JP2003120352A - Fuel switching method and device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a shock in traveling felt at fuel switching in a fuel switching method and device for switching two types of fuel over to supply either to an engine. SOLUTION: The fuel switching device has a fuel switching switch 24, a deceleration detecting mechanism 23 for detecting vehicle deceleration and fuel switching mechanisms 14 and 19 for switching over fuel. The fuel switching mechanisms 14 and 19 switch over fuel after the fuel switching switch 24 is operated for switching and when the deceleration detecting mechanism 23 detects vehicle deceleration. The fuel switching is desirably made when the engine is approximately at 1,500 rpm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel switching method and apparatus for selectively switching two types of fuel to supply them to an engine.

[0002]

2. Description of the Related Art Conventionally, as a fuel switching method for selectively switching between a gas fuel such as LPG (liquefied natural gas) and CNG (compressed natural gas) and a liquid fuel such as gasoline and supplying the fuel to a combustion chamber of an internal combustion engine. For example, when the fuel is switched, the fuel remaining in the fuel supply path is completely used up, and then another fuel to be switched and used is supplied (for example, JP-A-57-59048). ), Or a method of controlling increase / decrease of supply of any of the fuels in response to acceleration / deceleration of the vehicle at the time of fuel switching (for example, JP-A-63-230933).

[0003]

In any of the above-mentioned prior arts, the fuel switching timing is determined based on the will of the driver without being specified without considering the running state of the vehicle. ing. Therefore, if a fuel switching operation is performed during stable traveling, traveling shock may be caused by overrich or over lean due to fuel switching.

Particularly, in the former conventional technique,
Since the fuel in use is completely consumed from the fuel supply path and then switched to another fuel, a gas shortage state temporarily occurs and the shock of traveling becomes large.

Therefore, in the present invention, the changeover switch is operated to the fuel side which can be changed in advance, and when the vehicle decelerates after this changeover operation, the fuel is automatically changed over. Mix the shock of running with the shock of running that occurs during deceleration,
The purpose is to prevent the driver and passengers from feeling the shock of traveling due to fuel switching.

[0006]

In order to solve the above-mentioned problems, a first invention according to claim 1 is a fuel switching method for an engine, in which two kinds of fuel are switched and supplied to the engine. After switching the
When the vehicle is decelerated, the fuel is switched during the deceleration of the vehicle.

According to a second aspect of the present invention, in a fuel switching method of an engine for switching between two types of fuel to supply to the engine, the throttle valve is fully closed after the fuel switching switch is switched. The fuel switching method for an engine is characterized in that the fuel is switched during deceleration of the vehicle in the above state.

According to a third aspect of the present invention, in the first or second aspect of the invention, the engine speed is about 1500.
A fuel switching method for an engine, in which fuel switching is performed during deceleration of a vehicle in a region of rpm or higher.

According to a fourth aspect of the present invention, which is an apparatus for achieving the first aspect of the present invention, there is provided a fuel switching device for an engine for switching between two types of fuel and supplying the fuel to the engine. It has a deceleration detection mechanism for detecting deceleration of the vehicle and a fuel switching mechanism for switching fuel,
A fuel switching device for an engine, characterized in that, after the fuel switching switch has been switched, when the deceleration detection mechanism detects deceleration of the vehicle, the fuel switching mechanism switches the fuel.

A fifth aspect of the present invention is an apparatus for accomplishing the second aspect of the invention, wherein in the fourth aspect of the invention, the speed reduction mechanism determines that the speed is reduced when the throttle valve is fully closed. Is a fuel switching device for an engine configured as described above.

A sixth aspect of the present invention is an apparatus for accomplishing the third aspect of the invention, wherein in the fourth or fifth aspect of the invention, means for detecting the number of revolutions of the engine is provided, and This is a fuel switching device for an engine, in which the fuel switching is performed in a region where the number is about 1500 rpm or more.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described based on the embodiments shown in FIGS.

FIG. 1 is a block diagram of the entire system showing an embodiment of the present invention. An engine body 1 which is an internal combustion engine is provided with an intake manifold 4 which communicates with a combustion chamber 3 through an intake valve 2 thereof. The upstream side of the intake manifold 4 communicates with an air cleaner 6 via an intake passage 4a and a throttle valve 5.

