JP2011007048A - Screw compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve work efficiency of a screw compressor.SOLUTION: The screw compressor, sucking and compressing gas to be compressed for discharge to the outside, includes: a male rotor and a female rotor held in meshing engagement with each other; a mechanism for rotating the male rotor and the female rotor; a casing accommodating therein the male rotor and the female rotor; a bore portion formed in the casing to cover toothed portions of the male rotor and the female rotor; a plurality of working chambers formed in mating portions between a male toothed groove of the male rotor and a female toothed recess of the female rotor; and axial intake ports formed in the bore portion on a side at which gas to be compressed is sucked. In a rotation angle of rotation in which the working chamber has a nearly maximum volume, the axial intake port stops communication between the outside and the female toothed groove and communication between the outside and the male toothed groove in this order.

Description

  The present invention relates to a screw compressor and relates to a suction port.

  Many efforts have been expended in the past to improve the performance, ie energy efficiency and volumetric efficiency of screw compressors. Although there are many factors that determine performance, recent studies have shown that the profile of the suction port affects the performance of the screw compressor, particularly volumetric efficiency.

  Japanese Patent Application Laid-Open No. 6-288369 discloses an outline of a suction port suitable for a screw compressor having a working chamber in which volume change is temporarily interrupted.

  Japanese Patent Laid-Open No. 10-9164 discloses a method of increasing the suction flow rate by intermittently performing the suction operation. In JP-A-6-288369 and JP-A-10-9164, the conditions of the compressors that are suitable are limited, and the effects cannot be enjoyed with a general and many compressors.

  Further, in a screw compressor provided with a synchronous gear (timing gear), it is necessary to precisely adjust the rotational phase of the rotor teeth and the synchronous gear. A structure for facilitating this is disclosed in Japanese Patent Publication No. 62-2157. Further, improvement of the adjustment method is disclosed in Japanese Patent Laid-Open No. 1-155089. In general, the adjustment operation is performed by inserting a gauge into the meshing portion of the rotor and confirming the clearance between the rotor tooth surfaces. Japanese Examined Patent Publication No. 62-2157 adopts a structure in which a gauge is inserted through a hole formed in a main casing and is closed with a member which becomes a lid after adjustment. In Japanese Patent Laid-Open No. 1-155089, a gap between rotors is confirmed using a rotary encoder instead of manual work using a gauge.

JP-A-6-288369 Japanese Patent Laid-Open No. 10-9164 Japanese Patent Publication No.62-2157 Japanese Unexamined Patent Publication No. 1-155089

  The above-mentioned Japanese Patent Application Laid-Open No. 6-288369 or Japanese Patent Application Laid-Open No. 10-9164 has a condition in the structure and method of use of an applicable screw compressor, and has not been widely applied in general. Therefore, it has been a problem to embody a structure for increasing the amount of suction applicable to many screw compressors. Accordingly, in view of the above problems, the first object of the present invention is to smoothly and smoothly suck the compressed gas into the working chamber and improve the working efficiency of the screw compressor (the compressed gas suction efficiency). It is in.

  The above-mentioned Japanese Patent Publication No. 62-2157 is effective for adjusting the synchronous gear. However, it takes time and effort to remove the lid for adjustment and to reattach it after adjustment, and it is necessary to provide a lid and its attachment / detachment structure. Although there is a method of omitting the lid, depending on the position, there may be a reverse flow path through which the gas once sucked into the working chamber from the adjustment hole, and the compressor performance may be deteriorated. Japanese Patent Laid-Open No. 1-155089 is also an effective means, but it requires a work of fixing a device such as a rotary encoder to a compressor to be adjusted, and there is a problem that it takes time and effort. Therefore, a second object of the present invention is to make the meshing portion of the rotor visible from the outside of the casing without causing performance degradation, and to facilitate the rotational phase adjustment of the rotor pair and the synchronous gear.

  In order to solve the above problems, in a screw compressor that sucks and compresses a gas to be compressed and discharges the compressed gas to the outside, a male rotor and a female rotor meshing with each other, and a mechanism for rotating the male rotor and the female rotor A casing in which the male rotor and the female rotor are housed, a bore portion that is formed in the casing and covers the teeth of the male rotor and the female rotor, a male tooth groove of the male rotor, and a female of the female rotor A plurality of working chambers formed in a meshing portion with the tooth gap, and an axial suction port provided on a side of the bore portion for sucking the compressed gas, the axial suction port including the working chamber The communication is stopped in the order of the communication between the external and the female tooth groove, and the communication between the external and the male tooth groove, at the rotation angle at which the volume of the rotation is substantially maximum.

