JP4370895B2 - Heat shield for automobile exhaust system - Google Patents

Description

  The present invention relates to an improvement in a heat shield plate provided so as to cover a part of an exhaust system of an automobile, for example, a front surface of a catalytic converter.

For example, Patent Document 1 discloses a heat shield plate made of a metal plate that covers the surface of a catalytic converter so as to block radiant heat from the catalytic converter in an automobile exhaust system. The catalytic converter described in Patent Document 1 is an example arranged under the floor of a vehicle body. However, in recent years, there is a demand for early activation of a catalyst after starting. The catalytic converter tends to be located upstream, i.e., closer to the internal combustion engine, in the middle of the exhaust system from the internal combustion engine mounted in the engine room at the front of the vehicle body to the bottom of the vehicle body, that is, substantially in the engine room. May be placed.
Japanese Patent Laid-Open No. 8-312343

  When the catalytic converter is disposed in the engine room as described above, the temperature in the engine room, particularly the ambient temperature in the vicinity of the catalytic converter, tends to increase. This is more remarkable in recent passenger cars because the engine room is downsized and each component has a dense layout, so that the traveling wind does not pass easily.

  Therefore, the heat resistance of other peripheral components becomes a problem. For example, an air-fuel ratio sensor is generally attached on the upstream side of the catalytic converter. However, as a result of exposure to high temperatures, there is a concern that the seal portion and the like deteriorate and durability is lowered.

  The conventional heat shield as described in Patent Document 1 merely blocks the radiant heat from the catalytic converter.

  Therefore, the present invention uses a heat shield plate that is attached to cover the surface of the exhaust system such as a catalytic converter, and exhausts the high-temperature air in the engine room to the outside, thereby adjusting the ambient temperature around the exhaust system. It is intended to be lowered.

That is, the present invention covers the front side of the exhaust system toward the engine room on a portion inclined obliquely with respect to the vehicle longitudinal direction of the exhaust system from the internal combustion engine mounted in the engine room at the front of the vehicle body toward the bottom of the vehicle body floor. In a heat shield for an exhaust system of an automobile mounted as described above, a passage-shaped duct portion extending along the vertical direction is formed as a part of the heat shield, and its upper end opens into the engine room and the lower end is It is characterized by opening toward the rear of the vehicle at a height position below the vehicle body floor.

  When an automobile travels, a negative pressure is generated near the lower end opening of the duct portion due to the traveling wind flowing along the under floor of the vehicle body, and due to the pressure difference due to the negative pressure, air flowing from the upper end to the lower end in the duct portion is generated. A flow occurs. As a result, high-temperature air in the engine room is discharged to the bottom of the vehicle body through the duct portion, and outside air having a low temperature is actively taken into the engine room from the front of the vehicle body.

The heat shield plate is provided for the catalytic converter, for example. That is, the catalytic converter is attached in the middle of the exhaust system in a posture inclined with respect to the vehicle front-rear direction, and the heat insulating plate is a heat insulating plate for the catalytic converter that covers the front surface of the catalytic converter.

  In the case where an air-fuel ratio sensor is attached upstream of the catalytic converter, it is desirable that the upper end of the duct portion extends to the vicinity of the air-fuel ratio sensor.

  In addition, the duct portion can be provided in a passage shape along the side portion of the heat shield plate, and when the air-fuel ratio sensor is attached to the upstream side position of the catalytic converter, the air-fuel ratio is It is desirable that the duct portion is provided along the side portion of the heat shield plate on the side below the sensor.

  The duct portion can be formed by various methods. For example, the duct portion can be formed by bending a side edge of a heat shield plate made of a metal plate into a cylindrical shape.

  The lower end of the duct part may be formed to extend in a cylindrical shape below the lower edge of the other part of the heat shield plate. In this way, since the duct portion protrudes downward in a cylindrical shape, a negative pressure is more effectively generated at the lower end opening.

  According to the present invention, the high-temperature air can be efficiently discharged from the engine room to the outside using the heat shield attached to the exhaust system, and the ambient temperature around the exhaust system in the engine room can be lowered.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing a schematic configuration of a front portion of an automobile to which the present invention is applied. An engine room 2 is configured at a front portion of a vehicle body 1 so as to partition a compartment 3. A dash panel 4 is provided. In this embodiment, an in-line four-cylinder internal combustion engine 5 is mounted in the engine room 2 in a so-called horizontal mounting posture, and a radiator 6 is disposed at the front end of the vehicle body.

  The internal combustion engine 5 is configured such that an intake system (not shown) is disposed on one side face toward the front of the vehicle body 1 and an exhaust system 7 is disposed on the other side face toward the rear of the vehicle body. As the exhaust system 7, an exhaust manifold 8 communicating with the exhaust port of each cylinder is attached to the side surface of the cylinder head, and a catalytic converter 9 is connected to a collecting portion at the downstream end thereof, and at the outlet of the catalytic converter 9. An exhaust pipe 10 is connected. The exhaust pipe 10 extends to the rear of the vehicle body through the floor of the vehicle body 1, that is, the lower side of the floor panel 11. And since the said exhaust manifold 8 is attached to the comparatively high position of the internal combustion engine 5, the said catalytic converter 9 is arrange | positioned with the attitude | position inclined diagonally so that it may show in figure. That is, the catalytic converter 9 is accommodated in a space sandwiched between the internal combustion engine 5 and the dash panel 4, and is disposed obliquely along the front surface of the inclined dash panel 4. Reference numeral 13 denotes a front wheel.

