JPH0996260A - Fuel diffusion preventing mechanism for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel diffusion preventing mechanism for an internal combustion engine which can prevent diffusion to the atmosphere of fuel left in an intake system when the engine is stopped. SOLUTION: In an internal combustion engine provided with an injector 23 supplying gas fuel to an intake passage 16, a canister 31 and/or a shutoff valve 32 closing the intake passage 16, when the engine is stopped, are provided in the intake passage 16 in the upstream from the injector 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preventive mechanism for preventing diffusion of fuel into the atmosphere after the engine of an internal combustion engine having a fuel supply device in an intake passage is stopped.

[0002]

2. Description of the Related Art A fuel supply device for an automobile engine that uses compressed natural gas (CNG) as a fuel is provided with an engine intake system and a throttle valve that opens and closes an intake passage, and an upstream side of the throttle valve. It is connected to a venturi part that generates a negative pressure of intake air, a gas mixer that is connected to this venturi part and that has an on-off valve that adjusts the amount of CNG supplied to the combustion chamber of the engine, and an intake path on the upstream side of the venturi part. It is generally well known to have an air cleaner for purifying the intake air, an injector provided upstream of the throttle valve, and a regulator for reducing the CNG in the intake passage to the atmospheric pressure.

In this type of engine, the output can be adjusted by adjusting the intake amount of the air-fuel mixture of CNG according to the opening of a throttle valve that is appropriately operated. The above device causes CNG to flow into the venturi portion due to the intake negative pressure generated in the venturi portion during normal operation, and during deceleration,
The CNG injector is operated to inject CNG at a constant cycle and a constant pulse width.

[0004]

In the above technique, the CNG injector is operated during deceleration to inject CNG at a constant cycle and a constant pulse width. Therefore, the ignition key is turned off to stop the engine. However, there is a time lag until the CNG injector stops completely, CNG remains in the intake passage, and the remaining CNG passes through the gap between the intake passage and the throttle valve and further diffuses into the atmosphere through the air cleaner. There is a problem.

Similarly, in the case of the fuel injection system using an injector, the fuel remaining in the intake system when the engine is stopped passes through the gap between the intake passage and the throttle valve or the passage of the air flow rate control device and further passes through the air cleaner. There is a problem of diffusion into the atmosphere.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel diffusion preventing mechanism for an internal combustion engine which can prevent diffusion of fuel remaining in the intake system into the atmosphere when the engine is stopped. And

[0007]

According to the first aspect of the present invention,
An internal combustion engine having a gaseous fuel supply device for supplying gaseous fuel to an intake passage, wherein an intake valve upstream of the gaseous fuel supply device and / or an on-off valve for closing the intake passage when the engine is stopped It is characterized by having.

According to a second aspect of the present invention, in the fuel diffusion prevention mechanism for the internal combustion engine according to the first aspect, the exhaust valve is closed when the intake valve of the cylinder communicating with the intake passage is open. It is characterized by being set to.

According to a third aspect of the present invention, in the fuel diffusion prevention mechanism for an internal combustion engine according to the first or second aspect, a gas adsorbent disposed in the intake passage upstream of the gaseous fuel supply device, An on-off valve that closes the intake passage when the engine is stopped is provided upstream of the gas adsorbent.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 11 represents an internal combustion engine. The engine 11 uses CNG, which is a gaseous fuel, as fuel. The engine 11 has a cylinder block 12
And a cylinder head 13, and a combustion chamber 10 in which a piston 14 is slidably fitted therein is provided.
Are arranged. Since each cylinder has the same configuration here, the following description will be given using the first cylinder.

The cylinder head 13 is provided with an intake port 21 and an exhaust port 22 which communicate with the combustion chamber 10. An intake passage 16 is in communication with the intake port 21, while an exhaust passage 17 is in communication with the exhaust port 22.

An intake valve 18 that opens and closes between the combustion chamber 10 and the intake passage 16 and an exhaust valve 19 that opens and closes between the combustion chamber 10 and the exhaust passage 17 are provided in a portion of the cylinder head 13 facing each cylinder. Is provided. The opening and closing timings of the intake valve 18 and the exhaust valve 19 are controlled by the cam 20 so that the intake valve 18 does not open earlier than the exhaust valve 19 closes in this example. That is, the intake valve 18 and the exhaust valve 19 are set so as not to overlap at all. This helps to prevent the intake valve 18 and the exhaust valve 19 from being simultaneously open for zero time and to prevent fuel from flowing out of the exhaust passage 17 through the cylinder.

The exhaust passage 17 is provided with a muffler and a catalyst (both not shown) for purifying harmful substances in the exhaust gas. In the intake passage 16, an injector 23 as a fuel supply means for injecting CNG, a throttle valve 24 for opening and closing the intake passage 16, and an air cleaner 25 for filtering intake air are sequentially arranged from the downstream side of the intake passage 16. Has been done. Here, the downstream side of the intake passage 16 refers to a direction in which intake air flows toward the engine 11.

