US3894523A

US3894523A - Fuel supply system

Info

Publication number: US3894523A
Application number: US465504A
Authority: US
Inventors: Gerhard Stumpp
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1973-05-29
Filing date: 1974-04-30
Publication date: 1975-07-15
Anticipated expiration: 1992-07-15
Also published as: DE2327295A1; DE2327295B2; FR2231860A1; JPS5021124A; SE7407037L; BR7404307D0; GB1469551A; DE2327295C3; SE388664B; FR2231860B1

Abstract

A fuel supply system for mixture-compressing, externally ignited internal combustion engines is disclosed in which the influence of variable atmospheric pressure on the fuel-air mixture is compensated for by providing a secondary spring having pretension which is changeable in dependence on atmospheric pressure, this spring being fixed to a bellows which responds to atmospheric pressure. A primary control spring, together with the secondary spring, acts on a membrane which is part of a second pressure control valve.

Description

United States Patent 1 1 1111 3,894,523 Stumpp July 15, 1975 FUEL SUPPLY SYSTEM 2,284 687 6/1942 Schirnanek .1 123/75 13 3,680,535 8/1972 Eckert et al l 123/[39 AW [75] lnvemo" Gerhard Stump!" Stuttgart 3330.155 5/1973 Knapp 1, 123/139 AW Germany $835,828 9/1974 Knapp 123/139 AW [73] Assignee: Robert Bosch G.m.b.H., Stuttgart.

Germany Primary E.raminer-Wendell E. Burns Assistant ExaminerDavid Reynolds [22] Flled; 1974 Attorney, Agent, or F1'rmEdwin E. Greigg [Zl] Appl. No: 465,504

{57} ABSTRACT [30) Foreign Application Priority D A fuel supply system for mixture-compressing, exter- May 29 973 Germany 2327295 nally ignited internal combustion engines is disclosed in which the influence of variable atmospheric pres- {521 Us CL H 123/139 123/75 D sure on the fuel-air mixture is compensated for by pro- [5]] 1m CL I k A i 7/20 viding a secondary spring having pretension which is [58] Field of Search Aw 75 D changeable in dependence on atmospheric pressure, this spring being fixed to a bellows which responds to [561 References Cited atmospheric pressure. A primary control spring. to-

gether with the secondary spring, acts on a membrane 9 UNITED STATES PATENTS which is part of a second pressure control valve. 1.72 .042 9/1929 Junkers I23/75 D I 2,243,627 5/1941 Gregg 123/75 D 2 Claims, 1 Drawmg Figure FUEL SUPPLY SYSTEM BACKGROUND OF THE INVENTION This invention relates to a fuel supply system for mixture-compressing externally ignited internal combustion engines. The present invention relates. more particularly to such fuel supply systems in which the influence of variable atmospheric pressure on the fuel-air mixture is substantially fully compensated.

Fuel supply systems for mixture-compressing. extcr nally ignited internal combustion engines are known. in whose suction tube a measuring member and an arbitrarily actuatable throttle flap are sequentially disposed. The measuring member is moved in proportion to the air quantity flowing through the suction tube and against a preferably constant resetting force. The measuring member displaces the movable part of a quantity divider valve which meters an amount of fuel proportional to the air quantity. The resetting force is provided by a pressurized fluid which acts continuously upon a control slide. at preferably constant pressure. The pressurized fluid is delivered through a pressure line, the pressure of the fluid being changeable by means of at least one pressure control valve which can be controlled in dependence on motor parameters. The pressure control valve includes a heatable control element operating in a temperature-dependent fashion. the control element being embodied as a bimetallic spring. connected to a heat conducting arm which is heated by a heating element immediately after motor start-up. The heat conducting arm is thermally insulated from the environment. The bimetallic spring acts in opposition to the force of a control spring of the pressure control valve whenever the temperatures are below the operating temperature of the motor.

In fuel supply systems of the type described above. there is the problem that the fuel-air mixture is changed when the atmospheric pressure changes. For a geodetic altitude difference of L000 meters, the air density is changed by approximately l percent. This leads to a change in the fuel-air mixture by approximately percent.

