Claw pump

Abstract

A claw pump includes: a housing; two rotating shafts which are disposed parallel; a pair of rotors respectively fixed to the two rotating shafts; a rotary drive device driving the pair of rotors; and a suction port and discharge ports formed in a partition wall of the housing. The discharge ports are constituted by a first discharge port and a second discharge port. The first discharge port is formed at a position that communicates with an initial stage compression space formed at an initial stage of a compression stroke in a compression space that is formed by joining a first pocket and a second pocket. The claw pump includes an opening/closing mechanism which opens the first discharge port when a pressure of the initial stage compression space reaches a threshold and closes the first discharge port when the pressure does not reach the threshold.

Claims

1. A claw pump comprising: a housing including two side plates and a pump chamber formed between the two side plates, the pump chamber having a cross-sectional shape of two partially overlapping circles; two rotating shafts which are disposed parallel to each other inside the housing and are synchronously rotated in opposite directions to each other; a pair of rotors which are respectively fixed to the two rotating shafts inside the housing, each of the rotors being provided with two or more hook-shaped claws, the claws meshing with each other in a non-contact state; a rotary drive device which is configured to drive the pair of rotors so as to be rotated via the two rotating shafts; a suction port and discharge ports which are formed in a partition wall of the housing and communicate with the pump chamber, the discharge ports being respectively formed in the two side plates of the rotating shafts of the housing and being constituted by a first discharge port and a second discharge port which are formed at positions that communicate with a compression pocket formed by a set of the claws; and an opening/closing mechanism of the first discharge port and the second discharge port which is configured to discharge gas in the compression pocket formed by at least one set of the claws only via the first discharge port and to discharge the gas in the compression pocket formed by at least another set of the claws only via the second discharge port, while the pair of rotors rotate one revolution.

2. The claw pump according to claim 1, wherein the opening/closing mechanism is constituted by a first partition plate and a second partition plate, which are fixed to one of the two rotating shafts on opposite sides of the pair of rotors, the first partition plate is provided with an opening formed at a position that opens only the first discharge port when the at least one set of the claws forms the compression pocket in the housing, and the second partition plate is provided with an opening formed at a position that opens only the second discharge port when the at least another set of the claws forms the compression pocket in the housing.

3. The claw pump according to claim 2, wherein the claws comprise two claws formed on each of the pair of rotors at opposite positions to each other, the first partition plate is provided with the opening formed at a position that opens only the first discharge port when one set of the claws forms the compression pocket in the housing, and the second partition plate is provided with the opening formed at a position that opens only the second discharge port when another set of the claws forms the compression pocket in the housing.

4. The claw pump according to claim 3, wherein the first partition plate and the second partition plate are disposed between the pair of rotors and the side plates.

5. The claw pump according to claim 2, wherein the claws comprise three claws formed on each of the pair of rotors at equal intervals in a circumferential direction, the first partition plate is provided with the opening formed at a position that opens only the first discharge port when two sets of the claws form the compression pocket in the housing, and the second partition plate is provided with the opening formed at a position that opens only the second discharge port when another set of the claws forms the compression pocket in the housing.

6. The claw pump according to claim 5, wherein the first partition plate and the second partition plate are disposed between the pair of rotors and the side plates.

7. The claw pump according to claim 2, wherein the first partition plate and the second partition plate are disposed between the pair of rotors and the side plates.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is an exploded perspective view of a claw pump according to a first embodiment of the present invention.

(2) FIG. 2 is a view viewed from arrow A in FIG. 1.

(3) FIG. 3 is an exploded perspective view illustrating a state after the claw pump makes a half revolution.

(4) FIG. 4 is an exploded perspective view of a claw pump according to a second embodiment of the present invention.

(5) FIGS. 5(A) to 5(H) are front sectional views illustrating a claw pump according to the related art in a stroke order.

DESCRIPTION OF EMBODIMENTS

(6) Hereinafter, the present invention will be described in detail using embodiments illustrated in the drawings. Here, the dimensions, materials, shapes, and relative arrangements of components described in the embodiments are not intended to limit the scope of the invention thereto if not particularly defined.