An intake pressure sensor 7 for detecting the intake pressure in the intake passage 4a is provided in the intake passage 4a downstream of the throttle valve 5, and an engine control circuit based on the pressure detected by the intake pressure sensor 7 is provided. An intake pressure change amount within a predetermined time is calculated by an (ECU) 8 to determine whether or not the intake pressure change amount is larger than a set value. That is, a predetermined time (for example, 0.5 seconds)
When the intake pressure change exceeds a predetermined value, it is determined that the vehicle has been decelerated. The intake pressure sensor 7 and the ECU 8 constitute a deceleration detection mechanism.

A liquid fuel pump 10 is provided in a liquid fuel tank 9 which stores liquid fuel such as gasoline.
The liquid fuel supply path 1 is driven by driving the liquid fuel pump 10.
The liquid fuel to 1 is supplied under pressure. The downstream side of the liquid fuel supply path 11 communicates with a fuel supply unit 13 that supplies fuel to an injector (fuel injector) 12.

One injector 12 is provided in the intake manifold 4 and injects the high-pressure fuel in the fuel supply section 13 into the intake manifold 4 as is well known. The injector 12 is controlled to be opened and closed by the ECU 8. Has become.

A liquid fuel cutoff valve 14 for opening and closing the liquid fuel supply passage 11 is provided near the upstream side of the fuel supply portion 13 in the liquid fuel supply passage 11. The opening and closing of the liquid fuel cutoff valve 14 is controlled by the ECU 8, and these constitute a fuel switching mechanism.

A first fuel pressure sensor 15 for detecting the fuel pressure (fuel pressure) in the liquid fuel supply passage 11 is provided in the liquid fuel supply passage 11 upstream of the liquid fuel cutoff valve 14. The signal of the first fuel pressure sensor 15 is transmitted to the ECU 8.

A gas fuel pump 17 is provided in a gas fuel tank 16 which stores a gas fuel such as LPG or CNG, and the gas fuel pump 17 is driven to supply the gas fuel under pressure to a gas fuel supply passage 18. It has become so.
The downstream side of the gas fuel supply path 18 communicates with the fuel supply section 13.

A gas fuel cutoff valve 19 for opening and closing the gas fuel supply passage 18 is provided near the upstream side of the fuel supply portion 13 in the gas fuel supply passage 18. The opening and closing of the gas fuel cutoff valve 19 is controlled by the ECU 8,
This constitutes a fuel switching mechanism.

A second fuel pressure sensor 20 for detecting the fuel pressure (fuel pressure) in the gas fuel supply passage 18 is provided in the gas fuel supply passage 18 upstream of the gas fuel cutoff valve 19. The signal of the second fuel pressure sensor 20 is transmitted to the ECU 8.

The fuel supply unit 13 includes the fuel supply unit 1
A third fuel pressure sensor 21 for detecting the pressure of the fuel inside the fuel cell 3.
And a fuel temperature sensor 22 for detecting the temperature of the fuel in the fuel supply unit 13, and the respective signals are sent to the ECU.
It will be sent to 8th.

A well-known throttle sensor 23 for detecting the opening degree of the throttle valve 5 is provided on the throttle shaft portion of the throttle valve 5, and a signal of the throttle sensor 23 is transmitted to the ECU 8. There is. The throttle sensor 23 and the ECU 8 constitute a deceleration detection mechanism.

At the driver's seat, a manual fuel changeover switch 24 for switching between gas fuel and liquid fuel is provided, and a signal for this switching is transmitted to the ECU 8 to judge the switching.

Further, the ECU 8 is provided with a timer circuit, which measures the time from the switching operation of the fuel changeover switch 24, and when the fuel changeover condition is not satisfied within a set time, for example, 1 minute, the fuel is changed. It is designed to stop switching.

As is well known, the throttle valve 5 is connected to an accelerator pedal (not shown) via its throttle shaft or the like, and therefore, an accelerator switch (which detects whether or not the accelerator pedal is depressed). (Not shown) is provided so that the accelerator switch is turned on when the accelerator pedal is not depressed, that is, when the throttle valve 5 is fully closed.
A deceleration detection mechanism may be configured together therewith.

