JPH0142056B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing apparatus, and particularly to a magnetic recording and reproducing apparatus having a magnetic tape tension control function.

The tension control mechanism for the magnetic tape of a magnetic recording/reproducing device is such that a tension lever is provided near the supply reel, one end of which is used as a tension guide that contacts the magnetic tape, and the other end of which is brought into contact with a part of the supply reel. Generally, the reel is configured to regulate the rotational force of the supply reel. A conventional example will be described below with reference to the drawings.

FIG. 1 shows the conventional configuration of a magnetic recording and reproducing apparatus (hereinafter referred to as a VTR) that mainly records and reproduces video signals. Magnetic tape 2 wound around supply reel 1
The tape guides 3, 4, 5, rotating guide 6, erasing head 7, guide 8, rotating head device 9, guide 10, audio control head 11,
Capstan 12, pinch roller 13, guide 1
The tape reaches the take-up reel 15 through a tape running path constituted by 4.

When the VTR is in recording or playback mode, if the pinch roller 13 is pressed against the capstan 12 via the magnetic tape 2, the capstan 12
The magnetic tape 2 is transported in the direction of arrow a by the cooperative action of the pinch roller 13 and the magnetic tape 2 is wound around the take-up reel 15. The tension control device includes a tension lever 18 that is rotatably arranged around a shaft 17 located near the supply reel 1, and a tension lever 18 that is provided at one end of the tension lever 18 and that contacts the magnetic tape 2 and controls the length of the tape running path. a tension post 19 forming a section;
A felt 20 is attached to the other end. When the VTR is in recording or playback mode, the tension lever 18 is biased in the direction of arrow b by the action of a spring 21 provided between the tension lever 18 and a board (not shown), and the felt 20 comes into contact with the outer periphery 1' of the supply reel stand. When the VTR is in a recording or reproducing state, the magnetic tape 2 is transported in the direction of arrow a, and therefore the supply reel 1 also rotates in the direction of arrow c. Therefore, the supply reel 1 has a felt 2 on its outer circumference 1'.
0, the supply reel 1 receives the pressing force of the tension lever 18 which is biased in the direction of arrow b by the elastic force of the spring 21, and a rotational braking force acts on the supply reel 1 to prevent its rotation. This rotational braking force is applied to the magnetic tape 2 wound around the supply reel 1 and being transported in the direction of arrow a.
It acts to suppress the transfer of the magnetic tape 2, and serves as tape tension when recording and reproducing the magnetic tape 2.
The tension of the magnetic tape 2 can be set to a desired value by changing the elastic force of the spring 21 and adjusting the pressing force of the felt 20 against the outer circumference 1' of the supply reel stand to adjust the rotational braking force of the supply reel 1. Can be set to .

22 and 23 are rotating magnetic heads, which rotate in the direction of arrow d, and when the VTR is in the recording or playback state,
This is for recording video signals on the magnetic tape 2 or reproducing them from the magnetic tape 2.

Next, tension stabilization of the magnetic tape 2 in the conventional example will be described with reference to FIGS. 2 and 3. The tape tension of the magnetic tape 2 set in the above-described configuration changes as shown in FIG. 3 in response to changes in the winding diameter of the magnetic tape 2 wound around the supply reel 1. That is, when the winding diameter of the magnetic tape 2 wound around the supply reel 1 is large, the tension value of the magnetic tape 2 is small, and conversely, when the winding diameter is small, the tension value of the magnetic tape 2 is large. Become. Generally, the relationship between the change in the winding diameter of the magnetic tape 2 wound on the supply reel 1 and the tension tends to be as shown by the solid line A or the broken line B.

In order to reduce the change in tension of the magnetic tape 2 due to the change in the winding diameter of the magnetic tape 2 wound around the supply reel 1, conventionally, the contact area between the outer periphery 1' of the supply reel stand and the felt 20 is changed to reduce the tension on the supply reel 1. The rotational braking force of the supply reel 1 is reduced when the winding diameter of the magnetic tape 2 wound on the magnetic tape 2 is small, so that the tension of the magnetic tape 2 becomes the same as when the winding diameter is large. There is.

