JP2004076756A - Sliding bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sliding bearing having suppressed seizure, wear and corrosion in long-time use under the circumstances of high speed oscillation, high load and high temperature. <P>SOLUTION: The sliding bearings 5, 6 are mounted between each of shaft members of a crank shaft 1 and a piston pin 4 and each of cylindrical members of a large end portion 2a and a small end portion 2b of a connecting rod 2 externally fitted thereto in a peripherally displaceable manner, A W-DLC layer 3 is provided on a surface where sliding contact occurs. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a slide bearing used for a sliding portion such as a crankshaft and a connecting rod.
[0002]
[Prior art]
In general, a slide bearing is interposed between a crankshaft of an engine and a crank-side end (large end) of a connecting rod which is swingably fitted to the crankshaft. In such a sliding bearing, only a conforming layer for preventing initial wear is provided on the surface of a sliding bearing body made of metal.
[0003]
[Problems to be solved by the invention]
In the case of the installation location as described above, since the environment becomes a high-speed swing, a high load, and a high temperature, the conformable layer is likely to disappear at an early stage, and its life may be shortened.
[0004]
An object of the present invention is to solve the problem of extending the life of a plain bearing even if it is installed in such a location.
[0005]
[Means for Solving the Problems]
The present invention relates to a copper-based material which is interposed between a relatively displaceable shaft member and an outer member coaxially extrapolated to the shaft member, wherein at least a surface layer of the slide bearing body has lubricity. Alternatively, the sliding bearing is made of an aluminum-based soft metal and has a DLC layer formed on the soft metal sliding on at least one of the two members, wherein the DLC layer contains tungsten, and the soft metal surface And a DLC layer, wherein a two-layer structure including a Ni-based alloy layer on the slide bearing body side and a Cr layer on the DLC layer side is provided as an intermediate layer for improving adhesion.
[0006]
The shaft member includes a crankshaft and a piston pin in an internal combustion engine such as an engine, and the outer member includes a large end portion and a small end portion of a connecting rod. However, the present invention is not limited to this, and is applied to all of the shaft-like members and the outer members having the above relationship.
[0007]
According to the present invention, since the DLC layer having low friction and excellent seizure resistance, abrasion resistance, and corrosion resistance is provided on the surface where the sliding contact occurs, the crankshaft of the engine and the swingable with respect to the crankshaft are provided. Like a sliding bearing interposed between the connecting rod on the crank side (large end) and the piston end (small end) of the connecting rod and the piston pin. In the case of a sliding bearing that is applied in an oscillating, high-load, high-temperature environment, it is possible to achieve a particularly long life. Further, since the surface layer of the bearing body is made of a copper-based or aluminum-based alloy having lubricity, the life can be extended even after the DLC layer has disappeared due to wear or the like.
[0008]
In the above, when the DLC layer is provided on a metal surface, there is a problem that the adhesion is not sufficient under severe use conditions such as high load or high speed rotation, and the DLC layer peels off early. However, in the present invention, since the metal element tungsten is contained in the DLC layer, the adhesion to the metal surface is improved, and the durability of the plain bearing is improved.
[0009]
Further, when a DLC layer is provided on a soft metal represented by a copper-based or aluminum-based metal, there is a problem that the DLC layer, which is a hard film, cannot follow the deformation of the soft metal due to a contact load and peels off. Was. However, in the present invention, the hardness of the Ni-based metal layer and the Cr layer provided as the intermediate layer is intermediate between the hardness of the soft metal and the hardness of the DLC layer. Further, since the Ni-based alloy and the copper-based or aluminum-based metal, the Ni-based alloy and the Cr, and the Cr and the DLC layer are easily compatible with each other, the adhesion between the sliding bearing body and the DLC layer is improved as a result.
[0010]
Preferably, the thickness of the Ni-based alloy layer is set to 1 to 20 μm, and the thickness of the Cr layer is set to 0.4 to 0.6 μm. Here, when the Ni-based alloy layer and the Cr layer are less than the respective specified thicknesses, the effects of relaxation to deformation and conformity are lost, and when the thickness is more than the specified thicknesses, the effects are saturated and the processing (coating) cost is reduced. Expensive.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The details of the present invention will be described based on an embodiment shown in the drawings.
[0012]
1 and 2 show this embodiment. FIG. 1 is an exploded perspective view of an essential part of an engine to which the slide bearing of the present embodiment is applied, and FIG. 2 is an enlarged sectional view of special coatings 5b and 6b of the slide bearing of FIG.
[0013]
In FIG. 1, 1 is a crankshaft, 2 is a connecting rod, 3 is a piston, 4 is a piston pin, and 5 and 6 are plain bearings. The two-part large end 2a of the connecting rod 2 is fixed to the crankshaft 1 with bolts and nuts, and the small end 2b is connected to the piston 3 by a piston pin 4.
[0014]
One of the sliding bearings 5 has a structure divided into two in a semicircular arc shape, is interposed between the crankshaft 1 and the large end 2a of the connecting rod 2, and the other sliding bearing 6 has a cylindrical structure. And is interposed between the small end 2b of the connecting rod 2 and the piston pin.
