JPS6390633A - Transfer controlling method for binary fuel and device thereof - Google Patents

Abstract

PURPOSE:To prevent vehicle performance from getting worse, by starting the feed of liquid fuel or fuel gas after the elapse of each specified time since the transfer at the time of making it transfer from the fuel gas to the liquid fuel and vice versa, and restraining overrichness or overleanness from occurring. CONSTITUTION:In this device, there is provided with a first timer (d) measuring a first time at which a fuel gas flow rate before its transfer is continued since a point of time when a fuel transfer device (c) transfers from the fuel gas to liquid fuel. Also there is provided with a second timer (e) measuring a second time necessary to become the specified fuel gas flow rate since a point of time when the fuel transfer device (c) is transferred in contrast with this. And, at the time of transfer from the fuel gas to the liquid fuel, feed of the liquid fuel is started after the elapse of the first time, while at the time of transfer to the reverse, each of liquid and gas fuel feeding devices (a) and (b) is controlled by each of fuel feed controlling devices (g) and (f) in order to decrease a liquid fuel supply before transfer by degrees so as to bring a supply of the liquid fuel to zero at the elapse of the second time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a J3 dual fuel engine that supplies liquid fuel and gas fuel by switching between them. The present invention relates to a fuel switching method and device.

BACKGROUND OF THE INVENTION In recent years, natural gas has been reconsidered as an alternative energy source to oil, and the movement to utilize it as a fuel for automobiles has become active, especially in natural gas producing countries. Natural gas has methane as its main component, which has a low boiling point, so LPG, which has traditionally been used in some areas as a fuel for automobiles,
It is difficult to store liquids at room temperature, such as liquefied petroleum gas (liquefied petroleum gas), and compressed natural gas
d Natural Gas (also abbreviated as CNG) is filled in a gaseous state into a cylinder and mounted on a vehicle.

The supply system for gas fuels such as CNG is not necessarily fully established compared to liquid fuels such as gasoline and diesel oil (hereinafter sometimes referred to as "gasoline fuel"), which have traditionally been used as vehicle fuels. Therefore, engines that use only gas fuel as fuel are limited to special applications such as those installed on the ground.Generally, vehicle engines use dual fuels (gas fuel and gasoline) to avoid gas fuel shortages. Vehicles that can be used by switching to gasoline fuel from time to time or by switching to gasoline fuel at other times are becoming popular (eg, Japanese Patent Laid-Open No. 57-59048).

When switching between dual fuels, the response to starting and stopping the gas fuel supply is particularly poor, so it is necessary to adjust the fuel supply before and after switching.

In other words, the gas fuel stored at high pressure is normally reduced to near atmospheric pressure using a several-stage regulator, and then passed through a variable orifice that adjusts the opening to the negative pressure of the engine's intake pipe. Therefore, due to the presence of residual gas in the piping downstream of the gas fuel cutoff position at the time of switching, the gas fuel supply to the engine starts and stops at the cutoff position. A phenomenon occurs in which the start and stop of gas fuel supply are delayed by one hour compared to, for example, the case of liquid fuel supplied by intermittent injection from an injector. For this reason, conventionally, as described in, for example, Toku'IA No. 61-54898,
The deterioration in response during switching is suppressed by supplying liquid fuel for a predetermined period of time from the time of switching, equivalent to when the engine is idling.

Problems to be Solved by the Invention However, with the above-mentioned solution, a constant M of liquid fuel is supplied to the engine for a uniform period of time regardless of the operating state of the engine at the time of fuel switching. ,
When switching from gas fuel to liquid fuel at low speeds and low loads, the supplied gas fuel remains in the engine's intake pipe for more than a specified time, and a considerable amount of liquid fuel is added to this gas fuel when idling. When over-rich or when switching from gas fuel to liquid fuel at high speeds and high loads, the supplied gas fuel will be consumed within the specified time and the iU engine will be left with only liquid fuel, equivalent to when idling. In some cases, only 1/2 of the fuel was supplied, resulting in over-lean conditions.

