JPH06147035A - Detector of vapor adsorption quantity in canister - Google Patents

Abstract

PURPOSE:To make an amount of adsorption of fuel vapor predictively calculable by detecting the distribution of activated carbon in a state that the fuel vapor in a canister is saturated. CONSTITUTION:A sensor member 21 is inserted into activated carbon 2 after defining a direction toward an atmospheric inlet port 5 from a fuel vapor feed hole 3 as the longitudinal direction. This sensor member 21 is provided with a heater 21a and a thermometer 21b. When this heater 21a receives the specified energing energy from a sensor drive circuit 22, the sensor member 21 rises in temperature as a whole, and only a part, where liquid fuel exists, comes to a relatively low temperature. an adsorption quantity calculating circuit 23 predictively calculates an amount of fuel vapor being adsorbed in a canister 1 on the basis of energizing energy information to be fed out of the sensor drive circuit 22 and mean temperature information of the sensor member 21 to be fed out of the thermometer 21b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a canister vapor adsorption amount detecting device, and more particularly to a canister vapor adsorption amount detecting device for estimating how much fuel vapor is adsorbed in a canister.

[0002]

2. Description of the Related Art When an internal combustion engine is stopped in a sufficiently warmed-up state, a large amount of fuel vapor vaporized by residual heat is generated in a similarly warmed-up fuel tank. Therefore, although the fuel supply to the combustion chamber of the internal combustion engine has already stopped, the fuel vapor flows out into the intake passage.

Frequent starting and
Due to repeated stoppages, it is necessary to prevent the fuel vapor from being released from the intake passage into the atmosphere via the air filter or the like. Therefore, generally, in a vehicle-mounted internal combustion engine, a canister is provided between the fuel tank and the internal combustion engine so that the fuel vapor generated in the fuel tank is adsorbed by the canister.

The canister contains activated carbon inside, and a vapor passage and a purge passage are provided on one side of the activated carbon, and an atmosphere introduction hole is provided on the other side. The purge passage is a passage provided to connect the fuel tank and the canister, and the fuel vapor generated in the fuel tank is supplied through this vapor passage.

Since activated carbon is adsorbed on the fuel vapor supplied to the canister, its release to the atmosphere is prevented. Then, when the internal combustion engine is restarted and the intake negative pressure is supplied into the purge passage, this is used to release the fuel adsorbed together with the air sucked from the atmosphere introduction hole to the internal combustion engine.

By the way, in recent years, in response to the demand for higher performance of vehicles, the recovery and utilization of such fuel vapor is not limited to simply adsorbing the fuel vapor at the time of stop and purging at the time of start, but more efficiently. Required to be used.

For example, Japanese Unexamined Patent Publication (Kokai) No. 58-148259 discloses a device for detecting that the canister is saturated with fuel vapor for the purpose of preventing a problem caused when the fuel vapor is supplied beyond the adsorption capacity of the canister. Disclosure.

That is, when the fuel vapor exceeding the adsorption capacity is supplied to the canister, the fuel that cannot be fully adsorbed by the activated carbon will overflow to the outside from the air introduction hole provided in the canister as liquid fuel. Become.
Therefore, in the device described in the above publication, a thermistor is inserted inside the activated carbon and its resistance value is monitored, and if the thermistor is cooled by the liquid fuel adhering and its resistance value rises, the fuel vapor is saturated. I have decided.

When it is determined that the fuel vapor is saturated in the canister, the vapor passage is closed to stop the fuel vapor supply to the canister to prevent the fuel from flowing out of the atmosphere introducing hole of the canister. There is.

[0010]

However, with the above-mentioned conventional structure, it is only possible to determine whether the fuel vapor in the canister is saturated, and it is necessary to meet the recent demand for recovery and utilization of fuel vapor. Is not enough.

As a recent demand for the recovery and utilization of fuel vapor, for example, when the internal combustion engine is idling or when the load is light, in order to prevent the air-fuel ratio deviation due to the fuel purged from the canister, the amount of purged fuel is set to some extent. It is possible to estimate.

The amount of fuel to be purged is an amount determined by the amount of fuel vapor adsorbed in the canister. Therefore, in order to meet such requirements,
It is not enough to detect the saturation or unsaturation of the fuel vapor in the canister, and it is necessary to be able to detect how much fuel vapor is adsorbed in the canister.

