Patent Grant
11890721
The present invention relates to the method for processing a screw rotor used for a screw compressor etc. and a screw rotor lead correction calculation device.
A screw compressor using a screw rotor including a spiral member has been known as one form of a compressor used for a refrigeration device or an air compressor. The screw compressor is configured such that a pair of screw rotors engages with each other to form a compression chamber and these screw rotors are rotated in opposite directions relative to each other to suck gas fluid such as refrigerant or air and decrease the volume of the gas fluid to compress the gas fluid.
The method for performing ground finish for a spiral rotor groove portion (a tooth groove portion) formed at the screw rotor includes, for example, grinding with a grinding stone formed with a section corresponding to the shape of the rotor groove portion.
In ground finish for the screw rotor, a machining allowance (a polishing margin) and a contact area are different between the right and left sides of the grinding stone in a grinding stone traveling direction because the screw rotor is twisted. For this reason, force, i.e., grinding force (grinding resistance), is not evenly applied to the right and left sides of the grinding stone. Thus, deformation of a tooth-shaped sectional shape occurs at the screw rotor during grinding.
Regarding this phenomenon, JP-A-2016-14369 (Patent Document 1) describes that in a case where an inclined grinding stone for grinding a rotor of a screw compressor is moved parallel with an axial direction during rotation of the rotor to process the rotor into a predetermined rotor groove shape, a tooth-shaped sectional shape of a rotor groove portion is deformed.
In addition to this phenomenon, the form of contact between the grinding stone and the rotor groove changes every second at grinding stone input and outlet portions of the screw rotor, and for this reason, grinding force on the right and left sides of the grinding stone changes. Accordingly, the amount of deformation of the tooth-shaped sectional shape at the rotor groove portion changes. When the tooth-shaped sectional shape changes, such a change is a cause for degradation of the accuracy of the screw rotor. For this reason, Patent Document 1 describes that when the vicinity of a discharge-side end surface of the screw rotor is processed, the processing is performed with a theoretical value to which a correction value is added according to the amount of deformation of the sectional shape of the rotor groove portion due to the grinding force, and in this manner, deformation influence is cancelled out.
Moreover, Patent Document 1 also describes that a rotor rotary shaft is rotated with a theoretical value to which a correction amount is added according to the amount of rotation of the tooth-shaped sectional shape of the rotor groove portion due to the grinding force, and in this manner, influence of torsional deformation is cancelled out.
Patent Document 1: JP-A-2016-14369
As described above, Patent Document 1 describes the method in which the correction amount is, for performing ground finish, added to the theoretical value according to a lead error indicating the magnitude of deformation or torsion of the sectional shape of the screw rotor due to, e.g., a change in a torsional deformation amount due to a change in the grinding force during grinding with the grinding stone.
However, Patent Document 1 fails to describe the form of an error obtained by a measurer and the method for handling a correction amount for correction of the error.
Normally, the accuracy of the screw rotor is measured using a three-dimensional measuring instrument. The three-dimensional measuring instrument is a coordinate measuring instrument, and the error is displayed as a distance from proper measurement coordinates (a design value).
An amount necessary for correction of the groove lead error is a correction amount regarding a torsion angle. In a screw rotor grinding machine, processing is performed with the amount of movement of the grinding stone along the axis of the screw rotor and the rotation angle of the screw rotor being synchronized with each other. The lead of the screw rotor is determined by the movement amount of the grinding stone and the rotation angle of the screw rotor.
Thus, correction control data of the grinding machine necessary for correction of the lead error cannot be directly obtained from measurement results of the three-dimensional measuring instrument including the distance as the error at the axial position of the screw rotor.
Moreover, axial positions for starting, changing, and ending correction of the lead error are determined with reference to the center of the width of the grinding stone. However, an important position for measurement of the lead is an engagement position of male and female rotors called pitch circles, and for this reason, a difference in the engagement position of the male and female rotors is important for production of correction data. However, Patent Document 1 fails to consider the difference in the engagement position of the male and female rotors.
For these reasons, after ground finish by the grinding machine has been performed for the material of the screw rotor produced by, e.g., casting, a correction starting position and a correction amount for the grinding machine are experimentally determined with reference to an error between the axial position of the engagement position (a position on the pitch circle) of the male and female rotors obtained by the three-dimensional measuring instrument and the design value, and ground finish is performed again for the material of the screw rotor. Thereafter, this re-produced sample is measured. In a case where the error exceeds an acceptable value, the operation of determining the correction starting position and the correction amount for the grinding machine, performing ground finish for the material of the screw rotor, and measuring the sample is repeated again.
