JP2697402B2 - Evaporative fuel treatment system for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel processing apparatus for an internal combustion engine, and more particularly to a communication path for directly communicating a fuel tank with an intake pipe of an internal combustion engine (engine) to convey evaporative fuel to a combustion chamber. The present invention relates to an evaporative fuel processing apparatus for burning fuel.

[0002]

2. Description of the Related Art A purge passage is provided for directly communicating from a fuel tank of a vehicle to an intake pipe of an engine. Evaporated fuel (vapor) generated in the fuel tank is directly sent to an intake pipe, and the vapor is burned in a combustion chamber. 2. Description of the Related Art An evaporative fuel treatment device for an internal combustion engine is generally known. This type of evaporative fuel processing apparatus has a means for detecting the amount of generated vapor and a subtraction means for reducing the original amount of fuel injection by the fuel injection valve based on the detected amount of generated vapor. When a large amount flows into the intake pipe and the air-fuel ratio becomes rich, the fuel injection amount is reduced by the subtraction means,
The combustion chamber is configured to obtain a good air-fuel ratio.

[0003] However, in general, the vapor generated from the fuel tank is composed of a mixture of pure gasoline vapor generated from gasoline and the air sucked into the tank, and the mixing ratio is uncertain. . In particular, the air in the vapor acts to make the air-fuel ratio leaner as opposed to the gasoline vapor. For this reason, in the above-described evaporative fuel processing apparatus that simply subtracts and corrects the fuel injection amount from the value of the detected amount of generated vapor, the correct fuel injection amount is corrected in consideration of the distribution of gasoline vapor and air in the vapor. Can not do,
In practice, a good air-fuel ratio cannot be obtained.

[0004] The applicant of the present invention has previously proposed in Japanese Patent Application No. 3-221816 an evaporative fuel treatment apparatus for an internal combustion engine which has solved the above-mentioned problems. This evaporative fuel processing device has a purge passage directly communicating from the fuel tank to the intake pipe of the engine, a means for detecting a vapor generation amount of vapor generated from the fuel tank, and detecting a pure gasoline vapor amount in the generated vapor. Means for detecting the amount of gasoline in the vapor, and means for calculating the amount of air in the vapor, determine the distribution of the amount of gasoline vapor in the vapor and the amount of air, and correct the fuel injection amount in consideration of the distribution. Configuration.

According to this evaporative fuel treatment apparatus, the amount of generated vapor passing through the purge passage and the distribution between the amount of gasoline vapor and the amount of air in the vapor are clarified. The fuel injection amount can be corrected, and the air-fuel ratio control of the engine can be improved.

[0006]

In the above-described evaporative fuel processing apparatus (hereinafter simply referred to as the prior application) proposed by the present applicant, the entire amount of vapor generated from the fuel tank is immediately transferred to the intake pipe. Designed to be inhaled. However, in the device of the prior application, when the engine is under a high load, the pressure in the intake pipe increases, the pressure difference between the intake pipe and the fuel tank decreases, and the amount of vapor sucked into the intake pipe from the fuel tank decreases. A state occurs in which it decreases. For this reason, the vapor that is not sucked into the intake pipe remains in the fuel tank, thereby increasing the internal pressure of the fuel tank. Then, due to the increase in the internal pressure of the fuel tank, the amount of vapor actually sucked from the fuel tank into the intake pipe becomes larger than the amount of vapor estimated by the above-mentioned vapor generation amount detecting means (the vapor generation amount detecting means The amount of vapor generation is estimated from the fuel temperature in the tank), and as a result, the correction of the fuel injection amount becomes inaccurate. As described above, in the device of the prior application, since the vapor remaining in the fuel tank is not taken into account, optimal control of the air-fuel ratio cannot be realized.

Accordingly, the present invention has been made in view of the above problems, and takes into account the amount of residual vapor in a fuel tank that does not flow into an intake pipe, thereby correcting the fuel injection amount more accurately than in the prior application. It is another object of the present invention to provide an evaporative fuel processing apparatus for an internal combustion engine capable of performing optimal air-fuel ratio control.

[0008]

FIG. 1 is a block diagram showing the principle of the present invention for achieving the above object. As shown in the figure, the present invention has a communication passage 14 for directly communicating a fuel tank 11 and an intake pipe 13 of an internal combustion engine 12 and detects a fuel evaporation amount of the evaporated fuel evaporated from the fuel tank 11. Evaporative fuel for an internal combustion engine having an amount detecting means 15 and a fuel correction amount calculating means 17 for correcting the fuel injection amount from a fuel injection valve 16 based on the fuel evaporation amount detected by the fuel evaporation amount detecting means 15 In the processing apparatus, the fuel tank 1
1 is not sucked into the intake pipe 13 and the fuel tank 11
A remaining fuel vapor amount calculating means for calculating the remaining fuel vapor amount remaining in the fuel tank; and a fuel amount detected by the fuel evaporation amount detecting means based on the remaining fuel vapor amount calculated by the remaining fuel vapor amount calculating means. Purge amount correction means 19 for correcting the evaporation amount to obtain a purge amount purged to the intake pipe 13;
Is configured to correct the fuel injection amount from the fuel injection valve 16 based on the purge amount corrected by the purge amount correction means 19.

