JP2003035214A - Evaporated fuel control device for fuel tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the fuel vapor from being released to the atmosphere in feeding the fuel. SOLUTION: A feed pipe 111 of a sealed fuel tank 11 is connected to an upper space of a liquid level in a tank by means of a circulating line 111a, and a vent valve 131 composed of a solenoid valve is mounted on the breather piping connecting the upper space of the liquid level in the tank to a canister 10. An electronic control unit(ECU) 30 adjusts the internal pressure of the fuel tank in feeding the fuel from the feed pipe, and adjusts a flow rate of a gas circulated in the feed pipe from to the tank through the circulating line to adjust the pressure in the feed pipe approximately equal to the atmospheric pressure during feeding. Whereby the negative pressure is applied to the feed pipe, and the increase of the absorption of the fuel vapor by the canister caused by the intrusion of the air into the tank with the fuel, and the release of the fuel vapor form the feed pipe to the atmospheric air can be effectively prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporated fuel control device for a fuel tank, and more particularly to a fuel for adjusting the pressure inside the fuel tank when refueling the fuel tank to reduce the amount of evaporated fuel discharged from the fuel tank to the outside. The present invention relates to an evaporated fuel control device for a tank.

[0002]

2. Description of the Related Art In order to prevent evaporative fuel from being diffused into the atmosphere from a fuel tank of an internal combustion engine, particularly a fuel tank of an automobile engine, the fuel tank is provided with a closed structure so that the evaporated fuel (fuel vapor) is outside the tank. Prevented from leaking,
So-called closed fuel tank systems are known. In a closed tank, for example, when the temperature of the fuel in the tank becomes high due to the return of high-temperature return fuel during engine operation, the pressure in the tank may become higher than atmospheric pressure due to evaporation of the fuel. If the pressure in the tank is higher than the atmospheric pressure when refueling the tank, there is a problem that the fuel vapor in the tank is released from the refueling opening to the atmosphere when the refueling opening is opened for refueling.

For this reason, there has been devised a vaporized fuel diffusion prevention device for a closed tank which lowers the pressure in the fuel tank prior to the start of refueling to prevent the vaporization of fuel vapor into the atmosphere during refueling. An example of this type of evaporated fuel emission prevention device is disclosed in Japanese Patent Laid-Open No. 8-112279. The device of the publication has a lid opening device for opening a lid (lid) that covers the fuel filler port of the fuel tank. When the driver turns on the fuel filler switch, the fuel vapor in the fuel tank first receives the adsorbent. When the compressor that exhausts to the canister operates and the pressure in the tank becomes equal to or lower than the atmospheric pressure, the lid opening device operates to open the fuel filler port, and permits fueling through the fuel filler port.

As a result, in the device of the above publication, the pressure inside the tank is always atmospheric pressure or lower when the refueling port is opened, so that the fuel vapor is prevented from being released to the atmosphere from the opened refueling port. To be done. Further, in the device of the publication, a filler duct (fuel filler pipe) into which a fuel filler nozzle is inserted at the time of refueling is provided in the fuel tank, and a vent connecting the space above the liquid level in the fuel tank and a portion near the fuel filler pipe inlet A pipe (circulation line) is provided.

Normally, the circulation line is provided to prevent negative pressure from being generated near the inlet of the fuel supply pipe during refueling. During refueling, the jet of fuel from the refueling nozzle flows into the refueling pipe. Since this jet entrains the air around the inside of the fuel supply pipe and flows into the tank, a negative pressure is generated in the fuel supply pipe. When a negative pressure is generated in the fuel supply pipe, the fuel stays in the fuel supply pipe in order to provide a head difference required for the fuel to flow from the fuel supply pipe into the tank. When the negative pressure in the oil supply pipe increases, the liquid level of the fuel that stays in the oil supply pipe also rises, so when the negative pressure in the oil supply pipe increases to a certain extent, the liquid level in the oil supply pipe reaches the liquid level detection opening provided in the oil supply nozzle. However, there is a problem that refueling becomes impossible because refueling is automatically stopped.

Even if the fuel cannot be refilled, the air is supplied into the fuel tank and the pressure in the fuel tank rises. In order to prevent this pressure increase, if the gas in the space above the liquid level in the tank is discharged to the canister by, for example, exhaust means, not only the air but also the fuel vapor in the tank mixed with air will be discharged to the canister. . Therefore, the amount of fuel that supplements the fuel vapor discharged outside the tank is evaporated from the liquid surface. That is, when air flows into the fuel tank during refueling, the amount of fuel evaporated in the fuel tank increases. In this case, since the evaporated fuel is discharged to the canister by the exhaust means, when air flows into the tank, the amount of fuel vapor sent to the canister increases and the adsorbent of the canister is saturated with the adsorbed fuel vapor. There are cases.

The circulation line is provided for the purpose of preventing the generation of negative pressure and the entrainment of air at the inlet portion of the oil supply pipe. Since the circulation line communicates with the space above the liquid level in the fuel tank and the fuel filler pipe inlet, if the pressure at the fuel filler inlet decreases due to air entrainment of fuel during refueling, the liquid level in the tank from the circulation line decreases. The gas in the upper space (a mixture of air and the time fuel) is supplied to the inlet portion of the oil supply pipe. Therefore, it is possible to prevent the pressure from decreasing at the inlet portion of the oil supply pipe. The gas supplied from the circulation line to the inlet of the fuel supply pipe is entrained in the jet of fuel and flows into the fuel tank again. Therefore, the gas in the space above the liquid surface of the fuel tank circulates through the circulation line and the oil supply pipe, and the inflow of air from the outside into the fuel tank is prevented.

[0008]

However, in the device disclosed in Japanese Patent Laid-Open No. 8-112279, the internal pressure of the fuel tank is controlled to atmospheric pressure or lower before refueling is started.
The fuel tank internal pressure is not controlled during refueling. In order to prevent negative pressure and air entrapment at the inlet of the oil supply pipe, always supply the same amount of gas as the amount of gas removed from the inlet of the oil supply pipe by the entrainment of the fuel jet through the circulation line. There is a need to. Therefore, in consideration of the pressure loss of the gas passing through the circulation line, the internal pressure of the fuel tank needs to be such that the above amount of gas always flows through the circulation line to the inlet portion of the fuel supply pipe.

In the device disclosed in Japanese Patent Laid-Open No. 8-112279, since the internal pressure of the fuel tank is not controlled during refueling, the internal pressure of the fuel tank during refueling may not always be an appropriate pressure. In this case, for example, when the internal pressure of the fuel tank becomes lower than an appropriate value, the amount of gas supplied through the circulation line becomes insufficient, and the insufficient amount of air is entrained in the fuel flow and enters the fuel tank. There arises a problem that the production amount of fuel vapor increases. Further, when the fuel tank internal pressure during refueling becomes higher than an appropriate value, the amount of gas supplied to the refueling pipe inlet portion through the circulation line becomes excessive,
There is a problem that the gas containing the fuel vapor is released from the refueling port to the atmosphere.

In view of the above-mentioned problems of the prior art, the present invention controls the pressure in the fuel tank to an appropriate value during refueling, and saturates the adsorbent in the canister due to an increase in the production amount of fuel vapor in the fuel tank, An object of the present invention is to provide an evaporated fuel control device for a fuel tank, which can prevent the release of fuel vapor to the atmosphere.