This conventional case employs a technique in which the cycle of experimentally determining the correction starting position and the correction amount and grinding the material of the screw rotor is repeated many times through trial and error until a value within target accuracy is obtained. Moreover, in this screw rotor processing method through trial and error, the number of trials is increased when high target accuracy is set, and therefore, it is difficult to obtain a sufficiently high accuracy value.
Further, even when production is performed once with the determined correction starting position and the determined correction amount, if replacement of, e.g., the grinding stone or a dresser influencing the grinding force is performed, the process of determining the correction starting position and the correction amount through trial and error needs to be performed again.
As described above, in the conventional ground finish method through trial and error, ground finish for the screw rotor material and measurement are repeated until the value within the target accuracy is obtained. For this reason, such a process is an inefficient process requiring time, and is a cause for interference with production.
Moreover, the correction data for the processing machine is produced through trial and error. For this reason, the prospect for the accuracy of the lead of the screw rotor obtained from the correction data determined as necessary cannot be provided before ground finish for the material of the screw rotor, and appropriateness of such accuracy cannot be evaluated.
An object of the present invention is to provide a screw rotor processing method and a screw rotor lead correction calculation device so that correction data for obtaining a screw rotor with a high-accuracy lead can be obtained from a lead error with respect to a reference lead of a screw rotor obtained by ground finish for the material of the screw rotor.
For accomplishing the above-described object, the present invention relates to a screw rotor processing method for correcting a lead error of a screw rotor to process the screw rotor. The method includes grinding the material of the screw rotor, measuring, as a distance, a lead error with respect to a reference lead at an axial position (a Z-direction position) of a rotor groove portion of the screw rotor produced by grinding, calculating, based on the lead error measured as the distance, a lead correction amount for correction of the lead error and a lead correction starting position as an axial position of the screw rotor for starting the lead correction, and grinding the screw rotor based on the calculated lead correction amount and the calculated lead correction starting position.
Another feature of the present invention relates to a screw rotor lead correction calculation device for obtaining correction data for correction of a lead error of a screw rotor. The screw rotor lead correction calculation device includes an initial data input section configured to input an error (δ) as a distance with respect to a reference lead at each axial position of a rotor groove portion of the screw rotor, and a processing machine input correction amount/position output section configured to compute and output, based on the error as the distance input to the initial data input section, a lead correction amount with respect to the reference lead and a lead correction starting position as an axial position for starting lead correction.
According to the screw rotor processing method and the screw rotor lead correction calculation device of the present invention, there is an advantageous effect that the correction data for obtaining a screw rotor with a high-accuracy lead can be obtained from the lead error with respect to the reference lead of the screw rotor obtained by ground finish for the material of the screw rotor.
Hereinafter, a specific embodiment of a screw rotor processing method and a screw rotor lead correction calculation device according to the present invention will be described with reference to the drawings. In each figure, elements with the same reference numerals are used to represent identical or equivalent elements.
A first embodiment of the present invention will be described with reference to
First, one example of a processing machine configured to perform ground finish for a screw rotor will be described with reference to
In
Moreover, the processing machine 2 is configured such that a lathe dog 2c fixed to the screw rotor 1 and a driver (a driving plate) 2e fixed to a rotary mechanism 2d of the processing machine 2 are coupled to each other to rotate the screw rotor 1.
A reference numeral 3 indicates a grinding stone to be rotatably driven by a grinding stone driver 3a. The grinding stone 3 is arranged inclined with respect to the center axis of the screw rotor 1, and is formed in such a grinding stone shape that a screw rotor groove portion (hereinafter also merely referred to as a “rotor groove portion”) 1a can be processed into a tooth groove shape at such an inclination angle. Moreover, the grinding stone 3 is a so-called form grinding stone whose outer peripheral portion is formed by a diamond dresser so that the rotor groove portion 1a can be ground into a final finished shape in an inclination state.
Note that for reducing deflection of the screw rotor 1 upon grinding, steady rests 2f configured to support the vicinity of both ends of the rotor groove portion 1a are provided. The steady rests 2f are not necessarily provided in the case of a short screw rotor 1.
