Background Art With the significant advances in automobile performance, there have been corresponding improvements to occupant safety as well as to vehicle service and repair. This includes improved occupant safety devices, improved vehicle crash worthiness, and improved engine reliability. One element of these improvements has been the added electronic content of the automobile operating systems; both control and fault diagnosis. The leading application for developing electronic content has been in connection with control of engine performance; primarily directed toward reduced emissions, but increasingly used to provide improved engine diagnostics. This allows for more accurate repairs and also provides forewarning to the operator of potential engine failure. All of this results in greater security to the automobile occupants as well as better repair programs.

One aspect, however, of the automobile's operating systems that has not received as many advances in technology is the vehicle signal lamp subsystems. These include the brake warning lamps, turn signals and hazard lamps. Each of these systems are important to vehicle and occupant safety as well as to the safety of other drivers and to pedestrians. Notwithstanding the past improvements and reliability of these systems, they each remain fundamentally the same in terms of their operation and/or control. Each of these prior art systems operate in an electromechanical fashion. The brake lamp system is actuated with closure of a brake switch connected to the brake pedal, such that when the brake pedal is depressed the switch closes and applies 12 VDC to the brake lamps.

While this system has high reliability due to its simplicity, there is no immediate notice to the driver of a failure in the brake lamp system. Such a failure could include a failed switch which, although the braking system operates, fails to provide the excitation voltage to the lamps. Alternatively, a common problem is burn out of one or more of the brake lamps. These failures generally take time to discover and are usually determined by verbal warnings from other parties.

A similar situation occurs with the turn signal system which is manually actuated through driver movement of a steering wheel mounted wand to either a left turn or right turn signal position. This actuates a thermal Aflasher@ unit which provides a mechanical duty cycle switch in applying 12 VDC to the vehicle's turn signal lamps. Here again, the most common failure is a burned out turn signal lamp which is not immediately discoverable by the driver but which may cause severe hazards by failure to give a turn signal notice to either oncoming or following vehicles, depending on whether a front bulb or rear bulb is out. A final safety signaling system is the automobile's hazard lamp system, which uses the vehicle's brake and turn signal lamps, and the turn signal flasher unit, which oscillates the excitation to these lamps so as to produce a flashing signal. The hazard lamps, whenever activated, i. e. stationary or moving vehicle, provide an essential safety warning to other drivers, such that any loss of lamp performance may severely hamper the function.

A further emphasis with regard to the safety importance of providing a driver warning of these signal failures is that there is no known probability to a failure pattern. In other words, a single bulb failure in the turn signal system removes any notice to those persons approaching the vehicle from the direction of the failed lamp. Similarly, a failure of the brake lamps associated with one side of a vehicle (either left or right) can completely eliminate braking notice to following vehicles if the operating lamp side is obscured or, in darkness, may provide the illusion of a motorcycle rather than an automobile.

Disclosure of Invention One object of the present invention is to provide improved operation of an automobiles signaling lamps, including its turn signal lamps, hazard lamps, and brake lamps. Another object of the present invention is to provide a system for automatically detecting lamp failures. A still further object of the present invention is to provide notice of lamp failure to the operator to permit early correction. A still further object of the present invention is to maintain a record of detected lamp failures which may be automatically read by external diagnosis equipment thereby providing for lower cost repair.

According to the present invention, the actuation of a motor vehicle signaling device is controlled by, and its performance monitored by, a microprocessor based control which is responsive to a signaling state command entered by an operator. In further accord with the present invention the control includes detection circuitry for notifying the microprocessor of the presence of an operator commanded signaling state, and actuator circuitry for actuating the signaling device in response to a microprocessor command signal. In still further accord with the present invention, during actuation of the signaling device the microprocessor receives the sensed actual magnitude of the device excitation current and compares this actual value with reference values indicative of nominal operation, to record error messages in memory of the existence of non operational signaling devices in dependence on a difference value magnitude between the actual value and the reference value.

