ENGINE PARAMETER MONITORING SYSTEM

Abstract: System for monitoring an engine operating parameter, such as oil pressure, which varies in proportion to engine speed, monitors the parameter relative to an upper and lower setpoint. Oil pressure is sensed by a transducer (122) and the sensed pressure is monitored by a pair of comparators (252, 266) which compare the sensed oil pressure with reference voltages corresponding to the upper and lower setpoints. The reference voltages may be selectively altered by a switch (124) in order to change the pressure setpoints. The outputs of the comparators (252, 266) control an annunciator (16) which indicates when the monitored pressure is below either of the setpoints. A circuit (75) is provided to inhibit operation of the annunciator (16) by the comparators (252) monitoring pressure relative to the uper setpoint when the engine's speed is below a predetermined value. The output of the comparator (266) monitoring pressure relative to the lower setpoint controls a service-hour meter (18) to provide an indication of the total elapsed time that the engine is running.

Description: Description Engine Parameter Monitoring System Technical Field The present invention broadly relates to vehicle monitoring systems, and deals more particularly with a device implemented method for monitoring oil pressure in an engine having pressurized, oil lubrication system. Background Art Various types of systems have been de¬ vised in the past for monitoring the oil pressure of a vehicle's engine. Earlier types of monitoring devices consisted of a pressure operated, mechanical switch which controlled an alarm, such as a warning light, when the oil pressure was outside a particular range being monitored. More recently, computerized systems have been resorted to for monitoring oil pressure as evidenced by U.S. Patent No. 3,964,018 issued on June 15, 1976 to Strait et al. The system disclosed in this prior patent provides for mon¬ itoring the condition of a plurality of vehicle sensors for oil, water, temperature and the like. This system compares a sensed parameter, such as oil pressure, with a particular range of values stored in a memory and activates an alarm if the sensed parameter is outside the normal operating range. One problem which is unique to mon¬ itoring oil pressure involves the fact that the pressure varies in proportion to engine speed, particularly at the lower speed ranges. Conse- quently, some problems which occur in a pressurized oil lubrication system are unique to specific ranges of engine speeds. For example, a clogged oil filter can be detected at higher engine speeds when oil pressure is at a relatively high level but .cpl5 cannot be detected at near idle speed when the oil pressure is relatively low. Disclosure of the Invention The present invention overcomes the disadvantages of prior art monitoring systems by monitoring oil pressure relative to an upper and lower setpoint. In accordance with one aspect of the invention, the speed of the engine is sensed using a circuit which measures the frequency of the vehicle's electrical alternator which is driven by the engine. An oil pressure transducer delivers an analog signal proportional to oil pressure to a pair of comparators each adapted for comparing the magnitude of the signal with first and second reference voltages respectively corres¬ ponding to the upper and lower setpoints. The upper and lower setpoints respectively correspond to the lowest values of oil pressure which are normal for an upper and lower range of engine speed. A pair of control circuits deliver output signals from the comparators to an annunicator which provides a warning indication when the sensed oil pressure is below either the upper or lower setpoint. The annunciator is activated at any time the sensed pressure is below the lower setpoint, however, a logic circuit inhibits acti¬ vation of the annunciator in response to the sensed pressure being less than the upper setpoint until engine speed reaches a predetermined level, which is normally well above idle speed. The OMPI upper and lower setpoints may be conveniently altered by a programmable input which changes the reference voltages associated with each of the comparators. The logic circuit includes a counter for counting pulses proportional to the frequency of the alternator and produces a control signal which enables the annunciator to be activated in response to the sensed pressure falling below the upper setpoint when engine speed has reached the preselected value. The output of the comparator monitoring the oil pressure relative to the lower setpoint enables a service-hour meter in order to record the elapsed time that the engine is running . In accordance with another aspect of the invention a novel method of monitoring oil pressure is provided which comprises the steps of sensing the speed of the engine, monitoring oil pressure relative to first and second preselected setpoints, providing a warning in response to the monitored oil pressure being less than the upper setpoint and the sensed engine speed being greater than a preselected value. Brief Description of the Drawings FIGURE 1 is a block diagram of an engine parameter monitoring system which forms the preferred embodiment of the present invention; FIGURE 2 is a detailed schematic diagram of the preferred form of the oil pressure sensor shown in FIGURE 1; FIGURE 3 is a detailed schematic diagram of alternate form of the oil pressure sensor shown in FIGURE 1; and, FIGURE 4 is a detailed schematic diagram of the logic circuit shown in FIGURE 1. Best Mode For Carrying Out