Abstract:
A timing light for measuring timing of spark ignition has separate displays of engine RPM and timing advance. Another aspect of the invention provides a flashlight function which triggers the flash tube of the timing light to produce a constant bright light source for locating timing marks within an engine compartment. The flashlight function can be incorporated into a dual display digital timing light, or other timing light designs. A dedicated control on the timing light functions to place the flash tube in a continuous flashlight mode.

Description:
FIELD OF THE INVENTION 
     The present invention pertains generally to electronic testing equipment and, more particularly, to electronic instruments for monitoring or measuring the performance of machinery such as internal combustion engines. 
     BACKGROUND OF THE INVENTION 
     Precise ignition timing and idle adjustments are essential in order to achieve maximum fuel economy and performance in internal combustion engines. Because timing changes with engine RPM and load, it is important to be able to measure timing not only at initial or base timing, as is done with a conventional timing light, but also to be able to measure timing advance, which is possible with digital timing lights and advance timing lights. Most engines require that both initial and advance timing calibrations be set or checked at specific engine RPMs, or in some cases with a specific vacuum applied to the vacuum advance diaphragm on the distributor, or in some cases by the vehicle&#39;s onboard computer. In the case of engines which are equipped with breaker point ignition systems, it will be necessary to set point dwell before adjusting timing. 
     Car manufacturers specify engine timing measured in degrees at certain engine speeds measured in RPM. Engine speed has to be maintained at a specified value for the timing reading to be valid. On a conventional digital timing light, the operator uses a switch to manually toggle a single display between the tachometer mode (reading engine RPM) and the timing mode (reading timing in degrees of advance). 
     Prior to beginning the timing check procedure, the stationary timing mark located on the engine must be found. On some engines, finding the timing mark is difficult or even impossible without a flashlight or some other source of light. Several timing light models available on the market have a small flashlight integrated into the case. The flashlight consists of an incandescent bulb, a lens, a bulb holder, an on/off switch, and some miscellaneous wires. The disadvantages of this design are that the light produced by the bulb is not very bright, the light bulb needs to be replaced periodically when it fails due to burning up or filament breakage due to a mechanical shock. Adding this feature also significantly increases the cost. 
     SUMMARY OF THE INVENTION 
     In the proposed design, the flash tube normally used to produce a strobe of light for engine timing measurements is also used to illuminate the engine compartment when looking for the timing marks. Depressing the flashlight button will interrupt the normal mode of operation and cause the flash tube to flash at a relatively high rate of approximately, for example, 25 Hz or higher regardless of the engine speed. At this high flashing rate, the human eye will perceive the light spot created by the flash tube and the lens in front of it as light essentially without flicker. When the flashlight button is released, the timing light switches back to normal mode of operation. 
     In a microcontroller or microprocessor controlled timing light, a flashlight on/off switch is required to add the flashlight feature of the invention. The software of a microcontroller or microprocessor controlled timing light generates a signal to trigger the flash tube at a relatively high rate to produce a light which is perceived by the human eye as continuous or constant. In other timing light designs, a flashlight on/off switch and a small circuit need to be added. This circuit will generate a square wave with a frequency of 25 Hz or higher to drive the flash-tube triggering circuit. The advantages of the new design are; brighter light (since the Xenon flash tubes produce brighter light than small incandescent bulbs); fewer parts, lower cost, and higher reliability since no additional parts are needed (light bulb, bulb holder, and lens, etc.). 
     A digital timing light with two displays simultaneously presenting engine speed and timing simplify the operation and allow to monitor engine speed constantly during the process of measuring the timing. This is especially useful for a one-person operation when a mechanic needs to manually operate the throttle with one hand to maintain proper engine speed, point the flashing light at the stationary and moving timing marks, operate the Increase and Decrease Advance switches, and read the displays. In accordance with several objects of the invention, there is provided a device for measuring and displaying information pertaining to the operation of a spark-ignited internal combustion engine, including a housing having a gripping portion and a pointing portion, a flash tube mounted within the pointing portion behind a lens at a distal end of the pointing portion, the flash tube electrically connected to a control circuit operative to sense electrical pulses from an engine and to control a triggering voltage supplied to the flash tube, a first display in the housing connected to the control circuit and operative to display a running speed of an engine, and a second display in the housing connected to the control circuit and operative to display an indication of timing of an engine. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     In the accompanying Figures 
     FIG. 1 is a elevation of an engine timing measurement device of the present invention; 
     FIG. 2 is a rear elevation of an engine timing measurement device of the present invention; 
     FIG. 3 is a block diagram of flashlight control circuitry of an engine timing measurement device of the present invention, and 
     FIG. 4 is a block diagram of alternate flashlight and dual display control circuitry of an engine timing measurement device of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIGS. 1 and 2, there is shown a timing light device, indicated generally at  10 . The device  10  has a housing  11  which includes an angular bend which forms a gripping portion  12  and a pointing portion  14 . A lens  15  is mounted at the tip of pointing portion  14 , and within the pointing portion behind lens  15  is mounted a light source, indicated generally at  17 , such as an electrically energized lamp or flash tube, which is typically a Xenon charged vessel with integral electrodes connected to a power circuit. The power source to the lamp  17  is controlled by a control circuit described further herein and also located within the housing  11 . An electrical cord  16 , connected to the internal circuitry, exits from the gripping portion  12  of the housing  11  and terminates in battery connection clips and an inductive pick-up as is conventionally known. 
