JPH06264834A - Fuel evaporation gas discharge suppression device - Google Patents

Abstract

PURPOSE:To control the opening/closing of a purge control valve while avoiding the leakage of the overrich fuel evaporation gas and the discharge of the un burned gas even when an on-vehicle computer is abnormal. CONSTITUTION:A proportional control valve 27 is opened or closed by the control signal from a duty output backup circuit 49. The duty output backup circuit 49 is constituted of two AND circuits 91, 92, an inverter inverting the input of one AND circuit 92, and an OR circuit 93. The AND circuits 91, 92 are inputted with the CPU abnormality signal FCPU, and they output the purge valve control output duty ratio D calculated and outputted by a CPU 40 to the proportional control valve 27 as it is when the CPU 40 is normal. When the CPU 40 is abnormal, the injection backup signal B/UTAu generated by an injection backup circuit 48 hardware-wise is outputted to the proportional valve 27. When the air flow meter voltage is a prescribed value or below, the output of the AND circuit 91 is set to the low level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel evaporative emission control device for introducing fuel evaporative emission generated in a fuel tank into an intake passage to prevent the fuel evaporative emission from being discharged into the atmosphere. In particular, the present invention relates to a fuel evaporative emission control device of the type in which the control computer adjusts the purge amount according to the engine operating state.

[0002]

2. Description of the Related Art In recent years, in automobiles and the like, it has become obligatory to equip a fuel evaporative emission control device to prevent the fuel evaporative emission generated in a fuel tank from being released into the atmosphere. The fuel evaporative emission control device adsorbs fuel evaporative emission generated in a fuel tank to a charcoal canister, introduces it into an intake pipe during operation of an internal combustion engine, and burns it together with a fuel mixture. Depending on the operating condition, the introduction of this fuel evaporative gas may cause the air-fuel ratio to become overrich and cause engine stall. Therefore, in order to avoid such an overrich state, a device for controlling the opening and closing of the purge passage according to the operating state has been proposed (for example, JP-A-61-1996).
No. 2, JP-A-62-20669, US Pat. No. 4,821,701).

In these devices, an on-vehicle computer is used to control the opening and closing of the purge control valve. For this reason, it is common to fix the purge control valve to either open or closed when the vehicle-mounted computer is abnormal.

[0004]

However, if the purge control valve remains open and fixed when the amount of fuel evaporative gas is large, the air-fuel ratio becomes overrich and engine stall occurs. On the contrary,
If the purge control valve remains closed and fixed when the amount of fuel evaporative gas is large, there is a problem that the amount of fuel evaporative gas that exceeds the adsorption force of the charcoal canister will leak out from the atmospheric hole of the canister. It was

In this way, in the configuration in which the purge control valve is fixed to open or closed when the vehicle-mounted computer is abnormal,
There was a problem no matter which one was fixed. As a system for performing computer control of an idle speed control valve (ISCV), as a countermeasure against a computer abnormality, a system is known in which, when a computer abnormality is detected, an ISCV control duty is created based on an engine speed signal. (JP-A-1-294935)
issue). However, when this technique is directly applied to the fuel evaporative emission control device, there are the following problems.

That is, if the purge control valve is controlled to open and close based on the engine speed signal, purging is performed even during fuel cut operation, and this is directly discharged from the exhaust pipe as unburned gas. There was a problem of being lost. Further, since the engine speed and the intake air amount are irrelevant, there is a possibility of causing an overrich state. Therefore, in the configuration in which the purge control is performed based on the engine speed when the vehicle-mounted computer is abnormal, in the end, there is not much difference from the case where the purge control valve is fixed to open or closed.

Therefore, in the present invention, the opening and closing of the purge control valve can be controlled even when the vehicle-mounted computer is in an abnormal state, and the fuel-evaporated gas is discharged while avoiding the overrich of the fuel mixture and the leakage of the fuel-evaporated gas. It is an object of the present invention to provide a device capable of suppressing the above.

[0008]

The fuel evaporative emission control device of the present invention, which has been completed to achieve the above object, sucks the fuel evaporative gas generated in the fuel tank as shown in FIG. An introduction passage to be introduced into the pipe, a purge control valve provided in the introduction passage for adjusting the purge amount of the fuel evaporative gas according to the open / closed state, an operation state detection means for detecting the operation state of the engine, and the detection In a fuel evaporative emission control device that includes an on-vehicle computer that controls the opening and closing of the purge control valve in accordance with an operating state, an abnormality detecting unit that detects an abnormality of the on-vehicle computer, and a hardware type when the on-vehicle computer is abnormal. An abnormal-time purge means for controlling the opening and closing of the purge control valve according to the length of the fuel injection signal provided from the backup circuit. .