Although not shown, well-known engine speed detecting means is provided, and fuel switching is also performed when the engine speed during deceleration is judged to be a predetermined value or more based on the engine speed detecting means. To control.

Next, the switching control of these fuels when LPG is used as the gaseous fuel and gasoline is used as the liquid fuel in the above configuration will be described.

First, the case where the vehicle is traveling with the engine driven by LPG fuel and the vehicle is switched to traveling with gasoline fuel will be described with reference to the flow chart shown in FIG.

First, the driver manually switches the fuel selector switch 24 from the LPG fuel side to the gasoline fuel side (step 101).

When the fuel selector switch 24 is switched, the timer circuit in the ECU 8 is cleared to zero (step 102) and then the time measurement is started (step 103), and the vehicle is decelerated under predetermined conditions. The ECU 8 determines whether or not (step 104).

This determination method is performed when the throttle sensor 23 and the ECU 8 determine that the throttle valve 5 is fully closed (low intake air region), that is, when the normal fuel supply due to the intake air is cut off, or , When the accelerator pedal is depressed and the accelerator pedal is turned on, that is, when the normal fuel supply due to the intake air is cut off, it is determined that the vehicle has been decelerated. In addition, the intake pressure sensor 7 and the ECU 8 may determine that the intake pipe internal pressure in the downstream portion of the throttle valve 5 has been decelerated when the pressure in the intake pipe changes more than a set value for a predetermined time, for example, 0.5 seconds. Good.
Alternatively, it may be determined that the vehicle has been decelerated by the above and or.

Then, as described above, when it is determined that the fuel supply is cut (F / C) and decelerated, it is determined that the fuel switching condition is satisfied, and the process proceeds to the next step.

It is desirable that the fuel is switched at an engine speed of about 1500 rpm or more in order to reduce the traveling shock caused by the fuel switching. Therefore, the engine speed is about 1 when the engine speed detection means is used.
It is desirable to move to the next step assuming that the fuel switching condition is satisfied when the deceleration (fuel cut) signal is input during traveling at 500 rpm or more.

After the fuel changeover switch 24 is changed over, the time is measured by the timer circuit while the fuel changeover condition is not satisfied, that is, while the predetermined deceleration is not performed (step 105). Then, the set time (for example, 1
Wait for the input of fuel switching conditions until (minutes) has not elapsed. After the fuel changeover switch 24 is changed over, if the fuel changeover condition is not satisfied for the set time or more, the fuel changeover switch 24 is returned to the LPG side (step 10).
6) The operation ends without performing the fuel switching operation, and the vehicle runs with the LPG fuel as it is.

When the fuel switching condition is satisfied within the set time, the LPG fuel pump 17 is stopped (step 107) and the LPG shutoff valve 19 is closed (step 108).

Thereafter, the transmission of a signal for increasing the opening time (τ) in the opening / closing operation of the injector 12 is started (step 109), and the gas fuel supply passage 18 and the fuel supply portion 13 downstream of the shutoff valve 19 are started. , LPG fuel remaining in the injector 12 is promptly consumed. afterwards,
Driving the fuel pump 10 for gasoline (step 11)
0).

After the fuel pump 10 is driven, it is judged by the first fuel pressure sensor 15 and the ECU 8 whether or not the gasoline fuel has been boosted to a predetermined fuel pressure capable of being favorably injected from the injector 12, for example, 0.3 MPa or more. (Step 111). If the fuel pressure has not increased above a predetermined fuel pressure, the pressure increase is awaited. When the fuel pressure is increased to a predetermined value or more, the τ amplification signal to the injector 12 is stopped (step 112), the cutoff valve 14 for gasoline is opened (step 113), and gasoline fuel is injected from the injector 12. Run by jetting.

As described above, if the fuel changeover switch 24 is switched to the gasoline fuel side while the vehicle is running on the LPG fuel, the vehicle is automatically switched to the gasoline fuel when the vehicle is in a predetermined deceleration state, and thereafter. Is driven by gasoline fuel.

