DE4104011C1 - IC engine control system - uses EGR and low heat conduction inlet manifold with matching of inlet air to injected fuel volume - Google Patents

Abstract

The IC engine load regulator makes use of a device to control the temp of the intake air. A system to reduce heat transfer between air flow and intake line wall should be fitted on the intake line (2) downstream of the device. Pref. the line is made of low heat-conducting material downstream of the device and the line wall here is coated in a heat insulating layer. The device pref. consists of an exhaust return line (4) which issues into the intake line and whose section is controlled by a first valve (5). USE/ADVANTAGE - IC engine intake air flow is adapted to injected fuel volume and thus engine load by temp variation to retain stoichiometric conditions.

Description

The invention relates to a device for control according to the load of a mixture-compressing internal combustion engine Preamble of claim 1.

From DE-Z: "Motortechnische Zeitschrift MTZ 27/1966, Issue 7, pp. 283-290 is known to reduce the gas exchange losses the Brenn engine load not pre-specified in the intake line see throttle valve, but via a corresponding change change in the density of the fresh air drawn in due to influence to control the temperature of this intake air. Disadvantage egg Such control of the engine load exists in the fact that in non-stationary operation, i.e. immediately after a Change in the load specification, which is abge from the internal combustion engine given power is due to the given heat capacity of the Suction line only hesitantly to this new load signal fits. The internal combustion engine consequently has a bad one Response behavior after a change in the load specification.

The invention has for its object a load control contraption to create with which an optimal response behavior of the Internal combustion engine after predetermined changes in the load be, i.e. in non-stationary operation, can be reached.  

This task is characterized by the characteristics of the Claim 1 solved.

A change in the load specification and thus a change in the tem temperature of the intake air causes a change in the density of the sucked fresh air flow and thus a change in the fresh air mass actually introduced into the combustion chamber. To a stoichiometric or approximately stoichiometric mixture (λ = 1) to be able to comply with this changed fresh air mass finally adjusted the amount of fuel injected. These adjusted fuel injection quantity naturally also causes a corresponding change in the engine load. Is z. B. a reduction in the internal combustion engine to be delivered required, the tem temperature of the intake air increases, due to the resultant density reduction a lower fuel injection quantity to get (mixture must remain stoichiometric), namely ge nau the fuel injection quantity that the required combustion engine power corresponds. Since immediately after the Reduction of the load specification the temperature of the intake pipe wall is even lower than the temperature of the now he warmed intake air flow, part of the heat of the An flows suction air flow into the wall of the intake air wall. This one in the wall flowing heat flow is immediately after the Än change in the load specification is greatest and is constantly decreasing until finally the temperature of the wall equals the tempera of the intake air flow.

By means of the reduction means provided according to the invention the heat transfer between the intake air flow and the wall the suction line is now immediately after the load heat from the intake air flow into the wall current (heat quantity / time unit) reduced to a minimum. The according to the intake air flow also experiences no significant Lowering the temperature or increasing the density, so that immediately after  the reduction of the load specification ent one of this load specification injected reduced amount of fuel is injected. In order to becomes a quick response of the internal combustion engine achieved after changing the load specification. So it gets through the invention prevents that after reducing the load default a relatively large heat flow into the wall of the An suction line flows off and thus a strong lowering of the An suction air temperature is caused.

In an analogous manner, the invention is used for an increase the load specification prevents a larger heat flow from the Intake pipe wall in the cooler intake in this case air flow flows, so that here also a significant change the intake air temperature due to a relatively large amount of heat current is prevented and thus also for a short time a correspondingly increased force after increasing the load specification amount of substance is injected and therefore the desired Performance is available.

The device for influencing the intake air temperature can, as proposed in claim 5, also be an exhaust gas recirculation device, with which an additional reduction of the NO _x emission can be achieved. In this case, the response of the internal combustion engine after a load change is further improved if the exhaust gas recirculation line also consists of a material with low thermal conductivity or if the inner wall of the exhaust gas recirculation line is seen with a heat-insulating layer. It can therefore flow here immediately after a change in the exhaust gas recirculation rate to change the engine load only a minimal heat flow from the exhaust gas into the wall of the exhaust gas recirculation line or vice versa.