[0009]

According to the present invention, the remaining evaporated fuel amount calculating means 18 is provided.
Calculates the amount of residual evaporated fuel remaining in the fuel tank 11 without being sucked from the fuel tank 11 into the intake pipe 13. The purge amount correcting unit 19 corrects the fuel evaporation amount detected by the fuel evaporation amount detecting unit 15 based on the remaining evaporated fuel amount in the fuel tank 11 calculated by the remaining evaporated fuel amount calculating unit 18, and , The purge amount actually purged into the intake pipe 13 is calculated. For this reason, the fuel correction amount calculating means 17 is provided with the purge amount correcting means 1 as described above.
The fuel injection amount from the fuel injection valve 16 is corrected with high accuracy based on the accurate purge amount obtained in step 9.

[0010]

FIG. 2 shows a system configuration diagram of an embodiment of the present invention. This embodiment is an example in which the present invention is applied to a four-cylinder four-cycle spark ignition type internal combustion engine (engine) 40 as the internal combustion engine 12 shown in FIG. 1, and is controlled by a microcomputer 21 and an engine control computer (ECU) 22, which will be described later.

In FIG. 2, reference numeral 23 denotes a fuel tank (corresponding to the fuel tank 11). A fuel temperature sensor 24 for measuring a fuel temperature is provided in the fuel tank 23, and a remaining fuel amount in the fuel tank 23. Is installed. Fuel temperature sensor 24,
The signals from the fuel remaining amount sensor 25 are output to the microcomputer 21.

Reference numeral 41 denotes an intake pipe of the engine 40 (corresponding to the intake pipe 13), and an air cleaner (not shown) is provided at an opposite end of the combustion chamber 40a. In the intake pipe 41, from the upstream side where the air cleaner is provided,
An air flow meter 42, a throttle valve 43, a surge tank 44, and a fuel injection valve 45 are provided. The air flow meter 42 detects the amount of air taken into the intake pipe 41,
This detection signal is output to the microcomputer 21. A fuel circulation line 47 is provided between the fuel injection valve 45 and the fuel tank 23, and the fuel in the fuel tank 23 is constantly circulated by the fuel circulation pump 46. The fuel injection valve 45 injects a fixed amount of fuel into the intake pipe 41 only during a time instructed by an injection command from the ECU 22. Therefore, the time during which fuel injection is performed in the fuel injection valve 45 directly corresponds to the fuel injection amount.

[0013] Evaporated fuel (vapor) from the fuel tank 23
The line 26 includes a canister line 26 b that passes through the tank pressure control valve 27 to the canister 30, and a vacuum switching valve (VSV) from the fuel tank 23.
And a direct line 26a (corresponding to the communication path 14) which leads to an engine 40 (corresponding to the internal combustion engine 12) via an electromagnetic valve 31 referred to as the internal combustion engine 12.

The canister 30 is filled with an adsorbent such as activated carbon, and an air inlet 30a is provided below the adsorbent. A purge line 33 is provided from the canister 30 to communicate with the engine 40 via another solenoid valve 32. The tank internal pressure control valve 27 prevents the vapor from flowing from the fuel tank 23 toward the canister 30 during engine operation by setting the opening pressure higher than the atmospheric pressure. The solenoid valve 31 has its valve opening adjusted by a control signal from the microcomputer 21 as will be described later.
Adjust the vapor flow rate to 1. Also, the solenoid valve 31
When the negative pressure of the intake pipe is applied to the inside of the fuel tank, new vapor is prevented from being generated from the fuel tank.

The direct line 26a through which the vapor from the fuel tank 23 is transported and the purge line 33
Is connected to the surge tank 44 in the present embodiment, but the connection portion may be any portion on the intake pipe 41.

As is well known, the vapor generated from inside the fuel tank 23 while the engine is stopped is discharged to the canister line 26b.
And is adsorbed by the activated carbon in the canister 30 to prevent release to the atmosphere. Then, at the time of idling operation immediately after the start of the engine, air is introduced from the atmosphere introduction port 30a of the canister 30 using the negative pressure in the surge tank 44 (the electromagnetic valve 32 is in an open state). The fuel adsorbed on the activated carbon is released. And
This fuel is drawn into the intake pipe 41 through the purge line 33 and is burned in the combustion chamber 40a.

During the continuous operation of the engine 40, the temperature of the fuel rises by circulating through the fuel circulation line 47 through the fuel injection valve 45 where the temperature of the fuel becomes high. The vapor generated as the fuel temperature rises is reduced by the surge valve 4 when the solenoid valve 31 is opened appropriately.
Utilizing the negative pressure in 4, the air is sucked into the intake pipe 41 through the direct line 26a and burned as described above. However, for example, when the engine operates at a high load and the intake pipe 41
When the pressure inside the fuel tank 23 rises,
The pressure difference between the inside and the inside decreases, and the flow rate of the vapor in the direct line 26a decreases. For this reason, it becomes impossible for the entire amount of generated vapor to be immediately sucked into the intake pipe 41, and residual vapor that temporarily stays in the fuel tank 23 is generated.

