JP5429085B2 - Turbocharger - Google Patents

Description

  The present invention relates to a supercharger used for an internal combustion engine (also referred to as an engine) mounted on a vehicle such as an automobile.

  For example, in an engine for an automobile, a supercharger (also called a turbocharger) is known that compresses intake air using the fluid energy of exhaust gas to increase the air density and thereby increase the engine output.

  The supercharger includes a turbine wheel provided in the middle of the exhaust passage and disposed in the turbine housing, and a compressor impeller provided in the middle of the intake passage and disposed in the compressor housing.

  In operation, when the turbine wheel is rotated by the pressure of the exhaust gas, the rotational force is transmitted to the compressor impeller via the turbine shaft, and the intake air is supercharged toward the combustion chamber by the rotation of the compressor impeller.

  The turbine wheel and the compressor impeller are connected by a rotating shaft, and the rotating shaft is rotatably supported by a slide bearing such as a floating bush or a radial bearing such as a rolling bearing (for example, Patent Documents 1 to 3). 3). The oil in the oil pan of the internal combustion engine is sucked up by an oil pump and supplied to the radial bearing.

JP-A 61-135933 Japanese Utility Model Publication No. 2-105545 JP 2008-31859 A

  In the conventional example according to Patent Document 1, the vibration of the turbine shaft is suppressed by increasing the amount of lubricating oil supplied to the turbocharger in the turbo rotation region where the vibration amount of the turbine shaft increases, that is, in the over rotation region. Thus, although the turbocharger is prevented from being damaged, there is no mention of leakage of oil supplied to the radial bearing that supports the turbine shaft, and naturally there is no idea of solving the oil leakage.

  In the conventional example according to Patent Literature 2, when the back surface of the rotor becomes negative pressure during the low speed rotation region of the engine or during deceleration, the oil present in the bearing chamber passes through the back chamber provided on the back side of the rotor and Since it is sucked out to the intake pipe, when the back surface of the rotor becomes negative pressure, the back chamber of the rotor is opened to the atmosphere so that the negative pressure disappears to prevent the oil from being sucked out. I have to. However, this conventional example does not have a technical idea of lowering the oil supply pressure to the bearing housing for the purpose of preventing oil suction.

  In the conventional example according to Patent Document 3, in the turbocharger with an electric motor, when the pressure of the blade rear surface portion of the turbine wheel or the compressor wheel is reduced during operation of the turbocharger, the oil supplied to the bearing portion is discharged from the exhaust pipe or intake air of the engine. Since it is sucked into the pipe, when the pressure on the blade back surface portion decreases, the pressure on the blade back surface portion and the hollow portion (bearing arrangement side) are made substantially equal to prevent the oil from being sucked out. Yes. However, this conventional example does not have a technical idea of lowering the oil supply pressure to the bearing housing for the purpose of preventing oil suction.

  In view of such circumstances, the present invention provides a turbocharger configured to rotatably support a rotating shaft provided with a turbine wheel and a compressor impeller with a radial bearing, to the outside of the oil supplied to the radial bearing. The purpose is to suppress or prevent sucking.

A turbocharger according to the present invention includes an oil supply device for supplying oil to a radial bearing that rotatably supports a rotating shaft provided with a turbine wheel and a compressor impeller, and an oil supply pressure by the oil supply device. An oil pump for sucking out oil in an oil pan of an internal combustion engine, and oil for supplying oil discharged from the oil pump to an installation area of the radial bearing. A path, a bypass oil path connected to an inlet side and an outlet side of the oil pump in the oil path, and an opening degree provided in the bypass oil path and controlled by the control device from the oil path. and a flow control valve for controlling the supply pressure of the oil supplied to the installation region, the controller, the radial Bear If the condition that increases the possibility that the oil supplied to the turbine is sucked into the turbine housing or compressor housing is satisfied, and if it is determined that the condition is satisfied, the condition is not satisfied In contrast, the opening degree of the flow control valve is controlled so as to set the oil supply pressure lower.

  In the turbocharger having such a premise configuration, when the back pressure of the turbine wheel becomes negative, the oil supplied to the radial bearing is more likely to be sucked out to the turbine wheel, and the back surface of the compressor impeller When the pressure becomes negative, there is a high possibility that the oil supplied to the radial bearing is sucked out to the compressor impeller side. That is, the state in which the back pressure of the turbine wheel or the back pressure of the compressor impeller is negative is one of the conditions that increase the possibility of oil suction.

