DE2340541A1 - PROTECTIVE DEVICE FOR AN ARRANGEMENT FOR EXHAUST GAS DETOXIFICATION FROM COMBUSTION POWER MACHINES - Google Patents

Description

23405A1

R. 1633
3.8.1973 Ka / Kb

Attachment to
Patent application

ROBERT BOSCH GMBH, 7 Stuttgart 1

Protective device for an arrangement for exhaust gas detoxification from internal combustion engines

The invention relates to a protective device for an arrangement for reducing harmful proportions of the Exhaust emissions from internal combustion engines, their exhaust systems has at least one thermal and / or catalytic reactor for aftertreatment of the exhaust gas from the internal combustion engine.

In known exhaust gas detoxification devices for internal combustion engines, thermal and / or catalytic reactors are provided in the exhaust system of the internal combustion engine. For example, so-called two-bed catalytic converters are known which are arranged in the exhaust system of an internal combustion engine, the internal combustion engine being operated with a rich fuel mixture. In a first catalyst bed of the two-bed catalyst, the nitrogen oxides NO contained in the exhaust gas are converted with the carbon monoxide CO to carbon dioxide CO and nitrogen N _? reduced. In the second catalyst bed of the two-bed catalyst, the remaining carbon is removed with the addition of secondary air.

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monoxide CO to carbon dioxide C0 _? and the hydrocarbons CH contained in the exhaust gas are _{oxidized to carbon dioxide CO n} and water.

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In such exhaust gas decontamination systems there is the problem that the catalysts against temperatures at which they must be destroyed, must be protected. So that the catalysts under normal operating conditions, e.g. B. in City operation, reaching sufficiently high temperatures for the aftertreatment of the exhaust gas, they are as close as possible installed at the outlet of the internal combustion engine. As a result, under unfavorable conditions, e.g. when driving at full load for a long time, Inadmissibly high temperatures occur in the catalytic converter. The temperature increase can be even more dangerous, if as a result of malfunctions in the ignition system, e.g. if the spark plug connector has fallen off or a spark plug is defective, one or more cylinders of the internal combustion engine are supplied with a combustible fuel-air mixture, in the Combustion chamber of the internal combustion engine, however, no combustion takes place. This creates the ignitable fuel-air mixture Ejected unburned or incompletely burned and gets into the or the in the exhaust system of the internal combustion engine arranged catalysts that are at a high temperature level. Due to the suddenly fed excess energy, the temperature in the catalyst (s) is also increased to a great extent, so that the catalyst temperature assumes inadmissibly high values and the catalyst is destroyed.

In order to avoid such destruction, devices have become known in which the catalytic converters immediately, bypass channels controlled by a valve are provided. If the catalyst temperature is too high here, a Bypass to the catalyst (s) opened and the exhaust gas bypassed the aftertreatment devices. this

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leads to the fact that the exhaust gas regulations are not complied with in such cases, since the catalyst bypasses Exhaust gas stream contains high concentrations of the harmful constituents carbon monoxide j hydrocarbons and nitrogen oxides. In addition, the design effort in such solutions is relatively large.

The invention is based on the object to protect To develop arrangements for exhaust gas detoxification a device that is easy and inexpensive to implement and that for the exhaust gas aftertreatment devices in the cases described above is a sufficient and provides reliable protection.

This object is achieved according to the invention in that the combustion process in individual cylinders or groups of cylinders characterizing sensors are provided, which are used in processes that lead to an impermissible temperature increase in the Exhaust system or at least one of the catalytic converters lead to the shutdown of the supply of fuel or the fuel-air mixture to trigger individual cylinders or groups of cylinders causing the temperature increase.

Further advantageous refinements and expedient developments of the invention result in connection with the subclaims from the following description an exemplary embodiment and from the accompanying drawing, which shows a protective device in a schematic representation for an arrangement for exhaust gas detoxification from internal combustion engines shows.

The drawing shows an internal combustion engine 1 to which air is supplied via an intake pipe 2. The intake pipe 2 is divided into individual branch lines 3, ^, 5 and Γ, in each of which an injection valve 7, 8, 9 and 10 is arranged. Each cirser injection valve ¹ e is for one of the parMT ^r learners of the Brennkraf ir.?.:-; chine 1 dependent time

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opened by a control unit 11. The control unit 11 for the electronically controlled gasoline injection is therefore Via lines 12, 13 »I ^ and 15 each with one of the injection valves 7j8,9 and 10 connected. In the connection lines 12, 13, 14 and 15 are each an opener 16, 17, 18 and 19 arranged.