The microcomputer 21 for controlling the operation of each section having the above-described configuration has a hardware configuration as shown in FIG. 2, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted.

In FIG. 3, a microcomputer 21
Denotes a central processing unit (CPU) 50, a read-only memory (ROM) 51 storing a processing program, and a random access memory (RA) used as a work area.
M) 52, a backup RAM 53 that retains data even after the engine is stopped, an input interface circuit 54, an A / D converter 56 with a multiplexer, an output interface circuit 55, etc., which are interconnected via a bus 57. Have been.

The A / D converter 56 is a fuel temperature sensor 2
4, a fuel temperature detection signal from the fuel remaining amount sensor 25, an intake air amount detection signal from the air flow meter 42, an engine speed signal, and the like are sequentially switched through the input interface circuit 54 and periodically. Take it in, convert it to analog / digital and convert it to bus 5
7 sequentially. The output interface circuit 55
The signal processed by the CPU 50 is input via the bus 57 and sent to the electromagnetic valve 31 and the ECU 22 to control them. The ECU 22 controls the fuel injection time of the fuel injection valve 45 and the solenoid valve 32 based on the input signal. In the idle state after the engine is started, the solenoid valve 32 controls the valve opening degree substantially proportional to the intake air amount of the engine 40. The control of the fuel injection time of the fuel injection valve 45 will be described later in detail.

FIG. 4 shows the microcomputer 2 having the above configuration.
FIG. 2 is a block diagram showing the configuration of the processing content in FIG.

The contents of the processing by the microcomputer 21 include a solenoid valve flow calculating device 60 (corresponding to the fuel evaporation amount detecting means 15, the remaining evaporated fuel amount calculating means 18 and the purge amount correcting means 19), and an electromagnetic valve driving circuit. And a fuel correction amount calculating device 80 (corresponding to the fuel correction amount calculating means 17).

As will be described later in detail with reference to a flowchart, the solenoid valve flow calculation device 60 estimates the amount of vapor generated from the fuel tank 23 and obtains the remaining vapor amount remaining in the fuel tank 23. Then, the differential pressure across the solenoid valve 31 is determined from the increase in the internal pressure of the fuel tank 23 due to the generation of the residual vapor and the negative pressure of the intake pipe 41 corresponding to the load of the engine. The opening of the solenoid valve 31 is determined by the ratio between the maximum flow rate and the actual vapor flow rate. The valve opening determined by the solenoid valve flow calculation device 60 as described above is transmitted to the solenoid valve drive circuit 70, and the solenoid valve 3 is controlled so that the vapor flows to the target flow rate without excess or shortage.
1 opens.

On the other hand, as will be described in detail later, the fuel correction amount calculating device 80 calculates the excess gasoline sucked into the intake pipe 41 from the actual vapor flow rate at the solenoid valve 31 obtained by the solenoid valve flow calculating device 60. Calculate the steam amount and air amount,
Correction of the original fuel injection time by the fuel injection valve 45 obtained by the ECU 22 is performed.

The CPU 50 in the microcomputer 21 having the above-described structure, in accordance with the program stored in the ROM 51, detects the fuel evaporation amount detecting means 15, the remaining evaporated fuel amount calculating means 18, the purge amount correcting means 19, and the fuel correcting amount calculating means. 17 is realized.

First, the processing for calculating the initial target flow rate of the solenoid valve 31 for realizing the fuel evaporation amount detecting means 15 will be described with reference to the flowchart shown in FIG. The target flow rate of the solenoid valve 31 is an amount of vapor (a mixture of gasoline vapor and air) estimated as the temperature in the fuel tank 23 rises. When the target flow rate is as described above,
When the amount of vapor that can be sucked into the intake pipe 41 due to the negative pressure of the intake pipe 41 is larger than the amount of vapor generated from the fuel tank, the entire amount of vapor generated can be sucked into the engine 40. Further, by opening the valve too much, it is possible to prevent the negative pressure of the intake pipe 41 from being applied to the fuel tank 23 to generate new vapor in the fuel tank 23 as described above. The target flow rate obtained here is corrected by a target flow rate correction routine 200 described later.

FIG. 5 shows a flow chart of a solenoid valve flow rate calculation routine for realizing the fuel evaporation amount detecting means 15.

When the routine 100 shown in FIG. 3 is started by interruption every period Δtc seconds, first, the current fuel temperature Tn is read from the RAM 52 in which the signal from the fuel temperature sensor 24 is processed and held ( Step 10
1). Next, a vapor generation amount TQn at the fuel temperature Tn read in step 101 is calculated by interpolation from a vapor generation amount map 300 shown in FIG. 9 stored in the ROM 51 in advance (step 102). This map 3
Reference numeral 00 denotes an experimentally determined relationship between the fuel temperature T and the integrated vapor generation amount TQ from -20 ° C. fuel temperature per liter of the space volume Va of the fuel tank 23 described later to T ° C. is there. Therefore, the unit of the vapor generation amount TQn is (liter / liter).

