JPH0321744B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement in an evaporative fuel control device for an engine that supplies evaporated fuel from a fuel tank to an intake passage.

(Prior Art) Conventionally, as disclosed in Japanese Utility Model Application Publication No. 59-40561, an evaporative fuel control device for this type of engine has been equipped with a tank port on one side of a charcoal canister container filled with activated carbon. The tank port is connected to the fuel tank, and the purge port is connected to the intake passage of the engine to remove the evaporated fuel generated in the fuel tank when the engine is stopped. The vaporized fuel is adsorbed on activated carbon, and when the engine is started, the air introduced from the atmospheric port due to intake negative pressure causes the adsorbed fuel to be separated from the activated carbon and sucked into the intake passage. It is known what has been done.

(Problems to be Solved by the Invention) Incidentally, in such an engine evaporative fuel control device, a communication control valve is provided that connects the purge port to the intake passage. This control valve is opened only in the load range to effectively burn the evaporated fuel.

However, in this case, the supply of evaporated fuel to the intake passage is started or stopped by opening and closing the control valve as the engine operating conditions change, so the air-fuel ratio in the intake passage changes rapidly, causing the engine output torque to change. The problem is that it becomes unstable.

This invention has been made in view of the points related to the present invention, and its purpose is to gradually change the amount of evaporated fuel supplied to the intake passage in accordance with changes in engine operating conditions, thereby reducing fluctuations in the air-fuel ratio. The purpose is to make the process run smoothly.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention includes a fuel storage section for storing fuel and a fuel vapor adsorbent for adsorbing vaporized fuel in the fuel storage section. An adsorbent built-in part, an evaporative fuel supply passage that communicates the adsorbent built-in part and an intake passage that supplies intake air to the engine, a solenoid valve that opens and closes the evaporated fuel supply passage, and an operating state that detects the engine operating state. a detection means, a basic signal generating means for generating a basic signal for controlling the electromagnetic valve based on the output of the operating state detecting means, and a basic signal generating means for generating a basic signal for controlling the electromagnetic valve based on the output of the operating state detecting means; and a changing means for changing the manner in which the basic signal changes gradually, the basic signal comprising a duty ratio of opening and closing of the electromagnetic valve and a duty control frequency that is approximately inversely proportional to the duty ratio. That is.

(Function) With the above configuration, a solenoid valve that opens and closes the evaporated fuel supply passage, an operating state detecting means that detects the engine operating state, and a basic signal that controls the solenoid valve based on the output of the operating state detecting means are generated. After the engine starts, if the operating state detection means determines that the purge control region is reached, the solenoid valve is opened by the basic signal generated by the basic signal generation means to prevent evaporation. While the adsorbed fuel of the fuel adsorbent is purged, if it is determined that the adsorbent is not in the purge control region, the electromagnetic valve is closed by the basic signal and the purge is stopped.

Further, since the basic signal generated by changing with the change in the engine operating state is provided with a changing means for changing the changing state of the basic signal such that the basic signal is gradually changed, the basic signal generated by the basic signal generating means is Since the signal gradually changes and the amount of vaporized fuel supplied to the intake passage gradually increases or decreases, the air-fuel ratio in the intake passage changes smoothly.

Furthermore, since the basic signal of the basic signal generating means consists of the duty ratio of the opening/closing of the solenoid valve and the duty control frequency that is approximately inversely proportional to the duty ratio, , the set duty ratio becomes smaller, and the frequency of duty control increases accordingly, so that purge is performed at a smaller rate.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 shows a schematic configuration of an evaporative fuel control device for an engine according to an embodiment of the present invention, in which 1 is an engine, 2 is an intake passage for supplying intake air to the engine 1, and 3 is an exhaust gas from the engine 1. The intake passage 2 is an exhaust passage for discharging
A throttle valve 4 is provided to control the amount of intake air supplied to the engine 1.

Reference numeral 5 denotes a fuel tank 5 serving as a fuel storage section for storing fuel, and an upper space of the fuel tank 5 is provided with an evaporative fuel for adsorbing evaporated fuel into the upper space via an evaporative fuel supply passage 6a. Adsorbent 7
It is communicated with a canister container which is a built-in part of the adsorbent.

Further, the canister container 7 is communicated with the intake passage 2 downstream of the throttle valve 4 via the evaporated fuel supply passage 6b, and after the engine 1 is started, an atmospheric port 9 provided in the canister container 7 is connected to the canister container 7. 7 is sucked into the intake passage 2 by the intake negative pressure, and the flow of this atmosphere causes the adsorbed fuel of the evaporated fuel adsorbent 8 to be separated and sucked into the intake passage 2 for purging. I have to.

Further, a solenoid valve 10 is provided in the fuel vapor supply passage 6b to linearly change the passage area of the fuel vapor supply passage 6b. The solenoid valve 10 is
Duty control is performed by a controller 11 included in the CPU, and signals of the rotational speed and boost pressure of the engine 1 are input to the controller 11.

