JP2007263217A - Torque limiter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque limiter, in which shortage of lubricating oil on a sliding face is prevented, a usable temperature range is wide, and abnormal noise property, abrasion resistance, and durability are excellent. <P>SOLUTION: In the torque limiter, an outer ring 2 is rotatably disposed to the outside of an inner ring 1, a small-diameter coil part 3a is provided to fasten a coil spring 3, which is assembled between the inner and outer rings, to an outer diameter face of the inner ring 1, one bent piece 4a of bent pieces formed at both ends of the coil spring 3 is connected with the outer ring 2, and the other bent piece 4b is connected with an adjusting ring 5 which is rotatably press-fit into an opening end part of the outer ring 2. The inner ring is sintered metal body, and is formed by impregnating the inner ring 1 with liquid grease having worked penetration of 400 or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a torque limiter that transmits and interrupts rotational torque.

There are torque limiters used in office machines, etc., that use the radial binding force against the inner ring of the spring, and those that generate friction by pressing the friction against the friction plate in the thrust direction with the spring. Both have a mechanism for generating torque by frictional force.
Lubricants such as lubricating oil and lubricating grease are used to prevent wear, abnormal heat generation, seizure noise, and the like between the inner ring of the torque limiter and the spring or friction plate, between the friction plate and the friction plate. Further, the inner ring of the torque limiter is a metal sintered body, which is a lubricating mechanism that is used by impregnating a lubricant. The performance required for the torque limiter is to ensure lubricity so that sliding between the inner ring and the coil spring is performed properly. How long an oil film is secured and maintained, metal contact is suppressed, and friction is maintained. The performance of the torque limiter depends on whether the coefficient can be stabilized. In particular, a torque limiter used in a paper feeding device such as a copying machine or a printer or a tension mechanism such as a ribbon or sheet is required to have a lubricant that is extremely small in torque fluctuation and does not generate metal contact noise.
Conventionally, base oil has been synthesized as a torque limiter lubricating oil or lubricating grease that has a low torque fluctuation, which can extend the life of the torque limiter by suppressing metal contact due to oil film breakage, and has excellent resin resistance. 1% by weight to 8% by weight of at least one phosphate ester selected from an aliphatic phosphate ester and a phosphite ester with respect to the total amount of the lubricating oil. A torque limiter lubricating oil or lubricating grease is known (see Patent Document 1).

  In order for the torque limiter to properly slide between the inner ring and the coil spring, it is indispensable to have a lubricating action by lubricating oil or lubricating grease at the sliding interface. As shown in FIG. 5, in an ordinary oil-impregnated bearing with an inner diameter sliding, as the shaft rotates, the lubricating oil impregnated inside oozes out to the inner diameter surface due to the effect of pumping and heat generation, and performs the lubricating action. . That is, when the shaft rotates, the oil inside the bearing is sucked out, and the oil flows from the upper portion where the hydraulic pressure is low toward the sliding portion that receives the high hydraulic pressure. The oil wedge generated by the oil flow lifts the shaft from the bottom surface of the bearing and functions to prevent contact between metals. Further, the shaft is displaced in the rotational direction by the flow of oil entering, and the hydraulic pressure distribution on the bearing inner diameter surface is as shown in FIG.

However, in the case of the torque limiter, as a sectional view of the torque limiter, as shown in FIG. 4 in which the portion B of FIG. 3 showing the coil spring 3 and the inner ring 1 is enlarged, it is in contact with the coil spring 3 when viewed on the circumference. There is a part that is not in contact with the part that is. There is no change in pressure in the portion that is not in contact with the coil spring 3 such as the portion a, and there is no element that the lubricant oozes out. In the vicinity where the coil spring 3 is in contact like the portion b, a difference in pressure occurs when viewed locally, but the effect is considered to be insignificant compared to the case of the oil-impregnated bearing. As described above, the torque limiter has a structure in which the lubricant in the inner ring 1 is not easily oozed out, so that the lubricant is hardly oozed out.
In addition, when lubricating oil is used as the lubricant, scattering and evaporation are likely to occur, and the oozing state is likely to fluctuate due to changes in ambient temperature. As a result, there is a problem that abnormal noise is generated and wear is easily promoted.
On the other hand, when lubricating grease (miscibility of less than 400) is used as the lubricant, it is less likely to scatter or evaporate compared to the lubricating oil, but it requires a familiar operation after assembly or when grease is filled. There is a demerit such as inconvenient handling due to excess grease overflowing.
JP 2002-249794 A

