JP5650453B2 - EGR cooler system and flow path switching valve - Google Patents

Description

  The present invention relates to an EGR cooler system that cools EGR gas, and a flow path switching valve that can switch between introduction and non-introduction of EGR gas to the EGR cooler.

  Conventionally, an EGR (exhaust gas recirculation) system has been adopted to reduce NOx in exhaust gas in diesel engines and the like. In this EGR system, when high-temperature exhaust gas is circulated to the intake side as it is, exhaust gas that has been expanded at high temperature is supplied to the intake manifold. For this reason, the proportion of exhaust in the cylinder increases. As a result, the amount of air in the cylinder decreases, combustion efficiency deteriorates, and exhaust components such as NOx also deteriorate.

  For this reason, in the EGR system, an EGR cooler that cools EGR gas (exhaust gas) by heat exchange with cooling water is arranged in a part of the EGR passage, and the hot EGR gas is cooled by the EGR cooler. Thus, an EGR system with an EGR cooler that recirculates to the intake manifold (hereinafter referred to as an EGR cooler system) has been developed. In such an EGR cooler system, when the temperature of the cooling water is low such as when the engine is started or cold, the cooling of the EGR gas becomes supercooled, and conversely, the combustion efficiency in the cylinder and the exhaust component are deteriorated. When the engine temperature is lower than normal or when the cooling water temperature is cold, the EGR gas is allowed to flow through a bypass flow path that is connected around the passage of the EGR cooler. A bypass valve (flow path switching valve) is used to switch between using and not using the EGR cooler.

  In such a bypass valve, Patent Document 1 discloses a technique in which a swing valve (valve element) is fastened and fixed to a valve shaft (valve shaft) with a screw (screw). In the technique of Patent Document 1, the swing valve swings about the valve shaft as the valve shaft rotates. Thereby, the swing valve is between the first position that opens the first flow path and closes the second flow path, and the second position that closes the first flow path and closes the second flow path. The EGR gas flow path is switched between a flow path passing through the EGR cooler and a flow path not passing through the EGR cooler.

JP 2010-24872 A

However, the technique disclosed in Patent Document 1 has the following problems.
When the swing valve is disposed at the first position, the EGR gas flows from the first flow path to the second flow path through the inside of the EGR cooler. At this time, due to the pressure loss of the EGR gas generated when the EGR gas passes through the EGR cooler, a differential pressure of the EGR gas is generated between the first flow path and the second flow path. Therefore, a difference occurs in the pressure of EGR gas received between the first flow path side surface and the second flow path side surface in the swing valve.

  Here, FIG. 11 is a schematic diagram of the periphery of a swing valve in a conventional bypass valve represented by the bypass valve of Patent Document 1. FIG. FIG. 11 shows a state in which the swing valve 100 is brought into contact with the valve seat (valve seat) 102 and the valve seat (valve seat) 104 to block the first flow path 106 and the second flow path 108.

  At this time, since the valve shaft 110 is restrained by the bearing 112 as shown in FIG. 12, the force is generated by the differential pressure of the EGR gas generated between the first flow path 106 and the second flow path 108 in the swing valve 100. The receiving part is a force point, and the part where the swing valve 100 and the valve seat 102 abut is a fulcrum. Due to this action, tensile stress is generated in the neck 116 of the screw 114. For this reason, the durability of the screw 114 is lowered, and there is a possibility that the flow path switching operation by the swing valve 100 becomes unstable. The maximum stress is generated in the portion α.

  In particular, as shown in FIG. 11, the swing valve 100 contacts only the front valve seat 102 and makes a line contact, does not contact the depth side valve seat 104, and does not contact the swing valve 100 and the valve seat 104. In the case where a gap δ is generated, a larger tensile stress is generated at the neck portion 116 of the screw 114.

  Further, if the moment around the central axis of the valve shaft 110 due to the force received by the swing valve 100 due to the differential pressure of EGR gas generated between the first flow path 106 and the second flow path 108 is large, the swing valve 100 is swung. In order to achieve this, it is necessary to rotate the valve shaft 110 with a large torque. Therefore, a high output is required for an actuator (not shown) for rotating the valve shaft 110, and the actuator becomes large. Therefore, the EGR cooler system and the bypass valve are increased in size.

  Therefore, the present invention has been made to solve the above-described problems, and it is an object to provide an EGR cooler system and a flow path switching valve that improve the stability of the flow path switching operation by the valve body. To do.