  The catalytic converter 9 contains a catalyst carrier in a metal casing, has a cylindrical shape with an elliptical cross section, and both front and rear end portions have a substantially conical shape. In addition, as for the cross-sectional shape of the ellipse of this catalytic converter 9, the vehicle width direction is the major axis direction. An air-fuel ratio sensor 12 such as an oxygen sensor for detecting the exhaust composition is attached to an outlet portion of the exhaust manifold 8 on the upstream side of the catalytic converter 9. In particular, the air-fuel ratio sensor 12 is attached to the side position of the outlet portion of the exhaust manifold 8, that is, the position in the left-right direction when viewed from the front of the vehicle, because of the layout relationship with other components.

  A heat shield plate 21 made of a metal plate is attached so as to cover the front surface of the catalytic converter 9, that is, the surface facing the front or the lower side of the vehicle. As shown in the cross-sectional shape of FIG. 2, the heat shield plate 21 has a bottom wall portion 21 a that extends from side to side in a flat plate shape so as to cover the entire width direction of the catalytic converter 9, and left and right side wall portions. 21b rises so as to cover the side surface of the catalytic converter 9, and has a substantially U-shaped cross-section as a whole, and the side edge constituting the side wall portion 21b is extended and bent inward into a tubular shape. A passage-shaped duct portion 22 is formed on each of the left and right sides. In the illustrated example, the duct portion 22 has a flat cross-sectional shape elongated in the vertical direction, and the side wall portion 21b has a double wall structure having an inner side wall 21c and an outer side wall 21d. Further, the heat shield plate 21 extends linearly in the longitudinal direction of the catalytic converter 9 with substantially the same cross-sectional shape. Therefore, most of the catalytic converter 9 except the upper surface portion is covered with the heat shield plate 21, and the pair of duct portions 22 are linearly extended along the side portions of the heat shield plate 21. And extends in the vertical direction and in the front-rear direction in parallel with the inclined catalytic converter 9.

  The upper end 22 a of the duct portion 22 is located above the upstream end of the catalytic converter 9 and opens directly into the engine room 2. In particular, it reaches the vicinity of the air-fuel ratio sensor 12. As described above, the air-fuel ratio sensor 12 is arranged on either the side, that is, on the left or right side, so that the upper end 22a of one duct portion 22 opens below the air-fuel ratio sensor 12. Further, the lower end 22 b of the duct portion 22 extends below the downstream end of the catalytic converter 9, and opens at a height position protruding below the floor of the vehicle body 1, that is, below the floor panel 11.

  FIGS. 3 and 4 show an example of a mounting structure of the heat shield plate 21 to the catalytic converter 9. A nut 25 is welded to a side portion of the catalytic converter 9, and an inner side constituting the duct portion 22. The wall 21c is fastened between the nut 25 and the bolt 26. Here, as shown in FIG. 4, a small hole 27 for the bolt 26 is formed in the inner wall 21c, and a larger diameter for tightening the bolt 26 is formed in the outer wall 21d. A work hole 28 is formed. In addition, it is also possible to attach via a bracket etc. so that opening may not arise in the duct part 22. FIG.

  In the configuration as described above, as shown in FIG. 5, the traveling wind accompanying the traveling of the vehicle flows along the lower surface of the vehicle body 1 as indicated by the arrow W, so that the lower end 22b of the duct portion 22 protruding below the floor is formed. A negative pressure region 28 is generated in the vicinity. Thereby, a pressure difference arises between the upper end 22a and the lower end 22b of the duct part 22 which makes | forms a channel | path shape, and the flow of the air like the arrow H which flows through the duct part 22 below generate | occur | produces. Accordingly, the air in the engine room 2, particularly the high-temperature air near the upper portion of the catalytic converter 9 is sucked out and discharged below the floor. As the flow from the inside of the engine room 2 to the lower floor occurs in this way, new air is actively taken into the engine room 2 from the front of the vehicle. Therefore, the ambient temperature in the engine room 2, particularly the temperature around the catalytic converter 9, is effectively reduced. In particular, since the upper end 22a of the one duct portion 22 opens below the air-fuel ratio sensor 12, a flow that flows into the duct portion 22 across the periphery of the air-fuel ratio sensor 12 is obtained, and the air-fuel ratio sensor 12 is securely connected. Can be cooled. Therefore, the durability of the air-fuel ratio sensor 12 is improved.

