# Patent

## Title
Reciprocating motor

## Abstract

A reciprocating motor including a piston operatively connected with a magnet unit, a cylinder having an open end to receive the piston and having a groove formed at a circumference along an outer surface thereof near the open end, a stator assembly positioned around the cylinder and cooperating with the magnet unit to allow the piston to reciprocate within the cylinder, and a ring member being placed into the groove of the cylinder to be frictionally urged towards a portion of the stator assembly to maintain contact with and hold the portion of the stator assembly in place on the outer surface of the cylinder.

## Background
This application is a continuation application of U.S. application Ser. No. 10/494,952 filed on May 7, 2004, now U.S. Pat. No. 7,285,880 and claims priority to PCT Application No. PCT/KR2003/001870 filed on Sep. 9, 2003, and Korean Patent Application No. 10-2002-0054718 filed in Korea on Sep. 10, 2002. The entire contents of these applications are incorporated by reference in its entirety.


TECHNICAL FIELD
The present invention relates to a reciprocating motor and, more particularly, to a reciprocating motor capable of preventing a stator from moving in an axial direction.
BACKGROUND ART
In general, a reciprocating motor includes an outer stator and an inner stator which are disposed with a certain interval therebetween and a magnet frame having a magnet deposed between the outer stator and the inner stator, so that when power is applied to a winding coil wound around the stator, the magnet frame is linearly and reciprocally moved by an interaction of the stator and the magnet frame. The reciprocating motor is commonly used for a reciprocating compressor, and as its piston and the magnet frame are connected, the piston is reciprocally moved.
FIG. 1 is a sectional view of a conventional reciprocating motor, and FIG. 2 is a sectional view taken along line II-II of FIG. 1.
The conventional reciprocating motor includes an outer stator 104 in a cylindrical form with a plurality of thin lamination sheets laminated and a winding coil 102 wound therein, an inner stator 106 disposed at an inner circumferential surface of the outer stator 104 with a certain air gap therebetween and having a cylindrical form with a plurality of thin lamination sheets laminated, a magnet 108 disposed in a circumferential direction between the outer stator 104 and the inner stator 106, and a magnet frame 110, at which a plurality of the magnets 108 are fixed, being connected to a piston 118 to be reciprocally moved.
The piston 118 is disposed in a cylinder 120 and linearly and reciprocally moved according to the operation of the motor, compressing a fluid.
The outer stator 104 is supported by a support frame 124, and a support ring 114 is inserted at both sides thereof in order to maintain the cylindrical form.
Also, the inner stator 106 is fixed at an outer circumferential surface of the cylinder 120 by a press-fit method or an adhesive, and a support ring 116 is inserted at both sides of the inner stator 106 in order to support the plurality of lamination sheets.
The operation of the conventional reciprocating motor will now be described.
When power is applied to the winding coil 102, a flux is formed around the winding coil 102, forming a closed loop along the outer stator 104 and the inner stator 106. The magnet is linearly moved to an axial direction by the interaction of the flux formed between the outer stator 104 and the inner stator 106 and the flux formed by the magnet 108. When the direction of the electric current is changed alternately, the flux direction of the winding coil 102 is changed so that the magnet 108 is linearly and reciprocally moved.
According to the movement of the magnet 108, the magnet frame 110 to which the magnet 108 is fixed is linearly and reciprocally moved, and thus, the piston 118 is linearly and reciprocally moved.
However, the conventional art has a problem that because the inner stator 106 is fixed at the outer circumferential surface of the cylinder 120 by the press-fit method, the inner stator 106 is moved along with the magnet 108 in the axial direction by the vibration generated when the magnet 108 is moved reciprocally.
In addition, in the case that the inner stator 106 is fixed at the outer circumferential surface of the cylinder 120 by the adhesive and so on, an assembly operation is not easy.
DISCLOSURE OF THE INVENTION
Therefore, it is an object of the present invention to provide a reciprocating motor capable of improving reliability of a motor by preventing an inner stator from moving in an axial direction caused by vibration of a linearly moved magnet as the motor is used for a long time.
To achieve the above object, there is provided a reciprocating motor including: an outer stator; an inner stator disposed at an inner circumferential surface of the outer stator with an air gap therebetween and mounted at an outer circumferential surface of a cylinder; a magnet disposed to be linearly movable between the outer stator and the inner stator; and a locking unit installed at the lateral face of the inner stator and preventing the inner stator from moving in an axial direction.
The locking unit includes a locking groove formed at the outer circumferential surface of the cylinder in a circumferential direction and a locking ring inserted into the locking groove and adhered closely at the lateral face of the inner stator.
The locking groove is formed in a way that its one side is at a right angle and the other side narrows inwardly, forming a tilt angle.
An inner side of the locking ring is inserted into the locking groove and an outer side thereof is supported at the lateral face of the inner stator.
In order to achieve the above object, there is also provided a reciprocating motor including: an outer stator; an inner stator disposed at the inner circumferential surface of the outer stator with a certain air gap and disposed at the outer circumferential surface of a cylinder; a magnet disposed to be linearly movable between the outer stator and the inner stator; and a locking unit consisting of a locking groove formed at the outer circumferential surface of the cylinder in a circumferential direction, and a locking ring elastically supported at the locking groove and at the lateral face of the inner stator to prevent the inner stator from moving in an axial direction.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a conventional reciprocating motor;
FIG. 2 is a sectional view taken along line II-II of FIG. 1;
FIG. 3 is a sectional view of a reciprocating motor according to a first embodiment of the present invention;
FIG. 4 is an enlarged view of a part ‘A’ of FIG. 3 showing a locking unit of an inner stator according to the first embodiment of the present invention;
FIG. 5 is a sectional view of another case of the locking groove of the locking unit in accordance with the present invention;
FIG. 6 is a perspective view of a locking ring according to the first embodiment of the present invention;
FIG. 7 is a perspective view of a locking ring of a locking unit according to a second embodiment of the present invention; and
FIG. 8 is a sectional view of a locking unit according to the second embodiment of the present invention.



MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS
A first embodiment of the present invention will now be described with reference to the accompanying drawings.
There can be a plurality of embodiments of the reciprocating motor in accordance with the present invention, and a preferred embodiment will now be described.
FIG. 3 is a sectional view of a reciprocating motor according to the present invention.
The reciprocation motor includes: a cylindrical outer stator 4 fixed at a support frame 2; an inner stator 6 disposed at an inner circumferential surface of the outer stator 4 with a certain air gap 5 therebetween and forming a flux therebetween; a winding coil 8 wound in the outer stator 4 or the inner stator 6; a magnet 10 disposed to be linearly movable between the outer stator 4 and the inner stator 6; a magnet frame 12 connected between the magnet 10 and an element desired to be reciprocally moved and transferring a reciprocal movement of the magnet 10 to the element; and a locking unit for preventing the inner stator 6 from moving in an axial direction.
In case that the reciprocating motor is applied to a reciprocating compressor, the element is a piston 18, for example, which is moved linearly and reciprocally in the cylinder 16 for a compressing operation. As shown, the cylinder 16 has an opened end 17 to receive the piston 18 and another end 19 opposing the opened end 17.
The outer stator 4 has a cylindrical form as a plurality of lamination sheets are laminated radially in the circumferential direction, and is supported by the support frame 2.
The inner stator 6 has a cylindrical form with a plurality of lamination sheets laminated radially in the circumferential direction, has a support ring 20 inserted at both sides to support the lamination sheets, and is mounted at the outer circumferential surface of the cylinder 16.
That is, the inner circumferential surface of the inner stator 6 is mounted at the outer circumferential surface of the cylinder 16. One side of the inner stator 6 is supported by the support frame 2 or a protruded portion of the cylinder 16, and the other side is supported by the locking unit which prevents the inner stator 6 from moving in an axial direction.
As shown in FIG. 4, the locking unit includes a locking groove 30 formed at the outer circumferential surface of cylinder 16 in a circumferential direction and a locking ring 32 inserted into the locking groove 30 and adhered closely to the lateral face 34 of the inner stator 6.
The locking groove 30 is formed at the outer circumferential surface of the cylinder 16 in the circumferential direction with a certain width and depth, and has a greater width (N) than a thickness (L) of the locking ring 32 so that the locking ring 32 can be easily inserted thereinto. That is, the width (N) of the locking groove 30 is the sum of the thickness (L) of the locking ring 32 and the inward width (M) from the lateral face 34 of the inner stator 6.
As shown in FIG. 4, the locking groove 30 is formed such that both sides 36 and 38 are at a right angle, or such that, as shown in FIG. 5, one side 40 is at a right angle and the other surface 42 is at a tilt angle, forming a slant surface with the width of the locking groove 30 becoming narrow inwardly. FIG. 5 also illustrates the groove 30 is formed at a circumference along an outer surface 15 of the cylinder 16 near the opened end 17.
In the case that the locking groove 30 has the slant surface, it is easy to insert the locking ring 32, so that the assembling is convenient. In more detail, and as shown in FIG. 5, the locking groove 30 includes a groove opening having a first edge 41 and a second edge 43 in which the first edge 41 is closer to the open end 17 (see FIG. 3) of the cylinder 16 than the second edge 43.
As shown in FIG. 6, the inner surface of the locking ring 32 is adhered closely to the side of the locking groove 30 and its outer surface is supported at the lateral face 34 of the inner stator 6. And, an opening portion 34 is formed at the one side of the locking ring 32 to facilitate assembling and has a certain elastic force in the opening direction. That is, in assembling after the opening portion 34 is opened, the locking ring 32 is inserted into the locking groove 30.
