JPH09317460A - Flexible tube for automobile exhaust system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible tube for an automobile exhaust system to satisfy all demand performance, such as small and light, a low cost, high displacement absorbing ability, and high durability, and set a spring constant to an arbitrary value according to displacement direction of a tension or compression and increase a practicable value. SOLUTION: A flexible tube for an automobile exhaust system comprises a bellows 3 to absorb displacement of two exhaust pipes 1 and 2; an outer cover 5 formed in a cylindrical shape to cover the outer periphery of the bellows 3; first and second protectors 7' and 7" respectively connected to the two end parts of the bellows 3; and first and second plate compression springs 6' and 6" respectively located between one end part of the outer cover 5 and the first protector 7' and between the other end part of the outer cover 5 and the second protector 7" and having characteristics wherein the compression side is a high spring constant and the tension side is a low spring constant and fixing the two end parts of the spring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible tube for an automobile exhaust system having a bellows for absorbing a relative displacement between a first exhaust pipe attached to an engine side of an exhaust system for a vehicle and a second exhaust pipe attached to a muffler side. Belongs to the technical field.

[0002]

2. Description of the Related Art Conventionally, as flexible tubes for automobile exhaust systems, for example, those listed below are known.

(1) Japanese Utility Model Laid-Open No. 61-187916 The flexible tube described in this publication, as shown in FIG. 10, has a bellows connected to an exhaust pipe, an outer blade arranged on the outer periphery of the bellows, The protector is provided at both ends of the outer blade and includes spot protectors for spot welding the outer blade and the bellows.

(2) Japanese Utility Model Laid-Open No. 2-14418 As shown in FIG. 11, the flexible tube described in this publication includes a bellows connected to an exhaust pipe, and spring support pipes arranged on the outer circumferences of both ends of the bellows. The spring material is provided between the spring branch pipes.

(3) Japanese Utility Model Laid-Open No. 4-6523 As shown in FIG. 12, the flexible tube described in this publication is arranged on the outer periphery of a bellows connected to an exhaust pipe, and one end is fixed to the bellows. And a compression spring interposed between a clamp member fixed to the other end of the outer blade and a cylindrical body fixed to the bellows.

[0006]

However, in the above-mentioned conventional flexible tube for an automobile exhaust system,
There are problems listed below.

(1) In the flexible tube shown in FIG. 10, the spring constant of the flexible tube is greatly affected by the manufacturing variation of the outer blade, and the absorption characteristic of the vibration displacement varies. Further, the outer blade made by braiding stainless steel wire is expensive. Therefore, the bellows with a large number of peaks used to secure the vibration displacement absorption characteristics increase the size, and the outer blade used to protect the bellows increases the cost.

(2) In the flexible tube shown in FIG. 11, since the central portion of the bellows is exposed to the outside, the bellows is easily damaged by flying stones and the like, and the bellows durability is poor. Also, since the spring material protrudes greatly outward,
A flexible tube with a large outer diameter. When mud or the like adheres to the spring material that protrudes to the outside in a largely exposed state during traveling, the spring characteristics change and the desired displacement absorbability cannot be obtained.

(3) Since the flexible tube shown in FIG. 12 basically uses an outer blade made by knitting a stainless steel wire, it has the problem of the above (1). In addition, although the compression spring enhances the absorbency against tensile displacement, the absorbency against compressive displacement cannot be expected to improve.

As described above, each of them has advantages and disadvantages, and they do not satisfy all the performances required for a flexible tube for an automobile exhaust system, such as small size, light weight, low cost, high displacement absorption, and high durability. It is desired to develop a new flexible tube in place of the commonly used flexible tube shown in FIG.

The problem to be solved by the present invention is for an automobile exhaust system having a bellows which absorbs the relative displacement of a first exhaust pipe attached to the engine side of a vehicle exhaust system and a second exhaust pipe attached to the muffler side. A flexible tube with high practical value that satisfies all the required performances of small size, light weight, low cost, high displacement absorption, and high durability, and can set the spring constant arbitrarily according to the displacement direction of tension or compression. To provide.