In the present invention, when the condition that the possibility of oil suction is high is established, the supply pressure of oil supplied to the radial bearing is set low, so the amount of oil to be sucked out decreases. Therefore, it becomes possible to suppress or prevent the oil suction. Further, the oil supply device provided in the supercharger of the present invention can control the oil supply pressure with a relatively simple configuration, which is advantageous in suppressing an increase in equipment cost.

  Preferably, the control device estimates the back pressure of the turbine wheel using a map indicating an isoline of the back pressure of the turbine wheel using the fuel injection amount to the internal combustion engine and the engine speed as parameters. Pressure estimation processing, and impeller back pressure estimation processing for estimating the back pressure of the compressor impeller using a map showing isolines of the back pressure of the compressor impeller using the fuel injection amount to the internal combustion engine and the engine speed as parameters And a determination process for determining whether at least one of the results estimated in the two estimation processes is a negative pressure, and if a positive determination is made in this determination process, the rear pressure of the turbine wheel or the compressor impeller And a setting process for setting the oil supply pressure lower than when the back pressure is positive.

  In this configuration, the control device specifies a mode in which the back pressure of the turbine wheel and the back pressure of the compressor impeller are estimated. This specification is advantageous in suppressing an increase in equipment cost including the cost of the sensor and its installation cost as compared with a case where the back pressure is directly detected by a sensor or the like.

  In this configuration, when it is determined that at least one of the back pressure of the turbine wheel and the back pressure of the compressor impeller has become a negative pressure, the back pressure is the positive pressure of the oil supplied to the radial bearing. It is set smaller than the case of. As a result, the amount of oil to be sucked out decreases, so that the oil sucking out can be suppressed or prevented.

  And in the said structure, when the opening degree of a flow control valve is made small, for example, since the quantity which the oil discharged from an oil pump flows in into a bypass oil path decreases, the oil pressure in an oil path becomes high. On the other hand, when the opening degree of the flow control valve is increased, the amount of oil discharged from the oil pump flows into the bypass oil passage increases, so that the oil pressure in the oil passage decreases. In this way, it is possible to change the oil supply pressure from the oil passage to the radial bearing installation region by controlling the opening degree of the flow control valve with the control device.

  Preferably, the radial bearing is installed in an opposed annular space between the intermediate region of the rotating shaft and the bearing housing, and the radial bearing is supplied to the radial bearing at a position closer to the turbine wheel and a position closer to the compressor impeller than the radial bearing. Sealing portions for damming outflow of oil outside are provided, respectively, a rear chamber of the turbine wheel is provided outside the sealing portion on the back side of the turbine wheel, and the sealing portion is provided on the back side of the compressor impeller. The compressor impeller back chambers are respectively provided on the outer side.

  In this configuration, the location where the radial bearing is installed and the location where each back pressure of the turbine wheel and the compressor impeller is generated are specified.

  According to the present invention, in the supercharger, it is possible to suppress or prevent the oil that is supplied to the radial bearing that rotatably supports the rotating shaft provided with the turbine wheel and the compressor impeller from being discharged to the outside.

1 is a diagram showing a schematic configuration in an embodiment of an internal combustion engine including a supercharger according to the present invention. It is a figure which shows the cross section of the supercharger of FIG. It is a figure which shows schematic structure by one Embodiment of the oil supply apparatus for supplying oil to the supercharger of FIG. It is a flowchart for demonstrating the operation | movement by the control apparatus of FIG. It is a figure which shows the map used when estimating the back surface pressure Ptbn of a turbine wheel in step S3 of FIG. FIG. 5 is a diagram showing a map used when estimating a back pressure Pimp of the compressor impeller in step S3 of FIG. 4. It is a figure which shows the map used when estimating the turbo rotation speed Nt in step S3 of FIG.

  BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.

  1 to 7 show an embodiment of the present invention. In this embodiment, the example which applied this invention to the internal combustion engine provided with a single turbo supercharger is given.

  The internal combustion engine 1 shown in FIG. 1 is equipped with a supercharger 20. The supercharger 20 supercharges the air sucked into the internal combustion engine 1 from the intake passage 2 using the pressure of the exhaust discharged from the internal combustion engine 1 to the exhaust passage 3.

