JP7287080B2 - Magnetic rotary encoder and rolling bearing unit - Google Patents

Description

The present invention relates to a magnetic rotary encoder and a rolling bearing unit.

A rolling bearing unit is known that includes a rolling bearing and a magnetic rotary encoder that is a sensor that measures the rotational state (for example, rotational speed and rotational direction) of a rotating ring of the rolling bearing. As a magnetic rotary encoder, there is known one in which a magnet portion formed in an annular shape from a magnetic resin material, which is a mixture of magnetic powder and a binder resin, is joined to a slinger, which is an annular member. (See Patent Document 1, for example).

This rolling bearing unit is used to measure the rotation state of automobile wheels. The deformation could not follow the deformation of the slinger, and there was a risk of cracks occurring in the magnet part. That is, the impact resistance of the magnet portion was insufficient. In addition, when exposed to high temperatures, the resin that serves as the binder for the magnets oxidizes and deteriorates, making it difficult for the magnets to stretch or bend. was more likely to occur. That is, the heat resistance of the magnet portion was insufficient.

Although an impact resistance improver and an antioxidant are added to the magnetic resin material of the rolling bearing unit disclosed in Patent Document 1, the performance requirements for rolling bearing units used in automobiles are becoming more and more stringent. Therefore, further improvements in impact resistance and heat resistance have been desired for the magnet portion of the magnetic rotary encoder.

JP-A-2007-3223

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic rotary encoder and a rolling bearing unit in which cracks are less likely to occur in magnet portions even when repeatedly exposed to high-temperature and low-temperature environments.

A magnetic rotary encoder according to an aspect of the present invention includes: a magnet portion formed annularly of a magnetic resin material containing magnetic powder, a polyamide resin, an amine-based antioxidant, and 2-mercaptobenzimidazole; A slinger that is an annular member joined to the polyamide resin has a water absorption of 0.7% by mass or less when left in water at 23 ° C. for 24 hours, and the content of the amine antioxidant and 2-mercaptobenzimidazole in a weight ratio of 2:1 to 1:2.
A rolling bearing unit according to another aspect of the present invention includes the magnetic rotary encoder according to the above aspect, and a rolling bearing having a rotating ring and a stationary ring, wherein the slinger of the magnetic rotary encoder is the rotating ring of the rolling bearing. The gist is that it was attached to the

INDUSTRIAL APPLICABILITY The magnetic rotary encoder and rolling bearing unit according to the present invention are less prone to cracks in the magnet portion even when repeatedly exposed to high-temperature and low-temperature environments.

1 is a partial longitudinal sectional view showing the structure of a deep groove ball bearing provided with a magnetic rotary encoder, which is one embodiment of a rolling bearing unit according to the present invention; FIG.

An embodiment of the invention is described below. In addition, this embodiment shows an example of this invention, Comprising: This invention is not limited to this embodiment. In addition, various changes or improvements can be added to the present embodiment, and forms to which such changes or improvements are added can also be included in the present invention.

A magnetic rotary encoder according to one embodiment of the present invention includes a magnet portion formed into an annular shape of a magnetic resin material containing magnetic powder, a polyamide resin, an amine-based antioxidant, and 2-mercaptobenzimidazole; a slinger, which is a toric member joined to the portion. This polyamide resin is a low water-absorbing resin having a water absorption rate of 0.7% by mass or less when left in water at 23° C. for 24 hours. In addition, the mass ratio of the content of the amine-based antioxidant and the content of 2-mercaptobenzimidazole (hereinafter sometimes referred to as "MBI") in the magnetic resin material is in the range of 2:1 to 1:2. is.

A rolling bearing unit according to an embodiment of the present invention includes the magnetic rotary encoder according to the embodiment and a rolling bearing having a rotating ring and a stationary ring. The slinger of the magnetic rotary encoder is attached to the rotating ring of the rolling bearing, and the magnet portion of the magnetic rotary encoder rotates in the same rotational state as the rotating ring of the rolling bearing. Therefore, by measuring the rotation state of the magnet portion, it is possible to measure the rotation state of the rotating ring of the rolling bearing.

Since the magnetic resin material that constitutes the magnet portion of the magnetic rotary encoder contains the amine antioxidant and MBI in the above mass ratio, the synergistic effect of the two prevents oxidation deterioration of the polyamide resin and reduces flexibility. is less likely to occur. Therefore, the magnet portion of the magnetic rotary encoder of this embodiment has excellent impact resistance and heat resistance. Therefore, the magnetic rotary encoder and the rolling bearing unit of the present embodiment have high magnetic characteristics and high-precision measurement of the rotating state because the magnet portion is unlikely to crack even if it is repeatedly exposed to high-temperature and low-temperature environments. possible and reliable.

