JP4349864B2 - Torque limiter - Google Patents

Description

  The present invention relates to a torque limiter that transmits torque by a hysteresis torque generated between a permanent magnet and a hysteresis material.

  A torque limiter using hysteresis torque is used in a sheet feeding / separating device such as a copying machine, a printer, and a facsimile, and a reel base driving device of an audio / video device.

  FIG. 1 shows a torque limiter disclosed in JP-A-6-235447 (Patent Document 1). The torque limiter 3 is applied to a paper feeding friction roller (rubber roller) 1.

  The torque limiter 3 includes a first rotating body 8 having a cylindrical outer peripheral portion 7 and a second rotating body 10 having a cylindrical inner peripheral portion 9. The 2nd rotary body 10 consists of a bottomed cylindrical main-body part 10a and the cover body 10b. The torque limiter 3 is assembled in the procedure of inserting the first rotating body 8 into the main body portion 10b of the second rotating body 10 and then attaching the lid 10b.

  The first rotating body 8 is connected to a drive mechanism (not shown) through a metal shaft 11, and the second rotating body 10 is fitted to the rubber roller 1 at the bottom. The first rotating body 8 and the second rotating body 10 are installed on the same axis, are positioned in the radial direction and the axial direction by contact with the sliding portions 12a and 12b, and can rotate with respect to each other. ing.

A cylindrical permanent magnet 13 is fixed to the cylindrical outer peripheral portion 7 of the first rotating body 8 with an adhesive. A cylindrical semi-hard magnetic material (hysteresis material) 5a is fixed to the cylindrical inner peripheral portion 9 of the second rotating body 10 by press-fitting. There is a predetermined gap G between the cylindrical permanent magnet 13 and the cylindrical semi-hard magnetic body 5a, and torque is transmitted between the two rotating bodies by a hysteresis torque generated between the two.
JP-A-6-235447 (FIG. 1)

  In the torque limiter disclosed in Japanese Patent Application Laid-Open No. 6-235447, in order to prevent the displacement of the first rotating body 8 in the axial direction, the first rotating body 8 is stopped by a stop at the sliding portions 12a and 12b. The vertical movement is restricted.

  In order to realize a smooth rotational movement, the central axis of the cylindrical semi-hard magnetic body 5a, the central axis of the upper sliding portion 12a, and the central axis of the lower sliding portion 12b should be completely matched. It is. However, in an actual product, there is a slight misalignment between the above three locations due to dimensional errors that are unavoidable in manufacturing.

  Due to such misalignment, the first rotating body 8 tries to align the central axis of the upper sliding portion 12a with the central axis of the semi-hard magnetic body 5a during operation, or the lower sliding portion. An attempt is made to match the central axis of 12b with the central axis of the semi-hard magnetic body 5a. For this reason, the first rotating body 8 rotates while rolling, so that the first rotating body 8 intermittently comes into contact with the stop portions of the upper and lower sliding portions 12a and 12b, and generates a rattling sound.

  Specifically, at the time of slip (a state where the first rotating body 8 is fixed and the second rotating body 10 rotates, or a state where the second rotating body 10 is fixed and the first rotating body 8 rotates), a semi-hard magnetic body The bearing 10c of the second rotating body 10 and the shaft 8a of the first rotating body 8 come into contact with each other due to the attractive force between the 5a and the permanent magnet 13, and a cogging (sounding noise) is generated at each rotation period, and a jam (paper jam) ) Or double feed.

  An object of the present invention is to provide a highly reliable torque limiter that does not generate cogging.

  The torque limiter according to the present invention has a first rotating body having a cylindrical outer peripheral portion and a cylindrical inner peripheral portion facing the cylindrical outer peripheral portion, and is coaxial with the first rotating body with respect to each other. A second rotating body provided rotatably, a cylindrical permanent magnet fixed to one of the cylindrical outer peripheral portion and the cylindrical inner peripheral portion, and the other of the cylindrical outer peripheral portion and the cylindrical inner peripheral portion A cylindrical hysteresis material that generates a hysteresis torque between the cylindrical permanent magnet and the permanent magnet, and a suction force between the cylindrical permanent magnet and the cylindrical hysteresis material opposed to each other in the circumferential direction. Suction force enhancing means for locally strengthening in the region.

  According to the present invention having the above-described configuration, the first rotating body is always biased toward the region where the suction force is strong and comes into contact with the second rotating body by the action of the suction force increasing means. The backlash inside can be prevented. Therefore, the first rotating body does not vibrate and stable characteristics can be obtained.

  In one embodiment, the suction force increasing means is provided in one hysteresis torque generating element fixed to the cylindrical inner peripheral portion of the second rotating body. For example, one hysteresis torque generating element is a cylindrical hysteresis material. In this case, the cylindrical hysteresis member has a deformed portion capable of locally increasing the suction force in a part of the circumferential direction.

