Lysholm compressors

Abstract: A Lysholm compressor comprises male and female rotors (1,2) which are rotatably accommodated within a casing structure comprising two part-cylindrical walls (9a,9b) which constitute a casing (3) and merge together at two cusps (10,11) which project inwardly towards one another. A suction port (4) and a discharge port (6) are provided at respective axial ends of the casing (3). A silencer chamber (13,14) is defined between at least one of the cusps (10,11) and respective associated outer wall portions (12, 15) which are situated outside the associated cusp and are integral with the casing (3). The or each silencer chamber (13,16) has a respective opening (14,17) which communicates with the suction port (4) and the discharge port (6), respectively.

Description: The present invention relates to Lysholm compressors which are used, for example, for superchargers in automotive engines and more particularly to casing structures for such compressors. More specifically, the invention relates to a Lysholm compressor casing structure which is adapted to accommodate intermeshing male and female rotors and which comprises two part-cylindrical walls which constitute a casing and merge together at two cusps which project inwardly towards one another, a suction port at one axial end of the casing and a discharge port at the other axial end of the casing. JP 07 217563 A which is considered as the closest state of the art discloses the features described in the preamble of claims 1 and 2. Fig. 1 is a schematic perspective view of a known Lysholm compressor of the type referred to above, which comprises parallel intermeshing male and female rotors 1 and 2 rotatably accommodated in an accommodation space 7 within a casing 3. The rotors 1 and 2 are counter-rotated in the directions of the arrows to suck air 5 into the space 7 through a suction or inlet port 4 at one axial end of the casing 3. The air 5 is compressed by the rotors 1 and 2 and is discharged through a discharge port 6 at the other axial end of the casing 3 adjacent to the intermeshing portions 8 of the rotors 1 and 2. As best shown in Fig. 2, which is a schematic vertical sectional view of the compressor in Fig. 1, and Fig 3, which is a view in the direction of the arrows III in Fig. 2, the casing 3 comprises part-cylindrical walls 9a and 9b which are of substantially uniform thickness and which surround the majority of the peripheries of the rotors 1 and 2 except for the intermeshing portions 8. The casing 3 further comprises a pair of opposed cusps 10 and 11 which project inwardly from the walls 9a and 9b towards the intermeshing portions 8 of the rotors 1 and 2. In the Lysholm compressor shown in Figs. 1 to 3, rotation of the rotors 1 and 2 in the directions of the arrows shown in Fig. 1 causes the air 5 induced through the port 4 to pass through the space 7 whilst being compressed by the rotors 1 and 2, the compressed air 5 then being discharged out of the casing 3 through the port 6. This construction is disadvantageous in that it generates much noise during operation. It is conventionally proposed for the purpose of suppressing the noise that specially designed suction and discharge ports 4 and 6 be used or that the piping connected to the ports 4 and 6 be provided with noise suppressor means, such as a silencer or resonator (not shown). However, the designed ports are not very effective at suppressing the noise. More specifically, the cusps 10 and 11 of the casing 3 have low stiffness and tend to cause vibration of the walls, thereby generating noise; such noise due to vibration of the walls may not be easily suppressed merely by specially designed ports. Even if noise were satisfactorily suppressed by specially designed ports, the latter would increase the resistance to the air 5 flowing into and out of the space 7, resulting in impairment of the performance of the compressor. On the other hand, when the compressor described above is used, for example, as a supercharger for an integral combustion engine of a vehicle and noise suppressor means, such as a silencer or resonator, are provided in the piping connected to the suction and discharge ports 4 and 6, it is difficult to arrange this piping with the noise suppressor means in association with other equipment and machinery in the vehicle. Moreover, the arrangement of the noise suppressor means remote from the compressor impairs the noise-suppressing effect. Accordingly it is the object of the present invention to provide a Lysholm compressor and particularly a Lysholm compressor casing structure therefor