JP2018035770A - Evaporative fuel treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for properly grasping fluctuations in the flow rate of purge gas from a pump.SOLUTION: An evaporative fuel treating device comprises: a canister for storing evaporative fuel; a control valve that is arranged in a purge passage bringing the canister and the intake passage of an internal combustion engine into communication with each other, and is switched between a close state of closing the purge passage and an open state of opening the purge passage; a pump for delivering purge gas containing the evaporative fuel in the canister to the intake passage via the purge passage; and a control part. The control part specifies a flow rate learning value α (S26) showing a fluctuation of the flow rate of the purge gas that is delivered from the pump to the intake passage, from the reference flow rate, by using an air-fuel ratio of the internal combustion engine in a period in which the control valve is in the open state and the purge gas is delivered to the intake passage by the pump.SELECTED DRAWING: Figure 2

Description

  The present specification relates to a fuel vapor processing apparatus mounted on a vehicle.

  Patent Document 1 discloses an evaporative fuel processing apparatus. The evaporative fuel processing apparatus includes a canister that stores fuel evaporated in a fuel tank, a control valve that is disposed in a purge path that communicates the canister and the intake path, and a pump that is disposed in the purge path. The evaporative fuel processing apparatus drives a pump to send a mixed gas of evaporative fuel and air in the canister (hereinafter referred to as “purge gas”) to the intake path via the purge path.

  The evaporative fuel processing device suppresses or stops the flow rate from the pump when the air-fuel ratio is rich, and increases the flow rate from the pump when the air-fuel ratio is lean to increase the fuel supplied to the internal combustion engine. Control the amount.

Japanese Patent Laid-Open No. 2002-213306

  When the flow rate of the purge gas by the pump varies, the air-fuel ratio varies. For this reason, it is required to appropriately grasp the flow rate of the purge gas from the pump. The flow rate of the purge gas from the pump may vary due to individual differences of pumps or aging. In the present specification, a technique capable of appropriately grasping the variation in the flow rate of the purge gas from the pump is provided.

  The technology disclosed in the present specification relates to a fuel vapor processing apparatus mounted on a vehicle. The evaporative fuel processing apparatus is disposed in a canister for storing evaporative fuel, a purge path that communicates the canister and an intake path of the internal combustion engine, a closed state that closes the purge path, and an open that opens the purge path A control valve for switching to a state, a pump for sending purge gas containing evaporated fuel in the canister to the intake path through the purge path, the control valve is in the open state, and the purge gas by the pump Using the air-fuel ratio of the internal combustion engine while the engine is being sent to the intake path, a specifying unit that specifies an index indicating variation from the reference flow rate of the purge gas flow sent from the pump to the intake path And comprising.

  In a situation where the purge gas is sent to the intake path by the pump, if the flow rate of the purge gas from the pump varies, the flow rate of the purge gas deviates from the reference flow rate. As a result, the fuel amount supplied to the internal combustion engine is different from the assumed fuel amount. For this reason, if the amount of fuel supplied to the internal combustion engine is controlled based on the reference flow rate, the air-fuel ratio may be lost. In the above configuration, the index indicating the variation in the flow rate of the pump is specified using the deviation of the air-fuel ratio of the internal combustion engine while the purge gas is being sent to the intake path by the pump. According to this configuration, in order to grasp the variation in the flow rate, the variation in the flow rate of the pump is detected using a device (for example, an air-fuel ratio sensor) that detects an air-fuel ratio without providing a dedicated detection device (for example, a pressure sensor). It is possible to specify an index indicating. Thereby, it is possible to appropriately grasp the variation in the flow rate of the purge gas from the pump.

  The flow rate of the purge gas delivered by the pump may be adjustable depending on the opening of the control valve. The evaporative fuel processing apparatus uses the index and the pressure in the intake passage to send out the control valve while the control valve is fully open and the purge gas is sent out to the intake passage by the pump. An estimation unit that estimates the flow rate of the purge gas may be further provided. According to this configuration, the flow rate of the purge gas from the pump can be estimated in consideration of the variation in the flow rate. At this time, it is possible to identify the flow rate of the purge gas supplied from the pump to the intake path by estimating the opening degree of the control valve by estimating the flow rate of the purge gas from the pump when the control valve is fully open. it can.

  The evaporative fuel processing apparatus may further include a determination unit that determines that the pump is not operating normally using the index. When the flow rate of the purge gas from the pump is greatly deviated from the reference flow rate, the index deviates from the normal range. For this reason, it can be determined using the index that the pump is not operating normally.

  The specifying unit specifies the index at a timing when the concentration of the evaporated fuel in the purge gas is stable and the pressure in the intake passage is shifted from a state lower than a reference value to a state higher than the reference value. May be. When the purge concentration of the evaporated fuel in the purge gas is stabilized, the amount of fuel supplied to the internal combustion engine is adjusted so that the air-fuel ratio becomes a predetermined air-fuel ratio (for example, ideal air-fuel ratio) in accordance with the stable purge concentration. Is done. When the pressure in the intake path shifts from a low state to a high state, the flow rate of purge gas sent from the purge path to the intake path decreases due to the difference between the pressure in the intake path and the pressure in the purge path. For this reason, of the total flow rate of purge gas supplied from the purge route to the intake route, the ratio of the flow rate of purge gas sent from the purge route to the intake route due to driving of the pump increases. Thereby, mainly due to variations in the flow rate of the purge gas from the pump, the amount of evaporated fuel supplied to the internal combustion engine changes, and the air-fuel ratio fluctuates to the rich side or the lean side. The identification unit identifies the index by using the deviation of the air-fuel ratio before the air-fuel ratio is adjusted by controlling the amount of fuel supplied to the internal combustion engine in a situation where the variation in the flow rate of the purge gas from the pump becomes significant can do.

