DE10319332B3 - Heat limitation method for automobile IC engine using engine control device for heat limitation when delivered torque does not increase further upon increase in heat - Google Patents

Abstract

The invention relates to a method and a control device (15) for limiting the amount of heat supplied to an internal combustion engine (11). If a torque request is made, the control unit (15) determines setpoints for actuators (12 ... 14), for example for the throttle valve, the boost pressure, the injection, which have a direct influence on the supply of heat. Other setpoints, such as the ignition timing, have a direct influence on the efficiency of the energy conversion. In order to optimize the torque requirement, it is proposed according to the invention to monitor the supply of heat into the internal combustion engine (11) by means of the control unit (15). Furthermore, it is proposed that the supply of heat is limited to a predetermined limit value when the actual torque (TQI_AV) emitted by the internal combustion engine no longer rises or the increase in the actual torque (TQI_AV) falls below a predetermined limit value.

Description

The The invention is based on a method or a control device for limitation the amount of heat supplied to an internal combustion engine, a control unit for a desired one Torque output by the internal combustion engine as the actual torque should be specified, setpoints that are in actuators for example for the Throttle valve, injection, ignition, boost pressure, etc. processed and these setpoints are both the efficiency of energy conversion as well as the heat supply in affect the internal combustion engine, according to the genus of the secondary Expectations 1 and 10. In known engine control units, for example Actual torque delivered by the internal combustion engine (effective torque) determined with the help of a torque model. As a rule, from the driver of the vehicle, for example via the accelerator pedal or one In-vehicle equipment, e.g. a torque request to the speed controller (Target torque) specified.

A generic torque model is for example in the DE 197 12 843 C2 described. It is proposed here to record the pedal position of an accelerator pedal. An estimate for the desired torque is derived cyclically from the pedal position and at least one operating variable of the internal combustion engine, which is then available on the clutch of the vehicle. A target value for the desired torque is determined from the estimated value. Furthermore, the change in time is formed from the target value of the desired torque and is limited to a predetermined change value in a predetermined value range around the zero value of the desired torque.

Of further known is the torque request to a maximum Flow value for the Limit fuel. This is to prevent that Injector constantly open and there is no longer any regulation. Furthermore is known, the supply of heat limit to protect components of the internal combustion engine. The has the disadvantage, however, that in the internal combustion engine disposal standing performance in full under all operating conditions Scope is usable.

In the DE 100 46 446 A1 describes a method for controlling an internal combustion engine via interventions in at least one manipulated variable of the internal combustion engine. For a first variable as a work to be performed or a target torque to be provided, a corresponding target heat quantity is determined, taking into account the current actual efficiency, for which at least one associated control variable is set in accordance with the value of the target heat quantity. Furthermore, the actual amount of heat is recorded, a target efficiency being determined from the actual amount of heat, taking into account work to be performed or a target torque to be provided, which may correspond to the first variable or another variable that is to be a target Moment or work to be performed on the crankshaft is formed. At least one manipulated variable of the internal combustion engine is then promptly set in accordance with a setting of the determined target efficiency.

The The invention is based on the object of a method or a control unit specify with which the heat supply is limited in the internal combustion engine when increasing Heat supply no significant change of the actual torque can be achieved. This task comes with the features of the independent claims 1 and 10 solved.

at the inventive method or the control unit to limit the amount of heat supplied to an internal combustion engine with the characterizing features of the independent claims 1 and 10 gives the advantage that the amount of heat generated by the combustion of fuel and fresh gas the energy supply in the internal combustion engine causes, is limited if it turns out that the further Heat supply not an increase of the torque request leads. It is considered particularly advantageous that this Measure on the one hand an overheating the internal combustion engine or its parts is avoided. on the other hand is achieved by limiting fuel in particular saved and the exhaust gas emissions especially at full load operation be improved as an increase the energy supply only with disproportionate More consumption leads to an increase in performance. Another advantage results the fact that lower quality fuel can be used without the internal combustion engine being damaged as a result.

By those in the dependent Measures listed claims are advantageous developments and improvements in the secondary claims 1 and 10 given method or the control unit. In particular the limit can be selected in this way that one on the target torque related optimal efficiency of the internal combustion engine achieved becomes.

