JP5160197B2 - Sliding member and manufacturing method thereof - Google Patents

Description

The present invention, lubricity on the sliding surface by solid bodies lubricating coating has been applied, but the sliding member such as the intermediate shaft, and a manufacturing method thereof.

  A pair of shaft members that are extendable in the axial direction and coupled so as to be integrally rotatable in the rotation direction around the shaft via a spline sliding portion composed of an external spline portion and an internal spline portion, and are provided with steering Lubricating oil such as grease is used for lubrication between the sliding surfaces of the both spline portions of a constantly sliding shaft represented by an intermediate shaft disposed between a steering shaft and a pinion shaft of the apparatus. In addition, a solid lubricating film may be formed on at least one of both sliding surfaces and used in combination with lubricating oil. In some cases, the solid lubricating coating is used alone.

  This is because the sliding shaft always slides in the axial direction while receiving a twisting force in the rotation direction, so that grease or the like is lost from the sliding surfaces of both spline portions, so-called oil film breakage is likely to occur. This is because it is necessary to maintain good lubrication at that time. In addition to having good lubricity, the solid lubricant film has a certain degree of film thickness and excellent wear resistance in order to prevent backlash between the two spline parts, and is different at the start of sliding. In order to prevent the generation of sound, so-called squeak noise, the difference between the coefficient of static friction and the coefficient of dynamic friction is small, and good stick-slip resistance is also required.

The solid lubricant film is baked after a coating agent containing, for example, a resin solid content as a film forming component and a solid lubricant is applied to the sliding surface by a general application method such as spray application or immersion. Formed with. As the solid lubricant, inorganic lubricants such as molybdenum disulfide (MoS ₂ ) and graphite powder, fluororesin powders such as polytetrafluoroethylene (PTFE), and the like are used (see, for example, Patent Document 1).
JP 2005-324599 A

  However, the conventional solid lubricant film described above has a problem that sufficient lubricity and stick-slip resistance cannot be obtained, and good wear resistance cannot be obtained. In addition, in the conventional manufacturing method described above, it is not easy to control the thickness of the solid lubricant film, and in particular, a substantially uniform thickness is provided on the surface having uneven shapes such as the sliding surfaces of both the spline portions. In order to form the solid lubricant film, it requires skill, and even if a skilled worker performs the work, the solid lubricant film having a uniform thickness with excellent film thickness accuracy over the entire sliding surface There is a problem that cannot be formed. This is presumably because the coating agent applied to the sliding surface by spray coating or the like tends to gather at the recessed corners of the sliding surface due to its own surface tension.

When the thickness of the solid lubricating coating varies, there arises a problem that the play between the two spline portions described above cannot be reliably prevented. Therefore, a solid lubricating film is formed thicker than the clearance between both spline portions, and when the external spline portion is inserted into the internal spline portion, the excess portion of the film is also scraped off. However, in this case, there arises a new problem that material is wasted .

An object of the present invention is to provide a sliding member in which good lubricity is imparted to a sliding surface by a solid lubricating film excellent in lubricity, stick-slip resistance, wear resistance and the like. Further, the manufacturing method object of the present invention, while controlling the film thickness and the respective characteristics such as high precision, without causing waste of materials, efficiently, capable of producing a sliding member in which the solid lubricant film is formed Is to provide .

The present invention provides a pair of metals that can be expanded and contracted in the axial direction via a spline sliding portion composed of an external spline portion and an internal spline portion, and can be integrally rotated in a rotational direction around the shaft. An intermediate shaft provided with a shaft member as a member and disposed between a steering shaft and a pinion shaft of a steering device, and at least one sliding surface of the external spline portion and the internal spline portion, A sliding member characterized in that a solid lubricating film containing a resin solid content and fluororesin powder and having a scratch hardness (pencil method) of 3H or more is formed . According to the present invention, the fluororesin powder is included and the scratch hardness is in the above range, so that the solid lubricating film is imparted with good lubricity, and the solid lubricating film has high strength, In addition, it has sufficient adhesion to the shaft member as a base and can have appropriate flexibility. Therefore, according to the present invention, it is possible to provide a sliding member in which good lubricity is imparted to the sliding surface by a solid lubricating film excellent in lubricity, stick-slip resistance, wear resistance, and the like. .

The resin solid content is excellent in adhesion to the shaft member as a metal member, and in consideration of forming a solid lubricating film having excellent scratch hardness, good flexibility, and excellent wear resistance even in the above range. Then, it is preferable to use an alkyd resin.

