Patent Application
20110180617
The present invention relates to an electric heating device that heats fluid by using a heating element, and a vehicle air conditioner including the same.
In a vehicle such as a car, when a vehicle interior is heated, air inside and outside the vehicle interior is taken in, and an air temperature is adjusted to a predetermined air blowing temperature by air heated by heat exchange with fluid, which is a heating medium, and cooling air cooled by heat exchange, and the temperature-adjusted air is blown into the vehicle interior. In this case, the fluid that becomes a heat source for heating is heated by a heating unit before the heat exchange with the air. In an electric car or the like that do not have an engine and thus cannot use waste heat of the engine as the heat source of the heating unit, an electric heating device is used as the heating unit. As the electric heating device, a device that uses a plurality of heating elements that generate heat by energization has been known.
In Patent Literature 1, an electric heating device having a plurality of circulation chambers and heating chambers is disclosed. A medium flows into the respective circulation chambers, and a heating element is held in the respective heating chambers. The medium that flows in the circulation chambers is heated by the heating element held in the heating chambers. Patent Literature 1 discloses that the medium is a fluid medium. Further, it also discloses that the heating element is a PTC (Positive Temperature Coefficient) element. The PTC element generates heat by being energized.
Generally, when maximum output is required for the electric heating device, all heating elements are energized. When required output is zero, energization to all heating elements is suspended. When the output required for the electric heating device is intermediate output, which is in between the maximum output and zero, a part of the heating elements is energized, and energization to the remaining heating elements is suspended.
As described in Patent Literature 1, when a plurality of circulation chambers, as flow paths in which fluid flows, are provided in the inside of the electric heating device, a flow rate in each of the circulation chambers of the medium supplied from an inlet port is not always uniform, and the flow rate will deviate. Generally, a quantity of heating of fluid by the heating elements depends on an amount of fluid to be heated. As described above, therefore, at the time of intermediate output when apart of the heating elements is energized, in view of heating efficiency, it is desired that fluid is heated by energizing the heating element in a circulation chamber having a larger flow rate, and energization in a circulation chamber having a smaller flow rate is suspended.
However, in Patent Literature 1, because performing heating according to the flow rate of the medium in the circulation chamber is not taken into consideration, when the heating element in the circulation chamber having a small flow rate is energized, the quantity of heating becomes less, and as a result, heating efficiency decreases and unnecessary power is consumed.
The present invention has been achieved to solve the above problems, and an object of the present invention is to provide an electric heating device that can efficiently heat fluid at the time of intermediate output, and a vehicle air conditioner including the electric heating device.
According to an aspect of the present invention, an electric heating device includes: a plurality of flow paths in which fluid flows; and a plurality of heating modules arranged adjacent to the flow paths and including heating elements that generate heat by energization. At a time of intermediate output, the heating element in the heating module provided adjacent to a flow path among the plurality of flow paths having a relatively large flow rate of fluid is energized.
According to the electric heating device, at the time of intermediate output, a flow path among the plurality of flow paths having a relatively large flow rate of fluid is heated. Because a quantity of heat that can be provided to fluid flowing in the flow path increases as the flow rate of fluid increases, heating efficiency at the time of intermediate output can be improved. Further, because a predetermined quantity of heat can be acquired quickly, supply of fluid to the electric heating device can be stopped at an early stage. Therefore, power or the like required for supplying fluid to the electric heating device can be reduced.
Advantageously, in the electric heating device, the heating element is a PTC element.
The PTC element generates heat by energization. Upon reaching a certain temperature, the PTC element largely increases its resistance and is held at the certain temperature. Further, as the temperature increases, a value of an electric current flowing in the PTC element decreases. According to the electric heating device, therefore, an abnormal temperature increase in the heating module can be prevented. Further, power consumption required for generating heat in the heating elements can be reduced.
Advantageously, the electric heating device includes: a first header that is provided at one end of the flow paths and supplies fluid to the flow paths; and a second header that is provided at the other end of the flow paths and collects fluid discharged from the flow paths. The first header includes a fluid supply port for supplying fluid into the first header, and the second header includes a fluid discharge port for discharging fluid to outside of the second header.
