JP4353032B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purification device for an internal combustion engine, and more specifically, a state in which exhaust gas from the internal combustion engine is guided to a main catalyst device through an exhaust passage and exhaust gas flowing through the exhaust passage according to an operating state of the internal combustion engine. The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that is switched to a state in which it is led from a passage to a catalyst passage branched and returned to an exhaust passage through another catalyst device.

  2. Description of the Related Art Conventionally, a catalyst passage that branches from an internal combustion engine to an exhaust passage that continues from a main catalyst device to an upstream side of the main catalyst device and rejoins, a catalyst device that is provided in the catalyst passage, and the exhaust gas in the catalyst passage An exhaust emission control device for an internal combustion engine has been proposed that includes an on-off valve provided at a predetermined position between a branch point of the catalyst passage and a rejoining point in the passage (see, for example, Patent Document 1). In this conventional exhaust purification device, when the internal combustion engine is cold, the on-off valve is closed so that the exhaust from the internal combustion engine is guided from the exhaust passage to the catalyst passage, and the exhaust is returned to the exhaust passage after passing through the catalyst device. When the internal combustion engine is warmed up, the on-off valve is opened to guide the exhaust from the internal combustion engine to the main catalyst device through the exhaust passage.

In a state where the on-off valve is opened when the internal combustion engine is warmed up, the downstream pressure of the catalyst device in the catalyst passage becomes smaller than the upstream pressure due to resistance loss at the on-off valve and the exhaust passage wall. Due to this pressure difference, the exhaust gas flowing through the exhaust passage flows in from the upstream opening of the catalyst passage, and this causes the deterioration of the catalyst device provided in the catalyst passage. In order to prevent this, in the above-described conventional exhaust purification device, a protrusion is provided at the downstream outlet of the catalyst passage so that the dynamic pressure due to the exhaust gas flowing through the exhaust passage acts on the downstream outlet of the catalyst passage. The downstream pressure and the upstream pressure of the apparatus are balanced.
JP-A-9-317449

  By the way, in the high-speed and high-load operation region of the internal combustion engine, the flow velocity of the exhaust gas flowing through the exhaust passage becomes high. In such a situation, the suction effect from the upstream opening of the catalyst passage by the exhaust gas flowing at high speed in the exhaust passage increases, and the upstream pressure of the catalyst device in the catalyst passage tends to decrease. For this reason, as in the conventional exhaust gas purification device described above, even if a certain exhaust gas flow rate is assumed and dynamic pressure due to the exhaust gas acts on the downstream outlet of the catalyst passage, the exhaust gas flow rate is assumed. When the flow velocity changes, the dynamic pressure acting on the downstream outlet of the catalyst passage also changes, and as a result, the balance between the downstream pressure and the upstream pressure of the catalyst device in the catalyst passage is lost.

  The present invention has been made to solve the above-described conventional problems. Even when the exhaust flow rate changes in the high-speed and high-load operation region of the internal combustion engine, the upstream pressure and the downstream pressure of the catalyst device in the catalyst passage are changed. The present invention provides an exhaust purification device for an internal combustion engine capable of maintaining an appropriate balance.

  An exhaust emission control device for an internal combustion engine according to the present invention is provided in a catalyst passage that branches off and rejoins an exhaust passage that extends from the internal combustion engine to the main catalyst device on the upstream side of the main catalyst device, and the catalyst passage. An exhaust gas purification apparatus for an internal combustion engine having a catalyst device and an on-off valve provided at a predetermined position between a branch point of the catalyst passage and a rejoining point in the exhaust passage, wherein the on-off valve is open. A physical quantity detecting means for detecting a physical quantity related to a difference between an upstream pressure and a downstream pressure of the catalytic device in the catalyst passage, and the catalyst in the catalyst passage based on the physical quantity detected by the physical quantity detecting means. The apparatus has a pressure balance control means for controlling the upstream pressure and the downstream pressure of the apparatus to be the same.

  With such a configuration, when the on-off valve is opened when the internal combustion engine is warmed up, the exhaust from the internal combustion engine is guided to the main catalyst device through the exhaust passage. In this state, a physical quantity related to the difference between the upstream pressure and the downstream pressure of the catalytic device in the catalyst passage is detected, and based on the physical quantity, the upstream pressure and the downstream pressure of the catalytic device become the same. Controlled. Even if the flow rate of the exhaust gas flowing through the exhaust passage changes and the balance between the upstream pressure and the downstream pressure of the catalyst device changes, the balance is based on the physical quantity related to the difference between the upstream pressure and the downstream pressure. To be controlled.

