JP2861672B2 - Evaporative fuel processor for engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In order to prevent fuel evaporated from a fuel tank from diffusing into the atmosphere, fuel vapor is adsorbed on an activated carbon canister, and fuel accumulated in the activated carbon canister is purged into an intake pipe under predetermined operating conditions (by the atmosphere). The fuel is injected into the cylinder together with the fuel injected from the injector.

However, if a purge gas which is not measured by an air flow meter is added, the control air-fuel ratio is affected, so that a purge valve (purge control valve) is opened during the air-fuel ratio feedback control (JP-A-2-1963).
No. 1).

Although the air-fuel ratio shifts to the rich side when the purge valve is opened, the air-fuel ratio feedback correction coefficient α shifts to the lean side from the control center (1.0), and eventually reaches a certain value (for example, 0.8). ), The air-fuel ratio is kept within the catalyst window (a predetermined width around the stoichiometric air-fuel ratio) even during the purge.

[0005]

By the way, in order to keep the purge rate (the ratio of the purge valve flow rate to the intake air amount) constant, the purge valve is opened according to the operating conditions of the engine (for example, the engine speed and the basic injection amount). It is conceivable to assign degrees.

However, unlike a valve driven by a step motor, in a purge valve whose valve opening degree is determined according to the ON duty, the rising duty (duty when the purge valve starts to open) changes depending on the purge valve temperature. Therefore, when the temperature becomes different from the temperature at which the valve opening is determined, the purge valve flow rate differs even if the same ON duty is given. As shown in FIG. 13, at a high temperature where the rising duty is large, the opening of the purge valve is delayed, so that the purge valve flow rate is reduced. At a low temperature with a small rising duty, the opening of the purge valve is early and the purge valve flow rate is small. As a result, the flow rate varies. Due to this flow rate variation, an air-fuel ratio error during purge (a deviation from the stoichiometric air-fuel ratio) also increases.

Accordingly, the present invention obtains the rising duty of the purge valve (directly detects or predicts it based on a learning value), and raises the basic duty according to the operating condition with the rising duty, thereby causing variation in the flow rate of the purge valve. To prevent

[0008]

According to a first aspect of the present invention, as shown in FIG. 1, a means 41 for judging a purge ON / OFF condition in response to an operation condition signal and a purge O / O based on the judgment result.
In an evaporative fuel processing apparatus for an engine, comprising: a purge valve for adjusting a purge gas amount according to a purge valve duty under N conditions; a means 43 for calculating a basic duty of the purge valve according to operating conditions; Means 44 for detecting a rising duty to start opening and means 45 for calculating the purge valve duty by adding the rising duty to the basic duty are provided.

The second invention is, as shown in FIG. 26, a means 41 for judging the purge ON / OFF condition in response to an operation condition signal. An evaporative fuel processing device for an engine, comprising: a purge valve 42 for adjusting the amount;
Means 43 for calculating the basic duty of the purge valve 42 according to the operating conditions; and calculating the purge valve duty by adding the learning value stored in the memory 51 under the purge ON condition to the basic duty based on the determination result. Means 52 for calculating an air-fuel ratio feedback correction amount α from an output of an air-fuel ratio sensor (for example, an O ₂ sensor) 53 so that the air-fuel ratio falls within the catalyst window;
A means 55 for sampling the purge valve duty at a timing when the air-fuel ratio feedback correction amount α changes by switching the purge ON and OFF, and the sampled purge valve duty (itself or its average value). Means 56 for updating the learning value stored in the memory 51 is provided.

A third invention, as shown in FIG. 27, comprises means 41 for judging a purge ON / OFF condition in response to an operation condition signal, and purging gas in accordance with a purge valve duty under the purge ON condition based on the judgment result. An evaporative fuel processing device for an engine, comprising: a purge valve 42 for adjusting the amount;
Means 43 for calculating the basic duty of the purge valve 42 according to the operating conditions; and calculating the purge valve duty by adding the learning value stored in the memory 51 under the purge ON condition to the basic duty based on the determination result. Means 52 for detecting the timing at which the purge valve 42 starts to open or the timing of valve seating;
Means 62 for sampling the purge valve duty at this timing and means 63 for updating the learning value stored in the memory 51 based on the sampled purge valve duty (itself or an average thereof) are provided. Was.

