Abstract:
A battery power source device is provided for supplying high electric power used for a drive power source for a vehicle. The battery power source device includes a battery box for storing a plurality of batteries arranged in a connected state in a battery storage room, an inlet opening for introducing a temperature control medium into the battery storage room, an outlet opening for discharging the medium from the battery storage room to the outside, a medium circulation passage for leading the medium discharged from the outlet opening to the inlet opening for feeding into the battery storage room again, and a medium transport device for forcing the medium flow.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a battery power source device for supplying high electric power used for a drive power source for a vehicle.  
           [0003]    2. Description of Related Art  
           [0004]    Generally, the output of a rechargeable battery is from about 1 to 5 volts. When a high output voltage is necessary for an application such as a power source for the drive of a vehicle, a battery power source device which consists of a large number of rechargeable batteries  1  is required. These rechargeable batteries  1  are connected in series, and arranged in both lengthwise and widthwise directions within a battery box  2 , as shown in a schematic longitudinal sectional view of FIG. 3. In this battery power source device, charge and discharge control is conducted so as to maintain the battery power source device in a state always capable of supplying a required level of electric power.  
           [0005]    Since the temperature of the rechargeable battery  1  increases when it is charged and discharged, it is necessary for a battery power source device to provide cooling to limit such temperature increases. On the other hand, since temperature dependence of the internal resistance of the rechargeable battery  1  becomes vary large when the rechargeable battery  1  is used in a place at low temperatures, difference in individual battery characteristics among the rechargeable batteries  1  becomes large if as much difference in temperature as they are at an ordinary temperature is present among the rechargeable batteries  1 . As a consequence, overall control of the rechargeable batteries  1  is often prevented. Thus, it becomes necessary to quickly increase the temperatures of the individual rechargeable batteries  1  to a temperature where any decrease of battery performance no longer remains a problem. Additionally, the temperatures of the rechargeable batteries  1  should be maintained at a uniform level when such a battery power source device including a large number of the rechargeable batteries  1  is used at low temperatures. In addition, the dependency of the battery characteristics of each rechargeable battery  1  on temperature makes it necessary to maintain the temperatures of the entire arrangement of rechargeable batteries  1  at a uniform level.  
           [0006]    Thus, controlling the temperatures of the individual rechargeable batteries  1  in a conventional battery power source device consists of adopting an arrangement for cooling the individual rechargeable batteries  1  by opening one end of the battery box  2  to form an air inlet opening  3 , providing an air outlet passage  4  on the other end, and providing a fan  7  inside the air outlet passage  4  which is driven to blow air in one direction through the battery box  2 , thereby forcing air E to flow between the individual rechargeable batteries  1 . In addition, when the rechargeable batteries  1  are used in a low temperature, it is known to use a battery heater such as a combustion heater or an electrical heater, installed on the battery box  2  so as to maintain the individual rechargeable batteries  1  at a predetermined temperature (such as one disclosed in Japanese Patent Laid-Open Publication No. Hei. 6-231807).  
           [0007]    However, a problem with the temperature control described above is that, air E having flowed from the air inlet opening  3  flows downstream while absorbing heat from the rechargeable batteries  1  when it passes through between the rechargeable batteries  1 , the temperature of the air E increases as it flows downstream. Thus, while the rechargeable batteries  1  on the side of the air inlet opening  3  are efficiently cooled by exchanging heat with the air E at a low temperature, the rechargeable batteries  1  on the side of the air outlet passage  4  are hardly cooled since they are exposed to the air E heated as a result of the heat exchange with the rechargeable batteries  1  on the upstream side. Consequently, the individual rechargeable batteries  1  are not uniformly cooled. As a result, there is such a problem that a large temperature difference is present between the rechargeable batteries  1  on the side of the air inlet opening  3  and the rechargeable batteries  1  on the side of the air outlet passage  4 .  
