JP2019035388A - Oil-free screw compressor - Google Patents

Abstract

To correct, with field balance, dynamic imbalance of at least one of a screw rotor and a motor rotor in an oil-free screw compressor.SOLUTION: An oil-free screw compressor 1 comprises a balance adjustment component 31 provided on at least one of an end part 23e of a motor rotor shaft 23 and an end part 13c of a screw rotor shaft 13, and configured to adjustably attach a load eccentric to a common axial line α of the screw rotor shaft 13 and motor rotor shaft 23.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an oil-free screw compressor.

  In the oil-free screw compressor disclosed in Patent Document 1, a shaft (screw rotor shaft) having one of a pair of screw rotors, and an output shaft of a motor for rotating the screw rotor, that is, a motor rotor shaft, Is composed of one shaft. Bearings are provided at three locations on the shaft. That is, the shaft is rotatably supported by the bearings at both ends of the screw rotor shaft and the bearings at the end of the motor rotor shaft (the end opposite to the screw rotor).

JP-A-2005-76511

  In an oil-free screw compressor such as that disclosed in Patent Document 1, due to the dynamic imbalance of at least one of the screw rotor and the motor rotor, the rotating shaft may bend due to centrifugal force. In general, the shaft diameter of the shaft of the oil-free screw compressor is thinner than the shaft diameter of the shaft of the oil supply type screw compressor, so that the amount of deflection due to dynamic imbalance tends to increase. When the amount of bending becomes large, for example, when the shaft comes into contact with the non-contact shaft seal portions (viscos seals) at both ends of the screw rotor, it may cause a problem such as abnormal vibration.

  About a screw rotor and a motor rotor, after correcting dynamic imbalance independently using a balance testing machine etc., respectively, the vibration of the axis | shaft in rotation can be reduced to some extent by assembling it integrally in a casing. However, even if such individual corrections are made, dynamic imbalance occurs in the entire oil-free screw compressor due to manufacturing errors and assembly errors of the casing and the like. Therefore, correction of dynamic imbalance in field balance, that is, correction of dynamic imbalance in a state of being integrally assembled in the casing is required. However, in the conventional oil-free screw compressor including the one disclosed in Patent Document 1, the dynamic imbalance between the screw rotor and the motor rotor is corrected after the assembly because of the structure covered by the casing. Have difficulty.

  In the oil-free screw compressor in which the motor rotor shaft is coaxially and fixedly provided with respect to the screw rotor shaft, the dynamic unbalance of at least one of the screw rotor and the motor rotor is corrected by field balance. The challenge is to make it possible.

  The present invention includes a compressor body including a pair of screw rotors that mesh with each other, a motor rotor shaft that is coaxially and fixedly provided to a screw rotor shaft provided with one of the pair of screw rotors, and the motor rotor. A motor having a motor rotor fixed to a shaft; a first bearing portion rotatably supporting the screw rotor shaft on a side opposite to the motor with respect to the screw rotor; and the motor with respect to the screw rotor. A second bearing portion that rotatably supports the screw rotor shaft on the same side, and a third bearing portion that rotatably supports the motor rotor shaft on the side opposite to the compressor body with respect to the motor rotor, An end opposite to the motor rotor with respect to the third bearing portion of the motor rotor shaft and the first bearing portion of the screw rotor shaft Wherein the screw rotors and a balance adjustment component for adding an eccentric load to at least one of the opposite end, to provide an oil-free screw compressor with.

