JP2936904B2 - Fuel tank pressure controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel tank pressure control device, and more particularly to a fuel tank pressure control device for appropriately controlling the internal pressure of a fuel tank when an internal combustion engine is operated and stopped.

[0002]

2. Description of the Related Art Evaporated fuel (vapor) generated in a fuel tank of an internal combustion engine is adsorbed by an adsorbent in a canister, and the adsorbed fuel is sucked into an intake system of the internal combustion engine and burned under predetermined operating conditions. In the evaporative purge system, when a large amount of fuel vapor is generated in the fuel tank and the fuel vapor is supplied to the canister beyond the capacity of the canister, the fuel vapor in the canister overflows and the fuel vapor leaks to the atmosphere.

In order to prevent such a phenomenon, it is necessary to reduce the amount of fuel vapor (amount of vapor) generated in the fuel tank as much as possible. Have been.

However, the fuel temperature of the main tank immediately after the engine is stopped receives heat from the fuel having a high fuel temperature in the sub-tank, and further, the exhaust pipe around the tank (still hot immediately after the stop).
, It rises for a few minutes after the stop, which generates a large amount of vapor. When the engine stops, no vapor is released from the canister to the engine intake system.
All the vapor generated at this time is discharged into the canister, which is a problem.

Therefore, the present applicant has previously filed Japanese Patent Application No. 4-185.
In No. 174, when the engine is operating, the tank pressure is controlled to be higher than the atmospheric pressure, and when the engine is stopped, the tank pressure is controlled to be higher than the set pressure during the engine operation in the positive pressure direction. A pressure control device in a fuel tank with a control valve was proposed.

[0006]

In the fuel tank pressure control device proposed by the applicant of the present invention, the negative pressure of the canister purge is introduced into the diaphragm chamber of the tank pressure control valve during operation of the engine. controlling the tank pressure as indicated by I from the setting pressure P by the diaphragm and spring tank pressure control valve to a pressure obtained by subtracting the negative pressure P _C of the canister purge.

However, when the activated carbon in the canister is deteriorated or when a large amount of vapor is adsorbed in the canister, the pressure loss of the canister increases according to the degree of the deterioration and the amount of vapor adsorbed. a negative pressure is increased to be guided to the diaphragm chamber as indicated by II, when the negative pressure P _C of the canister purge than the set pressure P is increased, the tank pressure control valve will fully open.

[0008] If the tank internal pressure control valve is completely opened, it is impossible to prevent spillage (a phenomenon in which fuel jumps out of the fuel tank into the vapor passage from the fuel tank to the canister when the vehicle turns). Since the liquid level gradually rises, the cutoff valve for over-injection does not operate well, and over-injection occurs.

Further, since the negative pressure of the canister is directly introduced into the fuel tank through the fully opened tank internal pressure control valve, a large amount of vapor from the fuel tank is adsorbed by the canister, and further, the vapor from the canister to the intake system. Is sucked in a large amount, so that the air-fuel ratio becomes rough and the exhaust emission deteriorates.

The set pressure of the tank internal pressure control valve is assumed to be a large value in consideration of the large amount of vapor adsorption of the canister and the deterioration of the activated carbon, and the large amount of vapor adsorption of the canister and the deterioration of the activated carbon as shown by III in FIG. It is conceivable to prevent the tank internal pressure control valve from fully opening during engine operation, but in such a case, the set pressure during normal engine operation will be a value that is almost the same as when the operation was stopped. However, generation of a large amount of vapor immediately after the engine is stopped cannot be prevented.

The present invention has been made in view of the above points, and by providing a lower limit to the canister purge negative pressure,
An object of the present invention is to provide a fuel tank pressure control device that solves the above problems.