The present invention is a manufacturing method for manufacturing the sliding member of the present invention, the surface of the shaft member as a base for forming the solid lubricating film, degreasing treatment, chemical treatment, Alternatively, in the state of blasting and the shaft member immersed in a resin coating containing a resin solid content and a fluororesin powder of 5% by mass to 20% by mass with a counter electrode, a processing voltage of 20V to 150V Hereinafter, the step of electrodeposition coating under a treatment time of 30 seconds to 300 seconds and the coating film are fired under a treatment temperature of 220 ° C. to 240 ° C. and a treatment time of 15 minutes to 45 minutes. And a process.

  According to the above manufacturing method, as a feature of the electrodeposition coating method, the influence of surface tension is eliminated, and the surface having a concavo-convex shape, such as a sliding surface of a spline part, is excellent in film thickness accuracy and uniform. In addition to forming a solid lubricating film having a sufficient thickness, the film thickness can be controlled to an arbitrary value with high accuracy by adjusting the electrodeposition coating conditions and the firing conditions within the above ranges. For this reason, the film thickness can be controlled with high accuracy within a range in which no play occurs, for example, in accordance with the clearance between both spline portions, and waste of material can be eliminated.

In addition, by adjusting the electrodeposition coating conditions and the firing conditions within the above ranges, the scratch hardness of the formed solid lubricant film can be controlled with high accuracy within the range described above. Furthermore, the content ratio of the fluororesin powder in the solid lubricant film to be formed can be controlled by controlling the composition of the resin paint used for electrodeposition coating under the above conditions. Therefore, it is possible to remove the oily dirt remaining on the surface of the shaft member by degreasing or blasting, and to eliminate the influence of the dirt on the electrodeposition coating. Undercoat film suitable for electrodeposition coating by chemical treatment In combination with the ability to form a sliding member with good lubricity on the sliding surface by a solid lubricating film excellent in lubricity, stick-slip resistance, wear resistance, etc. It does not occur and can be manufactured with good reproducibility.

ADVANTAGE OF THE INVENTION According to this invention, the sliding member by which favorable lubricity was provided to the sliding surface with the solid lubricating film excellent in lubricity, stick-slip resistance, abrasion resistance, etc. can be provided. Further, according to the present invention, while controlling the film thickness and the respective characteristics such as high precision, without causing waste of materials, efficiently manufacturing process for producing a sliding member in which the solid lubricant film is formed Can be provided .

(Solid lubricant to be film)
The solid lubricating film formed on the sliding surface of the shaft member of the sliding member of the present invention includes a resin solid content and a fluororesin powder, and has a scratch hardness (pencil method) of 3H or more. It is. Well before Symbol solid body lubricating coating with a fluorine-containing resin powder, by the scratch hardness is within the above range, and has a good lubricity, high strength, and with respect to the shaft member as a base In addition to having excellent adhesion, it itself has moderate flexibility and is excellent in lubricity, stick-slip resistance, wear resistance, and the like.

That is, in the prior SL solid body lubricating coating, the scratch hardness is limited to 3H or more, in the following soft solid lubricating coating 2H, resistance sticks require - in order to slip, wear resistance can not be obtained is there. The upper limit of the scratch hardness is not particularly limited, and any solid lubricant film up to the upper limit of the scratch hardness that can be formed can be used depending on the type of resin solid content to be used. For example, when an alkyd resin, an epoxy resin, or an acrylic resin is used as the resin solid content, the upper limit of the scratch hardness of the solid lubricant film is 4H, and when the polybutadiene resin is used as the resin solid content, The upper limit of the scratch hardness is 5H. Note that the scratch hardness of the solid lubricating coating is determined according to the present invention by using Japanese Industrial Standard JIS K5600-5-4: 1999 “Paint General Test Method—Part 5: Mechanical Properties of Coating—Section 4: Scratch Hardness (Pencil Based on the measurement method defined in “Method)”, the measurement is performed at room temperature (15 to 35 ° C.).

As the resin solid content, any of various resins that can be used for the solid lubricating film can be used. For example, as the resin solid content for the solid lubricating film formed by electrodeposition coating and baking, alkyd resin, epoxy 1 type, or 2 or more types, such as resin, an acrylic resin, and a polybutadiene resin, are mentioned. Among these, alkyd resins are preferred in view of excellent adhesion to the shaft member as a metal member and formation of a solid lubricating film excellent in scratch hardness, good flexibility, and wear resistance within the above range.

