COMBUSTION ENGINE DIAGNOSTIC DEVICE

Abstract

Diagnostic device for an internal combustion engine, wherein the internal combustion engine includes a variable geometry turbocharger and wherein the turbocharger includes a variable vane, a linkage mechanism configured to operate the variable vane, and an actuator configured to drive the linkage mechanism, the diagnostic device includes the following: a control unit configured to control the opening degree of the variable blade by controlling the actuator, wherein the control unit determines that an abnormality has occurred in the connection mechanism of the turbocharger if an operating time of the internal combustion engine in a predetermined operating range exceeds a predetermined upper limit and a differential pressure between a target boost pressure, which is determined according to an operating condition of the internal combustion engine, and an actual boost pressure exceeds a predetermined upper limit.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a diagnostic device for an internal combustion engine. STATE OF THE ART

[0002] For example, a variable geometry turbocharger (turbocharger) with a multitude of variable vanes at a turbine inlet is known for an internal combustion engine in a vehicle. The turbocharger includes a linkage mechanism for simultaneously operating the multitude of variable vanes and an actuator for driving the linkage mechanism. By controlling the actuator, the opening degrees of the variable vanes are controlled, and thus the boost pressure is controlled. PATENT LITERATURE

[0003] JP 2016-205350A describes a variable nozzle control system. US 2011 / 0110767A1 and DE 19837834B4 describe methods and systems for diagnosing a vehicle internal combustion engine. SUMMARY OF THE INVENTIONAL PROBLEM

[0004] In the case of the internal combustion engine, it was found that operating the engine within a specific operating range promotes deterioration of the linkage mechanism compared to operating it within other ranges. It was also found that if operating time within this specific range exceeds an upper limit, the linkage mechanism becomes abnormal, leading to malfunctions such as an inability to generate the desired boost pressure.

[0005] It is preferable to promptly detect any abnormality in the connection mechanism and warn the user in order to rectify it early.

[0006] The present disclosure has been made in light of the foregoing situations. The invention is based on the objective of providing a diagnostic device for an internal combustion engine that is capable of immediately detecting an abnormality in the connection mechanism of a variable geometry turbocharger. SOLUTION TO THE PROBLEM

[0007] This problem is solved by the features of the independent claim. Advantageous embodiments of the invention are described in the dependent claims. One aspect of the present disclosure provides a diagnostic device for an internal combustion engine. wherein the internal combustion engine includes a variable geometry turbocharger and wherein the turbocharger includes a variable vane, a linkage mechanism configured to operate the variable vane, and an actuator configured to drive the linkage mechanism, the diagnostic device includes the following: a control unit configured to control the degree of opening of the variable vane by controlling the actuator, wherein the control unit determines that an abnormality has occurred in the connection mechanism of the turbocharger when an operating time of the internal combustion engine in a predetermined operating range exceeds a predetermined upper limit and a differential pressure between a target boost pressure determined according to an operating condition of the internal combustion engine and an actual boost pressure exceeds a predetermined upper limit.

[0008] Preferably, the predetermined operating range is an operating range in which the number of rotations of the internal combustion engine is large and the load on the internal combustion engine is low.

[0009] Preferably, the connection mechanism includes a rotary element and a rotatable lever that engages with and is coupled to the rotary element, and the abnormality of the connection mechanism is abnormal wear on a contact part between the rotary element and the lever. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0010] According to the present disclosure, it is possible to immediately detect an abnormality in the connection mechanism of the variable geometry turbocharger. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic view representing a configuration of an embodiment of the present disclosure. Fig. Figure 2 is a front view showing a configuration of the connection mechanism. Fig. 3A represents a characteristic map. Fig. 3B represents a characteristic map. Fig. 3C represents a characteristic map. Fig. Figure 4 is a flowchart that represents a control routine for the opening degree of a variable blade. Fig. 5 is a flowchart that represents a routine of diagnostic processing. DESCRIPTION OF THE EXECUTION FORMS

[0011] One embodiment of the present disclosure is described below with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to this embodiment.

