US 3605711 A
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Sept. 20, 1971 FUSQ DEVICE FOR LIMITING THE SUPPLY OF FUEL TO A DIESEL ENGINE AS A FUNCTION OF THE ENGINE EXHAUST TEMPERATURE Filed Sept. 9, 1969 United States Patent Ofice 3,605,711 DEVICE FOR LIMITING THE SUPPLY OF FUEL TO A DIESEL ENGINE AS A FUNCTION OF THE ENGINE EXHAUST TEMPERATURE Oscar Fuso, Turin, Italy, assignor to Fiat Societa per Azioni, Turin, Italy Filed Sept. 9, 1969, Ser. No. 856,291 Claims priority, application Italy, Sept. 19, 1968, 53,200/ 68 Int. Cl. F02d 7/00 US. Cl. 123-140MC 3 Claims ABSTRACT OF THE DISCLOSURE This invention provides a device which is effective automatically to limit the range of permitted movement of a fuel supply control element in response to a temperature sensed in the engine exhaust gases when said temperature exceeds a given threshold value. Overheating of the engine when working in rarefied air is thereby avoided.
The present invention relates to a device for automatically reducing the supply of fuel to a Diesel engine as a function of the temperature of the engine exhaust gases.
It is known that, as the altitude at which a Diesel engine is operated increases, the temperature of the exhaust gases gradually increases because of the consequent rarefaction of the air which is mixed With the fuel. Such high exhaust gas temperatures could lead to dangerously high temperatures for the components of the engine, and to avoid this it is necessary to reduce the supply of fuel to the engine. It is clearly desirable that such reduction of the fuel supply be effected automatically, and, moreover, should be discontinued when the temperature of the exhaust gases has returned to an admissible value. The above mentioned reduction of fuel supply is particularly necessary when a Diesel engine operates at intervals at an elevated height.
An object of the present invention is to provide a device applicable to a Diesel engine and operable automatically to limit the supply of fuel to the engine when the temperature of the engine exhaust gases exceeds a predetermined value.
A further object of the invention is to provide a device of the above mentioned type capable of operating on the normal fuel supply regulator in a diesel engine which can be set in two indicated positions in one of which it permits a greater supply of fuel and in the other of which it permits a reduced supply.
The characteristic feature of the device according to the invention lies in the fact that it comprises a temperature sensing element for sensing the exhaust gas temperature to provide a signal which is referred in an amplifier unit to a reference level corresponding to a predetermined threshold temperature, and which is effective automatically when the sensed temperature exceeds said threshold temperature to actuate means for limiting the permitted range of movement of a mechanical control element which regulates the fuel supply to the engine, said means being inoperative, permitting a full range of movement of the control element when the exhaust gas temperature falls below a further predetermined value.
Further characteristic features of the invention will be apparent from the detailed description which follows, given by way of non-limiting example, with reference to the accompanying drawing, which illustrates schematically the application of a device according to the invention to a diesel engine.
In the drawing a fuel injection pump 1 of a Diesel engine is indicated in broken outline. The pump 1 has a Patented Sept. 20, 1971 longitudinally displaceable rack 2 for regulation of the fuel delivery of the pump 1. The rack 2 projects beyond the exterior of the pump 1, its projecting part being surrounded by a tubular casing 3 in which a plunger 4 is mounted, for sliding movement. The plunger 4 is provided with an axial abutment member comprising a projection 2a against which the rack 2 bears when in a position of maximum fuel delivery.
A spring 5 within the casing 3 urges the plunger 4 away from the rack 2 towards an end closure, 3a, of the casing 3 and into engagement with an adjustable stop 6 which is screwed into said end closure 3a. When the plunger 4 is in engagement with the stop 6 the rack 2 has a maximum range of movement and when the rack 2 abuts the projection 2a it permits maximum fuel delivery by the pump 1, the stop 6 being adjustable to allow variation of the maximum fuel delivery.
A temperature sensing element 8 is disposed in the exhaust gas outlet of the engine (not shown) and provides a signal, in this example, an electrical signal, having an intensity proportional to the temperature of the exhaust gases. This signal is passed to an amplifier unit 9 in which it is referred to a reference level corresponding to a predetermined threshold value of the exhaust gas temperature. The amplifier unit 9 is connected to electrical supply lines 10 and controls the connection of the supply lines 10 to an actuator unit 11 operatively associated with the excitation coil of an electro-valve 12. The amplifier unit 9 normally disconnects the actuator unit 11 from the supply lines 10, but when the signal from the sensing element 8 exceeds the reference level the amplifier unit 9 connects the supply lines 10 to the actuator 11, energising the latter.
