Patent Application
20060113999
1. Field of the Invention
This invention relates to a timing light for use with an internal combustion engine to accurately measure ignition timing, particularly a timing light having a focused light source permanently or removably attached onto or near an engine for which timing information is desired.
2. Discussion of Related Art
As an internal combustion engine operates, pistons slidable within one or more cylinders cause a crankshaft within the engine to rotate by means of connecting rods attached both to the pistons and the crankshaft. In internal combustion engines of the gasoline type, the pistons compress an air/fuel mixture while moving toward an end of the cylinders. A spark plug then ignites the air/fuel mixture, causing the piston to slide down the cylinder, thereby rotating the crankshaft. Ignition timing refers to the location of a piston within a cylinder relative to the instant the spark plug fires. Ignition retard is ignition occurring after the piston has passed top dead center, whereas ignition advance is ignition that occurs before the piston reaches top dead center.
Conventionally, one method of measuring ignition timing has been to illuminate a timing mark provided on a periphery of a rotating engine component, usually a pulley, at the instant an engine spark plug fires. At the moment the light flashes, the illuminated timing mark on the pulley appears stationary and is compared to scale marks on the engine proximate to a periphery of the rotating engine component. Ignition timing can then be determined by comparing the mark on the pulley and the marks on the engine block. Ignition timing can thereafter be adjusted to correspond to a predetermined specification.
One example of an illumination timing device is U.S. Pat. No. 4,713,617 issued to Michalski. The Michalski reference discloses a hand-held digital timing light that includes a pistol-type housing, a lamp mounted therein, and a pickup cable that attaches to a portion of an engine to sense engine ignition. Once the pickup cable is connected to the engine, a user aims the device at an area of the engine where a rotating member is located, with an indicator mark adjacent to a scale fixably attached to a stationary portion of an engine. The lamp flashes at an instant related to engine ignition, and ignition timing is measured by the position of the indicator mark relative to the scale.
Another example is U.S. Pat. No. 5,610,327 issued to Becker, et al., which relates to a hand-held ignition timing device for measuring diesel ignition timing. The Becker reference discloses the use of both a visible laser diode and a xenon lamp housed within a pistol-shaped housing. The visible laser diode emits a beam of visible laser light to illuminate a reflective tape adhesively provided on a periphery of a flywheel. A photodiode within the housing detects the beam of visible laser light reflected from the reflective tape, informing a control circuit of the location of a piston within an engine cylinder. The device also includes a knock sensor located in close proximity to the engine cylinder being used to measure ignition timing. The knock sensor detects vibration caused by combustion within a cylinder. Once the photodiode detects visible laser light reflected from the reflective tape, the device identifies the impending combustion within the cylinder and prepares to flash the xenon lamp. The xenon lamp flashes once the device receives the next signal from the knock sensor. The visible laser diode and reflective tape are necessary because diesel engines do not have ignition wires or spark plugs. Therefore, the device must be able to discriminate between vibrations that are the result of combustion in the cylinder being used to determine ignition timing and that due to other engine cylinders. Ignition timing is measured at the instant the xenon lamp flashes by the position of a timing mark on the flywheel relative to scale marks on a stationary part of the engine adjacent to the flywheel.
One problem associated with hand-held devices such as Michalski and Becker is that the ignition timing perceived by an observer will vary from the true ignition timing, because, for example, the user observes the shadows cast by the timing and scale marks due to lighting effects associated with the handheld device, rather than the marks themselves, when determining timing. Additionally, the locations of the shadows cast by the marks change, even if only by a slight amount, due to a change in position of both the light source and the observer each time a measurement is made. Therefore, because both the handheld device and the observer can be positioned at any location, the handheld devices impart a large amount of error in measuring ignition timing. This error can be detrimental to the proper function and performance of modern engines because of the extreme precision with which modern internal combustion engines are designed.
Another example is U.S. Pat. No. 3,857,086 to Mooney, et al., which relates to a process for establishing ignition timing for a reciprocating internal combustion engine. The patent discloses a transducer inserted into a socket fixably attached to an engine block. The transducer generates an electrical signal whenever a groove located on a circumferential edge of a vibration damper travels past the transducer. A clamp attaches to an ignition cable, sensing an ignition signal therein. A comparator circuit compares the two signals to determine ignition timing.
An additional example is U.S. Pat. No. 6,429,658 to Thomsen, et al., which relates to an ignition timing device for an internal combustion engine. Thomsen discloses a sensor secured proximate to a timing port and a timing mark provided on a periphery of a pulley. The sensor creates a timing mark signal when the timing mark passes the sensor, as the pulley rotates. Also disclosed is an ignition sensor that creates an ignition signal indicative of the occurrence of an ignition spark. The ignition sensor can take the form of an inductive clamp or a timing light and a light detector. A comparator receives both the timing mark signal and the ignition signal and provides an output signal indicative of the time difference between those signals.
Devices such as those disclosed by Mooney and Thomsen, while having a sensor fixed in some fashion to an engine, do not disclose the use of a highly focused and accurate timing measurement mechanism. Further, with the prior art, a user is precluded from directly observing ignition timing by referencing the location of a timing mark on a rotating engine component relative to a mark fixed to the stationary engine.
