JP3090692U - Shield structure of magnetic recording / reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shield structure for shielding a noise invading a head amplifier circuit of a magnetic recording / reproducing apparatus, which can be configured with a simpler structure and at a lower cost. A head amplifier circuit is provided on a printed circuit board, and a ground pattern is formed on a lower surface of the printed circuit board so as to surround the head amplifier circuit. Boss 1 that connects printed circuit board 1 to chassis 8 by connecting holes 7 provided in chassis 8 and ground pattern 4 with connecting pattern 6 to project printed circuit board 1 into chassis bottom plate 9
The deck 12 is placed on the printed circuit board and screwed on the printed circuit board.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a shield structure of a magnetic recording / reproducing apparatus, such as a video device, which blocks electromagnetic waves from entering from a printed circuit board side or from the outside.

[0002]

[Prior art]

 In general, radiated electromagnetic waves are generated from electrical equipment and affect external and internal circuits. However, the same applies to magnetic recording / reproducing devices, and various shield structures have been conventionally known. In particular, the head amplifier circuit in the magnetic recording / reproducing apparatus is easily affected by external noise, and therefore a special shield is provided. For example, when a signal recorded on a video tape is detected by a head, this signal level is very low and must be amplified by a head amplifier circuit, but the low level reduces external noise. A shield is required to shut off.

FIG. 3 is a conventional example showing a shield structure of a video deck, which is in a separated state before a video deck 21 is attached to a chassis 22. A printed circuit board 24 is mounted at a predetermined distance from the bottom 23 of a chassis 22 made of a metal plate, and the video deck 21 is mounted on the printed circuit board 24. FIG. 4 shows a state in which the video deck 21 is mounted. A shield plate 25 is interposed between the printed board 24 and the video deck 21.

A leaf spring 26 is attached above the shield plate 25, and when the video deck 21 is mounted on the pedestals 27 a, 27 b, and 27 c and screwed, the leaf spring 26 comes into contact with the bottom of the video deck 21, As a result, the video deck 21 and the chassis 22 are connected to each other via the shield plate 25, so that they have the same potential. The head amplifier circuit is housed inside the shield plate 25, but the structure is not affected by the video deck 21 and other noises by the metal shield plate 25.

[0005] In such a shield structure, it is necessary to manufacture a shield plate 25 having a leaf spring 26, and a head amplifier circuit must be specially formed in the shield plate 25. Expenses will be high. In addition to the manufacturing cost, it is necessary to attach the independently manufactured shield plate 25 to the printed circuit board 24.

Alternatively, a head amplifier circuit may be formed on a printed circuit board without incorporating a head amplifier circuit in such a shield plate, and a shield cover may be attached so as to cover the head amplifier circuit. Also in this case, it is necessary to specially manufacture the shield cover and attach it to the printed circuit board, which incurs high costs.

The “shield structure of a magnetic recording / reproducing apparatus” disclosed in Japanese Patent Application Laid-Open No. H11-86426 provides a good shield effect without causing a contact failure when a circuit board is assembled to a chassis, and furthermore, a shield plate is used. It is not necessary, so that the structure can be simplified and the assembling process can be simplified to reduce the cost.

In other words, the “shield structure of the magnetic recording / reproducing apparatus” is designed to shield radio waves from entering the circuit board side in the magnetic recording / reproducing apparatus or from the outside. The part from the part to the chassis rib is shielded by a plating layer, and the upper end surface of the shielded chassis rib and the circuit board are pressed against the upper end face of the chassis rib with the conductive elastic body attached to the circuit board. Thus, it is configured to conduct electricity. In the case of this shield structure, chassis ribs must be provided on the bottom surface of the chassis, plating must be performed, and an elastic body must be attached to the circuit board.

[0009]

[Problems to be solved by the invention]

 As described above, the shield structure in the conventional magnetic recording / reproducing apparatus has the above-mentioned problems. The problem to be solved by the present invention is this problem, and a shield structure that can be configured with a simpler structure and at a lower cost is provided.

[0010]

[Means for solving the problem]

 The shield structure according to the present invention does not use a shield plate, and the head amplifier circuit provided on the printed circuit board is configured to surround the periphery with a ground pattern also formed on the printed circuit board. The ground pattern surrounding the head amplifier circuit has a shielding function, but the shape of the ground pattern is free.However, the connecting pattern is extended from the ground pattern to an appropriate position, and a hole is provided at the end of the extended connecting pattern. Are provided so as to insert screws for fixing the printed circuit board.

Meanwhile, a printed circuit board is arranged on the bottom plate of the chassis, a deck is mounted on the printed circuit board, and the deck is attached to the chassis by screws. Therefore, the connecting pattern extending from the ground pattern formed around the head amplifier circuit is in contact with the chassis, and is connected to the deck via screws. Therefore, the ground pattern surrounding the head amplifier circuit has the same potential as the deck and the chassis, so that noise intrusion into the head amplifier circuit can be shielded. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0012]

【Example】

 FIG. 1 shows a printed circuit board 1, on which a head amplifier circuit 3 is mounted on an upper surface 2 of the printed circuit board 1. The head amplifier circuit 3 is a circuit for amplifying an extremely weak signal contained in a video tape or the like, and the specific circuit configuration is not limited. A ground pattern 4 is formed on the lower surface 5 so as to surround the head amplifier circuit 3 around the head amplifier circuit 3.

