Abstract:
A card connector has a plurality of contact terminals, each of which comprises a fixed portion securely fixed in a connector housing and a spring portion having a contact portion at an end thereof opposite the fixed portion and extending from the fixed portion to be elastically displaceable. A card having a plurality of contact pads formed thereon is accommodated and held in the connector housing in such a way that the plurality of contact pads engage the associated contact portions of the plurality of contact terminals arranged in the connector housing. A cross section of the spring portion is changed along its length by changing its width or thickness so that a mass of a part of the spring portion of each contact terminal near the fixed portion is larger than a mass of a part of the spring portion near the contact portion.

Description:
[0001]    This application is based on application No. 2001-024424 filed Jan. 31, 2001 in Japan, the content of which is incorporated hereinto by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a card connector mounted on electronic devices, such as cellular phones, telephones, PDAs (personal digital assistants), portable audio devices and cameras, and an elastic contact piece built into the card connector, and more particularly to improvements of these for improving their impact resistance and for providing a contact structure with no electrical short breaks.  
           [0004]    2. Description of the Related Art  
           [0005]    In electronic devices such as cellular phones, telephones, PDAs and cameras, a variety of functions are added by inserting an IC card with a built-in memory and even a control circuit, such as a SIM (subscriber identity module) card, an MMC (multimedia card), a Smart Media (tradename), an SD (super density; or secure digital) card and a Memory Stick (tradename).  
           [0006]    The card connector for removably accommodating such an IC card has a plurality of contact terminals formed from metal leaf springs in a connector housing which are brought into contact with a plurality of contact pads formed on a front or back surface of the inserted IC card to electrically connect the IC card to the electronic device on which the connector is mounted. The contact pads of the IC card include a power supply pad connected to a power supply line and a plurality of signal pads for transferring a variety of signals. These pads are connected through the contact terminals of the card connector to the associated power supply circuit and a variety of signal processing circuits of the electronic device.  
           [0007]    When an electronic device having such a card connector loaded with a card should fall applying impacts or vibrations to the connector, the contact pads of the inserted card may part from the contact terminals of the connector depending on the magnitude of the impacts, causing a so-called short break in which electrical conduction is interrupted momentarily, and in an extreme case the card may get out of the connector.  
           [0008]    If such an accident occurs while data is being written from the electronic device into the card, the data being written may be lost or data stored in the card damaged, or in the worst case the memory card itself may fail.  
           [0009]    [0009]FIG. 6 shows an example of a conventional contact terminal  60  incorporated in such a card connector.  
           [0010]    The contact terminal  60  is supported in a connector housing like a cantilever and has a terminal portion  61  soldered to a contact pad or the like of a printed circuit board, a fixed portion  62  securely press-fitted in the connector housing, and an elastically displaceable spring portion  63 . The spring portion  63  is bent a predetermined angle to the fixed portion  62  and has a contact portion  64  at its front end side. The contact portion  64  is curved upwardly convex for engagement with the contact pad of the card.  
           [0011]    In this conventional contact terminal  60 , the spring portion  63  between the fixed portion  62  and the contact portion  64  has almost constant thickness and width over its entire length. Hence, the mass distribution of the spring portion  63  of the conventional contact terminal is almost uniform and therefore the center of gravity a of the spring portion  63  including the contact portion  64  is located near the contact portion  64 .  
           [0012]    When such a conventional contact terminal is applied an impact as a result of fall of an electronic device, an impact force or inertial force at time of impact acts on the spring portion  63  uniformly over the entire length. In other words, the impact force acts on the center of gravity a near the contact portion  64 . Therefore, when the conventional contact terminal is subjected to impacts or vibrations, the spring portion  63  can easily be elastically displaced or deformed, resulting in a momentary electrical break between the contact pads of the card and the contact portions of the contact terminals. The conventional contact terminals, as described above, have a problem of low impact resistance or low vibration resistance.  
           [0013]    It is conceivable to increase the impact resistance of the card by setting large the contact pressure of the contact portion making up the contact terminal. This method, however, also increases the operation force required to insert or withdraw the card at the same rate and thus degrades the operability of the card in terms of card insertion and withdrawal.  
