US3835828A

US3835828A - Fuel supply system

Info

Publication number: US3835828A
Application number: US00386980A
Authority: US
Inventors: H Knapp
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1972-09-07
Filing date: 1973-08-09
Publication date: 1974-09-17
Anticipated expiration: 1991-09-17
Also published as: GB1450579A; FR2163279A5; DE2243921A1

Abstract

In a fuel supply system for an externally ignited internal combustion engine with compression of the fuel/air mixture, in which air flow-measuring means and a randomly operable throttle valve are arranged successively in the air intake suction pipe of the engine, and the meauring means is moved, in proportion to the air amount flowing through the suction pipe, against an at least substantially constant resetting force and thereby displaces the movable member of a distributing valve arranged in the fuel line in order to meter a fuel amount proportional to the air amount, and wherein a pressure liquid of at least substantially constant pressure, which is continuously delivered through a pressure line, serves to transmit the resetting force and acts upon a control slide valve to effect the resetting, the pressure of the liquid being variable by means of at least one regulated pressure control valve which is controlled in dependence on characteristic engine data, there is described an improved control cell adapted for temperature-dependent operation and which comprises a cell housing, bimetallic spring means, and heat-conducting tongue means jointly mounted in the housing for the conduction of heat from the tongue means to the bimetallic spring means and insulated against heat losses to the housing, electrical heating means associated with the tongue means, and fuel pressure regulating means comprising a control spring mounted in the housing, the bimetallic spring means being adapted for engaging the control spring and reducing the force of the spring at temperatures below the operational temperature of the engine.

Description

United States Patent [191 Knapp 1 FUEL SUPPLY SYSTEM [75] Inventor: Heinrich Knapp,

Leonberg-Silberberg, Germany 1 s g w R999! B9 91 mbH St Germany 22 Filed: Aug. 9, 1973 21 Appl. 190.; 386,980

[30] Foreign Application Priority Data Sept. 7, 1972 Germany 2243921 [52] US. Cl... 123/119 R, 123/139 AW, 123/179 G [51] Int. Cl F02m 69/00 [58] Field of Search..... 123/119 R, 139 AW, 179 G Primary Examiner-Manuel A. Antonakas Assistant ExaminerS. J. Richter Attorney, Agent, or FirmEdwin E. Greigg [5 7] ABSTRACT In a fuel supply system for an externally ignited internal combustion engine with compression of the fuel- 1 Sept. 17, 1974 lair mixture, in which air flow-measuring means and a randomly operable throttle valve are arranged succes sively in the air intake suction pipe of the engine, and the meauring means is moved, in proportion to the air amount flowing through the suction pipe, against an at least substantially constant resetting force and thereby displaces the movable member of a distributing valve arranged in the fuel line in order to meter a fuel amount proportional to the air amount, and wherein a pressure liquid of at least substantially constant pressure, which is continuously delivered through a pres sure line, serves to transmit the resetting force and acts upon a control slide valve to effect the resetting, the pressure of the liquid being variable by means of at least one regulated pressure control valve which is controlled in dependence on characteristic engine data, there is described an improved control cell adapted for temperature-dependent operation and which comprises a cell housing, bimetallic spring means, and heat-conducting tongue means jointly mounted in the housing for the conduction of heat from the tongue means to the bimetallic spring means and insulated against heat losses to the housing, electrical heating means associated with the tongue means, and fuel pressure regulating means comprising a control spring mounted in the housing, the bimetallic spring means being adapted for engaging the control spring and reducing the force of the spring at temperatures below the operational temperature of the engine.

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SHEET 1 OF 2 j////// ////I///// III PAIENImSEP 1 71914 SHEEI 2 OF 2 hag n E:

FUEL SUPPLY SYSTEM BACKGROUND THE INVENTION valve are arranged successively in the air intake suction pipe of the engine, and the measuring means is moved, in proportion to the air amount flowing through the suction pipe, against an at least substantially constant resetting force and thereby displaces the movable member of a distributing valve arranged in the fuel line in order tometer a fuel amount proportional to the air amount, and wherein a pressure liquid of at least substantially constant pressure, which is continuously delivered through a pressure line, serves to transmit the resetting force and acts upon a control slide valve to effect the resetting, the pressure of the liquid being variable by means of at least one regulated pressure control valve which is controlled in dependence on characteristic engine data, and which contains a control cell whose operation is temperature-dependent.

