Turbocharger control device

Abstract

To more accurately estimate the temperature of a seal ring that seals a gap around a turbine shaft on a turbine housing side.SOLUTION: A turbocharger control device of the present disclosure is for controlling a turbocharger including: a turbine housing provided in an exhaust passage of an internal combustion engine mounted on a vehicle; a turbine wheel disposed in the turbine housing; a compressor wheel that is connected to the turbine wheel via a turbine shaft and is disposed in a compressor housing provided in an intake passage of the internal combustion engine; a bearing housing supporting the turbine shaft via bearings between the turbine housing and the compressor housing; and a seal ring that seals a gap around the turbine shaft on the turbine housing side. The turbocharger control device estimates the temperature of the seal ring in consideration of the temperature of exhaust gas in the turbine housing.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a control device for a turbocharger that includes a seal ring that seals a gap around a turbine shaft on the turbine housing side. [Background technology]

[0002] Conventionally, there is known a turbocharger including a turbine housing provided in an exhaust passage of an internal combustion engine, a compressor housing provided in the exhaust passage, a turbine wheel disposed in the turbine housing, a compressor wheel connected to the turbine wheel via a turbine shaft and disposed in the compressor housing, and a bearing housing supporting the turbine shaft via a bearing between the turbine housing and the compressor housing (see, for example, Patent Document 1). In this turbocharger, a gap (rotational sliding gap) around the turbine shaft is sealed by a seal ring disposed in the bearing housing so as to be adjacent to the turbine wheel, and a seal ring disposed in the bearing housing so as to be adjacent to the compressor wheel. This seal ring prevents leakage of lubricating oil supplied into the bearing housing and inflow of high-temperature exhaust gas from the turbine housing into the bearing housing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-086705 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned turbocharger, the temperature of the lubricating oil in the bearing housing may rise depending on the operating state of the internal combustion engine, leading to carbonization of the lubricating oil, so it is necessary to appropriately cool the inside of the bearing housing in response to the temperature rise of the object of lubrication cooling. In order to appropriately cool the inside of the bearing housing, it is necessary to accurately estimate the temperature of the seal ring on the turbine housing side, which tends to become hot.

[0005] Therefore, a main object of the present disclosure is to more accurately estimate the temperature of a seal ring that seals a gap around a turbine shaft on the turbine housing side. [Means for solving the problem]

[0006] The turbocharger control device disclosed herein includes a turbine housing provided in an exhaust passage of an internal combustion engine mounted on a vehicle, a turbine wheel disposed within the turbine housing, a compressor wheel connected to the turbine wheel via a turbine shaft and disposed within a compressor housing provided in an intake passage of the internal combustion engine, a bearing housing that supports the turbine shaft via a bearing between the turbine housing and the compressor housing, and a seal ring that seals a gap around the turbine shaft on the turbine housing side, and estimates the temperature of the seal ring by taking into account the temperature of the exhaust gas in the turbine housing.

[0007] The control device for a turbocharger disclosed herein estimates the temperature of a seal ring that seals a gap around the turbine shaft on the turbine housing side, taking into account the temperature of exhaust gas in the turbine housing. This makes it possible to reflect the amount of heat transferred from the turbine housing, which has a high heat capacity, to the seal ring in the estimated temperature value of the seal ring, particularly in a case where the internal combustion engine is stopped immediately after being operated at high load with intake air compressed by the turbocharger. As a result, it becomes possible to more accurately estimate the temperature of the seal ring that seals a gap around the turbine shaft on the turbine housing side.

[0008] The control device may estimate the temperature of the exhaust gas in the turbine housing by taking a weighted average of the temperature of the exhaust gas flowing into the turbine housing and the temperature of the exhaust gas flowing out of the turbine housing, thereby making it possible to more accurately estimate the temperature of the exhaust gas in the turbine housing.

[0009] Furthermore, a lubricating oil for lubricating the turbine shaft and the bearing, and cooling water for lubricating the turbine shaft and the bearing may be supplied into the bearing housing, and the control device may estimate the temperature of the seal ring based on the previous temperature of the seal ring, the previous temperature of the wall of the lubricating oil passage, the temperature of the turbine shaft, the temperature and flow rate of the cooling water, and the temperature of the exhaust gas in the turbine housing.

[0010] The control device may also be configured to operate a pump that supplies the cooling water into the bearing housing when the operation of the internal combustion engine is stopped and the temperature of the seal ring is equal to or higher than a predetermined threshold value, thereby making it possible to effectively suppress carbonization of the lubricating oil in the bearing housing.

