JP2007223534A - Fuel tank system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel tank system which can diagnose the presence or absence of a hole in a fuel tank and a piping system for fuel across the whole system. <P>SOLUTION: The fuel tank system A is provided with the fuel tank T, a filler pipe 3, a vapor return tube 4, a jet pump P1, a means for retaining pressure, and a pressure monitoring means. One end of the filler pipe 3 is connected to the fuel tank T, and the other end thereof is connected to the oil-feeding opening 3a. Then one end of the vapor return tube 4 is connected to the fuel tank T, and the other end thereof is connected to the oil-feeding opening 3a of the filler pipe 3. A three-way joint 4b is provided to the downward bend 4a located at the midpoint of the vapor return tube 4. The jet pump P1 absorbs the fuel built-up at the downward bend 4a and returns it to the fuel tank T. Then the means for retaining pressure cuts off the interior of the system including the fuel tank T and the vapor return tube 4 from the outside, and the pressure monitoring means monitors the pressure of the interior of the system. A check valve V1, which prevents the fuel from flowing from the jet pump P1 side to the three-way joint 4b side, is provided in proximity to the jet pump P1 of a built-up fuel suction pipe 6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel tank system including a vapor return tube having one end communicating with an upper space of a fuel tank of an automobile and the other end communicating with a filler port of a filler pipe.

2. Description of the Related Art Conventionally, a center tank vehicle is known in which a fuel tank is disposed below a front seat of a vehicle, a wide space is formed below a rear seat, and a passenger compartment on the rear side of the vehicle body is enlarged (for example, Patent Document 1). reference).
In such a fuel tank system for a vehicle, fuel vapor can be supplied to the fuel tank by evaporating fuel generated in the upper space of the fuel tank at the time of fuel supply through the breather pipe to the atmosphere from the fuel supply port. I am doing so.

On the other hand, the fuel tank system for vehicles of the US specification has an evaporative fuel recovery device (both evaporative fuel emission suppression device or ORVR) that prevents the evaporative fuel generated in the upper space of the fuel tank from being released into the atmosphere when fuel is injected. (See, for example, Patent Document 2).
In the evaporative fuel recovery device, for example, a canister that adsorbs evaporative fuel generated from a fuel tank, an evaporative fuel passage that connects the tank and the canister, and a part of the evaporative fuel are returned to the vicinity of the filler pipe filling port to evaporate A vapor return tube that reduces the amount of fuel generated is mainly provided.

  In addition, in the US specification fuel tank system, whether there is a hole in the fuel tank or the fuel piping system, the negative pressure in the fuel tank and piping system using the negative pressure of the intake pipe of the engine In some cases, a failure detection device is provided for detecting and diagnosing whether the negative pressure state is maintained or the atmospheric pressure state is detected by an internal pressure sensor.

  By the way, the center tank vehicle has a vehicle body frame at a low position between the fuel tank and the fuel filler port arranged at the rear of the vehicle body. Therefore, in order to avoid interference with the vehicle body frame, the filler pipe and the breather pipe A downward bending portion having a middle curved downward is provided.

  In a breather pipe having such a downward curved portion, fuel in which evaporated fuel is liquefied or fuel that has flowed in due to shaking of the fuel tank may stay in the downward curved portion. As a result, there arises a problem that fuel cannot be supplied even if the fuel tank is not filled with fuel.

FIG. 7 is an enlarged cross-sectional view of a main part showing a three-way joint with a check valve installed in a conventional breather pipe.
Therefore, as shown in FIG. 7, the breather pipe 100 is provided with a three-way joint 200 in the downward curved portion 110 where the fuel stays. The three-way joint 200 sucks the stayed fuel and sends it to the fuel tank. A staying fuel suction pipe 300 connected to a jet pump (not shown) is connected. In the jet pump, when the engine is operated, a negative pressure is generated by the fuel passing through the venturi nozzle of the jet pump, and the fuel staying in the lower curved portion 110 of the breather pipe 100 due to the negative pressure is supplied to the fuel tank. It is to suck.
Thereby, the fuel staying in the downward bending portion 110 is sucked by the jet pump provided in the staying fuel suction pipe 300.

