JP2000046141A - Pre-load dynamic torque measuring method for ball screw and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device capable of measuring pre-load dynamic torque over an almost total length of a screw shaft. SOLUTION: A screw shaft 14 is supported by centers 92, 106, rotation of a spindle 78 is transmitted by a rotation transmitting device 98. A wheel 152 is connected by a connecting device 154 to a moving member 118 provided movably in the parallel direction to the screw shaft 14 in a device main unit 70, to be engaged with the screw shaft 14. A spherical part 56 of a torque transmitting member 40 mounted incapable of relative rotation in a nut 16, by a pair engaging surfaces of an engaging member 134 of a load measuring device mounted in the moving member 118, is interposed from both sides, rotation of the nut 16, 18 is impeded. When the screw shaft 14 is rotated, the nuts 16, 18 are moved along the screw shaft 14, and the wheel 152 is moved along the screw shaft 14, to move the moving member 118 at an equal speed in the same direction to/as the nuts 16, 18, so as to measure pre-load dynamic torque over an almost total length of the screw shaft 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method and apparatus for measuring a preload dynamic torque of a ball screw.

[0002]

2. Description of the Related Art A ball screw is formed by screwing a screw shaft and a nut through a ball, and is widely used for moving a moving member such as a tool rest of a lathe. Some of the ball screws are designed to remove backlash and increase rigidity by applying a preload to the ball. For example, a preload is applied to a ball by providing a pair of nuts and sandwiching a spacer between the pair of nuts.

[0003] A method of measuring the preload dynamic torque of a ball screw to which a preload is applied in this manner is already known.
The preload dynamic torque is a torque required to keep the screw shaft or the nut rotating without applying an external load to the ball screw to which a predetermined preload is applied. Conventionally, the measurement of preload dynamic torque is described in "JIS Handbook Machine Elements"
As described in B1192 (published by the Japan Standards Association), when the screw shaft is rotated, the force required to prevent the rotation of the nut is measured by a load cell, and the measured value is used as the measured value. The preload dynamic torque is calculated by multiplying the distance between the line of action of the force and the axis of the screw shaft. If the preload dynamic torque is measured, it is possible to know, for example, the manufacturing accuracy of the ball screw and the suitability of the magnitude of the preload based on the measurement result, to avoid using a ball screw with poor manufacturing accuracy, or to adjust the preload appropriately. The size can be adjusted. However, in the conventional method of measuring the preload dynamic torque, it was difficult to measure the preload dynamic torque over the entire length of the screw shaft and to evaluate the entire ball screw. The force required to keep the nut from rotating
This is because the range that can be measured by the load cell was limited.

