DE3303350A1 - Control device for the charging pressure of an internal combustion engine with turbo charger - Google Patents

Abstract

A control device for the charging pressure of an internal combustion engine with turbo charger is proposed, it being possible to lower the charging pressure as a function of the signals of at least one knocking sensor (28, 29). As a function of the parameters of load (GP) and speed of rotation (n), the charging pressure (pL) is set via a control device (23, 21). This adjustment takes place electronically, in particular via a charging pressure characteristic diagram which is stored in a memory (40, 41). In order to lower the charging pressure when knocking signals occur, the output signal of a knocking control stage (52) is preferably used for the ignition of the internal combustion engine in order to achieve a simple design of the electronic device. By means of the exact electronic adjustment of the charging pressure, in addition to optimising the operational data of the internal combustion engine (consumption, power, exhaust gas), knocking is largely avoided right from the outset. <IMAGE>

Description

-18352

1 .2.1983 Ve / Hm

ROBERT BOSCH GMBH, 7OOO STUTTGART 1

Control device for the boost pressure of an internal combustion engine with a turbocharger

State of the art

The invention "relates to a control device for the Boost pressure of an internal combustion engine with a turbocharger the genre of the main claim. Such a device is known, for example, from DE-PS 30 28 9HU " The boost pressure is also reduced depending on knock signals, but there is no electronic one Pre-control of the boost pressure, so that on the one hand no optimal boost pressure can be set and on the other hand the boost pressure in the pilot control cannot be based on the knock limit. For this reason with this solution, the knock limit is often reached. are exceeded, so that a more complex knock control necessary depending on the knock intensity will. Optimizing the boost pressure is hardly possible.

Advantages of the invention

The 'control device according to the invention with the characterizing Features of the main claim has the advantage that the boost pressure over a boost pressure map very precisely for maximum performance, low consumption, favorable exhaust gas values, etc. depending on the respective Operating state (load, speed) can be optimized. This turns into a knocking operation - if at all still occur very rarely and can then by lowering the boost pressure and / or by adjusting the ignition timing can be eliminated very quickly.

The control device according to the invention with the characterizing features of independent claim ^1. J has besides the advantages of the exact setting of the boost pressure by electronic means the further advantage that moved through a single knock control level of both the ignition timing at a pounding operation after late, as well as the boost pressure can be lowered . This not only means relatively little effort for the control of both variables, but also has the further advantage that knocking is eliminated in most cases due to the very fast ignition timing adjustment, so that the lowering of the boost pressure is only in a few extreme cases remains limited, in which the ignition timing alone is not sufficient. In most cases, the influence on the torque of the motor remains small.

The measures listed in the subclaims are advantageous developments and improvements of the Measures listed in the independent claims are possible.

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drawing

An "embodiment of the invention is in the drawing and explained in more detail in the following description. Figure 1 shows a basic circuit diagram of an internal combustion engine with exhaust gas turbocharger and electronic control of the boost pressure and FIG. 2 is a block diagram the electronic control device.

Description of the embodiment

In the basic circuit diagram shown in Figure 1 is an internal combustion engine 10 is shown, which the necessary air for combustion through an air filter 11, a. ' Air flow meter 12, a compressor 13 of an exhaust gas turbocharger 1U, a charge air cooler 15 and a Air distributor 16 is supplied. The exhaust gas becomes an exhaust gas turbine 18 of the exhaust gas turbocharger via an exhaust manifold 17 » 1U and discharged via exhaust pipes 19. The exhaust gas turbine 18 is bridged by a bypass 20, into which a boost pressure control valve 21 is connected. The boost pressure control valve 21 can be against the pressure of a Open spring 2 with the aid of the boost pressure, which is supplied via a line 22 from the outlet of the compressor 13 is. For this purpose, a solenoid valve 23 is connected in line 22, which by controlling the via line 22 The boost pressure control valve 10 adjusts the boost pressure supplied. In principle, of course, a single one could also be used Solenoid valve can be switched into the bypass 20.