which generates less noise and may be readily mounted in a vehicle. According to one aspect of the present invention a Lysholm compressor casing structure of the type referred to above is characterised in that a silencer chamber is defined between one of the cusps and an outer wall portion, which is situated outside the said one cusp and is integral with the casing, and has an opening in communication with the suction port. According to a further aspect of the present invention the Lysholm compressor casing structure is characterised in that a silencer chamber is defined between one of the cusps and an outer wall portion which is situated outside the said one cusp and is integral with the casing and has an opening in communication with the discharge port. Thus a Lysholm compressor casing structure in accordance with the present invention may have a silencer chamber defined between a respective one of the cusps and an associated outer wall portion situated outside the cusp and integral with the casing and having an opening in communication with either the suction port or the discharge port. Accordingly to a further aspect of the present invention the noise suppression is further enhanced if two such silencer chambers are provided communicating with the suction port and the discharge, respectively. The invention relates also to a Lysholm compressor comprising male and female rotors which intermesh at a region and/or are rotatably accommodated within a casing structure of the type defined above. Further features of the invention will be apparent from the following description of three preferred embodiments of the invention which is given by way of example with reference to Figures 4 to 9 of the accompanying drawings, in which: Fig. 4 is a schematic vertical sectional view of a first embodiment of the present invention; Fig. 5 is a view in the direction of the arrows V in Fig. 4; Fig. 6 is a view similar to Fig. 4 of a second embodiment of the invention; Fig. 7 is a view in the direction of the arrows VII in Fig. 6; Fig. 8 is a further view similar to Fig. 4 of a third embodiment of the invention; and Fig. 9 is a view in the direction of arrows IX in Fig. 8. Those components which are essentially the same as those described in conjunction with Fig. 1 to 3 are referred to by the same reference numerals. The Lysholm compressor shown in Figs. 4 and 5 comprises male and female rotors 1 and 2 and a casing 3 for rotatably accommodating the rotors 1 and 2. The casing 3 comprises two part-cylindrical walls 9a and 9b which are of substantially uniform thickness and surround the majority of the rotors 1 and 2 except for their intermeshing portions 8. The part-cylindrical walls 9a and 9b merge at a pair of opposed cusps 10 and 11 which extend inwardly towards the intermeshing portions 8 of the rotors 1 and 2. The casing 3 is provided at one axial end with a suction port 4 and at the other axial end with a discharge port 6 adjacent the intermeshing portions 8 of the rotors 1 and 2. A stagnation space constituting a suction-side silencer chamber 13 is defined by the cusp 10 and the adjacent portions of the part-cylindrical walls and an outer wall portion 12 outside the cusp 10 and integral with the casing 3. The silencer chamber 13 has a suction-side opening 14 in communication with the suction port 4. The shape, size and other details of the silencer chamber 13 and also of the opening 14 may be freely selected. In use, rotation of the rotors 1 and 2 causes the air 5 induced through the suction port 4 to pass through the accommodation space 7 in the casing 3 whilst being compressed by the rotors 1 and 2, and the compressed air is discharged through the discharge port 6 at the other end of the casing 3 adjacent to the intermeshing portions 8 of the rotors. Any noise due to pressure fluctuations of the air 5 sucked through the port 4 can be effectively suppressed due to the presence of the silencer chamber 13. The noise-suppressing effect is maximised since the silencer chamber 13 is adjacent to the source of noise generation by the compressor. The cusp 10 is reinforced and thus stiffened by the presence of the outer wall portion 12, so that any vibration of the cusp 10 is suppressed, thereby suppressing the generation of noise by vibration. Figs. 6 and 7 illustrate a further embodiment of the present invention in which a stagnation space constituting a discharge-side silencer chamber 16 is defined by the other cusp 11 and adjacent portions of the part-cylindrical walls and an outer wall portion 15 outside the cusp 11 and integral with the casing 3. The silencer