JPH0347930B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inertial force balance device for a Pilger rolling mill for manufacturing seamless steel pipes and the like.

[Conventional technology and its problems]

In general, a Pilger type rolling mill equipped with Pilger mill rolls has a special caliper between a pair of Pilger mill rolls and a mandrel rod, as shown in Japanese Patent Publication No. 51-43472. The raw pipe is rolled to produce seamless steel pipe.
Its structure and operation can be explained using the schematic diagram of a conventional Pilger type rolling mill that is generally in practical use as shown in FIG. and attach the connecting rod 5 to the crank arm 3.
A pilger mill stand 8 equipped with a pair of pilger mill rolls 7, 7 is connected to the tip of the connecting rod 5, and a connecting rod 6 for the V balancer is connected to the tip of the connecting rod 5. Suspend the balancer 6'.

Then, the main motor rotates the crankshaft 2 at a rotational speed ω
When rotated at a constant speed, the pilger mill stand 8 reciprocates via the crank arm 3 and connecting rod 5. As a result, Pilger Mill Roll 7
is rotated by a rack and pinion (not shown),
Roll the raw pipe. To put this further into perspective, when the pilger mill roll 7 rotates and the raw tube into which the mandrel rod is inserted moves forward, the roll 7 bites into the raw tube, and when the roll 7 rotates further, the raw tube has the finished size. The raw tube is then rolled away from the contact of the rolls 7. On the other hand, the raw tube stops while being rolled by the rolls 7, but moves forward as soon as it becomes free from the rolls 7.

As described above, the Pilger type rolling mill that has been put into practical use in the past employs a crank mechanism to reciprocate the Pilger mill stand 8 on which the Pilger mill roll 7 is mounted, with great force. An unbalance occurs due to the inertial force of the reciprocating motion induced by the inertial force and the couple due to the inertial force. In order to eliminate this unbalance, the fan-shaped balancer 4 and the V-balancer 6' are provided as described above. There is.

However, in the conventional Pilger type rolling mill, the following disadvantages occur due to the installation of the fan-shaped balancer 4 and the V-balancer 6'. That is, (1) the fan-shaped balancer 4 and the V-balancer 6' are installed, which increases the size. (2) In the fan-shaped balancer 4 and the V-balancer 6', the first-order term (the first-order term in the well-known general formula expressing the inertia force of reciprocating motion; the same applies hereinafter) based on the rotational speed ω of the crankshaft 2 is used. Balance can be eliminated, but unbalance in higher order terms cannot be eliminated. In order to reduce the unbalance of the higher-order terms, the ratio between the length R of the crank arm 3 and the length L of the connecting rod 5 must be reduced, so the length L of the connecting rod 5 becomes large and the equipment The whole becomes larger. (3) Since the imbalance of higher-order terms of the rotational speed ω of the crankshaft 2 cannot be eliminated, originally,
Connecting rod 5 generates a large inertial force proportional to the square of ω.
If the speed increases, a structure that can withstand this inertial force becomes unrealistic, and therefore there is a limit to how high the speed can be increased. (4)V
Because the balancer 6' is provided, for example, a Pilger mill rolling mill for cold-rolling a φ260 mm raw pipe requires foundation work approximately 8 m deep, which in turn makes maintenance around the V-balancer 6' difficult.

On the other hand, in a Pilger type rolling mill that reciprocates a Pilger mill stand equipped with a pair of Pilger mill rolls, a piston rod of an air cylinder is connected to the Pilger mill stand, and compressed air is applied to both sides of the piston connected to the piston rod. An inertial force balancing method has been proposed in which air is supplied to balance the inertial force of the reciprocating motion of the pilger mill stand (see British Patent No. 1355733).

However, when testing such proposals,
As shown in Figure 3, the inertial force of the reciprocating motion (solid line)
and the compressed air pressure (dashed line) of the air cylinder connected to the Pilger mill stand. It was found that the changes do not match, that is, the two are not balanced, and the above proposal alone cannot be applied as is to a practical Pilger type rolling mill.

