JPH109008A - Engine control device - Google Patents

Abstract

(57) [Summary] An object of the present invention is to avoid unnecessary purging as much as possible while preventing fuel vapor from leaking to the atmosphere during idling. An air-fuel ratio feedback control using oxygen sensors (27L, 27R) is performed. The fuel vapor from the fuel tank 31 is adsorbed on the canister 33 and the purge valve is opened, whereby the fuel vapor from the canister is supplied to the surge tank 3 together with air as a purge gas. The fuel concentration in the purge gas is determined based on the feedback correction value. When the fuel concentration is equal to or lower than a predetermined value during idling, the purge execution is prohibited or the purge amount is reduced because the evaporation capacity of the canister 33 is sufficient and the evaporated fuel does not leak to the atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention controls the idling speed so that the engine speed reaches a predetermined target idling speed when the engine is idling, and purges fuel vapor from a fuel tank into an engine intake system. The present invention relates to an engine control device as described above.

[0002]

2. Description of the Related Art In an engine, particularly an engine for a vehicle such as an automobile, the amount of bypass air that bypasses a throttle valve is feedback-controlled so that the engine speed becomes a predetermined target idle speed during idling. More specifically, an ISC valve is provided as opening adjustment means for adjusting the opening of the bypass passage that bypasses the throttle valve, and the ISC valve is controlled by feedback.

On the other hand, purging fuel evaporated from a fuel tank into an intake system of an engine is also performed. This vaporized fuel is usually adsorbed by the canister. When a predetermined purge execution condition is satisfied, a purge valve provided in a purge path between the canister and the engine intake passage is opened to adsorb to the canister. The evaporated fuel is purged to the intake passage together with the air from the air opening of the canister.

[0004] Purging of fuel vapor may be performed at idle, but purging of fuel vapor causes a change in engine speed. In other words, the purge amount has the same effect as substantially increasing the bypass air amount. Therefore, the bypass air amount, that is, the opening degree of the air amount adjusting means is increased by an amount equivalent to the purge amount. The reduction is performed (for example, see Japanese Patent Application Laid-Open No. 6-101519).

[0005]

When a large amount of fuel vapor is adsorbed on the canister and becomes saturated, the fuel vapor leaks from the air opening of the canister into the atmosphere. Recently, it has been strongly desired to reduce or prevent the leakage of evaporated fuel to the atmosphere as much as possible. Therefore, the opportunity to purge the evaporated fuel adsorbed in the canister to the engine intake system has been increased. It has been desired that the suction capacity of the canister be sufficiently ensured. From such a viewpoint, a large amount of evaporative fuel must be purged even during idling.

On the other hand, purging evaporated fuel during idling, especially purging a large amount, is a cause of instability of idling speed, and it is desired to avoid it as much as possible.

The present invention has been made in view of the above circumstances, and it is possible to prevent the idling speed from becoming unstable while increasing the amount of fuel vapor as much as possible during idling. And a control device for the engine.

[0008]

To achieve the above object, the present invention adopts the following method. That is, in an engine control device that controls the engine speed to a predetermined target idle speed during idling, a purge gas from a purge passage connected to a fuel tank is purged to an engine intake system during idling. Purge control means, a state quantity detection means for detecting the state quantity of the purge gas, and when the detected state quantity is equal to or less than a predetermined value, a suppression means for suppressing the purge amount,
It is provided with.

According to the above method, when the state quantity of the purge gas is equal to or less than a predetermined value, that is, when there is sufficient room to keep the evaporated fuel in the purge system, the purge amount is suppressed and a stable idle The rotation speed can be obtained. Conversely, when the state quantity is larger than the predetermined value, the purge amount is not suppressed, so that a margin for keeping the fuel vapor in the purge system is secured. Preferred embodiments of the present invention based on the above method are as described in claims 2 and 3 in the claims.

