DE3007336A1 - DEVICE FOR KNOCKING CONTROL OF AN INTERNAL COMBUSTION ENGINE - Google Patents

Description

R. 6085

January 29, 1980 Mü / Kö

ROBERT BOSCH GMBH, 7OOO Stuttgart 1

Device for knock control of an internal combustion engine

State of the art

In contrast to "soft" combustion, "knocking" in Otto engines and diesel engines is sudden and therefore undesirable combustion process. Depending on the strength, knocking sounds like a fine ringing to a hard one Hammering. Depending on the extent of the head will be longer term Piston and engine overloaded and bearings knocked out. Irrespective of this, the performance of the internal combustion engine drops with heavy knocking.

The cause of knocking in internal combustion engines has long been known, and it is known that in Otto engines the tendency to knock decreases, e.g. with less spray ignition and changed fuel metering and with diesel engines e.g. with a lower advance injection. For economic reasons, it is necessary to operate the internal combustion engine cheap near the knock limit. Because this knock limit fluctuates depending on the operating status, a so-called knock control proves to be beneficial.

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Above all, in connection with the Otto engine, various solutions are known, e.g. depending on the degree of Knocking, the ignition timing or the ignition angle must be adjusted. This serves as the measure for knocking Output signal of a knock sensor in the form of a structure-borne noise-sensitive component.

Due to asymmetries, e.g. in the provision of the mixture, a three-cylinder cylinder occurs in the individual cylinders Internal combustion engine unevenly strong knocking. It is therefore desirable to tap each and every one To capture cylinder. If more than one sensor per motor is used for this, there are already two embodiments known:

1. The signals from each sensor are processed and evaluated individually (for pure measurement purposes). This method delivers good results, but the effort is very high because the electronics connected downstream of the sensor must be present several times according to the number of sensors.

2. The signals from all sensors are combined into one signal by summation. The advantage of this procedure lies in the reduction in the effort required for the evaluation electronics, as these only have 1-channel design got to. The disadvantage compared to 1. is the poor Hutz-to-noise ratio. For example, knock sensors according to the principle of acceleration measurement, interference signals from closing valves of other cylinders with transferred.

The aim of the invention is to combine the advantages of both previously known methods while avoiding them

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Disadvantage. This is realized by the multiplex control device described below.

Advantages of the invention

The device according to the invention with the features of the main claim enables the detection of very precisely Knocking noises from individual cylinders and therefore also a correspondingly precise knock control of essential operating parameters, such as fuel metering and ignition angle for gasoline engines and, for example, setting the start of injection for diesel engines. Depending on the effort, the Individual control of the individual sizes for one or more cylinders possible.

Compared to the already known embodiment (1.) by using the device according to the invention, the expenditure on electronic components for signal evaluation significantly reduced, as the evaluation electronics are only 1-channel.

Compared to the already known version according to (2.), which is also a 1-channel version the detection reliability for knocking by using the device according to the invention with approximately the same effort much improved.

An embodiment of the invention is shown in the single figure of the drawing and is described below described and explained in more detail.

Description of an exemplary embodiment

An internal combustion engine 10 is shown with external ignition

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that is coupled to an air intake pipe 11 and to an exhaust pipe 12. With a fuel metering device 13 is designated. It represents a controlled carburetor and receives, among other things, a control signal via a line I ¹ I from a knock control stage 15. The four spark plugs of the 4-cylinder internal combustion engine have the reference numbers 16 to 19 For example, each of the four cylinders is assigned its own head sensor 22 to 25, the output lines of which are routed to a multiplex control device 26. This multiplex control device 26 enables signals from individual knock sensors 22 to 25 to be switched through to an input 27 of the knock control stage 15 in succession.

With regard to the correct detection and processing of cylinder-related knock signals, the multiplex switching device 26 work at the same speed as the crankshaft. Then only those knock signals are given forwarded to the knock control stage 15 and processed, which are currently queried as desired. One Overlapping with interfering signals from other cylinders, e.g. valve noises, is due to the use of the multiplex switch 26 avoided.

In the example shown, a knock sensor is assigned to each of the cylinders. Of course, a individual knock sensor cylinder groups can be assigned. Furthermore, the knock control arrangement 15 acts both on the ignition control stage 20 and on the fuel metering stage 13, depending on the degree of knocking the

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Ignition timing for each cylinder and the Fuel metering can be changed. Of course, the knock control device 15 can also alternatively either on the ignition control stage 20 or on the fuel metering device 13 act.

In the P. all an internal combustion engine with compression ignition (diesel engine) the knock control device 15 is connected to an injection start adjustment device.

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Claims (3)

R. 60 8 5 January 29, 1980 MÜ / Kö ROBERT BOSCH GMBH, 7OOO Stuttgart 1 Expectations ί l) Device for knock control of an internal combustion engine with a control unit for at least one operating parameter and several in connection with the control unit standing knock sensors attached to the internal combustion engine, characterized in that the signal outputs the individual knock sensors (22 to 25) via a multiplex switch (26) with a knock control stage (15) as Part of the control unit are coupled. 2. Device according to claim 1, characterized in that that the cycle time of the multiplex switch (26) has a fixed relationship to the speed of the crankshaft. 3. Device according to claim 1 or 2, characterized in that starting from the knock control stage (15) the Control variables for one or more cylinders (ignition timing and / or Gemxsch metering in the Otto engine, start of injection in the case of the diesel engine) are individually adjustable. 130037/0202