JP2010174825A - Blowby gas reduction device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blowby gas reduction device of an internal combustion engine, suppressing deterioration of emission during warming up of a catalyst. <P>SOLUTION: The blowby gas reduction device 70 of the engine 10 performs warming up of the catalyst and adjusts a blowby gas amount supplied from an engine body 20 to an intake passage 49 by an electric PCV valve 74, and operates a ventilation opening VB of the PCV valve 74, based on the engine operation condition. When an engine load L and an engine speed NE are an engine load L1 and an engine speed N1, respectively, the ventilation opening VB when catalyst warmup control is completed, is an opening demand value VBT1, and when the engine load L and the engine speed NE are also the engine load L1 and the engine speed NE1, respectively, the ventilation opening VB during execution of the catalyst warmup control is an opening demand value VBT2, the opening demand value VBT2 being set less than the opening demand value VBT1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention adjusts the amount of blow-by gas supplied from an engine body to an intake passage of an internal combustion engine that performs catalyst warm-up by means of an electric ventilation control valve. The present invention relates to a blow-by gas reduction device for an internal combustion engine that operates an opening degree.

  As the blow-by gas reduction device, for example, the one described in Patent Document 1 is known. In conventional blow-by gas reduction devices including the device described in this document, the amount of blow-by gas supplied from the engine body to the intake passage is adjusted by operating the opening degree of the ventilation control valve based on the engine operating state. I am doing so.

  On the other hand, in an internal combustion engine equipped with an exhaust catalyst, in order to activate the exhaust catalyst when it is in a low temperature region, the temperature of the exhaust catalyst is increased using a catalyst warming device such as a secondary air introduction device or an airflow control valve. The catalyst warm-up control is generally performed.

Japanese Patent Laid-Open No. 2006-183640

  By the way, in the internal combustion engine that includes the blow-by gas reduction device and executes the catalyst warm-up control, when blow-by gas is supplied from the engine body to the intake passage during the catalyst warm-up control, the following problems are posed. Become. That is, the amount of hydrocarbons (HC) in the exhaust discharged from the combustion chamber increases with the supply of blow-by gas even though the catalyst cannot sufficiently purify the exhaust. It becomes worse.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a blow-by gas reduction device for an internal combustion engine that can suppress deterioration of emissions during catalyst warm-up.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 adjusts the amount of blow-by gas supplied from the engine body to the intake passage by an electric ventilation control valve for an internal combustion engine that performs catalyst warm-up, and is based on the operating state of the engine. In the blow-by gas reduction device for an internal combustion engine that operates the opening degree of the ventilation control valve, the opening degree of the ventilation control valve when the engine operating state is in the operating state A and the catalyst warm-up is completed is set as the opening degree B1. The opening degree of the ventilation control valve when the operating state is the operating state A and the catalyst warm-up is being executed is defined as the opening degree B2, and the opening degree B2 is set to be smaller than the opening degree B1. It is said.

  In this invention, the opening degree of the ventilation control valve when the catalyst warm-up is executed is set smaller than the opening degree of the ventilation control valve when the catalyst warm-up is completed, so that the catalyst is supplied to the combustion chamber during the catalyst warm-up. The amount of blow-by gas is reduced. Accordingly, it is possible to suppress the deterioration of the emission during the warming up of the catalyst.

The block diagram which shows typically the structure of the engine about one Embodiment which actualized the blow-by gas reduction apparatus of the internal combustion engine of this invention. The flowchart which shows the process sequence about "PCV request | requirement amount setting process at the time of a catalyst warm-up" performed by the electronic controller of the embodiment.

1 and 2, an embodiment in which the blow-by gas reduction device for an internal combustion engine of the present invention is embodied as a blow-by gas reduction device for a port injection internal combustion engine will be described.
As shown in FIG. 1, the engine 10 includes an engine body 20 that obtains power through combustion of a mixture of air and fuel, an intake device 40 that supplies external air to the combustion chamber 31 of the engine body 20, and an engine body. An exhaust device 50 that sends exhaust from the engine 20 to the outside, an electronically controlled blow-by gas reduction device 70 that supplies blow-by gas generated in the engine body 20 to the intake device 40, and electronic control that comprehensively controls these devices Device 80.