SUMMARY OF THE INVENTION It is the principal object of the present invention to provide a fuel supply system of the kind described above in which the influence of atmospheric pressure on the fuel-air mixture is substantially compensated.

The foregoing object, as well as others which are to become clear from the text below, is achieved according to the present invention in a fuel supply system of the type described above by disposing. parallel to a control spring, a second spring, the pretension of the second spring being changeable in dependence on the atmospheric pressure.

The disposition of the second spring parallel to the principal control spring has the advantage that. during a failure of the member, preferably a bellows. which measures the atmospheric pressure. the pressure of the pressure medium is changed only by the amount required for the equalization of the atmospheric pressure. Thus, the fuel supply system and the vehicle itself remain operational.

The degree of compensation can be influenced by a choice of the elastic properties of the second spring.

An advantageous embodiment of the present invention is such that one end of the second spring is supported by a closed bellows which responds to the atmospheric pressure. the other end being supported on a spring support plate or cup. Because of the presence of a second spring. the closed bellows is loaded only by a small force. The second spring is suitably so dimensioned that it is very nearly relaxed at sea level barometric pressure. but its pretension ought to be large enough so as to avoid wear and tear due to vibration.

BRIEF DESCRIPTION OF THE DRAWING The sole FIGURE is a view. partially in section. of an exemplary embodiment of a fuel supply system according to the present invention in simplified formv DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In the fuel supply system shown. the combustion air flows in the direction of the arrow. shown farthest to the right. through an air filter I. through a suction tube sector 3. in which is disposed a measuring member (air sensor) 4. further through a connecting tube 5. and a suction tube sector 6 containing an arbitrarily actuatable throttle flap 7 and thence onto one or several cylinders (not shown) of an internal combustion engine. The measuring member 4 embodied as a plate. is disposed in the suction tube sector 3 transverse to the direction of air flow. and moves within the suction tube sector 3 according to an approximately linear function of the air quantity flowing through the suction tube 3. 5. 6. wherein. if the resetting force acting upon the measuring member 4 is constant. and if the air pressure prevailing ahead of the measuring member 4 is also constant. then the pressure prevailing between the measuring member 4 and the throttle flap 7 is constant as well. The measuring member 4 directly controls a dividing and metering valve 8. A lever I0 is connected to the measuring member 4 and is pivotablc about a pivot 9. Thus. setting movements of the measuring member 4 are transmitted. via a projection ll, onto a control slide 12 of the metering valve 8. An end of the control slide 12. which faces away from the projection II. is actuated by a pressurized medium acting as a resetting force on the measuring member 4.

Fuel supply takes place through a fuel pump [6 driven by an electric motor 17. The fuel pump 16 pumps fuel from a container 36 and delivers it through a line 18 to the metering valve 8. From the line 18 fuel flows into a channel 19 within the housing of the metering valve 8. This channel 19 ends in an annular groove 20 which is connected. via bores 2|. with an internal bore 22 which. together with reliefs in the control slide 12, forms an annular groove 23. Depending on the position of the control slide 12, the annular groove 23 more or less overlaps control slits 24 through which the metered fuel can reach channels 25 which lead to the individual (not shown) injection valves of the internal combustion engine. A portion ofthe fuel flows from the annular groove 20 into a channel 26 and further to an annular groove 27 and. via bores 28, into a line 29 which communicates via a damping throttle 30 with a pressure chamber 31 into which extends a face 13 of the control slide 12.

The fuel serving as pressure medium flows through the line 29 to a pressure control valve 32 which is a flat seat valve having a membrane 33 and a fixed valve seat 34. Overflowing fuel flows without pressure through a line 35 back into the fuel container 36. The membrane 33 is loaded by a spring 37 whose pretension is adjustable depending on characteristic motor parameters. For this purpose, there exists a three-dimensional cam 38 rotatable in unison with the throttle flap 7 and slidable axially depending on the reduced pressure prevailing in the suction tube 3, 5, 6, downstream from the throttle flap 7. The three-dimensional cam 38 is mounted axially slidable on a shaft 39 fixed to the arbitrarily rotatable throttle flap 7. The rotation of the shaft 39 is transmitted by an angular motion transfer lever 40 to the three-dimensional cam 38 whose one face is attached to a membrane 41 ofa partial vacuum chamber 42.

