JPH10259765A - Internal pressure control device for fuel tank and tank internal pressure control valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control diffusion of evaporated fuel in a canister during the decrease of fuel temperature when an engine is stopped and prevent the occurrence of a trouble, such as blow-by of evaporated fuel. SOLUTION: A canister 10 is connected to a fuel tank 5 through a first evaporation passage 8 and a tank internal pressure regulation valve 11 is disposed in the evaporation passage 8. An atmosphere port 13 to introduce outside air is formed in the canister 10 and an electromagnetically-driven atmosphere intake valve 14 is disposed at the tip part of the atmosphere port 13. An ECU 20 controls opening and closing operation of the atmosphere intake valve 14 so that an internal pressure in a tank is fluctuated with a given width in a negative pressure region during the decrease of fuel temperature when an engine is stopped. In this case, through opening of the atmosphere intake valve 14, high speed outside air flows in the canister 10 and this constitution performs back purge of evaporated fuel and narrows an evaporated fuel diffusion layer in the canister 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel tank internal pressure control device provided with an evaporative fuel release mechanism and a tank internal pressure control valve.

[0002]

2. Description of the Related Art Conventionally, an automobile engine is provided with an evaporative fuel release mechanism for temporarily adsorbing evaporative fuel (evaporative gas) generated in a fuel tank to a canister and then releasing the evaporative fuel to an engine intake system. Further, such an evaporative fuel release mechanism has also been used in a tank internal pressure control device for controlling the pressure in the fuel tank (tank internal pressure) to a desired value (for example, Japanese Patent Application Laid-Open No. Hei 7-21750).
No. 4).

FIG. 25 is a configuration diagram schematically showing a conventional general tank internal pressure control device. In the figure, a canister 43 for adsorbing evaporated fuel generated in the fuel tank 41 is connected to the fuel tank 41 via an evaporation passage 42. The canister 43 is provided with an atmosphere port 44 for introducing outside air. A tank internal pressure adjusting valve 45 for adjusting the pressure in the fuel tank 41 (tank internal pressure) is provided in the evaporation passage 42, and the tank internal pressure adjusting valve 45 evaporates from the canister 43 to the fuel tank 41. An internal pressure suction valve 45a that allows the flow of fuel and air, and an internal pressure discharge valve 45b that allows the flow of evaporated fuel and air from the fuel tank 41 to the canister 43
It is composed of Both the internal pressure suction valve 45a and the internal pressure discharge valve 45b are mechanical check valves.

Further, the canister 43 and the engine intake pipe 4
A purge valve 48 is disposed in a purge passage 47 connecting the engine 6 and the engine 6.
It is opened according to the intake negative pressure generated at. In such cases,
The opening operation of the purge valve 48 allows the inside of the canister 43 to be ventilated with fresh air, so that the suction function of the canister 43 is restored.

Here, focusing on the behavior of the tank internal pressure when the engine is stopped, the temperature of the fuel in the tank (fuel temperature)
Changes according to the change of the outside air temperature, so when the fuel temperature decreases following the outside air temperature, the tank internal pressure decreases due to the condensation of the evaporated fuel and reaches the negative pressure level. Further, when the fuel temperature rises following the outside air temperature, the tank internal pressure reaches the positive pressure level. FIG. 26 shows a state where the engine is stopped for 48 hours (2 hours).
FIG. 7 is a time chart showing changes in fuel temperature and changes in tank internal pressure associated with changing the outside air temperature in a predetermined pattern over a period of days.

In contrast to the behavior shown in FIG. 26, in the tank internal pressure control device having the configuration shown in FIG. 25, when the internal pressure of the tank rises due to the increase of the fuel temperature, the evaporation in the fuel tank 41 via the internal pressure discharge valve 45b. The fuel was discharged, thereby preventing the tank pressure from rising excessively. In addition, when the internal pressure of the tank decreases with a decrease in the fuel temperature, outside air is sucked in through the internal pressure suction valve 45a, thereby preventing overcondensation of the fuel vapor.

[0007]

However, the above-described conventional apparatus has the following problems during the cooling period when the fuel temperature decreases. That is, in the conventional apparatus, the internal pressure suction valve 45a for controlling the negative pressure level of the tank internal pressure opens when the tank internal pressure becomes the valve opening pressure of the internal pressure suction valve 45a (operating pressure of the check valve), and the outside air is released. Is introduced. However, at this time, since the negative pressure level of the tank internal pressure slightly decreases due to the introduction of the outside air, the internal pressure suction valve 45a closes immediately after opening. When the negative pressure is increased by closing the internal pressure suction valve 45a, the internal pressure suction valve 45a is opened again.
In short, the internal pressure suction valve 45a repeats the above-mentioned opening and closing operations little by little during the fuel cooling period.

Therefore, in the above-mentioned negative pressure region, the amount of outside air that can be sucked in through the atmosphere port 44 and the canister 43 is very small, and the flow velocity thereof is slow. In this case, since the flow velocity of the outside air introduced into the canister 43 is lower than the diffusion speed of the evaporated fuel (HC) adsorbed on the canister 43, the diffusion area of the adsorbed HC in the canister 43 is expanded. If HC diffusion is not suppressed in this way, for example, when the tank internal pressure rises due to an increase in fuel temperature, the diffused HC is pushed by the air-fuel mixture or air flowing in the canister 43, and the HC is discharged from the atmosphere port 44. That is, a problem such as blowing through the canister 43 occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to suppress the diffusion of HC in a canister and reduce the amount of HC in a canister during a fuel cooling period such as when the engine is stopped. It is an object of the present invention to provide a fuel tank internal pressure control device and a tank internal pressure control valve that can solve the problem of blow-through of fuel.

[0010]

In order to achieve the above object, in the fuel tank internal pressure control device according to the present invention, the evaporated fuel generated in the fuel tank is once adsorbed to the canister and then discharged to the engine intake system. And a fuel vapor release mechanism. The invention according to claim 1 is characterized in that the engine stop detecting means for detecting that the operation of the engine has been stopped, and that the intake of outside air into the canister is permitted or prohibited, and An on-off valve for controlling pressure; and control means for controlling the on-off operation of the on-off valve so that the pressure in the fuel tank fluctuates by a predetermined width within a negative pressure range when the engine is stopped.

In short, when the outside air temperature changes while the engine is stopped, the fuel temperature (fuel temperature) in the fuel tank changes accordingly, and during the cooling period of the fuel, the pressure in the tank becomes negative pressure level due to the condensation of the evaporated fuel. Reach In such a case, in the conventional apparatus, the negative pressure level is adjusted in the vicinity of the opening pressure of the internal pressure suction valve, but only by opening and closing the internal pressure suction valve in small increments, and the amount of the evaporated fuel (HC) in the canister is reduced. Diffusion could not be suppressed. On the other hand, in the configuration of the present invention, the on-off valve (for example, the atmospheric suction valve) is opened and closed with a predetermined pressure range. Therefore, high-speed outside air flows through the canister. That is,
When the outside air is introduced at once, the flow rate of the outside air exceeds the diffusion rate of HC. Therefore, a so-called "back purge" in which HC leaves the canister and returns to the fuel tank becomes possible, and the HC diffusion layer in the canister is narrowed. As a result, the diffusion of HC in the canister can be suppressed, and the problem that the diffused HC blows through the canister and is discharged to the atmosphere when the pressure in the fuel tank rises to the positive side is solved.

Here, FIG. 7 is a diagram schematically showing an HC diffusion layer region in the canister 10. As shown in FIG. 7A, when the flow velocity in the diffusion direction (downward in the figure) is large, HC is diffused.
Although the diffusion layer is widened, if the flow velocity in the back purge direction (upward in the figure) is large as shown in (b), the HC diffusion layer will be narrowed.

According to a second aspect of the present invention, as the specific means for realizing the first aspect, the control means is configured to allow the detected pressure in the fuel tank to be allowed during a fuel cooling period. When the maximum negative pressure is reached, the on-off valve is opened. Here, it is desirable that the allowable maximum negative pressure is set based on the negative pressure side pressure resistance of the fuel tank, as described in claim 3. In this case, by increasing the negative pressure to the maximum negative pressure within the allowable range and then opening the on-off valve at a stroke, a sufficient flow velocity in the canister can be obtained, and the effect described in claim 1 above. Can be obtained more reliably.

In the invention described in claim 4, the control means opens the on-off valve when the pressure in the fuel tank detected by the pressure detection means in the tank reaches the allowable maximum negative pressure. Thereafter, the on-off valve is closed at a predetermined negative pressure on the positive pressure side by a predetermined width from the maximum negative pressure. That is, during the fuel cooling period, the on-off valve
The opening / closing operation is repeated between the allowable maximum negative pressure and the predetermined negative pressure on the positive pressure side by a predetermined width from the maximum negative pressure. In this case, for example, as shown in FIGS. 4 and 5, the opening / closing operation of the release valve (atmospheric intake valve) is performed within a negative pressure region by a predetermined width (in FIG. 4,
When the valve is opened, a large flow velocity in the canister is generated in the suction direction (back-purge direction). Therefore, the above-described effects can be reliably obtained. In FIG. 5, for comparison,
Changes in the tank internal pressure and the canister flow velocity in the conventional apparatus are shown by two-dot chain lines.

Incidentally, it is desirable that the pressure width at the time of opening and closing the on-off valve be set to 100 Pa or more.
300-500 to suppress the level of C blow-through to a low level
It is good to set in the range of Pa. Further, it is desirable that the negative pressure when the on-off valve is closed is set to -50 Pa or less.

On the other hand, the invention according to claim 5 is characterized in that an engine stop detecting means for detecting that the operation of the engine has been stopped, and that the intake of outside air into the canister is permitted or prohibited and the fuel is stopped. An on-off valve for controlling the pressure in the tank, and control means for controlling the on-off operation of the on-off valve for a predetermined time width so that the pressure in the fuel tank fluctuates within a negative pressure range when the engine is stopped. It has.

The structure of the present invention is obtained by partially changing the structure of the control means in the above-described claim 1. However, even if the on-off valve is controlled by the time width as described in the present invention, Actually, similarly to the first aspect, the pressure in the fuel tank repeatedly increases and decreases within a predetermined pressure range. Therefore, also in the configuration of the present invention, the diffusion of HC in the canister is suppressed, and when the pressure in the fuel tank rises to the positive side, the diffused HC blows through the canister and is discharged to the atmosphere. Problems can be eliminated.

According to a fifth aspect of the present invention, as described in the sixth aspect, the opening period and the closing period of the on-off valve are determined in accordance with the time width corresponding to the amount of change in the pressure in the fuel tank. It is good to be constituted as follows. In this case, the pressure change with time can be estimated from the amount of change in the fuel tank pressure, and if the timing of valve opening and closing is determined based on the estimation result, the fluctuation width of the fuel tank pressure can be properly adjusted. It can be set. As a result, the accuracy of the tank internal pressure control can be secured, and the reliability can be improved.

The on-off valve according to the present invention may be: an atmospheric suction valve provided at an atmospheric port of the canister, as described in claim 7, or Preferably, a tank internal pressure suction valve is provided between the canister and the fuel tank.

