JP2017180321A - Evaporated fuel treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaporated fuel treatment device capable of introducing a correct amount of purge gas to an intake path.SOLUTION: An evaporated fuel processing device 20 has a canister 19 for adsorbing an evaporated fuel evaporated in a fuel tank 14, a purge passage 22a through which a purge gas sent to an intake path 34 from the canister 19 passes, and a concentration detecting portion 57 for detecting concentration of the purge gas passing through the purge passage 22a. The concentration detecting portion 57 has a first detecting portion and a second detecting portion connected in series. The first detecting portion is a type to detect gas density of the purge gas on the basis of differential pressure at the time when the purge gas passes through the first detecting portion. The second detecting portion is a type to detect viscosity of the purge gas on the basis of the differential pressure at the time when the purge gas passes through the second detecting portion.SELECTED DRAWING: Figure 1

Description

  This specification discloses the technique regarding an evaporative fuel processing apparatus. In particular, an evaporative fuel processing device is disclosed that purges evaporative fuel generated in a fuel tank into an intake path of an internal combustion engine for processing.

  Patent Document 1 discloses an evaporative fuel processing apparatus. In Patent Document 1, a sensor for detecting the fluid density of air introduced into the canister and a sensor for detecting the fluid density of purge gas sent from the canister to the internal combustion engine are arranged, and based on the ratio or difference between the fluid densities of the two. The concentration of the purge gas is calculated, and the flow rate of the purge gas introduced into the intake path is determined based on the calculated gas concentration.

JP-A-6-101534

  In Patent Document 1, the concentration of purge gas is calculated using a sensor that detects the fluid density, and the supply amount (flow rate) of the purge gas is determined. In order to stabilize the air-fuel ratio (A / F) of the internal combustion engine, it is necessary to introduce the purge gas accurately into the intake passage at the determined flow rate. Therefore, in the case of Patent Document 1, it is necessary to separately provide a sensor (flow meter) for detecting the flow rate of the purge gas in order to introduce the purge gas into the intake passage at an accurate flow rate. The present specification provides a technique for realizing an evaporative fuel processing apparatus that can introduce a purge gas into an intake passage with an accurate amount while eliminating a sensor that detects a flow rate of the purge gas.

  The evaporated fuel processing apparatus disclosed in the present specification includes a canister, a purge passage, and a concentration detection unit. The canister adsorbs the evaporated fuel evaporated in the fuel tank. The purge passage is connected between the intake passage of the internal combustion engine and the canister. Purge gas sent from the canister to the internal combustion engine passes through the purge passage. The concentration detector has a first detector and a second detector connected in series. The concentration detector detects the concentration of purge gas passing through the purge passage. In this fuel vapor processing apparatus, the first detector is a type that detects the gas density of the purge gas based on the differential pressure when the purge gas passes through the first detector. The second detector is a type that detects the viscosity of the purge gas based on the differential pressure when the purge gas passes through the second detector.

上記式（１）において、Ｑ１は第１検出部を通過するパージガスの流量、ΔＰ１は第１検出部で測定された差圧、Ｃは流量係数、Ｋは管路係数、ρはガス密度を示している。

上記式２において、Ｑ２は第２検出部を通過するパージガスの流量、ΔＰ２は第２検出部で測定された差圧、μは粘性係数、ｌは管路長さ、ｄは管路直径を示している。 In the fuel vapor processing apparatus, the concentration detector includes two detectors (first detector and second detector) connected in series. The first detection unit detects a differential pressure when the purge gas passes through the first detection unit, and uses the following equation (1) to determine the flow rate Q1 of the purge gas passing through the first detection unit and the gas density ρ of the purge gas. Get a function. The second detection unit detects a differential pressure when the purge gas passes through the second detection unit, and uses the following equation (2) to determine the flow rate Q2 of the purge gas passing through the second detection unit and the viscosity coefficient of the purge gas. Get a function of μ. Since the first detection unit and the second detection unit are connected in series, the flow rate Q1 and the flow rate Q2 are equal. The concentration detector detects the gas density ρ and the viscosity coefficient μ such that the flow rate Q1 and the flow rate Q2 are equal. The gas density ρ and the viscosity coefficient μ are correlated with the gas concentration of the purge gas. Therefore, the gas concentration of the purge gas can be detected based on the results of the gas density ρ and the viscosity coefficient μ. Further, the flow rate of the purge gas passing through the concentration detection unit (that is, the flow rate Q1, Q2) can be calculated from the result of the gas density ρ or the viscosity coefficient μ using the following formula (1) and / or (2). it can.

In the above formula (1), Q1 is the flow rate of the purge gas passing through the first detector, ΔP1 is the differential pressure measured by the first detector, C is the flow coefficient, K is the pipe coefficient, and ρ is the gas density. ing.

In the above equation 2, Q2 is the flow rate of the purge gas passing through the second detector, ΔP2 is the differential pressure measured by the second detector, μ is the viscosity coefficient, l is the pipe length, and d is the pipe diameter. ing.

上記式（１）において、Ｑ１は第１検出部を通過するパージガスの流量、ΔＰ１は第１検出部で測定された差圧、Ｃは流量係数、Ｋは管路係数、ρはガス密度を示している。

上記式２において、Ｑ２は第２検出部を通過するパージガスの流量、ΔＰ２は第２検出部で測定された差圧、μは粘性係数、ｌは管路長さ、ｄは管路直径を示している。 The present specification also discloses a method for detecting the concentration and flow rate of the purge gas passing through the purge passage in the following fuel vapor processing apparatus. The evaporated fuel processing device is connected between a canister that adsorbs evaporated fuel evaporated in a fuel tank, and an intake path of the internal combustion engine and a canister, and a purge passage through which purge gas sent from the canister to the intake path passes. And a concentration detector. The concentration detector is connected in series with the first detector for detecting the gas density of the purge gas from the differential pressure when the purge gas passes, and is connected in series with the first detector, and from the differential pressure when the purge gas passes, A second detection unit for detecting viscosity is included. In this method, the differential pressure measured by the first detector is substituted into the following formula (1), the differential pressure measured by the second detector is substituted into the following formula (2), and the following formula (1) and The gas density and viscosity at which the flow rates Q1 and Q2 in (2) are equal are obtained, the concentration of the purge gas is calculated from at least one of the calculated gas density and viscosity, and the purge gas concentration is calculated from at least one of the calculated gas density and viscosity. Calculate the flow rate.

In the above formula (1), Q1 is the flow rate of the purge gas passing through the first detector, ΔP1 is the differential pressure measured by the first detector, C is the flow coefficient, K is the pipe coefficient, and ρ is the gas density. ing.

In the above equation 2, Q2 is the flow rate of the purge gas passing through the second detector, ΔP2 is the differential pressure measured by the second detector, μ is the viscosity coefficient, l is the pipe length, and d is the pipe diameter. ing.

