CN109990762B

CN109990762B - Ball screw with inclination detector

Info

Publication number: CN109990762B
Application number: CN201711497742.XA
Authority: CN
Inventors: 陈志远; 苏中源; 林志哲; 黄肇达
Original assignee: Industrial Technology Research Institute ITRI
Current assignee: Industrial Technology Research Institute ITRI
Priority date: 2017-12-29
Filing date: 2017-12-29
Publication date: 2022-05-17
Anticipated expiration: 2037-12-29
Also published as: CN109990762A

Abstract

The invention discloses a ball screw with an inclination detector, which comprises a screw, two screw caps, a pipeline, a plurality of balls and an inclination detector. The screw extends axially of the axis. The two nuts are sleeved on the screw rod so that the two nuts can move along the axial direction. The inclination detector is arranged between the two nuts and is used for detecting the inclination angle and the pre-pressure of the two nuts. The tilt detector includes a force-receiving element, at least one first strain sensor and at least one second strain sensor. The force-bearing element comprises a point-symmetrical annular structure, and the annular structure is provided with two planes which are parallel to each other. The two parallel planes are respectively contacted with the two screw caps.

Description

Ball screw with inclination detector

Technical Field

The present invention relates to a ball screw, and more particularly, to a ball screw having a tilt detector for detecting a tilt and a variation in a pre-pressure of a nut.

Background

The ball screw is a transmission mechanical component which installs the steel balls between the screw cap and the screw rod and converts the rotary motion of the steel balls in the screw cap into linear motion. The ball screw has the characteristics of high precision, long service life, capability of performing high-speed forward and reverse transmission and the like.

For various precision machining processes of a composite processing machine, signals for monitoring the magnitude of the pre-pressure and the temperature change of the ball screw in real time are increasingly required. How to feed back these signals to the controller in real time as the basis for subsequent precision control and fault diagnosis has become one of the future technical development trends of intelligent ball screws.

The conventional ball screw senses the pre-pressure of the ball screw through a pressure sensor installed in a nut, and thus, whether the precision of the ball screw is deviated or not is judged. The conventional ball screw is only provided with pre-pressure sensing of a nut, so that pre-pressure change caused by temperature change cannot be compensated. On the other hand, some existing ball screws only have a temperature sensor and do not have a reference strain sensor, and therefore the magnitude of the pre-pressure caused by temperature change cannot be accurately calculated. In addition, after the conventional ball screw is used for a long time, the contact surface between the nut and the sensor becomes a non-parallel surface, and the nut is inclined. The inclined nut easily causes increased abrasion between the nut and the screw, thereby affecting the service life and precision of the ball screw.

Disclosure of Invention

The present invention is directed to a ball screw, which can detect the inclination of a nut and the variation of pre-pressure, so that the ball screw can be operated without the nut being inclined, thereby preventing the ball screw from being worn and prolonging the service life of the ball screw.

To achieve the above object, the ball screw of the present invention includes a screw, two nuts, a tube, a plurality of balls, and a tilt sensor. The outer surface of the screw has a first groove. The inner surface of each nut has a second groove. The screw extends in the axial direction of the axis. The two nuts are sleeved on the screw rod so that the two nuts can move along the axial direction. The pipeline is formed by the first groove and the corresponding second groove. The plurality of balls are arranged in the pipeline. The inclination detector is arranged between the two screw caps and used for detecting the inclination angles of the two screw caps, and the inclination detector comprises a stress element, at least one first strain sensor and at least one second strain sensor. The force-bearing element comprises at least one annular structure with two planes, wherein a normal vector on a first tangent plane of the annular structure is parallel to the axial direction, and the transverse plane and the axial line are intersected at the first intersection point. Wherein, two planes are parallel to each other and two planes contact with two nuts respectively, and at least one ring structure is a point symmetry structure which takes the first intersection point as a first symmetry point.

The ball screw of the present invention includes a screw, two nuts, a pipe, a plurality of balls, and an inclination detector. The outer surface of the screw has a first groove. The inner surface of each nut has a second groove. The screw extends in the axial direction of the axis. The two nuts are sleeved on the screw rod so that the two nuts can move along the axial direction. The pipeline is formed by the first groove and the corresponding second groove. The plurality of balls are arranged in the pipeline. The inclination detector is arranged between the two screw caps and used for detecting the inclination angles of the two screw caps, and the inclination detector comprises a stress element, at least one first strain sensor, at least one second strain sensor, at least one reference strain sensor and at least one temperature sensor. The force-bearing element has at least one ring structure. The at least one annular structure is provided with two planes, a normal vector on a first tangent plane of the at least one annular structure is parallel to the axial direction, and the first tangent plane and the axial line are intersected at a first intersection point. Wherein, two planes are parallel to each other and two planes contact with two nuts respectively. The at least one annular structure is a point-symmetric structure taking the first intersection point as a first symmetric point. The at least one first strain sensor and the at least one second strain sensor are arranged in the high strain area of the stressed element. The at least one reference strain sensor and the at least one temperature sensor are arranged in the low strain area of the stressed element.