[0015]
The sliding bearings 5 and 6 are configured by forming special coatings 5b and 6b on the surfaces of the sliding bearing bodies 5a and 6a, respectively.
[0016]
The special coatings 5b and 6b will be described with reference to FIG.
[0017]
The sliding bearing bodies 5a and 6a are configured by bonding a copper-based, aluminum-based, or copper-aluminum-based alloy layer to the surface of a back metal made of mild steel, structural steel, or the like.
[0018]
The special coatings 5b and 6b include a nickel (Ni) alloy layer b1, a chromium (Cr) layer b2, and a diamond-like carbon layer b3 containing tungsten as intermediate layers from the surfaces of the sliding bearing bodies 5a and 6a upward. Including. For convenience of explanation, a diamond-like carbon layer containing tungsten is referred to as a W-DLC layer, and a diamond-like carbon layer containing no tungsten is referred to as a DLC layer.
[0019]
The Ni alloy layer b1 and the Cr layer b2 are for improving the adhesion between the plain bearing bodies 5a, 6a and the W-DLC layer b3. The W-DLC layer b3 is set to have a composition in which the amount of tungsten is increased toward the Cr layer b2. As a result, the amount of carbon is increased toward the surface. The special coatings 5b and 6b can be formed by a plating method, a physical vapor deposition (PVD) method, a chemical vapor deposition (CVD) method, a plasma CVD method, an ion beam forming method, an ionization vapor deposition method, or the like. At this time, the Ni alloy layer b1, the Cr layer b2, and the W-DLC layer b3 are sequentially formed in this order.
[0020]
Here, a method of forming the Ni alloy layer b1 by the plating method and the Cr layer b2 and the W-DLC layer b3 by the sputtering method, which is an example of the PVD method, will be described.
[0021]
First, when the Ni alloy layer b1 is generated by plating, the slide bearing bodies 5a and 6a are subjected to organic solvent cleaning, acid treatment, and electrolytic cleaning, and then a nickel layer of about submicron is formed by electrolytic nickel plating. Then, it is immersed in a nickel plating bath to perform electroless plating. As a result, the Ni alloy layer b1 is formed with a thickness of 1 to 20 μm, more preferably 1 to 5 μm on the sliding surface 10 of the sliding bearing bodies 5a and 6a.
[0022]
Next, when generating the Cr layer b2 by the sputtering method, Cr is used as a target, and Ar gas is used as an introduction gas. Then, the discharge process is performed by setting the pressure in the chamber at about 10-3 to 10 [Torr], the discharge voltage at 100 to 500 [V], and the current at 0.5 to 5 [A]. Thereby, the Cr layer is formed on the sliding contact surface 10 of the sliding bearing bodies 5a, 6a with a thickness of 0.4 to 0.6 μm.
[0023]
Next, in forming the W-DLC layer b3 on the Cr layer b2, tungsten carbide (WC) or tungsten (W) is used as a target, and Ar gas and hydrocarbon gas are used as an introduction gas. Then, the pressure in the chamber is set to about 10-3 to 10 [Torr], and the discharge process is performed. During the film formation, the amount of carbon (C) is increased by increasing the amount of hydrocarbon gas or shielding the target by a shutter.
[0024]
By the way, the special coatings 5b and 6b have, for example, a W-DLC layer b3 of 1.0 μm or more, a hardness of 1000 to 2000 in Vickers hardness (Hv), and a roughness of the outermost surface of Ra (center line average roughness) is controlled to 0.1 μm or less. However, when the special coatings 5b and 6b are partially formed on the target component, masking may be appropriately performed.
[0025]
In the sliding bearings 5 and 6 described above, the inner and outer sliding contact surfaces are covered with the special coatings 5b and 6b composed of the Ni alloy layer b1, the Cr layer b2, and the W-DLC layer b3. Due to the strong connection therebetween, the W-DLC layer b3 can be firmly adhered and coated on the sliding contact surfaces of the sliding bearing bodies 5a, 6a. Therefore, even if there is no lubricating component between the sliding bearings 5 and 6 and the mating member that makes sliding contact, the sliding bearings 5 and 6 maintain good sliding contact and are stable for a long period of time, and the W-DLC layer b3 peels off. This makes it possible to greatly contribute to the improvement of reliability, for example, the durability is improved.
[0026]
Further, since the surface layer of the sliding bearing body is made of a lubricating copper-based or aluminum-based metal, the life can be extended even after the DLC layer has disappeared due to abrasion or the like.
[0027]
Meanwhile, the above-mentioned special coatings 5b and 6b can have a structure as shown in FIG. The special coatings 5b and 6b are formed from the surfaces of the sliding bearing bodies 5a and 6a upward, from an intermediate layer composed of a Ni alloy layer b1 and a Cr layer b2, a tungsten carbide (WC) layer b4 and a DLC layer b3. ' Note that in FIG. 3, a required number of WC layers b4 and DLC layers b3 'are alternately stacked on the DLC layer b3' to form a hierarchical structure. Moreover, in this embodiment, as exaggeratedly shown in FIG. 3, the thickness of each WC layer b4 is set to be gradually smaller from the metal base material side to the outermost surface side. The thickness of each DLC layer b3 'is set to be gradually larger from the metal base material side to the outermost surface side.
