JPH0734914A - Fuel supply control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a fuel supply control device for an internal combustion engine provided with both a gas fuel supply device and a liquid fuel supply device, which is small in size, low in cost, and high in control accuracy. CONSTITUTION:A fuel supply control device is constituted so that CNG fuel for correcting the air-fuel ratio control or the like can be injectedly supplied through a fuel injection valve 15 constituting a gasoline fuel supply device. Thus, the capacity of a mixer 48 for supplying CNG fuel can be set small, so that the miniaturization of the device and the cost reduction of the product can be achieved. Relatively high-pressure CNG fuel can be injectedly supplied as correction CNG fuel in the vicinity of a combustion chamber, and also the control accuracy and control responsiveness at the time of CNG fuel supply control can be enhanced. Further, if a small amount of gasoline is supplied for enhancing lubricity of the fuel injection valve 15 at the time of CNG fuel supply, the durability of the injection valve 15 can be also enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device for an internal combustion engine, and more particularly to a gas fuel supply device for supplying a gas fuel and a liquid fuel supply device for supplying a liquid fuel, and switching the fuel type. The present invention relates to a fuel supply device for an internal combustion engine used.

[0002]

2. Description of the Related Art Gasoline, light oil, etc. are mainly used as a fuel for an internal combustion engine. In view of various problems such as pollution by harmful exhaust substances and exhaustion of resources, C has recently been used as an alternative fuel.
NG (compressed natural gas), LNG (liquefied natural gas), etc. are receiving attention. Therefore, in order to solve the above problems, as a fuel supply device for switching and supplying different types of fuel, Japanese Utility Model Laid-Open No. 63-125154 discloses the same vaporizer for LNG and methanol reformed gas. An engine is provided for use in which a smooth fuel switch upstream of the carburetor is provided without running out of fuel. Further, Japanese Patent Application Laid-Open No. 3-210037 discloses an engine that supplies gasoline and alcohol, which are liquid fuels, detects the oxygen concentration in exhaust gas with an oxygen sensor, and calculates the average value of the fuel correction amount during feedback control. The fuel tank is separated into two tanks at the time of refueling in order to detect and memorize the mixing ratio of gasoline and alcohol by the calculation and to suppress the combustion fluctuation due to the fluctuation of the calculated mixing ratio caused by the fuel supply. However, the fuel is supplied only from the separated one of the fuel tanks, and the fuel is supplied from the fuel tank side (the side not refueled) in which the calculated mixing ratio is maintained until the next feedback control is performed. I'm trying to do.

[0003]

However, in such a conventional fuel supply device for an internal combustion engine which selectively supplies different fuel types, when the liquid fuel and the gas fuel are used in combination, the liquid fuel is used. Since the supply means of and the supply means of gas fuel were provided completely independently,
There are problems that the operating efficiency is poor, the layout of the fuel supply means is difficult, and the product cost increases. Furthermore, since each of the fuel supply means is independent,
Since it is necessary to set a large capacity corresponding to the maximum fuel supply amount, the control accuracy and control responsiveness could not be improved.

Further, when the gas fuel and the liquid fuel are switched or used by mixing, the following problems remain. That is, liquid fuel has a delay related to fuel adhesion to the side wall of the combustion chamber and control responsiveness, whereas gas fuel does not have such a delay because it mixes with air faster than liquid fuel. In addition, since the differences in characteristics between liquid fuel and gas fuel have not been taken into consideration in the past, in engines that use both gas fuel and liquid fuel, low emission, low fuel consumption, and high output performance must be obtained. Was difficult.

Further, in a gas fuel supply device for supplying only gas as fuel through an electromagnetic valve or the like, a sliding portion or a valve seat exposed to the gas fuel because the gas fuel does not have lubricity. In some parts, sticking (sticking), scuffing (adhesion), etc. occur, which hinders the supply of good gas fuel, resulting in poor air-fuel ratio control and poor drivability. The present invention has been made in view of such conventional circumstances,
In an internal combustion engine provided with a gas fuel supply device and a liquid fuel supply device, the device does not become large in size, at low cost,
Moreover, it is an object of the present invention to provide a fuel supply control device for an internal combustion engine with high control accuracy. Another object of the present invention is to provide a fuel supply control device for an internal combustion engine, which can prolong the life of the fuel injection valve even when the gas fuel is continuously injected by the fuel injection valve. It is also an object of the present invention to provide a fuel supply control device for an internal combustion engine, which can improve fuel economy, exhaust performance, and output at the time of fuel switching, and further improve vehicle drivability, by suppressing the air-fuel ratio step in.

[0006]

Therefore, the fuel supply control device for an internal combustion engine according to the present invention, as shown in FIG.
Internal combustion engine provided with a gas fuel supply system for supplying a gas fuel, a liquid fuel supply system for supplying a liquid fuel, and a fuel switching means for switching the operation of the two fuel supply systems to switch a fuel type to be supplied. In the fuel supply device of the above, the gas fuel supply system and the liquid fuel supply system are configured to include a common fuel injection valve, and different types of fuel are switched from the common fuel injection valve and injected and supplied. Configured.

In the fuel switching means, a fuel supply passage upstream of the shared fuel injection valve selectively communicates with the shared fuel injection valve in accordance with the supplied fuel, a gas fuel supply passage, and a liquid fuel supply passage, It may be configured to be switched to. The fuel supply control device for an internal combustion engine according to the present invention, as shown in FIG. 2, lubricates the shared fuel injection valve when the gas fuel is injected and supplied to the internal combustion engine through the shared fuel injection valve. In addition, the fuel injection valve lubricating means for mixing the liquid fuel into the gas fuel may be included.