In the exhaust system 20 of the internal combustion engine, a thermal reactor 21 and a catalytic reactor 22 are arranged, in which the proportion of harmful substances in the exhaust gas is to be reduced. One of two temperature sensors 23 and 2k , which are connected to a control unit 25, is arranged in each of the reactors 21 and 22. In addition, the control unit 25 is connected to temperature sensors 26, 27, 28 and 29, which are arranged in individual branch pipes 30, 31, 32 and 33 of the exhaust system 20 of the internal combustion engine 1, which are assigned to the cylinders of the internal combustion engine. Depending on the temperatures determined by the temperature sensors 23,2 * 4, 26,27,28 and 29, the control unit 25 actuates the contacts 16 to 19 via the connections indicated by broken lines and thereby interrupts the electrical leads to at least one of the injection valves 7 , 8,9 or 10, so that the fuel supply to the relevant cylinder of the internal combustion engine 1 is interrupted.

The mode of operation of the protective device described is the following:

If it is determined with the aid of the temperature sensor 23 or 2k that the temperature in one of the actuators 21 or 22 has exceeded a threshold value which is normally not reached

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has, with the help of the temperature sensors 26,27,28 or 29 found in which of the individual cylinders of the internal combustion engine 1 no proper combustion of the fuel-air mixture takes place, or which of the cylinders of the internal combustion engine is responsible for the increase in the catalyst temperature responsible for. As a criterion for the occurrence of misfires in a cylinder, the rapid drop in temperature in the exhaust port directly behind the relevant one applies. Cylinder exhaust. If the relevant cylinder of the internal combustion engine is determined in which the combustion is due to some malfunction of the fuel-air mixture does not take place, the control unit 25 determines the cylinder associated with the determined cylinder Contact 16 or 17 or 18 or 19 actuated and the fuel supply to the corresponding cylinder of the internal combustion engine interrupted, in which the valve 7 or 8 or 9 or 10 is not more can be actuated by the electronic control unit 11. Instead of the one in the supply lines to the injection valves lying switch contacts 16 to 19, which are designed as NC contacts, can also be used, the NO contacts if the combustion process fails in a cylinder of the internal combustion engine, the excitation winding of one of the Short-circuit injectors 7 to 10. Instead of Switching contacts can also be used with semiconductor switches.

So that the electronic control unit 25 is one of the switching contacts 15 to 19 triggers when a certain temperature threshold is exceeded in one of the reactors, the temperatures in the branch lines 30 to 33 of the individual cylinders of the Internal combustion engine compared with each other and that cylinder is determined which has the lowest temperature. After this cylinder has been determined, the control current to the injection valve of this cylinder is interrupted. Parallel for this purpose, optical or acoustic signaling devices are actuated, to indicate to the operator of the internal combustion engine, for example the driver of a motor vehicle, that a

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Cylinder of the internal combustion engine is not working properly.

It is particularly advantageous in the solution described that only the fuel supply to that cylinder is interrupted in which no combustion process takes place anyway. There is thus no additional torque drop in the internal combustion engine due to the shutdown of the fuel supply.

In a second, further not shown embodiment, the signal which indicates that in a Cylinder no or no complete combustion takes place, also from the temperatures in the branch lines to 33 of the exhaust system 20 of the internal combustion engine will. Depending on these temperatures, the feed line to one of the injection valves 7 to can then again 10 in the branch lines 3 to 6 of the intake pipe 2 of the internal combustion engine 1 are interrupted.

Another possibility consists in not keeping the temperatures of the individual cylinders in the internal lines 30 to 33 of the exhaust system 20 of the internal combustion engine measure, but to determine by temperature sensors in the cylinder heads of the internal combustion engine. This will result in the cylinder head cooling of the internal combustion engine temperature sensor for lower temperatures for use. this means a simplification and cheaper construction the protective device.

Combustion that does not take place or incomplete combustion in a cylinder of the internal combustion engine 1 can also be determined from the combustion pressure in the cylinders of the internal combustion engine. To this Purpose is one in each cylinder of the internal combustion engine Provide pressure sensor.

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An ignition that is not working properly can also be detected by measuring the ion current or ignition current.

A simplification of the device described can also be achieved if not the temperatures of the monitors the individual cylinders and then actuates the solenoid valves assigned to the individual cylinders but when cylinder groups and the solenoid valves assigned to these cylinder groups are monitored and operated will.

Another way of preventing impermissible temperature increases in the reactors is to use individual To provide intake pipes leading to the respective cylinders of the internal combustion engine control flaps, which are dependent on the reactor temperature can be pivoted, the flap being closed that is in the intake pipe of that cylinder which triggers the temperature increase. Dr? .Bei must be through suitable Facilities, for example by a check valve, ensure that air is drawn in from the environment v.crden, so that too high a negative pressure in the cylinder dri 'internal combustion engine and thus too great a loss of power in the internal combustion engine is avoided.

