JP5434142B2 - Control device for variable nozzle turbocharger - Google Patents

Description

  The present invention relates to a control device for a variable-nozzle variable turbocharger having a variable nozzle.

  2. Description of the Related Art As a turbocharger that is driven by engine exhaust energy and supercharges intake air, a variable displacement type equipped with a variable nozzle is known. In Patent Document 1, exhaust energy is obtained from an intake air amount representing an exhaust flow rate and a fuel injection amount, and a target opening degree of a variable nozzle at the time of transition is set based on the exhaust energy.

JP 2006-299828 A

  However, the exhaust energy upstream of the exhaust turbine that is actually received by the exhaust turbine, that is, the turbine inlet energy, changes according to the engine operating state even at the same exhaust flow rate. For example, the temperature and pressure on the upstream side of the exhaust turbine are different between a transient state where the engine load changes, such as during acceleration and deceleration, and a steady state where the engine load does not change. The entrance energy will be different. Therefore, the exhaust energy supplied to the exhaust turbine cannot be accurately predicted only from the exhaust flow rate, and even if the target opening of the variable nozzle is set from the exhaust energy, the setting accuracy is low.

  The present invention has been made in view of such problems. That is, a variable nozzle turbocharger according to the present invention includes an exhaust turbine provided in an exhaust passage of an engine, a variable nozzle provided in an opening on the inlet side of the exhaust turbine, and adjusting a capacity of the turbocharger. And an actuator that drives the variable nozzle in accordance with the target opening value. The control device of the present invention calculates turbine inlet energy based on the exhaust flow rate, the turbine inlet temperature upstream of the exhaust turbine, and the turbine inlet pressure upstream of the exhaust turbine, and the turbine inlet The opening degree target value is set based on energy.

  The exhaust flow rate (mass flow rate) is obtained, for example, by adding the intake flow rate (mass flow rate) detected by an air flow meter and the fuel injection amount. The turbine inlet temperature uses, for example, a sensor output value of a turbine inlet temperature sensor provided on the upstream side of the exhaust turbine, and preferably takes into account changes in the fuel injection amount so as to compensate for the response delay of this temperature sensor. Desired. The turbine inlet pressure is detected by, for example, a turbine inlet pressure sensor provided on the upstream side of the exhaust turbine.

  According to the present invention, the turbine inlet energy supplied to the exhaust turbine can be accurately estimated in consideration of the exhaust flow rate, the turbine inlet temperature upstream of the exhaust turbine, and the turbine inlet pressure. Based on the inlet energy, the target opening value of the variable nozzle can be set with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS The structure explanatory drawing which shows the whole structure of the diesel engine to which the control apparatus of the variable nozzle turbocharger which concerns on one Example of this invention was applied. Configuration diagram. The characteristic view which shows the control map of a nozzle opening target value. The calculation block diagram which shows the calculation process of turbine inlet_port | entrance energy. The calculation block diagram which shows the correction calculation process of turbine inlet_port | entrance temperature. The characteristic view which shows the control map of a temperature correction basic value. Explanatory drawing which shows the change of the boost pressure of a present Example and a comparative example. Explanatory drawing which shows the change of the turbine inlet pressure of a present Example and a comparative example.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an overall configuration of a diesel engine 1 to which an embodiment of the present invention is applied. The EGR passage 4 connecting the exhaust passage 2 and the collector portion 3a of the intake passage 3 so as to supply exhaust gas to the intake passage 3 is provided with a diaphragm type EGR valve 6 that responds to a control pressure from a pressure control valve (not shown). ing. The EGR valve 6 is controlled by the control unit 5 via the pressure control valve, and obtains a predetermined EGR rate (exhaust recirculation amount / (intake air amount + exhaust recirculation amount)) according to operating conditions. Yes. For example, the EGR rate becomes maximum in the low speed and low load region, and the EGR rate decreases as the rotational speed and load increase. In the vicinity of the intake port of the intake passage 3, an electrically controlled throttle valve 9 for adjusting the intake air amount (fresh air amount) is provided, and the opening degree of the throttle valve 9 is controlled by the control unit 5.

