US3828742A

US3828742A - Engine control system

Info

Publication number: US3828742A
Application number: US00247651A
Authority: US
Inventors: R Weis
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1972-04-26
Filing date: 1972-04-26
Publication date: 1974-08-13
Anticipated expiration: 1991-08-13
Also published as: BE798746A; CA997038A; JPS4954706A; JPS5614856B2

Abstract

A control system for monitoring and controlling an engine as a function of engine speed is provided. The control system includes a control device which continuously monitors engine speed sensed through a magnetic pickup means and causes engine shutdown by means of an engine shutdown device when an overspeed condition occurs. In addition, the control device actuates a warning device when an underspeed condition occurs.

Description

finite Stats Patent 1191 111 3,828,742 Weis 1 Aug. 13, 1974 ENGINE CQNTRQL SYSTEM 3,601,103 8/1971 Swiden 123/102 3,623,464 11/1971 Pat' [75] inventor: Chllhcothe 3,722,485 3/1973 01122111 123/102 [73] Assignee: Qaterpillar Tractor (10., Peoria, 111.

Primary ExaminerLaurence M. Goodridge [22] Flled' 1972 Assistant ExaminerCort Flint [21] Appl. No.: 247,651 Attorney, Agent, or Firm-Phillips, Moore,

Weissenberger, Lempio & Strabala [52] US. Cl. 123/102, 123/118, 123/148 S,

290/40 A [57] ABSTRACT [51] 1111. Q1. F0251 11/00 A control S ystem for monitormg and controllmg an [58] new of Search 3 engine as a function of engine speed is provided. The 1 3/19 l 90/4 control system includes a control device which continuously monitors engine speed sensed through a mag- [56] References cued netic pickup means and causes engine shutdown by UNITED STATES PATENTS means of an engine shutdown device when an over- 1,470,277 10/1923 Loftus 123/ 1 18 speed condition occurs. In addition, the control device 1 irzgover 123/148 S actuates a warning device when an underspeed condimson non occurs 3,291,246 12/1966 Colling et al. 123/102 3,572,302 3 1971 Wollesen 123/118 4 Claims, 3 Drawing Figures 1 Q CR- J 212%2121'33 DIFFERENTIATOR Mdfii'ifiB tPhia WQE Ri TOR $555189 1 L I E E I l E l I l l l I 12 1 24 26 28 30 32 r34 30; l A 1 i 1 m. i 1 etites estsat i 1- 1 38 42 1 I l i 52 54 46 4% d 14 1 ir/2111:112 f 1 3112111122 l l l 1 11 1 i 56 l 1 1 l l PAIENIEI] III; I 3 I974 SHEET 1 [IF 2 SIES'T SSIIN ZO vERsREEo) SPEED CONTROL QVARNINO DEVICE LIGHT 0R HORN (UNDERSPEED) I POWER E- SOURCE I6 z MAGNETIC SQUARING MONOSTABLE FILTER METER RANcE PICK-UP AMPLIFIER DIFFERENTIATOR MULTIVIBRATOR INTECRATOR SELECTOR L T r-MA E, i I

REFERENCE VOLTAGE COMPARATOR AMPLIFIER I REFERENCE VOLTAGE METER I I I I I I I I v I I I I I I I I I I I I I I I I ENGINE CONTROL SYSTEM CROSS-REFERENCE TO RELATED APPLICATION Cross-reference is made to related Application Ser. No. 141,230, filed May 7, 1971 now US. Pat. No. 3,714,509, issued Jan. 20, 1973.

BACKGROUND OF THE INVENTION This invention relates to a speed monitor and control system for engines. More particularly, this invention concerns a control system having a control device for causing engine shutdown when an overspeed condition occurs and activates a warning device or alternatively causes engine shutdown when an underspeed condition occurs.

In manufacturing or rebuilding engines such as internal combustion engines, it is usual for the engine to be tested in order to uncover any possible defects prior to commercial use. The engines are conventionally installed in engine test cells and run-in, sometimes for many hours. Frequently, the engines are not attended or are only partially attended during this period.

Typically, speed control systems are used in this engine test environment to prevent undesirable overspeed or underspeed conditions. This is due to the fact that when an engine undergoing testing, or in a permanent stationary installation for that matter, begins to overspeed, it is necessary that the engine be shut down as soon as possible to prevent damage to the engine from occurring. Conversely, engine damage can also occur during an underspeed condition since engine auxiliary equipment, i.e., cooling pump, cooling fan, lube oil pump, etc., is run at too slow a speed to efficiently carry away heat generated by the engine.

