A thermally conditioned vehicle seat

TECHNICAL FIELD

The subject invention relates to a thermally air conditioned seat in an automotive vehicle by using air from the HVAC system of the vehicle.

BACKGROUND OF THE INVENTION

The thermal comfort of passengers in a vehicle is conventionally provided by the central heating, ventilation and air conditioning (HVAC) module of the vehicle. Passengers are heated or cooled by convection through the surrounding medium in the interior of the vehicle. More recently, vehicle seating systems have been described that provide for dedicated heating and cooling of the occupant by an independent thermoelectrically energized unit incorporated into a vehicle seat. These units typically consist of one or more thermoelectric (TE) modules, heat exchangers, and fans, and are operated by allowing the fan to blow cabin air over the hot and cold sides of the thermoelectric, resulting in heat being absorbed from the air on the cold side and released to the air on the hot side. The cooled air is directed through or over the seat to the occupant's body surface, whereas the warmed air is rejected into the vehicle cabin, for instance under or behind the seat. Because these thermoelectrically climate controlled seats use cabin air as the medium, which generally is initially cold in heating mode and warm in cooling mode, there is necessarily a deliberate transient thermal response of the seating system.

The cooling and heating of a passenger in an automotive vehicle can most effectively be obtained by applying the thermal condition directly to the human being. The current automotive air conditioning systems utilize ducts at the floor to heat, and ducts leading to vents in the instrument panel to cool. The effectiveness in attempting to cool or heat occupants in an automobile is significantly lost to the surrounding air and thermal mass, as only part of the heat exchange is directed toward the passenger.

The optimum effect is attained by applying the conditioned air as directly as possible to the human passenger. This is accomplished by flowing conditioned air to the passenger seat from a known source like the HVAC module or a thermoelectric cooler/heater dedicated to the seat, as illustrated in U. S. Patents Re. 38,128 to Gallup et al., 5,924,766 to Esaki et al., and 6,079,485 to Esaki et al., and PCT application WO 99/58907 to Bell.

However, the air from the HVAC module on initial startup is not thermally conditioned. In the case of heating, it takes time to warm the coolant due to the thermal inertia of the engine. In the case of cooling, it takes time for the typical Rankine A/C cycle to cool air. On the other hand, a dedicated thermoelectric device to heat or cool the ambient air from the vehicle cabin does have the thermal capacity vis-à-vis the electrical power available to provide optimum comfort. In other words, the electrical power required to energize the thermoelectric heat exchanger for adequate comfort is quite significant and sometimes not practical. In the heating mode, the passenger is not satisfied with the level of warmth. In cooling mode, the passenger is not satisfied with the cooling effect and even feels cold and clammy, as the thermoelectric does not dehumidify the air. The reason for this is that the dew point temperature is below the thermoelectric cooling temperature and little to no dehumidification takes place. When the humidity is very high in the passenger cabin, the thermoelectric device will collect condensed moisture without being able to eliminate it.

SUMMARY OF THE INVENTION

The subject invention provides thermally conditioned air to passages in a seat of an automotive vehicle having a HVAC module for supplying heating and cooling air to a cabin vent and is distinguished by exchanging heat with the heating and cooling air from the HVAC module in an auxiliary heat exchanger before delivery to the seat passages of the seat assembly, i.e., by an auxiliary air-conditioning device in the ductwork between the HVAC module and the seat passages of the seat assembly.

Therefore, the subject invention provides a thermoelectric device in series with thermally conditioned air from an HVAC module to provide the ultimate comfort to the passenger upon initial warm-up and cool down, and in steady state operation. The invention differs from the prior art by using preconditioned air from the HVAC module rather than cabin air for the hot and cold side of a thermoelectric device. The placement of the thermoelectric device in series with the HVAC increases the effectiveness in cooling or heating the passenger and significantly reduces the initial time to reach the desired comfort level of the seat occupant, i.e., a faster cool-down in the cooling mode and/or warm-up in the heating mode of the vehicle seat than would otherwise be obtained using unconditioned air flows.

Because the thermoelectric device operates using preconditioned HVAC module air, the temperature range, -7°C-27°C, of operation is narrower than in known systems,-15°C-40°C, in the first 2-10 minutes of operation and the average temperature of operation is shifted to a lower temperature (from 27.5°C to 10°C).