[0012]

[Means for Solving the Problems]

(Solution 1) In order to achieve the above object, in the invention according to claim 1, both ends are connected to the first exhaust pipe and the second exhaust pipe, and a bellows for absorbing displacement of both exhaust pipes and a plate member A cylindrical outer cover that covers the outer circumference of the bellows, a first protector and a second protector connected to both ends of the bellows, between one end of the outer cover and the first protector, and between the outer cover and the outer cover. A first flat plate compression spring and a second flat plate compression spring, which are respectively interposed between the other end and the second protector, and have the characteristics that the compression side has a large spring constant and the tension side has a small spring constant, and both ends of the spring are fixed. It is characterized by having.

Therefore, when an external force acts on the flexible tube and the first exhaust pipe and the second exhaust pipe are displaced in the axial direction of the pipe, the compressive load and the tensile load are different from those of the bellows.
Acts on both flat plate compression springs.

Therefore, even if the thickness of the bellows is reduced and the spring constant of the bellows is set low, the total spring constant of the flexible tube can be supplemented by both flat plate compression springs, and the size and weight of the flexible tube can be reduced. To be achieved.

When an external force is applied to the first exhaust pipe and the second exhaust pipe to displace them in the axial direction of the pipe, the bellows and the first and second exhaust pipes
The displacement is absorbed by the second flat plate compression spring that compresses or pulls and deforms in accordance with the acting direction of the load.
Even if an external force acts on the first exhaust pipe and the second exhaust pipe to displace them in the bending direction or the shearing direction, the bellows and the flat plate compression springs, which have a high degree of freedom of deformation, follow the acting direction of the load. It is absorbed by bending and shearing. That is, the displacement absorbing action using both the bellows and the first and second flat plate compression springs is achieved.

Furthermore, since the external force applied to the flexible tube is distributed to the bellows and both flat plate compression springs, the load on the bellows is reduced.

Further, when at least one of the first flat plate compression spring and the second flat plate compression spring is compressed by an excessive load, the close contact between the flat plates of the flat plate compression spring serves as a displacement regulating stopper.

In addition, when there is a stone bounce or the like during traveling, the outer cover protects the bellows and the first and second parts.
The flat compression spring is prevented from being deformed or damaged.

In addition, since the first and second flat plate compression springs have the characteristics that the compression side has a large spring constant and the tension side has a small spring constant, the tension displacement direction varies depending on how the first and second flat plate compression springs are mounted. The spring constant can be arbitrarily set, for example, the spring constant can be set differently depending on the compression displacement direction.

(Solution 2) In the invention according to claim 2,
The flexible tube for an automobile exhaust system according to claim 1, wherein the first flat plate compression spring and the second flat plate compression spring both have a spring mounting span that is shortened when a tensile load is applied and both are spring mounted when a compression load is applied. The feature is that it is attached so that the span is long.

Therefore, both flat plate compression springs are compressed on the tensile displacement side, and both flat plate compression springs are pulled on the compression displacement side.
A flexible tube having spring characteristics of a large spring constant on the tensile displacement side and a small spring constant on the compression displacement side can be obtained.

(Solution means 3) In the invention according to claim 3,
The flexible tube for an automobile exhaust system according to claim 1, wherein the first flat plate compression spring and the second flat plate compression spring both have spring mounting spans that are long when a tensile load is applied and are spring mounted when a compressive load is applied. The feature is that it is attached so that the span is shortened.

Therefore, both flat plate compression springs are pulled on the tensile displacement side, and both flat plate compression springs are compressed on the compression displacement side.
A flexible tube having spring characteristics of a small spring constant on the tensile displacement side and a large spring constant on the compression displacement side can be obtained.

(Solution means 4) In the invention of claim 4,
The flexible tube for an automobile exhaust system according to claim 1, wherein one spring mounting span of the first flat plate compression spring and the second flat plate compression spring is shortened when a tensile load is applied, and the other is shortened when a compression load is applied. It is characterized in that it is mounted so that only the spring mounting span of is shortened.

