DE2537758A1 - High quality record turntable - uses hydrodynamic bearings and controlled speed drive with velocity feedback tachometer - Google Patents

Abstract

The design consists of a turntable (1) with a large truncated cone shaped central projection which rests in a suitable bearing (2) separated from it by a film of low viscosity oil. Slots are cut in the central projection according to accepted hydrodynamic bearing design practice. At the circumference of the table a dust exluding configuration (3) and a drive arrangement (4, 5) are mounted. This consists of a toothed cylinder (4) driven by a coil (5) mounted on the chassis of the equipment (6). Two alternative forms of central hydrodynamic bearing are available both cylindrical rather than cone shaped. In one case the table drive is provided by a motor incorporated in the table, while a velocity feedback control circuit is driven from a tachogenerator again incorporated in the table. Alternatively a magnetically coupled digital velocity transducer may be used.

Description

Turntable assembly for turntables The invention relates to turntable assemblies for turntables with a turntable that is supported on a pedestal by a bearing arrangement is rotatably mounted, and a motor for generating a turntable operating speed of the turntable (e.g. 16 rpm, 33 rpm, 45 rpm and 78 rpm).

Usually the turntable is supported by a solid / solid contact bearing assembly supported, which bearing assembly can be a bearing of the engine. Such designs are satisfactory in very many cases, but entail considerable manufacturing costs to achieve high quality for modern hi-fi systems. In particular arise Problems when trying to economically maintain a constant speed of rotation to achieve that is substantially free from torque fluctuations, which a Cause rumbling noises, yowling and rapid pitch fluctuations, and without that vertical vibrations through the bearing assembly of any supports of the Device.

The invention is based on the object of a turntable arrangement to develop that is improved in this respect.

The turntable assembly according to the invention differs for this purpose in that the bearing arrangement is hydrodynamic and a fluid of high Toughness is located between the relatively rotatable parts of the assembly and pump grooves to support the turntable axially and radially, the grooves so are dimensioned and directed and the fluid has such a viscosity that the turntable is stored without solid / solid storage contact at speeds below the turntable operating speed. Such a storage arrangement works Generating pressure during rotation, so that an overpressure film (e.g. made of oil, mercury or grease or a combination thereof, for example mercury with a layer of fat floating on top of the mercury) to prevent storage separation to maintain. It was found that with conventional bearings usual torque fluctuations are essentially eliminated.

One suitable form of such a bearing arrangement is a spiral groove bearing denotes, in which at least one of its bearing elements contains grooves that extend extend essentially in Archimedes' Spralbahnen and those mentioned Powers produce.

In operation, the platter and the moving part of the float Motor on a film or on filming of the fluid to establish a solid / solid contact to avoid and allow the turntable to move at a constant Speed essentially without bearing rumble, yowling and pitch fluctuations or vertical vibrations that are transmitted via the bearing from the support will.

For a turntable that is intended for private use an O1 or grease of sufficient viscosity are used as storage medium, to store the turntable at a speed that is much lower than the lowest Operating speed of the turntable (16 rpm) and does not coast when the turntable is reversed.

The motor can be a linear motor, in particular a curvilinear motor, be. The motor can then have a stator that carries motor windings and a Gap limited in which the rotor rotates without contact with the stator, which the latter is arranged on one side of the axis of rotation, and with an annular Cooperating rotor of circular cross-section, which is coaxial with the turntable is and is borne by it.

It is desirable that a pickup head is supported so that it is movable on a path which is essentially opposite to that of the stator is, i.e. is essentially contained in a quadrant, which is the stator containing quadrant is opposite to interference between the stator field and the cartridge head to a minimum. For extra protection of For its part, the turntable is preferably non-magnetic on the pickup head.

In other embodiments, the motor is a center-bearing rotary drive motor without mechanical contact between its rotor and its stator, e.g. a motor with asynchronous hysteresis, an induction motor, an eddy current motor, a brushless one DC motor, or a synchronous motor, possibly a hysteresis motor.

A speed sensing element can also be used for the turntable can be provided in order to obtain an output corresponding to a speed control element is fed to enable servo control of the turntable speed.

The sensing element can be an AC tachometer generator, the one supplies AC voltage proportional to the speed, or a digital device # nit Using magnetic or electro-optical effects to create a signal, whose frequency is proportional to the speed.

To better understand the invention and how it is carried out reference is made, for example, to the accompanying drawings namely show: FIG. 1 a view in section through the center line of an embodiment the turntable assembly according to the invention; 2 shows part of a hydrodynamic Storage; 3 shows part of a linear motor for the arrangement according to FIG. 1; Fig. 4a to 4f circuit diagrams; Fig. 5 shows a preferred form of storage for the turntable assembly according to Fig. 1; FIG. 6 shows a detail of FIG. 5; and Figures 7a and 7b are a view in section or in plan view with the turntable removed from a further embodiment.