Next, the fuel temperature T at the time of execution of the previous routine
A vapor generation amount QL generated when the fuel temperature rises from ₀ to the current fuel temperature Tn is determined. This vapor generation amount Q
L is the difference between the previous vapor generation amount TQ ₀ stored in the previous routine and the current vapor generation amount TQn, that is,
It can be calculated by QL = TQn-TQ ₀ (step 103).

Next, by subtracting the fuel remaining amount Vs obtained from the fuel remaining amount sensor 25 from the tank capacity Vt,
The current tank space volume Va is calculated (see FIG. 2, step 104). Vapor generation amount obtained in step 103 QL is a vapor generation amount per tank space volume Va1 liters when the fuel temperature increases from T ₀ to Tn.
Therefore, the target flow rate Q per unit time (1 sec) at the time of execution of the current routine is obtained from QL × Va / Δtc.
t (liter / sec) can be obtained (step 1)
05).

Next, for the time of next execution of the routine, replaces the vapor generation amount TQn at current fuel temperature Tn in TQ ₀ (step 106). Then, the new TQ ₀ and the target flow rate Qt obtained in step 105 are newly added to RA.
This routine is stored in M52 (step 107).
00 is ended (step 108).

The map 30 referred to in step 102
0, as described above, the fuel temperature T and the tank space volume V
a Fuel temperature per liter -20 ° C to fuel temperature T ° C
Although the relationship with the accumulated vapor generation amount TQ up to this is stored, it may be calculated by the following equation (1) instead.

[0033]

(Equation 1)

R: Gas constant Pa: Pressure of fuel tank (≒ atmospheric pressure) Pg (T): Gasoline vapor pressure at fuel temperature T (° K) Gasoline vapor pressure Pg (T) is given by the following equation (2) ).

[0035]

(Equation 2)

Here, Tb: boiling point (55 ° C.) Tc: fuel temperature (° C.) Next, the target flow rate Qt of the solenoid valve 31 for realizing the remaining evaporated fuel amount calculating means 18 and the vapor amount correcting means 19 is calculated by using the remaining vapor. FIG. 6 shows processing contents to be corrected by the influence of
This will be described based on the flowchart shown in FIG. FIG. 6 shows the target flow rate Q of the solenoid valve 31 obtained in the routine 100 shown in FIG.
4 shows a routine for correcting t.

This routine 200 corresponds to the routine 10 described above.
0 in the solenoid valve flow rate calculation device 60 shown in FIG.
Executed every d seconds. First, the remaining vapor amount ΔQ (i−i) in the fuel tank 23 at the end of the previous routine.
1) The presence or absence of (unit: liter) is determined (step 210).

When vapor remains in the fuel tank 23, that is, when ΔQ (i-1)> 0, the tank space volume V
The remaining vapor amount ΔQ (i−1) is added to “a”, and the total volume is divided by the tank space volume Va to obtain a coefficient (Va + ΔQ (i−1)) / Va of the tank internal pressure rise. That is, the coefficient (Va + ΔQ (i−1)) / Va is V
a + ΔQ (i−1) is converted to tank space volume Va
Shows the amount of pressure rise when compressed, and is obtained from the principle of PV = constant. Then, this coefficient is set to the atmospheric pressure Pat, which is the pressure in the tank when no vapor remains.
By multiplying m, the pressure Ptank in the fuel tank 23 when the residual vapor amount of ΔQ (i-1) remains in the tank is obtained (step 211). At this time, it is assumed that the tank internal pressure control valve 27 of the canister line 26b shown in FIG. 2 is kept closed.

When no vapor remains, that is, ΔQ (i
If -1) = 0, the pressure Ptank in the fuel tank 23 becomes the atmospheric pressure Patm as it is (step 212).

Next, similarly to the map 300, the ROM 51
From the map 310 shown in FIG.
A negative pressure Pm in the intake pipe 41 with respect to the engine load is obtained by interpolation (step 213). Map 310 is
The relationship between a value Q / N obtained by dividing the intake air amount Q in the intake pipe 41 by the number of revolutions N of the engine 40 and the negative pressure Pm in the intake pipe 41 at that time is obtained by an experiment. A signal from the air flow meter 42 is processed to obtain the intake air amount Q
The one stored in advance in M52 is read. The Q / N is generally used as a value indicating the load state of the engine. As can be seen from the map 310, the negative pressure (pressure) Pm in the intake pipe 41 also increases as the engine load increases.

Next, by subtracting the negative pressure Pm in the intake pipe 41 from the atmospheric pressure Patm, the solenoid valve when the pressure in the fuel tank 23 is the atmospheric pressure, that is, when the residual vapor is not considered. The differential pressure ΔPm before and after 31 is obtained (step 214).