Therefore, one of the flat plate compression springs compresses on the tensile displacement side and the other of the flat plate compression springs compresses on the compression displacement side. Therefore, different compression springs are used as the first flat plate compression spring and the second flat plate compression spring. When a spring having a constant is used, a flexible tube having arbitrarily different spring characteristics on the tensile displacement side and the compression displacement side can be obtained by selecting the spring constant. In addition, as the first flat plate compression spring and the second flat plate compression spring,
When a spring having the same compression spring constant is used, the flexible tube has the same spring characteristics on the tensile displacement side and the compression displacement side.

(Solution means 5) In the invention according to claim 5,
The flexible tube for an automobile exhaust system according to any one of claims 1 to 4, further comprising a stopper that defines a maximum length of a spring mounting span between the first flat plate compression spring and the second flat plate compression spring. .

Therefore, the maximum displacement is restricted on the tensile displacement side of the flat plate compression spring having a small spring constant, so that it is possible to prevent the bellows from being fully extended and compressed and deformed by an excessive load.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) First, the configuration will be described.

The first embodiment corresponds to the invention described in claims 1, 2, and 5.

FIG. 1 is a half sectional view showing a flexible tube for an automobile exhaust system according to Embodiment 1, and FIG. 2 is Embodiment 1
FIG. 6 is a perspective view showing a flat plate compression spring applied to the flexible tube of FIG.

In FIGS. 1 and 2, A is a flexible tube, 1 is a first exhaust pipe, 2 is a second exhaust pipe, 3 is a bellows, 5 is an outer cover, and 6'is a first flat plate compression spring.
6 "is the second flat plate compression spring, 7'is the first protector, 7"
Is a second protector.

The bellows 3 has both ends connected to the first exhaust pipe 1 and the second exhaust pipe 2 and is provided to absorb the displacement of the exhaust pipes 1 and 2.

The bellows 3 is made of a material having a thickness of 0.1 mm.
Using a thin multi-layer product in which two stainless steel thin plates with a thickness of 2 mm (previously 0.3 mm) were stacked, the number of peaks was significantly reduced (21 to 28 peaks → 8 to 9 peaks), and an equivalent spring Got a constant.

The outer cover 5 is formed of a plate material in a cylindrical shape that covers the outer periphery of the bellows 3, and is constructed by integrally welding the central cover 51 and the two side covers 52 'and 52 ". Then, the central cover 51 is formed with stopper portions 51a ′, 51a ″ by bending both ends inward, and the side cover 5
2 ′ and 52 ″ are formed with cover-side spring fixing portions 52a ′ and 52a ″ by bending the respective ends inward.

The first protector 7 'and the second protector 7 "are connected (spot-welded) to both ends of the bellows 3, respectively. Both protectors 7' and 7"
A first protector-side spring fixing portion 7a 'and a second protector-side spring fixing portion 7a "are formed toward the inner surface of the outer cover 5.

As shown in FIG. 2, the first flat plate compression spring 6'and the second flat plate compression spring 6 "are formed by winding a corrugated flat plate into a coil spring shape. The compression side has a large spring constant and the tension side has a small spring side. It is a spring that has the characteristic of a spring constant.

The first flat plate compression spring 6'has a cover side spring fixing portion 52a 'which has a short spring mounting span when a tensile load is applied to the flexible tube and a long spring mounting span when a compressive load is applied. It is interposed between the first protector side spring fixing portion 7a 'and both ends of the spring are fixed to the spring fixing portions 52a' and 7a 'by welding or caulking.

The second flat plate compression spring 6 ", like the spring 6 ', has a spring mounting span that becomes shorter when a tensile load acts on the flexible tube and becomes longer when a compressive load acts on the cover side spring fixing portion. 52a "and the second protector-side spring fixing portion 7a" are interposed, and both ends of the spring are fixed to the spring fixing portions 52a "and 7a" by welding or caulking.

The stopper clearances t ', t "are provided between the first protector-side spring fixing portion 7a' and the stopper portion 51a 'and between the second protector-side spring fixing portion 7a" and the stopper portion 51a ". Is intervening.

FIG. 3 is a perspective view showing an automobile exhaust system to which the flexible tube of the first embodiment is applied.