From the ground pattern 4, elongated connecting patterns 6, 6 extend left and right, and are provided at the ends of the connecting patterns 6, 6 through holes 7, 7. The holes 7, 7 are holes through which screws for attaching the printed board 1 to the chassis are inserted. The holes 7, 7 are provided at appropriate positions, and the connecting pattern 6 extends to the holes 7. Here, the ground pattern 4 formed to surround the head amplifier circuit 3 is completely separated from patterns constituting other circuit blocks.

FIG. 2 is a cross-sectional view showing the case where the printed circuit board 1 is mounted. Bosses 10 and 10 are projected from the bottom plate 9 of the chassis 8, and the printed circuit board 1 is placed on the bosses 10 and 10. You. Therefore, the printed circuit board 1 has a predetermined gap 11 interposed between the printed circuit board 1 and the bottom plate 9 of the chassis 8. A head amplifier circuit 3 is provided on the upper surface of the printed board 1, and a deck 12 is mounted on the printed board 1.

Since the deck 12 placed on the printed circuit board is screwed, the screws 13, 13 are inserted through the holes 7, 7 of the printed circuit board 1 from the holes provided in the deck 12, and , 10 into the screw holes. Therefore, the printed circuit board 1 and the deck 12 are attached to the bottom plate 9 of the chassis 8 by screws.

Meanwhile, the printed circuit board 1 is placed with the lower surface 5 abutting against the bosses 10, 10, so that the tips of the connecting patterns 6, 6 extending from the ground pattern 4 contact the bosses 10, 10, and the deck 12 is screwed. By being screwed at 13, 13, the deck 12 is connected to the bottom plate 9 of the chassis 8 via the screws 13, 13. As a result, the ground pattern 4 of the head amplifier circuit 3, the chassis bottom plate 9, and the deck 12 have the same potential.

As described above, since the ground pattern 4, the deck 12, and the chassis bottom plate 9 have the same potential, they are less susceptible to flying noise. For example, when noise from the outside hits the deck 12, the ground pattern 4, the deck 12, and the chassis bottom plate 9 are at the same potential, so that noise flows to the chassis 8, and the head amplifier Does not affect circuit 3.

As described above, in the shield structure according to the present invention, the head amplifier circuit is provided on the printed circuit board, the ground pattern is formed on the lower surface so as to surround the head amplifier circuit, and the screw is inserted. The printed circuit board is mounted on the chassis and connected to the holes by a connecting pattern, and a deck is mounted on the chassis and screwed on the printed circuit board. The following effects can be obtained.

[0019]

[Effect of the invention]

 In the shield structure according to the present invention, a head amplifier circuit is provided on a printed circuit board, and a ground pattern is formed on the lower surface so as to surround the head amplifier circuit. A hole is provided through the hole at a position where the connecting pattern is extended from the ground pattern, the printed circuit board is placed on the chassis, a deck is arranged on the printed circuit board, and the deck, the printed circuit board, and the deck are inserted through the screw holes. Since the chassis is fixed, the ground pattern and deck surrounding the head amplifier circuit and the chassis are kept at the same potential.

In this manner, noise that enters from the outside can be shielded by keeping the ground patterns at the same potential. This shield structure does not use a shield plate as in the past, does not require shield plating, is structurally simple, and the manufacturing cost is further reduced.

[Brief description of the drawings]

FIG. 1 is a printed circuit board surrounding a head amplifier circuit with a ground pattern.

FIG. 2 is a shield structure of the present invention in which a printed circuit board is attached to a chassis.

FIG. 3 is a development view of a conventional shield structure.

FIG. 4 shows a conventional shield structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed circuit board 2 Upper surface 3 Head amplifier circuit 4 Ground pattern 5 Lower surface 6 Connecting pattern 7 Hole 8 Chassis 9 Bottom plate 10 Boss 11 Clearance 12 Deck 13 Screw

Claims (1)

[Utility model registration claims] 1. A shield structure for shielding noise entering a head amplifier circuit of a magnetic recording / reproducing apparatus,
The head amplifier circuit is provided on a printed circuit board, a ground pattern is formed on the lower surface of the printed circuit board so as to surround the head amplifier circuit, and a hole provided for attaching the printed circuit board to a chassis is connected to the ground pattern. Connect in a pattern, place the printed circuit board on the boss protruding from the chassis bottom plate, and screw on the deck on the printed circuit board where the deck is placed, and insert the screws through the holes provided in the printed circuit board from the deck A shield structure for a magnetic recording / reproducing device, wherein the shield structure is screwed into a screw hole of a chassis.