JP2003075463A - Three-dimensional movement measuring instrument for ball of ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply a technology using a Hall element for analyzing the behavior of the ball of a ball screw. SOLUTION: A three-dimensional movement measuring instrument for ball of ball screw comprises a bearing 2, the ball screw 1 supported by the bearing 2, and a linearly moving body 6. The instrument also comprises a nut 8 screwed on the screw 2 through a magnetized ball 12' and three magnetic sensors 13X', 13Y', and 13Z' arranged on the peripheral surface of the nut 8. The sensors 13X', 13Y', and 13Z' are three-dimensionally arranged on a three-dimensional coordinate system fixed relatively to the nut 8. The three-dimensional movement of the ball is detected minutely by means of the magnetic sensors 13X', 13Y', and 13Z' arranged on the nut 8 so that the sensors 13X', 13Y', and 13Z' may make translation together with the magnetized ball 12' in the axial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional movement measuring device for balls of a ball screw.

[0002]

2. Description of the Related Art A ball screw, which is a mechanical element of a drive / transmission system, is excellent in mechanical efficiency, load capacity, and long-term stability of operation. In order to make more effective use of such excellent characteristics, higher speed and higher load have been achieved. Such speeding up and load increase lead to seizure of balls. The seizure of balls is due to the behavior of three-dimensional movement during high-speed revolution.
For speeding up, it is important to elucidate the speed limit at which sticking of balls appears.

With regard to balls of ball bearings, three-dimensional motion analysis has been vigorously carried out for a long time both theoretically and experimentally. The technology for optically knowing the ball's rotation and revolution is the oldest known. The magnetic technique of magnetizing the ball and measuring the magnetic axis of the ball is then known. Two magnetic techniques are known. One of them is a technique of measuring the magnetic axis of a magnetized ball with a coil sensor. The other one is a technique for measuring the magnetic axis with a Hall element. The measurement technique using the Hall element is known as the most excellent technique.

As the measurement using the hall element, there are known a rotary system measurement for measuring in a rotary coordinate system and a static system measurement for measuring in a stationary fixed coordinate system. In stationary system measurement, Hall elements are arranged on the outer ring on the fixed side on the three-dimensional coordinate axes respectively, and three Hall elements are arranged on the outer ring on the fixed side at a specific point while the magnetized ball makes one revolution. Is a technique for measuring the rotation motion of a magnetized ball by measuring the direction of the magnetic axis of.
In this technique, a three-dimensional oblique coordinate system with the center of the magnetized ball at a specific position as the origin is selected due to the arrangement of the Hall elements.

For precision tools such as machine tools and aircraft,
Ball screws are used with ball bearings. A mechanical element that is linearly driven through a ball screw is required to have further improved positional accuracy. The ball and its mechanical elements have not only rotational movement about the axis, but also slight relative movement in the axial direction. It is required to establish a technique to analyze the behavior of balls in a ball screw by using a Hall element.

[0006]

The object of the present invention is to establish a technique for applying the technique of using a Hall element to the analysis of the behavior of a ball screw ball.
It is to provide a dimensional motion measuring device.

[0007]

Means for solving the problem Means for solving the problem are expressed as follows. The technical matters appearing in the expression are accompanied by parentheses (), and numbers, symbols and the like are added. The numbers, symbols and the like are technical matters constituting at least one embodiment or plural examples of the embodiments or plural examples of the present invention, particularly the embodiment or examples. It corresponds to the reference numbers, reference symbols, etc. attached to the technical matters expressed in the drawings corresponding to. Such reference numbers and reference symbols clarify correspondences and bridges between the technical matters described in the claims and the technical matters of the embodiments or examples. Such correspondence / bridge does not mean that the technical matters described in the claims are limited to the technical matters of the embodiment or the examples.

The ball-screw ball three-dimensional motion measuring apparatus according to the present invention comprises a bearing (2), a ball screw (1) supported by the bearing (2), and a moving body (6) that moves linearly. It is fixed to the moving body (6) and the magnetized ball (1
2 ′) and a nut (8) screwed together, and a nut (8)
Three magnetic sensors (13
X ', 13Y', 13Z). The three magnetic sensors (13X ', 13Y', 13Z) are three-dimensionally arranged on a three-dimensional coordinate system fixed relative to the nut (8). A three-dimensional movement of the ball is detected in detail by means of a magnetic sensor arranged in the nut (8) so as to translate axially with the magnetized ball.