  An eccentric load is applied to at least one of the end portion of the motor rotor shaft and the end portion of the screw rotor shaft (hereinafter referred to as “shaft end portion”) by a balance adjusting component. Therefore, during the operation of the oil-free screw compressor (when the motor rotor shaft and the screw rotor shaft provided coaxially and fixedly are rotated), centrifugal force acting on the shaft end (that is, bending load on the shaft), Bending (bending) occurs between the screw rotor shaft and the motor rotor shaft. The shaft at the time of operation (rotation) caused by the dynamic unbalance of at least one of the screw rotor and the motor rotor is caused by the displacement of the shaft end caused by the centrifugal force due to the eccentric load being applied by the balance adjusting component. A portion with low tolerance of bending of the screw rotor shaft and the motor rotor shaft by superimposing the displacement of the end portion (that is, the displacement of the shaft end portion when the eccentric load due to the balance adjusting component is not applied) is canceled ( For example, it is possible to reduce shaft deflection at a shaft seal portion of the screw rotor shaft, a motor rotor shaft, or a portion where the gap between the screw rotor shaft and the casing is narrow. That is, the dynamic imbalance of at least one of the screw rotor and the motor rotor can be corrected by field balance.

  The balance adjusting component may include a main body fixed to the end opposite to the motor rotor with respect to the third bearing portion of the motor rotor shaft, and a weight removable from the main body. .

  A plurality of attachment holes may be provided on the peripheral surface of the main body, and one or a plurality of the weights may be attached to the attachment holes in a detachable manner.

  Further, a plurality of mounting holes may be provided on the end surface of the main body, and one or a plurality of the weights may be detachably attached to the mounting holes.

  The main body can adjust a common axial position of the screw rotor shaft and the motor rotor shaft with respect to the end of the motor rotor shaft opposite to the motor rotor with respect to the third bearing portion. It may be attached.

  The main body can adjust an angular position around a common axis of the screw rotor shaft and the motor rotor shaft with respect to the end portion opposite to the motor rotor with respect to the third bearing portion of the motor rotor shaft. It may be attached to.

  The screw rotor shaft and the motor rotor shaft are separate and may be fastened to each other by a fastening structure.

  The screw rotor shaft and the motor rotor shaft may be integrated.

  According to the present invention, in the oil-free screw compressor in which the motor rotor shaft is coaxially and fixedly provided with respect to the screw rotor shaft, the dynamic imbalance of at least one of the screw rotor and the motor rotor is reduced in the field balance. You can fix it.

1 is a cross-sectional view showing an oil-free screw compressor according to a first embodiment of the present invention. The enlarged view of the part II of FIG. The side view of a balance adjustment component. The partial cross section end view of a balance adjustment component. The conceptual diagram for demonstrating correction of dynamic imbalance. Sectional drawing similar to FIG. 2 which shows the balance adjustment component of a 1st alternative. The end view of the balance adjustment component of the 1st alternative. The end view of the balance adjustment component of the 2nd alternative. The side view of the balance adjustment component of the 3rd alternative. The side view of the balance adjustment component of the 3rd alternative. Sectional drawing similar to FIG. 2 of the balance adjustment component of the 4th alternative plan. Sectional drawing similar to FIG. 2 of the balance adjustment component of the 5th alternative. The end view of the balance adjustment component of the 5th alternative. Sectional drawing of the oil free screw compressor which concerns on 2nd Embodiment of this invention. The enlarged view of the part XV of FIG. Sectional drawing of the oil-free screw compressor which concerns on 3rd Embodiment of this invention. The enlarged view of the part XVII of FIG.

(First embodiment)
An oil-free screw compressor 1 according to the first embodiment of the present invention shown in FIGS. 1 and 2 includes a compressor body 2 and a motor 3. The screw rotor shaft 13 of the male rotor 11 provided in the compressor main body 2 and the motor rotor shaft 23 provided in the motor 3 are separate, but are arranged in series so as to have an axis α extending coaxially, that is, in a common horizontal direction. Is arranged. Further, as will be described later, the motor rotor shaft 23 is directly fixed to the screw rotor shaft 13 without a separate coupling. That is, the motor rotor shaft 23 and the screw rotor shaft 13 are fixedly provided without having a degree of freedom in the mounting angle of the mutual axis. Similarly, as will be described later, the screw rotor shaft 13 and the motor rotor shaft 23 that are fixed and integrated with each other are rotatably supported by three bearing portions 14, 15, and 25.

