JP2009013963A - Control device of turbocharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of further surely restraining damage by resonance of a turbine wheel, in a turbocharger having a variable nozzle. <P>SOLUTION: Three kinds of physical quantities of a turbo-rotating speed, turbine inlet pressure and variable nozzle opening are detected. When the whole these detecting values belong to an area prearranged to the respective detecting devices and capable of inducing the resonance of the turbine wheel, it is determined that the turbocharger becomes a state of inducing fatigue failure by the resonance of the turbine wheel (a fatigue accumulation state). When determining that the turbocharger becomes the fatigue accumulation state, the variable nozzle opening is changed, and the fatigue accumulation state is eliminated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a turbocharger control device for an internal combustion engine, and more particularly to a turbocharger control device having a variable nozzle.

  2. Description of the Related Art Conventionally, internal combustion engines for automobiles and the like are known in which a turbocharger is provided as a supercharger in order to improve output. Such a turbocharger includes a turbine wheel that rotates by blowing exhaust gas from an internal combustion engine, and a compressor wheel that rotates integrally with the turbine wheel and forcibly feeds air toward a combustion chamber of the internal combustion engine.

  As a turbocharger, a variable nozzle type that adjusts the supercharging pressure (intake pressure) of an internal combustion engine by changing the flow rate of exhaust gas blown to the turbine wheel has been proposed. In such a type of turbocharger, by opening and closing a variable nozzle (nozzle vane) provided on the exhaust path for blowing exhaust to the turbine wheel, the exhaust flow area of the exhaust path is changed, and the exhaust blown to the turbine wheel is changed. The flow rate is variable.

  Generally, in a turbocharger used to improve the output of an internal combustion engine mounted on a vehicle, a turbine wheel is provided in the turbine housing, and a compressor wheel is provided in the compressor housing. These turbine wheel and compressor wheel Are connected to each other by a rotor shaft so as to be integrally rotatable.

  Then, when the exhaust gas flowing through the exhaust passage of the internal combustion engine flows into the turbine housing, it passes through the turbine scroll around the turbine wheel and is then sprayed onto the turbine wheel. When the turbine wheel is rotated by the exhaust blowing, the rotation is transmitted to the compressor wheel via the rotor shaft, and the compressor wheel rotates. The air introduced into the internal combustion engine is supercharged by the rotation of the compressor wheel.

  In this connection, when the turbine wheel is rotated, the turbine wheel is vibrated at a frequency determined by the number of nozzles of the variable nozzle, and the turbine wheel may be damaged by inducing resonance. On the other hand, a technique is provided in which grooves in the circumferential direction are provided in the wall portion forming the fluid inlet channel of the variable nozzle to reduce the pressure difference in the nozzle and prevent damage to the turbine wheel (see, for example, Patent Document 1). ), And a technique for suppressing excitation at a frequency close to the natural frequency of the turbine wheel by making the pitch of the variable nozzles non-uniform (see, for example, Patent Document 2), after an engine stop operation, A technique is proposed in which the variable nozzle is controlled to the closed side after it is determined that the rotation of the engine has stopped, and the flow rate of the exhaust gas blown to the turbine wheel is prevented from becoming too fast (see, for example, Patent Document 3). ing.

However, the fatigue failure of the turbine wheel is caused by factors that affect the frequency of the force that excites the resonance of the turbine wheel, such as the number of turbo revolutions and the number of nozzles, and the factor that affects the excitation force that vibrates the turbine wheel. In some cases, it is difficult to sufficiently suppress the fatigue failure of the turbine wheel by the above-described conventional technology.
JP 2004-116313 A Japanese Patent Laid-Open No. 8-61002 JP 2003-129854 A

  An object of the present invention is to provide a technology that can more reliably suppress damage due to resonance of a turbine wheel in a turbocharger including a variable nozzle.

  In order to achieve the above object, the present invention has the following features. That is, it is determined whether the state of the turbocharger is a state in which damage due to resonance of the turbine wheel is induced based on the three factors of the turbo rotation speed, the turbine expansion ratio, and the variable nozzle opening. And when it determines with the state of a turbocharger being the state which induces the damage by resonance of a turbine wheel, a variable nozzle opening degree is changed and the said state in a turbocharger is canceled.

More specifically, a control device for a variable nozzle type turbocharger having a variable nozzle capable of changing an exhaust flow area when exhaust gas of an internal combustion engine is blown to a turbine wheel,
The turbocharger is induced to be damaged by resonance of the turbine wheel on the basis of the turbo rotation speed, the turbine expansion ratio that affects the excitation force by the exhaust to the turbine wheel, and the opening of the variable nozzle. Damage induction determination means for determining whether or not it is in a damage induction state;
A breakage induction state elimination means for eliminating the breakage induction state of the turbocharger by changing the opening of the variable nozzle when the breakage induction determination means determines that the turbocharger is in the breakage induction state; ,
It is characterized by providing.

  Here, in the variable nozzle type turbocharger, it is known that the resonance of the turbine wheel is easily induced when the excitation frequency determined from the turbo rotation speed and the number of nozzles is close to the natural frequency of the turbine wheel. . On the other hand, in the present invention, in addition to the condition that the excitation frequency of the turbine wheel is close to its natural frequency, the resonance of the turbine wheel is satisfied when the condition that the excitation force of the turbine wheel is larger than a certain level is satisfied. Focused on the triggering.

  And in the present invention, based on the three factors of the turbo rotation number that determines the excitation frequency of the turbine wheel, the turbine expansion ratio that determines the excitation force to the turbine wheel, and the opening of the variable nozzle, It is determined whether or not the turbocharger is in a damage-inducing state in which damage due to turbine wheel resonance is induced. Furthermore, in the present invention, when it is determined that the turbocharger is in the damage induction state, the opening degree of the variable nozzle is changed to cancel the damage induction state.