The origin (O or O1) of the three-dimensional coordinate system is 3
It coincides with the center point of the magnetic ball (12 ') at a specific position defined by the dimensional coordinate system. Such setting of the coordinate system can simplify the three-dimensional detection of the magnetic vector (14) and increase the accuracy of the data obtained as a result.

The three-dimensional coordinate system is a three-dimensional oblique coordinate system, and the three axes of the three-dimensional oblique coordinate system are the Z axis and the X'axis.
It is formed by Y'axis and three magnetic sensors (13X ',
13Y ′, 13Z) are arranged on the Z axis, a Z axis magnetic sensor (13Z), an X ′ axis magnetic sensor (13X ′) arranged on the X ′ axis, and a Y ′ axis. It is provided with a Y′-axis magnetic sensor (13Y ′). Such an arrangement is rational.

Three magnetic sensors (13X ', 13
Y ′, 13Z) are each formed of a Hall element,
The three Hall elements are the oblique coordinate component (V) of the magnetic axis vector (14) of the magnetizing ball (12 ′) at the origin in the oblique coordinate system.
-Z, V-X ', V-Y') can be directly detected. The Cartesian coordinate system with its origin as the origin is the Z-axis,
It is represented by an X-axis and a Y-axis, and has oblique coordinate components (V-Z, V-
X ′, V−Y ′) are orthogonal coordinate components (V−Z, V−X,
V-Y).

The unit vectors of the Z-axis, the X-axis, and the Y-axis are represented by k, j, and i, respectively, and the rotational movement of the sliding rotation of the magnetized ball is expressed using a constant J and a vector J passing through the origin. It is analyzed based on (iVx + jVy + kVz).

A linear guide (7) for guiding the linear movement of the moving body (6), a servomotor (5) axially coupled to the ball screw (1), an output shaft of the servomotor (5) and the ball screw (1). 2) and a ball bearing (4) interposed between the two), so that highly accurate measurement experiments can be performed at various rotation speeds.

The outer peripheral surface of the nut (8) is formed on a surface (9) having a direction intersecting with the axis of rotation of the ball screw (1), and the three magnetic sensors (13X ', 13Y', 1).
3Z) is arranged on the outer peripheral surface (9).
The outer peripheral surface (9) of the nut is formed in a surface having a direction intersecting with the axis of rotation of the ball screw, and two of the three magnetic sensors (13X ′, 13Y ′, 13Z) are the outer peripheral surface (9). ) Is located. Such an arrangement on the outer peripheral surface enables highly sensitive measurement of the magnetic vector (14).

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Corresponding to the drawings, in an embodiment of a ball screw according to the present invention, a support bearing is provided together with the ball screw. As shown in FIG. 1, the ball screw 1 has one end rotatably supported by a support bearing 2 and the other end rotatably supported by a support unit 3. The end of the ball screw 1 supported by the support unit 3 is axially coupled to the output shaft of the servomotor 5 via a ball joint 4.

The linear kinematic mechanical element 6 is screwed onto the ball screw 1. The linear kinematic mechanical element 6 comprises a nut (not shown) inside. The nut is fixed to the linear motion mechanical element 6 inside the linear motion mechanical element 6. The ball screw 1 is directly screwed into the nut. In order to prevent the linear motion mechanical element 6 from co-rotating with the ball screw 1, the linear motion mechanical element 6 is supported and guided by the linear guides 7 on both sides. Linear guides Both side guide surfaces of the linear guide 7 for guiding the linear movement of the mechanical element 6 are formed parallel to the axis of rotation of the ball screw 1.

FIG. 2 shows the appearance of the nut 8. As is well known, the nut 8 is formed with a plurality of guide circumferential grooves for guiding the rolling of a plurality of balls on one circumference on a cross section orthogonal to the axis or a surface intersecting with the nut. The ball, which is sandwiched between the spiral thread groove formed in the ball screw 1 and the guide circumferential groove of the nut 8 and rolls, theoretically moves forward and backward in the same body in the axial direction. According to the mechanical accuracy between the ball screw 1, the linear motion mechanical element 6 and the nut 8 and the spherical accuracy of the ball, sliding occurs between each ball and the thread groove of the ball screw 1, and Sliding occurs between the ball and the guide circumferential groove of the nut 8, and each ball is forced to undergo a rotation motion other than the natural rotation motion associated with its own revolution. The measurement of such unreasonable rotation motion is important for developing a three-dimensional motion measuring device for a ball of a high precision ball screw.

