WO2020091226A1

WO2020091226A1 - Compact air compressor with novel piston structure

Info

Publication number: WO2020091226A1
Application number: PCT/KR2019/012058
Authority: WO
Inventors: Jeong Cheol Jang; Jong Hyuk Kim; Wang Gyu Jeong
Original assignee: New Motech Co., Ltd.
Priority date: 2018-11-02
Filing date: 2019-09-18
Publication date: 2020-05-07
Also published as: KR102121123B1; KR20200050678A

Abstract

The compact air compressor according to the present invention comprises a block 40; a tubular cylinder 50 coupled to the block 40; a valve assembly 70 comprising a suction valve and a discharge valve to block a front end of the cylinder; a valve cover 80 covering the valve assembly to form a suction space 81a and a discharge space 81b on an upper part of the valve assembly 70; a piston 60 conducting a linear reciprocating motion in the cylinder 50; a stator 21 coupled to the block 40; a lower housing 11 installed on a lower part of the stator 21; a rotor 25 located to rotate relative to the stator 21; a rotation shaft 30 coupled to the rotor 25 to rotate integrally with the rotor 25 so as to be rotatably supported to the block 40; a crank part 32 converting a rotation motion of the rotation shaft 30 to a linear reciprocating motion of the piston 60; a connecting rod 34 formed with an insertion cylindrical part 34A into which a journal bearing 33 installed on the crank part 32 is inserted, and a rod part 34B extended from the insertion cylindrical part 34A to the front; and an upper ball bearing 30A and a lower ball bearing 30B installed on an upper part and a lower part of the rotation shaft 30, respectively, wherein the piston 60 comprises a piston supporter 61 coupled to a front end of the rod part 34B, a stopper 63 coupled to the piston supporter 61, and a piston ring 62 installed between the piston supporter 61 and the stopper 63.

Description

COMPACT AIR COMPRESSOR WITH NOVEL PISTON STRUCTURE

The present invention relates to a compact air compressor. More specifically, the present invention relates to a compact air compressor with a novel piston structure capable of preventing air leakage generated as a piston ring is pushed towards a bottom dead center during a compression process, thereby improving compression performance, and minimizing the loss of compression space.

In general, compressors are used to produce compressed air or to compress fluid such as refrigerant gas. Compressors are mainly classified into reciprocating piston type compressors which compress air by a reciprocating motion of a piston in a cylinder, and rotary vane type compressors which compress air by rotating a rotor in the cylinder. Rotary vane type air compressors make less noise, but there is difficulty in manufacturing small sized products, and thus rotary vane type air compressors are mainly applied to large sized compressors of 20 HP or more. In comparison, reciprocating piston type compressors are mainly applied to slightly small sized compressors of 20 HP or less.

Korean Patent No. 10-1745471 discloses a reciprocating piston type compressor of the above structure. The prior art discloses a cylinder coupling structure of a small reciprocating compressor which has a cylinder integrally coupled to a block to which a crank shaft is axially supported. According to the prior art, a supporting end pressing and supporting the cylinder is formed on the block, a hanging end is formed on the outer surface of the cylinder, a pressing bolt couples the block and the valve cover so that the valve cover presses a front end of the cylinder while the hanging end of the cylinder is supported by being hung on the supporting end, a cylinder insertion hole into which an end of the cylinder is inserted is penetratingly formed on the block, the supporting end is formed by a step formed on an inner wall of the cylinder insertion hole, and the cylinder is inserted in the cylinder insertion hole so that the hanging end is supported by being hung on the supporting end.

In particular, according to the prior art, in order to maintain smooth pumping, oil such as lubricating oil, etc. is pumped by an oil feeder formed on a crank shaft, so as to supply the oil to the surface of the crank shaft along an oil path such as a groove or a hole formed on the crank shaft, and the supplied oil is supplied to a journal and bearing configuring the crank part, and a piston converting the rotation motion of the crank shaft to a linear reciprocating motion, respectively, so as to allow the piston to move smoothly in the cylinder and reduce abrasiveness.