Further advantageous embodiments of the invention are the other subclaims.  

In the drawing, the invention is based on an embodiment example shown.

In detail shows

Fig. 1 shows an advantageous embodiment of the device according to the invention in a position Prinzipdar,

Fig. 2 in two diagrams the relationship between load specification α and exhaust gas recirculation rate or between load specification α and the proportion of the flowing in the exhaust gas heat exchanger designated in FIGS . 1 and 3 with ß intake air flow and

Fig. 3 another advantageous embodiment of the device according to the invention in a Prinzipdar position.

In Fig. 1 1 shows a vehicle driving mixture-compressing internal combustion engine with an air intake 2 and an exhaust pipe 3. An exhaust gas recirculation line 4 is branched off from the exhaust gas line 3 and opens into the intake line 2 . In the exhaust gas recirculation line 4 , a first valve device 5 , formed as a throttle valve, is arranged shortly before its confluence with the intake line 2 , via which the proportion of exhaust gas which is to be returned to the combustion chamber 6 of the internal combustion engine 1 can be changed as required. The fuel is injected via the fuel injector 7 . Upstream of the point 8, at which the exhaust gas recirculation line 4 opens into the intake pipe 2, is of the intake passage 2, a branch pipe branched off 9, which is passed through an exhaust heat exchanger 10 and downstream of this branch-off point, but still upstream of the point 8 of the mouth of the exhaust gas recirculation line 4, flows into the suction line 2 again. The exhaust gas heat exchanger 10 is connected to the exhaust line 3 . The exhaust pipe 3 connected to the exhaust gas heat exchanger 10 and the exhaust pipe 3 , from which the exhaust gas recirculation pipe 4 is branched off, are of course one and the same pipe. On a continuous presen- tation of this exhaust pipe 3 was omitted in the drawing for clarity. At the point of branching of the sub-line 9 is a flap-shaped mixing valve 11 is arranged, which is stepless between a position leading the intake air flow completely through the heat exchanger 10 (solid representation of the flap 11 ) and a part 9 completely closing position (dashed representation of the flap 11 ) is adjustable. The flap 5 , the flap 11 and the fuel injection nozzle 7 are controlled via the control lines 12 , 13 and 14 by an electronic control unit 15 as a function of the engine speed n and the load specification α. The internal combustion engine speed n is tapped from the crankshaft of the internal combustion engine 1 by means of a sensor 16 and transmitted to the electronic control unit 15 as a corresponding electrical signal via the measured value line 17 . The load predetermined signal α is picked up by the sensor 18 from the accelerator pedal 19 of the vehicle (deflection α of the accelerator pedal) and transmitted via the measured value line 20 as a corresponding electrical signal to the electronic control unit 15 . The exhaust gas recirculation line 4 and the intake line 2 downstream of the point at which the sub-line 9 opens into the intake line 2 are made of a material with extremely low thermal conductivity.

During operation of the internal combustion engine 1 , the control of the internal combustion engine load now takes place exclusively via the flaps 5 and 11 . This is done in the manner shown in diagrams 21 and 22 of FIG. 2. The diagram 21 shows the relationship between the exhaust gas recirculation rate (ordinate 23 ), that is to say between the position of the flap 5 and the load specification (abscissa 24 ) by the driver, that is to say the deflection α of the accelerator pedal 19 . The flap 5 in the exhaust gas recirculation line 4 is infinitely adjustable between a position " 0 " that completely closes the exhaust gas recirculation line 4 and a position "max" that completely releases this line 4 . The dashed line A corresponds to the idle position of the accelerator pedal 19 and the dashed line C corresponds to the position at full load. Diagram 21 thus shows that the flap 5, starting from its maximum open position "max" in idle A, is continuously guided towards the closed position with increasing load specification, up to full load, where it has finally reached its closed position 0 . The higher the exhaust gas recirculation rate, the greater is the preheating of the intake air (heat control) and the reduction of the oxygen content in the intake air (quality control). An additional increase in the intake air temperature in the low load range up to the Teilastbe rich (dashed line B) is achieved by the separate preheating of the intake air in the heat exchanger 10 ( Fig. 1). This is shown in diagram 22 in FIG. 2. The ordinate 25 of this diagram 22 shows the proportion of the intake air flow which is conducted via the partial line 9 as a function of the load specification α. This proportion is determined by the position of the flap 11 . If the flap 11 is in the solid position, that is, in the position at which the suction line 2 is completely closed, the entire intake air flow (100%) is conducted via the heat exchanger 10 . This is the case in idle A. With increasing load specification α, however, the flap 11 is rotated in the direction of the broken line position, so that the proportion of fresh air preheated in the heat exchanger 10 becomes ever smaller. When the dashed line B corresponding load specification α is reached, the mixing flap 11 has finally arrived in its position closing the partial line 9 , so that the entire intake air stream flows directly towards the combustion chamber 6 , that is to say from the load point B there is no more fresh air drawn in via the heat exchanger 10 , so that from this load point B the control or regulation of the engine load takes place exclusively via the exhaust gas recirculation (see diagram 21 ).