[0011]

According to the first aspect of the present invention, the evaporation of the fuel tank reduces the discharge amount of the evaporated fuel from the fuel tank to the outside by adjusting the pressure in the tank when refueling the fuel tank. A fuel control device, in which a fueling nozzle is inserted, a fueling pipe for guiding the fuel supplied from the fueling nozzle into a fuel tank, and an exhausting means for exhausting gas in a space above the liquid level in the fuel tank to a predetermined place And a circulation passage for connecting the liquid level upper space in the fuel tank to an inlet portion of the fuel supply pipe, and for circulating gas in the upper liquid level space in the fuel tank to the fuel pipe inlet portion during refueling from the fueling nozzle. When,
Pressure detecting means for detecting the pressure in the fuel tank, and the fuel tank internal pressure detected by the pressure detecting means during refueling from the refueling nozzle passes through the circulation passage from the fuel tank to the refueling pipe. There is provided an evaporated fuel control device for a fuel tank, comprising: a control unit that controls the operation of the exhaust unit so that a pressure of a predetermined flow rate of the gas flows in an inlet portion.

That is, in the first aspect of the invention, the operation of the exhaust means is controlled so that the fuel tank internal pressure reaches a predetermined target value during refueling. In this case, as the exhaust means, for example, an electromagnetic opening / closing valve arranged in the breather pipe connecting the liquid level upper space in the fuel tank and the canister is used, and the opening / closing control of this electromagnetic opening / closing valve is performed according to the internal pressure of the fuel tank. The pressure in the fuel tank can be controlled to a target value.

Further, as a target value in the tank internal pressure control, the difference between the tank internal pressure and the pressure of the circulating passage connecting portion of the oil supply pipe is equal to the circulating passage pressure loss when a predetermined amount of gas flows through the circulating passage. Is set. The amount of gas in the oil supply pipe that is wound by the fuel supplied from the oil supply nozzle is substantially constant if the oil supply flow rate is determined. Therefore, if gas equal to the amount of gas entrained by the fuel is supplied from the fuel tank to the inlet of the fuel supply pipe through the circulation passage, the air flows into the fuel tank and the evaporated fuel is released into the atmosphere. And can be prevented. Also,
The pressure difference at both ends of the circulation passage (that is, the pressure loss in the circulation passage) required for the above-mentioned amount of gas to flow through the circulation passage.
Can be calculated if the diameter and length of the circulation passage are determined. Further, since the pressure at the inlet of the fuel supply pipe is substantially equal to the atmospheric pressure, the required fuel tank internal pressure can be calculated if the pressure loss in the circulation passage is determined as described above. Therefore, if the refueling flow rate is determined, the target pressure in the tank during refueling is determined accordingly. For this reason, for example, when the refueling amount is assumed to be a standard value, the target pressure in the tank is calculated in advance, and the in-tank pressure is controlled to this target pressure during refueling so that the air flows into the fuel tank. It is possible to prevent the increase of the evaporated fuel and the release of the evaporated fuel to the atmosphere.

According to the second aspect of the present invention, there is provided the fuel vapor control device for a fuel tank, which adjusts the tank pressure when refueling the fuel tank to reduce the amount of fuel vapor discharged from the fuel tank to the outside. An oil supply pipe into which a fuel supply nozzle is inserted and which guides fuel supplied from the fuel supply nozzle into the fuel tank; an exhaust means for exhausting gas in the liquid tank upper space of the fuel tank to a predetermined location; A liquid passage upper space is connected to an inlet portion of the refueling pipe, and a circulation passage for circulating the gas in the upper liquid surface space in the fuel tank to the refueling pipe inlet portion during refueling from the refueling nozzle; A pressure detecting means for detecting a pressure; and a passage through the circulation passage which is required to maintain the pressure at the inlet portion of the oil supply pipe at substantially atmospheric pressure based on the oil supply flow rate during oil supply from the oil supply nozzle. Circulation amount setting means for setting the flow rate of the body, and internal pressure setting means for setting the target pressure in the fuel tank required to flow the gas at the flow rate set by the circulation amount setting means through the circulation passage. And a control means for controlling the operation of the exhaust means so that the pressure detected by the pressure detection means becomes the target pressure set by the internal pressure setting means. To be done.

That is, according to the second aspect of the present invention, there is provided circulation amount setting means for setting the target flow rate of the gas flowing through the circulation passage based on the refueling flow rate during refueling from the refueling nozzle. The refueling flow rate from the refueling nozzle may vary depending on the refueling location (gas station) or refueling nozzle. Therefore, if the refueling flow rate is always constant and the target pressure in the tank is set The internal pressure may not reach an appropriate value. Therefore, in the present invention, the refueling flow rate from the refueling nozzle is measured during refueling,
A gas entrainment flow rate of the fuel is calculated based on the measured refueling flow rate, and the entrainment flow rate is set as a gas circulation flow rate through the circulation passage. For example, the refueling flow rate can be calculated based on the tank internal pressure during refueling with the exhaust means activated. In the present invention, the required circulation flow rate is calculated based on the actual refueling flow rate, and the target pressure in the fuel tank is set based on this circulation flow rate. As a result, even when the refueling flow rate changes, it is possible to reliably prevent an increase in the evaporated fuel due to the inflow of air into the fuel tank and a release of the evaporated fuel to the atmosphere.

According to the third aspect of the present invention, there is provided a fuel tank evaporative fuel control device for adjusting the tank internal pressure when fueling a fuel tank to reduce the amount of evaporative fuel discharged from the fuel tank to the outside. A refueling nozzle is inserted and is inserted between a refueling pipe for guiding fuel supplied from the refueling nozzle into the fuel tank and an outer periphery of the refueling nozzle and an inner wall surface of the refueling pipe when the refueling nozzle is inserted. A mechanical seal that prevents the fuel vapor from being released into the atmosphere from the gap between the inner wall surface of the pipe, an exhaust unit that exhausts the gas in the space above the liquid level in the fuel tank to a predetermined location, and a liquid in the fuel tank The upper surface space is connected to a portion of the fuel supply pipe closer to the fuel tank than the mechanical seal, and the gas in the upper liquid surface space in the fuel tank is circulated in the fuel supply pipe during refueling from the fueling nozzle. A circulation passage, a pressure detecting means for detecting the pressure in the fuel tank, and a mechanical seal for adjusting the pressure of the oil supply pipe portion to which the circulation passage is connected during refueling from the refueling nozzle based on the refueling flow rate. Circulation amount setting means for setting the gas flow rate through the circulation passage, which is required to maintain the upper limit pressure at which no leakage occurs from the circulation passage, and the flow amount of gas set by the preceding circulation amount setting means for the circulation passage. Compare the pressure in the fuel tank that is required to flow through the fuel tank with the upper limit pressure in the fuel tank that does not cause the fuel to flow back from the fueling pipe to the outside when the fueling nozzle is removed from the fueling pipe after refueling. Then, whichever is smaller, the internal pressure setting means for setting the target pressure in the fuel tank during refueling, and the pressure detected by the pressure detection means are set by the internal pressure setting means. As will become target pressure, the fuel vapor control system for a fuel tank and a control means for controlling operation of said exhaust means is provided.

