JPH06159161A - Vaporized fuel processing equipment of internal combustion engine - Google Patents

Abstract

PURPOSE:To control the purge flow rate corresponding to the running condition of the engine by controlling the concentration of the vaporized fuel to be supplied to the suction system of the engine. CONSTITUTION:A bypass tube 29 to bypass a purge control valve 18 is provided, a solenoid valve 30, a mass flow rate meter 31 and a jet orifice 32 are arranged in the bypass tube 29, the vapor concentration is obtained from the bypass flow rate (volumetric flow rate) which is calculated from the difference before and after the jet orifice 32 and the detected value by the mass flow rate meter 31, and the opening of the purge control valve 18 and the fuel injection amount to be injected from a fuel injection valve 13 are controlled according to the vapor concentration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporated fuel processing apparatus for an internal combustion engine, and more particularly to an evaporated fuel processing apparatus for an internal combustion engine which controls the release of evaporated fuel containing HC adsorbed by a canister to an intake system.

[0002]

2. Description of the Related Art Conventionally, an evaporated fuel processing apparatus has been widely used which prevents the evaporated fuel generated in a fuel tank from being released into the atmosphere when the engine is stopped. The vaporized fuel processing device is configured to adsorb the vaporized fuel to the canister when the engine is stopped and to release (purge) the adsorbed vaporized fuel to the intake system when the engine is operating. For example, Japanese Utility Model Publication 60-21494. What is disclosed in the publication is known.

In the device disclosed in this document, a throttle and a flow rate control valve are arranged in parallel in an evaporated fuel discharge passage (purge pipe) for discharging evaporated fuel adsorbed in a canister to an intake system of an engine. An on-off valve is provided in series with the flow rate control valve, and these are used to control the amount of evaporated fuel released according to the engine load. That is, the flow control valve opens when the load of the engine reaches the first set value, the opening degree increases with the increase of the engine load, and the open / close valve has the load of the engine lower than the first set value. It is closed when the second set value is low or less and when the third set value is higher than the first set value or more. In this way, the emission amount of evaporated fuel is reduced at low load to ensure the traveling performance at low load running, and the emission amount of evaporated fuel is increased at medium load to stabilize the traveling performance at medium load. At the time of a high load that requires a high output, the discharge of the evaporated fuel is stopped to further improve the running performance.

[0004]

However, in the above-mentioned prior art, the flow rate control valve is controlled according to the operating state of the engine to control the purge flow rate, and the evaporation stored in the canister is adsorbed and stored. Depending on the amount of fuel, even if the purge flow rate through the flow control valve is the same, the mass of the vaporized fuel supplied to the intake system of the engine will differ due to the difference in the concentration of vaporized fuel flowing through the purge pipe, and the purge flow rate will be the operating state There is a problem that it is difficult to control the optimum flow rate according to the above.

The present invention has been made in view of the above problems, and controls the purge flow rate according to the operating condition of the engine by controlling the mass of the evaporated fuel supplied to the intake system of the engine. It is an object of the present invention to provide an evaporated fuel processing device for an internal combustion engine that can achieve the

[0006]

In order to achieve the above object, the present invention provides a canister for adsorbing and storing evaporated fuel generated from a fuel tank, and a first communication unit connecting the canister and an intake system of an internal combustion engine. An evaporated fuel processing apparatus for an internal combustion engine, comprising: a passage; and a first control valve that is interposed in the first communication passage and supplies the internal combustion engine with evaporated fuel according to a load of the internal combustion engine. Bypassing the first communication passage, the second amount smaller than the first evaporated fuel amount
Of a second communication passage for supplying the amount of the evaporated fuel to the internal combustion engine, and a second control valve interposed in the second communication passage, and the evaporated fuel passing through the second communication passage. It is characterized in that it has a concentration calculating means for detecting the concentration of.

Specifically, a mass flowmeter and a throttle are provided in the second communication passage, and the concentration calculating means is
It is characterized in that the concentration is calculated based on the volume flow rate value calculated according to the throttle and the load of the internal combustion engine and the output value of the mass flowmeter.

Further, it is preferable that the apparatus further comprises control means for controlling the first control valve according to a detection result of the concentration calculation means.

Further, the present invention comprises an operating state detecting means for detecting an operating state of the internal combustion engine, and a fuel injection amount calculating means for calculating a fuel injection amount based on a detection result of the operating state detecting means, It is also preferable to have a correction unit that corrects the fuel injection amount calculated by the fuel injection amount calculation unit according to the calculation result of the concentration calculation unit.

