CN110873037A

CN110873037A - Compressor and apparatus using the same

Info

Publication number: CN110873037A
Application number: CN201910157674.5A
Authority: CN
Inventors: 永田修平; 铃木启爱; 铃木遵自
Original assignee: Hitachi Global Life Solutions Inc
Current assignee: Meizhi Weiling application parts (Thailand) Co.,Ltd.
Priority date: 2018-08-29
Filing date: 2019-03-01
Publication date: 2020-03-10
Anticipated expiration: 2039-03-01
Also published as: JP2020033913A; CN110873037B; JP7079174B2

Abstract

The invention can reduce the friction loss between the piston and the cylinder and ensure the reliability. The compressor has a cylinder and a piston reciprocating in the cylinder in the front-rear direction, the piston has a piston sliding surface capable of sliding relative to the inner circumference of the cylinder on the top dead center side, a piston small diameter portion smaller in diameter than the piston sliding surface on the bottom dead center side, and a recess on the bottom dead center side of the inner circumference of the cylinder.

Description

Compressor and apparatus using the same

Technical Field

The present invention relates to a compressor and an apparatus using the same.

Background

Patent document 1 discloses a piston (0014, fig. 2 and 4) having a recess 7 over a wide range on the bottom dead center side in order to suppress the mass and friction of the piston.

Documents of the prior art

Patent document

Patent document 1: japanese Kokai publication Hei-2004-501320

Disclosure of Invention

Problems to be solved by the invention

When attempting to use a piston in which the bottom dead center side is recessed as shown in patent document 1 when the piston is supported by an oil film pressure between the piston side surface and the inner periphery of the cylinder tube, the distance between these components increases, and therefore, it is difficult to support the piston by the oil film pressure on the bottom dead center side. In this way, the influence of the force that the piston tries to rotate by the clockwise or counterclockwise torque in the side view becomes large. Therefore, the upper surface side or the lower surface side of the piston on the top dead center side and the lower surface side or the upper surface side of the piston on the bottom dead center side easily contact the cylinder tube. However, although the protection by the oil film pressure on the top dead center side is relatively effective, it is difficult to generate an oil film on the bottom dead center side as described above, and it is necessary to investigate the support on the bottom dead center side. However, patent document 1 does not disclose any content of such a study.

Means for solving the problems

In view of the above circumstances, the present invention provides a compressor including:

a cylinder barrel; and

a piston reciprocating in the cylinder barrel in the front-rear direction,

the piston is configured such that,

a piston sliding surface capable of sliding relative to the inner circumference of the cylinder barrel on the top dead center side,

a piston small diameter portion having a diameter smaller than the piston sliding surface on the bottom dead center side,

the cylinder has a recess on the bottom dead center side of the inner circumference thereof.

Drawings

Fig. 1 is a longitudinal sectional view of a compressor according to embodiment 1.

Fig. 2 is a side view of the piston of embodiment 1.

Fig. 3 is a sectional view a-a in fig. 1 of the cylinder tube of embodiment 1.

Fig. 4 is a side sectional view of the cylinder and the piston in the bottom dead center state in embodiment 1.

Fig. 5 is a rear view of the cylinder and the piston in the bottom dead center state of embodiment 1.

Fig. 6 is a perspective view of the cylinder tube of embodiment 1 viewed from above the bottom dead center side and below the top dead center side.

Fig. 7 is a schematic view of the boundary between the sliding portion and the non-sliding portion of the cylinder tube in embodiment 1.

Fig. 8 is a side sectional view of the cylinder and the piston in the bottom dead center state of comparative example 1.

Fig. 9 is a rear view of the cylinder and the piston in the bottom dead center state of comparative example 1.

Fig. 10 is a cross-sectional view of the cylinder and the piston in the bottom dead center state of comparative example 2.

Description of the symbols

1-cylinder, 2-connecting rod, 3-closed container, 4-piston, 5-stator, 6-rotor, 7-crankshaft, 9-piston pin, 1 a-radial bearing portion, 4 a-piston pin hole, 4 b-piston oil groove, 4 c-piston small diameter portion, 4 d-piston sliding portion, 4 e-connecting rod insertion hole, 7 a-crank pin, 8 a-upper side recess, 8 b-lower side recess, 20-compression element, 30-electric element, 35-lubricating oil, 50-compressor.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same 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 need to be present independently, and the following are permissible: one constituent element is constituted by a plurality of parts; the plurality of components are constituted by one member; a component is a part of another component; a part of a certain component overlaps with a part of another component.

