JP2005054696A - Leak diagnosing device of fuel evaporated gas control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leak diagnosing device of a fuel evaporated gas control system capable of preventing pressure loss against exhaust gas and intake air with high flow velocities from occurring in supplying oil and purging. <P>SOLUTION: This leak diagnosing device comprises a vent valve 10 capable of opening/closing a drain passage 9, a bypass passage 11 communicating the drain passage 9 with an introduction passage 2 while bypassing a canister 3 and the vent valve 10, a pressurizing pump 12 arranged in the bypass passage 11 to pressurize a closed space ranging at a fuel tank toward an engine intake system through the canister 3 which is formed when a purge control valve 7 in a purge passage 6 and the vent valve 10 are closed, a pressure sensor 14 detecting pressure in the closed space, and a controller 13 determining leakage from the closed space due to a variation in the pressure detected by the pressure sensor 14 after pressurization by closing the purge control valve 7 and the vent valve 10 and operating the pressurizing pump 12 in diagnosing the leak. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a leak diagnosis apparatus for a fuel evaporative gas control system.

  Conventionally, there has been proposed a leak diagnosis apparatus for judging leakage of a fuel evaporative gas control system (see Patent Document 1).

This is because the evaporated fuel introduced from the fuel tank through the evaporated fuel introduction passage is temporarily adsorbed by the adsorbent of the canister, and the evaporated fuel released from the adsorbent is opened by opening the purge control valve. The ECU pressurizes the closed space when the purge control valve in the passage from the fuel tank through the canister to the intake pipe is closed to a predetermined pressure P4, and then is connected in series with the reference orifice , And the pressure drop P1 of the tank pressure when the predetermined time T1 has passed is measured, and the pressure drop P2 of the tank pressure when the predetermined time T1 has passed after the closed space is pressurized to the predetermined pressure P4. And the leakage of the closed circuit space is determined by comparing the P3 (= P1-P2) value with the P2 value.
Japanese Patent Laid-Open No. 11-351078

  However, in the above conventional example, since a pressure pump is installed in the drain passage from the canister where pressure loss needs to be kept small in order to improve the fuel supply performance of the fuel tank, exhaust with a high flow rate at the time of refueling and purging Alternatively, intake air is made via a pressurizing pump, which increases passage pressure loss, and a sufficient exhaust flow rate or intake air flow rate cannot be obtained.

  Further, since exhaust or intake during refueling and purging is always performed via a pressurizing pump, a filter that prevents dust and water from entering the pressurizing pump is required. A large dust filter is required to avoid pressure loss against the material, and the layout of the filter is expected to be difficult.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a leak diagnosis apparatus for a fuel evaporative gas control system that does not cause pressure loss with respect to exhaust or intake air having a high flow rate during refueling and purging. And

  The present invention forms a vent valve that can open and close a drain passage, a bypass passage that connects the drain passage and the introduction passage by bypassing the canister and the vent valve, and when the purge control valve and the vent valve in the purge passage are closed. Pressure means disposed in the bypass passage for pressurizing the sealed space from the fuel tank to the engine intake system via the canister, pressure detecting means for detecting the pressure of the sealed space, and a purge control valve at the time of leak diagnosis The leak diagnosis apparatus is constituted by control means for closing the vent valve, operating the pressurizing means, and determining leakage of the sealed space based on a change in pressure detected by the pressure detecting means after pressurization.

  Therefore, in the present invention, the pressurizing means for pressurizing the sealed space at the time of leak diagnosis is disposed in the bypass passage that connects the drain passage and the introduction passage by bypassing the canister and the vent valve, so that the passage resistance of the drain passage can be reduced, It is possible to prevent an increase in pressure loss with respect to exhaust or intake air having a high flow rate during refueling and purge. Further, the dust filter for the fresh air introduced into the pressurizing means may be a small one corresponding to the discharge flow rate of the pressurizing means, and can be easily laid out in the bypass passage.

  Hereinafter, a leak diagnosis apparatus for a fuel evaporative gas control system according to the present invention will be described based on each embodiment.

(First embodiment)
FIG. 1 is a system configuration diagram showing a first embodiment of a leak diagnosis apparatus for a fuel evaporative gas control system to which the present invention is applied.

