JP2007162632A - Evaporated fuel control device of dual-fuel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress increase of torque when an evaporated fuel is purged while a gas fuel is supplied. <P>SOLUTION: This evaporated fuel control device of a dual-fuel engine operated on at least one of a gas fuel and a liquid fuel comprises air-fuel ratio control means 70, 74 changing the air-fuel ratio of the gas fuel fed into the engine between the state in which the air-fuel ratio is set leaner than the theoretical air-fuel ratio thereof and the state in which it is set equal to or richer than the theoretical air-fuel ratio at least during the operation on the gas fuel and evaporated fuel feed means 67, 70 feeding the evaporated fuel at the timing of feeding the evaporated fuel produced in a liquid fuel tank 63 and in the state in which the air fuel ratio is set leaner. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a purge control technique for evaporated fuel of a dual fuel engine operated with at least one of gaseous fuel and liquid fuel.

Conventionally, an engine that can be operated with gasoline in an emergency while being operated with gas fuel has been proposed. For example, Patent Document 1 discloses gas fuel (CNG) and liquid fuel (gasoline). In a bi-fuel engine to be switched and supplied, if the canister trap amount exceeds the predetermined value and the conditions to be purged when the gaseous fuel is supplied are satisfied, purge is performed after switching to the liquid fuel supply, causing deterioration in emission performance or knocking. Those that avoid occurrence are described.
JP 2005-220802 A

  In the above-mentioned Patent Document 1, switching to liquid fuel is performed every time purge is executed, but the output characteristics of the engine are greatly different between gaseous fuel and liquid fuel, so the driver feels uncomfortable with torque fluctuations at the time of fuel switching. Further, since the air-fuel ratio becomes rich at the time of purging, there is a problem that the torque suddenly fluctuates in the increasing direction and a torque shock occurs.

  This invention is made | formed in view of the above-mentioned subject, The objective is to implement | achieve the technique which can suppress the torque increase when purging evaporative fuel during gaseous fuel supply.

  In order to solve the above-described problems and achieve the object, a first aspect of the present invention is an evaporative fuel control device for a dual fuel engine operated with at least one of a gaseous fuel and a liquid fuel. An air-fuel ratio control means for switching between a state in which the air-fuel ratio of the gaseous fuel supplied to the engine is leaner than the stoichiometric air-fuel ratio and a state in which the stoichiometric air-fuel ratio or richer is set during operation at And evaporative fuel supply means for supplying the evaporative fuel in a state where the evaporative fuel generated in the liquid fuel tank is supplied and the air-fuel ratio is set to lean.

  According to this aspect, when the air-fuel ratio is lean, the amount of air is large, and the air-fuel ratio is kept lean even when the evaporated fuel is supplied. Therefore, the amount of increase in torque generated by purging the evaporated fuel is also reduced. Further, it is possible to suppress an increase in torque when the evaporated fuel is purged during the gaseous fuel supply.

  Further, in the second embodiment, further provided is a throttle opening control means for increasing the throttle opening when the air-fuel ratio is lean, and the throttle opening control means is synchronized with the timing of supplying the evaporated fuel. To control the throttle opening in the closing direction. According to this embodiment, the throttle opening is increased to increase the amount of air, and the throttle opening is controlled in the closing direction in synchronization with the timing of supplying the evaporated fuel. It can be corrected by the throttle opening.

  Further, in the third embodiment, the timing for supplying the evaporated fuel is when the trap amount of the canister for trapping the evaporated fuel exceeds an allowable amount or periodically. According to this aspect, it is possible to prevent the evaporated fuel trapped by the canister from exceeding an allowable amount and to leak the evaporated fuel from the canister during the gaseous fuel supply.

  In the fourth embodiment, the gaseous fuel is hydrogen gas, and the liquid fuel is gasoline. According to this aspect, in a dual fuel engine operated by hydrogen and gasoline, it is possible to suppress an increase in torque when the gasoline fuel trapped by the canister is purged during supply of hydrogen fuel.

  According to the present invention, it is possible to suppress an increase in torque when purging evaporative fuel while supplying gaseous fuel.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  The embodiment described below is an example as means for realizing the present invention, and the present invention can be applied to a modified or modified embodiment described below without departing from the spirit of the present invention.

[Engine configuration]
FIG. 1 is a cross-sectional view schematically showing a dual fuel engine according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of the dual fuel engine according to the present embodiment and its periphery.

