DE2245492C2 - Fuel metering system - Google Patents

Description

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4. Fuel metering system according to claim 3, characterized in that the flap (18) has the bypass cross-section (20) is still enlarged when the throttle valve (14) is rotated through 90 ° and the intake manifold cross-section is reduced.

5. Fuel metering system according to one of the preceding claims, characterized in that the bypass (17) bypasses measuring element (15) and throttle valve (14) and that as a measuring element and fuel metering element a carburetor (15) is used, which works in particular with a constant pressure gradient.

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The invention relates to a fuel metering system for mixture-compressing, externally ignited internal combustion engines with a suction pipe in which a main throttle valve controlling the throughput is arranged a sensor exposed to the exhaust gas of the internal combustion engine for the formation of the oxygen content characterizing output signal, corresponding to the one in an air bypass line, the one arranged in the intake manifold The air-fuel-fuel-air mixture generating device measures the air-metering element which controls the amount of fuel the internal combustion engine bypasses, arranged throttle member to control the supply of Additional air to the intake manifold of the internal combustion engine can be actuated, the throttle member at least one Adjusting device is assigned through which a basic setting of the throttle member as a function of the throttle valve position and an additional adjustment of the throttle element superimposed on the basic setting can be carried out as a function of the control signal of the measuring sensor according to German patent 22 04 192.

In this Kraftstoffzumeßanlage a throttle valve is also in the air bypass line as throttling device provided the same type as that of the main throttle valve in the intake manifold with a circular, the inner diameter of the tubular bypass line is ⁿ sßten disc on a L "ftb" ^r * ° ss! Eitun2 penetrating shaft is attached. This configuration has the disadvantage that the bypass throttle valve is tied to fixed geometric dimensions corresponding to the circular inner diameter of the bypass line and no adaptation to the requirements for the mixture composition in the respective internal combustion engine can be taken into account with the basic adjustment of the bypass throttle valve. Another disadvantage of the above solution is that an adjustment of the bypass throttle valve by the control compared to the precise angle tracking of the bypass throttle valve for adjusting the main throttle valve is much more noticeable with small gas throughputs or with a small throttle valve opening angle than with large throughputs or when the throttle valve is wide open . This means that the regulation must produce significantly smaller travel ranges at low load than at high load <ind that a multiplicative influence of a bypass throttle valve position correction carried out over the entire working range of the bypass throttle valve is not possible the mixture composition through the regulation has proportionally the same effect on the mixture composition in the other operating points, so that there an additional control intervention is not necessary if the conditions remain the same.

The invention is based on the object of the fuel metering system according to the main patent 22 04 192 so that it is possible to improve the air passage cross-section at the bypass throttle element in the air bypass line of the internal combustion engine to the air requirement of the internal combustion engine adapt to different throttle valve positions and a multiplicative control intervention of the above type to be realized.

According to the invention, this object is achieved in that a flap mounted on one side is used as the throttle element is provided with a rectangular area, which is in an air bypass line part with a corresponding rectangular Cross-section is arranged and that the end edge of the flap opposite wall of the air bypass line has a contour deviating from the circular path of the flap front edge, so that depending on Position of the flap a different passage cross-section can be set in a rectangular shape. at fixed assignment of adjustment of the throttle valve

to the bypass valve, if the appropriate choice is made, the Contour the desired, multiplicative control deviation can be achieved, d. H. it will be for a constant A change in the manipulated variable causes a proportional change in the total air volume throttle valve and bypass valve are also activated in the event of a sudden increase in the air flow in the intake manifold also causes a greater throughput in the bypass. The control amplifier can then the make the necessary correction in a much shorter time than is possible without the basic adjustment were.

The contour can be determined according to a differential equation, which from the requirement

= constant

15th

Here arises λ denotes the composition of the fuel-air mixture, wherein for a stoichiometric mixture λ = 1, the air ratio is the Ahgasmeßsonde turn engages each then in the control when any change of the air ratio A takes place. According to an advantageous embodiment of the invention, the surface having a contour is arranged on a part of the bypass pipe which is exchangeable. In this way it is relatively easy to

1. to attach such a contour at all and

2. A bypass pipe that is the same for most of the motors to have, in which only to adapt to the requirements that having the contour Part is selected accordingly.

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In any case, this can be relatively easy Way when changing the proportionality between fuel and air, this proportionality as such are maintained over the entire load and speed range.

According to an additional embodiment of the invention, the coupling ratio of the throttle valve rotation angle Oc _x to the bypass valve rotation angle a _{2 is} greater than

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According to the invention, the flap can thereby increase the bypass cross section even more if the throttle flap rotated through 90 ° already reduces the intake manifold cross section. As a result, regulation is not only possible for smaller, but also, in particular, larger air ratios λ which are required at full load.

