Control device for evaporation fuel

Abstract

To suppress fluctuation of engine torque.SOLUTION: A control device 60 for evaporation fuel includes: a correction section 64 that performs correction control for reducing a fuel amount of evaporation fuel included in purge gas from an injection amount of fuel to be injected from a fuel injector 23; and an opening learning section 63 for learning an opening of a regulating valve 55 in the case where an air-fuel ratio fluctuates when an opening of the regulating valve 55 is a predetermined opening or smaller. In the case where the air-fuel ratio has fluctuated and the opening of the regulating valve 55 is equal to or smaller than an opening leaned by the opening learning section 63, the correction section 64 determines whether the correction control is prohibited or continued in accordance with a direction in which the air-fuel ratio fluctuates relative to a theoretical air-fuel ratio.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for evaporated fuel. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been known an engine in which evaporated fuel generated in a fuel tank is adsorbed by a canister, and purge gas containing the evaporated fuel purged from the canister is supplied to an intake passage of the engine.

[0003] Patent Document 1 discloses an engine in which evaporated fuel from a fuel tank is adsorbed in a canister, and by appropriately opening a purge valve, the evaporated fuel adsorbed in the canister is purged together with air from an air opening into a surge tank that constitutes a part of the intake system. When the air-fuel ratio feedback correction value reverses between increasing and decreasing, the control device of Patent Document 1 learns the fuel concentration of the purge gas based on the average value of the current correction value at the time of the current reversal and the previous correction value at the time of the previous reversal, and controls so as to reduce the amount of fuel injected from the fuel injection valve by the amount of fuel contained in the purge gas that is determined based on the learned fuel concentration. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-68360 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the opening of the purge valve is small, the timing at which the purge gas flows into the intake pipe varies depending on the negative pressure state of the intake passage. When the amount of purge gas is less than expected, if the fuel injector injects fuel based on the expected flow rate of purge gas, the fuel supplied to the combustion chamber will be insufficient, the engine torque will be low, and hesitation (engine sluggishness) may occur. On the other hand, when the amount of purge gas is more than expected, if the fuel injector injects fuel based on the expected flow rate of purge gas, the fuel supplied to the combustion chamber will be excessive, the engine torque will be high, and shock may occur.

[0006] The present invention has been made in consideration of the above-mentioned problems, and has an object to suppress fluctuations in engine torque. [Means for solving the problem]

[0007] The present invention provides an evaporative fuel control device for a vehicle including a canister for temporarily adsorbing evaporative fuel, a purge passage for supplying purge gas containing evaporative fuel purged from the canister to an intake passage of an engine, and an adjusting valve for adjusting the flow rate of the purge gas supplied to the intake passage through the purge passage, the device comprising: a correction means for performing correction control to reduce the amount of fuel injected from a fuel injector by the amount of fuel equivalent to the amount of evaporative fuel contained in the purge gas; and a learning means for learning the opening of the adjusting valve when the air-fuel ratio fluctuates when the opening of the adjusting valve is equal to or less than a predetermined opening, wherein the correction means determines whether to prohibit or continue the correction control depending on the direction in which the air-fuel ratio fluctuates with respect to the stoichiometric air-fuel ratio when the air-fuel ratio fluctuates and the opening of the adjusting valve is equal to or less than the opening learned by the learning means. Effect of the Invention