That is, when the winding diameter of the magnetic tape 2 on the supply reel 1 is large, D _L is the winding diameter of the magnetic tape 2, T ₁ is the tension, F ₀ is the elastic force of the spring 18, and this elastic force F ₀ causes the tension lever to be The force with which the felt 20 provided at one end of the supply reel stand 1' presses the supply reel stand outer periphery 1' is f ₀ , the friction coefficient between the felt 20 and the supply reel stand outer periphery 1' is μ ₀ , and the diameter of the supply reel stand outer periphery 1' is If D _O is the tension of magnetic tape 2
The following relationship approximately holds true with T ₁ .

T ₁ =a・μ ₀・f ₀・D/D _L However, a is a proportionality constant determined by the tension control device, etc.

Therefore, when the winding diameter of the magnetic tape 2 on the supply reel 1 is small, if the winding diameter is D _S , the tension of the magnetic tape 2 increases by the ratio D _L /D _S from the above equation, and becomes T ₂ becomes. However, if the tension of magnetic tape 2 becomes T ₂ , tension post 1
Since the component force T _n at 9 also increases, the position of the tension post 19 slightly rotates about the shaft 17 in the direction of arrow e, as shown in FIG. A felt 20 provided at the other end of the tension lever 18
The gap between the supply reel stand outer circumference 1' also increases slightly,
These contact areas become smaller, and the coefficient of friction between the felt 20 and the outer periphery 1' of the supply reel stand becomes μ _L , which is a smaller value than μ _0. From the relationship in the above equation, the tension of the magnetic tape 2 changes from μ ₀ to μ _1. It becomes smaller by the amount changed and becomes stable as T ₃ .

In the conventional magnetic tape tension control device configured as described above, the relationship between the tension of the magnetic tape and the change in the winding diameter of the magnetic tape wound around the supply reel is expressed by curves A and 1 in FIG. 3, as described above. The tendency is shown in B. There is also another device in which the felt is brought into contact with almost the entire circumference of the outer periphery 1' of the supply reel stand, and the change in tension caused by the change in the winding diameter of the magnetic tape 2 is further reduced as shown in FIG.

As described above, the conventional magnetic tape tension control device can only perform magnetic tape tension control as shown in FIG. In other words, the tension differs depending on the diameter of the magnetic tape wound on the supply reel, and a particularly high tension is applied to the part where the magnetic tape has a small diameter. Not only does the load increase, but the VTR's wah and
This caused an increase in flatness and jitters. Furthermore, as shown in FIG. 4, recording is performed on the magnetic tape 2 by the rotating heads 22 and 23 when the diameter of the magnetic tape wound around the supply reel is large, that is, when the tension applied to the magnetic tape 2 is small. The inclination angle with respect to the running direction of the magnetic tape is slightly different between the magnetized track 27 and the recording magnetized track 28 when the diameter of the magnetic tape 2 is small, that is, when the tension is large.
This is because the magnetic tape 2 is under high tension.
As a result, especially when VTR compatible playback is performed, track deviation occurs when the diameter of the magnetic tape on the supply reel is small, causing deterioration in the playback image quality. moreover,
In recent years, VTRs have been trending toward smaller size and higher density recording.
Therefore, it has become necessary to slow down the magnetic tape transport speed, reduce the magnetization track pitch, and use thin magnetic tape. Under such circumstances, the magnetization track deviation tends to further increase when the magnetic tape diameter of the supply reel is small in compatible playback of the VTR as described above.

An object of the present invention is to eliminate these conventional drawbacks and to provide a device that can maintain the tension of a magnetic tape constant with a simple configuration even if the winding diameter of the magnetic tape wound on a supply reel changes. shall be.

The case where the present invention is applied to a VTR will be described below. In the embodiment of the present invention, parts corresponding to those in the conventional example shown in FIG. 1 are given the same reference numerals to avoid duplication of explanation.

