JP4249160B2 - Backflow prevention valve failure detection device - Google Patents

Description

  The present invention relates to an apparatus for determining a valve opening failure of a backflow prevention valve in an evaporative fuel purge system.

  Patent Document 1 describes that in an engine equipped with a supercharger, positive pressure from the supercharger is introduced into the canister to purge the evaporated fuel from the canister to the intake pipe of the engine.

Patent Document 2 provides a means for introducing a positive pressure into an evaporation system comprising a fuel tank, a vapor passage, a canister, and a purge passage, and the detection result of the pressure detection means when the positive pressure is introduced into the evaporation system. It is described that the presence or absence of abnormality of the evaporation system is determined based on the above.
JP 2005-36757 Patent No.2745966

  In an engine equipped with a supercharger, when the supercharger is operating, the intake pipe pressure downstream of the supercharger may be relatively positive with respect to the pressure of the evaporated fuel system. Therefore, a valve for preventing a backflow is provided in the purge passage for supplying the evaporated fuel from the canister for temporarily storing the evaporated fuel to the intake pipe. There is a need for an apparatus that accurately determines the valve opening failure.

  The failure determination device according to the present invention is provided in an engine that stores evaporated fuel from a fuel tank in a canister through a charge passage, and purges fuel in the canister to an intake passage through a purge passage through a purge control valve that is duty controlled. It is done. The apparatus includes a backflow prevention valve provided in the purge passage, and a pressure sensor that detects the pressure of an evaporated fuel system including a fuel tank and a canister. The apparatus further includes means for detecting an intersection between a pulsation waveform of the operation period of the purge control valve and a reference level based on an output of the pressure sensor, a means for determining a phase of the intersection with respect to a reference period, Determination means for determining a valve opening failure of the backflow prevention valve based on a phase difference between the obtained phase and a phase obtained before a predetermined period.

  The pressure of the evaporated fuel system pulsates according to the periodic operation of the purge control valve. The inventor of this application has discovered that the phase of pulsation is reversed when a valve opening failure occurs in the check valve. According to the present invention, by observing the phase of the pulsation of the pressure of the evaporated fuel system, it is possible to accurately determine a valve opening failure of the backflow prevention valve in the purge passage.

  In one form of this invention (Claim 2), the moving average of the output waveform of a pressure sensor is used as a reference level, and the means for detecting the intersection includes a current sample value of a pulsation waveform and a current value of the reference level. Is detected to cross the reference level from the negative side to the positive side.

  According to this aspect of the invention, it is possible to accurately detect a zero crossing of a waveform necessary for phase detection of pulsation.

  In one form of this invention (Claim 3), the means for obtaining the phase obtains the zero-crossing sine value and cos value when the period is set to 360 degrees with reference to the duty control period of the purge control valve. And each of the intersection sin value and cos value when the intake pipe pressure downstream of the turbocharger is relatively negative, and the intersection sin value and cos value when the intake pipe pressure is relatively positive The failure determination device according to claim 2, further comprising a phase difference calculating unit that calculates a phase difference of the pulsation by adding a square of a difference from each of the values.

  According to the embodiment of the present invention, the phase to be detected can be obtained from the sin value and the cos value, and the phase difference of the pulsation can be calculated by calculating the trigonometric function.

  In one form of this invention (Claim 4), the means for obtaining the phase corrects the phase based on a duty of a duty control of the purge control valve when the intersection is detected.

  Since the pulsation waveform of the pressure of the evaporated fuel system changes according to the duty of the purge control valve, the phase difference that is not affected by the duty is calculated by compensating for the change due to the duty. Thereby, even if the duty in the duty control of the purge control valve changes, the phase difference can be accurately calculated.

  According to still another aspect of the present invention (Claim 5), the engine includes a passage for supplying the evaporated fuel from the canister to the upstream side of the supercharger, and a second backflow prevention valve is provided in the passage. ing.

