Torque limiter

Abstract

To provide a torque limiter which is good in workability for assembly to achieve lower cost.SOLUTION: A torque limiter 1 includes an inner ring member 10 on the outer peripheral face of which a coil spring 40 is wound and held, and an outer ring member 30 arranged to cover the inner ring member 10, the inner ring member 10 having a head member 50 mounted at one axial end so as to be rotated integrally with the inner ring member 10, the coil spring 40 being formed on one axial end side of the inner ring member 10 and arranged between a flange part 12 opposed to the inner face of the outer ring member 30 and a head member 50, the head member 50 being held in an opening of the outer ring member 30 slidably with the outer ring member.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a torque limiter that limits a load torque accompanying rotation transmitted in one direction or rotation transmitted in two directions to a predetermined value or less. [Background technology]

[0002] Generally, a torque limiter is a device that blocks the transmission of torque exceeding a certain value when a large torque exceeding a certain value acts on a rotation transmission mechanism, and is installed, for example, on the roller portion of a paper transport mechanism (paper feed mechanism) of an electronic information device such as a printer or copier. Such torque limiters include a contact type that obtains rotational torque by mechanical friction, and as disclosed in Patent Document 1, for example, a known type includes an inner ring member (also called a bobbin), a coil spring that is press-fitted on the outer periphery of the inner ring member, and an outer ring member (also called a case member or housing) that fixes one end of the coil spring and covers the inner ring member.

[0003] In addition to limiting the load torque associated with rotation transmitted in one direction, torque limiters are also known that limit the load torque associated with rotation transmitted in both directions, as disclosed in Patent Document 2, for example. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2023-73602 [Patent Document 2] Patent Publication No. 2023-73603 Summary of the Invention [Problem to be solved by the invention]

[0005] The coil spring wound around the inner ring member is restrained from moving in the axial direction by contacting with a flange integrally formed on one end side of the inner ring member. For this reason, as shown in FIG. 2 of Patent Document 1, the coil spring needs to be inserted from the other end side of the inner ring member and installed at a predetermined position, and the distance from the insertion position to the installation position is long, which makes the installation of the coil spring difficult. In addition, when the inner ring member to which the coil spring is attached is inserted into the outer ring member, it is difficult to determine the insertion position where the end of the coil spring contacts and is fixed against the fixing portion (locking portion) formed on the inner surface of the outer ring member, making the installation difficult. Furthermore, the flange formed on the inner ring member slides against the outer ring member, and further, in a configuration in which a rubber roller is attached to the outer ring member, a radial load is applied from the rubber roller, so that wear is likely to occur at the contact portion between the flange and the outer ring member. In this case, if the outer ring member is made of a material that does not cause wear, the cost will be high.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a torque limiter which is easy to assemble and can be manufactured at low cost. [Means for solving the problem]

[0007] In order to achieve the above object, the torque limiter according to the present invention comprises an inner ring member having a coil spring wound around its outer peripheral surface, and an outer ring member arranged to cover the inner ring member, and an end of the coil spring wound around the inner ring member is fixed to the outer ring member, so that a predetermined torque is generated between the inner ring member and the outer ring member by the frictional force between the inner ring member and the coil spring while limiting the torque to a predetermined value or less. The inner ring member is provided with a head member attached to one axial end thereof so as to rotate integrally with the inner ring member, the coil spring is formed on one axial end of the inner ring member and is arranged between a flange portion facing the inner surface of the outer ring member and the head member, and the head member is held in an opening of the outer ring member so as to be slidable with the outer ring member.

[0008] According to the above-mentioned configuration, the coil spring can be assembled from a short distance toward the flange portion formed on one end side in the axial direction of the inner ring member before the head member is attached to the outer ring member, so that the distance to the assembly position of the coil spring is shortened and the assembly workability is improved. In addition, when the inner ring member to which the coil spring is assembled is assembled (inserted) into the outer ring member, the fixing portion for fixing the end of the coil spring formed on the outer ring member becomes easy to see, so that the end of the coil spring can be easily aligned and assembled. Furthermore, since the head member is attached separately from the inner ring member, even if the inner ring member is made of an expensive material that is resistant to wear, the head member can be made of a low-cost general material together with the outer ring member, and wear due to sliding friction between the head member and the outer ring member can be reduced. Effect of the Invention

