Select Signal Engine Diagnosing Apparatus

Abstract

The disclosure describes apparatus for disabling selected cylinders of an internal combustion engine for diagnostic purposes. The system and apparatus are preferably used in connection with an engine that includes a source of periodic cycles of ignition signals. When used with such an engine, the apparatus prevents one or more predetermined ignition signals in each cycle from energizing engine components, such as spark plugs, which normally receive the ignition signals. In order to achieve this purpose, the preferred apparatus embodiment described in the disclosure comprises a clock pulse generator that generates a uniform pulse in response to the receipt of each ignition signal from the engine. Counting means, such as bistable flip-flop circuits, are used to produce counting states representative of the number of pulses received from the clock pulse generator. Adjustable resetting means are used to reset the counting means to a predetermined counting state after the counting means has counted through a predetermined number of counting states, such as the number of cylinders in the engine being diagnosed. Removable setting means are employed to set the counting means to an initial counting state in response to the receipt of an ignition signal from a predetermined engine component, such as a spark plug. Adjustable selecting means generate a disabling pulse in response to a predetermined counting state of the counter, so that a particular cylinder of the engine may be disabled. A disabling device, such as a triac, responsive to the disabling pulse, conditions a predetermined ignition signal in each engine cycle so that the corresponding engine cylinder is disabled, thereby aiding the diagnosis of the engine.

Description

BACKGROUND OF THE INVENTION

This invention relates to engine diagnostic apparatus and method, and more particularly relates to apparatus and method for diagnosing an engine by disabling a predetermined component thereof.

Automobile owners frequently complain that the engines of their automobiles run roughly or appear to "miss" on one or more cylinders. In order to diagnose the engine when such operating conditions are encountered, automobile mechanics have tried to discover the cylinder which was "missing". In order to perform the diagnosis, many mechanics have found it useful to disable the cylinders of the engine one-at-a-time, and to observe the resulting engine performance. If a properly operating cylinder is disabled, the engine runs more rougly, whereas if a defective cylinder is disabled, little or no change in engine operation is observed. Thus, by systematically disabling the cylinders of the engine one-at-a-time, the mechanic may quickly locate the defective cylinder.

A variety of apparatus and method for performing the above-described engine diagnosis have been used in the past. For example, for some years, mechanics simply pulled a spark plug wire from its spark plug with a pair of insulated pliers in order to disable the corresponding engine cylinder. This method, however, was time-consuming and presented considerable shock hazard to the mechanic.

Additional apparatus and methods for semi-automatically disabling an engine cylinder have also been devised, but each has exhibited deficiencies that have limited its overall usefulness. For example, some such systems require that the apparatus be connected to a particular spark plug wire throughout the duration of the engine diagnosis. In addition, such systems require that a disabling time interval be set relative to the number of engine cylinders and the engine testing speed. This requirement seriously limits the range of engine speeds at which the diagnosis may be performed. One patent describing an engine diagnostic system of the above-described type is U. S. Pat. No. Re 26,163 (Heyer -- Feb. 28, 1967).

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the prior art engine diagnostic systems, applicant has invented an improved system for diagnosing an engine that includes a source of periodic cycles of ignition signals. As described herein, the invention may be used for preventing one or more predetermined ignition signals in each cycle, such as the signals produced by an engine spark distributor, from energizing engine components which are normally energized by the ignition signals.

According to a preferred feature of the invention, the apparatus for achieving this result comprises an input means for receiving the periodic cycles of ignition signals from the distributor. Generating means are provided for generating a clock pulse in response to the receipt of each ignition signal. Counting means are also provided for producing counting states representative of the number of pulses received from the generating means. By utilizing a resetting means that may be adjusted by the operator, the counting means may be readjusted to a predetermined counting state after it has counted through a number equal to the number of cylinders of the engine. The counting means are initially set by a setting means that generates a signal in response to the operation of a predetermined one of the engine components by an ignition signal. By operating an adjustable selecting means, the operator may produce a disabling pulse in response to a predetermined counting state of the counting means. For example, the operator may set the selecting means so that the ignition signal in each cycle which normally operates a particular cylinder is disabled. As a result, that cylinder is disabled during each cycle of engine operation. Disabling means responsive to the disabling pulse are also provided in order to prevent the selected ignition signal from energizing its corresponding spark plug.