An electronic control device 2k , which is preferably designed as a microcomputer, controls both the solenoid valve 23 by means of a signal sequence with a specific control duty cycle ST, as does an ignition control device 25 to which a signal ACtz is supplied

18 3 b 2

which already includes a retarded ignition point when the internal combustion engine is knocking. the Ignition times can be set in ignition control device 25 in a known manner as a function of further parameters P and, if necessary can be set as a function of a stored map. Such a parameter can for example the signal of the air flow meter 12 or be a temperature signal.

The supply lines for the spark plugs of the internal combustion engine are symbolic by arrows to simplify the illustration indicated.

The electronic control device 2U are reference mark signals BM and speed signals η supplied from the crankshaft 26 of the internal combustion engine via a Encoder assembly 27 are derived. In principle, you can other crankshaft-synchronous signals can also be used, such as those provided by an ignition distributor. Knock signals K from two knock sensors 28, 29 are also fed to the electronic control device. Instead of these two knock sensors 28, 29 can in principle also a single knock sensor or a larger number of knock sensors occur, whereby a knock sensor can be assigned to each cylinder. For evaluating the knock signals If there are several knock sensors, then the signal Z is one Cylinder recognition is necessary, which is derived from the reference mark encoder and an assignment of the knock signals allowed for the respective cylinder.

Finally, the electronic control _{device receives the signals p L from} a boost pressure sensor 30 in the air distributor 16 and a signal GP from a throttle valve position sensor 31, which is a load-dependent

Signal detected the position of the throttle valve 32 in the air supply duct of the internal combustion engine. In principle, can Of course, the position of the accelerator pedal can also be detected or another load signal can be used.

The principle mode of operation of the arrangement shown "is that when knocking occurs Operation knock signals K are generated, which cause the ignition to be retarded in order to turn off again knocking area to come out. This is done advantageously in that when knocking operation occurs, the ignition point is continuously continuous in steps is adjusted late and when the knocking stops Operation is gradually reset to the original value. Such an ignition timing adjustment is known for example from DE-OS 3 009 0 ^ 6. Furthermore, either simultaneously or only after a predetermined ignition timing retardation, the charging ' pressure of the exhaust gas turbocharger reduced by the fact that the "boost pressure control valve 21 in the bypass 20 of the exhaust gas turbine 18 is opened.

It goes without saying that, in addition to the control systems described and illustrated, a control device must also be provided for the injection processes of the internal combustion engine. These control processes are not shown to simplify the drawing. Of course, the electronic control device 2k, the ignition control device 25 and the injection control device can optionally be implemented as separate computers or in a common computer. In principle, the control device can also be implemented without gasoline injection with one or more carburetors.

In the block diagram of the electronic control device 2k shown in FIG.

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fields TV _T and p _T .... corresponding storage devices 1 + 0, 1 + 1 supplied. These can be, for example, as. ROM, PROM or EPROM be designed. Furthermore, a load signal GP1, which is derived from the throttle valve position signal GP, is fed to these memory devices I + O, 1 + 1. For this purpose, both the signal GP and the signal GP2 and a signal derived from the ignition timing adjustment, which will be discussed in greater detail later, are fed to a comparison point 1 + 2. The output signal of this comparison point 1 + 2 results in the signal GP1. The signal GP2 is formed in that the signal GP is passed through an evaluation element 1 * 3 for a D component and a downstream filter stage 1 + 1 +, the values below AGT. locks,
mm ^e

The value addressed in the memory 1 + 0 is fed via a reference junction U5 to a signal generator stage k-6 , in which, depending on this value, a pulse voltage with a certain control duty cycle ST- is generated to control the position of the solenoid valve 11. • This control duty cycle is preferably limited between and 85%. The output of the storage device 1 + 1 is connected via a low-pass filter 1 + 7 to a comparison point 1 + 8, which also provides the boost pressure actual value p _T. . ■

JjX STj

is fed. The output of the reference junction 1 + 8 is preferably via a switching element 1 + 9, a controller 50 PI characteristic and a limiting element 51 of the comparison point 1 + 5 supplied.

