JPH0871656A - U-shaped bent tube forming method and its formed body, cooling water passage of gun arm using the formed body - Google Patents

Abstract

PURPOSE: To provide a method for forming a U-shaped bent tube having an arc part of small radius, and a cooling water passage capable of easily arranged and formed in a gun arm and securing the cooling characteristic of the gun arm. CONSTITUTION: A cooling water passage of a gun arm l consists of a tubular member 5 continuous from an inlet and an outlet 3a, 3b of the cooling water embedded during the casting of the gun arm 1. The tubular member 5 is filled with the filling sand thereinside, and blocked with a lid member such as the shell sand at the end, and a tube holder is externally fitted thereto and the tubular member is bent to a U-shape forming an arc part of small radius.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a U-shaped bent pipe, its molded body, and a cooling water channel for a gun arm using the molded body.

[0002]

2. Description of the Related Art A gun arm for spot welding is provided with an electrode tip at the tip of an elongated arm portion, and a cooling water passage for suppressing a temperature rise due to heat generation of the electrode tip portion is provided therein. This cooling water path forms a circulation path that makes a U-turn from the water supply / drainage connection opening on the base side of the gun arm through the vicinity of the electrode tip on the tip side and returns to the connection opening again. This cooling water passage is simply configured by embedding a pipe passage made of a pipe member when the gun arm is cast.

A large-diameter pipe member is used to secure a flow rate of cooling water corresponding to the amount of heat generation in the elongated arm portion, and the height of the pipe passage is limited due to the small-diameter arm portion and restrictions on cooling characteristics. The center-to-center distance B of the parallel portion of the cooling water channel embedded in the arm having a vertically long cross section with the minimum diameter A in the direction is A / 2.
Therefore, the arc center radius Rm of the U-turn portion is limited to B / 2, that is, A / 4 or less. Specifically, the minimum diameter of the arm in the height direction is 22 mm.
In this case, the pipe center radius Rm must be 22/4 = 5.5 mm or less.

Generally, the U-turn portion of the pipe line can be easily processed into a U-shape by bending a pipe member made of a ductile material into an arc shape. However, in the case of the gun arm described above. , The radius of the arc is small,
Outer diameter d = 6.4 when using a commercially available pipe bender
Since the minimum bending radius of a pipe of mm is Rm = 15.2 mm (in case of Armtech, Imperial, etc.),
It is difficult to apply a bending process using a commercially available pipe bender. Specifically, according to the pipe bender, when bending without causing cracks in the pipe wall or collapsing of the pipe, the center line bending radius Rm of a copper pipe having an outer diameter d = 6 mm
Is a minimum of 9/16 inch (14.3 mm), and the elongation rate δ% of the member at this time is the reference length L0 = Rm and the post-forming length L1.
= Outer radius = Rm + d / 2, so δ = 100 (L1-L0)
/ L0 = 100 ((Rm + d / 2) -Rm) / Rm, that is, 50d /
It is represented by Rm, and specifically, δ = 50 · 6 / 14.3 = 21
%, And using this elongation to calculate the critical bending radius when d = 6.4 mm, Rm = 50 ・ 6.4 / 21 = 15.2
mm, therefore the minimum height A of the arm is A
Is limited to 4Rm = 4.15.2 = 60.8 mm or more.

Therefore, as an alternative to the above-mentioned bending process, two pipe members forming a reciprocating path are embedded in parallel at the time of casting of the gun arm, and later, holes aiming at both pipe members at the tip of the arm are penetrated between them. A technique (Japanese Patent Laid-Open No. 57-41874) has been proposed in which the U-turn portion is formed by filling the blind plug after processing the opening.

[0006]

However, in this method, the pipe member assembled in the mold at the time of casting the gun arm has its arrangement position changed due to expansion and contraction due to the flow of water in the mold and temperature change, and If it does not match the position of the through hole due to communication processing, it is not possible to secure the prescribed flow path cross-sectional area, and also a complicated process for forming the cooling water channel in the gun arm casting, including water leak inspection of the blind plug part. Therefore, improvement is desired in terms of construction period and cost.

An object of the present invention is, firstly, to simply work-mold a U-shaped pipe that can be embedded in an elongated arm portion of a gun arm, and secondly, by using the molded body thereof. It is to simply form the cooling water channel of the gun arm.

[0008]

In order to solve the above problems, firstly, a pipe is filled with a sand material for countering the collapse of a bent portion when the pipe is bent, and the sand material is filled. Bending the pipe into a U-shape, and fitting a pipe holder made of a pipe having an inner diameter substantially equal to the outer diameter of the pipe to the U-shaped parallel portion, and pressing the pipe holder to bring the parallel portion close to each other. In the same step, the pipe holder is provided with a guide portion for forming a parallel portion facing the bent portion of the pipe, thereby forming a U-shaped bent pipe.