In FIG. 3, A is a flexible tube, B is an exhaust pipe, C is a catalytic converter, and D is
Is a sub-muffler, E is a main muffler, and the flexible tube A is provided in the middle of an exhaust pipe B connecting an engine (not shown) and the catalytic converter C, and absorbs a displacement due to an input from an engine, a vehicle body or the like.

Next, the operation will be described.

[Bellows' spring constant setting action] First, when an external force acts on the flexible tube A and the first exhaust pipe 1 and the second exhaust pipe 2 are displaced in the axial direction of the pipe, the compression load and the tensile load are It acts on both the bellows 3 and the first and second flat plate compression springs 6 ', 6 ".

As a result, as in the bellows 3 of the first embodiment, a two-layer product which is thinner and has a smaller number of peaks than the conventional one is used as the bellows material, and the spring constant of the bellows 3 is set to a low constant value. However, it can be compensated by the spring constants of the flat plate compression springs 6 ′ and 6 ″, and the flexible tube A can be reduced in size, weight and cost.

[Displacement Absorbing Action] The displacement absorbing action when a load that causes displacement in the axial direction of the first exhaust pipe 1 and the second exhaust pipe 2 is input from the engine, the vehicle body or the like will be described.

When a compressive load is applied among the displacement loads, the bellows 3 is compressed and the first and second flat plate compression springs 6 ', 6 "are stretched in the pulling direction as the spring mounting span becomes longer, and both are compressed. The exhaust pipes 1, 2 are compressed and displaced.

When a tensile load of the displacement load is applied, the bellows 3 is pulled and the first and second flat plate compression springs 6 ', 6 "are shortened in the compression direction due to the shortened spring mounting span. The exhaust pipes 1 and 2 are tensilely displaced.

That is, due to the expansion and contraction of the bellows 3 and the first and second flat plate compression springs 6 ', 6 ", the displacement in which the tension and the compression are repeatedly vibrated in the axial direction of the tube is regularly absorbed.

An external force may be applied to the first exhaust pipe 1 and the second exhaust pipe 2 so as to displace them in the bending direction and the shearing direction in addition to the pipe axis direction. The bellows 3 having a high degree of freedom and the flat plate compression springs 6 ′ and 6 ″ are bent and sheared in accordance with the acting direction of the load to absorb the bending displacement and the shearing displacement.

[Bellows durability ensuring action] As will be described later, the durability of the bellows 3 is secured by sharing the load, preventing extension and compression deformation, and protecting from flying stones.

The external force applied to the flexible tube A is
Since the force applied to the bellows 3 and the force applied to the flat plate compression springs 6 ′ and 6 ″ are dispersed, the load on the bellows 3 is reduced.

Since the first and second flat plate compression springs 6 ', 6 "are compressed with respect to the tensile load, the first and second flat plate compression springs 6', 6" are subjected to an excessive tensile load. The close contact between the adjacent flat plates of the
Is prevented from being stretched.

With respect to the compressive load, the first and second flat plate compression springs 6 ', 6 "are pulled, but the tensile displacement is caused by the stopper clearances t', t" due to the contact with the stopper portions 51a ', 51a ". By being restricted, the compression deformation of the bellows 3 is prevented.

Since the flexible tube A is arranged so as to be exposed at the bottom of the vehicle, when a stone or the like is bounced by the tire while the vehicle is running, the bounced stone or the like may collide with the flexible tube A. The outer cover 5 that covers the entire outer circumference of the bellows 3 when there is a pebbles, etc.
This prevents the bellows 3 from being deformed or damaged. Since the outer cover 5 is also arranged to cover the outer circumferences of the first and second flat plate compression springs 6 ′ and 6 ″, deformation of the first and second flat plate compression springs 6 ′ and 6 ″ with respect to rocks, etc. Damage is also prevented.

[Function of setting spring characteristic of flexible tube] In setting the spring characteristic of the flexible tube A, the spring constant of the bellows 3 is a constant value determined by the selection of material and the number of peaks, but the first flat plate compression spring 6 'And the second flat plate compression spring 6 "have spring constants as shown in FIG.
The spring constant is large when the adjacent corrugated flat plates are in contact with each other and pressed against each other, and the spring constant is small when the adjacent corrugated flat plates are pulled apart from each other.

