JP2010190102A - Evaporation fuel purge control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaporation fuel purge control device for an internal combustion engine, not changing a variation in drive duty per unit time when switching a drive cycle. <P>SOLUTION: In an electronic control device in the evaporation fuel purge control device, when calculated drive duty is the switching factor drive duty for the drive cycle, the drive cycle when calculating the switching factor drive duty is regarded as a drive cycle immediately before switching, and the next drive cycle is switched to a cycle shorter or longer than the drive cycle immediately before switching after finishing the drive cycle immediately before switching. For example, when transferring to S6 through S4, S5, the next drive duty calculated in S3 is the switching factor drive duty as a switching factor for the drive cycle. In this case, the electronic control device switches to the short drive cycle after finishing the drive cycle immediately before switching while the drive cycle (long cycle) when calculating the drive duty in S3 is regarded as the drive cycle immediately before switching. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an evaporated fuel purge control device for an internal combustion engine that purges evaporated fuel generated in a fuel tank and adsorbed to a canister together with air to an intake system of the internal combustion engine through a purge valve.

  Fuel vapor generated from volatile liquid fuel is a substance subject to legal regulations for exhaust gas into the atmosphere. In order to suppress the release of the fuel vapor into the atmosphere, an internal combustion engine driven using volatile liquid fuel is generally provided with a purge control device. The purge control device includes a canister that temporarily stores fuel vapor generated in the fuel tank. The fuel vapor collected in the canister is appropriately purged from the canister to the intake passage of the internal combustion engine through the purge passage and the purge control valve, and mixed into the air taken into the internal combustion engine. The fuel vapor is burned in the combustion chamber of the internal combustion engine together with the fuel injected from the injector. The opening of the purge control valve provided in the purge passage is controlled based on the control signal output from the purge control means (control device) according to the required opening, and the flow rate of the purge gas purged to the intake passage is adjusted. To do.

  A duty control valve used as a purge control valve changes the drive cycle of duty control according to a required drive duty (see Patent Document 1 and Patent Document 2).

  For example, in Patent Document 2, the drive cycle of duty control is changed according to the required drive duty, that is, when the drive duty is small, control is performed with a long drive cycle (low frequency) to increase control accuracy, When the drive duty is large, control is performed with a short drive cycle (high frequency) to prevent pulsation of fluid passing through the purge control valve.

Japanese Utility Model Publication No. 07-030354 Japanese Patent Laid-Open No. 07-139440

  Incidentally, the purge rate update amount is corrected for each drive cycle in order to keep the change amount of the purge rate per unit time depending on the drive cycle in accordance with the required drive duty. (See (1)).

  Here, in order to increase the number of renewal opportunities, it is better that the drive cycle is short. On the other hand, if the drive cycle is short, the minimum energization time of the purge control valve is limited. It is better to lengthen the cycle. For this reason, as described above, conventionally, the drive cycle of the purge control valve is switched according to the drive duty.

  Conventionally, the purge rate is calculated by the following formula (1), and the drive cycle is obtained after the drive duty is calculated by the following formula (2). Therefore, the purge rate per unit time is changed when the drive cycle is switched. There was a problem that the amount of change of.

Purge rate = previous purge rate + purge rate update amount (1)
Drive duty = (Purge rate / Fully open purge rate) × 100 (2)
This problem will be explained. If the operating state of the internal combustion engine is constant, the fully-open purge rate is constant. Therefore, the formula for calculating the drive duty is expressed by the formula (1) and (2). Last drive duty) + (Drive duty update amount)
...... (3)
Can be replaced. The fully opened purge rate is the purge rate when the purge control valve is fully opened.

  Here, in the case of the drive cycle A that is currently a long cycle, for example, if the drive duty is increasing, the drive duty is calculated using the drive cycle A as shown in FIG. 11, refer to the drive duty indicated by the symbol □ in FIG.

  If the calculated drive duty exceeds the upper limit of the hysteresis region (see the upper limit of hysteresis in FIG. 11), the condition for switching the drive cycle is satisfied. When the duty becomes a value exceeding the upper limit of the hysteresis region, the driving cycle is switched (see the time indicated by the star on the time axis in FIG. 11). In this case, the drive cycle is switched to the drive cycle B, which is a short cycle, without changing the calculated drive duty (see symbol Δ in FIGS. 11 and 12).

Then, as shown by a thick line in FIG. 11, there is a problem that the amount of change in the drive duty per unit time changes when the drive cycle is switched.
When the purge gas is introduced into the engine intake system, the total amount of fuel supplied to the engine by the evaporated fuel in the purge gas increases. For this reason, the engine air-fuel ratio shifts to the rich side when the barge gas is supplied. However, the engine air-fuel ratio converges to the target air-fuel ratio by feedback control. In this case, if the engine air-fuel ratio at the time of introducing the purge gas greatly deviates from the target air-fuel ratio, the target of the engine air-fuel ratio will be improved even when the purge gas is introduced There is a problem that the amount of deviation from the air-fuel ratio increases and the time until convergence to the target air-fuel ratio becomes long. For this reason, when the change of the drive duty per unit time is changed between after switching and before switching at the time of switching of the driving cycle, the above problem may occur.

  An object of the present invention is to provide an evaporated fuel purge control device for an internal combustion engine in which the amount of change in drive duty per unit time does not change when the drive cycle is switched. is there.