[0009] According to the torque limiter of the present invention, by attaching a head member to the end of the inner ring member, it becomes easy to assemble the coil spring and the inner ring member to which the coil spring is attached to the outer ring member. In addition, by providing the head member, the head member and the outer ring member can be made of general materials (general resin materials, etc.), which makes it possible to reduce costs. [Brief description of the drawings]

[0010] [Figure 1] 3A is a cross-sectional view showing one configuration example of a torque limiter according to the present invention, FIG. 3A being a cross-sectional view taken along the longitudinal direction, FIG. 3B being a left side view, and FIG. [Diagram 2] FIG. 4 is a diagram showing a portion of the inner ring member into which a coil spring is assembled. [Diagram 3] FIG. 3 is an enlarged view of a main part of the configuration shown in FIG. 2. [Figure 4] 13A and 13B are diagrams showing modified examples of the head member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A torque limiter according to an embodiment of the present invention will now be described with reference to the accompanying drawings. 1(a) to 1(c) show an example of the configuration of a torque limiter according to the present invention.

[0012] The torque limiter 1 of this embodiment comprises a cylindrical inner ring member (also referred to as a bobbin) 10, a cylindrical outer ring member (also referred to as a case member or housing) 30 that is attached so as to cover the inner ring member 10, and a coil spring 40 that is wound and held on the outer circumferential surface of the inner ring member 10.

[0013] A head member 50 is attached to one axial end (the right end in FIG. 1) of the inner ring member 10 so as to rotate integrally with the inner ring member 10. This head member 50 is attached so as to close the opening at one end of the outer ring member 30 after the inner ring member 10 to which the coil spring 40 is assembled is inserted and fixed into the outer ring member 30 from one axial end (the right end in FIG. 1).

[0014] The torque limiter of this embodiment is configured as a bidirectional type that limits the load torque accompanying rotation in both directions to a predetermined value or less (bidirectional torque limiter). Therefore, the coil spring 40 extends in a spiral shape with adjacent windings in close contact with each other, and one end 40a and the other end 40b are each locked to a fixing portion formed on the inner surface of the outer ring member 30 to prevent rotation.

[0015] In this case, both ends 40a, 40b of the coil spring 40 are engaged with two of a plurality of ribs 31 formed on the inner surface 30a of the outer ring member 30 so as to extend axially at a predetermined interval along the circumferential direction, so that the coil spring 40 is prevented from rotating only in the direction in which it loosens.

[0016] In this configuration, a predetermined torque is generated between the inner ring member 10 and the outer ring member 30 in both rotational directions by the frictional force between the inner ring member 10 and the coil spring 40, while the torque is limited to a predetermined value or less. Specifically, when a clockwise or counterclockwise rotation is applied from the outer ring member 30 side, slip occurs when a torque of a certain value or more is applied to each rotation direction, and power transmission is prevented.

[0017] That is, for any load torque in either direction of rotation, when the load torque is below the respective torque limit value, the torque is transmitted (ON state), but when a load torque exceeding the torque limit value is applied, power transmission by rotation is prevented (OFF state). The torque for turning off the power transmission can be adjusted by the structure of the coil spring 40 (for example, the spring structure such as the wire diameter, winding diameter, and number of windings).

[0018] The coil spring 40 described above may be a one-way coil spring, and one of the ends 40a, 40b may be a one-way torque limiter that is engaged to prevent rotation with the rib 31 of the outer ring member 30. In this configuration, when a rotational torque of a certain value or more is generated in one direction from the outer ring member 30, the inner ring member and the coil spring are caused to slide (power transmission is turned off between the inner ring member 10 and the outer ring member 30).

[0019] That is, when the outer ring member 30 rotates in one direction, the one-way coil spring is tightened, and power transmission between the outer ring member 30 and the inner ring member 10 is turned on. When the outer ring member 30 rotates in the other direction, the one-way coil spring expands in the radial direction (loosens), and when the rotational force becomes large enough to exceed a predetermined torque, slippage occurs between the outer peripheral surface of the inner ring member 10 and the inner surface of the one-way coil spring attached thereto, and power transmission is turned off.

[0020] In such a one-way torque limiter, rotation in one direction is always in a power transmission state, and when a certain torque is applied to rotation in the reverse direction, slippage occurs between the inner ring member 10 and the outer ring member 30, and the power transmission is turned off. Incidentally, even in such a one-way torque limiter, the torque at which the power transmission is turned off can be adjusted by the spring structure of the coil spring 40.

