JPH04300041A - Method and device for form rolling of tube - Google Patents

Abstract

PURPOSE:To execute the thread form rolling without deteriorating the form rolling accuracy even in the case of a thin tube by executing the form rolling by setting a relative working speed to a high speed until a bite of a working die to a material to be worked reaches prescribed depth, and thereafter, setting it to a low speed. CONSTITUTION:A relative working speed is determined by a driving speed of a working die and a rotating speed of the working die. The rotating speed of the working die is set to a constant value in advance, and in the beginning of form rolling, working is executed by increasing the driving speed of the working die to V1, and from on the way, form rolling is executed by decreasing the driving speed of the working die to V2. From on the way, the relative working speed becomes low, force in the radial direction of the working die becomes small, and a deformation of a material to be worked can be suppressed. In such a way, thread rolling can be executed without deteriorating the form rolling accuracy even in the case of a thin tube.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for rolling pipes, particularly thin-walled pipes, and a rolling device used in the method.

0002

[Prior Art] Thread rolling into a pipe is usually done by rotating two or three processing dies formed into a desired shape and pressing them against the pipe, thereby rotating the pipe. It moves in the radial direction to machine the tooth profile on the pipe, following the tooth profile of the processing die.

[0003] Conventionally, for example, in thread rolling processing of pipes, driving of the processing die is performed using a hydraulic cylinder, and the processing speed is always constant.

0004

[Problem to be solved by the invention] However, when the rotational speed of the processing die is constant, if the driving speed of the processing die is increased, [driving speed of the processing die / rotational speed of the processing die] increases, The force applied in the radial direction of the tube increases. Also, as the machining stroke increases,
As the processing die is filled with the workpiece, the radial processing force increases.

[0005] When the radial working force becomes excessive during tube rolling, plastic deformation causes not only tooth profile formation but also deformation of the tube itself, degrading thread rolling accuracy.

On the other hand, conversely, reducing the driving speed of the machining die also causes disadvantages. That is, if the driving speed of the processing die is slow, slippage occurs between the processing die and the workpiece when the processing die contacts the pipe, resulting in a problem in which a tooth profile is not formed.

In other words, the rotational motion of the processing die must not be propagated to the workpiece, causing relative slip between the processing die and the workpiece. However, in order for the workpiece to start rotating and become equal to the rotational speed of the outer periphery of the processing die, a frictional force sufficient to overcome the inertial weight of the workpiece is required. That is, the driving torque of the workpiece generated by the cutting die biting into the workpiece must exceed the inertia torque of the workpiece.

From the above, it can be seen that if the driving speed and rotational speed of the processing die are constant during thread machining, the appropriate speed range is very narrowly limited. Especially in the case of thin-walled pipes or when the Young's modulus of the workpiece is small,
If the material is likely to yield due to a low yield point, etc., the pipe will more easily undergo plastic deformation, further deteriorating the thread rolling accuracy.

[0009] For this reason, for example, when rolling a thread into a thin-walled pipe made of copper alloy or aluminum alloy, which has a low yield point and a small Young's modulus, it is difficult to obtain a product with good rolling accuracy using conventional processing methods and rolling equipment. I couldn't do it.

The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to provide a highly accurate rolling method and rolling device for thin-walled copper alloy or aluminum alloy pipes. There is a particular thing.

[0011]

[Means for Solving the Problems] In order to achieve the above object, in the pipe rolling processing method of the present invention, the relative processing speed is kept high until the processing die sufficiently bites into the workpiece,
After the machining die has sufficiently penetrated the workpiece to a level that does not cause slippage, the relative machining speed is slowed down and the radial force is reduced to perform rolling.

[0012] Furthermore, in order to carry out the above-described processing method, the rolling device is equipped with either a mechanism that makes the running speed of the processing die variable, a mechanism that makes the rotational speed of the processing die variable, or Both of these are provided, and a variable speed control mechanism is added to slow down the relative processing speed during rolling.

The relative machining speed is determined by the driving speed of the machining die and the rotation speed of the machining die.

