JP2003269487A - Overload protecting mechanism and its assembling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a size and costs of an overload protecting mechanism. <P>SOLUTION: A cam 17 having recesses with a constant pitch is formed on inner diameter surface of an outer wheel 2 concentrically engaged with an inner wheel 1. A rolling element 3 is interposed between the cam 17 and the corresponding inner wheel 1. A C-type spring 4 is used as an elastic member for energizing the rolling element 3 for the cam 17. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload protection mechanism in various drive systems for mechanical loads and an assembling method thereof.

[0002]

2. Description of the Related Art In office equipment, home electric appliances, etc. equipped with a drive unit, an overload protection mechanism has been conventionally provided in the device drive unit in order to avoid an accident in which the drive unit is overloaded due to mishandling or the like and the device is damaged. It is generally provided.

A conventional overload protection mechanism is disclosed in, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent No. 321943, a torque limiter is configured by binding a coil spring to an abutting portion of an independent drive shaft, and between the drive shaft and the coil spring when an overload of a certain amount or more acts. It causes slippage and interrupts torque transmission.

Further, as disclosed in JP-A-9-4649, a friction type torque limiter also having a bearing function is interposed between a shaft sleeve and a pulley fitted concentrically, In some cases, when an overload of a certain amount or more is applied, slippage is caused to interrupt the transmission of torque.

[0005]

The overload protection mechanism in which the torque limiter using the coil spring is interposed in the drive shaft has an advantage that the mechanism is simple, but requires a space for mounting the coil spring. However, there is a problem that hinders downsizing of the device. Further, the above-mentioned overload protection mechanism in which the friction type torque limiter is interposed between the shaft sleeve and the pulley is excellent in compactness, but there is a problem that the structure is complicated and the cost becomes high.

Therefore, the present invention is excellent in compactness,
Moreover, it is an object of the present invention to provide an overload protection mechanism having a simple mechanism and a low cost.

[0007]

In order to solve the above-mentioned problems, the present invention provides a recessed cam portion having a constant pitch on the inner diameter surface of an outer ring fitted concentrically with the inner ring. An elastic member is provided between the cam portion and an inner ring corresponding to the elastic member to urge the rolling element to the recessed cam portion on the inner ring, and a predetermined torque is generated by the urging force of the elastic member. In the overload protection mechanism configured as described above, a C-shaped spring is used as the elastic member, the inner ring is provided with a spring accommodating portion concentric with the center thereof, and a required number of window holes are formed on the outer peripheral wall surface of the spring accommodating portion. The rolling element is fitted into the window hole and the recessed cam portion, and each rolling element is retractable by the C-shaped spring which is retractable in the spring accommodating portion and regulates rotation above a certain level. It is configured to be pressed against the portion.

According to the above construction, the inner ring and the outer ring, the rolling element and the C-shaped spring interposed therebetween constitute a torque limiter, and the rolling element is pressed by the C-shaped spring to be fitted into the recessed cam portion. A predetermined torque value is set by. When the load torque is less than the set torque value, torque is transmitted between the inner ring and the outer ring, but if an excessively large load torque is applied, the rolling element will pass over the recessed cam section and the inner ring and outer ring will be transmitted. Is relatively idle,
The torque transmission is cut off. Further, since the rolling elements engaged between the inner ring and the outer ring are pressed against the recessed cam portion by the C-shaped spring, the respective constituent members are not easily separated and are easy to handle.

In the above construction, as a rotation restricting means for the C-shaped spring, a radial restricting wall is provided in a part of the spring accommodating portion, and the opening of the C-shaped spring is provided on the restricting wall with a required expansion / contraction margin. It is possible to adopt a fitted structure. According to this configuration, the rotation range of the C-shaped spring is restricted, so that the C-shaped spring is stable.

A bearing boss portion is provided at one end of the inner ring, and the spring accommodating portion is opened to the end surface side where the bearing boss portion is provided, so that one end surface of the outer ring is rotatable with respect to the bearing boss portion. It is possible to adopt a configuration in which the spring accommodating portion is closed by its one end surface while being fitted. According to this configuration, the bearing portion that supports the outer ring can be configured at the bearing boss portion of the inner ring by a mechanism other than the torque limiter.