1 shows a vehicle fuel supply system using an evaporative fuel processing apparatus according to a first embodiment. 1 shows an evaporated fuel processing apparatus according to a first embodiment. The structure of a density sensor is shown. An example of a 1st detection part is shown. An example of a 1st detection part is shown. An example of a 2nd detection part is shown. The fuel supply system of the vehicle using the evaporative fuel processing apparatus of 2nd Example is shown. The evaporative fuel processing apparatus of 2nd Example is shown. The modification of the evaporative fuel processing apparatus of 2nd Example is shown. The modification of the evaporative fuel processing apparatus of 2nd Example is shown. The evaporative fuel processing apparatus of 3rd Example is shown. 1 shows an evaporative fuel supply system. The flowchart of the detection method of the density | concentration and flow volume of purge gas is shown. The relationship between the differential pressure | voltage in a density | concentration detection part and the flow volume of a pump is shown. The flowchart of the adjustment method of purge gas supply amount is shown. The flowchart of the adjustment method of purge gas supply amount is shown. The flowchart of the adjustment method of purge gas supply amount is shown. The flowchart of the adjustment method of purge gas supply amount is shown. The flowchart of the adjustment method of purge gas supply amount is shown. The timing chart of the adjustment process of purge gas supply amount is shown. The timing chart of the adjustment process of purge gas supply amount is shown. The flowchart of the adjustment method of purge gas supply amount is shown. The flowchart of the adjustment method of purge gas supply amount is shown. The flowchart of the adjustment method of purge gas supply amount is shown. The timing chart of the adjustment process of purge gas supply amount is shown. The timing chart of the adjustment process of purge gas supply amount is shown.

  The main features of the embodiments described below are listed. Note that the technical elements described below are independent technical elements, and exhibit technical usefulness alone or in various combinations.

(Feature 1) In the fuel vapor processing apparatus disclosed in this specification, the concentration detection unit includes a first detection unit and a second detection unit connected in series. The first detector is a type that detects the gas density of the purge gas based on the differential pressure when the purge gas passes through the first detector. The second detector is a type that detects the viscosity of the purge gas based on the differential pressure when the purge gas passes through the second detector. The concentration detection unit may be provided on the purge passage. Alternatively, a branch passage may be connected to the purge passage, and a concentration detector may be provided on the branch passage. By providing the concentration detector on the branch passage, it is possible to suppress an increase in the flow path resistance of the purge gas passing through the purge passage. Note that both ends of the branch passage may be connected to the purge passage so that the purge gas circulates through the purge passage and the branch passage. Alternatively, one end of the branch passage may be connected to the purge passage, and the other end may be connected to the canister, the fuel tank and the canister to a communication pipe or the like.

(Feature 2) The fuel vapor processing apparatus may include a pump that sends purge gas from the canister to the intake path. The pump may be disposed on the purge passage. When the branch passage is connected to the purge passage, the pump may be disposed on the purge passage or the branch passage. By providing the pump, the purge gas can be introduced into the intake passage regardless of the pressure state (positive pressure, negative pressure, normal pressure) in the intake passage. For example, in a vehicle having a supercharger, purge gas can be introduced into the intake path even when the intake path is in a positive pressure state.

(Characteristic 3) The fuel vapor processing apparatus includes a control valve that switches between a communication state in which the canister and the intake passage are communicated with each other via the purge passage, and a shut-off state in which the canister and the intake passage are shut off on the purge passage. May be. In addition to the control valve, the above-described branch path and pump may be provided. In this case, when the control valve is switched to the cutoff state while the pump is driven, the purge gas moves to the branch path, and the concentration of the purge gas can be detected by the concentration detector. The “control valve” may be a valve that switches only between a communication state and a shut-off state, or may be a valve that can adjust the opening degree. As the former type of valve, for example, there is a control valve that adjusts the flow rate of the purge gas during purging by duty-controlling the communication state and the cutoff state. Examples of the latter type of valve include a stepping motor type control valve. By adjusting the opening of the stepping motor type control valve, the flow rate of the purge gas during the purge can be adjusted.

(First embodiment)
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 includes a main supply path 10 for supplying fuel stored in the fuel tank 14 to the engine 2 and a purge supply path for supplying evaporated fuel generated in the fuel tank 14 to the engine 2. 22 is provided.

  The main supply path 10 is provided with a fuel pump unit 16, a supply pipe 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 an ECU (not shown). 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 pipe 12. The supply pipe 12 is connected to the fuel pump unit 16 and the injector 4. The fuel supplied to the supply pipe 12 passes through the supply pipe 12 and reaches the injector 4. The injector 4 has a valve (not shown) whose opening degree is controlled by the ECU. When the valve of the injector 4 is opened, the fuel in the supply pipe 12 is supplied to the intake pipe 34 connected to the engine 2.

  The intake pipe 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 pipe 34. A throttle valve 32 is provided in the intake pipe 34. When the throttle valve 32 is opened, intake is performed from the air cleaner 30 toward the engine 2. The throttle valve 32 adjusts the opening of the intake pipe 34 and adjusts the amount of air flowing into the engine 2. The throttle valve 32 is provided on the upstream side (the air cleaner 30 side) from the injector 4.

  The purge supply path 22 includes an evaporated fuel processing device 20 and a communication pipe 18 that communicates with the fuel tank 14 and the evaporated fuel processing device 20. The fuel vapor processing apparatus 20 includes a canister 19, a purge passage 22a, a pump 52, a concentration sensor 57, and a control valve 26 (Vacuum Switching Valve). The communication pipe 18 connects the fuel tank 14 and the canister 19. The canister 19, the pump 52, the concentration sensor 57, and the control valve 26 are disposed on the purge passage 22a. The control valve 26 is an electromagnetic valve controlled by the ECU, and is an electromagnetic valve whose duty is controlled by the ECU to switch between the communication state and the cutoff state. Further, instead of the control valve 26, a valve capable of adjusting the opening, such as a stepping motor control valve, may be used. Although details will be described later, the concentration sensor 57 includes two detection units connected in series.

  As shown in FIG. 2, the canister 19 includes an atmospheric port 19a, a purge port 19b, and a tank port 19c. The atmospheric port 19 a is connected to the air filter 15 via the communication pipe 17. The purge port 19b is connected to the purge passage 22a. The tank port 19 c is connected to the fuel tank 14 via the communication pipe 18. Activated carbon 19 d is accommodated in the canister 19. Of the wall surfaces of the canister 19 facing the activated carbon 19d, ports 19a, 19b and 19c are provided on one wall surface. A space exists between the activated carbon 19d and the inner wall of the canister 19 provided with the ports 19a, 19b and 19c. A first partition plate 19e and a second partition plate 19f are fixed to the inner wall of the canister 19 on the side where the ports 19a, 19b and 19c are provided. The first partition plate 19e separates the space between the activated carbon 19d and the inner wall of the canister 19 between the atmospheric port 19a and the purge port 19b. The first partition plate 19e extends to a space opposite to the side where the ports 19a, 19b and 19c are provided. The second partition plate 19f separates the space between the activated carbon 19d and the inner wall of the canister 19 between the purge port 19b and the tank port 19c.

