Abstract:
A battery disconnect device includes a housing with a trip/sense circuit, a sealed solenoid and two bars. The solenoid includes a spring loaded contactor disposed in a sealed chamber which normally bridges the bars and is constructed to provide a very low resistivity between the bars. When a coil of the solenoid is activated, in response, for example, to a low battery voltage, the contactor moves away from the bars and is kept in an open position by a magnet. The contactor can be closed or returned to the original position by a manual push button or by a close circuit operated from a remote switch. Additionally the contactor may be opened by using a remote button to act as an anti-theft device.

Description:
BACKGROUND OF THE INVENTION 
     A. Field of Invention 
     This invention pertains to a device which can be installed in a motor vehicle such as an automobile, a truck or a sports utility vehicle. More particularly, the subject invention pertains to a device which automatically disconnects the battery of motor vehicle and selectively reconnects the same on demand. 
     B. Description of the Prior Art 
     A critical part of any automotive vehicle is its battery which provides power for various primary and secondary systems. Normally an automotive battery can last for a relatively long time since its charge is refreshed continuously as the vehicle is operated. However, in some instances, such as for example, when a short occurs in the vehicle wiring, or a control switch malfunctions, a leakage current may flow even when the engine is off, discharging the battery. 
     In order to protect the battery from such an occurrence, several proposals have been made for devices that can interrupt undeniable leakage current flow. However, the devices proposed so far have disadvantageous features which makes them undesirable. One such feature is that they interpose a relatively high series resistance between the battery and the car wiring. Therefore a high IR drop is developed, especially at high current drains, thereby reducing the voltage that is available to the vehicle systems, wasting energy, and generating undesirable heat. 
     A further disadvantage of the proposed devices is that they may not stand up to the extremely hostile environment existing under the hood of motor vehicles. This environment is characterized by high temperatures as well as corrosive fumes which damage sensitive electronic circuitry. 
     OBJECTIVES AND SUMMARY OF THE INVENTION 
     In view of the above, it is an objective of the present invention to provide a battery disconnect device with a very low in line resistivity. 
     A further objective is to provide a device in which the moving parts are sealed in a water and air tight chamber so that they are protected from noxious fumes and other undesirable fluids. 
     Other objectives and advantages of the invention shall become apparent from the following description. 
     Briefly, a battery disconnect device for an automotive vehicle includes a sense/trip circuit that sense a preselected condition of a motor vehicle battery; connecting elements such as bars connecting said battery to the vehicular equipment; and a solenoid having a coil and a contactor disposed within a closed chamber and associated with said coil. The coil is activated when an abnormal condition is sensed. The contactor has a first position in which said contactor connects said connecting elements, a second position in which said contactor is removed from said connecting elements. A biasing spring is arranged to urge said contactor toward said first position to generate a force between said contactor and said connecting elements to reduce the in-line device resistivity. A magnet is also provided within the solenoid to keep the contactor in the second position, once the coil has been activated, said second position thereby being maintained even after the coil has been deactivated. A manual push button is used to move the contactor away from the first position until it snaps back to the first position. 
     Additional elements are used to provide other advantageous features. One such element is a remote trip circuit which allows the solenoid to be tripped remotely thereby allowing the device to be used as an antitheft device. In addition to the pushbutton, a remote close circuit may also be used to close the solenoid. The remote close circuit and/or the remote trip circuit could be activated by a portable transmitter. 
     The device may further include an indicator for showing when the battery is overcharged, as well as a shunt circuit to allow a trickle current to flow between the battery and the motor vehicle bus for powering certain equipment in the car. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an orthogonal view of a battery disconnect device constructed in accordance with this invention; 
     FIG. 2 shows a cross-sectional view of the connecting/disconnecting solenoid of the device of FIG. 1; 
     FIG. 3 shows a somewhat enlarged cross-sectional view of the solenoid of FIG. 2 open or disconnected position; and 
     FIG. 4 shows a block diagram for the control system used to operate the subject disconnect device. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1, a battery disconnect device  10  constructed in accordance with this invention includes a housing  12  with a base  14 , an input bar  16  and an output bar  18 . Each bar is provided with a corresponding hole  20  for connecting the positive cable device  10  between the battery and of a motor vehicle. Also attached to the housing  12  is a grounding lead  22  terminating with an eyelet  24 . The eyelet  24  is connected to the engine block (not shown) or other negative terminal. Housing  12  further includes a non-conductive shell  26  attached to the base  14  and forming a cavity for the various additional elements of the device  10 . A pushbutton  28  extends outwardly of shell  26  on a shaft  30 . 
     Referring now to FIGS. 2 and 3, base  14  is made of a plastic non-conductive material and the two bars  16 ,  18  are imbedded in the base in a manner which keeps them apart at distance of about ¼″ as shown. The bars  16  and  18  are preferably made of copper or a copper alloy and are coated with a silver layer (not shown) at least on their top surface. 