For grinding the rotor groove portion 1a of the screw rotor 1, the screw rotor 1 is rotated by the driver 2e while the inclined grinding stone 3 is moved parallel with the axis of the screw rotor 1, and in this manner, the rotor groove portion 1a is processed.
In grinding, grinding force as force by grinding is generated, and part of the processing machine 2 such as the grinding stone 3, the screw rotor 1, the centers 2a, 2b, and the driver 2e performs the processing while deforming. When the grinding force is constant, a deformation amount is also constant. Thus, certain correction data is provided so that high-accuracy processing can be performed. However, when the grinding force changes, the deformation amount changes accordingly, and for this reason, a processing error becomes greater.
Arrows illustrated in
Note that such a three-dimensional measuring instrument is not necessarily used, and the lead of the screw rotor 1 may be measured using a three-dimensional measuring instrument including no rotary table or a three-dimensional measuring instrument employing the technique of touching measurement points by a probe 4a of the three-dimensional measuring instrument one by one. Alternatively, during rotation of the screw rotor 1, the lead may be measured with a displacement gauge such as an electric micrometer.
In
A reference numeral 61 corresponds to a starting point of movement of the moving grinding stone 3, and a reference numeral 68 corresponds to an end point. In a case where there is no lead error in the screw rotor targeted for measurement, the lead measurement values for the screw rotor are displayed on the dashed line B (the reference lead) connecting the movement starting point 61 and the end point 68 to each other.
However, in the screw rotor 1 processed by the grinding machine 2 (see
After the measurement point 64, a coincidence with the reference lead is substantially shown. However, in the vicinity of the outlet (the outlet of the rotor groove portion) of the grinding stone 3, the error increases again, and increases until the measurement point 67 at the outlet of the rotor groove portion. Note that the pattern of the lead error of the screw rotor illustrated in
As described above, the measurement result of the lead error in the screw rotor is output as the error with respect to the dashed line B (the reference lead) at each position (Z1, Z2, Z3, . . . ) in the Z-direction, i.e., the distance to the dashed line B. For example, as illustrated in
Note that the biggest factor for the error with respect to the dashed line B is a change in the grinding resistance as described with reference to
In the grinding machine 2 illustrated in
In the present embodiment, the adjustment amount (a lead correction amount) in correction for eliminating the error is, in the grinding machine 2, obtained by the later-described technique, and the grinding machine 2 is controlled to perform grinding with the adjustment amount.
In
The axial position Z1 of the measurement point 62 illustrated in
Thus, for correcting the error δ1, the locus of passage of the grinding stone 3 is set such that the grinding stone 3 passes through a correction point 73 taking a rotation angle −dθ1 obtained by reversing (inverting) the sign of the rotation angle dθ1 corresponding to the error δ1 as a difference from the rotation angle θ1 corresponding to the ideal point 72 on the line 56 indicating the reference lead. In this manner, correction is made by the rotation angle dθ1 corresponding to the error δ1 due to unbalance grinding force, and therefore, the grinding stone 3 can perform the processing at the ideal point 72 on the reference lead.
Next, elimination of the rotation angle dθ1 corresponding to the error δ1 by the above-described technique will be described in more detail with reference to
As illustrated in
The correction lead (P0+dP1) is data inputtable to the grinding machine 2 illustrated in
Subsequently, a similar technique may be, as illustrated in
In
At the Z-direction position Z2 illustrated in
In an example of
For the processing, a correction lead for a position at a more-advanced angle than the measurement point 63 needs to be obtained. However, the correction lead is merely obtained by a technique similar to that described above and is similarly processed, and therefore, subsequent description will be omitted.
In description of correction of the lead error with reference to
When the rotation angle to be corrected is dθ and the reference lead is P0, a lead correction amount dP (dP1, dP2, . . . ) can be obtained by (Expression 1) below. That is, when a rotation angle to be corrected at a position with a rotation angle θi on the reference lead is dθi, a distance at a position in the Z-direction as the axial direction is Zi, the lead correction amount is dP, and the reference lead is P0, the lead correction amount dP can be obtained by the following expression.
Note that an index i indicates the order of the measurement point for which the lead error with respect to the reference lead at the Z-direction position of the rotor groove portion has been measured, and “i=0” corresponds to the origin of the rotation angle or the Z-direction position. Moreover, “i=1” corresponds to the position of Z1 or the position of θ1.