[0010]

According to the above construction, the concentration of the evaporated fuel in the second communication passage through which a smaller amount of the evaporated fuel passes through the first communication passage can be detected. Specifically, the concentration of the evaporated fuel is calculated based on the volume flow rate value and the output value of the mass flow meter.

Further, the purge flow rate is controlled by the first control valve in accordance with the fuel vapor concentration.

Further, the fuel injection amount is corrected according to the evaporated fuel concentration.

[0013]

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

FIG. 1 is an overall configuration diagram showing an embodiment of an evaporated fuel processing apparatus for an internal combustion engine according to the present invention.

In the figure, reference numeral 1 denotes an internal combustion engine (for example, simply referred to as an "engine" hereinafter) having four cylinders, a throttle body 3 is provided in the middle of an intake pipe 2 of the engine 1, and inside the throttle body 3. A throttle valve 3'is provided. Further, the throttle valve 3 ′ has a throttle valve opening (θ
TH) sensor 4 is connected and outputs an electric signal corresponding to the opening degree of the throttle valve 3 ′ and supplies it to an electronic control unit (hereinafter referred to as “ECU”) 5.

Further, a branch pipe 6 is provided downstream of the throttle valve 3'of the intake pipe 2, and an absolute pressure (PBA) sensor 7 is arranged at the tip of the branch pipe 6. Also, PB
The A sensor 7 is electrically connected to the ECU 5, and the absolute pressure PBA in the intake pipe 2 detected by the PBA sensor 7 is converted into an electric signal and supplied to the ECU 5.

An intake air temperature (TA) sensor 8 is mounted on the wall of the intake pipe 2 downstream of the branch pipe 7, and the intake air temperature TA detected by the TA sensor 8 is converted into an electric signal.
It is supplied to the ECU 5.

An engine water temperature (TW) sensor 9 composed of a thermistor or the like is attached to the cylinder peripheral wall filled with cooling water of the cylinder block of the engine 1, and the engine cooling water temperature TW detected by the TW sensor 9 is converted into an electric signal. It is converted and supplied to the ECU 5.

An engine speed (NE) sensor 10 is provided around a cam shaft or crank shaft (not shown) of the engine 1.
Is attached.

The NE sensor 10 outputs a signal pulse (hereinafter referred to as "TDC signal pulse") at a predetermined crank angle position every 180 degrees rotation of the crank shaft of the engine 1, and the TDC signal pulse is supplied to the ECU 5. .

Further, an oxygen concentration sensor (hereinafter referred to as "O2 sensor") 12 is provided in the middle of the exhaust pipe 11 of the engine 1.
Is provided, the oxygen concentration in the exhaust gas detected by the O2 sensor 12 is converted into an electric signal, and the ECU 5
Is supplied to.

The fuel injection valve 13 is provided for each cylinder between the engine 1 and the throttle valve 3'and slightly upstream of an intake valve (not shown) in the intake pipe 2. In addition, each fuel injection valve 13 is connected to a fuel tank 16 via a fuel pump 15 by a fuel supply pipe 14 and electrically connected to the ECU 5, and a signal from the ECU 5 causes a signal to be injected from the fuel injection valve 13.
The valve opening time of is controlled.

A purge pipe 17 is diverged between the throttle valve 3'of the intake pipe 2 and the branch pipe 6, and the purge pipe 17 is provided with a canister via a purge control valve 18 (first control valve). It is connected to 19.

The purge control valve 18 is provided in the intake pipe 2
And the canister 19 can communicate with each other. The valve body 20 has a wedge-shaped cross section and is movably arranged in the vertical direction, a casing 21 in which the valve body 20 is housed, and the valve body 20 in the vertical direction. A normally open solenoid valve 22 to be driven and a valve opening (lift) sensor (hereinafter, referred to as “L sensor”) 24 connected to the valve body 20 via a valve shaft 23 are provided. The solenoid valve 22 is electrically connected to the ECU 5, and the ECU
The valve lift amount of the valve body 20 in the vertical direction is duty-controlled based on the electric signal from 5. Further, the L sensor 24 is
The valve lift amount of the valve body 20 is detected and the electric signal is detected by the ECU.
Supply to 5.

The canister 19 contains an adsorbent 25 such as activated carbon and an outside air intake 26,
The two-way valve 27 is connected to the fuel tank 16 via an evaporated fuel flow passage 28. The two-way valve 2
Reference numeral 7 is composed of a positive pressure valve and a negative pressure valve.