  The diesel engine 1 includes a common rail fuel injection device 10. In the common rail type fuel injection device 10, the fuel pressurized by the supply pump 11 is temporarily stored in the pressure accumulating chamber (common rail) 13 through the high pressure fuel supply passage 12, and then, from the pressure accumulating chamber 13 to each cylinder. The fuel is distributed to the fuel injection nozzles 14 and injected according to the opening and closing of the fuel injection nozzles 14. The fuel pressure in the pressure accumulating chamber 13 is variably adjusted by a pressure regulator (not shown), and the pressure accumulating chamber 13 is provided with a fuel pressure sensor 15 for detecting the fuel pressure. .

  The diesel engine 1 further includes a variable nozzle turbocharger 21 that is provided with an exhaust turbine 22 and a compressor 23 on the same axis. The exhaust turbine 22 is located on the downstream side of the branch point of the EGR passage 4 of the exhaust passage 2, that is, the exhaust intake port 4A, and the capacity of the turbocharger is provided at the inlet side opening portion of the exhaust turbine 22, that is, the scroll inlet. This is a variable capacity type configuration having a variable nozzle 24 for adjusting the above. That is, when the opening of the variable nozzle 24 is small, the characteristics of the small capacity are suitable for conditions with a small exhaust flow rate such as a low speed region, and when the opening of the variable nozzle 24 is large, the characteristic is as in the high speed region. Large capacity characteristics suitable for conditions with a large exhaust flow rate. The variable nozzle 24 is driven by a diaphragm actuator 25 that responds to a control pressure (control negative pressure), and the control pressure is generated through a pressure control valve 26 that is duty-controlled.

  In the exhaust passage 2 on the downstream side of the exhaust turbine 22, as a catalyst for purifying the exhaust gas, in order from the upstream side, an oxidation catalyst 27, a NOx purification catalyst 28 that adsorbs, desorbs and purifies NOx in the exhaust, and exhaust gas A particulate trapping filter or DPF 29 is provided as an exhaust aftertreatment device that traps exhaust particulate (PM) therein and periodically removes or regenerates the deposited PM by a method such as combustion.

  An air flow meter 31 for detecting the amount of intake air, that is, the amount of fresh air is disposed upstream of the compressor 23 interposed in the intake passage 3, and an air cleaner 32 is positioned further upstream. An intercooler 33 is provided between the compressor 23 and the collector unit 3a to cool the supercharged hot air.

The control unit 5 that controls the pressure control valve 26 and the like includes a supercharging pressure sensor 41 that detects a supercharging pressure, a water temperature sensor 42 that detects a cooling water temperature, an accelerator, in addition to the detection signal of the air flow meter 31 described above. an accelerator opening sensor 43 that detects the depression amount of the pedal, the intake air temperature sensor 44 for detecting the intake air temperature, the rotational speed sensor 45 for detecting an engine rotational speed, provided on the upstream side of the exhaust turbine 22 in the exhaust passage 2, the turbine inlet A turbine inlet pressure sensor 46 that detects the pressure RPTIN, a turbine inlet temperature sensor 52 that is provided upstream of the exhaust turbine 22 in the exhaust passage 2 and outputs a sensor output value RTTIN corresponding to the turbine upstream temperature, and an oxidation catalyst in the exhaust passage 2 27 to the first oxygen sensor 47 for detecting the oxygen concentration upstream of the exhaust passage 2 A second oxygen sensor 48 for detecting the oxygen temperature between the NOx purification catalyst 28 and the DPF 29; an inlet temperature sensor 49 for detecting the inlet temperature of the DPF 29; an outlet temperature sensor 50 for detecting the outlet temperature of the DPF 29; Detection signals of sensors such as the DPF differential pressure sensor 51 for detecting the differential pressure are input.

  The turbine inlet pressure sensor 46 and the turbine inlet temperature sensor 52 are disposed in the vicinity of the exhaust outlet 4A of the EGR passage 4, and these sensor signals are used for actual EGR in addition to calculation of turbine inlet energy described later. It is also used for rate detection and estimation.

  In this embodiment, the turbine inlet energy EN_TIN on the upstream side of the exhaust turbine 22, which is the exhaust energy supplied to the exhaust turbine 22, is calculated. Based on the turbine inlet energy EN_TIN and the EGR rate, the variable nozzle 24 The target opening value is set. The actuator 25 of the variable nozzle 24 is driven so that the nozzle opening that is the opening target value is obtained. As shown in FIG. 2, the nozzle opening target value is basically set to the open side as the turbine inlet energy increases, and to the closed side as the EGR rate increases. The signal that is actually output to the actuator 25 is given in the form of an ON duty ratio of a pulse signal that drives the pressure control valve 26 that generates the control pressure (negative pressure). Is output to the actuator 25.

