Abstract:
A vehicle seat assembly includes a seating surface, wherein the seating surface defines a plurality of temperature controlled zones. At least one electrically actuated heating/cooling source provides one of heating and cooling to the plurality of zones. A controller individually controls electrical power supplied from the source to each zone and is operative to reduce power consumption in one zone relative to another zone in accordance with a predetermined profile designed to limit the overall power consumption of the assembly.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates in general to temperature controlled vehicle seating. 
     Cold and hot environmental conditions can result in similar temperatures on the surfaces of seats resulting in the discomfort of the seat occupant. Accordingly, seat heaters and/or seat coolers have been provided. The seat heaters and coolers are commonly integrated into seat backs and seat cushions. The seat heaters and coolers provide heating and cooling to the seat surfaces. The seat heaters and coolers are manually operated by the seat occupant or alternatively the seat heaters and coolers can operate autonomously following initial pre-set conditions by the seat occupant. 
     Typical seat heaters include a resistive electrical grid that produces heat when electrical power is applied thereto. The resistive electrical grid produces heat throughout the area in which the seat heater is integrated. Seat coolers typically include circulating conditioned (cooled/heated) or non-conditioned air by fans and specially vented areas for providing a flow of air through perforations in the seating surfaces of the seat. The cooling fans and specially vented areas cool the area in which the seat coolers are integrated. Typically, the seat heaters and coolers operate through the use of electrical power. 
     While seat heaters and coolers can be effective in heating and cooling areas of a seat, typical seat heaters and coolers can consume large amounts of electrical power. Thus, it would be desirable to provide an improved seat heater and cooler system that more efficiently heat and cool a seat. 
     SUMMARY OF THE INVENTION 
     This invention relates to a vehicle seat assembly including a seating surface, wherein the seating surface defines a plurality of temperature controlled zones. At least one electrically actuated heating/cooling source provides one of heating and cooling to the plurality of zones. A controller individually controls electrical power supplied from the source to each zone and is operative to reduce power consumption in one zone relative to another zone in accordance with a predetermined profile designed to limit the overall power consumption of the assembly. 
     Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a seat having a reduced power heat mat in accordance with this invention. 
         FIG. 2  is a front cross-sectional view of the seat and reduced power heat mat of  FIG. 1 . 
         FIG. 3  is a perspective view of the seat illustrating the heating grid of the reduced power heat mat of  FIG. 1 . 
         FIG. 4  is a series of graphs illustrating a heating sequence of heating grids of the reduced power heat mat of  FIG. 1 . 
         FIG. 5  is an alternate embodiment of the reduced power heat mat illustrating a cooling system. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, there is illustrated in  FIG. 1  a seat, indicated generally at  12 , having a plurality of reduced power heat mats  10  in accordance with this invention. As will be explained in detail below, the plurality of reduced power heat mats  10  define one type of an electrically actuated heating/cooling source for providing heat to the seat  12  in an efficient manner. 
     As further shown in  FIG. 1 , the vehicle seat  12  includes a seat back  14  and a seat cushion  16 . The seat back  14  includes a back support  18  and a plurality of back bolsters  20 . The seat cushion  16  includes a seat support  22  and a plurality of seat bolsters  24 . The back support  18  includes a low back area  26 , mid back area  28  and upper back area  30 . Similarly, the seat support  22  includes rear seat area  32 , mid seat area  34  and front seat area  36 . 
     In the embodiment shown in  FIG. 1 , a reduced power heat mat  10  is disposed in the back support  18  and in the seat support  22 . Alternatively, a reduced power heat mat  10  can be disposed only in the back support  18  or only in the seat support  22 . In yet another embodiment, a reduced power heat mat  10  can be disposed in any of the plurality of back bolsters  20  or seat bolsters  24 . 
     As further shown in  FIG. 1 , the reduced power heat mat  10  disposed in the seat support  22  includes a plurality of zones  38 ,  40 ,  42 ,  44 ,  46  and  48 . While the reduced power heat mat  10  positioned within seat support  22  has six zones, it should be understood that the reduced power heat mat  10  can contain more than six zones or less than six zones  30 . In the illustrated embodiment, the zones  38  and  40  generally correspond to the front seat area  34 , zones  42  and  44  generally correspond to the mid seat area  34  and zones  32  and  46  generally correspond to the rear seat area  32 . 
