JP2884925B2 - 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).
To rise for a few minutes after the shutdown, which generates a large amount of vapor. When the engine is stopped, the evaporated fuel is not released from the canister to the engine intake system, so that all the vapor generated at this time is discharged into the canister, which is a particular problem.

[0005] Therefore, conventionally, by setting the set pressure of the fuel tank internal pressure high when the engine is stopped, generation of a large amount of vapor immediately after the engine is stopped is suppressed, and the load and capacity of the canister are reduced. BACKGROUND ART A pressure control device is known (Japanese Utility Model Laid-Open No. 51-105906).

[0006]

However, in the above-mentioned conventional fuel tank pressure control device, since the tank internal pressure is released when the engine is operating, the fuel is discharged from the fuel tank to the canister when the vehicle is turning. The phenomenon of fuel jumping out of the passage) cannot be prevented.

Although a cut-off valve is provided to prevent over-injection during fuel injection in an engine operating state, the cut-off valve is inferior in accuracy and prevents fuel from flowing out of the fuel tank when the vehicle rolls over. However, when the fuel level gradually rises as in the case of refueling, it often does not work well. Therefore, in the above-described conventional apparatus, there is also a problem of over-injection in the engine operating state.

[0008] The present invention has been made in view of the above points,
To provide a fuel tank pressure control device that solves the above problems by controlling the tank pressure to a pressure higher than the atmospheric pressure during engine operation and providing a differential pressure between engine operation and engine stop. The purpose is to do.

[0009]

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 single control valve 13 having a first set pressure such that the pressure in the fuel tank 11 becomes a positive pressure when the internal combustion engine 10 is operating. When the operation of the engine 10 is stopped, the set pressure adjusting means 14 for setting the set pressure by the urging means 13c to a second set pressure larger than the first set pressure in the positive pressure direction is provided from the fuel tank 11 to the intake port. It is provided in the system up to the evaporated fuel purge unit 15 of the system.

[0010]

According to the present invention, during operation of the internal combustion engine 10, the pressure in the fuel tank 11 is set to the first positive pressure by the set pressure adjusting means 14 and the control valve 13. When the operation of the internal combustion engine 10 is stopped, the set pressure adjusting means 14 and the control valve 13
Accordingly, the pressure in the fuel tank 11 is controlled to the second set pressure which is larger in the positive pressure direction than during operation. Further, in the present invention, the control valve 13 for controlling the pressure in the fuel tank has a single structure.

[0011]

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 corresponds to the control valve 13, the check valve 27 and the first space 28 communicate with the vapor passage 26, and the second space 29 communicates with the first space 28 via the diaphragm 30. It is isolated. The diaphragm 30 is moved by the spring 31 in the second space 29 by the urging means 13c.
The spring force is urged downward in the figure.

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 34.

The tank internal pressure control valve 20 controls the first space 28 to a constant pressure by a spring 31 and a diaphragm 30. Also, if the tank pressure becomes negative,
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 vapor is returned to the fuel tank 21.

A second space 29 of the tank internal pressure control valve 20 is connected to a port 42 of the vapor passage 34 through a negative pressure passage 35. Further, the canister 36 is connected to an air inlet 38.
And is connected to an intake passage 43 downstream of the throttle valve 41 through a purge passage 39 and a vacuum switching valve (VSV) 40.
The intake passage 43 communicates with a combustion chamber of an engine 44 corresponding to the internal combustion engine 10. A part of the fuel injection valve 45 is protruded from the intake passage 43.

The pressure regulator 46 regulates the fuel pressure applied to the fuel injection valve 45 to a constant value. The electronic control unit 48 is configured by a microcomputer, and controls the fuel injection time of the fuel injection valve 45 and the opening / closing control of the VSV 40 based on various engine parameters. The negative pressure passage 35, the canister 36, the purge passage 39,
The set pressure adjusting means 14 is realized by the VSV 40 or the like.

[0017] In the above configuration, the discharge when the ignition switch (IG) is turned on at time t ₁ as shown in FIG. 3 (C), the fuel pump 22 shown in FIG. 2 is operating a fuel in the sub-tank 21b I do. The discharged fuel passes through a pipe 24 and passes through a pressure regulator 4
6, the fuel pressure is kept constant and is input to the fuel injection valve 45, while the excess fuel is supplied to the pressure regulator 4
6 and returned to the fuel tank 21 through the return pipe 25.

On the other hand, the evaporated fuel 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, since the port 42 is in communication with the air inlet 38 of the canister 36, the pressure P _{A of the} port 42
Is a value near the atmospheric pressure, and since no negative pressure is introduced into the negative pressure passage 35, the pressure P _{T in} the first space 28 of the tank internal pressure control valve 20 (this is equal to the tank internal pressure of the fuel tank 21) Is controlled to a pressure P set by the spring 31 and the diaphragm 30.