  The compressor body 2 includes casings 4 </ b> A and 4 </ b> B, and the end of the casing 4 </ b> A is closed with a cover 5. A casing 6 having both end openings provided in the motor 3 is connected to the casing 4B. One end (left end in the figure) of the casing 6 is closed by the casing 4B of the compressor body 2. A jacket 7 is inserted into the casing 6. A cylindrical portion 8 a having both end openings provided in the holder 8 is inserted into an opening at one end (right end in the drawing) of the jacket 7. The flange portion 8 b of the holder 8 is fixed to the jacket 7. A cylindrical portion 9 a included in the cover 9 is inserted into the cylindrical portion 8 a of the holder 8. The base portion 9 b of the cover 9 is fixed to the flange portion 8 b of the holder 8. In the figure of the cylindrical portion 8 a of the holder 8, the opening at the right end is closed by the base portion 9 b of the cover 9.

  A rotor chamber 10 formed in the casing 4B of the compressor body 2 accommodates a screw rotor pair, that is, a male rotor 11 and a female rotor 12.

  The screw rotor shaft 13 to which the male rotor 11 is fixed includes a first portion 13 a that protrudes from the male rotor 11 to the opposite side of the motor 3, and a second portion 13 b that protrudes from the male rotor 11 toward the motor 3. . The first portion 13 a of the screw rotor shaft 13 is rotatably supported by the first bearing portion 14. In the present embodiment, the first bearing portion 14 includes a ball bearing 14a held by the cover 5 and a roller bearing 14b held by the casing 4A. The second portion 13 b of the screw rotor shaft 13 is rotatably supported by the second bearing portion 15. In the present embodiment, the second bearing portion 15 includes a ball bearing 15a held by the casing 4B and a roller bearing 15b. A shaft seal portion 16 is disposed between the first bearing portion 14 and the rotor chamber 10, and a shaft seal portion 17 is also disposed between the second bearing portion 15 and the rotor chamber 10. In this embodiment, these shaft seal parts 16 and 17 are both visco seals. The shaft seals 16 and 17 may have a known seal or seal structure. An end portion 13 c of the first portion 13 a of the screw rotor shaft 13 on the side opposite to the male rotor 11 with respect to the first bearing portion 14 is located in the cover 5. A timing gear 18 is fixed to the end 13 c of the screw rotor shaft 13.

  The screw rotor shaft (not shown) of the female rotor 12 is rotatably supported and shaft-sealed by the same structure as the screw rotor shaft 13 of the male rotor 11 except that it is not connected to the motor rotor shaft 23. ing. A timing gear (not shown) that meshes with the timing gear 18 of the male rotor 11 is fixed to the screw rotor shaft of the female rotor 12.

  When the motor 3 is operated and the screw rotor shaft 13 connected to the motor rotor shaft 23 is rotationally driven, the male rotor 11 and the female rotor 12 rotate in a state where they are engaged with each other. As a result, the gas sucked from the suction port 19 of the compressor body 2 is compressed in the rotor chamber 10, and the compressed gas is discharged from the discharge port 20.

  In the casing 6 of the motor 3, a stator 21 fixed to the jacket 7 and a motor rotor 24 arranged with a gap with respect to the stator 21 and fixed to the motor rotor shaft 23 are accommodated. The motor rotor shaft 23 includes a first portion 23 a that protrudes from the motor rotor 24 toward the compressor body 2, and a second portion 23 b that protrudes from the motor rotor 24 to the opposite side of the compressor body 2. The second portion 23 b of the motor rotor shaft 23 is rotatably supported by a third bearing portion 25 (in this embodiment, a deep groove ball bearing) held by the holder 8.

