US3738346A

US3738346A - Vehicle internal-combustion engine fuel control and signal device

Info

Publication number: US3738346A
Application number: US00220800A
Authority: US
Inventors: J Goodman
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-01-25
Filing date: 1972-01-26
Publication date: 1973-06-12
Anticipated expiration: 1990-06-12

Abstract

A control for preventing damage to an internal-combustion engine from extended operation under excessive operating conditions where the engine power varies according to the flow of fuel to the engine (e.g., as in a diesel engine). The control includes a pair of fuel-limiting solenoid valves each having a plunger movable between a nonrestrictive position and a second position restricting the fuel flow to the engine. The windings of the valves, when energized, maintain the respective plungers in the nonrestrictive positions. The plunger of a first one of the valves, when in the second position, restricts fuel flow by a preset amount causing reduction in engine power sufficient to reduce its operating temperature but permitting continued normal operation at the reduced power. The other plunger, when in the second position, restricts fuel flow by a greater preset amount reducing engine power sufficiently to prevent continued normal operation. First switch means is connected with the first valve winding for controlling its energization and is responsive to an engine operating condition (i.e., lubricant temperature) operating to deenergize the winding if the condition (e.g., low lubricant pressure) warrants engine power reduction. Second switch means is connected with the winding of the second valve and similarly controls its energization, being responsive to another operating condition (e.g., lubricant pressure) for causing deenergization of the latter winding if discontinuing the normal operation of the engine is warranted by the operating condition (e.g., lubricant pressure too low). The control is especially useful with diesel truck engines.

Description

United States Patent Goodman June 12, 1973 VEHICLE INTERNAL-COMBUSTION combustion engine from extended operation under ex- ENGINE FUEL CONTROL AND SIGNAL cessive operating conditions where the engine power DEVICE varies according to the flow of fuel to the engine (e.g.,

as in a diesel engine). The control includes a pair of [75] Inventor Johnny GoodmanEast fuel-limiting solenoid valves each having a plunger [73] Assignee; Joseph J, Bristow, East Car nd I t, movable between a nonrestrictive position and a sec- 11]. 0nd position restricting the fuel flow to the engine. The

windings of the valves, when energized, maintain the [22] Flled' 1972 respective plungers in the nonrestrictive positions. The 2 A l N 220,300 plunger of a first one of the valves, when in the second Related U.S. Application Data [63] Continuation-in-part of Ser. No. 109,392, Jan. 25,

1971, Pat. No. 3,646,513.

[52] U.S. Cl. 123/198 DB, 340/53, 340/60 [51] Int. Cl...... F0lm l/24, B60q l/00,'F02d 35/00 [58] Field 01 Search 123/198 R, 198 D,

123/198 DB, 198 DC; 340/52, 53, 60, 57, 231

[56] References Cited UNITED STATES PATENTS 2,225,234 12/1940 Schettler 123/198 DB 3,159,036 12/1964 Miller et al..... 123/198 DB X 3,202,161 8/1965 Richards 123/198 D X 3,301,245 l/l967 Woodburn... 123/198 D 3,379,187 4/1968 Armbrust 123/198 D 3,431,555 3/1969 Leone 340/60 3,431,779 3/1969 Wilken et a1.... 340/52 R X 3,590,798 7/1971 Goodwin 123/198 D Primary Examiner-Al Lawrence Smith Attorney- Peter S. Gilster and Stuart N. Senniger [57] ABSTRACT A control for preventing damage to an intemalposition, restricts the fuel flow by a presetmount causing reduction in engine power sufficient to reduce its operating temperature but permitting continued normal operation at the reduced power. The other plunger when in the second position, restricts the fuel flow by a greater preset amount reducing engine power sufficiently to prevent continued normal operation. First switch means is connected with the first valve winding for controlling its energization and is responsive to an engine operating condition i.e., lubricant temperature) operting to deenergize the winding if the condition (e.g., low lubricant pressure) warrante engine power reduction. Second switch means is connected with the winding of the second valve and similarly controls its energization, being responsive to another operating condition(e.g., lubricant pressure) for causing deenergization of the latter winding if discontinuing the normal operation of the engine is warranted by the operating condition (e.g., lubricant pressure too low). The control is especially useful with diesel truck engines.

