JPS58196336A - Brake gear - Google Patents

Abstract

PURPOSE:To simplify the structure of a brake gear and to electrically control braking power by using a piezo-electric element as a damping member and utilizing minute expansion and contraction produced by applying an electric field for damping. CONSTITUTION:In order to efficiently obtain a braking effect, a brake shoe 28 is adhered to a damping member 11 of a bimorph structure in which two sheets of piezo-electric material are sticked together, and when an electric field is applied to the bimorph 11, the forward end thereof displaces in the arrow direction, so that the brake shoe 28 contacts the outer peripheral surface of a brake drum 26, and such displacement is checked by the drum. The drum 26 is pressed by force corresponding to such checked displacement. The frictional force corresponding to the coefficient of friction between the shoe 28 and the drum 26 is damping power. This damping power can be controlled precisely by controlling the applied electric field by a variable voltage DC power source 20.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brake device that electrically controls braking force using a piezoelectric element, and more specifically, an object of the present invention is to provide a brake device that is simple and has precise controllability. It is something.

Conventionally, electrically operated brake devices have generally used an electromagnetic plunger or a motor as an operating element. However, those that use electromagnetic plungers simply switch between an activated state and a non-actuated state electrically, and it is difficult to change the magnitude of the braking force according to the electrical input. However, its construction required several related parts, such as a lever mechanism and a spring. Also, with motors that use motors, it is possible to change the magnitude of the braking force, but
Quite a few parts were required to construct the motor. Such conventional devices have problems in that it is difficult to obtain a simple configuration that changes the braking force in accordance with electrical input, and it is difficult to precisely control the braking force. An example of this occurs, for example, when controlling pack tension in a tape recorder.

In a tape recorder, the sound quality is affected by the contact state of the tape with the magnetic head, but in order to obtain good head touch, the tension that pulls the tape in the opposite direction to the driving direction,
In other words, pack tension is required. Conventionally, a method often used in cassette tape recorders and the like is to apply a certain load to the supply reel stand using a spring or the like, and apply pack tension to the tape using the frictional force. However, this method has the disadvantage that pack tension increases because the radius of the tape feeding position decreases as the tape moves from the beginning to the end. When the back ten/con changes in this way, variations occur in the tape running system and head touch, which adversely affects sound quality.

Therefore, by controlling the braking force applied to the supply reel stand so as to cancel out the change in pack tension due to the change in tape radius, the pack tension of the tape can be kept constant.

The present invention provides, for example, a simple braking device that can electrically precisely control the braking force in the above-mentioned example, and an example in which it is applied to the above-mentioned pack tensioning device is shown below as an example. I will explain it together.

In the present invention, a piezoelectric element is used as a braking member, and the minute expansion and contraction that occurs when an electric field is applied is used to brake a member to be braked by frictional force. In order to obtain a more efficient braking effect, a bimorph braking member made of two piezoelectric materials bonded together is used. FIG. 1 shows a braking member and a supporting member having a bimorph structure. Reference numerals 18 and 18' denote support members for supporting the braking member, and 1o and 10' are rectangular piezoelectric materials made of piezoelectric ceramic, and electrodes 12, 12' and 14, 14' are provided on both sides, respectively.

The two piezoelectric ceramics are polarized in the thickness direction of the plates, and are bonded together with an adhesive 16 with their polarization directions aligned.

And it is connected to the voltage variable DC power supply 2o by wiring as shown in the figure. At this time, electric fields in opposite directions are applied to the piezoelectric materials 10° and 10', causing one side to expand and the other to contract, causing the tip to be displaced to the side as shown by the arrow. The displacement obtained by this bimorph structure is significantly larger than that obtained by simple expansion and contraction, and has the advantage of facilitating brake control.

FIG. 2 shows a back tension adding device which is an application example of a piezoelectric brake device using the above braking member. 11 is a bimorph which is a braking member, 22 is a supply reel shaft, 24 is a supply to rubos, 26 is a brake drum which is a braked member, and 22, 24 and 26 are connected during tape reproduction. A brake shoe 28 is bonded to the bimorph 11, and a support member 18.18' is attached to a fine movement device so that the gap between the brake shoe 28 and the brake drum 26 can be adjusted.

As shown in FIG. 1, a variable voltage DC power source 2o is wired to the bimorph as shown in the figure.

Further, in order to detect the radius of the supply reel, a rotation speed detection device 32 of the supply reel stand and a calculation device 34 that calculates the reel radius from the rotation speed are provided, and the output thereof is connected to the voltage variable DC power supply 20 as a control signal. There is.

The operation of this device will be briefly explained below.

