GATE ROTOR AND SCREW COMPRESSOR

TECHNICAL FIELD

The present invention relates to a gate rotor and to a screw compressor that uses the gate rotor.

BACKGROUND ART

A conventional screw compressor (refer to Patent Document 1: Japanese Patent No. 3731399) is known wherein a screw rotor 202 is housed inside a cylinder 210 of a casing 201, a gate rotor 203 meshes with the screw rotor 202, and a compression chamber that is formed by the intermeshing of the screw rotor 202 and the gate rotor 203 compresses a gas, as shown in the enlarged cross sectional view of FIG. 16.

Namely, a groove 221 of the screw rotor 202 and teeth 231 of the gate rotor 203 mesh to form the compression chamber. Furthermore, a low pressure gas is sucked into the compression chamber from one end side of the directions of an axis 202a of the screw rotor 202 and the low pressure gas is compressed in the compression chamber, after which compressed high pressure gas is discharged from an other end side of the directions of the axis 202a of the screw rotor 202.

The gate rotor 203 comprises: a gate rotor main body 230, which comprises the teeth 231; and a shaft 240, which fixes the gate rotor main body 230. The casing 201 supports the shaft 240.

Here, during operation of the compressor, the gas is compressed in the compression chamber, which increases the temperature of the screw rotor 202 and, in turn, the thermal expansion of the screw rotor 202. Moreover, the pressure in a gate rotor chamber L, which houses the gate rotor 203 in the casing 201, is low, and the temperature of the gas in the gate rotor chamber L is relatively low, which decreases the thermal expansion of the portion around the gate rotor chamber L in the casing 201. The portion around the gate rotor chamber L in the casing 201 is the portion that determines the distance between the axis 202a of the screw rotor 202 and an axis 203a of the gate rotor 203.

PATENT DOCUMENT 1

• Japanese Patent No. 3731399

DISCLOSURE OF THE INVENTION

Technical Problem

Nevertheless, in the conventional screw compressor, the casing 201 supports the gate rotor 203; therefore, during operation of the compressor, the thermal expansion of the screw rotor 202 steadily increases while the thermal expansion of the casing 201 decreases, thereby changing the distance between the axis 202a of the screw rotor 202 and the axis 203a of the gate rotor 203, which is a problem. Namely, during operation of the compressor, the temperature differential between the casing 201 and the screw rotor 202 causes the gate rotor 203 to flex, which is a problem.

At this time, the gate rotor main body 230 is fixed to the shaft 240 and consequently the teeth 231 of the gate rotor main body 230 bite into the groove 221 of the screw rotor 202, causing a great deal of wear in the teeth 231.

As a result, a gap between the teeth 231 of the gate rotor main body 230 and the groove 221 of the screw rotor 202 increases, which decreases the performance of the compressor.

Furthermore, in the conventional screw compressor, a high pressure chamber is provided to the portion around the cylinder 210 in the casing 201 and the temperature differential between the casing 201 and the screw rotor 202 is small; however, a high pressure chamber is not provided to the portion around the gate rotor chamber L of the casing 201, and therefore it is not possible to relieve the flexure of the gate rotor 203.

Accordingly, an object of the present invention is to provide a screw compressor wherein, even if a gate rotor flexes owing to a temperature differential between a casing and a screw rotor during operation of a compressor, the gate rotor is prevented, with a simple configuration, from biting into the screw rotor, which reduces the amount of wear of the gate rotor and prevents a decline in the compressor's performance, and a gate rotor that is used in the compressor.

Solution to Problem

To solve the abovementioned problems, a gate rotor according to a first aspect of the present invention comprises: a gate rotor main body; and a shaft to which the gate rotor main body is attached; wherein, the gate rotor main body comprises a plurality of teeth and a central hole; the shaft comprises a pedestal supporting the gate rotor main body on a surface, and an axle installed on the surface of the pedestal and inserted in the hole; and an elastic body is disposed between the axle of the shaft and the hole of the gate rotor main body.

According to the gate rotor of the present invention, the elastic body is disposed between the axle of the shaft and the hole of the gate rotor main body, which makes it possible for the gate rotor main body to slide on the pedestal of the shaft.

Consequently, if the gate rotor is used in a screw compressor and the teeth of the gate rotor main body mesh with the screw rotor and the casing supports the shaft, then, during operation of the compressor, even if the thermal expansion of the screw rotor steadily increases while the thermal expansion of the casing decreases and thereby the distance between the axis of the screw rotor and the axis of the gate rotor (i.e., the axle of the shaft) changes, the gate rotor main body slides on the pedestal of the shaft, and therefore an appropriate positional relationship, namely, an appropriate distance, is maintained between the screw rotor and the gate rotor main body.

As a result, the gate rotor main body is prevented from biting into the screw rotor, which reduces the amount of wear of the gate rotor main body and prevents the performance of the compressor from declining. In addition, useless motivity, which is generated by the gate rotor main body and the screw rotor pressing against one another, is reduced. In addition, a pressing force between the gate rotor main body and the screw rotor given by the elastic body can be maintained to the extent that gas does not leak.

