Processing device for vaporized fuel for a turbocharged internal combustion engine and control method for this

Abstract

Processing device (3) for vaporized fuel for a turbocharged internal combustion engine (1) comprising a compressor (2a) of a turbocharging device (2) and a throttle valve (6) in an intake manifold (4), - wherein the processing device (3) for vaporized fuel comprises: - a container (8) that receives evaporated fuel produced in a fuel tank (7); - a flushing control valve (12) that sets a flushing flow rate from the container (8); - a first purge path (21) extending from a downstream side of the purge control valve (12) to the intake pipe (4) on a downstream side of the throttle valve (6); - a second purge path (22) extending from the downstream side of the purge control valve (12) to an ejector (17), the ejector (17) being provided in a return pipe (15) which provides a connection between the intake pipe (4) on a downstream side of the compressor (2a) and the intake pipe (4) on an upstream side of the compressor (2a); and - a control unit (14) that controls the flushing control valve (12) based on control characteristic curve data, - wherein the control unit (14): - switches the control characteristic data between first control characteristic data for the first flushing path (21) and second control characteristic data for the second flushing path (22) when the first flushing path (21) and the second flushing path (22) are switched, and - increases the amount of fuel injected into the internal combustion engine (1) when the first purge path (21) and the second purge path (22) are switched.

Description

Application area

[0001] The present invention relates to processing devices for vaporized fuel for turbocharged internal combustion engines and to control methods therefor. In particular, the present invention relates to processing devices for vaporized fuel comprising a path by which vaporized fuel in a container is flushed into an intake pipe upstream of a compressor through an ejector which generates a vacuum using a compressed air stream, and to a control method therefor. State of the art

[0002] Patent document 1 discloses a processing device for evaporated fuel, comprising: a passage for evaporated fuel connecting a container and an intake passage on the upstream side of a compressor of a charging device; and an ejector provided in the passage for evaporated fuel, which flushes the evaporated fuel from the container using a differential pressure between the upstream and downstream sides of the compressor. Reference Document List Patent Document

[0003] Patent document 1: JP 2016- 176 390 A

[0004] JP 2016-176390A concerns a control unit for an internal combustion engine. The engine includes a supercharger, a three-way catalytic converter, a canister, a vaporized fuel channel, an ejector, and a purge control valve. The control unit includes an ECU configured to decrease the purge control valve's opening degree in response to a pressure increase on the downstream side of the supercharger during lean-burn operation. This is a range in which the engine's operating air-fuel ratio is leaner than its theoretical air-fuel ratio, and in which the downstream pressure of the supercharger is higher than the upstream pressure.

[0005] JP 2017-031 936 A discloses an engine control device configured to accurately estimate the pressure of a branch section between a first branch channel and a second branch channel in a purge channel. An ECU is equipped with a first pressure acquisition section that receives a first pressure, which is the pressure at a downstream end of a first branch passage; a second pressure acquisition section that receives a second pressure, which is the pressure at a downstream end of a second branch passage; and an estimating section that estimates the branch section pressure, which is the pressure of a branch section between the first branch channel and the second branch channel in a purge channel, based on the first and second pressures.

[0006] German patent DE 10 2016 110 097 A1 describes systems and methods for controlling the purging operation of a fuel vapor reservoir in a boost-pressure engine. The method involves purging stored fuel vapors from the fuel vapor reservoir to a compressor inlet via an ejector, bypassing a reservoir purge valve. The ejector is coupled to the fuel vapor reservoir via a separate channel located upstream of the reservoir purge valve, and the flow through the ejector can be controlled by a shut-off valve. The shut-off valve can be adjusted based on whether the engine is operating at boost pressure or not.

[0007] JP H07-238872A discloses a vaporized fuel processor designed to ensure high-volume scavenging during high-load operation of an engine. A Venturi tube section is formed upstream of a throttle valve in an intake manifold connected to an engine. A scavenging channel from a canister opens into part of the Venturi tube. Thus, a high vacuum is generated in the Venturi tube section during high-load operation, ensuring a sufficient scavenging volume. Summary of the invention: Problem to be solved by the invention

[0008] In a case where a processing device for evaporated fuel is provided with a first purge path through which evaporated fuel in a container is purged into an intake pipe on the downstream side of a throttle valve, and with a second purge path through which evaporated fuel in the container is purged into the intake pipe on the upstream side of a compressor by means of an ejector that creates a vacuum using a compressed air stream, there is a possibility of deterioration in the drivability and exhaust characteristics of the internal combustion engine if the purge flow rate is not precisely controlled, whichever path is used to purge the evaporated fuel.

[0009] The present invention was made with these conventional circumstances in mind. One object of the present invention is to provide a processing device for vaporized fuel for a turbocharged internal combustion engine and a control method therefor, which are capable of controlling the scavenging flow rate with high accuracy, regardless of whether a first or second scavenging path is used for scavenging vaporized fuel. Setup for solving the problem

[0010] The problem underlying the invention is solved according to the invention in processing devices for vaporized fuel by the features of claim 1 and alternatively by the features of claim 2, and in control methods for a processing device for vaporized fuel by the features of claim 7 and alternatively by the features of claim 8. Advantageous embodiments are the subject of the respective dependent claims.

[0011] According to one aspect of the present invention, a control unit switches, among other things, control characteristic curve data between first control characteristic curve data for the first flushing path and second control characteristic curve data for the second flushing path when the first flushing path and the second flushing path are switched.

[0012] According to a first aspect of the present invention, the amount of fuel injected into the internal combustion engine is increased when the first purge path and the second purge path are switched.