           [0008]    On the other hand, when the battery power source device is used at a low temperature, and the heater is installed to heat the rechargeable batteries  1  as described above, an independent cooler is necessary for use of the device at ordinary temperatures. Thus the structure becomes complicated, and as a consequence, the cost increases. As alternative means for increasing the temperatures of the rechargeable batteries without a heater, the rechargeable batteries are placed in a battery box in which a medium such as air does not flow, and the heat from the rechargeable batteries generated by charging and discharging is used to increase the temperatures of the rechargeable batteries. However, in this method, since the heat generation varies among the individual rechargeable batteries due to variation in the internal resistance or the temperature characteristics among the rechargeable batteries, or the heat dissipation varies among the rechargeable batteries due to the placement of the rechargeable batteries within the battery box, it is not possible to maintain the temperatures of the entire arrangement of rechargeable batteries at a uniform level.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention has been devised in light of the above-described problems, and has an object of providing a battery power source device including a simple and inexpensive constitution which serves to cool batteries if the temperature is at ordinary temperatures, and quickly increases the battery temperature to a temperature range which does not decrease the battery performance while the temperatures of the individual batteries are maintained uniform if the temperature is low during its use.  
           [0010]    To achieve the object above, a battery power source device according to the present invention includes a battery box for storing a plurality of batteries arranged in a connected state in a battery storage room, an inlet opening for introducing a temperature control medium into the battery storage room, an outlet opening for discharging the medium from the battery storage room to the outside, a medium circulation passage for leading the medium discharged from the outlet opening to the inlet opening for feeding into the battery storage room again, and a medium transport device for forcing the medium flow.  
           [0011]    If this battery power source device is used at low temperatures, since the temperature control medium such as air is introduced into the battery storage room again through the medium circulation passage for circulation after the medium has passed through the battery storage room, and consequently the temperature of the medium has increased due to heat exchange with the individual batteries, it is possible to quickly increases the temperatures of the individual batteries while the temperatures are maintained at a uniform level. In addition, if the battery power source device is used at ordinary temperatures, the individual batteries are cooled efficiently, and thus a proper temperature control effect is provided by discharging the temperature control medium outside from the outlet opening after the medium has flowed from the inlet opening, and has passed through the battery storage room. Thus, though this battery power source device has a simple constitution which includes only the medium circulation passage without a heater or a cooler, it prevents a variation in the temperature characteristics of the individual batteries due to temperature unevenness of the batteries both at low temperatures and at ordinary temperatures. As a result, overall performance brought about by the entire batteries is maintained to a proper state.  
           [0012]    It is preferable that the battery power source device further includes a selector valve mechanism for switching so as to selectively lead the temperature control medium discharged from the outlet opening either to an external outlet passage or the medium circulation passage, and a controller for controlling to switch the selector valve mechanism.  
           [0013]    In the constitution described above, it is preferable that the controller includes a function for controlling to switch the medium transport device so as to reverse the flow direction of the medium in this battery power source device.  
           [0014]    It is preferable that the battery power source device further includes a temperature sensor for detecting the temperature of a battery in the battery storage room, or the temperature of the temperature control medium at a predetermined point in the battery storage room, and that the controller control to switch the medium transport device in accordance with the temperature detected by the temperature sensor.  
           [0015]    It is preferred that the battery power source device further includes another selector valve mechanism for switching so as to selectively lead either the temperature control medium introduced from an inlet passage, or the temperature control medium introduced from the medium circulation passage into the battery storage room, and that the controller control to switch the two selector valve mechanisms in conjunction with each other.  
           [0016]    While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a schematic longitudinal sectional view showing a battery power source device according to one embodiment of the present invention;  
         [0018]    [0018]FIG. 2 is a characteristic chart showing a relationship between time of the battery operation and a battery temperature while conditions are changed when the battery power source device of the invention, and a battery power source device of comparative example are used at low temperatures; and  
         [0019]    [0019]FIG. 3 is a schematic longitudinal sectional view showing a conventional battery power source device. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    The following will describe a preferred embodiment of the present invention with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view showing a battery power source device according to one embodiment of the invention. In the drawing, a required number of rechargeable batteries  9  for supplying a necessary output voltage are stored in a battery storage room  10  of a battery box  8 , which is in a rectangular solid shape. The rechargeable batteries  9  are arranged in both lengthwise and widthwise directions, and are electrically connected. In the present embodiment, the rechargeable batteries  9  are placed such that each battery row includes the four rechargeable batteries  9  along a line orthogonal to a flow direction of air E, and the five battery rows exist along the flow direction.  
