GB1574628A

GB1574628A - Device for influencing the composition of the operating mixture fed to an internal combustion engine

Info

Publication number: GB1574628A
Application number: GB4577/77A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1976-02-07
Filing date: 1977-02-04
Publication date: 1980-09-10
Also published as: SE7701255L; JPS5297035A; IT1077607B; FR2340457A1

Description

(54) A DEVICE FOR INFLUENCING THE COMPOSITION OF THE OPERATING MIXTURE FED TO AN INTERNAL COMBUSTION ENGINE (71) We; ROBERT BOSCH GMBH, a German Company, of Postfach 50, 7 Stuttgart 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a device for influencing the composition of the operating mixture fed to an internal combustion engine.

In particular the present invention relates to a device of the type wherein a throttle element is arranged in a conduit opening into the intake pipe of an internal combustion engine and is adjustable in conformity with the adjustment of a mixture quantity control device in the intake pipe of the internal- combustion engine.

In known devices of this type for the influencing of the composition of the fuel/air mixture, a quantity of fuel is metered, in a specific desired ratio, to the quantity of air drawn in by the internal combustion engine. This has the advantage that the metering of fuel can be more readily controlled in that the quantity of fuel introduced is influenced far less by the pressure and the temperature than is the case during, for example, the metering of air. In internal combustion engines whose fuel/air mixture is to be accurately regulated to specific A values, the dependence of the torque obtained upon the quantity of fuel introduced is particularly troublesome when operating with a lean mixture at an air number A > 1, since, in this instance, the variation in'the torque is particularly great relative to the change in the air number A.

Modes of operation with A > I are of particular interest with respect to the fuel consumption, although, in this range, the aforesaid disadvantage is troublesome with various types of regulation, for example even when using the smooth running of the internal combustion engine as a regulating variable, since fresh torque variations are produced when there is a change in the quantity of fuel which is fed and which is regulated by the smooth running of the internal combustion engine.

A method has already been proposed in which the composition of the additional quantity of air is effected in dependence upon the setting of the mixture quantity control device, this dependence being controllable with a transmission factor varying between the value 0 and 1, by a regulating device which detects parameters of the internal combustion engine.

Although it is known to influence the fuel/air mixture by the feeding of additional air, this is effected in the known solutions either in direct dependence upon operating parameters or, for example, in direct dependence upon the position of the main butterfly valve in the intake pipe. The feeding of additional air to an operating mixture of specific composition produced, for example, by a carburettor, has, particularly in the case of mixture regulation corresponding to the smooth running of the internal combustion engine, the great advantage that, compared with the change in the fuel fed to the mixture, the change in the air fed to the mixture causes substantially smaller changes in the torque when operating in the lean range, and the regulation is not impaired by excessive fluctuations in the torque. Furthermore, regulation -by additional air is substantially more rapid owing to the smaller inertia -of the air and since the delays and idle times in the regulating circuit are smaller in this type of metering than when regulating the quantity of fuel. Furthermore, regulation by the proposed method is rendered substantially more rapid and more accurate by coarse control, preceding the actual regulation, in conformity with the position of the mixture quantity control device with additional multiplicative intervention in the transmission between the control device and the metering of the additional air.

According to the present invention there is provided a device for influencing the composition of the operating mixture, fed to an internal combustion engine, in accordance with a method in which gaseous media are fed by way of a metering crosssection which is variable proportionally to the setting of a mixture quantity control, this proportionality being controllable by means of a regulator which is adapted to detect the operating behaviour of the internal combustion engine, said device comprising a throttle element disposed in a conduit opening into an intake pipe and adapted to determine the metering crosssection, means for transmitting the setting of the mixture quantity control to the throttle element, and a second throttle element for also adjusting the metering cross-section of the conduit, the second throttle element being arranged to vary the free cross-section of the conduit and being operable by way of the regulator which is adapted to detect at least one operating parameter of the internal combustion engine.

A device in accordance with the present invention, has the advantage that it is of very favourable construction for performing a very accurate and rapid adjustment by simple means.