In this case, the staying fuel suction pipe 300 and the breather pipe 100 on both sides of the downward curved portion 110 are formed with undulating portions 310 and 120 that are formed higher toward the upper side. Therefore, the three-way joint 200 has a check valve 210 for preventing the fuel sucked by the jet pump toward the undulating portion 310 from returning again to the breather pipe 100 of the three-way joint 200 of the downward curved portion 110. is set up. As a result, the stagnation of fuel in the breather pipe 100 is eliminated, and smooth fuel supply can be performed.
JP 2000-85382 A (paragraph 0024, FIG. 1) JP-A-8-21317 (paragraph 0018, FIG. 1)

As the US specification of the center tank car, when equipped with an evaporative fuel recovery device, the vapor return tube also has a downward curved portion, and in order to suppress the amount of evaporative fuel generated, the same mechanism of the staying fuel suction as the conventional specification is used. Can be considered.
However, as the US specification, a failure detection device is also mounted at the same time. As a result, the failure detection device is retained by the check valve 210 when the breather pipe 100 is brought into a negative pressure state by the negative pressure of the intake pipe of the engine. Since the fuel suction pipe 300 is closed, there is a problem that it is impossible to detect a state where the staying fuel suction pipe 300 has a hole.

  Accordingly, the present invention has been invented to solve the above-described problems, and an object of the present invention is to provide a fuel tank system capable of diagnosing the presence or absence of a hole in a fuel tank and a fuel piping system as a whole.

  In order to solve the above problems, a fuel tank system according to claim 1 includes a fuel tank for storing fuel, a filler pipe having one end communicating with the fuel tank and the other end connected to a fuel filler port, and one end. Communicated with the upper space of the fuel tank, the other end communicated with the filler port of the filler pipe, a vapor return tube provided with a three-way joint in the lower curved portion formed in the middle, and the vapor return tube A jet pump for sucking the fuel staying in the downward curved portion through the staying fuel suction pipe and returning it to the fuel tank, and the system including the fuel tank, the filler pipe and the vapor return tube as the outside A fuel tank system comprising: a pressure holding means for shutting off; and a pressure monitoring means for monitoring the pressure in the system, wherein the staying fuel suction The type, a check valve for preventing from the jet pump side of fuel flow to the three-way joint side, characterized in that provided in the vicinity of the jet pump.

  According to the first aspect of the present invention, the stagnant fuel suction pipe is provided with a check valve for preventing backflow that prevents fuel from flowing from the jet pump side to the three-way joint side in the vicinity of the jet pump. . For this reason, when the inside of the system is shut off from the outside by the pressure holding means, the internal pressure of the vapor return tube is also introduced into the staying fuel suction pipe. Same internal pressure. For example, when the failure detection device detects whether a hole has been opened in the entire fuel tank or fuel piping system, the staying fuel suction pipe is also sealed to determine whether the hole has been opened with the same internal pressure. This can be done by diagnosing a change in pressure with the pressure monitoring means.

  A fuel tank system according to a second aspect is the fuel tank system according to the first aspect, further comprising negative pressure introducing means for making the inside of the system have a negative pressure.

  According to the second aspect of the present invention, when the vapor return tube is brought into a negative pressure state by the negative pressure introducing means for making the inside of the system negative, the negative pressure of the vapor return tube is also generated in the staying fuel suction pipe. Since it is introduced, the staying fuel suction pipe is also in a negative pressure state. For example, when detecting whether a hole has opened in the fuel tank or the entire fuel piping system using the failure detection device, the pressure in the piping system is increased from the negative pressure state to a negative pressure state in the staying fuel suction pipe. If a change in pressure, such as a change to the atmospheric pressure state, is measured, it is possible to diagnose whether or not the hole is opened by the pressure monitoring means.

  A fuel tank system according to a third aspect is the fuel tank system according to the first or second aspect, wherein the jet pump and the check valve are provided in a pump unit installed in the fuel tank. It is characterized by.

  According to invention of Claim 3, a jet pump and a check valve can be provided in a pump unit, and can be arrange | positioned in the position near each other.

