Abstract:
A method device for controlling a suction pressure of an internal combustion engine, particularly a diesel engine having an exhaust gas turbocharger. The compressor is connected to a suction line of the internal combustion engine via an actuating section having an actuating element for changing a cross-section of the actuating section. In the first step, the current suction pressure in the suction line of the internal combustion engine is determined. A compressor pressure of the compressor is determined by pressure sensors and compared to the suction pressure. Values corresponding to current operating data of the internal combustion engine are identified and an actuation signal is generated using a controller, based on the comparison; and changing the cross-section of the actuating section is adjusted by adjusting the actuating element using the actuating signals.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of PCT International Application No. PCT/EP2008/007764, filed Sep. 17, 2008, which claims priority under 35 U.S.C. §119 from German Patent Application No. DE 10 2007 045 622.2, filed Sep. 24, 2007, the entire disclosures of which are herein expressly incorporated by reference. 
     
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
       [0002]    The invention relates to a method and a device for regulating an intake pressure of an internal combustion engine, in particular diesel engine, having an exhaust gas turbocharger. 
         [0003]    Internal combustion engines, such as for example diesel engines, are frequently equipped with exhaust gas turbochargers. They have a turbine which is driven by the exhaust gas and which is coupled to a compressor. The compressor compresses the intake air in order to increase an intake pressure in an intake line for the internal combustion engine, as a result of which, for example, an acceleration behaviour of the vehicle with the internal combustion engine is achieved and the consumption of energy is reduced. 
         [0004]    However, the exhaust gas turbocharger cannot deliver sufficient air in every operating state of the internal combustion engine and therefore generate a sufficient intake pressure. In order to solve this problem, exhaust gas turbochargers with variable geometry have been proposed, in which, for example, guide vanes for turbines/compressors can be adjusted as a function of the respective operating state or operating data/parameters of the internal combustion engine. However, it is disadvantageous here that an exhaust gas turbocharger with variable geometry is costly and complex in terms of parts. Furthermore, it can be very maintenance-intensive, which increases the operating costs of a vehicle. In addition, it is also not always possible for an exhaust gas turbocharger with variable geometry to deliver the quantity of air required by the internal combustion engine. In particular in what is referred to as a non-steady-state range, such as for example acceleration, problems occur. If the exhaust gas turbocharger is optimized for such a non-steady-state range, it has a poor efficiency and an associated high level of fuel consumption in the steady-state range, for example when travelling at a constant velocity or with a constant engine speed. 
         [0005]    Furthermore, piston engines such as diesel engines with an exhaust gas turbocharger have, for example, an operating state when accelerating which is referred to as “turbo lag”. Here, when the throttle is opened the internal combustion engine does not react by increasing the rotational speed until after a certain delay time in which no exhaust gas energy, that is to say an insufficient exhaust gas pressure, is available to drive the exhaust gas turbocharger and therefore no compressed intake air with corresponding intake pressure is available. In order to get around this turbo lag, solutions have been proposed which are described in German Laid-Open Patent Applications DE 10 2006 008 783 A1 and DE 10 2006 785 A1. Here, compressed air, for example from a compressed air accumulator, is fed in a controlled fashion into the intake line of the internal combustion engine in order to cover the intake air demand of the internal combustion engine when said demand is increased. This is carried out by means of a component which is arranged in the intake line between the compressor of the turbocharger or an intermediate cooler connected downstream in the direction of flow and the intake manifold, and said component has a compressed air port with a flow rate control device and a controlled flap. When compressed air is fed in through the flow rate control device, the controlled flap is closed with the effect that the compressed air does not flow into the compressor of the exhaust gas turbocharger counter to the intake direction but rather flows directed into the intake line. When the compressed air supply ends, this flap is opened again. There is no description of controlling the intake pressure of an internal combustion engine, in particular at an excessively high compressor pressure of the exhaust gas turbocharger. 
         [0006]    The object of the present invention is therefore to make available a method and a device for regulating an intake pressure of an internal combustion engine, wherein the above disadvantages are overcome or significantly reduced and further advantages are obtained. 
