US 3823696 A
A regulating arrangement maintains proper fuel-air mixing ratios in a combustion engine by regulating the fuel-injection time as a function of airflow through the air-intake passage. The arrangement includes an electrically controllable fuel-injection valve, adjustable electric timing means for opening the valve for an adjustably predetermined time, and an adjusting member for adjusting such predetermined time. An airflow sensing member is operatively associated with the adjusting member and is mounted in the air-intake passage for displacement by air flowing through such passage. The sensing member is displaceable to a plurality of positions each corresponding to a different amount of airflow. A pneumatic damping unit is operative in response to airflow changes and applies to the sensing member a damping force which decreases with time. In this manner, the damping means opposes displacement of the sensing member in response to sudden and short-lasting changes in airflow conditions.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Mutschler et al.
[111 3,823,696 [451 July 16, 1974 ARRANGEMENT FOR REGULATING FUEL INJECTION  Inventors: Ulrich Mutschler, Nellingen;
Norbert Rittmannsberger, Stuttgart,
both of Germany  Assignee: Robert Bosch GmbH, Stuttgart,
Germany  Filed: July 17, 1972 211 Appl. No.: 272,256
 Foreign Application Priority Data July 17, 1971 Germany 2135824  US. Cl... 123/32 EA, 123/119 R, 123/139 AW  Int. Cl. F02m 51/00  Field of Search 123/32 EA, 119 R, 179 A  References Cited UNITED STATES PATENTS 2,985,160 5/1961 Armstrong 123/119 R 3,029,800 4/1962 Armstrong 123/119 R 3,482,558 12/1969 Casey et al 123/119 R Primary Examiner-Laurence M. Goodridge Attorney, Agent, or Firm-Michael S. Striker [5 7] ABSTRACT A regulating arrangement maintains proper fuel'air mixing ratios in a combustion engine by regulating the fuel-injection time as a function of airflow through the air-intake passage. The arrangement includes an electrically controllable fuel-injection valve, adjustable electric timing means for opening the valve for an adjustably predetermined time, and an adjusting member for adjusting such predetermined time. An airflow sensing member is operatively associated with the adjusting member and is mounted in the air-intake passage for displacement by air flowing through such passage. The sensing member is displaceable to a plurality of positions each corresponding to a different amount of airflow. A pneumatic damping unit is operative in response to airflow changes and applies to the sensing member a damping force which decreases with time. In this manner, the damping means opposes displacement of the sensing member in response to sudden and short-lasting changes in airflow conditions.
13 Claims, 8 Drawing Figures PATENHBJULI SEEM SHEET 1 BF 3 Fig.1
PATENTEQ JUL 1 55574 3.823.696
sum a nr 3 4 PATENTEUJUL 1 7 3 823 .696
saw a or 3 BACKGROUND OF THE INVENTION The invention relates to electrical and electronic fuel-injection control systems for combustion engines. More particularly, the invention relates to such systems of the type including an air-intake passage, a throttle valve disposed in such passage and operatively linked with the gas pedal.
Still more particularly, the invention relates to such systems as maintain proper fuel-air mixing ratios in a combustion engine by regulating the fuel-injection time, and thereby the amount of injected fuel as a function of airflow through the air-intake passage.
The invention furthermore relates to such systems as comprise one or more electromagnetically operated fuel-injection valves associated with one or more engine cylinders, and each valve being associated with a power transistor stage and a switching transistor stage, the switching stage being operated in synchronism with crankshaft rotation. Such systems furthermore include electrical timing means which effect valve opening for an adjustable period of time, in dependence-on the pressure within the air-intake passage. Such timing means conventionally comprise an energy-storing element, such as a capacitor or inductor, which is energized or deenergized at an adjustable rate dependent, in the prior art, on the air pressure within the air-intake passage. 7
The great advantageof such fuel-injection control systems is that they permit-very precise coordination between the quantity of injected fuel and the quantity of air which is drawn into the cylinder during the intake stroke of the piston. Such precise coordination of air and fuel permits the maintenance stoichiometric mixing ratios which result in nearly complete combustion of the fuel, which means reduced exhaust of air pollutants without a decrease in engine efficiency.
