JPH0257442B2 - - 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 type 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 shown in FIG. 2, which shows a conventional example.A crank arm 3 and a fan-shaped balancer 4 are fixed to a crankshaft 2 rotated by a main motor, and a connecting rod A pilger mill stand 8 equipped with a pair of pilger mill rolls 7, 7 is connected to the tip of the conrod 5, and a conrod 6 for the V balancer is connected to the tip of the conrod 5. Suspend the V 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. Along with the reciprocating movement, the pilger mill roll 7 is rotated by a rack and pinion (not shown) to roll the raw pipe. To put this further into perspective, when the pilger mill roll 7 rotates and the raw pipe into which the mandrel rod is inserted moves forward, the roll 7 bites into the raw pipe, and when the roll 7 rotates further, the raw pipe 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 consists of a Pilger mill stand 8 equipped with a Pilger mill roll 7.
A crank mechanism is used to reciprocate with great force, and imbalance occurs due to the inertial force of the reciprocating motion and the couple of inertial forces induced by the crank motion. In order to eliminate unbalance, the fan-shaped balancer 4 and the V-balancer 6' are provided as described above.

However, in the conventional Pilger type rolling mill, the following problems occur due to the installation of the fan-shaped balancer 4 and the V-balancer 6'. That is, 1) sector balancer 4 and V balance 6'
It is large because it is equipped with a. 2) In the fan-shaped balancer 4 and the V-balancer 6', the crankshaft 2
A first-order term based on the rotational speed ω of
(same below) can be eliminated, but the unbalance of 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 unbalance of higher-order terms of the rotational speed ω of the crankshaft 2 cannot be eliminated, originally ω
Since the connecting rod 5 receives a large inertial force proportional to the square of has its limits. 4)
Since it is equipped with the V balancer 6', for example, a Pilger mill rolling machine for rolling a φ260 mm raw pipe is
It requires foundation work approximately 8m deep, and as a result, V
Maintenance around the balancer 6' also becomes 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, the piston rod of an air cylinder is connected to the Pilger mill stand, compressed air from the air cylinder is supplied, and An inertial force balance method is known that attempts to balance the inertial force of the reciprocating motion of the Garmil stand (UK Patent No. 1355733).
(see specification).

However, in this known inertial force balance method, since the inertial force is balanced using compressed air whose volume can be reduced, not only the compressor and air cylinder for compressed air become large, but also the Pilger mill Even if you try to use compressed air to assist the rolling force of the rolls on the raw tube, compressed air cannot produce a strong force. Moreover, if an attempt is made to drive the air cylinder with compressed air to balance the inertia of the reciprocating motion, an excessive amount of energy will be required for the drive source.

[Means for solving problems]

Therefore, the present invention was created to solve all of the problems of the prior art at once. Specifically, one end of a coil spring with a constant spring constant is connected to a pilger mill stand, and the other end of the spring is connected to a hydraulic cylinder. In this connection, the spring force is made variable to balance the inertial force of the primary and higher order terms of the reciprocating motion of the Pilger mill stand, and to save as much energy as possible from external sources for balancing. The purpose of the present invention is to provide a balance device for a Pilger type rolling mill.

〔Example〕

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 embodiment is suitable for a so-called large-sized Pilger rolling mill that cold-rolls seamless steel pipes with a diameter of 260 mm. The values are balanced by a compression coil spring 9 attached to the Pilger mill stand 8.

Therefore, when the rotational speed ω of the crankshaft 2 is constant, it is sufficient to simply balance the first-order term of the inertial force of the reciprocating motion of the pilger mill stand 8 and the coil spring 9. Therefore, M: Weight of Pilger mill stand 8 α: Acceleration of displacement s of Pilger mill stand 8 k: Spring constant of coil spring 9 x: Displacement of hydraulic cylinder 10, Mα=k(s−x ) ...(1) becomes.

By the way, the approximate size of the spring constant k used here is determined as follows. Now, for simplicity, let R/L≪1. From the well-known first-order term of reciprocating inertia force, α=-ω ² s ...(2) is derived, so Equations (1) and (2) Therefore, x/s≒1−Mω ² /k...(3) Therefore, from equation (3), the displacement x of the hydraulic cylinder 10
In other words, the hydraulic cylinder 1
It is sufficient to select a spring constant k such that 0 hardly moves. In other words, when the rotational speed ω is at its maximum value at the crank angle, it is sufficient to determine the spring constant k such that x/s=0 in equation (3). (the problem becomes less as the problem increases), k=Mω ² max (4) is obtained. That is, if a coil spring 9 having a spring constant k obtained by equation (4) is used, the other end of the coil spring 9 (the opposite side to which it is attached to the pilger mill stand 8) may be a fixed end.