Expedient ^? The flaps are usually designed as pneumatically operated valves which are controlled by the negative pressure in the intake pipe of the internal combustion engine, with a solenoid valve for the control air being provided for servo control.

In internal combustion engines with two carburettors for two cylinders each, the fuel supply is either activated with the help of solenoid valves interrupted to at least one float chamber or the throttle valve of at least one carburetor to prevent further Mixture formation completely closed.

Also, in the shift operation of internal combustion engines, it may happen that the reactors be heated unacceptably high, since the reactors with incompletely burned fuel BW ORlQlNM. ' 509808/0214

of the fuel or the fuel-air mixture To interrupt at least partially exceeding the permissible catalyst temperature. It is in this case, however expedient to avoid particularly high exhaust emission peaks the fuel supply only after a delay of approx. 20 see. to turn off. During the time until the delayed shutdown of the fuel supply, the Air sucked into the intake manifold achieves better combustion.

The timing of the shutdown of the fuel during coasting operation can expediently with the help of a bimetal relay take place. To avoid damage to the reactors, the fuel supply is only switched on again when if the engine speed falls below a certain speed in overrun mode.

To improve operational safety and to protect against unnecessary actuation of the protective device, at least one further temperature sensor can be provided _; which is used in a lower temperature range to prevent the start-up of the protective device and thus to prevent an undesired interruption of the fuel supply.

Such a locking of the protective device is necessary because the combustion processes in the internal combustion engine in run according to a certain rhythm determined by the firing sequence and thus the cylinders of the internal combustion engine do not run at the same time, but emit exhaust gas one after the other. But since the temperature sensors 26 to 29, the exhaust gas temperature in the branch pipes 30 to 33 compare with each other, the protective device may be triggered undesirably if z. B. with a cold start of the cylinder 1 of the internal combustion engine is immediately ready for operation, but the other cylinders not with the first crankshaft revolutions but only for a short time start working later. In this case it would be for this

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Cylinder the protective device is effective and the fuel supply to these cylinders is interrupted. This can lead to that the internal combustion engine does not start at all or only works with some of the cylinders.

By the temperature sensor 40, for example in the exhaust system 20 can be arranged, it is ensured that a certain minimum temperature must be reached before the Protective device can be effective. For this purpose, the temperature sensor 40 is connected via a threshold switch 41 connected to the control unit 25, which is blocked by the output signal of the threshold switch 41 until a certain minimum temperature is exceeded. The temperature sensor 40 can be at any point in or be arranged in the vicinity of the internal combustion engine or in the exhaust system of the internal combustion engine. But it can also several temperature sensors can be arranged at the points mentioned, or one or more of the existing ones can also be used Temperature sensors 23, 24 or 26 to 29 or those temperature sensors that are located on the engine block, in the engine oil, in the cooling water Cooling air system of the internal combustion engine are arranged, can be used.

Another possibility for avoiding an undesired interruption of the fuel supply when starting the internal combustion engine is to provide a delay switching device, for example mechanically, electrically or can be triggered pneumatically. With the actuation of a starter switch 42, a starting motor 43 is in rotation offset. At the same time, a delay switch device 44 is triggered by actuating the starter switch, which for a arbitrarily determinable period of time blocked the protective device for interrupting the fuel supply. Appropriately the duration is chosen so that a safe start-up

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the internal combustion engine is guaranteed, but that a critical temperature of the catalytic reactor is not reached can be. The protective device can only take effect after the set time has elapsed and if one of the or several cylinders, the fuel supply to these cylinders interrupt.

In the exemplary embodiments described so far, the fuel supply is the one that triggers the temperature increase Cylinder interrupted. This protects the exhaust gas decontamination system, i.e. the downstream reactors, from overheating. However, the devices described have the disadvantage that the fuel supply is shut off at least as long as then Motor vehicle runs, i.e. until the next stop of the motor vehicle and the associated cooling of the internal combustion engine.

However, many misfires in motor vehicles only occur briefly, for example as a result of short-circuit connections or coking on the spark plug, etc. These misfires can, however, stop after a relatively short period of time, because For example, clean the corresponding contacts yourself, or remove contamination through flow effects. The internal combustion engine is then properly ignited again, for example. But since the fuel supply to the cylinder, whose ignition failed briefly, is now blocked, the restarting ignition is not noticed until the internal combustion engine is brought to a stop and thus cools down.