[0011]

In a purge valve in which the valve opening degree is determined according to the ON duty as in a linear solenoid drive, the duty at the start of opening is not zero, so if the purge valve is opened with a basic duty according to the operating conditions, There is less purge valve flow than required. In addition, the duty at the start of opening varies depending on the purge valve temperature,
Even when the engine load and rotation speed are the same, the purge valve flow rate differs between high and low temperatures.

In this case, in the first invention, the duty (rising duty) at which the opening of the purge valve starts to be detected is detected, and when the basic duty is raised by the rising duty, the demand expected from the basic duty is obtained. Volume flows through the purge valve. Even if the rise duty changes depending on the purge valve temperature, the required amount according to the operating conditions flows through the purge valve.

The timing at which the purge valve starts to open corresponds to the timing at which α changes. When the rising duty of the purge valve increases at a high temperature (the timing at which the purge valve starts to open is delayed), the timing at which α changes is delayed accordingly, and when the rising duty decreases at a low temperature (when the The opening timing becomes earlier), so that α changes earlier.

In this case, if the purge valve duty at the timing when α changes is sampled in the second invention, this purge valve duty corresponds to the rising duty with respect to the purge valve temperature at that time. The learning value is updated based on the learning value, and the next purge ON is performed with the purge valve duty calculated using the updated learning value.
When the purge valve is sometimes opened, the purge valve flow rate flows as required if the purge valve temperature is the same.

Further, since the rising duty is obtained from the change in α, a sensor for detecting the rising duty is unnecessary.

[0016]

FIG. 2 shows a control unit 2 comprising a microcomputer (for example, a 16-bit microcomputer) for controlling the engine.

The exhaust pipe 3 is provided with a three-way catalyst 4 for treating three harmful components such as CO, HC and NOx emitted from the engine. The three-way catalyst 4 can simultaneously treat the harmful three components only when the air-fuel ratio of the air-fuel mixture supplied to the engine is within a narrow range (catalyst window) around the stoichiometric air-fuel ratio. If the air-fuel ratio deviates slightly to the rich side from this catalyst window, CO, H
When the discharge amount of C increases and shifts to the lean side, a large amount of NOx is discharged.

For this reason, the control unit 2 performs feedback control of the fuel injection amount based on the actual air-fuel ratio signal from the O ₂ sensor 5 so that the three-way catalyst 4 can sufficiently exhibit its ability.

The output of the O ₂ sensor 5 provided upstream of the three-way catalyst 4 changes abruptly at the stoichiometric air-fuel ratio (approximately 1 V on the rich side of the stoichiometric air-fuel ratio and approximately 0 V on the lean side). Therefore, when the O ₂ sensor output is higher than the slice level (approximately 0.5 V), it is determined that the air-fuel ratio is on the rich side, and when it is lower than the slice level, it is on the lean side. If such determination is made in synchronization with the engine rotation, it is possible to determine whether the air-fuel ratio has just been reversed to the rich side (or lean side), or whether the air-fuel ratio is continuously on the same side of rich or lean.

From these determination results, immediately after the air-fuel ratio is reversed to the rich side, the step amount P is subtracted from the air-fuel ratio feedback correction coefficient α, and the integral amount I is subtracted from α until immediately before the air-fuel ratio is next reversed to the lean side. (Conversely, P is added to α immediately after the actual air-fuel ratio is inverted to the lean side, and I is added until immediately before the actual air-fuel ratio is next inverted to the rich side.) Immediately after the inversion of the air-fuel ratio, a large value of P is applied stepwise to change to the opposite side with good response, and after the step change, the air-fuel ratio is slowly changed to the opposite side with a small value of I. It stabilizes the feedback control.

Even if the operating conditions of the engine are different,
The ratio of the amount of intake air measured by the air flow meter 7 located upstream of the throttle valve 6 to the amount of fuel supplied from the injector 8 to the cylinder (that is, the air-fuel ratio)
The control unit 2 determines the valve opening pulse width (injection pulse width) of the injector 8 that is intermittently opened in synchronization with the engine rotation so that the air-fuel ratio becomes substantially the stoichiometric air-fuel ratio.

9 is a signal corresponding to the engine speed and Re and
The crank angle sensor 10 outputs an f signal (a reference position signal of the crank angle), and the throttle valve opening (T
VO), 11 is a water temperature sensor, 12 is a vehicle speed sensor, and these are also input to the control unit 2.

If the injector 8 is clogged due to aging, even if the injector 8 is driven with the same pulse width, the amount of supplied fuel is reduced. Depends on the lean side of the air-fuel ratio, but this can be dealt with by performing basic air-fuel ratio learning.

