JP5200731B2 - Exhaust gas purification system - Google Patents

Description

  The present invention relates to an exhaust gas purification system.

  The exhaust gas purification catalyst exhibits exhaust gas purification performance at a temperature higher than a predetermined temperature. Therefore, it is difficult to obtain sufficient exhaust purification performance immediately after cold start.

  Therefore, a small manifold catalyst is provided in the engine room. When the underfloor catalyst is in an inactive state immediately after a cold start, the exhaust shut valve is closed and the exhaust gas is passed through the manifold catalyst for purification, and the underfloor catalyst is in an active state. Research has been conducted on a technology for purifying exhaust gas by opening the valve body of the exhaust shut-off valve and flowing exhaust gas through the underfloor catalyst.

  However, with such a technique, there is a possibility that a sudden change in torque (torque step) may occur due to a sudden change in back pressure that occurs when the exhaust shut valve is opened and closed to change the exhaust gas flow path.

Therefore, in Patent Document 1, a sudden change in back pressure is prevented by slowly opening and closing the valve body of the exhaust shut valve.
JP 2007-154811 A

  However, the valve body of the exhaust shut-off valve is attached in a loosely fitted state. By doing so, the posture error of the valve body when the valve is closed is absorbed so that the exhaust gas does not flow reliably. Therefore, when the flow of exhaust gas is received, the valve body may vibrate and noise may be generated. Therefore, it is necessary to open and close the valve body in such a short time that the occupant does not notice the noise.

  Accordingly, the inventors of the present invention have found that the desired performance cannot be satisfied by the method of Patent Document 1 depending on engine specifications and operating conditions.

  The present invention has been made paying attention to such a conventional problem, and when the valve body of the exhaust shut valve that changes the flow path of the exhaust gas according to the operating state of the engine is opened and closed, the torque suddenly changes. An object of the present invention is to provide an exhaust gas purification system that does not generate (torque step).

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

The present invention relates to a main exhaust passage (10) through which exhaust gas discharged from an engine flows, and a plurality of valve bodies capable of changing the flow rate of exhaust gas by opening and closing portions of the flow passage cross section of the main exhaust passage (10). An exhaust shut-off valve (50) including 51-1, 51-2), an underfloor catalyst (20) provided in a main exhaust passage (10) downstream of the exhaust shut-off valve (50), and the exhaust shut-off valve (50) is once branched from the main exhaust passage (10) upstream of the exhaust shut-off valve (50) and upstream of the underfloor catalyst (20). There are times when the sub-exhaust passage (30) that joins again, the manifold catalyst (40) provided in the sub-exhaust passage (30), and the plurality of valve bodies (51-1, 51-2) are opened. the valve body from the opening of the (51-1), another valve body (51- ) And having a, a valve opening control means for opening the further valve member (51-2) after waiting for the time that does not cause torque step be opened.

  According to the present invention, when opening a plurality of valve bodies of the exhaust shut valve, since one valve body is opened and then another valve body is opened, the exhaust shut valve (valve body) It is possible to prevent a sudden change in torque (torque step) regardless of the opening and closing of the motor.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a basic configuration of an exhaust gas purification system according to the present invention.

  A main exhaust passage 10 provided in the engine E, an underfloor catalyst 20, a sub exhaust passage 30, and a manifold catalyst 40 are included.

  Exhaust gas discharged from the engine E flows through the main exhaust passage 10. An exhaust shut valve 50 is provided in the middle of the main exhaust passage 10. The exhaust shut valve 50 includes a first valve body 51-1 and a second valve body 51-2. The first valve body 51-1 rotates around the first shaft 52-1 to open and close a partial region of the flow passage cross section of the main exhaust passage 10. The second valve body 51-2 rotates around the second shaft 52-2 to open and close other areas of the cross section of the main exhaust passage 10. When the first valve body 51-1 and the second valve body 51-2 are opened, most of the exhaust gas discharged from the engine E flows through the main exhaust passage 10. When one of the first valve body 51-1 and the second valve body 51-2 is closed and the other is opened, part of the exhaust gas discharged from the engine E flows through the main exhaust passage 10. When the first valve body 51-1 and the second valve body 51-2 are closed, the exhaust gas does not flow through the main exhaust passage 10.

