Abstract:
In a portable power source system comprising a battery pack for accommodating at least one secondary battery and a mounting part for mounting the battery pack, the mounting part is disposed in power using equipment, the battery pack comprises a charge circuit having a charge terminal and a discharge circuit having a discharge terminal, the charge circuit comprises a control circuit for controlling a voltage and a current during charging, the mounting part comprises a protruding external terminal for connecting with the discharge terminal, the battery pack comprises an inserting part for inserting the external terminal, the discharge terminal is disposed in a concealed position inside the inserting part, the battery pack is movable from an initial position to a fixing position while the external terminal has been inserted in the inserting part, and connection between the external terminal and the discharge terminal is achieved at the fixing position.

Description:
BACKGROUND OF THE INVENTION 
   As power using equipment which uses a portable power source system, there are for example electric tools such as electric screwdrivers for use in the screw fastening work. The use of electric tools can significantly improve work efficiency. While electric tools have recently been available at home improvement centers and the like and come to be used for do-it-yourself, they have been mainly used in construction sites and the like for business purpose. 
   There are however some cases where a construction site or the like is not wired. Further, the presence of cords or the like may negatively affect working performance. For this reason, a battery pack is employed in electric tools which operate at relatively low voltage, such as screwdrivers. A typical battery pack accommodates plural secondary batteries therein as a power source. Such a battery pack is detachable and, for conducting charging, it is inserted into a charger specific to the battery pack. On a construction site or the like, even when a battery is run down halfway through the work, preparation of a spare battery pack allows replacement of the battery pack and continuation of the work. 
   The battery pack (Model No. EZ9025) for the electric tool (DRILL &amp; DRIVER, Model No. EZ6225) manufactured by Matsushita Electric Works, Ltd., one of the examples of the conventional battery packs, is described by reference to  FIGS. 15 to 17 . 
     FIG. 15  is an oblique view of the battery pack (EZ9025), and  FIG. 16  is a top plan view thereof. At the time of insertion of the battery pack into the electric tool, the battery pack is positioned by a guide  1  to be inserted, and then fixed to the electric tool with a latch  2 . On the upper end of the battery pack disposed while being exposed to the outside are a positive electrode terminal  3  both for charging and discharging, a charge negative electrode terminal  4  specifically for charging, a discharge negative electrode terminal  5  specifically for discharging, and a thermistor terminal  6 . 
     FIG. 17  shows a circuit diagram of the battery pack (EZ9025). A discharge circuit comprising the positive electrode terminal  3 , a secondary battery  7  and the discharge negative electrode terminal  5  is not provided with a current regulating device, whereas a charge circuit comprising the positive electrode terminal  3 , the secondary battery  7  and the charge negative electrode  4  is provided with a control circuit  8  and a thermal protector  9 , securing safety during charging. Further, a thermistor  10  is connected to the thermistor terminal  6 . During charging, the temperature of the battery pack is monitored with resistance values of the thermistor  10  to control charging according to the monitored temperatures. 
   As thus described, the conventional battery pack comprises the current regulating device in the charge circuit. The current regulating device will prevent a current from continuing to flow in the battery pack if the charger should suffer a breakdown. However, the discharge circuit is not provided with a current regulating device because there are cases where a heavy current temporarily flows and a total amount of the discharge current is regulated by the capacity of the secondary battery. 
   In the conventional battery pack, it is possible to charge the battery pack by connection between the discharge terminal and a large-sized battery such as a battery for automobiles, since the discharge terminal is in a state of exposure to the outside. There however is a safety problem in charging by the use of the discharge terminal because of the absence of the current regulating device in the discharge circuit. 
   For the purpose of protecting terminals of a battery pack from shock caused by dropping and the like, there has been proposed a structure where an external terminal is provided on the inner circumferential side of a lid of a loop-shaped battery pack (Japanese Laid-Open Patent Publication No. 2001-135287). Also in this structure, however, the discharge terminal is in a state of exposure to the outside and the connection between the discharge terminal and the large-sized battery is therefore possible. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention was made in view of what were described above, and relates to a portable power system having a so-called double action system, particularly aiming at provision of a portable power source system where connection between a discharge terminal of a battery back and an external terminal is achieved only when power using equipment is used. 
