JP2019120242A - Secondary air supply device for internal combustion engine - Google Patents

Abstract

To provide a secondary air supply device for an internal combustion engine capable of suppressing lowering of a flow rate of secondary air while suppressing a backflow of exhaust gas.SOLUTION: A secondary air supply device 20 includes a secondary air supply passage 10 for supplying secondary air to an exhaust passage 2 of an internal combustion engine. The secondary air supply passage 10 includes a branch pipe 13 branched from the secondary air supply passage 10, provided in a portion excluding a portion on the passage in which the secondary air flows and having a closed terminal.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a secondary air supply device for an internal combustion engine.

There is known a secondary air supply device for supplying secondary air to an exhaust passage in order to increase the temperature of a catalyst provided in the exhaust passage of an internal combustion engine (for example, Patent Document 1).
By the way, when the exhaust gas flows back to the secondary air supply passage connected to the exhaust passage, the control valve, the air pump and the like provided in the secondary air supply passage may be adversely affected by the exhaust heat. Therefore, in the secondary air supply device described in Patent Document 1, in order to suppress the backflow of the exhaust gas into the secondary air supply passage, an extended passage portion is provided in the middle of the secondary air supply passage.

JP 2007-247529 A

  By the way, if the extended passage portion is provided in the middle of the secondary air supply passage, the flow of the secondary air tends to be stagnated in the extended passage portion, so the flow rate of the secondary air introduced into the exhaust passage may be reduced. is there.

  The present invention has been made in view of these circumstances, and an object thereof is to provide a secondary air supply device for an internal combustion engine capable of suppressing a flow reduction of secondary air while suppressing backflow of exhaust gas. .

  A secondary air supply system for an internal combustion engine that solves the above problems includes a secondary air supply passage that supplies secondary air to an exhaust passage of the internal combustion engine. The secondary air supply passage has a branch passage branched from the secondary air supply passage and provided at a portion excluding a passage through which the secondary air flows, the end of which is closed.

  According to the same configuration, since the exhaust gas backflowing to the secondary air supply passage is retained in the branch passage provided in the portion excluding the passage on which the secondary air flows, the branch passage is formed in the secondary air supply passage. It is possible to suppress the backflow of the exhaust toward the secondary air upstream side of the branched position. And since this branch passage is provided in the part except the passage top where secondary air flows, it is hard to obstruct the flow of secondary air. Therefore, according to the same configuration, it is possible to suppress the flow reduction of the secondary air while suppressing the backflow of the exhaust gas.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a structure of an internal combustion engine to be applied with a secondary air supply device according to a first embodiment of the secondary air supply device of the internal combustion engine. The enlarged view of the 2nd supply passage with which the secondary air supply system of the embodiment is provided. The schematic diagram which shows the structure of the internal combustion engine which becomes an application object with the secondary air supply apparatus about 2nd Embodiment which materialized the secondary air supply apparatus of the internal combustion engine. Sectional drawing which shows the structure of the control valve with which the secondary air supply apparatus of the embodiment is equipped. The schematic diagram which shows the structure of the internal combustion engine which becomes an application object with the secondary air supply apparatus about 3rd Embodiment which materialized the secondary air supply apparatus of the internal combustion engine. Sectional drawing which expands and shows the structure of the 2nd supply passage with which the secondary air supply apparatus of the embodiment is provided. Sectional drawing which expands and shows the structure of the 2nd supply passage with which a secondary air supply apparatus is equipped about 4th Embodiment which materialized the secondary air supply apparatus of the internal combustion engine. Sectional drawing which expands and shows the structure of the 2nd supply passage with which the secondary air supply apparatus of the embodiment is provided.

First Embodiment
Hereinafter, a first embodiment in which a secondary air supply device for an internal combustion engine is embodied will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, in the internal combustion engine, combustion of a mixture of fuel and air is performed in a combustion chamber 1 in a cylinder, and the combustion gas is discharged to an exhaust passage 2 as exhaust gas. The exhaust gas is purified when passing through the catalyst 3 provided in the middle of the exhaust passage 2.

On the other hand, a secondary air supply device 20 for supplying secondary air to the exhaust gas is connected to a portion of the exhaust passage 2 located upstream of the catalyst 3 in the exhaust gas.
The secondary air supply device 20 includes a secondary air supply passage 10 having a first supply passage 10A and a second supply passage 10B for supplying secondary air to the exhaust passage 2, an air pump 5 for pressurizing and discharging air, and a secondary The control valve 6 controls the flow rate of air, and the control device 7 controls operation of the air pump 5 and the control valve 6.

  A control valve 6 is connected to the secondary air downstream side of the air pump 5 via the first supply passage 10A. The control valve 6 is a known valve having a valve body for adjusting the flow rate of the secondary air, and is open when the air pump 5 is operating and closed when the air pump 5 is not operating. An exhaust passage 2 is connected to the secondary air downstream side of the control valve 6 via the second supply passage 10B.