Further, reference numeral 29 is a bypass pipe bypassing the purge control valve 18, and its diameter is smaller than that of the purge pipe 17 so that a low flow rate can be passed as compared with the purge flow rate passing through the purge control valve 18. Has been done. And
An electromagnetic opening / closing valve 30, a mass flowmeter (heat wire type flowmeter) 31, and a jet orifice 32 are arranged in series in the conduit of the bypass pipe 29.

The electromagnetic on-off valve 30 has an electromagnetic valve 30 'of E
It is electrically connected to the CU 5 and controls the flow rate of the purge flowing through the bypass pipe 29 on / off under the control of the ECU 5. That is, the electromagnetic opening / closing valve 30 is a normally open type electromagnetic valve, which closes when the electromagnetic valve 30 'is excited (ON) and opens when the electromagnetic valve 30' is demagnetized (OFF).
ON / OFF control of the purge flow rate flowing through.

The mass flowmeter 31 utilizes the fact that when a platinum wire heated by passing an electric current is exposed to an air stream, its temperature lowers and its electric resistance decreases, and its output characteristic is that of an evaporated fuel. It changes according to the concentration, the flow rate, etc., and supplies the output signal to the ECU 5 according to these changes. Then, the fuel tank 16, the purge control valve 18, the electromagnetic opening / closing valve 30, the mass flow meter 31, the canister 19, and the two-way valve 2
The evaporative emission control system is constituted by 7.

The ECU 5 shapes the input signal waveforms from the various sensors described above to correct the voltage level to a predetermined level,
An input circuit having a function of converting into an analog signal value, a central processing unit (hereinafter referred to as "CPU"), a storage means for storing a calculation program executed by the CPU, a calculation result, etc., and the fuel injection. Valve 13 and purge control valve 1
8 and an output circuit for supplying a drive signal to the electromagnetic on-off valve 30.

The CPU determines various engine operating states such as a feedback control operating region and an open loop control operating region according to the oxygen concentration in the exhaust gas based on the various engine parameter signals described above, and determines the engine operating state. Accordingly, the injection time Tout of the fuel injection valve 13 synchronized with the TDC signal pulse is calculated based on the equation (1).
Is calculated.

Tout = Ti × K1 × KO2 + K2 (1) Here, Ti is a reference value of the injection time Tout of the fuel injection valve 13, and is the engine speed NE and the intake pipe absolute pressure PB.
It is read from the Ti map set according to A.

KO2 is an air-fuel ratio correction coefficient, which is set in accordance with the oxygen concentration in the exhaust gas detected by the O2 sensor 12 during feedback control, and in each of a plurality of open-loop control operating regions where feedback control is not performed. It is set according to the operating area.

K1 and K2 are correction coefficients and correction variables calculated according to various engine parameter signals, etc., so that various characteristics such as fuel consumption characteristics and engine acceleration characteristics can be optimized according to engine operating conditions. Is set to any value.

In the fuel vapor control system for an internal combustion engine thus constructed, when the fuel vapor reaches a predetermined set pressure, the positive pressure valve of the two-way valve 27 pushes open and the fuel vapor flows into the canister 19. It is adsorbed and stored by the adsorbent 25 in the canister 19.

Further, the purge control valve 18 and the solenoid opening / closing valve 3
For 0, the valve opening degree control and the on / off control are executed in accordance with the purge flow rate control processing shown in FIGS. 2 and 3 described later. Then, when at least one of the purge control valve 18 and the electromagnetic opening / closing valve 30 is opened, the evaporated fuel temporarily stored in the canister 19 is discharged from the outside air intake port 26 of the canister 19 due to the negative pressure in the intake pipe 2. The evaporated fuel is sucked into the intake pipe 2 through the bypass pipe 29 and / or the purge control valve 18 together with the sucked outside air, and the evaporated fuel is supplied to the engine 1.

Further, in the above vaporized fuel processing apparatus, as will be described later, the opening area A of the jet orifice 32 interposed in the second communication passage 29 and the absolute pressure P in the intake pipe.
The bypass flow rate (volume flow rate) QPJET is calculated according to BA and the bypass flow rate QPJET and the mass flowmeter 31.
Concentration of vaporized fuel (vapor concentration) based on the output value of
β is calculated. That is, in order to calculate the vapor concentration β, it is necessary to accurately measure the volume flow rate and the mass flow rate, and the mass flow meter 31 is provided on the downstream side of the jet orifice 32 where the flow of the evaporated fuel is stable. this is,
Due to fluctuations in the volume flow rate due to the valve opening of the purge control valve 18, fluctuations in the output value of the mass flowmeter 31 due to turbulence in the evaporated fuel flow due to fluctuations in the valve opening, and further due to fluctuations in the absolute pressure PBA in the intake pipe. This is to prevent overlapping of error factors such as influences, and accurately measures the volume flow rate and the mass flow rate at a position that is hardly affected by the valve opening degree of the purge control valve 18 and the fluctuation of the valve opening degree, This is to accurately calculate the vapor concentration β.

