Patent Grant
7553144
This application is based on Japanese Patent Application No. 2006-129216 filed on May 8, 2006, the contents of which are incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a gas compressor that rotates two rotors to suck, compress, and discharge gas.
2. Description of the Related Art
There has been conventionally known a gas compressor having two rotary rotors housed in a housing (e.g., JP-A-2005-220785). In this gas compressor, one end of the rotary shaft of each of the rotors is supported by a bearing hole of one housing head and the other end thereof is supported by a bearing hole of the housing.
To increase the discharge pressure of the gas compressor to high pressure, it is necessary to reduce a clearance between the rotors and the housing and to improve compression efficiency. In particular, in a gas compressor that does not use oil for improving seal performance between the rotors and the housing, it is greatly necessary to decrease the clearance. For this reason, the relative position of the housing to the housing head is usually determined by the use of positioning pins to improve the coaxial degree to which the bearing hole of the housing is coaxial with the bearing hole of the housing head, thereby the clearance between the rotors and the housing is decreased.
However, in the foregoing compressor, the accuracies with which pin holes are formed in the housing head and the housing are added to the accuracy of the coaxial degree to which the housing head is coaxial with the housing. Thus, the accuracy with which the housing head is coaxial with the housing deteriorates. Further, because bearing holes corresponding to the rotary shafts of the two rotors are formed in one housing head, the accuracies with which the respective bearing holes are formed are effected to the coaxial degree of the two bearing holes formed in the housing head. Thus, this presents a problem that the clearance between the rotors and the housing becomes large.
Moreover, because the pin holes need to be formed in the housing and the housing head with high accuracy, there is presented a problem that manufacturing cost increases. Further, when the housing head is positioned with respect to the housing by the use of a positioning pin, it takes much time to combine the housing head with the housing. This presents a problem that steps required to combine the housing head with the housing increase.
In view of the foregoing problems, it is an object of the present invention to provide a gas compressor capable of improving an accuracy with which housing heads are combined with a housing.
Further, it is another object of the present invention to reduce steps required to combine the housing heads with the housing.
According to an aspect of the present invention, a gas compressor includes a housing having a suction port and a discharge port, housing heads disposed to define an internal space with the housing, and two rotors housed in the internal space. The two rotors are rotatable around their rotary axes to form in the internal space a compression chamber in which gas sucked from the suction port is compressed, thereby discharging the compressed gas from the discharge port. Furthermore, the housing has an inner wall surface opposed to at least outer peripheral surfaces of the two rotors, and the housing heads are provided in correspondence to the respective rotors and have inner wall surfaces at end portions, opposed to one-end portions of the respective rotors. One end portion of a rotary shaft of each rotor is supported by the housing, and other end portion of the rotary shaft of each rotor is supported by the housing heads. In addition, the housing heads have a first outer peripheral portion corresponding to the inner wall surface of the housing and a second outer peripheral portion larger than the first outer peripheral portion, and the first outer peripheral portion of the housing heads is constructed to be fitted onto the inner wall surface of the housing.
Because the first outer peripheral portion of the housing heads is constructed to be fitted onto the inner wall surface of the housing, the inner wall surface of the housing can be used as a positioning hole for positioning the housing heads with respect to the housing. Thus, accuracies with which pin holes are formed in the housing and the housing heads are not added to the accuracies with which the housing heads are coaxial with housing. Hence, the coaxial degrees to which the housing heads are coaxial with the housing can be improved. As a result, the accuracies with which the housing heads are assembled with the housing can be improved and the clearances of the respective parts can be effectively reduced. Accordingly, it is possible to sufficiently reduce the quantity of leak of gas and to improve volume efficiency. In addition, it is possible to reduce steps required to combine the housing head with the housing.
For example, the housing heads corresponding to the respective rotors may have adjacent portions which overlap with each other in a direction parallel with a rotary axis of the rotors. Alternatively, the two rotors may be a male rotor and a female rotor, which have spiral projections formed on their outer peripheral surfaces to be engaged with each other.
Furthermore, the housing heads may be arranged without defining the compression chamber, or may be arranged to define the compression chamber.
Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments when taken together with the accompanying drawings. In which:
A first embodiment of the present invention will be described with reference to
The screw compressor of this embodiment includes a pair of screw-shaped male rotor 1 and female rotor 2, a rotation transmission mechanism 3 for rotating and driving the rotors 1, 2 by the rotational force of a driving source, a casing 4 for housing the pair of rotors 1, 2 and the rotation transmission mechanism 3, an input shaft 5 for receiving the rotational force of the driving source, and the like. In
The male rotor 1 and the female rotor 2 are respectively formed in the shape of a male screw so as to engage with each other, such that the male screw is formed of a spiral projection on the outer peripheral surface of each rotor. As shown in
The casing 4 includes a lubrication box 6, a rotor housing 7, housing heads 8, 9, and a head cover 10 which are arranged in this order from a position closer to the motor 50. The lubrication box 6, the rotor housing 7, and the head cover 10 are firmly assembled with each other with fastening means such as bolts or the like (not shown). The rotors 1, 2 and the rotation transmission mechanism 3 are housed in the casing 4 in a state in which they are separated from each other. The pair of rotors 1, 2 is housed in the cylindrical rotor housing 7 and the rotation transmission mechanism 3 is housed in the lubrication box 6. The rotor housing 7 is open on its one end side and the housing heads 8, 9 are arranged on the open side.
