JP5925664B2 - Exhaust gas deadline control device - Google Patents

Description

  The present invention relates to an exhaust gas cutoff control device used in, for example, a turbo system, an exhaust gas recirculation system (EGR system), an exhaust brake system, and the like.

  Patent Document 1 discloses a valve assembly used in an EGR system. According to the valve assembly described in this document, the flow rate of the exhaust gas passing through the gas passage can be adjusted. That is, the valve assembly includes a butterfly valve. The valve body of the butterfly valve is rotatable between a fully closed position where the exhaust gas flow rate is minimum and a fully open position where the exhaust gas flow rate is maximum. The valve assembly adjusts the flow rate of the exhaust gas by setting the valve body at a predetermined position.

JP 2004-263723 A JP 2007-285123 A

  By the way, when the temperature of the exhaust gas flowing through the gas passage changes, the temperature of the valve body colliding with the flow of the exhaust gas also changes. In addition, the temperature of the valve seat formed in the gas passage also changes. When comparing the valve body and the valve seat, the temperature change is greater in the valve body facing the exhaust gas flow than in the valve seat. For this reason, the amount of thermal deformation of the valve body is larger than that of the valve seat.

  Here, when the valve body and the valve seat are designed on the basis of a low temperature, the valve body is likely to be excessively pressed against the valve seat at a high temperature. In other words, the valve body has a larger amount of thermal expansion than the valve seat. For this reason, when the valve body and the valve seat are designed so that the valve body is seated on the valve seat in the fully closed position at a low temperature, the valve body tends to be excessively pressed against the valve seat at a high temperature. Therefore, it becomes difficult to move the valve body from the fully closed position to another position at high temperatures.

  On the other hand, when the valve body and the valve seat are designed based on the high temperature, a clearance is generated between the valve body and the valve seat at the low temperature. For this reason, when the valve body and the valve seat are designed so that the valve body is seated on the valve seat in the fully closed position at a high temperature, the valve body is separated from the valve seat at a low temperature. Therefore, a clearance is generated between the valve body and the valve seat at a low temperature, regardless of the fully closed position. Therefore, exhaust gas leaks from the upstream side of the valve body to the downstream side.

  As described above, even if the valve body and the valve seat are designed based on the low temperature, and the valve body and the valve seat are designed based on the high temperature, a demerit occurs. However, in order to ensure smooth operation of the valve body, it is necessary to allow the exhaust gas to leak at a low temperature and in the fully closed position, and to design the valve body and the valve seat based on the high temperature.

  Patent Document 2 discloses a valve opening / closing control device used in an EGR system. According to the valve opening / closing control device described in the same document, when the valve is switched to the fully closed position, the valve can be stopped at a control fully closed point set in front of the fully closed position (fully opened position side). . Patent Document 2 does not disclose or suggest the above-mentioned problem (the problem of exhaust gas leakage from the clearance at the fully closed position at a low temperature).

  Accordingly, an object of the present invention is to provide an exhaust gas cutoff control device in which exhaust gas is less likely to leak from the clearance between the valve body and the valve seat during full-close control.

  (1) In order to solve the above problems, an exhaust gas cutoff control device according to the present invention includes a valve having a valve body, a housing in which an exhaust gas passage having a valve seat to which the valve body can be attached and detached is formed, and the valve An actuator that drives the body, a fully open position that is the position of the valve body where the passage cross-sectional area of the exhaust gas passage is maximum, and a fully closed position that is the position of the valve body where the passage cross-sectional area is smaller than the fully open position A control unit having a storage unit in which a position is stored in advance, and a calculation unit that executes a fully-closed step of switching the valve body from an arbitrary position to the fully-closed position by controlling the actuator; An exhaust gas shut-off control device comprising: a position of the valve body where the valve body is seated on the valve seat as a contact position, and the calculation unit is applied from the fully closed position after the fully closed step. Move the valve body to the contact position. It is allowed, and executes the step pushing pressing the valve body in the valve seat with a predetermined pressing force. Here, the “passage cross-sectional area” means a cross-sectional area in a direction orthogonal to the extending direction of the exhaust gas passage.