13 Claims, 5 Drawing Figures FUEL BACK PRESSURE OIL TEMP I050 I051: giloe WATER OIL TEMP PRESSURE 7 DRIVER OIL WARNITNG DRIVER TEMP. WARNING ENGINE IOIo PAIENIED 3.738.346

am a (If 3 FIG. 1

-Wo WARNING LIGHT DRIVER WARNING OIL PRESSURE OIL TEMP.

ee I I l I OILTEMP I I L FROM FUEL C: SUPPLY F I G; 2

B B r a L um 2% 0UP VFW mFu s w T PATENTED 3; 738.346

SHEEIZBF3 Flea PATENIED m I 2 ms FIG.5

DRIVER ou WARNI-NG DRIVER TEMP. WARNING E LT N m mm P N 3 :4 E m m m R h JG M TIIIYIIIII O T 1 d l m M w x k WMHHHH J m m m m m B VEHICLE INTERNAL-COMBUSTION ENGINE FUEL CONTROL AND SIGNAL DEVICE CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of applicants allowed application Ser. No. 109,392 of the same title, filed Jan. 25, 1971, now U.S. Pat. No. 3,646,513.

BACKGROUND OF THE INVENTION This invention relates generally to automotive fuel controls and more particularly to a fuel control for preventing damage to an internal-combustion engine.

In the operation of trucks, such as large, long-haul truck tractors having diesel engines, there is a serious problem in the trucking industry of damage to such engines which results from extended operation at excessive temperatures. It often happens that a truck engine will be operated with greater power output and greater speed than is prudent, typically with indifference or deliberate disregard to the engine temperature For example, the truck may be driven for long periods with wideopen throttle. In truck engines having exhaust-driven turbochargers, an increase in exhaust temperature will provide even greater available power. A driver may therefore deliberately permit the engine temperature to become excessive for the purpose of obtaining greater power. In addition to these kinds of manhandling of an engine, there is a widespread problem caused by drivers who modify the fuel controls of an engine, such as by restricting the fuel return line for a diesel engine, in order to provide greater power output and greater engine speed. In any case, extended operation of the engine at the resultant excessive temperatures or under other excessive operating conditions may produce serious damage to the engine, such as cracked pistons, broken piston rings, and the like.

An additional consideration which should be taken into effect is that, with engines of the foregoing type, there are some operating conditions of the engine which warrant only that the engine power be reduced (e.g., to permit cooling). In this situation normal operation may be continued at the reduced power. However, other operating conditions (e.g., extreme overheating or very low oil pressure) may dictate that normal operation be discontinued.

Heretofore, there has been no effective means for preventing thermal damage to truck engines resulting from extended operation at excessive temperatures. Nor has there been a control providing for reduced power'normal operation in response to certain kinds of excessive operating conditions and also for discontinuance of normal operation in response to certain other kinds of excessive operation conditions.

Examples of the prior art may be found in U.S. Pats. Nos. 2,171,401, 2,629,047, 2,692,980, 2,870,753 and 3,431,555.

BRIEF DESCRIPTION OF THE INVENTION Among the several objects of the invention may be noted the provision of a fuel control for preventing damage to an internal-combustion engine due to extended operation under excessive operating conditions; the provision of such a control providing not only for reduced powernormal operation of the engine in response to certain kinds of excessive operating conditions but also for discontinuance of normal operation in response to certain other kinds of excessive operating conditions; the provision of such a control which is particularly useful in conjunction with diesel truck engines; the provision of such a control which is relatively tamper-proof; the provision of such a control which is fail-safe in operation; the provision of such a control which is highly reliable and long-lasting in operation; and the provision of such a control which is simply and economically constructed and installed. Other objects and features will be in part apparent and in part pointed out hereinafter.

Briefly, a control of the present invention is adapted to prevent damage to an internal-combustion engine resulting from extended operation under excessive operating conditions where the engine is of the type (such as a diesel truck engine) the power of which varies according to the flow of fuel to the engine.