[0004]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a method and apparatus for measuring a preload dynamic torque capable of measuring a preload dynamic torque over substantially the entire length of a screw shaft. According to the present invention, a method and an apparatus for measuring a preload dynamic torque according to the following aspects are provided. Each mode is divided into terms as in the claims, and each term is numbered,
Enter the number of another section as necessary.
This is to illustrate some of the technical features and combinations thereof described in the present specification, and the technical features and the combinations described in the present specification are limited to the following. Should not be interpreted. (1) A method for measuring a preload dynamic torque of a ball screw formed by screwing a screw shaft and a nut through a ball,
On the nut, a torque transmission member having an engagement portion is attached so as to be relatively non-rotatable, while the screw shaft is attached to a support device,
A preparatory step of supporting the screw shaft so as to be rotatable around the axis and immovable in the axial direction, and engaging the engaging portion of the torque transmitting member with a load measuring device; and rotating the screw shaft to rotate the screw shaft. Measuring the load applied to the load measuring device from the engagement portion over substantially the entire length of the screw shaft while moving the load measuring device along with the movement of the nut accompanying the nut. Method for measuring torque (claim 1). The load measuring device may be, for example, a device in which a load is automatically measured, such as a load cell, or, for example, an operator may read a measured value.
A device that requires the work of an operator may be used. Further, the load measuring device may be automatically moved along with the movement of the nut, or may be moved by an operator. In any case, it is desirable that the nut and the load measuring device be in a state where there is substantially no change in the relative position in the axial direction. Further, the screw shaft may be automatically rotated by a power rotating device, or may be rotated by an operator operating a rotating device such as a handle. When the screw shaft is rotated, the rotation of the nut is prevented by the load measuring device via the torque transmitting member, the nut is moved along the axis of the screw shaft, and the load (compression load or Tensile load) is measured by a load measuring device. This load is opposite in direction to the load required to prevent rotation of the nut, but of the same magnitude, and is equivalent to measuring the load required to prevent rotation of the nut. Due to the rotation of the screw shaft, the nut is moved from one end of the screw shaft to the other end, and the load measuring device measures the load while moving with the movement of the nut. From this, the load applied to the load measuring device is measured. The load is measured for "almost the entire length" of the screw shaft, but not for the "full length". One reason is that the nut does not move to the end of the screw shaft, leaving both ends. Because the load cannot be measured at both ends of the screw shaft.
This is because the measurement positions may be discrete. For example, when the load is automatically measured using a load cell as a load measuring device, the output value of the load cell is continuous, and the load can be measured for the entire length excluding both ends of the screw shaft. If this output value is continuously recorded as it is, the load will be measured for the entire length excluding both end portions of the screw shaft. However, when the output value is sampled by a computer, the process is performed at regular small intervals. In this case, the load is discretely measured at a plurality of measurement positions separated in a direction parallel to the axis of the screw shaft. In this case, the plurality of measurement positions are close enough to be said to be substantially continuous, and the load is measured over substantially the entire length of the screw shaft. The measurement position of the load may be set to a consciously discrete position. However, the measurement pitch is set to a size that can be said to have measured the load “about the entire length” of the screw shaft. The measurement pitch is set, for example, by a length or a ratio to the length of the screw shaft. In the former case, 10
mm or less, preferably 3 mm or less or 1
It is particularly desirable to set it to mm or less. In the latter case, the pitch may be set to 1/10 or less of the length of the screw shaft.
It is particularly desirable to set the pitch to 1/20 or less or 1/50 or less. The load thus measured has a one-to-one correspondence with the preload dynamic torque. When the load is measured, it is substantially equal to the preload dynamic torque is measured, and when the preload dynamic torque itself is measured. Similarly to the above, the evaluation of the ball screw becomes possible. For example, the manufacturing error of the ball screw such as the magnitude of preload, the cylindricity of the nut, the roundness of the screw shaft, the groove shape, the raceway surface roughness, the undulation in the spiral direction, the smoothness of operation,
It is possible to determine whether or not the torque fluctuation is appropriate. Therefore, it is not essential to convert the load into a residual pressure dynamic torque. Even without conversion, the above determination can be made over almost the entire length of the ball screw,
The evaluation can be performed with higher reliability than when the ball screw is evaluated based on the load measured for a part of the ball screw. Further, in a ball screw in which two nuts are provided and a spacer is sandwiched between the nuts and a preload is applied to the ball screw, the spacer for the preload dynamic torque of a set magnitude is obtained. The thickness (dimension in the direction parallel to the axis of the screw shaft) and the parallelism of the two nuts can be obtained. As the thickness of the spacer increases, the preload dynamic torque increases, and if the contact surface of the spacer with respect to the nut is inclined with respect to the axis, 2
The parallelism of the two nuts can be changed, and by changing the thickness of the spacer and the magnitude of the inclination, the spacer thickness and the parallelism at the time when the preload dynamic torque of the set magnitude is obtained can be known. If only one nut is provided and the nut leads are partially displaced and a preload is applied to the ball screw, the suitability of the nut leads is known. Furthermore, the shape of the thread groove of the screw shaft can be detected by the laser detector, and the relationship between the detection result and the measurement result of the preload dynamic torque can be analyzed. It is also possible to measure a change in load during one rotation of the screw shaft. In this case, it is desirable to make the rotation speed of the screw shaft smaller than when measuring the variation in load over substantially the entire length of the screw shaft. (2) The screw shaft is rotated by a power rotating device, and at least one of storing a measurement result of the load measuring device in a storage device and recording by a recording device is performed. (1)
The method for measuring the preload dynamic torque of the ball screw described in the paragraph. If the measurement result of the load measuring device is stored in the storage device, for example, the ball screw can be evaluated at an arbitrary time after the measurement based on the measurement result. Further, if the measurement result is recorded by a recording device, for example, an operator can easily evaluate the ball screw by visually observing the measurement result. The recording may be performed in parallel with the measurement, or may be collectively performed at an appropriate time after the measurement. (3) The ball according to the above (1) or (2), including a step of obtaining a preload dynamic torque based on the load measured by the load measuring device, in parallel with or after the measuring step. Preload dynamic torque measurement method for screws. As described above, the load and the preload dynamic torque have a one-to-one correspondence. When the load is measured, the ball screw can be evaluated. However, when the preload dynamic torque is calculated, the preload dynamic torque is calculated. The evaluation of the ball screw can be performed based on this. The preload dynamic torque is calculated by multiplying the load by the distance between the axis of the screw shaft and the line of action by which the engaging portion of the torque transmitting member applies a load to the load measuring device. In other words, it is possible to evaluate the ball screw. (4) The ball according to any one of (1) to (3), wherein the screw shaft is rotated in both forward and reverse directions, and a load is measured by the load measuring device during each rotation. Preload dynamic torque measurement method for screws. For example, if there is a manufacturing error in the screw shaft, the preload dynamic torque is not always the same between when the screw shaft rotates in the forward direction and when it rotates in the reverse direction. Therefore, if the screw shaft is rotated in the forward and reverse directions and the load is measured at each rotation, the state of the manufacturing error of the ball screw can be known more accurately. (5) An apparatus for measuring a preload dynamic torque of a ball screw formed by screwing a screw shaft and a nut through a ball,