  Further, at the rotation angle after the communication between the outside and the male tooth groove is stopped, the side of the working chamber that sucks in the gas to be compressed is covered with the wall surface of the bore portion.

  In addition, in a screw compressor that sucks and compresses compressed gas and discharges the compressed gas to the outside, a male rotor and a female rotor engaged with each other, a mechanism for rotating the male rotor and the female rotor, and the male rotor and A casing in which a female rotor is housed, a bore portion that is formed in the casing and covers the teeth of the male rotor and the female rotor, and a meshing portion between the male tooth groove of the male rotor and the female tooth groove of the female rotor A plurality of working chambers formed on the bore portion and an axial suction port provided on a side of the bore portion for sucking the compressed gas, and the outline of the axial suction port is such that the volume of the working chamber is substantially the same. At the rotation angle of the rotation that becomes the maximum, the contour on the surface that sucks the gas to be compressed that is the rear side of the male rotor by the rotation angle, and the female rotor by the rotation angle And a contour of a surface on the side for sucking in the compressed gas that is on the side, opening a surface for sucking in the gas to be compressed located on the opposite side to the rotation direction, and positioned on the side in the rotation direction The surface for sucking the compressed gas is closed.

  Furthermore, a radial suction port is provided which is a part of the outer peripheral surface of the bore portion and is provided at a position where the meshing portion is opened.

  According to the present invention, the working efficiency of the screw compressor can be improved.

It is a figure which shows the rotor pair of Example 1, and the outline of a suction port. FIG. 3 is a development view of the outer peripheral surface of the bore portion of the first embodiment. It is a cross-sectional schematic diagram of a conventional oil-free screw. It is the outline of the conventional rotor pair and suction port. It is a graph of the volume change of the working chamber of a screw compressor, and a suction flow rate.

Before describing the first embodiment, a general suction port of a screw compressor will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic cross-sectional view of a general screw compressor, and FIG. 4 is a diagram in which the outline of the suction port opened on the surface of the bore portion is overwritten on the perspective view of both rotors engaged with each other.
This screw compressor sucks and compresses a gas to be compressed and discharges it to the outside.

  The male rotor 1 and the female rotor 2 are housed in a bore portion 4 that is meshed with each other and formed inside the casing 3. That is, the male rotor 1 and the female rotor 2 are housed in the casing 3. The bore portion 4 is formed by two cylindrical holes that are partially overlapped so as to cover a tooth portion that is a portion where the teeth of the male rotor 1 and the female rotor 2 are formed. The inner surface of the bore portion 4 is composed of a male and female cylindrical outer peripheral surface and both end surfaces. The tooth groove 5 of the male rotor 1 hatched in FIG. 4 (hereinafter referred to as male tooth groove 5) and the tooth groove 6 of the female rotor 2 (hereinafter referred to as female tooth groove 6) are shown in FIG. Are communicated at the meshed portion and surrounded by the inner surface of the bore portion 4 to form a working chamber 9 which is a closed space. That is, the working chamber 9 is formed at the meshing portion between the male tooth groove 5 and the female tooth groove 6. A plurality of working chambers 9 are formed. Since minute gaps are provided on the outer periphery, the meshing portion, and the end surface of the male rotor 1 and the female rotor 2 so that the rotor rotates smoothly, the working chamber 9 is not a closed space in a strict sense, but a gap It is connected to the adjacent working chamber through. However, these gaps and the amount of gas leaking through them are negligible and are ignored here because they are not relevant to the subject matter of the present invention.

  Due to the rotation of the male rotor 1 and the female rotor 2, the working chamber 9 is created on the suction side end surface 7, and the internal volume is expanded while moving from there toward the discharge side end surface 8. While expanding the internal volume, the working chamber 9 communicates with a suction port which is a hole opened in the bore portion 4 communicating with the outside of the casing 3. Therefore, the gas to be compressed is sucked into the working chamber 9 from the outside of the casing 3 through the suction port. The outline of the suction port is formed so that the communication with the working chamber 9 is completed and closed when the volume of the working chamber 9 becomes almost maximum. Subsequently, in FIG. 3 or FIG. 4, the working chamber 9 turns around to the back side of the rotor pair, and the internal volume of the working chamber 9 is reduced, so that the gas trapped inside is compressed.