Fluid supplied from the fluid supply port to the first header sequentially flows from a flow path close to the fluid supply port toward a flow path away from the fluid supply port. Therefore, a static pressure distribution is generated in the first header. Also in the second header, a static pressure distribution is generated because static pressure near the fluid discharge port decreases most. Due to the static pressure distribution in the headers, a magnitude of flow rate of fluid differs in each flow path. According to the electric heating device, even when there is a difference in the magnitude of flow rate in the respective flow paths due to the static pressure distribution in the headers, heating efficiency at the time of intermediate output can be improved. Further, in the electric heating device, fluid is supplied from the first header to the flow path formed of a tubular structure, for example, a tube. Fluid discharged from the flow path is collected in the second header. Therefore, leakage of fluid to outside of the flow path can be suppressed, as compared with a structure in which flow paths are formed by partitioning a casing by walls or the like.
According to another aspect of the present invention, a vehicle air conditioner includes: a blower that takes outside air into an air flow path of an air conditioning unit and circulates air in a vehicle interior; a cooler that is arranged on a downstream side of the blower and cools outside air; and a heater that is arranged on a downstream side of the cooler and heats air cooled by the cooler. An electric heating device for heating fluid supplied to the heater is provided, and the electric heating device is the electric heating device discussed above, and includes a circulation circuit for circulating the fluid to the electric heating device.
By applying the electric heating device according to any one of inventions described above to a vehicle air conditioner, when adjustment of temperature to approximate an intermediate temperature between heating and cooling in an intermediate period (in the spring and autumn) is required, the electric heating device according to the inventions described above provided in the vehicle air conditioner is set to intermediate output at which a part of the heating elements is energized. At this time, the electric heating device can preferentially heat a flow path having a relatively large flow rate of fluid, and thus unnecessary power consumption can be suppressed and heating efficiency can be improved. As a result of improving the heating efficiency, the flow rate that becomes a required quantity of heating can be reduced, thereby enabling to suppress driving power of a fluid supply unit that supplying fluid, such as a pump. Particularly, in a case of an electric car, power consumption of the entire car can be suppressed, thereby enabling to increase its driving efficiency.
Advantageously, the vehicle air conditioner includes a controller that includes an in-vehicle temperature detector and instructs a predetermined output to the electric heating device according to an in-vehicle temperature detected by the in-vehicle temperature detector.
According to the vehicle air conditioner, optimum output control of the electric heating device provided in the vehicle air conditioner according to the in-vehicle temperature is realized. Therefore, the heating efficiency of the electric heating device is further improved, and power consumption by the vehicle air conditioner can be further suppressed. Particularly, in a case of an electric car, power consumption of the entire car can be suppressed, thereby enabling to increase its driving efficiency.
According to the electric heating device of the present invention, fluid can be heated efficiently at the time of intermediate output of the electric heating device. Further, according to the vehicle air conditioner of the present invention, at the time of intermediate output of the electric heating device, power consumption of the vehicle air conditioner can be reduced.
Exemplary embodiments of an electric heating device and a vehicle air conditioner according to the present invention will be explained below in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments.
As shown in
For example, the flow path 3 can have a tubular structure, and it can be a tube. A plurality of flow paths 3 are provided in parallel in the casing 9. The flow paths 3 are arranged so that a plurality of rows are formed in the lateral direction and in the longitudinal direction. In the electric heating device 1, the flow paths 3 are arranged in two rows in the longitudinal direction and in ten rows in the lateral direction; however, these can be appropriately changed according to a place where the electric heating device 1 is arranged and a required output. Particularly, the flow path 3 can be arranged in one row in the longitudinal direction.
The flow path 3 is provided such that one end face opens in the first header 11, and the other end face opens in the second header 13. That is, the first header 11 and the second header 13 are communicated with each other by the flow path 3. The first header 11 includes a fluid supply port 15 for introducing fluid into the first header 11. The second header 13 includes a fluid discharge port 17 for discharging fluid to outside of the second header 13. In the electric heating device 1, the fluid supply port 15 and the fluid discharge port 17 open in the same direction in the lateral direction.
The respective heating modules 5 are arranged between the flow paths 3 adjacent to each other in the lateral direction. In other words, the heating modules 5 are arranged between rows of the flow paths 3 in the lateral direction. In the electric heating device 1, eight heating modules 5 are provided between rows of the flow paths 3 in the lateral direction; however, the number thereof can be appropriately changed according to the arrangement of the flow paths 3, the configuration of the heating module 5 or the like. The heating module 5 includes the heating element 7, an electrode plate 19, and an insulating plate 21.
