JP2019190427A - Compressor and apparatus using the same - Google Patents

Abstract

To reduce slide losses in a crankshaft with a simple processing.SOLUTION: A compressor includes: a crankshaft 7 freely rotatable and having a substantially cylindrical shape; a radial bearing pivotally supporting the crankshaft and having a hollow cylindrical shape; lubricant supplied to a gap between the crankshaft and the radial bearing; and a planar cut part 7p provided in a region opposite to the radial bearing of the crankshaft.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a compressor and a device using the compressor.

  Patent Document 1 discloses a hermetic compressor in which a plurality of fine oil supply grooves 7p are provided on a crankshaft 7.

Japanese Patent Laying-Open No. 2015-7378

  According to Patent Document 1, although the groove depth of the fine oil supply groove 7p is referred to as about 10 μm (0036), no specific shape or processing method is further studied. However, it is desirable that the fine oil supply groove 7p be easily processed, and the influence on the lubrication performance varies depending on the shape, depth, and width of the fine oil supply groove 7p. Not.

The present invention made in view of the above circumstances,
A rotatable, substantially cylindrical crankshaft;
A hollow cylindrical radial bearing that pivotally supports the crankshaft;
Lubricating oil supplied to the gap between the crankshaft and the radial bearing;
It is a compressor which has a plane cut part provided in the field which counters the radial bearing among the crankshafts.

Longitudinal sectional view of the compressor of Example 1 Cross section of the compressor of Example 1 Side view of crankshaft of compressor of embodiment 1 Example 1 Lower shaft support and enlarged schematic view of the surrounding area Axial cross-sectional view of the crankshaft of Example 1 (taken along the AA cross section of FIG. 4 and focused on one flat cut portion, but the radial bearing portion is not shown) The AA cross section of FIG. 4 is taken and the radial bearing part and the plane cut part which opposes this are shown. Cross-sectional view of the crankshaft of the comparative example Figure 7 with radial bearing added The figure which shows the graph which compared the sliding loss which generate | occur | produces in the crankshaft of Example 1, and the sliding loss which generate | occur | produces in the crankshaft of a comparative example. Schematic diagram near the upper shaft support portion of the crankshaft of Example 1 Schematic diagram when the crankshaft 7 of the first embodiment is largely inclined in the radial bearing portion

  Embodiments of the present invention will be described below with reference to the accompanying drawings. Similar components are denoted by the same reference numerals, and the same description will not be repeated.

  The various components of the present invention do not necessarily have to be independent of each other. One component is composed of a plurality of members, a plurality of components are composed of one member, and one component is separated from another. And a part of a certain component and a part of another component are allowed to overlap.

[Overall configuration of compressor 50]
FIG. 1 is a longitudinal sectional view of a compressor 50 of this embodiment, and FIG. 2 is a transverse sectional view of the compressor 50 of this embodiment.
The compressor 50 takes a form in which an electric element 30 composed of a stator 5 and a rotor 6 and a compression element 20 composed of a cylinder 1, a piston 4, a connecting rod 2, and a crankshaft 7 are accommodated in an airtight container 3. The compression element 20 is configured to be positioned above the electric element 30. Lubricating oil 35 is stored at the bottom of the sealed container 3.

  The substantially cylindrical crankshaft 7 passes through the hollow cylindrical radial bearing portion 1a and is set to freely rotate with the vertical direction as the axial direction. A crankpin 7 a is connected to the upper end of the crankshaft 7 at a position eccentric from the rotation shaft of the crankshaft 7. A connecting rod 2 having one end connected to the crankpin 7a and the other end connected to the piston 4 is provided, whereby the piston 4 reciprocates when the crankpin 7a rotates eccentrically. A rotor 6 is provided below the crankshaft 7. When the rotor 6 rotates, the crankshaft 7 rotates and the crankpin 7a rotates eccentrically. With such a structure, the piston 4 reciprocates in the cylinder 1 as the crankshaft 7 rotates.