  When the turbine wheel 22 of the supercharger 20 is rotated by exhaust, the compressor impeller 24 is rotated accordingly, and the air sucked into the intake passage 2 from the air cleaner 4 is cooled by the intercooler 5 and its volume is compressed. Then, it is supplied to the combustion chamber of the internal combustion engine 1.

  Although not shown, blow-by gas leaking from the combustion chamber to the crank chamber with the operation of the internal combustion engine 1 is introduced into the ventilation case, and the mist-like (mist-like) contained in the blow-by gas in the ventilation case. Oil is separated. The blow-by gas from which the oil has been separated in this way is recirculated to the upstream side of the supercharger 20 (that is, between the air cleaner 4 and the supercharger 20) in the intake passage 2 via the blow-by gas passage 6. A PCV cooler 7 for cooling the blowby gas is provided in the middle of the blowby gas passage 6.

  Next, the supercharger 20 will be described in detail with reference to FIG. The supercharger 20 includes a turbine wheel 22 and a compressor impeller 24.

  The turbine wheel 22 is housed in a turbine housing 21 provided upstream of a catalytic converter (not shown) in the exhaust passage 3. On the other hand, the compressor impeller 24 is accommodated in a compressor housing 23 provided on the downstream side of the air cleaner 4 in the intake passage 2.

  The turbine wheel 22 is integrally formed at one axial end of the rotary shaft 25, and the compressor impeller 24 is integrally attached to the other axial end of the rotary shaft 25. The rotary shaft 25 is rotatably supported on the bearing housing 33 by two radial bearings 31 and 32.

  The turbine housing 21 is attached to one end of the bearing housing 33 in the axial direction, and the compressor housing 23 is attached to the other end of the bearing housing 33 in the axial direction.

  The two radial bearings 31 and 32 are substantially cylindrical slide bearings called metals and bushes, and are arranged in an axial direction in an annular space between the axial intermediate region of the rotary shaft 25 and the bearing housing 33. Is provided.

  Both radial bearings 31 and 32 are interposed in the annular space in a floating state so as to be relatively rotatable. However, a radial bearing (hereinafter referred to as a turbine-side radial bearing) 31 near the turbine wheel 22 is moved in the axial direction on the inner peripheral surface of the bearing housing 33 by two snap rings 35 and 36 that are locked to the bearing housing 33. Displacement is regulated. Further, a radial bearing 32 (hereinafter referred to as a compressor-side radial bearing) 32 near the compressor impeller 24 is formed in the bearing housing 33 by a single snap ring 37, a thrust bearing 38 and a thrust collar 34 that are locked to the bearing housing 33. The axial displacement on the peripheral surface is restricted.

  The axial direction of the rotary shaft 25 with respect to the bearing housing 33 is formed by sandwiching the thrust bearing 38 fastened to the bearing housing 33 at the flanges at both axial ends of the thrust collar 34 via a predetermined thrust gap. Displacement to is regulated. A thrust load acting on the rotary shaft 25 during operation of the supercharger 20 is supported by a thrust bearing 38 and a thrust collar 34. The thrust bearing 38 is formed of, for example, a synthetic resin material or a metal material having self-lubricating properties, and is substantially fan-shaped when viewed from one axial direction, and has a shape in which tapered land portions are provided at both axial ends. .

  Oil is supplied to the annular space in which the radial bearings 31 and 32 are arranged by the oil supply device 50.

  As shown in FIG. 3, the oil supply device 50 includes an oil pump 51, a piston-side oil passage 52, a supercharger-side oil passage 53, a hydraulically operated on-off valve 54, a bypass oil passage 55, and an electromagnetically operated flow rate. A control valve 56 and the like are provided.

  The oil pump 51 is driven by a crankshaft (not shown) of the internal combustion engine 1 and sucks up oil from the oil pan 1a. Oil discharged from the oil pump 51 is injected toward a piston (not shown) of the internal combustion engine 1 through a piston-side oil passage 52 and a jet nozzle (not shown). The oil discharged from the oil pump 51 passes through the supercharger side oil passage 53 branched from the middle of the piston side oil passage 52, and the annular space of the supercharger 20 (space where the radial bearings 31 and 32 are arranged). To be supplied.

  The hydraulically actuated on-off valve 54 is installed in the piston-side oil passage 52 downstream of the branching portion to the supercharger-side oil passage 53, and the oil pressure in the piston-side oil passage 52 is a predetermined threshold value. When it is above, it opens and closes when it is below the threshold.