  The present invention has been made in order to cope with such problems. There is no lack of lubricating oil on the sliding surface, the usable temperature range is wide, and the torque limiter is excellent in abnormal noise characteristics, wear resistance and durability. For the purpose of provision.

In the torque limiter of the present invention, an inner ring is fitted inside an outer member, a torque transmission member is interposed between the inner ring and the outer member, and when the inner ring outer diameter surface and the outer member rotate relative to each other, A torque limiter configured to generate a predetermined torque by friction between an inner ring and the torque transmission member, wherein the inner ring is made of a sintered metal body, and is a liquid grease having a blending degree of 400 or more. It is characterized by impregnating.
The mixing penetration in the present invention is 60 penetrations at 25 ° C. measured by the method defined in JIS K2220.

The inner ring is characterized in that the outer surface has a surface area ratio of 20% to 35%.
In the present invention, the surface open area ratio refers to the area ratio of the surface open area (the part where the pores of the sintered metal body are opened on the outer surface) in the unit area of the outer surface of the inner ring.

The liquid grease is characterized by comprising a synthetic hydrocarbon oil as a base oil and containing a thickener in an amount of 0.5 to 5% by weight based on the whole grease.
Further, the thickening agent for the liquid grease is a metal soap or a urea compound.

Since the torque limiter of the present invention is formed by impregnating the inner ring, which is a sintered metal body, with liquid grease having a miscibility of 400 or more, the liquid grease is applied to the outer diameter surface of the inner ring by the effect of the thickener. It is easy to adhere and a state where liquid grease is always present on the outer diameter surface of the inner ring is obtained, and good sliding is obtained between the coil spring and the inner ring. In addition, since it is a liquid grease with a blending degree of 400 or more, a familiar operation is not required, and torque fluctuations can be suppressed. In addition, liquid grease is always present on the outer surface of the inner ring regardless of the surrounding temperature change, so that it is possible to prevent abnormal noise and suppress wear.
In addition, since the surface area of the inner ring outer diameter surface is 20% to 35%, in addition to the liquid grease held on the inner ring outer diameter surface, liquid grease seeps out from the inner ring, It can be expected to prevent abnormal noise and suppress wear.

A torque limiter according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of the torque limiter. FIG. 2 is a perspective view showing a coil spring and an inner ring constituting the torque limiter. FIG. 3 is an enlarged cross-sectional view taken along line AA of FIG.
The above-described lubricating oil or lubricating grease is used to prevent the inner ring and spring or friction plate of the torque limiter, wear between the friction plate and the friction plate, abnormal heat generation, seizure noise, and the like. The torque limiter shown in FIG. 1 is a friction type torque limiter that generates torque by the binding force of the coil spring 3 to the inner ring 1.
The torque limiter shown in FIG. 1 to FIG. 3 is a small-diameter coil in which a coil spring 3 is incorporated between an inner ring 1 and an outer ring 2 rotatably provided on the outer side, and the outer diameter surface of the inner ring 1 is fastened to the coil spring 3. A portion 3a is provided, one of the bent pieces 4a and 4b formed at both ends of the coil spring 3 is connected to the closed end of the outer ring 2, and the other bent piece 4b is rotatable to the open end of the outer ring 2. It is connected to the adjusting ring 5 press-fitted into the.

