BACKGROUND OF THE INVENTION
Field of the Invention

The present invention relates to a method for manufacturing a pipe structure having a meandering shape, a spiral shape, or the like, for example, which is used as a constituent element of a heat exchanger or the like.

Description of the Related Art

A meandering pipe body A such as that shown in FIG. 1, for example, is available as a pipe structure used as a heat transfer pipe of a heat exchanger. The meandering pipe body A is constructed by forming a stainless-steel pipe 1 in a meandering shape, and includes a plurality of bend portions 10. Regions 11A, 11B near respective end portions of the pipe 1 are separated from each other in an x direction and extend in a y direction that intersects the x direction.

A method shown in FIG. 12, for example, is available as a method for manufacturing the meandering pipe body A. This manufacturing method includes a pipe manufacturing and press-cutting step S1, a pipe bending step S2, and a cutting and deburring step S3.

Here, the pipe manufacturing and press-cutting step S1, as shown in FIG. 13A, is a step for manufacturing a long, straight, stainless-steel pipe 1B and then cutting the pipe 1B into the pipe 1 of an appropriate length by pressing.

The pipe bending step S2, as shown in FIG. 13B, is a step for implementing a bending process a plurality of times so as to form the plurality of bend portions 10 in intermediate locations along the longitudinal direction of the pipe 1. The bending process is performed by, for example, wrapping a part of the pipe 1 around a peripheral surface of a rolling block of a pipe bender and pressing the part of the pipe 1 against the peripheral surface. Deformed portions 18 that are flattened by the cutting performed during the aforesaid pressing process exist on respective longitudinal direction end portions 11a, 11b of the pipe 1.

The cutting and deburring step S3, as shown in FIG. 13C, is a step for cutting the respective end portions 11a, 11b of the pipe 1 and deburring the cut locations. Cutting is performed to remove the deformed portions 18 and align y-direction positions of the respective end portions 11a, 11b. When the plurality of bending processes are performed on the pipe 1, an error (variation) occurs in the position of each bend portion 10, leading to a cumulative error in the pipe 1 as a whole, and as a result, the y-direction positions of the respective end portions 11a, 11b are likely to be misaligned such that positional deviation of a dimension L1 occurs therebetween. By performing the cutting described above, however, this positional deviation is eliminated. As will be described below with reference to FIGS. 2A to 2C and 3, when the meandering pipe body A is used as a heat transfer pipe of a heat exchanger HE, for example, it is desirable for the y-direction positions of the respective end portions 11a, 11b to be aligned.

As described below, there remains room for improvement in the prior art described above.

In the prior art described above, the respective end portions 11a, 11b of the pipe 1 are cut after completing the bending processes on the pipe 1, and therefore the cutting operation is complicated. As a result, the productivity of the meandering pipe body A is poor, and the manufacturing cost thereof is high. Hence, in these respects, there remains room for improvement.

In contrast to the above description, as shown in FIG. 14, for example, a pipe body in which the deformed portions 18 do not exist on the respective end portions 11a, 11b may be used as the pipe 1. However, when such a means is merely employed, the y-direction positions of the respective end portions 11a, 11b deviate by a certain dimension L2. Likewise in this case, therefore, it is necessary to perform a cutting step to align the positions of the respective end portions 11a, 11b. As a result, the problem described above remains unsolved.

CITATION LIST

PTL 1: Japanese Patent No. 3824621

PTL 2: Japanese Patent No. 5822285

PTL 3: Japanese Patent Application Publication No. 2019-126830

PTL 4: Japanese Patent Application Publication No. 2012-135797

SUMMARY OF THE INVENTION

An object of the present invention is to provide a manufacturing method for a pipe structure with which complicated processes such as cutting respective end portions of a pipe after bending the pipe can be eliminated, whereby a pipe structure such as a meandering pipe body in which the positions of the respective end portions are aligned can be manufactured appropriately and with favorable productivity.

To achieve the object described above, the present invention teaches the following technical means.

