JPS6139331Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a slip mechanism that connects a pair of gears so that they rotate together at all times, but slip (relatively rotate) when a relative torque of more than a predetermined value is applied. 2 in
This invention relates to a slip mechanism suitable for a number wheel.

Among the conventional slip mechanisms of this type, the following ones do not require any other members other than a pair of gears. That is, a rigid recess and an elastic recess facing each other near the center are formed in one thin metal gear, and the gripped part of the other synthetic resin gear can be rotated in both recesses. I was supporting it. The radial elastic force of the elastic concave portion is used to apply a radial frictional force to the gripped portion, so that both gears slip when a relative torque of a predetermined value or more is applied. .

However, in the conventional device described above, the predetermined torque must be determined based on the frictional force between the gripped portion having a small diameter and both of the recesses. The radial force applied to the gripping portion had to be extremely large, and as a result, the gripped portion was likely to wear out. especially,
Since the gripped portion is made of synthetic resin, and the two recesses that apply radial frictional force (elastic force) to the gripped portion are metal, the gripped portion suffers from considerable wear.

Furthermore, when assembling a synthetic resin gear, the elastic arm is forcibly displaced outward in the radial direction of the metal gear, but the strain caused by this forced displacement remains permanently and It was difficult to rotate and support the gripped part smoothly without rattling.

The object of the present invention is to provide a slip mechanism that eliminates the above-mentioned drawbacks.

The slip mechanism of the present invention that achieves the above purpose is
A synthetic resin gear with a small-diameter gripped part between a large-diameter disk part and a medium-diameter collar part, and a plate with a thickness slightly thinner than the length of the gripped part, with the gripped part in the center. a metal gear having a gripping hole through which the part is rotatably gripped and an insertion hole that communicates with the rotary gripping hole and into which the collar part can be inserted; An annular recess centered on the rotation center is provided on the plate surface of the metal gear,
The present invention is characterized in that a protrusion is provided that fits into the annular recess, restricts relative displacement of both gears in the radial direction, and causes the metal gear to flex with respect to the synthetic resin gear.

Embodiments of the present invention will be described below with reference to the drawings. In FIGS. 1 to 3 showing the first embodiment of the present invention, 1 is a synthetic resin gear, 2 is a metal gear, and both gears 1 and 2 have a predetermined relative torque as described later. They are connected so that they slip when activated. The synthetic resin gear 1 has a shaft hole 3 extending in the vertical direction at its center, and in order from top to bottom are a tooth portion 4, a large-diameter disk portion 5, a small-diameter gripped portion 6, and a medium-diameter collar. 7, and these parts 4, 5, 6, 7 are integrally molded. and,
An annular recess 8 having a radius r slightly smaller than the radius of the disk portion 5 is formed on the surface of the disk portion 5 facing the metal gear 2, with the rotation center 0 as the center.

The metal gear 2 is a disc portion 5 of the synthetic resin gear 1.
It has a plate shape with a diameter larger than that and a wall thickness slightly smaller than the axial length of the gripped portion 6, and is made of a metal material having sufficient elasticity, such as a spring steel material. The outer circumferential portion of the metal gear 2 is a toothed portion 9, while the plate surface thereof has a gripping hole 10 and an insertion hole 11 that communicate with each other by punching, for example.
is formed, and a dowel projection 12 is provided protrudingly. This gripping hole 10 is for rotatably gripping the gripped part 6 and is located at the center of the metal gear 2.
The insertion hole 11 is formed at an eccentric position and has a size that allows the collar portion 7 to be inserted therethrough. The dowel protrusion 12 is located at a radius r from the center of rotation, and its protruding height is slightly larger than the depth of the annular recess 8. Note that the gripping hole 10 is elongated, and its width l is slightly larger than its diameter so that the gripped portion 6 can be rotatably supported without wobbling.

Both gears 1 and 2 as described above are constructed by passing the collar portion 7 of the gear 1 through the gear 2 using the insertion hole 11, and then moving the gears 1 and 2 slightly relative to each other approximately in the radial direction. As a result, the gripped portion 6 of the gear 1 is rotatably supported in the gripping hole 10. In this state, the dowel protrusion 12 fits into the annular recess 8 and the first
The image shown is obtained. Here, as mentioned above,
Since the height of the dowel protrusion 12 is slightly larger than the depth of the annular recess 8, the metal gear 2 can be bent and given springiness as shown in the figure. Further, by fitting the dowel protrusion 12 into the annular recess 8, not only the positioning of the synthetic resin gear 1 and the metal gear 2 becomes easy, but also the effect of preventing the gears 1 and 2 from coming off can be obtained. , the assembled state shown in FIG. 1 is maintained unless a large radial external force is applied to both gears 1 and 2.