[0011] Furthermore, the internal combustion engine may be intermittently operated depending on the state of the vehicle. That is, the turbocharger control device of the present disclosure is extremely useful for protecting a turbocharger mounted on a vehicle in which so-called idle stop control is executed or a hybrid vehicle in which the internal combustion engine is started and stopped relatively frequently. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram illustrating an internal combustion engine to which a supercharger control device according to the present disclosure is applied; [Diagram 2] FIG. 2 is a schematic configuration diagram showing a supercharger of the internal combustion engine of FIG. [Diagram 3] FIG. 3 is a system diagram showing a cooling system associated with the turbocharger of FIG. 2. [Figure 4] FIG. 2 is a block diagram showing a control device for a turbocharger according to the present disclosure. [Diagram 5] 4 is a flowchart showing a procedure for cooling the turbocharger by the turbocharger control device of the present disclosure. [Figure 6] 5 is a flowchart showing a procedure for estimating the temperature of a seal ring by the control device for a turbocharger according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, an embodiment of the present disclosure will be described with reference to the drawings.

[0014] FIG. 1 is a schematic diagram illustrating an engine 10, which is an internal combustion engine controlled by an engine electronic control unit (hereinafter referred to as "engine ECU") 100 as a control device for a turbocharger according to the present disclosure. The engine 10 shown in the figure is a gasoline engine that converts the reciprocating motion of a piston 13, which accompanies the combustion of a mixture of a hydrocarbon fuel and air in a plurality of combustion chambers 12 formed in an engine block 11, into the rotational motion of a crankshaft (output shaft) 14, and is mounted on a vehicle in which so-called idle stop control is performed or a hybrid vehicle in which the engine is started and stopped relatively frequently. As shown in FIG. 1, the engine 10 includes, in addition to the engine block 11, the plurality of combustion chambers 12, the pistons 13, and the crankshaft 14, an air cleaner 15, an intake pipe 16, an electronically controlled throttle valve 17, a surge tank 18, a plurality of intake valves 19i that open and close the corresponding intake ports, exhaust valves 19e that open and close the corresponding exhaust ports, a plurality of fuel injection valves 20, a plurality of ignition plugs 21, and an exhaust pipe 22 that forms an exhaust passage. The fuel injection valve 20 may be one that injects fuel into an intake port as shown in the figure, or one that injects fuel directly into the combustion chamber 12. Furthermore, the engine 10 may be provided with both a port injection valve and an in-cylinder injection valve.

[0015] The engine 10 also includes an upstream purification device 23 and a downstream purification device 24, each of which is incorporated in the exhaust pipe 22, as exhaust gas purification devices. The upstream purification device 23 includes a NOx storage type exhaust gas purification catalyst (three-way catalyst) 230 that purifies harmful components such as CO (carbon monoxide), HC, and NOx in the exhaust gas from each combustion chamber 12 of the engine 10. The downstream purification device 24 includes a particulate filter (GPF) 240 that collects particulate matter (fine particles) in the exhaust gas, and is disposed downstream of the upstream purification device 23. In this embodiment, the particulate filter 240 is a porous filter carrying a NOx storage type exhaust gas purification catalyst (three-way catalyst). That is, the downstream purification device 24 is configured as a four-way catalyst having the purification function of a three-way catalyst and the collection function of particulate matter.

[0016] Furthermore, the engine 10 includes a coolant circulation passage 25 for cooling the engine block 11 etc., an electric pump 26, and a radiator 27. The electric pump 26 circulates coolant (LLC) through the coolant circulation passage 25. The radiator 27 cools the coolant that has absorbed heat from the engine block 11 etc. by heat exchange with air from traveling wind and an electric fan (not shown). A water temperature sensor 25t is also provided in the coolant circulation passage 25. The water temperature sensor 25t detects the temperature of the coolant that has absorbed heat from (flowed out of) the engine block 11.

[0017] In addition, the engine 10 includes a turbocharger 30 that compresses intake air by utilizing the energy of exhaust gas. As shown in Fig. 1, the turbocharger 30 is a turbocharger including a turbine wheel 31, a compressor wheel 32, a turbine shaft 33 that integrally connects the turbine wheel 31 and the compressor wheel 32, a wastegate valve 34, and a blow-off valve 35. As shown in Fig. 2, the turbine wheel 31 is rotatably disposed in a turbine housing 220 formed in the exhaust pipe 22 so as to be located upstream of the upstream purification device 23. Also, as shown in Fig. 2, the compressor wheel 32 is rotatably disposed in a compressor housing 160 formed in the intake pipe 16 so as to be located between the air cleaner 15 and the throttle valve 17.