  According to the exhaust gas deadline control device of the present invention, the calculation unit executes the fully closed step and the pressing step. In the fully closed step, the actuator moves the valve body from an arbitrary position to the fully closed position. In the pressing step, the actuator moves the valve body from the fully closed position to the contact position. In the contact position, the valve body is pressed against the valve seat. For this reason, at the time of full-closed control (for example, when a full-close instruction is issued to the control unit from a host control unit such as an ECU (Engine Control Unit)), from the clearance between the valve body and the valve seat, Leakage of exhaust gas can be suppressed.

  (1-1) Preferably, in the configuration of (1), the valve is a butterfly valve. The butterfly valve includes a valve shaft and a valve body. The valve body rotates around the axis of the valve shaft. According to this configuration, the radially outer end portion of the valve shaft in the outer peripheral edge of the valve body can be pressed against the valve seat at the contact position.

  (2) Preferably, in the configuration of (1), the storage unit does not store the contact position, and the calculation unit continues to apply the pressing force to the valve body in the pressing step. Better to do.

  The storage unit stores in advance a fully open position and a fully closed position. In the fully closed step, the calculation unit can recognize the position of the valve body. On the other hand, the contact position is not stored in the storage unit. For this reason, in the pressing step, the calculation unit cannot recognize the position of the valve body. That is, the calculation unit cannot determine whether or not the valve body has arrived at the contact position (whether or not the valve body is seated on the valve seat).

  In this regard, in the case of this configuration, in the pressing step, the actuator continuously applies a pressing force to the valve body. For this reason, although a calculating part cannot recognize the position of a valve body, a valve body can be reliably pressed on a valve seat.

  According to this configuration, for example, when the calculation unit determines whether or not the valve body is seated on the valve seat based on the load (load current, load voltage, etc.) of the actuator (in this case, of course, the above (1) )), The circuit configuration of the exhaust gas cutoff control device is simplified. For this reason, the manufacturing cost of the exhaust gas deadline control device can be reduced.

  (3) Preferably, in the configuration of the above (1) or (2), further comprising an opening direction biasing member that applies a biasing force to the valve body in a direction from the fully closed position toward the fully opened position. Better to do.

  Depending on the system in which the exhaust gas cutoff device of the present invention is used, it may be preferable from the viewpoint of fail-safe that the exhaust gas passage has a maximum cross-sectional area at the time of failure or the like. In this regard, the exhaust gas cutoff device of this configuration includes an opening direction biasing member. The opening direction biasing member always biases the valve body in the opening direction. For this reason, even if the driving force is not transmitted from the actuator to the valve body, the valve body can be set to the fully open position by the biasing force of the opening direction biasing member. That is, the passage sectional area of the exhaust gas passage can be maximized.

  Further, the pressing force applied by the actuator to the valve body in the pressing step acts in the opposite direction to the biasing force. According to this configuration, the valve body can be pressed against the valve seat against the urging force at the contact position.

  (4) Preferably, in the configuration according to any one of (1) to (3), a closing direction biasing member that applies a biasing force to the valve body in a direction from the fully opened position toward the fully closed position is further provided. It is better to have a configuration with.

  The closing direction biasing member constantly biases the valve body in the closing direction. In the pressing step, the pressing force applied to the valve body by the actuator acts in the same direction as the biasing force of the closing direction biasing member. According to this configuration, the valve body can be pressed against the valve seat by the urging force and the pressing force at the contact position.

  According to the present invention, it is possible to provide an exhaust gas deadline control device in which exhaust gas hardly leaks from the clearance between the valve body and the valve seat during the fully closed control.