[0012]

FIG. 1 is a block diagram showing the principle of a fuel tank pressure control device according to the present invention. As shown in FIG. 1, the present invention adsorbs evaporated fuel generated in a fuel tank 11 of an internal combustion engine 10 to an adsorbent in a canister 12 and then suctions the evaporated fuel into an intake system of the internal combustion engine 10 under predetermined operating conditions. In the fuel tank pressure control device of the evaporative purge system, at least one pair of the valve seat 13a and the valve body 13 is provided.
b, urging means 13 for urging valve body 13b toward valve seat 13a
c and a set pressure by the urging means 13c when the internal combustion engine 10 is operating.
The pressure set in the fuel tank 11 is set to a first set pressure such that the pressure in the fuel tank 11 becomes a positive pressure by using the negative pressure of the second pressure. It is prohibited that the first set pressure by the set pressure adjusting means 14 for setting the second set pressure larger in the positive pressure direction than the second set pressure and the first set pressure by the set pressure adjusting means 14 corresponding to the negative pressure of the canister 12 becomes lower than a predetermined value. Prohibiting means 15 provided in the system from the fuel tank 11 to the evaporated fuel purge section 16 of the intake system.

[0013]

According to the present invention, during operation of the internal combustion engine 10, the pressure in the fuel tank 11 is controlled to a first positive pressure by the set pressure adjusting means 14 and the control valve 13, and the first set pressure is The lower limit is set by the prohibiting means 15 irrespective of the negative pressure of the canister 12. When the operation of the internal combustion engine 10 is stopped, the pressure in the fuel tank 11 is increased in the positive pressure direction by the set pressure adjusting means 14 and the control valve 13 as compared with during operation.
Is controlled to the set pressure. Further, in the present invention, the control valve 13 for controlling the pressure in the fuel tank has a single structure.

[0014]

FIG. 2 is a block diagram showing a first embodiment of the present invention.
In the figure, a fuel tank 21 corresponds to the fuel tank 11 and includes a main tank 21a and a sub tank 21b. A fuel pump 22 is provided in the sub tank 21b, and a fuel gauge 23 is provided in the sub tank 21b.
It is provided within. The fuel pump 22 is connected to the pipe 2
It is communicated with 4. The sub-tank 21b is configured so that a part of the fuel is returned via the return pipe 25.

The fuel tank 21 is connected to a tank internal pressure control valve 20 via a vapor passage 26. The tank internal pressure control valve 20 is a mechanical control valve corresponding to the control valve 13 and has a check valve 27 and a first space 28 which respectively communicate with the fuel tank 21 via a vapor passage 26, and a second space 29. Are separated from the first space 28 via the diaphragm 30. Diaphragm 3
0 is a spring 31 in the second space 29,
A spring force is urged downward. The spring 31 constitutes the urging means 13c together with the diaphragm 30.

A valve element 32 is provided at the center of the diaphragm 30.
(Corresponding to 13b) is fixed, and when the operation is stopped, the valve body 32 closes the vapor inlet 33 (corresponding to the valve seat 13a) by the spring force of the spring 31 and the diaphragm 30. The vapor inlet 33 communicates with a canister 36 via a vapor passage 35.

The tank internal pressure control valve 20 controls the first space 28 to a constant pressure P ₁ by a spring 31 and a diaphragm 30. When the pressure in the tank becomes a negative pressure, the check valve 27 is opened, a negative pressure is introduced into the canister 36, the vapor adsorbed on the activated carbon 37 in the canister 36 is released, and the fuel is returned to the fuel tank 21. .

The tank internal pressure control valve 20 has a check valve 34 for preventing full opening between the second space 29 and the external space. Check valve 34 for preventing full opening is spring 3
Drawing by 4a, are structured to check ball 34b in the upward direction is biased force, negative pressure than the set pressure P ₂ of the second full-open preventing check valve 34 pressure by the spring 34a of the space 29 The valve opens when it becomes larger in the
The pressure in the space 29 of the atmospheric pressure direction, whereby by the pressure of the second space 29 repeats that closes again when reaching the set pressure P _2, setting the pressure in the second space 29 pressure P Hold at ₂ . This check valve 34 for preventing full opening
Constitutes the prohibiting means 15.

Further, the second space 29 of the tank internal pressure control valve 20 is connected to the vapor passage 35 and the port 4 through a negative pressure passage 39.
It is communicated by 1. In the middle of the negative pressure passage 39, a vacuum transmitting valve (VTV) 40 is provided.