In still further accord with the present invention the control circuitry includes interface circuitry operatively connected to the microprocessor and adapted for connective operability to external equipment which may access the error messages stored in memory in the performance of vehicle performance analysis. In still further accord with the present invention an alarm alerts the vehicle operator in real time of the existence of a priority error signal indicative of a safety failure condition.

The present invention provides for intelligent means to govern the operation of and to monitor the performance of an automobile's signaling devices.

The system includes detection and reporting of failure modes in the lamp excitation to permit efficient repair, as well as providing real time alarms to the vehicle operator in the event of a signal device failure constituting a safety failure condition.

These and other objects, features, and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying Drawing.

Brief Description of Drawing Fig. 1 is a system block diagram of one embodiment of the present invention; Fig. 2A and 2B is a schematic illustration of the embodiment of Fig 1; Fig. 3 is a flow chart diagram illustrating the process steps performed by the embodiment of Figs. 2A and B; Fig. 4 is a schematic representation of an alternative configuration of one element of the embodiment of Figs. 2A and B ; and Fig. 5 is a flow chart diagram illustrating additional processing steps that may be performed in connection with the alternative configuration of Fig. 4.

Best Mode for Carrying out the Invention Referring to Fig. 1, which illustrates in block diagram form the interconnection of the present motor vehicle multi-function control module 10 with the vehicle's signal lamp excitation circuitry. In the simplified Fig. 1 illustration the vehicle's signal lamps are shown as a lamp block 12 which is energized/actuated by signal currents selectively routed through a multifunction switch 14. The switch 14 is of a well known type multi-positionable function switch which is mounted within the operator's reach, typically as a wand on the steering column, and is responsive to operator control for selective actuation of-

the vehicle's turn signals and hazard lamps. As described in detail hereinafter with respect to, positioning of the switch 14 actuates various ganged switches to complete the current path to the selected function lamps.

In the present embodiment, the lamp excitation current is provided to the switch 14 on lines 16,18, and 20. The line 16 provides the turn signal lamp excitation current which is regulated by a turn signal control 22 which, when selectably actuated, provides the current from the line 18. The current on line 18 is similarly regulated by a flash rate control 24 which, when it is actuated, provides the current signal from the vehicle's power source 26 through a current sensor 28. Finally, line 20 provides the brake lamp excitation current through current sensor 30 and line 32 from the vehicle's brake switch 34, which connects line 32 to the vehicle power source 26 when the operator depresses the vehicle brake pedal 36.

The module 10 receives the sensed actual value of the combined turn signal and hazard lamp signal excitation current on line 18 from the current sensor 28, which provides a signal indicative of the sensed actual value on lines 38,40.

Similarly, the current sensor 30 provides the sensed actual value of the line 20 brake lamp excitation current to the module on lines 42,44. The module 10 also receives a key state signal on a line 46 from the vehicle's ignition switch 48. As described in detail hereinafter with respect to Figs. 2,3 the module selectably actuates the turn signal control 22 and the flash rate control 24 with gate signals provided on lines 50,52 respectively, in response to the sensed state of the vehicle operator's manipulation and operation of the multifunction switch 14, the brake pedal 36, and the ignition switch 48.

Referring now to Figs. 2A and B, which is a schematic diagram illustrating the circuit details of the multi-function module 10, the lamp block 12, muiti-function switch 14, the turn signal control 22, the flash rate control 24, and the current sensors 28,30. The elements in Figure 2 which are common to those in Fig. 1 have the same reference numerals. As will become more evident hereinafter, the present invention provides a multi-function module which controls

the operation of the automobile's signaling lamps, while also capable of identifying the existence of failed lamps and, under selected circumstances, send visible and/or audible warnings to the operator of the existence of a failure condition. The module may be adapted to various automobile signal lamp configurations as established by the automobile manufacturer. To the extent that the vehicle's signal lamps serve dual purposes, e. g. the turn signal lamps and the brake lamps also serve as the hazard lamps, and in some vehicle models the brake lamps also serve as the rear turn signal lamps, the present system has the ability to cross-correlate the measured values of excitation current in these different signaling functions to more closely identify, or even exactly identify, a failed lamp. This provides for a greater range and depth of diagnostics which may isolate failure modes to particular lamps and/or functional elements. The embodiment of Figs. 1-3 assume separate lamp functions for the turn signal and brake lamps, and Figures 4 and 5 assume the vehicle's brake lamps also serve as the rear turn signal.