  According to this, the turbocharger is in a state of inducing damage based on not only the turbo rotation speed that determines the excitation frequency of the turbine wheel but also the turbine expansion ratio that determines the excitation force to the turbine wheel and the opening of the variable nozzle. It can be determined whether or not. Therefore, the damage induction state can be determined with higher accuracy. If it does so, while being able to suppress more reliably the damage by the resonance of a turbine wheel, it can suppress that the opening degree of a variable nozzle is changed wastefully, and it becomes possible to maintain the operating performance of an internal combustion engine favorably.

In the above description, the damage due to the resonance of the turbine wheel includes that the turbine blade of the turbine wheel is actually destroyed due to resonance, and that fatigue is accumulated due to resonance and fatigue failure is promoted. . The turbine expansion ratio means the exhaust expansion rate before and after flowing into the turbine, and is actually defined by (pressure at the turbine inlet / pressure at the turbine outlet).

Further, in the present invention, the breakage induction determining means includes a variable nozzle opening degree detecting means for detecting the opening degree of the variable nozzle, a turbo rotational speed detecting means for detecting the turbo rotational speed, and a turbine of the turbocharger. Turbine inlet pressure detecting means for detecting the pressure at the inlet of
In a variable range of the opening of the variable nozzle, a limit nozzle opening that is an opening of the upper limit variable nozzle that can increase the excitation force due to exhaust to the turbine wheel and induce damage due to resonance of the turbine wheel is Set,
In the fluctuation range of the turbo rotation speed, a resonance induction region that is a rotation speed range that easily induces resonance of the turbine wheel is set,
In the fluctuation range of the pressure at the turbine inlet, a limit turbine inlet pressure is set, which is a lower limit pressure that can increase the excitation force due to exhaust to the turbine wheel and induce damage due to resonance of the turbine wheel,
In the breakage induced state, the opening degree of the variable nozzle detected by the variable nozzle opening degree detecting means is equal to or less than the limit nozzle opening degree, and the turbo rotational speed detected by the turbo rotational speed detecting means is the resonance induction. The pressure at the turbine inlet that belongs to the region and is detected by the turbine inlet pressure detection means may be equal to or higher than the limit turbine inlet pressure.

  That is, in the present invention, the opening of the variable nozzle, the turbo rotation speed, and the pressure at the inlet of the turbine are detected by sensors, respectively, and the detected opening of the variable nozzle is equal to or less than the limit nozzle opening. When the turbo rotation speed belongs to the resonance induction region and the detected pressure at the turbine inlet is equal to or higher than the limit turbine inlet pressure, it is determined that the turbocharger is in a failure induction state. Since the value of the turbine expansion ratio can be estimated by acquiring the pressure at the turbine inlet, detecting the pressure at the turbine inlet in the present invention means detecting the turbine expansion ratio. Almost equal.

  According to this, since all of the turbo speed, the turbine expansion ratio, and the opening of the variable nozzle are directly detected, it is possible to more accurately acquire the states of the three main factors that induce damage due to turbine wheel resonance. it can. In addition, since it is determined whether or not the turbocharger is in a state of inducing breakage depending on whether or not all the detected values are within a range in which breakage caused by resonance of the turbine wheel can be induced in advance. It is possible to determine whether or not the turbocharger is in a damage induced state by a simpler method.

Further, in the present invention, the breakage induction determining means includes variable nozzle opening degree detecting means for detecting the opening degree of the variable nozzle, compressor outlet pressure detecting means for detecting the pressure at the compressor outlet of the turbocharger, Turbine inlet pressure detection means for detecting pressure at the turbine inlet of the turbocharger,
In a variable range of the opening of the variable nozzle, a limit nozzle opening that is an opening of the upper limit variable nozzle that can increase the excitation force due to exhaust to the turbine wheel and induce damage due to resonance of the turbine wheel is Set,
In the pressure fluctuation range at the outlet of the compressor, a resonance inducing pressure range that is a pressure range in which resonance of the turbine wheel is likely to occur is set.
In the fluctuation range of the pressure at the turbine inlet, a limit turbine inlet pressure is set, which is a lower limit pressure that can increase the excitation force due to exhaust to the turbine wheel and induce damage due to resonance of the turbine wheel,
In the breakage induced state, the opening of the variable nozzle detected by the variable nozzle opening detecting means is equal to or less than the limit nozzle opening, and the pressure at the compressor outlet detected by the compressor outlet pressure detecting means is the pressure at the compressor outlet. The pressure at the inlet of the turbine that belongs to the resonance-induced pressure range and is detected by the turbine inlet pressure detection means may be equal to or higher than the limit turbine inlet pressure.

  That is, in the present invention, instead of detecting the turbo rotational speed by the turbo rotational speed detecting means as described above, the pressure at the compressor outlet is detected by the compressor outlet pressure detecting means. Then, the fact that the pressure at the outlet of the compressor belongs to the resonance-induced pressure range may be changed to that the turbo rotation speed belongs to the resonance-induced region, and may be one of criteria for determining whether or not the turbocharger is in a damage-induced state.

  Here, it is known that the compressor outlet pressure detecting means is mounted on a vehicle in an actual market at a certain frequency. Therefore, according to the present invention, it is not necessary to provide the turbo rotational speed detecting means for this purpose, and the turbocharger is brought into a damage-inducing state by using the compressor outlet pressure detecting means provided for other purposes. It can be determined whether or not. As a result, simplification and cost reduction of the apparatus can be promoted.

Further, in the present invention, the breakage induction determining means includes variable nozzle opening degree detecting means for detecting the opening degree of the variable nozzle, compressor outlet pressure detecting means for detecting the pressure at the compressor outlet of the turbocharger, Have
In a variable range of the opening of the variable nozzle, a limit nozzle opening that is an opening of the upper limit variable nozzle that can increase the excitation force due to exhaust to the turbine wheel and induce damage due to resonance of the turbine wheel is Set,
In the pressure fluctuation range at the outlet of the compressor, a resonance inducing pressure range that is a pressure range in which resonance of the turbine wheel is likely to occur is set.
A correction means for correcting the value of the limit nozzle opening according to the engine speed and fuel injection amount of the internal combustion engine;
The breakage induced state is detected by the compressor outlet pressure detecting means, wherein the opening degree of the variable nozzle detected by the variable nozzle opening degree detecting means is equal to or less than the limit nozzle opening degree corrected by the correcting means. The pressure at the outlet of the compressor may belong to the resonance-induced pressure range.

