JP2004085514A - Method and instrument for measuring lead of screw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an instrument for measuring lead of screw by which the error of the lead of a single male screw or female screw can be measured easily in three dimensions with high accuracy regardless of the shape of the screw. <P>SOLUTION: By rotating a stylus 11 around axis 1b of a screw 1 and moving the stylus 11 in the axial direction 1b along a thread groove 1a of the screw 1 in a state where the stylus 11 is abutted on the thread groove 1a with a prescribed pressure, the moving amounts of the stylus 11 in the direction of rotation and in the axial direction 1a are measured and the error of the lead of the screw 1 is measured from the moving amounts. Therefore, the error of the lead of the screw 1 can be measured easily with high accuracy for either one of a male screw or a female screw. In addition, since the stylus 11 is moved in the axial direction 1b along the thread groove 1a, the stylus 11 only requires a rotationally driving system, and the instrument for measuring the lead of the screw can be constituted with a simple structure. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for measuring a screw lead for measuring an error of a screw lead of a parallel male screw such as a metric screw, a unified screw, a trapezoidal screw, and a ball screw, and a female screw.
[0002]
[Prior art]
Conventionally, the measurement of a screw lead is performed by the following method.
A Measurement of male thread
a) A method of measuring the pitch of a shadow using a measuring microscope or a projector.
b) Judgment based on stop, as in the screw ring gauge.
c) In combination with a nut (female screw), a method of measuring the displacement of the nut with a dedicated measuring instrument (for a ball screw).
B Female thread measurement
d) A method of judging by stopping as shown in the screw plug gauge.
e) A method of measuring the displacement of a nut (female screw) with a special measuring instrument in combination with a male screw (for a ball screw).
[0003]
Among the methods for measuring such screw leads, the method a) can measure only the projected angle, that is, only two opposite screw leads in the radial direction of the male screw, and grasps the entire three-dimensional shape. Was an impossible method. In the methods b) and d), only pass / fail judgment can be made, and the numerical value of the screw lead cannot be converted. Further, the methods c) and e) cannot measure the screw lead of the male screw or the female screw alone because the accuracy is in the state where the male screw and the female screw are combined. Also, the measuring device was very expensive.
[0004]
Therefore, Patent Document 1 discloses a method and an apparatus for measuring a screw dimension, which are capable of three-dimensionally measuring a screw lead of a female screw alone. According to the disclosed method and apparatus, a female screw is rotated around a screw axis, and a measuring terminal (stylus) movably installed in the screw axis direction is slidably contacted with the rotating screw groove. The rotation angle of the screw and the amount of linear displacement of the measuring terminal are measured to enable three-dimensional measurement of the screw lead and detection of a lead error.
[0005]
[Patent Document 1]
JP 2002-5653 A (page 2 etc.)
[0006]
[Problems to be solved by the invention]
However, according to the method and apparatus disclosed in Patent Document 1, the movement of the measuring terminal slidably contacting the thread groove is controlled so as to advance by one lead for one rotation of the female screw. Therefore, there is a problem that it is difficult to control the movement without error, and the cost of the apparatus is unavoidable because the control mechanism must be configured with high accuracy.
In addition, when measuring, it is necessary to rotate the internal thread, but when the internal thread to be measured is formed on a large and heavy member such as a cylinder block or a connecting rod that constitutes an automobile engine, There is also a problem that it is difficult to rotate this, so that the measurement is not easy.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is capable of easily and accurately measuring three-dimensional errors of a screw lead of a male screw and a female screw independently of a screw shape. An object of the present invention is to provide a method and an apparatus for measuring a lead.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, a stylus is brought into contact with a screw groove of a screw to be measured, and a contact position between the screw groove and the stylus is set along the screw groove. In the method of measuring the screw lead by moving the stylus in contact with the thread groove, rotate the stylus around the axis of the screw to be measured, and in the axial direction according to the lead of the screw to be measured. By moving the stylus, the amount of movement in the rotational direction and the amount of movement in the axial direction are measured, and the lead error of the screw is measured based on these amounts of movement.
[0009]
According to a second aspect of the present invention, in the method of the first aspect, the measured screw is one of an internal thread and an external thread.