After a short time from the start of the air-fuel ratio feedback control, the average value of α is settled to a value larger than the control center (1.0) (α itself fluctuates around this value). If the battery is backed up as the air-fuel ratio learning value αm, the air-fuel ratio can be stored in the catalyst window from the beginning of the feedback control by increasing the injection pulse width by the learning value αm from the next engine operation. It is.

On the other hand, when the engine is stopped, the fuel evaporated from the fuel tank 15 and adsorbed by the activated carbon in the canister 16 is separated from the activated carbon when the atmosphere is introduced from outside the canister 16 during the operation of the engine, and the separated fuel is contained. Air (purge gas) is sucked into the intake passage.

A purge valve 21 is provided in a passage 18 that communicates the activated carbon canister 16 with the collector 17a of the intake manifold 17 in order to adjust the flow rate of the purge gas. The purge valve 21 is a valve driven by a linear solenoid. The purge valve 21 is driven by a pulse signal of a constant period (for example, a period of 6.4 ms) from the control unit 2, and the valve opening increases as the ON duty (ON time ratio) increases. Will increase.

If the purge valve 21 is stuck in the fully open state, the engine may stall (engine stall) or increase the idling speed due to the purge. Therefore, a VC negative pressure valve (diaphragm valve) is provided to prevent this. 22 is provided in the passage 18 in series with the purge valve 21. The VC negative pressure is a negative pressure that rises as shown in FIG. 3 with respect to the throttle opening TVO. As long as the accelerator pedal is released and the throttle valve 6 is closed, the VC negative pressure approaches the atmospheric pressure and the VC negative pressure becomes VC. The negative pressure valve 22 is closed. As a result, the passage 18 is blocked regardless of whether the purge valve 21 is opened or closed.

When the purge valve 21 is driven by a linear solenoid, the flow rate of the purge valve varies due to a change in the rising duty depending on the temperature of the purge valve.

In order to avoid this, the control unit 2 predicts the rising duty of the purge valve based on a learned value, and corrects the basic duty of the purge valve according to the operating condition based on the learned value.

For such control, the flow charts of FIGS. 4 to 9 are set up, and will be described below. In addition, the symbol indicating the quantity uses uppercase letters in principle,
Symbols and imperative statements sometimes used for operators are diverted from those used in programming languages.

(1) Purge cut conditions (1-1) When any of the following conditions <1> to <9> is satisfied, the purge valve duty (EVAP) is set to 0 to set the purge valve to zero. Close step by step (immediate cut). Under these conditions, the VC negative pressure valve 22 is closed, and accordingly, the purge valve 21 is also closed stepwise. Conversely, when all of these conditions are released, the valve is opened in stages.

<1> When the ignition switch is OFF (step 11 in FIG. 5). <2> At the time of engine stall determination (step 12 in FIG. 5). <3> When the starter switch is ON (step 13 in FIG. 5). <4> When the idle switch is ON (Step 14 in FIG. 5). <5> When the vehicle speed (VSP) falls below a predetermined value (VCPC #) (Step 15 in FIG. 5). <6> When the load is too small (Step 16 in FIG. 5).
For example, the cylinder air amount equivalent pulse width TP (or the basic injection pulse width TP0) and the purge lower limit allowable value (TPCP
C), and if TP <TPCPC, it is determined that the load is too small. TPCPC can also be obtained by looking up a table from the engine speed NE (with interpolation calculation). TP is the basic injection pulse width TP
0 (= KCONST # * Qs / NE)
It is known. KCONST # is a constant, and Qs is an intake air amount measured by an air flow meter. <7> When the load is too large (Step 17 in FIG. 5).
For example, the air flow rate QH0 and the purge upper limit allowable value (EVP
CQH #), and it is determined that the load is too large when QH0 ≧ EVPCQH #. QH0 is the air flow rate (volume flow rate) at the throttle valve, and the throttle opening TV
It is determined from O and the engine speed NE. <8> When the air-fuel ratio feedback control is not being performed (step 18 in FIG. 5). <9> Clamping (during stop of air-fuel ratio feedback control). (Step 19 in FIG. 5)

These conditions are checked, and if any of them is satisfied, the cut flag is set to 1 and the slow flag is set to 0 (steps 11 to 19 and 21 in FIG. 5). The cut flag = 1 indicates that the purge cut is performed in a stepwise manner. However, since it is sufficient to set the flag once, the routine exits from step 20 without proceeding to step 21 unless it is the first time in step 20.