In the illustrated example the electro-valve 12 is a threeway valve, being connected to a fluid pressure supply conduit 13, an exhaust conduit 14-, and a conduit 15 which communicates with an internal chamber 7 of the casing 3, defined between the end closure 3a and the plunger 4, the plunger 4 and the chamber 7 constituting a fluid pres sure actuator.
Under normal operating conditions of the engine, that is with the temperature of the engine exhaust gases below the predetermined threshold level, the actuator 11 is inoperative and the electro-valve 12 is in a first setting in which it connects the conduit 15 with the exhaust conduit 14: consequently the spring 5 displaces the plunger 4 to the right (as viewed) and holds it against the stop 6. The rack 2 is therefore able to move over the maximum range permitted by the setting of the stop 6, so that the engine can be fed with the maximum charge of fuel.
When the temperature of the exhaust gases reaches and exceeds the predetermined threshold level the amplifier unit 9 places the actuator unit 11 in connection with the supply lines 10, operating the unit 11 and causing the electro-valve 12 to be placed in a second setting in which it interconnects the supply conduit 13 and the conduit 15, causing fiuid pressure to be supplied to the chamber 7. The plunger 4 is displaced to the left as viewed until it engages an internal stop shoulder 3a in the bore of the casing 3: in this position the plunger 4 limits the excursion of the control rack 2 of the injection pump 1, thereby reducing the volumetric size of the maximum single charge of fuel supplied to the engine by the pump 1.
Should the exhaust gas temperature return below the predetermined threshold value, the actuator unit 11 will be de-energised, and the electro-valve 12 will return to its first setting, permitting normal operation of the pump 1 to be resumed.
The exhaust gas temperature below which the device disposes the valve 12 in its first setting can, if desired, be predetermined independently of the threshold temperature at which the device causes the valve 12 to change from its first into its second setting.
The device according to the invention as described can be readily applied to existing diesel engines, by easy modification of the mechanical controls thereof, by the simple mounting of the temperature sensing element 8 in the exhaust gas outlet of the engine, and by the addition of the amplifier unit 9, the actuator unit 11 and the electrovalve 12 in the circuit of the servo system as described.
It will be appreciated that practical details of the described embodiments may be varied Widely without departing from the scope of the appended claims.
1. A diesel engine having a device for limiting the supply of fuel to the engine according to the temperature of the exhaust gases, such device comprising:
a movable mechanical control element which regulates the fuel supply to the engine;
a temperature-sensing element for sensing the exhaust gas temperature and providing an electrical signal representative of such temperature;
an amplifier and threshold unit in which said signal is referred to a reference level corresponding to a threshold temperature;
limiting means actuatable by said amplifier and threshold unit when the sensed exhaust gas temperature rises above the threshold temperature and effective when so actuated to vary the permitted range of movement of said control element, said limiting means permitting a full range of movement of said control element while the sensed temperature is below the threshold temperature, said limiting means comprising a fluid pressure cylinder, an abutment member movable in said cylinder and adapted to operate on the control element, and a return spring urging the abutment member toward a position in which the abutment member permits a full range of movement of the control element;
a fluid supply conduit connected to said electro-valve;
a second conduit connected to said electro-valve and to said fluid pressure cylinder; and
an exhaust conduit connected to said electro-valve;
said electro-valve being controlled by said amplifier and threshold unit and being adapted to be actuated by said amplifier and threshold unit to connect said fluid supply conduit to said second conduit and said fluid pressure cylinder when the sensed temperature rises above the threshold temperature, thereby to cause said abutment member to be displaced against the action of said return spring to limit the permissible movement of the control element; and said electro-valve being adapted to be actuated by said amplifier and threshold unit to isolate the fluid supply conduit from the fluid pressure cylinder and to connect said second conduit and said fluid pressure cylinder to said exhaust conduit when the sensed temperature is below the threshold temperature.
2. An engine accordingto claim 1 wherein said fluid pressure cylinder is provided with a stop shoulder to limit the movement of the abutment member in a direction against the force of said return spring.
3. An engine according to claim 1, including an adjustable stop for determining the position of the abutment member under the influence of said return spring during normal operation of the engine.
References Cited UNITED STATES PATENTS 2,244,669 6/1941 Becker 123-1403 2,374,411 4/1945 Camner l23l40.3 2,720,751 10/1955 Kunz 39.28T 2,835,240 5/ 1958 Braun 123-1402 MARK M. NEWMAN, Primary Examiner C. R. FLINT, Assistant Examiner US. Cl. X.R. I23140MP