JP2003074415A - Fuel supply method in internal combustion engine and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably control injection of fuel gas by preventing the fuel gas from being overheated, in a fuel supply method using fuel gas and liquid fuel by switching them according to an operational condition. SOLUTION: Fuel gas is cooled by liquid fuel on the upstream side of a fuel gas injector 24. As a means for this cooling, a fuel gas transfer passage 15a forming a fuel gas supply passage and a liquid fuel transfer passage 10a forming a liquid fuel supply passage are disposed on the upstream side of the fuel gas injector 24 in the fuel gas supply passage so that heat of the fuel gas is transferred to the liquid fuel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply method and apparatus for an internal combustion engine.

[0002]

2. Description of the Related Art In recent years, LPG (liquefied petroleum gas) and CNG (compressed natural gas) have been used as alternative energy sources to gasoline, and these LPG and CNG are used as fuel for internal combustion engines of automobiles.

Such LPG and CNG (hereinafter, this L
When PG and CNG are collectively referred to as gas fuel) as a fuel for an internal combustion engine of an automobile, gas fuel and liquid fuel such as gasoline may be switched and used depending on the operating condition of the internal combustion engine.

As a fuel supply system for an internal combustion engine which uses such a gas fuel and a liquid fuel in combination, for example, a system as shown in FIG. 4 is disclosed in Japanese Patent Laid-Open No. 5-98994.

In the fuel supply system shown in FIG. 4, the liquid fuel in the liquid fuel (gasoline) tank 101 is jetted and supplied into the intake port 105 of the engine body 104 by the liquid fuel injector 103 through the liquid fuel passage 102. The system and the gaseous fuel in the gaseous fuel (CNG) cylinder 106 are jetted and supplied into the intake manifold 110 by the gaseous fuel injector 109 through the gaseous fuel passage 107 and the pressure reducing regulator 108.
It consists of a lineage.

[0006]

By the way, since the injector 103 for liquid fuel and the injector 109 for gaseous fuel as described above are arranged at the engine body 104 or in the vicinity thereof, the atmosphere of these injectors 103 and 109 is high. The temperature is high.

Therefore, the injector for gaseous fuel 1
In the conventional supply method in which the cooling means for cooling the vicinity of 09 is not provided, the injector for gaseous fuel 1
The gas fuel passage 107 immediately before 09 is heated to a high temperature by the ambient temperature, and there is a possibility that the gas fuel cannot be stably supplied to the gas fuel injector 109. Stable fuel injection control by the gas fuel injector 109 may occur. May not be possible.

Therefore, the present invention prevents the gas fuel from being heated to a high temperature in an internal combustion engine in which a liquid fuel such as gasoline and a gas fuel such as LPG or CNG are used in combination, particularly immediately before the injector for gas fuel. An object of the present invention is to provide a fuel supply method and device for an internal combustion engine that can perform stable injection control of gas fuel.

[0009]

In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a fuel supply for an internal combustion engine in which a gas fuel and a liquid fuel are switched and used according to an operating condition. In the method, there is provided a fuel supply method for an internal combustion engine, characterized in that the gas fuel is cooled by a liquid fuel on the upstream side of the gas fuel injector in the gas fuel supply passage.

According to the present invention, since the gas fuel on the upstream side of the gas fuel injector is cooled by the liquid fuel, in the gas fuel supplied in a liquefied state like LPG, its vaporization is suppressed and liquefied. Is supplied to the gas fuel injector in a stable state without being overheated in a gas fuel such as CNG supplied in a gas state, and the gas fuel is injected by the gas fuel injector. Control is performed stably.

A second aspect of the present invention is the fuel supply for an internal combustion engine according to the first aspect, wherein the liquid fuel is circulated through a liquid fuel tank to cool the gas fuel. Is the way.

By thus circulating the liquid fuel through the liquid fuel tank, the cooling action of the gas fuel can be enhanced by the cooled liquid fuel in the liquid fuel tank.

According to a third aspect of the present invention, in the second aspect of the present invention, when the temperature of the gas fuel on the upstream side of the gas fuel injector reaches a predetermined temperature or higher during use of the gas fuel. Further, it is a fuel supply method for an internal combustion engine in which liquid fuel is circulated through a liquid fuel tank.

As described above, the liquid fuel is circulated only when the temperature of the gas fuel becomes equal to or higher than the set temperature, so that the unnecessary temperature decrease of the gas fuel is prevented and the liquid fuel is circulated. The power consumption of the pump can be reduced.

