JPH01106971A - Evaporated fuel controller for engine - Google Patents

Abstract

PURPOSE:To prevent evaporated fuel from leakage and air fuel ratio from fluctuation by regulating the evaporated fuel to an intake system to fit the degree of fuel evaporation on the basis of alcohol mixing rate of fuel in a fuel reservoir. CONSTITUTION:An evaporated fuel conducting path 32 opening to an upper space of a fuel tank 30 is opened to the upper end of an adsorbent layer (activated charcoal) in a canister 40. An opening 40a in the upper end of canister 40 communicates to an evaporated fuel discharging path 45 provided with a flow regulating valve 47 through a diaphragm type switch valve 42. Floats 51-53 responsive to the alcohol mixing rate in the fuel are provided in the fuel tank 30, and detecting switches 55-57 responsive to these floats are connected to a control unit 100 for controlling the flow regulating valve 47. The control unit 100 calculates the degree of fuel evaporation on the basis of alcohol mixing rate to control the flow regulating valve 47 fitting the degree of evaporation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an evaporative fuel control device for an engine that causes evaporative fuel generated in a fuel tank or the like to be consumed as part of the fuel within the engine.

(Prior art) Automotive engines generally use gasoline as fuel, but for economical reasons, a mixed fuel obtained by mixing gasoline and alcohol such as methanol has been developed. Some have even been put into use. For example, Japanese Unexamined Patent Publication No. 57-122149 discloses an engine in which a fuel supply system is equipped with a carburetor and uses a mixed fuel. The alcohol concentration in the mixed fuel stored in the fuel mixture is detected, and the amount of air bleed in the carburetor is changed according to the detected output, thereby suppressing fluctuations in the air-fuel ratio due to differences in the alcohol concentration in the mixed fuel. There is.

In addition, with the main purpose of preventing air pollution in engines installed in automobiles, adsorbents such as activated carbon are used to absorb evaporated fuel generated in fuel reservoirs such as fuel tanks and float chambers of carburetors when the engine is stopped. A evaporated fuel processing system is provided in which evaporated fuel is stored in a canister, and when the engine is operating, the evaporated fuel is guided from the canister to the intake system using intake negative pressure to be consumed within the engine. Such an evaporative fuel processing system is also applied to an engine that uses the above-mentioned mixed fuel.

(Problems to be Solved by the Invention) However, in conventional engines in which the evaporative fuel treatment system is activated even when mixed fuel is used, problems arise due to differences in alcohol concentration in the mixed fuel. It is considered to be inconvenient. That is,
In mixed fuel, the mixing ratio of alcohol is not necessarily constant, but the alcohol concentration is said to vary over a relatively wide range. The degree of evaporation of the fuel mixture in the reservoir will vary depending on the alcohol concentration in the fuel mixture; therefore, once the evaporated fuel treatment system is configured for a given fuel mixture, other fuel mixtures may be used. In such a situation, the evaporated fuel treatment system may not be able to properly process the evaporated fuel.

For example, if the evaporative fuel treatment system is set to handle a predetermined mixed fuel, and a mixed fuel with a higher alcohol concentration than the predetermined mixed fuel is used, evaporated fuel will be guided from the fuel reservoir into the canister. The amount of evaporated fuel becomes excessive with respect to the amount of evaporated fuel supplied from the canister to the intake system, resulting in a problem that the excess evaporated fuel leaks out from the canister. Conversely, when a mixed fuel with a lower alcohol concentration than the above-mentioned predetermined mixed fuel is used, the amount of evaporated fuel guided from the fuel storage section into the canister is small, and is supplied from the canister to the intake system. As a result, the air-fuel ratio of the air-fuel mixture led from the intake system to the combustion chamber becomes leaner than the target value, which affects engine operating performance, exhaust purification performance, etc. This causes an inconvenience that results in a decrease in performance. - In view of this, the present invention is applicable to an engine that uses a mixed fuel obtained by mixing gasoline and alcohol, or an engine that selectively uses both such a mixed fuel and gasoline. It is said that the fuel vapor generated in the fuel storage section is guided to the intake system of the engine and consumed in the combustion chamber, and the mixing ratio of alcohol in the fuel stored in the fuel storage section is changed. Even in the case of leakage of evaporated fuel to the outside,
Another object of the present invention is to provide an evaporative fuel control device for an engine that can efficiently process evaporated fuel without deteriorating engine operating performance or exhaust purification performance.

(Means for Solving the Problems) In order to achieve the above-mentioned object, an engine evaporative fuel control device according to the present invention has the following basic configuration as shown in FIG.
An evaporative fuel supply means that guides evaporative fuel generated in a fuel storage section provided for the engine to the intake system of the engine, and a mixture that detects the mixing ratio of alcohol in the fuel stored in the fuel storage section or information related thereto. In addition to the ratio detection means, a supply amount control means is provided, and the supply amount control means controls the intake system by the evaporated fuel supply means in accordance with the detection output obtained from the mixture ratio detection means. The operation is performed to adjust the amount of evaporated fuel introduced to the fuel vapor.