The Invention Referring first to FIGURE 1, the present invention is broadly concerned with a system for monitoring an operating parameter of an engine which varies in accordance with the speed of the engine, and in connection with the illustrated embodiment the system is particularly adapted to monitor oil pressure in a vehicle engine having a pressurized oil lubrication system. The system includes an oil pressure sensor 10 having program¬ mable inputs 20 which allow the sensor 10 to monitor oil pressure relative to a lower preselected setpoint normally associated with engine idle speed, and an upper preselected set- point normally associated with above idle speed. The speed of the engine is sensed by a sensing means 13 which includes a conventional alternator 14 driven by the engine to produce an alternating electrical current. The alternator 14 delivers an alternating signal on line 14a to a logic circuit 12, which signal has a frequency proportional to the speed of the engine. The logic circuit 12 also receives signals on lines 110 and 114 from the oil pressure sensor 10. When the sensed engine oil pressure is at least as great as the lower setpoint, the signal present on the line 110 is operative to energize an elapsed time recorder 18 which records the elapsed time that the engine is running. In the event that the sensed oil pressure is below the lower setpoint, a signal is delivered on the line 110 to the logic circuit 12 which in turn activates an annunciator 16 which may take the form of an audible or visual alarm. The oil pressure sensor 10 continuously monitors oil pressure relative to the lower setpoint and, in -^- E ^ OMPI - IPO combination with the logic circuit 12, activates the annunciator 16 when the monitored pressure falls below the lower setpoint, regardless of the speed of the engine. The oil pressure sensor 10 also con¬ tinuously monitors the oil pressure relative- to the upper setpoint and delivers a signal on the line 114 to the logic circuit 12 when the mon¬ itored pressure falls below the upper setpoint. If the sensed engine speed is above a preselected value, normally well above idle speed, the logic circuit 12 activates the annunciator 16 when the monitored oil pressure is below the upper set point. However, the logic circuit 12 prevents activation of the annunciator 16 when the sensed engine speed is less than the preselected value, even though a signal is delivered on the line 114 from the oil pressure sensor 10 indicating that the monitored oil pressure is below the upper set point. Attention is now directed to FIGURE 2 wherein the preferred form of the oil pressure sensor 10 is shown in more detail. An essentially conventional oil pressure transducer 122 coupled with the vehicle's oil pressure system outputs an analog signal on line 260 which is proportional to the sensed oil pressure. Positive supply voltage is delivered through resistor 254 to the negative input 251 of a comparator 252 and to the negative input 255 of a comparator 266 via resistor 264, while the analog signal on the line 260 is de¬ livered to the positive (non-inverting) input of the comparator 252 via resistor 256 as well as to the positive (non-inverting) input 259 of the comparator 266 through resistor 262. As will be¬ come apparent hereinafter, the comparator 252 compares the magnitude of the signal present on the line 260 with a reference voltage corres¬ ponding to an upper setpoint for the oil pressure, while the comparator 266 compares the magnitude of the signal on the line 260 with a reference voltage corresponding to -a lower setpoint for the oil pressure. The negative input of the comparator 252 is coupled through the resistor 254 to power supply voltage, and by line 250 to the program¬ mable input 124. The programmable input 124 in¬ cludes a pair of comparators 224 and 236. The output of the comparator 224 is connected through a resistor 246 and the line 250 to the negative input 251 of the comparator 252 as well as to ground via the resistor 249. The output of the comparator 236 is coupled through the resistor 248 to the negative input 255 of the comparator 266. Additionally the negative input 255 is connected to ground by the resistor 268. The negative input of the comparator 224 is connected via line 230 to the negative input of the comparator 236 as well as to ground via resistor 228. The negative input of the comparator 236 is connected to a positive supply of voltage through resistor 238 and line 240. The positive input of the comparator 224 is connected to a positive supply voltage through resistors 226,244 and the line 240. The program¬ mable input 124 is connected between the resistors 226 and 244 which may include a switch, wiring harness or the like (not shown) to ground or float the input 124. The positive inputs of the comparators 236 and 224 are coupled to each other via line 126 and to the programmable input 124 through the resistor 226. It may therefore be appreciated that selectively grounding the programmable input O PI 124 will alter the reference voltage applied to the positive inputs of the comparators 224 and 236. By changing the reference voltage, the operating points of the comparators 224 and 236 are conveniently altered thereby to adjust the bias delivered to the negative inputs 251,255 of the comparators 252 and 266 respectively. Means 277 comprising resistors 276 and 278 are provided for altering the voltage applied to the positive (non-inverting) input of the com¬ parator 252 when the output 253 thereof goes high. The resistors 276, 278 are connected from the positive supply voltage to the positive input