When the tank internal pressure P _T exceeds the set value P,
Since the valve element 32 is pushed upward in the drawing against the spring force of the spring 31 and the diaphragm 30, the evaporated fuel input to the tank internal pressure control valve 20 receives the vapor fuel 33,
It is sent to the caster 36 through each of the vapor passages 34 and is adsorbed on the activated carbon 37 in the canister 36.

The aforementioned purge control conditions are operating conditions that 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 48 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. .

When the purge control conditions are satisfied, the time t ₂
The electronic control unit 48 determines that the VSV
40 is opened. Then, due to the negative pressure of the intake passage 43,
Atmosphere is introduced into the canister 36 from the air introduction port 38, and the fuel adsorbed on the activated carbon 37 is desorbed, and the evaporated fuel is sucked into the intake passage 43 through the purge passage 39 and the VSV 40, respectively. The activated carbon 37 is regenerated by the above-mentioned desorption, and prepares for the next vapor adsorption. Thus, as shown in FIG. 3 (B), the time t ₂ after the purge flow rate is gradually increased.

During the operation during the execution of the purge, the port 42
The pressure P _A of the negative pressure in accordance with the negative pressure in the intake passage 43, the negative pressure P _A is introduced into the second space 29 of the tank pressure control valve 20 through the negative pressure passage 35. as a result,
The pressure in the first space 29, that is, the tank pressure _PT is controlled to a pressure P-P _A lower than the pressure P set by the spring 31 and the diaphragm 30. Therefore, as shown in FIG. 3 (A), the time t ₂ after tank pressure P _T is the P-P _A. The pressure P set by the spring 31 and the diaphragm 30 because it is set higher than the negative pressure P _A of the pressure outlet is the same as positive and the set pressure P-P _A also P during operation .

Thereafter, when the operation is stopped at time t ₃ as shown in FIG. 3 (C), the VSV 40 shown in FIG. 2 is closed, whereby a negative pressure is not introduced into the port 42 and the pressure becomes the atmospheric pressure. The pressure is controlled to a high positive pressure P set by a spring 31 and a diaphragm 30, as shown in FIG.

As described above, according to the present embodiment, since the tank pressure _PT is maintained at a positive pressure even during operation, it is possible to prevent spillage and excessive injection. In addition, canister 3
Since the amount of vapor adsorbed on the fuel cell 6 is suppressed, it is possible to prevent a large amount of vapor from being sucked into the intake system from the canister 36 at the time of purging. When the operation is stopped, the tank pressure _PT is controlled to a higher pressure P than during operation, so that the fuel in the main tank 21a is
b, even if the temperature temporarily rises due to heat received from the exhaust pipe around the tank, etc.
Can be suppressed only by the differential pressure P _{A from that} during operation.

FIG. 4 is a block diagram of a second embodiment of the present invention. In the figure, the same components as those in FIG.
The description is omitted. In FIG. 4, a second space 29 of the tank internal pressure control valve 20 is connected to a port 51 in the middle of the purge passage 39 via a negative pressure passage 52.

In this embodiment, the negative pressure in the purge passage 39 near the canister 36 differs for each vehicle type due to differences in the shape of the engine 44, the pipe of the purge passage 39, and the shape of the canister 36. If the negative pressure outlet is provided in the vapor passage 34, the negative pressure may be insufficient. In this embodiment, a purge passage 39 having a larger negative pressure than the vapor passage 34 is provided with a port 51 as a negative pressure outlet, so that a sufficient negative pressure is obtained and the tank internal pressure control valve 2 is provided.
0 can be reliably operated.

FIG. 5 shows a configuration diagram of a third embodiment of the present invention. In the figure, the same components as those in FIG.
The description is omitted. This embodiment is characterized in that a vacuum transmitting valve (VTV) 55 is provided in the middle of the negative pressure passage 35 as compared with the first embodiment shown in FIG.

The VTV 55 comprises a check valve 55a and an orifice 55b, and when the negative pressure of the port 42 becomes high, the check valve 55a and the orifice 55
b through the second space 2 of the tank internal pressure control valve 20.
9 is transmitted. Conversely, the pressure of the port 42 is
9, the check valve 55a is closed and the port 42 and the second space 2 are passed through only the orifice 55b.
9 is communicated.

As described above, the purge control is performed by opening the VSV 40 only when the purge control conditions are satisfied, and the purge flow rate is controlled by the VSV 40 in order to minimize the adverse effect on the drivability and the exhaust emission. Is controlled to the optimum value. For this reason, the purge flow rate changes in accordance with the load of the engine 44. The purge flow rate is large during acceleration, and the negative pressure in the purge passage 39 is large during acceleration, whereas the negative pressure in the purge passage 39 is small during deceleration. Become.