On simple procedure for the limitation of the supply of heat is seen in the derivation of the determined actual torque over the amount of heat supplied to build. With the derivation can be easily determined be whether with further supply of heat or increasing the Energy the actual torque changes. Usually the torque increases proportionally with increasing energy supply on. Depending on the operating condition and fuel quality used, however for example, by interfering with the knock control (shift the ignition angle towards the late ignition) Rise in the actual torque may be limited, so that another Increase in heat input leads to no or only a slight increase in torque.

Especially Cheap is also the solution the increase in the actual torque to be monitored by comparing at least two subsequent measurement cycles. Since the measurements are carried out continuously anyway, the determined values for the actual torque are simply cached and then for the Comparison immediately available.

to Limitation of the heat supply advantageous operating parameters used. With Can help with these sizes the supply of heat be limited to physically reasonable values.

As very cheap is considered, a system feedback to limit the heat supply, preferably a signal to use a knock control. Because for example modern Otto engines are usually equipped with a knock control, their signal can also be used to limit the supply of heat without additional effort be used.

In practice the limitation of the heat supply in a simple manner by specifying the throttle valve position and / or Control the amount of fuel to be injected because these parameters direct influence on the supply of heat have in the internal combustion engine.

A another possibility is used to limit the supply of heat also seen in it, the boost pressure control and / or the limitation the degree of filling to control accordingly. Especially with supercharged engines the boost pressure for example above easily control the speed of the charging turbine.

A preferred application of the limitation of the supply of heat results in gasoline or diesel engines, especially if these engines in operated in the upper load range.

Is cheap also the solution that predetermined limit values are stored in an adaptation map of the control unit become. That way you can Limit values, for example, slightly on different engine variants be adjusted.

On embodiment the invention is shown in the drawing and is in the following Description closer explained.

1 shows schematically an arrangement for limiting the supply of heat and

2 shows a schematic representation of a block diagram with a control device for controlling an internal combustion engine.

With the method according to the invention according to the arrangement 1 it is achieved that the heat quantity supply (enthalpy supply) is limited to predetermined values if it turns out that with further energy supply or heat quantity supply, the actual torque determined no longer increases and is below predetermined limit values. In the 1 Function blocks shown form a method that is implemented in the form of a software program and in a control unit 15 ( 2 ) is implemented. The control unit 15 is with an appropriate memory 18 connected, in which, among other things, the specified limit values for the supply of heat, for example in the form of an adaptation map, are also stored for the different operating conditions.

First, using 1 the basic structure of the arrangement and then explains how it works. This in 1 The method shown is designed for an Otto engine, in particular with a turbocharger. Alternatively, it can also be used for diesel engines. It should be noted that diesel engines have no knock control and ignition angle adjustment, so that in this case no knock signal can be used to limit the supply of heat, but the limitation must be carried out with a different operating parameter.

In 1 is a product formation 1 recognizable with a first input A, to which an indexed reference torque TQI_REF is applied. The indexed reference torque TQI_REF serves as the basis for the actual torque TQI_AV emitted by the internal combustion engine. The signal of a basic ignition angle efficiency EFF_IGA_COR_KNK_FIL, which was corrected by a knock control, is applied to a second input B. The outcome of product formation 1 is with a + on gear of a first difference 3 connected and transfers to the first difference former 3 the actual torque TQI_AV determined with the aid of a torque model. The actual torque TQI_AV is buffered for each measuring cycle. The previous torque value 1 / z is in a first memory (delay element) 2 saved with an input of the first difference 3 connected is. The first difference generator is on the output side 3 with an x input of a division unit 6 connected. There is also an input to the division unit 6 with an output of a second difference former 5 connected, at whose + input D a signal MFF for the fuel quantity per working stroke is applied. The value 1 / z determined and buffered in the previous cycle is applied to an input, that in a second memory 4 was saved.

An output of the division unit 6 is with an input of a comparator 7 connected. Another input is with an output of a limit value 8th connected. The limit value specification 8th inputs E, F are connected via the operating variables 1 . 2 can be entered. In the limit specification 8th For example, predetermined limit values are stored in a map, which depend on the operating variables 1 . 2 be formed.

At an output G of the comparator 7 a signal LV_TQI_SP_LIM_ACT can be tapped. This signal is a flag for the display of an activated torque limitation. Furthermore, the output of the comparator 7 to an input of an evaluation unit 10 guided. To another input C of the evaluation unit 10 a signal TQI_SP_BAS is carried out (torque request for the determination of the heat quantity setpoint, raw value). Furthermore, in a third memory 9 the previous value 1 / z is saved at an output H of the evaluation unit 10 can be tapped under certain conditions, as will be explained later. An output of the third memory 9 is with a separate input of the evaluation unit 10 connected so that the stored previous value from the evaluation unit 10 can be read.