Fig. 1 shows a view in vertical section through the axis of rotation a turntable assembly with a circular non-magnetic turntable 1, which is mounted for rotation in an approximately horizontal plane and on its Top a centering pin 7 is attached, which is from the central opening of a record is recorded. The turntable 1 is also with the pin part of a hydrodynamic Bearing 2 provided in the form of a truncated cone on its underside, also with a simple labyrinth arrangement 3 to minimize the ingress of dust to hold, as well as with a thin electrically conductive cylinder 4, which is in the gap of a linear motor stator 5 and rotates in the circumferential direction of the turntable a Length of only a few inches, e.g. 75 mm (3 ") or less. A stand 6 is used to attach the linear motor stator 5 and forms the in its center Receiving part or the shell of the hydrodynamic bearing 2. This receiving part also has the shape of a truncated cone, but in this case is the lower one flat surface of the receiving part formed with suitably curved recesses, as shown in Fig. 2 in plan view, to the mode of operation of the hydrodynamic Allow storage. If necessary, these recesses can be in the journal part the storage are provided. In general can storage according to the principles and with the characteristics of known hydrodynamic spiral groove bearings, regardless of whether they are flat, spherical or conical in shape.

The recesses or grooves can be formed on both bearing parts and at least one of the parts can also be provided on the conical surface will. In addition, the recesses or grooves can have the shape of a wing.

The storage is filled with a suitable O1 or fat so that a fluidic storage film is formed, and the O1 or fat is of high viscosity, so that the turntable fully through the film at low speed (for example 7 rpm and definitely below 16 rpm), and the fat or O1 not leaks when the device is reversed.

The stator 5 has a coil arrangement, which is a moving Magnetic field generated across the stator gap when from a suitable AC power source is fed.

The cylinder 4 on the turntable is with a large number of incised vertical slots 8 shown in Fig. 3 and which together with the frequency of the alternating current cause the turntable to move rotates at the appropriate speed or at the appropriate speeds. The motor can either be operated from an alternating current network with a frequency of 50 Hz be or from an electronic oscillator and power amplifier of high Stability. In any case, the inclination of the slots in cylinder 4 is calculated as that it is adapted to the selected alternating current frequency.

The speed can either be through some form of electrodynamic Braking in which an additional path is introduced into the magnetic circuit will change something or by changing the frequency of the alternating current source will. In addition, the slots in the cylinder 4 can be at a small angle to the vertical be arranged to avoid speed fluctuations as each segment enters to reduce the magnetic field in the stator gap.

In one embodiment, the winding of the stator 5 is direct connected to the AC network, so that the network frequency for speed control serves. In another case, a separate transistor oscillator will be of high value Precision and an amplifier used to form an independent frequency standard, which can be changed by hand to choose the basic speed and small adjustments for musical pitch correction. From a speed sensor a feedback into the circuit can be provided, as schematically at 11 shown in fig.

Another embodiment of the invention is described in connection with Fig. 5 and 6 described. In this embodiment, a storage is provided, which is intended for operation in only one direction at 30 - 50 rpm and at 7 U / min is fluidly mounted. The bearing is hydrodynamic with an axial bearing 12 and radial bearings 14.

The thrust bearing 12 is of the center-around type (Fig. 6) and with inward pumping grooves 13. If -6 is used, a toughness of 0.175 2 of a tenacity of 0.175 x 10 -6 Re kp s / cm (2.5 x 10-6 Reyns.lb, sec / in.2) the axial bearing dimensions can be as follows: Number of slots 10 to 15 depth of the grooves 127 x 10 -4 mm (5 x 10 -4 inches) groove angle g 74.50 groove / rib ratio 1 Outer radius of the grooves 25.4 mm (1 inch) inner radius of the grooves 12.7 mm (0.5 inches).

Theoretically, the grooves are equiangular spirals, but they are not is absolutely necessary, as circular arcs are sufficient.

With this training, the storage should have a working distance of about 50 x 10 mm (about 2 x 1 10 inches).

The grooves are formed on the base of a cylindrical shaft 15 and cooperate with a low-friction plate 16 made of glacier D.U. "material, which is synthetic resin glued to a support plate 17 made of mild steel.

There is a number for the radial bearing of the turntable assembly Mutilated storage areas are provided that are used as well as tilt pillow bearings which all have a certain bearing rigidity in the unloaded state result. Although a purely radial load hardly occurs, the storage must be a Withstand the moment of 28.77 kg cm (0.25 lb.inches) plus the possible moment that the main axial load is due to the offset loading.

Tilt pillow bearings are unlikely in terms of cost advantageous, however, hydrodynamic bearings with surface mutilations or Controlled runout suppress half-speed whirl vibrations and seem suitable; of the mutilated storage areas is likely to be the herringbone groove shape be most effective and appropriate in the present context. Because a thrust bearing nominal diameter 25.4 mm (1 ") and a length of 101.6 mm (4") are possible for this Embodiment shows a double radial bearing arrangement, although a single one Radial bearing would also be possible.

In the particular embodiment shown, the axial Length of each individual radial bearing 14 is about half the bearing diameter and the distance between the centers of the bearings is about twice the diameter. The length of the shaft 15 for receiving the two radial bearings is approximately three times of the bearing diameter. These radial bearings are designed for radial play between the Shaft 15 and bushings 18 no more than 25.4 x 10 3 mm (1 x 10 3 ") and not less than 127 x 10 mm (5 x 10 4 "). With this design, the optimal groove angle 23.26 degrees and the axial groove length 11.43 mm (0.45 "). The Groove / rib width ratio is 1: 1.

The storage arrangement described above is in the cases suitable for which after the 51 has been placed in the storage arrangement the turntable assembly is not subjected to excessive inclination. However, if it is necessary to fill the O1 and then tilt the device, O-rings 19 can be provided in the assembly to during transport along with some suitable removable elements to act as a seal.

7a and 7b show a further embodiment in which a Rotary drive synchronous or asynchronous motor with a stator ring 20 and a rotor 21 attached to the bearing shaft 15 are provided.

In Fig. 7a and 7b sensing organs are shown in two alternative forms, to get speed feedback.

In one embodiment, the sensing element is a tachometer generator with a rotor 22 and a stator 23.

In the other embodiment, the sensing element is through an optical or magnetic analog-to-digital converter ring 24 having a scanning head (s) 25 formed.

In yet another embodiment, a bearing with a large diameter can be provided in which the motor is arranged coaxially is.

FIGS. 4a-4f show various alternatives in a schematic representation Control systems for the motor 26 of the turntable assembly. In Fig. 4a is the motor a synchronous motor and determines the mains frequency and the choice of windings by one Switch 9 the speed.

In the system of Fig. 4b, the synchronous motor 26 is by a Precision oscillator 10 regulated, the output frequency of which is controlled by a speed selector switch 9 is determined.

In the system of Fig. 4c, the synchronous motor 26 is by a variable oscillator 10 controlled, which is controlled by a controller 27, for which the setpoint is supplied by switch 9 and the actual value by the Tachometer generator 22, 23. The system according to FIG. 4d shows an alternative to FIG. 4c using the analog-to-digital converter 24.

In the systems of FIGS. 4e and 4f, voltage regulators 28 are for one Asynchronous motor 26 is provided, which in one case by the tachometer generator 22, 23 is regulated and in the other case by the analog-to-digital converter 24.

Patent claims:

Claims (13)

Claims: O turntable assembly for turntables with a turntable which is supported on a base by a bearing arrangement is, and a motor for generating a turntable operating speed of the turntable, characterized in that the bearing arrangement (2, Fig. 1, 12 and 14, Fig. 5) is hydrodynamic is, with a fluid of high viscosity between the relatively rotatable parts the bearing assembly is located and pump grooves for the axial and radial mounting of the Turntable (1) has which grooves are dimensioned and directed so that the Fluid which has such a viscosity that the turntable (1) does not have solid / solid bearing contact is stored at speeds below the operating speed of the turntable lie. 2. Arrangement according to claim 1, characterized in that the pump grooves are curved (Figs. 2 and 6). 3, arrangement according to claim 1 or 2, characterized in that the bearing assembly and its fluid are such that the turntable on the fluid stored at a speed below 16 rpm with no solid / solid bearing contact can be. 4. Arrangement according to claim 1, 2 or 3, characterized in that the motor is a linear motor with a wound stator (5) on one side the axis of rotation of the turntable (1) is arranged, and with an annular Rotor (4) which is carried essentially coaxially with the turntable (1). 5. Arrangement according to claim 4, with a pickup head for movement with reference to the turntable, characterized in that the stator (5) essentially in a first quadrant with respect to the axis of rotation of the turntable (1) and the cartridge head is on a path in the opposite quadrant is movable. 6. Arrangement according to claim 1, 2 or 3, characterized in that the Motor is a rotary drive electric motor, which is coaxial to the bearing arrangement (Fig. 7) is. 7. Arrangement according to claim 6, characterized in that the motor a turntable part surrounds a rotatable part of the bearing assembly wearing. 8. Arrangement according to claim 6, characterized in that the engine is surrounded by a turntable part, which is a rotatable part of the bearing assembly wearing. 9. Arrangement according to the preceding claims, characterized by a controller (27) for the motor (26), a turntable speed sensor (22, 23) and a feedback path for the controller including the sensing element. 10. Arrangement according to claim 9, characterized in that the engine is an asynchronous motor and the regulator is formed by a voltage regulator. 11. The arrangement according to claim 9, characterized in that the motor is a synchronous motor and the controller is formed by an adjustable frequency generator will. 12. Arrangement according to claim 9, 10 or 11, characterized in that that the sensing element (22, 23) is an analog-digital converter. 13. Arrangement according to the preceding claims, characterized in that that the turntable (1) is non-magnetic.