  In the oil-free screw compressor, the tooth surface of the male rotor 1 and the tooth surface of the female rotor 2 are engaged with each other, but it is necessary to maintain a minute gap therebetween. Therefore, the synchronous gear 10 that is a mechanism for rotating the male rotor 1 and the female rotor 2 is provided at the shaft ends of the male rotor 1 and the female rotor 2, and the rotation transmission is left to the synchronous gear 10. Therefore, it is necessary to precisely adjust the rotational phase between the male and female of the synchronous gear 10 and the rotational phase of the screw teeth. When the phase is viewed in detail, the backlash of the synchronous gear 10 is in a relative angular relationship so as to be accommodated in the backlash of the screw teeth.

  Example 1 will be described with reference to FIG. FIG. 1 is a diagram in which the outline of a suction port opened on the surface of the bore 4 is overwritten on the perspective view of the engaged male rotor 1 and female rotor 2. The working chamber 9 is at the position where the maximum volume is reached, and the working chambers arranged on the near side of the working chamber 9 are in the inhalation process by expanding the volume. The male rotor 1 and the female rotor 2 rotate in the direction of the arrow in the figure, and the working chamber moves from the front suction side end face 7 toward the discharge side end face 8 in the back direction. The suction port provided on the surface of the bore portion 4 is opened on the suction side end surface 7, is an axial suction port 11 provided on the side for sucking in the gas to be compressed, and the outer peripheral surface of the bore portion 4. And the radial suction port 12 provided at a position where the meshing portion between the female rotor 2 and the female rotor 2 is opened. These two suction ports are connected at the corner of the outer periphery of the suction side end face 7 to form one opening, which will be described separately from their shapes.

  The contour line that appears on the suction side end face 7 of the axial suction port 11 is composed of seven lines. They are the meshing line 13, the arc 14 along the male root diameter, the line 15 along the male tooth profile, the arc 16 along the male tooth tip diameter, the arc 17 along the female tooth tip diameter, and the female tooth profile. A line 18 and a circular arc 19 along the female root diameter form a circle. Among these, the contour lines that greatly affect the performance of the compressor are the line 15 along the male tooth profile and the line 18 along the female tooth profile, which will be described in detail.

  The working chamber 9 having the maximum volume indicated by hatching in FIG. 1 also faces the suction side end face 7 with the male tooth groove 5 and the female tooth groove 6. The outline of the tooth groove appearing on the suction side end face 7 is considered as being divided into two sides, the preceding side and the following side with respect to the rotation of the rotor. Of particular importance is the following side, focusing on the following side contour line 21 of the male tooth groove 5 and the following side contour line 22 of the female tooth groove 6 on the suction side end face 7.

  The line 15 along the male tooth shape of the axial suction port 11 is assumed to be along the follow-up side contour line 21 of the male tooth groove 5 facing the discharge side end face 8 of the working chamber 9 having the maximum volume. However, the accuracy of bringing the line 15 along the line 21 can allow an error of about 1/20 of the diameter of the rotor. In FIG. 1, for the sake of distinction, the contour 15 of the suction port and the follower contour 21 of the tooth gap are drawn apart from each other.

  The line 18 along the female tooth profile of the axial suction port 11 is assumed to be along the following contour 22 of the female tooth groove 6 at the rotational position earlier by the angle θf than the rotational angle at which the working chamber 9 has the maximum volume. Therefore, at the moment when the working chamber 9 shown in FIG. 1 reaches the maximum volume, the follow-up contour line 22 is after passing through the line 18 constituting the axial suction port. Regarding the position accuracy of the line 18, an error of about 1/20 of the rotor diameter can be allowed.

