JP2022053011A - EGR device for internal combustion engine - Google Patents

Abstract

To improve heat resistance of a valve seat.SOLUTION: An EGR device 10 recirculates part of an exhaust gas 9 in an exhaust passage 7 to an intake passage 5 via an EGR passage 12 communicating the intake passage 5 and the exhaust passage 7 of an internal combustion engine with each other. The EGR device 10 includes a valve housing 11, a valve seat 19 and an EGR valve 31. The valve housing 11 is formed of a material mainly composed of aluminum, and includes the EGR passage 12. The valve seat 19 has an annular shape and is disposed on an inner wall surface 17 around the EGR passage 12 of the valve housing 11. The EGR valve 31 includes a shaft 32 and a valve body 33, and is displaced in an axial direction of the shaft 32. Along with the displacement, the valve body 33 comes into contact with/separates from the valve seat 19 to open/close the EGR passage 12. On the inner wall surface 17, a cladding layer is formed through laser cladding so as to constitute the valve seat 19.SELECTED DRAWING: Figure 1

Description

The present invention relates to an EGR device for an internal combustion engine.

An EGR device is known that recirculates a part of the exhaust gas in the exhaust gas passage to the intake passage through an exhaust gas recirculation (EGR) passage that connects the intake passage and the exhaust passage of the internal combustion engine.
The EGR device includes a valve housing, a valve seat and an EGR valve. The valve housing is made of a material containing aluminum as a main component and has the above EGR passage. The valve seat forms an annular shape and is placed on the inner wall surface around the EGR aisle in the valve housing. The EGR valve comprises a shaft and a valve body disposed on the shaft and is displaced in the axial direction of the shaft. With the above displacement, the valve body separates and contacts the valve seat to open and close the EGR passage. The opening and closing of the EGR valve changes the opening degree to adjust the flow rate of the exhaust gas flowing through the EGR passage.

The valve seat is generally made of a sintered material, and the valve seat is fixed to the valve housing by press fitting on the inner wall surface (see, for example, Patent Document 1).

JP-A-2015-110912

However, in the above-mentioned conventional EGR device, when high-temperature exhaust flows through the EGR passage and the components of the EGR device are exposed to the high-temperature exhaust, the valve seat becomes hot, so that there is a problem in heat resistance.

An EGR device for an internal combustion engine that solves the above problems is an EGR device for an internal combustion engine that recirculates a part of the exhaust gas in the exhaust passage to the intake passage through an EGR passage that connects the intake passage and the exhaust passage of the internal combustion engine. In the apparatus, a valve housing formed of a material containing aluminum as a main component and having the EGR passage, an annular valve seat arranged on an inner wall surface around the EGR passage in the valve housing, a shaft and the shaft. A valve having a valve body arranged above and displaced in the axial direction of the shaft, and an EGR valve that opens and closes the EGR passage by separating and contacting the valve body with the valve seat due to the displacement. A clad layer is formed on the inner wall surface of the valve housing by laser cladding to form the valve seat.

According to the above configuration, the laser clad forms a clad layer on the inner wall surface of the valve housing. That is, the metal powder supplied to the inner wall surface of the valve housing where the valve seat is to be formed is melted by the laser beam. After the molten metal powder is welded to the planned formation site, it is cooled and solidified. An annular clad layer (building layer) is formed on the inner wall surface of the valve housing, and the valve seat is formed by this clad layer.

In the case of the laser clad, the molten metal powder enters the minute uneven portion at the planned formation portion of the valve housing and is welded, or is in close contact with the uneven portion at the boundary portion with the planned formation portion. Alloy. Therefore, the contact area between the inner wall surface of the valve housing and the boundary portion between the valve seat is larger than that when the sintered valve seat is press-fitted into the valve housing. Along with this, the heat of the valve seat is easily dissipated to the valve housing through the boundary portion where the contact area is increased. Even if high-temperature exhaust flows through the EGR passage and the components of the EGR device are exposed to high-temperature exhaust, the valve seat does not easily reach a high temperature, and the heat resistance of the valve seat is improved.

FIG. 3 is a partial cross-sectional view of an EGR device of an internal combustion engine according to an embodiment. A partial cross-sectional view showing the valve seat and its peripheral portion in FIG. 1 in an enlarged manner. FIG. 2 is a partial cross-sectional view showing an enlarged portion X in FIG.

