JP2004332596A - Thermoelectric generating set - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectric generating set with relatively simple structure having an EGR gas cooling function, by focusing attention to a point that the temperature of exhaust gas is lowered by heat-exchange in a cooling part of the thermoelectric generating set. <P>SOLUTION: The thermoelectric generating set generating power with thermo-element 111 by using the exhaust gas from an engine 10 of a vehicle as a high-temperature-side heat source and cooling fluid as a low-temperature-side heat source. The thermoelectric generating set has: a introducing flow passage 113 for introducing part of the exhaust gas that has passed through the thermo-element 111 to an intake side 12 of the engine 10; an introducing opening/closing valve 113a for opening/closing the introducing flow passage 113; and a control unit 120 for controlling opening of the introducing opening/closing valve 113a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thermoelectric generator for recovering thermal energy of exhaust gas of an engine as electric energy by a thermoelectric element.
[0002]
[Prior art]
2. Description of the Related Art As a conventional thermoelectric generator, for example, the one shown in Patent Document 1 is known. This is done by attaching one side of the thermoelectric element to the outer surface of the exhaust pipe that discharges the exhaust gas from the engine, and attaching the other side of the thermoelectric element to a water-cooled or air-cooled cooling unit. To generate an electromotive force according to the temperature difference between one side and the other side.
[0003]
Here, since the temperature of the exhaust gas decreases toward the downstream side, a high-temperature thermoelectric element is installed on the upstream side of the exhaust gas, and a low-temperature thermoelectric element is arranged on the downstream side of the exhaust gas. The thermoelectric generator has excellent durability and can obtain a large power output.
[0004]
On the other hand, as a technique using exhaust gas, an EGR gas cooling device is known as disclosed in Patent Document 2. This, when lowering the combustion temperature of the engine by introducing a part of exhaust gas to the intake side to reduce the NO _X in the exhaust gas, lowering the output of the engine by improving the charging efficiency of the combustion air In order to suppress the exhaust gas, the exhaust gas introduced to the intake side is cooled by a dedicated heat exchanger.
[0005]
[Patent Document 1]
JP 2000-286469 A
[Patent Document 2]
Japanese Patent Application Laid-Open No. 9-310995
[Problems to be solved by the invention]
However, although each of the above technologies uses exhaust gas, there is no relevance between the two and they are independent. In particular, in the EGR gas cooling device, the cost is increased due to the provision of the dedicated heat exchanger, and the mounting space must be secured.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a thermoelectric generator having a relatively simple configuration and an EGR gas cooling function, focusing on the above problem and the point that the exhaust gas is heat-exchanged by a cooling unit in the thermoelectric generator to lower the temperature. It is in.
[0009]
[Means for Solving the Problems]
The present invention employs the following technical means to achieve the above object.
[0010]
According to the first aspect of the present invention, there is provided a thermoelectric generator for generating electric power by the thermoelectric element (111) using the high-temperature side heat source as exhaust gas from the engine (10) of the vehicle and using the low-temperature side heat source as a cooling fluid. An introduction channel (113) for guiding a part of the exhaust gas after passing through (111) to the intake side (12) of the engine (10), and an introduction on-off valve (113a) for opening and closing the introduction channel (113). And a control device (120) for controlling the opening of the introduction on-off valve (113a) according to the load state of the engine (10).
[0011]
This enables the thermoelectric element (111) to generate electric power by utilizing the exhaust gas, and, in accordance with the load state of the engine (10), takes in the exhaust gas whose temperature is reduced when passing through the thermoelectric element (111). The EGR gas can be supplied to the side (12), and the cooling function of the EGR gas can be provided without preparing a dedicated heat exchanger.
[0012]
And the opening degree is controlled by the controller (120) and the branch channel (112) that branches and joins the main channel (11) through which the exhaust gas flows, as in the invention according to claim 2. In addition, a branch opening / closing valve (112a) for opening and closing the branch flow path (112) is provided, and a high-temperature side heat source is formed in the thermoelectric element (111) by exhaust gas supplied to the branch flow path (112). The control device (120) controls the degree of opening of the branch on-off valve (112a) and the introduction on-off valve (113a) as the load on the engine (10) decreases, so that the control device (120) is required especially at a low load. Therefore, the power generation function and the cooling function of the EGR gas can be simultaneously operated.