According to this fuel evaporative emission control device,
Even when the on-vehicle computer is abnormal, the purge control valve is not fixed to either the open valve or the closed valve, but the abnormal time purge means opens or closes the purge control valve according to the length of the fuel injection signal. Here, since the fuel injection signal is given from a backup circuit configured in hardware,
It can be obtained even when the vehicle-mounted computer is in an abnormal state. Further, the fuel injection signal from the backup circuit reflects the load (intake air amount) of the engine although it is incomplete.

Therefore, according to the fuel evaporative emission control device of the present invention, the amount of the fuel evaporative emission introduced into the intake pipe is adjusted to reflect the large intake air amount even when the vehicle computer is abnormal. Become. As a result, a large amount of purge is not performed even though the intake air amount is small, and a remarkable overrich state can be avoided. In particular, a large amount of fuel evaporative gas will not be purged even during fuel cut, and a large amount of unburned gas will not be discharged.

Further, even when the vehicle-mounted computer is abnormal, as long as the fuel injection is executed, the fuel evaporative emission is introduced into the intake pipe in some form even if the vehicle is stopped. There is no leakage. The fuel injection signal from the backup circuit does not completely reflect the intake air amount. Therefore, as described in claim 2, in the fuel evaporative emission control device according to claim 1, when the load condition of the internal combustion engine is equal to or less than a predetermined value, the abnormal-time purge means is irrespective of the fuel injection signal. It is preferable to provide guard means for keeping the purge control valve closed. With such a configuration, purging is prohibited when the actual intake air amount is small and the influence of purging is likely to occur at a low load, the occurrence of a significant overrich state is suppressed, and the occurrence of engine stall and the like can be prevented. it can.

Further, the injection backup circuit can be realized at a low cost because it is existing in the in-vehicle control unit (ECU).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing a configuration of an internal combustion engine having the configuration of this embodiment and peripheral devices thereof.

In FIG. 2, air is taken in from the air cleaner 1 and its flow rate is controlled by a throttle valve 2 which is interlocked with an accelerator pedal (not shown) operated by a driver, and an intake port 5 is supplied through a surge tank 3 and an intake pipe 4. Be guided to. The intake pipe 4 is provided with a fuel injection valve 6, and fuel is supplied to the fuel injection valve 6 from a fuel tank 7 through a fuel pipe (not shown).
Fuel is injected and supplied to the intake port 5. The air-fuel mixture generated in the intake port 5 is introduced into the combustion chamber 10 of the engine 9 via the intake valve 8. The combustion chamber 10 is partitioned by a piston 11, and the exhaust gas generated by the combustion of the air-fuel mixture is released to the atmosphere via an exhaust valve 12 and an exhaust pipe 13.

The air flow meter 14 is provided between the air cleaner 1 and the throttle valve 2 to output an analog signal according to the intake air amount, and an intake air temperature sensor 15 provided in a housing in which the air flow meter 14 is provided. Outputs an analog signal according to the intake air temperature. Throttle sensor 1
Reference numeral 6 is connected to the rotary shaft of the throttle valve 2 and outputs an analog signal according to the opening degree of the throttle valve 2 and outputs from an idle switch for detecting that the throttle valve 2 is substantially fully closed. The on-off signal IDL is also output. The air-fuel ratio sensor 17 is attached to the exhaust pipe 13 and outputs an analog signal according to the residual oxygen concentration in the exhaust gas. The water temperature sensor 18 is attached to the water jacket of the engine 9 and outputs an analog signal according to the engine cooling water temperature. The crank angle sensor 19 is provided so as to face a ring gear formed on the shaft of the distributor 20 connected to the crank shaft of the engine 9, and outputs a pulse signal at every predetermined crank angle.

Each sensor 14, 15, 16, 17, 18,
19 and battery 21 are control unit 22 (hereinafter referred to as “E
CU ”), and an analog signal corresponding to each sensor signal and the voltage of the battery 21 is sent to the ECU 22. Further, the fuel tank 7 is provided with a conduit 24 for guiding the fuel evaporative gas in the fuel tank 7 to the charcoal canister 23.
The fuel evaporative gas introduced into the fuel cell 3 is adsorbed by the activated carbon 25 contained in the charcoal canister 23. A conduit 26 is connected to the charcoal canister 23,
This conduit 26 is connected to the conduit 2 via an electromagnetic proportional control valve 27.
8 is connected. The conduit 28 is connected to an introduction port 29 opening in the surge tank 3. Therefore, the fuel evaporative gas generated in the fuel tank 7 is
After being adsorbed and held in the charcoal canister 23, the fuel evaporative gas adsorbed and held in the charcoal canister 23 is introduced into the surge tank 3 from the introduction port 29 through the conduit 26, the proportional control valve 27, and the conduit 28. It A relief valve 30 is provided in the fuel tank 7, and the conduits 24, 26, 28 and the proportional control valve 2 are provided.
When the fuel evaporative gas cannot be guided to the surge tank 3 and the pressure of the fuel evaporative gas in the fuel tank 7 becomes high, such as when the fuel evaporative gas 7 becomes clogged, the fuel evaporative gas is released from the relief valve 30.

