RELATED APPLICATION

Benefit is claimed to India Provisional Application No. 3507/CHE/2010, entitled "COMPRESSED NATURAL GAS (CNG) KIT FOR AT LEAST TWO WHEELED AUTOMOBILE" by Sandeep Shyamanur P, et Al., filed on November 22, 2010, which is herein incorporated in its entirety by reference for all purposes.

FIELD OF THE INVENTION

The present invention generally relates to the field of automobile. Particularly, the present invention relates to a compressed natural gas (CNG) kit for a four stroke engine for at least two wheeled automobile.

BACKGROUND OF THE INVENTION

The impact of using gasoline and diesel fuels in automobile engines has prone to increase air pollution, environmental damage, and health problems. Further, the gasoline fuels are non-renewable source of energy obtained from finite resources that will eventually dwindle and also becoming too expensive. Thereby, the need for alternative fuels has become greater. Accordingly, alternative fuels like gaseous fuels e.g., LPG, CNG, etc. have recently become attractive particularly for internal combustion engines for automotives in order to maximize fuel economy and minimize engine emissions.

Gaseous fuels hardly discharge any carbon monoxide (CO) as compared to gasoline and diesel since the exhaust fumes contains less harmful substance. According to emission test results, the CO emissions are around 80% less than gasoline and 40% less than the diesel. Hydrocarbon emissions are 60% less than the gasoline and 50% less than the diesel. Nitrous oxide emissions are around 80% less than the gasoline and 90% less than the diesel. Carbon dioxide which contributes to global warming is less.

The gaseous fuels like Compressed Natural Gas (CNG) have many advantages over gasoline fuels. The CNG is a fossil fuel substitute for gasoline and propane fuel. CNG is considered to be a more environmentally clean alternative to those fuels, and it is much safer than other fuels in the event of a spill. CNG fuel has better properties such as efficient combustion, lesser emission of gases with toxic materials, ability to give higher calorific values with good octane values. CNG has proven to be an excellent alternate for running the prime movers of automobiles nowadays due to a host of advantages such as abundant availability in nature, excellent compressibility, portability and yielding good calorific value and octane number with reduced quantum of toxic emissions coupled with complete burning after ignition. The composition of CNG is mainly methane (CH4) which constitutes about 90 to 95 % and other gases such as propane, iso-butane and butane.

The additional benefits of using of CNG as fuel for automobiles can be listed as being economical, being capable of burning out totally with no requirement of additives etc. The phenomenon of knocking experienced in engines when conventional fuels like gasoline are used and subsequent usage of lead compounds as anti knock additives resulting in poisonous emissions with flue gases can be eliminated while using CNG. The high octane value of CNG (around 130) enables it to qualify as a superior fuel and it is also capable of being burnt at hot and cold weather conditions unlike other fuels especially diesel which is known for its tendency to freeze down at lower temperatures for which additives are added to avoid it from getting frozen. CNG engines are superior in performance than engines run on gasoline fuel. Vehicles running on CNG fuel have superior starting and drivability, even under severe hot and cold weather conditions.

To overcome the limitations of usage of conventional gasoline fuels and derive the benefits of using CNG as fuel, the gasoline fuels in the automobiles has to be replaced by the CNG. However, most of the conventional automobiles include an engine which runs on gasoline fuels. Therefore, their exists a need for an conversion kit which can be fitted in the conventional vehicles to change the mode of working of the internal combustion engine using CNG as fuel.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to describe a compressed natural gas (CNG) kit for a four stroke engine for at least two wheeled automobile, which operates as an intermediate device for switching the internal combustion engine running on regular gasoline fuel to run on CNG fuel and vice versa, thus supporting efficient dual fuel system.

In one aspect, the present invention relates to a system including a cylinder for storing a high pressure CNG and coupled with a ON/OFF valve to control CNG flow, a first stage regulator coupled to the cylinder for reducing pressure of the high pressure CNG, and a second stage regulator for regulating low pressure CNG to a working pressure CNG. The system also includes a change over switch connected in series with the second stage regulator for switching the mode of fuel to be transferred to the four stroke engine, a pollution control unit coupled in series with the change over switch, wherein a metered amount of CNG is transferred according to different acceleration conditions of the four stroke engine; and a carburetor mixer for mixing the air with the CNG for the efficient working of the four stroke engine.

Accordingly, the present invention relates to a system wherein a knob in the change over switch facilitate changeover of fuel to the four stroke engine from gasoline to CNG and vice versa, and maintaining the dual fuel supply option to the vehicle at all times during operation.

Accordingly the present invention relates to the system consisting of an ignition cut off switch to cut off supply of fuel during accidents and while filling the fuel at the filling station.