A knock control stage 52 is the reference mark signal BM as well as knock signals K supplied to the knock sensors. the Knock control stage 52 generates an output signal Δ (Υ,, das includes the retarded ignition timing as a function of the occurrence of knocking combustion. This output signal is sent via a switching device

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53 alternatively one of two limiting ^{stages 5 1} +, 55 is supplied, which limit the value AOC to the value Oi ₁ "or OC _o . The limiting value OC _{1 of} the limiting stage 5 ^ is determined as a function of the speed η. The outputs of the limiting stages 5 ^, 55 are brought together in a comparison junction 56 and are sent to the ignition controller 25 as signal AOf

leads.

The output of the knock control stage 52 is also fed via a switching element 57 and a low-pass filter 58 to a further comparison point 59, at which an additional, borrowed value CC is applied, which corresponds to a prescribed maximum permissible ignition timing retardation. The output of this comparison point 59 is fed to the comparison point \ 2 via a control element 60.

A recognition stage 61 for differentiating between operating states of the internal combustion engine in which the exhaust gas turbocharger λ \ is effective or ineffective controls the. Switching device 53 as well as the switching elements U9 and 57. This detection takes place in that the turbocharger is basically ineffective in certain states of load GP and speed η. When the turbocharger is inactive, the two switching elements k9, 57 are open and the output of the knock control stage 52 is connected to the limiting stage 55. The switching elements and changeover switches mentioned can also be controlled directly via one of the characteristic maps kO , U1, since a specific boost pressure is assigned to each of the values stored there. In the case of boost pressures below a predeterminable limit value, the effect of the exhaust gas turbocharger is not considered to be given.

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The operation of the Ausführungsbeiapiels shown in Figure 2 consists essentially in that the ₅ Lad'edruck η as a function of speed and load GP (throttle position) is pre-controlled by means of the characteristic field stored in the memory kO TV _T. Each of the two values η and GP or ·. GP1 addressed storage values in the memory kO contains a certain pulse duty factor which controls the passage in the bypass 20 via the signal generator stage k6 and thus specifies the boost pressure. During constant travel or slow load changes, the GP signal corresponds to the GP1 signal (without taking into account any knocking processes). In the event of rapid load changes by the driver, the evaluation element U3 increases the boost pressure briefly above the new steady-state value or decreases it below the new steady-state value (D component). This improves the responsiveness of the turbocharger.

If the adjustment speed is below a definable value (Δ GP.), The output signal of the evaluation element k3 is suppressed by the filter stage kk. A control circuit for the boost pressure is superimposed on this control circuit for the boost pressure, ie connected in parallel. This control circuit corrects - if necessary - the boost pressure set by the pilot controls in order to achieve an even more precise setting. The control loop consists of a setpoint characteristic P ₅ - .. -, which is stored in the memory Hl, and which specifies the setpoints for the boost pressure as a function of η and GP1. These setpoint values are fed to the comparison junction h8 with a delay via the low-pass filter U ¹ J, the delay time being adapted to the dynamics of the build-up of boost pressure. Then the control deviation is reported to the controller

50 with preferably PI characteristics supplied and the correction values then in the limiting element

51 limited, e.g. to values between - 20 %. The through

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the correction value obtained is then added in the comparison junction ^ 5 to the default value of the duty cycle and fed to the signal generator stage h €. There the control signal is restricted to a pulse duty factor of 15 to 85 % , for example. The influences of component tolerances of the exhaust gas turbocharger and the bypass valve on the boost pressure and dynamic. Processes can be compensated by • the control loop. This control circuit is only switched on via the switching element k9 when there is an effective boost pressure. '. - ■

If knock signals K now occur, the ignition point is adjusted in a known manner by the knock control stage 52 in stages until there is no longer any knocking operation. This causes the control signal AOC. With effective operation of the turbocharger, this ignition adjustment is limited to a value OC due to knocking. This limitation takes place to avoid an excessively high exhaust gas temperature and is controlled as a function of the speed for exact setting. If the turbocharger is not active, the limiting value which allows a greater ignition timing adjustment becomes active by switching the switchover device 53.

