JP2009287533A - Evaporation fuel processing device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To preferably execute a combustion process of an evaporation fuel by preferably controlling a gas discharge amount in the evaporation fuel. <P>SOLUTION: An engine is provided with an evaporation fuel processing system 30 for supplying an evaporation gas of fuel to an air intake pipe 11 for a combustion process. The evaporation fuel processing system 30 comprises a first adsorbing part 33a and a second adsorbing part 33b for adsorbing the evaporation gas containing two or more fuel components with different properties for each component, and a first purge valve 38 and a second purge valve 39 each provided in purge pipes 35, 36 each connected with the adsorbing parts 33a, 33b for adjusting the gas discharge amount from the adsorbing parts 33a, 33b. An ECU 50 controls the opening degrees of the first purge valve 38 and the second purge valve 39 so that the purge amount may be adjusted each for the adsorbing parts 33a, 33b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an evaporative fuel processing apparatus for an internal combustion engine, and more particularly to an evaporative fuel processing apparatus for an internal combustion engine that supplies a fuel evaporative gas to an intake system of the internal combustion engine and performs combustion processing.

  Conventionally, evaporative gas (fuel evaporative gas) generated in a fuel tank or the like is temporarily stored in a canister, and the stored fuel evaporative gas is supplied (purged) to the intake system of the internal combustion engine and burned in the internal combustion engine. Evaporative fuel processing systems are known.

In recent years, alcohol fuels have attracted attention as alternatives to fossil fuels such as gasoline, against the backdrop of concerns about the depletion of petroleum resources and the mitigation of global warming. It is used as fuel for internal combustion engines. As an evaporative fuel processing system for an internal combustion engine using a mixed fuel of alcohol and gasoline, for example, a canister in which a first adsorbent layer that adsorbs a gasoline component and a second adsorbent layer that adsorbs an alcohol component are formed. Have been proposed (see, for example, Patent Document 1).
JP 59-226263 A

  However, in the canister of Patent Document 1, the fuel evaporative gas (gasoline) adsorbed on the first adsorbent layer and the fuel evaporative gas (alcohol) adsorbed on the second adsorbent layer have the same hole (in Patent Document 1). Since the fuel is discharged from the fuel outlet, it is impossible to individually adjust the gas discharge amount (purge amount) of alcohol and gasoline. For this reason, there is a concern that the component ratio (gas concentration) of the fuel evaporative gas released from the canister varies. In such a case, the theoretical air-fuel ratio differs between alcohol and gasoline, and as a result, there is a possibility that air-fuel ratio control cannot be performed properly.

  The present invention has been made to solve the above-described problems, and provides an evaporative fuel processing apparatus for an internal combustion engine that can suitably control the gas emission amount of the evaporative fuel and thus appropriately evaporate the evaporative fuel. The main purpose is to do.

  The present invention employs the following means in order to solve the above problems.

  According to a first aspect of the present invention, there is provided an evaporative fuel processing apparatus for an internal combustion engine that supplies a fuel evaporative gas to an intake system of an internal combustion engine and performs a combustion process. The evaporative gas containing two or more fuel components having different properties A plurality of adsorbing units, a plurality of adsorbing units, and a plurality of purge valves provided in gas discharge paths connected to the plurality of adsorbing units, respectively, for adjusting the amount of gas released from the adsorbing units; Each time the opening of the purge valve is controlled.

  According to the above configuration, the fuel evaporative gas (fuel evaporative gas) containing a plurality of components having different properties is adsorbed to the separate adsorbing portions, and the opening degree of the purge valve in the adsorbing portion is controlled for each adsorbing portion. Therefore, the amount of gas released from each component can be arbitrarily adjusted for each component. That is, in the configuration in which each component separately adsorbed by the adsorption unit is discharged from a single gas discharge path as in the prior art, the amount of gas released from each component cannot be individually adjusted for each component. For example, a gas release path is provided in each of the plurality of adsorption sections, and a purge valve is provided in each gas release path, and the opening of the purge valve is controlled for each of the plurality of adsorption sections. Each can be adjusted arbitrarily. As a result, the amount of gas released from the evaporated fuel can be suitably controlled, and consequently the evaporated fuel can be suitably burned.

  It is considered that the optimum component ratio in the released gas (purge gas) is different depending on the operating state of the internal combustion engine when the gas is released from each adsorption portion. In view of this point, the invention according to claim 2 sets which of the plurality of adsorbing parts performs gas discharge based on the operating state of the internal combustion engine. According to this configuration, since the respective gas discharge amounts of the respective components are changed according to the operating state of the internal combustion engine, the component ratio in the purge gas can be appropriately changed according to the operating state of the internal combustion engine.