[0013] According to an alternative second aspect of the present invention, the purge control valve is controlled on the basis of an estimated value of a concentration for evaporated fuel, and an update of the estimated value of the concentration for evaporated fuel is limited for use in controlling the purge control valve when the first purge path and the second purge path are switched. Effects of the invention

[0014] According to the present invention, it is possible to control the purge flow rate with high accuracy, regardless of whether the first or second purge path is used to purge the evaporated fuel, and thus it is possible to suppress the deterioration of the driving performance and exhaust gas characteristics of the internal combustion engine, even when the purge paths are switched. Brief description of the drawings Fig. Figure 1 is a system configuration view of an internal combustion engine according to an embodiment of the present invention. Fig. Figure 2 is a diagram showing the relationship between an intake manifold pressure and a pressure generated by an ejector according to the embodiment of the present invention. Fig. Figure 3 is a diagram showing the relationship between the intake manifold pressure and a purge flow rate according to the embodiment of the present invention. Fig. Figure 4 is a flowchart representing a drive control of a flushing control value according to an embodiment of the present invention. Fig. Figure 5 is a time sequence diagram to illustrate a change in the air-fuel ratio caused when purge paths are switched according to the embodiment of the present invention. Fig. Figure 6 is a time sequence diagram to illustrate a fuel quantity increase correction to suppress the change in the air-fuel ratio caused when the purge paths are switched according to the embodiment of the present invention. Fig. Figure 7 is a flowchart illustrating the fuel quantity increase correction that is performed when the purge paths are switched according to the embodiment of the present invention. Fig. Figure 8 is a time sequence diagram to illustrate a change in the estimated concentration caused when the rinsing paths are switched according to the embodiment of the present invention. Fig. Figure 9 is a time sequence diagram to illustrate a limitation of an update of the estimated concentration that is performed when the flushing paths are switched according to the embodiment of the present invention. Fig. Figure 10 is a flowchart illustrating a process for limiting an update of the estimated concentration that is performed when the rinsing paths are switched, according to the embodiment of the present invention. Implementation of the invention

[0015] The following describes embodiments of a processing device for vaporized fuel for a turbocharged internal combustion engine and a control method for it according to the present embodiment with reference to the accompanying drawings.

[0016] Fig. Figure 1 is a representation that depicts one aspect of the turbocharged internal combustion engine with the vaporized fuel processing device.

[0017] An internal combustion engine 1, which is in Fig. The assembly shown in Figure 1 comprises a turbocharger 2, which serves as a charging device, and a processing device 3 for vaporized fuel. The internal combustion engine 1 is attached to the vehicle.

[0018] In an intake pipe 4 of the internal combustion engine 1, a compressor 2a of the turbocharger 2, an intercooler 5 and a throttle valve 6 are provided in this order upstream.

[0019] The turbocharger 2 consists of a compressor 2a and a turbine (not shown). The exhaust gas flowing through an exhaust pipe rotates the turbine, which in turn rotates the compressor 2a connected to the turbine via a common shaft. This causes the compressor 2a to compress the intake air flowing through the exhaust pipe 4 and supply the compressed air to the combustion engine 1.

[0020] The turbocharger 2 is an example of a supercharging device. The internal combustion engine 1 can be equipped with a turbocharger, which is a supercharging device that drives a compressor by power supplied by a crankshaft.

[0021] The charge air cooler 5 cools the intake air compressed by the compressor 2a, that is, the compressed air.

[0022] The throttle valve 6 adjusts the amount of intake air drawn into the combustion engine 1 by adjusting the opening range of the intake pipe 4.

[0023] The processing device 3 for vaporized fuel flushes vaporized fuel produced in a fuel tank 7 into the intake pipe 4 of the internal combustion engine 1.

[0024] A container 8 is a device in which an adsorbent, such as activated carbon, which can adsorb and desorb the vaporized fuel, is filled into a housing.

[0025] Container 8 and fuel tank 7 are connected via a pipe 9 for vaporized fuel. The vaporized fuel produced in fuel tank 7 reaches container 8 via the pipe 9 for vaporized fuel and is adsorbed onto the adsorbent in container 8.

[0026] Container 8 is open to the atmosphere via a pipe 10.

[0027] Furthermore, the container 8 is connected to the intake pipe 4 on the downstream side of the throttle valve 6 by a first purge pipe 11.

[0028] The first flushing pipe 11 is equipped with a flushing control valve 12 and a first check valve 13 in this order from the container 8.

[0029] The flushing control valve 12 is a solenoid valve whose opening degree is controlled by an electrical signal output by an electronic control unit 14.

[0030] The electronic control unit 14 comprises a microcomputer equipped with a CPU, ROM, RAM, and the like. The electronic control unit 14, for example, controls the excitation of the flushing control valve 12 via a PWM controller to regulate the opening degree of the flushing control valve 12 and thus adjust the flushing flow rate.

[0031] The first check valve 13 is a mechanical valve that opens and closes based on a differential pressure between the upstream and downstream sides of the first check valve 13. The first check valve 13 opens when the intake manifold pressure IP, which is the pressure in the intake manifold 4 at the downstream side of the throttle valve 6, becomes negative and suction force is applied to the valve body.

[0032] The first purge pipe 11, which is equipped with the first check valve 13, forms a first purge path 21. That is, the first purge path 21 extends from the downstream side of the purge control valve to the intake pipe 4 on the downstream side of the throttle valve 6 and uses the vacuum in the intake pipe 4 on the downstream side of the throttle valve 6 to purge the vaporized fuel from the reservoir 8.

[0033] Furthermore, a return pipe 15 is provided, which provides a connection between the intake pipe 4 on the downstream side of the compressor 2a and the intake pipe 4 on the upstream side of the compressor 2a.

[0034] A nozzle section 15a is provided in the middle of the return pipe 15. The return pipe 15, which is arranged downstream of a nozzle section 15a, and the first flushing pipe 11, which is arranged between the flushing control valve 12 and the first check valve 13, are connected via a second flushing pipe 16.

[0035] The inner diameter of the nozzle area 15a gradually decreases towards the upstream side of the compressor 2a. This accelerates the compressed air flowing from the intake pipe 5 on the downstream side of the compressor 2a to the intake pipe 4 on the upstream side of the compressor 2a.

[0036] Subsequently, a static vacuum is created in the second purge pipe 16 by the flow of high-speed air injected from the nozzle area 15a, and air in the second purge pipe 16 is drawn into the flow of compressed air by the static pressure. Then the compressed air and the air in the second purge pipe 16 are discharged on the upstream side of the compressor 2a.

[0037] This means that an ejector 17 consists of the nozzle section 15a and the second purge pipe 16, which are connected on the downstream side of the nozzle section 15a. The vaporized fuel is purged from the container 8 by the negative pressure generated by the ejector 17.

[0038] A second check valve 18 is provided in the middle of the second flushing pipe 16.

[0039] Similar to the first check valve 13, the second check valve 18 is a mechanical valve that opens and closes based on a differential pressure between the upstream and downstream sides of the second check valve 18. The second check valve 18 opens when the pressure generated by the ejector 17 becomes negative and suction is applied to the valve body.

[0040] The second flushing pipe 16, which is equipped with the second check valve 18, and an ejector 17 of the return pipe 15 form a second flushing path 22.