It is a problem of known fuel metering systems of the above-described type that the heating-up period of the internal combustion engine is of different length depending upon the starting temperature, and that the temperature rise is much steeper in a heating-up period beginning at a starting temperature of +C than in such period beginning at a starting temperature of 20C. To obtain an ideal enrichment of the fuel mixture during the heating-up period, a control cell whose operation is temperature-dependent would be required in the pressure control valve, which in turn would effect the control pressure of the fuel metering system with the same time/temperature dependency as it would affect the heating-up of the engine.

It has been proposed to solve this problem by means of a system comprising an element of heat-expanding material or a heated bimetal spring, either of which achieves control of the fuel enrichment during the heating-up phase. However, such elements can not bring about an exact adaptation of the rise in control pressure to the actual, momentary rise of the engine temperature. Such elements could only achieve an exponential rise of the control pressure.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the present invention to provide improved control cell means in the pressure control valve of a fuel supply system in an engine of the type described hereinbefore, which cell means can vary the control pressure of a pressure liquid serving as a resetting force on an air flow measuring device, in a better approximation to the temperature rise during the heating-up period of the above-described type of engine, than do the hitherto known means.

This object is attained according to the invention by providing, as the control cell means in a fuel supply system of the type described above, a bimetal spring which is coupled to a heat-conducting tongue or strip heated immediately after starting by an electrical heater element. The mounting of the bimetal spring is heatinsulated against the surrounding parts of the system, and, at temperatures below the operational temperature of the engine, the bimetal spring acts against the force of a control spring of the pressure control valve mentioned hereinbefore. This arrangement has the advantage that, while the curve of the temperature rise with time is still exponential, its curvatures are so stretched due to delay in heating-up the bimetal spring that there is obtained with good approximation a substantially linear characteristic which accords well with the linear characteristic of engine heat-up.

According to another embodiment of the invention, the heat-conducting tongue consists of a metal strip disposed in parallel with the bimetal spring and being in heat-conductive contact with the bimetal spring at their joint fastening point. On the free tongue end there is mounted an electrical heater element, and the metal strip may bend to adopt varying distances from the bimetal spring, in accordance with a controllable varying heat transfer by radiation onto the bimetal spring. As an advantage hereof, the heating of the bimetal spring can be regulated according to the requirements of the engine run with fuel from the fuel supply system improved according to the invention.

In a further advantageous embodiment of the invention, an electrical series resistance can be switched into the current lead-in of the electrical heater element, at low starting temperatures, by means of a second bimetallic spring. This affords an even slower heating-up of the bimetal springs in accordance with the actual conditions prevailing in the engine at low starting temperatures, and, thereby, the control pressure is adjusted in accordance with the flat-shaped engine heat-up curves corresponding to low starting temperatures.

The invention will be better understood and further objects and advantages will become apparent from the ensuing detailed specification of preferred but merely exemplary embodiments taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematical view of a fuel supply system containing a preferred embodiment of control cell means according to the invention, and

FIG. 2 shows a diagram in which the temperatures and the control pressures of the pressure liquid, shown on the ordinate, are plotted against the time, shown on the abscissa, with temperature-time curves for the heatup of the engine being interposed therebetween.

DESCRIPTION AND OPERATION OF THE PREFERRED EMBODIMENT In FIG. 1 there is shown a fuel supply system in which air for combustion flows in the direction indicated by arrows through an air filter 1 into a zone 3 of an airintake suction pipe, in which zone a measuring plate 4 is arranged, and further, through a flexible connecting tube 5, into a zone 6 of the suction tube, which zone 6 contains a randomly operable throttle valve 7; from suction tube zone 6, the air flows into one or several cylinders (not shown) of the internal combustion engine. The measuring plate 4 is disposed in zone 3 transversely to the direction of air flow, and is displaceable in that zone in accordance with an approximately linear function of the air amount flowing through the suction tube. In this arrangement, the pressure prevailing between the measuring plate 4 and the throttle valve 7 remains constant, as long as the resetting force acting on measuring plate 4 and the air pressure prevailing upstream of measuring plate 4 also remain constant. Meaaway from nose ll.

lulu, uunsuring plate 4 controls directly a fuel metering and distributing valve 8. The displacements of measuring plate 4 are transmitted by means of a lever connected thereto and being adapted for swivelling motion about a pivot 9, and from lever 10 via a protruding nose [1 to a control slide 12 hearing nose l1 and being displaceable in axial direction in a central bore 22 of central housing 8b of the fuel metering valve 8.

Central valve housing 8b is surrounded by an external housing part 80. Fuel serving as a pressure liquid acts as a resetting force for measuring plate 4 on the frontal face 13 of control slide 12 at the opposite end of the latter from nose 11.