On the other hand, when all of the above conditions <1> to <9> are canceled, the cut flag = 0 and the slow flag = 1 (steps 11 to 19 in FIG. 5).
23). Since the slow flag = 1 indicates that the opening and closing of the purge valve is performed stepwise, the purge valve is gradually opened by the slow flag = 1 and the cut flag = 0. Note that when the purge valve is opened stepwise, setting of the flag once is sufficient, as in step 20 in the case of immediate cut (step 22 in FIG. 5).

(2) Purge Valve Opening Characteristics (2-1) Connection with Purge ON Condition When all of the above conditions <1> to <9> are canceled,
Until EVAP = EVAPT, (EVAPT * SP
The purge valve duty EVAP is increased at the speed of (EON #) (steps 31 to 35 and steps 31 to 3 in FIG. 6).
4, 36, 37).

Here, EVAPT is a purge valve target duty, and SPEON # is an opening speed of the purge valve.

FIG. 12 shows EVAP (purge valve duty).
When the control waveform is switched from the purge OFF to the purge ON, the control waveform is gradually increased toward the target duty EVAPT. At the time of switching from the purge ON to the purge OFF, the EVAP is set to 0 in steps (steps 31 and 38 in FIG. 6).

(2-2) Purge Valve Target Duty The purge valve target duty EVAPT is: EVAPT = EVAP0 + OFSTPV + VBOFPV ... [1] where EVAP0; purge valve basic duty OFSTPV; rising duty learning value VBOFPV; rising duty battery voltage The correction ratio is obtained (step 5 in FIG. 4). The calculated EVAPT is limited to the upper limit value (EVPMAX #) (steps 6 and 7 in FIG. 4).

The basic duty EVAP0 in the equation [1] is
Engine speed NE and pulse width TP equivalent to cylinder air amount
From this, a table containing the characteristics shown in FIG. 10 is obtained by lookup (with interpolation calculation) (step 3 in FIG. 4). The value of EVAP0 is set so that the purge rate (the ratio between the flow rate of the purge valve and the amount of intake air) is substantially constant under each operating condition.

If any of the sensors (O ₂ sensor, air flow meter, throttle sensor) has an abnormality (NG in the figure), EVAPT = NGEVP # is set (steps 1 and 2 in FIG. 4). NGEVP # is a target duty (constant rate) when the sensor is abnormal.

OFSTPV in the equation [1] is a learning value corresponding to the rising duty (simply called a learning value), and will be described in detail later. FIG. 13 shows the linear flow characteristic of the purge valve.
As shown in (2), if it is assumed that the object moves in parallel to the left and right according to the purge valve temperature (that is, the change in the inclination of the straight line is ignored), the basic duty EV is increased by the rising duty.
Since AP0 needs to be raised, the learning value OFSTPV is added to the basic duty EVAP0 as in the equation [1].

The rising duty battery voltage correction rate VBOFPV in the equation [1] is calculated from the battery voltage VB as shown in FIG.
A look-up table (with interpolation calculation) is obtained for a table containing the characteristic of No. 1 (step 4 in FIG. 4). VBOFP
V is a correction factor for which the rising duty varies depending on the voltage applied to the purge valve, and differs depending on the type of purge valve. FIG. 11 shows an example in which the purge valve is driven by a linear solenoid.

(3) Rising Duty Learning (3-1) Battery Backup The learning value OFSTPV is backed up by a battery.
When the control unit 2 is energized, OFSTPV = OFSTPV hold value (steps 41 and 42 in FIG. 7).

When the control unit 2 is initially energized, OFSTPV = INOFST # (steps 41 and 44 in FIG. 7). INOFST # is an initial value of OFSTPV for the first energization.

(3-2) Learning Reservation Conditions Since learning is reserved when switching to purge ON, the purge O
This is performed following the setting of the flag for instructing switching to N, and the learning reservation flag is set to 1 (step 23 in FIG. 5). The reason why the learning is reserved at the time of switching to the purge ON is to increase the frequency of the learning.

(3-3) Learning Interruption Condition When the following condition is satisfied, the learning is interrupted by setting the learning reservation flag to 0 (steps 54 to 5 in FIG. 8).
7).

<1> When the condition is other than that the air-fuel ratio feedback control is being performed and the clamp is not being performed (step 5 in FIG. 8)
5). This is because the condition during the air-fuel ratio feedback control and not during the clamping is set as the learning condition. <2> When the cut flag = 1 (Step 5 in FIG. 8)
6). This is because learning is not performed during cutting. <3> When the cut flag = 0 and the slow flag = 0 (steps 56 and 57 in FIG. 8). This is because learning is not performed after EVAP catches up with the target duty EVAPT.

