JP2001116052A - Synthetic resin gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the joining strength of the inside surface of a locking recessed groove and the outside surface of a spacer. SOLUTION: When using a rolling bearing, a steel outer ring 4 is fitted in and fixed to an aluminum alloy housing via a synthetic resin spacer 7. Creeping of the spacer 7 to the housing is prevented by the presence of the synthetic resin spacer 7 having a large linear expansion coefficient regardless of a temperature rise. An intermediater layer 10 for improving the joining strength of both a locking recessed groove 6 and the spacer 7 is arranged between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The composite part of a metal and a synthetic resin according to the present invention is used, for example, as a rolling bearing for preventing creep, made of an aluminum alloy constituting a generator for a car or a compressor for a car air conditioner, for example. It is used to rotatably support a steel rotary shaft inside the housing. Further, the present invention can also be applied to a synthetic resin gear for electric power steering used in automobiles, agricultural machines, construction machines, and the like.

[0002]

2. Description of the Related Art A housing of a compressor or the like is made of an aluminum alloy in order to reduce weight and improve heat dissipation. On the other hand, the components of the rolling bearing for supporting the rotating shaft inside the housing are made of steel (bearing steel) to ensure strength. When using a rolling bearing to support the rotating shaft inside the housing, the outer ring of the rolling bearing is fixed inside the housing, and the inner ring is similarly fixed outside the rotating shaft.

[0003] Incidentally, the temperature of a generator or a compressor rises during operation, but the linear expansion coefficient (thermal expansion coefficient) of the aluminum alloy constituting the housing is larger than the linear expansion coefficient of steel constituting the outer ring. Therefore, if no countermeasures are taken, the force holding the outer ring inside the housing at the time of temperature rise is reduced or lost. As a result, so-called creep occurs in which the outer ring rotates inside the housing with the rotation of the rotating shaft, and the inner peripheral surface of the housing and the outer peripheral surface of the outer ring are worn. When the wear due to such causes progresses, the outer ring rattles inside the housing, and abnormal noise and vibration are generated during operation of the generator and the like.

In order to solve such inconvenience, conventionally,
A rolling bearing for preventing creep as shown in FIG. 2 is used. This rolling bearing, like a normal rolling bearing, has an inner ring 2 having an inner raceway 1 on an outer peripheral surface, an outer race 4 having an outer raceway 3 on an inner peripheral surface, and a space between the inner raceway 1 and the outer raceway 3. A plurality of rolling elements (balls) provided to be able to roll freely
5 and 5. The rolling elements 5 are rotatably held inside a pocket 9 provided in the retainer 8 while being separated from each other in the circumferential direction.

Further, in order to prevent the outer race 4 from creeping on the housing, one or more (two in the illustrated example) are provided on the outer peripheral surface of the outer race 4 as shown in detail in FIG.
The locking grooves 6, 6 of the present invention are formed over the entire outer peripheral surface. The inner peripheral side portions of the synthetic resin spacers 7, 7 are locked in the locking grooves 6, 6, respectively.
The outer peripheral portion of each of the spacers 7 protrudes from the outer peripheral surface of the outer race 4 over the entire circumference.

In the rolling bearing configured to prevent creep as described above, the outer ring 4 is internally fitted and fixed to the inside of a housing made of an aluminum alloy via the spacers 7 made of synthetic resin. In the state where the inner ring is fixed, a gap is interposed between the outer peripheral surface of the outer ring 4 and the inner peripheral surface of the housing from a normal temperature.

When the temperature of the outer race 4 and the housing increases with the operation of the generator or the like, the size of the gap increases. However, since the linear expansion coefficient of the synthetic resin forming the spacers 7 and 7 is larger than the linear expansion coefficient of the aluminum alloy forming the housing, the outer ring 4 is connected to the inside of the housing regardless of the increase in the gap size. To prevent the outer race 4 from creeping against the housing.

[0008]

However, in the case of the conventional rolling bearing which is constructed and operates as described above and prevents creep, the outer surfaces of the spacers 7 and 7 and the inner surfaces of the locking grooves 6 and 6 are in contact with each other. Insufficient binding properties cause the following disadvantages.

The spacers 7, 7 are connected to the locking grooves 6, 6, respectively.
After injection molding into a portion, the outer diameter surface is ground to obtain a desired outer diameter. At this time, the spacers 7, 7
Slides with respect to the outer ring 4. As a result, the outer diameter of each of the spacers 7, 7 cannot be strictly regulated, and
The fitting strength of the spacers 7, 7 to the housing varies. For this reason, slippage tends to occur between the spacers 7 and the housing after the rolling bearing is assembled.

When the outer race 4 having the spacers 7, 7 fixed on the outer peripheral surface is pushed into the housing, the spacers 7, 7
Are easily dropped from the locking grooves 6.

When the rotary shaft is rotated after being assembled to the housing, slippage is likely to occur between the outer race 4 and the spacers 7,7. For example, in the synthetic resin constituting each of the spacers 7 and 7, a residual stress in the inner diameter direction acts at a low temperature, but when the rolling bearing is used at a high temperature, the residual stress is relaxed. As a result, each of the spacers 7, 7
The frictional force acting between the inner peripheral surface of the base and the bottom surface of each of the locking grooves 6, 6 is reduced, and the above-described slip occurs. When a nylon resin is used as a synthetic resin, the nylon resin absorbs water vapor in the atmosphere and swells, so that the same slip occurs even in a use state at normal temperature.

