JPH04353258A - Canister inside fuel adsorption quantity measuring device - Google Patents

Abstract

PURPOSE:To perform evaporation system self-diagnosis and air fuel ratio control at the time of purge with high precision by providing in a canister an adsorption quantity sensor to detect directly the adsorption quantity of evaporation fuel, making it possible to measure directly the adsorption quantity of evaporation fuel even if a vehicle is traveling. CONSTITUTION:At the time of engine stop, a purge valve 38 is closed, and evaporation fuel from a fuel tank 26 is introduced into a canister 34 and adsorbed by means of an adsorbent. Next, at the time of engine operation, the valve 38 is opened, and evaporation fuel adsorbed and retained inside the canister 34 is purged by introducing fresh air, and fed to the inside of an air intake passage 6 through the 2nd ventilation passage 32-2. At an evaporation system such as this, a static electricity adsorption quantity sensor which has a pair of electrode portions 42, 44 whose dielectric constant changes according to the increase of adsorbed evaporation fuel, is provided in the canister 34, and evaporation system malfunction diagnosis is conducted from its output signal by means of a control portion 24 on the basis of a phenomenon in which the output of an O2 sensor 22 is changed from 'rich' to 'lean'.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the amount of adsorbed fuel in a canister, and more particularly to an apparatus for measuring the amount of adsorbed fuel in a canister that can directly measure the amount of adsorbed fuel vapor in a canister.

0002

[Prior Art] Evaporative fuel that leaks into the atmosphere from fuel tanks, float chambers of vaporizers, etc. contains a large amount of hydrocarbons (HC) and is one of the causes of air pollution, and also causes fuel loss. Various techniques are known to prevent this problem. A typical example is to temporarily adsorb and hold the evaporated fuel in the fuel tank in a canister containing an adsorbent such as activated carbon, and then purge the evaporated fuel adsorbed and held by this adsorbent when the internal combustion engine is operating. There is an evaporative system that supplies the engine.

[0003] As this evaporative system, there is one shown in FIG. 7, for example. That is, in FIG. 7, 202 is an internal combustion engine, 204 is an intake manifold, 206 is an intake passage,
208 is an intake valve, 210 is a combustion chamber, 212 is a piston,
214 is an exhaust valve, 216 is an exhaust manifold, and 218 is an exhaust passage. The intake manifold 204 is provided with a fuel injection valve 220 that injects fuel into the combustion chamber 210. The exhaust manifold 206 also includes an exhaust passage 21.
An O2 sensor 222 is provided to detect the oxygen concentration within the air. This fuel injection valve 220 and O2 sensor 222
is communicated to the control unit (ECM) 224 of the internal combustion engine 202.

[0004] Further, a fuel supply passage 228 is connected to the fuel injection valve 220 for introducing fuel from a fuel tank 226. A fuel pump 230 that pumps the fuel in the fuel tank 226 to the fuel injection valve 220 is interposed in the middle of the fuel supply passage 228 .

In order to guide the vaporized fuel generated in the fuel tank 226, a ventilation passage 232 is provided, one end of which communicates with the upper end of the fuel tank 226, and the other end of which communicates with the intake passage 206.

In the middle of this ventilation path 232, there is a canister 2.
34 is interposed. Therefore, the air passage 232 is a first air passage 232-1 between the fuel tank 226 and the canister 234.
and a second air passage 232-2 between the canister 234 and the intake passage 206.

[0007] The canister 234 is connected to the internal combustion engine 202.
While the internal combustion engine 202 is stopped, the evaporated fuel generated in the fuel tank 226 is adsorbed and retained by the adsorbent, and while the internal combustion engine 202 is operating, the evaporated fuel retained in the intake air is purged by introducing fresh air, and this separated evaporated fuel is removed. is supplied to the intake passage 206 as purge fuel.

The second air passage 232-2 is provided with a purge valve 2 that opens and closes the second air passage 232-2 in order to supply and disconnect the separated evaporated fuel from the canister 234 to the intake passage 206.
36 are provided.