         [0007]    A basic idea of the invention is that an actuating element is provided in an actuating section in the intake line between the compressor of the exhaust gas turbocharger or a downstream intermediate cooler and the intake manifold of the internal combustion engine in order to influence the cross section of the intake line as a function of the intake pressure of the internal combustion engine. 
         [0008]    This advantageously ensures that this actuating element reduces the cross section of the actuating section of the intake line if the compressor of the exhaust gas turbocharger delivers a quantity of air which is too large for the current operating state at an excessively high pressure. The intake pressure downstream of the actuating element in the direction of flow can therefore be influenced by the position of said actuating element, in particular as a function of the intake pressure which is measured with a suitable measuring device. 
         [0009]    A method according to the invention for regulating an intake pressure of an internal combustion engine, in particular diesel engine, having an exhaust gas turbocharger whose compressor is connected to an intake line of the internal combustion engine via an actuating section which has an actuating element for changing a cross section of the actuating section, has the following method steps: 
         [0010]    acquisition of the current intake pressure in the intake line of the internal combustion engine and of a compressor pressure of the compressor by means of pressure sensors; 
         [0011]    comparison of the acquired current intake pressure and of the compressor pressure with setpoint values which correspond to current operating data of the internal combustion engine by a control unit, and generation of an actuating signal with said control unit on the basis of the comparison; and 
         [0012]    changing of the cross section of the actuating section as a function of the current intake pressure, compressor pressure and the current operating data by adjusting the actuating element by the actuating signals generated by the control unit, in order to regulate the intake pressure of the internal combustion engine. 
         [0013]    A further advantage is that either an exhaust gas turbocharger with a fixed geometry or an exhaust gas turbocharger with a variable geometry can be used, as a result of which the field of application of the invention is expanded. 
         [0014]    In a preferred embodiment, the intake pressure is acquired by at least one pressure sensor downstream of the actuating element in the direction of flow. It is also preferred here that a compressor pressure is measured by a further pressure sensor which is arranged upstream of the actuating element in the direction of flow. 
         [0015]    These pressure sensors can advantageously be arranged at a component, specifically the actuating section, which accommodates the actuating element. As a result, only a small amount of installation space is required. 
         [0016]    The measured values which are acquired by the pressure sensors are received by the control unit and can be adapted to a specific format for further processing. They are compared with setpoint values which correspond to current operating parameters or operating data of the internal combustion engine. The current operating data are obtained by communicating with an engine control device of the internal combustion engine. The control unit can, for this purpose, also communicate directly with corresponding measuring means. The setpoint values which correspond to the current operating state of the internal combustion engine, for the respective intake pressure to be controlled, are acquired from the current operating data, for example on the basis of stored table values and/or computational algorithms, and are compared with the current measured values. The comparison yields a difference which is used to generate actuating signals. If the difference is equal to zero, no actuating signals are generated. The actuating signals are used to control an adjustment unit for the actuating element. These may be, for example, current, voltage, pulse sequence, etc. 
         [0017]    In a further embodiment, the control unit is connected to measuring devices on the internal combustion engine which deliver data on, for example, pressure, mass flow rate, temperature, etc., which are significant not only for the control unit but also for the engine control device. The control unit can pass on these data to the engine control device to which it is connected, for example via a data bus. As a result, expenditure on cabling is saved, also allowing data to be transmitted more reliably. 
         [0018]    By comparing the setpoint values which correspond to the current operating data with the current intake pressure values, the control unit adjusts the actuating element in order to reduce the cross section of the actuating section when the current intake pressure is too high. When the current intake pressure is too low, the actuating element is adjusted in order to increase the cross section of the actuating section. Simple regulation of the intake pressure of the internal combustion engine is therefore possible. An excessively high compressor pressure with an excessively high mass flow rate is easily reduced by making the cross section smaller through a corresponding, diminishing position of the actuating element which may be, for example, a flap. 