[0021] The coil spring 40 of this embodiment is formed on one axial end of the inner ring member 10 and is disposed between the flange portion 12 facing the inner surface 30a of the outer ring member 30 and the head member 50.

[0022] The flange portion 12 is configured in an annular shape, and its outer diameter is formed to be slightly smaller than the inner surface 30a of the outer ring member 30. In addition, the inner ring member 10 on the opening side of the flange portion has a straight portion so that a coil spring 40 can be disposed therein. That is, the coil spring 40 is disposed on this straight portion, and its ends 40a, 40b are engaged with the rib 31 of the outer ring member 30 to prevent rotation, thereby generating a predetermined torque between the inner ring member 10 and the outer ring member 30 while limiting the torque to a predetermined value or less.

[0023] The coil spring 40 is pre-assembled to the inner ring member 10, and the inner ring member with the coil spring 40 assembled thereto is assembled (inserted) into a predetermined position in the outer ring member 30. In this case, a plurality of ribs 30d are integrally formed on the inner surface 30a of the outer ring member 30 so as to extend in the axial direction at predetermined intervals in the circumferential direction, and when the inner ring member 10 is inserted into the outer ring member 30, the flange portion 12 of the inner ring member abuts against the end faces 30d' of the ribs 30d, thereby positioning the inner ring member in the axial direction.

[0024] The head member 50 of this embodiment is formed in a substantially cap-like shape, and an annular recess 51 is formed on the axial inner surface side of the head member 50, into which the opening edge 10A of the cylindrically formed inner ring member 10 is fitted. The opening edge 10A fits into the annular recess 51, and the head member 50 is fixed to one axial end of the inner ring member 10. The head member 50 also includes an annular protrusion (flange) 52 that fits circumferentially slidably against the inner surface 30a of the outer ring member 30.

[0025] A plurality of protrusions 33 (three at intervals of approximately 120° in this embodiment) are formed at regular intervals on the inner surface on the opening side of the outer race member 30. Each protrusion 33 is formed to a size and shape that allows the annular protrusion 52 of the head member 50 to overcome it, and when the head member 50 is press-fitted into the opening 30b of the outer race member 30 and the annular protrusion 52 overcomes each protrusion 33, the head member 50 is held slidably (slidably in the circumferential direction) within the opening 30b of the outer race member 30 and is coupled to the end of the inner race member 10.

[0026] The head member 50 has an annular protrusion 55 that restricts the axial movement of the coil spring. When the head member 50 is held on the end of the inner ring member 10, the wound end (head side end face) of the coil spring 40 abuts against this annular protrusion 55 to restrict the axial movement of the coil spring 40, and is formed in an annular shape so as to protrude in the axial direction.

[0027] Further, a step 13 for receiving a wound end (an end on the flange side) of the coil spring 40 is formed on the opening side of the flange portion 12 of the inner ring member 10. That is, the coil spring 40 is disposed in the straight portion between the annular protrusion 55 of the head member 50 and the step 13 of the inner ring member 10.

[0028] In this way, by providing annular protrusions 55 on the head member 50 at both ends of the coil spring and providing a step 13 on the end side of the inner ring member 10, the contact conditions in the thrust direction of the coil spring (sliding of the coil spring) become the same, making it possible to reduce the torque difference in both directions.

[0029] In this case, the region L1 where the coil spring 40 is disposed (the distance between the annular projection 55 and the step 13 of the inner ring member 10) is formed to be longer than the spring length L2 of the coil spring 40, but if the distance L1 is made too long, it becomes difficult for the torque to stabilize immediately when the rotation speed is changed. For this reason, in a bidirectional torque limiter such as that of this embodiment, it is preferable to set the distance L1 to 0.5 mm or less (L1-L2≦0.5 mm) so that the torque stabilizes quickly when the rotation speed is changed.

[0030] The torque limiter (bidirectional torque limiter) of this embodiment is installed in the roller portion of a paper transport mechanism used in printers, copiers, etc. For this purpose, a rubber roller 70 is integrally attached to the outer peripheral surface of the outer ring member 30. The outer ring member 30 also has a sliding portion 36 that comes into contact with the outer surface of the inner ring member 10 on the other axial end side.