[0041] This means that the second flushing path 22 extends from the downstream side of the flushing control valve 12 to the ejector 17, which is provided in the return pipe 15, which provides a connection between the suction pipe 4 on the downstream side of the compressor 2a and the suction pipe 4 on the upstream side of the compressor 2a.

[0042] The second purge path 22 uses the vacuum created by the ejector 17 to purge the evaporated fuel from the container 8.

[0043] The vaporized fuel, which is adsorbed on the adsorbent of the container 8, is desorbed by the adsorbent into the air, which is introduced into the container 8 from the atmosphere through the pipe 10, by the intake pipe vacuum or the vacuum generated by the ejector 17, and afterwards the desorbed vaporized fuel is flushed through the first purge path 21 or second purge path 22 to the intake pipe 4.

[0044] This means that when the first check valve 13 is open, the vaporized fuel adsorbed on the adsorbent of the container 8 is flushed through the first purge path 21 on the downstream side of the throttle valve 6 into the intake pipe 4, while when the second check valve 18 is open, the vaporized fuel adsorbed on the adsorbent of the container 8 is flushed through the second purge path 22 on the downstream side of the compressor 2a into the intake pipe 4.

[0045] Here, the intake manifold pressure IP, which is the pressure in the intake manifold 4 on the downstream side of the throttle valve 6, increases when the load of the internal combustion engine increases, changing from a vacuum to a positive pressure. On the other hand, the ejector 17 generates a greater vacuum when the load of the internal combustion engine, i.e., the boost pressure, increases.

[0046] In the vaporized fuel processing device 3, the first check valve 13 opens and the second check valve 18 closes when the suction force acting on the first check valve 13 is greater than the suction force acting on the second check valve 18; in other words, when the intake manifold pressure IP is less than the pressure generated by the ejector 17. Conversely, the first check valve 13 closes and the second check valve 18 opens when the suction force acting on the second check valve 18 is greater than the suction force acting on the first check valve 13; in other words, when the pressure generated by the ejector 17 is less than the intake manifold pressure IP.

[0047] Thus, in the processing device 3 for vaporized fuel, in response to an increase in the load of the internal combustion engine, the state in which the vaporized fuel is purged through the first purge path 21 is switched to the state in which the vaporized fuel is purged through the second purge path 22.

[0048] Fig. Figure 2 is a diagram showing the relationship between the pressure ENP generated by the ejector 17 and the intake manifold pressure IP at the downstream side of the throttle valve 6.

[0049] The ejector 17 creates a vacuum before the intake manifold pressure IP at the downstream side of the throttle valve 6 reaches atmospheric pressure, and creates a greater vacuum as the intake manifold pressure IP at the downstream side of the throttle valve 6 increases.

[0050] Therefore, there is a point at which the intake manifold pressure IP at the downstream side of the throttle valve 6 and the pressure ENP generated by the ejector 17 are equal. If the intake manifold pressure IP is less than this point of agreement IPs (IPs < 0), the first check valve 13 opens and the second check valve 18 closes, whereas if the intake manifold pressure IP is greater than the point of agreement IPs, the first check valve 13 closes and the second check valve 18 opens.

[0051] Fig. 3 represents a ratio between the intake manifold pressure IP at the downstream side of the throttle valve 6 and the purge flow rate in each of the purge paths 21 and 22.

[0052] In the first purge path 21, through which evaporated fuel is purged using the vacuum at the downstream side of the throttle valve 6, the purge flow rate decreases as the intake manifold pressure IP at the downstream side of the throttle valve 6 increases and approaches IPs, which is a pressure at which the purge paths are switched.

[0053] When the intake manifold pressure IP on the downstream side of the throttle valve 6 increases and reaches IPs, the first check valve 13 closes and the second check valve 18 opens. This causes the purging through the first purge path 21 to be shut off, and the vaporized fuel to be purged through the second purge path 22 instead of the first purge path 21.

[0054] The purge flow rate of the second purge path 22 increases when the intake pipe pressure IP increases from IPs, that is, when the pressure generated by the ejector 17 increases as a result of an increase in the amount of compressed air flowing back through the return pipe 15, which is caused by an increase in the boost pressure.

[0055] The electronic control unit 14 controls the opening degree of the purge control valve 12 and the fuel injection quantity of a fuel injector 19 on the basis of measurement signals from various sensors that detect the operating conditions of the internal combustion engine 1.

[0056] The internal combustion engine 1 comprises, as various sensors, a first pressure sensor 31, which measures a pressure UCP in the intake manifold 4 on the upstream side of the compressor 2a; a second pressure sensor 32, which measures a pressure DCP in the intake manifold 4 on the downstream side of the compressor 2a; a third sensor 33, which measures the intake manifold pressure IP, which is a pressure in the intake manifold 4 on the downstream side of the throttle valve 6; an airflow sensor 34, which measures the intake air quantity QA of the internal combustion engine 1; a rotation sensor, which measures a rotational speed NE of the internal combustion engine 1; an intake air temperature sensor 36, which measures the intake air temperature IAT of the internal combustion engine 1; and an air-fuel ratio sensor 37, which determines the air-fuel ratio AFR of the internal combustion engine 1 based on an oxygen concentration in the exhaust gas of the internal combustion engine 1. measures.

[0057] Here, the electronic control unit 14 compares the air-fuel ratio AFR measured by the air-fuel ratio sensor 37 with a target air-fuel ratio and calculates an air-fuel ratio correction factor AFHOS to correct the fuel injection quantity of the fuel injector 19, so that the air-fuel ratio AFR measured by the air-fuel ratio sensor approaches the target air-fuel ratio.

[0058] Then the electronic control unit 14, acting as a purge control, calculates an estimated value of the concentration of the evaporated fuel based on an air-fuel ratio correction factor AFHOS, sets a purge control ratio based on the estimated value of the concentration for the evaporated fuel, etc., and calculates a drive operating cycle in the PWM control of the purge control valve 12 based on a control purge ratio and a maximum purge ratio, which is a purge ratio in the fully open state of the purge control valve 12.

[0059] A flowchart of Fig. 4 represents a control processing of the flushing control valve 12, which is executed by the electronic control unit 14.

[0060] The control sequence, which is shown in the flowchart of Fig. The process shown in Figure 4 includes a step to compare the suction forces of the flushing paths to determine whether the first flushing path 21 or the second flushing path 22 is used for flushing, and a step to switch control characteristic data for use in the control of the flushing control valve 12 between first control characteristic data suitable for the first flushing path 21 and second control characteristic data suitable for the second flushing path 22, based on the determined flushing path.

