JPS59130630A - Bending device for cylinder of heat exchanger - Google Patents

Abstract

PURPOSE:To minimize the buckling of fins and to enable manufacture of a cylindrical heat exchanger which is truly circular by providing projections on the surface of a rotating roll which bends the heat exchanger of a cross fin tube type. CONSTITUTION:A work 4 of a cross fin tube type consisting of a pipe 5 passed through many fins 6 is formed into a cylindrical shape around a bending roll 2. A large face pressure acts on the contact surfaces of the roll 2 and the fins 6 upon starting of bending, then the fins 6 are crushed by as much as the width of the projection 7a attached to the roll by said projection. The bending stress of the work 4 is received by the projection 7a and the pipe 5 and the fins 6 except the projecting part are not buckled, whereby the buckling of the fins is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a bending device for a cross-fin tube type heat exchanger.

[Background of the invention]

A conventional bending device is shown in FIG. It is configured to manufacture a cylindrical heat exchanger by holding the bending roll 2 and rotating the bending roll 2 in the illustrated direction. Note that the work 4 includes a pipe 5 with a large number of fins 6.
Since it is a cross-fin tube type that passes through the fins, the bending roll 2 and fins 6 are in direct contact, so the surface of the bending roll is made smooth to reduce friction with the fins 6 and prevent buckling of the fins. There is.

FIG. 2 shows changes in surface pressure between the bending row and the workpiece when bending is performed using the conventional technique. The song begins,
At the end of bending, the surface pressure between the bending roll and the fins increases. Therefore, when using fins with low buckling strength or when a large bending moment is required by increasing the number of pipe rows, the load applied to the fins at the contact surface between the bending roll and the fins increases the buckling strength of the fins. If the heat transfer area is exceeded, the fins may buckle and the heat transfer area in that area cannot be used effectively. Also, due to the buckling of the fins, a gap is created between the slide base and the workpiece, and the parts where the fins are buckled, that is, the bending start and bending ends 9
In some parts, the bending moment applied to the pipe becomes smaller and the bending radius becomes larger than in other parts, and an almost straight part of about 150 degrees may remain in the extreme kudzu-tai. Therefore, in a workpiece with two rows of pipes, only the inner pipe row is expanded to position the fins, and the outer pipes are not expanded to reduce the bending stress of the workpiece without work hardening. Then the song will be processed. After that, a method of hydraulically expanding the pipe outside the cylindrically bent workpiece may be adopted. 1~1~ In hydraulic pipe expansion, when pressure is applied to the inside of the pipe, the pipe deforms greatly in areas with low strength such as areas where there are no fins around the pipe or joints of the pipe, and cracks occur. There is a Vi limit to the pressurizing force, and the tube expansion rate is usually 1%.

Therefore, the contact thermal resistance between the fins and the pipes is large, which is an obstacle to improving the performance of the heat exchanger.

[Purpose of the invention]

In order to improve the above-mentioned drawbacks, the present invention is capable of bending an expanded heat exchanger into a cylindrical shape so that the fin expansion ratio is 1% or more, and minimizes buckling of the fins. The purpose is to provide a device that can.

[Summary of the invention]

In order to achieve the above objectives, the present invention provides a protrusion whose tip reaches the pipe on the surface of the bending roll that contacts the bending start and bending end portions where the fin buckles during processing.

[Embodiments of the invention]

An embodiment of the present invention will be explained with reference to FIG. One end of the workpiece 4 is clamped with a clamp 3 fixed to the bending roll, which has a protrusion 7 according to the present invention at a portion where the contact surface pressure between the bending roll and the fin is greater than the buckling load of the fin, and the bending roll 2 is moved as shown in the figure. By rotating in the direction V, the workpiece 4 is formed into a cylindrical shape around the bending roll 2. In order to prevent buckling of the fins during bending, the slide base 1 and the bending roll 2 are equipped with a synchronization mechanism, such as a rack and pinion, and the rotational speed of the bending drum is also variable. FIG. 4 shows a comparison of the buckling area ratio of the fin when a protrusion is provided at the portion where the contact surface pressure between the bending roll and the workpiece increases during bending and when there is no protrusion. If there is a protrusion, a large surface pressure acts on the contact surface between the bending roll 2 and the fin 6 at the same time as the bending process starts, as shown in FIG.
As a result, the fin is completely collapsed by the width of the protrusion, and the bending stress of the workpiece is received by the protrusion 7a and the pipe 5, and the fins 6 other than the protrusion do not buckle. As the bending process progresses, the fins 6 come into contact with the bending roll 2.
Since the number of fins 6 is sufficiently large, bending can be performed without buckling the fins 6. Further, even at the end of bending, by providing the protrusion 7b similar to that at the beginning of bending, the fins in the portion other than the protrusion 7b will not buckle.

FIG. 5 shows the effect that protrusions attached to the bending rolls have on the bending shape. If the pipe is not bent, the fins will buckle at the beginning and end of bending, and the bending moment applied to the pipe 5 will decrease, so even after the bending process, the pipe in that part will remain in a straight state for the most part. becomes. On the other hand, if there is a protrusion, the pipe 5 is held down by the protrusion, so that the bending moment applied to the pipe can be suppressed from decreasing, and the workpiece becomes close to a perfect circle.

〔Effect of the invention〕

According to the present invention, the fins have a sufficient expansion ratio. 1. Even when the heat exchanger is bent, the fins buckle only at the protruding portions attached to the bending rolls, and the fins do not buckle. This makes it possible to minimize the increase in ventilation resistance and the ineffective heat transfer area due to this, and to manufacture a heat exchanger with a nearly perfect circular cylindrical shape.

[Brief explanation of drawings]

Fig. 1 is a side view of the cylindrical bending device, Fig. 2 is the pressure distribution on the contact surface between the workpiece and the bending roll during bending, Fig. 3 is a side view of the cylindrical bending device according to the present invention, and Fig. 4 is Figure 5 shows the buckling area of the fin and its bending shape. 2...The song is a roll 7...Protruding stars 1 concave points 61 zu V-side I end

Claims (1)

[Claims] A device for manufacturing a cylindrical cross-fin tube type heat exchanger using rolls, characterized in that an appropriate number of protrusions are provided on the surface of the rotating roll of the cylindrical bending device. Cylindrical bending equipment.