  Examples of the alkyd resin include alkyd resins (pure alkyd resins, unsaturated polyester resins that are linear alkyds) that are condensates of polybasic acids such as phthalic anhydride and polyhydric alcohols such as glycerin and pentaerythritol. Alkyd resin modified with drying oil, non-drying oil, etc., modified with oil-modified alkyd resin, rosin, phenol resin, styrene, acrylic, urethane, epoxy resin, silicone resin, isocyanate, etc. It is also possible to use various modified alkyd resins that have been modified by maleation, addition of anhydride, or the like.

Examples of fluororesin powder include polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoroethylene / ethylene copolymer. One or two or more kinds of powders such as a polymer (ETFE) can be mentioned, and among them, PTFE powder is preferable. The fluororesin powder is excellent in film thickness accuracy, has a uniform thickness, and considering the formation of a solid lubricating film having a smooth surface and excellent lubricity, its particle size is 50% of the particle size distribution. The cumulative diameter D ₅₀ is preferably 0.2 μm or more and 10 μm or less.

Thickness of the solid body lubricating coating, for use as a lubricant for spline sliding portion, as described above, the clearance between the external spline portion constituting a spline sliding portion and the internal spline portion In addition, the clearance may be set within a range that does not exceed the clearance and does not cause backlash.

The sliding member of the present invention that pre-Symbol solid body lubricating coating is formed, the shaft member as a metal member, degreased surfaces forming the solid lubricating film, a step of chemical treatment or blast treatment, said shaft In a state where the member is immersed in a resin coating containing a resin solid content and a fluorine resin powder of 5% by mass to 20% by mass with a counter electrode, a processing voltage of 20V to 150V, a processing time of 30 seconds to 300%. The production method of the present invention includes a step of electrodeposition coating under conditions of seconds or less and a step of baking the coating film under conditions of a treatment temperature of 220 ° C. to 240 ° C. and a treatment time of 15 minutes to 45 minutes. Can be manufactured by.

According to the manufacturing method of the present invention, the solid lubricant film, while controlling the film thickness of the portion other than the concave portion and the respective characteristics such as high precision, without causing waste of materials, efficiently, the solid lubricant film The sliding member formed with can be manufactured. In the manufacturing method, as the degreasing treatment for removing oily dirt adhered to the surface of the shaft member on which the solid lubricating film is formed, for example, an organic solvent such as chlorinated hydrocarbon or petroleum hydrocarbon is used. Ordinary solvent degreasing treatment, normal alkali degreasing treatment, or electrolytic degreasing treatment in which the shaft member is immersed in an alkali washing bath, an acid washing bath or the like together with a counter electrode to perform an electrolytic treatment by functioning as a cathode or an anode. The degreasing process of this is mentioned. In addition, as chemical treatment, for example, zinc phosphate treatment, manganese phosphate treatment, manganese zinc phosphate treatment, zinc phosphate-lime treatment, iron phosphate treatment, phosphate alcohol treatment, phosphate chromic acid treatment, etc. Various treatments capable of forming an undercoat film suitable for coating are mentioned.

  The blasting process is usually a dry blasting process such as sand blasting, shot blasting, grit blasting, etc., classified according to the type of particles to be sprayed, and wet blasting in which the above particles are sprayed with pressurized water to which a rust preventive liquid is added Blasting. The conditions for degreasing and blasting may be as usual. The resin coating used for electrodeposition coating can be prepared by dissolving or dispersing the resin solid content and fluororesin powder described above in a solvent, particularly an aqueous solvent. As the aqueous solvent, water is used, and a mixed solvent of water and a water-soluble organic solvent can be used. A dispersant and other additives may be added to the resin paint.

In the resin coating, the blending ratio of the fluororesin powder in the total amount of solids forming the solid lubricating film (= resin solid content + fluororesin powder amount) is limited to 5% by mass to 20% by mass. The reason is as follows. That is, when the blending ratio of the fluororesin powder exceeds 20% by mass, the content of the resin solid content as a film forming component in the solid lubricating film to be produced is relatively reduced. The effect of improving the adhesion of the solid lubricating film to the shaft member as a metal member , setting the scratch hardness to the above range, or imparting good flexibility to the solid lubricating film is not obtained. For this reason, the stick-slip resistance, wear resistance, etc. of the solid lubricating coating are reduced.