Furthermore, when switching from liquid fuel to gas fuel, even at a time when there is almost no gas fuel supply immediately after the switch, only a considerable amount of liquid fuel is supplied during idling, resulting in over-lean conditions.

The present invention was created by M in view of such problems, and it eliminates the risk of A-bar lean or over-rich when switching, regardless of the operating condition at Akashi. It is an object of the present invention to provide a dual fuel switching control method and device that prevent deterioration of vehicle performance.

Means for Solving the Problems The above-mentioned problems with the prior art are due to the J3
When switching from gas fuel to liquid fuel, after a predetermined period of time during which the gas fuel flow rate before switching is maintained according to the engine operating state from the time of switching, the amount corresponding to the engine operating state is changed. When switching from liquid fuel to gas fuel, the supply of liquid fuel starts when the predetermined time required for the gas fuel flow rate to reach the gas fuel flow rate according to the engine operating status has passed from the time of switching. This problem is solved by a dual fuel cutoff M i, II fi1 method, which is characterized in that the amount of liquid fuel supplied before switching is gradually reduced according to the operating state of the engine so that the amount of fuel is reduced to zero. .

Further, the apparatus used to carry out the method includes a liquid fuel supply means a for supplying liquid fuel to the engine, a gas fuel supply means for supplying gas fuel to the engine, and a fuel supply means for switching between these supply means. C and fuel supply means C
A first timer d measures a predetermined time during which the gas fuel flow rate before the switching is continued depending on the operating state of the engine from the time when the gas fuel is switched from the gas fuel to the liquid fuel, and the fuel supply means C switches from the liquid fuel to the liquid fuel. When the second timer e measures the predetermined time required for the gas fuel to flow according to the operating state of the engine from the time of switching to gas fuel, and this fuel supply means C is switched to gas fuel. maintains the supply of gas fuel according to the operating state of the engine until the time measured by the first timer d elapses from the time when the fuel supply means C switches from gas fuel to liquid fuel before switching. a gas fuel supply control means f for controlling the gas fuel supply means C so as to maintain a gas fuel flow rate of When the measured time has elapsed, the supply of liquid fuel according to the operating state of the engine is started, and when the fuel supply means C has been switched to liquid fuel, the supply of liquid fuel according to the operating state of the engine is started. 1711B according to the operating state of the engine so as to continue and stop the supply of liquid fuel when the time measured by the second timer e has elapsed from the time when the fuel supply means C switched from liquid fuel to gas fuel. and a liquid fuel supply control stage q for controlling the liquid twisting 11 supply means a to gradually reduce the previous liquid fuel supply. do.

If the fuel supplied to the engine is switched to liquid fuel while the engine is being operated with gas fuel supplied,
From the time of switching, the supply of liquid fuel is started after a predetermined period during which the gas fuel flow rate before switching is maintained according to the operating state of the engine, and this duration is during engine operation at Akashi. Since it is set in advance according to the situation, the optimum air-fuel ratio is maintained.

On the other hand, if the fuel supplied to the engine is switched to gas fuel while the engine is being operated with liquid fuel supplied, the gas fuel flow rate will change depending on the engine operating status from the point of switching. The amount of liquid fuel supplied before switching is gradually reduced according to the operating state of the engine so that the amount of liquid fuel supplied becomes zero after a predetermined time period has elapsed, and the appropriate time is determined by the amount of liquid fuel supplied at the time of switching. Since it is set in advance according to the operating condition, the optimum air-fuel ratio is maintained.

Embodiments Hereinafter, preferred embodiments of the present invention will be explained with reference to the drawings b.

Referring to FIG. 2, an example of a dual fuel engine to which the present invention is applied is shown, in which the fuels include CNG and gasoline, which are filled into a cylinder 1 at a pressure of, for example, 200 Kg/att2. Gasoline in tank 2 is used. In the same figure, 3 is provided in the cylinder 1 and C
Valve used for filling and taking out NG, 4 is high pressure pipe 5
6 represents a high pressure regulator provided integrally with the shutoff valve 4, and 7 represents a low pressure regulator connected to the high pressure regulator 6 through piping 8. The shutoff valve 4 is composed of an electromagnetic valve configured using, for example, a solenoid, and is controlled to open and close by a signal sent from the C N G till 1 circuit 13 via a line 15 .