  According to this aspect, since the purge is performed on the upstream side and the downstream side of the supercharger, the evaporated fuel can be used efficiently.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of the apparatus of the present invention. In the intake system of the engine 11, an air filter 13, a supercharger 17, an intercooler 19, and a throttle valve 22 are provided. The fuel tank 23 communicates with the canister 27 via the charge passage 25, and the evaporated fuel is temporarily stored in the canister. The canister 27 is provided with a pressure sensor 28 for detecting the pressure of the evaporated fuel system.

  The canister 27 communicates with the intake pipe 21 through the purge passage 30. The purge passage 30 is provided with a purge control valve 29 and a backflow prevention valve 31. Further, the purge passage 30 branches into a passage 32 and communicates with the intake pipe 15 upstream of the supercharger 17 via the second backflow prevention valve 33 and the jet valve 35. The jet valve 35 returns a part of the air pressurized by the supercharger 17 to the upstream of the supercharger through the passage 36 as a jet flow. This jet flow generates a negative pressure in the passage 32, and the evaporated fuel is sucked into the jet flow in the jet valve. Details of the jet valve are described in Japanese Patent Application Publication No. 2005-30324 by the applicant.

  Fuel is supplied from a fuel tank 23 through a passage 24 to a fuel injection device (injector) (not shown) provided in the engine 11.

  The output of the pressure sensor 28 provided in the evaporated fuel (evaporation) system is sent to an electronic control unit (ECU) 50. The ECU 50 is essentially a computer, and includes a CPU that performs calculations, a random access memory (RAM) that provides a calculation work area, a read-only memory (ROM) that stores programs and data, and an input / output interface. . In FIG. 1, an ECU 50 is represented by a functional block diagram for realizing an embodiment of the failure determination device of the present invention.

  Referring to FIG. 2, the output waveform (A) of the pressure sensor 28 includes pulsations having the same cycle as the duty control due to the influence of the duty control of the purge control valve 29. In this embodiment, the purge control valve 29 is given a duty with a period of 80 milliseconds when the purge execution condition is satisfied. That is, according to the variable width pulse sent from the ECU 50 every 80 milliseconds, the valve is opened for the duration of the pulse width, and purge is performed. Purging through the purge passage 30 is performed in a state where the pressure of the evaporated fuel system is higher than the pressure of the intake pipe 21 (near the intake manifold), and when the purge control valve 29 is opened, the pressure of the evaporated fuel system is negative. When the valve 29 closes, the pressure of the evaporated fuel system recovers in the positive direction. Thus, pulsation is generated in the pressure of the evaporated fuel system in accordance with the duty control cycle of the purge control valve 29.

  The waveform shaping unit 51 of the ECU 50 extracts the pulsation waveform (B) of the duty control cycle (80 milliseconds in this embodiment) from the output waveform (A) of the pressure sensor 28 by filtering. At the same time, a reference level line (C) that is a moving average of a component obtained by removing the pulsation waveform (B) from the output waveform (A) over a predetermined period is obtained. This reference level line (C) can be considered as the pressure of the evaporated fuel system in the absence of pulsation.

  The zero-crossing detector 53 of the ECU 50 detects the intersection between the pulsation waveform (FIG. 2, (B)) and the reference level line (FIG. 2, (C)). A zero crossing detection method will be described with reference to FIG. The pulsation waveform (B) and the reference level line (C) are sampled at a predetermined cycle, and the previous pulsation waveform sample value is below the reference level line (this is called the pulsation waveform sample value is negative) From this, it is determined that a zero crossing has occurred when the current pulsation waveform sample value is on the reference level line (this is called a positive pulsation sample value). In FIG. 3, a zero crossing is detected when a pair of sample values indicated by open circles occur.

  The functions of the phase detection unit 55, the phase difference detection unit 57, and the valve failure determination unit 59 of the ECU 50 will be described with reference to FIGS. 4A shows an 80 millisecond control period of the purge control valve 29, and FIG. 4B shows an example of a pulse (PCS Duty) used for duty control. In the illustrated example, the duty ratio is 50%. The duty ratio is changed according to the state of the evaporated fuel.