The vacuum chamber 42 connects through a line 43 with a location within the suction tube 3, 5, 6, downstream from the throttle flap 7. lf the vacuum is sufficient. the cam 38 is axially displaced by the membrane 41 in opposition to the force of a reset spring 44. A pin 45 follows the cam 38 and, via a spring support cup 46, acts upon the spring 37 whose pretension determines the pressure of the pressure fluid medium acting as the resetting force on measuring member 4.

Branching off from the line 29 is a second line leading to a second pressure control valve 53 and further, via a return line 55 and without pressure, to the fuel container 36. The pressure control valve 53 makes it possible to control the pressure of the pressure fluid medium serving as the resetting force in a temperaturedcpendent and atmospheric pressure-dependent manner. The pressure control valve 53 is a flat seat valve having a fixed valve seat 57 and a membrane 58. The membrane 58 is loaded in the direction of closure of the valve 53 by a control spring 59 and a parallel second spring 63. The closing force of control spring 59 is transmitted by a pin 60 lodged between the membrane 58 and the control spring 59 and the parallel second spring 63. The pin 60 is held at one end by a support bearing 61 on the membrane 58 and at its other end by a spring retainer cup 62 which supports the control spring 59 and the second spring 63. Opposing the spring retainer cup 62 is a bimetallic spring 64 whose other end is secured on a bolt 65 pressed into the housing of pressure control valve 53. The bimetallic spring 64 is protected against heat loss by conduction to the housing of the pressure control valve 53 by an insulating member 66 disposed between the bolt 65 and the bimetallic spring 64. Disposed parallel to the bimetallic spring 64 is a heat conductor arm 68 which is in heatconducting contact at the commmon fastening location shared with the bimetallic spring 64.

Mounted on the heat conducting arm 68 is an electric heating element 69. One electrical connection 70 of the electric heating element 69 is connected to the positive pole of a battery or the like and the other electrical connection 72 can be connected with a ground contact 76 on the housing via the free end 75 ofa bimetallic spring 73 additionally fastened in the housing of the pressure control valve 53 in electrically insulated fashion. A parallel branch of the connection 72 leads to the ground contact 76 through a resistor 74, which can be shunted, that is shorted out. by the bimetallic spring 73 whenever it contacts the ground contact 76.

The end of the spring 63 opposite the spring retainer cup 62 is supported by a partially evacuated closed bellows 78 disposed in a chamber 79 which communicates with the atmosphere through a channel 80.

The method of operation of the above-described fuel supply system is set forth in the paragraphs which follow.

When the internal combustion engine is running, the fuel pump 16, driven by the electric motor 17, pumps fuel from the fuel container 36 through the line 18 to the metering valve 8. At the same time, the internal combustion engine aspirates air through the suction tube 3, 5, 6, which displaces the measuring member 4 from its normal, rest position.

Depending on the magnitude of this displacement of the measuring member 4, the lever 10, fixedly connected with the measuring member 4, moves the control slide 12, which opens a greater flow cross section of the control slits 24. The amount of fuel which reaches the (not shown) injection valves through these changeable flow cross sections thus corresponds to the instant position of the measuring member 4. A portion of the fuel flows from the annular groove 23 of control slide 12 through the channel 26 into the pressure chamber 31 where it impinges on the face 13 of the control slide 12 and it further flows through the line 29 to the first pressure control valve 32 and also through the line 50 to the second pressure control valve 53.

The direct and positive coupling of the measuring member 4 with the control slide 12 results in a constant ratio of air quantity and fuel quantity, as long as the operational characteristics of these two elements are sufficiently linear, which is a desired condition. Thus, the fuelair ratio would remain constant throughout the entire operational domain of the internal combustion engine. Yet it is necessary to make the fuel-air mixture richer or leaner. depending on the operational conditions of the internal combustion engine. This is accomplished through changing the resetting force acting on the measuring member 4.