chamber 16 has a discharge-side opening 17 in communication with the discharge port 6. The shape, size and other details of the silencer chamber 16 and opening 17 may be freely selected. Operation of the second embodiment is similar to that of the first embodiment and any noise due to pressure fluctuations of the air 5 discharged through the port 6 can be effectively suppressed due to the presence of the silencer chamber. The noise-suppressing effect is maximised since the silencer chamber 16 is adjacent to the source of noise generation by the compressor. The cusp 11 is reinforced and thus stiffened by the presence of the outer wall portion 15, so that any vibration of the cusp 11 is suppressed, thereby suppressing the generation of noise due to vibration. Figs. 8 and 9 illustrate a still further embodiment of the invention in which both suction- and discharge-side silencer chambers 13 and 16 like those in Figs. 4 and 5 and in Figs. 6 and 7 are defined by the cusps 10 and 11 and the adjacent portions of the part-cylindrical walls and the silencer outer wall portions 12 and 15, respectively. The silencer chambers 13 and 16 have suction- and discharge-side openings 14 and 17 in communication with the suction and discharge ports 4 and 6, respectively. In all three embodiments the noise suppression is attained with no substantial change in size of the casing 3 since, as mentioned above, the silencer chambers are defined between a respective cusp 10,11 and the associated outer wall portion 12,15 integral with the casing 3. Therefore, the compressor may be readily mounted in a vehicle or the like without difficulty in contrast to conventional compressors with silencers or the like connected to the piping leading to the suction and discharge ports. In the compressor shown in Figs. 8 and 9, the provision of both suction- and discharge-side silencer chambers 13 and 16 fulfils the effects of both the first and second embodiments and suppresses noise at both the suction- and discharge-sides. Moreover, it makes the outer shape of the whole of the casing 3 substantially cylindrical, so that the overall strength and rigidity is further increased. As a result, any vibration of the cusps 10 and 11 is further suppressed thereby further suppressing the generation of noise due to vibration.

Claims: A Lysholm compressor casing structure adapted to accommodate intermeshing male and female rotors (1,2) and comprising two part-cylindrical walls (9a,9b) which constitute a casing (3) and merge together at two cusps (10,11) which project inwardly towards one another, a suction port (4) at one axial end of the casing (3) and a discharge port (6) at the other axial end of the casing, characterised in that a silencer chamber (13) is defined between one of the cusps (10) and an outer wall portion (12) which is situated outside the said one cusp (10) and is integrally contiguous with the two part-cylindrical walls (9a, 9b) of the casing (3) and has an opening (14) in communication with the suction port (4) at the said one axial end. A Lysholm compressor casing structure adapted to accommodate intermeshing male and female rotors (1, 2) and comprising two part-cylindrical walls (9a, 9b) which constitute a casing (3) and merge together at two cusps (10, 11) which project inwardly towards one another, a suction port (4) at one axial end of the casing (3) and a discharge port (6) at the other axial end of the casing, characterised in that a silencer chamber (16) is defined between one of the cusps (11) and an outer wall portion (15) which is situated outside the said one cusp (11) and is integrally contiguous with the two part-cylindrical walls (9a, 9b) of the casing (3) and has an opening (17) in communication with the discharge port (6) at the said other axial end. A Lysholm compressor casing structure as claimed in Claim 2, characterised in that a silencer chamber (13) is defined between the other of the cusps (10) and a further outer wall portion (12) which is situated outside the said other cusp (10) and is integrally contiguous with the two part-cylindrical walls (9a, 9b) of the casing (3) and has an opening (14) in connection with the suction port (4) at the said one axial end. A Lysholm compressor which comprises male and female rotors (1,2) which intermesh at a region (8) and are rotatably accommodated in a casing structure as claimed in any one of claims 1 to 3.

Inventors: TAKEI NOBUO, TAKEI, NOBUO
Applicants: ISHIKAWAJIMA HARIMA HEAVY IND, ISHIKAWAJIMA-HARIMA JUKOGYO KABUSHIKI KAISHA
Application year: 1997
Main classification: F04C18
IPC codes: F04C29, F04C18