Free translation, Patent EP0885353B1

METHOD AND ARRANGEMENT FOR

CONTROLLING OR REGULATING THE POWER OF A

SUPERCHARGEABLE INTERNAL COMBUSTION ENGINE

Abstract

This invention relates to a process in which a position demand-value [wdksol] for the throttle valve in the intake manifold of the combustion engine is derived from a predetermined load demand-value [rlsol], a pressure demand-value [pssol] in the inlet manifold is determined from the load demand-value [rlsol], and a boost-pressure demand-value [plsol] is derived by combining the inlet manifold pressure demand-value [pssol] with a variable [dpdk] which predetermines a pressure drop across the throttle plate. Presetting the pressure drop across the throttle plate results in good drivability during dynamic operation and optimum efficiency in steady operation.

Description

Stand der TechnikState of the art

This invention concerns a method and arrangement to control the power of a superchargeable combustion engine by controlling the boost pressure and the position of an existing throttle plate in the intake manifold.

Such a method is known from DE 43 30 368 AI. According to this state of the art, the boost pressure and the throttle plate position are set independently from one another as a function of driver request or a specified value from the cruise control. In a first sphere of driver request or a specified value from the cruise control, power is mainly controlled on the basis of throttle plate position, and in a second sphere of driver request or a specified value from the cruise control, power is set mainly on the basis of boost pressure. There can also be a third sphere in which the throttle plate position and the boost are regulated jointly dependent on the driver input.

The dependencies of throttle plate position and boost on the driver pedal position are selected so that in the current operating mode optimum cylinder filling is attained in regard to power and fuel consumption.

The invention is base on the task to state a method and arrangement for controlling or regulating the power of a superchargeable internal combustion engine, whereby good drivability and optimum efficiency are reached.

Advantages of the Invention

According to this invention the problem is solved with the criteria of claims1 and 7, so that a position value for the throttle plate in the intake duct of the combustion engine is derived from a given load demand-value, so that from the load demand-value an intake duct pressure demand-value is derived, and so that a boost pressure demand-value is derived from a combination of the intake duct pressure demand-value with a quantity that specifies a pressure drop across the throttle plate. The pressure drop across the throttle plate can be regulated simply to optimize either drivability or engine efficiency according to the driver’s wish, enabling either a very sportive or economical driving mode.

Further advantageous developments of the invention arise from the sub-claims.

Description of an Implementation Example

Following, the invention is further explained by an implementation example illustrated by drawings showing:

Fig. 1 - Overview block diagram showing the control of a combustion engine

Fig. 2 - Block diagram for the control of throttle plate position and boost pressure control.

Fig. 3 - Block diagram showing the generation of a boost pressure demand‑value

Figure 1 shows a combustion engine [100] with an intake tract [102] and an exhaust path [104]. In the intake tract are arranged – seen in air flow direction – a metering sensor [105] for air mass [ml], a compressor [108] of a turbocharger, a pressure sensor [112] for boost pressure [p2], a temperature sensor [110] to measure the temperature [Tans] of the air ingested by the engine [100], and one or more injection jets [113]. The compressor [108] is driven via a drive connection [114] by a turbine [116] positioned in the exhaust path [104]. A bypass passage [118] bridges the turbine [116]. A bypass valve [120] is located in the bypass passage [118], whereby the boost pressure generated by the turbocharger can be controlled. Also attached to the combustion engine [100] are a knock sensor [122] that issues a knock signal [K] during knocking combustion, an engine speed sensor [123] for engine speed [nmot], and a temperature sensor [124] for engine temperature. The combustion engine [100] in this example has four cylinders [125], each equipped with one spark plug.