Now takes place during the operation of the internal combustion engine 1 starting from a load point P ₁ z. B. a positive Lastände tion to the value P ₂ (by appropriate variation of the load designation signal α), the Fig. 2 corresponding to the flap 5 in the exhaust gas recirculation line 4, by the value Δ _EGR towards the closed position and the mixing flap 11 because the Load point P ₂ lies above the limit value B by the value Δ _WT in the position closing the partial line 9 (dashed position in FIG. 1). Both the reduction in the proportion of the intake air flow which is passed through the heat exchanger 10 to 0% and the reduction in the exhaust gas recirculation rate by Δ _EGR lead to a reduction in the intake air temperature. The consequence of this is an increase in the air density and thus an increase in the air mass introduced into the combustion chamber 1 per intake stroke. The increase in the air mass introduced into the combustion chamber 1 through the exhaust gas recirculation is achieved not only as a result of a lowering of the intake air temperature, but also because an increase in the fresh air, ie the oxygen content in the intake air is generally associated with a decreasing exhaust gas recirculation rate. Taking into account the current engine speed n, the electronic control unit 15 now determines a fuel injection quantity that corresponds to this load point P ₂ and thus corresponds to an air mass assigned to the load point P ₂ .

The fuel injection quantity is always determined so that at least almost a stoichiometric mixture (λ = 1) lies. As a result of the now increased air mass, so too Fuel injection quantity and therefore also the power output elevated.

Since the increase in the load specification α has caused a reduction in the temperature of the intake air flow, the temperature of the intake line wall immediately after the change in the load specification is still at a higher temperature level, namely at the level corresponding to the load point P ₁ , there is between Intake air flow and suction line wall a temperature gradient, so that a heat flow from the suction line wall flows into the intake air flow (arrow 26 , Fig. 1). However, since according to the invention the intake line wall consists of a material with extremely low thermal conductivity, this heat flow and thus the increase in the temperature of the intake air flow up to the entrance into combustion chamber 1 is only minimal. The intake air flow thus occurs immediately after the change in the load specification from P ₁ to P ₂ with the temperature corresponding to the load point P ₂ in the combustion chamber 1 . This means that, of course, the fuel injection quantity can be set immediately after the change in the load specification to the value corresponding to the load point P ₂ without a temporary over-greasing of the mixture as a result of a slowly falling intake air temperature due to a greater heat transfer. The invention therefore has the effect that the internal combustion engine 1 delivers an increased output immediately after the increase in the load specification.

The same applies of course to the reverse case, that the load specification is reduced, for. B. from P ₂ to P _1. This change then leads to an increase in the intake air temperature (see diagrams 21 and 22 of FIG. 2). However, since the intake pipe wall sits immediately after the change in the load specification, a temperature corresponding to the load point P ₂ is lower, a heat flow now flows from the intake air flow into the intake pipe wall due to the temperature gradient (arrow 27 ). Since this heat flow is minimal due to the low heat conductivity of the intake pipe wall, the temperature change in the intake air flow is negligible up to the entry into the combustion chamber 1 , as in the previous case. Immediately after the change in the load specification, the fuel injection quantity can also be reduced to the value corresponding to the load point P ₂ , with the result that the internal combustion engine immediately delivers only an output corresponding to this load point P ₂ .

