EGR valve

Abstract

An EGR valve 1 comprises: a housing 3 having a flow passage 2; a valve seat 4 provided in the flow passage 2; a valve element 5 provided so as to be seatable on the valve seat 4; a valve stem 6 having the valve element 5 provided to one end thereof; an assembly hole 11 provided in the housing 3 and having an opening 11a that opens into the flow passage 2; a seal member 9 provided in the assembly hole 11; and a deposit-preventing plug 10 provided in the assembly hole 11 in the vicinity of the opening 11a. The deposit-preventing plug 10 is press-fitted into the assembly hole 11 so as to enclose the valve stem 6 in the vicinity of the opening 11a. The seal member 9 is press-fitted into the inside of the deposit-preventing plug 10, and is provided between the deposit-preventing plug 10 and the valve stem 6 so as to enclose the valve stem 6 and abut against the valve stem 6.

Description

EGR valve

[0001] The technology disclosed in the present specification relates to an EGR valve provided in an EGR passage of an exhaust gas recirculation device (EGR device).

[0002] Conventionally, as this type of technology, for example, the "EGR valve" described in the following Patent Document 1 is known. This valve is configured as a poppet-type electromagnetic valve. This valve opens and closes by driving a valve shaft provided in a housing with an actuator to reciprocate a valve body relative to a valve seat. An assembly hole is formed in the housing in the axial direction of the housing. The valve shaft is supported so as to be capable of stroking movement in the housing via a bearing assembled in the assembly hole. Further, in the assembly hole, a seal member is provided adjacent to the bearing for sealing between the assembly hole and the valve shaft. Furthermore, a deposit guard plug is provided adjacent to the seal member at an opening of the assembly hole. The deposit guard plug suppresses intrusion of deposits from a flow passage into the assembly hole.

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

[0004] However, in the EGR valve described in Patent Document 1, condensed water may intrude into the deposit guard plug provided adjacent to the seal member. If the intruded condensed water stays between the deposit guard plug and the seal member, there is a risk that the inner wall of the assembly hole is corroded by the condensed water. When the inner wall of the assembly hole is corroded, EGR gas and condensed water leak to the bearing and actuator side through a gap between the inner wall of the assembly hole and the outer periphery of the seal member, and there has been a concern that malfunction may occur in the valve shaft and the actuator.

[0005] The disclosed technology has been made in view of the above circumstances, and an object thereof is to provide an EGR valve capable of sealing with a seal member even if condensed water intrudes into a deposit guard plug from a flow passage, and preventing corrosion of the inner wall of an assembly hole caused by condensed water even if condensed water stays between the seal member and the deposit guard plug.

[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 stem provided at one end of the valve body; an assembly hole provided in the housing for assembling the valve stem and having an opening at one end that opens to the flow path; a sealing member provided in the assembly hole to seal the space between the housing and the valve stem; and a deposit guard plug provided near the opening to suppress the intrusion of deposits from the flow path into the assembly hole, wherein the deposit guard plug is press-fitted into the assembly hole so as to enclose the valve stem near the opening, and the sealing member is press-fitted inside the deposit guard plug and provided between the deposit guard plug and the valve stem so as to enclose the valve stem and contact the valve stem.

[0007] In this embodiment, the deposit guard plug performs a deposit guard function at the opening of the mounting hole, suppressing the intrusion of deposits from the flow path. Furthermore, since the deposit guard plug is press-fitted into the mounting hole, the space between the inner wall (housing) of the mounting hole and the deposit guard plug is sealed. Condensed water that enters the deposit guard plug from the flow path is then blocked from the inner wall of the mounting hole by the deposit guard plug. In addition, the space between the deposit guard plug and the valve stem is sealed by a sealing member.

[0008] The technology described in (2) is intended to be such that, in the embodiment of (1), the Depot Guard Plug includes a press-fit portion that is press-fitted into the assembly hole near the opening, a diameter-reducing portion whose outer diameter is reduced toward the flow path from the press-fit portion, and a sleeve portion that extends from the press-fit portion toward the opposite side of the flow path, and the sealing member is press-fitted inside the sleeve portion.

