In-car spark plug checker

Abstract

A testing device for internal combustion engine spark plugs and ignition elements in which the direct current from the battery is converted by a multivibrator circuit to intermittent pulsating direct current. The output current is fed through an ignition induction coil which may be the one of the engine, with a neon glow tube to indicate when the spark plug has fired. The output of the multivibrator circuit has a voltage regulator to adjust the circuit output and hence the output voltage from the ignition coil to match that at which the spark plug fires. Through use of auxiliary test electrodes in a measurable spaced gap, the process is duplicated in the test device as the duplicated voltage jumps the test gap, and indicates the voltage for discharge and plug condition.

Description

This invention relates to improvements in devices for testing spark plugs and ignition systems and parts for motor vehicles and other engines.

An object of the invention is to provide a novel and improved device for testing spark plugs and the ignition systems and parts of motor vehicle and other internal combustion engines.

Another object of the invention is to provide a novel and improved testing device for ignition spark plugs and parts to locate damaged spark plugs, incorrect or insufficient spark plug gap spacking, without the need for removal of the spark plug from the engine.

A further object of the invention is to provide a novel and improved testing device for spark plugs and other ignition parts, in which the action of the spark plugs is recreated as though the engine is running although the engine does not run while the test is being made, and in which means is provided for producing a suitable high voltage for actuating the spark plug, and measuring the size of the gap between the spark plug electrodes while the plug remains in the engine.

Still another object of the invention is to provide a novel and improved ignition and spark plug testing device in which the constant direct current from the car battery is converted by a multivibrator circuit into an intermittent pulsating current which is then fed through the induction coil of the car to produce a suitable high voltage to jump across the spark plug gap, visible indicating means being interposed in the circuit to show when the spark has jumped across the gap, and to measure the spacing of the gap electrodes.

Still a further object of the invention is to provide a novel and improved ignition and spark plug tester which is simple in design, is made of just a few readily available parts, and which can be made at low cost, and by mass production methods.

The above and other objects and advantages of the invention will become apparent from the following description of a preferred embodiment thereof, as illustrated in the accompanying drawings, forming a part hereof.

In the drawings:

FIG. 1 is a top plan view of the testing device according to the invention, the view being partly broken out to show the internal construction.

FIG. 2 is a schematic circuit diagram of a multivibrator circuit for converting the constant direct current to intermittent pulsating direct current.

FIG. 3 is a schematic circuit diagram showing the connections in the device of FIG. 1.

FIG. 4 is a view showing the device of FIG. 1, as connected to the automobile battery and outwardly through the ignition induction coil and to a spark plug on the engine.

In connection with motor vehicles, there is frequently trouble with the ignition system, the spark plugs, wiring and other elements, and this has made it necessary to frequently remove the spark plugs for inspection and testing apart from the engine. With the present high labor costs and the need for avoiding unnecessary work, such as removal of a sound and good spark plug, the present invention is intended to minimize or make unnecessary the removal of all the six or eight spark plugs in the typical car, until a good indication is found by the device as to which spark plug is defective or not properly gapped or leaky. By this means, the cost of inspecting a car is cut down, the good reliable results are obtained.

In order to understand clearly the nature of the invention and the best means for carrying it out, reference may be had to the drawings, in which like numerals denote similar parts throughout the several views.

As shown in FIG. 1, there is a main housing 10 with a cover wall 12 interconnecting side walls 13, 14, 15 and 16, to define an interior main chamber 17. Battery wires 18 and 19 are connected to the automobile battery 20 and extend inside the multivibrator box 21 which is disposed inside the main chamber 17. The box 21 may be made of suitable sheet material, insulated against electrical leakage, and a suitable electrical circuit for box 21 is shown at 22 in FIG. 2.

The purpose of box 21 is to convert the constant direct current voltage from the lead-acid type storage battery 20 to an intermittent direct current voltage at its output wires 23 and 24, thus recreating the action of the breaker points in the car. The output is thus fed by wires 23 and 24 through the ignition induction coil 25, which changes the normal 12 volts of the battery to approximately 20,000 volts or so, direct current. This is then fed through the neon bulb 26 to the spark plug 27 in the engine 28.

As is known, a spark plug if properly gapped draws approximately 300 volts per one-thousandth of an inch of the gap between the electrodes of the plug. For example, a spark plug having a gap of 0.035 inches will draw approximately 9,500 volts. So, it follows, that if we take the chopped voltage from the output wires 23 and 24 of the multivibrator circuit of FIG. 2, and connect a linear taper rheostat 29 as seen in FIG. 3 in wire 24, we can vary the voltage output of the multivibrator box unit 21. Hence, it is seen that the rheostat 29 being connected, it is moved by turning its knob 30 to move its contactor 31 longitudinally until the neon bulb 26 lights up.

This shows that the spark has cross the gap of the spark plug electrodes. In order to be able to tell if the spark jumped at the correct voltage, the test gap 32 shown in FIGS. 1 and 3, must be in use. As seen in FIGS. 1 and 3, the test gap 32 is a set or pair of electrodes 33 and 34, electrode 33 being stationary and mounted on a fixed arm 35, while movable electrode 34 is mounted on a nut 36 which is carried by a threaded screw shaft 37 rotatable by a knob 38, so that turning of the knob 38 moves the movable electrode 34 longitudinally away from or toward the fixed electrode 33. This thus recreates the spacing of the spark plug gap at which the spark jumps, as indicated by the lighting of the neon glow tube 26.