That is, according to the third aspect of the invention, the oil supply pipe is provided with a mechanical seal for sealing the gap between the nozzle and the oil supply pipe when the oil supply nozzle is inserted. For this reason, even if the pressure of the fuel tank side portion from the mechanical seal of the fuel supply pipe rises to the upper limit pressure of the seal, the evaporated fuel is not released from the tank side portion to the atmosphere. Further, the circulation passage is connected to the tank side portion of the fuel supply pipe, and prevents the pressure of the fuel supply pipe tank side portion from decreasing due to the entrainment of gas by the fuel flow. In this way, if the pressure on the fuel filler tank side can be made higher than atmospheric pressure, the fuel tank internal pressure should be set as high as possible within the range where refueling is possible to suppress the evaporation of fuel in the tank. It is preferable in that

Therefore, in the present invention, the target circulation flow rate of the gas flowing through the circulation passage is set based on the refueling flow rate as in the second aspect of the present invention. However, the target pressure in the fuel tank during refueling is the above target circulation flow rate. The upper limit pressure of the seal is added to the pressure loss of the circulation passage at that time. Also, if the pressure in the fuel tank during refueling becomes too high, the fuel in the refueling pipe overflows from the refueling port to the outside when the refueling is finished and the refueling nozzle is removed from the refueling pipe by the pressure in the tank. Return occurs. Therefore, in the present invention, the tank internal pressure set on the basis of the upper limit pressure of the seal and the target circulation flow rate is compared with the upper limit pressure in the tank in which backflow does not occur, and the smaller one is the target pressure in the tank. I am trying to set it as. As a result, in the present invention, it is possible to prevent the blowback and prevent the increase of the evaporated fuel in the tank and the release of the evaporated fuel to the atmosphere.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of an embodiment in which the present invention is applied to an automobile fuel tank. In FIG. 1, 100 is an internal combustion engine body, 1 is an intake passage of the internal combustion engine 100, and 3 is an air cleaner disposed in the intake passage 1. The intake passage 1 is provided with a throttle valve 6 that opens according to the operation of an accelerator pedal (not shown) by the driver. Reference numeral 11 in FIG. 1 denotes an engine fuel tank. The fuel oil in the tank 11 is boosted by the fuel pump 70 and is fed through the feed pipe 71 to the engine 1
No. 00 is pressure-fed to the fuel injection valve 101 of each cylinder.

The fuel tank 11 is provided with an oil supply pipe 111 for supplying oil into the tank. Further, in the present embodiment, a portion near the inlet (fuel filler port) 114 of the fuel filler pipe 111 communicates with the liquid level upper space in the fuel tank 11 through the circulation passage (circulation line) 111a. Circulation line 11
1a has a function of supplying the gas in the fuel tank 11 to the vicinity of the fuel filler port 114 at the time of fueling from the fuel filler port 114, and preventing the inside of the fuel filler pipe 111 from becoming negative pressure, as described later. Reference numeral 115 in FIG. 1 denotes a lid that covers the oil supply port 114 of the oil supply pipe 111. In the present embodiment, in order to refuel the tank from the refueling pipe 111, the lid 11
It is necessary to open 5 and remove the cap 113 provided at the filler opening 114 of the filler pipe. The lid 115 includes an actuator of an appropriate type such as a solenoid actuator, and an electronic control unit (ECU) 3 described later.
A lid opener 115a that opens the lid 115 by a drive signal from 0 is provided.

A breather pipe 13 is connected to the upper part of the tank 11 to connect a fuel oil liquid level upper space in the tank 11 to a canister 10 described later. A vent valve 131 such as a solenoid valve, a COV (CUT OFF VALVE) 132 and a RO, each of which is a float valve, are provided at a connecting portion between the breather pipe 13 and the tank 11.
V (ROLL OVER VALVE) 133 is provided. The vent valve 131, as will be described later,
The valve is opened by a drive signal from the ECU 30, and has a function of discharging the fuel paper in the fuel tank 11 to the canister 10 through the breather pipe 13.

In this embodiment, the vent valve 131 is always closed, and the fuel tank 11 is maintained in a sealed state. As a result, the fuel vapor generated by the evaporation of the fuel in the fuel tank 11 is sealed in the fuel tank 11 and does not leak outside. Therefore, the release of fuel vapor to the atmosphere is completely prevented. However, as a result of sealing the fuel tank 11, for example, the high temperature return fuel from the fuel injection valve 101 during engine operation is
When the temperature of the fuel in the tank rises due to the increase of the fuel vapor pressure, the fuel vapor pressure rises accordingly, and the pressure in the tank rises. In the present embodiment, the fuel tank 11 is provided with the pressure sensor 120 that detects the pressure in the space above the liquid level in the tank, and the tank internal pressure exceeds the allowable value (for example, the design pressure of the fuel tank) during engine operation. When rising, the vent valve 131 is opened, and the fuel vapor in the tank is released to the canister 10 through the breather pipe 13 to reduce the tank internal pressure.

The ROV 133 provided in the tank 11 is
The valve is closed due to the rise of the liquid level during refueling, and the connection between the vent valve 131 and the fuel tank 11 is cut off. In addition, ROV13
3 is a vent valve 131 and a tank 11 when the vehicle falls.
It also has a function of closing a connection portion with and preventing a large amount of fuel oil from leaking to the outside through the breather pipe 13. The COV 132 is arranged in parallel with the ROV 133 and shuts off the communication between the vent valve 131 and the tank 11 when the liquid level further rises above the ROV 133. CO
When the liquid level rises during refueling, V132 opens even after the ROV133 valve is closed to connect the tank 11 and the vent valve 131, but during the opening of the vent valve 131, the liquid level fluctuates due to the turning of the vehicle to the COV132 position. It has a function of closing the valve when the surface reaches or when the vehicle falls, and preventing the fuel oil from entering the breather pipe 13 through the vent valve 131.

Reference numeral 30 in FIG. 1 denotes an electronic control unit (ECU) of the engine. The ECU 30 includes a ROM (read only memory), a RAM (random access memory), a CPU (microprocessor), and a microcomputer having a known configuration in which input / output ports are connected to each other by a bidirectional bus. In addition to the basic control described above, in this embodiment, as will be described later, a tank internal pressure control operation is performed to adjust the tank internal pressure at the time of refueling to prevent the fuel vapor from increasing and the air from entering the tank.

For the above control, the output port of the ECU 30 is connected to the fuel injection valve 101 of the engine 100 via a drive circuit (not shown) to control the fuel injection amount from the fuel injection valve and to the vent valve 131. It is connected and controls the opening and closing of the vent valve 131. In the present embodiment, the vent valve 131 is a solenoid valve, and the opening / closing operation is repeated according to ON / OFF of the drive pulse signal from the ECU 30 input to the solenoid actuator. The flow rate of gas passing through the vent valve 131 increases in proportion to the ratio (duty ratio) of the on time (vent valve open) of the drive pulse signal in one cycle of the pulse signal. Therefore, the duty ratio has the same meaning as the valve opening of a normal control valve. Therefore, in the present specification, the vent valve 131
The duty ratio of the drive pulse signal may be referred to as the opening of the vent valve for convenience. In this case, the fully open state of the vent valve 131 corresponds to the state where the duty ratio of the drive pulse signal is 100%, and the fully closed state corresponds to the state where the duty ratio is 0. In addition, the vent valve 131
As a matter of course, even when a normal control valve is used, the following description is applied as it is by replacing the duty ratio with the valve opening degree.

An output port of the ECU 30 has an actuator for a purge control valve 15, which will be described later, CCV (CANISTER CLOSEURE V) via a drive circuit (not shown).
ALVE) 17 actuators,
In addition to controlling the operation of these valves, they are connected to the lid opener 115a via a drive circuit (not shown) to open the lid 115.

On the other hand, signals representing the engine speed, intake air amount, engine cooling water temperature, vehicle running speed, etc. are input to the input port of the ECU 30 from sensors (not shown) and the driver's switch. A lid opening switch (refueling switch) 140 that outputs a refueling signal in response to an operation is connected. Further, provided in the fuel tank 11,
The output of the pressure sensor 120 that detects the pressure in the tank is supplied to the input port of the ECU 30 via an AD converter (not shown).