[0012] Fig. Figure 1 is a schematic view representing a configuration of an embodiment of the present disclosure. An internal combustion engine (engine) 1 is a multi-cylinder engine mounted on a vehicle (not shown). In the present embodiment, the vehicle is a large vehicle, such as a truck, and the engine 1, as a vehicle power source mounted on the vehicle, is a four-cylinder in-line diesel engine. However, the types, shapes, uses, and the like of the vehicle and the internal combustion engine are not particularly limited. For example, the vehicle may be a small vehicle, such as a car, and the engine 1 may be a gasoline engine.

[0013] The engine 1 includes an engine body 2, an intake manifold 3 and an exhaust manifold 4 connected to the engine body 2, a turbocharger 14 and a fuel injection device 5. The engine body 2 includes structural components such as a cylinder head, a cylinder block and a crankcase, and moving components such as a piston, a crankshaft and a valve, which are housed in the structural components.

[0014] The fuel injection device 5 is a common-rail type fuel injection device and has fuel injectors, i.e., injectors 7, provided at each of the cylinders, and a common rail 8 connected to the injectors 7. The injector 7 is configured to inject fuel directly into a cylinder 9, i.e., into a combustion chamber. The common rail 8 is configured to maintain the fuel injected from the injectors 7 at a high pressure.

[0015] The intake duct 3 is primarily defined by an intake manifold 10, which is connected to the engine body 2 (specifically, a cylinder head), and an intake pipe 11, which is connected to an upstream end of the intake manifold 10. The intake manifold 10 is configured to distribute and supply intake air, sent from the intake pipe 11, to an intake port of each cylinder. The intake pipe 11 is supplied with an air filter 12, an air flow meter 13, a compressor 14C of the turbocharger 14, an intercooler 15, and an electronically controlled intake throttle valve 16, in the corresponding order from an upstream side. The air flow meter 13 is a sensor for detecting the amount of intake air per unit of time of the engine 1, i.e., the flow rate of intake air, and is also referred to as a MAF sensor or similar.

[0016] The exhaust channel 4 is primarily defined by an exhaust manifold 20, which is connected to the engine body 2 (specifically a cylinder head), and an exhaust pipe 21, which is connected to the exhaust manifold 20 on a downstream side. The exhaust manifold 20 is configured to collect exhaust gas sent from an exhaust port of each cylinder. A turbine 14T of the turbocharger 14 is provided at the exhaust pipe 21 or between the exhaust manifold 20 and the exhaust pipe 21. The exhaust pipe 21, located further downstream than the turbine 14T, is equipped from an upstream side with an oxidation catalyst 22, a diesel particulate filter (DPF) 23, a selective catalytic reduction (SCR) catalyst 24, and an ammonia oxidation catalyst 26, in that order.The exhaust gas channel 4 on an upstream side, particularly near an inlet of the NOx catalyst 24, is provided with an addition valve 25 for adding urea water as a reducing agent.

[0017] The turbocharger 14 is a variable geometry turbocharger. The turbocharger 14 has a plurality of variable vanes 28 for varying the opening degree of a nozzle at the turbine inlet, a linkage mechanism (described later) for simultaneously operating the variable vanes 28, and an actuator, i.e., a turboactuator 29, for driving the linkage mechanism. The turboactuator 29 of the present embodiment is formed by an electric motor, but could, for example, be formed by a pneumatic actuator, which is different from the electric motor.

[0018] The engine 1 also has an EGR device 30. The EGR device 30 has an EGR channel 31 for the return flow of a portion (referred to as "EGR gas") of exhaust gas in the exhaust channel 4 (particularly in the exhaust manifold 20) into the intake channel 3 (particularly in the intake manifold 10), an EGR cooler 32 for cooling the EGR gas flowing into the EGR channel 31, and an EGR valve 33 for regulating a flow rate of the EGR gas.

