DE3231766A1 - DEVICE FOR REGULATING THE IDLE SPEED IN AN INTERNAL COMBUSTION ENGINE - Google Patents

Description

6.8,1982 Mü / Hm

ROBERT BOSCH GMBH, 7OOO STUTTGART 1

Device for regulating the idling speed in an internal combustion engine

State of the art

The invention is based on a device for idling speed control according to DE-OS 30 39! +35. the There disclosed control device detects the speed of the internal combustion engine and controls it by means of a PID controller to a setpoint. For this purpose, the mixture or air throughput in the intake pipe is varied by either the throttle position or the air flow through the bypass duct to the throttle is changed.

So-called smoothness controls are known separately. In this context, smoothness means that the crankshaft runs smoothly. The running smoothness becomes less, or the uneven running is greater if, for example, the mixture in an externally ignited internal combustion engine is too strong

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is emaciated, so that not all. Combustion processes run more controlled. As a result, there are changes in the torque of the internal combustion engine, which in turn leads to uneven running and possibly to jerks. If the uneven running is based on a lean mixture, it can be countered by means of enrichment. Known smooth-running regulating devices therefore attempt to regulate to the so-called lean running limit in order to save fuel by influencing the composition of the mixture, ie, rich, lean. Examples of smoothness controls influencing the lambda value are: DE-OS 2! + 3 ¹ + 7 ^ 2, DE-OS 2k 17 187, DE-OS 29 39 590, US Pat. No. 3,789,816.

Previously known idle speed control devices, like the one mentioned at the beginning, only process a speed signal and perform a speed setpoint and -is compare. The speed setpoint can depend on the temperature, since the internal combustion engine is still cold there is an increased risk of the internal combustion engine dying off.

The disadvantage of the known idle speed control device is therefore that certain safety distances must be specified, but with a view to the lowest possible idle speed value (from fuel savings reasons) are not desirable.

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Advantages of the invention

With the control device according to the invention the idling speed can be limited to these safety margins, which, among other things, are temperature-dependent, almost covered "are, because the respective instantaneous behavior of the internal combustion engine is used for control purposes will. In other words, there is an extremely low idling speed determined by the quality of the engine combustion allows, which at the same time results in the lowest fuel consumption. Is limited downwards this speed, among other things, by the required throttle response.

drawing

An embodiment of the invention is shown in the drawing and is described and explained in more detail below. FIG. 1 shows a rough overview diagram of an internal combustion engine together with the most important units and a control unit as a single block, FIGS. 2 and 3 show two diagrams in which the uneven running is plotted against the speed at different temperatures and the curves of which show the control in the sense of the invention . Finally, FIG. H shows a rough block diagram of the device for regulating the idling speed.

Description of the exemplary embodiments

The exemplary embodiments relate to devices for Idle speed control in internal combustion engines with Smooth running as a measured variable. They enable the greatest possible

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going lowering of the idling speed, which is essential with regard to lowering the fuel consumption. In city traffic, for example, lowering the idling speed by 100 revolutions per minute can save up to 2% fuel. If the uneven running exceeds a certain target value, the amount of the mixture is increased again according to the invention. In the case of a gasoline engine, this is done by opening the throttle valve or opening the bypass section, while in the case of a diesel engine, the desired smoothness is achieved by adding a certain amount of fuel.

FIG. 1 shows a rough overview of an internal combustion engine 10 with external ignition with its most important components and control devices. 11 marks an air intake pipe, 12 an exhaust pipe. An air flow sensor 13, a throttle valve 1 k and an injection valve 15 are located one behind the other in the intake pipe 11. An electronic control unit bears the reference number 20. It receives input signals from a temperature sensor 21, a speed sensor 22 and the air flow sensor 13 and two arrows indicate the possibility of further influencing variables acting on the output signal (s) of the control unit 20. On the output side, the control device 20 is connected to the at least one injection valve 15, and also to the bypass actuator 17. Die

Throttle valve 1 k is directly influenced by the accelerator pedal 24 '. In the case of an electronic control of the throttle valve position, the bypass adjuster 17 is unnecessary in certain cases so that the control unit 20 can directly influence the position of the throttle valve via the dashed line 25. Finally, a line 23 also indicates an ignition timing control.

The basic structure of an internal combustion engine control shown in FIG as such is already state of the art. Depending on load and speed and correction variables such as the temperature of the cooling water, the control unit 20 determines injection quantity signals for the injection valve 15 and, among other things, additional control signals for the bypass actuator 17

It is now essential that a smooth running or rough running signal is formed in the control unit 20 and from it depending on an adjustment of the bypass adjuster 17 "resp. the throttle valve 14 takes place. This results in a higher air throughput in the intake pipe, which by means of of the air flow sensor 13 is detected and causes a higher injection quantity. In contrast to well-known In the case of the invention, systems will not immediately do this if the uneven running is too great Fuel quantity signal, but the air control signal and thus the amount of mixture varies.

The explanation of the device according to the invention the representations in FIGS. 2 and 3 are used.

In the case of the Otto engine, the scatter in the energy conversion in idle operation is very much dependent on

conditions such as engine temperature, air temperature, air flow rate, etc. This variance value, ie the uneven running of the engine, increases progressively with decreasing speed. Figure 2 shows an example
the course of uneven running values (LU) at different cooling water temperatures. Thereafter - mainly as a result of deteriorated mixture preparation and distribution as well as unfavorable ignition conditions - the uneven running increases with falling temperature.