[0009] Accordingly, when the internal combustion engine 202 is stopped, the evaporative fuel generated in the fuel tank 226 reaches the canister 234 from the first air passage 232-1 and is collected therein without being released into the atmosphere. At the same time, when the internal combustion engine 202 is operating, fresh air is introduced by the negative pressure generated in the intake passage 206, and the vaporized fuel in the canister 234 is supplied (purged) to the intake passage 206.

[0010] Further, as this evaporative system, for example, there are disclosed
It is disclosed in Japanese Patent No. 71169. Jitsukai 1986-18
The device described in Japanese Patent No. 8864 communicates a canister and an intake passage with a first air-fuel ratio control means that receives an output signal from an air-fuel ratio sensor and outputs a signal to a fuel supply device so as to set the air-fuel ratio to a predetermined value. a control valve provided in the adsorbed fuel release passage; a second air-fuel ratio control means for receiving an output signal from the air-fuel ratio sensor and outputting a signal to the control valve so as to set the air-fuel ratio to a predetermined value; and a second air-fuel ratio control unit. A switching means is provided for switching to control by the first air-fuel ratio control means when the air-fuel ratio cannot be controlled to a predetermined value by the means. Furthermore, the device described in Japanese Utility Model Application Publication No. 57-171169 includes a fuel sensor that detects the concentration of fuel gas remaining in the space between the bottom wall of the case and the support plate, and a fuel sensor based on the sensing output of this fuel sensor. The system is equipped with a detection circuit that drives an alarm indicator.

[0011]

[Problem to be Solved by the Invention] In recent years, in such evaporative systems, the system is controlled by a control section (
ECU) is required to check whether it is normal or not, and in order to comply with this check, there is a method to detect changes in feedback by the O2 sensor when purging evaporated fuel, and this method. Detection methods have been proposed, such as adding a method of measuring the pressure inside the fuel tank or measuring the weight of the canister.

However, in the method of detecting changes in feedback by the O2 sensor, when purging evaporated fuel, the air-fuel ratio is changed to rich or lean by purge air (air) depending on the amount of fuel components adsorbed to the canister. There was an inconvenience that it became impossible to judge because of the change.

Furthermore, the method of detecting the pressure in the fuel tank indirectly estimates the amount of adsorption in the canister, which has the disadvantage of low reliability.

Furthermore, the method of measuring the weight of the canister has the disadvantage that it is difficult to implement because of the vibrations of the vehicle while the vehicle is actually running.

[0015]

[Means for Solving the Problems] Therefore, in order to eliminate the above-mentioned disadvantages, the present invention provides a ventilation passage that communicates the inside of the fuel tank with the intake passage of the intake system of the internal combustion engine, and provides a ventilation passage that communicates the inside of the fuel tank with the intake passage of the intake system of the internal combustion engine. a canister is provided in the middle of the air passage, which adsorbs and holds the evaporated fuel generated in the fuel tank, and during operation of the internal combustion engine, allows the adsorbed and held evaporated fuel to be released and supplied to the intake passage by introducing fresh air; The canister is characterized in that an adsorption amount sensor that outputs an electric signal according to the adsorption amount of evaporated fuel is provided in the canister, and this intake air amount sensor is provided in communication with the control section of the internal combustion engine.

[0016]

[Operation] According to the structure of the present invention, since the adsorption amount sensor is provided in the canister, it is possible to directly measure the adsorption amount of evaporated fuel in the canister while the vehicle is running. The amount of evaporated fuel adsorbed can be accurately measured even when the fuel vapor is adsorbed, allowing self-diagnosis of the evaporative system and detailed control of the air-fuel ratio during purging.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described in detail and specifically below with reference to the drawings. 1 to 6 show embodiments of this invention. In FIG. 1, 2 is an internal combustion engine, 4 is an internal combustion engine, and 4 is an internal combustion engine.
1 is an intake manifold, 6 is an intake passage, 8 is an intake valve, 10 is a combustion chamber, 12 is a piston, 14 is an exhaust valve, 16 is an exhaust manifold, and 18 is an exhaust passage. The intake manifold 4 is provided with a fuel injection valve 20 that injects fuel into the combustion chamber 10. Further, the exhaust manifold 16 is provided with an O2 sensor 22 that detects the oxygen concentration within the exhaust passage 18. This fuel injection valve 20 and O2 sensor 22
is communicated to the control unit (ECM) 24 of the internal combustion engine 2.

