JP2007211655A - Evaporated-fuel treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the durability of an evaporated-fuel treatment device by detecting the state of evaporated fuel at proper timings. <P>SOLUTION: An ECU performs a program including steps of: (S102) operating a timer until a predetermined time is elapsed when the purge of fuel is turned off (YES in S100); (S104) turning on a solenoid valve; (S108) detecting the concentration of the evaporated fuel when the pressure detected by a differential pressure sensor is equal to or higher than a predetermined threshold Pa (YES in S106); and (S110) calculating the purged amount of fuel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus for processing evaporated fuel generated in a fuel tank, and more particularly to an evaporated fuel processing apparatus that adsorbs evaporated fuel to a canister and purges it into an intake passage.

  2. Description of the Related Art Conventionally, an evaporative fuel processing apparatus is known in which evaporative fuel generated in a fuel tank is temporarily adsorbed to a canister and evaporative fuel desorbed from the canister is purged into an intake passage of an internal combustion engine as necessary. As one type of such an evaporative fuel processing apparatus, an apparatus for calculating the evaporative fuel concentration in the air-fuel mixture purged in the intake passage prior to purging is disclosed.

  For example, Japanese Patent Laid-Open No. 5-18326 (Patent Document 1) accurately describes the fuel vapor concentration and / or volume flow rate of an evaporated mixture containing actual fuel vapor evaporated from a fuel tank and supplied to an engine intake system. An evaporative fuel control device that measures and accurately controls the air-fuel ratio based on these measurement results is disclosed. This evaporative fuel control device is provided between a canister that adsorbs fuel vapor generated from a fuel tank and an engine intake system, and purges an air-fuel mixture containing fuel vapor, and an engine intake system via the purge passage. And a purge control valve for controlling the flow rate of the fuel vapor supplied to the fuel. The evaporative fuel control device includes an air passage that communicates the purge passage and the atmosphere, a first mass flow meter that detects the flow rate of the air-fuel mixture that flows through the purge passage, and a second air flow that detects the flow rate of the air flowing through the air passage. A mass flow meter, an actual fuel vapor flow rate calculating means for calculating an actual fuel vapor flow rate based on output values of the first and second mass flow meters, and a target for setting a target fuel vapor flow rate according to the operating state of the engine The fuel vapor flow rate setting means and purge control means for comparing the set target fuel vapor flow rate with the actual fuel vapor flow rate and controlling the opening of the purge control valve according to the comparison result are provided.

  According to the evaporative fuel control device disclosed in the above-mentioned publication, the flow rate of the fuel vapor supplied from the purge passage to the intake pipe can be accurately obtained. Therefore, the control of the air-fuel ratio of the fuel mixture and the control of the purge control valve can be performed. The air-fuel mixture having a uniform air-fuel ratio can be supplied to the internal combustion engine regardless of the purge flow rate.

  Japanese Patent Laid-Open No. 6-101534 (Patent Document 2) obtains the purge fuel concentration using simple detection means, and calculates the purge fuel flow rate from the purge fuel concentration, thereby controlling the air-fuel ratio during the purge. An evaporative fuel processing apparatus that improves accuracy is disclosed. This evaporative fuel processing apparatus includes a purge valve that adjusts the amount of purge gas introduced into the intake pipe from the canister, means for calculating the flow rate of the purge valve in response to an operating condition signal, and air for purging guided to the canister And means for detecting the density of each fluid of the purge gas from the canister, means for calculating the purge fuel concentration according to the ratio or difference of the fluid densities, and calculating the purge fuel flow rate from the purge fuel concentration and the purge valve flow rate Means for correcting the basic injection amount according to the operating condition with the purge fuel flow rate, calculating the fuel injection amount during purging, and a device for supplying the fuel injection amount to the intake pipe. It is a feature.

  According to the evaporative fuel processing apparatus disclosed in the above-mentioned publication, the cost required for the detection means can be reduced, and the basic injection amount as the total amount can be made the same as that before purging, thereby improving the air-fuel ratio control accuracy during purging. be able to.

  In the fuel vapor processing apparatus disclosed in Patent Documents 1 and 2 described above, the flow rate or density of the air-fuel mixture is detected in the passage for purging the air-fuel mixture into the intake passage, and the air flow rate or density in the passage opened to the atmosphere. The fuel vapor concentration is calculated from the ratio of the detection results.

In Patent Documents 1 and 2, the flow rate or density is detected while air-fuel mixture or air is allowed to flow through each passage by applying the negative pressure of the intake passage to each passage. In this configuration, if the pulsation occurs in the negative pressure in the intake passage, the flow rate or density fluctuates, so that the calculation accuracy of the evaporated fuel concentration based on the detection result of the flow rate or density deteriorates. Further, when the negative pressure in the intake passage is small, the flow rate of the air-fuel mixture or air in each passage decreases, so that the detection of the flow rate or density becomes difficult.
Japanese Patent Laid-Open No. 5-18326 JP-A-6-101534

  Therefore, the applicant of the present invention depressurizes the detection passage having a throttle with a decompression means such as a pump, and closes the shut-off pressure that blocks the atmosphere side of the throttle, the air pressure that connects the throttle and the atmosphere, and the mixture that communicates the throttle and the canister. Research has been conducted on an evaporative fuel treatment device that detects the mixed gas pressure as a differential pressure at both ends of the throttle and calculates the evaporated fuel concentration based on the cutoff pressure, the air pressure, and the mixed pressure. In such a fuel vapor processing apparatus, since the detection passage is depressurized by the pump, the differential pressure of the detection target is stable unless the detection condition is changed, and the flow rate of air or air-fuel mixture is sufficiently secured in the detection passage.

  However, in such a fuel vapor processing apparatus, the pump is operated each time the concentration of fuel vapor is detected. For this reason, if the pump is operated regardless of the generation state of the evaporated fuel, the evaporated fuel concentration is detected when the evaporated fuel concentration is low, or the durability of the pump deteriorates due to frequent operation of the pump. There is a problem of doing. Therefore, high performance of the pump is required, and the cost of the pump may increase.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an evaporative fuel processing apparatus that detects the state of evaporative fuel at an appropriate time and improves durability. is there.