A manufacturing method for a pipe structure provided by the present invention includes a pipe bending step for implementing for a plurality of times a bending process of bending a part of a straight pipe by wrapping the part around a peripheral surface of a rolling block in order to form a plurality of bend portions in intermediate locations along a longitudinal direction of the pipe, a region near a front end portion on a bend start side of the pipe and a region near a rear end portion on a bend end side being separated from each other in a predetermined x direction and extending in a y direction that intersects the x direction, wherein, when a final bending process is implemented during the pipe bending step, a position of the rear end portion of the pipe is determined, and relative y-direction positions of the pipe and the rolling block are controlled on the basis of the position of the rear end portion so that after the final bending process, a y-direction position of the rear end portion is aligned with a y-direction position of the front end portion.

The pipe structure can be set as a meandering pipe body or a spiral pipe body.

Preferably, detecting means for detecting the rear end portion of the pipe is used in an operation for controlling the relative y-direction positions of the pipe and the rolling block on the basis of the position of the rear end portion, and by using the detecting means, the pipe is positioned so that the rear end portion of the pipe is disposed a predetermined dimension away from the rolling block in the y direction.

Preferably, the predetermined dimension is a y-direction dimension from the rolling block to the front end portion of the pipe in a state where the pipe and the rolling block have been positioned to implement a first bending process on the pipe.

Preferably, the manufacturing method for a pipe structure according to the present invention includes a step for determining a projection dimension in the y direction from the rolling block to the front end portion of the pipe when positioning the pipe and the rolling block to implement the final bending process, wherein the predetermined dimension is set at a value corresponding to the projection dimension.

Preferably, a pipe on which respective longitudinal direction end portions have been laser-cut is used as the straight pipe.

Other features and advantages of the present invention will become more apparent from the embodiment of the invention that is described below with reference to the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing an example of a meandering pipe body serving as a pipe structure;

FIG. 2A is a sectional plan view showing an example of a heat exchanger that uses the pipe structure shown in FIG. 1, FIG. 2B is a front sectional view of FIG. 2A, and FIG. 2C is a right-side sectional view of FIG. 2B;

FIG. 3 is an exploded sectional plan view of FIG. 2A;

FIG. 4 is an illustrative view showing an example of a series of operation steps of a manufacturing method for a pipe structure (the meandering pipe body) according to the present invention;

FIG. 5A is an illustrative view showing a pipe manufacturing and press-cutting step of FIG. 4, and FIG. 5B is an illustrative view showing a laser-cutting step of FIG. 4;

FIG. 6A is a schematic sectional plan view showing an example of main parts of a pipe bender used in a pipe bending step of FIG. 4, and FIG. 6B is a VIB-VIB sectional view of FIG. 6A;

FIG. 7 is a schematic sectional plan view illustrating an operation of the pipe bender shown in FIGS. 6A and 6B;

FIGS. 8A to 8G are illustrative views showing the pipe bending step of FIG. 4;

FIGS. 9A and 9B are front views showing other examples of meandering pipe bodies;

FIG. 10A is a plan view showing an example of a spiral pipe body serving as the pipe structure, and FIG. 10B is an XB-XB sectional view of FIG. 10A;

FIGS. 11A to 11F are illustrative views showing the pipe bending step when manufacturing the spiral pipe body shown in FIGS. 10A and 10B;

FIG. 12 is an illustrative view showing a series of operation steps according to the prior art;

FIGS. 13A to 13C are schematic illustrative views respectively showing the operation steps of FIG. 12; and

FIG. 14 is a front view showing another example of the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention will be described specifically below with reference to the figures.

The manufacturing subject of the manufacturing method for a pipe structure according to this embodiment, similarly to the prior art described above, is the meandering pipe body A shown in FIG. 1. Accordingly, identical or similar elements to the prior art have been allocated identical reference symbols to the prior art.

First, the meandering pipe body A will be described.

As described above, the meandering pipe body A is constructed by forming the stainless-steel pipe 1, for example, in a meandering shape, and includes the plurality of bend portions 10, each of which has a bend angle of 180 degrees, and a plurality of straight portions 11 connected via the plurality of bend portions 10. The regions 11A, 11B near the respective end portions of the pipe 1 are separated from each other in the x direction, which is a horizontal width direction in FIG. 1, and extend in the y direction. The x and y directions intersect each other.