  The electromagnetically operated flow control valve 56 is installed in the piston oil passage 52 in the middle of a bypass oil passage 55 connected to the discharge side and the inlet side of the oil pump 51. The opening degree of the flow control valve 56 is controlled by the control device 100. When the opening degree of the flow control valve 56 is reduced, the amount of oil discharged from the oil pump 51 flows into the bypass oil passage 55 is reduced, so that the oil pressure in the piston-side oil passage 52 is increased. On the other hand, when the opening degree of the flow control valve 56 is increased, the amount of oil discharged from the oil pump 51 flows into the bypass oil passage 55 increases, so that the oil pressure in the piston-side oil passage 52 decreases. Thus, by controlling the opening degree of the flow control valve 56 with the control device 100, the oil pressure in the piston-side oil passage 52 can be changed, and the opening / closing operation of the opening / closing valve 54 can be controlled. The on-off valve 54 is opened when the internal combustion engine 1 is at a high load, that is, high hydraulic pressure, and is closed when the hydraulic pressure is low.

  Moreover, if the opening degree of the flow control valve 56 is increased, the oil supply pressure supplied from the oil pump 51 to the supercharger side oil passage 53 can be set low, while the opening degree of the flow control valve 56 is reduced. The oil supply pressure supplied from the oil pump 51 to the supercharger side oil passage 53 can be set high.

  Incidentally, an introduction oil passage 33 a connected to the supercharger side oil passage 53 is provided inside the bearing housing 33. The downstream side of the introduction oil passage 33 a is opened toward the outer peripheral surfaces of the radial bearings 31 and 32. The radial bearings 31 and 32 are provided with oil holes 31a and 32a penetrating inward and outward in the radial direction at a plurality of locations in the circumferential direction and the axial direction.

  As a result, the oil supplied to the outer peripheral side of the radial bearings 31 and 32 via the supercharger side oil passage 53 and the introduction oil passage 33a is also supplied to the inner peripheral side of the radial bearings 31 and 32 via the oil holes 31a and 32a. Supplied. The oil supplied between the radial bearings 31 and 32 and the bearing housing 33 and between the radial bearings 31 and 32 and the rotary shaft 25 is held in a film shape. It acts as a damper that suppresses vibration in the direction and axial direction. This oil film is called an oil film damper. The excess oil supplied to the annular space in which the radial bearings 31 and 32 are disposed is discharged from the lower oil discharge passage 33b on the lower side of the bearing housing 33 and returned to the oil pan 1a.

  By the way, the oil supplied to the annular space passes from the both sides in the axial direction of the rotating shaft 25 to the outside, and these oils flow in the internal flow path 21a of the turbine housing 21 and the internal flow of the compressor housing 23. Seal rings 41 and 42 are provided to prevent leakage into the passage 23a.

  The seal ring 41 on the turbine wheel 22 side is mounted in a large-diameter outer peripheral groove near the turbine wheel 22 on the rotary shaft 25 and is in contact with the inner peripheral surface of the turbine side shoulder of the bearing housing 33. The inner peripheral surface of the shoulder on the turbine side has a larger diameter than the sliding contact surface of the radial bearing 31.

  On the other hand, the seal ring 42 on the compressor impeller 24 side is mounted in an outer peripheral groove of a seal sleeve 43 that is externally fitted to the rotary shaft 25, and contacts the inner peripheral surface of the annular back plate 23 b of the compressor housing 23. Has been. In addition, although the seal rings 41 and 42 are piston rings in this embodiment, the kind is not specifically limited.

  Further, in this embodiment, an oil damming portion (reference number omitted) for making it difficult for oil to reach the area where the seal rings 41 and 42 are present inside the area where the seal rings 41 and 42 are installed. ) Is provided.

  First, the oil damming portion on the turbine housing 21 side will be described. An outer peripheral groove 25 a is provided on the back side of the turbine wheel 22 in the rotary shaft 25. The outer circumferential groove 25 a receives oil that has passed through the turbine-side radial bearing 31 and drops it downward in the vertical direction so as to be directed toward the oil drain path 33 b of the bearing housing 33. This makes it difficult for oil to reach the turbine side seal ring 41 side. This outer peripheral groove 25a functions as an oil damming portion.

