EGR device

Abstract

EGR device, comprising: a housing (2) defining an EGR passage (5) through which an EGR gas flows; a shaft (7) which is rotatably supported by the housing (2) via a bearing (8); a valve body (11) connected to the shaft (7) so as to adjust a flow passage area of ​​the EGR passage (5) by rotating together with the shaft (7); and an actuator (20) connected to an end portion of the shaft (7) to drive the shaft (7), wherein the bearing (8) comprises a first bearing (25) supporting one end portion of the shaft (7) and a second bearing (26) supporting the other end portion of the shaft (7); Sealing elements (27) are arranged on one end portion of the shaft (7) to prevent the fluid from flowing into the actuator (20); the sealing elements (27) comprise a first sealing element (27b) made of fluoroplastic and a second sealing element (27a) made of a fluorine-containing rubber; the actuator (20), the second sealing element (27a), the first sealing element (27b) and the EGR passage (5) are arranged in this order along the axial direction of the shaft; the housing (2) has a chamber (30) accommodating the second bearing (26) which is insulated from the outside; and the second bearing (26) is made of a PPS plastic material to which a fluoroplastic is added.

Description

TECHNICAL FIELD

[0001] The present application relates to an EGV device that circulates a portion of exhaust gas from an exhaust passage to an intake passage. STATE OF THE ART

[0002] An EGR device which circulates a part of exhaust gas from an exhaust passage to an intake passage via an EGR passage of an engine mounted on a vehicle is known (exhaust gas circulated to the intake passage is hereinafter referred to as EGR gas).

[0003] Furthermore, it is known that the EGR device has a cantilevered configuration to simplify its structure. Such an EGR device is formed with a housing, a shaft, a valve body, and an actuator, which are described in detail below.

[0004] The housing has an EGR passage therein through which the EGR gas flows. One end of the shaft is rotatably supported by the housing via a bearing. The valve is connected to the shaft in such a way that it adjusts the flow area of ​​the EGR passage by rotating in unison with the shaft. The actuator is connected to one end of the shaft to rotate the shaft.

[0005] This means that in such an EGR device, the shaft is supported via the housing only by the bearing located at one end of the shaft. Furthermore, a sealing element is arranged at one end of the shaft to prevent fluid from flowing into the actuator.

[0006] In recent years, the need to circulate a large amount of EGR gas in the engine has emerged to further improve fuel efficiency and reduce exhaust emissions. However, when a large amount of EGR gas is circulated into the EGR passage, the EGR device, which has a cantilevered configuration, is likely to be unable to adequately support the valve. Although the shaft is considered to have a bearing mechanism at both ends, there is a need to form a new, additional bearing on the housing (see Patent Literature 1).

[0007] In a case where an additional bearing is formed on the housing, gas and condensate are likely to flow into the housing through a receiving space of the additional bearing. By isolating the receiving space of the additional bearing from the outside, the gas and condensate can be prevented from escaping from the housing.

[0008] However, since the additional bearing is exposed to a strong acid environment, the metal additional bearing is likely to corrode. STATE OF THE ART LITERATURE PATENT LITERATURE

[0009] Patent Literature 1: JP 2011-058536 A

[0010] JP 2015-59463 A discloses an EGR control valve having an annular protrusion on the inner periphery of a cylindrical portion that is a flow passage wall of a valve body of a housing, the tip of the protrusion being used as a valve seal of the housing. On the upstream and downstream sides of the protrusion, respectively, flow passage wall surfaces are formed that are recessed in a direction in which a clearance with respect to an outer peripheral end surface of an EGR valve is longer than an air gap formed between the outer peripheral end surface of the EGR valve and the valve seal during full closure of the EGR control valve. Thus, this structure can prevent the retention of strongly acidic condensate in the air gap that is the tip of the protrusion.

[0011] JP 2008-133954 A discloses a sliding member provided on a sliding portion of a sliding bearing for a valve device having a bearing outer periphery made of metal as the outer peripheral portion. A resin sliding layer is formed on an inner diameter portion of the outer peripheral metal of the bearing by injection molding a resin material to form an inner diameter surface sliding portion on the inner diameter surface of the sliding bearing as the sliding portion. The resin material contains an injection-moldable resin base material, a solid lubricant, and a non-porous granular filler. The mixing amount of the resin base material, the solid lubricant, and the granular filler is within a predetermined range, and the ratio of the major axis to the minor axis of the granular filler is less than 5.A fine depressed portion is provided in the surface of the bearing outer peripheral metal which contacts the resin sliding layer, wherein both the size and the depth of the depressed portion are within a predetermined range. SUMMARY OF THE INVENTION

[0012] It is an object of the present application to provide a structure in which an additional bearing is prevented from corroding when a shaft of an EGR device has a receiving mechanism formed at both ends.