[Means for solving problems]

Therefore, the present invention was created to solve the problems of the prior art. Specifically, an air cylinder is attached to a pilger mill stand, and the inertia of the reciprocating motion of the pilger mill stand is transferred to the air cylinder. When balancing the pressure of the sealed air, the changes in inertia force and the pressure of the compressed air are perfectly balanced with respect to the rotational angle and rotational angular velocity of the crankshaft that reciprocates the pilger mill stand. The object of the present invention is to provide a balance device for a Pilger type rolling mill.

Embodiment Hereinafter, the structure of the present invention will be explained in detail with reference to the embodiment shown in FIG. Note that the same parts as in the conventional example shown in the second figure are denoted by the same reference numerals, and the explanation thereof will be omitted.

[Basic control]

This example is suitable for a so-called large Pilger rolling mill that cold-rolls seamless steel pipes with a diameter of 260 mm and generates approximately 60 TON of inertia during reciprocating motion. In order to balance the inertial force of the reciprocating motion of the Pilger mill stand 8 with the pressure of the air sealed in the air cylinder 9 connected to the Pilger mill stand 8, the change in inertial force with respect to the rotational angle and rotational angular velocity of the crankshaft and the change in compressed air First, the maximum inertia force with respect to the rotation angle θ of the reciprocating motion of the Pilker mill stand 8 and the air piston 10 are to be balanced.
Balance the pressure of the compressed air at the initial stroke end.

By the way, as is well known, in an air piston used as an air spring, from the general formula expressing the load at a given stroke, A: Active area of the air cylinder 9 P ₀ : Initial pressure of the air cylinder 9 l ₀ : If the length is equivalent to the initial volume of the air piston 10, the air compression is adiabatic compression, and the rotational speed ω of the crankshaft 2 is constant, then P ₀ l ^k ₀ = Pw{l ₀ −(s− x)} ^k ... is derived.

In addition, here, k: polytropic index Pw: Pressure at any position of air cylinder 9 s: displacement of pilger mill stand 8 x: Displacement of hydraulic cylinder 12 from neutral shall be.

On the other hand, in FIG. 1, the pilger mill stand 8 is connected to an air piston 10 via an air piston rod 11.
Since the air volume can be adjusted by operating the hydraulic cylinder 12 (details will be described later), by operating the hydraulic cylinder 12, the maximum inertial force and the rotation angle θ of the crankshaft 2 reciprocating in the pilger mill stand 8 can be adjusted. , the compressed air pressure Pmax at the initial stroke end of the air piston 10 can be balanced.

Therefore, in order to operate the hydraulic cylinder 12 and determine the initial volume-equivalent length _l0 of the air piston 10, the inertia force and the pressure Pmax are set as Pmax=-M/A(s¨)max+ _P0 ... Bye. Here, M: weight of Pilger mill stand 8, and Pw when x=0, s=R is Pmax
Then, from the formula, assuming that the rotational speed ω is constant, l ₀ = Pmax ^1/k・R/Pmax ^1/k −P ₀ ... This l ₀ is calculated by the position command calculation unit 13 in FIG. Hydraulic cylinder 1 with the obtained signal j1
2 should be activated.

However, even when the rotational speed ω is constant, the inertial force changes moment by moment as the rotation angle θ changes, as described above, and this change does not match the change in the compressed air pressure. In order to achieve complete balance, the hydraulic cylinder 12 is operated in accordance with the rotation angle θ, and the air volume, that is, the pressure of the compressed air is adjusted in accordance with the rotation angle θ.

Therefore, the crankshaft 2 is attached to the hydraulic cylinder 12.
A displacement command value X is given according to the rotation angle θ. In other words, the displacement command value x ^is expressed as ^follows : If _{x =} X in the formula ^, then It is obtained by A+P ₀ ....

Therefore, in order to calculate the formula, the rotational angular velocity and rotational angle θ detected by the pulse generator 28 attached to the crankshaft 2 are given to the position command calculation unit 13, and the signal j1 is used to calculate the rotational angular velocity and the rotational angle θ. 12 is activated to obtain a predetermined air volume, or pressure, of compressed air.

Next, the above-mentioned outline will be supplementarily explained based on FIG. 1. That is, the air cylinder 9 has a front chamber 14, which is a forward movement chamber, on both sides of the air piston 10.
A rear chamber 15 which is a double movement chamber is formed, and each chamber 14,1
5, the first air sub-cylinder 16 and the second air sub-cylinder 17 are communicated with each other. A common rod 18 is passed through the first and second air sub-cylinders 16 and 17, and each piston is fixed to the rod 18. A hydraulic piston 19 of the hydraulic cylinder 12 is fixed to the center of the rod 18. In order to apply hydraulic pressure to the hydraulic piston 19, servo valves 20 communicating with both sides of the hydraulic piston 19 are provided. Note that 21 indicates a hydraulic pressure source.