[0010]

According to the first aspect of the present invention, it is possible to satisfy a high level of reduction in the chance of purging the purge gas to the atmosphere and stabilization of the idle speed.

According to the second aspect, purging is prohibited, and this is extremely preferable in stabilizing the idle speed.

According to the third aspect, it is possible to stabilize the idle speed by reducing the purge amount while securing a margin for keeping the evaporated fuel in the purge system by performing the purge.

According to the fourth aspect, it is preferable in view of a margin for keeping the fuel vapor in the purge system.

According to the fifth aspect, it is possible to accurately know the margin for keeping the evaporated fuel in the purge system by using the fuel concentration.

According to the sixth aspect, the fuel concentration is accurately determined by utilizing the feedback correction value, which is preferable in that the effect corresponding to the fifth aspect can be sufficiently obtained.

According to the seventh aspect, it is possible to know the margin for keeping the fuel vapor in the purge system by a simple method of setting the outside air temperature which greatly affects the generation of the fuel vapor as the state quantity. .

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 denotes an engine,
In the embodiment, the engine is a V-type engine (V-type six-cylinder engine). The intake passage 2 of the engine 1 has a surge tank 3, and a common intake passage 4 connected to the surge tank 3 has an air cleaner 5, an air flow meter 6, A throttle valve 7 is provided. Also,
The common intake passage 4 is provided with a bypass passage 8 that bypasses the throttle valve 7, and the bypass passage 8 is connected to an ISC valve (rotation speed adjusting means) 9 having a continuously variable opening.

Surge tank 3 and left bank 1 of engine 1
L and each of the cylinders has an independent intake passage 1
The fuel injection valves (fuel supply means) 12L are connected to the respective independent intake passages 11L. Similarly, the surge tank 3 and the right bank 1 of the engine 1
R and each of the cylinders is an independent intake passage 1
The fuel injection valves 12R are connected to the respective independent intake passages 11R.

The exhaust passage 21 of the engine 1 is connected to the left bank 1
It has a left branch exhaust passage 22L for 1L, a branch exhaust passage 22R for the right bank 11R, and a collective exhaust passage 23 in which the 22L and 22R are assembled. In the collective exhaust passage 23, an upstream oxygen sensor (O ₂ sensor) 24, an exhaust gas purification catalyst (three-way catalyst) 2
5. A downstream oxygen sensor 26 is provided. Further, an oxygen sensor 27L or 27R is disposed in the branch exhaust passages 22L and 22R at a position downstream of an exhaust collecting portion from each cylinder.

Reference numeral 31 denotes a fuel tank. The fuel tank 31 and the surge tank 3 are connected by a purge path 32. This purge path 32 is connected to the canister 3.
3, connected to an upstream purge passage 34 connecting the canister 33 and the fuel tank 3, a downstream purge passage 35 connecting the canister 33 and the surge tank 3, and a downstream purge passage 35. The purge valve 36 is provided. Reference numeral 33a denotes an air opening of the canister 33.

Each of the oxygen sensors 24, 26, 27L, 2
7R has an output signal inverted (the output voltage largely changes) depending on whether the air-fuel ratio is richer or the return than the stoichiometric air-fuel ratio. And the oxygen sensor 24
And 26 are the deterioration judgment (diagnosis) of the exhaust gas purification catalyst 25
It is provided for. More specifically, at one time during the air-fuel ratio feedback control for setting the air-fuel ratio to the stoichiometric air-fuel ratio, the oxygen sensor
By comparing the number of inversions of the output signal (H1) with the number of inversions (H2) of the output signal of the oxygen sensor 26, it is determined whether or not the catalyst 25 has deteriorated (for example, H1 / H2). If the indicated reversal ratio is equal to or greater than a predetermined reference value, it is normal, and if it is less than the reference value, it is determined to be deteriorated.