Example 1

Fig. 1 is a longitudinal sectional view of a compressor 50 of the present embodiment. For convenience of explanation, the gravitational acceleration direction is set to the downward direction, the top dead center side in the reciprocating direction of the piston is set to the forward direction, and the bottom dead center side is set to the backward direction.

[ compressor 50]

In the compressor 50, an electric element 30 and a compression element 20 are housed in a sealed container 3, wherein the electric element 30 is composed of a stator 5 and a rotor 6, and the compression element 20 is composed of a cylinder 1, a piston 4, a connecting rod 2 connected to the piston 4 on the bottom dead center side, and a crankshaft 7. The compression element 20 is located above the electric element 30. The lubricant 35 is stored in the bottom of the closed casing 3.

The substantially cylindrical crankshaft 7 is rotatably provided in the vertical direction in an axial direction through the hollow cylindrical radial bearing portion 1 a. A crank pin 7a is formed at the upper end of the crankshaft 7 at a position eccentric from the rotation axis of the crankshaft 7. A connecting rod 2 having one end connected to one end of the crank pin 7a and the other end connected to the piston 4 is provided, whereby the piston 4 reciprocates when the crank pin 7a performs eccentric rotation. A rotor 6 is provided at a lower portion of the crankshaft 7, and when the rotor 6 rotates, the crankshaft 7 rotates, and the crank pin 7a eccentrically rotates. According to such a configuration, the piston 4 reciprocates in the cylinder 1 in accordance with the rotation of the crankshaft 7.

[ piston 4]

Fig. 2 is a schematic side view of the piston 4 of the present embodiment. The piston 4 is a piston pin type piston into which a piston pin 9 is inserted, and includes: a piston pin hole 4a as an insertion hole of the piston pin 9; a piston sliding surface 4d which is located closer to the top dead center than a part or the whole of the piston pin hole 4a and is slidable with respect to the wall surface of the cylinder tube 1; and a small piston diameter portion 4c located closer to the bottom dead center than a part of the piston pin hole 4a and having a smaller diameter than the piston sliding surface 4 d. A piston oil groove 4b is provided in a circumferential direction (preferably, one rotation in the circumferential direction) on, for example, a front-rear direction center side of the piston sliding surface 4 d.

The piston sliding surface 4d is a cylindrical surface that slides on the inner peripheral surface of the cylinder tube 1. The diameter of the piston small-diameter portion 4c is smaller than the outer diameter of the piston sliding surface 4d, and at least the contact between the piston small-diameter portion 4c and the inner circumferential surface of the cylinder 1 is not usually generated. When the piston pin 9 is fitted, the upper end and the lower end of the piston pin 9 are located inside the piston small-diameter portion 4 c.

[ wall surface of cylinder tube 1]

Fig. 3 is a longitudinal sectional view of the cylinder tube 1 of the present embodiment, and is a cross section a-a shown in fig. 1. The cylinder tube 1 surrounds a cylindrical space having a length longer than the length of the piston 4 except for the bottom dead center side, with a diameter slightly larger than the outer diameter of the piston 4. The piston can be inserted from the bottom dead center side, and can reciprocate. An upper concave portion 8a and a lower concave portion 8b which are non-contact (non-sliding) with respect to the piston sliding surface 4d are formed in opposite directions at the end portion of the cylinder tube 1 on the bottom dead center side. In the present embodiment, the upper recess 8a penetrates the upper wall surface of the cylinder 1, and the lower recess 8b does not penetrate the lower wall surface of the cylinder 1. The

recesses

8a and 8b are components including edges as boundaries between these members and the inner peripheral surface of the cylinder tube in the

recesses

8a and 8b, respectively.

With a known structure, the lubricating oil is supplied between the piston 4 and the cylinder 1 through the upper recessed portion 8 a. The lower recess 8b has a right-left width described later, and the piston 4 can easily make two-point contact.