  Next, the oil damming portion on the compressor housing 23 side will be described. An oil deflector 44 is provided in the axially opposing space between the annular back plate 23 b of the compressor housing 23 and the bearing housing 33. The oil deflector 44 creates an annular space on the outer periphery of the rotary shaft 25 for receiving the oil that has passed through the compressor-side radial bearing 32, and the lower side receives oil from the lower side of the annular space. A guide portion 44b is provided for flowing down and leading to the oil drainage passage 33b. The outer surface of the annular wall portion 44 a along the radial direction in the oil deflector 44 is disposed so as to face the inner peripheral portion of the annular back plate 23 b of the compressor housing 23 in the axial direction via a gap. The gap created by the annular wall 44a of the oil deflector 44 and the annular back plate 23b of the compressor housing 23 facing each other exerts an oil damming action by being set to a dimension that restricts the passage of oil. It is an oil damming section. This makes it difficult for oil to reach the compressor-side seal ring 42 side.

  The seal rings 41 and 42, the turbine-side oil damming portion, and the compressor-side oil damming portion correspond to the sealing portion described in the claims.

  Next, the control device 100 for controlling the operations of the internal combustion engine 1 and the supercharger 20 will be described. The control device 100 is a known ECU (Electronic Control Unit), and mainly includes a CPU, a ROM, a RAM, and the like. The ROM stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU executes various arithmetic processes based on various control programs and maps stored in the ROM. The RAM is a memory that temporarily stores calculation results in the CPU, data input from each sensor, and the like. The backup RAM is a nonvolatile memory that stores data to be stored when the internal combustion engine 1 is stopped, for example. It is memory.

  The internal combustion engine 1 includes a crank angle sensor 201 for detecting the rotational speed Ne of the internal combustion engine 1, an accelerator opening sensor 202 for detecting the depression amount of the accelerator pedal 9, and a water temperature of the internal combustion engine 1. In the water temperature sensor 203, the intake pressure sensor 204 for detecting the intake pressure (intake manifold pressure or supercharging pressure) Pim on the downstream side of the intercooler 5, the air flow meter 205 for detecting the intake air amount Ga, and the exhaust passage 3 A pressure sensor 206 for detecting the upstream pressure of the catalytic converter (not shown) is provided. Here, only the sensors related to the characteristic configuration of the present invention are presented.

  The control device 100 determines the fuel injection amount and the fuel injection timing based on the engine speed Ne obtained from the detection signal of the crank angle sensor 201, the opening of the throttle valve 8 obtained from the detection signal of the accelerator opening sensor 202, and the like. The command value (target value) is calculated, and the fuel injection amount and fuel injection timing of a fuel injection valve (not shown) are controlled based on these command values.

  In addition, as will be described in detail below, the control device 100 determines the supply pressure of oil supplied to the radial bearings 31 and 32 of the supercharger 20 by the oil supply device 50 according to the operating state of the supercharger 20. I try to control it.

  When the internal combustion engine 1 is started or during normal operation, basically, the oil supply device 50 sets the oil supply pressure for the piston (not shown) of the internal combustion engine 1 to a value near the maximum capacity of the oil pump 51. Control is to be executed. The oil pump 51 is generally set to a capacity that has a margin than the capacity required in design. Therefore, if it is fixed only to the high hydraulic pressure control, there is a concern that when the internal combustion engine 1 is operated at a light load, the oil supply to the piston or the like becomes excessive, resulting in friction loss and deterioration of fuel consumption. . Therefore, when a specific condition other than the start time and the normal operation is satisfied, the oil supply pressure for the piston or the like is set low by the oil supply device 50 in order to reduce the friction loss as much as possible. It is like that. The specific conditions include, for example, a water temperature Tc that is equal to or lower than a warm-up completion temperature (for example, 95 ° C.) and an engine speed Ne that is medium or about half the maximum speed (for example, 2600 rpm).

  In addition, when the back pressure of the turbine wheel 22 (referred to as turbine back pressure Ptbn) becomes negative during the operation of the turbocharger 20, the oil supplied to the radial bearings 31 and 32 by the oil supply device 50 is The possibility of being sucked out into the internal flow path 21a of the turbine housing 21 through the facing gap 26 with the bearing housing 33 is increased. Further, when the back pressure of the compressor impeller 24 (impeller back pressure Pimp) becomes negative, the oil supplied to the radial bearings 31 and 32 by the oil supply device 50 is compressed between the compressor impeller 24 and the annular back plate 23b of the compressor housing 23. The possibility of being sucked out into the internal flow path 23a of the compressor housing 23 through the opposing gap 27 becomes high.