Therefore, both flat plate compression springs 6 ', 6 "are compressed with respect to tensile displacement, and both flat plate compression springs 6', 6" are pulled with respect to compressive displacement. As shown in FIG. 5, the spring characteristic of is a tensile displacement-tensile force characteristic with a large inclination (large spring constant) on the tensile displacement side, and a small inclination (small spring constant) on the compression displacement side-tensile displacement-tensile It becomes a force characteristic.

That is, when the automobile exhaust system is designed so that the tensile force acts more than the compression force by setting the engine mount, the exhaust system support mount, etc., the flexible tube A of the first embodiment is applied. Effective displacement absorption is possible.

Next, the effect will be described.

(1) A bellows 3 having both ends connected to the first exhaust pipe 1 and the second exhaust pipe 2 for absorbing displacement of both the exhaust pipes 1 and 2, and a tube covering the outer circumference of the bellows 3 with a plate material. -Shaped outer cover 5, a first protector 7 ′ and a second protector 7 ″ connected to both ends of the bellows 3, and one end of the outer cover 5 and the first protector 7 ′.
It is interposed between the protector 7 ′ and the other end of the outer cover 5 and the second protector 7 ″, and has a characteristic that the compression side has a large spring constant and the tension side has a small spring constant, and both ends of the spring are fixed. Since the first flat plate compression spring 6 ′ and the second flat plate compression spring 6 ″ are provided, it is possible to satisfy all the required performances of small size and light weight, low cost, high displacement absorption, and high durability, and whether it is tension or compression. It is possible to provide the flexible tube A having a high practical value in which the spring constant can be arbitrarily set according to the displacement direction of.

(2) The spring mounting spans of the first flat plate compression spring 6'and the second flat plate compression spring 6 "both become shorter when a tensile load acts, and both become longer when a compressive load acts. Since the flexible tube A is mounted as described above, the flexible tube A can have a spring characteristic of a large spring constant on the tensile displacement side and a small spring constant on the compression displacement side.

(3) Since the stopper portions 51a 'and 51a "for defining the maximum length of the spring mounting span of the first flat plate compression spring 6'and the second flat plate compression spring 6" are provided, both of which have a small spring constant. The maximum displacement is restricted on the tensile displacement side of the flat plate compression springs 6 ', 6 ", and the compression deformation of the bellows 3 due to an excessive load can be prevented.

(Embodiment 2) First, the configuration will be described.

FIG. 6 is a half sectional view showing a flexible tube for an automobile exhaust system according to a second embodiment corresponding to the invention described in claims 1, 3 and 5.

The flexible tube A'of this Embodiment 2 has a first flat plate compression spring 6'and a second flat plate compression spring 6 ".
Are different from the first embodiment in that the spring mounting span is increased when a tensile load is applied and the spring mounting span is shortened when a compressive load is applied.

With the change in the mounting of the flat plate compression springs 6 ', 6 ", the outer cover 5 is constructed by welding the main cover 53, the two side covers 54', 54" and the sub-cover 55 together. ing. A stopper portion 53a 'is formed on the main cover 53 by bending one end portion inward, so that the side covers 54', 54 "are formed.
The cover-side spring fixing portions 54a ′ and 54a ″ are formed by bending the respective ends inward, and the sub-cover 55 has the stopper portion 5 formed by bending one end inward.
5a 'is formed.

The first flat plate compression spring 6'has a spring mounting span which is long when a tensile load is applied and is short when a compressive load is applied thereto.
a ′ and the first protector-side spring fixing portion 7a ′ are interposed, and the spring both ends are respectively fixed to the spring fixing portions 54a ′, 7a ′.
It is fixed to a'by welding or caulking.

The second flat plate compression spring 6 "has a cover side spring fixing portion 54 which has a long spring mounting span when a tensile load is applied and a short spring mounting span when a compressive load is applied.
a "and the second protector-side spring fixing portion 7a" are interposed between the spring fixing portions 54a ", 7a.
It is fixed to a "by welding or caulking.

The rest of the configuration is the same as that of the first embodiment, and the explanation is omitted.

Next, the operation will be described.

