Turbocharger cooling control system

Abstract

To provide a cooling control device for turbochargers that can cool them without excess or deficiency. [Solution] The turbocharger has a controller for controlling the amount of cooling water, in which a first cooling water passage is provided inside the bearing housing and a second cooling water passage is provided inside the compressor housing. The controller includes a turbine-side cooling water amount calculation unit S4 that determines the required amount of cooling water to flow through the first cooling water passage based on the temperature and flow rate of the exhaust gas flowing into the turbine, a compressor-side cooling water amount calculation unit S3 that determines the required amount of cooling water to flow through the second cooling water passage based on the temperature of the air sent out from the compressor and the amount of air taken in, and an effective cooling water amount calculation unit S5 that determines the effective amount of cooling water to circulate throughout the first and second cooling water passages based on the required amount of cooling water determined by the turbine-side cooling water amount calculation unit, the required amount of cooling water determined by the compressor-side cooling water amount calculation unit, and the load of the internal combustion engine.

Description

Technical Field

[0001] The present invention relates to a turbocharger that is driven by the energy of the exhaust gas of an internal combustion engine to pressurize and compress the intake air, and particularly to a control device for cooling the turbocharger.

Background Art

[0002] A turbocharger rotates a turbine by the exhaust gas discharged from an internal combustion engine, and sucks and pressurizes air by a compressor integrated with the turbine. As such, the turbocharger is exposed to high temperatures, generates heat by compressing air, and further generates frictional heat at the sliding parts associated with rotation, so its temperature environment is quite severe. The thermal effects that appear in the turbocharger are various. For example, when the temperature on the compressor side rises, the insoluble components contained in the lubricating oil are concentrated and hardened, and this adheres to the compressor as a deposit, reducing the compressor efficiency. On the contrary, when the temperature is excessively low, the viscosity of the lubricating oil increases, and as a result, the energy consumed to stir or shear the lubricating oil increases, and so-called losses may increase.

[0003] Patent Document 1 describes a device that takes into account the latter's influence due to low temperature. The device described in Patent Document 1 is a device that provides a water jacket in the compressor housing to cool the compressor housing by water, and is configured to reduce the amount of cooling water flowing through the water jacket when the temperature of the internal combustion engine (for example, the cooling water temperature) is low, that is, during so-called cold periods. Therefore, according to the device described in Patent Document 1, the temperature of the turbocharger is not excessively reduced, so the viscosity of the lubricating oil can be maintained low, and the resistance or power loss due to the lubricating oil can be avoided or suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] The apparatus described in Patent Document 1 is configured to water-cool the compressor housing, but to control the amount of cooling water so that its temperature does not drop excessively. Therefore, when the internal combustion engine and turbocharger are operating steadily, overheating of the compressor housing can be prevented by flowing cooling water appropriately through the water jacket. However, as mentioned above, the turbocharger rotates the turbine using the exhaust gas from the internal combustion engine, so the turbine housing and the turbine-side part of the bearing housing are heated by the heat of the exhaust gas, causing their temperature to rise. A seal ring is provided between the turbine housing and the bearing housing to prevent exhaust gas from flowing into the bearing housing, so if the temperature rises excessively, the seal ring may be damaged or its durability may decrease. The apparatus described in Patent Document 1 does not have a means to suppress the temperature rise of the bearing housing, and therefore cannot solve technical problems such as damage to the seal ring.

[0006] Furthermore, by providing cooling water channels or a water jacket inside the bearing housing, it is possible to cool the bearing housing together with the compressor housing. However, the compressor housing's temperature rises mainly due to the heat generated by compressing air, while the turbine housing's temperature rises due to the exhaust gas. Therefore, the factors causing the temperature rise and the allowable temperatures differ between the compressor housing and the turbine housing. Consequently, even if the compressor housing and the turbine housing or the turbine side of the bearing housing are water-cooled together, insufficient cooling may occur in one of them, or if the amount of cooling water is increased to resolve this, overcooling of the other may occur. Conventionally, such cooling deficiencies and excesses have not been considered, and no device is known to resolve such technical problems.