It is preferable that the fuel injection valve lubricating means includes a lubricating fuel supply pump that discharges and mixes the lubricating liquid fuel into the gas fuel. The fuel injection valve lubrication means includes a liquid fuel supply passage for feeding the liquid fuel discharged from the liquid fuel supply pump, and a fuel on the upstream side of the shared fuel injection valve for switching the fuel supplied by the fuel switching means. A surplus not used for lubrication from a bypass passage connecting the supply passage, the lubricating fuel supply pump interposed in the bypass passage, and the fuel supply passage between the liquid fuel supply pump and the lubricating fuel supply pump. The liquid fuel return passage for returning the liquid fuel to the liquid fuel supply source, and an opening / closing valve for opening and closing the liquid fuel return passage for lubrication. When supplying the fuel for lubrication, the fuel supply pump is provided. In addition to the operation, the lubricating fuel supply pump may be operated and the opening / closing valve may be opened.

The gas fuel supply system may include a mixer for mixing only the gas fuel with the intake air on the upstream side of the intake throttle valve, or only the gas fuel is injected into the engine intake system. It may be configured to include a gas fuel injection valve for supply. By the way, an operating state detecting means for detecting an operating state of the engine is included, and the fuel switching means switches the fuel supplied to the internal combustion engine to a gas fuel or a liquid fuel according to the operating state of the engine. You can also

Further, it is preferable that the fuel supply system for the shared fuel injection valve is provided with a mechanism for adjusting the fuel supply pressure while returning a part of the supplied fuel to the fuel supply source. Further, a residual fuel amount estimating means for estimating a residual amount of the fuel before switching which remains in the fuel supply system after switching the supplied fuel and continues to be sucked into the engine for a predetermined time after switching, and is estimated by the residual fuel amount estimating means. It is preferable to include a post-switching fuel supply amount correction means for correcting the fuel amount supplied from the fuel supply device after switching based on the residual fuel amount.

The residual fuel amount estimating means estimates the residual amount of the fuel based on the fuel supply delay time constant corresponding to the supply amount of the supply fuel before the switching immediately before the switching, and the fuel supply amount after the switching is estimated. When the correction means calculates the supply amount of the fuel supplied after the switching, the switching is performed based on the residual amount of the supply fuel before switching based on the time constant and the fuel supply delay time constant of the supplied fuel after switching. It is also possible to correct the supply amount of the post supply fuel.

[0012]

With the above structure, in the fuel supply device for an internal combustion engine according to the present invention, when switching between gas fuel and liquid fuel to be supplied, gas fuel and liquid fuel are injected and supplied from a common fuel injection valve. To do. The fuel supply passage on the upstream side of the shared fuel injection valve is switched by the fuel switching means to a gas fuel supply passage selectively communicating with the shared fuel injection valve according to the supplied fuel and a liquid fuel supply passage. If
Fuel can be switched with a simple structure.

Further, a fuel injection valve lubricating means for lubricating the common fuel injection valve is provided, and a small amount of liquid fuel having better lubricity than gas fuel is supplied to the common fuel injection valve when the gas fuel is supplied. By doing so, the poor lubrication of the shared fuel injection valve can be improved. For example, if the fuel injection valve lubrication means is configured to include a lubrication fuel supply pump that discharges and mixes liquid fuel into gas fuel, the liquid fuel is reliably supplied against high-pressure gas fuel supply pressure. can do. Further, the fuel injection valve lubricating means recirculates a lubricating fuel supply pump interposed in the bypass passage, and a surplus liquid fuel not used for lubrication to the liquid fuel supply source from a downstream side of the lubricating fuel supply pump. A lubricating liquid fuel return passage and an opening / closing valve for opening and closing the lubricating liquid fuel return passage are included so that the liquid fuel is constantly supplied to the lubricating fuel supply pump when the lubricating fuel is supplied. In this case, the supply of the lubricating liquid fuel is made responsive and the surplus fuel can be returned to the liquid fuel supply source, so that the overload of the liquid fuel supply pump can be suppressed. Further, as compared with the case where only the lubrication fuel supply pump is configured, it is sufficient to pressurize the liquid fuel pressurized by the liquid fuel supply pump in the previous stage by the lubrication fuel supply pump. Can be converted.

If the fuel supply system for the shared fuel injection valve is provided with a mechanism for adjusting the fuel supply pressure while recirculating a part of the supplied fuel to the fuel supply source, a stable fuel supply pressure can be maintained at all times. Therefore, the fuel supply amount from the shared fuel injection valve can be accurately controlled. Further, for example, the residual fuel amount estimating means is configured to estimate the residual amount of the fuel based on a fuel supply delay time constant corresponding to the supply amount of the supply fuel before switching before switching, and after the switching. When the fuel supply amount correction means calculates the supply amount of the fuel supplied after the switching, based on the residual amount of the supply fuel before the switching based on the time constant and the fuel supply delay time constant of the supply fuel after the switching based on the time constant. It is possible to correct the supply amount of the supplied fuel after the switching and correct the fuel supply amount in the fuel supply device after the switching to a desired amount according to the residual fuel amount at the time of the switching. It is possible to suppress the air-fuel ratio difference caused by the above. As a result, good fuel switching is performed, fuel efficiency, exhaust performance, and output can be improved, and vehicle drivability can also be improved.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 3 showing the configuration of the first embodiment,
In the intake passage 12 of the engine 11, an air flow meter 13 for detecting the intake air flow rate Q _air and an accelerator pedal are interlocked,
A throttle valve 14 that controls the intake air flow rate Q _air is provided, and an electromagnetic fuel injection valve 15 that constitutes a liquid fuel supply device is provided at each of the intake ports branched for each cylinder downstream.
FIG. 3 also shows an enlarged view of each fuel injection valve 15 part. A throttle sensor 30 for detecting the opening of the throttle valve 14 is additionally provided.

