JPH0932661A - Evapotranspired gas control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a large quantity of purge and to improve absorption capacity of a canister by measuring acoustic velocity in purge air, temperature of the purge air and a flow rate of the purge air, computing necessary air capacity to perfectly burn the purge air in accordance with their measured results and correcting an air-fuel ratio. SOLUTION: Evapotranspired gas of a fuel tank 1 is absorbed by an absorbent 18 of a canister 3. Thereafter, evaporated gas is introduced to an acoustic velocity detection device 14 through a purge line 8 as purge air by opening a purge control valve 9 during high rotation of an engine. This device 14 receives a supersonic pulse emitted from a supersonic wave transmitting element 15 and reflected by an inwall of the device and computes acoustic velocity by a control part 17 from a time difference of transmission. An air-fuel ratio is corrected by computing necessary air capacity per purge air unit volume from this acoustic velocity and purge air temperature by a temperature sensor 16 and finding a flow rate of the purge air from the value, suction air pressure and opening of the valve 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vaporized gas control device for accurately burning a vaporized gas vaporized from a fuel tank of an internal combustion engine using a volatile fuel such as gasoline in a combustion chamber of the internal combustion engine. It is a thing.

[0002]

2. Description of the Related Art FIG. 2 and FIG.
2 shows a conventional vaporized gas control device disclosed in Japanese Patent No. 3752, FIG. 2 shows a configuration of the vaporized gas control device, and FIG. 3 shows a configuration of an HC concentration sensor used in this device. In FIG. 2, 1 is a fuel tank for storing volatile fuel, 2 is a check valve provided in the middle of the pipe from the fuel tank 1 to the canister 3, and 4 is provided in the canister 3 and takes in air into the canister 3. 2 for the intake air for introducing intake air from the air cleaner 6 into the combustion chamber 7, 8 for a purge line connecting the canister 3 and the intake pipe 5, 9 for a purge control valve for opening and closing the purge line 8, and 10 for This is a throttle valve that controls the amount of intake air in the combustion chamber 7. 11 is the purge line 8
An HC concentration sensor for detecting the concentration of hydrocarbons (hereinafter referred to as HC) in the vaporized gas provided in the HC concentration sensor 11
As shown in FIG. 3, consists of a gas sensitive film resistor 12 and a supporting electrode 13 that supports the gas sensitive film resistor 12, and the gas sensitive film resistor 12 is a film resistor having a film in which conductive carbon powder is fixed with silicone resin. The silicon resin swells depending on the concentration of HC and its resistance value changes, and the concentration of HC can be detected by the change of the resistance value.

In such a conventional vaporized gas control device, the fuel such as gasoline contained in the fuel tank 1 contains a large amount of volatile components, and the vaporized mixture of various kinds of HC gas in the fuel tank 1 at high temperature. When gas is generated and the gas pressure exceeds a certain value, the check valve 2 opens, flows into the canister 3, and is trapped by the adsorbent provided in the canister 3. Since the adsorbing capacity of the adsorbent is limited, the purge control valve 9 is opened during the high rotation operation, and the various kinds of HC are purged by the air sucked from the air holes 4.
A mixture containing gas (hereinafter referred to as purge air) is introduced into the combustion chamber 7 via the purge line 8 and the intake pipe 5, and is burned together with a normal mixture. The HC concentration sensor 11 detects the total molar concentration of HC in the purge air, and based on this, controls the throttle valve 10 to correct the air-fuel ratio.

In a general automobile internal combustion engine without an HC concentration sensor, the air-fuel ratio cannot be corrected based on such a purge amount. Therefore, in order to suppress HC in the exhaust gas, the purge amount per time is reduced. However, since the adsorbent cannot be effectively purged, when the amount of vaporized gas is large, it exceeds the adsorption capacity of the canister and HC may be released into the atmosphere. On the other hand, in the transpiration gas control device having the HC concentration sensor as described above, since the total molar concentration of HC in the purge air is detected and the air-fuel ratio is corrected by the HC concentration sensor as described above, a large amount of purge is performed to some extent. However, the air-fuel ratio can be corrected by following this, and the purge amount per time can be increased, so that the capacity of the adsorbent can be improved.