  The underfloor catalyst 20 is disposed in the main exhaust passage 10 on the downstream side of the exhaust shut valve 50. The underfloor catalyst 20 has a large capacity and a large amount of exhaust gas purification.

  The sub exhaust passage 30 once branches from the main exhaust passage 10 upstream of the exhaust shut-off valve 50 and joins again to the main exhaust passage 10 downstream of the exhaust shut-off valve 50 and upstream of the underfloor catalyst 20. To do.

  The manifold catalyst 40 is disposed in the sub exhaust passage 30. The manifold catalyst 40 has a smaller capacity than the underfloor catalyst 20 and a small amount of exhaust gas purification, but can be activated quickly when high-temperature exhaust gas flows.

  FIG. 2 is an enlarged perspective view of the vicinity of the exhaust shut-off valve.

  The basic structure of the exhaust shut-off valve used in this embodiment is disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-8284, and will be briefly described here. Hereinafter, matters common to the first valve body and the second valve body will be described by appropriately omitting “-1” and “−2” at the end of the reference numerals.

  Exhaust shut valve 50 includes a valve body 51, a shaft 52, and a plate 53. The exhaust shut-off valve 50 according to the present embodiment has a single-shaft two-valve structure in which two valve bodies 51 are attached to one shaft 52 via two plates 53.

  An arm 54 is fixed to the tip of the shaft 52. The shaft 52 is rotated by moving the arm 54 up and down by an actuator (not shown).

  The plate 53 is fixed to the shaft 52. In the present embodiment, two plates 53 are fixed to one shaft 52. Each plate 53 has a large hole (not shown).

  A thin pin 11 a is fixed to the valve body 51. This pin 11 a is inserted through the hole of the plate 53. The tip of the pin 11a is fixed by the holding ring 11b. Due to such a structure, the valve body 51 is attached to the plate 53 with play (backlash).

  Since the valve body 51 is attached to the plate 53 with play (backlash), the exhaust gas discharged from the engine E by steadily closing the main exhaust passage 10 when the valve body 51 rotates around the shaft 52. It does not flow reliably (for details, see Japanese Patent Application Laid-Open No. 2008-8284).

  In such a structure, if the valve body 51 is held at an intermediate opening degree, the valve body 51 is rattled due to the flow of exhaust gas, and an abnormal noise is generated. Further, since the flow resistance of the exhaust gas is large, the holding torque of the actuator becomes great. Therefore, it must be fixedly held in the fully closed state or fully opened state as shown in FIG. That is, with the exhaust shut valve having such a structure, the valve body cannot be maintained at an intermediate opening degree.

  However, in such an exhaust shut-off valve, when the valve body is fully opened from the fully closed state, a sudden change in torque (torque step) may occur due to the exhaust gas flowing at a stroke and the back pressure suddenly changing.

  Therefore, in the present embodiment, as described above, the first valve body 51-1 that opens and closes a partial area of the flow passage cross section of the main exhaust passage 10 and the other area of the flow passage cross section of the main exhaust passage 10 are opened and closed. The second valve body 51-2 is provided. When the exhaust shut-off valve is fully opened from the fully closed state, the first valve body 51-1 is first fully opened, and then the second valve body 51-2 is fully opened after a certain period of time. Hereinafter, specific contents of this control will be described.

  FIG. 3 is a flowchart showing the main routine of the control logic of the exhaust gas purification system according to the present invention. The controller repeatedly executes the following processing every minute time (for example, 10 milliseconds) during engine operation.

  In step S1, the controller determines whether the underfloor catalyst is in an active state. Specifically, it may be determined based on the temperature of the exhaust gas flowing through the underfloor catalyst. The exhaust gas temperature may be detected by, for example, an exhaust gas temperature sensor installed at the inlet of the underfloor catalyst. Alternatively, it may be estimated from an integrated value of the amount of air taken into the engine. If the underfloor catalyst is in an active state, the process proceeds to step S7, and if not, the process proceeds to step S2.