Known arrangementsof this type employ a sensing mechanism which does not directlymonitor the airflow, but instead monitors the air pressure. Such known arrangements comprise a pressure-responsive inductive element located downstream of the gas-pedalcontrolled throttling valve. Such inductive element forms part of a timing circuit, for instance a multivibrator, which controls the length of time during which the valve is held open. Variations in prevailing pressure affect the inductance value of the inductor and as a result can be made to change the ON-time of one of the alternately conductive transistors of the multivibrator, for instance. Conventionally, the multivibrator is triggered in synchronism with crankshaft or camshaft rotation. A great problem of such systems is that the air resistance characteristic in the intake passage is highly speeddependent, and accordingly changes in the inductance of the inductive sensor can not be madeto reflect the actual airflow in a simple manner. Thus, complex compensating arrangements are used in the prior art to coordinate the actual values of inductance with the different valve-opening times necessary.
It has already been proposed, to simplify such fuelinjection control systems by replacing the pressureresponsive inductor with a pivotably displaceable spring-biased baffie plate mounted in the air-intake passage. The pivot axis of such baffle plate is located at the side of the intake passage, and the baffle plate will assume an angularly displaced position corresponding to the degree of airflow through the air-intake passage. The timing means for the fuel-injection control arrangement may again include a multivibrator whose ON-time is for instance determined by the resistance of 'a variable resistor having a slidable wiper. A mechanical linkage connects the baffleplate to the wiper in force-transmitting manner, so that angular deflection of the baffle plate effects a corresponding resistance change of the variable resistor, and accordingly a change of the rate at which the energy-storing element of the multivibrator charges or discharges.
However, such known construction is not very effective, because of pressure pulsations which develop in the air-intake passage, particularly when the airthrottle valve is fully or nearly fully open i.e., at high loads. The suction downstream of the throttle valve is of course a function of the intake stroke of the cylinder. When the throttle valve is nearly closed, the air flow sucked into the cylinder past the throttle valve will be quite even; however, when the valve is more open, the airflow is less even, and characterized by many sudden and short-lasting variations. These variations produce corresponding movements of the baffle plate, and result in pulsating resistance values of the variable resis tor. Inasmuch as the fuel-injection time is very short, such superimposed oscillations of the resistance value can interfere very greatly with proper timing action, and result in a greatly reduced combustion efficiency. Actually this difficulty arises even at lower speeds, and particularly in four-cylinder four-stroke engines.
SUMMARY OF THE INVENTION It is accordingly a general object of the invention to overcome the disadvantages of the prior art.
. It is a more particular object to provide a novel fuelinjection control arrangement which overcomes such disadvantages.
It is a further object to provide a novel control arrangement including electrical timing means and an improved airflow transducer.
It is a related object to provide such control arrangement with an airflow transducer of very simple and sturdy construction.
'It is another object to provide such an airflow transducer which is quickly responsive to changes in air-flow actually corresponding to changes in gas-pedal position and/or changes in intake suction associated with different parts of the intake stroke, but which is largely unresponsive to the higher-frequency airflow variations superimposed upon the aforementioned airflow changes.
It is a concomitant object to provide such an arrangement which is unresponsive to airflow variations lying within a particular frequency range.
It is another object to provide'such an airflow transducer which is responsive to relatively slow changes in airflow'actually corresponding to the relatively slow changes of gas-pedal position.
It is'a similar object to make such transducer responsive to relatively slow airflow variations associated with It is a related and more specific object to make such transducer quickly responsive to airflow changes whose frequency is in a first lower range, and unresponsive to airflow changes whose frequency is in a predetermined second higher range associated with stray airflow changes.
