JPH0565711B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel vapor emission control device for an internal combustion engine.

[Conventional technology]

BACKGROUND ART It is widely practiced to adsorb fuel vapor generated in a fuel tank or a carburetor to a charcoal canister, and to cause the adsorbed fuel vapor to be desorbed from the charcoal canister and purged into an intake system. However, because it is not possible to increase the capacity of a carbonated canister due to restrictions such as installation space and price, it is not possible to increase the capacity of a carbonated canister, so it is difficult to efficiently adsorb fuel vapor to the carbonated canister and desorb fuel vapor from the carbonated canister. It has become important to do well.

In Japanese Patent Application Laid-Open No. 58-133466 and Japanese Utility Model Application No. 58-137858, two passages with different cross-sectional areas are provided between the charcoal canister and the purge port of the intake system, and a solenoid valve or vacuum valve is installed. A technique is disclosed in which one of the two passages is selectively used by a control valve. According to these publications, when the fuel temperature is high, a passage with a larger cross-sectional area is used, and when the fuel temperature is low, a passage with a smaller cross-sectional area is used.
In other words, as the fuel temperature increases, the amount of fuel vapor generated increases, so a large passage is used to increase the amount of fuel vapor released from the charcoal canister, and when the fuel temperature is low, the amount of fuel vapor generated increases. Since the passage area is small, the air-fuel ratio can be prevented from becoming lean by restricting the amount of air that passes through the carbon canister and is taken into the intake system.

[Problem that the invention seeks to solve]

As described above, the conventional fuel vapor emission prevention device that switches between two passages having different cross-sectional areas depending on the temperature of the fuel operates extremely effectively during engine operation. However, in general, when the fuel temperature is high, a large amount of fuel vapor is generated in the fuel tank, so if the engine is stopped under such conditions, a large amount of the generated fuel vapor may be adsorbed by the charcoal canister. become. Even though a large amount of fuel vapor is adsorbed on the canister, if the fuel temperature drops when the engine is restarted, in the case of the prior art, the fuel vapor adsorbed on the canister is purged. Since the smaller of the two passages with different cross-sectional areas provided for The problem is that it does not recover.

[Means for solving problems]

The fuel vapor emission suppressing device according to the present invention includes a canister that adsorbs and collects fuel vapor generated in a fuel tank, and a canister and an engine intake air in order to purge the fuel vapor collected in the canister. a first passage means having a relatively large passage area connecting the system; a second passage means having a relatively small passage area connecting the canister and the intake system of the engine;
and a valve means for selectively opening one of the second passage means, a temperature detecting means for detecting the temperature of the fuel, and controlling the valve means based on the output of the temperature detecting means to adjust the temperature of the fuel. control means for opening the first passage means when the temperature of the fuel is higher than a predetermined value and opening the second passage means when the temperature of the fuel is lower than the predetermined value; Moreover, the control means includes an engine stop temperature storage means that stores the temperature of the fuel when the engine is stopped even after the engine has stopped, and a temperature of the fuel detected by the temperature detection means when the engine is restarted. and when the temperature of the fuel stored in the engine stop temperature storage means is higher than the predetermined value, the first
and means for opening the passage means.

〔Example〕

FIG. 2 shows a fuel vapor emission control device according to the present invention, in which 10 is a surge tank connected to an intake manifold (not shown) of an internal combustion engine, 12 is a throttle body, and therein is a known throttle valve 1.
4 is placed. The surge tank 10 and the throttle body 12 form an intake passage for the internal combustion engine, through which air flows in the direction of arrow A and is supplied to a combustion chamber (not shown). The throttle body 12 has a throttle valve 1 when fully closed at idle.
Purge port 1 is located slightly upstream of position 4.
6 is provided. Since the purge port 16 is located upstream of the position of the throttle valve 14 when the throttle valve 14 is fully closed, negative intake pressure does not act on the purge port 16 at idle, and when the throttle valve 14 is opened from the idle position, the purge port 16 Intake negative pressure is now applied to the

Reference numeral 18 denotes a known charcoal canister, which has a case filled with activated carbon. Charcoal canister 18 has a fuel vapor inlet port 20, a fuel vapor outlet port 22, and an atmosphere inlet port 24, as is known in the art. The fuel vapor intake port 20 is connected to the fuel tank 2 via a pipe 26.
8 is connected to the upper space. The fuel vapor extraction port 22 is connected to a port 34 of a three-way solenoid valve 32 by a pipe 30. Atmospheric intake port 24 is open to the atmosphere.