  On the other hand, when the blending ratio of the fluororesin powder is less than 5% by mass, the effect of imparting good lubricity to the solid lubricant film by the fluororesin powder cannot be obtained, and therefore the lubricity of the solid lubricant film decreases. , Wear resistance and the like are reduced. In addition, the various effects described above due to the resin solid content and fluororesin powder are made even better to form a solid lubricant film with even better lubricity, stick-slip resistance, wear resistance, etc. In consideration of this, the blending ratio of the fluororesin powder in the resin coating is preferably 5% by mass to 20% by mass, particularly 7% by mass to 20% by mass, even in the above range.

Specifically, the electrodeposition coating involves immersing the shaft member and the counter electrode in the resin paint, and setting one of them as an anode and the other as a cathode and applying a DC voltage between them. It is carried out. The polarities of the shaft member and the counter electrode can be arbitrarily set according to the composition of the resin coating used, etc., but the resin solid coating contains an alkyd resin and uses a resin coating containing a fluororesin powder. In this case, it is preferable to perform electrodeposition coating (anion electrodeposition coating) using the shaft member as an anode and the counter electrode as a cathode. Moreover, when performing the said anion electrodeposition coating, it is preferable to add the neutralizing agent to a resin solution, and to adjust the pH to 7-11.

As the counter electrode, for example, an electrode made of a metal having corrosion resistance such as stainless steel is used. When selective electrodeposition is applied only to a specific surface of the shaft member , that is, the sliding surface of the external spline part or internal spline part, only the specific surface is immersed in a resin paint for electrodeposition. Applying paint, masking the surface other than the specific surface, immersing in resin paint with only the specific surface exposed, and selectively electrodepositing only the exposed surface do it.

The reason why the treatment voltage in electrodeposition coating is limited to the above range is as follows. That is, in the treatment voltage is less than 20V, on the surface of the shaft member, a continuous coating film having a predetermined thickness is because can not be formed and thus the solid lubricant film, when the processing voltage exceeds 150V, the surface of the shaft member The film thickness variation of the coating film is increased, and subsequent firing makes it impossible to form a solid lubricating film with excellent film thickness accuracy, uniform thickness, smooth surface and excellent lubricity. Because.

Furthermore, the reason why the electrodeposition coating processing time is limited to the above range is that if the processing time is less than 30 seconds, a continuous coating film having a predetermined thickness, and thus a solid lubricating coating film cannot be formed on the surface of the shaft member. This is because even if the treatment time exceeds 300 seconds, the thickness of the coating film cannot be increased any more. In addition, although the other conditions of electrodeposition coating are not specifically limited, It is preferable that process temperature (liquid temperature during process) is 20 to 30 degreeC. As a control method during electrodeposition coating, constant voltage control is common, but constant current control may be performed.

Firing is preferably performed in the air or in an inert atmosphere. The firing temperature is limited to the above range when the temperature is less than 220 ° C., the formed solid lubricant film has a scratch hardness of 2H or less, and the required stick-slip resistance, wear resistance, etc. This is because it cannot be obtained, and when it exceeds 240 ° C., the formed solid lubricating film becomes brittle. In addition, the firing treatment time is limited to the above range because if the treatment time is less than 15 minutes, the solid lubricant film to be formed has a scratch hardness of 2H or less, and the required stick-slip resistance, This is because wearability and the like cannot be obtained, and when it exceeds 45 minutes, the formed solid lubricating film becomes brittle.
(Sliding member)
The sliding member of the present invention, through a spline sliding portion composed of a d-click star null spline and the internal spline portion, stretchable in the axial direction, and integrally rotatably coupled to a rotation direction about the axis And an intermediate shaft disposed between a steering shaft and a pinion shaft of the steering device. In the intermediate shaft, at least one of the external spline portion and the internal spline portion. on one of the sliding surfaces, it is characterized in that the previous SL solid body lubricating coating formed. According to the present invention, good lubricity can be imparted to the sliding surface of the sliding member by the solid lubricating film.

  FIG. 1 is a perspective view showing an external spline portion 51a provided at an end of an inner shaft member 51 constituting an example of an embodiment of an intermediate shaft 5 as an example of a sliding member of the present invention. . FIG. 2 is a perspective view of the outer shaft member 52 that constitutes the intermediate shaft 5 together with the inner shaft member 51, with a part of a cylindrical internal spline portion 52a provided at the end portion cut away. . Referring to FIG. 1, a large number of keys 51 b are arranged on the outer peripheral surface of the end portion of the inner shaft member 51 connected to the outer shaft member 52 from the outer peripheral surface toward the radially outer side. The external spline portion 51a is configured to protrude in parallel with the axial direction of 51 and at equal intervals in the circumferential direction.