FIG. 5 shows the configuration of this embodiment. In the figure, 29 is a tape guide, and 29 is a supply reel 1.
The magnetic tape 30 is provided near the magnetic tape 30 and comes into contact with the magnetic surface side of the magnetic tape 30 to form a part of the running path. 31
Similarly, a tape guide is provided on the inlet side of the rotary head device 9, has the same configuration as the tape guide 29, and forms part of the running path of the magnetic tape 30. Details of these tape guides 29 and 31 will be described later. Reference numeral 32 denotes a tape guide resistance detection circuit that detects the resistance value of the magnetic tape 30 between the tape guides 29 and 32 as a voltage therebetween, and provides an output corresponding to the resistance value to the comparison circuit 33. Reference numeral 34 is a reference voltage generation circuit, which determines the running mode of the magnetic tape 30 (recording, playback, rewinding, fast forwarding, stopped state).
A reference voltage is applied to the comparator circuit 33 in accordance with the above. The comparison circuit 33 compares the output v p from the reference voltage generation circuit 34 and the output _{v p from} the tape guide resistance detection circuit 32 in accordance with the running mode of the magnetic tape 30, and the difference is v ₁ The signal is outputted as a signal and given to the power amplification circuit 35. Reference numeral 36 denotes an electric motor directly connected to the supply reel 1, to which the output signal v _n of the power amplification circuit 35 is applied, thereby applying braking torque to the supply reel 1 during tape running.

FIG. 6 shows the cross-sectional structure of the magnetic tape 30. This magnetic tape is made by depositing conductive metal magnetic materials such as Co and Ni on one side of a polyethylene terephthalate film 37 with a thickness of about 10 μm.
A magnetic thin film layer 38 of about 0.1 μm is formed. FIG. 7 shows a vacuum deposition apparatus for manufacturing this magnetic tape 30. As shown in the figure, the polyethylene terephthalate film 37 is guided from a delivery roller 39 around which the polyethylene terephthalate film 37 is wound to the outer periphery of a roller 40 rotating in the direction of arrow k, and is wound onto a take-up roller 41. At that time, the magnetic materials Co, Ni38a
When heated, the vapor 38b of Co, Ni, etc. is deposited on the surface of the polyethylene terephthalate film 37. Thereafter, the magnetic tape 30 can be obtained by cutting it into desired dimensions. In addition,
In addition to the above-mentioned methods, magnetic tape can be manufactured by applying a magnetic material together with an adhesion medium,
The plating method, sputtering method, etc. are common.
FIG. 8 is a diagram showing the relationship between the elongation λ due to tension of the magnetic tape 30 and the electrical resistance R ₀ .
As is clear from the figure, the magnetic tape 30 exhibits a characteristic that as its elongation λ increases, its electrical resistance R ₀ also increases accordingly. That is, the elongation λ is λ ₁ to _{λ 3}
In between, the electric resistance _R0 also becomes _R1 to _R3 , and there is a region where a proportional relationship occurs between the two. magnetic tape 30
Since the amount of elongation λ is determined by the magnitude of the tension applied to it, the relationship between the tension applied to the magnetic tape 30 and the electrical resistance _R0 is also proportional within the range of _R1 to _R3 . There will be.

Next, the configurations of the tape guides 29, 31 and the tape guide voltage detection circuit 32 will be described using FIG. 9.

Since the tape guides 29 and 31 have the same configuration as described above, one of them will be explained here as a representative. The tape guide 29 has, on its upper side, a magnetic tape contact surface 42 for contacting and guiding the magnetic surface side of the magnetic tape 30, and convex portions 43, 44 on both sides thereof for regulating the running height position of the magnetic tape 30. There is. Further, on the lower side, there is a connection fixing part 4 connected to one end of the input side of the tape guide voltage detection circuit 32.
Further, on the lower side thereof, there is provided a threaded portion 50 which is tightened and fixed to the board 46 of the VTR via insulating spacers 47 and 48 with screws 49. The surface of the magnetic tape contact surface 42 is particularly precisely processed so as to ensure stable contact with the magnetic surface of the magnetic tape 30. The convex portions 43, 44, the wire connection fixing portion 45, and the threaded portion 50 below are integrally made of stainless steel or the like.