According to the prior art, in addition, the piston and the connecting rod are coupled by a connecting pin, and the connecting rod and the journal are connected by a connecting pin. Therefore, in order to allow the piston to conduct linear reciprocating motion smoothly and to reduce abrasiveness of the parts, a crank shaft having an oil feeder for supplying oil must be used, and accordingly, the reciprocating piston type compressor of the prior art requires a feature for sealing so that the oil does not leak outside. Also, the compressor comprises a journal and a bushing on the outer circumferential surface of the crank shaft to help the crank shaft to rotate smoothly. Accordingly, there are problems such that the constitution of the compressor gets complex, and the crank shaft requires precise processing. Further, due to the increase in the number of parts, the assembly process becomes very complex and the manufacturing cost increases.

In order to solve the above problems, Japanese Patent Publication No. 5657055 excludes the feature of connecting the connecting rod and the journal with the connection pin. Furthermore, the prior art forms a groove in the diameter direction in a piston head. This groove prevents the piston ring from contacting the valve during the compression process. However, by the formation of steps, there are quite a lot of dead spaces in a cylinder space. Additionally, as re-expansion air is formed during a suction process, the compression performance is degraded by the air leakage.

Accordingly, the present inventors suggest an air compressor with a novel structure which can solve the above-mentioned problems.

It is an object of the present invention to provide a compact air compressor capable of improving the supporting force of a piston ring by high pressure during a compression process, thereby preventing the degradation of compression performance.

It is another object of the present invention to provide a compact air compressor with a piston structure capable of minimizing the loss of compression space.

It is yet another object of the present invention to provide a compact air compressor capable of operating the piston more stably.

The above objects and other inherent objects of the present invention can be all achieved by the present invention explained below.

According to the present invention, the compact air compressor comprises a block 40; a tubular cylinder 50 coupled to the block 40; a valve assembly 70 comprising a suction valve and a discharge valve to block a front end of the cylinder; a valve cover 80 covering the valve assembly to form a suction space 81a and a discharge space 81b on an upper part of the valve assembly 70; a piston 60 conducting linear reciprocating motion in the cylinder 50; a stator 21 coupled to the block 40; a lower housing 11 installed on a lower part of the stator 21; a rotor 25 located to rotate relative to the stator 21; a rotation shaft 30 coupled to the rotor 25 to rotate integrally with the rotor 25 so as to be rotatably supported to the block 40; a crank part 32 converting a rotation motion of the rotation shaft 30 to a linear reciprocating motion of the piston 60; a connecting rod 34 formed with an insertion cylindrical part 34A into which a journal bearing 33 installed on the crank part 32 is inserted, and a rod part 34B extended from the insertion cylindrical part 34A to the front; and an upper ball bearing 30A and a lower ball bearing 30B installed on an upper part and a lower part of the rotation shaft 30, respectively, wherein the piston 60 comprises a piston supporter 61 coupled to a front end of the rod part 34B, a stopper 63 coupled to the piston supporter 61, and a piston ring 62 installed between the piston supporter 61 and the stopper 63, and the outer circumferential part of the piston ring 62 is bent to the front, and a cross section thereof has a "U" shape.

According to the present invention, preferably, a part bent in the back of the "U" shaped form of the piston ring is supported by a piston ring supporting part 61B that protrudes to the front from the outer circumferential part of the piston supporter 61.

According to the present invention, preferably, a stopper bent part 63B having a bent shape in the outer circumferential part is formed in the back of the stopper 63, and the stopper bent part 63B supports a part bent in the front of the piston ring 62.

According to the present invention, preferably, the front of the stopper 63 has a pair of vertical cutting parts 63C which are cut in the vertical direction and have an inclined shape towards the diameter direction.