Accordingly, even if the gate rotor flexes owing to the temperature differential between the casing and the screw rotor during operation of the compressor, the gate rotor is prevented, with a simple configuration, from biting into the screw rotor, which reduces the amount of wear of the gate rotor and prevents the performance of the compressor from declining.

In addition, in a gate rotor according to a second aspect of the present invention, the elastic body is a leaf spring.

According to the gate rotor of the second aspect of the present invention, because the elastic body is a leaf spring, the elastic body can be configured simply.

In addition, in a gate rotor according a third aspect of the present invention, the leaf spring is an annular wave spring or a spiral spring.

According to the gate rotor of the third aspect of the present invention, because the leaf spring is an annular wave spring or a spiral spring, the leaf spring can be configured simply.

In addition, in a gate rotor according to a fourth aspect of the present invention, the elastic body is an annular rubber member.

According to the gate rotor of the fourth aspect of the present invention, the elastic body is an annular rubber member, which makes it possible to configure the elastic body simply.

In addition, a screw compressor according to a fifth aspect of the present invention comprises: a casing comprising a cylinder; a cylindrical screw rotor meshing with the cylinder; and the gate rotor meshing with the screw rotor; wherein, the teeth of the gate rotor main body of the gate rotor mesh with the screw rotor; and the shaft of the gate rotor is supported by the casing.

According to the screw compressor of the fifth aspect of the present invention, the gate rotor is provided, therefore, during operation of the compressor, even if the thermal expansion of the screw rotor steadily increases while the thermal expansion of the casing decreases and thereby the distance between the axis of the screw rotor and the axis of the gate rotor (i.e., the axle of the shaft) changes, the gate rotor main body slides on the pedestal of the shaft, and therefore an appropriate positional relationship, namely, an appropriate distance, is maintained between the screw rotor and the gate rotor main body.

As a result, the gate rotor main body is prevented from biting into the screw rotor, which reduces the amount of wear of the gate rotor main body and prevents the performance of the compressor from declining. In addition, useless motivity, which is generated by the gate rotor main body and the screw rotor pressing against one another, is reduced. In addition, a pressing force between the gate rotor main body and the screw rotor given by the elastic body can be maintained to the extent that gas does not leak.

Accordingly, even if the gate rotor flexes owing to the temperature differential between the casing and the screw rotor during operation of the compressor, the gate rotor is prevented, with a simple configuration, from biting into the screw rotor, which reduces the amount of wear of the gate rotor and prevents the performance of the compressor from declining.

A screw compressor according to a sixth aspect of the present invention comprises a screw rotor, a gate rotor, a gate rotor shaft, and an elastic body. The screw rotor has a plurality of helical grooves in its outer circumferential surface and is rotatable. In the gate rotor, an opening is formed at its center. Around the opening of the gate rotor, a plurality of teeth, which mesh with the grooves of the screw rotor, are radially disposed. The gate rotor shaft is inserted in the opening of the gate rotor with a gap. The elastic body is disposed in the gap between the opening of the gate rotor and the gate rotor shaft, and/or is disposed around at least one of the plurality of locking pins that stop the rotation of the gate rotor around the gate rotor shaft.

According to the screw compressor of the sixth aspect of the present invention, a gap is formed around the gate rotor shaft; furthermore, the elastic body is disposed in the gap around the gate rotor shaft, and/or is disposed around at least one of the locking pins of the plurality of locking pins that stops the rotation around the gate rotor shaft, or both, which makes it possible to absorb the extension of the teeth of the gate rotor in the radial directions.

A screw compressor according to the seventh aspect of the present invention is the screw compressor according to the sixth aspect of the present invention, wherein the elastic body, which is disposed in the gap, gives an elastic force in the radial directions of the gate rotor toward one of the plurality of locking pins with respect to the gate rotor.

According to the screw compressor of the seventh aspect of the present invention, the elastic body, which is disposed in the gap, gives an elastic force to the gate rotor in the radial directions toward the locking pin with respect to the gate rotor; thereby, the elastic body can effectively absorb in the radial directions the extension of the teeth, whose movement in the radial directions is restrained by the locking pin.

A screw compressor according an eighth aspect of the present invention is the screw compressor according to the sixth aspect of the present invention, wherein the elastic body disposed in the gap is ring-shaped and fills the entire gap.

According to the screw compressor of the eighth aspect of the present invention, the elastic body disposed in the gap is ring-shaped and fills the entire gap, which makes it possible to absorb the extension of the teeth of the gate rotor in the radial directions. In addition, filling the entire gap with the ring-shaped elastic body makes it possible to further extend the life span of the teeth of the gate rotor.

A screw compressor according to a ninth aspect of the present invention is the screw compressor according to any one aspect from the sixth through the eighth aspects of the present invention, wherein one locking pin of the plurality of the locking pins is a floating pin. The floating pin connects the gate rotor shaft and the gate rotor via more play than the other locking pins.

In the screw compressor according to the ninth aspect of the present invention, one of the locking pins is the floating pin connecting the gate rotor shaft and the gate rotor via more play than the other locking pins, which secures for the floating pin a larger mobility margin than the other locking pins have; therefore, it is possible to absorb the extension of the teeth of the gate rotor in the radial directions.

