JPH0429867B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dual fuel supply system for an internal combustion engine.
The device according to the present invention uses, for example, a non-compressible ignitable fuel (low cetane number) such as alcohol or gasoline, uses a fuel with excellent self-ignitability (high cetane number) such as light oil as an ignition source, and uses light oil as an ignition source such as alcohol, etc. It is used in internal combustion engines that inject the main fuel either before or at the same time as the main fuel.

Prior Art In order to burn a non-compression ignitable fuel (low cetane number fuel) such as alcohol or gasoline in a compression ignition engine, that is, a diesel engine, it is necessary to use a self-ignitable fuel (high cetane number) such as light oil as an ignition source. It is necessary to inject the fuel (auxiliary fuel) into the engine cylinder before or at approximately the same time as the non-compression ignitable fuel (main fuel). For this reason, a dual fuel supply system has been proposed that has a relatively simple configuration and is capable of injecting two different types of fuel from a single injection nozzle.

FIG. 1 is a diagram of a conventional device, in which the main fuel is supplied from the main fuel tank 1 through a pipe 26 to the main fuel pump 2.
is introduced into the fuel injection pump 3 through the pipe 27, and is pumped to each injection nozzle 11, 12,
It is injected and supplied into the engine cylinder from 13 and 14.

On the other hand, the auxiliary fuel is sent from the auxiliary fuel tank 4 to the pressure feeding device 6 by the auxiliary fuel pump 5, and the piston 7
The liquid is fed under pressure and supplied to each nozzle 11, 12, 13, and 14. Here, the operation of the pumping device 6 for pumping auxiliary fuel will be explained. The auxiliary fuel sent by the auxiliary fuel pump 5 is checked by the check valve 9 and is held in the pumping device 6.

Further, the pumping piston 7 is set to the pumping pressure by a spring 8 and is driven by the main fuel introduced from the main fuel branch point 38 through the pipe 29. The main fuel pressurized by the injection pump 3 overcomes the force of the spring 8, pushes the piston 7 upward, and forces the auxiliary fuel to the nozzle 13. The pressure-fed fuel is held between the injection nozzle 13 and the pipe 33 by the check valve 10.

On the other hand, the structure of the injection nozzle 11 includes a nozzle needle 17, a fuel hole 16 for main fuel that opens toward the nozzle tip in the direction of injection hole 18, and a fuel hole 15 for auxiliary fuel.

The pressure feeding device 6 and the injection nozzles 11, 12, 1
The piping connections 3 and 14 are very distinctive and are arranged to take advantage of the injection order of a multi-cylinder engine.
In other words, the phase is shifted every 180℃, and the pressure of the main fuel in the first cylinder is connected to the pressure feeding device 6 connected to the third cylinder, and the main fuel in the third cylinder is transferred to the pressure feeding device 6 of the fourth cylinder. It's becoming like that.

Figure 2 shows each cylinder (No. 1
~No. 4) This is a time chart explaining the change in the injection nozzle internal pressure (P). At a crank angle of 0°, the pressure in the first cylinder increases, and after passing the valve opening pressure of P ₀ , t ₀
The main fuel is injected from the injection nozzle for a time of . At the same time, the pressure of the auxiliary fuel pumping device connected to the third cylinder, which is the next injection cylinder, is also increased by the pressure of the main fuel in the first cylinder to _P1 , which is the spring force in the pumping device, and Auxiliary fuel is filled into the cylinder nozzle.

Here, the auxiliary fuel pressure P ₁ takes a lower value than the nozzle valve opening pressure P ₀ , so it does not reach the valve opening, and during t ₁ , P ₁
remains held. Next, when the crank angle reaches 180° and the pressure of the main fuel in the third cylinder exceeds P ₀ , the needle in the nozzle lifts and the auxiliary fuel and the main fuel are injected. Such a cycle is repeated in sequence according to the injection order, making it possible to supply dual fuel of auxiliary fuel and main fuel.

Figure 3 explains the state of the spray from the injection nozzle.The tip of the spray contains auxiliary fuel F(S).
Gas oil, which is , is injected behind it, and alcohol, which is main fuel F(M), is injected behind it.

