JP5045566B2 - Hard thin coat bearing structure - Google Patents

Description

  The present invention relates to a hard thin film coated bearing structure including a shaft and a bearing.

Many of the bearing structures (slide bearing structures) used in various machines are such that an alloy shaft is received by an alloy bearing (bearing metal) (see, for example, Patent Documents 1 and 2). However, a bearing structure for a hydraulic machine including a ceramic bearing (for example, see Patent Document 3) is also known. The shaft surface or bearing surface is coated with a hard thin film such as a DLC (Diamond-like Carbon) thin film, and oil (lubricating oil) is supplied directly between the shaft surface and the bearing surface in the shaft or bearing. There is also known a bearing structure in which a passage is formed.

Japanese Patent Laid-Open No. 08-159142 JP 2002-266848 A Japanese Utility Model Publication No. 5-27340

  The above-described bearing structure in which the shaft surface or bearing surface is coated with a hard thin film and oil is supplied directly between the shaft surface and the bearing surface (hereinafter referred to as a conventional bearing structure) has good wear resistance, etc. Has advantages. However, as a result of intensive research, the inventor suddenly deteriorated in performance because the conventional bearing structure has a substantially constant bearing spacing (details will be described later). It was found that the friction coefficient may increase).

  Accordingly, an object of the present invention is to provide a hard thin film coated bearing structure in which the shaft surface or the bearing surface is coated with a hard thin film, and oil is directly supplied between the shaft surface and the bearing surface, and the above phenomenon is unlikely to occur. Is to provide.

  In order to solve the above problems, the hard thin film coated bearing structure of the present invention has a hard thin film formed on at least one of the shaft surface and the bearing surface of the shaft, and the shaft or the bearing An oil supply passage having an oil outlet on the shaft surface or the bearing surface is formed, and the shaft surface of the shaft and / or the bearing surface of the bearing is at an arbitrary position in the circumferential direction of the shaft. It has the structure processed into the shape where the bearing clearance gap of the location where the distance of the axial center direction (direction parallel to an axial center) of the said axis | shaft from an exit is separated becomes wider.

  That is, in order to develop a high-performance hard thin film coated bearing structure, the present inventor “a structure in which a shaft surface or a bearing surface is coated with a hard thin film, and oil is directly supplied between the shaft surface and the bearing surface. As a result of diligent research, the inventors have found that the performance of the conventional bearing structure having such a configuration and having substantially the same bearing clearance at each position may deteriorate. It has also been found that such a phenomenon occurs as a result of peeling of a part of the hard thin film on the shaft surface / bearing surface (and as a result of acceleration of damage to the sliding surface by the peeled hard substance). It was.

Here, peeling of the hard thin film generally occurs when a high surface pressure is locally applied, or in a conventional bearing structure, a part that can cause a high surface pressure to be applied to a part of the hard thin film. Considering that it is fine particles such as metal powder supplied between the sliding surfaces together with the oil, if the conventional bearing structure is improved so that the fine particles are discharged from between the sliding surfaces in a short time, “suddenly Thus, it is possible to realize a hard thin film coated bearing structure in which a phenomenon such as “deteriorating performance” hardly occurs. And “the shaft surface of the shaft and / or the bearing surface of the bearing is located at a position where the axial distance of the shaft from the oil outlet is further away at an arbitrary position in the circumferential direction of the shaft. By adopting a configuration in which the gap is processed into a wider shape, the fine particles supplied between the sliding surfaces are positively affected by the negative pressure effect caused by oil spill and the effect of expanding the bearing gap. Since it was conceived that it can be discharged to the outside, the hard thin film coated bearing structure having the above configuration has been invented.

  It should be noted that the oil supply passage formed in the shaft or in the bearing of the hard thin film coated bearing structure of the present invention has a shaft surface / bearing surface even if it has an oil outlet having a shape that goes around the shaft surface / bearing surface. It may have a plurality of oil outlets. Further, the hard thin film formed on the shaft surface of the shaft and / or on the bearing surface of the bearing may be a thin film made of a material harder than the shaft material / bearing material. A thin film such as titanium nitride, chromium nitride, or silicon carbide is desirable.

  Further, when realizing the hard thin film coated bearing structure of the present invention, the bearing interval at a location where the axial distance of the shaft from the oil outlet is within a predetermined range is set to a constant value. You can also leave. However, if the width of the portion where the bearing interval is a constant value (the length of the shaft in the axial direction) is excessively wide, the occurrence probability of the above phenomenon cannot be sufficiently reduced. For this reason, the width of the part is desirably 60% or less of the width of the sliding part, which can sufficiently reduce the probability of occurrence of the above phenomenon.