One aspect of the present invention made to solve the above problems is an EGR cooler having an EGR cooler that cools EGR gas and a flow path switching valve that switches between introduction and non-introduction of the EGR gas into the EGR cooler. In the system, the flow path switching valve selectively selects the plurality of flow paths for switching between a housing provided with a plurality of flow paths through which the EGR gas flows and a flow path provided in the housing through which the EGR gas flows. A valve body integrated with the valve body, and a partition wall provided in the housing to form the plurality of flow paths, the valve body being fixed to the valve shaft. A curved bent portion provided between one part and a second part capable of contacting the partition wall is provided, and the valve body is formed only on one side with respect to the valve shaft in the radial direction of the valve shaft. The second The first portion includes a first surface connected to the outer peripheral surface of the bent portion and a second surface connected to the inner peripheral surface of the bent portion, and the partition wall is configured such that two branch walls branch from one wall. The length of one of the branch walls that is formed and abuts the first surface of the second part is smaller than the length of the other branch wall that abuts the second surface of the second part, the branch wall, said been found provided between the inlet flow passage of EGR gas to introducing the EGR gas inlet channel to flow into the interior of the flow path switching valve to the EGR cooler, the first site, It is fastened with a screw and fixed to the valve shaft .

According to this aspect, since the valve body includes the curved bent portion provided between the first portion fixed to the valve shaft and the second portion that can contact the partition wall, the second portion is the partition. When the second part receives the differential pressure of the EGR gas between the plurality of flow paths when it is in contact with the wall, the stress that can be generated in the fixed part of the first part with the valve shaft is reduced. Therefore, the durability of the portion fixed to the valve shaft in the first portion is improved. Therefore, the stability of the flow path switching operation by the valve body is improved. Moreover, since the length of one branch wall with which the 1st surface of a 2nd part contact | abuts a partition wall is smaller than the length of the other branch wall with which the 2nd surface of a 2nd part contact | abuts, The communication port between the plurality of divided flow paths is close to the valve shaft. Therefore, when the first surface of the second part contacts one branch wall, the moment acting on the second part is reduced by receiving the differential pressure of the EGR gas between the plurality of flow paths. Therefore, it is possible to reduce the torque required to rotate the valve shaft. Therefore, the actuator for rotating the valve shaft can be reduced in size, and the EGR cooler system can be reduced in size. Further, since the first part is fastened by the screw and fixed to the valve shaft, the first part is securely fixed to the valve shaft by the fastening force of the screw. Therefore, the stability of the switching operation of the flow path by the valve body is more reliably improved. Further, since the valve body has a bent portion, when the second portion is in contact with the partition wall, the stress generated in the neck portion of the screw due to the second portion receiving the differential pressure of EGR gas between the plurality of flow paths. To reduce. Therefore, the durability of the screw is improved. Therefore, the stability of the flow path switching operation by the valve body is improved.

Another aspect of the present invention, which has been made to solve the above problems, includes a housing having a plurality of flow paths through which a fluid flows, and the plurality of flow paths provided in the housing for switching the flow paths of the fluid. In a flow path switching valve having a valve body that opens and closes automatically, a valve shaft integrated with the valve body, and a partition wall that is provided in the housing and forms the plurality of flow paths, the valve body includes the valve A curved bent portion provided between a first portion fixed to the shaft and a second portion capable of contacting the partition wall, wherein the valve body is configured to have the valve shaft in a radial direction of the valve shaft. The second portion includes a first surface connected to the outer peripheral surface of the bent portion and a second surface connected to the inner peripheral surface of the bent portion, and the partition wall includes one Two branch walls are branched from the wall, and the second portion of the second portion is The length of the one branch wall with which the surface abuts is smaller than the length of the other branch wall with which the second surface of the second portion abuts, and the one branch wall allows the fluid to flow through the flow path. et disposed between the inlet flow path for introducing the fluid and the inlet passage to be introduced into the changeover valve portion for cooling is, the first site, it is fixed to the valve shaft are fastened by a screw It is characterized by.

  According to the EGR cooler system and the flow path switching valve according to the present invention, the stability of the flow path switching operation by the valve element is improved.