(7) (First Embodiment)

(8) Next, a claw pump according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3. In FIGS. 1 and 2, a claw pump 10A according to the embodiment includes a housing 12 that forms a pump chamber therein. The housing 12 is constituted by a cylinder 14 having a cross-sectional shape of two partially overlapping circles, and a pair of side plates 16a and 16b which block both end faces of the cylinder 14. The cylinder 14 is provided with a suction port 18, and the suction port 18 is disposed at a position that communicates with an inlet pocket P.sub.0 in which suctioned gas g is not compressed.

(9) Inside the housing 12, two rotating shafts 20a and 20b are arranged parallel to each other. Inside the housing 12, rotors 22a and 22b are respectively fixed to the rotating shafts 20a and 20b. The rotating shafts 20a and 20b extend toward the outside of the housing 12, and end portions of the rotating shafts 20a and 20b are connected to a rotary drive device (not illustrated). The rotating shafts 20a and 20b are synchronously rotated in opposite directions to each other by the rotary drive device. The rotors 22a and 22b are rotated in the opposite directions to each other at the same speed by the rotary drive device. The rotors 22a and 22b are provided with two claws 24a and two claws 24b which have a hook shape and mesh with each other in a non-contact state (with a fine gap therebetween). The two claws are disposed at positions at 180 degrees to each other in the circumferential direction. The rotor 22a is provided with a first concave portion 25a formed on the downstream side of the first claw 24a. The rotor 22a is provided with a second concave portion 25a formed on the downstream side of the second claw 24a. Here, the downstream side mentioned here is the downstream side with respect to the rotational direction of the rotor 22a.

(10) The gas g is suctioned into the inlet pocket P.sub.0 from the suction port 18 by the rotation of the rotors 22a and 22b. Next, the inlet pocket P.sub.0 into which the gas g flows is divided into a first pocket P.sub.1 enclosed by the housing 12 and the rotor 22a, and a second pocket P.sub.2 enclosed by the housing 12 and the rotor 22b. As the rotors 22a and 22b further rotate, the first pocket P.sub.1 and the second pocket P.sub.2 join such that a compression pocket P is formed. Immediately after the joining, an initial stage compression space Pe is formed. Thereafter, the compression pocket P is reduced in size and an end stage compression space Pc is formed. In this compression process, the gas g in the compression pocket P is compressed.

(11) The side plates 16a and 16b are respectively provided with discharge ports 26a and 26b which are formed in regions closer to the rotating shaft 20a than the rotating shaft 20b. The discharge ports 26a and 26b are disposed at positions which communicate with the end stage compression space Pc when the end stage compression space Pc is formed by the claws 24a and 24b. The discharge ports 26a and 26b are disposed at the same position in the circumferential direction of the rotating shaft 20a and have the same shape.

(12) A partition plate 28a having a circular outer shape is fixed to the rotating shaft 20a between the side plate 16a and the rotor 22a inside the housing 12. In addition, a partition plate 28b having a circular outer shape is fixed to the rotating shaft 20a between the side plate 16b and the rotor 22a. The partition plates 28a and 28b are respectively provided with openings 30a and 30b. The openings 30a and 30b are disposed substantially in the same region in the radial direction from the rotating shaft 20a. The openings 30a and 30b are disposed at positions at 180 degrees to each other about the rotating shaft 20a in the circumferential direction. In other words, the openings 30a and 30b are formed to substantially have point symmetry (that is, twofold symmetry) about the rotating shaft 20a. Fine gaps are provided between the outer circumferences of the partition plates 28a and 28b and the inner circumference of the housing 12 to an extent that the gas g does not leak.

