JP3074840B2 - Evaporative fuel processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel processing apparatus, and more particularly, to a canister for adsorbing and holding evaporative fuel from a fuel tank in the middle of the passage, which provides a passage connecting an intake passage of an internal combustion engine and a fuel tank. The present invention relates to an evaporative fuel processing device provided.

[0002]

2. Description of the Related Art Evaporated fuel leaking into the atmosphere from a fuel tank, a float chamber of a vaporizer, etc. contains a large amount of hydrocarbons (HC) and is one of the causes of air pollution. Because of the connection, various techniques for preventing this are known. As a typical example, the fuel vapor in the fuel tank is temporarily adsorbed and held in a canister containing an adsorbent such as activated carbon, and the fuel vapor adsorbed and held in the canister is released (purged) during operation of the internal combustion engine.
There is an evaporation system that supplies the fuel to the internal combustion engine.

[0003] As an evaporative fuel processing apparatus, there is one disclosed in Japanese Patent Application Laid-Open No. 58-185966. The evaporative fuel loss prevention device disclosed in this publication includes a first evaporative fuel passage for introducing evaporative fuel in a fuel tank,
A second evaporative fuel passage connected to the canister; a third evaporative fuel passage connected to the engine air cleaner and / or the crankcase; and a second evaporative fuel passage and a third evaporative fuel passage. And a detecting means for detecting a saturated state of the canister and outputting a signal for operating the solenoid valve. When the electromagnetic valve is inoperative, the first evaporative fuel passage and the second evaporative fuel passage are communicated with each other and introduced into the fuel tank. The fuel vapor in the fuel tank is introduced into the air cleaner and / or the crankcase, and the fuel adsorbing member in the canister is saturated and liquefied from the canister. It prevents fuel emissions and reduces air pollution.

[0004] Furthermore, there is one disclosed in Japanese Utility Model Laid-Open No. 58-100251. The fuel evaporation loss prevention device in a carburetor disclosed in this publication adsorbs fuel vapor generated in a carburetor float chamber when the engine is stopped, and adsorbs the fuel vapor using a suction negative pressure in an intake pipe when the engine is operating. In addition to having a structure in which fuel is sucked into the intake system and burned, a switching valve for switching between an adsorption passage leading from the float chamber to the canister and a purge passage leading from the canister to the purge port of the intake pipe is provided. It works in conjunction with the ignition switch.

[0005] Furthermore, there is a technique disclosed in Japanese Utility Model Laid-Open No. 59-110370. The startability improving device for a carburetor-type internal combustion engine disclosed in this publication connects a downstream portion of a throttle valve of a carburetor of the internal combustion engine to a negative pressure tank via a check valve, and bypasses the check valve. An on-off valve is provided, and the on-off valve is opened when the engine is started.
When stopped, it is switched to close.

[0006]

As shown in FIG. 6, in the conventional evaporative fuel treatment apparatus, an intake passage 110 of an internal combustion engine (not shown) and a fuel tank 116 are connected by a passage 120, and 1 that adsorbs and holds the evaporated fuel in the fuel tank 116
22 are provided.

The fuel tank 116 and the canister 12
A check valve 130 is provided in the middle of the first passage 124 between the two, and a solenoid valve (VSV) 142 functioning as a purge amount control valve for controlling the purge amount is provided in the middle of the second passage 126 between the canister 122 and the intake passage 110. ing.

The internal pressure of the fuel tank 116 is controlled to a constant value by the check valve 130, thereby suppressing the generation of evaporated fuel as evaporation.

Further, as shown in FIG. 7, the solenoid valve 130 is map-controlled by a control unit (not shown) to which a load and an engine speed Ne are inputted.

As a result, when the internal pressure of the fuel tank is controlled by the check valve, the pressure control accuracy also varies due to the variation of the components of the check valve, and the reliability is reduced, which is disadvantageous in practical use. .

In addition, since the purge control by the solenoid valve is performed independently of the amount of generated fuel, that is, constantly performed, the purge amount becomes insufficient when the amount of generated fuel is large such as at a high temperature. There is a possibility that HC can not be sufficiently released from the canister.

[0012]

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned disadvantages, the present invention provides an evaporative fuel treatment apparatus having a canister for adsorbing and holding evaporative fuel in a passage connecting an intake passage of an internal combustion engine and a fuel tank. In the device, the passage is formed by a first passage connecting the fuel tank and the canister, and a second passage connecting the canister and the intake passage, and a check valve is provided in the middle of the first passage. A first passage between the canisters is branched to provide a branch passage, a tank pressure control valve is provided in the branch passage in parallel with the check valve, and a pressure sensor for detecting an internal pressure of the fuel tank is provided; A control unit having a function of controlling the opening and closing of the pressure control valve in the tank in accordance with a detection signal from the pressure sensor during operation of the engine is provided. A purge amount control valve is provided in the middle of the second passage to control the opening and closing of the purge amount control valve according to the operation state of the internal combustion engine, and to open and close the purge amount control valve according to the opening and closing control of the pressure control valve in the tank. It is characterized in that a function of correcting control is also provided in addition to the control unit.