Such a magnetic rotary encoder and rolling bearing unit of this embodiment can be suitably used in the field of automobiles. Since automobiles often come into contact with water such as rainwater and muddy water, magnetic rotary encoders and rolling bearing units used in automobiles also come into contact with water. Therefore, if the polyamide resin has a high water absorption rate, the magnet portion may swell due to water absorption, and the necessary magnetic properties may be impaired. If the polyamide resin is a low water-absorbing resin having a water absorption of 0.7% by mass or less when left in water at 23° C. for 24 hours, swelling of the magnet portion and deterioration of magnetic properties due to water absorption are less likely to occur.

Here, the reason why the synergistic effect of the amine-based antioxidant and MBI makes it difficult for the polyamide resin to deteriorate due to oxidation will be described. Polyamide resin is often oxidatively deteriorated when used in a high temperature environment of 100 to 175 ° C., but 4,4'-bis (α, α-dimethylbenzyl) diphenylamine (hereinafter also referred to as "CD") ), oxidative degradation is suppressed because the amine antioxidant provides hydrogen to the polymer radicals generated by thermal decomposition and oxidation to stop the auto-oxidation reaction chain. be done.

On the other hand, since various radicals are generated from hydroperoxides produced by the antioxidant action of the amine-based antioxidant, the hydroperoxides also cause oxidative deterioration of the polyamide resin. However, when MBI is blended, MBI converts hydroperoxides into stable alcohols, thereby suppressing oxidative deterioration caused by hydroperoxides. Moreover, MBI is present near amine-based antioxidants such as CD in the magnetic resin material due to acid-base interaction, so the combined use of amine-based antioxidants and MBI has a high anti-oxidation effect. .
Thus, when both the amine-based antioxidant and the MBI are blended in the polyamide resin, the synergistic effect thereof provides an excellent anti-oxidative deterioration effect.

If the mass ratio of the content of the amine-based antioxidant and the content of MBI in the magnetic resin material is within the range of 2:1 to 1:2, the effect of preventing oxidation deterioration of the polyamide resin is excellent, and the amine MBI tends to improve the oxidation deterioration prevention effect of the polyamide resin by the system antioxidant. In addition, the magnetic properties and mechanical strength of the magnet portion are excellent.

The amount of the amine antioxidant and MBI in the magnetic resin material is 0.5 parts by mass or more and 2 parts by mass or less of the amine antioxidant and 0.25 parts by mass of 2-mercaptobenzimidazole with respect to 100 parts by mass of the polyamide resin. parts by mass or more and 2 parts by mass or less. With such a compounding amount, the effect of preventing oxidation deterioration of the polyamide resin is more excellent, and the amine-based antioxidant and MBI are less likely to exude from the magnet portion.

Next, each component contained in the magnetic resin material will be described in detail.
<Regarding magnetic powder>
The type of magnetic powder that can be used is not particularly limited, but considering magnetic properties and weather resistance, ferrite magnetic powder such as strontium ferrite, barium ferrite, samarium-iron-nitrogen, samarium-cobalt , neodymium-iron-boron and other rare earth magnetic powders are suitable. One of these magnetic powders may be used alone, or two or more of them may be used in combination.

In addition, when the main usage environment is high temperature (for example, about 150 ° C.), or when high magnetic properties (BHmax exceeds 2.0 MGOe) are required, rare earth magnetic powder is used, and low magnetic properties (BHmax is 1 .6 to 2.0 MGOe), it is preferable to use ferrite magnetic powder as the main component in consideration of cost.

The content of the magnetic powder in the magnetic resin material varies depending on the type of the magnetic powder, but can be, for example, 70% by mass or more and 95% by mass or less. The molding of the magnet portion is performed at a temperature equal to or higher than the melting point of the polyamide resin that is the binder.
In order to improve the dispersibility of the magnetic powder and the interaction between the magnetic powder and the binder, a silane coupling agent having an organic functional group such as an amino group or an epoxy group is added to the magnetic resin material. good too.

<About polyamide resin>
The type of polyamide resin is not particularly limited as long as it has a water absorption of 0.7% by mass or less when left in water at 23° C. for 24 hours. ), polyamide 612 (PA612), polyamide 610 (PA610), modified polyamide 6T (PA6T), polyamide 9T (PA9T), polyamide MXD6 (PAMDX6).