[Crankshaft 7]
FIG. 3 is a side view of the crankshaft 7 of this embodiment. The crankshaft 7 has a small diameter portion 7i on the axial center side, an upper shaft support portion 7m on the upper end side in the axial direction, and a lower shaft support portion 7n on the lower end side in the axial direction. The small diameter portion 7i has a smaller shaft diameter than the upper shaft support portion 7m and the lower shaft support portion 7n. When the crankshaft 7 rotates and the piston 4 reciprocates, a radial force acts on the crankshaft 7 by the action of the piston 4 on the fluid. Each of the upper shaft support portion 7m and the lower shaft support portion 7n is in contact with the radial bearing portion 1a, preferably via the lubricating oil 35, and supports this force. On the other hand, since the gap between the small diameter portion 7i and the radial bearing portion 1a is relatively large, the upper shaft support portion 7m and the lower shaft support portion 7n are mainly mechanically connected, and as a flow path for the lubricating oil 35. Has the effect of.

  A spiral groove on the outer periphery of the crankshaft 7 is capable of pumping up the lubricating oil 35 stored at the bottom when the crankshaft 7 rotates over the lower shaft support portion 7n, the small diameter portion 7i, and the upper shaft support portion 7m. 7d is provided. The spiral groove 7d has a lead angle that is inclined upward toward the opposite direction to the rotation direction of the crankshaft 7.

  Lubricating oil 35 is introduced into the gaps between the lower shaft support portion 7n, the small diameter portion 7i, and the upper shaft support portion 7m and the radial bearing portion 1a through the spiral groove 7d during operation of the compressor. The clearance dimension between the small diameter portion 7i and the radial bearing portion 1a is relatively large, and no large oil film pressure is generated. On the other hand, the gap between the lower shaft support portion 7n or the upper shaft support portion 7m and the radial bearing portion 1a is relatively small, and a relatively large oil film pressure is generated. For this reason, the radial load applied to the crankshaft 7 is pivotally supported by the upper shaft support portion 7m and the lower shaft support portion 7n.

  Although depending on the type of the lubricating oil 35, generally when a radial load is applied to the crankshaft 7 by setting the clearance between the upper shaft support portion 7 m and the lower shaft support portion 7 n and the radial bearing portion 1 a to several μm to several tens μm. An oil film pressure can be generated.

(Plane cut part 7p)
FIG. 4 is an enlarged schematic view of the lower shaft support portion 7n of this embodiment and its surroundings.

    A plurality of flat cut portions 7p are provided in the lower shaft support portion 7n, which is a region facing the radial bearing 1a, in which a side circumferential surface having a circular cross section is recessed toward the inner diameter side. The flat cut portion 7p has an upper end communicating with the small-diameter portion 7i, and a lower end located above the lower end of the radial bearing portion 1a.

    The flat cut portion 7p is designed in such a direction that the lubricating oil 35 is introduced into the flat cut portion 7p from the small diameter portion 7i side when the crankshaft 7 rotates. That is, the plane cut portion 7p is provided with a lead angle θ that is inclined downward toward the direction opposite to the rotation direction of the crankshaft 7. As illustrated in FIG. 4, the lead angle θ is clockwise with respect to the end of the flat cut portion 7p with reference to an imaginary straight line extending in the circumferential direction of the crankshaft 7 (θ = 0 °). It can be set to 0 ° <θ ≦ 90 °.

  The flat cut portion 7p is formed, for example, by a removal process of pressing a rotary blade against the lower shaft support portion 7n. The plane cut portion 7p is configured by a substantially plane, but depending on the accuracy of the processing jig, it may be configured by a gently curved surface instead of a strict plane.

  Considering the machining process, the removal shape of the flat cut portion 7p is determined by two parameters of the pressing amount of the rotary blade and the lead angle. The radial removal amount by the flat cut portion 7p and the chord length of the flat cut portion 7p are dependent on each other and are determined by the pressing amount of the rotary blade. On the other hand, the groove 7q as in a comparative example to be described later is determined by three parameters of groove depth, groove width, and lead angle, and has one more parameter to be controlled by the rotary blade during processing. From the viewpoint of production workability, it can be said that the structure of the flat cut portion 7p of this embodiment is easier to process than the comparative example described later.