[0019] In the present embodiment, an electronic control unit (hereinafter referred to herein as "ECU" (Electronic Control Unit)) 100, which forms a control unit or control device, is provided. The ECU 100 includes a CPU, a ROM, a RAM, input / output ports, a storage device, and the like. The ECU 100 is configured and programmed to control the injectors 7, an intake throttle valve 16, the additive valve 25, the EGR valve 33, and the turbo actuator 29.

[0020] In the present embodiment, a speed sensor 40 for detecting the engine speed (specifically revolutions per minute (rpm)) and an accelerator pedal opening degree sensor 41 for detecting the accelerator pedal opening degree are provided in addition to the air flow meter 13. Additionally, exhaust gas temperature sensors 42, 43, 44 and 46 for detecting exhaust gas temperatures (intake gas temperature) on upstream sides or near inlets of the oxidation catalyst 22, the DPF 23, the NOx catalyst 24 and the ammonia oxidation catalyst 26, and a differential pressure sensor 45 for detecting a pressure difference between exhaust gas pressures on the upstream and downstream sides of the DPF 23 are provided.

[0021] A boost pressure sensor 47 for detecting boost pressure is also provided. In the present embodiment, the boost pressure sensor 47 is located on the intake manifold 11 on the downstream side of the intake throttle valve 16 and immediately upstream of the intake manifold 10. However, the location of the sensor is arbitrary. For example, the boost pressure sensor 47 can be located on the intake manifold 10. Output signals from the sensors are transmitted to the ECU 100.

[0022] The diagnostic device of the present embodiment includes at least the ECU 100 and is configured to detect an abnormality of the connection mechanism of the turbocharger 14. This is described in detail below.

[0023] Fig. Figure 2 represents a configuration of the connection mechanism 50 of the turbocharger 14. As is well known, the turbocharger 14 has a turbine housing configured to rotatably receive a turbine wheel, and a central housing connected to the turbine housing and configured to rotatably support a turbine shaft. Fig. Figure 2 shows only the central housing 51 in a state where the housings are separated from each other. A reference numeral 52 indicates a mounting surface of the central housing 51 on the turbine housing. As can be seen from this, Fig. 2 shows the connection mechanism 50, seen from the turbine side in one direction (one thickness direction of the drawing sheet). Fig. 2) a central axis (i.e., a turbine axis) of the turbine shaft. A reference sign RO indicates a radius line extending from the turbine axis on a right-hand upper side outside of Fig. 2 extends to. The mounting surface 52 is provided with a plurality of screw holes 53 to which bolts (not shown) are attached when the turbine housing is fastened to the central housing 51 by the bolts. The connecting mechanism 50 is accommodated in a connecting mechanism receiving chamber 54 between the turbine housing and the central housing 51.

[0024] The variable blades 28 are provided at equal intervals around the turbine axis. The variable blades 28 are arranged in nozzle channels (not shown) in the turbine casing so that they surround the turbine wheel. One end of a blade shaft 55 is fixed to the variable blade 28. The blade shaft 55 is rotatably mounted, being inserted in a shaft hole (not shown) of a nozzle backplate, which is fixed to the central casing 51 and defines the nozzle channel. A base end of a blade arm (so-called claw) 56, which serves as a first arm with a forked tip end, is fixed to the other end of the blade shaft 55. This allows the variable blade 28, the blade shaft 55, and the blade arm 56 to rotate integrally about a center point of the blade shaft 55.

[0025] To generate the rotation, a ring plate 57, configured to run on the turbine axis, is attached to the central housing 51 so that it can rotate about the turbine axis. The ring plate 57 is received in the connecting mechanism receiving chamber 54. Fig. Figure 2 shows the ring plate 57 transparently. The variable blade 28 is actually arranged on a surface side (a front side in the thickness direction of the drawing sheet) of the ring plate 57, and the blade arm 56 is arranged on a back side (an inside side in the thickness direction of the drawing sheet) of the ring plate 57. The blade shaft 55 is slidably inserted in an elongated hole 58 formed in the ring plate 57 and extending circumferentially.