  As shown in FIG. 2, the second supply passage 10B has a main passage 11 connecting the control valve 6 and the exhaust passage 2 and provided with a curved portion 11W in the middle. A portion on the secondary air downstream side of the curved portion 11W in the main passage 11 is a linear portion 11L extending linearly. Further, the second supply passage 10B is a pipe that constitutes a passage branched from the curved portion 11W of the main passage 11, and includes a branch pipe 13 linearly connected to the straight portion 11L. The branch pipe 13 extends, for example, upward in the vertical direction, and its end portion is closed. Further, the inner diameter of the branch pipe 13 is substantially the same as the inner diameter of the straight portion 11L.

The operation and effects of the present embodiment will be described.
(1) As shown in FIG. 2, the exhaust gas (shown by a broken line) flowing back from the exhaust passage 2 to the second supply passage 10B of the secondary air supply passage 10 is a secondary air (dashed-dotted line) in the second supply passage 10B. Flows into the branch pipe 13 provided at a portion other than the main passage 11 through which it flows and stays in the branch pipe 13. Therefore, the backflow of the exhaust toward the secondary air upstream side of the position where the branch pipe 13 branches in the second supply passage 10B is suppressed. Therefore, the adverse effect of the exhaust heat is suppressed from being exerted on the members constituting the secondary air supply device 20 such as the control valve 6 and the air pump 5. Further, since the branch pipe 13 is provided at a portion excluding the upper side of the main passage 11 through which the secondary air flows, the secondary air is difficult to flow into the branch pipe 13 and the flow of the secondary air is not easily blocked. Therefore, it is possible to suppress the flow reduction of the secondary air while suppressing the backflow of the exhaust gas.

  (2) Further, if the extended passage portion is provided in the middle of the secondary air supply passage as in the prior art, condensed water and deposits of the exhaust gas easily accumulate in the extended passage portion. On the other hand, in the present embodiment, the branch pipe 13 extends vertically upward in a state of being linearly connected to the straight portion 11L of the main passage 11, and the inner diameter of the branch pipe 13 is substantially the same as the inner diameter of the straight portion 11L. Because of this, it is also possible to suppress the accumulation of condensed water and deposits of the exhaust in the branch pipe 13.

Second Embodiment
Next, a second embodiment in which a secondary air supply device for an internal combustion engine is embodied will be described with reference to FIGS. 3 and 4.

  The second supply passage 10B described in the first embodiment is provided with the branch pipe 13. On the other hand, as shown in FIG. 3, the second supply passage 10 </ b> C of the present embodiment does not have the branch pipe 13 and is configured by one passage. And the secondary air supply apparatus 20 of this embodiment is equipped with the control valve 60 shown in FIG. 4 as a control valve which adjusts the flow volume of secondary air.

  As shown in FIG. 4, the control valve 60 is provided with a main body portion 61, and a flow path 62 through which secondary air flows, a valve body 63 for opening and closing the flow path 62, and a valve in the main body portion 61. An electromagnetic coil 64 for driving the body 63 is provided. Further, in the main body portion 61, an opening on the secondary air upstream side in the flow passage 62 is configured, and the inlet opening 65 to which the first supply passage 10A is connected, and the secondary air downstream in the flow passage 62. An outlet opening 66 is provided which constitutes an opening and is connected to the second supply passage 10C.

  Further, an outlet-side flow passage 67 is formed in the inside of the main body portion 61 to form a flow passage 62 extending linearly from the outlet opening 66 toward the inside of the main body portion 61. A wall 68 is provided at the end of the valve, that is, at a position facing the outlet opening 66 at the outlet side channel 67. Further, the flow passage 62 on the secondary air upstream side of the outlet flow passage 67 has a generally obtuse angle with respect to the formation direction K of the outlet flow passage 67 (the direction from the outlet opening 66 toward the inside of the main body 61). It is formed to be connected to the outlet-side flow path 67 from the following direction.

The operation and effects of the present embodiment will be described.
(1) As shown in FIG. 4, the exhaust gas (shown by a broken line) flowing back from the exhaust passage 2 to the outlet-side flow passage 67 of the control valve 60 via the second supply passage 10C faces the outlet opening 66 And the wall 68 provided at the site where the fluid flows is stagnant in the vicinity of the wall 68. Therefore, the backflow of the exhaust gas toward the secondary air upstream side with respect to the outlet-side flow passage 67 in the flow passage 62 is suppressed. Therefore, it is possible to suppress that the adverse effect of the exhaust heat is exerted on the members constituting the secondary air supply device 20 such as the control valve 60 and the air pump 5. Further, the secondary air (shown by the alternate long and short dash line) flowing from the inlet opening 65 into the flow path 62 does not hit the wall 68 when flowing into the outlet side flow path 67, so the flow of secondary air is obstructed. It is hard to be done. Therefore, also in the present embodiment, it is possible to suppress the flow reduction of the secondary air while suppressing the backflow of the exhaust gas.