[0018] As shown in Fig. 2, the turbine shaft 33 is rotatably disposed in a bearing housing 300 fixed between the turbine housing 220 and the compressor housing 160. The bearing housing 300 holds a bearing 36 and rotatably supports the turbine shaft 33 via the bearing 36. An oil passage 37 for circulating a lubricating oil that lubricates and cools the turbine shaft 33, the bearing 36, etc., and a refrigerant passage 38 for cooling the inside of the bearing housing 300 are formed in the bearing housing 300. Hydraulic oil as a lubricating oil is supplied to the oil passage 37 from a hydraulic control device (not shown) that adjusts the pressure of hydraulic oil from a mechanical oil pump (not shown) driven by the engine 10.

[0019] The refrigerant passage 38 in the bearing housing 300 is incorporated in a cooling system 40 that circulates cooling water. As shown in FIG. 3, the cooling system 40 includes an intercooler 41, a refrigerant circulation passage 42, an electric pump 44 that circulates the cooling water as a refrigerant in the refrigerant circulation passage 42, and a radiator 45. The refrigerant passage 38 in the bearing housing 300 is incorporated in parallel with the intercooler 41 with respect to the refrigerant circulation passage 42, and the cooling water is supplied into the refrigerant passage 38 in response to operation of the electric pump 44. The intercooler 41 is installed in the intake pipe 16 of the engine 10 so as to be located between the compressor housing 160 and the throttle valve 17. The intercooler 41 exchanges heat between the air compressed by the compressor wheel 32 and the cooling water flowing through the refrigerant circulation passage 42, and cools the compressed and heated air. The radiator 45 cools the cooling water that has flowed through the intercooler 41 and the refrigerant passage 38 in the bearing housing 300 by exchanging heat with air produced by running or air from an electric fan (not shown).

[0020] Furthermore, seal rings 39t and 39c are disposed between the bearing housing 300 and the turbine shaft 33. The seal ring 39t is disposed between the bearing housing 300 and a portion of the turbine shaft 33 close to the turbine wheel 31, and seals the gap between the bearing housing 300 and the turbine shaft 33 (the gap around the turbine shaft 33) on the turbine housing 220 side. The seal ring 39c is disposed between the bearing housing 300 and a portion of the turbine shaft 33 close to the compressor housing 160, and seals the gap between the bearing housing 300 and the turbine shaft 33 (the gap around the turbine shaft 33) on the compressor housing 160 side. As a result, the seal rings 39t and 39c suppress leakage of lubricating oil and cooling water supplied into the bearing housing 300, inflow of high-temperature exhaust gas from the turbine housing 220 into the bearing housing 300, and the like.

[0021] The wastegate valve 34 of the turbocharger 30 is a flow control valve, and is installed in a bypass pipe 225 connected to the exhaust pipe 22 so as to bypass the turbine housing 220 (turbine wheel 31) as shown in Fig. 1. By adjusting the opening degree of the wastegate valve 34, it is possible to change the ratio between the amount of exhaust gas flowing through the bypass pipe 165 and the amount of exhaust gas rotating the turbine wheel 31 and the compressor wheel 32. That is, in the turbocharger 30, it is possible to adjust the supercharging pressure Pc in the engine 10 by adjusting the opening degree of the wastegate valve 34. In addition, by fully opening the wastegate valve 34, it is possible to substantially stop compression of the intake air by the turbocharger 30 (compressor wheel 32).

[0022] 1, the blow-off valve 35 of the turbocharger 30 is installed in a bypass pipe 165 connected to the intake pipe 16 so as to bypass the compressor housing 160 (compressor wheel 32). By opening the blow-off valve 35, it is possible to release the pressure (excess pressure) between the compressor wheel 32 of the intake pipe 16 and the throttle valve 17. This makes it possible to suppress deterioration of the responsiveness of the throttle valve 17 and the occurrence of surging. The blow-off valve 35 may be a check valve that opens when the pressure on the downstream side of the compressor wheel 32 becomes higher than the pressure on the upstream side by a predetermined value or more.

[0023] The engine ECU 100 that controls the engine 10 includes a microcomputer having a CPU, ROM, RAM, input / output interfaces, etc. (not shown), various drive circuits, various logic ICs, etc. As shown in Fig. 4, the engine ECU 100 obtains detection values ​​of the crank angle sensor 14a, the air flow meter 16a, the intake pressure sensor 16p, the boost pressure sensor 16c, the intake air temperature sensor 16t, the throttle opening sensor 17o, the surge pressure sensor 18p, the temperature sensor 18t, the upstream air-fuel ratio sensor 22f, the downstream air-fuel ratio sensor 22r, the water temperature sensor 25t, the outside air temperature sensor 28, the atmospheric pressure sensor 29, etc., via an input port (not shown).

