Abstract:
A plug-in replacement relay for automotive use incorporating a security system ( 43 ) to control the actuation of the relay is disclosed. The plug-in replacement relay derives its power supply from bridge rectifier(s) ( 33, 37 ) having their inputs connected across the coil socket connector (pins  85, 86 ) and/or the switching contacts ( 11 ) (pins  30, 87 ), allowing polarity free connection. An inhibitor circuit ( 31 ) ensures that the contacts ( 11 ) are actuated only when intended.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application is a continuation of patent application having U.S. Ser. No. 10/275,212, filed 01 Nov. 2002, which claims priority to International Application No. PCT/AU01/01075 (published as International Publication No. WO 02/18186), filed 28 Aug. 2001 and designating the United States, which in turn claims priority to Australian Provisional Application No. PQ 9739, filed 28 Aug. 2000, the entire disclosures of which are incorporated herein by reference. 
     
    
     
       BACKGROUND OF INVENTION  
         [0002]    This invention relates to a control unit for supplying power to a circuit, and in particular to such a control circuit for an automotive application.  
           [0003]    In a modern automobile, relays are often used to obviate the need for high current capacity wiring being routed to control switches in the vehicle cabin, and also to obviate the need for such control switches to be rated to carry such high currents. An application of such is the use of a relay having its coil connected to the high beam circuit, and its high current contacts used to make a circuit to driving lights. Without the use of the relay, the extra current load of the driving lights, in addition to the high beam current load of the existing driving lights, would result in failure of the high/low beam switch and/or the headlight switch with normal vehicle wiring. While this could be obviated in vehicle manufacture by including heavier wiring and heavier rated switches, so that in the event a vehicle owner decided to install driving lights, the vehicle circuitry would be of a sufficient rating, this is generally not done, in order to save manufacturing costs.  
           [0004]    For similar cost saving measures, such relays, which are usually electromechanical devices, although there is no reason why they could not be solid state (ie transistorised), have been utilised in other parts of the vehicle circuitry. This includes for switching the vehicle ignition circuitry and the vehicle fuel pump and fuel injection circuitry. In this manner, the more expensive high current capacity wiring can be run on as short a route as possible, in circuit with the vehicle fuse box, the relay contacts, and the ignition coil (or ignition coils) primary (which can carry at least 4 amps), and similarly in circuit with any fuel pumps and fuel injection pressurisation pumps. The relay coils, which require perhaps 5% or less current to actuate than the load drawn by the circuits that the contacts actuate, can utilise much lighter wiring connected to the vehicle ignition switch, and a much lower current rating on the contacts in the vehicle ignition switch than would be the case if the circuits were connected to the ignition switch directly.  
           [0005]    A very obvious application of such an arrangement is in the solenoid assembly which is used to actuate the vehicle starter motor. However in the case of the starter motor, the solenoid is only operated when the vehicle ignition is turned to the “start” position.  
           [0006]    In the case of relays which connect to the ignition and any fuel pump circuitry, these must be actuated when the ignition is set to both the “run” and “start” positions.  
           [0007]    Modern vehicle immobilisers, which can be stand-alone or incorporated into alarm systems, are usually wired into the circuitry in a vehicle to interrupt power to the vehicle ignition or fuel pump(s), unless over-ridden by a person who has the key to the alarm. In the past, keys were literally just that, although in more modern alarms electronic keys have been proposed, from simple resistive networks, numeric keypads, and to complex encryption techniques involving binary code strings and code hopping arrangements. In all of these arrangements, the immobiliser must be wired into the vehicle circuitry. This involves modifying existing vehicle circuitry in order to fit the immobiliser, which is time consuming and requires some knowledge of the vehicle circuitry on the part of the installer, or investigation to determine the nature of the vehicle circuitry when the installer is not familiar with it.  
           [0008]    It is an object of this invention to provide an immobiliser system which overcomes some of the above problems, or at least provides an alternative to known immobiliser systems.  
           [0009]    Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.  
         SUMMARY OF INVENTION  
         [0010]    In accordance with the invention there is provided a self contained relay incorporating actuation authorisation means, said self contained relay having switching means for use in switching a circuit, and control means to actuate said switching means, said self contained relay having first input means for receiving a control current for said control means, said actuation authorisation means having second input means for receiving an encrypted code, memory means containing a stored code allocated to said relay, comparator means for comparing said encrypted code with said stored code, where said control means actuates said switching means in response to said first input means receiving said control current, when said comparator means determines said encrypted code matches said stored code; wherein active circuitry in said relay derives its power supply via at least one bridge rectifier connected to rectify power derived from one or more of said first input means, said switching means, and an available chassis ground. In this manner the self contained relay is polarity independent, and will work as a plug-in replacement, regardless of the polarity of wiring in the original equipment.  