  According to a first aspect of the present invention, there is provided an evaporative fuel processing mechanism for purging evaporative fuel collected in a canister together with air to an intake system of an internal combustion engine via a purge control valve, and a driving cycle of the purge control valve according to an engine state. A calculating means for calculating a driving duty of the purge control valve every time, when the driving duty increases or decreases, the updating amount of the driving duty is calculated to be constant according to the driving period; Vaporized fuel for an internal combustion engine comprising calculation means and control means for driving and controlling the purge control valve by switching the drive cycle of the purge control valve to a cycle shorter or longer than the current drive cycle in accordance with the drive duty In the purge control apparatus, the control means is configured such that the driving duty calculated by the calculating means is a driving duty of a driving cycle switching factor (hereinafter referred to as switching factor driving). If the calculation means calculates the switching factor driving duty, the driving cycle is the driving cycle immediately before switching, and after the driving cycle immediately before switching is over, the next driving cycle is immediately before the switching. The gist of the fuel vapor purge control device for an internal combustion engine is to switch to a shorter cycle or longer cycle than the drive cycle.

  According to a second aspect of the present invention, in the first aspect, after the calculation of the drive duty of the calculation means, the control means uses a short cycle or a long period used by the calculation means to calculate the drive duty in the next drive cycle. A reservation drive cycle of a cycle is set, and the calculation means calculates a drive duty of the purge control valve corresponding to the reservation drive cycle at the start of the next drive cycle.

  A third aspect of the present invention is the case where, in the second aspect, when the calculation means calculates a drive duty corresponding to the reserved drive cycle in the reserved drive cycle, the drive duty is changed from increasing to decreasing. When the calculation result of the drive duty corresponding to the reserved drive cycle is equal to or greater than the first threshold value, the control means switches the drive cycle from a long cycle to a short cycle to drive the purge control valve, When the calculation means calculates a drive duty corresponding to the reserved drive cycle in the reserved drive cycle, the drive duty is changed from a decrease to an increase, and the drive duty corresponding to the reserved drive cycle is When the calculation result is less than the second threshold value, which is greater than the first threshold value, the control means switches the drive cycle from a short cycle to a long cycle to control the drive of the purge control valve. The features.

  The invention of claim 4 is the case where, in claim 2, when the calculation means calculates a drive duty corresponding to the reserved drive cycle in the reserved drive cycle, the drive duty is changed from increasing to decreasing. When the calculation result of the drive duty corresponding to the reserved drive cycle is less than the first threshold, the control means controls the purge control valve while keeping the drive cycle long, and the calculation means When calculating the drive duty corresponding to the reserved drive cycle in the reserved drive cycle, the drive duty is changed from decreasing to increasing, and the calculation result of the drive duty corresponding to the reserved drive cycle is: When it is equal to or greater than a second threshold value that is greater than the first threshold value, the control means drives and controls the purge control valve while keeping the drive cycle short.

  According to the first aspect of the present invention, when the drive duty calculated by the calculation means becomes the switching factor drive duty, the control means, after the drive cycle when the switching factor drive duty is calculated, The purge control valve is driven and controlled with the same drive cycle as the drive cycle when the switching factor drive duty is calculated as the drive cycle immediately before switching, and the drive cycle is switched after the drive cycle immediately before switching is completed. Therefore, according to the first aspect of the invention, there is an effect that the change amount of the drive duty per unit time does not change when the drive cycle is switched.

  According to the invention of claim 2, after the calculation of the drive duty of the calculation means, the control means sets a reserved drive cycle of a short cycle or a long cycle that the calculation means uses for calculating the drive duty in the next drive cycle. The setting means calculates the drive duty of the purge control valve corresponding to the reserved drive cycle at the start of the next drive cycle. As a result, according to the invention of claim 2, when starting the drive cycle, the drive duty of the purge control valve corresponding to the reserved drive cycle can be calculated, and the effect of the invention of claim 1 can be easily realized. Can be done.

  According to the invention of claim 3, when the current driving cycle is a long cycle and the driving duty is changed from increasing to decreasing, the calculation result of the driving duty corresponding to the reserved driving cycle is: When it is equal to or greater than the first threshold, the control means switches the next drive cycle from the long cycle to the short cycle. For this reason, when the drive duty does not increase continuously, the purge control valve is not driven with a long drive cycle when the drive duty is equal to or greater than the first threshold.

  According to the invention of claim 3, when the current drive cycle is a short cycle and the drive duty is changed from decrease to increase, the calculation result of the drive duty corresponding to the reserved drive cycle is When it is less than the second threshold, the control means switches the next driving cycle from the short cycle to the long cycle. For this reason, when the drive duty does not decrease continuously, the purge control valve is not driven with a short drive cycle when the drive duty is less than the second threshold.

  According to the invention of claim 4, when the current driving cycle is a long cycle and the driving duty is changed from increasing to decreasing, the calculation result of the driving duty corresponding to the reserved driving cycle is: When it is less than the first threshold, the control means keeps the next driving cycle as a long cycle. For this reason, when the drive duty does not increase continuously, the purge control valve is not driven with a short drive cycle when the drive duty is less than the first threshold.

  According to the invention of claim 4, when the current drive cycle is a short cycle and the drive duty is changed from a decrease to an increase, the calculation result of the drive duty corresponding to the reserved drive cycle is When the drive duty does not decrease continuously, the control means keeps the drive cycle longer when the drive duty is greater than or equal to the second threshold. The purge control valve is not driven in a cycle.

