A system for use with an internal combustion engine which reduces, or eliminates, engine knock and attendant engine damage. An audio transducer is placed on an engine cylinder to convert audio signals occurring within the combustion chamber into an electrical signal. This signal is sampled and filtered and the amplitudes of two time-sequenced segments are compared. One of those segments is timed for an interval during which detonation, if any, is likely to occur, and the other of these segments is timed for an interval during which no detonation is likely to occur. When the amplitude of the sample from the segment of likely detonation exceeds the amplitude of the sample from the segment of unlikely detonation, by a predetermined amount, extra fuel is momentarily added to the combustion chamber to slow down the rate of combustion and cool the walls of the combustion chamber.

Patent
   RE32667
Priority
Sep 09 1987
Filed
Sep 09 1987
Issued
May 17 1988
Expiry
Sep 09 2007
Assg.orig
Entity
Large
3
7
EXPIRED
1. A knock detection and prevention circuit for an internal-combustion engine, comprising:
transducer means for converting audio signals indicative of engine combustion and occurring within a combination combustion chamber of the engine into an electrical signal which is characterized, for each engine cycle, by one phase during which any detonation is likely to occur and by another phase during which detonation is unlikely to occur,
means for sequentially sampling and filtering from said respective phases separate segments of said electrical signal whereby separate filtered-sample signals are produced from the sampling of said respective phases,
means for comparing the amplitude of the filtered-sample signal from a sequentially first segment of said electrical signal, with amplitude of the filtered-sample signal from a sequentially second segment of said electrical signal, and
threshold means responsive to a predetermined difference in the amplitude of said first and second filtered-sample signals for increasing the rate of fuel supply to the combustion chamber of the internal combustion engine.
2. A knock-detection and prevention circuit according to claim 1, in which comparator means is connected to said transducer means for comparing transducer-output voltage against a predetermined reference voltage, said predetermined reference voltage being selected for correspondence with the predetermined amplitude difference beyond which said threshold means is responsive, said comparator means providing an amplified output signal to said threshold means and with an amplitude exceeding the predetermined difference to which said threshold means is responsive, whereby knock-prevention measures are automatically initiated as a fail/safe procedure in the event of transducer output voltage which fails to exceed said reference voltage.
3. A knock-detection and prevention circuit according to claim 1, in which the internal combustion chamber is of multi-cylinder variety and said transducer means is mounted to the cylinder head of the engine cylinder most prone to detonation knocking.
4. A knock-detection and prevention circuit according to claim 3, in which said threshold means is responsive to said predetermined difference to increase the rate of fuel supply to all cylinders of the engine.
5. A knock-detection and prevention circuit according to claim 4, in which said threshold means is also responsive to said predetermined difference to retard the spark timing of the engine.
6. A knock-detection and prevention circuit according to claim 1, wherein said sequential filtering and sampling means includes first timing means responsive to an ignition pulse applied to the combustion chamber for initiating a first sampling period.
7. A knock-detection and prevention circuit according to claim 6, in which the timing of said first timing means is approximately 1.5 milliseconds.
8. A knock-detection and prevention circuit according to claim 7, in which said 1.5 milliseconds timing is ± about 2 percent.
9. A knock-detection and prevention circuit in accordance with claim 6, wherein said sequential filtering and sampling means further includes a first filtering and sampling circuit responsive to said first timing means for extracting a first filtered sample from said electrical detonation signal during said first sampling period.
10. A knock-detection and prevention circuit in accordance with claim 9, wherein said sequential filtering and sampling means further includes a second timing means responsive to the termination of said first sampling period for initiating a second sampling period.
11. A knock-detection and prevention circuit according to claim 10, in which the timing of said first timing means is approximately 1.5 milliseconds and in which the timing of said second timing means is approximately 2.2 milliseconds.
12. A knock-detection and prevention circuit according to claim 11, in which said 2.2 millisecond timing is ± about 2 percent.
13. A knock-detection prevention circuit in accordance with claim 10, wherein said sequential filtering and sampling means further includes a second filtering and sampling circuit responsive to said second timing means for extracting a second filtered sample from said electrical detonation signal during said second sampling period, said second sampling period occurring later in time than said first sampling period.
14. A knock-detection and prevention circuit according to claim 13, wherein said fuel-supply increasing means increases the fuel supply to the combustion chamber when the voltage amplitude of the second filtered-sample signal exceeds the voltage amplitude of the first filtered-sample signal by a predetermined amount.
15. A knock-detection and prevention circuit according to claim 14, in which the degree to which said fuel-supply increasing means increases the fuel supply is proportional to the degree to which the voltage amplitude of the second filtered-sample signal exceeds that of the first filtered-sample signal.
16. A knock detection and prevention circuit for an internal-combustion engine, comprising:
transducer means for converting audio signals indicative of engine combustion and occurring within a combustion chamber of the engine into an electrical signal which is characterized, for each engine cycle, by one phase during which any detonation is likely to occur and by another phase during which detonation is unlikely to occur,
means for sequentially sampling and filtering from said respective phases separate segments of said electrical signal whereby separate filtered-sample signals are produced from the sampling of said respective phases,
means for comparing the amplitude of the filtered-sample signal from a sequentially first segment of said electrical signal, with amplitude of the filtered-sample signal from a sequentially second segment of said electrical signal, and
means responsive to a difference in the amplitude of said first and second filtered-sample signals for increasing the rate of fuel supply to the combustion chamber of the internal combustion engine. 17. A knock-detection and prevention circuit according to claim 16, in which said means responsive to amplitude-difference comprises threshold means responsive to a predetermined difference in said amplitudes for retarding the spark timing of the engine.