It is an arrangement plan of an exhaust gas deadline control device of a first embodiment. It is a perspective view of the exhaust gas deadline control device. It is the III-III direction sectional drawing of FIG. It is a schematic diagram of the exhaust-gas deadline method which the same exhaust-gas deadline control apparatus performs. It is an enlarged view in the circle V of FIG. It is an enlarged view of the vicinity of the valve seat when the exhaust gas of the exhaust gas cutoff control device is hot. It is a schematic diagram which shows the difference in the leakage amount in the presence or absence of a pressing step. It is a schematic diagram of the exhaust-gas deadline method which the exhaust-gas deadline control apparatus of a reference form performs.

  Hereinafter, embodiments of the exhaust gas deadline control device of the present invention will be described.

<First embodiment>
[Configuration of exhaust gas deadline control device]
First, the configuration of the exhaust gas deadline control device of the present embodiment will be described. FIG. 1 shows a layout of the exhaust gas deadline control device of the present embodiment. FIG. 2 is a perspective view of the exhaust gas cutoff control device. FIG. 3 shows a cross-sectional view in the III-III direction of FIG. Note that FIG. 3 shows a low temperature when the temperature of the exhaust gas is low.

  As shown in FIG. 1, a turbocharger 92 is disposed between the intake system 90 and the exhaust system 91. The exhaust gas cutoff control device 1 according to the present embodiment is disposed in a bypass pipe 910 that bypasses the turbocharger 92 in the exhaust system 91.

  As shown in FIGS. 1 to 3, the exhaust gas cutoff control device 1 mainly includes a housing 2, a butterfly valve 3, a motor 4, a control unit 5, a default spring 7, a link mechanism unit 8, It has. The motor 4 is included in the concept of the “actuator” of the present invention. The default spring 7 is included in the concept of the “opening direction biasing member” of the present invention.

(Housing 2)
As shown in FIG. 1, the housing 2 is disposed in a bypass pipe 910. As shown in FIG. 3, the housing 2 includes an exhaust gas passage 20, a first sleeve 21, and a second sleeve 22. The first sleeve 21 and the second sleeve 22 are each made of stainless steel and have a cylindrical shape. The end surface in the axial direction of the first sleeve 21 and the end surface in the axial direction of the second sleeve 22 are abutted from the axial direction in a state of being radially displaced from each other.

  A valve seat 210 is set in a portion of the inner circumferential edge of the axial end face of the first sleeve 21 that is disposed radially inward from the inner circumferential edge of the axial end face of the second sleeve 22. Similarly, a valve seat 220 is set in a portion of the inner circumferential edge of the axial end surface of the second sleeve 22 that is disposed radially inward of the inner circumferential edge of the axial end surface of the first sleeve 21. Yes. The exhaust gas passage 20 is disposed on the radially inner side of the first sleeve 21 and the second sleeve 22. The exhaust gas flows through the exhaust gas passage 20 from the first sleeve 21 toward the second sleeve 22.

(Butterfly valve 3)
The butterfly valve 3 is disposed in the housing 2. The butterfly valve 3 can open and close the exhaust gas passage 20. The butterfly valve 3 includes a valve body 30 and a valve shaft 31. The valve shaft 31 is made of stainless steel and has a round bar shape. The valve body 30 is made of stainless steel and has a disk shape. A diameter portion of the valve body 30 is fixed to the valve shaft 31. The valve body 30 is rotatable inside the exhaust gas passage 20. The outer peripheral edge of the valve body 30 can be attached to and detached from the valve seats 210 and 220.

  As shown in FIG. 2, one end of the valve shaft 31 protrudes outside the housing 2. The protruding portion of the valve shaft 31 is made of stainless steel and is rotatably supported inside a cylindrical valve shaft support boss 310. A cylindrical spacer 311 made of stainless steel is mounted around the outer periphery of the valve shaft support boss 310. The default spring 7 is mounted on the outer peripheral surface of the spacer 311. That is, the spacer 311 prevents interference between the default spring 7 and the valve shaft support boss 310. One end of the default spring 7 is locked to a valve side arm 82 described later. The other end of the default spring 7 is locked to the housing 2. The default spring 7 biases the valve body of the butterfly valve 3 in the opening direction (the direction from the fully closed position P1 to the fully opened position P2 shown in FIG. 3).