1 is a schematic diagram of an evaporative fuel purge control device according to an embodiment of the present invention. The flowchart of a part of purge control which the electronic control apparatus 40 performs similarly. Similarly, explanatory drawing of a drive duty and a drive period. FIG. 6 is a relationship diagram between a driving duty and a driving cycle. FIG. 6 is a relationship diagram between a driving duty and a driving cycle. FIG. 6 is a relationship diagram between a driving duty and a driving cycle. FIG. 6 is a relationship diagram between a driving duty and a driving cycle. FIG. 6 is a relationship diagram between a driving duty and a driving cycle. FIG. 6 is a relationship diagram between a driving duty and a driving cycle. FIG. 6 is a relationship diagram between a driving duty and a driving cycle. Explanatory drawing of the drive duty and drive period of a prior art. FIG. 6 is a relationship diagram between a driving duty and a driving period in the prior art.

An evaporated fuel purge control apparatus for an internal combustion engine according to an embodiment of the present invention will be described with reference to FIGS.
First, an outline of the evaporated fuel purge control device will be described. As shown in FIG. 1, an internal combustion engine 10 includes a fuel injection valve 12 that injects fuel from a fuel tank 21 into a combustion chamber 11 via a fuel supply path (not shown), and the injected fuel and intake air. And an ignition plug 13 for igniting each air-fuel mixture. The combustion chamber 11 is connected to an intake passage 14 constituting a part of the intake system and an exhaust passage 15 constituting a part of the exhaust system. A surge tank 16 is provided in the middle of the intake passage 14, and a throttle valve (for example, electronically controlled) 17 for adjusting the amount of intake air is further provided on the upstream side.

  On the other hand, the evaporated fuel purge control device is provided with an evaporated fuel processing mechanism 30. The evaporative fuel processing mechanism 30 includes a canister 31 connected to the fuel tank 21 via a vapor passage 32, and a purge passage 33 connecting the canister 31 and the surge tank 16 constituting the intake system. The evaporative fuel processing mechanism 30 further includes an air introduction passage 34 for introducing air into the canister 31 and a purge valve (VSV) 35 for opening and closing the purge passage 33.

  Here, the evaporated fuel generated in the fuel tank 21 is introduced into the canister 31 from the fuel tank 21 through the vapor passage 32 and is once adsorbed by the adsorbent provided therein. Then, the purge valve 35 is opened and the atmosphere is introduced into the canister 31 through the atmosphere introduction passage 34, so that the fuel adsorbed in the canister 31 is purged as purge gas into the surge tank 16 through the purge passage 33 ( Released). The fuel contained in the purge gas is combusted in the combustion chamber 11 together with the fuel injected from the fuel injection valve 12. Further, the flow rate of the purge gas purged to the intake system (surge tank 16) in this way is adjusted by the purge valve 35. The purge valve 35 is a duty-controlled purge control valve that adjusts the flow rate by adjusting the opening according to the duty of the electrical signal that drives the valve. The purge valve 35 has a structure that is closed by the negative pressure described above, that is, the force that pushes the valve body biased by a spring or the like in the valve closing direction in the same direction increases as the intake pipe negative pressure increases (the vacuum side). A purge valve is used that is configured to be larger (closer to the value).

  Further, purge control for the internal combustion engine 10 and air-fuel ratio control that is control of the fuel injection amount by the fuel injection valve 12 are performed by the electronic control unit 40 in an integrated manner. In order to execute each of these controls, the electronic control device 40 is connected with various sensors for detecting the operating state of the internal combustion engine 10 and the detection signals from these sensors are appropriately captured. The electronic control device 40 corresponds to control means and calculation means.

  For example, the electronic control unit 40 is provided in the intake pressure sensor 51 for detecting the pressure (intake pressure) in the surge tank 16 and the exhaust passage 15 to detect the oxygen concentration of the combustion gas (air-fuel ratio of the mixture). The detection signals of the oxygen sensor 52 are respectively input. Further, detection signals from a rotational speed sensor 53 for detecting the engine rotational speed, an accelerator sensor 54 for detecting the depression amount (accelerator opening) of an accelerator pedal (not shown), and the like are input to the electronic control unit 40, respectively. ing.

  Each control such as purge control and air-fuel ratio control is executed by the electronic control unit 40 based on the operating state of the internal combustion engine 10 and the running state of the vehicle detected by these sensors 51 to 54 and the like. In addition, the electronic control device 40 includes a program 41 for executing each control, a calculation map, a memory 41 that stores various data calculated when the control is executed, and the like.

  Here, the air-fuel ratio control and the purge control will be briefly described. The air-fuel ratio control is based on the output of the oxygen sensor 52 so that the weight ratio of the intake air amount to the fuel injection amount, that is, the air-fuel ratio (A / F) is basically kept near the theoretical air-fuel ratio. This is performed by feedback control of the 12 fuel injection amounts.

  On the other hand, in the purge control, since the vapor concentration is not known immediately after the engine is started, the purge valve 35 is opened little by little. When the purge valve 35 is opened at once, the air-fuel ratio (A / F) or the air-fuel ratio feedback control center (F / B center) is shifted. Therefore, even if there is a shift, the purge valve 35 is slowly moved to the extent that the air-fuel ratio feedback is applied. Open it little by little. In this way, the initial vapor concentration is determined (learning of vapor concentration).