Ptank−Patm obtained by subtracting the atmospheric pressure Patm from the pressure Ptank in the fuel tank 23 when the residual vapor obtained in step 211 remains in the tank is:
The pressure rise of the fuel tank 23 due to the residual vapor is shown. Therefore, by adding this pressure rise Ptank-Patm to the differential pressure ΔPm obtained in step 214,
The differential pressure ΔP before and after the solenoid valve 31 when the residual vapor amount of ΔQ (i−1) remains in the tank to increase the pressure in the tank is obtained (step 215). Fuel tank 2
The differential pressure ΔP also increases in comparison with ΔPm by an increase in the pressure in 3.

Next, the maximum flow rate Qmax in the fully opened state of the solenoid valve 31 at the time of the differential pressure ΔP is obtained by interpolation from the map 320 shown in FIG. 11 stored in the ROM 51 in advance (step 216). The map 320 shows the relationship between the differential pressure ΔP before and after the electromagnetic valve 31 obtained in step 215 and the maximum flow rate Qmax in the fully opened state of the electromagnetic valve 31 when the differential pressure ΔP exists,
It is obtained based on the relationship of the maximum flow rate Qmax∝ (Ptank−Pm) ^1/2 .

Next, the RA calculated in the above routine 100 is used.
A target flow rate Qt of the solenoid valve 31 stored in M52;
A comparison is made between the maximum flow rate Qmax of the solenoid valve 31 obtained in step 216 (step 220).

When the target flow rate Qt is larger than the maximum flow rate Qmax, the vapor represented by Qt-Qmax remains in the fuel tank 23 as a residual vapor in the current routine without being sucked into the intake pipe 41. For this reason, Qt-Qmax is added to the previous residual vapor amount ΔQ (i−1) to obtain the residual vapor amount ΔQ (i−1) in the next routine (step 221). In this case, the new target flow rate Qtt in which the maximum flow rate Qmax in the solenoid valve 31 is corrected.
(Step 222).

On the other hand, when the target flow rate Qt is smaller than the maximum flow rate Qmax, all the vapor generated in the fuel tank 23 is sucked into the intake pipe 41 through the solenoid valve 31.
Here, first, the presence or absence of the residual vapor amount ΔQ (i−1) in the fuel tank 23 at the end of the previous routine is determined again in the same manner as in step 210 (step 230).
The reason is that if residual vapor is left in the tank, a process shown in the next step 231 is required to remove the residual vapor from the tank.

When the residual vapor remains in the tank, the residual vapor amount ΔQ (i−i) is added to the target flow rate Qt which is the current generated vapor amount obtained in the routine 100.
1/8 of 1) is added and this is set as a corrected new target flow rate Qtt (step 231). Therefore, the residual vapor amount ΔQ (i−1) is calculated from the previous residual vapor amount ΔQ (i−1).
The value obtained by subtracting 1/8 of 1) is the residual vapor amount ΔQ (i−1) in the next routine (step 23).
3).

As described above, the residual vapor amount ΔQ to be added to the generated vapor (target flow rate Qt) in one routine.
By limiting (i-1) to 1/8 of the remaining vapor amount ΔQ (i-1) to obtain a new target flow rate Qtt, it is possible to prevent a sudden increase in the amount of vapor flowing into the intake pipe 41 from the fuel tank 23. This can prevent the air-fuel ratio from deteriorating. In this part of the flow, the target flow rate Qt, that is, the amount of generated vapor is the maximum flow rate Q of the solenoid valve 31.
Even if the residual vapor amount ΔQ (i−1) added to the generated vapor amount is limited to 1/8 as described above, the residual vapor gradually disappears from the fuel tank 23 by repeating the routine. .

If there is no remaining vapor in the tank in step 230, the routine 100
The target flow rate Qt, which is the current amount of generated vapor obtained in the above, becomes the new target flow rate Qtt as it is (step 23).
2).

Next, the above steps 222, 231, 23
The electromagnetic valve opening is calculated so that the corrected new target flow rate Qtt obtained in step 2 flows through the electromagnetic valve 31 without any excess or shortage (step 240). Here, the new target flow rate Q
The valve opening α of the solenoid valve 31 is determined from the ratio of tt to the maximum flow rate Qmax of the solenoid valve 31 obtained from the pressure difference between the solenoid valve 31 in step 216 (step 24).
1), this routine 200 ends (step 24)
2).

In the device of the prior application, the pressure in the fuel tank is regarded as the atmospheric pressure without considering the residual vapor in the fuel tank, and the pressure in the intake pipe is represented by the amount of intake air in the intake pipe. The maximum flow rate of the solenoid valve was determined.
Further, the target flow rate in the solenoid valve and the valve opening degree of the solenoid valve obtained from the target flow rate and the maximum flow rate are not taken into account of the residual vapor.

