JP2006177498A - Sprocket - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sprocket for maintaining smooth operation without making lubricating oil exist thereon. <P>SOLUTION: The sprocket 11 has a plurality of teeth 12 applied around a chain 13. Over at least surfaces of the teeth 12, a DLC coating film 20 is formed which is composed of an amorphous structure mainly containing carbon. For the DLC coating film, only a metal target is sputtered on at least the surfaces of the teeth to form a bond layer to which a metal target and a graphite target are sputtered at the same time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to improvements in sprockets used in power transmission mechanisms of various machines including sprockets used in, for example, bicycles and motorcycles.

  Patent Document 1 discloses a structure in which noise countermeasures are taken for a roller chain that meshes with a sprocket and transmits power.

Patent Document 2 discloses a structure in which zinc-nickel alloy plating is applied to the surfaces of plates, pins, bushes, and rollers constituting a chain. The coating by zinc-nickel alloy plating has both rust prevention performance by zinc and a glossy appearance by nickel.
JP 59-106741 A Japanese Patent Application Laid-Open No. 07-127698

  However, with conventional sprockets, the sliding contact parts of the plates, pins, bushes, and rollers that make up the sprocket may wear out, so the intervention of lubricating oil is indispensable and frequent lubrication is required. There is a problem that the lubricating oil scatters to the surroundings to cause contamination.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a sprocket that can maintain a smooth operation without interposing lubricating oil.

  The present invention is applied to a sprocket having a plurality of teeth hung around a chain.

  A DLC coating film made of an amorphous structure mainly composed of carbon is formed on at least the tooth surface.

  According to the present invention, because of the structure in which the DLC coating film having a high hardness is formed on the surface of the sprocket teeth, the friction force acting on the sliding contact portion with the chain is reduced by the smooth DLC coating film having a low friction coefficient. The mechanical efficiency with which the chain transmits power can be increased, and the service life of the sprocket and chain can be extended. Furthermore, noise generated from the meshing part of the sprocket and the chain can be reduced.

  Further, since the sprocket and the chain can ensure smooth operability without supplying lubricating oil, the sprocket and the chain can be operated in an oil-free state. As a result, the sprocket can be used in a clean room, for example, by preventing the lubricating oil from scattering or generating dust from the lubricating oil.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, the sprocket 11 has a plurality of teeth 12 arranged at a predetermined pitch on the outer peripheral portion thereof, and transmits power through a chain 13 that is wound around each tooth 12. Yes. The sprocket 11 is formed of, for example, a stainless material, and is the gist of the present invention, but the DLC coating film 20 made of an amorphous structure mainly composed of carbon is formed on the surfaces of the teeth 12 of the sprocket 11. The thickness of the DLC coating film 20 is a dimension of about several μm or less, for example.

  The DLC coating film 20 is formed by an unbalanced magnetron sputtering method (hereinafter referred to as “UBM sputtering method”).

  As shown in FIG. 3, the principle of sputtering is that a plasma is formed by glow discharge between an anode and a target 41 in a vacuum into which an inert gas such as argon is introduced. The atoms of the target 41 are blown off by being collided with each other, and the atoms are deposited on the work (sprocket 11) 21 arranged to face the target 41 to form a film.

  In the UBM sputtering method, magnetic fields 42 and 43 having different magnetic characteristics in the central portion and the peripheral portion of the target 41 are arranged in the sputter evaporation sources 40a to 40d, and one of the lines of magnetic force generated by the strong magnetic field 42 while forming plasma. When the part reaches the vicinity of the workpiece 21 and a bias voltage is applied to the workpiece 21, the substance constituting the target material 41 is deposited on the workpiece 21.

  FIG. 4 shows a basic configuration of the UBM sputtering apparatus 50. Four sputter evaporation sources 40 a to 40 d are provided in the vacuum chamber 51, the work 21 is placed on a self-revolving work table 56 disposed at the center thereof, and the work 21 is coated. A flat target as a film material is attached to the sputter evaporation sources 40a to 40d. The vacuum chamber 51 is filled with a predetermined amount of an inert gas such as argon and a hydrocarbon gas such as methane gas.

  Sputter evaporation sources 40a and 40c use graphite as a target, and sputter evaporation sources 40b and 40d use metal as a target.

  As shown in FIG. 2, the DLC coating film 20 has a nickel plating layer 61 formed on the surface of the stainless steel workpiece 21, and a bond layer 62, an intermediate layer 63, and a top layer 64 are sequentially laminated on the surface of the nickel plating layer 61. Formed.

  FIG. 5 shows how the target output changes when the DLC coating film 20 is formed.

  The bond layer 62 is formed as a metal film by sputtering only the metal targets 40b and 40d. In forming the bond layer 62, as shown in FIG. 5, the metal target output of the sputter evaporation sources 40b and 40d is set to 100%, and the graphite target output of the sputter evaporation sources 40a and 40c is kept constant at 0%. Sputtering is performed for a predetermined time.