  According to a first aspect of the present invention, there is provided a fuel vapor processing apparatus that purges fuel vapor generated in a fuel tank into an intake passage of an internal combustion engine. The internal combustion engine is mounted on a vehicle. This evaporative fuel processing device is provided with a canister for adsorbing evaporative fuel generated in a fuel tank, a detection passage connected to the canister and having a restriction in the passage, and provided on one side of the detection passage with the restriction in between. A first switching means for switching between the communication between the air and the atmosphere and the communication between the throttle and the canister, and a pressure reducing pressure for reducing the pressure of the detection path connected to the detection passage on the opposite side of the first switching means across the throttle. Means, a second switching means for switching between the first switching means and the pressure reducing means in the detection passage to one of the communication state and the shut-off state, and the gas in the fuel tank or the evaporated fuel processing device Each of a plurality of predetermined states combining a physical quantity detecting means for detecting a physical quantity corresponding to the pressure, a state of the first switching means, a state of the second switching means, and a state of the pressure reducing means. In, including a pressure sensing means for sensing the pressure generated iris, based on the output of the pressure detecting means, and a fuel vapor state calculating means for calculating a state of the fuel vapor. The pressure detection means includes means for detecting the pressure when the vehicle condition satisfies a predetermined condition and the physical quantity detected by the physical quantity detection means is equal to or greater than a value corresponding to the predetermined pressure. Including.

  According to the first invention, the evaporative fuel state calculating means has a plurality of predetermined states in which the state of the first switching means, the state of the second switching means, and the state of the pressure reducing means (for example, pump) are combined. The state (for example, concentration) of the evaporated fuel is calculated based on the pressure generated in the throttle in each of the above. For example, the detection passage is decompressed by the decompression means, (1) the second switching means is shut off, and the shut-off pressure when the atmosphere side of the throttle is closed, and (2) the second switching means is in the communication state. The air pressure when the first switching means is switched so that the throttle and the atmosphere communicate with each other, and (3) the first pressure reducing means is set so that the throttle and the canister communicate with each other with the second switching means in the communication state. The state of the evaporated fuel can be detected based on the mixed pressure at the time of switching. Thereby, since the detection passage is decompressed by the pump, the pressure generated in the throttle to be detected is stabilized, and the flow rate of air or air-fuel mixture is sufficiently secured in the detection passage. Therefore, detection itself does not become difficult due to deterioration in calculation accuracy due to pulsation and a decrease in the flow rate of air or air-fuel mixture. Further, the pressure detecting means satisfies a condition in which the state of the vehicle is determined in advance (for example, a condition that the vehicle is running and the purge process is stopped), and the detected fuel tank or evaporated fuel process If the physical quantity corresponding to the pressure of the gas in the apparatus (for example, the pressure in the air passage, the exhaust temperature of the internal combustion engine, the intake air temperature of the internal combustion engine, and the outside air temperature) is equal to or greater than a predetermined value corresponding to the pressure, The generated pressure is detected, the concentration of the evaporated fuel is calculated, and it can be determined that the amount of generated evaporated fuel is large in the fuel tank. Therefore, when the physical quantity corresponding to the pressure of the gas in the fuel tank or the evaporated fuel processing apparatus is equal to or greater than the value corresponding to the predetermined pressure, the state of the evaporated fuel is calculated. Can be detected. Accordingly, when the purge process is performed based on the detected state, it is possible to suppress the release of the evaporated fuel to the atmosphere and process the evaporated fuel with high accuracy. Further, the state of the evaporated fuel can be detected only when the amount of the evaporated fuel adsorbed by the canister is large. Therefore, the operation frequency of the decompression means (pump) can be reduced compared with the case where the pump is operated regardless of the generation state of the evaporated fuel. Therefore, it is not necessary to excessively increase the required capacity for the durability of the pump. That is, it is possible to improve the durability of the component (pump that is a decompression unit) that operates when the state of the evaporated fuel is detected. Therefore, it is possible to provide a fuel vapor processing apparatus that detects the state of fuel vapor at an appropriate time and improves durability.

  In the evaporated fuel processing apparatus according to the second invention, in addition to the configuration of the first invention, the physical quantity detection means includes means for detecting the pressure of the gas in the fuel tank or the evaporated fuel processing apparatus.

  According to the second aspect of the invention, the higher the pressure in the fuel tank or the evaporated fuel processing device, the more evaporated fuel is adsorbed by the canister. Accordingly, when the detected pressure is equal to or higher than a predetermined pressure, the state (e.g., concentration) of the evaporated fuel is detected, so that the amount of evaporated fuel adsorbed by the canister is large (the concentration is high). ) Can be detected.

  The evaporative fuel processing apparatus according to the third invention further includes a sealing means for sealing the evaporative fuel processing apparatus in addition to the configuration of the second invention. The evaporative fuel processing device includes means for detecting the pressure of the gas in the evaporative fuel processing device when the evaporative fuel processing device is sealed by the sealing means while communicating with the fuel tank.

  According to the third aspect of the invention, the fuel tank is in a state where there is a lot of evaporated fuel by sealing the evaporated fuel processing device by the sealing means while communicating with the fuel tank and detecting the gas pressure in the evaporated fuel processing device. It is possible to detect with high accuracy.

  The evaporative fuel processing apparatus according to the fourth invention further includes a sealing means for sealing the fuel tank in addition to the configuration of the second invention. The evaporative fuel processing apparatus includes means for detecting the gas pressure in the fuel tank when the fuel tank is sealed by the sealing means.

  According to the fourth invention, by detecting the gas pressure in the fuel tank when the fuel tank is sealed by the sealing means, it is accurately detected whether or not the fuel tank is in a state where there is a lot of evaporated fuel. be able to.

  In the fuel vapor processing apparatus according to the fifth aspect of the invention, in addition to the configuration of the first aspect, the physical quantity detection means is at least one of an outside air temperature, an exhaust temperature of the internal combustion engine, and an intake air temperature of the internal combustion engine. Means for detecting.