Reference numeral 10 in FIG. 1 denotes a canister for adsorbing the fuel vapor in the fuel tank. Canister 10
Is a space above the fuel liquid level of the fuel tank 11 via the breather pipe 13 via the vent valve 131, and the intake passage 1 via the purge pipe 14 via the purge control valve 15.
Further, the atmosphere communication pipe 18 is connected to the atmosphere portion near the fuel filler port 114 via the CCV 17 and the filter 19. The purge control valve 15 is provided with an actuator of an appropriate type such as a solenoid actuator, and opens according to a signal from the ECU 30 to allow the canister 1 to operate.
0 and the intake passage 1 are communicated with each other to purge the canister 10.

Further, the air communication pipe 18 is provided with an air filter 19 and the above-mentioned CCV 17. The air filter 19 removes foreign matter in the air flowing into the canister 10 from the atmosphere communication pipe 18 at the time of performing a purge described later. The CCV 17 includes an actuator of an appropriate type such as a solenoid actuator, and
Atmosphere communication pipe 18 and canister 1 according to the control signal from
The communication with 1 is cut off.

When the vent valve 131 and the CCV 17 are opened while the purge control valve 15 is closed, the fuel tank 11
A mixture of fuel vapor and air flows into the canister 10 from the space above the liquid surface via the breather pipe 13. The inside of the canister is filled with an evaporated fuel adsorbent 50 such as activated carbon. When the pressure in the fuel tank 11 is higher than the atmospheric pressure, the gas containing the fuel vapor in the fuel tank 11 passes through the adsorbent 50 in the canister 10 and then the CCV 17
And the atmosphere communicating pipe 18 to be released into the atmosphere. As a result, only the air after the fuel vapor is removed by the adsorbent 50 in the canister is released from the atmosphere communication pipe 18, and the fuel tank 11 is prevented from releasing the fuel vapor to the atmosphere. The internal pressure of can be reduced.

When the purge control valve 15 and the CCV 17 are opened while the engine 1 is operating and a negative pressure is generated in the intake passage 1, the intake passage 1 is opened in the canister 10 via the purge passage 14. Negative pressure acts on the internal pressure of the canister to lower the atmospheric pressure. Therefore, when the purge control valve 15 is opened, clean air from which foreign matter has been removed by the filter 19 flows from the atmosphere communication pipe 18 into the canister 10.
This air releases the adsorbed fuel vapor from the adsorbent 50, becomes a mixed gas (purge gas) of the fuel vapor and air, flows from the purge passage 14 into the engine intake passage 1, and is burned in the engine combustion chamber. This prevents the adsorbent 50 from being saturated with fuel vapor.

In the present embodiment, the vent valve 131 is normally held closed as described above, and is opened only when the tank internal pressure rises beyond the allowable limit and when refueling is performed as described later. The valve is adapted to adsorb the fuel vapor in the tank to the canister 10. Therefore, the capacity of the canister 10 is set to be relatively small as compared with the case of a normal open type fuel tank that constantly supplies fuel vapor to the canister.

Next, the control of the fuel tank pressure during refueling will be described. When refueling the fuel tank 11 at a refueling station or the like, the refueling port lid 115 is opened, the refueling port cap 113 is removed, the refueling nozzle is inserted into the refueling pipe 111, and fuel is injected from the refueling nozzle. In this case, a jet of fuel supplied from the fueling nozzle is generated in the fueling pipe. This jet entrains the surrounding gas in the oil supply pipe 111 and flows into the tank, so that the inside of the oil supply pipe becomes a negative pressure. Therefore, the atmosphere flows into the oil supply pipe through the gap between the oil supply port 114 and the inserted oil supply nozzle, is entrained in the jet flow, and enters the tank. The air that has entered the fuel tank 11 is mixed with the fuel vapor in the space above the liquid surface to form a mixture.

On the other hand, during refueling, the tank internal pressure rises due to the rise of the liquid level in the tank due to refueling and the invading air.
If the pressure in the tank rises excessively, fuel will not be able to flow from the oil supply pipe 111 into the tank, making it impossible to refuel. Therefore, in order to prevent the pressure in the tank from rising, it is necessary to open the vent valve 131 to exhaust the air-fuel mixture in the space above the liquid surface in the tank 11 to the canister 10. In this case, if the internal pressure of the fuel tank 11 is kept constant, the canister 10 passes through the vent valve 131.
The amount of the air-fuel mixture flowing into the fuel tank 11 becomes equal to the volume of the gas replaced by the rise in the liquid level in the fuel tank 11 and the volume of the air entering the fuel tank by refueling.

Therefore, the larger the amount of air entering the fuel tank due to refueling (air entrainment of fuel), the larger the amount of gas supplied to the canister 10. However, as described above, the air that has entered the fuel tank mixes with the fuel vapor to form a mixture. Therefore, not only the air is exhausted to the canister 10, but the fuel vapor is exhausted together with the air. Therefore, when the amount of air entering the fuel tank increases, the amount of fuel vapor flowing into the canister 10 also increases accordingly.

Further, as described above, in the case of the closed fuel tank system, the fuel vapor is supplied to the canister only when the internal pressure of the fuel tank becomes excessively high or when fueling is limited. Has become. For this reason, in the closed fuel tank system, the adsorbent capacity of the canister is set smaller than that of the normal open fuel tank system in which the fuel vapor is constantly supplied from the fuel tank to the canister, and the amount of fuel vapor that can be adsorbed at one time is set. Is relatively small.

Therefore, when the amount of air entering the fuel tank 11 increases due to the air entrainment of fuel and the amount of fuel vapor flowing into the canister 10 increases, the adsorbent in the canister 10 becomes saturated with fuel vapor. After that, the fuel vapor passes through the canister 10 and is released to the atmosphere. Further, when the refueling flow rate is large and the amount of air entrained by the fuel is large, a relatively large negative pressure may be generated in the refueling pipe. When the negative pressure in the oil supply pipe increases, fuel accumulates in the oil supply pipe to a height corresponding to the pressure difference between the oil supply pipe and the tank, and as the negative pressure in the oil supply pipe increases, the pressure in the tank (positive pressure) increases. ) Is larger, the liquid level of the retained fuel is higher. For this reason, when the negative pressure in the refueling pipe increases, the fuel liquid level in the refueling pipe reaches the liquid level detection hole of the refueling nozzle, and the automatic stop (auto stop) mechanism of the refueling device operates to make it impossible to continue refueling. The problem arises.

In the present embodiment, in order to prevent the intrusion of air into the fuel tank and the operation of the auto stop mechanism due to the entrainment of fuel, the circulation line 11 is provided in the oil supply pipe 111.
1a (FIG. 1) is provided. That is, when the inside of the fuel supply pipe 111 becomes a negative pressure at the time of refueling, the gas (mixture of air and fuel vapor) in the liquid level upper space of the fuel tank 11 having a relatively high pressure passes through the circulation passage 111a and the vicinity of the fuel supply port 114. Will flow into. As a result, the pressure in the vicinity of the oil supply port 114 of the oil supply pipe 111 becomes substantially atmospheric pressure, and
Ambient air is prevented from flowing into 4. The gas flowing into the oil supply pipe 111 from the circulation line 111a is entrained in the jet of fuel in the oil supply pipe 111, returns to the fuel tank together with the fuel, and again flows into the circulation line from the liquid level upper space. In this case, since there is no invasion of air from the outside, the fuel tank internal pressure does not increase due to the air entrainment of fuel, and the amount of fuel vapor flowing into the canister 10 does not increase.