[0028]
Here, a method of forming the special coatings 5b and 6b by a sputtering method, which is an example of the PVD method, will be mainly described with reference to FIG. Here, since the step of forming the intermediate layer has been described above, the description is omitted.
[0029]
In forming the WC layer b4, tungsten carbide (WC) or tungsten (W) is used as a target, and Ar gas is used as an introduction gas. Then, the discharge process is performed by setting the pressure in the chamber at about 10 −3 to 10 [Torr], the discharge voltage at 200 to 700 [V], and the current at 2 to 10 [A]. Thus, a WC layer b4 made of amorphous carbon is formed on the Cr layer.
[0030]
Next, in generating the DLC layer b3 ', a discharge treatment is performed at a discharge voltage of 200 to 700 [V] and a current of 2 to 10 [A] using Ar gas, hydrocarbon gas, or the like as an introduced gas. As a result, the DLC layer b3 'is laminated on the WC layer b4.
[0031]
Thereafter, as shown in FIG. 3, a required number of WC layers b4 and DLC layers b3 'are alternately stacked on the DLC layer b3' to form a hierarchical structure. At this time, the thickness of the WC layer b4 is set to be gradually thinner from the sliding bearing bodies 5a and 6a to the outermost surface side, and the thickness of each DLC layer b3 'is set to be the smallest from the sliding bearing bodies 5a and 6a. The thickness is gradually increased toward the surface. Each of these layers is not formed at the boundary surface, but is diffused and bonded at the atomic level.
[0032]
Even with the special coatings 5b and 6b described above, the adhesion to the sliding contact surface 10 is improved similarly to the special coatings 5b and 6b shown in FIG. 2 described above, and the wear resistance and the like of the DLC layer b3 ', which is the uppermost layer, are improved. It will be demonstrated over the long term. Therefore, as the sliding bearings 7 and 8, the DLC layer b3 'is hardly peeled off, and the durability is improved. For example, it is possible to greatly contribute to the improvement of reliability.
[0033]
In the W-DLC layer b3 and the DLC layer b3 ', the graphite structure (SP2) and the diamond structure (bonding: SP3) coexist, and the bonding force between the carbon atoms constituting them is strong. Abrasion and damage are less likely to occur, and at the same time, since it is hard and has excellent surface smoothness, the sliding contact operation becomes extremely smooth and abrasion hardly occurs.
[0034]
Further, if necessary, a lubricating oil or grease made of a fluoropolymer such as perfluoropolyether (PFPE) may be applied or sealed inside the sliding bearing. In this case, since the W-DLC layer b3 and the DLC layer b3 'have extremely good wettability of the fluorine-based lubricant applied to the inside of the slide bearing, the W-DLC layer b3 and the DLC layer b3' have the same surface. The lubricating oil layer is less likely to break. Even if the lubricating oil layer is interrupted, the W-DLC layer b3 and DLC layer b3 'can prevent direct contact between the sliding bearing body and the mating member.
[0035]
The present invention is not limited to the above embodiment, and the following modifications are possible.
[0036]
(1) The intermediate layer may be omitted, may be a single layer, or may be three or more layers.
[0037]
(2) Only the DLC layer b3 'containing no tungsten may be provided on the surfaces of the sliding bearing bodies 5a and 6a.
[0038]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, even if it installs under severe environment of high-speed rocking | fluctuation, a high load, and high temperature, the long life can be achieved.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of an engine, a crankshaft, and a connecting rod to which a sliding bearing of the present embodiment is applied. FIG. 2 is a partially enlarged cross-sectional view of a special coating of the sliding bearing of FIG. 1 FIG. Partial enlarged cross-sectional view showing deformation of coating film [Description of reference numerals]
DESCRIPTION OF SYMBOLS 1 Crankshaft 2 Connecting rod 3 Piston 4 Piston pin 5, 6 Sliding bearing 5a, 6a Sliding bearing body 5b, 6b Special coating b1 Ni layer b2 Cr layer b3 W-DLC layer b3 'DLC layer

Claims (2)

A copper-based or aluminum-based soft material that is interposed between a relatively displaceable shaft member and an outer member that is coaxially externally inserted with respect to the shaft member, and at least a surface layer of the slide bearing body has lubricity. A plain bearing comprising a metal and a DLC layer formed on the soft metal sliding on at least one of the two members,
The DLC layer contains tungsten, and comprises an Ni-based alloy layer on the slide bearing body side and a Cr layer on the DLC layer side as an intermediate layer for improving adhesion between the soft metal surface and the DLC layer. A plain bearing having a layer structure. The plain bearing according to claim 1,
A sliding bearing, wherein the thickness of the Ni-based alloy layer is set to 1 to 20 μm, and the thickness of the Cr layer is set to 0.4 to 0.6 μm.

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