[Lubrication]
When lubricating oil 35 is supplied and supported between two solids that move relative to each other, pressure increases due to movement of lubricating oil 35 due to the relative movement, and contact between the two solids can be suppressed. . In this specification, the “slow wedge effect” and the “steep wedge effect” are particularly noted.

(Slow wedge effect)
When the flow passage cross-sectional area of the moving lubricating oil 35 decreases and the flow passage cross-sectional area approaches 0, the lubricating oil 35 is compressed and a large pressure (oil film pressure) is generated (wedge effect). For example, when considering a system composed of a hollow cylindrical fixed surface, a smooth columnar rotating surface stored in the hollow region, and a lubricating oil disposed between them, the wedge effect is Occurs when the gap between the rotating surface and the fixed surface is gradually narrowed by being eccentric from the fixed surface. Even in the case where the concave portion is provided on the side circumferential surface of the rotating surface (crankshaft 7) as in the present embodiment and the comparative example, the basic shape of the crankshaft 7 is a columnar shape. It is believed that some degree of wedge effect occurs, although it is weakened by. In this specification, the wedge effect formed by the columnar rotating surface and the hollow cylindrical fixed surface is referred to as a “gradual wedge effect”. This is named because the oil film pressure is generated in a relatively wide range because the gap between the rotating surface and the fixed surface is gradually narrowed.

  The “gradual wedge effect” exhibits a great effect when the rotating surface (crankshaft 7) is greatly decentered. This is because the degree of decrease in the cross-sectional area of the flow path increases as the rotational surface becomes more eccentric. Therefore, the wedge effect increases as the load increases (the amount of work due to compression of the piston 4 is large and the force to decenter the crankshaft 7 is large).

(Steep and rust effect)
When the flow passage cross-sectional area of the moving lubricating oil 35 is sharply reduced, a large oil film pressure is generated due to the wedge effect described above. In the present specification, in view of the sharp decrease in the channel cross-sectional area, it is distinguished from the gradual wedge effect and referred to as the “steep rust effect”. When the concave portion is provided on the side peripheral surface of the rotating surface (crankshaft 7) as in the present embodiment or the comparative example, the location where the lubricating oil 35 in the concave portion flows into the non-concave portion has a steep channel cross-sectional area. This is a place where the “reduces a rust effect”. The pressure resulting from the “steep rust effect” is generated in a relatively narrow range around the place where the flow path cross-sectional area sharply decreases.

[Details of lubrication by flat cut 7p]
As will be described later, the “steep wedge effect” becomes dominant at the stepped step and the “gradual wedge effect” is reduced. However, according to the flat cut portion 7p of the present embodiment, the flow path cross-sectional area is reduced. With the space that maintains the smooth reduction of, the "slow rust effect" and the "steep rust effect" can both be achieved. That is, according to the flat cut portion 7p as in the present embodiment, it is possible to realize performance with excellent balance.

FIG. 5 is an axial sectional view of the crankshaft 7 of the present embodiment (taken from the AA sectional view of FIG. 4 and focusing on one flat cut portion 7p. However, the radial bearing portion 1a is not shown), FIG. FIG. 4 is a cross-sectional view taken along the line AA of FIG. 4 and shows a radial bearing portion 1a and a flat cut portion 7p facing the radial bearing portion 1a. A plurality of ways of expressing the plane cut portion 7p of this embodiment can be considered, but for example, the following explanation is possible.
The plane cut portion 7p is formed of a substantially flat surface, and has two connection points (referred to as tangent lines 7r) to an unprocessed region (region before processing of the plane cut portion 7p) as shown by a broken line in FIG. Has a ridge line (referred to as a vertex in the axial cross-sectional view of the crankshaft 7), but no other. That is, there are only two ridge lines for one plane cut portion 7p. In addition, when the processing of the plane cut portion 7p is performed along the axial direction (when the lead angle θ is 90 °), the ridge line extends along the axial direction of the crankshaft 7. In the case of a cut other than the flat cut portion 7p (for example, a groove structure 7q as in a comparative example described later), a ridge line other than the two tangent lines 7r is generated. These ridge lines include at least those that exceed 180 ° in a cross sectional view (see φ3 and φ4 in FIG. 7 as a comparative example. “An angle φ3 and φ4 of the crankshaft portion remaining after cutting” exceeds 180 °. )