           [0011]    By way of explanation the first input means of said self contained relay can be equated to the control coil of a standard relay (at least when the comparator determines a code match), and the switching means can be equated to the contacts of a standard relay.  
           [0012]    Typically the switching means will comprise switch contacts, used to switch electric current. In one preferred application the switching means will switch power to the primary circuit of the ignition coil for a Kettering ignition internal combustion engine. In an alternate application the switching means will switch power to a fuel pump in either or both of a fuel system for a vehicle or a fuel injection system for an internal combustion engine. It will be understood that the switching means could be solid state, such as a transistor, a silicon controlled rectifier, or a triac.  
           [0013]    Typically the control means could comprise the coil of an electromechanical relay having the switching means and the base or gate of a transistor, scr, or triac, along with associated driver circuitry as required.  
           [0014]    The comparator means may be an analog device which compares derived analog signals (such as those derived from resistive networks or voltage or current references or from d/a converters) or a micro-processor or PLA based or other electronic arrangement that compares said encrypted code in the form of a serially transmitted binary code, with said stored code.  
           [0015]    Preferably said active circuitry in said self contained relay derives its power supply from said first input means.  
           [0016]    Alternatively, said active circuitry in said self contained relay may derive its power supply from said switching means.  
           [0017]    As a further alternative, said active circuitry in said self contained relay may derive its power supply from both said first input means and said switching means.  
           [0018]    In accordance with a preferred feature of any of the alternatives for deriving the power supply, where part of the power supply is referenced to a chassis ground, for convenience the self contained relay may also be connected to the chassis ground for the purposes of deriving the power supply.  
           [0019]    Preferably said encrypted code is a serial binary code, and said second input means receives said encrypted code from a radio receiver located in said self contained relay. In this arrangement, the encrypted code can be transmitted from a hand held remote control transmitter, or a removable transmitter that is powered from a connector providing power for this purpose. In a motor vehicle application, the connector may be a socket fitted to the vehicle dashboard, or the existing or a fitted cigar/cigarette lighter socket.  
           [0020]    Alternatively, said encrypted code is a serial binary code, and said second input means receives said encrypted code from an amplifier circuit which is connected to said first input means, said encrypted code being impressed onto the power supply from a removable transmitter that is powered from a connector providing power for this purpose. In a motor vehicle application, the connector may be a socket fitted to the vehicle dashboard, or the existing or a fitted cigar/cigarette lighter socket.  
           [0021]    Preferably said self contained relay incorporates an inhibitor circuit which prevents said switching means being actuated unless there is a voltage differential across said first input means.  
           [0022]    Preferably said inhibitor circuit incorporates an optoisolator having its input connected to said first input means. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0023]    Two particular preferred embodiments of the invention will now be described with reference to the drawings in which:  
         [0024]    [0024]FIG. 1 is a circuit diagram for a code transmitter unit for a vehicle immobiliser according to the first embodiment;  
         [0025]    FIGS.  2  to  4  are a circuit diagram for a self contained relay according to the first embodiment; and  
         [0026]    FIGS.  5  to  7  are a circuit diagram for a self contained relay according to the second embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0027]    Both embodiments are plug in replacement relays for automotive use, which incorporate actuation authorisation means, which allows the relay to function as an immobiliser, without requiring modification of the vehicle wiring, which is always required with immobilisers of known type, with the exception of those which are fitted as factory standard. Such relays can be fitted to actuate the starter motor solenoid, actuate wiring to the ignition system, and actuate fuel pumps of the general type or fuel pumps utilised in fuel injection systems. Without the authorisation actuating means allowing operation of the relay, it is not possible to operate the circuit that the relay is connected to, which renders the vehicle inoperable. The embodiments are both built into relay housings along with switching means in the form of the contacts  11  and control means in the form of the actuation coil  13 , and connected to the relay terminals  15 , with the actuation authorisation means interposing between the relay terminals  15  and the actuation coil  13 .  
         [0028]    The first embodiment uses a plug-in module  17  shown in FIG. 1, which has contacts  19  and is contained in a housing (not shown) so as to be receivable in a cigarette lighter socket in a motor vehicle dashboard or other interior fitting. The circuitry of the plug-in module  17 , when powered, generates a 52.5 kHz FSK coded signal which is superimposed on the wiring of the vehicle.  