In Figs. 2A and B, the lamp block 12 includes left and right pairs of turn signals 54,56 as well as right and left pairs of brake lamps 58,60. The turn signal lamps are actuated through the turn signal switch 62 enclosed within the multi-function switch 14, and provides the left and right lamp current excitation signal path from the line 16 with closure of the contacts as marked in Figs. 2A and B. The multi-function switch also includes a hazard switch function 64 which when placed by the operator in the ON position provides the current excitation signal path from the line 18. With the hazard switch in the normally off position the current excitation signal path from the line 20 is completed to the right and left pairs of brake lamps 58,60.

The brake lamp current on line 20 is provided through current sensor 30 and line 32 in response to closure of the brake switch 34 with applied pressure to the brake pedal 36 by the operator. In the Figs. 2A and B embodiment the sensor 30 is a series resistor, the value of which is scaled in dependence on the anticipated magnitude of the lamp excitation signal, i. e. the current load. In the present embodiment the brake lamp filament resistance is on the order of 45 to 50

ohms, and with a 12 volt DC vehicle power source the four brake lamp nominal current load is 1.0 ampere. In this example, the resistance value of the sensor 30 may be on the order of one ohm. This provides a balance between nominal input signal scaling and power dissipation of the sensor, which in this case is 1.0 volt and 1 watt respectively. It should be understood, however, that there is a good degree of latitude in selecting the resistance value based on the requirements of the particular application. Similarly, the resistor type may be any known type deemed suitable for the application by those skilled in the art.

The current excitation signal on the line 18 to the multifunction switch 14 is also provided through a resistor type current sensor 28, which is similar in type and construction to the current sensor 30 described hereinabove. In the Fig 2 embodiment the line 18 maximum current load is the approximate equivalent of the four parallel pairs of lamps (54,56,58 and 60), each with a filament resistance of from 45 to 50 ohms, or an approximate resistance of 6 ohms for the combination. For a hazard signaling condition and a vehicle power source 26 of 12 VDC, the nominal hazard current load is 2 amperes. Alternatively, the same current sensor supplies the turn signal current on the line 16 when the turn signal control 22 is enabled. The turn signals, two lamp excitation, produces an approximate current draw of 0.5 ampere. Considering a balance of scale factor for the turn signal current measurement and the power dissipation produced by the hazard signal excitation, the resistance for the current sensor 28 may be changed, however, is design choice, which may be made by those skilled in the art on a case by case basis.

The output of the current sensors 28,30 is provided as a voltage signal on lines 38,40 and 42,44 respectively to the module 10. The sensed signal is applied differentially to operational amplifier circuitry 70 for the sensor 28 and to operational amplifier circuitry 72 for the sensor 30. The operational amplifier circuitry is well known and includes the use of an operational amplifier, typically a model type 741 or equivalent with an open loop gain of 50,000 v/v, which is connected in a closed loop voltage follower configuration with the scaling resistors shown. The nominal closed loop gain is 1.0 volt/volt, but may be

adjusted upward or downward to achieve the desired input signal/output signal scale balance.

The voltage signal output of the amplifier circuits 70,72 are coupled through resistor/capacitor (RC) filters 74,76 to the B and E inputs, respectively of a microprocessor 78. The voltage signal magnitude to the microprocessor inputs are limited by zener diodes 80,82 to protect against over voltage due to voltage transients as may occur in a motor vehicle power source. The microprocessor is a known type, such as the MOTOROLA model MC68HC05 family of 8 bit microprocessors, or equivalents thereof as may be deemed suitable by those skilled in the art for the intended application. A higher performance microprocessor may be used if greater programming ability is required for the performance of failure diagnostics or more input/output capability is required.