The control includes first and second fuel-limiting so lenoid valves each controlling the flow of fuel to the engine. Each valve has a fuel control plunger movable from a first position permitting unrestricted flow of fuel through the respective valve to the engine to a second position restricting flow of fuel through the respective valve to the engine. Each valve further includes a winding adapted when energized to maintain the respective plunger in its first position and when deenergized to permit movement of the plunger to its second position. The arrangement is such that the plunger of the first valve when in the second position restricts fuel flow by a first preset reduced amount causing reduction in engine power sufficient to reduce the operating temperature of the engine but to permit continued normal operation at the reduced power. However, the plunger of the second valve when in the second position restricts fuel flow by a greater preset reduced amount to cause reduction in engine power sufficient substantially to prevent its continued normal operation.

First switch means is connected in a circuit with the winding of the first valve for controlling its energization. This switch means is responsive to an operating condition of the engine, operating to cause deenergization of the winding when the operating condition becomes sufficiently excessive to warrant reduction in engine power. Second switch means is similarly connected in a circuit with the winding of the second valve for controlling its energization. The latter switch means is also responsive to an operating condition of the engine and operates to cause deenergization of the last said winding when this operating condition is so excessive as to warrant discontinuing normal operation of the engine. Accordingly, the engine power is protectively reduced to prevent damage to the engine under excessive operating conditions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a pictorial illustration of a fuel control of the present description, shown for use with a diesel engine of the type employed in trucks;

FIG. 2 is a schematic circuit diagram of the present control;

FIG. 3 is a vertical cross-section of a fuel-limiting solenoid valve of the present control;

FIG. 4 is a horizontal cross-section of the fuellimiting solenoid valve taken along line 4-4 of FIG. 3; and

FIG. 5 is a schematic illustration of an improved embodiment of a fuel control according to the present invention, including a pair of fuel-limiting solenoid valves, one of which is represented in cross section.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and more particularly to FIGS. 1 and 2, a fuel-limiting solenoid valve of the present invention, designated generally 11, is installed in the fuel input line 13 leading from a fuel supply tank to the fuel injection pump 15 of a diesel truck engine 17. Engine 17 is of the type of engine the power (and thus the speed) of which varies according to flow of fuel thereto. Thus the engine speed may be throttlecontrolled through operation of injection pump 15 by varying the amount of fuel delivered by the engine fuel injectors. As will be clear, however, the engine speed and the amount of power the engine can deliver may be reduced by restricting the flow of fuel delivered by line 13 by operation of solenoid valve 11.

Referring to FIG. 2, solenoid valve 1 1 includes a fuel control plunger 19 adapted to be operated by a solenoid winding 21. Plunger 19 is movable from a first position, permitting unobstructed flow of fuel to the engine fuel pump 15 through line 13 to a second position as illustrated. In this second position, plunger 19 causes reduction of the flow of fuel to a preset reduced amount determined by an adjusting screw 23. This reduced amount is predetermined to be sufficient to cause the engine power to diminish, thereby to reduce the operating temperature of engine 17 even if the truck driver should deliberately attempt to maintain full throttle operation, et cetera. Winding 21 is adapted when energized to maintain plunger 19 in the first position for unobstructed fuel flow and when deenergized to permit movement of plunger 19 under bias of a compression spring 25 to the second position.

Connected in a series circuit to one side of winding 21, the other side of which is grounded, are the normally closed contacts 27 of an oil temperature switch 29, and the normally open contacts 31 of an oil pressure switch 33. This series circuit is adapted to be connected to the hot" side of a power source constituted by the usual truck storage battery 35 by the closing of one set of contacts 37 of the usual key-operated main or master switch 39 of the truck, which is manually operated to close contacts 37 for normal operation of the truck.

' Both oil temperature switch 29 and oil pressure switch 33 may be physically mounted on engine 17 and connected to the so-called oil gallery thereof. Oil temperature switch 29 constitutes switch means responsive to the engine operating temperature, and contacts 29 thereof are adapted to open, thereby deenergizing' winding 21, when the engine temperature exceeds a preset level, e.g., an oil temperature of 235F. Oil pressure switch 33 constitutes switch means responsive to the engine oil pressure, and contacts 31 thereof are adapted to remain open for oil pressures below a preset level, e.g., 15 psi, but to close at or above that level.