Advantageous developments and improvements in the present invention are possible. A particularly advantageous embodiment of the present invention has throttle elements in the form of flat sliders.

The first and the second flat sliders are guided closely one above the other in a flange of the conduit and each has as opening in the region of the free cross section of the conduit, the common flowthrough cross section of the said sliders being variable by displacing the flat sliders until the cross section of the conduit is fully closed. By virtue of this embodiment accurate guidance of the flat sliders and thus satisfactory sealing relative to the atmosphere can be achieved in a simple manner. The vacuum in the intake pipe of the internal combustion engine acts upon the flat sliders so as to press them tightly one against the other in an advantageous manner, thus also resulting in satisfactory sealing.

In another advantageous development of the present invention, throttle element comprises a butterfly valve over which engages a slotted cylindrical filling body acting as a second throttle element in the form of a piston valve which is sealingly fitted in the conduit and which is displaceable axially of the spindle of the butterfly valve by an actuating device controlled by the regulating device.

By virtue of a device in accordance with the present invention, the metering crosssection in the conduit leading to the intake pipe can be proportionally controlled in conformity with the set flow-through crosssection of the main butterfly valve in the intake pipe. Furthermore, it is advantageous that the control of this metering crosssection is effected at the same location with the retaining of the given pressure ratios.

The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a first embodiment of the present invention having a piston valve arranged coaxially of the by-pass butterfly valve; Figure 2 shows a second embodiment of the present invention in which flat sliders are used, one slide valve being adjusted in accordance with the throttle valve adjustment and another flat slide being adjusted in dependence upon a further operational parameter, to thus vary the metering cross-section of a by-pass air conduit; Figure 3 shows a third embodiment as a development of the embodiment of Figure 2, having window like flow-through crosssections in the flat sliders; Figure 4 shows a fourth embodiment of the present invention having tubular throttle elements; and Figure 5 is a side elevation of the embodiment of Figure 4.

Figure 1 shows a first embodiment of the invention in which conduit 7' is associated with an intake pipe 1 such that the extended spindle 10' of a main butterfly valve 5 acts simultaneously as a butterfly valve spindle of a butterfly valve 8' arrariged in the conduit 7'. The butterfly valve 8' is associated with the main butterfly valve such that the butterfly valve 8' is also closed when the main butterfly valve is closed. The conduit 7' has a rectangular cross section in the region of the butterfly valve 8'. The butterfly valve 8' is also of rectangular construction. A cylindrical piston valve 71 is fitted in a cup-shaped insert 70 fitted into the conduit 7' coaxially of the butterfly valve spindle 10'. The piston valve has, on its side facing the butterfly valve 8', a longitudinal slot 72 and a blind bore 73 which is disposed coaxially of the butterfly valve spindle 10 and which accommodates a compression spring 74 which is supported in the bore 73 opposite the butterfly valve spindle 10'. The longitudinal slot 72 and the blind bore 73 are adapted to the cross section of the butterfly valve 8' and the butterfly valve spindle 10' such that the piston valve is sealingly displaceable across the butterfly valve 8' until it abuts against the oppositely located wall of the conduit 7'.

When in this position, the piston valve 71 has fully closed two openings 75 - and 76 which are provided in the cup-shaped insert 70 and which correspond to the free cross section of the conduit 7' at this location.

For the purpose of actuating the piston valve 71, the side of the piston valve remote from the butterfly valve 8' has a spigot 78 which projects outwardly through an axial bore 79 in the bottom of the cup-shaped insert 70. In this embodiment, an actuating rod 26 is connected to the spigot, and the other end of the actuating rod 26 is acted upon by the piston 27 of a servomotor 28.