  The radial suction port 12 opens to a position where the portion close to the suction side end surface 7 of the meshing portions of the male rotor 1 and the female rotor 2 can be seen from above, and communicates with the working chamber 29 in the process of suction while the internal volume is expanding. ing. The contour line 23 in which the working chamber is in the traveling direction of the contour has a shape along the male tooth tip line 24 and the female tooth tip line 25 that form the contour on the side preceding the traveling direction of the working chamber 29. . The working chamber 29 is a working chamber two before the working chamber 9 having the maximum volume. Also, the working chamber 29 immediately after the working chamber 29 and before the working chamber 9 having the maximum volume is immediately after being closed with respect to the axial suction port 11.

  FIG. 2 is a developed view of the outer peripheral surface of the bore so that the positional relationship between the working chamber and the suction port can be easily understood. The central vertical line 31 is called an expansion-side cusp 31 at the intersection of the outer cylindrical surfaces of the male and female bores 4. The vertical lines 32 on both the left and right sides mean the compression side cusp 32 that is an intersection line of the outer peripheral surface of the bore portion on the back side in FIG. The diagonal line is a tooth tip line that divides the male and female tooth spaces. The working chamber 9 having the maximum volume is indicated by a male tooth groove 5 and a female tooth groove 6. By the rotation of the rotor, the male tooth groove 5 and the female tooth groove 6 move upward in the direction of the arrow in FIG. The lower horizontal line means the suction side end face 7, and the upper horizontal line means the discharge side end face 8.

  In FIG. 2, the axial suction port 11 is shown as an opening that is described adjacently below the bore, and communicates with the working chamber 9 by its male contour 15 and female contour 18. It can be determined whether or not. By overwriting the axial suction port 11 in FIG. 2, the communication relationship with the working chamber 29 can be easily understood.

  That is, the axial suction port 11 communicates between the outside of the compressor and the female tooth groove 6 at the rotation angle of the rotation of the male rotor 1 and the female rotor 2 where the volume of the working chamber 9 is substantially maximum, It is a shape which stops communication in the order of communication with the male tooth groove 5. Further, in the rotation angle of the rotation of the male rotor 1 and the female rotor 2 after the communication between the outside of the compressor and the male tooth groove 5 is stopped, the side of the working chamber 9 that sucks in the gas to be compressed is the bore portion 4. Covered with walls.

  Further, the outline of the axial suction port 11 is such that the compressed gas on the rear side of the male rotor 1 at the rotation angle of the male rotor 1 and the female rotor 2 at which the volume of the working chamber 9 becomes substantially maximum. Including a contour on the surface on the suction side and a contour on the surface on the suction side of the compressed gas that is the rear side of the female rotor 2 according to the rotation angle, and is located on the opposite side to the rotation direction. The surface for sucking in the compressed gas is opened, and the surface for sucking in the compressed gas located on the rotation direction side is closed.

  The screw compressor described above operates as follows.

  1 and 2, the rotation of the rotor causes all the working chambers to move from the suction side end surface 7 toward the discharge side end surface 8, expanding the internal volume to reach the maximum volume working chamber 9, and thereafter It turns to the reduction of the internal volume. FIG. 5 shows a change in the internal volume, and also shows a graph obtained by time-differentiating the change. The graph obtained by differentiating the change in the internal volume with respect to time means a tendency that the volume flow rate sucked into the working chamber changes with time. FIG. 5 shows the opening period of each suction port with respect to the working chamber.

The working chamber continues to increase in internal volume after it occurs on the suction side end face 7 at the rotation angle θ ₀ , while the working chamber continues to communicate with the axial suction port 11. At the angle θ ₁ , the portion facing the suction side end face 7 of the working chamber is separated into the male rotor 1 side and the female rotor 2 side. At substantially the same time, communication with the radial suction port 12 is started facing the outer periphery f of the bore 4. For a while from the angle θ ₁ , the flow rate for sucking the compressed gas increases, but the compressed gas is sucked into the working chamber through the axial suction port 11 and the radial suction port 12. Because of the wide opening area by the axial suction port 11 and the radial suction port 12, the pressure loss of the passing gas is small, and the compressed gas can be sucked smoothly.

