JPH0229548Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a cassette-type tape recorder applied to car stereos and the like.

When the car stereo is stopped, even a cassette-type tape recorder with good sound quality can be used.
It is known from experience that when a car starts running and is subjected to severe vertical vibrations, the wah becomes louder and the sound quality deteriorates, especially when there is a lot of tape remaining.

In order to find out what this wow is like, we measured the wah by applying 1G vertical vibration to an existing cassette tape recorder while changing the frequency, and found the wah (RMS) characteristics shown in Figure 1. was gotten. In this characteristic, it can be seen that wow of more than 1% occurs at vibrations around 40Hz and 100Hz or more, but when this is measured with audible correction, as shown in Figure 2, wow occurs at vibrations over 100Hz. (WRMS)
is less than 0.2%, a value that is hardly a problem, whereas wah at around 40Hz still remains.
It was found that 0.2% or more was present, and this caused poor sound quality.

In order to find out what causes this 40Hz wow, the structures of tape recorders and cassettes and their operations during play will be discussed with reference to FIGS. 3 to 8.

The cassette is constructed by storing a tape 2 in a cassette case 1 formed of two upper and lower plates 1a and 1b.
b, and is wound onto reels 3a and 3b from both ends. Therefore, when the diameter of one winding becomes larger, the diameter of the other winding becomes smaller, and the figure shows a state in which the tape 2 is fully wound around the reel 3b on the supply side. The feature of the cassette is that by not providing flanges on the reels 3a and 3b, the distance between the centers of the reels 3a and 3b is narrowed and the cassette is compact. The tape 2 is now wound in stages around 3b. Therefore, in order to prevent the tape 2 from coming into direct contact with the inner wall surface of the case 1 and causing friction, a gap is created between the reels 3a and 3b and the upper and lower wall surfaces of the case 1. By inserting sheets 5a and 5b called retainers, respectively, the reels 3a and 3
b is held in the middle of case 1.

Inside the case 1, in addition to the tape 2 and reels 3a and 3b, guide rollers 6a and 6b, a pressure pad 7, etc. are housed.
A pair of capstan shaft insertion holes 8a and 8b, positioning pin insertion holes 9a, 9b, 9c and 9d, a pair of pinch roller insertion holes 10a and 10b, reel shaft insertion holes 11a and 11b, and a magnetic head insertion hole 12 are drilled. There is. Incidentally, 3a' and 3b' are engagement claws protruding from the inner peripheral surfaces of the reels 3a and 3b at equal intervals of 60 degrees.

On the other hand, a cassette tape recorder includes a pair of reel shafts 20a and 20b, a capstan shaft 21,
Equipped with a pinch roller 23, a magnetic head 24, etc.
When the cassette is installed, the reel shafts 20a and 2
0b enters the cassette through the reel shaft insertion holes 11a and 11b and engages with the reels 3a and 3b in the rotational direction, and the capstan shaft 21 enters the capstan shaft insertion hole 8a. When the play state is set, the pinch roller 23 enters the cassette through the pinch roller insertion hole 10a and inserts the capstan shaft 2.
The tape 2 is sandwiched between the tape 2 and the capstan shaft 21, and the tape 2 is run at a constant speed in cooperation with a capstan shaft 21 rotating at a constant speed. Further, the magnetic head 24 enters the cassette through the magnetic head insertion hole 12, sandwiches the tape 2 between it and the pressure pad 7, and reproduces the contents of the tape 2 running at a constant speed.

In the playing state as described above, the reel shaft 20a
The reel shaft 20b functions as a tape winder and is rotationally driven by a drive source (not shown), whereas the reel shaft 20b
serves as a tape supply, and although it is not driven by a drive source, it is designed to give a constant back tension to the tape 2.

A conventional example of this supply side reel shaft 20b will be described in detail. In FIGS. 5 and 6, C is a chassis of a cassette tape recorder, and an upright shaft _20b1 is vertically installed on this chassis. Upright shaft 20
A reel shaft main body 20b ₂ having a regular hexagonal cross section is rotatably supported on b ₁ , and a reel shaft main body 20b ₂ is rotatably supported on the outer periphery of the shaft main body 20b ₂ . The cylindrical hub _20b3 is fitted so as to fit. The cylindrical hub 20b ₃ is biased in one direction by a spring 20b ₄ compressed between it and the shaft body 20b ₂ , and is kept in the illustrated state by a presser member 20b ₅ fitted onto the shaft body 20b ₂ . is maintained. As described above, the shaft main body 20b ₂ , the cylindrical hub 20b ₃ , the spring 20b ₄ , and the holding member 20b _{5 are integrated into a unit, and the upright shaft 20b 5} is fixed to the upright shaft 20b ₁ so that they do not come off the upright shaft 20b 1 .
It is held in the state shown in the figure by a stopper _20b6 attached to the tip of _b1 . The leaf spring 20b ₇ compressed between the collar of the upright shaft 20b ₁ and the shaft body 20b ₂ is
This is to give back tension to the tape 2 by creating a constant friction between the reel shaft unit and the upright shaft _20b1 . The reel shaft 20b having the above-mentioned configuration is such that, when the cassette is installed, even if the reel claw 3b' of the cassette rides on the outer circumferential claw 20b' ₃ of the cylindrical hub 20b ₃ , the cylindrical hub 20b ₃ can escape. . However, if this is not necessary, as shown in Figure 7,
A shaft body 20b ₂ with a pawl 20b' ₂ directly provided on the outer periphery is rotatably supported on the upright shaft 20b ₁ , and the leaf spring 2
It is also possible to simply configure it so that friction occurs at _0b7 .