  The motor rotor shaft 23 is provided with a connecting hole 23c extending in the axis α direction from the end surface of the first portion 23a. The tip of the second portion 13b of the screw rotor shaft 13 is inserted into the connecting hole 23c. The first portion 23a of the motor rotor shaft 23 and the second portion 13b of the screw rotor shaft 13 are integrally connected by a key 26 in the connection hole 23c. The motor rotor shaft 23 is provided with an insertion hole 23d extending in the direction of the axis α from the end surface of the second portion 23b and communicating with the connection hole 23c. The fastening rod 27 is inserted through the insertion hole 23d. Male screw portions 27 a and 27 b are provided at both ends of the fastening rod 27. One male screw portion 27 a of the fastening rod 27 is located in the connection hole 23 c and is screwed into a female screw portion 13 d provided in the second portion 13 b of the screw rotor shaft 13. The other male screw portion 27 b of the fastening bolt 27 protrudes from the end surface of the second portion 23 b of the motor rotor shaft 23. A nut 28 is screwed into a portion protruding from the second portion 23b of the male screw portion 27b. Between the nut 28 and the end surface of the second portion 23 b of the motor rotor shaft 23, a main body 32 of a balance adjusting component 31 described later and a washer 29 are interposed. By tightening the nut 28, the screw rotor shaft 13 and the motor rotor shaft 23 are fastened to each other. That is, the motor rotor shaft 23 and the screw rotor shaft 13 are fastened to each other by the fastening rod 27 and the nut 28 in a state where the motor rotor shaft 23 and the screw rotor shaft 13 are integrally connected by the key 26. The key 26, the fastening rod 27, and the nut 28 are an example of a fastening structure in the present invention.

  A balance adjustment component 31 is provided at a portion opposite to the motor rotor 24 with respect to the third bearing portion 25 of the second portion 23 b of the motor rotor shaft 23, that is, at an end portion 23 e of the motor rotor shaft 23. 3 and 4 together, the balance adjustment component 31 includes a relatively flat disk-shaped main body 32 and a weight 33 detachably attached to the main body 32.

  The main body 32 of the balance adjusting component 31 is formed with a connection hole 32b extending in the axis α direction from the end surface 32a on the compressor main body 32 side (left side in the drawing). A small-diameter portion 23f provided at the tip of the end portion 23e of the motor rotor shaft 23 is accommodated in the connection hole 32b. The main body 32 is provided with an insertion hole 32d that extends in the direction of the axis α from the end surface 32c opposite to the compressor main body 32 (right side in the drawing) and communicates with the connection hole 32b. The above-described fastening rod 27 is inserted through the insertion hole 32 d and thereby penetrates the main body 32 and is inserted into the insertion hole 23 d of the motor rotor shaft 23. The main body 32 is fixed to the end portion 23 e of the motor rotor shaft 23 by being sandwiched between the nut 28 and the end portion 23 e of the motor rotor shaft 23 via a washer 29. Pin holes 23g and 32e are formed in the end surface of the end 23e of the motor rotor shaft 23 and the hole bottom of the connection hole 32b of the main body 32, respectively. The rotation angle position about the axis α of the main body 32 is held with respect to the end portion 23e of the motor rotor shaft 23 by the pins 34 inserted through the pin holes 23g and 32e.

  A plurality (eight in this embodiment) of housing holes 32g are provided on the peripheral surface 32f of the main body 32 of the balance adjusting component 31. Each housing hole 32g is provided with a female screw portion 32h. A weight 33 can be detachably attached to each housing hole 32g. Specifically, a male screw portion 33a is provided on the outer periphery of the weight 33, and the weight 33 can be held in the housing hole 32g by screwing the male screw portion 33a into the female hole portion 32h.