However, in the target flow rate correction routine 200 as described above, in step 211, the pressure Ptank of the fuel tank 23 when the residual vapor is present is determined.
In step 213, the pressure Pm in the intake pipe 41 is obtained, and in steps 214 to 216, the pressure difference between the pressures Ptank, Pm,
That is, the maximum flow rate Qmax of the solenoid valve 31 in consideration of the residual vapor is determined from the pressure difference before and after the solenoid valve 31. Then, in step 220, the maximum flow rate Qmax is compared with the vapor generation amount Qt,
33, the remaining vapor amount ΔQ in the next routine
(I-1) is calculated. Thus, routine 20
At step 0, the entire part of the series before step 210 to step 240 implements the remaining evaporated fuel amount calculating means 18.

In steps 222, 231, and 232, the residual vapor amount ΔQ (i−
1) and the maximum flow rate Qmax of the solenoid valve 31, the initial target flow rate Qt is determined by taking the residual vapor into consideration into the intake pipe 4.
In step 1, the target flow rate Qtt is actually corrected (purged). As described above, the steps 222, 231, and 23 are operated based on the result of the remaining evaporated fuel amount calculating means 18.
The part 2 realizes the purge amount correcting means 19. Therefore, in step 241, the target flow rate Qtt and the maximum flow rate Q
The valve opening degree α of the solenoid valve determined from max also takes into account residual vapor.

Then, the valve opening α obtained in step 241 is output to the solenoid valve driving circuit 70 shown in FIG. 4, and the solenoid valve driving circuit 70 opens the solenoid valve 31 to a desired valve opening α. . The valve opening α is actually controlled by the pulse width of the pulse signal. That is, the valve opening degree is changed by increasing or decreasing the opening time (corresponding to the pulse width) of the electromagnetic valve 31 that repeats opening and closing by a pulse signal.
By doing so, the accuracy of the flow rate corresponding to the valve opening of the solenoid valve 31 is improved.

Next, the fuel correction amount estimating logic in the fuel correction amount calculating device 80 for realizing the fuel correction amount calculating means 17 will be described with reference to the flowchart shown in FIG.

The concept of the fuel correction is to estimate the amount of pure gasoline vapor and the amount of air contained in the vapor from the fuel tank 23, respectively, and to determine the ratio thereof, that is, the mixture ratio on the richer side than the stoichiometric air-fuel ratio. In some cases, reduce the fuel injection amount,
Conversely, when the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, the fuel injection amount is increased.

FIG. 7 is a flowchart of a fuel correction amount calculation routine executed in the fuel correction amount calculation device 80. The routine 120 has the same cycle Δ as the routine 100.
Processing is performed in tc seconds. First, the current fuel temperature Tn
Is read from the RAM 52 as in the routine 100 (step 121). Next, the gasoline vapor generation amount Qtn at the fuel temperature Tn read in step 121 is calculated by interpolation from the gasoline vapor generation amount map 330 shown in FIG. 12 stored in the ROM 51 in advance (step 122). The map 330 is obtained by an experiment in which the relationship between the fuel temperature T and the integrated gasoline vapor generation amount Qt from the fuel temperature of −20 ° C. per liter of the tank space volume Va to the fuel temperature T ° C. is obtained.

Next, the fuel temperature T at the time of execution of the previous routine
The gasoline vapor generation amount Qgv per liter of tank space Va generated when the fuel temperature rises from ₀ to the current fuel temperature Tn is determined. This gasoline steam generation Q
gv is the difference between the previous gasoline vapor generation amount Qt ₀ stored at the time of execution of the previous routine and the current gasoline vapor generation amount Qtn, that is, Qgv = Q, similarly to the routine 100.
It can be calculated by tn-Qt ₀ (step 123).

Next, the gasoline vapor generation amount Qg per liter of tank space volume Va obtained in step 123
From v, the amount of gasoline vapor generated per unit time from the fuel tank 23 is determined. Here, in the present invention, since the vapor remaining in the fuel tank 23 is taken into account, the tank space volume to be multiplied by the gasoline vapor generation amount Qgv is calculated by adding the tank space volume Va to the previous routine in step 210 of the routine 200. This is the sum of the residual vapor amount ΔQ (i−1) at the end. Therefore, Qg
Based on v × (Va + ΔQ (i−1)) / Δtc, a gasoline vapor generation amount Qg (liter / sec) per unit time (1 sec) at the time of execution of the current routine in which the fuel temperature has increased from T ₀ to Tn is obtained. (Step 124). As described above, in the steps so far, the gasoline vapor generation amount Qg in the vapor generated by the same method as the routine 100 can be obtained.

Next, by subtracting the gasoline vapor generation amount Qg from the corrected new target flow amount Qtt of the solenoid valve 31 obtained in the routine 200, the air generation amount Qa per unit time in the vapor (liter / liter) is obtained. sec) (step 125).

Next, the fuel injection amount conversion values Tg and Ta are obtained by multiplying the gasoline vapor generation amount Qg and the air generation amount Qa by the coefficients Kg and Kp, respectively (step 12).
6). The coefficient Kg is a conversion constant for converting the amount of gasoline vapor expressed in liters into a substantial fuel injection amount (fuel injection time) corresponding to this gasoline amount,
The coefficient Kp is a conversion constant for converting the generated air amount into a fuel injection amount (fuel injection time) that is a stoichiometric air-fuel ratio.