  The specifying unit may specify the index when the concentration of the evaporated fuel in the purge gas is higher than a predetermined value. When the purge concentration is low, even if the flow rate of the purge gas from the pump varies, the variation of the air-fuel ratio is small. By specifying the index in a situation where the purge concentration is relatively high, the index can be specified in a situation where the fluctuation of the air-fuel ratio becomes large due to the fluctuation of the flow rate of the purge gas from the pump.

  The vehicle may include a concentration correction unit that corrects the concentration of the evaporated fuel in the purge gas using the air-fuel ratio. The specifying unit may prohibit the density correction unit from correcting the density when the index should be specified. According to this configuration, the purge concentration is corrected, and based on the corrected purge concentration, the amount of fuel supplied to the internal combustion engine is adjusted, whereby fluctuations in the air-fuel ratio shift can be suppressed.

1 shows an outline of a fuel supply system for an automobile. The flowchart of a pump determination process is shown. The reference flow rate with respect to the pressure in the intake path and the corrected flow rate corrected based on the index are shown. The data map which shows the difference with the reference | standard flow volume with respect to the pressure of an intake passage is shown. The time chart of each part of the vehicle in a pump determination process is shown. The flowchart of a density | concentration estimation process is shown. The reference flow volume with respect to the pressure of the intake passage of a modification, and a correction flow volume are shown.

  With reference to FIG. 1, the fuel supply system 6 provided with the evaporative fuel processing apparatus 20 is demonstrated. The fuel supply system 6 is mounted on a vehicle and supplies a main supply path 10 for supplying the fuel stored in the fuel tank 14 to the engine 2 and the evaporated fuel generated in the fuel tank 14 to the engine 2. An evaporative fuel path 22 is provided.

  The main supply path 10 is provided with a fuel pump unit 16, a supply path 12, and an injector 4. The fuel pump unit 16 includes a fuel pump, a pressure regulator, a control circuit, and the like. The fuel pump unit 16 controls the fuel pump according to a signal supplied from the ECU 100. The fuel pump pressurizes and discharges the fuel in the fuel tank 14. The fuel discharged from the fuel pump is regulated by a pressure regulator and supplied from the fuel pump unit 16 to the supply path 12. The supply path 12 is connected to the fuel pump unit 16 and the injector 4. The fuel supplied to the supply path 12 passes through the supply path 12 and reaches the injector 4. The injector 4 has a valve (not shown) whose opening degree is controlled by the ECU 100. When the valve of the injector 4 is opened, the fuel in the supply path 12 is supplied to the intake path 34 connected to the engine 2.

  The intake path 34 is connected to the air cleaner 30. The air cleaner 30 includes a filter that removes foreign substances from the air flowing into the intake passage 34. A throttle valve 32 is provided in the intake path 34 between the engine 2 and the air cleaner 30. When the throttle valve 32 is opened, intake is performed from the air cleaner 30 toward the engine 2 as indicated by an arrow in FIG. The ECU 100 adjusts the amount of air flowing into the engine 2 by changing the opening area of the intake passage 34 by adjusting the opening of the throttle valve 32. The throttle valve 32 is provided on the upstream side (the air cleaner 30 side) from the injector 4.

  A fuel vapor path 22 is arranged along the main supply path 10. The evaporative fuel path 22 is a path through which evaporative fuel generated in the fuel tank 14 moves from the fuel tank 14 via the canister 19 to the intake path 34. As will be described later, the evaporated fuel is mixed with air in the canister 19. A mixed gas of evaporated fuel and air mixed by the canister 19 is called a purge gas. An evaporated fuel processing device 20 is provided in the evaporated fuel path 22. The fuel vapor processing apparatus 20 includes a canister 19, a control valve 26, a pump 48, and a control unit 102 in the ECU 100.

  The fuel tank 14 and the canister 19 are connected by a tank path 18. The canister 19 is connected to the pump 48 via the purge path 23. The pump 48 is connected to the control valve 26 via the purge path 24. The control valve 26 is connected to the intake path 34 via the communication path 28. The purge paths 23 and 24 are connected to the intake path 34 between the injector 4 and the throttle valve 32 via the control valve 26 and the communication path 28. An intake manifold IM is disposed at a position of the intake path 34 to which the communication path 28 is connected.

  A control valve 26 is disposed between the communication path 28 and the purge path 24. The control valve 26 is an electromagnetic valve that is controlled by the control unit 102, and is a valve that is controlled by the control unit 102 to switch between an opened state that is opened and a closed state that is closed. The control unit 102 executes duty control that continuously switches between the open state and the closed state of the control valve 26 according to the duty ratio determined by the air-fuel ratio or the like. In the open state, the purge path 24 is opened, and the canister 19 and the intake path 34 are communicated. In the closed state, the purge path 24 is closed, and the canister 19 and the intake path 34 are blocked on the purge path 24. The duty ratio represents the ratio of the period of the open state in the combination period of the one set of open state and closed state that are mutually continuous. The control valve 26 adjusts the flow rate of the gas containing the evaporated fuel (that is, purge gas) by adjusting the duty ratio (that is, adjusting the switching timing between the open state and the closed state). The duty ratio is an example of the “opening degree” of the control valve 26.

