Description SYSTEM FOR USING WASTE ENERGY OF HYBRID VEHICLE

COMPRISING INNER COMBUSTION ENGINE, HYBRID

SYSTEM, AND SYSTEM FOR USING WASTE ENERGY OF

INNER COMBUSTION ENGINE FOR GENERATING

ELECTRIC ENERGY Technical Field

[1] The present invention relates to a system for using waste energy of a hybrid vehicle comprising an inner combustion engine, a hybrid system, and a system for using waste energy of an inner combustion engine for generating electric energy. Background Art

[2] Due to the fact that fossil fuel reserves are finite and exhaust gas generated from fossil fuel causes environmental pollution, various measures have been sought, which can increase the thermal efficiency of vehicles and reduce an amount of generated exhaust gas. A representative outcome thereof is a hybrid vehicle. In such a hybrid vehicle, an inner combustion engine and an electric motor are selectively used to drive the hybrid vehicle. More specifically, the hybrid vehicle is driven by electric energy stored in a battery in an interval where efficiency is low when the hybrid vehicle is driven by the inner combustion engine. Further, the hybrid vehicle is driven by the inner combustion engine in an interval where efficiency is high when the hybrid vehicle is driven by the inner combustion engine. Simultaneously, a battery connected to the inner combustion engine is charged with electric energy. Therefore, it is possible to reduce a used amount of fossil fuel and to increase the heat-exchange efficiency of the vehicle.

[3] A representative example of such a hybrid vehicle is disclosed in Korea Patent Registration No. 0136743. FIG. 1 is a diagram showing the construction of the hybrid vehicle disclosed in Korea Patent Registration No. 0136743. As shown in FIG. 1, the conventional hybrid vehicle includes an electric motor 10 for driving the vehicle, a battery 20 for supplying electric power to the electric motor 10, a generator 30 for charging the battery, an inner combustion engine 40 which is separated from the electric motor 10 so as to drive the generator 30, a starting device 44 of the inner combustion engine 40, and an exhaust gas purifying device 42. The conventional hybrid vehicle is driven by the inner combustion engine in an interval where the driving efficiency of the inner combustion engine 40 is excellent, for example, in a constant-speed driving interval (more than 60km/h). Further, in an interval where the

driving efficiency of the inner combustion engine 40 is not excellent, or in an interval where a large quantity of pollutants is included in exhaust gas, for example, in an initial driving interval of the engine or an engine idle interval, the inner combustion engine 40 is stopped, and the hybrid vehicle is driven by the electric motor 10 using electric energy stored in the battery 20. In addition, when the inner combustion engine 40 is driven, the generator 30 is driven by the inner combustion engine so as to generate electric energy such that the battery 20 is charged with the electric energy.

[4] In the conventional hybrid vehicle, when the inner combustion engine 40 is driven, exhaust gas having a higher temperature than normal-temperature air is generated. However, the exhaust gas is discharged to the external air as it is. Further, to reduce the pressure and temperature of the exhaust gas, a separate component should be provided in the vehicle. Therefore, there is a fundamental limit in increasing the thermal efficiency of the vehicle. Further, there has not been provided an effective and realizable system which recovers waste heat of an inner combustion engine and additionally converts the recovered waste heat into energy. Disclosure of Invention Technical Problem

[5] The present invention provides a system for using waste energy of a hybrid vehicle comprising an inner combustion engine, which recovers waste heat discarded when an exhaust stroke of the inner combustion engine is performed or the respective components of the inner combustion engine are cooled down, thereby maximizing heat energy conversion efficiency, a hybrid system, and a system for using waste energy of an inner combustion engine for generating electric energy. Technical Solution

[6] According to an aspect of the invention, there is provided a system for using waste energy of a hybrid vehicle having an inner combustion engine, the hybrid vehicle including an electric motor for driving the hybrid vehicle; a battery for supplying electric power to the electric motor; a first generator for charging the battery; an inner combustion engine that is separated from the electric motor so as to selectively drive the first generator or directly drive the hybrid vehicle; and an exhaust unit for discharging exhaust gas generated from the inner combustion engine. The system comprises a first heat exchanger that heat-exchanges the exhaust gas, discharged by the exhaust unit, with first working fluid; a burner that selectively heats the first working unit heat-exchanged with the exhaust gas; a turbine that is driven by the first working fluid which is selectively heated by the burner after being heat-exchanged with the exhaust gas; a second generator that is driven with the turbine so as to generate electric energy; a cooling unit that cools down the first working fluid passing through the

turbine; and a power sending unit that sends the electric energy generated by the second generator to the battery.