2 and 3 are flowcharts showing the purge flow rate control processing in this embodiment, and this program is executed in the background.

First, in step S1, it is determined whether or not a failure diagnosis of the evaporative emission control system is underway. The failure diagnosis of the evaporative emission control system is to forcibly set the evaporative emission control system to a predetermined negative pressure state and measure the change over time in the internal pressure of the fuel tank after the negative pressure state is set. By this, it is determined whether or not there is a failure. If the answer to step S1 is affirmative (YES), step S7
On the other hand, while the process proceeds to (FIG. 3), the answer is negative (NO), that is, if the evaporative emission control system is not diagnosing failure, step S2.
Then, it is determined whether the engine 1 is in the starting mode (during cranking). If the answer is affirmative (YES), the water temperature TWCR at the time of starting is stored as the engine cooling water temperature TW in step S3, and then the flag F02 in step S4.
Is reset to "0" and the process proceeds to step S7 (FIG. 3).
On the other hand, if the answer to step S2 is negative (NO), the process proceeds to step S5 and it is determined whether the engine is stalled. Then, if the answer is affirmative (YES), step S7.
If the answer is negative (NO) while proceeding to (Fig. 3),
Further, in step S6, it is determined whether or not the fuel supply is stopped (fuel cut). And the answer is affirmative (YE
When the answer is negative (NO), the process proceeds to step S9, and it is determined whether the flag F02 is "1". When the answer is affirmative (YES), the process proceeds to step S11, while when the answer is negative (NO), that is, when the flag F02 is not "1", the process proceeds to step S10. In step S10, the water temperature TWCR in the start mode stored in step S3 is stored.
Is greater than a predetermined value TWCRP (for example, 70 ° C.). Then, if the answer is negative (NO), that is, if the engine is started in the cold state in which the water temperature TWCR at the time of start is equal to or lower than the predetermined value TWCRP, the process proceeds to step S11.
As described above, if the answer to step S9 is affirmative (YES), the process of step S10 is not performed and step S1 is performed.
The process proceeds to step S1 to step S2 described later.
This is because the process of 3 need only be executed once after the start.

Next, at step S11, it is judged whether or not the current water temperature TW is smaller than a predetermined value TWPC1 (for example, 50 ° C.), and if the answer is affirmative (YES), that is, the current engine cooling water temperature TW is predetermined. When the water temperature is lower than the value TWPC1 (for example, 50 ° C.), the process proceeds to step S7.

The answer to step S11 is negative (N
O), that is, the current engine cooling water temperature TW is a predetermined value TWP
When the temperature is C1 (for example, 50 ° C.) or higher, it is determined that the engine is in the warm-up process, and the process proceeds to the next step S12. In step S12, the current engine cooling water temperature T
It is determined whether W is smaller than a predetermined value TWPC2 (for example, 70 ° C.). The answer is affirmative (YES), that is, the current engine cooling water temperature TW is the predetermined value TWPC2 (for example, 70
℃), that is, TWPC1 <TW <TW
If it is PC2, the process proceeds to step S13, and it is determined whether or not the engine is in the idle state. When the answer is negative (NO), that is, when the vehicle is running, step S14
On the other hand, if the answer to step S13 is affirmative (YES), that is, if the engine cooling water temperature TW is TWPC1 <TW <T
When WPC2 and idle state, step S
Proceed to 7. The answer to step S12 is negative (N
O), that is, the warm-up progresses and the current water temperature TW is equal to the predetermined value T
When it becomes WPC2 or more, the process proceeds to step S16, and it is determined whether or not the engine is currently in the idle state. If the answer is negative (NO), that is, if the vehicle is running, the process proceeds to step S17, while the answer to step S16 is affirmative (YE).
If S), the process proceeds to step S14.