In another aspect, the present invention relates to a method of supplying a CNG fuel for a automobile having at least two wheels including steps of sensing engine's accelerated condition and position of knob of a change over switch, regulating pressure of the CNG by a fist stage regulator and a second stage regulator till it reaches a pollution control unit (PCU), sensing a suction pressure in the PCU by a vacuum diaphragm through a vacuum connector connected between an engine manifold and the PCU through a vacuum hose, mixing exact amount of CNG with the air by a carburetor mixer, and supplying the mixture to the four stroke engine of the four stroke engine for two wheeled automobile for efficient running of the four stroke engine.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Example embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which:

Figure 1 illustrates a schematic diagram of a compressed natural gas (CNG) conversion kit for four stroke engine for at least two wheeled automobile, in accordance with the present invention;

Figure 2 illustrates an exploded view of a first stage regulator in the CNG conversion kit for four stroke engine for at least two wheeled automobile, in accordance with the present invention;

Figure 3 illustrates an exploded view of a second stage regulator in the CNG conversion kit for four stroke engine for at least two wheeled automobile, in accordance with the present invention;

Figure 4 illustrates a schematic representation of a fuel change over switch in the CNG conversion kit for four stroke engine for at least two wheeled automobile, in accordance with the present invention;

Figure 5 illustrates a schematic representation of a pollution control unit (PCU) in the CNG conversion kit for four stroke engine for at least two wheeled automobile, in accordance with the present invention;

Figure 6 illustrates an exploded view of a carburetor mixer in the CNG conversion kit for four stroke engine for at least two wheeled automobile, in accordance with the present invention; and

Figure 7 shows a line diagram of the CNG conversion kit assembly for four stroke engine for at least two wheeled automobile, in accordance with present invention.
Other features of the present embodiments will be apparent from the accompanying drawings and from the detailed description that follows.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to the compressed natural gas (CNG) conversion kit for a four stroke engine for at least two wheeled automobile. In one embodiment, the CNG conversion kit helps to switch over the internal combustion engine of for four stroke engine for at least two wheeled automobile running on gasoline fuel to run on a CNG fuel, thus supporting dual fuel system. The CNG gas from the cylinder passes through the regulators to a change over switch and to the input collar of pollution control unit (PCU) as such a metered quantity of fuel is delivered to the internal combustion engine of the four stroke engine for two wheeled automobile as per the four stroke engine's requirement.

The terms 'CNG kit' and 'CNG conversion kit' are used interchangeably throughout the document.

Figure 1 illustrates a schematic diagram of a CNG conversion kit for four stroke engine for four stroke engine for at least two wheeled automobile, in accordance with the present invention. The CNG conversion kit (100) includes a CNG cylinder (102), a first stage regulator (104), a second stage regulator (106), a change over switch (108), a pollution control unit (110), and a carburetor mixer (112) connected in series as shown in Figure 1. The CNG cylinder (102) is a seamless steel component made in heat process without any welding. The said cylinder (102) is fixed to the vehicle by means of cylinder clamps (114). The mechanical type of ON/OFF valve is fixed rigidly to the CNG cylinder (102) to control gas flow. It is designed to handle higher working pressure of CNG gas (e.g., up to 250 bar), wherein the CNG is stored at maximum pressure of 220 bar in the CNG cylinder (102). The valve has the threaded portion to hold the first stage regulator (104) in which the pressure is reduced to 4kg/cm2 rigidly.

Further, the low pressure CNG fuel passes to the second stage regulator (106) (wherein the pressure is reduced to 0.0208 kg/cm2) through a flexible hose (116) and then to the change over switch (108) through low pressure hose (118). The CNG then passes to the input collar of the PCU (110). The change over switch (108) selects the mode of fuel to be transferred (e.g., CNG from the cylinder (102) or gasoline from the petrol tank (134)). The PCU (110) includes idling adjusting screw (120) and a MFC adjusting screw (122) which plays a vital role during different acceleration condition of the four stroke engine (126).

The CNG fuel further flows to the carburetor mixer (112) through a vacuum hose (136) and a vacuum connector (138), wherein the air and fuel mixture takes place using the air filter (124) and which is then supplied to the four stroke engine (126) through the four stroke engine manifold (128) in a such way that a metered quantity of fuel is delivered to the internal combustion engine (126) of four stroke engine for two wheeled automobile as per its requirement. In addition, an ignition cut off switch (130) is provided to cut off the supply of the fuel during emergency and while filling the fuel at the filling station. Also, a gas pressure indicator (132) displays the pressure of CNG present in the CNG cylinder (102).

Figure 2 illustrates an exploded view of a first stage regulator (104) in the CNG conversion kit, m accordance with the present invention. The outer body of the first stage regulator (104) is made up of brass material. The first stage regulator (104) perform four major functions like fuel filling, fuel gauge, excess pressure relief and mainly gas flow pressure regulation mechanism, wherein the gas pressure is reduced to 4 bar. The low pressure gas is passed to the second stage regulator (106) through a pigtail hose (118).