Present control systems being used with engines incorporate optical meter control relays as a control device for activating the engine shutdown device during an overspeed condition. Actuation of this and other 40 functions is initiated by the optical meter relay when a light path between a lamp and a photocell is interrupted at a predetermined point on the meter by the meter indicator. This type of switching arrangement has an inherent time lag between actual engine speed and meter-indicated speed due to the inclusion of mechanical components having inertia effects. Thus, with present devices, it is possible for actual engine speed to be significantly higher than the maximum desired speed and thus in an overspeed condition before the optical meter relay indicates the reaching of said maximum. A corresponding effect occurs when the minimum or underspeed condition is considered.

In the aforementioned cross-referenced application, a speed control device similar to that of the instant invention is disclosed which effectively eliminates time lag in another application. The present invention involves a new combination and use of a speed control device having improved time lag characteristics.

SUMMARY AND OBJECTS OF THE INVENTION The present invention comprises an all-solid-state as opposed to mechanical speed control device for monitoring and controlling speeds of an engine, such as an internal combustion engine, during testing. A magnetic pickup device on the engine feeds a signal to the speed control device where it is processed and fed to a pair LII of comparator amplifiers. A reference voltage source associated with each comparator amplifier provides a signal proportional to the maximum speed and minimum speed desired, respectively. The comparator amplifiers continuously compare the reference voltage input with the speed signal originating from the magnetic pickup device. In an overspeed condition, an engine shutdown device is signal by the first comparator amplifier to shut down the engine. In an underspeed condition, a warning device is activated to call the operators attention to the underspeed condition or shut down the engine, as desired.

It is, therefore, the principal object of this invention to provide an improved engine speed control system.

It is a further object of this invention to provide an engine control system having an improved speed control device.

It is a still further object of this invention to provide an engine speed control device having improved time lag characteristics over those currently available.

It is a still further object of this invention to provide an engine control system for sensing engine speed and which shuts down the engine at incipient overspeed and activates a warning device at incipient underspeed.

It is a still further object of this invention to provide a new combination and use of a speed control device having improved time lag characteristics for controlling engine speed.

Other objects and advantages of the present invention will become apparent from the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an overall schematic view of the instant invention in its normal working environment;

FIG. 2 is a schematic diagram of a portion of the same in somewhat greater detail; and

FIG. 3 is a schematic circuit diagram of the same.

DETAILED DESCRIPTION FIG. I shows generally at 1.0 a speed control system of the present invention. The magnetic pickup device 12 is mounted on the engine 14 in close proximity to an inner gear (not shown) in the engine. In the alternative, this pickup device or means could be mounted on a dynamometer (not shown) which would be coupled to the output shaft of the engine. A signal proportional to the engine speed is transmitted from magnetic pickup 12 to a speed control device 16 having a power supply 18 connected thereto. The power supply may be as is conventional in the art.

As will hereinafter be described, the speed control device continuously compares actual engine speed with both a maximum desired as well as a minimum desired engine speed. If the actual engine speed exceeds the desired maximum, a signal is transmitted to the engine shutdown device 20 to shut down the engine. This engine shutdown device could be one of various types of devices including a dynamometer, fuel shutoff, air shutoff, or any combination of these devices. The dynamometer application would, of course, result in the stalling of the engine to accomplish shutdown. This dynamometer may be as commercially available from the General Electric Company as a Water Gap Induction 5 Dynamometer Model No. IG774. As an alternate, a

If, on the other hand, actual engine speed dropped below the desired minimum, a signal would be transmitted from the control device 16 to warning device 22. This device could be a light or horn which would signal the operator to take appropriate remedial action. In the alternative, an engine shutdown device like the aforementioned device, could be substituted so as to shut down the engine when the underspeed condition occurs.

Turning now to FIGS. 2 and 3, the speed control system will be described in more detail. As aforementioned, magnetic pickup 12, mounted adjacent to a rotating internal gear (not shown) on the engine, senses the speed of the rotating gear and transmits a sine wave signal as shown in block diagram 12. The sine wave signal is sent to squaring amplifier 24 of speed control device 16 where it is amplified and changed to a square wave for each sine wave. From the squaring amplifier, the signal is sent to a differentiator 26 where the square wave is differentiated to produce sharp positive and negative pulses, as shown in block diagram 26. The positive pulse resulting from the differentiator 26 is sent to a monostable multivibrator 28, which produces a pulse or signal of fixed width and height while the negative pulse is sent to ground.

The monostable multivibrator output signal is then sent to a filter integrator circuit 30, which is an integrated-circuit operational amplifier with a resistance capacitance feedback loop. The circuit integrates the positive signal pulses over a fixed time period and produces as an output a DC voltage level as a function of the frequency of the pulses received.