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: <ul id="ul0001" list-style="none" compact="compact"><li>Figure 1 is a schematic view of an automotive vehicle combined with the auxiliary air-conditioning device for thermally conditioning a seat assembly in the vehicle; and</li><li>Figure 2 is a schematic view of the auxiliary air-conditioning device.</li></ul>

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the Figures, an automotive vehicle is illustrated in Figure 1 and an auxiliary air-conditioning device is illustrated in Figure 2.

The automotive vehicle includes a body defining a passenger cabin <b>20.</b> A seat assembly <b>22</b> is disposed in the cabin <b>20</b> and has seat passages <b>24</b> for thermally conditioning a seat occupant with air, e.g., the vehicle seat assembly <b>22</b> may have a perforated seat cushion that will allow air to pass through.

The cabin <b>20</b> has at least one and normally a plurality of cabin vents <b>26</b> in the vehicle for conveying air into the cabin <b>20.</b> A well known HVAC module <b>28</b> supplies heating and cooling air and cabin ductwork <b>30</b> conveys the heating and cooling air from the HVAC module <b>28</b> to the cabin vent <b>26</b> and seat ductwork <b>32</b> conveys the heating and cooling air from the HVAC module <b>28</b> to the seat passages <b>24</b> of the seat assembly <b>22.</b>

An auxiliary air-conditioning device comprising a thermo-electric device <b>34</b> is disposed in the seat ductwork <b>32</b> for heating and cooling air from the HVAC module <b>28</b> for delivery to the seat passages <b>24</b> of the seat assembly <b>22.</b> The vehicle includes an electrical system <b>36</b> including a battery and an alternator for supplying electrical power and the thermo-electric device <b>34</b> is connected electrically to the electrical system <b>36</b> for receiving electrical power there from. The thermo-electric device <b>34</b> includes a seat side <b>38</b> and a cabin side <b>40</b> that include a seat duct for conveying air from the seat side <b>38</b> to the seat passages <b>24</b> and a cabin <b>20</b> duct for conveying air form the cabin side <b>40</b> to a cabin vent <b>26.</b>

As alluded to above, the ductwork <b>32</b> includes a HVAC duct for conveying air from the HVAC module <b>28</b> to the auxiliary air-conditioning device, and a flow divider <b>42,</b> illustrated as a pointed wall, is disposed in the HVAC duct for dividing air between the seat and cabin sides <b>40</b> of the auxiliary air-conditioning device from the HVAC module <b>28.</b> The wall 42 divides air from the HVAC module <b>28</b> for passing through the seat side <b>38</b> and the cabin side <b>40.</b>

The auxiliary air-conditioning device includes a heat exchanger <b>44</b> disposed between the seat <b>38</b> and cabin <b>40</b> sides for transferring heat therebetween. More specifically, the heat exchanger <b>44</b> includes a thermoelectric element or module <b>46</b> disposed between the seat and cabin sides <b>40</b> with a first heat exchanger <b>48</b> on the seat side of the thermoelectric element <b>46,</b> and a second heat exchanger <b>50</b> on the cabin side <b>40</b> of the thermoelectric element <b>46.</b> A thermal insulation <b>52</b> is between the seat <b>38</b> and cabin <b>40</b> ducts downstream of the auxiliary air-conditioning device <b>34</b> for inhibiting the transfer of thermal energy between the seat <b>38</b> and cabin <b>40</b> ducts.

The auxiliary air-conditioning device <b>34</b> may be supported by the seat assembly <b>22</b> for efficiency and response time, as discussed below, or mounted in vehicle close thereto via the seat duct being flexible for allowing relative movement between the said seat assembly and the auxiliary air-conditioning device.

As will be appreciated, the invention provides a method of providing thermally conditioned air to passages <b>24</b> in a seat <b>22</b> of an automotive vehicle having a HVAC module <b>28</b> for supplying for supplying heating and cooling air to a cabin vent <b>26</b> wherein the method comprises the steps of delivering heating and cooling air from the HVAC module <b>28</b> to the seat passages <b>24</b> of the seat assembly <b>22,</b> and exchanging heat with the heating and cooling air from the HVAC module 28 by an auxiliary heat exchange <b>34</b> before delivery to the seat passages <b>24</b> of the seat assembly <b>22.</b>

The step of utilizing an auxiliary air-conditioning device <b>34</b> is further defined as utilizing electrical power from the vehicle electrical system <b>36</b> to drive the auxiliary heat exchange.