  In FIG. 1, a leak diagnostic apparatus for a fuel evaporative gas control system introduces an evaporative fuel in a fuel tank 1 through an introduction passage 2 and temporarily adsorbs the adsorbent filled therein, A purge passage 6 for supplying the evaporated fuel released from the adsorbent to the intake system 5 of the engine 4, a purge control valve 7 disposed in the purge passage 6, and an exhaust passage when the evaporated fuel in the fuel tank 1 is introduced into the canister 3. And a vent valve disposed in the drain passage 9 for connecting the canister 3 to an internal space such as a vehicle cross member 8 that is shielded from dust and rainwater so as to become a fresh air introduction passage when purging to the purge passage 6 10 and the bypass passage 11 and the bypass passage 11 for connecting the fresh air inlet side and the introduction passage 2 with respect to the vent valve 10 of the drain passage 9. And pressurizing pump 12, the purge control valve 7, and constitutes a control unit 13 for controlling the vent valve 10 and the pressure pump 12.

  The canister 3 is provided with a main chamber 3C and a sub chamber 3D, which are partitioned by a partition wall 3B having a communication passage 3A below, filled with an adsorbent such as activated carbon, and the upper portion of the main chamber 3C through the introduction passage 2. The upper space in the fuel tank 1 and the purge passage 6 communicate with the air cleaner 5B and the throttle valve 5C downstream of the intake manifold 5A, respectively, while the upper portion of the sub chamber 3D is communicated with the interior space of the vehicle cross member 8 and the like via the drain passage 9. Communicating with

  When the purge control valve 7 is closed (during non-purge), evaporated fuel from the fuel tank 1 is introduced through the introduction passage 2 using the drain passage 9 as an exhaust passage and temporarily supplied to the adsorbent in the canister 3. Adsorb to. Further, at the time of purging when the purge control valve 7 is opened, fresh air is introduced from the drain passage 9 into the canister 3 by the negative intake pressure to release the evaporated fuel adsorbed on the adsorbent in the canister 3, and the purge passage 6 Is sent out into the intake manifold 5 </ b> A and is sucked into the combustion chamber of the engine 4.

  The purge control valve 7 is closed during normal time (non-purge time), and when purging is determined by the control unit 13 to satisfy the purge condition, for example, about 10 to 30 Hz according to the signal of the control unit 13. ON-OFF (open / close) at a frequency of, and the ON / OFF time ratio is changed according to the operating conditions, and the purge flow rate of the fuel evaporative gas from the canister 3 to the intake manifold 5A is optimally controlled.

  The vent valve 10 is a normally open type electromagnetic valve, which is opened during normal operation and purging, and is closed by the control unit 13 to shut off the drain passage 9 at the time of leak diagnosis for judging leakage of the fuel evaporative gas control device. Together with the purge control valve 7 in the shut-off state, a sealed space including the canister 3, the introduction passage 2, and the fuel tank 1 is formed.

  The pressurizing pump 12 disposed in the bypass passage 11 is driven when the control unit 13 determines a leak of the fuel evaporative gas control device, and seals fresh air through the bypass passage 11 and the drain passage 9. The sealed space can be pressurized by sending it to the space. The pressure in the sealed space is detected by a pressure sensor 14 disposed in the fuel tank 1, and the pressure information is input to the control unit 13.

  The pressurizing pump 12 incorporates a check valve 12A that allows air to flow from the bypass passage 11 to the sealed space but blocks flow from the sealed space to the bypass passage 11, and adds pressure from the sealed space during the leak check. Air leakage through the pressure pump 12 is prevented. A dust filter 15 that blocks dust and water contained in the intake air is disposed on the suction side of the pressurizing pump 12 in the bypass passage 11.

  The control unit 13 is not limited to the following description as the purge condition. For example, the engine operating state is at the time of start-up, at low water temperature, at high load, at deceleration of accelerator off, at fuel cut, etc. There is a barge condition when the vehicle speed is less than about 8 km / h and the idle determination is ON and the air conditioner is operating, or when the engine is in the same operating state as described above and the idle determination is OFF. In other cases, the purge control valve 7 is controlled to be shut off because the purge condition is not satisfied.

  The control unit 13 is also in a state where the vehicle is stopped with the engine 4 stopped as a diagnostic condition, and if necessary, for example, when conditions such as the outside air temperature, water temperature, and stop time are satisfied, the fuel evaporative gas The purge control valve 7, the vent valve 10, and the pressurizing pump 12 are each controlled for leak determination for determining leakage of the control device.

  FIG. 2 is a flowchart showing details of a leak diagnosis process for determining leakage of the fuel evaporative gas control device, which is periodically executed by the control unit 13. The details of the leak diagnosis process for determining leakage of the fuel evaporative gas control device will be described below with reference to the flowchart of FIG.