[0031] As described above, since the roller-integrated torque limiter receives radial load, it is preferable to set the contact length L3 of the sliding portion 36 to a certain length or more, specifically, 2.5 mm or more, in order to reduce wear due to the radial load (prevent rattling due to diameter expansion).

[0032] In addition, the torque limiter of this embodiment is configured as a bidirectional torque limiter, which reduces the torque difference depending on the rotation direction and quickly stabilizes the torque when the rotation direction changes. That is, as described above, the torque difference can be reduced by configuring the conditions (contact conditions) regulated between one winding end of the coil spring 40 and the annular protrusion 55 and between the other winding end and the step 13 to be the same. Also, as described above, the axial movement of the coil spring 40 when changing the rotation direction is made as small as possible (L1-L2≦0.5 mm), so that the torque is quickly stabilized when the rotation direction changes.

[0033] As shown in Fig. 3, the facing surface 55a of the annular protrusion 55 facing the coil spring 40 is configured to be inclined substantially parallel to the winding end 40A of the coil spring 40 (inclined in a spiral shape similar to the winding of the coil spring). In this case, as shown by the solid line in Fig. 3, if the facing surface 55a of the annular protrusion 55 is not inclined (intersecting with the helical angle of the coil spring), the winding end of the coil spring 40 and the edge R of the annular protrusion 55 will be in point contact, and the lubricant will not be able to enter, which causes abnormal noise and stick-slip (chatter). In this embodiment, the inclination of the facing surface 55a reduces the point contact and allows the lubricant to enter, thereby preventing the occurrence of abnormal noise and chatter.

[0034] The inclination angle α depends on the configuration of the coil spring 40, but if the spiral angle of the coil spring 40 relative to the axial direction is θ, the inclination angle α should be greater than 0° and less than 3° with respect to θ (0°).

[0035] It is also preferable that the above-mentioned inclined surface is formed on the side of the step 13 that receives the opposite end of the coil spring 40. That is, by configuring the opposing surface 13a (see FIG. 2) of the step 13 that faces the coil spring 40 to have an inclination that is approximately parallel to the wound end of the coil spring 40, it is possible to prevent the occurrence of abnormal noise and stick-slip.

[0036] Next, the assembly process of the above-mentioned torque limiter 1 will be described. First, the coil spring 40 is assembled at a predetermined position in the inner ring member 10. The assembly of the coil spring 40 is performed in a short straight section near the opening of the inner ring member 10, which makes it easy to assemble the coil spring 40. Then, in this state, the inner ring member 10 is inserted axially into the outer ring member 30. In FIG. 1, the inner ring member 10 is inserted from the opening 30b side of the outer ring member 30. As the inner ring member 10 is inserted into the outer ring member 30, the flange portion 12 comes into contact with the end face 30d' of the rib 30d of the outer ring member 30, and the inner ring member 10 is positioned in the axial direction.

[0037] During the above-mentioned operation of inserting the inner ring member 10 into the outer ring member 30, the ends 40a, 40b of the coil spring 40 assembled to the inner ring member 10 and the rib 31 of the outer ring member 30 can be visually confirmed, making it easier to grasp the assembly position (insertion position) relative to the rib 31 of the outer ring member 30 and facilitating the assembly work.

[0038] After the inner race member 10 is assembled into the outer race member 30, the head member 50 is attached to the opening 30b of the outer race member 30. At this time, the inner race member 10 serves as a guide for centering, so that the head member 50 can be attached smoothly. Then, the annular recess 51 formed on the axially inner side of the head member 50 fits into the opening edge 10A of the inner race member 10, and the annular protrusion 52 of the head member 50 rides over the protrusion 33 formed on the inner surface on the opening side of the outer race member 30, so that the head member 50 is held circumferentially slidably in the opening 30b of the outer race member 30 and is coupled to the end of the inner race member 10.

[0039] In the assembly operation described above, the inner ring member 10 to which the coil spring 40 is attached is assembled, and is performed on the opening side of the outer ring member 30 before the head member 50 is fixed, so that accurate positioning and assembly can be performed quickly.

[0040] In the above-described configuration, the head member 50 can be integrally formed from a general-purpose resin such as polyacetal. That is, by forming the head member 50 from such a general-purpose resin, it is possible to prevent wear of the outer ring member 30. Moreover, the outer ring member 30 may also be formed from the same general-purpose resin as the head member 50 in order to reduce costs.