In addition to this, there is also known a device that uses the purged fuel from the canister to improve the startability of the internal combustion engine. In this case, however, the canister when the internal combustion engine is restarted is It is preferable that the fuel vapor is saturated. Therefore, when the purge fuel is used for such an application, it is necessary to control the fuel vapor adsorbed during the operation of the internal combustion engine to a state immediately before saturation.

Therefore, also in this case, similarly to the case of the above example, it is required to be able to detect how much fuel vapor is adsorbed in the canister, and the saturation of the fuel vapor is required as in the above-mentioned conventional configuration. The demand cannot be met only by detecting unsaturation.

The present invention has been made in view of the above points, and detects the amount of adsorbed fuel vapor by estimating how much of the activated carbon present in the canister is filled with fuel vapor. It is an object of the present invention to provide a vapor adsorption amount detection device for a canister that enables the above.

[0016]

The above object can be achieved by a vapor adsorption amount detecting device for a canister having the following configuration.

Activated carbon is housed inside the canister to adsorb the fuel vapor. The canister is provided with a fuel vapor supply hole on one side and an air introduction hole on the other side across the activated carbon.

The sensor member is inserted into the activated carbon with the direction from the fuel vapor supply hole toward the air introduction hole being the longitudinal direction. The sensor member is a member that generates heat over its entire length when energized and outputs a signal according to its average temperature.

A sensor driving means is provided to supply a predetermined energizing energy to the sensor member. The sensor driving means appropriately drives the sensor member and provides the adsorption amount estimating means with information on the energizing energy being supplied to the sensor member.

The adsorption amount estimating means detects the fuel existing in the canister based on the information on the energizing energy supplied from the sensor driving means and the information on the average temperature of the sensor member supplied from the sensor member. Detects the amount cooled by the heat of vaporization, and based on this detection value,
Estimate the amount of fuel vapor adsorbed in the canister.

[0021]

In the canister vapor adsorption amount detecting device having the above structure, when fuel vapor is supplied to the canister from the fuel vapor supply hole, activated carbon existing in the vicinity of the fuel vapor supply hole of the activated carbon is quickly saturated. Reach When the supply of the fuel vapor is further continued, the distribution of the activated carbon that has reached the saturated state gradually progresses toward the atmosphere holes and finally spreads over the entire canister.

Further, when the fuel vapor adsorbed in the canister is purged, when air flows in through the air holes, the fuel vapor adsorbed by the activated carbon near the air holes is quickly desorbed accordingly. To be done. And
When the fuel is further purged, the distribution of the unsaturated carbon that has become unsaturated due to the desorption of the fuel vapor gradually progresses toward the fuel vapor supply hole.

The sensor member is inserted in the activated carbon with the longitudinal direction of the saturated distribution or the unsaturated distribution in the adsorption or desorption process of the fuel vapor. Therefore, when almost no fuel vapor is adsorbed in the canister, the sensor member is inserted into the unsaturated activated carbon over almost the entire length.

On the other hand, when the fuel vapor is adsorbed until the canister becomes saturated, the sensor member contains the liquid fuel between the particles due to saturation over almost the entire length. It has been inserted into activated carbon.

The sensor driving circuit supplies a predetermined energizing energy to the sensor member. As a result, the sensor member generates heat, and the portion inserted in the unsaturated activated carbon heats up to a predetermined temperature by its own heat generation.

On the other hand, a part of the sensor member inserted into the activated carbon containing the liquid fuel due to saturation is deprived of a part of the energizing energy as heat of vaporization of the liquid fuel, and is inserted into the unsaturated carbon. The temperature becomes lower than that of the part where it is. That is, the average temperature of the sensor member becomes lower as the saturated region of the activated carbon stored in the canister increases, that is, as the amount of fuel vapor adsorbed in the canister increases.

Therefore, the adsorption amount estimating means uses the above-mentioned characteristics as heat of vaporization of liquid fuel based on the energizing energy supplied to the sensor member and the average temperature of the sensor member. The amount of fuel vapor adsorbed in the canister is estimated based on the amount of heat generated.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an embodiment of a canister vapor adsorption amount detecting device according to the present invention. In the figure, 1 is
The canister used for the apparatus of a present Example is shown. The activated carbon 2 that adsorbs the fuel vapor supplied to the canister 1 is housed inside the canister 1. Above the activated carbon 2, a fuel vapor supply hole 3 and a fuel purge hole 4 are provided. Further, below the activated carbon 2, there is provided an air introduction hole 5 that communicates the inside of the canister 1 with the atmosphere.

