JPH06159155A - Canister saturation detecting device and control device - Google Patents

Abstract

PURPOSE:To provide a device to detect the saturation of a canister to adsorb the vapor fuel and control the saturation according to the detected results. CONSTITUTION:In an air fuel ratio feedback control device which is provided with an engine speed detecting sensor 13 to detect the engine speed, a vacuum sensor 6 to detect the pressure in the suction tube, a throttle sensor 15 to detect the opening of a gas pedal, an O2 sensor 10 to detect the oxygen content in the exhaust gas, and a computer 11 to execute the computation from the outputs of the respective sensors, a sensor 14 to detect the temperature in a canister 2 and a purge valve 3 to control the fuel vapor amount to be introduced into the suction tube are provided. The concentration of the fuel vapor to be purged is obtained by the difference of the air fuel ratio to be generated according to the opening/closing of the purge valve 3 and the purge flow rate of the fuel vapor, and in addition, the saturation of the canister 2 is detected by the temperature in the canister 2. The fuel is cooled according to the detected results to control the saturation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a canister saturation detection device and a control device for adsorbing fuel vapor generated from a fuel tank.

[0002]

2. Description of the Related Art As an example of this type of fuel vapor control device for an internal combustion engine, there is a technique disclosed in Japanese Utility Model Laid-Open No. 56-8836.

In an automobile equipped with an internal combustion engine or the like, fuel vapor is generated from a fuel tank while the engine is stopped. This fuel vapor is sent to a canister by a pipe,
Adsorbed on the activated carbon in the canister. The canister is connected to the intake system of the engine by a pipe and also to the atmosphere, so when the engine starts, the negative pressure of the intake pipe acts on the canister, and the atmosphere is drawn into the canister. Causes fuel vapor to escape from the activated carbon,
That is, it is purged and taken into the intake system of the engine, mixed with the intake air and burned.

When the fuel vapor is purged from the activated carbon in the canister, it is an endothermic reaction. Therefore, if the temperature of the activated carbon canister is low, it becomes difficult for the fuel vapor to separate from the activated carbon.

Therefore, in the above-mentioned conventional technique, the activated carbon canister is surrounded by a water jacket, and warmed engine cooling water is caused to flow into and out of the activated carbon canister, whereby the temperature of the activated carbon canister is immediately raised at the time of engine start and is adsorbed on the activated carbon. The fuel vapor that was being used is being purged quickly.

[0006]

However, when the engine is operating, the generation of fuel vapor becomes active due to the influence of the warmed-back fuel from the injector for injecting the fuel, and the canister releases the fuel vapor. If not sufficiently done, the canister after the engine is stopped becomes oversaturated in a short time, and the fuel vapor is discharged to the atmosphere, which is not preferable.

Therefore, the present invention can favorably detect the saturation of the canister, and according to the detection result,
It is an object of the present invention to provide a canister saturation detection device and a control device capable of constantly suppressing the canister saturation during engine operation to a low level.

[0008]

As a means for solving the above-mentioned problems, the present invention according to claim 1 controls the air-fuel ratio of the engine to a predetermined value in accordance with the oxygen concentration in the exhaust gas of the engine. Air-fuel ratio feedback control means, a canister for adsorbing fuel vapor generated from the fuel tank of the engine, a temperature detection means for detecting the temperature in the canister, and a purge of the fuel vapor introduced into the intake pipe of the engine. A purge valve for controlling the flow rate and a control circuit for controlling the opening degree of the purge valve are provided, and the control circuit has a difference in the air-fuel ratio between when the fuel vapor is introduced into the intake pipe and when the fuel vapor is not introduced, and A fuel vapor concentration calculating means for calculating the concentration of the fuel vapor based on the purge flow rate of the fuel vapor; and a concentration of the fuel vapor and a temperature in the canister. Flip and provides a canister saturation detection device, characterized in this that a saturation calculating means for calculating a degree of saturation of the canister.