[0007] The present invention has been made in view of the above technical problems, and aims to provide a turbocharger cooling control device that can cool the compressor housing and bearing housing without excess or deficiency by circulating cooling water through a series of cooling water passages formed inside them. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides a turbocharger cooling control device comprising: a turbine housing housing a turbine rotated by the exhaust of an internal combustion engine; a compressor housing housing a compressor for pressurizing and compressing the intake air of the internal combustion engine; and a bearing housing rotatably holding a shaft on which the turbine is provided at one end and the compressor is provided at the other end, wherein a first cooling water passage is provided inside the bearing housing and a second cooling water passage communicating with the first cooling water passage is provided inside the compressor housing, and the device comprises a controller for controlling the amount of cooling water flowing through the first cooling water passage and the second cooling water passage. The controller is characterized by comprising: a turbine-side cooling water volume calculation unit that determines the required amount of cooling water to flow through the first cooling water passage based on the temperature of the exhaust gas flowing from the internal combustion engine to the turbine and the flow rate of the exhaust gas; a compressor-side cooling water volume calculation unit that determines the required amount of cooling water to flow through the second cooling water passage based on the temperature of the air sent out from the compressor and the amount of air inhaled by the compressor; and an effective cooling water volume calculation unit that determines the effective amount of cooling water to circulate throughout the first and second cooling water passages based on the required amount of cooling water determined by the turbine-side cooling water volume calculation unit, the required amount of cooling water determined by the compressor-side cooling water volume calculation unit, and the load of the internal combustion engine. [Effects of the Invention]

[0009] In this invention, when an internal combustion engine is supercharged by sending exhaust gas from the engine to a turbine and rotating a compressor, the required amount of cooling water to flow through the first cooling water passage is determined based on the temperature and volume of the exhaust gas. That is, the amount of cooling water required to cool the turbine-side portion of the bearing housing is determined. Furthermore, the required amount of cooling water to flow through the second cooling water passage is determined based on the amount of air drawn in by the compressor and the temperature of the air compressed by the compressor. That is, the required amount of cooling water required to cool the compressor housing is determined. Then, based on these required amounts of cooling water and the load of the internal combustion engine, the actual amount of cooling water to flow, i.e., the effective amount of cooling water, is determined. For example, when the load of the internal combustion engine is low, the greater of the two required amounts of cooling water is used as the effective amount of cooling water. Therefore, insufficient cooling is avoided, and even if the amount of cooling water is increased from a state where a certain amount of cooling water is flowing, the cooling efficiency does not increase significantly, thus avoiding overcooling. Furthermore, under moderate load conditions, the effective cooling water volume is less than the sum of the individual cooling water volumes. That is, the effective cooling water volume is calculated by adding the individual required cooling water volumes corrected by a predetermined coefficient. Moreover, under even higher load conditions, the effective cooling water volume is the sum of the individual required cooling water volumes. In all of these cases, since the effective cooling water volume is determined by including the cooling water volumes required by both the turbine and compressor sides, the turbocharger can be cooled without causing insufficient or excessive cooling. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing the intake and exhaust systems of a supercharged internal combustion engine. [Figure 2] This is a schematic cross-sectional view of the turbocharger. [Figure 3] This is a flowchart illustrating an example of control in an embodiment of the present invention. [Figure 4] This is a schematic diagram showing an example of a map that defines the control range based on engine speed and engine load ratio. [Modes for carrying out the invention]

[0011] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the embodiments described below are merely examples of how the present invention can be implemented and do not limit the invention.

