Outer shell unit and method of manufacturing the unit

A manufacturing method for an outer shell unit (10) provided with a cylindrical outer shell (3) housing a damping force generating mechanism and a knuckle bracket (7) mounted on the outer shell (3) to connect a knuckle. The knuckle bracket (7) is fixed by welding to the outer shell (3) after closing the bottom (31) of the outer shell (3) with a closing process. Consequently productivity is increased due to the fact that the number of processing operations for cutting an inlay and the number of operations for assembling the lower cap are reduced because the bottom is formed using a closing process. Furthermore productivity is increased since it is not necessary to seal the bottom by welding since the sealing characteristics of the bottom of the outer shell are ensured by the closing process.

FIELD OF THE INVENTION

This invention relates to an outer shell unit provided with a shock absorber which absorbs vibration or impacts. In particular, this invention relates to a structure and a method of manufacture therefore as applied to an outer shell unit provided with a strut-type shock absorber in the suspension system of a vehicle.

BACKGROUND OF THE INVENTION

In addition to their original function of generating a damping force, strut-type shock absorbers in the suspension system of a vehicle also play a role as a structural member positioning the vehicle wheels as a component in the suspension member.

FIG. 16shows a prior-art example of a strut-type shock absorber1. The outer side of this shock absorber1is provided with an outer shell unit10storing a damping force generating mechanism. The outer shell unit10is provided with a cylindrical outer shell3, a spring guide6mounted by welding onto the outer shell3and supporting a suspension spring and a knuckle bracket7mounted by welding on the outer shell3and connected to a knuckle.

The knuckle bracket7is fixed by welding after press-fitting onto the outer shell3. The upper and lower ends7e,7fof a single-plate type of knuckle bracket7are respectively fixed to the outer shell3by welding.

Inlays32,37are formed by a mechanical process on both ends of the outer shell3. A rod guide9is mounted on the upper end of the inlay32. A lower cap27is mounted on the lower end of the inlay37(seeFIG. 19). The outer peripheral section of the lower cap27is welded to the lower end of the outer shell3together with the lower end7fof the knuckle bracket7and the bottom of the outer shell3is sealed.

As shown inFIGS. 17(a) and (b), the outer shell3is rotated about the substantially perpendicular center axis O when welding the upper end7eof the knuckle bracket7to the outer shell3. A flat welding technique is employed in which the torch61of the arc-welding unit is oriented downwardly towards the corner between the outer peripheral face3aof the outer shell3and the upper end7eof the knuckle bracket7. The shape of the welded section is in the form of a lap weld with a partial fillet weld.

As shown inFIGS. 18(a) and (b), when welding the lower end7fof the knuckle bracket7and the lower cap27across the entire periphery of the outer shell3, the outer shell3is rotated about the center axis O which is inclined through an angle of 60 degrees with respect to the horizontal plane. A flat welding technique is employed in which the torch61of the arc-welding unit is oriented downwards towards the corner between the lower end3bof the outer shell3, the lower end7fof the knuckle bracket7and the lower cap27. The shape of the welded section has a specific shape comprising a characteristic flare, a lap weld and a partial fillet weld. Consequently highly accurate welding techniques and considerable welding time is required.

As shown inFIGS. 18(b), (c), the lower end6aof the spring guide6is welded simultaneously with the above at three positions to the outer peripheral face3aof the outer shell3. The shape of this welded section is in the form of a lap weld.

The assembly line process for the outer shell3comprises the steps in {circle around (1)}{circle around (2)}{circle around (3)}{circle around (4)}{circle around (5)}{circle around (6)}{circle around (7)} as shown inFIG. 19andFIG. 20.

{circle around (1)} A pipe member is cut through in order to form a work41comprising a right circular cylinder.

{circle around (2)} A drawing operation is performed along the work41in order to form a narrow radius section38.

{circle around (3)} A drawing operation is performed on the lower end of the work41in order to form a narrow radius section39.