An apparatus main body, a support device provided on the apparatus main body, and supporting the screw shaft so as to be rotatable around its axis and immovable in the axial direction, and a rotating device for rotating the screw shaft supported by the support device A torque transmitting member, comprising: a moving member supported by the device main body and supported by the supporting device so as to be movable in a direction parallel to the screw shaft; and an engaging portion, the torque transmitting member being attached to the nut so as to be relatively non-rotatable. And a load measuring device attached to the moving member to prevent the rotation of the torque transmitting member by engaging with the engaging portion, and to measure a load required for the prevention. A moving device for moving the nut in the same direction at the same speed as the rotation of the nut in rotation; According to the preload dynamic torque measuring device described in this section, the preload dynamic torque measuring method described in (1) can be performed, and the operations and effects described in relation to the section can be obtained. The moving device may include a traction member as described below, and may be a device that moves the moving member based on the rotation of the screw shaft, may include a dedicated power source, and may be configured to detect a movement of the nut by the detecting device. The apparatus may be configured to move the moving member in the same direction at the same speed as the movement of the nut while controlling the power source. Also, a feed screw (not necessarily a ball screw) is provided separately from the ball screw whose preload dynamic torque is to be measured, and the feed screw is rotated by a common drive source with the ball screw to be measured, thereby moving the moving member. You may move it. (6) a traction member that engages with the screw shaft and moves in the same direction at the same speed as the nut with rotation of the screw shaft, and a connection that connects the moving member to the traction member; The ball screw preload dynamic torque measuring device according to the mode (5), including a device (claim 3). The moving member may be connected to a nut to be measured, and may be moved by moving the nut. However, in this case, a moment load is applied to the nut by the moving member, and the measured value of the load measuring device becomes a value affected by the moment load, and the measurement accuracy is reduced. On the other hand, in this aspect, since the traction member is moved based on the rotation of the screw shaft to cause the moving member, the moving member does not apply a moment load to the nut to be measured, thereby avoiding a decrease in measurement accuracy. Is done. (7) The ball screw preload dynamic torque measuring device according to (6), wherein the traction member is a wheel that is rotatably held around a single axis by a holding device and is engaged with the screw shaft at an outer peripheral edge. Claim 4). The wheel is rotatably held around an axis different from the axis of the screw shaft,
If the screw shaft is rotated, it is moved in a direction parallel to the screw shaft while moving in the screw groove. The outer periphery of the wheel functions as a part of the thread of the nut screwed to the screw shaft, and the wheel is moved at the same speed and in the same direction as the nut to be measured by the rotation of the screw shaft. The device moves with the nut and measures the load. The traction member is not limited to the wheel, and may be configured by, for example, a nut (referred to as a traction nut) different from the nut to be measured. The tow nut is screwed onto the screw shaft,
The moving member is engaged. With the rotation of the screw shaft, the tow nut moves the moving member while moving in the same direction at the same speed as the nut to be measured, but in the portion where the tow nut of the screw shaft is screwed, Since the nut to be measured cannot be screwed and the load cannot be measured, the load measurement range of the screw shaft is narrowed accordingly. In the case of a wheel, on the other hand, the load cannot be measured on the portion of the screw shaft where the wheel is engaged and the portion between the portion and the nut, but the wheel engages with the screw shaft compared to the nut. The area where the load cannot be measured can be reduced by engaging the wheel at a position as small as possible on the screw shaft as close as possible to the nut, which is suitable for towing a moving member. Further, since the wheel can be engaged with the screw shaft from the radial direction, it is easier to engage and disengage than the tow nut. (8) The support device supports the wheel rotatably around the one axis, and the axial direction of the support shaft can be changed three-dimensionally to a desired direction. The ball screw preload dynamic torque measuring device according to the above mode (7), including a direction changing device that can be fixed to the ball screw. As long as the axial direction of the support shaft can be changed to a desired direction in three dimensions, regardless of the direction in which the wheel is engaged with the screw shaft, the lead angle of the screw shaft may vary. Even in this case, the wheel can be engaged with the screw groove in a posture along the screw groove (a posture that is not inclined with respect to the longitudinal direction of the screw groove). The semi-circular shape is substantially the same as the semi-circular shape having a cross-sectional shape perpendicular to the longitudinal direction of the groove, which facilitates manufacture. Further, the wheel can be engaged with a plurality of types of screw shafts having different lead angles, and a common wheel can be used to measure the preload dynamic torque of the plurality of types of ball screws. (9) The coupling device includes a rotation arm that is rotatably provided around a rotation axis substantially parallel to the axis of the screw shaft and supports the wheel via the holding device, wherein the wheel is The ball screw preload dynamic torque measuring apparatus according to the above mode (7) or (8), wherein the preload dynamic torque measuring apparatus is engaged with the screw shaft by rotation of a rotation arm. By the rotation of the rotation arm, the wheel is engaged with the screw shaft by its own weight, and the wheel can be easily engaged with the screw shaft. (10) The connecting device includes a relative position changing device that can change a relative position between the traction member and the moving member in a moving direction of the moving member. A ball screw preload dynamic torque measuring device according to item 1. Providing a relative position change device, if the towing member and the moving member, so that the relative position in the moving direction of the moving member can be changed, for example, the engagement position of the towing member with respect to the screw shaft,
The position is as close as possible to the nut, the distance between the nut and the portion of the screw shaft where the traction member is engaged can be shortened, and the range where the load on the screw shaft is not measured can be reduced. (11) The ball screw preload dynamic torque measuring device according to any one of (5) to (10), wherein the moving member is supported by the device main body via a ball linear guide. The ball linear guide includes a guide rail which is a linear guide member, and a guide block which holds the ball rotatably and circulatively and is fitted to the guide rail, and slides between the guide rail and the guide flock. The resistance is small, and the movement of the moving member is smoothly guided. As a result, the load measuring device has a high tracking accuracy with respect to the nut and can accurately detect the relationship between the axial position of the screw shaft and the load, and the sliding resistance of the moving member causes the screw shaft to bend and the load measuring accuracy. And the load can be measured with higher accuracy. (12) The rotation device is a power rotation device that includes a drive source and rotates the screw shaft by power.
(11) The ball screw preload dynamic torque measuring apparatus according to any one of the above (11). As the drive source, for example, an electric rotary motor, which is a kind of an electric motor, is preferably a servomotor or a step motor capable of controlling the rotation angle and the rotation speed with high accuracy. The operator may rotate the screw shaft.However, if the screw shaft is rotated by power, it is possible to improve the measurement accuracy of the preload dynamic torque by keeping the rotation speed of the screw shaft constant, and it is easy to automate the measurement of the load. Become. (13) The load measuring device includes an engagement member, and one of the engagement member and the engagement portion of the torque transmission member includes a spherical portion, and the other includes the torque transmission member connected to the screw shaft. Any of (5) to (12), provided with a pair of engaging surfaces that are substantially perpendicular to the locus drawn by the engaging portion when rotated about the axis of the shaft, and that sandwich the spherical portion from both sides. The ball screw preload dynamic torque measuring device according to any one of claims 1 to 5 (claim 5). When the spherical portion is provided on the engaging portion of the torque transmitting member, for example, the engaging portion is provided with an arm portion extending in the radial direction of the nut to be measured, and the spherical portion is provided at the tip of the arm portion. Just fine. When a spherical portion is provided on the engaging member of the load measuring device, for example, a U-shaped engaging member is attached to the tip of the measuring element of the load measuring device, and one of the arms of the U-shape and the measuring element are connected to each other. What is necessary is just to mount it orthogonally, and to provide a spherical part at the tip part of the other arm. The spherical portion is sandwiched from both sides by a pair of engaging surfaces provided on the engaging portion of the torque transmitting member. According to this aspect, both forward and reverse rotations of the torque transmitting member are prevented by the engaging member, and both the compressive load and the tensile load are measured. Further, the torque transmitting member and the engaging member of the load measuring device come into contact with each other at one point of the spherical portion and the engaging surface. Therefore, if one point is located on the axis of the tracing stylus of the load measuring device, the rotational moment can be prevented from acting on the tracing stylus, and the load measuring accuracy can be improved. (14) The support device includes a pair of centers provided coaxially opposite each other and engaged with center holes formed on both end surfaces of the screw shaft, respectively. The ball screw preload dynamic torque measuring device according to any one of the above. The screw shaft is accurately positioned by the pair of centers, and is rotated around the axis with high precision. (15) One of the pair of centers is coaxially attached to a main shaft rotatably supported by a headstock, and the other is capable of changing the position of the center of the moving member in a direction parallel to the moving direction of the moving member. Attached to a supported tailstock,
The ball screw preload dynamic torque measuring apparatus according to mode (14), wherein the pair of centers, the headstock and the tailstock constitute the supporting device. By changing the position of the tailstock, a plurality of types of screw shafts having different lengths can be supported. (16) The ball screw preload dynamic torque measuring device according to (15), wherein the rotating device includes a spindle rotating device for rotating the spindle, and a rotation transmitting device for transmitting rotation of the spindle to the screw shaft. .