  FIG. 4C shows a pulsation component of the pressure of the evaporated fuel system. Solid line pulsation is a pulsation component that appears in the output of the pressure sensor 28 when the backflow prevention valve 31 is in a normal state and the intake pipe 21 is in a relatively negative pressure and purge is performed through the purge passage 30. Indicates. On the other hand, when the supercharger 17 is operating, the intake pipe 21 becomes relatively positive pressure and purges from the jet purge valve 35 to the upstream of the supercharger via the second backflow prevention valve 33 and the purge branch path 32. Is done. The pulsation of the wavy line in FIG. 4C indicates a pulsation component that appears in the output of the pressure sensor 28 in a state where the backflow prevention valve 31 of the purge passage 30 is in a valve opening failure. That is, since the intake pipe 21 is at a positive pressure, the intake air flows back to the evaporated fuel system through the backflow prevention valve 31 that has failed to open, the pulsation waveform is inverted, and the phase is shifted 180 degrees.

  The phase detection unit 57 of the ECU 50 measures the time from the start point of the cycle to the zero crossing point of the pulsation waveform from negative to positive every cycle of the duty control of the purge control valve 29 (for example, 80 milliseconds), This is the pulsating waveform phase. That is, the duty control cycle is set to 360 degrees, and the time when a zero crossing from negative to positive occurs is converted into an angle to obtain a phase.

  (D) in FIG. 4 shows the period from the zero crossing to the zero crossing of the solid line pulsation waveform, and (E) shows the time from the start point of the duty control period to the zero crossing, which is represented by the solid line pulsation. The waveform phase. (F) shows the period from the zero crossing to the zero crossing of the pulsating waveform of the wavy line, and (G) shows the time from the starting point of the duty control period to the zero crossing, and this is the phase of the pulsating waveform of the wavy line And

  The phase difference detection unit 57 is a difference between the phase of the solid pulsation waveform when the intake pipe 21 is relatively negative pressure and the phase of the pulsation waveform of the wavy line when the intake pipe 21 is relatively positive pressure. Thereafter, it is calculated by an operation described with reference to FIG. The valve failure determination unit 59 determines that a valve opening failure has occurred in the check valve 31 when the phase difference thus calculated is larger than a predetermined value.

  Next, with reference to FIG. 5, the process executed by the apparatus of the present invention will be described. The process shown in the flowchart of FIG. 5 is repeatedly executed, for example, every 10 milliseconds, and one overall process is completed by executing a plurality of times. First, it is determined whether or not the value of the thinning counter is 1 (101). In this embodiment, the thinning counter divides the duty control period of 80 milliseconds every 10 milliseconds and performs calculation every 10 milliseconds. If the counter value is 1, step 103 is performed. In step 107, the value of the phase counter for measuring the pulsation phase is reset to 0, and in step 107, the thinning counter is set to 8 as the start point of the duty control cycle. If the thinning counter is not 1 in step 101, the process proceeds to step 105, the counter is decremented (subtracted by 1), and the process proceeds to step 109. The process proceeds through step 105 until the duty cycle of 80 milliseconds ends, and when it reaches 80 milliseconds, the phase counter is reset to 0 (103) and the thinning counter is set to 8.

  In step 109, it is determined whether or not the count number of the NG counter has reached a predetermined number. The NG counter is incremented when the pulsation phase difference exceeds a predetermined threshold value in step 151 described later. When the count number of the NG counter has reached the predetermined number, it is determined that the backflow prevention valve 31 has failed to open, and the failure detected flag is set to 1 (141).

  If the value of the NG counter has not reached the predetermined number in step 109, it is determined whether the count value of the OK counter has reached the predetermined number (111). In step 151 described later, the OK counter is incremented (added by 1) when the phase difference of the pulsation waveform is equal to or smaller than a predetermined threshold value (153).

  If the value of the OK counter has reached the predetermined number, it is determined that no valve opening failure has occurred in the backflow prevention valve 31, the OK counter and the NG counter are reset to 0 (143), and a new valve opening failure has occurred. Start the detection process.