{circle around (4)} A cutting operation is performed on the inner periphery of the lower end of the work41in order to form an inlay37.

{circle around (5)} A cutting operation is performed on the inner periphery of the upper end of the work41in order to form an inlay32. A rod guide9is engaged to the inlay32in a separate step.

{circle around (6)} The work41is cleaned with a flushing operation.

{circle around (7)} The lower cap27is press fitted to the inlay37of the work41and fixed by a caulking operation.

The above steps are all automatically performed in a single production line.

The welding line for the outer shell unit10comprises the steps in {circle around (1)}{circle around (2)}{circle around (3)}{circle around (4)}{circle around (5)}{circle around (6)}{circle around (7)}{circle around (8)} as shown inFIG. 20.

{circle around (1)} A number or identification sign of the component is stamped on the work41.

{circle around (2)} The knuckle bracket7is press fitted to the outer shell3.

{circle around (3)} The upper end7eof the knuckle bracket7is welded to the outer shell3.

{circle around (4)} The lower end7fof the knuckle bracket7and the lower end6aof the spring guide6are welded at the same time to the outer shell3. The upper end7eof the knuckle bracket7and the lower end6aof the spring guide6are welded at the same time to the outer shell3.

{circle around (5)} A leakage test is performed in order to confirm the sealing characteristics of the bottom of the outer shell3and the work41is cleaned as above.

{circle around (6)} A drilling operation is performed on each bolt hole7c,7din the knuckle bracket7.

{circle around (7)} The width between respective flanges7band the knuckle bracket7is corrected.

{circle around (8)} A hose bracket is welded to the outer shell3.

The above steps are all automatically performed in two production lines.

OBJECT OF THE INVENTION

However the prior-art method of producing an outer shell unit requires time in order to weld the spring guide6and the knuckle bracket7in the welding line to the outer shell3. Consequently it is necessary to provide for two welding lines as opposed to a single processing line in order to maintain productivity.

In particular, due to the fact that material strength as well as sealing characteristics are required in the welded section in which the lower end7fof the knuckle bracket7and the lower cap27are welded across the entire periphery of the outer shell3, it is difficult to increase the speed of welding operations and consequently the cycle time in the welding line increases. It is therefore an object of this invention to provide a highly productive method of manufacturing an outer shell unit.

It is therefore an object of this invention to provide a highly productive method of manufacturing an outer shell unit.

It is a further object of this invention to provide an outer shell unit which displays high productivity.

DISCLOSURE OF THE INVENTION

This invention increases productivity by reducing the number of cutting operations on an inlay and the number of processes for assembling the lower cap by forming a bottom using a closing process.

Since the sealing characteristics of the bottom of the outer shell are maintained when using a closing process, it is possible to increase productivity due to the fact that it is not required to seal the bottom by welding.

Since the lower end of the outer shell is drawn into a tapering shape by the closing process, it is possible to perform a smooth press-fitting operation of the knuckle bracket onto the outer shell. Consequently the reduction in the number of drawing operations applied to the outer shell improves productivity.

Since the sealing characteristics of the bottom of the outer shell in this invention are maintained by the closing process, it is not required to seal the bottom by welding. Thus it is possible to perform high-speed welding operations and shorten the cycle time in the welding line by using a method of vertical downward welding.

This invention provides a protrusion projecting from the bottom of the outer shell in order to ensure sealing characteristics of the bottom. Furthermore the structure is simplified since it is possible to directly engage the knuckle with the outer shell by providing a threaded section in the

BEST METHOD FOR CARRYING OUT THE INVENTION

In order to describe the invention in greater detail, the preferred embodiments will be outlined below with reference to the accompanying drawings.

