JP2008008423A - Torque limiter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate attachment work of a coil spring with respect to an inner ring, in a friction type torque limiter wherein one end of the inner ring inserted into an outer annular member is rotatably supported in the inside of the outer annular member, a coil spring is attached to an outside diameter surface of the inner ring with the prescribed tightening allowance, the other end of the inner ring is inserted into a lid member fitted to an inside diameter surface of the outer annular member, one end of the coil spring is fitted to the outer annular member, and the other end thereof is fitted to the lid member, and the prescribed torque is generated by fastening force of the coil spring. <P>SOLUTION: A tilt guide surface 21 having an end having a minimum outside diameter D is provided on the one end of the inner ring 2 inserted into the outer annular member 1, and the relationship between the minimum outside diameter D and the coil spring 3 in the natural state is as follows; D<C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a torque limiter, and more particularly to an improvement in the assemblability of a friction torque limiter using a coil spring.

  2. Description of the Related Art Conventionally, a friction type torque limiter incorporating a coil spring is attached to a paper feeding unit in an office machine such as a printer or a copying machine in order to add a required torque to a paper feeding roller (Patent Document 1).

In the torque limiter disclosed in the above-mentioned patent document, a coil spring is mounted with a predetermined tightening margin on the outer diameter surface of the inner ring inserted in the outer ring member so as to be relatively rotatable, and one end portion of the coil spring is attached to the outer ring surface. While being engaged with the inside of the ring member, the other end is engaged with the inner surface of the lid member of the outer ring member. When the coil spring is subjected to a diameter expanding action due to the relative rotation of the inner ring and the outer ring member, the binding force on the inner ring is reduced and a constant torque is generated.
Japanese Patent Laying-Open No. 2006-10060 (FIG. 1)

  FIG. 3 attached herewith shows the relationship between the inner ring 23 and the coil spring 22 in the torque limiter. The inner ring 23 is subjected to normal chamfering at one end thereof. The chamfered portion 24 eliminates the corners of the component and makes it difficult to cause a defect or the like, and is usually C0.4 (axial length is 0.4 mm, inclination angle is 45 °). The outer diameter of the inner ring 23 is indicated by A, and the minimum outer diameter of the chamfered portion 24 is indicated by B.

  On the other hand, the coil spring 22 is formed by densely winding a metal wire having a square cross section into a straight shape, and the inner diameter thereof is indicated by C. The inner diameter of the coil spring 22 is increased to A, and the coil spring 22 is attached to the outer diameter surface of the inner ring 23. A-C is the allowance. Since the inner diameter C of the coil spring 22 and the minimum outer diameter B of the chamfered portion 24 are in a relationship of B> C, when the coil spring 22 is attached to the outer diameter surface of the inner ring 23, the above B or A is forcibly applied. It is necessary to assemble while expanding the diameter by applying a radial force exceeding.

  This assembly is an operation that resists spring elasticity and is therefore extremely unstable, and causes deformation such as twisting and falling of the spring. Moreover, since an operator requires very big force, it becomes an increase factor of work man-hours.

  Accordingly, an object of the present invention is to make it possible to easily attach the coil spring 22 to the outer diameter surface of the inner ring 23.

  In order to solve the above-described problems, the present invention provides an outer ring member 1, an inner ring 2 inserted into the outer ring member 1, and a coil spring mounted on the outer diameter surface of the inner ring 2 with a required tightening allowance. 3 and an annular lid member 4 mounted on the inner diameter surface of one end of the outer ring member 1, and the inner end of the inner ring 2 is rotatably supported inside the outer ring member 1. The outer end of the coil spring 3 is exposed to the outside through the lid member 4, and one end of the coil spring 3 is engaged with the inside of the outer ring member 1, and the other end is engaged with the lid member 4. In the torque limiter, the inclined guide surface 21 is formed when the coil spring 3 is pushed into the outer diameter surface of the inner end portion of the inner ring 2, and the minimum outer diameter D of the inclined guide surface 21 is inserted into the coil spring 3. It was set as the structure formed smaller than the internal diameter C of a side end part.

  According to the above configuration, since the end of the coil spring 3 is fitted to the inclined guide surface 21 in a state where the end of the coil spring 3 is in contact with the opposite end of the inner ring 2, the inclination of the inclined guide surface 21 thereafter. The coil spring 3 can be mounted on the outer diameter surface of the inner ring while expanding the diameter of the coil spring 3 by applying a force that is relaxed according to the angle.

  As described above, according to the present invention, when the coil spring is assembled to the inner ring of the torque limiter, the coil spring can be expanded from the beginning while being along the inclined guide surface. The difficulty of expanding the diameter is eliminated, and it can be mounted smoothly. Thereby, abnormal deformation such as twisting or falling of the spring is prevented, and the number of assembling steps can be reduced and the quality of the product can be improved.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  The torque limiter of the embodiment shown in FIG. 1 is mounted with an outer ring member 1, an inner ring 2 inserted into the outer ring member 1 so as to be relatively rotatable, and an outer diameter surface of the inner ring 2 with a required tightening allowance. It comprises a coil spring 3 and an annular lid member 4 mounted on the inner diameter surface of one end of the outer ring member 1.

  The outer ring member 1 is made of plastic, and a shaft hole 5 is formed at one end thereof, and a bearing portion 6 having a larger diameter is formed inside the shaft hole 5. The inner end portion of the inner ring 2 is supported by the bearing portion 6 so as to be concentric with the outer ring member 1 and relatively rotatable. In addition, a spring accommodating portion 8 having a larger diameter is formed inside the bearing portion 6 via a stepped portion 7, and the coil spring 3 mounted on the outer diameter surface of the inner ring 2 is accommodated therein. The spring accommodating portion 8 is opened to the other end portion of the outer ring member 1 while maintaining its inner diameter, and the lid member 4 is fitted to the inner diameter surface of the open end portion.