Next, the operation of the controller 11 will be explained using the flowchart shown in FIG. 2. After starting, the set duty ratio _D0 is initialized to 0 in step _S1 , and then the engine speed and boost pressure are changed in step _S2 . Based on the signal, it is determined whether or not the engine 1 is in a purge control area set outside the low rotation and low load area, and if NO is outside the purge control area, the purge control is stopped in step _S3 . YES in the _purge control area.
In this case, proceed to the next step _S4 to perform purge control.
Proceed to.

In step _S4 , a target duty ratio _D1 of the solenoid valve 10 is determined to perform purging according to the engine speed and load. Then, in step _S5 , the difference S= _D1 - _D0 between the target duty ratio _D1 and the set duty ratio _D0 is calculated, and if S>0, the set duty ratio _D0 is smaller than the target duty ratio _D1 , the step In step _S6 , a positive constant K is added to the set duty ratio _D0 . On the other hand, when the set duty ratio _D0 is larger than the target duty ratio _D1 and S<0, K is added from the set duty ratio _D0 in step _S7 . pull,
Also, the set duty ratio D ₀ is the target duty ratio D ₁
When S=0, which is equal to , D ₀ is held as is.

Next, in step _S8 , the duty control frequency f
is set to be approximately inversely proportional to the set duty ratio _D0 . Then, in step _S9 , the solenoid valve 1 is adjusted based on the set duty ratio _D0 and the set frequency f.
0 is activated, and in the next step _S10 , it is determined whether the set duty ratio _D0 has reached the target duty ratio _D1.If YES, that is, _D0 matches _D1 , the process returns to step _S2 . D ₀ has not reached D ₁
If NO, the process returns to step _S5 and the operation of adding or subtracting K is continued so that _D0 matches _D1 .

In the above flow, the operating state detection means 1 detects the operating state of the engine 1 in step _S2 .
At the same time, in step _S9 , a basic signal generating means 13 for controlling the solenoid valve 10 is formed based on the output of the operating state detecting means 12, and in steps _S15 to _S17 , the basic signal generating means 13 is configured. A changing means 14 is configured to change the manner in which the basic signal changes so that the basic signal generated in the basic signal changes gradually.

Therefore, in the above embodiment, as shown in FIG. 3, if the target duty ratio D ₁ is set by entering the purge control region from outside the purge control region, for example, Since the duty ratio D ₀ gradually increases by K, the amount of vaporized fuel supplied to the intake passage 2 due to purge gradually increases, so that the air-fuel ratio of the intake passage 2 changes smoothly. The output torque of the engine 1 is stable, and when this engine 1 is mounted on a vehicle, good running performance can be obtained.

Incidentally, even when moving from the purge control region to outside the purge control region, the set duty ratio D ₀ gradually decreases by K, and the same effect can be obtained.

Furthermore, since the frequency f of duty control is approximately inversely proportional to the set duty ratio D ₀ , the set duty ratio D ₀ is small in the purge control region close to the low rotation and low load region of the engine, and this causes the frequency f is set high and purge is performed in small increments, so the intake air and evaporated fuel are mixed well, contributing to improved combustibility.

(Effects of the Invention) As explained above, according to the evaporative fuel control device for an engine according to the present invention, the basic signal is controlled so that the above-mentioned change in the basic signal that changes and occurs as the engine operating condition changes is gradually performed. Since the change means for changing the manner in which the signal changes is provided, the basic signal generated by the basic signal generating means gradually changes, and the amount of vaporized fuel supplied to the intake passage gradually increases or decreases. The air-fuel ratio in the passage changes smoothly, and the engine's output torque becomes stable.

Furthermore, since the basic signal of the basic signal generating means consists of a duty ratio for opening and closing the solenoid valve and a duty control frequency that is approximately inversely proportional to the duty ratio, in the purge control region close to the low rotation and low load region of the engine, Since the frequency of duty control is increased and purge is performed at a smaller rate, intake air and evaporated fuel are mixed well, improving combustibility.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic configuration diagram of an engine evaporative fuel control device, FIG. 2 is a flowchart showing the operation of the controller, and FIG.
The figure is an explanatory diagram showing the operation of the solenoid valve. DESCRIPTION OF SYMBOLS 1...Engine, 2...Intake passage, 5...Fuel tank, 6b...Evaporative fuel supply passage, 8...Evaporative fuel adsorbent, 10...Solenoid valve, 12...Operating state detection means, 13... Basic signal generating means, 14... changing means.

Claims (1)

[Claims] 1. A fuel storage part that stores fuel, an adsorbent built-in part that contains an evaporated fuel adsorbent that adsorbs evaporated fuel in the fuel storage part, and an intake passage that supplies intake air to the engine are connected to each other. an evaporated fuel supply passage to open and close the evaporated fuel supply passage; an operating state detection means for detecting the operating state of the engine; and a basic signal for controlling the solenoid valve based on the output of the operating state detection means. and a changing means for changing the manner in which the basic signal changes so that the basic signal that changes and is generated as the engine operating condition changes gradually. An evaporative fuel control system for an engine, wherein the signal is comprised of a duty ratio for opening and closing the electromagnetic valve and a duty control frequency that is approximately inversely proportional to the duty ratio.