The heat exchanger HE shown in FIGS. 2A to 2C is constructed using the plurality of meandering pipe bodies A. More specifically, in the heat exchanger HE, the plurality of meandering pipe bodies A are housed in a case 7 so as to be stacked in an up-down height direction and so as to deviate from each other positionally in a left-right horizontal width direction. The respective end portions 11a, 11b of each meandering pipe body A are drawn out to the exterior of the case 7, and water inlet and hot-water outlet headers 8a, 8b are attached thereto. Water to be heated and hot water flow into and out of the meandering pipe body A through the headers 8a, 8b. An intake port 70 and an exhaust port 71 for heating gas such as combustion gas generated by a burner, not shown in the figures, are provided in the case 7. The meandering pipe bodies A function as heat transfer pipes for recovering heat from the heating gas. The water to be heated is heated while flowing through the meandering pipe bodies A, and as a result, warm water for use in a hot water supply is generated.

When manufacturing the heat exchanger HE described above, the headers 8a, 8b are attached to the respective end portions 11a, 11b of each meandering pipe body A, as shown in FIG. 3. In this case, it is a requirement to align not only x-direction positions of the respective end portions 11a, 11b, but also the y-direction positions thereof. When the y-direction positions of the respective end portions 11a, 11b deviate from each other, unevenness occurs in the manner in which the water to be heated and the hot water flow through the headers 8a, 8b. Moreover, when the positional deviation in the y direction is large, attachment of the headers 8a, 8b may be impeded. The manufacturing method for a pipe structure according to this embodiment can respond to this requirement. The content thereof will be described below.

In the manufacturing method for a pipe structure (the meandering pipe body A) according to this embodiment, as shown in FIG. 4, a pipe manufacturing and press-cutting step Sa, a laser-cutting step Sb, and a pipe bending step Sc are performed in succession.

The pipe manufacturing and press-cutting step Sa, as shown in FIG. 5A, is a step for manufacturing a long, straight pipe 1A. The pipe 1A is formed by press-cutting respective end portions thereof. Further, manufacture (pipe manufacture) of the pipe to be press-cut is realized by rounding a flat plate-shaped stainless-steel member, for example, into a round pipe shape and joining a mating portion thereof by laser welding or the like.

The laser-cutting step Sb, as shown in FIG. 5A, is a step for acquiring the pipe 1 of a predetermined length La, shown in FIG. 5B, by laser-cutting the pipe 1A described above. By performing laser-cutting, deformed portions such as flattened portions are not generated on the respective end portions 11a, 11b of the pipe 1. Moreover, burrs are unlikely to occur. Hence, there is no need to perform a cutting step for removing the flattened portions or deburring. The length La of the pipe 1 is identical to an overall length dimension (a flow passage length) of the finally acquired meandering pipe body A.

The pipe bending step Sc is a step for implementing a bending process on the pipe 1 a plurality of times so as to form the pipe 1 in a meandering shape as a whole. A pipe bender PB such as that shown in FIGS. 6A and 6B, for example, is used to bend the pipe 1.

The basic configuration of the pipe bender PB is known from the prior art (see Japanese Patent Application Publication No. 2019-126830 and Japanese Patent Application Publication No. 2012-135797, for example), and includes a rolling block 2, a pressure die 3, and a clamping die 4. The pipe bender PB also includes a pipe chuck 5 and a position sensor 6.

The rolling block 2 is capable of rotating horizontally about a shaft portion 20, and a pipe insertion recess 21 is provided in an outer peripheral surface thereof so that a part of the outer peripheral surface of the pipe 1 can be inserted therein. The pipe insertion recess 21 includes a curved portion 21a curved into an arc shape over an angle range of 180 degrees, and rectilinear portions 21b, 21c connected to respective ends of the curved portion 21a. A plurality of recessed groove portions 22 are provided at appropriate intervals in the curved portion 21a. When the pipe 1 is bent, the recessed groove portions 22 serve as sites for facilitating compressive deformation of an inside region of the bend portion 10.

The pressure die 3 is a block-shaped member having a pipe insertion recess 31 formed continuously in a side face thereof, and is capable of reciprocating in the x direction and the y direction when positioned beside the rolling block 2. When the rolling block 2 is rotated, the pressure die 3 presses the pipe 1 on the opposite side to the rolling block 2, and as a result, bending deformation can be applied to the pipe 1.