         [0029]    The plug-in module  17  has a micro-processor  21  which is programmed to periodically transmit serially encoded 32 bit data string using frequency shift keying (FSK) code. The data is conveyed to power FET driver  23  which via a series resonant circuit  25  and simple band pass filter  27 , drives transformer  29  which couples the signal via a very low impedance coupling to the power line, impressing the data on the motor vehicle wiring.  
         [0030]    Referring to FIGS.  2  to  4 , in the relay terminals  15 , terminal numbers  30 ,  85 ,  86 , and  87  are identified. These terminal numbers  30 , and  85 ,  86 ,  87  are the normal numbers on the standard Bosch or Siemens automotive relay. While other manufacturers may use the same pin compatibility, and/or perhaps the same terminal numbering, it will be understood that there are manufacturers who use neither, and changes will be needed in these instances to ensure that the wiring of the plug-in module matches the socket. In the standard Bosch or Siemens automotive relay, terminal numbers  85  and  86  are always connected to the standard equipment relay coil and the polarity is variable. Terminal number  30  is the common relay contact of the standard equipment relay and terminal number  87   a  the normally closed contact. Terminal number  87  is the normally open contact of the standard equipment relay. The polarity across any of these contacts for the standard equipment relay is again variable. It will be understood that the polarity is variable, depending upon how the relay is wired into the vehicle wiring at the point of manufacture.  
         [0031]    When 12 volts appears across terminal numbers  85  and  86 , this is the signal to initiate the process to close the internal immobiliser relay. An inhibitor circuit in the form of an opto-isolator circuit  31  is provided to ensure that process initiation does not commence unless there is a differential across terminal numbers  85  and  86 . The reason for the novel use of the opto-isolator  31  and not a simple bridge circuit, is that it is possible to have a positive potential on either terminal numbers  85  and  86  or both. Process initiation should only commence when there is a differential across terminal numbers  85  and  86  and not when they are both high.  
         [0032]    Again due to polarity variations likely to be encountered, bridge rectifier  33  is used to ensure correct polarity for the 5 volt regulator  35 . Should power for any reason not be available on terminal numbers  85  and  86  prior to the signal to energise (on these pins) a second source of power which has to be polarity corrected is available on the normally open terminal number  87  and  30 . Any necessary polarity correction is accomplished by bridge rectifier  37 .  
         [0033]    The following description is made with reference to an application where the standard equipment starter motor relay is replaced by the relay of the first embodiment. As the ignition switch is switched through “accessory” and then “ignition-on” positions, power is supplied to the plug-in module  17 , which the driver will have plugged into cigarette lighter socket. If there is no power though available at terminal numbers  85  and  86  to energise the unit, there is power though available across terminal numbers  30  and  87 . The relay of the embodiment therefore has power derived from terminal numbers  30  and  87  and decodes and verifies the signal supplied by the plug-in unit  17 . The FSK signal is picked off the power line from point VP and passed through a band pass filter  39  with clipping diodes  41 . This small signal is then put into microprocessor  43  which amplifies the signal and decodes it, comparing it with one of the codes stored in its memory. Should the code be valid a signal is outputted to switch  45  which will energise the relay coil  13 , when a signal is received from opto-isolator  31 . The use of opto isolator  31  ensures that the relay coil  13  is energised only when power is supplied at terminals  85  and  86 , and not immediately that the code is determined to be valid. This enables the embodiment to be employed as a replacement starter motor relay.  
         [0034]    During the start phase in many motor vehicles, power is lost to the cigarette lighter socket as the ignition switch is turned to the “start” position. The microprocessor  43  includes further memory to temporarily store the received signal, so that the information is available to enable the microprocessor  43  to carry out the operations, resulting in eventual energisation of the relay coil  13  and closure of the relay contacts  11 . In an alternative embodiment, this function could be provided by a small rechargeable battery or miniaturised large capacitor (0.5 F or more).  
         [0035]    The second embodiment is similar to the first embodiment, except that it uses standard wireless radio transmission to the relay of the embodiment, which is shown in FIGS.  5  to  7 . The coding used is random encrypted to avoid code grabbing.  
         [0036]    Like numerals describe like parts and functions. Additional componentry comprises radio receiver  47  to receive the RF signal from the transmitter, the serial binary signal from the receiver  47  is then compared against the code stored in the EEROM  49  by microprocessor  43 .  
         [0037]    The transmitter unit can take the form of a normal hand held remote controlled high frequency random encrypted transmitter unit, however, in another embodiment the transmitter can be built into a unit that plugs into the cigarette lighter socket. As soon as the ignition is turned on the transmitter transmits a signal to the immobiliser.  
         [0038]    It should be appreciated that the scope of the invention is not limited to the particular embodiment disclosed herein.