The fuel injection valve 15 is opened and closed by an injection pulse signal from a control unit 50 having a built-in microcomputer to inject a predetermined amount of gasoline fuel into the intake port. Gasoline fuel is pumped from a fuel pump 17 installed in a fuel tank 16 and is inserted into a gasoline supply passage 18 as a fuel switching means. A first three-way solenoid valve (S / V1) 19 has a B gate and a C gate. Are set so that they are communicated with each other, so that they are introduced into the fuel gallery 20 and are supplied to each fuel injection valve 15 that is communicatively connected thereto. A second three-way solenoid valve (S / V2) 21 is provided on the downstream side of the fuel gallery 20, and gasoline fuel is connected between the C gate and the B gate of the second three-way solenoid valve (S / V2) 21. By being set, the pressure is introduced into the pressure regulator 22 provided in the return passage 23, where the pressure is adjusted to a predetermined pressure, and the fuel injection amount of the fuel injection valve 6 is stabilized. The excess gasoline fuel is returned to the fuel tank 16 through the return passage 23.

Further, a water temperature sensor 29 for detecting the temperature Tw of cooling water in the cooling jacket of the engine 11 is provided, and the air-fuel ratio of the intake air-fuel mixture is detected by detecting the oxygen concentration in the exhaust passage (not shown). Air-fuel ratio sensor
31 is provided, and a three-way catalyst (not shown) that purifies the exhaust by oxidizing CO and HC in the exhaust and reducing NO _{X in} the exhaust is provided further downstream.

A crank angle sensor 32 is built in the distributor (not shown in FIG. 3), and the crank unit angle signal output from the crank angle sensor 32 in synchronization with the engine rotation is counted for a certain period of time, or The engine rotation speed N is detected by measuring the cycle of the crank reference angle signal. That is, the air flow meter 13, the water temperature sensor 29, the throttle sensor 30, and the crank angle sensor 32 constitute an engine operating state detecting means.

An ignition signal is sent to an ignition plug (not shown) of the engine 11 from an ignition circuit incorporated in the control unit 50, and the fuel in the cylinder is ignited in accordance with the signal. Further, the engine 11 includes a CNG fuel supply device 41 that supplies CNG fuel as gas fuel. CN
G fuel is stored in the CNG fuel tank 42 at a high pressure (for example, approximately 200
stored in kg / cm ^2), the tank valve (S / V) 43, by respectively opening the shut valve 45, CN in multistage depressurization valve 46
G fuel is introduced. The supply pressure of the CNG fuel is detected by the pressure sensor 44, and the output signal from the pressure sensor 44 is sent to the control unit 50 and used for CNG fuel supply control and the like. Further, the tank valve (S / V) 43 or the shutoff valve 45 should be provided with a function as a safety valve for stopping the supply of the CNG fuel when the supply pressure from the CNG fuel tank 42 exceeds a predetermined pressure. However, it is preferable to prevent damage to the engine 11.

The pressure stage of the multi-stage pressure reducing valve 46 is, for example, 3 stages, the first stage is 50 kg / cm ² , the second stage is 10 kg / cm ² , the third stage is 0.3 kg / cm ² , and the third stage is The CNG fuel whose pressure is reduced to 0.3 kg / cm ² is supplied to the mixer 48 provided upstream of the throttle valve 14 via the first CNG fuel supply passage 47. In the mixer 48, the first CNG fuel supply passage
47 is branched into a bifurcated passage 47a and a bifurcated passage 47b which are once bifurcated and rejoined. The branch passage 47a is adjusted in accordance with the intake negative pressure of the engine 11 by adjusting the passage area of the branch passage. An adjusting screw 48a for setting the basic supply amount of CNG fuel is provided, and the other branch passage 47 is provided.
A duty control valve 48b, which is driven to open and close according to a drive pulse signal from the control unit 50, is interposed in b. That is, the basic CNG fuel is supplied to the engine 11 via the adjusting screw 48a and by opening / closing the duty control valve 48b with a predetermined pulse width.

Here, the supply of the corrected CNG fuel amount by the fuel injection valve 15 will be described. First, the first three-way solenoid valve (S / V1) 19 is set to communicate with the gates A to C, and the gate A is connected to the gate A. Through the connected second CNG fuel supply passage 49, the second stage CNG fuel of 10 kg / cm ² is introduced into the fuel gallery 20 and can be supplied to the fuel injection valve 15. Then, by setting the gate C and the gate A of the downstream second three-way solenoid valve (S / V2) 21 to communicate with each other, the pressure by the CNG fuel pressure regulator (damper) 48 is stabilized, and the fuel injection valve 15 The CNG fuel amount accurately metered according to the injection pulse width control is injected and supplied with high responsiveness. The surplus CNG fuel that has passed through the CNG fuel pressure regulator (damper) 48 is returned to the second CNG fuel supply passage 49 by the CNG fuel return passage 50. By the way, the pressure regulator 22 and the CNG fuel pressure regulator (damper) 48 are provided separately, but a single pressure is provided so that the pressure regulator can be shared between the gasoline fuel supply and the CNG fuel supply. The regulator is a fuel gallery 20 upstream of the second three-way solenoid valve (S / V2) 21.
The valve opening pressure is made variable according to the fuel type, and the second three-way solenoid valve (S / V2) 21 is provided at the outlet of the valve.
It is also possible to switch the fuel return passage by, for example, the like.