  That is, in the present invention, as described above, instead of detecting the pressure at the turbine inlet by the turbine inlet pressure detecting means, the value of the limit nozzle opening is corrected by the engine speed and the fuel injection amount, so that the turbocharger is corrected. Was determined to be in a damage-induced state.

  Here, in the vehicle in the current market, the values of the engine speed and the fuel injection amount are generally detectable. In the present invention, the pressure at the inlet of the turbine is substituted by correcting the value of the limit nozzle opening by the values of the engine speed and the fuel injection amount that can be easily detected in this way. According to this, simplification and cost reduction of the apparatus can be further promoted.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  In the present invention, in a turbocharger including a variable nozzle, damage due to resonance of the turbine wheel can be more reliably suppressed.

The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a schematic diagram showing an internal combustion engine, an intake / exhaust system, and a control system thereof in the present embodiment. As shown in FIG. 1, the upstream portion of the intake passage 2 and the downstream portion of the exhaust passage 3 in the internal combustion engine 1 are each connected to a turbocharger 4. The turbocharger 4 includes a compressor wheel 5 for supercharging and sending air to the downstream side of the intake passage 2 and a turbine wheel 6 that rotates when the exhaust gas passing through the exhaust passage 3 is blown. When the turbine wheel 6 rotates, the compressor wheel 5 rotates integrally with the turbine wheel 6, thereby increasing the intake air amount of the internal combustion engine 1 and improving the output of the internal combustion engine 1.

  In the turbocharger 4, a variable nozzle 7 is provided on an exhaust path for blowing exhaust to the turbine wheel 6. The variable nozzle 7 is a valve mechanism that opens and closes to change the exhaust flow area of the exhaust path, and makes the flow rate of exhaust blown to the turbine wheel 6 variable by changing the exhaust flow area. As described above, in this embodiment, the rotational speed of the turbocharger 4 is changed by changing the flow rate of the exhaust gas, and the supercharging pressure (intake pressure) of the internal combustion engine 1 is adjusted.

  As an actuator for operating the variable nozzle 7, a direct current (DC) motor 9 that is driven and controlled by a control signal from the ECU 20 described later is employed. By driving this DC motor 9, the variable nozzle 7 is opened and closed. When the variable nozzle 7 is displaced to the closing side, the flow rate of the exhaust gas blown to the turbine wheel 6 is increased, the rotational speed of the turbocharger 4 is increased, and the supercharging pressure of the internal combustion engine 1 is increased. Further, when the variable nozzle 7 is displaced to the opening side, the flow rate of the exhaust gas blown to the turbine wheel 6 becomes small, the rotational speed of the turbocharger 4 becomes low, and the supercharging pressure of the internal combustion engine 1 decreases.

  The internal combustion engine 1 is provided with a crank position sensor 13 that detects an angle of a crankshaft (not shown). The intake passage 2 is provided with a compressor outlet pressure sensor 15 for detecting the pressure at the compressor outlet of the turbocharger 4, and the exhaust passage 3 is provided with a turbine inlet pressure sensor 17 for detecting the pressure at the turbine inlet. It has been. Further, a nozzle opening sensor 11 for detecting the opening of the variable nozzle 7 is provided in the vicinity of the DC motor 9 that drives the variable nozzle 7, and the turbo rotation speed is set near the compressor wheel 5 of the turbocharger 4. A turbo rotation sensor 19 for detection is provided.

  The internal combustion engine 1 is also provided with an ECU 20 for controlling the operation of the internal combustion engine 1. And each said sensor and ECU20 are electrically connected, The output signal from each sensor is input into ECU20.

  Here, as described above, when the variable nozzle 7 is displaced to the closing side, the exhaust gas from the internal combustion engine 1 is throttled when passing through the variable nozzle 7 and the flow velocity is increased. Then, due to the uneven flow in the circumferential direction of the exhaust accelerated by the variable nozzle 7, an excitation force having a frequency determined by the turbo rotation speed and the number of nozzles acts on the turbine wheel 6. When the frequency of the excitation force is close to the natural frequency of the turbine wheel 6, resonance of the turbine wheel 6 may be induced to induce fatigue failure of the turbine wheel 6.

On the other hand, conventionally, the turbo rotation speed of the turbocharger 4 is detected by the turbo rotation sensor 19, and the frequency of the excitation force determined by the turbo rotation speed and the number of nozzles of the variable nozzle 7 is the natural frequency of the turbine wheel 6. It was trying to detect that it was close to. In such a case, the fatigue failure of the turbine wheel 6 has been suppressed by changing the turbo rotation speed so that resonance is not induced in the turbine wheel 6.

  However, in practice, in addition to the frequency of the excitation force, the amplitude, that is, the intensity of the excitation force also affects the strength of resonance induced in the turbine wheel 6. Therefore, in order to avoid fatigue failure of the turbine wheel 6, it is necessary to control not only the frequency of the excitation force but also the factors that affect the strength of the excitation force.

  Therefore, in the present embodiment, the turbo rotation speed detected by the turbo rotation sensor 19 includes the pressure at the turbine inlet detected by the turbine inlet pressure sensor 17 and the variable nozzle opening detected by the nozzle opening sensor 11. It was decided to determine whether or not the turbocharger 4 is in a state that can induce fatigue failure of the turbine wheel 6 using the three factors added.

  Next, the principle of determining whether or not the turbocharger 4 can induce fatigue failure of the turbine wheel 6 due to the above three factors will be described with reference to FIG. The horizontal axis in FIG. 2 indicates the engine speed, and the vertical axis indicates parameters that affect the resonance of the turbine wheel 6. More specifically, the graph of the change in the variable nozzle opening that is feedback-controlled so that the internal combustion engine 1 maintains the maximum torque in accordance with the engine speed changes in the upper row and changes in accordance with the variable nozzle opening. The graph of the turbo rotation speed and the graph of the turbine inlet pressure are shown in the middle and lower stages.