With the shutoff valve 4 open, the gas fuel is first reduced in pressure from 4 to 6 to 9/as2 by the high pressure regulator 6, and then
0.1 to 0°2 K with low pressure regulator 7! j /
The pressure is reduced to c-waste 2, and the piping 12 and variable orifice 10
The variable orifice 10 is driven by a pulse signal sent from the CNG control circuit 13 via the line 14. Rotation of the possible stepper motor sets the desired orifice opening, thereby regulating the CNG fuel feeder.

On the other hand, the gasoline fuel in the gasoline tank 2 is supplied by a nouel bomb 16 provided in the gasoline tank 2.
The fuel is sent to the injector 19 at a predetermined pressure via the pipe 17 and a fuel filter 18 provided in the middle. The injector 19 is actually provided for each cylinder 1 and is connected to the gasoline fuel control circuit 22 via the gland 21.
Pressurized gasoline fuel, which is controlled to open and close in response to electrical drive pulses sent from the intake valve and is sent at a predetermined pressure, is intermittently injected into the intake passage 11 (intake boat section) near the intake valve (not shown).

The flow of the intake air sucked in through the air cleaner 44 is detected by the air sensor 23 having the movable vane 24. The intake air hl is controlled by a throttle valve 25 that is linked to an accelerator pedal (not shown). Interlocking with the throttle valve 25, the throttle valve 25
is in the closed position or idle position).
A signal from the torque position switch 40 is sent to the CNG control circuit 13 and the gasoline fuel control circuit 2 via a line 41.
Sent to 2.

The air-fuel mixture formed by mixing CNG in the mixer 26 or injecting gasoline fuel by the injector 19 is combusted in a combustion chamber (not shown) in the engine body 27, and the exhaust gas after the combustion is It is discharged into the atmosphere via the exhaust passage 28 and a catalytic converter 29 provided in the middle thereof.

The air flow sensor 23 is provided in the intake passage 11' upstream of the throttle valve 25, and generates a voltage determined by the position of the movable vane 24, which rotates in response to changes in the amount of intake air. This output voltage is fed to the gasoline fuel control circuit 22 via line 30. Reference numeral 31 represents an air flow sensor actuator for driving the movable vane 24. This actuator 31 is connected to the gasoline fuel control circuit 22 via a line 32, and when the fuel selector switch 9 is on the gasoline side, the air flow sensor actuator J3 is used to drive the movable vane 24. 24 is in a freely rotatable state, and when the fuel selector switch 9 is on the CNG side, the movable vane 24 is controlled so as to open the intake air passage.

33 is an engine distributor that outputs a pulse signal every time the crankshaft rotates by a predetermined angle, and this pulse signal is sent to the CNG control circuit 13 and the gasoline fuel control circuit 22 via a line 34.

The exhaust passage 28 generates an output in response to the oxygen concentration in the exhaust gas, that is, has two different values depending on whether the air-fuel ratio is on the lean side or the steep side with respect to the stoichiometric air-fuel ratio. An 02 sensor 35 is provided which generates an output voltage of 0.02 and the output voltage of this sensor is fed via line 36 to the gasoline fuel F1 control circuit 22.

A conduit 37 is provided downstream of the throttle valve 25 in the intake passage 11.
An intake pipe pressure sensor 9-383 is provided through the line 39, and this sensor sends a voltage signal generated in response to the negative pressure in the intake passage 11 to the CNG control circuit 13 and the gasoline fuel control circuit 22 via the line 39. send to.

The fuel selector switch 9 connects CNG via lines 42 and 43.
For example, an open/close signal indicating that the fuel has been switched is sent to the control circuit 13 and the gasoline fuel control circuit 22.

FIG. 3 is a block diagram showing one embodiment of the gasoline fuel control circuit 22 shown in FIG.

The voltage signals from the air flow sensor 23.02 sensor 35 and the intake pipe pressure sensor 38 are sent to an analog-to-digital 〈△/D) converter 50 having an analog multiplexer function, and are sent to a central processing unit (CPJJ).
The signals are sequentially converted into binary signals in accordance with instructions from 52.