[0061] In step S101, the electronic control unit 14 calculates an intake manifold pressure IP on the downstream side of the throttle valve 6 based on the measurement signal of the third pressure sensor 33.

[0062] In step S102, the electronic control unit 14 calculates the pressure ENP generated by the ejector 17.

[0063] The electronic control unit 14 calculates the pressure UCP in the intake pipe 4 on the upstream side of the compressor 2a on the basis of the measurement signal of the first pressure sensor 31 and calculates the pressure DCP in the intake pipe 4 on the downstream side of the compressor 2a on the basis of the measurement signal of the second pressure sensor 32.

[0064] Then the electronic control unit 14 calculates the pressure ENP generated by the ejector on the basis of a difference between the pressure UCP in the intake pipe 4 on the upstream side of the compressor 2a and the pressure DCP in the intake pipe 4 on the downstream side of the compressor 2a, that is, a differential pressure between the upstream and downstream sides of the compressor 2a.

[0065] Furthermore, the electronic control unit 14 estimates the pressure DCP in the intake pipe 4 on the downstream side of the compressor 2a based on the load and speed of the combustion engine 1, the intake air temperature IAT and the like, and sets an estimated or measured value of the atmospheric pressure to be the pressure UCP in the intake pipe 4 on the upstream side of the compressor 2a in order to obtain the pressure ENP generated by the ejector 17 based on these pressure values.

[0066] Next, in step S103, the electronic control unit 14 determines whether the rinsing is carried out through the first rinsing path 21.

[0067] In step S103, the electronic control unit 14 compares the intake manifold pressure IP at the upstream side of the throttle valve 6 and the pressure ENP generated by the ejector 17.

[0068] If the pressure ENP generated by the ejector 17 is less than or equal to the pressure IP in the intake pipe 4 on the downstream side of the throttle valve 6, the electronic control unit 14 determines that the purging is carried out through the second purging path 22, whereas if the intake pipe pressure IP on the downstream side of the throttle valve 6 is less than the pressure ENP generated by the ejector, the electronic control unit 14 determines that the purging is carried out through the first purging path 21.

[0069] When rinsing is performed via the first rinsing path 21, the process proceeds to step S104, in which the electronic control unit 14 selects the control characteristic curve data stored for the first rinsing path 21 as control characteristic curve data for use in the control of the rinsing control valve 12.

[0070] The control characteristic data for the first purge path 21 are suitable for a condition in which purging is carried out via the first purge path 21, that is, a condition in which the suction force generated by the intake manifold pressure IP acts on the reservoir 8 on the downstream side of the throttle valve 6 to purge the vaporized fuel. The control characteristic data for the first purge path 21 have been pre-adapted through experiments and simulations and are stored in a memory of the electronic control unit 14.

[0071] On the other hand, if the flushing is carried out via the second flushing path 22, the process proceeds to step S105, in which the electronic control unit 14 selects the control characteristic curve data stored for the second flushing path 22 as control characteristic curve data for use in the control of the flushing control valve 12.

[0072] The control characteristic data for the second purge path 22 are suitable for a condition in which purging is performed through the second purge path 22, that is, a condition in which the suction force generated by the pressure ENP produced by the ejector 17 acts on the reservoir 8 to purge the vaporized fuel. The control characteristic data for the second purge path 22 are pre-adapted through experiments and simulations and stored in a memory of the electronic control unit 14. After selecting the control characteristic data in step S104 or step S105, the process proceeds to step S106, in which the electronic control unit 14 calculates the drive operating cycle using the selected control characteristic data and controls the purge control valve 12 via PWM control using the calculated drive operating cycle.

[0073] The control characteristic curve data mentioned above represent, for example, the relationship between the operating conditions, such as the purge flow rate and the intake vacuum, and the drive operating cycle, as shown in Fig. 4 shown.

[0074] In other words, the control characteristic data includes a conversion characteristic for converting information about a flushing state into an opening degree command of the flushing control valve 12.

[0075] Furthermore, the control characteristic data includes, for example: data representing a characteristic for obtaining the duty cycle of the negated component based on a differential pressure between atmospheric pressure and intake manifold vacuum and the battery voltage, which is the supply voltage; data representing a characteristic for obtaining a maximum scavenging flow rate based on a differential pressure between atmospheric pressure and intake manifold vacuum and the engine speed; a factor used to obtain the estimated value of the evaporated fuel concentration from the air-fuel ratio correction factor AFHOS; and a factor used to obtain the fuel correction quantity from the estimated value of the evaporated fuel concentration.

[0076] Each factor used for the aforementioned control characteristic curve data includes switching between filters in accordance with the flushing paths.

[0077] This means that the control characteristic curve data with a suitable value, which varies depending on whether the cleaning is carried out by the first flushing path 21 or by the second flushing distance 22, are selected in steps S104 and S105.

[0078] Because the electronic control unit 14 switches between the control characteristic curve data suitable for a case in which the purging is carried out through the first purging path 21 and those suitable for a case in which the purging is carried out through the second purging path 22, it is possible to control the purging flow rate with high accuracy, whichever path is used for purging, and it is possible to suppress the deterioration of the driving behavior and exhaust gas characteristics of the internal combustion engine 1 that could be caused by switching the purging paths.

[0079] In addition to the switching process of the control characteristic data, which is performed on the basis of the purge paths, the electronic control unit 14 can perform a fuel quantity increase correction to prevent the air-fuel ratio from becoming leaner due to a temporary interruption of the flow of vaporized fuel into the cylinder at the time of the purge path switchover.

[0080] The time graph of Fig. Figure 5 is a diagram to illustrate that the air-fuel ratio fluctuates when the purge paths are switched.

[0081] When the intake manifold pressure IP at the downstream side of the throttle valve 6 increases in response to the increase in the accelerator pedal opening degree, and the intake manifold pressure IP reaches or exceeds the IPs, the first check valve 13 closes and the second check valve 18 opens instead of the first check valve 13, so that in Fig. 5 the flushing path 21 is switched to the second flushing path 22.

[0082] At the time of switching between the purge paths, which is carried out in this manner, a delay can occur before the vaporized fuel flows through the purge path after the switchover and into the cylinder of the internal combustion engine, so that the air-fuel ratio may be temporarily leaner during the delay period. This leaner air-fuel ratio can cause torsional vibrations of the internal combustion engine 1.