For this reason, conventionally, the cross-sectional shape of the locking grooves 6, 6 has been changed from a simple rectangle as shown in FIG. 3 to a modified cross-section as shown in FIG. 4, or as shown in FIG. By forming the groove, the outer surfaces of the spacers 7 and 7 (FIG. 2) and the locking grooves 6 and 6 are formed.
The contact area with the inner surface of the outer ring 4 is increased so that the spacers 7 and 7 do not slip easily with respect to the outer ring 4 (in the case of FIG. 4), or the spacers 7 and 7 hardly come out of the locking grooves 6 and 6 (see FIG. 4). 5). However, such a change in the shape of the locking grooves 6, 6 has an incomplete anti-slip effect and is not a fundamental solution, but also complicates working of the locking grooves 6, 6. This causes problems such as high production costs.

[0013] A similar problem also exists in worm wheels incorporated in, for example, electric power steering devices.
That is, as shown in FIG. 6, the electric power steering apparatus transmits the rotational driving force of the electric motor 11 to the steering shaft 1 via the worm 12 and the worm wheel 13.
4 is transmitted. The worm wheel 13 is formed by molding a synthetic resin around a metal boss.

That is, as shown in FIG. 7, a metal boss 16 is provided at the center of the cavity 15 of the injection molding die.
In the state supported by the above, the synthetic resin is injected into the cavity 15 and solidified. As a synthetic resin to be injected, a nylon 6 resin is used, and a worm wheel 13 made of a synthetic resin having a metal boss 16 is used. As the synthetic resin, in addition to the nylon 6, nylon 66 and those containing glass fibers are used.

In the case of such a worm wheel 13, it is necessary for the function of the electric power steering device to prevent a deviation between the outer peripheral surface of the metal boss 16 and the inner peripheral surface of the synthetic resin portion. It is. However, in the past,
The two peripheral surfaces are not particularly connected to each other, and the rotational force is transmitted only by frictional force. Therefore, a slip occurs between the two peripheral surfaces with use over a long period of time, The problem that torque transmission efficiency is reduced occurs.

The composite part of the present invention comprising a metal and a synthetic resin comprises:
The present invention has been made in view of the above circumstances.

[0017]

According to the present invention, there is provided a composite part of a metal and a synthetic resin, comprising a metal inner part, a synthetic resin outer part provided on the outer peripheral side of the inner part, and a synthetic resin outer part. And an intermediate layer provided between the inner component. The intermediate layer is a phosphate conversion coating or a low-temperature sulfurizing coating.

[0018]

The composite part of the metal and the synthetic resin of the present invention configured as described above has an intermediate layer, so that the bonding strength between the outer part and the inner part is increased, and the part between these two parts is formed. Slip is less likely to occur.

[0019]

First, as a first embodiment of the present invention, a case where the present invention is applied to a rolling bearing for preventing creep will be described. Rolling bearing for preventing creep of the present invention,
Like the conventional rolling bearing that prevented creep as described above,
As shown in FIG. 2, an inner ring 2 having an inner ring track 1 on the outer peripheral surface
An outer ring 4 having an outer raceway 3 on an inner peripheral surface; a plurality of rolling elements 5, 5 provided to be able to roll between the inner raceway 1 and the outer raceway 3; The locking concave grooves 6, 6 formed over the entire circumference thereof, and the respective outer peripheral side portions thereof are fixed to the outer ring while the respective inner peripheral side portions are locked by the locking concave grooves 6, 6, respectively. 4 is provided with spacers 7, 7 made of synthetic resin protruding from the outer peripheral surface over the entire circumference. The corners of the locking grooves 6, 6 have a curvature radius of 0.1 mm or more in order to prevent the spacers 7, 7 locked in the locking grooves 6, 6 from cracking. Part is formed.

In particular, in the rolling bearing for preventing creep according to the present invention, as shown in FIG. 1, an intermediate surface of a phosphate conversion coating or a low-temperature sulfurizing coating is formed on the inner surface of the locking groove 6. It is characterized in that the layer 10 is formed and a synthetic resin constituting the spacer 7 is bonded to the intermediate layer 10.

As the phosphate chemical conversion coating, a manganese phosphate chemical conversion coating, a zinc phosphate chemical conversion coating, a zinc calcium phosphate chemical conversion coating, or the like can be preferably used. Further, as the low-temperature sulfurizing treatment film, an iron sulfide film obtained by a low-temperature sulfurizing treatment can be preferably used.

The basic operation of the rolling bearing for preventing creep according to the embodiment of the present invention, which is configured as described above, that is, by the synthetic resin spacer 7 having a large linear expansion coefficient,
The function of preventing the steel outer ring 4 from rotating inside the aluminum alloy housing when the temperature rises is the same as that of the above-described conventional rolling bearing for preventing creep.

In particular, in the case of the rolling bearing for preventing creep according to the embodiment of the present invention, the connection between the outer surface of the spacer 7 and the inner surface of the locking groove 6 is improved by providing the intermediate layer 10. I do. As a result, the spacer 7 does not rotate with respect to the outer ring, or the spacer 7 does not fall out of the locking groove 6.