     As further shown in  FIG. 1 , the reduced power heat mat  10  disposed in the back support  18  includes a plurality of zones  50 ,  52 ,  54 ,  56 ,  58  and  60 . While the reduced power heat mat  10  positioned within the back support  18  has six zones, it should be understood that the reduced power heat mat  10  can contain more than six zones or less than six zones  30 . In the illustrated embodiment, the zones  50  and  60  generally correspond to the lower back  26 , zones  52  and  58  generally correspond to the mid back area  28  and zones  54  and  56  generally correspond to the upper seat area  30 . 
     As shown in  FIG. 2 , the seat cushion  16  includes a base material  62  covered by a seat trim covering  64 . The base material  62  is adapted to provide padding to the seat cushion  16 . In one embodiment, the base material  62  is a synthetic foam material. In another embodiment, the base material  62  can be another material sufficient to provide padding to the seat cushion  16 . As shown in  FIG. 2 , the seat trim covering  64  is adapted to provide a protective and aesthetically pleasing cover. In one embodiment, the seat trim covering  64  is a fabric based material. In another embodiment, the seat trim covering  64  can be another material, such as for example leather, sufficient to provide a protective and aesthetically pleasing cover. 
     As further shown in  FIG. 2 , the seat cushion  16  also includes a reduced power heat mat  10 . The reduced power heat mat  10  includes an upper layer  66 , a plurality of heat sources  68  and a lower layer  70 . The upper layer  66  and lower layer  70  are adapted to protect the plurality of heat source  68  from incidental damage and electrically isolate the heat sources  68  from other portions of the seat cushion  16 . In the illustrated embodiment, the upper layer  66  and the lower layer  70  are made of a felt material. Alternatively, the upper layer  66  and the lower layer  70  can be another material, such as for example a fabric based material, sufficient to protect the plurality of heat source  68  from incidental damage and electrically isolate the heat sources  68  from other portions of the seat cushion  16 . While  FIG. 2  illustrates a space between the upper layer  66 , the plurality of heat sources  68  and the lower layer  70 , it should be understood that the upper layer  66  may be in contact with the plurality of heat sources  68 , and the plurality of heat sources  68  may be in contact with the lower layer  70 . While the illustrated embodiment shows an upper layer  66 , a plurality of heat sources  68  and a lower layer  70 , it should be understood that additional layers, such as for example a thermally reflective layer, can be used. 
     Referring now to  FIG. 3 , a seat cushion  16  is shown including the seat trim covering  64  and the reduced power heat mat  10 . As previously described, the seat cushion  16  includes rear seat area  32 , mid seat area  34  and front seat area  36 . The rear seat area  32  includes zones  48  and  46  of the reduced power heat mat  10 , the mid seat area  34  includes zones  42  and  44  of the occupant sensing heat mat  10 , and the front seat area  36  includes zones  38  and  40  of the reduced power heat mat  10 . 
     As shown in  FIG. 3 , zones  38 ,  42  and  46  each include a heat source  68 . The plurality of heat sources  68  are adapted to provide heat to the seat cushion  16 . Although for clarity purposes, a heat source  68  is not shown in zones  40 ,  44  and  48 , it should be understood that a heat source  68  is also included in zones  40 ,  44  and  48 . 
     As illustrated in  FIG. 3 , each heat source  68  includes a resistive electric grid  72  and a plurality of grid terminals  74 . In the illustrated embodiment, the resistive electric grid  72  is made of electrically resistant wires arranged in a pre-determined pattern. In another embodiment, the resistive electric grid can be made of another electrically resistant material, such as for example conductive carbon fiber, arranged in a pre-determined pattern. The resistive electric grid  72  is adapted to receive electric power through the grid terminals  74  and provide heat as the electric power flows through the grid  72 . The resistive electric grids  72  are rated for a heating density according to the desired heating effect. In one embodiment, the resistive electric grids  72  are rated for a heating density in a range from about 200 watts/m 2  to about 1200 watts/m 2 , where heat density is defined as the amount of heat dissipated for a given physical area. In another embodiment, the resistive electric grids  72  can be rated for a heating density of more than 1200 watts/m 2  or less than 200 watts/m 2 . 