  According to the fuel tank system of the first aspect of the present invention, by monitoring the change in pressure by shutting off the inside of the system with the pressure holding means, holes are formed throughout the fuel piping system including the staying fuel suction pipe. You can diagnose whether it is open or not.

  According to the fuel tank system of the second aspect of the present invention, the negative pressure is introduced into the system with the negative pressure introducing means to monitor the negative pressure state, so that the hole is formed throughout the fuel piping system including the staying fuel suction pipe. You can diagnose whether it is open or not.

  According to the fuel tank system of claim 3 of the present invention, the jet pump and the check valve can be easily installed at positions close to each other, and the jet pump and the check valve are provided in the pump unit. Since the number of parts and the number of assembling steps can be reduced, piping connection work can be facilitated.

With reference to FIGS. 1-5, an example of the fuel tank system which concerns on embodiment of this invention is demonstrated. FIG. 1 is a schematic view showing an arrangement state of a fuel tank in a fuel tank system according to an embodiment of the present invention.
First, prior to describing the fuel tank system A according to the embodiment of the present invention, a vehicle C equipped with the fuel tank system A, a filler pipe 3 mounted on the vehicle C, and a vapor return tube 4. The fuel tank T will be described.

≪Vehicle configuration≫
As shown in FIG. 1, in a vehicle C equipped with a fuel tank system A, a fuel tank T is disposed below the front seat 1, the rear side (luggage floor Ca) of the passenger compartment is enlarged, and the center of gravity is lowered. This is a so-called center tank car. In such a vehicle C, the fuel filler port 3a is disposed on the rear side of the rear seat 2, and the lengths of the filler pipe 3 and the vapor return tube 4 that connect the fuel filler port 3a and the fuel tank T are increased. In the vehicle C, the floor panel Cb is disposed on the rear side of the front seat 1 so that the rear seat 2 can be folded flat with respect to the luggage floor Ca. For this reason, in order to avoid interference with the floor panel Cb and the like, the vapor return tube 4 is formed with a downward curved portion 4a whose middle is curved downward so that the fuel in which the evaporated fuel is liquefied is retained. Is laid out.

  FIG. 2 is an exploded perspective view of a main part showing an arrangement state of the fuel tank and the vapor return tube in the fuel tank system according to the embodiment of the present invention.

≪Fuel tank configuration≫
The fuel tank T shown in FIG. 2 is a tank for storing fuel. On the upper surface of the fuel tank T, a vapor return that incorporates a pump unit P toward the inside and a float valve that closes when the tank is full. A float 5 and a refueling float 7 having a built-in float valve are also provided.

≪Configuration of filler pipe≫
The filler pipe 3 is a pipe for sending fuel supplied from the fuel filler port 3a to the fuel tank T. One end of the filler pipe 3 is connected to the lower side surface of the fuel tank T via the filler neck tube 3b and the inlet valve V3. Is connected to the fuel filler opening 3a.

≪Configuration of vapor return tube≫
The vapor return tube 4 shown in FIG. 2 reduces the generation amount of evaporated fuel by returning a part of the air (evaporated fuel) in the upper space in the fuel tank T to the vicinity of the filler port 3a of the filler pipe 3 during fueling. For example, a plurality of pipes are connected in series. One end of the vapor return tube 4 is connected to a vapor return float 5 provided in the upper space in the fuel tank T, and the other end is connected to the vicinity of the filler port 3a of the filler pipe 3 via a check valve V2. The three-way joint 4b attached to the staying fuel suction pipe 6 is connected to the downward curved portion 4a formed in the middle.

  In the downward curved portion 4a of the vapor return tube 4, there is a possibility that a part of the evaporated fuel in the fuel tank T flows and the liquefied fuel stays and closes the vapor return tube 4. A jet pump P1 (see FIG. 4) is provided via a check valve V1 in the staying fuel suction pipe 6 branched from the vapor return tube 4 in order to suck this staying fuel and return it to the fuel tank T. .

  FIG. 3 is an enlarged cross-sectional view showing a three-way joint installed on the vapor return tube of the evaporated fuel recovery apparatus according to the embodiment of the present invention.