According to a second aspect, in the apparatus according to the first aspect, a fuel cooling device for cooling the fuel in the fuel tank is provided, and the control circuit determines whether the canister saturation is equal to or higher than a predetermined saturation. There is provided a canister saturation degree control device having a determination means for controlling, and activating the fuel cooling device when the saturation degree is equal to or higher than the predetermined saturation degree.

[0010]

According to the first aspect of the present invention, the concentration of the fuel vapor to be purged is determined from the difference in the air-fuel ratio when the fuel vapor is purged and when it is not purged, and the purge flow rate of the fuel vapor. And then detect the temperature inside the canister,
From these, the saturation level of the canister (the ratio of the adsorption amount at each time to the adsorption amount when the canister is saturated) is detected. Further, according to claim 2, the temperature of the fuel is lowered according to the detection result of the saturation degree, the saturation degree of the canister during engine operation is suppressed to a low level, and the canister after the engine is stopped becomes oversaturated in a short time. Prevent it from happening in advance.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a canister saturation detection device and a control device of the present invention will be described based on an embodiment shown in the drawings.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention and is a block diagram of a canister saturation detection device and a control device.

In the apparatus of the present embodiment, 1 is a fuel tank, and in the fuel tank 1, a fuel pump 1 for pressure-feeding the fuel to an injector 7 for injecting the fuel.
6 is provided. Reference numeral 2 denotes a canister for adsorbing fuel vapor, and this canister 2 is provided with a canister temperature sensor 14 for detecting the temperature inside the canister 2. Reference numeral 5 denotes an intake manifold for introducing air into the engine, and a vacuum sensor 6 for detecting a negative pressure in the manifold 5 is arranged in the intake manifold 5. Furthermore, the INTE MANIGHOLD 5
Due to the negative pressure inside, the fuel vapor adsorbed in the canister 2 is released, that is, is purged, and is introduced into the intake manifold 5, and a flow rate of the released fuel vapor in the middle of the purge pipe. A purge valve 3 for controlling the above is installed.

Further, a throttle sensor 15 for detecting the accelerator opening is provided on the upstream side of the inflow air in the intake manifold 5, and air is introduced into the combustion chamber 8 on the downstream side of the inflow air of the intake manifold 5. Intake ports 17 are provided according to the number of cylinders, and the intake ports 17 are provided with injectors 7. Further, a rotation speed detection sensor 13 that detects the rotation speed of the engine is installed in the engine body 18. Reference numeral 19 denotes an exhaust pipe for discharging exhaust gas after combustion in the combustion chamber 8, and the exhaust pipe 1
O ₂ sensor 1 for detecting the oxygen concentration in the exhaust gas
0 is provided. 12 is a return from the injector
Reference numeral 11 denotes a fuel cooling device including a fuel-cooler 33 for cooling the fuel, and reference numeral 11 denotes an engine computer (ECU) including a microcomputer that performs a calculation process described later based on a signal from each sensor.

As described above, in an automobile equipped with an engine or the like, fuel vapor is generated from the fuel tank 1 while the engine is stopped. This fuel vapor is sent to the canister 2 through the pipe 20, and the activated carbon in the canister 2 is discharged. Is adsorbed on. The canister 2 is connected to an intake manifold 5 which is an intake system of the engine by a page pipe 9,
Further, since the air is also communicated with the atmosphere via the atmosphere discharge port 4, when the engine is operated, the negative pressure in the intake manifold 5 acts on the canister 2 and the atmosphere is sucked into the canister 2. The fuel vapor is purged from the activated carbon, is sucked into the intake system of the engine, is mixed with the intake air, and is introduced into each combustion chamber 8 through the intake port 17,
It will burn.

Further, in the exhaust gas after combustion, conversion efficiency, that NO _X in the three-way catalyst, HC, purification rate of CO is known as the best when combustion in the engine is performed at the stoichiometric air-fuel ratio Based on the theory, feedback control is performed based on the signal from the O ₂ sensor 10 so that combustion is always performed at the stoichiometric air-fuel ratio.

However, since the fuel vapor is added to the fuel injection amount of the injector 7 corresponding to the pressure in the intake pipe obtained by the vacuum sensor 6, the deviation of the air-fuel ratio is detected by the O ₂ sensor 10.