[0008] According to the present invention, fluctuations in engine torque can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing a schematic configuration of a vehicle equipped with a control device for evaporated fuel; [Diagram 2] FIG. 2 is a diagram illustrating an example of a functional configuration of a control device. [Diagram 3] 5 is a flowchart showing an example of a process performed by a control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The embodiment according to the present invention is a control device 60 for evaporative fuel in a vehicle including a canister 52 for temporarily adsorbing evaporated fuel, a purge passage 54 for supplying purge gas containing evaporated fuel purged from the canister 52 to the intake passage 20 of the engine 10, and a regulating valve 55 for adjusting the flow rate of the purge gas supplied to the intake passage 20 through the purge passage 54, and includes a correction means for performing correction control to reduce the amount of fuel injected from the fuel injector 23 by the amount of evaporated fuel contained in the purge gas, and a learning means for learning the opening degree of the regulating valve 55 when the air-fuel ratio fluctuates when the regulating valve 55 is equal to or smaller than a predetermined opening degree. When the air-fuel ratio fluctuates and the opening degree of the regulating valve 55 is equal to or smaller than the opening degree learned by the learning means, the correction means determines whether to prohibit or continue the correction control depending on the direction in which the air-fuel ratio fluctuates with respect to the theoretical air-fuel ratio. In this way, by determining whether to prohibit or continue the correction control depending on the direction in which the air-fuel ratio varies with respect to the stoichiometric air-fuel ratio, it is possible to suppress variations in engine torque. EXAMPLES

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a diagram showing a schematic configuration of a vehicle 1 equipped with a fuel vapor control device (hereinafter, referred to as the control device) according to this embodiment. Note that Fig. 1 is simplified for the sake of convenience in explaining this embodiment, and components that are normally equipped in a vehicle are assumed to be equipped even if they are not shown in the figure. A vehicle 1 according to the embodiment includes an engine 10 as an internal combustion engine, an intake passage 20, an exhaust passage 30, a fuel tank 40, an atmospheric pressure sensor 41, an accelerator opening sensor 42, and the like.

[0012] The engine 10 performs a series of strokes consisting of an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke. The engine 10 has a combustion chamber 12 in which a piston 11 is housed so as to be capable of reciprocating, an ignition plug 13 disposed within the combustion chamber 12, an intake valve 15 positioned between the combustion chamber 12 and an intake port 14, an exhaust valve 17 positioned between the combustion chamber 12 and an exhaust port 16, etc. The configuration of the engine 10 is not particularly limited, and various known engines can be applied.

[0013] The intake passage 20 is a passage that guides intake air taken in from outside the vehicle 1 to the combustion chamber 12 via the intake port 14. The intake passage 20 is formed, for example, by an intake pipe. In the intake passage 20, a throttle valve 21, a surge tank 22, and a fuel injector 23 are arranged in this order from the upstream side.

[0014] The throttle valve 21 adjusts the flow rate of the intake air by opening and closing. The throttle valve 21 adjusts the flow rate of the intake air based on the control of the control device 60. The surge tank 22 temporarily stores the intake air, and then straightens and guides the intake air to the combustion chamber 12. An intake pressure sensor 24 is disposed in the surge tank 22. The intake pressure sensor 24 transmits information about the detected intake pressure to the control device 60. Fuel injector 23 injects fuel pumped from fuel tank 40 into intake passage 20. Fuel injector 23 adjusts the amount of fuel injected under the control of control device 60. Note that fuel injector 23 is not limited to injecting fuel into intake passage 20, and may be configured to inject fuel into combustion chamber 12.

[0015] The exhaust passage 30 is a passage through which exhaust gas combusted in the combustion chamber 12 is exhausted to the outside of the vehicle 1 via the exhaust port 16. The exhaust passage 30 is formed, for example, by an exhaust pipe. An air-fuel ratio sensor 31 is disposed in the exhaust passage 30. The air-fuel ratio sensor 31 transmits information on the detected air-fuel ratio of the exhaust gas to the control device 60.

[0016] Fuel tank 40 stores liquid fuel to be supplied to fuel injector 23. Note that within fuel tank 40, evaporated fuel is generated from the liquid fuel. The atmospheric pressure sensor 41 transmits information about the detected atmospheric pressure to the control device 60 . The accelerator opening sensor 42 transmits to the control device 60 information on the detected amount of accelerator pedal operation by the driver.

[0017] The vehicle 1 also includes an evaporated fuel supply system 50 for supplying evaporated fuel (vapor) to the intake passage 20 without discharging it into the atmosphere. The evaporated fuel supply system 50 includes a vapor passage 51, a canister 52, a purge passage 54, a regulating valve 55, and the like.