[7] The range of variation in amount and temperature of exhaust gas of a vehicle is significantly different depending on a driving state of the vehicle. Therefore, the burner for heating the first working fluid such that the first working fluid reaches a temperature enough to drive the turbine is mounted so as to assist the waste heat recovery through the driving of the turbine. Accordingly, when the first working fluid heat-exchanged with the exhaust gas does not reach a temperature enough to drive the turbine, for example, when the first working fluid does not reach the boiling point thereof immediately after being heat-exchanged with the exhaust gas, the burner between the turbine and the first heat exchanger additionally heats the exhaust gas such that the exhaust gas can reach a temperature enough to drive the turbine.

[8] The vehicle may include various vehicles such as a car, a train and so on.

[9] In this structure, waste heat included in the exhaust gas is recovered by the first working fluid and is then used to rotate the turbine such that secondary power generation is performed. Therefore, waste heat generated from the inner combustion engine is recovered, which makes it possible to further increase the thermal efficiency of the hybrid vehicle.

[10] Preferably, the system further comprises a temperature measuring unit that measures the temperature of the first working fluid. The burner heats the first working fluid, when the temperature of the first working fluid passing through the first heat exchanger is equal to or less than a boiling point thereof.

[11] Depending on the driving condition of the engine, the temperature of exhaust gas may change in a wide range. Further, the temperature of the first working fluid, which is heat-exchanged with the exhaust gas, may change depending on the driving condition of the vehicle. Therefore, as described above, the driving of the burner is controlled depending on the temperature of the first working fluid. Accordingly, it is possible to further increase the efficiency of the system for using waste energy of a hybrid vehicle having an inner combustion engine.

[12] Preferably, the system further comprises a heat absorbing unit that absorbs heat around the inner combustion engine by using second working fluid; a heat storage tank that stores the second working fluid passing through the heat absorbing unit; a circulation line that is disposed in such a manner that the second working fluid circulates through the heat storage tank and the heat absorbing unit; a diverging line that diverges at a diverging point on the circulation line such that the second working fluid is introduced into the heat storage tank after being heat-exchanged with the first working fluid introduced into the burner; and a second- working-fluid circulation system having a diverging valve disposed at the diverging point.

[13] In this structure, the second working fluid heated by the inner combustion engine is stored and circulated. Then, the second working fluid is heat-exchanged with the first working fluid such that waste heat discarded around the inner combustion engine is also recovered. Therefore, it is possible to further increase the thermal efficiency of the hybrid vehicle.

[14] Preferably, a cooling line through which cooling fluid for cooling down the inner combustion engine flows is constructed so as to pass through the heat storage tank, and the exhaust unit is constructed so as to pass through the heat storage tank such that the second working fluid within the heat storage tank is heat-exchanged with exhaust gas and cooling water.

[15] In this structure, waste heat discarded around the inner combustion engine is recovered by the second working fluid such that cooling heat of the inner combustion engine, which is recovered by the cooling line when the first working fluid is heated, is also used. Therefore, it is possible to further increase the thermal efficiency of the hybrid vehicle.

[16] Preferably, the system further comprises a temperature measuring unit that measures the temperature of the second working fluid such that the diverging valve introduces the second working fluid into the diverging line when the temperature of the second working fluid is equal to or more than a predetermined temperature.

[17] In this structure, only when the temperature of the second working fluid is higher than that of the first working fluid, the second working fluid is heat-exchanged with the first working fluid such that the first working fluid, which should drive the turbine through the heat exchange with the second working fluid, is prevented from being deprived of heat.

[18] Preferably, the first working fluid is a material of which the boiling point is lower than that of water.

[19] When such a material as ammonia or alcohol, of which the boiling point is lower than that of water, is used as the first working fluid, the first working fluid heated by the exhaust gas can be phase-changed into gas even at a relatively low temperature. Accordingly, when the turbine is driven by the first working fluid, a high-temperature heat source is not necessary.

[20] Preferably, the turbine is a micro turbine. When the turbine is composed of a micro turbine, the volume and weight of the system for using waste energy of a hybrid vehicle having an inner combustion engine can be reduced, which makes it possible to easily apply the system to the hybrid vehicle.

[21] According to another aspect of the invention, a hybrid system comprises an inner combustion engine; a first generator that converts at least a portion of driving force, generated from the inner combustion engine, into electric energy; and a second

generator that operates separately from the first generator. The second generator converts waste energy, included in exhaust gas of the inner combustion engine, into electric energy. Preferably, the inner combustion engine is constructed to recover waste heat generated from a gasoline or diesel engine for driving a vehicle. Accordingly, waste heat of the inner combustion engine, which has been discarded as exhaust gas in the conventional system, is recovered so that energy efficiency increases.