If any of the sensors is abnormal, O
FSTPV = NGOFS #, and the learning is interrupted (steps 51 to 53 in FIG. 8).

(3-4) Update of Learning Value The average value ALPAV of the air-fuel ratio feedback correction coefficient for the first time after learning is stored in ALPST of the memory (steps 58 and 60 in FIG. 8). The ALPST stores the ALPAV before switching to the purge ON state.

However, ALPST is stored only when α is stable (for example, when | ALPAV04−ALPAV | <DALPAH #) (steps 59 and 60 in FIG. 8). Here, ALPAV04 is the AL four times before
PAV and DALPAH # are predetermined values.

The learning value OFSTPV is updated by switching the purge ON to α <ALPST + ALPLMT #
(Steps 61 and 6 in FIG. 8).
2). When the purge is turned on, α moves from ALPST to a smaller side, but it is determined that α has changed only when the amount of movement of α (ALPST−α) reaches a predetermined value (ALPLMT #). That is, ALPLMT # corresponds to a dead zone, and thereby stabilizes the learning value.

At this timing, the learning value is updated according to OFSTPV = (EVAP-VBOFPV)... [2]. Since α changes at the timing when the purge valve starts to open, (EVAP−VBOFPV) at the timing when α changes corresponds to the rising duty at the purge temperature at that time, and is therefore entered into the OFSTPV of the memory. is there.

At the timing when α changes, (EVAP-
Since the value of VBOFPV actually varies every time, OFSPV = (EVAP-VBOFPV) * WEGHT # + OFSTPV * (1-WEGHT #) [3] where WEGHT #; 8 step 62). (EVAP-VB
By obtaining the current learning value (OFSTPV on the left side) by a weighted average of the previous learning value (OFSTPV on the right side) and the previous learning value (OFSTPV on the right side), the variation for each time is suppressed. In addition, not only the weighted average value but also a simple average value of predetermined times can be used.

After the update, the learning reservation flag is set to 0,
The updated OFSTPV is restricted between the upper limit value (OFSMAX #) and the lower limit value (OFSMIN #) (step 64 in FIG. 8).

(3-6) Air-fuel ratio feedback correction coefficient ALPAV is calculated by a known method often used in basic air-fuel ratio learning. For example, when ALPAV is added to the step amount P, ALPAV = (α + ALPO) / 2 where ALPO is obtained by α immediately before the addition of the preceding P (steps 73 and 7 in FIG. 9).
7). The ALPAV thus obtained changes every half cycle of α as shown by the broken line in FIG.

Further, since the old value of ALPAV is required for determining the stability of α, four memories (ALPAV01, ALPAV02, ALPAV0) are provided in addition to ALPAV.
3, ALPAV04), and the value of ALPAV03 is added to the ALPAV04 when the step amount P is added.
ALPAV02 to ALPAV03, ALPA
The value of V01 is set to ALPAV02, and the ALPA calculated this time.
The value of V is transferred to ALPAV01 (steps 73 and 76 in FIG. 9).

However, when the feedback control is started during the clamping in the air-fuel ratio feedback control, the ALPAV is calculated from the first cycle of the control after the release of the clamp. Therefore, when the addition count counter value of P (COUTP) is less than 3, Set ALPAV = 1.0 (steps 75 and 80 in FIG. 9). Of course, during clamping in the air-fuel ratio feedback control, both ALPAV and ALPO are 1.0 (steps 71 and 72 in FIG. 9).

Here, the operation of this example will be described with reference to FIG.

At the time of switching from purge OFF to purge ON, the purge valve duty EVAP increases stepwise from the point A in FIG. 15 toward the target duty EVAPT, but before the purge valve is opened, the average value of α (ALPA
V) does not change and is the same as immediately before the purge is turned on.

Assuming that the purge valve temperature is higher than the previous purge ON time without changing the load and the rotation speed of the engine, the rise duty of the purge valve becomes larger than the previous time. For example, when the purge valve was opened at the point B in FIG.
At this point, α is shifted to a smaller side from point D in FIG. 15 corresponding to this valve opening, and it is determined that α has changed at the timing when point E is reached.