The fuel injection valve 20 also includes a fuel tank 2.
A fuel supply passage 28 that leads fuel from 6 is connected thereto. A fuel pump 30 is interposed in the middle of the fuel supply passage 28 to forcefully feed the fuel in the fuel tank 26 to the fuel injection valve 20.

In order to guide the evaporated fuel generated in the fuel tank 26, a ventilation passage 32 is provided, one end of which communicates with the upper part of the fuel tank 26, and the other end of which communicates with the intake passage 6. This ventilation path 32 constitutes an evaporation system.

A canister 34 is located in the middle of this ventilation path 32.
is intervened. Therefore, the air passage 32 is connected to the fuel tank 26.
and a second ventilation path 32-2 between the canister 34 and the intake passage 6.

The canister 34 adsorbs and holds vaporized fuel generated in the fuel tank 26 in an adsorbent made of activated carbon when the internal combustion engine 2 is stopped, and also holds intake air by introducing fresh air while the internal combustion engine 2 is operating. The evaporated fuel is released (
purge), and the separated evaporated fuel is supplied to the intake passage 6 as purge fuel.

A check valve 36 is provided in the middle of the first ventilation path 32-1.

Further, the second ventilation passage 32-2 is provided with a purge valve 38 that opens and closes the second ventilation passage 32-2 in order to supply and disconnect the separated evaporated fuel from the canister 34 to the intake passage 6.

Further, an adsorption amount sensor 40 is provided within the canister 34 to measure the adsorption amount of evaporated fuel. In this embodiment, the adsorption amount sensor 40 is composed of, for example, two opposing electrode sections, a first electrode section 42 and a second electrode section 44, and as shown in FIG. The electric capacitance C as an electric signal between the first electrode section 42 and the second electrode section 44 is outputted to the control section 24 via an amplifier (AMP) 46. Said first electrode part 4
2 and the second electrode part 44 are buried in an adsorbent, which is activated carbon, in a spaced manner.

Next, the operation of this embodiment will be explained.

When the internal combustion engine 2 is stopped, the evaporated fuel generated in the fuel tank 26 reaches the canister 34 through the first air passage 32-1, and is adsorbed and held by the adsorbent in the canister 34. .

When the internal combustion engine 2 is operated, the vaporized fuel adsorbed and held in the canister 34 is purged by introducing fresh air, and is supplied into the intake passage 6 from the second air passage 32-2.

By the way, in this embodiment, when vaporized fuel is adsorbed by the adsorbent in the canister 34, the dielectric constant between the first and second electrode sections 42 and 44 of the adsorption amount sensor 40 changes. , the capacitance changes. That is, if the capacitance is C, the permittivity of the dielectric is Σ, the opposing area of the first and second electrode parts 42 and 44 is A, and the interval between the first and second electrode parts 42 and 44 is t, The capacitance is obtained by C=0.0885ΣA/t.

More specifically, when the evaporated fuel is adsorbed to the adsorbent in the canister 34, the air inside the adsorbent is replaced by the fuel, so the dielectric constant Σ is 1 to 1 for the liquid 2 to 1 for the air. The capacitance C is replaced by the one in the 9th place, and the capacitance C becomes larger with respect to the amount of adsorption, as shown in FIG. However, adsorption is an exothermic reaction and is accompanied by heat generation. Therefore, a temperature sensor (not shown) is provided in the vicinity of the first and second electrode sections 42 and 44, and the capacitance shown in FIG. 2 is corrected based on the output current from this temperature sensor. It is something that can be measured.

The adsorption amount sensor 40 outputs its capacitance C to the control section 24 via the amplifier 46. This control unit 24 performs, for example, diagnosis of the evaporation system. In other words, as shown in FIG. 3, if the adsorption amount is at a certain level, the O2 sensor 22 changes from lean to rich, while if the adsorption amount is less than a certain level, the O2 sensor 22 changes from rich to lean. Changes to This performs a failure diagnosis of the evaporative system.