The idle speed control in the subject of Figure 1 can now take place with regard to the representation of Figure in such a way that initially an upper setpoint Idling speed nL is used, which experience has shown to im-

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mer provides sufficient running smoothness (point a). In the following, the amount of the mixture becomes a setpoint value for the uneven running LU_. withdrawn
(Point b), in which an idling speed nL1 is then set. As the temperature rises, the speed can continue with the same rough running setpoint
can be withdrawn up to the value nL2 (point c). Is associated with the control unit 20
so-called learning control system available,
then the respective idle control does not always have to start from point a, but the speed value obtained in the previous idle operating state is stored and this value is used as the new output variable for the control in the subsequent idle operating case.

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In a special case it can happen - e.g. after a long drive under full throttle - that the desired value for the idle speed drops below a speed value that is suitable for example due to the accuracy of the mixture quantity or for a useful throttle response (curve for \ s * 3 in Figure 2). This is achieved by introducing a lower idle speed value nL. locked out. This means a mm ^&

Regulation of the idle speed in the range between the minimum and maximum idle speed, where a certain rough running setpoint is regulated.

FIG. 3 shows a change in the mode of operation of the idle speed control shown in FIG. 2 insofar as a combination of lean and speed control is shown there. This regulation is of particular importance with regard to low CO pollutant emissions during the warm-up phase of the engine. In this case, a comparatively rich idle mixture composition is initially set (eg 2 % CO), (a, b) which is emaciated in the subsequent step, (c, d) (eg to 0.5 % CO). The control is then carried out as shown in FIG.

As a further addition, the smooth running control on the mixture side can be added with an ignition angle control can be combined in order to achieve an optimum with regard to all company sizes.

In the case of an idle speed control for a The diesel internal combustion engine uses the smoothness control in the control circuit for the quantity-determining element. As the diesel engine usually with

Excess air is driven, corresponds to the change the mixture quantity "in the case of a gasoline engine, essentially the change in the injection quantity in the case of a diesel engine.

The way the uneven running detection can be very be multi-layered. Possible are:

a) Circulation times of the crankshaft T, determination of Changes in the cycle time or the differential quotient

b) ion current measurement in the combustion chamber,

c) pressure fluctuations in the combustion chamber,

d) light intensity fluctuations, as well as

e) Measuring these and other specific quantities in the exhaust pipe.

With regard to the computer controls generally used today in connection with the motor vehicle, it is advisable to implement the invention via appropriate programming of the computer, ie purely in terms of software. For the sake of completeness, FIG. K shows an arrangement in a block diagram for implementing the functions according to the invention.

An uneven running detection stage is denoted by 30, with 31 and 32 signal transmitters for a maximum and a minimum idle speed nL and nL. . One of

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external variables influenceable setpoint control stage carries the reference numeral 33 and finally a lambda target value stage the symbol 3 ^ ·. Setpoint and actual value of the Uneven running are compared by means of a comparator 36 and the result is more or less additional Steps ultimately fed to the bypass regulator 17. The ones mentioned, interposed

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Levels are used to limit the control range. A maximum value selection stage ensures that the uneven running control is only possible above a minimum idling speed, a subsequent minimum value selection stage 30 ensures an upper speed limit. Finally, a further maximum value selection stage kO enables different ones to be implemented
Lambda controls according to the representation of
Figure 3.

The individual minimum and maximum selection levels are in each case by means of dashed lines and switches It-1 to U3 arranged within these lines can be bridged to indicate that the individual limitation levels are optionally provided as required can.

If the idea of the invention is known, the realization of the individual blocks for the average person skilled in the switching and control sector Problem, so that there is no need to specify them in detail.

Claims (1)

^R 1 8 Ο ¹ 4 6.8.i9o2 mi / Hm? ROBERT BOSCH GMBH, TOOO STUTTGART 1 Expectations Device for regulating the idling speed at an internal combustion engine, characterized in that control variables can be varied depending on the smooth running are. 2. Device for regulating the idling speed of an internal combustion engine with external ignition, thereby characterized in that the mixture or air throughput in the intake pipe can be changed depending on the smoothness is. 3. Device according to claim 2, characterized in that the mixture or. Air flow in the suction pipe can be changed by means of a bypass actuator (17) and / or an electronically controllable throttle valve is. k. Device according to claim 1 or 2, characterized in that depending on the smoothness in addition to the change in the mixture or. Air throughput in the intake pipe, the ignition timing is also adjustable. 5. Device according to at least one of claims 1 to h, characterized by a combination of smoothness control via mixture amount and mixture composition (Figure 3). 6. Device according to claim 5, characterized in that the intervention in the mixture composition preferably takes place during warm-up. 7. Device according to at least one of claims 1 to 6, characterized in that a minimum idle speed value (nL.) and / or a maximum empty mm running speed value (nL) as a limitation of the smoothness control is provided. 8. Device according to claim 1, characterized in that in a self-igniting internal combustion engine the injected fuel quantity can be changed depending on the smoothness. 9. Device according to at least one of claims 1 to 8, characterized in that for detecting smoothness preferably a speed, ion current, pressure or light fluctuation signal is evaluated.