  When the purge rate is known, the deviation of the A / F or F / B center by the oxygen sensor 52 (deviation from the control center 1.0) is regarded as the deviation of the vapor concentration, and the vapor concentration learning value is updated. If the oxygen sensor 52 is a linear oxygen sensor, the A / F deviation is known from the deviation of the vapor concentration, and if the oxygen sensor is not linear, the deviation of the F / B center of the air-fuel ratio feedback control from the deviation of the vapor concentration. Recognize. Thus, although the purge gas having such a flow rate is now purged, the deviation of the A / F or F / B center is considered to be caused by the deviation of the vapor concentration, and the learning value of the vapor concentration is updated. Actually, the learning value of the vapor concentration is updated little by little while seeing a slight deviation of the center of A / F or F / B. After that, the control enters that the lower limit area of the duty is not used.

  While the purge is being performed by the purge control, a fuel injection amount reduction correction is performed to subtract the fuel amount contained in the purge gas from the fuel injection amount injected from the fuel injection valve 12. In general, the fuel injection amount reduction correction is performed by adjusting the valve opening time of the fuel injection valve 12. The amount of fuel in the purge gas is estimated and calculated every predetermined time by the electronic control unit 40 based on the learned vapor concentration and the like. Then, based on the calculated fuel amount, an injection time necessary for injecting the fuel amount from the fuel injection valve 12 is calculated, and the above reduction correction is performed.

  Next, “VSV drive duty calculation for setting the drive cycle of the purge valve 35 (including switching of the drive cycle) and calculating the drive duty in the characteristic purge control executed by the electronic control unit 40 of the present embodiment. The drive cycle and reservation drive cycle setting routine ”will be described.

  A series of processes shown in the flowchart of FIG. 2 is executed by the electronic control unit 40 as an interrupt process for each drive cycle. It is assumed that the fully open purge flow rate (fully open purge air flow rate) has already been calculated based on the operating state of the internal combustion engine before the series of processes shown in FIG. The “fully opened purge flow rate” is a fully opened purge flow rate map (illustrated) based on parameters representing the operating state of the internal combustion engine 10 such as the engine rotational speed (engine rotational speed) and the load factor. It is calculated with reference to (omitted).

  In step 1 (hereinafter, step is referred to as S) 1, it is determined whether or not the current drive duty is increased. This determination is made based on whether or not the operating state of the internal combustion engine is stable. Specifically, the electronic control unit 40 performs air-fuel ratio feedback control at a predetermined control cycle shorter than the drive cycle, and the air-fuel ratio feedback correction coefficient FAF is calculated during this control. In S1, if the air-fuel ratio feedback correction coefficient FAF is within a predetermined range (a range larger than the constant KFAF85 (FAF = 0.85) and smaller than the constant KFAF15 (FAF = 1.15)), the internal combustion engine It is determined that the operating state is stable and the driving duty increases. In S1, if the air-fuel ratio feedback correction coefficient is outside the predetermined range, it is determined that the operating state of the internal combustion engine is not stable and the driving duty is decreased.

  If it is determined in S1 that the drive duty is increased (the determination in S1 is “YES”), in S2, when this flowchart is executed in the previous drive cycle, the reserved drive cycle becomes the long drive cycle A. It is determined by referring to the history stored in the memory 41 whether it is set or whether the driving cycle B is set to a short cycle. The setting of the reservation drive cycle will be described later.

  In S2, when the reserved drive cycle is set to the long drive cycle A, the process proceeds to S3, and when the reserved drive cycle is set to the short drive period B, the process proceeds to S10. In this embodiment, the long drive period A is set to 102 ms and the short drive period B is set to 65 ms. However, these numerical values are merely examples, and any other values can be used as long as purge control can be performed efficiently. It may be a numerical value.

  In S3, the next drive duty is calculated. The next drive duty is calculated by the following equation (1). The next drive duty is a drive duty executed after this process.

Drive duty = previous drive duty + ΔA + (1)
Here, the previous drive duty is a drive duty calculated and executed in the previous drive cycle. ΔA + is a drive duty update amount for increasing the drive duty in the long-cycle drive cycle A, and is a preset amount. That is, since the reserved drive cycle is set to the long drive cycle A in S3, ΔA + is added.

  Subsequently, in S4, it is determined whether or not the drive duty calculated in S3 is equal to or higher than the upper limit G of the hysteresis region. In the present embodiment, the upper limit G of the hysteresis region is set to 18%, but is not limited to this value, and may be another value. In S4, if the drive duty calculated in S3 is greater than or equal to the upper limit G of the hysteresis region, the process proceeds to S5, and if the drive duty is less than the upper limit of the hysteresis region, the process proceeds to S9.

  In S5, it is determined whether or not the previous drive cycle is a long drive cycle A. In S5, when the previous drive cycle is the long drive cycle A, the process proceeds to S6, and when the previous drive cycle is the short drive period B, the process proceeds to S7.

  When the process proceeds to S6, the drive cycle is set to the long drive cycle A, the reserved drive cycle is set to the short drive cycle B, and stored in the memory 41, and the routine of this flowchart is temporarily terminated. The If the process passes through S6, the routine is ended with the drive duty calculated in S3, and then the purge valve 35 is duty-controlled by the electronic control unit 40.

Here, when the process proceeds to S6 via S4 and S5, the next drive duty calculated in S3 corresponds to a switching factor driving duty that becomes a switching factor of the driving cycle.
Note that the setting of the driving cycle, the setting of the reserved driving cycle, and the calculated driving duty are stored in the memory 41, respectively.