At the output H of the evaluation unit 10 the signal TQI_SP_ENTH can be tapped, which corresponds to the setpoint of the torque after the limitation of the heat supply. The actuators of the internal combustion engine are then acted on with this signal.

The mode of operation of this arrangement is explained in more detail below. A torque request is usually made by signal generators 16 . 17 triggered by the driver of the vehicle, for example by actuating the accelerator pedal, switching an electrical consumer such as lighting, heating, air conditioning, etc. However, it can also be initiated by a vehicle system, for example by a speed controller or an idle controller. The torque request specifies a target torque TQI_SP that the internal combustion engine 11 outputs TQI_AV as actual torque. Since the actual torque TQI_AV cannot be measured directly, it is determined using a specified torque model. The target torque TQI_SP supplies target values for the various actuators 12 . 13 , ... 14 the engine control 15 , for example for the throttle valve, injection, boost pressure regulator etc. These parameters have a direct influence on the supply of heat, while other actuators such as the ignition timing adjustment (ignition angle adjustment) have a direct influence on the efficiency through a knock control.

Especially in the upper load range of the internal combustion engine 15 Operating conditions can occur in which the reduction in efficiency cannot be compensated for by increasing the amount of heat supplied. Every further increase in the heat quantity supply leads to a disproportionate increase in the efficiency intervention, so that the effective engine torque TQI_AV (corresponding to the actual torque) is reduced and positive feedback effects can occur, since the corrected ignition angle efficiency is used when determining the setpoint for the filling level becomes. This problem is solved with the control device according to the invention 15 and the algorithm solved by an optimal, sensible limitation of the heat supply.

With regard to the mode of operation, the two inputs A, B of the product formation 1 the two signals TQI_REF and EFF_IGA_BAS_COR_KNK_FIL created. Both signals together give the effective torque, which is also referred to as the actual torque TQI_AV. The actual torque TQI_AV is at the output of product formation 1 available and will be sent to the first difference-maker 3 transfer. A correspondingly designed torque model was used to calculate the actual torque TQI_AV.

In the first difference 3 the previous value 1 / z for the actual torque is also given, which is determined in the previous calculation cycle and in the first memory 2 (Delay element 2 ) was saved. This value is now subtracted from the current actual torque TQI_AV. Alternatively, it is provided that several values or average values are taken into account in the subtraction.

At the output of the first difference generator 3 a difference value is then available, which consists of the current actual torque TQI_AV and the actual torque from the last calculation cycle was determined. This difference value arrives at the x input (multiplication input) of the division unit 6 ,

The same calculation is carried out with the MFF signal (fuel flow or fuel mass). The MFF signal is applied to a second difference former 5 given and compared there with the previous value 1 / z, that in the second memory 4 is saved. The difference value for the fuel flow is applied to the input (division input) of the division unit 6 given.

By dividing the two difference values (difference of the torques / difference of the fuel masses) one obtains a gradient which is at the output of the division unit 6 is tapped. This gradient is the effective torque increase over the energy supply increase. The gradient should always be greater than zero. He is going to an input of the comparator 7 given that is formed with the relative operator <=. The gradient is compared with a map size that the limit transmitter 8th is removed. The result of the comparison is available at output G as signal LV_TQI_SP_LIM_ACT. The signal LV_TQI_SP_LIM_ACT shows the activated limitation of the torque.

About the inputs E, F can Values for map sizes created so that the gradient can be controlled with it. Become for example, map sizes <0.5 or close to Filed 0, it means that it makes little sense, more torque to build up, because then the torque increase is bought with too much fuel would.

In the limit transmitter 8th In the simplest case, a limit value <= 0 can be saved. The advantage of storing a limit map is that there is no restriction. The map contains various limit values that depend, for example, on the engine speed and the load (fuel, fresh gas quantity).