  Since the fuel evaporative gas adsorbed in each adsorbing portion is released to the intake system of the internal combustion engine, it is considered that the gas release affects the change in the air-fuel ratio of the internal combustion engine. Further, when the discharged gas contains a plurality of components having different theoretical air-fuel ratios, it is considered that the degree of influence on the change in the air-fuel ratio differs depending on the component ratio in the released gas. In view of this point, the invention described in claim 3 is applied to an air-fuel ratio control system that performs air-fuel ratio control so that the air-fuel ratio of the internal combustion engine matches a target value. Air-fuel ratio detection means for detecting the air-fuel ratio of the internal combustion engine, including two or more different fuel components. In addition, based on the air-fuel ratio detected by the air-fuel ratio detecting means, it is set which of the plurality of adsorbing parts gas discharge is performed. According to this configuration, since the gas discharge amount of each component is changed according to the air-fuel ratio of the internal combustion engine, the component ratio of the released gas can be appropriately adjusted according to the air-fuel ratio of the internal combustion engine.

  When the lean degree of the actual air-fuel ratio is large, it is considered that the actual air-fuel ratio is matched with the target value earlier by positively releasing fuel components having a high theoretical air-fuel ratio. In view of this, the invention according to claim 4 is a fuel having a relatively large stoichiometric air-fuel ratio among the two or more fuel components as the lean degree with respect to the target value of the air-fuel ratio detected by the air-fuel ratio detecting means is larger. The opening degree of the purge valve is controlled so that the components are released with priority. According to this configuration, when the lean degree of the actual air-fuel ratio is large, the fuel component having a relatively large stoichiometric air-fuel ratio is preferentially supplied to the intake system of the internal combustion engine. Can be resolved earlier. Here, when a mixed fuel containing alcohol and gasoline is used as the fuel for the internal combustion engine, the gasoline corresponds to a fuel component having a relatively large theoretical air-fuel ratio.

  When the internal combustion engine is under a high load (for example, when the vehicle is accelerated, when the internal combustion engine is started, when the vehicle is traveling uphill), it is required to increase the output of the internal combustion engine. It is desirable that more components are contained in the released gas. In view of this, the invention according to claim 5 is directed to the fuel according to the fifth aspect, wherein the evaporative gas includes two or more fuel components having different calorific values due to combustion, and the higher the load of the internal combustion engine, the relatively larger the calorific value. The opening degree of the purge valve is controlled so that the components are released with priority. By doing so, the output of the internal combustion engine can be increased efficiently when the load is high, and as a result, the operating performance of the internal combustion engine can be improved.

  Various properties such as theoretical air-fuel ratio, calorific value, volatility and the like are different between gasoline and alcohol. Therefore, when a mixed fuel containing gasoline and alcohol is used for an internal combustion engine, it is considered that the component ratio varies in the evaporated gas in the fuel tank. In addition, in the conventional technology in which each component is released from a single gas discharge path, the component ratio of the purge gas varies due to the difference in the properties of gasoline and alcohol in addition to the variation in the component ratio of the fuel evaporative gas. It is considered a thing. In view of this point, the invention according to claim 6 is characterized in that the evaporative gas includes a gasoline component and an alcohol component, and the purge valve adjusts a gas release amount of an adsorption portion to which the gasoline component is adsorbed. A first purge valve and a second purge valve that adjusts a gas release amount of the adsorption portion to which the alcohol component is adsorbed, and controls the opening degrees of the first purge valve and the second purge valve, respectively. According to this configuration, since the above invention is applied when using a mixed fuel of gasoline and alcohol, it is possible to individually control the amount of gas released from each adsorption portion in gasoline and alcohol.

  According to a seventh aspect of the present invention, the internal combustion engine includes a fuel cell engine that uses alcohol as a component of fuel, and the fuel includes an alcohol component. In addition, an adsorption portion where an alcohol component is adsorbed among the plurality of adsorption portions and a fuel storage portion for the fuel cell engine are connected by the gas discharge path. According to this configuration, since the alcohol component collected by the adsorption unit is transferred to the fuel storage unit for the fuel cell engine, the alcohol contained in the evaporated gas can be used as fuel for the fuel cell engine.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. In the present embodiment, an engine control system is constructed for an in-vehicle multi-cylinder engine that is an internal combustion engine. In this engine, at least one of gasoline and alcohol (for example, ethanol or methanol) is used as fuel. That is, in the engine, gasoline alone fuel is used, or mixed fuel in which alcohol is mixed in an arbitrary ratio is used. In the control system, an electronic control unit (hereinafter referred to as an ECU) is used as a center to control the fuel injection amount and ignition timing. FIG. 1 shows an overall schematic configuration diagram of the engine control system.