(Motor 4)
The motor 4 is connected to the butterfly valve 3 via a link mechanism portion 8 to be described later. The motor 4 includes a motor case 40 and a drive shaft 41. The motor case 40 houses a motor body (not shown). The drive shaft 41 protrudes from the motor case 40 to the outside. The drive shaft 41 and the motor body are connected by a speed reduction mechanism (not shown) including a plurality of gears.

(Link mechanism 8)
The link mechanism unit 8 includes a motor side arm 80, an intermediate arm 81, and a valve side arm 82. The link mechanism unit 8 has a folded scale shape (Z-shape) as a whole. The motor side arm 80 and the valve side arm 82 are each made of iron. On the other hand, the intermediate arm 81 is made of stainless steel. The motor side arm 80, the intermediate arm 81, and the valve side arm 82 each have a thin plate shape.

  One end of the motor side arm 80 is fixed to the drive shaft 41. The other end of the motor side arm 80 is swingably connected to one end of the intermediate arm 81. The other end of the intermediate arm 81 is swingably connected to one end of the valve side arm 82. The other end of the valve side arm 82 is fixed to one end of the valve shaft 31 passing through the valve shaft support boss 310.

(Control unit 5)
The control unit 5 is disposed integrally with the motor 4. The control unit 5 controls the drive of the motor 4. As shown in FIG. 1, the control unit 5 includes a calculation unit 50 that is a CPU (central processing unit, microcomputer). The computing unit 50 includes a storage unit 51. The storage unit 51 is an EEPROM (electrically erasable programmable read-only memory). The storage unit 51 stores a fully closed position P1 and a fully open position P2 of the valve body 30 of the butterfly valve 3.

  The calculation unit 50 controls the motor 4 by PWM (Pulse-Width Modulation). The calculating part 50 can set the valve body 30 to a desired opening degree between the fully closed position P1 and the fully open position P2.

  The learning of the fully closed position P1 and the fully open position P2 is executed from when the exhaust gas deadline control device 1 is assembled to before being mounted on the vehicle. Specifically, first, a position learning unit (not shown) is connected to the control unit 5. Next, the butterfly valve 3 is actually driven by the control unit 5. Then, the fully closed position P1 (the opening degree of the valve body 30 where the passage cross-sectional area of the exhaust gas passage 20 is minimized during vehicle operation) and the fully open position P2 (the valve body where the passage cross-sectional area of the exhaust gas passage 20 is maximized during vehicle operation). 30 opening degree) and the storage unit 51. Finally, the position learning unit is removed from the control unit 5. The opening degree of the valve body 30 corresponding to the fully closed position P1 and the fully open position P2 varies depending on the engine and the vehicle type.

  An ECU 99 is connected to the control unit 5 as a host control device. The control unit 5 controls the opening and closing of the butterfly valve 3 based on a control instruction from the ECU 99.

[Exhaust gas deadline]
Next, an exhaust gas deadline method executed by the exhaust gas deadline controller 1 of the present embodiment will be described. FIG. 4 shows a schematic diagram of an exhaust gas deadline method executed by the exhaust gas deadline control apparatus of the present embodiment. When the ECU 99 shown in FIG. 1 instructs the control unit 5 to be fully closed (instruction to rotate the valve body 30 to the fully closed position P1), the calculation unit 50 executes the exhaust gas closing method.