Front chamber 14 and rear chamber 15 of the air cylinder 9
is equipped with a check valve 22, a relief valve 23, a pressure reducing valve 24, and an air circuit 26 with a low pressure air reducer 25. Therefore, when the Pilger mill stand 8 reciprocates, the air piston 10 also reciprocates, causing the front chamber 14 and the rear chamber 15, and the first and second air sub-cylinders communicating with these chambers 14 and 15, respectively. The air at the initial pressure P ₀ that is set to a low pressure and sealed in the chambers 16 and 17 is compressed. Using the pressure of the compressed air as an air spring, the inertia of the reciprocating movement of the pilger mill stand 8 can be balanced. (See the two-dot chain line in Figure 3).

[Improved balance accuracy]

Next, in this embodiment, the above-mentioned theoretically calculated values are corrected as follows to improve the balance accuracy.
That is, since the rotational angular velocity detected from the pulse generator 28 and the inertia force at the rotational angle θ can be calculated, by dividing the value by the effective area A of the air cylinder 9, a predetermined compressed air pressure can be obtained.
That is, the inertia force balance pressure calculating section 29 calculates this, and the inertia force balance pressure of the compressed air required at that time can be obtained. The inertial force balance pressure value j2 is given to the amplifier 30. On the other hand, the pressure detector 31 that detects the actual compressed air pressure in the front chamber 14 or the rear chamber 15 detects the actual pressure obtained via the changeover switch 32, and uses the actual pressure value j3 as a feedback signal. and compare it with the inertia force balance pressure value j2,
The difference is applied as a correction signal to the amplifier 33 that provides the position command value X, thereby improving the accuracy of the inertial force balance.

In addition, a tension detector 34 is attached to the cooking rod 5, and its feedback gain Kcc is used as a correction signal j4.
The position of the rod 18 is detected by the position detector 34 of the rod 18, and is applied to the amplifier 33 as a correction signal j5 with a feedback gain kf. The accuracy of the inertial force balance has been improved, taking into account frictional forces, etc.

[Change of rotation speed ω]

In this embodiment, the engine can be operated by changing the rotational speed ω of the crankshaft 2. That is, by controlling the servo valve 20 using the rotational speed ω, the hydraulic piston 19 is positioned at a predetermined position, the air volume of the first and second air sub cylinders 16 and 17 is changed, and the air volume of the air cylinder 9 is changed. Front room 1
4 and the rear chamber 15 can be changed, that is, the pressure of compressed air can be changed. Therefore, in order to control the servo valve 20, the signal J1, which is based on the rotation angular velocity detected from the pulse generator 28 attached to the crankshaft 2, is applied to the servo valve 20 to control the air cylinder according to a predetermined rotation angular velocity. 9 air volumes can be obtained. and,
For example, the rotational speed ω is changed in the following cases. In other words, when cold rolling a φ260 mm raw pipe, if a large number of raw pipes are serially rolled and rolled continuously, ω is lowered from the maximum value of, for example, 130 rpm to 70 rpm at the start and end of each raw pipe. This is a case where the material is rolled to prevent cracking in that area. Therefore, in this embodiment, as long as the air cylinder 9 that can obtain the maximum rotational speed ωmax is set,
The rotational speed ω below this can be changed as appropriate, and the compressed air pressure can be obtained accordingly.

This example uses a so-called large Pilger rolling mill (Cold Reducing Mill) that rolls seamless steel pipes.
However, the present invention is not limited thereto, and may be applied to, for example, a Pilger type rolling mill for steel plates or steel bars. Further, although it is preferable that one air cylinder forms the front chamber and the rear chamber, separate air cylinders may be used to form the front chamber and the rear chamber.

