EGR valve

Abstract

To suppress the ingress of condensed water from the flow path into the assembly hole. [Solution] The EGR valve 1 comprises a housing 3 having a flow path 2, a valve seat 4 provided in the flow path 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, an assembly hole 3a in the housing 3 through which the valve stem 6 passes, a bearing 8 supporting the valve stem 6 in the assembly hole 3a, and a deposit guard plug 10 provided in the assembly hole 3a on the side closer to the flow path 2 than the bearing 8. The deposit guard plug 10 includes a through hole 10a through which the valve stem 6 passes, and a tip portion 10b facing the flow path 2, and 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.

Description

Technical Field

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

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[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 flow along the inner wall of the flow path and enter the assembly hole via the gap between the valve shaft and the depogard plug. In particular, when the condensed water that has entered the assembly hole stays in the gap between the depogard plug and the seal member, there is a concern that the inner wall of the assembly 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 that can suppress the ingress of condensed water from the flow path into the assembly hole. [Means for solving the problem]

[0006] To achieve the above objective, the technology described in claim 1 is 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 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 portion facing the flow path, 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.

[0007] According to the above technology configuration, 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] To achieve the above objective, the technology described in claim 2 is intended to be the technology described in claim 1, wherein the return portion of the deposit guard plug is spaced apart from the inner wall of the flow path.

[0009] According to the configuration of the above technology, in addition to the effects of the technology described in claim 1, the return portion of the Depot Guard Plug is separated from the inner wall of the flow path, so that the surface of the return portion becomes 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. [Effects of the Invention]

[0010] According to the technology described in claim 1, it is possible to suppress the ingress of condensed water from the flow path into the assembly hole.

[0011] According to the technology described in claim 2, in addition to the effects of the technology described in claim 1, the intrusion of condensed water from the flow path into the assembly hole can be further suppressed. [Brief explanation of the drawing]

[0012] [Figure 1] A cross-sectional view showing the EGR valve in the fully closed position, according to one embodiment. [Figure 2] An enlarged cross-sectional view showing the portion enclosed by the dashed rectangle in Figure 1, relating to one embodiment. [Modes for carrying out the invention]

[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 to the intake passage, and is used to adjust the EGR gas flow rate.

[0014] [Regarding 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 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 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 around the valve stem 6. 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 flow path 2 formed in the housing 3 has an inlet 2a into which EGR gas is introduced and an outlet 2b into 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 located inside the stator 22, and an output shaft 12 located 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 Fig. 1, in the fully closed state where the valve body 5 is seated on the valve seat 4, when the magnet rotor 23 rotates in one direction, due to the screwing relationship between the male screw 12a of the output shaft 12 and the female screw 27a of the rotor body 27, against the biasing force of the second compression spring 32, the output shaft 12 performs a stroke movement downward in the thrust direction (the downward direction in Fig. 1) while rotating in one direction. Due to this stroke movement of the output shaft 12, the valve body 5 together with the valve shaft 6 performs a stroke movement downward in the direction of Fig. 1, and the valve body 5 separates from the valve seat 4 to open the valve.

[0021] On the other hand, in the fully open state (not shown in the figure) where the valve body 5 is maximally separated from the valve seat 4, when the magnet rotor 23 rotates in the opposite direction, due to the screwing relationship between the male screw 12a of the output shaft 12 and the female screw 27a of the rotor body 27 and the biasing force of the second compression spring 32, the output shaft 12 performs a stroke movement upward in the thrust direction (the upward direction in Fig. 1) while rotating in the opposite direction. Due to this stroke movement of the output shaft 12, the valve body 5 together with the valve shaft 6 performs a stroke movement upward in the direction of Fig. 1, and the valve body 5 approaches the valve seat 4 to close the valve, reaching the fully closed state shown in Fig. 1.

[0022] [Regarding the Depo Guard Plug] Fig. 2 shows an enlarged cross-sectional view of the portion surrounded by the one-dot chain line rectangle S1 in Fig. 1. As shown in Figs. 1 and 2, the Depo Guard Plug 10 has a substantially cylindrical shape and includes a through-hole 10a through which the valve shaft 6 passes and a tip portion 10b facing the flow path 2. The tip portion 10b is provided with a bent-back portion 10ba bent back in the radially outer direction centered on the through-hole 10a and in the direction of the bearing 8 (lip seal 9). This bent-back portion 10ba is arranged at a distance D1 (see Fig. 2) from the inner wall of the flow path 2 and the opening 3aa of the assembly hole 3a.

[0023] [Regarding the Action and Effect of the EGR Valve] As described above, the configuration of the EGR valve 1 in this embodiment provides a return portion 10ba at the tip 10b of the deposit guard plug 10 facing the flow path 2, which is bent radially outward from the through hole 10a and toward the bearing 8. Therefore, when a large amount of condensed water flows through 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, and the return portion can also be formed in multiple stages. [Industrial applicability]

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

[0028] Flow channel 3 Housing 3a Assembly hole 4 valve seats 5 Valve body 6 Valve stem 8 bearings 10 Depot Guard Plugs 10a through hole 10b Tip 10ba return section

Claims

1. A housing having a flow path for EGR gas, A valve seat provided in the aforementioned flow path, A valve body provided so as to be seatable on the valve seat, A valve stem is provided integrally with the valve body to move the valve body relative to the valve seat, The housing is provided with an assembly hole through which the valve shaft passes, A bearing provided in the assembly hole for supporting the valve shaft so that it can move in a stroke, A deposit guard plug is provided in the assembly hole on the side closer to the flow path than the bearing, to prevent deposits from entering the assembly hole from the flow path. In an EGR valve equipped with, The deposit guard plug is substantially cylindrical in shape and includes a through hole through which the valve stem passes and a tip portion facing the flow path. 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. An EGR valve characterized by the following features.

2. In the EGR valve according to claim 1, The return portion of the deposit guard plug is spaced apart from the inner wall of the flow path. An EGR valve characterized by the following features.

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