In addition, in the process of assembling the piston pin 9 and the connecting rod 2 to the piston 4, the piston pin 9 is easily assembled by passing through the cutout portion of the upper side concave portion 8 a.

[ clockwise/counterclockwise rotational moment in the side view of the piston 4]

Fig. 4 is a schematic side view of the piston 4 and the cylinder tube 1 of the present embodiment at the position B-B in fig. 3 in a cross section in the front-rear direction of the bottom dead center, and fig. 5 is a rear view in the state of fig. 4.

The piston 4 has a diameter slightly smaller than the outer diameter of the inner peripheral surface of the cylinder 1 when viewed from the front-rear direction, and faces the inner peripheral surface of the cylinder 1 through a gap to which lubricating oil is supplied. The piston 4 can oscillate due to the clearance, but is supported by an oil film pressure generated by the reciprocation. However, since the piston 4 of the present embodiment has a small diameter on the bottom dead center side, it is difficult to make the support by the oil film uniform on the top dead center side and the bottom dead center side. Therefore, in the present embodiment, the piston 4 is likely to rotate in the clockwise direction or the counterclockwise direction when viewed from the side, and the upper surface and the lower surface of the piston 4 may be in point contact with the inner circumferential surface of the cylinder 1.

The reason for such a swing is an axial deviation between the driving force in the direction from the top dead center to the connecting rod 2 via the piston pin 9 received by the piston 4 and the direction vector in the direction from the bottom dead center to the pressure of the compressed gas in the cylinder chamber. In the case where the direction vectors of the two forces do not exist on the same axis, the piston 4 generates a torque. It is preferable to design and manufacture the compressor so that the vectors in the two directions are matched, but in order to facilitate the assembly process of the compressor components, a predetermined gap is set between the components, and these components have a machining tolerance. Thus, in an actual product, the piston 4 may generate a torque.

The research result of the inventor confirms that: the direction of torque generation is clockwise in the side view of fig. 4, that is, the direction in which the top dead center side of the upper surface and the bottom dead center side of the lower surface of the piston 4 contact the cylinder tube 1. This is because, when the connecting rod 2 is fitted to the piston pin 9, the connecting rod 2 receives a downward force due to its own weight, and therefore, in a design in which a tolerance is assumed, the connecting rod 2 is displaced downward from a design position, and on the other hand, a position on which a force due to a pressure acts can be predicted with high accuracy in a previous design. As described above, the force in the direction toward the top dead center by the connecting rod 2 is likely to act on the lower side of the center of gravity with respect to the torque around the center of gravity of the piston 4, and the gas pressure is uniformly applied to the top face of the piston 4.

Therefore, as illustrated in fig. 4, the piston 4 of the present embodiment is easily applied with a torque such that the upper surface of the piston sliding surface 4d contacts the cylinder tube 1 on the top dead center side, and the lower surface of the piston sliding surface 4d or the lower surface of the piston small diameter portion 4c contacts the cylinder tube 1 on the bottom dead center side. At this time, when the number of upper and lower contact points of the piston 4 is one, the piston 4 tries to swing about an axis connecting the upper and lower contact points when it receives a moment about the axis of the piston pin hole 4 a. As a result, the piston 4 continues to collide with the wall surface of the cylinder tube 1 in response to the external force applied to the piston 4, and the reliability of the compressor is reduced. In the present embodiment, in order to stably hold the piston 4 in the cylinder 1, the lower surface can be supported by two or more points of contact, as illustrated in fig. 5.

For example, it is preferable in terms of mechanics to ensure that the contact points of the piston 4 with the cylinder tube 1 add up to three points which, as shown in fig. 5, are in the form of a regular triangle when viewed from the bottom dead center direction toward the top dead center direction. Suitably, the distance between the two points of the support point at the lower surface is about 1.7 times (1.3 times or more, preferably 1.6 times or 1.65 times or more, and less than 2.0 times, preferably 1.8 times or 1.75 times or less) the piston radius. If the distance between the two points is too small, the piston 4 may be in a mechanically unstable holding state, as in the case where the number of contact points on the lower surface is one, and the reliability of the compressor may be reduced.