Pulse signals for each predetermined crank angle from the distributor 33 are sent to a well-known speed signal forming circuit provided in the input interface circuit (110 circuit) 54, thereby forming a binary signal representing the rotational speed of the engine. Ru. Further, this pulse signal is used, along with other pulse signals for each predetermined angle, to form an interrupt request signal for calculating the fuel injection pulse width, a fuel injection start signal, a cylinder discrimination signal, and the like.

The signal from the stop position switch 40 is
10 circuits 54 to predetermined pit positions and are temporarily stored.

The signal from the fuel selector switch 9 is also sent to the I10 circuit 5.
4 is sent to a predetermined pit position, and an interrupt request signal for activation/stop of the injector 19, an activation signal for the air 70-sensor actuator 31, and a gasoline fuel injection start time and end time at the time of fuel switching, which will be described later. It is used to create set/reset signals for timers that measure

In the output interface circuit (110 circuit) 56,
A well-known fuel injection control circuit including a register and the like is provided, and the I10 circuit 56 forms an injection pulse signal having the pulse width from binary data regarding the injection pulse width sent from the CPU 52. This injection pulse signal 1 is transmitted to the injector 1 via a drive circuit (not shown).
It is sent to 9a to 19d sequentially or simultaneously to energize them. As a result, the amount of fuel corresponding to the pulse width of the injection pulse signal is injected. Also,
This I10 circuit 56 is provided with a circuit that forms a binary signal for driving the air flow sensor actuator 31, and this signal causes the air flow sensor actuator 31 to move when the vane 24 is in the intake air passage when in the CNG fuel mode. Fully open and lock in this state,
When in gasoline fuel mode, the vane 24 is unlocked so that it can rotate freely according to the amount of intake air.

The Δ/D converter 50 and I10 circuits 54 and 56 are connected via a common bus 62 to a CPU 52, a random access memory (RAM) 58, and a read-only memory (ROM) 60, which are the main components of the microcomputer. 43, data and instructions are transferred via this bus 62.

The ROM 60 contains a main processing routine program, an interrupt processing routine program for calculating the fuel injection pulse width, an interrupt processing routine program for calculating various correction coefficients, and a program from the time of fuel switching from CNG to the start of fuel injection. Stop the fuel injection after cutting to the CNG every time - 1 t.
] Gram (timer function) and other programs,
Furthermore, various data necessary for these calculation processes are stored in advance.

On the other hand, FIG. 4 is a block diagram of one embodiment of the CNG control circuit 13 shown in FIG. 2 in Table 1. In this case, the hardware such as the A/D converter 2950', CPU 52', I10 circuit 54' and 56', RΔM 58', and ROM 60' has the basic function and configuration of the gasoline fuel control circuit shown in FIG. Since it is based on the hardware of , we will omit its explanation.

As the gasoline fuel control circuit 22 and the CNG control circuit 13, various configurations different from those described above can be applied. For example, without providing a speed signal forming circuit in the I10 circuits 54 and 54', it is also possible to configure the CPUs 52 and 52' to receive pulse signals for each predetermined crank angle and form speed signals using software. be. Furthermore, the air fuel cometer actuator 31 and the cutoff valve 4 may be configured to be directly connected to the fuel selector switch 9 without going through the control circuits 22 and 13 as described above.

The operation of the above-mentioned microcomputer will be explained below.

In the gasoline fuel mode, that is, when the fuel cut-off switch 9 is on the gasoline fuel side, the gasoline fuel control circuit 22 is activated and operates based on the intake air intake data from the air 70 sensor 23 and the engine speed data from the distributor 33. , First, M fuel injection cycles are calculated. This basic fuel injection amount is corrected each time according to signals from other sensors, and the injector 19 is driven by a fuel injection pulse formed according to the corrected fuel injection amount. Since this kind of processing routine is well known,
The explanation will be omitted.