The fuel vapor supply hole 3 communicates with the upper portion of the fuel tank 15 via the purge passage 11 and the constant pressure release valve 12. The constant pressure release valve 12 includes a valve body 12a that controls conduction of the purge passage 11 and a valve body 12a that is connected to a fuel tank 13
It is a one-way valve consisting of a spring 12b that pushes to the side,
The valve is opened only when the pressure inside the fuel tank 13 becomes equal to or higher than a predetermined pressure.

Therefore, when the temperature of the fuel tank 13 rises and fuel vapor is generated to such an extent that the internal pressure of the fuel tank 13 exceeds a predetermined pressure, the constant pressure release valve 12 opens,
Fuel vapor is supplied to the canister 1. As a result, the internal pressure of the fuel tank 13 drops, and when the internal pressure becomes lower than a predetermined pressure, the constant pressure release valve 12 is closed and the supply of fuel vapor is interrupted.

The fuel purge hole 4 of the canister 1 has an intake passage 16 through a purge control valve 14 and a purge passage 15.
Of the throttle valve 17. The purge control valve 14 is a control valve that can be opened / closed by remote control from the outside, and when the purge control valve 14 is opened, the fuel purge hole 4 and the purge passage 15 communicate with each other.

By the way, when the internal combustion engine is in operation, intake negative pressure is constantly generated in the intake passage 16. Therefore, as long as it communicates with the downstream of the throttle valve 17,
In the purge passage 15, intake negative pressure is always generated during the operation of the internal combustion engine. Therefore, if the purge control valve 14 opens during the operation of the internal combustion engine,
Intake negative pressure is introduced through the fuel purge hole 4.

As described above, on the opposite side of the fuel purge hole 4 with the activated carbon 2 interposed, there is the air introduction hole 5 communicating with the atmosphere. Therefore, when an intake negative pressure is introduced from the fuel purge hole 4, air flows into the canister 1 from the atmosphere introduction hole 5. The inflowing air passes through the activated carbon 2 and is supplied from the fuel purge hole 4 to the internal combustion engine through the purge passage 14.

Here, when the fuel vapor flowing from the fuel tank 13 is adsorbed on the activated carbon 2 of the canister 1, the adsorbed fuel vapor is discharged from the fuel purge hole 4 together with the air passing through the activated carbon 2. It will be spilled and purged into the internal combustion engine. As described above, the apparatus according to the present embodiment effectively recovers and utilizes the fuel vapor through the canister 1 by appropriately controlling the purge control valve 14 while maintaining the internal pressure of the fuel tank 13 within a predetermined pressure. It is a configuration that can.

In FIG. 1, reference numeral 21 indicates a sensor member which is a main part of the apparatus of this embodiment. The sensor member 21 is inserted into the activated carbon 2 in the central portion of the canister 1 with the direction from the fuel vapor supply hole 3 side toward the atmosphere introduction hole 5 side being the longitudinal direction. The sensor member 21 has a heater 21a extending over the entire length of the sensor member 21 inside the main body having excellent thermal conductivity.
And a thermometer 21b.

The heater 21a is used in the sensor drive circuit 22.
Is energized with a predetermined energy, and a heat quantity corresponding to the energized energy is emitted. The heater member 21 is thereby heated over its entire length. The thermometer 21b is composed of, for example, a thermocouple, measures the temperature of the heater member 21 over the entire length, and outputs a signal corresponding to the average temperature.

In FIG. 1, reference numeral 23 indicates an adsorption amount estimation circuit. The adsorption amount estimation circuit 23 is connected to the thermometer 21b and supplied with a signal corresponding to the average temperature of the sensor member 21, and the sensor drive circuit 22 provides information on the energized energy supplied to the heater 21a. Is receiving.

The operation of the vapor adsorption amount detecting device for the canister will be described below. Prior to that, the relationship between the average temperature of the sensor member 21 and the adsorption amount of fuel vapor will be described.

FIG. 2 shows the average temperature of the sensor member 21 output from the thermometer 21b when the sensor drive circuit 22 supplies a constant energizing energy to the heater 21a, as an example of driving the apparatus of this embodiment. 3 is a graph showing the relationship with the amount of fuel vapor adsorbed in the canister 1. This graph shows that the average temperature of the sensor member 21 decreases as the adsorption amount of the fuel vapor increases.