[0026] A first rotating element is rotatably attached to a rear portion of the ring plate 57. In the present embodiment, the first rotating element is a polygonal, specifically quadrilateral and specifically square, rotating part (so-called upper part) 59. The rotating part 59 is attached to the ring plate 57 via a shaft 60 and can rotate about a center point of the shaft 60.

[0027] The blade arm 56 is engaged with and coupled to the rotary piece 59. That is, the forked tip section of the blade arm 56 encloses two parallel side surfaces of the rotary piece 59 and is thus engaged with the rotary piece 59. The forked tip section of the blade arm 56 and the two side surfaces of the rotary piece 59 can contact each other, forming two contact parts 61. The contact parts 61 have a small dimensional gap. However, when input is applied from one of the blade arm 56 and the rotary piece 59 to the other, the gap disappears, and the blade arm 56 and the rotary piece 59 come into contact with each other.

[0028] In contrast, an operating part 62, extending radially outwards, is formed at a circumferential point of the ring plate 57, and a second rotating element is rotatably attached to a rear portion of the operating part 62. In the present embodiment, the second rotating element is a polygonal, specifically quadrilateral and specifically square, operating rotating part (so-called segment) 63. The operating rotating part 63 is attached to the operating part 62 via an operating rotating part shaft 64 and can rotate about a center point of the operating rotating part shaft 64. It should be noted that the radius line RO shown passes through the center point of the operating rotating part shaft 64.

[0029] An operating shaft 65 is arranged on a radially outer side of the operating shaft 64, based on the turbine axis and on the same radius RO. The operating shaft 65 is inserted through a shaft hole (not shown) in the central casing 51 and is rotatably mounted. A base end of an operating arm (so-called claw) 66, a second arm with a forked tip end, is fixed to one end of the operating shaft 65, which is located inside the central casing 51. The operating arm 66 is larger than the blade arm 56. In contrast, a base end of an actuator lever (not shown), the tip end of which is coupled to the turbo actuator 29, is fixed to the other end of the operating shaft 65, which is located outside the central casing 51. This allows the operating arm 66, the operating shaft 65, and the actuator lever to rotate integrally about a center point C of the operating shaft 65.

[0030] The operating arm 66 is also engaged with and coupled to the operating rotary piece 63. That is, the forked tip section of the operating arm 66 encloses two parallel side surfaces of the operating rotary piece 63 and is thus engaged with the operating rotary piece 63. The forked tip section of the operating arm 66 and the two side surfaces of the operating rotary piece 63 can contact each other and form two contact parts 67. The contact parts 67 have a small dimensional gap. However, when input is applied from one of the operating arm 66 and the operating rotary piece 63 to the other, the gap disappears and the operating arm 66 and the operating rotary piece 63 come into contact with each other.

[0031] According to the configuration of the connection mechanism 50, actuation is transmitted to the operating arm 66 via the actuator lever and the operating shaft 65 when the turbo actuator 29 is actuated to change the opening degree of the variable blade 28, thereby rotating the operating arm 66. This rotation causes the ring plate 57 to rotate about the turbine axis. At this point, the operating pivot 63 is rotated in a reverse direction to the direction of rotation of the operating arm 66 to allow the rotations. During the rotations, the contact parts 67 of the operating arm 66 and the operating pivot 63 come into contact or close contact, so that a driving force is transmitted from the operating arm 66 to the operating pivot 63.