[0024] The crank angle sensor 14a detects the rotational position (crank position) of the crankshaft 14. The air flow meter 16a detects the intake air amount Qa upstream of the compressor wheel 32 of the intake pipe 16. The intake pressure sensor 16p detects the intake pressure Pin upstream of the compressor wheel 32 of the intake pipe 16. The intake air temperature sensor 16t detects the intake temperature Tin upstream of the compressor wheel 32 of the intake pipe 16. The boost pressure sensor 16c detects the boost pressure Pc, which is the pressure of air compressed by the compressor wheel 32 between the compressor housing 160 of the intake pipe 16 and the intercooler 41. The throttle opening sensor 17o detects the opening TH of the throttle valve 17. The surge pressure sensor 18p detects the surge pressure Ps, which is the pressure of the air in the surge tank 18, and the temperature sensor 18t detects the surge temperature Ts, which is the temperature of the air in the surge tank 18. The upstream air-fuel ratio sensor 22f detects an upstream air-fuel ratio AFf, which is the air-fuel ratio of exhaust gas flowing into the upstream purification device 23, upstream of the upstream purification device 23, and the downstream air-fuel ratio sensor 22r detects a downstream air-fuel ratio AFr, which is the air-fuel ratio of exhaust gas flowing into the downstream purification device 24, downstream of the upstream purification device 23.

[0025] The engine ECU 100 calculates the rotation speed Ne of the engine 10 (crankshaft 14) based on the crank position from the crank angle sensor 14a, and calculates a load factor KL based on the intake air amount Qa from the air flow meter 16a and the rotation speed Ne of the engine 10. The load factor KL is the ratio of the volume of air actually taken in during one cycle to the stroke volume per cycle of the engine 10. The engine ECU 100 controls the throttle valve 17, the multiple fuel injection valves 20, the multiple ignition plugs 21, etc. based on the rotation speed Ne, the load factor KL, etc. Furthermore, the engine ECU 100 controls the wastegate valve 34 and the blow-off valve 35 of the turbocharger 30, the electric pump 26, and the electric pump 44 of the cooling system 40.

[0026] In a vehicle in which idle stop control is executed or a hybrid vehicle, the engine 10 is started and stopped relatively frequently, and the operation of the engine 10 may be stopped immediately after the engine 10 is operated at high load with the intake air compressed by the turbocharger 30. In such a case, the temperature of the lubricating oil (hydraulic oil) in the bearing housing 300 may rise and the lubricating oil may be carbonized, and it becomes necessary to cool the inside of the bearing housing 300 in response to the temperature rise. For this reason, in a vehicle equipped with the engine 10, the engine ECU 100 executes the routine of FIG. 5 while the operation of the engine 10 is stopped in response to the establishment of an engine stop condition or immediately after the ignition switch is turned off.

[0027] 5, the engine ECU 100 acquires the temperature Tsr of the seal ring 39t on the turbine housing 220 side, the temperature Tbr of the bearing 36, and the wall temperature To near the oil outlet of the oil passage 37, which are separately estimated (calculated) (step S100). Next, the engine ECU 100 determines whether the temperature Tsr of the seal ring 39t acquired in step S100 is less than a predetermined threshold value Tsrref (step S110). If the engine ECU 100 determines that the temperature Tsr of the seal ring 39t is less than the threshold value Tsrref (step S110: YES), the engine ECU 100 determines whether the temperature Tbr of the bearing 36 acquired in step S100 is less than a predetermined threshold value Tbrref (step S120). Furthermore, when it is determined that the temperature Tbr of the bearing 36 is lower than the threshold value Tbrref (step S120: YES), the engine ECU 100 determines whether the wall temperature To acquired in step S100 is lower than a predetermined threshold value Toref (step S130).

[0028] The threshold values ​​Tsrref, Tbrref, and Toref are all determined in advance through experiments, analyses, and the like as upper limit values ​​of the temperature of the seal ring 39t, the bearing 36, or the above-mentioned wall portions at which it is deemed that there is no risk of carbonization (coking) of the lubricant due to an oil film breakdown or the like occurring in the gap between the turbine shaft 33 and the bearing 36. When the engine ECU 100 determines that the wall temperature To of the oil passage 37 is lower than the threshold value Toref (step S130: YES), it determines that it is not necessary to cool the inside of the bearing housing 300 to suppress the occurrence of carbonization of the lubricant, and stops the operation of the electric pump 44 of the cooling system 40 or keeps the electric pump 44 in an operation-stopped state (step S140), and ends the routine of FIG.