From the foregoing it will be seen that so long as the oil temperature is below the operating value for switch 29, i.e., 235F., and the oil pressure is above the operating value for switch 33, a circuit for energizing winding 21 will be completed, assuming key switch contacts 37 are closed, from battery 35, through contacts 37, through

contacts

27 and 31, and winding 21. Plunger 19 thus will be maintained in the first position providing unobstructed fuel flow for normal engine operation.

However, heating of the engine to the preset value, e.g., of 2 35F., will open contacts 27 and thereby deenergize winding 21. Alternatively, a reduction in lubricant pressure, e.g., to less than the preset level of 15 psi, will open contacts 31 and deenergize winding 21. Such an oil pressure reduction may be caused, for example, either by excessive oil temperature or some other failure in the oil system, such as insufficient oil. In any case, operation of either oil temperature switch 29 or oil pressure switch 33 will cause plunger 19 to restrict the flow of fuel and thereby protectively reduce the speed of the engine, so as to reduce its operating temperature.

It will be noted that upon start-up of the engine, oil

pressure is not developed until the engine attains normal running speed. Hence, contacts 31 of oil pressure switch 33 remain open until running speed is attained. Accordingly, at engine start-up, plunger 19 is in the fuel flow-reducing position. However, this does not prevent the engine from being started since less fuel is required for starting than running. Moreover, this is advantageous in preventing the engine from being over speeded prior to build-up of adequate lubricant pressure. That is, fuel flow will be limited until contacts 31 of the oil pressure switch close. Of course, a bypass switch could be connected across contacts 31, if desired, for use in starting the engine.

A driver-warning provision of the present invention includes a further oil temperature switch 41 having a set of normally open contacts 43 which are connected with a conventional signal or warning light 45 in a series circuit between ground and the junction of switch contacts 37 with pressure switch contacts 31. Signal light 45 is positioned for being observed by the truck driver. Oil temperature switch 41 is selected to have an operating temperature, at which contacts 43 thereof are adapted to close, which is a few degrees less than the operating temperature of temperature switch 29. For example, contacts 43 may close at about 225F. It has been found that if the operating temperature of the truck engine starts to become excessive, there will be a short time lag, of about a minute, for example, before the temperature can climb the last. few degrees (i.e., 10F. in this case). Accordingly, signal light 45 will be energized to signal the driver that the temperature has exceeded 225F. (i.e., the present operating temperature of switch 41). The driver will then have warning that, if the engine continues to be operated with too much throttle, etc., solenoid valve 11 will shortly be operated by switch 29 to cause an engine-speed reduction. So warned, the driver may reduce speed or shift to a lower gear and thus avoid a fuel reduction. As will be seen, operation of key switch 39 is also adapted to connect this warning circuit to battery 35 for normal operation.

Referring to FIGS. 3 and 4, fuel-limiting solenoid valve 11 is shown to comprise a cylindrical valve body or block 47 having a drilled concentric cylindrical bore 49 in which plunger 19, also cylindrical, is axially slidable between its aforesaid first and second positions. Plunger 19 is shown in its second position. A cylindrical sleeve 51 includes an annular flange 53 threaded into a concentric recess 54 at the top of body 47 and extends upward from body 47. Sleeve 51 also includes a drilled tubular concentric recess 55 providing an extension of bore 49. Compression spring 25 is fitted into a tubular concentric recess 57 at the upper end of plunger 19 and bears against the ends of

recesses

55 and 57 for biasing plunger 19 for downward movement which is limited by a setscrew 59 screwed into block 47. Setscrew 59 bears against the lower surface of plunger 19 when the latter is in the fuel limiting second position shown. A lock nut 61 is screwed into a tapped recess 63 for locking setscrew 59 in position. Lock nut 61 may be safety-wired in position and a seal 65 applied to the safety wire. A truck driver or other person is thus prevented from tampering with setscrew 59, a broken wire or seal being evidence of such tampering.

A thin, cylindrical metal cap 67 is fitted over the upper end of block 47. The upper end of sleeve 51 is threaded and extends through an aperture 69 in the top of cap 67. A knurled, threaded collar 71 is screwed onto this threaded portion of sleeve 51 to secure cap 67. Winding 21is axially wound in the annular space 73 between sleeve 51 and cap 67.