A three-way joint 4 b shown in FIG. 3 is a bifurcated joint member for connecting the staying fuel suction pipe 6 to the vapor return tube 4. The three-way joint 4b is disposed in the downward curved portion 4a of the vapor return tube 4, and the liquefied fuel accumulated in the downward curved portion 4a is liquefied by the jet pump P1 (see FIG. 4). It is arranged to suck up and collect from 6. For this reason, the three-way joint 4b is installed at a low position where the liquid can be stored, and sucks out the fuel.
The staying fuel suction pipe 6 connected to the three-way joint 4b is connected to the jet pump P1 via the check valve V1 (see FIGS. 4 and 5).

≪Configuration of fuel tank system≫
The fuel tank system A shown in FIG. 5 includes an evaporative fuel recovery device B for preventing evaporative fuel generated at the time of refueling and preventing it from flowing out, and an internal pressure sensor S to be described later, A failure detection device O for diagnosing whether or not there is a hole in the fuel piping system by detecting pressure is provided. The fuel tank system A sucks the fuel staying in the fuel tank T, the filler pipe 3, the vapor return tube 4, and the downward curved portion 4a of the vapor return tube 4 through the staying fuel suction pipe 6. And introducing a negative pressure to make the inside of the system (the fuel tank T and the fuel piping system) including the fuel pump T, the filler pipe 3 and the vapor return tube 4 negative. Means, negative pressure holding means for holding the negative pressure in the system, and pressure monitoring means for monitoring the pressure in the system.

Here, the negative pressure introducing means, the negative pressure holding means, and the pressure monitoring means are a failure detection device O described later that detects holes and leaks in the fuel tank T and the fuel piping system.
The negative pressure introduction means includes an intake manifold 22 that is an intake passage of the engine E, a drain shut valve V7, a purge adjustment electromagnetic valve V8, an ECU that controls the drain shut valve V7 and the purge adjustment electromagnetic valve V8, and a fuel tank T. And a fuel piping system.
The negative pressure holding means includes a drain shut valve V7, a purge adjustment solenoid valve V8, an ECU that controls the drain shut valve V7 and the purge adjustment solenoid valve V8, a fuel tank T and a fuel piping system, and a predetermined internal system. And an internal pressure sensor S for detecting whether or not a negative pressure is generated.
The pressure monitoring means mainly comprises an internal pressure sensor S for detecting the negative pressure held by the negative pressure holding means and the ECU.

  FIG. 4 is an enlarged cross-sectional view of the pump unit showing the installation state of the check valve and the jet pump of the fuel tank system according to the embodiment of the present invention. FIG. 5 is a schematic view showing a fuel tank system according to an embodiment of the present invention.

  As shown in FIGS. 4 and 5, in the fuel tank system A, when a suction force is generated in the jet pump P1, a check valve V1 composed of a one-way valve that enables suction of the liquid retained in the downward curved portion 4a. Is provided in the vicinity of the jet pump P <b> 1 disposed in the staying fuel suction pipe 6.

≪Check valve configuration≫
As shown in FIG. 5, the check valve V1 has a reverse flow for preventing fluid from flowing from the jet pump P1 connected to one end of the staying fuel suction pipe 6 to the three-way joint 4b connected to the other end. It is a valve for prevention. While the engine E is stopped and the fuel tank T is being refueled, the check valve V1 causes the fuel in the fuel tank T to flow from the return pipe 10 to the sub jet pump P2, the jet pump P1, and the staying fuel suction pipe. 6 is installed so as to prevent it from flowing into the downward bending portion 4a.

  The check valve V1 is provided in the vicinity of the jet pump P1 so that the failure detection device O described later can detect whether or not there is a hole in the staying fuel suction pipe 6 between the check valve V1 from the three-way joint 4b. It is done. As shown in FIG. 5, the check valve V1 is installed at a undulating portion 6a formed higher upward from the downward curved portion 4a of the staying fuel suction pipe 6, or at a position lowered beyond the undulating portion 6a. ing.