  According to the fifth invention, the higher the outside air temperature, the exhaust temperature of the internal combustion engine, and the intake air temperature of the internal combustion engine, the higher the temperature of the fuel tank. When the temperature of the fuel tank is high, the amount of evaporated fuel generated is large. Therefore, the pressure in the fuel tank or the evaporated fuel processing apparatus is high. That is, when at least one of the outside air temperature, the exhaust gas temperature, and the intake air temperature is high, it can be determined that the pressure in the fuel tank or the evaporated fuel processing apparatus is also high. Therefore, when at least one of the outside air temperature, the exhaust gas temperature, and the intake air temperature is equal to or higher than a value corresponding to a predetermined pressure, the canister can be detected by detecting the state (e.g., concentration) of the evaporated fuel. It is possible to detect that the amount of evaporated fuel adsorbed on the fuel is large (high concentration).

  In the fuel vapor processing apparatus according to the sixth aspect of the invention, in addition to the configuration of any one of the first to fifth aspects, the predetermined condition is that the vehicle is traveling and the purge process is stopped. This is the condition.

  According to the sixth aspect of the invention, it is possible to detect a state in which the amount of evaporated fuel is high (a state in which the concentration is high) when the vehicle is traveling and the purge process is stopped.

  According to a seventh aspect of the present invention, there is provided a fuel vapor processing apparatus according to any one of the first to sixth aspects of the present invention, wherein the fuel vapor adsorbed by the canister is supplied to the intake air of the internal combustion engine based on the detected state of the fuel vapor. Purge means for purging the passage is further included.

  According to the seventh aspect, the evaporated fuel generated in the fuel tank is released to the atmosphere by purging the evaporated fuel adsorbed by the canister to the intake passage based on the detected state (for example, concentration). Can be processed with high accuracy.

  In the evaporated fuel processing apparatus according to the eighth invention, in addition to the configuration of any one of the first to seventh inventions, the state of the evaporated fuel is the concentration of the evaporated fuel.

  According to the eighth invention, by detecting the concentration of the evaporated fuel, it is possible to accurately detect a state where the amount of the evaporated fuel is large.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  As shown in FIG. 1, the fuel vapor processing apparatus according to the present embodiment includes a fuel tank 10, a passage 100, a canister 12, a purge passage 102, a purge valve 14, a concentration detector 150, and a pump 22. And the electromagnetic valve 24, the air filters 50 and 52, and the ECU 20. The evaporated fuel processing device purges the evaporated fuel generated in the fuel tank 10 in the internal combustion engine.

  The fuel tank 10 and the tank port 54 of the canister 12 are connected via a passage 100. An adsorbent such as activated carbon is accommodated in the canister 12. The evaporated fuel generated in the fuel tank 10 flows through the passage 100 and is adsorbed by the adsorbent in the canister 12.

  The purge port 56 of the canister 12 and the purge valve 14 are connected via the purge passage 102. The purge valve 14 is connected to the downstream side of the throttle valve 18 in the intake passage 16. The evaporated fuel adsorbed by the canister 12 is purged into the intake passage 16 by opening the purge valve 14. The purge valve 14 opens or closes according to a control signal received from an ECU (Electronic Control Unit) 20. The purge valve 14 may be adjusted in opening degree according to a control signal received from the ECU 20. Further, the opening degree of the throttle valve 18 is adjusted in accordance with a control signal received from the ECU 20.

  The atmospheric port 58 of the canister 12 is connected to one end of the atmospheric passage 104. The other end of the atmospheric passage 104 is opened to the atmosphere via the air filter 52. The solenoid valve 24 is provided between the air filter 52 and the atmospheric port 58.

  The electromagnetic valve 24 is a three-way valve, and the atmospheric port 58 is normally opened to the atmosphere via the atmospheric passage 104 and the air filter 52 as shown in FIG. When the purge valve 14 is opened in this state, the evaporated fuel adsorbed by the canister 12 is purged to the downstream side of the throttle valve 18 through the purge passage 102 due to the negative pressure of the intake passage 16.

  The solenoid valve 24 is further connected to one end of the passage 106. The other end of the passage 106 is connected between the pump 22 and a sub-canister 36 described later. When the solenoid valve 24 is switched (turned on), the passage 106 and the atmospheric port 58 are communicated with each other. At the time of leak check of the evaporated fuel processing apparatus according to the present embodiment, the solenoid valve 24 is switched (turned on). At this time, the passage 106 connected to the pump 22 as decompression means and the atmospheric port 58 are communicated. In this state, when the pump 22 is operated in accordance with a control signal from the ECU 20, the fuel tank 10, the passage 100, the canister 12, the purge valve 14, the purge passage 102, the detection passage 110, a part of the atmospheric passage 104, and the passage 106. The pressure is reduced and a leak check is performed.

  The concentration detection unit 150 includes a differential pressure sensor 40, a sub-canister 36, electromagnetic valves 30 and 32, a throttle 34, detection passages 110 and 112, and an atmospheric passage 114.

  One end of the detection passage 110 is connected to the purge port 56. Note that one end of the detection passage 110 may be connected in the middle of the purge passage 102. The other end of the detection passage 110 is connected to one end of the detection passage 112 via the electromagnetic valve 32. The other end of the detection passage 112 is opened to the atmosphere via the air filter 50. One end of the atmospheric passage 114 is connected to the electromagnetic valve 32. Further, the other end of the atmospheric passage 114 is opened to the atmosphere via the air filter 50. In the detection passage 112, a throttle 34 is provided between the electromagnetic valve 32 and the air filter 50.

  The electromagnetic valve 32 causes the throttle 34 and the atmosphere to communicate with each other according to a control signal from the ECU 20 (that is, the detection passage 112 and the atmospheric passage 114 communicate with each other: in the following description, the electromagnetic valve 32 is also described as OFF. ), And the throttling 34 and the detection passage 110 (that is, the detection passage 110 and the detection passage 112 are connected to each other: also referred to as electromagnetic valve 32 on in the following description).