Here the working chamber 29 of servomotor 28 is supplied by way of the pressure line 33 with a mixed pressure adjusted by the threeposition solenoid valve 32. It will be appreciated that, alternatively, in borderline cases, this pressure may be either the feed pressure fed to the valve by way of the line 35, or the float chamber pressure fed by way of the pressure line 34. According to the value of the pressure established in the working chamber 29, the piston valve 71 is displaced over the butterfly valve 8' to a greater or lesser extent against the force of the spring 74. The free cross section in the air conduit 7', established by the butterfly valve 8' in conformity with the position of the main butterfly valve, is thereby additionally reduced to a greater or lesser extent. As soon as the pressure prevailing in the working chamber 29 of the servomotor 28 is equal to the pressure in the pressure chamber 30, the compression spring 74 brings the piston valve 71 into its extreme postion at the greatest distance from the butterfly valve 8', and the cross section established by the butterfly valve 8' is fully opened.

Various forms of actuating device can of course be substituted and the regulating variables used, can of course be changed.

This device has the advantage that it can be fitted very compactly in the form of an insert into an air by-pass conduit. Thus, utilizing a pressure head at the butterfly valve 8' which is equal to the pressure head at the main butterfly valve 5, it is also possible to obtain a rapid regulating action by varying the metering cross section.

Figure 2 shows a variant for varying the metering cross section in a conduit 7" leading to the intake pipe 1 of the internal combustion engine downstream of the main butterfly valve 5. For this purpose, a flange 87 is inserted into the conduit 7 and has a rectangular opening 88 whose edges form portions of guide grooves 86. A first flat slider 84 is displaceable in the guide grooves adjacent to the uppermost plane of the flange and is connected to an actuating rod 83 outside the flange. Furthermore, a second flat slider 89 is displaceable in the guide grooves 86 at right angles to the first flat slider 84. The second flat slider 89 is located below the first flat slider 84 in the direction of flow and abuts sealingly thereagainst. An actuating rod 91 is secured to the second flat slider 89 outside the flange.

For the purpose of clarity, the countermember of the flange 87 with the portion of the conduit 7" on the intake side is only indicated in the drawing. It will be appreciated that a seal is provided between the parts of the flange in order to ensure a sealed connection between the two parts of the flange and to ensure that the flat sliders 84 and 89 are inserted into the flange in a sealed manner. By virtue of the fact that the flat sliders are displaceable at right angles to one another, the cross section of the opening 88 reduced by the first flat slider 84 can again be varied by the position of the second flat slider 89. In the extreme case, the cross section of the opening is either fully open or fully closed.

The first flat slider 84 is actuated by means of the actuating rod 83 whose other end has a slot 85 which extends transversely of the direction of displacement of the flat slider 84 and which is engaged by a pin 81 of a crank 82 rigidly connected to the spindle 10 of the main butterfly valve 5. The end of the actuating rod 91 of the second flat slider 89 is in the form of a toothed rack 92 which is engaged by a pinion 93 connected to a worm wheel 94. The worm wheel 94 is driven by way of a worm 95 by means of a reversible electric motor 96 controlled by a regulating device 43. The regulating device is connected by way of a lead to a known oxygen measuring probe arranged in a portion of the exhaust gas system.

In conformity with the voltage signals produced by the oxygen probe, the electric motor 96 is controlled by the regulating device to increase or reduce the cross section at the opening 88 adjusted by the first flat slider 84.

The electric motor is controlled in accordance with the same principles on which solenoid valve 32 is controlled in the embodiment described above. In the embodiments described above, the piston valve 71 may be adjusted by means of an electric motor instead of being actuated hydraulically or pneumatically. Similarly, instead of an electric motor, an adjusting magnet or a heatable bimetal spring, adapted to the conditions, can be used as the drive in the same way as the hydraulic actuating device of Figure 1 or a pneumatic actuating device.

It will be appreciated that, instead of using the regulating variable produced by an oxygen measuring probe, a different parameter characterising the operating behaviour of the internal combustion engine may be used to obtain an optimum composition of the exhaust gas, for the purpose of controlling the regulating device 43. By way of example, the smooth running of the internal combustion engine may serve this purpose, the variations in the pressure characteristics in the combustion chambers of the internal combustion engine, or the fluctuations of the torque relative to the fluctuations in the engine speed, may be maintained in a known manner by means of a measurement pick-up. Furthermore; it has been proposed to use ion current probes to detect the composition of the mixtures which are burnt in the combustion chamber of the internal combustion engine, and to influence the formation of the mixture by the regulating variables produced by the ion current probes.