It is sectional drawing of the EGR cooler system of Example 1. FIG. 1 is a cross-sectional view of a bypass valve of Example 1. FIG. It is AA sectional drawing of FIG. It is sectional drawing of a swing valve. It is a figure explaining dispersion | distribution of the force from a swing valve. It is a figure which shows a mode that a swing valve contacts a valve seat. It is a figure which shows the mode of the stress which generate | occur | produces in the neck part of a screw. It is a figure which shows the correction | amendment Goodman diagram showing the influence of the stress of the neck part of a screw which acts on a fatigue limit. It is sectional drawing of the bypass valve of Example 2. FIG. FIG. 6 is a cross-sectional view of a bypass valve according to a modification of the second embodiment. It is a schematic diagram of the periphery of a swing valve in a conventional bypass valve. It is a figure which shows a mode that a tensile stress generate | occur | produces in the neck part of a screw.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Example 1
[Description of EGR cooler system and bypass valve]
<Outline of EGR cooler system>
FIG. 1 is a cross-sectional view of an EGR cooler system 1 according to the first embodiment.
As shown in FIG. 1, the EGR cooler system 1 includes a bypass valve 10 and an EGR cooler 12. The EGR cooler 12 is integrated with the bypass valve 10 to constitute the EGR cooler system 1. The bypass valve 10 is an example of the “flow path switching valve” in the present invention.

<Structure and operation of bypass valve>
FIG. 2 is a cross-sectional view of the bypass valve 10 according to the first embodiment. FIG. 3 is a cross-sectional view taken along the line AA of FIG.
The bypass valve 10 is a flow path switching valve for switching between introduction and non-introduction (bypass) of EGR gas to the EGR cooler 12. As illustrated in FIG. 2, the bypass valve 10 according to the first embodiment includes a housing 14 provided with a plurality of flow paths through which EGR gas flows, a swing valve 16 provided in the housing 14, and the swing valve 16. And a valve shaft 18 that has been made into a valve. The swing valve 16 is means for selectively opening and closing a plurality of flow paths in order to switch the flow paths through which the EGR gas flows. The swing valve 16 is an example of the “valve element” of the present invention, and the valve shaft 18 is an example of the “valve shaft” of the present invention.

  The housing 14 is formed of an aluminum alloy, and a partition wall 20 having a substantially Y-shaped cross section is provided in the housing 14 so that two branch walls branch from one wall. . The partition wall 20 forms a plurality of channels such as an inflow channel 22, an introduction channel 24, and a discharge channel 26 inside the housing 14. The inflow channel 22 is a channel through which EGR gas flows into the bypass valve 10. The introduction flow path 24 is a flow path for introducing EGR gas that has flowed into the bypass valve 10 into the EGR cooler 12 (more specifically, a cooler core 58 described later). The discharge passage 26 is a passage through which EGR gas (hereinafter also referred to as “EGR cooler gas”) that has been introduced into the EGR cooler 12 (more specifically, a cooler core 58 described later) and passed through the EGR cooler 12 is discharged from the EGR cooler 12. is there.

  As shown in FIG. 2, the partition wall 20 includes a first wall 28 (upper right side wall in FIG. 2), a second wall 30 (upper left side wall in FIG. 2), and a third wall 32 (lower wall in FIG. 2). The first wall 28 and the second wall 30 are formed to branch from the third wall 32. The first wall 28 of the partition wall 20 is provided between the inflow channel 22 and the introduction channel 24 and partitions the inflow channel 22 and the introduction channel 24. Further, the second wall 30 of the partition wall 20 is provided between the inflow channel 22 and the discharge channel 26, and partitions the inflow channel 22, the discharge channel 26, and an outflow channel 34 described later. Further, the third wall 32 of the partition wall 20 is provided between the introduction flow path 24 and the discharge flow path 26 and partitions the introduction flow path 24 and the discharge flow path 26. Furthermore, the introduction flow path 24 and the discharge flow path 26 open to the EGR cooler 12 side (the lower surface of the housing 14 in FIG. 2) of the housing 14, and the inflow flow path 22 is the opposite side to the EGR cooler 12 (the housing in FIG. 2). 14 upper surface). The first wall 28 and the second wall 30 are examples of the “branch wall” in the present invention.

  Further, the housing 14 is formed with an outflow channel 34 communicating with the discharge channel 26. The outflow passage 34 is a passage through which EGR gas (or EGR cooler gas) flows out of the bypass valve 10 and is provided at the position of the side surface (the left side surface in FIG. 2) of the housing 14 in the first embodiment. In particular, it is not limited to this position.