  As shown most clearly in FIG. 4, when viewed from the direction in which the axis α extends, the plurality of receiving holes 32g are provided radially with an angular interval (equal angular interval in the present embodiment) about the axis α. ing. Therefore, if the weight 33 is attached to any one of the accommodation holes 32g, or the weight 33 is attached to the plurality of accommodation holes 32g so as not to be rotationally symmetric with respect to the axis α, the end 23e of the motor rotor shaft 23 is attached. Thus, an eccentric load is applied. In this state, when the oil-free screw compressor 1 is operated and the motor rotor shaft 23 and the screw rotor shaft 13 are rotated, centrifugal force corresponding to the eccentric load by the balance adjusting component 31 acts on the end portion 23e of the motor rotor shaft 23 ( That is, a bending load corresponding to the eccentric load can be applied to the end portion 23e of the motor rotor shaft 23). As a result, the motor rotor shaft 23 to which the balance adjusting component 31 is attached is bent (bent), so that the end portion 23e of the motor rotor shaft 23 is swung, and other than the end portion 23e of the motor rotor shaft 23. The portion and the screw rotor shaft 13 can also be bent (see the bending curve A1 in FIG. 5). The bending due to the eccentric load of the balance adjusting component 31 is made to the bending of the motor rotor shaft 23 and the screw rotor shaft 13 due to the dynamic unbalance of the male rotor 11 and the motor rotor 24 (see the bending curve A2 in FIG. 5). By superimposing them so as to cancel each other, it is possible to reduce the bending of the screw rotor shaft 13 at the shaft sealing portions 16 and 17 during the operation of the oil-free screw compressor 1 (see the bending curve A3 in FIG. 5).

  In FIG. 5, the deflection amounts in the shaft seal portions 16 and 17 due to the dynamic imbalance of the male rotor 11 and the motor rotor 24 are δ11 and δ21. These deflection amounts δ11 and δ21 are offset by the deflection amounts δ12 and δ22 in the shaft seal portions 16 and 17 caused by the eccentric load of the balance adjusting component 31, and are reduced to the deflection amounts δ13 and δ23.

  The balance adjusting component 31 can be accessed simply by removing the cover 9, and it is not necessary to take out the male rotor 11 from the casings 4 </ b> A and 4 </ b> B and to take out the motor rotor 24 from the casing 6. That is, the correction of the dynamic imbalance by the balance adjusting component 31 can be executed in a state where the oil-free screw compressor 1 is installed.

  As described above, the dynamic imbalance of the male rotor 11 and the motor rotor 24 can be corrected by the field balance by attaching the weight 33 to the main body 32 of the balance adjusting component 31 and applying an eccentric load.

  The direction and magnitude of the eccentric load applied to the end portion 23e of the motor rotor shaft 23 can be adjusted by the balance adjusting component 31 by the following method. First, it can be adjusted according to which of the plurality of accommodation holes 32g the weight 33 is attached. Further, it can be adjusted depending on which position in the accommodation hole 32g the weight 33 is attached. That is, the centrifugal force generated by the weight 33 increases as the weight 33 is attached to a position far from the axis α in the accommodation hole 32g.

  Referring to FIG. 2, the greater the distance L in the axis α direction from the center of the third bearing portion 25, which is the bearing closest to the balance adjustment component 31, to the position of the center of gravity of the balance adjustment component 31, the greater the load on the balance adjustment component 31. The bending moment generated at the end 23e of the motor rotor shaft 23 is increased. Accordingly, the greater the distance L, the smaller the centrifugal force generated by the balance adjusting component 31, that is, the smaller the number of weights 33 attached to the main body 32, the less the screw rotor shaft 13 in the shaft seal portions 16, 17. The displacement can be appropriately reduced. On the other hand, the longer the distance L, the longer the shaft length of the motor rotor shaft 23 and the larger the motor 3. From the viewpoint of setting the shaft length of the motor rotor shaft 23 within a structurally acceptable range, the distance L is set to three times or less (L / D ≦ 3) of the shaft diameter D of the portion corresponding to the distance L of the motor rotor shaft 23 It is preferable.

In order to appropriately reduce the amount of bending of the motor rotor shaft 23 in the shaft seal portions 16 and 17 as conceptually shown in FIG. 5, in order to determine which position in which accommodation hole 32g the weight 33 is attached, In addition to trial and error, there are the following methods. In other words, from the vibration values in the following three states 1 to 3, the direction and amount of bending when the weight 33 is not attached to the shaft seal portions 16 and 17 and the relationship between the centrifugal force caused by the weight 33 are calculated. In order to minimize the amount of bending at the shaft sealing portions 16 and 17, it is possible to determine at which position of which accommodation hole 32g of the main body 32 the weight 33 is attached.
State 1: State in which the weight 33 is not attached State 2: State in which the weight 33 is attached to the appropriate accommodation hole 32g State 3: State in which the weight 33 is attached to the accommodation hole 32g at a position different from the state 2.