  The engine body 20 is provided with a cylinder block 21 that burns an air-fuel mixture of fuel injected through the injector 27 and air supplied through the intake device 40 in the combustion chamber 31. A crankcase 22 that supports the crankshaft 26 in cooperation with the cylinder block 21 is attached to the lower portion of the cylinder block 21. An oil pan 23 for storing lubricating oil supplied to each part of the engine 10 is attached to the lower portion of the crankcase 22. A cylinder head 24 on which valve system components are arranged is attached to the upper part of the cylinder block 21. A head cover 25 is attached to the upper portion of the cylinder head 24 to suppress the splashing of the lubricating oil to the outside due to the driving of the valve system components.

  A crank chamber 32 for accommodating the crankshaft 26 is formed inside the cylinder block 21 and the crankcase 22. Inside the cylinder head 24 and the head cover 25, a valve operating chamber 33 is formed to accommodate valve operating parts. The crank chamber 32 and the valve operating chamber 33 are connected to each other by a communication chamber 34 formed inside the cylinder block 21.

  The intake device 40 is provided with a throttle body 41 that accommodates a throttle valve 42 that adjusts the flow rate of air (hereinafter referred to as “intake”) taken into the device from the outside. An air cleaner 43 that removes foreign matter in the intake air is provided on the upstream side of the throttle body 41. An air intake 44 that takes in outside air into the apparatus is provided at the inlet of the air cleaner 43. An intake hose 45 is provided between the inlet of the throttle body 41 and the outlet of the air cleaner 43 to connect them. An intake manifold 46 is provided on the downstream side of the throttle body 41 to supply intake air that has passed through the throttle body 41 to each intake port of the cylinder head 24. The intake manifold 46 is provided with a surge tank 47 that retains intake air that has passed through the throttle body 41, and a plurality of sub-pipes 48 that supply intake air in the tank 47 to each intake port of the cylinder head 24. That is, in the intake device 40, the intake air is supplied to the engine body through the passage in the air intake 44, the passage in the air cleaner 43, the passage in the intake hose 45, the passage in the throttle body 41, and the passage in the intake manifold 46. An intake passage 49 is formed to be fed into the vehicle 20. An air flow control valve 61 that generates a tumble flow in the combustion chamber 31 is provided downstream of the throttle valve 42 in the intake passage 49.

  The exhaust device 50 is provided with an exhaust manifold 51 that collects exhaust exhausted from the exhaust ports of the cylinder head 24. Exhaust gas from the exhaust manifold 51 is sent to the outside through the exhaust passage 52. The exhaust passage 52 is provided with an exhaust catalyst 53 for purifying harmful substances in exhaust gas such as HC, and a secondary air introduction device 62 for supplying secondary air upstream of the exhaust catalyst 53.

  The blow-by gas reduction device 70 has a function of supplying blow-by gas flowing out from the combustion chamber 31 to the crank chamber 32 to the intake device 40 and a function of supplying intake air purified by the air cleaner 43 from the intake device 40 to the valve operating chamber 33. And it is comprised as an apparatus provided with the function which adjusts the quantity of blowby gas supplied to the intake device 40 from the engine main body 20. FIG. Specifically, the engine 10 is provided with the following components as elements constituting the reduction device 70.

  That is, a first ventilation pipe 71 is provided between the cylinder block 21 and the surge tank 47 as a passage for supplying blow-by gas from the crank chamber 32 to the surge tank 47. A second ventilation pipe 72 is provided between the intake hose 45 and the head cover 25 as a passage for supplying intake air from the intake passage 49 to the valve operating chamber 33. An oil separator 73 that separates oil contained in the blow-by gas from the gas is provided at the connection portion of the first ventilation pipe 71 on the cylinder block 21. Further, an opening on the oil separator 73 side in the first ventilation pipe 71 is an electronic control valve that adjusts the flow rate of the mixed gas of the blowby gas and the intake gas (hereinafter, “PCV gas”) mixed in the crank chamber 32. PCV valve 74 is provided. The PCV valve 74 is attached to the surface of the cylinder block 21. The valve body of the valve 74 is driven by an actuator 75. Here, a stepping motor is used as the actuator 75.