FIG. 4 is a diagram for explaining an example of fuel switching, in which the opening of the throttle valve, the engine speed,
A timing chart shows the relationship with the fuel switching timing.

In FIG. 4, it is assumed that the driver switches the fuel changeover switch 24 to the gasoline fuel side in a state where the LPG fuel is used, the opening of the throttle valve 5 is 20 deg, and the engine speed is 2000 rpm. Then, since the vehicle is not in the decelerated state at the time of the switching (point A in FIG. 4), the fuel is not immediately switched.

After that, when the driver releases the accelerator pedal and the throttle valve 5 is fully closed (point B in FIG. 4), it is judged that the vehicle is decelerated by signals from the accelerator switch or throttle sensor 23 and the intake pressure sensor 7. The operation after step 107 in the flowchart of FIG. 2 is performed. Therefore, in the deceleration region where the throttle valve 5 is fully closed, and within the region where the engine speed is 1500 rpm or more and which is indicated by the diagonal lines in FIG. 4, the LPG fuel is switched to the gasoline fuel at the position indicated by the point C in FIG.
After that, the vehicle runs on gasoline fuel.

In the setting of FIG. 4, fuel switching is not performed even when the above deceleration signal is input when the engine speed is 1500 rpm or less. But,
This fuel switching is not limited to when the engine is rotating at 1500 rpm or more, but is set within a range of a desired rotation speed.

Next, with reference to the flow chart shown in FIG. 3, a description will be given of a case where the vehicle is running with the engine driven by gasoline fuel and the running mode is switched to LPG fuel.

First, the driver manually switches the fuel selector switch 24 from the gasoline fuel side to the LPG fuel side (step 201).

When the fuel changeover switch 24 is changed over, the timer circuit in the ECU 8 is cleared to zero (step 202) and then the time measurement is started (step 203) and the process proceeds to step 204 and LP is started.
It is determined whether the engine can be driven even if the G fuel is injected from the injector 12, that is, whether the condition for switching to the LPG fuel is satisfied.

To satisfy the conditions for switching to the LPG fuel, for example, the engine cooling water temperature is 10 ° C. or higher, 2 minutes or more after the engine is started, and the LPG fuel pressure is 0.6 MPa or higher. LPG tank internal combustion temperature 0 ℃
At the above time, it is assumed that the condition for switching to LPG fuel is satisfied.

When the above-mentioned switching condition is not satisfied, the fuel changeover switch 24 is returned to the original state, that is, to the gasoline side (step 205), and the process ends.

When the switching condition is satisfied, the routine proceeds to step 206. This step 206 determines whether or not the vehicle has decelerated under a predetermined condition, and the determination method is the same as step 104 when the fuel is switched from LPG to gasoline. That is, similarly to the above, the throttle sensor 23, the accelerator pedal, and the intake pressure sensor 7 determine whether or not the fuel switching condition is satisfied. Further, similarly to the above, the engine speed may be taken into consideration.

After the fuel changeover switch 24 is changed over, the time is measured by the timer circuit while the same fuel changeover condition as described above is not satisfied (step 207). Then, while the set time (for example, 1 minute) has not elapsed, the input of fuel switching conditions is waited for. After the fuel changeover switch 24 is changed over, if the fuel changeover condition is not satisfied for the set time or more, the fuel changeover switch 24 is returned to the gasoline fuel side (step 208) and the operation is ended without performing the fuel changeover operation. Then, run on gasoline fuel.

When the fuel switching condition is satisfied within the set time, the fuel pump 10 for gasoline is stopped (step 209) and the shutoff valve 14 for gasoline is closed (step 210).

After that, the transmission of a signal for amplifying the opening time (τ) in the opening / closing operation of the injector 12 is started (step 211), and the fuel supply passage 11 in the gasoline fuel supply passage 11 downstream from the cutoff valve 14 for gasoline is started. The gasoline fuel remaining in the injector 13 and the injector 12 is promptly consumed.

After that, the fuel pump 17 for the LPG is driven (step 212).