According to the present invention, preferably, the crank part 32 comprises a main body 32A, a journal 32B which protrudes to the upper part of the main body and is fit-pressed and coupled to an inner race of the journal bearing 33, and an eccentric hole 32C which is formed at the lower part of the main body 32A and is coupled to an upper end of the rotation shaft 30.

The present invention provides a compact air compressor capable of improving the supporting force of a piston ring by high pressure during a compression process, thereby preventing the degradation of compression performance, minimizing the loss of compression shape, and operating the piston more stably.

Fig. 1 is a perspective view illustrating a compact air compressor according to the present invention;

Fig. 2 is a plan view illustrating a compact air compressor according to the present invention;

Fig. 3 is an exploded perspective view illustrating a compact air compressor according to the present invention;

Fig. 4 is a cross-sectional view illustrating a compact air compressor according to the present invention;

Fig. 5 is a plan view illustrating a piston, a connecting rod, and a crank part of the compact air compressor according to the present invention; and

Fig. 6 is a cross-sectional view illustrating the piston and the connecting rod of the compact air compressor according to the present invention.

Hereinafter, the present invention will be explained in detail with reference to the drawings attached.

Fig. 1 is a perspective view illustrating a compact air compressor according to the present invention, Fig. 2 is a plan view illustrating a compact air compressor according to the present invention, Fig. 3 is an exploded perspective view illustrating a compact air compressor according to the present invention, and Fig. 4 is a cross-sectional view illustrating a compact air compressor according to the present invention.

According to Figs. 1 to 4, the compact air compressor according to the present invention comprises a lower housing 11, a stator 21, a rotor 25, a rotation shaft 30, a connecting rod 34, a block 40, a cylinder 50, a piston 60, a valve assembly 70, a valve cover 80, and a pressing bolt 90.

The lower housing 11 is a case for accommodating the assembly so as to protect an assembly of a stator 21 assembled with a block 40, in which a bottom part 11A and a ball bearing insertion cylindrical part 11B extending upwards from an outer edge of the bottom part 11A in a tubular shape having its upper part open, are protrudingly formed in the middle. Also, the fixing plate seat 22 coupled to a lower part of the lower housing 11 absorbs the vibration generated during pumping, and is supported by four vibration isolation springs 23 which prevent the vibration from being delivered to the housing 11.

The stator 21 generates an electromagnetic force for rotating the rotor 25 when power is applied. Additionally, a lower supporting frame 21A fixing the stator 21 is coupled and fixed to a lower housing 11.

The rotor 25 of the present invention is located inside the stator 21 to rotate relative to the stator 21. The rotation shaft 30 is coupled to the rotor 25 to rotate integrally with the rotor 25. As illustrated in Figs. 3 and 4, the rotation shaft 30 is coupled to the rotor 25 to rotate integrally with the rotor 25. Additionally, the rotation shaft 30 is rotatably supported to the block 40. In other words, the upper ball bearing 30A coupled to an upper part of the rotation shaft 30 is installed on the block 40 and thus supports the rotation of the rotation shaft 30. The lower ball bearing 30B inserted into a lower part of the rotation shaft 30 is installed in the ball bearing insertion cylindrical part 11B of the lower housing 11.

By means of these features, according to the present invention, the rotation shaft 30 may rotate freely by an upper ball bearing 30A and a lower ball bearing 30B, and thus the conventional oil fueling by a crank shaft is not required, and a structure for preventing oil leakage according to oil fueling is unnecessary. The constitution of the compressor is simpler than the conventional compressor which comprises a journal and a bushing on the outer circumferential surface of the crank shaft to help the crank shaft to rotate smoothly. The number of assembly parts may be reduced, thereby making the assembly process easier and reducing manufacturing cost. In particular, the present invention provides a ball bearing type compressor which does not require oil fueling. Therefore, even if the elasticity of the vibration isolation spring 23 increases in correspondence to the vertical motion along the rotation shaft according to the rotation of the rotation shaft 30, this does not bother the linear reciprocating motion of the piston 60. Accordingly, the noise caused by using a vibration isolation spring 23 having even stronger elasticity can be reduced more effectively. Also, it becomes possible to install a vibration isolation spring 23 without changing the structure of the fixing plate seat 22 coupled to a lower part of the lower housing 11.