The advantages of using the above-described apparatus are at once apparent. Due to the unique combination of components described herein, after the counting means is initially set, the setting means may be removed throughout the duration of the engine diagnosis. In addition, since each ignition signal is counted, the diagnosis may be performed at any engine speed. In addition, there is no need to utilize any auxiliary apparatus such as an oscilloscope, in order to initially set the apparatus into a proper operating condition. As a result, by using the techniques taught herein, engine diagnosis may be performed with a degree of accuracy and convenience heretofore unattainable.

DESCRIPTION OF THE DRAWINGS

These and other advantages and features of the present invention will hereafter appear for purposes of explanation, but not of limitation, in connection with the accompanying drawings, in which like numbers refer to like parts throughout, and in which:

FIG. 1 is a block diagram, schematic representation of a preferred embodiment of the invention shown in connection with an exemplary engine to be diagnosed;

FIG. 2 is a schematic diagram illustrating the manner in which FIGS. 3-6 should be arranged;

FIGS. 3-6 are electrical schematic drawings of portions of the apparatus shown in block diagram form in FIG. 1;

FIG. 7 is a drawing illustrating the approximate shapes of signals generated at the like-identified portions of the apparatus shown in FIGS. 1-5;

FIG. 8 is a schematic drawing of a preferred form of diode gating matrix used in connection with the invention; and

FIG. 9 is a schematic drawing of a preferred form of a NAND gate used in connection with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, the embodiment of the invention shown herein may be used for the diagnosis of an engine, such as exemplary internal combustion engine 10. Engine 10 comprises eight cylinders into which are fitted spark plugs 1-8. The spark plugs are energized through wires 21-28 respectively, which originate in a conventional spark distributor 40. Distributor 40 is connected to the primary circuit of a conventional coil 42 through a conductor 44. In a well-known manner, distributor 40 creates reoccurring cycles of eight ignition signals (one ignition signal for each spark plug of the engine) which are conducted through conductor 44 to the primary of coil 42. By means of a set of contact points and a condenser (not shown), high voltage signals are conducted from the coil secondary through conductor 46 to a rotor (not shown) of the distributor. The rotor then distributes the high voltage signals through wires 21-28 to the spark plugs in a well-known manner.

Referring to the drawings, a preferred form of engine diagnostic apparatus made in accordance with the present invention basically comprises an input circuit 50, a disabling circuit 56, a generating circuit 70, a counting circuit 110, a resetting circuit 230, a setting circuit 240, a selecting circuit 280, an analyzing circuit 450, and a power supply 470.

Referring to FIGS. 1 and 3, input circuit 50 comprises an input terminal 52 that is connected to conductor 44 by a lead line 54.

Referring to FIG. 3, disabling circuit 56 comprises a triac 58 having a gate 60, a main terminal 62 connected to a ground potential conductor 68, and a second main terminal 64. The disabling circuit also comprises a 4.5 ohm resistor 66 connected as shown. The placement of resistor 66 is an important feature, since it prevents signals on input terminal 52 from being completely shorted to ground when the triac is operated. Applicant has also found that a triac is particularly appropriate for use in the disabling circuit shown in FIG. 3.

Still referring to FIG. 3, generating circuit 70 comprises a first circuit branch 71 for receiving positive ignition signals comprising a diode 72; resistors 73, 74, 75 and 76; a capacitor 77, and a transistor 78. Generating circuit 70 also comprises a second circuit branch 79 for receiving negative ignition signals comprising diodes 80 and 81; resistors 82-88, a capacitor 89, and transistors 92-94. Transistors 92-94 are supplied with a positive bias voltage through a power supply conductor 95. Transistors 92-94 also comprise a means for inverting the polarity of the negative ignition signals with respect to the polarity of the positive ignition signals received by the first circuit branch 71. As a result of this operation, the first circuit branch 71 and the second circuit branch 79 produce resultant signals each having the same polarity. Signals from the first circuit branch are applied to an input terminal 98 of a clock pulse generator 96, and signals from the second circuit branch 79 are applied to an input terminal 99 of clock pulse generator 96.

As shown in FIG. 9, clock pulse generator 96 is a NAND gate comprising diodes 105a-105d, resistors 106a-106e, and transistors 107a-107c.