This invention relates to a knock-prevention system for an internal-combustion engine with timed ignition and more particularly to an electronic circuit which will detect the occurrence of engine knocking and initiate corrective steps to reduce the knock and prevent engine damage.

Engine "knock" or "detonations" in an internal-combustion engine are caused by uncontrolled and rapid combustion in the combustion chamber leading to the undesirable generation of heat and pressure; this is attributable to variations in the octane of available fuel, and the prospect is for greater knocking as octane ratings reduce. Knock, when severe, causes a loss of engine efficiency and can cause severe engine damage, such as pitting, cracking or even destruction of the pistons or of the walls surrounding the combustion chamber. This problem is particularly severe with two-cycle engines and when such engines are used in a marine environment, the consequences of engine damage can be catastrophic.

It is, therefore, an object of the instant invention to prevent unnecessary engine damage by reducing, or eliminating, engine knock.

It is a specific object of the instant invention to reduce or eliminate knock with an inexpensive and uncomplicated electronic circuit readily adaptable for use with two-cycle engines.

Various knock-control circuits are known for use with internal-combustion engines, which circuits attempt to control knock merely by adjustment of the spark timing. However, known spark-control circuits cause exhaust-gas temperatures to rise, resulting in development of additional heat in the combustion chamber. Such added heat is undesirable, as it can result in additional or more severe engine damage.

It is, therefore, a still further object of the instant invention to reduce, or eliminate, knock in an internal combustion engine, by means which will reduce heat development in the combustion chamber.

In accordance with a first aspect of the invention, audio signals indicative of engine combustion and occurring within a combustion chamber in an internal combustion engine are detected and converted into an electrical detonation signal. Usually, one cylinder is more prone to knocking detonation than other cylinders of the engine, and therefore the cylinder most prone to such knocking is selected for this audio-signal detection.

It is a feature of the invention that the detected electrical detonation signal is sequentially filtered and sampled, and that the voltage amplitude of first and second samples are compared at a voltage-comparator circuit.

It is a further feature of the invention that the first sample is taken from the detected electrical signal during a first time interval which is earlier in the time than a second time interval which is predetermined to include the electrical detonation signal. The second sample is taken from the detected electrical signal during the second time interval, and knock prevention is initiated when the second sample is greater in amplitude than the first sample by a predetermined amount.

It is a still further feature of the invention that engine knock is prevented, or combustion-chamber heat development is reduced, in response to the initiation of knock prevention, by momentarily increasing the fuel supply to the combustion chamber, which increase in fuel supply serves to slow down the combustion process and cool the walls of the combustion chamber.

Still another feature is the provision of a fail-safe feature in the knock-suppressing circuitry.

These and other objects and features of the invention will be more readily understood by reference to the following detailed description and accompanying drawings.

In the drawings:

FIG. 1 is an electrical block diagram schematically depicting a gated knock-detection circuit of the instant invention; and

FIG. 2 is a succession of electrical waveforms occurring in the circuit of FIG. 1, and presented to the same time scale60 compares and filters signals E and F, and the output of the comparison from the differential amplifier is applied to detonation-control circuitry. In FIG. 1, this is shown by legend to comprise a detonation-threshold detector 70 and a line 71 connected directly to fuel enrichment control means for the engine (not shown). Threshold detector 70 consists of a voltage-level detection circuit which monitors the varying DC output voltage of the differential amplifier. When this level exceeds a preset voltage value, an output signal is generated which is applied to detonation-control circuitry. In FIG. 1, this is shown by legend to comprise a supplied in line 72 for proportional control of spark-retardation in ignition timing of the involved engine, and switch 73 in line 72 will be understood to indicate the optional or selective use of retardation control, depending upon performance of the engine. The fuel-enriching signal in line 71 to the throttle-control means (not shown) of the engine; provides generally, the a maximum enrichment is in the order of 10 percent of current fuel flow to the entire engine, and preferably (as also suggested by legend) the degree of enrichment is proportional to the extent of detonation-signalexcess over threshold. FIG. 1 also shows that the same output signal from detector 70 may be supplied in line 72 for proportional control of spark-retardation in ignition timing of the involved engine, and switch 73 in line 72 will be understood to indicate the optional or selective use of retardation control, depending upon performance of the engine. The added fuel of the enrichment slows down the rate of combustion in the combustion chamber and also serves to cool the walls of the combustion chamber. Fuel enrichment can be in the range up to 20 percent; and if selected, spark timing can be retarded by approximately 8 degrees at the time the fuel supply is enriched. These figures are to be considered illustrative for a six-cylinder, two-cycle engine of the type shown in my said patent.

