JPH04330362A - Purge air control device for evaporation system - Google Patents

Abstract

PURPOSE:To adjust a purge amount to a proper value by detecting the running state of an internal combustion engine and the temperature of fuel in a fuel tank and performing duty control of a purge valve based on detecting information. CONSTITUTION:An intake air amount, a throttle opening, and the number of revolutions of an engine are inputted as running state information to a control part 22 from an airflow meter 24, a throttle opening sensor 26, and an igniter 28, respectively. Further, the temperature of fuel in a fuel tank 18 is inputted to the control part 22 from a fuel temperature sensor 46. The control part 22 performs duty control of a purge valve 42 based on information from the sensors 24, 26, 28, and 46 during running of an engine to effect purge of a canister 38. The duty control calculates a duty value from a control map based on a running state and a fuel temperature to control the purge valve 42.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a purge air control device for an evaporative system, and more particularly to a purge air control device for an evaporative system that can appropriately control the amount of purge as the amount of evaporated fuel increases or decreases.

0002

2. Description of the Related Art Some internal combustion engines installed in vehicles are equipped with an evaporation system in order to prevent evaporative fuel generated in a fuel tank or the like from being released into the atmosphere while the engine is stopped. In an evaporation system, a canister is interposed in the middle of a ventilation passage that communicates an intake passage of an internal combustion engine with a fuel tank, and a purge valve is interposed in the middle of the ventilation passage between the canister and the intake passage. The evaporative system closes the purge valve when the engine is stopped and temporarily adsorbs and holds the evaporated fuel in the canister. When the engine is running, the purge valve is opened to introduce fresh air into the canister, and this fresh air purges the adsorbed and held evaporated fuel. (separated) and supplied to the intake passage.

[0003] Such an evaporative system is disclosed in Japanese Patent Laid-Open No. 57-52663. The system disclosed in this publication aims to prevent sudden changes in the purge amount and avoid unnecessary fluctuations in the air-fuel ratio by controlling the duty of the purge valve to gradually open and close it.

0004

However, in some conventional evaporative systems, the purge valve is controlled depending on the operating state of the internal combustion engine. In this evaporative system, the duty value is read out from a map set based on the engine speed, intake air amount, intake negative pressure, etc. as the operating state, and the purge valve is set to the duty value according to the operating state of the internal combustion engine. It's in control.

However, the amount of vaporized fuel generated increases or decreases depending on the temperature state, and increases particularly at high temperatures. For this reason, in the evaporative system that controls the duty of the purge valve according to the operating conditions, if the purge amount is set based on room temperature, there will be a problem that the purge amount of vaporized fuel will be insufficient at high temperatures. This has the disadvantage of affecting the air-fuel ratio. This effect on the air-fuel ratio is particularly
It becomes large during transient operations such as acceleration and deceleration, which has the disadvantage of deteriorating drivability and also has disadvantages in terms of exhaust gas purification. Furthermore, if the purge amount is insufficient for the increased amount of vaporized fuel generated at high temperatures, there is a risk that the vaporized fuel will be released into the atmosphere.

[0006]

[Means for Solving the Problems] In order to eliminate such inconveniences, the present invention provides a canister that is interposed in the middle of a ventilation passage that communicates the intake passage of an internal combustion engine with a fuel tank, and that the canister and the intake air In an evaporative system in which a purge valve is interposed in the middle of the ventilation path between the air passage and the passage, an operating state sensor for detecting the operating state of the internal combustion engine is provided, and a fuel temperature sensor is provided for detecting the fuel temperature of the fuel tank, The present invention is characterized in that a control means is provided for controlling the duty of the purge valve according to the operating state and fuel temperature detected by the operating state sensor and the fuel temperature sensor.

[0007]

[Operation] According to the structure of the present invention, the control means
By controlling the duty of the purge valve according to the operating state and fuel temperature detected by the operating state sensor and the fuel temperature sensor, the purge amount can be controlled not only according to the operating state but also the fuel temperature state.

