JP2012063017A - Driving shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving shaft capable of preventing outbreaks of looseness and seizure due to abrasion by maintaining superior sliding between abutment surfaces over more long time when grease is used up in comparison with a case of coating with a resin film.SOLUTION: In this driving shaft 1, a surface of a key 21 of a male spline part 22 of a male spline shaft 2 out of the male spline shaft 2 and a female spline shaft 3, including an abutment surface 21a as a power transmitting surface to the other, is coated with a continuous diamond-like carbon film (6) having a Vickers hardness Hv of 1000 or more, a friction coefficient μ of 0.25 or less, and a film thickness in the abutment surface of at least 1-5 μm.

Description

  The present invention relates to a drive shaft used for power transmission in railway vehicles, steel rolling mills, automobiles, and the like.

  For example, in a railway vehicle, the drive shaft for transmitting power from the engine to the axle via a torque converter is a shaft that depends on the vertical movement of the running wheel, the swing of the carriage when passing a curve, etc. It is necessary to transmit power while expanding and contracting in the direction. For this reason, as the drive shaft, a shaft provided with a male spline shaft and a female spline shaft that can be expanded and contracted in the axial direction and is connected so as to be able to transmit power in the rotational direction around the shaft is generally used. The drive shaft provided with the male spline shaft and the female spline shaft is also used for a drive shaft for connecting a motor and a rolling roll, a propeller shaft of an automobile, a steering shaft, a handle joint, etc. in a steel rolling mill. .

  The drive shaft with male spline shaft and female spline shaft can be rotated while allowing the outer periphery of the male spline shaft and the inner periphery of the female spline shaft to slide in the axial direction of both spline shafts. Formed with spline parts with contact surfaces (power transmission surfaces) that contact in the direction and transmit power, and engage each spline part so that the contact surfaces contact each other when the drive shaft rotates There are drive shafts.

  The drive shaft is filled with grease in order to ensure smooth sliding in the axial direction between the contact surfaces that are in contact with each other when the shaft rotates. However, since the grease is pushed out to the outside gradually as the spline shaft repeatedly expands and contracts in the axial direction, the grease eventually runs out, and there is a problem of looseness due to metal wear and seizure. .

  Therefore, at least one of the contact surfaces of the two spline shafts is coated with a resin film having a smaller friction coefficient than that of a metal such as stainless steel constituting the two spline shafts, and having good sliding properties. When cutting occurs, it has been proposed to maintain sliding as soon as possible with the resin film so that no play or seizure occurs immediately.

  For example, in Patent Document 1, in the rotating shaft that is the drive shaft, at least one of the spline portions of both spline shafts, the contact surface to the other spline portion is made of a resin such as polyphenylene sulfide or polybutylene terephthalate. It describes that it is coated with a coating, and that the coating contains a filler such as calcium carbonate and a solid lubricant.

Further, in Patent Document 2, in a coupling member having a fitting portion to another member such as a spline portion, the fitting portion includes a first resin layer made of polyphenylene sulfide resin and the first resin. It describes that it coat | covers with the 2nd resin layer which consists of resin of nylon etc. which covers a layer.
Further, in Patent Document 3, in a telescopic shaft for vehicle steering as a drive shaft, the contact surface of the spline portion of both spline shafts to the other spline portion is coated with a polytetrafluoroethylene (PTFE) coating, respectively. It is described to do.

JP 2001-336543 A (claims 1 to 3, columns 0005 to 0010) JP2003-11280A (Claims 1-2, columns 0005 to 0007) JP 2003-54421 A (Claim 1, columns 0006 to 0009)

  However, in the case of a resin coating, there is a case where the effect of maintaining the sliding of the contact surface is not sufficient when the grease runs out. In particular, the spline part abuts on a railway vehicle drive shaft that rotates at a high speed and often expands and contracts in the axial direction at a high speed, and a steel rolling mill drive shaft that applies a very high load to the abutment surface. When the surface is coated with a resin film, the film is worn and disappears in a very short time when the grease runs out. Therefore, the effect of maintaining the sliding of the abutting surface by the resin coating lasts only for a very short time when the grease breaks out, and then, in a short time, the occurrence of looseness due to metal wear and seizure There is a problem that causes.

  The object of the present invention is to maintain good sliding between the contact surfaces over a longer period of time when grease breakage occurs as compared with the case of coating with a resin coating, An object of the present invention is to provide a drive shaft that can prevent generation, burn-in, and the like.