  The activated carbon 19d adsorbs the evaporated fuel from the gas flowing into the canister 19 from the fuel tank 14 through the communication pipe 18 and the tank port 19c. The gas after the evaporated fuel is adsorbed passes through the atmospheric port 19a, the communication pipe 17, and the air filter 15 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 19d is supplied to the purge passage 22a from the purge port 19b. The first partition plate 19e separates the space to which the atmospheric port 19a is connected from the space to which the purge port 19b is connected. The first partition plate 19e prevents the gas containing the evaporated fuel from being released into the atmosphere. The second partition plate 19f separates the space to which the purge port 19b is connected from the space to which the tank port 19c is connected. The second partition plate 19f prevents gas flowing into the canister 19 from the tank port 19c from moving directly to the purge passage 22a.

  The purge passage 22 a connects the canister 19 and the intake pipe 34. The evaporated fuel (purge gas) adsorbed by the canister 19 is introduced into the intake pipe 34 through the purge passage 22a. A pump 52, a concentration sensor 57, and a control valve 26 are provided on the purge passage 22a. The pump 52 is disposed between the canister 19 and the concentration sensor 57 and pumps the purge gas to the intake pipe 34. Typically, when the engine 2 is driven, the intake pipe 34 has a negative pressure. Therefore, the evaporated fuel adsorbed by the canister 19 can be introduced into the intake pipe 34 due to a pressure difference between the intake pipe 34 and the canister 19. However, by disposing the pump 52 in the purge passage 22a, when the pressure in the intake pipe 34 is not sufficient to draw the purge gas (a positive pressure at the time of supercharging or a negative pressure, the absolute value of the pressure) Even if the value is small), the evaporated fuel adsorbed by the canister 19 can be supplied to the intake pipe 34. Further, by disposing the pump 52, a desired amount of evaporated fuel can be supplied to the intake pipe.

  The concentration sensor 57 is disposed between the pump 52 and the control valve 26, and detects the concentration of barge gas passing through the purge passage 22a. In addition, as long as it is between the canister 19 and the control valve 26, the order of the pump 52 and the concentration sensor 57 may be reversed. That is, from the canister 19 toward the intake pipe 34, the pump 52, the concentration sensor 57, and the control valve 26 may be arranged in this order, or the concentration sensor 57, the pump 52, and the control valve 26 may be arranged in this order. . In the evaporated fuel processing apparatus 20, when the control valve 26 is opened with the pump 52 driven, the purge gas passes through the concentration sensor 57 and is introduced into the intake pipe 34. While supplying the purge gas to the intake pipe 34, the concentration of the purge gas can be detected.

Ｑ１：第１検出部を通過するパージガスの流量、ΔＰ１：第１検出部で測定された差圧，Ｃ：流量係数，Ｋ：管路係数

Ｑ２：第２検出部を通過するパージガスの流量，ΔＰ２：第２検出部で測定された差圧，μ：粘性係数，ｌ：管路長さ，ｄ：管路直径 As shown in FIG. 3, the concentration sensor 57 includes a first detection unit 102 and a second detection unit 104. The first detection unit 102 and the second detection unit 104 are connected in series. Therefore, the purge gas that has passed through the first detection unit 102 also passes through the second detection unit 104. That is, the flow rate of the purge gas passing through the first detection unit 102 and the flow rate of the purge gas passing through the second detection unit 104 are the same. The first detection unit 102 is a type that measures the differential pressure when the purge gas passes and detects the gas density of the purge gas based on the measured differential pressure. The second detection unit 104 is a type that measures the differential pressure when the purge gas passes and detects the viscosity of the purge gas based on the measured differential pressure. Specifically, the relationship between the flow rate Q1 shown in the following formula (1) and the gas density ρ is obtained by the first detection unit 102, and the flow rate Q2 and the viscosity coefficient μ shown in the following formula (2) are obtained by the second detection unit 104. A relationship is obtained. There is a correlation between the gas density ρ and the concentration of the purge bath. Further, the viscosity coefficient μ and the concentration of the purge gas have a correlation. The concentration of the purge gas can be detected by obtaining the gas density ρ and the viscosity coefficient μ such that the flow rates Q1 and Q2 are equal.

Q1: Flow rate of purge gas passing through the first detector, ΔP1: differential pressure measured by the first detector, C: flow coefficient, K: pipe coefficient

Q2: flow rate of purge gas passing through the second detector, ΔP2: differential pressure measured by the second detector, μ: viscosity coefficient, l: pipe length, d: pipe diameter

  Various types of sensors can be used as the detection unit constituting the density sensor 57. Here, an example of the detection unit constituting the density sensor 57 will be described with reference to FIGS. 4 to 6. FIG. 4 shows a detection unit 102a with a built-in Venturi tube 72. The detection unit 102a is an example of a first detection unit. The arrow 60 indicates the direction in which the purge gas flows. The venturi pipe 72 is connected to the purge passage 22a. Specifically, end portions (large diameter portions) 72a and 72c of the venturi pipe 72 are connected to the purge passage 22a. The central portion (throttle portion) 72b of the venturi tube 72 has a smaller flow path area than the end portions 72a and 72c. Therefore, a differential pressure is generated between the central portion 72b and the end portions 72a and 72c. A differential pressure sensor 70 is connected to an end portion (upstream end portion) 72a and a central portion 72b on the side where the purge gas is introduced. The detection unit 102a detects the pressure difference between the end portion 72a and the central portion 72b with the differential pressure sensor 70. In the detection part 102a, the relationship between the flow rate Q1 and the gas density ρ is obtained by the above equation (1) by detecting the differential pressure between the end part 72a and the central part 72b.

  FIG. 5 shows the detection unit 102b in which the orifice tube 74 is built. The detection unit 102a is also an example of a first detection unit. Both ends of the orifice pipe 74 are connected to the purge passage 22a. In the center of the orifice pipe 74, an orifice plate 74b having an opening 74a is provided. Therefore, the central portion (throttle portion) of the orifice pipe 74 has a smaller flow area than the end portion. In the detection unit 102b, a differential pressure is generated between the upstream side and the downstream side of the orifice plate 74b. A differential pressure sensor 70 is connected to the upstream side and the downstream side of the orifice plate 74b. The detection unit 102b detects the pressure difference between the upstream side and the downstream side of the orifice plate 74b with the differential pressure sensor 70. By detecting the differential pressure between the upstream side and the downstream side of the orifice plate 74b, the detection unit 102b obtains the relationship between the flow rate Q1 and the gas density ρ according to the above equation (1).

  FIG. 6 shows the detection unit 104 having a built-in capillary viscometer 76. The detection unit 104 is an example of a second detection unit. Both ends of the capillary viscometer 76 are connected to the purge passage 22a. Inside the capillary viscometer 76, a plurality of capillaries 76a are arranged. In the detection unit 104, a differential pressure is generated between the upstream side and the downstream side of the capillary tube 76a. A differential pressure sensor 70 is connected to the upstream side and the downstream side of the capillary tube 76a. The detection unit 104 detects the pressure difference between the upstream side and the downstream side of the capillary tube 76a with the differential pressure sensor 70. By detecting the differential pressure between the upstream side and the downstream side of the capillary tube 76a, the detection unit 104 obtains the relationship between the flow rate Q2 and the viscosity coefficient μ according to the above equation (2).