     As shown in FIG. 2, on a rear surface  13  of the gripping portion  12 , is provided a dual display, indicated generally at  20 , and a cluster of control buttons indicated generally at  25 . The dual display includes a first display  21 , and a second display  22 . Each display may be, for example, a series of LEDs, LCDs, illuminated LCDs, or any other suitable means for displaying alpha-numeric information. In a preferred embodiment, the first display  21  is electronically configured to numerically indicate an operating RPM of an engine to which the device is connected. The second display is electronically configured to numerically indicate a measured timing of the engine, in degrees of advance. This dual display thus simultaneously displays both engine RPM and timing. This allows the user to monitor engine speed constantly during the process of measuring and adjusting the timing. For example, to measure and adjust the timing of an engine, the user must aim the timing light at a timing mark on the engine, set the engine RPM by throttle control, and read the timing advance indication of the device. With the dual display  20 , the user does not have to toggle or switch between an RPM display or readout and a timing advance display in addition to the other tasks of controlling engine RPM and adjusting the timing. 
     To operate the device, the terminals of the electrical cord  16  are connected to a power source, such as a battery and ground, and the inductive lead about the number one spark plug wire. The device is powered up by depressing the ON button  26 . Upon power-up the device displays engine RPM in the tachometer display which may be, for example, the first display  21 . The unit may be configured to power-up in a 4 cycle mode, and can be toggled to a 2 cycle mode by operation of button  27 . An advance timing indication is displayed in degrees in, for example, the second display  22 . The advance is increased by depressing the increase button  28 , and decreased by depressing the decrease button  29 . 
     The control circuitry described herein generates a periodic trigger voltage to the flash tube in the device according to current signals picked up through the inductive lead of cable  16  and the preset value of timing advance. FIG. 3 schematically represents one type of circuit for triggering the flash tube at a high enough rate which will produce light perceived by the human eye as a continuous or constant light. The flashlight button  30 , when depressed functions to apply pulses created by a square wave generator  35  (FIG. 3) to a flash tube power and triggering circuit  36  which in turn applies trigger pulses to the flash tube  17 . In a preferred embodiment, the flash tube power and triggering circuit supplies a signal of, for example, approximately 25 Hz to the flash tube to produce a light which appears to the human eye as a continuous or constant light, in the manner of a flashlight. The brightness of a typical timing light flash tube, which is triggered at a high enough rate to produce what is perceived as a continuous light is generally much greater than the brightness of a battery powered flashlight with an incandescent light bulb. Therefore, the invention provides a superior light source useful for locating timing marks in engine compartments. As used herein, the term “continuous” refers to a light which appears to the human eye as a constant light source, even though the light may be flashing at a high rate. 
     FIG. 4 schematically illustrates certain components of a flashlight and dual display digital control circuit, indicated generally at  40 , used in an alternate embodiment of the device  10 , which also includes the dual tachometer and advance displays, and the flashlight function. In the circuit  40 , the flash tube operation is controlled through a microprocessor or microcontroller  42 , which also sends commands to separate display drivers  44  and  46  of LEDs or other suitable display means of the described first and second displays  21  and  22 . For example, driver  44  is connected to four seven-segment LEDs  441 ,  442 ,  443  and  444  which together provide a four digit RPM tachometer display. Similarly, driver  46  is connected to three seven-segment LEDs  461 ,  462  and  463  which together provide a three digit degrees advance display to the tenths place. 
     The flashlight switch  31 , actuated by button  30  as described above, switches an input of the microprocessor  42 , which is programmed to generate an appropriate signal supplied to the flash tube power and triggering circuit  36  to trigger the flash tube at a sufficiently high frequency to produce a light source which appears continuous to the human eye. As mentioned above, the high frequency triggering of the flash tube produces a light perceived by the human eye to be continuous or constant, and which is much brighter than a conventional battery powered incandescent flashlight. 
     The invention thus provides an improved device for measuring and displaying information on the timing of a spark-ignited internal combustion engine, wherein information on engine speed and timing advance is continuously and simultaneously displayed during use of the device. The device further provides the convenience of a bright continuous light source for locating a timing mark on an engine by the flash tube of the device, thereby eliminating the need for a separate light source. 
     Although the invention has been described with reference to certain preferred and alternate embodiments, it will be appreciated that certain modifications and variations could be made by those of ordinary skill in the art which would fall within the scope of the invention as defined by the accompanying claims and equivalents thereto.