In the CNG mode, that is, when the fuel selector switch 9 is on the CNG side, the CNG control circuit 13 functions, and based on data regarding intake pipe pressure from the intake pipe pressure sensor 38 and engine four-speed rotation data from the distributor 33, First, use these data as parameters in ROM6.
The basic opening of the variable orifice 10 stored in 0' is read out. This basic u) 1 degree is corrected each time according to signals from other sensors, and the variable orifice 10 is driven to achieve the corrected opening degree. This type of processing routine can also be configured based on the same idea as the gasoline fuel mode described above, so its explanation will be omitted.

Next, regarding the control at the time of mode switching, which is characteristic of the present invention,
This will be explained in detail using a flowchart and timing chart 1.

Fig. 5 is a step-by-step diagram related to control when switching from gasoline fuel to CNG, and Fig. 6 is a timing chart showing the operation of each member at that time. -1. Fuel at step 70! , 7J vehicle switch 9 has been switched from the gasoline fuel mode to the CNG mode. If it is determined that the switch 9 has not been switched, the process proceeds to step 78 and the control in the gasoline fuel mode described above is continued. The reason why the variable orifice 10 is kept fully open in the gasoline fuel mode is to prevent fluctuations in the air-fuel ratio and deterioration of engine startability due to incomplete gas sealing between the high-pressure side regulator 6 and the variable orifice 10. be.

On the other hand, if it is determined in step 70 that the mode has been switched to CNG mode, the cutoff valve 4 is closed in step 71, and the variable orifice 10 is driven to a predetermined opening degree A by the stellar 772. This opening degree Δ is an opening degree that corresponds to the operating state of the engine in the CNG mode described above. In step 73, the airflow hinge actuator 31 starts to drive, and the vane 24 of the airflow hinge is thereby displaced from position B to fully open position C depending on the operating state of the engine in the gasoline fuel mode. It is locked in this state. The time required for this displacement is typically approximately 2
00+ns. Next, in step 74, the timer starts counting, and in step 76, the timer starts counting for a predetermined time t, which will be described later. The operations from step 75 onwards are continued until the time elapses. In step 75, the fuel injection 131ffl of the injector 19 is injected into the gasoline fuel tank for a predetermined period t from ff1D depending on the operating state of the engine in J5.

After the elapsed time, it starts decreasing to zero. It is desirable that the rate of decrease is constant. This predetermined time t. is the time required for the CNG flow to reach ffi and E commensurate with the engine operating condition from the time of fuel switching,
The data exposed to the signals from the intake pipe pressure sensor 38 and the distributor 33 are used as parameters.
It is mapped in the OM 60 and is taken out as appropriate depending on the operating state of the engine at the time of pJ change. At step 76, a predetermined time t is reached. If it is determined that h<h has elapsed, the routine proceeds to step 77, where the gasoline fuel injection is completely stopped, this routine is ended, and the process shifts to the previous CNG[-] mode control.

FIG. 7 shows 70-dx□-1- related to the control when switching from CNG to gasoline fuel, and FIG. 8 is a timing chart showing the operation of each member at that time. In step 90, it is determined whether or not the fuel cut-off switch 9 has been switched from the CNG mode to the gasoline fuel mode.
Then, the control in the CNG mode described above is continued. on the other hand,
If it is determined in step 90 that the CNG mode has been switched to gasoline fuel mode, the cutoff valve 4 is closed in step 91. Next, in step 92, the air 70-sensor vane 24 is unlocked in response to the amount of intake air. In step 93, the timer starts integrating, and in step 94, a countdown is performed to start injection of gasoline fuel after the fuel changeover switch 9 is actuated.

In step 95, the variable orifice 10 is maintained at the same position as before switching, and in step 96, the operations of steps 94 and 95 are continued until the timer reaches the predetermined time t1. This predetermined time [1] is the time during which the supply of CNG at a flow rate ff1E corresponding to the operating state of the engine at the time of fuel switching is continued, and data based on the signals from the intake pipe pressure tip 38 and the distributor 33 are used as parameters. It is mapped in advance in ROM60,
'C is taken out as appropriate depending on the operating condition of the engine. If it is determined in step 96 that the predetermined time t1 has elapsed, the process proceeds to step 97, where gasoline fuel corresponding to the amount of intake air measured by the vane position B of the air flow sensor 23 at that time is supplied. Shifts to gasoline fuel mode control. Also, step 9
At step 9, the variable orifice 10 is fully opened, and this routine ends. in this case,[! 11. When switching from CNG to gasoline fuel, each gasoline fuel pipe 17.
In order to prevent vapor from being generated in the fuel pump 20 and the gasoline fuel being injected near the discharge point, the fuel pump 16 should be operated at all times to keep the gasoline fuel circulating at all times. desirable.

