US3583374A

US3583374A - Fuel injection system for internal combustion engines

Info

Publication number: US3583374A
Application number: US796526A
Authority: US
Inventors: Hermann Scholl; Hermann Hoelle
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1968-02-13
Filing date: 1969-02-04
Publication date: 1971-06-08
Anticipated expiration: 1988-06-08
Also published as: GB1254164A; JPS4940577B1; NL6902200A; ES363555A1; DE1776161A1; AT295242B; BE728296A; DE1601364A1; FR1597281A; DE1776161B2; SE341688B

Abstract

A fuel injection system for internal combustion engines wherein a transducer sends electric signals to an electronic control circuit which opens the fuel injection valves for intervals of variable length. The intensity of signals which the transducer transmits to the control circuit (and hence the length of intervals during which the valves inject fuel into the cylinders of the engine) is a function of two parameters, namely, the manifold pressure and the differential between manifold pressure and atmospheric pressure. The signals are produced by an inductance whose core is adjustable by a diaphragm and one or more evacuated containers as a function of the two parameters.

Description

Inventors Hermann Scholl Stuttgart; Hermann Hoelle, Stuttgart-Kaltental, both of, Germany Appl. No. 796,526

Filed Feb. 4, 1969 Patented June 8, 1971 Assignee Robert Bosch G.m.b.H.

Stuttgart, Germany Priority Feb. 13, 1968, Sept. 30, 1698 Germany P 16 01364.2 and P17 76161.4

FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES 26 Claims, 12 Drawing Figs.

US. Cl 123/32E, 123/ 1 40M? Int. Cl F0211 5/00 123/32,

Field of Search [5 1 References Cited UNITED STATES PATENTS 2,414,617 1/1947 Summers 123/1403 2,988,881 6/1961 Reggio l23/140.3X 3,126,879 3/1964 Canfield .lr.. 123/1403 3,128,751 4/1964 Dahl et al. 123/1403 3,319,613 5/1967 Begley etal. 123/32E-l 3,338,221 8/1967 Scholl 123/32E-l Primary ExaminerLaurence M. Goodridge Attorney-Michael S. Striker ABSTRACT: A fuel injection system for internal combustion engines wherein a transducer sends electric signals to an electronic control circuit which opens the fuel injection valves for intervals of variable length. The intensity of signals which the transducer transmits to the control circuit (and hence the length of intervals during which the valves inject fuel into the cylinders of the engine) is a function of two parameters, namely, the manifold pressure and the differential between manifold pressure and atmospheric pressure. The signals are produced by an inductance whose core is adjustable by a diaphragm and one or more evacuated containers as a function of the two parameters.

FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION The present invention relates to internal combustion engines in general, and more particularly to improvements in internal combustion engines for use in automotive vehicles. Still more particularly, the invention relates to improvements in fuel injection systems for internal combustion engines, especially to fuel injection systems wherein the valves which admit fuel from the source of fuel to the cylinders of the engine are controlled by electronic means.

It is already known to make the operation of fuel injection systems for internal combustion engines dependent on the pressure in the intake manifold, i.e., to select the amounts of fuel which are injected during each cycle of operation of the internal combustion engine as a function of manifold pressure. The exact rate at which the amounts of injected fuel vary in response to changes in manifold pressure is determined by the designer. For example, the designer can select a particular spring constant or he can employ certain specific electronic or electrical parts in the control circuit of the fuel injection system. Such rate depends to a large extent on the type of the internal combustion engine.

It was found that the operation of presently known fuel injection systems is not entirely satisfactory, mainly because the rate at which the amounts of fuel which is injected per cycle vary as a function of changes in manifold pressure is not selected by full consideration of all factors which influence the operation of an internal combustion engine. On the one hand, an internal combustion engine should operate with maximum efficiency at full load, i.e., the cylinders should receive a rich fuel-air mixture which is obtained by injecting a large amount of fuel. On the other hand, the cylinders should receive a lean mixture of fuel and air when the engine is operated at a partial load, for example, when the vehicle in which the engine is installed is to be operated in city traffic. By furnishing a lean mixture when the engine operates at partial load, the injection system insures that the fuel is fully combusted so that the products of combustion contain a relatively small percentage of carbon monoxide and hydrocarbons as well as that the engine consumes a relatively small quantity of fuel. The aforediscussed requirements for the quality of the fuel-air mixture during operation at full load and at partial load are in part contradictory; therefore, the designers invariably resort to a fuel injection system which is a compromise between an optimum system for operation at full load and an optimum system for operation at partial load. In certain presently known fuel injection systems, the operator of the engine must actuate a switch which changes the rate at which the fuel injection system admits fuel as a function of changes in manifold pressure when the engine is operated at full load so that the cylinders of the engine then receive a mixture which is rich in fuel. Such solution is reasonably satisfactory; however, the fuel injection system is complicated, expensive and prone to malfunction. Furthermore, conventional fuel injection systems are suitable for use in connection with engines which are operated at sea level but not when the engine is operated at a substantial height above sea level, or vice versa.

SUMMARY OF THE INVENTION An object of our invention is to provide a fuel injection system which is constructed and assembled in such a way that it can insure optimum injection of fuel under a wide variety of circumstances and particularly when the engine operates at full load or at partial load.

Another object of the invention is to provide a novel transducer for use in the just outlined fuel injection system.

A further object of the invention is to provide a transducer which insures satisfactory injection of fuel regardless of changes in atmospheric pressure, i.e., regardless of the distance between the location of the engine and sea level.

An additional object of the invention is to provide a fuel injection system which can employ several components of presently known fuel injection systems.

Still another object of the invention is to provide a fuel injection system which can be readily installed in or combined with many types of internal combustion engines and which is adjustable so that it can insure optimum injection of fuel into each of a variety of different engine types.

A concomitant object of the invention is to provide an electronic fuel injection system with a novel transducer which can regulate the operation of electronic components in dependency on manifold pressure as well as a function of one or more additional factors which influence the operation of an internal combustion engine, either at partial load or at full load.

The invention is embodied in a structure which is preferably incorporated in an automotive vehicle and includes an internal combustion engine having cylinder means and intake manifold means connected with the cylinder means, a source of fuel, valve means for controlling the admission of fuel from the source to the cylinder means, electronic control means operative to open the valve means for intervals of variable length, and transducer means for regulating the operation of control means. The transducer means comprises regulating means (preferably including a deformable diaphragm or an analogous regulating element and one or more evacuated containers with deformable wall means) which is adjustable as a function of pressure changes in the manifold means and as a function of changes in differential between the pressure in manifold means and atmospheric pressure.