The locking ring is formed so that its right and left portions are asymmetrical centering on the opening portion, and is formed so that its right and left portions are asymmetrical centering on the opening portion. Also, at least one of the locking rings is disposed at the locking groove.
The operation of the reciprocating motor according to the present invention will now be described.
When power is applied to the winding coil 8, a flux is formed around the winding coil 8, forming a closed loop along the outer stator 4 and the inner stator 6. The magnet 10 is linearly moved in an axial direction by the interaction of the flux formed between the outer stator 4 and the inner stator 6 and the flux formed by the magnet 10.
Also, when the direction of the electric current applied to the winding coil 8 is alternately changed, the flux direction of the winding coil 8 is changed so that the magnet 10 is linearly and reciprocally moved.
Then, as the magnet frame 12 with the magnet 10 fixed thereto is linearly and reciprocally moved, an element such as the piston 18 is linearly reciprocally moved.
At this time, the locking unit prevents the inner stator 6 disposed at the outer circumferential surface of the cylinder 16 from moving in the axial direction which is caused by the vibration generated during the linear and reciprocating movement of the magnet 10.
That is, the axial movement of the inner stator 6 in the axial direction is prevented because the locking ring 32 is adhered closely to the lateral face 34 of the inner stator 6 in a state of being inserted in the locking groove 30 formed at the outer circumferential surface of the cylinder 16.
FIG. 7 is perspective view of the locking ring of a locking unit according to a second embodiment of the present invention, and FIG. 8 is a sectional view of a locking unit according to the second embodiment of the present invention.
A locking unit according to the second embodiment of the present invention includes a locking groove 50 formed at an outer circumferential surface of the cylinder 16 in the circumferential direction, and a locking ring 52 elastically supported in the locking groove 50 and at the lateral face 34 of the inner stator 6 and preventing the inner stator 6 from moving in the axial direction.
One side of the locking groove 50 is positioned on the same straight line as the lateral face 34 of the inner stator 6, and the locking groove 50 is formed to have a greater width than a thickness of the locking ring 52.
The locking ring 52 includes a ring portion 54 supported at the lateral face 34 of the inner stator 6 and having an opening portion 62 at the one side thereof and an elastic support portion 56 extended with a certain interval inwardly from the inner circumferential surface of the ring portion 54 so as to be elastically supported in the locking groove 50.
Herein, the elastic support portion 56 includes a first support portion 58 extended at a certain tilt angle inwardly from the ring portion 54, and a second support portion 60 bent at a certain angle from the first support portion 58 so as to provide an elastic force in such a direction that the first support portion 58 and the second support portion 60 are smoothed.
The locking unit according to the second embodiment prevents the inner stator 6 from moving in the axial direction since the ring portion 54 of the support ring 52 is adhered closely to the lateral face 34 of the inner stator 6 and the elastic support portion 56 is elastically supported at the locking groove 50 of the cylinder 16.
As described above, the reciprocating motor in accordance with the present invention can improve reliability of the motor by preventing the inner stator from moving in the axial direction in the way of forming the locking groove at the outer circumferential surface of the cylinder, inserting the locking ring into the locking groove and supporting the locking ring at the lateral face of the inner stator.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