Further, it is possible to adopt a construction in which the window hole is provided outside the movement range of the open portion of the C-shaped spring housed in the spring housing portion. With this configuration, it is possible to avoid the inconvenience that the rolling element falls into the separation portion of the C-shaped spring.

Further, it is possible to adopt a structure in which a metal outer ring rolling element is fitted in a large number of recesses provided at a constant pitch on the inner diameter surface of the outer ring, and the recessed cam portion is formed between each outer ring rolling element. . According to this configuration, when an overload is applied,
Since the rolling elements rotate while colliding with the metal outer ring rolling elements one after another, the wear resistance is improved compared to the case of sliding contact with the resin outer ring, and continuous collision noise causes overload on the user. Can be notified.

Further, by adopting a constitution in which the window holes of the inner ring are provided at a plurality of equal positions in the circumferential direction, the C-shaped spring is uniformly compressed at the time of torque interruption, and the urging force to each rolling element is made uniform. be able to.

Further, when the outer ring rolling element is incorporated in the concave portion of the outer ring inner diameter surface as described above, the center point of the concave portion exists inside the concave portion, and the outer ring rolling element is snap-fitted to the concave portion. Can be configured. When the outer ring rolling element is snap-fitted to the recess, a large number of outer ring rolling elements can be held in the outer ring during assembly,
Assembly is improved.

As a method of assembling the above-mentioned overload protection mechanism, the present invention is such that an inner ring fitting portion for fitting the inner ring and an outer ring fitting for fitting the outer ring to the inner diameter surface of an annular jig body. A joint part is formed continuously in the axial direction, a fitting groove of the rolling element is provided on the inner diameter surface of the inner ring fitting part over the entire length, and an assembly jig is used in which a magnet is mounted on the outer surface of the fitting groove, respectively. After the inner ring is fitted to the inner ring fitting portion of the assembly jig, the rolling element is installed and held in the fitting groove by the magnetic force of the magnet, then the C-shaped spring is installed, and the outer ring is further installed. A method was adopted in which the outer ring fitting portion was fitted and then the assembly of the inner ring, the rolling element and the C-shaped spring was pushed into the outer ring to complete the assembly.

[0016]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the accompanying drawings. The overload protection mechanism of the first embodiment shown in FIGS. 1 to 3 includes an outer ring 2 fitted concentrically with the inner ring 1, three inner ring rolling elements 3 and C interposed therebetween. The shaped spring 4 is a constituent member.

The inner ring 1 is provided with a shaft hole 5 in the center thereof, and a rotation preventing key 6 is provided on the inner peripheral surface of the shaft hole 5. A bearing boss portion 7 is provided on an end surface of the shaft hole 5 on the one end side. Further, the spring accommodating portion 8 opened to the bearing boss portion 7 side
Are provided coaxially with the shaft hole 5. This spring storage part 8
Is an annular space provided over a range of slightly less than 360 °, and the spring accommodating portion 8 causes the inner ring 1 to have the above-mentioned shaft hole 5
It is divided into a shaft portion 9 and a peripheral wall portion 11. Further, a regulating wall 12 is provided which extends a part of the spring accommodating portion 8 between the shaft portion 9 and the outer peripheral wall portion 11 so as to regulate the rotation of the C-shaped spring 4 within a certain range as described later.

A rectangular window hole 13 is formed in the outer peripheral wall portion 11 so as to extend inward and outwardly of the spring accommodating portion 8 at three circumferentially divided positions.
Are provided except for the portion of the restriction wall 12.

The outer ring 2 is provided with an end wall 15 at one end of a peripheral wall 14, and a fitting hole 16 rotatably fitted to the bearing boss portion 7 of the inner ring 1 is provided at the center of the end wall 15. It is provided. Further, recessed cam portions 17 are formed on the inner peripheral surface of the peripheral wall 14 at a constant pitch in the circumferential direction. Each recessed cam portion 17
As shown in FIG. 2A, has a shallow arc-shaped cross section and is provided over the entire width of the inner peripheral surface. Also,
On the inner surface of the end wall 15, a recessed guide step portion 18 concentric with the fitting hole 16 is provided at a position close to the recess cam portion 17, and the guide step portion 18 has the outer peripheral wall. The inner diameter surface of the portion 11 is fitted (see FIG. 2B) and serves as a rotation guide portion.

