JP7448413B2 - torque limiter - Google Patents

Description

The present invention relates to a torque limiter that limits the load torque associated with rotation transmitted in one direction or rotation transmitted in both directions to a predetermined value or less, and in particular relates to a torque limiter with features on an inner ring member. .

In general, a torque limiter is a device that cuts off the transmission of torque when a large torque exceeding a certain value acts on a rotation transmission mechanism.For example, a torque limiter is used to cut off the transmission of torque in a rotation transmission mechanism. It is installed on the roller part of the mechanism. There are contact type torque limiters that obtain rotational torque through mechanical friction, and include an inner ring member (also called a bobbin), a coil spring tightly fitted around the outer periphery of the inner ring member, and one end of the coil spring. A device is known that includes a fixed portion and an outer ring member (case member) that covers the inner ring member. Furthermore, there are known torque limiters that limit the load torque associated with rotation transmitted in both directions, in addition to limiting the load torque associated with rotation transmitted in one direction.

The inner ring member used in a conventional torque limiter is, for example, made of sintered metal, polyphenylene sulfide (PPS), polyether ether ketone (PEEK), or polyeximethylene, as disclosed in Patent Document 1. It is common to mold using a resin material such as resin (POM).

JP2006-10060

In recent years, there has been an increasing demand for high quality torque limiters that are compact, high torque, and highly durable.In particular, since a coil spring is wound around the inner ring member, large frictional force (torque) acts on it. In order to improve quality, the constituent material of the inner ring member around which the coil spring is wound becomes important. If the inner ring member is made of a resin material or sintered metal as described above, it is possible to achieve a certain level of performance, but this is especially true for torque limiters where the outer diameter is 20 mm or less and a torque higher than about 500 gf cm is applied. , cannot exhibit sufficient performance. Specifically, inner ring members made of resin materials do not have sufficient durability, and those made of metal include sintered metal or steel materials that are hardened, smoothed, and plated or coated to improve sliding properties. However, at high torque, the fluctuation becomes large and sufficient performance cannot be achieved. Furthermore, since it is not possible to replenish lubricant during the process, the torque fluctuates due to wear, making it difficult to maintain constant quality over a long period of time.

The present invention has been made based on the above-mentioned problems, and an object of the present invention is to provide a torque limiter that is small in size and high in torque, yet has good durability and good sliding characteristics.

In order to solve the above problems, the present invention provides an inner ring member having a coil spring wound around and held on the outer peripheral surface thereof, and an outer ring member disposed so as to cover the inner ring member and to which an end of the coil spring is fixed. In the torque limiter that generates a predetermined torque between the inner ring member and the outer ring member by the frictional force between the inner ring member and the coil spring, the inner ring member is made of polyether ether ketone or polyphenylene sulfide. It is characterized in that it is constructed by adding a filler comprising carbon fiber, polytetrafluoroethylene, and graphite to the base material.

The inner ring member of the torque limiter configured as described above is made of a composite material made of polyetheretherketone or polyphenylene sulfide as a base material, to which a filler containing carbon fiber, polytetrafluoroethylene, and graphite is added. . Polyetheretherketone (hereinafter also referred to as PEEK) and polyphenylene sulfide (hereinafter also referred to as PPS) are materials commonly used when forming the inner ring member from a resin material. By adding it, durability (wear resistance) and sliding characteristics can be improved. That is, the inventor of the present invention has improved durability (wear resistance) by forming the inner ring member from a composite material to which a certain material (filler) is added, instead of forming the inner ring member from a single resin material. ) and sliding properties, and came up with the idea of the present invention. Among the materials added to PEEK or PPS, which are used as base materials, carbon fiber (hereinafter also referred to as CF) mainly contributes to improving strength and abrasion resistance (improving durability), as well as improving sliding resistance. Contributes to improving dynamic characteristics. Among the added materials, polytetrafluoroethylene (hereinafter also referred to as PTFE) and graphite contribute to improving sliding properties, and the former has particularly good properties in terms of low friction, while the latter It has good heat resistance, load resistance, and wear resistance against frictional heat caused by high torque and increased pressure of coil springs, and these functions complement each other to stabilize performance.

In addition to the above-mentioned PEEK, polyphenylene sulfide (hereinafter also referred to as PPS), polyimide (hereinafter also referred to as PI), etc. can be used as the base material, but when we conducted the performance test described later, we found that the base material As for the material, PEEK was able to exhibit the most excellent properties. Therefore, if the inner ring member is formed of a composite material with the above-mentioned filler on such a base material, even if the torque limiter is made smaller and constructed as a high-torque type, the torque limiter with excellent durability and sliding characteristics can be achieved. It becomes possible to configure a limiter. Note that even if polyphenylene sulfide is used as the base material, it is possible to expect some effect.