In a further embodiment of the invention, it is therefore ensured that that the shut-off of the fuel supply to the cylinder of the internal combustion engine triggering the temperature increase is only possible within a certain time interval takes place, but that afterwards the fuel supply is fx'-input again and that after it has taken place Release of the fuel supply is checked again whether the

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Gas temperature in the exhaust pipe behind the relevant cylinder outlet continues to drop or rise. Increases the If the temperature does not rise, then misfiring and the fuel supply to which the temperature increase still occur cylinder triggering the catalytic converter continues to be interrupted.

When measuring the temperature in the catalytic converter, the reverse applies Conditions: the fuel cut-off is completely lifted when the catalytic converter temperature is at the review falls off.

By the measure described it is achieved that at Ignition failure that stops after a short time, the fuel supply does not run until the next time it is switched off and the associated cooling of the internal combustion engine remains switched off, but after the corresponding Time interval is switched on again and that in the event that the ignition then works properly again, the fuel supply is maintained. Only if the Release of the fuel supply again to an impermissible Increase in the temperature of the exhaust gas detoxification device or an increase in a signal characteristic thereof leads, the fuel supply is interrupted again. In the The drawing shows that in the connecting line from the control unit to the switching contacts 15 to 19 monostable Trigger stages 50, 51, 52 and 53 are connected. If the control device 25 gives the command to one of the switching contacts 16,17,18 or 19 separate, this is done via one of the monostable flip-flops 50,51,52 or 53. The control unit 25 viird corresponding monostable multivibrator is triggered and blocks the fuel supply for the duration of its unstable switching state, by the corresponding switching contact 16,17,18 or respectively for the duration of the unstable switching state. 19 is opened. Then it closes Switching contact with the tilting back of the monostable multivibrator in its' stable switching state, so that for a certain period of time fuel is supplied again. The ignition works the internal combustion engine is normal again, then no temperature increase in the reactors 21 and 22 or at the measuring points in the ^ or branch connection of the exhaust manifold or in the event of a drop in temperature enter the exhaust pipe behind the cylinder outlet. Through this

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the control unit 25 does not initiate a new interrupt command the fuel supply off. If, on the other hand, the ignition device is still disturbed, the temperature becomes

rise at the measuring points in the reactors 21 and 22 fall in the exhaust pipe downstream of the cylinder outlet, respectively, and thereby the control unit 25 outputs again a switching pulse which brings in its unstable switching position one of the monostable multivibrator 50.51 ₅ 52 and 53, respectively, so that via one of the switching contacts 16, 17, 18 or 19, the fuel supply to the cylinder which triggers the temperature increase is interrupted.

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Claims (1)