  In the engine 10 shown in FIG. 1, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11 (intake passage), and an air flow meter 13 for detecting the intake air amount is provided downstream of the air cleaner 12. . A throttle valve 14 whose opening degree is adjusted by a throttle actuator 15 such as a DC motor is provided on the downstream side of the air flow meter 13. The opening degree of the throttle valve 14 (throttle opening degree) is detected by a throttle opening degree sensor built in the throttle actuator 15.

  A surge tank 16 is provided on the downstream side of the throttle valve 14. The surge tank 16 is provided with an intake pipe pressure sensor 17 for detecting the intake pipe pressure. The surge tank 16 is connected to an intake manifold 18 that introduces air into each cylinder of the engine 10. In the intake manifold 18, an electromagnetically driven fuel injection that injects fuel near the intake port of each cylinder. A valve 19 is attached.

  An intake valve 21 and an exhaust valve 22 are provided at an intake port and an exhaust port of the engine 10, respectively. The air-fuel mixture is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust gas after combustion is discharged to the exhaust pipe 24 (exhaust passage) by the opening operation of the exhaust valve 22.

  A spark plug 27 is attached to the cylinder head of the engine 10 for each cylinder. A high voltage is applied to the spark plug 27 at a desired ignition timing through an ignition device (not shown) including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 27, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion.

  The exhaust pipe 24 is provided with a catalyst 25 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas. Further, on the upstream side of the catalyst 25, an oxygen sensor 26 is provided for detecting the air-fuel ratio (oxygen concentration) of the air-fuel mixture using the exhaust gas as a detection target. In the present embodiment, the oxygen sensor 26 is an A / F sensor that outputs a wide-range air-fuel ratio signal proportional to the oxygen concentration in the exhaust gas.

  Further, the engine 10 is provided with an evaporated fuel processing system 30 that collects fuel evaporative gas generated in the fuel tank and purges the gas into the engine 10. In FIG. 2, the schematic block diagram of the evaporative fuel processing system 30 is shown. In FIG. 2, one end of a conduit 32 is connected to the fuel tank 31, and a canister 33 for adsorbing and collecting fuel evaporative gas generated in the fuel tank 31 is connected to the other end of the conduit 32. .

  With regard to the canister 33, particularly in the present embodiment, when a mixed fuel of gasoline and alcohol is stored as fuel in the fuel tank 31, the mixed fuel is adsorbed by components (gasoline and alcohol separately). A plurality of suction portions are provided. In addition, a purge pipe as a gas discharge path is connected to each of the plurality of adsorption portions, and a purge valve is provided in each of the purge pipes.

  Specifically, the canister 33 has a first suction portion 33a and a second suction portion 33b, and the suction portions 33a and 33b are accommodated in separate containers. Among these, the 1st adsorption | suction part 33a is connected with the fuel tank 31 by the conduit | pipe 32, and the 2nd adsorption | suction part 33b is connected with the 1st adsorption | suction part 33a by the conduit | pipe 34. Further, one end of a purge pipe 35 is connected to the second adsorption part 33b, and the intake pipe 11 (surge tank 16) is connected to the other end of the purge pipe 35. Furthermore, one end of the purge pipe 36 is connected to the first adsorption part 33 a, and the other end of the purge pipe 36 is connected to the purge pipe 35. An air introduction hole 37 through which outside air is introduced is provided in a part of the first adsorption part 33a and the second adsorption part 33b.

  A first purge valve 38 is provided in the middle of the purge pipe 36, and a second purge valve 39 is provided in the middle of the purge pipe 35. Then, by opening the first purge valve 38, the first adsorption part 33a and the surge tank 16 are communicated, and by opening the second purge valve 39, the second adsorption part 33b and the surge tank 16 are communicated. Is done. These purge valves 38 and 39 are electromagnetically driven, and their opening degree is adjusted by energization control of each valve.

  A check valve 41 is provided in the middle of the conduit 32. When the vapor pressure in the fuel tank 31 exceeds a predetermined value, the pressure valve of the check valve 41 is opened, and the fuel tank 31 and the first adsorbing portion 33a are communicated. In addition, an electromagnetically driven valve may be provided instead of the check valve 41, and the communication between the fuel tank 31 and the first adsorbing portion 33a may be controlled by controlling energization to the electromagnetically driven valve. In addition, an electromagnetically driven atmospheric release valve 42 is provided in the atmospheric introduction hole 37, and its opening degree is adjusted by energization control. Further, an electromagnetically driven solenoid valve 44 is provided in the middle of the conduit 34, and gas movement between the first adsorption portion 33a and the second adsorption portion 33b is allowed when the valve is opened, and when the valve is closed, Movement is prohibited.