Hereinafter, an embodiment of the EGR device of an internal combustion engine will be described with reference to the drawings.
As shown in FIG. 1, the EGR device 10 of the present embodiment has an exhaust 9 in the exhaust passage 7 via an EGR passage 12 communicating the intake passage 5 and the exhaust passage 7 of an internal combustion engine such as a gasoline engine or a diesel engine. It is a device that recirculates a part of the exhaust gas to the intake passage 5. The EGR device 10 is mounted on the internal combustion engine for the purpose of reducing nitrogen oxides (NOx) contained in the exhaust gas 9 discharged from the internal combustion engine.

As shown in FIGS. 1 and 2, the EGR device 10 includes a valve housing 11, a valve seat 19, and an EGR valve 31.
The valve housing 11 has the EGR passage 12. The valve housing 11 is formed by using a material (aluminum or an aluminum alloy) containing aluminum as a main component. The upstream end 13 of the EGR passage 12 is open at the end surface 14 of the valve housing 11, and the downstream end 15 of the EGR passage 12 is open at the side surface 16 of the valve housing 11. The exhaust 9 flows into the inside of the valve housing 11 from the upstream end 13 and flows out of the valve housing 11 from the downstream end 15.

The valve seat 19 forms an annular shape and is arranged on the inner wall surface 17 around the EGR passage 12 in the valve housing 11. More specifically, on the inner wall surface 17 of the valve housing 11, an annular recess 18 surrounding a part of the EGR passage 12 in the flow direction of the exhaust 9 is formed at a portion where the valve seat 19 is planned to be formed. A build-up layer called a clad layer is formed in the recess 18 by laser clad (also referred to as a laser clad processing method) to form a valve seat 19. As shown in FIG. 3, the valve seat 19 has a convex curved surface 21.

At the time of laser cladding, metal powder is supplied to the recess 18. As the metal powder, for example, a material containing copper as a main component (copper or a copper alloy) is used. A laser beam is irradiated from the laser beam irradiating device toward the recess 18. This irradiation is performed while the bulb housing 11 and the laser beam irradiating device are moved relative to each other, for example, relatively rotated. The metal powder is melted by a laser beam. The molten metal powder is welded to the recess 18 and then cooled and solidified. An annular clad layer (building layer) is formed in the recess 18, and the valve seat 19 is formed by this clad layer.

As shown in FIGS. 1 and 2, the EGR valve 31 includes a shaft 32 and a disk-shaped valve body 33. The end of the shaft 32 is fitted to the center of the valve body 33. The valve body 33 is fixed to the shaft 32. As shown in FIG. 3, the outer peripheral portion of the valve body 33 has a convex curved surface 34 that swells toward the valve seat 19. The outer diameter of the valve body 33 is maximum at the upstream end of the exhaust 9 in the flow direction. The outer diameter becomes smaller toward the downstream side in the flow direction. The EGR valve 31 is supported by the valve housing 11 on the shaft 32. The EGR valve 31 is displaced in the axial direction (vertical direction in FIG. 1) of the shaft 32 by an actuator (not shown) attached to the valve housing 11. The displacement amount of the EGR valve 31 is changed according to the operating condition of the internal combustion engine. The EGR valve 31 changes the opening degree by separating and contacting the valve seat 19 with the valve main body 33 in accordance with the above displacement, and adjusts the flow rate of the exhaust gas 9 flowing through the EGR passage 12.

When the EGR valve 31 is displaced to the upstream side in the flow direction, the valve body 33 moves away from the valve seat 19 to the upstream side. Further, the EGR valve 31 is displaced to the downstream side, so that the valve body 33 approaches the valve seat 19. The valve body 33 closes the EGR passage 12 by coming into contact with the curved surface 21 of the valve seat 19 at the curved surface 34.

Further, in the present embodiment, the curvature of the curved surface 21 of the valve seat 19 at the contact portion of the valve body 33 with the curved surface 34 is smaller than the curvature of the curved surface 34 with the curved surface 21. A curved surface 21 is formed on the surface. In other words, the curved surface 21 is formed so that the radius of curvature R1 at the portion of the curved surface 21 in contact with the curved surface 34 is larger than the radius of curvature R2 at the portion of the curved surface 34 in contact with the curved surface 21. There is. This formation may be performed only by the laser clad, or may be performed by the laser clad and the subsequent processing.