A screw compressor according to a tenth aspect of the present invention is the screw compressor according to the ninth aspect of the present invention, wherein the elastic body is ring-shaped and is disposed around the locking pin that is the floating pin.

According to the screw compressor of the tenth aspect of the present invention, the elastic body is ring-shaped and is disposed around the locking pin that is the floating pin, which makes it possible to absorb the extension of the teeth of the gate rotor in the radial directions.

Advantageous Effects of Invention

According to the gate rotor of the first aspect of the present invention, the elastic body is disposed between the axle of the shaft and the hole of the gate rotor main body; therefore, when the gate rotor is used in the screw compressor, even if the gate rotor flexes owing to a temperature differential between a casing and a screw rotor during operation of a compressor, the gate rotor is prevented, with a simple configuration, from biting into the screw rotor, which reduces the amount of wear of the gate rotor and prevents a decline in the compressor's performance.

According to the second aspect of the present invention, the elastic body can be configured simply.

According to the third aspect of the present invention, the leaf spring can be configured simply.

According to the fourth aspect of the present invention, the elastic body can be configured simply.

The screw compressor according to the fifth aspect of the present invention comprises the gate rotor; therefore, even if the gate rotor flexes owing to the temperature differential between the casing and the screw rotor during operation of the compressor, the gate rotor is prevented, with a simple configuration, from biting into the screw rotor, which reduces the amount of wear of the gate rotor and prevents the performance of the compressor from declining.

According to the sixth aspect of the present invention, the extension of the teeth of the gate rotor in the radial directions can be absorbed. Thereby, the tips of the teeth of the gate rotor no longer rub against and wear the far walls of the grooves of the screw rotor, which makes it possible to prevent the gate rotor from wearing.

According to the seventh aspect of the present invention, the elastic body can effectively absorb in the radial directions the extension of the teeth, whose movement in the radial directions is restrained by the locking pin.

According to the eighth aspect of the present invention, it is possible to absorb the extension of the teeth of the gate rotor in the radial directions; furthermore, filling the entire gap with the ring shaped elastic body makes it possible to further extend the life span of the teeth of the gate rotor.

According to the ninth aspect of the present invention, the floating pin can secure a larger mobility margin than the other locking pins can, which makes it possible to absorb the extension of the teeth of the gate rotor in the radial directions.

According to the tenth aspect of the present invention, it is possible to absorb the extension of the teeth of the gate rotor in the radial directions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a transverse cross sectional view that shows a first embodiment of gate rotors and a screw compressor of the present invention.

FIG. 2 is a plan view of a gate rotor main body in FIG. 1.

FIG. 3 is a cross sectional view taken along the A-A line in FIG. 2.

FIG. 4 is a plan view of one of the shafts in FIG. 1.

FIG. 5 is a cross sectional view taken along the B-B line in FIG. 4.

FIG. 6 is a plan view of one of the gate rotors in FIG. 1.

FIG. 7 is a cross sectional view taken along the C-C line in FIG. 6.

FIG. 8 is a plan view of a second embodiment of one of the gate rotors of the present invention.

FIG. 9 is a configuration diagram of the principal parts of a single screw compressor according to a third embodiment of the present invention.

FIG. 10 is a front view of the single screw compressor in FIG. 9.

FIG. 11 is a configuration diagram that shows the arrangement of the screw rotor and the gate rotors in FIG. 9.

FIG. 12 includes a front view (a) and a rear view (b) of the portion at which one of the gate rotors and one of the gate rotor supports in FIG. 9 are connected.

FIG. 13 is an enlarged view of a circumferential portion of a coil spring that is disposed in a gap around the shaft of one of the gate rotors in FIG. 9.

FIG. 14 is a broken front view of one of the gate rotors, one of the gate rotor supports, and one of the gate rotor shafts in FIG. 9.

FIG. 15 is a partial enlarged cross sectional view of the vicinity of one of the O-rings and one of the holes for restraining the rotation of one of the gate rotors in FIG. 11.

FIG. 16 is an enlarged cross sectional view of a conventional screw compressor.

EXPLANATION OF THE REFERENCE NUMERALS/SYMBOLS/SIGNS

• 1 Casing
• 10 Cylinder
• 12 Through hole
• 13 Discharge port
• 2 Screw rotor
• 2a Axis
• 21 Groove
• 3, 3A Gate rotors
• 3a Axis
• 30 Gate rotor main body
• 30a Axis
• 31 Tooth
• 32 Hole
• 33 Pinhole
• 40 Shaft
• 40a Axis
• 41 First shaft
• 42 Second shaft
• 43 Pedestal
• 43a One surface
• 44 Tooth
• 45 Pinhole
• 5 Elastic body (leaf spring)
• 5A Elastic body (rubber member)
• C Compression chamber
• L Gate rotor chamber
• S Gap
• 101 Screw compressor
• 102 Screw rotor
• 103 Casing
• 104 Shaft
• 105 First gate rotor
• 106 Second gate rotor
• 108, 109 Gate rotor shafts
• 111 Groove
• 112 Tooth
• 121 Opening
• 122 Gap
• 123 Guide pin
• 124 Floating pin
• 127 Gate rotor support
• 128 Coil spring (first elastic body)
• 129 O-ring (second elastic body)

BEST MODE FOR CARRYING OUT THE INVENTION

• The following text explains the present invention in detail based on the embodiments illustrated.