[0009] In this embodiment, the reduced-diameter portion of the deposit guard plug exhibits a deposit guard function that suppresses the intrusion of deposits at the opening of the assembly hole. Furthermore, since the press-fit portion of the deposit guard plug is press-fitted into the assembly hole, the space between the housing and the press-fit portion is sealed. In addition, condensed water that enters the deposit guard plug is blocked from the inner wall of the assembly hole by the deposit guard plug, and the space between the sleeve portion and the valve stem is sealed by the sealing member.

[0010] The technology described in (3) is intended to reduce the diameter of the diameter-reducing portion of the Depot Guard Plug in a funnel shape toward the flow path, in the embodiment of (2).

[0011] In this embodiment, the Depot Guard Plug has a constricted diameter portion facing the flow path that constricts in a funnel shape toward the flow path, making it easier for condensed water generated on the surface of the constricted diameter portion to flow down toward the tip of the constricted diameter portion.

[0012] The technology described in (4) is intended to be such that, in the embodiment of (3), the reduced diameter portion of the Depot Guard Plug has a flat stepped portion at the boundary with the press-fit portion.

[0013] According to this embodiment, since the reduced diameter portion has a flat stepped portion at the boundary with the press-fit portion, when press-fitting the Depot Guard Plug, which has the sealing member assembled in advance, into the assembly hole from the opening, it becomes possible to apply pressure by placing a jig against the stepped portion.

[0014] According to the technology described in (1), even if condensed water enters the deposit guard plug from the flow path, it can be sealed by the sealing member, and even if condensed water accumulates between the sealing member and the deposit guard plug, corrosion of the inner wall of the assembly hole due to condensed water can be prevented.

[0015] According to the technology described in (2), even if condensed water enters the deposit guard plug from the flow path, it can be sealed by the sealing member, and even if condensed water accumulates between the sealing member and the deposit guard plug, corrosion of the inner wall of the assembly hole due to condensed water can be prevented.

[0016] (3) According to the technology described above, the adhesion and retention of condensed water in the narrowed diameter section can be suppressed.

[0017] The technology described in (4) makes it possible to improve workability when press-fitting the Depot Guard plug into the assembly hole.

[0018] A front view showing a partially cut EGR valve according to the first embodiment. A cross-sectional view showing an enlarged portion of the area enclosed by the dashed line in Figure 1 according to the first embodiment. A perspective view showing the Depot Guard Plug according to the first embodiment. A cross-sectional view showing the Depot Guard Plug and the sealing member according to the first embodiment. A front view showing a partially cut EGR valve according to the second embodiment. A cross-sectional view showing an enlarged portion of the area enclosed by the dashed rectangle in Figure 5 according to the second embodiment.

[0019] Several embodiments of the EGR valve will be described in detail below with reference to the drawings.

[0020] <First Embodiment> First, a first embodiment of the EGR valve will be described.

[0021] [Configuration of the EGR valve] Figure 1 shows a partially cut-off front view of the EGR valve 1 of this embodiment. Figure 2 shows an enlarged cross-sectional view of the area enclosed by the dashed rectangle S1 in Figure 1. The EGR valve 1 is installed in the EGR passage (not shown) which recirculates a portion of the exhaust gas discharged from the engine to the exhaust passage as EGR gas to the intake passage. The EGR valve 1 is used to adjust the flow rate of the EGR gas in the EGR passage.

[0022] As shown in Figure 1, the EGR valve 1 has a poppet-type valve structure. The EGR valve 1 comprises a housing 3 having a flow path 2 for EGR gas, a valve seat 4 provided in the middle of the flow path 2, a substantially umbrella-shaped valve body 5 provided so as to be seatable on the valve seat 4, a valve stem 6 with the valve body 5 provided at one end, and a drive unit 7 for reciprocating the valve stem 6 together with the valve body 5 in the axial direction.