  One example of the deformed portion is a convex portion protruding radially inward from one axial end of the cylindrical hysteresis member. Another example of the deformed portion is a thick portion in which the thickness of the cylindrical hysteresis material is increased. The thickness of the thick part may gradually increase from one end in the axial direction toward the other end.

  Still another example of the deformed portion is a portion in which the axial length of the cylindrical hysteresis member is locally increased.

  In another embodiment, the attractive force enhancing means is provided on a cylindrical permanent magnet. For example, the attractive force enhancing means is a magnetic force enhancing unit that increases the magnetic force of a partial region in the circumferential direction of the cylindrical permanent magnet.

  FIG. 2 is a cross-sectional view showing an embodiment of the present invention. The torque limiter shown in the figure includes a first rotating body 21 having a cylindrical outer peripheral portion, a second rotating body 22 provided coaxially with the first rotating body 21 and rotatable relative to each other, and the first rotating body 21. A cylindrical permanent magnet 23 fixed to the outer peripheral portion and a cylindrical hysteresis member 24 fixed to the inner peripheral portion of the second rotating body 22 are provided. Torque between the first rotating body 21 and the second rotating body 22 is transmitted by the hysteresis torque generated between the cylindrical permanent magnet 23 and the cylindrical hysteresis member 24.

  The second rotating body 22 includes a lower housing member 22b composed of a bottom wall and a cylindrical wall with an open upper end, and an upper housing member 22a attached to the upper end of the cylindrical wall. The first rotating body 21 has a center hole 25 through which a shaft (not shown) is inserted.

  In the illustrated embodiment, the first rotating body 21 includes a columnar central projecting portion 30 having an enlarged diameter in a substantially central region. The lower housing member 22 b of the second rotating body 22 includes a cylindrical standing wall 31 that surrounds a lower portion of the first rotating body 21. The cylindrical standing wall 31 supports the central overhanging portion 30 from below and is in sliding contact with the outer peripheral portion of the lower portion of the first rotating body 21.

  The torque limiter 20 includes attraction force increasing means for locally increasing the attraction force between the cylindrical permanent magnet 23 and the cylindrical hysteresis member 24 that are circumferentially opposed in a partial region in the circumferential direction. . In the illustrated embodiment, the suction force increasing means is provided on the hysteresis member 24 that is a hysteresis torque generating element fixed to the cylindrical inner peripheral portion of the second rotating body 22. Specifically, the cylindrical hysteresis member 24 has a deformed portion capable of locally increasing the suction force in a part of the circumferential direction.

  FIG. 3 shows a cross section of the hysteresis member 24 taken along line AA in FIG. As is apparent from this figure, the hysteresis member 24 includes a convex portion 24a that protrudes radially inward from one end in the axial direction. The convex portion 24a faces the lower end surface of the permanent magnet 23 with a predetermined gap.

FIG. 4 is an enlarged view of a contact portion between the central projecting portion 30 of the first rotating body 21 and the cylindrical standing wall 31 of the second rotating body 22. In the region where the convex portion 24a exists, the attractive force between the permanent magnet 23 and the hysteresis material 24 is locally strong. Therefore, as indicated by an arrow D in FIG. 4, the first rotating body 21 is always urged toward a region having a strong suction force and contacts the second rotating body 22. Specifically, the cylindrical standing wall 31 and the central overhanging portion 30 are in contact with each other in a region surrounded by a broken line B, and the cylindrical standing wall 31 and the outer peripheral portion of the lower portion of the first rotating body 21 are in contact with each other in a region surrounded by a broken line C. .

In this way, play during rotation of the first rotating body 21 can be prevented. Accordingly, the first rotating body 21 does not vibrate, and stable characteristics can be obtained.

  In addition, since a load always acts on a part of the cylindrical standing wall 31 of the lower housing member 22b, a coating or the like may be applied to increase the strength and wear resistance of this part. Since it is not practical to coat a part in the circumferential direction, the coating may be applied to the upper end surface and the entire inner circumferential surface of the cylindrical standing wall 31.

  FIG. 5 shows another example of a hysteresis material having a deformed portion, where (a) is a plan view and (b) is a longitudinal sectional view. The illustrated cylindrical hysteresis member 40 has a thick portion 41 having a partially increased thickness. In the region where the thick portion 41 is located, the attractive force between the permanent magnet and the hysteresis material 40 becomes strong.

  FIG. 6 shows still another example of the hysteresis member having a deformed portion, where (a) is a plan view and (b) is a longitudinal sectional view. The illustrated cylindrical hysteresis member 50 has a thick portion 51 having a partially increased thickness. In this embodiment, the thickness of the thick part 51 is gradually increased from one end in the axial direction toward the other end. That is, since the lower part of the thick part 51 is thicker than the upper part, an attractive force directed obliquely downward acts on the first rotating body. Therefore, the first rotating body comes into local contact with the second rotating body in a stable manner, and the play during rotation is prevented.