[0083] To prevent the air-fuel ratio from becoming leaner, the electronic control unit 14 corrects the fuel injection quantity of the fuel injector 19 to increase the fuel injection quantity when the flow of vaporized fuel into the cylinder is temporarily interrupted as a result of the switching of the purge paths.

[0084] Fig. 5 represents an air-fuel ratio fluctuation that occurs during acceleration of the internal combustion engine 1, in which the first purge path 21 is switched to the second purge path 22; however, even during deceleration of the internal combustion engine 1, in which the second purge path 22 is switched to the first purge path 21, the air-fuel ratio becomes leaner during a deceleration period until the vaporized fuel flows through the switched first purge path 21 and into the cylinder of the internal combustion engine 1.

[0085] The time graph of Fig. Figure 6 represents the fuel correction quantity, the air-fuel ratio and the torsional vibrations in a case where the electronic control unit 14 performs the fuel injection quantity increase correction sequence at the time of switching the purge paths.

[0086] The electronic control unit 14 corrects the fuel injection quantity to increase it for a predetermined time using the switching point of the purge paths as a reference point.

[0087] This increases the injection quantity of fuel injector 19 when the flow of vaporized fuel into the cylinder is temporarily interrupted. Thus, the increased fuel injection quantity from fuel injector 19 compensates for the reduced flow of vaporized fuel into the cylinder. This prevents the air-fuel ratio from becoming leaner and thus avoids the torsional vibrations that can be caused by a leaner air-fuel ratio.

[0088] In the case of fuel quantity increase correction, the electronic control unit 14 can determine a time to start an increase in quantity based on the difference ΔNP between the intake manifold pressure IP at the downstream side of the throttle valve 6 and the pressure ENP generated by the ejector 17, and can variably adjust the increase period and / or the increase correction quantity based on the rate of change of the difference ΔNP.

[0089] This means that the electronic control unit 14 begins to increase the amount of fuel at the time when the difference ΔNP becomes less than or equal to a threshold value, in other words, when the difference ΔNP reaches or approaches the switching point of the purge paths, and the electronic control unit 14 sets a longer increase period when the rate of change of the difference ΔNP decreases, and sets the larger amount to be increased when the rate of change of the difference ΔNP decreases.

[0090] When the rate of change of the difference ΔNP increases, the delay period until the vaporized fuel flows through the switched first purge path 21 and into the cylinder of the internal combustion engine 1 is short, thus preventing the air-fuel ratio from becoming leaner. Therefore, the electronic control unit 14 sets a shorter increase period and a smaller amount to be increased than those set in a case where the rate of change of the difference ΔNP is slow, in order to prevent an excessive increase in the amount of fuel.

[0091] Because the electronic control unit 14 variably sets the increase period and / or the increase correction quantity, which is the quantity to be increased, on the basis of the rate of change of the difference ΔNP, it is thus possible to prevent the fluctuation of the air-fuel ratio that can occur at the time of switching the purge paths in both cases where the load of the internal combustion engine 1 changes suddenly or gradually.

[0092] The electronic control unit 14 can be set so that the electronic control unit 14 performs the fuel quantity increase sequence during acceleration of the internal combustion engine 1, during which the first purge path 21 is switched to the second purge path 22, and does not perform the fuel quantity increase sequence during deceleration of the internal combustion engine 1, during which the second purge path 22 is switched to the first purge path 21.

[0093] The flowchart of Fig. Figure 7 represents the fuel quantity increase sequence that is executed by the electronic control unit 14 when the purge paths are switched.

[0094] In step S201, the electronic control unit 14 estimates the concentration for the evaporated fuel based on the purging ratio and the air-fuel ratio correction factor AFHOS.

[0095] Next, the electronic control unit 14 calculates the intake manifold pressure IP in the intake manifold 4 on the downstream side of the throttle valve 6 based on the measurement signal of the third pressure sensor 33.

[0096] In step S203, the electronic control unit 14 calculates the pressure ENP generated by the ejector 17 on the basis of a difference between the pressure UCP in the intake pipe 4 on the downstream side of the compressor 2a and the pressure DCP in the intake pipe 4 on the downstream side of the compressor 2a.

[0097] Then, in step S204, the electronic control unit 14 determines whether the absolute value of the difference ΔNP between the intake manifold pressure IP and the pressure ENP generated by the ejector 17 is less than or equal to a predetermined value α.

[0098] In a state where the flushing is carried out through the first flushing path 21, the electronic control unit 14 determines, for example, in step S204 whether the intake pipe pressure IP increases in the direction of atmospheric pressure and approaches the pressure ENP generated by the ejector 17 in order to determine whether a condition for switching from the first flushing path 21 to the second flushing path 22 is met.

[0099] When the absolute value of the difference ΔNP between the intake manifold pressure IP and the pressure ENP generated by the ejector 17 becomes less than or equal to the predetermined value α, in other words, when the absolute value of the difference ΔNP approaches the switching point at which the intake manifold pressure IP and the pressure ENP generated by the ejector 17 approach each other, the sequence of the electronic control unit 14 proceeds to step S205. The electronic control unit 14 then receives the magnitude of the change in the difference ΔNP between the intake manifold pressure IP and the pressure ENP generated by the ejector 17 within a predetermined time, that is, the rate of change of the difference ΔNP.

[0100] In the next step S206, the electronic control unit 14 sets at least the amount to be increased or the increase period of the fuel injection quantity on the basis of the estimated value of the concentration for the evaporated fuel and the rate of change at the difference ΔNP.

[0101] The increase period is set such that a time at which the absolute value of the difference ΔNP between the intake manifold pressure IP and the pressure ENP generated by the ejector 17 becomes less than or equal to the predetermined value α is set to be a time to start the increase of the quantity, and a time to end the increase correction is set on the basis of a time, an integrated engine speed or an integrated number of injection times.

[0102] Here, the electronic control unit 14 can adjust the larger quantity to be increased and / or the longer increase period if the estimated value of the concentration for the vaporized fuel increases, that is, if the air-fuel ratio becomes leaner due to the interruption of the flow of vaporized fuel.

[0103] Because the period during which the flow of vaporized fuel is interrupted increases when the rate of change of the difference ΔNP is slow, the electronic control unit 14 can also set a larger quantity to be increased and / or a longer increase period when the rate of change of the difference ΔNP decreases.