[0023] The housing 3 is provided with an assembly hole 11 for assembling the valve stem 6. One end of the assembly hole 11 is an opening 11a that opens into the flow path 2. The drive unit 7 is composed of, for example, a stepper motor. Figure 1 is a cross-sectional view of the components other than the drive unit 7. The valve seat 4 is provided separately from the housing 3. The housing 3 is made of aluminum. In this embodiment, a detailed explanation of the drive unit 7 is omitted.

[0024] This EGR valve 1 adjusts the flow rate of EGR gas in the passage 2 by moving the valve body 5 axially relative to the valve seat 4 and changing the opening between the valve body and the valve seat 4. Figure 1 shows the closed state with the valve body 5 seated on the valve seat 4.

[0025] As shown in Figure 1, the valve stem 6 extends downward from the drive unit 7 and is assembled perpendicularly to the housing 3 in the assembly hole 11. The valve body 5 seats (contacts) and separates from the valve seat 4 as the valve stem 6 reciprocates. A thrust bearing 8 is provided in the assembly hole 11 to support the valve stem 6 so that it can reciprocate. A sealing member 9 is provided in the assembly hole 11 to seal the space between the housing 3 and the valve stem 6. A deposit guard plug 10 is provided in the assembly hole 11 near the opening 11a to suppress the intrusion of deposits from the flow path 2 into the assembly hole 11. The deposit guard plug 10 is positioned in the assembly hole 11 from the opening 11a to the vicinity of the thrust bearing 8. The sealing member 9 is positioned adjacent to the thrust bearing 8 and inside the deposit guard plug 10.

[0026] [Configuration of Depot Guard Plug and Seal Member] Figure 3 shows a perspective view of the Depot Guard Plug 10. Figure 4 shows a cross-sectional view of the Depot Guard Plug 10 and the seal member 9. The Depot Guard Plug 10 is made of a metal such as SUS. The Depot Guard Plug 10 is press-fitted into the assembly hole 11 so as to enclose the valve stem 6 near the opening 11a. The seal member 9 is made of an elastic material such as rubber. The seal member 9 is press-fitted inside the Depot Guard Plug 10 and is provided between the Depot Guard Plug 10 and the valve stem 6 so as to enclose the valve stem 6 and contact the valve stem 6.

[0027] As shown in Figures 2 to 4, the Depot Guard Plug 10 includes a press-fit portion 10a that is press-fitted into the assembly hole 11 near the opening 11a, a reduced-diameter portion 10b whose outer diameter decreases toward the flow path 2 from the press-fit portion 10a, and a sleeve portion 10c that extends from the press-fit portion 10a toward the opposite side of the flow path 2. As shown in Figure 2, the press-fit portion 10a is press-fitted into the assembly hole 11, but the sleeve portion 10c is not press-fitted into the assembly hole 11, and a gap 12 is provided between it and the inner wall of the assembly hole 11.

[0028] As shown in Figures 2 to 4, the reduced diameter portion 10b of the Depot Guard Plug 10 narrows in diameter in a funnel shape toward the flow path 2. This reduced diameter portion 10b has a flat stepped portion 10d at its boundary with the press-fit portion 10a.

[0029] As shown in Figure 4, the sealing member 9 is press-fitted into the inside of the sleeve portion 10c. The sealing member 9 includes a cylindrical press-fit portion 9a that is press-fitted into the sleeve portion 10c, and a lip-shaped lip portion 9b that contacts the outer circumference of the valve stem 6 inside the press-fit portion 9a. A metal ring 13, which serves as the framework, is embedded inside the press-fit portion 9a.