  Note that the facing gap 26 between the turbine wheel 22 and the bearing housing 33 and the facing gap 27 between the compressor impeller 24 and the annular back plate 23b of the compressor housing 23 correspond to the back chamber described in the claims. .

  The situation in which the turbine back pressure Ptbn or the impeller back pressure Pimp becomes negative in this way is, for example, when the idling operation of the internal combustion engine 1 is continued for a long time, when the vehicle speed is reduced, or when the vehicle speed is slowly accelerated. A situation where pulsation or exhaust pulsation occurs may be mentioned.

  Therefore, in this embodiment, it is checked whether or not a condition that increases the possibility that the oil supplied to the radial bearings 31 and 32 is sucked into the turbine housing 21 or the compressor housing 23 is satisfied, and the condition is satisfied. If the condition is not satisfied, the oil supply device 50 sets the supply pressure of the oil supplied to the radial bearings 31 and 32 lower than that in the case where the condition is not satisfied, thereby suppressing or preventing the oil suction. I have to.

  One of the conditions is that at least one of the turbine back pressure Ptbn and the impeller back pressure Pimp is a negative pressure.

  Hereinafter, the control mode of the oil supply pressure will be described in detail with reference to the flowchart of FIG. In the flowchart of FIG. 4, a control operation mainly including the control device 100 is illustrated. This flowchart is started at regular intervals (for example, about several milliseconds to several tens of milliseconds) during operation of the internal combustion engine 1.

  First, in step S1, information related to the operating state of the internal combustion engine 1 and the supercharger 20 is acquired. Here, for example, the rotational speed Ne of the internal combustion engine 1 is calculated based on the input signal from the crank angle sensor 201, and the target throttle opening and the target fuel injection amount Q are calculated based on the input signal from the accelerator opening sensor 202. To do.

  In the subsequent step S2, it is determined whether or not a condition that the oil supply pressure by the oil supply device 50 cannot be changed to a low oil pressure is satisfied. Here, for example, when the oil supply pressure to the piston needs to be a high hydraulic pressure, such as when the internal combustion engine 1 is started, or when some abnormality that makes it difficult to control the oil supply device 50 occurs. It is determined that a condition that the oil supply pressure cannot be changed to a low oil pressure is satisfied.

  Further, in step S3, the turbine back pressure Ptbn, the impeller back pressure Pimp, and the turbo speed Nt are estimated. For example, the turbine back pressure Ptbn is estimated using the map shown in FIG. 5, the impeller back pressure Pimp is estimated using the map shown in FIG. 6, and the turbo speed Nt is estimated using the map shown in FIG.

  The maps shown in FIGS. 5 to 7 are isolines of the turbine back pressure Ptbn, the impeller back pressure Pimp, and the turbo speed Nt, each of which uses the rotational speed Ne of the internal combustion engine 1 and the fuel injection amount Q as parameters. , Which is created in advance based on experiments and stored in the ROM of the control device 100.

  In addition, in the hatched areas in the maps shown in FIGS. 5 to 7, the turbine back pressure Ptbn and the impeller back pressure Pimp are likely to pulsate, and the valley of the pressure pulsation becomes negative pressure, and oil suction is generated. It is an area of concern and is referred to as an oil suction concerned area.

  Furthermore, the region with cross-hatching in the map shown in FIG. 7 is a region where the turbo rotation speed Nt is high and there is a risk of insufficient lubrication, which is referred to as an insufficient lubrication concern region. To do. The oil suction concern area and the insufficient circulation concern area are empirically set in advance based on the capacity of the supercharger 20 to be used.

  Specifically, in step S3, the engine speed Ne and the target fuel injection amount Q acquired in step S1 are plotted on the two-dimensional coordinates of each map shown in FIGS. The back pressure Ptbn, the impeller back pressure Pimp, and the turbo speed Nt are calculated.

  Thereafter, in step S4, it is determined whether or not the accelerator pedal 9 is turned off. If an affirmative determination is made in step S4, that is, if the accelerator is off, the process proceeds to step S5, whereas if a negative determination is made, that is, if the accelerator is not turned off, the process proceeds to step S6.