That is, the intermediate layer 10 which is a phosphate chemical conversion treatment film or a low-temperature sulfurizing treatment film not only firmly bonds to the steel outer ring 4 but also forms the intermediate layer 10 and the spacer 7.
The binding force with the chromium also increases significantly. The increase in the bonding force between the intermediate layer 10 and the spacer 7 is due to the following reasons (1) to (3).

(1) Since a large number of fine irregularities are present on the surface of the intermediate layer 10, the contact area between the intermediate layer 10 and the synthetic resin forming the spacer 7 is increased. (2) The spacer 7 is fixed to the intermediate layer 10 by the anchor effect based on the engagement between the irregularities and the synthetic resin. (3) The spacer 7 is fixed to the intermediate layer 10 due to the interaction of the polar groups of both the film constituting the intermediate layer 10 and the synthetic resin constituting the spacer 7. In particular, the hydroxyl group (-OH) of the phosphate chemical conversion coating and the amide group (-NHCO) of a polyamide resin such as nylon.
-) Or an ester group (-COO-) of a polyester resin such as polybutylene terephthalate is strongly bonded by a hydrogen bond. By combining these, the bonding force between the spacer 7 and the outer ring 4 is remarkably increased. Enhanced.

The results of experiments conducted by the present inventors to confirm the effects of the present invention are shown in the following table.

[0027]

[Table 1]

In this table, the column of the intermediate layer indicates the type of the intermediate layer 10 formed on the inner surface of the locking groove 6, the column of the synthetic resin indicates the type of the synthetic resin forming the spacer 7, and the groove shape. In the columns, the drawing numbers indicating the cross-sectional shapes of the locking concave grooves 6 are respectively shown. In the column of the starting torque, the locking groove 6 is used.
Represents the magnitude of the starting torque when the spacer 7 locked to the outer ring 4 is slid with respect to the outer ring 4. The larger the starting torque is, the larger the coupling force between the spacer 7 and the outer ring 4 is, and it is possible to obtain a good quality rolling bearing in which creep is prevented. From this, it is understood that the present invention can provide a rolling bearing in which good quality creep is prevented. The experimental conditions not described in the above table are as follows.

A. Outer ring and locking groove Outer ring diameter (outer diameter) 35mm Outer ring width 11mm Locking groove width 2.2mm Locking groove depth 0.7mm

B. Conditions for Forming Intermediate Layer 10 (1) When Forming Intermediate Layer 10 of Phosphate Chemical Conversion Coating The intermediate layer 10 was formed by the following process. Pre-lock groove 6
Of the heat-treated outer ring 4 formed with an alkaline aqueous solution (FC-43 manufactured by Nippon Parker Rising Co., Ltd.)
60 ”) for 10 minutes and then with water → 30-40
Immersed in a surface conditioning liquid (Aleparen VM, manufactured by Nippon Parker Rising Co., Ltd.) heated to 60 ° C. for 60 seconds, but preparene Z-based, FIXODIN 5N-5 and the like can be used as appropriate. Immersion in the treatment liquid → The type of the chemical treatment liquid to be washed with water, the treatment liquid temperature and the treatment time are as follows. a. When the intermediate layer is a manganese phosphate conversion coating Type of treatment solution Nippon Parker Rising Co., Ltd.
"Palphos M1A" (trade name) manufactured by Nippon Parker Rising Co., Ltd. Treatment liquid temperature: 95 ° C Treatment time: 10 minutes b.
"Palbond L47" (trade name) manufactured by Nippon Parker Rising Co., Ltd. Treatment liquid temperature 55 ° C Treatment time 5 minutes c. When the intermediate layer is a zinc calcium phosphate chemical conversion treatment film
“Fericoat 7” (trade name) Processing liquid temperature 80 ° C Processing time 5 minutes

(2) In the case of forming the intermediate layer 10 of the sulfidation treatment film After degreasing the heat-treated outer ring 4 in which the locking groove 6 is formed in advance, the sulfur-containing alkali molten salt heated to 190 ° C. Then, it was immersed for 10 minutes to form a diffusion layer of iron sulfide on the surface of the outer ring 6 (Corbet treatment). The experiment was performed to determine the coupling strength between the locking groove 6 and the spacer 7. If the intermediate layer 10 is formed on the inner surface of the locking groove 6,
In order to achieve the purpose of the experiment, the intermediate layer 10 was formed on the entire surface of the outer ring 4. In an actual case, as shown in FIG. 1, it is sufficient to form the intermediate layer 10 only on the inner surface of the locking groove 6. However, when the intermediate layer 10 is a phosphate film or a sulfurized film, Since the film itself has excellent lubricating properties, the intermediate layer 10 may be formed on the entire surface without performing masking during film formation.

C. Molding Conditions of Spacer 7 The spacer 7 was molded by injection molding the synthetic resin described in the above table into the locking groove 6. When the intermediate layer 10 was provided, injection molding was performed after the operation of forming the intermediate layer 10. The dimension T at which the spacer 7 protrudes from the outer peripheral surface of the outer ring 4 after the molding was set to 10 μm. The conditions for injection molding are as follows.
The injection temperature was 20 ° C., the mold temperature was 80 ° C., the injection time was 1.0 second, the injection pressure was 130 MPa, and the cooling time was 20 seconds. When the synthetic resin was polybutylene terephthalate, the resin temperature was set to 255 ° C., and the other conditions were the same as those for nylon 11.