The procedure of performing the screw rotor processing method for processing the screw rotor with the corrected lead as described above will be described below with reference to
First, at a step S101, the grinding machine 2 illustrated in
At a step S103, the rotation angle θ at a spot for which the error needs to be corrected and an error amount (the rotation angle dθ corresponding to the error δ) at such a spot are determined using the technique of correcting the lead error of the screw rotor as described with reference to
At a step S104, the correction amount “−dθ” with respect to the correction rotation angle (the rotation angle at the spot for which the error needs to be corrected) θ is obtained based on determination results, which are obtained at the step S103, of the rotation angle θ and the error amount dθ at the spot for which the error needs to be corrected, the correction amount being to be input to the grinding machine 2.
At a step S105, the correction lead and the lead correction amount are computed based on the correction amount “−dθ” obtained at the step S104, and control data (the lead correction amount and a lead correction position) of the grinding machine 2 is corrected. By the processing machine 2 to which the correction data has been input as described above, the material of the screw rotor is newly ground, and in this manner, a second sample is produced (a step S106). Next, at a step S107, lead measurement is performed for the produced second sample, and processing similar to that of the step S102 is performed.
At a step S108, it is determined whether or not the second sample has a value within a reference value of a target lead with respect to the reference lead. When the second sample has the value within the reference value of the target lead, production of the sample by the processing machine 2 ends. In a case where the second sample does not reach the reference value of the target lead, the processing returns to the step S103 again, and operation at the steps S103 to S108 is performed based on the error (a Z-value and a δ-value) with respect to the reference lead of the previously-produced sample. Similar operation is repeated until a sample having a value within the reference value of the target lead is produced.
When the produced sample reaches the reference value of the target lead, the processing proceeds to a step S109, and production of the screw rotor begins with data on production of the sample having the value within the reference value of the target lead.
Next, a lead correction calculation device configured to calculate the above-described data for correction of the lead error of the screw rotor will be described with reference to
The lead correction calculation device 100 includes an initial data input section 101 configured to input initial data such as a measurement value measured by the above-described three-dimensional measuring instrument 4, a correction amount addition section 102 configured to additionally input the correction amount for the lead error in a case where the measured lead is not within the reference value of the target lead, and a processing machine input correction amount/position output section 103 configured to compute and output data, such as the lead correction amount and a lead correction starting position, to be input to the control section (not shown) of the grinding machine 2 illustrated in
The initial data input section 101 is configured such that a model is selected by, e.g., pull-down operation to invoke base data in the calculation program of the lead correction calculation device 100, the base data being input and stored in advance based on design data such as the reference lead and groove length of such a model.
Note that the measurement results (the view of the measurement results printed on the paper as illustrated in
Moreover, the initial data input section 101 includes a lead measurement value input section 106 configured to input the Z-direction position for which the lead needs to be corrected and the lead correction amount (corresponding to the error δ of the measured lead with respect to the reference lead) at such a position. In this example, lead measurement data for eight measurement points P1 to P8 can be input. For example, measurement data corresponding to the measurement points 61 to 68 illustrated in
Further, it is configured such that not only data on the measured lead of one surface (L1) of the rotor groove portion 1b but also data on the measured lead of the other surface (L2) can be input.
The correction amount addition section 102 is a section configured to input data for correcting the initial data of the initial data input section 101 in a case where the second sample does not have the value within the reference value of the target lead at the step S108 of
The processing machine input correction amount/position output section 103 is an area for calculating and outputting (displaying) the data to be input to the grinding machine 2 illustrated in
The lead correction amount at each position in the Z-direction can be calculated using (Expression 1) described above based on the theory described with reference to
Moreover, #11 to #13 display the positions (the positions in the Z-direction) to which the lead correction amounts of #1 to #3 corresponding to the grinding starting section are provided. Further, #14 to #16 display the positions to which the lead correction amounts of #4 to #6 corresponding to the grinding end section are provided.
In addition, a selection button 104 configured to instruct output selection is provided so that it can be selected on which surface of the rotor groove portion 1b data is used to calculate the lead correction amount and the corresponding lead correction position.
When the control data of the grinding machine 2 is corrected using the above-described calculation results, i.e., the lead correction amounts #1 to #6 and the values of the lead correction positions #11 to #16 to which the lead correction amounts are to be provided, the grinding machine can perform grinding with the control data taking lead correction into consideration.