[0012] Figure 1 schematically shows the intake and exhaust system of a supercharged internal combustion engine (engine) 1. The basic configuration of the turbocharger 2 that provides supercharging is the same as that of a conventionally known turbocharger, and it has a turbine 3 driven by the exhaust of the engine 1 and a compressor 4 that is rotated by the turbine 3 to pressurize and compress the intake air. The turbine 3 and compressor 4 are equipped with impellers at both ends of a shaft that is rotatably held by a bearing housing 5, and the impeller rotates by receiving exhaust and pressurizes and compresses the air.

[0013] The exhaust manifold 6 of engine 1 is connected to turbine 3. A catalytic converter 7 and filter 8 are provided on the exhaust side of turbine 3 to purify the exhaust gas. On the other hand, an air cleaner 9 is provided on the intake side of compressor 4, and an airflow meter 10 is provided to detect the amount of air drawn in through the air cleaner 9. An intercooler 11 is connected to the discharge side of compressor 4 to cool the compressed and heated supercharged air. An inlet temperature sensor 12 is provided to detect the temperature on the inlet side of the intercooler 11, and an outlet temperature sensor 13 is provided to detect the temperature on the outlet side of the intercooler 11. The supercharged air cooled by the intercooler 11 is drawn into engine 1 via a throttle valve 14 and surge tank 15.

[0014] Figure 2 is a schematic cross-sectional view of a turbocharger 2 used in an embodiment of the present invention. A turbine shaft 16 is provided passing through the bearing housing 5, and this turbine shaft 16 is rotatably held by a bearing 17 provided inside the bearing housing 5. A compressor wheel 18 is provided at one end of the turbine shaft 16, and a turbine wheel 19 is provided at the other end.

[0015] The compressor 4 has a compressor housing 20 that houses a compressor wheel 18, and the compressor housing 20 is mounted in close contact with one side of the bearing housing 5.

[0016] The compressor housing 20 is equipped with an air intake 21 that extends along the same axis as the compressor wheel 18. In addition, a spiral-shaped air passage 22 is formed on the outer circumference of the compressor wheel 18, with the cross-sectional area gradually decreasing towards the tip.

[0017] The turbine housing 23, which houses the turbine wheel 19, is attached in close contact to the other side of the bearing housing 5. The turbine housing 23 has an exhaust passage 24 formed on the outer circumference of the turbine wheel 19, which is spiral-shaped and whose cross-sectional area gradually decreases towards the tip (towards the center of the turbine housing 23) in order to blow exhaust from the engine 1 onto the turbine wheel 19. In the example shown in Figure 2, two exhaust passages 24 are formed. Furthermore, an exhaust port 25 that houses the turbine wheel 19 and extends along the same axis as the turbine wheel 19 is provided in the turbine housing 23.

[0018] A seal ring 26 is fitted to the turbine wheel 19 side end of the turbine shaft 16. This seal ring 26 tightly adheres to the inner circumferential surface of the bearing housing 5, thereby creating an airtight seal between the inside of the turbine housing 23 and the area in the bearing housing 5 where the bearing 17 is located.

[0019] The turbocharger 2 is provided with a water jacket or a cooling water passage for cooling (hereinafter, these are collectively referred to as a cooling water passage). First, inside the compressor housing 20, a cooling water passage (hereinafter, temporarily referred to as a C cooling water passage) 27 is formed mainly for cooling to avoid or suppress deposits due to the increase in the temperature of the lubricating oil. The C cooling water passage 27 corresponds to the second cooling water passage in the embodiment of the present invention, and is a cavity formed inside the compressor housing 20. In the example shown in FIG. 2, it is formed in an annular shape so as to surround the outer peripheral side of the compressor wheel 18. An inflow pipe 28 is connected to the C cooling water passage 27, and cooling water is supplied from the inflow pipe 28.

[0020] Also, a cooling water passage (hereinafter, temporarily referred to as a B cooling water passage) 29 is formed inside the bearing housing 5. The B cooling water passage 29 corresponds to the first cooling water passage in the embodiment of the present invention, and is a cavity formed inside the bearing housing 5. In the example shown in FIG. 2, it is formed in an annular shape so as to surround the outer peripheral side of the aforementioned seal ring 26.