  The adsorbing portions 33a and 33b are filled with adsorbents 43a and 43b having different adsorption performances. In the present embodiment, as the adsorbents 43a and 43b, an adsorbent (for example, activated carbon or zeolite) capable of selectively adsorbing each component using a difference in molecular weight is used. Specifically, the pore diameter of the adsorbent 43a of the first adsorption portion 33a is larger than the pore diameter of the adsorbent 43b of the second adsorption portion 33b. As a result, a component having a relatively large molecular weight (gasoline component) is selectively adsorbed by the first adsorption unit 33a, and a component having a relatively small molecular weight (alcohol component) is selectively adsorbed by the second adsorption unit 33b. It has come to be.

  In the evaporative fuel processing system 30, purge control of the fuel evaporative gas in the fuel tank 31 is performed by adjusting the opening of each valve. Specifically, first, when the vapor pressure in the fuel tank 31 becomes equal to or higher than a predetermined value and the check valve 41 is opened, the fuel tank 31 and the first adsorption portion 33a are communicated. As a result, the fuel evaporative gas in the fuel tank 31 is transferred to the first adsorption portion 33a through the conduit 32. At this time, the gasoline component in the fuel evaporative gas is adsorbed by the adsorbent 43a of the first adsorbing portion 33a, whereas the alcohol component passes through the first adsorbing portion 33a and passes through the conduit 34 to the first. 2 is transferred to the adsorption unit 33b. And it adsorb | sucks to the adsorption agent 43b of the 2nd adsorption | suction part 33b.

  Further, after the fuel evaporative gas is adsorbed by the adsorbing portions 33a and 33b, for example, when the first purge valve 38 and the second purge valve 39 are opened, intake negative pressure acts on the purge pipes 35 and 36. At that time, when the atmosphere release valve 42 is opened, outside air is introduced into the first adsorption portion 33a and the second adsorption portion 33b through the atmosphere introduction hole 37, and is adsorbed by the adsorbents 43a and 43b in the adsorption portions 33a and 33b. The evaporated fuel gas is released and purged to the intake pipe 11 (surge tank 16). Thereby, the fuel evaporative gas generated in the fuel tank 31 is combusted in the combustion chamber 23. During the purge to the surge tank 16, it is preferable to close the electromagnetic valve 44 in order to reliably block the gas movement between the first adsorption unit 33a and the second adsorption unit 33b.

  Returning to the description of FIG. 1, the engine 10 is provided with a coolant temperature sensor 29 for detecting the coolant temperature and a crank angle sensor 28 for outputting a rectangular crank angle signal for each predetermined crank angle of the engine.

  As is well known, the ECU 50 is mainly composed of a microcomputer (hereinafter referred to as a microcomputer) 41 composed of a CPU, ROM, RAM, and the like, and executes various control programs stored in the ROM, so that the engine operation state can be changed each time. In response, various controls of the engine 10 are performed. That is, the microcomputer 51 of the ECU 50 inputs detection signals from the various sensors described above, calculates the fuel injection amount and ignition timing based on the various detection signals, and drives the fuel injection valve 19 and the ignition device. To control. As control of the fuel injection amount, the microcomputer 51 performs air-fuel ratio control so that the air-fuel ratio detected by the oxygen sensor 26 matches a target value (for example, the theoretical air-fuel ratio). In addition, the microcomputer 51 controls energization of various electromagnetically driven valves in the evaporated fuel processing system 30 to control their driving.

  By the way, in the evaporative fuel processing, when a mixed fuel of gasoline and alcohol is stored in the fuel tank 31, the evaporative gas of the mixed fuel may be, for example, an engine operating state or a mixing ratio of gasoline and alcohol in the mixed fuel. As a result, the component ratio in the evaporated gas varies. Further, the adsorption performance and desorption performance with respect to the adsorbent are different between gasoline and alcohol. Therefore, if the purge of gasoline and alcohol is controlled by a single purge valve, the component ratio (gas concentration) in the fuel evaporative gas (purge gas) released from the canister 33 will vary, and the air-fuel ratio will be There is a risk of deviation from the target value. That is, when the component ratio (gas concentration) in the purge gas varies, the component ratio of the fuel (fuel from the fuel injection valve 19 + purge gas) actually supplied into the combustion chamber 23 changes accordingly. On the other hand, when the fuel is composed of a plurality of components having different properties, the stoichiometric air-fuel ratio is generally different between the components. For example, gasoline (theoretical air-fuel ratio 14.7) is ethanol (theoretical air-fuel ratio 9) between gasoline and ethanol. The theoretical air-fuel ratio is larger than that. For this reason, when the component ratio of the purge gas varies, it cannot always be said that an appropriate amount of fuel is supplied to make the air-fuel ratio coincide with the target value, and as a result, the air-fuel ratio deviates from the target value. There is concern.