Although the thickness of the intermediate layer 10 is determined by design, if the thickness is excessively large, the thickness of the intermediate layer 10 is reduced.
, The strength of the connection between the locking groove 6 and the spacer 7 is insufficient, and the spacer 7 may rotate with respect to the outer ring 4. On the other hand, if the thickness is too small, the coating constituting the intermediate layer 10 tends to be non-uniform, and the bonding strength between the locking groove 6 and the spacer 7 is also insufficient. May rotate. In consideration of the above, the thickness of the intermediate layer 10 is 1 to 10 μm (more preferably 3 to 8 μm) when the coating forming the intermediate layer 10 is a phosphate chemical conversion coating, In the case of a treated film, the thickness is 3 to 15 μm (more preferably 5 to 10 μm). The thickness of each film is adjusted by the composition of the processing solution and the immersion time in the processing solution.

Next, a second embodiment in which the present invention is applied to a worm wheel for an electric power steering device will be described. First, the boss 16 that constitutes the worm wheel 13 (FIG. 6) is made of carbon steel (S20C) as shown in FIG.
It was formed in an annular shape as shown in (A). The outer peripheral surface of the boss 16 may be knurled as shown in FIG. The shape of the boss 16 is shown in FIGS.
A shape as shown in FIG. Among them, the one shown in FIG. 10 has one ridge 18 formed on the outer peripheral surface, the one shown in FIG. 11 has one groove 19 formed, and the one shown in FIG. The book has grooves 19 formed therein. The corners of the concave grooves 19 are curved with an appropriate radius of curvature. Further, the cross-sectional shape of each of the grooves 19, 19 may be trapezoidal or dovetailed. Further, the outer peripheral surface of the boss 16 may be knurled or provided with one or more grooves (including splines) extending in the axial direction to support the rotational torque.

First, a manganese phosphate chemical conversion treatment is performed on the outer peripheral surface of the boss 16 having a knurled outer peripheral surface having a depth of 1.0 mm as shown in FIG. did. Clean the boss 16 with alkali (at 50-60 ° C for 10
Min) → water washing → surface conditioning liquid (select from Preparen VM, Preparen Z system, Fixoxin 5N-5 manufactured by Nippon Parker Rising Co., Ltd.) for 60 seconds → 95 ° C
5 minutes in a chemical conversion solution (Parphos-M1A, manufactured by Nippon Parker Rising Co., Ltd.) → Rinse with water

By such a process, the boss 16 having the manganese phosphate conversion coating formed on the outer peripheral surface is set in an injection mold in a state as shown in FIG. (TW300 manufactured by Co., Ltd.) was injected, and a synthetic resin was fixed around the boss 16. The mold temperature during injection molding is 120 ° C, the resin temperature is 315 ° C,
The injection pressure was 110 MPa.

The worm wheel 13 used in the electric power steering apparatus was formed by forming teeth on the outer peripheral surface of the synthetic resin fixed around the boss 16 by cutting. Worm wheel 1 obtained in this way
Sample No. 3 was excellent in heat resistance and oil resistance, and did not slip between the outer peripheral surface of the metal boss 16 and the inner peripheral surface of the synthetic resin portion even after long-term use. The above cavity 1
If a tooth having a tooth shape is adopted as 5, the above-mentioned cutting becomes unnecessary.

Next, in order to examine the influence of the type of the synthetic resin constituting the worm wheel 13 and the type of treatment applied to the outer peripheral surface of the boss 16 on the bonding strength between the boss and the synthetic resin portion, the present inventor examined the present invention. A description will be given of an experiment performed by the company.

First, in order to determine the optimum type of synthetic resin, nylon 6 is used as a nylon synthetic resin for injection molding.
(Amilan CM1017 manufactured by Toray Industries, Inc.), nylon 6
6 (Ube nylon 2020U5 manufactured by Ube Industries, Ltd.)
0), aromatic nylon (Ultramid TKR4350, manufactured by BASF) and nylon 46 (TW300, manufactured by Nippon Synthetic Rubber Co., Ltd.). Further, as a comparative nylon, "MC" nylon MC901 manufactured by Nippon Polypenco Co., Ltd. was prepared.

In order to evaluate the resistance to breakage based on residual stress during injection molding, heat resistance, oil resistance, and mechanical properties at high temperatures, a dumbbell test piece for tensile test (JIS No. 1 type) was used. Test piece) was prepared. This specimen is
"MC" nylon was prepared by cutting, and other nylon synthetic resins for injection molding were prepared by injection molding. Each of the test pieces thus obtained was subjected to a tensile test using an autograph manufactured by Shimadzu Corporation. The test was carried out at room temperature (23 ° C.) under the condition that the material was made absolutely dry. The results of the tensile test are shown in the table below.

[0041]

[Table 2]

The distortion due to the molding shrinkage of the nylon synthetic resin for injection molding is about 2%, and this distortion is caused by the metal boss 1.
6 It is known that it acts as a tangential stress on the outer peripheral surface portion. The magnitude of this stress is approximately 60 MPa (= tensile elastic modulus × strain) when stress relaxation during molding is ignored. Therefore, in order to obtain the worm wheel 13 which is not easily broken by the injection molding, a material having a large tensile strength and a large tensile yield elongation is preferable. From the description in the above table, it is understood that nylon 46 satisfies these conditions.

