JPH0730344U - Dual fuel engine - Google Patents

Abstract

(57) [Summary] (Modified) [Objective] To provide a dual fuel engine with a simple structure, low cost, and high thermal efficiency. [Composition] Compressed natural gas (C
NG) In an area where the load is small with the injector 11 that supplies fuel, a carburetor 13 that supplies gasoline fuel, a throttle valve opening sensor 18 that detects the opening of the throttle valve 12, and an engine rotation sensor 19 that detects the engine speed Load detecting means for detecting the load of the vehicle, and gasoline fuel and CN depending on the size of the load.
A dual-fuel engine, comprising: a fuel stop valve 15 that alternately switches between G fuel and G fuel.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a dual-fuel engine that supplies gas fuel at high load and liquid fuel at low load to switch between gas fuel and liquid fuel.

[0002]

[Prior art]

 Conventionally, in an engine that uses gasoline as a fuel (a representative fuel of the above liquid fuel), a method of setting a high compression ratio has been adopted as a measure to improve the thermal efficiency of the engine. There is a problem that abnormal combustion occurs and the output cannot be increased. In response to this, fuel with high knock resistance has been used, but in recent years, a desirable fuel for the global environment has been sought, and natural gas has attracted attention as a fuel to replace gasoline. A high compression ratio engine that uses compressed natural gas (hereinafter referred to as CNG) having a higher octane number as a fuel has been proposed. Since CNG contains methane gas as a main component, it cannot be stored in a liquid state at room temperature like LPG (liquefied petroleum gas), and therefore, it is compressed in a gas state and filled in a cylinder. This CNG fuel has a low energy storage density per 1 kilogram of fuel tank, which is assumed to be the fuel tank of a gasoline vehicle, which is about 20% lower than that of gasoline fuel, so the mileage per cylinder filling is short and the usage is special. Limited to use. Under these circumstances, recently, a vehicle is being developed in which gas fuel and liquid fuel can be switched and used. As an example of use in such a vehicle engine, Japanese Patent Laid-Open No. 63-68728 discloses an engine in which liquid fuel and CNG are switched and supplied according to a driving state. .

[0003]

[Problems to be solved by the device]

 However, in the engine as described above, CNG fuel has a short mileage in a practical vehicle, and frequent fuel supply becomes a problem. Further, in the above-described binary fuel engine, since the compression ratio is changed depending on the type of fuel, there is a problem that the structure is very complicated and the cost is high. In view of such conventional problems, the present invention provides a dual fuel engine that can reduce the number of times of refueling CNG fuel, has a simple structure, is low in cost, and has high thermal efficiency. To aim.

[0004]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the present invention provides a dual fuel engine including a means for supplying a gas fuel, a means for supplying a liquid fuel, and a switching means for switching the fuel supply means. The compression ratio is set to a high compression ratio suitable for gas fuel, while the engine load detection means is provided, and when the load detected by this is equal to or greater than the preset load judgment value, the switching means is switched to gas. It is characterized in that the fuel is switched to the fuel, and the switching means is switched to the liquid fuel when the load judgment value is equal to or less than the load judgment value.

[0005]

[Action]

 According to the above configuration, the compression ratio of the engine is set to a high compression ratio suitable for gas fuel with a high octane number, but liquid fuel is supplied in the middle and low load range where knocking is less likely to occur, and knocking easily occurs. When the high load area is entered, the liquid fuel is automatically switched to the gas fuel supply. Therefore, the liquid fuel can be used under a high compression ratio, and lean combustion with high thermal efficiency can be performed. In addition, since gas fuel is consumed only under high load, the number of refueling cycles can be reduced, and since it is not necessary to change the compression ratio according to the type of fuel, the structure is simple, and the dual fuel engine can be manufactured at a low cost. Can be achieved.

[0006]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. In the figure, 1 is a dual fuel engine, 2 is a cylinder block of the engine 1, 3 is a cylinder head, and 4 is a combustion chamber formed on a cylinder 5 below the cylinder head 3. An intake port 6 and an exhaust port 7 are opened on both sides of the ceiling of the combustion chamber 4, and are opened and closed by an intake valve 8 and an exhaust valve 9 at predetermined timings. An ignition plug 10 is arranged near the top of the ceiling of the combustion chamber 4. Further, the intake port 6 is provided with an intake pipe having an injector 11 (gas fuel supply means) for injecting CNG fuel, a throttle body having a throttle valve 12 attached thereto, and a carburetor 13 (liquid fuel supply means) for supplying gasoline fuel. ) Are sequentially connected to form the intake system 14 of the engine 1. Further, a gasoline fuel stop valve 15 in which gasoline fuel supplied to the carburetor 13 is controlled to be shut off or connected by a control device described later is connected from the gasoline fuel tank to the carburetor 13. It is arranged in the middle of the supply pipe 16.