  As shown in the figure, the variable nozzle opening as the target value of the feedback control increases as the engine speed increases. Further, as the engine speed and the variable nozzle opening increase, the turbo speed in the turbocharger 4 and the turbine inlet pressure also increase.

  Here, as shown in the upper part of FIG. 2, the variable nozzle opening is provided with a threshold value of the limit nozzle opening VN% 1, and the limit nozzle opening or a region closer to the limit nozzle opening is the turbine wheel 6. This is a large opening area of the excitation force that can induce resonance. That is, when the variable nozzle opening belongs to the large excitation force opening region, the passage area of the exhaust blown to the turbine wheel 6 is narrowed, so that the exhaust is blown from the variable nozzle 7 to the turbine wheel 6 with a stronger momentum. Therefore, in this region, the excitation force with respect to the turbine wheel 6 may increase, and resonance of the turbine wheel 6 may be induced.

  Further, as shown in the graph of the turbo rotational speed in the middle stage of FIG. 2, a turbine wheel resonance region where the turbo rotational speed is Nt1 or more and Nt2 or less is provided in the fluctuation range of the turbo rotational speed. This region is a region where the frequency of the excitation force applied to the turbine wheel 6 determined by the turbo rotation speed and the number of nozzles of the variable nozzle 7 (or the number of nozzle vanes) approaches the natural frequency of the turbine wheel 6. Therefore, resonance of the turbine wheel 6 is easily induced in this region.

  Further, as shown in the lower graph of the turbine inlet pressure in FIG. 2, a threshold value of a critical turbine inlet pressure Pi1 is provided in the range of fluctuation of the turbine inlet pressure, and the turbine inlet pressure is equal to or more than this value. The high region is an excitation force high pressure region in which resonance of the turbine wheel 6 can be induced. That is, when the turbine inlet pressure belongs to the large excitation force pressure region, the momentum of the exhaust blown to the turbine wheel 6 becomes stronger. Therefore, in this region, the excitation force with respect to the turbine wheel 6 may increase, and resonance of the turbine wheel 6 may be induced.

In this embodiment, the variable nozzle opening detected by the nozzle opening sensor 11 belongs to the large excitation force opening area, and the turbo rotation speed detected by the turbo rotation sensor 19 belongs to the turbine wheel resonance area. When the turbine inlet pressure detected by the turbine inlet pressure sensor 17 belongs to the large excitation force pressure region, it is determined that the turbocharger 4 is in a fatigue accumulation state in which fatigue failure due to resonance of the turbine wheel 6 is induced. It was decided to.

  More specifically, in the example of FIG. 2 (when the engine torque is full torque), it can be determined that the turbocharger 4 is in a fatigue accumulation state when the engine speed is within the range of ΔN.

  FIG. 3 is a graph showing the fatigue accumulation state in this example from a viewpoint different from FIG. In the graph of FIG. 3, the horizontal axis represents the variable nozzle opening, and the vertical axis represents the turbine inlet pressure. The curve in FIG. 3 is a curve when the fuel injection amount is changed at an arbitrary engine speed in 1 of the internal combustion engine, and the turbo speed is set to a constant value of Nt1 and Nt2. Therefore, in the graph in which the vertical axis and the horizontal axis are determined as described above, the excitation force large opening region, the excitation force large pressure region, and the turbine wheel resonance region are shown as in FIG. A region where the excitation force large opening region, the excitation force large pressure region, and the turbine wheel resonance region overlap corresponds to the fatigue accumulation state.

  In this embodiment, when it is determined that the turbocharger 4 is in a fatigue accumulation state, the variable nozzle opening is set to an opening larger than the target value of the feedback control as shown in the upper part of FIG. The variable nozzle opening was removed from the large excitation force opening region. If it does so, the fatigue accumulation state in the turbocharger 4 can be eliminated and the resonance of the turbine wheel 6 and the fatigue failure due to the resonance can be suppressed.

  FIG. 4 shows a flowchart of a fatigue accumulation state determination elimination routine in the present embodiment. This routine is a program stored in a ROM (not shown) provided in the ECU 20 and is executed by the ECU 20 at predetermined intervals while the internal combustion engine 1 is in operation.

  When this routine is executed, first, in S101, output signals from the turbo rotation sensor 19, the turbine inlet pressure sensor 17, and the nozzle opening sensor 11 are input to the ECU 20. As a result, the values of the variable nozzle opening VN%, the turbo rotation speed Nt, and the turbine inlet pressure Pi are read into the ECU 20. When the processing of S101 ends, the process proceeds to S102.

  In S102, the lower limit value and the upper limit values Nt1 and Nt2 of the turbo rotational speed that determine the turbine wheel resonance region, the lower limit value Pi1 of the turbine inlet pressure that determines the large excitation force pressure region, and the excitation force Reference is made to VN% 1, which is the upper limit value of the variable nozzle opening, which establishes the large opening region. Note that these values are stored in the ROM of the ECU 20 and are referred to by being read from the ROM. When the process of S102 ends, the process proceeds to S103.

  In S103, it is determined whether or not the turbo speed of the turbocharger 4 belongs to the turbine wheel resonance region. Specifically, the turbo rotation speed Nt read in S101 is compared with the lower limit value and the upper limit values Nt1 and Nt2 of the turbine wheel resonance region referred in S102, and Nt1> Nt or Nt> Nt2 is established. It is determined whether or not to do so. If an affirmative determination is made here, it is determined that the turbo rotation speed does not belong to the turbine wheel resonance region, so the routine proceeds to S108. On the other hand, if a negative determination is made, it is determined that the turbo rotation speed belongs to the turbine wheel resonance region, so the routine proceeds to S104.

