JPH09276940A - Mandrel for bending core of heat exchanger and method for bending core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the buckling of a fin and to obtain a heat exchanger having high permeability and good heat exchangeability by increasing contact resistance with edge part of the plate fin on the surface of a mandrel and arranging a slippage preventing means for preventing the slippage between them at the time of bending a core. SOLUTION: The core 3 is imposed between adjacent base plate 6 and bending plate 7, and the mandrel 4 is positioned at the bending part of the core 3. Successively, the outer force in the arrow mark direction is applied to the bending plate 7 and the core is bent. At this time, as the mandrel 4 the one providing with slippage preventing means 5 having many cross-cut knurling grooves on the outer surface. The cross-cut grooves are the one arranging many parallel fine grooves so as to be mutually crossed. The depth and the pitch of the grooves are suitably selected so that the friction resistance with the tip part of the plate fin 1 becomes the max.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mandrel for guiding when a core of an air conditioning heat exchanger is bent by applying an external force, and a core bending method using the mandrel.

[0002]

2. Description of the Related Art A heat exchanger for air conditioning is provided with a flat plate-shaped core in which tubes are fixed through a large number of plate fins arranged in parallel, and an external force is applied to the core for compactness. The one bent into a letter shape is used. Conventionally, the core is bent as follows. The base plate and the bending plate are arranged in parallel on the same plane, and the heat exchanger core is placed between them. Then, a bending guide mandrel is arranged at the bending position of the core on the upper surface of the base plate. The mandrel is held so as to sandwich the core with the base plate. Then, by rotating the bending plate around the mandrel, the core was formed in an L shape as an example.

[0003]

However, in such a bent core, a buckling portion 1b is often generated in a part of the plate fin 1 at the curved portion as shown in FIG. This buckling portion, in FIG. 7, when an external force is applied to the core 3 to bend it around the mandrel 4,
As a result of an experiment, it has become clear that slippage occurs between the plate fin 1 and the curved portion in contact with the mandrel 4 and buckling is likely to occur. That is, the edge 1a of the plate fin 1 is moved to the mandrel 4 as shown in FIG.
It moves to the left as shown, and is displaced from the normal direction of the mandrel 4. At this time, it was found that the external force applied to the core 3 acts in the plane direction of the plate fin 1 and the tip of the plate fin 1 is curved, so that the core 3 easily buckles at the curved portion. Conversely, when the tip of the plate fin 1 is located in the normal direction of the mandrel 4 as shown in FIG. 9, it was found that the plate fin 1 does not buckle easily against external force in the direction of the arrow.

The plate fin 1 may be partially provided with a slight bent portion in advance. In this case,
There is a case where the sliding direction is opposite to that in FIG. 8 during bending. It has been experimentally confirmed that even if a slight partial bending is present in advance, if there is no slip at the tip of the fin, there is sufficient supporting force for external force and buckling does not occur. The present invention has been devised based on the above findings, and its configuration is as follows.

[0005]

A core bending mandrel of a heat exchanger according to the present invention uses a flat plate-shaped core 3 in which tubes 2 are fixed through a large number of plate fins 1 arranged in parallel. In the mandrel 4 that is brought into contact with the surface of the core 3 by applying an external force to the surface of the core 3 and bends the plane of the core using it as a guide, the contact resistance between the surface of the mandrel 4 and the edge 1a of the plate fin 1 is increased. Is added to prevent slippage between the two when the core is bent.

In addition to the structure of the first aspect of the present invention, the second aspect of the present invention includes, as the anti-slip means 5, a plurality of knurled grooves in the shape of kerfs crossing the curved surface of the mandrel. . Further, the third aspect of the present invention is the above first aspect.
In addition to the configuration of the invention described above, as the slip prevention means 5,
The curved surface of the mandrel is subjected to sand shot processing or satin processing. In addition to the structure of the first aspect of the present invention, the fourth aspect of the present invention includes the slip prevention means 5
As described above, the curved surface of the mandrel is coated with a soft resin material or a rubber material. Next, the core bending method of the heat exchanger of the present invention uses the mandrel of the first invention, contacts it with the surface of the flat plate-shaped core 3, and applies an external force from the back surface side of the core 3, The plane of the core 3 is curved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, each embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a preparatory step of a bending step of core bending using a core bending mandrel of a heat exchanger of the present invention, and FIG. 2 shows the bending step. In this core 3, plate fins 1 having a large number of tube insertion holes that are aligned with each other are arranged side by side, and U-shaped tubes 2 are inserted into the tube insertion holes, and the end portions of the respective tubes 2 are inserted. The U-bend pipes are connected to each other to form a meandering coolant flow path, and the entire core is formed in a flat plate shape. The core 3 is placed between the adjacent base plate 6 and bending plate 7, and the mandrel 4 is positioned at the bent portion of the core 3. The mandrel 4 is held at that position by a supporting member (not shown). Next, an external force in the direction of the arrow is applied to the bending plate 7 to bend it as shown in FIG. At this time, as the mandrel 4, a mandrel 4 having an anti-slip means 5 in which a large number of groove-shaped knurled grooves intersect with each other is used. The cross pattern is arranged so that a large number of parallel thin grooves intersect with each other. The depth and pitch of the groove are appropriately selected so that the sliding frictional resistance with the tip of the plate fin 1 is maximized.