Next, FIG. 14A shows the relationship between the tensile strength and the temperature of each material, and FIG. 14B shows the degree to which the tensile strength changes when each material is left in air at 120 ° C. The degree to which the tensile strength changes when each material is left in grease (Maltemp manufactured by Kyodo Yushi Co., Ltd.) at 120 ° C. is shown in FIG.
○ indicates nylon 46, △ indicates nylon 6, □ indicates nylon 66, × indicates aromatic nylon, and ◎ indicates MC nylon. From the description of FIG. 14, it is understood that nylon 46 is suitable as a material for a worm wheel requiring heat resistance, durability, and oil resistance.

Next, the effect of the type of treatment applied to the outer peripheral surface of the boss 16 on the bonding strength between the boss and the synthetic resin portion was examined. First, a simple ring as shown in FIG.
Boss 1 with knurling of 1.0mm depth on the outer peripheral surface
The outer peripheral surface of 6 is subjected to the processing shown in the following (1) to (11),
Further, nylon 46 was injection-molded on the outer peripheral portion of the boss 16 using an injection molding die as shown in FIG.
The resin temperature during injection molding is 310 ° C and the mold temperature is 140
C., the injection time was 2.2 seconds, the holding pressure was 130 MPa, and the cooling time was 20 seconds.

(1) Untreated (2) Silane coupling treatment (3) Shot blasting (4) Silane coupling treatment after shot blasting (5) Formation of 1 μm treated film by manganese phosphate conversion treatment (6) Manganese phosphate conversion (7) Formation of 5 μm treatment film by manganese phosphate conversion treatment (8) Formation of 5 μm treatment film by manganese phosphate conversion treatment, silane coupling treatment (9) Treatment of 5 μm by zinc phosphate conversion treatment Film formation (10) 2 μm treated film formation by manganese phosphate conversion treatment (11) 10 μm treatment film formation by manganese phosphate conversion treatment

After the surface treatment as described above is performed and nylon 46 is injection-molded on the outer peripheral side, the fixing force between the outer peripheral surface of the metal boss 16 and the inner peripheral surface of the worm wheel 13 made of nylon 46 is shown in FIG. The measurement was performed using a test device as shown in FIG. The test apparatus includes a receiving table 20 that supports the lower surface of the worm wheel 13 and a pressing piece 21 that presses the upper surface of the boss 16. The inner diameter of the cradle 20 is larger than the inner diameter of the worm wheel 13 and smaller than the outer diameter.
The outer diameter of the pressing piece 21 is larger than the inner diameter of the boss 16 and smaller than the outer diameter.

By using such a test apparatus, a load in the thrust direction is applied from the pressing piece 21 to the boss 16, the boss 16 is displaced in the axial direction with respect to the worm wheel 13, The relationship between the magnitude of the applied load and the amount of displacement (displacement) in the axial direction was measured. The results are shown by curves (1) to (11) in FIG. The sign of each curve corresponds to the sign indicating the processing method. As is apparent from the description of FIG. 13, the outer peripheral surface of the boss portion 16 has an appropriate thickness (2
-10 μm, more preferably 3 to 7 μm), the boss 16 and the worm wheel 1
It can be seen that the bonding force with No. 3 increases.

The reason why the formation of the chemical conversion coating film increases the bonding strength is thought to be the same as in the case of the first embodiment described above. If the coating thickness is less than 2 μm, it is difficult to cover the entire outer peripheral surface of the boss portion 16 with the coating, and there is a portion where the coating does not exist when viewed microscopically. And the worm wheel 13 becomes weaker. Conversely, when the film thickness exceeds 10 μm, the film itself having low strength is liable to be broken by the force in the shear direction, and the above-mentioned bonding strength is also weakened.

As the synthetic resin for forming the worm wheel 13, a resin obtained by adding glass fibers or whiskers to the nylon 46 can be preferably used. Examples of the whiskers to be used include “Tismo”, a potassium titanate whisker manufactured by Otsuka Chemical Co., Ltd., and “Albolex”, an aluminum borate whisker manufactured by Shikoku Chemicals Co., Ltd. .

Further, according to the present invention, in addition to the rolling bearing for preventing creep or the worm wheel for electric power steering as in the first and second embodiments described above, a metal hub is provided at the center. And other composite parts such as a synthetic resin pulley having

[0051]

The composite part of a metal and a synthetic resin according to the present invention is constructed and operates as described above. However, due to the improvement of the bonding strength between the metal inner part and the synthetic resin outer part, both parts are improved. Since it is possible to prevent the parts from shifting and moving, the reliability of various mechanical devices incorporating the composite parts can be improved.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing a first embodiment of the present invention and corresponding to a portion A in FIG. 2;

FIG. 2 is a partial cross-sectional view of a rolling bearing in which creep has been prevented according to the present invention.

FIG. 3 is a cross-sectional view of an outer race showing a first example of a cross-sectional shape of a locking groove.

FIG. 4 is a cross-sectional view of the outer race showing the second example.

FIG. 5 is a cross-sectional view of an outer ring showing the third example.

FIG. 6 is a perspective view of a main part of the electric power steering device.

FIG. 7 is a sectional view of an injection mold for forming a worm wheel made of a synthetic resin.

FIG. 8 shows a first example of a boss, (A) is an end view,
(B) is the figure seen from the side of (A).

FIG. 9 is a longitudinal sectional view showing a test device for measuring a bonding strength.