On the other hand, 17 is a control device having a computer for controlling the injection amount of the CNG fuel of the injector 11 according to the operating condition of the engine and controlling the injection stop of the injector 11. The control device 17 reads each output signal from a load detecting means, which is composed of a throttle valve opening sensor 18 for detecting a throttle valve opening and an engine rotation sensor 19 for detecting an engine speed, which are inputted to the control device 17. A switch composed of the injector 11 and the stop valve 15 for calculating the load of the engine and switching the supply of the gasoline fuel and the CNG fuel to the engine 1 based on the load judgment value preset in the control device 17. I try to control the means.

The operation of the dual fuel engine 1 configured as above will be described. When the engine 1 is in operation, the control device 17 reads output signals from the throttle valve opening sensor 18 that detects the throttle valve opening and the engine rotation sensor 19 that detects the engine speed. When the load is calculated and it is determined that it is larger than the load determination value stored in the control device 17 in advance, the compression ratio of the engine 1 is set to a high compression ratio (for example, 14 to 15) suitable for CNG fuel. Therefore, at such a high load, abnormal combustion such as knocking is likely to occur in gasoline fuel, so the control device 17 sends a stop signal to the gasoline to switch the fuel supplied to the engine 1 to CNG fuel having high knock resistance. The fuel is sent to the stop valve 15, and the stop valve 15 is closed to cut off the gasoline fuel. At the same time, the injector 11 Sends a normal operation signal from the control device 17 to inject the CNG fuel into the engine 1, and when it is determined that the load of the engine 1 is smaller than the load determination value, the injector of the computer of the control device 17 is used. 11 to stop the injection of CNG fuel to the engine 1, and at the same time, send a signal from the control device 17 to open the gasoline fuel stop valve 15 to the stop valve 15 and open the stop valve 15 to open the gasoline fuel. The supply pipe 16 is communicated with the carburetor 13 so that gasoline fuel is supplied to the engine 1 by a normal carburetor operation.

In this embodiment, the CNG fuel is supplied by the injector 11 and the gasoline fuel is supplied by the carburetor 13. However, the invention is not limited to this, and the gasoline fuel is supplied by the injector 11 and the CNG fuel is supplied. A supply means for supplying this with a mixer for mixing this with air may be used. Further, it may be a supply means configured to inject both CNG and gasoline fuel with an injector. Further, although gasoline and CNG have been described as the binary fuel, the present invention is not limited to these, and other liquid fuel or gas fuel may be used. For example, combinations of methanol and CNG, LPG and CNG, gasoline and other high octane number gas can be mentioned.

[0010]

[Effect of device]

 As described above, according to the present invention, the compression ratio of the engine is set to a high compression ratio suitable for CNG fuel with a high octane number, and both CNG and gasoline fuels are switched according to the load of the engine. A simple, inexpensive, high thermal efficiency, low-pollution engine with lean combustion can be achieved, and since CNG fuel is used only in the high load range, the consumption of CNG fuel is small and fuel supply is possible. The effect of reducing the number of times is also obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a system configuration of a dual fuel engine according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Dual fuel engine 11 Injector (fuel supply means and switching means) 12 Throttle valve 13 Carburettor (fuel supply means) 15 Stop valve (switching means) 17 Control device 18 Throttle valve opening sensor (load detection means) 19 Engine rotation sensor (Load detection means)

Claims (1)

[Scope of utility model registration request] 1. A dual fuel engine comprising a means for supplying a gas fuel, a means for supplying a liquid fuel, and a switching means for switching the fuel supply means, the compression ratio of the engine being a high value suitable for the gas fuel. When the compression ratio is set and the load detection means of the engine is provided, the switching means is switched to the gas fuel when the load detected by the engine is equal to or more than a preset load determination value, and the load is less than or equal to the load determination value. The dual fuel engine is characterized in that the switching means is switched to liquid fuel.