Figure 4 shows the relationship between time t and change in injection amount per unit time dQ/dt.
Auxiliary fuel light oil F(S) and main fuel alcohol F(M)
It can be seen that the injection timing is performed with a phase difference. Therefore, by injecting a small amount of light oil ahead of the alcohol, a flame is created by self-ignition of only the light oil.
Since the alcohol is injected later towards the flame, the combustion of the alcohol is facilitated, and the engine can also be operated with alcohol, which is a non-compression ignitable fuel.

However, in actual operating conditions, that is, in a wide range of operating ranges, the conventional method limits the operable range. Fig. 5 shows its operating characteristics, and shows how the ignition range (FR) changes with light oil pressure feed using the conventional method.

In Fig. 5, the horizontal axis represents the engine speed N, the vertical axis represents the load W, FR represents the ignition region, and M-
FR represents the misfire area and MAX represents the maximum output.
Now, if the operating range indicated by the L ₂ line (2A [mm ³ /st cyl]) decreases from the amount of light oil supplied to the L ₂ line,
If the operating range decreases to L ₁ line (A [mm ³ /st・cyl]) and increases, then L ₃ line (3A [mm ³ /st・cyl])
This expands the operating range to st/cyl]). In order to cover the entire operating range, it would be sufficient to increase the amount of diesel oil supplied to the maximum extent possible, but this would mean that there is no point in using alcohol fuel, so it is necessary to supply the maximum amount of alcohol and ensure stable operating conditions. In order to achieve this, the amount of light oil supplied must be varied according to the operating characteristic diagram shown in FIG.

In this way, in the conventional technology, the amount of diesel oil supplied is kept constant due to its structure, so if you try to secure the operating range, the amount of alcohol used decreases, and if you try to increase the amount of alcohol, the operating range increases. There is a problem that securing a driving range and increasing the use of alcohol are not compatible with each other.

OBJECT OF THE INVENTION In view of the problems of the prior art, the purpose of the present invention is to
It is based on the idea that the operating state of the engine is detected by a rotation speed detection sensor and a load detection sensor, and the auxiliary fuel system is controlled to achieve the optimal amount of auxiliary fuel by comparing it with the ignition operating range built into the microcomputer. The objective is to cover the entire operating range while ensuring the maximum amount of main fuel.

Structure of the Invention In the present invention, an injection nozzle is provided with a main fuel port and an auxiliary fuel port that separately supply main fuel and auxiliary fuel to the tip of the injection nozzle needle, a main fuel injection pump, and an injection nozzle other than the injection nozzle that supplies the auxiliary fuel. an auxiliary fuel pumping device for filling the injection nozzle below the valve opening pressure of the injection nozzle with the injection pressure of the main fuel; a rotation speed sensor that detects the rotation speed of the internal combustion engine; a load sensor that detects the load of the internal combustion engine; There is provided a dual fuel supply device for an internal combustion engine, comprising: control means for controlling the pumping amount of the auxiliary fuel pumping device according to the rotation speed and load detected by a rotation speed sensor and a load sensor. Ru.

Embodiment A dual fuel supply system for an internal combustion engine as an embodiment of the present invention is shown in FIG. Reference numeral 1 indicates a main fuel tank, which is connected to the main fuel pump through a pipe 26, and after being pressurized, the main fuel is sent to the fuel injection pump 3 through the pipe 27. The main fuel is pumped by the fuel injection pump 3 at high pressure, usually 120 kg/cm ³ or more, and reaches the main fuel port 16 of the injection nozzle 11 through the pipe 28 and the pipe 30, pushing up the nozzle needle 17 and into the injection hole 18. More sprayed.

Figure 6 Since the device is a 4-cylinder engine, the injection nozzles are 11, 12, 13, and 14, respectively, and the injection pump 3
connected to. The auxiliary fuel is connected from the auxiliary fuel tank 4 to the auxiliary fuel pump 5 through a pipe 31, and after being pressurized is sent to the auxiliary fuel pumping device 6 through a pipe 32.