[0015] The fourth and fifth inventions according to claims 4 and 5 are a fuel supply device for achieving the above-mentioned fuel supply method, and the fourth invention is a gas fuel and a liquid fuel according to an operating condition. In a fuel supply device for an internal combustion engine that switches between and, the heat of the gas fuel is conducted to the liquid fuel through the gas fuel supply passage and the liquid fuel supply passage on the upstream side of the gas fuel injector in the gas fuel supply passage. A fuel supply device for an internal combustion engine, which is characterized in that it is arranged as described above.

In a fifth aspect based on the fourth aspect, a heat transfer section made of a heat transfer material is provided in the gas fuel supply path upstream of the gas fuel injector, and the gas fuel is supplied into the heat transfer section. A fuel supply device for an internal combustion engine in which a passage and a liquid fuel supply passage are formed by using a member forming a heat transfer section as a common wall.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described based on the embodiment shown in FIGS.

FIG. 1 is a diagram showing the configuration of the entire system to which the present invention is applied. An engine body 1 which is an internal combustion engine is provided with an intake manifold 4 which communicates with a combustion chamber 3 through an intake valve 2 thereof. The upstream side of the intake manifold 4 communicates with an air cleaner 6 via a throttle valve 5.

Exhaust manifold 7 of the engine body 1
Is provided with an O ₂ sensor 7a.

A liquid fuel pump 9 is provided in a liquid fuel tank 8 storing liquid fuel such as gasoline, and the liquid fuel is pressurized and supplied to a liquid fuel supply passage 10 by driving the liquid fuel pump 9. It has become so. A downstream side of the liquid fuel supply passage 10 is connected to a heat transfer section 11 which is a fuel supply section. Excess fuel of the liquid fuel supplied into the heat transfer section 11 is returned to the liquid fuel tank 8 through the liquid fuel return path 12.

A gas fuel pump 14 is provided in a gas fuel tank 13 which stores a gas fuel such as LPG or CNG, and the gas fuel is pressurized to a gas fuel supply passage 15 by driving the gas fuel pump 14. It is supplied in the state. The downstream side of the gas fuel supply path 15 is communicated with the heat transfer section 11. Excess fuel of the gas fuel supplied into the heat transfer section 11 is returned to the gas fuel tank 13 through the gas fuel return path 16.

The liquid fuel supply passage 10 is provided with a liquid fuel cutoff valve 17 which is located upstream of the heat transfer section 11 and which is an electromagnetic valve for opening and closing the liquid fuel supply passage 10.

The gas fuel supply passage 15 is provided with a gas fuel cutoff valve 18 which is located upstream of the heat transfer section 11 and which is an electromagnetic valve for opening and closing the gas fuel supply passage 15.

The shut-off valves 17 and 18 are opened and closed by an engine control circuit (hereinafter also referred to as ECU) 20 based on output signals from respective sensors described later when the driver switches the fuel changeover switch 19. It has become so.

The heat transfer section 11 is made of a heat transfer material having a high heat conductivity, for example, a metal material such as aluminum or stainless steel. As shown in FIG. 2, the liquid fuel supply passage 10 is provided in the member 11a. The liquid fuel heat transfer path 10a is formed, and the upstream side of the liquid fuel heat transfer path 10a is formed as shown in FIG.
The liquid fuel supply passage 10 shown in FIG. 2 is communicated with, and the downstream side is communicated with the liquid fuel return passage 12. Further, the liquid fuel heat transfer path 10a is directly formed in the member 11a by drilling or molding. Further, a gas fuel heat transfer path 15a constituting the gas fuel supply path 15 is formed in the member 11a, and the upstream side of the gas fuel heat transfer path 15a is the gas fuel supply path shown in FIG. 15, and the downstream side communicates with the gas fuel return path 16. The gas fuel heat transfer path 15a is directly formed in the member 11a by drilling or molding. These heat transfer paths 10a and 1
5a are arranged close to each other so that the heat of the gas fuel in the gas fuel heat transfer path 15a can be easily transferred to the liquid fuel in the liquid fuel heat transfer path 10a.