[0005]

As described above, in the conventional transpiration gas control device, the capacity of the adsorbent can be improved by correcting the air-fuel ratio, but the gas-sensitive film resistance is used for the HC concentration sensor to reduce the air-fuel ratio. Therefore, there is a problem as described below. That is, in the gas-sensitive film resistor 12, the silicone resin deteriorates when exposed to HC gas for a long time, so that the secular change in the resistance value cannot be avoided, and therefore a large error occurs in the detection of the HC concentration. Is. Further, since the silicon resin does not swell in response to a change in the atmosphere, even if there is a sudden change in the HC concentration, it cannot follow this and the HC concentration cannot always be detected accurately. Further, the amount of air required to burn HC per unit volume is determined by the number of carbon and hydrogen atoms contained in HC, but the purge air contains HC molecules having various molecular structures, Since the component ratio changes depending on the type of gasoline and the temperature of the fuel tank or canister, etc., the amount of air required for combustion also changes accordingly. HC
Since it is possible to measure only the total molar concentration of, the amount of air required for the combustion cannot be accurately calculated, and there is a corresponding error in the correction of the air-fuel ratio. In particular, when the HC concentration in the purge air is high, the correction amount of the air-fuel ratio becomes large, but the correction error also becomes large and the HC in the exhaust gas is greatly increased. There was a limit, and there was also a limit to improving the capacity of the adsorbent.

The present invention has been made in order to solve the above problems and is excellent in durability and responsiveness.
Accurate calculation of the amount of corrected air required for purging enables a large amount of purging to maximize the adsorption capacity of the canister and to obtain a vaporized gas control device that emits very little HC into the atmosphere. The purpose is.

[0007]

In the vaporized gas control apparatus according to the present invention, the sonic velocity in the purged air is measured in a purge line for introducing the purged air from the canister that temporarily adsorbs the vaporized gas into the intake pipe of the internal combustion engine. Means to do
In addition to providing a means for measuring the temperature, a means for measuring or calculating the flow rate of the purge air is provided, and based on these measured sound velocity, temperature and flow rate, the amount of air required to completely burn the purge air is accurately measured. This is calculated and the air-fuel ratio is corrected. Also, an ultrasonic transmitter / receiver is provided in the purge line as a means for measuring the sound velocity in the purge air, and a means for detecting the intake pipe pressure and the opening degree of the purge control valve is provided as a means for measuring or calculating the flow rate of the purge air. is there.

Further, in an internal combustion engine that uses gasoline as a fuel, it is assumed that all the molecules contained in the purge air are pentane, and the amount of air required to burn this is calculated based on the speed of sound, temperature and flow rate. The air-fuel ratio is corrected. Furthermore, when the amount of air required to completely burn the purge air is calculated and this exceeds the limit of correction of the air-fuel ratio, the purge control valve is controlled to make the flow rate of purge air within the correction limit of the air-fuel ratio. It is intended to prevent HC from being released into the atmosphere by limiting

[0009]

In the evaporative gas control device constructed as described above, the sonic velocity and temperature in the purge air are first measured by the sonic velocity detecting means and the temperature detecting means, and based on this, the purge air per unit volume is completely burned. The required air amount is calculated, and the required air amount for the purge air flow rate is calculated from this calculation result and the output of the purge air flow rate measuring means, and the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is corrected based on this calculation result. To do. In addition, of the molecular components of HC having various molecular structures contained in the purge air, molecules having a high component ratio are selected, and the amount of air for completely burning the selected components is set to sonic velocity, temperature, and flow rate. Calculate based on and correct the air-fuel ratio. Furthermore, when the amount of air required to completely burn the purge air is calculated and this exceeds the limit of correction of the air-fuel ratio, the purge control valve is controlled and the flow rate of purge air is kept within the correction limit of the air-fuel ratio. Since it is limited, HC is not released into the atmosphere.