Thus, during operation with CNG fuel, CNG fuel having a low pressure is supplied from the mixer 48 as the basic CNG fuel, and the correction C for air-fuel ratio control or the like is performed.
As the amount of NG fuel, CNG fuel having a high pressure is injected and supplied from the fuel injection valve 6 with high responsiveness (because the pressure is high and it can be supplied from the intake port close to the combustion chamber,
High responsiveness is realized). By the way, the ratio between the basic CNG fuel amount and the corrected CNG fuel amount is 80 to 90 (mixer 48
Side): about 20 to 10 (fuel injection valve 6 side), that is, the correction CNG fuel amount corresponding to air-fuel ratio control, water temperature correction, acceleration increase correction, CNG supply pressure / temperature correction is small, so The CNG fuel can be supplied only by the fuel injection valve 15.

By the way, the return passage 23 for gasoline fuel
The gasoline supply passage 18 and the gasoline supply passage 18 can be freely connected and disconnected via a return valve 24, and the gasoline supply passage
Between the 18 and the fuel gallery 20, the first three-way solenoid valve (S /
A bypass passage 25 that bypasses the V1) 19 is provided, and a dripper pump 26 and an orifice 27 are provided in the middle of the bypass passage 25. Such a structure constitutes the fuel injection valve lubricating means.

Explaining such a constitution, even during the operation with CNG fuel, the fuel pump 17 is driven to feed gasoline to the gasoline fuel supply passage 18, and the gates B to C are closed. 1 3-way solenoid valve (S / V1) 19
By supplying the gasoline to the dripper pump 26 by bypassing, for example, if the pressure in the fuel gallery is 10 kg / cm ² , the dripper pump 26 is driven so that the gasoline pressure becomes higher than that, and through the orifice 27. Dripping hole 28
Drop a smaller amount of gasoline upstream of the fuel gallery 20. This dripping gasoline will be supplied to the fuel injection valve 15 through the fuel gallery 20, so that the liquid fuel having lubricity adheres to the sliding portion and the valve seat portion of the fuel injection valve 15. Therefore, problems such as sticking (sticking) and scuffing (adhesion) can be prevented. Therefore, an accurate fuel amount can be supplied by pulse width control even if a gas body such as CNG fuel having no lubricity is continuously supplied. In order to atomize the dropped gasoline, the dropping hole 28 may be provided with a venturi, a cutout protruding hole, or the like. By the way, the excess gasoline related to the lubrication is sent to the return passage 23 and returned to the fuel tank 16 by opening the return valve 24. In the present embodiment, the bypass passage 25 is provided, but of course, a passage that connects the fuel tank 16 and the fuel gallery 20 independent of the fuel supply passage 18 is provided, and a dripper pump 26 or the like is provided in the middle of the passage. You may do it.

The fuel supply control performed by the control unit 50 in the fuel supply device having the above-described structure according to the present invention will be described with reference to the flow chart shown in FIG. In step 1 (indicated as S1 in the figure; hereinafter the same), the fuel pump 17 is driven at the time of starting, and the tank valve (S / V) 43 is opened so that any fuel can be supplied. .

In step 2, it is determined whether the engine should be operated with CNG fuel or gasoline fuel. This determination is made by the control unit 50, for example, as shown in FIG.
This is performed for each operation area as shown in. That is, in the low temperature region, the CNG fuel vaporizes better than the gasoline fuel, so the CNG fuel is supplied to improve the starting performance and the exhaust performance. Then, at the time of restart and during the warm-up operation in which the water temperature rises to a predetermined temperature (generally 50 to 60 ° C), the CNG fuel supply control is continued, and even after the warm-up is completed, in the low / medium load region. In city driving, etc., in order to improve fuel efficiency and exhaust performance, CNG fuel supply control is performed while performing air-fuel ratio feedback control. Then, when the CNG fuel supply control is continued at high rotation speed and high output, the gaseous fuel may diffuse in the intake system, and the volume efficiency of air intake may decrease, resulting in a decrease in output. Is switched to the gasoline supply control to achieve higher output.

Regarding whether or not the output is high, for example, the intake air flow rate Q _air is detected by the air flow meter 13, the engine rotation speed N is detected by the detection signal from the crank angle sensor 32, and the basic fuel amount Tp is determined. It can be obtained by calculation, or it may be determined based on a signal from the throttle sensor 30 whether or not the throttle valve 14 is fully opened or near full opening. Further, whether or not it is necessary to reduce the exhaust gas is determined based on whether the catalyst has not reached the activation temperature or based on a signal from the water temperature sensor 29. Regarding whether or not to improve fuel efficiency (improvement of fuel economy), the pressure sensor 44 confirms the residual pressure of the CNG fuel, and supplies the CNG fuel when it is confirmed that the CNG fuel remains. Is done in this way.

Further, the acceleration operation state is detected by detecting the rate of change of the throttle opening based on the signal from the throttle sensor 30, and the gasoline fuel supply control is switched according to the acceleration state to obtain good acceleration performance. You may do it.
Further, it goes without saying that the driver may manually switch the selection. Of course, in the fuel supply control, it is of course premised that the remaining amount of gasoline and the remaining amount of CNG fuel can be detected to operate with the required fuel.