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method and an apparatus for measuring a preload dynamic torque of a ball screw according to an embodiment of the present invention will be described below in detail with reference to the drawings. FIGS. 1 and 2 show a state in which a ball screw 12 is set in a ball screw preload dynamic torque measuring apparatus 10 according to an embodiment of the present invention. The ball screw 12 is formed by screwing a screw shaft 14 and nuts 16 and 18 via balls (not shown) and fitting a pair of spacers 20 serving as preload applying members. The ball screw 12 is a preloaded ball screw.

As shown in FIG. 5, center holes 22 and 24 are provided on both end surfaces of the screw shaft 14 in the axial direction. A split-type rotation transmission tool 26 is detachably fixed to one end of the screw shaft 14. Rotation transmission tool 2
6 includes a first member 28 and a second member 30 that sandwich the screw shaft 14 from a direction perpendicular to the axis, and the first and second members 28 and 30 serve as fixing means in a state where the screw shaft 14 is sandwiched from both sides. A bolt 32 is screwed into the first and second members 28 and 30, and the first and second members 28 and 30 are fixed to each other with the screw shaft 14 interposed therebetween. On the first member 28, an arm portion 34 is provided so as to project in a direction orthogonal to the axis of the screw shaft 14.

The two nuts 16 and 18 are connected to a pair of keys 19 (FIG. 5) fitted over the nuts 16 and 18.
, Only one of which is shown) prevents relative rotation and a pair of spacers 2 between the nuts 16 and 18.
0 is fitted. Each of the pair of spacers 20 has an arc shape close to a semicircle, and the pair of keys 19 is
At positions between zero, the nuts 16 and 18 are fitted over key grooves 21 provided respectively. Key 19
Are fixed to the nut 16 by screws 23, and the pair of spacers 20 are respectively fitted to two pins 25 that are provided on the end face of the nut 16 and form the falling-off prevention protrusions. 18 is prevented from falling off.

When the key 19 and the spacer 20 are attached,
The nut 18 is rotated with the pair of spacers 20 fitted to the pair of pins 25 provided on the nut 16 so as to approach the nut 16. The nut 18 is further rotated by a small angle from the state in which the nut 18 is in contact with the spacer 20, and the key grooves 21 provided in the nuts 16 and 18 are provided.
The key 19 is inserted into the two keyways 21 with the phases of
And fixed to the nut 16 with the screw 23. As a result, the balls held by the nuts 16 and 18 are pressed against the groove side surfaces of the screw shaft 14 opposite to each other, and a preload is applied to the ball screw 12. After the relative rotation of the nuts 16 and 18 is prevented by the key 19, the spacer 20 having a width larger than the size of the gap between the nuts 16 and 18 is sandwiched, and the state where the preload is applied to the ball screw 12 is maintained. Is done. By changing the thickness of the spacer 20, the amount of preload applied to the ball screw 12 is adjusted.

One of the two nuts 16, 18 is a flanged nut having a flange 38 extending radially outward. This nut 16
As shown in FIG. 5, the torque transmitting member 40 is attached so as not to rotate relatively. As shown in FIGS. 3 and 4, the torque transmission member 40 includes a ring-shaped grip portion 42 and an engagement portion 44. The grip portion 42 is provided with slits 46 and 48 at two locations separated from each other in the diametric direction. When the grip portion 42 is fitted to the nut 16, a bolt 50, which is a type of fixing means, is attached to the nut 16. By being screwed in a direction perpendicular to the axial direction, the grip portion 42 tightens the nut 16 and the torque transmitting member 40
Are mounted so that they cannot rotate relative to each other. The engaging portion 44 is
It includes an arm portion 54 extending outward from the grip portion 42 in the radial direction, and a spherical portion 56 provided at an extending end of the arm portion 54. The torque transmitting member 40 is a component of the preload dynamic torque measuring device 10.

The preload dynamic torque measuring device 10 will be described. As shown in FIGS. 1 and 2, the preload dynamic torque measuring device 10
The apparatus body 70 has a longitudinal shape, and a headstock 76 is provided at one end of the apparatus body 70 in the longitudinal direction. A spindle 78 is mounted on the headstock 76 so as to be rotatable about an axis that is horizontal and parallel to the longitudinal direction of the apparatus main body 70, and is rotated by a spindle rotating device 80. The spindle rotating device 80 includes a servomotor 82 as a drive source, a rotation transmission device that includes timing pulleys 84 and 86 and a timing belt 88 and that transmits the rotation of the servomotor 82 to the spindle 78. The servo motor 82 is an electric rotary motor that is a type of an electric motor that is a type of a drive source.
The motor is capable of controlling the rotation angle and the rotation speed with high accuracy. A step motor may be used instead of the servo motor 82.

As shown in FIG. 5, a center 92 is mounted on the main shaft 78 coaxially with the main shaft 78. Main shaft 78
Further, an engaging portion 94 is provided in a position deviated from the rotation axis of the main shaft 78 (hereinafter, referred to as the main shaft rotation axis) in parallel with the main shaft rotation axis. The engaging portion 94 has a notch 96 formed at a distal end portion extending in a direction orthogonal to the main shaft rotation axis, and has a yoke shape. The notch 96 has the rotation transmitting tool 26
The arm portion 34 provided on the first member 28 is fitted, and is fixed to the engaging portion 94 by a set screw 97 which is a kind of fixing means. The engaging portion 94 and the rotation transmitting device 26 constitute a rotation transmitting device 98, and together with the main shaft rotating device 80, constitute a power rotating device 100 which is a kind of rotating device.