  (2) Since the flow path 62 in the control valve 60 generally has a complicated shape, the flow of the secondary air is likely to be disturbed when flowing through the flow path 62. Therefore, in the present embodiment, the wall 68 is provided to the control valve 60 in which the flow is originally easily disturbed. Therefore, compared with the case where the wall 68 is provided at a portion where the secondary air flows in a rectified state (for example, a portion extending linearly in the second supply passage 10C), the installation of the wall 68 corresponds to the secondary air flow. It is possible to reduce the impact.

  In addition, since the site | part opened and closed by the valve body 63 in the flow path 62 is generally a narrow flow path and complex shape, it is a site | part which the flow of secondary air tends to disturb especially. Therefore, in order to reduce the influence of the installation of the wall 68 on the flow of secondary air as much as possible, it is preferable to provide the wall 68 in the vicinity of the part opened and closed by the valve body 63 in the flow path 62.

Third Embodiment
Next, a third embodiment embodying a secondary air supply device for an internal combustion engine will be described with reference to FIGS. 5 and 6.

  As shown in FIG. 5, the control valve 6 provided in the secondary air supply device 20 of the present embodiment is the same as the control valve 6 of the first embodiment. Further, the second supply passage 10C included in the secondary air supply device 20 of the present embodiment does not have the branch pipe 13 and is configured by one passage as in the second supply passage 10C of the second embodiment. ing. However, as shown in FIG. 6, the second supply passage 10 </ b> C of the present embodiment has an orifice 30 inside.

  As shown in FIG. 6, on the inner peripheral surface of the second supply passage 10 </ b> C, a tapered orifice 30 is provided in which the hole diameter decreases toward the downstream side of the secondary air. In the present embodiment, the orifice 30 is assembled to the inner circumferential surface of the second supply passage 10C, but the orifice 30 may be integrally formed on the inner circumferential surface of the second supply passage 10C.

The second supply passage 10C is connected to the exhaust passage 2 so that the secondary air upstream side of the second supply passage 10C is directed vertically upward.
The operation and effects of the present embodiment will be described.

  (1) As shown in FIG. 6, when the exhaust gas (shown by a broken line) flowing backward from the exhaust passage 2 to the second supply passage 10C passes through the orifice 30, the secondary air having the smallest pore diameter at the orifice 30 Exhaust will pass from the downstream site. Therefore, the flow passage cross-sectional area of the portion through which the exhaust gas flows is rapidly reduced from the flow passage cross-sectional area of the portion where the orifice 30 is not provided in the second supply passage 10C to the minimum flow passage cross-sectional area of the orifice 30; When passing through the orifice 30, a large turbulence occurs in the exhaust, and the exhaust does not easily pass through the orifice 30. Therefore, the backflow of the exhaust gas in the second supply passage 10C toward the secondary air upstream side of the orifice 30 can be suppressed. Therefore, the adverse effect of the exhaust heat is suppressed from being exerted on the members constituting the secondary air supply device 20 such as the control valve 6 and the air pump 5.

  On the other hand, when the secondary air (shown by the alternate long and short dash line) flowing from the control valve 6 into the second supply passage 10C passes the orifice 30, the flow passage cross-sectional area of the secondary air gradually decreases Therefore, compared to the case where the exhaust gas passes through the orifice 30, the secondary air is less likely to be disturbed. Therefore, the secondary air is more likely to pass through the orifice 30 as compared with the case where the exhaust gas passes through the orifice 30. That is, the flow of secondary air when passing through the orifice 30 is less likely to be obstructed as compared with the flow of exhaust when passing through the orifice 30. Therefore, also in the present embodiment, it is possible to suppress the flow reduction of the secondary air while suppressing the backflow of the exhaust gas.

  (2) The second supply passage 10C is connected to the exhaust passage 2 so that the secondary air upstream side of the second supply passage 10C is vertically upward. Here, if the orifice does not have a tapered shape, for example, it is flat and there is only a hole, there is a possibility that the condensed water of the exhaust may be accumulated on the wall surface located on the upstream side of the secondary air in the orifice. is there. In this respect, in the present embodiment, the orifice 30 has a tapered shape in which the hole diameter decreases toward the downstream side of the secondary air. Therefore, as shown in FIG. 6, even if condensed water G of the exhaust adheres to the wall surface located on the upstream side of the secondary air in the orifice 30, the adhered condensed water G adheres along the wall surface of the orifice 30 in the vertical direction It flows downward and falls into the exhaust passage 2 from the hole of the orifice 30. Therefore, it can suppress that the condensed water G accumulates on the wall surface located in the secondary air upstream side in the orifice 30. As shown in FIG.