As described above, the member 11a having high thermal conductivity
Both heat transfer paths 10a and 15a are directly formed in the heat transfer section 1
By making the member 11a constituting 1 the common wall of both heat transfer paths 10a, 15a, the heat of the gas fuel in the gas fuel heat transfer path 15a is transferred to the liquid fuel in the liquid fuel heat transfer path 10a. The heat transfer efficiency for heat transfer can be improved, and the formation of both heat transfer paths 10a, 15a becomes easy.

A liquid fuel injector 23 is provided in communication with the liquid fuel heat transfer path 10a, and the liquid fuel injector 23 is provided in the intake manifold 4 as shown in FIG. The liquid fuel in the heat transfer passage 10a for liquid fuel is injected into the intake manifold 4 by the injector 23 for liquid fuel.

A gas fuel injector 24 is provided in communication with the gas fuel heat transfer path 15a, and the gas fuel injector 24 is provided in the intake manifold 4 as shown in FIG. Heat transfer path for fuel 1
The gas fuel in the liquefied state or the gas fuel in the vaporized state in 5a is injected into the intake manifold 4 by the injector for gas fuel 24.

The on-off valves of the injectors 23 and 24 are controlled by the engine control circuit (ECU) 20.

The member 11a of the heat transfer section 11 is provided with a pressure sensor 25 for detecting the pressure of the gas fuel in the heat transfer passage 15a for gas fuel and a temperature sensor 26 for detecting the temperature of the gas fuel. There is. The output signals of both sensors 25, 26 are input to the engine control circuit (ECU).

Next, an example of switching control of these fuels when gasoline is used as the liquid fuel and LPG is used as the gas fuel in the above configuration will be described with reference to FIG.

First, when the ignition switch is turned on (started), a liquid fuel pump (hereinafter referred to as a gasoline pump in this example) 9 is driven (step 1), and a liquid fuel cutoff valve (hereinafter referred to as a gasoline in this example). The shutoff valve 17 is opened (step 2), the liquid fuel injector (hereinafter, referred to as a gasoline injector in this example) 23 is driven (step 3), and the engine is started. This engine is started with gasoline fuel regardless of the temperature of the engine in consideration of startability, and after the engine is started, the engine control circuit 20
The internal timer circuit is set so that the engine is driven by gasoline fuel until a predetermined time, for example, about 1 minute has elapsed.

Next, after starting the engine, it is judged whether or not the fuel is switched from liquid fuel (hereinafter referred to as gasoline in this example) to gas fuel (hereinafter referred to as LPG in this example) (step 4). This determination is made based on the engine cooling water temperature, the oil temperature, the gas fuel temperature by the temperature sensor 26, etc., and when the conditions for switching to the LPG are satisfied, for example, when the engine water temperature is 45 ° C. or higher, 1 minute after the engine is started When the above has elapsed, the ECU shifts to steps 5 to 10.

That is, when the condition for switching to the LPG is satisfied, the gas fuel pump (hereinafter referred to as the LPG pump in this example) 14 is driven (step 5), and the gasoline cutoff valve 17 is closed ( Step 6),
The gasoline pump 9 is stopped (step 7), the gasoline injector 23 is stopped (step 8), the LPG shutoff valve 18 is opened (step 9), and the gas fuel injector (hereinafter referred to as LPG injector in this example).
24 is driven (step 10).

As a result, the engine is operated by using LPG as fuel.

During this operation, L
It is determined whether or not the temperature of the PG has risen to a predetermined temperature (step 11). That is, the temperature of the LPG in the gas fuel heat transfer path 15a in the heat transfer section 11 is detected by the temperature sensor 26, the output signal thereof is input to the ECU, and the ECU determines whether or not the temperature is equal to or higher than a predetermined temperature. For example, LPG
The temperature (delivery fuel temperature) is set to 60 ° C. in consideration of the hysteresis of control.

When it is determined that the temperature of the LPG is equal to or higher than a predetermined temperature, the gasoline pump 9 is driven (step 12) and the gasoline is shut off while the LPG pump 14 and the LPG injector 24 are driven as described above. The valve 17 is opened (step 13). The gasoline injector 23 is not driven.