The inter-tape guide resistance detection circuit 32 is composed of a DC amplifier circuit whose input ends are connected to the tape guides 29 and 31, respectively, as shown in FIG. The +Vc.c. power source is connected to the collector of the transistor T _r , one end of the resistor R ₁₀ , and the tape guide 31.
are connected to each other, and one ends of a capacitor C ₁₀ , a resistor R ₁₁ , and a resistor R ₁₂ are connected to the grounding wire. At the base of the transistor T _r are resistors R ₁₀ , R ₁₁ and a capacitor C ₁₀
The other end of the tape guide 29 is connected to the tape guide 29. By the way, the tape guides 29 and 31 have the same structure as described above, and the magnetic tape 30 is placed above them.
a magnetic tape contact surface 42 on which the magnetic surface of the magnetic tape is guided in contact;
and is electrically insulated from the VTR board 46. Further, as described above, the magnetic tape 30 has a magnetic material such as Co or Ni deposited thereon, which has conductivity. Therefore, an electric resistance R ₅ occurs between the tape guides 29 and 31, which form part of the tape running path of the VTR and are in contact with the magnetic surface side of the magnetic tape 30. This electrical resistance R ₅ is
Starting from the part where the magnetic tape 30 is in contact with the magnetic surface side of the tape guide 29, the guides 4, 5,
Length l ₅ of the magnetic tape 30 from the rotation guide 6 to the tape guide 31 via the erasing head 7
Depends on. The electrical resistance R ₅ of the magnetic tape 30 between the tape guides 29 and 31 is as follows in FIG.
It is connected as shown by the broken line between the base of the transistor T _r and the +Vc.c power supply terminal.
Then, the output of the tape guide resistance detection circuit 32
v _p is determined according to the value of the electrical resistance R ₅ and is applied to the comparator circuit 33 as the emitter voltage of the transistor T _r .

By the way, the tension of the magnetic tape 30 in the recording and playback state of the VTR is determined by the tape guide 31.
When the tension value is set to T ₅₁ between the tape guide 2 and the rotating head device 9,
The _electrical resistance R ₅ of the magnetic tape 30 between the tape guides 9 _and 31 is indicated by R ₅₁ in FIG.

Electrical resistance _R5 of the magnetic tape 30 between the tape guides 29 and 31 and the resistance detection circuit 32 between the tape guides
_As mentioned above, there is a proportional relationship with the output v _p of Added tension T ₅
Since it is approximately proportional to the tension T 5 , the output v _p changes in proportion to the tension T ₅ . Therefore, the 10th
As shown in the figure, when the tension of the magnetic tape 30 is _T51 , the electric resistance _R5 of the magnetic tape 30 between the tape guides 29 and 31 shows a value of _R51 , and the inter-guide resistance detection circuit at this time 32 outputs
v _p indicates the value v ₅₁ . The state of the VTR in this case is the recording mode or the playback mode. For example, if a rotational load fluctuation occurs on the supply reel 1 on which the magnetic tape 30 is wound, or when the guides 3, 4, 5 in the middle of the tape running path The gap between the tape guide 31 and the rotary head device 9 may be caused by the adhesion of dust floating in the atmosphere, which changes the contact friction force of the magnetic tape 30 and causes fluctuations in running load. When the tension T ₅ of the magnetic tape 30 slightly increases from the initial setting value T ₅₁ to T ₅₃ , the elongation λ of the magnetic tape 30 also increases. The electrical resistance R ₅ of the magnetic tape 30 between the tape guides 29 and 31 also increases slightly from R ₅₁ to R ₅₃ , and the output of the inter-guide resistance detection circuit 32
v _p is slightly lower than v ₅₁ as shown in Figure 10, v ₅₃
becomes the value of Conversely, the tension of magnetic tape 30
If T ₅ decreases from T ₅₁ to T ₅₂ for some reason, the elongation λ of the magnetic tape 30 also decreases. And the electrical resistance R ₅ of the magnetic tape 30 is R ₅₁
It decreases from R to R ₅₂ , and the output v _p of the inter-guide resistance detection circuit 32 has a value of v ₅₂ which is slightly higher than v ₅₁ . That is, the tension T ₅ of the magnetic tape 30
and the output v _p of the inter-guide resistance detection circuit 32 are inversely proportional to each other, and the tension T ₅ of the magnetic tape 30
When is small, the output v _p of the inter-guide voltage resistance circuit 32 becomes high. This output v _p is given to the comparator circuit 33 .