As shown in FIG. 2, the nut 8 is formed with at least two oblique V groove surfaces 9 and a cylindrical surface 11 as outer peripheral surfaces. The balls 12 are arranged along the spiral thread groove of the ball screw 1, and a prescribed number of ball groups roll and revolve in the guide circumferential groove of the nut 8. Certain balls 12 of the defined number are magnetized. The magnetized balls are hereinafter referred to as magnetized balls 12 '. In the embodiment shown in the drawings, the center line around the axis of the guide circumferential groove of the nut 8 is located not on the plane orthogonal to the axis but on the intersecting surface intersecting with the axis of rotation of the ball screw 1.

One of the balls 12 making one revolution in the guide circumferential groove is designated by the reference numeral 12 '. A locus of an intersection point where a straight line passing through the center of the ball 12 'and orthogonal to the cylindrical surface 11 intersects with the cylindrical surface 11 is a line A1-A2 in the figure.
It is represented by. The line A1-A2 is now an ellipse rather than a circle. The outermost line (the elliptical line on the outermost side in the axial direction) of the oblique V groove surface 9 coincides with one end line of the cylindrical surface 11. A set of line segments on the innermost line of the oblique V groove surface 9 and orthogonal to the innermost line thereof, and on the outermost line of the oblique V groove surface 9 and orthogonal to the outermost line thereof are the oblique V The groove surface 9 is formed.

The foot of the perpendicular line from the center point of the ball 12 'to the oblique V-groove surface 9 is shown by the point B1. The locus of the foot of the perpendicular line that descends from the center of the moving ball 12 ′ to the oblique V-groove surface 9 is shown by line B1-B2. Line C1-C2
Is on the other oblique V-groove surface 9 similarly to the line B1-B2.

The origin O is defined by the center point of the ball indicated by the reference symbol O1 in FIG. Line A, passing through origin O
The line orthogonal to 1-A2 is defined as the Z axis. A line passing through the origin O and orthogonal to the oblique V groove surface 9 (or a line passing through the origin O and obliquely intersecting the oblique V groove surface 9 at a constant angle) is defined as an X axis'. The line connecting the origin and the point moved on the line B1-B2 around the rotation axis center line by the specified angle at the intersection of the X'axis and the oblique V groove surface 9 is as shown in FIGS. 2 and 3. To
Defined as the Y'axis. X ', Y', and Z form a three-dimensional oblique coordinate system.

FIG. 4 shows the positional relationship between the above-mentioned three-dimensional oblique coordinate system and the three-dimensional orthogonal coordinate system. The origin of the three-dimensional orthogonal coordinate system Z-XY shown in FIG. 4 coincides with the origin O described above. The Z-axis of the three-dimensional oblique coordinate system coincides with the Z-axis of the three-dimensional Cartesian coordinate system. The Hall element group includes a Z-axis Hall element 13Z, an X′-axis Hall element 13X ′,
The Y-axis Hall element 13Y is included. The Z-axis hall element 13Z is on the Z-axis and is arranged on the line A1-A2. The X′-axis Hall element 13X ′ is on the X′-axis and is arranged on the line B1-B2. The Hall element 13Y 'on the Y'axis is on the Y'axis and is arranged on the line B1-B2. It is preferable that the other two elements are arranged on the line A1-A2 at equal intervals with respect to the Z-axis Hall element 13Z. It is preferable that the other two elements are arranged on the line B1-B2 at equal intervals with respect to the X′-axis Hall element 13X ′. It is preferable that the other two elements are arranged on the line B1-B2 at equal intervals with respect to the Y′-axis Hall element 13Y ′.

The angle between the Z axis and the X'axis is θ-ZX '
Indicated by. In the figure, the hyphen of θ-ZX ′ is omitted, and ZX ′ is indicated by a subscript. The angle between the Z axis and the Y ′ axis is indicated by θ−ZY ′. The angle between the X axis and the Y ′ axis is indicated by θ−XY ′. X
The angle between the axis and the X'axis is shown as θ-XX '. The angle between the Y-axis and the X'-axis is indicated by θ-YX '. The angle between the X-axis and the X′-axis is indicated by θ−XX ′. The angle between the Y axis and the Y ′ axis is θ−YY ′.
Indicated by.