Therefore, in this embodiment, the difference between the air-fuel ratio when the fuel vapor is being purged and when it is not being purged,
The concentration of the fuel vapor is obtained from the purge flow rate of the fuel vapor, the saturation degree of the canister 2 is estimated, and the canister is cooled based on the result. The details will be described below.

2 and 3 show the operation of this embodiment.
2 is a flow chart of air-fuel ratio feedback control when the purge valve 3 is closed and fuel vapor is not purged, and FIG. 3 is a flow chart of canister saturation detection.

That is, as shown in FIG. 2, in step 100, the engine computer 11 determines the engine speed NE from the signal of the rotation speed detection sensor 13 and the vacuum speed.
The intake sensor pressure PM is calculated by the exhaust sensor 6 and the accelerator opening TA is calculated by the throttle sensor 15.

Further, in step 101, the exhaust conduit 19
On the basis of the detection signal of the O ₂ sensor 10 disposed in the engine, the output of electromotive force suddenly changes at the exhaust gas concentration bordering on the stoichiometric air-fuel ratio. , The ratio of deviation from the theoretical air-fuel ratio is calculated as the air-fuel ratio correction coefficient λ _i .

Next, at step 102, the intake pipe pressure P
The average value λ of the air-fuel ratio correction coefficient corresponding to M at a predetermined time is calculated and stored. Then, in step 103, the engine speed NE, intake pipe pressure PM, accelerator opening TA,
With the average value λ of the air-fuel ratio correction coefficient as a parameter, the fuel injection amount, that is, the drive pulse width TAUIN of the injector 7
J is calculated by the formula for calculating the injection pulse width in the flow chart. Here, κ represents a correction coefficient that changes depending on the engine water temperature and the like.

Based on the above calculation result, in step 104, the injector 7 is driven for TAUINJ time, so that fuel corresponding to the operating condition and having the stoichiometric air-fuel ratio is supplied.

Next, the canister saturation detection flow chart
Is shown in FIG. In step 200, the engine computer 11 permits the fuel vapor page depending on whether or not the average value λ of the air-fuel ratio correction coefficient is calculated by the air-fuel ratio feedback control when there is no fuel vapor described above. To judge. If the air-fuel ratio feedback control is not completed and the average value λ has not been obtained, the processing shown in FIG. 3 is not performed, but if the calculation of the average value λ of the air-fuel ratio correction coefficient is completed, Purge valve 3 described above in step 201
The value of the average value λ of the air-fuel ratio correction coefficient obtained by the air-fuel ratio feedback control in the closed state is λ '
Replace with.

Next, at step 202, the intake air amount Q is calculated based on the equation (1). Here, KTP represents a coefficient corresponding to the charging efficiency, which is stored in the ECU as a constant, and V represents the engine displacement.

[0026]

[Equation 1] Q = (NE / 60) × (PM / 760) × KT
P × (V / 2) Next, in order to calculate and set the opening degree of the purge valve 3 in step 203, the opening degree of the purge valve 3 is gradually increased while the deviation of the air-fuel ratio is monitored by the O ₂ sensor 10. Then, when the air-fuel ratio becomes stable, calculation of the fuel vapor concentration starts. The detailed control of this step 203 is performed in the following procedure.

When the output of the O ₂ sensor 10 is rich (in excess of the stoichiometric air-fuel ratio) and λ ′ ≦ Δλ, the control purge rate tPRGR _i (purge flow rate relative to intake air amount) Corresponding to the ratio) is calculated. Further, the output of the O ₂ sensor 10 is rich, and λ ′>
In the case of Δλ, the control purge rate tPRG is calculated by the equation 2 (b).
R _i is calculated. Furthermore, when the output of the O ₂ sensor 10 is lean (a state that is too small for the stoichiometric air-fuel ratio), Equation 3
The control purge rate tPRGR _i is calculated based on Here, Δλ represents the guard value of the air-fuel ratio correction coefficient set in consideration of the influence on the fuel injection due to the rapid input of the air-fuel ratio correction coefficient.