[0010]
According to a third aspect of the present invention, in the method of the first or second aspect, the stylus can be moved in a rotational direction and an axial direction by a moving mechanism having a non-contact support portion. It is characterized by having.
[0011]
According to a fourth aspect of the present invention, in the method according to any one of the first to third aspects, a balance weight is connected to the stylus, and the stylus is moved in the axial direction by the weight of the balance weight. It is characterized.
[0012]
An apparatus for measuring a screw lead according to claim 5, wherein the stylus is brought into contact with the screw groove of the screw to be measured, and the contact position between the screw groove and the stylus is moved along the screw groove. An axial moving portion that is movable along the axial direction of the measured screw; a stylus mounting portion that is held by the axial moving portion and that is rotatable around the axial direction of the measured screw; A stylus attached to the stylus attachment portion, a rotation drive system connected to the stylus attachment portion, and rotation angle measuring means for measuring a rotation angle and an axial movement amount of the stylus attachment portion; and linear displacement. Measuring means is provided.
[0013]
According to a sixth aspect of the present invention, in the invention of the fifth aspect, the rotary drive system and the stylus mounting portion have a magnetic portion made of a magnetic material, and the rotary drive system and the stylus mounting portion. Are characterized by being connected via a magnetic part in a non-contact manner by magnetic force.
[0014]
According to a seventh aspect of the present invention, in the invention of the fifth aspect, the stylus mounting portion has a stylus attached to a tip thereof so as to be in contact with a thread groove of an internal thread. .
[0015]
According to an eighth aspect of the present invention, in the invention of the fifth aspect, the stylus mounting portion has a stylus attached to a tip thereof so as to be able to abut a screw groove of the screw. .
[0016]
According to a ninth aspect of the present invention, in the invention of the eighth aspect, the stylus mounting portion is provided with a cylindrical connecting tool to which a stylus is mounted.
[0017]
According to a tenth aspect of the present invention, in the invention of the fifth aspect, the stylus mounting portion is rotatably held by an axial moving portion via a non-contact bearing. It is characterized by the following.
[0018]
According to an eleventh aspect of the present invention, in the invention according to any one of the fifth to tenth aspects, the axial movement unit includes a guide and a slider installed along the axial direction. It is characterized by being held movably in the axial direction via a slide portion.
[0019]
According to a twelfth aspect of the present invention, in the invention according to any one of the fifth to eleventh aspects, the axial moving part is connected to a balance weight, and can be moved in the axial direction by the weight of the balance weight. It is characterized by the above.
[0020]
According to a thirteenth aspect of the present invention, in the invention of the twelfth aspect, the balance weight forms a non-contact balance weight portion and a balance weight guide installed along the axial direction. I do.
[0021]
According to a fourteenth aspect of the present invention, in the screw lead measuring device according to any one of the fifth to thirteenth aspects, the position of the stylus mounting portion is adjustable by the XY table. Features.
[0022]
[Action]
According to the method for measuring a screw lead of the present invention configured as described above, the stylus is rotated around the axis of the screw, and is moved according to the thread groove, so that the amount of movement in the rotational direction of the stylus and the axial Since the movement amount is measured, the screw lead can be measured in three dimensions. In particular, since the stylus is rotated around the axis of the screw, even if the screw is formed on a large and heavy member such as a cylinder block or a connecting rod, it is not necessary to rotate these large members, so that it is simple. Can measure the screw lead. Further, since the stylus is rotated in the state of being in contact with the thread groove and is moved in the axial direction according to the thread groove, the measurement of the screw lead can be performed without providing a stylus axial movement control mechanism. .
[0023]
The measurement of the screw lead can be applied to both a female screw and a male screw. In the case of a female screw, a stylus can be installed in a screw hole, turned outward, and contacted with a screw groove. Further, in the case of a male screw, a stylus can be provided on the outer peripheral side of the screw so that the stylus faces inward and abuts the screw groove. Therefore, by making the stylus replaceable, it is possible to measure both the internal thread and the external thread with one device. In addition, it is possible to easily measure the measurement of screws having different sizes by replacing the stylus.
[0024]
Further, if the movement of the stylus in the rotation direction and the movement in the axial direction are performed by a moving mechanism having a non-contact support portion, the friction generated in the support portion is eliminated, and the rotation direction and the axial direction are eliminated. The error of the measurement of the movement amount of the object can be reduced, and the accuracy of the measurement can be improved.
