers where the relationship between main engine speed and load can be changed freely, or conversely, for power generation engines where the speed is constant and the load can be changed freely, the optimum fuel consumption rate is determined. Operation is not possible with the above fuel injection system.

Figure 2 shows the amount of movement Z of the rack 8, which indicates the rotation angle of the plunger 1 of the fuel injection device, and the optimum advance angle αopt.
It was created by measuring the engine speed at each engine speed.
The optimum advance angle αopt when the engine load torque, that is, the fuel injection amount (easy position) is a constant value.
is α ₁ at γ ₁ rotation speed, whereas γ
At ₂ revolutions, αopt becomes α ₂ , and at γ ₃ revolutions, α opt becomes α _3. As shown in this figure, if the advance angle α can be easily controlled during operation, the fuel injection amount can be optimized. be able to.

Conventionally, in large engines using this type of fuel injection pump, the advance angle α can be adjusted by adjusting the phase of the cam when the engine is stopped, but it is generally impossible to operate the engine. The driving force by the cam is 10~
This is because it is extremely difficult in terms of reliability and structure to provide such a structural part with a mechanism that can be easily changed during operation, as the weight can reach as much as 20 tons.

If you want to change the phase of the cam relative to the crankshaft while operating a large engine, and if this is difficult due to the mechanical structure, you can optimize the fuel injection amount by fluidically processing the change in advance angle α. The present invention is a devised solution to this problem. In view of the above, the inventor sets the minimum advance angle α in the practical operating range with a cam, and separately adds supplementary fuel supply prior to the start of pressure feeding from the plunger, thereby achieving the same effect as increasing the advance angle α. As a result of a comparative study between this method and a method in which the maximum advance angle in the practical operating range is set by a cam and the discharge amount is bypassed to the suction side after the plunger starts pumping with a volume equivalent to a decrease in the advance angle α, the latter was found. This led to the adoption of the In the former method, a small fuel pump is installed in addition to the original fuel injection pump, and the amount of oil is added when necessary, making the discharge amount of the small fuel pump variable. Since the installation of the small pump is too large-scale, it is economically unfeasible.

The first purpose of the present invention is to set the cam so as to obtain the maximum advance angle in the practical operating range of the fuel injection pump, and then set the cam to the maximum advance angle in the practical operating range of the fuel injection pump, and then discharge the fuel after the plunger starts pumping fuel at a flow rate corresponding to a decrease in the advance angle α. This is a method of bypassing the amount to the pump suction side, fluidly processing the advance angle, and controlling the fuel injection start timing by a program, and the second and third inventions are devices for implementing this method. The second purpose of the present invention is to
An oil drain valve is provided that is mechanically connected to the fuel injection pump by a lever or the like and moves in synchronization, and has an opening Y that is the bottom dead center of the pump cam (Y is adjustable). The stroke length corresponding to Y bypasses the fuel so that it does not take part in the pressure increase. Further, the third invention has the same object as the second invention, and the opening degree of the oil drain valve at the bottom dead center of the fuel injection pump cam can be controlled by a stepper (or pulse) motor. The lead angle can be changed all at once by sending pulses to the stepper motors in synchronization with a pulse generator, or can be individually adjusted by sending fine adjustment pulses individually.

To specifically explain the present invention, as _described above with reference to _FIG . lower γ ₂ ,
If γ becomes ₃ , the fuel injection rate will not be optimal, and unless the advance angle α is decreased, the optimal advance angle αopt will be reached.
do not become. In Figure 3, the maximum practical rotation speed is γ
If the optimal advance angle αopt is γ when it is set to ₁ , then
Optimal lead angle α for low rotational speeds γ ₂ and γ ₃
opt becomes α ₂ and α ₃ , respectively. In other words, the lead angle is less than the maximum lead angle γ by β, so αopt=γ
−β. In the present invention, in order to actively process the advance angle correction corresponding to β, the fuel in the upper chamber of the plunger of the fuel injection pump is bypassed to the fuel intake side only during the movement of the plunger corresponding to β, and the engine The start timing of fuel injection into the cylinder can be delayed. That is, considering the crank angle as a base in Fig. 4, for the crank angle E at the top dead center of the engine cylinder, when the maximum advance angle α (α is variable) = γ, the fuel injection start position R, the fuel injection pump Assuming that the bottom dead center of the cam is O, the phase difference θ between the cam bottom dead center O and the fuel injection start position R, and the position R' of the corrected advance angle α, α = γ - β, and the actual engine rotation The optimum advance angle αopt in the numerical value, that is, the advance angle α at the practical rotational speed is set to be longer than when the maximum rotational speed γ is reached by β before fuel injection is started.

