JPS6321982B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic tape running device, and for example, to a magnetic tape running device configured to drive two reels around which a magnetic tape is wound by motors directly connected to each reel. In conventional tape running devices such as those used in video tape recorders, the shape of the reel has been limited to a standardized dimension taking into consideration the winding diameter ratio. Therefore, it is not designed as an optimal dimension for high-speed running when, for example, rapidly forwarding a tape, and the maximum equivalent inertia converted to the motor shaft on the take-up side is not necessarily the minimum value. That is, it was thought that by winding the tape onto one reel, the maximum equivalent moment of inertia would also decrease monotonically as the hub diameter of the other reel decreased. For this reason, conventional tape running devices have disadvantages in that the start-up time when the reel hub rotates is relatively long, and the power consumption of the motor is also relatively large. Therefore, the main purpose of this invention is to find out that there is a minimum value for the maximum equivalent inertia, and to utilize this to shorten the rise time and reduce the power consumption of the motor using a completely new idea. An object of the present invention is to provide a magnetic tape running device in which the dimensions of the magnetic tape are determined. To summarize the present invention, in a magnetic tape running device configured to wind and drive a magnetic tape wound between two reel hubs onto one of the reel hubs using a driving means, the reel hub diameter is
The constant a ₀ determined by the inertia of the driving means, the moment of inertia a ₂ of the hub of the reel with a unit radius, the moment of inertia a _t of the magnetic tape that is wound by the unit radius without passing through the hub, and the other hand. The maximum equivalent inertia of the driving means is determined based on the radius _r0 of a circle equal to the area occupied by the magnetic tape when the entire amount of the magnetic tape is wound around the reel hub of . . The above objects and other objects and features of the present invention will become more apparent from the detailed description given below with reference to the drawings. FIG. 1 is an illustrative diagram showing the basic components of this invention. In the figure, a first reel 2 and a second reel 4 are provided at a predetermined interval. The first reel 2 is rotationally driven by a first motor 3, and the second reel 4 is rotationally driven by a second motor. A magnetic tape 1 is wound between the first reel 2 and the second reel 4. Here, r _t is the maximum tape winding radius of the magnetic tape 1, _rh is the reel hub radius, l _t is the tape width of the magnetic tape 1, and l _h is the height of the reel hub. Further, FIG. 1 shows a state in which the magnetic tape 1 is wound on the first reel 2 on the left side. FIG. 2 is a diagram schematically showing the relationship between the winding diameter of the magnetic tape and the equivalent inertia, and FIG. 3 is a diagram schematically showing the relationship between the diameter of the reel hub and the maximum and minimum equivalent inertia. Figure 4 is a diagram illustrating the relationship between the winding diameter of a magnetic tape (a value made dimensionless by the maximum winding diameter) and the equivalent inertia using the reel hub diameter as a parameter, and Figure 5 shows the relationship between the maximum equivalent inertia and the equivalent inertia. FIG. 3 is a diagram schematically showing the relationship between the reel hub diameter and the reel hub diameter using the magnitude of the motor inertia as a parameter. All of these figures 2 to 5 illustrate relationships obtained through calculation. The equivalent inertia including the two motors 3 and 5 converted into the winding motor shaft shown in Fig. 1 increases monotonically as the tape winding diameter increases, as shown in Fig. 2. It reaches its maximum when the side tape winding radius reaches its maximum. On the other hand, the rise time is proportional to the equivalent inertia. Therefore, in order to reduce the rise time, the above-mentioned maximum value should be made as small as possible, and at the same time, the required motor power consumption can also be reduced by the smaller equivalent inertia. By the way, the maximum equivalent inertia J _nax changes as shown by straight line 1 shown in FIG. 3 depending on the reel hub diameter. Furthermore, the minimum equivalent inertia J _nio changes as shown by straight line 2 in FIG. On the other hand, under a certain fixed reel hub diameter r _h , the reel changes parallel to the vertical axis from the bottom to the top, from the start of winding to the center of winding to the end of winding, as shown in the schematic diagram in Figure 3. do. The important point to note here is that the change in the maximum value is r _h = √ (δ will be explained in detail later)
has the minimum value at . Therefore, by determining the reel hub diameter so that the maximum equivalent inertia is minimized, the rise time can be minimized, and the required motor power consumption can be reduced by the smaller equivalent inertia. This will be explained in more detail with reference to FIGS. 2 and 4. According to Figure 4, when the reel hub diameter r _h is smaller than √ when the tape length is constant, the equivalent inertia changes as shown by 1, and when r _h is larger than √, the equivalent inertia changes as shown by 3. When r _h is equal to √, it changes as shown by 2. Note that 1, 2, and 3 shown in FIG. 4 are 1, 2, and 3 in FIG. 3, respectively.