The crank part 32 is installed on an upper part of the rotation shaft 30. The crank part 32 comprises a main body 32A, a journal 32B which protrudes to the upper part of the main body and is fit-pressed and coupled to an inner race of the journal bearing 33, and an eccentric hole 32C which is formed at the lower part of the main body 32A and is coupled to an upper end of the rotation shaft 30. In other words, an inner race of the journal bearing 33 is coupled to the journal 32B of the crank part 32, and an outer race of the journal bearing 33 is fit-pressed into an insertion cylindrical part 34A of the connecting rod 34. Accordingly, when the rotation shaft 30 rotates, the journal bearing 33 eccentrically rotates, and thus the piston 60 connected to the connecting rod 34 substantially conducts a linear reciprocating motion. This structure guarantees a stable reciprocating motion of the piston 60.

As such, the crank part 32 coupled to the rotation shaft 30 and the journal bearing 33 converts the rotation of the rotation shaft 30 into a linear reciprocating motion of the piston 60 together with the connecting rod 34.

The block 40 of the present invention supports the rotation shaft 30 and is coupled to the cylinder 50. According to the present invention, the cylinder 50 is not integrally formed with the block 40, but the cylinder 50 is formed separately to be coupled to a cylinder coupling part 42 of the block 40. The block 40 is formed to have a shaft supporting part 41 formed in a horizontal plate shape supported by the rotation shaft 30, and a cylinder coupling part 42 formed in a vertical plate shape perpendicular to the shaft supporting part 41. The cylinder 50 is insertedly installed on the cylinder insertion hole 45.

The cylinder 50 has the guide protrusion inserted into a guide groove formed on an outer surface of the cylinder 50 while being inserted into the cylinder insertion hole 45, so that the cylinder 50 is inserted into the cylinder insertion hole 45 moving only in the longitudinal direction.

Meanwhile, the present invention has a structure in which a suction muffler 43 and a discharge muffler 44 for reducing the noise caused by the pulsation of the fluid generated during pumping are integrally formed with the block 40. In other words, the suction muffler 43 and the discharge muffler 44 are respectively formed on both sides of a shaft supporting part 41 whose shaft is supported. In particular, the cylinder coupling part 42 is located between the suction muffler 43 and the discharge muffler 44. Each end of the suction muffler 43 and the discharge muffler 44 is connected to both sides of the shaft supporting part 41 to be mutually connected in a structure arranged in a "ㄷ" shape in the order of the suction muffler 43, the cylinder coupling part 42 and the discharge muffler 44, thereby reinforcing the strength of the block 40. An inlet introducing fluid and an outlet discharging the fluid are formed in the suction muffler 43. A suction filter for filtering impurities included in the air or refrigerant sucked in is coupled to the inlet of the suction muffler 43. A suction connection pipe 93 is connected to the outlet of the suction muffler 43, so that the suction muffler 43 is connected to a suction space 81a of the valve cover 80.

An inlet introducing fluid and an outlet discharging the fluid are formed in the discharge muffler 44. A discharge connection pipe 94 is connected to the inlet of the discharge muffler 44, so that the discharge muffler 44 is connected to a discharge space 81b of the valve cover 80 through the discharge connection pipe 94. Also, a pipe connection hole 44a is coupled to the outlet of the discharge muffler 44.

The cylinder 50 of the present invention is formed in a circular tubular shape so as to form a space compressing fluid such as air or refrigerant by the reciprocating motion of the piston 60. The piston 60 conducts the reciprocating motion inside the cylinder 50 so as to compress and discharge fluid such as the air or refrigerant sucked into the cylinder 50. The valve assembly 70 comprises a suction valve and a discharge valve to block a front end of the cylinder. This feature is disclosed in detail in a prior art, Korean Patent No. 10-1745471, and thus detailed explanation in this regard is omitted.