     In the illustrated embodiment, the resistive electric grids  72  use D.C. electrical power flowing through the grids  72  to produce heat. The direct current is in a range from about 0.5 amps to about 4.0 amps at a voltage in a range from about 6.0 volts to about 18.0 volts. In another embodiment, the resistive electric grids  72  can use another type of electric power, sufficient to flow through the grids  72  and provide heat. 
     While the heat sources  68  illustrated in  FIG. 3  are resistive electric grids, it should be understood that other heat sources, such as for example thermal electric devices or conductive carbon fibers, sufficient to provide heat to the seat cushion  16  can be used as electrically actuated heating/cooling sources. 
     The grid terminals  74  are connected to a controller  76  by a plurality of grid connectors  78 . As will be explained in detail later, the controller  76  is adapted to provide a plurality of functions. The controller  76  is connected to a power supply  80  by a plurality of power supply connectors  82 . The power supply  80  is adapted to provide a supply of electrical power to the controller  76 . In the illustrated embodiment, the power supply  80  provides D.C. electrical power. In another embodiment, the power supply  80  can provide another type of electrical power, such as for example A.C. power. 
     The controller  76  includes a master switch (not shown) adapted to turn the power supply  80  on and off. In the illustrated embodiment, the controller  76  controls the electrical power supplied to the resistive electric grids  72  by turning the power supply  80  on and off. The controller  76  also includes a power transfer switch (not shown) adapted to transfer electrical power applied from one zone to another zone. As described above, the seat cushion  16  includes rear seat area  32  having zones  46  and  48 , mid seat area  34  having zones  42  and  44 , and front seat area  36  having zones  38  and  40 . The rear seat area  32  generally corresponds to the buttocks area of a seat occupant, the mid seat area  34  generally corresponds to the thigh area of a seat occupant, and the front seat area  36  generally corresponds to the knee area of a seat occupant. The electrical power applied to each of the heat sources  68  within the zones  38 ,  40 ,  42 ,  44 ,  46  and  48  is varied according to a pre-determined power management profile contained within the controller  76 . The power management profile is adapted to reduce the overall power requirements of the reduced power heat mat  10  by energizing individual heat sources  68  or combinations of heat sources  68  for specific and sequential periods of time rather than energizing all of the heat sources  68  within all of the zones  38 ,  40 ,  42 ,  44 ,  46  and  48  at the same time. 
     In one example of a power management profile, electrical power is applied to the heat sources  68  in a sequential rotation starting with zones  46  and  48  corresponding to the buttocks area of the seat occupant, continuing with zones  42  and  44  corresponding to the thigh area of the seat occupant, and ending with zones  38  and  40  corresponding to the knee area of the seat occupant. In this embodiment, electrical power is applied to the heat sources  68  in the zones  46  and  48  in approximately 60% of the overall time, 25% of the time electrical power is applied to zones  42  and  44 , and the remaining approximate 15% of the time electrical power is applied to zones  38  and  40 . The division of time that the heat sources  68  in the zones have electrical power applied is defined as a power management profile. This example of a power management profile is graphically illustrated in  FIG. 4 . The first graph represents zones  46  and  48 , the second graph represents zones  42  and  44  and the third graph represents zones  38  and  40 . Each graph represents the temperature of the respective zones over time. Each graph includes time periods t 1  through t 10  and further includes a target zone temperature, designated as the set point temperature. In one embodiment, the time period t 1  is approximately two minutes. In another embodiment, the time period t 1  can be more or less than two minutes. The set point temperature is defined as the desired steady state temperature. The set point temperature is variable and can be set at any desired level. As shown in the first graph, electrical power applied to the heat sources  68  in zones  46  and  48  during the time period t 1  causes the heat sources in zones  46  and  48  to heat. The temperature in zones  46  and  48  rises for the duration of the time period t 1 . As shown in the second and third graphs, electrical power is not applied to the heat sources  68  in zones  38 ,  40 ,  42  and  44  during the time period t 1 . At the conclusion of time period t 1 , the electrical power is cutoff from the heat sources  68  in zones  46  and  48 . 
     As further shown in  FIG. 4  at the beginning of time period t 2 , the electrical power is transferred from the heat sources  68  in zones  46  and  48  to the heat sources  68  in zones  42  and  44 . Electrical power still has not been applied to the heat sources in zones  38  and  40 . Accordingly during time period t 2 , the heat sources  68  in zones  42  and  44  produce heat and the heat sources  68  in zones  46  and  48  start to cool. At the conclusion of time period t 2 , the electrical power is cutoff from the heat sources  68  in zones  42  and  44 . 