The proportional control valve 27 communicates with conduit 26 I
OUT port 3 through N port 31 and conduit 28
2 has a housing 33 in which a coil 34, a valve body 35 and a spring 3 are provided in the housing 33.
6 are provided. The proportional control valve 27 variably controls the passage area between the valve body 35 and the OUT port 32 depending on the position of the valve body 35 provided in a movable state. That is, the proportional control valve 27, normally the valve body 35, is set to the state where the passage area becomes zero by the spring 36. However, by supplying an exciting current to the coil 34, the valve body 35 is driven and the OUT port 32. Is configured to open, that is, by continuously changing and controlling the exciting current to the coil 34, the valve element 35
The flow rate of the fuel evaporative gas passing between the OUT port 32 and the OUT port 32 is controlled. In this case, the exciting current for the coil 34 controls the voltage applied to the coil 34 by controlling the ratio of the ON time TON (duty TON / T) to the constant period T as shown in FIG.
It is controlled by performing M. By changing this duty ratio, the average flow rate passing between the valve element 35 and the OUT port 32 changes as shown in FIG.

The proportional control valve 27 is driven by the ECU 22 like the fuel injection valve 6. Next, the configuration of the ECU 22 will be described with reference to FIG. In the figure, 40 is a central processing unit (CPU) that executes calculations such as fuel injection time and fuel evaporative gas introduction according to a predetermined program, 41 is a read-only memory (ROM) that stores programs and data in advance, and 42. Is a readable / writable memory (R
AM), 43 are digital input ports for inputting a pulse signal from the crank angle sensor 19 and an ON / OFF signal IDL from an idle switch in the throttle sensor 16, 4
Reference numeral 4 has an A / D conversion function for inputting an analog signal from the air flow meter 14, the intake air temperature sensor 15, the throttle sensor 16, the air-fuel ratio sensor 17, the water temperature sensor 18 and the battery 21 and converting the analog signal into a digital amount. An analog input port, 45 is an output circuit for outputting a drive signal to the fuel injection valve 6 and for converting a voltage applied to the coil 34 of the proportional control valve 27 into a pulse voltage signal having a predetermined duty ratio, and 47 is each of the above Data bus connecting circuits mutually, 48 is injection signal B / UTAU when CPU is abnormal
Injection back-up circuit that outputs in a hardware manner, 49 is C
A duty output backup circuit for backing up the output to the proportional control valve at the time of PU abnormality, 50 is a voltage comparator for comparing the air flow meter input voltage with a comparison potential, 5
Reference numeral 1 is an output port for sending a signal from the CPU 40 to the output circuit 45.

In the ECU 22 having the above structure, the signals from the respective sensors are processed by the input ports 43 and 44 and stored in the RAM 42. And R in CPU40
RAM42 according to the program stored in OM41
The calculation of the fuel injection time and the duty ratio for determining the fuel evaporative gas introduction amount is executed at predetermined timings using various data stored therein, and the calculation result is stored in the RAM 42. Thus, the RAM is obtained by the CPU 40.
Each calculation result stored in 42 is converted into an output signal according to the calculation result by the output circuit 45 in synchronization with the rotation of the engine 9 or at every predetermined time, and is converted to the fuel injection valve 6 or the proportional control valve 27. Is output.

The calculation of the fuel injection time is first obtained from the analog signal from the air flow meter 14 and is performed in the RAM 4
2 and the engine speed N stored in the RAM 42 obtained from the pulse signal from the crank angle sensor 19, the intake air quantity Q / N per engine revolution is calculated. The basic injection time T is calculated from this Q / N.
It is executed by the procedure of finding P. Next, when the feedback control for the stoichiometric air-fuel ratio is being executed, the basic injection time is calculated according to the correction value KA / F for the stoichiometric air-fuel ratio which is obtained from the analog signal from the air-fuel ratio sensor 17 and stored in the RAM 42. Correct TP. Water temperature sensor 1
8 and the correction values KTHW and KTHA set according to the engine cooling water temperature and the intake air temperature obtained from the analog signals of the intake air temperature sensor 15, and the effective injection time TE is obtained. Next, the invalid injection time TV set according to the change in the battery voltage is obtained, and this invalid injection time TV is added to the effective injection time TE to add the fuel injection time TINJ.
Ask for.