The ignition timing device of the instant invention solves the problems identified above, as well as others, by having a focused light source fixed at a single position in close proximity to a portion of an engine where ignition timing is measured, along with retard/advance functionality permitting the use of an indicator mark, located, for example, on a rotating member of the engine, for measuring ignition timing and providing a precise retard or advance of ignition timing.
According to a first aspect of the invention, the ignition timing light includes a focused light source, a securing member to permanently or removably fix the light source to the engine or engine compartment, an ignition indication sensor, a varying indication locator, such as a mark on a rotating engine member, and a control box having a readout and a retard/advance functionality to manipulate when the focused light source flashes. A narrow, focused light beam emitted from the focused light source provides for precise alignment of the reflected beam with the locator provided on the rotating engine member. Also, because the securing member fixes the focused light source at a single location, measurement error caused, for example, by lighting effects associated with traditional handheld timing devices having omnidirectional light sources is reduced.
According to a second aspect of this invention, the ignition timing light of the instant invention includes a secondary light source permanently or removably attached with the focused light source. In one variation, the secondary light source flashes in unison with the focused light source and improves the ignition timing measurement when the measurement is made for example, under bright ambient conditions or at other times when illumination of the locator is obscured. The secondary light source allows an observer to view the locator on the rotating engine component when the apparent stationary position of the locator is not coincident with the beam emitted from the focused light source.
According to a third aspect of the invention, the focused light source, the control box, and the ignition indication sensor communicate via a wired, wireless, or fiber optic link.
Additional advantages and novel features of the invention will be set forth in part in the description that follows, and in part will become more apparent to those skilled in the art upon examination of the following or upon learning by practice of the invention.
Other aspects of the present invention will be better understood from the following description, along with the accompanying drawings, wherein:
The present invention relates to an ignition timing device for measuring the ignition timing of an internal combustion engine, an embodiment of the present invention comprising a control box 10, a light assembly 20, and an ignition indication sensor 25. The control box 10, light assembly 20, and the ignition indication 25 sensor communicate, for example, via a wired, wireless, or fiber optic link, and are powered, for example, via an internal power source, such as an internal battery, or via connection to a vehicle battery.
Additionally, the ignition timing device of the instant invention includes a retard/advance functionality to advance or retard when the focused light source 80 flashes relative to engine ignition. The retard/advance functionality allows, for example, for the elimination of scale marks 70 when measuring ignition timing, rather than requiring determination of the apparent location of the indicator 60 relative to any one of the scale marks 70. Alternatively, a single reference mark 110 may be used. An example of a method for delaying the flash signal is disclosed in U.S. Pat. No. 5,767,681 issued to Huang, the contents of which are hereby incorporated by reference in their entirety.
In operation, the ignition indication sensor 25 senses ignition via, for example, a spark plug wire of the engine 30, and transmits a corresponding ignition detection signal to the control box 10. In response, the control box 10 transmits a flash signal to the light assembly 20. The flash signal causes the focused light source 80 to emit a brief narrow, focused light beam that projects onto the outer periphery of the rotating engine member 50 creating a narrow, focused reflection point 115, with the focused reflection point 115 either being coincident with the position of the indicator 60 or at a location ahead or behind the indicator 60, relative to rotation of the member 50. Even when the engine is idling, numerous ignitions signals occur over a short period of time. In response, the focused light source 80 flashes rapidly, making indicator 60 appear to be stationary relative to the reflection point 115 on the outer periphery of the rotating member 50 (see further description below with regard to
Optionally, the secondary light source 90 flashes in unison with the focused light source 80, improving the ignition timing measurement when the indicator 60 initially falls far from the reflection point 115 of the focused light beam (e.g., to create an enhanced reflection from the indicator 60, thereby highlighting the location of the indicator 60 relative to the reflection point 115 of the focused light beam) or, for example, when ignition timing measurements are being made in bright ambient light conditions or other conditions necessitating enhancement of the location of the indicator 60. In one embodiment, the stroboscopic function may be enabled or disabled, such as via a switch located at the control box 10 or at the light assembly 20.
In another embodiment, the secondary light source 90 operates continuously (i.e., non-stroboscopically) to provide general illumination of the timing light area.
In operation, the retard/advance of the engine 30 is adjusted (e.g., by advancing or retarding ignition) until the indicator 60 aligns with the reflection point 115 for the light beam, as shown in
In one embodiment, a selected amount of ignition advance or retard (e.g., measured in degrees) may be input to the control box 10 (e.g., as shown in
The ignition timing light of the instant invention increases the accuracy of measuring ignition timing over the prior art in at least the following ways. First, the focused light beam emitted from the focused light source establishes an extremely narrow reflection point with which the indicator aligns when the timing selected is reached, in contradistinction to omnidirectional stroboscopic light sources typically used in the prior art. Second, the focused light beam stands in sharper contrast to the ambient conditions, permitting the observer to more easily align the indicator. Third, the closeness of the light assembly to the outer periphery of the pulley reduces or entirely eliminates shadows or other inaccuracies created by standard illumination of the indicator and the scale marks. This closeness permits the observer to align the indicator, rather than the shadow formed thereby. Error associated with shadows is further reduced because the light incident upon the outer periphery of the pulley is always emitted from the same location relative to the pulley.
Example embodiments of the present invention have now been described in accordance with the above advantages. It will be appreciated that these examples are merely illustrative of the invention. Many variations and modifications will be apparent to those skilled in the art.