  Referring to FIG. 2, the outer shaft member 52 has an end portion 52c connected to the inner shaft member 51 formed in a cylindrical shape into which the external spline portion 51a is inserted, and an inner peripheral surface of the tube. A plurality of key grooves 52b meshed with the keys 51b of the external spline portion 51a from the inner peripheral surface outward in the radial direction are parallel to the axial direction of the outer shaft member 52 and in the circumferential direction. The internal spline portion 52a is formed by being recessed at equal intervals. A clearance is set in the engaging portion between the key 51b of the external spline portion 51a and the key groove 52b of the internal spline portion 52a as in the conventional case.

Then, the stuffing said clearance, to ensure good lubrication, of the external spline portion 51a and the internal spline portion 52a, on at least one surface (sliding surface), the solid lubricating coating is formed. The spline sliding portion is configured by inserting the external spline portion 51a into the internal spline portion 52a while meshing the key 51b constituting the external spline portion 51a with the key groove 52b constituting the internal spline portion 52a. Thus, both shaft members 51 and 52 are connected to each other so that they can extend and contract in the axial direction and transmit power in a rotational direction around the shaft.

As described above, since the solid lubricant film itself has good lubricity, lubricating oil such as grease is applied to the meshing portion of the intermediate shaft 5 between the key 51b and the key groove 52b. Although it does not need to be filled, lubricating oil can be filled to lubricate between the spline portions 51a and 52a together with the solid lubricating film. FIG. 3 is a schematic configuration diagram of a column type EPS 1 as an example of a steering device in which the intermediate shaft 5 is incorporated.

  Referring to FIG. 3, a column type EPS 1 includes a steering shaft 3 to which a steering wheel 2 as a steering member is connected, an intermediate shaft 5 connected to the steering shaft 3 via a universal joint 4, A pinion shaft 7 connected to the intermediate shaft 5 via a universal joint 6 and a rack tooth 8a meshing with a pinion tooth 7a provided in the vicinity of the end of the pinion shaft 7 and extending in the left-right direction of the automobile. It has a rack bar 8 as a rudder shaft. The pinion shaft 7 and the rack bar 8 constitute a rack and pinion mechanism A as a steering mechanism.

  The rack bar 8 is supported in a linearly reciprocable manner in a housing 9 fixed to the vehicle body via a plurality of bearings (not shown). Further, both end portions of the rack bar 8 protrude to both sides of the housing 9, and tie rods 10 are coupled to the respective end portions. Each tie rod 10 is connected to a corresponding steering wheel 11 via a corresponding knuckle arm (not shown). When the steering wheel 2 is operated and the steering shaft 3 is rotated, this rotation is converted into a linear motion of the rack bar 8 along the left-right direction of the automobile by the pinion teeth 7a and the rack teeth 8a. 11 is steered.

  The steering shaft 3 is divided into an input-side upper shaft 3 a that is continuous with the steering wheel 2 and an output-side lower shaft 3 b that is continuous with the pinion shaft 7, and both shafts 3 a and 3 b are the same via a torsion bar 12. Are connected to each other so as to be rotatable relative to each other. The torsion bar 12 is provided with a torque sensor 13 for detecting a steering torque from a relative rotational displacement amount between the shafts 3a and 3b. The torque detection result of the torque sensor 13 is an ECU (Electric Control Unit). : Electronic control unit) 14.

  The ECU 14 drives and controls the steering assist electric motor 16 via the drive circuit 15 based on a torque detection result, a vehicle speed detection result given from a vehicle speed sensor (not shown), and the like. The output rotation of the electric motor 16 is decelerated via the speed reducer 17 and transmitted to the pinion shaft 7 and converted into a linear motion of the rack bar 8 to assist steering. The speed reducer 17 is a worm shaft (small gear) 18 as an input shaft that is rotationally driven by an electric motor 16, and a worm wheel that meshes with the worm shaft 18 and is connected to the lower shaft 3 b of the steering shaft 3 so as to be integrally rotatable. (Large gear) 19.

The column type EPS 1 of the example shown in the figure having the above-described parts includes a key 51b of the external spline part 51a constituting a spline sliding part of the intermediate shaft 5 and a key groove 52b of the internal spline part 52a during steering. even subjected to any high surface pressure to the meshing portion, the solid lubricating coating to maintain a good lubrication, and oil film shortage, stick with it - because slippage does not occur, for example caused a slip sound, an unpleasant feeling to the driver Can be prevented.