  1 and 2, the dual-uel engine of the present embodiment is realized by a rotary engine that is operated by being supplied with at least one of hydrogen as a gaseous fuel and gasoline as a liquid fuel.

  The rotary engine 1 includes a rotor housing 2 having a trochoidal inner peripheral surface and side housings 4 having planar inner surfaces arranged on both sides thereof. The rotary engine 1 constitutes a so-called two-rotor rotary engine in which the rotor 6 is disposed in each of two spaces defined by the three side housings 4 and the rotor housing 2.

  Each rotor 6 is supported by an eccentric shaft (eccentric shaft) 8 and is configured to rotate eccentrically with the eccentric shaft 8. Around the rotor 6, working chambers 10, 11, 12 surrounded by the housings 2, 4 and the rotor 6 are formed. The volume of each working chamber 10, 11, 12 changes due to the eccentric rotation of the rotor 6. The eccentric shaft 8 is rotated by rotation of the rotor 6 through a series of intake, compression, expansion, and exhaust strokes in the working chambers 10, 11, and 12, and the rotational force is not shown in the figure as power from the eccentric shaft 8. Is output to the drive shaft.

  In the following description, it is assumed that the configurations of the two rotors on the downstream side of the throttle valve are the same.

  Two spark plugs 14 and 15 are attached to each rotor housing 2 in which the two rotors 6 are arranged. An intake port 16 and an exhaust port 18 are formed in the side housing 4. An intake passage 20 is connected to the intake port 16, and air is introduced into the working chamber 10 through the intake passage 20. Further, an exhaust port 22 is connected to the exhaust port 18, and exhaust gas in the working chamber 12 is exhausted through the exhaust passage 22. Such a configuration is substantially the same for each rotor 6.

  The rotor 6 rotates clockwise in FIG. 1, and in the illustrated state, the compression stroke is performed in the working chamber 10 and the expansion stroke is performed in the working chamber 11.

  The two spark plugs 14, 15 are arranged in series with respect to the rotation direction of the rotor 6, that is, aligned in the vertical direction, and the rotor housing 2 has a plug hole for each of the spark plugs 14, 15. 14a and 15a are formed.

  The arrangement and size of the spark plugs 14 and 15 and the plug holes 14a and 15a are determined so as to reduce gas blow-through when the apex seal 7 of the rotor 6 passes through the plug holes 14a and 15a. That is, when the apex seal 7 passes the spark plug 14 on the rear side (trailing side) with respect to the rotation direction of the rotor 6, the working chamber 10 that is in the compression stroke and the operation that is in the expansion stroke. Since the pressure difference with the chamber 11 is large and gas is easily blown out, the spark plug 14 is disposed at a position far from the combustion chamber (working chamber), and the diameter of the plug hole 14a is smaller than that of the plug hole 15a.

  On the other hand, when the apex seal 7 passes through the spark plug 15 on the front side (leading side) with respect to the rotation direction of the rotor 6, the working chamber 10 which is in the compression stroke and the exhaust stroke from the expansion stroke are entered. Since the pressure difference with the working chamber 11 is small, the spark plug 15 is arranged at a position close to the combustion chamber (working chamber), and the diameter of the plug hole 15 a is formed to be equal to the diameter of the spark plug 15.

[Configuration around the engine]
Next, the configuration around the engine will be described.

  As shown in FIG. 2, a throttle valve 24 is disposed upstream of the intake passage 20, and an air cleaner 26 is disposed upstream of the throttle valve 24. Further, an EGR device 30 for returning a part of the exhaust gas in the exhaust passage 22 to the intake passage 20 is provided on the downstream side of the exhaust passage 22. The EGR device 30 includes an EGR passage 32 that connects the exhaust passage 22 and the intake passage 20, an EGR cooler 34 that cools the exhaust gas recirculated into the EGR passage 32 to increase the density, and an EGR that controls the EGR rate. And a valve 36.

  Further, in the vicinity of the intake port 16 on the most downstream side of the intake passage 20, a gasoline injector 61 that supplies gasoline as liquid fuel from the intake port 16 and mixes the mixture with air into the working chamber, and gaseous fuel A port injection type hydrogen gas injector (hereinafter referred to as “port injection type injector”) 40 for supplying an air-fuel mixture, which is injected from the intake port 16 and mixed with air, into the working chamber is mounted.