In this embodiment, adjustment of the first flat slider 84 for controlling the free cross section at the opening 88 is effected in conformity with the actuation of the butterfly valve. By virtue of the chosen arrangement having the crank 82 and the guide slot 85, one obtains a variation in the flow-through cross section at the opening 88 proportional to the opening cross section of the intake pipe at the main butterfly valve.

The variation is proportional to the expression (I-cosrp), wherein P represents the aperture angle of the butterfly valve. In this manner, one obtains an initial control of the metering cross section of the conduit 7 or of the quantity of secondary air fed and, by way of the actuation of the second flat slider 89, a correcting regulating intervention is achieved by means of which the initially controlled cross section can be varied. Thus, regulation of the quantities of additional air is effected rapidly and very accurately.

It will be appreciated that the first flat slider 84 may be adjusted against the force of the spring by means of an eccentric connected to the butterfly valve spindle 10, instead of being adjusted by the drive shown in Figure 6.

Figure 3, shows, in a simplified form, an improved embodiment of a first and second flat slider for controlling the flow-through cross section at the opening 88 of the conduit 7. In this embodiment, the flat sliders 84' and 89', which are guided in grooves 86 of the flange 87 in the same manner as in the embodiment of Figure 6, have window-shaped cutaway portions 97 and 98 respectively. The flat sliders 84' and 89' are displaceable in the same manner, and the window-shaped cutaway portions 97 and 98 are congruent in shape and, when the sliders are in one end position, can be made to coincide such that the entire area of the cut-away portion is fully open, thus allowing maximum passage of secondary air in the conduit 7. When the sliders are in their other extreme positions, each slider has fully closed the windowshaped cutaway portion in the other slider.

In the present case, in contrast to the embodiment of Figure 2, the actuating rod 83' is movably connected to the first flat slider 84' and its other end is secured to the crank 82 of the butterfly valve spindle 11 by way of a hinge 99. This constitutes a substantial simplification of the adjusting drive of the first flat slider 84'. When the actuating rod 83' has an adequate length L, and when the crank 82' has a small crank radius R, it is still possible for the free cross section of the conduit 7 to follow the free aperture cross section at the butterfly valve 5 with sufficient accuracy.

Advantageously, a cable pull acting against spring force may be used instead of an actuating rod. The actuating rod 91 may be driven in the manner shown in Figure 6.

This embodiment has the advantage that the flat sliders guided in the flange 87 can be sealed in a substantially better way.

Advantageously, the vacuum prevailing downstream of the metering point in the conduit 7 presses the flat sliders sealingly against one another in the region in which they abut against one another, so that, without having to provide a separate seal, a leakage of air which would falsify the regulation, cannot occur at this location, The same applies to the guidance of the second flat slider 89' in the flange 87.

Figure 4 and Figure 5 show another variant of the cross section control in the conduit 7. In this embodiment, a first, tubular slider 102 is fitted in a guide portion 101 of the conduit 7 and its axis intersects the axis of the conduit 7 at right angles thereto. The first slider is sealingly guided in a transverse bore 103 in the guide portion 101 and is secured against rotation. The end faces of the tubular slider 102 are closed and one of its ends extends out of the guide portion 101. In this instance, the first slider 102 has an actuating rod 104 whose other end has, like the actuating rod 83 of Figure 6, a guide slot 105 which lies at right angles to the direction of displacement of the first slider 102. The guide slot 105 is engaged by the pin 81 of the crank 82 connected to the main butterfly valve spindle 10.

The tubular slider 102 has a-recess 106 in the form of a slotted hole which, when the first slider 102 is in any displaced position, leaves the intake side cross section of the conduit 7 fully open at the point at which the conduit enters the guide portion 101.

The first tubular slider 102 has at its other side a preferably rectangular or square opening 106' which determines the maximum flow-through cross section of the conduit 107 and which remains in the region of the free cross section of the conduit 7 when the first slider 102 is in any displaced position.