The electrode plate 19 is electrically connected to a substrate 25 shown in
The substrate 25 has a function of energizing the electrode plate 19 provided in the heating module 5 via the protrusion 19a of the electrode plate 19. When the electrode plate 19 is energized, the heating element 7 provided in contact with the electrode plate 19 is energized to generate heat. The heating element 7 can be a PTC element, which is a positive-temperature-coefficient thermistor element. The PTC element generates heat by energization. Upon reaching a certain temperature, the PTC element largely increases its resistance, and is held at a certain temperature. Further, as the temperature increases, a value of an electric current flowing in the PTC element decreases.
A controller 27 determines output of the electric heating device 1 based on a detection value of the temperature or the like at a predetermined place, and transmits a control signal corresponding to the output to the substrate 25. The output of the electric heating device 1 can be mainly divided into three, that is, maximum output, intermediate output, and minimum output. When the electric heating device 1 is controlled to the maximum output, the substrate 25 is controlled to energize all of the electrode plates 19. When the electric heating device 1 is controlled to the minimum output, in other words, when the output is controlled to be zero, the substrate 25 is controlled to suspend energization to all of the electrode plates 19. When the electric heating device 1 is controlled to the intermediate output, which is in between the maximum output and the minimum output, the substrate 25 is controlled to energize parts of the electrode plates 19 and suspend energization to the remaining electrode plates 19.
An operation of the electric heating device 1 is explained below. Fluid boosted by a fluid supply unit (not shown), for example, by a pump is supplied into the first header 11 via the fluid supply port 15. Fluid supplied to the first header 11 flows sequentially from the flow path 3 closest to the fluid supply port 15. Fluid flowing into the flow path 3 is heated by heat exchange with the heating module 5 provided adjacent to the flow path 3 and flows out to the second header 13. Fluid flowing out to the second header 13 is discharged to outside of the second header 13 via the fluid discharge port 17.
At this time, a quantity of heat that can be given to fluid flowing in the adjacent flow path 3 by the heating module 5 can be indicated by the following equation 1.
Q=k·A·(Tp−Tw)
K∝QS (Equation 1)
In the equation, Q denotes a quantity of heat given to fluid by the heating module 5, k denotes an overall heat transfer coefficient indicating thermal conductivity, A denotes a heat transmission area, Tp denotes a surface temperature of the heating element 7, Tw denotes a temperature of fluid, and QS denotes a flow rate of fluid in the flow path 3. The overall heat transfer coefficient k and the flow rate QS of fluid are substantially in a proportional relation, and when QS increases, k also increases. In the electric heating device 1, the heat transmission area A is constant, and the temperature Tw of fluid is constant.
At the time of intermediate output of the electric heating device 1, the heating element 7 held by a part of the heating module 5 is energized by the substrate 25 via the electrode plate 19. When it is assumed that the temperature of the heating element 7 at the time of energization is constant, the quantity of heat Q given to fluid by the heating module 5 increases, as the flow rate QS increases. The electric heating device 1 preferentially selects and energizes a heating element held by the heating module 5 provided adjacent to the flow path 3 having a relatively large flow rate of fluid.
The flow rate of fluid in the respective flow paths 3 is explained here.
As described above, the fluid having flown into the first header 11 from the fluid supply port 15 flows sequentially from the flow path 3 closest to the fluid supply port 15 toward the flow path 3 away from the fluid supply port 15. Therefore, in the first header 11, the flow rate of fluid decreases as moving away from the fluid supply port 15 and flow velocity becomes slow. Along with this, as shown in
The flow rate of fluid in the respective flow paths 3 is determined based on a static pressure difference ΔP between the first header 11 and the second header 13 where the flow path 3 is located. That is, the flow rate of fluid flowing in the flow path 3 increases, as the static pressure difference ΔP between the first header 11 and the second header 13 increases. According to
That is, at the time of intermediate output of the electric heating device 1, in the lateral direction in the cross-sectional surface of the casing 9 orthogonal to the longitudinal direction of the flow path 3, the heating element 7 held by the heating module 5 adjacent to the flow path 3 positioned on the outermost side is preferentially selected and energized.
According to the electric heating device 1, at the time of intermediate output, the flow path 3 having a relatively large flow rate of fluid, of the flow paths 3, can be preferentially selected and heated. That is, in the lateral direction in the cross-sectional surface of the casing 9 orthogonal to the longitudinal direction of the flow path 3, the flow path 3 on the outermost side can be preferentially selected and heated. The quantity of the heat Q that can be given to fluid by the heating module 5 increases as the flow rate QS of fluid flowing in the flow path 3 increases. Therefore, when the electric heating device 1 is used, heating efficiency at the time of intermediate output can be improved.