The C-shaped spring 4 is formed by bending a strip-shaped spring steel into a C-shape with an open portion 19 left in a part thereof, and is housed in the spring housing portion 8 of the inner ring 1 in a radial direction with a margin. At the same time, the opening portion 19 is engaged with the restriction wall 12. Due to this engagement, the movement of the C-shaped spring 4 in the circumferential direction is restricted to a certain range L.

The inner ring rolling element 3 (only expressed as "rolling element" in the claims) is formed by a metal roller, and has three window holes 13 of the inner ring 1 and its corresponding holes. It is fitted into the recessed cam portion 17 of the outer ring 2 facing the outside. Each inner ring rolling element 3 is pressed against the outer peripheral surface of the C-shaped spring 4, and the C-shaped spring 4 is slightly contracted to exert a predetermined pressing force on the recessed cam portion 17 by its repulsive elasticity. The torque value is set by the pressing force, the shape of the recessed cam portion 17, and the like.

In the assembled state as described above,
C-shaped spring 4 and window hole 13 (the inner ring rolling element 3 fitted in this
However, as for the positional relationship of (1), one end of the open end is the regulation wall 12
The window hole 13 is set to be outside the distance L at a position away from the position by a distance L (see FIG. 2A). In addition, at the position where the C-shaped spring 4 is separated by the distance L on the opposite side (see the dashed line in the figure), the window hole 1
3 is set to be outside that distance L. By setting such a positional relationship, it is possible to prevent the inner ring rolling element 3 from falling into the open portion 19 even if the C-shaped spring 4 moves to the maximum in both left and right directions.

The overload protection mechanism of the first embodiment is as described above. The drive shaft connected to the drive source such as the motor is inserted through the shaft hole 5 of the inner ring 1 and the outer ring 2 is belted. Then, the drive torque is transmitted to the load. When the load torque is smaller than the above torque value, the inner ring 1, the inner ring rolling element 3, and the outer ring 2 rotate integrally to transmit the drive torque to the load.

On the other hand, when an excessive load larger than the set torque is applied due to mishandling or the like, the inner ring rolling element 3 receives the driving torque of the inner ring 1 and causes the C-shaped spring 4 to contract so that the recessed cam portion 17 is released. After escape (see FIG. 3 (a)), the recessed cam portion 17 is successively dropped and escaped, and the inner ring 1 idles with respect to the outer ring 2 to interrupt the transmission of torque.
This protects the drive source from overload.

In the above, the case of transmitting torque from the inner ring 1 side to the outer ring 2 side has been described, but the same applies to the case of transmitting torque in the opposite direction. Also, the recessed cam portion 17
By forming the axial cross-sectional shape of (1) to be bilaterally symmetrical, the same torque can be generated regardless of whether the shaft is rotated left or right. Further, the shape of the window hole 13 of the inner ring 1 may be, as shown in FIG. 3B, a cutout portion 21 provided in a part of the rectangular hole, in addition to the rectangular shape described above.

Next, in the overload protection mechanism of the second embodiment shown in FIGS. 4 and 5, the recessed cam portion 17 is not directly provided on the inner diameter surface of the outer ring 2, but a constant pitch is formed on the outer diameter surface. The cylindrical columnar fixing pins 23 made of metal are respectively fitted into the large number of concave portions 22 provided in 1., and the concave cam portions 17 are formed by the intervals (valley portions) between the fixing pins 23. In this case, the distance a between the fixing pins 23 is set to the inner ring rolling element 3
Set to be smaller than the diameter b of the
In (a), the inner ring rolling element 3 is repeatedly brought into and out of the recessed cam portion 17 while making metal contact with the fixed pin 23 one after another. Thereby, the wear resistance is improved as compared with the case where the recessed cam portion 17 is directly provided on the resin outer ring 2 and the inner ring rolling element 3 is slidably contacted thereto, and the resin outer ring 2 can be adopted. Further, since a continuous impact sound is generated due to the contact between the metals at the time of overload, the user can hear the occurrence of the overload. Further, by enclosing the lubricant in the torque generating portion such as the recessed cam portion 17, it is possible to suppress the occurrence of wear even if the generated torque becomes large.

