JP2005344572A - Thermoelectric generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectric generator using engine cooling water as a low-temperature side heat source and capable of improving warming-up performance of an engine at low-temperature start. <P>SOLUTION: In this thermoelectric generator, exhaust gas from the engine 10 serves as a high-temperature side heat source, and cooling water of the engine 10 serves as the low-temperature side heat source. Power generation is performed by a thermoelectric element 111. Inside an engine cooling water circuit 20 in which cooling water is circulated between the engine 10 and a radiator 21 for cooling the cooling water, a bypass flow passage 22 for bypassing the radiator 21 is provided. The cooling water serving as the low-temperature side heat source is cooling water flowing on flow passages 24a, 24b in the engine side 10 from the bypass flow passage 22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermoelectric generator that recovers thermal energy of engine exhaust gas as electric energy by a thermoelectric element.

  As a conventional thermoelectric generator, for example, the one shown in Patent Document 1 is known. In this system, power is generated by a thermoelectric element using engine exhaust gas as a high-temperature side heat source and outside air as a low-temperature side heat source. Here, a bypass passage is provided that bypasses the engine exhaust pipe through a plurality of branch pipes. The thermoelectric element is brought into contact with the bypass passage. Then, an electromagnetic valve that opens and closes each branch pipe is provided, and when the exhaust gas temperature becomes a predetermined value or more, the electromagnetic valve is individually closed by the control unit to control the exhaust gas flow rate in the bypass passage. The high temperature side temperature of the element is kept at a constant temperature below the heat resistance temperature.

  Further, as shown in Patent Document 2, a low temperature side heat source using cooling water for engine cooling is known, and a stable low temperature side heat source is easily secured.

  In the technique of the above-mentioned Patent Document 1, in the exhaust gas temperature range lower than a predetermined value, the power generation amount is determined by the course of the exhaust gas temperature and the outside air temperature at that time, and an effective power generation amount is positively obtained. I don't see the idea.

  In the technique of Patent Document 2, since the heat of the exhaust gas is absorbed by the cooling water, the temperature rise of the cooling water is increased depending on the amount of power generation, which may lead to engine overheating. In order to prevent this, it is necessary to consider the enlargement of the radiator.

  Therefore, the applicant of the present invention (Japanese Patent Application No. 2004-92699) first, as shown in FIG. 9, the high temperature side heat source of the thermoelectric element 111 is the exhaust gas flowing through the exhaust pipe 11 of the engine 10, and the low temperature side heat source is the radiator 21. The temperature generated in the thermoelectric element 111 increases as the radiator margin heat radiation capacity ΔQx obtained by removing the cooling loss Qe of the engine 10 from the heat radiation capacity Qr of the radiator 21 when the engine 10 is operated. The thermoelectric generator 100 was devised so as to provide variable means for changing the supply conditions of the exhaust gas (or cooling water) to the thermoelectric element 111 so that the difference becomes large.

  Specifically, the variable means includes, for example, a branch passage 11a that branches from the exhaust pipe 11, a branch opening / closing valve 11b that opens and closes the branch passage 11a, and a control device 120 that controls the opening degree of the branch opening / closing valve 11b. Thus, the high temperature side heat source is formed in the thermoelectric element 111 by the exhaust gas supplied to the branch flow path 11a. Further, the low temperature side heat source of the thermoelectric element 111 is formed by the cooling water after passing through the radiator 21 in order to ensure a larger temperature difference from the high temperature side heat source.

The control device 120 controls the opening of the branch on / off valve 11b to be increased as the radiator margin heat dissipation capacity ΔQx increases, and thereby the operation of the engine is not required without increasing the size of the radiator. A thermoelectric generator that can secure the maximum amount of power generation according to the load.
Japanese Utility Model Publication No. 63-162916 JP 2000-297699 A

  However, since the cooling water serving as the low temperature side heat source is taken out from between the outlet side of the radiator 21 and the thermostat 23 disposed in the connection portion of the bypass flow path 22, regardless of the open / closed state of the thermostat 23. The cooling water always flows through the radiator 21, is cooled, and returns to the engine 10. Depending on the balance between this cooling and the heat absorption from the exhaust gas in the thermoelectric element 111, the warm-up performance of the engine 10 at the time of cold start Could make it worse.