The drive shaft of the present invention comprises a male spline shaft (2) and a female spline shaft (3),
The male spline shaft (2) is integrally formed of metal as a whole, and the outer surface of the male spline shaft (2) connected to the female spline shaft (3) has a radial direction from the outer peripheral surface. A large number of keys (21) project outwardly to form a male spline part (22),
The female spline shaft (3) is integrally formed of metal as a whole, and the end of the female spline shaft (3) connected to the male spline shaft (2) is an end on the male spline shaft (2) side. An opening (30) is formed in the tube, and the male spline portion (22) is inserted into the inside through the opening (30). A large number of key grooves (31) meshed with the key (21) of the male spline part (22) are recessed toward the outside in the direction to form a female spline part (32),
Both side surfaces of each key (21) constituting the male spline portion (22) and both side surfaces of each key groove (31) constituting the female spline portion (32) are contact surfaces as power transmission surfaces ( 21a) (31a)
The male spline shaft (2) and the female spline shaft (3) are engaged with the key (21) and the key groove (31) and slide in the contact surfaces (21a) (31a) in the axial direction. A drive shaft (1) that can be expanded and contracted in the axial direction in a state in which it can be contacted, and is connected so as to be able to transmit power in a rotational direction around the shaft,
Adjacent to the contact surface (21a), the top surface (21b), and the outer peripheral surface of the male spline shaft (2), which are both side surfaces of each key (21) constituting the male spline portion (22). The bottom surface (21c) between the keys (21) is continuous with a Vickers hardness Hv of 1000 or more, a friction coefficient μ of 0.25 or less, and at least a thickness of the contact surface (21a) of 1 to 5 μm. Covered with a diamond-like carbon film (6),
The contact surfaces (31a) that are both side surfaces of each key groove (31) constituting the female spline portion (32), the bottom surface (31b) of the key groove (31), and the adjacent key grooves (31) The top surface (31c) of the ridge (36) is not covered with the diamond-like carbon film (6) and the metal base is exposed, and the male spline portion (22) and the female spline portion (32 ) Is filled with grease,
The male spline part (22) and the female spline part (32) are characterized by being expanded and contracted in the axial direction at high speed while rotating at high speed.

According to the present invention, the Vickers hardness Hv is 1000 or more between the contact surface as a power transmission surface that is both sides of the key of the male spline part, the top surface of the key, and the bottom surface between adjacent keys. It is coated with a strong diamond-like carbon film (DLC film) that has high hardness and does not wear out and disappear in a short time even if grease breaks, and the DLC film has a friction coefficient μ In addition to having good slidability of 0.25 or less, the film thickness of at least the contact surface is 1 to 5 μm. It is possible to maintain good sliding between the contact surfaces (power transmission surfaces) over a long period of time, and to prevent play and seizure due to wear of metals.
By adding tungsten to the DLC film, the adhesion of the DLC film to the base can be further improved and the friction coefficient μ can be further reduced.

It is a partially cutaway front view showing the whole drive shaft concerning one embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1 showing a portion where the male spline portion of the male spline shaft and the female spline portion of the female spline shaft, which are the main parts of the drive shaft of the above example, are engaged. It is sectional drawing to which some male spline parts were expanded. It is sectional drawing to which a part of female spline part was expanded. In the Example of this invention, it is a figure explaining the outline of the apparatus which performed the slip test of the DLC film. In the Example of this invention, it is a figure explaining the outline of the apparatus which performed the rolling test of the DLC film. It is a graph which shows the relationship between the contact surface pressure of the SUJ2 ball | bowl calculated | required in the rolling test, and the frequency | count of rotation until a DLC film reaches the lifetime.

  FIG. 1 is a partially cutaway front view showing the entire drive shaft according to an embodiment of the present invention. 2 is a cross-sectional view taken along the line II-II in FIG. 1, showing a portion where the male spline portion of the male spline shaft and the female spline portion of the female spline shaft are meshed, which is a main part of the drive shaft of the above example. FIG. 3 is an enlarged cross-sectional view of a part of the male spline part, and FIG. 4 is an enlarged cross-sectional view of a part of the female spline part.

  Referring to FIGS. 1 and 2, the drive shaft 1 of this example includes a male spline shaft 2 and a female spline shaft 3 both of which are made of metal such as stainless steel. On the outer peripheral surface of the end portion connected to the female spline shaft 3, a large number of keys 21 are parallel to the axial direction of the male spline shaft 2 from the outer peripheral surface outward in the radial direction. The male spline portion 22 is configured to protrude at equal intervals. Further, a cross shaft joint 4 for connecting the drive shaft 1 to a drive input shaft or drive output shaft (not shown) at the end 23 of the male spline shaft 2 opposite to the side where the male spline portion 22 is formed. Is connected.

  1 and 2, the female spline shaft 3 has a cylindrical shape in which an opening 30 is formed at the end on the male spline shaft 2 side, and the male spline portion 22 is inserted into the inside through the opening 30. And a plurality of key grooves 31 meshed with the key 21 of the male spline portion 22 from the inner peripheral surface outward in the radial direction from the inner peripheral surface. A female spline portion 32 is formed in parallel with the axial direction of 3 and recessed at equal intervals in the circumferential direction. A cross shaft joint 5 for connecting the drive shaft 1 to a drive output shaft or drive input shaft (not shown) is connected to the end 33 of the female spline shaft 3 opposite to the opening 30 side.