When the process proceeds to S7, since the previous drive cycle is the short drive cycle B, the recalculation of the drive duty is performed by the following equation (2).
Drive duty = previous drive duty + ΔB + (2)
Note that ΔB + is a drive duty update amount for increasing the drive duty in the short drive cycle B, and is a preset amount. That is, in S5, ΔB + is added because the previous drive cycle is the short drive cycle B. Here, the amount of change in unit time of the drive duty update amount ΔA + and the drive duty update amount ΔB + is set to be the same.

  Subsequently, the process proceeds from S7 to S8. In S8, the drive cycle is set to the short drive cycle B, the reserved drive cycle is set to the short drive cycle B, and the routine of this flowchart is temporarily ended. Is done. If the process passes through S8, the routine is terminated with the drive duty calculated in S7, and then the purge valve 35 is duty-controlled by the electronic control unit 40.

  When the process shifts from S4 to S9, in S9, the drive cycle is set to the long drive cycle A, the reserved drive cycle is set to the long drive cycle A, and the routine of this flowchart is temporarily ended. Is done. When this step S9 is passed, the purge valve 35 is duty-controlled by the electronic control unit 40 after completing this routine with the drive duty calculated in step S3.

  Further, when the process shifts from S2 to S10, since the reserved drive cycle is the short drive cycle B, the drive duty recalculation in the short drive cycle B is performed in the following equation (3) in S10.

Drive duty = previous drive duty + ΔB + (3)
That is, when the drive duty increases, when the reserved drive cycle is set to the short drive cycle B, when the next drive cycle is switched to the short cycle as in S6, or already, the drive cycle Is a short drive cycle B, and only in the case of S8 and S11 described later, the drive duty update amount ΔB + is added in S10.

  In S11, the drive cycle is set to the short drive cycle B, the reserved drive cycle is set to the short drive cycle B, and the routine of this flowchart is temporarily terminated. If the process passes through S11, the routine is terminated with the drive duty calculated in S10, and then the purge valve 35 is duty-controlled by the electronic control unit 40.

Next, a case will be described in which it is determined in S1 that the drive duty does not increase but decreases (determination in S1 is “NO”).
If “NO” is determined in S <b> 1, when this flowchart is executed in the previous drive cycle in S <b> 12, the reserved drive cycle is set to the long drive cycle A or the short drive cycle B is set. Is determined by referring to the history stored in the memory 41. In S12, when the reserved drive cycle is set to the short drive cycle B, the process proceeds to S13, and when the reserved drive cycle is set to the long drive period A, the process proceeds to S20.

In S13, the next drive duty is calculated. The next drive duty is calculated by the following equation (4).
Drive duty = previous drive duty-ΔB-(4)
Here, ΔB− is a drive duty update amount for reducing the drive duty in the short drive cycle B, and is a preset amount. That is, in S13, since the reserved drive cycle is set to the short drive cycle B, ΔB− is subtracted.

  In S14, it is determined whether the drive duty calculated in S13 is less than the lower limit K of the hysteresis region. In the present embodiment, the lower limit K of the hysteresis region is set to 13%, but is not limited to this value, and may be another value. The lower limit K of the hysteresis region corresponds to the first threshold value. In S14, if the drive duty calculated in S3 is less than the lower limit K of the hysteresis region, the process proceeds to S15, and if the drive duty is equal to or greater than the lower limit K of the hysteresis region, the process proceeds to S19.

  In S15, it is determined whether or not the previous drive cycle is a long drive cycle A. In S15, when the previous drive cycle is the short drive cycle B, the process proceeds to S16, and when the previous drive cycle is the long drive period A, the process proceeds to S17.

  When the process proceeds to S16, the drive cycle is set to the short drive cycle B, the reserved drive cycle is set to the long drive cycle A, and the routine of this flowchart is temporarily ended. If the process passes through S16, the routine is ended with the drive duty calculated in S13, and then the purge valve 35 is duty-controlled by the electronic control unit 40.

Here, when the process proceeds to S16 via S14 and S15, the next drive duty calculated in S13 corresponds to a switching factor driving duty that becomes a switching factor of the driving cycle.
When the process proceeds to S17, since the previous drive cycle is the long drive cycle A, the drive duty is recalculated by the following equation (5).

Drive duty = Previous drive duty-ΔA- (5)
ΔA− is a drive duty update amount for reducing the drive duty in the long drive period A, and is a preset amount. That is, in S15, ΔA− is subtracted because the previous drive cycle is the long drive cycle A. Here, the amount of change in unit time between the drive duty update amount ΔA− and the drive duty update amount ΔB− is set to be the same.

The absolute values of the drive duty update amounts ΔA + and ΔA− are the same. The absolute values of the drive duty update amounts ΔB + and ΔB− are the same.
Subsequently, the process proceeds from S17 to S18. In S18, the drive cycle is set to the long drive cycle A, the reserved drive cycle is set to the long drive cycle A, and the routine of this flowchart is temporarily ended. Is done. If the process passes through S18, the routine is ended with the drive duty calculated in S17, and then the purge valve 35 is duty-controlled by the electronic control unit 40.

  When the process proceeds from S14 to S19, the drive cycle is set to the short drive cycle B and the reserved drive cycle is set to the short drive cycle A in S19, and the routine of this flowchart is temporarily ended. Is done. If the process passes through S19, the routine is ended with the drive duty calculated in S13, and then the purge valve 35 is duty-controlled by the electronic control unit 40.

  Further, when the process proceeds from S12 to S20, the reserved drive cycle is the long drive cycle A. Therefore, in S20, the recalculation of the drive duty in the long drive cycle A is performed by the following equation (6).

