JPS6132726B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rotation transmission device that requires high-speed and highly accurate rotation transmission, such as a rotating head cylinder section of a VTR (video tape recorder). A challenge faced by VTR mechanisms, particularly the rotating head cylinder, is how to correctly maintain and reproduce the relative speed and position of the head and tape. If there is any unevenness in the relative speed between the tape and the head, this will cause fluctuations in the time axis of the reproduced signal, and these fluctuations will appear as changes in the color of the screen or sideways shaking, so they must be minimized as much as possible. The performance required for these rotational transmissions is small rotational unevenness. 2. Small lateral vibration. Two points are required. A conventional VTR head assembly has a structure using ball bearings, as shown in the example shown in FIG. In FIG. 1, reference numeral 1 denotes a rotating head cylinder (upper cylinder), which is rotated at 1800 rpm in the case of a two-head helical scan type VTR.
Reference numeral 3 denotes a head, which is attached to the rotary head cylinder 1. Reference numeral 4 denotes a rotating shaft, which is supported by radial bearings 5 and 6 in the thrust and radical directions. 7 is a bushing, which is connected to the rotating shaft 4;
and is further fixed to the rotary head cylinder 1. Reference numerals 9, 10, and 11 denote sleeves, which are fixed under preload in order to eliminate backlash in the thrust direction of the radial bearings 5, 6. 1
2 is a housing, which is a case that houses the bearings 5 and 6. The above cylinder structure has the following problems. (a) The rotating cylinder 1 has a cantilever structure. The reason for this is that when replacing head 3, rotating cylinder 1
This is to enable easy removal of the rotary shaft 4 from the rotating shaft 4. Furthermore, providing a bearing on the upper part of the rotating cylinder 1 poses a major hindrance to compactness. (b) Two bearings are required to support the rotating shaft.
Since the rotating cylinder 1 is required to have rigidity and precision during rotation, the cylinder is provided with two radial bearings that also serve as thrust support. Furthermore, it is desirable to install the two bearings at a considerable distance (dimension 1 in FIG. 1) from the viewpoint of accuracy and rigidity, and this is a major obstacle to compactness. (c) Recent trends in VTR cylinders include higher recording densities, and in order to improve cylinder rotational accuracy, DD motors (direct drive motors) are now being incorporated directly into the cylinders. In this case, the total length of the cylinder (dimension L in Figure 1) will increase by the size of the DD motor. As explained in (a), (b), and (c) above, it can be said that making the cylinder more compact is the most important requirement for VTR devices, as is increasing the precision of rotation. In particular, the height of recent home VTR devices is limited by the height (dimension L) of the cylinder, which is the biggest problem when considering the development of VTR devices into portable types. The present invention provides a rotation transmission device that can be used in a head assembly device of a VTR having the above-mentioned problems, and one embodiment thereof will be described below with reference to the drawings. FIG. 2 shows an embodiment in which the present invention is applied to a VTR cylinder. 13 is an upper cylinder which is a rotated body, 14 is a rotating sleeve, 15 is a rotating sleeve set screw, 16 is a metal bearing, and 17 is a central fixed shaft. The rotating sleeve 14 is made of, for example, hard aluminum (A1-P3-H) in order to reduce the weight of the rotating part (low inertia), and is rotatably fitted to the central fixed shaft 17. metal bearing 1
Reference numeral 6 constitutes a first bearing portion, which is press-fitted into the rotating sleeve 14. The rotating sleeve 14 and the upper cylinder 13 are also fastened together with a rotating sleeve set screw 15. 18 is a radial ball bearing, 19 is a thrust retaining ring, 20 is a center fixing shaft set screw, 21 is a center fixing shaft base, and 22 is a fixing ring. The center fixed shaft 17 is fastened to the center fixed shaft base 21 by a center fixed shaft set screw 20. The metal bearing 16 is wear-resistant and is made of, for example, a low-cost aluminum bearing alloy (AJ2). The center fixed shaft 17 is made of case hardened steel (SNCM23), for example.
A surface-hardened steel that has been treated with tufftride is used. The radial ball bearing 18 constitutes a second bearing part,
The thrust retaining ring 19 and the fixing ring 22 fix the inner shaft of the radial ball bearing 18 to the rotating sleeve 14. 23 is a direct drive motor amatter (DD motor amatter), 24 is an amatter fixed bush, 25 is a head signal detection ferrite on the fixed side, 26 is a head signal detection ferrite on the rotating side,
27 is the PG coil, 28 is the lower housing, 29
30 is a center fixed shaft base set screw, and 30 is a lower cylinder. 31 is a head, and 32 is a head position adjustment screw. The head position adjustment screw 32 allows fine adjustment of the protrusion amount and indexing angle of the head 31. In this way, the rotating head assembly of the present invention
The bearing structure is such that the upper cylinder 13, which serves as a rotating flywheel, rotates around a shaft with one end fixed. Taking the structure shown in FIG. 2 as an example, its characteristics are listed as follows. (1) High rigidity and rotational accuracy can be obtained. As mentioned above, the structure of the conventional rotary head assembly in FIG. 1 is a cantilevered structure;
In order to strengthen the rigidity of the rotating shaft and increase precision, it was necessary to make the distance (dimension 1) between the two ball bearings as far apart as possible, but there was a limit due to the restriction of the cylinder dimensions. However, in the structure of the present invention, since the metal bearing 16 is installed exactly at a portion corresponding to the inner wall of the upper cylinder 13, the spacing between both bearings 16 and 18 can be made larger than in the conventional structure, and the head can be easily replaced. It is also easy to attach and detach the upper cylinder 13 for this purpose. Also, tape tension (radial load, 50g~
Since the metal bearing 16 is provided at a position where a force of about 100 g is applied, the support is not cantilevered.
For the reasons described above, the structure of the present invention provides extremely high rigidity and highly accurate rotation. (2) It is compact. In this structure, as mentioned above, the metal bearing 16
corresponds to the inner wall of the upper cylinder 13, so the overall length can be shortened by the length that accommodates one bearing. Therefore, as shown in Figure 2, even with a built-in DD motor, the cylinder becomes extremely compact. Furthermore, when the VTR device is made portable, the features (1) and (2) above become even more effective. This is because the rigidity against inertial loads on the upper cylinder 13 due to movement of the entire device is much better than in conventional structures that are essentially cantilevered structures. (3) Easy to assemble. In the structure of the present invention, each part can be assembled as a unit as shown in FIG. 3, and the combination of each unit is extremely easy. Next, the outline of the assembly process will be explained as follows. First, the unit 34 consisting of the rotating sleeve 14 and the metal bearing 16 press-fitted therein is placed into the unit 35 consisting of the radial ball bearing 18, the lower housing 28, the lower cylinder 30, etc., and the radial ball bearing 18 is fastened to the rotating sleeve 14. do.
Further, various parts such as the PG coil 27 are attached to the lower housing 28. Next, the unit 33 consisting of the upper cylinder 13 and the like is fitted and fastened to the unit 34. Finally, the center fixed shaft 17 and the center fixed shaft base 2
1 is assembled from the bottom, and the central fixed shaft base 21 and the lower housing 28 are fastened together while applying a preload to the radial ball bearing 18. As can be seen from the above explanation, the assembly work of this cylinder structure is extremely simple. A conventional cylinder whose shaft is rotationally driven (first
In Figure), in order to assemble into a unit, the lower cylinder must be separated into two parts, upper and lower, and the DD motor must be built in between. In other words, in the conventional structure, the lower cylinder is separated into two parts in the middle of the two ball bearings to form the lower cylinders A and B, and after incorporating the DD motor, the two ball bearings are processed simultaneously in the assembled state. Measures were taken to achieve concentricity (not shown above). However, according to this structure, sufficient precision can be obtained in the assembled state by ensuring only the component precision of the rotating sleeve 14, lower housing 28, and central shaft fixed base 21, and there is no need to separate the lower housing as in the conventional case. It is. Now, another embodiment based on the present invention will be described. Fig. 4 shows a case where the first bearing part, which corresponds to the metal bearing 16 in Fig. 3, is a pivot bearing, 37 is a pivot bearing, 38 is a lid for fixing the pivot bearing, and 39 is a fixing part for the pivot bearing part. The set screw 40 of the lid is a conical part. This conical portion 40 is formed at the tip of the central fixed shaft 17,
The pivot bearing portion 38 is enclosed within the rotating sleeve 14 and engages with the conical portion 40. Further, the thrust retaining ring 19 applies a thrust load to the central fixed shaft 17 so that the conical portion 40 maintains contact with all the balls of the pivot bearing 37. Therefore, it can be sufficiently adapted not only to the thrust direction but also to the radial load (50 g to 100 g) applied to the upper cylinder 13, and the rotational accuracy is numerically superior to that of the cylinder structure with the configuration shown in FIG. 2 using metal bearings. In this structure, a miniature instrument rolling bearing is used as the radial ball bearing 18 in order to achieve a high precision ratio. Instrument rolling bearings have lightweight cages and open raceways to minimize contact area. The lubricant used is soft synthetic oil grease for medium speeds. Further, the preload applied to the radial ball bearing and the pivot bearing portion 37 in the thrust direction can be changed depending on the tightening condition of the screw of the thrust retaining ring 19. The preload is the result of considering bearing life, rotational accuracy, and thermal expansion that occurs during use of ball bearings due to elastic vibration3.
Kg~5Kg was the appropriate value. FIG. 5 is a structural diagram in which magnets 41 and 42 are used instead of the radial ball bearing 18 in FIG. 4. 41 is the rotating side magnet, 4
2 is a fixed side magnet, 43 is a lower retaining ring of the rotating side magnet, and 44 is an upper retaining ring. The magnets are axially magnetized so that both magnets 41 and 42 attract each other. The stationary side magnet 42 is fixed to the lower housing 28 with an adhesive, and the rotating side magnet 41 is also fixed with a lower retaining ring 43 and an upper retaining ring 44. In this structure, the thrust direction of the rotating sleeve 14 is supported by the attraction force of the magnets 41 and 42, and high rotational accuracy can be obtained by the pivot bearing 37 and the non-contact magnetic bearing structure. Figure 5 shows the structure for supporting in the thrust direction.
Of course, radial support is also possible if a magnet magnetized in the radial direction is used. FIG. 6 shows a case where a jewel bearing is used instead of the pivot bearing 37. Reference numeral 45 denotes a catch seat, which is made of sapphire in the shape of a conical receiver, and is fixed to the cup 46 with adhesive. For example, Safaya is a synthetic industrial product (100% aluminum oxide).
It is widely used as a jewel bearing for low-torque watches and instruments. Synthetic lubricating oil (silicone) was used as a lubricant by dripping. This configuration realizes a bearing structure with high precision and long life. FIG. 7 is a structural diagram when the first bearing portion is a radial ball bearing. 47 is a radial ball bearing, 4
8 is a bearing fixing bush A, and 49 is a bearing fixing bush B. This structure allows a cylinder structure that is low cost and easy to adjust. Now, let us consider the radial rigidity of each cylinder structure in FIGS. 2 to 7. The rotational precision required for VTR head assemblies is characterized by extremely high accuracy compared to other audio equipment. In particular, the radial direction of the cylinder is associated with changes in relative velocity between the tape and the cylinder, so great rigidity is required. If the cylinder is moved radially by δ due to the radial load caused by the tape tension,
If the relative velocity between the tape and the cylinder is displaced by .DELTA.v, the change in relative velocity between the tape and the cylinder will be as follows. Δv=δ・ω ₀ (1) However, ω ₀ : Reference rotation speed (=1800rpm) If the allowable spec for deviation from the reference rotation speed (relative speed) of the VTR cylinder is ε%, then the cylinder should be adjusted so as to satisfy the following equation. It is necessary to determine the stiffness of ε>δω ₀ /rω ₀ ×100 (2) where r=rotation radius Now, in this cylinder structure in which one end of the central fixed shaft 17 is fixed, the radial direction displacement δ of the cylinder is as follows. δ64pl ³ /3πEd ⁴ (3) where E: Coefficient of longitudinal elasticity of the central fixed shaft 17 d: Vertical axis diameter L of the central fixed shaft 17: Dimension in Fig. 4 If the shaft diameter dφ is made sufficiently large in equation (3), Although the radial rigidity of the cylinder increases, the shaft diameter is limited by the sizes of other parts of the cylinder, and in the case of a home video camera, which is an embodiment of the present invention, d=6φ was the maximum. Therefore, by changing the material of the central fixed shaft 17, the radial direction displacement δ and the deviation (%) from the reference relative velocity are determined as shown in Table 1. However, L=57mm, d=6φ, P=100g (tape tension), and r=30mm.

[Table] From the results of the above discussion, it can be seen that if the specs of a VTR cylinder are, for example, ε = 0.010%, it is sufficient to use a high-rigidity material such as carbide or ferrotic for the central fixed shaft. As described above, according to the present invention, it has become possible to realize a rotation transmission device having a cylinder structure that has various features such as compactness, high precision, high rigidity, and low cost. Of course, the basic structure of the present invention can be applied to other audio equipment, tape decks, players, video disks, etc., or industrial equipment such as magnetic drum devices, sheet disks, etc., or various devices that have a drive unit and require high-precision rotation. Applicable to equipment.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of a conventional VTR cylinder using ball bearings, Fig. 2 is a sectional view of a VTR cylinder which is an embodiment of the present invention, and Fig. 3 is an illustration of how to assemble the cylinder shown in Fig. 2. Figure 4 is a cross-sectional view of the cylinder structure when the first bearing part is a pivot bearing, Figure 5 is a cross-sectional view when the second bearing part is a magnetic bearing, and Figure 6 is a cross-sectional view of the cylinder structure when the second bearing part is a magnetic bearing. FIG. 7 is a cross-sectional view when the first bearing portion is a pivot jewel bearing, and FIG. 7 is a cross-sectional view when the first bearing portion is a radial ball bearing. 13... Upper cylinder (rotated body), 14...
Rotating sleeve, 16...Metal bearing, 17...Center fixed shaft, 18...Radial ball bearing, 23...Direct drive amater, 28...Lower housing, 30...Lower cylinder, 37...Pivot bearing, 40 ... Conical part, 41, 42 ... Rotating side and stationary side magnet, 45 ... Seat, 47 ...
Radial ball bearing.

Claims (1)

[Scope of Claims] 1. A central fixed shaft whose one end is supported by a substrate, a rotating sleeve rotatably fitted to the central fixed shaft, and a rotated body detachably attached to the rotating sleeve; Means having a first bearing part and a second bearing part that support the rotary sleeve, interposing the first bearing part between the rotary sleeve and the central fixed shaft and rotationally driving the rotary sleeve. A rotation transmission device characterized in that: is provided between the first and second bearing portions. 2. The rotation transmission device according to claim 1, wherein the first bearing portion is interposed between the rotating sleeve and the central fixed shaft at a position corresponding to the inner wall of the rotated body. 3. The rotation transmission device according to claim 1, wherein the means for rotationally driving the rotary sleeve is a direct drive motor. 4. The rotation transmission device according to claim 1, wherein the first bearing portion is a metal bearing press-fitted into the rotation sleeve. 5. The rotation transmission device according to claim 1, wherein the first bearing portion is a radial ball bearing. 6. The rotation transmission device according to claim 1, wherein the first bearing portion is a pivot bearing portion formed between the rotating sleeve and the tip of the center fixed shaft. 7. The rotation transmission device according to claim 1, wherein the second bearing portion is a radial ball bearing interposed between the rotating sleeve and the base plate. 8. Claim 1, characterized in that the second bearing portion is composed of a permanent magnet fixed to the rotating sleeve and another permanent magnet fixed to the substrate.
Rotation transmission device as described in section.