JP3443946B2 - Engine fuel vapor treatment system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine fuel vapor treatment system.

[0002]

2. Description of the Related Art Evaporated fuel generated from a fuel tank is adsorbed and trapped (referred to as "trap"), temporarily stored in a canister, and the evaporated fuel is discharged (referred to as "purge") from a canister in a predetermined operation region. In an engine equipped with an evaporated fuel processing device adapted to supply the intake air to the intake passage,
When the concentration of the evaporated fuel in the purge gas (referred to as “purge concentration”) changes, the degree of deviation of the air-fuel ratio changes even if the opening rate of the purge valve is the same. Therefore, it is essentially necessary to perform purge control according to the purge concentration. is there. However, it is difficult to directly detect the purge concentration. Therefore, for example, as described in JP-A-2-245461, the purge concentration is estimated by looking at the output of the air-fuel ratio sensor,
Conventionally, a purge control device has been proposed in which the valve opening speed of the purge valve is adjusted according to the estimated purge concentration.

[0003]

In the engine fuel vapor treatment system, the purge amount is controlled as quickly as possible while suppressing the deviation of the air-fuel ratio when the fuel vapor trapped in the canister is purged and supplied to the intake passage. In order to achieve a large amount of purge by increasing the purge amount to the required amount, the purge amount is gradually increased to the required amount at the start of purging as described above, the purge concentration is estimated, and the estimated purge concentration is set to the gradually increasing rate of the purge amount. It is required to perform the control to reflect it. However, by estimating the purge concentration in this way,
When the purge control according to the estimated purge concentration is performed, for example, when the first purge is started after the engine is started, there is no purge gas between the purge valve and the intake system. There is a delay before it is supplied to the engine, and the output of the air-fuel ratio sensor during that time does not reflect the purge concentration, resulting in an erroneous determination. Then, the purge amount is excessively increased due to an erroneous determination that the purge concentration is low, and as a result, the air-fuel ratio becomes overrich when the purge gas actually enters the intake system, causing a problem such as engine stall. Further, even if the problems associated with the estimation of the purge concentration are excluded, the delay of the purge bus supply at the start of the purge and the subsequent rapid change in the purge supply amount cause the air-fuel ratio fluctuation. Therefore, prevention of air-fuel ratio fluctuation including overrich due to erroneous determination of purge concentration at the start of purging is a technical problem that must be solved in order to realize large-scale purging.

An object of the present invention is to solve the above problems, and it is an object of the present invention to prevent the occurrence of air-fuel ratio fluctuations such as overrich due to erroneous determination of purge concentration estimation at the start of purge.

[0005]

As a means for solving the above-mentioned problems, the present invention provides, as described in claim 1, an evaporated fuel storage means for storing evaporated fuel generated in a fuel system, and the above-mentioned evaporation. A purge passage that connects the fuel storage means to the intake system, a purge valve that opens and closes the purge passage, and discharges the evaporated fuel from the evaporated fuel storage means and supplies it to the intake system when a predetermined purge execution condition is satisfied. As a means for solving the above-mentioned problems, in an engine fuel vapor treatment apparatus equipped with a purge control means for controlling a purge valve, as described in claim 1, the purge valve is temporarily opened before starting purge in a predetermined operating region. It is proposed to provide a pre-purge valve opening means for valve operation.

[0006] In the configuration according to the claim 1, wherein the predetermined operating region is intended to differential pressure across the purge valve was set to a predetermined value smaller than the operating region, the purge before the valve opening hands
The stage must not let the purge gas flow into the intake system before starting the purge.
Temporarily open the purge valve to the extent that the purge gas
Good to those of accumulating the purge passage, for example, billing
As described in Item 2 , the purge gas is supplied to the intake system before the purge is started at the time of engine startup, that is, during cranking.
To the extent that does not flow out to the temporarily the previous Symbol purge valve opens
It is preferable that a valve is used to store the gas in the purge passage . Then, the purge valve is opened temporarily by the pre-purging valve opening means.
Specific opening may that shall hold the purge valve as claimed in claim 3 in a predetermined open state, also, according
As described in Item 4 , the purge valve is a duty control type solenoid valve, and it is preferable that the predetermined valve opening state is a valve opening rate of 100%.

Further, according to the above structure, as described in claim 5 , the air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber by adjusting the fuel supply amount is supplied to the combustion chamber. Air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture, feedback correction amount setting means for setting a feedback correction amount based on the deviation of the air-fuel ratio detected by the air-fuel ratio detection means from the target value, and the feedback correction amount Feedback correction means for correcting the fuel supply amount based on the feedback correction amount set by the setting means, and purge for estimating the concentration of evaporated fuel in the purge gas based on the feedback correction amount set by the feedback correction amount setting means The concentration estimating means and the purge amount of the evaporated fuel discharged from the evaporated fuel storage means and supplied to the intake system, and Is particularly suitable in engines with evaporation correcting means for correcting, depending on the concentration of the vaporized fuel estimated by the purge concentration estimation means at least one of the fuel supply amount.