When the leading end of the female tooth groove 36 reaches the discharge-side end face 8, the volume expansion speed gradually decreases thereafter, and the suction flow rate starts to decrease. Around that time, the radial suction port 12 is closed with respect to the working chamber at an angle θ ₂ . It should be noted here that, as shown in FIG. 2, the leading edge of the male tooth groove 35 reaches the discharge side end face 8 after the leading edge of the female tooth groove 36 reaches the discharge side end face 8. . For this reason, even if the suction flow rate into the female tooth groove 36 first decreases, the suction flow rate into the male tooth groove 35 continues for a certain period of time. Therefore, in the meshing portion where the male tooth groove 35 and the female tooth groove 36 communicate with each other, a flow 33 from the male tooth groove 35 that continues to flow into the female tooth groove 36 whose volume expansion has slowed across the expansion side cusp 31 is generated. appear. The inertia of the inhaled gas traveling in the male tooth groove 5 also increases the flow 33 to the female tooth groove 6.

When the suction side end face 7 of the female tooth groove 36 is open, if the flow 33 from the male tooth groove 35 to the female tooth groove 36 is strong, a reverse flow 34 occurs with respect to suction. This reverse flow 34 is not preferable because it reduces the suction flow rate of the compressor and lowers the efficiency. In the first embodiment, the female-side contour line 18 of the axial suction port 11 is closed earlier than the male-side contour line 15 and has an effect of preventing the backflow 34, which contributes to an improvement in the efficiency of the compressor. FIG. 5 shows an operation of closing the axial suction port 11 with respect to the female tooth groove 36 at an angle θ ₃ .

  By closing the line 18 along the female tooth shape early, the opening area of the suction port may be reduced, and an increase in pressure loss may be a concern. However, as shown in FIG. 5, since the suction flow rate becomes extremely small near the maximum volume, the opening area is sufficiently secured only on the male side, and there is no problem of increased pressure loss.

At the rotation angle θ _{4 at} which the working chamber volume is maximized, the male-side axial suction port 11 that has been opened to the end is closed, and the suction process is completed.

  The radial suction port 12 can be used not only as a gas suction flow path but also as an insertion hole for a gauge that is sandwiched between the male and female tooth surfaces when adjusting the fixed position of the synchronous gear. The opening does not need to extend over the entire length of the teeth, and it is sufficient if the opening has a length of one tooth or more in the axial direction as shown in FIGS. The method for adjusting the fixed position of the synchronous gear is described in detail in Japanese Patent Publication No. 62-2157 and Japanese Patent Application Laid-Open No. 1-155089, and will be briefly described here. There is a continuously elongated gap between the two rotors, and the gap gauge is inserted into this predetermined position, and the rotor is fixed to the shaft while adjusting the rotational phase of the synchronous gear. When inserting the clearance gauge, workability is good if the meshing portions of the male rotor 1 and the female rotor 2 can be seen from the radial direction. This is because the gauge and the operator's hand are easy to enter, and the position can be easily observed. The radial suction port 12 of the first embodiment has a convenient position and size in that sense.

  However, an excessive radial suction port 12 has been found to degrade compressor performance. For example, the radial suction port 12 that is closed at the position of the working chamber 9 (that is, the male tooth groove 5 and the female tooth groove 6) having the maximum volume is geometrically maximal, and the hatched lines connected to the contour lines 21 and 22 in FIG. It becomes a part of the contour. With such a radial suction port, when the suction flow rate decreases, the compressed gas sucked into the working chamber 9 from the axial suction port 11 exits from the radial suction port 12 due to inertial force or centrifugal force. It becomes a backflow. Therefore, contrary to the intention to reduce the pressure loss and increase the suction amount, there is an adverse effect of reducing the suction amount by backflow. The compressed gas that has flowed backward has increased the temperature by touching the walls of the high-temperature rotor and bore, so that even if it is re-inhaled into the subsequent working chamber, it expands and adversely affects the mass flow rate. May also affect.

  On the other hand, the radial suction port 12 which is limited in size as in the first embodiment and closes earlier than the axial suction port 11 is already closed at the time when the backflow can occur and does not have an adverse effect? Even if it exists, it is extremely small.

  In the first embodiment, the axial suction port 11 and the radial suction port 12 can be applied individually, and even in that case, the respective effects can be enjoyed. On the other hand, when both are provided, a new synergistic effect can also be enjoyed. The synergistic effect is an increase in inhalation volume due to a reduction in pressure loss in the inhalation process. The change in the working chamber volume and the change in the suction flow rate tend to be as shown in FIG. On the other hand, when reaching the maximum volume and reaching the stage where the suction flow rate decreases, the opening area may be small as described above, and it is important to prevent backflow.