FIG. 5 shows an embodiment of the present invention, in which a pipe connects the plunger upper chamber 21 of the BOSCH type fuel injection pump A explained in FIG. It was established. The pump outlet port 19 of the plunger upper chamber 21 of the fuel injection pump A is connected to the valve chamber inlet port 44, and the outlet port 45 is connected to the pump suction chamber port 20. A valve body 31 is provided in a cylinder 32 of the oil drain valve so as to slide, and the valve body 31 is coupled to the center portion of a lever 37. One end of the lever 37 is the plunger 1
, and the other end connects to the positioning mechanism. This mechanism is constructed by connecting a screw 35 of a stepper motor 36 with a nut 34. One valve body 3
1 has an opening degree Y at the bottom dead center of the cam 14, and the position of the nut 34 on the position setting mechanism, that is, the screw 35 is adjusted so that the phase difference of the crank angle at this time corresponds to θ shown in FIG. Set. This setting can also be set manually.

Next, to explain the operation of this embodiment, when the plunger 1 rises from the bottom dead center of the cam 14 as the cam rotates, the opening degree Y of the valve 31 closes synchronously, and when the valve 31 is fully closed, the plunger 1 rises from the bottom dead center of the cam 14. The entire extruded volume of 1 is used to compress the upper chamber 21, and the rest is exactly the same as the conventional fuel injection process. Regarding FIG. 4, R is the fuel injection start position in a state where the oil drain valve C is not provided. The position of the nut 34 on the screw 35 of the position setting mechanism is set so that the initial valve opening is set so that the advance angle is delayed by the adjustment angle β according to the present invention. As the valve opening degree Y gradually decreases, the pressure P ₁ in the plunger upper chamber 21 increases and reaches the opening pressure P ₀ of the valve 4 just before the length ε from the closed position of Y. later
The pressure increases to _P2 , and fuel is injected from the nozzle 12 of the automatic injection valve B at the injection valve opening pressure _Pc . One end of the lever 37 is directly connected to the moving part of the plunger 1, and the other end is directly connected to the position setting mechanism.
This mechanism can be operated even while the engine is running. The amount to be manipulated is determined by detecting the rack position and engine rotational speed, deriving the optimal advance angle corresponding to the engine operating state using an optimal advance angle calculation program that is pre-built in a separate calculation device, and then outputting the signal. This pulse is applied to a pulse oscillator to rotate each stepper motor by the same amount at the same time, thereby automatically adjusting the opening of the oil drain valve. The stepper motor 36 is
This is a motor that rotates by a predetermined rotation angle for each pulse of the pulse train sent out from the pulse oscillator 47. Therefore, if N pulses are sent out, it will rotate by N times. If the same pulse train is sent to the stepper motors 36 attached to each cylinder, all the stepper motors will rotate with the same phase and the same rotation angle. Alternatively, if different pulse trains are applied to each engine cylinder individually, the rotation angles can be adjusted accordingly.

In this way, each pulse motor can generate a pulse oscillator 4 without any mechanical coupling between each oil drain valve attached to each cylinder.
The pulses sent from 7 give the same amount of rotation all at once. The rotation of each stepper motor is applied to the screw 35 and converted into a linear displacement by the nut 34, which moves the other end of the lever 37. The valve body 31 of the oil drain valve is connected to the movement of the plunger 1 and the stepper motor 3.
It will move with a nearly linear combination of rotation angles of 6,
The advance angle α is uniquely determined by the rotation angle of the stepper motor. 48 is a setter for setting the advance angle to be given to each cylinder at once, that is, the number of pulses to be sent out all at once, and 42 is a setter for the number of pulses to be finely adjusted for each cylinder individually.