As shown in FIGS. 1 and 2, a tailstock 104 is provided at the other end in the longitudinal direction of the apparatus main body 70 so as to be movable in a direction parallel to the main shaft rotation axis. Tailstock 1
Numeral 04 is supported so that the position in the direction parallel to the main shaft rotation axis can be changed, and is fixed to the apparatus main body 70 at a desired position by a fixing device (not shown). Tailstock 1
In 04, a center 106 is provided coaxially opposite the center 92 of the headstock 76. The center 92 is held by the center holding member 108 and the center holding member 1
08 is urged toward the headstock 76 side by a spring member as an elastic member, which is a kind of urging means provided in the inside. The center holding member 108 is held by the tailstock 104 so as to be movable in the axial direction, and the position in the axial direction is adjusted.
The pair of centers 92 and 106, the headstock 76, and the tailstock 104 constitute a support device 108 that supports the screw shaft 14 so as to be rotatable about its axis and immovable in the axial direction. The screw shaft 14 of the ball screw 12
Is concentrically supported by the pair of centers 92 and 106, and the axis of rotation of the main shaft and the axis of the screw shaft 14 are concentric as described later.

As shown in FIGS. 1 to 3, the apparatus main body 70 has a linear guide rail 116 as a guide member.
It is provided at a position corresponding to the main shaft 78 in a horizontal direction that is parallel to the main shaft rotation axis and perpendicular to the main shaft rotation axis, and configures the apparatus main body 70. On the guide rail 116,
The moving member 118 is movably fitted. The moving member 118 is supported so as to be movable in a direction parallel to the screw shaft 14 supported by the centers 92 and 106, and the center 106 is positioned in a direction parallel to the moving direction of the moving member 118. It is variably supported by the tailstock 104. As shown in FIGS. 3 and 5, a guide block 120, which is a pair of guided members, is fixed to the moving member 118 by fixing means (not shown). The guide block 120 is movably fitted to the guide rail 116 while holding the plurality of balls 122 in a rotatable and circulable manner.
0, the ball 122 and the guide rail 116 constitute a ball linear guide 124.

Although not shown, the apparatus main body 70 is provided with two dogs, and the moving member 118 is provided with a moving end detection switch 128 (see FIG. 6). The moving end detection switch 128 is constituted by a limit switch. When the moving member 118 moves and the dog operates the moving end detection switch 128, it is detected that the moving member 118 has reached the moving ends on the headstock 76 side and the tailstock 104 side. The dog and the moving end detecting switch 128 constitute a moving end detecting device. Moving end detectors are not limited to limit switches and dogs.
It may be configured by a photoelectric sensor or a proximity switch including a light emitting unit and a light receiving unit.

As shown in FIG. 3, a load measuring device 130 is provided on the movable member 118 on one side in a horizontal direction perpendicular to the main shaft rotation axis with respect to the main shaft rotation axis. The load measuring device 130 includes a load cell 132 and an engagement member 134. The load cell 132 is a strain gauge type load cell, and a load (including both a tensile load and a compressive load) applied to the input member 136 is internally converted into an electric signal corresponding to the magnitude of the load. The input member 136 is provided with a male screw 138,
34 is detachably fixed by screwing.

The engaging member 134 has an engaging portion 140 having a U-shaped cross section, and a female screw portion 144 perpendicular to a pair of engaging surfaces 142 forming the engaging portion 140. The width between the pair of engagement surfaces 142 is slightly larger than the diameter of the spherical portion 56 of the torque transmitting member 40. The engaging member 134 is screwed to the male screw 138 of the input member 136 at the female screw portion 144, and is fixed to the input member 136 by screwing the lock nut 146. Engagement member 134
In the position, the pair of engaging surfaces 142 is vertical and parallel to the main shaft rotation axis, the U-shaped opening of the engaging portion 140 is directed upward, and the intermediate position of the pair of engagement surfaces 142 is the main shaft rotation axis. Adjusted to match position. The pair of engagement surfaces 142 are formed along a locus drawn by the spherical portion 56 when the torque transmitting member 40 is rotated around the axis of the screw shaft 14 with the ball screw 12 set in the preload dynamic torque measuring device 10. It is a right angle.

The moving member 118 is moved by the moving device 150 in the same direction at the same speed as the movement of the nuts 16 and 18 accompanying the rotation of the screw shaft 14. Moving device 150
4 and 5 includes a wheel 152 serving as a traction member and a connecting device 154 for connecting the moving member 118 to the wheel 152. In FIG. 3, the detailed illustration of the moving device 150 is omitted. The coupling device 154 includes a bracket 156 and the like. Bracket 15
6 is fixed to a vertical side surface of the movable member 118 on the tailstock 104 side, and after being projected upward from the support member 74, the movable member 1 is moved horizontally and at right angles to the main shaft rotation axis.
18 and then further extend horizontally and in a direction parallel to the axis of rotation of the main shaft.

A groove 160 is provided in the extension 158 in parallel with the axis of rotation of the main shaft.
Are movably fitted. Groove 160 of extension 158
Is formed in a portion provided with a pair of elongated holes 164 extending parallel to the main shaft rotation axis. A bolt 166 inserted through the bracket 162 is projected into the elongated hole 164, and a nut 168 is screwed into the elongated hole 164. I have. The nut 168 has a rectangular cross section perpendicular to the axis, and is engaged with the side surface of the elongated hole 164 to prevent rotation. Therefore, the bolt 166
Can be tightened or loosened by rotating the
Can be fixed to the bracket 156 or the fixing can be released.

As shown in FIG. 4 and FIG. 5, the bracket 162 holds a rotation shaft 170 so as to be rotatable around an axis parallel to the main shaft rotation axis.
72 is fixed. The pivot arm 172 is connected to the center 9
2 and 106 so as to be rotatable around a rotation axis parallel to the axis of the screw shaft 14. The rotation limit of the rotation arm 172 in the direction away from the main shaft rotation axis is defined by a stopper member 174 (see FIGS. 4 and 5) provided on the bracket 162.

As shown in FIG. 5, a support shaft 182 is fixed to the end of the rotation arm 172 extending from the rotation shaft 170 in parallel with the main shaft rotation axis. The support shaft 182 is projected from the rotating arm 172 toward the tailstock 104 side.
A spherical portion 184 is provided on the protruding end, and a casing 186 is fitted around the spherical portion 184 so as to be rotatable in a three-dimensional direction. The shoe 188 is accommodated in the casing 186, and the male screw member 190 is screwed to the female screw members 192 and 194 which are held by the casing 186 so as to be non-rotatable and movable in the axial direction. 194 presses shoe 188 against spherical portion 184, and casing 186 is fixed to support shaft 182.

