JPS584411A - Wire tension controller of scanner - Google Patents

Abstract

PURPOSE:To ensure the smooth supression of the wire vibration, by providing a friction damping member which has a contact with a face of a tension arm in its turning direction. CONSTITUTION:Two friction members 12 are stuck to the inside of a foot end part of a plate spring 13, and these members 12 are pressed to a plane of a tension arm 3, i.e., to a face vertical to the rotary shaft of a roller 21 by the force of the spring 13. The spring constant is set as spring 13> wire 1>tension spring 4, and the spring force is set as the sum of the static friction force of the member 12> spring 4 respectively. A certain amount of tension is applied to the wire 1 while a motor 6 is at pause. When the motor 6 is started, the member 12 retards the working of the arm 3 to suppress the wire vibration.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scanning device that reciprocates and drives a recording head of a printer, a reading head of an image reading device, an exposure optical system of a copying machine, etc. This invention relates to a wire tension adjustment device that automatically adjusts.

Referring to FIG. 1, the wire tension adjustment device generally consists of a movable roller 23. It is composed of a tension arm 3 and a tension coil spring 4 to which this roller shear is pivotally connected. The wire 1 is connected to a fixed guide roller 22, a pulley 5, and a movable roller 21.
A motor 6 is connected to the pulley 5 either directly or indirectly via a reduction gear, and a carriage 7 is fixed to this wire 1. The carriage 7 is movably guided by a guide bar +8t parallel to the axis of the platen 9, and is driven by the motor 6 in forward and reverse rotation and double drive. In the example shown in FIG. 1, a recording head is mounted on the carriage 7.

Since the tension coil spring 4 constantly applies a rotational force in the counterclockwise direction about the fixed shaft 1o to the tension arm 3, a tension equivalent to the tension force of the coil spring 4 is constantly applied to the wire 1.

Problems with this type of tension adjustment device include an increase in the wire tension due to the stationary inertia of the carriage 7 when the wire 1 drive starts, and a corresponding rotation of the tension arm 8, and an increase in the wire tension when the wire 1 drive stops. The wire tension increases due to the kinetic inertia of the tension arm 8, and the tension arm 8 rotates and the wire vibrates accordingly. The rotation of the tension arm 3 lowers the tension on a part of the wire, which may cause the wire to become loose and the wire l to come off the guide roller 22 or the pulley 5.

The vibration of the wire causes speed irregularities in the carriage 7.

Therefore, conventionally, as shown in FIG. 1, a brake shoe 11 is pressed against the side of the center of rotation of the tension arm 3 to suppress the expansion of the fill spring 4. According to this, the brake shoe 11 applies resistance to the rotation of the tension arm 8, and vibrations are suppressed. However, if the pressing force of the shoe 11 is increased in an attempt to sufficiently suppress vibration, the arm 8
Since the rotational resistance becomes large, the load on the motor 6 is large at the start of scanning, and the power of the motor 6 must be increased. As the power increases, the vibration also increases. When the pressing force of the shoe 11 is reduced, the tension arm 3 rotates more easily, and even if the carriage is stopped when the motor 6 is started, the tension arm 8 rotates and loosens the wire, so the load on the motor 6 is small and the motor 6 is started. is smooth, and the power of the motor 6 may be small. However, the vibration is large. As described above, the conventional braking method in which the tension arm 8 is supported by the shoe 11 so as to face each other in the rotational direction cannot obtain a sufficient effect.

The invention disclosed in Japanese Patent Publication No. 56-280 combines a mechanism, such as a tension arm nirachet mechanism, which allows the tension arm to rotate in the high tension direction but prevents it from rotating in the low tension direction. There is.

According to this, since the tension arm is prevented from returning to the low tension direction, vibrations are suppressed to some extent. However, when the wire stretches, the engagement of the ratchet mechanism is determined by the stretched state, so the tension of the wire becomes greater than the spring force of the tension spring when the wire contracts. Since the tension arm cannot rotate in the direction to loosen the wire at the start of scanning, the motor load is large and the motor power must be increased.