  The physical quantity is not particularly limited as long as it has a quantitative relationship with the difference between the upstream pressure and the downstream pressure of the catalyst device in the catalyst passage, and even if the physical quantity causes the difference, The physical quantity that appears as a result of the difference may be the difference itself.

  Specifically, the physical quantity detection means may include means for detecting the difference itself between the upstream pressure and the downstream pressure of the catalyst device in the catalyst passage as the physical quantity.

  In this case, the upstream pressure and the downstream pressure are controlled to be the same based on the difference between the upstream pressure and the downstream pressure of the catalyst device in the catalyst passage.

  The physical quantity detection means may include means for detecting the rotation speed and load of the internal combustion engine as the physical quantity.

  The rotational speed and load of the internal combustion engine are expressed as the flow velocity of the exhaust gas passing through the exhaust passage. Due to the flow velocity flowing through the exhaust passage, a difference between the upstream pressure and the downstream pressure of the catalyst device in the catalyst passage occurs. The higher the rotation speed and the higher the load, the higher the flow rate of the exhaust gas, and the greater the suction effect from the upstream opening of the catalyst passage by the exhaust gas flowing through the exhaust passage at a high speed. Becomes larger. In this way, the balance between the upstream pressure and the downstream pressure of the catalyst device is controlled based on the rotational speed and load of the internal combustion engine related to the difference between the upstream pressure and the downstream pressure of the catalyst device.

  Further, the physical quantity detection means may have means for detecting a difference between an upstream temperature and a downstream temperature of the catalyst device as the physical quantity.

  A high upstream pressure of the catalyst device indicates that a large amount of exhaust gas flows into the upstream passage portion of the catalyst device in the catalyst passage, and a high downstream pressure of the catalyst device indicates that the catalyst device in the catalyst passage. This indicates that the amount of exhaust gas flowing into the downstream side passage portion is large. Therefore, the difference between the upstream temperature and the downstream temperature of the catalyst device reflects the difference between the upstream pressure and the downstream pressure. Thus, based on the difference between the upstream temperature and the downstream temperature related to the difference between the upstream pressure and the downstream pressure of the catalyst device, the upstream pressure and the downstream pressure of the catalyst device become the same. Controlled.

  Further, the physical quantity detection means can have means for detecting the bed temperature of the catalyst device as the physical quantity.

  When a difference between the upstream pressure and the downstream pressure of the catalyst device in the catalyst passage occurs, exhaust flows through the catalyst passage, and the bed temperature of the catalyst device rises according to the flow rate. Therefore, the bed temperature of the catalyst device reflects the difference between the upstream pressure and the downstream pressure of the catalyst device. In this way, the balance between the upstream pressure and the downstream pressure of the catalyst device is controlled based on the bed temperature of the catalyst device related to the difference between the upstream pressure and the downstream pressure of the catalyst device.

  In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the pressure balance control means may include an on-off valve control means for adjusting an opening degree of the on-off valve.

  With such a configuration, the flow rate of the exhaust gas flowing through the exhaust passage is controlled according to the opening degree of the on-off valve. The difference between the upstream pressure and the downstream pressure of the catalyst device in the catalyst passage changes according to the exhaust flow velocity in the exhaust passage controlled in this way. Thereby, the balance between the upstream pressure and the downstream pressure is controlled.

  Further, when the on / off valve is controlled in this way, it is not necessary to separately provide a part for controlling the flow rate of the exhaust passage, and the configuration is not complicated.

  Further, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the pressure balance control means includes an upstream valve provided at a predetermined position between the on-off valve in the exhaust passage and a branch point to the catalyst passage. And means for controlling the opening degree of the upstream valve.

  With such a configuration, if the upstream valve is controlled to have an opening degree that closes the exhaust passage, the flow rate of the exhaust gas flowing through the exhaust passage decreases. The difference between the upstream pressure and the downstream pressure of the catalyst device in the catalyst passage changes according to the flow velocity in the exhaust passage controlled in this way. Thereby, the balance between the upstream pressure and the downstream pressure is controlled.

  Furthermore, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the pressure balance control means includes: a downstream valve provided in the exhaust passage near the rejoining point of the catalyst passage; and the downstream valve. And a means for controlling the opening degree.