  In view of the above problems, an object of the present invention is to provide a thermoelectric generator capable of improving the warm-up performance of an engine at a low temperature start in the case where engine cooling water is used as a low temperature side heat source.

  In order to achieve the above object, the present invention employs the following technical means.

  In the invention according to claim 1, in the thermoelectric power generation apparatus in which the high temperature side heat source is the exhaust gas from the engine (10), the low temperature side heat source is the cooling water of the engine (10), and the thermoelectric element (111) generates power, In the engine cooling water circuit (20) in which the cooling water circulates between the engine (10) and the radiator (21) for cooling the cooling water, a bypass flow path (22) for bypassing the radiator (21) is provided. The cooling water serving as the low temperature side heat source is characterized by being cooling water flowing through the flow paths (24a, 24b) located closer to the engine (10) than the bypass flow path (22).

  Thus, when the engine (10) is started at a low temperature, the cooling water can be supplied to the thermoelectric element (111) by flowing to the bypass flow path (22) side, so that it is not cooled by the radiator (21). In addition, since the temperature can be raised by heat absorption from the exhaust gas, the warm-up performance of the engine (10) can be improved.

  The invention according to claim 2 is characterized in that the flow paths (24a, 24b) are flow paths (24a, 24b) on the downstream side of the radiator (21).

  Thereby, after the warm-up of the engine (10) is completed, the cooling water can be flowed to the radiator (21) side, and the cooling water whose temperature has been lowered can be used as the low-temperature side heat source, so the high-temperature side heat source (exhaust gas) It is possible to increase the power generation amount by increasing the temperature difference.

  In the invention according to claim 3, the radiator margin heat radiation capacity (ΔQx) obtained by removing the cooling loss (Qe) of the engine (10) from the heat radiation capacity (Qr) of the radiator (21) when the engine (10) is operated. A variable means for varying the supply condition of at least one of exhaust gas and cooling water to the thermoelectric element (111) is provided so that the temperature difference generated in the thermoelectric element (111) becomes larger as the temperature becomes larger. .

  As a result, it is possible to provide heat radiation by the amount of heat absorbed by the cooling water from the exhaust gas by the radiator margin heat radiation capacity (ΔQx). Then, by supplying exhaust gas or cooling water corresponding to the heat radiation capability to the thermoelectric element (111), maximum power generation is possible without increasing the size of the radiator (21).

  In addition, the code | symbol in the bracket | parenthesis of each said means shows a corresponding relationship with the specific means of embodiment description mentioned later.

(First embodiment)
The thermoelectric power generation apparatus 100 of the present invention is applied to a vehicle having a water-cooled engine 10 and generates power by a temperature difference between exhaust gas and cooling water in a thermoelectric element 111. First, the basic configuration will be described with reference to FIGS.

  As shown in FIG. 1, the engine 10 is provided with an intake pipe (not shown) for sucking combustion air and an exhaust pipe 11 for discharging exhaust gas after combustion. A throttle valve whose opening is variable according to the amount of depression of an accelerator pedal provided in the vehicle is provided in the intake pipe.

  The engine 10 is controlled to operate optimally by an engine control device (not shown). Specifically, an engine speed signal, a throttle valve opening signal, a vehicle speed signal, and the like are input to the engine control device. A map in which the fuel injection amount is associated with the engine speed signal and the throttle valve opening signal is stored in advance, and the required fuel is injected into the intake pipe side at a predetermined timing based on this map. . The engine control device is connected to a control device 120 (described later) so as to be able to exchange signals with each other.

  The engine 10 is provided with an engine coolant circuit 20. The engine coolant circuit 20 is a circuit in which the coolant in the engine 10 is circulated from the coolant outlet portion 13a through the radiator 21 to the coolant inlet portion 13b by the water pump 12. Here, the water pump 12 is an engine-driven pump that operates by receiving the driving force of the engine 10. Then, the cooling water is cooled by the heat radiation of the radiator 21, and the operating temperature of the engine 10 is appropriately controlled.