The gas flow by the blow-by gas reduction device 70 is shown below.
When the engine is under low load, the negative pressure on the downstream side of the throttle valve 42 is large, so that blow-by gas flows from the crank chamber 32 to the surge tank 47 via the oil separator 73, the PCV valve 74, and the first ventilation pipe 71. Become. At this time, intake air flows into the valve operating chamber 33 from the intake hose 45 through the second ventilation pipe 72. On the other hand, since the pressure in the crank chamber 32 and the valve operating chamber 33 is high at a high engine load, blow-by gas flows from the crank chamber 32 into the surge tank 47 via the oil separator 73, the PCV valve 74, and the first ventilation pipe 71. At the same time, blow-by gas flows from the valve operating chamber 33 to the intake hose 45 via the second ventilation pipe 72. Note that, under the same engine operating state, the opening of the PCV valve 74 (hereinafter referred to as “ventilation opening VB”) increases, that is, the passage area of the inlet of the first ventilation pipe 71 increases. Accordingly, the flow rate of the PCV gas flowing through the first ventilation pipe 71 increases.

  The electronic control unit 80 is connected to a crank position sensor 81, an air flow meter 82, a throttle position sensor 83, a catalyst temperature sensor 84, and the like as various sensors for assisting the control. The crank position sensor 81 is provided in the vicinity of the crankshaft 26 and outputs a signal corresponding to the rotation angle of the shaft 26. The electronic control unit 80 calculates the rotational speed of the crankshaft 26 (hereinafter, “engine rotational speed NE”) based on this signal. The air flow meter 82 is provided upstream of the throttle valve 42 and the opening of the second ventilation pipe 72 in the intake passage 49, and outputs a signal corresponding to the mass flow rate of the intake air flowing through the intake passage 49. The electronic control unit 80 calculates the amount of intake air (hereinafter referred to as “intake amount GA”) supplied to the combustion chamber 31 based on this signal. The throttle position sensor 83 is provided in the vicinity of the throttle valve 42 and outputs a signal corresponding to the opening of the valve 42 (hereinafter referred to as “throttle opening VT”). The catalyst temperature sensor 84 is provided on the exhaust catalyst 53 and outputs a signal corresponding to the temperature of the catalyst 53 (hereinafter, “catalyst temperature TS”).

  The electronic control unit 80 performs various controls such as throttle control, injection control, ventilation control, and catalyst warm-up control after grasping the driver's request and engine operating state based on the detection results of the sensors.

  In the throttle control, the intake air amount GA is adjusted by changing the throttle opening VT by operating the throttle valve 42. In the injection control, the fuel injection amount (hereinafter referred to as “injection amount QI”) is adjusted by changing the valve opening time by operating the injector 27, and the injection amount QI is increased and corrected when the engine 10 is cold started. Improve startability. In the ventilation control, the PCV gas flow rate (hereinafter referred to as “PCV flow rate GB”) is adjusted by changing the ventilation opening degree VB by operating the PCV valve 74. Further, in the catalyst warm-up control, when it is determined that the catalyst temperature TS is lower than a determination value (hereinafter referred to as “determination value TX”), the exhaust catalyst 53 is driven by driving the air flow control valve 61 and the secondary air introduction device 62. Promotes warmth. The determination value TX is set in advance through a test or the like as a value for determining whether or not the exhaust catalyst 53 is in an active state that can sufficiently purify the exhaust gas. In many cases after the engine 10 is started, there is a state in which the increase in the injection amount QI accompanying the cold start and the catalyst warm-up control are performed in parallel.

Here, the detail of the control structure of ventilation control is demonstrated.
In this control, a required amount of PCV flow rate GB (hereinafter referred to as “PCV required amount GBT”) is set based on the engine load L and the engine speed NE, and the actual PCV flow rate GB is maintained at this required amount GBT. Is set as a required value (hereinafter referred to as “opening required value VBT”), and the actual ventilation opening VB (hereinafter referred to as “opening actual value VBR”) is maintained at this required value VBT. Therefore, the actuator 75 of the PCV valve 74 is controlled. The engine load L is, for example, the ratio of the actual intake amount GA to the maximum value of the intake amount GA that can be supplied to the combustion chamber 31 at that time, or the injection amount QI with respect to the maximum value of the injection amount QI of the injector 27. The ratio of the actual value (required value of the injection amount QI) can be grasped as an index.