[0018] The vapor passage 51 is a passage that guides the evaporated fuel generated in the fuel tank 40 to the canister 52. The vapor passage 51 is formed of a pipe that connects the fuel tank 40 and the canister 52 to each other. The canister 52 temporarily adsorbs the evaporated fuel generated in the fuel tank 40. The canister 52 has activated carbon as an adsorbent therein, and adsorbs the evaporated fuel that flows in from the fuel tank 40 through the vapor passage 51. The canister 52 is also open to the atmosphere through an atmospheric passage 53.

[0019] The purge passage 54 is a passage that supplies purge gas containing evaporated fuel purged from the canister 52 to the intake passage 20 of the engine 10. The purge passage 54 is formed of a pipe that communicates between the canister 52 and the intake passage 20. Here, the purge passage 54 is configured to be connected to the intake passage 20 between the throttle valve 21 and the surge tank 22, but may be configured to be connected to the surge tank 22. The regulating valve 55 regulates the flow rate of the purge gas supplied to the intake passage 20 through the purge passage 54. The regulating valve 55 is disposed midway through the purge passage 54. The regulating valve 55 regulates the flow rate of the purge gas based on the control of the control device 60.

[0020] In the evaporated fuel supply system 50, evaporated fuel generated in the fuel tank 40 is guided to the canister 52 through a vapor passage 51 and temporarily adsorbed by the canister 52. When the engine 10 starts, the intake passage 20 becomes negative pressure, so that by opening the regulating valve 55, purge gas containing evaporated fuel purged from the canister 52 is supplied to the intake passage 20 through a purge passage 54. The purge gas supplied to the intake passage 20 mixes with a mixture of the intake air taken in through the throttle valve 21 and the fuel injected from the fuel injector 23, and flows into the combustion chamber 12. Therefore, the evaporated fuel contained in the purge gas is burned in the combustion chamber 12, so that the evaporated fuel can be prevented from being discharged from the fuel tank 40 into the atmosphere.

[0021] The vehicle 1 also includes a control device 60. The control device 60 controls the entire vehicle 1. For example, an ECU (Electronic Control Unit) can be used as the control device 60. The control device 60 has a CPU, a ROM, a RAM, and the like as a hardware configuration. The ROM stores programs and predetermined information for controlling the engine 10, the evaporative fuel supply system 50, and the like in advance. The RAM is a work memory that temporarily stores programs and data. The CPU reads out the programs stored in the ROM, expands them in the RAM, and executes them to control the engine 10, the evaporative fuel supply system 50, and the like.

[0022] FIG. 2 is a diagram illustrating an example of a functional configuration of the control device 60. As shown in FIG. The control device 60 includes a valve control unit 61 , a concentration learning unit 62 , an opening degree learning unit 63 , and a correction unit 64 . The valve control unit 61 controls the flow rate of the purge gas supplied to the intake passage 20 by controlling the opening and closing of the regulating valve 55 .

[0023] The concentration learning unit 62 learns the vapor concentration of the purge gas supplied to the intake passage 20 by opening the regulating valve 55. The vapor concentration is the ratio of evaporated fuel contained in the purge gas. Since the vapor concentration varies depending on the amount of evaporated fuel adsorbed in the canister 52 and varies depending on the environment of the vehicle 1, the concentration learning unit 62 updates the vapor concentration by learning at each sampling time. Specifically, the concentration learning unit 62 instructs the valve control unit 61 to control the adjustment valve 55 so that a constant amount of purge gas is supplied to the intake passage 20. Next, the concentration learning unit 62 controls the amount of fuel injected from the fuel injector 23, etc., so that the air-fuel ratio becomes a target air-fuel ratio (for example, a theoretical air-fuel ratio) based on information on the air-fuel ratio detected by the air-fuel ratio sensor 31. At this time, the mixture flowing into the combustion chamber 12 contains the evaporated fuel in the purge gas in addition to the fuel injected from the fuel injector 23, so that a difference occurs between the actual air-fuel ratio detected by the air-fuel ratio sensor 31 and the target air-fuel ratio. The difference (deviation amount) between the actual air-fuel ratio and the target air-fuel ratio is due to the amount of evaporated fuel in the purge gas. Therefore, the concentration learning unit 62 learns the vapor concentration (the ratio of evaporated fuel contained in the purge gas) based on information on the difference between the actual air-fuel ratio and the target air-fuel ratio.