  A sub-canister 36 is provided between the diaphragm 34 and the air filter 50. A solenoid valve 30 is provided between the sub-canister 36 and the throttle 34. The solenoid valve 30 is a normally-closed two-way solenoid valve that brings the throttle 34 and the sub-canister 36 into communication (on) or shuts off (off) according to a control signal from the ECU 20.

  The pump 22 is provided between the air filter 50 and the sub-canister 36. Similar to the canister 12, the sub-canister 36 contains an adsorbent such as activated carbon. Therefore, when the detection passage 110 and the detection passage 112 are in communication with each other, when the pump 22 operates and the detection passage 112 is depressurized, the evaporated fuel adsorbed in the canister 12 is sucked into the detection passage 112. . When the mixture of air and evaporated fuel that has passed through the throttle 34 passes through the sub-canister 36, the sub-canister 36 adsorbs the evaporated fuel and removes the evaporated fuel from the mixture. For this reason, even if the mixture of air and evaporated fuel passes through the throttle 34, the differential pressure sensor 40 detects the pressure of the air that has passed through the throttle 34.

  The differential pressure sensor 40 is connected to the atmospheric passage 114 and the detection passage 112 between the pump 22 and the sub-canister 36 and detects the pressure generated in the throttle 34. In the present embodiment, the differential pressure sensor 40 includes an air passage 114 connected to the atmosphere through the air filter 50 and the air pressure in the detection passage 112 between the pump 22 and the sub-canister 36, that is, the pump 22 and the throttle 34. The pressure difference with the atmospheric pressure (ie, atmospheric pressure) is detected. Therefore, the differential pressure detected by the differential pressure sensor 40 during operation of the pump 22 is substantially equal to the differential pressure between the ends of the throttle 34 in a state where the electromagnetic valve 30 is open. In addition, when the solenoid valve 30 is closed, the detection passage 112 is closed on the suction side of the pump 22, so that the detection pressure of the differential pressure sensor 40 during the operation of the pump 22 is the cut-off pressure of the pump 22. Substantially equal.

  Based on the pressure detection signal received from the differential pressure sensor 40 of the concentration detection unit 150, the ECU 20 detects the state of the evaporated fuel in the mixture of the air purged into the intake passage 16 and the evaporated fuel. In the present embodiment, the state of evaporated fuel refers to the concentration of evaporated fuel, but is not particularly limited to the concentration as long as it is a physical quantity related to the amount of evaporated fuel. The ECU 20 controls the fuel injection amount from a fuel injection valve (not shown) according to the calculated concentration of evaporated fuel and the air-fuel ratio detected by an air-fuel ratio sensor (not shown).

  The ECU 20 detects the concentration of the evaporated fuel in the gas flowing through the throttle 34 based on the differential pressure when the gas passes through the throttle 34. The characteristic of the pressure and flow rate of the pump 22 has a linear function characteristic that changes so that the flow rate decreases as the pressure increases as shown by the thick line in FIG. On the other hand, the pressure and flow rate characteristics (orifice characteristics) in the throttle 34 are based on Bernoulli's theorem, as shown by the thin line in FIG. Due to the quadratic function characteristics. Further, when the concentration of the evaporated fuel increases, the flow rate with respect to the pressure changes to the decreasing side. Therefore, as shown by the broken line in FIG. 2, the orifice characteristic when the concentration is D% has a characteristic that the increase in flow rate is smaller with respect to the increase in pressure than the orifice characteristic when the concentration is zero%. .

  Specifically, the characteristic of the pump 22 is defined by Q (flow rate) = K1 (constant) × (P (pressure) −Pt (cutoff pressure). The orifice characteristic of the throttle 34 is Q (flow rate). = K3 (value defined by the inner diameter of the throttle 34) × √ (ΔP (differential pressure) / ρ (density))

The concentration of the gas flowing through the throttle 34 depends on the gas density. The density ratio ρ _Air / ρ _HC between the density [rho _HC of the gas when the mixture of air and fuel vapor in the density [rho _Air and aperture 34 of the gas when the air aperture 34 flows flows, [rho _Air / ρ _HC = ΔP _HC (mixture pressure) / [Delta] P _{air (pneumatic) (Q air} (air flow rate) _{/ Q HC} (flow rate of the mixed ^gas)) is calculated by the ^second equation. Note that Q _Air / Q _HC = (Pt−ΔP _Air ) / (Pt−ΔP _HC ). Based on the calculated density ratio ρ _Air / ρ _HC between the air-fuel mixture and air, the concentration of the air-fuel mixture is calculated.

  As described above, in the present embodiment, the sub-canister 36 is provided between the pump 22 and the throttle 34. When the sub-canister 36 is installed between the pump 22 and the throttle 34 and the evaporated fuel is removed from the air-fuel mixture that has passed through the throttle 34, the differential pressure detected by the differential pressure sensor 40 is smaller than when the sub-canister 36 is not installed. Increases (increases on the negative pressure side). As a result, the air pressure detected by the differential pressure sensor 40 when only air passes through the throttle 34 and the mixed atmospheric pressure detected by the differential pressure sensor 40 when the mixture of air and evaporated fuel passes through the throttle 34. The difference value of becomes larger. As a result, a sufficiently large detection gain G can be ensured with respect to the pressure resolution of the differential pressure sensor 40, so that the relative detection accuracy of the mixed pressure with respect to the air pressure, and thus the calculation accuracy of the evaporated fuel concentration, is improved.

Specifically, for example, if the mixed pressure ΔP _GAS is detected by the differential pressure sensor 40, a gas having a flow rate of Q ′ _Air flows from the sub canister 36 due to the characteristics of the pump 22 as shown by the solid line in FIG. 3. At this time, the flow rate after the evaporated fuel is adsorbed in the sub-canister 36 is Q ′ _Air , and the characteristics of the pressure and the flow rate before the sub-canister 36 are as shown by the broken line in FIG. The adsorption flow rate is large. Because both ends the pressure of the sub canister 36 are substantially equal, the flow rate Q _GAS corresponding to the mixture pressure [Delta] P _GAS the characteristics shown by the broken line in FIG. 3 is calculated. By providing the sub-canister 36 as described above, the mixing pressure ΔP _GAS when the concentration is assumed to be D% is compared with ΔP ′ _GAS detected as the mixing pressure when the sub-canister 36 is not provided. Become bigger. That is, since the difference from ΔP _Air becomes large, a sufficiently large detection gain G can be ensured with respect to the pressure resolution.