  As described above, in this embodiment, the canister 33 includes a plurality (two in this embodiment) of adsorbing portions 33a and 33b, and each component of the fuel is adsorbed separately. In this configuration, particularly in the present embodiment, the purge pipes 35 and 36 of the adsorption portions 33a and 33b are provided with the first purge valve 38 and the second purge valve 39, respectively, and their opening degrees are controlled separately. To adjust the gas emission amount for each component. Further, when the opening / closing control of the purge valve is performed, the opening of the first purge valve 38 and the second purge valve 39 is adjusted based on the detected air / fuel ratio, thereby suppressing the fluctuation of the air / fuel ratio due to the purged evaporated fuel. .

  FIG. 3 is a flowchart showing the procedure of purge control in the present embodiment. This process is performed by the microcomputer 51 of the ECU 50 at predetermined intervals.

  In FIG. 3, first, in step S11, it is determined whether or not a purge execution condition is satisfied. As purge execution conditions, for example, the coolant temperature of the engine 10 is equal to or higher than a predetermined temperature indicating completion of warm-up of the engine 10, fuel cut by deceleration is not being executed, the engine rotation speed is equal to or higher than a predetermined value, It is assumed that the intake air amount is a predetermined amount or more. If the purge execution condition is satisfied, the process proceeds to step S12, and the detected air-fuel ratio AF detected by the oxygen sensor 26 is read. In step S13, the detected air-fuel ratio AF is further leaner than the predetermined value AFle on the lean side. It is determined whether it is in the area (strong lean area). When the detected air-fuel ratio AF is in the strong lean region, the process proceeds to step S14, the first purge valve 38 is opened, and the second purge valve 39 is closed. That is, when the degree of leanness of the detected air-fuel ratio AF is relatively large, the purge amount of the fuel component (alcohol component) having a small theoretical air-fuel ratio is set to zero, and the purge amount of the fuel component (gasoline component) having a large theoretical air-fuel ratio is set to zero. By setting the predetermined amount, the actual air-fuel ratio is brought close to the target air-fuel ratio as early as possible with a small purge amount.

  On the other hand, if the detected air-fuel ratio AF is not in the strong lean region, the process proceeds to step S15, and it is determined whether or not the detected air-fuel ratio AF is in a richer region (strong rich region) than the predetermined value AFri on the rich side. judge. If the detected air-fuel ratio AF is in the strong rich region, the process proceeds to step S16 where the first purge valve 38 is closed and the second purge valve 39 is opened. That is, when the richness of the detected air-fuel ratio AF is relatively large, the purge amount of the gasoline component is set to zero and the purge amount of the alcohol component is set to a predetermined amount, so that the change in the air-fuel ratio due to the evaporated fuel purge is minimized. And suppressing over-richness.

  In addition, when gasoline and alcohol (ethanol in this embodiment) are compared, alcohol is inferior in volatility compared to gasoline and the amount of evaporation from the fuel tank 31 is small. Therefore, when it is estimated by a known method such as measuring the gas flow rate of the second adsorption portion 33b that the adsorption amount or purge amount of alcohol is almost zero, the gasoline is purged instead of alcohol. May be.

  In addition, when the detected air-fuel ratio AF is not in the strong rich region, that is, when the air-fuel ratio lean region is in the region on the rich side (weak lean region) with the predetermined value AFle as the boundary, or in the rich region of the air-fuel ratio, the predetermined value AFri If it is in the lean side region (weakly rich region), the process proceeds to step S17, and the open / close state of the first purge valve 38 and the second purge valve 39 is maintained as they are. That is, in the present embodiment, the open / close state of the purge valves 38 and 39 is switched by giving hysteresis to the detected air-fuel ratio.