  If only the plane cut portion 7p is processed on the side peripheral surface of the lower shaft support portion 7n, the shape of the cross-sectional view (AA cross section view of FIG. 4) is substantially convex (inside the lower shaft support portion 7n). The line segment connecting any two points taken is in the lower shaft support 7n.

  The plane cut portion 7p is a substantially straight line (a gentle curve depending on the accuracy of the processing jig) in a cross-sectional view.

(Oil film pressure at the flat cut portion 7p)
As illustrated in FIG. 6, the radial gap 7s located between the crankshaft 7 and the radial bearing portion 1a is relatively large in the region where the flat cut portion 7p is disposed, and the other region (lower side) The portion of the shaft support portion 7n excluding the flat cut portion 7p) becomes relatively small. Further, the radial bearing portion 1a has a hollow cylindrical shape, the unprocessed crankshaft 7 has a cylindrical shape arranged in the hollow portion of the radial bearing portion 1a, and the plane cut portion 7p as a processed portion is taken along the AA cross section. Since the flat cut portion 7p has a substantially straight shape, the center side has a larger size of the gap 7s, and the tangent line 7r side has a smaller size of the gap 7s.

  When the crankshaft 7 rotates in the rotation direction, the lubricating oil 35 present in the gap 7s moves in the rotation direction at a speed smaller than the rotation speed of the crankshaft 7, and as illustrated by the arrows in FIG. When viewed from the surface of the crankshaft 7, it moves in the counter-rotating direction. That is, a force is received in the counter-rotating direction (right direction in FIG. 6) along the width direction of the flat cut portion 7p. Then, since the gap dimension gradually decreases (the cross-sectional area of the flow path decreases) as it approaches the ridgeline 7r (angle φ1 side), the pressure of the lubricating oil 35 (oil film pressure) increases due to the stagnation of the flow. Although this phenomenon is close to the above-mentioned “gradual wedge effect”, the degree of decrease in the cross-sectional area of the flow path is steeper than in the case where there is no flat cut portion 7p, so the “steep wedge effect” is also included.

  Further, since the flat cut portion 7p has a lead angle θ, when the crankshaft 7 rotates, the lubricating oil 35 is axially directed (in FIG. 6) by the frictional force (viscous force) with the crankshaft 7 that is the rotating surface. , Receiving force in the direction perpendicular to the paper surface). As a result, the force along the extending direction of the flat cut portion 7p (see FIG. 4) is received together with the force in the rotational direction described above, so that the supply amount of the lubricating oil 35 can be easily increased.

  Further, as illustrated in FIG. 4, since the lower end of the flat cut portion 7p is located above the lower end of the radial bearing portion 1a, the lubricating oil 35 flows in the direction of the solid arrow and reaches the lower end of the flat cut portion 7p. As a result, the gap 7s is sharply narrowed by the termination of the flat cut portion 7p. As a result of the flow stagnation, the pressure of the lubricating oil 35 (oil film pressure) increases. This increase in pressure corresponds to the “steep wedge effect” described above.

(Suitable range of lead angle θ)
As the lead angle θ of the flat cut portion 7p increases, it becomes difficult to introduce the lubricating oil 35 into the flat cut flow path 7s, so the “steep wedge effect” at the end portion of the flat cut portion 7p decreases.
On the other hand, when the lead angle θ is reduced, the circumferential width of the flat cut portion 7p is widened, and the proportion of the flat cut portion 7p on the surface of the lower shaft support portion 7n is increased. If the ratio of the flat cut portion 7p is too large, the influence of the (unprocessed) “slow rust effect” generated in the lower shaft support portion 7n becomes very small, and the crankshaft 7 is brought into the radial bearing 1a due to an increase in load. Even when approaching (even if the work amount due to compression of the piston 4 is large and the force for decentering the crankshaft 7 is large), the effect of the wedge effect is small, so that sufficient pressure is not generated and the oil film may break. Increase.