  The intermediate layer 63 is formed as a gradient composition film of metal and carbon by simultaneously sputtering the metal target of the sputter evaporation sources 40b and 40d and the graphite target of the sputter evaporation sources 40a and 40c, and gradually changing the target output. In forming the intermediate layer 63, as shown in FIG. 5, the metal target output of the sputter evaporation sources 40b and 40d is temporarily reduced from 100%, while the graphite target output of the sputter evaporation sources 40a and 40c is reduced to 0. Sputtering is performed for a predetermined time with a primary increase from%.

  The top layer 64 simultaneously sputters the metal target of the sputter evaporation sources 40b and 40d and the graphite target of the sputter evaporation sources 40a and 40c to make the target output substantially constant, and the sputter evaporation sources 40b and 40d and the sputter evaporation source 40a. , 40c, sputtering is performed for a predetermined time while keeping the sputtering rate of the graphite target within a predetermined range.

  In forming the top layer 64, as shown in FIG. 5, the metal target output of the sputter evaporation sources 40b and 40d is about 10%, and the graphite target output of the sputter evaporation sources 40a and 40c is kept constant at about 90%. The ratio of the metal contained in the top layer 64 is set in the range of 3 to 18%. More desirably, the ratio of the metal contained in the top layer 64 is set in the range of 3 to 12%.

  Next, the operation will be described.

  After forming the nickel plating layer 61 on the surface of the work 21 made of stainless steel, the bond strength of the DLC coating film 20 with respect to the base material can be increased by providing the bond layer 62 with a metal ratio of 100%.

  An intermediate layer 63 made of a gradient composition film of metal and carbon that gradually reduces the metal ratio is provided on the bond layer 62 having a metal ratio of 100%, and a top layer 64 mainly composed of carbon is formed on the intermediate layer 63. By providing, the bonding strength of the top layer 64 in the DLC coating film 20 can be increased.

  By setting the metal ratio of the top layer 64 in the range of 3 to 18%, the adhesion and toughness of the top layer 64 can be improved, and cracking or peeling occurs when the workpiece 21 is deformed by a high load. Can be prevented. And the fall of the hardness of the top layer 64 can be suppressed and abrasion resistance can be ensured.

  As shown in FIG. 6, the relationship between the ratio of the metal contained in the top layer 64 and the toughness and hardness increases the toughness and hardness of the top layer 64 by setting the metal ratio in the range of 3 to 18%. It is done. Furthermore, by setting the ratio of the metal contained in the top layer 64 within a range of 3 to 12%, both the toughness and hardness of the top layer 64 can be remarkably increased.

  On the other hand, conventionally, since the ratio of the metal contained in the top layer was 0%, there was a problem that adhesion and toughness were insufficient, and the top layer was likely to be cracked or peeled off.

  As a result, even if the DLC coating film 20 is formed on the surface of the workpiece 21 that receives a high load, the DLC coating film 20 is prevented from being cracked or peeled off, and can be put to practical use.

  Due to the structure in which the DLC coating film 20 having a high hardness is formed on the surface of the teeth 12 of the sprocket 11, the frictional force acting on the sliding contact portion with the chain 13 is reduced by the smooth DLC coating film 20 having a low friction coefficient. In addition, the mechanical efficiency with which the chain 13 transmits power can be increased, and the life of the sprocket 11 and the chain 13 can be extended. Furthermore, noise generated from the meshing portions of the sprocket 11 and the chain 13 can be reduced.

  Furthermore, since the sprocket 11 and the chain 13 can ensure smooth operability without supplying lubricating oil, the sprocket 11 and the chain 13 can be operated in an oil-free state. As a result, the sprocket 11 can be used in a clean room, for example, by preventing the lubricating oil from splashing or generating dust from the lubricating oil.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The present invention can be used for sprockets used for power transmission of various machines.

The side view of the sprocket which shows embodiment of this invention. Sectional drawing of a DLC coating film similarly. Explanatory drawing which similarly shows the principle of a sputtering method. The block diagram of a UBM sputtering device similarly. The characteristic view which shows a mode that a target output similarly changes. The characteristic view which shows the relationship between the ratio of the metal contained in a top layer, toughness, and hardness similarly.

Explanation of symbols

11 sprocket 12 teeth 13 chain 20 DLC coating film 21 work 40a to 40d sputter evaporation source 50 UBM sputtering device 61 plating layer 62 bond layer 63 intermediate layer 64 top layer

Claims (3)

In a sprocket having a plurality of teeth hung around a chain,
A sprocket characterized in that a DLC coating film made of an amorphous structure mainly composed of carbon is formed on at least the tooth surface.   The sprocket according to claim 1, wherein a nickel plating layer is formed at least on the surface of the teeth, and the DLC coating film is formed on the surface of the nickel plating layer.   The DLC coating film is formed by sputtering only a metal target on at least the surface of the teeth to form a bond layer, and simultaneously sputtering a metal target and a graphite target on the bond layer and gradually changing the target output. A top layer having a metal ratio in the range of 3 to 18% was formed by sputtering a metal target and a graphite target at the same time and making the target output substantially constant on the intermediate layer. The sprocket according to claim 1 or 2.

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