Drive duty = previous drive duty-ΔA- (6)
That is, when the drive duty decreases, when the reserved drive cycle is set to the long drive cycle A, when the next drive cycle is switched to the long cycle as in S16, or already, the drive cycle Is the long drive cycle A, and only in the case of S18 and S21 described later, the drive duty update amount ΔA− is subtracted in S20.

  In S21, the drive cycle is set to the long drive cycle A, the reserved drive cycle is set to the long drive cycle A, and the routine of this flowchart is temporarily terminated. When this step S21 is passed, the purge valve 35 is duty-controlled by the electronic control unit 40 after completing this routine with the drive duty calculated in step S20.

  As described above, the electronic control unit 40 performs duty control on the purge valve 35 based on the calculated or recalculated driving duty for each of the set driving period A or driving period B.

Next, specific examples will be described. 3 to 8 are explanatory diagrams of specific examples, which are realized by executing the above flowchart.
(When drive duty is increasing: Example 1)
In this case, S1 in the flowchart of FIG. 2 is determined to be “YES”.

When the following two conditions (a) and (b) are satisfied, the purge valve 35 is controlled with the calculated drive duty without switching the drive period to the long drive period A.
(A) The drive cycle in which the purge valve 35 was driven last time is the drive cycle A.

  (B) The previous drive duty of driving the purge valve 35 is less than the upper limit G of the hysteresis region (the portion corresponding to ○ in FIGS. 3 and 4), and the calculated next drive duty is equal to or greater than the upper limit G of the hysteresis region ( 5 is a portion corresponding to □ in FIGS. 3 and 4. In addition, next time, the reserved drive cycle is reserved (set) to the drive cycle B having a short cycle.

  In this case, after the reservation drive cycle is set, when the flowchart of FIG. 2 is executed next, the process proceeds from S1 (“YES”) → S2 (“NO”) → S10 in FIG. Then, the next drive duty after the long drive period A has elapsed in S10 is calculated by Equation (3). That is, the drive duty update amount ΔB + is added to the previous drive duty to obtain the next drive duty (portion corresponding to Δ in FIGS. 3 and 4). Further, in S11 of FIG. 2, a driving cycle B is set, and the purge valve 35 is duty-controlled in this driving cycle.

(When drive duty is decreasing: Example 2)
In this case, S1 in the flowchart of FIG. 2 is determined as “NO” and processed.
When the following two conditions (a) and (b) are satisfied, the purge valve 35 is driven and controlled with the calculated drive duty without switching the drive period to the short drive period B.

(A) The drive cycle in which the purge valve 35 was driven last time is the drive cycle B.
(B) The drive duty that last driven the purge valve 35 is equal to or higher than the lower limit K of the hysteresis region (the portion corresponding to the circle in FIGS. 5 and 6), and the calculated next drive duty is less than the lower limit K of the hysteresis region ( FIG. 5 is a portion corresponding to □ in FIG. 5. In the next time, the reserved driving cycle is reserved to the long driving cycle A.

  In this case, after the reservation drive cycle is set, when the flowchart of FIG. 2 is executed next, the process proceeds from S1 (“NO”) → S12 (“YES”) → S20 in FIG. Then, the next drive duty after the long drive period A has elapsed in S20 is calculated by equation (6). That is, the drive duty update amount ΔA− is subtracted from the previous drive duty to obtain the next drive duty (portion corresponding to Δ in FIGS. 5 and 6). Further, in S21 of FIG. 2, the driving cycle B is set, and the purge valve 35 is duty-controlled in this driving cycle.

  Next, for example, in the previous control cycle and the current control cycle, the determination of S1 in the flowchart of FIG. 2 may be that the drive duty does not continuously increase or the drive duty does not decrease continuously. .

  In this case, the purge valve 35 is not driven with a short drive cycle B when the drive duty is low, or the purge valve 35 is not continuously performed with a long drive cycle A when the drive duty is high. Yes.

Specific examples thereof will be described with reference to FIGS.
(Example 3)
In Example 3, when the drive duty does not increase continuously, that is, “YES” is determined in the previous S1, the reserved drive cycle is set to the short drive cycle B, and “NO” is set in the next S1. Is determined.

  In this S1, it is determined as “NO”, in S12, it is determined as “NO”, and in S13, the drive duty is calculated by the equation (4). In the next S14, if the next drive duty calculated in S13 is equal to or greater than the lower limit K of the hysteresis region, the drive cycle is switched to the drive cycle B (65 ms) as in the reserved drive cycle, and the purge valve 35 is turned on. Will drive.

  In FIG. 7, ◯ is the position at the time of the previous drive cycle in Example 3, □ is the position of the next drive duty calculation result in S13, and Δ is the reserved drive cycle This is the position where

(Example 4)
Example 4 is a case where the drive duty does not increase continuously as in Example 3.
In this S1, it is determined as “NO”, in S12, it is determined as “NO”, and in S13, the drive duty is calculated by the equation (4). In the next S14, if the drive duty calculated in S13 is less than the lower limit K of the hysteresis region, if the previous drive cycle is the drive cycle A, which is a long cycle, it is determined as “YES” in S15, and S17 The next drive cycle is recalculated. In this case, the next drive duty is calculated with the long drive cycle A (102 ms) without switching the drive cycle to the reserved drive cycle. Thereafter, the purge valve 35 is driven without switching the driving cycle.

  In FIG. 8, ◯ is the position at the time of the previous drive cycle in Example 4, □ is the position of the next drive duty calculation result in S17, and Δ is the drive cycle. This is the position without switching to the reserved drive cycle.