10A and 10B show a second example of the boss, in which FIG. 10A is an end view, and FIG. 10B is a sectional view.

11A and 11B show a third example of the boss, where FIG. 11A is an end view and FIG. 11B is a sectional view.

12A and 12B show a fourth example of the boss, where FIG. 12A is an end view and FIG. 12B is a cross-sectional view.

FIG. 13 is a diagram showing a test result of measuring a bonding strength.

FIG. 14 is a diagram showing the effect of the type of material on the tensile strength.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner ring track 2 Inner ring 3 Outer ring track 4 Outer ring 5 Rolling element (ball) 6 Locking groove 7 Spacer 8 Cage 9 Pocket 10 Middle layer 11 Electric motor 12 Warm 13 Worm wheel 14 Steering shaft 15 Cavity 16 Boss 17 Core pin 18 ridge 19 concave groove 20 pedestal 21 pressing piece

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[Procedure amendment]

[Submission date] September 22, 2000 (2009.2)
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

[Title of the Invention] Gear made of synthetic resin

[Claims]

1. A synthetic resin gear comprising a metal boss and a nylon 46 gear provided on the outer peripheral side of the boss.

2. Between the outer peripheral surface of the boss and the inner peripheral surface of the gear,
The synthetic resin gear according to claim 1, wherein an intermediate layer that is a phosphate conversion coating or a low-temperature sulfurizing coating is interposed.

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial applications]inventionPertain toSynthetic resin gear
Is, for example,,Electricity used in automobiles, agricultural machines, construction machinery, etc.
Synthetic resin gear for dynamic power steeringUse as
To.

[0002]

2. Description of the Related Art An electric power steering apparatus is shown in FIG.
As shown in FIG.
12, through the worm wheel 13, the steering wheel
It is configured to transmit to the shaft 14. Electric power
Weight reduction of steering gear and reduction of noise during driving
In order to achieve this, the worm wheel 13
By molding synthetic resin around the metal boss
It is possible to configure.

[0003] That is, as shown in FIG.
A metal boss 16 is attached to the center of the
While being supported by the synthetic resin,
The fat is poured and solidified. Conventionally, as a synthetic resin to be injected,
Using a nylon 6 resin and having a metal boss 16
It is considered that the worm wheel 13 is made of synthetic resin.
I have. As the synthetic resin, in addition to the nylon 6,
Use ILON 66 or those containing glass fibers.
It is considered to be used.

[ 0004 ]

[ 0005 ]

[ 0006 ]

[ 0007 ]

[0008]

SUMMARY OF THE INVENTION Electric power steering
High reliability and durability for gears incorporated in
Performance is required, the strength of each part must be secured
No.

On the other hand, nylon 6 and nylon 66
In this case, the electric power steering device
When used in high-temperature environments or when steering
Depending on the size of the auxiliary power to be applied to the
There may be a case where a sufficient margin cannot be secured in terms of strength.

[ 0010 ]

[ 0011 ]

[ 0012 ]

[ 0013 ]

[ 0014 ]

In the case of the worm wheel 13 as described above , there is no deviation between the outer peripheral surface of the metal boss 16 and the inner peripheral surface of the synthetic resin portion. Required for functionality. However, conventional case, between the both peripheral surfaces Orazu simply considering that performs transmission of the rotational force only by the frictional force by considering that bind specifically
Which was. For this reason, it will be used in more severe environments in the future
In such a case, there is a possibility that a slippage occurs between these two peripheral surfaces with use over a long period of time, and a problem such as a reduction in torque transmission efficiency may occur.

The gear made of synthetic resin of the present invention has been invented in view of the above circumstances.

[0017]

SUMMARY OF THE INVENTION Synthetic resin gear of the present invention
Is a metal boss and a nut provided on the outer peripheral side of this boss.
And a gear made of ILON 46. Also, preferably,
Between the outer peripheral surface of the boss and the inner peripheral surface of the gear, phosphate conversion
Treatment layer or low-temperature sulfurizing treatment intermediate layer
I'm making it.

[0018]

The gear made of the synthetic resin of the present invention configured as described above uses nylon 46 as the synthetic resin constituting the gear.
Therefore, the strength of this gear can be sufficiently secured . or,
Preferred structure, by providing the intermediate layer, and the gear
The coupling force with the hub is increased, and slippage between these two components is less likely to occur.

[ 0019 ]

【Example】

[ 0020 ]

[ 0021 ]

[ 0022 ]

[ 0023 ]

[ 0024 ]

[ 0025 ]

[ 0026 ]

[ 0027 ]

[ 0028 ]

[ 0029 ]

[ 0030 ]

[ 0031 ]

[ 0032 ]

[ 0033 ]

[0034] described with regard to the embodiments of the present invention is applied to the worm wheel for an electric power steering apparatus.
First, the worm wheel 1 which is the gear described in the claims
3 ( FIG. 1 ) is provided with a boss 16 provided at the center of carbon steel (S2
0C) to form an annular shape as shown in FIG . The outer peripheral surface of the boss 16 may be knurled as shown in FIG. Further, the shape of the boss 16, can be employed shape as shown in FIGS. 4-6. 4 shows one in which one ridge 18 is formed on the outer peripheral surface, FIG. 5 shows one in which one concave groove 19 is formed, and FIG. The book has grooves 19 formed therein. The corners of the concave grooves 19 are curved with an appropriate radius of curvature. Further, the cross-sectional shape of each of the grooves 19, 19 may be trapezoidal or dovetailed. Further, the boss 16
The outer peripheral surface of the roller can be knurled or provided with one or more grooves (including splines) extending in the axial direction to support the rotational torque.