  In step S2, the controller determines whether the required acceleration is greater than the reference acceleration A1. The presence or absence of the acceleration request may be detected from the accelerator pedal depression amount or the throttle valve opening. The reference acceleration A1 is a reference value for determining whether the required acceleration is equal to or greater than the slow acceleration, and is set in advance according to the vehicle characteristics. If the requested acceleration is larger than the reference acceleration A1, the process proceeds to step S5, and if not, the process proceeds to step S3.

  In step S3, the controller resets the acceleration delay counter and the valve opening delay counter. These counters will be described later.

  In step S4, the controller executes a valve closing process. The subroutine for the valve closing process will be described later.

  In step S5, the controller resets the valve opening delay counter and the valve closing delay counter. These counters will also be described later.

  In step S6, the controller executes acceleration request time processing. This acceleration request processing subroutine will also be described later.

  In step S7, the controller resets the valve closing delay counter and the acceleration delay counter. These counters will also be described later.

  In step S8, the controller executes a valve opening process. The subroutine for the valve opening process will also be described later.

  FIG. 4 is a flowchart showing a subroutine for valve closing processing of the exhaust gas purification system according to the present invention.

  In step S41, the controller determines whether or not both the first valve body 51-1 and the second valve body 51-2 are open. If so, the process proceeds to step S42; otherwise, the process proceeds to step S43.

  In step S42, the controller closes the second valve body 51-2 while opening the first valve body 51-1.

  In step S43, the controller determines whether or not both the first valve body 51-1 and the second valve body 51-2 are closed. If so, the process proceeds to step S46; otherwise, the process proceeds to step S44.

  In step S44, the controller increments the valve closing delay counter.

  In step S45, the controller determines whether or not the valve closing delay counter has exceeded a reference count value. This reference count value is a count value of the time when the torque changes suddenly and no step is produced even when the first valve body 51-1 and the second valve body 51-2 are in the single valve open state to the double valve close state. And set in advance through experiments. The process once exits until the valve closing delay counter exceeds the reference count value, and if it exceeds, the process proceeds to step S46.

  In step S46, the controller closes both the first valve body 51-1 and the second valve body 51-2.

  FIG. 5 is a flow chart showing a subroutine of acceleration request processing of the exhaust gas purification system according to the present invention.

  In step S61, the controller determines whether or not both the first valve body 51-1 and the second valve body 51-2 are closed. If so, the process proceeds to step S62; otherwise, the process proceeds to step S64.

  In step S62, the controller resets the acceleration delay counter.

  In step S63, the controller opens the first valve body 51-1 while closing the second valve body 51-2.

  In step S64, the controller determines whether or not both the first valve body 51-1 and the second valve body 51-2 are open. If so, the process proceeds to step S68; otherwise, the process proceeds to step S65.

  In step S65, the controller determines whether the required acceleration is greater than the reference acceleration A2. The reference acceleration A2 is a reference value for determining whether or not the requested acceleration is a rapid acceleration. That is, the reference acceleration A2 is larger than the above-described reference acceleration A1. The reference acceleration A2 is set in advance according to the vehicle characteristics. If so, the process proceeds to step S66; otherwise, the process proceeds to step S62.

  In step S66, the controller increments the acceleration delay counter.

  In step S67, the controller determines whether or not the acceleration delay counter has exceeded a reference count value. This reference count value is a count value of the time when the torque changes suddenly and no step is produced even if the first valve body 51-1 and the second valve body 51-2 are opened from the one-valve state to the both-valve state. It is set through experiments in advance according to the required acceleration. The process once exits until the acceleration delay counter exceeds the reference count value, and if it exceeds, the process proceeds to step S68.

  In step S68, the controller opens both the first valve body 51-1 and the second valve body 51-2.

  FIG. 6 is a flowchart showing a subroutine of valve opening processing of the exhaust gas purification system according to the present invention.

  In step S81, the controller determines whether or not both the first valve body 51-1 and the second valve body 51-2 are closed. If so, the process proceeds to step S82; otherwise, the process proceeds to step S83.

  In step S82, the controller opens the first valve body 51-1 while closing the second valve body 51-2.

  In step S83, the controller determines whether or not both the first valve body 51-1 and the second valve body 51-2 are open. If so, the process proceeds to step S86; otherwise, the process proceeds to step S84.

  In step S84, the controller increments the valve opening delay counter.

