GB2162671A - Monitoring system - Google Patents
Monitoring system Download PDFInfo
- Publication number
- GB2162671A GB2162671A GB08521242A GB8521242A GB2162671A GB 2162671 A GB2162671 A GB 2162671A GB 08521242 A GB08521242 A GB 08521242A GB 8521242 A GB8521242 A GB 8521242A GB 2162671 A GB2162671 A GB 2162671A
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- Prior art keywords
- rail
- circuit
- shut down
- fault
- resistor
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- 238000012544 monitoring process Methods 0.000 title claims abstract description 30
- 231100001261 hazardous Toxicity 0.000 claims abstract description 4
- 239000000446 fuel Substances 0.000 claims description 4
- 230000001681 protective effect Effects 0.000 abstract 2
- 230000004888 barrier function Effects 0.000 description 11
- 238000010586 diagram Methods 0.000 description 9
- 230000003137 locomotive effect Effects 0.000 description 8
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/22—Safety or indicating devices for abnormal conditions
- F02D41/222—Safety or indicating devices for abnormal conditions relating to the failure of sensors or parameter detection devices
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B77/00—Component parts, details or accessories, not otherwise provided for
- F02B77/08—Safety, indicating, or supervising devices
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D17/00—Controlling engines by cutting out individual cylinders; Rendering engines inoperative or idling
- F02D17/04—Controlling engines by cutting out individual cylinders; Rendering engines inoperative or idling rendering engines inoperative or idling, e.g. caused by abnormal conditions
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
- G08B29/12—Checking intermittently signalling or alarm systems
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B3/00—Engines characterised by air compression and subsequent fuel addition
- F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Computer Security & Cryptography (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Combined Controls Of Internal Combustion Engines (AREA)
Abstract
In a monitoring arrangement in which a plurality of sensor outputs are judged for the existence of a fault, and appropriate protective arrangements are actuated when a fault is detected, the monitoring arrangement is periodically tested by injecting simulated fault signals from the sensors and determining whether the appropriate protective arrangement is actuated. The arrangement is applicable to safety devices for use in hazardous environments. <IMAGE>
Description
SPECIFICATION
Monitoring system
This invention relates to a monitoring system and particularly, but not exclusively, to a system for monitoring an engine operating in a hazardous area.
Where a monitoring system is used in conditions where high reliability is required, such a monitoring system should not only be capable of indicating a malfunction in the apparatus which is monitoring but should also be capable of indicating a malfunction in itself. It is accordingly an object of this invention to provide a monitoring system capable of indicating such a malfunction.
According to this invention there is provided a monitoring system comprising a set of sensors, fault detecting means responsive to the sensors providing a signal for controlling system shut down, a drive circuit for a solenoid operated element, said drive circuit having an input connected to the shut down control signal, and a system checking arrangement comprising means for temporarily applying a signal indicative of a fault condition to the output of each sensor in turn and means for checking that each time such a signal is applied to one of the sensors the output of the drive circuit assumes its shut down condition.
In this monitoring system, both faults which occur in the fault detecting means and faults which occur in the drive circuit will be detected.
This invention will now be described In more detail by way of example, with reference to the accompanying drawings, in which:
Figure 1 shows the general layout of a locomotive for operating in an underground mine;
Figure 2 is a block diagram of a system for monitoring the diesel engine of a mine locomotive, the system being constructed in accordance with the present invention;
Figure 3 is a circuit diagram of a barrier circuit and a prebarrier circuit which forms part of the monitoring system of Figure 2;
Figure 4 is a block diagram of a tachometer circuit forming part of the monitoring system;
Figures 5a and 5b are circuit diagrams of sensors forming part of the monitoring system;
Figure 6 is a circuit diagram of a solenoid drive circuit forming part of the monitoring system;
Figure 7 is a circuit diagram of a sensor checking circuit forming part of the monitoring system;;
Figure 8 is a circuit diagram of two sets of comparators which form part of the monitoring system;
Figure 9 is a circuit diagram of a memory and display circuit forming part of the monitoring system; and
Figure 10 is a circuit diagram of a system checking circuit also forming part of the monitoring system.