         SUMMARY OF THE INVENTION  
         [0014]    The present invention has been accomplished under these circumstances and it is an object of the invention to provide a card connector which has improved impact and vibration resistances of the contact terminals to enhance the capability of the connector to hold a card at time of impact.  
           [0015]    Another object of the invention is to provide an elastic contact piece with improved impact and vibration resistances which can remain engaged with a mating object at all times even when subjected to impacts or vibrations.  
           [0016]    According to one aspect of the present invention, there is provided a card connector having a plurality of contact terminals, each of the contact terminals comprising: a fixed portion securely fixed in a connector housing and a spring portion having a contact portion at an end thereof opposite the fixed portion and extending from the fixed portion to be elastically displaceable; wherein a card having a plurality of contact pads formed thereon is accommodated and held in the connector housing in such a way that the plurality of contact pads contact the associated contact portions of the plurality of contact terminals arranged in the connector housing; wherein a mass of a part of the spring portion of each contact terminal near the fixed portion is set larger than a mass of a part of the spring portion near the contact portion as by changing a cross section of the spring portion along its length.  
           [0017]    A means for realizing the above includes:  
           [0018]    (1) increasing the cross section of the spring portion of each contact terminal from the contact portion side toward the fixed portion side,  
           [0019]    (2) increasing the width of the spring portion from the contact portion side toward the fixed portion side, and  
           [0020]    (3) increasing the thickness of the spring portion from the contact portion side toward the fixed portion side.  
           [0021]    With this invention, since the mass of a part of the spring portion of each contact terminal near the fixed portion is set larger than that of the spring portion near the contact portion, the center of gravity is located closer to the fixed portion than in the conventional contact terminal. Thus, the impact force or inertial force distribution in the spring portion when subjected to impacts is such that its magnitude in the spring portion is larger on the fixed portion side than on the contact portion side. The impact force acting on the center of gravity therefore is closer to the fixed portion than in the conventional contact terminal. This makes the contact portion in contact with the contact pad of the card less easily displaceable or deformable at time of impact, thus more reliably preventing a momentary electrical interruption when subjected to impacts or vibrations.  
           [0022]    According to another aspect of the present invention, there is provided an elastic contact piece comprising: a fixed portion for supporting the contact piece like a cantilever; and a spring portion having a contact portion at an end thereof opposite the fixed portion and extending from the fixed portion to be elastically displaceable; wherein the elastic contact piece has its contact portion pressed under pressure against a mating object; wherein a mass of a part of the spring portion of each contact piece near the fixed portion is set larger than a mass of a part of the spring portion near the contact portion.  
           [0023]    In addition to the contact terminals for signal and power supply connection, the elastic contact piece can also be used for a variety of kinds of switches, such as a switch for detecting the position of a write protect button on a card and a card recognition switch for detecting the presence or absence of a card in the connector, and also for a braking piece for applying a braking force to the card to prevent it from jumping out of the connector during the card ejection operation or a card locking mechanism for preventing the card from slipping off.  
           [0024]    In the elastic contact piece of this invention, because the center of gravity of the spring portion is shifted toward the fixed portion, the contact portion of the elastic contact piece is made less easily displaced or deformed. This prevents more reliably the contact portion in contact under pressure with a mating object from disengaging from it due to impacts or vibrations.  
       
    
    
       [0025]    The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    [0026]FIG. 1 is a perspective view showing an example of an IC card to be inserted into a card connector of the present invention;  
         [0027]    [0027]FIG. 2 is a perspective view showing an outline construction of an embodiment of the card connector of the invention;  
         [0028]    [0028]FIG. 3 is a perspective view showing a first embodiment of a contact terminal used in the card connector of the invention;  
         [0029]    [0029]FIG. 4 is a perspective view showing a second embodiment of the contact terminal used in the card connector of the invention;  
         [0030]    [0030]FIG. 5 is a horizontal cross section showing an example of a write protect detection switch; and  
         [0031]    [0031]FIG. 6 is a perspective view showing a conventional contact terminal. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0032]    Now, embodiments of this invention will be described in detail by referring to the accompanying drawings.  