  The engine coolant circuit 20 is provided with a bypass passage 22 that bypasses the radiator 21 and a thermostat 23 that adjusts the coolant flow rate to the radiator 21 side or the bypass passage 22 side. Incidentally, when the cooling water temperature is equal to or lower than the first predetermined temperature (for example, 85 ° C.), the radiator 21 side is closed by the thermostat 23 and the cooling water flows through the bypass flow path 22 side, thereby preventing the cooling water from being overcooled. . This corresponds to a case where the cooling water is not sufficiently heated (for example, at a low temperature start) immediately after the engine 10 is started, and warm-up of the engine 10 is promoted. Further, the thermostat 23 starts to open the radiator 21 side when the engine 10 has been warmed up and the coolant temperature exceeds the first predetermined temperature, and reaches the bypass flow path 22 side at a temperature equal to or higher than the second predetermined temperature (for example, 90 ° C.). Is closed and the radiator 21 side is fully opened.

  The engine coolant circuit 20 is provided with a heater hot water circuit 30 in which a heater core 31 is disposed in parallel with the radiator 21 to form a coolant circuit. The heater core 31 is a heat exchanger for a heating device that heats air for air conditioning using cooling water (hot water) as a heat source.

  The thermoelectric generator 100 uses the exhaust gas after combustion of the engine 10 and the cooling water of the cooling water circuit 20, and includes a thermoelectric generator 110 and a control device 120.

  In the thermoelectric generator 110, a later-described branch flow path 11a and an engine inlet-side flow path 24a are provided in a thermoelectric element 111 that generates power using the Seebeck effect.

  That is, the branch flow path 11a is a flow path formed so as to branch from the exhaust pipe 11 of the engine 10 and merge again with the exhaust pipe 11, and allows a part of the exhaust gas to flow. The branch flow path 11 a is brought into contact with one side surface of the thermoelectric element 111 so that the exhaust gas becomes a high temperature side heat source of the thermoelectric element 111. Further, a branch opening / closing valve (electromagnetic valve) 11b for opening and closing the branch passage 11a is provided on the upstream side of the exhaust gas with respect to the thermoelectric element 111 in the branch passage 11a.

  On the other hand, the engine inlet-side flow path 24a is a flow path that is closer to the engine 10 than the bypass flow path 22, and here, is a flow that is downstream of the radiator 21 and connects the thermostat 23 and the cooling water inlet portion 13b. The road. The engine inlet side flow path 24a is brought into contact with the other side surface of the thermoelectric element 111. That is, the cooling water flowing through the thermostat 23 from the bypass channel 22 or the cooling water passing through the radiator 21 and flowing through the thermostat 23 is supplied to the thermoelectric element 111 side, and this cooling water becomes a low-temperature side heat source of the thermoelectric element 111. I have to.

  The control device 120 has a shaft torque map, a cooling loss heat amount map of the engine 10, a water flow rate map of the engine 10, a reference heat release amount map of the radiator 21, an opening degree map of the branch on-off valve 11b, and various arithmetic expressions described below. The degree of opening of the branch on-off valve 11b is controlled based on these maps and arithmetic expressions.

  In the present embodiment, the branch passage 11a, the branch opening / closing valve 11b, and the control device 120 form variable means for changing the supply condition of exhaust gas to the thermoelectric element 111.

  Hereinafter, various maps and arithmetic expressions will be described. As shown in FIG. 2, the shaft torque map is obtained by associating the fuel injection amount L obtained from the engine control device with the shaft torque T in advance, and is used for calculating the shaft torque T when the engine 10 is operated. It is done. Then, the shaft output P is calculated from the shaft torque T and the engine speed Ne obtained from the engine control device on the basis of Equation 1.

(Equation 1)
Shaft output P = a × engine speed Ne × shaft torque T
Note that a is a constant.

  As shown in FIG. 3, the cooling loss heat quantity map is obtained by previously relating the engine rotation speed Ne and the cooling loss heat quantity Qe of the engine 10 with the shaft output P as a parameter (here, no load P1 to full load P7). And is used to calculate the cooling loss heat quantity Qe when the engine 10 is operated. Incidentally, the cooling loss heat quantity Qe is obtained by multiplying the total combustion heat quantity of the fuel in the engine 10 by the cooling loss, and is a heat quantity radiated by the radiator 21.

  As shown in FIG. 4, the water flow rate map has a water pump characteristic Δhp with the engine speed Ne (Ne1 to Ne4..., Which is proportional to the speed of the water pump 12) as a parameter, The water flow resistance characteristic Δht including the cooling water circuit 20 and the heater hot water circuit 30 is shown, and is used to calculate the engine water flow rate Ve flowing through the engine 10.

