JP7633052B2 - Exhaust Pipe Fittings - Google Patents

Description

The present invention relates to an exhaust pipe joint that connects an upstream exhaust pipe and a downstream exhaust pipe that constitute an exhaust pipe that discharges exhaust gas from an engine.

Conventionally, it has been known to install an expandable bellows tube in an exhaust pipe that discharges engine exhaust gas, for example, to absorb thermal deformation (thermal expansion and contraction) of the engine.

For example, Patent Document 1 discloses an exhaust pipe structure that includes a front bank exhaust pipe connected to the exhaust manifold of the front bank of a V-type engine that is arranged transversely at the front of the vehicle, and a rear bank exhaust pipe that connects the exhaust manifold of the rear bank and the front bank exhaust pipe. An elastically deformable flexible pipe is attached to the front bank exhaust pipe upstream of the junction where the front bank exhaust pipe joins the rear bank exhaust pipe.

The flexible pipe has a cylindrical bellows structure with a bellows-like structure covered with a cylindrical cover. The bellows can expand and contract in the axial direction and bend. In addition, the upstream end of the bellows is welded and fixed over the entire circumference of the upstream exhaust pipe that constitutes the front bank exhaust pipe, and the downstream end is welded and fixed over the entire circumference of the downstream exhaust pipe that constitutes the front bank exhaust pipe.

JP 2020-159316 A

However, as mentioned above, if the upstream exhaust pipe and downstream exhaust pipe are covered with a bellows pipe and both ends of the bellows pipe are welded in place around their entire circumference, the mass and costs will increase. Also, the bellows pipe must be large to absorb relatively large thermal deformation (thermal expansion and contraction), which not only increases the mass and cost but also may reduce the freedom of exhaust system layout. For this reason, there has been a demand for smaller, lighter joints while maintaining the ability to absorb thermal deformation and seal exhaust gas.

The objective of the present invention is to provide an exhaust pipe joint that can be made smaller and lighter while maintaining its ability to absorb thermal deformation and seal exhaust gas.

The exhaust pipe joint according to one embodiment of the present invention is characterized by comprising an upstream exhaust pipe whose upstream end is connected to the exhaust port of the engine, a downstream exhaust pipe whose upstream end overlaps with the upstream exhaust pipe in the axial direction and is loosely fitted in the upstream exhaust pipe so as to be freely slidable, a gasket that is axially slidably disposed in the gap between the upstream exhaust pipe and the downstream exhaust pipe in the overlapping region of the upstream exhaust pipe and seals the gap between the upstream exhaust pipe and the downstream exhaust pipe, and an elastic member that is axially slidably disposed alongside the gasket in the gap between the upstream exhaust pipe and the downstream exhaust pipe in the overlapping region of the upstream exhaust pipe and the downstream exhaust pipe, absorbing axial displacement of the upstream exhaust pipe and the downstream exhaust pipe.

The present invention makes it possible to reduce the size and weight of the joint while maintaining its ability to absorb thermal deformation and seal against exhaust gas.

1 is a diagram showing an overall configuration of an engine equipped with an exhaust pipe to which an exhaust pipe joint according to an embodiment is applied; FIG. 2 is a diagram showing the layout of an exhaust pipe (exhaust system layout) to which an exhaust pipe joint according to an embodiment is applied. FIG. 2 is a cross-sectional view showing a configuration of an exhaust pipe joint (before assembly) according to the embodiment. FIG. 2 is a cross-sectional view showing the configuration of the exhaust pipe joint (after assembly) according to the embodiment.

Below, a preferred embodiment of the present invention will be described in detail with reference to the drawings. Note that in the drawings, the same reference numerals will be used for the same or corresponding parts. In addition, in each drawing, the same elements will be given the same reference numerals, and duplicate explanations will be omitted.

First, an exhaust pipe joint 1820 according to an embodiment will be described with reference to Figures 1 to 4. Figure 1 is a diagram showing the overall configuration of an engine 10 equipped with an exhaust pipe 18 to which an exhaust pipe joint 1820 is applied. Figure 2 is a diagram showing the layout (exhaust system layout) of an exhaust pipe 18 to which an exhaust pipe joint 1820 is applied. Figure 3 is a cross-sectional view showing the configuration of the exhaust pipe joint 1820 (before assembly to the engine). Figure 4 is a cross-sectional view showing the configuration of the exhaust pipe joint 1820 (after assembly to the engine).