  First, the case where the exhaust gas is at a low temperature will be described. The exhaust gas deadline method has a fully closed step and a pressing step. In the fully closed step, the motor 4 is fully closed from an arbitrary opening degree (specifically, an arbitrary opening degree between the fully opened position P2 and the fully closed position P1) as shown in FIG. The valve body 30 is rotated to the position P1. As shown in FIG. 4, between the fully open position P2 and the fully closed position P1, the calculating part 50 is carrying out duty ratio fluctuation | variation control of the motor 4. FIG. The duty ratio is calculated from the equation: duty ratio (%) = τ / T × 100, where τ is the pulse width of the pulse wave of the drive signal for the motor 4 and T is the period. For this reason, in the fully closed step, the calculation unit 50 controls the motor 4 with a desired duty ratio. When the valve body 30 arrives at the fully closed position P1, the calculation unit 50 once sets the duty ratio to zero.

  In the pressing step, the motor 4 rotates the valve body 30 from the fully closed position P1 to the contact position P3 as shown in FIG. That is, in the rotation direction (opening / closing direction) of the valve body 30, the contact position P3 is set in the closing direction of the fully closed position P1 (the direction opposite to the fully opened position P2). Between the fully closed position P1 and the contact position P3, the calculation unit 50 controls the motor 4 to have a fixed duty ratio. For this reason, in the pressing step, the motor 4 rotates the valve body 30 with a constant pressing force F1. Note that the pressing force F1, that is, the duty ratio in the duty ratio fixed control, takes into consideration the amount of heat generated by the motor 4, damage to the gears of the link mechanism 8 and the speed reduction mechanism, the biasing force F2 of the default spring 7 in the opening direction, and the like. Are set in advance. The duty ratio is stored in the storage unit 51 shown in FIG.

  FIG. 5 shows an enlarged view in the circle V of FIG. As shown in FIGS. 3 and 5, the valve body 30 is pressed against the valve seat 220 with a predetermined pressing force F1 at the contact position P3. The pressing force F1 is obtained when the ECU 99 shown in FIG. 1 issues a full-close instruction to the control unit 5 (or after the full-close instruction, the ECU 99 gives the next instruction to change the opening degree of the valve body 30). The motor 4 is continuously applied from the motor 4 to the valve body 30. For this reason, the amount of exhaust gas leakage from the upstream side (first sleeve 21 side) to the downstream side (second sleeve 22 side) is reduced.

  As indicated by the alternate long and short dash line in FIG. 5, even when the valve body 30 reaches the fully closed position P1, a clearance C1 exists in the radial direction between the valve body 30 and the valve seat 220. Here, the valve body 30 and the valve seat 220 are designed based on the case where the temperature of the exhaust gas is high. For this reason, the clearance C1 at a low temperature is relatively large. Therefore, if the pressing step is not executed, the valve body 30 stops at the fully closed position P1, so that the amount of exhaust gas leakage from the upstream side to the downstream side increases.

  Next, the case where the exhaust gas is hot will be described. The case where the exhaust gas is high is the same as the case where the exhaust gas is low. FIG. 6 shows an enlarged view of the vicinity of the valve seat when the exhaust gas of the exhaust gas cutoff control device of the present embodiment is high temperature. FIG. 6 corresponds to FIG.

  As shown in FIG. 6, when the exhaust gas is hot, the valve body 30 is thermally expanded radially outward. For this reason, compared with the case where exhaust gas is low temperature, the clearance C2 in the fully closed position P1 becomes small. That is, C2 <C1. Even in this case, since the valve body 30 is rotated to the contact position P3 in the pressing step, the leakage amount of the exhaust gas from the upstream side to the downstream side is reduced.

[Effects of exhaust gas deadline control device]
Next, the effect of the exhaust gas deadline control device 1 of this embodiment will be described. According to the exhaust gas shut-off control device 1 of the present embodiment, when the ECU 99 shown in FIG. 1 issues a full-close instruction to the control unit 5, as shown in FIG. The valve body 30 is rotated from the position of the body 30 to the contact position P3. As shown in FIG. 3, the motor 4 continuously presses the valve element 30 against the valve seat 220 with a predetermined pressing force F <b> 1 while the full-close instruction is issued. For this reason, when the ECU 99 shown in FIG. 1 issues a full-close instruction, the exhaust gas leaks from the clearances C1 and C2 between the valve body 30 and the valve seat 220 as shown in FIGS. Can be suppressed.