  With such a configuration, the degree of partial obstruction of the exhaust flow on the rejoining point side of the catalyst passage in the exhaust passage changes according to the opening degree of the downstream valve. Such a change in the exhaust flow on the side of the rejoining point of the catalyst passage in the exhaust passage particularly affects the downstream pressure of the catalyst device in the catalyst passage. Thereby, the balance between the upstream pressure and the downstream pressure of the catalyst device is controlled.

  In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the upstream end portion of the catalyst passage is joined to the exhaust passage at an angle at which it is more susceptible to dynamic pressure due to exhaust gas flowing through the exhaust passage than the downstream end portion. It can be.

  With such a configuration, it is possible to prevent the downstream pressure of the catalyst device in the catalyst passage from becoming smaller than the upstream pressure due to resistance loss of the on-off valve and the exhaust passage wall, and in the initial state before the pressure balance control, the catalyst device It becomes possible to balance the upstream pressure and the downstream pressure.

  According to the exhaust gas purification apparatus for an internal combustion engine according to the present invention, in a state where the on-off valve is open and the exhaust gas from the internal combustion engine is guided to the main catalyst device through the exhaust passage, the branching and rejoining with respect to the exhaust passage is performed. A physical quantity related to the difference between the upstream pressure and the downstream pressure of the catalyst device provided in the catalyst passage is detected, and based on the physical quantity, the upstream pressure and the downstream pressure of the catalyst device are the same. Therefore, even if the exhaust gas flow rate changes in the high-speed and high-load operation region of the internal combustion engine, the balance between the upstream pressure and the downstream pressure of the catalyst device in the catalyst passage can be properly maintained. .

  An exhaust emission control device for an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings.

  The exhaust gas purification apparatus for an internal combustion engine according to the first embodiment of the present invention is configured as shown in FIG.

  In FIG. 1, an exhaust passage 10 connected to an exhaust manifold of an engine (internal combustion engine) extends to a main catalyst device (for example, a NOx storage reduction catalyst device). A catalyst passage 20 branched from the upstream side of the main catalyst device and rejoining the exhaust passage 10 is joined to the exhaust passage 10. The catalyst passage 20 is provided with a catalyst device 30 (for example, a three-way catalyst device) having a function of removing exhaust components different from that of the main catalyst device. An opening / closing valve 12 for opening and closing the exhaust passage 10 is provided at a predetermined position between a branch point where the upstream opening 21 of the catalyst passage 20 faces in the exhaust passage 10 and a rejoining point where the downstream opening 22 of the catalyst passage 20 faces. Yes. Further, a pressure sensor 51 is installed in the catalyst upstream side passage portion 23 located on the upstream side of the catalyst device 30 in the catalyst passage 20, and the catalyst downstream side passage portion 24 located on the downstream side of the catalyst device 30 in the catalyst passage 20. Is provided with a pressure sensor 52.

  The negative pressure of the negative pressure tank 41 connected to the intake pipe is applied to the actuator 40 via the adjustment valve 42, and the actuator 40 is provided in the exhaust passage 10 via the drive mechanism 43 according to the negative pressure applied. The open / close valve 12 is driven. The control unit 50 (ECU) is provided in the detected pressure signal Pu from the pressure sensor 51 provided in the catalyst upstream side passage portion 23 of the catalyst passage 20 and the catalyst downstream side passage portion 24 of the catalyst passage 20 as described above. The detected pressure signal Pd from the pressure sensor 52 is input, and the negative pressure applied to the actuator 40 is controlled by adjusting the atmospheric pressure flowing into the regulating valve 42 based on the detected pressure signals Pu and Pd. By controlling the negative pressure applied to the actuator 40 in this way, the opening degree of the on-off valve 12 is controlled.

