JP2001115904A - Vaporized fuel purging device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equalize the vaporized fuel purge distribution ratio between respective banks in an engine having plural cylinder banks. SOLUTION: A first purge passage 32 is extended from an upper part of a fuel tank 26 to be communicated with a canister 34 through a two-way valve 33, a second purge passage 35 to introduce mixed gas of fresh gas and vaporized fuel gas is extended from the canister 34, and this purge passage 35 is opened downstream of a throttle valve 14, upstream of a branch part 13c branched from a throttle chamber 15 to passages 13a, 13b communicated with intake chambers 7a, 7b for respective banks, and roughly at a center. The vaporized fuel purge distribution ratio is thus equalized between banks of the engine 1 to equalize the air-fuel ratio between the banks, exhaust emission is improved, deterioration of travelling performance by surge or the like caused by irregularity of the air-fuel ratio between the banks can be prevented, and engine vibration at the time of idling can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel purging apparatus for an engine having a plurality of cylinder banks, wherein the purge distribution ratio of the evaporative fuel between the banks is made uniform.

[0002]

2. Description of the Related Art In general, in a vehicle such as an automobile using an engine as a driving power source, various technologies for controlling an engine are employed to prevent air pollution and conserve resources. The evaporated fuel gas is adsorbed on activated carbon or the like in the canister and temporarily stored so that the evaporated gas of the fuel generated in the canister is not discharged to the atmosphere, and the evaporated fuel gas in the canister is transferred from the intake passage to the engine through the intake passage under the set operation conditions. There is a so-called evaporative fuel purge device that sucks the fuel into the combustion chamber.

For example, JP-A-6-193520 discloses that a fuel tank and an inlet side of a canister are connected by a first purge line, and an outlet side of the canister and an inlet side of a purge solenoid valve are connected to a second purge line.
A purge line connects the outlet side of the purge solenoid valve and a downstream side of the throttle body as an intake system with a third purge line, thereby adsorbing fuel vapor from the fuel tank to the canister and purging the fuel vapor. An evaporative fuel supply device (evaporative fuel purge device) that is introduced into an intake system through a solenoid valve is disclosed.
Japanese Patent Application Laid-Open No. Hei 6-221233 discloses a first purge line connected to a fuel tank, a second purge line connected to a surge tank provided in a portion of the intake pipe near the engine, and both purge lines. An evaporative fuel recovery system (evaporative fuel purge device) including a canister interposed therebetween is disclosed.

[0004]

However, in an engine having a plurality of cylinder banks, the purged fuel vapor becomes non-uniform in each bank due to the mounting conditions of the fuel vapor purging device and the restrictions on equipment. If the opening position of the purge passage communicating with the intake system of the engine having two banks is connected to one bank side as in the prior art, there is a possibility that the purge passage is introduced into the bank on the side where the purge passage opens. As a result, the purge amount of the evaporated fuel increases, and the air-fuel ratio becomes relatively rich. For this reason, variations in the air-fuel ratio between the banks occur, and the variations in the air-fuel ratio cause deterioration in exhaust emission and running performance due to surges and the like.

The present invention has been made in view of the above circumstances, and in an engine having a plurality of cylinder banks, the distribution ratio of purged fuel vapor among the banks is made uniform, and the variation in the air-fuel ratio between the banks is eliminated. It is an object of the present invention to provide an evaporative fuel purge device for an engine that equalizes the air-fuel ratio between banks.

[0006]

In order to achieve the above object, an invention according to a first aspect of the present invention is directed to an engine having a plurality of cylinder banks, wherein an intake system of the engine is provided with a fuel tank for purging evaporated fuel generated in a fuel tank. In the purge device, an opening position of the purge passage for guiding the evaporated fuel in the intake system is disposed in front of and substantially at a center of a branch portion where the intake passage branches to each bank.

That is, according to the first aspect of the present invention, a purge passage for guiding evaporated fuel generated in a fuel tank to an intake system is provided.
An intake passage of an engine having a plurality of cylinder banks is opened in front of and substantially at the center of a branch portion branching to each bank, so that the purge distribution ratio of evaporated fuel between the banks is made uniform.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of an engine system according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an engine,
In this embodiment, a horizontally opposed 6-cylinder engine is shown. A cylinder block 2 of the engine 1 is divided into two banks on both sides of a crankshaft. An intake port 4 and an exhaust port 5 are formed in a cylinder head 3 of each bank.

