JP2002266889A - Torque limiter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bi-directional torque limiter having a simple structure and using an energizing member. SOLUTION: This torque limiter comprises a first shaft rotation around an axis; a cylindrical member externally inserted on the first shaft to be freely relatively rotated around the axis; an energizing member externally inserted on the cylindrical member and energizing the cylindrical member in a radially inward direction; and a second shaft connected to the cylindrical member to be incapable of relatively rotating around the axis. The cylindrical member is adapted to be radially deformed due to energizing force by the energizing member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a torque limiter using a biasing member such as a coil spring, a C-ring or a leaf spring.

[0002]

2. Description of the Related Art Torque limiters, which function effectively in both directions about an axis, are used for various purposes such as a paper feed unit of a printer or a copier. As a conventional bidirectional torque limiter, a powder-type torque limiter is known in which a permanent magnet is provided on each of opposing portions of a drive shaft and a driven shaft, and a powder-like magnetic material is interposed between the opposing portions. . Another type of bidirectional torque limiter is a coil spring type in which a pair of coil springs having opposite winding directions is extrapolated around a drive shaft, and one end of each of the pair of coil springs is locked to a driven shaft. Things exist.

However, since the former powder type torque limiter uses a magnet, the cost is increased, and the magnetic force may affect other members.

On the other hand, in the latter coil spring type, although there is no adverse effect on other members due to magnetic force, it is necessary to provide at least two coil springs. Not
There is a problem that the cost is increased due to an increase in the number of parts and an increase in manufacturing processes.

Further, the coil spring type has a structure in which one end of one coil spring and one end of the other coil spring are locked to a driven shaft, so that a rattling occurs when the rotation direction of the drive shaft is changed. There is also. That is, since one end of each of the two separate coil springs is locked to a single driven shaft, it is necessary to provide a margin in the locking portion between the two coil springs and the driven shaft. Therefore, there is a problem that the torque load is not immediately applied after the rotation direction of the drive shaft is changed.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above prior art, and has as its main object to provide a simple bidirectional torque limiter using a biasing member.

[0007]

In order to achieve the above object, the present invention provides a first shaft which rotates around an axis, and a cylindrical member which is externally rotatable around the first shaft relative to the first shaft. The cylindrical member includes an urging member that is fitted around the cylindrical member and urges the cylindrical member radially inward, and a second shaft that is connected to the cylindrical member so as to be relatively non-rotatable about an axis. A torque limiter configured to be deformable in a radial direction by an urging force of the urging member is provided.

Preferably, the cylindrical member has a slit extending in an axial direction.
Further, the biasing member may be a coil spring.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a torque limiter according to the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal side view of a torque limiter 1 according to the present embodiment. FIG. 2 is an exploded schematic view of the torque limiter 1.

As shown in FIGS. 1 and 2, the torque limiter 1 includes a first shaft 10 that rotates around an axis and the first shaft 10.
A cylindrical member 2 extrapolated to the shaft 10 so as to be relatively rotatable around the axis.
0, and a coil spring 3 externally fitted to the cylindrical member 20
0, and a second shaft 40 connected to the cylindrical member 30 so as not to rotate relatively around the axis. In the following description, an example will be described in which the first shaft 10 is used as a driving member connected to a driving shaft, and the second shaft 40 is used as a driven member connected to a driven shaft. However, it is of course possible to reverse the relationship between the two.

The first shaft 10 is preferably provided with an axial hole 1.
1 so that a drive shaft (not shown) can be inserted through the axial hole 11.
Further, a concave portion 12 for engaging with the drive shaft is formed at one end 10a of the first shaft 10, so that the first shaft 10 surely rotates together with the drive shaft. .

FIGS. 3A to 3C show a side view, a front view and a bottom view of the cylindrical member 20, respectively. As shown in FIG. 3, the cylindrical member 20 includes a hollow main body 21 having an axial hole 22 that receives the first shaft 10, and an axial direction from one end 21 a and the other end 21 b of the main body 21. First extending piece 24 and second extending piece 2 extending outward
5 is provided.

The main body 21 has a slit 23 extending in the axial direction, so that it can expand and contract in the radial direction. That is, the cylindrical member 20 is compressed radially inward when an external force is applied by the slit 23 formed in the main body portion 21, whereby the outer diameter of the axial hole 21 changes. ing.