[0028]

[Number 2] _{(b) tPRGR i = tPRGR i-1} -0.1 ( b) tPRGR _i = tPRGR _i-1

[0029]

## EQU3 ## tPRGR _i = tPRGR _i-1 +0.02 Furthermore, the control purge rate tPRG calculated above.
From R _i , the maximum purge flow rate calculated from the interpolation calculation by the six combinations showing the relationship between the intake pipe internal pressure and the maximum purge flow rate shown in Table 1, and the intake air amount Q calculated above, the purge valve Drive DUT
The Y value is determined. This drive DUTY value is expressed as a drive DUTY value with 100 ms as one cycle.

[0030]

[Table 1]

[0031]

[Equation 4] Next, at step 204, the average value λ ′ of the air-fuel ratio correction coefficient during purging is calculated. Further in step 205, λ _i '
And the absolute value of the difference between λ _{i -3} 'and 1% or less, the purge flow rate Q'is calculated according to Equation 5. Further, if the absolute value of the difference is 1% or more, it is calculated again from the engine intake air amount Q according to Formula 1. Here, C is the flow coefficient, Δp is the pressure difference between the upstream and downstream of the purge valve, that is, the difference between the atmospheric pressure and the negative pressure of the vacuum sensor output, γa is the specific gravity of air, and g is the gravitational acceleration. Also, A is a
It shows the valve opening area of the di-valve, which is given by the product of the full-valve area of the purge valve and the drive duty value.

[0032]

[Equation 5]

Further, in step 207, the fuel consumption amount F ₀ of the engine is calculated by the equation (6). Where TAU
INJ 'represents the fuel injection pulse width during execution of the fuel vapor purge, INJQ represents the product of the static flow rate of the injector 7 and the number, and r _G represents the specific gravity of the fuel.

[0034]

[Equation 6]

Next, in step 208, purging is performed from the average value λ'of the air-fuel ratio correction coefficient when the fuel vapor is included and the average value λ of the air-fuel ratio correction coefficient when the fuel vapor is not included, according to the equation (7). The fuel vapor concentration F is calculated.

[0036]

[Equation 7] Next, at step 209, the temperature inside the canister 2 is detected. As shown in FIG. 4, the canister saturation changes depending on the temperature inside the canister, as shown by a solid line in the case of 80 ° C. and a broken line in the case of 20 ° C., for example. Therefore, in step 210, the canister saturation degree due to the temperature change in the canister 2 is estimated from FIG.
If the saturation degree is larger than the predetermined value in 1, the canister 2
Since it is necessary to reduce the fuel vapor supplied to the fuel cooling device 12, the fuel cooling device 12, which will be described later, is operated in step 212, and the guard value Δλ of the air-fuel ratio correction coefficient at this time is 0. Will be set to 75. If the saturation is less than the predetermined value, step 2
At 14 and 215, the fuel cooling device 12 is stopped, and the guard value Δλ of the air-fuel ratio correction coefficient is set to 0.85.

Next, FIG. 5 shows the structure of the fuel cooling device 12 for controlling the generation of fuel vapor. This uses a refrigeration cycle of a vehicle air conditioner. The fuel cooling device 12 of the present embodiment includes a second liquid pipe 23 that guides a refrigerant from the main cycle 22 of the vehicle air conditioner to the fuel cooling device 12, a fuel cooling device 12 that cools the fuel, and a fuel cooling device 12. The second suction pipe 25 for returning the refrigerant to the main cycle 22, the amplifier 25 for outputting a drive signal according to the saturation of the canister 2 detected by the method described above, and the control of the refrigerant flowing into the fuel cooling device 12 are controlled. And a solenoid valve 26.

The refrigeration cycle of the vehicle air conditioner includes a compressor 27, a condenser 28, and a reservoir tank 29.
The fuel cooling device 12 is arranged in parallel with the evaporator 31 in the main cycle 22 although it is composed of the expansion valve 30 and the evaporator 31. That is, the first liquid pipe 31 that connects the reservoir tank 29 and the expansion valve 30 branches to the second liquid pipe 23 that communicates with the fuel cooling device 12, and the first intake pipe that connects the compressor 27 and the evaporator 31. 32
The second suction pipe 25 that leads from the fuel cooling device 12 to the fuel cooling device 12 is branched. Further, a solenoid valve having a fixed throttle is arranged in the middle of the second liquid pipe.

