JP2618970B2 - Engine fuel supply system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for supplying fuel to an engine,
More specifically, the present invention relates to an evaporative fuel supply device that appropriately suppresses the air-fuel ratio fluctuation due to the supply of the evaporative fuel.

2. Description of the Related Art There is a well-known engine system in which fuel evaporated in a fuel tank or the like is trapped on a canister to prevent air pollution, and the trapped fuel is returned to an air-fuel mixture.

Further, as disclosed in Japanese Patent Application Laid-Open No. 61-19962, a so-called linear purge system is also disclosed. In this publication, a duty control valve is provided between the intake passage and the canister. The duty ratio for controlling the purge flow rate to the intake path is set such that the purge flow rate increases when the intake air amount is large, and the duty ratio controls the purge flow rate when the intake air amount is small.
The control is performed so that the purge flow rate is reduced. By doing so, the fluctuation of the air-fuel ratio due to the inflow of the purge gas is suppressed to a minimum.

(Problems to be Solved by the Invention) By the way, the above-mentioned canister and the fuel tank are not always in continuous communication. Generally, an on-off valve is interposed, and the gas pressure difference between the canister and the tank becomes a predetermined value. (See (a) of FIG. 8), and this valve is opened to communicate. That is, when this on-off valve is opened (eighth
(See (b) in the figure.) In the figure, the evaporated fuel gas accumulated in the tank moves to the canister side in a large amount in a short period of time, so that the total amount of purge flow does not change.
The fuel components are getting richer. The flow of the rich purge gas into the intake passage causes a large change in the air-fuel ratio (see FIG. 8 (d)). In FIG. 8, in order to clarify the location of the problem, it is assumed that the intake air amount is constant (constant load), and therefore the purge flow rate is constant by the linear purge. This represents the air-fuel ratio fluctuation.

That is, in the linear purge system, the purge amount is controlled in accordance with the intake air amount regardless of the open / closed state of the open / close valve. And the fuel concentration in the purge gas is significantly different. The non-linear fluctuation of the fuel concentration is a factor that greatly degrades the air-fuel ratio control, particularly by the linear purge flow rate control.

Therefore, the present invention has been proposed to eliminate the above-mentioned drawbacks of the conventional example, and its object is to provide an air-fuel ratio supplied to an engine regardless of the open / close state of an on-off valve provided between a canister and a fuel tank. The present invention proposes an evaporative fuel supply device for an engine that suppresses fluctuations in the fuel vapor.

(Means and Actions for Solving the Problems) As shown in FIG. 1, the configuration of the present invention for achieving the above-mentioned objects comprises a canister for trapping evaporated fuel, a fuel tank and the canister. A first communication pipe for communicating and guiding the fuel vapor to the canister; and a first communication pipe provided in the middle of the first communication pipe, and changing the first communication pipe from a closed state to an open state under a predetermined condition. A second communication path for communicating a purge gas purged from the canister to the intake path, and a second communication path provided in the middle of the second communication pipe. A flow control means for controlling the flow rate of the purge gas substantially linearly; and a correction means for correcting the purge gas flow rate by the flow rate control means in a decreasing direction when the on-off valve is in an open state. That Features.

(Example) Hereinafter, an example in which the present invention is applied to a fuel injection engine will be described with reference to the accompanying drawings.

FIG. 2 is an overall view of the engine. In the figure, reference numeral 1 denotes an air cleaner, and 2 denotes a hot wire air flow meter. Reference numeral 11 denotes an engine body, and reference numeral 20 denotes an engine control unit (ECU) that controls the engine.

By the air flow meter 2, the intake air amount Q _a is measured.
Reference numeral 3 denotes a throttle valve, the opening of which is a signal T from the ECU 20.
V adjusts through the actuator 4. The opening TVO of the slot valve 3 is monitored by an opening sensor 7. At idle, the throttle valve 3 is in a fully closed state, and a signal IDLE is generated by a switch (not shown) in the sensor 7 according to the fully closed state. The upstream and downstream of the throttle valve are bypassed by a bypass passage 5. The amount of air passing through the passage 5 is controlled by the opening ratio of the duty solenoid valve 6 based on a signal ISC from the ECU 20. During idling, the idling engine speed is controlled by the amount of air controlled by the solenoid valve 6 passing through the bypass passage.