Incidentally, the center point p of the recess 22 is formed so as to be inside thereof (see FIG. 5B). Therefore, the distance c between the open ends of the recess 22 is equal to the diameter d (=
It is made slightly smaller than the diameter of the fixing pin 23). As a result, the fixing pin 23 is snap-fitted into the recess 22,
Easy to install.

The other difference from the first embodiment is that the shaft 24 is integrally provided at the center of the inner ring 1.
A point where a gear 25 is formed on the outer peripheral surface of the outer ring 2, the window hole 1
3 is 5 points (therefore, there are 5 inner ring rolling elements 3). Others are the same as in the case of the first embodiment. The shaft 24 may be omitted and the inner ring 1 may be provided with the shaft hole 5 as in the case of the first embodiment.

Next, a method of assembling the overload protection mechanism as described above will be described for the case of the first embodiment.

FIG. 6 shows a jig 26 for carrying out this assembling method. The jig 26 is an annular jig body 2
It consists of 7 and 3 magnets 28. The jig body 27 has an inner ring fitting portion 29 and an outer ring fitting portion 31 which are concentrically formed continuously on the inner diameter surface in the axial direction, and a step portion 32 is provided between the two. The inner ring fitting portion 29 has a length that allows the entire inner ring 1 to fit therein, while the outer ring fitting portion 31 has a length that allows the open end portion of the outer ring 2 to fit therein. Axial grooves 33 are provided at circumferentially equally divided positions on the inner diameter surface of the inner ring fitting portion 29. In addition, the jig body 2 corresponding to the groove 33
The magnet 28 is mounted on the outer diameter surface of 7.

7 (a) to 7 (e) show an assembling method of the overload protection mechanism using the jig 26 described above.
First, as shown in FIG. 7A, the inner ring 1 is fitted into the inner ring fitting portion 29 of the jig 26. At this time, the positioning is performed so that the window hole 13 of the inner ring 1 faces the groove 33. Next, FIG.
As shown in (b), the inner ring rolling element 3 is inserted from the outer ring fitting portion 31 side into the void formed by the window hole 13 and the groove 33 facing the window hole 13. By the insertion, the inner ring rolling element 3 is attracted and held in the groove 33 by the magnet 28, so that it does not come off. Next, as shown in FIG. 7C, the C-shaped spring 4
Is inserted into the spring storage portion 8. As a result, each inner ring rolling element 3
Is urged in the outer radial direction by the spring force of the C-shaped spring 4.

Further, as shown in FIG. 7 (d), the outer ring 2
After fitting the open side end of the outer ring fitting part 31,
As shown in (e), the inner ring 1 is pushed into the outer ring 2 together with the inner ring rolling element 3 and the C-shaped spring 4. The inner ring 1, the inner ring rolling element 3, the C-shaped spring 4, and the outer ring 2 are integrated by the pushing, and the above-mentioned overload protection mechanism is obtained by removing the inner ring 1, the inner ring rolling element 3, the C-shaped spring 4, and the outer ring 2.

The overload protection mechanism of the second embodiment described above is also assembled in the same manner, but in this case, the outer ring fitting portion 31 is formed so as to have an inner diameter that fits into the outer ring 2 having the gear 25. Further, the groove 33 of the inner ring fitting portion 29 is formed at five equal positions. Further, each fixing pin 23 is attached by previously snap-fitting into the recess 22 of the outer ring 2.

[0034]

As described above, according to the invention relating to the overload protection mechanism, a plurality of rolling elements fitted into the recessed cam portion are pressed in the outer diameter direction by a common C-shaped spring. Therefore, the number of parts is reduced, the size is reduced, the structure is simplified, and the device can be manufactured at low cost.

Also, by forming the concave cam portion of the outer ring in the valley between the fixing pins made of metal, even if the outer ring is made of resin, the torque generating portion has high wear resistance and is clear when overloaded. Since such a sound is generated, it is possible to know the occurrence of the defect at an early stage. Further, by forming the recess so that the center of the recess into which the fixing pin is fitted is located inside the recess, the fixing pin is snap-fitted and the outer ring is easily handled during assembly.

Further, by using the jig with the magnet, the rolling elements incorporated in the inner ring can be easily handled and the assembling work can be streamlined.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a first embodiment.