Next , a manganese phosphate chemical conversion treatment is performed on the outer peripheral surface of the boss 16 having a knurling process with a depth of 1.0 mm on the outer peripheral surface in a simple annular shape as shown in FIG. gave. Clean the boss 16 with alkali (at 50-60 ° C for 10
Min) → water washing → surface conditioning liquid (select from Preparen VM, Preparen Z system, Fixoxin 5N-5 manufactured by Nippon Parker Rising Co., Ltd.) for 60 seconds → 95 ° C
5 minutes in a chemical conversion solution (Parphos-M1A manufactured by Nippon Parker Rising Co., Ltd.)

By such a process, the boss 16 having the manganese phosphate conversion coating formed on the outer peripheral surface is set in an injection mold in a state as shown in FIG. (TW300 manufactured by Co., Ltd.) was injected, and a synthetic resin was fixed around the boss 16. The mold temperature during injection molding is 120 ° C, the resin temperature is 315 ° C,
The injection pressure was 110 MPa.

The worm wheel 13 used in the electric power steering apparatus was formed by forming teeth on the outer peripheral surface of the synthetic resin fixed around the boss 16 by cutting. Worm wheel 1 obtained in this way
Sample No. 3 was excellent in heat resistance and oil resistance, and did not slip between the outer peripheral surface of the metal boss 16 and the inner peripheral surface of the synthetic resin portion even after long-term use. The above cavity 1
If a tooth having a tooth shape is adopted as 5, the above-mentioned cutting becomes unnecessary.

Next, in order to examine the influence of the type of the synthetic resin constituting the worm wheel 13 and the type of treatment applied to the outer peripheral surface of the boss 16 on the bonding strength between the boss and the synthetic resin portion, the present inventor examined the present invention. A description will be given of an experiment performed by the company.

First, in order to determine the optimum type of synthetic resin, nylon 6 is used as a nylon synthetic resin for injection molding.
(Amilan CM1017 manufactured by Toray Industries, Inc.), nylon 6
6 (Ube nylon 2020U5 manufactured by Ube Industries, Ltd.)
0), aromatic nylon (Ultramid TKR4350, manufactured by BASF) and nylon 46 (TW300, manufactured by Nippon Synthetic Rubber Co., Ltd.). Further, as a comparative nylon, "MC" nylon MC901 manufactured by Nippon Polypenco Co., Ltd. was prepared.

In order to evaluate the resistance to breakage based on residual stress during injection molding, heat resistance, oil resistance, and mechanical properties at high temperatures, a dumbbell test piece for tensile test (JIS No. 1 type) was used. Test piece) was prepared. This specimen is
"MC" nylon was prepared by cutting, and other nylon synthetic resins for injection molding were prepared by injection molding. Each of the test pieces thus obtained was subjected to a tensile test using an autograph manufactured by Shimadzu Corporation. The test was carried out at room temperature (23 ° C.) under the condition that the material was made absolutely dry. The results of the tensile test are shown in the table below.

[0041]

[ Table 1 ]

The distortion due to the molding shrinkage of the nylon synthetic resin for injection molding is about 2%, and this distortion is caused by the metal boss 1.
6 It is known that it acts as a tangential stress on the outer peripheral surface portion. The magnitude of this stress is approximately 60 MPa (= tensile elastic modulus × strain) when stress relaxation during molding is ignored. Therefore, in order to obtain the worm wheel 13 which is not easily broken by the injection molding, a material having a large tensile strength and a large tensile yield elongation is preferable. From the description in the above table, it is understood that nylon 46 satisfies these conditions.

Next, FIG. 7A shows the relationship between the tensile strength and the temperature of each material, and FIG. 7B shows the degree to which the tensile strength changes when each material is left in air at 120 ° C.
The degree to which the tensile strength changes when each material is left in grease (Maltemp manufactured by Kyodo Yushi Co., Ltd.) at 120 ° C. is shown in FIG. In addition, ○ indicates nylon 46, Δ indicates nylon 6, □ indicates nylon 66,
X represents aromatic nylon, and ◎ represents MC nylon. From the description of FIG.
It turns out that it is suitable as a material for worm wheels that require heat resistance, durability and oil resistance.

Next, the effect of the type of treatment applied to the outer peripheral surface of the boss 16 on the bonding strength between the boss and the synthetic resin portion was examined. First, a simple ring as shown in FIG.
Boss 1 with knurling of 1.0mm depth on the outer peripheral surface
The outer peripheral surface of 6 is subjected to the processing shown in the following (1) to (11),
Further, nylon 46 was injection-molded on the outer peripheral side portion of the boss 16 by an injection molding die as shown in FIG .
The resin temperature during injection molding is 310 ° C and the mold temperature is 140
C., the injection time was 2.2 seconds, the holding pressure was 130 MPa, and the cooling time was 20 seconds.