Secondly, there is provided a cooling water passage extending from the cooling water supply / discharge part formed on the base side of the gun arm to the vicinity of the electrode tip part on the tip side of the arm part and returning to the cooling water supply / discharge part again, and casting In a gun arm to be molded, a single continuous conduit was formed from the cooling water supply / discharge section by the molded body, and this cooling conduit was formed by embedding this conduit at the time of casting molding of the gun arm. It is preferable that the center-to-center distance of the U-shaped parallel portions of the conduit be approximately half or less of the minimum diameter of the arm portion.

[0010]

The first U-shaped bent pipe is bent into a U-shape and then pressed by the pipe holder fitted onto the U-shaped parallel portion. At this time, the guide portion of the pipe holder is While molding the parallel part facing the bent part of the pipe, the sand material filled in the pipe holds the outer periphery of the bent part, so that the bent part with a small radius can be formed without crushing the pipeline or cracking the pipe wall. Molded.

Since the cooling water passage of the second gun arm is formed by a single U-shaped pipe member, there is no need for external machining, and there is no leakage or clogging in the narrow arm portion. Is formed. By arranging the distance between the centers of the U-shaped parallel portions to be approximately half the minimum diameter of the arm portion or less and arranging the parallel portion in the center portion of the arm portion, the cooling characteristic of the thin arm portion is secured.

[0012]

Embodiments will be described below with reference to the accompanying drawings.

FIG. 1 is a side view and a plan view of a gun arm according to an embodiment of the present invention. The gun arm 1 is provided with a cooling water passage formed by one continuous pipe member 5 extending from the cooling water supply / discharge ports 3a and 3b opened in parallel on the base 2 side thereof to the vicinity of the electrode tip portion 4 on the tip side.

The pipe member 5 is formed into a U-shape forming a bent portion 6 having a small radius by a bending method described later.
By embedding a character-shaped pipe at the time of casting the gun arm 1, a cooling water channel consisting of one continuous pipe line without leakage or clogging is formed inside the gun arm 1. In the cooling water passage, when the center-to-center distance B of the parallel reciprocating pipes exceeds 1/2 of the minimum height A of the gun arm, the cooling performance of the central portion is impaired. 1 of A
By setting the center-to-center distance B to be equal to or less than / 2, cooling of the central portion of the gun arm is ensured. In this case, since the outer peripheral side of the gun arm is cooled by the outside air, sufficient cooling can be ensured by making the center-to-center distance B smaller, including the case where the gun arm is relatively long. However, by setting the minimum distance between the pipes arranged in parallel to 1 mm or more, it is possible to secure the circulation of the hot water during the casting of the gun arm, to secure the fixing of the pipes inside the gun arm and to secure the cooling efficiency of the center part. Become.

2 and 3 are process diagrams of a U-shaped bending method for a pipe member according to the present invention. The pipe member 7 made of a copper annealed pipe is filled with a filling sand material 8 such as silica sand,
The end is closed with a cover material 9 such as shell sand, and bending is performed by a pipe bender with a radius twice the target bending radius, and then an inner diameter substantially equal to the outer diameter of the pipe member 7 (clearance is preferably 0.5 mm or less. ) Having a pipe holder 10
Is externally fitted and pressed by a vise 11 to bend the target bending radius. A guide portion 10a for preventing the escape of the pipe by facing the bent portion of the pipe and forming a parallel portion is extended to the pipe holder 10 at an angle of α = 45 to 60 °.

The filling sand material 8 of the pipe member 7 is a round shape having a high packing density and also having fine irregularities on the surface and having a large friction resistance (for example, a round shape such as Zr sand, glass beads, and alumina balls). Alternatively, it may be a pusher-shaped one, specifically, Naigai Cera beads 6 manufactured by Naigai Ceramics Co., Ltd.
# 750, # 1450, etc. in addition to 0 # 1000, volume ratio Vf =
Vibration filling is performed using a vibrator so as to be 60% or more (filling density 1.8 or more), and the pressure strength of the shell sand of the lid material 9 is 50 kg / cm 2 or more. By holding the outer periphery of the bent portion during bending, the filling sand material 8 enables bend molding with a small radius without causing crushing of the pipe line and cracking of the pipe wall, and is placed in the thin arm portion of the gun arm. It is possible to obtain one installable U-shaped pipe member. In the embodiment, in order to fit a gun arm having a minimum height of 22 mm, a bend center line radius R of a copper pipe having an outer diameter of 6.4 and a wall thickness of 0.8 is used.
Bending of m = 5.5 mm and elongation δ = 50.6.4 / 5.5 = 58.2% could be achieved.