FIG. 2 (a) Same sectional view (B) Sectional drawing of the bb line of (a) figure

FIG. 3A is a sectional view of the same as above when an overload occurs. (B) A perspective view of a modified example of the above window hole

FIG. 4A is a sectional view of the second embodiment. (B) Sectional drawing of the bb line of (a) figure

FIG. 5 (a) A sectional view of the same as above when an overload occurs. (B) Enlarged sectional view of the above-mentioned recess

FIG. 6A is a sectional view of a jig. (B) A reduced view of the arrow b (C) Reduced view of arrow c

FIG. 7A is a sectional view of the assembly process.

FIG. 7B is a sectional view of the assembly process.

FIG. 7C is a sectional view of the assembly process.

FIG. 7D is a sectional view of the assembly process.

FIG. 7E is a sectional view of the assembly process.

[Explanation of symbols]

1 inner ring 2 outer ring 3 Inner ring rolling element 4 C type spring 5 shaft holes 6 keys 7 Bearing boss 8 Spring storage 9 Shaft 11 Outer wall 12 regulatory wall 13 window holes 14 Perimeter wall 15 End wall 16 Mating hole 17 Recessed cam part 18 guide steps 19 Open section 21 Separation part 22 recess 23 fixing pin 24 axes 25 gears 26 jigs 27 Jig body 28 magnets 29 Inner ring fitting part 31 Outer ring fitting part 32 steps 33 groove

Claims (8)

[Claims] 1. A recessed cam portion having a constant pitch is provided on an inner diameter surface of an outer ring fitted concentrically with the inner ring, and a rolling element is interposed between the recessed cam portion and the inner ring corresponding to the recessed cam portion. In an overload protection mechanism in which an elastic member for urging the rolling element against the recessed cam portion is provided in the inner ring and a predetermined torque is generated by the urging force of the elastic member, a C-shaped spring is used as the elastic member. The inner ring is provided with a spring accommodating portion that is concentric with the center of the inner ring, a required number of window holes are provided on the outer peripheral wall surface of the spring accommodating portion, and the rolling element is fitted into the window hole and the recessed cam portion. The overload protection mechanism is characterized in that each rolling element is pressed against the recessed cam portion by the C-shaped spring that is retractable and stored in the spring storage portion while restricting rotation above a certain level. 2. As a rotation restricting means of the C-shaped spring, a radial restricting wall is provided in a part of the spring accommodating portion, and an open part of the C-shaped spring is fitted to the restricting wall with a required expansion / contraction margin. The overload protection mechanism according to claim 1, wherein the overload protection mechanism is provided. 3. A bearing boss portion is provided at one end portion of the inner ring, and the spring accommodating portion is opened to an end surface side provided with the bearing boss portion, so that one end surface of the outer ring is rotatably attached to the bearing boss portion. The overload protection mechanism according to claim 1 or 2, wherein the spring accommodating portion is closed by one end surface of the spring accommodating portion when fitted. 4. A C housing the window hole in the spring housing portion.
The overload protection mechanism according to claim 1, wherein the overload protection mechanism is provided outside the range of movement of the open portion of the shaped spring. 5. A metal outer ring rolling element is fitted into a large number of recesses provided at a constant pitch on the inner diameter surface of the outer ring, and the recessed cam portions are formed between the outer ring rolling elements. The overload protection mechanism according to claim 1. 6. The overload protection mechanism according to claim 1, wherein the window holes of the inner ring are provided at a plurality of equal positions in the circumferential direction. 7. The center point of the concave portion on the inner diameter surface of the outer ring is present inside the concave portion, and the outer ring rolling element is snap-fitted to the concave portion. Overload protection mechanism. 8. An inner ring fitting portion into which the inner ring fits and an outer ring fitting portion into which the outer ring fits are continuously formed in an axial direction on an inner diameter surface of an annular jig body. A fitting groove for the rolling element is provided on the inner diameter surface of the mating portion over the entire length, and an assembling jig is used in which magnets are attached to the outer surfaces of the fitting groove. After that, the rolling element is installed and held in the fitting groove by the magnetic force of the magnet, then the C-shaped spring is installed, the outer ring is fitted to the outer ring fitting portion, and then the inner ring is rolled. Moving body and C
A method for assembling an overload protection mechanism, wherein the shaped spring assembly is pushed into the outer ring to complete the assembly.