A support shaft 200 is screwed and fixed to an end of the casing 186 opposite to the side fitted to the spherical portion 184, and is fixed to a protruding end of the support shaft 200 from the casing 186. The wheel 152 is mounted so as to be rotatable about the axis of the support shaft 200 and immovable in the axial direction. By rotating the casing 186 about the spherical portion 184, the axial direction of the support shaft 200 can be changed three-dimensionally to a desired direction, and the outer peripheral edge of the wheel 152 is rotated to the screw groove of the screw shaft 14. At any position in the direction, the engagement can be performed in a posture that does not incline with respect to the longitudinal direction of the thread groove. Thereby, the cross-sectional shape of the outer peripheral edge of the wheel 152 can be a semicircle substantially equal to the semicircle having a cross-sectional shape perpendicular to the longitudinal direction of the thread groove, and the manufacture is easy. In this measurement mode, the support shaft 18
2, casing 186, shoe 188, male screw member 19
0, the internal thread members 192 and 194 constitute a direction changing device, and constitute a holding device 204 together with the support shaft 200. The wheel 152 is connected to the turning arm 172 via the holding device 204, and the bracket 156 and the turning Axis 17
0, connected to the moving member 118 by a connecting device 154 including a rotating arm 172. In other words, the holding device 204 can also be said to be a component of the coupling device 154.

In this embodiment, as shown in FIG. 4, the wheel 152 is engaged with the screw groove from obliquely above, and the axial direction of the support shaft 200 is up and down and back and forth (the rotation axis of the ball screw 12). And a direction perpendicular to both the up and down directions).
In FIGS. 3 to 5, the wheels 152 and the like are not tilted in the axial direction or are tilted only in one direction for ease of illustration. By adjusting the position in the groove 160 of the bracket 162 in the direction parallel to the main shaft rotation axis, the direction parallel to the main shaft rotation axis of the wheel 152 (the direction parallel to the screw shaft 14 and the moving member 118 The position of (moving direction) is adjusted.
In this measurement mode, the groove 16 provided in the bracket 156
0, the long hole 164, the bolt 166, and the nut 168 constitute a relative position changing device.

The preload dynamic torque measuring device 10 is controlled by a control device 210 shown in FIG. The control device 210
PU (processing unit) 212, ROM 21
4, mainly a computer 220 including a RAM 216 and a bus 218 connecting them. The input interface 222 is connected to the bus 218, and the moving end detection switch 128, the load cell 132 and the input device 224 are connected to the bus 218. Bus 218 also has
The main interface 228 is connected and the drive circuit 23
The servomotor 82, the recording device 240, and the display device 242 are connected via 0, 232, and 234. The display device 242 includes, for example, a CRT display. In the present embodiment, the recording device 240 records the measured preload dynamic torque on paper, which is a type of recording medium. Further, a detection signal of the encoder 244 provided in the servomotor 82 is input from the input interface 222 to the control device 210. RAM2
16, a preload dynamic torque memory 25, as shown in FIG.
0 is provided with the working memory. RAM2
The portion provided with 16 preload dynamic torque memories 250 is
It constitutes a storage device. Further, the ROM 214 stores various programs necessary for measuring the preload dynamic torque and the like.

When measuring the preload dynamic torque, first, the ball screw 12 is set in the preload dynamic torque measuring device 10 and FIG.
The state shown in FIG. That is, the ball screw 12 is provided with the headstock 76 and the tailstock 1 in the center holes 22, 24 of the screw shaft 14.
The centers 92 and 106 of the screw shaft 04 are engaged, and are supported by the support device 110 so as to be rotatable about the axis of the screw shaft 14 and immovable in the axial direction. The position of the tailstock 104 in the direction parallel to the moving direction of the moving member 118 is the screw shaft 1
4 according to the length. Further, the torque transmission member 40 is attached to the nut 16 so as not to rotate relatively, and the spherical portion 56 is
34 are sandwiched from both sides by a pair of engagement surfaces 142. Further, the arm 34 provided on the first member 28 of the rotation transmitting tool 26 is fitted into the notch 96 of the engaging portion 94 provided on the main shaft 78, and is fixed by the set screw 97. Furthermore, the rotation arm 172 is rotated, and the outer peripheral edge of the wheel 152 is engaged with the screw groove of the screw shaft 14. The step of setting the ball screw 12 in the preload dynamic torque measuring device 10 in this way is a preparation step.

The connecting device 154 includes a moving member 118.
The wheel 152 is provided on the surface of the tailstock 104 side of the tailstock 104 and further provided in a direction extending from the rotating arm 172 toward the tailstock 104 side. Is engaged. At this time, the casing 186 is rotated around the spherical portion 184 to adjust the axial direction of the support shaft 200 three-dimensionally.
Reference numeral 52 is engaged with the screw groove in a posture corresponding to the size of the lead of the screw shaft 14. In addition, a direction parallel to the main shaft rotation axis of the wheel 152 with respect to the moving member 118 (moving member 1
18), the wheel 152 is positioned on the screw shaft 1
4 is changed so as to engage with a portion as close to the nut 18 as possible.

The preload dynamic torque is measured in accordance with the preload dynamic torque measurement conditions specified in JIS. The measurement conditions are as follows: (1) The measurement is performed without the seal attached.
(2) The rotation speed of the screw shaft 14 is 100 rotations / minute.
(3) The viscosity of the lubricating oil is ISO VG 68 specified in JIS K2001 (Industrial Lubricating Oil Viscosity Classification). Further, the operator uses the input device 224 to input the length of the screw shaft 14, the reference value of the torque variation coefficient, the product number of the ball screw 12, the production number, and the like. The torque variation coefficient is an amount obtained by dividing the standard deviation of the preload dynamic torque by the average value, and is usually expressed as a percentage.