These objects, and others which will become apparent hereafter, can be met by a regulating arrangement which maintains proper fuel-air mixing ratios in a combustion engine by regulating the fuel-injection time as a function of airflow throughthe air-intake passage. Such arrangement includes an electrically controllable fuel-injection valve, adjustable electric timing means for opening the ,valve for an adjustable predetermined time, and adjusting means for adjusting such predetermined time. An airflow sensing member is operatively associated with the adjusting means and mounted in the air-intake passage for displacement, by air flowing through the passage, to any of a plurality of different positions respectively corresponding to different amounts of airflow. Pneumatic damping means is operative in response to airflow changes for applying to the sensing member a damping force which decreases with time and which in that manner reduces the sensitivity of the sensing member to sudden and short-lasting changes in airflow conditions.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understoodupon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic overall illustration of a regulating arrangement according to the invention;
FIG. 2 is a detailed view of a portion of the timing circuitry of FIG. 1;
FIG. 3 is a longitudinal section through the air-intake passage of the engine shown in FIG. 1, and depicting sensing means and pneumatic damping means according to the invention;
FIGS. 4-7 are views similar to FIG. 3, but illustrating different sensing means and/or different pneumatic damping means according to the invention; and
FIG. 8 illustrates a modification of part of the damping means of FIG. 6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The illustrated arrangement regulates fuel injection in a four-cylinder four-stroke internal combustion engine 10, provided with four electromagnetically concal timing means'which is synchronized with the rotation of (schematically illustrated) camshaft 17 by means of an interrupter 18 coupled with the camshaft. Interrupter 18 generates two rectangular pulses LJ for each rotation of camshaft 17, and these pulses are used for the generation of an OPEN-pulse S which is trans mitted to the solenoid of a valve 11. The duration T determines the length of time during which the'fuelinjection valve 11 is open, and in that way determines the amount of fuel which is injected. The correspondence is very precise because, as already indicated, the fuel is injected at constant'pressure, for example 2 atm. The solenoid windings 19 of the valves are each connected in series with a respective coupling resistor 20 and connected to a common amplifier andd power stage 21, which contains at least apower transistor indicated schematically in FIG. 1 as transistor 22, the collector-emitter path of the transistor being connected in series with the coupling resistor 20. The other end of each solenoid winding 19 is connected to ground.
It is emphasized that the electrical timing arrangement, as such, does not form part of the invention and can be of any conventional type.
In the combustion engine illustrated, a mixture of fuel andair is ignited by a separate ignition system, and the amount of fuel injected into the cylinder is to be carefully coordinated with the amount of air which enters during the intake stroke of the piston, so as to result in the most complete combustion possible. For the sake of efficiency, moverover, it is important that there be no substantial excess of air. In order to maintain the desired stoichiometric ratio between fuel and air, a regulating arrangement is provided.
The regulating arrangement includes airflow sensing means generally designated LM in FIG. 1 and located in the'air-intake passage 25 downstream of the air filter 26 but upstream of the throttle valve 28 associated with the gas pedal. In simple terms, the airflow sensing means of FIG. 1 comprises a baffle plate 30 whose angular orientation is indicative of airflow, and which is mechanically coupled to the wiper 31 of a variable resistor R. Wiper 31, as will later be appreciated, constitutes adjusting means for varying the fuel injection time. Variable resistor R is incorporated in a transistor switching circuit TS which provides timing signals whose duration is a function of the resistance of resistor R.
FIG. 2 illustrates somewhat schematically the circuitry contained in transistor switching-circuit TS. It is strongly emphasized that such circuitry may be of many conventional types.
Unit TS comprises two alternately conductive transistors, namely an input transistor T and an output transistor T which are cross-coupled in a manner common in multivibrators. The circuit further includes an energy-storing element C, here in the form of a simple capacitor; a modified but equivalent'circuit could employ an inductor. The duration of the discharge of capacitor C determines the Onand OFF-times of transistors T T and thereby the duration of the fuelinjection. Clearly, precise regulation of the fuel injection will require a precise control of the discharge of capacitor C.
The circuit TS is triggered-by interrupter 18, which can be a mechanical interruptor or a unit incorporating a multivibrator, and which generates the prolonged triggeringpulses LJ. As already mentioned, interruptor 18 issynchronized with camshaft rotation and effects a connection between capacitor C and an energy source C for the duration of a pulse LJ corresponding to a predetermined angular rotation of the camshaft. During such time, a charging current 1,, flows through the capacitor, and the capacitor voltage increases. In the illustrated embodiment, it isassumed that interruptor 18 comprises a (non-illustrated) multivibrator which is in one state for 180 of camshaft rotation and in its other state during the subsequent 180 of camshaft rotation.