         [0033]    In the following embodiments, descriptions concern a case where this invention is applied to a connector for a double-height card called an SD card.  
         [0034]    [0034]FIG. 1 shows an SD card  20  as an IC card (memory card) as seen from the bottom or back side thereof. The SD card  20  has an upper body portion  21  with a thickness t and a lower body portion  23  slightly narrower in width than the upper body portion  21 . That is, the card  20  has stepped portions  27  formed along both side edges. The upper body portion  21  has a triangular cut-off corner portion  22  at one front corner to prevent erroneous insertion.  
         [0035]    The lower body portion  23  has a plurality of recessed portions  24  in its front area, in each of which a contact pad  25  is arranged. The contact pads  25  have a  9 -pin structure including a power supply pin and signal pins for data, command, clock and others.  
         [0036]    A side surface of the card  20  is formed with a notch (recess)  28  in which a write protect button  26  is slidably arranged in card insertion/withdrawal directions (directions of arrow A). The write protect button  26  can assume two positions, a write disable position and a write enable position and is slidable between these two positions.  
         [0037]    [0037]FIG. 2 is a perspective view showing an embodiment of a card connector  1  into which the card  20  described above is to be loaded.  
         [0038]    This card connector  1  is mounted on electronic devices such as cellular phones, PDAs, portable audio devices, small portable game machines and cameras, and the card  20  is inserted into the connector  1  with the contact pad surface facing down.  
         [0039]    The connector housing  2  comprises a housing body  10  molded from an insulating material such as resin and a cover  15  shaped or molded from a metal or resin. The connector housing  2  has a top portion  3 , a bottom plate portion  4 , side portions  5  and a rear portion  6 , all these portions being combined to form a card accommodating portion  7 . The card  20  is inserted from a card insertion opening  33  formed at the front of the housing  2 .  
         [0040]    The left and right side portions  5  are each formed with a guide groove  50 , and the card is inserted or retracted along the guide grooves  50  with the contact pad surface of the card facing down. Each of the guide grooves  50  has an upper wall  51 , a side wall  52  and a lower wall  53 . From the edge of the lower wall of each guide groove  50  a side wall  59  extends downwardly. In this example, the upper walls  51  of the guide grooves  50  are formed by the cover  15 .  
         [0041]    In the housing  2  is formed an abutment wall (not shown) against which the front end of the inserted IC card  20  is abutted. At one corner of the abutment wall is formed a protruding corner wall  36  which engages the cut-off corner portion  22  of the IC card  20 .  
         [0042]    The bottom plate portion  4  of the housing is formed with a plurality of press-fit grooves  32  in which a plurality (in this example, nine) of contact terminals  40  are positioned and press-fitted.  
         [0043]    [0043]FIG. 3 is an enlarged view of a first embodiment of the contact terminal  40  to be securely press-fitted in the press-fit groove  32 .  
         [0044]    As shown in FIG. 3, each of the contact terminals  40  is formed from a metal cantilevered leaf spring piece and has a terminal portion  41  to be soldered to the contact pad of a printed circuit board in an electronic device, a fixed portion  42  to be securely fixed into the press-fit groove  32 , and an elastically displaceable spring portion  43 . The spring portion  43  is bent a predetermined angle relative to the fixed portion  42  and has on its front end side a contact portion  44  that is curved upwardly convex for engagement with the contact pad  25  of the card  20 . These contact terminals  40  are pushed under pressure into the press-fit grooves  32  from the front side of the connector housing  2  where they are securely held.  
         [0045]    In the contact terminal  40  of FIG. 3, the spring portion  43  between the contact portion  44  and the fixed portion  42  progressively increases in width toward its base (on the side of the fixed portion  42 ). If the width of the base of the spring portion  43  is taken as W 1  and the width of the front as W 2 , the ratio of W 1 /W 2  is preferably equal to or more than 2.  
         [0046]    While the contact terminal of FIG. 3 has the width of the fixed portion  42  set almost equal to the width W 1  of the base of the spring portion  43 , it may be set wider or narrower than the width W 1  of the base.  