In the air suction valve according to the seventh aspect of the invention, if the valve is closed, the canister can be maintained in a negative pressure state, and HC adsorbed on the canister (activated carbon) is easily released.
Therefore, the problem of HC diffusion can be easily improved when back purge is required. Further, in the internal pressure suction valve according to the eighth aspect, since a mechanically used internal pressure suction valve (for example, reference numeral 45a in FIG. 25) can be used instead, the configuration can be simplified, and the size and space can be reduced. Becomes

On the other hand, the ninth aspect of the present invention relates to a mechanical tank pressure control valve.
A negative pressure setting valve that is communicated with the fuel tank and opens when the maximum negative pressure allowed in the tank acts, a negative pressure chamber closed by the negative pressure setting valve, And a negative pressure setting valve that opens on the positive pressure side from the negative pressure level that opens, and a pressure release valve that opens the inside of the fuel tank with the opening, and the internal pressure of the negative pressure chamber. A pressure gradually changing member for gradually changing the pressure.

According to the above configuration, after the negative pressure setting valve is opened during the fuel cooling period, the pressure release valve opens and closes with a predetermined pressure width (width of the tank internal pressure). That is, the negative pressure setting valve is opened by the negative pressure in the tank, and when the negative pressure in the tank is introduced into the negative pressure chamber via the negative pressure setting valve, the negative pressure in the negative pressure chamber also causes the pressure release valve to open. Open similarly. When the pressure release valve opens, the negative pressure setting valve closes because the negative pressure level in the fuel tank decreases, but the pressure in the negative pressure chamber changes little by little by the pressure gradually changing member to the positive pressure side. Therefore, after the negative pressure setting valve is closed, the pressure release valve does not immediately close but continues to be open, and closes with a time delay.

Therefore, each time the pressure relief valve is opened, a large amount of outside air flows through the canister at a high speed each time. That is, when the outside air is introduced at once, the flow rate of the outside air exceeds the diffusion rate of HC. Therefore, a so-called "back purge" in which HC leaves the canister and returns to the fuel tank becomes possible,
The HC diffusion layer in the canister is narrowed. As a result, the diffusion of HC in the canister can be suppressed, and the problem that the diffused HC blows through the canister and is discharged to the atmosphere when the pressure in the fuel tank rises to the positive side is solved.

It is desirable that the tank internal pressure control valve of the ninth aspect is configured as in the following tenth to twelfth aspects. According to the tenth aspect of the present invention, the opening pressure of the negative pressure setting valve is set based on the negative pressure resistance of the fuel tank. In this case, the negative pressure is increased to a maximum negative pressure within an allowable range. , A sufficient flow velocity in the canister can be obtained. Further, it is possible to prevent a problem that excessive negative pressure is applied to the fuel tank and the fuel tank is deformed.

According to the eleventh aspect of the present invention, the pressure gradually changing member is constituted by a throttle provided on the wall surface defining the negative pressure chamber. In this case, the pressure gradual change member required to obtain the above-described excellent effects can be embodied with a simple configuration.

In the twelfth aspect of the present invention, when the pressure release valve is closed, the negative pressure chamber is closed, and when the pressure release valve is opened, the pressure gradually changing member is configured to have a small aperture area. Is composed. In this case, after the pressure release valve is closed, the negative pressure chamber is maintained at the predetermined negative pressure level. Therefore, when the tank internal pressure is in the negative pressure region and the opening and closing of the pressure release valve are repeated, the responsiveness of the opening and closing operation is improved.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings. The device of this embodiment is provided with an evaporative fuel release mechanism that once adsorbs the evaporative fuel generated in the fuel tank of the vehicle to the canister and then releases the evaporative fuel to the engine intake system. A normally open solenoid valve (atmospheric intake valve) is provided. The air intake valve is connected to an electronic control unit (hereinafter referred to as an ECU).
) To control the tank internal pressure at the time of engine stop to a desired state. Hereinafter, the detailed configuration and operation will be described.

FIG. 1 is a configuration diagram showing an outline of a fuel tank internal pressure control device according to this embodiment. In FIG. 1, an intake pipe 2 connected to an engine 1 includes an engine 1
In addition, an injector 3 for injecting fuel (gasoline) is provided, and a throttle valve 4 that is interlocked with the operation of an accelerator pedal (not shown) is provided. The fuel tank 5 is connected to the injector 3 via a fuel supply passage (not shown).
More fuel is fed. The fuel tank 5 is provided with a tank cap 6 that is opened at the time of refueling. The tank cap 6 is provided with a refueling switch 7 for detecting that the cap 6 is opened at the time of refueling. Have been.

A canister 10 is connected to the fuel tank 5 via a first evaporative passage 8 and a second evaporative passage 9. The canister 10 is connected to the fuel tank 5.
Activated carbon as an adsorbent for adsorbing evaporated fuel (evaporated HC) generated in the inside is stored. The first evaporation passage 8 is provided with a mechanical tank internal pressure adjusting valve 11 for adjusting the pressure (tank internal pressure) in the fuel tank 5. The tank internal pressure adjusting valve 11 is an internal pressure suction valve 11 a. And the internal pressure discharge valve 11b. Internal pressure suction valve 1
1a and the internal pressure discharge valve 11b are check valves connected in parallel in opposite directions. In this case, the internal pressure suction valve 11a opens when the tank internal pressure reaches a predetermined negative pressure level to increase the tank internal pressure, and the internal pressure discharge valve 11b opens when the tank internal pressure reaches a predetermined positive pressure level. As a result, the tank internal pressure is reduced.

An electromagnetically driven oil supply valve 12 is provided in the second evaporation passage 9. This refueling valve 12 is
Normally, that is, when there is no command signal from the ECU 20 (at the time of non-excitation), it is configured as a "normally closed valve" that keeps the valve closed, and the valve opens only when a signal is input from the ECU 20 (at the time of excitation). Specifically, when the fuel supply switch 7 is turned on when the tank cap 6 is opened, the ECU 20 opens the fuel supply valve 12 in accordance with the ON signal, and the fuel tank 5
The inside and the canister 10 are communicated with each other.

The canister 10 is provided with an atmosphere port 13 for introducing outside air. At the tip of the atmosphere port 13, an electromagnetically driven atmosphere suction valve 14 constituting an on-off valve is provided.
Are arranged. The atmospheric suction valve 14 is operated normally, that is, when there is no command signal from the ECU 20 (when not energized).
Is configured as a “normally open valve” that keeps the valve open.
The valve closing operation is performed only when a signal is input from the device 20 (at the time of excitation).
The detailed operation will be described later.

A purge passage 15 is connected between the canister 10 and the downstream side of the throttle valve 4 in the intake pipe 2, and evaporated fuel supplied from the canister 10 passes through the purge passage 15 through the intake pipe 2. (Upstream of the intake manifold, not shown). A purge valve 16 having a check valve mechanism is disposed in the purge passage 15, and the purge valve 16 is opened according to the intake negative pressure generated in the intake pipe 2. That is,
If the canister 10 and the intake pipe 2 are communicated via the purge passage 15 by the opening operation of the purge valve 16, fresh air in the atmosphere is introduced into the canister 10 via the atmosphere suction valve 14 and the atmosphere port 13. . Then, the interior of the canister 10 is thus ventilated with fresh air, and the adsorbed fuel of the canister 10 is sent into the intake pipe 2 in accordance therewith, whereby the adsorption function of the canister 10 is restored.

The ECU 20 includes a well-known input signal processing circuit,
It comprises an arithmetic circuit, an output signal circuit (drive circuit), a power supply circuit, and the like, and opens the oil supply valve 12 in accordance with the detection signal of the oil supply switch 7 as described above. Furthermore, E
The CU 20 sequentially receives detection signals from the tank internal pressure sensor 17 attached to the fuel tank 5 to detect the tank internal pressure PT, and controls the opening and closing operation of the atmospheric suction valve 14 based on the detection result. Incidentally, the ECU of the present embodiment
Battery power is always supplied to the ECU 20 regardless of the operation position (ON position, OFF position, ACC position) of the ignition key switch of the vehicle. Execute the calculation program.

Next, the operation of the fuel tank internal pressure control device configured as described above will be described. First, the outline of the operation of the present apparatus will be described with reference to the time chart of FIG. FIG. 3 shows a change in the tank internal pressure PT and a control content thereof in accordance with changes in the outside air temperature and the fuel temperature in a state in which the engine is stopped, and a period from t1 to t4 in the figure relates to the gist of the present embodiment. This corresponds to the control period. Before the time t1 in the figure, the air suction valve 14 is kept open.

That is, if the outside air temperature is lower than the temperature (fuel temperature) of the fuel in the fuel tank 5 when the engine is stopped, the fuel temperature drops following the outside air (this period is called a fuel cooling period). ). At this time, the tank pressure PT changes from a positive pressure to a negative pressure due to the condensation of the evaporated fuel in the fuel tank 5. Then, when the tank internal pressure PT reaches a predetermined set value P1 in the negative pressure region, the atmospheric suction valve 14 that has been open is closed. In the present embodiment, the above set value P1 is set to “−500 Pa”. Note that P2 in the drawing is the valve opening pressure of the internal pressure suction valve 11a formed of a check valve, and P2 is set to a value slightly higher than the set value P1 (specifically, about -600 Pa). .

When the atmospheric suction valve 14 is closed, the purge valve 16 in the middle of the purge passage 15 is a check valve that opens due to the negative pressure of the intake pipe during engine operation; Is normally closed, the intake of the outside air into the fuel tank 5 is stopped, and the tank internal pressure PT increases toward the negative pressure side.

Thereafter, when the tank internal pressure PT increases to the negative pressure side and reaches a predetermined set value P3 at the timing of t2 in the figure, the atmospheric suction valve 14 is opened. Here, the set value P
Numeral 3 corresponds to the maximum negative pressure allowed during the fuel cooling period. In the present embodiment, the pressure is set to “−2900 Pa” based on the negative pressure resistance of the fuel tank 5. More specifically, a diaphragm valve (not shown) for preventing a dent of the fuel tank 5 is provided inside the tank cap of the fuel tank 5, and its valve opening pressure is generally -3000.
Since it is about -4000 Pa, P3 = -2900 Pa in the present embodiment based on that.

At the timing of t2, since the tank internal pressure PT has reached a sufficiently large value in the negative pressure region, the outside air is introduced into the canister 10 at a stretch via the atmospheric suction valve 14 and the atmospheric port 13. As a result, a large amount of evaporated fuel (HC) in the canister 10 is released and returned to the fuel tank 5 (that is, a large amount of back purge is performed). Along with such introduction of outside air, a direction in which HC diffusion is narrowed in the canister 10 (back purge direction).
Since the flow rate of outside air and HC is increased, HC diffusion is suppressed.

Thereafter, the tank internal pressure PT rises to the positive pressure side in accordance with the opening of the atmospheric suction valve 14, and when the tank internal pressure PT reaches a predetermined set value P4 at the timing of t3 in the figure, the atmospheric suction valve 14 is closed to introduce outside air. Is stopped. In the present embodiment,
Based on the above set value P3 (= -2900 Pa), the set value P4 is set to "-2600 Pa". Thereafter, if the fuel temperature still tends to decrease (during the cooling period), the tank internal pressure PT changes to the negative pressure side. Therefore, when the tank internal pressure PT reaches the set pressure P3 again, the air suction is performed. The valve 14 is opened, and thereafter, when the tank internal pressure PT reaches the set pressure P4, the atmospheric suction valve 14 is closed. Thus, the atmospheric suction valve 14 operates at a pressure width determined by the set pressures P3 and P4 (| P3-P4 | = 300P
The opening / closing operation is repeated with a).