FIG. 1shows a cross section of a shock absorber. This strut-type shock absorber1is provided with a rod2connected to the vehicle body, an outer shell3connected to the knuckle (not shown) which supports the vehicle shaft, a rod guide9which supports the rod2to slide freely on the outer shell3, an inner tube4which partitions an oil storage chamber18with gas enclosed in a section on-the inner side of the outer shell3, a piston5which is connected to the tip of the rod2and which partitions the inner section of the inner tube4into an upper oil chamber16and a lower oil chamber17, a piston valve11which generates a damping force during an extension stroke and a base valve generating a damping force during a compression stroke. The shock absorber1comprises a damping force generating mechanism in the outer shell3for damping vibrations on the vehicle wheels.

During an extension stroke in which the rod2displaces upwardly, the upper oil chamber16is pressurized and working oil flows into the lower oil chamber17through the piston valve11in order to generate a damping force. During this operation, working oil corresponding to the retraction of the rod2opens the base valve12from the oil storage chamber18and flows into the lower oil chamber17almost without resistance.

During a compression stroke in which the rod2displaces downwardly, working oil in the lower oil chamber17opens the piston valve11and flows into the upper oil chamber16almost without resistance. During this operation, working oil corresponding to the intrusion of the rod2flows into the oil storage chamber18through the base valve12from the lower oil chamber17in order to generate a damping force.

The strut-type shock absorber1is provided with a spring guide6supporting the lower end of a suspension spring and a knuckle bracket7connected to the knuckle. The shock absorber1plays the role of positioning the vehicle wheels by acting as a section of a suspension member.

An annular step35is formed by extrusion molding with a blister process alone the outer shell3. The spring glide6is fixed by press fitting to the step35. In this manner, it is not necessary to weld the spring guide6to the outer peripheral face3aof the outer shell3.

FIG. 2shows a process for forming a step35using a blister operation, i.e., bulge forming. The blister operation unit comprises a jig52retaining a work41such as a pipe member, an outer mold53encircling the outer side of a work41, an inner mold54disposed on the inner side of a work41and a wedge-shaped engaging member56which displaces the inner mold54in a radial direction. A work41retained on the jig52is encircled by the outer mold53, the inner mold54is disposed on the inner side of the work41and the engaging member56is pressed by a force P onto the inner mold54. As a result, the inner mold54expands radially and a step35is formed by the resulting swelling along the work41in an annular shape corresponding to the shape of the outer mold53and the inner mold54.

The spring guide6has an engaging section6awhich engages with the outer shell3and a sheet6bwhich supports the lower end of the suspension spring. The spring guide6is integrated by a pressing operation.

The outer shell3has a cylindrical main body30and a bottom31which covers the lower end of the main body30. The bottom31of the outer shell3is integrated to the main body30of the outer shell3by a plastic process or plastic forming termed a closing process. In this manner, the sealing characteristics of the bottom31of the outer shell3can be maintained and it is therefore not required to seal the bottom31by welding.

FIG. 3shows the process of forming a bottom31using a closing process. The device used in the closing process comprises a chuck42retaining a work41such as a pipe member, a cored bar44disposed coaxially with respect to the work41by a retaining bar43on the inner side of the work41, a die45rotating about a shaft having a predetermined offset S from the work41and a heating coil46heating the die43. The work41, the cored bar44and the die45are rotated in the same direction.

The die45has an inner peripheral face45aformed in a concave cylindrical shape and a curved face45bformed in a substantially concave spherical shape. The cored bar44has a cylindrical outer peripheral face44a,a curved face44bprojecting substantially in the shape of a sphere and an indentation44cprovided in the center of the curved face44b.

The closing process is such that the open end of the work41between the die45and the cored bar44is gradually constricted by pressing the die45onto the work41with a force P while rotating the work41, the cored bar44and the die45in the same direction. The bottom31is formed closing and sealing the opening into a conical cylinder. The bottom31inclines with an angle α with respect to a face which is orthogonal to the central axis O. The angle α is set for example to 30 degrees (π/6rad).

The central section of the bottom31is closed by constricting the work41between the die45and the cored bar44. During this operation, a protrusion34is formed on the work41and projects into the indentation44cof the cored bar44. Consequently it is possible to ensure sealing of the bottom31by providing a protrusion34which projects into the outer shell3from the bottom31.