Valve block 47 includes a fuel inlet port 75 and a fuel outlet port 77 both communicating with bore 49. Fuel outlet port 77 is substantially in registry with fuel inlet port 75. It will be understood that fuel line l3 is connected to inlet port 75 and outlet port 75 is connected by a short fuel line to fuel pump 15, each by suitable compression fittings screwed into respective drilled

recesses

79 and 81. Plunger 19 is provided with an annular groove 83. When plunger 19 is in its first position for unobstructed fuel flow, i.e., is magnetically attracted to its uppermost position within bore 49 (as viewed in FIG. 3) by winding 21, groove 83 is aligned generally with fuel inlet and

fuel outlet ports

75 and 77. However, in its second position (illustrated) with winding 21 deenergized, plunger 19 moves against setscrew 59 so that groove 83 is moved out of alignment with inlet and

outlet ports

75 and 77 by a preset distance determined by setscrew 59, thereby causing reduced fuel flow between these inlet and outlet ports. Thus setscrew 59 provides means for adjustably limiting movement of plunger 19.

A fuel pressure test port 85 of smaller diameter than

ports

75 and 77 but in registry with the latter ports may also be provided as illustrated to permit a pressure gauge to be connected at a threaded recess 87. This permits precise calibration of the position of plunger 19 by adjustment of setscrew 59. Recess 87 may be plugged after calibration with a nipple.

It should be observed that a control of the present invention is substantially fail-safe. If any of the components fail or power from the battery is interrupted (as by a drivers intentional cutting of the leads), winding 21 of solenoid valve 11 will be deenergized, causing plunger 19 to move to its fuel-limiting position.

In order to provide even greater assurance against unauthorized tampering with the circuit, the circuit lead, designated 89 in FIG. 2, extending from oil temperature switch 29 and connecting its contacts 27 to winding 21, is provided with a shield 91. Shield 91 may comprise metal tubing or suitable braided or armored flexible tubing. Shield 91 prevents tampering not only by making it difficult to gain access to lead 89, but also by giving the appearance of an oil line or the like. This causes the driver or other would-be tamperer to believe that cutting or removing the shield would release oil, et

cetera. This oil-line appearance may be enhanced by employing compression-type or

knurled fittings

93 and 95 at the ends of shield 91.

Referring now to FIG. 5, the invention is shown to include a pair of

identical solenoid valves

101 and 103 each being adapted to limit fuel in a manner similar to valve 11 of FIGS. 14.

Valves

101 and 103 are connected in series so that fuel flows from a fuel supply (such as from the fuel injection pump of a truck) via fuel input line 13 through the valve body 101a of valve 101, through the valve body 103a of valve 103, thence via a fuel outlet line 13 to fuel injectors (now shown) of the diesel engine which drives the truck. As before, the engine power (and, of course, its speed under a given load) varies according to the flow of fuel to the injectors. Hence, the engine power may be reduced by restricting the flow of fuel delivered via line 13' through operation of either of valves 10] and 103.

As illustrated, valve 101 includes a fuel control plunger 10lb movable between a retracted first position, in which it is adapted to be maintained by energization of a solenoid winding 1010, and a fuel-limiting second position upon deenergization of the winding. In the retracted or first position, plunger 101]; permits unrestricted fuel, the fuel flowing into a fuel inlet chamber 101d, through a port 101e below the plunger, and thence through a fuel outlet passage 101 f. Plunger 101b is shown in the second position in which it closes port 1016 to restrict the flow of fuel to a preset reduced amount determined by an adjustment screw 101g. The latter controls flow of fuel through a bypass passage l0lh interconnecting inlet chamber 101d and outlet passage 1011'. A compression spring l01h biases plunger 101b for movement from the first to the second position.

In accordance with this invention, screw 101g is adjusted so that, when plunger 101b is in the position shown, fuel through valve 101 is limited by a preset amount such as 20 percent. Thus the engine power is reduced accordingly by an amount predetermined to be sufficient to reduce the operating temperature of the engine (assuming the temperature to be so high that it constitutes an excessive operating condition for the engine). However, the power reduction effected by the limiting action of valve 101 is such that continued normal operation is possible at the reduced power.

