# US 5,706,655 A · Thin-walled double pipe exhaust manifold

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- Number: US 5,706,655 A
- Document ID: US5706655A
- Status: Granted
- Kind: A
- Application number: 08/452,122
- Filed: 1995-05-26
- Granted: 1998-01-13
- Earliest claimed: 1994-05-27
- Assignees: Calsonic Corporation
- Inventors: Takashi Kojima; Yasuo Fukae
- Web page: https://patentgrep.com/patent/US5706655A

## CPC

- F01N 13/102: {having thermal insulation}
- F01N 13/141: {Double-walled exhaust pipes or housings}
- F01N 2260/10: for avoiding stress caused by expansions or contractions due to temperature variations
- F02F 2001/008: {Stress problems, especially related to thermal stress}
- F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16)
- F02F: CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES

## Abstract

A thin-walled double pipe exhaust manifold comprises a double pipe consisting of a comparatively thin inner tube and a comparatively thick outer tube, both spaced apart from each other adiabatically through an aperture defined between these tubes. The inner tube is formed with at least one bead portion for relieving thermal stresses induced in the inner tube. To effectively reduce thermal stresses by way of thermal expansion or contraction, the bead portion is provided around each heat spot similarly to the temperature distribution of each heat spot.

## Claims

### Claim 1

A thin-walled double pipe exhaust manifold for internal combustion engines, comprising:
a thin-walled main double pipe including an inner tube and an outer tube, said tubes being spaced apart from each other adiabatically through a space defined between said tubes;
a plurality of thin-walled branch pipes connected to said main double pipe and including an inner tube and an outer tube, said tubes being spaced apart from each other adiabatically through a space defined between said tubes; and
relief means for relieving thermal stresses induced in said inner tube, said relief means including at least one bead portion formed at said inner tube;
wherein said bead portion formed in the vicinity of heat spots against each of which exhaust gases blow at a given inflow angle.

### Claim 2 (depends on 1)

The exhaust manifold as claimed in claim 1, wherein a thickness of said inner tube is less than a thickness of said outer tube.

### Claim 3 (depends on 1)

The exhaust manifold as claimed in claim 1, wherein said bead portion includes an annular bead having a raised portion with a sinusoidal waveform in cross-section, and wherein a radius of curvature of said raised portion is two or more times as large as a height of said raised portion.

### Claim 4 (depends on 1)

The exhaust manifold as claimed in claim 1, wherein said bead portion is shaded around each of said heat spots to correspond with a temperature distribution of each of said heat spots.

### Claim 5

A thin-walled double pipe exhaust manifold for internal combustion engines, comprising:
an inner tube and an outer tube, said tubes being spaced apart from each other adiabatically through a space defined between said tubes, said inner tube having a main tube section and a plurality of input branches,
wherein exhaust gases are blown into the main tube section through the input branches and form heat spots along the main tube section at points along the main tube section against which the exhaust gases blow as the exhaust gases exit the input branches and enter the main tube section, and
wherein the main tube section includes at least one bead portion at one of the heat spots.

### Claim 6 (depends on 5)

The exhaust manifold as claimed in claim 5, wherein a thickness of said inner tube is less than a thickness of said outer tube.

### Claim 7 (depends on 5)

The exhaust manifold as claimed in claim 5, wherein said bead portion includes an annular bead having a raised portion with a sinusoidal waveform in cross-section, and wherein a radius of curvature of said raised portion is at least two times as large as a height of said raised portion.

### Claim 8 (depends on 5)

The exhaust manifold as claimed in claim 5, wherein the main tube section includes at least one bead portion at each of the heat spots.

### Claim 9 (depends on 8)

The exhaust manifold as claimed in claim 8, wherein said at least one bead portion at each of the heat spots does not extend completely around the circumference of the main tube section.

### Claim 10 (depends on 5)

The exhaust manifold as claimed in claim 5, wherein the at least one bead portion at one of the heat spots does not extend completely around the circumference of the main tube section.

### Claim 11 (depends on 5)

The exhaust manifold as claimed in claim 5, wherein said bead portion is shaped around said one of the heat spots to correspond with a temperature distribution of said one of the heat spots.