[ Torque when viewed from the front-rear direction ]

When the piston 4 is positioned near the top dead center, the pressure difference between the inside and the outside of the cylinder chamber is large, and therefore the piston 4 is strongly pressed against the wall surface of the cylinder 1 and is in a restricted state. At this time, the axis of the piston 4 is substantially parallel to the axis of the cylinder 1. On the other hand, when the piston 4 is located near the bottom dead center, the pressure difference between the inside and the outside of the cylinder chamber is small, and the restricting force of the piston 4 is small. Therefore, when the piston 4 is located near the bottom dead center, the axis of the piston 4 and the axis of the cylinder 1 lose a substantially parallel state due to slight imbalance of the external force, and it can be said that the piston 4 and the cylinder 1 are in a state in which point contact is easily caused. In addition, near the bottom dead center, the amount of overlap between the cylinder tube 1 and the piston 4 is small, and is therefore unstable in terms of mechanics. In a state of being unstable in terms of mechanics, the piston 4 may collide with the wall surface of the cylinder tube 1 many times, and is not recommended from the viewpoint of friction loss and reliability.

Therefore, it is most preferable to improve the contact relationship of the piston 4 with respect to the cylinder 1 at the bottom dead center. In the present embodiment, when the top-dead-center side surface of the piston 4 at the bottom dead center contacts (e.g., makes point contact with) the inner circumferential surface of the cylinder 1, the bottom-dead-center side surface contacts the edge of the lower recess 8 b. By setting the width of the lower recess 8b to be smaller than the lateral dimension of the piston 4 and to be in a range including the center of the piston 4 in the lateral direction, at least one portion on the left and right sides of the edge can be brought into contact with the piston 4. Normally, the vicinity of the center of the lateral dimension contacts the cylinder tube 1 on the top dead center side of the piston 4, so that the left and right portions of the contact position between the top dead center sides can be supported on the bottom dead center side. Therefore, at least three points of contact are generated, and thus the torque in the right-left direction (the moment around the axis of the piston pin hole 4 a) can be supported.

In this way, in the present embodiment, the position at which the lower surface of the piston 4, which is substantially circular when viewed in the reciprocating direction, contacts the wall surface of the cylinder tube 1 can be adjusted by the width of the lower recess 8 b. In the present embodiment, the distance (contact interval) between two points at which the cylinder wall surface lower portion contacts the piston 4 is set to be less than 2 times (i.e., the diameter) of the piston radius (the radial dimension of the piston sliding surface 4 d), preferably, to be in the range of 1.3 times to 1.7 times, and the hole diameter of the piston pin hole 4a is set to be smaller than the distance (contact interval) between two points at which the cylinder wall surface lower portion contacts the piston 4. At this time, the piston 4 can be in contact with the cylinder 1 at three points, and the distance (contact interval) between the two points at which the lower portion of the cylinder wall surface can be in contact with the piston 4 is relatively wide. Therefore, the piston 4 can be stably held in the cylinder 1 even in the vicinity of the bottom dead center, and the piston 4 can be suppressed from colliding with the wall surface of the cylinder 1a plurality of times.

Further, by restricting the piston 4 by the piston pin 9 fitted in the vertical direction, it is possible to suppress the swing in the left-right direction (clockwise direction or counterclockwise direction when viewed from the front-rear direction).

Fig. 6 is a perspective view of the cylinder tube 1 of the present embodiment on the bottom dead center side. An end surface 1z orthogonal to the front-rear direction is provided at a bottom dead center side end portion of the cylinder tube 1, and a cylindrical space extending in the front-rear direction is provided at a center side of the end surface 1 z. In which space a piston 4 is inserted.

The upper concave portion 8a and the lower concave portion 8b are provided so as to extend in the forward direction after cutting a part of the end surface 1 z. Edges that are boundaries between the upper concave portion 8a and the lower concave portion 8b and the inner circumferential surface of the cylinder are substantially convex in the left-right direction in the range of the inner circumferential surface of the cylinder. In the present embodiment, the upper concave portion 8a is formed in a substantially arc shape protruding toward the top dead center side and the lower concave portion 8b is formed in a substantially circular shape (substantially semicircular shape within the range of the inner peripheral surface of the cylinder tube) in a plan view. The respective edges are smoothly connected to the inner circumferential surface of the cylinder tube 1. When the

concave portions

8a and 8b are formed in a circular shape or an arc shape, the radii of curvature thereof are preferably substantially the same.