The supply of fuel to fuel metering valve 8 takes place by means of a fuel pump 16 driven by an electromotor 17. Pump 16 aspirates fuel from a fuel reservoir 36 and delivers it via a fuel line 18 into a duct 19 provided in the external annular housing part 8a of fuel metering valve 8. Duct 19 opens into an annular groove 20 extending about the periphery of central housing 812 between the latter and external housing part 812. Radial bores 21 lead from annular groove 20 to the central bore 22 of central housing 8b. Central axial bore 22 houses the control slide 22 which latter is of cylindrical shape and has in its middle portion a circumferential groove 23 constituted by a reduced diameter portion of slide 12 between the two full diameter end portions thereof.

Depending upon the position of the control slide 12 in axial bore 22, slide groove 23 will register more or less completely with

radial control slots

24 and 24 extending from the inner wall of bore 22 through central valve housing 8!) and communicating with ducts 25 and 25', respectively, which are provided in the external housing part 8a and are connected to fuel-injection valves (not slgwn) of the internal combustion engine, thus permitting metered fuel to flow to these injection valves. A part of the fuel from annular groove 20 flows via a bypass duct 26 into an annular groove 27 provided in the periphery of central housing 8b and external housing part 8a in the end portion of central housing 8a away from slide nose 11. Annular groove 27 communicates with a fuel line 29, leading away from the housing of valve 8, via radial bores 28. On the other hand, groove 27 communicates via the same bores 28 and via a throttle passage 30 with a pressure chamber 31 being defined in central bore 22 between the end wall of the latter and the frontal face of control slide 12 Fuel flowing via line 29 to a pressure control valve 32 serves as the pressure fluid in the control system now to be described. Valve 32 is a flat seat valve comprising a membrane 33 and rigid valve seat constituted by the rim of lead-in duct 34 into which line 29 opens. Overflowing excess fuel is recycled free from pressure through a return line 35 back to fuel reservoir 36. Valve membrane 33 is biassed by means of a spring 37 whose initial tension is variable in dependence on engine data. This is achieved by means of a cam 38 which is mounted on a shaft 39, bearing the flap of throttle valve 7, for rotation with the latter, and is axially displaceable along shaft 39 in dependence on the reduced pressure prevailing in the suction tube downstream of throttle valve 7. A rotation of shaft 39 is transmitted to cam 38 by means of an angle-shaped key 40. The free end of cam 38 is rotatably mounted in a bearing 41a fastened on the adjacent face of a membrane 41 which separates the interior of valve 32, housing cam 38, from a reduced-pressure chamber 42. The latter is connected by means of a line 43 to the zone 6 of the suction tube downstream of throttle valve 7. if there is a sufficient reduction of pressure in chamber 42, cam 38 will be moved axially against the force of a compressible resetting spring 44. A pencil-shaped pin 45, the blunt end of which follows cam 38, will be axially displaced by the movement of cam 38 and abuts with its opposite end the inner wall of a spring-retaining cap member 46. Displacement of the latter caused by the axial displacement of pin 45 will compress spring 37 which is retained by cap member 46. The degree of compression of spring 37 determines the pressure exerted by pressure liquid to reset the measuring plate 4.

A fuel line 50 branches off from line 29 and conveys fuel to a second pressure control valve 53 through fuel inlet 54, and fuel is recycled from valve 53 to the fuel reservoir36 through a fuel return line 55. Pressure control valve 53 affords a temperature-dependent regulation of the resetting pressure exerted by the fuel portion serving as pressure liquid; this valve 53 comprises ing of fua inlet tube 57 which opening isobttirated by a valve membrane 58 which is biassed by a membrane spring 59 in valve-closing direction. A tubular connecting member 60 is fastened at its one end in a bearing 61 attached to membrane 58 and rests with its other end in a bearing 62 attached to membrane spring 59, thus transmitting the valve-closing force of the latter spring to the former membrane. A bimetallic blade spring 64 is fastened at its one end by means of a nut 67 to a bolt 65 mounted in the housing 53a of valve 53, while the other, free end of bimetallic spring 64 protrudes into the interior of valve housing 53a and is provided with a forked end 64a adapted for engaging bearing 62 on membrane spring 59. An insulating means 66 is placed between bolt 65 and bimetallic spring 64 and prevents heat losses by the spring due to heat conduction to the housing 530 of valve 53. A heat-conducting tongue 68 is fixed on bolt 65 jointly with bimetallic spring 64. it extends substantially parallel to the bimetallic spring 64 in valve housing 53a and is in heatconducting contact with spring 64 through their common mounting on bolt 65.