The solenoid valve 32 further has two ports 36 and 38 and is configured to selectively connect the port 34 to either the port 36 or the port 38.
On the other hand, the pipe 40 is connected to the purge port 16 described above.
are connected, and a pipe 42 and a pipe 44 are branched in parallel from this pipe 40, and a first pipe 4
2 is connected to the port 36 of the solenoid valve 32 and the second
The pipe 44 is connected to the port 38 of the solenoid valve 32. As can be seen in FIG. 2, the second pipe 4
4 is provided with a restriction 46, so that the passage area of the first pipe 42 is larger than the passage area of the second pipe 44.

The solenoid valve 32 is controlled by a control means 50.
In this embodiment, a temperature sensor 52 is provided at the bottom of the fuel tank 28, and its detection signal is input to the control means 50. Further, a detection signal from the vehicle speed sensor 54 is input to the control means 50.

As shown in FIG. 3, the control means 50 includes a central processing unit (CPU) 56, a read-on memory (ROM) 58, a random access memory (RAM) 60, and a backup program (RAM).
62, which are interconnected by a bus 64.
The detection signals of various sensors are input to the input interface 6.
6 and output interface 68
A control signal is sent to the solenoid valve 32 via the solenoid valve 32. A central processing unit (CPU) 56 executes arithmetic processing according to a program stored in a read-only memory (ROM) 58, and stores a random access memory (RAM) 60 and a backup program (RAM) 6.
2 stores the latest detection signals from various sensors as data. The data stored in the random access memory (RAM) 60 disappears when the engine stops, but the backup RAM (RAM) 62 has a memory element that is directly connected to the battery power supply, so the data does not disappear even if the engine is stopped. Memory data can be retained.

FIG. 1 shows a solenoid valve 3 that is executed according to a program stored in a read-on memory (ROM) 58.
2 shows a flowchart for the control, for example
It is activated every 30msec. In step 70, the temperature of the fuel in the fuel tank 28 is set to a predetermined value T _F
Basically, if YES, proceed to step 70 to control the large purge passage, and if NO, proceed to step 81 to control the small purge passage. Here, what is the purge passage size?
The electromagnetic valve 32 is energized to connect the ports 34 and 36 of the electromagnetic valve 32, and thus the charcoal canister 18
is connected to the purge port 16 via the first pulse 42 with a large passage area, and a small purge passage means that the energization to the solenoid valve 32 is stopped and the charcoal canister 18 is connected to the purge port 16 through the first pulse 42 with a small passage area. This means that it is connected to the purge port 16 via the two pipes 44.

The present invention further builds on the above basics by storing the fuel temperature when the engine is stopped, and when the detected fuel temperature is low when the engine is restarted, when the stored temperature is higher than a predetermined value. It includes means for connecting pipes 42 with larger passage areas for a predetermined time. That is, according to the above-mentioned basics, when starting with a low fuel temperature, the second pipe 44 with the throttle 46
However, according to the present invention, the first pipe 42 having a large passage area is connected even when starting with a low fuel temperature if certain conditions are met.

To accomplish this, according to FIG. 1, after step 71, a purge memory flag f _P is set (step 72). In this embodiment, the purge memory flag f _P is set at the temperature _TF at which the passage should be switched during operation, but it can be set at a temperature different from _TF . Then, data indicating that this purge memory flag _fP has been set is stored in the backup RAM (RAM) 62 shown in Fig. 3, and this data is erased even after the engine is stopped as data when the engine is stopped. Therefore, this data can be used when restarting the engine. If the fuel temperature is low when the engine is stopped, the purge memory flag _fP is not set.

Return to step 70 and check the fuel tank 28 during startup.
If the temperature of the fuel within is higher than the predetermined value _TF , the cycle from step 71 to step 72 will be repeated. If the temperature of the fuel in the fuel tank 28 is lower than T _F at the time of startup, the process proceeds to step 73, where it is determined whether the purge memory flag 72 is set. If not set, step
Proceed to 81. If it is set, the process goes to step 74, and it is determined whether the counter is zero. If the counter C is zero, the process goes to step 75, where the counter C is set to N, and the process goes to step 76.
If the counter C is not zero, the process jumps to step 76. Therefore, when step 74 is passed for the first time, counter C is set.