Next, the same value Tg is calculated from the fuel injection amount conversion value Ta.
Is subtracted to calculate an injection amount (injection time) correction value ΔTp (step 127). Here, when the relationship of Ta> Tg, that is, ΔTp is positive, the target flow rate Qtt actually purged to the intake pipe 41 obtained in the routine 200 is determined by:
This indicates that the mixture ratio of gasoline vapor and air is leaner than the stoichiometric air-fuel ratio. Conversely, if Ta <Tg, that is, ΔTp is negative, gasoline vapor and air in the target flow rate Qtt This indicates that the mixture ratio with is richer than the stoichiometric air-fuel ratio. When Ta = Tg, the vapor has just reached the stoichiometric air-fuel ratio, and ΔTp = 0
Becomes

As described above, the above steps 126 and 127 are performed.
Thus, the injection amount (injection time) correction value ΔTp can be obtained, and the fuel correction amount calculating means 17 is realized.

Next, for the next execution of the routine, the gasoline vapor generation amount Qtn at the current fuel temperature Tn is changed to Qt.
_Replace with ₀ (step 128). And the new Q
t ₀ and the injection amount correction value ΔTp obtained in step 127 are newly stored in the RAM 52 (step 129), and the routine 120 is terminated (step 130).

As described above, the fuel correction amount calculation routine 12
According to 0, the gasoline vapor generation amount Qg corrected in consideration of the residual vapor amount ΔQ (i−1) in the fuel tank 23 in step 124 is obtained, and the air generation similarly corrected in step 125. The quantity Qa can be determined. Therefore, the injection amount correction value ΔTp for correcting the mixture ratio of gasoline vapor and air in the vapor to the stoichiometric air-fuel ratio becomes accurate in consideration of the residual vapor in the tank.

The map 330 in step 122 includes:
As described above, the fuel temperature T and the tank space volume Va1
The relationship between the accumulated gasoline vapor generation amount Qt from the fuel temperature of −20 ° C. per liter to the fuel temperature T ° C. is stored. Alternatively, the relationship may be calculated by the following equation (3).

[0067]

(Equation 3)

[0068] However, Pa: pressure in the fuel tank (≒ atmospheric pressure) Pg (Tn): gasoline vapor pressure when the fuel temperature Tn (° K) QL: between fuel temperature Tn～T ₀ obtained by the formula (1) The accumulated vapor generation amount per liter of tank space volume Va is sent to the engine control computer (ECU) 22 in the injection amount correction value ΔTp obtained in the above step 127. FIG. 8 shows an injection amount calculation routine 1 processed in the ECU 22.
40 shows a flowchart of 40.

In FIG. 8, the air flow meter 42
Is multiplied by the conversion coefficient Kp used in step 126 of the fuel correction amount calculation routine 120 to obtain the basic injection amount T by the fuel injection valve 45.
Calculate p (step 141). This basic injection amount Tp
Is a fuel injection amount for making the intake air amount Qs a stoichiometric air-fuel ratio when there is no vapor suction in the intake pipe 41.

Then, the basic injection amount Tp is corrected by adding the injection amount correction value ΔTp obtained in the routine 120 to the basic injection amount Tp obtained in step 141, and the fuel injection valve 45 actually outputs the correction value. The fuel injection amount Tp 'to be injected is obtained (step 142), and this routine 140
Is ended (step 143).

Since a pulse signal (drive signal) having a pulse width of the fuel injection amount Tp 'is supplied to the fuel injection valve 45, the actual fuel injection amount (fuel injection time) Tp' is Lean side of the stoichiometric air-fuel ratio (Δ
When Tp is positive, the basic injection amount (basic injection time) Tp is increased, and when it is rich (ΔTp is negative), the basic injection amount (basic injection time) Tp is controlled to an optimal state so as to decrease. .

As described above, the injection amount correction value ΔTp for correcting the mixture ratio of gasoline vapor and air in the vapor to the stoichiometric air-fuel ratio.
Even if the distribution between the gasoline vapor amount in the vapor generated from the fuel tank 23 and the air amount changes, the fuel injection amount is appropriately increased or decreased by the injection amount correction value ΔTp, and the air-fuel ratio of the engine is increased. Good control.

As described above, according to the present embodiment, the target vapor amount correction routine 200 clarifies the residual vapor amount ΔQ (i−1) in the fuel tank 23, and based on the residual vapor amount ΔQ (i−1). In order to correct the generated vapor amount Qt generated from the fuel tank 23 (same as the target flow rate Qt of the solenoid valve 31 obtained by the routine 100), the target flow rate Qtt actually sucked into the intake pipe 41 is affected by the residual vapor. Being considered and accurate. Then, by the fuel correction amount calculation routine 120, the amount of gasoline vapor and the amount of air contained in the generated vapor are also corrected by the remaining vapor, respectively, and an accurate injection amount correction value ΔTp in consideration of the remaining vapor is obtained. Then, in the injection amount calculation routine 140, the original fuel injection amount Tp is corrected by the accurate injection amount correction value ΔTp. As a result, according to the present embodiment, the fuel injection amount is corrected with higher precision than in the prior application, and the air-fuel ratio of the engine can be more optimally controlled.