As the output signal leaves the filter integrator circuit, it takes two

paths

32 and 34, with signal 32 going to a meter range selector 36 while signal 34 continues on to take two

separate paths

38 and 40. The output of the meter range selector 36 is sent to meter 42 for visual readout of engine speed. This visual indication of the engine speed is used for operator reference only and does not exercise any control over the machine functions, so that any time lag between the meter and actual engine operation is not important for the efficient operation of the engine. It should be noted that the signal on path 38 is identical with the signal on path 40 and that both are proportional to engine speed. The signal on path 38 is input to a first comparator amplifier 44 while the signal of path 40 is input to a second comparator amplifier 46. The reference voltage mechanism, as will hereinafter be described, is connected to each comparator amplifier. A first or a maximum speed reference voltage mechanism 48 produces a maximum speed reference voltage signal which is input along path 50 to comparator amplifier 44. In like manner, a minimum speed reference voltage mechanism 52 sends a minimum speed voltage signal along path 54 to comparator amplifier 46. Logically, the first comparator amplifier 44 controls the high-speed function and the second comparator amplifier 46 controls the low-speed function. I

In operation, as long as the actual engine speed sensed by magnetic pickup device 12 is intermediate to the maximum and minimum desired speeds,

comparator amplifiers

44 and 46 will not transmit signals. However, when the output of filter integrator transmitted along

paths

34, 38, 40 exceeds either one of the present reference voltage signals, the output of the comparator amplifier will change state. This will energize one of the associated relays 55 or 56 which will, in turn, cause either the engine shutdown device 20 or the warning device 22 to be activated depending upon the amplifier involved.

Reference voltage mechanisms

48 and 52 are digivider/digidecade-type devices which have a five-decade, ten-position capacity for accurate variation of the particular engine device which the control device controls. In the alternative, these may be preset, nonvariable devices.

Power source 18 may be any standard-design power source. The power supply can use standard 1 l0-volt AC power which is converted to a $12 and a 4-volt DC output for operating various components of the control system.

While the above discussion has disclosed an application of the control system using an internal combustion engine, it is to be understood that other applications are possible and that therefore such is by way of example only. The system could be used with a gas turbine engine or even a DC electric motor where the aperture circuit could be de-energized by the shutdown device.

It is to be understood that the foregoing description is merely illustrative of the preferred embodiment of the invention, and that the scope of the invention is not to be limited thereto but is to be determined by the scope of the appended claims.

What is claimed is:

1. In an engine, a-speed monitor and control system comprising: sensing means positioned so as to'measure rotational speed of the engine, means generating an actual speed signal proportional to sensed rotational speed, said signal being directed along two separate paths, first reference means creating a first reference signal proportional to a desired maximum rotational speed, first comparator means receiving the signal from one of said paths for comparing said actual speed signal with said first reference signal, engine shutdown means for shutting down the engine when said actual speed signal passes said maximum rotational speed, second reference means creating a second reference signal proportional to a desired minimum rotational speed which is less than said maximum rotational speed, second comparator means receiving the signals from the other of said paths for comparing said actual speed signal with said second reference signal, and warning means operable by said second comparator means for indicating a speed below said desired minimum, and wherein said means for generating an actual speed signal comprises means generating an output signal in the form of a sine wave, means converting said sine wave output signal into a square wave output signal for each sine wave, means differentiating said square wave output signal into an output signal in the form of positive and negative pulses, means converting said positive pulses into an output signal in the form of square waves having fixed width and height and sending said negative pulses to ground, and means integrating said square visual means.

Claims

1. In an engine, a speed monitor and control system comprising: sensing means positioned so as to measure rotational speed of the engine, means generating an actual speed signal proportional to sensed rotational speed, said signal being directed along two separate paths, first reference means creating a first reference signal proportional to a desired maximum rotational speed, first comparator means receiving the signal from one of said paths for comparing said actual speed signal with said first reference signal, engine shutdown means for shutting down the engine when said actual speed signal passes said maximum rotational speed, second reference means creating a second reference signal proportional to a desired minimum rotational speed which is less than said maximum rotational speed, second comparator means receiving the signals from the other of said paths for comparing said actual speed signal with said second reference signal, and warning means operable by said second comparator means for indicating a speed below said desired minimum, and wherein said means for generating an actual speed signal comprises means generating an output signal in the form of a sine wave, means converting said sine wave output signal into a square wave output signal for each sine wave, means differentiating said square wave output signal into an output signal in the form of positive and negative pulses, means converting said positive pulses into an output signal in the form of square waves having fixed width and height and sending said negative pulses to ground, and means integrating said square waves having fixed width and height so as to produce said actual speed signal.

2. The invention of claim 1 wherein said sensing means is a magnetic pickup.

3. The invention of claim 1 wherein said warning means for indicating an underspeed condition comprise audible means.

4. The invention of claim 3 wherein said warning means for indicating an underspeed condition comprise visual means.