  And based on Formula 2 from the engine water flow rate Ve obtained from the engine water flow rate Ve map, the radiator water flow rate Vw flowing through the radiator 21 is calculated.

(Equation 2)
Radiator water flow rate Vw = K x Engine water flow rate Ve
K is a constant determined from each resistance coefficient of the radiator 21, the bypass passage 22, the thermostat 23, and the heater core 31.

  As shown in FIG. 5, the reference heat release map has the radiator water flow rate Vw (low flow rate Vw1 to high flow rate Vw4...) Obtained by Equation 2 as a parameter, and the air flowing into the front surface of the core portion of the radiator 21. The front wind speed va and the reference heat release amount Qr of the radiator 21 are related in advance, and are used to calculate the reference heat release amount Qr when the engine 10 is operating. Here, the front wind speed va is determined by using the vehicle speed v obtained from the engine control device, and is calculated by Equation 3 in consideration of resistance due to the bumper and grill of the vehicle. .

(Equation 3)
Front wind speed va = b × vehicle speed v
In addition, b is a constant and is set to 1/5 here.

  As shown in FIG. 6, the opening degree map associates the exhaust heat radiation amount Qex and the opening degree of the branch opening / closing valve 11b in advance. Here, the exhaust heat release amount Qex is a heat amount equal to the surplus heat amount ΔQx of the radiator 21 calculated by the following mathematical formula 4.

(Equation 4)
Allowable heat amount ΔQx = reference heat release amount Qr−cooling loss heat amount Qe = exhaust heat release amount Qex
The opening degree of the branch opening / closing valve 11b is associated so as to increase as the exhaust heat radiation amount Qex increases.

  Next, the operation based on the above configuration will be described. In the operation of the engine 10, combustion air is sucked from the suction pipe according to the opening of the throttle valve, and is mixed with fuel injected from an injector (not shown) and burned. The exhaust gas after combustion is purified by a catalyst (not shown) and discharged from the exhaust pipe 11 to the atmosphere. Further, by the operation of the water pump 12, the coolant circulates through the engine coolant circuit 20 and the heater warm water circuit 30.

  At the time of low temperature start when the temperature of the cooling water is equal to or lower than the first predetermined temperature, the thermostat 23 closes the radiator 21 side, and the cooling water circulates through the engine 10 through the bypass passage 22 and the engine inlet side passage 24a, Some of the cooling water circulates in the heater hot water circuit 30. The control device 120 increases the opening degree of the branch opening / closing valve 11b (full opening), and performs power generation by the thermoelectric element 111.

  When the warm-up of the engine 10 is finished and the temperature of the cooling water exceeds the first predetermined temperature, the thermostat 23 opens the radiator 21 side, and the cooling water passes through the radiator 21 and the engine inlet side flow path 24a. And a part of the cooling water circulates in the heater hot water circuit 30. The control device 120 adjusts the opening degree of the branch on-off valve 11b based on the maps shown in FIGS. FIG. 7 shows the control flow at that time, and the details will be described below.

  First, various signals (data such as fuel injection amount L, engine speed Ne, throttle valve opening Bk, vehicle speed v, etc.) are read in step S100, and cooling heat loss Qe is calculated in step S110. That is, the shaft torque T corresponding to the fuel injection amount L at that time is calculated from the shaft torque map of FIG. 2, and the shaft output P is calculated as a × Ne × T from Equation 1. Then, from the cooling loss heat quantity map of FIG. 3, the engine speed Ne at that time and the cooling loss heat quantity Qe corresponding to the shaft output P obtained above are calculated.

  Next, in step S120, a reference heat release amount Qr is calculated. Here, the engine water flow rate Ve is calculated from the intersection of the pump characteristic Δhp and the water flow resistance characteristic Δht at the engine speed Ne at that time from the water flow rate map of FIG. Further, the radiator water flow rate Vw is calculated from the engine water flow rate Ve using Formula 2. Then, a reference heat release amount Qr corresponding to the front wind speed va (calculated using Formula 3) at the radiator water flow rate Vw at that time is calculated from the reference heat release amount map of FIG.

  Next, in step S130, the heat loss ΔQx is calculated as Qr−Qe from Equation 4 using the cooling heat loss Qe and the reference heat dissipation amount Qr.