The method is further defined as dividing <b>42</b> the heating and cooling air from the HVAC module <b>28</b> into a seat side <b>38</b> and a cabin side <b>40</b> and the step of exchanging heat is further defined as exchanging heat between the seat side <b>38</b> and the cabin side <b>40.</b> The method continues by conveying air from the seat side <b>38</b> to the seat passages <b>24</b> and conveying air from the cabin side <b>40</b> to the cabin via a cabin vent <b>26.</b> The method further includes the step of dividing <b>42</b> air from the HVAC module <b>28</b> between the seat <b>38</b> and cabin <b>40</b> sides. The method also includes inhibiting <b>52</b> the transfer of thermal energy between the air from the seat side <b>38</b> to the seat passages <b>24</b> and the air from the cabin side <b>40</b> to the cabin vent <b>26.</b> The method is most efficient by conveying the heating and cooling air from the HVAC module <b>28</b> to the seat passages <b>24</b> solely by an air mover in the HVAC module <b>28.</b> In other words, there is no air movement or propulsion device between the HVAC module <b>28</b> and the seat assembly <b>22.</b>

The air will be supplied from the HVAC module <b>28</b> after a mixing chamber to allow thermally conditioned dry air to enter a set of ductwork <b>32.</b> The supplied air will then enter the thermoelectric device <b>34</b> placed as close as possible to the seat assembly <b>22,</b> as alluded to above, preferably supported on the seat assembly <b>22.</b> The placement of the thermal electric device <b>34</b> as close as possible to the seat assembly <b>22</b> is important to the efficiency of the inventive combination and to minimize the empty or static air between the seat <b>22</b> and thermoelectric heat device <b>34</b> that would not be conditioned on initial startup of the vehicle.

The current invention supplies conditioned air to the seat assembly <b>22</b> at a low flow rate, typically around five to ten percent (5-10%) of the total airflow to each seat at high blower setting and diminishing to one to two percent (1%-2%) of total <b>airflow to each seat at low blower setting. A typical airflow percentage for each seat is set forth in this table:</b><tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="3" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="52.50mm" /><colspec colnum="2" colname="col2" colwidth="52.50mm" /><colspec colnum="3" colname="col3" colwidth="52.50mm" /><thead valign="top"><row><entry namest="col1" nameend="col3" align="left"><b>Percent of Total Airflow Directed Toward Seats</b></entry></row><row><entry namest="col1" nameend="col1" align="left"><b>Blower setting</b></entry><entry namest="col2" nameend="col2" align="left"><b>Driver Seat Airflow</b></entry><entry namest="col3" nameend="col3" align="left"><b>Passenger Seat Airflow</b></entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">HI</entry><entry namest="col2" nameend="col2" align="left">5%-10%</entry><entry namest="col3" nameend="col3" align="left">5%-10%</entry></row><row><entry namest="col1" nameend="col1" align="left">M1</entry><entry namest="col2" nameend="col2" align="left">3.5%-7%</entry><entry namest="col3" nameend="col3" align="left">3.5.%-7%</entry></row><row><entry namest="col1" nameend="col1" align="left">M2</entry><entry namest="col2" nameend="col2" align="left">1.5%-3%</entry><entry namest="col3" nameend="col3" align="left">1.5.%-3%</entry></row><row><entry namest="col1" nameend="col1" align="left">LO</entry><entry namest="col2" nameend="col2" align="left">1%-2%</entry><entry namest="col3" nameend="col3" align="left">1%-2%</entry></row><row rowsep="1"><entry namest="col1" nameend="col3" align="justify"><i>Table-Typical Seat Airflow Percentages</i></entry></row></tbody></tgroup></table></tables>

However, conditioned air from an HVAC module <b>28</b> takes time to warm the air depending upon the temperature of the coolant or of the refrigerant. The initial warm-up and cool down can be accelerated as the thermoelectric device <b>34</b> operates for the first few minutes, then the HVAC module <b>28</b> conditioned air is utilized to comfort the passenger. These modules and devices will work in combination to provide the optimal cooling or heating with minimal electrical power consumption.