The modified polyamide 6T is a polycondensate obtained by changing part of the terephthalic acid of polyamide 6T, which is a polycondensate of hexamethylenediamine and terephthalic acid, to at least one of adipic acid and isophthalic acid (specifically, PA6T/66, PA6T/6I, PA6T/6I/66), a polycondensate (PA6T/M-5T) in which part of the hexamethylenediamine of polyamide 6T is changed to methylpentanediamine, repeating polyamide 6T and ε-caprolactam A polycondensate (PA6T/6) or the like is used as a unit. Polyamide MXD6 is a polycondensate of meta-xylenediamine and adipic acid.

Since these polyamide resins are low water-absorbing polyamide resins as described above, they can be used as a binder having water resistance. It can be said that polyamide 6T, polyamide 9T and polyamide MXD6 are more preferable.
The method for measuring the water absorption of the polyamide resin is not particularly limited, but examples include the method specified in ISO 62 and the A method specified in JIS K7209. When measuring the water absorption, a plate-shaped sample having a length of 60 mm, a width of 60 mm, and a thickness of 1 mm was prepared by melt-molding a polyamide resin. to measure.

When manufacturing the magnetic resin material, there may be a step of mixing the polyamide resin and the magnetic powder and pelletizing the mixture with an extruder or the like. Therefore, the polyamide resin preferably has dispersibility with the magnetic powder. Further, it is preferable that the material components are uniformly distributed in the magnet portion.

<About amine antioxidant>
The type of amine-based antioxidant is not particularly limited, but diphenylamine-based compounds such as 4,4'-(α,α-dimethylbenzyl)diphenylamine and 4,4'-dioctyldiphenylamine, and N,N' -diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N,N'-bis(1-methylheptyl) -p-phenylenediamine, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, etc. Examples include phenylenediamine compounds.

The magnetic resin material may contain other components such as additives and reinforcing materials as long as the object of the present invention is not compromised. Additives include, for example, impact resistance improvers, heat stabilizers, inorganic fillers, plasticizers, flame retardants, antistatic agents, delustering agents, nucleating agents, weather stabilizers, ultraviolet absorbers, colorants, separating agents. A templating agent can be mentioned.

A thermal stabilizer is used to improve the thermal stability during melt molding of the magnetic resin material, and for example, a phosphorus compound is preferably used.
Also, the impact resistance improver is used to reduce vibrations and impacts applied to the magnet portion, and for example, an elastic material is preferably used. Examples of elastic materials include the following resins and rubber materials.

That is, examples of resins include modified low-water-absorbing polyamide resins. This modified low water-absorbing polyamide resin is a block copolymer having a hard segment composed of the low water-absorbing polyamide resin and a soft segment composed of at least one of a polyester component and a polyether component. Modified polyamide resins having polyamide 11 or polyamide 12 as hard segments are commercially available as modified low water-absorbing polyamide resins. When the hard segment of the modified low-water-absorbent polyamide resin is the same as that of the low-water-absorbent polyamide resin used as the binder, the compatibility between the binder and the impact resistance improver is improved.

Examples of rubber materials include styrene-butadiene rubber, acrylic rubber, acrylonitrile-butadiene rubber, carboxyl-modified acrylonitrile-butadiene rubber, silicone rubber, fluorinated silicone rubber, chloroprene rubber, hydrogenated acrylonitrile-butadiene rubber, carboxyl-modified hydrogenated acrylonitrile-butadiene rubber, carboxyl-modified Examples include modified styrene-butadiene rubber, fluororubber, and ethylene-propylene non-conjugated diene rubber. One of these rubber materials may be used alone, or two or more may be used in combination.

Among these rubber materials, acrylic rubber, acrylonitrile-butadiene rubber, carboxyl-modified acrylonitrile-butadiene rubber, silicone rubber, Hydrogenated acrylonitrile-butadiene rubber, fluororubber, and carboxyl-modified hydrogenated acrylonitrile-butadiene rubber are preferred.

Furthermore, among these rubber materials, acrylic rubber, carboxyl-modified acrylonitrile-butadiene rubber, carboxyl Modified hydrogenated acrylonitrile-butadiene rubber and carboxyl-modified styrene-butadiene rubber are preferred.

These rubber materials are preferably fine particles having an average particle size of 30 nm or more and 300 nm or less. If the average particle size is less than 30 nm, the cost is high and the particles are too fine to easily deteriorate. If the average particle size exceeds 300 nm, the dispersibility may deteriorate and it may become difficult to uniformly improve the impact resistance.