There is a branch point 38 between the main fuel pipe 28 and the pipe 30, and the pipe 2
At 9, the main fuel is taken into the auxiliary fuel pumping device 6 and is in contact with the piston 7. The piston 7 is pushed down by a spring 8, and when the main fuel overcomes the force of the spring 8, the piston rises and auxiliary fuel is pumped out. At this time, the check valves 9 and 10 force-feed the auxiliary fuel only to the injection nozzle 13. A disk 19 with slits cut out at equal intervals is attached to the rotation shaft of the injection pump 3, and a rotation speed sensor 20
The engine speed is detected. injection pump 3
A position sensor 22 is attached to a control rack 21 for controlling the injection quantity of the fuel cell 1, and a signal is inputted to a calculation device 23 through signal lines 34 and 35, respectively. Since the position of the control rack 21 changes depending on the engine load, the position sensor 22 plays the role of an engine load sensor.
A signal line 36 connects the current controller 24 from the calculation device 23.
A signal is output to control the auxiliary fuel pump 5 via the signal line 37. As the computing device 23, a microcomputer type device can be used.

The operation of the FIG. 6 apparatus is described below. When the engine is operated, the injection pump 3 also rotates in synchronization, and the disc 19 attached to the rotating shaft also rotates as indicated by the arrow
It rotates like AR1 and generates an on/off voltage signal to the rotation speed sensor. This signal is calculated by the calculation device 23.
The number of engine revolutions per unit time is detected by counting with the reference clock. Furthermore, the position of the control rack is known by a position sensor 22 installed opposite to the control rack 21 that controls the injection amount, and is converted into a load amount by a calculation device 23, which provides assistance according to the operating range shown in FIG. A signal corresponding to the amount of fuel is output to the current controller 24, and the current controller 24 transmits a current value corresponding to the output signal of the calculation device 23 to the auxiliary fuel pump 5 via the signal line 37. Changing the rotation speed and changing the supply amount to the auxiliary fuel pressure feeding device 6,
The amount filled into the auxiliary fuel port 15 in the injection nozzle 11 is changed.

Auxiliary fuel (light oil) of A [mm ³ /st cyl] in Figure 5
If the engine was operated in the ignition range of 2A [mm 3 /st cyl] and then moved to higher rotation, the fuel amount of A [mm ³ /st・cyl] would enter the misfire region, so the fuel amount should be increased towards 2A [mm ³ /st・cyl]. According to the judgment of the calculation device 23, the pump rotation speed of the auxiliary fuel pump 5 is increased via the current controller 24, and the amount of auxiliary fuel into the auxiliary fuel pumping device 6 is increased. The opposite operation occurs when the amount of auxiliary fuel is reduced due to a decrease in rotational speed and load.

An example of the operation of the computing device 23 in the apparatus shown in FIG. 6 is shown in the flowchart of FIG. 13.

Start at step S100, input the pulse signals of the disk 19 and rotation speed sensor 20 at step S101, count the time between pulses P-P using the built-in reference clock at step S102, and calculate the number of pulses per unit time at step S103. Calculate the rotation speed Ne.
In step S104, it is determined whether the engine rotation speed Ne is 0 or not. If it is 0, the engine does not rotate, so fuel is not injected, and the process continues in step S104.
Return to before S101. If Ne is other than 0 in step S104, that is, the engine is running, step
Proceeding to S105, the signal from the position sensor 22 attached to the control rack 21 of the injection pump 3 is input, and in step S106, the injection amount Q of alcohol is read from the R-Q table shown in FIG.

In Figure 11, the horizontal axis is the alcohol injection amount Q
[mm ³ /st·cyl], and the vertical axis represents the control rack position R [mm]. In step S107, the engine speed Ne calculated in step S103 is set to the 10th
Minimum amount of light oil q according to the Ne-Q table shown in the figure
Read out [mm ³ /st・cyl].

In Figure 10, the horizontal axis is the engine speed Ne
[rpm] and the vertical axis is the alcohol injection amount Q [mm ³ /st・
cyl]. In step S108, the auxiliary fuel pump current value I corresponding to the value of q is read from the q-I table shown in FIG. 12, and in step S109, the I value is output to the current controller 24.