  In the torque limiter, when the inner ring 1 is rotated in the direction opposite to the winding direction of the coil spring 3 when viewed from the adjustment ring 5 side, the small diameter coil portion 3a of the coil spring 3 is expanded in the diameter increasing direction by contact with the inner ring 1. Although a force acts, since the bent piece 4 of the small-diameter coil portion 3a is connected to the outer ring 2, the small-diameter coil portion 3a is reduced in diameter and the inner ring 1 is tightened. For this reason, the rotation of the inner ring 1 is transmitted to the outer ring 2 via the coil spring 3, and the outer ring 2 rotates in the same direction as the inner ring 1. When the load on the outer ring 2 increases and the binding force with which the small diameter coil portion 3a of the coil spring 3 tightens the inner ring 1 becomes smaller than the frictional force at the contact portion between the small diameter coil portion 3a and the inner ring 1, the space between the inner ring 1 and the small diameter coil portion 3a As a result, slippage occurs, and transmission of rotational torque to the outer ring 2 is interrupted.

  Further, when the inner ring 1 is rotated in the winding direction of the coil spring 3, the small-diameter coil portion 3a of the coil spring 3 is enlarged in the opposite direction to the above, causing slippage between the inner ring 1 and the small-diameter coil portion 3, and the outer ring 2 Transmission of rotational torque to is interrupted.

In the torque limiter, the number of parts is small, the assembly is easy and the manufacturing cost is low, and when the adjustment ring 5 is rotated with respect to the outer ring 2, the inner diameter of the small-diameter coil portion 3a of the coil spring 3 changes. Therefore, the magnitude of torque that can be transmitted from the inner ring 1 to the outer ring 2 can be adjusted.
In the torque limiter, when the torque transmission is interrupted, the inner ring 1 rotates in contact with the small-diameter coil portion 3a. Therefore, the contact portion between the inner ring 1 and the small-diameter coil portion 3a is likely to be worn. 1 is made of a sintered metal body and is impregnated with a liquid grease having a miscibility of 400 or more.

  The inner ring 1 used in the torque limiter of the present invention is a sintered metal body, and has pores formed between the sintered particles inside, and liquid grease is impregnated in the pores. In the manufacturing process of the inner ring 1, first, a metal powder such as copper or iron and an additive such as graphite are mixed, and this mixture is filled in a mold and compression-molded into an inner ring shape. The molded product is sintered and sized and then impregnated with liquid grease by vacuum impregnation. After impregnation, the oil is drained so that the liquid grease is thinly and uniformly attached to the outer surface of the inner ring. Depending on the sintered state, a heat treatment for hardening and a barrel treatment for removing scale caused by the heat treatment can be performed between the sizing and the oil impregnation treatment.

In the torque limiter, the impregnated liquid grease does not generate a pumping action as described above, so that the liquid grease does not easily exude. Therefore, it is necessary to appropriately set the surface area ratio of the outer diameter surface in order to allow the liquid grease to exude accurately.
The surface aperture ratio of the outer diameter surface of the inner ring used in the torque limiter of the present invention is preferably 20% to 35%. When the surface porosity is less than 20%, the liquid grease impregnated in the sintered metal is difficult to ooze out to the inner ring surface, so that only the liquid grease held on the surface is lubricated. . In addition, if the surface area ratio is greater than 35%, the liquid grease impregnated inside the sintered metal tends to scatter and evaporate. Abnormal noise or wear may occur.
The surface open area ratio can be adjusted by the particle diameter of the powder and the density of the green compact. In the present invention, a metal powder having a particle size of 100 mesh or less is used, and the surface open area ratio can be adjusted to the above range by forming the green powder density in the range of 6.4 to 7.2 g / cm ³ . Further, the surface porosity can be finely adjusted by performing sizing, coining, and barrel treatment after sintering.

  The outer ring, which is an external member of the torque limiter of the present invention, is formed of a resin such as polycarbonate resin, polyphenylene sulfide resin, acrylonitrile-butadiene-styrene resin, or polyacetal resin with good workability. In these, since it is excellent in oil resistance, it is preferable to use a polyacetal resin.