The signals produced by clock pulse generator 96 are transmitted to counting circuit 110 through a circuit comprising an output terminal 100, a resistor 101, a capacitor 102, and conductors 103, 104.

Referring to FIGS. 4 and 5, counting circuit 110 comprises bistable flip-flop circuits 112, 150 and 192 described as follows:

Bistable flip-flop circuit 112 comprises resistors 114-124, capacitors 128-130, diodes 133-134, transistors 136-138, and conductors 140-144, connected as shown.

Bistable flip-flop circuit 150 comprises resistors 152-162, capacitors 167-170, diodes 174-175, transistors 179-181, and conductors 184-189, connected as shown.

Bistable flip-flop circuit 192 comprises resistors 194-202, capacitors 206-209, diodes 213-214, transistors 217-218, and 235- 223-226, connected as shown.

Referring to FIGS. 4 and 5, resetting circuit 230 comprises a diode 232, a resistor 234, and conductors 23514 238, connected as shown.

Referring to FIG. 3, setting circuit 240 comprises a coil 242 that may be placed adjacent any of the spark plug wires 21-28 at the option of the operator. Coil 242 is connected through a conductor 244 and a circuit comprising capacitors 246, 247 and inductor 248 to the input of a transistor 250. Transistor 250, together with resistors 252-254 and capacitor 255, operate as a class A amplifier. The output of transistor 250 is conducted through an AND gate 257 to a monostable multivibrator 260 that produces a three millisecond pulse utilized as a noise-blanking signal. The duration of the noise-blanking signal is controlled by the values of capacitors 261 and 262. The output of multivibrator 260 is connected through an AND gate 264 to another monostable multivibrator 266 that integrates the output pulse of multivibrator 260 to produce a 100 nano second rise time, fifteen volt, 500 microsecond pulse. The duration of this pulse is determined by the values of capacitors 268 and 269. The output from multivibrator 266 is conducted through a driver circuit comprising resistors 270, 274, 275, a transistor 272, a diode 276 and an output conductor 224. Transistor 272 is arranged as an emitter follower with a low impedance output for driving parallel gates and capacitive loads.

Referring to FIGS. 3-6, selecting circuit 280 comprises a gating circuit 382 and a switching circuit 370 described as follows: Gating circuit 282 comprises diode decoding circuit pairs 285, 286; 287, 288; and 289, 290 that are connected to bistable flip-flop circuits 112, 150, and 192, respectively. Each of the diode decoding circuit pairs is identical and may be understood from the following description of decoding pair 285, 286. As shown in FIG. 8, pair 285, 286 comprises diodes 291-306 connected as shown.

Gating circuit 282 also comprises a diode decoding circuit 310 that is identical to the diode arrangement shown in FIG. 8.

Referring to FIG. 5, gating circuit 282 further comprises conductors 330-337 that receive a biasing current through resistors 340-347, respectively. In addition, diodes 330-332 receive biasing current through a resistor 353 and are connected to a common conductor 354.

Referring to FIG. 3, the output of decoding circuit 310 is connected to an emitter follower driver stage comprising a transistor 355, resistors 356, 357, capacitor 358, and a diode 360. The output of the driver stage is connected to the gate of triac 58 over a conductor 362.

Referring to FIG. 6, switching circuit 370 comprises an engine select switch 371 that includes wafer switches 372, 374 that are ganged on a single shaft and are shown in the four cylinder engine position. Switches 372 and 374 comprise conducting segments 374-377 and 380-383, respectively, that are interconnected with various contacts as shown. Switching circuit 370 also comprises a cylinder select device 390 comprising switches 391-399. Switches 391-399 are shown in their "out" position in FIG. 6. If any of switches 391-398 are pushed to their "in" position (moved in an upward direction as shown in FIG. 6), that switch may be moved to its "out" position by operating switch 399. Each of switches 391-398 comprise a front terminal 401, a middle terminal 402, and a rear terminal 403. When switches 391-398 are located in their "in" positions, their middle terminals 402 are connected to their rear terminals 403. When switches 391-398 are located in their "out" positions, their front terminals 401 are connected to their middle terminals 402.

Referring to FIGS. 4, 5 and 6, switch circuit 370 is connected to conductors 330-337 by additional conductors 430-437, respectively.