  Therefore, from the viewpoint of the balance between the “steep wedge effect” and the “slow wedge effect”, it is desirable to set the lead angle in the range of 20 ° to 60 °.

(Suitable range of cut amount)
Further, regarding the flat cut portion 7p, the amount of cut from the surface of the side surface of the crankshaft 7 (see FIG. 5) For the virtual straight line C passing through the center of the crankshaft 7, If the distance from the “intersection point” to “intersection with the plane cut portion 7p” is too long, the width in the circumferential direction of the plane cut portion 7p becomes wide, which is not preferable for the same reason as when the lead angle is shallow. On the other hand, when the cut amount is shallow, the dimension of the gap 7s becomes narrow, the effect of reducing the friction loss is small, and the lubricating oil 35 tends to be insufficient. Therefore, it is desirable to set the cut amount in the range of 5 μm to 25 μm.

[Comparative example]
FIG. 7 is an axial sectional view of a crankshaft 7 ′ of a comparative example, and FIG. 8 is a diagram in which a radial bearing 1a is added to FIG.
The groove structure 7q of the comparative example is formed by a removal process using two or more surfaces (the blade tool tip and the blade tool side surface) in the processing jig (rotating blade). Therefore, the groove structure 7q is composed of two or more substantially flat surfaces. For example, in the case of a groove having a triangular cross section, there are two surfaces formed by the removal process, and in the case of a groove 7q having a rectangular cross section as illustrated in FIG. 7, there are three surfaces formed by the removal process. Therefore, since the groove structure is inevitably composed of a plurality of surfaces, it has three or more ridge lines.
The lubrication by the groove structure 7q as in the comparative example is dominated by the “steep wedge effect” that can generate the oil film pressure in a relatively narrow range. On the other hand, considering that the “gradual wedge effect” occurs in a structure in which the bearing gap gradually narrows, the “gentle wedge effect” is unlikely to occur in the groove structure 7q. This is because the groove structure 7q has a substantially constant groove depth and a wide bearing gap, so that the reduction in the flow path cross-sectional area is very small. Therefore, as the number of groove structures 7q is increased, the “steep wedge effect” increases, but the “gradual wedge effect” decreases.

(Contrast between Example and Comparative Example)
FIG. 9 is a graph showing a comparison between the sliding loss that occurs in the crankshaft 7 of the present embodiment and the sliding loss that occurs in the crankshaft 7 ′ of the comparative example. The vertical axis is the sliding loss, and the loss when the surface of the lower shaft support portion 7n is not processed is 1. The horizontal axis indicates the load applied to the crankshaft 7.

  Comparing the two, it can be seen that, in general, the specification of the groove structure 7q realizes reduction of the sliding loss in the low load region, but the sliding loss is deteriorated in the high load region. On the other hand, it can be seen that the specification of the flat cut portion 7p realizes reduction of sliding loss in a wide load region. The reason why such a tendency is obtained will be described.

  As described above, since the “gradual wedge effect” exhibits a large effect when the crankshaft 7 is greatly decentered, the “gradual wedge effect” increases as the load increases. From this effect, the oil film pressure generated in the example is higher than that in the comparative example under a high load condition, and the bearing load capacity is large. This is a structure that can achieve both “slow wedge effect” and “steep wedge effect” in the embodiment, whereas the comparative example can generate pressure in a relatively wide range as described above. This is because it has a structure in which the “slow and rust effect” is unlikely to occur, and the bearing load capacity under high load conditions is low.

  Then, in the high load condition, since the oil film thickness of the lower shaft support portion 7n can be made thicker than the comparative example, the friction loss can be suppressed low, which is excellent from the viewpoint of reliability. Can be.

