JPH03279659A - Lpg engine - Google Patents

Abstract

PURPOSE:To prevent stalling of an engine, and to save waster of fuel by providing a LPG vaporizing means for vaporizing LPG, a mixing means for mixing combustion air with LPG, and an air-fuel ratio regulating means for regulating the flow area of a fuel passage. CONSTITUTION:A LPG vaporizing means 1 vaporizes LPG. A mixing means 7 mixes combustion air with LPG. An air-fuel ratio regulating means 10 regulates the flow area of a fuel passage 4. When a cold decelerating operational condition of an engine is detected, the LPG being supplied to the mixing means through the LPG vaporizing means is cut off by the air-fuel ratio regulating means 10. Thus, the air-fuel ratio of the mixture being supplied to the engine can be prevented from becoming excessively rich, and also stalling of the engine and waste of fuel can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an LPG engine, and particularly to an LPG engine that can achieve good air-fuel ratio control even in a cold deceleration operating state of the engine.

[Conventional technology]

Regarding the LPG engine, a conventional technology similar to the present invention is described in Japanese Patent Application Laid-Open No. 106959/1983, and a schematic diagram of this system is shown in FIG. 3 attached to this specification.

LPG is stored in a liquefied state at high pressure in a fuel tank (not shown).

The fuel tank communicates with a vaporizer 1, which is vaporization means, through a fuel passage equipped with a filter and a solenoid shutoff valve (not shown).

The LPG supplied to the vaporizer l is supplied to the - regional pressure valve 2a.
It is depressurized and flows into the regional pressure chamber 2, where it is vaporized to a pressure slightly higher than atmospheric pressure. Then, when flowing from the -regional pressure chamber 2 into the secondary pressure reducing chamber 3 through the secondary pressure reducing valve 3a, the pressure is further reduced and the pressure is regulated to be approximately equal to atmospheric pressure.

The main fuel passage 4 between the secondary decompression chamber 3 and the intake system 5 is provided with a main fuel amount control valve 10 that changes the area of the passage.

This main fuel amount control valve 10 has a stepping motor 10a that is driven according to the operating state of the engine.
The rotational force of the stepping motor IOa is converted into reciprocating motion to operate the needle valve 6.

The needle valve 6 changes the flow path area of the valve hole 9 formed in the venturi portion 8 of the mixer 7, that is, the effective cross-sectional area of the main fuel supply passage 4, by reciprocating.

With the above structure, the air-fuel ratio of the air-fuel mixture supplied to the engine is controlled according to the operating state of the engine.

[Problem to be solved by the invention]

However, according to this structure, when the engine is in a cold operating state where the engine has not been sufficiently warmed up, the main fuel amount control valve 10 is not fully opened because the air-fuel ratio needs to be richer than during normal operation. adjusted to a similar state.

In this state, when the engine shifts to a deceleration operating state, the throttle valve 12 becomes almost fully closed, and the amount of air taken into the engine decreases. Therefore, the force with which the LPG in the secondary pressure reduction chamber 3 is sucked into the mixer 7 becomes weaker, and the secondary pressure reduction valve 3a is closed.

However, when the engine is not sufficiently warmed up, the regulator 1 cannot exhibit sufficient vaporization ability, and therefore liquefied LPG tends to accumulate inside the first decompression chamber 2.

Therefore, even if the fuel supplied to the regulator 1 is cut during deceleration operation, the liquefied LPG inside the first pressure reducing chamber 2 will vaporize over time and the pressure will rise, pushing the secondary pressure reducing valve 3a open from the inside. and flows into the secondary decompression chamber 3.

As mentioned above, since the main fuel amount control valve 10 is close to fully open, a large amount of the LPG is supplied from the secondary decompression chamber 3 to the mixer 7. Therefore, during deceleration operation, although the amount of air taken into the engine is small, a large amount of LPG is supplied to the mixer 7, and the air-fuel ratio of the air-fuel mixture becomes overrich.

This makes it less likely that the engine will stall, and
There is also a waste of fuel.