The slit 23 is, of course,
It is not necessary to be formed over the entire axial direction of the main body,
Various forms are applicable. For example, as shown in FIG. 4, the slit may be a concave portion 23 ′ opened in the end of the main body 21 along the axial direction. In such a case, in order to secure a movable range in the radial direction of the main body 21, a plurality of the concave portions 23 'can be formed along the circumferential direction.

The coil spring 30 is externally fitted to the main body 21 of the cylindrical member 20, and presses the main body 21 radially inward. That is, the first
When the shaft 10 is inserted into the axial hole 21 of the cylindrical member 20, the coil spring 30 presses the cylindrical member 20 radially inward, whereby the first shaft 10 rotates when the first shaft 10 rotates. A frictional force corresponding to the urging force of the coil spring 10 is generated between the outer peripheral surface of the cylindrical member 10 and the inner peripheral surface of the axial hole 21 of the cylindrical member 20. Therefore, the first shaft 1
0 is smaller than the urging force of the coil spring 30, the cylindrical member 20 rotates together with the first shaft 10. When the driving force exceeds the urging force, the first member 10 rotates.
The shaft 10 rotates relative to the cylindrical member 20.

The second shaft 40 is connected to the cylindrical member 20 so as not to rotate relatively around the axis. In the present embodiment, the second shaft 40 is
And a flange portion 42 extending radially inward from the inner peripheral surface of the main body portion 41. The main body 41 has an inner diameter larger than the outer diameter of the coil spring 30. The flange portion 42 is located on the other end side of the main body portion 41 and has a central opening 43 having at least the same diameter as the axial hole 11 of the first shaft 10. The central opening 43 is the first shaft 1
It is provided to prevent interference with a drive shaft (not shown) inserted into the 0 axis hole 11. Further, the flange portion 4
2 is formed with a slit 44 which engages with the second extending piece 25 of the cylindrical member 20, whereby the second shaft 4 is formed.
0 and the cylindrical member 20 cannot be rotated relative to each other. The connection structure between the second shaft 40 and the cylindrical member 20 is not limited to the illustrated form, and various forms are applied.

The torque limiter 1 according to the present embodiment is
Further, a lid member 50 for closing an opening on one end side of the main body 41 of the second shaft 40 is provided. Preferably, the lid member 50 is a ring-shaped member that is elastically fitted into the hollow portion of the main body 41 of the second shaft 40. The lid member 50
A slit 51 that engages with the first extending piece 24 of the cylindrical member 20 can be formed in the first member. Such a lid member 50
By providing the cylindrical member 20, the second member
Detachment from the shaft 40 can be effectively prevented.

Each of the above components can be formed using various materials, but preferably, the first shaft 10, the cylindrical member 20,
The second shaft 40 and the lid member 50 can be made of a resin such as polyacetal, thereby reducing the manufacturing cost. In addition, when it is used for a product having a severe temperature environment, it can be made of metal such as steel.
Further, in the present embodiment, the coil spring 30 is used, but various urging members such as a C-ring and a leaf spring can be used as long as the cylindrical member 20 can be compressed radially inward.

In the torque limiter 1 having such a configuration, the following effects can be obtained in addition to the various effects described above. First, even if the first shaft 10 is rotated in any direction around the axis while using a simple and inexpensive configuration using a biasing member such as a coil spring instead of utilizing magnetic force. Thus, power transmission from the first shaft 10 to the second shaft 40 can be reliably and promptly interrupted in accordance with the rotational torque applied to the first shaft 10.

That is, as shown in FIG. 5, a conventional torque limiter 100 using a coil spring includes a drive-side member 101 connected to a drive shaft and the drive-side member 101.
And a driven-side member 103 engaged with one end 102a of the coil spring 102. When the driving-side member 101 rotates in the direction of arrow S for tightening the coil spring 102, The drive side member 101 and the driven side member 103 rotate together by the fastening force of the coil spring 102, and
When the driving side member 101 rotates in the direction of arrow U to loosen the coil spring 102, the coil spring 1
02, the fastening force to the drive side member 101 is weakened, and the drive side member 101 rotates relative to the coil spring 102.