And, the lower concave portion 8b projects in the forward direction. Whereby edges are formed at the left and right sides and thus at least two-point contact is easily made.

Here, it is considered that the lubricating oil is supplied to the sliding surface between the cylinder tube 1 and the piston 4. Fig. 7 is a schematic diagram showing the boundary between the non-sliding portions (

recesses

8a and 8b) and the sliding portion (cylinder inner circumferential surface) on the inner circumferential surface of the cylinder tube 1 according to the present embodiment. In the figure, black line arrows indicate the sliding direction, and hollow arrows indicate the oil flow direction. Since the lubricant drops or is accumulated in the non-sliding portion through the non-sliding portion, the flow of the lubricant is directed from the non-sliding portion toward the sliding portion. Therefore, the lubricating oil is introduced into the sliding portion by the drawing-in caused by the sliding of the piston 4. If the edge is convex in the left-right direction as in this embodiment, a large amount of lubricant can move to the sliding portion with sliding, and thus the lubricity can be improved.

The compressor of the present embodiment can be applied to other apparatuses such as a refrigerator.

Comparative example 1

Fig. 8 is a longitudinal cross-sectional view of the piston 4 and the cylinder 1 of comparative example 1 at the bottom dead center, which is not provided with the piston small diameter portion 4c of the piston 4 and the lower recess portion 8b of the cylinder 1. Fig. 9 is a schematic view of comparative example 1 at bottom dead center as viewed from the bottom dead center direction. In fig. 8 and 9, components other than the cylinder 1 and the piston 4 are not shown.

In comparative example 1, the contact on the lower surface side is likely to be a one-point contact. When the piston 4 receives a moment about the axis of the piston pin hole 4a, it tries to swing about the axis connecting the upper and lower contact points. In this comparative example, since the third contact point supporting the swing is not provided, the piston 4 and the cylinder tube 1 repeatedly contact each other due to the rotation in the left-right direction, and the reliability is lowered.

Comparative example 2

Fig. 10 is a longitudinal cross-sectional view of comparative example 2 in which the piston small diameter portion 4c is provided only on the front-rear direction center side and the lower recessed portion 8b is not provided. Since the piston sliding surface 4d is also formed on the bottom dead center side, the cylinder wall surface end portion easily comes into one-point contact with the piston sliding surface 4d on the bottom dead center side. Therefore, the piston small diameter portion 4c preferably includes the entire range where the piston 4 is exposed from the cylinder tube 1 at the bottom dead center as in embodiment 1.

Claims

1. A compressor, characterized by comprising:

a cylinder barrel; and

a piston reciprocating in the cylinder barrel in the front-rear direction,

the piston is configured such that,

2. The compressor of claim 1,

when a clockwise or counterclockwise torque is applied to the piston in a side view of the piston,

when viewed from the front-rear direction of the piston,

one upper dead center side of the upper side and the lower side of the piston sliding surface is approximately contacted with the cylinder barrel at least one position,

the other of the upper side and the lower side is substantially in contact with the edge of the concave portion at a position larger than the number of substantially contacting points.

3. The compressor of claim 1,

when viewed from the front-rear direction of the piston,

one of the upper side and the lower side of the piston is substantially in contact with the cylinder at least at one location,

the other of the upper side and the lower side of the piston is substantially in contact with the edge of the recess at least one of the left side and the right side with respect to the one portion.

4. A compressor according to any one of claims 1 to 3,

the maximum width of the recess in the left-right direction exceeds the radius of the piston.

5. A compressor according to any one of claims 1 to 4,

the maximum width of the recess in the left-right direction is less than 1.8 times the radius of the piston.

6. A compressor according to any one of claims 1 to 5,

the edge of the recess is convex in either left or right direction.

7. A compressor according to any one of claims 1 to 5,

the shape of the edge of the recess is convex in the forward direction.

8. A compressor according to any one of claims 1 to 7,

the recess is located at the end of the cylinder at the bottom dead center and in a region where an end surface perpendicular to the front-rear direction is cut.

9. A compressor according to any one of claims 1 to 8,

the concave portion is opposed to the concave portion, and the two concave portions have substantially the same radius of curvature.

10. An apparatus comprising the compressor according to any one of claims 1 to 9.