JP2899090B2 - Synthetic resin rotor for ultrasonic motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic motor utilizing vibration of a piezoelectric body, and particularly to a rotor made of a synthetic resin having a desirable flexural modulus.

[Related Art] In an ultrasonic motor, a traveling wave is generated in a stator by a piezoelectric body, and the traveling wave is applied to a rotor pressed against the stator to rotate the rotor. Generally, the rotor is made of aluminum, and a slider is bonded to a surface of the rotor in contact with the stator so that traveling waves can effectively act on the rotor, so that appropriate friction is generated between the two.

[Problem to be Solved by the Invention] The rotor is rotated by the traveling wave of the stator. As a result of the study of the present inventors, the rotation characteristics of the rotor have a great relationship with the elastic modulus of the material forming the rotor. Yes, a resin composition comparable to a longitudinal elastic modulus of 720,000 kgf / cm ² , such as aluminum, has not been found yet, and it has been found that it is difficult to form a rotor using a synthetic resin.

Furthermore, as a slider to be bonded to an aluminum rotor, there is a conventional aromatic polyester resin, Econole E1.
01, a resin composition filled with polytetrafluoroethylene (PTFE) (cannot be injection molded) was processed into a sheet shape of 0.2 to 0.5 mm thick, and then punched into the slider shape shown in the drawing. By bonding the aluminum rotor with an adhesive such as epoxy resin, it is necessary to generate an appropriate frictional force between the stator and the aluminum rotor and to provide wear resistance.

As described above, the present invention has a trade-off phenomenon that the slider has an excellent wear resistance while having an appropriate frictional resistance with the stator, and has a very high elastic modulus like an aluminum rotor. There has been an extremely difficult task that cannot be considered with very common sense, such as whether a synthetic resin composition is feasible and what minimum elastic modulus is required.

The present invention finds a resin composition that solves these problems at once, and by integrally molding the aluminum rotor portion and the slider portion with the same material, it is possible to reliably obtain a synthetic resin rotor having desirable characteristics. It is another object of the present invention to produce a lightweight ultrasonic motor having less friction noise.

[Means for Solving the Problems] The present invention provides a thermoplastic resin for solving the above problems.
40 to 60 parts by weight, 15 to 30 parts by weight of potassium titanate whisker, 15 to 35 parts by weight of carbon fiber, 5 to 15 parts by weight of polytetrafluoroethylene powder is an ultrasonic rotor formed of a resin composition , Its flexural modulus is 13
By molding to a mass of 10,000 kgf / cm ₂ or more, desirably 230,000 kgf / cm ₂ or more, a conventional aluminum rotor portion and a PTFE / Econol slider portion can be integrated. Moreover, the rotational performance of the ultrasonic motor incorporating the synthetic resin rotor is very good, and unlike the conventional product, there is no need to bond the slider and the rotor, so the output performance is stable and the reliability is increased. By making the rotor itself a resin, friction noise was reduced and weight reduction became possible. Further, if the mold is finished to a desired shape, almost no finishing is required only by injection molding, so that the production efficiency is extremely high, which is expected to greatly contribute to the spread of ultrasonic motors in the future.

In the present invention, as the thermoplastic resin that can be used, there is no particular limitation, but from the viewpoint of sliding heat generation and durability, engineering plastics, in particular, polyphenylene sulfide,
Heat-resistant engineering plastics such as polyethersulfone, polyetherimide, liquid crystal polymer, polyetheretherketone, polyetherketone, polyamideimide, and polyimide are preferable, and among them, polyphenylenesulfide is most practical at present.

The reason for limiting the amount of use to 40 to 60 parts by weight is that
If the amount is less than 40 parts by weight, the injection moldability deteriorates, and if it exceeds 60 parts by weight, it is difficult to achieve a flexural modulus of 130,000 kgf / cm ₂ or more.

As potassium titanate whiskers, commercially available ones having an average fiber diameter of 0.1 to 2 μm and an average fiber length of 5 to 100 μm can be used as they are, and those having an aspect ratio (average fiber length / average fiber diameter) of 10 or more from the viewpoint of reinforcing effect. Is preferred. Potassium titanate whiskers have a Mohs hardness of 4 and a mating material (using a relatively soft metal such as phosphor bronze as a stator), in addition to the strength and flexural modulus improvement effects of whiskers (single crystal fibers). It is not harmful, and is effective in generating a frictional force for following the traveling wave generated in the stator. Further, the micro-reinforced fibers (typically, the average fiber diameter is 0.3 μm and the average fiber length is 15 μm) also serve to make the surface of the molded article extremely smooth (improve the mold transferability).