The valve cover 80 covers an upper part of the valve assembly 70 and the valve assembly so as to form a suction space 81a and a discharge space 81b on the upper part of the valve assembly 70. Inside the valve cover 80, a diaphragm 81 for dividing the suction space 81a and the discharge space 81b is formed and coupled to an upper part of the valve plate so as to cover the upper part of the valve plate in a state having a cover gasket therebetween for sealing. The present invention has a structure in which the valve cover 80 is coupled to the block 40 by a pressing bolt 90, so that first the valve cover 80 presses a valve plate 70, and then the cylinder 50 is pressed and coupled to the block 40.

The suction connection pipe 93 is a tube for connecting the suction muffler 43 to a suction space 81a of the valve cover 80. Referring to the drawings, the suction connection pipe 93 has an end connected to an outlet of the suction muffler 43, and the other end connected to an inlet formed in a suction space 81a of the valve cover 80. The discharge connection pipe 94 is a tube for connecting the discharge muffler 44 to a discharge space 81b of the valve cover 80. Referring to the drawings, the discharge connection pipe 94 has an end connected to an inlet of the discharge muffler 44, and the other end connected to an outlet formed in a discharge space 81b of the valve cover 80.

Meanwhile, the present invention has a structure in which the cylinder 50, the valve assembly 70 and the valve cover 80 are coupled being separated into a feet pipe and a feet so that the discharge connection pipe 94 can be easily assembled during the process of being coupled to the block 40 by a pressing bolt 90. Detailed explanation in this regard is disclosed in detail in a prior art, Korean Patent No. 10-1745471, and thus shall be omitted.

Fig. 5 is a plan view illustrating a piston 60, a connecting rod 34, and a crank part 32 of the compact air compressor according to the present invention, and Fig. 6 is a cross-sectional view illustrating the piston 60 and the connecting rod 34 of the compact air compressor according to the present invention.

As illustrated in Figs. 5 and 6, the connecting rod 34 comprises a rod part 34B at one side of the insertion cylindrical part 34A, and has a coupling hole 34C formed in one side of the rod part 34B. Also, a piston 60 is coupled to a rod part 34B of the connecting rod 34 inserted into the cylinder 50, and may be coupled in a manner of fastening a coupling bolt 64 to a coupling hole 34C. Various well-known coupling manners other than the manner of coupling with a coupling bolt 64 as illustrated above may be applied.

As such, the connecting rod 34 comprises a rod part 34B at one side of the insertion cylindrical part 34A, thereby avoiding the conventional coupling by a connecting pin. Accordingly, the number of parts of the piston 60 and connecting rod 34 may be reduced. In addition, oil does not have to be fueled to the connecting pin, etc., and thus constitutional elements according to oil fueling can be excluded.

The piston 60 of the present invention comprises a piston supporter 61 coupled to a front end of the rod part 34B, a stopper 63 coupled to the piston supporter 61, and a piston ring 62 installed between the piston supporter 61 and the stopper 63. The piston supporter 61 comprises a through hole 61A which is formed in the middle to have a coupling bolt 64 penetrate therethrough, and a piston ring supporting part 61B formed to protrude to the front from the outer circumferential part of the piston supporter 61. The piston ring 62 has a ring shape, and when the piston ring 62 is coupled between the piston supporter 61 and the stopper 63, the outer circumferential part thereof is bent to the front and thus the cross section of the piston ring 62 has a "U" shape as illustrated in Fig. 6. The part bent in the back of the "U" shaped form of the piston ring 62 is supported by the piston ring supporting part 61B.