In FIG. 1, when the heater 21a is energized with a predetermined energy in a state where no fuel vapor is adsorbed in the canister 1, the heater 21a passes the activated carbon 2 through the main body of the heater member 21. To heat. In this case, the portion of the sensor member 21 that is inserted into the activated carbon 2 can be regarded as having substantially the same environment in any portion, and a temperature difference in the sensor member 21 hardly occurs (in FIG. 1). , T ₁ = T ₂ = T ₃ = T ₄ ).

Then, the heat generated by the heater 21a is conducted from the activated carbon 2 existing in the vicinity of the central portion to the activated carbon 2 existing in the peripheral portion, and finally radiated to the outside of the canister 1. That is, the temperature of the heater member 21 is
The energy supplied to a and the energy radiated to the outside of the canister 1 converge to a temperature at which they are in an equilibrium state.

Here, the internal pressure of the fuel tank 13 increases,
When the constant pressure release valve 12 opens, the fuel generated in the fuel tank 13 flows into the canister 1 through the purge passage 11 as described above. At this time, the fuel vapor flows into the canister 1 from the fuel vapor supply hole 3 and is adsorbed by the activated carbon 2 having adsorption ability.

At the initial stage when no fuel vapor is adsorbed in the canister 1, all the activated carbon 2 has an adsorbing ability, so that the fuel vapor that has flowed into the canister 1 is located near the fuel vapor supply hole 3. It is adsorbed on the existing activated carbon 2. Then, when the fuel vapor further continues to flow in and the adsorption capacity of the activated carbon 2 existing near the fuel vapor supply hole 3 decreases, the fuel vapor flowing into the canister 1 gradually exists at a position away from the fuel vapor supply hole 3. Activated carbon 2
Will be adsorbed on.

Therefore, when the fuel vapor is continuously supplied from the fuel tank 13, the activated carbon 2 existing in the upper part of the canister 1 is saturated with the fuel vapor, and when the activated carbon 2 existing in the lowermost part is saturated, the entire canister 1 is discharged. It's saturated.

By the way, when the fuel vapor is further supplied after the activated carbon 2 is saturated with the fuel vapor, the fuel vapor that cannot be adsorbed is liquefied and liquid fuel is generated between the activated carbon particles. Therefore, the liquid fuel adheres to the part of the sensor member 21 that has been inserted into the already saturated activated carbon 2. When the liquid fuel adheres to the sensor member 21, the adhered liquid fuel is vaporized by the heat supplied from the heater 21a.

That is, the portion of the sensor member 21 that is inserted into the saturated activated carbon 2 is eventually cooled by the maximum heat of vaporization that vaporizes the liquid fuel, and is inserted into the unsaturated activated carbon. The temperature is lower than that of the part where

Further, as described above, the thermometer 21b in the sensor member 21 of the apparatus of this embodiment outputs a signal corresponding to the average temperature of the entire temperature. Therefore, when the canister 1 is gradually saturated with the fuel vapor as the fuel vapor is supplied, the temperatures of T _{1 to} T _{4 in} FIG. 1 become lower in that order, and the temperature is output from the thermometer 21b as shown in FIG. The value of the applied signal also decreases accordingly.

Next, the case where the fuel is purged from the state where the fuel vapor is adsorbed in the canister 1 will be described.

When the purge control valve 14 is opened during the operation of the internal combustion engine, the intake negative pressure is introduced into the canister 1 as described above. Therefore, from the air introduction hole 5, the canister 1
Air flows inward. The air flows through the activated carbon 2 to the fuel purge hole 4, but when the activated carbon 2 adsorbs the fuel vapor, the air is desorbed when flowing through the activated carbon 2.

In this way, when the fuel vapor is desorbed by the air flowing in through the air introduction hole 5, the activated carbon 2 existing on the air introduction hole 5 side is desorbed first.
And finally, the activated carbon 2 existing on the fuel purge hole 4 side
When the desorption is performed, all the fuel vapor in the canister 1 is purged.

Therefore, regardless of whether it is the adsorption process or the desorption process, when only a small amount of the fuel vapor is adsorbed in the canister 1, the air introduction hole 5 of the sensor member 21 inserted in the activated carbon 2 is introduced into the atmosphere introduction hole 5. The near portion has a relatively high temperature, and when a large amount of fuel vapor is adsorbed, the entire sensor member 21 including the portion near the atmosphere introduction hole 5 has a relatively low temperature.