At least a portion of the regulating means is preferably adjustable continuously in response to changes of pressure differential within a predetermined range. For example, the lower limit of such range may correspond to a pressure differential of 050 Torr and the upper limit of such range may correspond to a pressure differential of -200 Torr. It is also preferred to design the regulating means in such a way that it is adjustable only as a function of changes in absolute manifold pressure when the magnitude of pressure differential is within at least two predetermined ranges.

The transducer means preferably further comprises an inductance with one or more coils surrounding a reciprocable core which causes the coils to transmit to the electronic control means signals whose intensity is a function of the axial position of the core. The latter is adjustable by the diaphragm and/or by the container or containers.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved fuel injection system itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon 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 view of a fuel injection system for a four-cylinder internal combustion engine;

FIG. 2 is a schematic sectional view of a first transducer for use in the fuel injection system;

FIG. 3 is a schematic sectional view of a modified transducer;

FIG. 4 is a sectional view of a transducer which is analogous to the schematically represented transducer of FIG. 2;

FIG. 5 is a sectional view as seen in the direction of arrows from the line V-V of FIG. 4;

FIG. 6 is a plan view of the diaphragm in the transducer of FIG. 4;

FIG. 7 is a diagram illustrating the operation of the fuel injection system at sea level;

FIG. 8 is a similar diagram illustrating the operation of the fuel injection system at a considerable height above sea level;

FIG. 9 is a fragmentary sectional view of a transducer which constitutes a modification of the transducer shown in FIG. 4;

FIG. 10 is a diagram illustrating the operation of a fuel injection system which embodies the transducer of FIG. 9 at sea level;

FIG. 11K is a diagram illustrating the operation of the fuel injection system embodying the transducer of FIG. 9 at a considerable height above sea level; and

FIG. 12 is a fragmentary sectional view of still another transducer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a four-cylinder internal combustion engine 10 receiving fuel from an electronically operated fuel injection system which embodies our invention. The four spark plugs 1111 of the engine 10 receive high-voltage surges from a customary ignition coil, not shown. The four cylinders of the engine 10 are connected with the branches of an intake manifold I2 and each such branch accommodates an electromagnetically operated fuel injection valve 13. The valves 13 are screwed into the respective branches of the intake manifold I2 and each thereof is connected with a closed-circuit fuel pipe line I5 by way of a discrete supply conduit M. Fuel in the pipe line I5 is maintained under a constant pressure, for example, at 2 atmospheres superatmospheric pressure. If an injection valve 13 is opened in response to flow of current through the winding of the corresponding electromagnet for a predetermined interval t the amount of injected fuel is directly proportional to the length of such interval.

The fuel pipe line 15 accommodates a filter 116 and a fuel pump 18 which is driven by an electric motor 17. The pump 18 causes fuel to circulate in the pipe line IS in the direction indicated by arrows whereby the pump draws fuel from and recirculates such fuel through a tank 19. The pipe line 15 further accommodates a pressure regulator 20 which is installed downstream of the supply conduits M and returns surplus fuel to the tank I9 by way of a return conduit 21 of the pipe line. The parts M to 21 together constitute a source of fuel for the engine 10.

The inlet of the intake manifold 12 accommodates a throttle 25 which is pivotable about a fixed axis and can change its position in response to depression of a pedal 26 in the customary way. The throttle 25 is mounted downstream of an air filter 27. By depressing the pedal 26 when the engine 10 is running, the operator changes the pressure in the intake manifold 112 (such pressure will be called manifold pressure for short). If the pedal 26 maintains the throttle 25 in fully open position, the manifold pressure approximates the pressure of surrounding air, i.e., the atmospheric pressure which depends on the prevailing weather conditions (high-pressure or low-pressure) and from the distance between the location of the engine and sea level. The atmospheric pressure at sea level approximates 760 Torr (one Torr is 1/760 of an atmosphere and corresponds roughly to the pressure of a mercury column of 1 millimeter). At a height of 2,400 meters above sea level, the atmospheric pressure is only about 540 Torr. If the pedal 26 permits or causes the throttle 25 to assume its fully closed position, the manifold pressure depends on two additional factors, namely, on rotational speed of the engine 10 and on the closing angle alpha of the throttle. Thus, the manifold pressure is a function of the operating conditions of the engine.

The manifold pressure can be determined in a number of ways. In accordance with one procedure, the manifold pressure is compared with zero pressure (absolute vacuum). Such absolute manifold pressure is 760 Torr at sea level and 540 Torr at a height of 2,400 meters when the throttle 25 assumes its fully open position. The second procedure includes comparing the manifold pressure with the pressure of surrounding air, i.e., to a pressure which fluctuates within a reasonably wide range in dependency on prevailing weather conditions as well as in dependency on location of the engine with reference to the sea level. When one resorts to the second procedure, the pressure of surrounding air is considered to be zero pressure. A manifold pressure which is lower by Torr than atmospheric pressure can be said to correspond to a negative pressure of 100 Torr or to a pressure differential of 100 Torr between manifold pressure and atmospheric pressure. The relationship between such values will be readily understood with reference to FIGS. 7 and 8. FIG. 7 illustrates the relationship for conditions at sea level and FIG. 8 the relationship for conditions at a height of 2,400 meters above sea level. The absolute pressure p, in the intake manifold 12 is measured along the abscissa, the pressure differential p between manifold pressure and atmospheric pressure is also measured along the abscissa, and the injection time intervals t, is measured along the ordinate.

The control means for periodically opening and closing the fuel injection valves 13 is synchronism with rotational speed of the engine 10 comprises an electronic control circuit which is shown schematically in FIG. I and includes a monostable multivibrator 28 whose output is connected with an amplifier 29. The amplifier 29 includes a switchover device which can alternately transmit amplified output signals of the multivibrator 28 to the left-hand or to the right-hand pair of fuel injection valves 113. The two left-hand valves 113 are connected with one output of the amplifier 29 by way of discrete resistors 30, and the two right-hand valves I3 are connected with the other output of the amplifier 29 by a second pair of discrete resistors 31. Each valve 13 is further connected with the ground. The multivibrator 28 and amplifier 29 are connected to the ground and to the positive pole of an energy source, for example, to positive pole of the battery in an automotive vehicle.