The thermoelectric subassembly or device <b>34</b> shown in Figure 2 to supply conditioned air to the heated and cooled seat assembly <b>22</b> includes a thermoelectric element <b>46,</b> seat <b>48</b> and cabin <b>50</b> side heat exchangers, ductwork <b>32,</b> a divider <b>42</b> that sends air flow to the seat <b>48</b> or cabin<b>50</b> side of the thermoelectric element <b>46,</b> and thermal insulation <b>52</b> downstream from the heat exchanger <b>44.</b> The air T_a originating from the central HVAC module <b>28</b> of the vehicle is propelled through the thermoelectric device <b>34</b> by the fan built into the HVAC module <b>28,</b> the fan of the HVAC module <b>28</b> being the sole motivation for moving the conditioned air T_a to the seat assembly <b>22.</b> A fraction T_seat of the air T_a from the HVAC module <b>28,</b> determined by the flow divider <b>42,</b> or other dividing device, serves to heat or cool the seat <b>22,</b> the other fraction T_cabin is used to manage the heat load imposed by the thermoelectric element <b>46</b> and is dumped into the cabin <b>20.</b> The seat <b>48</b> and cabin <b>50</b> side of the heat exchanger <b>44</b> utilize air flows originating from the main HVAC module <b>28</b> of the vehicle as opposed to air from the cabin <b>20.</b> By the use of the appropriate ductwork <b>32</b> and thermal insulation <b>52,</b> a fraction T_seat of the preconditioned air T_a from the HVAC module <b>28</b> may be directed over the seat side <b>38</b> of the heat exchanger <b>44</b> and to the seat assembly <b>22,</b> the remaining fraction T_cabin being directed over the cold side <b>50</b> of the heat exchanger <b>44</b> and to the cabin <b>20;</b> these fractions being fixed at an optimum value by the shape of the proportioning fixed flow divider <b>42.</b>

In operation, the HVAC module <b>28</b> directs pre-cooled (in cooling mode) or preheated (in heating mode) air (T_a) from the HVAC module <b>28</b> over the seat and cabin sides of the Thermoelectric (TE) device <b>34.</b> This TE device <b>34,</b> driven by an electrical current I, causes further cooling or heating of the air on the cold side of the TE device <b>34,</b> and the heat absorbed from the cold side is pumped to and liberated from the hot side via the hot side <b>50</b> of the heat exchanger <b>44.</b> Two important parameters of a TE device <b>34</b> are the cooling power Q and the coefficient of performance (or refrigerating efficiency) COP. The efficiency of any cooling system, be it a vapor-compression system or a thermoelectric system, is defined as the <i>Coefficient of Performance</i> (COP), which is, by definition, the amount of heat extracted on the cold side divided by the work (electric energy) required, W: COPC=Q_C/W. Cooling power, Q, and coefficient of performance, COP, are a function of the current (I) in the TE device <b>34</b> and the seat <b>48</b> and cabin<b>40</b> side temperatures T_seatand T_cabin, respectively. When the auxiliary air conditioning device is in the cooling mode, T_c=T_seat and T_h=T_cabin and the expressions for COP and Q can be expressed as the following:<maths id="math0001" num="(1)"><math display="block"><mrow><mtext mathvariant="italic">Q</mtext><mtext>=</mtext><msub><mrow><mtext mathvariant="italic">SIT</mtext></mrow><mrow><mtext mathvariant="italic">C</mtext></mrow></msub><mtext>-</mtext><mtext mathvariant="italic">K</mtext><mtext>Δ</mtext><mtext mathvariant="italic">T</mtext><mtext>-</mtext><mfrac><mrow><mtext>1</mtext></mrow><mrow><mtext>2</mtext></mrow></mfrac><msup><mrow><mtext mathvariant="italic">I</mtext></mrow><mrow><mtext>2</mtext></mrow></msup><mtext mathvariant="italic">R</mtext></mrow></math><img file="EP1598223A2_D0001.tif" /></maths> and<maths id="math0002" num="(2)"><math display="block"><mrow><mtext mathvariant="italic">COP</mtext><mtext>=</mtext><mfrac><mrow><msub><mrow><mtext mathvariant="italic">SIT</mtext></mrow><mrow><mtext mathvariant="italic">C</mtext></mrow></msub><mtext>-</mtext><mtext mathvariant="italic">K</mtext><mtext>Δ</mtext><mtext mathvariant="italic">T</mtext><mtext>-</mtext><mfrac><mrow><mtext>1</mtext></mrow><mrow><mtext>2</mtext></mrow></mfrac><msup><mrow><mtext mathvariant="italic">I</mtext></mrow><mrow><mtext>2</mtext></mrow></msup><mtext mathvariant="italic">R</mtext><mtext></mtext></mrow><mrow><mtext mathvariant="italic">I</mtext><mtext>(</mtext><mtext mathvariant="italic">S</mtext><mtext>Δ</mtext><mtext mathvariant="italic">T</mtext><mtext>+</mtext><mtext mathvariant="italic">IR</mtext><mtext>)</mtext></mrow></mfrac></mrow></math><img file="EP1598223A2_D0002.tif" /></maths> where S is the thermoelectric power of the module (in units of V/K), K is the module thermal conductance (in W/K), and R is the module resistance (in ohms); Δ<i>T</i>=<i>T</i>_<i>H</i>-<i>T</i>_<i>C</i>. For example, for Tavg=20°C=(1/2)(Th+Tc<i>)</i>, typical values for the thermoelectric parameters (see for instance <u>www.ferrotec.com</u>) are S =.053 V/K, K =.51 W/K, and R = 2.4 ohm. The resulting dependencies of Q and COP on I are shown in the following graph:<img file="EP1598223A2_D0003.tif" />