[0104] The electronic control unit 14 can set the quantity to be increased or the increase period to a fixed value and the other to a variable value, based on the estimated value of the concentration of the vaporized fuel and the rate of change of the difference ΔNP. Alternatively, the electronic control unit 14 can set both the quantity to be increased and the increase period variably based on the estimated value of the concentration of the vaporized fuel and the rate of change of the difference ΔNP.

[0105] Furthermore, the electronic control unit 14 can variably adjust the quantity to be increased based on the estimated value of the concentration for the evaporated fuel and the increase duration based on the rate of change of the difference ΔNP.

[0106] When the electronic control unit 14 determines the quantity to be increased and the increase period of the fuel injection quantity, the process proceeds to step S207, in which a process to correct the fuel injection quantity of the fuel injector 19 is carried out based on the quantity to be increased in order to continue the increase period that is set after the absolute value of the difference ΔNP between the intake manifold pressure IP and the pressure ENP generated by the ejector 17 becomes less than or equal to the predetermined value α.

[0107] Even if the flow of vaporized fuel into the cylinder is temporarily interrupted at the time of switching between the first purge path 21 and the second purge path 22, it is thus possible to prevent the air-fuel ratio of the internal combustion engine 1 from becoming leaner, so that it is possible to prevent torsional vibrations that could be caused by the leaner air-fuel ratio.

[0108] In the processing device 3 for the evaporated fuel, which is provided with the first purge path 21 and the second purge path 22, the suction force is reduced near the switching point in both cases of the first and second purge paths 21 and 22, and thus the amount of evaporated fuel desorption from the container 8 decreases, which leads to a decrease in the estimated value of the concentration for the evaporated fuel.

[0109] If the purge is then temporarily stopped to learn the air-fuel ratio, etc., in this state where the estimated concentration has decreased near the switchover point, the update of the estimated concentration is stopped and the lower value obtained immediately before the purge is stopped is maintained.

[0110] If the purge paths are switched while purge is stopped, and purge is then restarted in a state where the suction force generated by the switched purge path increases, purge control valve 12 is controlled based on the lower estimated concentration that has been maintained; however, a larger quantity of the vaporized fuel is actually desorbed, resulting in a higher actual concentration than the estimated value. This causes purge control valve 12 to open excessively, resulting in a richer air-fuel ratio.

[0111] Fig. Figure 8 represents a change in the air-fuel ratio that is caused when the scavenging is stopped in the state where the intake force is smallest near the switching point, in the deceleration state of the internal combustion engine 1, in which the second scavenging path 22 is switched to the first scavenging path 21 and the scavenging is then restarted in a state where the scavenging is carried out by the first scavenging path 21.

[0112] In Fig. As the load of the internal combustion engine 1 decreases while scavenging is performed through the second scavenging path 22, the suction force generated by the ejector 17 weakens as the boost pressure decreases, and thus the amount of vaporized fuel desorbed from the reservoir 8 decreases. Consequently, the estimated value of the vaporized fuel concentration decreases, and the amount of desorption decreases as it approaches the scavenging path switchover point.

[0113] If the purge for learning the air-fuel ratio, etc., is stopped near the switchover point where the amount of desorption is smallest, the estimated concentration obtained immediately before stopping is maintained, and then the estimation of a concentration is restarted with the maintained estimated concentration, which is used as the initial value at the time of the purge restart, and the drive operating cycle of the purge control valve 12 is calculated on the basis of the estimated concentration.

[0114] Here, at the point when the update of the estimated concentration is stopped—in other words, at the point when purging is stopped—the concentration of the vaporized fuel is low because the evaporated fuel's suction force is weak near the switchover point. However, when purging restarts, the purging is carried out through the first purge path 21, and the amount of vaporized fuel desorbed through the first purge path 21 is greater than the amount desorbed when purging is stopped. Therefore, the estimated concentration maintained while purging is stopped is lower than the actual concentration.

[0115] The electronic control unit 14 calculates the drive operating cycle of the purge control valve 12 based on this estimated concentration, which is lower than the actual value. This excessively increases the amount of vaporized fuel flowing into the cylinder and enriches the air-fuel ratio. The enriched air-fuel ratio causes torsional vibrations.

[0116] The electronic control unit 14 corrects the estimated value of the concentration for the evaporated fuel by determining the enrichment of the air-fuel ratio as a result of the inflow of the evaporated fuel through the first purge path 21 to a higher value after the purge restarts, in order to reduce the opening degree of the purge control valve 12 in response to the update of the estimated value in order to bring the air-fuel ratio closer to the target value again.

[0117] The electronic control unit 14 limits the update of the estimated value of the concentration for the evaporated fuel near the switching point between the first purge path 21 and the second purge path 22 in order to reduce fluctuations in the air-fuel ratio caused by the deviation between the estimated concentration and the actual concentration, as described above.

[0118] The time graph of Fig. 9 represents a change in the estimated concentration, a change in the air-fuel ratio and a change in the drive operating cycle of the purge control valve 12 at the time when the electronic control unit 14, near the switching point of the purge paths, limits the update of the estimated value of the concentration for the evaporated fuel for use in the purge control.

[0119] The electronic control unit 14 executes a sequence to stop an update of the estimated value of the evaporated fuel concentration for use in the purge control; in other words, a sequence to limit the update of the estimated value of the evaporated fuel concentration when the difference ΔNP between the intake manifold pressure IP and the pressure ENP generated by the ejector 17, which is outside a range in which the estimated value is maintained (hereinafter referred to as the “maintenance range”), the range of which includes the switchover point, falls within the maintenance range, and when a condition is met in which the amount of evaporated fuel desorbed from the reservoir 8 falls below the set value.

[0120] In the example in Fig. 9, when the load of the internal combustion engine 1 decreases while the purging through the second purging path 22 is being carried out and the switchover point is approaching, the updating of the estimated value of the concentration for the evaporated fuel is stopped, so that a previous value of the estimated concentration is maintained.

[0121] Although the actual concentration decreases as the difference ΔNP approaches the switchover point, a value that is maintained immediately before the difference ΔNP falls into the maintenance range is thus maintained as the estimated concentration.

[0122] Even if the purge is stopped while the estimated concentration is maintained, it is thus possible to prevent the estimated concentration, which is lower than at least the set value, from being used as the initial value in the purge control at the time the purge is restarted, and thus it is possible to ensure that the enrichment of the air-fuel ratio, which could be caused by the estimated concentration, is lower than the actual concentration at the time the purge is restarted.