According to the present invention, a torque limiter with good durability and good sliding characteristics can be obtained even if it is small and high torque type.

FIG. 1 is a sectional view showing an example of the configuration of a torque limiter according to the present invention. The graph which shows the result of the durability test about the torque limiter (set torque is 500gf*cm) which has the inner ring member which used PPS as a base material, and used CF as a filler material. The graph which shows the result of the durability test about the torque limiter (set torque is 600 gf*cm) which has the inner ring member which used PPS as a base material, and used CF as a filler material. The graph which shows the result of the durability test about the torque limiter (set torque is 800gf*cm) which has the inner ring member formed by using PPS as a base material, and using CF as a filler material. The graph which shows the result of the durability test about the torque limiter (set torque is 500gf*cm) which has the inner ring member which used PPS as a base material, and made filler material CF and PTFE. The graph which shows the result of the durability test about the torque limiter (set torque is 600gf*cm) which has the inner ring member which used PPS as a base material, and made filler material CF and PTFE. The graph which shows the result of the durability test about the torque limiter (set torque is 800gf*cm) which has the inner ring member which used PPS as a base material, and made filler material CF, PTFE, and graphite. The graph which shows the result of the durability test about the torque limiter (set torque is 750 gf*cm) which uses PEEK as a base material, and has an inner ring member in which no filler is mixed. A graph showing the results of a durability test for a torque limiter (set torque is 500 gf·cm) having an inner ring member made of PEEK as a base material and CF, PTFE, and graphite as fillers. The graph which shows the result of the durability test about the torque limiter (set torque is 800 gf*cm) which has the inner ring member which used PEEK as a base material, and made filler material CF, PTFE, and graphite. The graph which shows the result of the durability test about the torque limiter (set torque is 500gf*cm) which has the inner ring member which used PI as a base material, and made filler material CF, PTFE, and graphite. The graph which shows the result of the durability test about the torque limiter (set torque is 850gf*cm) which has the inner ring member formed by using PI as a base material, and using CF, PTFE, and graphite as a filler material. A graph showing the results of a durability test on a torque limiter (set torque is 800 gf·cm) having an inner ring member made of sintered metal. A list summarizing the results of the durability tests shown in FIGS. 2 to 13.

Embodiments of the torque limiter according to the present invention will be described below.
FIG. 1 is a sectional view showing an example of the configuration of a torque limiter.

The torque limiter shown in FIG. 1 is configured to transmit torque in one direction, and includes an inner ring member (bobbin) 10 formed in a cylindrical shape and a cap shape that is attached to cover the inner ring member 10. It includes an outer ring member 20 and a coil spring 30 attached to the outer peripheral surface of the inner ring member 10.

One end 30a of the coil spring 30 is fixed to the outer ring member 20, and when rotational torque in one direction is generated in the outer ring member 20, the coil spring 30 is tightened and the inner ring member 10 and the outer ring member 20 are fixed (locked state). ). Further, when rotational torque in the opposite direction is generated in the outer ring member 20, the coil spring 30 becomes loose in the radial direction from the fixed end, and slip friction occurs between the inner ring member 10 and the coil spring 30, generating a constant torque. (power transmission state). That is, the torque limiter 1 shown in the figure is fixed (locked) when rotating in one direction, and functions as a constant torque power transmission between the inner ring member 10 and the outer ring member 20 when rotating in the opposite direction.

As described above, the torque limiter according to the present invention is characterized by the constituent material of the inner ring member 10, and the torque limiter shown in FIG. 1 is shown as an example of a configuration to which the present invention can be applied. . Therefore, the configuration and arrangement of the inner ring member 10, outer ring member 20, and coil spring 30, specific means for switching ON/OFF of power transmission, unidirectional and bidirectional, etc. are limited to specific configurations. isn't it.

Next, a performance test (durability test) conducted on the torque limiter 1 shown in FIG. 1 by changing the constituent material of the inner ring member 10 will be described.
The torque limiters used in the test were prepared with multiple types of torque limiters with different set torques (the set torque is generated by the spring force of the coil spring 30 wound around the inner ring member 10), and these were used in a known torque tester. It was installed and tested for durability and torque variation. The evaluation of high torque characteristics shall be determined based on the results of durability and torque fluctuation in tests where the set torque is 600 gf cm or more.What kind of inner ring member should be used (for resin base material An evaluation test was conducted to determine what kind of filler should be added.
The following tests were conducted using torque limiters with an outer diameter of 15 mm or 14 mm and a set torque of 500 gf·cm or more, which is considered to be effective.