Referring to FIG. 3, analyzing circuit 450 comprises integrated circuits 452, 453 that are each identical to NAND gate 96 (FIG. 9). Analyzing circuit 450 also comprises transistor 454, capacitors 456, 457, resistors 458, 459, diodes 460, 461, and output conductors 462, 463. Output conductors 462, 463 may be used to operate a tachometer and an oscilloscope, respectively, in a well known manner.

Referring to FIG. 5, power supply 470 comprises a source of 117 volt A.C., 60 cycle electrical power 471 that is connected to a transformer 474 through a switch 472 and a fuse 473. The power supply also comprises a rectifier 475 and a regulating Zener diode 476. Additional components, such as a diode 477, resistors 478-481, transistors 483-484, and capacitors 486-490 are used to regualte the voltage supplied to conductor 95. An integrated circuit 492 serves as a reference amplifier and a predriver for transistor 484.

The operation and method aspect of the invention will now be described assuming that eight-cylinder engine 10 is to be diagnosed. In order to operate the system, lead 54 is connected between distributor conductor 44 and input terminal 52. Likewise, lead 244 is connected between coil 242 and the input to setting circuit 240. Coil 242 is then positioned adjacent any desired spark plug wire, such as wire 21 which is connected to the number one cylinder of engine 10. Engine select switch 371 must be rotated clockwise to the eight cylinder position so that the segments of wafer switches 372 and 374 are likewise advanced clockwise through two contact positions. Switch 399 should also be depressed so that all of switches 391-398 are in their "out" position.

After the apparatus is adjusted in the foregoing manner, the engine is started and may be operated at any speed. When the engine is operated, ignition signals of the type shown by wave form A of FIG. 7 are conducted over conductor 54 to input terminal 52. Since these signals are positive, they are conducted through diode 72 and resistor 73 to form signals such as those schematically shown by wave form B of FIG. 7. Resistors 73, 74 and capacitor 77 form a voltage divider low pass filter network that filters signal B. REsistor 75 serves as a bias resistor for transistor 78 and as a current limiting resistor when a signal is received at the base of transistor 78. Transistor 78 is normally biased in a non-conductive state, but is switched to its conductive state by an ignition signal. When an ignition signal is received, transistor 78 rapidly conducts and forms a signal having wave shape C of FIG. 7 on its collector. Signal C is then conducted to clock pulse generator 96.

If a negative ignition signal is received at input terminal 52, it passes through diode 80 and is filtered by resistors 82, 83 and capacitor 89. Resistor 84 serves as a biasing and current limiting device for transistor 92. Transistor 92 is normally nonconducting, but is switched to its conducting state by a negative ignition signal. The conduction of transistor 92 drives transistor 93 into cutoff, and transistor 93, in turn, inverts the signal applied to its base. The voltage appearing across transistor 93 causes current to flow through diode 81, thereby driving transistor 94 into saturation. This mode of operation produces a wave shape on the collector of transistor 94 (i.e., at point C'), which is the same as wave shape C of FIG. 7. Thus, if a negative ignition signal is present, a signal such as signal C is conducted to input terminal 99 of clock pulse generator 96. As a result, generator 96 produces a clock pulse signal whether the ignition signal is positive or negative with respect to ground. This is an important feature, since the production of a clock pulse signal is secured automatically, without requiring the operator to determine whether the engine being diagnosed has a positive or negative ignition system.

Clock pulse generator 96 operates as a wave-shape amplifier on the signals conducted to its input terminals 98, 99. The generator provides a fast rise-time with a constant amplitude pulse which time base varies linearly with the time base of the ignition signal duration. This is also an important feature, since it enables the clock pulse generator to produce a clock pulse of appropriate duration irrespective of the speed at which the engine is operated. Clock pulse generator 96 produces a signal of the type shown by wave shape D in FIG. 7 which is conducted over conductors 103, 104 to counting circuit 110. The output of generator 96 is also used to drive auxiliary circuit 450. This circuit, in turn, may be used to operate an ignition oscilloscope, tachometer, or timing light.