The measuring parameters for the load and the rpm of the engine are the throttle flap position and the suction tube vacuum (reduced pressure), so that the resetting force is suitably changed depending on these parameters. This is done in that, depending on the position of the throttle flap 7 or depending on the magnitude of the pressure in the suction tube 3, 5, 6, the force of the spring 37 in the first pressure control valve 32 is changed by appropriate rotation or axial displacement of the three dimensional cam 38. For example, during full load operation, if the throttle flap 7 is in a position in which the suction tube 3, 5, 6, is fully open, then the maximum power is desired which requires a relatively rich mixture. Since the pretension of the spring 37 of the first pressure control valve 32 determines the fuel pressure which acts on the face 13 of the control slide 12, it is necessary to reduce somewhat the resetting force acting on the measuring member 4, so that control slide 12 will be pushed into a position in which the control slits 24 are opened wider and a correspondingly larger amount of fuel is injected. Conversely, during partial load operation, the result is a relatively smaller deflection of the measuring member 4 because of the relatively higher pressure acting on the face 13 of control slide 12', this leans out the fuel-air mixture.

In overrunning operation, when the pressure in the suction tube is sharply reduced, the cam 38 is displaced against the force of the reset spring 44 so that the spring 37 of the first pressure control valve 32 is further compressedv This increases the resetting force acting against the measuring member 4 which ensures that the measuring member 4 is not displaced and no fuel injection takes place in spite of small amounts of leakage air" which might flow past the closed throttle flap 7. When the motor is warming up and until the operational motor temperature is reached, the mixture enrichment is determined in a temperature-dependent manner by the control pressure influenced by the second pressure control valve 53. The control process is thus dependent on the external temperature when the motor is started. The control pressure is determined by the closing force exerted by the control spring 59 and the secondary spring 63 onto the membrane 58. However. whenever the temperature lies below the operational temperature of the internal combustion engine. the bimetallic spring 64 acts on the spring retainer cup 62 and opposes the control spring 59 and the secondary spring 63. In this way. the force transmitted to the membrane 58 is reduced. However, immediately after starting, the electric heating element 69 heats the bimetallic spring 64, and as a consequence. the force transmitted by the bimetallic spring 64 to the spring retainer cup 62 is reduced. The rate of this reduction depends on the amount of heat transmitted to bimetallic spring 64. It is desired that this reduction of the force transmitted by bimetallic spring 64 to the spring retainer cup 62 be as linear as possible with respect to time. while corresponding to the warm-up of the internal combustion engine, and. for this reason, the electric heating element 69 is not directly connected with the bimetallic spring 64. but rather is disposed on the heat conducting arm 68 which is capable of transmitting heat to the bimetallic spring 64 only by heat conduction at the common fastening point. The amount of the bending of the heat conducting arm 68 towards or away from the bimetallic spring 64, depends on the amount of heat which is radiated to the bimetallic spring 64 which can be changed. In this way. and in an advantageous manner. one can obtain an adaptation of the tension vs. time behavior of the bimetallic spring 64 in the warmup phase so as to correspond to the warm-up characteristics of different engines. The desired basic pretension is achieved in that the bolt 65 is set to different depths within the housing of pressure control valve 53 or in that the elastic characteristics of the control spring 59 are changed.

When the starting temperatures are below 0C., it is necessary to delay heating the bimetallic spring 64. This is done by means of the resistor 74 in the current supply to the electric heating element 69. During normal starting temperatures, the resistor 74 is shunted by the supplementary bimetallic spring 73 so that the electric heating element 69 is fully powered. In the drawing. the bimetallic spring 73 is shown in the position in which it shunts the resistor 74. Disposed parallel to and acting in the same direction as the control spring 59 is the second spring 63 acting on the membrane 58, via the pin 60. The pretension of the secondary spring 63 can be changed, depending on the atmospheric pressure, in that its one end is supported tn the closed bellows 78 located in the chamber 79 which communicates with atmospheric pressure through the channel 80.