The means for timing the output signals of the monostable multivibrator 28 comprises a switch 36 which is actuated by a cam 35 driven by the crankshaft 34 of the engine 10. The crankshaft 34 is indicated by phantom lines. The cam 35 has two lobes which are located diametrically opposite each other so that the switch 36 closes twice during each revolution of the crankshaft 34. The monostable multivibrator 28 produces an output signal in response to each closing of the switch 36. Such signal is amplified by the amplifier 29 and is transmitted to the left-hand or to the right-hand pair of fuel injection valves 13. As stated before, energization of electromagnets in the left-hand valves 13 alternates with energization of electromagnets in the right-hand valves.

The length of intervals t, corresponds to the length of time during which the output of the monostable multivibrator 28 furnishes a signal to the amplifier 29. The length of such intervals is determined by a novel transducer 37 which is connected with the intake manifold 12 by a conduit 38 and with an input of the monostable multivibrator 28 by conductor means 39. The transducer 37 serves as a means for converting the manifold pressure into an electric control signal which is transmitted to the monostable multivibrator 28 by way of conductor means 39 and whose intensity determines the length of intervals t,. The operation of the transducer 37 can be based on any one of several principles; as a rule, changes in manifold pressure which is communicated to the transducer 37 via conduit 38 cause a change in the resistance of one or more resistors, a change in the capacitance of one or more capacitors or a change in the inductance of one or more coils. In the embodiments which are illustrated in FIGS. 26, 9 and 12, the transducer comprises two coils. A complete circuit of a transducer which employs a variable inductance is disclosed, for example, in German Patents Nos. 1,231,954 and 1,193,728 which are assigned to the same assignee. Shortly outlined, the length of intervals I, is changed in such a way that, when the manifold pressure is low (i.c., when the throttle 23 is closed or nearly closed), the intervals I, are shorter (for example, in the range of 2 milliseconds). If the manifold pressure is higher (i.c., when the throttle 25 is moved to, or close to, fully open position), the intervals t, are longer (for example, in the range of 8 milliseconds). The length of intervals t, can further depend on one or more additional parameters, for example, on the r.p.m. and/or on temperature of the engine 10.

In the transducers which are shown in FIGS. 2 to 6, the inductance of two coils is varied in response to displacement of an iron core. The core is shifted in response to changes in manifold pressure and more particularly as a function of absolute pressure in the intake manifold 12 on the one hand and as a function of the differential between manifold pressure and atmospheric pressure on the other hand. This renders it possible to accurately conform the length of intervals t, to the operating conditions with a minimum of outlay.

FIG. 2 illustrates schematically certain details of a first transducer 37A. This transducer comprises a housing 43 which is connected with the intake manifold (not shown) by conduit 38. The housing accommodates a deformable or movable regulating element here shown as a diaphragm 44 whose marginal portion is fixedly secured to the housing 43 and which divides the interior of the housing into

chambers

45, 46. The housing has an opening or port 47 which enables the chamber 45 to remain in permanent communication with the atmosphere. The chamber 46 is connected with the intake manifold 12 by the conduit 38. The maximum deflection of the central portion of diaphragm 44 in a sense to respectively reduce the volume of

chambers

45, 46 is determined by two

stops

48, 49 which are mounted in the housing 43. Each of these stops is preferably adjustable, for example, by being threadedly connected with the housing 43 or in another suitable way. The central portion of the diaphragm 44 is connected with one end of a motion transmitting rod 50 the other end of which is connected to one deformable wall of an evacuated container 53. The other deformable wall of the container 53 is connected with a second motion transmitting rod 54 which is further connected with one end of a soft iron core 55. The other end of the core 55 is connected with a yieldable biasing means here shown as a helical spring 56 which is secured to an end wall of the housing 43 and is installed in the chamber 46. The core 55 is reciprocable in a bore 58 provided in a frame 57 of rectangular outline which is installed in the housing 43. The frame 57 guides the core 55 and has an internal annular recess for two

induction coils

59, 60. If the core 55 is shifted in a direction to the left, as viewed in FIG. 2, the inductance of

coils

59, 60 increases. If the core 55 is caused to move in a direction to the right, the inductance of

coils

59, 60 decreases. The

parts

55, 57, 59 and 60 together constitute an electrical adjusting means for the electronic control circuit 2829. The transducer 37A operates as follows:

It is assumed that the diaphragm 44 is subjected to a mechanical stress so that it bears against the right-hand stop 49 which is installed in the chamber 46. If the pressure in the chamber 46 is rather low (for example, p,,=300 Torr), the con tainer 53 expands considerably and shifts the core 55 in a direction to the right against the opposition of the spring 56 which tends to move the core toward the diaphragm 44. The inductances of

coils

59, 60 decrease and the length of intervals 2, is reduced accordingly, i.e., the duration of signals produced by the monostable multivibrator 28 is short and the valves 13 inject fuel for short periods of time. Thus, the cylinders of the engine receive relatively small quantities of fuel. This is indicated by the lower portion 64 of the curve shown in FIG. 7.

if the diaphragm 44 continues to remain in engagement with the stop 49 but the manifold pressure p, rises in response to opening of the throttle 25, the container 53 undergoes deformation and the spring 56 shifts the core 55 in a direction to the left so that the length of intervals 1, increases and the valves 13 inject greater quantities of fuel. This is indicated by the broken-line portion 65 of the curve shown in FIG. 7.