[22] According to a further aspect of the invention, a system for using waste energy of an inner combustion engine for generating electric energy comprises an electric energy collecting unit; a first generator for supplying electric energy to the electric energy collecting unit; an inner combustion engine for driving the first generator; an exhaust unit for discharging exhaust gas generated from the inner combustion engine; a first heat exchanger that heat-exchanges the exhaust gas, discharged by the exhaust unit, with first working fluid; a turbine that is driven by the first working fluid heat- exchanged with the exhaust gas; a second generator that is driven with the turbine so as to generate electric energy; and a power sending unit that sends the electric energy, generated by the second generator, to the electric collecting unit.

[23] Preferably, the system further comprises a heat absorbing unit that absorbs heat around the inner combustion engine by using second working fluid; a heat storage tank that stores the second working fluid passing through the heat absorbing unit; a circulation line that is disposed in such a manner that the second working fluid circulates through the heat storage tank and the heat absorbing unit; a diverging line that diverges at a diverging point on the circulation line such that the second working fluid is introduced into the heat storage tank after being heat-exchanged with the first working fluid; and a second- working-fluid circulation system having a diverging valve disposed at the diverging point.

[24] Preferably, a cooling line through which cooling fluid for cooling down the inner combustion engine flows is constructed so as to pass through the heat storage tank, and the exhaust unit is constructed so as to pass through the heat storage tank such that the second working fluid within the heat storage tank is heat-exchanged with exhaust gas and cooling water.

[25] Preferably, the system further comprises a temperature measuring unit that measures the temperature of the second working fluid such that the diverging valve introduces the second working fluid into the diverging line when the temperature of the second working fluid is equal to or more than a predetermined temperature.

[26] Preferably, the first working fluid is a material of which the boiling point is lower than that of water.

[27] Preferably, the turbine is a micro turbine.

Advantageous Effects

[28] According to the present invention, waste heat included in exhaust gas generated from the inner combustion engine is recovered, which makes it possible to increase the heat energy conversion efficiency of the vehicle.

[29] Further, waste heat discharged around the inner combustion engine is recovered, which makes it possible to increase the heat energy conversion efficiency of the vehicle.

[30] Furthermore, waste heat discharged through cooling fluid for cooling down the inner combustion engine is recovered, which makes it possible to increase the heat energy conversion efficiency of the vehicle. Brief Description of the Drawings

[31] FIG. 1 is a diagram showing the construction of a conventional hybrid vehicle driving system.

[32] FIG. 2 is a diagram illustrating a system for driving a hybrid vehicle, to which a system for using waste energy of an inner combustion engine according to the invention is applied. Best Mode for Carrying Out the Invention

[33] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[34] FIG. 2 is a diagram illustrating a system for driving a hybrid vehicle, to which a system for using waste energy of an inner combustion engine according to the invention is applied.

[35] As shown in FIG. 2, the system for driving a hybrid vehicle includes an electric motor 33 for driving the hybrid vehicle; a battery 19 for supplying electric power to the electric motor 33; a first generator 14 for charging the battery 19; an inner combustion engine 29 which is separated from the electric motor 33 so as to selectively drive the first generator 14 or directly drive the vehicle; and an exhaust unit for discharging exhaust gas generated from the inner combustion engine 29, the exhaust unit having an exhaust gas collecting tube 11, an exhaust manifold 5 and so on. The first generator 14 is constructed so as to convert a portion of torque of an engine output shaft 13 of the inner combustion engine 29 into electric energy, unlike a second generator 6 which will be described below. Meanwhile, the exhaust unit includes an exhaust line for collecting and discharging exhaust gas and a catalyst for purifying exhaust gas. In the above-described conventional hybrid vehicle, the inner combustion engine 29 and the driving electric motor 33 are selectively used to drive the hybrid vehicle in an interval where efficiency is more excellent. In an interval where the efficiency is more excellent when the vehicle is driven by the inner combustion engine 29, the inner

combustion engine 29 transmits the output torque to a driven shaft 31 or the first generator 14 of the vehicle by a power division mechanism 30. Further, when the output torque of the engine output shaft 13 of the inner combustion engine 29 is transmitted to the driven shaft 31 of the vehicle, the output torque is transmitted through a decelerator 32 having first and second deceleration gears. The first deceleration gear is rotated by the engine output shaft 13 of the inner combustion engine 29, and the second deceleration gear is geared with the first deceleration gear so as to transmit an output to the driven shaft 31. In this case, the engine output of the inner combustion engine 29 is transmitted through the power division mechanism 30 to the decelerator 32, the first generator 14 and so on by power transmission shafts 15. Further, the driving electric motor 33 also transmits power to the decelerator 32 through the power transmission shafts 15. The electric energy generated by the first generator 14 is stored in the battery 19 through an inverter 17 having a rectifying unit for rectifying an alternating current. The inverter 17, the battery 19, and the driving electric motor 33 are connected to an electric energy transmission cable 18 for transmitting electric energy. The driven shaft 31 has wheels 34 mounted thereon so as to drive the vehicle.