  The gasoline injector 61 is connected to a gasoline tank 63 via a gasoline supply passage 62A, and gasoline is pumped from the gasoline tank 63 by a gasoline pump 62B. The space in the gasoline tank 63 where no gasoline is stored is connected to the canister 65 via the evaporated fuel passage 64, and the gasoline evaporated in the tank 63 is introduced to the canister 65 via the evaporated fuel passage 64. Then, it is adsorbed by the canister 65 and trapped. The canister 65 has an air intake port 65a at the bottom thereof and is made of a breathable member filled with activated carbon or the like. Inside the gasoline tank 63, a sensor for detecting the remaining amount of gasoline stored in the tank 63 and a sensor for detecting the temperature of the tank 63 are provided.

  The canister 65 is connected to the intake passage 20 on the downstream side of the throttle valve 24 via a purge passage 66, and a purge control valve 67 is disposed in the middle of the purge passage 66. The opening / closing operation of the purge control valve 67 is electromagnetically controlled, and the evaporated fuel trapped in the canister 65 is supplied (purged) to the intake passage 20 when the valve is opened (that is, when ON).

  Further, each of the rotor housings 2 is provided with a direct injection hydrogen gas injector (hereinafter referred to as “direct injection injector”) 42 that directly injects hydrogen gas as gaseous fuel into the working chamber 10. The port injection type and direct injection type injectors 40 and 42 are connected to a hydrogen high-pressure gas tank 52 through a hydrogen gas supply passage 50 branched in the middle, and hydrogen gas is supplied from the hydrogen high-pressure gas tank 52 as gaseous fuel. .

  The discharge port of the hydrogen high-pressure gas tank 52 is provided with a stop valve 54 for controlling the discharge of hydrogen gas from the tank 52 to the hydrogen gas supply passage 50, and the hydrogen gas supply passage 50 downstream of the stop valve 54. Is provided with a shutoff valve 56 for controlling the hydrogen gas supply amount (hydrogen supply pressure) to the injectors 40 and 42. The hydrogen gas supply passage 50 downstream of the shutoff valve 56 is provided with a hydrogen gas pressure sensor 58 that detects the residual pressure in the passage.

  The direct injection injector 42 is attached to the rotor housing 2 at an angle directed toward the ignition plugs 14 and 15 with respect to the working chamber 10. The reason why the direct injection injector 42 is provided is that the fuel is a gas in the port injection injector 40 alone, and the charging efficiency of hydrogen gas from the intake port 16 to the working chamber 10 is deteriorated. In other words, the fuel injection efficiency is increased by directly injecting hydrogen gas into the working chamber 10 in the compression stroke after the intake port 16 is closed by the direct injection injector 42.

  As will be described later, the rotary engine 1 according to the present embodiment basically injects hydrogen gas into the working chamber 10 in the compression stroke to increase the intake charging efficiency. The injection timing starts after the intake stroke is completed and when a predetermined rotor rotation angle is reached (when the rotor 6 is in the position shown in FIG. 1), and ends after the required amount has been injected. The injection amount is adjusted by the opening / closing amount of a solenoid valve (not shown) provided inside each injector 40, 42.

  The injectors 40 and 42 are connected to a control unit (Electronic Control Unit; hereinafter referred to as “ECU”) 70, and the ECU 70 controls the switching of injection, the injection timing, the injection amount, and the like of the injectors 40 and 42.

The rotary engine 1 includes a hydrogen gas pressure detection signal from the hydrogen gas pressure sensor 58, an ignition detection signal from the distributor 71 connected to the spark plugs 14 and 15, and a throttle opening sensor for detecting the opening of the throttle valve 24. 72, a throttle opening detection signal from 72, an intake air amount detection signal from an air flow sensor 73 for detecting the intake air amount in the intake passage 20 upstream of the throttle valve 24, and an oxygen concentration in the exhaust gas in the exhaust passage 22 are detected. The oxygen concentration detection signal from the linear O ₂ sensor 74 and the hydrogen gas flow rate detection signal from the hydrogen gas flow meter 75 for detecting the flow rate of the hydrogen gas flowing through the hydrogen gas supply passage 50 are input.