The engine 10 is, for example, a horizontally opposed four-cylinder engine. The engine 10 is an in-cylinder injection engine that directly injects fuel into the cylinders. In the engine 10, air taken in from an air cleaner 16 is throttled by an electronically controlled throttle valve (hereinafter, simply referred to as a "throttle valve") 13 provided in an intake pipe 15, passes through an intake manifold 11, and is taken into each cylinder formed in the engine 10. Here, the amount of air taken in from the air cleaner 16 is detected by an air flow meter 14 arranged between the air cleaner 16 and the throttle valve 13. In addition, a vacuum sensor 30 that detects the pressure in the intake manifold 11 (intake manifold pressure) is arranged inside a collector section (surge tank) that constitutes the intake manifold 11. Furthermore, a throttle opening sensor 31 that detects the opening of the throttle valve 13 is arranged in the throttle valve 13.

The cylinder head has an intake port 22 and an exhaust port 23 for each cylinder (only one bank is shown in Figure 1). Each intake port 22 and exhaust port 23 is provided with an intake valve 24 and an exhaust valve 25 that open and close the intake port 22 and exhaust port 23, respectively.

Each cylinder of the engine 10 is fitted with an injector 12 that injects fuel into the cylinder. The injector 12 injects fuel pressurized by a high-pressure fuel pump (not shown) directly into the combustion chamber of each cylinder.

The cylinder head of each cylinder is also fitted with a spark plug 17 that ignites the mixture, and an igniter-equipped coil 21 that applies high voltage to the spark plug 17. In each cylinder of the engine 10, the mixture of intake air and fuel injected by the injector 12 is ignited by the spark plug 17 and combusted. Exhaust gas after combustion is discharged through an exhaust pipe 18.

The exhaust pipe 18 is provided with an exhaust gas recirculation device (hereinafter referred to as "EGR (Exhaust Gas Recirculation) device") 40 that recirculates (returns) a portion of the exhaust gas discharged from the engine 10 to the intake manifold 11 (intake system) of the engine 10. The EGR device 40 has an EGR pipe 41 that connects the exhaust pipe 18 (downstream of the collection section 185) of the engine 10 with the intake manifold 11, and an EGR valve 42 that is installed on the EGR pipe 41 and adjusts the exhaust gas recirculation amount (EGR amount).

The opening degree of the EGR valve 42 is controlled (duty controlled) by an electronic control unit (hereinafter referred to as "ECU") 50. That is, the ECU 50 controls the amount of exhaust gas recirculated (recirculated) by adjusting the opening and closing amount of the EGR valve 42 according to the operating state of the engine 10. Note that the EGR valve 42 may be of a vacuum type or one driven by a stepping motor or the like.

Now, with reference to FIG. 2 as well, the layout of the exhaust system of the engine 10 will be described. A #1 exhaust pipe 181 is connected to the exhaust port 23 of the #1 cylinder. A #2 exhaust pipe 182 is connected to the exhaust port 23 of the #2 cylinder. Similarly, a #3 exhaust pipe 183 is connected to the exhaust port 23 of the #3 cylinder, and a #4 exhaust pipe 184 is connected to the exhaust port 23 of the #4 cylinder. Here, the explosion order (ignition order) of the engine 10 is the first cylinder (#1) - the third cylinder (#3) - the second cylinder (#2) - the fourth cylinder (#4), and the exhaust gas from each cylinder is discharged to the respective exhaust pipes 181-184 every 180° CA.

The #1 exhaust pipe 181 and the #2 exhaust pipe 182 are joined together, and the #3 exhaust pipe 183 and the #4 exhaust pipe 184 are joined together. Both are then further joined together downstream (at the joining section 185). In other words, the four #1 to #4 exhaust pipes 181 to 184 attached to each cylinder (cylinder #1 to cylinder #4) of the engine 10 are joined together at the joining section 185. A joining exhaust pipe 186 is connected to the joining section 185.

An exhaust purification catalyst (catalyst) 20 is installed in the exhaust pipe 186 (downstream of the collecting section 185). The exhaust purification catalyst 20 is a three-way catalyst that simultaneously oxidizes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas and reduces nitrogen oxides (NOx), thereby purifying harmful gas components in the exhaust gas into harmless carbon dioxide ( _CO2 ), water vapor ( _H2O ), and nitrogen ( _N2 ).