  First, in step S1, it is determined whether or not the engine 4 and the vehicle are stopped. If the engine 4 and the vehicle are stopped, the process proceeds to step S2. If the engine 4 and the vehicle are not stopped, the current time is determined. The process ends. While the engine 4 is stopped, for example, it can be determined by a change in signal value from a position sensor (POS sensor) 20 that measures the crank angle position of the engine 4, and when the vehicle is stopped, it is determined by a signal from a vehicle speed sensor 21. To do.

  In step S2, if necessary, it is determined whether or not the condition of the leak diagnosis, for example, the outside air temperature, the water temperature, the stop time, and the like is satisfied and the vehicle is in a stable state. If the vehicle is not stable immediately after stopping, etc., it waits until it is stabilized, and proceeds to step S3. The outside air temperature is obtained by the outside air temperature sensor 22, the water temperature is obtained by the coolant temperature sensor 23, and the stop time is obtained by measuring the time after changes in the signal values of the vehicle speed sensor 21 and the POS sensor 20 are stopped. Can do.

  In step S3, the vent valve 10 is closed, and together with the purge control valve 7 in the shut-off state, a sealed space is formed by the fuel tank 1, the introduction passage 2, and the canister 3. In step S4, the pressurizing pump 12 is driven to close the sealed space. Pressurize by supplying outside air. Outside air passes through the drain passage 9 and the bypass passage 11 and is supplied to the sealed space in a state where dust and water are removed by the dust filter 15.

  In step S5, the pressure P1 in the sealed space is determined based on the pressure signal from the pressure sensor 14, and it is determined whether or not the pressure P1 exceeds the threshold value. The drive of the pump 12 is stopped. Since the check valve 12A for blocking the flow from the sealed space to the bypass passage 11 is arranged in the pressurizing pump 12, the outflow of air from the sealed space after the pressurizing pump 12 is stopped is prevented.

  In step S7, based on the pressure information from the pressure sensor 14 at that time, the pressure in the fuel tank 1 (sealed space) is set as P1 (initia1), and the process proceeds to step S8.

  In step S8, after a predetermined time has passed, the process proceeds to step S9. In step S9, the pressure P1 in the fuel tank 1 (sealed space) is measured again based on the pressure information from the pressure sensor 14, and this is measured. Let P1 (after).

  In step S10, a difference between the pressure P1 (init1) in step S7 and the pressure P1 (after) in step S9 is obtained, and it is determined whether or not the difference is equal to or greater than a predetermined threshold value. That is, if there is a leak in the fuel evaporative gas control system, the pressure in the pressurized sealed space is not maintained, and a diagnosis is performed using the fact that the pressure drops over time. As a result, if the difference is equal to or greater than a predetermined value set by the threshold value, the process proceeds to step S11. In step S11, a determination result of “leak” is stored. If the difference is less than the predetermined value, the process proceeds to step S12. In S12, the determination result “no leak” is stored, and the current process is terminated. The stored determination result is displayed on an indicator (not shown) to inform the driver of the failure.

  In the present embodiment, the following effects can be achieved.

  (A) a vent valve 10 that can open and close the drain passage 9, a bypass passage 11 that connects the drain passage 9 and the introduction passage 2 with the canister 3 and the vent valve 10 in communication with each other, a purge control valve 7 in the purge passage 6, and A pressurizing pump as a pressurizing means disposed in the bypass passage 11 for pressurizing a sealed space formed when the vent valve 10 is closed and extending from the fuel tank 1 to the intake system 5 of the engine 4 via the canister 3. 12, a pressure sensor 14 as pressure detection means for detecting the pressure in the sealed space, and at the time of leak diagnosis, the purge control valve 7 and the vent valve 10 are closed, the pressure pump 12 is operated, and the pressure sensor 14 after pressurization And a control unit 13 as a control means for judging leakage of the sealed space by a change in the detected pressure due to the leak diagnosis device. Form was.

  That is, since the pressure pump 12 that pressurizes the sealed space at the time of leak diagnosis is disposed in the bypass passage 11 that connects the drain passage 9 and the introduction passage 2 by bypassing the canister 3 and the vent valve 10, the passage resistance of the drain passage 9. Thus, it is possible to prevent an increase in pressure loss with respect to exhaust or intake air having a high flow rate during refueling and purging.

  (A) In addition, the dust filter 15 for fresh air introduced into the pressurizing pump 12 as the pressurizing means takes into consideration only the discharge flow rate (several L / min) of the pressurizing pump 12 and is very small in size. And can be easily laid out in the bypass passage 11.