[0010]

【Example】

Embodiment 1 FIG. The calculation of the required air amount per unit volume of purge air based on the speed of sound and temperature is performed as follows. First, the relationship between the sound velocity in an ideal gas and the molecular weight is expressed by the following equation. V = √ (γRT * 1000 / M) (1) However, V: sound velocity [m / s], γ: specific heat ratio, R: gas constant R = 8.2056 [J / K · mo
l], T: absolute temperature [° K], M: molecular weight [g / mo]
l], in equation (1), the sound velocity V and the absolute temperature T are detected by the detecting means. Also, the molecular weight M
For the specific heat ratio γ,
In the case of a mixed gas of gas and air, the molecular weight M of each component
And the specific heat ratio γ are weighted averaged to obtain the average value of the overall molecular weight and the specific heat ratio. These average values are expressed by the following equation. Mmean = Σ (C1 · M1 + C2 · M2 + ·· Ci · Mi) (2) γmean = Σ (C1 · γ1 + C2 · γ2 + ·· Ci · γi) (3) However, Ci: the concentration of the i-th component, each of the above The formula shows that the sound velocity becomes slower as more HC having a large molecular weight M is contained, and the HC molecule is represented as CmHn by the number of carbon and hydrogen bonded thereto. As shown in the formula), the number of carbon C is largely controlled by m, so that the sound velocity in the purge air becomes slower as more HC molecules having a large amount of carbon are contained. M = 12m + n (4) On the other hand, the combustion of HC molecules is represented by the chemical formula (5). Therefore, the air volume Vair required to burn 1 liter of CmHn, which is a unit volume, is as shown in the formula (6). Become. CmHn + (m + 1 / 4n) O2 → m · CO2 + 1 / 2n · H2O (5) Vair = (m + 1 / 4n) /0.21 [liter] (6) As described above, the more HC molecules having a large amount of carbon, the more The sound velocity becomes inversely slow, and the required air volume increases proportionally.

Various kinds of HC are contained in the evaporated gas of gasoline, and for each of the seven main types of compounds, each compound alone has a sound velocity of 0 to 0 compared to the sound velocity in the atmosphere. Attached Table 1 shows that the mol% of HC when mixed with air so as to change by 10% and the amount of air that can completely burn the mixture are calculated with the oxygen content in the air being 21%. In the table, C4H10 to C7H16 are paraffinic, C7H14 is heptene, C6H6 is benzene, and C7H9 is toluene. Those with a negative sign in the required air amount indicate that there is more than the required amount of air in the mixture. is there.

[0012]

[Table 1]

As shown in Table 1, the ratio of the number of carbon atoms to hydrogen atoms, m / n, changes depending on the molecular structure of the HC molecule, and the required amount of air changes accordingly. It is difficult to accurately know the amount of air required for combustion of gas from the speed of sound. However, as described above, since the required air amount and the sound velocity largely contribute to m, which is the number of carbon C, the method of calculating the air amount by the sound velocity is more effective than the conventional method of measuring the total mol% of HC. The required air amount can be calculated more accurately.

In the actual purge air, n-butane, isopentane, and n-pentane account for 40% or more of the total HC, and benzene, toluene, etc. account for 3% or less. This ratio is so large depending on the type of gasoline. Since there is no change, assuming that all HC in the purge air is pentane, substituting these molecular weights into the above equations (1) to (6) and calculating the air volume based on the speed of sound and temperature produces a large error. Does not occur. Therefore, the air-fuel ratio can be corrected without a large error by calculating the amount of air required to completely burn pentane per unit volume and calculating the required amount of air from this air amount and the flow rate of purge air. it can.

FIG. 1 shows the structure of a vaporized gas control apparatus according to an embodiment of the present invention. In the figure, the same parts as those in the above-mentioned conventional example are designated by the same reference numerals, and detailed description thereof will be omitted. In the figure, 14 is a sonic velocity detecting device inserted in the purge line 8. The sonic velocity detecting device 14 has an ultrasonic wave transmitter / receiver 15 and a temperature sensor 16 for measuring the temperature of purge air therein, and the ultrasonic wave transmitter / receiver 15 is an ultrasonic wave. Sound waves are transmitted, ultrasonic waves reflected from the inner wall of the sound velocity detecting device 14 are received, and the sound velocity in the purge air is measured by the time difference between the transmission and reception. Reference numeral 17 is an input of the ultrasonic transmitter / receiver 15 and the output of the temperature sensor 16 and various information such as the pressure of the intake pipe 8 and the opening degree of the purge control valve 9 to calculate the required air amount and correct the air-fuel ratio. A control unit that controls the opening of the purge control valve 9 based on the calculation result of the required air amount, 18 is an adsorbent held in the canister 3, and the adsorbent 18 is also used in the conventional device.