The arrangement of FIG. 2 permits initiation of the discharge period immediately following the termination of the charging period, which for example can occur after the camshaft has rotated 0, 360, 720, etc. when the conductive output transistor T becomes nonconductive. Simultaneously, the non-conductive transistor T becomes conductive because, as a result of blocking of transistor T the base voltage of transistor T is sufficiently high to turn the transistor T, on and establish a flow of base current throughresistors 35 and 36. The energy acccumulated by capacitor'C during charging is discharged through diode 37 and the emitter-collector path of transistor T Regulating means E maintains the discharge current constant, this being a well known expedient in time base generators, and thus the capacitor voltage decreases linearly. It will be appreciated that during the ON-time of T its collectoremitter voltage is low, and so the positive capacitor electrode willbe at a low voltage. The more negative terminal of the capacitor accordingly will enforce upon the base of T a voltage which maintains the transistor T off. However, as the capacitor voltage decreases during discharge, the base voltage of T will rise until eventually a forward-bias is achieved. At that point T will go on, and its greatly lowered collector voltage will terminate the forward-bias of the base of T After the discharge period, when T is off, charging current can not flow through capacitor C via resistor39, because of diode 37. Capacitor C will recharge only at the beginning of the next charging pulse LJ, namely, after a camshaft rotation of 180, 540, etc. It is emphasized that thecircuitry of FIG. 2 is merely exemplary. It is extremely well known how to provide such timing circuitry, and many equivalents will be obvious.
At rotational speeds of less than 2,000 RPM and at high loads, the air sucked through the intake passage towards the engine 10 will exhibit marked pulsations. These can result in oscillations of baffle plate about an angular position not actually corresponding to the average airflow. In order to avoid the faulty regulation of fuel-injection which can result, the regulating arrangements described below include not only airflow sensors, but also pneumatic damping arrangements which counteract the tendency of the baffle plate 30 to oscillate about a mean value in response to highfrequency airflow pulsations, but which permit the baffle plate 30 to quickly respond to flow changes having a real significance for the combustion process.
FIG. 3 illustrates an airflow sensing means 30 having a form of a first baffle plate mounted for pivotal movement about an axis 41 located to one side of the airintake passage 25. A damping member'42 constitutes a first dashpot portion and has the form of a second baffle plate which shares the movement of the first plate 30. Damping plate 42 is of rectangular outline and is pivotable through a damping chamber 45 which has the shape of a sector of a cylinder and is defined by a wall which constitutes a second dashpot portion. The periphery of damping plate 30 defines with the inner peripheral wall 44 of chamber 45 a very limited pressure-leakage clearance 43. It will be appreciated that damping plate 42 in part defines the dashpot chamber 45, and that movement of the damping plate 42 causes a variation in the volume of damping chamber 45. A small pressure-leakage opening 46 is provided on the face of the damping plate .42, in addition to opening 43. In the steady-state, the pressure P in damping chamber 45 is equal to the pressure P in the section of passage 25 immediately downstream of baffle plate 30. Each of plates 30, 42 has'a major surface facing this section of passage 25, and advantageously these surfaces are of equal area so that the forceexerted by reason of suction pressure P will be the same on both plates. Accordingly, variations in P cannot of themselves produce displacement of plates 30, 42, because of the torques developed on plates 30, 42 cancel. However, when the pressure P changes, the pressure P will tend to approach such new value of P due to the provision of pressure-leakage openings 46 and 43. Accordingly, as the pressure is equalized, a new steady-state angular orientation of plate 30, indicative of the changed airflow conditions, is established. Moreover, this pressure equalization occurs at a limited rate. This rate is so chosen that equalization does not occur in response to pressure pulsations having a frequency of for example more than about 30 Hz; thus sensing member 30 tends not to respond to such high-frequency pulsations. (The figure of 30 Hz has been determined by empirical testing of a four-cylinder four-stroke combustion engine). In particular, the cross-section of the pressure-leakage opening 46and/or the clearance 43 is so selected that when for example the engine is accelerated and the airflow changes rapidly, the pressure equalization in response to such rapid airflow change will occur in about 1/10 second, a response time significantly greater than the time of stray airflow pulsations.