As a result, the gasoline in the liquid fuel tank (gasoline tank) 8 is supplied to the liquid fuel supply passage 10, the gasoline cutoff valve 17, and the heat transfer passage 10 for liquid fuel in the heat transfer section 11.
a. Returning to the liquid fuel tank (gasoline tank) 8 through the liquid fuel return path 12, and repeating this circulation. By the circulation of the gasoline, the gasoline in the gasoline tank 8 having a temperature lower than the ambient temperature of the heat transfer section 11 flows through the liquid fuel heat transfer path 10a. As a result, the heat of the LPG is transferred to the gasoline in the gas fuel heat transfer path 15a via the member 11a, the LPG in the gas fuel heat transfer path 15a is cooled, and vaporization in front of the LPG injector 24 is suppressed. Then, the LPG is stably supplied to the LPG injector 24 in a liquid state.

Due to the cooling action, the temperature of the LPG in the gas fuel heat transfer path 15a is lowered to a predetermined temperature or lower (55
When the temperature becomes less than or equal to (° C.), the temperature is detected by the temperature sensor 26 (step 14), and based on the output signal, the ECU 2
The gasoline pump 9 is stopped by 0 (step 15)
At the same time, the gasoline cutoff valve 17 is closed (step 16). That is, the cooling action of LPG by gasoline is stopped.

Thereafter, the LP is controlled by the fuel control as described above.
The engine is operated using G as fuel.

Because of the above, even when switching to LPG fuel, especially in the high temperature state of the engine, liquid L
Since PG can be supplied to the LPG injector 24, stable fuel injection becomes possible.

The example shown in FIG. 3 is an example in which LPG is used as the gas fuel, but the present invention can also be applied to the case of using CNG in place of this LPG.

When this CNG is used, the CNG in the heat transfer section 11 is in a gas state. Even in this case, the CNG in the gas state is cooled by the liquid fuel (gasoline) as described above, and stable CNG injection control from the CNG injector becomes possible.

[0044]

As described above, according to the present invention, the gas fuel supplied to the gas fuel injector is not overheated even when the engine is in a high temperature state. for that reason,
Gas fuel supplied in a liquefied state such as LPG can be supplied to the gas fuel injector in a liquefied state by suppressing its vaporization, and in gas fuel supplied in a gas state such as CNG, its density The change can be suppressed and supplied to the gas fuel injector. Therefore, stable injection control of gas fuel is possible even in a high temperature state of the engine.

According to the second aspect of the invention, the cooling action of the gas fuel can be enhanced.

According to the third aspect of the present invention, it is possible to prevent the temperature of the gas fuel from unnecessarily lowering and to reduce the power consumption of the liquid fuel pump.

According to the inventions of claims 4 and 5,
It is possible to provide a device that exhibits the above effects.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an entire system showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a heat transfer section in the present invention.

FIG. 3 is a flowchart showing an example of fuel control according to the present invention.

FIG. 4 is a diagram showing a conventional system.

[Explanation of symbols]

1 Internal combustion engine (engine body) 8 Liquid fuel tank 9 Liquid fuel pump 10 Liquid fuel supply path 10a Heat transfer path for liquid fuel 11 Heat transfer section 11a Member forming heat transfer section 13 Gas fuel tank 14 Gas fuel pump 15 Gas fuel supply path 15a Gas fuel heat transfer path 23 Liquid Fuel Injector 24 Gas fuel injector

Claims (5)

[Claims] 1. A fuel supply method for an internal combustion engine, wherein gas fuel and liquid fuel are switched and used according to operating conditions. In the gas fuel supply passage, the gas fuel is cooled by the liquid fuel upstream of the gas fuel injector. A method for supplying fuel in an internal combustion engine, comprising: 2. The fuel supply method for an internal combustion engine according to claim 1, wherein the liquid fuel is circulated through the liquid fuel tank to cool the gas fuel. 3. The liquid fuel is circulated through the liquid fuel tank when the temperature of the gas fuel on the upstream side of the gas fuel injector reaches or exceeds a preset value during use of the gas fuel. The method of supplying fuel in an internal combustion engine according to claim 2. 4. A fuel supply device for an internal combustion engine, which uses gas fuel and liquid fuel by switching between them depending on operating conditions, in a gas fuel supply passage upstream of a gas fuel injector, and a gas fuel supply passage and liquid fuel. A fuel supply device for an internal combustion engine, wherein the supply passage is arranged so that heat of the gas fuel is conducted to the liquid fuel. 5. A heat transfer section made of a heat transfer material is provided upstream of the gas fuel injector in the gas fuel supply path, and a gas fuel supply path and a liquid fuel supply path are provided in the heat transfer section.
The fuel supply device for an internal combustion engine according to claim 4, wherein the members forming the heat transfer section are formed as a common wall.