[Upper shaft support 7m]
FIG. 10 is a schematic view of the crankshaft 7 according to the present embodiment in the vicinity of the upper shaft support portion 7m, and FIG. 11 is a schematic view when the crankshaft 7 of the present embodiment is largely inclined in the radial bearing portion 1a. The upper shaft support 7m has a circular cross section excluding the spiral groove 7d, but its diameter is narrow in the vicinity of the upper end of the radial bearing 1a. It is comprised so that there may be a difference of μm to several tens of μm. That is, when viewed in a side view, the upper shaft support portion 7m of the crankshaft 7 has an upper shaft support portion inclined region 7t.

  When the plane cut portion 7p is provided on the surface of the lower shaft support portion 7n as in the present embodiment, the “gradual wedge effect” that is generated is smaller than that when it is not processed. Therefore, when a large load is applied to the crankshaft 7, the amount of axial inclination of the crankshaft 7 may increase. At this time, under conditions where the load on the crankshaft 7 is large and the rotational speed is low, the upper shaft support portion 7m and the upper end portion of the radial bearing portion 1a are likely to come into contact with each other, which may cause an increase in friction loss.

  In the present embodiment, since the upper shaft support portion inclined area 7t exists in the upper shaft support portion 7m, contact between the upper shaft support portion 7m and the upper end portion of the radial bearing portion 1a can be effectively avoided. When the crankshaft 7 is tilted, the upper shaft support portion inclined region 7t and the radial bearing portion 1a are substantially parallel to each other on the tilt direction side, so that the upper end edge of the radial bearing portion 1a is difficult to contact the upper shaft support portion 7m. Therefore, it is possible to realize a crankshaft with low friction loss even at high loads.

As described above, according to the present embodiment, it is possible to provide a hermetic compressor that is easy to process, has low friction loss, and high reliability. The flat cut portion 7p may be provided on the upper shaft support portion 7m, and the upper shaft support portion inclined region 7t may be provided on the lower shaft support portion 7n.
The compressor of a present Example is applicable to a refrigerator and other apparatuses.

DESCRIPTION OF SYMBOLS 1 ... Cylinder 2 ... Connecting rod 3 ... Sealed container 4 ... Piston 5 ... Stator 6 ... Rotor 7 ... Crankshaft 1a ... Radial bearing part 7i ... Small diameter Part 7m: Upper shaft support part 7n: Lower shaft support part 7p: Planar cut part 7d ... Spiral groove 20 ... Compression element 30 ... Electric element 35 ... Lubricating oil 50 ...・ Compressor 7q ・ ・ ・ Groove structure

Claims (8)

A rotatable, substantially cylindrical crankshaft;
A hollow cylindrical radial bearing that pivotally supports the crankshaft;
Lubricating oil supplied to the gap between the crankshaft and the radial bearing;
A compressor having a flat cut portion provided in a region of the crankshaft facing the radial bearing.   The compressor according to claim 1, wherein the flat cut portion has only two ridge lines.   The compressor according to claim 1, wherein the flat cut portion has a substantially convex shape in a cross-sectional shape of a region of the crankshaft where the flat cut portion is disposed.   The compressor according to any one of claims 1 to 3, wherein the flat cut portion is substantially linear in a cross-sectional view.   The compressor according to any one of claims 1 to 4, wherein the flat cut portion has a lead angle of 20 ° or more and 60 ° or less.   The compressor according to any one of claims 1 to 5, wherein the flat cut portion has a cut amount of 5 µm to 25 µm. The crankshaft is pivotally supported by the radial bearing at an upper pivotal support and a lower pivotal support,
One of the upper shaft support portion and the lower shaft support portion has the flat cut portion,
The other of the upper shaft support portion and the lower shaft support portion has a diameter of a height at which the vicinity of the end portion of the radial bearing is located, and the other central side end portion of the upper shaft support portion and the lower shaft support portion from the height. The compressor according to any one of claims 1 to 6, further comprising a shaft support portion inclined region smaller than the diameter of the shaft support portion.   The apparatus provided with the compressor as described in any one of Claims 1 thru | or 7.

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