  Although the detection units 102a, 102b, and 104 have been described above, other types of detection units can be used in the evaporated fuel processing apparatus 20. What is important is that the concentration sensor 57 detects a gas density of the purge gas based on the differential pressure when the purge gas passes through the detection unit (first detection unit), and the purge gas passes through the detection unit. In other words, a detection unit (second detection unit) of a type that detects the viscosity of the purge gas based on the differential pressure is provided, and the first detection unit and the second detection unit are connected in series. Thereby, the relationship between the flow rate of the purge gas passing through the first detection unit and the gas density of the purge gas (the above equation (1)), and the relationship between the flow rate of the purge gas passing through the second detection unit and the viscosity coefficient of the purge gas (the above equation ( 2)) is obtained, and the gas density and viscosity coefficient can be obtained so that the flow rates of the equations (1) and (2) are equal. The gas concentration of the purge gas can be obtained from the gas density and the viscosity coefficient. Further, the flow rate of the purge gas can be calculated from the above formula (1) or (2) without using a flow meter.

(Second embodiment)
With reference to FIG.7 and FIG.8, the evaporative fuel processing apparatus 20a is demonstrated. The evaporated fuel processing device 20 a is a modification of the evaporated fuel processing device 20. Specifically, the evaporated fuel processing device 20a differs from the evaporated fuel processing device 20 in that a branch path 22b is connected to the purge passage 22a. In the fuel vapor processing apparatus 20a, a switching valve 90 is provided in the purge passage 22a. In addition, about the fuel vapor processing apparatus 20a, the same reference number is attached | subjected to the same component as the fuel vapor processing apparatus 20, and description may be abbreviate | omitted.

  The evaporated fuel processing apparatus 20a includes a canister 19, a purge passage 22a, a pump 52, a control valve 26, a branch passage 22b, a concentration sensor 57, a switching valve 90, and an air introduction pipe 92. The switching valve 90, the pump 52, and the control valve 26 are disposed on the purge passage 22a. One end of the branch passage 22 b is connected to the purge passage 22 a upstream of the pump 52, and the other end is connected to the purge passage 22 a downstream of the pump 52. A concentration sensor 57 is provided on the branch passage 22b. Instead of the control valve 26, a valve capable of adjusting the opening, such as a stepping motor control valve, may be used.

  The purge passage 22 a connects the canister 19 and the intake pipe 34. A pump 52 and a control valve 26 are provided on the purge passage 22a. The pump 52 draws the purge gas in the canister 19 through the purge passage 22a in the direction of arrow 60, and pushes the purge gas toward the intake pipe 34 through the purge passage 22a in the direction of arrow 66. A branch passage 22b is connected to the purge passage 22a. A concentration sensor 57 is disposed on the branch passage 22b. More specifically, the branch passage 22 b includes a first branch pipe 56 and a second branch pipe 58. One end of the first branch pipe 56 is connected downstream of the pump 52 (on the intake pipe 34 side). One end of the second branch pipe 58 is connected upstream of the pump 52 (on the canister 19 side). The other ends of the first branch pipe 56 and the second branch pipe 58 are connected to the concentration sensor 57. The concentration sensor 57 detects the concentration of barge gas passing through the branch passage 22b.

  In the evaporated fuel processing apparatus 20a, when the control valve 26 is opened while the pump 52 is driven, the purge gas moves in the direction of the arrow 66 and is introduced into the intake pipe 34. When the control valve 26 is closed while the pump 52 is driven, the purge gas moves in the direction of the arrow 62 and the concentration sensor 57 detects the concentration. During the purge execution, the control valve 26 is repeatedly opened and closed based on the duty ratio in order to adjust the supply amount of the purge gas to the intake pipe 34. The evaporative fuel processing apparatus 20a can detect the concentration of the purge gas by using the timing at which the control valve 26 is closed during the purge execution. The concentration sensor 57 is provided on the branch passage 22b and is not provided on the purge passage 22a. Therefore, the evaporated fuel processing device 20a can suppress an increase in the resistance of the purge passage 22a, and can suppress the amount of purge gas supplied to the intake pipe 34 from being limited. The purge gas can also be supplied to the concentration sensor 57 while supplying the purge gas to the intake pipe 34 by adjusting the inner diameters of the purge passage 22a and the branch passage 22b. In this case, the concentration of the purge gas supplied to the intake pipe 34 can be detected in real time.

  A switching valve 90 is provided in the purge passage 22a. The switching valve 90 is disposed on the upstream side of the pump 52. An atmosphere introduction pipe 92 is connected to the switching valve 90. The switching valve 90 can switch between a state in which the purge passage 22a is connected to the canister 19 (first state) and a state in which the purge passage 22a is connected to the atmosphere introduction pipe 92 (second state). By switching the switching valve 90, the differential pressure detected by the concentration sensor 57 when air passes through the branch passage 22b is compared with the differential pressure detected by the concentration sensor 57 when purge gas passes through the branch passage 22b. can do. By comparing the pressure difference between the two, the characteristics of the pump 52 (the flow rate passing through the pump at a predetermined rotational speed) can be calculated. Even if the output (rotation speed) of the pump 52 is the same, the flow rate of the fluid passing through the pump 52 varies depending on the density (concentration) of the fluid passing therethrough. By providing the switching valve 90 and comparing the differential pressure of the air passing through the concentration sensor 70 with the differential pressure of the purge gas, the flow rate characteristic of the pump 52 can be obtained, and the detection accuracy of the purge gas concentration is improved. An accurate amount of purge gas can be introduced into the intake pipe 34. Note that the switching valve 90 and the atmospheric introduction pipe 92 contribute to improving the detection accuracy of the purge gas concentration, and the purge gas concentration can be detected even if the switching valve 90 and the atmospheric introduction pipe 92 are omitted. .

  Like the fuel vapor processing apparatus 20b shown in FIG. 9, the concentration sensor 57 and the temperature sensor 59 may be arranged on the branch path 22b. Moreover, the concentration sensor 57 and the pressure gauge 71 may be arrange | positioned on the branch path 22b like the evaporative fuel processing apparatus 20c shown in FIG. The pressure gauge 71 is provided upstream of the concentration sensor 57. In the evaporated fuel processing device 20c, a temperature sensor (see FIG. 9) may be further disposed on the branch path 22b. When both ends of the branch path 22b are connected to the purge passage 22a as in the fuel vapor processing apparatuses 20a to 20c, the pump 52 may be omitted and a venturi pipe (see FIG. 4) may be connected to the purge passage 22a. . In this case, the purge gas can be supplied to the concentration sensor 57 while supplying the purge gas to the intake pipe 34 by connecting the second branch pipe 58 to the central portion (throttle portion) of the venturi pipe. The concentration of the purge gas supplied to the intake pipe 34 can be detected in real time.