  The control valve 26 may be a stepping motor type control valve whose opening degree (in other words, the flow area of the purge gas) can be adjusted.

  A pump 48 is disposed between the purge path 24 and the purge path 23. The pump 48 is a so-called vortex pump (also called a cascade pump or a Wesco pump) or a centrifugal pump. The pump 48 is controlled by the control unit 102. When the pump 48 is driven, purge gas is sucked into the pump 48 from the canister 19 through the purge path 23. The purge gas sucked into the pump 48 is boosted in the pump 48 and sent to the purge path 24. The purge gas sent to the purge path 24 passes through the purge path 24, the control valve 26 and the communication path 28 and is supplied to the intake path 34.

  The canister 19 is connected to the pump 48 via the purge path 23. The canister 19 includes an atmospheric port 19a, a purge port 19b, and a tank port 19c. The atmospheric port 19 a communicates with the atmosphere via the atmospheric path 17 and the air filter 42. The air may flow into the canister 19 from the air port 19a through the air path 17 after passing through the air filter. At this time, the air filter 42 prevents foreign substances in the atmosphere from entering the canister 19.

  The purge port 19b is connected to the purge path 23. The tank port 19 c is connected to the fuel tank 14 via the tank path 18.

  Activated carbon (not shown) is accommodated in the canister 19. The activated carbon adsorbs evaporated fuel from the gas flowing from the fuel tank 14 into the canister 19 through the tank path 18 and the tank port 19c. The gas after the evaporated fuel is adsorbed passes through the atmospheric port 19a and the atmospheric path 17 and is released to the atmosphere. The canister 19 can prevent the evaporated fuel in the fuel tank 14 from being released to the atmosphere. The evaporated fuel adsorbed by the activated carbon is supplied to the purge path 23 from the purge port 19b.

  The control unit 102 is connected to the pump 48 and the control valve 26. The control unit 102 includes a CPU and a memory such as a ROM and a RAM. The control unit 102 controls the pump 48 and the control valve 26.

  Next, the operation of the evaporated fuel processing apparatus 20 will be described. When the engine 2 is in operation and the purge condition is established, the control unit 102 performs a purge process for supplying purge gas to the engine 2 by duty-controlling the control valve 26. When the purge process is executed, the purge gas is supplied in the direction indicated by the arrow in FIG. The purge condition is a condition that is established when the purge process for supplying the purge gas to the engine 2 is to be executed, and is manufactured in advance according to the cooling water temperature of the engine 2 and the evaporated fuel concentration of the purge gas (hereinafter referred to as “purge concentration”). This is a condition set in the control unit 102 by a person. The control unit 102 constantly monitors whether the purge condition is satisfied while the engine 2 is being driven. The control unit 102 controls the duty ratio of the control valve 26 based on the concentration of the purge gas and the air flow meter 39 disposed in the intake passage 34. The air flow meter 39 measures the amount of air that passes through the intake passage 34 and is supplied to the engine 2. Thereby, the purge gas adsorbed by the canister 19 is introduced into the engine 2.

  When executing the purge process, the control unit 102 drives the pump 48 to supply the purge gas to the intake passage 34. As a result, the purge gas can be supplied even when the negative pressure in the intake passage 34 is small. Note that the control unit 102 may switch between driving and stopping of the pump 48 in accordance with the supply state of the purge gas during the purge process.

  The ECU 100 controls the throttle valve 32. The ECU 100 also controls the amount of fuel injected by the injector 4. Specifically, the amount of injected fuel is controlled by controlling the valve opening time of the injector 4. When the engine 2 is driven, the ECU 100 calculates a fuel injection time per unit time injected from the injector 4 to the engine 2 (that is, a valve opening time of the injector 4). In order to maintain the air-fuel ratio at the target air-fuel ratio (for example, the ideal air-fuel ratio), the fuel injection time corrects the reference injection time specified in advance by experiments. The air-fuel ratio sensor 36 is disposed in the exhaust path 38 of the engine 2. Further, the ECU 100 corrects the injected fuel amount based on the purge gas flow rate and the purge concentration.

  The ECU 100 executes concentration estimation processing for estimating the purge concentration using the air-fuel ratio detected by the air-fuel ratio sensor 36. The concentration estimation process is repeatedly executed while the purge process is being executed. As shown in FIG. 6, in the concentration estimation process, first, in S52, the ECU 100 causes the detected air-fuel ratio to deviate from a predetermined reference air-fuel ratio (for example, the theoretical air-fuel ratio (= 14.7)). The deviation coefficient indicating whether or not Specifically, the control unit 102 calculates the deviation coefficient by subtracting the reference air-fuel ratio from the detected air-fuel ratio, dividing by the reference air-fuel ratio, and multiplying by 100.

  The higher the ratio of fuel in the gas supplied to the engine 2, the smaller the air-fuel ratio. When the air-fuel ratio is richer than the reference air-fuel ratio, the fuel ratio is high, and the detected air-fuel ratio is smaller than the reference air-fuel ratio. For this reason, the deviation coefficient becomes a negative value. On the other hand, when the air-fuel ratio is leaner than the reference air-fuel ratio, the fuel ratio is low, and the detected air-fuel ratio is larger than the reference air-fuel ratio. For this reason, the deviation coefficient becomes a positive value.

