JP5623709B2 - Gear for power device and method for manufacturing gear for power device - Google Patents

Description

The present invention relates to a gear for a power unit that is used in a state where a surface of a gear that is incorporated in a power unit and transmits a driving force is covered with a hard carbon film, and a method for manufacturing the gear.

  A technology that increases the power transmission efficiency by reducing the frictional resistance of the tooth surface by applying a hard carbon film such as DLC (Diamond Like Carbon) to the tooth surface of the gear and combining it with a lubricant containing a specific component. It is known from Patent Document 1 below.

JP 2005-61610 A

  By the way, the gear incorporated in the power unit includes a tooth surface that transmits a driving force when the power device is accelerated and a tooth surface that transmits a driving force (braking force) when the power device is decelerated. Surface) and the frequency of the load are larger than those of the latter tooth surface (deceleration tooth surface). However, since the conventional one does not consider the thickness of the hard carbon film on the accelerating tooth surface and the deceleration tooth surface, the thickness of the hard carbon film on the accelerating tooth surface is large enough to satisfy the durability of the accelerating tooth surface. If set to, the thickness of the hard carbon film on the speed reduction tooth surface becomes excessive, and there is a problem that wasteful costs increase. In addition, if the thickness of the hard carbon coating on the deceleration tooth surface is set to a size that satisfies the durability of the deceleration tooth surface, the thickness of the hard carbon coating on the acceleration tooth surface is insufficient and the durability of the acceleration tooth surface is insufficient. There is a problem to do.

  The present invention has been made in view of the above circumstances, and a gear for a power device that achieves both cost and durability by specifying the thickness of the hard carbon coating on the accelerating tooth surface and the reducing tooth surface of the gear, and its An object of the present invention is to provide a method for manufacturing a gear.

In order to achieve the above object, according to the first aspect of the present invention, there is provided a gear for a power unit that is used in a state in which a surface of a gear that is incorporated in a power unit and transmits a driving force is coated with a hard carbon film. Thus, there is proposed a gear for a power device, wherein the thickness of the hard carbon film on the tooth surface to which a load is applied during acceleration of the power device is made larger than the thickness of the hard carbon film on the other tooth surfaces.

  According to a second aspect of the present invention, there is provided the method for manufacturing a gear for a power unit according to the first aspect, wherein the hard carbon film is formed by the PVD method while rotating the work machined into a gear shape. Therefore, a method of manufacturing a gear for a power unit is proposed in which the direction of rotation is the same as the direction in which the gear rotates when the power unit is accelerated.

  The acceleration tooth surface 11 of the embodiment corresponds to a tooth surface to which a load is applied during acceleration of the power unit of the present invention, and the speed reduction tooth surface 12 of the embodiment corresponds to another tooth surface of the present invention.

According to the first aspect, of the hard carbon film of the power unit gear that is used in a state where the surface is coated with a hard carbon film, the thickness of the hard carbon film of the tooth surface applied load during acceleration of the power unit The thickness of the hard carbon film on the other tooth surface is larger than the thickness of the hard carbon film on the other tooth surface. It is possible to prevent the thickness of the hard carbon film on the deceleration tooth surface subjected to a small load from becoming excessive, thereby contributing to cost reduction.

  According to the second aspect of the present invention, when the hard carbon film is formed by the PVD method while rotating the work machined into a gear shape, the direction of rotation is the same as the direction of rotation of the gear during acceleration of the power unit. Therefore, the hard carbon film of the accelerating tooth surface is adhered by attaching more particles on the acceleration tooth surface on the advance side in the rotation direction of the workpiece and less on the deceleration tooth surface on the delay side in the rotation direction of the workpiece. The thickness of the coating can be made larger than the thickness of the hard carbon coating on the speed reduction tooth surface.

The figure which shows thickness distribution of the hard carbon film of the acceleration tooth surface of a gearwheel, and a deceleration tooth surface. The figure which shows the structure of the film-forming apparatus of the hard carbon film by PVD method. The schematic diagram which shows the principle of the film-forming apparatus of a hard carbon film.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  The gear G of the present embodiment is a bevel gear disposed in a power transmission path that transmits the driving force of an automobile engine to driving wheels. As shown in FIG. , And a deceleration tooth surface 12 that transmits a driving force (braking force) when the vehicle is decelerated (during engine braking). The surface of the gear G is coated with a hard carbon film 13 containing DLC (Diamond Like Carbon). DLC is made of amorphous carbon or hydrogenated carbon and has high hardness and low coefficient of friction.

  In forming the DLC film, an underlayer such as Ti or Cr or a DLC intermediate layer doped with a metal element is usually interposed in order to improve adhesion to a gear made of molybdenum steel or the like. .

  The thickness of the hard carbon film 13 is different between the acceleration tooth surface 11 and the deceleration tooth surface 12, and the thickness of the hard carbon film 13 on the acceleration tooth surface 11 is larger than the thickness of the hard carbon film 13 on the deceleration tooth surface 12. It has become.

  Table 1 shows that the thickness of the hard carbon film 13 on the accelerating tooth surface 11 is larger than the thickness of the hard carbon film 13 on the decelerating tooth surface, and the gear G (three examples of A, B, and C) of the embodiment is reversed. The result of the endurance test performed on the gear G (3 examples of D, E, and F) of the comparative example in which the thickness of the hard carbon film 13 on the accelerating tooth surface 11 is smaller than the thickness of the hard carbon film 13 on the decelerating tooth surface. It is shown.