Thus, in step 2, CNG
When it is determined that the operating condition is fuel, the process proceeds to step 3, and when it is determined that the operating condition is gasoline fuel, the process proceeds to step 8. Here, the fuel supply control of CNG fuel (steps 3 to 6) will be described.

In step 3, in order to operate with CNG fuel, the shut valve 45 is opened to introduce the CNG fuel into the multi-stage pressure reducing valve 46, and the first three-way solenoid valve 19 is connected to the gate A and the gate C. It is set to communicate with each other, CNG fuel is supplied into the fuel gallery 20, and the gate C and the gate A of the second three-way solenoid valve 21 are set to communicate with each other. As a result, the CNG fuel can be supplied to the mixer 48, the duty control valve 48a, the fuel injection valve 15, and the pressure regulator 22.

In step 4, the return valve 24 is opened and the dripper pump 26 is operated. In addition,
At this time, as described above, the drive amount of the dripper pump 26 may be variably controlled so that the gasoline fuel can be dropped from the dropping hole 28 against the CNG fuel pressure in the fuel gallery 20. Even if the CNG fuel as a gas body is injected and supplied by the fuel injection valve 15 in step 4, a small amount of lubricating gasoline is mixed in, and the gasoline on the sliding portion or the valve seat portion of the fuel injection valve 15 is included. Therefore, problems such as sticking (sticking) and scuffing (adhesion) can be prevented.

In step 5, the basic fuel supply amount and the corrected fuel amount in the CNG fuel supply control are calculated. Such calculation is performed as follows. That is, the intake air flow rate Q _air is detected by the air flow meter 13, and the engine rotation speed N is detected by the detection signal from the crank angle sensor 32.
Is detected, and the basic fuel amount Qfc ₀ (= k × Q _air / N, k is a constant) is calculated.

The water temperature correction coefficient Kw is the water temperature sensor.
Control unit 50 based on the signal from 29
Determined by the table look stored in. Further, the load correction coefficient K _MR is similarly determined based on the signal from the throttle sensor 30 and the engine rotation speed N. Further, during the transient operation, various correction coefficients are determined according to the CNG fuel supply pressure / supply temperature detected from the signals from the pressure sensor 44 and a CNG fuel temperature sensor (not shown).

Further, the air-fuel ratio sensor 31 detects the oxygen concentration in the exhaust gas to detect the air-fuel ratio of the intake air-fuel mixture, and the feedback correction coefficient DeltaA / F set based on the detected air-fuel ratio by another routine is calculated. Read in. Accordingly, the CNG correction fuel amount is calculated according to the following equation. Qfc ₁ = Qfc ₀ x (Kw + K _MR + ...) x DeltaA
/ F + Ts (Ts is the voltage correction amount) In step 6, the basic fuel supply amount Qfc _{0 is set} to the mixer
The amount is supplied to the engine 11 through the adjusting screw 48a of 48 and by the duty control valve 48a which is opened and closed by a drive pulse signal from the control unit 50. Then, in order to supply the corrected fuel amount Qfc ₁ to the engine 11, a drive signal having a drive pulse width of the corrected fuel flow rate Qfc ₁ is sent from the control unit 50 to the fuel injection valve 15 to perform opening / closing control, and the corrected fuel amount Qfc ₁ CNG fuel is supplied by injection. The total CNG fuel injection amount at this time is calculated as Qfc
₂ (= Qfc ₀ + Qfc ₁ )

In this way, since the corrected fuel flow rate Qfc ₁ is injected and supplied from the fuel injection valve 15, that is, the CNG fuel has a high pressure (for example, 10 kg / cm ² ), and the intake port close to the combustion chamber. Since it is injected and supplied to the engine 11 from
High responsiveness will be realized. In the present embodiment, all the correction fuel amounts are injected from the fuel injection valve 15, but of course the duty control valve
The duty control valve 48a may be made to bear the fuel supply amount of the duty control valve 48a. Further, the fuel injection valve 15 can be used to perform interrupt injection or the like, so that, for example, the acceleration can be improved with good responsiveness. Further, in step 4, the amount of gasoline that is dripped and supplied is detected from the discharge amount of the dripper pump 26, and the gasoline amount is subtracted from the basic injection amount Qfc ₀ or the corrected injection amount Qfc _1. The good thing is self-evident.

After that, the routine proceeds to step 7, where it is judged whether the operation of the engine 11 has been stopped. When it is determined that the operation is stopped, the routine proceeds to step 8, where the operation of the gasoline fuel pump 17 is stopped and the solenoid valve 43 provided in the CNG fuel tank 42 is stopped.
To close the flow. On the other hand, if it is determined that the operation is continued, the process returns to step 2 and the CNG is performed again.
It is determined whether or not the fuel operation condition is satisfied.

Here, the gasoline fuel control (steps 8 to 11) in the case where it is judged in step 2 that the operating conditions are for gasoline will be described. In step 8, the shut valve 45 is closed to stop the supply of the CNG fuel, and the first three-way valve solenoid valve 19 is switched so that the gate B and the gate C are communicated with each other, and the gasoline fuel is supplied to the fuel gallery 20. Then, the second three-way solenoid valve 21 is switched so that the gate C and the gate B communicate with each other.

In step 9, the return valve 24 is closed so that the gasoline discharged from the fuel pump 17 does not bypass the return passage 23. Then, the operation of the dripper pump 26 is stopped. In step 10, as in the case of step 6, the basic fuel amount in the gasoline fuel supply control is calculated, various correction coefficients are calculated, and the final gasoline fuel injection amount Qfg ₁ [= Q including the corrected fuel amount is included.
fg ₀ × (1 + Kw + K _MR + ...) × Delta A / F].