The diaphragm 44 is designed in such a way that it abuts against the right-hand stop 49 when the pressure differential approximates p equals or exceeds 200 Torr (i.e., when the difference between manifold pressure and atmospheric pressure approaches or exceeds 200 Torr). The point 66 on the curve of FlG. 7 indicates that differential p at which the diaphragm 44 moves against the stop 49 in response to increasing p,,. When the pressure differential approximates 50 Torr, the diaphragm 44 moves into abutment with the stop 48 (see the point 67 on the curve shown in FIG. 7). When the pressure differential p is between about 50 and about 200 Torr, the diaphragm 44 assumes a corresponding intermediate position somewhere between the

stops

48 and 49. This is indicated by the portion 68 of the curve shown in FlG. 7. The differential p of between 50 and 200 Torr corresponds to the transition between operation of the engine 10 under partial load and full load. If the pressure differential p is less than 50 Torr (i.e., if the throttle 25 is moved to or near to fully open position), the operation of the transducer 37A shown in FlG. 2 is represented by the portion 69 of the curve which is illustrated in FIG. 7. It will be seen that the portion 69 is parallel with but offset with reference to the broken-line portion 65 in a direction toward higher values. The length of intervals t, then increases by a value t When the engine is operated at full load (portion 69 of the curve shown in FIG. 7), the valves 13 admit large quantities of fuel so that the cylinders of the engine 10 receive a rich fuel-air mixture. When the engine 10 is operated at partial load, its cylinders receive a lean mixture (see the portion 64 of the curve shown in FlG. 7). In the transition zone (portion 68 in FIG. 7), the quantity of fuel in the mixture entering the cylinders of the engine 10 rises gradually to insure optimum operation of the engine during acceleration. Such quantity then depends only on the absolute manifold pressure.

The diaphragm (regulating element) 44 and the evacuated container 53 constitute the regulating means of the transducer 37A. Such regulating means is adjustable as a function of changes in p and p,,. The intensity of signals received by the monostable multivibrator 28 from the adjusting means 55, 57, 59, 60 depends on the momentary position of the regulating means, i.e., on the extent of deformation of diaphragm 44 and on the extent of deformation of the walls of evacuated container 53.

The curve of FlG. 7 illustrates the transitory stage of engine operation between partial load and full load at sea level. FIG. 8 shows a curve which represents the same transitory stage of engine operation at a height of 2,400 meters above sea level. Such heights are often reached when an automotive vehicle is used on mountain roads. lt will be seen that the transition from lower portion 64' to upper portion 68' begins at a point 66, namely at a pressure p,, of about 350 Torr. The maximum-load position of the diaphragm 44 is reached at the point 67, namely at a manifold pressure p,,=500 Torr. The diaphragm 44 then bears against the stop 48 in the chamber 45. It will be seen that the engine 10 can be operated at maximum possible efficiency not only at sea level but also in mountains. in the latter instance, and assuming that the engine is operated at maximum load, the cylinders receive less fuel than at sea level. As a rule, the maximum rate of fuel admission at 2,400 meters is about 60 percent of maximum rate of fuel admission at sea level. This is due to the fact that the engine cannot consume more fuel at a substantial distance above sea level because it cannot receive requisite amounts of oxygen. The improved transducer automatically regulates the amounts of injected fuel in dependency on location of the engine with reference to sea level.

The transducer 378 of FIG. 3 is similar to the transducer 37A of FIG. 2. All such parts of the transducer 373 which are clearly identical with or analogous to parts of the transducer 37A are denoted by similar reference numerals. The chamber 46 of the housing 43 is connected with the intake manifold by conduit 38. The conductors 39 which constitute the terminals of induction coils 59, 60 are connected with the multivibrator 28. The left-hand end wall of the housing 43 is connected with a rod 72 which is further connected with one deformable wall of the evacuated container 53. The other deformable wall of the container 53 is connected with one end of a motion transmitting rod 73 which is also connected with one deformable wall of a second container 74. The latter communicates with the atmosphere by way of a flexible hose 75. The other deformable wall of the second container 74 is connected with one end of the core 55 by a motion transmitting rod 76. The core 55 is reciprocable in the frame 57 and is biased by helical spring 56 in the same way as described in connection with FIG. 2. The rod 76 is rigid with a yoke 77 having a bifurcated end portion with prongs or stops 40, 49' which flank a projection 70 of the rod 73.

The operation of the transducer 378 is as follows:

When the manifold pressure p,, changes, the first container 53 undergoes deformation. 1f the pressure differential p is less than 50 Torr, the projection 70 engages the stop 49'. If the pressure differential p exceeds 200 Torr, the projection 78 engages the stop 48. In addition, the projection 78 can assume an infinite number of intermediate positions between the stops 48, 49'. By properly dimensioning the container 74, the amounts ofinjected fuel vary in dependency on the location of engine with reference to the sea level in the same way as described in connection with FIGS. 7 and 3. A separate curve can be plotted for changes in the amounts of injected fuel at each height above the sea level.

The flexible hose 75 enables the second container 74 to influence the position of the core 55 with reference to the

coils

59, 60 in dependency on the atmospheric pressure. It is clear that this container can be replaced by other means which influenccs the output signal of the transducer 378 as a function of the manifold pressure p, and pressure differential p,,. For example, one could resort to a suitable link train or the like.

FIGS. 4 to 6 illustrate a third transducer 37D whose operation is similar to that of the transducer 37A of FIG. 2. The housing of the transducer 37D comprises two sections or shells 81, 32 which are fitted into each other at their open ends and are sealed by an O-ring 33. The lower part of the section 82 is formed with an annular internal surface or shoulder 04 provided with a circular groove for a sealing ring 85. A regulating element or diaphragm 06 with concentric annular corrugations (see H6. 6) has a ring-shapedmarginal portion which overlies the surface or shoulder 84 and sealing ring 85. A dished circular plate or stop 87 has an annular marginal clamping portion 80 which overlies the marginal portion of the diaphragm 06 and is secured to the shoulder 84 by screws 89 or analogous fasteners (only one shown in FIG. 4) so that the marginal portion of the diaphragm is sealingly secured to the housing section 92. The convex side of the stop 07 faces away from the diaphragm 36 and this stop is formed with a centrally located opening 90. The diaphragm 06 is also formed with a centrally located opening which accommodates a sleeve 93 having an annular shoulder 94 which abuts against the upper side of the diaphragm, as viewed in FIG. 4. A ring 95 abuts against the diaphragm 06 opposite the shoulder 94 and is held against axial movement with reference to the sleeve 93 by an annular flange or bead 96. Thus, the central portion of the diaphragm 36 is sealingly secured to the sleeve 93. The latter is formed with a tapped bore which receives an adjusting screw 97. The screw 97 is held in selected position by a lock nut 99. The upper end portion of the screw 97 is formed with a cylindrical male coupling portion or head 99.