[0029] On the other hand, when the engine ECU 100 determines that the temperature Tsr of the seal ring 39t acquired in step S100 is equal to or higher than the threshold value Tsrref (step S110: NO), the engine ECU 100 determines that it is necessary to cool the inside of the bearing housing 300 in order to suppress the occurrence of carbonization of the lubricant, and operates the electric pump 44 of the cooling system 40 for a predetermined time (step S150), and ends the routine of FIG. 5. When the engine ECU 100 determines that the temperature Tbr of the bearing 36 acquired in step S100 is equal to or higher than the threshold value Tbrref (step S120: NO), the engine ECU 100 operates the electric pump 44 of the cooling system 40 for a predetermined time (step S150), and ends the routine of FIG. 5. When the engine ECU 100 determines that the wall temperature To acquired in step S100 is equal to or higher than the threshold value Toref (step S130: NO), the engine ECU 100 operates the electric pump 44 of the cooling system 40 for a predetermined time (step S150), and ends the routine of FIG. 5. This makes it possible to cool the inside of the bearing housing 300 and effectively prevent the lubricating oil from carbonizing.

[0030] Continuing with reference to Fig. 6, the procedure for estimating the temperature Tsr of the seal ring 39t, the temperature Tbr of the bearing 36, and the wall temperature To of the oil passage 37 will be described. Fig. 6 is a flowchart showing a temperature estimation routine for estimating the temperatures of the seal ring 39t, etc. The temperature estimation routine shown in the figure is repeatedly executed by the engine ECU 100 at predetermined time intervals (very short time intervals) while the system of the vehicle equipped with the engine 10 is started.

[0031] At the start of the routine of FIG. 6, the engine ECU 100 acquires data necessary for temperature estimation, such as the intake air temperature Tin detected by the intake air temperature sensor 16t, the intake air pressure Pin (absolute pressure) detected by the intake air pressure sensor 16p, the supercharging pressure Pc (absolute pressure) detected by the supercharging pressure sensor 16c, the inlet gas temperature Tti, which is the temperature of the exhaust gas flowing into the turbine housing 220 (turbine wheel 31), the temperature (water temperature) Twsh of the cooling water in the coolant passage 38 of the supercharger 30 (bearing housing 300), and the amount of cooling water Qwsh passing through the coolant passage 38 (step S200). The inlet gas temperature Tti is the temperature (estimated value) of the exhaust gas flowing into the above-mentioned turbine housing 220 (turbine wheel 31), and is estimated separately based on the rotation speed Ne, the load factor KL, the upstream air-fuel ratio AFf, etc. of the engine 10. In addition, in step S200, the outside air temperature Tout detected by the outside air temperature sensor 28 is acquired as the cooling water temperature Twsh. However, when the temperature of the coolant in the refrigerant passage 38 is actually measured, the actual measured value may be used as the coolant temperature Twsh. Furthermore, the flow rate Qwsh of the coolant is estimated separately based on the rotation speed of the electric pump 44, the cross-sectional area of ​​the refrigerant passage 38, the cross-sectional area of ​​the heat transfer tube of the intercooler 41, and the like.

[0032] After the process of step S200, the engine ECU 100 estimates (calculates) an outlet gas temperature Tto, which is the temperature of the exhaust gas flowing out from the turbine housing 220 (the turbine wheel 31) to the downstream side, by using the following formula (1) (step S210). In formula (1), "Tti" is the inlet gas temperature Tti acquired in step S200. Also, in formula (1), "Tci" is the temperature of the air flowing into the compressor housing 160 (the compressor wheel 32), and in this embodiment, the intake air temperature Tin acquired in step S200 is used as the temperature Tci. However, the outside air temperature Tout detected by the outside air temperature sensor 28 may be used as the temperature Tci. Furthermore, in formula (1), "Pci" is the pressure of the air flowing into the compressor housing 160, and in this embodiment, the intake air pressure Pin (absolute pressure) acquired in step S200 is used as the pressure Pci. However, the atmospheric pressure Pout detected by the atmospheric pressure sensor 29 may be used as the pressure Pci. In addition, in formula (1), "Pco" is the pressure of the air (compressed air) sent out from the compressor wheel 32, and in this embodiment, the supercharging pressure Pc (absolute pressure) acquired in step S200 is used as the pressure Pco. In addition, in formula (1), "Kie" is the specific heat ratio between the intake air and exhaust gas of the engine 10.

[0033]

number

[0034] The above formula (1) is derived through the following procedure. That is, the work amount W of an ideal gas when it adiabatically changes from state (P1, V1, T1) to state (P2, V2, T2) can be expressed as the following formulas (2), (3), and (4) from Poisson's law and the gas state equation. In addition, if T1=Tci, P1=Pci, P2=Pco, and K=Ki (where "Ki" is the specific heat ratio of the intake air) in formula (3), the energy consumption work (compression work) Wc by the compressor wheel 32 can be obtained. Furthermore, if T1=Tti, T2=Tto, and K=Ke (where "Ke" is the specific heat ratio of the exhaust gas) in formula (4), the energy recovery work (expansion work) Wt by the turbine wheel 31 can be obtained.