Further, as shown in FIG. 4, even when the air-fuel mixture at the flow rate Q _GAS flows from the throttle 34, the evaporated fuel for the flow rate Q _HC is adsorbed by the adsorbent of the sub-canister 36. Therefore, the flow rate in the differential pressure sensor 40 is Q ′ _Air . At this time, a relationship of Q ′ _Air = Q _GAS −Q _HC is established. Assuming that all of the evaporated fuel in the air-fuel mixture flowing from the throttle 34 is adsorbed by the adsorbent of the sub-canister 36, since Q _HC = Q _GAS × D / 100, D = 100 × (1−Q ′ _Air / Q _GAS ).

Furthermore, as shown in FIG. 5, when the concentration of the evaporated fuel is zero%, the gas density is ρ _Air , and when the concentration of the evaporated fuel is 100%, the gas density is ρ _HC . Since the gas density ρ _GAS and the concentration D are in a linear relationship, the following equation holds: ρ _GAS = ρ _Air − (ρ _Air −ρ _HC ) × D / 100.

Further, as described above, when air having a flow rate of Q _Air flows through the throttle 34, Q _Air = K1 × (ΔP _Air −Pt) is established from the pump characteristics, and further, Q _Air = K3 × √ from the orifice characteristics. (ΔP _Air / ρ _Air ) is established.

Further, in the pump 22, if the pressure detected by the differential pressure sensor 40 is ΔP _GAS and the flow rate is Q ′ _Air , Q ′ _Air = K1 × (ΔP _GAS −Pt) is established from the pump characteristics. Further, when a gas mixture having a flow rate of Q _GAS flows through the restrictor 34, Q _GAS = K3 × √ (ΔP _GAS / ρ _GAS ) is established from the orifice characteristics.

When the above formulas are arranged, D = 50 × {−M (1) ± √ (M (1) ² −4 × M (2))}. Note that M (1) = 100 × P (1) ² × P (2) × ρ (1) −2 and M (2) = 1−P (1) ² × P2. Further, P (1) = (ΔP _GAS −Pt) / (ΔP _Air −Pt) and P (2) = ΔP _Air / ΔP _GAS , and ρ (1) = (ρ _Air −ρ _HC ) / (100 × ρ _Air ).

Thus, the concentration D is equal to the air density ρ _Air , the gas density (ie, evaporated fuel) ρ _HC , the cutoff pressure Pt, the air differential pressure ΔP _Air , and the mixing pressure ΔP _GAS when the fuel concentration is 100%. Calculated based on

That is, the ECU 20 operates the pump 22 to depressurize the detection passage 112, opens the electromagnetic valve 30, and switches the electromagnetic valve 32 so that the detection passage 112 and the atmospheric passage 114 communicate with each other, thereby reducing the air pressure ΔP _Air . Detected by the differential pressure sensor 40. As shown in FIG. 6, when detecting the air pressure ΔP _Air , the ECU 20 controls to open the electromagnetic valve 30 and switches the electromagnetic valve 32 so that the atmospheric passage 114 and the detection passage 112 communicate with each other. When the pump 22 is operated to depressurize the detection passage 112, the atmosphere flows through the air passage 114 through the air filter 50 as shown by the arrow in FIG. 6, and the solenoid valve 32, the throttle 34, the solenoid valve 30, and the sub-canister. It will be distributed in the order of 36. The ECU 20 detects the air pressure ΔP _Air using the differential pressure sensor 40.

  The ECU 20 operates the pump 22 to depressurize the detection passage 112 and detects the cutoff pressure Pt by the differential pressure sensor 40 when the electromagnetic valve 30 is closed. As shown in FIG. 7, when detecting the shut-off pressure Pt, the ECU 20 controls the solenoid valve 30 to close, operates the pump 22, and depressurizes the detection passage 112. 7, the gas in the left detection passage 112 circulates as shown by the arrows in FIG. That is, it is discharged to the atmosphere through the sub-canister 36, the pump 22 and the air filter 50. At this time, the ECU 20 detects the cutoff pressure Pt by the differential pressure sensor 40.

Further, the ECU 20 operates the pump 22 to depressurize the detection passage 112 and opens the electromagnetic valve 30 to switch the electromagnetic valve 32 so that the detection passage 112 and the detection passage 110 communicate with each other. At this time, the ECU 20 detects the mixed atmospheric pressure ΔP _GAS by the differential pressure sensor 40. As shown in FIG. 8, when detecting the mixed pressure ΔP _GAS , the ECU 20 controls to open the electromagnetic valve 30 and switches the electromagnetic valve 32 so that the detection passage 110 and the detection passage 112 are communicated with each other. When the detection passage 112 is depressurized by operating the pump 22, the gas containing the evaporated fuel adsorbed by the canister 12 is detected by the detection passage 110, the electromagnetic valve 32, the throttle 34, and the electromagnetic valve 30 as shown by the arrows in FIG. 8. And it distribute | circulates through the subcanister 36 in order and is discharge | released from the air filter 50 to air | atmosphere. The ECU 20 detects the mixed atmospheric pressure ΔP _GAS using the differential pressure sensor 40.

Further, the memory 20 of the ECU 20 stores in advance the air density ρ _Air and the gas density ρ _HC when the fuel vapor concentration is 100%. The ECU 20 calculates the evaporated fuel concentration D from the detected cutoff pressure Pt, air pressure ΔP _Air , mixed air pressure ΔP _GAS , stored air density ρ _Air , and gas density ρ _HC .

  In the evaporated fuel processing apparatus having the above-described configuration, the pump is operated every time the concentration of the evaporated fuel is detected. Therefore, if the pump is operated regardless of the generation state of the evaporated fuel, the evaporated fuel concentration is low. There is a problem that the fuel vapor concentration is sometimes detected, or the pump is frequently operated, thereby deteriorating the durability of the pump. Therefore, high performance of the pump is required, and the cost of the pump may increase.