[0025]
Further, when the balance weight is directly or indirectly connected to the stylus and the stylus is moved in the axial direction by the weight of the balance weight, the stylus is moved so as to accurately follow the thread groove. In this regard, the accuracy of the measurement can be improved. Furthermore, since the contact pressure at which the stylus contacts the thread groove can be adjusted by the weight of the balance weight, by setting the weight of the balance weight appropriately, it is possible to prevent the impression of the stylus from abutting on the thread groove. .
[0026]
Further, according to the screw lead measuring apparatus of the present invention described in claims 5 to 14, the excellent method of measuring a screw lead of the present invention as described above can be implemented.
The stylus can be detached from the stylus attachment portion or can be replaced for each stylus attachment portion, so that different size screws can be easily measured using styluses of different shapes. The stylus mounting portion is usually formed in a shaft shape, and can be inserted into a screw hole when measuring a female screw. Further, when measuring the male screw, the male screw may be formed in a cylindrical shape, and the male screw may be positioned in the cylindrical hole and the stylus mounting portion may be positioned around the cylindrical screw. However, according to the present invention, the shape of the stylus mounting portion is not limited to the above, and it is essential that the stylus be capable of transmitting rotation to the stylus and moving along the thread groove.
[0027]
In the case where the stylus attachment portion is cylindrical, the stylus can be provided on the inner surface of the stylus attachment portion inward. With this configuration, the rigidity of the stylus in all directions can be improved. In the present invention, when measuring a bolt (male thread), the measurement is performed by rotating the lead measuring stylus along the outer periphery of the bolt. At this time, if the length of the bolt is long, the moving distance of the stylus inevitably increases, and a moment load acts on the stylus due to the sliding resistance of the portion of the stylus tip that comes into contact with the thread. For this reason, the stylus always traces the thread while receiving a force in the measuring direction. If the bolt is long, the distance between the stylus fixing part and the contact part (measurement part) between the thread and the stylus becomes long, and the elastic deformation of the stylus due to the sliding resistance is directly linked to the measurement error. Such a problem can be solved by using the cylindrical stylus attachment as described above. The measurement accuracy is improved by the above.
In particular, for the deformation in which the stylus itself breaks, the influence on the measurement error is drastically reduced since the second moment of area is significantly improved.
[0028]
Further, if the driving force for rotationally driving the stylus is transmitted by the magnetic coupling as described in claim 6, the driving force can be transmitted in a non-contact manner, and vibrations from the driving means can be transmitted to the stylus. The transmission prevents the measurement accuracy from being reduced, and as a result, the measurement accuracy is further improved.
[0029]
Furthermore, if the balance weight can be moved up and down by a non-contact guide as described in claim 13, a decrease in measurement accuracy due to a roll of the balance weight or the like is prevented, and as a result, the measurement accuracy is further improved. The non-contact balance weight portion guided by the guide in a non-contact manner may be, for example, one having a non-contact air bearing.
[0030]
Further, in the apparatus of the present invention, when the position of the stylus shaft is adjustable by the XY table, the adjustment for aligning the center axis of the stylus shaft with the screw axis can be easily performed. The device can be easily measured.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0032]
FIG. 1 shows a principle diagram of a method for measuring a screw lead according to the present invention. In the figure, reference numeral 1 denotes a screw to be formed on the object to be measured. A stylus 11 attached to a rotatable stylus shaft 10 is brought into contact with the thread groove 1a of the female screw 1. The contact pressure between the stylus 11 and the thread groove 1a is adjusted by the weight of the balance weight 20. In this state, the stylus 11 is rotated around the central axis 1b of the female screw 1 as indicated by an arrow 3, and the stylus 11 is moved in the direction of the central axis 1b in accordance with the thread groove 1a by using the weight of the balance weight 20. Move as shown in FIG. At this time, the rotation amount and the axial movement amount of the stylus 11 are measured, and the lead error is measured from these movement amounts.
[0033]
FIGS. 2 to 6 show an example of a measuring device for a screw lead for implementing such a method.
The device is configured such that a stylus shaft 10 as a stylus attachment portion can rotate around a central axis 1b as indicated by an arrow 3 and can move (elevate) along a central axis 1b as indicated by an arrow 4. Have been. A stylus 11 is attached to a tip of the stylus shaft 10.