That is, by providing the circulation line 111a, the gas in the space above the liquid level in the fuel tank circulates through the refueling pipe, and the intrusion of air from the refueling port 114 and the negative pressure in the refueling pipe 111 are prevented. It is possible to prevent the increase. However, in some cases, simply providing the circulation line 111a may not always prevent air from entering the fuel tank.

That is, the circulation flow rate of the gas circulating in the oil supply pipe 111 through the circulation line 111a is determined by the fuel tank 1
1 It changes according to the pressure difference between the internal pressure and the pressure in the oil supply pipe 111. Therefore, for example, when the differential pressure in the circulation line 111a is smaller than an appropriate value, the circulation flow rate of the gas passing through the circulation line 111a becomes smaller than the amount of the gas entrained in the fuel, and the air flows into the fuel as much as the circulation flow rate is insufficient. Is caught in the fuel tank 11 and enters the fuel tank 11. When the differential pressure in the circulation line 111a is larger than an appropriate value, the circulation flow rate becomes larger than the amount of gas entrained in the fuel, and conversely, an excessive amount of gas (a mixture of air and fuel vapor) is supplied. It comes out to the atmosphere through the mouth 114.

In each of the embodiments described below, by controlling the pressure in the fuel tank 11 to an appropriate value during refueling, both intrusion of air into the fuel tank and release of fuel vapor into the atmosphere can be achieved. I try to prevent it.

(1) First Embodiment First, the most basic embodiment of the tank internal pressure control operation during refueling will be described. In this embodiment, the vent valve 131 is opened / closed during refueling to control the internal pressure of the fuel tank 11 to a predetermined target pressure P ₀ . This target pressure P
₀ is set so that the circulation flow rate of the gas flowing through the circulation line 111a becomes a predetermined value.

At the time of refueling, a gas having a flow rate equal to the amount of gas that is caught in the fuel supplied from the refueling nozzle and flows into the tank 11 from the refueling pipe 111 is circulated.
If it is circulated in the oil supply pipe through the oil supply pipe 111, both the invasion of air into the oil supply pipe 111 and the release of fuel vapor from the oil supply pipe 111 to the atmosphere are completely prevented. At this time, the pressure in the oil supply pipe becomes equal to the atmospheric pressure. On the other hand, the amount of gas entrained in the fuel supply pipe by the fuel (that is, the required gas circulation flow rate) is determined by the fuel flow rate (flow velocity) from the fuel supply nozzle. Further, the fuel flow rate from the fueling nozzle is in a substantially constant flow rate range although there are variations depending on each fueling station and the fueling nozzle. Therefore, in the present embodiment, a standard refueling flow rate (flow velocity) is set in advance from the above flow rate range, and the entrained amount of gas of fuel in refueling at this standard flow rate, that is, the standard gas circulation flow rate is set. It has been calculated.

Further, the specifications of the circulation line 111a (inner diameter,
Once the length is determined), the pressure difference (pressure loss) in the circulation line required to flow the gas with the standard circulation amount can be easily calculated. When the standard amount of gas circulates, the pressure in the oil supply pipe 111 becomes almost atmospheric pressure. Therefore, the tank internal pressure required to flow the gas with the standard circulation amount is a value obtained by adding the pressure loss calculated above to the atmospheric pressure. In the present embodiment, based on the actual specifications of the circulation line 111a and the standard gas circulation amount, the tank internal pressure required to supply the gas from the circulation line 111a to the oil supply pipe 111 with this circulation amount is calculated. Yes, ECU30
The target fuel tank pressure P ₀ is stored in the ROM. Then, the ECU 30 during refueling controls the opening / closing of the vent valve 131 so that the actual fuel tank internal pressure PT detected by the pressure sensor 120 matches the target fuel tank internal pressure P ₀ .

FIG. 2 is a flow chart specifically showing the fuel tank internal pressure control operation of the present embodiment described above. This operation is executed by the ECU 30. Figure 2, Step 2
01 is a lid opening switch 140 set by the vehicle driver.
This is an operation for detecting whether or not (FIG. 1) is turned on. When the lid opening switch 140 is turned on and a refueling signal is output, the ECU 30 operates the lid opener 115a to open the refueling port lid 115, so that the worker removes the refueling port cap 113 to perform refueling. Is possible. Therefore, when the lid opening switch 140 is turned on (when the refueling signal is input), it is expected that the driver has a will to refuel and that refueling is started following the operation of the switch 140.

Therefore, in this embodiment, when the lid opening switch 140 is turned on in step 201, the tank internal pressure control in step 203 and thereafter is executed. That is, in step 203, the current pressure PT in the fuel tank 11 is read from the pressure sensor 120, and in step 205, is the current pressure PT in the fuel tank 11 higher than the value P ₀ previously stored as the above-mentioned target tank pressure? Determine whether or not. Then, in steps 207 and 209, the vent valve 131 is opened when the current fuel tank internal pressure is higher than the target value, and closed when it is low.

As a result, the fuel tank pressure during refueling is
The pressure is maintained so that a gas having a circulation amount corresponding to the standard refueling flow rate is supplied from the fuel tank to the refueling pipe 111, and the invasion of air into the fuel tank and the release of the fuel vapor from the refueling port due to refueling are prevented. . Step 211 shows a judgment as to whether or not the refueling is completed. The end of refueling is determined, for example, by detecting whether or not the refueling port lid 115 is closed. If the refueling port lid 115 is open, that is, if refueling is not completed, until refueling is completed. The operations of steps 205 to 209 are repeated, and the tank internal pressure is maintained at the target pressure P ₀ .

The opening and closing operations of the vent valve 131 in steps 207 and 209 of FIG. 2 are operations with a duty ratio of the solenoid drive pulse of 100% (fully open) and 0% (fully closed), respectively.

(2) Second Embodiment Next, a second embodiment of the tank internal pressure control operation of the present invention will be described. In the first embodiment, the circulation gas flow rate required for the circulation line 111a is set to a constant value because it is set based on the standard oil supply flow rate,
Correspondingly, the target tank pressure P ₀ also has a constant value. However, in actuality, as described above, the refueling flow rate may not necessarily match the standard refueling flow rate depending on the refueling station or refueling nozzle.

Therefore, in the present embodiment, the actual refueling flow rate from the refueling nozzle is measured during refueling, and the gas circulation flow rate and the fuel tank target pressure are calculated based on this actual refueling flow rate. 3 and 4 are flowcharts specifically explaining the fuel tank internal pressure control operation of the present embodiment. This operation is executed by the ECU 30.

When the operation shown in FIG. 3 is started, first in step 301, the lid opening switch 140 is turned on. If the lid opening switch is turned on in step 301, the vent valve 13 in step 303.
1 is opened (fully opened), and the pressure sensor 1
At 20, the tank internal pressure PT is detected. And step 3
At 05, the tank internal pressure PT waits until it decreases to a predetermined value PT _0, and when PT <PT ₀ , the vent valve is closed (fully closed) at step 307. The predetermined pressure PT ₀ is a pressure at which the fuel vapor is not released to the atmosphere from the fuel filler port when the fuel filler cap 113 is removed for fueling, and is set to about atmospheric pressure.

Steps 309 and 311 are an operation for detecting the start of refueling from the refueling nozzle. In this embodiment,
It is determined whether refueling is started based on the fuel tank pressure increase rate during the vent valve closing (step 307). When refueling is started in a closed state in which the vent valve 131 is closed, the tank internal pressure rises at a relatively large speed as the tank liquid level rises. Therefore, in the present embodiment, the increase rate ΔPT of the tank internal pressure has a relatively large value Δ
When PT ₁ is exceeded, it is determined that refueling has started. That is, in step 309, the tank pressure increase width within a predetermined fixed time is calculated based on the detection value of the pressure sensor 120 to calculate the tank pressure increase rate ΔPT.
Then, in step 305, it is determined whether the calculated ΔPT exceeds a predetermined value ΔPT ₁ . Step 3
309 and step 311, ΔPT> in step 311
It is repeated until ΔPT ₁ .