  For example, the upstream side of the catalyst device 30 in the catalyst passage 20 in the initial state where the on-off valve 12 should be opened, that is, in the state where the flow velocity of the exhaust gas flowing through the exhaust passage 10 is minimized when the engine where the on-off valve 12 should be opened is warmed. The joining state of the downstream end and the upstream end of the catalyst passage 20 to the exhaust passage 10 is determined so that the pressure and the downstream pressure are balanced (so as to be the same). Specifically, in a state where the flow velocity of the exhaust gas flowing through the exhaust passage 10 is minimized when the engine is warmed up, the downstream pressure of the catalyst device 30 in the catalyst passage 20 tends to be lower than its upstream pressure. The downstream end of the catalyst passage 20 is joined to the exhaust passage 10 at an angle at which it is more susceptible to dynamic pressure due to exhaust gas flowing through the exhaust passage 10 than the upstream end thereof. More specifically, the upstream end of the catalyst passage 20 is joined substantially perpendicularly to the exhaust passage 10, while the downstream end of the catalyst passage 20 faces the upstream side of the exhaust passage 10. It is joined to the exhaust passage 10 in a slightly tilted state. The tilting angle compensates for the downstream pressure that tends to be lower than the upstream pressure of the catalyst device 20, and the dynamic pressure is such that the downstream pressure and the upstream pressure are balanced. Is determined by the angle acting on.

  In the exhaust gas purification apparatus for an internal combustion engine having the above-described structure, the on-off valve 12 is controlled to be closed by the control unit 50 when the engine is in a low-temperature and low-load operation region. In this state, the exhaust flowing from the engine through the exhaust passage 10 is guided to the catalyst passage 20 and returned to the exhaust passage 10 through the catalyst device 30.

  On the other hand, at the time of warm-up when the engine speed and load increase, the control unit 50 controls the on-off valve 12 to be in an open state. In this state, the exhaust gas flowing from the engine through the exhaust passage 10 is directly led to the main catalyst device.

  In the state where the on-off valve 12 is opened, the control unit 50 further executes processing according to the procedure shown in FIG.

  In FIG. 2, the control unit 50 acquires the detected pressure signals Pu and Pd from the pressure sensors 51 and 52 (S1), and based on those signals, the upstream pressure (Pu) of the catalyst device 30 in the catalyst passage 20 And a pressure difference ΔP (Pd−Pu) between the pressure and the downstream pressure (Pd) is calculated (S2). Then, the control unit 50 determines whether or not the pressure difference ΔP is larger than the reference pressure difference ΔP0 (S3). The reference pressure difference ΔP0 is set to zero or a value close thereto. In the situation where the pressure difference ΔP is equal to or less than the reference pressure difference ΔP0 (NO in S3), the control unit 50 controls the adjustment valve 42 so that the on-off valve 12 is maintained in the open state (1) (see FIG. 3). To do. In a situation where the pressure difference ΔP between the upstream pressure (Pu) and the downstream pressure (Pd) of the catalyst device 30 is equal to or less than the reference pressure difference ΔP0, the control unit 50 repeatedly executes the above-described processing (S1 to S3). The on-off valve 12 is maintained in the open state (1).

  When the rotational speed and load of the engine further increase to reach a further high speed and high load operation region, the flow velocity of the exhaust gas flowing through the exhaust passage 10 further increases. In such a situation, the upstream side pressure of the catalyst device 30 in the catalyst passage 30 is reduced due to the suction effect of the exhaust gas flowing through the exhaust passage 10 at a high speed, and the downstream pressure of the catalyst device 30 is increased by the increase in dynamic pressure due to the exhaust gas. When the pressure difference ΔP exceeds the reference pressure difference ΔP0 due to the increase (YES in S3), the control unit 50 opens the opening / closing valve 12 shown in FIG. ) To control the regulating valve 42 (S5). Thus, when the opening / closing valve 12 is maintained at the opening degree (2), the flow rate of the exhaust gas flowing through the exhaust passage 10 decreases, the pressure on the upstream side of the catalyst device 30 in the catalyst passage 30 increases, and the movement by the exhaust gas occurs. The pressure decreases and the downstream pressure of the catalyst device 30 decreases. As a result, the difference between the upstream pressure of the catalyst device 30 in the catalyst passage 30 and the downstream pressure thereof decreases.

  Based on the pressure difference ΔP between the upstream pressure (Pu) and the downstream pressure (Pd) of the catalyst device 30 in the catalyst passage 30 as described above, the control unit 50 sets the opening degree of the on-off valve 12 to the open state (1). By switching to one of the opening degrees (2), even if the flow rate of the exhaust gas flowing through the exhaust passage 10 changes in the high-speed and high-load operation region of the engine, the upstream pressure and the downstream pressure of the catalyst device 30 Is maintained within a range within the reference pressure difference ΔP0. That is, the upstream side pressure and the downstream side pressure of the catalyst device 30 are controlled to be substantially the same, and the balance between them is not lost, and the amount of exhaust flowing into the catalyst device 30 is minimized. And will be able to. As a result, deterioration of the catalyst device 30 can be prevented as much as possible.