         [0019]    In an alternative embodiment, when the current intake pressure is too low and the compressor pressure is too low, additional compressed air can be blown into the intake line, wherein the actuating element is adjusted under the control of the control unit in order to make the cross section of the actuating section smaller so as to prevent a backflow into the compressor. When the feeding in of compressed air ends, the actuating element is adjusted so as to make the cross section of the actuating section larger. For this purpose, the actuating section has, downstream of the actuating element in the direction of flow, an additional duct for the regulated, temporary feeding in of compressed air as a function of operating data of the internal combustion engine. Compressed air can also be fed in as a function of other operating data, for example in order to overcome the abovementioned turbo lag. 
         [0020]    An inventive device for regulating an intake pressure of an internal combustion engine, in particular diesel engine, having an exhaust gas turbocharger, has the following: 
         [0021]    an actuating section for connecting the intake line of the internal combustion engine to a compressor of the exhaust gas turbocharger; 
         [0022]    an actuating element which is arranged in the actuating section and has an adjustment drive for changing a cross section of the actuating section; 
         [0023]    a first pressure sensor for measuring a current compressor pressure of a compressor of the exhaust gas turbocharger; 
         [0024]    a second pressure sensor for measuring the current intake pressure in the intake line of the internal combustion engine; and 
         [0025]    a control unit for comparing measured data of the pressure sensors with setpoint values which correspond to current operating data of the internal combustion engine, and for generating actuating signals in order to adjust the actuating element with the adjustment drive in order to regulate the intake pressure as a function of the measured data of the pressure sensors and current operating data of the internal combustion engine. For particularly advantageous regulation, it is expedient if the actuating element can be adjusted by an adjustment drive in an infinitely variable fashion with position feedback. However, the setting positions of the actuating element can, of course, also be embodied in an incremental fashion. 
         [0026]    In an alternative embodiment, there is provision that the actuating section has an additional duct for letting in compressed air. As a result, a combined, advantageous device for regulating the intake pressure for adapting it to the operating states of the internal combustion engine is provided, and the actuating section is provided as a fresh air line section of a device for supplying fresh air for the controlled blowing in of compressed air. 
         [0027]    Other objects, advantages and novel features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  shows a schematic illustration of an internal combustion engine with an exhaust gas turbocharger and a device according to an embodiment of the present invention for regulating an intake pressure of the internal combustion engine; and 
           [0029]      FIG. 2  shows a schematic sectional illustration of an exemplary embodiment of an actuating section of the device according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Identical components or functional units with the same function are characterized by the same reference symbols in the figures. 
         [0031]      FIG. 1  shows a schematic illustration of an internal combustion engine  1  with an exhaust gas turbocharger  9  and a device according to the invention for regulating an intake pressure P 3  in an intake line  3  of the internal combustion engine  1 . The internal combustion engine  1  is, in this example, a diesel engine with six cylinders  2 , the intake line  3  and an exhaust line  4 . The intake line  3  is connected via an actuating section  10  to a compressor  12  of the exhaust gas turbocharger  9 , which is connected via an air filter  7  to the air inlet  5  for fresh air FL at an inlet pressure P 1 . The compressor  12  of the exhaust gas turbocharger  9  is coupled to an exhaust gas turbine  13  which is arranged in the exhaust line  4  upstream of an exhaust gas outlet  6  for exhaust gas AG of the internal combustion engine  1  and is driven by the exhaust gas AG. The compressor  12  generates a compressor pressure P 2  during operation of the internal combustion engine  1 , as a function of the exhaust gas flow rate and exhaust gas pressure of said internal combustion engine  1 . 
         [0032]    In this example, the actuating section  10  is also connected to a compressed air line  11  for feeding in compressed air DL. The compressed air DL is, for example, stored in a compressed air vessel and/or is generated by a compressed air system (not shown). For example, the latter can be a compressed air-generating system or an additional system which is present in a utility vehicle. 
         [0033]    An engine control device  8  is connected to injection systems of the cylinders  2 . In this respect, only one control line  14  is indicated symbolically. A further connection  15  is connected to a control unit  16  of the actuating section  10 . The engine control device  8  controls the internal combustion engine  1  in a known fashion and is not explained in more detail. It receives further measured data from the control unit  16  via the connection  15 , and this is explained in more detail below. 