[Spring characteristics setting action of flexible tube] Both flat plate compression springs 6 ', 6 "are pulled with respect to tensile displacement, and both flat plate compression springs 6', 6" with respect to compressive displacement.
As shown in FIG. 7, the spring characteristic of the flexible tube A ′ according to the second embodiment in which 6 ″ is compressed is a tensile displacement-tensile force characteristic with a small inclination (small spring constant) on the tensile displacement side, resulting in compression displacement. The tensile displacement-tensile force characteristics have a large inclination (large spring constant) on the side.

That is, when the automobile exhaust system is designed so that the compression force acts more than the tensile force by setting the engine mount and the exhaust system support mount, the flexible tube A'of the second embodiment should be applied. Can effectively absorb the displacement.

The other operations are the same as those in the first embodiment, and the description thereof will be omitted.

Next, the effect will be described.

In the second embodiment, the following effect is added to the effect (1) of the first embodiment.

(4) Since the stopper portions 55a 'and 53a "for defining the maximum length of the spring mounting span of the first flat plate compression spring 6'and the second flat plate compression spring 6" are provided, both of which have a small spring constant. The maximum displacement is restricted on the tensile displacement side of the flat plate compression springs 6 ′ and 6 ″, and it is possible to prevent the bellows 3 from fully extending due to an excessive load.

(5) The first flat plate compression spring 6'and the second flat plate compression spring 6 "both have a long spring mounting span when a tensile load is applied and a short spring mounting span when a compressive load is applied. Since it is mounted as described above, a flexible tube A ′ having a spring characteristic of a small spring constant on the tensile displacement side and a large spring constant on the compression displacement side can be obtained.

(Third Embodiment) First, the configuration will be described.

FIG. 8 is a half sectional view showing an automobile exhaust system flexible tube according to a third embodiment of the present invention, which corresponds to the first, fourth, and fifth aspects of the present invention.

The flexible tube A ″ according to the third embodiment has a first flat plate compression spring 6 ′ and a second flat plate compression spring 6 ″.
Are mounted so that the spring mounting span of the first flat plate compression spring 6 ′ becomes shorter when a tensile load acts and the spring mounting span of the second flat plate compression spring 6 ″ becomes shorter when a compressive load acts. Different from the first and second embodiments.

As the mounting of the flat plate compression springs 6 ', 6 "is changed, the outer cover 5 is constructed by welding the main cover 53, the two side covers 54', 54" and the sub-cover 55 together. ing. A stopper portion 53a 'is formed on the main cover 53 by bending one end portion inward, so that the side covers 54', 54 "are formed.
Has a stopper portion 54a 'and a cover-side spring fixing portion 54a "formed by bending the respective ends inward.
The sub-cover 55 has a cover-side fixing portion 55a 'formed by bending one end inward.

In the first flat plate compression spring 6 ', the cover side spring fixing portion 55 has a short spring mounting span when a tensile load is applied and a long spring mounting span when a compressive load is applied.
a ′ and the first protector-side spring fixing portion 7 a ′, and both ends of the spring are fixed to the spring fixing portions 55 a ′, 7 a, respectively.
It is fixed to a'by welding or caulking.

The second flat plate compression spring 6 "has a cover side spring fixing portion 54 having a long spring mounting span when a tensile load is applied and a short spring mounting span when a compressive load is applied.
a "and the second protector-side spring fixing portion 7a" are interposed between the spring fixing portions 54a ", 7a.
It is fixed to a "by welding or caulking.

The other structure is the same as that of the first embodiment, and the description thereof is omitted.

Next, the operation will be described.

[Spring Characteristic Setting Function of Flexible Tube] The third flat plate compression spring 6'is compressed against tensile displacement and the second flat plate compression spring 6 "is compressed against compressive displacement. As shown in FIG. 9, the flexible tube A ″ has a tensile displacement-tensile force characteristic having a spring constant determined by the compression spring constant of the first flat plate compression spring 6 ′ on the tensile displacement side, and on the compression displacement side. The tensile displacement-tensile force characteristic has a spring constant determined by the compression spring constant of the second flat plate compression spring 6 ″.