[0032] The rotation of the ring plate 57 causes the rotating element 59 to move circumferentially around the turbine axis. This changes the relative position of the rotating element 59 to the blade shaft 55, causing the rotating element 59 to rotate the blade arm 56 around the blade shaft 55. This causes the variable blade 28 to rotate around the blade shaft 55, thus changing the opening angle of the variable blade 28. During the rotation of the blade arm 56, the rotating element 59 also rotates around the shaft 60 in the opposite direction to the rotation of the blade arm 56. During the rotations of the blade arm 56 and the rotating element 59, the contact parts 61 of the blade arm 56 and the rotating element 59 come into contact or close contact, so that the driving force is transmitted from the rotating element 59 to the blade arm 56.

[0033] In the case of engine 1, it was found that operating engine 1 within a specific operating range promotes deterioration of the linkage mechanism 50 compared to operating it within other operating ranges. It was also found that if the operating time within this specific operating range exceeds an upper limit, the linkage mechanism 50 becomes abnormal, resulting in a malfunction such as an inability to generate the desired boost pressure.

[0034] This is described below. First, a part where deterioration is promoted during operation in the specific operating range is the contact parts 67 of the operating arm 66 and the operating rotating piece 63 of the connection mechanism 50. The specific operating range is an operating range R on one side of high speed and on the other side of low load, in which the engine speed Ne is high and the engine load (specifically a target fuel injection quantity Q) is low, as in Fig. 3C shown.

[0035] The operating arm 66 and the operating rotary piece 63 are made of a relatively rigid material because they transmit a high driving force against a driving reaction force received from the exhaust gas by the plurality of variable blades 28. During the rotations of the operating arm 66 and the operating rotary piece 63 (i.e., during the change in the opening degree of the variable blade), a problem does not particularly arise because the contact parts 67 are kept in contact with each other.

[0036] During the pause in the rotation of the operating arm 66 and the operating rotary piece 63, i.e., while the opening degree of the variable blade is held constant, the contact parts 67 are in a relatively free state. Consequently, the contact parts 67 rattle and vibrate due to the force received from the exhaust gas by the variable blades 28. This vibration promotes wear of the contact parts 67. Wear can be observed to be particularly pronounced on at least one of the end sections (i.e., the areas surrounding corner sections) of the two side faces of the operating rotary piece 63 and corresponding sections of the operating arm 66 with which the end sections come into contact.

[0037] In contrast, the opening degree of the variable vane also changes accordingly when an operating state of the motor changes, so that the vibration problem of the contact parts 67 does not occur as described above. However, if the operating state of the motor is constant, the opening degree of the variable vane is also kept constant, so that the vibration problem of the contact parts 67 occurs.

[0038] According to test results, it is confirmed that wear is predominantly promoted in the operating range (also referred to as the wear-promoting range) on both the high-speed and low-load sides. This is because the opening degree of the variable vane is often kept constant in the operating range R, for example, the operating state of the motor is often kept constant by high-speed movement.

[0039] If the wear of the contact parts 67 is accelerated and exceeds a permissible limit, an abnormality occurs, namely abnormal wear of the contact parts 67. When this abnormality occurs, the actual opening degree of the variable vane is insufficient compared to the target opening degree of the variable vane corresponding to a target boost pressure, resulting in insufficient boost pressure. Since the fuel injection quantity becomes relatively large in relation to the intake air quantity, a problem then arises in which the combustion gas temperature increases and the amount of NOx production increases.

[0040] As described above, the abnormality of the connection mechanism 50 is abnormal wear of the contact parts 67. Since the contact parts 61 of the blade arm 56 and the rotating piece 59 also have a similar configuration, similar abnormal wear occurs in the meantime, which can cause the malfunction described above. Therefore, in the present embodiment, the abnormal wear of the contact parts 61 of the blade arm 56 and the rotating piece 59 is also included in the abnormality of the connection mechanism 50.

[0041] It is preferable to detect the abnormality of the connection mechanism 50 immediately and to warn a user in order to rectify it at an early stage. Therefore, in the present embodiment, the abnormality of the connection mechanism 50 is detected immediately by the following method.