The end wall of the lower housing section 32 is provided with a centrally located tapped bore which receives an externally threaded hollow cylindrical cap 102. The upper end of the cap 102 surrounds the locknut 93 and the lower part of the sleeve 93 and extends close to an annular shoulder 103 of this sleeve. Thus, the sleeve 93 can move axially between the illustrated position in which it abuts against the stop 87 and a lower end position in which its shoulder 103 abuts against the upper end face of the cap (lower stop) 102. In the illustrated embodiment, the maximum stroke of the sleeve 93 is in the range of 1 millimeter, for example, 0.8 millimeter. This sleeve is coaxial with the cap 102 and the screw 97 is accessible from exterior of the

housing

81, 82 upon detachment of cap 102 from the section 02.

The diaphragm 86 divides the interior of the housing into two

chambers

104, 105 which are sealed from each other. The chamber 104 is located below the diaphragm (as viewed in FIG. 4) and is in communication with the atmosphere by way of a port or opening 106 in the shell 82. The upper chamber 105 is connected with the intake manifold by way of the con duit 30. At the point where the conduit 39 communicates with the chamber 105, there is provided a pressure relief valve 109 which is biased by a spring 107 and is provided with a throttling or flow-restricting orifice 109. The spring 107 is adjusted in such a way that the valve 108 opens when the pressure in conduit 38 exceeds the pressure in chamber by 0.05 kg/cm". This improves the characteristics of the engine during acceleration.

The upper housing section 01 is provided with a shoulder 112 which extends radially inwardly so that the upper part of the section 01 has a diameter which is less than the diameter of its open end. The shoulder 112 supports a ring-shaped platelike carrier 111 which is secured thereto by screws 110. The carrier 111 supports a substantially rectangular iron frame 116 which is secured thereto by two screws 114 and distancing elements 115. The frame 116 consists of a convoluted thin high-quality iron band and has two spaced parallel walls provided with registering centrally located bores 117. The interior of the frame 116 accommodates two induction coils 113, 119 the latter of which is convoluted around the former. The coils 118, 119 have a total of four terminals connected to an insulator 120 shown in FIG. 5. The insulator 120 connects the terminals of coils 118, 119 with conductors 39 and hence with the monostable multivibrator 28.

The upper portion of the frame 116 (as viewed in FIG. 4) is connected with a platelike carrier 122 connected with a leaf spring 123 which is similar to a second leaf spring 124 secured to the carrier 111. FlG. 5 shows that the leaf spring 124 comprises two

outer legs

125, 126 which are secured to adjoining projections of the carrier 111 by screws 127. The central leg 128 of the leaf spring 124 is secured to a soft iron core 129 which is reciprocable in aforementioned registering bores 117 of the frame 116. The leaf spring 124 further comprises two

transverse legs

132, 133 which are connected with the adjoining ends of the

legs

125, 126, 128. When the core 129 moves axially, the

legs

125, 126, 128 undergo deformation but prevent sidewise movement of the core. The construction and mounting of the leaf spring 123 correspond to those of the leaf spring 124.

The core 129 has a conical lower end portion 134 which penetrates deeper into the frame 116 (namely, into the lower bore 117) when the core is caused to move downwardly. This increases the inductance of coils 118, 119. The shape of the conical end portion 134 determines the rate at which the inductance increases in response to downward movement of the core 129.

The core 129 accommodates a hexagonal insert 135 of nonmagnetic material which has at its lower end a male coupling member or post 136 extending into a female coupling member or socket 137 which is affixed to one deformable wall of a first evacuated container 138. The other or lower deformable wall of the container 130 is fixedly secured to one deformable wall of a second evacuated container 140 by a motion transmitting connector 139. The lower deformable wall of the container 140 is connected with a second female coupling member or socket 144 which receives the aforementioned male coupling member or head 99 of the adjusting screw 97. The couplings provided by the

parts

136, 137 and 144, 99 form two universal joints or swivel joints which permit the evacuated

containers

133, 140 to assume a practically unlimited number of positions.

The upper part of the core 1 29 is formed with an enlarged portion 145 which serves as a retainer for one end of a helical spring 146. The other end of the spring 146 bears against an end wall 147 provided at the upper end of a tubular extension 143 of the section 81. The extension 148 further accommodates a U-shaped spring 149 having two prestressed arms or flanges which bear against a stud 150 connected to the core 129. When the core 129 moves axially, the arms of the U- shaped spring 149 (which is fixed in the extension 148) op pose axial movement of the stud 150 and produce friction to thereby damp movements of the diaphragm 36 and core 129. Thus, the

parts

149, 150 together constitute a damping device for the diaphragm 36 and core 129.

It will be seen that the adjusting means 116, 118, 119, 129 for the monostable multivibrator 28 and the diaphragm 86 are spaced from each other and that such space accommodates the evacuated

containers

138, 140.

The transducer 37D of FIGS. 4 to 6 operates as follows:

Once the transducer is installed in an automotive vehicle, the chamber 105 is connected with a source of fluid at a pressure of p =300 Torr during testing of the engine 10. This causes the diaphragm 86 to move the shoulder 94 of the sleeve 93 against the stop 87 (see FIG. 4). The stop 102 is then detached from the shell 82 and the adjusting screw 97 is then accessible from the exterior of the shell 82. This screw is rotated to insure that the point 154 of the curve shown in FIG. 7 corresponds to a prescribed injection interval 1 The chamber 105 is then connected with the surrounding atmosphere (p =750 Torr or thereabout) so that the pressure at both sides of the diaphragm 86 is the same. Thus, the spring 146 then shifts the diaphragm 86 downwardly by way of the core 129 and

containers

138, 140. The stop 102 is thereupon screwed into the section 82 until the operator obtains an upper point 155 (see the curve of FIG. 7) with a second prescribed injection interval t This determines the two ends of the curve which includes the

portions

64, 68, 69 of FIG. 7. The exact configuration of the curve depends on the shape of the conical lower end portion 134 on the core 129, the charac-' teristics of evacuated

containers

138, 140, the characteristic of spring 146, the characteristics of

springs

123, 124 and the spring characteristic (inherent rigidity) of the corrugated diaphragm 86. The latter is designed in such a way that the sleeve 93 abuts against the stop 87 up to a pressure differential of about 200 Torr (see the

points

66, 66 in FIGS. 7 and 8). If the pressure differential p decreases, the diaphragm 86 moves gradually in a direction away from the stop 87, as viewed in FIG. 4, and reaches the stop 102 when the pressure differential decreases to about 50 Torr (see the

points

67, 67 in FIGS. 7 and 8). It is clear that the above concrete values were given only by way of example because the exact magnitude of such values depends on the type of internal combustion engine and on the desired mode of operation of the engine. Also, the shape of

curve portions

64, 68, 69 and the position of

points

154, 155 is different for each engine type and is determined during testing of the engine. Therefore, as a rule, a transducer 37D which has been adjusted for use in a particular engine is not immediately transferable into another engine.