(Third embodiment)
With reference to FIG. 11, the evaporative fuel processing apparatus 20d will be described. The evaporative fuel processing apparatus 20d is a modification of the evaporative fuel processing apparatuses 20a, 20b and 20c. Specifically, the position where the downstream end of the branch path 22b (the outlet side of the purge gas in the branch path) is connected is evaporated. Different from the fuel processing devices 20a to 20c. In addition, about the evaporative fuel processing apparatus 20d, the same reference number is attached | subjected to the same components as the evaporative fuel processing apparatuses 20a-20c, and description may be abbreviate | omitted. In the evaporated fuel processing device 20d, a concentration sensor 57 and a pressure gauge 71 are arranged on the branch path 22b, similarly to the evaporated fuel processing device 20c. However, only the concentration sensor 57 may be disposed on the branch path 22b as in the evaporated fuel processing apparatus 20a, or the concentration sensor 57 and the temperature sensor 59 are disposed on the branch path 22b as in the evaporated fuel processing apparatus 20b. The concentration sensor 57, the pressure gauge 71, and the temperature sensor 59 may be disposed on the branch path 22b.

  In the evaporated fuel processing apparatus 20d, the second branch pipe 58 (a branch pipe on the downstream side of the branch path) is connected to the communication pipe 18. Therefore, the purge gas passing through the branch passage 22b moves into the canister 19 through the tank port 19c. The evaporative fuel processing apparatus 20d can also detect the concentration of the purge gas when the control valve 26 is closed and the purge gas passes through the branch path 22b. The tank port 19c is not disposed on the purge passage 22a, but the canister 19 is a component disposed upstream of the pump 52. Therefore, it can also be said that the evaporative fuel processing apparatus 20 d also has one end of the branch passage 22 b connected to the purge passage 22 a downstream of the pump 52 and the other end connected upstream of the pump 52.

  A switching valve 94 is arranged between the branch path 22b and the communication pipe 18. The switching valve 94 can be switched between a communication state in which the branch path 22 b and the communication pipe 18 communicate with each other and a shut-off state in which the space between the branch path 22 b and the communication pipe 18 is blocked. Therefore, it is possible to prevent the purge gas generated in the fuel tank 14 from being introduced into the purge passage 22a via the communication pipe 18 and the branch passage 22b. The evaporated fuel processing device 20d can increase the pressure in the branch path 22b by driving the pump 52 with the control valve 26 closed and the switching valve 94 closed (shut off state). By having such a configuration, the characteristics of the pump 52 can be detected.

  The operation of the purge supply path 22 when supplying purge gas to the intake pipe 34 will be described with reference to FIG. When the engine 2 is started, the pump 52 starts to be driven by the control of the ECU 100, and the control valve 26 starts to be opened and closed. The ECU 100 controls the output of the pump 52 and the opening degree (duty ratio) of the control valve 26 based on the concentration of the purge gas detected by the concentration sensor 57. The ECU 100 also controls the opening degree of the throttle valve 32. The canister 19 adsorbs the evaporated fuel in the fuel tank 14. When the pump 52 is started, the purge gas adsorbed by the canister 19 and the air that has passed through the air cleaner 30 are introduced into the engine 2. Several methods for detecting the purge gas concentration will be described below.

  FIG. 13 shows a flowchart for explaining a method for detecting the concentration of the purge gas and the flow rate of the purge gas. This method is performed to calculate the flow rate characteristic of the pump 52 and detect the flow rate of the purge gas passing through the pump 52 when the pump 52 has a predetermined rotation speed. This method is performed with the control valve 26 closed (no purge gas is introduced into the intake pipe 34). In addition, this method can be performed with the evaporative fuel processing apparatus provided with the switching valve 90 and the atmospheric | air_introduction pipe | tube 92 like evaporative fuel processing apparatus 20a-20d.

  First, the pump 52 is driven at a predetermined rotational speed by a control signal output from the ECU 100 (step S2). The ECU 100 maintains the control valve 26 in a closed state. Next, the switching valve 90 is switched by the control signal of the ECU 100 so as to connect the purge passage 22a and the air introduction pipe 92 (step S4). As a result, the atmosphere is introduced into the purge passage 22a. The air introduced into the purge passage 22a passes through the branch passages 56 and 58. That is, by driving the pump 52, the air circulates through the purge passage 22a and the branch passage 22b. At this time, the concentration sensor 57 detects the differential pressure P0 before and after the sensor (step S6). After the detection of the differential pressure P0 is completed, the switching valve 90 is switched to connect the purge passage 22a and the canister 19 by a control signal of the ECU 100 (step S8). Thereby, the purge gas is introduced into the purge passage 22a. The purge gas circulates through the purge passage 22a and the branch passage 22b. The concentration sensor 57 detects the differential pressure P1 before and after the sensor (step S10). After detecting the differential pressure P1, the purge gas concentration and flow rate are calculated (step S12), and the drive of the pump 52 is stopped (step S14).

  FIG. 14 shows the characteristics of the density sensor 57 (characteristics based on the differential pressure caused by the structure of the density sensor) and the flow characteristics of the pump 52. The horizontal axis indicates pressure, and the vertical axis indicates the flow rate of gas passing through the pump 52. A curve 80 shows the characteristics of the concentration sensor 57 when the atmosphere is introduced into the purge passage 22a, a curve 81 shows the characteristics of the concentration sensor 57 when the purge gas is introduced into the purge passage 22a, and a straight line 82 shows the purge passage 22a. Shows the flow rate characteristic of the pump 52 when the purge gas is introduced, and the straight line 83 shows the flow rate characteristic of the pump 52 when the atmosphere is introduced into the purge passage 22a.

  As is apparent from the differential pressures P0 and P1, when the pump 52 is driven at the same rotational speed, the differential pressure increases when the purge gas is introduced into the purge passage 22a than when the atmosphere is introduced. This is the result of the purge gas being denser than the atmosphere. Therefore, a desired amount of purge gas may not be introduced into the intake pipe 34 only by adjusting the output (rotation speed) of the pump 52.

  The atmosphere does not contain purge gas. That is, the density of the atmosphere is known. Therefore, the purge gas concentration can be detected by detecting the differential pressures P0 and P1. For example, the purge gas concentration can be calculated by calculating P1 / P0. The flow rate of the purge gas can be calculated from Bernoulli's equation. Therefore, the curves 80 and 81 can be created by accurately calculating the flow rate of the gas passing through the concentration sensor 57 from the concentration of the gas (purge gas, air). Further, the flow rate characteristic of the pump 52 can be obtained by comparing the difference between the flow rates of the purge gas and the atmosphere (curves 80 and 81) when the pump 52 is driven at a predetermined number of revolutions. The amount of purge gas supplied can be adjusted more accurately. The above method can be similarly calculated by measuring the pressure upstream of the sensor using the pressure gauge 71 (see FIGS. 10 and 11), regardless of the differential pressures P0 and P1 before and after the sensor. By performing the above method (steps S2 to S14), the flow rate characteristic of the pump 52 can be obtained and the detection accuracy of the purge gas concentration can be improved. Therefore, if necessary, the step of introducing the atmosphere into the purge passage 22a and measuring the differential pressure P0 before and after the sensor (steps S4 to S8) may be omitted. Even if steps S4 to S8 are omitted, the concentration of the purge gas can be detected.