The fuel filling valve is a fuel inlet path which works according to the mechanism of plug in and out. The mechanism has an ignition cut off switch (130) which senses removal of plug and shuts off the four stroke engine (126) by means of stopping ignition current for safety of fuel filling even in case of vehicle is in ON condition. After removing the plug, the fuel filling gun is inserted and fuel filled through a non-return valve towards the cylinder (102). Fuel flow automatically stops when pressure is equalized between filling station and the CNG cylinder (102), and hence the gun is removed. The non return valve stops gas flow in other direction and the filling cap plug is inserted back. The entire system is placed in safer environment with pressure relief valve. The fuel gauge is a pressure gauge which refers the gas pressure inside the cylinder (102) displayed on the gas pressure indicator (144). The gauge display gas pressure ranging from 0-300 bar. It is helpful to maintain filling and to gives alarm attention to the driver when the gas in the cylinder gets over.

The pressure relief valve releases excess pressure in case of emergency hike in pressure like due to external heat or damping. If the pressure reaches above 253 bar, the pressure relief valve releases nominal gas to the atmosphere to maintain the pressure inside the cylinder (102). The gas flow regulator reduces the gas pressure to 4 par pressure which is then delivered to the second stage regulator (106) (0.208 kg/cm2) through the pigtail hose (116). It has a pre-pressured spring and an injection type control valve which allows gas flow up to 4 bar. The major advantage of converting to low pressure is to avoid high pressure tubing which may cause major damage in case of accidents.

Figure 3 illustrates an exploded view of the second stage regulator (106) in the CNG conversion kit, in accordance with the present invention. The second stage regulator (106) is made up of cast zinc material. The second stage regulator (106) includes a spring loaded diaphragm to reduce the gas pressure below or equal to 0.0208kg/cm2 (600 water column pressure) which is the working pressure of the CNG flowing through the gas hose (118) to the PCU (110) to have an effective functioning. The gas hose (118) is made up of rubber material with threaded layers with the ID of 8mm, which is press fitted to the second stage regulator output and to fuel change over switch (108) inlet. The exploded view of the second stage regulator (106) includes the pig tail hose connector (302) to connect the CNG gas hose (118) to the second stage regulator (106), a regulator rubber washer (304), and an output collar (306) as shown in the Figure 3.

Figure 4 illustrates a schematic representation of a fuel change over switch (108) in the CNG conversion kit, in accordance with the present invention. The fuel change over switch (108) is purely a mechanical system made up of aluminum and Teflon fiber to help the movement of aluminum knob which changes fuel mode of gasoline and vise versa when necessary, by means of lever changing position. The fuel change over switch (108) includes a fuel mode indicating plate (402) which displays three options of fuel modes like gasoline, neutral and CNG. The automobilist can select the mode of fuel through the fuel selection lever (404) which the help of the display on the fuel mode indicating plate (402). The fuel mode indicating plate (402) and the fuel selection lever (404) are coupled by a stopper plate (406), the hose fixing clamp bolt (408), shaft (410) and the lock nut (412) as shown in Figure .4. The fuel mode is changed through the knob having a body having input collar ID of 6±0.1mm (414), a hose fixing clamp spring washer (416) and a hose fixing clamp nut (418).

Figure 5 illustrates a schematic representation of a pollution control unit (PCU) in the CNG conversion kit, in accordance with the present invention. The PCU (110) is a mechanical device having components to supply the fuel to the four stroke engine (126) as per the four stroke engine requirements without affecting the performance. The PCU (110) is regarded as the heart of the four stroke engine (126), which helps to give the finest, metered and well tuned supply of fuel to meet the required air fuel ratio. The PCU (110) meters the fuel supply as per the four stroke engine specific requirement and its speed. In general, the four stroke engine (126) converts the chemical energy of the fuel in association with ambient air to create the effective fuel burning to a heat energy which in turn is converted to a mechanical output.

The CNG gas from the second stage regulator (106) at the pressure of 0.0208 kg/cm2 is delivered to the PCU (110) based on which the fuel is metered to the four stroke engine (126) depending on its breathing conditions. The PCU (110) maps the four stroke engine (126) sectional power and RPM so as to deliver an appropriate fuel ratio proportional to air to the inlet manifold. The exploded view of the PCU (110) shows the different mechanical components for working of the PCU (110). The said mechanical components includes an atmosphere diaphragm (502), a PCU bottom (504), a screw (506), a PCU top (508), a MFC adjusting plate washer (510), a MFC adjusting screw (512), a MFC adjusting rubber washer (514), a MFC spring (516), an idling adjusting spring (518), an idling adjusting screw (520), a body fixing spring washer (522), a body fixing bolt (524), an input/MFC collar cap (526), and a vacuum collar cap (528) which are connected as shown in Figure 5.