An embodiment of the subject invention is shown in the drawing and is described in more detail below. It shows

F i g. 1 shows a greatly simplified representation of the internal combustion engine with a control loop,

F i g. 2 the controlled bypass section in cross section.

An internal combustion engine 11 is passed through a filter 12 and a suction pipe 13, in which an arbitrarily actuatable throttle valve 14 and a carburetor nozzle 15 with Fuel line 16 are arranged one behind the other, supplied with fuel-air-Ge-mix. Carburetor nozzle 15 and Throttle flaps 14 are bypassed by a bypass 17 of the suction pipe 13. In the bypass 17 is a bypass flap 18 arranged, which has an electrical input connected to the output of a control amplifier 25 is connected. In addition, the bypass flap 18 can be adjusted mechanically from the accelerator pedal 30, via that also the throttle valve 14 is adjusted.

The exhaust gases from the internal combustion engine 11 are collected in an exhaust manifold 19, the wall of which 20 is thermally isolated from the ambient air. The exhaust manifold 19 (exhaust pipe) opens into a catalytic reactor 21 with an outlet line 22. Upstream of the catalytic reactor 21 is in the wall 20 the exhaust manifold 19 an oxygen measuring probe 23 is arranged. The electrical output of the oxygen measuring probe 23 is connected to an input of the control amplifier 25 via a preamplifier 24. the The crankshaft of the internal combustion engine 11 drives a speed sensor, which is made up of a series circuit Pulse generator '32 and a frequency DC voltage converter 33 consists of the output of the frequency DC voltage converter 33 is connected to a second input of the control amplifier 25.

With the accelerator pedal 30, a travel sensor 31 is actuated, which is designed as a potentiometer The output voltage of the transducer 31 is proportional to the deflection angle of the accelerator pedal 30 and is with its output is connected to a third input of the control amplifier 25.

As soon as the bypass flap is adjusted so far and the additional air flow has decreased so that the air number λ falls below the value 038, the output voltage of the oxygen measuring probe 23 and, accordingly, the output voltage of the preamplifier 24 rises sharply. The bypass valve is thus readjusted in the control amplifier 25, always depending on the engine speed or the throttle valve position (engine load).

In Figure 2, the section of the bypass pipe 17 is enlarged shown, in which the bypass valve 18 is arranged. The bypass pipe 17 has in this section a rectangular cross-section, not shown in detail. The bypass flap 18 is on one side on a shaft 19 mounted and controls a likewise rectangular clear cross section 20 during the rotary movement.

The change in the cross section 2C with the angle of rotation of the flap 18 depends on that of the flap opposite arranged contour 21 of the wall of the bypass, which is arranged on an exchangeable insert part 22 The bypass flap 18 is actuated by a servomotor 23, which receives its manipulated variable from the control amplifier 25 receives. Depending on the requirements of the fuel metering system, an insert 22 with a corresponding Contour 21 can be used.

1 sheet of drawings

Claims (3)

Patent claims: 1. Fuel metering system for mixture-compressing, externally ignited internal combustion engines with an intake manifold in which one controls the throughput Main throttle valve is arranged with a sensor exposed to the exhaust gas of the internal combustion engine for the formation of an output signal characterizing the oxygen content, corresponding to the one in an air bypass line that contains an air that is arranged in the intake manifold and controls the amount of fuel metered bypassing the measuring organ of the fuel-air mixture generating device of the internal combustion engine, arranged throttle element for controlling the supply of additional air to the intake manifold of the internal combustion engine can be actuated, with at least one adjustment device assigned to the throttle element is through which a basic setting of the throttle body in Ah & Sngigkeit from the throttle valve position- {iinff and additional adjustment superimposed on the basic control the throttle member can be carried out as a function of the control signal from the sensor according to German patent 22 04 192, thereby characterized in that a one-sided mounted flap (18) with a rectangular surface is used as a throttle element is provided in an air bypass line part! is arranged with a corresponding rectangular cross-section and that the front edge of the flap opposite wall (22) of the air bypass line (17) one from the circular path of the flap front edge different contour (21), so that depending on the position of the flap tin different Passage cross-section (20>. Can be set in a rectangular shape. 2. Fuel metering system according to claim 1, characterized in that the one having a contour Surface (21) is arranged on a part (22) of the bypass pipe (17) which is exchangeable. 3. Fuel metering system according to claim ί or 2, characterized in that the coupling ratio of the throttle valve rotation angle λ to the bypass valve rotation angle _{2 is} greater than 1.