EP0135620B1

EP0135620B1 - Horizontal honing machine

Info

Publication number: EP0135620B1
Application number: EP83201382A
Authority: EP
Inventors: Albertus Martinus Van Dijk
Original assignee: Sanders Johannes Adrianus Cornelis
Current assignee: Sanders Johannes Adrianus Cornelis
Priority date: 1983-09-28
Filing date: 1983-09-28
Publication date: 1988-01-07
Also published as: DE3375097D1; ATE31658T1; EP0135620A1

Abstract

A horizontal honing machine for large and small stroke lengths comprises a frame with a guiding bar and a linearly driven sled (4) with a motor (5) for the rotating motion of the honing head (6). The drive of the sled (4) is moved by a direct current motor (1) with servo control and transistor adjustment, whereby the speed and point of reversal of the motion of the sled (4) in the stroke are almost independent from the load of the honing head (6) and are accurately repeating.

Description

The invention relates to a horizontal honing machine for working up bores in cylinders, for which a very good quality of the worked surface and a high accuracy of alignment are required, such as for example are required for cylinder walls of hydraulic and pneumatic devices.
The honing activity is effected by means of strips of grinding material, placed upon the circumference of a dilatable carrier tool (honing head), which is moved simultaneously axially and rotationally by a sled in the bore whereby a spiral grinding process, in both directions to and fro, is taking place.
^.Thus the polishing grooves are formed in a crosswise manner. In order to obtain an exactly parallel bore, the reversal motion of the axial drive is most critical.
Any slackening of speed or stagnation of the axial motion with regard to the continuously rotating motion will cause a local increase of grinding off more material, such that the bore will become locally wider.
Horizontal honing machines with a sled for bores of large stroke lengths (of 1000 mm up to 10.000 mm) are known from U.S-A-3237350, wherein the axial drive of the sled is carried out either hydraulically or mechanically. The disadvantage of a hydraulic drive of the sled is the fact that this requires an excess of installed power, in order to be enabled to deliver the power peak for fast reversal.
Consequently, the output efficiency of the hydraulic drive is poor. The disadvantages of the known electromechanical drives of the sled are the changing-over time, which is too long, and the inertia momentum of the moving accessories, resulting in a reversal motion which is too slow. Both systems show a less accurate reversal point mainly at high speed, which means that the honing process cannot be carried out with the optimal speed.
Working with long strokes gives rise to deflections of the carrier bar of the honing head.
In DE-B2-2347780 a honing machine for long strokes and small diameters of bores is described. According to said invention two carrier bars are used each of which is driven by a drive such that pulling and pushing are effected by separate carrier bars.
Honing of blind bores (i.e. having a bottom) is not possible with said equipment.
The present invention enables a quick reversal of the linear movement of the honing head without perceptible standstill.
The horizontal honing machine to be used for honing bores of small diameters and large strokes, comprising a frame with one guiding bar and a linearly driven carrier sled with a motor for the rotating motion of the honing head provided with strips of grinding material, is characterized according to the present invention in that the motion of the drive of the carrier sled is effected by a direct current servo motor with a servo control, tacho-generator and speed reducer, whereby the electrical regulation of speed and reversal point comprises a potentiometer, which delivers a voltage linearly proportional to the adjustment angle, a reed-relay and a servo-amplifier with a gradient generator, and an internal current circuit for adjustment of the rotational movement, such that the point of quick reversal of the linear movement of the honing head in the stroke is adjusted independently from the load of the honing head in order to obtain a quick reversal.
For the control of the servomotor three systems are appropriate.
The 'controlling can be effected by means of a three phase thyristor converter.
With this a three phase alternating tension is rectified, whereby the pulse frequency ranges from 150-300 Hz.
The controlling can also be effected by a direct current transistor regulator with electronic commutation steering a brushless synchrone motor having permanent magnets at the rotor and coil windings at the stator.
The current fed to the coils is electronically commuted.
The preferred embodiment of the servo control is a transistor regulator with pulse-width modulation. With this device the alternating tension is first rectified and subsequently equably chopped.
The tension at the rotor collector connections is influenced by varying the width of the pulses. The frequency of the pulses ranges from about 1000 to 10.000 Hz. With this device a motor with permanent magnet and a built-in tacho-generator is used.
The driving power may be provided by a closed circuit for speed regulation having short reaction periods.
Thereby the set speed and the reversal of the motion are independent from load and very accurate.
The switching over of the servo control can be effected by a sequence of signals, which is given according to a preset program for continuous production tasks. The axial speed during the honing process ranges between about 10 and 40 m/min.