A second tubular slider 108 is sealingly and coaxially fitted in the interior of the first tubular slider 102 and is rotatable by means of an actuating arm 109 outside the guide portion 101. The side of the second slider 108 facing the intake side of the conduit 7 also has an opening 110 which, when the second slider 108 is in any rotary position, allows passage to the interior of the tubular slider 108 with the full cross section of the conduit 107. The opposite side of the second tubular slider 108 also has an opening 111 whose cross section is congruent with the cross section of the opening 106'. These openings are associated with one another such that, when the sliders are in one extreme position relative to one another, these sliders have mutually fully closed the openings and, when in the other extreme position, have brought the openings 106 and 111 into register with one another.

In the same manner as in the embodiment of Figure 3, the first tubular slider 102 can be actuated, for pilot control, by the butterfly valve 5 in conformity with the free aperture cross section of the intake pipe 1.

With the second slider 108 retained in its initial position, the free cross section at the opening 106 is continuously opened in conformity with the movement of the butterfly valve. As already described with reference to Figure 2, this free section can be varied multiplicatively by a multiplication factor between 1 and 0 by turning the second slider 108 by means of the actuating arm 109.

Alternatively, however, the embodiment of Figures 4 and 5 can be constructed analogously to that of Figure 2, such that the free cross section of the opening 106' is controlled by the edge of the transverse bore 103 forming the transition to the cross section of the conduit 7, the first slider 102 being rotatable. The second slider 108 can then be in the form of a displaceable piston.

The actuation of one of the sliders in conformity with the control variable detected by the regulating device 43, which may be, for example, the signal from an oxygen measuring probe, is not confined to the type of actuation described with reference to Figure 2. An adjustable magnet, or a heatable bimetal spring adapted to the conditions, can be used in the same manner as a drive instead of an electric motor. Advantageously, however, actuation may be effected by means of an hydraulic servomotor or by means of a pneumatic servomotor.

The illustrated embodiments have the overall advantage of being compact structural units which can be used in conjunction with conventional carburettors or injection systems in which the quantity of intake air is measured. In the embodiments described, the conduit 7', 7" has been described as a secondary air conduit parallel to the mixture-producing and mixturemetering device of an internal combustion engine. It will be appreciated that a conduit of this type may also be in the form of an exhaust gas return pipe which introduces controlled quantities of exhaust gas into the intake pipe downstream of the butterfly valve. The feeding back of the exhaust gases also requires accurate metering of the particular quantity and a rapid change in the metering cross section upon changes in the operating conditions of the internal combustion engine. Correspondingly characteristic parameters of the internal combustion engine may then be used as control variables. The idling conditions and full load condition of the internal combustion engine are to be included in the regulation since, in these regions, a return of exhaust gas must be eliminated entirely so as to not influence in a negative manner, on the one hand, the smooth running of the engine and, on the other hand, the maximum output during full load.

WHAT WE CLAIM IS:- 1. A device for influencing the composition of the operating mixture, fed to an internal combustion engine, in accordance with a method in which gaseous media are fed by way of a metering crosssection which is variable proportionally to the setting of a mixture quantity.:control, this proportionality being controllable by means of a regulator which is adapted to detect the operating behaviour of the internal combustion engine, said device comprising a throttle element disposed in a conduit opening into an intake pipe'and adapted to determine the metering crosssection, means for transmitting the setting of the mixture quantity control to the throttle element, and a second throttle element for also adjusting the metering cross-section of the conduit, the second throttle element being arranged to vary the free cross-section of the conduit and being operable by way of the regulator which is adapted to detect at least one operating parameter of the internal combustion engine.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

leaves the intake side cross section of the conduit 7 fully open at the point at which the conduit enters the guide portion 101.

The first tubular slider 102 has at its other side a preferably rectangular or square opening 106' which determines the maximum flow-through cross section of the conduit 107 and which remains in the region of the free cross section of the conduit 7 when the first slider 102 is in any displaced position.