[0013]
In the invention according to claim 3, a catalyst for purifying exhaust gas is provided downstream of the power generation element (111) in the main flow path (11) or the branch flow path (112). Is characterized in that when it is determined from the temperature of the exhaust gas that the catalyst is in an inactive state, the branch on-off valve (112a) is controlled to be closed.
[0014]
This prevents the temperature of the exhaust gas from being reduced by the thermoelectric element (111), so that the activation time of the catalyst is not deteriorated.
[0015]
The invention according to claim 4 is characterized in that the cooling fluid is cooling water for cooling the engine (10).
[0016]
This makes it possible to form a stable low-temperature heat source by diverting the cooling water of the engine cooling water circuit (20).
[0017]
According to the fifth aspect of the present invention, in the vehicle, in addition to the engine cooling water circuit (20) for cooling the engine (10), the inverter (50) for controlling the operation of the traveling motor (40) so that the rotation speed is variable is used. Wherein the cooling fluid is cooling water for the inverter cooling water circuit (60) of the engine cooling water circuit (20) and the inverter cooling water circuit (60). And
[0018]
Thereby, in the engine cooling water circuit (20) and the inverter cooling water circuit (60), the cooling water temperature is usually set lower in the inverter cooling water circuit (60), so that the temperature difference between the engine cooling water circuit (60) and the exhaust gas is large. As a result, the amount of power generation (power generation efficiency) by the thermoelectric element (111) can be increased.
[0019]
Note that the reference numerals in parentheses of the above means indicate the correspondence with specific means described in the embodiment described later.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
The thermoelectric generator 100 of the present invention is applied to a vehicle having a water-cooled engine 10, and in addition to the original power generation function of the thermoelectric element 111, cooling of EGR (Exhaust Gas Recirculation) gas using exhaust gas after power generation. It has a function. First, the basic configuration will be described with reference to FIG.
[0021]
The engine 10 is provided with an intake pipe 12 for taking in air for combustion and an exhaust pipe 11 for discharging exhaust gas after combustion. In the intake pipe 12, a throttle valve 12a whose opening is variable in accordance with the depression amount of an accelerator pedal provided in a vehicle (not shown) is provided, and the intake air amount is adjusted.
[0022]
The engine 10 is provided with an engine cooling water circuit 20. The engine cooling water circuit 20 is a circuit in which cooling water in the engine 10 is circulated through the radiator 21 by the water pump 13. The cooling water is cooled by the radiation of the radiator 21, and the operating temperature of the engine 10 is appropriately controlled. Incidentally, the engine cooling water circuit 20 is provided with a bypass flow path 22 that bypasses the radiator 21 and a thermostat (flow control valve) 23 that adjusts the flow rate of the cooling water to the radiator 21 side or the bypass flow path 22 side. ing. When the cooling water temperature is equal to or lower than a predetermined temperature (for example, 90 ° 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 excessively cooled. This corresponds to, for example, a case where the temperature of the cooling water has not sufficiently increased, for example, immediately after the start of the engine 10, and the warm-up of the engine 10 is promoted.
[0023]
The engine cooling water circuit 20 is provided with a heater hot water circuit 30 in which a heater core 31 is provided so as to be in parallel with the radiator 21 to form a cooling water circuit. The heater core 31 is a heat exchanger for a heating device that heats air-conditioning air using cooling water (hot water) as a heat source.
[0024]
The thermoelectric generator 100 uses the exhaust gas after the combustion of the engine 10 and the cooling water of the cooling water circuit 20, and includes a thermoelectric generator 110 and a controller 120.
[0025]
In the thermoelectric generator 110, a branch channel 112 and a cooling water pipe 114, which will be described later, are disposed on a thermoelectric element 111 that generates power using the Seebeck effect.