[0035]

number

[0036] Also, if we assume that the transmission efficiency between the turbine wheel 31 and the compressor wheel 32 is 100%, the work consumed by the compressor wheel 32 Wc is equal to the work recovered by the turbine wheel 31 Wt, and the following equation (5) can be obtained by setting equation (3) = equation (4). Furthermore, for simplicity, if we assume that the adiabatic efficiency is 100% and Ki = Ke, the following equation (6) is obtained, and the above equation (1) is obtained by rearranging equation (6). By using equation (1) derived in this way, it is possible to more appropriately estimate the outlet gas temperature Tto of the turbine wheel 31.

[0037]

number

[0038] Next, the engine ECU 100 estimates the latest turbine wheel 31 temperature Ttb based on the turbine wheel 31 temperature Ttb derived the previous time the routine of Fig. 6 was executed (hereinafter referred to as the "previous temperature of the turbine wheel 31"), the inlet gas temperature Tti acquired in step S200, and the outlet gas temperature Tto estimated in step S210 (step S220). In step S220, the engine ECU 100 calculates a correction temperature ΔTtb by multiplying a value obtained by subtracting the inlet gas temperature Tti from the outlet gas temperature Tto of the turbine wheel 31 by a predetermined coefficient kt, and derives a value obtained by adding the correction temperature ΔTtb to the previous temperature of the turbine wheel 31 as the latest turbine wheel 31 temperature Ttb.

[0039] 6, based on the temperature Tts of the turbine shaft 33 (hereinafter referred to as the "previous temperature of the turbine shaft 33"), the temperature Tsr of the seal ring 39t (hereinafter referred to as the "previous temperature of the seal ring 39t"), and the temperature Tbr of the bearing 36 (hereinafter referred to as the "previous temperature of the bearing 36"), which were derived during the previous execution of the routine of FIG. 6, and the temperature Ttb of the turbine wheel 31 estimated in step S220 (step S230). In step S230, the engine ECU 100 derives a correction temperature ΔTts by substituting the previous temperature of the seal ring 39t, the previous temperature of the bearing 36, and the temperature Ttb of the turbine wheel 31 into a relational expression determined in advance through experiments and analysis, and derives a value obtained by adding the correction temperature ΔTts to the previous temperature of the turbine shaft 33 as the latest temperature Tts of the turbine shaft 33.

[0040] After processing step S230, the engine ECU 100 estimates the latest temperature Tsr of the seal ring 39t based on the previous temperature of the seal ring 39t and the wall temperature To of the oil passage 37 (hereinafter referred to as the "previous wall temperature of the oil passage 37") derived during the previous execution of the routine of Figure 6, the inlet gas temperature Tti on the turbine housing 220 side obtained in step S200, the outlet gas temperature Tto estimated in step S210, the cooling water temperature Twsh and the water flow rate Qwsh, and the temperature Tts of the turbine shaft 33 estimated in step S230 (step S240). In step S240, the engine ECU 100 derives the amount of heat transfer Hosr transferred from the oil passage 37 side to the seal ring 39t (wherein the direction from the oil passage 37 side toward the seal ring 39t is considered positive) based on the value obtained by subtracting the previous temperature of the seal ring 39t from the previous wall temperature of the oil passage 37 in the bearing housing 300 and the predetermined heat transfer coefficient between the oil passage 37 side and the seal ring 39t.

[0041] Furthermore, in step S240, the engine ECU 100 derives the amount of heat transfer Hwsr (where the direction from the cooling water to the seal ring 39t is considered positive) transferred from the cooling water in the refrigerant passage 38 to the seal ring 39t based on the value obtained by subtracting the previous temperature of the seal ring 39t from the temperature Twsh of the cooling water in the refrigerant passage 38 obtained in step S200, the amount of cooling water flowing Qwsh obtained in step S200, and a predetermined heat transfer coefficient between the cooling water and the seal ring 39t. Furthermore, in step S240, the engine ECU 100 derives the amount of heat transfer Htssr transferred from the turbine shaft 33 to the seal ring 39t (wherein the direction from the turbine shaft 33 to the seal ring 39t is considered positive) based on the value obtained by subtracting the previous temperature of the seal ring 39t from the temperature Tts of the turbine shaft 33 estimated in step S230 and the predetermined heat transfer coefficient between the turbine shaft 33 and the seal ring 39t.