  Further, the hard thin film coated bearing structure of the present invention has a structure in which “the shaft is a member having a bearing surface for eccentrically supporting the second shaft, and the oil supply passage has an oil inlet on the bearing surface. The second shaft is a member in which a second oil supply path having a second oil outlet at a position corresponding to the position of the oil inlet is formed, and the second shaft A hard thin film is formed on at least one of the shaft surface and the bearing surface of the shaft, and the shaft surface of the second shaft and / or the bearing surface of the shaft are arranged in the circumferential direction of the second shaft. It is also realized that the arbitrary position is processed into a shape in which the bearing gap at the location where the distance in the axial direction of the second shaft from the second oil outlet is further away becomes wider. I can do it.

  In addition, the hard thin film coat bearing structure of the present invention realized in such a form is used for the control (change) of the relative position between two members, and the hard thin film coat on which the hard thin film on each sliding surface does not easily peel off. It will function as a bearing structure. Therefore, if this hard thin film coated bearing structure is used as a component of a machine that needs to control the relative position between the two members (such as a variable compression ratio engine in which the cylinder block moves in the crankcase), it will last for a long time. It will be possible to manufacture a machine that operates stably across the board.

  According to the present invention, it is possible to provide a hard thin film coated bearing structure in which the phenomenon that performance is suddenly deteriorated is less likely to occur.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  First, an outline (basic configuration) of a variable compression ratio engine 20 using a hard thin film coat bearing structure according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, the variable compression ratio engine 20 holds a cylinder block 21 having a plurality of cylinders, and the cylinder block 21 so as to be movable in the axial direction of the cylinder (hereinafter referred to as the vertical direction). The engine includes a crankcase 22, a motor 41, two eccentric shaft assemblies 30, a plurality of free shaft housings 23, two eccentric shaft covers 25, and the like.

  Each eccentric shaft assembly 30 provided in the variable compression ratio engine 20 is a member in which a worm wheel 32, a plurality of free shafts 33, and a plurality of journals 34 are attached to a shaft portion 31, as shown in FIG. In FIG. 2, only one eccentric shaft assembly 30 is shown. However, the other eccentric shaft assembly 30 is configured such that the illustrated eccentric shaft assembly 30 passes through the axis of each cylinder of the cylinder block 21. It has an inverted configuration.

  The free shaft 33 is a columnar member formed in a state where a through hole having a shape through which a shaft portion 31 (a portion other than a mounting portion 31a described later) passes is eccentric. Although details of the free shaft 33 will be described later, the free shaft 33 has a central portion (a portion equidistant from both end surfaces / both bottom surfaces) and an oil supply hole communicating with the thickness direction at every predetermined angle (circumferential direction). (Equally spaced). Furthermore, the free shaft 33 is also a member in which a concave portion having a shape that connects each oil supply hole (a shape that goes around the inner surface of the free shaft 33) is formed on the inner surface thereof.

  The journal 34 is also a columnar member that is formed in a state in which a through hole having a shape through which the shaft portion 31 passes is eccentric. The journal 34 is also a member in which the same oil supply holes and recesses as the free shaft 33 are formed. In addition, although mentioned later for details, each oil supply hole formed in the free shaft 33 / journal 34 is a hole into which oil (lubricating oil) enters from the concave portion side and from which the oil comes out from the outer surface side. For this reason, below, the part of the outer surface side of each oil supply hole formed in the free shaft 33 / journal 34 is also referred to as an oil outlet.

  The shaft portion 31 is a columnar member having a columnar portion (hereinafter referred to as a mounting portion 31 a) having the same outer diameter as that of the journal 34 at the center thereof. The mounting portion 31a provided on the shaft portion 31 has its center position equal to the eccentric amount of the journal 34 (the distance between the center of the journal 34 and the center of the through hole provided in the journal 34). Has a shape shifted from the center position of the shaft portion 31.

  Further, the shaft portion 31 has an oil outlet at an attachment portion 31a and a mounting portion of the free shaft 33 / journal 34 (a portion facing the concave portion of the free shaft 33 / journal 34) inside the shaft portion 31, and an end surface of the shaft portion 31. This is a member in which an oil supply path having an oil inlet is formed.

  In the eccentric shaft assembly 30, the worm wheel 32 is fixed to the mounting portion 31 a of the shaft portion 31, each journal 34 is fixed to the shaft portion 31 in the same posture as the mounting portion 31 a, and each free shaft 33 is fixed to the shaft portion 31. It is attached so that it can rotate.