The output port 51 is equipped with a counter (not shown), sets the fuel injection time TINJ calculated by the CPU 40 as described above, and starts the countdown at a predetermined timing in synchronization with the rotation of the engine 9. The fuel injection valve 6 is energized until it becomes zero, and the fuel injection valve 6 is opened by performing the energization in this way to control the fuel injection amount.

The duty ratio of the output to the proportional control valve 27, which determines the amount of fuel evaporative gas introduced, is calculated according to a program stored in the ROM 41 as shown in FIG. To be executed. First, at step 101, it is determined whether the engine is starting or not. As the determination at the time of starting, the time when the starter 60 is on and the engine speed N is equal to or lower than a predetermined speed is the time of starting. If it is the starting time, step 112
If the engine is not started, the process proceeds to step 102. In step 102, it is determined whether or not it is within a predetermined time after starting. If it is within the predetermined time, the process proceeds to step 112, and if it is after the predetermined time has elapsed, the process proceeds to step 103. The predetermined time may be a short time, and is set to an arbitrary time within about 120 seconds, for example. In step 103, it is determined whether fuel is being cut. Whether or not the fuel is being cut is determined by, for example, the presence or absence of a fuel cut flag that is set when the idle switch is ON and the engine speed is equal to or higher than a predetermined speed. And if the fuel is being cut off, step 11
2, if the fuel is not being cut, the process proceeds to step 104.
In step 104, it is determined whether or not it is in the idle state. If it is in the idle state, the process proceeds to step 107, and if it is not in the idle state, the process proceeds to step 105.

In step 105, the ROM 41 shown in FIG.
The basic duty ratio DB is set according to the basic injection time TP and the engine speed N currently stored in the RAM 42 from the two-dimensional map stored and set inside. In addition,
The basic duty ratios DB of this two-dimensional map have little influence on the air-fuel ratio of the air-fuel mixture supplied to the engine 9 even if the intake amount of the fuel vapor increases as the intake air amount increases in a high load state. Therefore, the basic duty ratio DB is set so as to increase as the load increases.

In step 106, the ROM 41 shown in FIG.
The comparison injection time TO with respect to the effective injection time TE is set according to the basic injection time TP and the engine speed N currently stored in the RAM 42 from the two-dimensional map stored in the table, and the routine proceeds to step 109. . Each comparative injection time TO of this two-dimensional map is preset to a value smaller than the effective injection time TE corresponding to the theoretical air-fuel ratio in each region divided by the basic injection time TP and the engine speed N. , The comparison injection time T0 is a fixed value with respect to the intake air temperature THA and the engine cooling water temperature THW,
It may be increased or decreased according to HA or engine cooling water temperature THW.

When it is determined in step 104 that the engine is in the idle state, the basic duty ratio DB is set to 20% in step 107, and the comparative injection time TO is set to 1.6 ms in step 108. , Step 109
Proceed to. In step 109, the fuel injection time TINJ
The effective injection time TE calculated in the calculation and stored in the RAM 42 is compared with the comparative injection time TO.
In the comparison in step 109, during the feedback control with respect to the stoichiometric air-fuel ratio, the effective injection time TE is shortened if the air-fuel ratio becomes rich. Therefore, the effective injection time TE becomes shorter than the comparative injection time TO due to the fuel evaporation. This indicates that the air-fuel ratio has become remarkably rich due to the introduction of gas. Therefore, if TE <TO, the feedback duty ratio DFB set to the basic duty ratio DB in step 110 is set at the time of the previous passage of this routine. RAM4
The feedback duty ratio DFB-1 stored in 2 is set to a value smaller than the feedback duty ratio DFB-1 by a predetermined value ΔD1.
FB. If TE≥TO, then in step 111, a value larger than the previous feedback duty ratio DFB-1 by a predetermined value .DELTA.D2 is set as the current feedback duty ratio DFB. The predetermined values ΔD1 and ΔD2 in steps 110 and 111 are 1 to 3
It is set to a value of about%.

Further, the steps 101, 102, 103
If the answer is Yes in any of the steps and the process proceeds to step 112, the basic duty ratio DB is set to 0% in step 112, and the feedback duty ratio D is set in step 113.
FB is also 0%. In step 114, the basic duty ratio DB and the feedback duty ratio D obtained as described above
FB is added to obtain the output duty ratio D this time. In step 115, the current feedback duty ratio DFB obtained in step 110, step 112 or step 113 is set in the RAM 42 as DFB-1 for the next calculation. Then, in step 116, the output duty ratio D is output to the output circuit 45.