Referring now to Figure 1, a locomotive for operating in an underground mine has a cab 10 for the driver at one or both ends and a diesel engine 11 for providing drive to the locomotive wheels and also for driving a nominal 12 volt electric generator 12. The generator 12 is enclosed in a flameproof housing 13. The generator 12 provides power to the locomotive lamps through cables which are enclosed in flameproof sheathing. Both the lamps and their switches are enclosed in flameproof containers and the switches are controlled with compressed air.
The system shown in Figure 2 monitors the diesel engine 11 and as will be described causes the engine to shut down if a fault occurs. in this system, the generator 12 provides power to a pair of prebarrier circuits 14 and 15 which in turn provide power to a pair of barrier circuits 16 and 17 and also serve to protect the circuits 16 and 17 from voltage transients from the generator 12. The output currents and voltages of the barrier circuits 16 and 17 are limited to levels below those which are capable of causing an ignition spark. The circuits 14 to 17 are mounted in a FLAME PROOF container so that any sparks which may inadvertently be generated in one of the circuits cannot cause an explosion and the circuits are connected to the generator 12 through a cable which is enclosed in a flameproof sheath. The FLAME PROOF container is mounted adjacent to the generator 12.It should be appreciated that neither the circuitry which is supplied with power from the barrier circuit 16 and 17 nor their associated cables need be enclosed in flameproof containers as the power supply to such circuitry is kept below that at which an ignition spark can occur.
The barrier circuit 16 supplies power through a pair of cables 18 and 19 to a tachometer circuit 20 and a speedometer circuit 21. The tachometer circuit 20 receives pulses from a variable reluctance transducer mounted on the output shaft of the diesel engine 11 and the speedometer 21 receives pulses from a variable reluctance transducer 23 driven by one of the locomotive wheels, The tachometer 20 and speedometer 21 provide a display of engine speed and vehicle speed and also serve to detect overspeed conditions. Signals indicating overspeed conditions are supplied to a pair of opto isolators 24 and 25, the output signals from which are supplied respectively to a pair of cables 26 and 27 and 28 and 29.The opto isolators 24 and 25 serve to isolate electrically the circuitry supplied by barrier circuit 16 from that supplied by barrier circuit 17 so that there is no danger of the output powers of the two circuitries being added together.
The tachometer 20, speedometer 21 and opto isolators 24 and 25 are mounted in one of the cabs 10. If it is desired to display vehicle and engine speed in the other cab 10, then a second tachometer 20 and second speedometer 21 may be provided.
The cables 26 and 27 and 28 and 29 are connected to a circuit 30 which also receives signals from engine parameter sensors S, to S5 and S8 and Sg. The circuit 30 checks the signals from the sensors and also from the opto isolators 24 and 25 for open circuit faults and supplies output signals representing the various parameters which are sensed on a bus 31 to two sets of comparators 32. The comparators 32 detect fault conditions and provide signals on a bus 33 to a memory and display circuit 34. The comparators also provide a control signal SHUTDOWN on a rail 35 to a solenoid drive circuit 36, the signal SHUTDOWN assuming a low state when a fault is detected which requires engine shut down.The solenoid drive circuit 36 receives power through cables 37 and 38 from barrier circuit 17 and provides a driven signal via cables 39 and 40 to a solenoid operated fuel valve 41 which controls the fuel supply to the engine 11.
The solenoid drive circuit 36 provides the power supply for the circuits 30, 32 and 34 and also for a system checking circuit 42. The circuit 42 supplies a set of signals on a bus 43 to the sensor checking circuit 30 for checking the operation of the monitoring system and receives a signal CHECK on a rail 44 from the solenoid drive circuit 36. The circuit 42 also supplies a signal CROWBAR to circuit 36 on a cable 45 and as will be described in more detail below this signal causes shut down if a system fault is detected.
The circuits 30, 32, 34, 36 and 42 are mounted in a dust and water proof container and may be encapsulated in black pigmented epoxy resin so as to render them tamper proof and the resulting assembly is mounted at a central position in the locomotive.
The various circuits shown in Figure 3 will now be described in more detail.