After driving the fuel pump 17, it is confirmed by the second fuel pressure sensor 20 and the ECU 8 whether or not the LPG is maintained at a predetermined fuel pressure capable of being favorably injected from the injector 12, for example, 0.6 MPa or more ( Step 213). If the fuel pressure has not reached the predetermined value, the process waits until the fuel pressure is increased to the predetermined value. Then, when the fuel pressure is increased to a predetermined value or more, the τ amplification signal to the injector 12 is stopped (step 214), the shutoff valve 19 for LPG is opened (step 215), and the LPG fuel is used. To run.

As described above, if the fuel changeover switch 24 is switched to the LPG fuel side while the vehicle is running on gasoline fuel, it is automatically switched to LPG fuel when the vehicle enters a predetermined deceleration state, and thereafter. It is run on LPG fuel.

Since the state of switching from the gasoline fuel to the LPG fuel is similar to the state shown in FIG. 4, the gasoline and LPG in the case of the flow chart of FIG.
The state of supply and shut-off of is shown in parentheses in FIG.

[0057]

As described above, according to the present invention, the fuel is switched during deceleration of the vehicle when the vehicle is decelerated after switching the fuel changeover switch. Therefore, the shock of traveling due to fuel switching can be mixed into the shock of traveling due to deceleration of the vehicle, and there is an effect that the driver and passengers do not feel the shock due to fuel switching.

Further, by setting the fuel switching timing at the time of deceleration when the engine speed is about 1500 rpm or more, further shock is not felt.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an entire system showing an embodiment of the present invention.

FIG. 2 is a flow chart showing an embodiment when switching from LPG fuel to gasoline fuel in the present invention.

FIG. 3 is a flow chart showing an embodiment when switching from gasoline fuel to LPG fuel in the present invention.

FIG. 4 shows an example of fuel switching in the present invention, where (a) is a throttle valve opening, (b) is an engine speed and a deceleration region for switching fuel, and (c) is a fuel supply state. FIG.

[Explanation of symbols]

1 engine 5 Throttle valve 8 ECU 9 Liquid fuel tank 11 Liquid fuel supply channel 12 injectors 16 Gas fuel tank 18 Gas fuel supply path 14, 19 Shut-off valve that constitutes fuel switching mechanism 23 Throttle sensor that constitutes deceleration detection mechanism 24 Fuel changeover switch

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3G092 AA01 AA05 AB02 AB07 AB08                       DE01Y DE09Y DE10Y DF09                       DG09 EA11 EB05 FA04 GA13                       GB08 HA05Z HA06Z HB03Z                       HB04Z HE01Z HF00Z HF08Z                 3G301 HA01 HA22 HA24 JA04 KA16                       LB02 LB07 LC01 NA08 NB03                       NB13 NE23 PA07Z PA11Z                       PB00Z PB01Z PB08Z PE01Z                       PF00Z PF03Z

Claims (6)

[Claims] 1. A fuel switching method for an engine that switches between two types of fuel and supplies the fuel to the engine, and when the vehicle is decelerated after the fuel switching switch is switched, the fuel is switched during deceleration. A fuel switching method for an engine, characterized in that: 2. A fuel switching method for an engine that switches between two types of fuel and supplies the fuel to the engine, after the fuel switching switch has been switched, and during deceleration of the vehicle with the throttle valve fully closed. A fuel switching method for an engine, characterized in that the fuel is switched. 3. A fuel switching method for an engine according to claim 1, wherein the fuel switching is performed during deceleration of the vehicle in a region where the engine speed is about 1500 rpm or more. 4. An engine fuel switching device for switching between two types of fuel and supplying the engine with a fuel switching switch, a deceleration detection mechanism for detecting deceleration of a vehicle, and a fuel switching mechanism for switching fuel. A fuel switching device for an engine, characterized in that the fuel is switched by the fuel switching mechanism when the deceleration detecting mechanism detects deceleration of the vehicle after the fuel switching switch is switched. 5. The fuel switching device for an engine according to claim 4, wherein the deceleration mechanism is configured to determine deceleration when the throttle valve is fully closed. 6. A fuel switching device for an engine according to claim 4, wherein means for detecting the engine speed is provided, and the fuel is switched in a region where the engine speed is about 1500 rpm or more.