In the cooling water channel of the gun arm constructed as described above, a circulating water channel without leakage or clogging can be easily formed inside the gun arm by embedding a single continuous pipe line at the time of casting the gun arm. It is possible to improve the reliability of the cooling water passage portion and reduce the number of man-hours and the construction period without requiring a complicated post-process such as external processing such as opening and blind plugs and water leak inspection.

FIG. 4 is a side view and a plan view of a gun arm according to another embodiment of the present invention. The gun arm 13
Cooling water supply / discharge port 15 opening on the side surface on the base 14 side
The cooling water passage is formed of a single pipe member 17 extending from a, 15b to the vicinity of the electrode tip portion 16 on the tip side.

The pipe member 17 is provided with supply / discharge ports 15a, 1
5b has a U-shape with one end open and the other end closed.
This closed side is opened on the side surface of the gun arm 13 by the later hole processing. This gun arm is based on a specific mold construction scheme, which requires that the pipe member to be embedded at the time of casting is easily fixed in the mold and its positional accuracy can be secured. It enables casting with a small amount of shell sand without using a fixed baseboard.

[0020]

As described above, the first U-shaped bent pipe of the present invention is bent into a U-shape and then pressed through the pipe holder fitted to the U-shaped parallel portion, This time,
While the guide part of the pipe holder faces the bent part of the pipe to form a parallel part, the sand material filled in the pipe holds the outer periphery of the bent part so that the pipe line is not crushed and the pipe wall is not cracked. A bend with a small radius is formed.

The cooling water channel of the second gun arm is composed of a single pipe member embedded in the arm portion, and this pipe member is filled with sand for holding the outer periphery of the bent portion and bent. Since it is formed in a U-shape, a bent portion having a small radius is formed without collapsing the pipe line or cracking the pipe wall, and it is possible to embed it in a thin arm portion.

Therefore, it is possible to easily form a circulating water channel without leaks or clogging inside the gun arm, so that a complicated post-process such as external processing such as punching or blind plugs and water leakage inspection is required. As a result, the reliability of the cooling water passage portion can be improved, and the number of man-hours and the work period can be shortened.

The cooling water passage of the gun arm is a thin long arm portion by disposing it in the center portion of the arm portion as a pipe passage in which the center-to-center distance of the U-shaped parallel portions is approximately half or less of the minimum diameter of the arm portion. Coolability is secured up to the center of the.

[Brief description of drawings]

FIG. 1 is a process drawing of U-shaped bending of a pipe member according to the present invention.

FIG. 2 is a process drawing of U-shaped bending of the pipe member of the present invention.

FIG. 3 is a side view and a plan view of a gun arm according to an embodiment of the present invention.

FIG. 4 is a side view and a plan view of a gun arm according to another embodiment of the present invention.

[Explanation of symbols]

1, 13 ... Gun arm, 2, 14 ... Base, 3a, 3b,
15a, 15b ... Supply / discharge port, 4, 16 ... Electrode tip part,
5, 7 and 17 ... Pipe member, 6, 18 ... Bent portion, 8 ... Filled sand material, 9 ... Lid material, 10 ... Pipe holder, 11 ... Vise, A ... Height direction minimum diameter, B ... Center distance .

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shuji Nakamura 1-10-1 Shin-Sayama, Sayama-shi, Saitama Prefecture Honda Engineering Co., Ltd.

Claims (4)

[Claims] 1. A step of filling a sand material for counteracting crushing of a bent portion when bending the pipe into the pipe, and bending the pipe filled with the sand material into a U-shape, and the U-shaped parallel A pipe holder made of a pipe having an inner diameter substantially equal to the outer diameter of the pipe, and pressing the pipe holder to bring the parallel portion close to each other. A method for forming a U-shaped bent pipe, which comprises a guide portion for forming a parallel portion so as to face the portion. 2. A molded body molded by the method for molding a U-shaped bent pipe according to claim 1. 3. A cooling water passage extending from a cooling water supply / discharge section formed on the base side of the welding gun arm to the vicinity of the electrode tip section on the tip side of the arm section and returning to the cooling water supply / discharge section again.
In the gun arm to be cast-molded, the molded body according to claim 2 is used to form one continuous pipe from the cooling water supply / discharge section, and the pipe is formed by embedding the pipe during casting of the gun arm. Characteristic gun arm cooling water channel. 4. The gun arm cooling water passage according to claim 3, wherein in the pipe passage, a center-to-center distance between U-shaped parallel portions is approximately half or less of a minimum diameter in the height direction of the arm portion. Cooling channel for the gun arm.