As mentioned above, it is known that conventional torque limiters use sintered metal as the inner ring member or resin such as POM, PPS, PEEK, etc. By mixing filler with It is thought that it is possible to create a suitable configuration. In this case, it is possible to add a single filler to the base material, but considering the compatibility with the base material, the characteristics of the filler, and the overall performance as a composite material, It is considered preferable to add multiple types of fillers. For example, CF is thought to mainly contribute to improving strength and wear resistance (improving durability), but if the amount added is too large, it will cause wear to the coil spring that is the friction partner material, reducing durability. Alone alone is not sufficient to improve sliding properties. For this reason, it is conceivable to further add PTFE or graphite, which contributes to improving sliding properties. However, although PTFE has good properties, especially in terms of low friction, it lacks stability in terms of heat resistance and load capacity. It is considered preferable to also add graphite, which has good load and wear resistance.

An evaluation test (durability test) conducted to determine what kind of filler should be added to the base material will be described below.
In Figures 2 to 13, the horizontal axis represents the cumulative rotation speed, and the vertical axis represents fluctuations in slip torque (solid line corresponds to the scale on the left) and ripple (dashed line corresponds to the scale on the right). This is a graph. Specifically, the rotation status of the inner ring member was evaluated when rotation was continuously applied to the outer ring member of the torque limiter (the test piece was measured at multiple rotational speeds, but the characteristics are representative). Conditions for comparison: 200 rpm).

Generally, as the cumulative number of rotations increases, the transmitted torque decreases, but durability can be evaluated based on the rate of change, plus or minus, with respect to the initial value. This varies depending on the characteristics of the test piece and coil spring, the usage environment (test environment), etc., but it is thought that the rate of change becomes negative as the cumulative number of rotations increases due to factors such as wear. In addition, ripple is the detected difference between the maximum torque and the minimum torque that vary in the rotation period at each constant cumulative rotation speed, and it is possible to evaluate the fluctuation characteristics (slidability) based on this fluctuation rate. It is possible.
In the present invention, durability, sliding properties (fluctuation characteristics), and suitability for high torque are each evaluated in four stages (◎, ◯, △, ×).

Regarding durability, obtain the average torque fluctuation value, and mark a rate of change of ±3% or less with respect to the initial value as (◎), a rate of change of ±6% or less as (○), and a rate of change of ±12% or less as (△), and if the rate of change was greater than ±12% or could not pass 5 million revolutions, it was rated (x). ).

The fluctuation characteristics (sliding property; ripple) are evaluated by the variation rate of the difference (maximum fluctuation range) between the maximum torque and the minimum torque that are displaced in the rotation cycle, and within the life span, 4% or less ( ◎), 8% or less was rated (○), 12% or less was rated (△), and those larger than 12% were rated (x).

In addition, regarding high torque suitability, we will evaluate those with a set torque of 600 gf cm or more, and if both of the above durability and fluctuation characteristics are ◎, it will be evaluated as (◎). If both were ○ or more, it was evaluated as (〇), if both were △ or more, it was evaluated as (△), and if either was ×, it was evaluated as (×).
Hereinafter, the results (graphs) of the evaluation test will be explained with reference to FIGS. 2 to 13, and the evaluation results will be explained with reference to FIG. 14.

In the durability test shown in Figure 2 (A), a torque limiter (setting torque is 500 gf cm) having an inner ring member made of PPS as the base material and CF as the filler was prepared, and the results of the durability test of the torque limiter were conducted. This is a graph showing

In this test piece, the rate of change in torque is -10.3%, and the rate of variation in fluctuation characteristics is 5.7%. According to the above evaluation criteria, durability is (△) and fluctuation characteristics are (〇). The results were obtained.

The durability test in Figure 3 (a) shows the results of a durability test for a torque limiter (high torque setting of 600 gf cm) that has an inner ring member made of PPS as the base material and CF as the filler material. This is a graph showing.
In this test piece, the rate of change in torque is -10.4%, and the rate of variation in fluctuation characteristics is 4.7%. According to the evaluation criteria described above, durability is (△) and fluctuation characteristics are (〇). The results were obtained. Regarding high torque characteristics, a result of (△) was obtained from the results of durability and fluctuation characteristics.