  The ECU 70 calculates the engine speed from the ignition detection signal, the throttle valve opening from the throttle opening detection signal, the intake air amount from the intake amount detection signal, and the air-fuel ratio (Air / Fuel) from the oxygen concentration detection signal, respectively. The amount of evaporated fuel trap adsorbed by the canister 65 is estimated and calculated, and the ignition plugs 14 and 15 (distributor 71), the throttle valve 24, the port injection and direct injection injectors 40 and 42, and the gasoline injector are calculated based on these calculation results. 61 and the purge control valve 67 are controlled to execute EGR control and air-fuel ratio control (FIGS. 3 and 4), and purge control (FIG. 5) of the evaporated fuel adsorbed by the canister described later.

  Further, the rotary engine 1 is based on an operation of supplying hydrogen gas as fuel, and is switched to operation with gasoline in an emergency such as when the remaining amount of hydrogen gas falls below a predetermined amount.

  That is, when the ECU 70 determines that the remaining amount of hydrogen gas has become a predetermined amount or less based on the hydrogen gas flow rate detection signal from the hydrogen gas flow meter 75, the warning lamp 77 is turned on. Then, the driver who sees the warning lamp 77 operates the mode switch 76 provided on the instrument panel or the like in the passenger compartment to supply gasoline from the hydrogen operation mode in which hydrogen gas is supplied for operation. When the operation mode is switched to the gasoline operation mode to be operated, the ECU 70 inputs an operation signal of the mode changeover switch 76, changes from the hydrogen operation mode to the gasoline operation mode, and executes engine control.

  In place of or in addition to the mode changeover switch 76, the ECU 70 is configured to automatically switch from the gasoline operation mode to the hydrogen operation mode in accordance with the operation state shown in the map of FIG. May be.

  The ECU 70 includes a CPU that performs arithmetic processing using the above detection signals, a ROM that stores a program that executes engine control described later, a RAM that stores arithmetic results, and the like, and a control program stored in the ROM. To realize engine control.

  FIG. 3A is a map showing forms of EGR control and air-fuel ratio control in three torque regions, and FIG. 3B is a diagram showing the relationship between the air-fuel ratio and NOx emission amount.

  In the map of FIG. 3A, in a two-dimensional coordinate system using engine torque and engine speed as parameters, a region 1 (high torque region) and a region 2 (medium) are sequentially arranged from the high torque side to the low torque side. (Torque region) and region 3 (low torque region) are set. In region 1, a target operation mode in which the air-fuel ratio is the stoichiometric air-fuel ratio (λ = 1) is set. In the higher torque region than region 1, the air-fuel ratio is set richer than the stoichiometric air-fuel ratio. In region 2, the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and the air-fuel ratio (for example, λ = 2 or λ = 1 to 2.5) at which the NOx emission amount becomes substantially zero as shown in FIG. ) And an EGR lean combustion mode for performing EGR is set. In region 3, the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and the air-fuel ratio (for example, λ = 2 or λ = 1 to 2.5) at which the NOx emission amount becomes substantially zero as shown in FIG. On the other hand, the non-EGR lean combustion mode in which EGR is not performed is set.

  Note that the map of FIG. 3A is applied to both the hydrogen operation mode and the gasoline operation mode.

  FIG. 4 is an injection control map of the port injection type and direct injection type injectors 40 and 42 based on the engine speed.

  In FIG. 4, basically, from the viewpoint of high output, it is desirable that the hydrogen gas is supplied by 100% hydrogen gas in the compression stroke by the direct injection injector 42, but the engine speed is A (for example, 3000 rpm). If so, so-called pre-ignition, in which the hydrogen gas in the working chamber 10 in the compression stroke is ignited by the high-temperature combustion gas leaking from the adjacent working chamber 11 in the preceding expansion stroke through the plug hole. (Pre-ignition) is likely to occur. In particular, if there is a portion rich in hydrogen gas in the working chamber 10 in a high-load high-rotation region, pre-ignition tends to occur. For this reason, when the engine speed is A, the compression stroke injection is switched to the intake stroke injection to ensure a longer mixing time.

  However, even with the intake stroke injection, when the engine speed exceeds B (for example, about 6000 rpm), the mixing time is still insufficient and pre-ignition occurs and backfire occurs. Therefore, when the engine speed is B or more, hydrogen gas is supplied by a premixing method using both the direct injection injector 42 and the port injection injector 40 by intake stroke injection. In the premixing method, since a long mixing time can be secured, it is difficult for pre-ignition to occur even in a high rotation region. However, if 100% hydrogen gas is supplied in the intake stroke by the premixing method, the output is reduced. Therefore, after 70 to 80% of the total injection amount is partially injected in the intake stroke by the premixing method, the remaining 20 to 30% is controlled to be injected by the direct injection injector 42 in the compression stroke. Thereby, premature ignition in the compression stroke is suppressed and high output is achieved.