[0021] A communication passage 30 is provided to connect the C cooling water passage 27 and the B cooling water passage 29 in series. Therefore, the C cooling water passage 27 and the B cooling water passage 29 are part of a single continuous flow path. The communication passage 30 may be a pipe that penetrates inside the compressor housing 20 and the bearing housing 5, or may be a pipe attached to the outside of these housings 5 and 20. The connection position of the communication passage 30 to the C cooling water passage 27 is set at a higher position in the vertical direction than the connection position to the B cooling water passage 29. This is to allow the cooling water to flow down from the C cooling water passage 27 toward the B cooling water passage 29.

[0022] Furthermore, an outflow pipe 31 is connected to the B cooling water passage 29. The outflow pipe 31 is a pipe for refluxing the cooling water from the B cooling water passage 29 to the outside. Therefore, at least a part of it may be constituted by a pipe connected to the outside of the bearing housing 5 and extends upward from the B cooling water passage 29. And the outflow pipe 31 communicates with the cooling water regulator 32.

[0023] The cooling water regulator 32 is, in short, a device that flows cooling water through the above-mentioned cooling water passages 27 and 29 and appropriately adjusts its flow rate. As an example, it can be configured to include a pump driven by the engine 1 and a flow rate adjustment valve. Alternatively, the cooling water regulator 32 can be constituted by an electric pump whose discharge amount can be electrically adjusted. This cooling water regulator 32 is connected to a radiator 33 such as a radiator, and the above-mentioned inflow pipe 28 is connected to the radiator 33.

[0024] A controller 34 is provided that outputs a control command signal to the cooling water regulator 32 to control the flow rate of the cooling water. The controller 34 is mainly constituted by a microcomputer, performs calculations according to a predetermined program using the input data and the data stored in advance, and is configured to output the result of the calculation as a control command signal. The input data includes the air temperature T3 on the inflow side of the intercooler 11, the inflow air amount Ga detected by the air flow meter 10, the exhaust temperature T4 detected by a temperature sensor (not shown) provided on the inflow side of the turbine 3, the exhaust flow rate G4 detected by a flow meter (not shown) that detects the flow rate of the exhaust flowing into the turbine 3, the engine speed Ne, and the like. The data stored in advance includes a map that defines a control region based on the engine speed Ne and the engine load factor KL, and the like. Here, the engine load factor KL is the ratio of the current intake air amount to the maximum value of the intake air amount corresponding to the engine speed Ne. The map and the control executed by the controller 34 will be described later.

[0025] When engine 1 is running, its exhaust is blown onto the turbine wheel 19 via the exhaust passage 24, causing the turbine wheel 19 to rotate, and the compressor wheel 18, which is integrated with it, to rotate. As a result, air is drawn in from the intake port 21, and this air is pressurized and compressed as it flows through the air passage 22 before being supplied to engine 1 as intake air.

[0026] When engine 1 is running, the coolant regulator 32 rotates, causing the coolant to circulate. The coolant, whose temperature has been lowered in the radiator 33, is first supplied to the C coolant passage 27. As mentioned above, the C coolant passage 27 is located around the outer circumference of the compressor wheel 18, and therefore cools the compressed air, which has become hotter, and the compressor housing 20, which has been heated by that air, by absorbing heat from them. The coolant is then sent to the B coolant passage 29 through the communication passage 30. As mentioned above, the B coolant passage 29 is located inside the bearing housing 5, surrounding the seal ring 26, so the coolant supplied to the B coolant passage 29 cools the bearing housing 5 and the seal ring 26 by absorbing heat from them. The coolant is then sent to the radiator 33 via the coolant regulator 32, where it is cooled by heat dissipation into the air. When engine 1 is running, the coolant circulates as described above, cooling the turbocharger 2 and the intake air.