As described above, the conventional torque limiter 100 having only one coil spring has the same structure as the drive-side member 1.
When 01 rotates in the other direction (the direction of arrow S), a one-way clutch in which power transmission from the driving side member 101 to the driven side member 103 is not interrupted. When the driving-side member 101 rotates in a direction in which the coil spring 102 is loosened (the direction indicated by the arrow U), the conventional torque limiter causes the driving-side member 101 to move relative to the coil spring 102 only after the coil spring 102 is loosened. Do not start relative rotation. Therefore, there is also a problem that the response speed of power transmission cutoff to the driven side member 103 is delayed. Further, as described above, the conventional torque limiter is provided with a coil spring 10
Since the driving-side member 101 starts relative rotation with respect to the coil spring 102 by weakening the fastening force of No. 2, the fastening force of the coil spring fluctuates when shifting from the power transmission state to the power cutoff state. There is also a problem that the setting of the threshold torque becomes difficult.

On the other hand, the torque limiter according to the present embodiment has an effective torque limiter function for bidirectional rotation of the first shaft 10 while having a structure using an urging member such as a coil spring. It can be performed. further,
In the present embodiment, since the power transmission from the first shaft 10 to the second shaft 40 is not interrupted by weakening the fastening force of the urging member, the power transmission interrupt response speed can be increased. Further, in the present embodiment, the fastening force of the urging member does not change even when shifting from the power transmission state to the power cutoff state, so that the threshold torque can be set more accurately.

In addition to the above, in the conventional torque limiter, the coil spring 102 is directly
When the power transmission is interrupted, the drive-side member 101 slides in the circumferential direction with respect to the coil spring 102. Therefore, there is a problem that the lubricating oil applied between the coil spring 102 and the driving-side member 101 moves in the axial direction along the spiral shape of the coil spring, and the lubricating oil is likely to run out. On the other hand, in the present embodiment, since the first shaft 10 is configured so as to contact the cylindrical member 20 instead of the coil spring 30, the running out of the lubricating oil can be effectively prevented. Further, in such a configuration, the contact area between the first shaft 10 and the cylindrical member 20 can be increased, so that the durability can be improved and the threshold torque can be made constant.

There is also a coil spring type torque limiter in which a pair of coil springs having different winding directions are wound around a drive shaft to realize a two-way power transmission cutoff. However, two or more coil springs having different winding directions are provided. Therefore, there is a problem that the manufacturing cost is increased, and further, there is a problem similar to the torque limiter shown in FIG.

[0025]

According to the torque limiter of the present invention,
A first shaft rotating about an axis, a cylindrical member externally rotatable about the axis relative to the first shaft, and a fitting externally fitted to the cylindrical member to bias the cylindrical member radially inward A biasing member, and a second shaft connected to the cylindrical member so as to be relatively non-rotatable about an axis, since the cylindrical member is configured to be deformable in a radial direction by an urging force of the urging member, Although it has a simple structure using an urging member, the power shutoff function can be effectively exhibited in both directions around the axis.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view of an embodiment of a torque limiter according to the present invention.

FIG. 2 is an exploded schematic view of the torque limiter shown in FIG.

3 (a) to 3 (c) are a side view, a front view, and a bottom view of a cylindrical member of the torque limiter shown in FIG. 1, respectively.

FIG. 4 is a side view of a cylindrical member of another embodiment.

FIG. 5 is a diagram showing a conventional torque limiter. FIG. 5A shows a state in which the driven side member is removed,
FIG. 5B shows a state where the driven side member is mounted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Torque limiter 10 1st axis 20 Cylindrical member 23 Slit 30 Coil spring 40 2nd axis

Claims (3)

[Claims] 1. A first shaft that rotates about an axis, a cylindrical member that is externally fitted to the first shaft so as to be relatively rotatable around the axis, and that is externally fitted to the cylindrical member and radially inwards the cylindrical member. A second urging member coupled to the cylindrical member so as to be relatively non-rotatable about an axis;
A shaft, and the cylindrical member is biased by the biasing member,
A torque limiter configured to be deformable in a radial direction. 2. The torque limiter according to claim 1, wherein the cylindrical member has a slit along an axial direction. 3. The torque limiter according to claim 1, wherein the urging member is a coil spring.