FIG. 4 depicts another version of the airflow transducer arrangement. As in FIG. 3, the baffle plates 30, 42 are pivotable about a common axis 41, and the periphery of damping plate 42 again defines a pressureleakage clearance, here identified with numeral 54. A wall 51 defines a damping or dashpot chamber 52 to the right of clamping plate 42 and having a volume which is dependent on the position of plate 42. The part of damping chamber 52 not actually enclosed by plate 42 communicates freely through opening 53 with the section of conduit 25 upstream of sensing member 30. The peripheral clearance 54 permits only a relatively slow equalization of pressure between the pressure P in the upstream section of passage 25 and the pressure P in the enclosed portion of damping chamber 52. An elastic separating wall 55, herein the form of abellows, separates chamber 52 from the section of passage 25 downstream of plate 30. Bellows 55 is highly yieldablein longitudinal direction. As long as the pressure P, is constant, in the steady-state, the-pressures P and P: will remain equal; in the steady-state, damping plate 42 has no effect.
In the steady-state, the pressure P, will actually oscillate about a constant value, such oscillations constituting interference pressure pulsations superimposed upon the average value of pressure. These oscillations of P, are communicated to damping chamber 52 by way of readily yieldable bellows 55, and the pressure P will oscillate in the same manner as pressure P Thus, in a manner similar to FIG. 3, the very rapid pressure fluctuations of P, will have an efiect on plate 30 which crease) and, as just explained, this sudden change of pressure does not produce a net moment about axis 41. However, as the pressure P relatively slowly approaches the pressure P by way of airflow through pressure-leakage opening 54, a net moment can be exerted on plate 30. Clearly, a damping of the response of plate 30 is effected also during ordinary acceleration. The magnitude of the damping depends on the rate of airflow through pressure-leaking opening 54 and can be adjusted to meet the empirically determined requirements of a particular engine design.
If it should be necessary to make the compensation for the pulsating pressure so great that the sensing plate 30 cannot quickly enough follow the transitional change of intake airflow, it is possible to provide two biased flutter valves on the damping plate 42 oneof which is closed against the pressure P and the other of which is closed against the pressure P,,.
A functionally equivalent arrangement is illustrated in FIG. 5. Here, the transient clamping force is applied to plate 30 not by a plate 42, but rather by a lever 63 connected via linkage 62 with membrane 61. A second membrane 65 has the same function as bellows 55 in FIG. 4.
' Membranes 61, 65 define between themselves a damping or dashpot chamber having a pressureleakage opening 64. In the steady-state, pressure P, is equal to atmospheric pressure. If pressure P changes, pressure P changes in like manner upon displacement of membrane 65. The pressure P will relatively slowly return to atmospheric pressure, thereby permitting a relatively slow response of sensing member 30 to the change of P The rate of return of P to atmospheric pressure depends on the size of pressure-leakage opening 64, and can be so selected that, during a half-cycle of an interference pulsation of pressure P,, no significant pressure equalization between P and P can occur. As with the previously described embodiment, and in addition to opening 64, it is possible to provide two flutter valves on opposite sides of membrane 61, and such valves can if desired have a temperaturedependent' characteristic. Such temperature dependence can for instance be achieved by provision of bimetallic flat springs, which for example decrease the damping effect at lower temperatures. In this way it is possible to establish an enrichment of the fuel-air mixture at low running temperatures. As mentioned above, the interference pressure pulsations develop particularly at high loads, that is when the throttle valve 28 is fully or nearly fully open. In the embodiment of FIG.
8. valve means comprising a valve plate 76 upwardly biased by a tension spring 77. Valve plate 76 blocks communication between passage 71 and the downstream section 72 of passage 25 when the pressure difference on opposite sides of plate 76 is below a predetermined threshold value.