  Incidentally, as described above, the PCV required amount GBT is calculated based on the engine load L indicating the engine operating state and the engine rotational speed NE, and the parameters serving as the basis for calculating the PCV required amount GBT are as follows. Those directly related to the catalyst warm-up control execution conditions (here, the catalyst temperature TS) are not included. In other words, when the engine operating state (engine load L and engine speed NE) directly related to the calculation of the PCV required amount GBT is one of the engine operating states X, for example, In the engine 10, both the case where the catalyst warm-up control is executed when in the operating state X and the case where the catalyst warm-up control is not executed when in the operating state X can occur as the operating state. Means.

  Incidentally, in the engine 10 that includes the blow-by gas reduction device 70 having the above-described configuration and performs the catalyst warm-up control, when blow-by gas is supplied from the engine body 20 to the intake passage 49 during the catalyst warm-up control, the emission deteriorates. Has been confirmed. That is, when blow-by gas is supplied from the engine body 20 to the intake passage 49 when the exhaust catalyst 53 is not in an active state capable of sufficiently purifying exhaust gas as in the catalyst warm-up control, it is discharged from the combustion chamber. The amount of HC increases. Further, since the exhaust catalyst 53 that has not been warmed up cannot treat HC satisfactorily, the emission deteriorates due to this.

  Therefore, in the blow-by gas reduction device 70 of the present embodiment, the amount of PCV gas (blow-by gas) supplied from the engine body 20 to the intake passage 49 is determined when the control is completed during the catalyst warm-up control. By reducing the amount, the amount of blow-by gas supplied to the combustion chamber 31 during execution of the catalyst warm-up control is reduced. That is, when the engine load L and the engine rotation speed NE are at the engine load L1 and the engine rotation speed NE1, respectively, and the catalyst warm-up control is completed, the request amount GBT1 is set as the PCV request amount GBT, and the PCV valve is accordingly generated. The required opening degree value VBT of 74 is set to the required value VBT1. On the other hand, when the engine load L and the engine rotation speed NE are also at the engine load L1 and the engine rotation speed NE1 and the catalyst warm-up control is being executed, a request amount GBT2 smaller than the request amount GBT1 is set as the PCV request amount GBT. Accordingly, the required opening value VBT of the PCV valve 74 is set to a required value VBT2 smaller than the required value VBT1.

  In addition, through the setting of the PCV required amount GBT, the amount of blow-by gas supplied to the intake passage 49 is reduced under a situation where it is estimated that the exhaust catalyst 53 cannot sufficiently purify the exhaust gas. As a result, the deterioration of the emission during the execution of the catalyst warm-up control is suppressed.

  With reference to FIG. 2, the content of the “catalyst warm-up PCV request amount setting process” that defines a specific processing procedure related to the control of the PCV valve 74 described above will be described. This process is repeatedly executed at predetermined control intervals by the electronic control unit 80 during operation of the engine 10.

  In this process, it is first determined in step S110 whether or not catalyst warm-up control is being executed. Here, in order to confirm that the catalyst warm-up control is being executed, the condition is that the secondary air introduction device 62 is being driven and the airflow control valve 61 is being driven. That is, it is determined that the catalyst warm-up control is being executed based on the fact that the same condition is satisfied.

  When it is determined that the catalyst warm-up control is being executed, in the next step S120, a value smaller than the PCV required amount corresponding to the engine load L and the engine speed NE as the engine operating state at that time is set to the ventilation control. Is set as the PCV request amount GBT for. Specifically, the PCV gas flow rate GBX that is expected to contain the same amount of blowby gas that flows from the combustion chamber 31 to the crank chamber 32 is set as the PCV required amount GBT for ventilation control. The PCV gas flow rate GBX is set in advance through a test or the like and stored in the electronic control unit 80. Here, as a setting mode of the flow rate GBX of the PCV gas, the amount of blow-by gas flowing out from the combustion chamber 31 to the crank chamber 32 is grasped for each engine operation state, and the engine operation state is based on the grasped amount of blow-by gas. The thing which sets every PCV gas flow rate GBX is mentioned.