  By the way, the rotational speed and load of the engine appear as the flow velocity of the exhaust gas flowing through the exhaust passage 10. As described above, the difference between the upstream pressure and the downstream pressure of the catalyst device 30 in the catalyst passage 20 occurs due to the flow velocity of the exhaust gas flowing through the exhaust passage 10. Focusing on this, the rotational speed and load of the engine can be used as a physical quantity related to the difference between the upstream pressure and the downstream pressure of the catalyst device 30. That is, the control unit 50 can control the opening degree of the on-off valve 12 based on the rotational speed and load of the engine.

  In this case, the control unit 50 executes processing according to the procedure shown in FIG.

  The control unit 50 stores a control table 100 (see FIG. 4) representing the relationship between the rotational speed and load and the opening degree of the on-off valve 12 in a predetermined memory. In the control table 100, an operating region having a relatively low rotational speed and load on the lower side of the characteristic curve Lf1 (equal flow line) corresponding to when the engine is cold is associated with the closed state of the on-off valve 12, and the engine An operating region with a relatively high rotational speed and load on the upper side of the characteristic curve Lf1 corresponding to the time is associated with the open state (1) of the on-off valve 12 (see FIG. 3). Further, an operation region of higher rotation and high load on the upper side of the characteristic curve Lf2 is associated with the opening degree (2) of the on-off valve 12 (see FIG. 3).

  The control unit 50 acquires a detection signal (rotation speed, load) from an engine rotation speed sensor and a load (torque) sensor normally provided in the vehicle (S11), and acquires the detection signal with reference to the control table 100. The on-off valve 12 is controlled so that the opening degree corresponds to the rotational speed and the load (S12). Specifically, the on-off valve 12 is closed in an operation region where the rotational speed and load when the engine is cold are relatively low. In this state, the exhaust gas flowing from the engine through the exhaust passage 10 is guided to the catalyst passage 20 and returned to the exhaust passage 10 through the catalyst device 30. In an operation region where the rotational speed and load when the engine is warmed up are relatively high, the on-off valve 12 is controlled to the open state (1), and the exhaust from the engine is directly led to the main catalyst device through the exhaust passage 10.

  When the rotational speed and load of the engine further increase to enter a further high-speed and high-load operation region, the on-off valve 12 is controlled to the opening degree (2) (S12). In such a high-speed and high-load operation region of the engine, the exhaust gas flow rate in the exhaust passage 10 becomes very high, and as a result, the upstream pressure and the downstream pressure of the catalyst device 30 in the catalyst passage 20 as described above. Differences may occur. In such a situation, the opening / closing valve 12 is controlled to an opening (2) that throttles the exhaust passage 10, so that the speed of the exhaust gas flowing through the exhaust passage 10 is suppressed, and the upstream pressure of the catalyst device 30 in the catalyst passage 20 is reduced. An increase in the difference from the downstream pressure is prevented.

  The control unit 50 repeatedly executes the above-described processes (S11, S12) at a predetermined cycle, so that the upstream pressure and the downstream pressure of the catalyst device 30 are controlled to be the same, and the balance between them is appropriate. The amount of exhaust gas that is held and flows into the catalyst device 30 can be reduced as much as possible. As a result, deterioration of the catalyst device 30 can be prevented as much as possible.

  From the upstream gas inflow amount representing the amount of exhaust gas flowing into the catalyst upstream side passage portion 23 of the catalyst passage 20 and the downstream gas inflow amount representing the amount of exhaust gas flowing into the catalyst downstream side passage portion 24, the gas inflow rate ratio is Is defined as follows.

Gas inflow ratio = {Upstream gas inflow amount−Downstream gas inflow amount} / Upstream gas inflow amount The bed temperature of the catalyst device 30 provided in the catalyst passage 20 is generally shown in FIG. 5 according to the gas inflow amount ratio. It changes as shown.