[0042] In the present embodiment, the ECU 100 determines that an abnormality has occurred in the connection mechanism 50 of the turbocharger 14 if the operating time of the engine 1 in the wear-promoting range R exceeds a predetermined upper limit and a differential pressure between a target boost pressure, which is determined according to the operating state of the engine 1, and an actual boost pressure exceeds a predetermined upper limit.

[0043] If the operating time in the wear-promoting region R reaches a long duration, abnormal wear can occur on the contact parts 67. Therefore, in the present embodiment, the condition in which the operating time in the wear-promoting region R exceeds the predetermined upper limit R is set as a first condition for determining abnormality.

[0044] Meanwhile, abnormal wear occurs when the differential pressure between the target boost pressure and the actual boost pressure increases. Therefore, in the present embodiment, the condition in which the differential pressure between the target boost pressure and the actual boost pressure exceeds the predetermined upper limit is set as a second condition for determining abnormality.

[0045] In particular, in the present embodiment, the abnormality determination is only made in a case where both the first and the second conditions are met. Even if the first condition is met, it cannot be said that abnormal wear has occurred. The same applies to the second condition. In the present embodiment, the abnormality determination is carried out in a case where the second condition is met, provided that the first condition is met. Therefore, it is possible to suppress a false diagnosis and to correctly detect the abnormality of the connection mechanism 50.

[0046] Here, the operating time of engine 1 in the wear-promoting range R includes not only the operating time itself, but also a correlation value that correlates with the operating time. Examples of the correlation value include an integrated value of a fuel injection quantity (especially a target fuel injection quantity) or an intake air quantity.

[0047] The differential pressure between the target boost pressure and the actual boost pressure includes not only the differential pressure itself, but also a correlation value that correlates with the differential pressure. Examples of this correlation value include a feedback term Svfb, which is calculated when controlling the opening degree of the variable vane, described later.

[0048] It should be noted that the shape of the wear-promoting area R, which is in Fig. Figure 3C is shown only as an example, and a variety of shapes can be considered in addition to the one shown. The wear-promoting area R is appropriately set according to the result of an actual test.

[0049] The control and diagnostic processing of the present embodiment is described below. First, the control of the opening degree of the variable blade is described with reference to Fig. 4 described. The routine shown is executed repeatedly by the ECU 100 in each predetermined calculation cycle τ (for example, 10 ms).

[0050] In step S101, the ECU obtains 100 values ​​of an engine speed Ne, an accelerator pedal opening degree Ac and a boost pressure Pb, which are detected by the speed sensor 40, the accelerator pedal opening degree sensor 41 and the boost pressure sensor 47 respectively.

[0051] In step S102, the ECU 100 calculates a fuel injection quantity, specifically a target fuel injection quantity Q as an instructed injection quantity into the injectors 7 according to a predetermined map, as shown in Fig. 3A shown, based on the engine speed Ne and the accelerator pedal opening degree Ac.

[0052] It should be noted that the engine speed Ne, the accelerator pedal opening Ac, and the target fuel injection quantity Q are all engine parameters that indicate the engine's operating state. Therefore, the engine's operating state is defined by at least one of these three parameters. Additionally, the accelerator pedal opening Ac and the target fuel injection quantity Q are engine parameters that correspond to the engine load.

[0053] The ECU 100 then calculates a target opening degree Sv of the variable blade 28 in steps S103 to S106. The target opening degree Sv is calculated by summing a forward feedback (F / F) term Svff and a feedback (F / B) term Svfb.

[0054] In step S103, the ECU 100 calculates an F / F term Svff according to a predetermined map, as shown in Fig. 3B shown, based on the engine speed Ne and the target fuel injection quantity Q.

[0055] In step S104, the ECU 100 calculates a target boost pressure Pbt according to a predetermined map, as shown in Fig. Figure 3C is shown, based on the engine speed Ne and the target fuel injection quantity Q. It should be noted that the part shown with the dashed line in the map is the wear-inducing area R.