  Therefore, according to the present invention, when the ECU 20 satisfies the predetermined condition of the vehicle, the physical quantity corresponding to the pressure in the fuel tank 10 or the evaporated fuel processing device is a value corresponding to the predetermined pressure. The above is characterized in that the concentration of the evaporated fuel is detected.

  Specifically, the predetermined condition is that the vehicle is running and the purge process is stopped, and the ECU 20 determines that the electromagnetic valve 24 is satisfied when the predetermined condition is satisfied. Is switched on so that the eight atmospheric ports 58 and the passage 106 communicate with each other, and when the pressure detected by the differential pressure sensor 40 is equal to or higher than a predetermined pressure, the pressure generated in the throttle 34 is detected. Calculate the concentration of evaporated fuel. The “predetermined pressure” is not particularly limited as long as it can be determined that the amount of evaporated fuel adsorbed in the canister 12 is large (or the amount of evaporated fuel generated in the fuel tank 10 is large). Rather, it is adapted by experiment.

  Hereinafter, with reference to FIG. 9, a control structure of a program executed by ECU 20 mounted on the evaporated fuel processing apparatus according to the present embodiment will be described.

  In step (hereinafter, step is referred to as S) 100, ECU 20 determines whether or not the purge is stopped. Specifically, for example, the ECU 20 determines whether a purge process execution condition is satisfied based on the state of the vehicle. The ECU 20 determines that the purge process is being executed when the purge process execution condition is satisfied, and that the purge is stopped when the purge process execution condition is not satisfied. The purge process execution condition is, for example, a condition that the throttle opening is equal to or greater than a predetermined opening. The purge process execution condition is not limited to the throttle opening condition. For example, the absolute value of the negative pressure in the intake passage 16 detected by a negative pressure sensor (not shown) is a predetermined value. It may be the condition that it is above. If purging has been stopped (YES in S100), the process proceeds to S102. If not (NO in S100), the process returns to S100 and waits until the purge is stopped.

  In S102, ECU 20 activates a timer. In the present embodiment, ECU 20 operates the timer until a predetermined time A elapses. In S104, the ECU 20 switches the electromagnetic valve 24 so that the atmospheric port 58 and the passage 106 communicate with each other. In the present embodiment, the ECU 20 turns on the electromagnetic valve 24 until a predetermined time B elapses. At this time, the path from the differential pressure sensor 40 to the fuel tank 10 is preferably completely sealed or semi-sealed. In this way, the pressure in the fuel tank 10 can be accurately detected by the differential pressure sensor 40.

  In S106, ECU 20 determines whether or not the pressure detected by differential pressure sensor 40 is equal to or greater than a predetermined threshold value Pa. “Predetermined threshold value Pa” corresponds to the aforementioned predetermined pressure. The predetermined threshold value Pa is not particularly limited, and is a value adapted by experimentation or the like. If the pressure detected by differential pressure sensor 40 is equal to or greater than a predetermined threshold value Pa (YES in S106), the process proceeds to S108. If not (NO in S106), the process proceeds to S100.

  In S108, the ECU 20 calculates the evaporated fuel concentration. The calculation method is as described above, and detailed description thereof will not be repeated. In S110, ECU 20 calculates a purge amount. The ECU 20 calculates the purge amount based on the calculated evaporated fuel concentration. Regarding the calculation of the purge amount, for example, a map indicating the relationship between the evaporated fuel concentration and the purge amount is stored in a memory, and the purge amount is calculated based on the calculated evaporated fuel concentration and the map. Alternatively, the purge amount may be calculated from the calculated evaporated fuel concentration using a predetermined table or mathematical expression.

  The operation of ECU 20 mounted on the evaporated fuel processing apparatus according to the present embodiment based on the above-described structure and flowchart will be described with reference to FIGS. 10 and 11.

  At time T (0), if the purge process execution condition is not satisfied while the vehicle is traveling (NO in S100), the timer is activated (S102). At time T (1) when a predetermined time A elapses, the electromagnetic valve 24 is turned on, and the atmospheric port 58 and the passage 106 are communicated until a predetermined time B elapses. At this time, as shown in FIG. 11, when the solenoid valve 24 is turned on, the evaporated fuel in the fuel tank 10 flows along the arrow. That is, the evaporated fuel in the fuel tank 10 reaches the differential pressure sensor 40 through the canister 12 and part of the atmospheric passage 104, the electromagnetic valve 24 and the passage 106. Thereby, the pressure in the sealed path from the differential pressure sensor 40 to the fuel tank 10 can be detected. If the pressure detected by differential pressure sensor 40 does not exceed predetermined threshold value Pa (NO in S106), it is determined whether the purge process execution condition is satisfied (S100).

  If the purge process execution condition is not satisfied at time T (2) (NO in S100), the timer is activated (S102). The electromagnetic valve 24 is turned on at a time T (3) when a predetermined time A elapses. Then, at time T (4), when the pressure detected by differential pressure sensor 40 becomes equal to or higher than a predetermined threshold value Pa (YES in S106), the concentration of the evaporated fuel is detected. When the detection of the evaporated fuel concentration is completed at time T (5), the purge amount is calculated based on the calculated evaporated fuel concentration (S110).

  At time T (6), when the purge process execution condition is satisfied and purge is executed, the purge valve 14 is controlled so that the calculated purge amount is purged. Note that the ECU 20 may control the opening time and the closing time of the purge valve 14 or may control the opening degree of the purge valve 14.

  Next, the operation of the evaporated fuel concentration detection process executed from time T (4) to time T (5) will be described with reference to FIG.