The implementation method shown in FIG. 5 is, of course, just one example, and various similar mechanisms may be considered, but it goes without saying that all such mechanisms are included in the present application. Engine cylinders generally have slightly different characteristics, and it goes without saying that the above-mentioned individual fine adjustment pulses are necessary to adjust for these differences.

According to the advance angle control method and control device using the present invention, the previously established injection system remains as is, and even if the oil drain valve does not move from the fully closed position,
It still has exactly the same functions as the conventional injection system, and is extremely reliable in practice compared to other advance angle control devices.

Components required for lead angle adjustment have an inner diameter of 10~
Only a small oil drain valve of about 20mmφ, two pipes, and one set of levers are attached to a conventional injection pump, so no major modification is required, and the valve operating power is only about a few tens of watts. , compact and small.

Advance angle commands for all cylinders can be electrically performed, and no mechanical coupling mechanism or the like is required between the cylinders.

Features include the ability to adjust the advance angle at any time even while the engine is running.

[Brief explanation of the drawing]

Figure 1 is a side sectional view showing the operation of a conventional fuel injection system, Figure 2 is a chart showing the relationship between engine speed and optimal advance angle, and Figure 3 is the optimal advance angle at maximum load in the practical operating range. A chart showing the relationship between γ and the optimum advance angle at a load lower than γ, FIG. 4 is a chart showing the relationship between the oil pressure of the fuel injection valve and the advance angle to explain the operation of the present invention, and FIG. FIG. 2 is a side sectional view showing an embodiment to which the invention is applied. 1... Plunger, 2... Oblique groove, 3... Vertical groove, 4... Suction return valve, 5... Spring, 6... Suction oil pipe, 7... Injection pipe line, 8... Rack, pinion,
9... Governor, 10... Valve body, 11... Cylinder, 12... Nozzle, 13... Spring, 14... Cam, 15... Roller, 16... Cylinder, 18
...Crank, 19 ...Pump outlet port, 20
... Pump suction chamber port, 21 ... Upper chamber, 22
... Valve chamber, 23 ... Valve inlet port, 24 ... Suction hole, 25 ... Oil drain hole, 31 ... Valve body, 32 ... Valve casing, 34 ... Nut, 35 ... Screw, 36 ... Step motor, 37... lever,
42...Pulse regulator, 44...Valve inlet port,
45...Valve outlet port, 48...Pulse number setting device, A...Injection pump, B...Automatic injection valve, C...
...Drain valve.

Claims (1)

[Claims] 1. Starting fuel injection from an automatic injection valve with a closing nozzle, which is operated by the discharge pressure of a constant stroke relief hole type fuel injection pump that is driven independently for each cylinder of the engine, is practical for the engine. The injection pump drive cam is set in advance to achieve the maximum advance angle in the operating range, and at any engine load, the oil discharged from the injection pump is bypassed to the suction chamber to achieve the optimal advance angle. A fuel control method for a diesel engine characterized by control using an optimum advance angle calculation program. 2. A diesel engine that supplies and injects fuel using a constant stroke relief hole fuel injection pump that is driven independently for each cylinder of the engine and an automatic injection valve with a closing nozzle that is activated by the discharge pressure of the pump. In the fuel injection device, an oil drain valve is provided between the plunger upper pressure chamber of the injection pump and the fuel oil suction side, and a position setting mechanism is provided in which the valve body of the oil drain valve is provided separately from the position of the plunger. The position setting mechanism is a mechanism that applies a displacement proportional to the stepper motor or its rotation amount to the relative opening of the oil drain valve, and the position setting mechanism is a mechanism that applies a displacement proportional to the stepper motor or its rotation amount to the relative opening of the oil drain valve, and A fuel control device for a diesel engine, characterized in that it is equipped as an external device that sets the number of electrical pulses that can be rotated by a fine adjustment amount or individually and sends those pulse trains to a stepper motor attached to each cylinder.