  The check valve V1 introduces the negative pressure of the intake manifold 22 of the engine E in order to detect whether the failure detection device O has a hole in the fuel tank T of the fuel tank system A and the fuel piping system. In the meantime, since the negative pressure from the intake manifold 22 is stronger than the negative pressure generated by the jet pump P1, it is closed.

  As shown in FIG. 4, the check valve V1 includes a valve body V1c biased by a spring V1b so as to close a valve hole V1a communicating with the staying fuel suction pipe 6, and a negative pressure generated by the jet pump P1. The fuel is opened by the pressure and is configured to be able to suck the fuel retained in the downward curved portion 4a (see FIG. 5). The check valve V1 is disposed at the upper end of the pump unit P and is substantially flush with the upper surface of the fuel tank T.

≪Jet pump configuration≫
The jet pump P1 is a pump for sucking the fuel staying in the downward curved portion 4a of the vapor return tube 4 through the staying fuel suction pipe 6 and returning it to the fuel tank T (see FIG. 5). The jet pump P1 and the check valve V1 are provided in a pump unit P installed in the fuel tank T and are arranged in the vicinity of each other.

  As shown in FIG. 5, when the engine E is stopped, the jet pump P1 turns on an ignition switch (not shown) and drives the fuel pump P3 to drive the fuel in the fuel tank T to the engine E. Provided on the downstream side of the return pipe 10 branched from the pipe 9 via a pressure regulator 11 and a suction relief valve V4. Further, a downstream side of the return pipe 10 is continuously provided with a sub-jet pump P2 for suctioning into a fuel chamber (or pump unit P) in the fuel tank T.

  The jet pump P1 includes a venturi nozzle P1a (see FIG. 4). When the ignition switch is turned on after the engine E is stopped and fueled, the return pipe 10 is driven to the jet pump P1 as the fuel pump P3 is driven. Fuel is supplied. Then, in the jet pump P1, a negative pressure is generated by the fuel passing through the venturi nozzle P1a (see FIG. 4), and the fuel staying in the downward curved portion 4a of the vapor return tube 4 by the negative pressure passes through the staying fuel suction pipe 6. Via the fuel tank T.

≪Configuration of pump unit≫
As shown in FIG. 5, the pump unit P includes a suction filter 12 that removes foreign matters using a non-woven fabric, a fuel pump P <b> 3 that sends fuel to the injector 8, a pressure regulator 11 that adjusts the pressure of the fuel, and a suction relief valve. V4, a fuel level gauge (not shown) for detecting the fuel level in the fuel tank T, the jet pump P1, the sub jet pump P2 that assists the jet pump P1, and the vent pipe 14. And a cut valve V6 communicating with the vent relief valve V5.

≪Evaporative fuel recovery system configuration≫
The evaporative fuel recovery device B is a device that recirculates air in the upper space in the fuel tank T and evaporative fuel or captures evaporative fuel when fuel is supplied. This evaporative fuel recovery device B is formed of a canister 15 connected to a fuel tank T by a vent pipe 14 that is relatively thick and short and has a low resistance, the vapor return tube 4, the staying fuel suction pipe 6, and the It is mainly composed of the jet pump P1.

≪Canister configuration≫
As shown in FIG. 5, the canister 15 contains an adsorbent that is adsorbed by the evaporated fuel in the upper space in the fuel tank T pushed by the injected fuel when the fuel tank T is refueled. In order to prevent the evaporated fuel from being discharged into the atmosphere, a canister filter 15a for removing dust contained in the atmosphere taken in at the time of purging is also provided. The canister 15 is mainly provided with a canister filter 15a made of filter paper or the like, a drain shut valve V7, and an internal pressure sensor S.
In the drain pipe 16 between the canister 15 and the canister filter 15a, a drain shut valve V7 composed of an electromagnetic valve whose valve body is opened and closed by the ECU is arranged. Since most of the evaporated fuel in the fuel tank T flows into the canister 15 and does not flow into the atmosphere during refueling, the canister 15 is formed to be relatively large. The evaporated fuel becomes air purified by being adsorbed by an adsorbent made of activated carbon of the canister 15 and is discharged from the discharge pipe 17 to the atmosphere via the drain shut valve V7.