The knuckle bracket7comprises an engaging section7awhich engages with the outer shell3, a pair of flanges7bwhich sandwich the knuckle, and a hose bracket7g.Bolt holes7c,7dare formed on each flange7b.A knuckle is fixed to the knuckle bracket7by two bolts inserted into the bolt holes7c,7d.In order to ensure dimensional accuracy, both bolt holes7c,7dundergo a drilling operation after the knuckle bracket7is fixed by welding to the outer shell3. The knuckle bracket7is a single-plate type which is not provided with a reinforcing member between the flanges7b.

The knuckle bracket7is fixed by welding after being press-fitted to the outer shell3. It is possible to perform a smooth press-fitting operation on the outer shell3since the lower end of the outer shell3is drawn into a tapering shape using a closing process.

The upper and lower ends7e,7fof the single-plate type knuckle bracket7are fixed to the outer shell3by respective welded sections21,22.

As shown byFIGS. 4(a), (b), (c), welded section21on the upper side of the bracket is welded using a vertical downward welding method with the torch61of the arc-welding unit oriented towards the corner between the outer peripheral face3aof the outer shell3and the upper end7eof the knuckle bracket7. When applying this vertical downward welding method, the outer shell3is rotated about the central axis O which is disposed in a substantially horizontal plane. The torch61of the arc-welding unit is oriented to the lateral section of the outer shell3. The direction in which the outer shell3is rotated is set to a direction in which the position of the outer shell3facing the torch61rises as shown by the arrow inFIG. 4(b).

The horizontal plane including the central axis O of the outer shell3is taken to be a horizontal reference plane X. The vertical plane including the central axis O of the outer shell3is taken to be a vertical reference plane Y. The welding point W is defined by the intersection of a line extended from the torch61of the arc-welding unit with the outer peripheral face3aof the outer shell3.

The welding point W is either offset onto the horizontal reference plane X or to a position above the horizontal reference plane X by a predetermined length Lx. In this embodiment, the outer radius of the outer shell3is approximately 45 mm and the offset amount Lx is set in the range 0–10 mm.

The welding point W is offset from the vertical reference plane Y by a predetermined length Ly. The vertical downward welding method is performing by disposing the welding point W so that the vertical offset amount Lx is smaller than the horizontal offset amount Ly.

The torch angle θx of the torch61is inclined upwardly with respect to the horizontal reference plane X and is set to be smaller than the torch angle θy inclined with respect to the vertical reference plane Y. In this embodiment, the torch angle θx is set to the range 0–30 degrees (0–π/6 rad).

As shown inFIGS. 5(a), (b), the welded section21on the lower side of the bracket is welded using a vertical downward welding method with the torch61of the arc-welding unit oriented towards the corner between the lower end3bof the outer shell3and the lower end7fof the knuckle bracket7. In this vertical downward welding method, the outer shell3is rotated about the central axis O which is disposed in a substantially horizontal plane. The direction in which the outer shell3is rotated is set to a direction in which the position of the outer shell3facing the torch61rises as shown by the arrow inFIG. 5(a).

The welding point W is either offset onto the horizontal reference line X or to a position above the horizontal reference plane X by a predetermined length Lx. In this embodiment, the outer radius of the outer shell3is approximately 45 mm and the offset amount Lx is set in the range 0–10 mm.

The torch angle θx of the torch61is inclined upwardly with respect to the horizontal reference plane X is set to be smaller than the torch angle θy inclined with respect to the vertical reference plane Y In this embodiment, the torch angle θx is set to the range 0–15 degrees (0–π/12 rad).

The vertical downward welding method allows arbitrary setting of the offset amount Lx, the torch angle θx, as well as the rotation speed of the outer shell3, the voltage and the current of the torch in response to the outer radius of the outer shell3. A welding speed is obtained which is greater than that obtained by a welding device using a conventional flat welding method since a balance is produced between the welding speed and the drip rate of the flux.