  Next, in S54, the ECU 100 determines whether or not the deviation coefficient is within a predetermined range. The predetermined range is a range indicating that the purge concentration has not changed from the previous concentration estimation process, that is, a range that can be regarded as a detection error of the air-fuel ratio sensor 36, and is ± 5%, for example. When the deviation coefficient is within the predetermined range (YES in S54), in S56, the ECU 100 determines that the density change amount ΔD = 0, and proceeds to S60. On the other hand, when the deviation coefficient is outside the predetermined range (NO in S54), in S58, the ECU 100 calculates the concentration change amount ΔD = −deviation coefficient / purge gas rate, and proceeds to S60. The purge gas rate represents the ratio of the purge gas out of the total amount of intake gas sucked into the engine 2. The intake gas includes air sucked through the air cleaner 30 and the intake passage 34 and purge gas supplied from the evaporated fuel processing device 20 in the purge process. The amount of air sucked through the intake path 34 is detected by an air flow meter 39 disposed in the vicinity of the air cleaner 30. The flow rate of the purge gas is specified by a method described later. The ECU 100 calculates the purge gas rate by the following formula: purge gas rate = purge gas flow rate / (air amount + purge gas flow rate) × 100.

  In S60, the ECU 100 estimates the purge concentration by adding the concentration change amount ΔD specified in S56 or S58 to the purge concentration estimated in the previous S60. When there is no purge concentration estimated in the previous S60, it is determined that the purge concentration estimated in the previous S60 is zero. If a negative value is calculated in S60, the purge concentration is estimated to be 0%. The estimated purge concentration is stored in the ECU 100 while the ignition switch is on, and is updated by the concentration estimation process. When the ignition switch is switched from on to off, the ECU 100 deletes the estimated purge concentration.

  In the modification, the ECU 100 specifies the purge concentration using a concentration-flow rate data map that is specified in advance by experiments and stores the relationship between the purge concentration stored in the ECU 100 and the integrated amount of the purge gas flow rate. Also good. Further, the ECU 100 may correct the concentration-flow rate data map according to the deviation of the air-fuel ratio.

  The flow rate of the purge gas is specified by the control unit 102. Specifically, as shown in FIG. 3, the control unit 102 indicates that the control valve 26 is fully open (that is, the duty ratio = 1.0) and the pump 48 is rotated at a predetermined rotational speed during the purge process. When driving at X1 (for example, 12000 rpm), reference flow rate characteristic data 110 (hereinafter simply referred to as “data”) indicating the relationship between the flow rate of the purge gas delivered from the pump 48 and the pressure of the intake passage 34 (ie, intake manifold IM). 110 ") is stored. The data 110 is specified by an experiment in advance and stored in the control unit 102.

  The control unit 102 calculates the flow rate of the purge gas from the data 110 using the pressure of the intake manifold IM, the rotational speed X2 of the pump 48, and the duty ratio Y. Specifically, the flow rate Z corresponding to the pressure of the intake manifold IM is specified from the data 110 of the control valve 26. Next, the flow rate of the purge gas is calculated by multiplying the specified flow rate Z by the ratio X2 / X1 of the rotational speed of the pump 48 and the duty ratio Y of the control valve 26.

  The data 110 is specified by an experiment performed by extracting one or more pumps from a number of manufactured pumps and using the extracted pumps. Many pumps have variations due to individual differences due to manufacturing errors and the like. Also, variations due to aging of the pump 48 can occur. As a result, the relationship between the flow rate of the purge gas of the pump 48 and the pressure of the intake manifold IM may deviate from the relationship between the flow rate of the purge gas indicated by the data 110 and the pressure of the intake manifold IM.

  The control unit 102 specifies the relationship between the flow rate of the purge gas unique to the pump 48 and the pressure of the intake manifold IM, and executes a pump determination process for determining that the pump 48 is not operating normally. The pump determination process is started when the vehicle is started (for example, the ignition switch is switched from OFF to ON), and is executed periodically (for example, every 65 ms). When the vehicle is started, a learning completion flag, a learning start flag, a start condition flag, an execution condition flag, and a concentration estimation process prohibition flag, which will be described later, are set off. Also, the start condition timer starts counting. In the modification, the pump determination process may be executed irregularly.

  As shown in FIG. 2, in the pump determination process, first, in S12, the control unit 102 determines whether or not the learning completion flag is off. The learning completion flag is a flag that is switched from off to on when the flow rate learning value α is specified in the pump determination process (see S28). If the learning completion flag is on (NO in S12), the pump determination process is terminated. Once the learning complete flag is set on, it remains on until the vehicle is started and set off. For this reason, once the vehicle is started, once the flow rate learning value α is identified and the learning completion flag is set to ON, the vehicle is stopped (for example, the ignition switch is switched from ON to OFF) and restarted. Until it is done, the flow rate learning value α is not newly specified.

  When the learning completion flag is off (YES in S12), in S14, the control unit 102 determines whether or not a learning start condition is satisfied. The control unit 102 determines that the learning start condition is satisfied when all of the following four conditions (I) to (IV) are continuously achieved in the first period (for example, 2 seconds). The four conditions are (I) the pressure of the intake manifold IM (that is, the position where the evaporated fuel processing device 20 is connected in the intake passage 34) is less than a reference value (for example, 80 kPa), and (II) the purge process is executed. (III) the purge concentration is equal to or higher than a predetermined value (for example, 10%), and (IV) the purge concentration is stable.