Therefore, if springs having different compression spring constants are used as the first flat plate compression spring 6'and the second flat plate compression spring 6 ", the spring characteristics are arbitrarily different between the tension displacement side and the compression displacement side depending on the selection of the spring constant. Can be a flexible tube A ".

When springs having the same compression spring constant are used as the first flat plate compression spring 6'and the second flat plate compression spring 6 ", a flexible structure having the same spring characteristics on the tensile displacement side and the compression displacement side is used. Tube A ".

That is, when the vehicle exhaust system is designed such that the acting force of the compressive force and the acting force of the tensile force are slightly different depending on the setting of the engine mount and the exhaust system support mount,
By applying the flexible tube A ″ according to the third embodiment, it is possible to effectively absorb displacement in response to a slight difference in acting force.

The other operations are the same as those in the first embodiment, and the description thereof will be omitted.

Next, the effects will be described.

In the third embodiment, the following effect is added to the effect (1) of the first embodiment.

(6) Since the stopper portions 54a 'and 53a "for defining the maximum length of the spring mounting span of the first flat plate compression spring 6'and the second flat plate compression spring 6" are provided, both of which have a small spring constant. The maximum displacement is restricted on the tensile displacement side of the flat plate compression springs 6 ′ and 6 ″, and it is possible to prevent the bellows 3 from being fully extended and compressed and deformed by an excessive load.

(7) When a tensile load acts on the first flat plate compression spring 6'and the second flat plate compression spring 6 ", the spring mounting span of one of the first flat plate compression springs 6'becomes shorter, and the compression load is reduced. Since the second flat plate compression spring 6 ″ is mounted so that the spring mounting span of the other second flat plate spring 6 ″ becomes short when the flexible tube A has a spring characteristic in which the spring constant on the tensile displacement side and the spring constant on the compression displacement side are arbitrarily set. It can be

(Other Embodiments) Embodiments 1, 2, 3
In the above, an example is shown in which nothing is provided on the inner peripheral side of the bellows, but a cylindrical inner cover that covers the inner periphery of the bellows may be provided.

[0096]

According to the flexible tube for automobile exhaust system of the present invention, both ends are connected to the first exhaust pipe and the second exhaust pipe, and the bellows for absorbing the displacement of both exhaust pipes and the plate material. An outer cover formed in a tubular shape to cover the outer periphery of the bellows, a first protector and a second protector connected to both ends of the bellows, and an outer cover between one end of the outer cover and the first protector. A first flat plate compression spring and a second flat plate compression spring that are respectively interposed between the other end of the cover and the second protector and have the characteristics that the compression side has a large spring constant and the tension side has a small spring constant, and both ends of the spring are fixed. Since it is configured with and, it satisfies all the required performances of small size, light weight, low cost, high displacement absorption, and high durability, and the spring constant is arbitrary according to the displacement direction of tension or compression. There is an advantage that it is possible to provide a highly practical value can be set flexible tube.

According to the invention of claim 2, claim 1
In the flexible tube for automobile exhaust system described,
In addition to the above effects, the first flat plate compression spring and the second flat plate compression spring are mounted so that both the spring mounting span becomes short when a tensile load acts and the spring mounting span becomes long when a compressive load acts. It is possible to provide a flexible tube having spring characteristics of a large spring constant on the tensile displacement side and a small spring constant on the compression displacement side.

According to the invention of claim 3, claim 1
In the flexible tube for automobile exhaust system described,
In addition to the above effects, the first flat plate compression spring and the second flat plate compression spring are mounted such that the spring mounting span becomes long when a tensile load acts and the spring mounting span becomes short when a compressive load acts. It is possible to provide a flexible tube having a spring characteristic of a small spring constant on the tensile displacement side and a large spring constant on the compression displacement side.

According to the invention of claim 4, claim 1
In the flexible tube for automobile exhaust system described,
Since the first flat plate compression spring and the second flat plate compression spring are mounted so that only one spring mounting span becomes short when a tensile load acts and only the other spring mounting span becomes short when a compressive load acts, In addition to the above effects, by selecting a flat plate compression spring having different compression spring constants, it is possible to provide a flexible tube having arbitrarily different spring characteristics on the tensile displacement side and the compression displacement side.