When the concentration detection process of the evaporated fuel is executed at time T (4), power is supplied (turned on) to the differential pressure sensor 40 at time Ta (1) to warm up the differential pressure sensor 40. To be implemented. At time Ta (2) when a predetermined time elapses from time T (4) or time Ta (1), the pump 22 is activated (turned on), the detection passage 112 is depressurized, and electromagnetic The valve 30 is turned on, and the throttle 34 and the sub-canister 36 are in communication with each other in the detection passage 112. At this time, the air pressure ΔP _Air is detected by the differential pressure sensor 40. Then, after a predetermined time has elapsed from the time Ta (2) or at Ta (3) after detecting the air pressure ΔP _Air , the operation of the pump 22 is continued and the solenoid valve 30 is turned off to detect In the passage 112, the throttle 34 and the sub-canister 36 are cut off. At this time, the closing pressure Pt is detected by the differential pressure sensor 40. Furthermore, after a predetermined time has elapsed from time Ta (3) or at Ta (4) after detection of the shut-off pressure Pt, the operation of the pump 22 is continued and the solenoid valve 30 is turned on and detected. The passage 112 is in a communication state, and the electromagnetic valve 32 that is a three-way valve is turned on, so that the detection passage 110 and the detection passage 112 are connected. At this time, the mixed pressure ΔP _GAS is detected by the differential pressure sensor 40. The ECU 20 calculates the concentration of the evaporated fuel based on the detected air pressure ΔP _Air , cutoff pressure Pt, and mixed air pressure ΔP _GAS . Then, after a predetermined time has elapsed from the time Ta (4) or at Ta (5) after the detection of the mixed pressure ΔP _GAS , the evaporated fuel concentration detection process ends.

  As described above, according to the evaporated fuel processing apparatus according to the present embodiment, the detection passage is decompressed by the pump by detecting the concentration of the evaporated fuel based on the cutoff pressure, the air pressure, and the mixed atmospheric pressure. The pressure generated in the throttle to be detected is stabilized, and a sufficient flow rate of air or air-fuel mixture is ensured in the detection passage. Therefore, detection itself does not become difficult due to deterioration in calculation accuracy due to pulsation and a decrease in the flow rate of air or air-fuel mixture.

  Furthermore, when the gas pressure in the sealed passage from the differential pressure sensor to the fuel tank in the fuel vapor processing apparatus is high, it can be determined that the amount of fuel vapor adsorbed by the canister is large. . Therefore, when the concentration of the evaporated fuel is detected when the pressure of the gas in the atmospheric passage is equal to or higher than a predetermined threshold value Pa, the evaporated fuel with a high concentration can be detected. Thus, when the purge process is performed based on the detected concentration, the evaporated fuel can be processed with high accuracy while suppressing the release of the evaporated fuel to the atmosphere. Further, the concentration of the evaporated fuel can be detected only when the amount of the evaporated fuel adsorbed by the canister is large. Therefore, the operation frequency of the pump can be reduced as compared with the case where the pump is operated regardless of the generation state of the evaporated fuel. Therefore, it is not necessary to excessively increase the required capacity for the durability of the pump. That is, it is possible to improve the durability of a pump, a solenoid valve or the like that operates when detecting the concentration of the evaporated fuel. Therefore, it is possible to provide a fuel vapor processing apparatus that detects the fuel vapor state at an appropriate time and improves durability.

  In the present embodiment, the ECU executes the concentration detection process based on the pressure when the inside of the path from the differential pressure sensor to the fuel tank is sealed, but based on the pressure sensor provided in the fuel tank. The density detection process may be executed. At this time, it is preferable to detect the pressure in the fuel tank with the fuel tank completely or semi-sealed. In this way, the state of the evaporated fuel in the fuel tank can be detected with high accuracy.

  In the present embodiment, the concentration of the evaporated fuel is detected based on the pressure detected by the differential pressure sensor. For example, any one of the outside air temperature, the exhaust gas temperature of the internal combustion engine, and the intake air temperature of the internal combustion engine can be used. The state of the evaporated fuel may be detected based on this. That is, when the outside air temperature, the exhaust gas temperature of the internal combustion engine, and the intake air temperature of the internal combustion engine are high, the temperature in the fuel tank is high. Therefore, the amount of evaporated fuel is large and the pressure is high. That is, the outside air temperature, the exhaust gas temperature, and the intake air temperature are physical quantities corresponding to the pressure in the fuel tank, and if any one of the outside air temperature, the exhaust gas temperature, and the intake air temperature is high, the inside of the fuel tank or the evaporated fuel processing device. It can be determined that the pressure at is also high. Therefore, if any one of the outside air temperature, the exhaust gas temperature, and the intake air temperature is equal to or higher than a value corresponding to a predetermined pressure, the amount of evaporated fuel adsorbed by the canister is large when the concentration is detected. It is possible to detect the density when. Therefore, compared with the case where a pressure pump is operated irrespective of the generation | occurrence | production state of evaporative fuel, the operating frequency of a pressure pump can be reduced. Therefore, it is possible to improve the durability of components such as a pump and a solenoid valve that operate when detecting the concentration of the evaporated fuel.

<Modification>
Hereinafter, the evaporative fuel processing according to the modification of the embodiment of the present invention will be described. In the present modification, in the flowchart of FIG. 9 described in the above embodiment, in place of the on process of the solenoid valve 24 in S104, the on process of the solenoid valve 30 that is a two-way valve and the solenoid valve that is a three-way valve. 32 on-processes are different. Other configurations are the same as those in the first embodiment described above. Therefore, detailed description thereof will not be repeated here.

  The operation of ECU 20 mounted on the evaporated fuel processing apparatus according to the present embodiment based on the above-described structure and flowchart will be described with reference to FIGS. 13 and 14.

  At time T (0), if the purge process execution condition is not satisfied while the vehicle is traveling (NO in S100), the timer is activated (S102). Detection is performed until a predetermined time B elapses after the electromagnetic valve 30 which is a two-way valve and the electromagnetic valve 32 which is a three-way valve are turned on at a time T (1) when a predetermined time A elapses. The passage 112 and the detection passage 110 are communicated with each other.

  Until the predetermined time A elapses, as shown in FIG. 14A, the evaporated fuel generated in the fuel tank 10 is purged along the arrow of FIG. It flows from the port 56 to the front of the electromagnetic valve 32 through the detection passage 110. When the solenoid valve 32 is turned on, the detection passage 112 and the detection passage 110 are communicated. Therefore, as shown by an arrow in FIG. 14B, the evaporated fuel in the fuel tank 10 is detected by the detection passage 110, The pressure reaches the differential pressure sensor 40 through the solenoid valve 32, the throttle 34, the solenoid valve 30 and the sub-canister 36. Thereby, the pressure in the sealed passage from the differential pressure sensor 40 to the fuel tank 10 can be detected. If the pressure detected by differential pressure sensor 40 does not exceed predetermined threshold value Pa (NO in S106), it is determined whether the purge process execution condition is satisfied (S100).