(Second Embodiment)
3 and 4 show a second embodiment of the leak diagnosis apparatus of the fuel evaporative gas control system to which the present invention is applied, FIG. 3 is a system configuration diagram of the leak diagnosis apparatus, and FIG. 4 shows details of the leak determination processing. It is a flowchart to show. In this embodiment, a sub-canister is additionally provided in the drain passage of the canister to improve the evaporation emission. The same devices as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified.

  In FIG. 3, a sub-canister 25 is disposed in the drain passage 9. The sub-canister 25 is normally filled with an adsorbent so as to further adsorb the fuel evaporative gas that could not be separated by the (main) canister 3 into the air exhausted from the (main) canister 3. The sub-canister 25 captures and purifies dust contained in fresh air introduced through the drain passage 9 by the adsorbent. By arranging the sub-canister 25, the dust filter 15 arranged in the bypass passage 11 is abolished.

  The drain passage 9 is further provided with a second vent valve 26 between the sub-canister 25 and the fresh air inlet, and the second vent valve 26 is a normally open type that is normally open. And is controlled to be opened and closed by the control unit 13. Other configurations are the same as those in the first embodiment.

  In the fuel evaporative gas control system having the above configuration, when the purge control valve 7 is closed, the evaporative gas introduced from the fuel tank 1 through the introduction passage 2 is adsorbed by the adsorbent in the (main) canister 3. The evaporative gas that has not been separated by the (main) canister 3 is further separated from the exhaust air by the adsorbent in the sub-canister 25 and discharged to the outside.

  Further, during purge with the purge control valve 7 opened, outside air is introduced from the drain passage 9 into the (main) canister 3 via the sub-canister 25 and supplied to the intake manifold 5 </ b> A via the purge passage 6. The introduced air is purified by capturing dust contained in fresh air in the sub-canister 25 by the adsorbent, purging the evaporated fuel adsorbed by the adsorbent, and introduced into the (main) canister 3, and (main) canister The evaporated fuel adsorbed by the adsorbent 3 is purged and supplied to the purge passage 6.

  In this embodiment, the HC desorption of the sub-canister 25 can be preferentially promoted by closing the (main) vent valve 10 and operating the pressurizing pump 12 during the purge, thereby reducing the evaporation emission. Can be improved.

  The leak diagnosis is periodically executed by the control unit 13 based on the flowchart shown in FIG. Details of the leak diagnosis process in the present embodiment will be mainly described below based on the flowchart of FIG.

  Step S1 to Step S6 and Step S7 to Step S12 are the same as Step S1 to Step S12 of the first embodiment, and in this embodiment, the second vent valve 26 is provided between Step S6 and Step S7. Steps S13 to S15 are added.

  That is, the pressurizing process up to a predetermined threshold value in steps S3 to S6 is performed in the same manner as in FIG. 2, but at this time, fresh air introduced into the drain passage 9 is dusted by the sub-canister 25. Minutes are captured and purified by activated carbon, and the fuel vapor (HC) adsorbed on the sub-canister 25 is desorbed and returned to the sealed space. For this reason, prevention of HC diffusion from the main canister 3 is improved, and evaporation emission is improved. The HC desorbed from the sub-canister 25 is once adsorbed by the activated carbon of the main canister 3 and sucked into the engine at the next purge.

  In step S13, the second vent valve 26 is closed, and in step S14, the first vent valve 10 is opened. For this reason, the sealed space is expanded to the drain passage 9. In order to secure a time during which the pressure fluctuation in the sealed space due to the air flowing into the drain passage 9 and the bypass passage 11 is stabilized due to the expansion of the sealed space, a predetermined time in step S15 is secured.

  Then, the pressure P1 (initia1) and the pressure P1 (after) are measured in the subsequent steps S7 to S9, and the difference between the pressure P1 (initia1) and the pressure P1 (after) in step S9 is determined in step S10. Stored in step S12.

  In the present embodiment, in addition to the effects (a) and (b) in the first embodiment, the following effects can be achieved.

  (C) Since the drain passage 9 is equipped with the sub-canister 25 on the fresh air inlet side from the opening of the bypass passage 11, when performing the leak diagnosis, if the pressurizing pump 12 is driven to suck in fresh air, The fuel vapor (HC) adsorbed on the canister 25 can be desorbed, the function of preventing the HC diffusion from the (main) canister 3 is improved, and the evaporation emission is improved. The HC desorbed from the sub-canister 25 is once adsorbed by the activated carbon of the (main) canister 3 and sucked into the engine at the next purge.