Thus, simply providing the negative pressure outlet in the middle of the vapor passage 34 causes the pressure to repeatedly enter and exit in accordance with acceleration and deceleration, and the pressure in the first space 28 fluctuates greatly. It takes time to reach the set pressure.

Therefore, in this embodiment, as described above, the VTV
55 is provided to prevent a negative pressure drop when the negative pressure during deceleration is small. In addition, to match the set pressure during traveling, VT
The diameter of the orifice 55b in the V55 is set. Note that V
The TV 55 may of course be provided in the middle of the negative pressure passage 52 of the second embodiment shown in FIG.

Next, a fourth embodiment of the present invention will be described with reference to FIG. 5, the same components as those of FIG. 5 are denoted by the same reference numerals, and the description thereof will be omitted. The fourth shown in FIG.
In the embodiment, the negative pressure passage 35 and the purge passage 39 between the VTV 55 and the port 42 in the third embodiment of FIG.
1 and is characterized in that an orifice 62 is provided in the middle of the passage 61. The passage 61 communicates between a port 63 of the purge passage 39 and a junction 64 of the negative pressure passage 35. The orifice 62 is connected to the port 42 and the junction 6
4 may be provided.

As a result, in this embodiment, the negative pressure outlet can be provided at two places, the port 42 and the port 63.
The pressure P _A and the port 63 of the port 42 to the second space 29
The average pressure (P _A + P _B ) / 2 with the pressure P _B is introduced. As a result, the present embodiment has the following features.

As described in the third embodiment, the VTV
By setting the diameter of the orifice 55b in 55, the set pressure at the time of traveling can be adapted. However, if the diameter of the orifice 55b is too narrow, the negative pressure sent to the second space 29 is reduced. On the other hand, if the diameter of the orifice 55b is too large, a problem of negative pressure release will occur, so that the diameter of the orifice 55b must be finely adjusted. However, in the present embodiment, the set pressure during traveling can be adapted by the orifice 62 regardless of the diameter of the orifice 55b in the VTV 55, and the range of the set pressure is large.

In the second embodiment in which the port for taking out the negative pressure is only the port 51 (63) having a relatively large negative pressure, the negative pressure of the port 51 (63) is closer to the engine 44 than the port 55 (63). It is easily affected by the shape and the like, and it is necessary to finely adjust the set pressure for each vehicle type. However, in this embodiment,
Since the negative pressure of the port 63 and the average negative pressure of the port 42 that is hardly affected by the shape of the purge passage 39 are used, V
The requirements for the TV 55 and the orifice 62 do not greatly differ for each vehicle type.

Next, a fifth embodiment of the present invention will be described with reference to FIGS. 7 and 8 show the fifth embodiment of the present invention, respectively.
FIG. 7 shows a configuration when the engine is stopped, and FIG. 8 shows a configuration when the engine is running. The same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. 7 and 8, the tank internal pressure control valve 71 corresponds to the control valve 13,
The check valve 72 and the first space 73 communicate with the fuel tank 21 via the vapor passage 26. Vapor passage 3
4 is communicated with a check valve 72, and its vapor inlet 33 is closed or opened by a valve body 73.

The valve body 14 is fixed to the central portion of the diaphragm 75, in the figure by a diaphragm 75 and a spring 76 with a predetermined set value P _1, downward force is energized. Further, the spring 76 is located in the second space 77, one end is fixed to the pressing member 78, and the other end is fixed to the upper surface of the diaphragm 75.

The diaphragm 75 is provided between the first space 73 and the second space 73.
And the diaphragm 79 separates the second space 77 and the third space 80. A spring 81 is provided in the third space 80 so that the set pressure P ₂ can be obtained together with the diaphragm 79. One end of a shaft 82 is fixed to the center of the lower surface of the diaphragm 79, and when the operation is stopped, the other end of the shaft 82 is in contact with the upper surface of the diaphragm 75 as shown in FIG.

The first space 73 is equal to the tank internal pressure. The second space 77 is always kept at the atmospheric pressure by a port 83 formed in a side wall of the casing of the tank internal pressure control valve 71. The third space 80 communicates with the throttle valve 41 through the negative pressure passage 84.
Is connected to the intake passage 43 on the downstream side, so that a negative pressure is introduced during operation.

Next, the operation of this embodiment will be described. First, when at time t ₁₁ the ignition switch as shown schematically in FIG. 9 (B) the engine 44 is turned on is the start of operation, negative pressure in the intake passage 43 through the negative pressure passage 84 is tank pressure control valve 71 As shown in FIG. 8, the diaphragm 79 is
Is lifted upward in the figure against the spring force of. As a result, the shaft 82 is pulled up together with the diaphragm 79 as shown in FIG.
It is in a state apart from 5.