[0034]
In order to make the stylus shaft 10 rotatable, the stylus shaft 10 is connected to a center shaft 31 of an air bearing (radial direction, thrust direction) 30 which is a non-contact support portion (non-contact bearing). Note that the stylus shaft 10 and the center shaft 31 may be integrated. A vertical base plate 33 attached to one side of a cylindrical support 32 holding the air bearing 30 is connected to the slider 52. The elevating guide 51 and the slider 52 constitute a non-contact slide portion 50 which is a non-contact support portion using air pressure. The non-contact slide portion 50 causes the stylus shaft 10 to move in the vertical direction in FIG. It can be moved in a direction parallel to.
[0035]
In the air bearing 30, a small gap 30a is provided between the center shafts 31 as shown in FIG. 4, and the high pressure air is supplied to the small gap 30a to hold the center shaft 31 without friction. It is rotatable.
Further, in the non-contact slide portion 50, as shown in FIG. 5, a slider 52 is arranged so as to surround the elevating guide 51, and a small gap 50a is provided between the elevating guide 51 and the slider 52. By supplying high-pressure air to the small gap 50a, the slider 52 can be moved in the vertical direction while holding the slider 52 without friction.
[0036]
As shown in FIG. 6, the stylus shaft 10 is loosely inserted into a center hole 35a of a belt pulley 35 which is rotatable by a support bearing 34 provided on a support 32, and a cylindrical portion 35b of the belt pulley 35. Is connected to the belt pulley 35 by a power transmission pin 36 provided so as to penetrate laterally. A belt 39 is wound around a pulley portion 35 c of the belt pulley 35 between pulleys 38 fixed to a shaft of a motor 37 installed on one side of the support 32, and the stylus shaft 10 is driven by the driving force of the motor 37. It can be rotated. By configuring the rotation drive system for the stylus shaft 10 in this way, when the stylus shaft 10 is rotated by the motor 37, consideration is given so that vibration such as shaft runout on the motor 37 side is not directly transmitted to the stylus shaft 10. .
[0037]
A disk 40 is provided on the upper end side of the center shaft 31, and a rotation angle sensor 42 including a rotary encoder 41 is provided so as to face the disk 40. As described above, the amount of movement of the stylus 11 moved in the rotation direction of the arrow 3 by the motor 37 is measured by the rotation angle sensor 42 as rotation angle measuring means.
[0038]
The slider 52, the vertical base plate 33, the support 32 mounted on the vertical base plate 33, the air bearing 30, the motor 37, and the like are integrated with the stylus shaft 10 and the stylus 11 along the direction of the central axis 1b. And constitutes an axial moving unit that moves. The balance weight 20 is connected to the vertical base plate 33 via the steel belt 21 in consideration of the total weight of these axial moving parts. The steel belt 21 is movable by pulleys 23 and 24 mounted on a frame 22. When the balance weight 20 descends by its own weight as shown by a chain line, the steel belt 21 forms an axial moving portion via the steel belt 21. The slider 52 moves upward as shown by a chain line.
[0039]
Further, a measuring shaft 53 which is movable up and down in contact with the center shaft 31 is disposed above the center shaft 31 in the extending direction. One end of the measuring shaft 53 extends into the displacement sensor 54, and the movement amount of the stylus shaft 10 is reduced by a linear displacement sensor 55, which is a linear displacement measuring means, composed of the measuring shaft 53 and the displacement sensor 54. It can be measured.
[0040]
Further, the lifting guide 51 and the frame 22 are installed on a horizontal base plate 25, and the horizontal base plate 25 is mounted on an XY table 61 installed on a stationary board 60. The position of the stylus shaft 10 is adjusted two-dimensionally by the XY table 61. Thus, the female screw 1 installed below the stylus shaft 10 and the central axis 1b of the stylus shaft 10 can be accurately matched. The stationary platen 60 is provided with a handle 62 as shown in FIG. 3 so that the device can be carried.