  A swing valve 16 is provided in the inflow channel 22. The swing valve 16 is fastened and fixed to the valve shaft 18 by a screw 38 with one end (first portion 68, see FIG. 4) inserted into a groove 36 formed in the valve shaft 18. ing. The details of the swing valve 16 will be described later. The screw 38 is an example of the “screw” in the present invention.

  The valve shaft 18 is disposed substantially at the center of the partition wall 20 (the connecting portion of the first wall 28, the second wall 30, and the third wall 32). As shown in FIG. And is rotatably supported via. One end of the valve shaft 18 protrudes to the outside of the housing 14 and is connected to an actuator (not shown). Further, a resin or metal seal member 44 is provided inside the bearing 40 (inflow channel 22 side), and a resin or metal seal member 45 is provided inside the bearing 42 (inflow channel 22 side). Is provided. Thereby, leakage of EGR gas to the outside of the housing 14 is prevented.

  The swing valve 16 is swung by rotating such a valve shaft 18. That is, the swing valve 16 is operated by rotating the valve shaft 18 in both directions within a restricted angle range. The swing valve 16 is brought into contact with a valve seat (valve seat) 46 provided at the front end portion of the first wall 28 and a valve seat (valve seat) 50 provided on the inner surface 48 of the housing 14, thereby allowing inflow. While the flow path 22 and the introduction flow path 24 are blocked, the inflow flow path 22 and the discharge flow path 26 (outflow flow path 34) can be communicated with each other. The swing valve 16 is brought into contact with a valve seat (valve seat) 52 provided at the tip of the second wall 30 and a valve seat (valve seat) 56 provided on the inner surface 60 of the housing 14, thereby allowing inflow. While the flow path 22 and the discharge flow path 26 (outflow flow path 34) are blocked, the inflow flow path 22 and the introduction flow path 24 can be communicated with each other. Thereby, introduction of EGR gas into the EGR cooler 12 and non-introduction can be switched.

  In the housing 14, an in-valve cooling water passage 54 through which cooling water (refrigerant) for cooling the bypass valve 10 flows is formed. Thereby, since the bypass valve 10 is cooled by the cooling water flowing through the in-valve cooling water passage 54, the heat resistance can be secured even in the housing 14 made of aluminum alloy. The in-valve cooling water passage 54 communicates with an in-cooler cooling water passage (not shown) provided in the EGR cooler 12.

<Structure and operation of EGR cooler>
On the other hand, the EGR cooler 12 cools the EGR gas introduced by the bypass valve 10. As shown in FIG. 1, the EGR cooler 12 includes a cooler core 58. These cooler cores 58 are formed of an iron alloy (for example, stainless steel). A flow path 64 through which EGR gas flows is formed inside the cooler core 58.

  Further, as shown in FIG. 1, a partition plate 66 extending downward (in a direction away from the bypass valve 10) is disposed inside the cooler core 58. The partition plate 66 forms a substantially U-shaped flow path 64 inside the cooler core 58. The end portion of the partition plate 66 is in contact (surface contact) with the end portion of the partition wall 20 (third wall 32) formed in the housing 14 of the bypass valve 10. A plurality of partition plates 66 may be arranged.

  In the EGR cooler 12 having such a structure, the EGR gas that has flowed into the cooler core 58 from the introduction flow path 24 of the bypass valve 10 flows through the cooler core 58 and is discharged to the discharge flow path 26 of the bypass valve 10. And since the cooling water passage (not shown) is formed outside the cooler core 58, the EGR gas passing through the cooler core 58 is cooled by the cooling water flowing in the cooling water passage.

<Operation of EGR cooler system>
Next, the operation of the EGR cooler system 1 having the above-described configuration will be briefly described. First, when the cooling water temperature of the engine is equal to or lower than a predetermined temperature (when cold), the swing valve 16 is moved to the valve seat 46 of the first wall 28 of the partition wall 20 and the valve seat 50 of the housing 14 by an actuator not shown. It is made to contact with. As a result, in the bypass valve 10, the inflow channel 22 and the outflow channel 34 communicate with each other via the discharge channel 26, and the inflow channel 22 and the introduction channel 24 are blocked. Therefore, the EGR gas that has flowed into the inflow passage 22 of the bypass valve 10 from an EGR pipe (not shown) flows into the outflow passage 34. The EGR gas that has flowed out of the bypass valve 10 from the outflow passage 34 is supplied to an intake manifold (not shown). Thus, when cold, the EGR gas is supplied as it is to the intake manifold without passing through the EGR cooler 12.