## Claims

1. A reciprocating motor, comprising:
a piston operatively connected with a magnet unit;
a cylinder having an open end to receive the piston and having a groove formed at a circumference along an outer surface thereof near the open end;
a stator assembly positioned around the cylinder and cooperating with the magnet unit to allow the piston to reciprocate within the cylinder; and
a ring member being placed into the groove of the cylinder to be frictionally urged towards a portion of the stator assembly to maintain contact with and hold the portion of the stator assembly in place on the outer surface of the cylinder.

2. The motor of claim 1, wherein the stator assembly comprises:
an inner stator at the outer surface of the cylinder; and
an outer stator having a coil assembly and located around an outer surface of the inner stator with an air gap therebetween to accommodate and allow movement of the magnet unit to cause the piston to reciprocate due to electromagnetic energy generated between the coil assembly and the magnet unit.

3. The motor of claim 2, wherein the portion of the stator assembly is the inner stator.

4. The motor of claim 3, wherein the groove comprises:
a groove bottom;
a groove opening having a first edge and a second edge, the first edge being closer to the open end of the cylinder than the second edge; and
a first inner wall that starts from the first edge, slopes into the groove away from the open end of the cylinder and terminates at the groove bottom.

5. The motor of claim 4, wherein the groove bottom comprises:
a bottom wall having a width that is smaller than a width of the groove opening defined between the first edge and the second edge.

6. The motor of claim 5, wherein the groove further comprises:
a second inner wall that is between the second edge and the bottom wall, and that opposes the first inner wall.

7. The motor of claim 6, wherein the inner stator is positioned on the cylinder such that an end of the inner stator partially covers the groove opening above the second inner wall of the groove.

8. The motor of claim 7, wherein an amount that the end of the inner stator partially covers the groove opening is less that the width of the groove bottom.

9. The motor of claim 4, wherein the ring member placed in the groove has an edge portion in contact with a central area of the first inner wall.

10. The motor of claim 9, wherein a portion of the ring member being inserted into the groove has a thickness smaller than a width of the groove bottom.

11. A reciprocating motor comprising:
a cylinder having a first end with an opening and a second end opposing the first end;
a stator located around the cylinder, the stator having an outer portion and an inner portion with a gap therebetween; and
a fixation element that fixes the inner portion of the stator to the cylinder by being inserted into a channel of the cylinder formed along a circumferential portion near the first end.

12. The motor of claim 11, further comprising:
a piston received in the opening at the first end of the cylinder; and
a magnet connected with the piston and positioned in the gap.

13. The motor of claim 11, wherein the channel comprises:
a channel bottom;
a channel opening having a first edge and a second edge, the first edge being closer to the opening of the cylinder than the second edge; and
a first inner wall that starts from the first edge, slopes into the channel away from the opening of the cylinder and ends at the channel bottom.

14. The motor of claim 13, wherein the inner portion is positioned on the cylinder such that an end of the inner portion extends over the channel opening beyond the second inner wall of the channel.

15. The motor of claim 14, wherein a distance that the end of the inner stator extends over the channel opening is smaller than a bottom width of the channel bottom.

16. The motor of claim 11, wherein the fixation element placed in the groove has an edge that abuts with a middle region of an inclined inner wall of the channel.

17. The motor of claim 16, wherein a portion of the fixation element being inserted into the channel has a thickness that is less than a width of the channel bottom.

18. A piston housing for a motor with a stator assembly, the housing comprising:
a hollow cylindrical body having an open end and a closed end that opposes the open end to allow a piston to reciprocate therein; and
a groove formed along an outer circumference of the hollow cylindrical body adjacent to the open end,
wherein the groove comprises a groove opening, a groove bottom, and an inclined wall, the inclined wall being sloped from the groove opening towards the groove bottom in a direction away from the open end of the hollow cylindrical body, and
wherein a particular angle of the inclined wall facilitates insertion of an annular element into the groove and presses the inserted annular element towards a portion of the stator assembly to secure the stator assembly to the hollow cylindrical body.

19. The housing of claim 18, wherein the inclined wall has an intermediate portion that is in frictional contact with the annular element inserted into the groove.

20. The housing of claim 18, wherein a width of the groove bottom is greater than a width of at least a portion of the annular element being inserted into the groove.