The oxygen sensor 27L is connected to the fuel injection valve 1
The oxygen sensor 27R is for performing feedback control of the fuel injection amount from the 2L, and the oxygen sensor 27R is for performing feedback control of the fuel injection amount from the fuel injection valve 12R. Air-fuel ratio feedback control for obtaining the fuel ratio). When the deterioration of the catalyst 25 is determined, the air-fuel ratio feedback control of the fuel injection valves 12L and 12R is performed based on the output of the oxygen sensor 24 (the oxygen sensors 27L and 27R perform the air-fuel ratio feedback control). Not used for).

At the time of idling, the feedback control is performed on the ISC valve 9 so that the engine speed becomes a predetermined target idle speed, and the learning control is also performed. At the time of idling, purge control is performed, and by appropriately opening the purge valve 36, the evaporated fuel adsorbed on the canister 33 is removed together with the air from the atmosphere opening port 33a.
The gas is purged to the surge tank 3 which forms a part of the intake system.

FIG. 2 schematically shows a control system for feedback control, learning control, and purge control of the idle speed. In FIG. 2, U is a control unit configured using a microcomputer.
From the control unit U, the ISC valve 9 and the
A control signal is output to the valve 36. In addition to the output signal from the air flow meter 6, the control unit U
Appropriate sensors or switches (detection means) S1 to S
3. A signal from the SG is input. The sensor S1 detects the engine speed. The switch S2 detects that the accelerator is off (idle switch). The sensor S3 detects a range position of an automatic transmission (not shown). The sensor group SG is
In addition to S1 to S3, this is for detecting various data necessary for control described later.

At the time of idling, the opening of the ISC valve 9 is
There is a difference between when the purge is performed and when the purge is not performed. That is, the required amount of air required by the engine to reach the target idle speed is the sum of the amount of air leaking from the throttle valve 7 and the amount of bypass air passing through the bypass passage 8 when there is no purge. Become. On the other hand, when there is a purge, the sum of the leak air amount, the bypass air amount, and the purge amount is obtained. The amount of leakage from the throttle valve 7 does not differ depending on the presence or absence of the purge. Therefore, when the purge is present, the amount of the bypass air is equivalent to the amount of the purge compared to when there is no purge. (The degree of opening of the ISC valve 9) must be reduced.
The opening of the valve 9 is reduced.

The learning value GLN in the idle speed learning control is determined by the previous GLN, which is the previous value of the learning value, and the feedback correction amount IFB of the idle speed from the latest time to a plurality of times before. More specifically,
A predetermined reflection coefficient smaller than 1 (an example in which the average value of the correction amount IFB from the present time to a predetermined number of times before (a value obtained by dividing the integrated value of the IFB for the predetermined number of times of sampling by the number of times of sampling)) In this case, the value obtained by multiplying by）) is added to the previous GLN to obtain the current learning value G.
LN is calculated. The learning value GLN corresponds to the amount of leakage of the throttle valve.
Learning is not performed (learning value is not updated).

Next, the details of the control at the time of idling will be described with reference to the flowcharts of FIGS.
In the following description, Q indicates a step.

FIG. 3 is for determining the purge flow rate, that is, the opening degree (drive time) of the purge valve 36 corresponding to the purge flow rate. First, in Q21, the target purge rate is determined, which is determined as the mass ratio of the purge gas to the amount of intake air detected by the air flow meter 6 when the purge gas is regarded as the atmosphere (unit%). ). The target purge rate is initialized to 0 at this point, but is appropriately increased or decreased according to a feedback correction amount (a deviation amount from the stoichiometric air-fuel ratio) in the air-fuel ratio feedback control.

The target purge rate is set to be large within a range in which the air-fuel ratio feedback correction amount does not greatly deviate to the rich side so that the purge is performed as much as possible. That is, the target purge rate is gradually reduced when the air-fuel ratio feedback correction amount deviates by 10% or more, and is held when the air-fuel ratio feedback correction amount is in the range of 5 to 10%. If the feedback correction amount is less than 5%, it is gradually increased.