[36] The system for driving a hybrid vehicle, to which the system for using waste energy of a hybrid vehicle having an inner combustion engine according to the invention is applied, further includes a burner 27 which heats first working fluid; a turbine 8 which drives a second generator 6 while being rotated by the first working fluid heated by the burner 27; the second generator 6 which is driven by the turbine 8 so as to generate electric energy; a cooling unit 23 which cools down the first working fluid passing through the turbine 8; an electric power sending unit having a rectifying section (inverter) 22 for rectifying a current generated by the second generator 6 and wiring lines 26 for sending the rectified current to the battery 19; a first heat exchanger 12 which is disposed in such a manner that exhaust gas discharged by the exhaust unit is heat-exchanged with the first working fluid; and a temperature measuring unit (not shown) which measures the temperature of the first working fluid. The first working fluid is heat-exchanged with exhaust gas of the inner combustion engine 29 by the first heat exchanger 12 and is then evaporated to rotate the turbine 8. Then, the second generator 6 driven with the turbine 8 generates electric energy. In this case, the temperature of the exhaust gas of the inner combustion engine 29 varies depending on a driving state of the inner combustion engine 29 or the like. Therefore, when the exhaust gas does not reach a temperature enough to perform the generation of electric power using the turbine 8, the burner 27 is disposed so as to additionally increase the temperature of the exhaust gas. To turn on/off the burner 27, the temperature measuring unit is provided in an arbitrary space of a first working-fluid transfer pipe

disposed between the first exchanger 12 and the burner 27. As for the temperature measuring unit, various typical devices which are widely known for temperature measurement can be adopted. Preferably, the first working fluid is heated to a temperature close to a boiling point, through the heat exchange with the exhaust gas. Therefore, fluid with a low boiling point is selected as the first working fluid. For example, ammonia can be adopted. The turbine 8 is composed of a micro turbine, thereby contributing to reducing the volume and weight of the generation system using the first working fluid. Therefore, the generation system can be easily mounted on the vehicle. The cooling unit 23 can be composed of an air cooling device or water cooling device, which is widely known. Preferably, a pump 28 for circulating the first working fluid is disposed between the cooling unit 23 and the heat exchanger 12.

[37] The system for driving a hybrid vehicle, to which the system for using waste energy of a hybrid vehicle having an inner combustion engine according to the invention is applied, not only recovers waste heat included in the exhaust gas of the inner combustion engine 29 by using the generation system using the first working fluid, but also recovers waste heat discharged into the air when a cylinder and a cylinder head (not shown) of the inner combustion engine 29 are heated and cooled down. Therefore, thermal efficiency further increases. As shown in FIG. 2, the system further includes a heat absorbing unit 40 which heat-insulates and seals the inner combustion engine 29 and recovers heat discharged to the air around the inner combustion engine 29 by flowing second working fluid around the inner combustion engine 29; a heat storage tank 43 in which the second working fluid passing the heat absorbing unit 40 is introduced and stored; circulation lines 10 and 20 which are disposed in such a manner that the second working fluid circulates through the heat storage tank 43 and the heat absorbing unit 40; a diverging line 9 which diverges at a diverging point of the circulation lines 10 and 20 such that the second working fluid is introduced into the heat storage tank 43 after being heat-exchanged with the first working fluid introduced into the burner 8; and a second working fluid circulation system having a diverging valve 7 disposed at the diverging point. Preferably, a pump 24 for circulating the second working fluid is disposed on the circulation lines 10 and 20. Preferably, the heat storage tank 43 has a second working fluid inlet 2 for exchanging and filling up the second working fluid. As for the second working fluid, any fluid for heat storage, such as water or air, can be selected.