If the answer in step S10 is affirmative (YES), that is, if the water temperature TWCR at startup is higher than the predetermined value TWCRP and the engine is started in a warmed-up state, the process proceeds to step S19, and the air-fuel ratio is increased. It is determined whether or not feedback control is being performed. Then, when the answer is negative (NO), that is, when the air-fuel ratio feedback control is not currently being performed, the process proceeds to step S20, and the counter is set to a predetermined value NPRG (corresponding to a predetermined time after start),
Then, the process proceeds to step S14. On the other hand, in step S19
If the answer is YES (YES), that is, if the air-fuel ratio feedback control is being performed, it is determined in step S21 whether or not the predetermined value NPRG of the counter is larger than "0". Then, when the answer is affirmative (YES), that is, when the predetermined time has not elapsed after the start, the predetermined value NPR is obtained in step S22.
The G is decremented by "1", and the process proceeds to step S14 as described above.

When the answer to the step S21 is negative (NO), it is determined that a predetermined time has elapsed after the start and the engine is completely warmed up, and the flag F02 is set at step S23.
After setting to "1", the process of step S16 described above is performed, and the process proceeds to step S14 or step S17.

However, in step S7, the flag FPR is set.
GACT is set to "0", duty control of the purge flow rate by the purge control valve 18 is not performed, and the purge control valve 18 is left in the closed state. Further, in step S8, the solenoid valve 30 'is excited to electromagnetically open and close. The valve 30 is closed.

As described above, during the failure diagnosis of the evaporative emission control system, during the starting mode, during the engine stall and during the fuel cut, the flag FPRGACT is reset to "0" and the evaporative fuel intake system is entered. Is not purged (purge cut). Further, when the engine cooling water temperature TW is a low water temperature lower than a predetermined value TWPC1 (for example, 50 ° C.), and when the engine cooling water temperature TW is in an idle state even if TWPC1 <TW <TWPC2, the evaporated fuel is supplied to the intake system. Do not purge.

In step S14, the flag F
PRGACT is set to "0", the duty control of the purge control valve 18 is not performed, and the purge control valve 18 is left closed as described above. In step S15, the solenoid valve 30 'is demagnetized to open the solenoid opening / closing valve 30. To do.

That is, even when the vehicle is running, the engine cooling water temperature TW is within a predetermined range (TWPC1 <TW
When <TWPC2), the purge control valve 18 is closed and a low flow rate of evaporated fuel is purged into the intake system via the bypass pipe 29 so that the fuel is sent from the canister 19 during the warming process after the engine is started. The coming evaporated fuel containing a high concentration of hydrocarbons HC is supplied to the engine 1 to prevent the exhaust emission from being adversely affected.

The bypass pipe 29 is also used when the engine cooling water temperature TW is equal to or higher than the predetermined value TWPC2 and is in the idle state, and when the air-fuel ratio feedback control is not being performed.
Low flow rate purge via.

Further, even when the predetermined time has not elapsed after the start, the purge control valve 18 is closed and the low flow rate purge is performed through the bypass pipe 29. This is because even in the warm-up state, the vaporized fuel containing a high concentration of hydrocarbons HC is sent from the canister 19 within a predetermined time after the engine is started (immediately after the start of purging), so that the hydrocarbons HC are This is to prevent the exhaust emission from being adversely affected.

When the engine 1 is warmed up sufficiently and is not running in the idle state, the flag FPRGACT is set to "1" in step S17 to permit the duty control of the purge control valve 18, and then in step S18.
Then, the electromagnetic on-off valve 30 is opened, and the bypass pipe 29 can be purged.

4 and 5 are flow charts showing the duty control of the purge control valve 18 in this embodiment. This program is synchronized with a pseudo signal pulse generated every 40 ms by a timer incorporated in the ECU 5. And then executed.

In step S31, it is determined whether the engine 1 is in the starting mode. If the answer is negative (NO), that is, the basic mode, the process proceeds to step S32. In step S32, it is determined whether the flag FPRGACT set in the purge flow rate control process shown in FIGS. 2 and 3 is “1”, that is, whether the duty control of the purge control valve 18 should be performed. . If the answer to step S32 is affirmative (YES), the reduction coefficient KPAP after the start of purge is calculated in step S33. This weight reduction coefficient KPAP is a KPAP calculation routine (FIG. 8) described later.
Is calculated by

That is, the purge flow rate control by the purge control valve 18 depends on the intake air amount, but since the hydrocarbon HC concentration in the purge is still high at the stage where the integrated purge flow rate is small immediately after the start of the purge, It is necessary to suppress the flow rate and perform purging. Therefore, in this embodiment, the purge flow rate is reduced by using the reduction coefficient KPAP at this stage. This makes it possible to reduce the influence of the hydrocarbon HC on the exhaust emission even if the evaporated fuel containing the high concentration hydrocarbon HC is sent from the canister 19 immediately after the start of purging during traveling.