[0024] The opening learning unit 63 learns the opening of the regulating valve 55 in the case where the air-fuel ratio fluctuates when the regulating valve 55 is equal to or smaller than a predetermined opening. The correction unit 64 performs correction control to correct the injection amount when the fuel is injected from the fuel injector 23, based on the learned purge concentration, so that the actual air-fuel ratio becomes the target air-fuel ratio. Specifically, the correction unit 64 performs purge control to supply purge gas to the intake passage 20 by instructing the regulating valve 55 to open via the valve control unit 61. At this time, the correction unit 64 acquires information on the flow rate of the purge gas to be supplied to the intake passage 20 based on the current opening degree of the regulating valve 55 and the like. Next, the correction unit 64 calculates and acquires the amount of evaporated fuel contained in the purge gas from the flow rate of the purge gas and the learned vapor concentration. Next, the correction unit 64 performs correction control to correct the injection amount that needs to be injected from the fuel injector 23 according to the operation amount of the accelerator pedal detected by the accelerator opening sensor 42 by reducing the amount of evaporated fuel (fuel amount) calculated from the learned vapor concentration. In this way, by performing correction control to correct the injection amount injected from the fuel injector 23, the engine 10 can be operated so that the actual air-fuel ratio becomes the target air-fuel ratio.

[0025] Next, an example of processing by the control device 60 will be described with reference to the flowcharts of Figures 3(a) and (b). The flowcharts of Figures 3(a) and (b) are realized, for example, by the ECU, which is the control device 60, executing a program.

[0026] First, an example of a process in which the control device 60 learns the opening degree of the regulating valve 55 when the air-fuel ratio fluctuates will be described with reference to the flowchart of Fig. 3(a). The flowchart of Fig. 3(a) is started by the concentration learning unit 62 learning the vapor concentration. It is also assumed here that the valve control unit 61 opens the regulating valve 55 to supply purge gas to the intake passage 20, and the correction unit 64 performs correction control based on the vapor concentration learned by the concentration learning unit 62.

[0027] In S10, the opening degree learning unit 63 determines whether the opening degree of the regulating valve 55 is equal to or less than a predetermined opening degree. For example, the opening degree learning unit 63 can obtain information on the current opening degree of the regulating valve 55 by obtaining a control signal when the valve control unit 61 controls the regulating valve 55. In this way, the reason why it is determined whether the opening degree of the regulating valve 55 is equal to or less than a predetermined opening degree is that if the opening degree of the regulating valve 55 is equal to or less than the predetermined opening degree, there is a possibility that the flow rate of the purge gas may vary. Note that information on the predetermined opening degree is stored in advance in the control device 60. If it is equal to or less than the predetermined opening degree, the process proceeds to S11, and if it is greater than the predetermined opening degree, the process of the flowchart in FIG. 3(a) ends.

[0028] In S11, the opening degree learning section 63 determines whether or not there is a fluctuation in the air-fuel ratio. When the correcting unit 64 corrects and controls the air-fuel ratio to be the stoichiometric air-fuel ratio, and the actual air-fuel ratio fluctuates from the stoichiometric air-fuel ratio to the lean side or rich side by a predetermined amount or more, it is determined that the air-fuel ratio has fluctuated. Information on the predetermined amount of fluctuation is stored in the control device 60 in advance. If the air-fuel ratio has fluctuated, the process proceeds to S12, and if there is no fluctuating, the process of the flowchart in FIG. 3(a) is terminated.