In the present invention, the base oil used for the liquid grease can be used without limitation as long as it is a commonly used base oil. For example, mineral oil such as naphthenic, paraffinic, liquid paraffin, hydrodewaxed oil, polyglycol oil such as polyalkylene glycol, ether synthetic oil such as alkyl diphenyl ether and polyphenyl ether, diester oil, polyol ester oil, etc. Examples thereof include ester synthetic oils, silicone oils such as polydimethylsiloxane and polyphenylmethylsiloxane, hydrocarbon synthetic oils such as GTL base oil and poly-α-olefin oil, and base oils such as fluorine oil.
Among these, it is preferable to use a synthetic hydrocarbon oil because it is less aggressive against the resin.

The thickener used for the liquid grease in the present invention can be used without particular limitation as long as it is a commonly used thickener. Examples thereof include metal soaps such as lithium soap, lithium complex soap, high-strength soap, calcium complex soap, aluminum soap, and aluminum complex soap, and urea compounds such as diurea compounds and polyurea compounds.
Of these, lithium soap or urea compounds are preferably used because they are relatively inexpensive and can be used in a wide temperature range.

In the present invention, the thickener is blended in such a ratio that the resulting grease has a blending degree of 400 or more. Specifically, the thickener is preferably blended in an amount of 0.5 to 5% by weight based on the entire grease.
A liquid grease having a miscibility of 400 or more has both the fluidity and lubricity, which are the advantages of lubricating oil, and the retainability and non-evaporability, which are the advantages of grease. On the other hand, the lubricating oil has good fluidity and excellent lubricity, but tends to cause scattering and evaporation due to centrifugal force. On the other hand, normal grease (miscibility of less than 400) has a holding force and is difficult to scatter, but has a drawback of poor fluidity and large load.
Since the torque limiter of the present invention is impregnated with this liquid grease, the grease-like characteristics prevent the grease from scattering and evaporating, and a state that always exists on the outer surface of the inner ring is obtained. From such characteristics, good lubricity and appropriate fluidity can be obtained. As a result, a running-in operation or the like is unnecessary and torque fluctuations can be suppressed, and generation of abnormal noise and suppression of wear can be expected over a long period of time.

  In the torque limiter of the present invention, liquid grease is always present on the surface of the inner ring outer diameter surface, and good sliding can be obtained for a long time between the coil spring and the inner ring. Therefore, it is used for various industrial machines including office machines. It can be suitably used as a torque limiter.

It is sectional drawing of the torque limiter which concerns on one Example of this invention. It is a perspective view which shows the coiled spring and inner ring which comprise a torque limiter. It is a figure which shows the expanded cross section of the AA line of FIG. It is the figure which expanded the B section of FIG. It is a figure which shows the mechanism of the pump action in an oil-impregnated bearing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring 2 Outer ring 3 Coil spring 3a Small diameter step part 4a Bending piece (outer ring obstruction end side)
4b Folding piece (outer ring opening end side)
5 Adjustment ring

Claims (4)

An inner ring is fitted inside the outer member, a torque transmission member is interposed between the inner ring and the outer member, and the inner ring outer diameter surface and the torque transmission member are rotated during relative rotation between the inner ring and the outer member. A torque limiter configured to generate a predetermined torque by friction between
A torque limiter characterized in that the inner ring is made of a sintered metal body, and the inner ring is impregnated with liquid grease having a miscibility of 400 or more.   The torque limiter according to claim 1, wherein the inner ring has a surface area ratio of 20% to 35% on an outer diameter surface.   3. The torque limiter according to claim 1, wherein the liquid grease contains synthetic hydrocarbon oil as a base oil and contains a thickener in an amount of 0.5 wt% to 5 wt% with respect to the entire grease.   4. The torque limiter according to claim 1, wherein the liquid grease thickener is a metal soap or a urea compound.

Images