  That is, according to the processing of step S120, the PCV required amount corresponding to the engine load L and the engine speed NE at that time is set as the required amount GBTA, and the opening required value VBT corresponding to the required amount GBTA is set as the required value VBTA. As a PCV required amount set for ventilation control, a required amount GBTB smaller than the required amount GBTA by a predetermined amount ΔGBT is set, and the opening required value VBT is smaller than the required value VBTA. A small required value VBTB is set.

  Since the predetermined amount ΔGBT is set in advance for each engine operating state as described above, a different value is calculated according to the engine load L and the engine speed NE at that time. In addition, as a setting mode of the predetermined amount ΔGBT, a fixed value set in advance can be adopted instead of a mode in which the predetermined amount ΔGBT is made variable based on the engine load L and the engine speed NE.

  In the next step S130, it is determined whether or not the catalyst warm-up control has been completed. Here, based on the fact that the driving of the secondary air introduction device 62 and the airflow control valve 61 is stopped, it is determined that the catalyst warm-up has been completed. When it is determined that the catalyst warm-up is being continued, the process of setting the PCV request amount GBT to be smaller than the values corresponding to the engine load L and the engine speed NE is continued until the catalyst warm-up is completed.

  On the other hand, when it is determined that the catalyst warm-up has been completed, in the next step S140, the processing for setting the PCV request amount GBT to be smaller than the values corresponding to the engine load L and the engine speed NE is canceled. Thereafter, the PCV required amount GBT calculated according to the engine load L and the engine speed NE at that time is used for ventilation control. Thus, in the ventilation control, the PCV valve 74 is controlled based on the PCV required amount GBT.

According to the blow-by gas reduction device of the present embodiment, the following effects can be achieved.
(1) In this embodiment, when the engine load L and the engine rotational speed NE are at the engine load L1 and the engine rotational speed NE1, respectively, and the catalyst warm-up control is completed, the ventilation opening degree VB is set to the required value VBT1, and the engine load L When the engine rotational speed NE is also at the engine load L1 and the engine rotational speed NE1 and the catalyst warm-up control is being executed, the ventilation opening VB is set as the required value VBT2, and the required value VBT2 is set smaller than the required value VBT1. Like that.

  Thus, the amount of blow-by gas supplied to the combustion chamber 31 during the execution of the catalyst warm-up control is reduced. That is, the amount of blow-by gas supplied from the engine body 20 to the intake passage 49 is reduced under a situation where it is estimated that the exhaust catalyst 53 is not in an active state that can sufficiently purify the exhaust gas. Therefore, it is possible to suppress the deterioration of the emission during the execution of the catalyst warm-up control.

  (2) Since the ventilation opening VB of the PCV valve 74 is set to be small as described above during execution of the catalyst warm-up control, the intake passage downstream of the throttle valve 42 during idle operation during the execution of the control. The negative pressure in 49 can be increased. As a result, a sufficient negative pressure downstream of the throttle valve 42 can be secured without a device (so-called ejector) that increases the negative pressure during the catalyst warm-up control.

  (3) Further, during the execution of the catalyst warm-up control, the increase in the injection amount QI by the injection control is often performed, and as a result, the amount of HC discharged from the combustion chamber further increases. It is easy to do. On the other hand, in this embodiment, since the ventilation opening degree VB of the PCV valve 74 is set small during the execution of the catalyst warm-up control, the increase in the injection amount QI is corrected during the catalyst warm-up as described above. Even so, the absolute amount of HC flowing into the exhaust catalyst 53 can be reduced.

(Other embodiments)
In addition, the embodiment of the present invention is not limited to the contents exemplified in the above embodiment, and can be modified as shown below, for example.

  In the above embodiment, it is determined that the catalyst warm-up control is being performed based on the fact that the secondary air introduction device 62 and the airflow control valve 61 are being driven. The determination method is not limited to this. For example, it is possible to determine that the catalyst warm-up control is being executed based on the fact that the catalyst warm-up execution request is set (the catalyst temperature TS is lower than the determination value TX).

  In the above embodiment, it is determined that the catalyst warm-up control has been completed based on the secondary air introduction device 62 and the airflow control valve 61 being stopped, but it is determined whether the catalyst warm-up control has been completed. The method is not limited to this. For example, it can be determined that the catalyst warm-up control has been completed based on the cancellation of the catalyst warm-up execution request (the catalyst temperature TS being higher than the determination value TX).