         [0021]    An inlet duct  12  is connected with an inlet opening  11 , and simultaneously, an outlet duct  14  is connected with an outlet opening  13  in the battery storage room  10 . A circulation duct  17  is provided for communicating an entrance of the outlet duct  14  and an exit of the inlet duct  12  to each other. A selector valve member  18  for switching the flow of the air E between the outlet duct  14  and the circulation duct  17  is provided so as to move between the individual entrances of the outlet duct  14  and the circulation duct  17 . A fan  19  for forcing the air E flow is provided between the outlet opening  13  and the individual entrances of the outlet duct  14  and the circulation duct  17 .  
         [0022]    A temperature sensor  20  for detecting the temperature of the air E is provided at the inlet opening  11  of the battery box  8 . Temperature sensors  21  for respectively detecting the temperatures of the individual rechargeable batteries  9  in the five battery rows arranged along the flow direction are provided in contact with the rechargeable batteries  9 . These temperature sensors  20  and  21  are contact type sensors such as thermistors which detect a temperature based on a change of the resistance. A controller  22  controls to switch the rotation direction of the fan  19 , and simultaneously controls to switch the selector valve member  18  through an actuator  23  in accordance with temperature detection signals supplied from the individual temperature sensors  20  and  21 .  
         [0023]    The following will describe the operation of the battery power source device of the present embodiment. First, when the battery power source device is used at low temperatures, the controller  22  controls the actuator  23  to set the selector valve member  18  to a position indicated by solid lines. As a result, the outlet opening  13  of the battery storage room  10  is shut off from the outlet duct  14 , and communicates to the circulation duct  17 . In this state, the fan  19  is rotated in the forward direction by the controller  22 . Thereby, the air E is sucked from the inlet duct  12  into the battery storage room  10  through the inlet opening  11 , flows through the battery storage room  10 , flows out from the outlet opening  13 , passes through the circulation duct  17 , and then flows into the battery storage room  10  again from the inlet opening  11 . In this way, the air E circulates.  
         [0024]    This flowing air E absorbs heat from the rechargeable batteries  9  while it is flowing through the battery storage room  10 , and is discharged from the outlet opening  13  while its temperature is increased. Then, the air E flows into the battery storage room  10  again from the inlet opening  11  after passing through the circulation duct  17 . The temperature of the air E gradually increases as it repeats this circulation. Thus, the temperatures of the individual rechargeable batteries  9  quickly increase while these temperatures are maintained at a uniform level by the air E whose temperature increases gradually as it circulates.  
         [0025]    The controller  22  always monitors the temperatures of the individual rechargeable batteries  9  in the five rows based on the temperature detection signals supplied from the temperature sensors  21 . When the controller  22  determines that a difference in temperature between the rechargeable battery  9  at the inlet opening  11  and the rechargeable battery  9  at the outlet opening  13  reaches a predetermined value, 3° C. for example, the controller  22  controls to switch the rotation of the fan  19  from the forward direction to the reverse direction. As a result, since the fan  19  operates so as to blow the air E after passing through the circulation duct  17  into the battery storage room  10  from the outlet opening  13 , the air E circulates along the circulation route the same as that for the forward rotation of the fan  19  but in the opposite direction. Consequently, the phenomenon that the temperature at the outlet opening  13  is higher than the temperature at the inlet opening  11  among the rechargeable batteries  9  is avoided, and thus the uniformity of the temperature among the rechargeable batteries  9  increases.  