In S104, it is determined whether or not the turbine inlet pressure belongs to the large excitation force pressure region. Specifically, the turbine inlet pressure Pi read in S101 is compared with Pi1, which is the lower limit value of the excitation force high pressure region referred to in S102, and it is determined whether Pi <Pi1 is satisfied. The If an affirmative determination is made here, it is determined that the turbine inlet pressure does not belong to the large excitation force pressure region, and thus the process proceeds to S108. On the other hand, if a negative determination is made, it is determined that the turbine inlet pressure belongs to the large excitation force pressure region, and thus the process proceeds to S105.

  In S105, it is determined whether or not the variable nozzle opening belongs to the large excitation force opening region. Specifically, the variable nozzle opening VN% read in S101 is compared with VN% 1, which is the upper limit value of the excitation force large opening area referred to in S102, and VN%> VN% 1 is established. It is determined whether or not to do so. If an affirmative determination is made here, it is determined that the variable nozzle opening does not belong to the excitation force large opening area, and the process proceeds to S108. On the other hand, if a negative determination is made, it is determined that the variable nozzle opening belongs to the large opening area of the excitation force, and the process proceeds to S106.

  Here, when S106 is executed, the turbine inlet pressure belongs to the large excitation force pressure region, the turbo rotation speed belongs to the turbine wheel resonance region, and the variable nozzle opening belongs to the large excitation force opening region. Therefore, it is determined that the turbocharger 4 is in a fatigue accumulation state. Accordingly, in S106, the opening signal for the variable nozzle 7 is increased by a predetermined ΔOpen. When the process of S106 ends, the process proceeds to S107.

  On the other hand, it is determined in S103 that the turbo rotation speed does not belong to the turbine wheel resonance region, or it is determined in S104 that the turbine inlet pressure does not belong to the large excitation force pressure region, or the variable nozzle in S105. If it is determined that the opening does not belong to the excitation force large opening region, the process proceeds to S108. In S108, the variable nozzle opening signal is not changed and the variable nozzle opening is maintained. When the process of S108 is completed, the process proceeds to S107.

  In S107, the opening signal determined in S106 or S108 is output to the DC motor 9 which is an actuator for opening and closing the variable nozzle 7, thereby controlling the variable nozzle opening. When the process of S107 ends, this routine is temporarily ended.

  As described above, in the present embodiment, the variable nozzle opening degree, the turbo rotation speed, and the turbine inlet pressure are assumed as factors that induce the resonance of the turbine wheel 6. Then, when all of the three factors belong to a region in which resonance is likely to be induced, it is determined that the turbocharger 4 is in a fatigue accumulation state that induces fatigue failure due to resonance of the turbine wheel 6. Furthermore, when it is determined that the turbocharger 4 is in a fatigue accumulation state, the variable nozzle opening is made larger than the original target value of the feedback control to eliminate the fatigue accumulation state of the turbocharger 4.

  In the present embodiment, the variable nozzle opening is actually detected by the nozzle opening sensor 11, the turbo rotation speed is detected by the turbo rotation sensor 19, and the turbine inlet pressure is actually detected by the turbine inlet pressure sensor 17.

  According to this, all the factors that may induce resonance of the turbine wheel 6 are actually detected, and the occurrence of resonance of the turbine wheel 6 can be suppressed based on the measured value of the factor. As a result, resonance of the turbine wheel 6 can be more reliably suppressed, and fatigue failure of the turbine wheel 6 can be more reliably suppressed. Moreover, it can suppress changing the opening degree of the variable nozzle 7 from the target value of feedback control unnecessarily, and it can suppress deteriorating the driving performance of the internal combustion engine 1 unnecessarily.

In this embodiment, a turbocharger control device is configured including the ECU 20. Further, in this embodiment, the fatigue accumulation state corresponds to a breakage induced state. Further, in the present embodiment, the ECU 20 that executes the processes of S101 to S105 corresponds to a damage induction determination unit. Moreover, ECU20 which performs the process of S106 and S107 is corresponded to a damage induction state cancellation means.

  In this embodiment, the nozzle opening sensor 11 corresponds to variable nozzle opening detecting means. The turbine inlet pressure sensor 17 corresponds to turbine inlet pressure detection means. The turbo rotation sensor 19 corresponds to turbo rotation number detection means. The turbine wheel resonance region corresponds to a resonance induction region. The limit turbine inlet pressure Pi1 corresponds to the limit turbine inlet pressure.

  Next, a second embodiment of the present invention will be described. In this embodiment, instead of detecting the turbo rotation speed, the compressor outlet pressure of the turbocharger is detected, and the turbocharger is in a fatigue accumulation state from three detected values of the variable nozzle opening, the turbine inlet pressure, and the compressor outlet pressure. An example of determining that the

  FIG. 5 shows a schematic diagram of the internal combustion engine and its intake / exhaust system in the present embodiment. About the same structure as the structure demonstrated in Example 1, description is abbreviate | omitted using the same code | symbol. The difference between FIG. 5 and FIG. 1 is that the turbo rotation sensor 19 in FIG. 1 is omitted in FIG.

  Here, it is known that there is a one-to-one correspondence between the turbo speed and the compressor outlet pressure. Therefore, in this embodiment, instead of detecting the turbo rotation speed by the turbo rotation sensor 19, the compressor outlet pressure sensor 17 detects the compressor outlet pressure.

  FIG. 6 shows a graph in which the compressor outlet pressure is added to the parameter that affects the resonance of the turbine wheel 6. As can be seen from FIG. 6, the compressor outlet pressure increases in the same manner as the turbo rotational speed as the engine rotational speed increases.

  FIG. 7 shows a graph (so-called compressor map) showing the relationship between the intake air amount and the compressor outlet pressure. In the compressor map, the excitation force large opening region, the excitation force large pressure region, and the turbine wheel resonance region are represented as shown in FIG. Further, a region indicating the fatigue accumulation state is a hatched portion in FIG. Further, as can be seen from FIG. 7, the range of the compressor outlet pressure belonging to the turbine wheel resonance region changes depending on the engine speed. That is, the lower limit value Po1 and the upper limit value Po2 of the compressor outlet pressure that define the turbine wheel resonance region are functions of the engine speed (Ne).