At the output G of the comparator 7 the result is a logical 1 or 0 (incorrect or correct), which is saved as signal LV_TQI_SP_LIM_ACT. This signal is also sent to the evaluation unit 10 guided. The evaluation unit 10 is essentially a switch with the positions 0 and 1 , Has the result of the comparator 7 show that the gradient is smaller than the limit value of the limit transmitter 8th , then the signal LV_TQI_SP_LIM_ACT = logical 1, as in 1 is shown. If the switch is set to 0, ie if the limitation is not active, the unfiltered setpoint TQI_SP_BAS for the torque goes directly to output H. If the switch is open 1 is then the value 1 / z in the third memory 9 frozen. The value 1 / z from the last calculation is fed back again. The setpoint for the torque request after the limitation of the heat supply is available at output H. This is the setpoint, which is then implemented in an inverse torque model and the actuators 12 . 13 . 14 ( 2 ) is supplied. More torque can then not be requested, the heat supply has been successfully limited.

In an alternative embodiment of the invention, it is provided that the torque TQI_SP_ENTH is detected at the output H over a certain period of time and in the limit transmitter 8th to save so that it is learned directly that no greater torque can be generated. With this adaptation of the learning function, the torque of the motor can be limited to a reasonable value right from the start. This function could be used, for example, to avoid permanent corrections that are made by the knock control system due to an inferior fuel.

The block diagram of the 2 shows a schematic and highly simplified representation of an internal combustion engine 11 , which is designed, for example, as a gasoline engine with a turbocharger. The internal combustion engine 11 usually has a number of actuators 12 ... 14 such as throttle valve adjuster, boost pressure regulator, injection, ignition angle adjuster, knock regulator etc. The actuators 12 ... 14 are with the control unit 15 connected, which specifies the corresponding setpoints for setting a setpoint torque TQI_SP. The control unit 15 is also with a memory 18 connected in which all the required software programs, the limit values, maps and torque models are stored. The control unit is on the input side 15 with signaling devices 16 . 17 connected with which a torque request can be specified. Such signalers 16 . 17 can be, for example, the position of an accelerator pedal, a speed controller, an idle control or another control system.

Claims (11)

Method for limiting an internal combustion engine ( 11 ) supplied amount of heat, whereby a control unit ( 15 ) for a desired torque generated by the internal combustion engine ( 11 ) is to be output as the actual torque, specifies setpoints which are set in actuators ( 12 . 13 . 14 ) for example for the throttle valve, the injection, the ignition, the boost pressure etc. are processed and these setpoints both the efficiency of the energy conversion and the supply of heat to the internal combustion engine ( 11 ) influence because characterized in that the control unit ( 15 ) the supply of heat to the internal combustion engine ( 11 ) is monitored and the heat quantity supply is limited to a predetermined limit value if the actual torque (TQI_AV) emitted by the internal combustion engine, which is determined with the aid of a torque model, no longer increases as the quantity of heat increases or the increase in the actual torque (TQI_AV) exceeds a predetermined value Falls below the limit. A method according to claim 1, characterized in that the limit value is selected so that an optimal efficiency of the internal combustion engine (TQI_SP) related 11 ) is reached. Method according to one of the preceding claims, characterized characterized in that the derivation of the determined Actual torque above the fed heat is formed. A method according to claim 1 or 2, characterized in that that the limit for the actual torque (TQI_AV) by comparing at least two subsequent measuring cycles is determined. Method according to one of the preceding claims, characterized in that the limitation of the heat quantity supply by evaluating operating parameters to one for the internal combustion engine ( 11 ) physically meaningful value. Method according to one of the preceding claims, characterized characterized that a system feedback to limit the heat supply, in particular a knock control signal is used. Method according to one of the preceding claims, characterized characterized that the limitation of the heat supply by changing the Specification of the throttle valve position and / or the one to be injected Amount of fuel. Method according to one of the preceding claims, characterized characterized in that the supercharged internal combustion engine Limitation of the supply of heat with the help of a boost pressure control and / or with the help of the degree of filling he follows. Method according to one of the preceding claims, characterized characterized that the limitation of heat supply in a gasoline engine or diesel engine. Control unit for limiting the supply of heat in an internal combustion engine ( 11 ) according to one of the preceding claims, wherein the control device ( 15 ) has a program with which setpoints for actuators can be determined from a torque request and these setpoints both the efficiency of the energy conversion and the supply of heat in the internal combustion engine ( 11 ) influence, characterized in that the supply of the heat quantity can be limited by means of the program if the increase in the actual torque (TQI_AV) falls below a predetermined limit value with a further increase in the heat quantity. control unit according to claim 10, characterized in that the predetermined limit can be stored in an adaptation map.