An air-fuel ratio sensor 19 is attached between the collection section 185 of the exhaust pipe 18 and the connection hole of the EGR pipe 41 (upstream of the exhaust purification catalyst 20) to output a signal corresponding to the oxygen concentration and unburned gas concentration in the exhaust gas (i.e., to detect the air-fuel ratio of the mixture). A linear air-fuel ratio sensor (LAF sensor) capable of linearly detecting the air-fuel ratio is used as the air-fuel ratio sensor 19.

For example, the #2 exhaust pipe 182 and the #4 exhaust pipe 184, which are connected (fastened) to the left bank (LH head) of the engine 10, are each fitted with a thermal exhaust pipe joint 1820 that mainly absorbs thermal deformation (thermal expansion and contraction) in the left-right direction of the engine 10. Note that the exhaust pipe joint 1820 of the #2 exhaust pipe 182 and the exhaust pipe joint 1820 of the #4 exhaust pipe 184 have the same configuration, so here, the exhaust pipe joint 1820 of the #2 exhaust pipe 182 will be used as an example for explanation.

The #2 exhaust pipe 182 is mainly composed of an upstream exhaust pipe 1821, a downstream exhaust pipe 1822, and an exhaust pipe joint 1820 that retractably connects the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822.

The upstream end of the upstream exhaust pipe 1821 is connected to the exhaust port 23 (corresponding to the exhaust port) of the engine 10.

3 and 4, the downstream exhaust pipe 1822 has an upstream end that overlaps with the upstream exhaust pipe 1821 in the axial direction (they overlap each other), and is loosely fitted in the upstream exhaust pipe 1821 so as to be freely slidable (slidable). In this embodiment, the diameter of the downstream exhaust pipe 1822 at the overlapping portion 1823 is set to be larger than the diameter of the upstream exhaust pipe 1821, and the downstream exhaust pipe 1822 is configured to cover the upstream exhaust pipe 1821.

The exhaust pipe joint 1820 is mainly composed of gaskets 1825 and 1826 and a coil spring 1827.

The gaskets 1825 and 1826 are divided into two parts along the axial direction: a first gasket 1825 located on the upstream side and a second gasket 1826 located on the downstream side. The first gasket 1825 and the second gasket 1826 are each formed in a substantially cylindrical (tubular) shape, and are disposed axially slidably (slidably) in the annular gap defined by the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 in the overlap region (overlap portion 1823) where the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 overlap each other.

The first gasket 1825 and the second gasket 1826 seal the annular gap between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 to prevent exhaust gas from leaking from the exhaust pipe joint 1820. In other words, the first gasket 1825 and the second gasket 1826 maintain airtightness between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822. The first gasket 1825 and the second gasket 1826 are preferably made of heat-resistant stainless steel (e.g., SUS310S) that can withstand the high temperatures of exhaust gas and maintain elasticity.

The coil spring 1827 (corresponding to the elastic member described in the claims) is disposed axially slidably (slidably) in the annular gap defined by the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 in the overlapping region (overlap portion 1823) where the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 overlap each other. The coil spring 1827 is disposed alongside the first gasket 1825 and the second gasket 1826. In this embodiment, the coil spring 1827 is disposed between the first gasket 1825 and the second gasket 1826.

The coil spring 1827 absorbs axial displacement (relative displacement) between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 caused by thermal deformation (thermal expansion and contraction) of the engine 10. The coil spring 1827 is preferably made of heat-resistant stainless steel (e.g., SUS310S) that can withstand the high temperatures of exhaust gas and maintain its elasticity.

As described above, the first gasket 1825, the second gasket 1826, and the coil spring 1827 are formed and arranged, so that one (upstream) end of the first gasket 1825 abuts against the inner surface of the upstream end (tapered portion) of the downstream exhaust pipe 1822. The other (downstream) end of the first gasket 1825 abuts against one (upstream) end of the coil spring 1827. One (upstream) end of the second gasket 1826 abuts against the other (downstream) end of the coil spring 1827. The other (downstream) end of the second gasket 1826 abuts against the outer surface of the downstream end (tapered portion) of the upstream exhaust pipe 1821.

More specifically, the downstream end (opening) of the upstream exhaust pipe 1821 is tapered so as to widen outward. On the other hand, the upstream end (opening) of the downstream exhaust pipe 1822 is tapered so as to narrow inward.