The reason for limiting the blending amount to 15 to 30 parts by weight is that if it is less than 15 parts by weight, the flexural modulus is improved, the frictional force is maintained, and the surface smoothness of the molded product is maintained (the surface roughness is prevented by using carbon fiber together). ) On the other hand, if the effect is reduced, if it exceeds 30 parts by weight, the added amount of carbon fiber which has a large effect of improving the flexural modulus and the abrasion resistance and the PTFE which has a large effect of preventing the generation of friction powder,
This is because it becomes difficult to mix the required amount while maintaining the fluidity during injection molding.

As the carbon fiber, the bending is greater tensile modulus 3.5 million kgf / cm ₂ or more high-modulus carbon fibers the effect of improving the elastic modulus is desired, sufficiently in tensile modulus 2.4 million kgf / cm ₂ or more high-strength carbon fiber Can be used.

Conventionally, the PAN system was good in performance, but recently, the pitch system can be used satisfactorily. Commercial products usually have a fiber diameter of 10
μm, the fiber length is reinforcing effect and processability (extrusion molding for pellet production and injection molding for rotor production)
Therefore, those having a size of 0.5 to 6 mm, particularly 6 mm, are generally used and have excellent performance.

The compounding amount is suitably from 15 to 35 parts by weight, and if the amount is less than 15 parts by weight, it is difficult to bring the flexural modulus of the resin composition to 150,000 kgf / cm ₂ or more, while to 35 parts by weight or more. As a result, the workability, particularly the extrudability during pellet production, is poor, and the smoothness of the sliding surface of the rotor during injection molding is undesirably impaired.

As the polytetrafluoroethylene powder, a fine powder having an average particle diameter of 50 μm or less is desirable, and a fine powder having an average particle diameter of 10 μm or less is desirable.

Polytetrafluoroethylene is the partner material (phosphor bronze)
Has a function of improving the abrasion resistance (by reducing the generation of abrasion powder) of the resin composition by improving the slidability (lubricating property) with the resin composition. If the amount is less than 5 parts by weight, the effect is small. If the amount exceeds 15 parts by weight, not only the flexural modulus of the resin composition but also the strength (especially the impact strength) is problematic, and PTFE itself is considerably expensive. Therefore, it turned out to be uneconomical.

To produce the resin composition of the present invention, a thermoplastic resin,
A method is generally used in which potassium titanate whiskers, carbon fibers, and polytetrafluoroethylene powder are weighed in predetermined amounts, uniformly mixed by a blender such as a tumbler mixer, kneaded by a melt kneader such as an extruder, and then pelletized. It is.

Further, the synthetic resin rotor of the present invention can be produced very efficiently by setting the cylinder temperature, the mold temperature, the injection pressure and the injection time of the injection molding machine according to the thermoplastic resin used. is there.

In the resin composition of the present invention, a part of potassium titanate whisker or carbon fiber can be replaced with an inorganic filler such as talc, mica, graphite or the like, as long as the basic physical properties and the molding process are not hindered. In some cases, a coloring agent such as carbon black or a heat stabilizer suitable for the thermoplastic resin to be used may be blended.

According to the present invention, an aluminum rotor and a slider made of a synthetic resin (soft and abrasion resistant) are separately manufactured and assembled by bonding, so that a single rotor is manufactured. Because it can be manufactured by a very productive method of injection molding with a synthetic resin composition of the above, the reliability as a rotor, the friction noise is reduced, the weight can be reduced, and the production efficiency is improved. The economic effect is extremely large.

[Examples] The following examples are provided to further clarify the present invention.

Examples 1 to 5 and Comparative Examples 1 to 4 FORTRON W205 (PPS; Polyplastics Co., Ltd.)
Table 1 shows TISMO D102 (potassium fiber made of titanium; Otsuka Chemical Co., Ltd.), Vesfight HTA-C6-NR (carbon fiber; Toho Rayon Co., Ltd.) and Fluon L150J (polytetrafluoroethylene; Asahi Glass Co., Ltd.) After weighing according to the formulation shown in the above, mixed with a blender, using a 45 mm extruder,
The mixture was pelletized by a cutter while kneading and extruding at a cylinder temperature of 300 ° C. The obtained pellets are heated at a cylinder temperature of 300.
℃, mold temperature 130 ° C, injection pressure 1200kgf / cm ₂ , holding pressure 600kgf
The rotor was injection molded at / cm ₂ .

In addition, in order to investigate the basic physical properties of the same material, the following test pieces were molded in the same conditions as above using a metal mold for measuring physical properties and various physical properties were measured. The results are shown in Table 1.