  When the coolant temperature becomes equal to or higher than a predetermined temperature (after warming up), the swing valve 16 is brought into contact with the valve seat 52 of the second wall 30 of the partition wall 20 and the valve seat 56 of the housing 14 by an actuator (not shown). . Thereby, in the bypass valve 10, the inflow channel 22 and the introduction channel 24 communicate with each other, and the inflow channel 22 and the outflow channel 34 are blocked. Therefore, the EGR gas that has flowed into the bypass valve 10 from an EGR pipe (not shown) flows from the inflow passage 22 to the introduction passage 24. Then, the EGR gas that has flowed into the introduction flow path 24 is supplied to the EGR cooler 12. As a result, the EGR gas flows inside the cooler core 58. At this time, the EGR gas is cooled by cooling water that flows in a cooling water passage (not shown) provided so as to cover the outside of the cooler core 58. The cooled EGR gas (EGR cooler gas) is discharged from the cooler core 58 to the discharge passage 26 of the bypass valve 10 and then supplied from the outflow passage 34 to an intake manifold (not shown). Thus, after warming up, the EGR gas (EGR cooler gas) cooled by the EGR cooler 12 is supplied to the intake manifold.

<Structure and action of swing valve>
Next, the swing valve 16 of the bypass valve 10 will be described. FIG. 4 is a cross-sectional view of the swing valve 16. As shown in FIG. 4, the swing valve 16 includes a first portion 68, a second portion 70, and a bent portion 72.
The first portion 68 is a portion where the swing valve 16 is fastened and fixed to the valve shaft 18 with a screw 38. The first portion 68 is formed in a linear shape. Further, as shown in FIG. 3, screws 38 are fastened at three locations in the central axis direction of the valve shaft 18 in the groove 36 of the valve shaft 18. Note that the number of places where the screw 38 is fastened is not limited to three, and may be one, two, or four or more.

  The second portion 70 is formed in a linear shape. The second portion 70 includes a first surface 74 connected to the outer peripheral surface 73 of the bent portion 72 and a second surface 76 connected to the inner peripheral surface 75 of the bent portion 72. As shown in FIG. 2, the first surface 74 is brought into contact with the valve seat 52 of the second wall 30 of the partition wall 20 and the valve seat 56 of the housing 14, so The passage 26 (outflow passage 34) is shut off. Further, the inflow passage 22 and the introduction passage 24 are blocked by bringing the second surface 76 into contact with the valve seat 46 of the first wall 28 of the partition wall 20 and the valve seat 48 of the housing 14.

  The bent portion 72 is provided between the first portion 68 and the second portion 70. The bent portion 72 is formed in a curved shape (R shape). Accordingly, the direction in which the first portion 68 is formed (the M direction in FIG. 4) and the direction in which the second portion 70 is formed (the N direction in FIG. 4) intersect at an inclination angle θ. The inclination angle θ is 10 ° or more and less than 90 °, and particularly preferably close to 90 °.

<Effect of Example 1>
The effect of Example 1 as described above will be described below.
When the inflow channel 22 and the discharge channel 26 (outflow channel 34) are blocked, the EGR gas is introduced from the introduction channel 24 into the channel 64 of the EGR cooler 12, passes through the channel 64, and then is discharged. It is discharged to the passage 26. At this time, a pressure loss of EGR gas occurs inside the flow path 64, so that a differential pressure of EGR gas occurs between the inside of the inflow path 22 and the inside of the discharge path 26. Therefore, in the second portion 70, a difference is generated between the pressure of EGR gas received by the first surface 74 and the pressure of EGR gas received by the second surface 76.