When the fuel temperature starts to rise due to the rise in the outside air temperature, the tank internal pressure PT shifts to the positive pressure side. In this case, at the timing of t4, when the tank internal pressure PT reaches a predetermined set pressure P5 in the positive pressure region, the atmospheric suction valve 14 is opened. In the present embodiment, the set value P5 is set to “500P
The numerical value is set based on the valve opening pressure of the internal pressure discharge valve 11b. With the opening of the atmospheric suction valve 14, the amount of expansion of the evaporated fuel accompanying the rise in fuel temperature is introduced into the canister 10 via the first evaporation passage 8 and is adsorbed.
Thereafter, the tank internal pressure PT is maintained at the valve opening pressure of the internal pressure discharge valve 11b.

Next, a tank internal pressure control routine for controlling the tank internal pressure PT by opening and closing the atmospheric suction valve 14 as described above will be described with reference to the flowcharts of FIGS. Note that the flowchart is executed by the ECU 20 at a predetermined cycle (for example, every second) regardless of the operation position of the ignition key switch (IG switch).

When the tank internal pressure control routine starts, the ECU 20 first determines in step 101 whether or not the engine is stopped. Specifically, I
It is determined whether the G switch is at the OFF position. IG
If the switch is OFF, that is, if the engine is in the stopped state, the ECU 20 proceeds to step 102 and proceeds to step 102.
At 02, it is determined whether or not the present time is at the time of refueling the fuel tank 5. If the IG switch is ON, that is, if the engine is operating, the ECU 20 proceeds to step 104.

If it is determined in step 102 that the current time is for refueling, the ECU 20 proceeds to step 103 to open the refueling valve 12, and then proceeds to step 104. The determination as to whether or not the above-described refueling is performed is performed based on the output signal of the refueling switch 7 installed on the tank cap 6.

In step 104, the ECU 20 clears both the negative pressure mode flag F1 and the valve closing mode flag F2 to "0". Here, the negative pressure mode flag F1
Represents that the tank internal pressure PT in the engine stopped state is in a predetermined negative pressure region, and negative pressure control by the later-described atmospheric suction valve 14 is performed, and F1 = 0
Indicates that the negative pressure control is not performed when the engine is stopped, and F1 = 1 indicates that the negative pressure control is performed when the engine is stopped. Further, the valve closing mode flag F
2 is for performing negative pressure control with the engine stopped.
This indicates that the atmosphere suction valve 14 is in a closed state (excited state), where F2 = 0 indicates that the atmosphere suction valve 14 is in an “open state”, and F2 = 1 indicates that the atmosphere suction valve 14 is in an “open state”. Is in the "valve closed state".

After clearing the flags F1 and F2, E
In step 105, the CU 20 keeps the air suction valve 14 open and ends this routine. In short, when the engine is running (NO in step 101), the atmospheric suction valve 14 is kept open regardless of the state of the tank internal pressure PT. At this time, the evaporated fuel adsorbed on the canister 10 is supplied to the intake pipe 2 through the purge passage 16 together with the outside air sucked from the atmospheric suction valve 14 by the intake negative pressure. When refueling (when step 102 is YES), the air suction valve 14 and the refueling valve 12 are kept open. At this time, the evaporated fuel accumulated in the fuel tank 5 is pushed out by refueling, and is then pushed out of the second evaporation passage 9.
Through the canister 10.

On the other hand, when step 101 is YES and step 102 is NO (when the engine is stopped,
If not refueling), the ECU 20 proceeds to step 106
To read the tank internal pressure PT detected by the tank internal pressure sensor 17. Thereafter, the ECU 20 determines in a step 107 whether or not the negative pressure mode flag F1 is “0”. At this time, since the negative pressure mode flag F1 is cleared to "0" at the beginning of the engine stop, the ECU 2
In the case of 0, the affirmative determination is made in step 107 and the routine proceeds to step 108, where it is determined whether or not the tank internal pressure PT is equal to or less than a predetermined set value P1 (-500 Pa in the present embodiment).

If PT> P1 as shown before the timing of t1 in FIG.
Makes a negative determination in step 108 and proceeds to step 105, where the atmospheric suction valve 14 is kept open, and then this routine is terminated.

Further, when the tank pressure PT decreases, PT ≦ P
1 (after the timing of t1 in FIG. 4), the ECU 2
In the case of 0, an affirmative decision is made in step 108 and the routine proceeds to step 109, where the atmospheric suction valve 14 is closed. Further,
The ECU 20 determines in step 110 that the negative pressure mode flag F1
Is set to "1", and at step 111, "1" is set to the valve closing mode flag F2, and this routine is ended.

Once the negative pressure mode flag F1 is set, in the subsequent processing, the ECU 20 makes a negative determination in step 107 each time and proceeds to step 112. Then, in step 112, the ECU 20 determines whether or not the tank internal pressure PT is equal to or higher than a predetermined set value P5 (500 Pa in the present embodiment). Here, the case where PT ≧ P5 is satisfied corresponds to the case where the fuel temperature shifts from the cooling period to the heating period as the outside air temperature rises, for example, as shown near the timing of t4 in FIG. At the timing of t4, the tank internal pressure PT reaches the set value P5 of the positive pressure level, and the ECU 20 proceeds to steps 104 and 105 to clear the flags F1 and F2 and to open the atmospheric suction valve 14.

On the other hand, if PT <P5 as shown immediately after the timing of t1 in FIG.
Makes a negative determination in step 112 and returns to step 113 in FIG.
Proceed to. Then, the ECU 20 determines in a step 113 whether or not the valve closing mode flag F2 is “1”. F
If 2 = 1, that is, if the air intake valve 14 is currently in the closed state, the ECU 20 proceeds to step 114
And the tank internal pressure PT at that time is set to a predetermined set value P3 (−29 in the present embodiment) with the closing of the atmospheric suction valve 14.
00Pa) (whether PT ≦ P3)
Is determined. At this time, if the tank internal pressure PT does not reach the set value P3 during the lowering of the tank internal pressure PT, for example, as shown in the period between t1 and t2 in FIG.
> P3), the ECU 20 ends this routine as it is. Then, for example, if the tank internal pressure PT reaches the set value P3 at the timing of t2 in FIG. 4, the ECU 20 proceeds to step 115. The ECU 20 opens the air intake valve 14 in step 115, and further proceeds to step 11
In step 6, the valve closing mode flag F2 is cleared to "0", and then this routine ends.

If F2 = 0 in step 113, that is, if the air suction valve 14 is currently open, the ECU 20 proceeds to step 117, and the ECU 20 proceeds with the opening of the air suction valve 14. The tank pressure PT at that time is a predetermined set value P4 (-2600 Pa in the present embodiment).
Is determined (PT ≧ P4 is satisfied). At this time, if the tank internal pressure PT does not reach the set value P4 during the rise of the tank internal pressure PT (in the case of PT <P4), for example, as shown in the period from t2 to t3 in FIG. This routine ends.
Then, for example, at the timing of t3 in FIG.
If T reaches the set value P4, the ECU 20 proceeds to step 1
Proceed to 18. The ECU 20 closes the atmospheric suction valve 14 in step 118, and sets “1” in a valve closing mode flag F2 in step 119, and thereafter ends this routine.

Thereafter, during the fuel cooling period indicated by t1 to t4 in FIG. 4, steps 113 to 119 in FIG.
Is repeatedly performed, and the opening and closing of the atmospheric suction valve 14 is controlled. In the present embodiment, step 101 in FIG. 2 corresponds to an engine stop detecting unit described in claims.
Steps 113 to 119 in FIG. 3 correspond to control means.

Here, FIG. 5 is a time chart showing both the behavior of the tank internal pressure PT and the behavior of the flow velocity in the canister by the above-mentioned tank internal pressure control. The solid line in the figure indicates the behavior by the device of the present embodiment, and the two-dot chain line indicates the behavior by the conventional device (for example, the device shown in FIG. 25). According to the figure, in the conventional apparatus, even if the tank internal pressure is in the negative pressure region, the flow velocity in the canister in the suction direction (back purge direction) into the fuel tank 5 is considerably small,
It can be seen that HC diffusion in the canister 10 cannot be suppressed. This is because the opening and closing of the internal pressure suction valve for sucking outside air is repeated little by little. On the other hand, in the apparatus of the present embodiment, since the tank internal pressure PT is changed within a predetermined pressure range, the tank pressure PT is much higher in the suction direction (back-purge direction) than in the conventional apparatus (two-dot chain line in the figure). It can be seen that a large canister flow velocity can be obtained.

As shown by the arrows in FIG. 7, the HC diffusion layer in the canister 10 has a flow velocity in the canister in either the exhaust direction (downward in the figure) or the suction direction (upward in the figure). The area is determined depending on whether it is large in the direction. In the configuration of the present embodiment, as shown in FIG. 3B, the flow velocity in the suction direction, that is, the back purge direction is increased, and the diffusion layer is narrowed.

FIG. 6 is a graph showing the measurement result of the amount of HC in the canister 10 (grams) in the canister 10. The amount of HC in the through-hole at 12 hours after the end of the cooling period is indicated by a solid line. Comparing the apparatus of the present embodiment with the conventional apparatus shown by the two-dot chain line, it can be confirmed that the former is reduced to about 1/5 of the latter.

According to the present embodiment described in detail above, the following effects can be obtained. (A) In the present embodiment, the opening / closing operation of the atmospheric suction valve 14 is controlled so that the tank internal pressure PT fluctuates by a predetermined width within the negative pressure range when the engine is stopped. In this case, high-speed outside air flows through the canister 10 each time the air intake valve 14 is opened during the fuel cooling period. That is, when the outside air is introduced at once, the flow rate of the outside air exceeds the diffusion rate of HC. Therefore, the so-called “back-purge” in which the HC leaves the canister 10 and returns to the fuel tank 5 becomes possible,
The HC diffusion layer in the canister 10 is narrowed. As a result, HC diffusion in the canister 10 is suppressed, and at the same time, when the tank internal pressure PT rises to the positive side, the problem that the diffused HC blows through the canister 10 and is released to the atmosphere is eliminated. .

(B) A set value P3 (= -2900 Pa) is set as the maximum negative pressure allowed during the fuel cooling period, and when the tank internal pressure PT reaches the set value P3, the atmosphere release valve 14 is set. Was opened. More specifically, when the tank internal pressure PT reaches the set value P3, the air suction valve 14 is opened, and thereafter, the air suction is performed at a set pressure P4 (= -2600 Pa) on the positive pressure side by a predetermined width from the set value P3. The valve 14 was operated to close. That is, the air suction valve 14 repeats the opening and closing operation at a predetermined pressure range between the set value P3 and the set value P4 during the fuel cooling period. In this case, a sufficiently large flow velocity in the canister occurs in the suction direction (back-purge direction) in the opening operation of the atmospheric suction valve 14, and the effect described in (a) above can be more reliably obtained.