The VTV 40 comprises a check valve 40a and an orifice 40b. When the negative pressure of the port 41 becomes high, the check valve 40a and the orifice 40b are provided.
b through the second space 2 of the tank internal pressure control valve 20.
9 is transmitted. Conversely, the pressure of the port 41 is
9, the check valve 40a is closed and the port 41 and the second space 2 are passed through only the orifice 40b.
9 is communicated to prevent the negative pressure from being released.

The canister 36 has an air inlet 38, and is connected to an intake passage 45 downstream of a throttle valve 44 through a purge passage 42 and a vacuum switching valve (VSV) 40, respectively. The intake passage 45 communicates with a combustion chamber of an engine 46 corresponding to the internal combustion engine 10. A part of the fuel injection valve 47 protrudes from the intake passage 45.

The pressure regulator 48 adjusts the fuel pressure applied to the fuel injection valve 47 to a constant value. The electronic control unit 49 is configured by a microcomputer, and controls the fuel injection time of the fuel injection valve 47 and the opening / closing control of the VSV 43 based on various engine parameters. The set pressure adjusting means 14 is realized by the negative pressure passage 39, the VTV 40, the VSV 43 and the like.

Next, the operation of this embodiment will be described. First, when the engine is stopped, the VSV 43 is closed, and the second space 29 of the tank internal pressure control valve 20 is connected to the negative pressure passage 39 and the VTV 4.
The second space 29 is at atmospheric pressure because it is communicated with the air inlet 38 of the canister 36 via the activated carbon 37 of the canister 36.

[0024] Therefore, the pressure of the first space 28 of the tank pressure control valve 20, i.e. tank pressure P _T is controlled to set the pressure P ₁ by the spring 31 and the diaphragm 30 as indicated by the two Fig. The set pressure P ₁ is greater becomes the value of the positive pressure.

Next, the operation during engine operation will be described.
When the ignition switch (IG) is turned on, the fuel pump 22 shown in FIG. 2 is operated to discharge the fuel in the sub tank 21b. The discharged fuel enters the pressure regulator 46 through the pipe 24 and is input to the fuel injection valve 47 while keeping the fuel pressure constant, while the surplus fuel passes from the pressure regulator 48 through the return pipe 25 to the fuel tank 21. Will be returned within.

On the other hand, the evaporated fuel (vapor) generated in the fuel tank 21 enters the tank internal pressure control valve 20 through the vapor passage 26. Here, when the purge control condition is not satisfied even after the engine is started, the port 41 is communicated with the air inlet 38 of the canister 36, and therefore the port 41 is not connected.
The pressure P _C is the value near the atmospheric pressure, since the negative pressure passage 39 is not introduced negative pressure tank pressure P _T (which is the fuel tank 21 of the first space 28 of the tank pressure control valve 20 (Equal to the internal pressure) is controlled to the pressure P ₁ set by the spring 31 and the diaphragm 30.

When the tank internal pressure P _T exceeds the set value P ₁ , the valve body 32 is pushed upward in the drawing against the spring force of the spring 31 and the diaphragm 30, and is input to the tank internal pressure control valve 20. Evaporated fuel is vapor inlet 3
3. It is sent to the caster 36 through each of the vapor passages 35 and is adsorbed on the activated carbon 37 in the canister 36.

The above-mentioned purge control conditions are operating conditions which can minimize adverse effects on operability and exhaust emissions even if the air-fuel ratio is roughened by the purge. For example, the engine cooling water temperature is equal to or higher than a predetermined temperature, and the air-fuel ratio is set as a target value. During the feedback control of the fuel injection, the electronic control unit 49 determines that the purge control condition is satisfied when the intake air amount is equal to or more than a predetermined value and the fuel cut is not performed. .