  In step S85, the controller determines whether or not the valve opening delay counter exceeds the reference count value. This reference count value is a count value of the time when the torque changes suddenly and no step is produced even if the first valve body 51-1 and the second valve body 51-2 are opened from the one-valve state to the both-valve state. And set in advance through experiments. The process once exits until the valve opening delay counter exceeds the reference count value, and when it exceeds, the process proceeds to step S86.

  In step S86, the controller opens both the first valve body 51-1 and the second valve body 51-2.

  FIG. 7 is a view showing an open / close state of the exhaust shut-off valve when the control device according to the present invention is executed.

  In the following, in order to make the correspondence with the flowchart easier to understand, S is added to the step number of the flowchart.

(Immediately after cold start; underfloor catalyst is inactive)
When the underfloor catalyst 20 is in an inactive state and there is no acceleration request, the first valve body 51-1 and the second valve body 51-2 are closed. At this time, the controller repeats the process of steps S1, S2, S3, S4, S41, S43, and S46, and continues to close the first valve body 51-1 and the second valve body 51-2. Then, as shown in FIG. 7A, the exhaust gas flows into the manifold catalyst 40 and is purified, flows into the underfloor catalyst 20, and warms up the underfloor catalyst 20.

(When there is a request for acceleration while the underfloor catalyst is inactive)
If there is an acceleration request while the underfloor catalyst 20 is in the inactive state, the controller shifts the process from step S2 to S5 to S6. Then, the controller proceeds with the process in steps S6 → S61 → S62 → S63, and opens the first valve body 51-1 while closing the second valve body 51-2 as shown in FIG. 7B. In the next cycle, the process proceeds in the order of steps S1, S2, S5, S6, S61, S64, and S65. If the requested acceleration is large, the process proceeds from step S65 to S66 to S67. Until the acceleration delay counter exceeds the reference count value, steps S1 to S2 to S5 to S6 to S61 to S64 to S65 to S66 to S67. The process is repeated to maintain the state shown in FIG. 7B (the first valve body 51-1 is opened while the second valve body 51-2 is closed). When the acceleration delay counter exceeds the reference count value, the process proceeds from step S67 to S68, and the first valve body 51-1 and the second valve body 51-2 are opened as shown in FIG. . If the required acceleration decreases before the acceleration delay counter exceeds the reference count value, the acceleration delay counter is reset (steps S62 and S3). If the required acceleration increases again, the acceleration delay counter is incremented (step S62). S66).

(The catalyst under the floor is active)
When the underfloor catalyst 20 is activated, the controller advances the process in steps S1 → S7 → S8 → S81. At this time, if the first valve body 51-1 and the second valve body 51-2 are in the closed state, the controller advances the process from step S81 to S82, and the second valve body as shown in FIG. The first valve body 51-1 is opened while the valve 51-2 is closed. In the next cycle, the process proceeds in the order of steps S1, S7, S8, S81, S83, S84, and S85, and the process is repeated until the valve opening delay counter exceeds the reference count value (the second state shown in FIG. 7B). The first valve body 51-1 is kept open while the valve body 51-2 is closed. When the valve opening delay counter exceeds the reference count value, the process proceeds from step S85 to S86, and the first valve body 51-1 and the second valve body 51-2 are opened as shown in FIG. .

(The underfloor catalyst is deactivated again)
Even if the underfloor catalyst 20 is once activated, the exhaust gas temperature may be lowered and deactivated again due to, for example, continuous idling of the engine. At this time, the controller advances the process in steps S1, S2, S3, S4, S41, and S42, and opens the first valve body 51-1 as shown in FIG. 51-2 is closed. In the next cycle, the process proceeds in the order of steps S1, S2, S3, S4, S41, S43, S44, and S45, and the process is repeated until the valve closing delay counter exceeds the reference count value (see FIG. 7B). The second valve body 51-2 is kept closed while the first valve body 51-1 is opened. When the valve closing delay counter exceeds the reference count value, the process proceeds from step S45 to step S46, and the first valve body 51-1 and the second valve body 51-2 are closed as shown in FIG. .