Incidentally, the pressure width when opening and closing the air suction valve 14 is desirably set to 100 Pa or more.
It is good to set in the range of 500 Pa. In this case, it is possible to solve the problem that the valve closing period of the atmospheric suction valve 14 becomes too long, and an appropriate back purge cannot be performed during a transition period from the negative pressure to the positive pressure of the tank internal pressure PT. Also, the air suction valve 14
It is desirable that the negative pressure when the valve is closed is set to -50 Pa or less.

(C) In particular, in the present embodiment, since the set value P3 is set based on the negative pressure side withstand pressure of the fuel tank 5, the fuel tank 5 is deformed even when the negative pressure of the tank internal pressure PT is increased. There is no problem such as doing.

(D) In the present embodiment, FIG.
As described in the control flow of FIG. 3, the specified state of opening and closing of the air suction valve 14 is maintained by the flag operation. Therefore, the tank internal pressure control for obtaining the above effects can be easily and appropriately performed.

(E) In the present embodiment, the tank internal pressure PT when the engine is stopped is controlled using the air suction valve 14 provided at the air port 13 of the canister 10. In this case, if the air suction valve 14 is closed, the canister 10 can be maintained in a negative pressure state, and HC adsorbed on the canister (activated carbon) 10 is easily released. Therefore, the problem of HC diffusion can be easily improved when back purge is required.

Next, second to fifth embodiments of the present invention will be described with reference to the drawings. However, in the configuration of each of the following embodiments, the same components as those of the above-described first embodiment are denoted by the same reference numerals, and the description is simplified. The following description focuses on differences from the first embodiment.

(Second Embodiment) The second embodiment of the present invention
The embodiment will be described with reference to FIGS.
In the apparatus according to the first embodiment, when the tank internal pressure PT is controlled in a predetermined negative pressure range, the predetermined set value P
The opening / closing operation of the atmospheric suction valve 14 was controlled between 3 and P4. On the other hand, in the present embodiment, when controlling the tank internal pressure PT in the negative pressure region, the valve opening time and the valve closing time of the atmospheric suction valve 14 are set according to the amount of change (change speed) of the tank internal pressure PT. The opening / closing operation of the atmospheric suction valve 14 is controlled according to the set time.

FIG. 10 is a time chart showing an outline of the operation in the present embodiment. As shown in the figure, similarly to the device of the first embodiment, the tank internal pressure PT is set to a predetermined set value P1 (= −500P) in the fuel cooling period.
When the pressure drops to a), the atmospheric suction valve 14 which has been open is closed, and the negative pressure mode flag F1 is set.
Is set (timing at t11 in the figure). And
A predetermined time (the initial valve closing time T
Until 1), the closed state of the atmospheric suction valve 14 is maintained. Here, the initial valve closing time T1 is desirably set to a time of about 10 minutes (however, this time is determined by the canister 1).
It can be arbitrarily changed according to various conditions such as a capacity of 0).

At time t12 when the initial valve closing time T1 elapses from time t11, the atmospheric suction valve 14 shifts to the open state. At time t13 when a predetermined time (valve opening time T2) elapses from time t12. Until the timing, the open state of the atmospheric suction valve 14 is maintained. At the timing of t13, the atmospheric suction valve 14 is returned to the closed state again. From the timing of t13 to the timing of t14 when a predetermined time (valve closing time T3) elapses.
The closed state of the atmospheric suction valve 14 is maintained. Here, the valve opening time T2 and the valve closing time T3 are desirably set to about 10 minutes or less. In the present embodiment,
Average pressure change ΔPTave with reference to the map of FIG.
The time widths of T2 and T3 are variably set in accordance with the time (however, this time can be arbitrarily changed according to various conditions such as the capacity of the canister 10). The average pressure change amount ΔPTave is a change rate of the tank internal pressure PT, and corresponds to the inclination of the tank internal pressure PT in FIG.

Thereafter, as long as the fuel cooling period continues and the tank internal pressure PT is in the predetermined negative pressure range, the valve opening time T
At the same time, the air suction valve 14 is opened in the time width of 2 and the air suction valve 14 is closed in the time width of the valve closing time T3, whereby the opening and closing operation of the air suction valve 14 is repeated (FIG. In the period from t11 to t15).

FIGS. 8 and 9 are flowcharts showing a tank internal pressure control routine according to the present embodiment. This routine is similar to the control routine (FIGS. 2 and 3) according to the first embodiment. It is executed by the ECU 20 at a predetermined time period such as one second interval. In the flowchart, for convenience, the refueling valve 12 at the time of refueling is used.
The description of the opening process of the fuel supply valve is omitted, but if the fuel supply valve 12 is provided due to the configuration of the apparatus, the valve opening process of the fuel supply valve 12 (step 102, FIG. 103) may be added.

When the tank internal pressure control routine starts, the ECU 20 first determines in step 201 whether or not the engine is in a stopped state, that is, the IG switch is turned off.
It is determined whether or not it is at the FF position. If the engine is not stopped (IG switch = OFF), the ECU 20 proceeds to step 202 and clears both the negative pressure mode flag F1 and the valve closing mode flag F2 to "0". Here, the negative pressure mode flag F1 and the valve closing mode flag F2 are flags operated in the same manner as in the device of the first embodiment. After clearing the flags F1 and F2, the ECU 20
Opens the air intake valve 14 in step 203 and terminates this routine. In short, when the engine is running (NO in step 201), the atmospheric suction valve 14 is kept open regardless of the state of the tank internal pressure PT. At this time, the evaporated fuel adsorbed on the canister 10 is supplied to the intake pipe 2 via the purge passage 16 together with the outside air sucked from the atmospheric suction valve 14 by the intake negative pressure.

On the other hand, if step 201 is YES (when the engine is stopped), the ECU 20 executes step 2
In step 04, the tank internal pressure PT detected by the tank internal pressure sensor 17 is read. Further, the ECU 20 calculates an average pressure change amount ΔPTave as a change rate of the tank internal pressure PT in a subsequent step 205.

Thereafter, the ECU 20 determines in step 206 whether the negative pressure mode flag F1 is "0". At this time, since the negative pressure mode flag F1 has been cleared to "0" at the beginning of the engine stop, the ECU 20 makes an affirmative determination in step 206 and proceeds to step 207, where the tank internal pressure PT is reduced to a predetermined set value P1 (this embodiment). In the form
-500 Pa) or less.

If PT> P1 as shown before the timing t11 in FIG.
In step 20, a negative determination is made in step 207, and the routine proceeds to step 203, where the atmospheric suction valve 14 is kept open, and thereafter, this routine ends.

Further, when the tank internal pressure PT decreases and PT ≦ P
When it becomes 1 (after timing t11 in FIG. 10), EC
U20 makes an affirmative decision in step 207 and makes step 208
The air suction valve 14 is closed. Subsequently, the ECU 20 determines in step 209 that the initial valve closing time T1
Set. Here, the initial valve closing time T1 can be variably set according to, for example, the calculated average pressure change amount ΔPTave, but in the present embodiment, “T1 = 10
Minutes ”.

Thereafter, the ECU 20 sets "1" to the negative pressure mode flag F1 in step 210, and sets "1" to the valve closing mode flag F2 in step 211, and ends this routine.

Once the negative pressure mode flag F1 is set, in subsequent processing, the ECU 20 makes a negative determination in step 206 each time and proceeds to step 212. Then, in step 212, the ECU 20 determines whether or not the tank internal pressure PT is equal to or higher than a predetermined set value P5 (500 Pa in the present embodiment). Here, the case where PT ≧ P5 is satisfied, for example, as shown near the timing of t15 in FIG. 10, corresponds to the case where the fuel temperature accompanying the rise in the outside air temperature shifts from the cooling period to the heating period, At the timing of t15, the tank internal pressure PT reaches the set value P5 of the positive pressure level, and the ECU 20 proceeds to steps 202 and 203, clears the flags F1 and F2, and opens the atmospheric suction valve 14.

On the other hand, if PT <P5 as shown immediately after the timing of t11 in FIG.
In step 20, a negative determination is made in step 212, and the process proceeds to step 213. Then, the ECU 20 determines whether or not the initial valve closing time T1 has elapsed since the atmospheric suction valve 14 was closed, that is, since the negative pressure mode flag F1 was set.
If the initial valve closing time T1 has not elapsed, the ECU 20 terminates this routine as it is. If the initial valve closing time T1 has elapsed, the ECU 20 proceeds to step 214 in FIG. In the time chart of FIG. 10, step 213 is determined to be affirmative at the timing of t12 in FIG.

Then, the ECU 20 executes step 2 in FIG.
At 14, it is determined whether or not the valve closing mode flag F2 is "1". If F2 = 1, that is, if the air suction valve 14 is currently in the closed state, the ECU 20 proceeds to step 215, and the elapsed time from closing the air suction valve 14 is the valve closing time T3. Is determined. Here, the valve closing time T3 will be described later. In this case, for example, the timing of t12 in FIG.
At this timing, the ECU 20 makes an affirmative determination in step 215 and proceeds to step 216 to open the atmospheric suction valve 14. If the determination in step 215 is negative, the ECU 20 ends this routine.

The ECU 20 proceeds to the next step 217.
Sets the valve opening time T2 of the atmospheric suction valve 14. In setting the valve opening time T2, a time corresponding to the average pressure change amount ΔPTave is obtained using the map of FIG. In the map of FIG. 11, the valve opening time T2 is set to a smaller value as the average pressure change amount ΔPTave increases, and the maximum value of the valve opening time T2 is limited to 10 minutes. After setting the valve opening time T2, the ECU 20 proceeds to step 2
At 18, the valve closing mode flag F2 is cleared to “0”, and then the present routine ends.

If F2 = 0 in step 214, that is, if the air suction valve 14 is currently open, the ECU 20 proceeds to step 219 to open the air suction valve 14. It is determined whether or not the valve opening time T2 has elapsed since. Here, the valve opening time T2 is the time calculated in the process of step 217. In this case, for example, at the timing of t13 in FIG.
In the case of 0, the result of the determination in step 219 is affirmative and the routine proceeds to step 220, where the atmospheric suction valve 14 is closed. If the determination in step 219 is negative, the ECU 20 ends this routine.

Further, the ECU 20 executes the following step 221.
To calculate the valve closing time T3 of the atmospheric suction valve 14. When calculating the valve closing time T3, the map shown in FIG. 11 is used to calculate the average pressure change amount ΔPT similarly to the setting of the valve opening time T2.
Find the time according to ave. After setting the valve closing time T3, E
The CU 20 sets “1” to the valve closing mode flag F2 in step 222, and thereafter ends this routine.

Thereafter, during the fuel cooling period shown by t11 to t15 in FIG. 10, steps 214 to 214 in FIG.
The process of 222 is repeatedly performed, and the opening and closing of the atmospheric suction valve 14 is controlled. In the present embodiment, step 201 in FIG. 8 corresponds to an engine stop detecting unit described in claims, and steps 214 to 222 in FIG. 9 correspond to a control unit.

As described above, according to the second embodiment, the first
Similarly to the embodiment, while the HC diffusion in the canister 10 is suppressed, when the tank internal pressure PT increases to the positive side, the diffused HC blows through the canister 10 and is discharged to the atmosphere side. The defect is eliminated.