[Explanation of control flow]
FIG. 5 is a flowchart showing the purge control of the evaporated fuel according to the present embodiment. FIG. 6 is a time chart showing the operation of the purge control valve and the throttle opening and the torque fluctuation in the purge control of the evaporated fuel according to the present embodiment.

  In FIG. 5, the ECU 70 reads each detection signal from each sensor 58, 71 to 75, reads the engine speed from the ignition detection signal, the throttle valve opening from the throttle opening detection signal, the intake air amount from the intake amount detection signal, oxygen The air-fuel ratio is calculated from the concentration detection signal, and the fuel vapor trap amount adsorbed by the canister 65 is estimated and calculated (S11). In addition, an operation signal for the mode switch 76 is input.

  Next, the ECU 70 determines whether a condition for executing the hydrogen operation mode is satisfied (S13). Here, when the operation signal input from the mode switch 76 is in the hydrogen operation mode, it is determined that the condition for executing the hydrogen operation mode is satisfied. In the case where the ECU 70 automatically switches between the hydrogen operation mode, the gasoline operation mode, or the dual fuel operation mode in accordance with the operation state and the remaining fuel amount shown in the map of FIG. 3 instead of the mode changeover switch 76. It is determined from the operating state.

  In the hydrogen operation mode at S13, the ECU 70 determines whether the engine is operating in a lean region of the air-fuel ratio (S15). Here, when the engine operating region is region 2 or region 3 in the map of FIG. 3, it is determined that the engine is operating in the lean region.

  When it is in the lean operation region in S15, the ECU 70 sets the air-fuel ratio to lean (approximately λ = 2). Here, the ECU 70 increases the opening degree of the throttle valve 24 as compared with the theoretical air-fuel ratio or the rich operation, and the port injection type and direct injection type injectors so that the air-fuel ratio becomes λ = 2 from the relationship with the intake air amount. The hydrogen gas injection amount from 40 and 42 is adjusted.

Next, the ECU 70 determines whether a purge condition for the evaporated fuel is satisfied (S19). Here, it is estimated from the following (1) to (5) that the evaporated fuel trap amount adsorbed on the canister 65 is equal to or larger than a predetermined amount, and it is determined that the purge condition is satisfied when these conditions are satisfied. To do.
(1) When the duration of hydrogen operation mode (the time during which purging is not performed) has exceeded a predetermined time (2) The temperature of the gasoline tank 63 in the hydrogen operation mode is not less than a predetermined temperature (3) During purging executed in the gasoline operation mode, a value related to the evaporated fuel trap amount (for example, the opening time of the purge control valve 67 or the air-fuel ratio deviation during purging) is determined in advance. When the threshold value is exceeded (4) When the above conditions (1) and (3) are both satisfied (5) Periodically every predetermined time so that the trapped amount of evaporated fuel does not exceed the allowable amount When the purge condition is satisfied in S19 (YES in S19), the ECU 70 turns on (opens) the purge control valve 67 and executes the purge of the evaporated fuel (S21, FIG. 6 (a)).

  Further, the ECU 70 corrects the opening degree of the throttle valve 24 and controls the throttle opening degree in the closing direction (decreasing direction) so as to cancel the torque increase due to the purge (S23, FIG. 6B).

  Further, when the purge condition is not established in S19 (NO in S19), the ECU 70 turns off (closes) the purge control valve 67 and finishes the purge (S25), and corrects the opening of the throttle valve 24. Reset (S27).

  On the other hand, when not in the lean operation region in S15, the ECU 70 sets the air-fuel ratio to the theoretical air-fuel ratio (λ = 1). Here, the ECU 70 reduces the opening of the throttle valve 24 as compared with the lean operation, and from the port injection type and direct injection type injectors 40 and 42 so that the air-fuel ratio becomes λ = 1 from the relationship with the intake air amount. The hydrogen gas injection amount is adjusted (S29).

  When the hydrogen operation mode is not set in S13 (NO in S13), the ECU 70 executes the air-fuel ratio control (EGR control) according to the map of FIG. 3 because it is in the gasoline operation mode (S31).

  Further, the ECU 70 performs purge control based on the purge condition in the gasoline operation mode (S33).