In this case, if the value of (EVAP-VBOFPV) at the timing when it is determined that α has changed is newly taken in as the learning value OFSTPV, the new learning value rises with respect to the current purge valve temperature. Since the duty corresponds to the duty, if the purge valve temperature remains the same during the next purge, the purge valve flow rate flows as required.

Thereafter, even if the purge valve opens earlier at point B in FIG. 15 when the purge valve is turned on due to a decrease in the purge valve temperature, α changes at that time earlier. (EVAP at the timing
−VBOFPV) is smaller than that for the point C. If this value is taken into the learning value as the rising duty with respect to the current purge valve temperature, if the purge temperature is the same, the request for the next purge ON is also required. Volume flows through the purge valve.

As described above, the rising duty that changes depending on the purge valve temperature is predicted from the timing at which α changes, and the predicted rising duty (learning value) is calculated.
By correcting the basic duty of the purge valve by
The difference between the required amount determined according to the operating conditions and the actual purge valve flow rate can be reduced. If the purge valve flow rate as required can be made to flow, it is easy to keep the purge rate constant, which leads to a reduction in the air-fuel ratio error during the purge.

Also, at the timing when α changes, (EV
(AP-VBOFPV), a value obtained by further weighted averaging is used as a learning value OFSTPV, and (EVAP-VBOFPV)
Is suppressed from occurring for each time, and the learning value is stabilized.

Further, the reference of the moving amount of α is not the control center (1.0) but the ALPST (AL
(PAV), there is no need to be affected by steady-state errors in the air-fuel ratio (due to variations in the characteristics of the air flow meter or injector, etc.). When the reference of the movement amount of α is set to 1.0 at the control center, α <
If the ALPAV is shifted to a side smaller than the control center by a value slightly larger than the ALPLMT # due to clogging of the injector, α does not change by opening the purge valve. Also,
α <ALPLMT #, and it is determined that α has changed.

FIGS. 16 and 18 to 20 show a second embodiment, and FIGS. 17 and 18 to 20 show a third embodiment.

A normally closed pressure switch 31 shown in FIG. 16 and a normally closed constant differential pressure valve switch 32 shown in FIG. 17 are connected to a purge valve passage (a passage connecting the canister 16 and the collector portion 17a in FIG. 2). Is provided, the timing at which the purge valve 21 starts to open and the timing at which the purge valve 21 is seated can be detected by turning on and off these switches 31 and 32. 33 is a lead wire.

The purge gas flows through the purge valve due to the differential pressure across the purge valve 21. When the purge valve 21 is opened, the pressure in the purge valve passage 18 changes from atmospheric pressure to negative pressure (intake pipe negative pressure). Conversely, when the purge valve 22 is closed, the pressure in the purge valve passage 18 changes from negative pressure to atmospheric pressure.

In this case, when the pressure changes from the atmospheric pressure to the negative pressure, the pressure switch 31 and the constant pressure differential valve switch 32 are turned off (FIG. 16).
In FIG. 17, the negative contact moves the diaphragm 31a downward in the figure against the spring 31b, so that the movable contact 31c separates. In FIG. 17, the valve 32a moves leftward in the figure against the spring 32b due to the differential pressure across the valve 32a. And the movable contact 32c separates), and the switches 31 and 32 are closed by switching from the negative pressure to the atmospheric pressure. That is, when the switches 31 and 32 are turned off, it is the timing when the purge valve starts to open, and when the switches 31 and 32 are turned on, it is the valve seating timing.

In these two examples, the weighted average value of (EVAP-VBOFPV) (or (EVAP-VBOFPV) itself) at each timing when the switches 31 and 32 are turned off or turned on is used as the learning value OFSTPV. (Steps 56, 111, 62, 56, 112, 6 in FIG. 20)
2).

Therefore, at the time of switching between purge ON and OFF, the flag is slowly set to 1 and the purge valve 22 is opened and closed stepwise (steps 23 and 9 in FIG. 18).
1, learning reservation flag = 1 (FIG. 18)
Steps 23 and 91).

Even when switching to purge OFF, the flag is set to 0 slowly and the purge valve 22 is immediately closed under certain conditions (steps 11 to 16, 9 in FIG. 18).
2, 93), the learning value is not updated under these conditions (that is, the learning reservation flag = 0). The reason why the purge valve 22 is closed immediately under a certain condition is to avoid an influence on operability. The stepwise closing of the purge valve 22 is performed during clamping or when the load is large. Only in these cases is the chance of learning. However,
The frequency of learning becomes higher than learning only when switching to purge ON.