  Further, the concentration of the purge gas and the flow rate of the purge gas can be detected according to the flow shown in FIG. 15 by using the evaporated fuel processing apparatus 20d (see FIG. 11) provided with the switching valve 94. First, the pump 52 is driven at a predetermined rotational speed by a control signal output from the ECU 100 (step S3). ECU 100 maintains control valve 26 in a closed state. Next, the switching valve 90 is switched to connect the purge passage 22a and the air introduction pipe 92 by a control signal of the ECU 100 (step S5). Next, the switching valve 94 is switched by the control signal of the ECU 100 so as to connect the branch passage 22b and the communication pipe 18 (step S7). Thereby, the inside of the branch passage 22b is replaced with the atmosphere. Thereafter, the switching valve 94 is closed (the branch passage 22b and the communication pipe 18 are shut off (step S9), and the pressure P3 upstream of the concentration sensor 57 is detected by the pressure gauge 71 (step S11). After that, the switching valve 90 is switched so as to connect the purge passage 22a and the canister 19 by a control signal of the ECU 100 (step S13) The purge gas is introduced into the purge passage 22a, and then the switching valve 94 is connected to the branch passage 22b. Switching is made so as to connect the communication pipe 18 (step S15), and the inside of the branch passage 22b is replaced with purge gas, and then the switching valve 94 is closed (step S17). Detection is performed (step S19).

  After detecting the pressure P4, the concentration and flow rate of the purge gas are calculated (step S21), and the driving of the pump 52 is stopped (step S23). The pressures P3 and P4 are measured in a state where no gas flows (does not move) through the branch passage 22b (see also FIG. 14). Since the density of the atmosphere is known, the concentration of the purge gas can be calculated from (P4 / P3). Further, the flow rate characteristic (straight line 82) of the pump 52 when the purge gas is introduced into the purge passage 22a can be obtained from the pressure P1 and the pressure P4. Further, the flow rate characteristic (straight line 83) of the pump 52 when the atmosphere is introduced into the purge passage 22a can be obtained from the pressure P0 and the pressure P3.

  Next, a method for adjusting the supply amount of the purge gas when the purge gas concentration changes during the purge will be described with reference to FIG. This method can be performed with the above-described fuel vapor processing apparatuses 20a, 20b, 20c and 20d. In other words, the fuel vapor processing apparatus of the type that includes the branch path 22b and detects the concentration of the purge gas while the supply of the purge gas to the intake pipe 34 is stopped can be performed.

  The ECU 100 stores the purge gas concentration C1 detected by the concentration detection unit 21, drives the pump 52 at a predetermined rotation speed based on the concentration C1, and further controls the control valve 26 to purge the intake pipe 34. Adjust. The ECU 100 also stores a current value I1 that is supplied when the pump 52 is driven at a predetermined rotational speed. Hereinafter, the concentration C1 may be referred to as a storage concentration C1, and the current value I1 may be referred to as a storage current value I1. In step S20, the current measured density C2 is detected, and in step S21, the stored density C1 is compared with the measured density C2. When the difference between the stored concentration C1 and the measured concentration C2 is smaller than the predetermined value α (step S21: NO), the purge to the intake pipe 34 is continued based on the stored concentration C1, assuming that the change in purge gas concentration is within the allowable range. . When the difference between the stored density C1 and the measured density C2 is larger than the predetermined value α (step S21: YES), the process proceeds to step S22, and the current measured current value I2 supplied to the pump 52 is measured. Thereafter, the measured current value I2 supplied to the pump 52 is compared with the stored current value I1 (step S23). When the difference between the measured current value I2 and the current value I1 is smaller than the predetermined value β (step S23: NO), the purge to the intake pipe 34 is continued based on the stored concentration C1, assuming that the purge gas concentration change is within the allowable range. To do.

  When the difference between the current value I2 and the stored current value I1 is larger than the predetermined value β (step S23: YES), the ECU 100 stops opening / closing the control valve 26 and stops supplying the purge gas to the intake pipe 34 (step S24). ). Thereafter, the purge gas concentration is measured with the control valve closed (step S25), and the opening degree or duty ratio of the control valve 26 is determined according to the purge gas concentration obtained in step S25 (step S26). Thereafter, the purge is resumed (step S27).

  In the above method, when the changes in both the measured concentration C2 and the measured current value I2 are large, the purge gas concentration is detected again, assuming that the purge gas concentration change exceeds the allowable range. As described above, the flow rate of the pump 52 depends on the concentration of the purge gas. That is, as the purge gas concentration increases, the gas viscosity increases, and the current value for driving the pump 52 a predetermined number of times increases. When the change in the current value of the pump 52 exceeds the predetermined value β, the change in the concentration of the purge gas is large. In this case, if the purge is continued as it is, the A / F is greatly disturbed from the control value. Therefore, the A / F can be prevented from being disturbed by measuring the purge gas concentration again with the control valve 26 closed.

  As shown in FIG. 17, when one of the measured concentration C2 and the measured current value I2 is largely changed, the purge gas concentration may be detected again assuming that the purge gas concentration change exceeds the allowable range. . In this case, the measured concentration C2 is detected in step S20a, and the measured current value I2 is measured in step S22a. Thereafter, the storage density C1 and the measured density C2 are compared, and the constant current value I2 and the storage current value I1 are compared (step S23a). When the difference between the stored concentration C1 and the measured concentration C2 is larger than the predetermined value α, or when the difference between the current value I2 and the stored current value I1 is larger than the predetermined value β, the opening and closing of the control valve 26 is stopped (step S24a), and the purge gas Is measured (step S25a), the opening degree (duty ratio) of the control valve 26 is determined (step S26a), and the purge is restarted (step S27a). In this case, when the purge gas concentration changes, the change can be detected more reliably.

  A method for adjusting the supply amount of the purge gas when the concentration of the purge gas changes during the purge will be described with reference to FIGS. This method can be performed with the above-described fuel vapor processing apparatuses 20a, 20b, 20c and 20d. In other words, the fuel vapor processing apparatus of the type that includes the branch path 22b and detects the concentration of the purge gas while the supply of the purge gas to the intake pipe 34 is stopped can be performed. In this method, before purging the intake pipe 34, the gas remaining in the purge passage (the purge gas remaining when the previous purge is finished) is scavenged (that is, discharged to the intake pipe 34). ). When the gas remaining in the purge passage is scavenged, the evaporated fuel adsorbed by the canister 19 is introduced into the purge passage. 20 and 21 are timing charts showing the timing of purging and the on / off states of the pump 52 and the control valve 26. FIG. The pump 52 and the control valve 26 are controlled to be turned on / off by a control signal from the ECU 100.