[0013]

According to the invention as described above, a detection signal from a pressure sensor is input to the control unit when the internal combustion engine is operating, and the pressure control valve in the tank is opened and closed according to the detection signal from the pressure sensor. The pressure in the fuel tank is controlled to improve the pressure control accuracy, and the purge amount control valve is opened and closed according to the operation state of the internal combustion engine, and the purge amount control valve is controlled according to the open / close control of the tank pressure control valve. The opening / closing control is corrected, and the purge air amount is increased in accordance with the amount of fuel vapor generated in the fuel tank.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 to 3 show a first embodiment of the present invention. In FIG. 1, 2 is an internal combustion engine, 4 is an air cleaner, 6 is a throttle valve, 8 is a surge tank, 1
0 is an intake passage, 12 is a combustion chamber, 14 is an exhaust passage, and 16 is a fuel tank.

The internal combustion engine 2 has a fuel injection valve 18 provided in the intake passage 10 so as to be directed toward the combustion chamber 12. The fuel injection valve 18 is connected to the fuel tank 16 by a fuel passage (not shown).

The fuel in the fuel tank 16 is supplied to a fuel injection valve 18 via a fuel passage by a fuel pump (not shown), and is supplied to the combustion chamber 12 together with air to be burned. The exhaust gas generated by the combustion is discharged through the exhaust passage 14.

An intake passage 10 of the internal combustion engine 2, for example, a passage 20 for connecting the surge tank 8 and the fuel tank 16 downstream of the throttle valve 6 is provided, and a canister 22 for adsorbing and holding the evaporated fuel is provided in the middle of the passage 20. .

The passage 20 is divided into a first passage 24 connecting the fuel tank 16 and the canister 22 and a second passage 26 connecting the canister 22 and the intake passage 10.
And formed. In the middle of the first passage 24, a separator 28 is provided.

A check valve 30 is provided in the first passage 24, and a branch passage 32 is provided by branching the first passage 24 between the check valve 30 and the canister 22, ie, between the check valve 30 and the separator 28. The branch passage 32 is provided with an in-tank pressure control valve 34 as a first solenoid valve for controlling the in-tank pressure in parallel with the check valve 30.
A pressure sensor 36 for detecting the internal pressure of the internal combustion engine 2 is provided. When the internal combustion engine 2 is operated, a control unit 38 for opening and closing the tank pressure control valve 34 in accordance with a detection signal from the pressure sensor 36.
And a purge amount control valve 42, which will be described later, functioning as a second solenoid valve for controlling the purge amount is provided in the middle of the second passage 26, and the purge amount control valve 42 is opened and closed according to the operating state of the internal combustion engine 2. The control unit 38 also has a function of controlling the opening and closing control of the purge amount control valve 42 in accordance with the opening and closing control of the tank pressure control valve 34.
Is provided in addition to.

More specifically, a check valve 30 is provided in the first passage 24 between the fuel tank 16 and the separator 28.
The check valve 30 sets the pressure in the fuel tank 16 and the pressure in the canister 22 to predetermined pressures, and suppresses the amount of HC generated in the fuel tank 16.

An in-tank pressure control valve 34 is provided in parallel with the check valve 30. The in-tank pressure control valve 34 includes a valve element 34-1 and a solenoid 34-2.

A pressure passage 40 communicating with a pressure sensor 36 is provided at a branch point of the branch passage 32 between the check valve 30 and the fuel tank 16.

The control section 38 includes a tank pressure control valve 34 as a first solenoid valve, a purge amount control valve 42 as a second solenoid valve provided in the middle of the second passage 26, and a third solenoid described later. The valves 52 are connected to each other.

When the internal combustion engine 2 is operating, the control unit 38 opens the tank pressure control valve 34 in response to the detection signal from the pressure sensor 36, and removes the fuel vapor generated in the fuel tank 16 from the canister 22. And controls the opening and closing of the purge amount control valve 42 in accordance with the operation state of the internal combustion engine 2 and the opening and closing of the purge amount control valve 42 in accordance with the opening and closing control of the in-tank pressure control valve 34. Correct control.