     Still referring to  FIG. 4 , at the beginning of time period t 3 , the electrical power is transferred from the heat sources  68  in zones  42  and  44  to the heat sources  68  in zones  38  and  40 . No electrical power is applied to the heat sources  68  in zones  46 ,  48 ,  42  and  44 . Accordingly during time period t 3 , the heat sources in zones  38  and  40  produce heat and the heat sources  68  in zones  46 ,  48 ,  42  and  44  cool. At the conclusion of time period t 3 , the electrical power is cutoff from the heat sources  68  in zones  38  and  40 . The conclusion of time period t 3  completes one heating cycle. A heating cycle is defined as a series of time periods in which electrical power is applied on a sequential basis among all of the heat sources  68 . The time periods are not required to be equal in length. The sequence of applying the electrical power is also variable. At the completion of the heating cycle, all of the heat sources  68  in zones  38 ,  40 ,  42 ,  44 ,  46  and  48  have had electrical power applied and all of the heat sources  68  have produced heat. 
     The time period t 4  begins a new heating cycle and electrical power is again applied to the heat sources  68  in zones  46  and  48 . The remainder of time period t 4  and the time periods t 5  and t 6  complete the same heating cycle as time periods t 1 -t 3 . As further shown in  FIG. 4 , the completion of each heating cycle brings the temperature in each of the zones  38 ,  40 ,  42 ,  44 ,  46  and  48  closer to the set point temperature. 
     While not shown in  FIG. 4  for simplicity purposes, it should be understood that the cycling of electrical power in time periods beyond t 10  will continue until all of the zones  38 ,  40 ,  42 ,  44 ,  46  and  48  reach the set point temperature. At that time, the cycling of the electrical power among the zones  38 ,  40 ,  42 ,  44 ,  46  and  48  will maintain the set point temperature in the zones  38 ,  40 ,  42 ,  44 ,  46  and  48 . 
     Besides the benefit of reducing overall power consumed by the reduced power heat mat  10 , another benefit of the reduced power heat mat is the increase in perceived heat by the seat  12  occupant. Perceived heat is defined as heat recognized by a seat  12  occupant. In the illustrated embodiment, a seat  12  occupant will recognize the heat produced in the initial zones  46  and  48  corresponding to the rear seat area  32 . The natural functioning of the human body tends to conduct the heat on the surface of the body to other areas of the body not experiencing the heat. As a result, a seat occupant perceiving heat in the rear seat area  32  will naturally conduct that heat to areas of the body corresponding to the mid seat area  34  and front seat area  36 . At the end of time period t 1  and the beginning of time period t 2 , the zones  46  and  48  have had an initial temperature increase and the zones  44  and  42  are starting to have a temperature increase. The seat  12  occupant will perceive an overall warming of the seat cushion  16  due to the perception of heat flowing from various zones. As the cycling of the heating of zones continues, the perception of the heat by the seat occupant will also increase. 
     In summary, each heating cycle involves a series of time periods in which electrical power is applied on a sequential basis among all of the heat sources. If the time periods are unequal in length, the sequential application of electrical power to the heat sources  68  causes some of the zones to be heated longer than other zones. The unequal time periods, the sequence of the zones and the set point temperature can be pre-determined to define a power management profile. In the preceding example of a power management profile, electrical power was first applied to the heat sources  68  in zones  46  and  48  for approximately 60% of the time in a heating cycle. Next, electrical power was applied to the heat sources  68  in zones  42  and  44  for approximately 25% of the time in a heating cycle. Finally, electrical power was applied to the heat sources  68  in zones  38  and  40  for approximately 15% of the time in a heating cycle. 
     In another embodiment, the power management profile can be pre-determined to provide a different set point temperature and different heating times for the heat sources in the respective zones, such as for example applying electrical power to zones  46  and  48  approximately 65% of the overall time, 25% of the time electrical power is applied to zones  42  and  44 , and the remaining approximate 10% of the time electrical power is applied to zones  38  and  40 . 
     In yet another embodiment, any combination of zones can be energized simultaneously for any length of time and at any set point temperature. As an example of this embodiment, electrical power can be simultaneously applied to zones  46 ,  48 ,  44 , and  42  for approximately 70% of the overall time, and the remaining approximate 30% of the time electrical power is applied to zones  38  and  40 . 