(Function) In the evaporated fuel control device for an engine according to the present invention having the above-described configuration, the supply amount control means detects the fuel stored in the fuel storage section based on the detection output obtained from the mixture ratio detection means. The amount of evaporated fuel introduced into the intake system of the engine by the evaporated fuel supply means is adjusted according to the alcohol mixing ratio or information related thereto.

By doing this, even if the mixing ratio of alcohol in the fuel differs depending on the fuel used, the amount of evaporated fuel supplied to the intake system will depend on the degree of evaporation of alcohol in the fuel used. As the adjustment is made, there may be a situation where the evaporated fuel leaks to the outside, or the evaporated fuel is not sufficiently supplied to the intake system, and the air-fuel ratio deviates significantly from the target value to the negative side, resulting in poor engine operating performance and exhaust purification performance. This effectively prevents a situation where the fuel consumption decreases, and the evaporated fuel is efficiently consumed within the combustion chamber.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an example of an engine evaporative fuel control device according to the present invention, together with the main parts of an engine to which the device is applied.

In FIG. 2, a piston 121 inserted into the cylinder 11
Spark plug 17. An intake passage 15 and an exhaust passage 16 that connect a combustion chamber 19 are connected to an engine body 10 formed of an intake valve 13, an exhaust valve 14, and the like. An air filter 18 and a carburetor 20 are disposed in the intake passage 15 in this order from the upstream side. The carburetor 20 is provided with a float chamber 21, a pair of throttle valves 22 that are linked to an accelerator pedal, and main system and slow system fuel passages (not shown), and the engine is fed through each fuel passage. Fuel is supplied to the intake passage 15 in an amount depending on the operating state.

The float chamber 21 of the carburetor 20 is provided with a needle valve 27 that is opened and closed by a float 26. When the needle valve 27 is opened, the fuel tank 3
0 is supplied to the intake passage 15 through a fuel supply passage 25 in which a pump 23 is interposed. An evaporative fuel outlet passage 32 is provided in the upper space of the fuel tank 30.
One end is open, and the other end of the evaporated fuel outlet passage 32 is opened to the upper end of the evaporated fuel adsorbent Ji41 made of activated carbon or the like contained in the canister 40. An opening 40a provided at the upper part of the canister 40 is communicated with one end of an evaporative fuel discharge passage 45 in which a flow rate regulating valve 47 is interposed via a diaphragm type on-off valve 42, and the evaporative fuel is discharged. The other end of the passage 45 opens into the intake passage 15 on the downstream side of the throttle valve 22 in the carburetor 20 .

Note that the flow rate regulating valve 47 is configured such that the larger the pulse occupancy rate of the drive pulse signal Cp supplied from the control unit 100 (to be described later), the longer the flow rate regulating valve 47 becomes.

One end of a negative pressure introduction passage 44 is connected to the diaphragm chamber 42 a of the diaphragm type on-off valve 42 . The other end of this negative pressure introduction passage 44 is located upstream of the throttle valve 22 in the intake passage 15 when the throttle valve 22 is in a substantially fully closed state, and is substantially on the upstream side when the throttle valve 22 is opened beyond a predetermined opening degree. It opens at a portion downstream of the throttle valve 22.

In the fuel tank 30 that stores the fuel supplied to the intake passage 15, there is a mixture ratio detection sensor 50 that detects the mixing ratio of alcohol in the fuel stored therein.
is provided. The mixing ratio detection sensor 50 detects the mixing ratio of alcohol by detecting the specific gravity of the fuel, which determines the degree of evaporation of the fuel in the fuel tank 30. In other words, the specific gravity of the fuel corresponds to the mixing ratio of alcohol. For example, if methanol is used as the alcohol and is mixed with gasoline, the specific gravity η of the fuel is plotted on the vertical axis, and the fuel specific gravity is plotted on the horizontal axis. As shown in Figure 3, where the methanol mixing ratio A (wt%) is taken, the larger the methanol mixing ratio A, the larger the specific gravity η of the fuel. The difference is used to detect the mixing ratio of alcohol in the fuel in the fuel tank 30. Furthermore, the relationship between the degree of evaporation of the fuel and the mixing ratio A of methanol in the fuel is expressed by taking the Reid vapor pressure Ps, which represents the degree of evaporation of the fuel, on the vertical axis, and the mixing ratio A of methanol on the horizontal axis. As shown in FIG. 4, when the mixing ratio A of methanol is in the range of approximately 5% by weight or more and less than approximately 30% by weight, that is, in a range that includes the azeotropic point of gasoline and methanol, fuel evaporation occurs. The degree is relatively large, and the mixing ratio A is approximately 0% by weight or more and less than approximately 5% by weight, and approximately 3% by weight.
When the mixture ratio A is in the range of 0% or more and less than approximately 60% by weight, the degree of evaporation of the fuel is approximately the same as when only gasoline is used as a fuel. At this time, the degree of fuel evaporation is relatively small.