When ΔPT> ΔPT ₁ is satisfied in step 311, that is, when refueling is started, the pressure PU ₁ for opening the vent valve 131 is calculated in steps 313 to 317. Steps 313 to 317
In this operation, the refueling flow rate is temporarily measured with the vent valve 131 closed, and the circulation line 1 is based on the tentative refueling flow rate.
The temporary target circulation amount of 11a and the temporary in-tank target pressure PU ₁ for obtaining this target circulation amount are calculated. Then, in step 319, the tank pressure PT is equal to the target pressure PU.
_It is determined whether or not it has risen to _1, and when PT> PU ₁ , the vent valve is opened (fully opened).

That is, at the start of refueling, the fuel vapor is set to a relatively low value near atmospheric pressure in order to prevent the fuel vapor from being discharged from the refueling port 114. Therefore, if the vent valve 131 is immediately opened (fully opened) in this state, the pressure in the fuel tank does not rise and the amount of gas flowing through the circulation line 111a is insufficient, and a large amount of air may flow into the fuel tank. is there. Therefore, in the present embodiment, at the start of refueling, the pressure in the fuel tank rises to PU _{1, and} then the vent valve 131
Is to be opened.

The operations of steps 313 to 317 will be described in detail below. Step 313 is a temporary calculation operation of the refueling flow rate QF. In the present embodiment, as described later, an accurate refueling flow rate is calculated based on the convergence value of the fuel tank internal pressure after the vent valve is opened (step 32).
9) However, in step 313, in order to calculate the tank internal pressure PU ₁ for opening the vent valve 131, the refueling flow rate QF is temporarily calculated based on the increase rate ΔPT of the tank internal pressure PT.

That is, when the vent valve 131 is closed, the pressure increase rate ΔPT in the tank has a value corresponding to the tank liquid level increase rate, that is, the oil supply flow rate QF. In the present embodiment, the relationship between the oil supply flow rate QF and the tank internal pressure increase rate ΔPT is obtained in advance using the actual fuel tank 11. FIG. 5 is a diagram showing an example of the relationship between the oil supply flow rate QF and the tank internal pressure increase rate ΔPT. As shown in FIG. 5, the oil supply flow rate QF increases almost linearly as the tank internal pressure increase rate ΔPT increases.

In the present embodiment, the relationship of FIG.
Is stored in advance in the ROM of
Based on the tank internal pressure increase rate ΔPT at the start of refueling calculated in step 309, the provisional refueling flow rate Q
Calculate F.

Step 315 is a calculation operation of the temporary target circulation amount QR of the gas flowing through the circulation line 11a. As described above, the target circulation flow rate QR changes according to the refueling flow rate. In the present embodiment, the relationship between the refueling flow rate QF and the target circulation flow rate QR is obtained in advance using the actual fuel tank 11. FIG. 6 is a diagram showing an example of the relationship between the oil supply flow rate and the target circulation flow rate. As shown in FIG. 6, the target circulation flow rate QR
(That is, the gas entrainment amount of fuel) changes substantially linearly with respect to the oil supply flow rate QF.

In the present embodiment, the relationship of FIG.
In step 315, the temporary target circulation flow rate QR is calculated from the relationship shown in FIG. 6 based on the temporary oil supply flow rate QF calculated in step 313.

Step 317 shows a calculation operation of the in-tank target pressure PU ₁ required to give the target circulation flow rate QR. As described above, the pressure loss that occurs in the circulation line when the target circulation flow rate QR is flown can be easily calculated if the specifications of the circulation line are determined. Further, if the circulation line pressure loss when the target circulation flow rate QR is flown is obtained, the required fuel tank internal pressure (target pressure) can be calculated as [atmospheric pressure + pressure loss]. In the present embodiment, the relationship between the circulation flow rate QR and the pressure loss in the circulation line is calculated using the specifications of the actual circulation line 111a of the fuel tank 11, and the target tank pressure PTT is calculated.
The relationship between (atmospheric pressure + pressure loss) and the circulation flow rate QR is obtained in advance. FIG. 7 shows the target pressure PTT in the tank and the circulation flow rate QR.
It is a figure which shows the relationship with. In FIG. 7, the target pressure in the tank is represented by a gauge pressure. Therefore, the target pressure PTT increases in proportion to the square of the circulation flow rate QR.

In the present embodiment, the relationship of FIG.
It is stored in the ROM of 30 and in step 317, the temporary in-tank target pressure PU ₁ is calculated from the relationship of FIG. 7 based on the circulation flow rate QR calculated in step 315.

At step 318, the temporary target tank pressure P
After calculating U ₁ , in steps 318 and 319, wait for the fuel tank internal pressure PT to reach the target pressure PU ₁ and
When PT> PU ₁ , the vent valve 131 is opened (fully opened) in step 321. This prevents a large amount of air from entering the fuel tank at the start of refueling.

Steps 323 to 333 in FIG. 4 are the final target pressure PU ₂ in the fuel tank after opening the vent valve 131.
Is a calculation operation of. In the operations of steps 323 to 333, the provisional target of steps 313 to 317 is that the actual refueling flow rate is obtained based on the converged value of the fuel tank internal pressure after opening the vent valve 131 instead of the fuel tank internal pressure increase rate. This is different from the calculation operation of the pressure PU ₁ .

That is, when the vent valve 131 is opened (fully opened) in step 321 of FIG. 3, the gas replaced by the rise of the liquid level in the tank is discharged from the tank to the breather pipe 13.
Through which the fuel vapor is removed by the adsorbent, and then discharged to the atmosphere through the CCV 17, the atmosphere communication pipe 18, and the filter 19. When the refueling speed is constant, the flow rate of the gas discharged to the canister is also constant due to the rise of the liquid level in the tank. In this case, the pressure loss of the gas discharge path when the vent valve 131 is fully opened, that is, the pressure loss of the flow path from the vent valve 131 to the atmosphere through the canister 10 and the filter 19 changes depending on the flow rate of the gas discharged from the tank. To do. Further, the gas is finally released under the atmospheric pressure. Therefore, at the time of refueling with the vent valve 131 fully opened, the tank internal pressure becomes a pressure corresponding to the flow rate of the gas discharged from the tank. For this reason,
The convergent value of the tank internal pressure at the time of refueling when the vent valve 131 is fully opened represents the refueling flow rate.

In this embodiment, the actual fuel tank 1 is previously prepared.
1 and the exhaust system such as the breather pipe 13 and the canister 10 are used to experimentally determine the refueling flow rate QF and the convergent value of the pressure inside the fuel tank 11, and the result is the R of the ECU 30.
It is stored in OM. FIG. 8 is a diagram showing an example of the relationship between the oil supply flow rate QF and the ultimate value (convergence value) of the tank internal pressure. As shown in FIG. 8, the refueling flow rate increases as the convergence value of the tank internal pressure increases.

Steps 323 and 325 in FIG. 4 are an operation for determining whether or not the tank pressure has converged. That is, in step 323, the rate of change ΔPT of the tank internal pressure is calculated from the detection value of the pressure sensor 120, and in step 325, the rate of change ΔPT is compared to a predetermined value PT2 (PT2 is a comparison to the extent that the tank internal pressure has converged). It is determined that the tank internal pressure has reached the converged value when it becomes smaller than the target value. When the tank internal pressure converges in step 325, next, the converged tank internal pressure PT is read from the pressure sensor 120 in step 327, and in step 329, based on the converged pressure PT, the oil supply flow rate QF is calculated from the relationship of FIG. To calculate.