[0123] The flowchart of Fig. 10 represents a process for limiting the update of the estimated concentration performed by the electronic control unit 14 when the flushing paths are switched.

[0124] In step S301, the electronic control unit 14 calculates the intake manifold pressure IP based on the measurement signal of the third pressure sensor 33.

[0125] Next, in step S302, the electronic control unit 14 calculates the pressure ENP generated by the ejector 17 on the basis of a difference between the pressure UCP in the intake pipe 4 on the upstream side of the compressor 2a and the pressure DCP in the intake pipe 4 on the downstream side of the compressor 2a.

[0126] Then, in step S303, the electronic control unit 14 determines whether the difference ΔNP between the intake manifold pressure IP and the pressure ENP generated by the outside 17 is greater than or equal to the negative first predetermined value α1 and less than or equal to a positive second predetermined value α2, that is, whether the difference ΔNP is within the maintenance range of the estimated concentration defined by the first predetermined value α1 and the second predetermined value α2.

[0127] The maintenance range encompasses the switching point of the purge paths. The condition in which the difference ΔNP is within the maintenance range means that the difference ΔNP lies within a range around the switching point, and within a range in which the suction force in both purge paths is at its minimum, i.e., the amount of vaporized fuel desorption is at its minimum.

[0128] If the difference ΔNP is outside the maintenance range, that is, if it deviates from the switching point and the purge paths generate a suction force greater than or equal to the set value, the process proceeds to step S305, in which the electronic control unit 14 obtains and updates the estimated value of the concentration for the evaporated fuel while the purge is being performed, based on the air-fuel ratio correction factor AFHOS and the purge ratio.

[0129] If, on the other hand, the difference ΔNP is within the maintenance range, the process proceeds to step S304, in which the electronic control unit 14 maintains the previous estimated value of the concentration for the evaporated fuel without updating the estimated value.

[0130] Thus, if the difference falls within the maintenance range in a state that is outside the maintenance range, the electronic control unit 14 maintains the estimated concentration for the evaporated fuel, which is estimated immediately before the difference ΔNP falls within the maintenance range, for a period in which the difference ΔNP is within the maintenance range. If the difference ΔNP then deviates from the maintenance range, the electronic control unit 14 initiates another update of the estimated value of the concentration for the evaporated fuel.

[0131] Next, in step S306, the electronic control unit 14 determines whether a condition for allowing the rinsing is met.

[0132] The electronic control unit 14 determines that the purge permit condition is not met if there is a request to stop the purge, for example to perform an air-fuel ratio learning.

[0133] If the purging authorization condition is not met because there is a requirement to stop the purging, for example to perform an air-fuel ratio learning, the routine is terminated, and thus the electronic control unit 14 keeps the purging control valve 12 in a closed state.

[0134] As applied here, the closed state of the flushing control valve 12 is a state in which the drive operating cycle is 0% and no energy is supplied.

[0135] If, on the other hand, the purging approval condition is met, e.g. there is no requirement to stop the purging for air-fuel ratio learning, the process proceeds to step S307, in which the electronic control unit 14 compares the intake manifold pressure IP and the pressure ENP generated by the ejector 17 to determine whether the purging is carried out through the first purging path 21 or the second purging path 22.

[0136] When the electronic control unit 14 determines that the flushing is carried out through the first flushing path 21, the process proceeds to step S308, in which the electronic control unit 14 selects first control characteristic curve data stored for the first flushing path 21 as control characteristic curve data for use in the control of the flushing control valve 12.

[0137] If, on the other hand, the electronic control unit 14 determines that the flushing is carried out through the second flushing path 22, the process proceeds to step S309, in which the electronic control unit selects second control characteristic curve data stored for the second flushing path 22 as control characteristic curve data for use in the control of the flushing control valve 12.

[0138] The content of the processes in steps S308 and S309 is similar to that in steps S104 and 105 described above, and a detailed explanation is omitted.

[0139] After selecting the control characteristic data in step S308 or step S309, the process proceeds to step S310, in which the electronic control unit 14 calculates the drive operating cycle of the flushing control valve 12 using the selected control characteristic data, which are selected on the basis of the flushing path, and executes the PWM control of the flushing control valve 12 with the calculated drive operating cycle.

[0140] Because the electronic control unit 14 maintains the estimated value of the concentration for the evaporated fuel in the maintenance range around the switchover point, it is possible to prevent the decrease in the estimated concentration that could be caused by the decrease in the amount of desorption resulting from the reduction in the suction force generated by the purge path near the switchover point.

[0141] Even if the purge is temporarily stopped while the difference ΔNP is within the maintenance range and then the purge is restarted after the intake power increases, it is thus possible to reduce the difference between the actual concentration and the estimated value at the time of the purge restart, and thus it is possible to prevent the air-fuel ratio from becoming richer at the time of the purge restart.

[0142] The technical concepts described in the above embodiment can be combined as needed, as long as no conflict arises.

[0143] Although the present invention is described in detail with reference to the preferred embodiment, it is obvious that a person skilled in the art can make various modifications based on the basic technical concepts and teachings of the present invention.

[0144] For example, the switching sequence of the control characteristic data of the purge control valve 12 can be modified based on whether the first purge path 21 or the second purge path 22 is used to purge the evaporated fuel by adopting a sequence to correct reference control characteristic data based on the purge path.

[0145] The process for limiting the update of the estimated value of the concentration for the evaporated fuel at the time of switching between the first purge path 21 and the second purge path 22 can be modified not only by adopting a process to stop the update, but also by adopting a process to use a moving average value of the estimated concentration or a process to limit a deviation of the last value with respect to the previous value to a specified value or less.

[0146] A differential pressure sensor can be provided to measure the differential pressure between the pressure UCP in the intake pipe 4 on the upstream side of the compressor 2a and the pressure DCP in the intake pipe 4 on the downstream side of the compressor 2a. The electronic control unit 14 can then obtain the pressure ENP generated by the ejector 17 based on the measured value of the differential pressure sensor. Alternatively, a pressure sensor that directly measures the pressure ENP generated by the ejector 17 can be provided.