The clamping die 4 is a site for clamping the pipe 1 together with the rolling block 2 so as to exert a pulling action on the pipe 1, and a pipe insertion recess 41 is provided in a side face of the clamping die 4. By rotating the clamping die 4 together with the rolling block 2 in the direction of an arrow Na in FIG. 6A about the shaft portion 20, a part of the pipe 1 can be bent so as to wrap around the inner surface of the curved portion 21a of the rolling block 2, as shown in FIG. 7.

In FIG. 6A, the pipe chuck 5 is free to clamp and unclamp the pipe 1, and by advancing toward the rolling block 2 side while clamping the pipe 1, the pipe chuck 5 can perform an action for feeding the pipe 1 toward the rolling block 2 side. Further, the pipe chuck 5 can rotate the pipe 1 by rotating about the axial center of the pipe 1 (rotating in the direction of an arrow Nb in FIG. 6A) while clamping the pipe 1.

The position sensor 6 is a light-reflecting optical sensor having a light-emitting element and a light-receiving element, for example, and is capable of detecting a position of an edge of the rear end portion 11b of the pipe 1. In this embodiment, when the edge of the rear end portion 11b reaches a front surface of the position sensor 6 while the pipe 1 is fed toward the rolling block 2 side, the edge can be detected. The position sensor 6 corresponds to an example of the “detecting means for detecting the rear end portion” of the present invention. A light-transmitting optical sensor or a sensor other than an optical sensor may be used as the position sensor 6 instead of a light-reflecting optical sensor.

The pipe bending step Sc is performed by implementing processes such as those shown in FIGS. 8A to 8G. These processes will be described below.

First, as shown in FIG. 8A, the pipe 1 is set so as to be clamped between the rolling block 2 and the pressure die 3 and clamping die 4. At this time, a y-direction dimension Lb between (an edge of) the front end portion 11a of the pipe 1 and the rolling block 2 is set at a predetermined dimension. In this state, as shown in FIG. 8B, a first bending process is performed by rotating the clamping die 4 and the rolling block 2 in the direction of an arrow Na, and as a result, the bend portion 10 is formed.

Next, as shown in FIG. 8C, the orientation of the pipe 1 is changed by rotating the pipe chuck 5 in the direction of an arrow Nc, and the pipe chuck 5 is caused to advance toward the rolling block 2 side. The clamping die 4 and the rolling block 2 are returned to the original positions thereof so as to avoid interference with the pipe 1. In so doing, as shown in FIG. 8D, preparation for a second bending process can be implemented. Next, as shown in FIG. 8E, the second bending process is performed by again rotating the clamping die 4 and the rolling block 2 in the direction of the arrow Na, and as a result, the second bend portion 10 is formed.

As is evident from the first and second bending processes, in the pipe bending step Sc, an operation for implementing a bending process on the pipe 1 by rotating the clamping die 4 and the rolling block 2 after changing the orientation of the pipe 1 and feeding the pipe 1 toward the rolling block 2 side is implemented repeatedly. In so doing, a meandering pipe body A′ such as that shown in FIG. 8F is manufactured. The meandering pipe body A′ is in a state prior to implementation of a final bending process.

When the final bending process is performed on the pipe 1, control for positioning the pipe 1 is implemented in advance so that the edge of the rear end portion 11b of the pipe 1 is positioned on the front surface of the position sensor 6 and detected by the position sensor 6. In so doing, a dimension Lc from the edge of the rear end portion 11b to the center of the rolling block 2 is set accurately at a predetermined dimension. The dimension Lc is identical to the dimension Lb from the edge of the front end portion 11a to the center of the rolling block 2 in the initial set state shown in FIG. 8A, for example.

In the set state described above, as shown in FIG. 8G, the final bending process is performed by rotating the clamping die 4 and the rolling block 2. As a result, the meandering pipe body A shown in FIG. 1 is acquired. However, since relative positioning in the y direction has been carried out between (the edge of the rear end portion 11b of) the pipe 1 shown in FIG. 8F and the rolling block 2, the y-direction positions of the respective end portions 11a, 11b (the front end portion 11a and the rear end portion 11b) of the meandering pipe body A are aligned.