A second tubular slider 108 is sealingly and coaxially fitted in the interior of the first tubular slider 102 and is rotatable by means of an actuating arm 109 outside the guide portion 101. The side of the second slider

108 facing the intake side of the conduit 7 also has an opening 110 which, when the second slider 108 is in any rotary position, allows passage to the interior of the tubular slider 108 with the full cross section of the conduit 107. The opposite side of the second tubular slider 108 also has an opening 111 whose cross section is congruent with the cross section of the opening 106'. These openings are associated with one another such that, when the sliders are in one extreme position relative to one another, these sliders have mutually fully closed the openings and, when in the other extreme position, have brought the openings 106 and

111 into register with one another.

In the same manner as in the embodiment of Figure 3, the first tubular slider 102 can be actuated, for pilot control, by the butterfly valve 5 in conformity with the free aperture cross section of the intake pipe 1.

With the second slider 108 retained in its initial position, the free cross section at the opening 106 is continuously opened in conformity with the movement of the butterfly valve. As already described with reference to Figure 2, this free section can be varied multiplicatively by a multiplication factor between 1 and 0 by turning the second slider 108 by means of the actuating arm 109.

Alternatively, however, the embodiment of Figures 4 and 5 can be constructed analogously to that of Figure 2, such that the free cross section of the opening 106' is controlled by the edge of the transverse bore 103 forming the transition to the cross section of the conduit 7, the first slider 102 being rotatable. The second slider 108 can then be in the form of a displaceable piston.

The actuation of one of the sliders in conformity with the control variable detected by the regulating device 43, which may be, for example, the signal from an oxygen measuring probe, is not confined to the type of actuation described with reference to Figure 2. An adjustable magnet, or a heatable bimetal spring adapted to the conditions, can be used in the same manner as a drive instead of an electric motor. Advantageously, however, actuation may be effected by means of an hydraulic servomotor or by means of a pneumatic servomotor.

The illustrated embodiments have the overall advantage of being compact structural units which can be used in conjunction with conventional carburettors or injection systems in which the quantity of intake air is measured. In the embodiments described, the conduit 7', 7" has been described as a secondary air conduit parallel to the mixture-producing and mixturemetering device of an internal combustion engine. It will be appreciated that a conduit of this type may also be in the form of an exhaust gas return pipe which introduces controlled quantities of exhaust gas into the intake pipe downstream of the butterfly valve. The feeding back of the exhaust gases also requires accurate metering of the particular quantity and a rapid change in the metering cross section upon changes in the operating conditions of the internal combustion engine. Correspondingly characteristic parameters of the internal combustion engine may then be used as control variables. The idling conditions and full load condition of the internal combustion engine are to be included in the regulation since, in these regions, a return of exhaust gas must be eliminated entirely so as to not influence in a negative manner, on the one hand, the smooth running of the engine and, on the other hand, the maximum output during full load.

WHAT WE CLAIM IS:- 1. A device for influencing the composition of the operating mixture, fed to an internal combustion engine, in accordance with a method in which gaseous media are fed by way of a metering crosssection which is variable proportionally to the setting of a mixture quantity.:control, this proportionality being controllable by means of a regulator which is adapted to detect the operating behaviour of the internal combustion engine, said device comprising a throttle element disposed in a conduit opening into an intake pipe'and adapted to determine the metering crosssection, means for transmitting the setting of the mixture quantity control to the throttle element, and a second throttle element for also adjusting the metering cross-section of the conduit, the second throttle element being arranged to vary the free cross-section of the conduit and being operable by way of the regulator which is adapted to detect at least one operating parameter of the internal combustion engine.
2. A device as claimed in claim 1, in which