Since the Z-axis Hall element 13Z, the X'-axis Hall element 13X, and the Y-axis Hall element 13Y are both fixed to the nut 8, the magnetized ball 12 "is the Z-axis Hall element 13Z. While rotating with respect to the X′-axis Hall element 13X and the Y-axis Hall element 13Y, ideally, the translational movement is performed in the same body as the magnetized ball 12 ″ in the axial direction. The center point of the magnetized ball 12 ″ makes one revolution around the axis of rotation of the ball screw 1 and makes one pass through the origin O during one revolution of the nut 8 which does not rotate.

In FIG. 2, each point is geometrically set as follows. O1A1 = O1B1 = O1C1 = O2A2 = O2B2 =
O2C2 The magnetization vector 14 of the magnetizing ball 12 ″ at the moment when its center passes through the origin O is measured by the Z-axis Hall element 13Z, the X′-axis Hall element 13X, and the Y-axis Hall element 13Y. The Hall element can output a voltage that is directly proportional to the direction cosine of its magnetization vector, and both end points that are physically virtual points of the magnetization vector 14 always pass through the origin O. Three Hall elements measure. Three voltage V '
Is measured in an oblique coordinate system, and its voltage V ′ is converted to a voltage V in a rectangular coordinate system, and the conversion is represented by the following equation.

[0026]

[Equation 1] The voltage V and the voltage V ′ are represented by the following equation (2) of the linear combination.

[Equation 2] The matrix A of Expression (2) is expressed by the following expression.

[Equation 3]

The magnetic axis vector N, which is assumed to be on the spherical surface of the magnetic ball whose center point is located at the origin O, is given by the following equation. N = r / K (iVx + jVy + kVz) Here, i is a unit vector on the X axis, j is a unit vector on the Y axis, and k is a unit vector on the Z axis. r is the radius of the magnetic ball, and K is a constant. Output voltage pair (Vx, V
If y, Vz) is detected, the movement of the end point of the magnetic vector N on the spherical surface can be known.

The time point sequence in which the center point of the magnetic ball coincides with the origin O is obtained from the revolution cycle of the magnetic ball. When it is considered that there is slippage in the magnetic ball and the actual revolution cycle of the magnetic ball and the revolution cycle are slightly deviated, the time point sequence at which the center point of the magnetic ball coincides with the origin O is It is obtained as a time point sequence in which the scalar of the vector N has the maximum value. The rotation of the magnetic vector N of the magnetic ball measured on the time point sequence is a combination of the natural rotation angular velocity vector based on the revolution and the unreasonable rotation angular velocity vector based on the slip.
Such a composite vector is measured. Based on the remaining angular velocity vector of the rotation obtained by subtracting the natural angular velocity vector of the rotation from the composite vector, the existence of an unreasonable external force acting on the ball of the ball screw three-dimensional movement measuring device is quantitatively obtained.

FIG. 5 shows a front cross section of the nut 8. On the cross section, the center line 21 of the guide groove formed on the inner peripheral surface of the nut 8 is projected on the cross section with respect to the center line 21 of the spiral groove formed on the ball screw 1. Crossing. FIG. 6 shows a front cross section of the nut 8,
The guide circumferential groove of the nut 8 intersects a plane perpendicular to the axis orthogonal to the axis of rotation. The intersection of the spiral groove and the guide circumferential groove is a cause of generation of the axial thrusting force of the nut 8 with respect to the ball screw 1. An external force, which is so complicated as to be incomparable with the external force acting on the ball of the ball bearing, eventually acts on the balls sandwiched between the intersecting grooves. Such resultant external force can be quantitatively estimated by measuring the unreasonable rotation of the magnetic ball.

[0030]

The three-dimensional movement measuring device of the ball of the ball screw according to the present invention can analyze the three-dimensional movement of the ball which receives a complicated external force while translating with the nut in detail.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a three-dimensional movement measuring device for balls of a ball screw according to the present invention.

FIG. 2 is a plan view showing a nut.

FIG. 3 is a side view showing an arrangement coordinate system of Hall elements.

FIG. 4 is a plan view showing an arrangement coordinate system of Hall elements.