According to the manufacturing method described above, a state in which the final bend portion 10 (10b) is positioned lower than the other, intermediate, bend portions 10 by a certain dimension Ld, as shown in FIG. 9A, for example, or a state in which the final bend portion 10 (10b) is positioned higher than the other, intermediate, bend portions 10 by a certain dimension Le, as shown in FIG. 9B, for example, may occur. However, the y-direction positions of the respective end portions 11a, 11b are aligned appropriately, and therefore the acquired meandering pipe body A can be used favorably to manufacture the heat exchanger HE shown in FIGS. 2A to 2C. When the y-direction positions of the respective end portions 11a, 11b are misaligned, it is necessary to cut the respective end portions 11a, 11b in order to adjust the lengths thereof as means for eliminating the misalignment, but according to this embodiment, this is not necessary. Hence, the productivity of the heat exchanger HE can be improved, and the manufacturing cost thereof can be reduced.

FIGS. 10A and 10B show a spiral pipe body Aa serving as another example of the pipe structure according to the present invention.

In the spiral pipe body Aa, a plurality of bend portions 10 with a bend angle of 90 degrees are formed in intermediate locations along the longitudinal direction of the pipe 1 so that the pipe 1 is formed in a substantially rectangular spiral shape when seen from the front. The regions 11A, 11B near the respective end portions of the spiral pipe body Aa are separated from each other in the x direction and extend in the y direction. The spiral pipe body Aa can also be used as a heat transfer pipe of a heat exchanger.

The spiral pipe body Aa can be manufactured by performing a bending process such as that shown in FIGS. 11A to 11F, for example. FIGS. 11A to 11F are schematic views showing the positional relationship between the pipe 1 and the rolling block 2, and the other constituent elements of the pipe bender have been omitted.

First, in a state where the pipe 1 is lined up against the rolling block 2, as shown in FIG. 11A, the pipe 1 is bent by 90 degrees in the direction of an arrow Nd, as shown in FIG. 11B. Next, as shown in FIG. 11C, the pipe 1 is fed by a predetermined dimension in the direction of an arrow Ne, whereupon the pipe 1 is again bent by 90 degrees, as shown in FIG. 11D. By repeating this process, a spiral pipe body Aa′ is acquired in a form such as that shown in FIG. 11E.

The spiral pipe body Aa′ is in a state immediately before the final bending process, and before implementing the final bending process thereon, the edge of the rear end portion 11b of the pipe 1 is detected by the position sensor 6, whereupon the position of the pipe 1 is controlled so that a dimension Lc′ from the edge of the rear end portion 11b to the center of the rolling block 2 matches a dimension Lb′, shown in FIG. 11A, for example, from the edge of the front end portion 11a to the center of the rolling block 2. Next, as shown in FIG. 11F, the final bending process is implemented on the pipe 1 such that the y-direction positions of the front end portion 11a and the rear end portion 11b of the pipe 1 are aligned.

The present invention is not limited to the content of the embodiment described above. The specific configurations of the respective operation steps of the manufacturing method for a pipe structure according to the present invention may be variously modified within the intended scope of the present invention.

In the embodiment described above, as means for aligning the y-direction position of the rear end portion 11b of the pipe 1 with the y-direction position of the front end portion 11a after performing the final bending process on the pipe 1, the dimension Lc shown in FIG. 8F, for example, is made identical to the dimension Lb of FIG. 8A, but the present invention is not limited thereto. In the present invention, it is also possible to employ means for controlling the relative positions of the pipe 1 and the rolling block 2 by detecting the position of the front end portion 11a in the state shown in FIG. 8F, for example, using an appropriate sensor (for example, a sensor 6A indicated by virtual lines) so as to determine a projection dimension Lf in the y direction from the rolling block 2 to the front end portion 11a, and making the dimension Lc identical to a value corresponding to the projection dimension Lf (for example, a value acquired by adding the arc length of the bend portion 10 to the projection dimension Lf).

There are no limitations on the specific number and bend angle of the bend portions formed in the pipe. In the embodiment described above, the bend angle of the bend portions 10 formed in the meandering pipe body A is 180 degrees, and the bend angle of the bend portions 10 formed in the spiral pipe body Aa is 90 degrees, but other bend angles can be used. There are also no limitations on the specific bend radius of the pipe, the size and material of the pipe to be bent, and so on. An elliptical pipe may be used instead of a perfectly circular round pipe.

The pipe structure manufactured by the present invention is suitable for use as a heat transfer pipe of a heat exchanger, but can also be used in other applications. The pipe structure is not limited to a meandering pipe body or a spiral pipe body.