[0042] Additionally, in step S240, the engine ECU 100 estimates (calculates) the temperature Tth of the exhaust gas in the turbine housing 220 of the exhaust pipe 22 (=(α·Tti+β·Tto) / (α+β), where "α" and "β" are predetermined weights) by taking a weighted average of the inlet gas temperature Tti and the outlet gas temperature Tto. Furthermore, the engine ECU 100 derives the amount of heat transfer Hthr transferred from the turbine housing 220 side to the seal ring 39t (where the direction from the turbine housing 220 toward the seal ring 39t is considered positive) based on a value obtained by subtracting the previous temperature of the seal ring 39t from the estimated temperature Tth of the exhaust gas in the turbine housing 220 and a predetermined heat transfer coefficient between the turbine housing 220 side and the seal ring 39t. Then, the engine ECU 100 calculates a correction temperature ΔTsr based on the derived heat transfer amounts Hosr, Hwsr, Htssr, and Hthsr, and derives a value obtained by adding the correction temperature ΔTsr to the previous temperature of the seal ring 39t as the latest temperature Tsr of the seal ring 39t. Note that in step S240, the previous temperature of the turbine shaft 33 derived during the previous execution of the routine of FIG 6 may be used instead of the temperature Tts of the turbine shaft 33 estimated in step S230.

[0043] Next, the engine ECU 100 estimates the latest temperature Tsr of the bearing 36 based on the previous temperature of the bearing 36, the coolant temperature Twsh and the coolant flow rate Qwsh acquired in step S200, and the temperature Tts of the turbine shaft 33 estimated in step S230 (step S250). In step S250, the engine ECU 100 derives the amount of heat transfer Hwbr transferred from the coolant in the refrigerant passage 38 to the bearing 36 (the direction from the coolant toward the bearing 36 is defined as positive) based on a value obtained by subtracting the previous temperature of the bearing 36 from the coolant temperature Twsh, the coolant flow rate Qwsh, and a predetermined heat transfer coefficient between the coolant and the bearing 36. Furthermore, in step S250, the engine ECU 100 derives an amount of heat transfer Htsbr (the direction from the turbine shaft 33 to the bearing 36 is defined as positive) transferred from the turbine shaft 33 to the bearing 36 based on a value obtained by subtracting the previous temperature of the bearing 36 from the temperature Tts of the turbine shaft 33 and the heat transfer coefficient between the turbine shaft 33 and the bearing 36. Furthermore, the engine ECU 100 calculates a correction temperature ΔTbr based on the derived amounts of heat transfer Hwbr and Htsbr, and derives a value obtained by adding the correction temperature ΔTbr to the previous temperature of the bearing 36 as the latest temperature Tbr of the bearing 36. Note that in step S250 as well, the previous temperature of the turbine shaft 33 derived during the previous execution of the routine of FIG. 6 may be used instead of the temperature Tts of the turbine shaft 33 estimated in step S230.

[0044] After the process of step S250, the engine ECU 100 estimates the wall temperature To of the oil passage 37 based on the previous wall temperature of the oil passage 37 and the coolant temperature Twsh and the water flow rate Qwsh acquired in step S200 (step S260), and temporarily ends the routine of Fig. 6. In step S260, the engine ECU 100 derives the amount of heat transfer Hwo transferred from the coolant in the refrigerant passage 38 to the oil passage 37 side (the direction from the coolant side to the oil passage 37 side is defined as positive) based on a value obtained by subtracting the previous wall temperature of the oil passage 37 from the coolant temperature Twsh, the coolant flow rate Qwsh, and the heat transfer coefficient between the coolant and the oil passage 37 side. Furthermore, in step S260, the engine ECU 100 derives an amount of heat transfer Hsro (the direction from the seal ring 39t to the oil passage 37 is defined as positive) transferred from the seal ring 39t to the oil passage 37 based on a value obtained by subtracting the previous wall temperature of the oil passage 37 from the previous temperature of the seal ring 39t and the heat transfer coefficient between the seal ring 39t and the oil passage 37. The engine ECU 100 then calculates a correction temperature ΔTo based on the derived heat transfer amounts Hwo and Hsro, and derives a value obtained by adding the correction temperature ΔTo to the previous wall temperature of the oil passage 37 as the latest wall temperature To of the oil passage 37.

[0045] As described above, the engine ECU 100 that controls the turbocharger 30 of the engine 10 estimates the temperature of the seal ring 39t that seals the gap around the turbine shaft 33 on the turbine housing 220 side, taking into consideration the temperature Tth of the exhaust gas in the turbine housing 220 (step S240 in FIG. 6). As a result, in particular in a case where the engine 10 is stopped immediately after being operated at high load with intake air compressed by the compressor wheel 32 of the turbocharger 30, the amount of heat transferred from the turbine housing 220, which has a high heat capacity, to the seal ring 39t on the turbine wheel 31 side can be reflected in the temperature (estimated value) Tsr of the seal ring 39t. As a result, it becomes possible to more accurately estimate the temperature of the seal ring 39t that seals the gap around the turbine shaft 33 on the turbine housing 220 side.