[0147] The first flushing path 12 for carrying out the flushing in the intake pipe 4 on the downstream side of the throttle valve 6 and the second flushing path 22 for carrying out the flushing in the intake pipe 4 on the upstream side of the compressor 2a by the pressure ENP generated by the ejector 17 can be provided independently, and an electronically controlled flushing control valve can be provided in each flushing path. Reference number list 1 Internal combustion engine 2 turbochargers (charging device) 2a Compressor 3 Processing device for evaporated fuel 4 Intake pipe 6 Throttle valve 7 Fuel tank 8 containers 12 Flushing control valve 14 electronic control unit (control unit) 17 ejectors 21 first flushing path 22 second flushing path

Claims

[1] Processing device (3) for vaporized fuel for a supercharged internal combustion engine (1) with a compressor (2a), a supercharging device (2) and a throttle valve (6) in an intake pipe (4), - wherein the vaporized fuel processing device (3) comprises: - a container (8) which receives a vaporized fuel produced in a fuel tank (7); - a flush control valve (12) which sets a flush flow rate from the container (8); - a first purge path (21) extending from a downstream side of the purge control valve (12) to the intake pipe (4) on a downstream side of the throttle valve (6); - a second purge path (22) extending from the downstream side of the purge control valve (12) to an ejector (17), the ejector (17) being provided in a return pipe (15) providing a connection between the intake pipe (4) on a downstream side of the compressor (2a) and the intake pipe (4) on an upstream side of the compressor (2a); and - a control unit (14) which controls the flushing control valve (12) on the basis of control characteristic data, - wherein the control unit (14): - switches the control characteristic data between first control characteristic data for the first flushing path (21) and second control characteristic data for the second flushing path (22) when the first flushing path (21) and the second flushing path (22) are switched, and - increases a fuel injection quantity injected into the internal combustion engine (1) when the first purge path (21) and the second purge path (22) are switched. [2] Processing device (3) for vaporized fuel for a supercharged internal combustion engine (1) with a compressor (2a), a supercharging device (2) and a throttle valve (6) in an intake pipe (4), - wherein the vaporized fuel processing device (3) comprises: - a container (8) which receives a vaporized fuel produced in a fuel tank (7); - a flush control valve (12) which sets a flush flow rate from the container (8); - a first purge path (21) extending from a downstream side of the purge control valve (12) to the intake pipe (4) on a downstream side of the throttle valve (6); - a second purge path (22) extending from the downstream side of the purge control valve (12) to an ejector (17), the ejector (17) being provided in a return pipe (15) providing a connection between the intake pipe (4) on a downstream side of the compressor (2a) and the intake pipe (4) on an upstream side of the compressor (2a); and - a control unit (14) which controls the flushing control valve (12) on the basis of control characteristic data, - wherein the control unit (14): - switches the control characteristic data between first control characteristic data for the first flushing path (21) and second control characteristic data for the second flushing path (22) when the first flushing path (12) and the second flushing path (22) are switched, - controls the purge control valve (12) on the basis of an estimated value of a concentration for evaporated fuel, and - limiting an update of the estimated value of the vaporized fuel concentration for use in controlling the purge control valve (12) when the first purge path (12) and the second purge path (22) are switched. [3] A processing device (3) according to claim 1 or 2, wherein the control characteristic data includes a conversion characteristic for converting information about a purge state into an opening degree command of the purge control valve (12). [4] The processing device (3) according to claim 1 or 2, wherein the first purge path (21) is switched to the second purge path (22) based on an increase in the load of the internal combustion engine (1). [5] A processing device (3) according to claim 1 or 2, wherein the control unit (14) compares an intake pipe pressure on the downstream side of the throttle valve (6) and a pressure generated by the ejector (17) to determine whether the first purge path (21) or the second purge path (22) is used for purging. [6] The processing device (3) according to claim 1, wherein the control unit (14) changes at least an amount to be increased and an increasing period of the fuel injection amount based on a changing speed of a difference between the intake pipe pressure on the downstream side of the throttle valve (6) and the pressure generated by the ejector (17). [7] Control method for a processing device (3) for vaporized fuel of a supercharged internal combustion engine (1) with a compressor (2a), a supercharging device (2) and a throttle valve (6) in an intake pipe (4), - wherein the vaporized fuel processing device (3) comprises: - a container (8) which absorbs an evaporated fuel generated in a fuel tank (7); - a flush control valve (12) which sets a flush flow rate from the container (8); - a first purge path (21) extending from a downstream side of the purge control valve (12) to the intake pipe (4) on a downstream side of the throttle valve (6); and - a second purge path (22) extending from the downstream side of the purge control valve (12) to an ejector (17), the ejector (17) being provided in a return pipe (15) providing a connection between the intake pipe (4) on a downstream side of the compressor (2a) and the intake pipe (4) on an upstream side of the compressor (2a); - the control method comprising the steps: - determining whether the first flushing path (21) or the second flushing path (22) is used for flushing; - switching the control characteristic data for use in controlling the purge control valve (12) between first control characteristic data for the first purge path (21) and second control characteristic data for the second purge path (22) on the basis of the specific path used for purging, and - Increasing a fuel injection quantity injected into the internal combustion engine (1) when the first purge path (21) and the second purge path (22) are switched. [8] Control method for a processing device (3) for vaporized fuel of a supercharged internal combustion engine (1) with a compressor (2a), a supercharging device (2) and a throttle valve (6) in an intake pipe (4), - wherein the vaporized fuel processing device (3) comprises: - a container (8) which absorbs an evaporated fuel generated in a fuel tank (7); - a flush control valve (12) which sets a flush flow rate from the container (8); - a first purge path (21) extending from a downstream side of the purge control valve (12) to the intake pipe (4) on a downstream side of the throttle valve (6); and - a second purge path (22) extending from the downstream side of the purge control valve (12) to an ejector (17), the ejector (17) being provided in a return pipe (15) providing a connection between the intake pipe (4) on a downstream side of the compressor (2a) and the intake pipe (4) on an upstream side of the compressor (2a); - the control method comprising the steps: - determining whether the first flushing path (21) or the second flushing path (22) is used for flushing; - switching the control characteristic data for use in controlling the purge control valve (12) between first control characteristic data for the first purge path (21) and second control characteristic data for the second purge path (22) on the basis of the specific path used for purging, - controlling the purge control valve (12) on the basis of an estimated value of a concentration for evaporated fuel, and - limiting an update of the estimated value of the vaporized fuel concentration for use in controlling the purge control valve (12) when the first purge path (12) and the second purge path (22) are switched. [9] A control method according to claim 7 or 8, wherein the control characteristic data includes a conversion characteristic for converting information about a purge state into an opening degree command of the purge control valve (12). [10] A control method according to claim 7 or 8, wherein the first purge path (12) is switched to the second purge path (22) for purging based on an increase in the load of the internal combustion engine (1).

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