Patent Publication Number: US-2011074362-A1

Title: Battery unit

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 U.S.C. §119 from Japanese Patent Application No. 2009-228903 filed on Sep. 30, 2009, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     The present invention relates to a battery unit capable of an improvement in heat dissipation efficiency. 
     2. Description of the Related Art 
     In recent years, there is devised a battery capable of being charged with a large current as compared with a commonly used lithium-ion battery (hereinafter referred to as a new type battery). Since the new type battery has specifications which allow charging by passing a current larger than that for the lithium-ion battery, as a result, it becomes possible to charge the new type battery up to a fully charged condition in a time period shorter than that for the lithium-ion battery. 
     In the new type battery of this type, since a large current as compared with the lithium-ion battery is passed during the charging, it follows that an element or the like in a charging circuit generates heat. Consequently, it is necessary to provide a heat dissipation mechanism for the new type battery to suppress the heat generation of the charging circuit. 
     As a method for cooling a battery during the charging of a secondary battery, JP-A 2004-208470 discloses a charger in which a cooling unit surrounding the secondary battery is provided to absorb a rise in battery temperature occurring during the charging of the secondary battery. An object thereof is to provide the charger which can efficiently perform fast charging in a short time period while suppressing the rise in battery temperature during the fast charging by providing such a structure. 
     In the technique described in JP-A 2004-208470, the cooling unit surrounding the battery is provided. However, in a case where especially the cooling unit of the type which circulates a coolant (liquid) is provided, it becomes necessary to newly provide a waterproof mechanism. Since this method results in an increase in the size of the battery and an increase in cost due to the provision of the waterproof mechanism, a new mechanism for cooling the secondary battery is desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A general architecture that implements the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not limited the scope of the invention. 
         FIG. 1  is a perspective view showing an outer appearance of a battery unit according to an embodiment of the present invention; 
         FIG. 2  is a perspective view showing an internal structure of the battery unit according to the embodiment of the present invention; 
         FIG. 3  is a cross-sectional view showing the internal structure of the battery unit according to the embodiment of the present invention; and 
         FIG. 4  is a block diagram showing a system structure of the battery unit according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. 
       FIG. 1  is a perspective view showing an outer appearance of a battery unit according to the embodiment of the present invention. A battery unit  1  includes a main body case  2 . On a front face  2   a  of the main body case  2 , switches  3  and  4  each for operating the battery unit  1  are provided. These switches can be used as, e.g., power switches for turning on the power of the battery unit  1 . From a back face  2   b  of the battery unit  1 , a USB cable  5  is extended. At the tip of the USB cable  5 , a USB connector  6  for the connection with electronic equipment such as a computer or the like is provided. By connecting the USB connector  6  with a USB port provided in the electronic equipment such as the computer or the like, it is possible to supply power from the battery unit  1  to the electronic equipment. 
     On a side face  2   c  of the main body case  2 , a DC-IN jack  7  is provided. By an AC adaptor which is not shown, alternating current power inputted from a commercial power source is converted to direct current power. A DC plug of the AC adaptor is inserted into the DC-IN jack  7  to supply power to the battery unit  1 . The battery unit  1  uses the supplied power to perform the charging of a battery cell in the battery unit  1 . 
     On an upper face  2   d  of the main body case  2 , an indicator  8  is provided. The indicator  8  can be formed of five LEDs of an LED  8   a , an LED  8   b , an LED  8   c , an LED  8   d , and an LED  8   e . By the number of LEDs caused to light up among these five LEDs of the LED  8   a , the LED  8   b , the LED  8   c , the LED  8   d , and the LED  8   e , the remaining amount of the battery of the battery unit  1  can be indicated. 
     On a bottom face  2   e  of the main body case  2 , leg parts  9  for supporting the main body case are provided. Inside the main body case  2 , a circuit board  10  is provided. 
     As the difference between a conventional lithium-ion battery and the new type battery, specific figures will be presented as an example. When the charging of the conventional lithium-ion battery is performed, it is assumed that a current of 1.8 A can be passed. At this time, the charging is performed by passing the current of 1.8 A for two hours with respect to the capacity of the lithium-ion battery of 4000 mAh, and the battery is thereby charged up to 3600 mA (900). 
     On the other hand, as disclosed in the embodiment of the present invention, since the new type battery capable of being charged with a large current when compared with the lithium-ion battery has specifications which allow the charging by passing the current larger than that for the lithium-ion battery, as a result, it becomes possible to charge the battery up to the fully charged condition in a time period shorter than that for the lithium-ion battery. 
     When the charging of the new type battery is performed, it is assumed that the current of 21.6 A can be passed. At this time, since the charging is performed by passing the current of 21.6 A with respect to the capacity of the new type battery of 4000 mAh, the battery is charged up to 3600 mA (90%) in only 10 minutes. The charging performed in a relatively short time period by passing a large current is occasionally referred to as fast charging for convenience sake in the present embodiment. 