  Timing t0 indicates the timing when the vehicle is ready to travel. For example, the time when the engine 2 is started corresponds to the timing t0. At timing t0, gas remains in the purge passage, and the ECU 100 stores that the gas in the purge passage is not scavenged. At timing t0, the ECU 100 stores that the gas scavenging completion history is in an OFF state. At timing t0, the pump 52 and the control valve 26 are turned off. After starting the engine 2 (step S30), the pump 52 is driven with the control valve 26 being off (step S31: timing t1). The purge gas concentration is measured between timing t1 and timing t2 with the control valve 26 turned off (step S32). The method described above can be used as a method for measuring the concentration of the purge gas.

  When the purge gas concentration C11 detected in step S32 is lower than the predetermined value (step S33: YES), the process proceeds to step S34, and the control valve 26 is turned on for a predetermined time with the pump 52 turned on (timing t2 to t3). As a result, the gas remaining in the purge passage (the purge gas remaining when the previous purge is completed) can be scavenged from the purge passage. Note that the period during which the control valve 26 is turned on (timing t2 to t3) is determined based on the purge gas concentration C11 detected during the timing t1 to t2. Thereby, it is possible to suppress the A / F from being greatly disturbed by the purge gas scavenged in the intake pipe 34.

  When scavenging of the remaining gas is completed, the gas scavenging completion history is turned on (step S35, timing t3). The gas scavenging completion history continues to be kept ON while the engine 2 is driven. Further, after the scavenging of the remaining gas is completed, the control valve 26 is turned off while the pump 52 is driven (step S36, timing t3). Thereafter, the purge gas concentration C12 in the purge passage is detected (step S37). After detecting the purge gas concentration C12, the pump 52 is turned off (step S38, timing t4). The value of the gas concentration C12 detected between the timings t3 and t4 is used when the ECU 100 outputs a purge on signal (when the purge is actually started: step S39, timing t5). That is, when starting the purge, the opening degree of the control valve 26, the output of the pump 52, and the like are determined based on the value of the gas concentration C12.

  If the concentration C11 of the purge gas in the purge passage is higher than the predetermined value in step S33 (step S33: NO), the control valve 26 is not turned on at timing t2, as shown in FIG. Further, although scavenging in the purge passage is not actually finished, the process proceeds to step S35, and the gas scavenging completion history is turned on. In this case, when the purge is actually started (timing t5), the opening degree of the control valve 26, the output of the pump 52, and the like are determined based on the value of the gas concentration C11. When the gas concentration in the purge passage (concentration of residual gas) is high, if the gas is scavenged into the intake pipe 34, the A / F tends to be rich. In that case, nitrogen oxides tend to be easily generated in the exhaust gas. Therefore, when the concentration of the residual gas in the purge passage is higher than a predetermined value, scavenging in the purge passage is not performed, and the opening degree of the control valve 26, the output of the pump 52, and the like are determined based on the gas concentration C11.

  FIG. 19 shows a method for adjusting the supply amount of purge gas after timing t5 in FIG. When the purge is started at the timing t5, the pump 52 is driven between the timings t5 and t6, the control valve 26 is turned on, and the purge gas is supplied to the intake pipe 34. In step S40, it is determined whether a purge-off signal is output after timing t5. When the purge-off signal is output (step S40: YES), the control valve 26 is turned off (step S41, timing t6). At timing t6, the driving of the pump 52 is maintained (timing t6 to t7). Between the timings t6 and t7, the gas concentration C13 in the purge passage is detected (step S42). After detecting the gas concentration C13, the pump is turned off (step S43, timing t7). Thereafter, when a purge-on signal is output (timing t8), the control valve 26 is turned on and the pump 52 is turned on (step S44).

  During timing t8 to t9, the opening degree of the control valve 26, the output of the pump 52, and the like are determined based on the gas concentration C13. From timing t9 to t11, the same operation as timing t6 to t8 is performed. That is, the pump 52 is driven for a predetermined time (t9 to t10) in a state where the purge is off (t9 to t11), and the gas concentration C14 is detected.

  In the above method, the purge gas concentration is detected in the purge-off (control valve closed) state, and the opening degree of the control valve 26 and the output of the pump 52 are controlled based on the gas concentration. Since the concentration of the purge gas is known when the purge is started, the supply amount of the purge gas can be adjusted more accurately. Further, since the purge passage is scavenged between the start of the engine 2 and the start of purge, when the purge is started, the concentration of the purge gas supplied from the canister 19 is well reflected in the purge supply amount. Can do. Also, when scavenging the purge passage, since the concentration of the purge gas remaining in the purge passage is detected before scavenging, it is possible to prevent the A / F from being greatly disturbed during the scavenging.

  With reference to FIGS. 22 to 26, another method for adjusting the supply amount of the purge gas when the purge gas concentration changes during the purge will be described. This method has a branch path 22b, and detects the concentration of purge gas in a state where supply of purge gas to the intake pipe 34 is stopped (evaporated fuel processing devices 20a, 20b, 20c and 20d). Can be done with. In this method, the purge gas is supplied to the intake pipe 34 while correcting the concentration of the purge gas based on the temperature change of the engine 2. 25 and 26 are timing charts showing the timing of purging and the on / off state of the control valve 26. FIG. The on / off state of the control valve 26 is controlled by a control signal from the ECU 100.

  Typically, after starting the engine, the temperature of the engine increases. When the engine temperature rises, the temperature of the purge passage also rises, and the concentration of the purge gas in the purge passage changes. By detecting the concentration of the purge gas based on the temperature change of the engine, the concentration of the purge gas can be accurately detected, and the A / F can be prevented from being greatly disturbed. As the engine is driven, the engine water temperature (cooling water temperature) increases. In this method, the detection method of the purge gas concentration is changed depending on whether or not the engine water temperature exceeds a predetermined value.

  In step S50 of FIG. 22, it is determined whether or not the engine water temperature has exceeded a first predetermined value (for example, 15 ° C.). When the engine water temperature does not exceed the first predetermined value (step S50: NO), the measurement of the engine water temperature is repeated until the engine water temperature exceeds the first predetermined value. After the engine water temperature exceeds the first predetermined value (step S50: YES), when the gas concentration history of the purge gas is not stored in the ECU 100 (step S51: YES), the concentration of the purge gas with the control valve 26 closed. Is started (step S52, timings t20 to t21). The measurement of the purge gas concentration with the control valve 26 closed can be performed by the method described above. The gas concentration C15 when the purge gas concentration is stabilized is stored in the ECU 100 as a gas concentration history, and the gas concentration storage history is turned on (step S53, timing t21).