Next, in step S34, the density correction coefficient KPN is calculated. That is, the KPN calculation routine (FIG. 11) to be described later is executed to calculate the concentration (hereinafter, referred to as “vapor concentration”) β of the evaporated fuel passing through the bypass pipe 29, and the vapor is adjusted to correct the target purge flow rate QPOBJ. The KPN value is calculated based on the concentration β.

Next, in step S35, the target purge flow rate QPOBJ is calculated based on the equation (2).

[0055]

[Equation 1] ME is a value corresponding to the reciprocal of the engine speed, and To
utn is a value obtained by removing the air-fuel ratio correction coefficient KO2 and the battery voltage correction from the injection time Tout of the fuel injection valve 6 calculated by the expression (1). Therefore, Tout
n / ME has a value proportional to the intake air amount. Also, KP
OBJ indicates the purge ratio (for example, 10%) to the target purge ratio fuel injection amount.

Next, a step S36 finds the current value QPAIR of the purge flow rate based on the equation (3).

QPAIR = QPOBJ × KPAP × KPN (3) In the next step S37, the maximum flow rate QPBLIM with respect to the intake pipe absolute pressure PBA is searched by the table shown in FIG. 6, and in step S38 (FIG. 5), the above step is performed. Current value QPAIR of purge flow rate calculated in S36
The maximum flow rate QPBLIM is used as a limit value for the limit check. That is, the current value QPA of the purge flow rate
It is determined whether or not IR is larger than the maximum flow rate QPBLIM, and if the answer is affirmative (YES), that is, if the current value QPAIR is larger than the maximum flow rate QPBLIM, then step S3.
In step 9, the current value QPAIR is set to the maximum flow rate QPBLIM, and the process proceeds to step S40. If the answer is negative (NO), that is, if the current value QPAIR is less than or equal to the maximum flow rate QPBLIM, it means that the limit value has not been reached and step S40 is continued. Proceed to.

In step S40, the cumulative purge flow rate QPAIRT up to the previous time and the current purge flow rate value QPA
Addition of IR and new purge integrated flow rate QPAIRT
Calculate (will be the previous value of the next time).

Next, in step S41, the QPJET map is searched and the bypass flow rate (volume flow rate) QPJET is calculated.

That is, the QPJET map shows the opening area A of the jet orifice 32 and the absolute pressure PBA in the intake pipe.
A predetermined map value (corresponding to 100% air) is given in accordance with the above, and the bypass flow rate QPJET is read by searching the QPJET map or calculated by an interpolation method.

Next, in step S42, the subtractive purge flow rate QPAIRD is calculated based on the equation (4).

QPAIRD = QPAIR-QPJET (4) As a result, the flow rate of the flow through the purge pipe 17 is reduced and corrected.

Next, in step S43, the duty ratio DUTY of the purge control valve 18 is searched for the DUTY map set according to the subtractive purge flow rate QPAIRD calculated in step S42 and the intake pipe absolute pressure PBA.
To calculate. Here, the element for setting the duty ratio DUTY is the intake pipe absolute pressure PBA, because the evaporated fuel is sucked into the intake pipe by the intake pipe absolute pressure PBA, even if the intake air amount is the same, This is because the purge flow rate changes depending on the absolute pressure PBA in the intake pipe.

In the following step S44, the table shown in FIG. 7 is searched and the voltage correction value T corresponding to the battery voltage VB is calculated.
Calculate VBQPG. That is, since the operating state of the purge control valve 18 changes depending on the battery voltage VB, this point is taken into consideration. Then, in step S45, the duty ratio DUTY searched in step S43 is added to the voltage correction value TVBQPG searched in the table of FIG. 7 to calculate the final duty ratio DUTY this time.
Then, in step S46, the duty ratio DUT
If it is determined whether Y is larger than 100% and the answer is negative (NO), the duty ratio DUTY is set to the duty ratio obtained in step S42, and step S42 is performed.
At 48, the injected fuel is corrected. That is, the above formula (1)
A new fuel injection time is calculated by subtracting and correcting the purge flow rate corresponding to the target purge ratio KPOBJ from the fuel injection time Tout calculated by. Furthermore, when the desired evaporated fuel is not stored in the canister 19, the purge flow rate according to the target purge ratio KPOBJ (for example, 10%) may not be obtained. That is, depending on the subtraction purge flow rate QPAIRD, it may not be possible to obtain the purge flow rate according to the target purge ratio KPOBJ (for example, 10%), but in such a case, the subtraction purge flow rate QPAI.
Calculate the actual purge ratio (for example, 8%) according to RD,
The subtraction correction of the injected fuel is performed according to the actual purge ratio.