  Therefore, according to the EGR cooler system 1 and the bypass valve 10 of the first embodiment, the swing valve 16 is disposed between the first portion 68 fixed to the valve shaft 18 and the second portion 70 that can contact the partition wall 20. A curved bent portion 72 is provided. Therefore, when the first surface 74 of the second portion 70 of the swing valve 16 is brought into contact with the valve seat 52 and the valve seat 56 to shut off the inflow passage 22 and the discharge passage 26 (outflow passage 34). 5, the differential pressure of EGR gas between the inflow channel 22 and the exhaust channel 26 (received between the first surface 74 and the second surface 76 of the second portion 70 of the swing valve 16). The force F0 from the swing valve 16 generated by the differential pressure of EGR gas) is dispersed into the force F2 acting on the valve shaft 18 and the force F1 acting on the neck portion 78 of the screw 38. Therefore, the tensile stress that can be generated in the neck portion 78 of the screw 38 is reduced, and the durability of the screw 38 is improved. Therefore, the stability of the switching operation of the flow path through which the EGR gas flows by the swing valve 16 is improved. 5 is a diagram for explaining the dispersion of force from the swing valve 16, FIG. 5 (a) is a sectional view schematically showing the swing valve 16, and FIG. It is the figure which showed typically about dispersion | distribution of this force. 5B shows the direction in which the force F1 and the force F2 act is slightly changed from the direction shown in FIG. 5A so that the dispersion of the force from the swing valve 16 can be easily understood.

  In addition, by setting the inclination angle θ to 10 ° or more, the force from the swing valve 16 generated by the differential pressure of the EGR gas between the inflow channel 22 and the exhaust channel 26 can be reliably dispersed. Thereby, since the durability of the screw 38 is reliably maintained, the stability of the flow path switching operation by the swing valve 16 is reliably improved.

  Further, by setting the inclination angle θ to less than 90 °, the second portion 70 of the swing valve 16 does not cause a harmful effect when the swing valve 16 is fastened to the valve shaft 18 by the screw 38. Therefore, the swing valve 16 can be securely fastened to the valve shaft 18 by the screw 38.

  In particular, by making the inclination angle θ close to 90 °, the housing 14 can be reduced in size, the stability of the switching operation of the flow path by the swing valve 16 is reliably improved, and the valve shaft is reliably driven by the screw 38. The swing valve 16 can be fastened to 18.

  Further, since the swing valve 16 has the bent portion 72, the first surface 74 of the second portion 70 is brought into contact with the valve seat 52 and the valve seat 56, so that the inflow passage 22 and the discharge passage 26 (outflow passage). 34), as shown in FIG. 6, the valve shaft 18 is tightened following the swing valve 16, so that the first surface 74 of the second portion 70 of the swing valve 16 is connected to the valve seat 52. The valve seat 56 can be brought into surface contact with no gap. Therefore, the inflow channel 22 and the discharge channel 26 (outflow channel 34) can be reliably blocked. FIG. 6 is a diagram illustrating a state in which the first surface 74 of the second portion 70 of the swing valve 16 is in surface contact with the valve seat 52 and the valve seat 56 without a gap.

  Further, since the first portion 68 of the swing valve 16 is fastened by the screw 38 and is fixed to the valve shaft 18, the first portion 68 is reliably fixed to the valve shaft 18 by the fastening force of the screw 38. Therefore, the stability of the switching operation of the flow path through which the EGR gas flows by the swing valve 16 is more reliably improved.

  The swing valve 16 according to the first embodiment is fastened and fixed to the valve shaft 18 by the screw 38 at the first portion 68, but the present invention is not limited thereto, and the swing valve 16 is attached to the valve shaft 18 at the first portion 68. Even when fixed by welding, the same effect as described above can be obtained.

<Results of swing valve analysis>
Next, the analysis result performed about the swing valve 16 of Example 1 is demonstrated.
The neck portion 78 of the screw 38 has a stress σ1 generated by tightening the screw 38 and a differential pressure of EGR gas received by the first surface 74 and the second surface 76 of the second portion 70 of the swing valve 16 as described above. The generated stress σ2 acts. Therefore, the analysis was performed on the assumption that stress as shown in FIG. Note that the stress generated by the differential pressure of the EGR gas received by the first surface 74 and the second surface 76 of the second portion 70 of the swing valve 16 is affected by the fluctuation of the pressure of the inflowing EGR gas. It was assumed that it fluctuated while having a stress amplitude as shown in FIG. FIG. 7 is a diagram showing a state of stress generated in the neck portion 78 of the screw 38. As shown in FIG.