Next, the operation of the present embodiment configured as described above will be described. In addition, the effects caused by the action will also be described.
In the case of the laser clad, the molten metal powder enters the minute uneven portion on the bottom surface of the recess 18 and is welded, or is alloyed in a state of being in close contact with the uneven portion at the boundary portion with the recess 18. .. FIG. 3 shows an example in which the alloy layer 22 is formed at the boundary portion between the recess 18 and the valve seat 19.

Therefore, the contact area between the recess 18 and the valve seat 19 at the boundary portion is larger than that when the sintered valve seat is press-fitted into the valve housing (Patent Document 1 corresponds to this). Along with this, the heat of the valve seat 19 is easily dissipated to the valve housing 11 through the boundary portion where the contact area is increased. Even if the high-temperature exhaust 9 flows through the EGR passage 12 and the components of the EGR device 10 are exposed to the high-temperature exhaust 9, the valve seat 19 is suppressed from becoming hot and the heat resistance of the valve seat 19 is improved. Can be done.

By the way, when the EGR passage 12 is closed by the EGR valve 31, the valve body 33 comes into contact with the entire circumference of the valve seat 19 as shown in FIG. At the contact point, the gap between the valve body 33 and the valve seat 19 becomes zero, and the exhaust 9 is restricted from flowing between the valve body 33 and the valve seat 19. It is unlikely that the output of the internal combustion engine will decrease or the exhaust emission will deteriorate due to the leakage of the exhaust 9 when the EGR valve 31 is fully closed.

In particular, in the present embodiment, the curvature of the curved surface 21 at the contact portion with the curved surface 34 is smaller than the curvature of the curved surface 34 at the contact portion with the curved surface 21. Therefore, when the EGR valve 31 is fully closed, the contact area of the valve body 33 with respect to the valve seat 19 is smaller than that in the case where both curvatures are the same. Along with this, the surface pressure at the contact point of the valve body 33 with respect to the valve seat 19 increases. As a result, the leakage of the exhaust 9 when the EGR valve 31 is fully closed can be effectively suppressed. In other words, the amount of leakage can be reduced.

According to this embodiment, the following effects can be obtained in addition to the above.
-As described above, since the surface pressure of the valve body 33 with respect to the valve seat 19 is high when the EGR valve 31 is fully closed, the valve body 33 is in contact with the valve seat 19 and is not slippery with respect to the valve seat 19. , Easy to position in place.

It should be noted that the above embodiment can also be implemented as a modified example in which this is modified as follows. The above embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.

Contrary to the above embodiment, the EGR valve 31 is displaced to the upstream side in the flow direction of the exhaust 9, so that the valve body 33 approaches the valve seat 19 and is displaced to the downstream side, so that the valve body 33 is displaced. It may be away from the valve seat 19.

The curved surface 21 of the valve seat 19 may be composed of only curved portions that are curved with a single curvature, or may be composed of a plurality of curved portions that are curved with different curvatures from each other. The same applies to the curved surface 34 of the valve body 33.

The curvature of the curved surface 21 in contact with the curved surface 34 may be set to be larger than the curvature of the curved surface 34 in contact with the curved surface 21. Also in this case, the effect of suppressing the leakage of the exhaust gas 9 can be obtained as in the above embodiment.

When the leakage of the exhaust 9 when the EGR valve 31 is fully closed is tolerably small, the curvature of the curved surface 21 at the contact portion with the curved surface 34 is the curvature of the curved surface 34 at the contact portion with the curved surface 21. It may be set to be the same as.

5 ... Intake passage 7 ... Exhaust passage 9 ... Exhaust 10 ... EGR device 11 ... Valve housing 12 ... EGR passage 17 ... Inner wall surface 19 ... Valve seat 31 ... EGR valve 32 ... Shaft 33 ... Valve body

Claims (1)

In an EGR device of an internal combustion engine that recirculates a part of exhaust gas in the exhaust passage to the intake passage through an EGR passage that connects the intake passage and the exhaust passage of the internal combustion engine.
A valve housing formed of a material containing aluminum as a main component and having the EGR passage,
An annular valve seat disposed on the inner wall surface around the EGR aisle in the valve housing,
It is a valve that includes a shaft and a valve body arranged on the shaft and is displaced in the axial direction of the shaft. The EGR passage is caused by the valve body separating and contacting the valve seat with the displacement. An EGR device for an internal combustion engine, comprising an EGR valve that opens and closes the valve housing, and a clad layer is formed on the inner wall surface of the valve housing by a laser cladding to form the valve seat.

Images