The amount of these impact modifiers added is preferably 5% by mass or more and 60% by mass or less, more preferably 10% by mass or more and 40% by mass, based on the total amount of the low water-absorbing polyamide resin and the impact modifier. The following are more preferable. If the amount added is less than 5% by mass, the effect of improving impact resistance may be insufficient. On the other hand, if the amount added exceeds 60% by mass, although the impact resistance is improved, the amount of the low water-absorbing polyamide resin is relatively small, so the mechanical properties such as tensile strength are reduced and practicality is reduced. There is a risk.

The types and blending ratios of the components such as the magnetic powder and the polyamide resin blended in the magnetic resin material are determined by the amount of bending deflection of the test piece made of the magnetic resin material measured by the method described later in the section of Examples. is within the range of 2 mm or more and 15 mm or less, it can be appropriately selected according to the desired magnetic properties. If the magnet portion is formed of a magnetic resin material that has a bending deflection amount in the range of 2 mm or more and 15 mm or less, the magnet portion will have excellent heat resistance and impact resistance, and can be repeatedly used in high temperature and low temperature environments. It is possible to obtain a magnetic rotary encoder and a rolling bearing unit in which cracks are less likely to occur in the magnet portion even when exposed.

Next, each member constituting the magnetic rotary encoder will be described in detail.
<About the magnet part>
The magnet part is a member formed by forming a magnetic resin material into an annular shape. The magnet part can be manufactured by an injection molding method using a mold or the like, a compression molding method, or the like.

<About Slinga>
A slinger is an annular member that is joined to the magnet portion. The magnet part and the slinger are joined so as to form an annular shape as a whole.
Magnetic materials such as ferritic stainless steel (SUS430, etc.) and martensitic stainless steel (SUS410, etc.) are preferable for the material of the slinger because they do not easily degrade the magnetic properties of the magnet portion and have corrosion resistance. However, in the case of a rolling bearing unit provided with a protective member surrounding a magnetic rotary encoder, high corrosion resistance is not required, so cold-rolled steel (SPCC) or the like may be used in consideration of cost.

Although the method of joining the magnet portion and the slinger is not particularly limited, it may be performed by insert molding a magnetic resin material using the slinger as a core, or the separately manufactured magnet portion and the slinger may be joined together. You may perform by joining. In either method, an adhesive may be interposed between the magnet portion and the slinger, or they may be joined without using an adhesive.

Next, the rolling bearing unit will be described in detail. The rolling bearing unit of this embodiment includes a magnetic rotary encoder and a rolling bearing. This rolling bearing has a rotating ring and a stationary ring (non-rotating ring), and a slinger of a magnetic rotary encoder is attached to the rotating ring.

Therefore, the magnet portion of the magnetic rotary encoder rotates in the same rotational state as the rotating ring of the rolling bearing. The rotating state of the rotating ring of the bearing can be measured.

An example of a rolling bearing unit with a magnetic rotary encoder will now be described in more detail with reference to FIG.
The rolling bearing unit shown in FIG. 1 has a rolling bearing 10 and a magnetic rotary encoder 20 . Although the rolling bearing 10 is a deep groove ball bearing in the example of FIG. 1, the type of rolling bearing is not limited to the deep groove ball bearing, and other types of rolling bearings may be used. For example, radial type rolling bearings such as angular ball bearings, self-aligning ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, and self-aligning roller bearings, and thrust types such as thrust ball bearings and thrust roller bearings. of rolling bearings.

The rolling bearing 10 includes an outer ring 11 that is a stationary ring, an inner ring 12 that is a rotating ring, a plurality of rolling elements 13 that are freely rollable between the raceway surface of the outer ring 11 and the raceway surface of the inner ring 12, and the outer ring. 11 and the raceway surface of the inner ring 12, and a sealing device 15 that covers the opening of the gap between the outer ring 11 and the inner ring 12. Note that the retainer 14 and the sealing device 15 may not be provided.

The sealing device 15 includes a ring-shaped core metal 18 fixed to the inner peripheral surface of the outer ring 11 , a ring-shaped rubber seal portion 17 attached to the core metal 18 , and a bearing axial direction of the core metal 18 and the rubber seal portion 17 . an annular slinger 22 disposed on the outside and secured to the outer peripheral surface of the inner ring 12 . The rubber seal portion 17 has a substantially L-shaped cross section and is reinforced by a metal core 18 that also has a substantially L-shaped cross section. A seal lip portion of the rubber seal portion 17 is brought into sliding contact with the surface of the slinger 22 to seal the opening of the gap between the outer ring 11 and the inner ring 12 .