Referring now to Figure 3, the prebarrier circuit 14 has a pair of input terminals 50 and 51 and a pair of output terminals 52 and 53. The input terminal 50 is connected through four parallel connected resistors R, to the emitter of a PNP transistor T., the collector of which is connected to terminal 52. The terminal 50 is also connected through a pair of diodes D, and D2 to the base of transistor T, and the base of transistor T, is also connected through a resistor R to terminals 51 and 53. The barrier circuit 16 has a pair of output terminals 54 and 55 connected respectively to cables 18 and 19. Terminal 52 is connected through a 500mA fuse F. to a rail 56 which is connected through a 3.3ohm resistor R2 to terminal 54.Rail 56 is connected through a type BZY 93 zener diode
ZD, to terminal 55 and a further pair of zener diodes ZD2 and ZD3 are connected in parallel with zener diode ZD1. The zener diodes ZDl-ZD3 have a breakdown voltage of 7.5 volts and serves to limit the output voltage appearing at terminals 54 and 55 to this value and the resistor R2 limits the output current to 2.3A. This combination of voltage and current is below that at which an ignition spark can occur. In the present arrangement, the zener diode ZD, is operated in its breakdown state so that the full 7.5 volts are used but the current drawn is normally substantially less than 2.3A.The zener diodes ZD2 and ZD3 function if ZD, fails and becomes open circuit and the fuse F, protect zener diodes ZD,-ZD3 from damaging overcurrents. The transistor T, resistors R, and R2 and diodes D, and
D2 operate as a current limiter and serve to protect the fuse F, from transient voltages from generator 13. In the absence of high or transient voltages, transistor T, is operated in a saturated condition and so the voltage drop across this transistor is small and so has a negligible effect on the voltage available at terminals 54 and 55.
The prebarrier circuit 15 and barrier circuit 17 are generally similar to the circuits 14 and 16. However, in the barrier circuit 17, the fuse F, is replaced by 250mA fuse, the zener diode ZD1-ZD3 are replaced by type BZY 93 zener diode having a breakdown voltage of 13 volts, and the resistor R2 is replaced by a 6ohm resistor. Also, in the prebarrier circuit 15 the resistors R, are selected to provide protection for the 250mA fuse.
Referring to Figure 4 in the tachometer circuit 20, the output from transducer 22 is connected by a pair of rails 61 and 62 to the two inputs of an operational amplifier A,. A pair of diodes of opposing polarities and a resistor also connected across these two inputs. The non-inverting input is connected by a diode D2 to a 0V rail which is connected to cable 19, the inverting input is connected through a resistor R4 to a 5V rail which is connected to cable 18, and the output of amplifier A, is connected through a biasing resistor R5 to the 5V rail. The output of amplifier A, is connected to the input of a pulse counting circuit 63, the output of which is connected to the non-inverting input of an operational amplifier A2 configured as an adjustable Low gain voltage follower.The amplifiers A, and A2 each form one half of a type LM392 operational amplifier circuit. The output voltage of amplifier A is thus representative of engine speed and the output of this circuit is connected to the input of each of three type LM3914 bargraph generating circuits 64, 65 and 66. The bargraph generating circuits 64, 65 and 66 drive a set of light emitting diodes D4, each of which corresponds to a particular engine speed. The diodes D4 may be arranged in a row or circle and positioned where they may be easily viewed by the driver.
One of the outputs of bargraph circuit 66 corresponds to overspeed of engine 11 and this output is connected to rail 67. Consequently rail 67 goes low when overspeed occurs. In opto isolator 24, the 5V rail is connected through a pair of light emitting diodes D5, D to rail 67 and rail 67 is connected through a photodiode D2 and a resistor R6 to the 0V rail. Diode D7 is optically coupled to diode D6 and so when rail 67 goes low both diodes D, and D5 are latched into an energised state.
Diode D is optically coupled to a photodiode Ds connected in parallel with a resistor R7 and output terminals 68 and 69. Terminals 68 and 69 are connected to cables 26 and 27. Consequently, when overspeed is detected, the resistance between terminals 68 and 69 will fall.
Each of the sensors S, to Ss and S8 and Sg shown in Figure 2 senses either pressure or temperature.
An example of a temperature sensor is shown in
Figure 5a an an example of a pressure sensor is shown in Figure Sb. The temperature sensor comprises a thermistor Ra and resistor Rs connected between a pair of terminals 80, 81. The pressure sensor comprises a first pressure operated switch 82 connected between a pair of terminals 83 and 84, a second pressure operated switch 83 and a resistor Rio connected between terminals 83 and 84 and a resistor R,, connected between terminals 83 and 84. Switch 83 is arranged to close before the pressure reaches a fault level and switch 82 is arranged to close at the fault level thereby providing two stage operation. Resistor R1, is provided so that the sensor can be monitored for an open circuit fault.