In "Elektrische Ausrüstung", 15 (1974), nr. 5, pages 9-14, a dynamic servo drive system for power machines is described. The servo motor is a direct current motor; permanent magnet rotor is preferred. With this type of motor an optimal positional improvement can be obtained. It has been found, that because of its fast reaction and speed the honing operation can be done accurately and independently from the load in all kinds of bores.
The power drive used in accordance with the invention renders the possibility to retard the sled with the honing head at an axial speed of 30 m/min, to effect the reversal without perceptible standstill and to bring it to the set speed in the reverse direction again within 1/3 second. A second advantage of the drive according to the invention is the feature that with an equally remaining adjustment of the speed of the axial motion a very accurately set point of reversal of the sled is obtained, which is practically independent of the axial load and which will be repeated continually with exactness. This is of great importance in practice, for example for the honing of bores with blind bottoms. It appeared to be possible to make use of the optimal speed of the sled also for the honing of blind bores and in this respect to hone even at a distance of 2 to 3 mm only from the bottom. The power installed for the drive should be 15 kW at the utmost. The drive is delivering only the power which is to be used at any moment.
During the reversal the peak charge to drag and to start running up is in use consumed and during the further uniform speed of the stroke only the power for the motion of the honing head through the work piece is consumed. Therefore the total efficiency of the electrical drive is becoming higher than that of conventional systems. The drive with control according to the invention enables to make the reversal of the sled accurately also in case of high axial speed (40 m/min), so that during the honing of blind bores the optimal speed can be applied. If the servomotor has a low inertia momentum, it can endure the high strengths of current during short periods which are necessary for the start of running up and for the dragging operations. Because of these high speeds obtainable with said drive the machine is also appropriate for honing by means of novel cutting materials, such as boron nitride (The use of boron nitride is described i.a. in "Werkstatt und Betrieb", Ed. Hanser, 116, (1983), nr 6, p.399 a.f.).
The invention is further elucidated on the basis of the enclosed drawings 1 and 2. Figure 1 shows in part a schematic cross section of an embodiment according to the invention. Therein (1) is the servomotor, (2) a tacho-generator, (3) a reducer, (4) the sled, (5) the motor for the rotatory drive, (6) the honing head with the honing stone (7) in the work piece (8).
Figure 2 shows schematically the electrical control circuit of the installation. (1) is the servo motor, (2) the tachogenerator, (9) a potentiometer, (10) a reed-relay, (11) a gradient generator, (12) a servo amplifier, (13) an internal current circuit. The servomotor (1) has low inertia momentum and it can endure high currents during short periods, which are necessary for start and dragging. The tachogenerator (2) is mounted upon the shaft of the servomotor (1). The reducer (3) has a low inertial momentum too and its construction is with inconsiderable play. At the console for the operation of the device a potentiometer (9) is mounted, which delivers a voltage linearly proportional with the angle of adjustment. This adjusted value is switched over to the servo amplifier (12) by means of the reed-relay (10) with mercury contacts, which have a switching delay of about 2 milliseconds. The signal of the adjusted value is fed into the gradient generator (11), which transforms a non-linear signal into a value of voltage increasing or declining linearly with time, and thus provides for uniformly accelerated start and uniformly retarded dragging respectively of the motor (1).
The tachogenerator (2) at the shaft of the motor (1) delivers a voltage increasing linearly with speed of rotation and the polarity of which depends on the direction of rotation. This signal of the tachogenerator pursuant to the gradient generator (11) is compared with the adjusted value.
The servoamplifier (12) controls the current and the voltage for the motor (1) in such a manner, that the measured signal of the tachogenerator is consistent with the adjusted value, whereby the control circuit for the rate of speed is closed.
If the axial speed of the motor (1) alters as a consequence of the forces of honing and of mass, the system will instantaneously react and deliver a voltage and a rotatary moment appropriate to reduce the speed into the previous situation.
An internal current circuit (13) is added to provide for a feed-back signal in order to obtain a precise adjustment of the rotatary moment.
The drive renders the possibility to enable the sled and all the accessories connected with it as well as the honing equipment to move to and fro, with a speed of 40 m/min.
The sled will stop at the end of the stroke flexibly, and accurately reaccelerate without perceptible standstill.
The stroke depth is about 10.000 mm.
The displacement length is about 13.000 mm.
With a speed in the stroke of 30 m/min which occurs quite often, each the dragging and the accelerating distances should not be in excess of 40 mm. The following calculation demonstrates the favourable results with sled speeds up to 40 m/min.
Calculations for the frequency used speed of 30 m/min and with a dragging distance of 40 mm are as follows:
The load occurring with the servomotor for running up:
The running up and dragging respectively for the sled is uniformly accelerated and uniformly retarded respectively.
With a sled speed adjusted at 30 m/min the starting distance and the dragging distance are both 40 mm.

with uniformly accelerated running.
speed of rotation of the servo motor:
Angle acceleration of the servo motor:
Mass inertia momentum of mass moving to and fro:

J₃ calculated relating to the speed of rotation of motor:

Motor torque required for start with honing head loadless:
Dynamic start current J_dyn=22.76 · 1.22=27.77 Amp.
Motor torque required for maximal axial honing force:
Static motor current:

Maximal load of the servo motor:

Uniformly accelerated starting of the honing machine with stroke depth of 10.000 mm, under full load of honing head, up to 30 m/min in 0.16 sec:
The maximum torque is hardly higher than the continuously admissible torque of 30 Nm.
The maximum motor current is considerably lower than the admissible peak of 140 Amp.
Thus the servo motor has sufficient reserve strength.
At a sled speed of 40 m/min the same maximum charge takes place but it is lasting only
Servo amplifier:
The short duration starting current of 43.04 Amp is amply lower than the tolerable value of 50 Amp.
The current strength of 15.27 Amp. required during the uniform speed of stroke is about 50% of the current strength of 32 Amp., which is continuously tolerable.
The servo-amplifier is therefore sufficiently ample of construction.
Accuracy of control of the servo drive system:
The influence of the mass inertia of the servo motor is considerably higher than that of the sled plus the rotating drive plus the honing equipment.
The load effected by the honing force is relatively low.
Consequently this drive renders an accurate reversal which is almost independent from honing force.
Experiments have been performed in order to determine the accuracy of reversal with the horizontal honing machine according to the invention with a stroke depth of 2500 mm:
The results of the experiments are reported in the tables I and II.
Measurements have been made with gauge with 0.01 mm divided scale and 5 mm stroke depth.
The values of results of runs 2, 5,6,7 and 8 have been rounded off to 0.05 mm, the values of runs 9, 10 and 11 have been rounded off to 0.1 mm.
Measurements have been made under different load conditions and at two successive days in order to examine the influences of prolonged standstill periods and of cooling down.
From the first run until after run 8 no adjustment whatsoever of the machine had been altered.
For the augmentation of the speed in the stroke from 30 to 40 m/min the gauge has been displaced because then the running out distance of the sled was longer.
With a speed in the stroke of 30 m/min the measured spread of the point of reversal was 2.21 mm at the highest while the load of the honing force was varying from 0 to 1.02 kW.
With a stroke speed of 30 m/min and the same load the measured spread was 0.7 mm.
When the stroke speed was augmented to 40 m/min, the spread values were the same as with a speed of 30 m/min.
The augmentation of the rotational load is resulting from the increase of the speed in the stroke.
From the experimental runs and the measured values it appears that with the machine according to the invention an important progress with respect to the known systems of construction has been attained.

Claims

1. A horizontal honing machine to be used for honing bores of small diameter sizes and large strokes, comprising a frame with one guiding bar and a linearly driven carrier sled (4), with a motor (5) for the rotating motion of the honing head (6), which is provided with strips of grinding material, characterized in that the driving motion of the carrier sled (4) is effected by'a direct current servo motor (1) with a servo control, tachogenerator (2) and speed reducer (3), whereby the electrical regulation of speed and reversal point comprises a potentiometer (9), which delivers a voltage linearly proportional to the adjustment angle, a reed-relay (10) and a servo-amplifier (12), with a gradient generator (11) and an internal current circuit (13), for adjustment of the rotational movemement, such that the point of reversal of the linear movement of the honing head in the stroke is adjusted independently from the load of the honing head (6) in order to obtain a quick reversal.

2. Honing machine according to claim 1, characterized in that the servo control comprises a three phase thyristor converter.

3. Honing machine according to claim 1, characterized in that the servo control comprises a direct current transistor regulator with electronic commutation, controlling a brushless synchronous motor having permanent magnets at the rotor, and coil windings at the stator.

4. Honing machine according to claim 1, characterized in that the servo control comprises a pulse-width-modulated transistor regulator.

5. Honing machine according to one of the claims 1 to 4, characterized in that the switching over of the servo control is effected by a sequence of signals, which is given according to a preset programme for continuous production tasks.