  (D) Further, since the sub-canister 25 captures and purifies fresh air dust that also passes through the dust filter and uses activated carbon, the dust filter 15 disposed in the bypass passage 11 can be dispensed with.

  (E) The control unit 13 as the control means closes the vent valve 10 and serves as a pressurizing means when supplying the evaporated fuel in the canister 3 to the engine intake system 5 via the purge control valve 7 and the purge passage 6. When the pressure pump 12 is operated to return the fuel evaporation component adsorbed by the sub-canister 25 to the canister 3, the vent valve 10 is closed during the purge even if the leak diagnosis is not being performed. By activating the pressurizing pump 12, the HC desorption of the sub-canister 25 is preferentially promoted, and even if the purge is insufficient and the residual HC of the main canister 3 is large, the evaporation emission is improved. Can do.

  (F) A second vent valve 26 is provided on the fresh air inlet side of the sub-canister 25 in the drain passage 9, and the control unit 13 as the control means is configured to In order to enlarge the sealed space by closing the valve 26 and opening the vent valve 10 between the sub-canister 25 and the canister 3, and to determine leakage of the sealed space based on a change in the pressure detected by the pressure sensor 14, A sealed space including the drain passage 9 and the bypass passage 11 can be formed, and a wide range of leaks in the system can be diagnosed.

  In the second embodiment, the detection of leakage in the sealed space including the drain passage 9 and the bypass passage 11 sectioned by the second vent valve 26 has been described. Although not illustrated, the drain passage 9 and the bypass passage are not illustrated. The leak of the enclosed space similar to 1st Embodiment which does not include the channel | path 11 may be detected.

The system block diagram of the leak diagnostic apparatus of the fuel evaporative gas control system which shows one Embodiment of this invention. Flowchart that is also periodically executed by the control unit. The system block diagram of the leak diagnostic apparatus of the fuel evaporative gas control system which shows 2nd Embodiment of this invention. Flowchart that is also periodically executed by the control unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Introduction passage 3 Canister, (main) canister, main canister 4 Engine 5 Engine intake system 6 Purge passage 7 Purge control valve 9 Drain passage 10 Vent valve, (main) vent valve, 1st vent valve, main vent valve DESCRIPTION OF SYMBOLS 11 Bypass passage 12 Pressurization pump as pressurization means 13 Control unit as control means 14 Pressure sensor as pressure detection means 15 Dust filter 25 Subcanister 26 2nd vent valve

Claims (4)

A canister that stores an adsorbent that temporarily adsorbs the evaporated fuel guided from the fuel tank through the introduction passage, a purge passage that guides the evaporated fuel released from the adsorbent to the engine intake system, and the purge passage A purge control valve that controls the amount of gas led to the intake system through the purge passage, and exhausts the canister air when the evaporated fuel is introduced from the fuel tank into the canister and passes through the purge control valve and the purge passage. A fuel evaporative gas control device comprising: a drain passage that sucks into the canister when the evaporated fuel in the canister is supplied to the engine intake system;
A vent valve capable of opening and closing the drain passage;
A bypass passage for connecting the drain passage and the introduction passage by bypassing the canister and the vent valve;
A pressurizing means disposed in the bypass passage for pressurizing a sealed space from the fuel tank formed when the purge control valve and the vent valve in the purge passage are closed to the engine intake system via the canister;
Pressure detecting means for detecting the pressure in the sealed space;
Control means for closing the purge control valve and the vent valve at the time of leak diagnosis, operating the pressurizing means, and determining leakage of the sealed space based on a change in pressure detected by the pressure detecting means after pressurization. Leak diagnostic device for fuel evaporative gas control system.   The leak diagnosis apparatus for a fuel evaporative gas control system according to claim 1, wherein the drain passage is equipped with a sub-canister on the fresh air inlet side from the opening of the bypass passage.   The control means closes the vent valve when the evaporated fuel in the canister is supplied to the engine intake system via the purge control valve and the purge passage, and activates the pressurizing means to evaporate the fuel adsorbed by the sub-canister. 3. The leak diagnosis apparatus for a fuel evaporative gas control system according to claim 2, wherein the leak diagnosis apparatus is operated to return the components to the canister. The leak diagnostic apparatus includes a second vent valve on the fresh air inlet side of the sub-canister in the drain passage,
The control means expands the sealed space by closing the second vent valve and opening the vent valve between the sub-canister and the canister after pressurizing by the pressurizing means, and detecting pressure by the pressure detecting means 4. The leak diagnosis apparatus for a fuel evaporative gas control system according to claim 2, wherein leakage of the sealed space is determined based on a change in the fuel vapor.

Images