The solenoid drive circuit 36 shown in Figure 6 has a 12V rail 90 and a 0V rail 91 connected respectively to cables 38 and 37. Rail 90 is connected to the emitter of an NPN transistor T2-, the collector of which is connected through a thyristor TH to rail 91. The base of transistor T2 is connected through a resistor Rio to the collector of an NPN transistor
T3, the emitter of which is connected to rail 91 and the emitter and collector of which are bridged by capacitor C1. The base of transistor Tj is connected through a resistor Ri, to cable 35. The collector of transistor T2 and the 0V rail are connected through cables 39 and 40 and a set of diodes D,, to the solenoid 41.The collector of transistor T2 is also connected through a resistor R,7 and a light emitting diode D" to the base of an NPN transistor T4, the collector of which is connected through a resistor Rio to the 12V rail 90, and also through a light emitting diode D,2 to the 0V rail, and the emitter of transistor T4 is connected directly to the 0V rail.
The collector of transistor T. is further connected to the cable 44. Cable 45 is connected through a resistor Rio to the base of an NPN transistor Tj, the collector of which is connected to cable 44 and the emitter of which is connected through a resistor
R20 to the gate of thyristor TH. The gate of thyristor
TH is connected to the 0V rail through a capacitor
C2. The circuit 36 also includes a voltage regulator 95 connected between rails 90 and 91 and which supplies a 5V rail 96 and a voltage regulator 97 connected between the collector of transistor T, and the 0V rail and which provides a 5V power supply rail 98. The rails 96 and 98 are connected through a pair of diodes D, and D.5, a resistor R and a 7 volt diac 99 to the gate of thyristor TH.
Each of the regulators 95 and 97 comprises a type
LM340 voltage regulator and the output of each of these regulators is bridged with a 1 microfarad capacitor.
If the signal CROWBAR is low and the signal
SHUTDOWN is high, transistors T2 and T2 are turned on thereby supplying current to solenoid 41. If the signal SHUTDOWN goes low, transistors
T2 and T3 will be turned off thereby removing the current supply to solenoid 41. However, current flow through solenoid 41 will be maintained by its self-inductance but under these conditions the signal CHECK will go low. If the signal SHUTDOWN is maintained in its low state, the current and solenoid 41 will eventually fall to zero causing shut down of the engine 11. Thus, if the signal SHUT
DOWN goes low temporarily, this causes a signal
CHECK to go low but does not cause engine shut down. If the signal CROWBAR goes high, the thyristor TH fires thereby removing the current supply permanently from solenoid 41 and causing engine shut down.Also, if the voltage on one of the supply rails 96 or 98 rises above 9 volts, diac 99 will conduct and this will also cause engine shut down.
The sensor checking circuit 30 shown in Figure 7 comprises ten pairs of terminals TM, to Trio. The terminals TM, to TM5 are connected respectively to sensors S. to S5, the terminals TM and TM7 are connected respectively to the outputs of opto isolators 25 and 24 via cables 28 and 29 and 26 and 27, and terminals TM8 and TM9 are connected to sensors So and So. In the present example, the terminals TM,0 are not used. The sensors S, to So respectively sense engine lubricant pressure, transmission oil temperature, exhaust gas temperature, engine coolant temperature, and transmission oil temperature.The sensors S8 and So respectively sense the air temperature delivered by an engine driven compressor and the temperature of brake components.
The pair of terminals TM comprises a positive terminal and a negative terminal. The positive terminal is connected through a pair of resistors R20 and R2, to the 5V rail 96 and the negative terminals is connected through a resistor R22 to the base of an NPN transistor T,o. The emitter of this transistor is connected to the 0V rail 91 and its collector is connected through a resistor R23 to the 5V rail 96.