[0029] In S12, the opening learning unit 63 learns information on the current opening of the regulating valve 55. Specifically, the opening learning unit 63 can learn the opening of the regulating valve 55 at which the air-fuel ratio varies by storing the information on the opening of the regulating valve 55 acquired in S10. Even if the opening of the regulating valve 55 at which the air-fuel ratio varies is set in advance, variations occur in the opening and closing of the regulating valve 55 due to individual differences in the regulating valve 55. By learning the opening of the regulating valve 55 at which the air-fuel ratio varies as in S12, the variations due to the individual differences in the regulating valve 55 can be absorbed, and the accuracy of the information on the opening when the air-fuel ratio varies can be improved. When S12 ends, the process of the flowchart in FIG.

[0030] Next, an example of a process in which the control device 60 performs correction control to suppress the fluctuation of the engine torque will be described with reference to Fig. 3(b). Here, it is assumed that the opening degree of the regulating valve 55, which causes the air-fuel ratio to fluctuate, is learned by completing the process of the flowchart in Fig. 3(a). In S20, the valve control unit 61 opens the regulating valve 55 to supply purge gas to the intake passage 20, and the correction unit 64 performs correction control based on the vapor concentration learned by the concentration learning unit 62.

[0031] In S21, the correction unit 64 judges whether or not there is a fluctuation in the air-fuel ratio. This process is the same as S11 described above. That is, it judges whether or not the actual air-fuel ratio has fluctuated from the theoretical air-fuel ratio to the lean side or rich side by a predetermined amount or more. If there is a fluctuation in the air-fuel ratio, the process proceeds to S22, and if there is no fluctuation, the process of the flowchart in FIG. 3(b) is terminated.

[0032] In S22, the correction unit 64 judges whether the opening degree of the regulating valve 55 is equal to or less than the learned opening degree. Specifically, the correction unit 64 acquires information on the current opening degree of the regulating valve 55, that is, the opening degree of the regulating valve 55 when the air-fuel ratio fluctuates by a predetermined amount or more, and compares the acquired opening degree of the regulating valve 55 with the learned opening degree. If the opening degree of the regulating valve 55 is equal to or less than the learned opening degree, the process proceeds to S23, and if it is greater than the learned opening degree, the process of the flowchart in FIG. 3(b) is terminated.

[0033] Next, in the processing from S23 to S25, the correction unit 64 determines whether to prohibit or continue the correction control for reducing the amount of fuel injected from the fuel injector 23 by the amount of evaporated fuel contained in the purge gas, depending on the direction in which the actual air-fuel ratio fluctuates relative to the theoretical air-fuel ratio. In S23, the correction unit 64 determines whether the air-fuel ratio has changed to the lean side or to the rich side. Specifically, the correction unit 64 determines whether the air-fuel ratio determined in S21 has changed to the leaner side or the richer side of the stoichiometric air-fuel ratio. Here, a change to the leaner side corresponds to a case where the amount of purge gas is less than expected, and a change to the richer side corresponds to a case where the amount of purge gas is more than expected. If the air-fuel ratio fluctuates to the lean side, the correction unit 64 determines to prohibit the correction control and proceeds to S24. On the other hand, if the air-fuel ratio fluctuates to the rich side, the correction unit 64 determines to continue the correction control and proceeds to S25.

[0034] In S24, the correction unit 64 prohibits the correction control. Specifically, the correction unit 64 injects the fuel amount of the evaporated fuel contained in the purge gas without reducing the injection amount of the fuel injected from the fuel injector 23. Here, the case where the process proceeds from S23 to S24 is a case where the purge gas is less than expected. Therefore, if the correction control for reducing the injection amount of the fuel injected from the fuel injector 23 is continued, the fuel supplied to the combustion chamber 12 may become insufficient, the engine torque may decrease, and hesitation may occur. For this reason, the correction control is prohibited in S24 and the injection amount of the fuel injected from the fuel injector 23 is not reduced, so that the fuel supplied to the combustion chamber 12 is not insufficient. By prohibiting the correction control in this way, the engine torque is not decreased, and the occurrence of hesitation can be suppressed.