This is shown corresponding to 2 and 3. The power consumption of the motor can be determined depending on the magnitude of the shaded area in FIG. 2, which corresponds to the change in equivalent inertia from the start of tape winding to the end of tape winding. Now, as shown in Figure 4, if r _h > √, then r _h
The value of equivalent inertia is larger at any position of the radius than when is √, and both the rise time and motor power consumption are larger. on the other hand,
When r _h <√, r _h =√ only where the winding diameter is small.
Since the equivalent inertia is smaller than in the case of δ, both the rise time and power consumption are small, but
The portion where the equivalent inertia is small is narrow, and the magnetic tape 1 is normally used from the beginning to the end of the winding.
Overall, the rise time and motor power consumption are both shorter when r _h =√. Also,
Since the winding diameter ratio (ratio between the maximum winding diameter and the minimum winding diameter) is also small, tension control is easy. From the above, it can be seen that both the rise time and motor power consumption are most advantageous when the reel hub diameter r _h =√. Figure 5 shows the change in the maximum equivalent moment of inertia when the motor inertia is large and small.The larger the motor inertia is, the more the reel hub diameter r _h is set to √, which reduces the rise time and the motor It can be seen that this is more advantageous in reducing power consumption. Therefore, next, a method for determining the minimum value of the reel hub diameter r _h will be explained. Here, a ₀ is the motor inertia, and the moment of inertia of the hub of unit radius of the reel is a ₂
= π/2ρ _h l _h (ρ _h is the hub density, l _h is the hub height), moment of inertia of the magnetic tape 1 when the tape itself is wound for a unit radius without using the hub a _t = π/2ρ _t l _t (ρ _t is tape density, l _t is tape width), radius of a circle equal to the area covered by magnetic tape 1 when the entire amount of magnetic tape 1 is wound around one reel hub

[Formula] (where l is the total tape length and e is the tape thickness), the maximum equivalent inertia J _nax is expressed by the formula of the reel hub diameter r _h , J _nax = g (r _h ) = a ₀ r ₀ ² / r _h ² +2a ₀ +a _t r ₀ ⁴ + (2a _t +a ₂ ) r ₀ ² r _h ² +2a ₂ r _h ⁴ ...(1). r _h when J _nax becomes the minimum value can be found as the root of dJ _nax /dr _h =0. Here, from dJ _nax / dr _h = 0, 4a ₂ r _h ⁶ + (2a _t + a ₂ ) r ₀ ² r _h ⁴ −a ₀ r ₀ ² = 0...(2) Here, r _h ² = s, then to find r _h that satisfies the above equation (2), f(s) = 4a ₂ s ³ + (2a _t + a ₂ ) r ₀ ² s ² − _{a 0} r ₀ ² = 0
... Find the positive root s that satisfies (3), and then find the square root of this. That is, since a ₂ >0, a _t >0, r ₀ ² >0, the (3)
There is only one positive root s that satisfies the formula. If this value is δ, r _h (>0) that satisfies equation (2) is r _h =√
It can be expressed as δ. Also, J _nax at this time
certainly takes the minimum value. (by changing s, f(s)
If you create a change curve for , you will see that it is the minimum value, not the maximum value. ) The root δ of the cubic equation shown in equation (3) above can be expressed as equation (4). However, a=(2a _t +a ₂ ) ² r ₀ ⁴ ／48a ₂ ² ……(5) b=(2a _t +a ₀ ) ³ r ₀ ⁶ ／864a ₂ ³ −a ₀ r ₀ ² ／4a ₂ …… (6) Here, R=b ² /4+a ³ /27. In equation (3), if a ₂ = a _t can be considered (for example, if the reel hub is made of plastic, there is no problem with this approximation), then the motor used 3, 5 and the magnetic tape 1 alone can determine the optimum reel hub diameter. The value √ of the reel hub diameter r _h at this time can be determined from the positive root δ' of the cubic equation of the following equation (7), with a ₂ = a _t = a ₁ in the third equation. 4a ₁ s ³ + 3a ₁ r ₀ ² s ² −a ₀ r ₀ ² = 0 ...(7) More specifically, for example, if a magnetic tape with a tape thickness of μm, a total length of 200 m, and a width of 1/4 inch is used. When a motor with a motor inertia of 50 gcm ² is used, the maximum equivalent inertia becomes minimum at around r _h =15 mm. In the above explanation, a ₀ is the other parameter a ₂ ,
If a is negligible compared to _t , the optimum hub diameter does not need to change much even if the motor changes.