First Embodiment

FIG. 1 is a transverse cross sectional view of a first embodiment of gate rotors and a screw compressor of the present invention. This screw compressor is a single screw compressor and comprises: a casing 1, which comprises a cylinder 10; a cylindrical screw rotor 2, which mates with the cylinder 10; and gate rotors 3, which mesh with the screw rotor 2.

The screw rotor 2 comprises a plurality of helical grooves 21 in its outer circumferential surface. Each of the gate rotors 3 is spinning top-shaped and comprises on its outer circumferential surface a plurality of teeth 31 shaped as a gear. The grooves 21 of the screw rotor 2 intermesh with the teeth 31 of the gate rotors 3.

The intermeshing of the screw rotor 2 and the gate rotors 3 forms compression chambers C. Namely, the compression chambers C are spaces demarcated by the grooves 21 of the screw rotor 2, the teeth 31 of the gate rotors 3, and an inner surface of the cylinder 10 of the casing 1.

Two gate rotors 3 are disposed, one on each of the left and right sides of the screw rotor 2, such that they are point symmetric with respect to an axis 2a of the screw rotor 2. In the casing 1, gate rotor chambers L, wherein the gate rotors 3 are housed, are provided on the outer side of the cylinder 10. The gate rotor chambers L and the cylinder 10 communicate via through holes 12. The gate rotors 3 advance into the cylinder 10 via the through holes 12.

The screw rotor 2 rotates in the direction of an arrow R with the axis 2a for a center; attendant with the rotation of the screw rotor 2, the gate rotors 3 rotate with the axes 3a for centers, which compresses the gas inside the compression chambers C. The screw rotor 2 rotates by a motor (not shown), which is housed in the casing 1.

Namely, a low pressure gas is sucked into the compression chambers C from one end side of the directions of the axis 2a of the screw rotor 2, the low pressure gas is compressed in the compression chambers C, and compressed high pressure gas is discharged via discharge ports 13, which are on an other end side of the directions of the axis 2a of the screw rotor 2.

Each of the gate rotors 3 comprises a gate rotor main body 30 and a shaft 40, to which the gate rotor main body 30 is attached. The gate rotor main body 30 meshes with the screw rotor 2. The casing 1 supports the shaft 40. The gate rotor main body 30 is made of, for example, a resin, and the shaft 40 is made of, for example, a metal.

As shown in FIG. 2 and FIG. 3, the gate rotor main body 30 is shaped as a disc and comprises a plurality of teeth 31 on its outer circumferential surface and a hole 32 at its center. FIG. 2 is a plan view of the gate rotor main body 30, and FIG. 3 is a cross sectional view taken along the A-A line in FIG. 2.

The teeth 31 mesh with the grooves 21 of the screw rotor 2. The center of the hole 32 coincides with an axis 30a of the gate rotor main body 30. In addition, a pinhole 33 is provided to the gate rotor main body 30, and a positioning pin (not shown) is inserted therethrough.

As shown in FIG. 4 and FIG. 5, the shaft 40 comprises: a pedestal 43; a first shaft 41, which is provided to one surface 43a of the pedestal 43; and a second shaft 42, which is provided to an other surface of the pedestal 43. FIG. 4 is a plan view of the shaft 40, and FIG. 5 is a cross sectional view taken along the B-B line in FIG. 4.

The pedestal 43 comprises a plurality of teeth 44 on its outer circumferential surface. The teeth 44 correspond to the teeth 31 of the gate rotor main body 30. In addition, a pinhole 45 is provided to the pedestal 43, and a positioning pin (not shown) is inserted therethrough. The axis of the first shaft 41 and the axis of the second shaft 42 coincide with an axis 40a of the shaft 40. The casing 1 supports the second shaft 42 via a bearing.

As shown in FIG. 6 and FIG. 7, in the gate rotor 3, the gate rotor main body 30 is supported by the one surface 43a of the pedestal 43 of the shaft 40. The first shaft 41 of the shaft 40 is inserted into the hole 32 of the gate rotor main body 30. FIG. 6 is a plan view of the gate rotor 3, and FIG. 7 is a cross sectional view taken along the C-C line in FIG. 6.

An elastic body 5 is disposed in a gap S between the first shaft 41 of the shaft 40 and the hole 32 of the gate rotor main body 30. To make the elastic body 5 easy to identify in FIG. 6, it is shown in black.

The elastic body 5 is a leaf spring. The leaf spring is an annular wave spring. The mountain portions of the wave spring are positioned on the outer circumferential surface, and the valley portions of the wave spring are positioned on the inner circumferential surface. The mountain portions of the wave spring contact the inner circumferential surface of the hole 32 of the gate rotor main body 30, and the valley portions of the wave spring contact the outer circumferential surface of the first shaft 41 of the shaft 40. Furthermore, although not shown, the leaf spring may be a spiral spring.