FIG. 6shows the relationship between the torch angle θx and the spatter fall amount. The arc force is applied on the flux as shown by the arrow in the drawing and presses the flux in a forward direction. As a result, when the torch angle θx is set above 30 degrees, the amount of spatter fall increases rapidly.

When the torch angle θx is set to a large value, the bead width increases. Although this results in an improvement to the outward appearance, it also tends to result in insufficient fusion or failure of fusion. Consequently the bead line may become indented and reduce insufficient component strength. Insufficient fusion may result in an excessive leading edge in the flux and create an arc-shaped residue over the flux.

Consequently a torch angle θx set in a range of 0–30 degrees allows the spatter fall amount to be suppressed and thus effectively suppresses insufficient fusion or failure of fusion.

When the welding point W is disposed below the horizontal reference plane X and the offset amount Lx is set to a negative value, the shape of the bead is adversely affected since gravity acts in a direction in which the flux becomes separated from the outer shell3. Improved bead formation is obtained by disposing the welding point W above the horizontal reference plane X.

FIG. 7shows the general relationship of bead shape and the offset amount Lx, Ly of the welding point W located at A, B, and C. As the offset amount Lx decreases, the drip rate of the flux increases and the bead width increases. Conversely as the offset amount Lx increases, the drip rate of the flux decreases and the bead width narrows. When the rotation speed of the outer shell3is increased, the balance with respect to the drip rate for the flux fails and faults may result in the welding process.

When the knuckle bracket7is welded to the outer shell3, the offset amount Lx of the welding point W with respect to the horizontal reference plane X is set to increase as the outer radius of the outer shell3increases. In this embodiment, when the outer radius of the outer shell3is set to approximately 45 mm and the offset amount Lx is set in a range of 0–10 mm, a suitable drip rate for the flux is obtained and improved bead formation characteristics are obtained.

FIG. 8shows the process of manufacturing an outer shell unit10comprising a spring guide6, a knuckle bracket7and an outer shell3. The production line manufacturing the outer shell unit10is separated into a processing line for the outer shell3which processes the outer shell3, and a welding line for the outer shell unit10which mounts the spring guide6and the knuckle bracket7onto the outer shell3. As a result, the turnover rate required to form a single outer shell3in the processing line is made equal to the turnover rate required to form a single outer shell unit10in the welding line.

The processing line process for the outer shell3comprises the sequence of the process in {circle around (1)}{circle around (2)}{circle around (3)}{circle around (4)}{circle around (5)} as shown inFIG. 8andFIG. 9.

{circle around (1)} A pipe member is cut through in order to form a work41comprising a right circular cylinder.

{circle around (2)} A cutting operation is performed on the inner periphery of one end of the work41in order to form an inlay32. The rod guide9is engaged to the inlay32in a separate operation.

{circle around (3)} A closing process is performed on the other end of the work41in order to form a bottom31.

{circle around (4)} A blister operation is performed along the work41in order to form a step35.

The above processes are all automatically performed in a single production line.

The welding line for the outer shell unit10comprises the steps in {circle around (1)}{circle around (2)}{circle around (3)}{circle around (4)}{circle around (5)}{circle around (6)}{circle around (7)} as shown inFIG. 8.

{circle around (1)} A number or identification sign of the component is stamped on the work41.

{circle around (2)} The knuckle bracket7is press fitted to the outer shell3.

{circle around (3)} The upper end7eof the knuckle bracket7is high-speed welded using a vertical downward welding method to the outer peripheral face3athe outer shell3.

{circle around (4)} The lower end7fof the knuckle bracket7is high-speed welded using a vertical downward welding method to the lower end3bthe outer shell3.

{circle around (5)} The spring guide6is pressed fitted to the step35of the outer shell3.

{circle around (6)} A drilling operation is performed on each bolt hole7c,7din the knuckle bracket7.

{circle around (7)} The hose bracket8is welded to the outer shell3.

The above steps are all automatically performed in a single production line.