The output circuit 45 supplies a pulsed output signal having a duty ratio corresponding to the output duty ratio D to the proportional control valve 27, and in response to this output signal, the proportional control valve 2
7 attracts the valve body 35, and the valve body 35 and the OUT port 3
By variably controlling the passage area between the surge tank 3 and the fuel cell 2, the fuel evaporative gas corresponding to the passage area is introduced from the introduction port 29 into the surge tank 3.

In the above program, the comparison injection time T0 is set to a value corresponding to a value equal to or higher than the lower limit value at which the linearity characteristic of the injection amount of the fuel injection valve 6 is secured. By setting in this way, during the feedback control to the stoichiometric air-fuel ratio, the air-fuel ratio determined by the ratio of the sum of the injection amount from the fuel injection valve 6 and the introduction amount of the fuel evaporative gas and the air amount becomes the stoichiometric air-fuel ratio. Therefore, even if the injection amount from the fuel injection valve 6 is reduced by the air-fuel ratio feedback control and the effective injection time TE is shortened by the air-fuel ratio feedback control, if it is shorter than the comparative injection time TO, the fuel evaporative emission gas is reduced. Since the feedback duty ratio DFB is controlled so as to reduce the introduction amount of
Is controlled so as not to fall below the comparative injection time TO,
Therefore, it becomes possible to prevent the injection time from being set such that the linearity characteristic of the injection amount of the fuel injection valve 6 is impaired.

In the above-described embodiment, when the fuel evaporative gas is not introduced at the time of starting and within a predetermined time after the starting, there is a possibility that the fuel evaporative gas causes the air-fuel mixture to become overrich and that the engine cannot start or stall. Because there is. The determination in step 102 may be based on the number of revolutions instead of the time after the start.

Further, the reason why the introduction of the fuel evaporative gas is not executed during the fuel cut is that the fuel evaporative gas cannot be burned alone, so that the fuel evaporative gas is not burned but is directly discharged to the atmosphere. Although the comparative injection time TO is set for the effective injection time TE in the above embodiment, the comparative injection time TO may be for the basic injection time TP or the fuel injection time TINJ.

Therefore, in the above embodiment, since the amount of the fuel evaporative gas introduced is changed according to the amount of fuel injected from the fuel injection valve 6, the fuel evaporative gas can be introduced according to the state of the engine, and the mixture Since it is possible to introduce the fuel evaporative gas without significantly shifting the air-fuel ratio, the fuel evaporative gas can be introduced in a wide operating range including the idle state.

Next, the injection backup circuit 48 and the duty output backup circuit 4 which are the characteristic parts of this embodiment.
9, the voltage comparator 50, and the output circuit 45 will be described.
As shown in FIG. 9, the injection backup circuit 48 includes a backup injection signal generation circuit 71, a high rotation switch control circuit 72, a high rotation switch 73 switched by the high rotation switch control circuit 72, and a watchdog signal monitoring. A circuit 74 and a backup injection changeover switch 75 that is switched by the watchdog signal monitoring circuit 74 are provided.

The backup injection signal generation circuit 71 includes
As shown in FIGS. 9 and 10, the engine rotation signal NE, the starter signal STA, and the idle signal IDL are input. Then, as shown in detail in FIG. 10, the backup injection signal creation circuit 71 receives the NE terminal 81 to which the engine rotation signal NE is input, the STA terminal 82 to which the starter signal STA is input, and the idle signal IDL. I
It has a DL terminal 83 and an output terminal 84 for outputting the backup injection signal B / UTAU. The engine rotation signal NE is a pulse signal detected by the crank angle sensor 19 and changes as shown at the top of FIG. Further, the starter signal STA is a signal which becomes "1" when the starter is on and "0" when it is off, as shown in the third row from the top of FIG. In addition, the idle signal IDL
Is a signal which becomes "0" when the idle is on and "1" when it is off, as shown in the fourth row from the top of FIG.

In the backup injection signal generating circuit 71, between the NE terminal 81 and the output terminal 84,
Two comparators 85 and 86 are connected. At the negative input terminal of the first comparator 85, as shown in the second stage from the top of FIG. 11, it falls at the time of the fall of the engine rotation signal NE, and then has a time constant τ determined by the capacitor C1 and the resistor R1. A signal that changes accordingly is input. A predetermined comparison potential V1 is applied to the positive input terminal of the first comparator 85.
Has been entered. As a result, the first comparator 85
Outputs a signal that becomes high level for a short period of time after the engine rotation signal NE falls, as shown in the fifth row from the top of FIG. The output from the first comparator 85 switches the npn transistor TR1 connected immediately after.