[38] Meanwhile, the conventional inner combustion engine 40 has a cooling unit which protects the inner combustion engine and maximizes the efficiency of energy conversion cycle. In a typical inner combustion engine with a four-stroke cycle, a pipe through which cooling water circulates is constructed so as to pass around the inner combustion engine, and the cooling water is circulated by a cooling water circulating

pump 25. In the present invention, even the heat discarded by cooling water is used, thereby further increasing the thermal efficiency of the hybrid vehicle. That is, a cooling line 21 for cooling down the inner combustion engine 29 is constructed to pass through the heat storage tank 43, and the exhaust unit is also constructed to pass through the heat storage tank 43. Further, a portion of the cooling line 21 disposed inside the heat storage tank 43 and a portion of the exhaust unit disposed inside the heat storage tank 43 are constructed in such a manner that the second working fluid within the heat storage tank 43 can be heat-exchanged with exhaust gas and cooling water. The heat exchange efficiency of three kinds of fluids can be implemented by referring to a heat exchanger of a domestic boiler which is constructed in such a manner that combustion gas, hot water, and warm water are heat-exchanged.

[39] In the system for using waste energy of a hybrid vehicle having an inner combustion engine according to the invention, the diverging valve 7 is composed of a 3-way valve, and a temperature measuring unit is further provided to measure the temperature of the second working fluid such that the second working fluid is introduced into the diverging line 9 when the temperature of the second working fluid flowing in the circulation lines 10 and 20 are equal to or more than a predetermined temperature. In this structure, while the second working fluid stored in the heat storage tank 43 circulates through the heat absorbing unit 40 around the inner combustion engine 40, the second working fluid receives heat from the exhaust gas, the cooling water, and the air around the inner combustion engine 40. Then, when the second working fluid reach a predetermined temperature, the temperature of the first working fluid introduced into the burner 27 can be increased. At this time, when the temperature of the second working fluid is higher than that of the first working fluid introduced into the burner 27, the diverging valve 7 opens an outlet facing the diverging line and closes an outlet facing the heat storage tank such that the second working fluid is heat-exchanged with the first working fluid. In this case, the temperature measuring unit for measuring the temperature of the second working fluid can be composed of a temperature sensor 4 disposed in the heat storage tank or a temperature sensor (not shown) disposed at an arbitrary position selected between the second- working-fluid circulation lines 10 and 20.

[40] Now, the operation of the system for using waste energy of a hybrid vehicle having an inner combustion engine according to the invention will be described. In an initial driving interval of the vehicle or a vehicle idle state where the vehicle driving efficiency of the inner combustion engine is relatively low, the driving motor 33 is driven by electric energy stored in the battery 19 so as to drive the driven shaft 31 of the vehicle. Further, in a constant speed driving interval of the inner combustion engine 29 where the vehicle is driven at the economical speed of 60 to 100km/h, the

inner combustion engine 29 drives the first generator 14 and the vehicle driving shaft 31 such that electric energy is stored, and simultaneously, the vehicle is driven. At this time, the exhaust gas of the inner combustion engine 29 is heat-exchanged with the first working fluid by the first heat exchanger 12, and is then heat-exchanged with the second working fluid in the heat storage tank 43, while the exhaust gas is discharged to the air in the conventional system. Meanwhile, the first working fluid, which has acquired heat energy from the exhaust gas in the first heat exchanger 12, is additionally and selectively heated by the burner 27 and then drives the turbine 8 such that the second generator 6 connected to the turbine 8 additionally generates electric energy. Then, the generated electric energy is sent to the battery 19. Meanwhile, the second working fluid circulates while absorbing heat around the inner combustion engine 29. Then, the second working fluid is again heat-exchanged with the exhaust gas and cooling fluid (cooling water) in the heat storage tank 43 such that the temperature thereof gradually increases. When the temperature of the second working fluid becomes higher than that of the first working fluid introduced into the burner 27, the second working fluid is heat-exchanged with the first working fluid along the diverging line 9 so as to increase the temperature of the first working fluid for driving the turbine 8.

[41] Up to now, the system for using waste energy of a hybrid vehicle according to the present invention has been described. However, a system for using waste energy of an inner combustion engine according to another embodiment of the invention can be im plemented by referring to the system for using waste energy of a hybrid vehicle. The construction of the system for using waste energy of an inner combustion engine according to the invention is almost the same as that of the system for using waste energy of a hybrid vehicle, except that the burner 27 and the components for driving a vehicle using the inner combustion engine, that is, the power division mechanism 30, the battery 19, the electric motor 33 and so on are not provided. In this case, the electric energy generated by the first and second generators 14 and 16 can be collected by an electric energy collecting unit, for example, an electric energy sending unit including electric wires and an electric transformer or a separate battery.

[42] While the present invention has been described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications in form and detail may be made therein without departing from the scope of the present invention as defined by the following claims.

[43]

Industrial Applicability

[44] The present invention can be applied to a hybrid system in which an inner

combustion engine and an electric motor are combined.