As a result, the turnover rate required to form a single outer shell3in the processing line is made equal to the turnover rate required to form a single outer shell unit10in the welding line. As a consequence, it is possible to effectively increase the production amount since it is not necessary to operate one line while resting the other.

In the processing line for the outer shell3, since a bottom31is formed using a closing process, the number of operations required to assemble a lower cap or the number of operations required to cut the inlay or the number of drawing operations on the lower end of the outer shell3are reduced. Thus it is possible to shorten the cycle time required to form one outer shell3in the processing line.

In the welding line for the outer shell3, the spring guide6is press fitted to the outer shell3and welding operations on both components are omitted. Furthermore the upper and lower ends7e,7fof the knuckle bracket7are high-speed welded using a vertical downward welding method on the outer shell3. Thus it is possible to shorten the cycle time required to form a single outer shell unit10in the welding line.

It is possible to perform high-speed welding operations using a vertical downward welding method without the necessity to seal the bottom31by welding since sealing characteristics are ensured by use of a closing process on the bottom31of the outer shell3.

Another embodiment of this invention is shown inFIGS. 10(a), (b). In this embodiment, the knuckle bracket7may be a cylindrical double-plate type in which a reinforcing member15may be provided between each flange7b.The reinforcing member15is fixed between the flanges7bin order to increase the rigidity of the knuckle bracket7.

After the knuckle bracket7is press-fitted to the outer shell3, only the lower end7fof the knuckle bracket7is welded respectively to the outer shell3. Consequently there is not necessity to fit the upper end7eof the knuckle bracket7to the outer shell3by welding.

As shown inFIGS. 10(a), (b), a vertical downward welding method is used with the torch61of the arc-welding unit oriented towards the corner between the lower end3bof the outer shell3and the lower end7fof the knuckle bracket7. In this vertical downward welding method, the outer shell3is rotated about the central axis O disposed in a substantially horizontal plane. The direction in which the outer shell3is rotated is set to a direction in which the position of the outer shell3facing the torch61rises as shown by the arrow inFIG. 10(a).

The welding point W is either offset onto the horizontal reference plane X or to a position above the horizontal reference plane X by a predetermined length Lx. In this embodiment, the outer radius of the outer shell3is approximately 45 mm and the offset amount Lx is set in the range 0–10 mm.

The torch angle θx of the torch61is inclined upwardly with respect to the horizontal reference plane X and is set to the range 0–30 degrees (0–π/6 rad).

FIG. 11shows the process of manufacturing an outer shell unit10. The production line is separated into a processing line for the outer shell3which processes the outer shell3, and a welding line for the outer shell unit10which mounts the spring guide6and the knuckle bracket7onto the outer shell3. As a result, the cycle times of both lines is made equal.

The processing line for the outer shell3comprises the steps in {circle around (1)}{circle around (2)}{circle around (3)}{circle around (4)}{circle around (5)} as shown inFIG. 11. This is the same as the processing line shown inFIG. 8. The welding line for the outer shell unit10comprises the steps in {circle around (1)}{circle around (2)}{circle around (3)}{circle around (4)}{circle around (5)}{circle around (6)}{circle around (7)} as shown inFIG. 11.

{circle around (1)} A number or identification sign of the component is stamped on the work41.

{circle around (2)} The knuckle bracket7is press fitted to the outer shell3.

{circle around (3)} The lower end7fof the knuckle bracket7is high-speed welded using a vertical downward welding method to the lower end3bof the outer shell3.

{circle around (4)} The spring guide6is pressed fitted to the step35of the outer shell3.

{circle around (5)} A drilling operation is performed on each bolt hole7c,7din the knuckle bracket7.

{circle around (6)} The hose bracket8is welded to the outer shell3.

{circle around (7)} The stabilizer bracket19is welded to the outer shell3.