The fuel tank 16 in the first passage 24
A rollover valve 44 serving as a passage opening / closing mechanism is provided at an end on the side of the side, and the rollover valve 44 has a main body 46 and a float 48. The float part 48 includes:
An opening / closing projection (not shown) that closes the first passage 24 when the refueling of the fuel tank 16 is completed, that is, when the fuel tank 16 is full, is provided on the upper surface of the float portion 48 so as to be swingable.

Reference numeral 50 denotes an atmosphere passage for opening the canister 22 to the atmosphere, and reference numeral 52 denotes a third solenoid valve provided in the middle of the atmosphere passage 50.

That is, the control unit 38
As shown in (a), (b) and (c), the pressure sensor 3
6, the tank pressure control valve 34 is controlled to open and close according to the detection signal from the fuel tank 16 to control the tank pressure, which is the internal pressure of the fuel tank 16, and the tank pressure, and the purge amount control valve 42 is controlled according to the operating state of the internal combustion engine 2. Open / close control is performed, and purge flow control is performed by correcting the open / close control of the purge amount control valve 42 in accordance with the open / close control of the tank pressure control valve 34.

At this time, the total purge amount TPRG is obtained from the purge amount Pmap of the basic map and the correction value PPRG accompanying the change in the duty of the tank pressure control VSV (see FIG. 3A).

The purge amount Pmap of the basic map is shown in FIG.
As shown in (b), while being obtained from a map based on the load and the engine speed Ne, the tank pressure control V
Correction value PPRG due to change in SV duty
Is a value according to the determination level for increasing the purge flow rate as shown in FIG.

Next, the operation will be described.

When the internal combustion engine 2 is stopped, the in-tank pressure control valve 34 is kept closed.

When the internal combustion engine 2 is operating, the control unit 38 energizes the first solenoid valve 34 to open the branch passage 32, adsorbs the fuel vapor in the fuel tank 16 to the canister 22, and causes the fuel tank 16 to adsorb. The pressure in the fuel tank 16 is made substantially the same as the atmospheric pressure.

The rollover valve 44 opens the first passage 24.

At this time, the controller 38 controls the pressure sensor 3
6, a total purge amount TPRG is set based on the purge amount Pmap from the basic map and a correction value PPRG accompanying a change in the duty of the tank pressure control VSV so that the tank pressure becomes the target pressure. It has been calculated.

The purge amount Pmap of the basic map fluctuates due to a change in the load and / or the engine speed Ne, and a duty (duty) of the tank pressure control VSV.
The correction value PPRG accompanying the change fluctuates according to a preset judgment level.

That is, at high temperatures, the amount of fuel vapor generated in the fuel tank 16 increases, the tank pressure increases, the tank pressure control duty level increases, and the purge flow rate increases. is there.

Thus, when the internal combustion engine 2 is operated, the pressure control valve 34 in the tank is opened and closed by the detection signal from the pressure sensor 36, and the pressure in the fuel tank 16 can be duty-controlled. Is good, which is practically advantageous.

The opening and closing of the purge amount control valve 42 is controlled in accordance with the operation state of the internal combustion engine 2 and the opening and closing control of the purge amount control valve 42 is corrected in accordance with the opening and closing control of the in-tank pressure control valve 34. Thereby, the amount of purge air can be increased in accordance with the amount of evaporative fuel generated in the fuel tank 16.
The performance of the evaporation system can be improved, and in particular, the canister performance can be effectively utilized.

FIGS. 4 and 5 show a second embodiment of the present invention. In the second embodiment, parts that perform the same functions as in the first embodiment will be described with the same reference numerals.

The feature of the second embodiment is that the total purge amount TPRG is set to the purge amount Pmap of the basic map.
And the multiplier PPRG associated with a change in the duty of the tank pressure control VSV.

That is, as shown in FIGS. 5 (a), 5 (b) and 5 (c), duty control is performed so that the tank pressure becomes the target pressure during the operation of the internal combustion engine.

Then, similarly to the first embodiment, the pressure control valve in the tank can be opened / closed by the detection signal from the pressure sensor when the internal combustion engine is operating, and the pressure in the fuel tank can be controlled by the duty. The pressure can be controlled, and the pressure control accuracy can be improved.

Further, by controlling the opening and closing of the purge amount control valve in accordance with the operation state of the internal combustion engine and correcting the opening and closing control of the purge amount control valve in accordance with the opening and closing control of the pressure control valve in the tank. Since the amount of purge air can be increased in accordance with the amount of fuel vapor generated in the fuel tank, the performance of the evaporation system can be improved, and in particular, the canister performance can be effectively utilized.

