EGR valve

Abstract

An EGR valve 1 includes: a housing 3 having a flow passage 2; a valve seat 4 provided in the flow passage 2; a valve body 5 provided so as to be able to be seated on the valve seat 4; a valve shaft 6 integrally provided with the valve body 5; an assembly hole 3a through which the valve shaft 6 penetrates in the housing 3; a bearing 8 supporting the valve shaft 6 in the assembly hole 3a; and a deposit guard plug 10 provided in the assembly hole 3a on a side that is closer to the flow passage 2 than the bearing 8 is. The deposit guard plug 10 includes a through hole 10a through which the valve shaft 6 penetrates, and a tip part 10b facing the flow passage 2. The tip part 10b is provided with a return part 10ba bent back in a radial outer direction around the through hole 10a and in a direction toward the bearing 8.

Description

EGR valve

[0001] The technology disclosed in this specification relates to an EGR valve used to adjust the EGR gas flow rate in the EGR passage.

[0002] Conventionally, as this type of technology, for example, the "EGR valve" described in Patent Document 1 below is known. In this EGR valve, a bearing for supporting the valve shaft in a stroke motion is provided in the mounting hole of the housing. Also, a seal member for sealing between the housing and the valve shaft is provided adjacent to the bearing in the mounting hole. Further, a depo guard plug for preventing the intrusion of deposits from the EGR gas flow path into the mounting hole is provided adjacent to the seal member in the mounting hole. And for the seal member, in order to prevent seal failure due to the biting of foreign matter or deposits, the distance between the adjacent bearing and the seal member and the distance between the adjacent seal member and the depo guard plug are set to be larger than the maximum stroke of the valve shaft.

[0003] Japanese Patent Application Laid-Open No. 2013-7266

[0004] However, in the EGR valve described in Patent Document 1, in an environment below the dew point temperature of the EGR gas, when the EGR gas flows through the flow path, condensed water is generated due to condensation. Also, when a large amount of condensed water flows through the flow path, there is a risk that the condensed water will run along the inner wall of the flow path and enter the mounting hole via the gap between the valve shaft and the depo guard plug. In particular, if the condensed water that has entered the mounting hole stays in the gap between the depo guard plug and the seal member, there is a concern that the inner wall of the mounting hole will corrode.

[0005] This disclosed technology has been made in view of the above circumstances, and its purpose is to provide an EGR valve capable of suppressing the intrusion of condensed water from the flow path into the mounting hole.

[0006] (1) In order to achieve the above objective, one aspect of the present disclosure provides an EGR valve comprising a housing having a flow path for EGR gas, a valve seat provided in the flow path, a valve body provided so as to be seatable on the valve seat, a valve shaft provided integrally with the valve body for moving the valve body relative to the valve seat, an assembly hole provided in the housing through which the valve shaft passes, a bearing provided in the assembly hole for supporting the valve shaft so as to be able to move in a stroke, and a deposit guard plug provided in the assembly hole on the side of the assembly hole closer to the flow path than the bearing for preventing deposits from entering the assembly hole from the flow path, wherein the deposit guard plug is substantially cylindrical and includes a through hole through which the valve shaft passes and a tip facing the flow path, and the tip is provided with a return portion that is bent back radially outward from the through hole and in the direction of the bearing.

[0007] In this embodiment, the tip of the DepoGuard Plug facing the flow path is provided with a return portion that is bent back radially outward from the through hole and in the direction of the bearing. Therefore, when a large amount of condensed water flows through the flow path, the flow of condensed water that travels along the inner wall of the flow path toward the outer circumference of the valve stem is reversed at the return portion, and the intrusion of condensed water into the gap between the valve stem and the DepoGuard Plug is suppressed.

[0008] The technology described in (2) is intended to ensure that the return portion of the deposit guard plug is spaced apart from the inner wall of the flow path, in the embodiment of (1) above.

[0009] In this embodiment, the return portion of the Depot Guard Plug is spaced apart from the inner wall of the flow path, so that the surface of the return portion is discontinuous with respect to the inner wall of the flow path, and the flow of condensed water onto the surface of the return portion is suppressed.

[0010] (1) According to the technology described above, it is possible to suppress the intrusion of condensed water from the flow path into the assembly hole.

[0011] (2) According to the technology described in (2), the intrusion of condensed water from the flow path into the assembly hole can be further suppressed.