A further improvement in the response of the internal combustion engine 1 after changes in the load specification is achieved in that, on the one hand, the exhaust gas recirculation line 4 is made of a material with only low thermal conductivity and, on the other hand, the flap 5 specifying the exhaust gas recirculation rate un directly at the junction 8 of the exhaust gas recirculation line 4 is arranged in the suction line 2 . The low thermal conductivity of the material of the exhaust gas recirculation line 4 also leads to the fact that with large differences between the temperature of the recirculated exhaust gas flow and the wall of the exhaust gas recirculation line 4 after changes in the load specification, only a minimal heat flow from the exhaust gas flow into the wall of the exhaust gas recirculation line or vice versa can flow and thus the temperature of the recirculated exhaust gas flow does not change significantly when flowing through line 4 .

Since the flap 5 in the exhaust gas recirculation line 4 is closed at full load, so no exhaust gas is added to the intake air, the problem is that as a result that the exhaust gas recirculation line 4 is no longer flowed through by hot exhaust gases, the temperature of the exhaust gas recirculation line 4 into the sem load point drops relatively sharply, so that after a reduction in the load specification with the associated new exhaust gas recirculation, the temperature gradient between the exhaust gas recirculation flow and the wall of the exhaust gas recirculation line 4 becomes so great that, despite the lowest thermal conductivity of the material, the line 4 is still one, if only slightly gig is the response of the internal combustion engine 1 negative effect of reducing the temperature of the recirculated exhaust gas flow when flowing through the line 4 is ge. The arrangement of the flap 5 immediately Be the confluence of the exhaust gas recirculation line 4 rich in the suction line 2 is achieved, however, that by Pulsationsvorgänge also fully closed flap 5 exhaust gases from the Ab gas pipe 3 in the exhaust gas recirculation line 4 to the valve 5 reach , so that the line 4 is kept even in operating areas with closed flap 5 at a temperature level almost equivalent to the momentary exhaust gas temperature. After opening the flap 5 after a reduction in the load specification, a temperature gradient as high as that described above is therefore not to be expected.

In order to be able to keep the temperature of the exhaust gas recirculation line 4 during operation without exhaust gas recirculation at the level of the exhaust gases passing through the exhaust line 3 , it is also possible to branch off a bypass line 28 in the area of the flap 5 , upstream of this, the cross section of which via further flap 29 can also be controlled from the electronic control unit 15 via the control line 30 . This additional Liche advantageous embodiment of the invention is shown in dashed lines in FIG. 1 (bypass line 28 , control line 30 and flap 29 ). The bypass line 28 opens into the exhaust line 3 again, namely upstream of the heat exchanger 10 . The control of the two flaps 5 and 29 is such that when no exhaust gas recirculation is to take place (at full load), the flap 5 is closed and the flap 29 is opened. Thus, the major part of the exhaust gas recirculation line 4 is flowed through by the exhaust gas even in this operating state and consequently kept at a high temperature level. If the load specification α is now reduced, ie the flap 5 in the exhaust gas recirculation line 4 is opened to the extent corresponding to the new load point, the flap 29 in the bypass line 28 is simultaneously completely closed.

In order to be able to control the engine load down to never the first load ranges (idling range) by increasing the intake air temperature, it is advantageous to heat-isolate the exhaust line 3 and possibly also the bypass line 28 up to the heat exchanger 10 , so that the exhaust gas with a the highest possible temperature can enter the heat exchanger 10 .