In step 11, the control unit 50
From the above, a drive pulse signal having a pulse width of the final fuel injection amount Q _f1 is sent to the fuel injection valve 15, and gasoline fuel is injected and supplied to the engine 11 at the fuel injection amount Q _f1 . After that, the routine proceeds to step 7, where it is judged whether the engine 11 has been stopped. When it is determined that the operation is stopped, the process proceeds to step 8, the fuel pump 17 and the shut valve 43 are closed, and this flow is ended. On the other hand, when it is determined that the operation is continued, the routine proceeds to step 2, and the above fuel supply control is repeated.

By the way, when the CNG fuel and the gasoline fuel are switched, the fuel remaining before the switching in the fuel supply system is sucked into the engine 11 for a while even after the switching, and the air-fuel ratio difference caused by the fuel switching is caused. Therefore, the control unit 50 is provided with the following residual fuel amount estimating means and after-switching fuel supply amount correcting means so that the air-fuel ratio step difference correction is performed to absorb the air-fuel ratio step difference during fuel switching. Has become.

That is, the case where the switching operation from the gasoline fuel supply control to the CNG fuel supply control is performed in step 2 will be described. In step 5, for example, it is determined whether the duty control valve 48a is switched from the OFF state to the ON state or not. If it is determined that the duty control valve 48a is switched to the ON state, the gasoline fuel supply control is performed to C
A switching operation is performed for the NG fuel supply control, and at the time of such switching, wall flow fuel adhering to the intake port portion downstream of the fuel injection valve 15 or between the first three-way solenoid valve 19 and the second three-way solenoid valve 21. Gasoline fuel remains in the fuel gallery 20, etc. Therefore, the residual gasoline fuel is supplied to the engine 11 through the intake port and the fuel injection valve 15 for a while after the switching. Therefore, in step 5, the residual gasoline fuel amount QfgT is calculated and
The correction is made in consideration of fgT.

That is, the residual gasoline fuel QfgT is
The time constant Taug (expressed by the damping function) to consume
Final fuel quantity in gasoline fuel supply control immediately before switching
Qfg _{1 Final}Determined by map or calculation for each
Based on the QfgT (= Qfg _{1 Final}× Taug)
It In addition, shut-off valve 45
Inside the multi-stage pressure reducing valve 46 on the downstream side, the first CNG fuel supply passage 47
Of the intake passage 12 inside the mixer 48 and downstream of the mixer 48
In addition, in the second CNG fuel supply passage 49 and the fuel gallery 20
Filled with enough CNG fuel to supply to the engine 11.
Since it takes time to set, the delay time constant Tau
1 is the required amount Qfc in the CNG fuel supply state₂Each time
Or calculated. Therefore, CNG fuel
The required amount of CNG fuel at the start of supply is Qfc₂× (1 + Tau)
Becomes

As a result, the CNG fuel supply amount QfcT1 at the start of fuel switching becomes an amount obtained by subtracting the residual CNG fuel QfcT and adding the wall flow amount, as shown below. _{QfcT1 = Qfc 2 × (1 +} Tau) -QfgT = Qfc 2 × (1 + Tau1) -Qfg 1 Final × Taug Incidentally, the residual gasoline fuel quantity QfgT, and CNG fueling lag (Qfc ₂ × Tau) includes a mixer 48 described above This is done by correcting the basic fuel amount Qfc ₀ of the CNG fuel that the vehicle bears or the corrected fuel amount Qfc ₁ that the fuel injection valve 15 bears, but of course, both may be shared.

Thereafter, the engine 11 is operated with the fuel amount at the time of switching until the residual gasoline fuel amount QfgT is consumed or the CNG fuel supply delay is eliminated.
When the switching is completely completed (Tau and Taug are time constants and can be easily determined), the engine 11 is operated by the normal fuel injection amount Qfc ₂ (= Qfc ₀ + Qfc ₁ ) described above. In this way, it is possible to perform good control without air-fuel ratio step even at the time of fuel switching, it is possible to suppress harmful components of exhaust gas, deterioration of fuel consumption, and improve vehicle drivability.

On the other hand, in step 2, when the switching operation from the CNG fuel supply control to the gasoline fuel supply control is performed, the injection pulse signal from the control unit 50 is sent to the fuel injection valve 15 in step 10 described above.
It is determined whether or not the switching control from the OFF state to the ON state is performed to drive the valve to open, and when it is determined that the switching control is performed to the ON state, the switching operation is performed from the CNG fuel supply control to the gasoline fuel supply control. However, during such switching, the multistage pressure reducing valve 46 on the downstream side of the shut valve 45
CNG fuel remains in the first CNG fuel supply passage 47, the mixer 48, the intake passage 12 downstream of the mixer 48, the second CNG fuel supply passage 49, and the fuel gallery 20. The CNG fuel will be supplied to the engine 11 as it is. Therefore, the residual CNG fuel amount Q
It is necessary to calculate fcT and make a correction in consideration of this.

This calculation consumes the residual CNG fuel.
The time constant Tau (represented by a damping function) for
Final CNG fuel amount in the immediately preceding CNG fuel supply state
Qfc _{2 Final}Obtained by map or calculation for each
Based on the QfcT (= Qfc _{2 Final}X Tau1)
It has become so. In addition, the gasoline fuel supply status
Immediately after the switching operation is performed, the fuel injection valve 15 is provided.
There is no wall flow in the downstream manifold part.
Immediately after the switching operation, it adheres to the manifold part as a wall flow.
Fuel exists. Here, the fuel adheres as a wall flow
The time constant Taug1 for
It is obtained by a map or calculation for each required amount Qfg1.
Therefore, the required gasoline fuel amount at the start of gasoline fuel supply
Is Qfg₁X (1 + Taug1).