As another means for solving the above-mentioned problems, the present invention provides, as claimed in claim 6 , an evaporated fuel storage means for storing evaporated fuel generated in a fuel system, and the evaporated fuel storage means. A purge passage connected to the intake system, a purge valve that opens and closes the purge passage, and the purge valve is controlled so that the vaporized fuel is discharged from the vaporized fuel storage means and supplied to the intake system when a predetermined purge execution condition is satisfied. Purge control means, air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber by adjusting the fuel supply amount, and air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber A feedback correction amount setting means for setting a feedback correction amount based on a deviation of the air-fuel ratio detected by the air-fuel ratio detection means from a target value,
Feedback correction means for correcting the fuel supply amount based on the feedback correction amount set by the feedback correction amount setting means, and concentration of evaporated fuel in purge gas based on the feedback correction amount set by the feedback correction amount setting means And a purge concentration estimating means for estimating the purge concentration, and at least one of a purge amount and a fuel supply amount of the vaporized fuel released from the vaporized fuel storage means and supplied to the intake system as It is proposed to provide a purge concentration estimation limiting unit for limiting the estimation of the concentration of the evaporated fuel by the purge concentration estimating unit for a predetermined period from the start of purging in an engine fuel vapor processing apparatus provided with an evaporation correcting unit that corrects accordingly. It is a thing.

According to the sixth aspect of the present invention, the purge concentration estimating unit increases or decreases the purge concentration estimated value based on the feedback correction amount set by the feedback correction amount setting unit, and the purge concentration estimation limit is set. means, predetermined time period from the purge start good that shall to slow the degree of the estimated value increases or decreases.

[0010]

According to the first aspect of the present invention, the purge valve is opened when the purge execution condition is satisfied, for example, the evaporated fuel generated in the fuel system is stored in the evaporated fuel storage means and enters the air-fuel ratio feedback region. Then, the stored evaporated fuel is supplied to the intake system via the purge passage. Further, the purge valve is temporarily opened in the predetermined operation region before the purge is started. In the conventional evaporative fuel processing apparatus that does not have such a purge valve opening control, at the start of purging, especially at the beginning of the first purging after engine start, the purge valve is operated with or without a purge gas between the purge valve and the intake system. As a result, only the air initially enters the intake system from the purge passage, and the purge gas is supplied after a delay. Therefore, air-fuel ratio fluctuations occur. On the other hand, in the case of the present invention, as described above, the purge valve is temporarily opened before the purge is started, so that the purge gas is filled in the purge passage between the purge valve and the intake system. Also does not have a state in which only air is supplied, and therefore, only purge gas is supplied from the start of purge, and therefore,
The occurrence of air-fuel ratio fluctuations due to the purge delay is prevented.

[0011] Then, the predetermined operating region around purge valve differential pressure is the predetermined value smaller than the operating region,
In particular, when the engine is started, that is, during cranking as in the configuration according to claim 2 , the purge gas released by the temporary opening of the purge valve before the start of purging becomes large by appropriately setting the valve opening period. It is possible to prevent a portion from accumulating in the purge passage and almost not flowing into the intake system until the purge starts. At this time, as described in claim 3 , the purge valve is held in the predetermined open state for the predetermined period, so that the above-described operation becomes more effective. Further, according to the structure of claim 4 , the purge valve is a duty-controlled type solenoid valve, and the valve open rate is temporarily set to 100% before the purge is started, whereby the purge valve and the intake system are And the purge gas is sufficiently filled between. Also bill
According to the configuration of Item 5 , the concentration of the evaporated fuel in the purge gas, that is, the purge concentration is estimated based on the feedback correction amount, and at least one of the purge amount and the fuel supply amount is corrected according to the estimated purge concentration. . Then, the purge gas is stored in the purge passage before the purge is started, and the purge gas is supplied to the intake system at the same time as the purge is started, so that the purge concentration is reflected in the feedback correction amount from the beginning of the purge. It is possible to prevent erroneous determination in the density estimation.

According to the sixth aspect of the invention , the concentration of the evaporated fuel in the purge gas, that is, the purge concentration, is estimated based on the feedback correction amount, and the purge amount and the fuel supply amount are determined according to the estimated purge concentration. At least one is corrected. Then, the purge concentration estimation is limited for a predetermined period from the start of the purge, and specifically, the degree of increase or decrease of the purge concentration estimated value based on the feedback correction amount is made slow. As a result, it is possible to prevent erroneous determination of the purge concentration estimation when the supply of the purge gas is delayed at the start of the purge.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

[0014] Example 1. This embodiment limits purge concentration estimation for a predetermined period from the start of purge, and FIG. 1 is an overall system diagram thereof.