[0008]

Embodiments Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1 to 5 show an embodiment of the present invention. In FIG. 1, 2 is an internal combustion engine, 4 is an intake passage, and 6 is an exhaust passage. The intake passage 4 of this internal combustion engine 2 is provided with an air cleaner 8 at its starting end, a throttle valve 10 in the middle, and communicates with a combustion chamber 12 at its terminal end. The exhaust passage 6, which communicates with the combustion chamber 12 at its starting end, opens its terminal end to the atmosphere.

A fuel injection valve 14 is provided in the intake passage 4 of the internal combustion engine 2 and is oriented toward the combustion chamber 12 . The fuel injection valve 14 is connected to a fuel tank 18 by a fuel passage 16. The fuel in the fuel tank 18 is supplied to the fuel pump 20.
The fuel is supplied to the fuel injection valve 14 via the fuel passage 16, and is injected into the combustion chamber 12.

[0011] The fuel injection valve 14 is connected to a control section 22. The control unit 22 includes an air flow meter 24 that detects the amount of intake air, an opening sensor 26 that detects the opening of the throttle valve 10, and an operating state sensor that detects the operating state of the internal combustion engine 2. An igniter 28 is connected for detection. The igniter 28 is
Distributor 3 via ignition coil 30
Connected to 2. The control unit 22 controls these sensors 2
The fuel injection valve 14 is driven and controlled by the signals inputted from the internal combustion engine 4 to 28, and fuel is injected and supplied to achieve the air-fuel ratio required by the internal combustion engine 2.

An evaporation system 34 that processes evaporated fuel generated in the fuel tank 18 has one end communicating with the intake passage 4 downstream of the throttle valve 10 of the internal combustion engine 2, and the other end communicating with the fuel tank 18. A ventilation path 36 is provided, and a canister 38 is interposed in the middle of this ventilation path 36. The ventilation passage 36 includes a first ventilation passage 36 - 1 that communicates the fuel tank 18 and the canister 38 , and a first ventilation passage 36 - 1 that communicates the fuel tank 18 and the canister 38 .
and a second air passage 36-2 communicating with the intake passage 4. A check valve 40 is interposed in the middle of the first ventilation path 36-1. A purge valve 42 is interposed in the middle of the second intake passage 36-2. In addition,
Reference numeral 44 is a fresh air passage for introducing fresh air.

The evaporative system 34 closes the purge valve 42 when the engine is stopped to temporarily adsorb and hold evaporated fuel in the canister 38 through the first ventilation passage 36-1.
When the engine is running, open the purge valve 42 and close the canister 3.
8, fresh air is introduced through the fresh air passage 44, and the vaporized fuel adsorbed and retained by this fresh air is purged (separated) and supplied to the intake passage 4 through the second ventilation passage 36-2.

Purge valve 4 of this evaporative system 34
2 is connected to the control section 22. This control section 2
2 is also connected to a fuel temperature sensor 46 that detects the fuel temperature in the fuel tank 16. Thereby, the control unit 22 controls the purge valve 42 in accordance with the operating state and fuel temperature detected by the sensors 24 to 28, which are operating state sensors that detect the operating state of the internal combustion engine 2, and the fuel temperature sensor 46. do.

In this embodiment, first, as shown in FIG. 3, basic values are determined from a map of basic values according to the operating condition, which is set based on the engine speed and the load due to the intake air amount, intake negative pressure, etc. Read the value Pmap. Next, as shown in FIG. 4, a correction value Fprg is read from a map of correction values based on fuel temperature. These basic values Pma
From p and correction value Fprg, duty value Tprg
Calculate (Tprg = Pmap × Fprg)
. With this duty value Tprg, the purge valve 42
As shown in FIG. 5, the purge amount Q is controlled by controlling the duty.

Next, the operation will be explained.