When viewed in a cross section along the axial direction, the first gasket 1825 is formed in a wedge shape with one end (upstream side) conforming to the tapered surface of the tapered portion of the downstream exhaust pipe 1822. In other words, the one end (upstream side) is cut at the same angle as the taper angle of the tapered portion so that it faces the tapered surface (inner surface) of the tapered portion of the downstream exhaust pipe 1822. When viewed in a cross section along the axial direction, the first gasket 1825 protrudes (curves) in an arc shape radially inward so that the axial center abuts against the outer circumferential surface of the upstream exhaust pipe 1821.

Similarly, when viewed in a cross section along the axial direction, the second gasket 1826 has the other (downstream) end formed in a wedge shape that conforms to the tapered surface of the tapered portion of the upstream exhaust pipe 1821. In other words, the other (downstream) end is cut at the same angle as the taper angle of the tapered portion so that it faces the tapered surface (outer surface) of the tapered portion of the upstream exhaust pipe 1821. Also, when viewed in a cross section along the axial direction, the second gasket 1826 protrudes (curves) in an arc shape radially outward so that the axial center portion abuts against the inner peripheral surface of the downstream exhaust pipe 1822.

As shown in FIG. 4, the exhaust pipe joint 1820 is assembled to the engine 10 with the coil spring 1827 in a moderately compressed state. Therefore, when the #2 exhaust pipe 182 is assembled to the engine 10, the coil spring 1827 exerts a biasing force on the first gasket 1825 and the second gasket 1826 in a direction (axial direction) that increases the overlap between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822.

By configuring as described above, that is, by disposing the first gasket 1825 and the second gasket 1826 axially slidably in the gap between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 in the area where the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 overlap (overlap portion 1823), the gap between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 is sealed.

In addition, in the area where the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 overlap (overlap portion 1823), a coil spring 1827 is disposed in the gap between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 so as to be freely slidable in the axial direction, thereby absorbing the axial displacement (relative displacement) between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822. This eliminates the need to use a bellows pipe.

As described above in detail, according to this embodiment, since it is not necessary to use a bellows tube, the exhaust pipe joint 1820 can be made smaller and lighter. In addition, since welding of the bellows tube is also not necessary, the exhaust pipe joint 1820 can be made lighter. Meanwhile, since the first gasket 1825 and the second gasket 1826 are arranged axially slidably in the gap between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 in the area where the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 overlap, the gap between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 can be sealed. In addition, in the region where the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 overlap, the coil spring 1827 is disposed in the gap between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 so as to be freely slidable in the axial direction, so that the axial displacement (relative displacement) between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822 can be absorbed. As a result, according to this embodiment, it is possible to reduce the size and weight of the joint while maintaining the ability to absorb thermal deformation and seal exhaust gas.

In addition, according to this embodiment, the downstream end (opening) of the upstream exhaust pipe 1821 is formed in a tapered shape so as to expand outward, and the upstream end (opening) of the downstream exhaust pipe 1822 is formed in a tapered shape so as to narrow inward. One (upstream) end of the first gasket 1825 is formed in a wedge shape along the tapered surface of the tapered portion of the downstream exhaust pipe 1822, and the other (downstream) end of the second gasket 1826 is formed in a wedge shape along the tapered surface of the tapered portion of the upstream exhaust pipe 1821. In addition, the axial center of the first gasket 1825 protrudes (curves) in an arc shape radially inward so as to abut against the outer circumferential surface of the upstream exhaust pipe 1821, and the axial center of the second gasket 1826 protrudes (curves) in an arc shape radially outward so as to abut against the inner circumferential surface of the downstream exhaust pipe 1822. This makes it possible to improve the ability to absorb thermal deformation and seal against exhaust gases.

In particular, according to this embodiment, the exhaust pipe joint 1820 is assembled to the engine 10 with the coil spring 1827 in a moderately compressed state. Therefore, the coil spring 1827 can absorb thermal deformation in the axial direction (left and right direction) within the range of elastic deformation. In addition, the coil spring 1827 applies a biasing force to the first gasket 1825 and the second gasket 1826 in a direction (axial direction) that expands the overlap between the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822. Therefore, the ends of the first gasket 1825 and the second gasket 1826 are pressed against the tapered portions of the upstream exhaust pipe 1821 and the downstream exhaust pipe 1822, and are bent within the range of elastic deformation, generating surface pressure at the curved portion (contact portion), thereby enabling sealing performance to be exhibited.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications are possible. For example, in the above embodiment, the present invention is applied to a horizontally opposed engine 10, but the present invention can also be applied to, for example, a V-type engine or an in-line engine. Furthermore, the number of cylinders in the engine is not limited to four, and the present invention can also be applied to an engine having, for example, six, eight, or more cylinders.