The durability test in Fig. 4 (c) shows the results of a durability test for a torque limiter (set torque is set at high torque of 800 gf cm) that has an inner ring member formed using PPS as the base material and CF as the filler material. This is a graph showing.
In this test piece, the torque suddenly decreased at around 1.5 million cumulative rotations, making it impossible to perform the durability test itself, making it impossible to measure the rate of change in torque, and the variation rate of fluctuation characteristics being 7.7%. Met. According to the above-mentioned evaluation criteria, the results were as follows: (×) for durability and (○) for fluctuation characteristics. In addition, regarding high torque characteristics, a result of (x) was obtained from the results of durability and fluctuation characteristics.

According to the durability tests (a) to (c) above, the inner ring member made of PPS as the base material and only with CF added was not suitable for high-torque types with good durability and sliding characteristics. was gotten.

The durability test in FIG. 5(d) is a graph showing the results of a durability test for a torque limiter (set torque is 500 gf cm) that has an inner ring member made of PPS as a base material and CF and PTFE as fillers. It is.
In this test piece, the rate of change in torque is -6.8% and the rate of variation in fluctuation characteristics is 8.0%. According to the above evaluation criteria, both durability and fluctuation characteristics are rated as (○). Obtained.

The durability test in Figure 6 (E) is a durability test for a torque limiter (set torque is set at high torque of 600 gf cm) that has an inner ring member made of PPS as a base material and CF and PTFE as fillers. It is a graph showing the results.
In this test piece, the rate of change in torque was -17.8%, and the rate of variation in fluctuation characteristics was 11.4%. According to the above evaluation criteria, durability was (×) and fluctuation characteristics were (△). The results were obtained. In addition, regarding high torque characteristics, a result of (x) was obtained from the results of durability and fluctuation characteristics.

According to the durability tests in (d) and (e) above, the inner ring member made of PPS and added with CF and PTFE was not suitable for high torque settings with good durability and sliding characteristics. Obtained.

The durability test in Figure 7 (F) was conducted on a torque limiter (set torque is set at high torque of 800 gf cm) that has an inner ring member made of PPS as the base material and CF, PTFE, or graphite as the filler material. It is a graph showing test results.
In this test piece, the rate of change in torque is -3.9% and the rate of variation in fluctuation characteristics is 6.4%. According to the above evaluation criteria, durability is rated as (〇) and fluctuation characteristics as (〇). The results were obtained. Regarding high torque characteristics, a result of (○) was obtained from the results of durability and fluctuation characteristics.

According to the durability test described above, the inner ring member using PPS as the base material and adding CF, PTFE, and graphite had good durability and sliding characteristics, and was found to be suitable as a high-torque type. That is, although it was not as good as when the base material was PEEK, which will be described later, it was possible to obtain good results to some extent as a high-torque type.

The durability test in FIG. 8 (g) is a graph showing the results of a durability test for a torque limiter (set torque is set at high torque of 750 gf cm) whose inner ring member is made of PEEK (no filler) as a base material. .
In this test piece, the rate of change in torque is -17.5%, and the rate of variation in fluctuation characteristics is 6.6%. According to the above evaluation criteria, durability is (△) and fluctuation characteristics are (〇). The results were obtained. Regarding high torque characteristics, a result of (△) was obtained from the results of durability and fluctuation characteristics. As described above, in the conventional torque limiter in which the inner ring member is formed only from a resin material, when set to a high torque type, the durability and sliding characteristics are not sufficient.

The durability test in Figure 9 (h) shows the results of a durability test for a torque limiter (setting torque is 500 gf cm) that has an inner ring member made of PEEK as a base material and CF, PTFE, or graphite as a filler material. This is a graph showing.
In this test piece, the rate of change in torque was +2.9%/-1.8%, and the variation rate in fluctuation characteristics was 3.6%. According to the above evaluation criteria, both durability and fluctuation characteristics were rated as (◎). The results were obtained. Furthermore, the set torque was 500 gf·cm, which is not a high torque setting, but the torque characteristics were also good.

The durability test in Figure 10 (e) was conducted on a torque limiter (set torque is high at 800 gf cm) that has an inner ring member made of PEEK as a base material and CF, PTFE, or graphite as a filler material. It is a graph showing test results.
In this test piece, the rate of change in torque was +2.4%/-2.2%, and the variation rate in fluctuation characteristics was 2.9%. According to the above evaluation criteria, both durability and fluctuation characteristics were rated as (◎). The results were obtained. Regarding high torque characteristics, a result of (◎) was obtained from the results of durability and fluctuation characteristics. In addition, with this test piece, even when the cumulative number of rotations exceeded 5 million times and reached 10 million times, good results were obtained in both durability and fluctuation characteristics.