  For condition (I), the control unit 102 acquires the pressure of the intake manifold IM using the pressure sensor 35 installed in the intake manifold IM. With respect to condition (II), the control unit 102 determines that the purge process is being performed when the ECU 100 is executing the duty control of the control valve 26, and the purge process is performed when the duty control is not being performed. Is determined not to be executed. The condition (III) is determined by the control unit 102 using the purge concentration estimated by the concentration estimation process shown in FIG. Regarding condition (IV), the controller 102 determines that the purge concentration is stable when the purge concentration estimated by the concentration estimation process has not changed (that is, when ΔD = 0 in S56 of FIG. 6). to decide.

  When all of the four conditions (I) to (IV) are achieved, the control unit 102 switches the start condition flag from off to on, resets the start condition timer, and restarts counting. When any of the four conditions (I) to (IV) is not achieved, the control unit 102 switches the start condition flag from on to off, resets the start condition timer, and restarts counting. .

  In a situation where the learning start condition is satisfied (that is, a situation in which all four conditions (I) to (IV) are continuously achieved over the first period), the flow rate of the purge gas is relatively high. In this situation, the amount of fuel supplied to the engine 2 (that is, the total amount of fuel injected from the injector 4 and evaporated fuel in the purge process) is stable.

  When the learning start condition is satisfied (YES in S14), in S16, the control unit 102 switches the learning start flag from off to on and ends the pump determination process. If the learning start flag is already on, in S16, the learning start flag is kept on, and the pump determination process ends.

  On the other hand, when the learning start condition is not satisfied (NO in S14), in S18, the control unit 102 achieves any one of the four conditions of the learning start condition (I) to (IV). Whether or not a second period (for example, 3 seconds) has passed is determined. Specifically, the control unit 102 determines whether or not the start condition flag is off and the count value of the start condition timer is greater than or equal to the second period. In S18, since the learning start condition is not satisfied in S14 and the start condition flag is OFF, it is determined whether or not the count value of the start condition timer is equal to or longer than the second period. When the count value of the start condition timer is equal to or longer than the second period (YES in S18), in S19, the control unit 102 switches the learning start flag from on to off, and proceeds to S20. If the learning start flag is already off, the control unit 102 maintains the learning start flag off in S19.

  On the other hand, when the count value of the start condition timer is less than the second period (YES in S18), S19 is skipped and the process proceeds to S20. In S20, the control unit 102 determines whether or not an execution condition is satisfied. The control unit 102 determines that the execution condition is satisfied when all of the following four conditions (i) to (iv) are continuously achieved in the third period (for example, 1 second). The four conditions are (i) the learning start flag is on, (ii) the pressure of the intake manifold IM is equal to or higher than a reference value (for example, 80 kPa), (iii) the purge process is being executed, (iv) learning The completion flag is off.

  For condition (i), the control unit 102 determines whether or not the learning start flag in the control unit 102 is on. For condition (ii), the control unit 102 acquires the pressure of the intake manifold IM using the pressure sensor 35 as in the condition (I). Regarding condition (iii), the control unit 102 determines that the purge process is being performed when the ECU 100 is executing the duty control of the control valve 26, as in the condition (II). For condition (iv), the control unit 102 determines whether or not the learning completion flag in the control unit 102 is off.

  When all of the four conditions (i) to (iv) are achieved, the control unit 102 switches the execution condition flag from off to on and starts counting the execution condition timer. When any of the four conditions (i) to (iv) is not achieved, the control unit 102 switches the execution condition flag from on to off, resets the timer, and stops counting.

  When the execution condition is satisfied (YES in S20), in S22, the control unit 102 switches the concentration estimation process prohibition flag from off to on. When the concentration estimation process prohibition flag is on, the ECU 100 does not execute the concentration estimation process. Next, in S24, the control unit 102 specifies the flow rate learning value α (an example of “index”). Specifically, the control unit 102 calculates a deviation coefficient as in S52 of the density estimation process. Next, the control unit 102 specifies the flow rate learning value α by the flow rate learning value α = 1−deviation coefficient / 100. For example, when the deviation coefficient is −20 (that is, the air-fuel ratio is rich), the flow rate learning value α = 1.2.

  Next, in S26, the control unit 102 calculates a fully open flow rate characteristic. Specifically, in addition to the data 110 shown in FIG. 3, the control unit 102 stores in advance a pressure-flow rate difference data map indicating a difference from the reference flow rate with respect to the pressure of the intake manifold IM shown in FIG. The pressure-flow rate difference data map is specified by experiment and stored in advance. In the experiment, first, using a pump with a flow rate learning value α = 1.0, the control valve 26 is in a fully open state (that is, duty ratio = 1.0), and the pump has a predetermined rotation speed X1 (for example, 12000 rpm). , The reference flow rate that is the flow rate of the purge gas from the pump with respect to the change in the pressure of the intake manifold IM is specified. Thereby, the data 110 is specified.