  In addition, the structure of this invention is not limited to the thing of the example demonstrated above. For example, the intermediate shaft forms rolling grooves along the axial direction on the outer peripheral surface of the inner shaft member and the inner peripheral surface of the outer shaft member, respectively, and allows a plurality of balls to roll in the grooves. A so-called ball spline type structure may be employed in which both shaft members can be expanded and contracted in the axial direction via a ball and are coupled so as to be integrally rotatable in a rotation direction around the shaft. The solid lubricant film may be formed on at least one of the inner surface of the rolling groove and the outer surface of the ball.

Further, the steering device in which the intermediate shaft is incorporated is not limited to the column type EPS 1 shown in FIG. 3, and may be another type of EPS or a normal steering device having no steering assist function. To or the solid body lubricating coating, it is also possible to serve also as the function of the dust-preventing film. In addition, various design changes can be made without departing from the scope of the present invention.

<Examination of electrodeposition coating conditions>
The total amount of solids (= alkyd) that forms a solid lubricating film, including alkyd resin (S-161-LP manufactured by Dainippon Ink and Chemicals, Inc.) as resin solids and PTFE powder as fluororesin powder Resin paint in which the blending ratio of PTFE powder in (resin amount + PTFE powder amount) was 10% by mass was prepared. Next, after the surface of a rectangular general structural rolled steel (SS400) plate having a length of 30 mm × width 30 mm × thickness 6 mm as a model of the shaft member is subjected to solvent degreasing treatment, the film thickness is measured at a plurality of locations on one side. For this reason, partial masking was performed to provide a region where no film was formed.

  Next, the SS400 plate is immersed in the resin solution together with a stainless steel plate as a counter electrode, and is electrodeposited by constant voltage control at the treatment voltage and treatment time shown in Table 1, and then pulled up from the resin solution. After washing with water, it was dried to form a coating film. Then, the SS400 plate on which the coating film was formed was placed in a preheated electric furnace and baked in the atmosphere at a temperature of 230 ° C. for a treatment time of 20 minutes to produce a solid lubricating coating.

  While observing the state of the manufactured solid lubricant film, the level difference between the region where the film was not formed and the solid lubricant film surrounding the area was measured using a surface roughness meter, and the film thickness of the solid lubricant film was measured. The operation for obtaining was performed at the plurality of locations. Then, the film thickness variation measured within ± 30% of the target film thickness was evaluated as good surface smoothness, and the film thickness exceeding the above range was evaluated as poor surface smoothness.

  Furthermore, based on the measurement method prescribed in JIS K5600-5-4: 1999 “Paint General Test Method—Part 5: Mechanical Properties of Coating Film—Section 4: Scratch Hardness (Pencil Method)” described above. Then, the scratch hardness of the solid lubricant film was measured at room temperature (15 to 35 ° C.), and those having a scratch hardness of 3H or higher were evaluated as good and those having a scratch hardness of 2H or lower were evaluated as bad. Then, one of the above evaluations that had a failure was evaluated as a comprehensive evaluation failure, and one that had no failure was evaluated as a good overall evaluation. The results are shown in Table 1.

表１より、電着塗装における処理電圧を２０Ｖ以上〜１５０Ｖ以下、処理時間を３０秒以上〜３００秒以下としたとき、表面平滑性に優れた連続した固体潤滑被膜を、効率よく製造できることが確認された。

From Table 1, it is confirmed that a continuous solid lubricating film excellent in surface smoothness can be efficiently produced when the treatment voltage in electrodeposition coating is 20 V to 150 V and the treatment time is 30 seconds to 300 seconds. It was done.

<Examination of firing conditions>
The electrodeposition coating treatment voltage was fixed at 40 V, the treatment time was fixed at 120 seconds, and the coating film was baked at the firing temperature and treatment time shown in Table 2. A solid lubricating coating was prepared and evaluated in the same manner. The results are shown in Table 2.

表２より、焼成の温度を２２０℃以上〜２４０℃以下、処理時間を１５分以上〜４５分以下としたとき、表面平滑性に優れた連続した固体潤滑被膜を、効率よく製造できることが確認された。

From Table 2, it was confirmed that a continuous solid lubricating film excellent in surface smoothness can be efficiently produced when the firing temperature is 220 ° C. or higher and 240 ° C. or lower and the treatment time is 15 minutes or longer and 45 minutes or shorter. It was.