[0041]
In order to measure the lead of the internal thread 1 with the screw lead measuring device configured as described above, the tip of the stylus shaft 10 and the stylus are aligned with the stylus shaft 10 and the central axis 1b of the internal thread 1 being matched. The stylus 11 is positioned in the screw hole of the female screw 1 and the stylus 11 is brought into contact with the screw groove 1a. At this time, the balance weight 20 is fixed by a stopper (not shown) so as not to descend. Next, the stylus shaft 10 is rotated by driving the motor 37. At the same time, the balance weight 20 can be lowered by removing a stopper (not shown) so that the weight of the balance weight 20 is added to the vertical base plate 33.
[0042]
Then, the stylus 11 moves in the arrow 4 direction while rotating around the central axis 1b along the thread groove 1a while slidingly contacting the thread groove 1a. At this time, the amount of movement of the stylus 11 in the rotation direction can be measured by the rotation angle sensor 42, and the amount of movement of the stylus 11 in the direction of the central axis 1b can be measured by the linear displacement sensor 55. Further, the amount of movement of the stylus 11 in the linear direction can be measured by the linear displacement sensor 55 via the measuring shaft 53.
From these measured movement amounts, the three-dimensional shape of the lead is obtained.
The error of the screw lead is obtained by calculation from the difference between the geometric lead (calculated from the rotation angle and the nominal pitch) and the lead based on the measurement result.
[0043]
As described above, since the stylus 11 is rotated by the motor 37, it is not necessary to rotate the measured screw 2 on which the female screw 1 is formed. Therefore, the measurement can be performed regardless of the weight or shape of the screw 2 to be measured. In addition, since the movement of the stylus 11 in the direction of the central axis 1b is performed through the thread groove 1a using the own weight of the balance weight 20, an axial drive system for the stylus 11 is unnecessary, and the apparatus is simplified. be able to. Since the device can be simplified, it can be carried around, and the measuring place is not limited.
[0044]
Further, since the length of the stylus 11 can be set according to the hole diameter of the female screw 1, it is possible to measure the lead of the female screw having a wide range of diameters. In addition, the measurement is performed whether the female screw 1 is below the stationary platen 60 (for example, a female screw formed in a cylinder block) or the female screw 1 is above the stationary platen 60 (for example, a female screw of a nut). Is possible.
[0045]
The moving mechanism of the stylus 11 in the rotational direction is constituted by a non-contact structure via an air bearing 30, and the moving mechanism of the stylus 11 in the axial direction is constituted by a non-contact structure via a non-contact slide part 50. I have. Therefore, the contact portion in the measurement system is mainly only the contact portion between the stylus 11 and the thread groove 1a. As a result, the contact pressure between the stylus 11 and the thread groove 1a is kept constant, and the amount of movement of the stylus 11 is accurately measured by the rotation angle sensor 42 and the linear displacement sensor 55 without introducing an error due to friction. The screw lead can be measured with high accuracy. In the embodiment, the air bearing 30 and the non-contact slide portion 50 are used to form the non-contact structure. However, another non-contact support structure such as a magnetic bearing may be used.
[0046]
FIG. 7 shows another embodiment, in which a configuration example of a stylus mounting portion 71 and a stylus 72 when measuring the lead of the male screw 70 is shown. A cylindrical connector 73 is provided at the tip of the stylus mounting portion 71, and the stylus 72 is mounted inward on a support plate 74 provided at the lower end of the connector 73. The connection tool 73 can be loosely fitted on the outer peripheral side of the male screw 70. The male screw 70 is fixed to an inclination correction table 75 by a bolt holder 76, and the inclination of the male screw 70 is corrected by the inclination correction table 75 so that it can coincide with the central axis of the stylus mounting portion 71.
[0047]
In this device, the stylus 72 is rotated around the central axis 1b while the stylus 72 is in contact with the thread groove 70a of the male thread 70 by inserting the screw 70 into the center of the connecting tool 73, and Thus, it is possible to accurately measure the lead. In the case of measuring a long male screw, the stylus mounting portion 71 and the center shaft as well as the connecting tool 73 can be measured by making them cylindrical.
[0048]
The tilt correction table 75 can adjust the tilt in two directions orthogonal to each other, but may include a structure (that is, an XY table) that can also adjust the position in a plane in the two orthogonal directions. . In addition, the XY table 61 installed on the measuring device side of the screw lead can include an inclination correction structure. Then, since the measurement object 2 is formed obliquely, it is possible to measure a screw or a male screw.