Then, in step 331, the oil supply flow rate QF
Based on the above, from the relationship of FIG.
Based on the target circulation flow rate QR and the target circulation flow rate QR in step 333, the final target pressure PU ₂ in the tank is calculated from the relationship in FIG. 7 described above.

Then, in steps 335 to 341,
When the tank pressure PT detected by the pressure sensor 120 exceeds the target value PU ₂ , the vent valve 131 is opened (fully opened), and when it is equal to or less than the target value PU ₂ , the valve is closed (fully closed). The process is repeated until it is determined in step 343 that refueling is completed. As a result, in the present embodiment, the pressure in the fuel tank is controlled according to the actual refueling flow rate regardless of the variation in the refueling flow rate, and the infiltration of air into the fuel tank and the diffusion of fuel vapor into the atmosphere Is reliably prevented.

(3) Third Embodiment Next, another embodiment of the present invention will be described. In this embodiment, a mechanical seal is provided at the oil filler nozzle insertion portion of the oil filler pipe 111. FIG. 9 is a schematic view showing the arrangement of the mechanical seal 93. Mechanical seal 93
Is an annular member formed of an elastic body such as oil resistant rubber, and is attached to the inner circumference of the oil supply pipe 111. The oil supply nozzle 91 is inserted into the central hole of the mechanical seal 93, and sealing is performed by elastic contact between the outer circumference of the oil supply nozzle 93 and the inner circumference of the mechanical seal 93. For this reason, in the oil supply pipe 111 having the mechanical seal 93, the sealed section (mechanical seal 93
Even if the pressure of the portion located closer to the fuel tank 11) is increased up to the seal upper limit pressure of the mechanical seal 93 (the upper limit pressure at which leakage does not occur from the contact portion between the nozzle 91 and the seal 93), the refueling port 114 returns to the atmosphere. No fuel vapor is released.

When the mechanical seal 93 is provided as shown in FIG. 9, the circulation line 111a is connected to the sealed section of the oil supply pipe. When the mechanical seal 93 is provided and sealing is performed, entrapment of air into the fuel tank is prevented by the seal 93, but since gas in the sealed section of the oil supply pipe is entrained in the fuel, A large negative pressure may be generated in the sealed compartment, making it impossible to refuel. Therefore, even when the seal 93 is provided, it is necessary to introduce the gas in the fuel tank into the sealed section to prevent the negative pressure from being generated, and the circulation line 111a is provided.

Therefore, in order to keep the pressure in the sealed section of the fuel supply pipe 111 constant, a differential pressure is provided between the internal pressure of the fuel tank and the internal pressure of the sealed section, and the flow rate is equal to the amount of gas entrained in the fuel. As in each of the above-described embodiments, it is necessary to supply the gas from the circulation line 111a to the sealed section of the oil supply pipe.

In this embodiment, the amount of fuel vapor generated in the fuel tank is suppressed by maintaining the pressure in the fuel tank as high as possible during refueling. Even when the mechanical seal 93 is installed in the oil supply pipe 111, it is necessary to discharge the same amount of gas as the fuel supplied to the tank to the canister 10 during refueling in order to keep the tank internal pressure constant. On the other hand, in the tank, the fuel continues to evaporate from the liquid surface even during this period, and the evaporation rate of the fuel increases as the difference between the saturated vapor pressure of the fuel and the fuel vapor partial pressure in the tank increases. On the other hand, if the tank internal pressure is maintained at a low value, the fuel vapor partial pressure in the tank will correspondingly decrease, and the difference between the saturated vapor pressure of fuel and the fuel vapor partial pressure will increase accordingly, and the evaporation of fuel in the tank will increase. As the amount increases, the amount of fuel vapor discharged to the canister also increases. Therefore, in the present embodiment, the fuel tank pressure during refueling is maintained at a value as high as possible to suppress the evaporation of the fuel in the tank.

By the way, the allowable upper limit of the pressure in the fuel tank is determined by several factors. First, the fuel tank pressure cannot be set higher than the limit pressure (design pressure) on the strength of the tank. Further, when the tank internal pressure is increased, the pressure in the mechanical seal sealing section of the oil supply pipe 111 also rises accordingly. However, when the sealing section pressure exceeds the seal upper limit pressure, the fuel vapor leaks from the mechanical seal to the atmosphere. Further, if the tank internal pressure exceeds a certain value (blowback pressure), when the nozzle is removed from the oil supply pipe at the end of refueling, the tank internal pressure pushes the oil supply pipe 1
The so-called blowback occurs, in which the fuel inside 11 flows out from the fuel filler port. Therefore, in the present embodiment, the tank internal pressure is set so as not to exceed the above three pressures.

FIGS. 10 and 11 are flow charts for concretely explaining the tank internal pressure control operation of the present embodiment described above. This operation is executed by the ECU 30. Figure 1
In the operation of 0, steps 1001 to 1009 are
This is a tank internal pressure adjustment operation before refueling is started. Step 10
The operations from 01 to 1009 are the same as steps 301 to 3 in FIG.
Since it is the same as the operation of 07, detailed description is omitted.

Also in the present embodiment, step 10
At 11, it is determined whether or not refueling has started. Step 101
The operation of No. 1 is the same as the operation of Steps 304 and 305 in FIG.
Whether or not the refueling is started is determined based on the calculation of the above and whether or not the calculated ΔPT exceeds a predetermined value. Further, step 101
When it is determined that the refueling is started in step 1, the refueling flow rate Q is calculated in step 1013 using the tank internal pressure increase rate ΔPT detected in step 1011 based on the relationship of FIG.
F is calculated.

In step 1015, the circulation line 11 when a gas having an appropriate circulation flow rate with respect to the oil supply flow rate QF is flown.
The pressure loss calculation operation of 1a is shown. In the present embodiment, the pressure loss when the target circulation flow rate determined with respect to the refueling flow rate is caused to flow through the circulation line 111a is calculated in advance, and the relationship between the refueling flow rate QF and the pressure loss ΔPR as shown in FIG. 12 is obtained. . The relationship of FIG. 12 is stored in the ROM of the ECU 30 in advance. In step 1015, the pressure loss ΔPR of the circulation line 111a is calculated from the relationship of FIG. 12 based on the oil supply flow rate QF calculated in step 1013.

In step 1017 of FIG. 11, the target value PT of the tank internal pressure is calculated using the pressure loss ΔPR calculated above.
₀ is calculated as PT ₀ = ΔPR + PM. Here, PM is the seal upper limit pressure. That is, the in-tank target pressure PT ₀ calculated in step 1017 corresponds to the in-tank pressure in the case where the sealed section of the oil supply pipe 111 is maintained at the maximum pressure within the range where no leakage occurs from the mechanical seal.

In this embodiment, the pressure corresponding to the seal upper limit pressure of the mechanical seal and the design pressure P of the tank are set.
Three of TS and blowback pressure PTB are compared, and the minimum pressure of these is set as the target pressure in the tank during refueling. That is, in step 1019, step 101
The in-tank target pressure PT ₀ corresponding to the seal upper limit pressure calculated in 7 is compared with the tank design pressure PTS. If PT ₀ exceeds the tank design pressure PTS, step 1
At 021, the in-tank target pressure PT ₀ is reset to PTS. Then, at step 1023, PT ₀ is compared with the blowback pressure PTB. If PT ₀ exceeds PTB, at step 1025 the tank target pressure PT ₀ is set to PT ₀ .
Reset to B. The blowback pressure is obtained in advance by an experiment using an actual tank and is stored in the ROM of the ECU 30. As a result, the final value of the target pressure PT _{0 in} the tank is set to the minimum pressure of the tank internal pressure corresponding to the seal upper limit pressure, the tank design pressure, and the blowback pressure, which is the maximum pressure within the allowable range. Be set to pressure.