In the comparator circuit 33, the inter-guide voltage resistance circuit 32
The output v _p of the reference voltage generating circuit 34 is compared with the output v _p from the reference voltage generating circuit 34 . The output v _p from the reference voltage generating circuit 34 changes as shown in FIG. 11 depending on the running mode of the magnetic tape 30. 5 in Figure 11
1 indicates a stopped state, 52 indicates a recording/playback state, 53 indicates a fast-forwarding state, and 54 indicates a rewinding state.
When the VTR is in recording or playback mode, the comparator circuit 3
3, the difference between the output v ₅₁ of the inter-guide resistance detection circuit 32 and the output v _p 52 of the reference voltage generation circuit 34 is output as v ₁ . The output v ₁ of the comparator circuit 33 is applied to a power amplification circuit 35, and after predetermined signal processing is performed, it is applied as an output signal v _n to a motor 36 directly connected to the supply reel 1. As a result, the electric motor 36
generates rotational torque for applying a predetermined tension to the running magnetic tape 30.

Therefore, when the VTR is in recording or playback mode, the magnetic tape 3 wound around the supply reel 1
0 continues to be transported in the direction of arrow a shown in FIG. 5 by the cooperative action of the capstan 12 and the pinch roller 13, but the tension T ₅ applied to the magnetic tape 30 is set to the value T ₅₁ in FIG. 10. has been done.
In this state, the rotational eccentricity of the supply reel 1,
If there is uneven winding of the magnetic tape 30 wound on the supply reel 1, or if the running load of the magnetic tape 30 fluctuates, the tension _T51 of the magnetic tape 30 will fluctuate, for example, If it rises to T ₅₃ in Figure 10, the tape guides 29 and 31
At the same time, the electrical resistance R ₅ of the magnetic tape 30 between them becomes R ₅₃ . At the same time, the output v _p of the inter-tape guide voltage resistance circuit 32 also decreases from v ₅₁ to a value v ₅₃ and is applied to the comparison circuit 33, as shown in FIG. The comparison circuit 33 compares the voltage of the output v ₀ from the reference voltage generation circuit 34 at point 52 shown in FIG. 11 with the voltage of the output v ₅₃ , and generates an output according to the difference. This comparison circuit 33
The output of the motor 3 is amplified by the power amplification circuit 35 and
Join 6. In the end, the output signal v _n from the power amplifier circuit 35 applied to the electric motor 36 is
In response to a change in the tension T ₅ , if it is higher than the set value T ₅₁ , it is reduced and added by an amount corresponding to the change. Conversely, the tension of the magnetic tape 30
If T ₅ is lower than the set value T ₅₁ , it will be increased and added by an amount corresponding to the difference. Such changes occur continuously, and as a result, the electric motor 36
The tension T ₅ of the magnetic tape 30 is corrected to the set value T ₅₁ by , and if the tension T ₅ changes thereafter, the set value is corrected again by the above-mentioned operation.
Compensated up to T ₅₁ . The relationship between the tension of the magnetic tape 30 and the winding diameter of the magnetic tape wound on the supply reel 1 according to this embodiment is shown in FIG. The change in tension becomes extremely small.