However, in reality, R/L is not ≪1.0, so
Higher-order terms in the well-known general formula for reciprocating inertia cannot be ignored. Therefore, in this embodiment, the other end of the coil spring 9 is connected to the piston rod 11 of the hydraulic cylinder 10. That is, by controlling the position where the other end of the coil spring 9 and the hydraulic cylinder 10 are connected, the spring force of the coil spring 9 is changed and the higher-order terms of the inertial force are balanced. Therefore, the position control is performed as follows. The displacement command value X for the displacement x of the hydraulic cylinder 10 is determined from equation (1) as follows: X=M/ks+s (5). This displacement command value X is calculated by giving the rotational angular velocity detected from the pulse generator 12 attached to the crankshaft 2 to the calculating section 13. The value is converted into a corresponding pressure value, and is applied as a pressure command value j1 to the servo valve 14 that supplies hydraulic pressure to the hydraulic cylinder 10 to control the servo valve 14. Therefore, in this embodiment, it is possible to balance even the higher-order terms of the inertial force of the reciprocating motion of the pilger mill stand 8.

[Improved balance accuracy]

Furthermore, in this embodiment, for example, the frictional force generated in the reciprocating motion of the pilger mill stand 8 and the error between the calculated value and the actual value are taken into account to improve the balance accuracy. A tension detector 15 is installed, and the signal from the tension detector 15 is used as a correction signal j2, which is used as a feedback gain.
As Kcc, feedback is sent to the amplifier 16 to which the displacement command value X is given. The actual movement of the hydraulic cylinder 10 is detected by a position sensor 17 provided at the other end of the piston rod 11, and a signal j3 is fed back to the amplifier 6 as feedback kf. The stroke position is controlled so that it moves according to the displacement command value X.

[Assistance with rolling work]

In addition, since this embodiment uses the hydraulic cylinder 10, preset timings (for example, near crank angles of 90° and 270°), that is,
The horizontal force required at the peak of the rolling reaction force is assisted by the output of the hydraulic cylinder 10. Therefore, the main drive system (main motor 1, reduction gear, clutch, flywheel, crankshaft 2, crank arm 3, connecting rod 5, etc.) can be made smaller and lighter.

[Change of rotation speed ω]

In this embodiment, the rotational speed ω of the crankshaft 2 can be changed as follows to achieve proper operation. For example, in the operating mode diagram shown in FIG. 3, by operating the transmission or clutch (both not shown in FIG. 1) provided between the main motor 1 and the crankshaft 2, as shown in the E zone, When rolling a large number of raw pipes continuously, in order to prevent cracking between the start and end of each raw pipe, for example, set ω to the maximum value.
The rolling speed is reduced from 130rpm to 70rpm. In addition,
In the third diagram, the vertical axis represents ω, the horizontal axis represents time (sec), the solid line represents the rotational state of the crankshaft 2, and the broken line represents the rotational state of the flywheel.

In this embodiment, by the above-mentioned control, all terms of the inertial force of the reciprocating motion of the pilger mill stand 8 are well balanced with the coil spring 9 whose spring force is controlled by the hydraulic cylinder 10. be able to. Such a balanced state is shown in FIG. 4, and in this test, L = 4000 mm, R = 720 mm, and M≒
35TON, diameter of hydraulic cylinder 10 φ175mm/φ90mm
×2set (both sides), k≒400Kg/cm×2set (both sides), ω
= 45 rpm. The vertical axis represents force (TON) and the horizontal axis represents time (seconds) to illustrate the inertial force imbalance. In other words, Figure A is the overall diagram, and Figure B shows only the imbalance in Figure A, where the solid line represents the inertial force M x α, and the broken line represents the spring force k.
×s, the one-dot chain line shows the unbalance in the conventional example shown in FIG. 2, and the two-dot chain line shows the unbalance in the present embodiment. Here, the Pilger mill stand 8 is supported at two points on both sides when viewed from the reciprocating direction.
Figures a and b show the force acting on one point. As is clear from the diagram, the conventional example has an unbalance of 5TON, while the present example has an unbalance of 5TON.
Can be erased to less than 0.5TON.

In addition, as another embodiment of the present invention, a mass unbalancer as shown in FIG. 5 is attached to the crankshaft 2, and by using this together, the output load on the hydraulic cylinder 10 is reduced. Of course, such a mass unbalancer may be used alone. To explain FIG. 5, mass unbalancers 17 and 17' are attached to one ends of rotating shafts 18 and 19, and these rotating shafts 18 and 19 are rotatably attached to a frame 20 through which the crankshaft 2 is inserted. supported. In the figure, a small diameter gear 21 is fixed to the other end of the lower rotating shaft 18, and the small diameter gear 21 is rotated by a first gear 23 fixed to the crankshaft 2 via an idle gear 22. Here, the gear ratio between the first gear 23 and the small diameter gear 21 is 2/1. Further, an intermediate gear 24 is fixed to the other end of the upper rotating shaft 19, and the intermediate gear 24 is fixed to the upper rotating shaft 19.
is rotated by a second gear 25 fixed to the crankshaft 2. Here, the gear ratio between the second gear 25 and the medium gear 24 is 2/1. Therefore, the rotating shaft 18,
19 rotate in opposite directions to each other at twice the rotational speed of the crankshaft 2, and are balanced with the inertia force of the second-order term of the pilger mill stand 8.

Note that the present invention applies to a so-called large-sized Pilger rolling mill (Cold Reducing Tube rolling mill) that produces cold rolling.
It goes without saying that the present invention is not limited to a pilger type rolling mill that rolls steel plates or bars, and that the coil spring is not limited to a compression coil spring.

〔Effect of the invention〕

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

(1) Compared to conventional Pilger rolling mills equipped with V-balancers and fan-shaped balancers, the rolling mill is smaller, faster, easier to maintain, and simplifies foundation work.
Since the inertia of the Pilger mill stand's reciprocating motion can be balanced, no external force for balancing is required, resulting in energy savings.

(2) Since the spring force of the coil spring can be changed by the stroke of the hydraulic cylinder, even the higher-order terms of the inertia of the reciprocating motion of the pilger mill stand can be eliminated, so there is no need for a device to change the spring constant, and the structure is simple. , the product is rolled without vibration, which improves the quality of the product.

(3) Moreover, for example, if a spring with a spring force corresponding to the maximum rotational speed of the crankshaft is used to reduce the rotational speed of the crankshaft and press against the pilger mill stand with the inertia force halved, the The spring force prevents the reciprocating movement of the pilger mill stand, but in the present invention, the spring force is correspondingly reduced by stroke position control using a hydraulic cylinder, so that the reciprocating movement of the pilger mill stand at low rotational speeds is prevented. It can be done smoothly.

(4) In addition, since the stroke position of the hydraulic cylinder is controlled, it is possible to assist the horizontal force required when rolling the material on the Pilger mill roll, and the main force for reciprocating the Pilger mill stand. The drive system can be downsized.

(5) According to the present invention, since higher-order terms are balanced, there is no need for connecting rods, crank arms, and crankshafts that require machining or are made of high-grade materials to receive excessive force, and there is no need to increase their size. This will result in significant cost reductions. In addition to this, for example, in the case of the conventional case where only the first-order term is eliminated at the foundation bolt of the housing housing the Pilger mill stand (this is required for any Pilger mill stand), the second-order term At least the inertial force of must be supported, so higher speeds require significantly stronger foundation bolts. However, according to the present invention, since higher-order terms are also balanced,
As long as the foundation bolt supports the rolling horizontal reaction force,
This rolling horizontal reaction force is often not a function of rotational speed, so increasing the speed will not affect the foundation bolts. In other words, according to the present invention, the foundation bolts used at low rotational speeds are sufficient, and the inertia force corresponding to the increased speed can be supported via springs in the machine frame that does not require machining, and does not affect the foundation bolts. do not.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an embodiment of the present invention, Fig. 2 is a schematic diagram of a conventional example, Fig. 3 is an operation mode diagram of this embodiment, and Fig. 4 is an inertial force imbalance graph of this embodiment. Figure A is an overall view, Figure B is an enlarged graph showing only the unbalance of Figure A, and Figure 5 is a cross-sectional view of a main part of another embodiment. 7... Pilger mill roll, 8... Pilger mill stand, 9... Coil spring, 10... Hydraulic cylinder, 14... Servo valve, ω... Rotation speed.

Claims (1)

[Claims] 1. In an inertia force balance device for a Pilger rolling mill that converts rotational motion of a crankshaft into reciprocating motion and horizontally reciprocates a Pilger mill stand equipped with a pair of Pilger mill rolls, the Pilger mill stand Connect one end of the coil spring to
An inertial force balance device for a Pilger type rolling mill, characterized in that a hydraulic cylinder for supplying and discharging hydraulic pressure is connected to the other end of the coil spring via a servo valve controlled by the rotational angular velocity of the crankshaft.