Specific gravity: Measured with ASTM D792 Izod impact piece Flexural modulus: ASTM D790 Sliding characteristics: Suzuki friction and wear tester (manufactured by Toyo Baldwin) Counterpart agent: phosphor bronze (JIS C 5341), surface pressure 10 kgf / cm ₂ ,
Circumferential speed 30cm / sec, mileage 10km The rotor produced by injection molding the resin composition of each composition shown in Table 1 was incorporated into an ultrasonic motor in which the rotor 3 and the slider 3a shown in the drawing were integrated, and the actual machine test was performed to evaluate the motor characteristics. did. In the ultrasonic motor, a piezoelectric body 2 is adhered to a stator 1, and when a driving signal is applied to the piezoelectric body 2, a traveling wave is generated in the stator. Further, the rotor 3 is pressed against the stator 1 by a spring material 4 and is rotated by a traveling wave of the stator.

According to the test results, when the thermoplastic resin of Comparative Example 1 exceeds 60 parts by weight and the flexural modulus is less than 13 kgf / cm ₂ , the motor rotates but the current value is high and the efficiency is poor. On the other hand, a resin comprising 40 to 60 parts by weight of the thermoplastic resin shown in Examples 1 to 5, 15 to 30 parts by weight of potassium titanate whisker, 15 to 35 parts by weight of carbon fiber, and 5 to 15 parts by weight of polytetrafluoroethylene powder The rotor molded from the composition has a flexural modulus of 13 kg.
At f / cm ₂ or more, the efficiency of the motor was good, with the drive current value of the motor not so much as the current product.

Above all, the rotor prepared from Example 5 had a small current value, good motor efficiency, no generation of wear powder after 500 hours of operation, and no stator wear.

On the other hand, the polytetrafluoroethylene of Comparative Example 2 containing less than 5 parts by weight and the potassium titanate whisker of Comparative Example 3 containing less than 15 parts by weight are 100% or less.
After the operation for a long time, it was found that the former had large generation of abrasion powder and abrasion (damage) of the stator, and the latter also had large abrasion of the stator and was of low practicality.

From these facts, it can be concluded that the motor properties are greatly related to the flexural modulus of the rotor, and that the resin composition for the rotor within the scope of the present invention is appropriate in consideration of the durability of the ultrasonic motor.

Example 6 In the same manner as in Examples 1 to 5, Ultem 1010 (polyetherimide; GE), TISMO D102 (potassium titanate fiber; Otsuka Chemical Co., Ltd.), Vesfight HTA-C6-NR (carbon fiber; Toho Rayon Co., Ltd.) and Fluon L150J (polytetrafluoroethylene; Asahi Glass Co., Ltd.) were blended as shown in Table 2 to produce pellets using a kneading extruder with a cylinder temperature of 340 ° C.

The obtained pellets were heated at a cylinder temperature of 370 ° C and a mold temperature of 1
At 40 ° C., an injection pressure of 1200 kg / cm ₂ and a holding pressure of 600 kgf / cm ₂ , a rotor and a test piece for measuring physical properties were injection molded.

 The measured physical properties of the same material are shown in Table 2.

The rotor injection-molded with this composition was tested on an actual machine, and the motor characteristics were measured. As a result, good motor characteristics were obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view, partially cut away, of a synthetic resin rotor for an ultrasonic motor according to the present invention. 1; stator, 3; rotor, 3a; slider

Continued on the front page (72) Inventor Shinji Sagara 1508, Kurahake, Ora-cho, Oraku-cho, Oraku-gun, Gunma Prefecture-2 Kurakake Daiichi Industrial Park Fuku-ku Gunma Factory Co., Ltd. (72) Inventor Eiji Akutomo Euraku, Gunma Prefecture 1508-2 Kurakake, Akabori-cho, Kachikake Industrial Park Fukukoku Gunma Factory Co., Ltd. (56) References JP-A-2-197272 (JP, A) JP-A-3-285574 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H02N 2/00

Claims (2)

(57) [Claims] 1. A rotor of an ultrasonic motor in which a traveling wave is generated on a stator by a piezoelectric body and the traveling wave rotates a rotor pressed against the stator, the rotor comprises 40 to 60 parts by weight of a thermoplastic resin, potassium titanate. Whiskers 15-30
A synthetic resin rotor for an ultrasonic motor, which is formed by molding a resin composition comprising 5 parts by weight of carbon fiber, 15 to 35 parts by weight of carbon fiber, and 5 to 15 parts by weight of polytetrafluoroethylene powder. 2. The bending elastic modulus of the rotor according to claim 1 is 13
A synthetic resin rotor for an ultrasonic motor, wherein the rotor is 10,000 kgf / cm ² or more.