As explained above, the magnetic recording/reproducing apparatus according to the present invention detects fluctuations in the tension applied to the magnetic tape by using a resistance detection circuit at predetermined intervals so as to contact the magnetic layer of the magnetic tape in the tape running path. This output is directly detected as a variation in the electrical resistance of the magnetic tape between the arranged conductors, and this output is compared with a reference voltage corresponding to the running mode of the device, and the difference is used to control the tape tension control means of the supply reel. Since the braking torque is controlled using the driving signal, changes in the tension of the magnetic tape due to changes in the winding diameter of the magnetic tape wound on the supply reel are significantly reduced, and the tension is almost completely reduced. It can be made constant. Even if there is rotational eccentricity of the supply reel, uneven winding of the magnetic tape wound on the supply reel, or fluctuations in the contact friction force between the magnetic tape and the components of the tape running path, the magnetic tape tension can be effectively controlled. Can be held at a set value. Therefore, in conventional magnetic recording and reproducing devices, the magnetization track shift phenomenon occurs due to changes in the magnetic tape tension, the resulting deterioration of the playback image quality, and the wow and noise caused by changes in the magnetic tape tension.
Problems such as increased flutter and jitter have occurred, but according to the present invention, magnetic tape tension can be stabilized with a simple configuration. Since such problems can be solved, it is possible to further advance the miniaturization of recent magnetic recording/reproducing apparatuses, higher density recording, and thinner magnetic tapes.

[Brief explanation of drawings]

Fig. 1 is a plan view showing an example of a tape running system of a conventional magnetic recording/reproducing device, Fig. 2 is a plan view of its magnetic tape tension control device, and Fig. 3 is a plan view showing changes in the tape winding diameter of the supply reel and tension. FIG. 4 is a diagram showing the magnetization track by this device. FIG. 5 is a block diagram of a magnetic recording/reproducing apparatus according to an embodiment of the present invention, FIG. 6 is a sectional view showing an example of a magnetic tape used in this embodiment, and FIG.
The figure is a conceptual diagram for explaining an example of this magnetic tape manufacturing apparatus, FIG. 8 is a diagram showing the relationship between the elongation of the magnetic tape and its electrical resistance, and FIG. 9 is the structure of the tape guide in this embodiment. FIG. 10 is a diagram showing the relationship between the tension of the magnetic tape and the output of the tape guide voltage detection circuit, and FIG. 11 is a diagram showing the output generation of the reference voltage generation circuit. Diagram showing the state, 1st
FIG. 2 is a diagram showing the relationship between the change in tape winding diameter of the supply reel and the tension in this embodiment. 1... Supply reel, 9... Rotating head device, 1
2... Capstan, 13... Pinch roller, 1
5...Take-up reel, 29...Tape guide, 3
0... Magnetic tape, 31... Tape guide, 32
... resistance detection circuit between tape guides, 33 ... comparison circuit, 34 ... reference voltage generation circuit, 35 ... power amplifier, 36 ... electric motor, 37 ... polyethylene terephthalate film, 38 ... magnetic thin film layer.

Claims (1)

[Scope of Claims] 1. A plurality of conductors having a predetermined interval and arranged in a tape running path in contact with the magnetic layer side of the magnetic tape, and a plurality of conductors disposed between the plurality of conductors to conduct electricity of the magnetic tape. A resistance detection circuit for detecting resistance, and tape tension control means for controlling the tension of the magnetic tape according to an output of the detection circuit, and keeping the tension of the magnetic tape constant while the magnetic tape is running. A magnetic recording/reproducing device characterized by: 2. The magnetic device according to claim 1, which is a tape guide in which a plurality of conductors arranged in a tape running path form a pair, each of which is connected to an input end of a resistance detection circuit. Recording and playback device. 3. The tape tension control means has an electric motor coupled to the supply reel, and controls the braking torque of the electric motor to the supply reel according to the output of the resistance detection circuit, thereby making the tension of the magnetic tape constant during tape running. A magnetic recording and reproducing device according to claim 1, characterized in that: 4. The magnetic recording and reproducing device according to claim 1, wherein the magnetic tape has a magnetic layer made of a metallic magnetic material.