  FIG. 8 shows a flowchart of the fatigue accumulation state determination elimination routine 2 in the present embodiment. The difference between this routine and the fatigue accumulation state determination elimination routine shown in FIG. 4 is that the processing of S201 to S203 is executed instead of the processing of S101 to S103. Only the differences between this routine and the fatigue accumulation state determination elimination routine will be described below.

  When this routine is executed, first, in S201, output signals from the compressor outlet pressure sensor 15, the turbine inlet pressure sensor 17, and the nozzle opening sensor 11 are input to the ECU 20. As a result, the values of the compressor outlet pressure Po, the turbine inlet pressure Pi, and the variable nozzle opening VN% are read into the ECU 20. When the process of S201 ends, the process proceeds to S202.

In S202, the lower limit value and upper limit values Po1 (Ne) and Po2 (Ne) of the compressor outlet pressure, which determine the compressor outlet pressure range, corresponding to the turbine wheel resonance region, and the excitation force large pressure region are determined. Reference is made to Pi1, which is the lower limit value of the turbine inlet pressure, and VN% 1, which is the upper limit value of the variable nozzle opening degree which determines the large excitation force opening degree region. Note that the values of Po1 (Ne) and Po2 (Ne), which are the lower limit value and the upper limit value of the compressor outlet pressure, are functions of the engine speed Ne, and therefore the values of the engine speed Ne detected in S201. The corresponding value is read from the map. The values of Pi1 and VN% 1 are read from the ROM of the ECU 20. When the process of S202 ends, the process proceeds to S203.

  In S203, it is determined whether or not the compressor outlet pressure belongs to a range corresponding to the turbine wheel resonance region. Specifically, the compressor outlet pressure Po read in S201, and Po1 (Ne) which is the lower limit value and the upper limit value of the compressor outlet pressure for determining the compressor outlet pressure range corresponding to the turbine wheel resonance region referred to in S202. And Po2 (Ne) are compared to determine whether Po1 (Ne)> Po or Po> Po2 (Ne) is satisfied. If an affirmative determination is made here, it is determined that the turbo rotational speed does not belong to the turbine wheel resonance region as a result, and the process proceeds to S108. On the other hand, if a negative determination is made, it is determined that the turbo rotation speed belongs to the turbine wheel resonance region, so the routine proceeds to S104.

  Since the processing of S104 to S108 is equivalent to the fatigue accumulation state determination cancellation routine described in the first embodiment, description thereof is omitted.

  As described above, in this embodiment, when it is determined whether the turbocharger 4 is in a fatigue accumulation state, the turbo rotational speed is detected in addition to the variable nozzle opening and the turbine inlet pressure. Instead, the compressor outlet pressure was detected instead of the turbo speed. When all of them belong to a region that may induce resonance, it is determined that the turbocharger 4 is in a fatigue accumulation state that induces fatigue failure of the turbine wheel 6, and the variable nozzle opening is increased. Thus, the fatigue accumulation state of the turbocharger 4 was eliminated.

  According to this embodiment, it is not necessary to provide a turbo rotation sensor in the vicinity of the turbocharger 4 of the internal combustion engine 1, and the turbo rotation is performed using the compressor outlet pressure sensor 15 that is generally provided in a vehicle. It can be determined whether the number belongs to the turbine wheel resonance region. As a result, resonance of the turbine wheel 6 can be more reliably suppressed by a lower cost system. As a result, fatigue failure of the turbine wheel 6 can be more reliably suppressed.

  In this embodiment, the compressor outlet pressure sensor 17 corresponds to a compressor outlet pressure detecting means. Further, the compressor outlet pressure range determined by the lower limit value Po1 (Ne) and the upper limit value Po2 (Ne) of the compressor outlet pressure corresponds to the resonance induced pressure range.

  Next, Embodiment 3 of the present invention will be described. In this embodiment, the variable nozzle opening and the compressor outlet pressure are detected, and the value of the limit variable nozzle opening is corrected by the fuel injection amount, so that the turbocharger is in a fatigue accumulation state. An example of determination will be described.

  FIG. 9 shows a schematic diagram of the internal combustion engine and its intake / exhaust system in the present embodiment. The same components as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The difference between FIG. 9 and FIG. 1 is that the turbo rotation sensor 19 and the turbine inlet pressure sensor 17 are omitted in FIG.

Here, the point in which there is a one-to-one correspondence between the turbo rotation speed and the compressor outlet pressure has already been described in the second embodiment. In addition, it has been found that the turbine inlet pressure has a corresponding relationship with the fuel injection amount in the fuel injection valve 8. This is because if the fuel injection amount in the fuel injection valve 8 increases, the temperature of the exhaust gas rises and the turbine inlet pressure tends to increase.

  Therefore, in this embodiment, instead of detecting the turbo rotation speed by the turbo rotation sensor 19, the compressor outlet pressure sensor 15 detects the compressor outlet pressure. The nozzle opening sensor 11 detects the variable nozzle opening. On the other hand, the turbine inlet pressure is not detected. Here, the fuel injection instruction value to the fuel injection valve 8 is read into the ECU 20, and the turbine inlet pressure is detected by correcting the limit nozzle opening value set in the control range of the variable nozzle opening according to the value. To substitute.

  FIG. 10 is a graph showing the relationship between the limit variable nozzle opening, the engine speed, and the fuel injection amount. That is, as described above, if the fuel injection amount is large, the temperature of the exhaust gas becomes high and the turbine inlet pressure tends to increase. Further, when the engine speed increases, the amount of exhaust gas also increases, so that the turbine inlet pressure tends to increase. In the present embodiment, in consideration of this tendency, the limit variable nozzle opening value is corrected so as to increase as the fuel injection amount increases.

  In addition, correction is performed so that the value of the limit variable nozzle opening increases as the engine speed increases. This is a correction that takes into account that when the variable nozzle opening is the same, the higher the turbine inlet pressure, the greater the momentum of the exhaust blown to the turbine wheel 6 and the greater the excitation force. By this correction, the influence of the turbine inlet pressure on the vibration force on the turbine wheel 6 can be included in the value of the limit variable nozzle opening, so that detection of the turbine inlet pressure can be omitted.