In Figure 12, the horizontal axis is the minimum amount of light oil q [mm ³ /
st・cyl], and the vertical axis is the auxiliary fuel pump current I [m
A] represents.

When one routine is completed as described above, the process returns to step S100 through step S110.
Input the engine speed and control rack signals again and repeat the control.

A dual fuel supply system for an internal combustion engine as another embodiment of the present invention is shown in FIG. The device shown in FIG. 7 controls the amount of auxiliary fuel supplied to the auxiliary fuel pumping device 6 using a bypass valve 41. Pipes 42 and 43 are provided to communicate the pipe 31 between the fuel tanks 4, and the bypass valve 4
1, part of the fuel supplied from the auxiliary fuel pump 5 to the auxiliary fuel pumping device 6 is diverted to control the amount of fuel supplied. The bypass valve 41 is driven by a solenoid 40, and the solenoid 40 is controlled by a solenoid drive device 39. 44 is a signal line.

An example of the operation of the computing device 23 in the device shown in FIG. 7 is shown in the flowchart shown in FIG.

From step S120 to step S127, the sixth
The operation description is the same as in the figure. In step S128, the bypass valve 41 is intermittently controlled by the solenoid 40, so that the on-time t ₁ of the solenoid valve shown in FIG.
The duty ratio D=t ₁ /t ₂ expressed as the ratio of the on-off cycle time t ₂ is determined from the q-D table in FIG. 15, and the D value is output to the solenoid drive device in step S129.

In Figure 15, the horizontal axis is the minimum amount of light oil q [mm ³ /
st・cyl], and the vertical axis represents the duty ratio D.
At step S130, the process returns to step S120 and the control is repeated.

A dual fuel supply system for an internal combustion engine as another embodiment of the present invention is shown in FIG. The device shown in Figure 8 changes the lift amount of the piston of the pressure feeding device.
A piston 50 of the auxiliary fuel pumping device 45 has a wedge-shaped tip and is pressed downward by a spring 8. On the other hand, a stopper 51 facing the piston 50 also has a wedge-shaped tip, and is configured to be rotated by a rack 52 as indicated by an arrow AR4.

Further, the control rack 52 is connected to a linear solenoid 53, and the movable iron piece 54 is moved by the arrow arrow due to the balance between the spring 56 and the solenoid 55.
It moves like an AR3. Furthermore, the solenoid 55 is connected to a solenoid drive device 57 by a signal line 58 so that it can be operated in accordance with the output signal of the calculation device 23 as appropriate.

Now, the movement of the piston 50 is determined by the rotational position of the stopper 51 and is synchronized with the movement of the rack 52. In other words, when the rack 52 is pushed toward the auxiliary fuel pumping device 45, the piston 5
0 effective stroke decreases, and conversely the easy 52
When the fuel is pulled back toward the linear solenoid 53, the stroke increases, and the amount of auxiliary fuel supplied can be controlled.

An example of the operation of the computing device 23 in the apparatus shown in FIG. 8 is shown in the flowchart of FIG. 17.

Steps S140 to S147 are the same as those in FIGS. 6 and 7 above. Linear solenoid 53
The movable iron piece 54 is interlocked with the rack 52 of the auxiliary fuel pumping device 45, and the stopper 51 can be rotated by changing the current of the solenoid 55. Therefore, in step S148, the I value is read out from the q-I table shown in FIG.
In S149, output the I value to the solenoid drive device 57,
The current applied to the linear solenoid 53 can be changed.

A dual fuel supply system for an internal combustion engine as another embodiment of the present invention is shown in FIG. The device shown in FIG. 9 bypasses high-pressure fuel after the auxiliary fuel pumping device 6, and connects the auxiliary fuel pumping device 6 and the injection nozzle 13.
Pipe 6 via branch point 61 to pipe 33 between
2, 63 and a bypass valve 59 are attached. The pipe 63 is connected to the auxiliary fuel tank 4,
Bypassed fuel is returned to the tank. Bypass valve 59 is driven by solenoid 60 and controlled by a signal from solenoid driver 64 . In other words, when reducing the supply amount, calculation device 2
The solenoid 60 is turned on by the signal from 3.
The bypass valve 59 is opened and the fuel in the pipe 33 is returned to the auxiliary fuel tank 4. The operation of the computing device 23 in the device of FIG. 9 is similar to the operation of the computing device in the device of FIG.