     In the new type battery of this type, since the large current is passed during the charging when compared with the lithium-ion battery, it follows that an element or the like of a charging circuit generates heat. Consequently, it is necessary to provide a heat dissipation mechanism for the new type battery to suppress the heat generation of the element or the like of the charging circuit. 
       FIG. 2  is a perspective view showing an internal structure of the battery unit according to the embodiment of the present invention.  FIG. 3  is a cross-sectional view showing the internal structure of the battery unit according to the embodiment of the present invention. A description will be given of the heat dissipation mechanism provided inside the battery unit by using  FIGS. 2 and 3 . 
     Inside the battery unit  1 , the circuit board  10  is provided and, on an upper face  10   a  of the circuit board  10 , electronic components such as a charging circuit  12  and a processor  13  are mounted. The charging circuit  12  is an electronic component which generates heat by its own operation. Similarly, the processor  13  is also the electronic component which generates heat by its own operation. In the present embodiment, the charging circuit  12  and the processor  13  which generate heat by their own operations are occasionally referred to as heat generating components. 
     As has been described above, a battery cell  15  is a battery compatible with the fast charging capable of performing the charging in a relatively short time period by passing the large current. When the fast charging of the battery cell  15  of the present embodiment is performed, especially the charging circuit  12  generates heat. Accordingly, it is necessary to provide the heat dissipation mechanism for the heat generating components such as the charging circuit  12  and the processor  13  to suppress the heat generation of the heat generating components. 
     Inside the battery unit  1 , a heat sink  16  is provided. The heat sink  16  includes a first heat receiving part  17  which abuts the charging circuit  12  to receive heat from the charging circuit  12 , and a second heat receiving part  18  which abuts the processor  13  to receive heat from the processor  13 . 
     Between the charging circuit  12  and the first heat receiving part  17 , a heat conductive member  22  such as silicon grease or a heat conductive sheet is provided. In addition, between the processor and the second heat receiving part  18 , a heat conductive member  23  is also provided. 
     The heat sink  16  transfers heat received from the charging circuit  12  and the processor  13  via the first and second heat receiving parts  17  and  18 . The heat sink  16  is branched into heat transferring parts  26   a  and  26   b  on a heat transferring path. 
     The heat transferring part  26   a  is connected with a first heat dissipating member  28 . The first heat dissipating part  28  is thermally connected with the battery cell  15  and, between the first heat dissipating member  28  and the battery cell  15 , a heat conductive member  24  is provided. The battery cell  15  is a secondary battery in which an endothermic reaction occurs during the charging and an exothermic reaction occurs during discharging. During the charging of the battery cell  15 , the heat generating components such as the charging circuit  12  and the processor  13  generate heat but, by thermally connecting the heat generating components with the battery cell  15  using the heat sink  16 , the endothermic reaction during the charging of the battery cell  15  can be utilized for the heat dissipation. 
     In general, as the amount of current passed for the charging of the battery cell  15  increases, the amount of heat generated by the charging circuit  12  increases. However, since the endothermic reaction during the charging of the battery cell  15  concurrently progresses, it is considered that the endothermic reaction during the charging of the battery cell  15  can be adequately utilized. 
     In contrast to the case where the heat is only dissipated naturally by an air cooling using the first heat dissipating member  28 , by utilizing the endotherm as a chemical reaction occurring during the charging of the battery cell  15 , the heat dissipation efficiency of the battery cell  15  can be improved. 
     The heat transferring part  26   b  is connected with a second heat dissipating member  29 . With the provision of the second heat dissipating member  29 , the heat dissipation efficiency can be further improved to a level higher than that of the heat dissipation utilizing the battery cell  15  and the first heat dissipating member  28 . 
     In the present embodiment, the second heat dissipating member  29  is provided so as to contact an inner face  2   f  of the main body case  2 . The inner face  2   f  is positioned on the opposite side of the bottom face  2   e . The second heat transferring part  26   b  extending from the heat sink  16  is bent once in a region off the circuit board  10 , extends in a direction from the upper face  10   a  of the circuit board  10  toward a lower face  10   b , and abuts the second heat dissipating member  29 . 
     The second heat dissipating member  29  may be provided at an arbitrary position inside the main body case  2  but, in general, by providing the second heat dissipating member  29  on any of the inner face  2   f  of the main body case  2 , an inner face  2   g , an inner face  2   h , and an inner face  2   i , the heat dissipation efficiency is further improved. In addition, by providing the second heat dissipating member  29  especially on the inner face  2   f  positioned on the opposite side of the bottom face  2   e  of the battery unit  1 , the position of the second heat dissipating member  29  can be displaced from the position at which a user holds the battery unit  1  with his or her hand. 