         [0026]    On the other hand, when the battery power source device is used at ordinary temperatures, the controller  22  controls the actuator  23  to set the selector valve member  18  to a position indicated by a dash-double-dot line. As a result, the outlet opening  13  is shut off from the circulation duct  17 , and communicates to the outlet duct  14 . In this state, the fan  19  is rotated in the forward direction by the controller  22 . As a result, the air E is sucked from the inlet duct  12  into the battery box  8  through the inlet opening  11 , flows through the battery storage room  10 , flows out from the outlet opening  13 , and then discharged outside from the outlet duct  14 . Thereby, the cold air E always flows from the inlet duct  12  into the battery storage room  10 . This flowing air E absorbs the heat from the rechargeable batteries  9  so as to cool the rechargeable batteries  9  while it is passing through the battery storage room  10 , and is discharged outside from the outlet opening  13  through the outlet duct  14  while its temperature is increased. Thus, the individual rechargeable batteries  9  are always cooled efficiently by the cold air E while their temperatures are maintained at a uniform level.  
         [0027]    The controller  22  always monitors the temperatures of the individual rechargeable batteries  9  in the five rows based on the temperature detection signals supplied from the temperature sensors  21 . Simultaneously, the controller  22  monitors the temperature of the air E flowing from the inlet duct  12  based on the detection signal supplied from the temperature sensor  20 . When the controller  22  determines that it is necessary to further equalize the temperatures of the individual rechargeable batteries  9 , the controller  22  controls to switch the rotation of the fan  19  from the forward direction to the reverse direction. As a result, since the fan  19  operates so as to blow the air E sucked from the outlet duct  14  into the battery storage room  10  from the outlet opening  13 , the air E flows along the flow route the same as that for the forward rotation of the fan  19  but in the opposite direction. Consequently, the phenomenon that the temperature at the outlet opening  13  is lower than the temperature at the inlet opening  11  among the rechargeable batteries  9  is avoided, and thus the uniformity of the temperature among the rechargeable batteries  9  increases.  
         [0028]    As described above, the battery power source device uses a simple constitution where a special heater or a cooler is not used, the circulation duct  17  is provided so as to communicate the battery storage room  10  to each other, and the rotation direction of the fan  19  is switched according to the temperature difference between the parts of the rechargeable batteries  9 , or the temperature of the air E. With this constitution, the battery power source device heats or cools a large number of the rechargeable batteries  9  in the battery storage room  10  while the temperatures of the rechargeable batteries  9  are maintained at a uniform level whether the battery power source device is used at low or ordinary temperatures. Thus, the battery power source device prevents the variation of the battery characteristics caused by the change in battery temperatures.  
         [0029]    [0029]FIG. 2 is a characteristic chart showing temperature changes of the rechargeable batteries  9  while conditions such as the flow direction of the air E are changed when the battery power source device is used at low temperatures. This drawing shows results of the temperature changes of the rechargeable batteries  9  for four types of the flow of the air E. Namely, the fan  19  is maintained stationary as a first condition, the fan  19  rotates in the forward direction while the communication between the outlet opening  13  and the circulation duct  17  is shut off by the selector valve member  18  as a second condition, the fan  19  rotates in the forward direction while the communication between the outlet opening  13  and the outlet duct  14  is shut off by the selector valve member  18  as a third condition, and the fan  19  rotates in the forward direction while the communication between the outlet opening  13  and the outlet duct  14  is shut off by the selector valve member  18 , and the rotation direction of the fan  19  is switched when the difference in temperature between the rechargeable batteries  9  on the side of the inlet opening  11 , and the rechargeable batteries  9  on the side of the outlet opening  13  is 3° C. or more as a fourth condition. Therefore, the first and second conditions are similar to those for the conventional battery power source device, and the third and fourth conditions are those for the battery power source device of the embodiment described above.  
         [0030]    Characteristic curves C 11  and C 12  in FIG. 2 respectively show temperature changes of the rechargeable batteries  9  in the battery row at the inlet opening  11  and in the battery row at the center under the first condition. In this case, since the fan  19  is maintained stationary, and thus there are large variations in heat generation and heat dissipation of the rechargeable battery  9 , the temperature of the rechargeable battery  9  in the battery row at the center becomes the highest as the characteristic curve C 12  shows. Namely, there exist the batteries whose temperatures increase very rapidly and the batteries whose temperatures increase very slowly under the first condition. As a result, the uniformity of the battery temperatures becomes very low, and thus a large difference in temperature is generated.  