8 is a surge tank, 9 is a Injiekuta for injecting fuel, fuel injection quantity, the ECU 20, a pulse signal for defining an intake air amount Q _a, the fuel injection amount calculated based on the engine rotational speed N, and the like is controlled by τ. 11
Is an engine body, 15 is a piston, and 16 is a cylinder. 10 is a temperature sensor for measuring a coolant temperature T _W flowing through the cylinder 16.

Reference numeral 13 denotes an air-fuel ratio sensor whose output E is used for feedback control for purifying exhaust gas. 21 is an ignition coil, 22 is a distributor, 24 is an engine speed sensor (the output is the engine speed N), and 23 is a spark plug.

Reference numeral 27 denotes a fuel tank, reference numeral 26 denotes a canister for trapping the vaporized fuel, and reference numeral 30 denotes a communication pipe for guiding the vaporized fuel trapped by the canister 26 to the surge tank 8. Communication pipe
A valve 25 provided in the middle of 30 is a duty ratio control solenoid valve for controlling a purge flow rate. The aperture ratio of the solenoid 25 is controlled by a signal PC from the ECU 20. The fuel tank 27 is a canister 26
Are communicated by a communication pipe 31, and a check valve 29 and a two-way valve 28 are interposed in the middle of the communication pipe 31. The check valve 29 is normally closed to the atmosphere side, but opens to the atmosphere side to release the evaporated fuel gas to the atmosphere when the gas pressure in the tank 27 becomes too high. A cross-sectional view of the two-way valve 28 is shown in FIG. As shown in the figure, the two-way valve 28 is provided with valves 40 and 41, and these valves slide according to the difference between the pressure in the tank and the pressure in the canister, and one of the valves is opened. It has become. Since the valves 40 and 41 are urged in the closing direction by the springs 40a and 41a, respectively, they will not be opened unless the pressure difference exceeds a predetermined value.
A switch actuator 42 is connected to a valve 40 that opens when the pressure on the fuel tank 27 side increases, and when the valve 40 opens, the two switch contacts 43 are closed by the actuator 42. When the switch is closed, a signal V _SW = 1 is sent to the ECU 20. That is, the ECU 20
By monitoring the V _SW, whether the fuel gas from the tank 27 is supplied to the Kiyanisuta 26 it can be determined.

The air-fuel ratio control in the engine shown in FIG. 2 is performed by controlling the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber of the engine 11 based on the negative feedback control performed based on the output signal E of the air-fuel ratio sensor 13 and the evaporation control. The purge gas containing the fuel is controlled by controlling the purge flow rate.

In the former air-fuel ratio control based on feedback control, it is determined whether the exhaust gas is presently rich or lean based on the output E of the air-fuel ratio sensor 13 and the air-fuel mixture supplied to the combustion chamber of the engine is determined. the ratio, for the intake air amount Q _a had it occurred in measuring the air flow meter 2, is made Te cowpea to meter a injection amount τ of the fuel injected from Injiekuta 9. That is, if the basic fuel injection amount is τ ₀ and the correction coefficient of the air-fuel ratio feedback control is C _FB , then τ = τ ₀ (1 + C _FB + C ₀ ). Here, C ₀ is a correction term based on the engine water temperature T _W and the like.

On the other hand, the purge flow rate control of the rear vehicle determines the basic purge amount PC ₀ (so-called linear purge amount, an example of which is shown in FIG. 6A) based on the intake air amount, and further determines the two-way valve described above. when 28 is opened is that of correcting the basic amount of purge PC _0. Final purge flow PC in consideration of this correction, the correction coefficient is C _P, is expressed as PC = PC ₀ * C _P. By this correction, the air-fuel ratio fluctuation of the air-fuel mixture when the two-way valve 28 is opened can be suppressed.

Air-fuel ratio fed back control of this embodiment is well known, to explain the outline, the basic fuel injection amount based on the engine speed N and the intake air amount Q _a read τ
Calculate ₀ .