The embodiment of FIG. 7 provides for the enrichment of the fuel-air mixture upon acceleration of the motor, and especially upon opening movement of the damping action is greatly decreased, so that the fuel injection time can be increased very quickly in response to the increased air-flow. A pressure chamber 81 communicates with damping chamber 45 via conduit 80. Pressure chamber 81 is sealed at one end by an elastic wall or membrane 82. In the center of the membrane 82 there is provided a force-transmitting plate 83 which is linked to one of the arms of lever 84. The other arm of lever 84 is connected via mechanical linkage 85 with a throttle-follower member 86. When to effect engine acceleration, the throttle 28 is opened in the direction of the arrow, members 26, 85, 84 and 83 effect displacement of membrane 82 in direction of the arrow C virtually immediately. The resulting underpressure in chamber 81 is quickly communicated to damping chamber 45, and air flows from chamber 45 to cham ber 81 very quickly. When the throttle 28 is quickly opened in this manner, the pressure to the right (in FIG. 7) of plate 42 quickly drops, and the slow followup by the pressure to the left (in FIG. 7) of plate 42 normally effects the damping action. However, because the sudden opening of valve 28 results in flow of air from chamber 45 to chamber 81, the equalization of pressure to either side of plate 42 occurs far faster, and the damping is thus very greatly reduced. Indeed, the pressure will be equalized at a .highrate relative to the increase of air flow, and counterclockwise displacement of sensing member 30 can even occur somewhat faster than actually corresponds to the increase in airflow, and the fuel-air mixture will thus be especially enriched at the time of such acceleration.
The provision of pressure-leakage opening 46 limits the duration of such enrichment. That is, the angular displacement of plate 30 will exceed that corresponding to the actual airflow only until the pressure on either side of plate 42 is equalized. At that time, any further changes in airflow will again be responded to with damping action, except for similar sudden opening motions of throttle 28. The removal of damping action, it should be noted, occurs only in response to a sudden movement of throttle 28 in opening direction. When throttle 28 moves in opening direction the airflow is from chamber 45 to chamber 81, and this is permitted by check valve 88. However, if the-throttle 28 moves suddenly in closing direction, the direction of airflow is from chamber 81 to chamber 45, and such flow is greatly limited by check valve 88, and occurs only through permanently open pressure-leakage opening 89, whose flow area is relatively small.
FIG. 8 illustrates a modified version of FIG. 6 including temperature compensation. The auxiliary air pas:
sage 71 is again provided and leads into the valve chamber defined by valve body 91. A tapered valve member 93 regulates theflow of air through passage 92. Valve member 93 is biased towards closing position by bimetallic flat spring 94. Valve member 93 is moved to open position only when the pressure difference between passage section 72 and the interior of valve body 91 has reached a certain threshold value. However, the use of a bimetallic flat spring 94 causes this threshold pressure difference to change with temperature in a manner corresponding to the desired temperaturedependent-variations in the fuel-to-air ratio.
By suitable disposition of the juncture between auxiliary air passage 71 and damping chamber 45, the response to airflow can be made to vary in a desired manner on the load. The advantage of such expedient is that the reduction of the damping action during acceleration can be accomplished solely by pneumatic action, and without the mechanical linkages used in the equivalent embodiment of FIG. 7.
It will be understood that each of the'elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.
While the invention has been illustrated and described as embodied in an arrangement for fuelinjection regulation, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications witout omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.
What is claimed as new and desired to be protected by Letters Patent is set forth in appended claims.
1. A regulating arrangement which maintains proper fuel-air mixing ratios in a combustion engine by regulating the fuel-injection time as a function of the inflow rate of air through the air-intake passage, comprising an electrically controllable fuel-injection valve; adjustable timing means for opening said valve for an adjustable predetermined time; adjusting means for adjusting said predetermined time; an airflow sensing member operatively associated with said adjusting means and mounted in said air-intake passage for displacement by air flowing through said passage and impinging upon said member to any of a plurality of different positions respectively corresponding to different air inflow rates; and pneumatic damping means operative for opposing displacement of said sensing member in response to sudden and short-lasting changes in the air inflow rate, said pneumatic damping means comprising a dashpot arrangement having a first portion connected to said sensing member and sharing the movement thereof and a stationary second portion, the first and second portions of .said dashpot arrangement together defining a dashpot chamber having an air leakage opening and being movable relative to each other in a first direction decreasing the volume of saiddashpot chamber against the opposing damping force of air being compressed in said dashpot chamber and leaking out through said leakage opening, and movable relative to each other in opposite second direction increasing the volume of said dashpot chamber against the opposing damping force separating-the part of said dashpot chamber to one side of said second baffle plate from the section of said airintake passage downstream of said first baffle plate,
and wherein the part of said dashpot chamber to the other side of said second plate communicates freely with'the section of said air-intake passage upstream fia dji stbfiefitz w ..m
4. An arrangement as defined in claim 3, wherein said elastic separating wall comprises a bellows.
5. An arrangement as defined in claim 2, wherein said first baffle plate has a major surface facing the section of said air-intake passage downstream thereof, and wherein said second baffle plate has a major surface also facing said section of said air-intake passage, and wherein said major surfaces are of approximately equal area.