Next, FIG. 3 shows another embodiment of the mandrel 4 of the present invention. The anti-slip means 5 formed on the outer surface of the mandrel 4 is uneven by sand shot processing, or a matte finish by an appropriate means. It has been processed. As an example, the matte surface is sandpaper No. 120-1
Effective in the range of about 000. Next, FIG. 4 shows a mandrel 4 according to a third embodiment of the present invention. In this example, a soft synthetic resin film is coated on the outer surface of the mandrel 4 as a slip preventing means 5. For example, urethane, EPDM, NBR, or SRB has a hardness of Hz 50 to 1
Those around 00 are selected.

[0009]

The core bending mandrel of the heat exchanger and the core bending method of the present invention increase the contact resistance between the surface of the mandrel and the end edge 1a of the plate fin 1 and the sliding between the core and the core fin. Since the anti-slip means 5 for preventing the occurrence of the slip is applied, it is possible to prevent the fin crushing caused by the slip. Then, a heat exchanger having high air permeability and good heat exchange performance can be manufactured. According to the conventional method, when the mandrel 4 is brought into contact with the core, and the mandrel 4 is guided to apply an external force to the core 3, relative movement occurs at the contact portion of the plate fin 1 on the curved surface of the mandrel 4, and the plate fin 1 is moved as shown in FIG. The edge 1a of the fin 1 is bent from the normal direction of the mandrel 4. And plate fin 1
Since an external force in the direction of the arrow is applied to the tip, the tip thereof buckles, and the buckling portion 1b is formed on the plate fin 1 as shown in FIG. However, according to the present invention, the sliding between the mandrel 4 and the edge 1a of the plate fin 1 is prevented, so that the plate fin 1 and the mandrel 4 are always shown in FIG.
It has a large supporting force against an external force in the direction of the arrow and can prevent the fins from buckling.

[Brief description of drawings]

FIG. 1 is a mandrel 4 showing a first embodiment of the present invention.
3 shows the preparation stage for core bending by.

FIG. 2 is an explanatory view showing a bent state of the core.

FIG. 3 is a perspective view showing another embodiment of the mandrel 4 of the present invention.

FIG. 4 is a side view showing still another embodiment of the mandrel 4.

FIG. 5 is a schematic view of a bend according to a conventional core bending method.

FIG. 6 is an enlarged view of a part VI in FIG. 5;

FIG. 7 is an explanatory view showing the behavior of the plate fin 1 during core bending.

FIG. 8 is a partial explanatory view thereof.

FIG. 9 is an explanatory diagram showing a supporting force of the plate fin 1 when no slip occurs between the plate fin 1 and the mandrel 4.

[Explanation of symbols]

 1 plate fin 1a edge 1b buckling part 2 tube 3 core 4 mandrel 5 anti-slip means 6 base plate 7 bending plate 8 holding part

Claims (5)

[Claims] 1. A flat plate-shaped core 3 in which a tube 2 is fixed through a plurality of plate fins 1 arranged in parallel,
By applying an external force to the core 3, a mandrel 4 that is brought into contact with the surface of the core 3 and bends the plane of the core by using it as a guide. A mandrel for core bending of a heat exchanger, which is provided with a slip prevention means 5 for increasing the contact resistance of the core and preventing slip between the core and the core during bending. 2. The core bending mandrel for a heat exchanger according to claim 1, wherein the anti-slip means 5 comprises a curved surface of the mandrel 4 and a large number of knurled grooves in a cross shape. 3. The core bending mandrel for a heat exchanger according to claim 1, wherein the anti-slip means 5 is formed by subjecting the curved surface of the mandrel 4 to sand shot processing or satin processing. 4. The mandrel for core bending of a heat exchanger according to claim 1, wherein the anti-slip means 5 comprises a curved surface of the mandrel 4 coated with a soft resin material or a rubber material. 5. The heat exchanger according to claim 1, wherein the mandrel of claim 1 is brought into contact with the surface of the flat plate-shaped core 3 and an external force is applied from the back surface side of the core 3 to bend the flat surface of the core 3. Core bending method.