In FIG . 1, reference numeral 1 denotes an engine body of a rotary piston engine, which is a rotor housing 2 having a trochoidal inner peripheral surface and a pair of side housings 3 covering both sides thereof (the front side housing is not shown). .) And a substantially triangular rotor 5 eccentrically supported by an eccentric shaft 4.
Is configured to rotate in a planetary manner while being in sliding contact with the trochoidal inner peripheral surface of the rotor housing 2. Inside the casing, there are three working chambers 6A, 6B, 6C on the circumferential surface side of the rotor 5.
When the rotor 5 is rotated clockwise in FIG. 1, the volumes of the three working chambers 6A, 6B, 6C change, and suction, compression, and
The expansion and exhaust strokes are performed, and the driving force is extracted to the eccentric shaft 5.

In the rotor housing 2, two spark plugs 7 are arranged in the rotation direction of the rotor 5 before and after the compression top dead center position.
A and 7B are provided, and an exhaust port 8 is provided at the exhaust stroke position. A main intake port 9A and a sub intake port 9B are provided in the side housing 3 at the intake stroke position side by side in this order in the rotational direction of the rotor 5. A main intake passage 10A is connected upstream of the main intake port 9A, and a sub intake passage 10B is connected upstream of the sub intake port 9B.
Is connected, and an opening / closing valve 12 is installed in the auxiliary intake passage 10B. The main intake passage 10A and the auxiliary intake passage 10B join together on the upstream side, a fuel injection valve 11 is installed upstream thereof, and is further connected to the intake passage 10C upstream. Then, in the upstream side intake passage 10C, in order from the upstream side,
An air cleaner 13, a throttle valve 15 and a pressure sensor 14 are provided.

An exhaust passage 16 is connected to the exhaust port 8.

In FIG . 1, reference numeral 21 denotes a fuel tank, which has a strainer 22 and a fuel pump 23 built therein and a level gauge 24. One end of the fuel passage 25 is connected to the discharge side of the fuel pump 23, and the other end of the fuel passage 25 is connected to the fuel injection valve 11. Further, one end of a vapor passage 26 is connected to an upper portion of the fuel tank 21, an electromagnetic two-way valve 27 is interposed in the vapor passage 26, and the other end thereof is connected to a canister 28 for adsorbing and storing evaporated fuel. ing. Also, the vapor passage 2
6, a tank internal pressure sensor 29 is installed on the side close to the connection portion with the fuel tank 21.

The canister 28 includes a vapor passage 26.
A purge passage 30 is connected to a position lined up with, and a drain passage 31 is connected to the opposite side. Purge passage 30
The other end is connected to the throttle downstream of the upstream intake passage 10C, a duty solenoid type purge valve 32 is provided in the middle of the passage, and a chamber (expansion chamber) 33 constituting a volume portion is provided on the purge downstream side of the purge valve 32. is set up. A drain valve 35 is provided in the drain passage 29, and a filter 36 is provided on the tip side of the drain valve 35.

In FIG . 1, reference numeral 40 is an engine control unit composed of a microcomputer. The intake manifold boost pressure signal is input to the engine control unit 40 from the pressure sensor 14, and the engine rotation signal, the water temperature signal, the engine rotation signal, the water temperature signal, and the like from the rotation sensor, the water temperature sensor, the air-fuel ratio sensor, the atmospheric pressure sensor, the outside temperature sensor, etc. Various signals such as an air-fuel ratio signal, an atmospheric pressure signal, and an outside air temperature signal are input. The engine control unit 40 uses the above various signals to inject the fuel injection valve 11, the purge valve 32, the drain valve 35, the two-way valve 2
A control signal is output to 7 or the like to execute purge control and fuel injection control for realizing a large amount of purge.

In this embodiment, the basic control of purging and fuel injection is as follows.

[0022] First, the basic purge rate (KPRGBASE) calculated in accordance with the various signals in the preset air-fuel ratio feedback regions (F / B region), also depending on the purge amount integration value from the engine start (QPRGST) Purge rate guard value (KPRGST), fuel temperature (THF)
Purge rate guard value (KPRGTHF) according to the above, purge rate guard value (KPR) according to the deviation amount of the air-fuel ratio (A / F)
GCFB), the purge rate guard value (KPRGPG) according to the purge amount integrated value (QPRGPG), is calculated by the table of FIG.
The final purge rate (KPRG) is calculated from the basic purge rate (KPRGBASE) and these guard values. The basic purge rate (KPRGBASE) is a basic amount of the purge flow rate with respect to the engine intake air amount, and is a preset engine speed (Ne) and intake manifold boost pressure (PMTEL) as limit values due to the flow rate characteristics of the purge system hardware. Calculate with the table. Further, the purge rate guard value is also calculated by a preset map.

