JPH0634158U - Exhaust gas recirculation system for engine - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent oil from dripping from the edge of the return pipe insertion hole formed in the intake passage wall and mixing into the intake air. [Structure] An exhaust gas recirculation device for an engine, in which recirculation exhaust gas is introduced into intake air from a recirculation pipe 4 inserted into an insertion hole 2 bored in an intake passage wall of an intake system of a surge tank 1 or the like. A tapered surface 8 is formed at the end of the intake hole 2 on the intake passage side, and oil or the like flowing around the insertion hole 4 along the inner wall surface of the intake passage is transmitted along the tapered surface 8 to the inner peripheral surface of the insertion hole 2. To prevent dripping from the edge portion of the insertion hole 2 onto the reflux pipe 4.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an exhaust gas recirculation system for an engine equipped with a recirculation pipe for introducing recirculated exhaust gas into intake air.

[0002]

[Prior art]

 In an exhaust gas recirculation (hereinafter referred to as EGR) device that aims to reduce NOx in exhaust gas by recirculating a part of exhaust gas into intake air, a recirculation pipe is installed to introduce recirculation exhaust gas into intake air. Those inserted into the intake passage are disclosed in Japanese Utility Model Laid-Open No. 61-66664, Japanese Utility Model Laid-Open No. 62-135862, Japanese Utility Model Laid-Open No. 3-112561 and the like.

As such an EGR device, as shown in FIG. 3, for example, an insertion hole 22 is formed through a wall of a surge tank 21 that constitutes an intake passage, and a mounting seat 23 is formed on an outer surface thereof. A flange 25 is fixed to the base end of the reflux pipe 24 to be inserted by welding 26, the flange 25 is superposed on the mounting seat 23 via a gasket 27, and the outer surface of the flange 25 is attached to the EGR valve 30 via a gasket 28. It is known that the mounting flange 29 is superposed, and the mounting flange 29 of the EGR valve 30 and the flange 25 at the base end of the reflux pipe 24 are fastened and fixed to the mounting seat 23 with the mounting bolt 31.

[0004]

[Problems to be solved by the device]

 However, in the above configuration, oil or the like flowing along the inner wall surface of the surge tank 21 drops onto the return pipe 24 from the edge of the end of the insertion hole 22, and collects on the outer peripheral surface of the return pipe 24 to suck the intake air. There is a problem in that the effect of projecting the return pipe 24 into the intake flow path is not sufficiently exerted because it is scattered and mixed in.

In view of the above conventional problems, the present invention prevents exhaust gas recirculation from an engine in which oil is prevented from dripping from the edge portion of the recirculation pipe insertion hole formed in the intake passage wall and mixing into the intake air. The purpose is to provide a device.

[0006]

[Means for Solving the Problems]

 This invention is an engine exhaust gas recirculation system in which recirculation exhaust gas is introduced into intake air from a return pipe inserted into an insertion hole drilled in the intake passage wall of the intake system, at the end of the insertion hole on the intake passage side. It is characterized in that a tapered surface or a curved surface is formed.

[0007]

[Action]

 According to the present invention, since the tapered surface or the curved surface is formed at the end portion of the insertion hole for inserting the return pipe on the intake passage side, the oil flowing around the insertion hole along the inner wall surface of the intake passage, etc. Is guided along the inner peripheral surface of the insertion hole along the tapered surface or curved surface, and flows along this inner peripheral surface. It can be surely prevented from being mixed.

[0008]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1 and FIG. 2, reference numeral 1 is a surge tank of an intake system, in which an insertion hole 2 and a mounting seat 3 are formed in a wall at a proper place for introducing the recirculated exhaust gas. Reference numeral 4 denotes a recirculation pipe that is inserted into the insertion hole 2 to disperse and mix the recirculated exhaust gas into the intake air. A mounting flange 5 provided at the base end is mounted on the mounting seat 3, and the tip is It opens in the intake passage in the surge tank 2. Reference numeral 10 is an EGR valve arranged outside the flange 5 so as to be connected to the recirculation pipe 4, and 11 is an exhaust gas recirculation pipe connecting an exhaust pipe (not shown) and the EGR valve 10. Is.

In FIG. 1, the flange 5 presses the annular bulging ridge 6 and the base end, which are formed at a position spaced from the base end of the reflux pipe 4 to a proper distance corresponding to the thickness of the flange 5, and the base end. It is connected to the return pipe 4 by being sandwiched between the open enlarged portion 7. In the manufacturing process, the flange 5 having the tapered surface 5a formed on the outer surface of the inner peripheral portion is fitted to the base portion of the reflux pipe 4 having the bulging ridge 6, and the base end of the reflux pipe 4 is placed along the tapered surface 5a. You just have to crimp it. On the other hand, a taper surface 8 is formed at the end of the insertion hole 2 inside the surge tank 1. The tapered surface 8 is formed during casting of the surge tank 1 and is as-cast. A recess 9 is formed at the outer end of the insertion hole 2 into which the bulging ridge 6 is inserted with a margin, and the inner diameter of the insertion hole 2 is set smaller than the outer diameter of the bulging ridge 6.