On the other hand, a magnetic rotary encoder 20 that measures the rotational state (for example, rotational speed, number of rotations, rotational direction) of the inner ring 12 has a slinger 22 and a magnet portion 21 attached to the slinger 22 . Thus, in the rolling bearing unit of FIG. 1, the slinger 22 serves both as a member that constitutes the magnetic rotary encoder 20 and as a member that constitutes the sealing device 15 .

The slinger 22 is manufactured from a thin plate of ferritic stainless steel (SUS430 or the like), martensitic stainless steel (SUS410 or the like), or the like. The cylindrical portion of the slinger 22 is fitted to the outer peripheral surface of the inner ring 12, and the flange portion extends outward in the bearing radial direction from the cylindrical portion of the slinger 22 so that the slinger 22 has a substantially L-shaped cross section. None.

The magnet portion 21 is made of the magnetic resin material described above and fixed to the inner ring 12 via the slinger 22 . More specifically, the magnet portion 21 is attached to the surface of the flange portion of the slinger 22 facing outward in the axial direction of the bearing. Moreover, the magnet part 21 is a multipolar magnet, and N poles and S poles are alternately formed in the circumferential direction. The number of poles of the magnet portion 21 is preferably approximately 70 to 130 poles, more preferably 90 to 120 poles. A magnetic sensor 30 is arranged facing the outer side of the magnet portion 21 in the axial direction of the bearing. A measuring mechanism is configured to measure the rotational state.

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples.
Magnetic substance powder, polyamide resin powder, amine-based antioxidant, and 2-mercaptobenzimidazole (MBI) are mixed and kneaded at the compounding ratio shown in Table 1 (units of numerical values are parts by mass) to obtain a magnetic powder. A resin material was obtained. Then, the obtained magnetic resin material was melt-molded to manufacture a test piece to be used in the method for measuring bending properties specified in ISO178. However, the thickness of the test piece is 3.0 mm.

Strontium ferrite powder was used as the magnetic powder. Polyamide 12 was used as the polyamide resin. As the amine antioxidant, N,N'-diphenyl-p-phenylenediamine (hereinafter referred to as "DPPD") or 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (CD) was used.

After heat-treating the manufactured test piece under conditions of 150° C. and 96 hours, the amount of bending deflection at 23° C. was measured by the method for measuring bending properties specified in ISO178. However, the distance between fulcrums during bending measurement is 50 mm. Then, the amount of bending deflection after heat treatment is divided by the amount of bending deflection before heat treatment to calculate the retention rate of bending deflection amount. and impact resistance were evaluated. In Table 1, when the retention rate of bending deflection was 80% or more, it was "excellent", when it was 60% or more and less than 80%, it was "good", and when it was 40% or more and less than 60% "Possible" is shown, and "Failure" is shown when it is less than 40%.

As can be seen from the results shown in Table 1, Example 1 in which CD and MBI were used in combination had a higher deflection retention rate and a higher heat resistance than Comparative Example 2 in which only CD was used and Comparative Example 3 in which both were not used. Excellent toughness and impact resistance.

10 rolling bearing 11 outer ring (stationary ring)
12 inner ring (rotating ring)
20 magnetic rotary encoder 21 magnet unit 22 slinger 30 magnetic sensor

Claims (4)

a magnet portion formed in an annular shape of a magnetic resin material containing magnetic powder, a polyamide resin, an amine-based antioxidant, and 2-mercaptobenzimidazole; and a slinger, which is an annular member joined to the magnet portion; with
The polyamide resin has a water absorption rate of 0.7 mass% or less when left in water at 23 ° C. for 24 hours,
A magnetic rotary encoder, wherein the mass ratio of the content of the amine antioxidant to the content of the 2-mercaptobenzimidazole is 2:1 to 1:2. The magnetic resin material comprises 100 parts by mass of the polyamide resin, 0.5 parts by mass or more and 2 parts by mass or less of the amine antioxidant, and 0.25 parts by mass or more and 2 parts by mass or less of the 2-mercaptobenzimidazole, The magnetic rotary encoder according to claim 1, comprising: 3. The magnetic rotary encoder according to claim 1, wherein the amine antioxidant is 4,4'-bis(α,α-dimethylbenzyl)diphenylamine. A magnetic rotary encoder comprising the magnetic rotary encoder according to any one of claims 1 to 3 and a rolling bearing having a rotating ring and a stationary ring, wherein a slinger of the magnetic rotary encoder is mounted on the rotating ring of the rolling bearing. rolling bearing unit.

Images