The injector 23 is connected to a CNG cylinder 27 via a regulator 26 that regulates the pressure of CNG. The injector 23 is connected to a valve drive circuit 28 (not shown) and an engine control unit (hereinafter simply referred to as “ECU”) 30, which will be described later.
It is driven via the drive circuit 28 in response to the ON / OFF signals from 0, and CNG is injected into the intake passage 16.

The throttle valve 24 is connected to an accelerator pedal via a link system (not shown), and changes the opening of the valve according to the amount of depression of the accelerator pedal to increase or decrease the amount of air flowing through the intake passage.

The intake passage 1 upstream of the injector 23 and downstream of the element 29 of the air cleaner 25.
6 is provided with a canister 31 as a gas adsorbent that adsorbs CNG injected from the injector 23 after the engine 11 is stopped. Further, the intake passage 16 on the upstream side of the canister 31 opens and closes the intake passage 16. A shut-off valve 32 is provided as an opening / closing valve.

In this embodiment, both the canister 31 and the shutoff valve 32 are provided, but the canister 3
Even if only one or the shutoff valve 32 is provided, the diffusion of the gaseous fuel can be sufficiently prevented.

The canister 31 is formed by coating coconut husks or activated carbon on a fibrous substance, and forming holes to facilitate passage of air. Shut-off valve 3
The ECU 2 operates so that the intake passage 16 is closed when the engine 11 is stopped and opened when the engine 11 is operating.
Controlled by 30.

The ECU 30 is mainly composed of a well-known microcomputer having a ROM and a RAM, and a detection signal is inputted from an ignition switch 33 and other various sensors to an input end of an I / O port (not shown). In this example, the ignition switch 3
The activation and deactivation of the engine 11 is detected by turning on and off of 3.

Further, drive signals are output from the output end of an I / O port (not shown) of the ECU 30 to the drive circuit 28 connected to the injector 26 and the shutoff valve 32 at appropriate times.

The operation of the apparatus having the above-mentioned structure will be described below. When the ignition switch 33 is turned on and the engine 11 is started, the ECU 30 checks each function and sets an initial function such as an initial value. Subsequently, the ECU 30 takes in various operating conditions of the engine 11, outputs ON / OFF signals to the drive circuit 28, drives the injector 23, and injects CNG.

When the ignition switch 33 is turned off and the engine 11 is stopped, the ECU 30 operates the shutoff valve 32 to close the intake passage 16. After the engine 11 is stopped, the CNG remaining in the intake passage 16 is adsorbed by the canister 31. CNG on canister 31
Shut-off valve 3 even if the
Since 2 closes the intake passage 16, it is possible to prevent CNG from leaking into the atmosphere.

Since the opening timing of the intake valve 18 is set not to be earlier than the closing timing of the exhaust valve 19, CN
It is possible to prevent G from flowing out to the exhaust passage 17 via the cylinder.

The CNG adsorbed on the canister 31 is introduced into the cylinder and burned when the engine 11 is started next time. The present invention can be applied even when the power generation engine of the hybrid electric vehicle using the CNG engine for power generation is stopped. The present invention is particularly effective for an internal combustion engine that uses gas as fuel, but may use liquid as fuel.

[0025]

According to the present invention, an opening / closing valve for closing the canister and / or the intake passage is provided in the intake passage upstream of the fuel supply device so that the exhaust valve is closed when the intake valve is open. Since it is set to, the fuel remaining in the intake system can be prevented from diffusing into the atmosphere when the engine is stopped, which is effective in preventing air pollution.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fuel diffusion prevention mechanism of an internal combustion engine showing an embodiment of the present invention.

[Explanation of symbols]

 10 Combustion Chamber 11 Engine 12 Cylinder Block 13 Cylinder Head 14 Piston 16 Intake Passage 17 Exhaust Passage 18 Intake Valve 19 Exhaust Valve 20 Cam 21 Intake Port 22 Exhaust Port 23 Injector 24 Throttle Valve 25 Air Cleaner 26 Regulator 27 CNG Cylinder 28 Drive Circuit 30 ECU 31 canister 32 shut-off valve

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tadao Ikuhara 5-3-8, Shiba, Minato-ku, Tokyo ・ Mitsubishi Motors Corporation

Claims (3)

[Claims] 1. An internal combustion engine having a gas fuel supply device for supplying a gas fuel to an intake passage, wherein the gas adsorbent is provided in the intake passage upstream of the gas fuel supply device and / or the intake passage when the engine is stopped. A fuel diffusion preventing mechanism for an internal combustion engine, comprising an opening / closing valve for closing the fuel cell. 2. The fuel diffusion prevention mechanism for an internal combustion engine according to claim 1, wherein the exhaust valve is set to be closed when the intake valve of the cylinder communicating with the intake passage is open. A fuel diffusion prevention mechanism for an internal combustion engine. 3. The fuel diffusion prevention mechanism for an internal combustion engine according to claim 1 or 2, wherein a gas adsorbent disposed in the intake passage upstream of the gas fuel supply device and upstream of the gas adsorbent are disposed. A fuel diffusion prevention mechanism for an internal combustion engine, comprising an opening / closing valve for closing the intake passage when the engine is stopped.