  Therefore, as an analysis result, FIG. 8 shows the stress of the neck portion 78 of the screw 38 due to the tightening of the screw 38 on the fatigue limit of the screw 38 and the first surface 74 and the second surface 76 of the second portion 70 of the swing valve 16. The correction | amendment Goodman diagram showing the influence with the stress amplitude of the stress of the neck part 78 of the screw 38 which generate | occur | produces by the differential pressure | voltage of the received EGR gas is shown. In FIG. 8, the vertical axis represents the stress amplitude of the stress generated in the neck portion 78 of the screw 38 due to the differential pressure of the EGR gas received by the first surface 74 and the second surface 76 of the second portion 70 of the swing valve 16. Is the stress generated at the neck 78 of the screw 38 by tightening the screw 38. In this analysis, the differential pressure of EGR gas received by the first surface 74 and the second surface 76 of the second portion 70 of the swing valve 16 is set to 100 kPa.

  As shown in FIG. 8, the swing valve 16 of the first embodiment is included in a range where the screw 38 on the lower side of the modified Gutman line in the drawing does not undergo fatigue failure. Also, the stress amplitude is reduced to about 39% of the prior art swing valve that does not have the bend 72. And the safety factor of the swing valve 16 of Example 1 could be reduced to about 2.6 by reducing the stress amplitude in this way.

  From the above, according to the EGR cooler system 1 and the bypass valve 10 of Example 1, since the swing valve 16 includes the bent portion 72, it was confirmed that the durability of the screw 38 can be maintained. Therefore, it was confirmed that the stability of the flow path switching operation by the swing valve 16 is improved.

(Example 2)
Next, Example 2 will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and different points are mainly described.
<Structure and action of partition wall>
FIG. 9 is a cross-sectional view of a bypass valve 80 according to the second embodiment, and FIG. 10 is a cross-sectional view of a bypass valve 81 according to a modification of the second embodiment.
As shown in FIGS. 9 and 10, the partition wall 82 includes a first wall 84 (upper right side wall in FIGS. 9 and 10), a second wall 86 (upper left side wall in FIGS. 9 and 10), and a third wall. 88 (the lower wall in FIGS. 9 and 10), and is formed in a cross section so that the first wall 84 and the second wall 86 diverge from the third wall 88. The first wall 84 of the partition wall 82 is provided between the inflow channel 22 and the introduction channel 24 and partitions the inflow channel 22 and the introduction channel 24. The second wall 86 of the partition wall 82 is provided between the inflow channel 22 and the discharge channel 26, and partitions the inflow channel 22 from the exhaust channel 26 and the outflow channel 34. Further, the third wall 88 of the partition wall 82 is provided between the introduction flow path 24 and the discharge flow path 26 and partitions the introduction flow path 24 and the discharge flow path 26.

When the swing valve 16 is operated, the first surface 74 of the second portion 70 of the swing valve 16 comes into contact with the valve seat 92 at the tip of the second wall 86, or the second portion 70 of the swing valve 16 The second surface 76 contacts the valve seat 90 at the tip of the first wall 84.
In the partition wall 82 according to the second embodiment, the length of the first wall 84 and the length of the second wall 86 are different. Specifically, in the bypass valve 80 shown in FIG. 9, the length of the second wall 86 is smaller than the length of the first wall 84, and in the bypass valve 81 shown in FIG. 10, the length of the first wall 84 is the second wall. Less than 86 length.

<Effect of Example 2>
According to the bypass valves 80 and 81 of the second embodiment, the length of the first wall 84 and the length of the second wall 86 are different as shown in FIGS. 9 and 10. Therefore, in comparison with the case where the length of the first wall 28 is equal to the length of the second wall 30 as in the first embodiment, for example, in FIG. 9, the inflow channel partitioned by the second wall 86. The communication port between 22 and the discharge channel 26 approaches the valve shaft 18. Therefore, when the swing valve 16 contacts the valve seat 92 of the second wall 86, the position of the center C1 between the valve seat 92 and the valve seat 56 is close to the valve shaft 18. Therefore, the distance L1 between the central axis of the valve shaft 18 and the center C1 can be reduced. As a result, when a differential pressure of EGR gas received between the first surface 74 and the second surface 76 of the second portion 70 of the swing valve 16 is generated, the second portion 70 of the swing valve 16 is caused by the differential pressure. Since the moment around the central axis of the valve shaft 18 can be reduced, the amount of torque required to rotate the valve shaft 18 can be reduced. Therefore, the output of the actuator for rotating the valve shaft 18 can be reduced and reduced in size, and the bypass valve 80 can be reduced in size.
The bypass valve 81 shown in FIG. 10 can obtain the same effect because the distance L2 between the central axis of the valve shaft 18 and the center C2 (the center between the valve seat 90 and the valve seat 50) can be reduced. Can do.