On the other hand, the starter signal STA input from the STA terminal 82 is inverted by the inverter I1 located immediately thereafter, and the NAND circuit 87 and the other inverter I2 are inverted.
Entered in. In addition, the idle signal IDL input from the IDL terminal 83 is inverted by the inverter I3,
It is input only to the AND circuit 87.

The output terminal of the NAND circuit 87 and the output terminal of the inverter I2 are respectively connected to the pnp transistor T.
R11 and TR12 are connected. And each pnp
Resistors R11 and R12 connected to the collector terminals of the transistors TR11 and TR12, and another resistor R1
0 constitutes a parallel circuit and is connected to the collector terminal of the npn transistor TR1 shown in the upper part of the drawing together with the capacitor C10. Hereinafter, TR11 and STA transistor, TR
12 is called an IDL transistor.

The STA transistor TR11 puts the resistor R11 in parallel with the resistor R10 only when the starter is off. Further, the IDL transistor TR12 is
Resistor R12 only when idle is on and starter is off
Are connected in parallel with the resistor R10. Therefore, the three resistors R10, R11 and R12 are in parallel only when the starter is off and the idle is on. When the starter is off and the idle is off, the resistor R
10, R11 are connected in parallel. Then, when the starter is on, the STA transistor TR11 and the IDL transistor TR12 are turned off, and only the resistor R10 is alive.

In this way, the starter signal STA and the idle signal IDL form the time constant τ by the resistors R10 to R12 and the capacitor C10.
Npn transistor T connected immediately after the comparator 85 of
At the collector terminal of R1, as shown in the second stage from the bottom of FIG. 11, every time the first comparator 85 outputs a high level,
A signal waveform that changes differently depending on the on / off states of the starter and the idle switch is generated.

The signal waveform generated at the collector terminal of the npn transistor TR1 is compared with a predetermined voltage V2 by the second comparator 86, and is then supplied to another npn transistor TR2 connected downstream of the second comparator 86. Provides a switching signal. As a result of this switching signal, the output terminal 84 has the longest pulse at starter on, medium pulse at starter off and idle off, and shortest pulse at starter off and idle on, as shown at the bottom of FIG. Generate a signal.

In this way, the backup injection signal generation circuit 71 has three stages of backup injection signals each time the engine rotation signal NE is input from the crank angle sensor 19 in accordance with the states of the starter and the idle switch. B / UTAU is created in hardware.

As shown in FIG. 9, the engine speed signal NE is input to the high speed switch control circuit 72. Then, the high rotation switch control circuit 72 performs control by an internal hardware circuit to turn off the high rotation switch 73 when the input interval of the rotation signal NE becomes shorter than a predetermined value and turn it on in other cases. .

The watchdog signal monitoring circuit 74 has a C
The inverted signal (watchdog signal WD) from the PU 40 is input. The watchdog signal monitoring circuit 74 switches the backup injection changeover switch 75 to the backup injection signal B / UTAU side when the watchdog signal WD is no longer input by the internal hardware circuit, and otherwise the CPU injection signal. Control to switch to the side. When the watchdog signal WD is no longer input, the CPU abnormal signal FCPU is output.
This CPU abnormality signal FCPU is input to the output circuit 45 and the duty output backup circuit 49 as shown in FIG.

In this way, the injection backup circuit 48
When the CPU is normal, the CPU 40 outputs the injection signal TAU calculated by the CPU 40 as it is as the injection output.
When U is abnormal, the backup injection signal creation circuit 71 outputs the backup injection signal B / UTAU created by hardware. When the engine is rotating at high speed, the backup injection signal B / UTAU is not output and the fuel cut state is controlled.

Next, the duty output backup circuit 4
9 will be described. The duty output backup circuit 49 has a 3-input AND circuit 91 as shown in FIG.
A two-input AND circuit 92, an inverter for inverting one input of the AND circuit 92, and the AND circuit 9
It is composed of an OR circuit 93 which receives the outputs of 1 and 92 as inputs.

In the 3-input AND circuit 91, the comparison result signal from the voltage comparator 50 and the injection backup circuit 4 are supplied.
CPU abnormality signal FCPU from 8 and injection signal TAU (or B / UTAU) from injection backup circuit 48 as well.
And have been entered. By the way, the voltage comparator 50 is configured by a comparator in which the output voltage of the air flow meter 14 is input to the positive input terminal and a predetermined reference potential is input to the negative input terminal. Therefore, the voltage comparator 50 outputs a high level signal only when the air flow meter 14 outputs a voltage higher than a predetermined value.