  The free shaft housing 23 (FIG. 1) provided in the variable compression ratio engine 20 is a member for fixing the free shaft 33 of the eccentric shaft assembly 30 to the cylinder block 21 in a rotatable manner. The free shaft housing 23 includes a through hole having a shape (details will be described later) through which the free shaft 33 of the eccentric shaft assembly 30 passes with a predetermined clearance. The free shaft housing 23 is attached to the free shaft 33 portion of the eccentric shaft assembly 30 and then passes through the openings provided in the longitudinal side surfaces of the crankcase 22 (different from the shape shown in the figure). In the form of a member fixed to the cylinder block 21.

The crankcase 22 of the variable compression ratio engine 20 has a portion (main bearing in the figure) that functions as a bearing for each journal 34 and mounting portion 31a of the eccentric shaft assembly 30 by attaching the eccentric shaft cover 25. Is provided. Further, a drive shaft provided with a worm 42 (see FIGS. 1 and 2) is rotatably held in a lower portion of the crankcase 22 at a position where it engages with the worm wheel 32 of each eccentric shaft assembly 30. The two worms 42 provided in the drive shaft are formed with opposite screws.

  The variable compression ratio engine 20 is an engine configured such that oil (lubricating oil) from an oil pump (not shown) is supplied to the end portion of each shaft portion 31. In other words, in the variable compression ratio engine 20, the oil from the oil pump passes between the free shaft 33 and the shaft portion 31 (free shaft 33 and the free shaft 33) through each shaft portion 31 or through the supply hole of each free shaft 33. A portion where the shaft portion 31 slides), between the free shaft 33 and the free shaft housing 23, and the like.

  Based on the above, the configuration of each bearing structure (the hard thin film coated bearing structure according to the present embodiment) provided in the variable compression ratio engine 20 will be described in more detail below.

  The bearing structure (bearing structure including the free shaft 33 and the free shaft housing 23) provided at various locations of the variable compression ratio engine 20 is “at least one of the shaft surface of the shaft and the bearing surface of the bearing. A hard thin film is formed in the shaft or the bearing, and an oil supply passage having an oil outlet on the shaft surface or the bearing surface is formed in the shaft or the bearing. The bearing surface of the bearing clearance (space between the shaft surface and the bearing surface) at a position where the axial distance of the shaft from the oil outlet is further away at an arbitrary position in the circumferential direction of the shaft. It is processed into a shape that becomes wider.

  Specifically, as already described, an oil supply path having an oil outlet on the shaft surface is formed in the shaft portion 31 of the eccentric shaft assembly 30. The shaft surface (surface, On the outer surface, a DLC thin film is formed as schematically shown in FIG.

  On the other hand, as shown in the figure, the free shaft 33 that also functions as a bearing for the shaft portion 31 has a bearing surface (inner surface) having a bearing clearance at the center portion (portion where the oil outlet of the shaft portion 31 exists). Is the member that has been processed into a shape in which the bearing gap at the location farthest from the central portion is wider.

  Furthermore, the shaft surface (outer surface) of the free shaft 33 is in the axial direction of the free shaft 33 from the oil outlet of the free shaft 33 (the outer surface side portion of the oil supply hole formed in the free shaft 33). It is processed into a shape in which the bearing gap at a location farther away is wider. And the free axis | shaft 33 is a member which formed the DLC thin film on the axial surface processed in that way.

  In addition, although illustration is abbreviate | omitted, the free axis | shaft 33 is a member by which the bearing surface and the shaft surface were processed so that the said conditions may be satisfy | filled about the arbitrary positions of the circumferential direction. Further, the journal 34 of the eccentric shaft assembly 30 is also a member in which the axial surface is processed into the same shape as the axial surface of the free shaft 33 and a DLC thin film is formed on the processed axial surface.

  As described above, the hard thin film coated bearing structure (each bearing structure provided in the variable compression ratio engine 20) according to the present embodiment has an oil outlet (oil supply between the sliding surfaces) provided on the sliding surfaces. As the distance from the mouth increases, the bearing spacing is increased. Therefore, in the hard thin film coated bearing structure according to the present embodiment, the fine particles supplied together with the oil (lubricating oil) between the sliding surfaces cause the negative pressure effect due to the oil flowing out of the hard thin film coated bearing structure and the bearing gap. Due to the effect of expansion, it will be actively discharged to the outside. As a result, the hard thin film coated bearing structure according to the present embodiment suddenly deteriorates in performance compared to the bearing structure in which the bearing spacing is not particularly devised (the friction coefficient between the shaft and the bearing increases). It will function as something that is unlikely to occur.