[0049]
In this embodiment, the support plate 74 is provided at the tip of the connection tool 73, and the stylus 72 is provided on the support plate 74. However, as shown in FIG. , The stylus 72 is provided. The stylus 72 is desirably provided on the inner surface near the end surface of the connection tool 73. Also in this mode, the measurement can be performed by inserting the male screw 70 into the center hole of the connection tool 73. In this embodiment, the rigidity of the connecting tool 73 in all directions can be improved, the lead 73 is resistant to torsion and bending deformation, and the stylus 72 is stably positioned to improve measurement accuracy. In order to reduce the weight increase due to the cylindrical shape of the stylus connector 73, a lightweight material such as a ceramic or an aluminum material can be used as the material of the stylus mount.
Although the connecting device of FIG. 8 has been described as having a cylindrical shape, the connecting device 73a may be formed of a part of a cylindrical shape as shown in FIG. Similarly, the stylus 72 can be provided inward on the inner surface of the connection tool 73a to perform lead measurement. Also in the connection tool 73a having this shape, the effect of improving rigidity can be obtained. In the present specification, these shapes including the complete cylindrical shape are referred to as cylindrical shapes. The partially tubular connector 73a is suitable for measuring a large diameter screw 70 or a lead of a rotary die.
[0050]
Further, in the above embodiment, as shown in FIG. 6, the stylus shaft 10 is loosely inserted into the center hole 35a of the belt pulley 35 rotatable by the support bearing 34 provided on the support 32, and the vibration of the motor 37 Are not directly transmitted to the stylus shaft 10 and the misalignment occurring at the time of coupling or the rotational vibration caused by the misalignment is prevented.
In the above configuration, although the belt tension is not transmitted, since the power transmission pin 36 is in contact, the generation of weak rotational vibration cannot be completely prevented. In the future, non-contact driving without vibration may be required as the measurement accuracy becomes higher. FIG. 10 shows an embodiment for responding to such a request. In this embodiment, the same components as those in the above embodiment are denoted by the same reference numerals, and the description thereof will be omitted or simplified.
[0051]
That is, a magnetic portion 80 using a permanent magnet as a magnetic material is provided on the outer peripheral portion (usually the outer peripheral surface) of the stylus shaft 10, and in the magnetic portion 80, N poles and S poles are alternately arranged in the circumferential direction. Have been. On the other hand, on the inner surface of the pulley portion 35c of the belt pulley 35, a magnetic portion 81 using a permanent magnet as a magnetic material is provided so as to be able to face the magnetic portion 80. Also in the magnetic part 81, the N pole and the S pole are alternately arranged in the circumferential direction.
Note that, in this embodiment, the power transmission pin 36 used in the above embodiment is not used, and the stylus shaft 10 and the belt pulley 35 are not in contact with each other to form a magnetic coupling. As the material of the permanent magnet, a general material such as ferrite can be used. In particular, when the space between the magnetic portion provided on the outer peripheral portion of the stylus shaft 10 and the magnetic portion provided on the inner peripheral portion of the pulley portion 35c becomes large, a rare earth magnet such as neodymium having a large coercive force can be used.
[0052]
In the above embodiment, when the motor 37 is operated, the belt pulley 35 rotates via the belt 39, and the rotation of the belt pulley 35 causes the magnetic section 81 provided on the inner surface of the pulley section 35c to rotate. A magnetic force acts between the magnetic portion 81 and the magnetic portion of the stylus shaft 10, and a rotational force in the same direction is generated in the magnetic portion 80 as the magnetic portion 81 rotates. The stylus shaft 10 rotates together with the belt pulley 35 by this rotational force. At this time, the magnetic force acts on the stylus shaft 10 from the entire circumference and is not in contact with the belt pulley 35. Therefore, the stylus shaft rotates smoothly, and vibrations and the like are not transmitted to the stylus, and high accuracy is achieved. Can be measured.
[0053]
In this embodiment, the magnetic portion is provided on the inner surface of the pulley portion that is driven to rotate, facing the magnetic portion provided on the stylus shaft. However, depending on the location of the magnetic portion on the stylus shaft, the magnetic portion may be provided. The magnetic part opposing to the pulley may be provided other than the pulley part. In short, the installation location is not limited as long as it is rotated by a driving means such as a driving motor in accordance with the operation.