  From this, by detecting the bed temperature of the catalyst device 30, the gas inflow rate ratio corresponding to the bed temperature is determined based on the characteristics (see FIG. 5). The gas inflow ratio corresponds to the difference between the upstream pressure and the downstream pressure of the catalyst device 30. Focusing on this, the bed temperature of the catalyst device 30 can be used as a physical quantity related to the difference between the upstream pressure and the downstream pressure of the catalyst device 30. That is, the control unit 50 can control the opening degree of the on-off valve 12 based on the detection signal from the temperature sensor that detects the bed temperature of the catalyst device 30.

  In this case, if the balance between the upstream pressure and the downstream pressure amount of the catalyst device 30 is not lost, the gas flow rate ratio is maintained at a relatively small value, and the bed temperature of the catalyst device 30 is maintained at a relatively low temperature. The On the other hand, when the engine enters the high speed and high load operation region, the upstream pressure of the catalyst device 30 decreases and the downstream pressure increases as the flow velocity of the exhaust gas flowing through the exhaust passage 10 increases as described above. The downstream gas inflow amount increases, and the bed temperature of the catalyst device 30 increases. When the on-off valve 12 is controlled to the opening degree (2) based on the rising bed temperature in this way, the flow rate of the exhaust gas is suppressed and the downstream gas inflow amount is also suppressed. As a result, the bed temperature of the catalyst device 30 is lowered.

  In this manner, the bed temperature of the catalyst device 30 is detected, and the opening degree of the on-off valve 12 is either the open state (1) or the opening degree (2) so that the bed temperature is maintained at a relatively low value. By switching to the control, the upstream pressure and the downstream pressure of the catalyst device 30 are controlled to be the same, and the balance between them can be maintained appropriately.

  When the upstream gas inflow amount increases, the detection temperature in the catalyst upstream side passage portion 23 in the catalyst passage 20 increases, and when the downstream gas inflow amount increases, the detection temperature in the catalyst downstream side passage portion 24 in the catalyst passage 20 increases. To do. That is, the difference between the detected temperature in the catalyst upstream passage 23 and the detected temperature in the catalyst downstream passage 24 corresponds to the gas inflow rate ratio described above, and the upstream pressure and downstream of the catalyst device 30 are reduced. It can be used as a physical quantity related to the difference from the side pressure.

  In this case, the control unit 50 inputs a detection signal from the temperature sensor installed in the catalyst upstream passage 23 and a detection signal from the temperature sensor installed in the catalyst downstream passage 24. The control unit 50 opens the opening / closing valve 12 so that the difference between the upstream temperature and the downstream temperature of the catalyst device based on these detection signals is within a predetermined range. 2) and control to switch to either. As a result, the balance between the upstream pressure and the downstream pressure of the catalyst device 30 can be properly maintained.

  In each example described above, a physical quantity related to the difference between the upstream pressure and the downstream pressure of the catalyst device 30 (pressure difference ΔP between the upstream pressure and the downstream pressure of the catalyst device 30, the engine speed and the load). Based on the bed temperature of the catalyst device 30 and the difference between the upstream temperature and the downstream temperature of the catalyst device 30, the opening degree of the on-off valve 12 is set between the open state (1) and the opening degree (2) (see FIG. 3). Although the switching control is performed in any one of the above, the opening degree of the on-off valve 12 can be controlled in two or more stages or continuously based on the physical quantity.

  Next, a second embodiment of the present invention will be described.

  The characteristic part of the exhaust gas purification apparatus for an internal combustion engine according to the second embodiment of the present invention is shown in FIG. In this example, the flow rate of the exhaust gas flowing through the exhaust passage 10 is not controlled by the opening degree of the on-off valve 12 but is controlled by another valve different from the on-off valve 12. Other parts have the same configuration as the exhaust gas purification apparatus shown in FIG.

  In FIG. 6, an upstream valve 14 is provided at a predetermined position between the on-off valve 12 in the exhaust passage 10 and a branch point where the upstream opening 21 (see FIG. 1) of the catalyst passage 20 faces the exhaust passage 10. Then, the upstream valve 14 is further opened in the initial state in which the on-off valve 12 should be opened, that is, in the state where the flow velocity of the exhaust gas flowing through the exhaust passage 10 is minimized when the engine to be opened is opened (1 ), The exhaust at the downstream end and the upstream end of the catalyst passage 20 is balanced so that the upstream pressure and the downstream pressure of the catalyst device 30 in the catalyst passage 20 are balanced in the same manner as described above. The joining state to the passage 10 is determined.