[0027] When engine 1 is running and turbocharger 2 is performing supercharging, the amount of heat generated by compressor 4 and the amount of heat input to turbine 3 from exhaust gases vary depending on the operating state of engine 1, for example. That is, the amount of cooling required on the compressor 4 side and the amount of cooling required on the turbine 3 side (bearing housing 5 side) differ depending on the operating state of engine 1, and one of these required cooling amounts may increase relative to the other, or the relationship may be reversed. In the embodiment of the present invention, controller 34 determines the amount of cooling water to flow through each cooling water passage 27, 29 to satisfy both the cooling required by compressor housing 20 and the cooling required by bearing housing 5, and controls the cooling water regulator 32. An example of the control performed by controller 34 will be explained with reference to the flowchart shown in Figure 3.

[0028] The routine shown in Figure 3 is repeatedly executed by the controller 34 at predetermined short intervals. First, in step S1, the air temperature T3 at the inlet side of the intercooler 11 and the amount of incoming air Ga detected by the airflow meter 10 are obtained as data for the compressor 4 side. In parallel with this, in step S2, the exhaust temperature T4 flowing into the turbine 3 and the exhaust flow rate G4 flowing into the turbine 3 are obtained as data for the turbine 3 side.

[0029] In step S3, the amount of cooling water Qc required for the C cooling water channel 27 is calculated using the acquired air temperature T3 and inflow air volume Ga. More specifically, this calculation may be performed by continuously monitoring the air temperature T3, inflow air volume Ga, and the amount of cooling water flowing through the C cooling water channel 27, acquiring their history, and then determining the amount of cooling water Qc on the compressor side based on this history and a pre-prepared appropriate map. The functional configuration that performs the control in step S3 corresponds to the compressor-side cooling water amount calculation unit in the embodiment of the present invention.

[0030] On the other hand, in step S4, the amount of turbine-side cooling water Qb required in the B cooling water channel 29 is calculated using the acquired exhaust temperature T4 and exhaust flow rate G4. More specifically, this calculation may be performed by constantly monitoring the exhaust temperature T4, exhaust flow rate G4, and the amount of cooling water flowing through the B cooling water channel 29, acquiring their history, and determining the amount of turbine-side cooling water Qb based on that history and a pre-prepared appropriate map. The functional configuration that performs the control in step S4 corresponds to the turbine-side cooling water amount calculation unit in the embodiment of the present invention.

[0031] The calculated cooling water amounts Qc and Qb are then combined to calculate the actual amount of cooling water to be supplied (effective cooling water amount) Qt in step S5, and the routine shown in Figure 3 is terminated. The amount of cooling required on the compressor 4 side and the amount of cooling required on the turbine 3 side differ depending on the operating state and history of the engine 1. Therefore, the control in step S5 can be performed as follows, depending on the operating state of the engine 1. The functional configuration that executes this control in step S5 corresponds to the effective cooling water amount calculation unit in the embodiment of the present invention.

[0032] Figure 4 schematically shows an example of a map that defines the control region based on engine speed Ne and engine load ratio KL. In Figure 4, the symbol "X" indicates the low load region, the symbol "Y" indicates the medium load region, and the symbol "Z" indicates the high load region. In step S5, the region to which the load state of engine 1 belongs is determined from the map based on the engine speed Ne and engine load ratio KL. Based on this determination, the formula for calculating the effective coolant volume Qt is selected. For example, if engine 1 is in the low load region X, the effective coolant volume Qt is the larger of the compressor-side coolant volume Qc and the turbine-side coolant volume Qb.

[0033] When engine 1 is in the medium load region Y, the effective coolant flow rate Qt is calculated using the following formula. Qt = Qb × β + Qc × ω Here, β and ω are coefficients determined by experimentation or other means, both of which are less than "1" and whose sum is less than "1". These values ​​may also be pre-prepared as a map based on the operating state of engine 1.