An object of the present invention is to smoothly suppress the vibration of the wire without increasing the wire tension or increasing the motor load.

71 In order to achieve the above object, in the present invention, vibrations are damped by pressing a friction member against a surface along the rotational direction of the tension arm, that is, a surface perpendicular to the axis of the roller pivotally connected to the tension arm. According to this, when the wire tension increases at the time of starting the motor, the tension arm rotates in a direction to lower the tension when the tension exceeds the sum of the tensile force of the tension spring and the static friction force of the friction member. As the wire tension returns to its original state, the tension arm rotates in the direction of increasing the tension, but due to the frictional force applied, the rotation speed of the tension arm is low. Therefore, the friction member acts as a delay element with respect to the vibration frequency determined by the spring constant of the tension spring and the weight of the carriage. In other words, it acts as a filter. Therefore, the tension does not become particularly large, and the motor load does not increase substantially.

FIG. 2 shows an embodiment of the present invention. 12 in Figure 2
is a friction member, and 18 is a U-shaped leaf spring. 'Two friction members (one is 12) on the inner and side of the leg end of the leaf spring 18.
are fixed to each other, and these friction members are pushed against the plane of the tension arm 3, that is, by the spring force of the leaf spring 18, that is, the rollers 2.
is pressed against a surface perpendicular to the axis of rotation. Spring constant is leaf spring 18〉.

The relationship is set as wire 1 > tension spring 4,
The spring force is set in the relationship: sum of static friction forces of the members 12 (two pieces)>tension springs 4.

When the motor 6 is stopped, the tension spring 4 is
Because of the relationship of tensile force, a certain tension is applied to the wire l? ing. When the motor 6 is activated and the carriage 7 is driven to the right, the wire tension applied to the tension arm 8 is momentarily reduced, causing the tension arm 3 to rotate counterclockwise. However, when the carriage 7 begins to move rightward, a clockwise rotational force is applied to the tension arm 8, and the tension arm 3 attempts to rotate clockwise. Since the friction member applies a frictional force to the tension arm 8 during these initial vibrations, the response of the tension arm 3 is slow, and the rotation range of the tension arm 3 in the counterclockwise and clockwise directions is narrow. After that, the tension spring 4 and the carriage 7 try to continue vibrating, but since the friction member 12 delays the movement of the tension arm 8, the left-right movement of the vibration is canceled out, and the vibration is ultimately suppressed significantly.

In the above embodiment, the friction member 12 is pressed against the tension arm 3 by the force of the leaf spring 13, but the friction member is made of an elastic material such as rubber or a friction lining coated on the elastic material. may be compressed and supported by a rigid body, and the frictional force may be obtained by the compressive repulsive force of the elastic material.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a conventional wire tension adjustment device, and FIG. 2 is a perspective view showing an embodiment of the present invention. l: Wire 21.2. : Wire guide roller 3: Tension arm 4: Tension spring 5: Pulley 6: Motor 7: Carriage 81, 8 □: □ Guide bar 9 Nibraten lO: Fixed shaft ll Nibrake shoe 12 = Friction member 13: Leaf spring (
spring member)

Claims (1)

[Scope of Claims] (1) A scanning device in which a wire driven by a motor is stretched along a guide bar that guides a carriage; a roller is coupled to the wire, and the roller is mounted on a tension shaft pivoted about a fixed shaft; A wire tension adjustment device in which a spring member is pivotally attached to an arm and combines the tension arm with a spring member that applies a rotational force in the direction of stretching the wire, which is equipped with a friction braking member that comes into contact with a surface along the rotational direction of the tension arm. A wire tension adjustment device for a scanning device, characterized in that: (2) The scanning device according to claim 1, wherein the friction braking member is a combination of a friction member and a spring member that presses the friction member against the tension arm. (3) The friction control member is a combination of an elastic friction member and a rigid support member that supports the elastic friction member.
12. A wire tension adjustment device for a scanning device according to item 11.