  The control unit 50 is one of the above-described physical quantities (pressure difference ΔP between upstream pressure and downstream pressure of the catalyst device 30, engine rotation speed and load, bed temperature of the catalyst device 30, upstream temperature of the catalyst device 30. And the downstream temperature) are controlled by switching the opening degree of the upstream valve 14 between the open state (1) and the closed state (2). Under such control, the flow rate of the exhaust gas flowing through the exhaust passage 10 is increased and the exhaust gas can flow into the catalyst device 30 (for example, the situation where the difference between the upstream pressure amount and the downstream pressure amount of the catalyst device 30 can be large). , The upstream valve 15 is controlled to the closed state (2). As a result, as in the case of the first embodiment, the flow rate of the exhaust gas flowing through the exhaust passage 10 is suppressed, so that the balance between the upstream pressure and the downstream pressure of the catalyst device 30 is properly maintained. Become.

  Next, a third embodiment of the present invention will be described.

  The characteristic part of the exhaust gas purification apparatus for an internal combustion engine according to the third embodiment of the present invention is shown in FIG. This example is the same as in the case of the second embodiment in that the flow rate of the exhaust gas flowing through the exhaust passage 10 is not controlled by the opening degree of the on-off valve 12, but is controlled by a valve different from the on-off valve 12. There is a different installation position of the valve.

  In FIG. 7, the exhaust passage 10 is located downstream of the re-merging point where the downstream opening 22 of the catalyst passage 20 faces, more specifically, near the exhaust downstream side edge of the downstream opening 22 of the catalyst passage 20. A side valve 16 is provided. Then, the downstream valve 16 is further closed (2 in the initial state in which the on-off valve 12 is to be opened or closed, that is, in the state where the flow velocity of the exhaust gas flowing through the exhaust passage 10 is minimized when the engine to which the on-off valve 12 is to be opened is warmed. ), The downstream end portion and the upstream end portion of the catalyst passage 20 are joined to the exhaust passage 10 so that the upstream pressure and the downstream pressure of the catalyst device 30 in the catalyst passage 20 are balanced. Is decided. Specifically, both the upstream end and the downstream end of the catalyst passage 20 are joined to the exhaust passage 10 substantially perpendicularly.

  If there is no downstream valve 16 in such a joined state, the downstream pressure of the catalyst device 30 in the catalyst passage 20 as described above in the state where the flow velocity of the exhaust gas flowing through the exhaust passage 10 is minimized when the engine is warmed up. Tends to be lower than its upstream pressure. However, the downstream valve 16 that is in the closed state (1) partially obstructs the exhaust flow at the rejoining point of the catalyst passage 20 in the exhaust passage 10, and the catalyst passage 20 in accordance with the degree of obstruction of the exhaust flow. The downstream pressure increases. As a result, even if the downstream pressure of the catalyst device 30 in the catalyst passage 20 tends to be lower than the upstream pressure, the downstream pressure of the catalyst passage 20 is increased by the downstream valve 16 that is in the closed state (1). Thus, the balance between the upstream pressure and the downstream pressure of the catalyst device 30 is properly maintained.

  For example, the control unit 50 closes the opening degree of the upstream valve 16 based on the pressure difference ΔP between the upstream pressure and the downstream pressure of the catalyst device 30 obtained based on the detection signals from the pressure sensors 51 and 52. Control is switched to either (1) or open state (2). By such control, the upstream valve 15 is controlled to the closed state (1) in the initial state at the time of warm-up (the state where the pressure difference ΔP has not reached the reference pressure difference ΔP0). As a result, the balance between the upstream pressure and the downstream pressure of the catalyst device 30 is properly maintained as in the initial state described above. On the other hand, in a situation where the flow rate of the exhaust gas flowing through the exhaust passage 10 becomes high and the exhaust gas can flow into the catalyst device 30 (for example, a situation where the difference between the upstream pressure and the downstream pressure of the catalyst device 30 becomes large), the upstream valve 15 is controlled to the open state (2). As a result, the partial obstruction of the exhaust flow at the rejoining point of the catalyst passage 20 in the exhaust passage 10 is eliminated, and the downstream pressure of the catalyst device 30 is reduced. The balance with the downstream pressure is properly maintained.

  In the second embodiment and the third embodiment described above, the opening degree control of the upstream side valve 14 and the downstream side valve 16 is not two-stage switching control, but more stages or continuous steps. Switching control can also be performed.