     Base  14  has a top surface  32  with a circumferential groove  34 . When shell  26  is inserted over the base  14 , its lower edge fits into groove  34 . The groove  34  may be provided with a potting material or another similar insulating substance which renders the device  10  substantially air and water tight. On top surface  32 , the base  14  is formed with an integral member  36  defining a cylindrical opening  38 . 
     Referring now to FIG. 2, inside shell  26  there is provided a solenoid  40 . The solenoid  40  includes a tubular case  42  with two end walls  44 ,  46  formed with respective circular openings  48 ,  50 . The case  42  also has longitudinal openings which have been omitted for the sake of simplicity. Inside the case  42  there is a bobbin  50  made of a plastic material. This bobbin  50  has at one end a toroidal extension  52  arranged and constructed to fit into cylindrical opening  38  of member  30  as shown. A standard solenoid coil  54  is wound on the bobbin  50 . 
     Above the bobbin  50  there is a circular washer  56 . A permanent annular magnet  58  is disposed between washer  56  and end  44  of case  42 . 
     A plastic sleeve  60  and a metallic sleeve  62  extend axially through the shell  26 , opening  44  and bobbin  50 . 
     Pushbutton  30  is seated at the top end of the sleeve  60  with its shaft  32  extending through the sleeves  60  and  62  and terminating near the bottom wall  72  of sleeve  62  as shown. A spring  64  rests between the pushbutton  30  and a shoulder  66  on sleeve  62  and is used to bias the pushbutton upward. 
     A metallic rod  68  extends downwardly from the sleeve  62  and is slidable within the bobbin  50 . 
     The rod  68  has a top surface  70  which, when the rod  68  is in topmost position shown in FIG. 3, is adjacent to surface  72  of sleeve  62 . 
     At the end of rod  68  opposite surface  70 , a ring  74  is rotatably mounted on rod  68  so that it can spin around the longitudinal axis of the rod  70 . The ring  74  has a diameter which is much larger than the distance between the bars  16  and  18 . For example, the ring  74  can have a diameter equal to the widths of the bars  16  and  18 . Preferably ring  74  is made of silver, a silver alloy or other highly conductive material. Moreover, the ring  74  has a bottom annular surface  76  which is highly polished. A spring  78  is disposed between the ring  74  and a shoulder  80  formed on bobbin  50 . This spring  78  is used to bias ring  74  downwardly. 
     Rod  68  and sleeve  62  are made of a ferromagnetic material. 
     As seen clearly in FIGS. 2 and 3, the bobbin portion  52  and member  36  cooperate to form a closed tubular space  81  for ring  74 . In fact a sealant may be applied between these members to insure that the space  80  remains airtight and free of dirt, exhaust gases and other impurities. As the rod  68  slides longitudinal, the ring  74  reciprocates in this space  81 . Rod  68  and ring  74  collectively define a contactor for the solenoid  40  which contactor can be shifted from a closed position where the bars  16 ,  18  are electrically connected by ring  74  (shown in FIG. 3) where the bars  16 ,  18  are not connected electrically because the right  74  is spaced away therefrom. 
     Referring now to FIG. 4, typically the electrical circuitry  100  of an automotive vehicle includes a rechargeable battery  102  (the re-charger has been omitted for the sake of clarity) which feeds a battery bus  104 . An ignition coil  106  is selectively energized by bus  104  through a switch  108 . Various other auxiliary equipment collectively identified by numeral  110  are selectively energized by a respective switch  113 . Importantly, bus  104  is selectively connected to battery  102  by solenoid  40  in response to commands from a control circuit  113 . The control circuit  113  is physically mounted in housing  12  on a standard PC board (not shown). 
     In the simplest embodiment of the invention, the control circuit  113  includes a sense/trip circuit  114 . This circuit  114  senses the battery voltage and/or monitors current flowing from the battery and is used to sense an abnormal condition. For example, if switch  112  is defective, it may remain turned on and maintain some current through the auxiliary equipment  110  even after the engine is turned off. If the driver leaves the vehicle and is not aware of this problem, after some time, the current through the auxiliary equipment  110  drains the battery  102  sufficiently so that when the driver returns he will not be able to start his engine. This situation is avoided by the present invention because, the sense/trip circuit  114  senses that the battery is depleted before a critical voltage level is reached and causes the solenoid  40  to open thereby avoiding further discharge of the battery  102 . Alternatively, the circuit may sense current flow from the battery  102  while the engine is off. 
     Referring back to FIGS. 2 and 3, initially, i.e. under normal operating conditions, the coil  54  is de-energized, the rod  68  and attached ring  74  are in their low position in which the top surface  72  of the rod  68  is longitudinally spaced from the sleeve  62  and the ring  74  is pressed downwardly by spring  78  so that its surface  76  is in intimate contact with the top surfaces of the bars  16 ,  18 . The rod  68  and ring  74  are maintained in this position by spring  78 . Because of the high polish of the contacting surface  76  of the ring  74  and bars  16  and  18  as well as the biasing force of spring  78 , the resistivity between the bars  16  and  18 , i.e., the in line resistance between battery  102  and bus  104  is extremely low. The voltage drop across the bars in device constructed in accordance with this invention has been measured to be less than 0.02 volts at 200 amps. Therefore, the solenoid  26  presents only a very minimal in line resistivity and has no substantial impact on the voltage of bus  104 . 