In particular, in the present embodiment, the valve opening time T2 and the valve closing time T3 of the atmospheric suction valve 14 are set based on the average pressure change amount ΔPTave (change amount of the tank internal pressure PT), and these time periods T2 , T3 depending on the air intake valve 1
4 was opened or closed. In this case, the tank internal pressure P with the passage of time from the average pressure change amount ΔPTave
If the change in T can be estimated and the timing of opening and closing the atmospheric suction valve 14 is determined based on the estimation result, the fluctuation width of the tank internal pressure PT can be set appropriately. As a result, the accuracy of the tank internal pressure control can be secured, and the reliability can be improved.

In this embodiment, as described above, the valve opening time T2 and the valve closing time T3 of the air suction valve 14 are calculated using the same map (FIG. 11). May be. The times T2 and T3 may be given as experimental values or fixed values corresponding to specification values.

As a modification of the first and second embodiments, the air suction valve 1 in the negative pressure region is provided.
In the opening / closing control of No. 4, control according to the negative pressure level of the tank internal pressure PT (control based on the set values P3 and P4) and control according to the valve opening time T2 and the valve closing time T3 are embodied by the same device. You may make it. In such a case, the set values P3, P4, the valve opening time T2, and the valve closing time T3 are all determination factors for opening or closing the air suction valve 14, and for example, when the air suction valve 14 is opened. In
A process of determining whether or not the tank internal pressure PT has reached the set value P3 and a process of determining whether or not the elapsed time from the previous valve closing has reached the valve closing time T3 are performed. At the timing when the affirmative determination is made earlier, the valve opening process of the atmospheric suction valve 14 is performed. On the other hand, when the atmospheric suction valve 14 is closed, it is determined whether or not the tank internal pressure PT has reached the set value P4, and whether or not the elapsed time from the previous valve opening has reached the valve opening time T2. The process of determining whether or not the air suction valve 14 is closed is performed at a timing when one of the processes is determined to be affirmative.

To realize the above configuration, a control flow may be created by combining the flowcharts of FIGS. 2 and 3 and the flowcharts of FIGS. 8 and 9. According to the configuration, a more optimal timing Can open or close the air suction valve 14.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS. In the devices of the first and second embodiments, the tank internal pressure control is performed using the electromagnetic air suction valve 14 provided in the air port 13 of the canister 10, but the device of the present embodiment Then, the atmospheric suction valve 14 is eliminated, the internal pressure suction valve 11a in FIG. 1 is changed to a solenoid valve (called a suction solenoid valve), and the tank pressure is controlled using this suction solenoid valve. The details will be described below.

FIG. 12 is a block diagram showing the outline of the tank internal pressure control device according to the present embodiment.
A part of FIG. 1 in the embodiment is modified. In other words, the difference from FIG. 1 will be described. In FIG. 12, the atmospheric port 13 of the canister 10 is opened as it is, and the intake solenoid valve 31 constituting an on-off valve is provided in the first evaporation passage 8. Have been. The intake solenoid valve 31 is connected to the ECU 20
Opening / closing operation is performed based on a command signal from the controller to control the communication state between the fuel tank 5 and the canister 10. Note that the intake solenoid valve 31 is configured as a “normally closed valve” that normally keeps the valve closed (non-excitation), and opens only when a signal is input from the ECU 20 (excitation).

Next, an outline of the operation of the tank internal pressure control device of the present embodiment will be described with reference to a time chart of FIG. The figure shows the behavior in the state where the engine is stopped, and before t21 in the figure, the intake solenoid valve 31 is held in the open state.

That is, when the engine is stopped, in the fuel cooling period, the tank internal pressure PT changes from the positive pressure to the negative pressure due to the contraction of the evaporated fuel in the fuel tank 5. And
The tank internal pressure PT is a predetermined set value P1 in the negative pressure region.
When the pressure becomes (-500 Pa in the present embodiment), the negative pressure mode flag F1 is set. At this time, the intake solenoid valve 31 is kept in the closed state.

When the intake solenoid valve 31 is closed, the purge valve 16 in the middle of the purge passage 15 is a check valve that opens due to the intake pipe negative pressure when the engine is operating. Because the valve is normally closed, no outside air is sucked into the fuel tank 5, and the tank internal pressure PT increases toward the negative pressure side.

Thereafter, when the tank internal pressure PT increases to the negative pressure side and reaches a predetermined set value P3 (-2900 Pa in the present embodiment) at the timing of t22 in the figure, the intake solenoid valve 31 is opened. At this time, since the tank internal pressure PT has reached a sufficiently large value in the negative pressure region, the outside air is introduced into the canister 10 at a stretch via the atmosphere port 13. As a result, a large amount of fuel vapor in the canister 10 is separated and returned to the fuel tank 5 (that is, a large amount of back purge is performed). In addition, with the introduction of the outside air, the flow rate of the outside air and the HC in the canister 10 is increased in a direction of narrowing the HC diffusion (back purge direction).
HC diffusion is suppressed.

Thereafter, the tank internal pressure PT rises to the positive pressure side in accordance with the opening of the intake solenoid valve 31, and at a timing t23 in the figure, a predetermined set value P4 (−26 in the present embodiment).
(00 Pa), the intake electromagnetic valve 31 is closed, and the introduction of outside air is stopped. Thereafter, if the fuel temperature still tends to decrease, the tank internal pressure PT changes to the negative pressure side. Therefore, when the tank internal pressure PT reaches the set pressure P3 again (timing at t24), the intake solenoid valve 31 Is opened, and the intake solenoid valve 31 is closed when the tank internal pressure PT reaches the set pressure P4. In this way, the intake solenoid valve 31 repeats its opening and closing operations with a pressure width (| P3-P4 | = 300 Pa) determined by the set pressures P3 and P4.

When the fuel temperature starts to rise due to the rise in the outside air temperature, the tank internal pressure PT shifts to the positive pressure side. In this case, at the timing of t25, the tank internal pressure PT becomes a predetermined set pressure P5 in the positive pressure region (in the present embodiment, 500
When Pa) is reached, the intake solenoid valve 31 is opened. When the intake electromagnetic valve 31 is opened, the expansion amount of the evaporated fuel accompanying the increase in the fuel temperature is introduced into the canister 10 via the first evaporation passage 8 and is adsorbed. Thereafter, the tank internal pressure PT is maintained at the valve opening pressure of the internal pressure discharge valve 11b.

FIGS. 13 and 14 are flow charts showing a tank internal pressure control routine according to the present embodiment. This routine is performed at intervals of, for example, one second, similarly to the control routine according to the first and second embodiments. It is executed by the ECU 20 at a predetermined time period. In the flowchart, for convenience, the description of the opening process of the refueling valve 12 at the time of refueling is omitted, but if the refueling valve 12 is provided in the configuration of the apparatus, the refueling valve is similar to the above-described embodiment. Twelve valve opening processes (steps 102 and 103 in FIG. 2) may be added.

When the tank internal pressure control routine starts, the ECU 20 first determines in step 301 whether or not the engine is stopped, that is, the IG switch is turned off.
It is determined whether or not it is at the FF position. If the engine is not stopped (IG switch = OFF), the ECU 20 proceeds to step 302, and clears both the negative pressure mode flag F1 and the valve opening mode flag F3 to "0". Here, the negative pressure mode flag F1 is a flag that is operated in the same manner as in the devices of the first and second embodiments, whereas the valve opening mode flag F3 is a negative pressure control when the engine is stopped. At the time of execution, the intake solenoid valve 31 is in the open state (excited state)
F3 = 0 indicates that the intake solenoid valve 31 is in the "closed state", and F3 = 1 indicates that the intake solenoid valve 31 is in the "open state".

After clearing the flags F1 and F3,
In step 303, the CU 20 keeps the intake electromagnetic valve 31 closed and ends this routine. In short, when the engine is operating (NO in step 301), the intake solenoid valve 31 is kept closed regardless of the state of the tank internal pressure PT. At this time, the evaporated fuel adsorbed in the canister 10 is supplied to the intake pipe 2 through the purge passage 16 together with the outside air sucked from the atmosphere port 13 by the intake negative pressure.

On the other hand, if step 301 is YES (if the engine is stopped), the ECU 20 proceeds to step 3
In step 04, the tank internal pressure PT detected by the tank internal pressure sensor 17 is read. Thereafter, the ECU 20 determines in a step 305 whether or not the negative pressure mode flag F1 is “0”. At this time, when the engine is stopped, the negative pressure mode flag F1 is cleared to "0".
U20 makes an affirmative decision in step 305 and returns to step 306.
Then, it is determined whether or not the tank internal pressure PT is equal to or lower than a predetermined set value P1 (-500 Pa in the present embodiment).

If PT> P1 as shown before the timing of t21 in FIG.
In step 20, a negative determination is made in step 306, and the routine proceeds to step 303, where the intake solenoid valve 31 is kept in the closed state, and thereafter, this routine ends.

Further, when the tank pressure PT decreases, PT ≦ P
1 (after the timing of t21 in FIG. 15), EC
U20 makes an affirmative decision in step 306 to make a decision in step 307.
The routine proceeds to, where the negative pressure mode flag F1 is set to “1”, followed by terminating this routine. At this time, the state of the intake solenoid valve 31 is still maintained in the closed state.

Once the negative pressure mode flag F1 is set, in the subsequent processing, the ECU 20 makes a negative determination in step 305 each time and proceeds to step 308. Then, in step 308, the ECU 20 determines whether or not the tank internal pressure PT is equal to or higher than a predetermined set value P5 (500 Pa in the present embodiment). Here, a case where PT ≧ P5 is satisfied corresponds to a case where the fuel temperature shifts from a cooling period to a heating period with an increase in outside air temperature, for example, as shown near the timing of t25 in FIG. At the timing of t25, the tank internal pressure PT becomes the set value P5 of the positive pressure level.
, The ECU 20 proceeds to steps 302 and 303 to clear the flags F1 and F3,
Is closed.

On the other hand, if PT <P5 as shown immediately after the timing of t21 in FIG.
20 makes a negative determination in step 308 and proceeds to step 309 in FIG. Then, the ECU 20 determines in step 309
It is determined whether or not the valve opening mode flag F3 is "0". If F3 = 0, that is, the current intake solenoid valve 3
If 1 is in the valve closed state, the ECU 20 proceeds to step 310, and the tank internal pressure PT at that time is reduced to a predetermined set value P3 (in the present embodiment,
-2900 Pa) is reached (PT ≦ P3). At this time, for example, t2 in FIG.
As shown in the period from 1 to t22 or t23 to t24, if the tank pressure PT does not reach the set value P3 during the fall of the tank pressure PT (if PT> P3), EC
U20 ends this routine as it is. Then, for example, if the tank internal pressure PT reaches the set value P3 at the timing of t22 or t24 in FIG. 15, the ECU 20 proceeds to step 311. The ECU 20 opens the intake solenoid valve 31 in step 311 and sets the valve opening mode flag F3 to “1” in the following step 312, and thereafter ends this routine.