If it is determined that the purge control condition is satisfied, the electronic control unit 49 opens the VSV 43. Then, the atmosphere is introduced into the canister 36 from the atmosphere introduction port 38 by the negative pressure of the intake passage 45, and the activated carbon 3
The fuel adsorbed by the fuel cell 7 is desorbed and sucked into the intake passage 45 through the purge passage 42 and the VSV 43, respectively. The activated carbon 37 is regenerated by the above-mentioned desorption, and prepares for the next vapor adsorption.

During the operation during the execution of the purge, the port 41
Canister 3 that the pressure P _C of in accordance with the negative pressure in the intake passage 45
Therefore, the negative pressure P _C is introduced into the second space 29 of the tank internal pressure control valve 20 through the VTV 40 and the negative pressure passage 39. As a result, the pressure in the first space 28,
That tank pressure P _T is lower than the pressure P ₁ set by the spring 31 and the diaphragm 30 as indicated by the two 3, is controlled to P ₁ -P _C becomes pressure. Incidentally, the spring 31 and the pressure P ₁ set in the diaphragm 30 is set higher than the negative pressure P _C of the pressure outlet, the set pressure P ₁ -P _C during operation even positive like P ₁ Pressure.

Thereafter, when the activated carbon 37 of the canister 36 deteriorates or a large amount of vapor is adsorbed, the pressure loss of the canister 36 increases according to the degree of the deterioration and the amount of adsorbed vapor, and as a result, the negative pressure at the port 41 of the canister 36 becomes negative. pressure P _C is gradually increased to the negative pressure direction, as indicated by the two Fig.
Accordingly, the tank internal pressure _PT also changes in the negative pressure direction as shown in FIG.

Further, the negative pressure P at the port 41 is_C
Rises in the negative pressure direction, and the tank internal pressure control valve 20
Pressure P of check valve 34 for preventing full opening_TwoGreater than
When this happens, the check valve 34 for preventing full opening opens.
The pressure in the second space 29 is P _TwoLarger in the positive pressure direction
And the check valve 34 for preventing full opening is closed and the second space 29 is closed.
Pressure is negative pressure P_CNegative pressure.

Thus, the check valve 3 for preventing full opening is
By repeating the opening / closing valve 4, the pressure in the second space 29 is controlled so as not to drop below the set pressure P ₂ of the check valve 34 for preventing full opening as shown in FIG. 28, ie the tank pressure P _T
Is held at P ₁ -P ₂ (> 0) as shown in FIG.
The valve body 32 is prevented from being in a fully open state in which the valve body 32 is always separated from the vapor introduction port 33.

Therefore, according to the present embodiment, during operation, even if the pressure loss of the canister 36 becomes large due to the deterioration of the activated carbon 37 of the canister 36 and the large amount of adsorption of the vapor onto the activated carbon 37, the tank internal pressure control valve 20 can be operated. Since the tank internal pressure can be controlled to a positive pressure without being fully opened, the phenomenon that the fuel in the fuel tank 21 enters the canister at the time of turning of the vehicle and the over-injection at the time of fuel injection can be prevented, respectively.
Deterioration of purge control can also be prevented.

Further, in this embodiment, similarly to the fuel tank internal pressure control device proposed by the present applicant, the tank internal pressure _PT at the time of operation stop is higher than that during operation as can be seen from FIG. Therefore, even if the fuel temperature temporarily rises immediately after the operation is stopped and vapor is generated, the outflow of vapor into the canister 36 can be suppressed by the amount of the differential pressure during operation. The adsorptive capacity can be increased more than before.

FIG. 4 shows a system configuration diagram of a second embodiment of the present invention. 2, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. In FIG. 4, a passage 51 is provided at a junction 5 between the port 52 of the purge passage 42 and the negative pressure passage 39.
3 and communicate with each other. The orifice 54 is provided in the middle of the passage 51.

In the first embodiment, by setting the diameter of the orifice 40b in the VTV 40, it is possible to adjust the set pressure during traveling. However, if the diameter of the orifice 40b is reduced too much, it is sent to the second space 29. Since the negative pressure is reduced, it takes time to reach the set pressure, and conversely, the orifice 40
If the diameter of b is too large, a problem of negative pressure release from the second space 29 occurs. Therefore, it is necessary to finely adjust the diameter of the orifice 40b.