Now, suppose that when the cassette tape recorder having the above-described structure is in a playing state, vertical vibrations as indicated by the arrows in FIG. 4 are applied. When the frequency of vibration is extremely low, around 1Hz, reels 3a and 3b
moves up and down together with case 1 and chassis C, but
When the frequency increases, the reels 3a and 3b become stationary, and only the case 1 moves up and down together with the chassis C. As a result, the upper and lower walls of the case 1 violently collide with the reels 3a and 3b from above and below. When such a situation occurs, the tape 2 will expand and contract between the point a where it is held between the capstan shaft 21 and the pinch roller 23 and the point b at the winding end on the reel 3b.

By the way, the tape 2 between the points a and b resonates at a resonance frequency ₀ determined by the spring constant of the tape 2 and the moment of inertia of the tape wound on the reel 3b. Now, 2-3 usually added to tape 2
When we calculated ₀ for the back tension of g, we found that ₀ = 30-40Hz.

When the cassette tape recorder is in the playing state, the claw 3b' of the reel 3b on the supply side engages with the claw _20b'3 of the reel shaft 20b, as shown in FIG. 8a, and rotates the reel shaft 20b in the direction of the arrow. However, when the above-mentioned resonance occurs in the tape 2, the rotation of the reel 3b stops due to the elongation of the tape 2 (Fig. 8b), and the subsequent contraction causes the reel 3b to rapidly rotate. This causes the reel shaft 20b to rotate with a large force (FIG. 8c). For this reason, the reel shaft 20b and the reel 3
A repulsive force acts between the tape 2 and the tape 2, and together with the further elongation of the tape 2, the two claws 3b' and 20b' ₃ finally come to separate as shown in FIG. 8d. Once such a situation occurs, both nails 3b' and 20
Collisions and repulsions occur repeatedly between b' and ₃ , resulting in so-called jitter. Therefore, tape 2
It was found that the speed at which the magnetic head moves on the surface of the magnetic head 24 fluctuates, and this causes a large wah at around 40 Hz.

This invention was made in view of the above points,
The purpose is to provide a cassette type tape recorder which improves the sound quality by preventing the occurrence of large wah noises even when vertical vibrations are applied.

To this end, the present invention forms a pawl made of a viscoelastic material at least on the reel shaft of the tape supply side at the engaging part for the reel of the cassette, thereby creating a connection between the reel shaft of the tape supply side and the cassette reel. Collisions and repulsions that occur in the rotational direction are buffered by claws made of viscoelastic material in the engaging part, weakening the resonance of the tape at frequencies below 100Hz, thereby suppressing wow. .

Embodiments of the present invention will be described below with reference to FIGS. 9 to 18, in which the same or corresponding parts as in FIGS. 3 to 8 are given the same reference numerals.

9 to 11 show a reel shaft 20b on the tape supply side in a one-way cassette tape recorder. In the figure, the cylindrical hub _20b3 is made of a viscoelastic material such as plain rubber or butyl rubber, and has a claw 20 on its outer periphery that engages with the engaging claw 3b' of the reel 3b of the cassette.
b′ ₃ is formed. The holding member _20b5 is the 12th
As shown in the figure, its outer edge is extended and molded into a cap shape from a hard plastic material, and a slit _20b'5 is made in a portion of the cylindrical hub _20b3 corresponding to the pawl _20b'3 , and this slit 20b' A claw _20b'3 projects outward from ₅ . That is,
The outer surface of the cylindrical hub _20b3 , except for the claws _20b'3 , is covered by a holding member _20b5 made of a hard material. This allows the engaging pawl 3b' of the reel 3b to move smoothly onto the reel shaft 20b when the cassette is installed.
can be engaged with the pawl _20b'3 .

Other than the above-mentioned components, the reel shaft is the same as the reel shaft shown in FIGS. 5 and 6, so a description thereof will be omitted.