  FIG. 7 is a schematic diagram showing the difference in leakage amount with and without the pressing step. Α1 shown in FIG. 7 corresponds to the case where the valve body 30 is in the contact position P3 at the high temperature shown in FIG. α2 corresponds to the case where the valve body 30 is in the fully closed position P1 at the time of high temperature shown in FIG. β1 corresponds to the case where the valve body 30 is in the contact position P3 at the low temperature shown in FIG. β2 corresponds to the case where the valve body 30 is in the fully closed position P1 at the low temperature shown in FIG.

  As shown in FIG. 7, compared with the case where the pressing step is not executed, the amount of leakage is reduced by executing the pressing step regardless of the temperature of the exhaust gas (regardless of the size of the clearance). Can do. In particular, when the temperature of the exhaust gas is low (when the clearance is large), the amount of leakage can be reduced.

  Further, according to the exhaust gas cutoff control device 1 of the present embodiment, as shown in FIGS. 3 and 4, the motor 4 continuously pushes the valve body 30 after the valve body 30 exceeds the fully closed position P1. Pressure is being applied. For this reason, although the calculating part 50 shown in FIG. 1 cannot recognize the opening degree of the valve body 30, the valve body 30 can be reliably pressed on the valve seat 220. FIG.

  Further, according to the exhaust gas cutoff control device 1 of this embodiment, for example, based on the load current of the motor 4, the calculation unit 50 is compared with a case where it is determined whether or not the valve body 30 is seated on the valve seat 220. Thus, the circuit configuration of the exhaust gas cutoff control device 1 is simplified. For this reason, the manufacturing cost of the exhaust gas deadline control device 1 can be reduced.

  Moreover, as shown in FIG. 2, the default spring 7 is arrange | positioned at the exhaust-gas deadline control apparatus 1 of this embodiment. The default spring 7 always urges the valve body 30 in the opening direction. For this reason, even if the driving force is not transmitted from the motor 4 to the valve body 30, the valve body 30 can be set to the fully open position P2 shown in FIG. That is, the passage sectional area of the exhaust gas passage 20 can be maximized.

  Further, according to the exhaust gas cutoff control device 1 of the present embodiment, as shown in FIG. 6, the outer peripheral edge of the valve body 30 and the valve seat 220 are inclined in the same direction with respect to the radial direction of the valve body 30. ing. For this reason, even if the valve body 30 is thermally expanded radially outward, the outer peripheral edge of the valve body 30 can slide along the surface direction of the valve seat 220. Therefore, the outer peripheral edge of the valve body 30 is difficult to bite into the valve seat 220.

< Reference form>
The difference between the exhaust gas deadline control device of the reference form and the exhaust gas deadline control device of the first embodiment is only the setting of the duty ratio during execution of the exhaust gas deadline method. Here, only differences will be described.

FIG. 8 shows a schematic diagram of an exhaust gas deadline method executed by the exhaust gas deadline control apparatus of the reference embodiment. In addition, about the site | part corresponding to FIG. 4, it shows with the same code | symbol. As shown in FIG. 8, even if the valve body arrives at the fully closed position P1, the calculation unit does not set the duty ratio to zero. The calculation unit starts the duty ratio fixing control before the valve body arrives at the fully closed position P1.

The exhaust gas deadline control device of the reference form and the exhaust gas deadline control device of the first embodiment have the same operational effects with respect to the parts having the same configuration. As in the reference embodiment, the duty ratio does not have to be reduced to 0 at the fully closed position P1. That is, it is only necessary that the duty ratio fixing control is executed at least in the section from the fully closed position P1 to the contact position P3 (during the pressing step).

<Others>
The embodiment of the exhaust gas deadline control device of the present invention has been described above. However, the embodiment is not particularly limited to the above embodiment. Various modifications and improvements that can be made by those skilled in the art are also possible.