Therefore, the rotational speed of the processing die is kept constant, and the rolling speed of the processing die is increased at the beginning of the rolling process, as shown in FIG. If the rolling process is performed at a slower speed, the relative processing speed will be slowed down from the middle of the rolling process, and the radial force of the processing die will be reduced. Therefore, deformation of the workpiece can be suppressed.

[0015] In a general rolling device in which a hydraulic cylinder is used to drive the processing die, the speed at which the processing die is driven can be varied by changing the flow rate of oil fed into the cylinder. The driving speed of the die is fast, and if the flow rate is suppressed, the driving speed of the die becomes slower.

At this time, the flow rate of oil flowing out of the cylinder may be controlled by a meter-out circuit using an electromagnetic proportional valve as shown in FIG.

On the other hand, the above-mentioned switching point for the driving speed of the processing die is when the processing die has sufficiently penetrated into the workpiece to a level that does not cause slippage.
It is easiest for switching control to set this switching point in advance.

[0018] The present invention can of course perform thread rolling processing on pipes.
Rolling of hose nipples or similar items is also possible.

[0019]

[Example] φ20.6 x 1.70t x 500L pure copper tube (yield point strength (0.2% yield strength): 29kg/mm2
, breaking strength: 35 kg/mm2, breaking elongation: 7%, Young's modulus: 12000 kg/mm2) was set in a rolling device that uses a hydraulic cylinder to drive the processing die, and rolling was performed under the following conditions. I did it.・Processing die rotation speed: 480r. p. m.・Pressurized hydraulic pressure:
60kgf/cm2 ・Roll stroke: 2.0mm ・Processing is performed at a driving speed V1 = 12mm/min until the die stroke stroke is 1.82mm.・Die stroke from 1.82mm to 2.0mm is processed at driving speed V2 = 8.6mm/min.

The thread rolling device used is a rolling machine A that uses a hydraulic cylinder to drive in the processing dies, and the flow rate is controlled by a meter-out circuit using an electromagnetic proportional valve 1 to vary the driving speed of the processing dies. A relative machining speed control mechanism B is added to vary the relative machining speed by
The switching point of the driving speed was set in advance, and the moving position of the cylinder 2 was detected by the position detection device 3.

As shown in FIGS. 3 and 4, the rolling machine A has a ring 5 connected to a hydraulic cylinder 2 by a pin 4, which rotates as the hydraulic cylinder 2 moves up and down, and a ring support member 7 by a fixing bolt 6. The die holder 9 has a plurality of die holders 9 which are rotatably pivoted in the axial direction thereof and connected to the ring 5 by pins 8, and when the hydraulic cylinder 2 is raised, the ring 5 rotates in the direction of the arrow in FIG. When the ring 5 rotates, each die holder 9 approaches the workpiece 10 using the fixing bolt 6 as a fulcrum and causes the die 11 to bite into the workpiece 10, which is a conventionally known structural form. Figure 3,
In FIG. 4, L is the moving distance of the hydraulic cylinder 2 and the corresponding moving distance of the ring 5, and l is the stroke of the die 11.

On the other hand, the relative machining speed control mechanism B is installed in the hydraulic cylinder 2, detects the moving position of the hydraulic cylinder 2, and outputs a detection signal when the moving position of the hydraulic cylinder 2 reaches a preset switching point position. a controller 12 that generates an output signal when a detection signal from the position detector 3 is input; It consists of an electromagnetic proportional valve 1 that reduces the valve opening in proportion to the output when input, and when the position of the machining die 11, which is driven in with the movement of the hydraulic cylinder 2, passes a switching point, it flows out from the cylinder 2. Squeeze the amount of oil to slow down the driving speed of the dice.

FIG. 5 shows the operation of this relative machining speed control mechanism B.
Shown below. That is, as shown in FIG. 5(a), until the point preset in the position detection device 3 is reached, the valve opening of the electromagnetic proportional valve 1 is opened, the hydraulic cylinder 2 is moved at high speed, and the hydraulic cylinder 2 detects the position. When a preset point of the device 3 is reached, a signal is output from the position detection device 3 as shown in FIG. throttle, suppresses the amount of oil flowing out from the hydraulic cylinder 2,
The moving speed of the die is slowed down, and the relative machining speed of the die is slowed down.