[0045]

As described above in detail, according to the present invention, there is provided an evaporative fuel processing apparatus having a canister for adsorbing and holding evaporative fuel in a passage connecting an intake passage of an internal combustion engine and a fuel tank. A passage is formed by a first passage communicating with the canister and a second passage communicating with the canister and the intake passage, a check valve is provided in the middle of the first passage, and the first passage between the check valve and the canister is branched. A branch passage is provided, a tank pressure control valve is provided in the branch passage in parallel with the check valve, and a pressure sensor for detecting the internal pressure of the fuel tank is provided.
When the internal combustion engine is operating, a control unit having a function of opening and closing the pressure control valve in the tank in accordance with a detection signal from the pressure sensor is provided, and a purge amount control valve is provided in the middle of the second passage, and according to the operation state of the internal combustion engine. A function of correcting the opening / closing control of the purge amount control valve in accordance with the opening / closing control of the pressure control valve in the tank and the function of correcting the opening / closing control of the purge amount control valve is also provided in the control unit. Opening and closing the pressure control valve in the tank by the detection signal from the pressure sensor,
The pressure in the fuel tank can be controlled, and the pressure control accuracy is improved, which is practically advantageous. Further, by controlling the opening and closing of the purge amount control valve in accordance with the operation state of the internal combustion engine and correcting the opening and closing control of the purge amount control valve in accordance with the opening and closing control of the pressure control valve in the tank, the inside of the fuel tank is controlled. By increasing the amount of purge air in accordance with the amount of fuel vapor generated, the performance of the evaporative system can be improved, and in particular, canister performance can be effectively utilized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an evaporative fuel processing apparatus according to a first embodiment of the present invention.

2A is a diagram showing a tank pressure, FIG. 2B is a diagram showing a tank pressure control duty, and FIG. 2C is a diagram showing a purge flow rate control duty.

3A is a diagram showing a calculation formula of a total purge amount TPRG, FIG. 3B is a diagram showing a purge amount Pmap of a basic map based on a relationship between a load and an engine speed Ne, and FIG. FIG. 9 is a diagram illustrating a relationship between a control value and a correction value according to a change in duty of a control VSV.

FIGS. 4A and 4B show a second embodiment of the present invention, wherein FIG. 4A shows a tank pressure, FIG. 4B shows a tank pressure control duty, and FIG. 4C shows a purge flow rate control duty. FIG.

5A is a diagram showing a calculation formula of a total purge amount TPRG, FIG. 5B is a diagram showing a purge amount Pmap of a basic map based on a relationship between a load and an engine speed Ne, and FIG. 5C is a diagram of a tank pressure control VSV. Duty (dut
It is a figure which shows the relationship between y) and multiplier PPRG.

FIG. 6 is a schematic configuration diagram of a fuel vapor processing apparatus showing a conventional technique of the present invention.

FIG. 7 is a diagram showing a relationship between a load and an engine speed Ne.

[Explanation of symbols]

 Reference Signs List 2 internal combustion engine 4 air cleaner 6 throttle valve 8 surge tank 10 intake passage 12 combustion chamber 16 fuel tank 18 fuel injection valve 20 passage 22 canister 24 first passage 26 second passage 28 separator 30 check valve 32 branch passage 34 pressure control valve in tank 36 pressure sensor 38 control unit 40 pressure passage 42 purge amount control valve 44 rollover valve 52 third solenoid valve

Continuation of the front page (56) References JP-A 64-3067 (JP, U) JP-A 55-152350 (JP, U) JP-A 1-145623 (JP, U) (58) Fields surveyed (Int .Cl. ⁷ , DB name) F02M 25/08 F02M 25/08 301 F02M 37/00 301

Claims (1)

(57) [Claims] 1. An evaporative fuel processing apparatus having a canister adsorbing and holding evaporative fuel in a passage connecting an intake passage of an internal combustion engine and a fuel tank, wherein the first passage connects the fuel tank and the canister, and a canister. The second passage communicating with the intake passage forms the passage, a check valve is provided in the middle of the first passage, and the first passage between the check valve and the canister is branched to form a branch passage. the tank according to the the tank pressure control valve in parallel provided for the check valve, a pressure sensor for detecting the internal pressure of the fuel tank is provided, the detection signal from the pressure sensor during operation of the internal combustion engine
A control unit having a function of opening and closing the internal pressure control valve is provided ; a purge amount control valve is provided in the middle of the second passage;
The purge amount control valve is opened and closed according to the operating state of the fuel engine.
Control the opening and closing of the tank pressure control valve.
Function to correct the opening / closing control of the purge amount control valve.
An evaporative fuel processing apparatus provided in addition to the control unit .