An electric heating coil 69 is mounted on tongue 68 and is connected to the plus pole of a current source through lead 70 and to ground via a lead 72 having a branch point 71 from where a first branch leads to another bimetallic spring 73 mounted in the wall of valve housing 53a to insure an adequate electrical insulation, the tongue of which bimetallic spring is adapted for making contact with contactor 76 connected to ground, and from where a second branch leads to contactor 76 via a series resistance 74 which can be bridged by bimetallic tongue 75.

Spring membrane 59 can also be replaced by another type of spring having a non-linear characteristic or a helical spring, in which case the tension could be varied by an adjusting screw mounted in the valve housing 53a and acting on a spring retaining disk or the like means, thus offering further possibilities for adjustment.

The fuel supply system provided with the control cell means according to the invention operates in the following manner.

gilat valve seat constituted by the rimabout the open:

When the internal combustion engine is running, pump 16 driven by electromotor 17 aspirates fuel out of fuel reservoir 36 and delivers it under pressure via line 18 to metering valve 8. Simultaneously, the internal combustion engine aspirates air into the suction tube (3, 5, 6) and the air flow displaces the measuring plate 4 from its rest position shown in FIG. 1.

In accordance with the displacement of measuring plate 4, lever which is rigidly attached to measuring plate 4 moves control slide 12 into axial bore 22 whereby communication between

slots

24, 24 and annular groove 23 is widened and a greater cross sectional area is formed for the passage of fuel passing through slots 24, 24'. The increased fuel amount thus flowing through passages 25 and 25' to the injection valves (not shown) corresponds to the distance by which measuring plate 4 has moved from its rest position. Part of the fuel passing through annular slide groove 23 flows through duct 26 into pressure chamber 31, thus exerting pressure on the frontal face 13 of control slide 12, and from chamber 31 onward through lines 29 and to control

valves

32 and 53, respectively.

Due to the direct mechanical contact between the measuring plate 4 and lever 10 with the control slide 12, a constant ratio between the amount of air and fuel will be obtained as long as the characteristics of these two control elements are sufficiently linear as desired. If this can be achieved, the air/fuel ratio in the mixture would be constant over the whole working range of the engine. However, depending upon the actual working conditions of the internal combustion engine, a richer or poorer air/fuel mixture will be required, and the variability required for responding to these requirements is achieved according to the invention by altering the resetting force of the measuring plate 4.

Measurable variables for load and speed of the internal combustion engine are the throttle valve position and pressure reduction in the suction tube; therefore, the resetting force is varied most readily in dependence of these values. This is achieved by varying the force of spring 37 in first pressure control valve 32 in accordance with the position of throttle valve 7, and therefore with the pressure level in the suction tube, by a corresponding rotation and/or axial displacement of cam 38. If, for instance, the throttle valve 7 is in a position under full load, in which the suction tube is completely open, a maximal performance is desired, Le. a relatively rich mixture is required. To achieve this end, and since the tension of spring 37 in first pressure control valve 32 determines the fuel pressure which is exerted on the frontal face of control slide 12, the resetting force acting on the measuring plate 4 must be decreased, so that the control slide 12 will be moved to a position in which the control slots 24, 24' are opened more widely and a correspondingly larger fuel amount can be injected. In the reverse case, under partial load operation, a relatively smaller deflection of measuring plate 4 is obtained by a relatively higher pressure on the frontal face 13 of control slide 12.

When the engine runs under no load, cam 38 is displaced against spring 44 due to a strongly reduced pressure in the suction tube, which results in a compression of spring 37 of the first pressure control valve 32. The compression of spring 37 increases the resetting force of measuring plate 4, so that in spite of the leakage of small amounts of air which can escape past the closed throttle valve 7, no deflection of measuring plate 4 and, therefore, no fuel injection takes place.

During the heating-up phase of the engine until the operational temperature is reached, the enrichment of the air/fuel mixture is determined by the control pressure influenced by pressure control valve 53. In this case, control is effected in dependence on the ambient temperature at the start. The closing force transmitted from membrane spring 59 onto membrane 58 determines the control pressure in the supply system. At temperatures below the operational temperature, however, bimetallic spring 64 arrests the bearing 62 and rests against the membrane spring 59 thereby diminishing the force transmitted onto membrane 58 via pin 60. Immediately after starting, however, bimetallic spring 64 is warmed up by electrical heater element 69, thus bending spring 64 and reducing the arresting force exerted on membrane spring 59. This force reduction is time-dependent and corresponds to the amount of heat transmitted onto bimetallic spring 64. In order for the decrease of the force transmitted from bimetallic spring 64 onto membrane spring 59 per unit of time to be as linear as possible and to correspond to the heating-up curves of the engine per unit of time, the electrical heater element 69 is not directly attached to bimetallic spring 64, but is mounted on the heat-conducting tongue 68, which can transmit its heat to the bimetallic spring 64 by heat conduction via their joint mounting. By bending heat conducting tongue 68 more or less strongly, the amount of thermal radiation which is transmitted to the bimetallic spring 64 can be varied. It is thereby possible to obtain a favorable adaptation of the tension-time behavior of the bimetallic spring 64 in the heating-up phase of the engine to the heating-up behavior of different engines. The desired basic tension is obtained by screwing bolt 65 more or less deeply into the housing 53a of pressure control valve 53, or by changing the tension characteristic of membrane spring 59.