An intake manifold 6 is communicated with the intake port 4 of each cylinder, and the intake manifolds 6 of each cylinder for each bank are connected to intake chambers 7a and 7b. Furthermore, the intake chambers 7a, 7
A variable intake valve 8 driven to be opened and closed by an actuator 9 is interposed in a passage communicating with b.

A negative pressure tank 11 is connected to the actuator 9 via one-way valve 10 to one of the intake chambers 7a, and a switching solenoid valve provided in a passage connecting the actuator 9 and the negative pressure tank 11 is provided. 1
2, the operating pressure introduced into the actuator 9 is switched between negative pressure and atmospheric pressure in accordance with the engine operating range.

The intake chambers 7 corresponding to the respective banks
a, 7b, passages 13a, 13b extend upstream from respective positions on both sides of the variable intake valve 8, and these passages 13a, 13b
a and 13b collectively communicate with a throttle chamber 15 in which a throttle valve 14 interlocked with an accelerator pedal is interposed so that intake air is evenly distributed to each bank. An intake pipe 17 is connected to an upstream side of the throttle chamber 15 via an air chamber 16, and an air cleaner 18 is attached to an upstream side of the intake pipe 17. A chamber is provided in the middle of an air intake passage connected to the air cleaner 18. 19 is communicated.

The throttle chamber 15 is connected to a bypass passage 20 that bypasses the throttle valve 14. The bypass passage 20 is connected to an idle control valve (ISC valve) that constitutes an idle control device for controlling an idle speed. ) 21 is interposed, and the ISC valve 21 adjusts the air flow rate in the bypass passage 20.

A spark plug 22 for exposing a discharge electrode portion to the combustion chamber is attached to each cylinder of the cylinder head 3, and an air assist is provided immediately upstream of the intake port 4 of each cylinder of the intake manifold 6. An injector 25 is provided. In the air assist injector 25,
Fuel is supplied through a fuel supply passage 27 extending from the fuel tank 26, and the atomization of the injected fuel is promoted in a low rotation speed and low load region through an air assist passage 28 extending from the ISC valve 21. Assist air is introduced to perform the operation.

An in-tank type fuel pump 30 is provided in the fuel tank 26, and fuel from the fuel pump 30 is supplied to the air assist injector 25 through a fuel supply passage 27.
The pressure is fed to the pressure regulator 31, the excess fuel is returned from the pressure regulator 31 to the fuel tank 26, and the fuel pressure of the fuel supply system to the air assist injector 25 is adjusted to a predetermined pressure.

Further, as an evaporative fuel purging device for purging the evaporative fuel generated in the fuel tank 26 to the intake system, a first purge passage 32 extends from an upper portion of the fuel tank 26 and a two-way valve 33 is provided. It is in communication with an upper portion of a canister 34 having an adsorbing portion made of activated carbon or the like. The canister 34 is provided at its lower part with a fresh air inlet communicating with the atmosphere, and a second purge for introducing a mixture (evaporative gas) of fresh air from the fresh air inlet and the evaporated fuel gas stored in the adsorption section. A passage 35 extends from the top.

The second purge passage 35 is provided with the throttle valve 1
4, the passages 13 a, 13 communicating from the throttle chamber 15 to the intake chambers 7 a, 7 b of each bank.
An opening is provided in the intake system at a location substantially upstream and at the center of the branch portion 13c that branches to the path b. In the middle of the second purge passage 35, a canister purge control (CPC) duty solenoid valve whose valve opening is controlled in accordance with the duty ratio of the drive signal in order to control the purge ratio of evaporated fuel to intake air. 36, and this CP
On the upstream side of the C-duty solenoid valve 36, a chamber 37 for silencing airflow noise and pulsation noise generated when the CPC duty solenoid valve 36 operates is provided.

On the other hand, the exhaust ports 5 of the cylinder head 3 of the engine 1 are assembled in the cylinder head 3 for each bank and communicated with the exhaust pipe 38, and the exhaust pipe 38 of each bank is provided.
In addition, a catalytic converter 39 containing a three-way catalyst is interposed, and a catalytic converter 40 also containing a three-way catalyst is interposed at a collecting portion of the exhaust pipe 38 of each bank, and a muffler 42 is provided via a silencer 41. Is communicated to.

Further, EG is supplied from the exhaust pipe 38 of one bank.
An R (exhaust gas recirculation) passage 43 extends, and passages 13a, 13 extending from intake chambers 7a, 7b of each bank.
3b. In the middle of the EGR passage 43, E
An EGR valve 44 for adjusting the GR amount is interposed, and a part of the exhaust gas is recirculated to the intake system according to the degree of opening of the EGR valve 44.