[0012] A cross-sectional view showing the EGR valve in the fully closed position according to one embodiment. An enlarged cross-sectional view showing the portion enclosed by the dashed rectangle in Figure 1, according to one embodiment.

[0013] The EGR valve will be described in detail below with reference to the drawings for one embodiment. As is well known, the EGR valve is installed in the EGR passage, which flows a portion of the exhaust gas discharged from the engine to the exhaust passage as EGR gas into the intake passage, and is used to adjust the EGR gas flow rate.

[0014] [About the configuration of the EGR valve] Figure 1 shows a cross-sectional view of the EGR valve 1 in the fully closed position according to this embodiment. This EGR valve 1 is configured as both a poppet valve and an electrically operated valve. As shown in Figure 1, the EGR valve 1 comprises a housing 3 having a passage 2 for EGR gas, a valve seat 4 provided in the passage 2, a valve body 5 provided so as to be seatable on the valve seat 4, a valve stem 6 provided integrally with the valve body 5 to move the valve body 5 relative to the valve seat 4, an assembly hole 3a provided in the housing 3 through which the valve stem 6 passes, a step motor 7 for driving (stroke motion) the valve stem 6 together with the valve body 5, a thrust bearing 8 provided in the assembly hole 3a to support the valve stem 6 so as to be driveable (stroke motion), a lip seal 9 provided in the assembly hole 3a on the side closer to the passage 2 than the thrust bearing 8 for sealing the space between the housing 3 and the valve stem 6, and a deposit guard plug 10 provided in the assembly hole 3a on the side closer to the passage 2 than the lip seal 9 for preventing deposits from entering the assembly hole 3a from the passage 2.

[0015] As shown in Figure 1, the thrust bearing 8 is positioned closer to the stepper motor 7 (upper side in Figure 1) than the lip seal 9. The lip seal 9 is held in place by press-fitting into the assembly hole 3a. The assembly hole 3a has an opening 3aa that opens into the flow path 2. The thrust bearing 8, lip seal 9, and deposit guard plug 10 are held in the assembly hole 3a with the valve stem 6 as the center. The deposit guard plug 10 is held in place by press-fitting near the opening 3aa of the assembly hole 3a.

[0016] In this embodiment, the housing 3 is made of a metal material (for example, aluminum). The ends of the flow path 2 formed in the housing 3 are an inlet 2a into which EGR gas is introduced and an outlet 2b from which EGR gas is discharged. The valve seat 4 is provided in the middle of the flow path 2 and has a valve hole 4a that communicates with the flow path 2. The Depot Guard Plug 10 can be made of metal, resin, or rubber.

[0017] The valve stem 6 is provided between the stepper motor 7 and the flow path 2, and in Figure 1, it is positioned to penetrate the housing 3 vertically. The valve body 5 is fixed to the lower end of the valve stem 6, has a conical shape, and its conical surface is in contact with or separated from the valve seat 4. A spring receiver 11 is integrally provided at the upper end of the valve stem 6.

[0018] The stepper motor 7 includes a stator 22 containing a coil 21, a magnet rotor 23 provided inside the stator 22, and an output shaft 12 provided at the center of the magnet rotor 23. These components 12, 21-23, etc., are molded and covered by a resin casing 24. A connector 25 protruding laterally is integrally formed on the casing 24. Terminals 26 extending from the coil 21 are provided on the connector 25.

[0019] The output shaft 12 has a male thread 12a on its outer circumference. The lower end of the output shaft 12 is connected to a spring receiver 11 provided on the upper end of the valve stem 6. The magnet rotor 23 includes a rotor body 27 and a cylindrical plastic magnet 28 integrally provided on the outer circumference of the rotor body 27. A first radial bearing 29 is provided between the upper end of the rotor body 27 and the casing 24. A second radial bearing 30 is provided between the lower end of the plastic magnet 28 and the thrust bearing 8. These upper and lower radial bearings 29 and 30 support the magnet rotor 23 so that it can rotate inside the stator 22. A female thread 27a is formed in the center of the rotor body 27, which screws into the male thread 12a of the output shaft 12. A first compression spring 31 is provided between the magnet rotor 23 and the lower second radial bearing 30. A second compression spring 32 is provided between the spring receiver 11 and the second radial bearing 30, which biases the valve stem 6 toward the magnet rotor 23, that is, biases it in the closing direction so that the valve body 5 is seated on the valve seat 4.