Here, the turbine inlet energy EN_TIN is expressed by the following formula (1).
EN_TIN = CP × EQH_EXH × ETTIN + 1 / 2u ² × EQH_EXH (1)
“CP” is a constant pressure specific heat, “ETTIN” is the turbine inlet temperature, and “u” is the flow velocity upstream of the exhaust turbine 22. “EQH_EXH” is an exhaust flow rate (mass flow rate), and is obtained by adding the intake flow rate (mass flow rate) detected by the air flow meter 31 and the fuel injection amount.

Of the temperature sensor 52 and the pressure sensor 46 provided on the upstream side of the exhaust turbine 22, in general, the temperature sensor has low responsiveness at the time of transition and its detection accuracy is low, whereas the pressure sensor 46 is at the time of transition. Excellent response and high detection accuracy. Therefore, in order to improve the estimation accuracy of the turbine inlet energy EN_TIN, the above equation (1) is transformed into the following equation (2), and the turbine inlet pressure RPTIN detected by the pressure sensor 46 is used. Further, since the flow velocity at the inlet portion of the exhaust turbine 22 is slow, the “½u ² ” is a very small value, and the influence on the estimation accuracy is small, and is omitted.

EN_TIN = CV × EQH_EXH × ETTIN + RPTIN × V (2)
“CV” is a constant volume specific heat, which is a fixed value unique to the engine. “V” is a volume flow rate of the cylinder, and is obtained by multiplying the cylinder volume KVCE and the engine speed NE. “CV × EQH_EXH × ETTIN” on the right side corresponds to temperature energy, and “RPTIN × V” corresponds to pressure energy.

  FIG. 3 is a calculation block diagram showing the specific calculation contents of such turbine inlet energy EN_TIN. As shown in the figure, in actuality, after the exhaust temperature ETTIN is converted to an absolute temperature in the block B1, the unit of temperature energy is converted in the block B2 using the unit conversion coefficient KCONJ, and the unit in the block B3. The unit of the engine speed of pressure energy is converted using the conversion coefficient KCONM.

  FIG. 4 is a calculation block diagram showing a calculation process for compensating for a response delay of the turbine inlet temperature sensor 52. At the time of transition such as acceleration or deceleration, the actual turbine inlet temperature fluctuates mainly due to a change in fuel injection amount accompanying a change in engine load. The turbine inlet temperature ETTIN is obtained by correcting the sensor output value RTTIN of the turbine inlet temperature sensor 52 so as to compensate for the response delay of the temperature sensor 52 with respect to such temperature fluctuation.

  Specifically, first, temperature correction basic values are calculated for each of three main injections, after-injections, and post-injections having different injection timings. This is because the ratio of the fuel injection amount that contributes to the torque (that is, the ratio that is burned in the cylinder and taken out as engine output torque) differs from the ratio that does not contribute to the torque, depending on the individual injection. This is because, among the fuel injection amount that does not contribute to the above, the ratio of contribution to the increase of the turbine inlet energy, that is, the turbine inlet temperature by the combustion on the upstream side of the exhaust turbine 22 or in the exhaust turbine 22 is different.

  After-injection, which is injected after the main injection to obtain output, burns the unburned fuel remaining in the cylinder and suppresses the discharge of unburned fuel, contributing to torque more than the main injection The ratio of the fuel to be reduced is small, and the ratio that contributes to the increase of the turbine inlet temperature is relatively high. The post-injection injected after this after-injection is not intended to burn in the cylinder, but is intended to send fuel to the exhaust passage, mainly for soot combustion in the catalyst and catalyst temperature rise. The ratio of the fuel that contributes to the torque is smaller than that of the injection, and the ratio that contributes to the increase of the turbine inlet temperature is high.