If there is slight or rare knocking, the ignition timing adjustment is sufficient generally off to get out of the knocking area. Keeps the knocking however on, and this results in an ever greater ignition timing adjustment, so when the value is reached

OC i, which is preferably speed-dependent, made an additional lowering of the boost pressure. The low-pass filter 58 ensures by averaging that the charge pressure lowering only becomes effective if the knocking continues or repeats itself. About the control element

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the intervention in the boost pressure regulation and control is then undertaken in that the load value GP1 is changed via the comparison point k2 . This intervention of the knocking processes on the boost pressure will primarily occur when fuel is slightly more knock-resistant or when the intake temperatures are very high. The 'internal combustion engine is then effectively protected from knock damage. The switching element 5.7 ensures that the charge pressure is only intervened when the turbocharger is active.

It goes without saying that, in a simpler embodiment, the switching elements k9, 57 and the switching device 53 can be omitted. In this case, a single limitation stage 5 ^ is provided.

Of course, other known measures can also be taken to prevent knocking the operating state of the internal combustion engine off again to lead out of the knocking area. Such measures are for example water injection, addition of Knock-reducing agents and changing the fuel-air mixture.

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Claims (1)

K Us **. _R 183 52 1.2.1983 Ve / Hm ROBERT BOSCH GMBH, 7000 STUTTGART 1 Expectations f1 J control device for the boost pressure of an internal combustion engine with turbocharger, -wherein the boost pressure can be reduced as a function of the signals of at least one knock sensor, characterized in that a boost pressure map is stored in a memory {k0), by which the the parameters load (GP) and speed (n) the boost pressure (ρ) .., Jj u d he an adjusting device (23, 21) is set. 2. Control device according to claim 1, characterized in that an actual value transmitter (30) for the generated Boost pressure is provided and that the control circuit for setting the boost pressure is a control circuit (U1, UT to 51) is superimposed by the set boost pressure as a function of the within specifiable limits the control deviation can be corrected. 3. Control device according to claim 2, characterized in that the setpoints for the control loop in a target boost pressure map (U1) are stored and can be called up depending on the parameters load 'and speed. 33G3350 18352 k. Control device according to Claim 2 or 3j, characterized in that the setpoint values are passed via a low-pass filter (I) -T) to simulate the boost pressure dynamics. 5. Control device according to one of the preceding claims, characterized in that the parameter Load in a weighting element (^ 3) with a D component Is evaluated. 6. Control device according to claim 5 »characterized in that a digital filter (hk) is provided which suppresses the D component at adjustment speeds below a predeterminable value (A GP.). T. Control device for the boost pressure of an internal combustion engine with turbocharger, the boost pressure depending on the signals of at least one knock sensor can be lowered, characterized in that depending on the parameters load (GP) and speed (n) the boost pressure is specified electronically via an adjusting device (23, 21), the output signal a knock control stage (52) for the ignition of the internal combustion engine acts additionally on the load and / or speed signal. 8. Control device according to claim 7 »characterized in that that this output signal is passed through a low-pass filter (58). 9. Control device according to claim T or 8, characterized in that the output signal in a comparison junction with a predeterminable value ( OC ) ver ■ zm is equalized, with a lowering of the boost pressure when this value is exceeded. 1835 10. Control device according to claim 9 »characterized in that the predetermined value is speed-dependent. 11. Control device according to one of claims 7 to 10, characterized in that the output signal of the knock control stage (52) at least one limitation level (5 ^, 55) is supplied to limit the ignition timing adjustment during knocking operation. 12. Control device according to claim 11, characterized in that that the limit value can be set as a function of the speed (n). 13. Control device according to claim 11 or 12, characterized in that two limiting stages (5 ^ ₅ 55) with different adjustment limits are provided that a recognition stage (61) is provided for recognizing an operating state of the internal combustion engine in which the turbocharger is active, and that through this recognition stage (6i) a switchover between the limiting stages (5 ¹ +, 55) takes place in such a way that the adjustment is more narrowly limited when the turbocharger is active. 1 k. Control device according to claim 2, 7 or 13, characterized in that a recognition stage (61) is provided for recognizing an operating state of the internal combustion engine in which the turbocharger is active, and that through this recognition stage the additional boost pressure control circuit ( lt-1, 1 + 7 to 51) and / or the control of the boost pressure can be switched off as a function of the knock sensor signals. 8 χ 5 2 15. Control device according to one of the preceding claims, characterized in that the adjusting device is a "certain control duty cycle acted upon control valve (23) which controls the passage of a bypass to the turbocharger (1 h ).