The transducer of our invention can be readily designed and adjusted in such a way that the engine operates satisfactorily at partial load as well as at full load. At full load, the regulating means of the transducer is adjusted automatically as a function of the pressure differential p Another important advantage of the transducer is its robust and compact design as well as that it can be connected with the monostable multivibrator 28 by resorting to a small number of conductors. As stated before, the transducer can be modified further in a number of ways without departing from the spirit of our inven tion. Also, it is not necessary that one side of the diaphragm 86 of FIG. 4 be permanently exposed to atmospheric pressure, i.e., the pressure differential p, need not be maintained at all times. Moreover, one can employ a diaphragm which suddenly snaps over from a first to a second position in response to a predetermined pressure differential. However, the arrangement which was described in connection with FIGS. 4 to 6 has been found to be particularly suited for use in connection with internal combustion engines, to a large extent because the pressure differential p acts upon the diaphragm 86 at all times.

A comparison of FIGS. 7 and 8 will reveal the reasons for maintaining the diaphragm 86 under constant influence of pressure differential p i.e., for establishing such pressure dif ferential in addition to maintaining the diaphragm under the influence of absolute manifold pressure p,,. It would be possible to obtain the curve of FIG. 7 without subjecting the diaphragm 86 to the pressure differential p (for example, by imparting to the lower end portion 134 of the core 129 a particular shape); however, the difference t, in length of intervals t, at full load would then develop only at sea level but not when the engine is used at a substantial height above sea level. If the engine would be operated well above sea level, the intervals I, of fuel injection would correspond to-the lower portion 64 of the curve shown in FIG. 7. For example, if the length of intervals t, at 500 Torr in FIG. 8 is I00 percent, the length of such intervals is reduced to 82 percent if the diaphragm 86 is not subjected to the pressure differential p,,. In other words, the greatest output of the engine 10 at 2,400 meters above sea level would correspond to between 70 and percent of maximum output. The improved transducer enables the engine to automatically conform its operation at full load to the pressure ofsurrounding atmosphere.

In the transducer 37D, the diaphragm 86 abuts against the stop 87 at partial load so that it is not effective when the engine operates at partial load. However, it is often desirable to bring about a correction of operation in order to compensate for the influence of geographic height when the engine is operated at partial load. This can be achieved by resorting to a transducer 375 a portion of which is illustrated in FIG. 9. Cer tain parts of this transducer are denoted by numeralssimilar to those employed in FIGS. 46. The plate or stop 87 of FIG. 4 is replaced by a stop 159 which is made of springy material and is secured to the central portion of a dished spring 160. The marginal portion of the spring 60 is secured to the housing section 82 by a clamping ring 162 so that it bears against the marginal portion of the diaphragm 86. The head 99 of the adjusting screw 97 is connected to the diaphragm 86 by way of the sleeve 93 and this head supports one of two evacuated containers (not shown) corresponding to the containers 138, of FIG. 4. These containers serve as a means for effecting adjustments as a function of absolute pressure p,,. In order to insure full effectiveness of the pressure differential p upon the diaphragm 86, the dished spring 160 is provided with one, two or more passages or bores 164.

FIG. 10 illustrates the manner in which the core 129 of adjusting means in the transducer 375 is shifted as a function of absolute manifold pressure p,, (by way of the series-connected evacuated containers 138, 140) and as a function of the pressure differential p,,. The curve 0,, which is shown by heavy lines illustrates the dependency of intervals I, from absolute manifold pressure p,, and from the pressure differential p between manifold pressure and atmospheric pressure. The curve 0,, is a resultant of curves 0 and b,,. The curve a (indicated by broken lines) shows the variations of intervals I, as a function of changes in manifold pressure p,, (i.e., as a function of such adjustmentsof core 129 which are effected by the evacuated containers 138,140). The head 99 of the adjusting screw 97 serves as an element against which the evacuated containers I38, 140 react in effecting axial displacements of the core 129 by way of the insert 135 and parts 136- 138. The curve b, indicates changes in axial position of the head 99 as a function of changes in pressure differential p (i.e., the dif ference between manifold pressure p in chamber 105 and atmospheric pressure in chamber 106). The atmospheric pressure is assumed to equal 760 Torr at sea level and constitutes the zero point on the p -scale of FIG. 10. It is again assumed that the sleeve 93 which carries the head 99 abuts against the stop 102 when the pressure differential p, is between zero and 50 Torr. The spring characteristic of the diaphragm 86 is soft so that the diaphragm moves rapidly away from the stop 102 and toward the spring 149 of FIG. 4 when the pressure differential p begins to rise above 50 Torr. When the pressure differential p reaches 150 Torr, namely, when the absolute manifold pressure p,, equals 760 Torr minus 150 Torr 610 Torr, the sleeve 93 abuts against the stop 87. In the range where the pressure differential p rises from 50 Torr to I50 Torr, the curve b of FIG. 10 is rather steep. The partial load range begins at the pressure differential p of 150 Torr; if the pressure differential thereupon rises beyond such value, further shifting of the head 99 must be effected against the opposition of the relatively stiff dished spring so that the corresponding portion of the curve b, is less steep. By proper selection of characteristics of the spring 160 and diaphragm 86, the length of intervals I, as a function of p and p at sea level can be readily selected in such a way that it varies at an optimum rate, i.e., substantially as indicated by the curve shown in FIG. 7.

FIG. 11 illustrates the performance of the engine, i.e., changes in the length of intervals 1,, at a height of about 2,000 meters above sea level. The atmospheric pressure at such height is about 570 Torr. The curve a which is plotted as a function of the absolute pressure p,, remains unchanged; however, the curve b (which is plotted as a function of the pressure differential Pd) and the zero point of the p -scale are shifted in a direction to the left by a distance corresponding to a absolute pressure p =l90 Torr. This brings about a proper correction of amounts of injected fuel (the length of intervals 1,), not only in the partial load range but also in the full load range of engine operation. The amounts of injected fuel exceed the needs of the engine only when the absolute pressure p is less than 200 Torr, a situation which is unlikely to arise in actual use of an automotive vehicle. The curve of FIG. I] is a resultant of curves and b,.