The elastic body 5 continuously urges such that the axis 30a of the gate rotor main body 30 and the axis 40a of the shaft 40 coincide. Furthermore, if a force external to the gate rotor main body 30 is exerted, then the gate rotor main body 30 will counteract the elastic force of the elastic body 5 and move on the pedestal 43 of the shaft 40.

The pinhole 33 of the gate rotor main body 30 and the pinhole 45 of the shaft 40 overlap such that their axes coincide, and a positioning pin (not shown) is inserted therethrough.

According to the gate rotor 3 of the above configuration, the elastic body 5 is disposed between the shaft 41 of the shaft 40 and the hole 32 of the gate rotor main body 30, which makes it possible for the gate rotor main body 30 to slide on the pedestal 43 of the shaft 40.

Consequently, if the gate rotor 3 is used in a screw compressor and the teeth 31 of the gate rotor main body 30 mesh with the screw rotor 2 and the casing 1 supports the shaft 40, then, during operation of the compressor, even if the thermal expansion of the screw rotor 2 steadily increases while the thermal expansion of the casing 1 decreases and thereby the distance between the axis 2a of the screw rotor 2 and the axis 3a of the gate rotor 3 (i.e., the axis 40a of the shaft 40) changes, the gate rotor main body 30 slides on the pedestal 43 of the shaft 40, and therefore an appropriate positional relationship, namely, an appropriate distance, is maintained between the screw rotor 2 and the gate rotor main body 30.

As a result, the gate rotor main body 30 is prevented from biting into the screw rotor 2, which reduces the amount of wear of the gate rotor main body 30 and prevents the performance of the compressor from declining. In addition, useless motivity, which is generated by the gate rotor main body and the screw rotor pressing against one another, is reduced. In addition, a pressing force between the gate rotor main body 30 and the screw rotor 2 given by the elastic body 5 can be maintained to the extent that gas does not leak from the compression chamber C.

Accordingly, even if the gate rotors 3 flex owing to the temperature differential between the casing 1 and the screw rotor 2 during operation of the compressor, the gate rotors 3 are prevented, with a simple configuration, from biting into the screw rotor 2, which reduces the amount of wear of the gate rotors 3 and prevents the performance of the compressor from declining.

In addition, because the elastic body 5 is a leaf spring, the elastic body 5 can be configured simply. In addition, because the leaf spring 5 is an annular wave spring or a spiral spring, the leaf spring 5 can be configured simply.

According to the screw compressor with the above configuration, the gate rotors 3 are provided, and therefore even if the gate rotors 3 flex owing to the temperature differential between the casing 1 and the screw rotor 2 during operation of the compressor, the gate rotors 3 are prevented, with a simple configuration, from biting into the screw rotor 2, which reduces the amount of wear of the gate rotors 3 and prevents the performance of the compressor from declining.

Second Embodiment

FIG. 8 shows a second embodiment of the gate rotor according to the present invention. The second embodiment differs from the first embodiment in the configuration of an elastic body. Furthermore, symbols that are the same as those in the first embodiment have the same configuration as in the first embodiment, and any explanation thereof is therefore omitted.

In a gate rotor 3A of the second embodiment, an elastic body 5A is an annular rubber member. An outer circumferential surface of the annular rubber member contacts the inner circumferential surface of the hole 32 of the gate rotor main body 30, and the inner circumferential surface of the annular rubber member contacts the outer circumferential surface of the first shaft 41 of the shaft 40.

The elastic body 5A urges such that the axis of the gate rotor main body 30 and the axis of the shaft 40 always coincide. Furthermore, if an external force acts on the gate rotor main body 30, then the gate rotor main body 30 counteracts the elastic force of the elastic body 5A and moves on the shaft 40.

Accordingly, in addition to the effects and results of the first embodiment, the elastic body 5A can be configured simply because it is an annular rubber member.

Furthermore, the present invention is not limited to the embodiments discussed above. For example, there may be just one gate rotor shaft, the gate rotor main body may be attached to this one shaft, and the casing may support this one shaft. In addition, the quantity of the gate rotors may be increased or decreased.

Third Embodiment

Next, a third embodiment of the screw compressor of the present invention will be explained, referencing the drawings.

A conventional screw compressor that comprises a screw rotor, which has a helical groove, and gate rotors, each of which comprises a plurality of teeth that mesh with the helical groove, is known. It is often the case that the gate rotors are manufactured from a synthetic resin, which makes reducing the wear of the teeth of the gate rotors problematic.

Accordingly, as in the screw compressor disclosed in U.S. Pat. No. 4,890,989, a structure has been proposed wherein—to increase the number of degrees of freedom in the rotational directions of each of the gate rotor supports that support a gate rotor—a spring is used around a floating pin, thereby facilitating movement of the gate rotor in the rotational directions relative to the gate rotor support.