  Next, when a plurality of pumps having a flow rate learning value α different from 1.0 are used and the control valve 26 is fully opened and the pump is driven at a predetermined rotational speed X1, the pressure of the intake manifold IM is reduced. A flow rate that is the flow rate of the purge gas from the pump with respect to the change is specified. Then, it is created by calculating the difference between the specified flow rate corresponding to the pressure of the same intake manifold IM and the reference flow rate. FIG. 4 shows data 103, 104, 106, and 108 representing the flow rate differences when the flow rate learning value α is 0.8, 0.9, 1.1, and 1.2. However, the number of data can be appropriately set according to the possible range of the flow rate learning value α. Actually, the data 103, 104, 106, and 108 are each represented by a combination of numerical values of the pressure and flow rate difference of the intake manifold IM.

  The control unit 102 specifies data (for example, data 103) corresponding to the flow rate learning value α specified in S24 from the pressure-flow rate difference data map. Next, the control unit 102 calculates the fully-open flow rate characteristic by correcting the data 110 representing the reference flow rate using the identified data from the pressure-flow rate difference data map. For example, when the flow rate learning value α = 1.2 and the data 103 is identified from the pressure-flow rate difference data map, the control unit 102 sets the data 103 to the reference flow rate of the data 110 at the pressure of the same intake manifold IM. The data 110 is corrected by adding the flow rate difference (positive value). As a result, the fully open flow rate characteristic data 112 shown in FIG. 3 is calculated. On the other hand, for example, when the flow rate learning value α = 0.8 and the data 108 is specified from the pressure-flow rate difference data map, the control unit 102 sets the data to the reference flow rate of the data 110 at the pressure of the same intake manifold IM. The data 110 is corrected by adding 108 flow rate differences (negative values). As a result, the fully open flow rate characteristic data 114 shown in FIG. 3 is calculated.

  The fully open flow rate characteristic is the flow rate of the purge gas delivered from the pump 48 when the control valve 26 is in the fully open state (that is, the duty ratio = 1.0) and the pump is driven at the predetermined rotational speed X1. . When the fully open flow rate characteristic is specified, the control unit 102 calculates the purge gas flow rate from the fully open flow rate characteristic using the pressure of the intake manifold IM, the rotational speed X2 of the pump 48, and the duty ratio Y of the control valve 26. . Specifically, the flow rate Z corresponding to the pressure of the intake manifold IM is specified from the fully open flow rate characteristics. Next, the flow rate of the purge gas is calculated by multiplying the specified flow rate Z by the ratio X2 / X1 of the rotational speed of the pump 48 and the duty ratio Y of the control valve 26.

  Next, in S28, the control unit 102 switches the learning completion flag from off to on. Next, in S30, it is determined whether or not the flow rate learning value α is not less than the normal lower limit value and less than the normal upper limit value. When the flow rate learning value α is equal to or higher than the normal lower limit value and out of the range below the normal upper limit value, the flow rate of the purge gas delivered from the pump 48 is out of the normal range, and the pump 48 is operating normally. Most likely not working. When the flow rate learning value α is less than the normal lower limit value or greater than the normal upper limit value (NO in S30), in S32, the control unit 102 determines that the pump 48 is not operating normally, and determines A signal indicating the result is transmitted to the display device of the vehicle, and the pump determination process is terminated. In the display process, when a signal is received from the control unit 102, information indicating that the pump 48 is not operating normally is displayed. Thus, the driver can know that the pump 48 is not operating normally.

  On the other hand, when the flow rate learning value α is equal to or greater than the normal lower limit value and less than the normal upper limit value (YES in S30), S32 is skipped and the pump determination process is terminated.

  FIG. 5 shows the pressure of the intake manifold in the pump determination process, whether or not the purge process is performed, the deviation coefficient, the purge concentration, the learning start flag, the learning end flag, the flow rate learning value α, and the fully-open flow rate characteristics over time. Showing change.

  When the vehicle is started at time t0, the pump determination process is periodically executed. In addition to the pump determination process, a concentration estimation process is also periodically executed. During the period from the time t0 to the time t1, the learning start condition is not satisfied (that is, the purge concentration is not stable in the condition (IV)), and in the pump determination process, it is repeated YES in S12, NO in S14, and S18. YES or NO and NO are determined in S20. During this period, the flow rate when the pump 48 is fully opened is the flow rate learning value α stored in the control unit 102 at the time when the ignition switch was switched from on to off last time (that is, the pump determination process executed last). It is determined using the flow rate learning value α) specified in (1). During this period, the learning completion flag, the learning start flag, the start condition flag, the execution condition flag, and the concentration estimation process prohibition flag are off, the start condition timer is counted, and the execution condition timer is stopped.

  The purge concentration is not stable for a while after the vehicle is started. During this period, since the air-fuel ratio varies greatly depending on the purge concentration, it is difficult to specify variation in the flow rate of the purge gas from the pump 48 from the reference flow rate using the variation in the air-fuel ratio. At time t1, conditions (I) to (IV) are achieved, the start condition flag is switched from off to on, the count of the start condition timer is reset and restarted. At time t2, with the start condition flag kept on, the count of the start condition timer passes the first period, and the learning start condition is satisfied (YES in S14). Thereby, the learning start flag is switched from OFF to ON (S16).

  From time t2 to time t3, the learning start condition is satisfied. In the pump determination process, YES is performed in S12, YES in S14, and S16.