The collector is also connected through a diode D20 to a rail 109. The positive terminal is also connected to a rail 111 and in operation the voltage appearing on this rail represents engine lubricant pressure. The transistor T,0 serves to detect an open circuit fault both in the cables which connect the terminals TM, to sensor S, and in the sensor itself. If such a fault occurs, transistor T,0 is switched off thereby supplying a high signal to rail 109. The circuit associated with each pair of terminals TM2 to TM,0 is identical to that associated with terminals TM, and so will not be described. The positive terminals of the pairs of terminals TM2 to TM, are connected to rails 112 to 120.The rail 109 is connected through a resistor R24 to the base of an NPN transistor T,,, the collector of which is connected through a resistor R2 to the 5V rail 96 and the emitter of which is connected to the 0V rail.
The collector of transistor T,, is also connected to a rail 121 and, in the event of an open circuit fault, the signal on this rail goes low.
The circuit 30 also provides a reference voltage for the comparators 32, In order to achieve this, the 5V rail 96 is connected through a pair of resistors R27 and R28 and diode D2, to the 0V rail 91. The resistor R28 and diode D2, are bridged by a capacitor C. The junction of resistors R22 and R28 is connected to the non-inverting input of an operational amplifier A3. The output of amplifier A3 is connected to the base of an NPN transistor T,2, the collector of which is connected to the 5V rail 96 and the emitter of which is connected to a rail 130.
The rail 130 is also connected to the non-inverting input of amplifier A3. In operation, a reference voltage of approximately 2.5 volts appears on rail 130.
The reference voltage is monitored and in order to achieve this the rail 130 is connected to the noninverting input of an operational amplifier A4. The 5V rail 96 is connected through a pair of resistors
R29 and R3o and a diode D2 to the 0V rail and the junction of resistors R23 and R30 is connected to the inverting input of amplifier A4. Resistors R29 and R30 are chosen so that the output amplifier At goes low if there is a significant fall in the voltage on rail 130. The output of amplifier As is connected to a rail 122 and rail 122 is connected to the 5V rail through a further resistor R3. The amplifiers Ag and
At each form one half of a type LM392 operational amplifier.The rails 111 to 122 together form the bus 31 which is connected to the comparators 32.
In circuit 30, the bus 43 from the system checking circuit 42 is connected through a set of resistors indicated at R22 to rails 111 to 120.
In the circuit 32 as shown in Figure.8, rail 111 is connected through a resistor R4 to the positive input of a comparator CUP., the negative input of which is connected through a resistor R4, to the reference voltage rail 130. The output of comparator CP0 is connected to rail 35 and also through a resistor R42 to the 5V rail 96 and through a resistor R43 to its positive input.The resistors R2 and R2 shown in Figure 7 and the resistors associated with sensor S1 are chosen so that when the engine lubricant pressure falls to a value at which engine shut down should occur, the output of comparator CPi goes low, thereby causing the signal SHUT
DOWN on rail 35 to go low. The rails 112 and 122 are connected respectively to comparators CP2 to
CP,2 in a manner similar to that described for comparator CP,. If the voltage appearing on one of the rails 112 to 122 falls to a value at which shut down should occur, this will also cause the signal SHUT
DOWN to go low. When the signal SHUTDOWN goes low as explained above, an engine shut down is caused.Subsequently, it is impossible to sustain engine running until the fault which has caused the shut down has been cleared.
The rail 111 is connected through a resistor R44 to the negative input of a comparator CP2,. The 5V rail 96 is connected through a pair of resistors R45 and R45 and a diode D30 to the OV rail and the junction of resistors R45 and R43 is connected through resistor R42 to the positive input of comparator CP and through resistor R4a and D33 to the 0V rail. The output of comparator CP2, is connected through a resistor R49 to its positive input and also through resistor R50 to the 5V rail.Moreover, the output of comparator CP2. is connected to a rail 141. The resistors R45 to R43 function as a potential divider and supply a reference voltage to the positive input of comparators CP2,.
These resistors are selected so that the output of comparator CP21 goes high when the engine lubricant pressure falls to a value which is between its normal operational value and the value at which shut down must occur. Thus, a low signal on rail 141 provides an early warning that the engine lubricant pressure is falling to its shut down value and so gives an opportunity for the driver to take preventative action.
The rails 112 to 122 are associated with a set of comparators CP22 to CP32 and the connections associated with these comparators are similar to those associated with comparator Cup2. The outputs of comparators CP22 to CP32 are connected to rails 142 to 152. The resistors associated with comparators
CP22 to CP25 and CP28 and CP29 are selected so that the outputs of these comparators go high before the parameter being sensed reaches its shut down value so as to give an early warning. In the case of comparators CP26 and CP22, this is not possible and the signals on rails 146 and 147 go low when overspeed occurs.