  As described above, the exhaust gas purification apparatus for an internal combustion engine according to the present invention has the upstream pressure and the downstream pressure of the catalyst device in the catalyst passage even if the exhaust gas flow rate changes in the high speed and high load operation region of the internal combustion engine. A catalyst that has the effect of maintaining an appropriate balance and that guides the exhaust from the internal combustion engine to the main catalyst device through the exhaust passage according to the operating state of the internal combustion engine, and a catalyst that branches the exhaust flowing through the exhaust passage from the exhaust passage The present invention is useful as an exhaust emission control device for an internal combustion engine that is switched to a state where it is led to the passage and returned to the exhaust passage through another catalyst device.

An exhaust purification device for an internal combustion engine according to a first embodiment of the present invention The flowchart which shows the flow (the 1) of the process in a control unit It is a figure which shows the control state of an on-off valve. Flow chart showing the process flow (part 2) in the control unit It is a figure which shows the relationship between the bed temperature of a catalyst apparatus, and the gas inflow amount ratio to a catalyst apparatus. It is a figure which shows the characteristic part in the exhaust gas purification apparatus of the internal combustion engine which concerns on 2nd embodiment of this invention. It is a figure which shows the characteristic part in the exhaust gas purification apparatus of the internal combustion engine which concerns on 3rd embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Exhaust passage 12 On-off valve 14 Upstream valve 16 Downstream valve 20 Catalyst passage 21 Upstream opening 22 Downstream opening 23 Catalyst upstream passage section 24 Catalyst downstream passage section 30 Catalyst device 40 Actuator 41 Negative pressure tank 42 Control valve 43 Drive mechanism 50 Control unit (ECU)
51, 52 Pressure sensor

Claims (7)

A catalyst passage branched from the internal combustion engine to the main catalyst device upstream of the main catalyst device and recombined; a catalyst device provided in the catalyst passage; and the catalyst passage in the exhaust passage. An exhaust purification device for an internal combustion engine having an on-off valve provided at a predetermined position between a branch point and a re-merging point,
A physical quantity detecting means for detecting a physical quantity related to a difference between an upstream pressure and a downstream pressure of the catalyst device in the catalyst passage in the open state of the on-off valve;
Have a pressure balance control means for controlling so as to equalize the upstream pressure and the downstream pressure of the catalytic converter in the catalyst passages based on the physical amount detected by said physical quantity detecting means,
The pressure balance control means includes an upstream valve provided at a predetermined position between the on-off valve in the exhaust passage and a branch point to the catalyst passage;
An exhaust purification device for an internal combustion engine, characterized by comprising means for controlling the opening degree of the upstream valve . A catalyst passage branching upstream from the internal catalyst to the main catalyst device upstream of the main catalyst device and rejoining; a catalyst device provided in the catalyst passage; and the catalyst passage in the exhaust passage. An exhaust purification device for an internal combustion engine having an on-off valve provided at a predetermined position between a branch point and a re-merging point,
  A physical quantity detecting means for detecting a physical quantity related to a difference between an upstream pressure and a downstream pressure of the catalyst device in the catalyst passage in the open state of the on-off valve;
  Pressure balance control means for controlling the upstream pressure and the downstream pressure of the catalyst device in the catalyst passage to be the same based on the physical quantity detected by the physical quantity detection means,
The pressure balance control means includes a downstream valve provided in the vicinity of the downstream side of the rejoining point of the catalyst passage in the exhaust passage,
  An exhaust purification device for an internal combustion engine, characterized by comprising means for controlling the opening degree of the downstream valve. 3. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the physical quantity detection means has means for detecting a difference itself between an upstream pressure and a downstream pressure of the catalyst device in the catalyst passage as the physical quantity. . 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the physical quantity detection means includes means for detecting a rotation speed and a load of the internal combustion engine as the physical quantity. 2. The exhaust emission control device for an internal combustion engine according to claim 1, wherein the physical quantity detection means includes means for detecting a difference between an upstream temperature and a downstream temperature of the catalyst device as the physical quantity. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the physical quantity detection means includes means for detecting a bed temperature of the catalyst device as the physical quantity. 2. The internal combustion engine according to claim 1, wherein a downstream end portion of the catalyst passage is joined to the exhaust passage at an angle that is more susceptible to dynamic pressure due to exhaust gas flowing through the exhaust passage than an upstream end portion. Exhaust purification device.

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