     A further advantage of the invention is the ring  74  need not be tightly mounted on rod  70  but can be secured thereto such that it has a slight axial play. Therefore as the ring  74  is pressed against the bars  16 ,  18 , the ring  74  automatically adjusts to imperfections in the surfaces of the bars  16  and  18  as well as imperfections of its own surface  76 . 
     When the sense/trip circuit  114  senses an abnormal condition, (as described above) it energizes coil  54 . The coil  54  then induces a magnetic field within bobbin  50  and generates a magnetic force upwardly on rod  68  and ring  74 . This force is sufficient to overcome the downward force of spring  78  and to pull rod  68  and ring  74  upward to the open position shown in FIG.  2 . In this position, the ring  74  is spaced away from the bars  16  and  18  and hence disconnects bus  104  from the battery  102 . 
     Once the rod  68  is pulled upward into the bobbin  50  to the position shown in FIG. 2, its upper surface comes into contact with the lower surface  72  of sleeve  62 . As previously described, sleeve  62  is made of a ferromagnetic material and it is magnetized by its contact to the permanent magnet  58 . Therefore, once the rod  68  is in its upper or open position, it touches lower surface  72  and is maintained in this position even after the coil  54  is de-energized by the magnetic attraction of sleeve  62 . Hence coil  54  needs to be energized only for a very short time period, i.e., until the rod  68  moves upward. Thereafter, the coil  54  may be de-energized. The energy requested by the coil  54  is very small. 
     In one embodiment, the solenoid  26  is reset or closed as follows. Pushbutton  30  is biased upwardly out of the shell  26  by spring  64 . As seen in FIG. 3, in this configuration, shaft  32  attached to the pushbutton  30  is disposed inside the sleeve  62 . In order to close the solenoid  40 , the driver or a mechanic pushes the pushbutton  30  downward, thereby forcing the rod  32  to move axially downward through the sleeve  62  and push rod  68  away from the sleeve  62 . At a critical point, the downward force of spring  78  exceeds the upward magnetic force on rod  68  and forces the rod  68  to snap downward with the ring  74  bearing against the bars  16  and  18 . In this manner the solenoid is closed thereby making contact between battery  102  and bus  104 . 
     Several additional elements may be provided for the device described so far, thereby providing additional features. In one embodiment, a remote trip circuit  116  is provided. This circuit  116  may be activated by a switch  118  hardwired to another part of the vehicle, such as, for example, on the dash board. When the remote control trip device is operated, the trip circuit  114  opens the solenoid  40  in a manner similar to the operation described above. Thus, the device  10  may be used as an anti-theft device since the car will not start until the contact between bars  16 ,  18  is restored. 
     Alternatively, the switch  118  may be replaced by a portable remote control transmitter carried by the driver and a receiver in device  10  arranged so that when the transmitter is activated by the driver, the receiver receives a signal from the transmitter and in response sends a signal to the sense/trip device  114  causing the open command to be generated. In this configuration, the remote trip device  118  may be used as a theft deterrent means as well to disable the vehicle when not in use. 
     Another feature that may be added to the circuitry  100  is an electrical close circuit  120 . This electrical close circuit  120  may include another coil disposed within the housing of device  10  and arranged so that when it is activated, it pulls rod  70  away from sleeve  62  and cause it to snap to the closed position. Electrical close circuit  120  may be activated by a manual pushbutton on housing  12 , not shown, or may be activated by a remote close circuit  122 . Once again circuit  122  may be activated by a switch  124  disposed on the dash board and hard wired to the circuit  122 . Alternatively the switch  124  may be replaced by a portable transmitter which may activate circuit  122  to close the solenoid  40 . 
     Since the sense/trip circuit monitors the condition of the battery  102  anyway, it may also be used to detect an overcharge condition. If, for example, the sense/trip circuit  114  detects when the voltage of battery  102  is over a predetermined value, such as 13.8V, the sense/trip circuit generates an over voltage signal OV. This signal OV is used to drive an over voltage indication  132 . This indicator  132  may be disposed on the housing  12 , or it may be disposed remotely, for example on the dash board. 
     If a remote trip circuit  116  as well as a remote close circuit  122  are provided simultaneously then a single portable transmitter may be used selectively to activate both circuits. 
     The circuitry  100  may be also provided with a shunt circuit  130 . This circuit  130  is designed to allow a current of a predetermined value (which is relatively low as compared for example to the current used during ignition). This circuit  130  may be used to allow some of the auxiliary equipment  108  to get power from the bus  104  even if the solenoid is open, as long as this equipment does not draw too much current. The various circuits used to control the operation of the subject solenoid can be implemented by using a microprocessor to reduce power requests and size. 
     Obviously numerous modification may be made to the invention without departing from its scope as defined in the appended claims.