If F3 = 1 in step 309, that is, if the intake solenoid valve 31 is now in the open state, the ECU 20 proceeds to step 313, and the ECU 20 proceeds with the opening of the intake solenoid valve 31. The tank pressure PT at that time is a predetermined set value P4 (-2600 Pa in the present embodiment).
Is determined (PT ≧ P4 is satisfied). At this time, if the tank internal pressure PT does not reach the set value P4 during the rise of the tank internal pressure PT, for example, as shown in the period from t22 to t23 in FIG.
In the case of P4), the ECU 20 ends this routine as it is. Then, for example, if the tank internal pressure PT reaches the set value P4 at the timing of t23 in FIG. 15, the ECU 20 proceeds to step 314. The ECU 20 determines in step 314
To close the intake solenoid valve 31, and the following step 3
In step 15, the valve opening mode flag F3 is cleared to "0", and then this routine ends.

Thereafter, in the fuel cooling period shown by t21 to t25 in FIG. 15, step 309 in FIG.
Steps 315 to 315 are repeatedly performed, and the opening and closing of the intake solenoid valve 31 is controlled. In the present embodiment, FIG.
Step 301 corresponds to the engine stop detecting means described in the claims, and Steps 309 to 315 in FIG. 14 correspond to the control means.

According to the third embodiment described in detail above,
As in the above embodiments, the HC in the canister 10
While the diffusion is suppressed, when the tank internal pressure PT rises to the positive side, the problem that the diffused HC blows through the canister 10 and is released to the atmosphere is eliminated.

In this embodiment, the canister 10
The tank internal pressure PT when the engine is stopped is controlled by using the intake solenoid valve 31 provided in the first evaporation passage 8 that communicates with the fuel tank 5. In this case, a mechanically-used internal pressure suction valve (for example, reference numeral 45a in FIG. 25) can be used instead, so that the configuration can be simplified, and the size and space can be reduced.

In the device according to the third embodiment, the intake solenoid valve 31 provided in the first evaporation passage 8 as an on-off valve is used.
Is used to control the opening and closing of the intake solenoid valve 31 in accordance with the set values P3 and P4 during the fuel cooling period. However, as in the device of the second embodiment, the opening and closing time width (T1, T
2, T3), and sets the intake solenoid valve 3 according to the time width.
1 may be controlled to open and close.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIGS. In the devices of the first to third embodiments, E
On-off valves (atmospheric intake valve 14, intake solenoid valve 3) for controlling tank internal pressure PT by an arithmetic program by CU 20
1) is opened and closed, whereby HC in the canister 10
Although the problem of suppressing the diffusion and eliminating the HC blow-through has been eliminated, the apparatus of the present embodiment is provided with a tank internal pressure control valve capable of controlling the tank internal pressure PT by mechanical operation, and controlling the tank internal pressure. The main purpose is to obtain the same operation and effect as the above embodiments by the operation of the valve.

FIG. 16 is a configuration diagram showing an outline of a tank internal pressure control device according to the fourth embodiment. In the figure, a tank internal pressure control valve 51 is provided in a fuel passage between the fuel tank 5 and the canister 10, and has an approximately cylindrical shape with L1 as an axis. Tank internal pressure control valve 5
1 on the outer wall (casing 51 a), a tank communication port 52 communicating with the fuel tank 5, an atmosphere introduction port 53 opened to the atmosphere, and a fuel vapor (H
C), an HC suction port 54 for sucking C), an HC discharge port 55 for discharging the evaporated fuel to the canister 10, and a negative pressure introduction port 56 for introducing a negative pressure in the fuel tank 5. Is provided.

The negative pressure introducing valve 56 is provided with a negative pressure setting valve 57. The negative pressure setting valve 57 is connected to the negative pressure introduction port 5
6 has a spherical valve element 58 for opening and closing the valve element 6, and a compression coil spring 59 for constantly biasing the valve element 58 to the valve closing position. The compression coil spring 59 has a predetermined negative pressure level in the fuel tank 5 (in this embodiment, the set pressure P11 = −290).
When the pressure reaches 0 Pa), it contracts and opens the negative pressure introduction port 56. At this time, the set pressure P11 is a withstand pressure on the negative pressure side allowed in the fuel tank 5, and this negative pressure is applied to the negative pressure setting valve 57.
, The negative pressure setting valve 57 is opened.

First diaphragm chamber 60 as a negative pressure chamber
Is partitioned by a disk-shaped first diaphragm valve 61, and the first diaphragm valve 61 compresses a compression coil so as to close a communication path between the tank communication port 52 and the HC suction port 54. It is always urged downward by a spring 62 in the figure. Note that a spring receiver 63 is provided between the first diaphragm valve 61 and the compression coil spring 62. The set pressure P12 for opening the first diaphragm valve 61 is determined by the set load of the compression coil spring 62, and its value is determined by the opening pressure of the negative pressure setting valve 57 (set pressure P
The pressure is set to be somewhat higher than 11) (P12 = -2800 Pa in the present embodiment).

The first diaphragm valve 61 is made of a rubber material such as fluoro rubber having excellent durability against fuel (gasoline), and its peripheral edge is sandwiched by the casing 51a. Further, a negative pressure control orifice (throttle) 64 formed of a small-diameter through hole is formed in a part of the first diaphragm 61 on the side of the HC suction port 54. Here, in the present embodiment, the first diaphragm valve 61 corresponds to a pressure release valve, and the negative pressure control orifice 64 corresponds to a pressure gradually changing member.

On the other hand, in the lower part of the figure of the tank internal pressure control valve 51, the second diaphragm chamber 65 is partitioned by a disk-shaped second diaphragm valve 66. Incidentally, the second diaphragm valve 66 is made of a rubber material of the same material as the first diaphragm valve 61, and its peripheral edge is sandwiched by the casing 51a. In such a case, the second diaphragm valve 66 is constantly urged upward by a compression coil spring 67 so as to close the communication passage between the tank communication port 52 and the HC discharge port 55. Note that a spring receiver 68 is provided between the second diaphragm valve 66 and the compression coil spring 67. Second diaphragm valve 6
The valve opening pressure P13 of No. 6 is determined by the set load of the compression coil spring 67, and its value is set to a set pressure P13 in a predetermined positive pressure range (in the present embodiment, P13 = 1500)
Pa).

The operation of the tank internal pressure control valve 51 having the above configuration will be described with reference to FIGS. 17 and 18. FIG.
FIG. 7 is an operation explanatory diagram showing a state in which the first diaphragm valve 61 is opened. In short, when a negative pressure is generated in the fuel tank 5 and the negative pressure level (tank internal pressure PT) reaches the set pressure P11 which is the opening pressure of the negative pressure setting valve 57, the urging force of the compression coil spring 59 is resisted. Then, the valve element 58 moves to the valve opening position (moves to the left in the drawing). By the movement of the valve element 58, the negative pressure setting valve 57 is opened, and the tank internal pressure PT
Acts on the first diaphragm chamber 60 via the negative pressure setting valve 57 (PT ≦ set pressure P11).

At this time, since the diameter of the negative pressure control orifice 64 formed in the first diaphragm valve 61 is very small, the negative pressure in the tank is applied to the diaphragm valve 61 at once, and the urging force of the compression coil spring 62 is reduced. In opposition, the central portion of the first diaphragm valve 61 is displaced upward in the figure. Therefore, the tank communication port 52 and the HC suction port 54 are communicated with each other, and the outside air flows toward the fuel tank 5 as indicated by an arrow Q1 in the drawing due to the negative pressure in the tank acting on the tank communication port 52. When the outside air flows into the fuel tank 5, the tank pressure PT changes to the positive pressure side (PT> P11), and the negative pressure setting valve 57 closes. At the beginning of the closing of the negative pressure setting valve 57, the internal pressure of the first diaphragm chamber 60 is equal to the set pressure P1.
The negative pressure is maintained at substantially the same level as the negative pressure, and thereafter, when the negative pressure gradually escapes from the negative pressure control orifice 64 and the internal pressure of the diaphragm chamber 60 reaches the set pressure P12, the biasing force of the compression coil spring 62 causes The first diaphragm valve 61 closes.

FIG. 18 shows the second diaphragm valve 6.
6 is an operation explanatory view showing a state where the valve is opened. FIG. in short,
When evaporative fuel is generated in the fuel tank 5 and the tank internal pressure PT increases, pressure is applied to the outer peripheral portion of the upper surface of the second diaphragm valve 66. When the tank internal pressure PT exceeds the set pressure P13 for opening the second diaphragm valve 66, the central portion of the second diaphragm valve 66 moves downward in the figure against the urging force of the compression coil spring 67. Displace. Therefore,
The communication between the tank communication port 52 and the HC discharge port 55 is communicated, and the fuel vapor flows toward the canister 10 as indicated by an arrow Q2 in the figure. Thereafter, when the fuel vapor flows from the fuel tank 5 to the canister 10 and the tank internal pressure PT drops, the biasing force of the compression coil spring 67 closes the second diaphragm valve 66.

Next, the operation of the tank internal pressure control device having the above configuration will be described with reference to the time chart of FIG. The figure shows changes in the tank internal pressure PT due to changes in the outside air temperature and the fuel temperature when the engine is stopped (when the vehicle is left unattended), the opening / closing operation of the negative pressure setting valve 57 and the first diaphragm valve 61, and the first operation. 5 shows changes in the internal pressure of the diaphragm chamber 60.

That is, when the engine is stopped, the temperature (fuel temperature) of the fuel in the fuel tank 5 follows a change in the outside air temperature. Therefore, if the outside air temperature is lower than the fuel temperature, the fuel temperature drops following the outside air. At this time, the tank pressure PT changes to the negative pressure side due to the condensation of the evaporated fuel in the fuel tank 5,
In the tank internal pressure control valve 51, both the first and second diaphragm valves 61 and 66 are kept in a closed state, so that the negative pressure level in the fuel tank 5 gradually increases. Then, the tank internal pressure PT becomes a predetermined set value P in the negative pressure region.
At the timing of t31 when 11 (= -2900 Pa) is reached, the negative pressure setting valve 57 which has been in the closed state is opened, and the first diaphragm valve 61 is opened (the state of FIG. 17). At this time, the internal pressure of the first diaphragm chamber 60 also reaches a negative pressure level near the set value P11, similarly to the tank internal pressure PT.

When the first diaphragm valve 61 opens,
Since the tank internal pressure PT has reached a sufficiently large value in the negative pressure region, the outside air flows through the canister 1 through the atmosphere port 13.
0 is introduced at a stretch. Then, the outside air passing through the canister 10 is sucked into the fuel tank 5 through the tank internal pressure control valve 51. At this time, a large amount of evaporated fuel in the canister 10 is separated and returned to the fuel tank 5 (that is, a large amount of back purge is performed). With the introduction of the outside air, the outside air and the evaporated fuel (HC) in the canister 10 in the direction of narrowing the HC diffusion (back purge direction).
, The diffusion of HC is suppressed (see FIG. 7B).

Thereafter, the tank pressure PT changes from a decrease to an increase, and when PT> P11, the negative pressure setting valve 57 is closed. However, the internal pressure of the first diaphragm chamber 60 gradually changes to the positive pressure side due to the operation of the negative pressure control orifice 64.
The open state of the first diaphragm valve 61 is maintained. That is, the negative pressure control orifice 64 delays the release of the negative pressure from the first diaphragm chamber 61, and the first diaphragm valve 6
1 has a role of maintaining the open state, whereby the intake of the outside air into the fuel tank 5 is continued. Then, at the timing of t32, the first diaphragm chamber 60
When the internal pressure reaches the set pressure P12 (= -2800 Pa), the first diaphragm valve 61 is closed and the introduction of outside air is stopped.