What has been shown and described is a gated knock-detection circuit for detecting the presence of engine knock and for thereafter initiating preventive measures to reduce or eliminate the knock, thereby preventing the possibility of attendant engine damage. Knock-detection and prevention are accomplished by monitoring the audio frequencies generated by a detonation occurrence, to produce an electrical detonation signal. This signal is filtered and two samples are taken from sequential segments of the electrical detonation signal. The two samples are compared and, when the samples taken from the later-occurring segment exceed the voltage amplitude of the sample taken from the earlier occurring segment, it is determined that engine knock is commencing. When engine knock commences, fuel is added to the combustion chamber to slow down the rate of combustion and cool the walls of the combustion chamber, thereby reducing, or eliminating, engine knock and the possibility of attendant engine damage. Since proportional control and continuous samplings are taken and compared, the circuitry automatically assures enrichment and (if selected) retardation, to the minimum degree tolerated by the threshold at 70.

Generally speaking, the threshold at 70 should correspond to a "detonation" signal E which is at least 10 percent greater than the currently observed "ambient" signal F. The indicated 1.5 and 2.2 milliseconds times for the gate-signal intervals B, C are stated as preferred, in that ±2 percent variation is deemed to state a preferred tolerance range of these timed intervals. Lesser sampling intervals may produce equivalent results, as long as the ambient-signal sampling includes no part of the detonation-signal sampling; these samplings need not therefore be contiguous with each other, nor need the ambient sampling be contiguous with the ignition signal, but circuitry is much simpler for the case of contiguous intervals, as shown and described.

As a further and fail/safe feature of the invention, FIG. 1 also shows a differential amplifier 80, labeled "Loss-of-Sensor Detector" for monitoring whether or not there is sufficient output from audio transducer 10. At amplifier 80, the audio output level (at the "-" input) must equal or exceed the reference threshold voltage level (at the "+" input) to avoid generating a strong fail/safe signal in line 81 to the detonation detector 70. In other words, when detector 80 senses that transducer (10) output is inadequate, line 72 calls for maximum retardation, thus assuring engine safety.

While the embodiment illustrated in FIG. 1 is presently preferred, it may be desirable to subject the fuel enrichment signal on line 71 to control of the threshold detector 70 as shown in FIG. 3, wherein the same reference numerals are used as in FIG. 1 to designate the same or similar parts.

Although a specific embodiment embodiments of the invention has have been shown and described, it will be understood that various modifications may be made without departing from the spirit of this invention. For example, the invention will be seen to be applicable to four-cycle engines, whether fuel is supplied by injection or by carburetion; and digital techniques utilizing a microprocessor may be used in place of the described gating, filtering and comparison of analog data.

Staerzl, Richard E.

Patent Priority Assignee Title
10549833, Feb 13 2013 AB Volvo Penta Outboard motor including one or more of cowling, water pump, fuel vaporization suppression, and oil tank features
5003951, Mar 07 1989 Mitsubishi Denki Kabushiki Kaisha Control apparatus for internal combustion engine
5535722, Jun 27 1994 WILMINGTON TRUST FSB, AS ADMINISTRATIVE AGENT Knock detection system and control method for an internal combustion engine
Patent Priority Assignee Title
4243009, Sep 27 1979 Brunswick Corporation Detonation control apparatus for outboard motor
4440129, May 05 1979 Mitsubishi Denki Kabushiki Kaisha Ignition timing control system for internal combustion engine
4449501, Dec 31 1980 Lucas Industries Limited Device for adjusting engine timing
4535739, May 19 1983 Fuji Jukogyo Kabushiki Kaisha System for preventing knocking in a combustion engine
4552111, Jul 20 1982 MAZDA KABUSHIKI KAISHA Engine knocking detecting means
4565087, May 28 1983 Robert Bosch GmbH Method and apparatus for recognition of knocking in an internal combustion engine
4593553, Mar 10 1983 Robert Bosch GmbH Method for detecting engine knock in internal combustion engines
/
Executed onAssignorAssigneeConveyanceFrameReelDoc
Sep 09 1987Brunswick Corporation(assignment on the face of the patent)
Date Maintenance Fee Events
Mar 01 1990ASPN: Payor Number Assigned.
Oct 25 1990M173: Payment of Maintenance Fee, 4th Year, PL 97-247.
Sep 26 1994M184: Payment of Maintenance Fee, 8th Year, Large Entity.


Date Maintenance Schedule
May 17 19914 years fee payment window open
Nov 17 19916 months grace period start (w surcharge)
May 17 1992patent expiry (for year 4)
May 17 19942 years to revive unintentionally abandoned end. (for year 4)
May 17 19958 years fee payment window open
Nov 17 19956 months grace period start (w surcharge)
May 17 1996patent expiry (for year 8)
May 17 19982 years to revive unintentionally abandoned end. (for year 8)
May 17 199912 years fee payment window open
Nov 17 19996 months grace period start (w surcharge)
May 17 2000patent expiry (for year 12)
May 17 20022 years to revive unintentionally abandoned end. (for year 12)