FIGS. 21 to 25 show a fourth embodiment.
As shown in FIG. 21, when a vibration sensor 35 made of a piezoelectric element is provided at a position where the needle valve 21a of the purge valve 21 is seated (the outer wall 18a of the purge valve passage 18), the vibration sensor is caused by an impact due to the seating of the needle valve 21a. The output temporarily fluctuates finely as shown in FIG. In addition, 36 is a coating agent.

For this reason, from the output of the vibration sensor, the frequency detecting means 38 and the seating frequency detecting means (for example, a high-pass filter) 39 shown in FIG.
TF is determined, and this frequency is within a predetermined range (for example, a natural frequency FPCUT determined from a seating speed, a passage material, and the like).
# In the range of ± GPCUT # with respect to #, it is determined that the timing is such that the needle valve 22a is seated, and (EVAP-VBOFP) at that timing is determined.
The weighted average value of V) is updated as the learning value OFSTPV (steps 131 and 62 in FIG. 25).

In this example, since the learning is performed at the seating timing of the needle valve 21a, the learning reservation flag is set to 1 only at the time of switching to purge OFF (step 121 in FIG. 24).

As in the above three other embodiments, the switches 31 and 32 and the sensor 35 are provided, and the timing at which the purge valve 21 starts to open and the timing at which the needle valve 21a is seated are detected from these signals, so that The learning accuracy can be improved as compared with the embodiment. Since α (air-fuel ratio feedback correction coefficient) changes with a response delay with respect to the purge gas actually flowing into the cylinder, an error corresponding to this response delay occurs in the learning value in the previous embodiment.
Such learning errors do not occur in the three other embodiments.

However, since there is no need to provide a switch or a sensor in the above embodiment, the above embodiment is more advantageous in terms of cost.

In each of the second and third embodiments, learning is performed not only at the time of switching to purge ON, but also at the time of switching to purge OFF. Goes fast.

Although the embodiment has been described with an example in which a learning value is introduced, a value obtained by detecting a rising duty and directly adding the detected value to a basic duty may be used as a purge valve duty. The purge valve is not limited to a linear solenoid drive type, and may be a rotary valve as long as the opening degree is determined according to the ON duty.

[0080]

The first invention detects the rising duty at which the purge valve starts to open, and calculates the purge valve duty by adding the rising duty to the basic duty according to the operating conditions.
Even if the flow rate characteristics depend on the purge valve temperature, the required amount can be flowed.

The second invention calculates the purge valve duty by adding the learning value stored in the memory under the purge ON condition to the basic duty corresponding to the operating condition, while changing the purge valve duty to ON or OFF. Since the purge valve duty at the timing when the air-fuel ratio feedback correction amount changes is sampled and the learning value stored in the memory is updated based on the sampled purge valve duty, the first invention is provided. In addition to the effect described above, a sensor for detecting the rising duty is not required.

The third invention calculates the purge valve duty by adding the learning value stored in the memory under the purge ON condition to the basic duty according to the operating condition, while calculating the purge valve opening timing or Since the timing of valve seating is detected, the purge valve duty at this timing is sampled, and the learning value stored in the memory is updated based on the sampled purge valve duty. As there is no response delay like the correction amount,
The accuracy of learning can be improved compared to the second invention.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to a claim of the first invention.

FIG. 2 is a system diagram of one embodiment.

FIG. 3 is a characteristic diagram of a VC negative pressure and a VC negative valve lift;

FIG. 4 is a flowchart for explaining calculation of a purge valve target duty EVAPT.

FIG. 5 is a diagram showing a judgment of purge ON / OFF conditions and purge ON / OFF conditions.
It is a flowchart for demonstrating the setting of the flag which instruct | indicates OFF, and learning reservation.

FIG. 6 is a flowchart for explaining calculation of a purge valve duty EVAP during switching to purge ON.

FIG. 7 is a flow chart for explaining initialization of a learning value.

FIG. 8 is a flowchart for explaining determination of a learning interruption condition and updating of a learning value.

FIG. 9 is a flowchart for explaining calculation of an air-fuel ratio feedback correction coefficient α.

FIG. 10 is a characteristic diagram of a basic duty EVAP0 of the purge valve.

FIG. 11 shows a rising duty battery voltage correction rate V
It is a characteristic view of BOFPV.

FIG. 12 is a characteristic diagram showing a switching waveform of a purge valve.

FIG. 13 is a flow rate characteristic diagram of a purge valve driven by a linear solenoid.