On the other hand, in this embodiment, the orifice 54
Accordingly, the set pressure during traveling can be adapted regardless of the diameter of the orifice 40b in the VTV 40, and the range of the set pressure can be increased. The orifice 54 is connected to port 4
1 and the junction 53.

[0039] According to this embodiment, since the negative pressure outlet is two points to port 41 and port 52, the pressure P _C of the port 41 to the second space 29 of the tank pressure control valve 20
Pressure (P _D + P _C ) of pressure and pressure P _{D of} port 52 /
2 is introduced.

In this embodiment as well, the check valve 34 for preventing full opening is controlled so that the pressure in the second space 29 of the tank internal pressure control valve 20 does not become a value lower than the set pressure P ₂ on the negative pressure side. Even if the pressure loss of the canister 36 increases due to the deterioration of the activated carbon 37 and the adsorption of a large amount of vapor, the tank internal pressure control valve 20 can be prevented from being fully opened.

The present invention is not limited to the above-described embodiment. For example, in FIG. 2, the VTV 40 may not be provided, the VTV 40 may not be provided, and the negative pressure passage 39 may be provided.
May be connected to the purge passage 42.

[0042]

As described above, according to the present invention, the control valve for controlling the pressure in the fuel tank by setting the lower limit of the negative pressure of the canister is prevented from being fully opened. It is possible to prevent the fuel from intruding into the canister and prevent excessive injection during fuel injection, respectively. Further, since the negative pressure from the canister is not directly introduced into the fuel tank, the generation of vapor in the fuel tank can be suppressed, and the supply of a large amount of vapor to the intake system can be suppressed. It has features such as being able to prevent the deterioration of exhaust emission due to the inflow.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a configuration diagram of a first embodiment of the present invention.

FIG. 3 is a time chart for explaining the operation of FIG. 2;

FIG. 4 is a configuration diagram of a second embodiment of the present invention.

FIG. 5 is a time chart illustrating a problem to be solved by the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11, 21 Fuel tank 12, 36 Canister 13 Control valve 13a Valve seat 13b, 32 Valve 13c Urging means 14 Setting pressure adjusting means 15 Prohibiting means 20 Tank internal pressure control valve 26 Vapor passage 28 First space 29 First 2 space 30 Diaphragm 31, 34a Spring 33 Vapor inlet 34 Check valve for fully closing 34b Check ball 37 Activated carbon 39 Negative pressure passage 40 Vacuum transmitting valve (V
TV) 40a Check valve 40b, 54 Orifice 42 Purge passage 43 Vacuum switching valve (VSV) 49 Electronic control unit 51 Passage

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akinori Nagauchi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-6-33844 (JP, A) JP-A 64- 60423 (JP, A) JP-A-61-258963 (JP, A) JP-A-4-81558 (JP, A) JP-A-55-152350 (JP, U) JP-A-57-43350 (JP, U) 5-58 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02M 25/08 F02M 37/00 301 B60K 15/077

Claims (1)

(57) [Claims] 1. A fuel tank pressure control of an evaporative purge system in which evaporated fuel generated in a fuel tank of an internal combustion engine is adsorbed by an adsorbent in a canister and then drawn into an intake system of the internal combustion engine under predetermined operating conditions. A single control valve having at least a pair of valve seats and a valve body and biasing means for biasing the valve body to the valve seat; and setting by the biasing means when the internal combustion engine is operating. The pressure is set to a first set pressure such that the pressure in the fuel tank becomes a positive pressure using the negative pressure of the canister, and when the operation of the internal combustion engine is stopped, the set pressure by the urging means is set to the first pressure. A set pressure adjusting means for setting a second set pressure larger in the positive pressure direction than the set pressure of 1; and the first set pressure by the set pressure adjusting means corresponding to the negative pressure of the canister becomes equal to or less than a predetermined value. Prohibiting means for prohibiting the fuel tank from A pressure control device inside the fuel tank, which is provided in a system from the fuel gas purge section to the evaporative fuel purge section of the intake system.