  Since the radial suction port 12 of the first embodiment is opened in the middle of the suction process in which the suction amount increases, it can contribute to the reduction of the passage pressure loss, and it is closed at the end so that there is no adverse effect of causing backflow. effective.

  According to the first embodiment, the working chamber in the suction process sucks the gas to be compressed smoothly and with a low pressure loss, and can prevent the backflow that occurs immediately before the suction port is closed with the maximum volume. For this reason, it becomes possible to improve the working efficiency (intake efficiency of the gas to be compressed) of the screw compressor.

  Further, since the meshing portion of the male and female rotors can be seen from the radial suction port, it is easy to put the gauge between the tooth surfaces from the radial suction port, and the adjustment when fixing the synchronous gear is facilitated. Therefore, the assembly of the screw compressor can be performed quickly and accurately.

  The backflow from the female tooth groove immediately before the working chamber reaches the maximum volume is prevented from flowing into the suction flow path, and the gas transport amount is increased. In addition, the adjustment of the synchronous gear is easy due to the opening of the meshing portion, but there is no demerit of performance degradation.

DESCRIPTION OF SYMBOLS 1 Male rotor 2 Female rotor 3 Casing 4 Bore part 5 Male rotor tooth space 6 Female rotor tooth space (these tooth spaces become the working chamber 9)
7 Suction side end face 8 Discharge side end face 9 Working chamber 10 Synchronous gear 11 Axial suction port 12 Radial suction ports 13 to 19 Individual lines 21 constituting the outline of the axial suction port 21 Follow-up side contour line 22 of the male tooth groove 5 Female tooth groove 6 follow-up side contour line 23 advancing side contour line 24 of the axial suction port 12 male tooth tip line 25 female tooth tip line 29 working chamber (in the process of suction while the internal volume is expanding)
31 Expansion side cusp 32 Compression side cusp 33 Flow from male tooth groove to female tooth groove 34 Back flow from female tooth groove 35 Male tooth groove just before reaching discharge side 36 Female tooth groove reaching discharge side

Claims (4)

In a screw compressor that sucks and compresses the gas to be compressed and discharges it outside,
A male rotor and a female rotor meshing with each other;
A mechanism for rotating the male rotor and the female rotor;
A casing containing the male rotor and the female rotor;
A bore formed on the casing and covering the teeth of the male and female rotors;
A plurality of working chambers formed in a meshing portion between the male tooth groove of the male rotor and the female tooth groove of the female rotor;
An axial suction port provided on the side of the bore portion that sucks the compressed gas;
The axial suction port communicates the communication in the order of communication between the exterior and the female tooth groove, and communication between the exterior and the male tooth groove, at the rotation angle at which the volume of the working chamber is substantially maximum. A screw compressor characterized by a stopping shape. The screw compressor according to claim 1,
The screw that sucks the compressed gas in the working chamber at the rotation angle after the communication between the outside and the male tooth groove is stopped, and is covered with the wall surface of the bore portion. Compressor. In a screw compressor that sucks and compresses the gas to be compressed and discharges it outside,
A male rotor and a female rotor meshing with each other;
A mechanism for rotating the male rotor and the female rotor;
A casing containing the male rotor and the female rotor;
A bore formed on the casing and covering the teeth of the male and female rotors;
A plurality of working chambers formed in a meshing portion between the male tooth groove of the male rotor and the female tooth groove of the female rotor;
An axial suction port provided on the side of the bore portion that sucks the compressed gas;
The axial suction port has a contour on a surface on the side of suctioning the compressed gas that is behind the male rotor by the rotation angle at the rotation angle at which the volume of the working chamber is substantially maximum. Inhalation of the compressed gas located on the opposite side to the rotation direction, including a contour and a contour on a surface on the suction side of the compressed gas, which is the rear side of the female rotor according to the rotation angle A screw compressor characterized by opening a surface and closing a surface for sucking the compressed gas located on the rotation direction side. The screw compressor according to any one of claims 1 to 3,
A screw compressor, comprising: a radial suction port provided at a position on the outer peripheral surface of the bore portion where the meshing portion is opened.

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