The following signals are supplied to a control module [126]: The signal from the air mass flow meter [105], the signal [p2] from the pressure sensor [112], the signal [Tans] from the temperature sensor [110] for the temperature of the ingested air, the signal [K] from the knock sensor [112], the signal [nmot] from the engine speed sensor [123], the signal [Tmot] from the engine temperature sensor [124] and the signal [αP] from a driver pedal position transducer [128]. Outputs from the control module [126] are a signal [wdksol] for the servomotor [107] of the throttle plate [106], a signal [ldtv] for control of the bypass valve [120] and a signal [ti] for fuel metering through the injection nozzles [113]

The control module [126] contains the circuit shown in Fig. 2 for the control of throttle plate position and boost pressure. The input signal for the control circuit shown in Fig. 2 is a load demand‑value [rlsol] which is calculated from a torque demand‑vale under various influences, i.e. driver pedal position, vehicle speed regulation, transmission control, anti slip regulation. Since the derivation of the load demand‑value [rlsol] is not a matter of this invention, it will not be further discussed here.

The load demand‑value [rlsol] is directed to a junction [201] where the output is determined by a load actual‑value [rlist]. The load actual‑value [rlist] (also known as engine load) is determined in a processor [202] dependant on engine speed [nmot] and intake air mass flow [mL]. From the buffered load demand‑ and actual‑ values, a load controller [203] derives the control signal [wdksol] for the throttle plate positioning motor [107].

Also derived from the load demand‑value [rlsol] is the control signal [ldtv] for the bypass valve [120] that regulates the boost pressure. For that, the load demand‑value [rlsol] is directed to a processor [204] that is further discussed in connection with Fig. 3. In this processor, depending on engine speed [nmot], engine temperature [Tmot] and the intake manifold air temperature [Tans], an intake manifold pressure demand‑value [pssol] is derived from the load demand‑value [rlsol],

This intake pressure demand‑value [pssol] is combined in a junction [205] with a signal [dpdk] that corresponds to a pressure drop across the throttle plate. Fig. 3 presents the derivation of this signal [dpdk] from the load demand-value [rlsol] and other quantities in the processor [206].

The output signal of the junction [205] corresponds to a boost pressure demand-value [plsol]. In the junction [207] the output is determined between this boost pressure demand-value [plsol] and the boost pressure actual-value [plist]. The boost pressure actual-value [plist] is derived by a processor [208] from the sensor signal [p2] of the pressure sensor [112]. The resultant output signal [Ide] between the boost pressure demand- and actual-values is directed to a boost pressure controller [209] (i.e. PID-controller) that finally outputs a position signal [ldtv] for the bypass valve [120] of the turbocharger.

With the signal [dpdk] that corresponds to a pressure drop across the throttle plate, the boost pressure demand-value [plsol] can be increased or decreased arbitrarily relative to the intake pressure demand‑value [pssol]. For instance if, based on driver input, dynamic engine operation is demanded and good drivability is preferred, then the boost pressure demand-value [plsol] is increased relative to the intake pressure demand‑value [pssol]. In this driving mode, the engine has bad efficiency and operates not economically. However, if good efficiency is demanded, as in steady operation, then the signal [dpdk] is reduced until the boost pressure demand-value [plsol] corresponds approximately to the intake pressure demand‑value [pssol]. This shows that, with the controllable pressure drop [dpdk] at the throttle plate, rapid engine adaptation to the current driving mode is possible.       

As can be seen from Fig. 3, the intake pressure demand‑value [pssol] is produced in a divider [301] by division between the load demand-value [rlsol] and a factor [fupsrl]. For instance, this factor can be derived from a map (compare with processor [204] in Fig 2) as a function of engine speed [nmot], engine temperature [Tmot] and intake manifold temperature [Tans].

To arrive at the intake pressure demand‑value [pssol], a signal [prg] can be superimposed on the ratio of the load demand-value [rlsol] to the factor [fupsrl] in junction [302]. This signal [prg] specifies the partial pressure of the residual gas in the combustion chamber. Because of the valve overlap between exhaust end and inlet start, residual gas remains in the combustion chamber with a pressure of ca. 50… 150 mb.