of the comparator 252. Similarly, means comprising resistors 270 are provided for altering the voltage applied to the positive (non-inverting) input of the comparator 266 when the output 261 goes high. The resistors 246, 249 and 254 form a voltage divider network at the negative (inverting) input 251 of the comparator 252. Similarly, the resistors 248, 264 and 268 will form a voltage divider network at the negative (inverting) input 255 of the comparator 266. A positive supply of voltage to the oil pressure sensor 10 is provided by a voltage regu¬ lator which comprises capacitor 294, resistor 292, transistor 290, and zener diode 286. The logic circuit 12 referred to earlier with respect to FIGURE 1 includes means generally indicated within the broken line 79 in FIGURES 2 and 4, for generating warning signals when the monitored pressure is less than the upper or lower setpoints, using control signals output from the comparators 252 and 266. The generating means 79 includes a first portion comprising the transis¬ tors 214 and 284. The base of the transistor 284 -^- E ^ O PI is connected to the output of the comparator 252 through the resistor 282 as well as to a positive supply of voltage through the resistor 278. The collector of the transistor 284 is also connected to the positive voltage source through the resis¬ tor 280, while the emitter thereof is connected to . ground via the- resistor 296 and the diodes 298 as well as to the base of the transistor 214. The - - emitter of the transistor 214 is connected to ground through the resistor 300 while the collector thereof is connected via line 114 to the input of an inverter 116 (FIGURE 4). Another portion of the generating means 79 includes the transistors 208 and 274. The base of the transis- tor 274 is connected through a diode 272 to the output of the comparator 266 and to a positive supply voltage via the resistors 270 and 271. The collector of the transistor 274 is connected to the positive voltage source through the resistor 326 while the emitter thereof is connected to ground through the resistor 302 and the diode 304 as well as to the base of the transistor 208. The emitter of the transistor 208 is connected to ground through the resistor 306 while the collector thereof is coupled via the line 110 to the input of the inverter 112 (FIGURE 4). A high signal output from the comparator 266 turns on transistors 274 and 208 to produce a signal on line 110. The signal on the line 110 is inverted by inverter 112 and delivered through OR gate 94 to the reset inputs of a bank of intercon¬ nected flip-flops 86-92, the output of which on line 118 is delivered through OR gates 82 and 78 to the annunciator 16. Similarly, the signal output from the comparator 252 turns on the transistors 284 and 214 to deliver a signal on line 114 which is inverted through inverter 116 OMPI and then delivered via OR gate 108 to the reset inputs of a bank of interconnected flip-flops 100- 106. The Q output of flip-flop 106 is delivered via line 120 to one input of an AND gate 76 whose purpose will be discussed later in more detail. The output of the AND gate 76 is delivered through the OR gate 78 to the annunciator 16. The output of the comparator 266 is de¬ livered through diode 308 to the elapsed time indicator 18. The elapsed time indicator broadly comprises transistors 310, 312 and 314, as well as resistors 316, 318, 320, 324, 325 and thermistor 322, and delivers an energizing signal to a con¬ ventional service-hour meter 311. Referring now particularly to FIGURE 4, means for selectively inhibiting the delivery of the signal on the line 120 to the annunciator 16 is generally indicated within the broken line 75 and includes the AND gate 76. A second input to the AND gate 76 is delivered on line 74 from a logic circuit generally indicated at 77. The alternator 14 delivers a signal on the line 14a to the input of the inhibiting means 75 which pro¬ duces and delivers a control signal to the AND gate 76 when the engine has reached a predeter¬ mined value at which the annunciator is to be activated in the event that the monitored pressure falls below the upper setpoint. The signals on the line 14a have a frequency proportional to engine speed. The line 14a forms one input to an AND gate 28, a second input thereto being formed by line 30 which is adapted to be coupled with a suitable source of clock signals such as that derived from a conventional oscillator (not shown). The signals on the line 14a are therefore clocked through the gate 28 in accordance with the frequency of clock signals on the line 30 to the clock input of a conventional ripple counter 36. The reset input of the counter 36 is reset by clock signals derived on the lines 30 and 32 which are inverted by inverter 34. The Q1-Q7 outputs of the counter 36 are connected by AND gates 38, 40 and 44 as well as OR gate 42 to the clock inputs of flip-flops 50 and 54. The Q outputs of the flip-flops 50, 54 are in turn connected to the D inputs of the flip-flops 52 and 56. The inverted clock signals derived from the line 32 are delayed by AND gates 46 and 48 and employed to reset the flip-flops 50 and 54. The inverted clock signals are also delivered via the line 47 to the clock inputs of the flip-flops 52, 56. The counter 36 is operative to count the number of pulses corresponding to the frequency of the signal on the line 14a. The gates 38-44, in combination with the counter 36 and the flip-flops 50-56 produce a high signal on line 58 when the frequency of the signal on the line 14a reaches a prescribed value at which the annunciator 16 is to be activated in response