The canister 15 is connected to a sensor pipe 18 connected to the internal pressure sensor S and a purge pipe 19 connected to the intake manifold 22 via a purge adjustment electromagnetic valve V8.
When the drain shut valve V7 and the purge adjustment solenoid valve V8 are opened by a command from the ECU during a purge during the operation of the engine E, the evaporated fuel stored in the canister 15 is discharged into the drain pipe by the negative pressure of the intake manifold 22 16 is sucked into the canister 15 through the canister filter 15a and the drain shut valve V7, so that it is separated from the adsorbent and into the intake manifold 22 through the canister 15, the purge pipe 19, and the purge adjusting electromagnetic valve V8 together with the atmosphere. It comes to be supplied.
At this time, an ECU (not shown) connected to the drain shut valve V7, the purge adjustment solenoid valve V8, etc. controls the length of the open time of the purge adjustment solenoid valve V8 based on the signal of each sensor to evaporate The amount of fuel inhaled is adjusted.

  The intake manifold 22 is an intake passage of the engine E, and the air purified by the air cleaner 20 is supplied to the engine E through the throttle valve 21.

≪Configuration of failure detection device≫
The failure detection device O determines whether or not the fuel tank T of the fuel tank system A and the fuel piping system are in a state of leaking due to a hole in the intake manifold 22 that is an intake system of the engine E according to a command from the ECU. This is a device that uses the negative pressure to place the fuel tank T and the piping system in a negative pressure state, and detects whether the negative pressure state is kept by the internal pressure sensor S or an atmospheric pressure state. This failure detection device O mainly includes the negative pressure introducing means, the negative pressure holding means, and the pressure monitoring means.
The ECU is electrically connected to various sensors such as a drain shut valve V7, a purge adjustment solenoid valve V8, and a temperature sensor, and the drain shut valve V7, the purge adjustment solenoid valve V8, and the like based on signals from the various sensors. Control.

≪Operation of fuel tank system≫
Next, the operation of the fuel tank system A according to the embodiment of the present invention will be described mainly with reference to FIGS. 5 and 6. FIG. 6 is a flowchart showing the operation of the fuel tank system according to the embodiment of the present invention.

First, with reference to FIG. 5, the operation | movement by which the stay of a fuel is prevented in the downward curved part 4a of the vapor | steam return tube 4 is demonstrated.
When an ignition switch (not shown) is turned on, the fuel tank system A starts. As shown in FIG. 5, for example, after refueling, when the ignition switch is turned on to drive the fuel pump P3 and the engine E, the fuel is supplied from the engine E and the return pipe 10 as the fuel pump P3 is driven. Supplied to the jet pump P1. Then, surplus fuel is supplied from the return pipe 10 to the jet pump P1, and a negative pressure is generated by the fuel passing through the venturi nozzle P1a (see FIG. 4), and the negative pressure causes a stay in the downward curved portion 4a of the vapor return tube 4. The sucked fuel is sucked and returned from the return pipe 10 into the fuel tank T through the staying fuel suction pipe 6, the check valve V1, and the jet pump P1.
Thus, since the fuel staying in the downward curved portion 4a is sucked by the jet pump P1 and collected in the fuel tank T while the engine E is driven, the downward curved portion 4a of the vapor return tube 4 is collected. It is solved that it stays in.

Next, the operation at the time of refueling will be described with reference to FIG.
For example, when the engine E is stopped and fuel is supplied, fuel is injected into the fuel tank T from the fuel supply port 3a via the filler pipe 3. At this time, the evaporated fuel in the upper space in the fuel tank T can be smoothly supplied because the evaporated fuel of the same amount as the volume of the supplied fuel flows into the canister 15 from the vent pipe 14.
On the other hand, a part of the evaporated fuel in the upper space in the fuel tank T is returned to the vicinity of the fuel filler port 3a through the vapor return tube 4 and is returned to the filler pipe 3 again, so that the atmosphere becomes the fuel tank T. Since the flow into the inside is suppressed, the amount of fuel vapor generated can be reduced.

  That is, the evaporated fuel flowing into the canister 15 is adsorbed and stored by the adsorbent. The evaporated fuel that has passed through the canister 15 is adsorbed by the evaporated fuel, becomes air, passes through the drain shut valve V7 and the canister filter 15a, and is discharged into the atmosphere.