According to this structure, when the saturation of the canister 2 is equal to or higher than the predetermined value, the solenoid valve 26 is energized and the solenoid valve 26 is energized.
Is opened and the refrigerant flows into the fuel cooling device 12 to cool the high temperature fuel. If the saturation of the canister 2 does not reach the predetermined value, the solenoid valve 26 is de-energized and the refrigerant does not flow into the fuel cooling device 12.

Next, the effect of this embodiment is shown in FIG. FIG. 6 is a diagram showing the relationship between the vehicle leaving time and the canister saturation. In the conventional case shown by the alternate long and short dash line, the canister saturation immediately after the engine is stopped is in the B region, the canister saturation increases with respect to the vehicle standing time, and finally the supersaturated state occurs, and the overflow region shown by the shaded portion 33 occurs. , The fuel vapor is discharged from the atmosphere discharge port 4, but by controlling the saturation of the running canister and keeping the saturation of the canister immediately after the engine is stopped in the A region, the canister 2 becomes oversaturated. The release of fuel vapor to the atmosphere can be suppressed.

In the present embodiment, the temperature inside the canister is directly detected by the temperature detecting sensor, but the temperature detecting means is not limited to this. For example, the temperature inside the canister is cooled by the engine. It is also possible to substitute it by estimating from water temperature or intake air temperature.

[0042]

According to the present invention, according to the first aspect, the saturation degree of the canister is satisfactorily detected from the difference in the air-fuel ratio between when the fuel vapor is purged and when it is not purged and the purge flow rate. can do. According to the second aspect, the saturation of the canister can be constantly controlled to a low level when the engine is operating, according to the saturation detection result, thereby reducing the amount of fuel vapor released into the atmosphere when the vehicle is left unattended. You can

[Brief description of drawings]

FIG. 1 is a configuration diagram of a canister saturation detection device and a control device showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a processing procedure of air-fuel ratio feedback control.

FIG. 3 is a flow chart showing a processing procedure for canister saturation detection.
Chart.

FIG. 4 is a diagram showing the relationship between the canister saturation adsorption and the concentration of fuel contained in fuel vapor.

FIG. 5 is a configuration diagram of a fuel cooling device.

FIG. 6 is a diagram showing a relationship between vehicle leaving time and canister saturation.

[Explanation of symbols]

2 canister 3 purge valve 6 vacuum sensor 11 engine computer 10 O ₂ sensor 13 rotational speed detection sensor 14 canister temperature detection sensor 15 serving as temperature detection means 15 throttle sensor 12 fuel cooling device

Claims (2)

[Claims] 1. An air-fuel ratio feedback control means for controlling the air-fuel ratio of the engine to a predetermined value according to the oxygen concentration in the exhaust gas of the engine, and a canister for adsorbing the fuel vapor generated from the fuel tank of the engine. The control circuit includes: a temperature detection unit that detects a temperature in the canister; a purge valve that controls a purge flow rate of the fuel vapor introduced into an intake pipe of the engine; and a control circuit that controls an opening degree of the purge valve. Is a difference between the air-fuel ratio when the fuel vapor is introduced into the intake pipe and the case where the fuel vapor is not introduced, and a fuel vapor concentration calculating means for calculating the concentration of the fuel vapor based on the purge flow rate of the fuel vapor, A saturation degree calculating means for calculating the saturation degree of the canister according to the concentration of the fuel vapor and the temperature in the canister. Canister saturation detection device. 2. The device according to claim 1, further comprising a fuel cooling device that cools the fuel in the fuel tank, and the control circuit determines whether the canister saturation is equal to or higher than a predetermined saturation. The canister saturation degree control device, wherein the fuel cooling device is operated when the saturation degree is equal to or higher than the predetermined saturation degree.