However, the structure of this screw compressor is complex, and there are geometric limits to the precision of components and accuracy of assembly; consequently, there is a risk that a gap between the teeth of each of the gate rotors and the groove of the screw rotor is significant and that, furthermore, the size of the gap will vary largely. If variation occurs in the gap between the teeth of each of the gate rotors and the groove of the screw rotor in this manner, then the screw compressor structured as described in the abovementioned literature cannot absorb that gap variation.

In addition, thermal expansion and load fluctuations in the teeth of each of the gate rotors during operation unfortunately wear the teeth of gate rotors made of resin, which leads to a decline in performance. In particular, because the teeth of each of the gate rotors are generally taller than they are wide, when the teeth expand thermally, they extend greatly in the height directions (i.e., the radial directions). As a result of this extension of the teeth of each of the gate rotors in the radial directions, the tips of the teeth of each of the gate rotors tend to rub against and wear down the far wall of the groove of the screw rotor. The screw compressor structured as described in the abovementioned literature cannot absorb such an extension of the teeth of each of the gate rotors owing to such thermal expansion.

Accordingly, the third embodiment discussed below provides a screw compressor that can prevent the gate rotors from wearing and prevent performance from declining owing to that wear.

<Configuration of Single Screw Compressor 101>

A single screw compressor 101 shown in FIGS. 9 through 15 comprises: one screw rotor 102; a casing 103, which houses the screw rotor 102; a shaft 104, which constitutes a rotary shaft of the screw rotor 102; two gate rotors 105, 106; a thrust bearing 107, which supports the screw rotor 102 from the axial directions; and gate rotor shafts 108, 109, which are for the two gate rotors 105, 106, respectively.

The screw rotor 102 is a columnar rotor that has a plurality of helical grooves 111 in its outer circumferential surface. The screw rotor 102 can rotate integrally with the shaft 104 inside the casing 103. The thrust bearing 107 supports the screw rotor 102 in a direction that leads along the axial directions from the discharge side to the inlet side (i.e., in a direction that is the opposite of a gas inlet direction F1). One end of the shaft 104 is connected to the screw rotor 102, and an other end of the shaft 104 is connected to a drive motor (not shown) outside the casing 103.

The casing 103 is a cylindrically shaped member and rotatably houses the screw rotor 102 and the shaft 104.

Each of the two gate rotors, namely, the first gate rotor 105 and the second gate rotor 106, is a rotary body wherein an opening 121 is formed at the center and a plurality of teeth 112, which mesh with the grooves 111 of the screw rotor 102, is disposed radially around the opening 121; moreover, the first gate rotor 105 and the second gate rotor 106 are capable of rotating around the gate rotor shafts 108, 109, respectively.

The gate rotors 105, 106 of the third embodiment are manufactured from a synthetic resin. Accordingly, because they are used in the screw compressor 101, the gate rotors 105, 106 are preferably manufactured from a synthetic resin that can strongly withstand pressure and wear.

The gate rotor shafts 108, 109 are inserted in openings 121 of the two gate rotors 105, 106 and rotatably support the gate rotors 105, 106. Specifically, the gate rotor shafts 108, 109 comprise gate rotor supports 127, which support the gate rotors 105, 106. The gate rotor supports 127 are coaxially fixed to the gate rotor shafts 108, 109. The shape of the gate rotor supports 127 is substantially similar to, though dimensionally slightly smaller than, that of the gate rotors 105, 106. The gate rotors 105, 106 are fixed by pins 124 such that they cannot rotate with respect to the gate rotor supports 127. The gate rotor shafts 108, 109 are orthogonal to the shaft 104 of the screw rotor 102.

Inside the casing 103, the teeth 112 of the gate rotors 105, 106 are capable of meshing, through a slit 114 formed in the casing 103, with the helical grooves 111 of the screw rotor 102. The two gate rotors 105, 106 are disposed such that they are left-right symmetric to the center of rotation of the screw rotor 102. Furthermore, the gate rotors 105, 106 may be disposed such that they are up-down symmetric.

If the screw rotor 102 is rotated, then the teeth 112 of the first gate rotor 105 and the second gate rotor 106 can mesh sequentially with the grooves 111.

The gate rotor shafts 108, 109 are inserted in the openings 121 of the gate rotors 105, 106, respectively, with gaps 122 therebetween. The gate rotor shafts 108, 109 rotatably support the gate rotors 105, 106, respectively.

Each of the gaps 122 is preferably in the range of approximately 0.1 through 0.8 mm. Namely, if the gaps 122 are less than 0.1 mm, then the extension of the teeth of the gate rotors 105, 106 in the radial directions cannot be absorbed; in addition, if the gaps 122 exceed 0.8 mm, then rotational runout of the gate rotors 105, 106 increases, which makes it difficult for the teeth 112 to mesh with the grooves 111 properly; the above range is therefore set in consideration of these problems.

A coil spring 128, which is a first elastic body, is disposed in the gap 122 between the opening 121 of each of the gate rotors 105, 106 and the corresponding gate rotor shaft 108, 109.