In the lubrication box 6, there is provided with a lubrication oil space 11 for receiving the rotation transmission mechanism 3 and a lubrication oil to be supplied to the rotation transmission mechanism 3. Oil having the same viscosity as an engine oil, for example, may be used as the lubrication oil. Gears constructing the rotation transmission mechanism 3 are sprayed with the lubrication oil in the lubrication oil space 11, thereby being lubricated.
The rotor housing 7 and the housing heads 8, 9 form an inner space and this inner space constructs a rotor chamber 12 in which the pair of rotors 1, 2 are housed. The rotor housing 7 has a suction port 7a for sucking air into the rotor chamber 12 and a discharge port 7b for discharging the air outside the rotor chamber 12. The suction port 7a is formed on a side of the housing head 8, 9 in an end portion of the rotor housing 7 in the axial direction, and the discharge port 7b is formed on a side of the lubrication box 6 in an end portion of the rotor housing 7 in the axial direction.
A small clearance is formed between the outer peripheral ends of the rotors 1, 2 and the inner wall 12a opposed to the outer peripheral surfaces of the rotors 1, 2, thereby a seal structure is constructed. A compression chamber 12b for compressing air sucked from the suction port 7a is formed between grooves formed on the outer peripheries of the rotors 1, 2 and the inner wall 12a of the rotor chamber 12.
In the lubrication box 6, an input shaft 5 for receiving a rotational force from the motor 50 is disposed. A first bearing 13 is provided in the lubrication box 6 on a side of the motor 50 side, and a second bearing 14 is provided in the lubrication box 6 on a side of the lubrication oil space 11. The input shaft 5 is supported by the lubrication box 6 via these bearings 13, 14. Moreover, a first oil seal 15 for preventing lubrication oil supplied to the first and second bearings 13, 14 from flowing outside the casing 4 is fitted in an insertion hole which is formed in the lubrication box 6 and in which the input shaft 5 is inserted.
As described above, the rotors 1, 2 are rotated and driven by the rotation transmission mechanism 3. The rotation transmission mechanism 3 is constructed so as to transmit the rotation of the input shaft 5 to the male rotor rotary shaft 1a and the female rotor rotary shaft 2a and to rotate the pair of rotors 1, 2 synchronously. The rotation transmission mechanism 3 includes a coupling 16, first and second gears 17, 18, and the like. The coupling 16 transmits the rotation of the input shaft 5 driven by the motor 50 to the male rotor rotary shaft 1a in a coaxial manner, the gears 17, 18 transmit the rotation transmitted from the coupling 16 to the male rotor rotary shaft 1a and the female rotor rotary shaft 2a. The first and second gears 17, 18 are timing gears for synchronously rotating the pair of rotor gears 1, 2.
The male rotor rotary shaft 1a and the female rotor rotary shaft 2a have their one ends rotatably supported by the rotor housing 7 via third and fourth bearings 19, 20 and have their other ends rotatably supported by the housing heads 8, 9 via fifth and sixth bearings 21, 22. In the housing 7, a bearing hole for arranging the third and fourth bearings 19, 20 is formed. The first housing head 8 is provided with a bearing hole for arranging the fifth bearing 21. Furthermore, the second housing head 9 is provided with a bearing hole for arranging the sixth bearing 22.
Insertion holes, which are formed in the rotor housing 7 and into which the rotary shafts 1a, 2a are inserted, have second and third oil seals 23, 24 fitted thereon. The oil seals 23, 24 are provided to prevent the lubrication oil supplied to the third and fourth bearings 19, 20 from leaking into the rotary chamber 12. Further, insertion holes, which are formed in the housing heads 8, 9 and into which the rotary shafts 1a, 2a are inserted, also have fourth and fifth oil seals 25, 26 fitted thereon. The oil seals 25, 26 are provided to prevent grease sealed in the fifth and sixth bearings 21, 22 from leaking into the rotary chamber 12.
Next, the structure of the housing heads 8, 9 will be described.
As shown in
A head cover 10 is disposed outside the housing heads 8, 9. The head cover 10 has a depressed portion in which the second outer peripheral portions 8b, 9b of the housing heads 8, 9 are fitted. The head cover 10 functions as a cover for covering the surfaces opposite to the rotors 1, 2 in the housing heads 8, 9. The housing heads 8, 9 are covered with the head cover 10, thereby being closed from the outside.