The reflux pipe 4 and the EGR valve 10 are mounted by inserting the reflux pipe 4 into the insertion hole 2, superposing the flange 5 of the reflux pipe 4 on the mounting seat 3 via the gasket 12, and further attaching it to the outer surface of the flange 5. The mounting flange 14 of the EGR valve 10 is superposed via the gasket 13, and the mounting flange 14 of the EGR valve 10 and the flange 5 at the base end of the reflux pipe 4 are fastened and fixed to the mounting seat 3 by the mounting bolt 15.

In the above configuration, since the tapered surface 8 is formed at the inner end of the surge tank 1 of the insertion hole 2 into which the return pipe 4 is inserted, the tapered surface 8 is formed along the inner wall surface of the surge tank 1 around the insertion hole 2. The oil or the like that has flowed along the tapered surface 8 is guided to the inner peripheral surface of the insertion hole 2 and flows along this inner peripheral surface, and from the edge portion of the insertion hole 2 onto the return pipe 4. Oil, etc., will not be mixed into the intake air by dropping. Therefore, it is possible to greatly improve the oil penetration from the inner wall surface of the surge tank 1 into the intake air.

Since the inner peripheral portion of the flange 5 is sandwiched between the bulging projection 6 and the tapered enlarged portion 7 at the base portion of the reflux pipe 4, the reflux pipe 4 and the flange 5 are joined, It is not necessary to secure a welding width on the outer peripheral portion of the reflux pipe 4 as in the case where the flange 5 is joined to the base portion of the reflux pipe 4 by welding, and therefore, depending on the difference between the welding width and the height of the bulging ridge 6. As a result, the diameter of the flange 5 can be reduced, and small gaskets 12, 13 and EGR valve 10 can be used. Since the mounting seat 3, the gaskets 8, 9 and the EGR valve 10 can be downsized in this way, the degree of freedom in mounting design can be increased and the weight can be reduced.

Further, in the case of welding, if a thin-walled pipe is used as the reflux pipe 4, it may be damaged without heat treatment due to the heat effect. However, since welding is not performed in this embodiment, the thin-walled pipe is used to reduce the weight and improve the durability. Reliable.

Further, a recess 9 into which the bulging ridge 6 is inserted is provided at the outer end of the insertion hole 2, and the inner diameter of the insertion hole 2 is set to a diameter through which the bulging ridge 6 cannot pass, so that engine vibration and Even if the enlarged portion 7 is loosely engaged with the inner peripheral portion of the flange 5 due to thermal stress caused by the exhaust gas, the return pipe 4 does not drop into the surge tank 1.

Further, the bulging ridge 6 and the enlarged portion 7 can be easily formed by plastic working of the reflux pipe 4 with a small number of man-hours, and a welding work and a spatter removal process accompanied therewith are not required. The quality is improved because there is less waste, and it can be manufactured at low cost, and there is no risk of spatter remaining.

In the above embodiment, the tapered surface 8 is formed at the inner end of the insertion hole 2. However, since the oil or the like transmitted to the inner wall surface does not have to drip from the edge, it has an arc shape or the like. It may be formed on the curved surface. Further, although an example in which the return pipe 4 is arranged in the surge tank 1 is shown, the position of the return pipe 4 can be arranged at any appropriate position of the intake system such as the intake manifold.

[0018]

[Effect of device]

 According to the exhaust gas recirculation system for an engine of the present invention, the insertion hole for inserting the recirculation pipe is formed with a tapered surface or a curved surface at the end on the intake passage side. The oil, etc. that has flowed into the pipe is guided along the inner peripheral surface of the insertion hole along the tapered surface or curved surface, and flows along this inner peripheral surface, dripping from the edge of the insertion hole onto the reflux pipe. As a result, it is possible to reliably prevent oil and the like from mixing into the intake air, and it is possible to greatly improve the intrusion of oil and the like from the inner wall surface of the intake passage.

[Brief description of drawings]

FIG. 1 is a sectional view of a recirculation pipe arrangement portion in an embodiment of an exhaust gas recirculation device for an engine of the present invention.

FIG. 2 is an EGR for a surge tank in the same embodiment.
It is a fragmentary sectional view showing the attachment state of a valve and a reflux pipe.

FIG. 3 is a cross-sectional view of a recirculation pipe arrangement portion in an exhaust gas recirculation device for a conventional engine.

[Explanation of symbols]

 1 Surge tank 2 Insertion hole 4 Reflux pipe 8 Tapered surface

Claims (1)

[Scope of utility model registration request] 1. An exhaust gas recirculation system for an engine, wherein recirculation exhaust gas is introduced into intake air from a recirculation pipe inserted into an insertion hole formed in an intake passage wall of an intake system,
An exhaust gas recirculation device for an engine, wherein a tapered surface or a curved surface is formed at an end of the insertion hole on the intake passage side.