Valve 103, which is identical to valve 101, has its adjustment screw 103g set such that when the plunger of valve 103 is in its second position (like that shown for plunger 10lb), fuel flow through valve 103 is restricted by an even greater preset amount, e.g., 80 percent. This reduction is predetermined to be sufficient substantially to prevent continued normal operation of the engine. Preferably, the maximum power of the engine is reduced sufficiently to prevent the engine from operating at more than idle speed.

Connected in series between the circuit ground and the contacts 37 of key switch 39 are a normally closed set of contacts 105a of a fluid temperature sensor or switch 105. Winding 1010 of valve 101 is thus energized so long as contacts 105a remain closed (assuming contacts 37 also to be closed), thereby maintaining plunger l0lb in its first, or retracted, position. Sensor 105 is mounted to the engine in the same manner as switch or sensor 29 of FIG. 1 so as to be responsive to the oil temperature of the engine when the control is to be used with one particular type of diesel engine. Contacts 105a are preferably adapted to open when the engine oil temperature exceeds a preset level, e.g., 225F., thereby deenergizing winding 10lc. This temperature level is deemed to be an excessive operating condition for the engine warranting a reduction in engine power.

Temperature sensor 105 includes a further set of contacts 105b which are connected in series withthe driver warning light 45. Contacts 105b are normally open but are adapted to close when a slightly lower oil temperature, e.g., 220F., than for contacts 105a is exceeded. When contacts 105b close at this preset temperature level, the driver is given warning of relatively high engine oil temperatures. Thus, if the driver does not reduce power, he may expect that continued highpower operation will shortly result in fuel-limiting operation by valve 101 upon opening of contacts 105a.

Energization of winding 1030 of valve 103 is controlled by three sensors, viz., an engine lubricant oil pressure sensor 107, an engine coolant or water temperature sensor 109, and a fuel back pressure sensor 111. These sensors have respective sets of switch contacts 107a, 109a and 111a connected in a series circuit with winding 1030 between the circuit ground and contacts 37 of key switch 39. Accordingly, winding 1030 is energized (assuming contacts 37 to be closed) whenever all of the sets of contacts 107a, 109a and llla are closed, but is deenergized when any one of these contacts opens.

Oil pressure sensor 107 is mounted in the engine in the same manner as sensor 33 of FIG. 1 so as to be responsive to the engine lubricant oil pressure. Its contacts 107a are normally open but close when normal oil pressure is developed. Hence contacts'l07a are normally closed during operation of the engine but reopen when the lubricant pressure falls to a predetermined level, e.g., 12 psi. This low lubricant pressure level is deemed an operating condition of the engine so excessive as to warrant discontinuing normal operation of the engine.

Sensor 107 includes another set of contacts l07b. These are normally closed but remain open during normal operation of the engine, reclosing when the oil pressure drops to a preset level, such as 18 psi, greater than that causing opening of contacts 107a. Contacts l07b are connected in a series circuit with a signal light 113 between the circuit ground and contacts 37 of key switch 39. Signal light 113 is preferably mounted with signal light 45 in view of the driver. Light 113 is energized upon closing of contacts 107b for warning the driver of low engine oil pressure.

Water temperature sensor 109 is suitably oriented to as to be responsive to the engine water (i.e., coolant) temperature, its contacts 109a being normally closed but opening at a preset coolant temperature, such as 230F. This level is also deemed an engine operating condition so excessive as to warrant discontinuing normal operation.

Fuel back pressure sensor 111 is a conventional type of fluid pressure sensor suitably connected for being responsive to the pressure of fuel returned to the vehicle fuel supply. It will be understood that the control is used with an engine of the type including individual fuel injectors from which excess fuel is returned by a return line to the fuel supply. If the pressure of this return fuel is increased, i.e., if there is greater fuel back pressure, then the injectors tend to inject greater amounts of fuel and thus increase engine power excessively. There may be a temptation for some drivers of diesel trucks to crimp or constrict the fuel return line and thus increase the fuel back pressure in order to obtain greater engine power. Sensor 111 is responsive to an increase in fuel pressure, its contacts 111a being normally closed but opening at a preset fuel pressure level, such as 6 psi, to deenergize winding 1030. This preset level is similarly deemed an engine operating condition so excessive as to warrant discontinuing normal engine operation, since the high power resulting from an increase in back pressure could result in damage to the engine.