Here, K is a predetermined constant. The output E of the air-fuel ratio Ensa 13 read is equal to a predetermined slice level E ₀ or more, integrating the air-fuel ratio correction coefficient C _FB in the negative direction. That is, C _FB = C _FB − △ I ₀ . Here, ΔI ₀ is a predetermined integration constant. Conversely, if the sensor output E is less than the threshold value E _0, performing the integral of the positive direction. That is, C _FB = C _FB + △ I ₀ .

Next, the purge flow rate control will be described. First, the conditions under which the purge flow rate control is performed will be described with reference to FIG. The condition (F _PRG = 1) is a condition in which the air-fuel ratio feedback control execution condition * IDLE = 0 * T _W > T ₀ * {(NCL = 0) + INH = 0)} is satisfied. The air-fuel ratio feedback control execution condition refers to, for example, a case where the engine speed is equal to or higher than a certain speed. IDLE = 0 indicates that the vehicle is not currently idling. T ₀ is a predetermined threshold value for the engine coolant temperature T _W comparison. NCL = 0 means mechanical AT not shown in FIG.
(Automatic transmission) indicating that the vehicle is not currently in the neutral state. INH = 0 is also a signal from the AT and indicates that automatic shifting is not currently prohibited. The above flag
The F _PRG can be read at any time from an input port of a CPU (not shown) in the ECU 20.

With reference to FIG. 5, the purge flow rate control according to the present embodiment will be described. In step S2, the engine speed N, reads the basic fuel injection amount tau _0. As described above, the fuel injection amount is calculated and stored according to the air-fuel ratio control routine. In step S4, the signals IDLE, V _SW and flag F _PRG are read. In step S8, follow the flag F _PRG read connexion, if if the current is not in condition to be operated purge control execution, nothing, and returns to the main routine.

If the current state is such that the purge control execution operation is to be performed, the process proceeds to step S10, where the basic purge flow rate PC ₀ (according to the current engine speed N) is obtained from the purge flow rate map for linear purge control stored in the ECU 10. Duty ratio)
Is read. The characteristics of this map are shown in FIG. 6A. In addition, 6A
In the figure, a certain engine speed N and the intake air Q _{a at} that time are shown.
Is a map when the engine speed N is changed when τ ₀ is fixed to 1.3 ms as an example. As previously mentioned, Therefore, when τ ₀ is fixed, when N is increased, Q _a also increases, and the basic purge flow rate PC ₀ also increases according to the characteristics shown in FIG. 6A.

In step S12, the signal _WSW is checked. When V _SW = 0, since the valve 28 is currently closed, there is no inflow of rich evaporated fuel gas from the fuel tank 27, and therefore, it is not necessary to consider the air-fuel ratio fluctuation due to the rich gas. , the process proceeds to step S24, and "1" as the correction coefficient C _P. Then, in step S26, the final purge flow rate PC is determined to be PC = PC ₀ (∵C _P = 1), and in step S18, the duty solenoid valve 25 is opened according to the value of PC.

The control in the case where it is detected in step S12 that the valve 28 has been opened for the first time since the valve was closed will be described. In this case, step S12 → step S14 → step
Proceed to S16. In step S16, a timer (not shown) provided in the ECU 20 is started. Once started, this timer is a counter that counts up from 0 at regular intervals, and a CPU (not shown) in the ECU 20 can read the count value. Therefore, in step S18, the count value is read, and in step S20, it is checked whether the timeout value has been reached. This timeout value is a value corresponding to a time of 2 to 3 seconds, for example.

If it is determined in step S20 that the timeout has not yet occurred, the process proceeds to step S22, where a predetermined constant C _P0 (<
Connexion reading 1) from Matsupu, this value and the correction constant C _P for purge flow rate correction. In step S26, the final purge flow rate PC is calculated. The constant C _P0 has the following characteristics. That, tau _{0 =} the fundamental purge flow PC ₀ having the properties as Figure 6A which was 1.3 ms, when calculating the PC = PC ₀ * C _P, the final purge flow PC shown in Figure 6B
Are obtained.

The control operation limit such purge flow, whether V _SW at step S12 is detected as "0", if the timeout at step S20 is detected, and continues until any earlier state of. When any of the above condition is detected, the process proceeds to step S24, the correction coefficient C _P, and C _P = 1. After this, the normal basic purge flow rate PC
A purge gas having a flow rate according to ₀ (set in step S10) is introduced into the surge tank.