         [0047]    In the contact terminal  40  shown in FIG. 3, because the width of the spring portion  43  is made to increase toward its base (on the side of the fixed portion  42 ), the center of gravity b of the spring portion  43  including the contact portion  44  is closer to the base (on the fixed portion  42 ) than in the conventional contact terminal of FIG. 6. Thus, with this contact terminal  40 , when an impact is applied to the connector, the impact force acting on the center of gravity b is closer to the base (on the fixed portion  42  side) than in the conventional contact terminal. In other words, an impact force distribution or inertial force distribution in the spring portion  43  at time of impact is such that its magnitude increases toward the fixed portion  42  side. Therefore, the spring portion  43  of the contact terminal  40  is less easily displaced or deformed elastically than the conventional one, thereby reliably preventing a momentary electrical break between the contact pads  25  of the card  20  and the contact portions  44  of the contact terminals  40  when subjected to impacts or vibrations.  
         [0048]    Although in the contact terminal of FIG. 3 the width of the spring portion  43  is gradually increased toward the fixed portion  42 , the shape of the spring portion  43  may be arbitrary as long as the width WI of the spring portion  43  on the side of the fixed portion  42  is set larger than the width W 2  on the contact portion  44  side (front end side) and the center of gravity is located closer to the fixed portion  42  than in the conventional contact terminal. For example, the spring portion  43  may set roughly a half thereof on the front end side to have a constant narrow width and a remaining half on the base side to have a constant wide width.  
         [0049]    [0049]FIG. 4 shows a second embodiment of the contact terminal.  
         [0050]    In the contact terminal  40  of the second embodiment, the thickness of the spring portion  43  between the contact portion  44  and the fixed portion  42  gradually increases toward the base (on the fixed portion  42  side). If the thickness of the base is d 1  and the thickness of the front end d 2 , the ratio d 1 /d 2  is preferably equal to or larger than {fraction (3/2)}.  
         [0051]    While in the case of FIG. 4 the thicknesses of the fixed portion  42  and the terminal portion  41  are set almost equal to the thickness d 1  of the base of the spring portion  43 , these portions may be set to arbitrary thicknesses and may be larger or smaller than the thickness of the base d 1 .  
         [0052]    In the contact terminal of the second embodiment, because the thickness of the spring portion  43  is set to increase toward the base (on fixed portion  42  side), the center of gravity b of the spring portion  43  including the contact portion  44  is located closer to the base (on the fixed portion  42  side) than in the conventional contact terminal shown in FIG. 6. Hence, with this contact terminal  40  of FIG. 4, when the connector is subjected to an impact, the impact force acting on the center of gravity b is closer to the base, as in the contact terminal of FIG. 3. Hence, the spring portion  43  of the contact terminal  40  is less easily displaced or deformed elastically than the conventional one, thereby reliably preventing a momentary electrical break between the contact pads  25  of the card  20  and the contact portions  44  of the contact terminals  40  when subjected to impacts or vibrations.  
         [0053]    Although in the case of FIG. 4 the thickness of the spring portion  43  is progressively increased toward the fixed portion  42  side, the spring portion  43  may be formed in an arbitrary shape as long as the thickness d 1  of the spring portion  43  on the side of the fixed portion  42  is set larger than the thickness d 2  on the side of the contact portion  44  (front end side) and the center of gravity is located closer to the fixed portion  42  side than in the conventional contact terminal. For example, the spring portion  43  may have roughly a half thereof on the front end side formed in a constant small thickness and a remaining half on the base side formed in a constant large thickness so that the spring portion  43  has a stepped portion.  
         [0054]    In the contact terminal  40  shown in FIG. 3 and FIG. 4, since the width or thickness of the spring portion  43  is increased toward the fixed portion  42 , the cross section of the spring portion  43  is made to increase toward the fixed portion  42 , which in turn increases the cross-sectional mass of the spring portion  43  as it approaches the fixed portion  42 .  
         [0055]    It is also possible to set a part of the spring portion  43  near the fixed portion  42  larger in mass than a part of the spring portion  43  near the contact portion  44 . For example, by using different materials or different plating materials for these two parts of the spring portion  43 , the masses of the two parts of the spring portion  43 , one near the fixed portion  42  and the other near the contact portion  44 , may be differentiated.  