In FIG . 2, (a) is a map of the purge rate guard value (KPRGST) according to the purge amount integrated value (QPRGST) from engine start, and (b) is the fuel temperature (TH.
F) is a map of the purge rate guard value (KPRGTHF), (c) is a map of the purge rate guard value (KPRGCFB) according to the amount of deviation of the air-fuel ratio (A / F), and (d) is
It is a map of a purge rate guard value (KPRGPG) according to a purge amount integrated value (QPRGPG). In the map of the purge rate guard value (KPRGCFB) according to the A / F deviation amount, the value of the air-fuel ratio feedback correction amount (CFBN) that reflects the λ value (excess air ratio) is checked, and CFBN is set to a predetermined value on the fuel rich side. KPRGCFB is held (current value KPRGC) when it is in the range (upper threshold value KPCFBLAG1 or lower and lower threshold value KPRGCFBLAG2 or higher).
FB (n) = previous value KPRGCFB (n-1)),
When leaner than KPCFBLAG1, the previous value (KPR
GCFB (n-1)) is increased by a predetermined value KPRGCFBK1, and when it is richer than KPCFBLAG2, the previous value (KPRGCFB (n-1)) is changed to a predetermined value KPRGCFB.
I try to lower it by K2.

When the final purge rate (KPRG) is calculated,
Basic fuel injection pulse width per engine revolution (TE
2) (TE2 is the target of λ = 1 and the intake air amount (Q
a) and engine speed (Ne) calculated pulse width (TE1) with atmospheric pressure correction and intake air temperature correction) multiplied by engine speed (Ne) and constant (K) (Qa) is calculated and the final purge rate (KPR
G) is multiplied to calculate the purge flow rate (Q _P ). And
The duty value, that is, the purge duty (DPR
G), and a purge signal corresponding to the purge duty (DPRG) is output to drive the purge valve 32. Here, in the purge duty (DPRG), the horizontal axis represents the boost pressure (PMTEL) and the vertical axis represents the purge flow rate (Q
_P ) of the flow rate characteristic map showing the correspondence with the purge duty (MPDPRG) and the purge flow rate (Q
_P ), atmospheric pressure (ATM) and intake manifold boost pressure (PM)
It is set as a map value from the differential pressure (ATM-PMTEL) with respect to TEL).

Further, although addition of evaporation correction operation of the fuel injection pulse width, therefore, first, the transient purge duty subjected to better process so as to compensate the actual purge flow rate of delay with respect to the behavior of the purge valve 32 (DPRGN) calculate. Based on transient purge duty (DPRGN) calculates the actual purge flow rate (Q _P N), further calculates the actual purge rate (KPRG1). Here, the actual purge flow rate (Q _P N) is obtained from an actual purge flow rate characteristic map in which the horizontal axis represents the boost pressure (PMTEL) and the vertical axis represents the transient purge duty (DPRGN). Then, the actual purge rate (KPRG1) and the evaporation concentration correction coefficient (Q
EVAPO) and the correction coefficient (CQPRG) according to the degassing characteristics of the canister, in the form of the evaporation correction amount (CEVAP).
Calculate O). Then, this evaporation correction amount (CEVA
PO) as one of the correction factors to calculate the final fuel injection pulse width (T _P ), and output the injection pulse to output the fuel injection valve 1
Drive 1

The evaporation correction amount (CEVAPO) is for estimating the evaporation concentration on the basis of the deviation of the air-fuel ratio and reflecting the estimated purge concentration in the injection pulse width. Therefore, the center of the air-fuel ratio is set. The CFB value (CFBN) corresponding to the amount of deviation from (λ = 1) is calculated, and CFBN is compared with a threshold value by the map shown in FIG. 3 (a). QEV when it is between the threshold value KCFBLAG1 set to the side and the threshold value KCFBLAG2 set to the fuel rich side from λ = 1
APO is held (current value QEVAPO (n) = previous value QEVAPO (n-1)), and when leaner than KCFBLAG1, the previous value (QEVAPO (n-1)) is decreased by a predetermined value KQEVAPO, and KCFBLAG2.
On the rich side, the previous value (QEVAPO (n-1))
Is increased by a predetermined value KQEVAPO. KQEV above
APO is a gradient constant for estimation of the evaporation concentration, and is set according to the actual purge rate (KPRG1) by a map having different characteristics between starting and non-starting as shown in FIG. 3B.