[0035] In S25, the correction unit 64 continues the correction control. Specifically, the correction unit 64 reduces the injection amount of fuel injected from the fuel injector 23 by the amount of fuel vapor contained in the purge gas and injects the reduced amount. Here, the process proceeds from S23 to S25 when the amount of purge gas is greater than expected. Therefore, if the correction control for reducing the injection amount of fuel injected from the fuel injector is prohibited, the fuel supplied to the combustion chamber 12 becomes excessive, the engine torque becomes high, and a shock may occur. For this reason, the correction control is continued in S25 to reduce the injection amount of fuel injected from the fuel injector 23, so that the fuel supplied to the combustion chamber 12 does not become excessive. By continuing the correction control in this manner, the engine torque does not become high, and the occurrence of a shock can be suppressed.

[0036] In addition, in S25, in order to further suppress the occurrence of shock, it is preferable that the correction unit 64 reduces the amount of fuel injected from the fuel injector 23 by more than that of normal correction control. For example, the correction unit 64 reduces the amount of fuel injected from the fuel injector 23 in accordance with the amount of fluctuation of the air-fuel ratio to the rich side in S21. That is, it is preferable that the correction unit 64 reduces the amount of fuel injected from the fuel injector 23 as the amount of fluctuation of the air-fuel ratio to the rich side in S21 increases. When S24 and S25 are completed, the process of the flowchart in Fig. 3(b) is completed. Note that the control device 60 can continuously suppress the fluctuation of the engine torque by periodically performing the process of the flowchart in Fig. 3(b).

[0037] As described above, according to this embodiment, when the air-fuel ratio fluctuates and the opening of the regulating valve 55 is equal to or smaller than the opening learned by the opening learning unit 63, the correction unit 64 of the control device 60 determines whether to prohibit or continue the correction control depending on the direction in which the air-fuel ratio fluctuates with respect to the stoichiometric air-fuel ratio. In this way, by determining whether to prohibit or continue the correction control depending on the direction in which the air-fuel ratio fluctuates with respect to the stoichiometric air-fuel ratio, it is possible to suppress fluctuations in engine torque.

[0038] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and modifications and the like are possible within the scope of the present invention. [Explanation of symbols]

[0039] 1: vehicle 10: engine 11: piston 12: combustion chamber 13: spark plug 14: intake port 16: exhaust port 20: intake passage 21: throttle valve 22: surge tank 23: fuel injector 24: intake pressure sensor 30: exhaust passage 31: air-fuel ratio sensor 40: fuel tank 52: canister 54: purge passage 55: regulating valve 60: control device 61: valve control section 62: concentration learning section 63: opening degree learning section 64: correction section

Claims

1. A canister that temporarily absorbs evaporated fuel; a purge passage for supplying purge gas containing evaporated fuel purged from the canister to an intake passage of an engine; a regulating valve for regulating a flow rate of purge gas supplied to the intake passage through the purge passage, a correction means for performing a correction control to reduce an injection amount of fuel injected from a fuel injector by an amount of evaporated fuel contained in the purge gas; and a learning means for learning the opening degree of the regulating valve when the air-fuel ratio varies when the opening degree of the regulating valve is equal to or smaller than a predetermined opening degree, The correction means is A control device for evaporated fuel characterized in that, when the air-fuel ratio fluctuates and the opening degree of the regulating valve is equal to or less than the opening degree learned by the learning means, it is determined whether to prohibit or continue the correction control depending on the direction in which the air-fuel ratio fluctuates with respect to the stoichiometric air-fuel ratio.

2. The correction means is 2. The control device for evaporated fuel according to claim 1, wherein the correction control is prohibited when the air-fuel ratio fluctuates toward the lean side with respect to the theoretical air-fuel ratio and the opening degree of the regulating valve is equal to or smaller than the opening degree learned by the learning means.

3. The correction means is 3. The control device for evaporated fuel as claimed in claim 1, wherein when the air-fuel ratio fluctuates to the rich side of the theoretical air-fuel ratio and the opening degree of the regulating valve is equal to or less than the opening degree learned by the learning means, the correction control is continued.

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