As a result, the pressure in the first space 73, that is, the pressure _PT in the fuel tank 21, is increased by the set pressure P by the spring 76 and the diaphragm 75 as shown in FIG.
It becomes ₁ . Thereby, the tank internal pressure P during engine operation
_T is the set pressure P by the spring 76 and the diaphragm 75
₁ (positive pressure), the fuel tank 21
The amount of evaporative fuel (vapor) generated inside can be suppressed. The vapor having a tank internal pressure P ₁ or more is the valve body 7.
4 is pushed up, sent into the canister 36 through the vapor inlet 35 and the vapor passage 34, and adsorbed on the activated carbon 37. Then, when the VSV 40 is open, the adsorbed fuel is sucked from the canister 36 into the intake passage 43 through the VSV 40.

[0042] Then at time t ₁₂ the ignition switch as an off as shown schematically in FIG. 9 (B) Engine 44
Is stopped, no negative pressure is introduced into the negative pressure passage 84. Then, since the third space 80 is at atmospheric pressure, the diaphragm 79 is returned to a state in which the distal end of the shaft 82 abuts on the diaphragm 75 as shown in FIG.

As a result, the pressure P _T in the first space 73 becomes equal to the set pressure P ₁ by the spring 76 and the diaphragm 75.
The pressure is controlled to a value obtained by adding the set pressure P ₂ by the spring 81 and the diaphragm 79. That is, when the internal pressure of the fuel tank 21 is time t ₁₂ after the outage as shown in FIG. 9 (A), than the tank internal pressure P ₁ during operation further large becomes value to a positive pressure direction (P ₁ + P ₂₎ Can be switched. Thus, outflow of vapor that has been mass generated conventionally immediately after the shutdown is to differential pressure P only ₂ minutes canister 36 and during operation is suppressed.

In this embodiment, as in the previous embodiment, the tank internal pressure is controlled to a positive pressure both during operation and during operation stop by a single tank internal pressure control valve 71, and the tank internal pressure during operation stop is set higher than during operation. Can be controlled higher.

Further, the tank internal pressure control valve 20 of the above embodiment is used.
When the engine is used, the set pressure of the tank pressure during the operation of the engine 44 is a value corresponding to the negative pressure of the purge in the vicinity of the canister 36. When fuel evaporation in the fuel tank 21 becomes abnormally large due to fuel injection or the like, the purge negative pressure in the vicinity of the canister 36 becomes small, and as a result, the tank The pressure rises and the engine 44
There is a possibility that the tank internal pressure cannot be switched sufficiently to cope with the generation of vapor immediately after the operation is stopped.

On the other hand, in this embodiment, the set pressure of the tank pressure during operation of the engine 44 is P ₁ which is mechanically determined only by the diaphragm 75 and the spring 76, and is independent of the purge negative pressure near the canister 36. For this reason, there is a feature that it is hardly affected by the occurrence of the abnormality of the vapor.

[0047]

As described above, according to the present invention, during operation, the tank internal pressure is controlled to a positive pressure, so that the fuel in the fuel tank enters the canister when the vehicle turns and the fuel injection time is too short. Each injection can be prevented. When the operation is stopped, the tank internal pressure is controlled to a higher positive pressure than during operation.Therefore, even if the fuel temperature temporarily rises immediately after operation is stopped and vapor is generated, only the differential pressure from the operation Outflow to the canister can be suppressed, and thus the canister adsorption ability can be increased as compared with the conventional case. Further, the present invention has such a feature that the above-described two-stage switching of the fuel tank internal pressure during operation and during operation stop can be realized with a simple structure by a single control valve.

[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 configuration diagram of a third embodiment of the present invention.

FIG. 6 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram of a fifth embodiment of the present invention when operation is stopped.

FIG. 8 is a configuration diagram during operation of a fifth embodiment of the present invention.

FIG. 9 is a time chart for explaining the operation of FIGS. 7 and 8;

[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, 74 Valve 13c Urging means 14 Setting pressure adjusting means 15 Purge point 20, 71 Tank internal pressure control valve 26, 34 Vapor passage 30 , 75, 79 Diaphragm 31, 76, 81 Spring 28, 73 First space 29, 77 Second space 35, 84 Negative pressure passage 39 Purge passage 40 Vacuum switching valve (VSV) 42, 51, 63 Port 48 Electronic control unit 55 Vacuum transmitting valve (V
TV) 62 orifice 80 third space

Continuation of the front page (72) Inventor Akinori Nagauchi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-2-130254 (JP, A) JP-A-5-52156 (JP) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) 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. When the operation of the internal combustion engine is stopped, the set pressure by the urging means is set in a positive pressure direction with respect to the first set pressure. A pressure control device for controlling the pressure in the fuel tank, wherein a set pressure adjusting means for increasing the second set pressure is provided in a system from the fuel tank to the evaporative fuel purge section of the intake system.