As the purge condition in the gasoline operation mode, for example, when the following conditions (6) to (7) are both satisfied, the purge condition is satisfied.
(6) The engine water temperature is equal to or higher than a predetermined value (for example, 60 ° C.) (7) During the air-fuel ratio feedback control Further, the ECU 70 performs the evaporation during the purge executed in the gasoline operation mode used for the determination of the purge condition of (3). A value related to the fuel trap amount (for example, the opening time of the purge control valve 67 or the air-fuel ratio deviation amount during purging) is estimated and calculated (S35).

<Description of effects>
According to the above embodiment, the purge is executed in the hydrogen operation mode and the air-fuel ratio with a large amount of air is lean (S13 → S15 → S17 → S19 → S21). The fuel ratio is kept lean, and the amount of increase in torque generated by purging the evaporated fuel is also reduced, so that the torque increase Δt when purging is executed during the hydrogen operation mode can be suppressed (FIG. 6C).

  Further, when the air-fuel ratio is lean, the throttle opening is increased to increase the air amount (S17), and the throttle opening is controlled in the closing direction in synchronization with the purge (S21 → S23). The torque increase can be corrected by the throttle opening. That is, since the slot opening is throttled when the air-fuel ratio is rich, even if the throttle valve is further throttled during purging, the amount of air is small, so there is no effect of correcting the torque increase, and the amount of lean air is large. Sometimes purging is more effective.

  In addition, the purge conditions (1) to (4) above, in which the trap amount of the canister 65 is estimated to exceed the allowable amount, or periodically determined at predetermined times such that the trap amount of the evaporated fuel does not exceed the allowable amount. Therefore, it is possible to prevent the evaporated fuel trapped by the canister 65 from exceeding an allowable amount and the evaporated fuel from leaking from the canister 65 in the hydrogen operation mode.

1 is a cross-sectional view schematically showing a dual fuel engine according to an embodiment of the present invention. It is a block diagram which shows the dual fuel engine of this embodiment, and the structure of the periphery. (A) is a map showing forms of EGR control and air-fuel ratio control in three torque regions, and (b) is a diagram showing the relationship between the air-fuel ratio and NOx emission amount. It is an injection control map of port injection type and direct injection type injectors 40 and 42 based on engine speed. It is a flowchart which shows purge control of the evaporated fuel of this embodiment. It is a time chart which shows operation of a purge control valve and throttle opening, and torque variation in purge control of evaporated fuel of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotary engine 2 Rotor housing 4 Side housing 6 Rotor 10 Working chamber (compression stroke)
11 Working chamber (expansion stroke)
14, 15 Spark plug 16 Intake port 18 Exhaust port 24 Throttle valve 40 Port injection type hydrogen gas injector 42 Direct injection type hydrogen gas injector 61 Gasoline injector 63 Gasoline tank 65 Canister 67 Purge control valve 70 ECU
71 Distributor 72 Throttle opening sensor 73 Air flow sensor 74 Linear O ₂ sensor 75 Hydrogen gas flow meter 76 Mode switch 77 Warning lamp

Claims (4)

In an evaporative fuel control device for a dual fuel engine operated with at least one of gaseous fuel and liquid fuel,
Air-fuel ratio control that switches between a state in which the air-fuel ratio of the gaseous fuel supplied to the engine is leaner than the stoichiometric air-fuel ratio and a state in which the stoichiometric air-fuel ratio or richer is set during operation with at least gaseous fuel Means,
Evaporative fuel supply means for supplying the evaporative fuel in a state where the evaporative fuel generated in the liquid fuel tank is supplied and the air-fuel ratio is set to lean when operating with the gaseous fuel. Evaporative fuel control system for dual fuel engine. In a state where the air-fuel ratio is lean, further comprising throttle opening control means for increasing the throttle opening,
2. The evaporated fuel control device for a dual fuel engine according to claim 1, wherein the throttle opening control means controls the throttle opening in a closing direction in synchronization with a timing of supplying the evaporated fuel.   The evaporative fuel of the dual fuel engine according to claim 1, wherein the evaporative fuel is supplied at a timing when the trap amount of the canister for trapping the evaporative fuel exceeds an allowable amount or periodically. Control device.   2. The dual fuel engine evaporative fuel control device according to claim 1, wherein the gaseous fuel is hydrogen gas and the liquid fuel is gasoline.

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