[0013] This object is achieved by the EGR device having the features of claim 1. Advantageous further developments thereof can be found in the associated subclaims.

[0014] According to the present application, an EGR device is formed with a housing, a shaft, a valve body, and an actuator, which are described in detail below. The housing has an EGR passage therein through which the EGR gas flows. The shaft is rotatably supported by the housing via a bearing. The valve body is connected to the shaft such that a flow passage area or a flow passage cross-section of the EGR passage can be adjusted by rotating together with the shaft. The actuator is connected to one end of the shaft to rotate the shaft.

[0015] The bearing includes a first bearing supporting one end portion of the shaft and a second bearing supporting the other end portion of the shaft. Furthermore, a seal member preventing fluid from flowing into the actuator is disposed at one end portion of the shaft. The seal member includes a first seal member made of fluoroplastic and a second seal member made of fluorine-containing rubber. The actuator, the second seal member, the first seal member, and the EGR passage are arranged in this order along the axial direction of the shaft. The housing includes a chamber accommodating the second bearing and is insulated from the outside. The second bearing is made of PPS plastic or PPS resin with a fluoroplastic added thereto.

[0016] In a case where the shaft has a receiving mechanism formed at both ends, the second bearing corresponds to an additional bearing. The second bearing is made of PPS (polyphenylene sulfide) plastic material with a fluorine plastic material added. The PPS plastic material is a plastic material that has excellent heat resistance and acid resistance, and the fluorine plastic material is a plastic material that has excellent sliding properties.

[0017] Therefore, the PPS plastic material to which the fluoroplastic material has been added has excellent heat resistance, acid resistance and lubricity.

[0018] The second bearing will not corrode even when exposed to a strong acid environment. Even if the EGR device shaft is configured with a receiving mechanism formed at both ends, the second bearing, which is equivalent to an auxiliary bearing, can be prevented from corroding. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a local cross-sectional view of an EGR device. Fig. Figure 2A is a plan view of a second bearing. Fig. Figure 2B is a front view of the second bearing. Fig. 2C is a bottom view of the second bearing. EMBODIMENTS OF THE INVENTION

[0019] An embodiment of the present application will be described below. (Configuration of the embodiment)

[0020] Referring to Fig. 1, a configuration of an EGR device 1 according to an embodiment will be described.

[0021] The EGR device 1 circulates EGR gas from an exhaust passage to an intake passage of an engine mounted on a vehicle. The EGR device 1 is formed with a housing 2, a sensor housing 3, and the like, as explained below.

[0022] The housing 2 is made of metal, such as an aluminum alloy, by die-casting. An EGR passage 5 for circulating the EGR gas from the exhaust passage to the intake passage is formed in the housing 2.

[0023] The EGR gas exceeding a temperature of 200°C flows through the EGR passage 5. When the water content in the EGR gas is cooled down to condense, a strongly acidic condensate is generated in the EGR passage 5, which contains hydrochloric acid and sulfuric acid, which are formed from chlorine and sulfur contained in the fuel.

[0024] The housing 2 rotatably supports a shaft 7 via a bearing 8 and houses a motor 10 that drives the shaft 7. It should be noted that the shaft 7 is made of a heat-resistant material (stainless steel, heat-resistant steel, etc.) that exhibits excellent heat resistance. The shaft 7 is columnar and rotates around its axis. This means that the valve body 11 attached to the shaft 7 also rotates around the axis of the shaft 7.

[0025] The valve body 11 is connected to the shaft 7 via a plurality of bolts 12. The valve body 11 is a disc-shaped throttle valve that rotates together with the shaft 7 to adjust the flow passage cross-section of the EGR passage 5. It should be noted that both the valve body 11 and the bolts 12 are made of a heat-resistant material (stainless steel, heat-resistant steel, etc.) that has excellent heat resistance.