  6 to 13 show various alternatives of the balance adjustment component 31.

  In the alternative shown in FIGS. 6 and 7, the main body 32 of the balance adjusting component 31 is formed with a plurality of receiving holes 32g extending from the end face 32c in the direction along the axis α. As shown in FIG. 7, when viewed from the direction in which the axis α extends, the plurality of receiving holes 32g are provided at an angular interval (equal angular interval in this alternative) on a virtual circle C1 centered on the axis α. Yes. If the weight 33 is attached to any one of the housing holes 32g, or the weight 33 is attached to the plurality of housing holes 32g in an arrangement that is not rotationally symmetric with respect to the axis α, the end 23e of the motor rotor shaft 23 is An eccentric load is applied. As in the alternative shown in FIG. 8, the main body 32 may be provided with a plurality of receiving holes 32g provided on the two virtual circles C1 and C2 centered on the axis α with an angular interval. The main body 32 may be provided with receiving holes 32g on three or more virtual circles. Furthermore, a plurality of rows of receiving holes 32g provided in the peripheral surface 32f of the main body 32 as shown in FIGS. 3 and 4 may be provided in the direction of the axis α. Furthermore, the accommodation hole 32g may be provided on both the peripheral surface 32f and the end surface 32c of the main body 32.

  The alternative balance adjusting component 31 shown in FIGS. 9 and 10 includes a main body 32, but does not include a weight attached to the main body 32. The main body 32 has a shape that is not rotationally symmetric with respect to the axis α as viewed from the direction in which the axis α extends. Specifically, the main body 32 in this alternative includes a disk portion 32i and a protrusion 32j protruding from the disk portion 32i in a direction away from the axis α. By exchanging multiple types of main bodies 32 having protrusions 32j having at least one of shape, dimension, and protruding direction and attaching them to the end 23e of the motor rotor shaft 23, the direction and magnitude of the eccentric load are adjusted. it can.

  In the alternative balancing adjustment component 31 shown in FIG. 11, the main body 32 is attached to the end 23e of the motor rotor shaft 23 by a pair of nuts 35A and 35B. The motor rotor shaft 23 is provided with a male screw portion 23h. The main body 32 is provided with an insertion hole 32k penetrating between the end faces 32a and 32c. The hole diameter of the insertion hole 32k is set to be the same as or slightly larger than the outer diameter of the male screw portion 23h. The main body 32 is fixed to the end portion 23e of the motor rotor shaft 23 by being sandwiched between nuts 35A and 35B screwed into the male screw portion 23h. When the nuts 35A and 35B are loosened and separated from the main body 32, they can be moved in the direction of the axis α on the male thread portion 23f of the main body 32. Further, after the main body 32 is moved, the nuts 35A and 35B are tightened again, and the main body 32 is sandwiched between them, so that the main body 32 can be fixed at the moved position. That is, in this alternative, the position of the balance adjustment component 31 in the direction of the axis α can be adjusted with respect to the end 23e of the motor rotor shaft 23. The main body 32 may be provided with a female screw portion that is screwed into the male screw portion 23h instead of the insertion hole 32k.

  In the alternative balance adjustment component 31 shown in FIGS. 12 and 13, a serration portion 23 i is provided on the outer peripheral surface of the small diameter portion 23 f of the end portion 23 e of the motor rotor shaft 23. Further, a serration portion 32m that fits with the serration portion 23i is provided on the peripheral wall of the connection hole 32b of the main body 32 of the balance adjustment component 31 in which the small diameter portion 23f is accommodated. When the nut 28 and the washer 29 are removed from the fastening rod 27, the main body 32 of the balance adjusting component 31 can be removed from the end 23e of the motor rotor shaft 23. Once the main body 32 that has been removed is mounted on the end portion 23e of the motor rotor shaft 23 with the rotational angle position around the axis α being varied, the nut 28 and the washer 29 are screwed into the male thread portion 27b of the fastening rod 27. The main body 32 can be fixed to the end 23e of the motor rotor shaft 23 again. Since the small diameter portion 23f of the end portion 23e of the motor rotor shaft 23 and the main body 32 are fitted by the serration portions 23i and 32m, the main body 32 is made to have different rotational angle positions around the axis α and the end portion 23e of the motor rotor shaft 23. Can be fixed. That is, in this alternative, the angular position of the balance adjusting component 31 around the axis α can be adjusted with respect to the end portion 23e of the motor rotor shaft 23.