In Q22, the differential pressure across the purge valve 36 is determined (estimated). That is, the intake pressure is determined by correcting the engine operation state (for example, the engine speed and the intake air amount detected by the air flow meter 6) as a parameter according to the intake temperature. The differential pressure between the determined intake pressure and the detected atmospheric pressure is determined as the differential pressure across the purge valve 36.

In Q23, the upper limit value of the purge gas is set. This upper limit value setting corresponds to the maximum volume flow rate determined by the differential pressure before and after the purge valve 36 is fully opened (unit is liter per minute). Then, Q2
In 4, the mass conversion of the upper limit described above is performed (the unit is mass per second).

In Q25, based on the target purge rate in Q21 and the mass flow rate of the intake air amount detected by the air flow meter 6, within the range of the upper limit determined in Q24, the target purge mass (unit: second) Per mass) is determined (the purge gas is considered to be equivalent to the atmosphere).

In Q26, the mass flow rate in Q25 is converted to a volume flow rate to determine a target purge volume flow rate (unit is liter per minute). In Q27, the drive time of the purge valve 36 corresponding to the target volume flow rate of Q26 (open time per unit cycle, that is, a duty ratio is determined in consideration of the differential pressure determined in Q22).

In Q28, the driving time in Q27 is corrected by the battery voltage and the invalid duty (invalid time at the beginning of driving), and the driving time (duty ratio) after this correction and the purge valve 36 are adjusted. be opened.

FIG. 4 shows a control example of whether or not to suppress the purge amount during idling. In FIG.
First, in Q51, the state of the evaporative gas, that is, the purge gas is determined. This state determination is based on the fuel concentration in the purge gas as described later. In Q52, it is determined whether or not the fuel concentration is high. This Q
When the determination at 52 is YES, the purge system 32, that is, the canister 33 has little adsorbing power, and when the purge is not performed, there is a possibility that the evaporated fuel may leak from the atmospheric discharge port 33a. At this time, the flow shifts to Q53, where the purge valve 36 is opened to execute the purge (execution of the purge control shown in FIG. 3).

If NO in Q52, it is considered that the canister 33 has a sufficient adsorbing capacity for the evaporated fuel. In this case, the process proceeds to Q54, and the purging described above is prohibited ( The purge amount is zero).

Here, the purge system 32, that is, the canister 3
The fuel concentration in the purge gas indicating the state quantity of the purge gas indicating the remaining power for keeping the evaporated fuel in 3 is determined as a concentration learning value, for example, as follows. First, if the smoothing value of the air-fuel ratio feedback correction value CFB is 2% or more in the fuel increasing direction as a deviation from the target air-fuel ratio, that is, the CFB smoothing value continues to increase in the fuel increasing direction, and C
When FB exceeds 0% and becomes 2% or more, the gain is gradually reduced by a predetermined gain (gradual decrease), and the smoothed value of the correction value CFBB becomes 2% in the fuel decreasing direction as a deviation amount from the target air-fuel ratio.
If it is above, it is gradually increased by a predetermined gain (gradual increase). Then, in Q51, the density learning value learned and stored as described above is read, and in Q52, it is determined whether the read density learning value is larger than a predetermined value.

Note that the concentration learning value is 0 at the factory shipment stage.
And set the ignition switch to OFF
It is also stored and stored when it is done. The calculation (update) of the concentration learning value is performed when the purge gas flow rate is a predetermined small amount (for example, 3 liters per minute or less), when the cooling water temperature is lower than a predetermined temperature (for example, 80 ° C.), At the time (other than the steady state) and immediately after the start of the engine, the operation is not performed (the previous value is held as it is).