[0041] Since the coil spring 40 slides on the inner ring member 10, it is preferable to use a high-strength resin material, such as polyether ether ketone or polyphenylene sulfide as a base material, to which a filler containing carbon fiber, polytetrafluoroethylene, or graphite is added. This improves the durability (wear resistance) and sliding characteristics of the inner ring member 10.

[0042] 4(a) and (b) are diagrams showing modified examples of the head member. As described above, in a structure in which the head member 50 is made a separate structure from the inner ring member 10 and the outer ring member 30 and the inner ring member 10 to which the coil spring 40 is attached is assembled into the outer ring member 30 and then attached, it is possible to give the head member 50 various functions by adapting to mounting conditions, the addition of a transmission mechanism, etc., without affecting the function of the torque limiter.

[0043] For example, the head member 50A shown in Fig. 4(a) shows an example (gear type) in which a gear 58 is formed on the portion protruding in the axial direction. By forming such a gear 58, it becomes possible to arrange a torque limiter in the power transmission path. In addition, by integrally forming the gear 58 from a general resin, it becomes possible to effectively prevent wear of the mating gear.

[0044] The head member 50B shown in Fig. 4(b) has a U-shaped groove 59 formed in the portion protruding in the axial direction. In this configuration, a shaft (not shown) provided with a locking pin is inserted into the inside of the inner ring member 10, and the two can be fixed to prevent rotation. As a result, the shaft and the inner ring member 10 are fixed in rotation to transmit power.

[0045] Although the embodiment of the present invention has been described above, the present invention is not limited to the configuration of the above embodiment and can be modified in various ways. For example, the materials of construction of the inner ring member 10, the outer ring member 30, and the head member 50 are not limited. In addition, the shape of the head member 50 and the method of fixing it to the outer ring member 30 can also be modified as appropriate. [Explanation of symbols]

[0046] 1 Torque limiter 10 Inner ring member 30 Outer ring member 40 Coil spring 50, 50A, 50B Head parts 70 Rubber Roller

Claims

1. A torque limiter comprising an inner ring member having a coil spring wound around its outer peripheral surface, and an outer ring member disposed to cover the inner ring member, wherein an end of the coil spring wound around the inner ring member is fixed to the outer ring member, thereby generating a predetermined torque between the inner ring member and the outer ring member by friction between the inner ring member and the coil spring while limiting the torque to a predetermined value or less, a head member is attached to one axial end of the inner ring member so as to rotate integrally with the inner ring member; the coil spring is formed on one axial end side of the inner ring member and is disposed between a flange portion facing an inner surface of the outer ring member and the head member, The head member is held in the opening of the outer ring member so as to be slidable with the outer ring member. A torque limiter characterized by:

2. the head member is connected to an end of the inner ring member and has an annular protrusion that slidably fits with an inner surface of the outer ring member; The torque limiter as described in claim 1, characterized in that the annular protrusion overcomes protrusions formed in multiple locations on the inner surface of the end portion of the outer ring member, thereby holding the head member within the opening of the outer ring member so as to be slidable with the outer ring member.

3. 2. The torque limiter according to claim 1, wherein the head member has an annular protrusion that restricts axial movement of the coil spring.

4. 4. The torque limiter according to claim 3, wherein a surface of the annular projection facing the coil spring is inclined so as to be substantially parallel to a wound end portion of the coil spring.

5. The torque limiter according to claim 3, characterized in that a dimension L1 of the area in which the coil spring is arranged between a flange portion formed on one axial end side of the inner ring member and the annular protrusion is set so that L1-L2≦0.5 mm relative to a spring length L2 of the coil spring.

6. A rubber roller is attached to the outer peripheral surface of the outer ring member, the outer ring member has a sliding portion that contacts the inner ring member at the other end side in the axial direction, 2. The torque limiter according to claim 1, wherein the contact length of the sliding portion is set to 2.5 mm or more.

7. a flange portion of the inner ring member that slides against the inner surface of the outer ring member is formed with a step that receives a wound end portion of the coil spring, 2. The torque limiter according to claim 1, wherein a surface of the step facing the coil spring is inclined so as to be substantially parallel to a wound end of the coil spring.

8. 2. The torque limiter according to claim 1, wherein the head member is formed with a gear portion for transmitting power.

9. 9. The torque limiter according to claim 1, wherein the head member is integrally formed from a general-purpose resin.

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