     Normally, is difficult to provide a cooling fan inside the battery unit or an air hole for cooling in the case of the battery unit. Thus, in accordance with the battery unit according to the present embodiment, it is possible to efficiently perform the heat dissipation using the endotherm as the chemical reaction occurring during the charging of the battery cell, and the heat dissipation utilizing a heat pipe, the heat transferring members, and the heat dissipating members. 
       FIG. 4  is a block diagram showing a system structure of the battery unit according to the embodiment of the present invention. The battery unit  1  is formed of various parts in addition to parts shown in  FIG. 4 . However, in  FIG. 4 , a description is given by extracting the parts particularly related to the description of the embodiment of the present invention and omitting other parts. 
     The charging circuit  12  supplies a current for the charging with respect to the battery cell  15 . The charging circuit  12  includes a heat generating element  12   a  which generates heat when the charging of the battery cell  15  is performed. The charging circuit  12  also includes a temperature sensor  12   b  for detecting a temperature of the charging circuit  12 . The temperature sensor  12   b  detects a rise in temperature caused by the heat generation of the elements themselves such as an FET and a resistor in the charging circuit  12  resulting from the operation of the charging circuit  12 . A value of the temperature detected by the temperature sensor  12   b  is used for the control of the charging current passed by the charging circuit  12 . 
     The charging circuit  12  also includes a protecting element  12   c  represented by, e.g., a fuse in order to secure the safety of the charging circuit  12  and the battery unit  1 . 
     Inside the battery unit  1 , an EEPROM  15   a  for storing information on the battery cell  15  is provided. Inside the battery unit  1 , a temperature sensor  15   b  for detecting the temperature of the battery cell  15  is also provided. 
     The battery cell  15 , the EEPROM  15   a , and the temperature sensor  15   b  may be separately provided inside the battery unit  1 . Further, the battery cell  15 , the EEPROM  15   a , and the temperature sensor  15   b  may be brought together into one battery pack, and the battery pack may also be mounted inside the battery unit  1 . 
     The system of the battery unit  1  can read the information on the battery cell  15  from the EEPROM  15   a  via a power controller  31 . 
     In the EEPROM  15   a , there is stored the information related to the battery cell  15 , i.e., ID information on the battery cell  15 , the capacity of the battery cell  15 , a parameter related to charging control such as a completion current value when the battery cell  15  is fully charged, and information for indicating that the battery cell  15  is a battery compatible with the fast charging. 
     The power controller  31  performs the control of the charging circuit  12  based on the information read from the EEPROM  15   a.    
     In addition to the acquisition of the ID information on the battery cell  15 , the capacity of the battery cell  15 , the parameter related to the charging control of the battery cell  15 , and the information for indicating that the battery cell  15  is a battery compatible with the fast charging which have been mentioned in the above description, the power controller  31  can detect the temperature of the battery cell  15 , that the battery cell  15  is fully charged, that overvoltage/overcurrent occurs in the battery cell  15 , and that the battery cell  15  is in a low-battery state where the capacity thereof is lower than a given threshold value. 
     The power controller  31  reads the temperature of the charging circuit  12  from the temperature sensor  12   b  of the charging circuit  12 . The power controller  31  selects the charging current for charging the battery cell  15  to send the instruction for ON/OFF of the charging current to the charging circuit  12  based on the information read from the EEPROM  15   a  and the value of the temperature indicated by the temperature sensor  12   b  of the charging circuit  12 . 
     For the protection of the battery cell  15  and the charging circuit  12  inside the battery unit  1 , and for the safety of the user using the battery unit  1 , threshold values are individually set for the temperature of the battery cell  15  and the temperature of the charging circuit  12 . When the temperature of the battery cell  15  exceeds the threshold value, or when the temperature of the charging circuit  12  exceeds the threshold value, the control is performed by the power controller  31  such that the charging operation with respect to the battery cell  15  is suspended or the charging current supplied to the battery cell  15  is reduced. 
     The charging current supplied to the battery cell  15  may be minutely changed in accordance with the values of the temperatures detected by the temperature sensors  12   b  and  15   b . Alternatively, when both of the values of the temperatures detected by the temperature sensors  12   b  and  15   b  do not exceed the threshold values, the charging of the battery cell  15  may be performed by passing the large current, while the charging of the battery cell  15  may be performed by passing the current of the order of a few A which is lower than the large current when at least one of the temperatures detected by the temperature sensors  12   b  and  15   b  exceeds the threshold value. 
     As has been described above, according to the embodiment of the present invention, it is possible to provide a battery unit capable of an improvement in heat dissipation efficiency. 
     The present invention is not limited to the above-described embodiment and can be variously modified without departing from the gist thereof. 
     The invention is not limited to the foregoing embodiments but various changes and modifications of its components may be made without departing from the scope of the present invention. Also, the components disclosed in the embodiments may be assembled in any combination for embodying the present invention. For example, some of the components may be omitted from all the components disclosed in the embodiments. Further, components in different embodiments may be appropriately combined.