FIG. 14 is a waveform chart for explaining an average value ALPAV of α.

FIG. 15 is a waveform chart for explaining the operation of this embodiment.

FIG. 16 is a structural view of a pressure switch according to a second embodiment.

FIG. 17 is a structural diagram of a differential pressure switch according to a third embodiment.

FIG. 18 shows purge ON and OFF in the second and third embodiments.
9 is a flowchart for explaining condition determination, setting of a flag for instructing purge ON / OFF, and learning reservation.

FIG. 19 is a diagram showing purge ON and OFF of the second, third, and fourth embodiments.
9 is a flowchart for explaining calculation of a purge valve duty EVAP during switching to OFF.

FIG. 20 is a flowchart for explaining determination of a learning interruption condition and updating of a learning value in the second and third embodiments.

FIG. 21 is a diagram illustrating a vibration sensor according to a fourth embodiment;

FIG. 22 is an output waveform diagram of the vibration sensor according to the fourth embodiment.

FIG. 23 is a block diagram of a signal processing device of a vibration sensor according to a fourth embodiment.

FIG. 24 is a flowchart for explaining determination of purge ON / OFF conditions, setting of a flag for instructing purge ON / OFF, and learning reservation in the fourth embodiment.

FIG. 25 is a flowchart for explaining determination of a learning interruption condition and updating of a learning value according to the fourth embodiment.

FIG. 26 is a diagram corresponding to claims of the second invention.

FIG. 27 is a diagram corresponding to a claim of the third invention.

[Explanation of symbols]

2 Control unit 3 Exhaust pipe 4 Three-way catalyst 5 O ₂ sensor (air-fuel ratio sensor) 6 Throttle valve 7 Air flow meter 8 Injector 15 Fuel tank 16 Activated carbon canister 18 Purge valve passage 21 Purge valve 21a Needle valve 31 Pressure switch 32 Differential pressure valve switch 35 Vibration sensor 41 Purge condition determination means 42 Purge valve 43 Basic duty calculation means 44 Rise duty detection means 45 Purge valve duty calculation means 51 Learning value memory 52 Purge valve duty calculation means 53 Air-fuel ratio sensor 54 Feedback correction amount calculation means 55 Purge valve Duty sampling means 56 Learning value updating means 61 Timing detecting means 62 Purge valve duty sampling means 63 Learning value updating means

Continuation of front page (56) References JP-A-63-140843 (JP, A) JP-A-6-26386 (JP, A) JP-A-6-93910 (JP, A) JP-A-6-93900 (JP) , A) Patent No.2805995 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/00-41/40 F02M 25/08 301

Claims (3)

(57) [Claims] 1. A purge ON, OF, receiving an operation condition signal
Means for determining the condition of F, and purging O based on the determination result.
A means for calculating a basic duty of a purge valve according to operating conditions in an evaporative fuel processing apparatus for an engine including a purge valve that adjusts a purge gas amount according to a purge valve duty under N conditions; An evaporative fuel processing apparatus for an engine, comprising: means for detecting a duty; and means for calculating the purge valve duty by adding the rising duty to the basic duty. 2. A purge ON, OF receiving operation condition signal.
Means for determining the condition of F, and purging O based on the determination result.
A means for calculating a basic duty of a purge valve according to an operating condition in an evaporative fuel processing apparatus for an engine including a purge valve for adjusting a purge gas amount according to a purge valve duty under N conditions, and a purge ON condition based on the determination result. Means for calculating the purge valve duty by adding the learning value stored in the memory to the basic duty, and calculating the air-fuel ratio feedback correction amount from the output of the air-fuel ratio sensor so that the air-fuel ratio falls within the catalyst window. Means for sampling the purge valve duty at a timing when the air-fuel ratio feedback correction amount changes by switching between the purge ON and OFF.
Means for updating the learning value stored in the memory based on the sampled purge valve duty. 3. A purge ON / OFF operation in response to an operation condition signal.
Means for determining the condition of F, and purging O based on the determination result.
A means for calculating a basic duty of a purge valve according to an operating condition in an evaporative fuel processing apparatus for an engine including a purge valve for adjusting a purge gas amount according to a purge valve duty under N conditions, and a purge ON condition based on the determination result. Means for calculating the purge valve duty by adding the learning value stored in the memory to the basic duty, and means for detecting the timing at which the purge valve starts to open or the timing of valve seating. Means for sampling the purge valve duty, and means for updating a learning value stored in the memory based on the sampled purge valve duty.