In step 76, it is determined whether the vehicle speed V is greater than a predetermined value V _P. This step is to determine whether the conditions are such that fuel vapor purge should be performed.As mentioned above, since the purge port 16 is located slightly upstream of the throttle valve 14, there is no intake negative pressure at idle. Since the engine does not act, no purge is actually performed, and when the throttle valve 14 is opened and the vehicle is running, the intake negative pressure acts to perform the purge. Therefore, if the vehicle speed is not zero, it can be determined that the vehicle is not in an idling state, that is, it is in a purge state. Further, this condition determination can also be performed by detecting the throttle opening degree, etc. in addition to the vehicle speed.

If the answer in step 762 is NO, that is, if the purge condition is not met, the process proceeds to step 81, where the small purge passage is controlled. If the result in step 76 is YES, that is, the purge condition has been met by transitioning from the idle state to the running state, the process proceeds to step 77, where the counter C is decremented. Next, proceed to step 78 to determine whether the counter C has reached zero, and if no, proceed to step 78.
Proceed to 79 and control the purge passage size. step
The control of the purge passage size 79 continues for a predetermined time until the counter C becomes zero, and if the engine becomes idle during this time, the process proceeds from step 76 to step 81, so that counting is interrupted. Therefore, the predetermined time in this case is the total time under purge conditions. When the counter C becomes zero in step 78, it is determined that a predetermined time has elapsed, and the process proceeds to step 80, where the purge memory flag _fP is reset, and the process proceeds to step 81. Therefore, in step 73 of the next cycle, a negative determination is made and the process proceeds to step 81.

〔Effect of the invention〕

According to the fuel vapor emission suppressing device of the present invention, first, during engine operation, when the temperature of the fuel is high, the flow rate of air passing through the canister is increased to increase the amount of fuel vapor purged, as in the prior art. This reduces the load on the canister, and when the fuel temperature is low, the air passing through the canister is throttled to reduce the purge amount of fuel air, thereby preventing the air-fuel ratio from becoming lean.

In addition to this effect, especially according to the present invention, when the engine is stopped while the fuel temperature is high, a large amount of fuel vapor is adsorbed in the canister even when the engine is stopped, and when the engine is restarted, the engine is stopped. Even if the fuel temperature is low, the load on the canister is quickly reduced by increasing the flow rate of air passing through the canister for a predetermined period of time to increase the amount of fuel vapor purge, so the canister can be operated at any time. It becomes possible to use the canister with sufficient ability to adsorb fuel vapor.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of the control of the fuel vapor emission suppressing device according to the present invention, FIG. 2 is a system diagram of the fuel vapor emission suppressing device according to the present invention, and FIG. 3 is a configuration diagram of the control means. 12... Throttle body, 16... Purge port, 18... Canister, 28... Fuel tank, 32... Solenoid valve, 42... First pipe, 4
4...Second pipe, 52...Temperature sensor.

Claims (1)

[Claims] 1. A canister that adsorbs and collects fuel vapor generated in the fuel tank, and a relatively large canister that connects the canister and the intake system of the engine to purge the fuel vapor collected in the canister. a first passage means having a passage area; the canister and the intake system of the engine in parallel to the first passage means, also for purging fuel vapors collected in the canister; a connecting second passage means having a relatively small passage area; a valve means for selectively opening one of the first and second passage means; a temperature detection means for detecting the temperature of the fuel; The valve means is controlled based on the output of the temperature detection means to open the first passage means when the temperature of the fuel is higher than a predetermined value, and the temperature of the fuel is set to a predetermined value. control means for opening the second passage means when the temperature is lower than , and the control means further includes engine stop temperature storage means for storing the temperature of the fuel at the time of engine stop even after the engine is stopped; The temperature of the fuel detected by the temperature detection means when restarting the engine is lower than a predetermined value, and the temperature of the fuel stored in the temperature storage means when the engine is stopped is lower than a predetermined value. and means for opening the first passage means for a predetermined period of time when the fuel vapor emission is high.