[0026]
That is, the branch flow path 112 is a flow path formed so as to branch from the exhaust pipe (corresponding to the main flow path of the present invention) 11 of the engine 10 and to join the exhaust pipe 11 again. It is available for distribution. The branch channel 112 is configured to abut on one side of the thermoelectric element 111. A branch opening / closing valve (electromagnetic valve) 112 a for opening and closing the branch flow path 112 is provided on the branch flow path 112 on the upstream side of the exhaust gas with respect to the thermoelectric element 111.
[0027]
On the other hand, the cooling water pipe 114 is formed as a circuit that branches off from the upstream side of the radiator 21 of the engine cooling water circuit 20 and is connected to the water pump 13 side, and is in contact with the other side of the thermoelectric element 111. Like that.
[0028]
Further, as a characteristic part of the present invention, the introduction flow communicating from the branch passage 112 to the intake pipe 12 (corresponding to the intake side of the present invention) from the branch passage 112 on the downstream side of the exhaust gas with respect to the thermoelectric element 111 in the branch passage 112. The road 113 is provided. Further, the introduction flow path 113 is provided with an introduction opening / closing valve (electromagnetic valve) 113a for opening and closing the introduction flow path 113.
[0029]
Further, an exhaust gas temperature sensor 130 for detecting the temperature of the exhaust gas is provided in the exhaust pipe 11, and a temperature signal detected by the exhaust gas temperature sensor 130 is output to a control device 120 described later. I have. Here, the exhaust gas temperature is used as a representative characteristic indicating the load state when the engine 10 is operating. That is, the lower the exhaust gas temperature is, the lower the operating load of the engine 10 is, and the higher the exhaust gas temperature is, the higher the operating load of the engine 10 is.
[0030]
The control device 120 is provided to control the opening degree of the branch on-off valve 112a and the introduction on-off valve 113a based on the temperature detected by the exhaust gas temperature sensor 130. Specifically, as the detected temperature (exhaust gas temperature) is lower, the degree of opening of both on-off valves 112a and 113a is increased, and conversely, as the detected temperature (exhaust gas temperature) is higher, the open-close valves 112a and 113a are both turned on. The degree of opening is set in advance to be small.
[0031]
Next, the operation based on the above configuration will be described. The thermoelectric generator 100 of the present invention has a power generation function and an EGR gas cooling function as described at the beginning, and the power generation function will be described first.
[0032]
In the operation of the engine 10, combustion air is sucked from the suction pipe 12 according to the opening degree of the throttle valve 12a, mixed with fuel injected from an injector (not shown), and ignited and burned. Then, the exhaust gas after combustion is purified by a catalyst (not shown) and discharged from the exhaust pipe 11 to the atmosphere. The operation of the water pump 13 causes the cooling water to circulate through the engine cooling water circuit 20, the heater hot water circuit 30, and the cooling water pipe 114.
[0033]
The control device 120 adjusts the opening of the branch on-off valve 112a and the introduction on-off valve 113a according to the exhaust gas temperature signal obtained from the exhaust gas temperature sensor 130. That is, when the operating load of the engine 10 is low and the exhaust gas temperature is low, the control device 120 increases the opening of the branch on-off valve 112a. Then, a part of the exhaust gas flowing through the exhaust pipe 11 flows into the branch channel 112 side more. At this time, the thermoelectric element 111 is given a temperature difference by the exhaust gas of the branch flow channel 112 and the cooling water of the cooling pipe 114, and generates power. The electric power obtained by this power generation is charged into a charger (battery) (not shown) or used for operating various auxiliary devices.
[0034]
Further, as the operating load of engine 10 increases and the exhaust gas temperature increases, control device 120 decreases the opening of branch on-off valve 112a. Then, the amount of exhaust gas flowing on the branch flow channel 112 side is reduced, and the power generation action by the thermoelectric element 111 is suppressed.
[0035]
Next, the cooling function of the EGR gas will be described. When power is generated by the thermoelectric element 111 as described above, the exhaust gas is cooled by the cooling water in the cooling water pipe 114 on the opposite side. Then, the cooled exhaust gas flows through the introduction flow path 113 from the introduction opening / closing valve 113a whose opening degree is increased together with the branch opening / closing valve 112a, and flows into the suction pipe 12.