  The following second to fourth embodiments are the same as the first embodiment, unless otherwise specified. In the drawings relating to these embodiments, the same or similar elements as those in the first embodiment are denoted by the same reference numerals.

(Second Embodiment)
In the oil-free screw compressor 1 according to the second embodiment of the present invention shown in FIGS. 14 and 15, the balance adjusting component 31 having the same configuration as that of the first embodiment is provided at the end 23 e of the motor rotor shaft 23. In the present embodiment, the balance adjusting component 41 is also provided at the end 13 c of the screw rotor shaft 13.

  A plurality of accommodation holes 42b are provided in the peripheral surface 42a of the main body 42 of the balance adjusting component 41, and weights 43 can be detachably attached to the individual accommodation holes 42b. The specific structures of the accommodation hole 42b and the weight 34 are the same as the accommodation hole 32g and the weight 43 (see FIGS. 3 and 4) in the first embodiment, respectively.

  The end portion 13c of the screw rotor shaft 13 is provided with a male screw portion 13e. The main body 42 is provided with an insertion hole 42e penetrating between the end faces 42c and 42d. The hole diameter of the insertion hole 42e is set to be the same as or slightly larger than the outer diameter of the male screw portion 13e. The main body 42 is fixed to the end portion 13c of the screw rotor shaft 13 by being sandwiched between nuts 45A and 45B that are screwed into the male screw portion 13e. The position in the axis α direction can be adjusted. The main body 42 may be provided with a female screw portion that is screwed into the male screw portion 13e instead of the insertion hole 42e.

  The specific configuration of the balance adjustment component 41 on the screw rotor shaft 13 side is not limited to the same configuration as the balance adjustment component 31 on the motor rotor shaft 23 side in the first embodiment, and will be described with reference to FIGS. 6 to 13. Various alternative configurations may be employed.

(Third embodiment)
In the oil-free screw compressor 1 according to the third embodiment of the present invention shown in FIGS. 16 and 17, the balance adjusting component 41 having the same configuration as that of the second embodiment is provided at the end 13 c of the screw rotor shaft 13. However, no balance adjusting component is provided at the end 23e of the motor rotor shaft 23.

  The present invention is not limited to the embodiments, and various modifications are possible. The motor rotor shaft may be provided coaxially and fixedly with respect to the screw rotor shaft of the female rotor. The screw rotor shaft and the motor rotor shaft may be integrated. The specific structure of the balance adjusting component is not particularly limited as long as an eccentric load can be applied to a predetermined portion of the shaft. The balance adjustment part may reduce the displacement of the motor rotor shaft or the screw rotor shaft at a portion where the gap between the casing and the casing is narrow.

  In the above-described embodiment, the first bearing portion 14 includes the ball bearing 14a held by the cover 5 and the roller bearing 14b held by the casing 4A, but at least a bearing capable of supporting a radial load is provided. It only has to have. Further, in the above-described embodiment, the second bearing portion 15 includes the ball bearing 15a held in the casing 4B and the roller bearing 5b. However, as long as the second bearing portion 15 includes at least a bearing capable of supporting a radial load. Good.