In the above embodiment, the exhaust pipe joint 1820 is applied to the #2 exhaust pipe 182 and #4 exhaust pipe 184 connected to the left bank (LH head) of the engine 10, but it may also be applied to the #1 exhaust pipe 181 and #3 exhaust pipe 183 connected to the right bank (RH head) of the engine 10.

In the above embodiment, the diameter of the downstream exhaust pipe 1822 at the overlap portion 1823 is set to be larger than the diameter of the upstream exhaust pipe 1821, and the downstream exhaust pipe 1822 is configured to cover the upstream exhaust pipe 1821. However, conversely, the diameter of the upstream exhaust pipe 1821 may be set to be larger than the diameter of the downstream exhaust pipe 1822, and the upstream exhaust pipe 1821 may be configured to cover the downstream exhaust pipe 1822.

In the above embodiment, the gasket is divided into first gasket 1825 and second gasket 1826, but the gasket may be one piece (not necessarily divided into two). In that case, the coil spring 1827 is disposed at one end of the gasket.

In the above embodiment, the downstream end of the upstream exhaust pipe 1821 is tapered so as to expand outward, and the upstream end of the downstream exhaust pipe 1822 is tapered so as to narrow inward. However, for example, the downstream end of the upstream exhaust pipe 1821 may be bent outward at a right angle, and the upstream end of the downstream exhaust pipe 1822 may be bent inward at a right angle.

In the above embodiment, the coil spring 1827 is made of heat-resistant stainless steel (e.g., SUS310S), but it may also be made of heat-resistant rubber, for example.

REFERENCE SIGNS LIST 10 Engine 11 Intake manifold 18 Exhaust pipe 181 #1 exhaust pipe 182 #2 exhaust pipe 1820 Exhaust pipe joint 1821 Upstream exhaust pipe 1822 Downstream exhaust pipe 1823 Overlap portion 1825, 1826 Gasket (first gasket, second gasket)
1827 coil spring 183 #3 exhaust pipe 184 #4 exhaust pipe 185 collecting section 186 exhaust collecting pipe 19 air-fuel ratio sensor 20 exhaust purification catalyst 22 intake port 23 exhaust port

Claims (4)

an upstream exhaust pipe having an upstream end connected to an exhaust port of the engine;
a downstream exhaust pipe whose upstream end overlaps with the upstream exhaust pipe in the axial direction and which is loosely fitted in the upstream exhaust pipe so as to be freely slidable therein;
a gasket that is axially slidably disposed in a gap between the upstream exhaust pipe and the downstream exhaust pipe in a region where the upstream exhaust pipe and the downstream exhaust pipe overlap each other, and that seals the gap between the upstream exhaust pipe and the downstream exhaust pipe;
an elastic member that is arranged alongside the gasket and is slidable in the axial direction in a gap between the upstream exhaust pipe and the downstream exhaust pipe in a region where the upstream exhaust pipe and the downstream exhaust pipe overlap, and that absorbs axial displacement of the upstream exhaust pipe and the downstream exhaust pipe ,
The gasket is composed of a first gasket and a second gasket divided along the axial direction,
An exhaust pipe joint, wherein the elastic member is disposed between the first gasket and the second gasket . The upstream exhaust pipe has a downstream end formed in a tapered shape,
2. The exhaust pipe joint according to claim 1 , wherein the downstream exhaust pipe has an upstream end formed in a tapered shape. the first gasket has an end formed in a wedge shape that fits along a tapered surface of the tapered portion of the downstream exhaust pipe, and an axial center portion of the first gasket protrudes in an arc shape in a radial direction so as to abut against the upstream exhaust pipe,
3. The exhaust pipe joint according to claim 2, wherein an end of the second gasket is formed into a wedge shape that fits along the tapered surface of the tapered portion of the upstream exhaust pipe, and an axial center portion of the second gasket protrudes radially in an arc shape so as to abut against the downstream exhaust pipe. 4. The exhaust pipe joint according to claim 1, wherein the elastic member applies a biasing force to the gasket in a direction to expand an overlap between the upstream exhaust pipe and the downstream exhaust pipe when the exhaust pipe is assembled to an engine .

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