The mixture ratio detection sensor 50, which detects the mixing ratio of alcohol in the fuel by utilizing the difference in the specific gravity of the fuel, has three floats 51, 52 and 53 with different specific gravities arranged in the fuel tank 30. Detection switch 5
5.56 and 57. float 5
1 to 53 are in a state of sinking to the bottom of the fuel tank 30 when the mixing ratio A of methanol in the fuel in the fuel tank 30 is less than approximately 5% by weight, and in such a state, any of the detection switches 55 to 57 is depressed. When both are in the off state and the mixture ratio A is approximately 5% by weight or more and less than approximately 30% by weight, only the float 51 is in the floating state and the detection switch 55 is in the on state. A detection signal S, is obtained from 55 and is supplied to the control unit 100. Further, the mixing ratio A of methanol in the fuel in the fuel tank 30 is approximately 30% by weight.
If the above is less than approximately 60% by weight, the float 51
and 52 float up, both of the detection switches 55 and 56 are turned on (the state shown in FIG. 2), and the detection signal S
I and S2 are obtained and it is the control unit 1.
00.

Furthermore, when the mixing ratio A of methanol in the fuel in the fuel tank 30 is approximately 60% by weight or more, the floats 51 to 53 are all in a floating state, and the detection switches 55 to 57 are respectively turned on, Detection signal S...
S and S3 are each supplied to the control unit 100.

The control unit 100 to which the detection signals S, , S, and S3 are supplied receives the detection signals SI, St, and S3.
Based on this, the mixing ratio A of methanol in the fuel in the fuel tank 30 is detected, a driving pulse signal Cp having a pulse occupancy rate according to the mixing ratio A is formed, and the driving pulse signal Cp is supplied to the flow rate regulating valve 47. be made to do.

With the above-described configuration, the evaporated fuel generated in the fuel tank 30 is led to the canister 40 through the evaporated fuel outlet passage 32, and is adsorbed and held by the evaporated fuel adsorbent layer 41. When the engine is in an operating state other than idling, that is, when the throttle valve 22 is opened to a certain extent, negative pressure is introduced into the diaphragm chamber 42a through the negative pressure introduction passage 44, thereby causing the diaphragm type on-off valve 42 to open. is in an open state, and the evaporated fuel adsorbent layer 41
The evaporated fuel adsorbed and held in the canister 40 is guided to the intake passage 15 through the evaporative fuel release passage 45 accompanied by the atmosphere introduced from the atmosphere port 403 provided in the canister 40, and is then combusted in the combustion chamber 19. It is processed.

In this way, while the combustion process of the evaporated fuel is performed, the control unit 100 sets the mixture ratio A in which the degree of evaporation of the fuel is approximately the same as the degree of evaporation when only gasoline is used as the fuel. Hail, when none of the detection signals 81 to S3 is obtained and the detection signal S1
and S2 are obtained, the pulse occupancy rate of the drive pulse signal Cp supplied to the flow rate regulating valve 47 is set to a predetermined value Dx, and the mixture ratio A is set such that the degree of fuel evaporation is large. When only the detection signal SI is obtained,
The pulse occupancy rate of the drive pulse signal Cp supplied to the flow rate regulating valve 47 is set to a value greater than the value Dx by a predetermined value α. Furthermore, when any of the detection signals S, S, and S, which indicate the mixture ratio A at which the degree of fuel evaporation is small, is obtained, the pulse occupancy rate of the drive pulse signal Cp supplied to the flow rate regulating valve 47 is is set to a value smaller than the value Dx by a predetermined value β.

By doing so, even if the mixing ratio of methanol in the fuel stored in the fuel tank 30 is changed, if the degree of evaporation of the fuel is large, the opening period of the flow rate regulating valve 47 can be adjusted. Even if the evaporated fuel introduced into the canister 40 becomes relatively large due to the lengthened length, a corresponding amount of evaporated fuel is supplied to the intake passage 15, thereby preventing the situation in which the evaporated fuel leaks from the canister 40 to the outside. If this is avoided, or if the degree of fuel evaporation in the fuel tank 30 is determined to be small, the opening period of the flow rate adjustment valve 47 is shortened, and air lacking in evaporated fuel flows from the canister 40 to the intake passage 15. This prevents a large amount of fuel from being supplied, effectively preventing the air-fuel ratio from deviating significantly from the target value and deteriorating engine operating performance and exhaust purification performance, allowing evaporated fuel to be processed efficiently. be done.