(Example 5)
In Example 5, when the drive duty does not decrease continuously, that is, “NO” is determined in the previous S1, the reserved drive cycle is set to the short drive cycle B, and “YES” in the next S1. Is determined.

  In this S1, “YES” is determined, in S2, “YES” is determined, and in S3, the drive duty is calculated by the equation (1). In the next S4, if the next drive duty calculated in S3 is less than the upper limit G of the hysteresis region, the drive cycle is switched to the drive cycle A (102 ms) as in the reserved drive cycle, and the purge valve 35 is turned on. Will drive. In FIG. 9, ◯ is the position corresponding to the previous drive cycle in Example 5, □ is the position of the next drive duty calculation result in S 3, and Δ is the reserved drive cycle This is the position where

(Example 6)
Example 6 is a case where the drive duty does not decrease continuously as in Example 5.
In this S1, “YES” is determined. In S12, “YES” is determined. In S3, the drive duty is calculated by the equation (1). In the next S4, if the next drive duty calculated in S3 is equal to or greater than the upper limit G of the hysteresis region, if the previous drive cycle is a short drive cycle B, “NO” is determined in S5. In S7, the next drive cycle is recalculated. In this case, the next drive duty is calculated with a short drive cycle B (65 ms) without switching the drive cycle to the reserved drive cycle. Thereafter, the purge valve 35 is driven without switching the driving cycle.

  In FIG. 9, ◯ is the position at the time of the previous drive cycle in Example 6, □ is the position of the recalculation result of the next drive duty in S 7, and Δ is the drive cycle Is a position that is not switched to the reserved driving cycle.

According to the embodiment configured as described above, the following operational effects can be obtained.
The electronic control device 40 (control means, calculation means) in the evaporated fuel purge control apparatus of the present embodiment calculates the switching factor driving duty when the calculated driving duty becomes the driving factor of the driving cycle. The drive cycle at this time is set as the drive cycle immediately before switching, and after the drive cycle immediately before switching is completed, the next drive cycle is switched to a cycle shorter or longer than the drive cycle immediately before switching. For example, when the process proceeds to S6 via S4 and S5, the next drive duty calculated in S3 is a switching factor drive duty that becomes a switching factor of the drive cycle. In this case, the electronic control unit 40 sets the drive cycle A when the drive duty is calculated in S3 as the drive cycle A that is a long cycle, and the short drive cycle after the end of the drive cycle immediately before the switch. Switch to B.

  When the process proceeds to S16 via S14 and S15, the next drive duty calculated in S13 becomes a switching factor drive duty that becomes a switching factor of the drive cycle. In this case, the electronic control unit 40 sets the drive cycle B, which is a short cycle when the drive duty is calculated in S13, as the drive cycle immediately before switching, and after the end of the drive cycle immediately before switching, the long drive cycle Switch to A. As a result, in the present embodiment, there is an effect that the change amount of the drive duty per unit time does not change when the drive cycle is switched.

  In the present embodiment, the electronic control unit 40 (control unit, calculation unit) has a short cycle or a long cycle that is used by the electronic control unit 40 to calculate the drive duty in the next drive cycle after calculating the drive duty. Set the reservation drive cycle. Then, the electronic control unit 40 calculates the drive duty of the purge valve 35 corresponding to the reserved drive cycle at the start of the next drive cycle. As a result, according to the present embodiment, when starting the drive cycle, the drive duty of the purge control valve corresponding to the reserved drive cycle can be calculated, and the drive per unit time is generated when the drive cycle is switched. The effect that the change amount of the duty does not change can be easily realized.

  In the present embodiment, when the electronic control unit 40 (calculation unit) calculates the drive duty corresponding to the reserved drive cycle in the reserved drive cycle, the drive duty is changed from increasing to decreasing, When the calculation result of the drive duty corresponding to the reserved drive cycle is equal to or higher than the lower limit K (first threshold) of the hysteresis region, the drive cycle is switched from the long cycle to the short cycle, and the purge control valve is driven and controlled. That is, when it is determined as “NO” in S1 and the drive duty is decreasing, it is determined as “NO” in S12, the drive duty calculated in S13 is S14, and the hysteresis region lower limit K ( If it is equal to or greater than the first threshold value, the purge valve 35 is driven and controlled in S19 by switching the drive cycle to the short drive cycle B even in the case of the long drive cycle A last time.

  As a result, when the drive duty does not increase continuously, the purge control valve is not driven with a long drive cycle when the drive duty is equal to or higher than the lower limit K (first threshold) of the hysteresis region.

  Further, when calculating the drive duty corresponding to the reserved drive cycle in the reserved drive cycle, the drive duty is changed from decreasing to increasing, and the calculation result of the drive duty corresponding to the reserved drive cycle is: When the hysteresis region is less than the upper limit G (second threshold value), the purge control valve is driven and controlled by switching the drive cycle from a short cycle to a long cycle. That is, when “YES” is determined in S1 and the drive duty is increasing from a decrease to an increase, it is determined “YES” in S2, the drive duty calculated in S3 is S4, and the upper limit of the hysteresis region When it is less than G (second threshold), the purge valve 35 is driven and controlled in S9 even if the drive cycle B is a short cycle last time, the drive cycle is switched to the long drive cycle A.

  As a result, if the drive duty does not decrease continuously, the purge control valve is not driven with a short drive period when the drive duty is less than the upper limit G (second threshold) of the hysteresis region.