Bistable flip-flop circuits 112, 150 and 192 sequentially produce various counting states after the receipt of each clock pulse. After the flip-flop circuits have counted through eight separate counting states (the maximum number obtainable from three flip-flop circuits), the counters are automatically reset to an initial counting state. In order to commence the counting cycle of counting circuit 110 with a preselected cylinder of engine 10, coil 242 is placed adjacent the spark plug wire associated with that cylinder. For example, as shown in FIG. 1, coil 242 may be placed adjacent the spark plug wire corresponding to the number one cylinder of engine 10. As soon as a high voltage ignition signal is received by the spark plug of the number one cylinder, a trigger signal is induced in coil 242 and is conducted to the input of transistor 250. Transistor 250 amplifies the signal and conducts it to multivibrator 260. Multivibrator 260, in turn, produces a three millisecond output pulse that is utilized as a noise-blanking signal. The output pulse is at least as long as the duration of an individual ignition signal. This is an important feature, since it enables the setting circuit to reliably set the counting states of counting circuit 110. The pulse produced by multivibrator 260 is integrated by multivibrator 266 to form a 100 nanosecond rise time, 15 volt, 500 microsecond setting pulse that is impedance matched by transistor 272 and is transmitted over conductor 224 to each of flip-flop circuits 112, 150 and 192. As a result of this operation, transistors 136, 179, and 217 of flip-flop circuits 112, 150 and 192, respectively, are each switched to their conducting state. Thereafter, coil 242 may be removed from the engine, and counting circuit 110 will continue to produce the proper counting states with respect to the number one cylinder of engine 10. As clock pulses continue to be conducted to the counting circuit in response to ignition signals, the flip-flop circuits produce signals shown by wave shapes E, F and G in FIG. 7 at the corresponding points shown in FIGS. 4 and 5.

In order to disable a particular cylinder of the engine with respect to the number one cylinder, the operator presses the correspondingly-numbered switch of cylinder select device 390. For example, if the operator wants to disable the number one cylinder of engine 10, he presses switch 391. This results in the production on conductor 362 (FIG. 3) of a signal corresponding to wave shape H of FIG. 7. This signal is conducted to gate 60 of variac 58, thereby shunting the major portion of the corresponding ignition signal to ground potential. Although the voltage remaining at input terminal 52 is insufficient to fire the spark plug for the number one cylinder, there is a sufficient voltage developed across resistor 66 to operate the generating circuit. In this mode of operation, as long as switch 391 is depressed, the ignition signal in each cycle of 8 ignition signals which normally energizes the spark plug connected to the number one cylinder is disabled. As a result, the spark plug does not fire, thereby disabling the number one cylinder. In a like manner, the depression of switches 392-398 result in the production of signals having wave shapes I-O, respectively, of FIG. 7. The production of these signals disables the ignition signals which normally energize the spark plugs connected to cylinders 2-8 of engine 10, respectively.

If a six cylinder engine is to be diagnosed, engine select switch 371 is set to the "6" position. In this mode of operation, diode 232 of flip-flop circuit 192 is connected through switch 372 to resistor 234 of flip-flop circuit 150. By completing this connection, the flip-flop circuits are enabled to count through six counting states before being reset to their initial counting state. In order to disable a particular cylinder of the six cylinder engine, the operator need only depress the correspondingly-numbered one of switched 391-396. By depressing the switches, the operator produces on output conductor 362 signals having the wave shapes H-M of FIG. 7, respectively.

In order to diagnose a four cylinder engine, the operator merely moves engine select switch 371 to the "4" position. Through this mode of operation, diode 232 of flip-flop circuit 192 is connected to ground potential, thereby disabling the flip-flop. As a result, as soon as flip-flop circuits 112 and 150 have counted through four counting states, they are automatically reset to an initial counting state.

Of course, by simultaneously depressing more than one of switches 391-398, more than one cylinder of engine 10 may be simultaneously disabled. For example, by depressing switches 391 and 393, signals having wave shape P of FIG. 7 are produced on output conductor 362, thereby disabling the corresponding ignition signals for the number one and three cylinders.

Output conductor 362 may also be connected through a driver to an indicating means that will indicate when a particular one of signals I-O (FIG. 7) is being produced. This indication, in turn, will be made at the same time the piston of the corresponding cylinder is approximately in its top dead center position.

Those skilled in the art will recognize that the particular embodiment described herein may be altered and modified without departing from the true spirit and scope of the invention as defined in the accompanying claims.