  An annular seal member 35 made of rubber, resin, or the like is attached to the end of the female spline shaft 3 on the opening 30 side via a substantially cylindrical fixing member 34. The space between both the spline shafts 2 and 3 is sealed by contacting the outer peripheral surface of the male spline shaft 2 inserted into the cylinder. And when both the spline shafts 2 and 3 are repeatedly expanded and contracted in the axial direction by this seal, the grease sealed between the spline portions 22 and 32 of the two spline shafts 2 and 3 is pushed out to the outside. In addition to being suppressed, foreign matters such as dust are prevented from entering between the spline portions 22 and 32.

Referring to FIG. 2, a minute clearance is set in the meshing portion of both spline portions 22 and 32, and grease is sealed in the gap formed by this clearance.
Referring to FIGS. 2 and 3, each key 21 constituting male spline portion 22 has both side surfaces as contact surfaces 21 a as power transmission surfaces. 2 and 4, each of the key grooves 31 constituting the female spline portion 32 has both side surfaces facing the contact surface 21 a as power transmission surfaces when meshed with the key 21. The contact surface 31a. When the drive shaft 1 rotates, any one contact surface 21a of each key 21 and each contact surface 31a of each key groove 31 opposite to the contact surface 21a contact each other. Power is transmitted between the spline shafts 2 and 3.

Referring to FIG. 3, a contact surface 21 a that is both side surfaces of each key 21 constituting the male spline portion 22, a top surface 21 b, and an interval between adjacent keys 21 corresponding to the outer peripheral surface of the male spline shaft 2. The bottom surface 21c is covered with a continuous DLC film 6 having a Vickers hardness Hv of 1000 or more, a friction coefficient μ of 0.25 or less, and at least a thickness of a contact surface of 1 to 5 μm.
As a result, when the grease runs out, it is possible not only to prevent wear and seizure between the contact surfaces 21a and 31a, but also the key 21 and the key groove 31 are formed between surfaces other than the contact surfaces 21a and 31a. It is also possible to prevent seizure or the like from being worn even during the period.
Further, when the DLC film 6 is laminated on a metal base having a silicon film, a chromium film or the like formed thereon, the adhesion of the DLC film 6 can be improved and the friction coefficient μ can be lowered.

On the other hand, the contact surface 31a, the bottom surface 31b, and the top surface 31c of the ridge 36 between the adjacent key grooves 31 which are both side surfaces of each key groove 31 constituting the female spline part 32 engaged with the male spline part 22 are described. In this case, the metal base is exposed without being covered with the DLC film.
The surface of the female spline part 32 is not covered with the DLC film, and only the surface of the male spline part 22 is covered with the DLC film 6, and the function of the DLC film 6 is longer than that of the resin film. Over the period, it is possible to maintain good sliding of the contact surfaces 21a and 31a, and to prevent the occurrence of play due to wear between metals and seizure.

The DLC film can be formed by various conventionally known vapor deposition methods such as sputtering. An example of a method for forming a DLC film by sputtering is a chamber into which an introduction gas such as argon gas or hydrocarbon gas is introduced so that the pressure is 1.33 × 10 ⁻¹ to 1.33 × 10 ² Pa. The carbon is vapor-deposited on the predetermined surfaces of the spline shafts 2 and 3 by performing a discharge process on the carbon as a target under conditions of a voltage of 100 to 200 V and a current of about 2 to 10 A. Then, a DLC film having an amorphous structure in which a graphite (SP2) structure and a diamond (SP3) structure coexist is formed on the predetermined surface.

Examples of other film forming methods include physical vapor deposition (PVD) methods such as ion plating using ion beam evaporation using benzene as a source gas, plasma CVD methods using hydrocarbon compounds as film forming gases, and the like. And the chemical vapor deposition (CVD) method. Also, a spraying method such as plasma spraying using a plasma jet can be employed.
In addition, by including tungsten in the DLC film, the adhesion of the DLC film to the base can be improved and the friction coefficient μ can be reduced.

Hereinafter, the present invention will be described based on examples.
Formation of DLC film:
The DLC films of Examples 1 to 3 shown in Table 1 were formed on one surface of a stainless steel SUS440C substrate as a power transmission surface model by plasma CVD or sputtering. In the table, P-CVD in the column of the film formation method indicates a plasma CVD method, and PVD indicates a sputtering method.