6. An arrangement as defined in claim 1, wherein said sensing member comprises a pivotable baffle plate, and wherein said portions comprise two elastically yieldable wall portions, and wherein one of said wall portions separates said chamber from the section of said air-intake passage downstream of said first baffle plate, and wherein said first portion further includes mechanical linkage means connecting the other of said wall portions with said first baffle plate in forcetransmitting relationship therewith.
7. An arrangement as defined in claim 2, wherein said damping means further includes an auxiliary air passage leading from said dashpot chamber to the section of said air-intake passage donwstream of said first baffle plate, and pressure-responsive valve means for restricting air flow through said auxiliary passage.
8. An arrangement as definedin claim 2, said airintake passage including a throttling valve linked to the gas pedal and located downstream of said first baffle plate, wherein said damping means further includes a pressure chamber communicating with said dashpot chamber, and means connected to said throttle valve for varying the volume of said pressure chamber as a function of the position of said throttle valve.
9. An arrangement as defined in claim 8, wherein said damping means further defines a permanently open pressure-leakage opening between said pressure chamber and said dashpot chamber.
10. An arrangement as defined in claim 9, wherein said damping means further includes check valve means for regulating the flow of air between said pressure chamber and said dashpot chamber.
11. An arrangement as defined in claim 7, wherein said pressure-responsive valve means comprises a valve body and a helical biasing spring biasing said valve body in a predetermined direction.
12. A regulating arrangement. which maintains proper fuel-air mixing ratios in a combustion engine by regulating the fuel-injection time as a function of airflow through the air-intake passage, comprising an electrically controllable fuel-injection valve; adjustable electric timing means for opening said valve for an adjustable predetermined time; adjusting means for adjusting said predetermined time; an airflow sensing member operatively associated with said adjusting means and mounted in said air-intake passage for displacement by air flowing through said passage to any of a plurality of different positions respectively corresponding to different airflow conditions; and pneumatic damping means, operative in response to airflow changes, for applying to said sensing member a damping force which decreases with time, whereby to oppose displacement of said sensing member in response to sudden and short-lasting changes in airflow conditions, wherein said sensing member comprises a first pivotable baffle plate, and wherein said damping means comprises a damping chamger and a second baffle plate sharing the movement of said first plate and pivotably movable in said damping chamber and wherein said damping means defines a pressure-leakage opening in said damping chamber, wherein the periphery of said second baffle plate defines with the inner periphery of said damping chamber a clearance constituting said pressure-leakage opening, and wherein said damping chamber communicates via said pressure-leakage opening with the section of said passage downstream of said first baffle plate.
13. A regulating arrangement which maintains proper fuel-air mixing ratios in a combustion engine by regulating the fuel-injection time as a function of airflow through the air-intake passage, comprising an electrically controllable fuel-injection valve; adjustable electric timing means for opening said valve for an adjustable predetermined time; adjusting means for adjusting said predetermined time; an airflow sensing member operatively associated with said adjusting means and mounted in said air-intake passage for displacement by air flowing through said passage to any of a plurality of different positions respectively corresponding to different airflow conditions; and pneumatic damping means, operative in response to airflow changes, for applying to said sensing member a damping force which decreases with time, whereby to oppose displacement of said sensing member in response to sudden and short-lasting changes in airflow conditions, wherein said sensing member comprises a first pivotable baffle plate, and wherein said damping means comprises a damping chamber and a second baffle plate sharing the movement of said first plate and pivotably movable in said damping chamber and wherein said damping means defines a pressure-leakage opening in said damping chamber, wherein said pressureleakage opening is provided on said second baffle plate.