  Next, the relationship between the air-fuel ratio and the purge amount of each component will be described with reference to FIG. FIG. 4 is a time chart showing changes in the air-fuel ratio and the purge amount. In FIG. 4, when the purge execution condition is satisfied at time t10 and the detected air-fuel ratio AF reaches the strong lean region at time t11, the first purge valve 38 is opened and the second purge valve 39 is closed. As a result, the gasoline component is purged to the surge tank 16 with priority over the alcohol component. Thereafter, when the detected air-fuel ratio AF shifts to the rich side and the detected air-fuel ratio AF reaches the strong rich region at time t12, the first purge valve 38 is closed and the second purge valve 39 is opened. As a result, the alcohol component is purged to the surge tank 16 with priority over the gasoline component.

  According to the present embodiment described above, the following excellent effects are obtained.

  When a mixed fuel of gasoline and alcohol is stored in the fuel tank 31, the gasoline component of the evaporated gas in the fuel tank 31 is adsorbed to the first adsorption portion 33a, and the alcohol component is adsorbed to the second adsorption portion 33b. While being adsorbed by different adsorbing portions and individually controlling the opening degree of the first purge valve 38 and the second purge valve 39, the purge amount of each component can be arbitrarily adjusted for each component. As a result, the purge amount in the evaporated fuel can be suitably controlled, and consequently the evaporated fuel can be suitably burned.

  In addition, since the above configuration can be applied when the engine is driven with a mixed fuel of gasoline and alcohol, the effect obtained by arbitrarily adjusting the purge amount of each fuel component for each component is high. That is, the component ratio of the evaporated gas in the fuel tank 31 and the purge gas from the adsorbing portion varies due to the difference in properties between gasoline and alcohol. Further, since the theoretical air-fuel ratio differs between gasoline and alcohol, it is conceivable that the air-fuel ratio fluctuates when the purge gas component ratio fluctuates. For this reason, in an engine using a mixed fuel of gasoline and alcohol, it is preferable to separately adjust the purge amount of gasoline and alcohol, so that air-fuel ratio control is suitable for performing the combustion process of the evaporated fuel. Can be implemented.

  In order to determine which of the first adsorbing part 33a and the second adsorbing part 33b is to purge the evaporated gas based on the detected air-fuel ratio, the gasoline purge amount and the alcohol purge amount are set to the detected air-fuel ratio. It can be adjusted accordingly. In particular, in the present embodiment, when the detected air-fuel ratio is in the strong lean region, the purge of the fuel component (gasoline) having a higher theoretical air-fuel ratio is preferentially executed, so that the deviation from the target value in the air-fuel ratio is earlier. Can be resolved. Further, when the detected air-fuel ratio is in the strong rich region, the purge of the fuel component (alcohol) having a smaller theoretical air-fuel ratio is prioritized, so that the change in the air-fuel ratio due to the purge of evaporated fuel can be made as small as possible. As a result, the combustion process of the fuel evaporative gas can be performed while suppressing over-richness.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  In the above-described embodiment, the parameter indicating the engine operating state is the detected air-fuel ratio AF, and the purge amount of each component is adjusted based on the detected air-fuel ratio AF, but instead of or in addition to the detected air-fuel ratio. In addition, the purge amount of each component may be adjusted based on the engine load. Specifically, the fuel component (gasoline) having a larger theoretical air-fuel ratio is preferentially purged as the engine load is higher. If it carries out like this, an engine output can be efficiently raised at the time of the high load of the engine 10, and the driving | running performance of the engine 10 can be improved by extension. Specifically, for example, when the throttle opening and the engine rotation speed are used as parameters and the throttle opening is equal to or greater than a predetermined opening and the engine rotation speed is equal to or greater than a predetermined value, gasoline is satisfied. The components are preferentially purged, and if any of the above conditions is not satisfied, the alcohol components are preferentially purged.

  -In embodiment mentioned above, it is good also as a structure which preferentially purges a fuel component with a large theoretical air fuel ratio over a component with a small theoretical air fuel ratio in an engine starting period. For example, in the case of a mixed fuel of alcohol and gasoline, the gasoline is purged in preference to alcohol during the engine start period. By doing so, the ratio of the gasoline component in the purge gas is increased, so that the startability of the engine 10 can be improved.

  In the above-described embodiment, it is determined which purge of gasoline or alcohol is executed based on the detected air-fuel ratio, and the purge amount is made constant when the purge is executed. You may make it variable continuously or in steps based on the air-fuel ratio. Specifically, as shown in FIG. 5, for example, the gasoline purge amount may be increased from time t21 when the detected air-fuel ratio AF becomes a strong lean region to time t22 when it becomes a strong rich region. Alternatively, the alcohol purge amount may be increased from the time t22 when the detected air-fuel ratio AF becomes the strong rich region to the time when the detected air-fuel ratio AF becomes the strong lean region.

