JPS58114844A - Speed detecting method of numerically controlled hobbing machine - Google Patents

Abstract

PURPOSE:To prevent the variation of control lag due to the rotational irregularity of a hob by a method wherein the rotation of a work is controlled by a signal, which is obtained by levelling off the the outputs of a pulse encoder to detect the amount of rotation at predetermined intervals of time. CONSTITUTION:In case that a gear is cut by hobbing, the rotational irregularity is caused in the hob by means of the cutting force applied to the hob, resulting in exerting an adverse influence upon the synchronous rotation control of the work. An output pulse train of the encoder 7 denoting the revolution speed of the hob 1 is levelled off at predetermined intervals of time such as one revolution of the hob by means of a levelling-off circuit 14 of pulse inputs and the pulse train corresponding to sadi average value is outputted to a pulse distributing circuit 8a in order to synchronously rotate the work 13 mounted on a rotary table. In such a manner as described above, the change of the amount of lag of synchronous rotation control of the work due to the rotational irregularity of the hob is prevented, resulting in enabling to realize a highly accurate gear hobbing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed detection method for a numerically controlled (hereinafter referred to as NC) hobbing machine, and more particularly to one that eliminates the influence of uneven rotation of a hob shaft.

A hobbing machine, which is a gear cutting machine, conventionally has a hob cutter and a work table that are completely connected by a gear train, so the rotation of the work table is synchronized according to the rotation speed or movement of the hob cutter, so that they can operate independently. It doesn't move.

However, even in the case of an NC hobbing machine that does not have a gear train between the hob cutter and work table, it is of course important to synchronize the hob cutter and work table, but because the table axis tries to follow the movement of the hob axis, , synchronization becomes worse.

Here, a conventional example of an NC hobbing machine is shown in FIG.

A hob shaft driving gear 3 and a flywheel 4 are connected to the hob shaft 2 of the hob cutter 1, and a motor 5 is connected to the n1 hob shaft driving gear train 3. A gear train pHil for generating a Varnu is connected to the drive shaft of the gear 5, and this gear train 6 is connected to a Pal 7 encoder T. Parnuenko/1jNc! In the NC device S, a control signal is generated in accordance with the rotation of the motor 5, that is, the rotation of the hob cutter 1. A manuta ohm 11 is connected to a table motor 9 which is controlled and connected to an NC device 8 via a table shaft driving gear train 10 . This master ohm 11Fi is connected to the manutau ohm wheel 12 to rotate the workpiece 131 on the table.

In such a structure, the motor sO that rotates the hob shaft 2 is detected by the encoder RO.
The output machine is loaded into the NCl1fflil, and the table plate I is used for machining a screw wheel with a predetermined number of teeth and helix angle from the NC equipment.
It is controlled by giving the K command.

By the way, hob cutter 1 used for hobbing is No. 1! As shown in Figure (a), the serrated cutters 1.1 have a shape arranged in the circumferential direction, so the hob cutting process becomes an intermittent cutting process, causing uneven rotation on the hob shaft 2, causing momentary Hob shaft 2
The speed of the motor 5 varies with respect to the average speed ratio from the motor 5. If this fluctuation t is left as it is, the table delay amount will fluctuate and accuracy cannot be obtained. Therefore, we focused on the mounting position of the pulse encoder T, which is the mounting position that is not affected by the fluctuation, that is, the number of pulse encoders 7t - hob shaft l. Be sure to install the hob shaft through a pulse gear train separate from the hob shaft drive gear train 3 to prevent it from being affected by rotational irregularities that occur on the hob shaft 2, and also to prevent the rotation of the hob shaft 2 by using the flywheel 4t. By suppressing the amplitude of the unevenness and further improving the characteristics of the motor i, the rotational unevenness itself can be slightly reduced. As a result,
Even in the case of high-speed heavy cutting, a certain degree of machining can be achieved.

However, even with the above-mentioned means for eliminating rotation irregularities, high-degree machining cannot be achieved, and rotation irregularities of the hob shaft 2 cannot be completely eliminated even by improving the flywheel 4 and motor 5.

- As an example, the relationship between a conventional pulse train and rotational unevenness [shown in FIG. 3(,)(C)].

In this case, the output of the pulse encoder that can be detected at the smoothest rotating part of the hob shaft drive gear train 3 is:
In the case of no load, that is, when there is no cutting process f1 Fig. 3 (
&), and in the case of rough cutting, for example, the number of teeth is 12,130 rpm, the depth of cut is 17.5 mm, and the feed rate is 1 mm/raV, it will be as shown in Figure 3 (b),
For finishing machining, for example, the number of teeth is 12, 13 Or
pm, cutting depth of 8 cm, feed rate of 91 cm/reV, the result will be as shown in Fig. 3 (C).

Here, referring to FIG. 4, conventional NC! Set i to 1'il. The output from the pulse encoder T is taken into the NC device 8 and manually inputted to the pulse distribution circuit 8a. On the other hand, the pulse distribution circuit 81 stores the set signal from the tooth number command value circuit 8b. In this way, the rotation speed of the hob shaft and the number of cutting teeth of the workpiece are input to the pulse distribution circuit Ia, and the corresponding pulses are input to the smoothing circuit-d.This smoothing circuit S -, smoothing is performed with the time constant at-.

The output of the smoothing circuit 8d is input to the table motor 9 via the digital phase modulation circuit $e1, the position control circuit 8f, and the amplifier circuit sg. The table motor includes a tacho generator 9x for detecting the number of rotations and a resolver 9Y for detecting the position, and the outputs of these are individually fed back to the amplifier circuit 8g and the position control sub-path If for consideration.

In such a circuit, the smoothing circuit 84O time constant a
Although it is possible to make t a certain amount large to accommodate fluctuations in the output pulses of the pulse encoder T, the time constant cannot be made larger beyond a certain point because the following relationship exists.

Here, △ is the amount of table delay from the bob (■), F is the rotation speed of the table (■/m1n), Kp is the positional loose gain of the table motor (rad/5ee), and T8 is the time constant (set) of the smoothing circuit. be.

Thus, in view of the above-mentioned drawbacks, the present invention improves the characteristics of the rotor by adding a flywheel to eliminate rotational unevenness, and attaches a pulse encoder to a pulse gear train that is less affected by rotational unevenness. However, the improvement in accuracy is still not satisfactory, and we have developed a speed detection method for numerically controlled hobbing machines that improves the machining degree even further by eliminating drawbacks such as the inability to increase the time constant of the magnification circuit. For the purpose of providing.

In order to achieve this object, the present invention provides a numerical control hob II in which the output tNc of a pulse encoder attached to the hob is inputted to a tNc device to control the drive of the table. It is assumed that the data is averaged over a time interval and then input to the NC@ position.

The present invention will now be described in detail with reference to FIG. In Fig. 5, the same parts as in Fig. ts4 are given the same reference numerals. 411th
As clearly explained in the circuit explanation, the numoizing circuit wrsa
o Do not increase the time constant and keep it at the conventional value. On the other hand, the pulse encoder TO output pulse is sent to the pulse input averaging circuit 1.
4 is input.

In this pulse input averaging circuit 14! The pulse train shown in FIG. 6(&) having rotational irregularities is averaged to generate a new pulse train as shown in FIG. 6(b) based on the average value. In this case, the pulse train is averaged at appropriate time intervals in consideration of the period of uneven rotation, etc. The circuit configuration is connected to the Parnu encoder T → Parnu input averaging circuit 14 → Parnu distribution circuit 1m, so the pulse distribution circuit @ 凰 is connected to the output unevenness of Parmenin;-da 1, which causes the table delay amount to fluctuate. [The averaged pulse becomes human power. 1115 In the figure, hob 1, motor 5, tooth number command value @b luginuta 8C, digital phase change 11 circuit 8., position control circuit 11f, amplifier circuit ag.

The table motor 3, tacho generator IX, and resolver sY are the same as those shown in FIG.

As explained above, according to the present invention, conventionally FIG.
In order to eliminate fluctuations in the synchronized speed between the hob and table shown in Figure 7 (b) K, which occur when the table shaft tries to follow rotation irregularities as shown in Figure 7(b), the average of the fluctuating pulses from the pulse encoder caused by rotation irregularities can be eliminated. By creating a new averaged pulse train, it is possible to eliminate the cause of table delay variation, improve control accuracy of the table motor, and improve IvI cutting accuracy.

[Brief explanation of the drawing]

The first picture is a simplified configuration diagram of an NC hobbing machine, the iris 21 is an example of a hob cutter, and the 11-sided diagram ((a)) is a cross-sectional view of a cow cut. load, (b)
(c) is a pulse waveform diagram showing heavy cutting rough machining, (c) is a pulse waveform diagram showing finishing machining, Section 4... is a circuit block diagram mainly showing the NC device, and Fig. 5 is a speed detection method of a numerically controlled hobbing machine according to the present invention. In this example, block ■ mainly shows the NC device, Fig. 6 shows rotational unevenness with respect to time -) shows Parnuda 14% with rotational unevenness, (b) shows a waveform diagram showing the averaged pulse train, and Fig. 7g ( &) is a waveform @ of uneven rotation with respect to time, and FIG. 7 (111) is a waveform diagram showing the synchronization accuracy of the hob and table. In the drawing, 1iL hob cutter, 2 is a hob shaft, 2 is a motor, T is a pulse encoder, heat is an NC* position, - is a table motor, and 14 is a pulse input averaging circuit. Patent applicant Mitsubishi Heavy Industries, Ltd.

Claims (1)

[Claims] In a numerically controlled hobbing machine in which the output of a pulse encoder attached to the hob is input to an NC device to control the drive of the daple, the fluctuating pulse train output from the pulse encoder is averaged at appropriate time intervals, and then the A speed detection method for a numerically controlled hobbing machine that is characterized by the fact that it is equipped with an NC system and is manually operated.