Using the above-described screw rotor processing method or the above-described screw rotor lead correction calculation device, there is an advantageous effect that a screw rotor with high lead accuracy can be easily obtained.
Note that the screen of the lead correction calculation device 100 illustrated in
As long as the initial data input section 101 configured to input the measurement data and the processing machine input correction amount/position output section 103 configured to output the correction data for correction for the grinding machine 2 are provided on the screen, the minimum functions can be fulfilled. Thus, the correction amount addition section 102 may be omitted.
According to the lead correction calculation device 100 illustrated in
Note that the example where the lead error is measured from the measurement data obtained from the three-dimensional measuring instrument 4 and the numerical values are artificially input to the initial data input section 101 has been described. However, the measurement data may be automatically input to the lead correction calculation device 100 by cooperation with software of the three-dimensional measuring instrument 4. Alternatively, it may be configured such that the correction data (the lead correction amount and the lead correction position) output from the processing machine input correction amount/position output section 103 of the lead correction calculation device 100 is automatically transferred to the grinding machine 2 via an interface (not shown) of the lead correction calculation device 100 and is automatically input to a control device of the grinding machine 2. Alternatively, a technique may be employed, in which the obtained correction data is transferred to the grinding machine 2 via a memory medium such as a flash memory.
In a case where input and output of the correction data are automated as described above, the initial data input section 101, the correction amount addition section 102, the processing machine input correction amount/position output section 103, etc. are not necessarily displayed on the screen configuration illustrated in
In
In the screw rotor produced by the conventional technique, a maximum lead error of 46.3 μm is caused at a grinding stone outlet portion (the lower side as viewed in the figure). Moreover, at a grinding stone inlet portion (the upper side as viewed in the figure), a maximum lead error of 35.8 μm is caused.
Based on these measurement results, necessary data was input to the initial data input section 101 on the screen of the lead correction calculation device 100 illustrated in
The lead correction amount and the lead correction position displayed as a result on the screen were used and were reflected on the control data of the grinding machine 2, and the material of the screw rotor was ground to obtain the screw rotor. The lead measurement results of the resultant screw rotor are lead measurement lines 203, 204 illustrated in a right field of
As illustrated in
According to the present embodiment described above, the correction data to be input to the grinding machine 2 can be, upon processing of the screw rotor, accurately obtained based on the theory by means of the measurement results obtained from the position Z in the Z-direction (the axial direction) and the error (the lead error) in the direction perpendicular to the tooth surface with respect to the reference lead. Thus, the error between the inlet portion and the outlet portion for the grinding stone 3 in grinding of the screw rotor material can be reduced.
The initial data input section 101 configured to input the error to the screen of the lead correction calculation device 100 and the processing machine input correction amount/position output section 103 are provided. Thus, upon processing of the screw rotor, the correction data to be provided to the grinding machine can be easily obtained.
The correction data output from the lead correction calculation device 100 is input to the grinding machine 2 so that a screw rotor with a high-accuracy lead can be obtained. Thus, use of this high-accuracy screw rotor can easily provide a screw compressor with a less leakage loss of compressed gas and a high compression efficiency.
Note that the present invention is not limited to the above-described embodiment, and includes various modifications. Moreover, the above-described embodiment has been described in detail for the sake of clear description of the present invention, and the present invention is not limited to one including all configurations described above.
The present application is a continuation application of International Application No. PCT/JP2017/040050, filed on Nov. 7, 2017, the contents of which is incorporated herein by reference in its entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 20070240318 | Matsumiya | Oct 2007 | A1 |
| 20120184183 | Yanase | Jul 2012 | A1 |
| 20160107291 | Ozaki | Apr 2016 | A1 |
| Number | Date | Country |
|---|---|---|
| 06-159271 | Jun 1994 | JP |
| 2007-262936 | Oct 2007 | JP |
| 2016-14369 | Jan 2016 | JP |
| 2016014369 | Jan 2016 | JP |
| Entry |
|---|
| International Search Report of PCT/JP2017/040050 dated Feb. 6, 2018. |
| Number | Date | Country | |
|---|---|---|---|
| 20190283207 A1 | Sep 2019 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2017/040050 | Nov 2017 | US |
| Child | 16434190 | US |