On the other hand, the answer to step S46 is affirmative (YE
In the case of (S), the duty ratio DUTY is set to "100%" in step S47, the process proceeds to step S48, and the injection fuel reduction correction is performed as described above.

Then, the process proceeds to step S49, where the duty ratio D determined in step S42 or step S47 is determined.
Outputs UTY and ends this program.

If the answer to step S31 (FIG. 4) is affirmative (YES), that is, if the engine is in the start mode, the cumulative purge flow rate Q is determined in step S50.
Initialize PAIRT to "0", set the duty ratio DUTY to 0% in step S51, and set the duty ratio D
UTY (= 0) is output in step S49, and this program ends.

FIG. 8 is a flowchart of the weight reduction coefficient KPAP calculation routine executed in step S33 (FIG. 4).

In step S61, the table shown in FIG. 9 is used to search for the reduction coefficient KPAP according to the purge integrated flow rate QPAIRT. As is apparent from FIG. 9, the reduction coefficient KPAP is smaller than “1.0” and is set to be larger as the integrated purge flow rate QPAIRT increases.

Further, in the following step S62,
The correction coefficient KPTW according to the engine cooling water temperature TW is searched using the table shown in FIG. Considering such a correction coefficient KPTW, a high concentration of hydrocarbons HC may be purged because the catalyst is not activated at low water temperature, and the emission of hydrocarbons deteriorates the emission. In order to prevent this, the flow rate is suppressed and purging is performed. Therefore, the engine cooling water temperature T
The correction coefficient KPTW is set to decrease as W decreases.

Then, in step S63, the KPAP value and the KPTW value retrieved in steps S61 and S62 are multiplied to obtain the final reduction coefficient KP of this time.
Calculate AP. Next, at step S64, the weight reduction coefficient K
It is determined whether PAP is smaller than "1.0", and if the answer is affirmative (YES), this program ends. If the answer is negative (NO), the weight reduction coefficient KPAP is set to "1.0" (step S65), and this program ends.

FIG. 11 shows K for calculating the density correction coefficient KPN.
It is a flowchart of a PN calculation routine.

First, in step S71, as in step S41 described above, the QPJET map is searched to open the opening area A of the jet orifice 32 and the absolute pressure PBA in the intake pipe.
The bypass flow rate (volume flow rate) QPJET is calculated according to

Next, in step S72, the mass flow rate QHW detected by the mass flow meter 31 is read.

Next, in step S73, the VQ map is searched to calculate the actual vaporized fuel flow rate (vapor flow rate) VQ,
In step S74, the TQ map is searched to calculate the actual bypass flow rate TQ which is a mixture of evaporated fuel and air.

That is, when only air flows into the bypass pipe 29, the vapor concentration β is “0%”, so the bypass flow rate QPJET and the mass flow rate QHW become equal,
As the vapor concentration β increases, a difference occurs between the two.
Therefore, the above-mentioned VQ map and TQ map are EC
The actual bypass flow rate TQ is stored in the storage means of U5.
And the actual paper flow rate VQ is calculated.

Next, in step S75, the vapor concentration β is calculated based on the equation (5). β = VQ / TQ (5) Next, in step S76, the concentration correction coefficient KPN corresponding to the vapor concentration β is calculated using the table shown in FIG. 13, and this program ends.

By utilizing the concentration correction coefficient KPN calculated in this way, the duty control of the power control valve 18 is smoothly performed as described above, and the purge flow rate is adjusted to the optimum flow rate according to the operating state of the engine. Can be controlled to.

[0079]

As described above in detail, the present invention includes a canister for adsorbing and storing evaporated fuel generated from a fuel tank,
First connecting the canister and an intake system of an internal combustion engine
And a first control valve which is interposed in the first communication passage and supplies evaporated fuel according to the load of the internal combustion engine to the internal combustion engine. A second communication passage that bypasses the first communication passage and supplies a second evaporated fuel amount smaller than the first evaporated fuel amount to the internal combustion engine; and an intervening second communication passage. And a concentration calculating means for calculating the concentration of the evaporated fuel passing through the second communication passage. It is possible to detect the concentration of
The desired purge can be performed when a large amount of evaporated fuel is stored in the canister even when the vehicle is parked during idling or warming up.

Specifically, a mass flowmeter and a throttle are provided in the second communication passage, and the concentration calculating means is
Even if the purge flow rate is small, the concentration of the evaporated fuel is calculated by calculating the concentration based on the volume flow rate value calculated according to the load of the throttle and the internal combustion engine and the output value of the mass flowmeter. Can be calculated from the accuracy.