The ball screw 12 is connected to the preload dynamic torque measuring device 1
When set to 0, the servo motor 82 is started, the main shaft 78 is rotated, and the screw shaft 14 is rotated at the set rotation speed. The rotation of the torque transmitting member 40 is prevented by the engagement between the spherical portion 56 and the engaging member 134 of the load measuring device 130, and the rotation of the nuts 16 and 18 is prevented.
When the screw shaft 14 is rotated, the nuts 16 and 18 move along the screw shaft 14. In addition, the rotation of the screw shaft 14 causes the wheel 152 to roll in the screw groove while the screw shaft 1
4 and the moving member 118 to which the wheel 152 is connected is moved along the screw shaft 14 by the nuts 16 and 18.
At the same speed in the same direction.

When the movement of the moving member 118 to the moving end is detected by the moving end detecting switch 128, it can be understood that the nuts 16 and 18 have moved to the moving end. After the movement to the moving end, the screw shaft 14 is rotated in the opposite direction, and the nuts 16, 18 and the moving member 118 are moved in the opposite direction. When the nuts 16 and 18 and the moving member 118 are moved in either the forward direction or the reverse direction, the engaging member 134 prevents the rotation of the nuts 16 and 18 and the load is applied to the input member 136 of the load cell 132. In addition, the load cell 132 continues to supply an electrical signal corresponding to the load to the controller 210 while the nuts 16 and 18 move. The process of measuring the load in this manner is a measurement process, and the engagement portion 4 is provided over substantially the entire length of the screw shaft 14.
From 4, the load applied to the load measuring device 130 is measured.

In the control device 210, the load cell 1
A calculation is performed to calculate the preload dynamic torque by multiplying the load detected by 32 by the distance between the axis of the screw shaft 14 and the line of action of the load. In the present embodiment, the calculation of the preload dynamic torque is performed in parallel with the measurement of the load at intervals set by the number of pulses of the encoder 244, and the calculated preload dynamic torque is stored in the preload dynamic torque memory 250 by the encoder 2.
The output value is stored in association with the output value of G.44. The number of pulses is set to a magnitude that allows the measurement position of the preload dynamic torque to be substantially continuous.

The measurement of the preload dynamic torque is performed in each of the case where the screw shaft 14 is rotated in the forward direction and the case where the screw shaft 14 is rotated in the reverse direction. In each case, the preload dynamic torque is obtained substantially continuously. The preload dynamic torque is measured for almost the entire length of the screw shaft 14. The calculated preload dynamic torque is recorded by the recording device 240 on paper, which is a type of recording medium, as shown in FIG. This recording is performed in parallel with the calculation of the preload dynamic torque. The vertical axis of the graph shown in FIG. 8 is the preload dynamic torque, and the horizontal axis is the rotation angle of the servomotor 82. Actually, the magnitude of the preload dynamic torque is as shown in FIG.
However, for the sake of illustration, only the tendency of the fluctuation is shown here.

Further, based on the preload dynamic torque stored in the preload dynamic torque memory 250, the starting torque, the maximum value, the minimum value, the average value, and the variation coefficient of the preload dynamic torque are obtained.
It is displayed on the display device 242. These are the recording devices 240
May be recorded.

Based on the measured preload dynamic torque, for example, whether the spacer 20 is sized to apply an appropriate preload dynamic torque to the ball screw 12,
Is determined to operate smoothly. The magnitude of the fluctuation of the preload dynamic torque during one rotation of the screw shaft 14 may be determined. At this time, it is desirable to measure the preload dynamic torque by setting the rotation speed of the screw shaft 14 to be lower than 100 rotations / minute.

The manner in which the wheel 152 is connected to the side surface of the moving member 118 on the tailstock 104 side by the connecting device 154 and the preload dynamic torque of the ball screw 12 including the two nuts 16 and 18 is measured will be described. However, as shown in FIG. 9, the preload dynamic torque measuring device 10 connects the wheel 272 as a traction member to the side surface of the moving member 118 on the headstock 76 side by another connecting device 270.
The moving member 118 can also be moved in the same direction and at the same speed as the nut by the moving device 274 including the 70 and the wheel 272, so that the preload dynamic torque of another type of ball screw can be measured.

For example, as in a ball screw 280 shown in FIG. 9, the preload dynamic torque of a ball screw formed by screwing a screw shaft 282 and a nut 284 one by one via a ball can be measured. In the ball screw 280, a preload is applied by changing the size of the lead in the nut 284.

A torque transmission member 40 is attached to the nut 284 so as not to rotate relatively, and the rotation transmission member 26 is fixed to the screw shaft 282. The nut 284 has a smaller diameter than the nut 16 of the ball screw 12,
The arm portion 54 of the engaging portion 44 of the torque transmitting member 40 attached to the fourth member 4 has a length such that the spherical portion 56 is sandwiched from both sides by the pair of engaging surfaces 142 of the engaging member 134 of the load measuring device 130. ing.

A bracket 292 is fixed to a side surface of the movable member 118 on the side of the headstock 76 by a bracket 290. A rotation arm 296 is fixed to a rotation shaft 294 that is rotatably held around an axis parallel to the main shaft rotation axis by a bracket 292.
A support shaft 298 is fixed to the extended end of the 96 in parallel with the main shaft rotation axis. The support shaft 298 is axially movably fitted to the rotation arm 296 at the screw portion 300, and the nut 302 and the lock nut 304 are screwed together and fixed to the rotation arm 296.
Reference numeral 98 indicates that the position of the moving member 118 in the moving direction with respect to the rotating arm 296 can be changed.

A spherical portion 308 is provided at a protruding end of the support shaft 298 from the rotating arm 296 toward the tailstock 104 side.
A casing 310 is fitted in a three-dimensionally rotatable manner in the same manner as the casing 186, and a shoe (not shown) is pressed against the spherical portion 308 and fixed to the support shaft 298. The wheel 272 is rotatably supported by a fixed support shaft 312 on the casing 310. By changing the position of the support shaft 298 with respect to the rotation arm 296, the wheel 272 is moved in the moving direction of the moving member 118 with respect to the moving member 118 of the wheel 272. Can change position. In this measurement mode, the support shaft 298, the casing 310, the shoe (not shown), and the like constitute a direction changing device.
12, together with the holding device 314, and the screw portion 300, the nut 302, and the lock nut 304 of the support shaft 298 form a relative position changing device. The cross-sectional shape of the outer peripheral edge of the wheel 272 is a semicircular shape substantially equal to a semicircle that is a cross-sectional shape perpendicular to the longitudinal direction of the thread groove of the screw shaft 282, and the width of the outer peripheral portion including the outer peripheral edge (wheel 272
Is smaller than the width of the inner peripheral portion of the wheel 272, and the outer peripheral edge is sized to be able to engage with the thread groove of the screw shaft 282. The other components of the coupling device 270 that have the same functions as those of the coupling device 154 are denoted by the same reference numerals, and description thereof is omitted.

