Control device for supercharged engine

Abstract

To prevent occurrence of emulsion.SOLUTION: A control device 40 for a supercharged engine 10 includes; a first ventilation passage 30 communicating a part on a side more downstream than a compressor 22 in an intake passage 12 and also more upstream than a throttle valve 16, with a crank case 17; a second ventilation passage 31 communicating a part on a side more upstream than the compressor 22 in the intake passage 12, with the crank case 17; and a unidirectional valve 32 restricting a gas flow toward the intake passage 12 from the crank case 17 passing through the first ventilation passage 30. The control device is structured so as to make the supercharged engine 10 forcibly perform a supercharged operation by enhancing a supercharge efficiency of the compressor 22 and also reducing an opening ratio of the throttle valve 16 when a moisture accumulation amount in engine oil is large and also the supercharged engine 10 is operated in a natural intake region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a supercharged engine. [Background technology]

[0002] As shown in Patent Document 1, a supercharged engine is known in which ventilation of the crankcase is performed by providing a ventilation passage that connects the downstream side of the compressor with the crankcase via a one-way valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 57-013814 Summary of the Invention [Problem to be solved by the invention]

[0004] When the conventional supercharged engine described above is operating in the supercharged range, intake air pressurized by the compressor is introduced into the crankcase through a ventilation passage, allowing ventilation of the crankcase. However, when operating in the naturally aspirated range, the compressor does not pressurize the intake air, making it impossible to ventilate the crankcase. Therefore, if the engine continues to operate in the naturally aspirated range with cold engine oil, moisture generated during combustion and leaking into the crankcase will continue to accumulate in the crankcase. This moisture will then mix with the engine oil, causing emulsion. [Means for solving the problem]

[0005] A control device for a supercharged engine that solves the above problem is a device that controls a supercharged engine that has a turbine installed in an exhaust passage, a compressor installed in an intake passage, a throttle valve installed in a portion of the intake passage downstream of the compressor, a first ventilation passage that connects a portion of the intake passage downstream of the compressor and upstream of the throttle valve with a crankcase, a second ventilation passage that connects a portion of the intake passage upstream of the compressor with the crankcase, and a one-way valve that restricts the flow of gas from the crankcase to the intake passage through the first ventilation passage, and is configured to determine whether the amount of moisture accumulated in engine oil is high, and if it is determined that the amount of moisture accumulated is high while the supercharged engine is operating in the naturally aspirated range, to perform supercharging operation of the supercharged engine by increasing the supercharging efficiency of the compressor and reducing the opening rate of the throttle valve. [Effects of the Invention]

[0006] The above-described control device for a supercharged engine has the effect of suppressing the generation of emulsion. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating a configuration of an embodiment of a control device for a supercharged engine; [Figure 2] 10 is a flowchart of ventilation promotion control executed by the control device of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a control device for a supercharged engine will be described in detail below with reference to FIGS. <Configuration of the control device for supercharged engine> First, the configuration of the control device for a supercharged engine of this embodiment will be described with reference to Figure 1. A supercharged engine 10 to which the control device of this embodiment is applied is configured as a hydrogen engine that generates power by burning hydrogen.

[0009] As shown in Fig. 1, a supercharged engine 10 includes an intake passage 12, which is a passage through which intake air is introduced into a combustion chamber 11, and an exhaust passage 13, which is a passage through which exhaust gas is discharged from the combustion chamber 11. An air cleaner 14, which is a filtering device that purifies the intake air, and a throttle valve 16 are installed in the intake passage 12. The throttle valve 16 is a valve that changes the flow area of ​​the intake air in the intake passage 12 in accordance with a change in the opening ratio.

[0010] The supercharged engine 10 also includes a variable geometry turbocharger 20. The turbocharger 20 includes a turbine 21 installed in the exhaust passage 13, a compressor 22 installed in the intake passage 12, and a variable nozzle 23. The turbine 21 rotates in response to the blowing of exhaust gas flowing through the exhaust passage 13. The compressor 22 rotates in conjunction with the turbine 21 to pressurize the intake air. The variable nozzle 23 varies the opening area of ​​the exhaust gas blowing port toward the turbine 21. The compressor 22 is installed in the intake passage 12 downstream of the air cleaner 14 and upstream of the throttle valve 16.

[0011] Furthermore, the supercharged engine 10 has two passages, a first ventilation passage 30 and a second ventilation passage 31, which connect the intake passage 12 and the crankcase 17. The first ventilation passage 30 is a passage that connects the crankcase 17 to a portion of the intake passage 12 downstream of the compressor 22 and upstream of the throttle valve 16. The second ventilation passage 31 is a passage that connects the crankcase 17 to a portion of the intake passage 12 downstream of the air cleaner 14 and upstream of the compressor 22. A one-way valve 32 is installed in the first ventilation passage 30 to restrict the flow of gas from the crankcase 17 toward the intake passage 12.

[0012] The supercharged engine 10 configured as described above is controlled by a control device 40. An example of the control device 40 is an electronic control module for engine control. The control device 40 includes an arithmetic processing unit 41 and a storage device 42. The storage device 42 stores programs and data for controlling the supercharged engine 10. The control device 40 performs various processes for controlling the supercharged engine 10 by having the arithmetic processing unit 41 execute the programs read from the storage device 42. Various sensors for detecting the operating state of the supercharged engine 10 are connected to the control device 40. The various sensors include a water temperature sensor 43 and an oil temperature sensor 44 that detect the water temperature THW and the oil temperature THO of the supercharged engine 10, respectively, and an air flow meter 45 that detects the intake air amount GA. The control device 40 determines operation variables for the supercharged engine 10 based on the detection results of these sensors. The operation variables for the supercharged engine 10 determined by the control device 40 include the opening rate of the throttle valve 16 and the opening rate of the variable nozzle 23 of the turbocharger 20. The control device 40 then controls the operating state of the supercharged engine 10 by operating the actuators of the supercharged engine 10 in accordance with the determined operation amounts.

[0013] <Ventilation promotion control> Next, the ventilation promotion control executed by the control device 40 will be described with reference to Fig. 2. Fig. 2 shows a flowchart of the process executed by the control device 40 for the ventilation promotion control. The control device 40 repeatedly executes the process of Fig. 2 at predetermined control intervals while the supercharged engine 10 is in operation.

[0014] 2, the control device 40 first calculates the mixing rate VC and the evaporation rate VE in step S100. The mixing rate VC represents the amount of water that mixes into the engine oil per unit time in the crankcase 17. The evaporation rate VE represents the amount of water that evaporates from the engine oil per unit time in the crankcase 17. The control device 40 calculates the mixing rate VC based on the water temperature THW and intake air amount GA of the supercharged engine 10, and the evaporation rate VE based on the oil temperature THO.

[0015] Next, in step S110, the control device 40 calculates the moisture accumulation amount MO based on the mixing rate VC and the evaporation rate VE. The moisture accumulation amount MO represents the amount of moisture mixed into the engine oil. The control device 40 calculates the moisture accumulation amount MO by integrating the difference between the mixing rate VC and the evaporation rate VE. More specifically, when calculating the moisture accumulation amount MO, the control device 40 first subtracts the evaporation rate VE from the mixing rate VC. The control device 40 then updates the value of the moisture accumulation amount MO by adding the subtracted value to the value before the update, thereby calculating the moisture accumulation amount MO.

[0016] Next, in step S120, the control device 40 determines whether the moisture accumulation amount MO is equal to or greater than a predetermined threshold. The threshold is set as an upper limit of the moisture accumulation amount MO that can suppress emulsion generation within an acceptable range. If the control device 40 determines that the moisture accumulation amount MO is equal to or greater than the threshold (YES), the control device 40 proceeds to step S130. On the other hand, if the control device 40 determines that the moisture accumulation amount MO is less than the threshold (NO), the control device 40 ends the processing of FIG. 2 for the current control cycle.

[0017] When the process proceeds to step S130, the control device 40 determines in step S130 whether the current operating range of the supercharged engine 10 is the naturally aspirated range. Under normal control, the naturally aspirated range is an operating range in which the supercharged engine 10 is operated with natural aspiration. The operating range is determined, for example, based on the rotation speed and load factor of the supercharged engine 10. If the control device 40 determines that the engine is in the naturally aspirated range (YES), the control device 40 proceeds to step S140. On the other hand, if the control device 40 determines that the engine is not in the naturally aspirated range (NO), the control device 40 ends the process of FIG. 2 for the current control cycle.

[0018] When the process proceeds to step S140, the control device 40 increases the supercharging efficiency of the compressor 22 and reduces the opening rate of the throttle valve 16, thereby causing the supercharged engine 10 to perform supercharging operation. At this time, the control device 40 increases the supercharging efficiency of the compressor 22 by reducing the opening rate of the variable nozzle 23 to strengthen the blowing of exhaust gas onto the turbine 21. If the supercharging efficiency were increased alone, the intake air filling rate of the combustion chamber 11 would increase. Therefore, the control device 40 increases the supercharging efficiency while maintaining the intake air filling rate of the combustion chamber 11 by reducing the opening rate of the throttle valve 16. After processing step S140, the control device 40 ends the processing of FIG. 2 for the current control cycle.

[0019] <Actions and Effects of the Embodiment> The operation and effects of this embodiment will be described. 1, when the supercharged engine 10 is operating in supercharged mode, intake air pressurized by the compressor 22 is introduced into the crankcase 17 through the first ventilation passage 30. The introduced high-pressure intake air causes blow-by gas in the crankcase 17 to flow through the second ventilation passage 31 to the portion of the intake passage 12 upstream of the compressor 22. In this way, when the supercharged engine 10 is operating in supercharged mode, ventilation of the crankcase 17 is achieved. In contrast, when the engine is operating in naturally aspirated mode, the pressure downstream of the compressor 22 does not reach a higher pressure than atmospheric pressure, and therefore the crankcase 17 cannot be ventilated.

[0020] In this supercharged engine 10, some of the moisture produced by combustion in the combustion chamber 11 leaks into the crankcase 17. This moisture may then mix with the engine oil in the crankcase 17, causing emulsion. Note that the supercharged engine 10 of this embodiment is a hydrogen engine that uses hydrogen as fuel, which becomes water after combustion, and therefore produces a larger amount of moisture by combustion than a gasoline engine or the like.

[0021] The greater the intake air amount GA, the greater the amount of fuel burned in the combustion chamber 11, and therefore the greater the amount of moisture generated by combustion. This, in turn, increases the amount of moisture leaking from the combustion chamber 11 into the crankcase 17. Therefore, the greater the intake air amount GA, the higher the mixing rate VC of moisture into the engine oil. On the other hand, if the water temperature THW of the supercharged engine 10 is low, moisture that has flowed into the crankcase 17 as water vapor condenses and is more likely to mix with the engine oil. Therefore, the lower the water temperature THW, the higher the mixing rate VC of moisture into the engine oil. Therefore, the mixing rate VC can be calculated based on the water temperature THW and the intake air amount GA, as a value that increases as the water temperature THW decreases and increases as the intake air amount GA increases.

[0022] As the oil temperature THO rises, the water mixed in the engine oil evaporates. The amount of water evaporating from the engine oil increases as the oil temperature THO rises. Therefore, the evaporation rate VE of water from the engine oil can be calculated based on the oil temperature THO, and the higher the oil temperature THO, the higher the value becomes.

[0023] The amount of water mixed into engine oil per unit time increases by the mixing rate VC and decreases by the evaporation rate VE. Therefore, the amount of water accumulated in engine oil MO can be calculated as the integrated value of the difference between the mixing rate VC and the evaporation rate VE. The control device 40 of this embodiment calculates the amount of water accumulated in engine oil MO in this manner. Note that the mixing rate VC used to calculate the amount of water accumulated MO is calculated based on the water temperature THW and the intake air amount GA, and the evaporation rate VE is calculated based on the oil temperature THO. In this manner, the control device 40 calculates the amount of water accumulated in engine oil MO based on the water temperature THW, oil temperature THO, and intake air amount GA of the supercharged engine 10.

[0024] When engine oil containing water is stirred, emulsion occurs. The greater the amount of water accumulated in the engine oil, the more likely emulsion occurs. In this embodiment, an upper limit of the amount of water accumulated in the engine oil, MO, that can suppress emulsion formation within an acceptable range, is set as a threshold value. If the amount of water accumulated in the engine oil MO increases beyond the threshold value, emulsion exceeding the acceptable upper limit may occur.

[0025] On the other hand, as described above, in the supercharged engine 10, ventilation of the crankcase 17 is performed during supercharged operation. Therefore, even if the moisture accumulation amount MO exceeds the threshold, if the supercharged engine 10 is performing supercharged operation at that time, the moisture in the crankcase 17 is released into the intake passage 12 along with the blow-by gas, thereby suppressing the generation of emulsion. However, if the engine is performing naturally aspirated operation, the moisture in the crankcase 17 cannot be released, and the increase in the moisture accumulation amount MO cannot be stopped, resulting in the generation of emulsion.

[0026] In contrast, the control device 40 of this embodiment increases the supercharging efficiency of the compressor 22 and reduces the opening rate of the throttle valve 16 when the moisture accumulation amount MO is equal to or greater than the threshold value and the supercharged engine 10 is operating in the naturally aspirated range. This causes the supercharged engine 10 to perform supercharging operation in the naturally aspirated range where natural aspirated operation would normally be performed. As a result, the crankcase 17 is ventilated and moisture within the crankcase 17 is released, thereby suppressing the generation of emulsion.

[0027] According to the control device 40 for the supercharged engine 10 of this embodiment described above, the following effects can be achieved. (1) While the supercharged engine 10 is operating, the control device 40 determines whether the moisture accumulation amount MO in the engine oil is high. If the control device 40 determines that the moisture accumulation amount MO is high while the supercharged engine 10 is operating in the naturally aspirated range, the control device 40 increases the supercharging efficiency of the compressor 22 and reduces the opening rate of the throttle valve 16. As a result, the control device 40 causes the supercharged engine 10 operating in the naturally aspirated range to perform a supercharged operation and ventilate the crankcase 17. Ventilation of the crankcase 17 prevents further moisture from mixing into the engine oil. Therefore, the control device 40 of this embodiment has the effect of suppressing the generation of emulsion.

[0028] (2) The control device 40 of this embodiment calculates the amount of moisture accumulated in the engine oil MO based on the water temperature THW, oil temperature THO, and intake air amount GA of the supercharged engine 10. The lower the water temperature THW of the supercharged engine 10, the more likely moisture in the crankcase 17 will condense and be mixed into the engine oil. Furthermore, the higher the oil temperature THO, the more likely moisture in the engine oil will evaporate. Furthermore, the greater the intake air amount GA, the greater the amount of moisture generated by combustion and leaking into the crankcase 17. Therefore, the amount of moisture accumulated in the engine oil MO can be accurately calculated based on the water temperature THW, oil temperature THO, and intake air amount GA. The control device 40 then determines whether the amount of moisture accumulated in the engine oil MO is high based on whether the amount of moisture accumulated in the engine oil MO is equal to or greater than a predetermined threshold. Therefore, it is possible to accurately determine whether the amount of moisture accumulated in the engine oil MO is high.

[0029] (3) In this embodiment, the control device 40 calculates the mixing rate VC of water into the engine oil based on the water temperature THW and the intake air amount GA, and the evaporation rate VE of water from the engine oil based on the oil temperature THO. The control device 40 then calculates the amount of accumulated water MO by integrating the difference between the mixing rate VC and the evaporation rate VE. This allows the calculation of the amount of accumulated water MO based on the water temperature THW, the oil temperature THO, and the intake air amount GA to be performed simply and accurately.

[0030] (4) The control device 40 of this embodiment is applied to a hydrogen engine, which is prone to emulsion formation due to the large amount of water generated by combustion. Therefore, the application of the control device 40 of this embodiment is highly effective in suppressing emulsion formation.

[0031] (Other Examples) The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0032] <Calculation of moisture accumulation amount MO> It is also possible to calculate the moisture accumulation amount MO without determining the mixing rate VC and evaporation rate VE. For example, the change in the moisture accumulation amount MO per unit time can be calculated based on the water temperature THW, oil temperature THO, and intake air amount GA. Then, by integrating this change, the moisture accumulation amount MO can be calculated.

[0033] The moisture accumulation amount MO may be calculated without using one or more of the water temperature THW, the oil temperature THO, and the intake air amount GA. Also, parameters other than the water temperature THW, the oil temperature THO, and the intake air amount GA may be used to calculate the moisture accumulation amount MO.

[0034] <Other> It is also possible to determine whether the amount of accumulated water in the engine oil is high without calculating the value of the amount of accumulated water MO. For example, the determination can be made as follows: There are operating conditions of the supercharged engine 10 that make it easy for the amount of accumulated water in the engine oil to increase. The time that the supercharged engine 10 is operating under such operating conditions that make it easy for the amount of accumulated water to increase is measured, and if this time exceeds a certain time, it is determined that the amount of accumulated water is high.

[0035] In the above embodiment, a variable nozzle type turbocharger 20 is used. However, other types of turbochargers may be used as long as they are capable of adjusting the supercharging efficiency of the compressor 22. For example, a turbocharger may be used that includes a bypass passage that allows exhaust gas to bypass the turbine 21 and a wastegate valve that changes the flow area of ​​the exhaust gas in the bypass passage. In this case, the opening rate of the wastegate valve can be reduced to increase the flow rate of exhaust gas blown onto the turbine 21, thereby improving the supercharging efficiency of the compressor 22.

[0036] The control device 40 of the above embodiment and its modified examples can be similarly applied to supercharged engines other than hydrogen engines. (Additional notes) 4. The control device for a supercharged engine according to claim 1, wherein the supercharged engine is a hydrogen engine. [Explanation of symbols]

[0037] 10 Supercharged Engine 11 Combustion chamber 12 Intake passage 13 Exhaust passage 14 Air cleaner 16 Throttle valve 17 Crankcase 20 Turbocharger 21 Turbine 22 Compressor 23 Variable Nozzle 30 First Ventilation Passage 31 Second ventilation passage 32 One-way valve 40 Control device 41 Processing unit 42 Storage device 43 Water temperature sensor 44 Oil temperature sensor 45 Air flow meter

Claims

1. a one-way valve that restricts the flow of gas from the crankcase to the intake passage through the first ventilation passage, Determining whether or not there is a large amount of water accumulated in the engine oil; when it is determined that the amount of accumulated moisture is large while the supercharged engine is operating in a naturally aspirated range, performing a supercharged operation of the supercharged engine by increasing the supercharging efficiency of the compressor and reducing the opening rate of the throttle valve; A control device for a supercharged engine.

2. 2. The control device for a supercharged engine according to claim 1, wherein the moisture accumulation amount is calculated based on a water temperature, an oil temperature, and an intake air amount of the supercharged engine, and when the value of the calculated moisture accumulation amount is equal to or greater than a predetermined threshold value, it is determined that the moisture accumulation amount is large.

3. Calculating a mixing rate of water into the engine oil based on a water temperature and an intake air amount of the supercharged engine; Calculating an evaporation rate of water from the engine oil based on an oil temperature of the supercharged engine; Calculating the amount of accumulated moisture by integrating the difference between the mixing rate and the evaporation rate; 3. The control device for a supercharged engine according to claim 2, wherein the control device performs the following.

4. 2. The control device for a supercharged engine according to claim 1, wherein the supercharged engine is a hydrogen engine.

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