The present invention is based on the above-mentioned knowledge, and an object of the present invention is to provide an LPG engine that achieves good air-fuel ratio control even during deceleration in a cold operating state of the engine.

[Means to solve the problem]

The above problem is solved by an LPG engine having the following parts structure.

In other words, an LPG engine vaporizes liquefied LPG supplied from a fuel tank into LPG at a specified pressure.
vaporizing means; mixing means for mixing LPG supplied from the LPG vaporizing means with combustion air taken into the engine; disposed in the middle of a fuel passage communicating the LPG vaporizing means and the mixing means; an air-fuel ratio adjusting means for adjusting the flow area of the fuel passage; and a cold deceleration operation detecting means for detecting that the engine is not warmed up and is being decelerated; When cold deceleration operation is detected, the air-fuel ratio adjusting means closes the fuel passage.

[For production]

According to the present invention, the air-fuel ratio adjusting means closes the fuel passage communicating the LPG vaporizing means and the mixing means when the cold deceleration operating state of the engine is detected.

Here, if the engine is not warmed up enough,
Since the PG vaporization means cannot fully demonstrate its vaporization ability,
Liquefied LPG tends to accumulate inside.

Therefore, even if fuel is cut during deceleration operation of the engine, the liquefied LPG inside the LPG vaporizing means vaporizes over time, the pressure increases, and a large amount tends to flow into the mixing means.

However, since the fuel passage is closed by the air-fuel ratio adjusting means, LPG does not flow into the mixing means, and the air-fuel ratio of the air-fuel mixture supplied to the engine does not become overrich.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a system diagram of an intake system of an LPG engine according to an embodiment of the present invention.

LPG is stored in a liquefied state at high pressure in a fuel tank (not shown).

The fuel tank communicates with a vaporizer 1, which is a means for vaporizing LPG, by a fuel passage equipped with a filter and a solenoid shutoff valve (not shown).

The LPG supplied from the fuel tank to the vaporizer l is
- The pressure is reduced by the regional pressure valve 2a, and the gas flows into the regional pressure chamber 2, where it is vaporized into a gas at a pressure slightly higher than atmospheric pressure.

Then, it flows from the -region pressure chamber 2 into the secondary pressure reducing chamber 3 through the secondary pressure reducing valve 3a. Here, the pressure is further reduced and the pressure is regulated to be approximately equal to atmospheric pressure.

The main fuel passage 4 between the secondary decompression chamber 3 and the intake system 5 is provided with a main fuel quantity control valve IO that changes its passage area in a manner to be described later. This main fuel amount control valve 10 is an air-fuel ratio adjusting means that adjusts the air-fuel ratio of the air-fuel mixture supplied to the engine.

In the figure, 100 is an electronic control unit (ECU).

The electronic control unit 100 receives signals from various sensors indicating the operating state of the engine, such as a water temperature sensor 20, an idling switch 22, and an engine speed sensor 24.
The valve opening degree of the main fuel quantity control valve 10 is calculated based on this value, and the stepping motor 10a, which is the driving part of the main fuel quantity control valve IO, is driven based on the calculated value.

The rotational force of the stepping motor 10a is converted into a linear reciprocating motion by a screw mechanism to move the needle valve 6 forward and backward. As a result, the main fuel amount control valve 10 changes the flow path area of the valve hole 9 formed in the venturi portion 8 of the mixer 7, that is, the effective cross-sectional area of the main fuel supply passage 4.

Here, the mixer 7 is a mixing means that mixes the LPG supplied from the regulator I with the combustion air taken into the engine.

Reference numeral 12 in the figure represents a throttle valve that is rotated within the intake system 5 to control the amount of combustion air supplied to the engine.

When the amount of combustion air supplied to the engine increases, the negative pressure in the venturi section 8 of the mixer 7 increases in accordance with the amount of combustion air. Therefore, even if the opening degree of the main fuel amount control valve 10 is constant, the LPG in the secondary decompression chamber 3 of the vaporizer 1
is sucked into the mixer 7 according to its negative pressure.