Although the basic control is as described above, in this embodiment, since the estimation of the purge concentration is limited for a predetermined period from the start of the purge, the evaporation concentration correction coefficient (QEVAPO) is set at the time when the purge execution condition is satisfied. The initial value is set to 0 (zero) and the timer is set to prohibit the purge concentration estimation, that is, the calculation of the evaporation concentration correction coefficient (QEVAPO) for a predetermined period after the purge execution condition is satisfied. Instead of prohibiting the purge concentration estimation in this way, the slope constant (KQEVAPO), which is the degree of increase / decrease in the estimated evaporation concentration value, may be reduced to make the degree of increase / decrease in the estimated value slower. Then, in addition to such limitation of the purge concentration estimation, the purge is stopped for a predetermined period from the start of the purge.

The flow chart for performing a control of the purge and fuel injection in this embodiment is shown in FIGS. This flowchart comprises steps S101 to S113 in the front part shown in FIG. 4 and steps S114 to S119 in the rear part shown in FIG. 5. When started, first, various signals are read in S101, and then predetermined in S102. It is determined whether or not it is the F / B area. Then, if it is not the F / B area, the process directly returns. If it is in the F / B region, the process proceeds to S103, where the purge duty (DPRG) is set to a value F that is a purge flow rate that will not cause any trouble even if the purge gas having a concentration of 100% flows, and the timer value t is initialized at S104. Set the value t = 0. Then, in S105, t is incremented by 1,
In S106, it is determined again whether it is the F / B area, and the F / B area is
If it is not the area, the determination is repeated until it becomes the F / B area. If it is the F / B area, the process proceeds to S107. And S1
At 07, it is determined whether the timer value t has become equal to or more than the predetermined value E, and until the timer value t becomes equal to or more than the predetermined value E, S105
~ Repeat the processing of S107, the timer value t is a predetermined value E
If it becomes above, it will progress to S108.

In S 108, the basic purge rate (KPRGBA
SE) is calculated by the map. Then, in S109,
Purge rate guard value (KPRGST) according to the purge amount integrated value (QPRGST) from engine start, and purge purge rate guard value (KPRG) according to the fuel temperature (THF).
THF), the purge rate guard value (KPRGCFB) according to the deviation amount of the air-fuel ratio (A / F), and the integrated purge amount value (Q
Purge rate guard value (KPRGP) according to PRGPG
Each purge rate guard value of G) is calculated by the map of FIG. Then, the process proceeds to S110, where the basic purge rate (KPR
GBASE) and each guard value (KPRGST, KPR
The final purge rate (KPRG) is calculated by taking the minimum value of GTHF, KPRGCFB, and KPRPGG.

Next, in S111, the engine 1 basic fuel injection pulse width per revolution (TE2) to the engine rotational speed (Ne) and a constant (K) and a value obtained by multiplying the (intake air charging amount (Q
final purge ratio a)) is multiplied by (KPRG) calculates the purge flow rate (Q _P). Then, it is converted into a purge duty (DPRG) by a map in S112, and S11
At 3, the purge signal is output to drive the purge valve 32.

[0031] Then, in S114, to calculate the transient purge duty (DPRGN) by performing a smoothing process. Then, the actual purge flow rate (Q _P N) calculated based on the transient purge duty (DPRGN) in S115, divided by the actual purge rate in real purge flow rate in S116 (Q _P N) the intake air quantity (Qa) (KPRG1 ) Is calculated.

[0032] Then, in S117, the actual purge rate (KPR
The evaporation correction amount (CEVAPO) is calculated in the form of a product of G1), the evaporation concentration correction coefficient (QEVAPO), and the correction coefficient (CQPRG) according to the degassing characteristic of the canister. Then, in S118, the evaporation correction amount (CEVAPO) is used as one of the correction coefficients, and T _P = TE2 × (1 + CFB + C
The final fuel injection pulse width (T _P ) is calculated by the formula LC + CEVAPO) × (1 + CATV). Here, CFB is an air-fuel ratio feedback correction amount, CLC is a fuel injection valve tolerance correction amount, and CATV is a fuel response delay correction amount during a transition.

[0033] Then, driving the fuel injection valve outputs injection pulse in S119.

FIG . 6 is a flowchart for estimating the evaporation concentration correction coefficient (QEVAPO) for calculating the evaporation correction amount (CEVAPO) in S117 of FIG.
This routine consists of steps S201 to S214. When started, it is determined in S201 whether or not it is the F / B area, and if it is not the F / B area, the routine directly returns. Then, in the case of the F / B area, QEVA in S202
The initial value of PO is set to 0 (zero), and the timer value t is set to the initial value (t = 0) in S203. And S204
Then, the timer value t is incremented by 1, and it is determined again in S205 whether it is the F / B area. If it is not the F / B area, the determination is repeated until the F / B area is reached.
If it is a region, the process proceeds to S206. Then, in S206, it is checked whether the timer value t becomes equal to or more than the predetermined value E, and S204 to S206 until the timer value t becomes equal to or more than the predetermined value E.
When the timer value t becomes equal to or larger than the predetermined value E, the process proceeds to S207.