Thereafter, when the fuel temperature still tends to decrease (when the temperature is falling), the tank internal pressure PT changes to the negative pressure side again.
When the pressure reaches 11, the negative pressure setting valve 37 and the first diaphragm valve 61 are opened again. The negative pressure setting valve 3
7 and the opening and closing of the first diaphragm valve 61, the internal pressure of the first diaphragm chamber 60 rises and falls with a pressure width (| P11−P12 | = 100 Pa) determined by the set pressures P11 and P12. The internal pressure of the fuel tank 5 rises and falls with a pressure width of about 300 Pa. The pressure width of the tank internal pressure PT depends on the characteristics of the pressure change by the negative pressure control orifice 64, and the setting can be changed as appropriate according to the specifications of the tank internal pressure control device.

On the other hand, when the fuel temperature starts to rise due to the rise in the outside air temperature, fuel vapor is generated in the fuel tank 5, and the tank internal pressure PT shifts to the positive pressure side. In this case, the fuel vapor generated in the fuel tank 5 reaches the tank communication port 52, and the tank internal pressure PT becomes equal to the predetermined set pressure P13 in the positive pressure region.
(= 1500 Pa), the second diaphragm valve 6
6 is opened (the state of FIG. 18). With the opening of the second diaphragm valve 66, the expansion of the evaporated fuel accompanying the rise in fuel temperature is introduced into the canister 10 via the HC discharge port 55 and is adsorbed. Since the diffusion of HC is suppressed in the canister 10 as described above, when the fuel temperature shifts from a decrease to a rise, the diffused fuel evaporates from the canister 1.
It does not blow through the inside of zero and is not released to the atmosphere side.

During operation of the engine, outside air is sucked from the atmospheric port 13 of the canister 10 by the suction pipe negative pressure, and the evaporated fuel and outside air separated from the canister 10 are sent to the suction pipe 2 via the purge valve 16. At the time of refueling, the evaporated fuel stored in the fuel tank 5 is pushed out by refueling and sent to the canister 10 via the refueling valve 12.

As described above, according to the fourth embodiment, each time the first diaphragm valve 61 opens during the fuel cooling period, a high speed and a large amount of outside air flows through the canister 10 each time. . That is, when the outside air is introduced at once, the flow rate of the outside air exceeds the HC diffusion rate. As a result, the diffusion of HC in the canister 10 can be suppressed, and the disadvantage that when the tank internal pressure PT rises to the positive side, the diffused evaporated fuel blows through the canister 10 and is discharged to the atmosphere side is solved.

According to the present embodiment, the following effects can be obtained in addition to the above effects. In the tank internal pressure control valve 51, since the opening pressure of the negative pressure setting valve 57 is set based on the negative pressure resistance of the fuel tank 5, the negative pressure is increased to the maximum negative pressure within an allowable range, and a sufficient flow rate in the canister is obtained. Can be obtained. Further, it is possible to prevent a problem that an excessive negative pressure is applied to the fuel tank 5 and the fuel tank 5 is deformed.

A negative pressure control orifice 64 was provided in a part of the first diaphragm valve 61. The negative pressure control orifice 64 gradually changes the internal pressure of the first diaphragm chamber 60 when the first diaphragm valve 61 is opened and closed so that the tank internal pressure PT has a fluctuation range. In this case, the configuration for gradually changing the internal pressure of the first diaphragm chamber 60 can be simplified.

(Fifth Embodiment) The fifth embodiment of the present invention
The embodiment will be described with reference to FIG. In this embodiment, similarly to the above-described fourth embodiment, the same operation and effect as those of the above-described first to third embodiments can be obtained by the mechanical operation of the tank internal pressure control valve 51. It is intended.

FIG. 20 is a block diagram showing the outline of the tank internal pressure control device according to the fifth embodiment. The control device shown in FIG. 20 is a modification of the device according to the fourth embodiment. It is. Here, unlike the control device (FIG. 16) of the fourth embodiment, the tank internal pressure control valve 51 of the present embodiment is different from the control device (FIG.
3 is connected.

More specifically, the tank communication port 52 in FIG. 16 is configured as a canister communication port 71, and the canister communication port 71 is connected to the atmospheric port 13 of the canister 10. Further, the air introduction port 53 in FIG. 16 is configured as an intake negative pressure introduction port 72, and this intake negative pressure introduction port 72 is connected to the throttle downstream of the intake pipe 2 via the purge valve 16. Further, the HC intake port 54 and the HC discharge port 55 in FIG. 16 are configured as atmosphere introduction ports 73 and 74. In addition, the configurations of the negative pressure setting valve 57, the first and second diaphragm chambers 60 and 65, the first and second diaphragm valves 61 and 66, and the like conform to the configuration of FIG. Omitted.

According to the tank internal pressure control valve 51 shown in FIG. 20, when the fuel evaporated in the fuel tank 5 is condensed due to a decrease in the fuel temperature when the engine is stopped, as shown in the time chart of FIG. Since both the first and second diaphragm valves 61 and 66 in the tank internal pressure control valve 51 are kept closed, the tank internal pressure PT gradually increases toward the negative pressure side. Then, the tank internal pressure PT becomes a predetermined set value P11 (= -2900 Pa) in the negative pressure region.
(Timing t31 in the figure), the negative pressure setting valve 57, which has been in the closed state, opens, and the first diaphragm valve 61 also opens. At this time, the internal pressure of the first diaphragm chamber 60 also reaches a negative pressure level near the set value P11, similarly to the tank internal pressure PT.

When the first diaphragm valve 61 opens,
Since the tank internal pressure PT has reached a sufficiently large value in the negative pressure region, the air introduction port 73 of the tank internal pressure control valve 51
Outside air is introduced into the canister 10 at a stretch via a route from the canister communication port 71 to the atmosphere port 13 of the canister 10. Then, the outside air passing through the canister 10 is sucked into the fuel tank 5 via the internal pressure suction valve 11a of the tank internal pressure adjusting valve 11. At this time, a large amount of evaporated fuel in the canister 10 is separated and returned to the fuel tank 5 (that is, a large amount of back purge is performed). With the introduction of the outside air, the flow rate of the outside air and the evaporated fuel (HC) in the canister 10 is increased in the direction of narrowing the HC diffusion (back purge direction), so that the HC diffusion is suppressed.

Thereafter, the tank pressure PT changes from a decrease to an increase, and when PT> P11, the negative pressure setting valve 57 is closed. However, the internal pressure of the first diaphragm chamber 60 gradually changes to the positive pressure side due to the operation of the negative pressure control orifice 64.
The open state of the first diaphragm valve 61 is maintained. Thereby, the intake of the outside air into the fuel tank 5 is continued,
When the internal pressure of the first diaphragm chamber 60 is equal to the set pressure P12 (= −
When the pressure reaches 2800 Pa) (timing t32 in FIG. 19), the first diaphragm valve 61 is closed and the introduction of outside air is stopped. Thereafter, when the fuel temperature still tends to decrease (when the temperature is in the cooling period), the tank internal pressure PT changes to the negative pressure side again, so that when the tank internal pressure PT reaches the set pressure P11, the negative pressure setting valve is set. 37 and the first diaphragm valve 61 are opened.

On the other hand, the fuel temperature rises due to the rise of the outside air temperature,
When the fuel vapor in the fuel tank 5 expands and the tank internal pressure PT reaches a predetermined positive pressure level, the fuel vapor generated in the fuel tank 5 is discharged from the internal pressure discharge valve 11 of the tank internal pressure regulating valve 11.
b to the canister 10, and the canister 10
Is adsorbed. The air flowing along with the fuel vapor is not adsorbed by the canister 10 and reaches the canister communication port 71 communicating with the atmospheric port 13 of the canister 10.
At this time, the second diaphragm valve 66 is opened, and air is discharged from the atmosphere introduction port 74 into the atmosphere.

When the engine is operating, the negative pressure of the intake pipe acts on the outer peripheral portion of the lower surface of the second diaphragm valve 66, whereby the second diaphragm valve 66 opens against the urging force of the compression coil spring 67. At this time, the tank internal pressure control valve 51
The outside air is sucked into the canister 10 through the route of the atmosphere introduction port 74 → the canister communication port 71 → the atmosphere port 13, and the evaporated fuel and the outside air separated from the canister 10 are sent to the intake pipe 2 via the purge valve 16. .

As described above, according to the fifth embodiment, the fourth embodiment
In the same manner as in the embodiment, the HC diffusion in the canister 10 can be suppressed, and when the tank internal pressure PT increases to the positive side, the diffused fuel vapor blows through the canister 10 and is discharged to the atmosphere side. Can be eliminated.

When the outside air flows through the canister 10, the canister 1 according to the fourth embodiment (FIG. 16) is used.
While the pressure in 0 is atmospheric pressure, in the fifth embodiment, the canister 10 is in a negative pressure state. That is, the evaporated fuel adsorbed on the canister 10 is easily released, and the effect of preventing the diffusion of the evaporated fuel can be further enhanced.

Hereinafter, other embodiments of the present invention will be described. In the first and third embodiments, the set value P3 (see the time chart in FIG. 4) for shifting the tank internal pressure PT in the negative pressure region to the positive pressure side during the tank internal pressure control is set to the fuel cooling period. Is set to the maximum negative pressure (withstand pressure on the negative pressure side of the tank), which may be changed, and the set value P3 may be set closer to the positive pressure side than the negative pressure level described above. In this case, the set value P4 for shifting the tank internal pressure PT to the negative pressure side
(Refer to the time chart of FIG. 4). Similarly, the positive pressure level may be set higher than the negative pressure level described above. In short, any configuration may be used as long as the outside air is introduced into the canister 10 at a stretch by the opening and closing operation of the on-off valve, and HC diffusion can be suppressed by the back purge at that time. Specifically, the pressure width during the negative pressure control is set to 100
The above-mentioned various set values P1 to P5 may be arbitrarily changed as long as the configuration can be set to Pa or more (preferably 300 to 500 Pa).

The fact that the various set values of the pressure can be changed is the same as in the tank internal pressure control valve 51 in the fourth and fifth embodiments. The operation of the tank internal pressure control valve 51 allows the outside air to flow into the canister 10 at once. The operating pressure of the negative pressure setting valve 57 and the first diaphragm valve 61 may be arbitrarily changed as long as the configuration is such that HC diffusion can be suppressed by the back purge at that time.

Further, in each of the above embodiments, a method for confirming the operation position of the ignition key switch has been disclosed as means for detecting that the engine is in the stopped state.
Of course, it may be embodied by another method. For example, the engine stop state may be detected based on the fact that the engine speed is equal to or less than a predetermined minute rotation value or that the engine water temperature has been kept low for a long time.

The ambient temperature of the canister 10 may be detected, and the tank internal pressure control may be performed as described below in accordance with the detection result. If the ambient temperature of the canister 10 is high, HC is easily diffused, so that the on-off valve (atmospheric intake valve 14 or intake electromagnetic valve 31) is frequently opened and closed. Conversely, if the ambient temperature of the canister 10 is low, the diffusion of HC is slow, so the pressure width (between P3 and P4 in FIG. 4)
To increase. According to such control, HC diffusion can always be appropriately suppressed regardless of a change in the canister temperature. In addition, as a means for detecting the ambient temperature of the canister 10, a sensor for detecting the outside air temperature can be substituted.