The nominal voltage signal scaling at the microprocessor inputs is approximately 5.0 VDC for approximately 2.0 amperes, providing a scale factor of approximately 2.5 volts per amp. A 250 milliamp lamp current is, therefore, scaled to a nominal 0.50 VDC at the microprocessor input. This provides sufficient scale accuracy to permit the microprocessor to differentiate the excitation signal magnitude on a per lamp basis to detect inoperative lamps.

Associated with the operational amplifier circuitry 70,72 the module 10 also includes detection circuits 84,86. Referring to the line 18 current path, with the hazard switch 64 in the OFF position and the flash rate control 24 in the disabled (de-energized) state, there is no current flow and the voltage potential on the line 38 is at the bias voltage V+, of the detection circuit 84. If the hazard switch is positioned to the ON state current flows from the detection circuit through the brake lamp filaments causing the voltage on line 38 to drop. This LOW state is sensed at input A of the microprocessor as a hazard lamp signaling state command by the operator. As described in detail hereinafter with respect to Fig. 3, the microprocessor responds by switching on output transistor 87, which is a known type NPN transistor, such as an MMBT A06 or equivalent. When on, transistor 87 connects line 88 to signal ground 89, thereby allowing current to flow through the coil 90 of the flash control unit 24. This enables the flash

control unit, causing the relay wiper 92 to close to the contact 94 and allowing current flow to line 18 from the vehicle power source 26.

In a similar, but converse condition, the detection circuit 86 detects the brake signaling state. With no applied bias and with the brake switch open, the voltage potential on the line 42 and at input D of the microprocessor 78, is LOW (near zero). When the brake pedal is depressed the switch 34 closes applying V+ (power source 26) to line 32 and causing the line 42 and the microprocessor input D to go HIGH. This signifies a brake signaling state to the microprocessor 78 while simultaneously causing current flow through the brake lamps 58,60.

In the embodiment of Figs. 2A and B the turn signaling function is enabled only when the ignition key is in selected positions, or Astates; @ typically the ACCESSORY position and the RUN position. When in these selected states (which for convenience of description herein will collectively be referred to as the RUN state, the microprocessor 78 receives a discrete signal on line 46 from the vehicle's ignition switch circuitry 48 indicating that the ignition key is in the RUN state. In response to the RUN discrete signal at its C input the microprocessor turns on transistor 96, which is a known type NPN transistor similar to transistor 87. This connects line 98 to signal ground 89 allowing current to flow through coil 100 and enabling the turn signal control 22. With the control 22 enabled, the operator's positioning of the turn signal switch 62 to either direction causes detection circuitry 84 to sense a LOW on line 38. As described hereinabove, this enables the flash control unit 24 providing source current through line 18, line 16, and the turn signal switch to the selected turn signal lamps.

Referring now to Fig. 3, in the microprocessor's actuation and performance monitoring of the vehicle's signaling functions it performs a program routine 102, which may be one of several different program routines performed cyclically by the processor at prescribed intervals. The microprocessor enters the routine at 104 and decision 106 determines if the A input, i. e. the line 38 in the embodiment of Figs. 2A and B, is LOW, indicating a signaling state command entered by the operator. If the answer is NO the processor exits at 108; if YES,-

instructions 110 request enablement of the flash control unit (24, Figs. 2A and B).

The processor performs this step by providing a base drive signal to the transistor 87 as described hereinabove. However, since the signaling format for both the turn signal and hazard signal function is a flashing, or oscillating protocol, the processor actuates the transistor 87 at a prescribed duty cycle and pulse repetition frequency (PRF). This sets the flash rate of the lamps.