At S207, the air-fuel ratio feedback correction amount (CFB) is input. Then, in S208, the deviation amount (CFBN) from the center of the air-fuel ratio is calculated by using the arbitrarily set smoothing constant (KCFB).

Next, in S209, the threshold KCFBLAG1 in the map shown in FIG. 3 (a) and KCF
BLAG2 and the gradient KQEVAPO of estimation of the evaporation concentration are read. Then, in S210, CFBN becomes KCFBLAG.
CFBN is KCFBLA
When it is smaller than G2, the previous value (QEVAPO
A value obtained by increasing (n-1)) by a predetermined value KQEVAPO is set as a current evaporation correction density coefficient (QEVAPO (n)). When CFBN is KCFBLAG2 or higher,
In S212, it is determined whether CFBN is larger than KCFBLAG1. If CFBN is larger than KCFBLAG1, a value obtained by reducing the previous value (QEVAPO (n-1)) by a predetermined value KQEVAPO in S213 is used as the evaporative correction concentration coefficient (QEVAPO (QEVAPO ( n)). Also, S2
If CFBN is less than or equal to KCFBLAG1 in 12, that is, CFBN is a value between KCFBLAG1 and KCFBLAG2. In this case, the current value QE is determined in S214.
The previous value QEVAPO (n-1) is entered in VAPO (n).

[0037] According to this first embodiment, the predetermined time period from the purge start can be prevented by limiting the purge concentration estimate, from the misjudgment purge concentration estimated by the delay of purge gas supply at the start of the purge .

In addition, since the chamber (expansion chamber) 33 is provided in the purge passage 30 between the purge valve 32 and the intake system, the rapid concentration change of the purge gas supplied to the intake system at the start of the purge is alleviated. As a result, fluctuations in the air-fuel ratio due to sudden changes in the purge concentration are prevented.

[0039] Example 2. In the second embodiment, the purge valve is temporarily opened when the engine is started, the entire system is the same as that of the first embodiment, and the basic control of purge and fuel injection is the same as that of the first embodiment.

FIG . 7 is a flow chart for executing the purge valve opening at the time of starting of the second embodiment. This flowchart consists of steps S301 to S308. When started, the starter is turned ON in S301.
See if And if the starter is ON, S30
In 2, the purge duty is set so that the opening rate of the purge valve is 100%, and in S303, the timer value t is set to 0.
Set to (zero). Then, the count-up is performed in S304, and it is determined in S305 whether the timer value t has become the set value A or more, and the processes of S304 to S305 are repeated until the timer value t becomes the set value A or more. When the timer value t becomes equal to or larger than the set value A, the purge duty is turned off in S306. In addition, S301
If the starter is not ON in S307, it is checked in S307 if F / B is in progress. If it is in F / B, it means that the purge execution condition is satisfied. Therefore, in S308, the purge duty (DPR
G) is a value corresponding to the required purge flow rate. If the F / B is not in progress, the purge duty is turned off in S306.
To

Although the purge valve is temporarily opened at the time of starting in the second embodiment, it may be set to an operating region in which the differential pressure before and after the purge valve is smaller than a predetermined value except at the time of starting. Also, it may be set in such an operating region other than at the time of starting. Further, the valve opening period is set to a length such that the purge gas accumulates in the purge passage during the temporary valve opening period and does not flow out to the intake system.

[0042] According to the second embodiment, can be a purge gas prior to start purging is filled in the purge passage between the purge valve and the intake system, so as to supply the purge amount of time as configured purge start with, the purge delay It is possible to prevent the air-fuel ratio from fluctuating.

[0043] applications. This application example limits learning of air-fuel ratio feedback for a predetermined period from the start of purging. The overall system is the same as that of the first embodiment, and the basic control of purge and fuel injection is the same as that of the first embodiment.

FIG . 8 is a flow chart for executing the learning restriction of this application example . This flow is from S401 to S420
When started, various signals such as intake air amount, engine speed, water temperature are read in. Then, based on these signals, the basic injection pulse width corresponding to the filling amount per engine revolution is calculated in S402. This operation is usually no different from the general one.

Next, in S403, there speed and the load of the engine is in a predetermined area, and the water temperature is for example 60 ° C
As described above, it is determined whether or not the feedback condition that the catalyst is warmed up is satisfied. Then, if the feedback condition is satisfied, the feedback correction amount based on the air-fuel ratio deviation is calculated as usual in S404, while if the feedback condition is not satisfied, S4 is performed.
At 05, the feedback correction amount is set to a zero value.