Fig. 3 shows a further advantageous embodiment of the invention. In FIG. 3, components which are identical to those of FIG. 1 are also designated with the same reference numbers. This exemplary embodiment differs from that according to FIG. 1 only in the arrangement of the exhaust gas recirculation line 31 . This runs here within the Zy cylinder head 32 of the internal combustion engine 1 and is extremely short. It branches off from the combustion chamber 6 and opens into the intake line 2 shortly before the inlet valve 33 . The passage cross section of the exhaust gas recirculation line 31 is changed via a valve 34, which can also be controlled by the electronic control unit 15 . In nenwand the exhaust gas recirculation line 31 is provided with a heat-insulating coating 35 , which prevents that after a change in the load due to different temperatures between the exhaust gas recirculation stream and exhaust gas recirculation line 31 or in this case cylinder head 32 , too large a heat flow from the recycle stream into the cylinder head 32 or can flow in reverse. Of course, it is also conceivable in a further embodiment of the invention, the ü rigen lines - and this also applies to the exemplary embodiment according to FIG. 1 - not from a material with low thermal conductivity, but this on your gas stream facing inside with a to provide heat-insulating layer. This layer must in any case be provided on the inside in order to prevent a larger heat flow from flowing into the wall or from this into the respective gas flow.

The control and regulation of the internal combustion engine load also takes place in this exemplary embodiment according to the two diagrams 21 and 22 shown in FIG. 2.

In a further embodiment of the invention, it is also conceivable to control or regulate the engine load in the lower load range in a conventional manner via a throttle valve and only from the partial load range via an exhaust gas recirculation device. In this case, an exhaust gas heat exchanger and a controlled branching of the intake line would no longer be necessary. Of course, it is also possible to provide a device, as shown in FIGS. 1 and 3, also with a throttle valve in the suction line and to control or regulate the engine load in the idling range via this throttle valve.

Claims (11)

1. Device for controlling the load of a mixture-compressing internal combustion engine by means of at least egg ner device for influencing the temperature of the air mass flow sucked in via a suction line, characterized in that means for reducing the heat transfer between the air mass flow and the suction line wall are provided on the suction line ( 2 ) downstream of the device . 2. Apparatus according to claim 1, characterized in that the suction line ( 2 ) in the area downstream of the Einrich device made of a material with low thermal conductivity be. 3. Device according to one of claims 1 or 2, characterized in that the inner wall of the suction line ( 2 ) is provided in the region downstream of the device with a heat-insulating layer. 4. Device according to one of claims 1 to 3, characterized in that a device for influencing the temperature of the air mass flow sucked in via a suction line ( 2 ) is an exhaust gas recirculation line ( 4 , 31 ) opening into the suction line ( 2 ), the cross section of which is by means of a first valve device ( 5 , 34 ) is controllable. 5. Device according to one of claims 1 to 4, characterized in that a partial line ( 9 ) is branched off from the intake line ( 2 ), which is guided through a heat exchanger ( 10 ) provided in the exhaust line ( 3 ), that the partial line ( 9 ) opens out again into the intake line ( 2 ) and that a mixing valve device ( 11 ) is provided, via which the fresh air flow passing through the heat exchanger ( 10 ) can be controlled. 6. Device according to one of claims 4 or 5, characterized in that the exhaust gas recirculation line ( 31 ) is branched off directly from the combustion chamber ( 6 ) of the internal combustion engine ( 1 ) and opens into the intake line ( 2 ) in the cylinder head ( 32 ). 7. Device according to one of claims 4 or 5, characterized in that the exhaust gas recirculation line ( 4 ) from an exhaust pipe ( 3 ) of the internal combustion engine ( 1 ) is branched off. 8. Device according to one of claims 4 to 7, characterized in that the inner wall of the exhaust gas recirculation line ( 4 ) is provided with a heat-insulating layer ( 35 ). 9. Device according to one of claims 4 to 7, characterized in that the exhaust gas recirculation line ( 4 ) consists of a material with low thermal conductivity. 10. Device according to one of claims 4, 5, 8 or 9, characterized in that the cross section of the exhaust gas recirculation line ( 4 ) controlling valve device ( 5 ) is arranged in the region of its confluence with the suction line ( 2 ). 11. Device according to one of claims 4, 5 or 7 to 10, characterized in that upstream of the valve device ( 5 ) from the exhaust gas recirculation line ( 4 ) a bypass line ( 28 ) is branched, which opens again in the exhaust line ( 3 ) and the latter Cross section can be controlled by means of a further valve device ( 29 ), this further valve device ( 29 ) being held in its maximum open position when the first valve device ( 5 ) is closed and held in the closed position when the first valve device ( 5 ) is in an egg ner open position.