to a signal present on line 120. The frequency at which such monitoring takes place may be conveniently altered by means of a switch 24 which is connected between the line 22 and ground. The signal on the line 22 is inverted by inverter 26 and delivered to one input of the AND gate 40. It may therefore be appreciated that a high output signal from the AND gate 40 is provided only when a high signal is delivered from the inverter 26, which in turn is determined by the position of the frequency selec¬ tion switch 24. The control signal on the line 58 is delivered through an OR gate 60 to the reset inputs of a bank of interconnected flip-flops 62- - • fc TkHAi OMPI 72 which function to introduce a time delay in the processing of the signal; this time delay avoids false activation of the annunciator 16. The Q output of the flip-flop 72 is connected through line 74 to the second input of the AND gate 76. It may therefore be appreciated that a high signal is output from the AND gate 76 only when the Q outputs of the flip-flops 72 and 106 are high at the same time. The above mentioned circuits are reset by means of a reset signal on the line 96 which is inverted by the inverter 98 and delivered through the OR gates 60, 94 and 108. Attention is now directed to FIGURE 3 wherein an alternate form of the oil pressure sensor 10 is depicted. The program input 124 is connected via the lines 126 and 128 respectively to the NAND gates 130 and 134. The output of the NAND gate 130 is connected to the inputs of the AND gates 132 and 138, while the output of the NAND gate 134 is connected to the second input of the AND gate 132 as well as to one input of the AND gate 136. The second input of the AND gate 136 is coupled to the line 126 while the second input to the AND gate 138 is connected to the line 128. The inputs to the AND gate 140 are respec¬ tively connected to the lines 126 and 128. The outputs of the AND gates 132-140 are respectively connected to the inputs of the AND gates 172-178, a second input to the gates 172-178 being formed by the outputs of the comparators 160-166. The negative terminals of the comparators 160-166, as well as the negative terminals of the latter dis¬ cussed comparators 168 and 170 are connected to an output of the oil pressure transducer 122. The positive inputs to the comparators 160-170 are connected through the respectively associated variable resistors 150-158 to a positive supply voltage. The outputs of the AND gates 132-138 are connected to the inputs of an OR gate 180 whose output is in turn coupled to the input of the NAND gate 182, a second input to the NAND gate 182 being formed from the output of the comparator 168. The output of the AND gate 140 is connected to one input of the NAND gate 184, a second input thereto being formed from the output of the com¬ parator 170. The outputs of the AND gates 172-178 form the inputs of the OR gate 196 whose output is connected to the base of the transistor 202, the colleσtor-to-emitter path thereof being coupled across a positive supply voltage. The emitter of the transistor 202 is coupled through the diode 212 to the base of the transistor 214, the emitter of the transistor 214 being connected to ground while the collector thereof is coupled through the thermistor 216 and the line 114. The outputs of the NAND gates 182 and 184 are respectively coupled through the diodes 186 and 188 as well as the resistor 190 to the base of the transistor 192. The transistor 192 drives the base of the transistor 208 whose collector is coupled through the thermistor 210 to the line 110. O PI Industrial Applicability Referring now particularly to FIGURES 1, 2 and 4, in operation of the apparatus, the pro¬ gram input 124 is either grounded or allowed to float either by actuating a switch, selectively coupling the pins of a wiring harness, or the like, in order to select between two sets of upper and lower setpoints. Similarly, the switch 24 is actuated to either its open or closed position thereby selecting one of two frequencies at which monitoring of the upper setpoint takes place. Assuming that the programming input 124 is grounded, the positive (non-inverting) inputs of the comparators 224 and 236 are likewise grounded and the negative (inverting) inputs thereof are connected to the positive voltage source through a voltage divider comprising the resistors 228 and 238; consequently, the output of the comparator 224 goes low, thereby sinking cur- rent from the positive voltage source through the resistors 246, 249 and 254. Similarly, the output of the comparator 236 sinks current from the posi¬ tive voltage source through the resistors 248, 264 and 268. If, however, the programming input 124 is allowed to float, the positive inputs to the op amps 224 and 236 are connected to the positive voltage source and their respective outputs go high, thereby removing the resistors 246 and 248 from their corresponding voltage dividers net¬ works, thus changing the reference voltages applied to the negative inputs of comparators 252 and 266. The comparators 252 and 266 receive an analog signal on their positive inputs from the oil pressure transducer 122 through the resistors O PI WIPO 256 and 262 respectively. The output of the com¬ parator 252 is low when the sensed oil pressure is less than the upper point, thereby sinking cur¬ rent from the positive voltage source through the resistor 278, consequently, the transistor 284 is biased off, which in turn turns off the transis¬ tor 214, producing a high signal on the line 114. The signal on the line 114 is delivered through the inverter 116 and the OR gate 