[0020] As shown in Figure 1, in the fully closed state with the valve body 5 seated on the valve seat 4, the magnetic rotor 23 rotates in one direction. Due to the screw-to-screw relationship between the male thread 12a of the output shaft 12 and the female thread 27a of the rotor body 27, the output shaft 12 rotates in one direction and strokes downward in the thrust direction as shown in Figure 1, against the biasing force of the second compression spring 32. This stroke motion of the output shaft 12 causes the valve body 5 to stroke downward in Figure 1 together with the valve stem 6, causing the valve body 5 to separate from the valve seat 4 and open the valve.

[0021] On the other hand, in the fully open state (not shown) where the valve body 5 is furthest away from the valve seat 4, the magnetic rotor 23 rotates in the opposite direction. Due to the screw-to-screw relationship between the male thread 12a of the output shaft 12 and the female thread 27a of the rotor body 27, and the biasing force of the second compression spring 32, the output shaft 12 rotates in the opposite direction while stroking upward in the thrust direction as shown in Figure 1. This stroking motion of the output shaft 12 causes the valve body 5 to stroke upward in Figure 1 together with the valve stem 6, bringing the valve body 5 closer to the valve seat 4 and closing the valve, resulting in the fully closed state shown in Figure 1.

[0022] [About the Depot Guard Plug] Figure 2 shows an enlarged cross-sectional view of the area enclosed by the dashed rectangle S1 in Figure 1. As shown in Figures 1 and 2, the Depot Guard Plug 10 is substantially cylindrical and includes a through hole 10a through which the valve stem 6 passes, and a tip portion 10b facing the flow path 2. The tip portion 10b is provided with a return portion 10ba that is bent back radially outward from the through hole 10a and in the direction of the bearing 8 (lip seal 9). This return portion 10ba is positioned at a certain distance D1 (see Figure 2) from the inner wall of the flow path 2 and the opening 3aa of the assembly hole 3a.

[0023] [Operation and Effects of the EGR Valve] According to the configuration of the EGR valve 1 of this embodiment described above, the tip portion 10b of the deposit guard plug 10 facing the flow path 2 is provided with a return portion 10ba that is bent back radially outward from the through hole 10a and in the direction of the bearing 8. Therefore, when a large amount of condensed water flows into the flow path 2, as shown by the arrow in Figure 2, the flow of condensed water that travels along the inner wall of the flow path 2 toward the outer circumference of the valve stem 6 is reversed at the return portion 10ba, and the intrusion of condensed water into the gap between the valve stem 6 and the deposit guard plug 10 is suppressed. As a result, the intrusion of condensed water from the flow path 2 into the assembly hole 3a can be suppressed.

[0024] According to the configuration of this embodiment, the return portion 10ba of the Depot Guard Plug 10 is spaced apart from the inner wall of the flow path 2, so the surface of the return portion 10ba becomes discontinuous with respect to the inner wall of the flow path 2, and the flow of condensed water onto the surface of the return portion 10ba is suppressed. Therefore, the intrusion of condensed water from the flow path 2 into the assembly hole 3a can be further suppressed.

[0025] Furthermore, this disclosed technology is not limited to the embodiments described above, and it can be implemented by appropriately modifying a part of the configuration without departing from the spirit of the disclosed technology.

[0026] For example, the shape of the return portion 10ba of the deposit guard plug 10 in the above embodiment is just one example; the return portion can also be formed in multiple stages.

[0027] This disclosed technology can be used in EGR devices having an EGR passage.

[0028] Flow path 3 Housing 3a Assembly hole 4 Valve seat 5 Valve body 6 Valve stem 8 Bearing 10 Depot guard plug 10a Through hole 10b Tip 10ba Return part

Claims

1. An EGR valve comprising: a housing having a passage for EGR gas; a valve seat provided in the passage; a valve body provided so as to be seatable on the valve seat; a valve shaft provided integrally with the valve body for moving the valve body relative to the valve seat; an assembly hole provided in the housing through which the valve shaft passes; a bearing provided in the assembly hole for supporting the valve shaft so as to be able to move in a stroke; and a deposit guard plug provided in the assembly hole on the side of the passage closer to the passage than the bearing for preventing deposits from entering the assembly hole from the passage, wherein the deposit guard plug is substantially cylindrical and includes a through hole through which the valve shaft passes and a tip portion facing the passage, and the tip portion is provided with a return portion that is bent back radially outward from the through hole and in the direction of the bearing.

2. An EGR valve according to claim 1, characterized in that the return portion of the deposit guard plug is spaced apart from the inner wall of the flow path.

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