Conventional TE devices are operated such that either the COP, or the cooling power Q is maximized. When optimized for COP, the TE device is driven at current I_COP. This results, however, in a very low cooling power. If operated over a short period of time, however, the device may be operated at the current I_Q that maximizes the cooling power. Although this higher pumping capacity takes place at a lower COP, the TE device is operated at this current for only a short period of time. After a predetermined time period, the air T_a originating from the vehicle HVAC module <b>28</b> has cooled sufficiently that the current I of the TE device <b>34</b> may be turned down to I_COP to maximize its cooling efficiency.

The main advantage of the series HVAC module <b>28</b> and thermoelectric device <b>34</b> for seat cooling is that the steady-state cooling can be handled mostly by the HVAC module <b>28,</b> so that the thermoelectric device <b>34</b> can be optimized mainly for maximum cooling power. When operated in this scenario the seat climate control system has an improved transient response relative to a similar system that uses air originating from the cabin <b>20</b> for heat exchange.

In the operation of the climate control system, the TE device <b>34</b> is operated initially at a current that maximizes cooling or heating capacity and then, after a predetermined time period, it is operated at a lower current level, thereby improving the transient heating/cooling of the seat <b>22</b> relative to a climate control system using cabin air as the heat exchange medium.

The thermoelectric device <b>34</b> can be designed for cooling power, as opposed to COP. It is known in the art that thermoelectric devices are optimum for COP when they a have a high "thermoelectric figure of merit", Z, defined as:<maths id="math0003" num=""><math display="block"><mrow><msup><mrow><mtext>Z = S</mtext></mrow><mrow><mtext>2</mtext></mrow></msup><mtext>/ρκ</mtext></mrow></math><img file="EP1598223A2_D0004.tif" /></maths> where S is the Seebeck coefficient, p is the electrical resistivity and κ the thermal conductivity. To design a thermoelectric device <b>34</b> for maximum cooling power, set the derivative of equation (1) above with respect to current equal to zero, solve for current I, and then substitute that current into the same equation to obtain the maximum cooling power, resulting in:<maths id="math0004" num="(4)"><math display="block"><mrow><msub><mrow><mtext mathvariant="italic">Q</mtext></mrow><mrow><mtext>max</mtext></mrow></msub><mtext>=</mtext><mfrac><mrow><msup><mrow><mtext mathvariant="italic">S</mtext></mrow><mrow><mtext>2</mtext></mrow></msup><msub><mrow><mtext mathvariant="italic">T</mtext></mrow><mrow><mtext mathvariant="italic">C</mtext></mrow></msub><msup><mrow><mtext>​</mtext></mrow><mrow><mtext>2</mtext></mrow></msup></mrow><mrow><mtext>2</mtext><mtext mathvariant="italic">R</mtext></mrow></mfrac><mtext>-</mtext><mtext mathvariant="italic">K</mtext><mtext>Δ</mtext><mtext mathvariant="italic">T</mtext></mrow></math><img file="EP1598223A2_D0005.tif" /></maths>

Considering this equation (4), the optimum thermoelectric device <b>34</b> has a high Seebeck coefficient and a low electrical resistance, a property that is dependent on geometry. The optimum is now also relatively independent of thermal conductance during the transient, as, by definition, the temperature gradient starts at zero and remains relatively small (&lt;10°C) during the entire duration of the transient. The geometry of the thermoelectric device can be optimized for this typical application.

While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.