   A portable power source system in accordance with the present invention comprises a battery pack for accommodating at least one secondary battery and a mounting part for mounting the battery pack. The battery pack is detachable from the mounting part and exchangeable with a spare battery pack. The mounting part is disposed in power using equipment. 
   The battery pack comprises a charge circuit having a charge terminal and a discharge circuit having a discharge terminal, and the charge circuit comprises a control circuit for controlling a voltage and a current during charging. 
   The mounting part comprises a protruding external terminal for connecting with the discharge terminal of the discharge circuit, the battery pack comprises an inserting part for inserting the external terminal, and the discharge terminal is disposed in a concealed position inside the inserting part. 
   The battery pack is movable from an initial position to a fixing position while the external terminal of the mounting part has been inserted in the inserting part, and connection between the discharge terminal of the discharge circuit and the external terminal is achieved at the fixing position. 
   Above mentioned “the discharge terminal is disposed in a concealed position” means that the discharge terminal of the discharge circuit and the external terminal are not mutually connected in the initial position immediately after the insertion of the external terminal of the mounting part into the inserting part. The connection between the external terminal and the discharge terminal requires rotation of the battery pack from the initial position or sliding thereof in a direction different from the inserting direction. In such a structure, even when a lead wire or the like connected to a large-sized battery or the like is inserted into the inserting part, the lead wire cannot be connected to the discharge terminal. Hence the act of charging from the discharge terminal is prevented to secure safety. 
   Each of the charge terminal and the discharge terminal can comprise both a positive electrode terminal and a negative electrode terminal. In this case, the negative electrode terminal of the charge circuit and the negative electrode terminal of the discharge circuit are mutually electrically independent whereas the positive electrode terminal of the charge circuit and the positive electrode terminal of the discharge circuit are united and can employ the structure having the equivalent potential. Such a structure enables reduction in production cost because the charge circuit and discharge circuit comprise the common positive electrode terminal. Further, there is an advantage in this structure that the lead wire to be led out from the secondary battery and the common positive electrode terminal of the charge circuit and the discharge circuit can be constituted by a single metal part. 
   As for the metal part used can be metal plate in the form of a strip with an L-shaped top. For example, part of the top of the metal plate is disposed in a concealed position to serve as the positive electrode terminal in the discharge circuit; any of the other parts of the metal plate is exposed to the outside to serve as the positive electrode terminal of the charge circuit. 
   It is preferable that the battery pack comprises a thermistor terminal for temperature measurement. When the battery pack comprises the thermistor terminal, it is possible to charge the battery while measuring the temperature of the battery pack during charging. 
   It is further preferable that the charge circuit comprises a thermal protector. As for the thermal protector used can be conventionally known ones such as a thermostat, a PTC device and a thermal fuse. In the case where the charge circuit comprises the thermal protector, high safety can be secured even when a lead wire or the like connected to a large-sized battery is connected to the charge circuit. 
   With the discharge terminal disposed in a concealed position, there is no need for the discharge circuit to comprise a current regulating device. In the conventional configuration, on the other hand, it is essential for securing safety that the discharge circuit comprise the current regulating device especially when the secondary battery is a lithium-ion secondary battery. It is greatly advantageous that the discharge circuit does not need to comprise the current regulating device. 
   As the charge circuit comprises at least the control circuit, the charge terminal is not required to be concealed but may be exposed to the outside. When the charge terminal is exposed to the outside, the external terminal of the charger and the charge terminal of the battery pack can be mutually connected by a single action, i.e. insertion. 
   The portable power source system in accordance with the present invention is effective especially when the secondary battery is a lithium-ion secondary battery. For, the lithium ion secondary battery in particular requires protection since it is weak against overcharge. 