  According to this embodiment, when the exhaust shut-off valve is fully opened from the fully closed state, the first valve body 51-1 is first fully opened, and then the second valve body 51-2 is fully opened after a sufficient time. I made it. When the exhaust shut-off valve is fully closed from the fully open state, the second valve body 51-2 is first fully closed, and then the first valve body 51-1 is fully closed after a sufficient time. As a result, sudden changes in torque (torque steps) can be prevented regardless of whether the exhaust shut-off valve is opened or closed.

  If the exhaust shut-off valve is fully closed with the conventional structure, the temperature of the main exhaust passage immediately downstream of the exhaust shut-off valve is lowered. When the exhaust shut-off valve is fully opened after waiting for the under-floor catalyst to be activated, the exhaust gas staying immediately downstream of the exhaust shut-off valve flows into the under-floor catalyst, which may temporarily deactivate the under-floor catalyst. . However, if the first valve body 51-1 is first fully opened when the exhaust shut-off valve is fully opened from the fully closed state as in this embodiment, the temperature drop immediately downstream of the exhaust shut-off valve can be prevented, and A situation where the catalyst is temporarily deactivated does not occur.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention.

  For example, in the above description, the exhaust shut-off valve is configured to open and close the valve body in two stages, but it may be configured to open and close in multiple stages by using multiple valve bodies.

  Also, in the above description, when the upper valve element opens first and the lower valve element opens later, or when the lower valve element closes first and the upper valve element closes later. However, the reverse may be possible.

It is a figure which shows the basic composition of the exhaust gas purification system by this invention. It is the perspective view which expanded the vicinity of an exhaust shut valve. It is a flowchart which shows the main routine of the control logic of the exhaust gas purification system by this invention. It is a flowchart which shows the subroutine of the valve closing process of the exhaust gas purification system by this invention. It is a flowchart which shows the subroutine of the process at the time of the acceleration request | requirement of the exhaust gas purification system by this invention. It is a flowchart which shows the subroutine of the valve opening process of the exhaust gas purification system by this invention. It is a figure which shows the opening-and-closing state of an exhaust shut valve when the control apparatus by this invention is performed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Main exhaust passage 20 Underfloor catalyst 30 Sub exhaust passage 40 Manifold catalyst 50 Exhaust shut valve 51-1 1st valve body 51-2 2nd valve body

Claims (5)

A main exhaust passage through which exhaust gas discharged from the engine flows,
An exhaust shut-off valve including a plurality of valve bodies capable of changing the flow rate of exhaust gas by opening and closing part of the flow passage cross section of the main exhaust passage;
An underfloor catalyst provided in a main exhaust passage downstream of the exhaust shut-off valve;
A sub-exhaust passage that once branches from the main exhaust passage upstream from the exhaust shut-off valve, and that joins the main exhaust passage downstream from the exhaust shut-off valve and upstream from the underfloor catalyst;
A manifold catalyst provided in the sub exhaust passage;
When opening the plurality of valve bodies, after opening a certain valve body , wait for the passage of time without causing a torque step even if another valve body is opened. Valve opening control means for
An exhaust gas purification system. The valve opening control means sequentially opens the plurality of valve bodies when the underfloor catalyst changes from an inactive state to an active state.
The exhaust gas purification system according to claim 1 . The valve opening control means sequentially opens the plurality of valve bodies when an acceleration request becomes large even when the underfloor catalyst is in an inactive state.
The exhaust gas purification system according to claim 1 . A main exhaust passage through which exhaust gas discharged from the engine flows,
An exhaust shut-off valve including a plurality of valve bodies capable of changing the flow rate of exhaust gas by opening and closing part of the flow passage cross section of the main exhaust passage;
An underfloor catalyst provided in a main exhaust passage downstream of the exhaust shut-off valve;
A sub-exhaust passage that once branches from the main exhaust passage upstream from the exhaust shut-off valve, and that joins the main exhaust passage downstream from the exhaust shut-off valve and upstream from the underfloor catalyst;
A manifold catalyst provided in the sub exhaust passage;
When closing the plurality of valve bodies, after closing a certain valve body and waiting for the passage of time that does not cause a torque step even if another valve body is closed, the other valve body is closed. Valve closing control means for
An exhaust gas purification system. The valve closing control means sequentially closes the plurality of valve bodies when the underfloor catalyst is changed from an active state to an inactive state.
The exhaust gas purification system according to claim 4 .

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