  Next, in step S140, it is determined whether or not the surplus heat amount ΔQx is greater than zero. If it is determined not, the branch on-off valve 11b is closed in step S150, and the process returns to step S100. That is, this is a case where the load on the engine 10 is the highest and the cooling heat quantity Qe is radiated by the original reference heat radiation amount Qr. By stopping the supply of exhaust gas to the thermoelectric generator 110 side, the engine 10 The engine 10 is prevented from overheating by avoiding an increase in the temperature of the cooling water in the inlet side flow path 24a.

  On the other hand, if it is determined in step S140 that the surplus heat amount ΔQx is greater than zero, the exhaust heat release amount Qex is calculated in step S160. The exhaust heat release amount Qex is set as a value equal to the surplus heat amount ΔQx from Equation 4. Note that the surplus heat amount ΔQx is greater than zero means that the load on the engine 10 is low, and the radiator 21 has a heat dissipation capability for the surplus heat amount ΔQx while dissipating the cooling loss heat amount Qe of the engine 10. To do.

  In step S170, the opening degree of the branch on-off valve 11b is varied based on the opening degree map of FIG. That is, the larger the exhaust heat dissipation amount Qex, the larger the opening degree, and the amount of exhaust gas flowing into the branch flow path 11a is increased (the temperature on the exhaust gas side is increased). The power generation amount by the thermoelectric element 111 is positively increased by increasing the temperature difference from the cooling water. And the electric power obtained by this electric power generation is charged to the charger (battery) which is not shown in figure, and is used for various auxiliary machine operation | movement. At this time, the cooling water absorbs heat by the exhaust gas, and the heat absorption is provided by the surplus heat quantity ΔQx of the radiator 21.

  As described above, in the present invention, since the cooling water flowing through the engine inlet-side flow path 24a is used as the low-temperature heat source of the thermoelectric element 111, it flows through the bypass flow path 22 when the engine 10 is started at a low temperature. Cooling water can be supplied to the thermoelectric element 111, can be prevented from being cooled by the radiator 21, can be raised in temperature by absorbing heat from the exhaust gas, and can improve the warm-up performance of the engine 10. it can. Therefore, friction loss can be reduced and the fuel efficiency performance of the engine 10 can be improved. In addition, the heating capacity of the heater core 31 can be improved.

  In addition, when the engine 10 is warmed up, the cooling water flows through the radiator 21 by the operation of the thermostat 23, and the cooling water whose temperature has decreased can be used as a low-temperature heat source. The power generation amount can be increased by increasing the temperature difference.

  Further, as the surplus heat quantity ΔQex of the radiator 21 excluding the cooling heat quantity Qe of the engine 10 is increased from the reference heat release quantity Qr of the radiator 21 when the engine 10 is operated, the opening degree of the branch on-off valve 11b is increased. Therefore, heat can be released by the amount of heat absorbed from the exhaust gas by the surplus heat amount ΔQex. And by making the exhaust gas commensurate with the heat radiation possible flow into the branch flow path 11a, maximum power generation is possible without increasing the size of the radiator 21.

  And since the operation load which the original generator (alternator) requires in the engine 10 by the electric power generation of the thermoelectric element 111 can be reduced, the fuel consumption of the engine 10 can be improved.

(Second Embodiment)
A second embodiment of the present invention is shown in FIG. In the second embodiment, the flow rate of the cooling water serving as the low temperature side heat source is made variable with respect to the first embodiment.

  Here, with respect to the first embodiment, an engine inlet side branch flow path 24b branched from the engine inlet side flow path 24a and connected to the water pump 12 side is provided, and becomes a low temperature side heat source of the thermoelectric element 111. I am doing so.

  And the flow control valve 25 is provided in the branch point of the engine inlet side branch flow path 24b. The flow rate adjusting valve 25 is a valve that can adjust the flow rate of the cooling water to the engine inlet side flow path 24 a and the engine inlet side branch flow path 24 b, so that the opening degree is controlled by the control device 120. I have to. In the present embodiment, the engine inlet side branch flow path 24b, the flow rate adjustment valve 25, and the control device 120 form variable means for changing the condition for supplying the cooling water to the thermoelectric element 111.

  When the bypass 120 is opened by the thermostat 23 at low temperature start, the control device 120 increases the opening degree of the flow control valve 25 on the side of the engine inlet side branch 24b (full opening). And power generation by the thermoelectric element 111 is performed.