  FIG. 11 shows a flowchart of the fatigue accumulation state determination elimination routine 3 in the present embodiment. The difference between this routine and the fatigue accumulation state determination elimination routine 2 shown in FIG. 8 is that the processing of S301 to S302 and S304 is executed instead of the processing of S201 to S202 and S204. Only the differences between this routine and the fatigue accumulation state determination elimination routine 2 will be described below.

  When this routine is executed, first, in S301, the compressor outlet pressure sensor 15 detects the compressor outlet pressure Po, the nozzle opening degree sensor 11 detects the variable nozzle opening degree VN%, and these output signals are read into the ECU 20. Further, the engine speed Ne of the internal combustion engine 1 is read into the ECU 20 by the crank position sensor 13, and an instruction value of the fuel injection amount to the fuel injection valve 8 is read into the ECU 20. When the process of S301 ends, the process proceeds to S302.

  In S302, the lower limit value and the upper limit values Po1 (Ne) and Po2 (Ne) of the compressor outlet pressure, which determine the compressor outlet pressure range, corresponding to the turbine wheel resonance region, and the excitation force large opening range are determined. Reference is made to VN% 2 (Ne, Gf), which is the upper limit value of the variable nozzle opening. Note that the values of Po1 (Ne) and Po2 (Ne), which are the lower limit value and the upper limit value of the compressor outlet pressure, are functions of the engine speed Ne, and therefore the values of the engine speed Ne detected in S201. The corresponding value is read from the map. Further, since the value of VN% 2 (Ne, Gf) is a function of the engine speed Ne and the fuel injection amount Gf, it corresponds to the combination of the engine speed Ne and the fuel injection amount Gf detected in S301. The value is read from the map. When the process of S302 ends, the process proceeds to S203.

In S203, it is determined whether or not the compressor outlet pressure does not belong to a range corresponding to the turbine wheel resonance region. Specifically, the compressor outlet pressure Po read in S201, and Po1 (Ne) which is the lower limit value and the upper limit value of the compressor outlet pressure that defines the compressor outlet pressure range corresponding to the turbine wheel resonance region referred to in S202. ) And Po2 (Ne), and Po1 (Ne)> Po or Po> Po2
It is determined whether (Ne) is satisfied. If an affirmative determination is made here, it is determined that the turbo rotation speed does not belong to the turbine wheel resonance region, so the routine proceeds to S108. On the other hand, if a negative determination is made, it is determined that the turbo rotation speed belongs to the turbine wheel resonance region, so the process proceeds to S304.

  In S304, it is determined whether or not the variable nozzle opening belongs to the large excitation force opening area. Specifically, the variable nozzle opening VN% read in S301 and VN% which is the upper limit value of the excitation force large opening region as a function of the engine speed Ne and the fuel injection amount Gf referred to in S302. 2 (Ne, Gf) is compared, and it is determined whether or not VN%> VN% 2 (Ne, Gf) is satisfied. If an affirmative determination is made here, it is determined that the variable nozzle opening does not belong to the excitation force large opening area, and the process proceeds to S108. On the other hand, if a negative determination is made, it is determined that the variable nozzle opening belongs to the large opening area of the excitation force, and the process proceeds to S106.

  Since the processing of S106 to S108 is equivalent to the fatigue accumulation state determination elimination routine and the fatigue accumulation routine 2 described in the first embodiment, the description thereof is omitted.

  As described above, in this embodiment, when determining whether or not the turbocharger 4 is in a fatigue accumulation state, only the variable nozzle opening and the compressor outlet pressure are detected. Then, the detection of the turbine inlet pressure is substituted by correcting the value of the limit variable nozzle opening with which the detected variable nozzle opening is compared with the values of the engine speed and the fuel injection amount. Furthermore, when the compressor outlet pressure belongs to the range corresponding to the turbine wheel resonance region and the variable nozzle opening belongs to the corrected excitation force large opening region, the turbocharger 4 is in a fatigue accumulation state. It was determined that there was. In that case, the variable nozzle opening is increased to eliminate the fatigue accumulation state of the turbocharger 4.

  According to this, the fatigue accumulation state of the turbocharger 4 can be determined only by the detection signals from the two sensors, the compressor outlet pressure sensor and the nozzle opening degree sensor. In addition, the accuracy of the determination at this time is detected from three sensors, that is, a turbo rotation sensor, a turbine inlet pressure sensor, and a nozzle opening sensor, or from three compressor outlet pressure sensors, a turbine inlet pressure sensor, and a nozzle opening sensor. This can be equivalent to the case where the fatigue accumulation state of the turbocharger 4 is determined by the signal.

  Here, in many vehicles in the current market, since the compressor outlet pressure sensor and the nozzle opening sensor are provided, there is no need to add a sensor in this embodiment. Therefore, the resonance of the turbine wheel can be more reliably suppressed by the lower cost system, and the fatigue failure of the turbine wheel can be suppressed.