Further, by having the control means for controlling the first control valve according to the calculation result of the concentration calculation means, it is possible to control the barge flow rate to an optimum flow rate according to the operating state of the engine. Become.

Further, there is provided an operating state detecting means for detecting an operating state of the internal combustion engine, and a fuel injection amount calculating means for calculating a fuel injection amount based on a detection result of the operating state detecting means, the fuel injection amount calculation By having the correction means for correcting the fuel injection amount calculated by the means according to the calculation result of the concentration calculation means, it becomes possible to suppress the fluctuation of the air-fuel ratio of the air-fuel mixture due to the barge flow rate, and the exhaust characteristic Can be prevented from getting worse.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an evaporated fuel processing apparatus for an internal combustion engine according to the present invention.

FIG. 2 is a flowchart (1/2) showing a purge flow rate control process in the present embodiment.

FIG. 3 is a flowchart (2/2) showing a purge flow rate control process in this embodiment.

FIG. 4 is a flowchart (1/2) of duty control by the purge control valve in the present embodiment.

FIG. 5 is a flowchart (2/2) of duty control by the purge control valve in the present embodiment.

FIG. 6 shows the maximum flow rate QPB with respect to the absolute pressure PBA in the intake pipe.
It is a figure of the table which shows LIM.

FIG. 7 is a voltage correction value TVBQ according to the battery voltage VB.
It is a figure of the table which shows PG.

FIG. 8 is a flowchart of a KPAP calculation routine.

FIG. 9 is a table showing a reduction coefficient KPAP according to a purge integrated flow rate QPAIRT.

FIG. 10 is a correction coefficient KP according to the engine cooling water temperature TW.
It is a figure of the table which shows TW.

FIG. 11 is a flowchart of a KPN calculation routine.

FIG. 12 is a concentration correction coefficient KPN according to the vapor concentration β.
It is a table figure which shows.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 ECU (concentration calculation means, control means, fuel injection amount calculation means, correction means) 7 PBA sensor (operating state detection means) 10 NE sensor (operating state detection means) 16 fuel tank 17 purge pipe (first 18) Purge control valve (first control valve) 19 Canister 30 Electromagnetic on-off valve (second control valve) 31 Mass flow meter (concentration calculating means) 32 Jet orifice (concentration calculating means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Muramatsu 1-4-1, Chuo, Wako-shi, Saitama Inside Honda R & D Co., Ltd. (72) Inventor Shinichi Kitajima 1-4-1, Chuo, Wako-shi, Saitama Incorporated company Honda R & D Co., Ltd. (72) Inventor Fumio Hosoda 1-4-1 Chuo, Wako, Saitama Prefecture Incorporated Honda R & D Co., Ltd. (72) Inventor Koichi Hidano 1-4-1 Wako, Saitama Prefecture (72) Inventor Yoshihiko Kobayashi 143, Hagadai, Haga-cho, Haga-gun, Tochigi Prefecture PSG, Inc.

Claims (4)

[Claims] 1. A canister for adsorbing and storing evaporated fuel generated from a fuel tank, a first communication passage connecting the canister and an intake system of an internal combustion engine, and a canister interposed in the first communication passage. An evaporated fuel processing apparatus for an internal combustion engine, comprising: a first control valve that supplies a first amount of evaporated fuel according to a load of the internal combustion engine to the internal combustion engine; A second communication passage for supplying the internal combustion engine with a second evaporated fuel amount smaller than the first evaporated fuel amount, and a second communication passage interposed in the second communication passage.
And a concentration calculating means for calculating the concentration of the evaporated fuel passing through the second communication passage, the evaporated fuel processing device for an internal combustion engine. 2. A mass flowmeter and a throttle are provided in the second communication passage, and the concentration calculation means calculates the volumetric flow rate value and the volume flow value calculated according to the load of the throttle and the internal combustion engine. The evaporated fuel processing device for an internal combustion engine according to claim 1, wherein the concentration is calculated based on an output value of the mass flowmeter. 3. The evaporated fuel for an internal combustion engine according to claim 1, further comprising control means for controlling the first control valve according to a calculation result of the concentration calculation means. Processing equipment. 4. An operating state detecting means for detecting an operating state of the internal combustion engine, and a fuel injection amount calculating means for calculating a fuel injection amount based on a detection result of the operating state detecting means. 4. The internal combustion engine according to claim 1, further comprising a correction unit that corrects the fuel injection amount calculated by the calculation unit according to the calculation result of the concentration calculation unit. Evaporative fuel processor.