  In the above-described embodiment, the configuration is such that the gasoline purge is switched when entering the strong lean region, and the alcohol purge is switched when entering the strong rich region, but any one of the determination values (for example, stoichiometric) is used. It may be configured to switch whether to purge the fuel component. Alternatively, the fuel component purge may be switched based on at least one of the lean-side predetermined value AFle and the rich-side predetermined value AFri and the stoichiometry. For example, as shown in FIG. 6, from the time 31 when the detected air-fuel ratio AF enters the strong lean region to the time t32 when the detected air-fuel ratio AF reaches the stoichiometric range, the purge of gasoline is executed with priority. Further, after time t32 when the detected air-fuel ratio AF becomes richer than stoichiometric, the alcohol purge is preferentially executed. According to this configuration, when the lean degree of the air-fuel ratio becomes high, the fuel component (gasoline) having a larger theoretical air-fuel ratio is actively purged, so that the air-fuel ratio can be quickly returned to the vicinity of the stoichiometric ratio. . Further, when the air-fuel ratio becomes richer than the stoichiometric ratio, the fuel component (alcohol) having a smaller stoichiometric air-fuel ratio is preferentially purged, so that the fuel evaporative gas is suppressed while suppressing deviation from the target air-fuel ratio. The combustion process can be suitably performed. In the above configuration, when the air-fuel ratio is richer than stoichiometric, the purge valves 38 and 39 may both be closed and purge may not be executed.

  In the above-described embodiment, the adsorbents 33a and 33b are filled with adsorbents having different pore diameters in order to utilize the difference in molecular weight when adsorbing the components in the fuel to the different adsorbers 33a and 33b. Although it was set as the structure, the structure for making each component in a fuel adsorb | suck to another adsorption | suction part is not limited to this. For example, each component may be adsorbed by the separate adsorbing portions 33a and 33b using the difference in polarity of each component in the fuel. For example, in the case of a mixed fuel of gasoline and alcohol, gasoline is nonpolar, whereas alcohol has polarity. Therefore, it is preferable to fill the first adsorption part 33a with a relatively low or non-polar adsorbent (for example, activated carbon) and fill the second adsorption part 33b with a relatively high polarity adsorbent (for example, silica gel). Further, as another method, the state quantity of each fuel component is changed by pressurizing or depressurizing the evaporated fuel, or raising or lowering the temperature of the evaporated fuel, whereby the adsorbent in each fuel component is changed to the adsorbent. Adsorption may be selectively performed.

  In the above-described embodiment, the gasoline component is adsorbed by the first adsorbing unit 33a and then the alcohol component is adsorbed by the second adsorbing unit 33b. What is necessary is just to set suitably according to the adsorption agent in a part. For example, when each component is adsorbed by the different adsorbing parts 33a and 33b using the difference in polarity of the fuel component, the adsorbent 43a of the first adsorbing part 33a is made to have a high polarity and the adsorbing of the second adsorbing part 33b. The agent 43b has a low polarity or a non-polarity. In this way, after the alcohol is adsorbed by the first adsorption unit 33a, the gasoline is adsorbed by the second adsorption unit 33b.

  In the above-described embodiment, the canister 33 includes two adsorbing portions (the first adsorbing portion 33a and the second adsorbing portion 33b), but the number is not particularly limited, and the number of components in the fuel to be separated It is good also as a structure provided with three or more adsorption | suction parts according to. In that case, by providing a purge valve for each adsorption part, the gas release amounts (purge amounts) of three or more components can be individually adjusted. Moreover, in the said embodiment, although it was set as the structure which accommodates the 1st adsorption | suction part 33a and the 2nd adsorption | suction part 33b in a respectively separate container, the 1st adsorption | suction part 33a and the 2nd adsorption | suction part 33b are in one container. It is good also as a structure arranged in parallel. At this time, the purge pipe for the first adsorption part 33a and the purge pipe for the second adsorption part 33b are connected to the container, respectively, and a purge valve is installed for each of the purge pipes. The same effect as the embodiment can be obtained.

  In the above embodiment, the case where a fuel containing gasoline and alcohol (ethanol) is used as the mixed fuel has been described. However, a fuel containing components other than gasoline and alcohol may be used. For example, the present invention is applied when a fuel containing a component having a relatively large carbon number (for example, a hydrocarbon having 5 or more carbon atoms) and a component having a relatively small carbon number (for example, a hydrocarbon having 4 or less carbon atoms) is used. May be.