   The portable power source system in accordance with the present invention is suitable for a power source system for use in electric tools, electric vacuum cleaners, electric bicycles or electric motorbikes. 
   While the novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIG. 1  is an oblique view of a battery pack in accordance with one embodiment of the present invention. 
       FIG. 2  is a top plan view of the battery pack in accordance with one embodiment of the present invention. 
       FIG. 3  is an oblique view of an electric tool in accordance with one embodiment of the present invention. 
       FIG. 4  is a vertical sectional view of a mounting part of the battery pack in accordance with one embodiment of the present invention. 
       FIG. 5  is a vertical sectional view of the mounting part of  FIG. 4 , to which the battery pack of  FIG. 1  has been connected. 
       FIG. 6  is an oblique view of a charger of the battery pack in accordance with one embodiment of the present invention. 
       FIG. 7  is a side view of an electric bicycle in accordance with another embodiment of the present invention. 
       FIG. 8  is an oblique view of a battery pack in accordance with another embodiment of the present invention. 
       FIG. 9  is an oblique view of a mounting part of the battery pack in accordance with another embodiment of the present invention. 
       FIG. 10  is a rear view of the battery pack in accordance with another embodiment of the present invention. 
       FIG. 11  is a sectional view on the line A—A of  FIG. 10 . 
       FIG. 12  is a top plan view of the battery pack of  FIG. 8  connected to the mounting part of  FIG. 9 . 
       FIG. 13  is a sectional view on the line B—B of  FIG. 12 . 
       FIG. 14A  is a sectional view on the line C—C of  FIG. 12 . 
       FIG. 14B  is a sectional view on the line D—D of  FIG. 12 . 
       FIG. 15  is an oblique view of one example of conventional battery packs. 
       FIG. 16  is a top plan view of one example of conventional battery packs. 
       FIG. 17  is a circuit diagram of a conventional battery pack. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Embodiment 1 
   In the following, a description is given by reference to the drawings. 
   In the present embodiment, a portable power source system having a double action system in which an external terminal provided on a mounting part of an electric screwdriver as power using equipment is inserted into an inserting part of a battery pack, and the battery pack is then rotated. 
     FIG. 1  is an oblique view of the battery pack  100  in accordance with the present embodiment, and  FIG. 2  is a top plan view thereof.  FIG. 3  is an oblique view of the electric tool  300  in accordance with the present embodiment. 
   The electric tool  300  comprises a driver bit  11 , a driving part  12  and a battery pack mounting part  13 . Parts not directly concerned with the content of the present invention, such as an on/off switch and a selector switch, have been omitted from  FIG. 3 .  FIG. 4  is a vertical sectional view on the line IV—IV of the battery pack mounting part  13 . 
     FIG. 5  is a vertical sectional view of the mounting part  13  to which the battery pack  100  has been connected. The battery pack  100  comprises guides  1   b  and  1   c  for protection against reverse connection, which serve to position the battery pack when connected. The guides  1   b  and  1   c  move parallel with a guide groove  14  of the mounting part  13  so that the operation of rotating the battery pack clockwise can certainly be carried out while the battery pack has been inserted into the mounting part  13 . A latch  2   b  is fitted in a latching groove  2   c  provided in the mounting part  13  by rotating the battery pack clockwise to a fixing position. 
   The top of the battery pack  100  is provided with a groove  15  for the positive electrode terminal and a groove  16  for the negative electrode terminal, of the discharge circuit, and a positive electrode terminal  3   a  and a negative electrode terminal  5   a , made of a metal plate, of the discharge circuit are disposed in concealed positions inside the respective grooves. 
   The top of the battery pack  100  is also provided with a positive electrode terminal  3   b  and a negative electrode terminal  4 , of the charge circuit, which are in a state not concealed but exposed to the outside. The positive electrode terminal  3   b  of the charge circuit is united with the positive electrode terminal  3   a  of the discharge circuit and they have the equivalent potential. 