<Example 1>
The total amount of solids (= alkyd) that forms a solid lubricating film, including alkyd resin (S-161-LP manufactured by Dainippon Ink and Chemicals, Inc.) as resin solids and PTFE powder as fluororesin powder Resin paint in which the blending ratio of PTFE powder in (resin amount + PTFE powder amount) was 10% by mass was prepared. Next, a surface of a rectangular SS400 plate having a length of 30 mm × width of 30 mm × thickness of 6 mm as a model of the shaft member is subjected to solvent degreasing treatment, and then a region where no film is formed for film thickness measurement is provided on one surface thereof. Partial masking.

  Next, the SS400 plate is immersed in the resin solution together with a stainless steel plate as a counter electrode, and after electrodeposition coating by constant voltage control under the conditions of a processing voltage of 40 V and a processing time of 120 seconds, the SS400 plate is pulled up from the resin solution. After washing with water, it was dried to form a coating film. Then, the SS400 plate on which the coating film was formed was placed in a preheated electric furnace and baked in the atmosphere at a temperature of 230 ° C. for a treatment time of 20 minutes to produce a solid lubricating coating.

<Examples 2 to 5 and Comparative Examples 1 to 3>
As shown in Table 3, the blending ratio of PTFE powder in the total amount of solid content (= alkyd resin amount + PTFE powder amount) in the resin coating was adjusted, or the firing conditions were adjusted. A solid lubricating film was produced in the same manner as in Example 1 except that.

<Example 6>
The surface of the SS400 plate as a model of the shaft member is subjected to blasting instead of solvent degreasing, and PTFE occupies in the total amount of solid content (= alkyd resin amount + PTFE powder amount) in the resin coating. A solid lubricating film was produced in the same manner as in Example 1 except that the blending ratio of the powder was 20% by mass.

<Example 7>
As the resin solid content, a polybutadiene resin (BN-1015 manufactured by Nippon Soda Co., Ltd., abbreviated as PB in Table 3) is used instead of the alkyd resin, and a solid lubricant film is formed in the resin paint. A solid lubricating coating was produced in the same manner as in Example 1 except that the blending ratio of the PTFE powder in the total amount (= polybutadiene resin amount + PTFE powder amount) was 20 mass%.

<Evaluation>
The step of the solid lubricant film of Examples 1 to 7 and Comparative Examples 1 to 3 where the film was not formed and the solid lubricant film surrounding the area were measured using a surface roughness meter. It was set as the film thickness of the solid lubricating film. And, when the operation of manufacturing the solid lubricant film of each of the above Examples and Comparative Examples using the same resin paint and the operation of measuring the film thickness of the manufactured solid lubricant film were continuously performed 10 times, The measured film thickness variation of ± 0.5 μm or less was evaluated as good film thickness accuracy, and the film thickness exceeding 0.5 μm was evaluated as poor accuracy.

  In addition, the solid lubricant film of each of the above examples and comparative examples was subjected to a reciprocating friction tester, the mating material: SUJ2 (φ3 / 16 inch), test load: 4.9 N, test speed 40 mm / s (stroke 10 mm), test time: After a wear test under conditions of 10 minutes, the depth of the wear scar formed on the surface was measured using a surface roughness meter. Further, the difference between the maximum frictional behavior measured during the wear test was determined as the static friction coefficient and the stable value as the dynamic friction coefficient, and the stick-slip resistance of the solid lubricating coating was evaluated.

  Furthermore, based on the measurement method prescribed in JIS K5600-5-4: 1999 “Paint General Test Method—Part 5: Mechanical Properties of Coating Film—Section 4: Scratch Hardness (Pencil Method)” described above. Then, the scratch hardness of each of the solid lubricating coatings of the Examples and Comparative Examples was measured at room temperature (15 to 35 ° C.). The results are shown in Table 3. In addition, “below the limit” in the column of the wear scar depth in Table 3 indicates that the wear scar depth was below the measurement limit by the surface roughness meter.