  Further, when the warm-up of the engine 10 is finished and the cooling water flows to the radiator 21 side by the thermostat 23, the control device 120 allows a surplus heat amount ΔQx of the radiator 21 when the engine 10 is operated (the numerical formula of the first embodiment). 4) the larger the opening degree of the flow rate regulating valve 25 on the side of the engine inlet side branch flow path 24b is, the larger the amount of cooling water flowing through the engine inlet side branch flow path 24b is. The power generation amount by the thermoelectric element 111 is positively increased by increasing the temperature difference from the exhaust gas.

  As a result, when the engine 10 is started at a low temperature, the cooling water flowing through the bypass passage 22 can be supplied to the thermoelectric element 111 and can be prevented from being cooled by the radiator 21. The temperature can be raised, and the warm-up performance of the engine 10 can be improved. In addition, the heating capacity of the heater core 31 can be improved.

  In addition, when the engine 10 is warmed up, the cooling water flows through the radiator 21 by the operation of the thermostat 23, and the cooling water whose temperature has decreased can be used as a low-temperature heat source. The power generation amount can be increased by increasing the temperature difference. Then, since the amount of heat that can be absorbed by the cooling water from the exhaust gas can be provided by the surplus heat amount ΔQx, the size of the radiator 21 is increased by flowing the cooling water corresponding to the surplus heat amount ΔQx into the branch passage 24b on the engine inlet side. Maximum power generation is possible without doing so.

(Other embodiments)
In the first embodiment, the flow rate of the exhaust gas is assumed to be variable, and in the second embodiment, the flow rate of the cooling water is assumed to be variable. However, both (the exhaust gas and the cooling water) are variable. It may be combined.

  Further, for the purpose of improving the warm-up performance of the engine 10, the flow rates of both the exhaust gas and the cooling water may not be provided.

  Furthermore, the cooling water that serves as the low-temperature heat source may be the cooling water that flows through the flow path from the cooling water outlet 13 a of the engine 10 to the bypass flow path 22.

It is a schematic diagram which shows the whole structure in 1st Embodiment of this invention. It is a shaft torque map which shows the relationship between fuel injection quantity and shaft torque. It is a cooling loss calorie | heat amount map which shows the relationship between the engine speed which used the shaft output as a parameter, and an engine cooling loss calorie | heat amount. It is a water flow map which shows the pump characteristic with respect to an engine water flow, and a water flow resistance characteristic. It is a reference | standard heat dissipation amount map which shows the relationship between a front wind speed and the reference | standard heat dissipation of a radiator. It is an opening degree map which shows the relationship between exhaust heat radiation amount and the opening degree of a branch on-off valve. It is a control flowchart for controlling the opening degree of a branch on-off valve. It is a schematic diagram which shows the whole structure in 2nd Embodiment of this invention. It is a schematic diagram which shows the whole structure in the thermoelectric power generator which the present applicant devised previously.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 20 Engine cooling water circuit 21 Radiator 22 Bypass flow path 24a Engine inlet side flow path (flow path)
24b Engine inlet side branch flow path (flow path)
100 Thermoelectric generator 111 Thermoelectric element

Claims (3)

In the thermoelectric power generation apparatus that generates heat by the thermoelectric element (111) using the high temperature side heat source as exhaust gas from the engine (10) and the low temperature side heat source as cooling water of the engine (10),
A bypass flow path (22) that bypasses the radiator (21) in an engine cooling water circuit (20) in which the cooling water circulates between the engine (10) and a radiator (21) that cools the cooling water. Have
The thermoelectric generator according to claim 1, wherein the cooling water serving as the low temperature side heat source is cooling water flowing through the flow paths (24a, 24b) closer to the engine (10) than the bypass flow path (22).   The thermoelectric generator according to claim 1, wherein the flow paths (24a, 24b) are flow paths (24a, 24b) on the downstream side of the radiator (21).   The higher the radiator margin heat dissipation capacity (ΔQx) excluding the cooling loss (Qe) of the engine (10) from the heat dissipation capacity (Qr) of the radiator (21) when the engine (10) is operating, the greater the thermoelectric power. The variable means for varying supply conditions of at least one of the exhaust gas and the cooling water to the thermoelectric element (111) is provided so that a temperature difference generated in the element (111) becomes large. The thermoelectric generator according to claim 1 or 2.

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