When using the reel shaft 20b configured as described above, the engaging pawl 3b' of the reel 3b of the cassette is connected to the reel shaft 20b.
Even if the reel 3b and the reel shaft 20 collide with the claw 20b' ₃ of the reel 3b, the impact is buffered by the deformation of the claw 20b' ₃ made of a viscoelastic material.
The repulsive force generated between the two claws 3b' and 20b'3 is weakened, and it is possible to prevent the claws 3b' and _20b'3 from separating from each other as shown in FIG. 8d. Therefore, the resonance of the tape 2 becomes smaller, and as can be seen from the wow characteristics shown in FIGS. 13 and 14 measured for the embodiments shown in FIGS. 9 to 11,
1 before auditory correction, which conventionally occurred around 40Hz.
%, wah of 0.2% or more has disappeared after auditory correction.

FIGS. 15 and 16 show a reel shaft 20b that is applied to a so-called two-way cassette tape recorder that can play in two directions.
In this case, the reel shaft is used not only as a tape supply side but also as a tape winding side.
A configuration for this purpose is added to the reel shaft 20b.

That is, in the example of FIG. 15, the spring 20
Felts 31 and 32 pressed together by b ₄
The shaft body 20b ₂
A pulley 33 connected to the pulley 33 is added, and a gear 34 rotated by a drive source (not shown) can be selectively engaged with a gear 33a on the outer periphery of the pulley 33.

In the example shown in FIG. 16, a flat motor 35 is rotated when the reel shaft 20b is used on the tape winding side.
is fixed to the chassis C, and a reel shaft unit is fixed to the rotating shaft 35a of this motor 35. In this case, when the reel shaft 20b is used on the tape supply side, the motor 35 is not driven to rotate. Note that the spring 36 attached to the lower end of the rotation shaft 35a is used to generate friction for giving back tension to the tape 2.

In the reel shafts 20b shown in FIGS. 9, 15, and 16 described above, the cylindrical hub 20b ₃ is slidable in the axial direction of the shaft body 20b ₂ , but the function of the reel shaft itself is As such, there is no need for something like this. Therefore, as shown in FIG. 17, the shaft body 20b ₂ is made of a viscoelastic material, and the shaft body 20b ₂ itself is integrally provided with a pawl 20b' ₂ that engages with the pawl 3b' of the reel 3b. Further, the central pipe-shaped portion of the holding member 20b ₅ is press-fitted into the center hole of the shaft body 20b ₂ so that the upright shaft 20b ₁ and the shaft body 20b ₂ do not come into direct contact.

As described above, the present invention includes a pair of reel shafts rotatably provided on the chassis, and at least the reel shafts serving as the tape supply side are provided with claws made of a viscoelastic material and serving as engaging portions for the reels of the cassette. a hub member made of a hard material separately from the hub member, having a slit in a portion corresponding to the claw of the hub member and a tape portion in the upper part;
and a presser member freely fitted to the hub so as to cover parts other than the claws.

For this reason, during play on a cassette-type tape recorder, vertical vibrations are applied, causing the tape in the cassette to
Even if it resonates at a frequency of 100 Hz or less, the collision between the cassette reel and the pawl of the cylindrical hub is buffered by the viscoelastic material of the engaging part, and almost no repulsion occurs between them, so the cassette The resonance of the tape inside the tape can be suppressed to a minimum, making it possible to prevent the generation of the large wah that conventionally occurs, and thus providing a cassette-type tape recorder with improved sound quality.

[Brief explanation of the drawing]

Figures 1 and 2 are graphs showing the wah characteristics of a conventional cassette-type tape recorder before and after auditory correction, and Figure 3 is a plan view of the cassette-type tape recorder in play mode with one side of the cassette case removed. Figures 4 and 4 are cross-sectional views taken along the - line in Figure 3, and Figures 5 to 7 are cross-sectional views showing conventional tape supply side reel shafts. In particular, Figure 6 is a cross-sectional view taken along the - line in Figure 5. FIG. 8 is a simplified diagram for explaining the problems that arise when using the reel shafts shown in FIGS. 10 is a sectional view taken along the - line in FIG. 9, FIG. 11 is a plan view of the reel shaft in FIG. 9, and FIG. 12 is a side view of one member in FIG. 9. , FIGS. 13 and 14 are graphs showing the wah characteristics before and after auditory correction, respectively, measured by applying vertical vibration to a cassette tape recorder using the reel shaft shown in FIGS. 9 to 11. Figures to 17th
The figure is a sectional view corresponding to FIG. 9 of another embodiment. 3b...Reel, 3b'...Claw, 20b...Reel shaft, _20b'2 ...Claw, _20b5 ...Press member.

Claims (1)

[Scope of utility model registration request] A chassis is provided with a pair of reel shafts rotatably provided, and at least the reel shaft serving as the tape supply side is provided with a hub member made of a viscoelastic material and having a pawl that serves as an engaging portion for the reel of the cassette, and a hub member made of a hard material. The hub member is made separately from the hub member, has a slit at a portion corresponding to the claw of the hub member, and a tapered portion at the upper part, and is fitted to the hub member so as to cover the part other than the claw. 1. A vehicle-mounted cassette-type tape recorder, characterized in that said viscoelastic material damps resonance of the tape at a frequency of 100 Hz or less due to vibrations of an automobile.