FIG. 5 is a cross-sectional view showing a groove of a nut.

FIG. 6 is a sectional view showing a groove of a nut and a screw.

[Explanation of symbols]

1 ... Ball screw 2 ... Bearing 5 ... Servo motor 6 ... moving body 7 ... Linear guide 8 ... Nut 9 ... Surface (outer peripheral surface) 12 '... Magnetized balls 13X ', 13Y', 13Z ... Magnetic sensor 13X '... X'axis magnetic sensor 13Y '... Y-axis magnetic sensor 13Z ... Z-axis magnetic sensor 14 ... Magnetic axis vector

Continued front page    (72) Inventor Yoshimi Kagimoto             3-5-1, 717-1, Fukahori-cho, Nagasaki-shi, Nagasaki             Hishi Heavy Industries Ltd. Nagasaki Research Center (72) Inventor Akira Nakajima             1 Honjo-cho, Saga City, Saga Prefecture Saga University Science and Engineering             Undergraduate (72) Inventor Toshifumi Mawatari             1 Honjo-cho, Saga City, Saga Prefecture Saga University Science and Engineering             Undergraduate F term (reference) 2F034 AA08 DC01 DC02                 3J062 AB22 AC07 BA16 CD12 CD62

Claims (10)

[Claims] 1. A bearing, a ball screw supported by the bearing, a moving body that moves linearly, a nut fixed to the moving body and screwed into the ball screw via a magnetized ball, and A ball screw including three magnetic sensors arranged at a peripheral surface portion, wherein the three magnetic sensors are three-dimensionally arranged on a three-dimensional coordinate system fixed relative to the nut. 3D motion measuring device 2. A three-dimensional movement measuring device for a ball of a ball screw, wherein an origin of the three-dimensional coordinate system coincides with a center point of the magnetic ball at a specific position defined by the three-dimensional coordinate system. 3. The three-dimensional coordinate system is a three-dimensional diagonal coordinate system, and the three axes of the three-dimensional diagonal coordinate system are formed by a Z axis, an X ′ axis, and a Y ′ axis. The three magnetic sensors include a Z-axis magnetic sensor arranged on the Z-axis, an X′-axis magnetic sensor arranged on the X′-axis, and a Y′-axis magnetic sensor arranged on the Y′-axis. The three-dimensional movement measuring device for balls of a ball screw according to claim 2, further comprising a sensor. 4. The three magnetic sensors are each formed of a Hall element, and the three Hall elements each have an oblique coordinate component of a magnetic axis vector of the magnetized ball at the origin in the oblique coordinate system ( V-
Z, V-X ', V-Y') is detected. The three-dimensional movement measuring device of the ball of the ball screw according to claim 3. 5. An orthogonal coordinate system whose origin is the origin is represented by a Z-axis, an X-axis and a Y-axis, and the oblique coordinate component (V-
Z, V−X ′, V−Y ′) are orthogonal coordinate components (V−Z,
A three-dimensional movement measuring device for balls of a ball screw according to claim 4, which is converted into V-X, V-Y). 6. The unit vectors of the Z-axis, the X-axis and the Y-axis are represented by k, j and i, respectively, and the rotational movement of the magnetic ball sliding and rotating is expressed by using a constant J. Vector J (iVx + jVy) that passes through the origin
+ KVz) The three-dimensional movement measuring device of the ball of the ball screw according to claim 5, which is analyzed based on + kVz). 7. A linear guide for guiding the linear movement of the moving body, a servomotor axially coupled to the ball screw, and a ball bearing interposed between the output shaft of the servomotor and the ball screw. A three-dimensional movement measuring device for balls of a ball screw according to claim 1, further selected from claims 1 to 6. 8. The outer peripheral surface of the nut is formed in a surface having a direction intersecting with the axis of rotation of the ball screw.
The ball-screw ball three-dimensional motion measuring device according to claim 3, wherein one of the two magnetic sensors is arranged on the outer peripheral surface. 9. The outer peripheral surface of the nut is formed in a surface having a direction intersecting with the axis of rotation of the ball screw.
The ball-screw ball three-dimensional motion measuring device according to claim 3, wherein two of the magnetic sensors are arranged on the outer peripheral surface. 10. The three-dimensional movement measuring device for balls of a ball screw according to claim 4, wherein the three Hall elements are equidistant from the origin.