The stopper 63 has a circular ring shape, and comprises a through hole 63A formed in the middle, a bent-shaped stopper bent part 63B formed in the outer circumferential part at the back, and a pair of vertical cutting parts 63C which are cut in the vertical direction and have an inclined shape in the diameter direction. A coupling bolt 64 penetrates into the through hole 63A so that the coupling bolt 64 can be coupled to the coupling hole 34C of the rod part 34B. Therefore, in response to the abrasion of the piston 60 that may occur by using the compact air compressor of the present invention for a long period of time, the piston 60 may be replaced conveniently by disassembling a coupling bolt 64, thereby reducing cost, and making the assembly more convenient and extending the lifespan of the compressor.

The stopper bent part 63B is a part which supports a part bent in the front of the piston ring 62 so that the piston ring 62 can maintain the "U" shaped cross section. This shape prevents the air leakage when the piston ring 62 compresses the air, thereby improving the compression performance.

As illustrated in Fig. 3, the vertical cutting part 63C has both parts in the front of the stopper 63 cut in the vertical direction to have an inclined shape towards the diameter direction. According to prior art, the entire circumferential part in the front of the piston is cut, but this shape may cause loss of compression space by the steps in the upper part and lower part of the front of the piston. The shape of the vertical cutting part 63C allows the present invention to prevent loss of compression space.

The detailed description of the present invention described as above simply explains examples for understanding the present invention, but does not intend to limit the scope of the present invention. The scope of the present invention is defined by the accompanying claims. Additionally, it should be construed that simple modifications or changes of the present invention fall within the scope of the present invention.

Claims

A compact air compressor, comprising:

a block 40;

a tubular cylinder 50 coupled to the block 40;

a valve assembly 70 comprising a suction valve and a discharge valve to block a front end of the cylinder;

a valve cover 80 covering the valve assembly to form a suction space 81a and a discharge space 81b on an upper part of the valve assembly 70;

a piston 60 conducting a linear reciprocating motion in the cylinder 50;

a stator 21 coupled to the block 40;

a lower housing 11 installed on a lower part of the stator 21;

a rotor 25 located to rotate relative to the stator 21;

a rotation shaft 30 coupled to the rotor 25 to rotate integrally with the rotor 25 so as to be rotatably supported to the block 40;

a crank part 32 converting a rotation motion of the rotation shaft 30 to a linear reciprocating motion of the piston 60;

a connecting rod 34 formed with an insertion cylindrical part 34A into which a journal bearing 33 installed on the crank part 32 is inserted, and a rod part 34B extended from the insertion cylindrical part 34A to the front; and

an upper ball bearing 30A and a lower ball bearing 30B installed on an upper part and a lower part of the rotation shaft 30, respectively,

wherein the piston 60 comprises a piston supporter 61 coupled to a front end of the rod part 34B, a stopper 63 coupled to the piston supporter 61, and a piston ring 62 installed between the piston supporter 61 and the stopper 63, and the outer circumferential part of the piston ring 62 is bent to the front, and a cross section thereof has a "U" shape.
The compact air compressor according to claim 1, wherein a part bent in the back of the "U" shaped form of the piston ring is supported by a piston ring supporting part 61B that protrudes to the front from the outer circumferential part of the piston supporter 61.
The compact air compressor according to claim 1, wherein a stopper bent part 63B having a bent shape in the outer circumferential part is formed in the back of the stopper 63, and the stopper bent part 63B supports a part bent in the front of the piston ring 62.
The compact air compressor according to claim 1, wherein the front of the stopper 63 has a pair of vertical cutting parts 63C which are cut in the vertical direction and have an inclined shape towards the diameter direction.
The compact air compressor according to claim 1, wherein the crank part 32 comprises a main body 32A, a journal 32B which protrudes to the upper part of the main body and is fit-pressed and coupled to an inner race of the journal bearing 33, and an eccentric hole 32C which is formed at the lower part of the main body 32A and is coupled to an upper end of the rotation shaft 30.