108 to the reset inputs of the flip-flops 100-106. The flip-flops 100-106 are not reset by the low signal and a high signal is delivered from the Q output of the flip- flop 106 to one input of the AND gate 76 via the line 120. If a high signal is present on the line 74 (indicating that the engine has reached the speed at which monitoring relative to the upper set point is to commence), a high signal is output from the gate 76 and delivered through the OR gate 78 to the annunciator 16, thereby providing a warning that the monitored pressure is below the upper setpoint. If, however, the engine speed has not reached the value at which monitoring relative to the upper setpoint is to commence, the line 74 is low thus preventing the signal on the line 120 from being gated through the AND gate 76. When the sensed oil pressure rises above the upper setpoint, resulting in the analog voltage present on the line 260 exceeding the reference voltage and the negative input of the comparator 252, the output of the comparator 252 goes high; this high signal turns on the transis¬ tor 284. Upon output of a high signal from the comparator 252, an additional amount of current is supplied from the positive voltage source to the positive input of the comparator 252 through a feedback loop defined by the resistors 276 and * 4 278, thus increasing the voltage applied to this input. Effectively, the additional voltage applied through the feedback loop to the positive input of the comparator 252 results in a hysteresis type effect such that the analog voltage on line 260 corresponding to oil pressure must decrease to a level less than the normal reference voltage present on the negative input 251 of the comparator 252 by an amount equivalent to the voltage added by the positive voltage source and resistors 276 and 278 to cause the output 253 to go low. For example, the output 253 of the comparator 252 will go low when the sensed oil pressure falls below 30 PSI but thereafter will not go high until the sensed oil pressure reaches 35 PSI. When the analog signal on the line 260 delivered to the positive input of the comparator 266 exceeds the reference voltage on the negative input 255, the output 261 of the comparator 266 goes high. At this time, the sensed oil pressure is at least as great as the lower setpoint. The high signal at the output 261 of the comparator 266 turns off the diode 272 applying positive supply voltage to the base of transistor 274, thereby turning on the transistor 274 which in turn turns on the transistor 208. When the transistor 208 is on, current flows from the collector-to-emitter path thereof, to produce a low signal on line 110 which is delivered through the inverter 112, thereby producing a high signal. This high signal is delivered through OR gate 94 to the reset inputs of the flip-flops 86-92 which function as a signal time delay. When the reset inputs of the flip-flops 86-92 are 'high, the signal delivered to the annunciator 16 via the Q output of flip-flop 92, the line 118 and the OR O PI " £RNA1\0 gates 82 and 78 is likewise low, consequently, the annunciator 16 is disabled. When, however, the analog signal present on the line 260 falls below the reference value at the negative input 255 of the comparator 266, the transistors 274 and 208 are turned off; the resulting signal output from the inverter 112 is low and this low signal is delivered through the OR gate 94 to the resets of flip-flops 86-92. The low signal does not reset the flip-flops 86-92 and consequently a high signal is delivered through the OR gate 82, the line 83 and the OR gate 78 to the annunciator 16, thereby enabling the latter and providing a warning that the sensed oil pres- sure has dropped below the lower setpoint. When the output 261 of the comparator 266 goes high, additional current is supplied to the positive input 259 thereof from the positive supply voltage via the resistors 270; this addi- tional voltage applied to the positive input 259 effectively augments the voltage supplied by the oil pressure transducer 122 on the line 260 resulting in a hysteresis type effect similar to that previously described with reference to com- parator 252. The output 261 of the comparator 266 will not thereafter go low until the augmented voltage present on the positive input 259 falls below the reference voltage at the negative input 255. When the sensed oil pressure falls below the lower setpoint, the output 261 goes low sinking current from the positive voltage source through one of the resistors 270, thereby turning on the diodes 272 and 308 causing the transistor 274 to be turned off. With the transistor 274 off, the current flowing through one of the resistors 270 connected in feedback relationship to the com- parator 266 is reversed from the positive input of the comparator 266. With this additional voltage having been removed from the positive input 259, the analog voltage present on the line 260 must reach a higher level in order to cause the output 261 of the comparator 266 to go high, compared to the level required to cause the output 261 to go low. For example, when the sensed oil pressure falls below 9 PSI, the output 261 will go low but will not subsequently go high until the sensed oil pressure reaches 13 PSI. The signal output by the comparator 266 is also delivered through the diode 308 to the transistors 310, 312 and 314, thereby rendering each of the latter conductive and permitting cur¬ rent to flow through the thermistor 322 and the service-hour meter 311. The comparator 266 moni¬ tors the oil pressure relative to the lower set¬ point regardless of the