Effects of the Invention According to the present invention, since an appropriate amount of liquid fuel or gas fuel is supplied according to the operating condition when switching between dual fuels, the air-fuel ratio is leaner and overrich is prevented when switching between fuels. This eliminates the risk of overheating, prevents deterioration in vehicle performance, and prevents backfire that often occurs during lean conditions, thus reducing the air flow sensor's medium temperature. Damage to the ring plate is prevented. Furthermore, misfires and afterfires that tend to occur when overrich are prevented, and therefore damage to the catalyst, exhaust pipe, and muffler is prevented.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram showing the lumber configuration of the device of the present invention, Fig. 2 is a polysystem configuration diagram showing an embodiment of the engine to which the present invention is applied, and Fig. 3 is the structure shown in Fig. 2. Figure 4 is a block diagram showing an example of the CNG control circuit shown in Figure 2. Figure 5 is a block diagram showing an example of the CNG control circuit shown in Figure 2. ) [Coach 1? 6 is a timing chart of this control, FIG. 7 is a flowchart for explaining control when switching from CNG to gasoline fuel, and FIG. 8 is a timing chart of this control. 4... Shutoff valve, 6... High pressure regulator, 7... Low pressure regulator, 9... Changeover switch, 10... Variable orifice, 11.11'... Intake passage, 13... CNG Control circuit, 16... Fuel pump, 19... Injector, 22... Gasoline fuel control circuit, 23... Air flow sensor, 24... Movable vane, 27... Engine body, 2
8...Exhaust passage, 29...Catalytic converter, 3
3...Distributor.

Claims (2)

[Claims] (1) In a dual fuel engine that alternately supplies liquid fuel and gas fuel, when switching from gas fuel to liquid fuel, the gas fuel before switching is changed depending on the engine operating state from the time of switching. After a predetermined period during which the flow rate continues, the supply of liquid fuel is started in an amount that corresponds to the operating condition of the engine, and when switching from liquid fuel to gas fuel, the amount of liquid fuel that corresponds to the operating condition of the engine starts from the time of switching. The amount of liquid fuel supplied before switching is gradually reduced according to the operating state of the engine so that the amount of liquid fuel supplied becomes zero when the predetermined time required to reach the gas fuel flow rate has passed. Features dual fuel switching control method. (2) A liquid fuel supply means for supplying liquid fuel to the engine, a gas fuel supply means for supplying gas fuel to the engine, a fuel switching means for switching these supply means, and a fuel switching means for switching from gas fuel to liquid fuel. a first timer that measures a predetermined time during which the gas fuel flow rate before switching is continued according to the operating state of the engine from the time when the fuel switching means switches from liquid fuel to gas fuel; a second timer for measuring a predetermined time required to reach a gas fuel flow rate corresponding to the operating state of the engine; The gas fuel supply means continues the supply and maintains the gas fuel flow rate before switching from the time when the fuel switching means switches from the gas fuel to the liquid fuel until the time measured by the first timer elapses. gas fuel supply control means for controlling the fuel supply; and supplying liquid fuel according to the operating state of the engine when the time measured by the first timer has elapsed from the time when the fuel switching means switched from gas fuel to liquid fuel. and when the fuel switching means has switched to liquid fuel, the supply of liquid fuel according to the operating state of the engine is continued, and the second timer starts from the time when the fuel switching means switches from liquid fuel to gas fuel. Liquid fuel supply that controls the liquid fuel supply means to gradually reduce the liquid fuel supply amount before switching according to the operating state of the engine so as to stop the supply of liquid fuel when the time measured by has elapsed. 1. A dual fuel switching control device comprising a control means.