The ball screw 280 is set in the preload dynamic torque measuring device 10 like the ball screw 12. Although the number of the nut 284 is one, the wheel 272 is
18 is connected to the side of the headstock 76 on the side of the headstock 76, so that the screw shaft 282 is engaged with a portion of the tailstock 104 closer to the tailstock 104 than the nut 284, which is close to the nut 284.
After the ball screw 280 is set in the preload dynamic torque measuring device 10, the screw shaft 284 is rotated, and the ball screw 1
The preload dynamic torque is measured in the same manner as in 2.

The connecting device may be configured so that the support shaft for supporting the wheel can be attached to the turning arm in such a manner that the supporting shaft selectively projects from the turning arm toward the headstock and the tailstock. It is. In this case, the mounting position of the rotating arm with respect to the moving member may be changeable as in the above embodiment, but may not be changeable. In the former case, the relative position between the moving member and the wheel can be changed to four types by a combination of the projecting direction of the support shaft and the mounting position of the rotating arm. In the latter case, the connecting device Can be simplified.

Further, in each of the above embodiments, the calculation of the preload dynamic torque is performed for each set pulse number, but may be performed for each set time. This time is set to a length that allows the preload dynamic torque to be measured substantially continuously.

Further, in the above embodiment, the preload dynamic torque is measured according to the conditions defined in the JIS measurement standard, but the preload dynamic torque may be measured according to conditions other than these conditions.

In addition, without departing from the scope of the claims, the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a front view (partial cross section) showing a preload dynamic torque measuring device according to an embodiment of the present invention.

FIG. 2 is a plan view showing the preload dynamic torque measuring device.

FIG. 3 is a side view (partial cross section) showing the preload dynamic torque measuring device.

FIG. 4 is a side view (partially sectional view) showing a portion of the preload dynamic torque measuring device provided with a rotating arm.

FIG. 5 is an enlarged front view (partial cross section) showing a main part of the preload dynamic torque measuring device.

FIG. 6 is a block diagram schematically showing a control device for controlling the preload dynamic torque measuring device.

FIG. 7 is a RAM of a computer constituting the control device.
FIG. 3 is a diagram schematically showing the configuration of FIG.

FIG. 8 is a graph showing a preload dynamic torque measured by the preload dynamic torque measuring device.

FIG. 9 is a front view (partial cross section) showing another measurement mode of the preload dynamic torque measuring device.

[Explanation of symbols]

10: Preload dynamic torque measuring device 12: Ball screw
14: Screw shaft 16, 18: Nut 20: Spacing
40: Torque transmission member 44: Engagement part 54: Arm part 56: Spherical part 70: Device body
76: headstock 80: spindle rotation device 82: servo motor 92: center 98: rotation transmission device
100: power rotating device 104: tailstock 106:
Center 110: Supporting device 118: Moving member
124: ball linear guide 130: load measuring device 132: load cell 134: engaging member 14
2: engagement surface 150: moving device 152: wheel 204: holding device 210: control device 216: RAM 2
40: Recording device 270: Connecting device 272: Wheel 274: Moving device 280: Ball screw
282: screw shaft 284: nut 314: holding device

Claims (5)

[Claims] 1. A method for measuring a preload dynamic torque of a ball screw formed by screwing a screw shaft and a nut via a ball, wherein a relative rotation of a torque transmission member having an engagement portion with the nut is provided. While the screw shaft is attached to the support device,
A preparatory step of supporting the screw shaft so as to be rotatable about the axis thereof and immovable in the axial direction and engaging the engaging portion of the torque transmitting member with a load measuring device; and rotating the screw shaft to rotate the screw shaft. And measuring the load applied to the load measuring device from the engagement portion over substantially the entire length of the screw shaft while moving the load measuring device along with the movement of the nut accompanying the nut. Ball screw preload dynamic torque measurement method. 2. A device for measuring a preload dynamic torque of a ball screw formed by screwing a screw shaft and a nut through a ball, comprising: a device main body; and a screw shaft provided on the device main body. A supporting device rotatable about the axis of the shaft and immovable in the axial direction, a rotating device for rotating a screw shaft supported by the supporting device, and the screw supported by the supporting device by the device main body. A moving member supported so as to be movable in a direction parallel to an axis; a torque transmitting member provided with an engaging portion, which is attached to the nut so as to be relatively non-rotatable; and a torque transmitting member attached to the moving member and engaged with the engaging portion. A load measuring device for preventing rotation of the torque transmission member and measuring a load required for the rotation, and moving the moving member in the same direction at the same speed as the movement of the nut accompanying rotation of the screw shaft. Dynamic preload torque measuring device for a ball screw, characterized in that it comprises a mobile device for. 3. A traction member that engages with the screw shaft and moves in the same direction at the same speed as the nut with rotation of the screw shaft, and connects the moving member to the traction member. The ball screw preload dynamic torque measuring device according to claim 2, further comprising a coupling device. 4. The traction member is a wheel that is rotatably held around a single axis by a holding device and that engages with the screw shaft at an outer peripheral edge.
2. A ball screw preload dynamic torque measuring device according to claim 1. 5. The load measuring device includes an engaging member, and one of the engaging member and the engaging portion of the torque transmitting member includes a spherical portion, and the other includes the torque transmitting member. 3. A pair of engaging surfaces which are substantially perpendicular to the locus drawn by the engaging portion when rotated about the axis of the screw shaft and which sandwich the spherical portion from both sides. 4. The ball screw preload dynamic torque measuring device according to any one of 4.