  At time t3, the pressure of the intake manifold IM exceeds the reference value (NO in S14). At time t3, the period during which the condition (I) the intake manifold IM pressure is less than the reference value is not achieved is less than the second period (NO in S18), so whether or not the execution condition is satisfied. It is judged (S20). At time t3, conditions (i) to (iv) are achieved, the execution condition flag is switched from off to on, and the execution condition timer starts counting. After the time t3, in the pump determination process, it is repeatedly determined YES in S12, NO in S14, YES or NO in S18, and NO in S20.

  At time t4, with the execution condition flag kept on, the execution condition timer count passes the third period, and the execution condition is satisfied (YES in S20). Thereby, the flow learning value α is specified (S24), and the learning completion flag is switched from OFF to ON (S28). It should be noted that some time has elapsed from when the execution condition is established until the flow rate learning value α is specified and the learning completion flag is switched from OFF to ON. In FIG. It is shown. After time t4, the fully open flow rate is calculated using the fully open flow rate characteristic calculated in S26. For this reason, the fully open flow rate characteristic V1 using the reference flow rate is corrected to the fully open flow rate characteristic V2.

  Note that the time t4 is an example of timing at which the pressure of the intake manifold IM (that is, the intake passage 34) is shifted from a lower state to a higher state than a reference value. In this configuration, when the purge concentration is stabilized, the amount of fuel supplied to the engine 2 is adjusted so that the air-fuel ratio becomes a predetermined reference air-fuel ratio in accordance with the stable purge concentration. When the pressure of the intake manifold IM shifts from a low state to a high state, the flow rate of the purge gas delivered from the purge path 24 decreases due to the difference between the pressure of the intake manifold IM and the pressure of the purge path 24. For this reason, of the total flow rate of purge gas supplied from the purge path 24 to the intake manifold IM, the ratio of the flow rate of purge gas sent from the purge path 24 to the intake manifold IM due to driving of the pump 48 increases. For this reason, mainly due to the variation in the flow rate of the purge gas from the pump 48, the amount of evaporated fuel supplied to the engine 2 changes, and the air-fuel ratio changes to the rich side or the lean side. The evaporative fuel processing device 20 specifies the flow rate learning value α at the timing when the pressure of the intake manifold IM (that is, the intake passage 34) is shifted from the lower state to the higher state than the reference value, so that the air-fuel ratio is supplied to the engine 2. It can be specified by utilizing the deviation of the air-fuel ratio before being adjusted by controlling the amount of fuel supplied. In addition, when the pressure of the intake manifold IM is higher, the variation in the flow rate of the purge gas from the pump 48 becomes more significant. From this, by specifying the flow rate learning value α in a state where the pressure of the intake manifold IM is high, it is possible to specify the flow rate learning value α under a situation in which the variation appears remarkably.

  In a situation where the purge gas is sent to the intake path by the pump 48, if the flow rate of the purge gas by the pump 48 varies, the purge gas flow rate deviates from the reference flow rate. As a result, the fuel amount supplied to the engine 2 is different from the assumed fuel amount. For this reason, if the amount of fuel supplied to the engine 2 is controlled based on the reference flow rate (that is, the amount of fuel from the injector 4), the air-fuel ratio may be lost. In the evaporative fuel processing device 20, the flow rate learning value α indicating the variation in the flow rate of the pump 48 is specified by using the deviation of the air-fuel ratio of the engine 2 while the purge gas is being sent to the intake path 34 by the pump 48. According to this configuration, in order to grasp the variation in the flow rate, the variation in the flow rate of the pump 48 can be specified using the air-fuel ratio sensor without providing a dedicated detection device (for example, a pressure sensor). Thereby, it is possible to appropriately grasp the variation in the flow rate of the purge gas from the pump 48.

  Further, the flow rate of the purge gas from the pump 48 can be estimated by specifying the fully open flow rate characteristic using the flow rate learning value α.

  Furthermore, the fuel vapor processing apparatus 20 can determine that the pump 48 is not operating normally using the flow rate learning value α.

  The evaporative fuel processing apparatus 20 specifies the flow rate learning value α in a situation where the purge concentration is relatively high. Thus, the flow rate learning value α can be specified under the situation where the variation of the air-fuel ratio becomes large due to the variation of the flow rate of the purge gas from the pump 48.

  The evaporative fuel processing device 20 prohibits the concentration estimation process when specifying the flow rate learning value α. According to this configuration, the purge concentration is corrected, and the amount of fuel supplied to the engine 2 is adjusted based on the corrected purge concentration, whereby fluctuations in the air-fuel ratio shift can be suppressed. The timing when the execution condition is satisfied (YES in S20) is an example of “when an index should be specified”.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

(1) In the above embodiment, when calculating the fully open flow rate characteristic, data representing the pressure difference from the reference flow rate is specified using the pressure-flow rate difference data map shown in FIG. 4 (see S26). However, the control unit 102 does not store the pressure-flow rate difference data map, and the control unit 102 does not have to specify data representing the pressure difference from the reference flow rate. For example, as shown in FIG. 7, the control unit 102 may store in advance a pressure-flow rate data map indicating the flow rate of the purge gas when the control valve 26 is fully opened with respect to the pressure in the intake path. In S26 of the pump determination process, the flow rate characteristic data corresponding to the flow rate learning value α specified in S24 may be specified from the flow rate characteristic data 210, 212, 214, 216, 218.