  In the above embodiment, when a fuel cell engine using alcohol (for example, methanol) as a fuel is provided, the alcohol adsorbed by the second adsorption unit 33b may be purged to the fuel storage unit of the fuel cell engine. That is, instead of connecting the other end of the purge pipe 35 connected to the second adsorbing portion 33b to the surge tank 16, it is configured to connect to the fuel storage portion for the fuel cell engine. According to this configuration, since the alcohol component collected by the second adsorption unit 33b is transferred to the fuel storage unit for the fuel cell engine, the alcohol contained in the fuel evaporative gas is used as fuel for the fuel cell engine. be able to.

  In the embodiment described above, an A / F sensor that outputs a wide-range air-fuel ratio signal is used as the oxygen sensor 26. However, voltage signals that differ between the rich side and the lean side with respect to the stoichiometric air-fuel ratio (stoichiometry). It is good also as a structure using the O2 sensor which outputs. In this configuration, it is preferable that the alcohol purge is prioritized when the detected air-fuel ratio is rich, and the gasoline purge is prioritized when the detected air-fuel ratio is lean.

1 is an overall schematic configuration diagram of an engine control system. The figure which shows schematic structure of an evaporative fuel processing system. The flowchart which shows the process sequence of purge control. The time chart which shows transition of the air fuel ratio and the purge amount of each fuel component. The time chart which shows transition of the air fuel ratio of other embodiment, and the purge amount of each fuel component. The time chart which shows transition of the air fuel ratio of other embodiment, and the purge amount of each fuel component.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... Intake pipe, 16 ... Surge tank, 30 ... Evaporative fuel processing system, 31 ... Fuel tank, 33 ... Canister, 33a ... First adsorption part, 33b ... Second adsorption part, 35, 36 ... Purge pipe 38 ... first purge valve, 39 ... second purge valve, 41 ... check valve, 43a, 43b ... adsorbent, 50 ... electronic control unit (ECU), 51 ... microcomputer.

Claims (7)

In an evaporative fuel processing apparatus for an internal combustion engine that supplies a fuel evaporative gas to an intake system of an internal combustion engine to perform combustion processing,
A plurality of adsorbing portions for adsorbing evaporative gas containing two or more fuel components having different properties;
A plurality of purge valves that are respectively provided in the gas discharge paths connected to the plurality of adsorption units and adjust the amount of gas released from the adsorption unit;
Control means for controlling the opening of the purge valve for each of the plurality of adsorption portions;
An evaporative fuel processing apparatus for an internal combustion engine, comprising:   2. The evaporated fuel of the internal combustion engine according to claim 1, wherein the control unit sets which one of the plurality of adsorbing parts performs gas discharge based on an operating state of the internal combustion engine. Processing equipment. Applied to an air-fuel ratio control system that performs air-fuel ratio control so that the air-fuel ratio of the internal combustion engine matches a target value,
The evaporative gas includes two or more fuel components having different theoretical air-fuel ratios,
Air-fuel ratio detection means for detecting the air-fuel ratio of the internal combustion engine,
The said control means sets which gas discharge | release in which adsorption | suction part is performed among these adsorption | suction parts based on the air fuel ratio detected by the said air fuel ratio detection means, The said 1 or 2 is characterized by the above-mentioned. Evaporative fuel processing apparatus for internal combustion engine.   The control means preferentially releases a fuel component having a relatively large theoretical air-fuel ratio among the two or more fuel components as the lean degree of the air-fuel ratio detected by the air-fuel ratio detection means with respect to the target value increases. The evaporative fuel processing device for an internal combustion engine according to claim 3, wherein the opening degree of the purge valve is controlled. The evaporative gas includes two or more fuel components having different calorific values due to combustion,
5. The control device according to claim 1, wherein the control means controls the opening degree of the purge valve so that a fuel component having a relatively large calorific value is preferentially released as the load of the internal combustion engine is higher. The evaporative fuel processing apparatus of the internal combustion engine as described in any one of Claims. The evaporative gas includes a gasoline component and an alcohol component,
The purge valve includes a first purge valve that adjusts a gas discharge amount of the adsorption unit that adsorbs the gasoline component, and a second purge valve that adjusts a gas discharge amount of the adsorption unit that adsorbs the alcohol component. ,
The evaporated fuel processing apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the control means controls the opening degrees of the first purge valve and the second purge valve, respectively. The internal combustion engine includes a fuel cell engine having alcohol as a component of fuel,
The fuel includes an alcohol component,
7. The adsorbing portion to which an alcohol component is adsorbed among the plurality of adsorbing portions and the fuel storage portion for the fuel cell engine are connected by the gas discharge path. The evaporative fuel processing apparatus of the internal combustion engine according to one item.

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