On the other hand, the evaporated fuel that has flowed into the vapor return tube 4 is being refueled while the jet pump P1 is stopped as the engine E is stopped. However, since the staying fuel is removed by the jet pump P1 during travel, refueling It flows toward the mouth 3a side and returns to the filler pipe 3. As a result, at the time of refueling, the amount of air entering the fuel tank T from the refueling port 3a through the filler pipe 3 is suppressed, and the amount of evaporated fuel generated can be reduced.
Further, the check valve V1 prevents the fuel in the fuel tank T from flowing into the downward curved portion 4a of the vapor return tube 4 from the return pipe 10 through the stopped sub jet pump P2 and the jet pump P1. Yes. For this reason, the flow of the evaporated fuel flowing in the vapor return tube 4 is maintained so as to flow smoothly.

  The fuel level in the fuel tank T rises due to refueling, and float valves (not shown) provided in the vapor return float 5 and the refueling float 7 are closed, so that the fuel level in the filler pipe 3 is changed. Ascending, an auto-stop device of a fueling gun (not shown) is activated and fueling is finished.

Next, with reference to FIG. 5 and FIG. 6, the operation of hole diagnosis by the failure detection device O will be described.
First, when the ignition switch is turned on to start the engine E (step S1), negative pressure is generated in the intake manifold 22 (step S2).
Next, the negative pressure is introduced into the entire fuel tank T and the fuel piping system by the negative pressure introducing means. That is, when the rotation of the engine E is stabilized, the ECU opens the purge adjustment electromagnetic valve V8 and closes the drain shut valve V7, whereby the negative pressure of the intake manifold 22 is changed to the purge pipe 19, the canister 15, and The fuel tank T is reached via the vent pipe 14 and negative pressure is introduced into the entire fuel piping system.

  Subsequently, the entire fuel tank T and the entire fuel piping system are held in a negative pressure state by the negative pressure holding means. That is, when the ECU detects an appropriate pressure value with the internal pressure sensor S, the ECU closes the purge adjustment electromagnetic valve V8 while maintaining the drain shut valve V7 closed, and the intake manifold 22, the fuel tank T, and the fuel The communication with the piping system for use is cut off and the whole is kept in a negative pressure state (step S3).

  The pressure monitoring means monitors the pressure in the entire fuel tank T and the fuel piping system. That is, the ECU maintains the negative pressure state of the fuel tank T and the fuel piping system for a predetermined time, monitors the pressure by a signal from the internal pressure sensor S, and controls the fuel tank T and the entire fuel piping system. It is diagnosed whether the hole is opened (step S4).

  In this case, the staying fuel suction pipe 6 is not provided with a check valve V1 for preventing fuel from flowing from the jet pump P1 to the three-way joint 4b, but is provided near the jet pump P1. It has been. The check valve V1 is closed because the negative pressure from the intake manifold 22 is stronger than the negative pressure generated by the jet pump P1 while the negative pressure of the intake manifold 22 of the engine E is being introduced. It has become.

Accordingly, it is possible to diagnose whether the staying fuel suction pipe 6 has a hole as well as the vapor return tube 4.
As a result, the fuel tank system A can diagnose holes and leaks in the entire fuel piping system.

Then, the failure detection device O determines whether the negative pressure state is maintained from the pressure value detected by the internal pressure sensor S (step S5). When the negative pressure state is not maintained and the atmospheric pressure state is reached, the ECU determines that the fuel tank T and the piping system have holes and the evaporated fuel is leaking. Then, the ECU operates an alarm provided on the instrument panel or the like to warn the occupant that a hole has opened in the fuel tank T or the fuel piping system (step S6).
On the other hand, if the negative pressure state is maintained for a predetermined time, the hole diagnosis is terminated because no hole is formed in the fuel tank T or the fuel piping system.
As described above, the failure detection device O can diagnose the holes in the fuel tank T and the entire fuel piping system.

  The present invention is not limited to the above-described embodiment, and various modifications and changes can be made within the scope of the technical idea. The present invention extends to these modifications and changes. Of course.