As a result, the gasoline fuel supply amount QfgT1 at the start of fuel switching becomes an amount obtained by subtracting the residual CNG fuel QfcT and adding the wall flow amount, as shown below. _{QfgT1 = Qfg 1 × (1 +} Taug1) -QfcT = Qfg 1 × (1 + Taug1) -Qfc 1 Final × Tau1 Thereafter, the fuel quantity of the switching up to a residual CNG fuel quantity QfcT is consumed, or the wall flow is formed The engine 11 is operated by the above, and when the switching is completely completed (see Ta above).
u, Taug1 can easily determine because it is the time constant both), the engine 11 by a conventional fuel injection amount Qfg ₁ described above
Will be driven.

As described above, according to this embodiment,
Since the fuel injection valve 15 of the gasoline fuel supply device is also used during CNG fuel supply control, the mixer
The capacity of 48 can be set small, and the device can be downsized.
In addition to reducing product cost and injecting and supplying relatively high-pressure CNG fuel from the vicinity of the combustion chamber,
It is possible to improve control accuracy and control responsiveness during G fuel supply control. Moreover, since a small amount of gasoline is supplied to improve the lubricity of the fuel injection valve 15 during the CNG fuel supply control, the durability of the fuel injection valve 15 can be improved. Further, since the fuel injection valve 15 provided relatively near the combustion chamber bears a part of the fuel injection amount, it is possible to suppress the decrease in the filling efficiency due to the diffusion of the gas fuel, The output can be improved, the usable range of CNG fuel can be expanded, and the fuel cost can be reduced.

Then, when the CNG fuel supply control and the gasoline fuel supply control are switched, the air-fuel ratio difference caused by the difference in the fuel characteristics is corrected so as to be absorbed, so that a good air-fuel ratio control can be performed and harmful Emissions of exhaust components can be suppressed, fuel consumption can be improved, and vehicle drivability can be improved. If the fuel supply amount of the duty control valve 48a is to be borne by the fuel injection valve 15, the duty control valve 48a can be omitted, and the size and simplification of the device can be significantly reduced. it can.

Next, the second embodiment will be described. In the second embodiment, as shown in FIG. 5, in the configuration of the first embodiment, the mixer 48 is removed and the CNG is used instead.
A CNG fuel injection valve 51 for injecting and supplying fuel is provided and configured. Then, the pressure reducing valve of the two-stage configuration in which the third stage (that is, 0.3 kg / cm ² ) of the pressure reducing valve 46 in the first embodiment is removed.
It has been changed to 52. Since the other configurations are the same as those in the first embodiment, detailed description will be omitted.

Therefore, the second embodiment is different from the first embodiment in the CNG fuel supply control in the mixer 48.
CNG is not mixed with the intake air, but is directly supplied into the intake passage 12 by the CNG fuel injection valve 51. According to the present embodiment, as in the first embodiment, the fuel injection valve 15 of the gasoline fuel supply device is also used during CNG fuel supply control, so the capacity of the CNG fuel injection valve 51 is set small. It is possible to reduce the size of the device and reduce the product cost, and it is possible to improve the control accuracy and control responsiveness during CNG fuel supply control. Also, C
Since a small amount of gasoline is supplied to improve the lubricity of the fuel injection valve 15 during the NG fuel supply control, the durability of the fuel injection valve 15 can be improved. Further, since the fuel injection valve 15 provided relatively near the combustion chamber bears a part of the fuel injection amount, it is possible to suppress the decrease in the filling efficiency due to the diffusion of the gas fuel, The output can be improved, the usable range of CNG fuel can be expanded, and the fuel cost can be reduced. Moreover,
When switching between CNG fuel supply control and gasoline fuel supply control, the air-fuel ratio difference caused by the difference in the fuel characteristics is corrected so as to be absorbed, so that good air-fuel ratio control can be performed and emission of harmful exhaust components can be suppressed. In addition, it is possible to improve fuel efficiency and, in turn, vehicle drivability.

Further, as compared with the first embodiment, by removing the mixer 48, the structure can be simplified, the product cost can be further reduced, and the intake resistance is increased by the intake throttle by the mixer 48. As a result, it is possible to further improve the filling efficiency, reduce the emission amount of harmful exhaust components, increase the output, improve the fuel consumption, and so on. It should be noted that the mixer 48 or the CNG fuel injection valve 51 in each of the above-described embodiments can be eliminated, that is, only the fuel injection valve 15 can be used.
It is also possible to switch between G fuel and gasoline fuel for injection and supply. In this case, since the fuel supply system can be completely standardized, the number of parts can be significantly reduced, so that the product cost can be reduced, and at the same time, the rate of occurrence of part failure or the like can be reduced. Therefore, the reliability of the fuel supply device can be improved.

In the first and second embodiments, the fuel injection valve 15 is provided for each intake port, but it is of course not limited to the fuel injection valve 15 provided for each cylinder.

[0054]

As described above, according to the present invention,
Since the gas fuel supply device and the liquid fuel supply device inject and supply the respective fuels through at least the common fuel injection valve, the device can be downsized and the product cost can be reduced. The control accuracy and control response can be improved with the downsizing of the gas fuel supply device.

