JPS5935729B2 - Hobbing machine control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hobbing machine control device, and more particularly to a hobbing machine control device capable of rotating a hob shaft of a hobbing machine and a workpiece in accurate synchronization to machine highly accurate gears.

A hobbing machine is a machine tool that uses a hob to form an involute tooth profile, and uses the hob to perform gear cutting on a workpiece, such as a spur gear, helical gear, worm gear, or spline shaft.

It is a rotary blade that has a cutting edge along the thread on the outer periphery of the cylindrical hob shaft.

When machining gears on a workpiece using a curling hobbing machine, it is necessary to rotate the hob shaft and the workpiece in complete synchronization, and if this synchronized rotation is disrupted, high-precision gear machining cannot be performed.

For example, gears are generally machined on a workpiece by the hob shaft making exactly one rotation while the teeth move one pitch. However, if the hob shaft and workpiece do not rotate synchronously (out of sync), the teeth may be bent or the tooth pitch may be This causes various machining errors such as misalignment.

In conventional hobbing machines, the rotation of the hob shaft and the rotation of the workpiece are synchronized by coupling them with a gear, and the number of teeth formed on the workpiece is changed by changing the gear ratio of the coupling gear.

However, since such a hobbing machine must process many types of gears, it generally requires many types of coupling gears, leading to an increase in the size and cost of the device.

Therefore, one object of the present invention is to provide a hobbing machine control device that can accurately rotate a hob shaft and a crocodile holder in synchronization without using a coupling gear, and can also provide a small, low-cost hobbing machine. shall be.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of a hobbing machine control device according to the present invention.

In the figure, NC is a numerical control device including a control section 1a, a pulse distributor 1b, an LC pulse number correction circuit 1d, ! It has a j-barge pull counter 1e, a comparator 1f, and a 1-pulse generator 1g.

The control unit 1a outputs speed command values VNw and VNh according to the rotation speeds of the workpiece WK and the hob shaft HB.

The ratio of VNw and VNh is the rotational speed ratio m of the workpiece and the hob shaft.
be equivalent to.

The pulse distributors 1b and lc each receive the speed command value V.
A pulse distribution calculation is performed based on Nw and VNh, and a distributed pulse P with a frequency proportional to the speed command values VNw and VNh is generated.
Generates w and Ph.

The work pull counter 1e is normally incremented by +1 every time the distribution pulse Pw is generated, and is calculated by the hob pulse HPP' obtained by dividing the hob shaft position pulse HPP generated every time the hob shaft rotates by a predetermined amount into 1/m. Subtract 11 from that content.

If the content of the reversible counter 1e is greater than 10N, for example +2, the comparator 1f generates 11" on the line ld, and -N
(=-2) or less, 11" is generated on the line ls.

The 1 pulse generator 1g generates 1 pulse every time "1" appears in ls.

The pulse number correction circuit 1d adjusts the distribution pulse Pw when 'l'l'' occurs on the line Ild, that is, when the number of distribution pulses Pw for driving the workpiece is 2 or more than the number of hob pulses HPP'.
If 11" appears on the line ns and a pulse PC is generated from the 1 pulse generator 1g, that is, if the number of PwO becomes 2 or less than the number of HPP', the pulse PC is divided into a distribution pulse. Work drive pulse Pw is mixed with Pw.
' is output.

That is, the pulse number correction circuit 1d uses the workpiece drive pulse Pw'
The number of hob pulses HPP' is always equal to the number of hob pulses HPP', in other words, the rotation of the workpiece and the hob shaft are synchronized.

Note that 1h is a division period for dividing the hob shaft position pulse HPP into 1/m.

SVH and SVW are servo systems for driving the hob shaft and the workpiece, respectively, and position deviation generating units 2a and 3a output signals according to the position deviation: according to the speed deviation.

Speed deviation generators 2a, 3b that output signals; speed detectors 2cy3cm position detectors 2d, 3d
and respectively known velocity feedback loops VF, VF'
, position loops PF and PF' are formed.

M.H. MW is the drive that drives the hob shaft and workpiece, respectively.

Motor, HB is hob shaft, WK is workpiece, GH.

GW is a gear, PL1 and PL2 are pulleys, BLT is a belt, and RPC is a pulse distributor that generates one hob shaft position pulse HPP every time the hob shaft HB rotates by a predetermined amount.

Next, the present invention will be explained in detail.

When the pulse distributors 1b and 1c are given speed command values VNw and VNh from the control section 1a, the pulse distributors 1b and 1c use the speed command values VNw.

Distribution pulses Pw, Ph having frequencies f, w, fh proportional to vNh are generated.

These distribution pulses Pw. ph is applied to the servo system SVW and 5VHK as a position command.

Now, although not shown, the position deviation generating units 2a and 3a each add a distribution pulse Pw or ph thereinto to generate a feedback pulse FPh.

It has a reversible counter that subtracts FPw, a DA converter that converts the contents of the counter into A, and an amplifier.

Therefore, upon start-up, ie, after the start of pulse distribution, the contents of the reversible counter and the DA converter output begin to increase.

Then, with a predetermined delay, the motor MW is activated by this DA conversion output.

MH rotates and feedback pulse FPw is generated.

If FPH occurs, this feedback pulse FPW
, FPH is the corresponding position deviation generating section 2a.

It is input to the reversible counter 3a.

Thereafter, each motor MW, MH reaches a constant speed after a predetermined period of time, and in this steady state, the position deviation Pdw.

Pdh is maintained at a constant value.

In addition, the speed feedback loops VF and VF' are connected to each servo system SVH,
Since it is formed in the SVW, a servo system with good coordination is constructed.

Now, if the hob shaft HB and the workpiece WK are rotating accurately at the commanded speed, then the hob shaft and the workpiece are rotating correctly in synchronization, and the hob pulse HPP' and the distribution pulse Pw for driving the workpiece are The difference cannot be more than 2.

Therefore, the distribution pulse Pw for driving the workpiece is outputted from the pulse correction circuit 1d as the workpiece driving pulse Pw'.

In this state, as gear processing by the hobbing machine progresses and the hob bites into the workpiece, the load applied to the hob shaft HB increases.

Then, the rotational speed of the hob shaft driving motor MH decreases.

Along with this, the generation speed of the feedback pulse FPh decreases, the content of the reversible counter in the position error generator 2a increases, and the position error Pdh increases.

As a result, the voltage applied to motor MH increases, thereby increasing the rotational speed of motor MW.

Meanwhile, in parallel with the above, the synchronization control described below is performed.

That is, if the rotational speed of the hob shaft HB decreases, the generation speed of the hob shaft position pulse HPP generated from the pulse coder HPC decreases, and the content of the reversible counter 1e in the NC becomes 2 or more.

As a result, a line 1ldK''''1 appears, and the distribution pulse Pw for driving the workpiece is 1 in the Norse number correction circuit 1d.
Pulses are thinned out.

Thereafter, each time the content of the reversible counter becomes 2 or more, the distribution pulse is thinned out by one, and the workpiece drive pulse Pw'
is output as

That is, the pulse speed of the work drive pulse Pw' is the same as the hob axis H.
It will decrease as the rotational speed of B decreases.

From the above, even if the speed of the hob shaft HB fluctuates due to an increase or decrease in load, the servo system SVH, which has a position feedback loop and a speed feedback loop, quickly operates to bring the speed of the hob shaft to a steady speed.

At the same time, the number of drive pulses Pv' for driving the workpiece WK is increased or decreased (corrected) in accordance with the speed deviation of the hob shaft HB.

Therefore, even if a synchronization shift occurs due to a slight delay in the servo system SVH, accurate synchronization can be maintained by increasing or decreasing the number of drive pulses applied to the servo system SVW, in other words, the work position command.

As shown in Figure 2, the servo system SVH includes an fV converter FVC that converts the frequency of the distribution pulse ph for driving the hob shaft into a voltage, and a voltage that is proportional to the actual rotational speed of the hob shaft drive motor MH. Although it may be constructed of a speed detector VDT and a speed deviation device VDG that outputs a speed deviation signal, the restoring force to a steady speed is smaller than that of the servo system according to the present invention shown in FIG.

This is because in the present invention, as the actual speed vh decreases, the positional deviation Pdh increases, and the hob shaft drive motor MH
While the voltage applied to the motor (Pdh-vh) becomes considerably large, the voltage applied to the motor (Vc-vh) in FIG.
Vh) (Vc: constant at command speed) is the above (Pd
This is because it does not become as large as h−Vh).

That is, the speed feedback system shown in FIG. 2 alone has little responsiveness to speed fluctuations.

As a result, the load on the hob shaft increases and the hob shaft drive motor M
If the speed of H decreases, the speed fluctuation will be large and there will be a considerable time delay in returning to the steady speed.

Note that even if the number of drive pulses is reduced by the pulse number correction circuit 1d, the speed of the workpiece drive motor MW is
It does not decrease immediately due to the delay of W.

From the above, in the case shown in Fig. 2, the rotation of the hob shaft and the workpiece cannot be synchronized, and the teeth are bent by 10 to 20 μm in distance.

This is a fatal flaw in hobbing machines that require high-precision gear machining.

On the other hand, if a position feedback loop and a speed feedback loop are formed in the servo system SVH, even if the load becomes heavy, the restoring force to the steady speed will be large as described above, and the speed fluctuation will not become so large.

The synchronization deviation caused by this slight speed fluctuation can be corrected by reducing the workpiece driving pulse Pw'.

In the above description, the position detector 2d and the pulse coater HPC were provided separately, but they may be used in common.

As described above, according to the present invention, the hob shaft and the workpiece can be precisely rotated synchronously without using a coupling gear (purely electrically), and the gear can be machined with high precision.

Furthermore, since a coupling gear or the like is not required, the hobbing machine can be constructed in a small size and at low cost.

Furthermore, even if the load on the hob shaft changes and the speed of the hob shaft fluctuates, the restoring force to the steady speed is large and the speed drop can be minimized.
Furthermore, since the rotational speed of the workpiece is varied in accordance with the speed of the hob shaft, the rotations of the hob shaft and the workpiece can be accurately synchronized.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a hobbing machine control device according to the present invention, and FIG. 2 is another example of a servo system for driving a hob shaft. NC...Numerical control device, 1a...Control unit, 1b. 1c... Pulse distributor, 1d... Pulse number correction circuit, 1e... Reversible counter, SVH. SvW... Servo system, 2a, 3a...
...Position deviation generator, 2b, 3b...Speed deviation generator, 2c. 3c...Speed detector, 2d, 3d...
...Position detector, MH...Motor for driving the hob shaft, MW...Mokyu HPC for driving the workpiece...
...Pulse coder, HB...Hob shaft, WK
······work.

Claims (1)

[Claims] 1. A hobbing machine control device that rotates a hob shaft at a predetermined speed, rotates a workpiece periodically with the rotation of the hob shaft, and processes gears on the workpiece using a hob attached to the hob shaft. The servo system for driving the hob shaft is composed of a position feedback loop and a speed feedback loop, and a detection means for detecting the rotational position of the hob shaft or the hob shaft drive motor is provided, and a position signal generated from the detection means is provided. A hobbing machine control device characterized by rotating a workpiece drive motor in synchronization with a hob shaft drive motor. 2. Hobbing machine control according to claim 1, wherein the hobbing machine control corrects the position command signal according to the deviation between the position command signal applied to the work drive system and the position signal generated from the detection means. Device.