         [0034]    The actuating section  10  is in this example a fresh gas line section or fresh air line section such as is described in DE 10 2006 008 783 A1 and DE 10 2006 008 785 A1 in conjunction with an associated compressed air-generating means. A more detailed explanation will therefore not be given here. 
         [0035]      FIG. 2  is a schematic illustration of a longitudinal section through an exemplary embodiment of the actuating section  10  together with associated functional units. 
         [0036]    The actuating section  10  is composed of a tubular body which is connected by its right-hand side to an inflow section  28  for a fresh air inflow  17  to the compressor  12  of the exhaust gas turbocharger  9  (see  FIG. 1 ). Furthermore, an actuating element  20  in the form of a flap is arranged so as to be pivotable about a rotational axis  21  in the direction of flow (from right to left in  FIG. 2 ). The actuating element  20  is coupled to an adjustment unit  22  and a position sensor  23 . The through-cross section of the tubular body of the actuating section  10 , and therefore the inflow  17 , are embodied in a variable fashion with the actuating element  20 . In this example, the adjustment unit  22  is embodied for infinitely variable adjustment of the actuating element  20 . 
         [0037]    In the left-hand region of the actuating section  10 , an outflow section  29  is arranged which is connected to the intake line  3  for an outflow  18  (see  FIG. 1 ) and in which the intake pressure P 3  prevails. In this example, an additional duct  27  is arranged on the underside in the outflow section  29 , which additional duct  27  communicates by one end with the outflow section  29 . The other end of the supply section  27  is connected to a valve  30  which is embodied here as a solenoid valve and is embodied with its connection side for a compressed air inflow  19  of the compressed air line  11  (see  FIG. 1 ). 
         [0038]    The actuating section  10  also respectively has a measuring duct  26  upstream of the actuating element  20  in the direction of flow in the inflow section  28 , and downstream of the actuating element  20  in the direction of flow in the outflow section  29 . A measuring device  24 ,  25  is connected to each measuring duct  26 , each of which measuring devices  24 ,  25  is a pressure sensor in this example. 
         [0039]    The control unit  16  of the actuating section  10  is connected to the adjustment unit  22  and the position sensor  23  of the control element  20 , the measuring devices  24 ,  25  and to the valves  30  and  37 . Furthermore, it is connected to the engine control device  8  and has a port  31  for further connections, for example pressure sensors, temperature sensors, etc., of the exhaust gas line and/or of the exhaust gas turbocharger or at another location. 
         [0040]    The function of this device will now be described. 
         [0041]    If the intake pressure P 3  decreases owing to a certain operating condition of the internal combustion engine  1 , this operating condition is detected by sensors of the internal combustion engine  1 , for example sensors for the rotational speed, pressure, temperature. These measured values are available in the engine control device  8  and on a bus if a bus system is present in the vehicle, and said measured values can be called by the control unit  16 , for example via the connection  15  to the engine control device  8  and/or via the port  31 . The control unit  16  then determines, on the basis of these current operating data, a setpoint value, corresponding to this current operating state, for the intake pressure P 3  of the internal combustion engine  1 . 
         [0042]    The current value of the intake pressure P 3  is acquired by the second pressure sensor  25  and transferred to the control unit  16 . The associated current value of the compressor pressure P 2  is acquired by the first pressure sensor  25  and also transferred to the control unit  16 . The control unit  16  then compares the current value of the intake pressure P 3  with the setpoint value acquired on the basis of the operating data. Said setpoint value can also be stored in table form in a memory device. Calculation by means of a suitable algorithm is also possible. 