The rails 141 to 152 together form the bus 33 which is connected to the memory and display circuit 34.
In the memory and display circuit 34 shown in
Figure 9, rail 141 is connected through a resistor R50 to the base of an NPN transistor T25, the emitter of which is connected to the 0V rail 91 and the collector of which is connected through a relay coil
W, to the 5V rail 98. The collector of transistor T20 is also connected through a resistor Roi to the base of an NPN transistor T2,, the emitter of which is connected to the 0V rail 91 and the collector of which is connected through a relay coil W2 to the 5V rail 98. Both coils W, and W2 are bridged by a pair of diodes.The relay coils W1 and W2 form part of a magnetic latching relay which also includes relay contacts CT1. The relay contacts CT1 have a pole which is connected to the 0V rail 91 and a pair of output contacts connected respectively to the base of transistor T2, and to a rail 160. When the coil W2 is energised, the contacts latch in a position in which the 0V rail 91 is connected to the base of transistor T2, and when the coil W, is energised they are latched into a position in which the 0V rail is connected to rail 160. The rail 160 is connected through a cable 161, a light emitting diode
D4, and resistor R62 to a rail 162. The rail 162 is connected through a resistor R63 and a diode D33 to the 5V rail 56.In operation, if a low signal is present on rail 141, transistor T20 is off, transistor T2, is on, energising relay coil W2 until CT latches turning transistor T2, off. Light emitting diode D41 is not energised. If the signal on rail 141 goes high, then transistor T2 is turned on, transistor T21 is turned off, relay coil W, is energised thereby energising the light emitting diode D41.
Each of the rails 142 to 152 is associated with a magnetic relay and the connections for these relays are the same as those described with reference to rail 141. The rails 142 to 152 are also connected to a set of light emitting diodes D42 to D52. The light emitting diodes D4, to D02 are positioned in one of the cabs 10 and together form a display for the driver.
The memory and display circuit 34 also includes an auxiliary power supply indicated at 170. In the auxiliary power supply 170, the 12V rail 90 is connected through a pair of resistors R60 and R66, and a diode D00to a rail 171. The rail 171 is connected through a resistor R67, fuse F2 and a nickel cadmium battery 172 to the 0V rail 91. The resistor R62 is a current limiter for intrinsil safety purposes. The rail 171 is also connected through a push button switch 173 to rail 162. Under normal operating circumstances, the battery 172 is trickle charged. In the event of engine shut down, the normal power supply to rail 162 is removed.However, under these circumstances the magnetic relay associated with the fault will be latched in its fault condition and so by depressing switch 173 the associated light emitting diode is energised thereby indicating the fault which has caused shut down. It is to be appreciated that the magnetic relays together provide a memory which is capable of operating at the low currents which are available in the present system and which maintain their latched condition even after the supply current has been removed.
The system checking circuit is shown in Figure 10 and includes a pair of type CD4017 decade counters 190 and 191, and a clock pulse generator 192. Each of the counters 190 and 191 has ten count outputs 0o to Qg and each of these outputs goes high in turn in ascending numerical order in response to clock pulses. The clock pulse generator
192 is formed from a type 555 timer configured to give a clock period of 0.5S and a clock pulse is supplied to the CLOCK input of counter 190. The
CLOCK INHIBIT input of counter 190 is connected to the 0V rail 91. The Q3 output of counter 190 is connected to the CLOCK input of counter 191. The
CLOCK INHIBIT and RESET inputs of counter 191 are connected to the OV rail 91.The Q5 to Qg out
puts of counter 191 are connected through respective resistors to the inputs of inverters 200 to 209, the outputs of which are connected by the bus 43 to the resistors R32 shown in Figure 7. The 0o output of counter 190 is connected through a resistor to the input of an inverter 193, the output of which is connected through a resistor to the 5V rail 96.