speed of the engine. As previously indicated, the engine speed at which monitoring relative to the upper setpoint commences is determined by the position of the frequency selection switch 24. Assuming that the switch 24 has been positioned to select the appropriate frequency, the inhibiting means 75 is conditioned to deliver a control signal to the AND gate 76 via the line 74 when the engine speed has reached a predetermined value. The signal present on the line 14a which has a frequency proportional to the speed of the engine is gated by the clock signal present on the line 30 through the AND gate 28 to the clock input of the ripple counter 36. The counter 36 counts the number of pulses received from the AND gate 28 and delivers output signals on the Ql , Q3, Q5-Q7 outputs thereof to a plurality of logic gates generally indicated by the numeral 39. When the count of the counter 36 reaches a prescribed value, the output of the logic gates 39 is processed by the flip-flops 50-56 which deliver a high signal on line 58. The high signal on the line 58 passes through the OR gate 60 causing the flip-flops 62- 72 to generate the high signal on line 74. Assuming that a high signal is present on the line 120, the high signal on the line 74 results in a high output being delivered from the AND gate 76 to the annunciator 16, thereby activating the latter . The circuit described previously with reference to FIGURE 3 functions essentially identical to that shown in FIGURE 2. The program input 124 is employed to program the upper and lower setpoints while the variable resistors 150- 158 determine the particular value at which signal is output from the corresponding op amps 160-170. The lower setpoint is monitored by the °P amps 168 and 170. The value of the analog signal present on the line 123 from the oil pres¬ sure transducer 122 is compared with a reference value determined by the settings of the variable resistors 157 and 158. In the event that the pressure is below the lower setpoint, a signal is delivered either from the op amp 168 or 170 to the associated NAND gate 182 or 184; this latter men¬ tioned signal turns on the transistors 192 and 208 to deliver a signal on the line 110 which results in the activation of the annunciator 16 as pre¬ viously discussed. The comparators 160-166 likewise compare the magnitude of the analog signal on the line 123 with a reference value determined by the setting of the variable resistors 150-156. When the sensed pressure falls below the upper setpoint, a - SZ JLd O PI signal is output from the corresponding comparator 160-166 and is gated through the associated gate 172-178 and through the OR gate 196, thereby turning off the transistor 202 and turning on the transistor 214 which results in a signal being delivered on the line 114 to the inverter 116. A description of the operation of the ap¬ paratus will now be provided in connection with the monitoring of the oil pressure in a pressurized oil lubrication system for an internal combustion engine. When the sensed engine speed is below the lower setpoint, a warning signal is produced which energizes the annunciator 16. For example, assuming an operator initiates a normal engine starting procedure by turning on an igni¬ tion switch. The engine is stopped and the annunciator 16 is activated indicating that the oil pressure is below the lower setpoint. When the engine is started, the annunciator remains activated until the sensed oil pressure rises above the lower setpoint, which, for illustrative purposes, may be 13 PSI. If at any time the sensed oil pressure falls below the hysteresis affected lower setpoint, which for example may be approximately 9 PSI, the annunciator 16 is re¬ activated. Once the engine speed exceeds the pre¬ selected value determined by switch 24, the apparatus is operative to monitor the oil pres¬ sure relative to the upper set point, which may be by way of example 30 PSI. Assuming that the engine speed is above the preselected value, the annunciator 16 is activated when the oil pressure falls below 30 PSI and is not deactivated until the sensed pressure rises above the hysteresis affected upper setpoint of 35 PSI. Even though engine speed exceeds the preselected value, mon¬ itoring of engine oil pressure relative to the lower setpoint continues as a fail safe precau¬ tion. The monitoring system of the present invention is well adapted for monitoring various engine operating parameters which vary in a pre¬ scribed manner relative to the speed of the engine. The monitoring system may be employed in connection with motorized vehicles as well as other applications for engines, such as those used to drive stationary electrical generators for example . While the present invention has been described in connection with a particular example thereof, various modifications will become apparent to those skilled in the art. Other aspects, objects and advantages of the invention may be obtained from a study of the drawings, the disclosure and the appended claims. OMPI