That is, in system failure diagnosis, as shown in the flowchart of FIG. 4, when the program starts (step 102), it is determined whether the amount of adsorption is large (step 104), and if the adsorption amount is higher than a certain level. If step 104 is YES, it is determined whether or not the O2 sensor 22 is lean (step 106);
If the answer is NO, this determination is continued.

If YES in step 106, the purge is turned on, that is, the purge valve 38 is opened (step 108), and it is determined whether the O2 sensor 22 has changed from lean to rich (step 110).
). If step 110 is NO, it is determined that the evaporative system is malfunctioning (step 112), while if step 110 is YES, it is determined that the evaporative system is operating properly (step 114).

On the other hand, if the intake air amount is less than a certain level and NO in step 104, the O2 sensor 22
is rich or not (step 116). If NO in this step 116, the determination is continued.

If YES in step 116, the purge is turned on (step 118), and it is determined whether the O2 sensor 22 has changed from rich to lean (step 120).

[0035] If YES in this step 120,
While it is determined that the evaporation system is working well (
step 122), if NO in step 120,
It is determined that the evaporation system has failed (step 124).

As a result, even while the vehicle is running, failure diagnosis of the evaporative system can be easily and reliably performed based on the adsorbed amount of evaporated fuel.

Furthermore, as shown in FIG. 5, the purge valve 38
It can be diagnosed that the evaporative system is normal if the intake air amount deteriorates due to the operating state of the evaporative system.

Furthermore, as shown in FIG. 6, depending on the amount of adsorption,
When the condition changes from a state where no purge is performed, such as in the idle operating range of the internal combustion engine 2, to a condition where purge is performed, the purge valve 38 is activated.
By controlling the increase/decrease of the fuel in advance at the same time as operating the air-fuel ratio, it is possible to reduce variations in the air-fuel ratio, and finely control the air-fuel ratio.

[0039]

As is clear from the above detailed description, according to the present invention, an adsorption amount sensor that outputs an electric signal according to the adsorption amount of vaporized fuel is provided in the canister, and the intake amount sensor is connected to the internal combustion engine. By communicating with the control unit,
The amount of evaporated fuel adsorbed in the canister can be directly measured while the vehicle is running, and the amount of evaporated fuel adsorbed can be accurately measured even while the vehicle is running, allowing self-diagnosis of the evaporative system and emptying during purging. Fuel ratio control can be performed finely.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an evaporation system equipped with a fuel intake amount measuring device.

FIG. 2 is a diagram showing the relationship between the amount of adsorbed fuel vapor and the capacitance in an adsorption amount sensor.

FIG. 3 is a time chart when diagnosing the evaporative system.

FIG. 4 is a flowchart when diagnosing the evaporative system.

FIG. 5 is a time chart for measuring the adsorption amount of evaporated fuel depending on the operating status of the purge valve.

FIG. 6 is a time chart in which fuel control is increased or decreased in advance at the same time as the purge valve is operated.

FIG. 7 is a configuration diagram of a conventional evaporation system.

[Explanation of symbols]

2 Internal combustion engine 20 Fuel injection valve 22 O2 sensor 24 Control section 26 Fuel tank 32 Ventilation path 34 Canister 38 Purge valve 40 Adsorption amount sensor 42 First electrode part 44 Second electrode part

Claims (1)

[Claims] 1. A vent passage is provided that communicates the inside of the fuel tank with an intake passage of an intake system of an internal combustion engine, and the vent passage is provided to adsorb and hold evaporated fuel generated in the fuel tank when the internal combustion engine is stopped, and when the internal combustion engine is operating. In this case, a canister is provided in the middle of the ventilation passage, which releases the adsorbed and held evaporated fuel by introducing fresh air and supplies it to the intake passage, and inside this canister there is an adsorption device that outputs an electric signal according to the amount of adsorbed evaporated fuel. A device for measuring the amount of fuel intake in a canister, characterized in that the intake amount sensor is provided in communication with a control section of the internal combustion engine.