[0056] In step S105, the ECU 100 calculates an F / B term Svfb based on the differential pressure between the target boost pressure Pbt and the actual boost pressure Pb, which is obtained in step S101. Specifically, the ECU 100 calculates the differential pressure ΔPb = Pbt - Pb between the target boost pressure Pbt and the actual boost pressure Pb. Then, based on the differential pressure ΔPb, the F / B term Svfb is calculated according to a predetermined map (not shown). If the differential pressure ΔPb is positive, i.e., if the actual boost pressure Pb is lower than the target boost pressure Pbt, a negative F / B term Svfb is calculated on a boost pressure increase side. In contrast, if the differential pressure ΔPb is negative, i.e., if the actual boost pressure Pb is higher than the target boost pressure Pbt, a positive F / B term Svfb is calculated on a boost pressure take-off side.It should be noted that when calculating the F / B term Svfb, a summed value of a P term, an I term and a D term corresponding to the differential pressure ΔPb is preferably used as the F / B term Svfb according to a well-known PID control method.

[0057] In step S106, the ECU 100 calculates a target opening degree of the variable blade Sv (= Svff + Svfb) by adding the calculated F / F term Svff and F / B term Svfb.

[0058] In step S107, the ECU 100 controls the opening degree of the variable blade 28 to the target opening degree of the variable blade Sv. That is, the turbo actuator 29 is controlled so that the actual opening degree of the variable blade 28 coincides with the target opening degree of the variable blade Sv.

[0059] In this way, the control of the variable vane opening degree is achieved through a combination of flow-through (F / F) control via the F / F term Svff and flow-through (F / B) control via the F / B term Svfb. The F / F term Svff is a value that forms the basis for the target variable vane opening degree Sv and is a value at which the target boost pressure Pbt can essentially be implemented in a given current engine operating state. However, it is not always possible to implement the target boost pressure Pbt solely with the F / F term Svff because, for example, the actual engine operating state continues to change. Therefore, the feedback term Svsb is added, and the variable vane opening degree is precisely controlled, ensuring a stable implementation of the target boost pressure Pbt.

[0060] Meanwhile, when the actual boost pressure Pb is increased towards the target boost pressure Pbt by reducing the opening degree of the variable vane 28 (by narrowing the variable vane 28), the greater the differential pressure ΔPb, the greater the absolute value of the F / B term Svfb. However, if abnormal wear of the contact parts 67 occurs, the differential pressure ΔPb increases compared to a case where abnormal wear does not occur, and the absolute value of the F / B term Svfb reaches the predetermined limit. Therefore, the absolute value of the F / B term Svfb cannot be increased beyond the predetermined limit. In this case, it is not possible to fully correct the differential pressure ΔPb with the F / B term Svfb, so the actual opening degree of the variable vane and boost pressure become insufficient.In this case, the amount of fuel injected increases relative to the amount of intake air, so that the combustion gas temperature rises and the amount of NOx production increases.

[0061] The following is the diagnostic processing with reference to Fig. 5 described. The routine shown is also executed repeatedly in each predetermined calculation cycle τ by the ECU 100.

[0062] In step S201, the ECU 100 determines whether the operating state of the engine, defined by the engine speed Ne, detected by the speed sensor 40, and the target fuel injection quantity Q, calculated in step S102, is in the wear-promoting range R, based on the map of Fig. 3C.

[0063] If it is determined that the engine's operating condition is in the wear-promoting range R, the ECU 100 proceeds to step S202 and calculates an operating time tR in the wear-promoting range R by integration. That is, an operating time tR n When this routine is executed, the operating time tR is obtained by adding or integrating the calculation cycle τ. n-1 during execution of the previous routine (tR n = tR n-1 + τ) is calculated. Then the ECU 100 moves on to step S203.

[0064] If, on the other hand, it is determined that the operating condition of the engine is not in the wear-promoting range R, the ECU skips step S202 and goes to step S203.