  The type of valve is not limited to the butterfly valve 3. For example, a poppet valve may be used. The location of the exhaust gas deadline control device 1 is not particularly limited. You may arrange | position in an EGR system, an exhaust brake system, etc. As shown in FIG. 3, the magnitude of the pressing force F1 applied to the valve body 30 by the motor 4 at the contact position P3 is not particularly limited. It is only necessary that the rotational torque in the direction toward the valve seat 220 can be transmitted to the valve body 30.

  In the above embodiment, the default spring 7 is disposed as an example of the “opening direction biasing member” of the present invention. However, instead of the default spring 7, a return spring may be disposed as an example of the “closing direction biasing member” of the present invention. Further, the default spring 7 and the return spring may be used in combination.

1: Exhaust gas deadline control device.
2: housing, 20: exhaust gas passage, 21: first sleeve, 210: valve seat, 22: second sleeve, 220: valve seat.
3: butterfly valve, 30: valve body, 31: valve shaft, 310: valve shaft support boss, 311: spacer.
4: Motor (actuator), 40: motor case, 41: drive shaft.
5: control unit, 50: calculation unit, 51: storage unit.
7: Default spring (opening direction biasing member).
8: Link mechanism, 80: Motor side arm, 81: Intermediate arm, 82: Valve side arm.
90: Intake system, 91: Exhaust system, 910: Bypass piping, 92: Turbocharger, 99: ECU.
C1: clearance, C2: clearance, F1: pressing force, F2: urging force, P1: fully closed position, P2: fully open position, P3: contact position.

Claims (5)

A valve having a valve body;
A housing in which an exhaust gas passage having a valve seat to which the valve body can be attached and detached is formed;
An actuator for driving the valve body;
The fully open position, which is the position of the valve body where the passage cross-sectional area of the exhaust gas passage is maximized, and the fully closed position, which is the position of the valve body where the passage cross-sectional area is smaller than the fully open position, are stored in advance. A storage unit, and a control unit that executes a fully closed step for switching the valve body from an arbitrary position to the fully closed position by controlling the actuator,
An exhaust gas deadline control device comprising:
The position of the valve body where the valve body is seated on the valve seat as a contact position,
When an instruction to fully close the valve body is issued to the control unit from the host controller that controls the control unit,
The computing unit is
The fully closed step;
The valve body is moved from the fully closed position to the corresponding contact position , and the next instruction to change the opening degree of the valve body is given while the fully closed instruction is issued or after the fully closed instruction, A pressing step of pressing the valve body against the valve seat with a predetermined pressing force continuously until the upper control device delivers the control unit ;
The execution,
The drive shaft of the actuator is connected to a speed reduction mechanism unit composed of a plurality of gears,
The valve is a butterfly valve further having a valve shaft that rotates the valve body about an axis,
In the fully closed step, the calculation unit controls the duty ratio variation of the actuator,
In the pressing step, the calculation unit controls the actuator with a fixed duty ratio,
The exhaust gas cutoff control device characterized in that, when switching from the fully closed step to the pressing step, the calculation unit temporarily sets the duty ratio to 0 in the fully closed position .   The exhaust gas cutoff control device according to claim 1, further comprising an opening direction biasing member that applies a biasing force to the valve body in a direction from the fully closed position toward the fully opened position.   Furthermore, a link mechanism portion interposed between the drive shaft and the valve shaft is provided,
  The duty ratio in the pressing step is determined in advance in consideration of the amount of heat generated by the actuator, damage to the link mechanism, damage to the gear of the speed reduction mechanism, and the biasing force in the opening direction of the opening biasing member. The exhaust gas deadline control device according to claim 2, which is set.   The exhaust gas cutoff control device according to any one of claims 1 to 3, wherein the storage unit does not store the contact position.   The exhaust gas cutoff control device according to any one of claims 1 to 4, further comprising a closing direction biasing member that applies a biasing force to the valve body in a direction from the fully open position toward the fully closed position.

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