According to the durability tests (g) to (k) above, when the base material is PEEK, the durability and sliding characteristics are good by using an inner ring member containing CF, PTFE, and graphite. At the same time, optimum results were obtained as a high torque type. That is, when the base material was PEEK, it was more compatible with the three types of fillers described above than when the base material was PPS, and good results were obtained as a small, high-torque torque limiter.

The durability test in Fig. 11(C) shows the results of a durability test for a torque limiter (setting torque is 500 gf cm) that has an inner ring member made of PI as the base material and CF, PTFE, or graphite as the filler material. This is a graph showing.
In this test piece, the rate of change in torque was -6.1%, the rate of variation in fluctuation characteristics was 11.8%, and according to the above evaluation criteria, both durability and fluctuation characteristics were rated △.

The durability test shown in Fig. 12 (sa) was conducted on a torque limiter (set torque is set at high torque of 850 gf cm) that has an inner ring member made of PI as the base material and CF, PTFE, or graphite as the filler material. It is a graph showing test results.
In this test piece, the test piece was damaged at the cumulative number of rotations of 1.3 million times, so the experiment was stopped halfway. The rate of change in torque up to 1.3 million cumulative rotations is -8.1%, and the variation rate of fluctuation characteristics is 6.4%. According to the evaluation criteria described above, durability is (△) and fluctuation characteristics are ( The result was 〇). Further, based on the results, future trends were predicted and a result of (△) was obtained for high torque characteristics.

According to the above durability tests (g) and (s), when the base material is PI, even if the inner ring material is made of CF, PTFE, or graphite, it is as effective as using PEEK as the base material. There wasn't.

The durability test in FIG. 13(b) is a graph showing the results of a durability test for a conventional torque limiter (set torque is 800 gf·cm) having an inner ring member formed of sintered metal.
In this test piece, the rate of change in torque was -11.3%, the variation rate in fluctuation characteristics was 9.3%, and according to the above evaluation criteria, both durability and fluctuation characteristics were rated △. Furthermore, regarding high torque characteristics, a result of Δ was obtained from the results of durability and fluctuation characteristics.

As described above, even if the conventional torque limiter is made of a high torque type by using a sintered metal inner ring member, good results cannot be obtained in terms of durability and fluctuation characteristics.

FIG. 14 is a list summarizing the results of the durability tests shown in FIGS. 2 to 13.
As is clear from this list, when adding CF, PTFE, or graphite as a filler, it is preferable to use PEEK as the base material. An excellent torque limiter suitable for high-torque types can be obtained (see Fig. 10). In addition, in the case of using a similar filler, even if PPS is used as the base material, it is possible to obtain better results than sintered metal (see F in FIG. 7).

There is no particular limitation on the amount of the fillers added above, but based on the experimental results, the total content of fillers should be 60% by weight or less, and the lower limit is such that each filler can exhibit its performance. It is preferable to keep the content to about 10% by weight (with a minimum content of about 5% by weight).

Regarding the fillers described above, CF is in the form of short fibers and exclusively contributes to improving the strength and abrasion resistance (durability) of the base material. In addition, PTFE and graphite contribute to improving lubricity (slidability), but PTFE has a small intermolecular cohesive force and is excellent in low friction, while graphite has a low friction property due to sliding between carbon layers. In addition to friction properties, they have high heat resistance, load resistance, and wear resistance, and their functions complement each other.

Therefore, for the three fillers mentioned above, the upper limit of the total content is set at 60% by weight, and considering the functional balance of each filler, CF is 5 to 30% by weight, PTFE and graphite are 5 to 20% by weight. Preferably, it is expressed as % by weight.

1 Torque limiter 10 Inner ring member 20 Outer ring member 30 Coil spring

Claims (2)

an inner ring member around which a coil spring is wound and held; and an outer ring member disposed to cover the inner ring member and to which an end of the coil spring is fixed; the friction between the inner ring member and the coil spring is reduced. A torque limiter that generates a predetermined torque between the inner ring member and the outer ring member by force,
The inner ring member is made of polyetheretherketone or polyphenylene sulfide as a base material, and a filler containing carbon fiber, polytetrafluoroethylene, and graphite is added thereto ,
The filler is 15 to 60% by weight in total,
A torque limiter characterized in that the carbon fiber is added in an amount of 5 to 30% by weight, the polytetrafluoroethylene is added in an amount of 5 to 20% by weight, and the graphite is added in an amount of 5 to 20% by weight. The torque limiter according to claim 1, wherein the coil spring has a set torque of 500 gf cm or more and is wound around an inner ring member, and the overall outer diameter of the torque limiter is 20 mm or less. .