[0026] The rotational speed of the motor 10 is reduced by a combination of several gears, and an increased running torque is transmitted to the valve body 11. More specifically, the rotational speed of the motor 10 is reduced by a combination of a motor gear 14 that rotates with the motor 10, an intermediate gear 15 that is driven by the motor gear 14, and a final gear 16 that is driven by the intermediate gear 15. The shaft 7 rotates together with the final gear 16.

[0027] A combination of the motor 10 and the deceleration mechanism (the motor gear 14, the intermediate gear 15, the final gear 16), which decreases the speed output from the motor 10 and increases the running torque, corresponds to an actuator 20. The actuator 20 is connected to one end of the shaft 7 so as to drive the shaft 7.

[0028] Furthermore, the EGR device 1 is provided with a return spring 22 that positions the valve body 11 in only one valve closing direction. The return spring 22 is a single coil spring coiled in only one direction and arranged coaxially around the shaft 7.

[0029] The return spring 22 is arranged between the housing 2 and the final gear 16 to generate a spring force that positions the valve body 11 in the valve closing direction. That is, the final gear 16 and the like are rotated against the spring force of the return spring 22.

[0030] The sensor housing 3 is made of a plastic material and houses a sensor 24 that detects a rotation angle of the valve body 11. Note that the sensor 24 is a non-contact position sensor that detects an opening degree of the valve body 11 by detecting a rotation angle of the shaft 7. A flange of the housing 2 and a flange of the sensor housing 3 are connected via screws, thus unifying the body 2 and the sensor housing 3.

[0031] The bearing 8 includes a first bearing 25 supporting one end portion of the shaft 7 and a second bearing 26 supporting the other end portion of the shaft 7. The first bearing 25 is a ball bearing received by the housing 2. The first bearing 25 includes a sealing element 27 made of a fluorine-containing rubber 27a that prevents gas from flowing into the actuator 30 from the EGR passage 5.

[0032] Furthermore, a shaft seal 28 is arranged between the first bearing 25 and the EGR passage 5. The shaft seal 28 includes a sealing element 27 made of a fluoroplastic 27b, which prevents condensate from flowing into the actuator 20 from the EGR passage 5.

[0033] The sealing element 27, which prevents the gas and condensate from flowing into the actuator 20, is positioned at an end portion of the shaft 7.

[0034] The second bearing 26 is a plain bearing 26 recessed through the housing 2 and is made of PPS plastic material with fluoroplastic added. It should be noted that PPS plastic material is a plastic material that has excellent heat resistance and acid resistance. The addition of fluoroplastic material also ensures its sliding properties.

[0035] If the content of the fluoroplastic material in the PPS resin material is less than 35%, the sliding performance becomes insufficient, so that fretting wear of the second bearing 26 increases. Therefore, it is preferable that the content of the fluoroplastic material in the PPS resin material be not less than 35%. The second bearing 26 is press-fitted into a chamber 30. The chamber 30 is closed by a shutter 32, so that the chamber 30 is isolated from the outside.

[0036] As in Fig. 2A, Fig. 2B and Fig. 2C, the second bearing 26 is a cylinder having a gap 33 inclined relative to an axial direction so as to compensate for a difference in its linear expansion.

[0037] It should be noted that the gap 33 is inclined relative to the axial direction to prevent there from being a region where the shaft 7 has no contact surface in the axial direction, which would result in an increase in resistance when the shaft 7 slides.

[0038] Furthermore, since the second bearing 26 is made of a plastic material, the second bearing 26 can be formed by conventional injection molding, whereby its degree of design freedom is also high. (Advantage of the embodiment)

[0039] According to the present embodiment, the EGR device 1 includes the bearing 8, which includes the first bearing 25 supporting one end portion of the shaft 7 and the second bearing 26 supporting the other end portion of the shaft 7. Furthermore, the sealing member 27, which prevents fluid from flowing into the actuator 20, is disposed at one end portion of the shaft 7, and the housing 2 includes the chamber 30 that houses the second bearing 26 and is insulated from the outside. The second bearing 26 is made of a PPS resin material to which fluoroplastics material is added.