In comparison to the steps in the processing line as shown inFIG. 8above, this welding line adds the step of welding the stabilizer bracket19to the outer shell3and omits the step of high-speed welding of the upper end7eof the knuckle bracket7to the outer peripheral face3aof the outer shell3using a vertical downward welding method.

Using a cylindrical double-plate knuckle bracket7allows the stabilizer bracket19to be welded to the outer shell3in the same cycle time as that taken in the processing line. This is due to the fact that it is not necessary to fit the upper end7eof the knuckle bracket7to the outer shell3by welding.

Another embodiment is shown inFIGS. 12(a), (b), (c). In this embodiment, the step35formed by a blister operation on the outer shell3is omitted and the spring guide6may be fixed by welding to the outer peripheral face3aof the outer shell3.

A cylindrical double-plate knuckle bracket7may be provided which has a reinforcing member15between each flange7b.

After the spring guide6is press-fitted to the outer shell3, the lower end6cof the spring guide6is welded to the outer peripheral face3aof the outer shell3.

A high-speed welding operation comprising a downward welding method is used is used to weld the spring guide6to the outer peripheral face3aof the outer shell3. The torch61of the arc-welding unit is oriented towards the corner between the outer peripheral face3aof the outer shell3and the lower end6cof the spring guide6. The outer shell3is rotated about the central axis O which is disposed in a substantially horizontal plane. The direction in which the outer shell3is rotated is set to a direction in which the position of the outer shell3facing the torch61rises as shown by the arrow inFIG. 12(a).

The welding point W is either offset onto the horizontal reference plane X or to a position above the horizontal reference plane X by a predetermined length Lx. In this embodiment, the outer radius of the outer shell3is approximately 45 mm and the offset amount Lx is set in the range 0–10 mm.

The torch angle θx of the torch61is inclined upwardly with respect to the horizontal reference plane X and is set to the range 0–15 degrees (0–π/12 rad).

FIG. 13shows the process of manufacturing an outer shell unit10. The production line is separated into a processing line for the outer shell3which processes the outer shell3, and a welding line for the outer shell unit10which mounts the spring guide6and the knuckle bracket7onto the outer shell3. The cycle time of both lines is made equal.

The processing line for the outer shell3comprises the steps in {circle around (1)}{circle around (2)}{circle around (3)}{circle around (4)}.

{circle around (1)} A pipe member is cut through in order to form a work41comprising a right circular cylinder.

{circle around (2)} A cutting operation is performed on the inner periphery of one end of the work41in order to form an inlay32. The rod guide9is engaged to the inlay32in a separate step.

{circle around (3)} A closing process is performed on the other end of the work41in order to form a bottom31.

In comparison to the steps in the processing line as shown inFIG. 8, the processing line omits the process of forming the step35with the blister process along the work41.

The welding line for the outer shell unit10comprises the steps in {circle around (1)}{circle around (2)}{circle around (3)}{circle around (4)}{circle around (5)}{circle around (6)}{circle around (7)}.

{circle around (1)} A number or identification sign of the component is stamped on the work41.

{circle around (2)} The knuckle bracket7is press fitted to the outer shell3.

{circle around (3)} The lower end7fof the knuckle bracket7is high-speed welded using a vertical downward welding method to the lower end3bthe outer shell3.

{circle around (4)} The spring guide6is high-speed welded using a vertical downward welding process to the outer peripheral face3aof the outer shell3.

{circle around (5)} A drilling operation is performed on each bolt hole7c,7din the knuckle bracket7.

{circle around (6)} The hose bracket8is welded to the outer shell3.

{circle around (7)} The stabilizer bracket19is welded to the outer shell3.

In comparison to the steps in the processing line as shown inFIG. 8, the processing line adds the step of welding the stabilizer bracket19to the outer shell3and the step of welding the spring guide6to the outer shell3and omits the step of high-speed welding of the upper end7eof the knuckle bracket7to the outer peripheral face3aof the outer shell3and omits the step of press-fitting the spring guide6to the outer shell3.