As a result, the 3-input AND circuit 91 is constructed so that it can always output only the low level when the engine operating condition is less than the predetermined load. Further, the 3-input AND circuit 91 can only output a low level when the CPU is normal. When the CPU is abnormal and the airflow meter 14 outputs a voltage higher than a predetermined value, the backup injection signal B / UTA from the injection backup circuit 48 is output.
Output U as is.

On the other hand, the 2-input AND circuit 92 has a CP
The output duty ratio D for purge valve control, which is calculated by U40, and the CPU abnormality signal FCPU are input. Here, the CPU abnormality signal FCPU is inverted and input to the AND circuit 92. Therefore, this 2-input A
When the CPU is normal, the ND circuit 92 outputs the output duty ratio D as a purge valve control signal from the CPU 40 as it is.

As a result of such a configuration, the duty output backup circuit 49 is configured so that the CPU 4 operates when the CPU is normal.
0 outputs the output duty ratio D obtained by calculation as it is, and when the CPU is abnormal, the backup injection signal B / UTAU created by hardware in the injection backup circuit 48 is output as it is. When the CPU is in an abnormally low load operating state, the signal for controlling the purge valve is fixed at a low level, that is, the valve is fully closed.

Next, the state of the purge valve control when the CPU is abnormal in the system of the embodiment thus constructed will be described with reference to the timing chart of FIG. C
When the PU 40 is normal, a watchdog signal WD that periodically inverts is generated as shown in the leftmost part of the uppermost part in the figure. Therefore, the CPU abnormality signal FCPU by the watchdog signal monitoring circuit 74 is at low level. Further, during this period, the CPU 40 calculates and outputs the injection signal TAU and the output duty ratio D based on various detection signals and the like. As a result, the output duty ratio D from the CPU 40 is directly input to the proportional control valve 27 as an input voltage.

On the other hand, when the CPU 40 becomes abnormal, the watchdog signal WD does not invert as shown from time T1 onward in the uppermost row. As a result, the CPU abnormality signal FCPU output from the watchdog signal monitoring circuit 74 switches to high level. After that, the injection signal TA from the CPU 40
Neither U nor the output duty ratio D as the purge valve control signal can be obtained. Then, by the above-mentioned duty output backup circuit 49, in place of these signals, the backup injection signal B / UTAU created by hardware is used as the input voltage to the proportional control valve 27. This backup injection signal B / UTAU roughly reflects the intake air amount. As a result, even when the CPU is abnormal, the opening / closing control of the proportional control valve can be executed by reflecting the intake air amount.

When the engine load decreases and the output voltage from the air flow meter 14 decreases, the voltage comparator 50 switches to a low level output. As a result, the 3-input AND circuit 91 of the duty output backup circuit 49 can output only a low level output, and the proportional control valve 2
The input voltage to 7 is fixed at low level. Therefore, the proportional control valve 27 is fixed to be fully closed during the low load operation. By doing so, it is possible to prevent the occurrence of a situation in which the engine is stalled due to a remarkable overrich state due to purging during the low load operation.

When the engine speed becomes higher than a predetermined value, the control signal of the high speed switch control circuit 72 is inverted to high level, and as a result, the high speed switch 73 is turned off. Therefore, nothing is output from the injection backup circuit 48, and the proportional control valve 27 is also fixed to be fully closed. This prevents the purge from being performed during the fuel cut.

As described above, according to this embodiment, C
A backup injection signal B / UTAU generated by hardware in the injection backup circuit 48 even when a PU abnormality occurs
Is supplied to the proportional control valve 27 as a purge control signal.
Therefore, even when the CPU is abnormal, the purge control corresponding to the fuel injection amount can be continued. In this way, it is possible to solve the problems of the conventional engine stall due to overrich of the air-fuel ratio due to the fully open fixation and the leakage of the fuel evaporative gas from the canister due to the fully closed fixation.

When the intake air amount of the engine is small, the output to the proportional control valve 27 is fixed to OFF (fully closed),
Purging is not performed in the state where overrich is likely to occur due to the effect of purging. As a result, it is possible to avoid a situation in which an engine stall occurs during low load operation.

Further, when the engine speed exceeds a predetermined value, the backup injection signal B / UTAU is stopped, and accordingly, the output to the proportional control valve is also fixed to OFF. As a result, it is possible to prevent the engine speed from rising excessively in a hardware manner, and also to prevent the situation where unburned gas is discharged as it is during the fuel cut.