At starting temperatures below 0C, the heating-up of the engine per unit of time is represented by curves which are flatter the lower the temperature.

.FIG. 2 shows these heating-up curves of the engine designated by d. In order to adapt these curves to starting temperatures of about 20C, the heating-up of bimetallic spring 64 must be retarded still further which is achieved by means of the series resistance 74 in the current lead 72 from electrical heating coil 69 to ground. At normal starting temperatures, series resistance 74 is bridged by the second bimetallic spring 73, so that electrical heating coil 69 is heated up with the full current available. In FIG. 1 bimetallic spring 73 is shown in the position switching in series resistance 74.

This above-described improved system affords a regulation of the control pressure, and therewith also of the enrichment of the air/fuel mixture, which is adapted as far as possible to the actual operational requirements of the engine. This system takes into account the considerable differences in heating-up periods of an engine which occur at different starting temperatures.

What is claimed is:

1. In a fuel supply system for an externally ignited internal combustion engine with compression of the fuellair mixture, in which air flow-measuring means and a randomly operable throttle valve are arranged successively in the air intake suction pipe of the engine, and the measuring means is moved, in proportion to the air amount flowing through the suction pipe, against an at least substantially constant resetting force and thereby displaces a movable member of a distributing valve arranged in the fuel line in order to meter a fuel amount proportional to the air amount, and wherein a pressure liquid of at least substantially constant pressure, which is continuously delivered through a pressure line, serves to transmit the resetting force and acts upon a control slide valve to effect the resetting, the pressure of the liquid being variable by means of at least one regulated pressure control valve which is controlled in dependence on characteristic engine data, the improvement comprising, in combination, a control cell adapted for temperature-dependent operation and comprising a cell housing, bimetallic spring means, and heat-conducting tongue means jointly mounted in said housing for the conduction of heat from said tongue means to said bimetallic spring means and insulated against heat losses to said housing, electrical heating means associated with said tongue means, and fuel pressure regulating means comprising a control spring mounted in said housing, said bimetallic spring means being adapted for engaging said control spring and reducing the force of said spring at temperatures below the operational temperature of the engine.

2. The improvement as described in claim 1, wherein said tongue means comprise a metal strip arranged in parallel to said bimetallic spring means and having heat-transfer contact therewith at said joint mounting in said housing, said electrical heating means being mounted on a free part of said metallic strip.

3. The improvement as described in claim 2, wherein said control cell further comprises regulating means for regulating the heating up of said electrical heating means and thereby the degree of bending of said bimetallic strip.

4. The improvement as described in claim 3, wherein said regulating means comprise a second bimetallic spring means and a series resistance which can be switched-in by said second bimetallic spring means at low starting temperatures.

Claims

1. In a fuel supply system for an externally ignited internal combustion engine with compression of the fuel/air mixture, in which air flow-measuring means and a randomly operable throttle valve are arranged successively in the air intake suction pipe of the engine, and the measuring means is moved, in proportion to the air amount flowing through the suction pipe, against an at least substantially constant resetting force and thereby displaces a movable member of a distributing valve arranged in the fuel line in order to meter a fuel amount proportional to the air amount, and wherein a pressure liquid of at least substantially constant pressure, which is continuously delivered through a pressure line, serves to transmit the resetting force and acts upon a control slide valve to effect the resetting, the pressure of the liquid being variable by means of at least one regulated pressure control valve which is controlled in dependence on characteristic engine data, the improvement comprising, in combination, a control cell adapted for temperature-dependent operation and comprising a cell housing, bimetallic spring means, and heat-conducting tongue means jointly mounted in said housing for the conduction of heat from said tongue means to said bimetallic spring means and insulated against heat losses to said housing, electrical heating means associated with said tongue means, and fuel pressure regulating means comprising a control spring mounted in said housing, said bimetallic spring means being adapted for engaging said control spring and reducing the force of said spring at temperatures below the operational temperature of the engine.