  First, step S5 will be described. In this step S5, it is checked whether or not the turbo rotational speed Nt estimated in the step S3 is in the cross-hatching region (region where lubrication is insufficient) in FIG.

  If an affirmative determination is made in step S5, the flow proceeds to step S8, and high oil pressure control is performed to increase the oil supply pressure by the oil supply device 50, so that the amount of oil supplied to the radial bearings 31 and 32 is increased. Then, the process of this flowchart is complete | finished. Note that the oil supply pressure by the high hydraulic pressure control in step S8 is set to be the same as the high hydraulic pressure control performed at the time of starting the internal combustion engine 1 or during steady operation, but can be empirically specified by experiment. is there.

  On the other hand, if a negative determination is made in step S5, the flow proceeds to step S9, and low oil pressure control for lowering the oil supply pressure by the oil supply device 50 is performed to reduce the amount of oil supplied to the radial bearings 31 and 32. Then, the process of this flowchart is terminated. The oil supply pressure by the low hydraulic pressure control in step S9 is set to be lower than that in the case of the high hydraulic pressure control, but it is preferable to specify it empirically through experiments, for example, radial bearings 31 and 32. It is possible to set a value close to zero as long as the surrounding oil is not depleted.

  Next, step S6 will be described. In this step S6, it is checked whether or not the turbine back pressure Ptbn or impeller back pressure Pimp estimated in step S3 is a negative pressure (less than 0 kpa).

  If the negative pressure (Ptbn <0 kpa or Pimp <0 kpa) is satisfied, an affirmative determination is made in step S6, and the flow proceeds to step S9 described above to perform low hydraulic pressure control. On the other hand, if the positive pressure (Ptbn ≧ 0 kpa or Pimp ≧ 0 kpa), a negative determination is made in step S6, and the process proceeds to the subsequent step S7.

  In this step S7, it is checked whether or not the turbo rotational speed Nt estimated in the step S3 is in the hatching region (oil suction concern region) in FIG.

  If an affirmative determination is made in step S7, that is, if the turbo rotation speed Nt is in the oil suction concern region, the flow proceeds to step S9 described above and low oil pressure control is performed. On the other hand, if a negative determination is made in step S7, that is, if the turbo rotation speed Nt is not within the oil suction concern area, the flow proceeds to the above-described step S8 to perform high hydraulic pressure control.

  As described above, in the embodiment to which the present invention is applied, during the operation of the internal combustion engine 1 and the supercharger 20, the turbine back pressure Ptbn, the impeller back pressure Pimp, and the turbo rotation speed Nt are estimated, and the estimation result On the basis of the above, whether or not a condition is established that oil supplied to the radial bearings 31 and 32 of the turbocharger 20 is likely to be sucked into the internal passage 21a of the turbine housing 21 or the internal passage 23a of the compressor housing 23. When it is determined that the condition is satisfied, the oil supply pressure to the radial bearings 31 and 32 of the supercharger 20 is set as low as possible.

  In this way, when the situation where oil suction is likely to occur, the amount of oil to be sucked out is reduced as much as possible, so in the conventional example in which the oil supply pressure is not controlled as in this embodiment. In comparison, oil suction can be suppressed or prevented.

  As a result, it is possible to prevent a phenomenon in which oil-mixed air is introduced into the combustion chamber (not shown) of the internal combustion engine 1 and a phenomenon in which oil is discharged into the exhaust passage 3. Helps prevent outbreaks.

  In addition, as described above, the oil pump 51 provided in the oil supply device 50 is generally set to a capacity that has a margin beyond the capacity required in the design. For this reason, as in this embodiment, In the case of the conventional example in which no measures are taken for oil suction, it is expected that the amount of oil sucked will be excessive if the oil suction occurs. On the other hand, in this embodiment, since the oil pump 51 is used for the purpose of avoiding insufficient lubrication while using the large-capacity oil pump 51, the supercharger 20 can be sufficiently used in a steady state. Lubrication performance can be ensured, and oil suction can be suppressed or prevented when a specific condition is satisfied.

  In particular, in the above embodiment, as a condition for increasing the possibility of oil suction, only the determination as to whether or not the turbine back pressure Ptbn and the impeller back pressure Pimp are negative as in step S6 of FIG. Without specifying, it is determined whether or not the turbine back pressure Ptbn and the impeller back pressure Pimp are in the oil suction concern region of FIGS. 5 and 6 as in step S7 of FIG. It can be said that it is advantageous in increasing the suppression effect of the sucking-out.