When the tape is in playback mode, the supply reel boss 26 is pulled by the tape and rotates counterclockwise in the figure, which causes the brake drum 26 to also rotate counterclockwise via the supply reel shaft 22. At this time, when an electric field is applied to the bimorph 11 by the voltage +3r variable DC power supply 20, the tip is displaced in the direction of the arrow in the figure. When the brake shoe 2 is displaced to a certain extent,
8 comes into contact with the outer circumferential surface of the brake drum 26, and further displacement is prevented, so the brake drum 26 is held down with a force corresponding to the amount of the prevented displacement. Then, a force corresponding to the coefficient of friction between the brake shoes and the brake drum acts as a frictional force in a direction tangential to the outer circumferential surface of the brake drum, and applies brake torque to the supply reel shaft 22. This brake torque imparts pack tension to the tape via the supply reel boss 24. The brake shoes 28 are installed to prevent wear on the bimorph 11,
A shoe may also be provided on the brake drum side. Further, the gap between the brake knee and the brake drum does not necessarily have to be a positive value, and a fine movement device 3o is provided to adjust the initial braking force or gap by pressing the brake shoe against the brake drum. The braking method is not the above-mentioned 6F, but you can apply the initial brake as described above to move the range from pre to is bimorph 11 in the opposite direction
It is also possible to gradually reduce the braking force by displacing the brake force, or to utilize a well-known biting effect. Further, the method of applying frictional force to the brake drum is not limited to the method shown in this example. These braking forces can be precisely controlled by adjusting the applied electric field using the variable voltage DC power supply 2o.

Figure 3 shows changes in the supply reel tape radius, brake torque, and pack tension. The tape radius of the supply reel decreases as the tape runs, as shown in the figure, but if the brake torque applied to the supply reel shaft is changed as shown in the figure using the brake device, the pack tension will decrease from the beginning of the tape. It becomes constant at end 1. At this time, in order to control the braking force according to changes in the tape radius, the tape radius is calculated from the reel stand rotational speed detection device 32 shown in FIG. 2 and the rotational speed obtained from the detection device, and the corresponding braking force is calculated. an arithmetic device 34 that outputs a control signal for giving
It is equipped with The control number 1N from the arithmetic unit is a variable voltage DC type control input to the source 20 to control the applied electric field and thereby control the braking force.

In this way, a pack tension adding device that achieves good head touch and a stable running system can be realized using the piezoelectric brake device of the present invention.

This piezoelectric brake device is used not only for adding pack tension, but also when a relatively small braking force is required or when it is necessary to precisely control the braking force.
It is possible to take advantage of these characteristics and apply them. Furthermore, the braking force can be increased by using a plurality of piezoelectric elements.

When controlling the brake force, the control signal is a voltage, so it has the advantage of being relatively easy to control using an electric circuit, and since the piezoelectric element is a dielectric, almost no current flows, reducing power consumption. It has the advantage of being small. Furthermore, since the piezoelectric element directly converts an electrical quantity into a mechanical quantity, it has the advantage that it has a small number of parts and can realize a simple brake device.

As described above, the brake device of the present invention has a simple structure and can apply a relatively small amount of brake, and the braking force can be precisely controlled, it is easy to control electrically, and it consumes little power. In this respect, the bimorph structure makes it easier to control braking force, which is an advantage that conventional brake devices do not have. In addition, by applying this piezoelectric brake device to a pack tension adding device, it is possible to control the braking force simply and precisely, and as a result, the pack tension is kept constant, improving sound quality with good head touch and stabilizing tape running performance. This has an unprecedented effect in that the performance improvement I- can be achieved.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a piezoelectric element showing an embodiment of the present invention, FIG. 2 is a configuration diagram of a device according to an embodiment of the present invention, and FIG. 3 is an explanatory diagram of a cross-section tension control. 11...braking member, 18.18'...supporting member, 2o...variable voltage DC power supply, 26...
...Brake drum, 28...Brake shoe.

Claims (1)

[Scope of Claims] (1) A braking member made of a material exhibiting a piezoelectric effect, means for applying an electric field to this member in order to cause the braking member to expand and contract based on the piezoelectric effect, and a braking member comprising: A braking member that rotates or linearly moves with a support member that supports the braking member, and a means for associating the two so that a brake is applied to the braking member when the braking member is distorted, and an electric field is applied to the braking member by the electric field applying means. A braking device characterized in that the braking member, which is strained by a piezoelectric effect, applies a brake to the braked member by frictional force. (2) The brake device according to claim 1, characterized in that the applied electric field control means changes the applied electric field strength to change the frictional force exerted by the brake part iC, thereby enabling brake control. . (3) The brake device according to claim 1 or 2, wherein the braking member has a bimorph structure. (4) The brake device according to claim 1 or 2 or 3.iJI, which is used as a means for applying pack tension to the magnetic tape of a tape recorder. (5) Magnetic tape supply side 5. The brake device according to claim 4, wherein means for detecting the tape radius of the reel makes it possible to control pack tension in accordance with changes in the tape radius.