Accordingly, because a predetermined quantity of heat can be acquired promptly, supply of fluid to the electric heating device 1 can be suspended at an early stage. Therefore, power or the like required for supplying fluid to the electric heating device 1 can be reduced. When the flow rate of fluid to be supplied to the electric heating device 1 is adjusted according to the quantity of heat required for the desired output, the flow rate of fluid at the time of intermediate output can be decreased. Also with this configuration, power or the like required for supplying fluid to the electric heating device 1 can be reduced.
Further, the electric heating device 1 includes the first header 11 and the second header 13. The flow path 3 is for example, a tubular structure such as a tube, and the end face thereof opens in the first header 11 and the second header 13. Because fluid heated by heat exchange with the heating module 5 flows in the flow path 3, leakage of fluid to outside of the flow path can be suppressed, as compared with a structure in which the flow path 3 is formed by partitioning the casing 9 by walls or the like.
In the electric heating device 1, a difference occurs in the flow rate in the flow path 3 due to provision of the first header 11 and the second header 13. However, even in the case that the electric heating device 1 does not include the first header 11 and the second header 13, when a plurality of flow paths are provided in the casing, a difference in the flow rate of fluid between the respective flow paths occurs at least occasionally. In such a case, therefore, the heating module 5 provided adjacent to the flow path and having a relatively large flow rate of fluid is preferentially selected at the time of intermediate output of the electric heating device, so that the heating elements 7 held by the heating module 5 generate heat, thereby enabling to improve the heating efficiency at the time of intermediate output.
An electric heater or the like can be used as the heating element 7 in the electric heating device 1; however, it is desired to use the PTC element, which is the positive-temperature-coefficient thermistor element. The PTC element generates heat by energization. Upon reaching a certain temperature, the PTC element largely increases its resistance, and is held at the certain temperature. Further, as the temperature increases a value of an electric current flowing in the PTC element decreases. Accordingly, by using the PTC element as the heating element 7, abnormal temperature rise in the heating module 5 in the electric heating device 1 can be prevented. Further, consumed power can be reduced, and power consumption required for heat generation of the heating element 7 can be also reduced.
The electrode plate 19 held by the heating module 5 includes the protrusion 19a formed by protruding a part of the electrode plate 19. In the lateral direction in the cross-sectional surface of the casing 9 orthogonal to the longitudinal direction of the flow path 3, the protrusions 19a of the adjacent heating modules 5 are connected to each other. Accordingly, an energizing system 127 formed of two heating modules 5 is configured. In the electric heating device 101, four energizing systems are provided, and as shown in
The flow rate of fluid in the respective flow paths 3 when fluid flows in the flow path 3 in the electric heating device 101 is explained.
As viewed in
In the electric heating device 101, at the time of intermediate output, the heating element 7 held by the heating module 5 adjacent to the flow path 3 having a relatively large flow rate of fluid is preferentially energized. Specifically, the energizing system 127d formed of the heating module 5 that can heat the flow paths 3I, 3i, 3H, and 3h and the heating module that can heat the flow paths 3H, 3h, 3G, and 3g is preferentially energized by the substrate 25. The energizing system 127a is then preferentially energized, followed by the energizing system 127c. The number of systems to be energized is appropriately determined based on the output acquired by the electric heating device 101. Accordingly, for example, when two systems are to be energized, the energizing systems 127a and t 127d are energized. When three systems are to be energized, energization is performed with respect to the energizing systems 127a, 127d, and 127c.
In the verification example, the energizing system 127 is formed by connecting the protrusions 19a of the electrode plates 19 of two heating modules 5 with each other. However, like in the electric heating device 1, one energizing system can be formed of one heating module 5. In this case, the flow path to be heated can be finely selected as compared with a case that the one energizing system 127 is formed of two heating devices 7. On the other hand, like in the electric heating device 101, when plural heating modules 5 constitute the energizing system 127, the number of wiring connections from a power supply unit (not shown) can be less than the number of connections to the respective heating modules 5. Accordingly, in the electric heating device 101, weight reduction and space saving are realized. Further, the above configuration contributes to reduction of man-hour at the time of assembling the electric heating device 101.