(13) More specifically, the opening 30a overlaps the first concave portion 25a formed on the downstream side of the first claw 24a of the rotor 22a. The opening 30a is disposed at a position that overlaps discharge port 26a when a first set of the claws 24a and 24b (one set of claws) of the rotors 22a and 22b forms the end stage compression space Pc to enable the end stage compression space Pc and the discharge port 26a to communicate with each other. The opening 30b overlaps the second concave portion 25a formed on the downstream side of the second claw 24a of the rotor 22a. The opening 30b is disposed at a position that overlaps discharge port 26b when a second set of the claws 24a and 24b (the other set of claws) of the rotors 22a and 22b forms the end stage compression space Pc to enable the end stage compression space Pc and the discharge port 26b to communicate with each other.

(14) In this configuration, when the first set of claws 24a and 24b forms the end stage compression space Pc, the compressed gas in the end stage compression space Pc is discharged from the discharge port 26a via the opening 30a. Next, when the second set of claws 24a and 24b forms the end stage compression space Pc, the compressed gas in the end stage compression space Pc is discharged from the discharge port 26b via the opening 30b. Therefore, the compressed gas is alternately discharged from the discharge ports 26a and 26b. FIG. 1 illustrates a state in which the end stage compression space Pc formed by the claws 24a and 24b and the discharge port 26b communicate with each other via the opening 30b of the partition plate 28b. FIG. 3 illustrates a state in which the rotors 22a and 22b make a half revolution from the state of FIG. 1 and the end stage compression space Pc and the discharge port 26a communicate with each other via the opening 30a of the partition plate 28a.

(15) According to this embodiment, since the compressed gas is alternately discharged from the discharge ports 26a and 26b, compared to a claw pump according to the related art, the interval at which the discharge gas is discharged from the discharge ports 26a and 26b can be increased twice. Therefore, the time for which the discharged gas is mixed with cooled outside gas so as to be cooled can be increased. Accordingly, in a case where the pump chamber is at a low pressure, gas at a lower temperature than that according to the related art flows back to the discharge port and thus the initial temperature of the gas that is recompressed after flowing backward can be reduced. Therefore, an excessive increase in the temperature of the discharge gas after recompression can be prevented.

(16) As a result, the temperature of the discharge gas that is recompressed can be lowered, and an increase in the temperatures of components that come into contact with the discharge gas can be suppressed. Therefore, contact between the claws 24a and 24b of the rotors 22a and 22b or contact between the claws 24a and 24b and the inner surfaces of the housing 12 due to thermal expansion or deformation and breaking due to insufficient heat resistance can be suppressed. In addition, the amount of thermal expansion of each of the components decreases. Therefore, as the amount of thermal expansion decreases, the gaps between the components can be further reduced, which leads to an increase in pump efficiency. Furthermore, the degree of request of each of the components for heat resistance can be reduced, and thus a reduction in costs can be achieved.

(17) In addition, since only the partition plates 28a and 28b need to be used, a wide installation space is not necessary. In addition, since the partition plates 28a and 28b are fixed to the rotating shaft 20a and are interlocked with the rotating shaft 20a, a special drive device is not necessary, and an opening/closing mechanism can be simply formed with low costs. Furthermore, since the partition plates 28a and 28b are disposed between the rotors 22a and 22b and the right and left side plates 16a and 16b, a space in which the partition plates 28a and 28b are disposed outside the housing 12 is not necessary, and a compact pump configuration can be achieved.

(18) (Second Embodiment)

(19) Next, a second embodiment of the present invention will be described with reference to FIG. 4. In a claw pump 10B according to this embodiment, a pair of rotors 40a and 40b are provided with three claws 42a and three claws 42b having a hook shape. The claws 42a or 42b are disposed at equal intervals in the circumferential direction of the rotor 40a or 40b. The rotor 40a is provided with a first concave portion 45a formed on the downstream side of the first claw 42a. The rotor 40a is provided with a second concave portion 45a formed on the downstream side of the second claw 42a. The rotor 40a is provided with a third concave portion 45a formed on the downstream side of the third claw 42a. A partition plate 44a having a circular outer shape is fixed to the rotating shaft 20a between the side plate 16a and the rotor 40a. In addition, a partition plate 44b having a circular outer shape is fixed to the rotating shaft 20a between the side plate 16b and the rotor 40a.