Now, when a rotational force is applied to either one of the gears 1 and 2, the friction force of the dowel projection 12 against the disk portion 5, that is, the inner surface of the annular recess 8, causes the gears 1 and 2 to rotate together. When this rotational force becomes large enough to overcome the frictional force, both gears 1 and 2 will rotate relative to each other. Note that the elastic force of the metal gear 2 itself is used as the frictional force.

In this manner, in this embodiment, the annular recess 8 and the dowel protrusion 12 function both as a radial relative displacement regulating means for regulating the relative radial displacement of the two gears 1, 2, and as a slip means for permitting relative rotation of the two gears 1, 2 when the relative torque acting on the two gears 1, 2 reaches or exceeds a predetermined magnitude.

FIG. 4 shows a second embodiment of the invention. In this embodiment, a pair of insertion holes 11 communicating with the gripping holes 10 are provided in opposite directions of 180 degrees with respect to the rotation center 0. By doing so, it is possible to simplify the assembly work and to The weight of the gear 2 can be reduced.

FIG. 5 shows a third embodiment of the invention. In this embodiment, in the first embodiment, the dowel protrusion 12
Four of them are provided at equal intervals in the circumferential direction. Thereby, the relative torque value when both gears 1 and 2 start to rotate relative to each other can be increased.

FIG. 6 shows a fourth embodiment of the present invention. In this embodiment, a substantially U-shaped extraction hole 1 is formed on the plate surface of the metal gear 2.
3, an elastic arm 14 extending in the radial direction is formed, and a dowel projection 12 is provided protruding from the free end of the elastic arm 14. Of course, the elastic arm 14 is slightly erected toward the disk portion 5.
By doing so, the dowel protrusion 12 comes into contact with the inner surface of the annular recess 8 due to the elastic force (plate spring force) of the elastic arm 14, making it easier to perform delicate torque management.

As described above, the slip mechanism of the present invention includes a synthetic resin gear having a small-diameter gripped portion between a large-diameter disc portion and a medium-diameter collar portion, and A metal gear having a slightly thin plate thickness and having a gripping hole in the center through which the gripped part is rotatably gripped, and an insertion hole that communicates with the rotary gripping hole and into which the collar part can be inserted; An annular recess centered on the rotation center is provided in the plate surface of the disc part near the outer periphery of the disc part, and a ring-shaped recess centered on the rotation center of the disc part is provided in the plate surface of the metal gear. This gear is characterized by being provided with a protrusion that restricts relative displacement in the radial direction and allows the metal gear to deflect with respect to the synthetic resin gear. Therefore, according to the present invention,
Since the torque at which a slip is initiated is determined by the frictional force near the outer periphery of the disc portion, the torque for initiating a slip can be made sufficiently large, and torque management becomes easier. Moreover, the protrusions can bend the metal gear relative to the synthetic resin gear to provide spring properties, and the engagement of the protrusion with the annular recess allows positioning of the synthetic resin gear and the metal gear. Not only is this easier, but the effect of preventing both gears from slipping can be obtained. Further, the gripped portion of the synthetic resin gear is gripped only for rotation and is not subjected to large radial force by the metal gear, so that damage to the gripped portion can be prevented. Furthermore, when assembling, that is, when rotating and supporting the gripped part on the metal gear, there is no need to forcibly deform the metal gear, so the gripped part can be gripped without any distortion or the like. The parts can be rotated and supported smoothly without rattling.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is a perspective view of the synthetic resin gear in FIG. 1,
FIG. 3 is a perspective view of the metal gear in FIG. 1, and FIGS. 4 to 6 are plan views of metal gears in other embodiments of the present invention. 1...Synthetic resin gear, 2...Metal gear, 3
...Shaft hole, 4, 9...Tooth portion, 5...Disk portion, 6...
...Gripped part, 7...Brim part, 8...Annular recess, 1
0... Gripping hole, 11... Insertion hole, 12... Dowel projection, 14... Elastic arm, 0... Center of rotation.

Claims (1)

[Scope of Claim for Utility Model Registration] A synthetic resin gear having a small-diameter gripped part between a large-diameter disc part and a medium-diameter collar part, and a plate thickness slightly thinner than the length of the gripped part. and a metal gear having a gripping hole in the center through which the gripped part is rotatably gripped, and a metal gear having an insertion hole that communicates with the rotary gripping hole and into which the collar part can be inserted; On the plate surface of the disc part near the outer periphery,
An annular recess centered on the rotation center thereof is provided, and the plate surface of the metal gear is fitted with the annular recess,
A slip mechanism characterized by being provided with a protrusion that restricts relative displacement in the radial direction of both gears and deflects the metal gear with respect to the synthetic resin gear.