Next, see if during the purge in S406. If purging is in progress (satisfaction of purging conditions is satisfied), it is determined in S407 whether or not the previous purging was not performed. If the purging is not the previous purging, it means that the purge is started, and the counter is set in S408. In step S409, the learning value of the feedback correction amount is not updated but is fixed to the learning value when the previous feedback execution condition was satisfied (update prohibition). Then, using the previous value, the final injection pulse width is calculated in S410, and the injection is executed in S411.

If it is determined in S407 that the purging has started before the previous non-purging but not the previous non-purging, it is checked in S412 whether the counter is 0 (zero). If the counter is not 0, the counter is reset in S413. Subtract and S409
Go to and do not update the learning value.

If the counter becomes 0 in S412, S41
The counter is fixed at 0 (zero) in step 4, and in step S415, it is determined whether or not a learning condition such that the sampling number of the feedback correction amount has reached the set value while the water temperature is 80 ° C. or higher is satisfied. If the learning condition is not satisfied, the process proceeds to S409, and the learning value is not updated. If the learning condition is satisfied, the learning value is updated in S416.

When it is determined in S406 that purging is not in progress (purge execution condition is not satisfied), the counter is fixed to 0 (zero) in S417, it is determined in S418 whether the learning condition is satisfied, and the learning condition is satisfied. Updates the learning value when the purge execution condition is not satisfied in S419. If the learning condition is not satisfied, the process proceeds to S420 and the learning value is not updated.

[0050] According to this application example, by a predetermined period from the purge start to limit the degree of learning of the learning value of the feedback correction amount of the air-fuel ratio control, the effect of the air-fuel ratio variation due to the change in the purge concentration at the start of the purge It is possible to set a learning value that is not received.

In this application example , the learning value of the feedback correction amount is prohibited from being updated for a predetermined period from the start of purging, but for example, half of the previous learning value is half of the average value of the sampling value. Is added to obtain a new learning value, a new learning value is obtained by adding 1/3 of the average value of sampling values to 2/3 of the previous learning value only for a predetermined period from the start of purging. As described above, the learning degree may be limited by changing the reflection degree of the sampling value.

[0052]

Since the present invention is configured as described above, it is possible to prevent air-fuel ratio fluctuations such as overrich due to erroneous determination of purge concentration estimation at the start of purge.

[0053] In particular, according to the means according to claim 1 of the present invention, by temporarily opening the purge valve before starting purging in a predetermined operating region, the purge gas in the purge passage between the purge valve and the intake system It is possible to fill it and supply the purge amount as set at the same time when the purge is started, and it is possible to prevent the air-fuel ratio from fluctuating due to the delay in purge. By setting the predetermined operation region during engine starting, that is, during cranking, as in the configuration according to claim 2 , the purge gas is hardly discharged to the intake system and is accumulated in the purge passage to reliably prevent the purge delay. The above effect can be enhanced by holding the purge valve in a predetermined open state for a predetermined period as in the configuration according to claim 3 . According to the structure of claim 4 , the purge valve is temporarily opened at a rate of 1 before the purge is started.
By setting the state to 00%, it is possible to sufficiently fill the purge gas between the purge valve and the intake system to enhance the above effect. Further, according to the configuration of claim 5 , the concentration of the evaporated fuel in the purge gas, that is, the purge concentration is estimated based on the feedback correction amount, and at least one of the purge amount and the fuel supply amount is corrected according to the estimated purge concentration. However, since the purge gas is stored in the purge passage before the purge is started and the purge gas is supplied to the intake system at the same time as the purge is started, it is possible to prevent an erroneous determination in the purge concentration estimation at the start of the purge. .

Further , according to the means of claim 6 , the concentration of the evaporated fuel in the purge gas, that is, the purge concentration is estimated based on the feedback correction amount, and at least the purge amount and the fuel supply amount are determined according to the estimated purge concentration. In the case of correcting one, by restricting the purge concentration estimation for a predetermined period from the start of purge, it is possible to prevent the purge concentration estimation from being erroneously determined due to the delay of the purge gas supply at the start of purge. Specifically, by slowly increasing or decreasing the purge concentration estimated value based on the feedback correction amount, it is possible to limit the purge concentration estimation and prevent erroneous determination of the purge concentration estimation at the start of purge.

[Brief description of drawings]

FIG. 1 is an overall view of a first embodiment of the present invention

FIG. 2 is a map of a purge rate guard value according to the first embodiment of the present invention.

FIG. 3 is a map of an evaporation correction amount according to the first embodiment of the present invention.

FIG. 4 is a flowchart of the control of the purge and the fuel injection in the first embodiment of the present invention (first stage portion).

FIG. 5 is a flowchart of the control of purge and fuel injection in the first embodiment of the present invention (second part).

FIG. 6 is a flowchart for setting an evaporation correction coefficient according to the first embodiment of the present invention.

FIG. 7 is a flowchart for executing the purge valve opening at the time of starting in the second embodiment of the present invention.