In the present embodiment, the fuel vapor adsorption amount is estimated by utilizing the relationship between the fuel vapor adsorption amount and the average temperature of the sensor member. That is, the adsorption amount estimation circuit 23 detects the energy supplied to the heater 21a,
Based on the output signal of the thermometer 21b, the amount of heat used for vaporizing the liquid fuel in the canister 1 is calculated.

Based on this value, the extent to which the canister 1 is saturated with fuel vapor is estimated, and the amount of fuel vapor adsorbed in the canister 1 is estimated based on this estimation. .

As described above, the device of this embodiment utilizes the relationship between the amount of fuel vapor adsorbed in the canister 1 and the distribution of saturated activated carbon, and the fuel which cannot be detected by the conventional device. It is possible to detect the amount of vapor adsorption.
Therefore, by using the device of the present embodiment, the fuel vapor generated in the fuel tank is collected more efficiently,
It becomes possible to use.

In the apparatus of the above embodiment, the amount of fuel vapor adsorbed is estimated based on the difference in temperature detected by the thermometer 21b while the energy supplied to the heater 21a by the sensor drive circuit 22 is kept constant. However, the present invention is not limited to this, and the amount of adsorption may be estimated based on the energization energy supplied to the heater 21a and the average temperature of the sensor member 21 detected by the thermometer 21b.

Therefore, for example, the heater 21a may be energized so that the average temperature of the sensor member 21 is constant, and the fuel vapor supply amount may be estimated from the energized energy. FIG. 3 is a graph showing the relationship between the energization energy and the fuel vapor adsorption amount when the apparatus of the above-described embodiment is driven with this configuration. In this case, it is necessary as the fuel vapor adsorption amount increases. It shows that the energization energy tends to increase.

Further, in the above-mentioned embodiment, the sensor member 21 is constructed by holding the heater 21a and the thermometer 21b in the sensor member main body, but the present invention is not limited to this, and heat is generated by energization, and It is sufficient that the average temperature of the sensor member 21 can be measured. Therefore, for example, a configuration using a thermistor having the functions of the heater 21a and the thermometer 21b may be used.

[0058]

As described above, according to the present invention, when the amount of the fuel vapor adsorbed in the canister is large, it is used for the heat of vaporization of the fuel among the energy supplied to the sensor member inserted in the activated carbon. The rate of increase. Therefore, the temperature of the sensor member corresponds to the amount of fuel vapor adsorbed in the canister.

Therefore, according to the vapor adsorption amount detecting device for a canister of the present invention, the amount of fuel vapor adsorbed in the canister can be estimated based on the energization energy and the average temperature of the sensor member. Therefore, it has a feature that the fuel vapor can be recovered and used more effectively than the conventional device.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a canister vapor adsorption amount detection device according to the present invention.

FIG. 2 is a graph showing the relationship between the average temperature of the sensor member and the adsorbed amount of fuel vapor when a constant energizing energy is supplied to the sensor member of the apparatus of this embodiment.

FIG. 3 is a graph showing the relationship between the energization energy required to keep the average temperature of the sensor member of the device of the present embodiment constant and the adsorption amount of fuel vapor.

[Explanation of symbols] 1 canister 2 activated carbon 3 fuel vapor supply hole 4 fuel purge hole 5 atmosphere introduction hole 11 purge passage 12 constant pressure release valve 13 fuel tank 14 purge release valve 15 purge passage 21 sensor member 21a heater 21b thermometer 22 sensor drive Circuit 23 Adsorption amount estimation circuit

Claims (1)

[Claims] 1. An activated carbon for adsorbing fuel vapor is housed inside, and is adsorbed in a canister having a fuel vapor supply hole on one side and an atmosphere introduction hole on the other side across the activated carbon. A device for detecting a vapor adsorption amount of a canister that detects the amount of fuel vapor, wherein the activated carbon is inserted into the activated carbon as a longitudinal direction from the fuel vapor supply hole toward the atmosphere introduction hole, and is energized over the entire length. A sensor member that generates heat and outputs a signal according to an average temperature of the entire length; a sensor driving unit that supplies a predetermined energizing energy to the sensor member; an average temperature of the sensor member output from the sensor member; Based on the energization energy supplied to the sensor member by the sensor driving means, the sensor member is cooled by the heat of vaporization of the fuel existing in the canister. A canister vapor adsorption amount detection device, comprising: an adsorption amount estimation means for detecting the rejected amount and estimating the amount of the fuel vapor adsorbed in the canister based on the detected value.