  Actually, from the experimental results of various variable compression ratio engines 20 incorporating free shafts 33 and journals 34 having various surface shapes, if the difference between the bearing spacing at the oil outlet and the bearing spacing at the end is about 5 μm, It has been found that the probability of occurrence of the above phenomenon can be sufficiently reduced. Also, if the difference between the bearing spacing at the oil outlet and the bearing spacing at the end is about 5 μm, the probability of occurrence of the above phenomenon can be lowered even if the bearing spacing at the center portion of the hard thin film coated bearing structure is set to a constant value. It has also been confirmed that it can be done. However, it has also been found that if the width (length in the axial direction) of the portion where the bearing interval is a constant value is excessively increased, the occurrence probability of the above phenomenon cannot be lowered sufficiently. For this reason, when realizing (manufacturing) a hard thin film coated bearing structure having a portion with a constant bearing interval, the length of the portion can sufficiently reduce the probability of occurrence of the above phenomenon. It has been confirmed that it should be 60% or less of the width of the sliding portion.

  The variable compression ratio engine 20 from which the above experimental results were obtained has the minimum width of the free shaft 33 (the length in the left-right direction in FIG. 3), the width of the free shaft housing 23, and the bearing spacing of each hard thin film coated bearing structure. The values (bearing intervals in the portion where the oil outlet is present) are fixed to 40 mm, 38 mm, and 7.5 μm, respectively (only the surface shape of the free shaft 33 etc. is changed).

<Deformation>
The hard thin film coat bearing structure described above can be variously modified. For example, the hard thin film coated bearing structure can be transformed into a structure in which a hard thin film (thin film such as titanium nitride, chromium nitride, or silicon carbide) different from the DLC thin film is formed on the shaft surface. Also, the hard thin film coated bearing structure is deformed into one having a hard thin film formed on the bearing surface instead of on the shaft surface, or one having a hard thin film formed on both the shaft surface and the bearing surface. I can do it.

  The hard thin film coated bearing structure can be deformed into one in which the shape of the bearing surface is processed, or one in which the shape of the bearing surface and the shape of the shaft surface are processed. Of course, the hard thin film coated bearing structure described above may be used for a normal engine or may be used for a machine other than an engine.

1 is an exploded view of a variable compression ratio engine in which a hard thin film coated bearing structure according to an embodiment of the present invention is used. It is a principal part block diagram of a variable compression ratio engine. It is a block diagram of the hard thin film coat bearing structure with which a variable compression ratio engine is provided.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Variable compression ratio engine 21 ... Cylinder block 22 ... Crankcase 23 ... Free shaft housing 30 ... Eccentric shaft assembly 31 ... Shaft part 31a ... Mounting part 32 ... Worm wheel 33 ... Free shaft 34 ... Journal 41 ... Motor 42 ... Worm

Claims (3)

A hard thin film coated bearing structure including a shaft and a bearing,
A hard thin film is formed on at least one of the shaft surface of the shaft and the bearing surface of the bearing,
An oil supply path having an oil outlet on the shaft surface or the bearing surface is formed in the shaft or the bearing,
The shaft surface of the shaft and / or the bearing surface of the bearing,
The hard thin film characterized by being processed into a shape in which a bearing gap at a position where an axial distance of the shaft from the oil outlet is further away is wider at an arbitrary position in the circumferential direction of the shaft. Coated bearing structure. The hard thin film coat bearing structure according to claim 1, wherein a bearing interval at a portion where a distance in the axial direction of the shaft from the oil outlet is within a predetermined range is a constant value. The shaft is a member having a bearing surface for eccentrically supporting the second shaft, and as the oil supply path, a member having an oil inlet on the bearing surface is formed.
The second shaft is a member formed with a second oil supply path having a second oil outlet at a position corresponding to the position of the oil inlet;
A hard thin film is formed on at least one of the shaft surface of the second shaft and the bearing surface of the shaft;
The shaft surface of the second shaft and / or the bearing surface of the shaft;
The arbitrary position in the circumferential direction of the second shaft is processed into a shape in which the bearing gap at a position where the distance in the axial direction of the second shaft from the second oil outlet is further increased is wider. The hard thin film coat bearing structure according to claim 1 or 2, characterized by the above-mentioned.

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