(1) Untreated (2) Silane coupling treatment (3) Shot blasting (4) Silane coupling treatment after shot blasting (5) Formation of 1 μm treated film by manganese phosphate conversion treatment (6) Manganese phosphate conversion (7) Formation of 5 μm treatment film by manganese phosphate conversion treatment (8) Formation of 5 μm treatment film by manganese phosphate conversion treatment, silane coupling treatment (9) Treatment of 5 μm by zinc phosphate conversion treatment Film formation (10) 2 μm treated film formation by manganese phosphate conversion treatment (11) 10 μm treatment film formation by manganese phosphate conversion treatment

After the surface treatment as described above is performed and nylon 46 is injection-molded on the outer peripheral side, the fixing force between the outer peripheral surface of the metal boss 16 and the inner peripheral surface of the worm wheel 13 made of nylon 46 is shown in FIG. The measurement was performed using a test device as shown in FIG. The test apparatus includes a receiving table 20 that supports the lower surface of the worm wheel 13 and a pressing piece 21 that presses the upper surface of the boss 16. The inner diameter of the cradle 20 is larger than the inner diameter of the worm wheel 13 and smaller than the outer diameter.
The outer diameter of the pressing piece 21 is larger than the inner diameter of the boss 16 and smaller than the outer diameter.

By using such a test apparatus, a load in the thrust direction is applied from the pressing piece 21 to the boss 16, the boss 16 is displaced in the axial direction with respect to the worm wheel 13, The relationship between the magnitude of the applied load and the amount of displacement (displacement) in the axial direction was measured. Fig.
FIG. 9 shows curves (1) to (11). The sign of each curve corresponds to the sign indicating the processing method. As is clear from the description of FIG. 9 , the outer peripheral surface of the boss portion 16 has an appropriate thickness (2 to 1).
It can be seen that forming a chemical conversion coating of 0 μm (more preferably 3 to 7 μm) increases the bonding force between the boss 16 and the worm wheel 13.

The reason why the formation of the chemical conversion coating film increases the bonding strength is as follows. That is, phosphate conversion
Chemical conversion coatings such as heat-treated and low-temperature
In addition to being firmly connected to the steel boss 16,
The bonding force between the chemical conversion coating and the worm wheel 13
Increase significantly. In addition, chemical conversion coating and worm wheel
The increase in the bonding force with the 13 is due to the following reasons (1) to (3)
by. (1) There are many fine irregularities on the surface of the chemical conversion coating.
The chemical conversion coating and the worm wheel 13
The contact area with the constituent synthetic resin increases. (2) Anchor based on the engagement between the irregularities and the synthetic resin
Due to the effect, the worm wheel 13
And it is fixed. (3) The combination of the chemical conversion coating and the worm wheel 13
Due to the interaction of the polar groups with both the synthetic resin,
The arm wheel 13 is fixed to the chemical conversion coating. Special
A hydroxyl group (-OH) of the phosphate chemical conversion treatment film,
Amide groups (-N
HCO-) is strongly bonded by hydrogen bond.
By combining them, the worm wheel 13
And the boss 16 is significantly increased in bonding force. If the film thickness is less than 2 μm, it is difficult to cover the entire outer peripheral surface of the boss portion 16 with the film, and there is a portion where the film does not exist when viewed from a microscopic viewpoint. And the worm wheel 13 has a weaker coupling strength. Conversely,
If the film thickness exceeds 10 μm, the film itself having low strength is easily broken by the force in the shearing direction, and the above-mentioned bonding strength is also weakened.

As the synthetic resin for forming the worm wheel 13, a resin obtained by adding glass fibers or whiskers to the nylon 46 can be preferably used. Examples of the whiskers to be used include “Tismo”, a potassium titanate whisker manufactured by Otsuka Chemical Co., Ltd., and “Albolex”, an aluminum borate whisker manufactured by Shikoku Chemicals Co., Ltd. .

[ 0050 ]

[0051]

Since the synthetic resin gear of the present invention is constructed and operates as described above, it is attached to the steering shaft.
Even when the auxiliary power to be given is large,
Reliability can be sufficiently secured. Furthermore, if necessary, a hub
Improves the strength of the connection between
Properties can be further improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of an electric power steering apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an injection mold for forming a worm wheel made of a synthetic resin.

FIG. 3 shows a first example of a boss, (A) is an end view,
(B) is the figure seen from the side of (A).

FIG. 4 shows a second example of the boss, (A) is an end view,
(B) is a sectional view.

FIG. 5 shows a third example of the boss, (A) is an end view,
(B) is a sectional view.

FIG. 6 shows a fourth example of the boss, (A) is an end view,
(B) is a sectional view.

FIG. 7 is a diagram showing the effect of the type of material on the tensile strength.

FIG. 8 is a longitudinal sectional view showing a test device for measuring a bonding strength.

FIG. 9 is a diagram showing a test result of measuring a bonding strength.

[Description of Signs] 11 Electric motor 12 Worm 13 Worm wheel 14 Steering shaft 15 Cavity 16 Boss 17 Core pin 18 Protrusion 19 Depression groove 20 Receiving stand 21 Pressing piece

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 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuji Kawaike 2-17-1 Maehakodamachi, Maebashi City, Gunma Prefecture

Claims (1)

[Claims] An inner part made of metal, an outer part made of a synthetic resin provided on an outer peripheral side of the inner part, and an intermediate layer provided between the outer part and the inner part. This intermediate layer is a composite part of a metal and a synthetic resin, which is a phosphate conversion coating or a low-temperature sulfurizing coating.