the throttle element comprises a butterfly valve over which engages a slotted cylindrical filling element acting as the second throttle element in the form of a piston valve which is sealingly fitted in the conduit and which is displaceable axially of the spindle of the butterfly valve by an actuating device controlled by the regulating device.
3. A device as claimed in claim 2, in which the conduit has a rectangular cross-section in the effective region of the butterfly valve, and the piston valve is fitted into this crosssection.
4. A device as claimed in claim 1, in which the throttle element comprises a first slider which is coupled to the mixture quantity control device, and the second throttle element comprises a second slider which varies the metering cross-section of the conduit at the first slider and which abuts against the first slider and is adjustable transversely of the adjusting direction of the first slider by means of an actuating device controlled by the regulator.
5. A device as claimed in claim 4, in which the mixture quantity control device comprises a main butterfly valve arranged in the intake pipe of the internal combustion engine and is coupled to the first slider by way of an eccentric.
6. A device as claimed in claim 5, in which the eccentric is in the form of a crank arm on the spindle of the main butterfly valve, and a turning pin of the crank arm engages a guide slot extending transversely of the direction of displacement in an actuating member connected to the first slider.
7. A device as claimed in claim 5, in which the eccentric is in the form of a crank arm on the spindle of the main butterfly valve, and the first slider is connected to the crank arm by way of an actuating member which is movably connected to the first slider.
8. A device as claimed in any one of claims 4 to 7, in which the sliders are in the form of flat sliders.
9. A device as claimed in claim 8, in which the first and the second flat sliders are guided closely one above the other in a flange of the conduit and each has an opening in the region of the free cross section of the conduit, and the common flow-through cross-section of the said sliders is variable by displacing the flat sliders until the cross-section of the conduit is fully closed.
10. A device as claimed in claim 9, in which the openings are square and have edges which extend parallel to the direction of displacement.
11. A device as claimed in any one of the preceding claims 4 to 6, in which the sliders are in the form of tubes, one of which tubes is axially displaceable and the other is rotatable.
12. A device as claimed in claim 11, in which the tubes have respective openings which maintain a constant free cross-section in the conduit irrespective of their displacement relative to one another, the tubes also have respective metering openings in the region of the free crosssection of the conduit, the common flowthrough cross-section of which metering openings is variable by displacing the tubes relative to one another until the crosssection of the conduit is fully closed.
13. A device as claimed in any one of the preceding claims 4 to 6, in which a rotatable tubular slider acts as the first slider in whicha displaceable piston, acting as a second slider, is sealingly guided.
14. A device as claimed in any one of the preceding claims, in which the actuating device operates electromagnetically and comprises an electric motor, an electromagnet, or a bimetal spring.
15. A device as claimed in any one of the preceding claims 1 to 13, in which the actuating device comprises a pneumatic or hydraulic servomotor which is arranged to operate against the force of a spring and whose working pressure is variable between two adjusting pressures by means of a valve arrangement actuated by the regulator.
16. A device as claimed in claim 15, in which the adjusting pressure is, on the one hand, the pressure in the intake pipe directly downstream of an air filter for the internal combustion engine and, on the other hand, the pressure which is taken from the intake pipe downstream of the mixture quantity control device and which is stabilized by way of a pressure-regulating valve.
17. A device as claimed in claim 15, in an internal combustion engine in which the mixture is produced by means of a carburettor having a float chamber supplied by means of a fuel feed pump, the adjusting pressure being, on the one hand, the feed pressure of the fuel feed pump stabilized by a pressure-regulating valve and, on the other hand, being the fuel pressure in the float chamber.
18. A device as claimed in any one of the claims 16 or 17, in which the valve arrangement comprises a magnetically operable three-position valve which is controllable analogously or sequentially by the regulator.
19. A device as claimed in any one of the claims 16 or 17, in which the valve arrangement comprises two solenoid valves which are each arranged in a respective one of the pressure lines carrying the adjusting pressures and which are operable in anti phase by the regulator with a variable opening time ratio.
20. A device as claimed in any one of the preceding claims, in which the conduit is an air conduit by-passing the mixture quantity control device.
21. A device as claimed in any one of the preceding claims 1 to 19, with an internal combustion engine, in which the conduit is an exhaust gas feedback conduit leading from the exhaust gas collecting system of the internal combustion engine and opening into the intake pipe of the internal combustion engine downstream of a mixture producer and the mixture quantity control device.
22. A device for influencing the composition of the operating mixture, fed to an internal combustion engine, in accordance with a method in which gaseous media are fed by way of a metering crosssection which is variable proportionally to the setting of a mixture quantity control device, said device being constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.