FIG. 7 shows an operation progress of the control according to the control of the present embodiment in comparison with FIG. As shown in FIG. 4C, the purge flow rate is regulated for a few seconds after the valve 28 is opened, so that the fluctuation of the air-fuel ratio accompanying the flow rate is suppressed as much as possible. as a result. Deterioration of emission, and deterioration of drivability due to over-richness, over-lean, etc. of the air-fuel ratio of the air-fuel mixture are also prevented.

In the above embodiment, the case where the present invention is applied to a fuel injection type engine has been described. However, the present invention can be similarly applied to an engine with a carburetor.

Moreover, the characteristic of the correction coefficient C _P is been filed but for the time change having a constant value, generally, the two-way valve 28 is opened, dark evaporated fuel gas initially opened within Kiyanisuta 26 because those flows may be filed be such as to converge to "1" with the passage of the C _P time.

In the embodiment shown in FIG. 2, the engine of a mechanical AT vehicle is described as an example. However, signals such as NCL and INH are used only for executing the purge flow rate control, and the two-way valve 28 is opened. In view of the gist of the present invention that the air-fuel ratio fluctuation at the time is suppressed, the present invention can be applied to an MT (manual transmission) vehicle in the same manner.

Further, it is needless to say that the present invention is not limited to the configurations of the above-described embodiments and modified examples, and can be variously modified without departing from the gist of the present invention.

(Effect of the Invention) As described in detail above, according to the evaporative fuel supply device for an engine according to the present invention, when the open / close valve for controlling the communication state between the fuel tank and the canister is open, the fuel is supplied to the engine. Since the purge flow rate is regulated in a decreasing direction, the fluctuation given to the air-fuel ratio is small. Therefore, for example, the emission and the deterioration of driving performance are prevented.

[Brief description of the drawings]

FIG. 1 is a view showing a configuration of the present invention, FIG. 2 is a view of an engine system according to an embodiment to which the present invention is applied, FIG. 3 is a sectional view of a two-way valve 28 used in the embodiment, FIG. FIG. 5 is a diagram showing conditions for judging whether purge flow control should be performed, FIG. 5 is a flow chart for controlling operation of the embodiment, FIG. 6A is a diagram showing characteristics of purge flow in linear purge, and FIG. FIG. 7 is a timing chart illustrating the characteristics of the purge flow rate correction according to an example, FIG. 7 is a timing chart illustrating the operation result according to the present embodiment in time series, and FIG. 8 is a timing chart illustrating a problem in the conventional example. In the figure, 1 ... air cleaner, 2 ... hot wire type air flow meter,
3 ... Throttle valve, 4 ... Throttle valve actuator, 5 ... Bypass passage, 6 ... ISC solenoid valve, 7
…… Throttle opening sensor, 8 …… Surge tank, 9…
... Injector, 10 ... Water temperature sensor, 11 ... Engine body, 13 ... Air-fuel ratio sensor, 14 ... Catalyst converter, 15 ...
... Piston, 16 ... Cylinder, 20 ... Engine control unit (ECU), 21 ... Ignition coil, 22 ... Distributor, 23 ... Spark plug, 24 ... Rotation sensor, 25 ... Purge flow rate Solenoid valve, 26 ... Canister, 27 ... Fuel tank, 28 ... Two-way valve, 29
... check valves, 30, 31 ... communication pipes, 40, 41 ... sliding valves, 41a, 41b ... springs, 42 ... switch actuators, 43 ... switch contacts.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuo Kurumi Minami 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd.

Claims (1)

(57) [Claims] 1. A canister for trapping vaporized fuel, a first communication pipe for communicating a fuel tank with the canister, and for guiding evaporated fuel to the canister, and a first communication pipe in the middle of the first communication pipe. Provided under predetermined conditions,
An on-off valve for changing the first communication pipe from a closed state to an open state, a second communication for communicating the canister with an intake path of an engine, and for guiding purge gas purged from the canister to the intake path. A passage, a flow control means provided in the middle of the second communication pipe for controlling the flow rate of the purge gas substantially linearly; and a flow rate of the purge gas by the flow control means when the on-off valve is open. And a correcting means for correcting the pressure in a decreasing direction.