  The same processing is performed for each injection, but the main injection will be described as an example. In block B11, the difference between the current fuel injection amount QFIN and the fuel injection amount 1 / Z before the calculation (for example, 10 ms before) is calculated. A change amount (change rate / change speed) D_QFIN of the fuel injection amount is obtained, and based on the fuel change amount D_QFIN and the engine rotational speed NE, a control map of a preset temperature correction basic value in FIG. The fuel injection amount exhaust temperature conversion map M_KTIN_DQF is looked up, and a temperature correction basic value KTIN_DQF converted into a change in the turbine inlet temperature is calculated. As shown in FIG. 5, for example, when the fuel change amount D_QFIN increases during acceleration, the temperature correction basic value KTIN_DQF increases, and the turbine inlet temperature is corrected to the high temperature side.

  Similarly, after-injection and post-injection, the fuel change amounts D_QAFTERED and D_QPOSTED are obtained in blocks B12 and B13, respectively, and the after-injection amount exhaust temperature conversion maps M_KTIN_DQA and M_KTIN_DQP at the time of transition are obtained from this and the engine speed NE. Then, temperature correction basic values KTIN_DQA and KTIN_DQP are calculated.

  Here, as described above, the ratio of the fuel injection amount that does not contribute to the torque and contributes to the increase in the turbine inlet temperature is different, so that the exhaust temperature conversion map is adapted in advance for each injection. Have become separate.

  In block B14, an exhaust temperature pressure correction coefficient K_TBMPP is calculated based on the atmospheric pressure PATM and the turbine inlet pressure RPTIN. In block B15, the temperature correction basic values KTIN_DQF, KTIN_DQA, and KTIN_DQP at the three injection timings are added. In block B16, this added value is multiplied by the exhaust temperature correction coefficient K_TBMPP. That is, the temperature correction basic value is corrected by the atmospheric pressure PATM and the turbine inlet pressure RPTIN. In block B17, the multiplication value is subjected to a smoothing process (advance correction process) using the temperature sensor response time constant KTIN_T to calculate a final temperature correction value KTIN. In block B18, this temperature correction value KTIN is added to the output value RTTIN of the turbine inlet temperature sensor to obtain the final turbine inlet temperature ETTIN.

  The temperature sensor response time constant KTIN_T is obtained from the time constant map M_KTIN_T based on the exhaust flow rate EQH_EXH (or the exhaust temperature) and the engine speed NE in consideration of the heat capacity of the temperature sensor 52. In the annealing process in block B17, for example, a process of decreasing the temperature correction value KTIN with the passage of time is performed by multiplying the previous temperature correction value by a temperature sensor response time constant.

  As described above, in this embodiment, the ratio of the injected fuel that contributes to the increase of the turbine inlet temperature differs between the main injection, the after injection, and the post injection with different injection timings. By calculating the temperature correction basic value individually, the influence of each fuel injection on the turbine inlet temperature can be estimated with high accuracy, and the correction accuracy can be improved.

  In this way, because the turbine inlet energy is calculated in a manner that compensates for the response delay of the temperature sensor during a transient, the turbine inlet energy can be accurately calculated regardless of the engine operating state such as during steady state or transient state. Can do. Therefore, by setting the nozzle opening target value based on the turbine inlet energy and the EGR rate and performing feedforward control of the nozzle opening of the variable nozzle 24, it is possible to respond to engine operating conditions such as fuel injection amount and exhaust flow rate. It is also possible to omit the correction control and feedback control of the nozzle opening, greatly reducing the man-hours required for correction, and simplifying the control logic.

  With reference to FIGS. 6 and 7, characteristic A shows the characteristic of the present embodiment in which the nozzle opening target value is set by using the turbine inlet energy, and correction control and feedback control of the nozzle opening are omitted. The characteristic B shows the characteristic of the comparative example in which the nozzle opening target value is set based on the exhaust flow rate, and the correction control or feedback control of the nozzle opening is performed. The characteristic C is the target characteristic. Is shown. As shown in the figure, in this embodiment, although the correction control and feedback control of the nozzle opening are omitted, the boost pressure and the turbine inlet pressure (Ptin) rise quickly compared to the comparative example, It was confirmed that a characteristic close to the target characteristic C was obtained.

  In the above embodiment, the temperature correction basic value that contributes to the increase in the turbine inlet temperature is obtained from the change amount of the fuel injection amount and the engine rotation speed. However, the present invention is not limited to this, and the turbine inlet pressure, the exhaust air-fuel ratio, etc. It may be calculated in consideration of the above. Further, the turbine inlet temperature may be estimated from the engine speed, the fuel injection amount, the intake air-fuel ratio, the intake air temperature, etc. without using the temperature sensor.