The output of inverter 193 is connected through respective resistors to the inputs of a set of inverters 210 to 219. The inverters 200 to 219 are type
ULM2001 inverters. The outputs of the inverters 210 to 219 are connected respectively to the inputs of counters 200 to 209 and the outputs of inverters 210 to 219 are also connected through respective
resistors to the 0V rail 91. The Q7 output counter
190 is connected to cable 35 which provides the
signal CROWBAR.The Q7 output of counter 190 is
also connected through a resistor R30 to the base of
an NPN transistor T30, the emitter of which is con
nected to the 0V rail 91 and the collector of which
is connected to rail 122 which, as shown in Figure
8, is connected through respective resistors to the
positive inputs of comparators Cup12 and CP32. The
RESET input of counter 190 is connected to the
collector of an NPN transistor T3" the emitter of
which is connected to the 0V rail 91. The collector
of transistor T3, is also connected through a resis
tor R22 to the 5V rail 96.The base of transistor T3, is
connected through a resistor R33 to the 0V rail and
through a further resistor R24 to rail 44 which re
ceives the signal CHECK from the solenoid drive
circuit 36.
During each normal cycle of operation, the
counter 190 is initially reset. The count then ad
vances and when the Q3 output goes high this
causes counter 191 to advance. When the Q5 out
put of counter 190 goes high, this causes the out
put of inverter 193 to go low and so the outputs of inverters 210 to 219 go open circuit. Consequently, the output of the one of inverters 200 to 209 which is associated with a high output of counter 191 goes low and this causes the output of one of comparators CPi to CP,O to go low, thereby causing the signal SHUTDOWN to go low, and also one of comparators CP2, to CP30 to go high, thereby causing one of the light emitting diodes D41 to D50 to be energised temporarily.As a result of the signal
SHUTDOWN going low, the signal CHECK goes low thereby resetting counter 190 and the cycle repeats.
However, if there is a fault in one of the comparators CP, to Cup,0 or in the solenoid drive circuit, the signal CHECK will not go low and so counter 190 is advanced until its Q3 output goes high. This causes the signal CROWBAR to go high thereby firing thyristor TH and causing shut down. A high signal on output Q7 will also cause a low signal on rail 122 thereby setting the magnetic relay associated with the comparator CP32 and in this way the origin of the fault which has caused shut down will be stored.
The overall operation of the system will now be described.
In order to start the engine, the solenoid 41 is mechanically held in its on position. After the engine has started, if a fault in the engine occurs, this will cause engine shut down. If a short circuit occurs in one of the sensors S, to S5 and S8 and Sg or in their associated leads, this will also cause a signal SHUTDOWN to go low and cause shut down. If an open circuit occurs in one of the sensors, this will be detected by comparator CP,2 and cause a shut down. Also, as just explained, if a fault occurs in one of the comparators CPi to Cup,0 or in the solenoid drive circuit, this will also cause shut down.
After shut down has occurred, one of the magnetic relays shown in Figure 9 will be latched and by depressing button 173 the fault which caused the shut down can be detected. If one of the parameters monitored by sensors S1 to So or So and Sg approaches a fault condition, the associated one of light emitting diodes D4, to D50 will be energised thereby providing an early warning. If a recovery is subsequently made, the light emitting diode is deenergised and shut down does not occur.
In a modification of the tachometer circuit shown in Figure 4, the rail 67 is connected to several outputs of bargraph generating circuits through a selector switch. The switch may then be operated so as to select the engine speed at which shut down occurs. A similar modification may be made to the speedometer circuit 21. Both the tachometer circuit 20 and the speedometer circuit 21 may also be modified so that shut down is caused when engine or vehicle acceleration or deceleration exceeds a predetermined rate.
Although the present invention has been described with reference to monitoring a diesel engine of a mine locomotive, the various aspects of the invention have a wider application. For example, the prebarrier circuit described in Figure 3 is suitable for use in any system for monitoring an engine operating in a hazardous area. The system checking circuit shown in Figure 10 is suitable for checking any monitoring system where a high degree of reliability is required and the arrangement of magnetic latching relay shown in Figure 9 is suitable for any monitoring system in which the power supply is removed after shut down has occurred.
This application is divided from application number 8323146.
Claims (6)
1. A monitoring system comprising a set of sensors, fault detecting means responsive to the sensors for providing a signal for controlling system shut down, a drive circuit for a solenoid operated element, said drive circuit having an input connected to the shut down control signal, and a system checking arrangement comprising means for temporarily applying a signal indicative of a fault condition to the output of each sensor in turn and means for checking that each time such a signal is applied to one of the sensors the output of the drive circuit assumes its shut down condition.