Referring finally to FIG. l2, there is shown a portion of a further transducer 37F which constitutes a modification of

transducers

37D and 37E (FIGS. -t--6 and 9). This is a simplified transducer which does not embody means for changing the amounts of fuel at full load, i.e., the axially movable stop 102 of FIG. 4 is omitted. This stop is replaced by a stop in the form of a split ring 172 which is mounted on a tubular extension or neck 170 of the sleeve 93" which can be engaged by the stop 159 when the engine is operated at full load. The stop 172 moves downwardly (as viewed in FIG. 12) toward and against the stop 159 which is mounted in the dished spring I60 when the engine operates at full load, namely, when the pressure differential p is very low (between 0 and 50 Torr). The prestressed diaphragm 36 is then capable of effecting such movement of the stop I72 by way of the sleeve 93" which is secured to the central portion of the diaphragm. If the pressure differential p rises to the limit of the partial-load range between I00-200 Torr, preferably about 150 Torr), the head 99 can move axially to the extent determined by the play of the stop 159 between the stop 172 and the shoulder 193 of the sleeve 93". When the operation of the engine reaches the partial load range, the stop I59 abuts against the shoulder 193 (as shown in FIG. 12). If the pressure differential p rises still further, the sleeve 93" must be moved axially against the opposition of the relatively stiff dished spring 1160 so that the rate at which the sleeve 93" is shifted in response to incremental rises in pressure differential p is less than when p is below 150 Torr. The head 99 shares all axial movements of the sleeve 93".

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 without omitting features which fairly constitute essential characteristics of the generic and specific aspects of our con tribution to the art.

What we claim as new and desired to be protected by Letters Patent is set forth in the appended claims:

I. In a structure of the character indicated, particularly in an automotive vehicle, a combination comprising an internal combustion engine having cylinder means and intake manifold means connected with said cylinder means; a source of fuel; valve means for controlling the admission of fuel from said source to said cylinder means; control means operative to open said valve means for intervals of variable length; and transducer means for regulating the operation of said control means, said transducer means comprising regulating means adjustable as a function of pressure changes in said manifold means and as a function of changes in differential between the pressure in said manifold means and atmospheric pressure, at least a portion of said regulating means being adjustable continuously in response to changes of said differential within a predetermined range.

2. A combination as defined in claim I, wherein said range has a lower limit corresponding to a differential of between 0 and 50 Torr.

3. A combination as defined in claim 1, wherein said range has an upper limit corresponding to a differential of between I00 and 200 Torr.

4. In a structure of the character indicated, particularly in an automotive vehicle, a combination comprising an internal combustion engine having cylinder means and intake manifold means connected with said cylinder means; a source of fuel; valve means for controlling the admission of fuel from said source to said cylinder means; control means operative to open said valve means for intervals of variable length; and transducer means for regulating the operation of said control means, said transducer means comprising regulating means comprising at least one evacuated container having wall means deformable in response to changes in manifold pressure and a diaphragm deformable in response to changes in differential between the manifold pressure and atmospheric pressure, and stop means for limiting the extent of deformation of said diaphragm.

5. A combination as defined in claim 4, wherein at least a portion of said stop means is adjustable.

6. A combination as defined in claim 4, wherein said stop means comprises two stops located at the opposite sides of said diaphragm, one of said stops being adjustable and said diaphragm being arranged to abut against said one stop at a relatively low differential between the manifold pressure and atmospheric pressure.

7. In a structure of the character indicated, particularly in an automotive vehicle, a combination comprising an internal combustion engine having cylinder means and intake manifold means connected with said cylinder means; a source of fuel; valve means for controlling the admission of fuel from said source to said cylinder means; control means operative to open said valve means for intervals of variable length; and transducer means for regulating the operation of said control means, said transducer means comprising regulating means comprising at least one evacuated container having wall means deformable in response to changes in manifold pressure, a diaphragm having a marginal portion and being deformable in response to changes in differential between the manifold pressure and atmospheric pressure, a housing accommodating said regulating means, and means for securing said marginal portion to said housing, said evacuated container being adjacent to one side and being connected to said diaphragm.

ll. A combination as defined in claim 7, wherein the wall means of said container comprises a deformable wall which is connected with said diaphragm.

9. A combination as defined in claim 7, wherein the connection between said diaphragm and said container comprises a universaljoint.

10. A combination as defined in claim 9, wherein said universal joint is a swivel joint including a first portion which constitutes a socket and a second portion which constitutes a head and extends into said socket, one of said portion being secured to said diaphragm.

Ill. A combination as defined in claim 10, wherein said transducer means further comprises adjusting means for adjusting the position of said other portion of said swivel joint.

112. A combination as defined in claim 11, wherein said transducer means further comprises a housing for said regulating means, at least a portion of said adjusting means being accessible from the exterior of said housing.

13. A combination as defined in claim 12, wherein said transducer means further comprises adjustable stop means for limiting the deformation of said diaphragm in one direction, said stop means being coaxial with said adjusting means.

M. A combination as defined in claim 13, wherein said stop means is detachably secured to said housing and wherein said adjusting means is accessible upon detachment of said stop means.

15. In a structure of the character indicated, particularly in an automotive vehicle, a combination comprising an internal combustion engine having cylinder means and intake manifold means connected with said cylinder means; a source of fuel; valve means for controlling the admission of fuel from said source to said cylinder means; control means operative to open said valve means for intervals of variable length; and transducer means for regulating the operation of said control means, said transducer means comprising regulating means comprising at least one evacuated container having wall means deformable in response to changes in manifold pressure, a diaphragm deformable in response to changes in differential between the manifold pressure and atmospheric pressure, a housing accommodating said regulating means, and adjusting means for transmitting to said control means signals whose intensity is a function of the deformation of said diaphragm, said evacuated container being disposed between said adjusting means and said diaphragm.

16. A combination as defined in claim 15, wherein said adjusting means comprises a portion which is fixedly mounted in said housing and said diaphragm comprises a marginal portion clampingly secured to said housing, said transducer means further comprising means connecting said diaphragm with said container and means connecting said container with a movable portion of said adjusting means.