(2) In the pump determination process of the above embodiment, the control unit 102 does not have to execute the processes of S26 to S32. For example, in the pump determination process, the control unit 102 may specify the flow rate learning value α (S24) and end the pump determination process. In this case, a device other than the control unit 102 (for example, the ECU 100) may estimate the flow rate. Or the control part 102 does not need to perform the process of S30-S32. The control unit 102 may specify the flow rate learning value α (S28) and end the pump determination process. Alternatively, the control unit 102 may identify the flow rate learning value α (S24), execute S28 to S32 without executing S26, and end the pump determination process.

(3) In the pump determination process of the above embodiment, the control unit 102 does not have to execute the process of S22, that is, prohibiting the purge concentration estimation process.

(4) The processing order of the pump determination processing is not limited to the order shown in FIG. For example, the processing of S30 and S32 may be executed after S26, and then S28 may be executed. Alternatively, the process of S22 may be executed before the execution condition flag of S20 is on and the count of the execution condition timer exceeds the third period. In this case, the timing between the times t3 and t4 is an example of “when the index should be specified”.

(5) The pump determination process of the above embodiment includes that all four conditions (I) to (IV) are achieved as learning start conditions. However, at least one of the conditions (I) to (IV) may not be achieved as the learning start condition. For example, when the three conditions (I) to (III) are continuously achieved for the first period, it may be determined that the learning start condition is satisfied (YES in S14). .

(6) In the pump determination process of the above embodiment, the execution condition includes that all four conditions (i) to (iv) are achieved. However, at least one of the conditions (i) to (iv) may not be achieved as the execution condition. For example, when the three conditions (i), (iii), and (iv) are continuously achieved over the third period, it is determined that the execution condition is satisfied (YES in S14). May be.

(7) The timing at which the pressure of the intake manifold IM (i.e., the intake passage 34) is shifted from a state lower than the reference value to a higher state is the time t3 immediately after the pressure of the intake manifold IM exceeds the reference value. Alternatively, it may be a timing between time t3 and time t4 when a predetermined period has elapsed after the pressure of the intake manifold IM exceeds the reference value.

(8) The purge concentration may be detected by, for example, a purge concentration detection device arranged on the purge path 24.

(9) The control unit 102 may be arranged separately from the ECU 100.

(10) In the above embodiment, the purge gas flow rate is estimated using the flow rate learning value α, and thereby the fuel amount to the engine 2 (that is, the injected fuel amount of the injector 4) is controlled. However, the ECU 100 corrects at least one of the duty ratio of the control valve 26 and the rotational speed of the pump 48 by using at least one of the flow rate learning value α and the purge gas flow rate estimated from the flow rate learning value α, so The flow rate may be adjusted (for example, adjusted so that the purge gas flow rate becomes the reference flow rate).

(11) In the above embodiment, when the flow rate learning value α is specified in the pump determination process (S24 in FIG. 2), the learning completion flag is set to ON. Thus, once the flow rate learning value α is specified while the ignition switch is on, the ignition switch is switched from on to off, the learning completion flag is switched from on to off, and then the ignition switch The flow rate learning value α is not specified until is switched from OFF to ON. However, the control unit 102 specifies the flow rate learning value α a plurality of times until the ignition switch is switched from OFF to ON and then switched from ON to OFF. The flow rate learning value α stored in 102 may be updated. For example, when the learning completion flag is on for a predetermined period, the control unit 102 may switch the learning completion flag from on to off.

  The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Engine 6: Fuel supply system 10: Main supply path 14: Fuel tank 16: Fuel pump unit 19: Canister 20: Evaporative fuel processing device 23: Purge path 24: Purge path 26: Control valve 28: Communication path 30: Air cleaner 32: Throttle valve 34: Intake path 48: Pump 100: ECU
102: Control unit

Claims (6)

An evaporative fuel processing device mounted on a vehicle,
A canister for storing evaporated fuel;
A control valve that is disposed in a purge path that connects the canister and an intake path of the internal combustion engine, and that switches between a closed state that closes the purge path and an open state that opens the purge path;
A pump for sending purge gas containing evaporated fuel in the canister to the intake path via the purge path;
The control valve is in the open state, and the purge gas sent from the pump to the intake passage is used by using the air-fuel ratio of the internal combustion engine while the purge gas is sent to the intake passage by the pump. An evaporative fuel processing apparatus comprising: a specifying unit that specifies an index indicating variation in a flow rate from a reference flow rate. The flow rate of the purge gas delivered by the pump can be adjusted by the opening of the control valve,
The flow rate of the purge gas delivered by the pump while the control valve is fully open and the purge gas is delivered by the pump to the intake passage using the indicator and the pressure of the intake passage. The evaporative fuel processing apparatus of Claim 1 further provided with the estimation part to estimate.   The evaporated fuel processing apparatus according to claim 1, further comprising a determination unit that determines that the pump is not operating normally using the index.   The specifying unit specifies the index at a timing when the concentration of the evaporated fuel in the purge gas is stable and the pressure in the intake passage is shifted from a state lower than a reference value to a state higher than the reference value. The evaporated fuel processing apparatus according to any one of claims 1 to 3.   5. The evaporated fuel processing apparatus according to claim 1, wherein the specifying unit specifies the index when the concentration of the evaporated fuel in the purge gas is higher than a predetermined value. 6. The vehicle includes a concentration correction unit that corrects the concentration of the evaporated fuel in the purge gas using the air-fuel ratio,
The evaporated fuel processing apparatus according to any one of claims 1 to 5, wherein the specifying unit prohibits the concentration correction unit from correcting the concentration when the index is to be specified.

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