Claims: Clai s 1. In a system for monitoring oil pres¬ sure which varies in acco.rdance with the speed of an engine, the improvement comprising: first means (122) for sensing said oil pressure of said engine and" del ivering a first signal in response to said sensed, .oil pressure; second means (266) for comparing said first signal to a first preselected setpoint and delivering a first warning signal in response to said first signal being less than said first setpoint; third means (252) for comparing said first signal to a second preselected setpoint and delivering a second warning signal in response to said first signal being less than said second setpoint; and, fourth means (255) for deactivating said first and second warning signals in response to said first signal being greater than third and fourth preselected setpoints, respectively. 2. A system, as set forth in claim 1, including fifth means (13) for sensing the speed of said engine, comparing said sensed speed to a fifth setpoint and delivering a second signal in response to said sensed speed being less than said fifth setpoint; and, sixth means (75) for blocking said first warning signal in response to receiving said second signal. 3. A system, as set forth in claim 1, including seventh means (20) for adjusting the values of said first, second, third, and fourth preselected setpoints. 4. A system, as set forth in claim 2, wherein said fifth setpoint is adjustable to a plurality of different values. 5. In a system for monitoring an operating parameter of an engine which varies in accordance with the speed of said engine, the improvement comprising: first means (13) for sensing the speed of said engine; second means (252) for monitoring said parameter relative to a first preselected value and delivering a first warning signal in response to said parameter being less than said first pre¬ selected value; and third means (266) for monitoring said parameter relative to a second preselected value and delivering a second warning signal in response to said parameter being less than said second preselected value; and, fourth means (75) for blocking the delivery of said first warning signal in response to the sensed engine speed being less than a third preselected value. 6. A system as set forth in Claim 5, including fifth means (79) for delivering a control signal in response to either said first or second warning signals. 7. A system as set forth in claim 6, including an annunciator (16) for providing a -gtRE OMPI warning indication in response to the delivery of said control signal. 8. A system as set forth in claim 6, wherein said fifth means (79) includes a logic gate (78) having a first input (83) connected to said second means (266), a second input (85) con¬ nected to said fourth means (75), and an output (15) for delivering said control signal. 9. A system as set forth in claim 5, wherein said fourth means (75) includes a logic gate (76) having at least one input connected to said second means for receiving said first warning signal . 10. A system as set forth in claim 9, wherein said first means (13) includes means (14) for generating an alternating electrical signal having a frequency proportional to the speed of said engine and said fourth means (75) includes means (36) for counting the frequency of said alternating electrical signal. 11. A system as set forth in claim 10, wherein said fourth means (75) includes: means (30) for producing timing signals; and means (28) for gating said timing signals to said counting means (36) in accordance with the frequency of said alternating electrical signal. 12. A system as set forth in claim 10, wherein said fourth means (75) includes logic means (39) for outputting an enabling signal when the count in said counting means (36) reaches a magnitude corresponding to said third preselected value, said logic means (39) being connected bet¬ ween said logic gate (76) and said counting means (36). 13. A system as set forth in claim 5, including means (24) for altering said third pre- selected value. 14. A system as set forth in claim 5, including fifth means (22) for sensing the magni¬ tude of said engine parameter and generating a third signal proportional in value to said engine parameter. 15. A system as set forth in claim 14, including sixth means (20) for altering said first and second preselected values. 16. A system as set forth in claim 15, o wherein said second and third means (252,266) each include a comparator having a first input connected to said fifth means (122). 17. A system as set forth in claim 16, wherein said sixth means (20) includes a pair of 5 operational amplifiers (224,236) each having a programmable input (124), each of said operational amplifiers (224,226) having an output (250), each of said comparators (252,266) having a second input (253,255) connected to the output (250) of 0 each of said operational amplifiers (224,226). 18. A system as set forth in claim 5, including: fifth means (277) for altering said first preselected value in response to said parameter exceeding said preselected value; and sixth means (270) for altering said second preselected value in response to said par¬ ameter exceeding said second preselected value. 19. A system as set forth in claim 18, wherein : said second and third means (252,266) respectively include a comparator having an input (253,259) and an output (253,261), said fifth means includes a resistor (276) connected between the corresponding input (257) and output (253), and said sixth means (270) includes a resistor (270) connected between the corresponding input (259) and output (261). 20. Apparatus for monitoring operating parameters of a vehicle provided with an engine having a pressurized oil lubrication system, com¬ prising: first means (122) for sensing the oil pressure in said lubrication system and producing a first signal having a magnitude proportional to the magnitude of the sensed pressure; second means (13) for sensing the speed of said engine and producing a second signal which varies in accordance with the sensed speed; third means (266) for monitoring the value of the sensed oil pressure relative to a first preselected value and producing a third signal in response to the monitored value being less than said first preselected value; fourth means (252) for monitoring the value of the sensed oil pressure relative to second preselected value and producing a fourth signal in response to the monitored value being less than said second preselected value; fifth means (16) for generating an alarm in response to receipt of either of said third or fourth signals; and sixth means (75) for preventing receipt of said fourth signal by said fifth means in response to said second signal being less than a third preselected value. 