By the way, these remarkable actions and effects are
This is achieved by performing purge control based on the backup injection signal B / UTAU when the CPU is abnormal. For example, if the purge control is performed based on the NE signal when the CPU is abnormal, it will be difficult to control the purge to be stopped during the fuel cut, and the problem of unburned gas discharge will occur. Further, if the purge control is performed according to the vehicle speed signal, this also has a problem that unburned gas is discharged when the high speed switch is operating.

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments and can be implemented in various modes without departing from the scope of the invention. For example, the present invention can be applied to a system in which the fuel evaporative gas is directly introduced into the intake pipe without using the charcoal canister, for guarding at low load by the idle signal IDL. Is.

[0058]

As described above in detail, according to the fuel evaporative emission control device of the present invention, the purge control valve can be opened and closed even when the on-vehicle computer becomes abnormal, and the purge control at the time of this abnormality is achieved. However, since it is based on the fuel injection signal output from the backup circuit by hardware, the purge can be continued in a manner that reflects the intake air amount to some extent. As a result, it is possible to prevent the engine from stalling due to the overrich state, and conversely, the fuel vaporized gas from leaking from the introduction passage.

Particularly, according to the apparatus of the second aspect, since the purging is not performed in the state where the influence of the purging is likely to occur in the air-fuel ratio, the occurrence of a remarkable overrich state is suppressed,
It is possible to effectively prevent the occurrence of engine stalls and the like.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram illustrating a basic configuration of the present invention.

FIG. 2 is a schematic configuration diagram showing a system configuration of an embodiment.

FIG. 3 is a block diagram of a control system in the embodiment.

FIG. 4 is a waveform diagram of a voltage signal applied to the coil of the proportional control valve in the example.

5 is a duty ratio (TON / T) of the waveform shown in FIG.
FIG. 6 is a characteristic diagram showing the flow rate of fuel vaporized gas passing between an output port and a valve body for

FIG. 6 is a flowchart of a program for obtaining an output duty ratio D that controls the passage area between the output port and the valve body in the embodiment.

FIG. 7 is a map showing the setting of the basic duty ratio DB in the embodiment.

FIG. 8 is a comparative injection time T0 (unit: m
It is a map which shows the setting of s).

FIG. 9 is a block diagram showing a schematic configuration of an injection backup circuit in the embodiment.

FIG. 10 is a detailed circuit diagram of a backup injection signal generation circuit in the injection backup circuit.

FIG. 11 is a timing chart showing a relationship among an input signal, an output signal, and a signal at a main position of the backup injection signal generation circuit.

FIG. 12 is a timing chart showing the operation of the embodiment.

[Explanation of symbols]

3 ... surge tank, 4 ... intake pipe, 6 ... fuel injection valve, 7 ... fuel tank, 9 ... engine, 14 ...
・ Air flow meter, 15 ・ ・ ・ Intake air temperature sensor, 16 ・ ・
・ Throttle sensor, 17 ・ ・ ・ Air-fuel ratio sensor, 18 ・
..Water temperature sensor, 19 ... Crank angle sensor, 22 ..
..Control unit, 23 ... Charcoal canister,
27 ... Proportional control valve, 40 ... CPU, 45 ...
Output circuit, 48 ... Injection backup circuit, 49 ...
-Duty output backup circuit, 50 ... Voltage comparator, 60 ... Starter, 71 ... Backup injection signal generation circuit, 72 ... High rotation switch control circuit,
73 ... High rotation switch, 74 ... Watchdog signal monitoring circuit, 75 ... Backup injection changeover switch.

Claims (2)

[Claims] 1. An introduction passage for introducing the fuel evaporative gas generated in a fuel tank into an intake pipe, and a purge control valve provided in the introduction passage for adjusting a purge amount of the fuel evaporative gas according to an open / closed state. In a fuel evaporative emission control device comprising an operating condition detecting means for detecting an operating condition of an engine and an on-vehicle computer for controlling opening and closing of the purge control valve according to the detected operating condition, an abnormality of the on-vehicle computer is detected. An abnormality detecting means for detecting and an abnormal time purging means for controlling the opening and closing of the purge control valve according to the length of a fuel injection signal given from a backup circuit constituted by hardware when the vehicle-mounted computer is in an abnormal state are provided. A fuel evaporative emission control device. 2. The fuel evaporative emission control device according to claim 1, wherein when the load condition of the internal combustion engine is not more than a predetermined value, the abnormal-time purge means controls the purge control valve regardless of the fuel injection signal. A fuel evaporative emission control device, comprising a guard means for keeping the valve closed.