According to this embodiment, in the conventional mechanism where the machining speed is constant, the outer diameter is 20.6 mm and the pitch is 2 m.
Minimum wall thickness for rolling m thread into SGP pipe: 3.5m
Since the copper tube we tried this time is made of a material with inferior rolling workability compared to SGP tubes, the minimum wall thickness should be even larger, but we decided to deform the tube itself to a wall thickness of 1.7 mm. Thread rolling processing was possible without causing any problems or deteriorating thread rolling accuracy.

In the above-mentioned embodiment, the moving speed of the cylinder 2 was controlled by a meter-out circuit using the electromagnetic proportional valve 1, but direct control is also possible by using a hydraulic cylinder such as a stepping cylinder that can control the driving speed. It is.

[0026] The machining force required for driving the machining die is not large when the pipe wall thickness is small or when the pipe is made of a material that easily yields, such as copper alloy or aluminum alloy. Therefore, the rolling machine need not be hydraulically driven but may be mechanically driven by a screw or the like. In this case, by adding a servo mechanism to the motor or the like, it becomes possible on the control side to change the driving speed of the machining die during thread forming during thread forming.

On the other hand, as mentioned above, the relative machining speed is the relative speed of the machining die and the rotation speed of the machining die, so it is also possible to change the relative machining speed by keeping the machining die constant and changing the rotation speed of the machining die. Machining speed can be varied.

Therefore, the driving speed of the processing die is kept constant, and at the beginning of the rolling process, the rotation speed of the processing die is slowed down to improve the die's penetration into the workpiece material, and after the switching point, the processing die By increasing the rotational speed of the machining die, it is also possible to reduce the relative driving speed of the machining die, thereby reducing the radial force of the machining die, and suppressing deformation of the workpiece.

[0029] This method can be realized by adding a servo mechanism to the motor for rotating the processing die in terms of the mechanism of the rolling machine. The rotational torque of the motor must be sufficiently large to prevent deterioration.

In the previous explanation, the relative machining speed is slowed down by varying either the driving speed of the processing die or the rotational speed of the processing die, but it is possible to slow down the relative processing speed by varying either the driving speed of the processing die or the rotational speed of the processing die. It is also possible to slow down the relative machining speed by changing this.

Furthermore, the switching point of the driving speed or rotational speed of the processing die does not necessarily have to be set in advance as described above, but it is possible to detect the start of rotation (co-rotation) of the workpiece due to contact with the processing die. It is also possible to make the switch.

[0032] The above-mentioned methods for sensing the start of rotation of the workpiece include a method of detecting a change in the rotational torque of a machining die by a change in current value, and a method of detecting the rotation of a support part (for example, a roller bearing) of the workpiece. method etc. can be adopted.

[0033]

[Effect] Since the present invention is constructed as described above, as is clear from the above embodiments, it is possible to reduce the rolling accuracy of thin-walled pipes, which were conventionally considered impossible to perform thread rolling with precision. It is now possible to perform thread rolling processing without any damage.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing changes in relative processing speed in the pipe thread rolling method of the present invention.

FIG. 2 is an explanatory diagram of a meter-out circuit that controls the cylinder rising speed in an embodiment of the thread rolling device of the present invention.

FIG. 3 is a side view showing an embodiment of a thread rolling machine.

FIG. 4 is a sectional view of the same.

FIG. 5 is an operation explanatory diagram showing one embodiment of a relative machining speed control mechanism.

[Explanation of symbols]

A Rolling machine B Relative machining speed control mechanism

Claims (2)

[Claims] Claim 1: In the pipe rolling process, the relative machining speed based on the driving speed of the machining die and the rotation speed of the machining die is set to be high until the machining die bites into the workpiece reaches a predetermined depth, A pipe rolling method characterized in that the rolling process is then performed at a low speed. 2. Relative machining by the relative driving speed and rotational speed of the processing die during rolling processing, comprising at least one of a mechanism that makes the driving speed of the processing die variable and a mechanism that makes the rotational speed of the processing die variable. A pipe rolling processing device characterized by having a relative processing speed control mechanism that slows down the speed.