JP2548166Y2 - Fuel gas purifier - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a fuel gas system provided between a fuel tank of an automobile and an internal combustion engine, for example, by guiding excess fuel gas generated in the fuel tank into the internal combustion engine and burning it. The present invention relates to a fuel gas purification device for purifying fuel.

[0002]

2. Description of the Related Art In internal combustion engines such as automobiles, a purifying device is provided to prevent fuel gas (gasoline vapor) generated in a fuel tank from scattering into the atmosphere. The conventional purification device guides the gas generated in the fuel tank to an adsorption device called a canister, where the gas is temporarily stored, and when the engine starts, the gas is guided from the canister to the internal combustion engine. By burning, extra fuel gas has been treated.

[0003] In such a fuel gas purifying apparatus, an H (hydrocarbon) concentration detecting gas contained in vaporized gasoline is detected.
The provision of a C sensor is being considered. The HC sensor utilizes the fact that the electric resistance of a semiconductor element changes by contact with a gas. As shown in FIG. 5, a tin oxide SnO ₂ semiconductor thin film 11 is deposited on a ceramic substrate The heater 12 is provided on the back surface of the. The heater 12 is heating means for operating the sensor element under heating conditions, and the heating temperature is controlled by a temperature sensor 13. In the figure, "14"
Is an electrode for measuring the element resistance of the tin oxide semiconductor.

When the concentration of flammable gas such as gasoline is measured by such an HC sensor, the element resistance (Ω) with respect to the concentration of flammable gas (volume%) is as shown in FIG. Using this relationship, the concentration of the fuel gas passing through the fuel gas purifier is measured to control the amount of fuel injected from the fuel injector of the internal combustion engine.

[0005]

In the conventional fuel gas purifying apparatus, the gas stored in the canister is guided to the internal combustion engine to be burned together with ordinary fuel. However, with the increase in the capacity of the canister. Since the amount of gas supplied from the canister also increases, and the ratio of the amount of gas purification (purge) to the amount of injection from the fuel injector also increases, the mixing ratio of fuel and gas supplied to the internal combustion engine is optimized. In order to maintain the conditions, it is necessary to accurately measure the amount of purge supplied from the canister, and to precisely control the injection amount from the fuel injector so as to reduce the amount of fuel corresponding to the amount.

However, the conventional HC sensor has a problem in the responsiveness of the output of the HC sensor to the actual increase in the concentration. That is, as shown in FIG. 8, the actual gas concentration increases rapidly in about 1 to 2 seconds immediately after the gas supply from the canister is started, and thereafter the concentration gradually decreases. As shown in FIG. 7, the element output obtained by the HC sensor does not reach the original concentration until several seconds to several tens of seconds have elapsed since the start of gas supply from the canister, and the rising characteristics of the sensor are improved. Needed.

The present invention has been made in view of such a problem of the prior art, and immediately responds to a sudden change in the concentration of a gas to be purged, and transmits a control signal corresponding to the purge amount to the fuel. It is an object of the present invention to provide a device for purifying fuel gas output to an injection device.

[0008]

In order to achieve the above object, the fuel gas purifying apparatus of the present invention is provided with a fuel injection means through a guide passage for excess fuel gas generated in the fuel tank. In an apparatus for purifying fuel gas introduced into a fuel supply passage of an internal combustion engine, an on-off valve provided in the guide passage for opening and closing the guide passage, and the guide passage between the on-off valve and the fuel supply passage are provided. A concentration detecting means for detecting the concentration of the fuel gas in the guide passage; a fuel gas supply means for supplying the fuel gas from the fuel tank into the fuel supply passage; and a concentration detecting means for detecting the concentration of the fuel gas. Based on the fuel gas concentration, the inclination angle of the concentration rise curve immediately after the opening / closing valve is opened is calculated, and the estimated concentration is calculated from the calculation result and the information of the fuel gas concentration with respect to the previously stored inclination angle. And control means for outputting a signal for controlling the fuel injection amount of the fuel injection means based on the estimated concentration until a predetermined time has elapsed since the opening and closing valve was opened. I have.

[0009]

In a gas sensor using a tin oxide SnO ₂ semiconductor or the like, when the concentration of a gas to be detected changes, the element temperature also changes. This element temperature is immediately corrected by a temperature control circuit. Thereafter, the element resistance changes so that the oxygen partial pressure is in an equilibrium state according to the gas concentration to be detected.
The gas concentration can be detected by measuring the change in the resistance value, but it takes time for the oxygen partial pressure to reach an equilibrium state in accordance with the gas concentration, and the responsiveness is reduced.