[0036]
This has the same effect as an EGR gas cooling device that cools exhaust gas with a dedicated heat exchanger and then allows the exhaust gas to flow into the intake side, without reducing the output of the engine 10. lowering the combustion temperature, thereby reducing the concentration of NO _X in the exhaust gas.
[0037]
In addition, as the exhaust gas temperature increases with the operating load of the engine 10, the control device 120 decreases the opening of the introduction on-off valve 113a together with the branch on-off valve 112a. Then, the amount of exhaust gas flowing through the introduction flow channel 113 is reduced, and the cooling effect of the EGR gas is suppressed.
[0038]
For example, when the exhaust gas temperature is lower than the predetermined determination temperature after the engine 10 is started and the exhaust gas purifying catalyst (not shown) does not become active, the control device 120 closes the branch on-off valve 112a, and The power generation by 111 is stopped. That is, the temperature of the exhaust gas during power generation is suppressed from being lowered, and the activation of the catalyst is prioritized.
[0039]
As described above, in the present invention, the power generation using the exhaust gas can be performed by the thermoelectric element 111. In addition, since the introduction passage 113 for guiding a part of the exhaust gas after passing through the thermoelectric element 111 to the intake side is provided, the exhaust gas cooled by the cooling water in the cooling water pipe 114 is supplied to the inside of the intake pipe 12. And a cooling function of the EGR gas can be provided without preparing a dedicated heat exchanger.
[0040]
More specifically, the operation load required for the original generator (alternator) in the engine 10 can be reduced by the power generation of the thermoelectric element 111. Then, pumping loss of the engine 10 is reduced by introducing the exhaust gas into the suction pipe 12. Further, the warming-up of the engine 10 is promoted by the cooling water in the cooling water pipe 114 that has absorbed heat from the exhaust gas, so that the friction loss can be reduced and the fuel efficiency of the engine 10 can be generally improved. In addition, the heating performance of the heater core 31 can be improved by the cooling water in the cooling water pipe 114 that has absorbed heat from the exhaust gas.
[0041]
Further, since the control device 120 controls the opening degree of the branch on-off valve 112a and the introduction on-off valve 113a to be larger as the operating load of the engine 10 becomes lower, the control device 120 is particularly required at a low load. The power generation function and the EGR gas cooling function can be operated simultaneously.
[0042]
In addition, when the exhaust gas temperature is low and the catalyst is in an inactive state, the control device 120 controls the branch on-off valve 112a to be closed, so that the temperature decrease of the exhaust gas due to the thermoelectric element 111 is suppressed, There is no deterioration in the activation time of the catalyst.
[0043]
(2nd Embodiment)
FIG. 2 shows a second embodiment of the present invention. The second embodiment is applied to a hybrid vehicle having a driving motor 40 in addition to the engine 10.
[0044]
The traveling motor 40 operates by receiving electric power from a battery (not shown), and the rotation speed is controlled by the inverter 50. In the hybrid vehicle, the engine 10 and the traveling motor 40 are selectively used as a traveling drive source according to traveling conditions of the vehicle. The inverter 50, the traveling motor 40, and the battery (not shown) are provided with an inverter cooling water circuit 60 for cooling various heat generated during control and operation.
[0045]
An inverter radiator 61 is provided in the inverter cooling water circuit 60, and the cooling water is circulated by the electric pump 63. A cooling water pipe 114 for the thermoelectric generator 110 is connected to the upstream side and the downstream side of the electric pump 63. A radiator 62 for thermoelectric generation for dissipating heat absorption is provided. Incidentally, a reserve tank 64 for absorbing the expansion and contraction due to the temperature change of the cooling water is provided upstream of the inverter radiator 61 of the inverter cooling water circuit 60.
[0046]
The operation of the second embodiment is basically the same as that of the first embodiment, except that the amount of power generation can be improved by using the cooling water of the inverter cooling water circuit 60 for the cooling water pipe 114. .