[0030] [Operation and Effects of the EGR Valve] According to the configuration of the EGR valve 1 of this embodiment described above, the deposit guard plug 10 is press-fitted into the assembly hole 11 so as to enclose the valve stem 6 near the opening 11a. The sealing member 9 is press-fitted inside the deposit guard plug 10 and is provided between the deposit guard plug 10 and the valve stem 6 so as to enclose the valve stem 6 and contact the valve stem 6. Therefore, the deposit guard plug 10 exhibits a deposit guard function at the opening 11a of the assembly hole 11, suppressing the intrusion of deposits from the flow path 2. Also, since the deposit guard plug 10 is press-fitted into the assembly hole 11, the space between the inner wall (housing) of the assembly hole 11 and the deposit guard plug 10 is sealed. Then, condensed water that enters the deposit guard plug 10 from the flow path 2 is blocked from the inner wall of the assembly hole 11 by the deposit guard plug 10. Furthermore, the space between the deposit guard plug 10 and the valve stem 6 is sealed by the sealing member 9.

[0031] More specifically, the reduced-diameter portion 10b of the deposit guard plug 10 provides a deposit guard function that suppresses the intrusion of deposits at the opening 11a of the assembly hole 11. Furthermore, since the press-fit portion 10a of the deposit guard plug 10 is press-fitted into the assembly hole 11, the space between the housing 3 and the press-fit portion 10a is sealed. In addition, condensed water that enters the deposit guard plug 10 is blocked from the inner wall of the assembly hole 11 by the deposit guard plug 10. Moreover, the space between the sleeve portion 10c and the valve stem 6 is sealed by the sealing member 9. For this reason, even if condensed water enters the deposit guard plug 10 from the flow path 2, it can be sealed by the sealing member 9, and even if condensed water accumulates between the sealing member 9 and the deposit guard plug 10, corrosion of the inner wall of the assembly hole 11 by condensed water can be prevented. As a result, it is possible to prevent EGR gas and condensed water from leaking to the thrust bearing 8 and drive unit 7 through the gap between the inner wall of the assembly hole 11 and the outer circumference of the sealing member 9, thereby ensuring the normal operation of the valve shaft 6 and drive unit 7.

[0032] According to the configuration of this embodiment, the Depot Guard Plug 10 has a diameter-reduced portion 10b facing the flow path 2 that narrows in a funnel shape toward the flow path 2, so that condensed water generated on the surface of the diameter-reduced portion 10b flows down toward the tip of the diameter-reduced portion 10b. Therefore, adhesion and retention of condensed water at the diameter-reduced portion 10b can be suppressed.

[0033] According to the configuration of this embodiment, the reduced diameter portion 10b has a flat stepped portion 10d at the boundary with the press-fit portion 10a. Therefore, when press-fitting the Depot Guard Plug 10, which has the sealing member 9 pre-assembled, into the assembly hole 11 from the opening 11a, it becomes possible to apply pressure to the stepped portion 10d with a jig 20 (shown by a dashed line in Figure 4). This improves the workability when press-fitting the Depot Guard Plug 10 into the assembly hole 11.

[0034] <Second Embodiment> Next, a second embodiment of the EGR valve will be described. In the following description, components having the same or similar functions as those in the first embodiment will be denoted by the same reference numerals, and the differences will be described in particular.

[0035] [Configuration of the EGR valve] This embodiment differs from the first embodiment in terms of the type of EGR valve. Figure 5 shows a partially cut-out front view of the EGR valve 30 of this embodiment. Figure 6 shows an enlarged cross-sectional view of the area enclosed by the dashed rectangle S2 in Figure 5.

[0036] As shown in Figure 5, the EGR valve 30 has a double eccentric valve structure. The EGR valve 30 comprises a housing 3 having a flow path 2 for EGR gas, a valve seat 4 provided in the flow path 2, a substantially disc-shaped valve body 5 provided so as to be seatable on the valve seat 4, a valve stem 6 with the valve body 5 provided at one end, and a drive unit 7 for rotating the valve stem 6 together with the valve body 5.

[0037] The housing 3 is provided with an assembly hole 11 for assembling the valve stem 6. One end of the assembly hole 11 is an opening 11a that opens into the flow path 2. Figure 5 shows a cross-sectional view of the components other than the drive unit 7. The valve seat 4 is provided separately from the housing 3.