Moreover, an O-ring 129, which is a second elastic body, is disposed around, of a locking pins 123, 124, at least the floating pin 124; each pair of the locking pins 123, 124 stop the rotation of the gate rotors 105, 106 around the gate rotor shafts 108, 109, respectively.

Thus, the gaps 122 are formed around the gate rotor shafts 108, 109; furthermore, the coil springs 128, which are disposed in the gaps 122 around the gate rotor shafts 108, 109, together with the O-rings 129, which are disposed around the floating pins 124, make it possible to absorb the extension of the teeth 112 of the gate rotors 105, 106 in the radial directions.

Here, the gaps between the tips of the teeth 112 of the gate rotors 105, 106 and the far walls of the grooves 111 of the screw rotor 102, namely, the tip gaps, are adjusted at the inlet temperature during low load operation or at room temperature (i.e., ambient temperature) such that the tips of the teeth 112 of the gate rotors 105, 106 contact the far walls of the grooves 111 of the screw rotor 102.

Coil springs 128 disposed in the gaps 122 give an elastic force to the corresponding gate rotor 105, 106 in the radial directions partially toward the corresponding guide pin 123, which is one of the locking pins 123, 124, with respect to the gate rotor 105, 106. Thereby, the coil springs 128 can effectively absorb in the radial directions the extension of the teeth 112, whose movement in the radial directions is restrained by the guide pins 123.

The gate rotor shafts 108, 109 and the gate rotors 105, 106 are connected in the state in which the floating pins 124 have more play than the other locking pins (i.e., the guide pins 123) have.

The floating pins 124 tightly mate with the gate rotors 105, 106 such that there is no play; however, the gate rotors 105, 106 are in a loose connected state such that there is play (i.e., mobility margin) with respect to the gate rotor supports 127 in the rotational directions of the gate rotors 105, 106 as well as in the radial directions.

Accordingly, of the two locking pins, the floating pins 124 can secure a larger mobility margin—that is, the floating pins 124 can secure a larger mobility margin than the guide pins 123 can—which makes it possible to absorb the extension of the teeth 112 of the gate rotors 105, 106 in the radial directions.

The play (i.e., the mobility margin) of the floating pins 124 in the radial directions of the gate rotors 105, 106 is set to approximately 0.1 through 0.8 mm such that the amount of extension in the radial directions of the teeth 112 of the gate rotors 105, 106 owing to thermal expansion can be absorbed. If it is less than 0.1 mm, then the extension of the teeth 112 cannot be sufficiently absorbed by the mobility margin of the floating pins 124, and if it exceeds 0.8 mm, then the smooth rotation of the gate rotors 105, 106 is adversely affected, both of which are problems.

Each of the O-rings 129, namely, the second elastic bodies, is ring shaped and disposed around the corresponding floating pin 124. The O-rings 129 are capable of absorbing the extension of the teeth 112 of the gate rotors 105, 106 in the radial directions.

Each of the O-rings 129 is a ring shaped member manufactured from an elastic material that flexes more easily than the gate rotors 105 (i.e., that has a low Young's modulus). For example, the O-rings 129 can be manufactured from a synthetic rubber, a synthetic resin, or some other elastic material.

In addition, discharge ports 110, which are for discharging compressed refrigerant gas inside the casing 103, are openings formed in the outer circumferential surface of the casing 103 such that there is one for the first gate rotor 105 and one for the second gate rotor 106.

During the rotation of the screw rotor 102, the discharge ports 110 open at an appropriate position of the outer circumferential surface of the casing 103 such that communication with the grooves 111 in the outer circumferential surface of the screw rotor 102 is possible.

<Explanation of the Operation of the Single Screw Compressor 101>

The single screw compressor 101 shown in FIGS. 9 through 15 compresses the gas as follows.

First, when the shaft 104 receives a rotational driving force from the motor (not shown) external to the casing 103, the screw rotor 102 rotates in the direction indicated by arrows R1 (refer to FIG. 9). At this time, the teeth 112 of the two gate rotors 105, 106, which mesh with the helical grooves 111 of the screw rotor 102, are pressed to the inner walls of the helical grooves 111, and thereby the gate rotors 105, 106 rotate in the directions of arrows R2. At this time, on the near side of the paper plane of the screw rotor 102 in FIGS. 9 and 10, the volumes of the compression chambers on the near side of the paper plane, which are formed and partitioned by the inner surface of the casing 103, the grooves 111 of the screw rotor 102, and the teeth 112 of the gate rotor 105, are reduced. In addition, on the far side of the paper plane of the screw rotor 102, the volumes of the compression chambers on the far side of the paper plane, which are formed and partitioned by the inner surface of the casing 103, the grooves 111 of the screw rotor 102, and the teeth 112 of the gate rotor 106, are reduced.

Taking advantage of the reduction of the volumes of the two compression chambers, the refrigerant F1 (refer to FIG. 10) introduced via an inlet side opening 115 of the casing 103 prior to compression is guided to the compression chambers immediately before the grooves 111 and the teeth 112 mesh with one another, the refrigerant is compressed by the reduction of the volumes of the compression chambers while the grooves 111 and the teeth 112 mesh, and, immediately after the grooves 111 and the teeth 112 unmesh, the compressed refrigerant F2 (refer to FIG. 10) is discharged via the discharge ports 110, which open on both the far and near sides of the paper plane (refer to FIG. 10) corresponding to the gate rotors 105, 106.