21. Apparatus as set forth in claim 20, wherein said second means (13) includes means (14) for producing an alternating electrical current. 22. Apparatus as set forth in claim 20, wh.erein said third means " (266) includes a comparator for comparing the magnitude of said first signal with said first preselected value. 23. Apparatus as set forth in claim 22, wherein said fourth means (252) a comparator for comparing the magnitude of said first signal with said second preselected value. 24. Apparatus as set forth in claim 23, including seventh means (20) for altering said first and second preselected values. 25. Apparatus as set forth in claim 20, wherein said sixth means (75) includes: first logic means (77) for delivering a control signal in response to said second signal; and second logic means (76) for gating said fourth signal to said fifth means in response to delivery of said control signal. 26. Apparatus as set forth in claim 20, including seventh means (18) for recording the elapsed time during which said engine is running. 27. Apparatus as set forth in claim 26, wherein said seventh means (18) includes a service-hour meter (311) and circuit means (310,312,314,322) for delivering a control signal to said service-hour meter (311). 28. Apparatus for monitoring the oil pressure in an engine having a pressurized oil lubrication system, comprising: first means (14,14a) for sensing the speed of said engine; second means (122) for sensing the oil pressure in said lubrication system and delivering a first signal proportional to the magnitude of the sensed pressure; a first comparator (266) for comparing the magnitude of said first signal with a first reference value corresponding to a first oil pres¬ sure level and delivering a second signal in response to the magnitude of said first signal being greater than the value of said first reference value; «< gTREAlr O PI a second comparator (252) for comparing the magnitude of said first signal with a second reference value corresponding to a second oil pressure level and delivering a third signal in response to the magnitude of said first signal being greater than the value of said second reference value; an annunciator (16) for providing an alarm when the sensed oil pressure is less than at 0 least one of said first or second oil pressure levels; a first circuit (274, 208, 110, 112, 86, 88, 90, 92, 118, 82, 83) for delivering a first control signal to said annunciator (16) in 5 response to delivery of said second signal; a second circuit (284, 214, 114, 116, 100, 102, 85, 104, 106, 120), for delivering a second control signal to said annunciator (16) in response to delivery of said third signal; and o third means (75) for inhibiting the delivery of said signal to said annunciator (16) in response to the sensed engine speed being less than a predetermined value. 29. Apparatus as set forth in claim 28, 5 wherein: said first means (14) includes an electrical alternator, and said second means (122) includes a pres¬ sure transducer. 0 30. Apparatus as set forth in claim 28, including fourth means (20) for altering said first and second reference values. - !J E OMPI 31. Apparatus as set forth in claim 28, wherein said third means (75) includes a logic gate (76) having an output (86) connected to said annunciator (16) and an input (120) connected to said second circuit (284, 214, 114, 117, 100, 102, 104, 106, 85, 102). 32. A method of monitoring the oil pressure in an engine having a pressurized oil lubrication system, comprising the steps of: (A) sensing the speed of said engine; (B) monitoring the oil pressure in said lubrication system relative to a first preselected setpoint; (C) monitoring said oil pressure rela¬ tive to a second preselected setpoint; (D) providing a warning in response to the oil pressure monitored in step (B) being less than said first preselected setpoint; (E) providing a warning only in response to the oil pressure monitored in step (C) being less than said second preselected setpoint and the speed sensed in step (A) being greater than a third preselected setpoint. 33. A method, as set forth in claim 32, wherein steps (B) and (C) each include the sub- steps of: producing a first signal proportional to the magnitude of said oil pressure, and comparing the magnitude of said first signal with the value of a reference signal corresponding to the associated setpoint. -gJRE O PI _ WIPO 34. A method, as set forth in claim 32, wherein step (A) includes the substep of genera¬ ting an alternating electrical signal having a frequency proportional to the speed of said 5. engine. 35. A method, as set forth in claim 32, wherein steps (B) and (C) are performed concurrently. 36. A method as set forth in claim 32, 0 wherein step (D) is performed at all levels of sensed engine speeds.

Inventors: FUZZELL JOSEPH E, PFLEDERER MARK R, ROBINSON TOMMY E, FUZZELL, JOSEPH, E., PFLEDERER, MARK, R., ROBINSON, TOMMY, E.
Applicants: CATERPILLAR TRACTOR CO, CATERPILLAR TRACTOR CO.
Application year: 1983
Main classification: B60Q1
IPC codes: F01M1, G07C5, G08B21