As another embodiment of the present invention, if a mass unbalancer as shown in FIG. 4 is attached to the crankshaft 2, it is possible to downsize the air cylinder control system. To explain FIG. 4, mass unbalances 36, 36' are attached to one ends of rotating shafts 37, 38, and these rotating shafts 37, 38 are rotatably attached to a frame 39 through which the crankshaft 2 is inserted. support In the figure, a small gear 40 is fixed to the other end of the lower rotating shaft 37, and the small diameter gear 40 is rotated by a first gear 42 fixed to the crankshaft 2 via an idle gear 41. Here, the gear ratio between the first gear 42 and the small diameter gear 40 is 2/1. Further, the upper rotating shaft 38 has an intermediate gear 43 fixed to its other end, and the intermediate gear 43 has a second gear 44 fixed to the crankshaft 2.
It meshes with. Here, the gear ratio between the second gear 44 and the medium gear 43 is 2/1. Therefore, the rotation axes 37 and 38 are opposite to each other in the crankshaft 2.
It rotates at twice the rotational speed of , and balances it with the inertia force of the second-order term of the pilger mill stand 8.

〔Effect of the invention〕

In summary, since the present invention employs the configuration described in the claims, the following effects are achieved.

Compared to conventional Pilger rolling mills equipped with V-balancers and fan-shaped balancers, which are in practical use, it is smaller, faster, easier to maintain, and easier to construct foundations. This allows the inertia of the reciprocating motion of the Pilger mill stand to be balanced, so excessive external energy is not required for balancing.

In conventional equipment, changes in inertia during the reciprocating motion of the Pilger mill stand and changes in compressed air pressure are matched (balanced) by the maximum inertia during constant speed rotation, and increase during acceleration/deceleration or during low speed strokes. However, according to the present invention, the air volume of compressed air is controlled by a hydraulic cylinder that is controlled based on the rotation angle and rotational angular velocity of the crankshaft, so it can be used over the entire range from startup to regular rotation. It is possible to match the changes in both, that is, it is possible to perfectly balance the inertial force and the pressure of compressed air (see the chain double-dashed line in FIG. 3).

Even if you change the rotational speed at which the Pilger mill stand reciprocates to achieve the optimum speed for the material or improve operating efficiency, the compressed air pressure can be easily changed during acceleration and deceleration. Since the so-called spring constant can be easily changed, operation can be performed continuously.

Since a hydraulic cylinder operated by a servo valve is provided to control the pressure of compressed air, the control device can be simplified.

According to the present invention, since higher-order terms are balanced, there is no need for connecting rods, crank arms, crankshafts, etc. made of high-quality materials that require machining to receive excessive force, and there is no need to increase the size. Cost reduction can be achieved. In addition to this, for example, the foundation bolts of the housing for storing the Pilger mill stand (which is required for any Pilger mill stand) are At least the inertia force described in the next term must be supported by this, so as the speed increases, stronger foundation bolts will be required.

However, according to the present invention, since higher-order terms are also balanced, the foundation bolt only needs to support the rolling horizontal reaction force, and since this rolling horizontal reaction force is almost unrelated to the rotation speed, it is possible to increase the speed. However, it does not affect the foundation bolts and can be used at low rotation speeds.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an embodiment of the present invention, Fig. 2 is a schematic diagram of a conventional example, and Fig. 3 shows inertial force against crank angle, general compressed air pressure, and compressed air pressure of this embodiment. The graph shown in FIG. 4 is a main part diagram of another embodiment of the present invention. 7... Pilger mill roll, 8... Pilger mill stand, 9... Air cylinder, 12... Hydraulic cylinder, 20... Servo valve.

Claims (1)

[Claims] 1. An inertial force balance device for a Pilger rolling mill that converts rotational motion of a crankshaft into reciprocating motion to horizontally reciprocate a Pilger mill stand equipped with a pair of Pilger mill rolls, An air cylinder having a forward movement chamber and a backward movement chamber is mounted on the Pilger mill stand, and the air volumes of these forward movement chambers and backward movement chambers are determined by detecting the rotation angle and rotational angular velocity of the crankshaft. An inertial force balance device for a Pilger rolling mill that is controlled by a hydraulic cylinder via a servo valve based on a detection signal. 2. An inertial force balance device for a Pilger rolling mill according to claim 1, wherein the forward movement chamber, the return movement chamber, and the sub-air cylinder are communicated with each other, and the air volume of these sub-air cylinders is controlled by a hydraulic cylinder. .