FIG. 8 is a flowchart for executing learning restriction at the start of purging in an application example of the present invention.

[Explanation of symbols]

1 engine body 21 Fuel tank 26 vapor passage 28 canisters 30 Purge passage 31 Drain passage 32 Purge valve 33 chambers (expansion room) 40 Engine control unit

Continuation of the front page (56) Reference JP-A-4-72453 (JP, A) JP-A-4-112959 (JP, A) Actually open 3-114566 (JP, U) Actually open 57-103356 (JP , U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02M 25/08 301 F02M 25/08

Claims (6)

(57) [Claims] 1. A vaporized fuel storage means for storing vaporized fuel generated in a fuel system, a purge passage for connecting the vaporized fuel storage means to an intake system, a purge valve for opening and closing the purge passage, and a predetermined purge execution condition. there a fuel vapor treatment system for an engine equipped with a purge control means for controlling the purge valve so as to supply to the intake system by releasing fuel vapor from the fuel vapor reservoir means when satisfied, the purge
Do not let the purge gas flow into the intake system before starting the purge in an operating region where the differential pressure across the valve is smaller than a predetermined value.
Purge gas opens temporarily the purge valve to the extent
An evaporative fuel treatment system for an engine, characterized in that pre-purge valve opening means for accumulating the fuel in the purge passage is provided. 2. A steam for storing evaporated fuel generated in a fuel system.
Connect the generated fuel storage means and the evaporated fuel storage means to the intake system.
A continuous purge passage and a purge for opening and closing the purge passage
When the valve and the specified purge execution conditions are met, the vaporization is performed.
Evaporative fuel is discharged from the fuel generation reservoir and supplied to the intake system.
Equipped with purge control means for controlling the purge valve.
In the evaporated fuel processing apparatus for the engine , the purge gas is introduced into the intake system before starting the purge at the time of starting the engine.
Open the purge valve temporarily until it does not flow out.
Pre-purge valve opening hand that stores the purge gas in the purge passage
An evaporative fuel treatment system for an engine, characterized in that a step is provided . Wherein said by the purge before the valve opening means purge
The evaporative fuel treatment system for an engine according to claim 1 or 2 , wherein the temporary opening of the valve is held in a predetermined open state. Wherein said purge valve is a duty-controlled
The evaporative fuel treatment system for an engine according to claim 3 , wherein the evaporative fuel treatment device is constituted by a solenoid valve, and the predetermined valve opening state is a valve opening rate of 100%. 5. An air-fuel ratio control means for controlling an air-fuel ratio of an air-fuel mixture supplied to the combustion chamber by an engine, and an air-fuel ratio for detecting an air-fuel ratio of the air-fuel mixture supplied to the combustion chamber. Detection means, a feedback correction amount setting means for setting a feedback correction amount based on a deviation of the air-fuel ratio detected by the air-fuel ratio detection means from a target value, and a feedback correction amount set by the feedback correction amount setting means. Feedback correction means for correcting the fuel supply amount based on the feedback correction amount, purge concentration estimation means for estimating the concentration of the evaporated fuel in the purge gas based on the feedback correction amount set by the feedback correction amount setting means, and the evaporated fuel storage means At least one of the purge amount and the fuel supply amount of the evaporated fuel discharged from the Serial purge concentration estimating means by evaporative fuel processing apparatus according to claim 1, 2, 3 or 4, wherein the engine with the evaporation correcting means for correcting, depending on the concentration of the evaporated fuel that has been estimated. 6. A vaporized fuel storage means for storing vaporized fuel generated in a fuel system, a purge passage connecting the vaporized fuel storage means to an intake system, a purge valve for opening and closing the purge passage, and a predetermined purge execution condition. Purge control means for controlling the purge valve so that the evaporated fuel is discharged from the evaporated fuel storage means and supplied to the intake system when
Air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber by adjusting the fuel supply amount, air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber, and the air-fuel ratio detection Feedback correction amount setting means for setting a feedback correction amount based on the deviation of the air-fuel ratio detected by the means, and the fuel supply amount based on the feedback correction amount set by the feedback correction amount setting means. Feedback correction means, and a page concentration estimation means for estimating the concentration of the evaporated fuel in the purge gas based on the feedback correction amount set by the feedback correction amount setting means and increasing or decreasing the purge concentration estimated value , At least the purge amount and the fuel supply amount of the evaporated fuel discharged from the evaporated fuel storage means and supplied to the intake system. One is an evaporated fuel processing apparatus for an engine, which is provided with an evaporation correction means for correcting the other according to the concentration of the evaporated fuel estimated by the purge concentration estimation means. Degree of increase / decrease in the estimated value in the concentration estimation of evaporated fuel
An evaporative fuel treatment system for an engine, characterized in that a purge concentration estimation limiting means for slowing down the engine is provided.