  The inner ring 2 is formed of a porous sintered oil-impregnated alloy or the like, the inner diameter surface 16 thereof is formed to have the same diameter as the shaft hole 5, and a pair of opposed notches 17 are provided at the ends protruding from the outer ring member 1. It is formed.

  The lid member 4 is formed in an annular shape, and has an engagement rib 9 in the circumferential direction on its outer diameter surface, and the engagement rib 9 is fitted in an engagement groove 10 formed on the inner diameter of the outer ring member 1. Is done. The spring housing portion 8 is closed by the lid member 4, and the outer end portion of the inner ring 2 passes through the inner diameter surface of the lid member 4 and is exposed to the outside.

  The coil spring 3 is formed by a straight coil in which a wire having a square cross section is tightly wound, and a radially outwardly bent portion 11 formed at one end thereof is provided in the step portion 7 of the spring housing portion 8. The engagement protrusion 12 is engaged with the engagement protrusion 12 in the circumferential direction. Further, the bent portion 13 formed at the other end is similarly engaged with the engaging protrusion 14 provided on the inner surface of the lid member 4 in the abutting state. The lid member 4 is fitted with a large frictional force so as not to rotate in a normal state.

  Meanwhile, the inclined guide surface 21 is larger at the inner end portion of the inner ring 2 than the conventional chamfered portion 24 (indicated by reference numeral 24 in FIG. 2 for comparison) (that is, the axial length L is large). Is formed. The minimum outer diameter D of the tip of the inclined guide surface 21 is formed smaller than the inner diameter C of the coil spring 3 (that is, D <C). The difference (A−C) between the inner diameter C of the coil spring 3 and the outer diameter A of the inner ring 2 becomes a tightening allowance, and the size of this tightening allowance is set to be the same as in the conventional case. The axial length L of the inclined guide surface 21 is 0.5 mm to 1.5 mm, and the inclination angle θ is 10 ° to 40 ° (in consideration of the ease of inserting the coil spring 3, it is preferably 10 ° to 30 °. ) Within the range.

  As long as the relationship between the minimum outer diameter D at the tip of the inclined guide surface 21 and the inner diameter C of the coil spring 3 is maintained, the inclined guide surface 21 is C1 (L = 1 mm and θ = 45). Chamfering of (°) to C3 (L = 3 mm and θ = 45 °) may be used.

  The torque limiter of the embodiment is configured as described above, and the shaft 20 inserted through the inner ring 2 and the shaft hole 5 and the inner ring 2 are coupled by a pin 25 that stands on the notch portion 17. The outer ring member 1 is fixed to a frame or the like. When the inner ring 2 integrated with the shaft 20 is rotated relative to the outer ring member 1, the binding force of the coil spring 3 is reduced, and a predetermined torque is generated. The torque limiter generates a predetermined torque with respect to the rotation of the shaft 20 in both directions.

  When assembling, the coil spring 3 is inserted and pushed in from the inner end (end portion on the inclined guide surface 21 side) of the inner ring 2 in advance, and is moved along the inclined guide surface 21 to the outer diameter surface. Then, it inserts in the outer ring member 1, and makes the cover member 4 fit. When the lid member 4 is rotated in the winding direction of the coil spring 3 with an appropriate tool, the engagement protrusion 14 of the lid member 4 is engaged with the bent portion 13 of the coil spring 3 to rotate the coil spring 3. If it does so, the bending part 11 of an other end will be engaged with the engagement protrusion 12, and the coil spring 3 will be stabilized.

(A) Sectional view of the embodiment, (b) Front view of coil spring (A) Enlarged sectional view when attaching a coil spring to the inner ring same as above, (b) Partial enlarged sectional view of (a) figure Partially enlarged sectional view when attaching a coil spring to the inner ring of the conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outer ring member 2 Inner ring 3 Coil spring 4 Lid member 5 Shaft hole 6 Bearing part 7 Step part 8 Spring accommodating part 9 Engaging rib 10 Engaging groove 11 Bending part 12 Engaging protrusion 13 Bending part 14 Engaging protrusion 16 Inner diameter surface 17 Notch 20 Shaft 21 Inclined Guide Surface 22 Coil Spring 23 Inner Ring 24 Chamfer 25 Pin

Claims (2)

  An outer ring member (1), an inner ring (2) inserted into the outer ring member (1), and a coil spring (3) mounted on the outer diameter surface of the inner ring (2) with a required tightening margin; The outer ring member (1) comprises an annular lid member (4) mounted on the inner diameter surface of one end of the outer ring member (1), and the inner end of the inner ring (2) is rotatable within the outer ring member (1). And the outer end portion of the coil spring (3) is exposed to the outside and the one end portion of the coil spring (3) is engaged with the inside of the outer ring member (1). In the torque limiter having the other end engaged with the lid member (4), an inclined guide surface (21) is formed when the coil spring (3) is pushed into the outer diameter surface of the inner end of the inner ring (2). The minimum outer diameter D of the inclined guide surface (21) is equal to the inner diameter C of the coil spring (3) in its natural state. Torque limiter, characterized in that it is formed small.   The torque limiter according to claim 1, wherein the inclined guide surface (21) has an axial length L of 0.5 mm to 1.5 mm and an inclination angle θ of 10 ° to 30 °.

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