  If the OK count has not reached the predetermined number, the number of pulsation waveform phase detections in a state where the pressure in the intake pipe 21 downstream of the turbocharger is equal to or lower than the predetermined value (this state is referred to as negative pressure) reaches the predetermined value. If the pressure reaches the predetermined value (113), the number of detections of the phase of the pulsation waveform in a state where the pressure of the intake pipe 21 is equal to or higher than the predetermined value (this state is called positive pressure) is predetermined. It is determined whether the value has been reached (115).

  If the determinations in steps 113 and 115 are Yes, the process proceeds to step 151, and it is determined whether or not the phase difference (calculated in step 139 described later) is equal to or smaller than a predetermined value. If it is less than the predetermined value, the OK counter is incremented (153). If it exceeds the predetermined value, the NG counter is incremented (155), and then various parameters are reset to proceed to the next process.

  If the determination in steps 113 and 115 is No, the process proceeds to the process from step 117 onward for calculating the phase and phase difference of the pulsation waveform. First, by the method described with reference to FIGS. 2 and 3, it is detected that the pulsation waveform (B) intersects the reference level line (C) in the direction from negative to positive, and the pulsation intersection flag is set to 1. It is judged whether it is done (117). If the pulsation crossing flag is not set to 1, the current process is exited, and the process from step 101 to step 117 is repeated until the pulsation crossing flag is set to 1.

  If the pulsation crossing flag is set to 1 in step 117, the process proceeds to step 119, and the detected phase is corrected. The phase of the pulsation waveform is represented by the length of the arrow period shown in FIG. 4E, that is, the count value of the phase counter. In FIG. 4, the pulsation waveform is shown as a clean sine wave, but the actual pulsation waveform is deformed by the pulse width (duty ratio) of the duty control in FIG. The difference between the phase of the pulsation waveform when the intake pipe 21 is on the negative pressure side and the phase of the pulsation waveform when the intake pipe 21 is on the positive pressure side is detected. In these two different states, the purge control valve May have different duty ratios. In this case, since the method of deformation of the pulsation waveform is different, the phase difference cannot be accurately calculated if a point that intersects the reference level line is used as the phase.

  Therefore, the phase magnitude (unit: hours, seconds) indicated by the arrow in FIG. 4 (E) represented by the phase count CCROS of the pulsation waveform detected by the phase counter is corrected by the following calculation to obtain the duty The influence of the ratio is removed, and the phase value POS is calculated by converting into the angle expression (119).

POS = (CCROS-PGC × 0.0004) /0.08 × 3.14 × 2 (1)
Here, PGC is a duty ratio of a pulse for duty-controlling the purge control valve (a ratio of 0% to 100% with respect to a time when the pulse is turned on in a duty cycle of 80 milliseconds). It was found that the phase (time count) in which a zero crossing from negative to positive occurs in a period of 80 ms has a fluctuation range of 40 ms depending on the duty ratio. PGC × 0.0004 is the percentage of PGC divided by 100 and converted to a decimal number, which is multiplied by 40 ms, or 0.04 s. By subtracting PGC x 0.0004 from CCROS, phase (time) variation due to duty ratio is corrected. Divide this phase (time) by 80 ms of the period multiplied by 2π (π is the pi, 3.14) to obtain the angle representation phase POS.

  When the phase of the angle expression is obtained, the process proceeds to step 121, where the table is searched to obtain the sin value and the cos value corresponding to this phase. When the pressure PB of the intake pipe 21 (intake manifold) is less than or equal to the predetermined value (123), the process proceeds to step 133. If the number of phase detections on the negative pressure side is greater than or equal to the predetermined value, the process proceeds to step 139 for calculating the phase difference. move on. If the number of phase detections has not reached the predetermined value, an average value of the sin value and the cos value is calculated (135). In short, instead of using the phase value detected in one process, the average of the phases detected in a plurality of processes is calculated and used. The detection number counter is incremented and the phase difference calculation step 139 is entered.