2. A system as claimed in Claim 1 further including means responsive to each sensor for detecting the occurrences of an open circuit fault.
3. A system as claimed in Claim 1 or Claim 2 in which the monitoring circuitry further includes a set of magnetic relays driven by the fault detecting means and a set of display elements responsive to the outputs of the magnetic relays.
4. A system as claimed in Claim 3 in which an auxiliary power supply is provided for the display elements.
5. A system as claimed in Claim 3 or Claim 4 in which the fault detecting means comprises two sets of comparators, each set of comparators including a comparator responsive to each of said sensors, the outputs of the first set of comparators being combined to provide the shut down control signal, and the outputs of the second set of comparators driving respective ones of said magnetic relays.
6. A system as claimed in any one of the preceding claims in which the monitoring system is a monitoring system for operating in a hazardous area and the solenoid operated element is a solenoid operated fuel valve which controls the supply of fuel to the engine.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08521242A GB2162671A (en) | 1983-08-27 | 1985-08-24 | Monitoring system |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08323146A GB2145858A (en) | 1983-08-27 | 1983-08-27 | Monitoring system |
| GB08521242A GB2162671A (en) | 1983-08-27 | 1985-08-24 | Monitoring system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8521242D0 GB8521242D0 (en) | 1985-10-02 |
| GB2162671A true GB2162671A (en) | 1986-02-05 |
Family
ID=26286805
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08521242A Withdrawn GB2162671A (en) | 1983-08-27 | 1985-08-24 | Monitoring system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2162671A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2240626B (en) * | 1990-01-31 | 1993-09-29 | Servo Corp Of America | Integrity test for acoustic bearing defect detector |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB961949A (en) * | 1959-12-03 | 1964-06-24 | Scully Signal Co | Method of and system for discriminating failures |
| GB1019004A (en) * | 1961-07-24 | 1966-02-02 | Siemens Ag | Safety device for reactors,chemical processes and the like with automatic control |
| GB1064945A (en) * | 1962-09-20 | 1967-04-12 | Honeywell Inc | Improvements in fuel burner control systems |
| GB1108258A (en) * | 1964-12-31 | 1968-04-03 | Kernforschung Gmbh Ges Fuer | Method and device for the supervision of an electrical control system, especially of a safety switching system of a nuclear reactor |
| GB1251510A (en) * | 1967-12-27 | 1971-10-27 | ||
| GB2054923A (en) * | 1979-06-30 | 1981-02-18 | Mather & Platt Alarms Ltd | Self-testing alarm systems |
| GB2086111A (en) * | 1980-10-23 | 1982-05-06 | Northern Eng Ind | Analogue Control Systems |
| GB2105504A (en) * | 1981-09-09 | 1983-03-23 | Merrick Scale Mfg Company | Coal pipe monitor |
-
1985
- 1985-08-24 GB GB08521242A patent/GB2162671A/en not_active Withdrawn
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB961949A (en) * | 1959-12-03 | 1964-06-24 | Scully Signal Co | Method of and system for discriminating failures |
| GB1019004A (en) * | 1961-07-24 | 1966-02-02 | Siemens Ag | Safety device for reactors,chemical processes and the like with automatic control |
| GB1064945A (en) * | 1962-09-20 | 1967-04-12 | Honeywell Inc | Improvements in fuel burner control systems |
| GB1108258A (en) * | 1964-12-31 | 1968-04-03 | Kernforschung Gmbh Ges Fuer | Method and device for the supervision of an electrical control system, especially of a safety switching system of a nuclear reactor |
| GB1251510A (en) * | 1967-12-27 | 1971-10-27 | ||
| GB2054923A (en) * | 1979-06-30 | 1981-02-18 | Mather & Platt Alarms Ltd | Self-testing alarm systems |
| GB2086111A (en) * | 1980-10-23 | 1982-05-06 | Northern Eng Ind | Analogue Control Systems |
| GB2105504A (en) * | 1981-09-09 | 1983-03-23 | Merrick Scale Mfg Company | Coal pipe monitor |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2240626B (en) * | 1990-01-31 | 1993-09-29 | Servo Corp Of America | Integrity test for acoustic bearing defect detector |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8521242D0 (en) | 1985-10-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |