JP6299677B2 - Internal combustion engine ventilation system - Google Patents

Description

  The present invention relates to a ventilation system for an internal combustion engine having a configuration in which blow-by gas generated in a crankcase flows into an intake passage.

  In an internal combustion engine, blow-by gas that leaks into a crankcase from a gap between a piston and a cylinder bore of a cylinder block is forcibly returned to an intake passage, that is, a combustion chamber using intake negative pressure. .

  Patent Document 1 discloses an example of a device that returns blow-by gas to a combustion chamber. The internal combustion engine of Patent Document 1 is provided in a first passage that connects the inside of the crankcase to an intake passage upstream of the throttle valve, a second passage that connects the inside of the crankcase to an intake passage downstream of the throttle valve, and a second passage. And a solenoid valve. The solenoid valve is controlled in principle based on the engine speed and the pressure in the intake passage. And the apparatus of patent document 1 feedback-controls the open state of a solenoid valve based on the output signal from the pressure sensor for detecting the pressure in a crankcase, in order to make the inside of a crankcase into a negative pressure state, As a result, the amount of the recirculated gas is minimized and an attempt is made to suppress the deterioration of the combustion state.

Japanese Patent Laid-Open No. 9-068028

  By the way, the oil in an internal combustion engine has the characteristic that the viscosity changes according to the temperature change, and has the tendency to splash according to the viscosity. For example, when the viscosity of the oil is relatively low, the oil is likely to be splashed in the crankcase as compared with the case where the viscosity is relatively high, and thus oil mist is likely to occur. If more fresh air is introduced in a situation where oil mist is likely to occur, more oil is contained in the recirculated gas including fresh air and blow-by gas that is recirculated to the intake passage. This is not preferable because it increases the amount of oil consumed in an internal combustion engine, for example. On the other hand, introduction of fresh air is effective for sufficient ventilation in the crankcase.

  Therefore, the present invention has been made in view of such circumstances, and an object thereof is to ventilate the inside of the crankcase while suppressing the introduction of oil into the intake passage.

According to one aspect of the invention,
A throttle valve provided in the intake passage, a PCV passage connected to the downstream intake passage on the downstream side of the throttle valve and communicating with the inside of the crankcase, and an upstream intake passage on the upstream side of the throttle valve; A ventilation system for an internal combustion engine, comprising: an air passage communicating with the inside of the crankcase; and a PCV valve provided in the PCV passage and having an opening degree adjusted,
Viscosity acquisition means for acquiring the viscosity of the oil of the internal combustion engine;
An internal combustion engine comprising PCV valve control means for controlling the opening degree of the PCV valve so that the opening degree of the PCV valve becomes smaller when the viscosity of the oil obtained by the viscosity obtaining means is low than when the oil viscosity is high A ventilation system is provided.

  Preferably, the ventilation system of the internal combustion engine includes pressure acquisition means for acquiring the pressure of the downstream intake passage, and the PCV valve control means is the pressure of the downstream intake passage acquired by the pressure acquisition means. And a target reflux gas flow rate of the reflux gas flowing through the PCV passage and the atmospheric passage based on the viscosity of the oil obtained by the viscosity obtaining means, and the flow rate of the reflux gas becomes the target reflux gas flow rate. The PCV valve is controlled as follows.

  More preferably, the ventilation system of the internal combustion engine includes an engine rotation speed acquisition means for acquiring the engine rotation speed, and the PCV valve control means is provided when the engine rotation speed acquired by the engine rotation speed acquisition means is high. The target reflux gas flow rate is calculated as a smaller value than when it is low.

  According to the above aspect of the present invention, the PCV valve control means controls the opening degree of the PCV valve so that the opening degree of the PCV valve becomes smaller when the oil viscosity of the internal combustion engine is low than when it is high. Therefore, when the oil has a relatively low viscosity, the gas flow inside the engine body is suppressed. As a result, the introduction of oil into the intake passage accompanying the gas flow can be suppressed. Therefore, according to one aspect of the present invention, an exceptional effect is achieved in that the inside of the crankcase can be ventilated while suppressing the introduction of oil into the intake passage.

1 is a schematic cross-sectional view of a ventilation system for an internal combustion engine according to an embodiment of the present invention. It is a graph showing the change tendency of the pressure of an intake passage, and the total ventilation in a predetermined operation area. It is a graph for calculation of a correction value. It is a flowchart for PCV valve control.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a ventilation system of an internal combustion engine to which an embodiment of the present invention is applied. As shown in the figure, an engine (internal combustion engine) 10 includes a cylinder block 12, a piston 14, a crankcase 16, a cylinder head 18, a head cover 20 that covers the cylinder head 18 from above, and oil as an oil reservoir. A pan 22. In the present specification, the cylinder block 12, the crankcase 16, the cylinder head 18, the head cover 20, and the oil pan 22 are outer shell structures that define an internal region of the engine body 10 ′ of the engine 10. .

  Blow-by gas is gas that leaks into the crankcase 16 from the gap between the piston ring of the piston 14 and the cylinder bore of the cylinder block 12, and is generated in the crankcase 16. This blow-by gas contains a large amount of hydrocarbons and moisture. For this reason, blow-by gas can cause deterioration of engine oil and rust inside the engine. Moreover, since hydrocarbons are contained, it is not environmentally preferable to release the blow-by gas to the atmosphere as it is. Therefore, the blow-by gas is forcibly returned to the intake passage through a route described later using the intake negative pressure. As will be described later, the flow of blow-by gas and fresh air when the engine is lightly loaded is schematically shown by arrows in FIG.

  A throttle valve 26 is provided in the intake passage 24. The intake passage (downstream intake passage) 24d on the downstream side of the throttle valve 26 and the inside of the head cover 20 are communicated with each other by a PCV passage 28 connected to the downstream intake passage 24d. Here, PCV is an abbreviation for Positive Crankcase Ventilation. Further, the intake passage (upstream intake passage) 24u on the upstream side of the throttle valve 26 and the inside of the head cover 20 are communicated with each other by an atmospheric passage 30 connected to the upstream intake passage 24u. The PCV passage 28 may be referred to as a first reflux passage, and the atmospheric passage 30 may be referred to as a second reflux passage. A PCV valve 32 is provided in the PCV passage 28. By adjusting the opening degree of the PCV valve 32, the communication state between the downstream side intake passage 24d and the head cover 20 is adjusted. The PCV valve 32 is provided in the opening of the PCV passage 28 into the engine body 10 ′, but may be provided in the middle of the PCV passage 28. The throttle valve 26 and the PCV valve 32 are each configured as an electromagnetic control valve.

  The cylinder block 12 and the cylinder head 18 are provided with an oil dropping passage 34 that allows the inside of the head cover 20 and the inside of the crankcase 16 to communicate with each other. The oil dropping passage 34 here is a passage for dropping the oil remaining on the cylinder head 18 after finishing the lubrication of the valve system toward the oil pan 22, and at the same time, the blow-by gas in the crankcase 16 is removed from the head cover. 20 is a passage for ascending and moving toward the inside 20. The blow-by gas that moves upward from the crankcase 16 toward the head cover 20 includes oil mist generated by stirring and evaporation of the oil in the crankcase 16. For example, the inside of the head cover 20 and the inside of the crankcase 16 communicate with each other via the oil dropping passage 34. Accordingly, since the PCV passage 28 is connected to each of the downstream side intake passage 24d and the inside of the head cover 20, the downstream side intake passage 24d and the inside of the crankcase 16 are communicated with each other. Similarly, the atmospheric passage 30 allows the upstream intake passage 24u to communicate with the inside of the crankcase 16. In addition to the oil drop passage 34, a dedicated passage through which fresh air and blow-by gas circulate may be provided through the head cover 20 and the crankcase 16.

  As shown in the figure, when the engine is lightly loaded, the throttle valve 26 is controlled to the closed side, the negative pressure in the downstream intake passage 24d is increased, and the PCV valve 32 is opened (that is, the opening degree is increased). The blow-by gas in the crankcase 16 passes through the oil drop passage 34 and the head cover 20 and is returned to the downstream intake passage 24d through the PCV passage 28 as a recirculation gas together with fresh air, and then burned in the combustion chamber in the cylinder block 12. The At this time, fresh air mainly enters the head cover 20 through the atmospheric passage 30 and reaches the crankcase 16, and then can return to the intake passage 24 through the oil drop passage 34 and the PCV passage 28. .

  On the other hand, although not shown, when the engine is heavily loaded, the throttle valve 26 is opened largely beyond a predetermined opening, while the PCV valve 32 is controlled to the closed side. At this time, the blow-by gas in the head cover 20 is returned to the intake passage 24 through both the PCV passage 28 and the atmospheric passage 30 or through the atmospheric passage 30.

  Thus, in the engine 10, the blow-by gas in the crankcase 16 is introduced into the head cover 20, returned to the intake passage 24, and then burned.

  The engine 10 includes an ECU (electronic control unit) 50. The ECU 50 is constituted by a microcomputer including an arithmetic device (for example, CPU), a storage device (for example, ROM, RAM), an A / D converter, an input interface, an output interface, and the like. The input interface includes an engine rotation speed sensor 52 for detecting the engine rotation speed, a pressure in the intake passage 24 (that is, an intake pipe pressure), particularly an intake pressure sensor for detecting the pressure in the downstream intake passage 24d here. 54, an oil temperature sensor 56 for detecting the temperature of lubricating oil (hereinafter referred to as oil) of the engine 10 is electrically connected. The engine rotation speed sensor 52 corresponds to engine rotation speed acquisition means, the intake pressure sensor 54 corresponds to pressure acquisition means, and the oil temperature sensor 56 acquires the viscosity of oil as will be apparent from the description to be described later. It corresponds to the viscosity acquisition means for. Although not shown, the input interface detects an accelerator opening sensor for detecting the amount of depression of an accelerator pedal (not shown), a throttle opening sensor for detecting the opening of the throttle valve 26, and an intake air amount. An air flow meter for detecting the temperature of the engine coolant and a water temperature sensor for detecting the coolant temperature are electrically connected. The ECU 50 is electrically connected to the fuel injection valve and the PCV valve 32 from the output interface so that the engine 10 can be smoothly operated or operated in accordance with a preset program based on outputs (that is, detection signals) from these various sensors. The operation signal (drive signal) is output to More specifically, the ECU 50 outputs an operation signal to the PCV valve 32 (that is, to control the actuator for driving the PCV valve) in order to adjust and control the opening degree of the PCV valve 32. Accordingly, a part of the ECU 50 functions as a PCV valve control means for controlling the opening degree of the PCV valve.

  The ECU 50 functions as an acquisition unit that acquires the oil viscosity (or a value corresponding thereto) based on the output of the oil temperature sensor 56, and the pressure in the downstream intake passage based on the output of the intake pressure sensor 54. It functions as an acquisition unit that acquires (or a value corresponding thereto), and further functions as an acquisition unit that acquires the engine rotation speed (or a value corresponding thereto) based on the output of the engine rotation speed sensor 52. The water temperature sensor may be used as the viscosity detection means. When estimating the oil viscosity based on the engine operating state or its history, the engine load sensor such as the intake pressure sensor 54 and the engine rotation speed sensor 52 are used. May be a viscosity detecting means.

  By the way, when the blow-by gas is returned to the intake passage, the oil of the engine 10 may also flow into the intake passage together with the reflux gas. In the engine 10, the PCV passage 28 and the atmospheric passage 30 are directly connected to the head cover 20. In the inner region of the head cover 20 and the cylinder head 18, for example, the oil is easily splashed by the rotation of the respective camshafts of the intake / exhaust valves IV and EV, and is partially atomized. For example, when the pressure of the intake passage 24 is considerably low (compared to atmospheric pressure) when the engine 10 is lightly loaded, fresh air flows into the head cover 20 through the atmospheric passage 30 as described above, and blow-by gas Flows out to the intake passage 24 as recirculation gas together with fresh air. Further, since fresh air also reaches the crankcase, the oil mist in the crankcase 16 is also included in the reflux gas. Therefore, the atomized oil is moved or further atomized by the flow of gas such as fresh air or blow-by gas in the engine body 10 'and is carried to the intake passage. Such an outflow of oil from the engine body 10 ′ to the intake passage is not preferable for the engine 10. For example, it is not preferable in view of the performance of the engine 10 that the oil that has flowed out adheres to the intake passage 24, the intake valve IV, the combustion chamber, and the like, and deposits are generated. In addition, it is not preferable that the oil amount in the engine 10 is reduced due to the oil outflow in view of the lubrication performance. Furthermore, it is not preferable for the control of the combustion state that the spilled oil burns in the combustion chamber. Therefore, it is desired to prevent or suppress the outflow of oil from the engine body 10 '.

  On the other hand, the properties of oil vary greatly depending on its viscosity. For example, the lower the viscosity of the oil, the more easily the oil is agitated due to the movement of various members and the influence of gas flow, and more easily atomized. Therefore, here, the oil outflow is suppressed by controlling the PCV valve 32 while paying attention to the viscosity of the oil. Hereinafter, the description will be further continued based on FIGS.

  Here, the introduction of the above-described reflux gas into the intake passage will be further described with reference to FIG. In FIG. 2, the horizontal axis represents the pressure in the downstream intake passage 24d (that is, the intake pressure), and the vertical axis represents the flow rate of the reflux gas flowing through the PCV passage 28 and the atmospheric passage 30. The relationship between the pressure in the passage and the flow rate of the reflux gas is shown. However, the horizontal axis indicates the difference between the pressure in the intake passage and the atmospheric pressure. That is, the horizontal axis in FIG. 2 is determined so that the pressure in the intake passage increases as it goes to the right side, and the pressure in the intake passage approaches the atmospheric pressure as it goes to the right side. The amount of decrease in the pressure of the intake passage 24 from the atmospheric pressure increases toward the left side of the horizontal axis in FIG. A line L1 in FIG. 2 indicates a reference for controlling the flow rate of the reflux gas as the total amount of the flow rate of the gas flowing through the PCV passage 28 and the flow rate of the gas flowing through the atmospheric passage 30. A line L2 indicates the flow rate of blow-by gas out of the flow rate of the reflux gas. That is, the difference between the flow rate of the reflux gas (line L1) and the flow rate of the blow-by gas (line L2) corresponds to the flow rate of fresh air contained in the reflux gas.

  As shown in FIG. 2, the flow rate (line L2) of the blow-by gas increases as the pressure in the intake passage 24, particularly the downstream intake passage 24d increases (closer to the atmospheric pressure). This is because the in-cylinder pressure increases as the pressure in the downstream side intake passage 24d approaches atmospheric pressure, and the flow rate of blow-by gas that leaks into the crankcase from the gap between the piston and the cylinder bore increases. The amount of blow-by gas generated is uniquely determined by the pressure in the downstream intake passage 24d and is not affected by the opening of the PCV valve 32.

  As described above, the line L1 indicates the reference flow rate of the reference reflux gas for controlling the PCV valve 32. This reference reflux gas flow rate was tested in advance as an amount that can reduce the oil consumption while sufficiently ventilating the crankcase when the oil has the reference viscosity and the engine speed is the reference speed. It is determined based on. Here, the reference recirculation gas flow rate is determined based on experiments in advance so as to increase as the pressure in the downstream side intake passage 24d is lower than the atmospheric pressure.

  The reference recirculation gas flow rate is corrected to the target recirculation gas flow rate in accordance with a change in engine speed and a change in oil viscosity. Then, the opening degree of the PCV valve 32 is controlled so that the actual reflux gas flow rate becomes the target reflux gas flow rate.

  A variable region, that is, a variable width from the reference recirculation gas flow rate to the target recirculation gas flow rate is defined as a region R in FIG. The region R is a region between the line L1a and the line L1b extending so as not to intersect the line L1 in FIG. Note that the line L1 extends between the line L1a and the line L1b. Line L1a is defined as the upper limit of the target reflux gas flow rate, and line L1b is defined as the lower limit of the target reflux gas flow rate. In particular, the variable region of the target recirculation gas flow rate is suitable for the engine 10 described above by introducing oil into the intake passage while preferably introducing fresh air into the engine body 10 '(for example, a crankcase). It is determined based on experiments so as to suppress the disadvantages (specifically, deposit generation in the intake passage and the like, reduction of oil amount, deterioration of combustion state) as much as possible.

  Then, the correction value for deriving the target recirculation gas flow rate is calculated and determined based on the mapped data shown in FIG. In FIG. 3, the correction value is determined such that the lower the oil viscosity, the lower the target reflux gas flow rate. In FIG. 3, the correction value is determined so that the target reflux gas flow rate decreases as the engine speed increases. As the engine speed increases, oil mist is more likely to occur with the rotation of the crankshaft or camshaft, for example. It is for lowering. In FIG. 3, the horizontal axis represents the engine rotation speed, the vertical axis represents the oil viscosity, and a correction value (or correction coefficient) calculation map is shown.

  In FIG. 3, the engine rotation speed corresponding to the reference engine rotation speed is denoted as N0 so that the engine rotation speed is the reference engine rotation speed corresponding to the line L1. That is, when the engine rotational speed is higher than the reference engine rotational speed, it is indicated by plus in FIG. 3, and when the engine rotational speed is lower than the reference engine rotational speed is indicated by minus.

  Similarly, in FIG. 3, the viscosity corresponding to the reference viscosity is expressed as V0 so that the oil viscosity is the reference viscosity. That is, the higher the oil viscosity is, the higher the reference viscosity is, and the more positive the oil viscosity is in FIG. 3, and the lower the oil viscosity is, the lower the oil viscosity is in FIG.

  For example, when the engine rotational speed is the reference engine rotational speed and the oil viscosity is the reference viscosity, 1 (corresponding to c3) is calculated as the correction value. In the lower right region in FIG. 3, the correction value becomes small. For example, 0.8 (corresponding to e1) is calculated as the correction value for the engine speed and oil viscosity corresponding to the line L1b. Further, the correction value increases in the upper left area in FIG. 3, and for example, 1.2 (corresponding to a5) is calculated as the correction value for the engine speed and oil viscosity corresponding to the line L1a. Note that the arrow in FIG. 3 indicates that the correction value tends to increase toward the tip of the arrow. That is, if the engine rotational speed is the same, when the viscosity of the oil is a second viscosity (for example, the viscosity in the lowest region in FIG. 3) lower than the first viscosity that is the reference viscosity, for example, it is the first viscosity. A smaller correction value is calculated so that the flow rate of the recirculation gas, particularly the fresh air flow rate thereof, is smaller than when Further, if the oil viscosity is the same, when the engine rotation speed is a second rotation speed (for example, the engine rotation speed in the rightmost region of FIG. 3) higher than the first rotation speed that is the reference engine rotation speed, for example, A smaller correction value is calculated so that the flow rate of the reflux gas, particularly the fresh air flow rate, is smaller than when the rotation speed is the first rotation speed. In FIG. 3, the correction value at a1 is smaller than the correction value at a5 at the same engine speed, and the correction value at e1 is smaller than the correction value at e5 at the same engine speed. The correction value at e5 is smaller than the correction value at a5 at the same viscosity, and the correction value at e1 is smaller than the correction value at a1 at the same viscosity.

  Here, the control of the PCV valve 32 will be described based on the flowchart of FIG. However, the engine 10 is preset so that the PCV valve 32 is opened when the operating state is in a predetermined operating region. For example, the PCV valve 32 is preset so as to be closed when in a specific high-load operation region including the full load and during idle operation. The control of the PCV valve 32 described based on the flowchart of FIG. 4 is when the engine operating state is in a predetermined operating region where the PCV valve 32 is opened. It should be noted that the operating region in which the engine is operating is determined by searching for data set in advance based on the engine speed and engine load detected based on the output of the engine speed sensor 52, or This is performed by performing a predetermined calculation based on the data. As the engine load, a value based on at least one of the output of the intake pressure sensor 54, the output of the accelerator opening sensor, the output of the throttle opening sensor, and the output of the air flow meter may be used.

  In step S401, a reference reflux gas flow rate is calculated. Here, the intake pressure detected (acquired) based on the output from the intake pressure sensor 54 is used. Then, the reference recirculation gas flow rate is calculated by searching the data of the line L1 as shown in FIG. 2 based on the intake pressure. The reference recirculation gas flow rate may be obtained by calculating according to a predetermined calculation formula determined based on data as shown in FIG.

  In step S403 after step S401, a correction value is calculated. Based on the output of the engine rotation speed sensor 52, the engine rotation speed is detected (obtained). Further, the viscosity of the oil is detected (obtained) by searching predetermined data or performing a predetermined calculation based on the output of the oil temperature sensor 56. Generally, there is a correlation that the viscosity of the oil decreases as the temperature of the oil increases, and the viscosity of the oil is determined based on this relationship. Then, a correction value is calculated by searching data as shown in FIG. 3 based on the acquired engine rotation speed and oil viscosity. However, here, the correction value is determined in steps. That is, the data in FIG. 3 is divided into squares, and a unique correction value is defined for each square. The correction value may be obtained by calculation according to a predetermined calculation formula determined based on data as shown in FIG.

  In the next step S405, the target reflux gas flow rate is calculated. The target reflux gas flow rate is calculated by performing a predetermined calculation based on the reference reflux gas flow rate calculated in step S401 and the correction value calculated in step S403. For example, the target reflux gas flow rate is calculated by applying a correction value to the reference reflux gas flow rate.

  In the next step S407, the target valve opening degree of the PCV valve 32 is calculated. As the target valve opening, the relationship between the target recirculation gas flow rate and the target valve opening is determined in advance based on experiments so that the opening degree on the fully open side is calculated as the target recirculation gas flow rate in step S405 increases. Yes. The calculation of the target valve opening may be performed by searching for data (not shown), or may be performed by a predetermined calculation based on the data.

  In step S409, the PCV valve 32 is controlled so that the opening degree of the PCV valve becomes equal to the target valve opening degree calculated in step S407. A sensor for detecting the opening degree of the PCV valve may be further provided so as to more accurately control the opening degree of the PCV valve 32.

  In the above embodiment, the correction value is obtained based on the engine rotation speed and the oil viscosity, but the correction value may be obtained based only on the oil viscosity. The present invention allows various embodiments that control the opening of the PCV valve based at least on the viscosity of the oil.