  If PB is equal to or greater than the predetermined value (125), the process proceeds to step 127, and if the number of times of phase detection on the positive pressure side is equal to or greater than the predetermined value, the process proceeds to phase difference calculation step 139. If the number of phase detections has not reached the predetermined value, the average value of the sine value and the cos value is calculated (129), the positive pressure side phase detection number counter is incremented (131), and the routine proceeds to step 139. In FIG. 5, instead of moving from step 137 and step 131 to step 139, the process exits at EXIT, and the average value of the phase difference is calculated when the number of detected phases exceeds a predetermined value at step 127 or 133. You may make it perform.

  In step 139, the negative pressure side phase and positive pressure side phase and positive pressure side average value NEGASIN and cos value average value NEGACOS and positive pressure side sin value average value POSIN and cos value average value POSCOS are calculated by the following calculation. The difference DPOS from the phase is calculated.

DPOS = (POSSIN-NEGASIN) ² + (POSCOS-NEGACOS) ² (2)

After the phase difference is calculated in this way, when this process is entered, step 151 is reached. If the phase difference is equal to or smaller than the predetermined value, it is determined that the backflow prevention valve 31 is operating normally, and the OK counter is incremented. (153) and various parameters are reset (157). If the phase difference exceeds a predetermined value, it is determined that the check valve 31 has a valve opening failure, and the NG counter is incremented (155). When the count value of the NG counter becomes equal to or greater than a predetermined value (109), the failure determination is confirmed and the failure detected flag is set to 1 (141). Thus, a valve opening failure of the backflow prevention valve 31 is detected.

  Although the present invention has been specifically described with reference to the embodiments, the present invention is not limited to such embodiments.

The figure which shows the whole structure of the engine used as the object of this invention. The wave form diagram which shows a mode that a pulsation waveform and a reference level line are extracted from the output of a pressure sensor. The figure which shows the principle which detects the crossing of a pulsation waveform and a reference level line. The figure explaining the mechanism which detects the phase of the zero crossing in a pulsation waveform. The flowchart which shows the flow of the process of this invention.

Explanation of symbols

17 Turbocharger
28 Pressure sensor
29 Purge control valve
31 Backflow prevention valve
50 Electronic control unit (ECU)

Claims (5)

In an engine that stores evaporated fuel from a fuel tank in a canister through a charge passage, and purges fuel in the canister to a suction passage through a purge passage through a purge control valve that is duty-controlled.
A backflow prevention valve provided in the purge passage;
A pressure sensor for detecting a pressure of an evaporated fuel system including the fuel tank and the canister;
Means for detecting an intersection between a pulsation waveform of the operation cycle of the purge control valve and a reference level based on an output of the pressure sensor;
Means for determining a phase of the intersection with respect to a reference period;
Based on the phase difference between the phase obtained this time and the phase obtained before a predetermined period, a determination means for determining a valve opening failure of the backflow prevention valve;
A failure determination device comprising:   The reference level is a moving average of the output waveform of the pressure sensor, and the means for detecting the crossing compares the current sample value of the pulsation waveform with the current value of the reference level, thereby generating a pulsation waveform. The failure determination device according to claim 1, which detects that the reference level crosses from the negative side to the positive side. The means for obtaining the phase obtains the sin value and cos value of the intersection when the period is set to 360 degrees with reference to the duty control period of the purge control valve,
The intersection sine value and cos value when the intake pipe pressure downstream of the turbocharger is relatively negative, and the intersection sine value and cos value when the intake pipe pressure is relatively positive, respectively. The failure determination device according to claim 2, further comprising a phase difference calculation unit that calculates a phase difference of the pulsation by adding a square of a difference from each.   The failure determination device according to claim 3, wherein the means for obtaining the phase corrects the phase based on a duty of duty control of the purge control valve when the intersection is detected. 5. The engine according to claim 1, wherein the engine includes a supercharger, a passage for supplying evaporated fuel from the canister to the upstream of the supercharger, and a second backflow prevention valve provided in the passage. The failure determination apparatus in any one.

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