If the fuel injection valve lubricating means is provided so that a small amount of liquid fuel for lubrication is supplied to the shared fuel injection valve even when the gas fuel is supplied, the shared fuel injection valve Sticks and scuffs can be prevented, and the durability of the shared fuel injection valve can be improved. Further, if the residual fuel amount estimating means and the switched fuel supply amount correcting means are provided to correct the difference in air-fuel ratio when switching between the gas fuel supply control and the gasoline fuel supply control. In addition, good air-fuel ratio control can be performed at the time of fuel switching, emission of harmful exhaust components can be suppressed, fuel consumption can be improved, and vehicle drivability can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration according to claim 1 of the present invention.

FIG. 2 is a block diagram showing a configuration according to claim 2 of the present invention.

FIG. 3 is an overall configuration diagram according to a first embodiment of the present invention.

FIG. 4 is a flowchart according to the first embodiment of the present invention.

FIG. 5 is an overall configuration diagram according to a second embodiment of the present invention.

FIG. 6 is a diagram showing an example of a fuel switching condition according to the present invention.

[Explanation of symbols]

 11 Engine 12 Intake passage 13 Air flow meter 15 Fuel injection valve 16 Fuel tank 17 Fuel pump 19 First three-way solenoid valve 20 Fuel gallery 21 Second three-way solenoid valve 24 Return valve 25 Bypass passage 26 Dripper pump 30 Throttle sensor 31 Crank angle sensor 41 CNG fuel supply device 42 CNG fuel tank 43 Shut valve 47 First CNG fuel supply passage 48 Mixer 49 Second CNG fuel supply passage 50 Control unit 51 Gas fuel injection valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area F02M 61/16 U 9248-3G

Claims (11)

[Claims] 1. A gas fuel supply system for supplying a gas fuel, a liquid fuel supply system for supplying a liquid fuel, and a fuel switching means for switching the operation of the two fuel supply systems to switch the fuel type to be supplied. In the fuel supply apparatus for an internal combustion engine, the gas fuel supply system and the liquid fuel supply system are configured to include a shared fuel injection valve, and different types of fuel are switched from the shared fuel injection valve. A fuel supply control device for an internal combustion engine, characterized by performing injection supply. 2. A gas fuel supply passage upstream of the shared fuel injection valve, the gas fuel supply passage selectively communicating with the shared fuel injection valve according to the supply fuel by the fuel switching means.
2. The fuel supply control device for an internal combustion engine according to claim 1, wherein the liquid fuel supply passage is switched to. 3. A fuel injection valve lubricating means for mixing liquid fuel into the gas fuel for lubricating the shared fuel injection valve when the gas fuel is injected and supplied to the internal combustion engine through the shared fuel injection valve. 3. The fuel supply control device for an internal combustion engine according to claim 1, wherein the fuel supply control device is configured as follows. 4. The internal combustion engine according to claim 3, wherein the fuel injection valve lubricating means includes a lubricating fuel supply pump for discharging and mixing the lubricating liquid fuel into the gas fuel. Engine fuel supply control device. 5. A liquid fuel supply passage for feeding the liquid fuel discharged from a liquid fuel supply pump by the fuel injection valve lubrication means, and a shared fuel injection valve upstream in which the fuel supplied by the fuel switching means is switched. The bypass passage connecting the fuel supply passage on the side, the lubrication fuel supply pump interposed in the bypass passage, and the fuel supply passage between the liquid fuel supply pump and the lubrication fuel supply pump for lubrication. A liquid fuel return passage for lubrication for returning excess liquid fuel not used to the liquid fuel supply source; and an on-off valve for opening / closing the liquid fuel return passage for lubrication. The fuel supply pump is operated, the lubrication fuel supply pump is operated, and the on-off valve is opened. Fuel supply control system of the engine. 6. The gas fuel supply system comprises a mixer for mixing the gas fuel with the intake air on the upstream side of the intake throttle valve.
2. A fuel supply control device for an internal combustion engine according to any one of 1. 7. The gas fuel supply system includes a gas fuel injection valve for injecting and supplying the gas fuel to an engine intake system, according to any one of claims 1 to 6.
5. A fuel supply control device for an internal combustion engine according to claim 3. 8. An operating state detecting means for detecting an operating state of the engine is included, and the fuel switching means switches the fuel supplied to the internal combustion engine to a gas fuel or a liquid fuel according to the engine operating state. The fuel supply control device for an internal combustion engine according to any one of claims 1 to 7. 9. A fuel supply system for the shared fuel injection valve is provided with a mechanism for adjusting a fuel supply pressure while returning a part of the supplied fuel to a fuel supply source. The fuel supply control device for an internal combustion engine according to any one of claims 1 to 8. 10. A residual fuel amount estimating means for estimating a residual amount of fuel before switching, which remains in the fuel supply system after switching the supplied fuel and continues to be sucked into the engine for a predetermined time after switching, and the residual fuel amount estimating means. The fuel supply amount after switching, which corrects the amount of fuel supplied from the fuel supply device after switching, based on the residual fuel amount estimated by Item 9
2. A fuel supply control device for an internal combustion engine according to any one of 1. 11. The residual fuel amount estimation means estimates the residual amount of the fuel based on a fuel supply delay time constant corresponding to the supply amount of the supply fuel before the switching immediately before the switching, and the residual fuel supply amount after the switching. When the correction means calculates the supply amount of the fuel supplied after the switching, the switching is performed based on the residual amount of the supply fuel before switching based on the time constant and the fuel supply delay time constant of the supplied fuel after switching. The fuel supply control device for an internal combustion engine according to claim 10, wherein the supply amount of the post-supply fuel is corrected.