         [0056]    Next, FIG. 5 shows a write protect detection switch SW arranged inside the side portion  5  of the connector housing  2  of FIG. 2.  
         [0057]    This switch SW comprises two cantilevered contact leaf springs  80 ,  90  whose contact portions to be brought into contact with the card  20  are staggered. The engagement and disengagement between these two contact leaf springs  80 ,  90  can detect the position of the write protect button  26 .  
         [0058]    The contact leaf spring  80  has a terminal portion  81  securely soldered to a printed circuit board of an electronic device, a fixed portion  82  rigidly fixed in the connector housing  2 , a spring portion  83 , and a contact portion  84  engaged with the side portion of the card  20 .  
         [0059]    The contact leaf spring  90  is similarly made from a metal piece having a terminal portion  91 , a fixed portion  92 , a spring portion  93  and a contact portion  94 . The spring portion  93  is formed with a contact projection  95  that contacts the contact leaf spring  80 .  
         [0060]    The front end portion of the contact leaf spring  80  is bent downwardly of the connector so that it does not interfere with the other contact leaf spring  90 .  
         [0061]    When the write protect button  26  of the card  20  is situated at a position shown in FIG. 5, the two contact leaf springs  80 ,  90  are in contact with each other through the contact projection  95  of the contact leaf spring  90  and the switch SW is in a turn-on state. When the write protect button  26  is slid to the other position, the contact leaf springs  80 ,  90  are parted from each other, turning the switch SW off.  
         [0062]    In this switch structure, because the two contact leaf springs  80 ,  90  are brought into or out of contact with each other according to the position of the write protect button  26 , this connection and disconnection can be electrically detected to determine in which of the positions the write protect button  26  of the IC card  20  is set, the write disable position or the write enable position.  
         [0063]    In these two contact leaf springs  80 ,  90  making up the write protect detection switch SW, the width or thickness of the spring portion  83 ,  93  is increased toward the base, as shown in FIG. 3 or FIG. 4, to increase the cross-sectional mass of the spring portion  83 ,  93  as it approaches the base. Thus, the spring portions  83 ,  93  of the contact leaf springs  80 ,  90  are less easily displaced or deformed elastically than the conventional ones, making the switch more resistant to impacts. This can reliably prevent undesired or erroneous detection due to impacts or vibrations.  
         [0064]    In addition to the construction consisting of two contact leaf springs, the write protect detection switch may also be constructed of a single contact leaf spring and a fixed piece. The present invention can also be applied to this single contact leaf spring switch.  
         [0065]    (Variation)  
         [0066]    While in the above embodiments the spring portion  43  is extended in one direction to form an elastic contact piece  40 , this invention can also be applied to a folded type contact terminal in which the spring portion  43  is folded.  
         [0067]    The elastic contact piece of the present invention may also be applied to a card recognition switch that detects the presence or absence of a card in the connector, to a braking piece that applies a braking force to the card to prevent the card from jumping out of the connector when ejected, or to a card locking piece that prevents the card from slipping off.  
         [0068]    Further, while the embodiments above have been described to use an SD card as the IC card  20 , this invention may also be applied to card connectors for IC cards such as SIM card, MMC card, Smart Media (tradename) and Memory Stick (tradename). The structures of the card connectors for these cards may be determined appropriately according to the cards used.  
         [0069]    As described above, with the card-connector of this invention, because the mass of a part of the spring portion on the side of the fixed portion of the contact terminal is set larger than the mass of a part of the spring portion on the side of the contact portion, the center of gravity of the spring portion is located closer to the fixed portion than in the conventional contact terminal. This arrangement makes the contact terminal difficult to elastically displace or deform, thus more reliably preventing a momentary electrical break between the contact terminals and the contact pads of the card when applied impacts or vibrations.  
         [0070]    Further, with the elastic contact piece of the present invention, because the center of gravity of the spring portion is located closer to the fixed portion than in the conventional contact piece, it is possible to more reliably prevent the contact portion from parting from the mating object when subjected to impacts or vibrations.  
         [0071]    The present invention has been described in detail with respect to preferred embodiments, and it will now be that changes and modifications may be made without departing from the invention in its broader aspects, and it is the intention, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit of the invention.