  In the present embodiment, the ECU 20 that executes the processes of S301 to S302 corresponds to a correcting unit. Further, in the above embodiment, when it is determined that the turbocharger 4 is in a fatigue accumulation state in which fatigue failure due to resonance is induced, the opening degree of the variable nozzle 7 is increased to eliminate the fatigue accumulation state. An example was described. However, depending on the material and shape of the turbine wheel, it may be possible that the vibration is directly damaged by the vibration due to the resonance rather than the fatigue being accumulated by the induction of the resonance. Of course, the idea of the present invention can be applied to such a case.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematic structure of the internal combustion engine in Example 1 of this invention, its intake-exhaust system, and a control system. It is a figure for demonstrating the factor which influences the induction | guidance | derivation of resonance of the turbine wheel in Example 1 of this invention, and the range which the possibility of resonance of a turbine wheel arises in each factor. It is another figure for demonstrating the factor which influences the induction | guidance | derivation of resonance of the turbine wheel in Example 1 of this invention, and the range which the possibility of resonance of a turbine wheel arises in each factor. It is a flowchart which shows the fatigue accumulation state determination cancellation routine in Example 1 of this invention. It is a figure which shows schematic structure of the internal combustion engine in Example 2 of this invention, its intake / exhaust system, and a control system. It is a figure for demonstrating the factor which influences induction | guidance | derivation of the resonance of the turbine wheel in Example 2 of this invention, and the range which the possibility of resonance of a turbine wheel arises in each factor. It is another figure for demonstrating the factor which influences the induction | guidance | derivation of resonance of the turbine wheel in Example 2 of this invention, and the range which the possibility of resonance of a turbine wheel arises in each factor. It is a flowchart which shows the fatigue accumulation state determination cancellation routine 2 in Example 2 of this invention. It is a figure which shows schematic structure of the internal combustion engine in Example 3 of this invention, its intake-exhaust system, and a control system. It is the figure which showed the change by the fuel injection amount and the engine speed of the value of the limit variable nozzle opening degree in Example 3 of this invention. It is a flowchart which shows the fatigue accumulation state determination cancellation routine 3 in Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Intake passage 3 ... Exhaust passage 4 ... Turbocharger 5 ... Compressor wheel 6 ... Turbine wheel 7 ... Variable nozzle 8 ... Fuel injection valve 9 ... DC motor 11 ... Nozzle opening sensor 13 ... Crank position sensor 15 ... Compressor outlet pressure sensor 17 ... Turbine inlet pressure sensor 19 ... Turbo rotation sensor 20 ... ECU

Claims (4)

A control device for a variable nozzle type turbocharger having a variable nozzle capable of changing an exhaust flow area when exhaust gas of an internal combustion engine is blown to a turbine wheel,
The turbocharger is induced to be damaged by resonance of the turbine wheel on the basis of the turbo rotation speed, the turbine expansion ratio that affects the excitation force by the exhaust to the turbine wheel, and the opening of the variable nozzle. Damage induction determination means for determining whether or not it is in a damage induction state;
A breakage induction state elimination means for eliminating the breakage induction state of the turbocharger by changing the opening of the variable nozzle when the breakage induction determination means determines that the turbocharger is in the breakage induction state; ,
A turbocharger control device comprising: The breakage induction determining means detects variable nozzle opening degree detecting means for detecting the opening degree of the variable nozzle, turbo rotational speed detecting means for detecting the turbo rotational speed, and pressure at the turbine inlet of the turbocharger. Turbine inlet pressure detection means,
In a variable range of the opening of the variable nozzle, a limit nozzle opening that is an opening of the upper limit variable nozzle that can increase the excitation force due to exhaust to the turbine wheel and induce damage due to resonance of the turbine wheel is Set,
In the fluctuation range of the turbo rotation speed, a resonance induction region that is a rotation speed range that easily induces resonance of the turbine wheel is set,
In the fluctuation range of the pressure at the turbine inlet, a limit turbine inlet pressure is set, which is a lower limit pressure that can increase the excitation force due to exhaust to the turbine wheel and induce damage due to resonance of the turbine wheel,
In the breakage induced state, the opening degree of the variable nozzle detected by the variable nozzle opening degree detecting means is equal to or less than the limit nozzle opening degree, and the turbo rotational speed detected by the turbo rotational speed detecting means is the resonance induction. 2. The turbocharger control device according to claim 1, wherein the pressure at the turbine inlet that belongs to the region and is detected by the turbine inlet pressure detection means is equal to or higher than the limit turbine inlet pressure. 3. The breakage induction determining means includes variable nozzle opening degree detecting means for detecting the opening degree of the variable nozzle, compressor outlet pressure detecting means for detecting pressure at the outlet of the compressor of the turbocharger, and inlet of the turbine of the turbocharger. Turbine inlet pressure detection means for detecting the pressure at
In a variable range of the opening of the variable nozzle, a limit nozzle opening that is an opening of the upper limit variable nozzle that can increase the excitation force due to exhaust to the turbine wheel and induce damage due to resonance of the turbine wheel is Set,
In the pressure fluctuation range at the outlet of the compressor, a resonance inducing pressure range that is a pressure range in which resonance of the turbine wheel is likely to occur is set.
In the fluctuation range of the pressure at the turbine inlet, a limit turbine inlet pressure is set, which is a lower limit pressure that can increase the excitation force due to exhaust to the turbine wheel and induce damage due to resonance of the turbine wheel,
In the breakage induced state, the opening of the variable nozzle detected by the variable nozzle opening detecting means is equal to or less than the limit nozzle opening, and the pressure at the compressor outlet detected by the compressor outlet pressure detecting means is the pressure at the compressor outlet. 2. The turbocharger according to claim 1, wherein the pressure at the inlet of the turbine belonging to a resonance-induced pressure range and detected by the turbine inlet pressure detection means is equal to or higher than the limit turbine inlet pressure. Control device. The breakage inducing determination means has variable nozzle opening degree detecting means for detecting the opening degree of the variable nozzle, and compressor outlet pressure detecting means for detecting the pressure at the compressor outlet of the turbocharger,
In a variable range of the opening of the variable nozzle, a limit nozzle opening that is an opening of the upper limit variable nozzle that can increase the excitation force due to exhaust to the turbine wheel and induce damage due to resonance of the turbine wheel is Set,
In the pressure fluctuation range at the outlet of the compressor, a resonance inducing pressure range that is a pressure range in which resonance of the turbine wheel is likely to occur is set.
A correction means for correcting the value of the limit nozzle opening according to the engine speed and fuel injection amount of the internal combustion engine;
The breakage induced state is detected by the compressor outlet pressure detecting means when the opening degree of the variable nozzle detected by the variable nozzle opening degree detecting means is equal to or less than the limit nozzle opening degree corrected by the correcting means. 2. The turbocharger control device according to claim 1, wherein the pressure at the outlet of the compressor is in a state belonging to the resonance-induced pressure range.

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