  Furthermore, when using feedback correction control of the nozzle opening of the variable nozzle based on the supercharging pressure, when the turbine inlet energy exceeds a predetermined value, the feedback correction control is prohibited, and the turbine inlet energy and the EGR rate are You may make it switch to the feedforward control toward the nozzle opening target value set based on.

DESCRIPTION OF SYMBOLS 1 ... Diesel engine 2 ... Exhaust passage 5 ... Control unit 21 ... Variable nozzle turbocharger 22 ... Exhaust turbine 24 ... Variable nozzle 25 ... Actuator 26 ... Pressure control valve 46 ... Turbine inlet pressure sensor 52 ... Turbine inlet temperature sensor (temperature) Detection means)

Claims (7)

An exhaust turbine provided in the exhaust passage of the engine, a variable nozzle provided in an inlet side opening of the exhaust turbine and adjusting the capacity of the turbocharger, and driving the variable nozzle in accordance with a target opening value In a control device for a variable nozzle turbocharger comprising an actuator,
A turbine inlet temperature sensor that is provided upstream of the exhaust turbine and detects a turbine inlet temperature;
A turbine inlet pressure sensor for detecting a turbine inlet pressure upstream of the exhaust turbine;
Turbine inlet energy calculation means for calculating turbine inlet energy based on an exhaust flow rate, a turbine inlet temperature upstream of the exhaust turbine, and a turbine inlet pressure upstream of the exhaust turbine;
Opening target value setting means for setting the opening target value based on the turbine inlet energy;
Temperature correction means for correcting the sensor output value of the turbine inlet temperature sensor based on at least the amount of change in the fuel injection amount and calculating the turbine inlet temperature;
Have
The turbine inlet energy calculation means calculates the turbine inlet energy by adding the temperature energy obtained based on the exhaust flow rate and the turbine inlet temperature and the pressure energy obtained based on the turbine inlet pressure. ,
A control device for a variable nozzle turbocharger. An exhaust turbine provided in the exhaust passage of the engine, a variable nozzle provided in an inlet side opening of the exhaust turbine and adjusting the capacity of the turbocharger, and driving the variable nozzle in accordance with a target opening value In a control device for a variable nozzle turbocharger comprising an actuator,
Turbine inlet energy calculation means for calculating turbine inlet energy based on an exhaust flow rate, a turbine inlet temperature upstream of the exhaust turbine, and a turbine inlet pressure upstream of the exhaust turbine;
Opening target value setting means for setting the opening target value based on the turbine inlet energy;
A turbine inlet temperature sensor provided upstream of the exhaust turbine;
Temperature correction means for correcting the sensor output value of the turbine inlet temperature sensor based on at least the amount of change in the fuel injection amount and calculating the turbine inlet temperature;
A control device for a variable nozzle turbocharger. The temperature correction means calculates a temperature correction basic value for each fuel injection at different injection timings based on the change amount of the fuel injection amount and the engine speed, and outputs the sensor output based on these temperature correction basic values. 3. The variable nozzle turbocharger control device according to claim 1, wherein the turbine inlet temperature is calculated by correcting the value. The variable nozzle according to any one of claims 1 to 3, wherein the temperature correction means performs a smoothing process using a predetermined response time constant so that the temperature correction value decreases with time. Turbocharger control device. The above turbine inlet energy is EN_TIN,
Constant volume specific heat is CV,
The exhaust flow rate is EQH_EXH,
The turbine inlet temperature is ETTIN,
The turbine inlet pressure is RPTIN,
If the volume flow of the cylinder is V,
The turbine inlet energy calculation means includes:
EN_TIN = CV × EQH_EXH × ETTIN + RPTIN × V
The control device for a variable nozzle turbocharger according to any one of claims 1 to 4 , wherein the turbine inlet energy is calculated by the above equation. It said temperature correction means, according to claim 1 or 2, characterized in that the direction of correction by the change of the post injection amount than the correction due to a change in the main injection amount is increased corrects the sensor output value of the turbine inlet temperature sensor Variable nozzle turbocharger control device. An EGR valve capable of adjusting the EGR rate is provided in the EGR passage for returning the exhaust gas to the intake passage.
The variable opening turbocharger according to any one of claims 1 to 6, wherein the opening degree target value setting means sets the opening degree target value based on the turbine inlet energy and the EGR rate. Machine control device.

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