In operation of the control of FIG. 5, assuming key switch contacts 37 to be closed, valve windings 101C and 103s are normally energized and thus fuel flow to the engine is normally unrestricted. Of course, upon start-up of the engine, contacts 107a will be open until the engine develops normal oil pressure. Accordingly, fuel flow will be limited by valve 103 by percent, for example. However, as before, this does not prevent the engine from being started and advantageously assures that the engine will not be speeded up until there is adequate oil pressure.

If, during operation of the engine, it becomes overheated sufficiently to open contacts 10512, the driver will be warned by signal light 45. Upon continued overheating, opening of contacts 105a will deenergize solenoid winding 101c and thus fuel will be limited by valve 101 sufficiently to permit the engine to cool under reduced power operation, yet without preventing continued normal operation, allowing the truck to be driven along at reduced power, perhaps using a lower gear.

On the other hand, excessive operating conditions warranting discontinuing normal engine operation, such as low engine oil pressure, high coolant temperature, or significant fuel back pressure, will cause deenergization of winding 103c. When one of these conditions occurs, valve 103 will restrict fuel flow sufficiently to prevent continued normal engine operation, i.e., at no greater than idle speed. However, the driver is forewarned of such protective control action by illumination of signal light 113. Thus, if there is continued over-temperature operation, it is expected that the oil pressure will drop sufficiently to close contacts 107]: to give a warning signal in advance.

As in the case of the embodiment of FIGS. 1-4, the present embodiment is fail-safe in that component failure or circuit interruption will permit one or both of the solenoid valve plungers to move to the fuel-limiting position.

To assure against tampering with the leads for solenoid windings l0lc and 103e, the leads may be provided with shields and 117 as in the case of the previous embodiment.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying draw- I ings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A control for preventing damage to an internalcombustion engine from extended operation under excessive operating conditions, the power of said engine varying according to the flow of fuel thereto, said control comprising:

first and second fuel-limiting solenoid valves each controlling the flow of fuel to the engine, each valve having a fuel control plunger movable from a first position permitting unrestricted flow of fuel through the respective valve to the engine to a second position restricting flow of fuel through the respective valve tothe engine, each valve including a winding adapted when energized to maintain the respective plunger in said first position and when deenergized to permit movement of the plunger to said second position, the plunger of said first valve when in the second position restricting fuel flow by a first preset reduced amount causing reduction in engine power sufficient to reduce an excessive operating condition of the engine but to permit continued normal operation thereof at the reduced power, the plunger of said second valve when in the second position restricting fuel flow by a greater preset reduced amount to cause reduction in engine power sufficient substantially to prevent continued normal operation thereof;

first switch means connected in a circuit with the winding of said first valve for controlling the energization thereof, said switch means being responsive to said excessive operating condition of the engine and operative to cause deenergization of the winding when the operating condition warrants reduction in .engine power;

second switch means connected in a circuit with the winding of said second valve for controlling the energization thereof, said second switch means being responsive to an operating condition of the engine and operative to cause deenergization of the last said winding when the latter operating condition becomes so excessive as to warrant discontinuing normal operation of the engine; whereby the engine power is protectively reduced to prevent damage to the engine under excessive operating conditions.

2. A control as set forth in claim 1 wherein the operating condition to which said first switch means is respon'sive is the operating temperature of the engine, said first switch means causing deenergization of the first said winding when said operating temperature exceeds a preset level.

3. A control as set forth in claim 2 wherein said operating temperature of the engine to which said first switch means is responsive is constituted by the engine lubricant temperature, said first switch means comprising a fluid temperature sensor having a set of normally closed contacts connected in series with the first said winding and adapted to open at a preset lubricant temperature level.