FIG. 2 is a control flowchart executed within the electronic control unit 100, and represents means for detecting cold deceleration operation.

This control is repeatedly executed at predetermined time intervals.

First, in step 201, the cooling water temperature T is compared with a specified value. If T<K (YES), the cooling water temperature T is lower than the specified value and the engine is not sufficiently warmed up, that is, cold operation is being performed.

In step 202, flag F is used to check whether the idle switch is on. If F=1 (YES), it indicates that the idle switch is ON, and the throttle valve 12 is almost fully closed.

In step 203, a comparison is made to see if the engine speed N is greater than or equal to No. If N≧No (YES), this indicates that the engine speed is higher than the idle link state.

When all the three conditions of steps 201, 202, and 203 described above are satisfied, the cold deceleration operation state is reached, and in step 204, the valve hole 9 is fully closed by the needle valve 6 of the main fuel amount control valve 10. do.

If any of the three conditions described above is not satisfied, the cold deceleration operation state is not established, and step 204 is skipped and the process proceeds to the main control flowchart.

Here, in a cold operating state in which the engine is not sufficiently warmed up, the vaporizer 1 cannot sufficiently exhibit its vaporizing function, so that liquefied LPG tends to accumulate inside the -region pressure chamber 2.

Therefore, even if the fuel supplied from the fuel tank to the Hoechlyzer 1 is cut during engine deceleration, the liquid LPG accumulated inside the -region pressure chamber 2 will vaporize over time and the pressure will increase.

As a result, the LPG pushes open the secondary pressure reducing valve 3a, flows into the secondary pressure reducing chamber 3, and then tries to flow in a large amount to the mixer 7 side. Furthermore, during deceleration, the amount of combustion air taken into the engine decreases. Therefore, if a large amount of LPG is mixed with a small amount of combustion air, the air-fuel ratio will become overrich.

However, in this embodiment, during cold deceleration operation, the valve hole 9 is fully closed by the needle valve 6 of the main fuel quantity control valve IO as described above, so LPG does not flow into the mixer 7. .

Note that the small diameter bypass passage 4b (see Fig. 1) is used only when the throttle valve 12 is wide open.
Because it has a structure in which water flows through it, it is closed when the engine is decelerating.

Therefore, during cold deceleration operation, the air-fuel ratio of the air-fuel mixture supplied to the engine does not become overrich, and engine stalling and fuel waste do not occur.

1- [Effects of the Invention] According to the present invention, when the cold deceleration operating state of the engine is detected, LP is supplied from the LPG vaporizing means to the mixing means.
G is cut off by the air-fuel ratio adjusting means.

Therefore, the air-fuel ratio of the air-fuel mixture supplied to the engine does not become overrich, and engine stalling and fuel waste do not occur.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an intake system of an LPG engine according to an embodiment of the present invention, and FIG. 2 is a control flowchart of the LPG engine according to an embodiment of the present invention. FIG. 3 is a system diagram of the intake system of a conventional LPG engine. ■ ...Regulator (vaporization means) 7 ...Mixer (mixing means) 10 ...Main fuel quantity control valve (air-fuel ratio adjustment means) 20
... Water temperature sensor ... Idle sensor ... Rotation speed sensor 0 ... Electronic control unit (cold deceleration operation means)

Claims (1)

[Claims] Liquefied LPG supplied from a fuel tank is LP at a specified pressure.
LPG vaporization means for vaporizing LPG into G, and LP supplied from the LPG vaporization means to combustion air taken into the engine.
a mixing means for mixing G; an air-fuel ratio adjusting means disposed in the middle of a fuel passage communicating the LPG vaporizing means and the mixing means and adjusting a flow area of the fuel passage; and a cold deceleration operation detecting means for detecting that the engine is in deceleration operation, and when the cold deceleration operation state of the engine is detected, the air-fuel ratio adjusting means controls the fuel passage. An LPG engine characterized by a closed system.