         [0043]    If the current value of the intake pressure P 3  is considered to be too high after this comparison by the control unit  16 , that is to say a difference between the current intake pressure P 3  and the setpoint value is, for example, greater than zero, said control unit  16  generates an actuating signal and transfers it to the adjustment unit  22  for adjusting the actuating element  20 , which makes the cross section of the inflow section  28  smaller as a function of the current excessively high intake pressure P 3 . As a result, although the compressor pressure P 2  upstream of the actuating element  20  is increased, the air flow rate which is let through decreases, with the effect that the intake pressure P 3  decreases until the difference between the current intake pressure P 3  and the setpoint value becomes zero. The control unit  16  can therefore regulate an intake pressure P 3  which is the optimum one for the respective operating state of the internal combustion engine  1 . The position sensor  23 , which transfers a current position of the actuating element  20  to the control unit  16 , is also used for this purpose, and a let-through air flow rate of the inflow section  29  can be calculated or acquired from said current position, for example again by means of stored table values. As a result, the fuel consumption is reduced and the performance of the internal combustion engine  1  is improved. 
         [0044]    If the intake pressure P 3  is too low, the control unit  16  controls the actuating element  20  in such a way that the cross section of the inflow section  29  is made larger and the intake pressure P 3  increases until the difference becomes zero again. 
         [0045]    In the exemplary embodiment shown here with the connection of the compressed air line  11 , if the compressor pressure P 2 , measured by the first pressure sensor  24 , is too low, the valve  30  is opened and compressed air DL is blown as compressed air inflow  19  through the additional duct  27  into the actuating section  10  and therefore into the intake line  3  in order to increase the intake pressure P 3 . In this context, the control unit  16  simultaneously actuates the actuating element  20  in such a way that it prevents the compressed air inflow  19  from flowing back into the inflow section  29  by making the cross section of the inflow section  29  smaller or by closing it. 
         [0046]    Through selective setting of the actuating element  20  and also of the valve  30 , it is possible to regulate the intake pressure P 3  by measured pressure values in the intake line  3  in such a way that the associated intake pressure P 3  is regulated for the respective operating state of the internal combustion engine  1 . The compressed air supply can also be used to overcome what is referred to as a turbo lag, for example when accelerating, in a way which is independent of the regulation of the intake pressure P 3 , as is stated above. 
         [0047]    The invention is not restricted to the exemplary embodiments described above. It can be modified within the scope of the appended claims. For example: 
         [0048]    The valve  30  can also be controlled pneumatically or electro-pneumatically. 
         [0049]    The actuating section  10  can be a fresh gas line section of the compressed air device described in German Patent Publication Nos. DE 10 2006 008 783 A1 and DE 10 2006 008 785 A1 and can be coupled to it. 
         [0050]    The control unit  16  can also be a component of the engine control device  8 . 
         [0051]    Furthermore, the control unit  16  can be connected to measuring devices of the internal combustion engine  1 , which measuring devices supply measured values relating to the pressure, temperature, mass flow rate, etc. These values do not have to be relevant to the control unit  16 . However, said control unit  16  can, for example, process or adapt said values and/or pass them on to the engine control device  8 . In this context, for example, the associated installation work for cables is dispensed with, which cuts costs. 
         [0052]    The actuating element  20  may be embodied, for example, as a flap or differently. For example, an actuating valve could be used, but in such a case its actuating time would have to be taken into account. 
         [0053]    The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof. 
       LIST OF REFERENCE SYMBOLS 
       [0000]    
       
         Internal combustion engine 
         Cylinder 
         Intake line 
         Exhaust line 
         Air inlet 
         Exhaust gas outlet 
         Air filter 
         Engine control device 
         Exhaust gas turbocharger 
         Actuating section 
         Compressed air line 
         Compressor 
         Exhaust gas turbine 
         Control line 
         Connection 
         Control unit 
         Fresh air inflow 
         Outflow 
         Compressed air inflow 
         Actuating element 
         Rotational axis 
         Adjustment unit 
         Position sensor 
         First pressure sensor 
         Second pressure sensor 
         Measuring duct 
         Additional duct 
         Inflow section 
         Outflow section 
         Valve 
         Port 
         AG Exhaust gas 
         DL Compressed air 
         FL Fresh air 
         P 1  Inlet pressure 
         P 2  Compressor pressure 
         P 3  Intake pressure