However, in the present invention, attention is paid to the fact that the equilibrium state has already been determined by the initial value of the element resistance, and the estimated concentration is obtained by calculating the inclination angle of the variation curve of the initial value of the element resistance. A signal for controlling the injection amount from the fuel injection means is output based on the estimated concentration. That is, the on-off valve of the guide passage is opened, excess fuel gas is guided to the concentration detecting means, and the gas concentration immediately after the on-off valve is opened is taken into the control means from the concentration detecting means. The control means calculates and calculates the inclination angle of the density rise curve based on the taken-in density information, and obtains an estimated density stored in advance in association with the curve. Until a predetermined time has elapsed since the opening and closing of the on-off valve, the information on the estimated concentration is output to the fuel injection means, and the fuel injected into the internal combustion engine is controlled so as to have the optimum injection amount.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a fuel gas purifying apparatus according to an embodiment of the present invention, FIG. 2 is a flowchart showing a control procedure in control means of the embodiment, and FIG. 3 is an output of a concentration detecting means according to the embodiment. FIG. 4 is a graph showing the relationship between the concentration estimated by the purification device of the embodiment, the actual concentration, and the concentration obtained by the concentration detecting means.

First, as shown in FIG. 1, in this embodiment,
Excess fuel gas generated in the fuel tank 1 is supplied to the guide passage 2
The fuel gas is led to the canister 9 via a, where the fuel gas is temporarily stored. This is because when the internal combustion engine such as the engine is stopped, even if the fuel gas is supplied to the fuel supply passage 4, it cannot be purified by combustion. Therefore, in order to properly collect the excess fuel gas generated in the fuel tank 1, an adsorbing means such as the canister 9 is provided between the fuel tank 1 and the fuel supply passage 4 as in the present embodiment. Preferably. However,
The fuel gas purifying device of the present invention is not limited to the device provided with the canister 9.

The fuel gas purifying apparatus of this embodiment has a guide passage 2b for guiding the fuel gas stored in the canister 9 to the fuel supply passage 4 of the internal combustion engine. A purge control valve 5 (opening / closing valve) is provided in the guide passage 2b. The purge control valve 5 is preferably a one-way valve in order to prevent backflow from the fuel supply passage 4,
The present invention is not particularly limited, and any structure may be used as long as it can open and close the guide passage 2b. The operation of opening and closing the purge control valve 5 is performed by a signal from the control means 8.

The opening / closing operation of the purge control valve 5 may be performed by outputting a signal from a controller other than the control means 8 according to the present embodiment. Must be configured to be captured. This is because, as will be described later, when purging the fuel gas by opening the purge control valve 5, the present invention estimates the fluctuation state of the initial value of the gas concentration passing through the guide passage 2b for a predetermined time. This is because it is necessary to know the point in time when the purification operation is started.

An HC sensor 6 (for detecting the concentration of the fuel gas passing through the guide passage 2b) is provided downstream of the purge control valve 5, that is, in the guide passage 2b between the purge control valve 5 and the fuel supply passage 4. Concentration detecting means). The HC sensor 6 utilizes the fact that the electric resistance of a semiconductor element changes due to contact with a gas. Similar to a conventional HC sensor (see FIG. 5), a tin oxide SnO ₂ semiconductor thin film is formed on a ceramic substrate 10. On the back surface of the ceramic substrate 10, a heater 12 is provided. The heater 12 is heating means for operating the sensor element under heating conditions, and the heating temperature is controlled by a temperature sensor 13. Note that “14” in the figure is an electrode for measuring the element resistance of the tin oxide semiconductor thin film 11.

When a flammable gas such as gasoline is brought into contact with such an HC sensor 6, the flammable gas concentration (vol.%)
Since there is a correlation as shown in FIG. 6 with respect to the element resistance (Ω), the gas concentration can be obtained by measuring the element resistance of the HC sensor 6.