The engine 1 is provided with sensors for detecting an engine operating state. That is, the throttle opening sensor 50a and the throttle valve 1 are attached to the throttle valve 14 interposed in the throttle chamber 15.
A throttle sensor 50 having a built-in idle switch 50b that is turned ON when fully closed is connected to the throttle valve 14
Downstream of the throttle valve 14, an intake pipe pressure sensor 51 for detecting an intake pipe pressure downstream of the throttle valve 14 is provided. The air chamber 16 has an intake air temperature sensor 5 for detecting the intake air temperature.
Two are facing.

Further, a knock sensor 53 is attached to each bank of the cylinder block 2 of the engine 1, and a cooling water temperature sensor 55 faces a cooling water passage 54 formed in the cylinder block 2. A linear air-fuel ratio sensor 56 is disposed upstream of the catalytic converter 39 of the exhaust pipe 38 of each bank.
On the downstream side of the catalytic converter 40 interposed in the collecting portion of
An O2 sensor 57 is provided.

A crank angle sensor 5 is mounted on the outer periphery of a crank rotor 58 which is mounted on the crankshaft of the engine 1.
9 and a half with respect to the crankshaft.
A cylinder discriminating sensor 61 is provided opposite to a cam rotor 60 connected to a rotating camshaft.

The engine 1 is electronically controlled by an electronic control unit (not shown). That is, the electronic control unit processes a detection signal from each sensor / switch, a battery voltage, and the like, and based on various data stored in a memory, various learning value data, fixed data, and the like, a fuel injection amount,
Calculate the ignition timing, the target idle speed, the target purge rate of the evaporative fuel, the target EGR rate, etc., and perform fuel injection control, ignition timing control, idle speed control, evaporative fuel purge control, EG
Engine control such as R control is performed.

Here, in the fuel vapor purge control,
The purge amount is controlled by varying the duty ratio of the drive signal to the CPC duty solenoid valve 36 interposed in the second purge passage 35 that guides the evaporative gas from the canister 34 to the intake system. Control is performed such that the purge rate for the intake air amount becomes the target purge rate according to the region.

At this time, the evaporative gas from the canister 34 is opened to the intake system of the second purge passage 35, that is, to a branch portion branched to the passages 13a and 13b communicating with the intake chambers 7a and 7b of each bank. The branch 13c, together with the intake air passing through the throttle valve 14, is purged from the upstream and substantially center of the passage 13a, and the passages 13a,
13b flows evenly.

That is, the position of the opening of the second purge passage 35 to the intake system is disposed substantially upstream of and at the center of the branch 13c into the passages 13a and 13b for uniformly distributing the intake air to the respective banks. Therefore, the purge amount of the evaporative gas is equally distributed to each bank without being biased to one of the two banks.

As a result, the distribution ratio of the evaporative gas between the banks is made uniform, and the variation in the air-fuel ratio between the banks in the air-fuel ratio control is eliminated. It is also possible to eliminate variations in the air-fuel ratio between cylinders. As a result, good air-fuel ratio controllability can be obtained to reduce exhaust harmful components such as CO, NOx, HC, etc., and not only can exhaust emissions be improved, but also surges caused by variations in air-fuel ratio between the banks can be achieved. Thus, it is possible to prevent the running performance from deteriorating due to the like and reduce the engine vibration during idling.

[0028]

As described above, according to the present invention, the purge passage for guiding the evaporative fuel generated in the fuel tank to the intake system is formed by branching the intake passage of an engine having a plurality of cylinder banks into each bank. The opening is provided before and at substantially the center, so that the purge distribution ratio of the evaporated fuel between the banks can be made uniform, and the air-fuel ratio between the banks can be made uniform to improve the exhaust emission. It is possible to prevent running performance from deteriorating due to surge or the like caused by variations in the air-fuel ratio between the banks, and reduce engine vibration during idling.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an engine system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine 13c ... Branch part 26 ... Fuel tank 32, 35 ... Purge passage

Claims (1)

[Claims] 1. An evaporative fuel purging device for an engine having a plurality of cylinder banks for purging evaporative fuel generated in a fuel tank into an intake system of the engine, wherein an opening in the intake system of a purge passage for guiding the evaporative fuel is provided. An evaporative fuel purging device for an engine, wherein a position is provided in front of and substantially at a center of a branch portion where an intake passage branches to each bank.