  In the present embodiment, when the electronic control unit 40 (calculation unit) calculates the drive duty corresponding to the reserved drive cycle in the reserved drive cycle, the drive duty is changed from increasing to decreasing, When the calculation result of the driving duty corresponding to the reserved driving cycle is less than the lower limit K (first threshold value) of the hysteresis region, the purge valve 35 is driven and controlled while the driving cycle is long.

  That is, when it is determined as “NO” in S1 and the drive duty is changed from increasing to decreasing, it is determined as “NO” in S12, and the driving duty calculated in S13 is S14. When it is less than the lower limit K (first threshold value) and the previous drive cycle A is a long cycle (“YES” in S15), the next drive cycle is recalculated in S17. In this case, the next drive duty is calculated with the long drive cycle A (102 ms) without switching the drive cycle to the reserved drive cycle. Thereafter, the purge valve 35 is driven in the drive cycle A.

  As a result, when the drive duty does not increase continuously, the purge control valve is not driven with a short drive cycle at a drive duty less than the lower limit K (first threshold) of the hysteresis region.

  In the present embodiment, when the electronic control unit 40 calculates the drive duty corresponding to the reserved drive cycle in the reserved drive cycle, the drive duty is changed from decreasing to increasing, and the reserved driving is performed. When the calculation result of the drive duty corresponding to the cycle is equal to or greater than the upper limit G (second threshold) of the hysteresis region, the purge valve 35 is driven and controlled with the drive cycle kept short.

  That is, when the determination is “YES” in S1 and the drive duty is decreasing from the increase, the determination is “YES” in S2, the drive duty calculated in S3 is S4, and the hysteresis region If it is equal to or greater than the upper limit G (second threshold) and the previous drive cycle B is a short cycle ("NO" in S5), the next drive cycle is recalculated in S7. In this case, the next drive duty is calculated with a short drive cycle B (65 ms) without switching the drive cycle to the reserved drive cycle. Thereafter, the purge valve 35 is driven in the driving cycle B.

In addition, the said one Embodiment can also change the structure suitably as follows, for example.
In the above embodiment, the purge valve 35 has a characteristic (purge valve characteristic) that is difficult to open as the intake pipe negative pressure increases, but the present invention is not limited to this. For example, the duty-controlled purge valve has a characteristic that the deviation between the duty and the flow rate ratio (decrease in the flow rate linearity) due to the change in the operating state such as the intake pressure as described above becomes easier to open as the intake pipe negative pressure increases. It is also applicable to

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 30 ... Evaporative fuel processing mechanism, 31 ... Canister, 35 ... Purge valve (purge control valve), 40 ... Electronic control apparatus.

Claims (4)

An evaporative fuel processing mechanism for purging the evaporative fuel collected in the canister together with air to the intake system of the internal combustion engine via the purge control valve, and the purge control valve for each drive cycle of the purge control valve according to the engine state Calculating means for calculating a driving duty, wherein the driving duty is increased or decreased; a calculating means for calculating the driving duty update amount to be constant according to the driving period; and the driving duty In accordance with the above, in the evaporated fuel purge control device for an internal combustion engine comprising control means for driving the purge control valve by switching the drive cycle of the purge control valve to a cycle shorter or longer than the current drive cycle,
The control means calculates the switching factor driving duty when the driving duty calculated by the calculating means becomes a driving duty of a driving cycle switching factor (hereinafter referred to as switching factor driving duty). The evaporative fuel of the internal combustion engine is characterized in that the driving cycle at this time is set as the driving cycle immediately before switching, and after the driving cycle immediately before switching is ended, the next driving cycle is switched to a cycle shorter or longer than the driving cycle immediately before switching. Purge control device. The control means sets a short period or a long period reserved drive period used by the calculation means to calculate the drive duty in the next drive cycle after the calculation of the drive duty of the calculation means,
2. The evaporative fuel purge control device for an internal combustion engine according to claim 1, wherein the calculation means calculates a drive duty of the purge control valve corresponding to the reserved drive cycle at the start of the next drive cycle.   When the calculation means calculates the drive duty corresponding to the reserved drive cycle in the reserved drive cycle, the drive duty is changed from increase to decrease, and the drive duty of the drive duty corresponding to the reserved drive cycle is When the calculation result is equal to or greater than the first threshold, the control unit switches the drive cycle from a long cycle to a short cycle to drive the purge control valve, and the calculation unit performs the reservation at the reserved drive cycle. When calculating the drive duty corresponding to the drive cycle, the drive duty is shifted from decrease to increase, and the calculation result of the drive duty corresponding to the reserved drive cycle is larger than the first threshold value. 3. The internal combustion engine according to claim 2, wherein when less than a threshold value, the control means switches the drive cycle from a short cycle to a long cycle to drive the purge control valve. 4. The evaporative fuel purge controller. When the calculation means calculates the drive duty corresponding to the reserved drive cycle in the reserved drive cycle, the drive duty is changed from increase to decrease, and the drive duty of the drive duty corresponding to the reserved drive cycle is When the calculation result is less than the first threshold, the control means controls the purge control valve while maintaining a long drive period, and the calculation means corresponds to the reserved drive period in the reserved drive period. When calculating the drive duty to be performed, the drive duty is changed from decrease to increase, and the calculation result of the drive duty corresponding to the reserved drive cycle is not less than the second threshold value which is larger than the first threshold value. 3. The evaporative fuel purge control apparatus for an internal combustion engine according to claim 2, wherein the control means drives and controls the purge control valve with a short drive cycle.

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