This preferred embodiment of the invention permits compensation for the undesired fuel-air mixture change due to a change in the geodetic altitude by varying the control pressure of the pressure fluid medium adjusted by the pressure control valve 53 and hence by varying the resetting force acting on the measuring member 4. Thus, for example. when the atmospheric pressure decreases, the control pressure of the pressure fluid medium increases. If the bellows 78 fails. the control pressure is changed only by this amount ofcorrection pressure,- whereas the fuel supply system and hence the internal combustion engine itself remain fully operational. The second spring 63 is so dimensioned that it is nearly relaxed at sea level barometric pressure.

lt is to be appreciated that the foregoing detailed description of the illustrated embodiment of a fuel supply system has been given by way of example. Numerous other embodiments and variants are possible without departing from the spirit and scope of the present invention. the scope being defined in the appended claims.

What is claimed is:

l. In a fuel supply system for mixture-compressing. externally ignited internal combustion engines. in whose suction tube a measuring member and an arbitrarily actuatable throttle flap are sequentially disposed and wherein the measuring member is moved in proportion to air quantity flowing through the suction tube and against a preferably substantially constant resetting force. which air quantity displaces a movable part of a quantity divider valve which meters an amount of fuel proportional to the air quantity and wherein the resetting force is provided by a pressurized fluid which acts continuously upon a control slide with a preferably constant pressure which is delivered through a pressure line. and wherein the pressure ofthe fluid is changeable by at least one pressure control valve which can be controlled in dependence on at least one motor operating parameter and which includes a heatable control element operating in a temperature-dependent manner. the control element being embodied as a bimetallic spring connected to a heat conducting arm which is heated by a heating element immediately after motor start-up and which is thermally insulated from the environment, the bimetallic spring acting in opposition to the force of a first control spring of the at least one pressure control valve whenever the temperature is below the motors operating temperature the improvement comprising pressure sensitive means responsive to atmospheric pressure; and a second control spring installed to act in parallel to said first control spring. the pretension of said second spring being changeable in dependence on atmospheric pressure as sensed by said pressure sensitive means, said second spring being coupled to said pressure sensitive means.

2. A fuel supply system according to claim 1. further including a spring retaining cup, and wherein one end of said second spring is supported by a bellows means which responds to atmospheric pressure and constitutes said pressure sensitive means, and the other end of said second spring being supported by said spring retaining cup.

Claims

1. In a fuel supply system for mixture-compressing, externally ignited internal combustion engines, in whose suction tube a measuring member and an arbitrarily actuatable throttle flap are sequentially disposed and wherein the measuring member is moved in proportion to air quantity flowing through the suction tube and against a preferably substantially constant resetting force, which air quantity displaces a movable part of a quantity divider valve which meters an amount of fuel proportional to the air quantity and wherein the resetting force is provided by a pressurized fluid which acts continuously upon a control slide with a preferably constant pressure which is delivered through a pressure line, and wherein the pressure of the fluid is changeable by at least one pressure control valve wHich can be controlled in dependence on at least one motor operating parameter and which includes a heatable control element operating in a temperature-dependent manner, the control element being embodied as a bimetallic spring connected to a heat conducting arm which is heated by a heating element immediately after motor start-up and which is thermally insulated from the environment, the bimetallic spring acting in opposition to the force of a first control spring of the at least one pressure control valve whenever the temperature is below the motor''s operating temperature the improvement comprising pressure sensitive means responsive to atmospheric pressure; and a second control spring installed to act in parallel to said first control spring, the pretension of said second spring being changeable in dependence on atmospheric pressure as sensed by said pressure sensitive means, said second spring being coupled to said pressure sensitive means.

2. A fuel supply system according to claim 1, further including a spring retaining cup, and wherein one end of said second spring is supported by a bellows means which responds to atmospheric pressure and constitutes said pressure sensitive means, and the other end of said second spring being supported by said spring retaining cup.