[0038] This EGR valve 30 rotates the valve stem 6, causing the valve body 5 to rotate relative to the valve seat 4. This rotation of the valve body 5 changes the opening between it and the valve seat 4, thereby adjusting the flow rate of EGR gas in the passage 2. Figure 5 shows the closed state with the valve body 5 seated on the valve seat 4.

[0039] As shown in Figure 5, the valve stem 6 extends laterally from the drive unit 7 and is assembled horizontally to the housing 3 in the assembly hole 11. The valve body 5 seats (contacts) and separates from the valve seat 4 as the valve stem 6 rotates. A pair of radial bearings 15A and 15B are provided in the assembly hole 11 to rotatably support the valve stem 6. A sealing member 9 is provided in the assembly hole 11 to seal the space between the housing 3 and the valve stem 6. A deposit guard plug 10 is provided in the assembly hole 11 near the opening 11a to suppress the intrusion of deposits from the flow path 2 into the assembly hole 11. The deposit guard plug 10 is positioned in the assembly hole 11 from the opening 11a to the vicinity of the radial bearing 15A. The sealing member 9 is positioned adjacent to the radial bearing 15A and inside the deposit guard plug 10.

[0040] [Configuration of Deposit Guard Plug and Seal Member] As shown in FIG. 6, the deposit guard plug 10 and the seal member 9 of this embodiment have a substantially similar configuration to that of the first embodiment, although their shapes differ somewhat.

[0041] [Actions and Effects of EGR Valve] According to the configuration of the EGR valve 30 in this embodiment described above, equivalent actions and effects can be obtained, although the model is different from that of the EGR valve 1 of the first embodiment.

[0042] It should be noted that the disclosed technology is not limited to the above embodiments, and a part of the configuration can be appropriately changed and implemented without departing from the spirit of the disclosed technology.

[0043] (1) In each of the above embodiments, as shown in FIGS. 1, 2, 5 and 6, the reduced diameter portion 10b of the deposit guard plug 10 is formed such that the outer diameter is reduced in a funnel shape from the press-fit portion 10a toward the flow passage 2. In contrast, the reduced diameter portion of the deposit guard plug may be formed such that the outer diameter is reduced stepwise from the press-fit portion toward the flow passage. (2) In each of the above embodiments, a flat stepped portion 10d is provided at the boundary between the press-fit portion 10a and the reduced diameter portion 10b of the deposit guard plug 10, but this stepped portion may be omitted.

[0044] The disclosed technology can be applied to an EGR device provided in an engine.

[0045] 1 EGR valve 2 Flow passage 3 Housing 4 Valve seat 5 Valve body 6 Valve shaft 9 Seal member 10 Deposit guard plug 10a Press-fit portion 10b Reduced diameter portion 10c Sleeve portion 10d Stepped portion 11 Assembly hole 11a Opening portion 30 EGR valve

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 stem provided at one end of the valve body; an assembly hole provided in the housing for assembling the valve stem, having an opening at one end that opens to the passage; a sealing member provided in the assembly hole to seal the space between the housing and the valve stem; and a deposit guard plug provided near the opening to suppress the intrusion of deposits from the passage into the assembly hole, wherein the deposit guard plug is press-fitted into the assembly hole so as to enclose the valve stem near the opening; and the sealing member is press-fitted inside the deposit guard plug and provided between the deposit guard plug and the valve stem so as to enclose the valve stem and contact the valve stem.

2. An EGR valve according to claim 1, wherein the deposit guard plug includes a press-fit portion that is press-fitted into the assembly hole near the opening, a reduced-diameter portion whose outer diameter decreases toward the flow path from the press-fit portion, and a sleeve portion that extends from the press-fit portion toward the opposite side of the flow path, and the sealing member is press-fitted inside the sleeve portion.

3. An EGR valve according to claim 2, characterized in that the reduced diameter portion of the deposit guard plug has an outer diameter that is funnel-shaped toward the flow path.

4. An EGR valve according to claim 3, characterized in that the reduced diameter portion of the deposit guard plug has a flat stepped portion at the boundary with the press-fit portion.

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