4. A control as set forth in claim 3 further comprising signal means, said fluid temperature sensor including a further set of contacts connected in a circuit with the signal means and operating to energize the signal means for signalling operation thereof when the lubricant temperature exceeds a further preset level less than the preset level causing operation of the first said contacts, thereby to give warning prior to engine power reduction resulting from operation of the first said contacts.

5. A control as set forth in claim 1 wherein the operating condition to which said second switch means is responsive is the engine lubricant pressure, said second switch means causing deenergization of the second said winding upon the engine lubricant pressure falling below a preset level.

6. A control as set forth in claim 5 wherein said second switch means comprises a fluid pressure sensor having a set of contacts connected in series with the second said winding and normally closed during operation of the engine but adapted to open at said preset engine lubricant pressure level.

7. A control as set forth in claim 6 further comprising signal means, said fluid pressure sensor including another set of contacts connected in a circuit with the signal means and operating to energize the signal means for signalling operation thereof when the lubricant pressure falls below another preset level greater than the preset level causing opening of the first said contacts, thereby to give warning prior to engine power reduction resulting from operation of the first said contacts.

8. A control as set forth in claim 5 wherein the plunger of said second valve when in the second position restricts fuel flow by an amount sufficient to cause the engine to operate at substantially no greater than idling speed.

9. A control as set forth in claim 5 wherein the engine is of the type including fuel injectors from which excess fuel is returned to a fuel supply, the engine power being improperly increased upon increase in the back pressure of fuel being returned to the fuel supply, the control also comprising further switch means also connected in a circuit with the winding of said second valve, said further switch means being responsive to said fuel back pressure and operative to cause deenergization of the latter winding upon the fuel back pressure exceeding a preset level.

10. A control as set forth in claim 9 wherein said further switch means comprises a fluid pressure sensor having a set of normally closed contacts connected in a series circuit with the winding of said second valve and adapted to open at said preset fuel pressure level.

11. A control as set forth in claim 5 further comprising an additional switch means responsive to the temperature of coolant for the engine, said additional switch means being also connected in a circuit with the winding of said second valve and operative to cause deenergization of the latter winding upon the engine coolant temperature exceeding a preset level.

12. A control as set forth in claim 11 wherein said additional switch means comprises a fluid temperature sensor having a set of normally closed contacts connected in a series circuit with the winding of said second valve and adapted to open at said preset coolant temperature level.

13.;A control as set forth in claim 1 wherein each of said plungers is biased for movement from the first position toward the second position.

Claims

1. A control for preventing damage to an internal-combustion engine from extended operation under excessive operating conditions, the power of said engine varying according to the flow of fuel thereto, said control comprising: first and second fuel-limiting solenoid valves each controlling the flow of fuel to the engine, each valve having a fuel control plunger movable from a first position permitting unrestricted flow of fuel through the respective valve to the engine to a second position restricting flow of fuel through the respective valve to the engine, each valve including a winding adapted when energized to maintain the respective plunger in said first position and when deenergized to permit movement of the plunger to said second position, the plunger of said first valve when in the second position restricting fuel flow by a first preset reduced amount causing reduction in engine power sufficient to reduce an excessive operating condition of the engine but to permit continued normal operation thereof at the reduced power, the plunger of said second valve when in the second position restricting fuel flow by a greater preset reduced amount to cause reduction in engine power sufficient substantially to prevent continued normal operation thereof; first switch means connected in a circuit with the winding of said first valve for controlling the energization thereof, said switch means being responsive to said excessive operating condition of the engine and operative to cause deenergization of the winding when the operating condition warrants reduction in engine power; second switch means connected in a circuit with the winDing of said second valve for controlling the energization thereof, said second switch means being responsive to an operating condition of the engine and operative to cause deenergization of the last said winding when the latter operating condition becomes so excessive as to warrant discontinuing normal operation of the engine; whereby the engine power is protectively reduced to prevent damage to the engine under excessive operating conditions.

2. A control as set forth in claim 1 wherein the operating condition to which said first switch means is responsive is the operating temperature of the engine, said first switch means causing deenergization of the first said winding when said operating temperature exceeds a preset level.

13. A control as set forth in claim 1 wherein each of said plungers is biased for movement from the first position toward the second position.