As already mentioned in connection with Fig. 2, the signal [dpdk] representing the pressure drop across the throttle plate, is superimposed on the intake pressure demand‑value [pssol] in a junction [303 in Fig. 3] from which the boost pressure demand-value [plsol] finally results. The signal [dpdk] is taken from a map [KFDPDK] that is stored in a processor [304]. The value of the signal [dpdk], taken from of the map [KFDPDK], depends on the engine speed and a ratio of the load demand-value [rlsol] to a maximum attainable load value [rlmax] generated in the divider [305]. This maximum attainable load value [rlmax] depends, for example, on engine speed [nmot], engine knocking as determined by the knock sensor [122], engine temperature [Tmot], intake manifold temperature [Tans] and the atmospheric elevation.

So the signal [dpdk], reflecting the pressure drop across the throttle plate, can be adapted very flexibly to the driving mode, the output signal from the map [KFDPDK] is multiplied in junction [306] with a correction factor [fdpdk] which is generated in a processor [307]. Input signals for this processor are a minimum value [FDPDKMN] for the correction factor, a time constant [TDPDK] and the output signal of a OR gate [308] that acts as OR-junction between a signal [B_ldob] indicating overboost activation, and a signal [B_ldobsp] indicating an overboost lock time.

When the driver signals dynamic, sportive driving via the pedal, thereby causing one of the two signals [B_ldob] or [B_ldobsp] to appear at the OR gate [308], then the correction value [fdpdk] is set in the processor [307] to a value of 1, and maintains this value of 1 so long as one of the signals is present. If the driving mode changes by a transition to steady driving, the processor [307] reduces the correction factor [fdpdk] according to the time constant [TDPDK] from the value 1 to the minimum value [FDPDKMN] which lies between 0 and 1. Reduction of the correction factor [fdpdk] also reduces the signal [dpdk] that is superimposed on the intake pressure demand‑value [pssol], whereby the pressure drop across the throttle plate recedes in order to optimize engine efficiency. The correction factor [fdpdk] could also be influenced by a driver operated device (i.e. switch) to force, for example, a particularly sportive driving mode.

Claims

1.        A method for controlling or regulating the power of a superchargeable internal combustion engine by controlling or regulating the boost pressure and the position of a throttle plate in the intake duct, thus characterized that a position value [wdksol] for the throttle plate [106] is derived from a given load demand-value [rlsol], that an intake pressure demand‑value [pssol] is determined from the load demand-value [rlsol], and that a boost pressure demand-value [plsol] is derived from the combination of the intake pressure demand‑value [pssol] with a quantity [dpdk] that forces a pressure drop at the throttle valve [106].

 

2.        A method according to claim 1, thus characterized that the intake pressure demand‑value [pssol] is derived from the ratio of the load demand-value [rlsol] and a factor [fupsrl] that depends on engine speed [nmot], engine temperature [Tmot] and the temperature [Tans] of the ingested air.

3.        A method according to claim 2, thus characterized that the partial pressure of the residual gas [prg] is added to the intake pressure demand‑value [pssol].

4.      A method according to claim 1, thus characterized that the quantity [dpdk] for the pressure drop across the throttle plate [106] is read from a map [304] depending on engine speed [nmot] and the load demand-value [rlsol].

5.        A method according to claim 1, thus characterized that the quantity [dpdk] for the pressure drop across the throttle plate [106] is read from a map [304] depending on engine speed [nmot] and the ratio of the load demand-value [rlsol] and a maximum attainable load value [rlmax].

6.        A method according to claim 4 or 5, thus characterized that the value read from the map [304] is augmented by a correction factor [fdpdk] that is set to a higher value during dynamic driving than during steady driving.

7.        A method according to claim 6, thus characterized that the correction factor [fdpdk] is set to a value of 1 in dynamic driving and, during transition to steady driving, is reduced to a value between 0 and 1.

8.        An arrangement for power control of a turbocharged combustion engine that controls or regulates the position of a throttle plate located in the intake duct, thus characterized that first means [201, 202] are available that derive a position value [wdksol] for the throttle plate [106] from a load demand-value [rlsol], that second means [204] are available that derive an intake pressure demand‑value [pssol] from the load demand-value [rlsol], and that a boost pressure demand-value [plsol] results from a combination [205] of the intake pressure demand‑value [pssol] with a quantity [dpdk] that forces a pressure drop across the throttle plate.