Instructions 112 require a wait interval for bulb warm-up before instructions 114 command the processor to sample the I R current sense value at the processor's B input (Figs. 2A and B). The value at B is a voltage value which is scaled to an equivalent magnitude of current flow through resistor 28 (Figs. 2A and B). This represents the sensed actual magnitude of the current flowing through line 18 in the sample interval. Decision 116 determines if the I Bvalue is substantially equivalent to the nominal current value associated with all hazard lamps actuated. The microprocessor includes a read only memory (ROM) one portion of which includes a plurality of stored reference signals, each reference signal being representative of the nominal value of excitation current magnitude associated with various combinations of illuminated lamps. As an example, assuming the 250 milliamp lamps described above for the brake lamps, the nominal current magnitude for the full four lamp complement is 1.0 ampere; three lamps would be 750 ma, two lamps 500 ma, etc. These reference signals may be stored in a look-up table format. Decision 116 is based on the assumption that the hazard lamps are illuminated and the reference signal associated with a full lamp set illumination of the hazard function is compared to the sensed value of I R.

If the answer to decision 116 is YES, it is assumed that the signaling state command was associated with selection of the hazard function and that all lamps are operational, and the routine exits at 108. If the answer is NO it is not certain if this is due to a bad lamp or if the hazard function is not selected. As shown in Figs. 2A and B, in the present embodiment of the vehicle signaling system, including the multi-function switch 14, the turn signaling function and the hazard signaling function are mutually exclusive due to the relationship of the turn signal and hazard signal switches 62,64. Therefore, in response to a NO answer

to decision 116, decision 118 determines if the key state (processor input C in Figs. 2A and B) is HIGH indicating enablement of the turn signal control.

Although this doesn't necessarily indicate a signaling state command for the turn signals, if the answer is NO it eliminates the uncertainty of turn signal lamp actuation and instructions 120 require that a device trouble code (DTC) be recorded to the effect of a bad hazard signal lamp. Since the hazard lamps are in reality either the turn signal lamps or the brake signal lamps a further quantification of the number of bad lamps is left to measurements associated with those functions. Following the DTC recording step in instructions 120 instructions 122 command that the PRF of the flash control be doubled, or sufficiently changed in a manner to provide an indication to the operator that the system is not working properly. Following instructions 122 decision 124 determines if the switch sense A is still LOW indicating a continuing signaling state by the operator. If YES, the processor exits at 108 and repeats the routine in the next cycle. If the answer is NO, indicating no further signaling state, instructions 126 command that the flash control be turned off and the processor turns off transistor 87 and exits at 108.

If the answer to decision 118 is yes, indicating the enablement of the turn signal function, decision 128 determines if I B is substantially equal to that associated with the nominal excitation signal magnitude for full complement illumination of the turn signals. If YES, the processor exits, and if NO, decision 130 determines if the sensed current is substantially equivalent to that associated with all minus one lamp operating in this vehicle system embodiment. If YES, instructions 132 command an error message DTC report of one bad turn signal lamp; if the answer to 130 is NO decision 134 determines if the sensed current is substantially equivalent to that associated with all but two lamps operating; i. e. two of three lamps not operating. If YES instructions 136 command an error message DTC report of two bad turn signal lamps. Finally, if the answer to decision 134 is NO, instructions 138 command the error message DTC report of more than two bad lamps. Following instructions 132,136 and 138 the processor

executes instructions 122 to provide notice to the operator of the turn signal circuitry malfunction, and eventually exits the routine as described hereinbefore.

Referring now to Fig. 5, the microprocessor 78 (Figs. 2A and B) enters the brake performance monitoring routine 139 at 140, and decision 142 determines if the D input to the processor 78 (Figs. 2A and B) is HIGH. As described hereinbefore line 42 and the processor D input are high in the presence of closure of the brake switch 34 in response to application of the brake pedal 36.

If the answer to decision 142 is NO, the routine exits at 144. If the answer is YES, instructions 146 require a pause to allow for bulb warm-up prior to sampling the sensed brake current IE in instructions 148. The sensed IE value is presented at the E input of the processor as a scaled voltage signal equivalent of the sensed current magnitude by operational amplifier circuitry 72 (Figs. 2A and B), as previously described.