  After the gas concentration memory history is turned on, the control valve 26 is turned on to start purging (step S54, timing t22). When starting the purge, the opening degree of the control valve 26 and the flow rate (output) of the pump 52 are determined based on the gas concentration C15. In addition, when the gas concentration of the purge gas is stored in the ECU 100 (step S51: NO), the purge is started based on the stored gas concentration. That is, when the gas concentration is not stored (the gas concentration storage history is OFF), the gas concentration is measured and the purge is started without starting the purge (first purge after starting the engine). During the purge, it is measured whether the engine water temperature is lower than a second predetermined value (for example, 60 ° C.) (step S55: YES) or higher than the second predetermined value (step S55: NO). In this method, the correction method of the purge gas concentration differs depending on whether or not the engine water temperature is lower than the second predetermined value. If it is greater than or equal to the second predetermined value, the process proceeds to step 56 in FIG. When purge is on (control valve 26 is on) in step S56 (step S56: YES), if the feedback deviation from the A / F sensor is less than or equal to the predetermined value A1 (step S57: NO), the purge is continued (step S58). ). The case where the feedback deviation amount from the A / F sensor is larger than the predetermined value A1 (step S57: YES) will be described later. Note that the concentration of the purge gas stored in the ECU 100 may be corrected based on the feedback deviation amount without stopping the purge (while continuing the purge) by using the feedback deviation amount from the A / F sensor. . By correcting the gas concentration, the supply amount of the purge gas can be adjusted more accurately.

  In step S56, when the purge is off (timing t23, step S56: NO), the process proceeds to step S59, and it is determined whether the purge off period (timing t23 to t24) is longer than the predetermined time T1. When the period t23-t24 is longer than the predetermined time T1 (step S59: YES), the purge gas concentration is measured in the purge-off state (step S60). The gas concentration C16 when the purge gas concentration is stabilized is stored in the ECU 100 (step S61), and at the next purge start timing t24, the process returns to step S54 in FIG. 22, and the opening degree of the control valve 26 is based on the concentration C16. And the flow rate of the pump 52 is controlled, and the purge is continued.

  In step S59, if the purge-off period is shorter than the predetermined time T1 (eg, period t25-t26) (step S59: NO), the purge gas concentration cannot be detected during purge-off. In this case, the gas concentration C16 stored in the ECU 100 when the purge is turned off (timing t25) (the gas concentration measured when the previous purge is turned off) is used as the gas concentration used at the next purge timing (timing t26). Store as C17 (step S62). Thereafter, the process returns to step S54 in FIG. 20, and the opening of the control valve 26 and the flow rate of the pump 52 are controlled based on the gas concentration C17 (gas concentration C16), and the purge is continued.

  Here, the case where the feedback deviation amount from the A / F sensor is larger than the predetermined value A1 in step S57 of FIG. 23 (step S57: YES) will be described with reference to FIG. In this case, even in the purge-on state (timing t22 to t23), the control valve 26 is turned off for a predetermined time (step S63, timing t22a), and the purge gas concentration C19 is measured (step S64). That is, the purge is substantially turned off. The gas concentration C19 when the concentration of the purge gas is stabilized is stored in the ECU 100 (step S65), and the purge is restarted (control valve is turned on) (step S66, timing t22b). Returning to step S54 in FIG. 22 at timing t22b, the opening of the control valve 26 and the flow rate of the pump 52 are controlled based on the gas concentration C19, and the purge is continued.

  Next, with reference to FIG. 24 and FIG. 25, the case where the engine water temperature of FIG. 22 is more than a 2nd predetermined value (step S55: NO) is demonstrated. Typically, in the vehicle, when the engine water temperature becomes equal to or higher than a second predetermined value (for example, 60 ° C.), A / F learning is started. When the engine water temperature is equal to or higher than the second predetermined value (step S55: NO), the control valve 26 is turned off to stop the purge (step S70, timing t27). With the purge stopped, measurement of the purge gas concentration and A / F learning are started (step S71). If the purge gas concentration is not stable (step S72: NO), the detection is continued until the purge gas concentration is stabilized. After the purge gas concentration is stabilized (step S72: YES), the detected gas concentration C18 is stored in the ECU 100 (step S73). Thereafter, it is determined whether or not A / F learning is completed (step S74). When the A / F learning is completed (step S74: YES), the control valve 26 is turned on (step S75, timing t28), and the control valve is controlled based on the concentration obtained by correcting the gas concentration C18 by A / F feedback. The opening (duty ratio) of 26 and the flow rate of the pump 52 are controlled, and the purge is continued.

  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. 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: Internal combustion engine 14: Fuel tank 19: Canister 20: Evaporative fuel processing device 22a: Purge passage 34: Intake passage 57: Concentration detector

Claims (7)

A canister that adsorbs the evaporated fuel evaporated in the fuel tank;
A purge passage connected between the intake path of the internal combustion engine and the canister, through which purge gas sent from the canister to the intake path passes;
A concentration detector that has a first detector and a second detector connected in series, and detects the concentration of purge gas passing through the purge passage;
With
The first detector is a type that detects the gas density of the purge gas based on the differential pressure when the purge gas passes through the first detector.
The second detection unit is a fuel vapor processing apparatus that detects the viscosity of the purge gas based on a differential pressure when the purge gas passes through the second detection unit. A branch passage connected to the purge passage,
The evaporated fuel processing apparatus according to claim 1, wherein the concentration detection unit is disposed on the branch path. It is arranged on the purge passage on the intake path side from the concentration detection unit, and is in a communication state in which the canister and the intake path are communicated via the purge passage, and in a cutoff state in which the canister and the intake path are blocked on the purge passage. A control valve to switch,
A pump that delivers purge gas from the canister to the intake path;
A branch passage connected to the purge passage,
The evaporated fuel processing apparatus according to claim 1, wherein the purge gas circulates through the concentration detection unit when the pump is driven with the control valve in a shut-off state.   The evaporated fuel processing apparatus according to claim 3, wherein the concentration detection unit is disposed on the branch path.   The evaporated fuel processing apparatus according to any one of claims 1 to 4, wherein the first detection unit includes a throttle portion therein.   The evaporated fuel processing apparatus according to any one of claims 1 to 5, wherein the second detection unit includes a plurality of capillaries therein. A canister that adsorbs the evaporated fuel evaporated in the fuel tank;
A purge passage connected between the intake path of the internal combustion engine and the canister, through which purge gas sent from the canister to the intake path passes;
A first detector that detects the gas density of the purge gas from the differential pressure when the purge gas passes, and a first detector that is connected in series with the first detector and detects the viscosity of the purge gas from the differential pressure when the purge gas passes. A concentration detector including two detectors;
A method for detecting the concentration and flow rate of purge gas passing through a purge passage in an evaporative fuel processing apparatus comprising:
Substituting the differential pressure measured by the first detector into the following formula (1),
Substituting the differential pressure measured by the second detector into the following equation (2),
Obtain the gas density and viscosity at which the flow rates Q1 and Q2 in the following equations (1) and (2) are equal,
A method of calculating the purge gas concentration from at least one of the calculated gas density and viscosity and calculating the flow rate of the purge gas from at least one of the calculated gas density and viscosity.

In the above formula (1), Q1 is the flow rate of the purge gas passing through the first detector, ΔP1 is the differential pressure measured by the first detector, C is the flow coefficient, K is the pipe coefficient, and ρ is the gas density. ing.

In the above equation 2, Q2 is the flow rate of the purge gas passing through the second detector, ΔP2 is the differential pressure measured by the second detector, μ is the viscosity coefficient, l is the pipe length, and d is the pipe diameter. ing.

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