  The film thickness of the hard carbon film 13 is an average value of the film thicknesses of the tooth tip, tooth center and tooth root of the tooth surface of the gear G. In addition, the endurance test method is that the gear G is incorporated in the transmission of an automobile, and after running in a mode in which acceleration, deceleration and shifting are performed under certain conditions, the state of the hard carbon film 13 is visually observed, and wear is recognized. Those that did not show OK and those that showed wear were determined as NG. The test results of the three examples of the gears G of the embodiments A, B, and C were all OK, and the test results of the three examples of the gear G of the examples D, E, and F of the comparative example were all NG.

  As described above, the acceleration tooth surface 11 of the gear G may be subjected to a large load more frequently than the speed reduction tooth surface 12, but the durability can be increased by increasing the thickness of the hard carbon film 13 on the acceleration tooth surface 11. Can be increased. On the other hand, by reducing the thickness of the hard carbon film 13 of the deceleration tooth surface 12 which is advantageous in terms of durability compared to the acceleration tooth surface 11, it is possible to prevent the hard carbon film 13 of the deceleration tooth surface 12 from becoming unnecessarily thick. It is possible to contribute to down, and it is possible to achieve both the durability of the gear G and the cost reduction.

  Next, a method for manufacturing the gear G having the hard carbon film 13 will be described with reference to FIGS.

  As shown in FIG. 2, a UBMS (unbalanced magnetron sputtering system) 21 for forming a hard carbon film 13 on a base material of a gear G by a physical vapor synthesis method (PVD) includes a vacuum chamber 22. A work table 24 that can revolve clockwise around the revolving shaft 23 is arranged at the center. On the work table 24, six works W, which are the gears G before forming the hard carbon film 13, are arranged at equal intervals in the circumferential direction so as to surround the revolution shaft 23. W rotates about the rotation axis 25... In the same clockwise direction as the revolution direction. A flat target 27 serving as a material for the hard carbon film 13 is attached to four UBM sources 26 arranged at equal intervals on the peripheral wall of the vacuum chamber 22. A heater 29 is disposed on the peripheral wall of the vacuum chamber 22.

  In order to form the hard carbon film 13 on the surface of the work W ... set on the work table 24, first, the inside of the vacuum chamber 22 is depressurized to a high vacuum, and then the work W ... or the inside of the vacuum chamber 22 is degassed. For this purpose, preheating is performed by the heater 29. A negative bias voltage is applied to the workpiece W, and the generated Ar ions collide with the workpiece W. Thereby, in order to improve the adhesion of the hard carbon film 13, the surface of the workpiece W is etched and cleaned, and the temperature of the workpiece W is increased.

  Subsequently, when the glow discharge is started by supplying power to the UBM sources 26..., The generated Ar ions collide with the target 27, and the work exists in the position where the atoms / molecules of the target 27 blown off by the sputter evaporation phenomenon face each other. A hard carbon film 13 is deposited on the surface of W. At that time, by diffusing a part of Ar plasma that has converged on the surface of the target 27 to the workpieces W, the amount of sputtered particles irradiated on the workpieces W can be increased.

  In the process of forming the hard carbon film 13 on the surface of the workpiece W as described above, as shown in FIG. 3, the workpiece W rotates in the clockwise direction, so that the workpiece W is positioned on the advance side in the rotation direction. The probability that the sputtered particles collide with the accelerating tooth surface 11 is higher than the probability that the sputtered particles collide with the decelerating tooth surface 12 positioned on the delay side in the rotation direction. As a result, the thickness of the hard carbon film 13 on the acceleration tooth surface 11 can be made larger than the thickness of the hard carbon film 13 on the deceleration tooth surface 12.

  As described above, according to the present embodiment, the acceleration tooth surface 11 of the gear G can be formed by a simple method of depositing sputter particles while forming the hard carbon film 13 while rotating the workpiece W of the gear G. The thickness of the hard carbon film 13 can be made larger than the thickness of the speed reduction tooth surface 12.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

  For example, although an automobile is shown as a power unit in the embodiment, the present invention can be applied to any other power unit.

  The gear G of the embodiment is a bevel gear, but may be any other type of gear.

  In the embodiment. A sputtering method is employed as the physical vapor synthesis method (PVD), but an arc ion plating method can also be employed.

11 Accelerated tooth surface (tooth surface to which load is applied when the power unit is accelerated)
12 Deceleration tooth surface (other tooth surfaces)
13 Hard carbon coating G Gear W Work

Claims (2)

A gear for a power unit that is used in a state where a surface of a gear (G) that is incorporated in a power unit and transmits a driving force is coated with a hard carbon film (13),
The thickness of the hard carbon film (13) on the tooth surface (11) to which a load is applied during acceleration of the power unit is greater than the thickness of the hard carbon film (13) on the other tooth surface (12). Gear for power equipment. It is a manufacturing method of the gear for power units according to claim 1,
The hard carbon film (13) is formed by the PVD method while rotating the workpiece (W) processed into a gear shape, and the direction of the rotation is the direction in which the gear (G) rotates during acceleration of the power unit. The manufacturing method of the gear for power devices characterized by making it the same.

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