  FIG. 7 shows still another example of a hysteresis material having a deformed portion. A permanent magnet 72 is fixed to the first rotating body 71, and the cylindrical hysteresis member 60 surrounds the permanent magnet 72 with a predetermined gap. The hysteresis member 60 has a deformed portion by cutting one end portion in an oblique direction. That is, in this embodiment, the deformed portion is a portion in which the axial length of the cylindrical hysteresis member 60 is locally increased. Since the first rotating body 71 is biased toward the locally elongated portion and further exerts a downward biasing force so as to balance up and down, as a result, the first rotating body 71 is inclined downward (see FIG. 7 is biased toward the lower left). Therefore, the first rotating body comes into local contact with the second rotating body in a stable manner, thereby preventing rattling during rotation.

  As described above, according to the present invention, the first rotating body is always urged toward the region where the suction force is strong and contacts the second rotating body by the action of the suction force increasing means. Prevents backlash during rotation. In this way, there is no occurrence of cogging (sounding noise), and it is possible to prevent the occurrence of defective operations such as jamming and double feeding.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

  For example, unlike each embodiment described above, a hysteresis material may be fixed to the first rotating body, and a permanent magnet may be fixed to the second rotating body. In this case, you may make it provide a deformed part as mentioned above in a permanent magnet. Since the first rotating body that passes through the shaft requires a good rotational balance, it is desirable to avoid providing a deformed portion in the hysteresis torque generating element fixed to the first rotating body. Therefore, it is preferable to provide a deformed portion in the hysteresis torque generating element fixed to the second rotating body.

  The suction force increasing means is not limited to the deformed portion. For example, the attractive force enhancing means may be formed by a magnetic force enhancing part that increases the magnetic force of a partial region in the circumferential direction of the cylindrical permanent magnet.

It is sectional drawing which shows the conventional torque limiter. It is sectional drawing which shows one Embodiment of this invention. It is sectional drawing of the hysteresis material seen along line AA of FIG. It is sectional drawing which expands and shows a part of FIG. It is a figure which shows the other example of a hysteresis material, (a) is a top view, (b) is a longitudinal cross-sectional view. It is a figure which shows the further another example of a hysteresis material, (a) is a top view, (b) is a longitudinal cross-sectional view. It is sectional drawing which shows the further another example of a hysteresis material.

Explanation of symbols

  20 Torque limiter, 21 First rotating body, 22 Second rotating body, 22a Upper housing member, 22b Lower housing member, 23 Permanent magnet, 24 Hysteresis material, 24a Convex part, 25 Center hole, 30 Center overhang part, 31 Cylinder Standing wall, 40 Hysteresis material, 41 Thick part, 50 Hysteresis material, 51 Thick part, 60 Hysteresis material, 71 First rotating body, 72 Permanent magnet.

Claims (9)

A first rotating body having a cylindrical outer periphery;
A second rotating body having a cylindrical inner peripheral portion facing the cylindrical outer peripheral portion and provided coaxially with the first rotating body and rotatable relative to each other;
A cylindrical permanent magnet fixed to one of the cylindrical outer peripheral portion and the cylindrical inner peripheral portion;
A cylindrical hysteresis material that is fixed to the other of the cylindrical outer peripheral portion and the cylindrical inner peripheral portion and generates a hysteresis torque with the permanent magnet;
A torque limiter, comprising: an attraction force increasing means for locally increasing an attraction force between the cylindrical permanent magnet and the cylindrical hysteresis member that are circumferentially opposed in a partial region in the circumferential direction. 2. The torque limiter according to claim 1, wherein the attraction force increasing means is provided in one hysteresis torque generating element fixed to a cylindrical inner peripheral portion of the second rotating body. The one hysteresis torque generating element is the cylindrical hysteresis material,
The torque limiter according to claim 2, wherein the cylindrical hysteresis member has a deformed portion capable of locally increasing a suction force in a part in a circumferential direction. The torque limiter according to claim 3, wherein the deformed portion is a convex portion protruding radially inward from one axial end of the cylindrical hysteresis member. The torque limiter according to claim 3, wherein the deformed portion is a thick portion in which a thickness of a cylindrical hysteresis material is increased. The torque limiter according to claim 5, wherein a thickness of the thick portion is gradually increased from one end in the axial direction toward the other end. The torque limiter according to claim 3, wherein the deformed portion is a portion obtained by locally increasing the axial length of the cylindrical hysteresis member. The torque limiter according to claim 1, wherein the attraction force increasing means is provided on the cylindrical permanent magnet. 9. The torque limiter according to claim 8, wherein the attraction force increasing means is a magnetic force increasing portion that increases the magnetic force of a partial region in the circumferential direction of the cylindrical permanent magnet.

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