In the vaporized gas control device thus constructed, the vaporized gas in the fuel tank 1 is adsorbed by the adsorbent 18 of the canister 3. While the engine is rotating at high speed, the purge control valve 9 is opened, and the atmosphere is introduced from the atmosphere hole 4 to be purged, and is introduced as purge air into the sonic velocity detecting device 14 via the purge line 8. Sound velocity detector 1
In 4, the ultrasonic wave transmitter / receiver 15 emits an ultrasonic wave pulse, the ultrasonic wave pulse reflected from the inner wall of the sound velocity detecting device 14 is received, and the control unit 17 calculates the sound velocity from the time difference between transmission and reception. Further, the output of the temperature sensor 16 is the control unit 1
7, the required air amount per unit volume of purge air is calculated from the sound velocity and the temperature. Furthermore, the intake pipe 8
The pressure and the opening of the purge control valve 9 are input to calculate the flow rate of the purge air, and the total required air amount is calculated by these, and the control unit 17 corrects the air-fuel ratio.
Since the calculation of the required air amount is performed by measuring the sound velocity of the purge air as described above, the error is small even if the type of the gas to be measured in the purge air is slightly different. A large amount of purge air can be purged without adversely affecting the exhaust gas. If the HC concentration of the purge air is too high, the purge amount is controlled so that the vaporized gas in the canister 3 is purged while the purge amount is controlled within the correction limit of the air-fuel ratio, and the purge amount is increased or decreased according to the HC concentration. The adsorption capacity of the agent can be maximized and HC is not released into the atmosphere.

[0017]

As described above, according to the present invention, the ultrasonic wave is used to measure the speed of sound in the purge air, and the air required to burn the purge air per unit volume is measured from the speed of sound and temperature. The amount of air is calculated, the flow rate of purge air is calculated, and the amount of air required for complete combustion is calculated from both, and the air-fuel ratio is corrected and the purge amount is controlled. Excellent and highly accurate correction of the air-fuel ratio, the evaporated gas of the canister can be purged without adversely affecting the operating condition of the internal combustion engine, exhaust gas, etc., and the adsorption capacity of the canister can be maximized. The vaporized gas control device can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a transpiration gas control device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional evaporation gas control device.

FIG. 3 is a configuration diagram of an HC concentration sensor used in a conventional device.

[Explanation of symbols]

1 Fuel Tank, 3 Canister, 4 Atmosphere, 5 Intake Pipe, 8 Purge Line, 9 Purge Control Valve, 14 Sonic Speed Detector 15 Ultrasonic Transceiver, 16 Temperature Sensor, 17 Control Section,

Claims (5)

[Claims] 1. A fuel tank, a canister having an adsorbent for temporarily adsorbing vaporized gas generated from the fuel tank, and vaporized gas adsorbed by the adsorbent of the canister is used as purge air in an intake pipe of an internal combustion engine. In a vaporized gas treatment system of an internal combustion engine equipped with a purge line to be introduced and a purge control valve provided in the purge line to control the introduction of vaporized gas into the intake pipe, the speed of sound in the purged air is measured in the purge line. Means for measuring the temperature of the purge air, and means for measuring or calculating the flow rate of the purge air, in order to completely burn the purge air based on the sonic velocity, temperature and flow rate measured by these means. Is equipped with a control unit that calculates the required air amount of the air-fuel ratio and corrects the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine based on the calculation result A transpiration gas control device characterized by the above. 2. When the amount of air required to completely burn the purge air exceeds the correction limit of the air-fuel ratio, the purge control valve is controlled to bring the flow rate of the purge air within the correction limit of the air-fuel ratio. The vaporized gas control device according to claim 1, wherein the vaporized gas control device is limited. 3. A means for measuring the speed of sound in the purge air comprises:
The ultrasonic wave transmitter / receiver provided in the purge line, and is configured to measure the time until the ultrasonic wave pulse sent out is reflected by the wall surface and returns.
Alternatively, the evaporation gas control device according to claim 2. 4. The means for calculating the flow rate of purge air is calculated using the intake pipe pressure of the internal combustion engine and the valve opening of the purge control valve as inputs. Transpiration gas control device. 5. In an internal combustion engine that uses gasoline as fuel, the amount of air required for complete combustion of purge air is
The transpiration gas according to claim 1 or 2, wherein all the molecules contained in the purge air are pentane, and are calculated by substituting the necessary amount of air for burning the pentane. Control device.