(20) Two openings 46a and 46b are bored in the partition plate 44a, and a single opening 46c is bored in the partition plate 44b. The openings 46a, 46b, and 46c are disposed at substantially the same position in the radial direction from the rotating shaft 20a. The openings 46a, 46b, and 46c are disposed at equal intervals of 120 degrees in the circumferential direction about the rotating shaft 20a. In other words, the openings 46a, 46b, and 46c are formed to have threefold symmetry about the rotating shaft 20a. In addition, fine gaps are provided between the outer circumferences of the partition plates 44a and 44b and the inner circumference of the housing 12 to an extent that the gas g does not leak.

(21) More specifically, the opening 46a overlaps the first concave portion 45a formed on the downstream side of the first claw 42a of the rotor 40a. The opening 46a is disposed at a position that overlaps discharge port 26a when a first set of the claws 42a and 42b (one set of claws) of the rotors 40a and 40b forms the end stage compression space Pc to enable the end stage compression space Pc and the discharge port 26a to communicate with each other. The opening 46b overlaps the second concave portion 45a formed on the downstream side of the second claw 42a of the rotor 40a. The opening 46b is disposed at a position that overlaps discharge port 26a when a second set of the claws 42a and 42b (another set of claws) of the rotors 40a and 40b forms the end stage compression space Pc to enable the end stage compression space Pc and the discharge port 26a to communicate with each other. The opening 46c overlaps the third concave portion 45a formed on the downstream side of the third claw 42a of the rotor 40a. The opening 46c is disposed at a position that overlaps discharge port 26b when a third set of the claws 42a and 42b (yet another set of claws) of the rotors 40a and 40b forms the end stage compression space Pc to enable the end stage compression space Pc and the discharge port 26b to communicate with each other. The other configurations are the same as those of the first embodiment.

(22) In this configuration, when the first set of claws 42a and 42b forms the end stage compression space Pc, the compressed gas in the end stage compression space Pc is discharged from the discharge port 26a via the opening 46a. Next, when the rotors 40a and 40b rotate 120 degrees and the second set of claws 42a and 42b forms the end stage compression space Pc, the compressed gas in the end stage compression space Pc is discharged from the discharge port 26a via the opening 46b. When the rotors 40a and 40b further rotate 120 degrees and the third set of claws 42a and 42b (the remaining set of claws) forms the end stage compression space Pc, the compressed gas in the end stage compression space Pc is discharged from the discharge port 26b via the opening 46c.

(23) According to this embodiment, the time interval at which the compressed gas is discharged from the discharge ports 26a and 26b can be increased, and thus the gas at a lower temperature flows backward. Therefore, an excessive increase in the temperature of the discharge gas after recompression can be prevented.

INDUSTRIAL APPLICABILITY

(24) According to the embodiment, a claw pump in which an increase in the temperature of a discharge gas can be avoided and problems caused by the temperature increase can be solved can be realized by simple and low-cost means.

REFERENCE SIGNS LIST

(25) 10A, 10B, 100 CLAW PUMP

(26) 12, 102 HOUSING

(27) 14 CYLINDER

(28) 16a, 16b SIDE PLATE

(29) 18, 108 SUCTION PORT

(30) 20a, 20b, 110a, 110b ROTATING SHAFT

(31) 22a, 22b, 40a, 40b, 112a, 112b ROTOR

(32) 24a, 24b, 42a, 42b, 114a, 114b CLAW

(33) 26a, 26b DISCHARGE PORT

(34) 28a, 28b, 44a, 44b PARTITION PLATE

(35) 30a, 30b, 46a, 46b, 46c OPENING

(36) 116 DISCHARGE PORT

(37) P COMPRESSION POCKET

(38) Pe INITIAL STAGE COMPRESSION SPACE

(39) Pc END STAGE COMPRESSION SPACE

(40) P.sub.0 INLET POCKET

(41) P.sub.1 FIRST POCKET

(42) P.sub.2 SECOND POCKET

(43) g GAS