Expectations 1./Protective device for an arrangement to reduce harmful components of the exhaust emissions from internal combustion engines, whose exhaust system has at least one thermal and / or catalytic reactor for aftertreatment of the exhaust gas of the internal combustion engine, characterized in that that the combustion process in individual cylinders or cylinder groups characterizing sensors (26-29) is provided be that in the case of an impermissible temperature increase in the exhaust system (20) or at least one of the catalytic converters (21,22) leading processes in the internal combustion engine (1) the shut-off of the supplied fuel or the fuel-air mixture to individual the temperature increase trigger the causing cylinders or cylinder groups. 2. Protection device according to claim 1, characterized in that in the vicinity of each cylinder or each cylinder group the internal combustion engine (1) a temperature sensor (26-29) is provided, which is one of the temperature of the exhaust gas Cylinder or the cylinder group supplies a corresponding electrical signal which, when a threshold value is exceeded the supply of the fuel or the fuel-air mixture 509808 / 02U to which the exceeding of the threshold value triggers the cylinder. 3- Protection device according to claim 1 or 2, characterized in that a temperature sensor (23,2 ^J I) is arranged in at least one of the catalytic converters (21,22) to be protected against overheating, which provides the threshold value at which the supply is switched off of the fuel or the fuel-air mixture to the cylinder or cylinder group causing the temperature increase. H. Protective device according to one of Claims 1 to 3, characterized in that the temperature sensor or sensors (26-29) for detecting the exhaust gas temperature from the individual cylinders or cylinder groups are arranged in the exhaust manifold of the exhaust system of the internal combustion engine. 5. Protection device according to one of claims 1 to 3 » characterized in that the temperature sensor or sensors (26-29) for detecting the exhaust gas temperature from the individual cylinders or cylinder groups are arranged in the cylinder heads of the internal combustion engine. 6. Protection device according to one of claims 1 to 5 _}, characterized in that an electrical control device (25) for determining the difference between the catalyst and 509808 / 02U -15- the exhaust gas temperature is provided, which is a switching device (16-19) for switching off the supply of fuel or the fuel-air mixture to at least one Triggers a cylinder or a group of cylinders. 7. Protection device according to claim 1, characterized in that for generating a combustion process in the Internal combustion engine characterizing electrical signal at least one pressure sensor is provided, wherein when exceeded a predetermined threshold value, the supply of the fuel or the fuel-air mixture to a Cylinder or a cylinder group is interrupted. 8. Protection device according to one of claims 1 to 7j characterized in that with the shutdown of the supply of fuel or the fuel-air mixture to a cylinder or a group of cylinders, a warning signal is triggered for the user of the internal combustion engine. 9. Protection device according to one of claims 1 to 8, characterized in that the fuel supply is switched off at least one injection valve of the internal combustion engine is interrupted. 10. Protection device according to one of claims 1 to 8, characterized 509808 / 02U " ^lb ~ characterizedj that the supply of the fuel-air mixture by closing at least one pivotable flap in one leading to a cylinder of the internal combustion engine Suction pipe is interrupted. 11. Protection device according to claim 10, characterized in that that the pivotable flaps are designed as pneumatically operated valves that are controlled by the negative pressure in the intake pipe the internal combustion engine can be controlled, with a servo solenoid valve is provided for the control air. 12. Protection device according to one of claims 1 to 8, characterized in that in internal combustion engines with two carburetors the fuel supply to one of the carburetors, in particular is interrupted via the ed η solenoid valve. IJ, protective device according to one of claims 1 to 8, characterized characterized in that in internal combustion engines with two carburetors, the formation of the fuel-air mixture through Closing the starter flap at least one carburetor is prevented. I ^. Protective device according to one of Claims 1 to 13, characterized in that during pushing operation -17- '509808 / 02U 2 3 Λ Ο 5 Λ 1 the internal combustion engine shut off the fuel or of the fuel-air mixture takes place with a delay after the permissible catalyst temperature is exceeded, the temperature increase during the delay time Cylinder causing additional air is supplied. 15. Protection device according to claim 14, characterized in that the delay by a time relay, in particular can be triggered by a bimetal relay. 16. Protection device according to one of claims 1 to 15> characterized in that at least one temperature sensor is provided which is dependent on the temperature the protective device in the exhaust system of the internal combustion engine blocked. 17. Protection device according to claim l6, characterized in that the temperature sensor in the exhaust system of the internal combustion engine is arranged. 18. Protection device according to claim l6, characterized in that the temperature sensor on or near the Internal combustion engine is arranged. 19. Protection device according to one of claims 1 to l8, characterized in that as a temperature sensor at least 509808 / 02U -18- 23Λ05ΛΊ -18- one of the temperature sensors (23, 2k or 26 to 29) serving to monitor the temperature in the exhaust system of the internal combustion engine is used. 20. Protection device according to one of claims 1 to 18, characterized in that at least one am as a temperature sensor In the engine block, in the engine oil, in the cooling water and / or in the cooling air system the internal combustion engine arranged temperature sensor is used. 21. Protection device according to one of claims 16 to 20, characterized in that the temperature sensor with a Threshold switch is connected, which is below a one Minimum temperature corresponding switching threshold an electrical blocking the response of the protective device Signal delivers. 22. Protection device according to one of claims 1 to 15, characterized in that at least one with the starting process the internal combustion engine triggerable timer is provided, which the protective device for an arbitrarily determinable Blocked time after startup. 509808 / 02U 23A05A1 23 · Protective device according to one of Claims 1 "to 22, characterized in that the interruption of the fuel supply 'in a certain time interval after exceeding the corresponding threshold value is maintained and that afterwards for a short time Time interval the fuel supply can be switched on again and that when the gas temperature behind the cylinder outlet does not rise, or the catalyst temperature does not drop, the fuel supply can be shut off again by the protective device. 24. Protection device according to claim 23, characterized in that that at least one S timer (50-53) is provided is that at least one of the switching devices (16-19) is actuated for a certain period of time in such a way that that the fuel supply to which the temperature increase in the catalytic converter triggering cylinder of the internal combustion engine is interrupted that after the period of time has elapsed the timer actuates the switching device (16-19) in such a way that the fuel is supplied again and that when the guest door is behind the cylinder outlet does not rise or the catalyst temperature does not fall, the timer over at least one of the Switch directions (16-19) to restart the fuel supply interrupts. 25. Protection device according to claim 11, characterized in that when the flap is closed, in particular air is sucked in via an idle valve » 509808/0214 BATH ORIGINAL Read e ί te ORIGINAL INSPECTED