     While the embodiment shown in  FIG. 4  includes transferring electrical power from the heat sources  68  in the various zones  38 ,  40 ,  42 ,  44 ,  46  and  48  based on a time variable, it should be understood that the transfer of electrical power from the heat sources  68  to other heat sources  68  can be triggered based on reaching the set point temperature before the end of a specific time period. As further shown in  FIG. 4 , during time period t 10 , electrical power is applied to the heat sources  68  in zones  46  and  48 . During this time period, the temperature in zones  46  and  48  reach the set point temperature in the middle of the time period. At this time, a sensor (not shown) senses the temperature in zones  46  and  48  and signals the controller  76  as to the zone temperature. In the illustrated embodiment, the sensor is disposed in the upper layer  66  of the seat cushion  16 . In another embodiment, the sensor can be positioned anywhere within the seat cushion  16  sufficient to sense the temperature in any of the zones  38 ,  40 ,  42 ,  44 ,  46  and  48 . 
     If the controller  76  determines the set point temperature has been reached prior to the end of a time period, the controller  76  can transfer the electrical power from the heat sources in one zone to the heat source in another zone prior to the end of a specific time zone. Another benefit of the reduced power heat mat  10  is that only a single sensor (not shown) is required. 
     In another embodiment, a seat cushion  116  can be cooled using a power management profile. As shown in  FIG. 5 , the seat cushion  116  is shown including a seat trim covering  164  and a cooling mat, schematically illustrated at  110 . The seat cushion  116  includes rear seat area  132 , mid seat area  134  and front seat area  136 . The rear seat area  132  includes zones  148  and  146 , the mid seat area  134  includes zones  142  and  144 , and the front seat area  136  includes zones  138  and  140 . The cooling mat  110  functions as an electrically actuated heating/cooling source providing cooling to the plurality of zones. The cooling mat  110  can be any suitable structure in the form of a relatively flat mat or can be any other structure, e.g. as conduits and perforation formed in seat for providing cooling and/or air flow to selected ones of the zones. 
     As further shown in  FIG. 5 , a cooling mechanism  188  is connected to the cooling mat  110  by a plurality of cooling ducts  190 . The plurality of cooling ducts  190  connects each of the zones  138 ,  140 ,  142 ,  144 ,  146  and  148  to the cooling mechanism  188 . The cooling mechanism  188  is adapted to provide cooled air to the cooling ducts  190 . It should be understood that the term cooled air may include cabin air and/or conditioned air such as from a vehicle heating, ventilation, and air conditioning (HVAC) system. In the illustrated embodiment, the cooling mechanism  188  has a cooling capacity in a range from about 200 watts/m 2  to about 1200 watts/m 2 . In another embodiment, the cooling mechanism  188  can have a cooling capacity of more than 1200 watts/m 2  or less than 200 watts/m 2 . As illustrated in  FIG. 5 , the cooling mechanism  188  is a thermal electric device. In another embodiment, the cooling mechanism  188  is another device, such as for example a small air conditioner, sufficient to provide cooled air. The cooling mechanism  188  also includes a controller (not shown). The controller generally performs the same functions as the controller  76  described above. 
     Referring again to  FIG. 5 , a fan mechanism  192  is connected to the cooling mechanism by fan ducts  194 . The fan mechanism  192  is adapted to provide a flow of air to the cooling mechanism  188 . The flow of air to the cooling mechanism  188  being sufficient to urge the cooled air from the cooling mechanism  188  through the duct  190  to the cooling mat  110 . 
     In a similar manner as described for the reduced power heating mat  10 , the cooled air provided to the zones of the cooling mat can be sequential cycled, by the controller, between the zones of the cooling mat. The sequential cycling is set according to a pre-determined power management profile. The pre-determined power management profile determines the time each zone receives cooled air from the cooling mechanism  188  and the order in which the zones are cycled. 
     Additionally, a sensor (not shown) senses the temperature in the zones and signals the controller as to the zone temperature. If the controller determines a cooling set point temperature has been reached prior to the end of a cooling time period, the controller can cause the flow of air from the fan mechanism  192  to by-pass the cooling mechanism  188  through a plurality of fan by-pass ducts  196 . 
     In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.