Fourth Embodiment
Next, a fourth embodiment in which the secondary air supply device for an internal combustion engine is embodied will be described with reference to FIGS. 7 and 8.

  The secondary air supply device 20 of the present embodiment differs from the secondary air supply device 20 of the third embodiment only in the internal structure of the second supply passage 10C. So, below, the secondary air supply apparatus 20 of this embodiment is demonstrated focusing on such a difference.

  As shown in FIG. 7, on the inner peripheral surface of the second supply passage 10C provided in the secondary air supply device 20 of the present embodiment, the backflow of the exhaust gas from the exhaust passage 2 to the control valve 6 is suppressed while the control valve A check valve 40 is provided to allow the secondary air to flow from 6 to the exhaust passage 2.

  The check valve 40 is provided on a valve body 42 for opening and closing the inside of the second supply passage 10C, a shaft 41 for rotatably supporting the valve body 42, and the shaft 41, and the valve body 42 is on the secondary air upstream side. And a spring 43 for biasing the same. Further, on the inner peripheral surface of the second supply passage 10C, a projection 44 is provided which functions as a valve seat of the valve body 42 while restricting the rotation of the valve body 42 to the secondary air upstream side.

The operation and effects of the present embodiment will be described.
(1) As shown in FIG. 7, when the introduction of secondary air into the exhaust passage 2 is not performed, the valve body 42 biased by the spring 43 is in contact with the projection 44, and the check valve 40 Is closed. Therefore, the backflow of the exhaust gas on the secondary air upstream side of the valve body 42 in the second supply passage 10C is suppressed. Therefore, the adverse effect of the exhaust heat is suppressed from being exerted on the members constituting the secondary air supply device 20 such as the control valve 6 and the air pump 5.

  On the other hand, when the secondary air is introduced into the exhaust passage 2, the valve body 42 is pushed by the secondary air and rotated toward the secondary air downstream side, so that the valve body 42 from the projection 44 When it leaves, the check valve 40 is in the open state. Therefore, the secondary air flowing from the control valve 6 is introduced into the exhaust passage 2 through the second supply passage 10C. As described above, according to the present embodiment, the secondary air can be supplied to the exhaust passage 2 while suppressing the backflow of the exhaust gas.

  (2) Further, the separation amount of the valve body 42 from the projection 44 at the time of introduction of the secondary air, that is, the valve opening amount of the check valve 40 may be arbitrarily set by adjusting the spring constant of the spring 43. It is possible to adjust the flow rate of the secondary air introduced into the exhaust passage 2 by adjusting the valve opening amount.

  Note that, for example, when an excessive amount of secondary air is introduced into the exhaust passage 2, the temperature rise of the catalyst 3 may be hindered. Therefore, by appropriately setting the spring constant of the spring 43, it is also possible to suppress the introduction of such an excessive amount of secondary air into the exhaust passage 2.

The present embodiment can be modified as follows. The present embodiment and the following modifications can be implemented in combination with one another as long as there is no technical contradiction.
In the third embodiment, the second supply passage 10C is connected to the exhaust passage 2 so that the secondary air upstream side of the second supply passage 10C is directed vertically upward. In addition, the second supply passage 10C may be connected to the exhaust passage 2 so that the secondary air upstream side of the second supply passage 10C faces in a direction different from the upper side in the vertical direction. Even in this case, at least the function and effect of (1) described in the third embodiment can be obtained.

The structure of the check valve 40 described in the fourth embodiment is an example, and a check valve having another structure may be used.
The branch pipe 13 described in the first embodiment, the orifice 30 described in the third embodiment, and the check valve 40 described in the fourth embodiment may be applied to the first supply passage 10A.

  DESCRIPTION OF SYMBOLS 1 ... combustion chamber, 2 ... exhaust passage, 3 ... catalyst, 5 ... air pump, 6 ... control valve, 7 ... control device, 10 ... secondary air supply passage, 10A ... 1st supply passage, 10B ... 2nd supply passage, DESCRIPTION OF SYMBOLS 10C ... 2nd supply passage, 11 ... Main passage, 11W ... Curved part, 11L ... Straight part, 13 ... Branch pipe, 20 ... Secondary air supply apparatus, 30 ... Orifice, 40 ... Check valve, 41 ... Axis, 42 ... valve body 43 spring 44 projection 60 control valve 61 main body 62 flow path 63 valve body 64 electromagnetic coil 65 inlet opening 66 outlet opening 67 ... outlet side channel, 68 ... wall.

Claims (1)

A secondary air supply passage for supplying secondary air to the exhaust passage of the internal combustion engine,
The secondary air supply passage has a branch passage which is branched from the secondary air supply passage and is provided at a portion excluding the passage through which the secondary air flows, and having a closed end passage. apparatus.