Next, the operation of the screw compressor of this embodiment will be described.
When the pair of rotors 1, 2 are synchronously rotated by the rotation transmission mechanism 3, air is sucked from the suction port 7a formed on the side of the housing heads 8, 9 in the rotor housing 7, into the compression chamber 12b. At this time, with the rotation of the pair of rotors 1, 2, the compression chamber 12b moves from the housing heads 8, 9 to the lubrication oil space 11 to decrease its volume. Thus, air in the compression chamber 12b is gradually compressed and pressurized and is moved to the lubrication oil space 11.
When the rotational angles of the pair of rotors 1, 2 reach specified angles, the compression chamber 12b reaches the discharge port 7b formed on the side of the lubrication oil space 11 in the rotor housing 7, thereby the compression chamber 12b, which has been tightly closed, is brought to a state opened at the discharge port 7b. Thus, the air compressed in the compression chamber 12b is discharged from the discharge port 7b.
According to the first embodiment, when the first outer peripheral portions 8a, 9a of the housing heads 8, 9 are inserted into the end portions of the rotor chamber 12 of the rotor housing 7 in which the rotors 1, 2 are housed, the housing heads 8, 9 can be assembled to the rotor housing 7. At this time, because the respective housing heads 8, 9 are fitted in the inner wall 12a of the rotor chamber 12, the positions of the respective housing heads 8, 9 to the housing 7 are determined. In this manner, because the inner wall 12a of the rotor chamber 12 is used as a positioning hole for positioning the housing heads 8, 9 to the rotor housing 7, the accuracies with which pin holes are formed in the rotor housing 7 and the housing heads 8, 9 are not added to the accuracy with which the housing heads 8, 9 are coaxial with the housing 7. Thus, this can improve the coaxial degree to which the housing heads 8, 9 are coaxial with the rotor housing 7.
Moreover, the housing heads 8, 9 are divided from each other and bearing holes corresponding to the two rotors 1, 2 are formed in the different housing heads 8, 9. Thus, the coaxial degree to which two bearing holes after combining the housing heads 8, 9 with the rotor housing 7 are coaxial with each other can be improved, thereby the clearance between the rotors 1, 2 and the inner wall 12a of the rotor chamber 12 can be decreased and hence compression efficiency can be improved.
In this embodiment, the housing heads 8, 9 are separated from each other, so gas in the rotor chamber 12 may leak outside from the clearance between the housing heads 8, 9. To prevent the gas from leaking outside, the head cover 10 is arranged to cover the housing heads 8, 9. Therefore, the rotor chamber 12 can be shut from the outside and hence the hermeticity of the rotor chamber 12 can be ensured.
Still further, the first outer peripheral portions 8a, 9a of the housing heads 8, 9 move along the inner wall 12a of the rotor chamber 12. Therefore, the housing heads 8, 9 can be positioned also in the axial direction. With this, it is easy to regulate the clearance of the end surfaces of the rotors 1, 2 and hence to reduce the number of steps required to assemble the housing heads 8, 9 to the rotor housing 7.
Still further, the inner wall 12a of the rotor chamber 12 is used as the positioning hole for positioning the housing heads 8, 9 to the rotor housing 7. Thus, this can eliminate the need for forming pin holes for positioning the rotor housing 7 and the housing heads 8, 9, and hence can reduce the cost required to form the rotor housing 7 and the housing heads 8, 9.
Next, a second embodiment of the present invention will be described with reference to
In the second embodiment, as shown in
As described above, the adjacent housing heads 8, 9 overlap each other in the axial direction of the rotors 1, 2, so the contact area between the housing heads 8, 9 can be increased and hence the clearance between the housing heads 8, 9 can be decreased. With this, it is possible to prevent the gas in the rotor chamber 12 from leaking outside from the clearance between the housing heads 8, 9 and hence to prevent the efficiency of the compressor from decreasing. Moreover, in the screw compressor using the screw rotors 1, 2, the pressure in the rotor chamber 12 is increased as compared with a Root's compressor, so the construction of this embodiment is especially effective.
Next, a third embodiment of the present invention will be described with reference to
According to the foregoing construction of the third embodiment, the end surfaces of the housing heads 8, 9 are not used as the surfaces constructing the compression chamber 12. Thus, it is possible to prevent the gas in the rotor chamber 12 from leaking outside from the clearance between the housing heads 8, 9. The construction of the third embodiment may be combined with the construction of the second embodiment. That is, the overlapped structure of the first and second housing heads 8, 9 described in the second embodiment may be used for the housing heads 8, 9 of the third embodiment.
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.
For example, in the respective foregoing embodiments have been shown examples in which the present invention is typically applied to the screw compressor. However, the present invention can be applied also to a Root's compressor or the other type compressor.
Moreover, the respective embodiments are constructed so as to compress air by the compressor but may be constructed so as to compress other gas.
Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-129216 | May 2006 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20070258841 A1 | Nov 2007 | US |