According to the invention of claim 5, claim 1
The flexible tube for an automobile exhaust system according to claim 4 is provided with a stopper that defines a maximum length of a spring mounting span between the first flat plate compression spring and the second flat plate compression spring. It is possible to prevent the bellows from being fully stretched or compressed and deformed by the load.

[Brief description of drawings]

FIG. 1 is a half sectional view showing a flexible tube for an automobile exhaust system according to Embodiment 1 of the present invention.

FIG. 2 is a perspective view showing a flat plate compression spring used in the flexible tube of the first embodiment.

FIG. 3 is a perspective view showing an automobile exhaust system to which the flexible tube of the first embodiment is applied.

FIG. 4 is a diagram showing when a flat plate compression spring having a large spring constant is compressed (b) and when a flat plate compression spring having a small spring constant is pulled (b).

FIG. 5 is a tensile displacement-tensile force characteristic diagram of the flexible tube of the first embodiment.

FIG. 6 is a half sectional view showing a flexible tube for an automobile exhaust system according to a second embodiment of the present invention.

FIG. 7 is a tensile displacement-tensile force characteristic diagram of the flexible tube of the second embodiment.

FIG. 8 is a half sectional view showing a flexible tube for an automobile exhaust system according to a third embodiment of the present invention.

FIG. 9 is a tensile displacement-tensile force characteristic diagram of the flexible tube of the third embodiment.

FIG. 10 is a half sectional view showing a flexible tube for an automobile exhaust system of Conventional Example 1.

FIG. 11 is a front view (a) and a side view (b) showing a flexible tube for an automobile exhaust system of Conventional Example 2.

FIG. 12 is a half sectional view showing a flexible tube for an automobile exhaust system of Conventional Example 3.

[Explanation of symbols]

 A flexible tube 1 first exhaust pipe 2 second exhaust pipe 3 bellows 5 outer cover 6'first flat plate compression spring 6 "second flat plate compression spring 7'first protector 7" second protector 51a ', 51a "stopper part

Claims (5)

[Claims] 1. A bellows (3) having both ends connected to a first exhaust pipe (1) and a second exhaust pipe (2) for absorbing displacement of both exhaust pipes (1), (2), and a plate member. An outer cover (5) formed in a cylindrical shape to cover the outer circumference of the bellows (3) with a first protector (7 ') and a second protector (7 ") respectively connected to both ends of the bellows (3). And between the one end of the outer cover (5) and the first protector (7 '), and the other end of the outer cover (5) and the second protector (7').
A first flat plate compression spring (6 ') and a second flat plate compression spring, which are respectively interposed between the protector (7 ") and have a large spring constant on the compression side and a small spring constant on the tension side and fixed at both ends of the spring. (6 ″), and a flexible tube for an automobile exhaust system, comprising: 2. The flexible tube for an automobile exhaust system according to claim 1, wherein the first flat plate compression spring (6 ′) and the second flat plate compression spring (6 ″) are both spring-attached when a tensile load is applied. A flexible tube for an automobile exhaust system, characterized in that it is mounted so that the spring mounting span becomes long when the span becomes short and a compressive load acts. 3. The flexible tube for an automobile exhaust system according to claim 1, wherein the first flat plate compression spring (6 ′) and the second flat plate compression spring (6 ″) are both spring-attached when a tensile load is applied. A flexible tube for an automobile exhaust system, characterized in that the spring mounting span is shortened when the span becomes long and a compressive load acts. 4. The flexible tube for an automobile exhaust system according to claim 1, wherein one of the first flat plate compression spring (6 ′) and the second flat plate compression spring (6 ″) is used when a tensile load is applied. A flexible tube for an automobile exhaust system, characterized in that it is mounted so that only the mounting span is shortened and only the other spring mounting span is shortened when a compressive load is applied. 5. The flexible tube for an automobile exhaust system according to claim 1, wherein a maximum length of a spring mounting span between the first flat plate compression spring (6 ′) and the second flat plate compression spring (6 ″). A flexible tube for an automobile exhaust system, which is provided with stoppers (51a '), (51a ") that regulate the height.