≪Modification≫
In the embodiment described above, the negative pressure in the intake passage of the engine E is introduced into the system by the negative pressure introducing means, and the negative pressure state is maintained by the negative pressure holding means and then the negative pressure state is monitored by pressure monitoring. By monitoring by means, holes and leaks in the system are detected, but it is not limited thereto.
For example, the fuel tank system A according to the present invention includes at least pressure holding means (drain shut valve V7 and purge adjustment electromagnetic valve V8) for shutting off the system from the outside, and pressure monitoring means (ECU) for monitoring the pressure in the system. If there is a failure detection device O and an internal pressure sensor S), it is possible to detect that there is a hole or a leak in the system.

That is, in the fuel tank system A, even if no negative pressure is introduced by the negative pressure introducing means, the pressure is changed from when the system is sealed by sealing the inside of the system with the pressure holding means. It is possible to detect holes and leaks by monitoring the presence / absence of this with the pressure monitoring means.
Thus, in the fuel tank system A, the negative pressure introducing means can be omitted, and the negative pressure introducing means may be appropriately installed.

≪Other variations≫
For example, the check valve V1 and the jet pump P1 shown in FIG. 4 are formed separately and connected via piping, and each is provided in the pump unit P. However, the check valve V1 and the jet pump P1 are integrated. It may be formed as follows.
The check valve V1 may be a known check valve, and the jet pump P1 may be an electric pump. The sub jet pump P2 may be omitted depending on the shape of the fuel tank T and the position of the pump.

It is the schematic which shows the arrangement | positioning state of the fuel tank in the fuel tank system which concerns on embodiment of this invention. It is a principal part disassembled perspective view which shows the arrangement | positioning state of the fuel tank and vapor return tube in the fuel tank system which concerns on embodiment of this invention. It is an expanded sectional view showing a three-way joint installed in a vapor return tube of a fuel tank system concerning an embodiment of the present invention. It is an expanded sectional view of the pump unit which shows the installation state of the check valve and jet pump of the fuel tank system concerning the embodiment of the present invention. It is the schematic which shows the fuel tank system which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the fuel tank system which concerns on embodiment of this invention. It is a principal part expanded sectional view which shows the three-way joint with a non-return valve installed in the conventional breather pipe.

Explanation of symbols

3 Filler pipe 3a Refueling port 4 Vapor return tube 4a Downward curved portion 4b Three-way joint 6 Stagnant fuel suction pipe 22 Intake manifold (negative pressure introducing means)
A Fuel tank system B Evaporated fuel recovery device E Engine ECU (Negative pressure introducing means, negative pressure holding means, pressure monitoring means)
O Failure detection device (pressure monitoring means)
P pump unit P1 jet pump S internal pressure sensor (negative pressure holding means, pressure monitoring means)
T Fuel tank V1 Check valve V7 Drain shut valve (negative pressure introducing means) Negative pressure holding means)
V8 Purge adjustment solenoid valve (negative pressure introducing means, negative pressure holding means)

Claims (3)

A fuel tank for storing fuel;
A filler pipe having one end communicating with the fuel tank and the other end connected to a fuel filler;
A vapor return tube in which one end communicates with the upper space of the fuel tank and the other end communicates with the filler opening of the filler pipe, and a lower curved portion formed in the middle, and a three-way joint is provided;
A jet pump for sucking the fuel retained in the downward curved portion of the vapor return tube through the retained fuel suction pipe and returning the fuel to the fuel tank;
Pressure holding means for shutting off the inside of the system including the fuel tank, the filler pipe and the vapor return tube;
A fuel tank system comprising pressure monitoring means for monitoring the pressure in the system,
A fuel tank system, wherein the staying fuel suction pipe is provided with a check valve in the vicinity of the jet pump for preventing fuel from flowing from the jet pump side to the three-way joint side.   The fuel tank system according to claim 1, further comprising negative pressure introducing means for making the inside of the system negative pressure.   3. The fuel tank system according to claim 1, wherein the jet pump and the check valve are provided in a pump unit installed in the fuel tank. 4.

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