The state quantity of the purge gas can be set as the outside air temperature. That is, the higher the outside air temperature, the larger the amount of fuel vapor generated. Therefore, when the outside air temperature is equal to or lower than a predetermined temperature, for example, 0 ° C. or lower, the purge execution can be prohibited or the purge amount can be reduced. Also, the outside air temperature is indirectly detected as the engine cooling water temperature at the time of starting the engine, and when the cooling water temperature is equal to or lower than a predetermined temperature, for example, 0 ° C. or lower, the purge execution can be prohibited or the purge amount can be reduced. . Furthermore, outside air temperature (cooling water temperature)
When the outside air temperature is equal to or lower than the predetermined temperature and the fuel concentration is equal to or lower than the predetermined value, the purge execution may be prohibited or the purge amount may be reduced in consideration of both the fuel concentration and the fuel concentration.

When the state quantity of the purge gas is equal to or less than a predetermined value,
Instead of prohibiting the execution of the purge, the purge amount may be reduced.

Although the embodiment has been described above, the present invention is not limited to this. For example, the target of the purge amount may be set using a map value created and stored in advance.

The density learning value is used for setting the target purge amount as described above and for setting the limit of the target purge rate described later.
In the air-fuel ratio feedback control, the fuel injection valve 12
When the fuel injection amount from L and 12R is reduced by the amount of fuel contained in the purge gas, it can be used for calculating the amount of fuel contained.

The concentration learning value is calculated based on the air-fuel ratio field of the left and right banks.
When the feedback control is performed independently, only the air-fuel ratio feedback correction value for the left bank is used, or only the air-fuel ratio feedback correction value for the right bank is used. The determination can be made using only the common feedback correction value. When the air-fuel ratio feedback control is performed for the left and right banks using the oxygen sensor 24, the concentration learning value may be determined using the common feedback correction value.

The present invention can be grasped as a control method, and each step shown in the flowchart, various intakes such as sensors and valves, and the like are included in the functional contents (upper concept of the function). It can also be expressed by adding the name of the means.
Furthermore, the object of the present invention is not limited to what is explicitly specified, but implicitly includes providing what is equivalent to what is described as substantially advantageous or preferable.

[Brief description of the drawings]

FIG. 1 is an overall system diagram showing one embodiment of the present invention.

FIG. 2 is a simplified diagram showing an example of a control system.

FIG. 3 is a flowchart showing a control example of the present invention.

FIG. 4 is a flowchart showing a control example of the present invention.

[Explanation of symbols]

 1: Engine 2: Intake passage 8: Bypass passage 9: ISC valve (for adjusting idle speed) 31: Fuel tank 32: Purge system 33: Canister 36: Purging valve U: Control unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location F02M 25/08 301 F02M 25/08 301M 301U 301J

Claims (7)

[Claims] 1. An engine control device for controlling an engine speed to a predetermined target idle speed during idling, wherein a purge gas from a purge system connected to a fuel tank is supplied to the engine during idling. Purge control means for purging the system, state quantity detection means for detecting the state quantity of the purge gas, and suppression means for suppressing the purge amount when the detected state quantity is equal to or less than a predetermined value. An engine control device characterized by the above-mentioned. 2. The engine control device according to claim 1, wherein said suppressing means is set to prohibit purging of an engine intake system. 3. The system according to claim 1, wherein the suppression means permits the purge gas to be purged into the engine intake system, and when the detected state quantity is equal to or less than a predetermined value, a ratio when the detected state quantity is larger than the predetermined value. An engine control device that is set to reduce the purge amount. 4. The canister according to claim 1, wherein a canister is provided in the purge system, and the state quantity is a value related to an amount of evaporated fuel trapped in the canister. A control device for an engine. 5. The engine control device according to claim 4, wherein the state quantity is a fuel concentration. 6. An air-fuel ratio feedback control means for performing feedback control of a fuel amount supplied to an engine so that an actual air-fuel ratio becomes a target air-fuel ratio. The control of the engine, wherein the purge gas is set to be purged to the engine intake system during the control, and the fuel concentration in the purge gas is determined based on a feedback correction value of the air-fuel ratio. apparatus. 7. The engine control device according to claim 4, wherein the state quantity is an outside air temperature.