In this embodiment, the final value of the target pressure in the tank is set to the minimum value of the three values of the tank internal pressure corresponding to the seal upper limit pressure, the tank design pressure, and the blowback pressure. , The tank design pressure is set to a value sufficiently higher than the other two. Therefore, instead of comparing the above three, the pressure in the tank corresponding to the seal upper limit pressure calculated in step 1017 is compared with the blowback pressure, and the smaller value of the two is the final value of the target pressure in the tank. It may be set as.

From the above, the final value P of the target pressure in the tank P
After setting T ₀ , in steps 1027 to 1035, the tank internal pressure is maintained at the target value PT ₀ until the refueling is completed by opening / closing the vent valve 131. Step 1
The operations from 027 to 1035 are the same as the operations from steps 335 to 343 in FIG. With the above operation, in a fuel tank system with a mechanical seal in the refueling pipe, it is possible to set the fuel tank internal pressure to the maximum value within the allowable range while preventing backflow at the end of refueling and atmospheric release of fuel vapor. Therefore, generation of fuel vapor can be suppressed.

[0081]

According to the invention described in each claim, the pressure in the fuel tank is controlled to an appropriate value during refueling, and the adsorbent in the canister is saturated due to an increase in the production amount of fuel vapor in the fuel tank. Also, there is a common effect that it is possible to prevent the release of fuel vapor into the atmosphere.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment in which the present invention is applied to an automobile fuel tank.

FIG. 2 is a flowchart illustrating a first embodiment of a fuel tank internal pressure control operation.

FIG. 3 is a part of a flowchart illustrating a second embodiment of an internal pressure control operation of a fuel tank.

FIG. 4 is a part of a flowchart illustrating a second embodiment of an internal pressure control operation of a fuel tank.

FIG. 5 is a diagram showing an example of a relationship between an oil supply flow rate and a tank internal pressure increase rate.

FIG. 6 is a diagram showing an example of a relationship between an oil supply flow rate and a target circulation flow rate.

FIG. 7 is a diagram showing an example of a relationship between a target pressure in a tank and a circulation flow rate.

FIG. 8 is a diagram showing an example of the relationship between the oil supply flow rate and the ultimate value of the tank internal pressure.

FIG. 9 is a schematic view showing a mechanical seal arrangement.

FIG. 10 is a part of a flowchart illustrating a third embodiment of an internal pressure control operation of a fuel tank.

FIG. 11 is a part of a flowchart illustrating a third embodiment of an internal pressure control operation of a fuel tank.

FIG. 12 is a diagram showing an example of a relationship between an oil supply flow rate and a circulation line pressure loss.

[Explanation of symbols]

10 ... Canister 11 ... Fuel tank 30 ... Electronic control unit (ECU) 111 ... Oil supply pipe 111a ... Circulation line 120 ... Pressure sensor 131 ... Vent valve

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masahiro Kimura             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. F term (reference) 3D038 CA25 CB01 CC04 CC05 CC13                       CC16                 3G044 BA10 DA03 EA05 EA08 FA04                       GA03 GA23 GA27

Claims (3)

[Claims] 1. A fuel tank evaporative fuel control device for adjusting an internal pressure of a fuel tank when refueling the fuel tank to reduce the amount of evaporated fuel discharged from the fuel tank to the outside, wherein a refueling nozzle is inserted, An oil supply pipe for guiding the fuel supplied from the nozzle into the fuel tank, an exhaust means for exhausting the gas in the fuel tank upper liquid level space to a predetermined place, and a fuel tank inner liquid level upper space for the oil supply pipe. A circulation passage connected to the inlet portion for circulating the gas in the upper liquid level space in the fuel tank to the fuel filler pipe inlet portion during refueling from the refueling nozzle, and a pressure detecting means for detecting the pressure in the fuel tank. During refueling from the refueling nozzle, the fuel tank internal pressure detected by the pressure detecting means passes through the circulation passage from the inside of the fuel tank to the refueling pipe inlet portion at a predetermined flow rate. So that the pressure body flow, evaporative fuel control apparatus for a fuel tank and a control means for controlling operation of said exhaust means. 2. A fuel tank evaporative fuel control device for reducing the amount of evaporative fuel discharged from the fuel tank to the outside by adjusting the pressure inside the fuel tank when refueling the fuel tank. An oil supply pipe for guiding the fuel supplied from the nozzle into the fuel tank, an exhaust means for exhausting the gas in the fuel tank upper liquid level space to a predetermined place, and a fuel tank inner liquid level upper space for the oil supply pipe. A circulation passage connected to the inlet portion for circulating the gas in the upper liquid level space in the fuel tank to the fuel filler pipe inlet portion during refueling from the refueling nozzle, and a pressure detecting means for detecting the pressure in the fuel tank. During refueling from the refueling nozzle, based on the refueling flow rate,
Circulation amount setting means for setting the flow rate of the gas passing through the circulation passage required to maintain the pressure at the inlet portion of the oil supply pipe at approximately atmospheric pressure, and the gas having the flow rate set by the circulation amount setting means Internal pressure setting means for setting the target pressure in the fuel tank required to flow through the circulation passage, and the pressure detected by the pressure detecting means becomes the target pressure set by the internal pressure setting means. And a control means for controlling the operation of the exhaust means, and an evaporated fuel control device for a fuel tank. 3. A fuel tank evaporative fuel control device for adjusting the pressure inside the fuel tank to reduce the amount of evaporative fuel discharged from the fuel tank to the outside when refueling the fuel tank, the refueling nozzle being inserted, A fuel supply pipe that guides fuel supplied from a nozzle into the fuel tank, and is inserted between the outer periphery of the fuel supply nozzle and the inner wall surface of the fuel supply pipe when the fuel supply nozzle is inserted. A mechanical seal for preventing vapor from being released to the atmosphere, an exhaust means for exhausting gas in the upper liquid level space in the fuel tank to a predetermined place, and a liquid upper space in the fuel tank for the fuel pipe. A circulation passage that is connected to a portion closer to the fuel tank than the mechanical seal, and that circulates the gas in the upper liquid surface space inside the fuel tank into the fuel supply pipe during refueling from the fuel nozzle. A pressure detecting means for detecting a tank inside pressure, during refueling from the fuel supply nozzle, based on the oil flow rate,
Circulation amount setting means for setting a gas flow rate through the circulation passage, which is required to maintain the pressure of the oil supply pipe portion to which the circulation passage is connected to the upper limit pressure at which leakage does not occur from the mechanical seal, Circulation amount Internal pressure of the fuel tank required to flow the gas of the flow rate set by the setting means through the circulation passage, and external from the oil supply pipe when the oil supply nozzle is removed from the oil supply pipe after the end of oil supply In comparison with the upper limit pressure in the fuel tank at which no fuel reflow occurs, an internal pressure setting means for setting the smaller one as the target pressure in the fuel tank during refueling, and the pressure detected by the pressure detection means is the internal pressure. An evaporative fuel control device for a fuel tank, comprising: control means for controlling the operation of the exhaust means so that the target pressure set by the setting means is reached.