  In particular, the differential pressure of EGR gas received between the first surface 74 and the second surface 76 of the second portion 70 of the swing valve 16 causes the first surface 74 to contact the valve seat 92 and the valve seat 56. When the inflow channel 22 and the discharge channel 26 (outflow channel 34) are blocked and the inflow channel 22 and the introduction channel 24 are communicated with each other, the flow rate becomes larger. Therefore, as shown in FIG. 9, by making the length of the second wall 86 smaller than the length of the first wall 84, the force received by the second portion 70 of the swing valve 16 around the central axis of the valve shaft 18. Since the moment can be further reduced, the magnitude of torque required to rotate the valve shaft 18 can be further reduced. Therefore, the output of the actuator for rotating the valve shaft 18 can be further reduced to reduce the size, and the bypass valve 80 can be further reduced in size.

It should be noted that the above-described embodiment is merely an example and does not limit the present invention in any way, and various improvements and modifications can be made without departing from the scope of the invention.
In the above embodiment, EGR gas is taken as an example, but the present invention is not limited to this, and the flow path switching valve of the present invention can be applied to other fluids.

DESCRIPTION OF SYMBOLS 1 EGR cooler system 10 Bypass valve 12 EGR cooler 14 Housing 16 Swing valve 18 Valve shaft 20 Partition wall 22 Inflow flow path 24 Introduction flow path 26 Discharge flow path 28 1st wall 30 2nd wall 32 3rd wall 34 Outflow flow path 38 Screw 46 (first wall) valve seat 50 (housing) valve seat 52 (second wall) valve seat 56 (housing) valve seat 68 first part 70 second part 72 bending part 73 outer peripheral surface 74 first Surface 75 Inner peripheral surface 76 Second surface 78 Neck portion 80 Bypass valve 81 Bypass valve 82 Partition wall 84 First wall 86 Second wall 88 Third wall 90 (First wall) Valve seat 92 (Second wall) Valve seat

Claims (2)

In an EGR cooler system having an EGR cooler that cools EGR gas, and a flow path switching valve that switches between introduction and non-introduction of the EGR gas to the EGR cooler,
The flow path switching valve selectively opens and closes the plurality of flow paths to switch between a housing provided with a plurality of flow paths through which the EGR gas flows and a flow path provided in the housing through which the EGR gas flows. A valve body, a valve shaft integrated with the valve body, and a partition wall provided in the housing and forming the plurality of flow paths,
The valve body includes a curved bent portion provided between a first portion fixed to the valve shaft and a second portion capable of contacting the partition wall,
The valve body is formed only on one side with respect to the valve shaft in the radial direction of the valve shaft,
The second part includes a first surface connected to the outer peripheral surface of the bent portion and a second surface connected to the inner peripheral surface of the bent portion,
The partition wall is formed so that two branch walls are branched from one wall, and the length of one of the branch walls with which the first surface of the second part abuts is the second part of the second part. Smaller than the length of the other branch wall with which the surface abuts,
The one the branch wall of said been found provided between the inlet flow passage of EGR gas to introducing the EGR gas inlet channel to flow into the interior of the flow path switching valve to the EGR cooler,
The first part is fastened by a screw and fixed to the valve stem;
EGR cooler system. A housing having a plurality of flow paths through which fluid flows, a valve body provided in the housing for selectively opening and closing the plurality of flow paths to switch the fluid flow paths, and a valve shaft integrated with the valve body And a flow path switching valve having a partition wall provided in the housing and forming the plurality of flow paths,
The valve body includes a curved bent portion provided between a first portion fixed to the valve shaft and a second portion capable of contacting the partition wall,
The valve body is formed only on one side with respect to the valve shaft in the radial direction of the valve shaft,
The second part includes a first surface connected to the outer peripheral surface of the bent portion and a second surface connected to the inner peripheral surface of the bent portion,
The partition wall is formed so that two branch walls are branched from one wall, and the length of one of the branch walls with which the first surface of the second part abuts is the second part of the second part. Smaller than the length of the other branch wall with which the surface abuts,
The branch wall of the one is found disposed between the inlet flow path for introducing the fluid into a portion for cooling the fluid inflow passage for flowing inside the flow path switching valve,
The first part is fastened by a screw and fixed to the valve stem;
A flow path switching valve.

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