Claims

What is claimed is:

1. In a system for diagnosing an engine including a source of periodic cycles of ignition signals, improved apparatus for preventing one or more predetermined ignition signals in each cycle from energizing engine components which are normally energized by said predetermined ignition signals comprising in combination:

input means for receiving said periodic cycles of ignition signals from said source;

generating means for generating a clock pulse in response to the receipt of each ignition signal by the input means, said generating means comprising clock means for producing in response to each ignition signal a clock pulse having a predetermined amplitude and having a duration proportional to the duration of the ignition signal;

counting means for producing counting states representative of the number of pulses received from said generating means;

adjustable resetting means for resetting the counting means to a predetermined counting state after the counting means has counted through a predetermined number of counting states;

removable setting means for setting the counting means to an initial counting state in response to the operation of a predetermined one of the engine components by an ignition signal;

adjustable selecting means for producing a disabling pulse in response to a predetermined counting state of the counting means; and

disabling means responsive to the disabling pulse for preventing any simultaneously-occurring ignition signal from energizing the engine component normally energized by the simultaneously-occurring ignition signal.

2. Apparatus, as claimed in claim 1, wherein the generating means further comprises:

first means for receiving positive ignition signals from the input means and for receiving negative ignition signals from the input means;

second means for inverting the polarity of the negative ignition signals with respect to the polarity of the positive ignition signals to produce resultant signals each having the same polarity; and

third means for conducting the resultant signals to the clock means.

3. Apparatus, as claimed in claim 1, wherein the setting means comprises:

means adapted to be positioned adjacent a predetermined engine component for producing a trigger signal in response to the receipt of an ignition signal by the engine component;

monostable multivibrator means for producing in response to the trigger signal an output pulse having a duration at least as long as the duration of the ignition signal from said engine component;

integrating means for integrating the output pulse to produce a setting signal; and

means for transmitting the setting signal to the counting means, whereby the counting means is set to an initial counting state.

4. Apparatus, as claimed in claim 1, wherein the disabling means comprises a triac for conducting current in opposite directions.

5. In a system for diagnosing an engine including a source of periodic cycles of ignition signals, improved apparatus for preventing one or more predetermined ignition signals in each cycle from energizing engine components which are normally energized by said predetermined ignition signals comprising in combination:

input means for receiving said periodic cycles of ignition signals from said source;

generating means operatively connected to the input means for generating a clock pulse in response to the receipt of each ignition signal by the input means;

counting means operatively connected to the generating means for producing counting states representative of the number of pulses received from said generating means, said counting means comprising first, second and third binary flip-flop circuits each having an input circuit and an output circuit and each capable of producing a single output pulse for each two pulses transmitted to its input circuit;

adjustable resetting means operatively connected to the counting means for resetting the counting means to a predetermined counting state after the counting means has counted through a predetermined number of counting states;

removable setting means operatively connected to the counting means for setting the counting means to an initial counting state in response to the operation of a predetermined one of the engine components by an ignition signal;

disabling means operatively connected to the selecting means and responsive to the disabling pulse for preventing any simultaneously-occurring ignition signal from energizing the engine component normally energized by the simultaneously-occurring ignition signal.

6. Apparatus, as claimed in claim 5, wherein the selecting means comprises:

a first conductor;

a second conductor;

a third conductor;

a fourth conductor;

a fifth conductor;

a sixth conductor;

a seventh conductor;

an eighth conductor;

first gating means for connecting each of said conductors to the output circuit of the first binary flip-flop circuit;

second gating means for connecting each of said conductors to the output circuit of the second binary flip-flop circuit;

third gating means for connecting each of said conductors to the output circuit of the third binary flip-flop circuit;

a source of ground potential;

switching means for selectively applying ground potential to all except a predetermined one of the first through eight conductors;

an output conductor; and

fourth gating means operatively connected to the first through eighth conductors for transmitting a pulse appearing on the predetermined one of the first through eighth conductors to the output conductor.

7. Apparatus, as claimed in claim 5, wherein the resetting means comprises:

first means for disabling the third bistable flip-flop circuit so that the counting means resets to a predetermined counting state after counting through four counting states; and

second means for interconnecting the second bistable flip-flop circuit and the third bistable flip-flop circuit and so that the counting means resets to a predetermined counting state after counting through six counting states.