[0054]
Next, in the above-described embodiment, the measurement is performed while the stylus moves up and down. At this time, the weight of the member including the stylus is adjusted by the balance weight 20 via the roller so as not to affect the measurement error. Balanced. As shown in FIG. 2, the balance weight 20 does not particularly guide in the lateral direction so as to follow a slight movement of the head. That is, the balance weight is suspended only by the belt 21 to which the stylus or the like is tied.
[0055]
Since the lead measurement is a high-precision measurement, high-speed axis movement is not performed, so that the measurement time is relatively long, for example, 1 minute or more. Therefore, if the balance weight fluctuates during the measurement, there is a problem that it is directly linked to the measurement error.
Such lateral movement of the balance weight can be restricted by sliding the balance weight while supporting it with a guide. However, in this method, since there is a sliding resistance, vibration may be generated in the weight and transmitted to the stylus, which is not suitable for a lead measuring machine requiring a fine feed.
[0056]
FIG. 11 shows an embodiment in which the support of the balance weight can be performed in a non-contact manner. In this embodiment, the same components as those in the above embodiment are denoted by the same reference numerals, and the description thereof will be omitted or simplified.
[0057]
That is, the balance weight 90 has the guide hole 91 formed in the center portion on the lower side, and the inner surface of the guide hole 91 is ground. On the other hand, on the stationary platen 60, a precision guide shaft (balance weight guide) 92 is erected upward so as to be insertable into the guide hole 91 with a small gap 93a. The small gap 93a between the guide hole 91 and the precision guide shaft 92 is configured so that compressed air is supplied. The balance weight 90 and the precision guide shaft 92 are formed by a non-contact balance weight portion using air pressure. 93. The compressed air can be supplied from either the balance weight 90 side or the precision guide shaft 92 side. However, if it is assumed that the compressed air is supplied from the balance weight 90 side, the elastic force of the compressed air supply tube and the like are reduced by the balance weight 90. In order to affect the movement, it is desirable to supply compressed air from the precision guide shaft 92 side to the small gap 93a. In this case, by providing the precision guide shaft 92 with a porous material or providing an air supply hole, it is possible to supply compressed air from the outside.
[0058]
If the balance weight 90 is moved while supporting the balance weight 90 in a non-contact manner by the non-contact balance weight portion 93, the balance weight 90 moves smoothly in the vertical direction, and the lateral movement reduces the sliding resistance. Regulated without increasing. This further improves the lead measurement accuracy.
[0059]
In the above description, the case where the guide shaft is inserted into the guide hole of the balance weight has been described. However, a guide hole is provided on the guide side, and a part of the balance weight is inserted into the guide hole so as to be in a non-contact manner. It is also possible to perform a guide.
[0060]
【The invention's effect】
As described above, according to the present invention, the stylus in contact with the thread groove is rotated, and the stylus is moved in the axial direction of the screw according to the thread groove, so that the amount of movement in the rotational direction and the axial direction of the stylus is reduced. Since the measurement is performed, the error of the screw lead can be measured easily and with high accuracy for both the male screw and the female screw. In addition, since the stylus is moved in the axial direction according to the thread groove, the stylus only needs to be provided with a rotary drive system, and the measuring device can be simply configured.
[Brief description of the drawings]
FIG. 1 is a principle diagram of the present invention.
FIG. 2 is a side view of the screw lead measuring device according to the embodiment of the present invention.
FIG. 3 is a front view of the screw lead measuring device.
FIG. 4 is a cross-sectional view showing a non-contact support section that rotatably supports a stylus mounting section.
FIG. 5 is a cross-sectional view showing a non-contact support unit that supports the axial movement unit so as to be movable in the screw axis direction.
FIG. 6 is an enlarged sectional view of a portion of a rotary drive system of a stylus of the screw lead measuring device.
FIG. 7 is a diagram showing a stylus shaft and a stylus portion when measuring a thread lead of a male screw in another embodiment of the present invention.
FIG. 8 is a front sectional view showing a stylus shaft and a stylus in another embodiment of the present invention, a partially enlarged view at the front, and a bottom view.
FIG. 9 is a bottom view showing a modified example of the stylus attachment.