         [0031]    Characteristic curves C 21  and C 22  respectively show temperature changes of the rechargeable batteries  9  in the battery row at the inlet opening  11  and in the battery row at the outlet opening  13  under the second condition. Under the second condition where the air E flows only in one direction, it was turned out that though the uniformity of the battery temperatures is almost excellent, it is impossible to quickly increase the battery temperature up to a high temperature.  
         [0032]    Characteristic curves C 31  and C 32  respectively show temperature changes of the rechargeable batteries  9  in the battery row at the inlet opening  11  and in the battery row at the outlet opening  13  under the third condition. Characteristic curves C 41  and C 42  respectively show temperature changes of the rechargeable batteries  9  in the battery row at the inlet opening  11  and in the battery row at the outlet opening  13  under the fourth condition. Under the third and fourth conditions which circulate the air E as in the battery power source device of the embodiment described above, it was turned out that the battery temperatures increase quickly while the uniformity of the battery temperatures is maintained. Further, under the fourth condition which switches the flow direction of the air E when the difference in temperature between the rechargeable batteries  9  reaches the predetermined value in addition to circulating the air E, the uniformity of the battery temperatures increases further.  
         [0033]    As the dash-double-dot line in FIG. 1 shows, it is more preferable to provide a selector valve member  24  for switching so as to selectively communicate either the inlet duct  12  or the circulation duct  17  to the inlet opening  11 , and to switch this selector valve member  24  in association with the selector valve member  18 . Namely, both of the selector valve members  18  and  24  are controlled by the controller  22  so as to selectively switch between a state where the entrance and the exit of the circulation duct  17  are closed simultaneously, and a state where the outlet duct  14  and the inlet duct  12  are closed simultaneously. As a result, since the air E is circulated while the introduction of cold air from the inlet duct  12  is prevented when the battery power source device is used at low temperatures, the temperatures of the rechargeable batteries  9  increase quickly. On the other hand, since the entire air E from the inlet duct  12  is prevented from flowing into the circulation duct  17 , and thus efficiently flows into the battery storage room  10  when the battery power source device is used at ordinary temperatures, the rechargeable batteries  9  are efficiently cooled.  
         [0034]    While the embodiment above is described for the case where the cylindrical rechargeable batteries  9  are used, it is apparent that a similar effect is achieved when primary batteries or rechargeable batteries in another shape such as a prismatic shape are used. Also, air E is used as the temperature control medium, and simultaneously the fan  19  is used as the medium transport device in the embodiment, it is possible to properly select to use another temperature control medium or another medium transport device.  
         [0035]    The battery power source device of the present invention has such a constitution that the temperature control medium passes through the battery storage room while the temperature thereof increases by the heat exchange with the batteries, and is introduced into the battery storage room again through the medium circulation passage so as to circulate. Thus, it is possible to increase the temperatures of the individual batteries while the temperatures are maintained at a uniform level, when the battery power source device is used at low temperatures. On the other hand, the individual batteries are efficiently cooled by discharging the temperature control medium outside from the outlet opening after the temperature control medium has flowed from the inlet opening, and then has passed through the battery storage room. Thus, the excellent temperature control effect is achieved when the battery power source device is used at ordinary temperatures. Consequently, though this battery power source device has the inexpensive constitution which simply includes the medium circulation path, the battery power source device prevents the variation of the temperature characteristics of the individual batteries due to unevenness of the individual battery temperatures whether the battery power source device is used at low temperatures or at ordinary temperatures, thereby maintaining excellent overall performance of the entire batteries.  
         [0036]    Although the present invention has been fully described in connection with the preferred embodiment thereof, it is to be noted that various changes and modifications apparent to those skilled in the art are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.