DE2131424B2 - Method and device for preventing the bouncing back of a plunger coil armature that is movable back and forth in a constant magnetic field from at least one travel limit stop - Google Patents

Description

50

The invention relates to a method and a device for preventing a bouncing back Plunger coil armature movable back and forth in a constant magnetic field from at least one travel limit stop.

The rebound of mechanical components in the case of larger increasing operating speeds is particularly undesirable because there are limits to the possible operating speed. For example, in the case of data processing systems, the operating speed the entire system often depends on the operating speed of a mechanical device, for example a printer.

Devices with floating in a constant magnetic field f. Plunger coil anchors are known from the USA.-Patentschnft 3470399 and the laid-out documents of the German patent application B 18 28421d ^r . In the known arrangements, no travel limit stops are provided for the moving coil armatures and consequently no measures are taken to prevent the moving coil armatures from bouncing back.

The invention is the task of Zugpinde, a method for preventing the rebound of a in a constant magnetic field reciprocating plunger armature, whose path of at least a path limit stop is limited to create.

In terms of solving this problem, such a method according to the invention is characterized in that the point in time of the impact of the armature on the stop is determined by the change in the voltage induced in the moving coil resulting from the associated armature delay and a current pulse at this point in time generated in the plunger coil and thereby a coil magnetic field is built up, the force of which pushes the plunger coil armature against the stop.

The invention brings technical progress that by preventing or at least the essential Reduction of the bouncing back of the plunger coil armature from the limit stop a considerable increase in the speed of operation of an electromechanical device, which contains movable components actuated by moving coil armatures, can be achieved.

If the plunger coil, as is known, for example, from the documents laid out in German patent application B 18 2842Id ¹ , has a center tap via which, depending on the direction of movement of the plunger coil armature, one half of the coil is excited, the time of the armature impact on the Stop preferably uses the change in the voltage induced in the respective non-energized coil half and, based on this determination, amplifies the current in the respective energized coil half.

A device for carrying out the method according to the invention is an electronic one Circuit marked which responds to said change in the voltage induced in the plunger coil responds to the impact of the anchor and those necessary to prevent the anchor from bouncing back Applies current pulse to the plunger coil.

Such a device can, if used to prevent the bounce back of one in a plunger coil with center tap movable plunger coil armature is used and the excitation current of each energized plunger coil halves each by a semiconductor switch connected in series with the same is controlled, a further current path connected in parallel to said semiconductor switch containing the controlling semiconductor switch, which is controlled by the non-energized coil half by means of the in it generated upon impact of the armature on the stop as a result of the change in the induced voltage Voltage pulse controlled and thereby becomes conductive.

A preferred embodiment of the invention is described below with reference to the drawings, for example described. It shows

F i g. 1 part of an access mechanism for a

n magnetic disk storage in which the invention Is used

Flg. 2 voltage-time diagrams of the T & uctwpule of the mechanism shown in Fig. 1 applied voltage pulses and a distance-time diagram, the moving coil armature with and without application of the method according to the invention shows,

Fig. 3 is a circuit diagram of a preferred embodiment a device according to the invention for Execution of the method according to the invention, and

Fig. 4 diagrams of the at different points the one in Fi ^. 3 specified circuit occurring voltage forms.

The arrangement shown in Fig. 1 is part of the Ziigriffsroechanismus for a magnetic disk storage. A magnetic write head arranged on a slide in this disk storage device can be displaced radially over the magnetic disk by rotating a guide spindle 1. Once the write head has reached the desired track, the rotation of the spindle 1 is stopped by two pawls 2, which engage the teeth of a ratchet wheel 3 seated on the spindle 1. A rotation of the ratchet wheel by one tooth moves the write head by one track on the magnetic disk.

The pawls 2 are attached to leaf springs 4. whose path to the ratchet wheel is limited by stops 5. The leaf springs 4 and the stops 5 are attached to parts 6 of a frame 16. Ratchet springs 7 urge the pawls 2 into engagement with the ratchet wheel.

If the writing head is to be moved to another disk track {stationary }, a plunger coil arrangement, partially visible on the right-hand side in FIG. 1 , is excited and a yoke 8 attached to a plunger coil armature is moved away from the ratchet wheel. Arranged on the yoke 8 drivers 9 capture the pawls 2 and pull them away from the ratchet wheel 3 so that they can perform a rotary movement and bring about an adjustment of the writing head.

The plunger coil arrangement consists of a C-shaped yoke 10 which conducts the magnetic foot and a central pole piece 11 to which a permanent magnet 11a is attached. In the cylinder gap 12 formed between the yoke 10 and the central pole piece 11, in which a strong magnetic field prevails, the plunger coil armature 14 carrying a plunger coil 13 is arranged to be movable to and fro. The diving coil 13 is a coil with a center tap, one half of which can be excited for the purpose of moving the moving coil armature in one direction and the other half of which can be excited for the purpose of moving the armature in the other direction . The shaft 18 of the yoke 8 fastened to the moving coil armature 14 is guided on the one hand in a guide 15, 17 fastened on the frame 16 and on the other hand in a bore 19 of the pole piece 11. A radial collar 20 stiffens the fastening of the yoke shaft 18 on the plunger coil armature 14.

The plunger coil arrangement is screwed to a holding element 21 fastened to the frame 16. A stop pad 22 attached to the inside of the holding element 21 facing the plunger coil armature 14 limits the movement of the plunger coil armature in the direction of the ratchet wheel 3. Another stop pad 23 on the end face of the pole piece 11 limits the armature movement in the direction of ratchet 3 away. Both cushions 22 and 23 are made of elastic material and consume kinetic energy of the moving coil armature on impact and thereby dampen the tendency to rebound.

It has been shown, however, that the remaining rebound is so strong that it is premature Locking of the ratchet wheel or unwanted releasing of the ratchet wheel can result, whereby the print head over the wrong disk

trace comes to rest.

The path-time curve for the moving coil armature displacement when releasing and locking the ratchet wheel is, t in FIG. 2c shown. The F i g. 2 a and 2 b show the course of the applied to the plunger coil

is voltage pulses for loosening or locking the ratchet wheel. According to FIG. 2a, the plunger coil half lying between the terminals 24 and 25 is excited to release the Klrokenrades, the excitation voltage for rapid acceleration of the plunger coil armature from the rest position to a high value Vl between a time fl and i2 and then to a lower value V2 is reduced aui which the excitation voltage is maintained even after reaching the stop 23 by the moving coil armature so long, the moving coil armature bu move in the other direction and again 3 oil ratchet lock soli. As shown in FIG. 2 c, the plunger coil armature reaches the stop 23 after a displacement d at time i3.

If no measures are taken to prevent bounce back, the anchor bounces as if the dip in the path curve can be seen, back several times.

In the same way as just described , the ratchet wheel 3 is locked by moving the armature in the opposite direction, for which purpose the other half of the plunger coil located between the terminals 24 and 26 is now excited. Again, the excitation voltage between times i4 and tS denotes

high value Vl and then the smaller value Vl up to the point in time Π at which the next loosening process begins. From Fig. 2c it can be seen that when the stop 22 is reached at time / 6 , the armature bounces back again , if

no measures have been taken to prevent bounce back.

The problem of the armature bouncing back is solved in that immediately after the impact on the stop in the respectively energized coil half

a short, strong locking current pulse is generated

which presses the armature against the stop

This pulse is in Fig. 2a and 2b in Zeitpunki

r3 or 16 starting with dashed lines.

To the locking current pulse in the correct

To make the point in time effective, it is necessary to determine the point in time of the impact of the anchor on the stop. For this purpose , the change in the respective anchor delay resulting from the impact of the anchor

non-excited half-induced voltage detected. The voltage pulse induced in the coil half that is not used for the notch movement is used to trigger a circuit that generates the excitation current in the respective excitation

th coil half briefly amplified by the aforementioned locking current pulse and thereby counteracts a rebound of the armature.

A circuit for generating the locking

Current pulses are shown in Fig. 3, Fi g. 4 shows the voltage curves occurring at various points in this circuit. In the in Fi g. 3, for the sake of simplicity, the parts of the circuit which are used to generate the locking pulse and the voltage Vi at the start of the excitation voltage pulse are only shown for one coil half, namely the coil half between terminals 24 and 25, and the corresponding ones Circuit parts for the other coil half are omitted for the sake of clarity.

Between the end connections 25 and 26 of the plunger coil and ground is a parallel circuit of two transistors Tl, T2bzw. TS, T6 arranged. The center connection 24 of the plunger coil is connected to the positive operating voltage. Depending on whether one of the transistors Tl. T2 or the other transistors TS, T6 are turned on, a current flows through one or the other coil half. A resistor 27 or 28 is connected between the emitters of the transistors T2 and TS and ground. The transistors T2 and TS are provided for switching the low coil excitation current corresponding to the holding voltage Vl , while the transistors Tl and T6 are used for switching the initial excitation current corresponding to the high initial excitation voltage Vi and the locking current pulses.

The transistors T2bzw. TS can be controlled by transistors T3 and T4. The transistors T3 and T4 are in turn controlled via their bases 29 and 30, respectively. If the transistor T3 is switched on, the base of the transistor T2 is practically at ground potential and the transistor T2 is blocked. If the transistor T3 is blocked, the transistor T2 is conductive and a current corresponding to the voltage VI flows through the coil half located between the terminals 24 and 25. In the same way, the holding current in the other half of the coil lying between terminals 24 and 25 is switched by the transistors T4 and TS.

To generate the initial excitation current corresponding to the initial voltage Vl, a monostable multivibrator 32 is controlled via a terminal 31, which according to FIG. 4a supplies an output voltage pulse lasting from time rl to time ti. This voltage pulse arrives at the base of the transistor Tl via an OR gate 33. As a result, the transistor Tl is switched on and the strong initial excitation current flows through the corresponding half of the coil. The voltage curve at the collector of the transistor Tl is shown in Fig. 4b.

The curve in FIG. 4 c shows the course of the voltage induced in the other half of the coil, which is determined by the movement of the plunger coil armature in the magnetic field and the excitation current in the excited coil half being affected. If the armature strikes the stop at time i3, the change in the aforementioned voltage induced its polarity in the other half of the coil. The voltage appearing at terminal 26

The change arrives through the capacitive coupling through a capacitor 38 to the base of a transistor 77, which is normally in the conductive state. Due to the voltage changes at the terminal 26, the transistor Tl is blocked periodically

to and switched on, whereby the in F i g. 4 d shown voltage curve occurs at the collector of the transistor Tt . The voltage curve is shown in FIG. 4 d for the case that no locking current pulse to prevent the recoil of the

kers is applied to the coil, which is why the last two voltage pulses of the curve in Fig. 4d the Correspond to rebound movements of the armature.

The locking current pulse is generated by taking the voltage signal a) from the collector of the transistor

ao T7 via an AND circuit 35 another monostable Multivibrator 34 controls whose output signal via the OR gate 33 the transistor Tl turns conductive and thereby a large current through the between the terminals 24 and 25

as coil half causes. Two further entrances to the AND gate 35 are connected to a delay circuit 37 and a pulse circuit 36. The entrance the delay circuit 37 and the set input of the pulse circuit 36 are connected to the output

of the monostable multivibrator 32 connected. The delay circuit 37 generates as shown in FIG. 4 e one Impulse that coincides with the rise in the collector voltage of transistor T7 as a result of the bounce back of the anchor coincides with the stop.

The delay time ό is so long that this pulse does not coincide with that caused by the blocking of the transistor at the time f2 caused rise in the collector voltage of the transistor T7 coincides.

Accordingly, the pulse circuit 36 is at the time point f 1 by the output signal of the monostable Multivibrator 32 is set and applies a positive signal to the corresponding input of the AND circuit 35 at. At time fl + ό the delayed exit appears

output signal of the monostable multivibrator 32 at the output of the delay circuit 37 u »* tf applied another input of the AND circuit 35 with a positive signal. As soon as in time f3 the impact of the anchor occurs »also becomes the

third input of the AND circuit due to the rise in the collector voltage of transistor T7 positive and the monostable multivibrator 34 is activated. This becomes the one shown in Figure 4g Locking current impulse to suppress the locking

generated anchor bounce. The output of the monostable multivibrator 34 also represents the pulse circuit 36, the output signal of which is shown in Fig. 4f.

For this purpose 4 sheets of drawings

Claims (4)

, Claims: 1. Method of preventing a bounce back in a constant magnetic field δ Binding and moving rope coil anchor of at least one path delimiting end, characterized in that the point in time the impact of the anchor on the stop due to the associated anchor deceleration The resulting change in the voltage induced in the plunger coil is determined and in this Time a current pulse is generated in the plunger coil and a coil magnetic field is built up, the force of which affects the plunger coil »5 anchor pushes against the stop 2. The method according to claim 1, wherein the plunger coil has a center tap via which, depending on the direction of movement of the plunger coil armature, one coil half is excited in each case. »° characterized in that the change in the voltage induced in the respective non-excited coil half is used to determine the time of impact of the armature on the stop and that, on the basis of this determination, the current in the respectively excited coil half is increased. 3. Device for performing the method according to claim 1 or 2, characterized by an electronic circuit (Fig. 3) which responds to said change in induced in the plunger coil Tension on impact of the anchor responds and to prevent the rebound of the armature applies the required current pulse to the plunger coil. 4. Device according to claim 3 for carrying out the method according to claim 2, wherein the excitation current of the respectively excited coil half is controlled by a semiconductor switch connected in series with the same, characterized by a further, one of said semiconductor switches (Γ2 or TS) connected in parallel Current path controlling semiconductor switch (7Ί or Td), which is controlled by the non-excited coil half by means of the voltage pulse generated in it when the armature hits the stop as a result of the change in the induced voltage and is thereby conductive.