In the target flow rate correction routine 200, when the engine is in low load operation, that is, when the differential pressure across the solenoid valve 31 increases, the maximum flow rate Qmax at the solenoid valve 31 becomes smaller than the vapor flow rate from the fuel tank 23. When the generated amount Qt is larger than the generated amount Qt, the target flow rate Qtt of the solenoid valve 31 is added to a part of the remaining vapor amount ΔQ (i-1) (step 231), whereby the fuel tank 23 using the remaining vapor is added.
Internal pressure rise can be reduced as compared with the prior application. When the internal pressure of the fuel tank 23 rises and becomes larger than the opening pressure of the tank internal pressure control valve 27, vapor generated during continuous operation of the engine 40 flows into the canister 30, and in this case, the size of the canister 30 increases. I have to. However, according to the configuration of the present embodiment, the increase in the internal pressure of the fuel tank 23 is reduced as described above, so that it is possible to prevent the canister from increasing in size.

Furthermore, high temperature gasoline vapor during normal operation of the engine contains a large amount of high boiling point components in gasoline, causing deterioration of the canister 30. However, as in the present embodiment, by performing the optimal air-fuel ratio control so that the vapor does not pass through the canister 30 during the normal operation of the engine, deterioration of the canister 30 can be prevented.

[0076]

As described above, according to the present invention, the residual fuel vapor amount calculating means determines the residual fuel vapor amount remaining in the fuel tank, and the purge amount correcting means purges the intake pipe based on the residual fuel vapor amount. Correction of the fuel injection amount when evaporative fuel generated from the fuel tank is drawn into the intake pipe of the internal combustion engine requires more accurate As a result, the air-fuel ratio of the engine can be more optimally controlled, and the emission of the internal combustion engine is improved.

Further, since the purge amount correcting means accurately obtains the purge amount purged to the intake pipe based on the residual evaporated fuel amount, the generated residual evaporated fuel is reflected on the purge amount to suppress the rise in the internal pressure of the fuel tank. And as a result,
An increase in the size of the canister can be prevented.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a system configuration diagram of an embodiment of the present invention.

FIG. 3 is a diagram illustrating a hardware configuration of the microcomputer illustrated in FIG. 2;

FIG. 4 is a block diagram showing a configuration of processing contents in a microcomputer 21 shown in FIG.

FIG. 5 is a flowchart illustrating a solenoid valve flow rate calculation routine.

FIG. 6 is a flowchart illustrating a target flow rate correction routine.

FIG. 7 is a flowchart illustrating a fuel correction amount calculation routine.

FIG. 8 is a flowchart illustrating an injection amount calculation routine.

FIG. 9 is a diagram showing a map of a relationship between a fuel temperature and a vapor generation amount per liter of tank space amount.

FIG. 10 is a diagram showing a map of a relationship between an engine load and a negative pressure in an intake pipe.

FIG. 11 is a diagram showing a map of a relationship between a differential pressure before and after the solenoid valve in consideration of residual vapor and a maximum flow rate in a fully opened state of the solenoid valve.

FIG. 12 is a diagram showing a map of a relationship between fuel temperature and gasoline vapor generation amount per liter of tank space amount.

[Explanation of symbols]

 11, 23 Fuel tank 12, 40 Internal combustion engine (engine) 13, 41 Intake pipe 14 Communication path 15 Fuel evaporation amount detecting means 16, 45 Fuel injection valve 17 Fuel correction amount calculating means 18 Remaining evaporated fuel amount calculating means 19 Purging amount correction Means 21 Microcomputer 22 Engine control computer (ECU) 24 Fuel temperature sensor 25 Fuel remaining amount sensor 31, 32 Solenoid valve 42 Air flow meter

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toru Kisokoro 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-2-503942 (JP, A) JP-A-62- 135625 (JP, A)

Claims (1)

(57) [Claims] 1. A fuel evaporation amount detecting means having a communication path for directly communicating a fuel tank with an intake pipe of an internal combustion engine, and detecting an evaporation amount of evaporated fuel evaporating from the fuel tank. A fuel correction amount calculating means for correcting the fuel injection amount from the fuel injection valve based on the fuel evaporation amount detected by the means, wherein the fuel is taken into the intake pipe from the fuel tank. The remaining fuel vapor amount remaining in the fuel tank, and the remaining fuel vapor amount detected by the fuel vapor amount detecting means based on the remaining fuel vapor amount calculated by the remaining fuel vapor amount calculating means. Purge amount correction means for correcting a fuel evaporation amount to obtain a purge amount purged to the intake pipe, wherein the fuel correction amount calculation means includes a purge amount correction means for detecting a purge amount to be purged into the intake pipe. An evaporative fuel processing device for an internal combustion engine, wherein the fuel injection amount from the fuel injection valve is corrected based on the purge amount corrected by the correction.