Furthermore, if a _t is negligible compared to a ₂ and a ₀ , the optimum hub diameter does not need to be changed even if the overall length or thickness of the tape changes. In this way, by finding the root of the above equation (3), a guideline for the optimal hub diameter can be given, and a value close to √ may be taken as the hub diameter. In addition, in the above-mentioned embodiment, the two reels 2 and 4
Although the description has been made for the case where the motors 3 and 5 directly rotate and drive the motors 3 and 5, the present invention is not limited to this, but can also be applied to a magnetic tape running device in which two reels are driven from one drive motor via a belt and a pulley. is also possible. In this case, the value of the inertia obtained by converting the inertia of the drive motor into the rotation axis of the belt and pulley may be substituted for a ₀ . As described above, according to the present invention, the rise time in a high-speed tape running device is minimized by determining the hub diameter of the reel so that the maximum equivalent inertia is minimized depending on the motor and magnetic tape used. In addition, since the required torque of the motor is reduced, power consumption can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an illustrative diagram showing the basic components of this invention. FIG. 2 is a diagram schematically showing the relationship between the winding diameter of the magnetic tape and the equivalent inertia. FIG. 3 is a diagram schematically showing the relationship between the diameter of the reel hub and the maximum and minimum equivalent inertias. FIG. 4 is a diagram schematically showing the relationship between the winding diameter of the magnetic tape and the equivalent inertia using the reel hub diameter as a parameter. FIG. 5 is a diagram schematically showing the relationship between the maximum equivalent inertia and the reel hub diameter using the magnitude of the motor inertia as a parameter. In the figure, 1 is the magnetic tape, 2 and 4 are reels, 3 and 5 are motors, r _t is the maximum tape winding radius, r _h
is the reel hub radius, l _t is the tape width, and l _h is the reel hub height.

Claims (1)

[Scope of Claims] 1. A magnetic tape running device configured to wind and drive a magnetic tape wound between two reel hubs onto either one of the reel hubs using a drive means, wherein the reel hub diameter is A constant a ₀ determined by the inertia of the driving means, the moment of inertia a ₂ of the hub of the reel with a unit radius, and the moment of inertia a _t of the magnetic tape that is wound by the unit radius without passing through the reel hub. , a radius of a circle equal to the area occupied by the magnetic tape when the entire amount of the magnetic tape is wound around the one reel hub;
A magnetic tape running device, characterized in that the maximum equivalent inertia of the driving means determined based on _r0 is set to a value that is minimized. 2. The magnetic tape running device according to claim 1, wherein the drive means is two drive motors that directly drive each of the two reel hubs, and the inertia of the drive means is motor inertia. 3. The drive means includes a drive motor and a transmission means for transmitting the rotational force of the drive motor to the rotation shaft of the reel hub, and the inertia of the drive means is calculated by converting the motor inertia of the drive motor to the rotation shaft. 2. The magnetic tape running device according to claim 1, wherein the magnetic tape running device has an inertia.