Decision 150 determines if the sensed current value is substantially equal to that of the nominal current load for illumination of a full brake lamp complement. As described hereinbefore with respect to the routine of Fig. 3 the reference signals stored in the processor's memory include a plurality of reference signals indicative of the nominal current values associated with illumination of the full brake lamp complement and also those current values corresponding to illumination of successively fewer numbers of operating lamps so as to thereby mimic the current conditions associated with multiple brake lamp failures.

If the answer to decision 150 is YES the routine exits, and if the answer is NO decision 152 determines if there is one lamp failure. If this answer is YES instructions 154 command the processor to report an error message DTC report of a bad brake lamp, after which the routine exits at 144. If the answer to 152 is NO then decision 156 finally determines if there is a failure of two lamps only. If this answer is YES then instructions 158 require that the Instrument Panel (I/P) Brake Warning Lamp be illuminated at a low repetition rate flash to provide a visual warning to the operator that there are two brake lamps that are out. As shown in Figs. 2A and B, the processor responds to the instructions by-

turning on transistor 159 at a prescribed duty cycle and PRF, and allowing current flow through the I/P Brake Lamp from the vehicle V + power source and producing a pulsed illumination of the lamp. Instructions 160 require a DTC error message of two bad brake lamps to be written to memory.

If the answer to decision 156 is NO, meaning that there are more than two brake lamps that are not operating, instructions 162 request the I/P Brake Warning Lamp be set at a higher frequency pulse repetition rate, thereby signifying a greater safety hazard. Instructions 164 then require a DTC error of more than two bad brake lamps. Following instructions 160 or 164 the routine is exited at 144.

The reproduction of the Fig. 5 flow chart in this application is to demonstrate a capability of the present system to diagnose failures as associated with particular ones of the vehicle's signaling lamps. Of course the more information provided the processor the more powerful and accurate is the diagnosis. However, even in situations where information is limited but lamps provide dual function, there may be opportunities for diagnosis through cross correlation of results. Referring to Fig. 4, in those model vehicles in which the brake lamps also function as the rear turn signal lamps, as shown by the alternative configuration lamp block 12A, multifunction switch 14A, and turn signal switch 62A, there is further opportunity to cross correlate brake and turn signal data.

The following examples illustrate the level of diagnostics that can be performed by the microprocessor's review of the recorded DTC codes in a signaling configuration in which the vehicle brake lamps are also used to perform the rear turn signaling function.

(1) DTC codes for two bad brake lamps as well as two bad turn signal lamps.

The assumption is that there are two bad brake lamps on the same side, although which side is unknown.

(2) DTC codes for two bad brake lamps and one bad turn signal lamp.

The assumption is that there is one bad brake lamp on each side.

(3) DTC code for one bad turn signal lamp and no brake lamp DTC codes.

The assumption is that the bad turn signal lamp is in the front (4) DTC code for one bad turn signal lamp and one bad brake lamp.

The assumption is that the bad turn signal lamp is in the back.

The illustrated diagnostics are limited in ability, however, they may be improved with added programming steps. For example, if the processor records all good turn signal lamp indications after a DTC of 2 bad turn signal lamps in the same RIJN interval it can be concluded with near certainty that two lamps are bad on one side.

In the present module all of the DTC error messages are stored in micro processor memory and may be accessed by external diagnostic equipment 170 (shown in phantom, Figs. 2A and B) through an output interface 172. This permits ready and efficient diagnosis of the performance history for the signaling system in a manner that may be automated to the same extent as analysis and diagnosis of the vehicle's engine, thereby providing for more thorough and more timely repairs.

Although the invention has been shown and described with respect to a best mode embodiment thereof, it should be understood by those skilled in the art that various changes, omissions, and additions may be made to the form and detail of the disclosed embodiment without departing from the spirit and scope of the invention, as recited in the following claims.