As shown in FIG. 2, the control section 22 controls when the internal combustion engine 2 is stopped (100) and when the internal combustion engine 2 is driven (101).
Also, when the purge is off (102), the purge valve 42 is turned off (103) and the second air passage 36-2 is closed. Thereby, the evaporated fuel in the fuel tank 18 is adsorbed and held in the canister 38 by the first passage 36-1.

When the purge is turned on (104) when the internal combustion engine 2 is driven (101), the purge valve 42 is turned on. The control unit 22 calculates a duty value Tprg from a basic value Pmap read from a map of basic values based on operating conditions and a correction value Fprg read from a map of correction values based on fuel temperature, and controls the duty of the purge valve 42.

At this time, if the fuel temperature in the fuel tank 18 is low (105), the correction value Fprg based on the fuel temperature
As a result, the duty value Tprg becomes small (106), the ratio of the open time of the purge valve 42 becomes small, and the purge amount is reduced (107).

On the other hand, if the fuel temperature in the fuel tank 18 is high (
108), the duty value Tprg becomes large (1
09), the ratio of the open time of the purge valve 42 increases, and the amount of purge increases.

In this way, the control section 22 controls the duty of the purge valve 42 so as to adjust the purge amount according to the operating conditions and fuel temperature. Thereby, the purge amount can be controlled according to not only the operating state but also the fuel temperature state. Therefore, the purge amount can be appropriately controlled as the amount of vaporized fuel generated increases or decreases due to changes in fuel temperature, and there is no shortage of vaporized fuel purge amount at high temperatures, eliminating the effect on the air-fuel ratio. can do. By eliminating this influence on the air-fuel ratio, it is possible to avoid deterioration in drivability, and it is also advantageous in terms of exhaust gas purification. Furthermore, it is possible to avoid the possibility that evaporated fuel will be released into the atmosphere.

[0022]

As described above, according to the present invention, it is possible to control the purge amount depending not only on the operating condition but also on the fuel temperature condition. Therefore, the purge amount can be appropriately controlled as the amount of evaporated fuel increases or decreases, and there is no shortage of evaporated fuel purge amount at high temperatures, eliminating the effect on the air-fuel ratio and improving driveability. This makes it possible to avoid a decrease in the fuel efficiency, and also to be advantageous in cleaning the exhaust gas, and also to avoid the possibility that evaporated fuel will be released into the atmosphere.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a purge air control device showing an embodiment of the present invention.

FIG. 2 is a control flowchart.

FIG. 3 is a diagram showing a map of basic values based on engine speed and load.

FIG. 4 is a diagram showing a map of correction values based on fuel temperature.

FIG. 5 is a diagram showing the relationship between purge amount and fuel temperature.

[Explanation of symbols]

2 Internal combustion engine 4 Intake passage 6 Exhaust passage 8 Air cleaner 10 Throttle valve 12 Combustion chamber 14 Fuel injection valve 16 Fuel passage 18 Fuel tank 20 Fuel pump 22 Control section 24 Air flow meter 26 Opening sensor 28 Igniter 30 Ignition coil 32 Distributor 34 Evapo system 36 Ventilation path 38 Canister 40 Check valve 42 Purge valve 44 New air passage 46 Fuel temperature sensor

Claims (1)

[Claims] 1. An evaporative pump comprising: a canister interposed in the middle of a ventilation passage communicating between an intake passage and a fuel tank of an internal combustion engine; and a purge valve interposed in the middle of the ventilation passage between the canister and the intake passage. In the system,
An operating state sensor is provided for detecting the operating state of the internal combustion engine, and a fuel temperature sensor is provided for detecting the fuel temperature of the fuel tank, and the internal combustion engine is operated according to the operating state and fuel temperature detected by the operating state sensor and the fuel temperature sensor. A purge air control device for an evaporative system, characterized in that it is provided with a control means for duty-controlling a purge valve.