When the four stroke engine (126) gets started, the vacuum diaphragm senses a suction pressure in the PCU (110) through the vacuum connector, which has the ID of 2.5 ±0.1 mm, connected between the four stroke engine manifold (128) and the PCU (110) through a vacuum hose. The said operation allows the opening of ON/OFF rubber valve, mounted over the control lever, which seats on the input bush of the ID 5 in the PCU (110). This rubber valve allows the flow of fuel through the MFC to the four stroke engine (126) through the carburetor mixer (112). The four stroke engine (126) vacuum also acts on the atmosphere diaphragm (502), made up of polythene calendared by nitrile rubber of 'A' grade 40, which helps control the gas flow as per the four stroke engine (126) requirement. The PCU (110) also works as backfire deflector. When backfire takes place in the four stroke engine (126), a positive wave is created in the four stroke engine (126) manifold which pushes the vacuum diaphragm and simultaneously stops supply of fuel. Because of this, there is no possibility of the fame entering the cylinder (102).

Figure 6 illustrates an exploded view of a carburetor mixer (112) in the CNG conversion kit, in accordance with the present invention. The carburetor mixer (112) is a device which mixes air and fuel, passes the mixture to the four stroke engine (126) of the vehicle. The orifice type of carburetor mixer (112) is placed next to the PCU (110) inline and intakes fuel by a collar (602) of ID 5+0.2mm. This unit facilitates the inflow of gas into the carburetor mixer (112), only at this point a correct amount of air is drawn from the air filter (124) by reducing the inlet diameter to 18mm of the vehicle. The carburetor mixer (112) is made of aluminum alloy die cast material.

The exploded view of the carburetor mixer (112) includes a collar (602), a carburetor mixer body (604), a carburetor mixer sleeve (606), a carburetor mixer nut (608), a carburetor mixer clamp (610) and a carburetor mixer clamp bolt (612) as shown in Figure 6. The requirements of air fuel mixtures, viz., rich mixture as well as lean mixture depend upon the conditions of operation of the vehicle (cold or normal operating conditions). It is to be noted that during operations such as cold starting of the vehicle, the four stroke engine may require a richer mixture to enable the vehic/e start especially in case of spark assisted ignition engines.

Figure 7 shows a line diagram of the of the CNG conversion kit assembly in a four stroke engine for two wheeled automobile, in accordance with present invention. As shown in the figures, the kit fits to the space available in the vehicle and hence, no extension in the vehicle is needed:

We Claim:
1. A Compressed Natural Gas (CNG) kit for a four stroke internal combustion (IC) engine of at least two wheeled automobile comprising:

a cylinder containing a high pressure CNG;

a first stage regulator coupled to the cylinder configured to reduce the high pressure CNG to a low pressure CNG;

a second stage regulator coupled to the first stage regulator configured for regulating the low pressure CNG to the working pressure CNG;

a change over switch connected with the second stage regulator configured for selecting a mode of fuel to be transferred to the four stroke IC engine;

a pollution control unit (PCU) coupled with the change over switch configured for transferring metered amount of CNG according to different acceleration conditions of the four stroke engine; and

a carburetor mixer coupled with the pollution control unit configured for mixing atmospheric air with the CNG for the efficient working of the four stroke IC engine.

2. The system as claimed in claim 1, wherein the CNG gas pressure is regulated in two stages by the first stage regulator and the second stage regulator considering safety aspects and to provide working pressure for an effective functioning.

3. The system as claimed in claim 1, wherein a knob in the change over switch facilitate changeover of fuel to the four stroke IC engine from gasoline to CNG and vice versa, maintaining the dual fuel supply option to the vehicle at all times during operation.

4. The system as claimed in claim 1, wherein the flow of CNG from the cylinder to the two stages of pressure regulators, the PCU, the carburetor mixer and to the four stroke IC engine is enabled by suitable tubular means such as hose.

5. The system as claimed in claim 1, wherein the system consists of an ignition cut off switch to cut off the supply of the fuel during accidents and while filling the fuel at the filling station.

6. A method of supplying a compressed natural gas (CNG) fuel for four stroke

engine for at least two wheeled automobile comprising steps of:

sensing an acceleration condition of a four stroke IC engine and a position of knob of the change over switch;

regulating the pressure of the CNG by a fist stage regulator and a second stage regulator till it reaches a working pressure;

sensing a suction pressure in a pollution control unit by a vacuum diaphragm through a vacuum connector; and

supplying an exact amount of CNG mixed with air by a carburetor mixer to the four stroke IC engine.