DESCRIPTION OF SYMBOLS 1 Oil free screw compressor 2 Compressor main body 3 Motor 4A, 4B Casing 5 Cover 6 Motor casing 7 Jacket 8 Holder 8a Tubular part 8b Flange part 9 Cover 9a Tubular part 9b Base part 10 Rotor chamber 11 Male rotor 12 Female Rotor 13 Screw rotor shaft 13a First part 13b Second part 13c End part 13d Female thread part 13e Male thread part 14 First bearing part 14a Ball bearing 14b Roller bearing 15 Second bearing part 15a Ball bearing 15b Roller bearing 16, 17 Shaft seal part 18 Timing gear 19 Suction port 20 Discharge port 21 Stator 23 Motor rotor shaft 23a First part 23b Second part 23c Connection hole 23d Insertion hole 23e End part 23f Small diameter part 23g Pin hole 23h Male thread part 23i Serration part 24 Motor rotor 25 Third bearing part 6 Key 27 Fastening rod 27a, 27b Male thread portion 28 Nut 29 Washer 31 Balance adjusting part 32 Main body 32a Left end surface 32b Connection hole 32c Right end surface 32d Insertion hole 32e Pin hole 32f Peripheral surface 32g Housing hole 32h Female thread portion 32i Circular plate 32j Projection 32k Insertion hole 32m Serration part 33 Weight 33a Male thread part 34 Pin 35A, 35B Nut 41 Balance adjustment component 42 Main body 42a Peripheral surface 42b Receiving hole 42c, 42d End face 42e Insertion hole 45A, 45B Nut α axis L diameter D Distance C1, C2 Virtual circle A1, A2, A3 Deflection curve δ11, δ21, δ12, δ22, δ13, δ23 Deflection amount

Claims (10)

A compressor body comprising a pair of screw rotors that mesh with each other;
A motor including a motor rotor shaft coaxially and fixedly provided to a screw rotor shaft provided with one of the pair of screw rotors, and a motor rotor fixed to the motor rotor shaft;
A first bearing portion rotatably supporting the screw rotor shaft on a side opposite to the motor with respect to the screw rotor;
A second bearing portion rotatably supporting the screw rotor shaft on the same side as the motor with respect to the screw rotor;
A third bearing portion rotatably supporting the motor rotor shaft on the side opposite to the compressor body with respect to the motor rotor;
At least one of an end of the motor rotor shaft opposite to the motor rotor with respect to the third bearing portion and an end of the screw rotor shaft opposite to the screw rotor with respect to the first bearing portion. An oil-free screw compressor comprising a balance adjusting part for applying an eccentric load.   2. The oil-free screw compressor according to claim 1, wherein the balance adjusting component is provided at the end portion opposite to the motor rotor with respect to the third bearing portion of the motor rotor shaft. The balance adjusting part is
A main body fixed to the end opposite to the motor rotor with respect to the third bearing portion of the motor rotor shaft;
The oil-free screw compressor according to claim 2, further comprising a weight that can be attached to and detached from the main body. A plurality of mounting holes are provided on the peripheral surface of the main body,
The oil-free screw compressor according to claim 3, wherein one or a plurality of the weights are detachably attached to the attachment hole. A plurality of mounting holes are provided on the end surface of the main body,
The oil-free screw compressor according to claim 3, wherein the one or a plurality of weights are detachably attached to the attachment holes.   The main body can adjust a common axial position of the screw rotor shaft and the motor rotor shaft with respect to the end of the motor rotor shaft opposite to the motor rotor with respect to the third bearing portion. The oil-free screw compressor according to any one of claims 3 to 5, which is attached.   The main body can adjust an angular position around a common axis of the screw rotor shaft and the motor rotor shaft with respect to the end portion opposite to the motor rotor with respect to the third bearing portion of the motor rotor shaft. The oil-free screw compressor according to any one of claims 3 to 6, which is attached to the compressor.   8. The balance adjustment component according to claim 1, wherein the balance adjustment component is provided at an end of the screw rotor shaft opposite to the screw rotor with respect to the first bearing portion. 9. Oil-free screw compressor.   The oil-free screw compressor according to any one of claims 1 to 8, wherein the screw rotor shaft and the motor rotor shaft are separate and are fastened to each other by a fastening structure.   The oil-free screw compressor according to any one of claims 1 to 8, wherein the screw rotor shaft and the motor rotor shaft have an integral structure.

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