   The top of the battery pack  100  is further provided with a thermistor terminal  6  to form, together with a thermistor housed in the battery pack, such a circuit as shown in  FIG. 17 . 
   As shown in  FIG. 4 , a positive electrode terminal  17  and a negative electrode terminal  18 , of the mounting part  13 , are in L-shape and they are first inserted into the wider portions of the groove  15  for the positive electrode terminal and the groove  16  for the negative electrode terminal, of the discharge circuit, respectively. They then move to the narrower portions by rotation of the battery pack, and the curved tips of the positive electrode terminal  17  and the negative electrode terminal  18  are connected, respectively, to the positive electrode terminal  3   a  and the negative electrode terminal  5   a , of the discharge circuit, disposed in concealed positions, as shown in  FIG. 5 . A spring  19  is built into the battery pack, and the spring  19  can prevent failure of the aforesaid connection by pressing those terminals. 
   The battery pack  100  houses, in addition to a secondary battery  7 , a control circuit, a thermistor and a thermal protector. An internal circuit including those parts is placed on a print substrate  20 . The wiring of the internal circuit is the same as that of the conventional battery pack shown in  FIG. 17 . 
   As obvious from  FIG. 2 , in the portable power source system in accordance with the present embodiment, even when the lead wires or the like connected to a large-sized battery or the like are inserted into the groove  15  for the positive electrode terminal and the groove  16  for the negative electrode terminal, those lead wires cannot be connected to the positive electrode terminal  3   a  and negative electrode terminal  5   a  of the discharge circuit because of complete concealment of the terminals  3   a  and  5   a  from the outside. The act of charging from the discharge terminal is therefore prevented, to secure safety. 
     FIG. 6  shows an oblique view of a charger  600  for the battery pack  100 . Parts not directly concerned with the content of the present invention, such as an on/off switch and a charged-state indication light, have been omitted from  FIG. 6 . 
   The charger  600  comprises a positive electrode terminal  17   b , a negative electrode terminal  18   b , a thermistor terminal  6   b  and a guide groove  14   b . Prescribed terminals of the battery pack  100  are respectively connected to prescribed terminals of the charger  600  by fitting of the guide  1   b  of the battery pack  100  into the guide groove  14   b  of the charger  600 . That is, when charging is conducted with the charger, the terminals of the battery pack and those of the charger can be mutually connected by the single action of inserting the battery pack into the charger, which can be readily operated. 
   It is to be noted that, although the electric tool was exemplified in the present embodiment, the types of the power using equipment are not particularly limited. Further, the similar power source system is suitable especially for electric vacuum cleaners and the like. 
   Embodiment 2 
   Below, a description is given by reference to the drawings. 
   In the present embodiment described is a portable power source system having a double action system where an external terminal provided on a mounting part of an electric bicycle as power using equipment is inserted into an inserting part of a battery pack, and the battery pack is then slid in a direction perpendicular to the inserting direction. 
     FIG. 7  is a side view of the electric bicycle  700  in accordance with the present embodiment. A mounting part  24  of a battery pack  23  is disposed on the back of a sheet tube  22  supporting a saddle  21 . An antitheft key  25  is used for detachment of the battery pack  23 . 
     FIG. 8  is an oblique view of the battery pack  23  in accordance with the present embodiment, and  FIG. 9  is an oblique view of the mounting part  24 . A guide groove  26  is provided in each long side face of the battery pack  23 , and guides  27  to be fitted in the guide grooves  26  are disposed on the mounting part  24 . 
   For the disposition of the battery pack  23  on the mounting part  24 , the battery pack  23 , positioned by the guide grooves  26  and the guides  27 , is first shifted vertically to the mounting face of the mounting part  24 . Thereafter, the battery pack  23  is slid in parallel with the mounting face to a fixing position. 
   In the lower part of the back face of the battery pack  23  provided are: a concave part  28   a  for a positive electrode terminal, a concave part  28   b  for a negative electrode terminal, of a charge circuit, a concave part  28   c  for a thermistor terminal, and a concave part  28   d  for a positive electrode terminal and a concave part  28   e  for a negative electrode terminal, of a discharge circuit. Further, in the upper part of the back face of the battery pack  23  provided is a locking concave part  28   f.    