[0065] In step S203, the ECU 100 determines whether the operating time tR, which is calculated in step S202, exceeds a predetermined upper limit tRlim.

[0066] If it is determined that the operating time exceeds the predetermined upper limit, the ECU 100 determines in step S204 whether the differential pressure ΔPb, calculated in step S105, exceeds a predetermined upper limit ΔPblim.

[0067] If it is determined that the differential pressure exceeds the predetermined upper limit, the ECU 100 determines that an abnormality has occurred in the connection mechanism 50, specifically that abnormal wear has occurred on the contact parts 67 of the operating arm 66 and the operating rotary piece 63, as determined in step S205. In this case, the ECU 100 activates a warning device (for example, a warning light, not shown) to prompt the user to perform an early inspection and maintenance. Additionally, the ECU 100 stores a diagnostic code corresponding to the abnormality, so that the abnormal location can be easily specified during subsequent maintenance. In this way, the abnormality of the connection mechanism 50 is detected immediately. After step S205, the routine is complete.

[0068] If, on the other hand, step S203 determines that the operating time tR does not exceed the upper limit tRlim, and step S204 determines that the differential pressure ΔPb does not exceed the upper limit ΔPblim, the ECU 100 terminates the routine.

[0069] As described above, according to the present embodiment it is possible to immediately detect the abnormality of the connection mechanism 50 of the variable geometry turbocharger 14.

[0070] Although the embodiment of the present disclosure has been described in detail, other different embodiments of the present disclosure are also conceivable. For example, the operating rotary piece 63 and the rotating piece 59 as the rotating element can have a different shape, for example, a polygonal shape other than a square one, such as a hexagonal shape.

[0071] The embodiment of the present disclosure is not limited to the foregoing embodiment, and all modifications, applications, and equivalents that are within the spirit of the present disclosure as defined in the claims are included in the present disclosure. Therefore, the present disclosure should not be interpreted in a limited way and can be applied to any other technology within the spirit of the present disclosure.

[0072] The present application is based on the Japanese patent application No. 2018-184212 filed on September 28, 2018, the contents of which are incorporated herein by reference. COMMERCIAL APPLICABILITY

[0073] The diagnostic device for the internal combustion engine of the present disclosure is useful because it makes it possible to immediately detect the abnormality of the connection mechanism of the variable geometry turbocharger. REFERENCE MARK LIST 1 Internal combustion engine (engine) 14 turbochargers 14T Turbine 28 variable bucket 29 Turbo actuator 50 connection mechanism 56 Shovel arm 59 Turning piece 61 Contact part 63 Operating rotary joint 66 Operating arm 67 Contact part 100 electronic control units (ECUs) R wear-promoting area

Claims

Diagnostic device for an internal combustion engine, wherein the internal combustion engine includes a variable geometry turbocharger and wherein the turbocharger includes a variable vane, a linkage mechanism configured to operate the variable vane, and an actuator configured to drive the linkage mechanism, wherein the diagnostic device comprises: a control unit configured to control a degree of opening of the variable vane by controlling the actuator, wherein the control unit determines that an abnormality in the linkage mechanism of the turbocharger has occurred when an operating time of the internal combustion engine in a predetermined operating range exceeds a predetermined upper limit and a differential pressure between a target boost pressure, determined according to an operating condition of the internal combustion engine, and an actual boost pressure exceeds a predetermined upper limit. Diagnostic device for the internal combustion engine according to claim 1, wherein the predetermined operating range is an operating range in which the number of rotations of the internal combustion engine is large and the load of the internal combustion engine is low. Diagnostic device for the internal combustion engine according to claim 1 or 2, wherein the connection mechanism comprises a rotary element and a rotatable lever which engages in and is coupled to the rotary element, and wherein the abnormality of the connection mechanism is abnormal wear on a contact part between the rotary element and the lever.

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