Effects of the Invention According to the present invention, when operating a compression ignition engine using a non-compression ignition fuel such as alcohol or gasoline as the main fuel, it is possible to cover the entire operating range while ensuring the maximum amount of the main fuel.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a conventional dual fuel supply system for an internal combustion engine, Fig. 2 is a diagram showing a time chart of the system shown in Fig. 1, Fig. 3 is a diagram showing the spray state of the system shown in Fig. 1, and Fig. 4 is a diagram showing a spray state of the system shown in Fig. 1. The figures are a diagram showing the injection characteristics of the device shown in Figure 1, a diagram explaining the characteristics of the dual fuel supply device, and a diagram 6
The figure shows a dual fuel supply system for an internal combustion engine as one embodiment of the present invention, FIGS. 7, 8, and 9 show other embodiments of the present invention, and FIGS.
12 is a diagram for explaining the operation of the device in FIG. 6, FIG. 13 is a flowchart showing an example of the operation of the calculation device in the device in FIG. 6, and FIGS. 14 and 15 are the device in FIG. 7. 16 is a diagram for explaining the operation of the 7th
FIG. 17 is a flowchart showing an example of the operation of the calculation device in the device shown in FIG. 8. FIG. (Explanation of symbols), 1...Main fuel tank, 2...
Main fuel pump, 3... Injection pump, 4... Auxiliary fuel pump, 5... Auxiliary fuel pump, 6... Auxiliary fuel pumping device, 7... Piston, 8... Spring, 9, 10... Check valve , 11, 12, 13, 1
4...Injection nozzle, 15...Auxiliary fuel port, 1
6...Main fuel port, 17...Needle, 18...
... Nozzle hole, 19 ... Disc, 20 ... Rotation speed sensor,
21...Control rack, 22...Position sensor, 23...Calculation device, 24...Current controller, 2
5... Orifice, 26, 27, 28, 29, 3
0, 31, 32, 33...pipe, 34, 35,
36, 37...signal line, 38...branch point, 39...
... Solenoid drive device, 40 ... Solenoid, 4
1... Bypass valve, 42, 43... Pipe, 44
...Signal line, 45...Auxiliary fuel pressure feeding device, 50...
... Piston, 51 ... Stopper, 52 ... Rack, 53 ... Linear solenoid, 54 ... Movable iron piece, 55 ... Solenoid, 56 ... Spring,
57...Solenoid drive device, 58...Signal line,
59...Bypass valve, 60...Solenoid, 61
... Branch point, 62, 63 ... Pipe, 64 ... Solenoid drive device, 65 ... Signal line.

Claims (1)

[Claims] 1. An injection nozzle equipped with a main fuel port and an auxiliary fuel port that separately supply main fuel and auxiliary fuel to the tip of the injection nozzle needle, a main fuel injection pump,
An auxiliary fuel pumping device that fills auxiliary fuel to a level below the valve opening pressure of the injection nozzle using the injection pressure of the main fuel of an injection nozzle other than the injection nozzle, a rotation speed sensor that detects the rotation speed of the internal combustion engine, and a rotation speed sensor that detects the rotation speed of the internal combustion engine. An internal combustion engine characterized by comprising a load sensor that detects a load, and a control means that controls the pumping amount of the auxiliary fuel pumping device according to the rotational speed and load detected by the rotational speed sensor and the load sensor. Engine dual fuel supply system. 2. The device according to claim 1, wherein the control means controls the pumping amount of the auxiliary fuel pumping device in the form of controlling the fuel amount before the auxiliary fuel pumping device. 3. The device according to claim 1, wherein the control means controls the pumping amount of the auxiliary fuel pumping device in the form of controlling the stroke of a pumping piston of the auxiliary fuel pumping device. 4. The device according to claim 1, wherein the control means controls the pumping amount of the auxiliary fuel pumping device in the form of controlling the pumping amount after the auxiliary fuel pumping device.