A pointer 40 moves with the nut 36 and points to a scale 41, graduated in thousandths of an inch, with possibly a vernier arrangement for easy reading, to give a reading of the gap spacing as which the plug fired. The test wire 42 from the ignition coil 25 is connected to the test gap adapter terminal 43 and the rheostat 29 is moved to increase the primary voltage. The specified gap to be tested is set on gap scale 41. Once the neon glow lamp 26 lights, this shows that the spark has jumped the gap of the test electrodes 33 and 34, which are at the correct gap setting. A movable marker 47 located above the rheostat scale 48 is thus moved to the position of the rheostat. The rheostat is then retracted by knob 30, and the test wire 42 is removed and replaced onto the spark plug to be tested. The procedure is put to work, and depending on the location at which the neon bulb lights in comparison to the marked position of marker 47, the condition and gap of the plug can be ascertained.

A momentary on-off switch 50 is pressed while moving the rheostat knob 30, so as to increase the life of the neon bulb. Once the bulb lights, the button 50 is released which disconnects the unit 21 from the test wire 42.

A separate test wand may also be used, and connected to spring clip 51. The test wand is provided with a loosely fitting clamp which is placed around the secondary spark plug wire, and is slided up and down around the wire, so that if the neon bulb lights, there is leakage in the wire insulation, and is should be replaced.

As seen in the circuit of FIG. 2, there is shown a multivibrator for converting the constant smooth direct current of the battery, to intermittent pulsating current. For example, the components shown are: (a) R1 and R4, 60 ohm five watt resistors; (b) R2 and R3 are 10000 ohm, 2.5 watt resistors; (c) C1 and C2 are 1 microfarad 25 volt capacitors; (d) Q1 and Q2 are transistors, such as No. 2N148 or equivalents. The rheostat 29 is of a linear tapered slide type of about 5 watts capacity, and must regulate from zero to 12 volts in linear intervals.

Advantages of the present device are simplicity in use and low production cost which will allow a fair profit to be obtained. As said, it eliminates the need for removing spark plugs for testing, and also enables the insulation on the wires to be tested for leakage. Although I have described a preferred embodiment of the invention in specific terms, it is to be understood that various changes may be made in size, shape, materials and arrangement without departing from the spirit and scope of the invention as claimed.

Claims

Having herein described the invention, what is claimed as new is:

1. A device for testing spark plugs as contained in an engine and other internal combustion engine ignition parts, comprising electronic convertor means connectable to a direct current engine battery for converting the output current of said battery to intermittent pulsating current, ignition coil means connectable to the output terminals of said convertor means for raising the voltage output therefrom to a voltage sufficiently large to jump across a spark plug gap, and adjustable gaugeable voltage gauge means for measuring the voltage at which a spark discharge on a spark plug being tested jumps across its spark gap, and said convertor means comprising multivibrator circuit means, transistor, resistor and capacitor means connected in said multivibrator circuit means and formed with input wiring terminals connectable to said battery, and output wiring terminals for delivery outwardly therefrom a direct current intermittent pulsating current.

2. The construction of claim 1, and wherein said ignition induction coil means is connectable to said output wiring terminals of said multivibrator circuit means for substantially increasing the voltage obtained from said battery, to a voltage sufficiently high and of suitable nature for jumping the gap of a spark plug connected thereto.

3. The construction of claim 2, and comprising wire means connected to said output terminals first normally open switch means interposed in at least one of said wire means connected to one of the said output terminals, for temporarily closing said circuit for current flow, and paired first and second gauge electrodes, means for moving at least one of said electrodes into spaced relation to the other electrode, to form a gauge spark gap therebetween, and whereby said spacing between said electrodes is adjustable until a spark jumps therebetween.

4. The construction of claim 3, and comprising threaded shaft means, knob means for rotating said shaft means, nut means carried threadedly on said shaft means and blocked against rotation thereon, said second gauge electrode being carried on said nut means for movement longitudinally therealong as said knob rotates said shaft means, for varying the interspacing between said first and second gauge electrode means.

5. The construction of claim 4, and comprising pointer means carried by said nut and movable therewith, graduated scale means disposed near said pointer means, whereby the position of said pointer means is exhibited by its proximity to any part of said graduated scale means.

6. The construction of claim 5, and comprising neon glow tube means interposed in the circuit of said induction coil means, for being illuminated when said spark jumps the spark plug gap, and rheostat means interposed in the output circuit of said multivibrator circuit means for regulating and adjusting the output voltage to match and equal that at which the spark jumped the spark plug gap.

7. The construction of claim 6, and comprising measuring means carried by said graduated scale means for direct reading of the gap spacing of said spark plug in both thousandths of an inch and in voltages at which said spark jumps the gap.

8. The construction of claim 7, and comprising momentary on-off switch means for closing said circuit momentarily and then to open the same, to conserve the life of said neon glow tube.