In each of the above embodiments, a mechanical check valve is used as the purge valve, but the purge VSV (Va) for controlling the purge flow rate in accordance with a control signal from the ECU 20 is used.
cuumSwitching Valve). in this case,
The opening of the purge VSV is adjusted by a duty ratio signal based on pulse width modulation from the ECU 20, and the canister 1
Adjust the purge flow rate of air containing fuel vapor from zero.

Further, the on-off valve (atmospheric intake valve 14 or intake electromagnetic valve 31) and the refueling valve 12
May be integrated, and both valves may be selectively used by the control program of the ECU 20.

The tank internal pressure control valve 51 in the fourth and fifth embodiments may be embodied as shown in FIGS. 21 to 24, and the effects described above can be obtained in such a case. In the tank internal pressure control valve 51 of FIG. 21, instead of the negative pressure control orifice 64 of the tank internal pressure control valve 51 shown in FIG. 16, a negative pressure control as a pressure gradually changing member is provided near the center of the first diaphragm valve 61. An orifice (aperture) 81 is provided. The negative pressure control orifice 81 is provided as a through hole that penetrates the first diaphragm valve 61 and the spring receiver 63. The bucket 8 is provided in a passage communicating with the port 83 so that the negative pressure of the fuel tank 5 does not act on the first diaphragm chamber 60 through the negative pressure control orifice 81.
2 are provided. That is, the negative pressure control orifice 81
When the first diaphragm valve 61 is closed, the first diaphragm chamber 60 is closed, and when the first diaphragm valve 61 is opened, the internal pressure of the first diaphragm chamber 60 is gradually changed through a minute opening. Let it.

According to the tank internal pressure control valve 51 shown in FIG. 21, in the fuel temperature drop period, after the negative pressure acts on the first diaphragm chamber 60 and the first diaphragm valve 61 opens, the negative pressure The first diaphragm valve 61 closes a predetermined time after the closing of the setting valve 57 (similar to the fourth embodiment). After the first diaphragm valve 61 is closed,
The first diaphragm chamber 60 is maintained at a predetermined negative pressure level (near the set pressure P12). Therefore, when the opening and closing of the first diaphragm valve 61 is repeated, the responsiveness of the opening and closing operation is improved.

In the tank pressure control valve 51 shown in FIG.
Instead of providing the negative pressure control orifice 64 in the diaphragm valve 61, a throttle passage 85 as a pressure gradually changing member is provided in the wall surface (the casing 51a) of the first diaphragm chamber 60. In the middle of the throttle passage 85, the same passage 85
An adjusting screw 86 for adjusting the opening area of is provided. In this case, the degree of the pressure gradual change can be adjusted by the screwing amount of the adjusting screw 86 (however, the adjusting screw 86 may be omitted as appropriate).

In the tank internal pressure control valve 51 shown in FIG. 23, a plate 91 made of an air-permeable thin plate is assembled to the first diaphragm valve 61 as another configuration of the pressure-gradual change member. In the tank internal pressure control valve 51 shown in FIG. 24, a plate 93 made of an air-permeable thin plate like the plate 91 is assembled to a passage 92 provided on the wall surface of the first diaphragm chamber 60. As the air-permeable thin plate, a porous sintered metal made of aluminum or stainless steel may be used, or a porous ceramic material may be used. In such a configuration, the first through the holes of the plates 91 and 93 may be used. The negative pressure of the first diaphragm chamber 60 is gradually released.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an outline of a fuel tank internal pressure control device according to an embodiment of the invention.

FIG. 2 is a flowchart illustrating a tank internal pressure control routine according to the first embodiment.

FIG. 3 is a flowchart showing a tank internal pressure control routine continued from FIG. 2;

FIG. 4 is a time chart showing an outline of an operation in the first embodiment.

FIG. 5 is a time chart showing changes in the tank internal pressure and changes in the flow velocity in the canister.

FIG. 6 is a graph showing the flow-through HC amount over time.

FIG. 7 is a schematic diagram showing a state of HC diffusion in the canister.

FIG. 8 is a flowchart illustrating a tank internal pressure control routine according to the second embodiment.

FIG. 9 is a flowchart showing a tank internal pressure control routine continued from FIG. 8;

FIG. 10 is a time chart showing an outline of an operation in the second embodiment.

FIG. 11 is a map for setting a valve opening time and a valve closing time of an atmospheric suction valve according to an average pressure change amount.

FIG. 12 is a configuration diagram showing an outline of a fuel tank internal pressure control device according to a third embodiment.

FIG. 13 is a flowchart illustrating a tank internal pressure control routine according to a third embodiment.

FIG. 14 is a flowchart showing a tank internal pressure control routine continued from FIG. 13;

FIG. 15 is a time chart showing an outline of an operation in the third embodiment.

FIG. 16 is a configuration diagram showing an outline of a fuel tank internal pressure control device according to a fourth embodiment.

FIG. 17 is an operation explanatory view showing a state in which a first diaphragm valve of a tank internal pressure control valve is opened in a fourth embodiment.

FIG. 18 is an operation explanatory view showing a state in which a second diaphragm valve of the tank internal pressure control valve is opened in the fourth embodiment.

FIG. 19 is a time chart showing an outline of an operation in the fourth embodiment.

FIG. 20 is a configuration diagram showing an outline of a fuel tank internal pressure control device according to a fifth embodiment.

FIG. 21 is a sectional view showing a configuration of a tank internal pressure control valve according to another embodiment.

FIG. 22 is a sectional view showing a configuration of a tank internal pressure control valve according to another embodiment.

FIG. 23 is a sectional view showing a configuration of a tank internal pressure control valve according to another embodiment.

FIG. 24 is a cross-sectional view showing a configuration of a tank internal pressure control valve according to another embodiment.

FIG. 25 is a configuration diagram showing an outline of a tank internal pressure control device according to a conventional technique.

FIG. 26 is a time chart showing changes in fuel temperature and tank internal pressure according to changes in outside air temperature.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Intake pipe, 5 ... Fuel tank, 8 ... 1st evaporation path which comprises an evaporative fuel release mechanism, 10 ... Canister which comprises an evaporative fuel release mechanism, 14 ... Atmospheric intake valve which comprises an on-off valve Reference numeral 15 denotes a purge passage which constitutes an evaporative fuel release mechanism, 16 denotes a purge valve which constitutes an evaporative fuel release mechanism, 17 a tank internal pressure sensor which constitutes a tank internal pressure detector, 20 a engine stop detecting means and a control means ECU 31 that performs an on-off valve (in-tank pressure suction valve); 51 an in-tank pressure control valve; 57 a negative pressure setting valve; 60 a first diaphragm chamber that forms a negative pressure chamber; A first diaphragm valve constituting a pressure release valve; 64, 81: a negative pressure control orifice constituting a pressure gradually varying member (throttle); 85: a throttle passage constituting a pressure gradually varying member; Air permeability plates constituting the gradual change member.

(72) Inventor Atsushi Yoshinaga Atsushi 14 Iwatani, Shimowasakucho, Nishio City, Aichi Prefecture Inside the Japan Automobile Parts Research Laboratory (72) Inventor Katsuo Hokugami 14th Iwatani, Shimowasukamachi, Nishio City, Aichi Prefecture Japan Automobile Co., Ltd. Inside the Parts Research Laboratory (72) Inventor Kazuto Maeda 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Nobuhiko Koyama 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation

Claims (12)

[Claims] An internal pressure control device for a fuel tank having an evaporative fuel release mechanism for releasing an evaporative fuel generated in a fuel tank into a canister and then releasing the evaporative fuel to an engine intake system. Engine stop detecting means for detecting that the operation has been performed; an on-off valve for permitting or prohibiting the intake of outside air into the canister to control the pressure in the fuel tank; Control means for controlling the opening and closing operation of the on-off valve so that the pressure fluctuates by a predetermined width in the negative pressure region. 2. The fuel cell system according to claim 1, further comprising: a tank pressure detecting means for detecting a fuel tank pressure, wherein said control means detects the fuel tank pressure.
2. The internal pressure control device for a fuel tank according to claim 1, wherein the on-off valve is opened when a maximum negative pressure allowed during a fuel cooling period is reached. 3. 3. The fuel tank internal pressure control device according to claim 2, wherein the allowable maximum negative pressure is set based on a negative pressure resistance of the fuel tank. Internal pressure control device. 4. The control means opens the on-off valve when the detected internal pressure of the fuel tank reaches the maximum allowable negative pressure, and thereafter, the control means opens the open / close valve by a predetermined width greater than the maximum negative pressure. 4. The internal pressure control device for a fuel tank according to claim 2, wherein the on-off valve is closed only at a predetermined negative pressure on the positive pressure side. 5. An internal pressure control device for a fuel tank having an evaporative fuel release mechanism for releasing an evaporative fuel generated in a fuel tank into a canister and then releasing the evaporative fuel to an engine intake system, wherein the operation of the engine is stopped. Engine stop detecting means for detecting that the operation has been performed; an on-off valve for permitting or prohibiting the intake of outside air into the canister to control the pressure in the fuel tank; Control means for controlling the opening / closing operation of the on-off valve at a predetermined time interval so that the pressure fluctuates in the negative pressure region. 6. An internal pressure control system for a fuel tank according to claim 5, further comprising means for calculating an amount of change in the pressure in the fuel tank, wherein the control means controls a time width corresponding to the amount of change in the pressure in the fuel tank. A valve opening period and a valve closing period of the on-off valve in accordance with the internal pressure control apparatus. 7. The on-off valve according to claim 1, wherein the on-off valve comprises an air suction valve provided at an air port of the canister.
An internal pressure control device for a fuel tank according to any one of the above. 8. The fuel tank internal pressure control device according to claim 1, wherein the on-off valve comprises a tank internal pressure suction valve provided between the canister and the fuel tank. 9. An internal pressure control valve for use in an internal pressure control device for a fuel tank having an evaporative fuel release mechanism for once adsorbing the evaporative fuel generated in the fuel tank to a canister and then releasing the evaporative fuel to an engine intake system, A negative pressure setting valve which is communicated with the fuel tank and opens when a maximum negative pressure allowed in the tank acts, a negative pressure chamber closed by the negative pressure setting valve, and the negative pressure chamber A pressure release valve that shuts off the outside and opens on the positive pressure side from the negative pressure level at which the negative pressure setting valve opens, and opens the inside of the fuel tank with the opening, and the internal pressure of the negative pressure chamber And a pressure gradually changing member for gradually changing pressure. 10. The tank internal pressure control valve according to claim 9, wherein the valve opening pressure of the negative pressure setting valve is set based on a negative pressure side pressure resistance of the fuel tank. 11. The pressure change member according to claim 9, wherein the pressure change member is a throttle provided on a wall defining the negative pressure chamber.
0. The tank internal pressure control valve according to 0. 12. The pressure-varying member according to claim 10, wherein the pressure-releasing member seals the negative pressure chamber when the pressure release valve is closed, and has a small opening area when the pressure release valve is opened. Tank pressure control valve.