17. A combination as defined in claim 16, wherein said transducer means further comprises biasing means opposing the displacement of said movable portion by said regulating means.

18. In a structure of the character indicated, particularly in an automotive vehicle, a combination comprising an internal combustion engine having cylinder means and intake manifold means connected with said cylinder means; a source of fuel; valve means for controlling the admission of fuel from said source to said cylinder means; control means operative to open said valve means for intervals of variable length; and transducer means for regulating the operation of said control means, said transducer means comprising regulating means comprising at least one evacuated container having wall means deformable in response to changes in manifold pressure, a diaphragm having a marginal portion and being deformable in response to changes in differential between the manifold pressure and atmospheric pressure, a housing for said regulating means, and stop means for limiting the deformation of said diaphragm in one direction, said housing comprising an annular surface abutting against said marginal portion of said diaphragm, and means for clamping said marginal portion against said surface, said stop means being connected with said clamping means.

19. A combination as defined in claim 18, wherein said clamping means forms an integral part of said stop means and wherein said stop means is a dished plate.

20. In a structure of the character indicated, particularly in a automotive vehicle, a combination comprising an internal combustion engine having cylinder means and intake manifold means connected with said cylinder means; a source of fuel; valve means for controlling the admission of fuel from said source to said cylinder means; control means operative to open said valve means for intervals of variable length; and transducer means for regulating the operation of said control means, said transducer means comprising regulating means comprising at least one evacuated container having wall means deformable in response to changes in manifold presan automotive vehicle a combination comprising an internal combustion engine having cylinder means and Intake manifold means connected with said cylinder means; a source of fuel; valve means for controlling the admission of fuel from said source to said cylinder means; control means operative to open said valve means for intervals of variable length; and transducer means for regulating the operation of said control means, said transducer means comprising regulating means comprising at least one evacuated container having wall means deformable in response to changes in manifold pressure, a regulating element deformable in response to changes in differential between the manifold pressure and atmospheric pressure, a housing for said regulating means, and elastic stop means for limiting the deformation of said regulating element.

23. A combination as defined in claim 22, wherein said regulating element is a diaphragm having a marginal portion clampingly secured to said housing and a central portion, said stop means comprising a ring connected with the central portion of said diaphragm and a dished spring having a marginal portion secured to said housing.

24. In a structure of the character indicated, particularly in an automotive vehicle, a combination comprising an internal combustion engine having cylinder means and intake manifold means connected with said cylinder means; a source of fuel; valve means for controlling the admission of fuel from said source to said cylinder means; control means operative to open said valve means for intervals of variable length; and transducer means for regulating the operation of said control means, said transducer means comprising regulating means comprising at least one evacuated container having wall means deformable in response to changes in manifold pressure, a housing for said regulating means, a diaphragm having a marginal portion secured to said housing and dividing the interior of the latter into two chambers one of which communicates with the atmosphere and the other of which communicates with said manifold means so that said diaphragm is deformable in response to changes in differential between the pressure in said manifold means and atmospheric pressure, and stop means in said other chamber to limit the extent of deformation of said diaphragm in a direction away from said one chamber, said stop means comprising a dished spring fixedly mounted in said housing and being concentric with said diaphragm.

25. A combination as defined in claim 24, wherein said transducer means further comprises a sleeve fixed to the central portion of said diaphragm and reciprocably received in a ring forming part of said stop means and concentrically secured to said spring, said sleeve being provided with second stop means which limits the extent of its movement with reference to said ring.

26. A combination as defined in claim 25, wherein said second stop means comprises a split ring on a neck portion of said sleeve.

Claims

1. In a structure of the character indicated, particularly in an automotive vehicle, a combination comprising an internal combustion engine having cylinder means and intake manifold means connected with said cylinder means; a source of fuel; valve means for controlling the admission of fuel from said source to said cylinder means; control means operative to open said valve means for intervals of variable length; and transducer means for regulating the operation of said control means, said transducer means comprising regulating means adjustable as a function of pressure changes in said manifold means and as a function of changes in differential between the pressure in said manifold means and atmospheric pressure, at least a portion of said regulating means being adjustable continuously in response to changes of said differential within a predetermined range.

2. A combination as defined in claim 1, wherein said range has a lower limit corresponding to a differential of between 0 and 50 Torr.

3. A combination as defined in claim 1, wherein said range has an upper limit corresponding to a differential of between 100 and 200 Torr.

8. A combination as defined in claim 7, wherein the wall means of said container comprises a deformable wall which is connected with said diaphragm.

9. A combination as defined in claim 7, wherein the connection between said diaphragm and said container comprises a universal joint.

11. A combination as defined in claim 10, wherein said transducer means further comprises adjusting means for adjusting the position of said other portion of said swivel joint.

12. A combination as defined in claim 11, wherein said transducer means further comprises a housing for said regulating means, at least a portion of said adjusting means being accessible from the exterior of said housing.

14. A combination as defined in claim 13, wherein said stop means is detachably secured to said housing and wherein said adjusting means is accessible upon detachment of said stop means.

20. In a structure of the character indicated, particularly in a automotive vehicle, a combination comprising an internal combustion engine having cylinder means and intake manifold means connected with said cylinder means; a source of fuel; valve means for controlling the admission of fuel from said source to said cylinder means; control means operative to open said valve means for intervals of variable length; and transducer means for regulating the operation of said control means, said transducer means comprising regulating means comprising at least one evacuated container having wall means deformable in response to changes in manifold pressure, a regulating element deformable in response to changes in response to changes in differential between the manifold pressure and atmospheric pressure, and damping means for damping deformation of said regulating means.

21. A combination as defined in claim 20, wherein said transducer means further comprises a housing for said regulating means and said damping means, said damping means comprising resilient means.

22. In a structure of the character indicated, particularly in an automotive vehicle, a combination comprising an internal combustion engine having cylinder means and intake manifold means connected with said cylinder means; a source of fuel; valve means for controlling the admission of fuel from said source to said cylinder means; control means operative to open said valve means for intervals of variable length; and transducer means for regulating the operation of said control means, said transducer means comprising regulating means comprising at least one evacuated container having wall means deformable in response to changes in manifold pressure, a regulating element deformable in response to changes in differential between the manifold pressure and atmospheric pressure, a housing for said regulating means, and elastic stop means for limiting the deformation of said regulating element.