Note that when the fuel stored in the fuel tank 30 is only gasoline, the detected methanol mixing ratio is 0.
Since the amount is 0% by weight, the vaporized fuel is treated as described above in accordance with 0% by weight.

The control of evaporated fuel as described above is mainly carried out by the operation of a microcomputer built into the control unit 100. An example of a program executed by such a microcomputer will be explained with reference to the flowchart in FIG. do.

In the program represented by the flowchart of FIG. 5, after the start, at decision 101, a detection signal 8
The judgment is made based on whether at least one of the detection signals S1 to S3 is supplied, and at least one of the detection signals S and S3 is supplied.
is supplied, the mixing ratio A is approximately 5% by weight.
Therefore, the process proceeds to decision 103, and in decision 103, it is determined whether the mixing ratio A is approximately 5% by weight or more and less than approximately 30% by weight based on whether only the detection signal is supplied. do. If only the detection signal S is not supplied, it is determined that the mixing ratio A is approximately 5% by weight or more and not less than approximately 30% by weight, and in decision 104, it is determined that the mixing ratio A is approximately 30% by weight or more and approximately not less than 30% by weight. It is determined whether or not it is less than 60% by weight based on whether only the detection signal S2 is supplied together with the detection signal S, and only the detection signal S2 is supplied together with the detection signal S. In this case, since the mixing ratio A is approximately 30% by weight or more and less than approximately 60% by weight, the process proceeds to process 105, and if it is not only the detection signal S2 that is supplied together with the detection signal Sl, the mixing ratio A is It is determined that the amount is approximately 30% by weight or more and not less than approximately 60% by weight, and therefore, the detection signal S3 is also supplied in addition to the detection signal S2, so the process proceeds to process 108. In process 105, drive pulse signal Cp
The pulse occupancy rate is set to the value Dx, the process proceeds to process 106, the drive pulse signal Cp having the pulse occupancy rate of the value Dx is supplied to the flow rate regulating valve 47, and the process returns. If it is determined in decision 101 that the mixing ratio A is less than approximately 5% by weight, the process directly proceeds to process 105, executes processes 105 and 106 in the same manner as described above, and returns.

On the other hand, if it is determined in decision 103 that the mixing ratio A is approximately 5% by weight or more and less than approximately 30% by weight, in process 107, the pulse occupancy rate of the drive pulse signal Cp is set to the value Dx by a value α. The driving pulse signal Cp having the pulse occupancy is supplied to the flow rate regulating valve 47 in process 106, and the process returns to the original state. Also, in decision 104, the mixing ratio A is approximately 3.
In the process 108, which is proceeded after it is determined that the weight % is not less than 0 weight % and not less than approximately 60 weight %, the drive pulse signal C
The pulse occupancy rate of p is set by subtracting the value β from the value Dx, and in process 106, the drive pulse signal Cp having the pulse occupancy rate is supplied to the flow rate regulating valve 47, and the process returns to the original state.

(Effects of the Invention) As is clear from the above description, according to the evaporated fuel control device for an engine according to the present invention, the amount of evaporated fuel supplied to the intake system is adjusted according to the degree of evaporation of fuel in the fuel storage section. Therefore, even if the mixing ratio of alcohol in the fuel stored in the fuel storage section is changed, there will be a situation where the evaporated fuel leaks to the outside or the air-fuel ratio changes from the target value. It is possible to effectively prevent a situation in which engine operating performance and exhaust purification performance are deteriorated due to a large deviation toward the negative side, and evaporated fuel can be efficiently processed.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram showing an evaporative fuel control device for an engine according to the present invention in accordance with the claims, and FIG. 2 shows an example of the evaporative fuel control device for an engine according to the present invention to which it is applied. A schematic configuration diagram shown together with the engine, FIGS. 3 and 4 are characteristic diagrams used to explain the operation of the example shown in FIG. 2, and FIG. It is a flow chart showing an example of a program executed by such a microcomputer when the microcomputer is used. In the figure, 10 is the engine body, 15 is an intake passage, 20 is a carburetor, 30 is a fuel tank, 32 is an evaporated fuel outlet passage, 4
0 is a canister, 42 is a diaphragm type on-off valve, 45 is an evaporated fuel discharge passage, 47 is a flow rate adjustment valve, 50 is a mixture ratio detection sensor, 51°, 52 and 53 are floats, 55.5
6 and 57 are detection switches, and 100 is a control unit.

Claims (1)

[Claims] A fuel vapor supply means that guides vaporized fuel generated in a fuel storage section provided for the engine to the intake system of the engine, and detects the mixing ratio of alcohol in the fuel stored in the fuel storage section or information related thereto. and a supply amount control means that adjusts the amount of evaporated fuel guided to the intake system by the evaporated fuel supply means in accordance with the detection output obtained from the mixture ratio detection means. An evaporative fuel control device for an engine comprising: