JPS6252755A - Rotary head assembly for magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain excellent recording and reproduction with less track deviation regardless of ambient temperature changes by forming a rotary cylinder and a stationary cylinder with a plastic material having less linear expansion coefficient. CONSTITUTION:A rotary cylinder 3A and a stationary cylinder 4A are made of a plastic material with less linear expansion coefficient to suppress the displacement from the standard locus on the magnetic tape 2 of a recording/ reproducing head 1 due to the change in the ambient temperature within an excellent recording/reproduction. The linear expansion coefficient (x) of the plastic material forming the cylinders 3A, 4A is to be between nearly 10<-6>/ deg.C and -10<-6>/ deg.C. The plastic material is obtained by arranging such as 60% of polycarbonate, 20% glass fiber and 20% carbon fiber to suppress the linear expansion coefficient in wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention is particularly useful for rotating head assemblies of magnetic recording and reproducing devices such as video tape recorders (VTRs) and digital audio tapes (DATs). The present invention relates to a rotary head assembly that is capable of suppressing the amount of displacement from within the limit necessary for recording and reproducing to perform good recording and reproducing.

[Conventional technology]

2 and 3 show a conventional rotary head assembly for a VTR, with FIG. 2 being a longitudinal sectional view and FIG. 3 being a perspective view. In the figure, (1) is a recording and reproducing head that records and reproduces information on a magnetic tape (2), and (3) is a recording and reproducing head (1).
), and (4) is a fixed cylinder. Both the rotating cylinder (3) and the fixed cylinder (4) are made of aluminum or plastic material. (5) is a ball bearing (6).

The rotating shaft (7) is supported by the fixed cylinder (4), and (8) is a flange that directly connects the rotating shaft (5) and the rotating cylinder (3), and is fixed to the rotating shaft (5) by press fitting or shrink fitting. (9) is a lead groove formed on the outer peripheral surface of the fixed cylinder (4) to guide the running of the magnetic tape (2).

Next, the operation will be explained. The rotating cylinder (3) is rotated by rotating the rotating shaft (6) with an electric motor, and the rotating cylinder (recording/reproducing head 0 supported by J)
The magnetic tape (2) also rotates to record and reproduce information on the magnetic tape (2) running along the lead groove (9) of the fixed cylinder (71).

[Problem that the invention seeks to solve]

As mentioned above, the rotating cylinder and fixed cylinder of the conventional rotating head device are made of aluminum or plastic materials. Due to the influence of thermal expansion and contraction of the cylinder, there was a problem in that the recording/reproducing head was displaced from the standard trajectory (trajectory at 20° C.), and during reproduction, the recording/reproducing head was displaced from the adjacent recording trajectory, causing noise.

This invention was made in order to solve the problems of the conventional ones, and it suppresses the amount of displacement from the reference trajectory to within the limit necessary for recording and reproducing, regardless of changes in ambient temperature, and performs good recording and reproducing. It is an object of the present invention to provide a rotary head assembly in which the rotational speed is increased.

[Means for solving problems]

The rotary head assembly according to the present invention is made of a plastic material with a small coefficient of linear expansion so that the amount of displacement from the standard trajectory of the recording/reproducing head for placing the rotary cylinder and the fixed cylinder on the magnetic tape is kept within the limit necessary for noiseless reproduction. It was formed by

[Effect]

The rotating cylinder and fixed cylinder provided in this invention are
As long as they are used within the intended operating temperature range, in other words, within the allowable temperature change range from the standard temperature of the rotating head assembly, the thermal expansion and contraction of the rotating cylinder and fixed cylinder will be small.
Perform good recording and playback.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, the same parts as in the conventional one shown in FIG. 2 are given the same reference numerals, and their explanations will be omitted. In the figure, (3
A) is a rotary cylinder corresponding to (3) in Fig. 2, (4A
) is a fixed cylinder D corresponding to (4) in Fig. 2, and these rotating cylinders (3A) and fixed cylinders (4A)
is a plastic material with a small coefficient of linear expansion so as to suppress the amount of displacement of the recording/reproducing head (1) from the standard trajectory on the magnetic tape (2) due to changes in ambient temperature to within the limit necessary for good recording and reproduction. It is formed from. More specifically, the diameter of the rotating cylinder (3A) and the fixed cylinder (4A) at standard temperature is D1, the coefficient of linear expansion of the plastic material is x1, the maximum allowable temperature change from the standard temperature of the rotating head assembly is 11 ) and the fixed cylinder (4A) at the standard temperature, where ±Z is the allowable amount of change in diameter from the diameter, then DXyXx≦Izl, that is, X≦IZ/Deyl.

Applying this to the VH3 type rotary head assembly, the diameter of the rotating cylinder (3A) and fixed cylinder (4A) at a standard temperature of 20°C is D = 62■, y; 40
°C (i.e. temperature range from -20 °C to 60 °C), Z = 25
Assuming that m is the linear expansion coefficient X of the plastic material forming the rotating cylinder (3A) and the stationary cylinder (4A), it is approximately between 10-'/'C and -10-'/1: that is, X≦1.
It must be io-'/°Cl.

Such plastic materials include, for example, polycarbonate 6
0%, glass fiber 201 and 20% carbon fiber (both weight %) for suppressing the coefficient of linear expansion. Further, by delicately adjusting the ratio of the blending, the coefficient of linear expansion can be made zero, and it goes without saying that this is most preferable.

Note that the maximum allowable temperature change varies depending on whether the product is being shipped to a cold region or a warm region.
℃~ζ50℃, -30℃−20℃=−50℃, and the maximum allowable temperature change is 50'C.

As described above, by forming the rotating cylinder (3A) and the stationary cylinder (4A) from a plastic material with a small coefficient of linear expansion, recording and reproduction within a range of less than the maximum allowable temperature change from the standard temperature will cause track deviation. Therefore, good recording and reproduction can be performed regardless of changes in ambient temperature.

〔Effect of the invention〕

As described above, according to the present invention, since the rotating cylinder and the fixed cylinder are made of a plastic material with a small coefficient of linear expansion, it is possible to perform good recording and reproduction with little track deviation regardless of changes in ambient temperature. When molding the obtained 0 or 1 rotation cylinder and fixed cylinder, thermal expansion and contraction is small, so that a rotary head assembly with high product precision can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of a conventional rotary head device, and FIG. 3 is a perspective view of the external appearance of the rotary head device shown in FIG. In the figures, (1) is a recording/reproducing head, (3A) is a rotating cylinder, and (4A) is a fixed cylinder.In each figure, the same reference numerals indicate the same or corresponding parts. Agent: Masuo Oiwa, Patent Attorney Figure 1 Figure 3

Claims (2)

[Claims] (1) In a rotating head assembly of a magnetic recording/reproducing device, which has a rotating cylinder that supports a recording/reproducing head, and a fixed cylinder that rotatably supports the rotating cylinder and guides the running of a magnetic tape, the rotary head assembly is fixed to the rotating cylinder. A magnetic recording/reproducing apparatus characterized in that the cylinder is made of a plastic material with a small coefficient of linear expansion so as to suppress the amount of displacement of the trajectory of the recording/reproducing head on the magnetic tape from the standard trajectory to within the limit necessary for recording/reproducing. Rotating head assembly of the device. (2) The diameter of the rotating cylinder and the fixed cylinder at the standard temperature is D, the coefficient of linear expansion of the plastic material is x, the maximum allowable temperature change from the standard temperature of the rotating head assembly is y, and the standard temperature of the rotating cylinder and the fixed cylinder is The rotary head of the magnetic recording and reproducing device according to claim 1, wherein x≦|z/D·y|, where the allowable amount of change in diameter from the diameter D in is ±z. assembly.