  In the above embodiment, the catalyst warm-up control is performed by driving the secondary air introduction device 62 and the airflow control valve 61 together. However, the contents of the catalyst warm-up control are not limited to this. For example, it is also possible to employ catalyst warm-up control in which one of the secondary air introduction device 62 or the airflow control valve 61 is omitted and only the other device is driven.

  In the above embodiment, when it is determined that the catalyst warm-up control is being performed, the PCV gas flow rate GBX is set as the PCV request amount GBT. However, the setting mode of the PCV request amount GBT during the catalyst warm-up control is It is not limited to this. That is, if the PCV required amount GBT during the catalyst warm-up control is smaller than the values corresponding to the engine load L and the engine speed NE, it is allowed to set an appropriate value within this range. The For example, “0” may be set as the PCV request amount GBT, and the PCV valve 74 may be kept closed during the catalyst warm-up control. Alternatively, the PCV required amount GBT corresponding to the engine load L and the engine rotational speed NE, which is corrected to a decrease by a certain amount, can be set as the PCV required amount GBT during execution of the catalyst warm-up control.

  In the above embodiment, the first ventilation pipe 71 connecting the crank chamber 32 and the surge tank 47 is used, but the configuration of the first ventilation pipe 71 is not limited to this. For example, what connects the valve operating chamber 33 and the surge tank 47 as the 1st ventilation piping 71 can also be provided. In short, if the blow-by gas of the engine body 20 is supplied to the downstream side of the throttle valve 42, the configuration of the first ventilation pipe 71 can be changed as appropriate.

  In the above embodiment, the second ventilation pipe 72 that connects the valve operating chamber 33 and the intake hose 45 is used, but the configuration of the second ventilation pipe 72 is not limited to this. For example, what connects the intake hose 45 and the crank chamber 32 as the 2nd ventilation piping 72 can also be provided. In short, if the intake air is supplied to the engine body 20 from the upstream side of the throttle valve 42, the configuration of the second ventilation pipe 72 can be changed as appropriate.

  In the above embodiment, the engine 10 is assumed to be of the port injection type, but the present invention can be similarly applied to the cylinder injection type. Further, the configuration as the blow-by gas reduction device 70 is not limited to the configuration exemplified in each embodiment. In short, with regard to the blow-by gas reduction device having an electric PCV valve, the present invention can be applied to any engine as long as it is an internal combustion engine equipped with the same. It is possible to achieve the effects.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 20 ... Engine main body, 21 ... Cylinder block, 22 ... Crank case, 23 ... Oil pan, 24 ... Cylinder head, 25 ... Head cover, 26 ... Crankshaft, 27 ... Injector, 31 ... Combustion chamber, 32 ... Crank , 33 ... Valve operating chamber, 34 ... Communication chamber, 40 ... Intake device, 41 ... Throttle body, 42 ... Throttle valve, 43 ... Air cleaner, 44 ... Air intake, 45 ... Intake hose, 46 ... Intake manifold, 47 ... Surge Tank, 48 ... sub pipe, 49 ... intake passage, 50 ... exhaust device, 51 ... exhaust manifold, 52 ... exhaust passage, 53 ... exhaust catalyst, 61 ... air flow control valve, 62 ... secondary air introduction device, 70 ... blow-by gas reduction 71, first ventilation pipe, 72 ... second ventilation pipe, 73 ... oil set Regulator, 74 ... PCV valve (ventilation control valve), 75 ... actuator, 80 ... electronic control unit, 81 ... crank position sensor, 82 ... flow meter, 83 ... throttle position sensor, 84 ... catalyst temperature sensor.

Claims (1)

For an internal combustion engine that performs catalyst warm-up, the amount of blow-by gas supplied from the engine body to the intake passage is adjusted by an electric ventilation control valve, and the opening degree of the ventilation control valve is operated based on the engine operating state In a blow-by gas reduction device for an internal combustion engine,
When the engine operation state is the operation state A and the opening degree of the ventilation control valve when the catalyst warm-up is completed is the opening degree B1, the engine operation state is the operation state A and the catalyst warm-up is being executed. An opening degree of the ventilation control valve is set as an opening degree B2, and the opening degree B2 is set smaller than the opening degree B1.

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