[0034] Furthermore, if engine 1 is in the high-load region Z, the compressor-side cooling water volume Qc and the turbine-side cooling water volume Qb may be added together to obtain the effective cooling water volume Qt (=Qc+Qb).

[0035] Therefore, in the embodiment of the present invention, the amount of coolant (effective coolant amount Qt) to be continuously circulated in the coolant passages 27 and 29 between the compressor housing 20 and the bearing housing 5 is determined by calculating the amount of coolant required in each of the coolant passages 27 and 29 based on the operating state of the engine 1, and then arbitrating these required amounts of coolant. This ensures that cooling is performed without excess or deficiency. In other words, it is possible to effectively prevent or suppress the formation of deposits on the compressor 4 side and the deterioration of the seal ring 26 on the turbine 3 side or the bearing housing 5 side.

[0036] It should be noted that the present invention is not limited to the configuration described above, and the shape and position of each cooling water passage can be appropriately changed within the scope of the objectives of the present invention. For example, if a diffuser is provided in the compressor housing, the diffuser may be configured as part of the cooling water passage. Furthermore, calculation formulas that include other parameters may be used to calculate each required amount of cooling water, and the arbitration of the required amount of cooling water to determine the actual amount of cooling water may be performed by calculations other than those described above. In addition, the operating state (or load) of the engine (internal combustion engine) considered during the arbitration may be determined based on other parameters, regardless of the rotational speed and engine load ratio. [Explanation of symbols]

[0037] 1 Engine 2 Turbochargers 3 Turbines 4 Compressors 5 Bearing Housing 6. Exhaust Manifold 7. Catalytic Converter 8 filters 9. Air cleaner 10 Airflow Meter 11 Intercooler 12. Inlet temperature sensor 13 Outlet temperature sensor 14 Throttle valve 15 Surge Tank 16 Turbine shaft 17 bearings 18 Compressor Wheels 19 Turbine Wheel 20 Compressor Housing 21 Inlet 22 Airflow channels 23 Turbine Housing 24 Exhaust passage 25 Exhaust vents 26 sealing rings 27 Cooling Channel 28 Inflow pipe 29 Cooling Channel 30 Communication path 31 Outflow pipe 32 Cooling water regulator 33 Heat sink 34 controllers G4 Exhaust Flow Rate Ga Inflow air volume KL engine load ratio Ne Engine speed Qb Turbine-side cooling water volume Qc Compressor-side cooling water volume Qt Actual Cooling Water Volume T3 Air Temperature T4 Exhaust Temperature X Low load area Y Medium load area Z High load area

Claims

[Claim 1] A turbocharger cooling control device comprising: a turbine housing housing a turbine rotated by the exhaust of an internal combustion engine; a compressor housing housing a compressor for pressurizing and compressing the intake air of the internal combustion engine; and a bearing housing rotatably holding a shaft on which the turbine is provided at one end and the compressor is provided at the other end, wherein a first cooling water passage is provided inside the bearing housing, and a second cooling water passage communicating with the first cooling water passage is provided inside the compressor housing, The system includes a controller that controls the amount of cooling water flowing through the first cooling water channel and the second cooling water channel. The aforementioned controller, A turbine-side cooling water volume calculation unit that determines the required amount of cooling water to flow into the first cooling water channel based on the temperature of the exhaust gas flowing from the internal combustion engine to the turbine and the flow rate of the exhaust gas, A compressor-side cooling water volume calculation unit that determines the required amount of cooling water to flow through the second cooling water channel based on the temperature of the air sent out from the compressor and the amount of air drawn in by the compressor, Based on the required amount of cooling water determined by the turbine-side cooling water amount calculation unit, the required amount of cooling water determined by the compressor-side cooling water amount calculation unit, and the load of the internal combustion engine, the effective cooling water amount calculation unit determines the effective amount of cooling water to be circulated throughout the first cooling water passage and the second cooling water passage. A turbocharger cooling control device characterized by having the following features.

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