  The reason will be explained. In the first place, the oil suction concern region includes a situation where the turbine back pressure Ptbn and the impeller back pressure Pimp pulsate, the pressure pulsation valley becomes negative pressure, and the pulsation peak becomes positive pressure. . That is, the case where the turbine back pressure Ptbn and the impeller back pressure Pimp are in the oil suction concern region in FIGS. 5 and 6 means that the negative pressure and the positive pressure are alternately generated. ing. Therefore, as in the above-described embodiment, if the low hydraulic pressure control is performed when the turbine back pressure Ptbn and the impeller back pressure Pimp are in the oil suction concern region, the positive pressure is close to the negative pressure. Since it is possible to perform low oil pressure control at any time, it is advantageous in increasing the oil suction suppression effect.

  In addition, this invention is not limited only to the said embodiment, It can change suitably in the range equivalent to the claim and the said range. Examples are given below.

  In the above embodiment, an example is given in which the back pressure Ptbn of the turbine wheel 22 and the back pressure Pimp of the compressor impeller 24 are estimated. However, the present invention is not limited to this example. Although not shown, the back pressure Ptbn and the back pressure Pimp of the compressor impeller 24 can be detected using sensors or the like.

  The present invention can be applied to, for example, a supercharger provided in an internal combustion engine.

1 Internal combustion engine
2 Intake passage
DESCRIPTION OF SYMBOLS 3 Exhaust passage 20 Supercharger 21 Turbine housing 22 Turbine wheel 23 Compressor housing 24 Compressor impeller 25 Rotating shaft 31 Turbine side radial bearing 32 Compressor side radial bearing 33 Bearing housing 41 Turbine side seal ring 42 Compressor side seal ring 43 Seal sleeve 44 Oil Deflector 50 Oil supply device 51 Oil pump 52 Piston side oil passage 53 Supercharger side oil passage 54 Hydraulically operated on-off valve 55 Bypass oil passage 56 Electromagnetically operated flow control valve 100 Control device

Claims (3)

An oil supply device for supplying oil to a radial bearing that rotatably supports a rotating shaft provided with a turbine wheel and a compressor impeller, and a control device for controlling oil supply pressure by the oil supply device;
The oil supply device includes an oil pump that sucks out oil in an oil pan of an internal combustion engine, an oil passage for supplying oil discharged from the oil pump to an installation area of the radial bearing, and the oil passage in the oil passage. A bypass oil passage connected to the inlet side and the outlet side of the pump, and supply of oil that is provided in the bypass oil passage and is supplied from the oil passage to the installation area by controlling the opening degree by the control device A flow control valve for controlling pressure,
The control device examines whether or not a condition that increases a possibility that oil supplied to the radial bearing is sucked into the turbine housing or the compressor housing is satisfied, and determines that the condition is satisfied, The supercharger characterized by controlling the opening degree of the said flow control valve so that the said oil supply pressure may be set low compared with the case where conditions are not satisfied. The turbocharger according to claim 1, wherein
The control device is a turbine back pressure estimation process for estimating the back pressure of the turbine wheel using a map showing an isoline of the back pressure of the turbine wheel using the fuel injection amount to the internal combustion engine and the engine speed as parameters. When,
An impeller back pressure estimation process for estimating the back pressure of the compressor impeller using a map showing an isoline of the back pressure of the compressor impeller using the fuel injection amount to the internal combustion engine and the engine speed as parameters;
A determination process for determining whether at least one of the results estimated in the two estimation processes is a negative pressure;
When an affirmative determination is made in this determination process, a setting process for setting the oil supply pressure lower than that in the case where the back pressure of the turbine wheel or the back pressure of the compressor impeller is positive is performed. Turbocharger. In the supercharger according to claim 1 or 2,
The radial bearing is installed in an opposed annular space between the intermediate region of the rotating shaft and the bearing housing. The radial bearing is closer to the turbine wheel and the compressor impeller than the radial bearing is outside the oil supplied to the radial bearing. A sealing part is provided for blocking the outflow,
A rear chamber of the turbine wheel is provided outside the sealing portion on the rear side of the turbine wheel, and a rear chamber of the compressor impeller is provided outside the sealing portion on the rear side of the compressor impeller. A turbocharger characterized by

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