The element resistance value from the HC sensor 6 is taken into the control means 8 and converted into a gas concentration here. However, as described above, since the HC sensor 6 has a problem in rising response, the control unit 8 of the present embodiment, to estimate the actual concentration raised by a predetermined time T ₁ of the time of rising, which was configured to output a signal for controlling the fuel injection amount from the fuel injector 3 as a correction value I have.
That is, the element output of the HC sensor 6 to be used and the inclination angle of the rise are measured in advance for various gas concentrations, and this information is stored in the control means 8. And
Based on the element output taken from the HC sensor 6, an initial value of the inclination angle is calculated, and the concentration corresponding to the inclination angle is retrieved from information stored in advance. This makes it possible to estimate the actual increase in the concentration immediately after the start-up, and based on this estimated value, the fuel injector 3
And outputs a signal so as to control the injection amount.

The time when the estimated concentration is used is a predetermined time T ₁ after the purge control valve 5 is opened and the gas is introduced from the canister 9 into the guide passage 2b.
And only is this is managed by a signal from the timer 15, which after a predetermined time T ₁ elapses is because actual concentration change is not caused a problem in the responsiveness of the HC sensor 6 for a gradual . Therefore, the predetermined time T ₁ is
The output of the HC sensor 6 is determined by the pipe diameter of the HC sensor 6, the opening / closing characteristics of the purge control valve 5, and the like.
It can be appropriately selected depending on various states such as 8%, 95%, and 90%.

The downstream side of the guide passage 2b is connected to a fuel supply passage 4 of the internal combustion engine, and an orifice 7 is formed at a connection portion of the fuel supply passage 4 to the guide passage 2b. The orifice 7 causes a difference between the internal pressure of the guide passage 2b and the internal pressure of the fuel supply passage 4 and, when the pressure difference exceeds a certain value, causes the flow of the fuel gas passing through the orifice 7 to be choked. It functions to stably maintain the flow rate of the fuel gas supplied from the guide passage 2b to the fuel supply passage 4. In this embodiment, the orifice 7 is provided in the guide passage 2b.
And the fuel gas supply means is constituted by connecting the downstream of the orifice 7 to the fuel supply passage 4. However, the fuel gas supply means of the present invention is not limited to this. The gas may be supplied into the fuel supply passage by the above method.

Reference numeral "3" in the drawing denotes a fuel injector (fuel injection means) for injecting fuel such as gasoline stored in the fuel tank 1 into the fuel supply passage 4 by the suction pump 16 in the form of a mist. By mixing with the intake air adjusted by the opening degree of the valve 17, a gas having an appropriate mixing ratio is supplied into a cylinder of an internal combustion engine (not shown).

Next, the operation of the purification device according to the present embodiment will be described with reference to the flowchart shown in FIG. First, it is checked whether or not the engine, which is the internal combustion engine, has been started. If the engine has been started, the zero point of the HC sensor 6 is reset with the purge control valve 5 of the guide passage 2b closed. (Steps 1-3). This is because a semiconductor thin film element such as tin oxide shifts its zero point when left for a long time. When the engine is stopped, the gas cannot be purified by burning the gas. Therefore, the gas is absorbed and stored in the canister 9.

Next, the purge control valve 5 is opened and the fuel gas stored in the canister 9 is supplied to the HC sensor 6.
At the same time, the signal that the purge control valve is opened is taken into the control means, and the timer 15 is set to t = 0.
(Steps 4 and 5). A predetermined time t from t = 0
₀ , preferably for 0.1 to 2 seconds, the concentration information from the HC sensor 5 is taken into the control means 8 (steps 6 and 7).

The control means 8 calculates and obtains the inclination angle of the density rise curve based on the taken-in density information. This inclination angle is, for example, the inclination angle of the element output about 0.1 to 2 seconds after the purge control valve 5 is opened, and the value of this inclination angle is associated with the control means 8 in advance as shown in FIG. Search the estimated concentration curve stored in. For example, in FIG. 3, when the inclination angle immediately after the purge control valve 5 is opened is (A), the actual concentration rise curve is (A), so the information of the concentration curve of (A) is searched. (Steps 8-9). Similarly, when the tilt angle is (b), the actual density rise curve is (B), and when the tilt angle is (c), the actual density rise curve is (C). Then, the information on the estimated concentration is output to the fuel injector 3, and control is performed so that the fuel injected into the internal combustion engine has an optimum injection amount.