Using a cylindrical double-plate knuckle bracket7allows the stabilizer bracket19and the spring guide6to be welded to the outer shell3in the same cycle time as that taken in the processing line since it is not necessary to fit the upper end7eof the knuckle bracket7to the outer shell3by welding.

The process of stamping a number or an identification sign of the component on the work41may be performed in the processing line.

In another embodiment as shown inFIG. 14, a knuckle20supporting the vehicle shaft may be directly fixed to the outer shell3. The knuckle20has the function of positioning the vehicle wheel as a section of a suspension member.

The knuckle20has an engagement hole24which is engaged with the outer shell3from below. The outer shell3has a cylindrical main body30and a tapering section (a knuckle mounting section) engaging the engaging hole24of the knuckle20with the lower end of the main body30. The tapering section34is inclined to taper downwardly and is engaged in the engagement hole24of the knuckle20which inclines in the same manner.

The outer shell3has a bottom31covering the lower end of the main body30and a threaded section36projecting from the bottom31. The threaded section36projects downwardly through the engagement hole24of the knuckle20.

A washer23and a nut25are provided. The washer23acts as a fixing member which is inserted into the threaded section36and abuts with the lower end face of the engagement hole24of the knuckle20. The nut25acts as a fixing member which is threadably engaged with the threaded section36. The engagement hole24of the knuckle20is engaged with the tapering section34of the outer shell3and fixed through the washer23by the nut25which is threadably engaged with the threaded section36.

The protrusion33comprises a bottom31, a threaded section36and a tapering section34of the outer shell3. The protrusion33is integrated with the main body30of the outer shell3by a molding process termed a closing process. In this manner, the sealing characteristics of the bottom31of the outer shell3are ensured and it is not required to seal the bottom31by welding.

FIG. 15shows the process of forming a protrusion33, a bottom31and a tapering section34using the closing process. The closing processing unit comprises a chuck42retaining a work41such as a pipe member, a cored bar44disposed coaxially with respect to the work41by a retaining bar43on the inner side of the work41, a die45rotating about a shaft having a predetermined offset S from the work41and a heating coil46heating the die43. The work41, the cored bar44and the die45are rotated in the same direction.

The die45has a cylindrical tapering face45aformed in a concave tapering shape and a cylindrical inner peripheral face45cformed in the center of a curved face45b.

The cored bar44has a cylindrical outer peripheral face44a,a curved face44bprojecting substantially in the shape of a sphere and an indentation44cprovided in the center of the curved face44b.

The closing process is such that the open end of the work41between the die45and the cored bar44is gradually constricted by pressing the die45onto the work41with a force P while rotating the work41, the cored bar44and the die45in the same direction. The bottom31is formed closing and sealing the opening into a conical cylinder.

The central section of the bottom31is closed by constricting the work41between the die45and the cored bar44. During this operation, the protrusion33is formed to project into the indentation45cof the die45on the work41.

Threading is engraved onto the protrusion33by a mechanical process in order to form the threaded section36.

As shown above, the knuckle20is engaged to the tapering section34of the outer shell3and is fixed by a nut25which is threadably engaged to the threaded section36. As a result, the cycle time can be shortened and productivity can be thereby increased since the welding process in the prior-art example in which the knuckle bracket is welded onto the outer shell can be omitted.

It is not necessary to seal the bottom31by welding since the bottom31of the outer shell3is closed using a closing process. Thus closure of the bottom31can be ensured by providing a protrusion33projecting towards the outer side of the outer shell3from the bottom31.

An annular step projecting from the outer peripheral face of the outer shell3may be formed as a knuckle mounting section which is inserted into the engagement hole24of the knuckle in the outer shell3. Furthermore a member fixed between the nut25and the bottom31of the outer shell3may be formed in the knuckle20.

INDUSTRIAL APPLICABILITY

As shown above, the outer shell unit and the method of manufacture therefore according to this invention is related to a shock absorber which damps vibration and shocks. In particular, the invention relates to an application to a strut-type shock absorber in a vehicle suspension system.