A blower 203, a cooler 204, a heater 205, which is an air conditioning heat exchange unit, and an air mix damper 206 are provided in the casing 202. A tank 207, a pump 208, and the electric heating device 101 according to the verification example described above are provided outside of the casing 202. The tank 207, the pump 208, the electric heating device 101, and the heater 205 constitute a fluid circulation route 209 in which fluid, which is a heating medium, circulates.
The blower 203 sucks outside air or air in the vehicle interior to increase pressure, and feeds air to a downstream side of the blower 203 in the air flow path 202A. The cooler 204 cools air fed from the blower 203. The cooler 204 includes an expansion valve, an evaporator or the like, to cool air passing through the cooler 204 by heat of vaporization generated when a refrigerant circulating therein evaporates.
The heater 205 heats air passing through the cooler 204 and cooled. A flow path in which fluid heated by the electric heating device 101 flows and a flow path in which air passes are provided inside the heater 205. Air is heated by heat exchange between fluid heated by the electric heating device 101 and air passing through the heater 205.
The air mix damper 206 adjusts a rate between a quantity of air that passes through the heater 205 and a quantity of air that flows bypassing the heater 205, to adjust a temperature of air mixed on the downstream side thereof. When heating is not required, the entire air is caused to bypass the heater 205 to reduce a pressure loss.
The tank 207 temporarily holds a part of the heating medium that circulates in the fluid circulation route 209. The tank 207 is arranged between the heater 205 and the pump 208 in the fluid circulation route 209. The pump 208 compresses fluid and supplies the fluid to the electric heating device 101. The pump 208 is arranged between the tank 207 and the electric heating device 101 in the fluid circulation route 209.
The downstream side of the casing 202 is connected to a plurality of vents that blow the temperature-adjusted air into the vehicle interior via a blowing-mode switching damper and duct.
As shown in
At the time of heating the vehicle interior (in the winter), all four systems are energized, and fluid in the flow path 3 is heated by the respective heating modules 5. Heated fluid is fed to the heater 205 and heat-exchanged with air in the vehicle air conditioner 201, and the heated air is blown into the vehicle interior. Accordingly, heating is efficiently performed in a short time. On the other hand, at the time of cooling the vehicle interior (in the summer), because energization with respect to all four systems is suspended, fluid in the flow path 3 is not heated. At this time, because fluid does not need to be supplied to the electric heating device 101, the pump 208 is also suspended, thereby suppressing the power consumption.
Further, during an intermediate period (in the spring and autumn), by a train crew, adjustment of temperature can be required to adjust a set temperature in the vehicle interior to an intermediate one in between heating and cooling. That is, hot air and cold air are mixed substantially at a 50:50 ratio and adjusted, and the temperature-adjusted air is blown into the vehicle interior. When a predetermined temperature value is detected by the temperature sensor installed in the vehicle interior, the controller 27 transmits an instruction value of intermediate output to the electric heating device 101, and two systems are energized to heat fluid.
At this time, as explained with reference to
The flow rate of fluid can be also reduced to acquire a required quantity of heating, and power required to drive the pump for supplying fluid to the electric heating device 101 can be reduced. That is, a time (a flow rate) required for feeding fluid to acquire the required quantity of heating can be reduced, thereby reducing driving power of the pump. When the air conditioner according to the present embodiment is applied to an electric car, power consumption of the entire car can be reduced, thereby enabling efficient driving.
According to the vehicle air conditioner 201, because the electric heating device 101 according to the first embodiment is used for heating fluid, which is a heating medium, power used for air conditioning in the vehicle interior can be reduced. As described above, the electric heating device 101 has high heating efficiency at the time of intermediate output. Accordingly, at the time of intermediate output of the electric heating device 101, the flow rate of fluid circulated by the pump 208 can be reduced, and power consumed for driving the pump 208 can be also reduced. In the vehicle air conditioner 201, the electric heating device 101 according to the verification example is used; however, the electric heating device 1 can be also used.
As described above, the electric heating device according to the present invention is useful for efficiently heating fluid flowing in the device at the time of intermediate output, and particularly suitable to be used as a heat source of an electric car or the like in which waste heat of an engine cannot be used as a heat source of a heating unit. Furthermore, the vehicle air conditioner according to the present invention is useful for decreasing the power to be used for air-conditioning in a vehicle interior.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-017432 | Jan 2010 | JP | national |