FIG. 10 is an enlarged cross-sectional view of a portion of a rotary drive system of a stylus of a screw lead measuring device according to another embodiment of the present invention.
FIG. 11 is a view showing a guide structure of a balance weight according to still another embodiment of the present invention.
[Explanation of symbols]
1 Female thread
1a Screw groove
2 Measurement object
5 Male thread
5a thread groove
6 Tilt correction table
7 bolt jig
10 Stylus shaft
11 Stylus
12 stylus
13 Connection Tools
14 Support plate
20 Balance weight
21 steel belt
22 frames
23 pulley
24 pulley
25 Horizontal base plate
30 air bearing
31 Center shaft
32 Support
33 Vertical base plate
34 Support bearing
35 belt pulley
35a center hole
35b tubular part
35c pulley
36 Power transmission pin
37 motor
38 pulley
39 belt
40 disk
41 Rotary encoder
42 Rotation angle sensor
50 Non-contact slide part
51 Lifting guide
52 Slider
53 shaft
54 Displacement Sensor
55 Linear displacement sensor
60 stationary board
61 XY table
62 handle
70 Male Screw
70a Male thread groove
71 Stylus mounting part
72 stylus
73 Connector
73a connection tool
80 Magnetic part
81 Magnetic part
90 Balance weight
91 Guide hole
92 Precision guide shaft
93 Non-contact balance weight section

Claims (14)

In a method in which a stylus is brought into contact with a thread groove of a screw to be measured and a contact position between the thread groove and the stylus is moved along the thread groove to measure a screw lead, the stylus is brought into contact with the thread groove. Rotating the stylus about the axis of the measured screw, and moving the stylus in the axial direction according to the thread groove of the measured screw, measuring the amount of movement of the stylus in the rotational direction and the amount of movement in the axial direction. A method for measuring a screw lead, comprising measuring a lead error of the screw based on a movement amount. The method according to claim 1, wherein the measured screw is one of a female screw and a male screw. The method according to claim 1, wherein the stylus is movable in a rotational direction and an axial direction by a moving mechanism including a non-contact support portion. The method according to any one of claims 1 to 3, wherein a balance weight is connected to the stylus, and the stylus is moved in the axial direction by the weight of the balance weight. In a device for measuring a screw lead by bringing a stylus into contact with a thread groove of a screw to be measured and moving a contact position between the screw groove and the stylus along the screw groove, the device is movable along the axial direction of the screw to be measured. An axial moving portion, a stylus mounting portion held by the axial moving portion and rotatable around the axial direction of the screw to be measured, and a stylus mounted on the stylus mounting portion. A rotation drive system is connected to the stylus mounting portion, and a rotation angle measuring device and a linear displacement measuring device for measuring a rotation angle and an axial movement amount of the stylus mounting portion are provided. Screw lead measuring device. The rotation drive system and the stylus attachment portion have a magnetic portion made of a magnetic material, and the rotation drive system and the stylus attachment portion are connected via a magnetic portion in a non-contact manner by magnetic force. The screw lead measuring device according to claim 5. The screw stylus measuring device according to claim 5, wherein the stylus mounting portion is provided with a stylus capable of abutting on a thread groove of a female screw at a tip. 6. The screw lead measuring device according to claim 5, wherein a stylus capable of contacting a screw groove of a screw is attached to a tip of the stylus attachment portion. 9. The screw lead measuring device according to claim 8, wherein the stylus mounting portion is provided with a cylindrical connecting tool to which a stylus is mounted. The screw lead measuring device according to any one of claims 5 to 9, wherein the stylus mounting portion is rotatably held by an axial moving portion via a non-contact bearing. The said axial direction moving part is hold | maintained movably in an axial direction via the non-contact slide part comprised by the guide and slider which were installed along the axial direction, The axial direction is characterized by the above-mentioned. The screw lead measuring device according to any one of the above. The screw lead measuring device according to any one of claims 5 to 11, wherein the axial moving portion is connected to a balance weight, and is movable in the axial direction by the weight of the balance weight. 13. The screw lead measuring device according to claim 12, wherein the balance weight forms a non-contact balance weight portion with a balance weight guide installed along the axial direction. The screw lead measuring device according to any one of claims 5 to 13, wherein the axial moving unit is configured to adjust a position of a stylus mounting unit by an XY table.

Images