[0040] In a case where the shaft has a receiving mechanism at both ends or a both-end receiving mechanism, the second bearing 26 corresponds to an additional bearing. Since the second bearing 26 is formed of PPS resin material with fluoroplastic material added, the second bearing 26 does not corrode even when exposed to a strong acid environment. Even if the shaft 7 of the EGR device 1 is configured to have a receiving mechanism at both ends, the second bearing 26, which corresponds to an additional bearing, can be prevented from corroding.

[0041] Since the second bearing 26 is a mass component, its effect will not disappear due to abrasion or peeling unlike a coating agent.

[0042] The second bearing 26 is press-fitted into the chamber 39. The chamber 30 is closed by the closure 32, so that the chamber 30 is insulated from the outside. Therefore, gas and condensate do not escape from the housing 2.

[0043] The shaft seal 28 is arranged between the first bearing 25 and the EGR passage 5. The shaft seal 28 includes the sealing element 27 made of fluororesin 27b, which prevents condensate from flowing into the actuator 20 from the EGR passage 5. By using fluororesin 27b as the sealing element 27, which prevents condensate from flowing into the actuator 20 from the EGR passage 5, penetration of condensate can be prevented more reliably than in the case of using a component made of rubber, which swells due to the condensate, thus deteriorating its sealing efficiency.

[0044] The first bearing 25 is a ball bearing supported by the housing 2. The first bearing 25 includes the sealing element 27 made of a fluorine-containing rubber 27a, which prevents gas from flowing from the EGR passage 5 into the actuator 30. By using the fluoroplastic 27a as the sealing element 27, gas from which condensation water is generated can be reliably prevented from flowing into the actuator 20.

[0045] Therefore, according to the present embodiment, after the condensate is removed by the shaft seal 28, the fluorine-containing rubber of the ball bearing can prevent the gas from flowing into the actuator 20. (Modification)

[0046] The present application is intended to cover various modifications and equivalent arrangements.

[0047] According to the above embodiment, for example, although the second bearing 26 is a plain bearing, the second bearing 26 may be a roller bearing such as a ball bearing or a needle bearing.

Claims

[1] EGR device, comprising: a housing (2) defining an EGR passage (5) through which an EGR gas flows; a shaft (7) which is rotatably supported by the housing (2) via a bearing (8); a valve body (11) connected to the shaft (7) so as to adjust a flow passage area of ​​the EGR passage (5) by rotating together with the shaft (7); and an actuator (20) connected to an end portion of the shaft (7) to drive the shaft (7), wherein the bearing (8) comprises a first bearing (25) supporting one end portion of the shaft (7) and a second bearing (26) supporting the other end portion of the shaft (7); Sealing elements (27) are arranged on one end portion of the shaft (7) to prevent the fluid from flowing into the actuator (20); the sealing elements (27) comprise a first sealing element (27b) made of fluoroplastic and a second sealing element (27a) made of a fluorine-containing rubber; the actuator (20), the second sealing element (27a), the first sealing element (27b) and the EGR passage (5) are arranged in this order along the axial direction of the shaft; the housing (2) has a chamber (30) accommodating the second bearing (26) which is insulated from the outside; and the second bearing (26) is made of a PPS plastic material to which a fluoroplastic is added. [2] The EGR device according to claim 1, wherein the second sealing member (27a) is provided on the first bearing (25). [3] EGR device according to claim 2, further comprising: a shaft seal (28) provided between the EGR passage (5) and the first bearing (25), wherein the first sealing element (27b) is provided in the shaft seal (28). [4] The EGR device according to claim 3, wherein the second seal member (27a) has a plate-shaped portion, is in contact with a lateral surface of the shaft at its radially inner periphery, and is in contact with an inner periphery of an annular space accommodating the first bearing (25) at its radially outer periphery. [5] The EGR device according to claim 3 or 4, wherein the first sealing member (27b) includes a radially outer portion having a plate shape and a radially inner portion having a tubular shape. [6] EGR device according to claim 5, wherein the shaft seal (28) includes a large diameter member having a cup shape and a small diameter member having a cup shape; the small diameter element is received in the large diameter element and is placed on a radially inner side of the large diameter element; and the first sealing element (27b) is located along the axial direction between the small diameter element and the large diameter element. [7] The EGR device according to claim 6, wherein the radially inner portion is located between the shaft and the small diameter member in a radial direction. [8] The EGR device according to claim 1, wherein the radially inner portion protrudes toward the EGR passage.

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