[0024] The calculate and obtain such estimated concentration is from by opening the purge control valve 5 and the predetermined time T _1, after the predetermined time T ₁ elapses is directly an element output from the HC sensor 6 This information is output to the fuel injector 3 only by converting it into the gas concentration, and the fuel injected into the internal combustion engine is controlled so as to have the optimum injection amount (steps 10 to 12). This is after a predetermined time T ₁ elapses is because no problem occurs in the responsiveness of the HC sensor 6 for change in concentration of the gas passing through the guide passage 2b is gentle.

As described above, in the purifying apparatus of this embodiment, it takes time for the gas sensor using the tin oxide SnO ₂ semiconductor or the like to reach the equilibrium state of the oxygen partial pressure according to the gas concentration to be detected, and the response time is short. Despite the drawback that the characteristics are reduced, this equilibrium state is already determined by the initial value of the element resistance, and the inclination angle of the variation curve of the initial value of the element resistance is calculated and estimated. It is configured to obtain a concentration and to output a signal for controlling the injection amount from the fuel injector 3 based on the estimated concentration. As a result, as shown in FIG. 4, the start-up response immediately after the start of the purge operation is improved, and the fuel injection amount to the engine can be controlled to an optimum value.

In the above-described embodiment, the HC sensor 6 using a semiconductor element has been described as an example of the concentration detecting means. However, the concentration detecting means of the present invention is not limited to this. A type sensor, a contact combustion type sensor, and the like can also be applied.

[0027]

According to the present invention, the inclination angle of the concentration rise curve immediately after the opening / closing valve is opened is calculated based on the gas concentration detected by the concentration detecting means, and this calculation result is stored in advance. An estimated concentration is obtained from the information of the gas concentration with respect to the inclination angle, and a signal for controlling the fuel injection amount of the fuel injection means based on the estimated concentration is output until a predetermined time has elapsed since the opening / closing valve was opened. Therefore, the responsiveness to a sudden change in the concentration of the gas to be purged is improved. As a result, a control signal corresponding to the purge amount can be immediately output to the fuel injection device, and the fuel of the optimum injection amount can be supplied to the internal combustion engine.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a fuel gas purifying apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure in control means of the embodiment.

FIG. 3 is a graph showing a relationship between an output of a density detecting unit and an estimated density according to the embodiment.

FIG. 4 is a graph showing a relationship between the concentration estimated by the purification device of the embodiment, the actual concentration, and the concentration obtained by the concentration detecting means.

FIG. 5 is a perspective view showing a conventional HC sensor.

FIG. 6 is a graph showing the relationship between the concentration and the element resistance by a conventional HC sensor.

FIG. 7 is a graph showing a fall characteristic and a rise characteristic of an element output by a conventional HC sensor.

FIG. 8 is a graph showing a change in concentration in a conventional fuel gas purification device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel tank 2a, 2b ... Guide passage 3 ... Fuel injector (fuel injection means) 4 ... Fuel supply passage 5 ... Purge control valve (open / close valve) 6 ... HC sensor (concentration detection means) 7 ... Orifice (fuel gas supply means) 8) Control means 9 ... Canister 10 ... Ceramic substrate 11 ... Tin oxide thin film 12 ... Heater 13 ... Temperature sensor 14 ... Electrode 15 ... Timer 16 ... Suction pump 17 ... Passage opening / closing valve

Claims (1)

(57) [Scope of request for utility model registration] An excess fuel gas generated in a fuel tank (1) is passed through a guide passage (2a, 2b) to a fuel supply passage (4) of an internal combustion engine provided with fuel injection means (3). An on-off valve (5) provided in the guide passage (2a, 2b) for opening and closing the guide passage (2a, 2b); an on-off valve (5) and the fuel supply passage. A concentration detection means (6) provided in the guide passage (2a, 2b) between the fuel tank (1) and the fuel tank (1), for detecting the concentration of fuel gas in the guide passage (2a, 2b). ), A fuel gas supply means (7) for supplying a fuel gas into the fuel supply passage (4) and a fuel gas concentration detected by the concentration detection means (6). Calculate the inclination angle of the concentration rise curve immediately after opening (t ₀ ) An estimated concentration is obtained from the calculation result and the information of the fuel gas concentration with respect to the inclination angle stored in advance, and the estimated concentration is obtained until a predetermined time (T ₁ ) elapses after the on-off valve (5) is opened. Control means (8) for outputting a signal for controlling the fuel injection amount of the fuel injection means (3) based on the control of the fuel injection means (3).