[0047]
That is, in the engine cooling water circuit 20, the cooling water temperature is usually set to 90 ° C. to 110 ° C. by setting the specifications of the radiator 21 and the thermostat 23 in order to maintain the engine 10 in a suitable operating state. On the other hand, in the inverter cooling water circuit 60, the inverter 50, the traveling motor 40, the battery (not shown) and the like are normally maintained at a temperature of 60 ° C. in order to ensure the life thereof.
[0048]
Therefore, as compared with the first embodiment in which the cooling water of the engine cooling water circuit 20 is used for the thermoelectric generator 110, the cooling water of the inverter cooling water circuit 60 is used, so that the exhaust gas and the cooling water in the thermoelectric element 111 are separated. Since the temperature difference can be increased, the amount of power generated by the thermoelectric element 111 (power generation efficiency) can be increased.
[0049]
The radiator 61 for the inverter and the radiator 62 for the thermoelectric generation may be set as one without being provided individually. According to this, although the basic physique becomes large, the radiator tank is required. By reducing the number of the radiators and eliminating the dead space between the radiators 61 and 62, a radiator that is totally inexpensive and has high heat exchange efficiency can be obtained.
[0050]
(Other embodiments)
In the first and second embodiments, the operation load condition of the engine 10 using the exhaust temperature sensor 130 has been described as to grasp the temperature of the exhaust gas is not limited to this, O ₂ concentration in the exhaust gas Alternatively, the intake pressure in the intake pipe 12 may be used.
[0051]
Further, as the cooling fluid forming the low-temperature side heat source of the thermoelectric element 111, for example, air (air cooling type) using outside air may be used instead of the cooling water of the engine cooling water circuit 20 or the inverter cooling water circuit 60.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an overall configuration according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram illustrating an entire configuration according to a second embodiment of the present invention.
[Explanation of symbols]
10 engine 11 exhaust pipe (main flow path)
12 Intake pipe (intake side)
Reference Signs List 20 engine cooling water circuit 40 traveling motor 50 inverter 60 inverter cooling water circuit 100 thermoelectric generator 111 thermoelectric element 112 branch flow path 112a branch on-off valve 113 introduction flow path 113a introduction on-off valve 120 controller

Claims (5)

A thermoelectric generator for generating electric power by a thermoelectric element (111) using a high-temperature side heat source as exhaust gas from an engine (10) of a vehicle and a low-temperature side heat source as a cooling fluid,
An introduction channel (113) for guiding a part of the exhaust gas after passing through the thermoelectric element (111) to an intake side (12) of the engine (10);
An introduction on-off valve (113a) for opening and closing the introduction flow path (113);
A thermoelectric generator including a control device (120) for controlling an opening degree of the introduction on-off valve (113a) according to a load state of the engine (10). A branch channel (112) that branches and joins the main channel (11) through which the exhaust gas flows,
An opening degree is controlled by the control device (120), and a branch on-off valve (112a) for opening and closing the branch flow path (112) is provided.
In the thermoelectric element (111), the exhaust gas supplied to the branch flow path (112) forms the high-temperature side heat source,
The control device (120) performs control such that the degree of opening of the branch on-off valve (112a) and the introduction on-off valve (113a) increases as the load on the engine (10) decreases. The thermoelectric generator according to claim 1. A catalyst for purifying the exhaust gas is provided downstream of the power generation element (111) in the main flow path (11) or the branch flow path (112).
3. The control device according to claim 2, wherein when the controller determines that the catalyst is in an inactive state based on a temperature of the exhaust gas, the controller controls the branch on-off valve to be closed. 4. Thermoelectric generator. The thermoelectric generator according to any one of claims 1 to 3, wherein the cooling fluid is cooling water for cooling the engine (10). The vehicle has an inverter cooling water circuit (60) for cooling an inverter (50) for controlling the operation of a traveling motor (40) so that the rotation speed is variable, in addition to an engine cooling water circuit (20) for cooling the engine (10). )
The said cooling fluid was the cooling water of the said inverter cooling water circuit (60) among the said engine cooling water circuit (20) and the said inverter cooling water circuit (60). 3. The thermoelectric generator according to any one of 3.

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