  In the above embodiment, the PCV passage 28 is directly connected to the head cover 20. However, the PCV passage 28 may be directly connected to any part of the outer shell structure of the engine body 10 ′ other than the head cover. The PCV passage is a passage for allowing blow-by gas generated in the crankcase 16 to flow in the downstream side intake passage 24d on the downstream side of the throttle valve. Therefore, the PCV passage can be connected to various places where the blow-by gas can flow to the downstream intake passage. In other words, the PCV passage is configured to directly connect the inside of any of the cylinder block 12, the crankcase 16, the cylinder head 18, the head cover 20, and the oil pan 22 and the downstream side intake passage. In particular, except for the head cover, the pipe member defining the PCV passage can be directly connected to either the cylinder block 12 or the crankcase 16. For example, when the PCV passage is directly connected to the crankcase 16, oil mist is likely to occur in the crankcase as the crankshaft rotates and the oil returns to the oil pan. Therefore, even in this case, according to the present invention, oil can be prevented from flowing out when blow-by gas is returned.

  Further, in the above embodiment, the correction value is calculated based on the viscosity of the oil, and the target reflux gas flow rate is calculated. In the above embodiment, the correction value is variable in steps, and the target reflux gas flow rate is obtained using the correction value. In calculating the correction value, the correction value may be calculated stepwise in only two stages, when the oil viscosity and / or the engine speed is low and when it is high. Further, for example, the correction value for calculating the target reflux gas flow rate may be continuously variable so that the target reflux gas flow rate is continuously decreased as the oil viscosity decreases. In the above embodiment, the target reflux gas flow rate is calculated after calculating the correction value. However, the step of calculating the correction value may be omitted, and the target reflux gas flow rate or the target valve opening may be directly calculated based on the output of the oil temperature sensor 56. Further, in the present embodiment, the target recirculation gas flow rate is calculated in controlling the opening degree of the PCV valve 32, but this is substantially the same as calculating the target fresh air flow rate, and is included in that sense. This is because the blow-by gas flow rate is uniquely determined with respect to the pressure in the downstream side intake passage. Therefore, if the target recirculation gas flow rate is calculated, the target fresh air flow rate is also uniquely determined by subtracting the blow-by gas flow rate therefrom. It is.

  Embodiments of the present invention are not limited to the above-described embodiments and modifications. All modifications, applications, and equivalents included in the spirit of the present invention defined by the claims are included in the present invention. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

DESCRIPTION OF SYMBOLS 10 Engine 12 Cylinder block 16 Crankcase 18 Cylinder head 20 Head cover 22 Oil pan 24 Intake passage 24d Downstream intake passage 24u Upstream intake passage 26 Throttle valve 28 PCV passage 30 Atmosphere passage 32 PCV valve 34 Oil drop passage 56 Oil temperature sensor

Claims (2)

A throttle valve provided in the intake passage, a PCV passage connected to the downstream intake passage on the downstream side of the throttle valve and communicating with the inside of the crankcase, and an upstream intake passage on the upstream side of the throttle valve; A ventilation system for an internal combustion engine, comprising: an air passage communicating with the inside of the crankcase; and a PCV valve provided in the PCV passage and having an opening degree adjusted,
Viscosity acquisition means for acquiring the viscosity of the oil of the internal combustion engine;
Pressure acquisition means for acquiring the pressure of the downstream side intake passage;
The viscosity than when higher when the viscosity of the obtained oil lower by acquisition means such that said opening of the PCV valve becomes smaller, Bei example a PCV valve control means for controlling an opening degree of the PCV valve,
The PCV valve control means circulates between the PCV passage and the atmospheric passage based on the pressure of the downstream intake passage acquired by the pressure acquisition means and the viscosity of the oil acquired by the viscosity acquisition means. Calculating a target reflux gas flow rate of the gas, and controlling the PCV valve so that the flow rate of the reflux gas becomes the target reflux gas flow rate,
Ventilation system for internal combustion engines. An engine rotation speed acquisition means for acquiring the engine rotation speed;
The PCV valve control means calculates the target reflux gas flow rate as a smaller value when the engine speed acquired by the engine speed acquisition means is high than when it is low.
The ventilation system for an internal combustion engine according to claim 1 .

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