Characteristics of the Third Embodiment

(1)

In the screw compressor 101 of the third embodiment, the gaps 122 are formed around the gate rotor shafts 108, 109; furthermore, the coil springs 128, which are disposed in the gaps 122 around the gate rotor shafts 108, 109, together with the O-rings 129, which are disposed around the floating pins 124, make it possible to absorb the extension of the teeth 112 of the gate rotors 105, 106 in the radial directions. Thereby, the tips of the teeth 112 of the gate rotors 105, 106 no longer rub against and wear the far walls of the grooves 111 of the screw rotor 102, which makes it possible to prevent the gate rotors 105, 106 from wearing.

(2)

In addition, it is possible to control the gaps between the tips of the teeth 112 of the gate rotors 105, 106 and the far walls of the grooves 111 of the screw rotor 102, that is, the tip gaps. For example, the tip gaps are also automatically adjusted in accordance with changes in the operating conditions. Thereby, it is possible to prevent the performance of the screw compressor 101 from declining.

(3)

Moreover, because the degrees of freedom in fabrication accuracy and assembly accuracy of the screw compressor 101 increase, the manufacturing cost can be reduced.

(4)

Moreover, even if the refrigerant gas, which is the compression medium, or the like is introduced to the screw compressor 101 in the liquid state and transitions to a so-called liquid compression state and the load applied to the teeth 112 of the gate rotors 105, 106 fluctuates, it is possible to prevent both the teeth 112 of the gate rotors 105, 106 from wearing abnormally and the gate rotors 105, 106 and the screw rotor 102 from seizing. Thereby, the reliability of the screw compressor 101 can be improved.

For example, because the present embodiment comprises the gaps 122, which are between the openings 121 of the gate rotors 105, 106 and the gate rotor shafts 108, 109, the coil springs 128, which are disposed in the gaps 122, and the O-rings 129, which are disposed around the floating pins 124, the gate rotors 105, 106 can move in the radial directions, which makes it possible to release refrigerant in the liquid state from the tip gaps to the outside of the screw compressor 101, even if abnormal liquid compression occurs.

(5)

Furthermore, in the screw compressor 101 of the third embodiment, the coil springs 128 disposed in the gaps 122 give elastic forces, in the radial directions of the gate rotors 105, 106, partially toward the guide pins 123 with respect to the gate rotors 105, 106. Accordingly, the coil springs 128 can effectively absorb the extension of the teeth 112, whose movement in the radial directions is restrained by the guide pins 123, in the radial directions.

(6)

In the screw compressor 101 of the third embodiment, one of the locking pins 123, 124 is the floating pins 124 that connect the gate rotor shafts 108, 109 and the gate rotors 105, 106, respectively, in the state wherein they have more play than the other locking pins (i.e., the guide pins 123) do, which secures for the floating pins 124 a larger mobility margin than the guide pins 123 have; thereby, it is possible to absorb the extension of the teeth 112 of the gate rotors 105, 106 in the radial directions.

(7)

In the screw compressor 101 of the third embodiment, the O-rings 129, which are the second elastic bodies, are ring shaped and disposed around the floating pins 124, which makes it possible to absorb the extension of the teeth 112 of the gate rotors 105, 106 in the radial directions.

In addition, if the dimensions and material properties of the O-rings 129 are modified appropriately in accordance with, for example, the extension of the teeth 112 of the gate rotors 105, 106 in the radial directions, the wearing of the tooth tips, and the like, then it is also possible to extend the life spans of the gate rotors 105, 106.

Modified Example of the Third Embodiment

(A)

The third embodiment explained a configuration wherein two types of elastic bodies, namely, the coil springs 128, which are disposed in the gaps 122 around the gate rotor shafts 108, 109, and the O-rings 129, which are disposed around the floating pins 124, are provided, but the present invention is not limited thereto.

As a modified example of the present invention, the extension of the teeth 112 of the gate rotors 105, 106 in the radial directions can be absorbed even if a configuration is adopted wherein only one of the elastic bodies, namely, the coil springs 128, which are disposed in gaps 122 around the gate rotor shafts 108, 109, or the O-rings 129, which are disposed around the floating pins 124, is provided.

(B)

The third embodiment explained the coil springs 128 as an example of elastic bodies disposed in the gaps 122 in the present invention, but the present invention is not limited thereto; for example, ring shaped elastic bodies may fill the entire gaps 122. In such a case, it is possible to absorb the extension of the teeth 112 of the gate rotors 105, 106 in the radial directions over the entire circumferences of the gate rotors 105, 106.

In addition, filling the entire gaps 122 with the ring shaped elastic bodies makes it possible to further extend the life span of the teeth 112 of the gate rotors 105, 106.

INDUSTRIAL APPLICABILITY

The present invention makes it possible to widely adapt a screw compressor that comprises a screw rotor and gate rotors.