[0046] In step S240, the engine ECU 100 estimates the temperature Tth of the exhaust gas in the turbine housing 220 by taking a weighted average of the inlet gas temperature Tti, which is the temperature of the exhaust gas flowing into the turbine housing 220, and the outlet gas temperature Tto, which is the temperature of the exhaust gas flowing out from the turbine housing 220, and estimates the temperature of the seal ring 39t based on the previous temperature of the seal ring 39t, the previous wall temperature of the oil passage 37, the temperature Tts of the turbine shaft 33, the temperature Twsh and the water flow rate Qwsh of the cooling water, and the temperature Tth of the exhaust gas in the turbine housing 220. This makes it possible to more appropriately estimate the temperature Tth of the exhaust gas in the turbine housing 220, and further improve the estimation accuracy of the temperature of the seal ring 39t. In addition, by changing the weights α and β for each vehicle model on which the engine 10 is mounted, the temperature Tth of the exhaust gas in the turbine housing 220 can be accurately estimated for each vehicle model.

[0047] Furthermore, when the operation of the engine 10 is stopped and the temperature (estimated value) Tsr of the seal ring 39t is equal to or higher than a predetermined threshold value Tsrref, the engine ECU 100 operates the electric pump 44 that supplies cooling water into the bearing housing 300 (steps S110 and S150 in FIG. 5). This effectively prevents the lubricating oil from carbonizing in the bearing housing 300, and therefore effectively protects the turbocharger 30 mounted on a vehicle in which so-called idle stop control is executed or a hybrid vehicle in which the engine 10 is started and stopped relatively frequently.

[0048] In the above embodiment, the refrigerant circulation passage 25 and the refrigerant circulation passage 42 may be integrated, and one of the electric pumps 26 and 53 may be omitted. The engine 10 to which the turbocharger 30 and the engine ECU 100 are applied may be a diesel engine, an LPG engine, or a hydrogen engine.

[0049] The present disclosure is not limited to the above embodiment, and various modifications can be made within the scope of the present disclosure. Furthermore, the above embodiment is merely a specific form of the invention described in the Summary of the Invention, and does not limit the elements of the invention described in the Summary of the Invention. [Industrial Applicability]

[0050] The present invention can be used in the turbocharger manufacturing industry and the like. [Explanation of symbols]

[0051] 10 engine, 11 engine block, 12 combustion chamber, 13 piston, 14a crank angle sensor, 15 air cleaner, 16 intake pipe, 160 compressor housing, 165 bypass pipe, 16a air flow meter, 16p intake pressure sensor, 16s boost pressure sensor, 16t intake temperature sensor, 17 throttle valve, 17o throttle opening sensor, 18 surge tank, 18p surge pressure sensor, 18t temperature sensor, 19e exhaust valve, 19i intake valve, 20 fuel injector, 21 spark plug, 22 exhaust pipe, 220 turbine housing, 225 bypass pipe, 22f upstream air-fuel ratio sensor, 22r downstream air-fuel ratio sensor, 23 upstream purification device, 230 exhaust gas purification catalyst, 24 downstream purification device, 240 particulate filter, 25 Coolant circulation passage, 25t water temperature sensor, 26 electric pump, 28 outside air temperature sensor, 29 atmospheric pressure sensor, 30 turbocharger, 31 turbine wheel, 32 compressor wheel, 33 turbine shaft, 34 wastegate valve, 35 blow-off valve, 36 bearing, 37 oil passage, 38 coolant passage, 39c, 39t seal ring, 300 bearing housing, 40 cooling system, 41 intercooler, 42 coolant circulation passage, 44 electric pump, 45 radiator, 100 engine electronic control unit (engine ECU).

Claims

[Claim 1] A control device for a turbocharger including a turbine housing provided in an exhaust passage of an internal combustion engine mounted on a vehicle, a turbine wheel disposed within the turbine housing, a compressor wheel connected to the turbine wheel via a turbine shaft and disposed within a compressor housing provided in an intake passage of the internal combustion engine, a bearing housing supporting the turbine shaft via a bearing between the turbine housing and the compressor housing, and a seal ring sealing a gap around the turbine shaft on the turbine housing side, a control device for a turbocharger that estimates a temperature of the exhaust gas inside the turbine housing by taking a weighted average of a temperature of the exhaust gas flowing into the turbine housing and a temperature of the exhaust gas flowing out of the turbine housing, estimates a temperature of the seal ring taking into account the estimated temperature of the exhaust gas inside the turbine housing, and operates a pump that supplies cooling water into the bearing housing when operation of the internal combustion engine is stopped and the estimated temperature of the seal ring is equal to or higher than a predetermined threshold value.

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