  Since the duct portion 22 has a double wall structure in which the side wall portion 21b of the heat shield plate 21 has an inner wall 21c and an outer wall 21d, it contributes to improving the rigidity of the heat shield plate 21 and from the catalytic converter 9. The original heat shielding effect for blocking the radiant heat is further enhanced.

  Next, FIGS. 6 and 7 show a second embodiment of the present invention. In this embodiment, the duct portion 22 is formed only on one of the left and right sides where the air-fuel ratio sensor 12 is located. That is, in this example, the air-fuel ratio sensor 12 is mounted on the left side when viewed from the front of the vehicle, and the duct portion 22 is provided on one side portion of the heat shield plate 21 on the lower side. The duct portion 22 is formed by bending the side edge of the heat shield plate 21 made of a metal plate into a cylindrical shape, as in the first embodiment.

  FIG. 8 shows a third embodiment in which the duct portion 22 is formed by combining two metal plates 21 </ b> A and 21 </ b> B as the heat shield plate 21. In this example, the inner wall 21c of the duct portion 22 having a double wall structure is formed as a part of the inner metal plate 21A, and the outer wall 21d is formed as a part of the outer metal plate 21B. It is welded outside the portion 22. In such a configuration, the metal plates 21A and 21B can be obtained by simple press working. The bottom wall portion 21a is in a state where the two metal plates 21A and 21B are in close contact with each other.

  Next, FIGS. 9 and 10 show a fourth embodiment in which the lower edge of the bottom wall portion 21a is cut out relatively short. In other words, with respect to the lower edge position of the bottom wall portion 21a, the lower ends 22b of the left and right duct portions 22 are extended downward in a cylindrical shape.

  According to this embodiment, since the lower end 22b of the duct portion 22 protrudes under the floor in a cylindrical shape, the negative pressure generated by the traveling wind becomes more reliable, and the negative pressure obtained near the lower end 22b is strengthened. As a result, the amount of air flowing through the duct portion 22 increases. In addition, since the position of the lower edge of the bottom wall portion 21a is relatively upward, it is advantageous for securing the minimum ground clearance of the vehicle.

  Although the present invention has been described with respect to the embodiment in which the internal combustion engine 5 is mounted horizontally on the vehicle body 1, the present invention is not limited to this, and as shown in FIG. The same applies to the case where the internal combustion engine 5 is mounted vertically.

  Further, even when the catalytic converter 9 is not disposed in the engine room 2, for example, by attaching a heat shield so as to cover the exhaust pipe passing through the front of the dash panel 4, and providing a duct part in the same, It is possible to obtain a cooling action.

1 is a longitudinal sectional view of a front portion of an automobile showing an embodiment of the present invention. Sectional drawing along the AA line of FIG. Sectional drawing which shows an example of the attachment structure of a heat shield. The perspective view of the heat shield principal part similarly. Explanatory drawing explaining the effect | action of a duct part. The side view of the principal part which shows 2nd Example. Sectional drawing along the BB line of FIG. Sectional drawing which shows 3rd Example of the heat shield which consists of two metal plates. The side view of 4th Example which provided the notch. The front view seen from the arrow C of FIG. The longitudinal cross-sectional view of the front part of the motor vehicle which shows the Example applied to the exhaust system of a vertical internal combustion engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Car body 2 ... Engine room 4 ... Dash panel 9 ... Catalytic converter 21 ... Heat shield 22 ... Duct part

Claims (7)

Heat shield that is attached to cover the front of the exhaust system toward the engine room on the part of the exhaust system that is mounted in the engine room at the front of the vehicle body and that is inclined with respect to the vehicle longitudinal direction In the board,
As a part of this heat shield plate, a passage-shaped duct portion extending in the vertical direction is formed, the upper end thereof opens into the engine room, and the lower end opens toward the rear of the vehicle at a height position below the vehicle body floor. A heat shield for an exhaust system of an automobile. A catalytic converter is attached in the middle of the exhaust system in a posture inclined with respect to the longitudinal direction of the vehicle , and the heat shield is a heat shield for the catalytic converter that covers the front surface of the catalytic converter. The heat shield for an exhaust system of an automobile according to claim 1.   The heat insulation of an exhaust system of an automobile according to claim 2, wherein an air-fuel ratio sensor is attached upstream of the catalytic converter, and an upper end of the duct portion extends to the vicinity of the air-fuel ratio sensor. Board.   4. A heat shield plate for an automobile exhaust system according to claim 1, wherein the duct portion is provided along a side portion of the heat shield plate.   An air-fuel ratio sensor is attached to a side position on the upstream side of the catalytic converter, and the duct portion is provided along a side portion of the heat shield plate on the side below the air-fuel ratio sensor. The heat shield for an exhaust system of an automobile according to claim 2.   6. The heat shield plate for an automobile exhaust system according to claim 4, wherein the duct portion is formed by bending a side edge of the heat shield plate into a cylindrical shape.   7. The automobile exhaust system shielding according to claim 1, wherein a lower end of the duct portion extends in a cylindrical shape downward from a lower edge of another portion of the heat shielding plate. Hot plate.

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