Abstract A shut-down system for an internal combustion engine having a magneto circuit which when grounded causes the engine to shut down. A normally open sensor switch responsive to some malfunction of the engine grounds the magneto circuit through an "indicator" circuit when the sensor switch closes. To avoid arcing with sufficient energy release to ignite flammable mixtures of gases or dust which might occur when ordinary switch contacts are operated, non-arcing solid state switches are used in those parts of the system which handle ignition levels of electrical energy and means are provided for reducing to non-ignition levels the electrical energy that is handled by ordinary switch contacts in the system. In addition, means may be provided to remove magneto primary voltage from the system for a short period of time while the engine is being started up so that the magneto circuit is not grounded by operation of the sensor switch before the engine reaches running conditions. The system can be extended to accommodate any number of indicator circuits and sensor switches. A "test without kill" feature may be added in order to test the integrity of the sensor switch wiring and the proper functioning of the overall system without killing the engine. Further, a hard-ground feature may be included in the event the impedance of a coil in the indicator circuit through which the magneto circuit is grounded is too high to effectively ground the magneto circuit. Also, a manual shut-down or "kill" switch may be included. In addition, a matrix arrangement for connecting various sensor switches and indicator circuits may be employed to reduce the number of indicator circuits required to identify uniquely four or more primary sensor points and to provide a redundant shut-down path should one of the indicator circuits fail.
In a shut-down system for an internal combustion engine having a magneto circuit, said shut-down system including at least one sensor contact switch operable in response to a malfunction of said engine, and at least one indicator means which includes a switching means for generating a signal indicative of said malfunction, the improvement comprising: a first semiconductor current switch having a control terminal coupled to said sensor contact switch to change the conducting state of said first semiconductor switch in response to a malfunction of said engine and having a current switching terminal coupled to said switching means to generate said signal indicating said malfunction and a second semiconductor current switch having a control terminal coupled to said switching means to change the state of said second semiconductor current switch to its conducting state in response to a malfunction indication and having a current switching terminal connected through a low impedance path to said magneto circuit, said second semiconductor current switch providing a low impedance current conducting path from said magneto circuit which disables said engine.
Claim 2
Dependent Claim
176 words
In a shut-down system for an internal combustion engine having a magneto circuit, said shut-down system including at least one sensor contact switch operable in response to a malfunction of said engine, and at least one indicator means which includes a switching means for generating a signal indicative of said malfunction, the improvement comprising: a first semiconductor current switch having a control terminal coupled to said sensor contact switch to change the conducting state of said first semiconductor switch in response to a malfunction of said engine and having a current switching terminal coupled to said switching means to generate said signal indicating said malfunction and a second semiconductor current switch having a control terminal coupled to said switching means to change the state of said second semiconductor current switch to its conducting state in response to a malfunction indication and having a current switching terminal connected through a low impedance path to said magneto circuit, said second semiconductor current switch providing a low impedance current conducting path from said magneto circuit which disables said engine.
Claim 3
Dependent Claim
32 words
A shut-down system as recited in claim 1 including means connected to said magneto circuit and said indicator means for delaying operation of said shut-down system for a selected period of time.
Claim 4
Dependent Claim
46 words
A system as recited in claim 2 including means connected between said magneto circuit and said indicator means for testing operation of said sensor switch and said indicator means to ensure integrity of said sensor switch and proper functioning of said system without stopping said engine.
Claim 5
Dependent Claim
32 words
A system as recited in claim 3 including an additional ground circuit connected into said indicator means to ground said magneto circuit when the impedance in said indicator means is too high.
Claim 6
Dependent Claim
46 words
A system as recited in claim 4 including a matrix arrangement of diodes connected between said sensor switch and said indicator means to reduce the number of indicator means required to identify sensor points and to provide a redundant shut-down path should one indicator means fail.
Claim 7
Dependent Claim
70 words
A shut-down system for an internal combustion engine as recited in claim 1 including a plurality of sensor contact switches, each closeable to ground in response to a different malfunction of said engine; and a plurality of indicator means, each indicator means connecting a different one of said sensor contact switches to said magneto circuit to ground said magneto circuit upon closing of any one of said sensor contact switches.