Slip test:
As shown in FIG. 5, the substrate 90 of each of the above embodiments is fixed to the tip of the rotating shaft S with the surface on which the DLC film 91 is formed facing up, and then the 5/32 ″ SUJ2 ball B does not rotate. In the fixed state, the rotary shaft S was rotated at a sliding speed of 0.1 m / s while applying pressure of 1.0 GPa and pressing the surface of the DLC film 91 as indicated by a white arrow in the figure. The DLC film 91 and the SUJ2 ball B were rotated until the sliding distance reached 360 m, and the friction coefficient μ was obtained from the stress applied to the SUJ2 ball B in the rotation direction of the substrate 90 at the end of the test. In addition, after the test, the length of wear traces generated on the surface of the DLC film 91 was measured, and the above test was performed on the substrate 90 made of stainless steel SUS440C in which the DLC film 91 was not formed on the surface for comparison. Table 2 shows the results. Shown. Here, the conventional example 1 in the table indicates a substrate made of stainless steel does not form a DLC film 91.

  From the table, it was confirmed that by forming a DLC film on the surface of a stainless steel substrate, the friction coefficient can be greatly reduced and wear due to sliding can be prevented. Further, by laminating a DLC film on a silicon film or chromium film formed on the base, the adhesion of the DLC film can be improved and the friction coefficient μ can be reduced, and by adding tungsten to the DLC film, It was found that the adhesion can be further improved and the friction coefficient μ can be further reduced.

Rolling test:
As shown in FIG. 6, the substrate 90 of each of the above embodiments is immersed in a container C filled with spindle oil (6.6 mm 2 / s) L as a lubricating oil with the surface on which the DLC film 91 is formed facing up. Then, on the DLC film 91, 3/8 ″ SUJ2 balls B (11 pieces) constituting the thrust ball bearing, the cage R and the inner ring IR were assembled, and the rotating shaft S was attached to the inner ring IR. As shown by the white arrow in the figure, while rotating the SUJ2 ball B against the surface of the DLC film 91 with a constant contact surface pressure, the rotation axis S is rotated at a rotation speed of 1200 times per minute to a maximum of 108 rotations. The test for determining the number of rotations until the DLC film 91 reaches the end of its life was repeated for several different contact surface pressures, and the results are shown in Fig. 7. The DLC film of Example 3 has 108 rotations. Even if it is rotated to the end, it will not reach the end of its life. Although the results could not be described, it was confirmed that the lifetime was long, and when Examples 1 and 2 were compared, the lifetime of the DLC film was obtained by laminating the DLC film on the silicon film formed on the base. It was found that can be improved.

DESCRIPTION OF SYMBOLS 1 ... Drive shaft, 2 ... Male spline shaft, 3 ... Female spline shaft, 21a, 31a ... Contact surface (power transmission surface), 6 ... DLC film

Claims (2)

It has a male spline shaft (2) and a female spline shaft (3),
The male spline shaft (2) is integrally formed of metal as a whole, and the outer surface of the male spline shaft (2) connected to the female spline shaft (3) has a radial direction from the outer peripheral surface. A large number of keys (21) project outwardly to form a male spline part (22),
The female spline shaft (3) is integrally formed of metal as a whole, and the end of the female spline shaft (3) connected to the male spline shaft (2) is an end on the male spline shaft (2) side. An opening (30) is formed in the tube, and the male spline portion (22) is inserted into the inside through the opening (30). A large number of key grooves (31) meshed with the key (21) of the male spline part (22) are recessed toward the outside in the direction to form a female spline part (32),
Both side surfaces of each key (21) constituting the male spline portion (22) and both side surfaces of each key groove (31) constituting the female spline portion (32) are contact surfaces as power transmission surfaces ( 21a) (31a)
The male spline shaft (2) and the female spline shaft (3) are engaged with the key (21) and the key groove (31) and slide in the contact surfaces (21a) (31a) in the axial direction. A drive shaft (1) that can be expanded and contracted in the axial direction in a state in which it can be contacted, and is connected so as to be able to transmit power in a rotational direction around the shaft,
Adjacent to the contact surface (21a), the top surface (21b), and the outer peripheral surface of the male spline shaft (2), which are both side surfaces of each key (21) constituting the male spline portion (22). The bottom surface (21c) between the keys (21) is a continuous diamond-like carbon having a Vickers hardness Hv of 1000 or more, a friction coefficient μ of 0.25 or less, and at least a contact surface thickness of 1 to 5 μm. Covered with a membrane (6),
The contact surfaces (31a) that are both side surfaces of each key groove (31) constituting the female spline portion (32), the bottom surface (31b) of the key groove (31), and the adjacent key grooves (31) The top surface (31c) of the ridge (36) is not covered with the diamond-like carbon film (6) and the metal base is exposed, and the male spline portion (22) and the female spline portion (32 ) Is filled with grease,
The drive shaft characterized in that the male spline part (22) and the female spline part (32) are expanded and contracted in the axial direction at high speed while rotating at high speed.   The drive shaft according to claim 1, wherein the diamond-like carbon film (6) contains tungsten.

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