   On the mounting face of the mounting part  24 , a positive electrode terminal  30  and a negative electrode terminal  31 , both in L-shape, are provided in a position opposed to the concave part  28   d  for the positive electrode terminal and to the concave part  28   e  for the negative electrode terminal, respectively. Further, on the mounting face, a hook window  29  is provided in a position opposed to the locking concave part  28   f . On the respective concave faces of the concave part  28   a  for the positive electrode terminal and the concave part  28   b  for the negative electrode terminal, of the charge circuit, as well as the concave face of the concave part  28   c  for the thermistor terminal, the respective terminals are exposed. 
     FIG. 10  is a back view of the battery pack  23  of the present embodiment, and  FIG. 11  is a sectional view on the line A—A of  FIG. 10 . A blind plate  32  is provided each on the concave part  28   d  for the positive electrode terminal and the concave part  28   e  for the negative electrode terminal, of the discharge circuit. The positive electrode terminal  33  and the negative electrode terminal  34 , of the discharge circuit, are concealed by the blind plate  32 . The locking concave part  28   f  is divided by a partition  35  into two concave parts  28   fa  and  28   fb.    
     FIG. 12  shows a top plan view of the battery pack  23  connected to the mounting part  24 . Although the guides  27  are fitted in the guide grooves  26  when the battery pack is in a state shown in  FIG. 12 , they have been omitted from  FIG. 12 .  FIG. 13  is a sectional view on the line B—B of  FIG. 12 ,  FIG. 14A  is a sectional view on the line C—C of  FIG. 12 , and  FIG. 14B  is a sectional view on the line D—D of  FIG. 12 . 
   In  FIG. 13 , a locking system part  36  comprises a hook  39  and a cylinder  38  supported by a spring  37 . The hook  39 , initially fitted in the concave part  28   fa , is shifted over the partition  35  into the concave part  28   fb  by sliding of the battery pack  23  in parallel with the mounting face of the mounting part  24  from an initial position to a fixing position. Thereat, locking with the key  25  becomes possible. 
   In the initial position where the hook  39  is in a state of fitting in the concave part  28   fa , the positive electrode terminal  33  and the negative electrode terminal  34 , of the discharge circuit, provided in the battery pack  23 , are not connected respectively to the positive electrode terminal  30  and the negative electrode terminal  31 , of the mounting part  24 . These terminals of the discharge circuit and the mounting part  24  are mutually connected by the sliding of the battery pack thereafter. As shown in  FIG. 14A , on the other hand, a thermistor terminal  40 , a positive electrode terminal  41  of the charge circuit and the like, to be used during charging, are closed with a lid. 
   Also in the present embodiment, the positive electrode terminal  33  and the negative electrode terminal  34 , of the discharge circuit, are disposed in a position concealed by the blind plate  32 , as evident from  FIGS. 13 and 14B . Even with insertion of lead wires or the like connected to a large-sized battery or the like into the concave part  28   d  for the positive electrode terminal and the concave part  28   e  for the negative electrode terminal, therefore, the lead wires can be connected to neither the terminals  33  nor  34 . Hence the act of charging from the discharge terminal is prevented so as to secure safety. 
   It should be noted that, although the electric bicycle was exemplified in the present embodiment, the types of the power using equipment are not particularly limited. Further, the similar power source system is suitable especially for electric motorbikes. 
   As thus described, according to a portable power source system of the present invention, the discharge terminal is disposed in a concealed portion to enable the connection between the discharge terminal and the external terminal by a double action system so that high safety can be secured with a simple structure. 
   Although the present invention has been described in terms of the presently preferred embodiments, it is to be understood that such disclosure is not to be interpreted as limiting. Various alterations and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains, after having read the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alterations and modifications as fall within the true spirit and scope of the invention.