  If the purge process execution condition is not satisfied at time T (2) (NO in S100), the timer is activated (S102). The electromagnetic valves 30 and 32 are turned on at a time T (3) when a predetermined time A elapses. Then, at time T (4), when the pressure detected by differential pressure sensor 40 becomes equal to or higher than a predetermined threshold value Pa (YES in S106), the concentration of the evaporated fuel is detected. When the detection of the evaporated fuel concentration is completed at time T (5), the purge amount is calculated based on the calculated evaporated fuel concentration (S110).

  At time T (6), when the purge process execution condition is satisfied and purge is executed, the purge valve 14 is controlled so that the calculated purge amount is purged.

  As described above, according to the evaporated fuel processing apparatus according to this modification, it is possible to obtain the same effects as those of the evaporated fuel processing apparatus according to the above-described embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the structure of the evaporative fuel processing apparatus which concerns on this Embodiment. It is a figure which shows the relationship between the flow volume and pressure based on a pump characteristic and an orifice characteristic. It is a figure which shows the relationship between the flow volume and pressure based on a pump characteristic and an orifice characteristic in the case of having a subcanister. It is a figure which shows the difference of the flow volume of the gas of the upstream and downstream of a subcanister. It is a figure which shows the relationship between the density | concentration of evaporative fuel, and the density of gas. It is a figure which shows the path | route which the gas distribute | circulates at the time of the detection of an air pressure. It is a figure which shows the path | route through which the gas distribute | circulates at the time of detection of a deadline pressure. It is a figure which shows the path | route which the gas distribute | circulates at the time of the detection of mixing atmospheric pressure. It is a flowchart which shows the control structure of the program performed by ECU mounted in the evaporative fuel processing apparatus which concerns on this Embodiment. It is a timing chart which shows operation | movement of ECU mounted in the evaporative fuel processing apparatus which concerns on this Embodiment. It is a figure which shows the path | route through which the gas distribute | circulates at the time of judgment whether the density | concentration detection process of evaporative fuel is performed. It is a timing chart which shows operation | movement when ECU mounted in the evaporated fuel processing apparatus which concerns on this Embodiment performs the concentration detection process of evaporated fuel. It is a timing chart which shows operation | movement of ECU mounted in the evaporative fuel processing apparatus which concerns on the modification of this Embodiment. It is a figure which shows the path | route which the gas distribute | circulates at the time of judgment whether the concentration detection process of the evaporative fuel in the modification of this Embodiment is performed.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Fuel tank, 12 Canister, 14 Purge valve, 16 Intake passage, 18 Throttle valve, 20 ECU, 22 Pump, 24, 30, 32 Solenoid valve, 34 Restrictor, 36 Sub canister, 40 Differential pressure sensor, 50, 52 Air filter , 54 tank port, 56 purge port, 58 atmospheric port, 100, 106 passage, 102 purge passage, 104, 114 atmospheric passage, 110, 112 detection passage, 150 concentration detector.

Claims (8)

An evaporative fuel processing apparatus that purges evaporative fuel generated in a fuel tank into an intake passage of an internal combustion engine, the internal combustion engine being mounted on a vehicle,
A canister that adsorbs the evaporated fuel generated in the fuel tank;
A detection passage connected to the canister and having a restriction in the passage;
A first switching means provided on one side of the detection passage across the diaphragm, for switching communication between the diaphragm and the atmosphere and communication between the diaphragm and the canister;
A depressurization means for depressurizing the detection path, connected to the detection path on the opposite side of the first switching means across the throttle;
Second switching means for switching between the first switching means and the decompression means in the detection path to one of a communication state and a blocking state;
Physical quantity detection means for detecting a physical quantity corresponding to the pressure of the gas in the fuel tank or the evaporated fuel processing device;
Pressure for detecting the pressure generated in the throttle in each of a plurality of predetermined states obtained by combining the state of the first switching unit, the state of the second switching unit, and the state of the decompression unit Detection means;
Evaporative fuel state calculating means for calculating the state of the evaporated fuel based on the output of the pressure detecting means,
The pressure detection means detects the pressure when the state of the vehicle satisfies a predetermined condition and the physical quantity detected by the physical quantity detection means is equal to or greater than a value corresponding to a predetermined pressure. An evaporative fuel processing apparatus, comprising means for   The evaporated fuel processing apparatus according to claim 1, wherein the physical quantity detection means includes means for detecting a pressure of a gas in the fuel tank or the evaporated fuel processing apparatus.   The evaporated fuel processing apparatus further includes a sealing means for sealing the evaporated fuel processing apparatus, and the gas in the evaporated fuel processing apparatus when the evaporated fuel processing apparatus is sealed by the sealing means while communicating with the fuel tank. The evaporated fuel processing apparatus according to claim 2, comprising means for detecting the pressure of the fuel.   The evaporative fuel processing device further includes a sealing means for sealing the fuel tank, and further includes means for detecting a pressure of gas in the fuel tank when the fuel tank is sealed by the sealing means. The evaporative fuel processing apparatus according to 2.   2. The evaporated fuel processing apparatus according to claim 1, wherein the physical quantity detection means includes means for detecting at least one of an outside air temperature, an exhaust temperature of the internal combustion engine, and an intake temperature of the internal combustion engine.   The evaporated fuel processing apparatus according to any one of claims 1 to 5, wherein the predetermined condition is a condition that the vehicle is running and the purge process is stopped.   The evaporated fuel processing device further includes a purge means for purging the evaporated fuel adsorbed by the canister into the intake passage of the internal combustion engine based on the detected state of the evaporated fuel. The evaporative fuel processing apparatus in any one of.   The evaporated fuel processing apparatus according to claim 1, wherein the state of the evaporated fuel is a concentration of evaporated fuel.

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