表３より、樹脂塗料における、固体潤滑被膜を形成する固形分の総量（＝アルキド樹脂量＋ＰＴＦＥ粉末量）中に占めるＰＴＦＥ粉末の配合割合が５質量％未満であった比較例１、２の固体潤滑被膜は、潤滑性が十分でないため、引っかき硬度が３Ｈ以上であるにも拘らず、摩耗痕の深さが５．０μｍ以上と大きく、耐摩耗性が不良になることが判った。また、ＰＴＦＥ粉末の配合割合が２０質量％を超える比較例４の固体潤滑被膜は、引っかき硬度がＨであって軟らかすぎるため、摩耗痕の深さが５．０μｍと大きく、やはり耐摩耗性が不良になることが判った。さらに、前記各比較例の固体潤滑被膜は、いずれも、静摩擦係数と動摩擦係数との差が０．１１以上と大きいことから、耐スティック−スリップ性が低いことも判った。

From Table 3, the solids of Comparative Examples 1 and 2 in which the blending ratio of the PTFE powder in the total solid content (= alkyd resin amount + PTFE powder amount) in the resin coating was less than 5% by mass Since the lubricating coating has insufficient lubricity, it has been found that the wear scar depth is as large as 5.0 μm or more and the wear resistance is poor despite the scratch hardness being 3H or more. In addition, the solid lubricating film of Comparative Example 4 in which the blending ratio of the PTFE powder exceeds 20% by mass has a scratch hardness of H and is too soft. It turned out to be defective. Further, it was also found that the solid lubricating coatings of the comparative examples had low stick-slip resistance because the difference between the static friction coefficient and the dynamic friction coefficient was as large as 0.11 or more.

  On the other hand, the solid lubricating film of Examples 1 to 7 in which the blending ratio of the PTFE powder in the resin coating was in the range of 5% by mass to 20% by mass and the scratch hardness was in the range of 3H or more In addition, the wear scar depth is less than 5.0 μm, and the wear resistance is excellent, and the difference between the static friction coefficient and the dynamic friction coefficient is as small as 0.10 or less, and the stick-slip resistance is excellent. Was confirmed.

It is a perspective view which shows the external spline part provided in the edge part of the inner shaft member which comprises an example of embodiment of the intermediate shaft as an example of the sliding member of this invention. It is a perspective view which cuts and shows a part of cylindrical internal spline part provided in the edge part of the outer shaft member which comprises an intermediate shaft with the said outer shaft member. It is a schematic block diagram of column type EPS as an example of a steering device in which the said intermediate shaft is integrated.

Explanation of symbols

1: Column type EPS, 2: Steering wheel, 3: Steering shaft, 3a: Upper shaft, 3b: Lower shaft, 4: Universal joint, 5: Intermediate shaft (sliding member), 6: Universal joint, 7: Pinion Shaft, 7a: Pinion teeth, 8: Rack bar, 8a: Rack teeth, 9: Housing, 10: Tie rod, 11: Steering wheel, 12: Torsion bar, 13: Torque sensor, 15: Drive circuit, 16: Electric motor 17: reduction gear, 18: worm shaft, 51: inner shaft member, 51a: external spline portion, 51b: key, 52: outer shaft member, 52a: internal spline portion, 52b: key groove, 52c: end portion

Claims (4)

A pair of shafts as a metal member that can be expanded and contracted in the axial direction through a spline sliding portion composed of an external spline portion and an internal spline portion, and can be integrally rotated in a rotational direction around the shaft. An intermediate shaft provided between a steering shaft and a pinion shaft of a steering device, wherein at least one sliding surface of the external spline portion and the internal spline portion has a resin solid content fluororesin powder and a scratch hardness sliding member characterized by (pencil method) der Ru solid body lubricating coating or 3H is formed. The surface of the shaft member on which the solid lubricant film is to be formed is degreased, chemically or blasted, and then the shaft member , together with the counter electrode, is solid resin and fluorine of 5% by mass to 20% by mass. After electrodeposition coating under conditions of a treatment voltage of 20 V to 150 V and a treatment time of 30 seconds to 300 seconds in a state immersed in a resin coating containing resin, the coating film is heated to a temperature of 220 ° C. to 240 ° C. The sliding member according to claim 1, wherein a solid lubricating film is formed by firing under a treatment time of 15 minutes to 45 minutes. The sliding member according to claim 1 or 2, wherein the resin solid content is an alkyd resin. A manufacturing method for producing a sliding member according to any one of claims 1 to 3, the shaft member as a base to form a solid lubricating coating, the surface to form the solid lubricant coating degreasing A process of chemical treatment, blast treatment, and the shaft member are immersed in a resin coating containing a resin solid content and a fluororesin powder of 5% by mass to 20% by mass with a counter electrode. The step of electrodeposition coating under conditions of a voltage of 20 V to 150 V, a processing time of 30 seconds to 300 seconds, and a coating temperature of 220 ° C. to 240 ° C., a processing time of 15 minutes to 45 minutes. method for producing a sliding member, which comprises a step of firing in conditions.

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