The ball screw of the present invention includes a screw, two nuts, a pipe, a plurality of balls, and an inclination detector. The outer surface of the screw has a first groove. The inner surface of each nut has a second groove. The screw extends in the axial direction of the axis. The two nuts are sleeved on the screw rod so that the two nuts can move along the axial direction. The pipeline is formed by the first groove and the corresponding second groove. The plurality of balls are arranged in the pipeline. The inclination detector is arranged between the two screw caps and used for detecting the inclination angles of the two screw caps, and the inclination detector comprises a stress element, at least one first strain sensor, at least one second strain sensor, at least one reference strain sensor and at least one temperature sensor. The force-bearing element comprises at least one annular structure with two planes. Wherein the normal vector on the first tangent plane of at least one annular structure is parallel to the axial direction, and the first tangent plane and the axial line are intersected at a first intersection point; the at least one first sensing unit comprises at least one first recess, at least one first column and at least one first hole; the at least one second sensing unit comprises at least one second cavity, at least one second column and at least one second hole. The normal vector on a third section where the at least one first sensing unit and the at least one second sensing unit are located is parallel to the axial direction, the third section intersects with the axis at a third intersection point, the two planes are parallel to each other and are respectively contacted with the two nuts, and the at least one annular structure is a point-symmetric structure taking the first intersection point as a first symmetric point. The at least one first sensing unit and the at least one second sensing unit are point-symmetrically arranged in the at least one annular structure by taking the third intersection point as a third symmetrical point. The flexural rigidity of the at least one first sensing unit and the flexural rigidity of the at least one second sensing unit are respectively smaller than the flexural rigidity of the stressed element. Two ends of the at least one column are respectively connected with the upper surface and the lower surface of the at least one first recess. The at least one first hole is arranged in the at least one first column body to form two first supporting walls, each first supporting wall comprises at least one outer wall surface and at least one inner wall surface, an outer joint angle is defined by the at least one outer wall surface and the upper surface of the at least one first recess or the lower surface of the at least one first recess, an inner joint angle is defined by the at least one inner wall surface and the upper surface of the at least one first recess or the lower surface of the at least one first recess, the inner joint angle is larger than the outer joint angle, and the at least one reference strain sensor and the at least one temperature sensor are arranged on the upper surface of the at least one first recess or the lower surface of the at least one first recess.

The ball screw of the present invention includes a screw, two nuts, a pipe, a plurality of balls, and an inclination detector. The screw extends in the axial direction of the axis. The two nuts are sleeved on the screw rod so that the two nuts can move along the axial direction. The inclination detector is arranged between the two screw caps and used for detecting the inclination angles of the two screw caps and enabling the plurality of balls and the corresponding first grooves and the second grooves to generate pre-pressure. The tilt detector further includes a force-receiving element having two planes and a plurality of strain sensors. Two planes of the stress element are parallel to each other and are respectively contacted with the two nuts. The force-bearing element further comprises at least one annular structure, and the shape of the annular structure is an equilateral polygon. At least one strain sensor is disposed on an outer side of each side of the ring structure.

In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.

Drawings

FIG. 1A is a schematic perspective view of a ball screw according to an embodiment of the present invention;

FIG. 1B is an enlarged schematic view of the ball screw of FIG. 1A;

FIGS. 1C and 1D are schematic views illustrating the mounting of the reflow element and the balls of FIG. 1B;

FIG. 1E is an oblique view of the nut of FIG. 1B;

FIG. 2A is an exploded view of a nut and tilt detector of the ball screw of FIG. 1A;

FIG. 2B is an enlarged view of the tilt detector of FIG. 2A and a first section;

FIG. 2C is an enlarged view of the tilt detector of FIG. 2B rotated 180 degrees in the direction X1;

FIG. 2D is an enlarged view of the tilt detector of FIG. 2B and another second section;

FIG. 2E is an enlarged view of the tilt detector of FIG. 2B and another third section;

FIGS. 3A and 3B are schematic diagrams illustrating the sensing of the applied force of the tilt detector of FIG. 1B;

FIG. 4A is an exploded view of a ball screw nut and tilt detector in accordance with another embodiment of the present invention;

fig. 4B is an enlarged view of the tilt detector of fig. 4A.

Description of the symbols

100: ball screw

110: screw rod

120: nut cap

121: locating hole

130: pipeline

140: a plurality of balls

150: tilt detector

151. 151 c: force-bearing element

1511. 1511 c: first sensing unit

1522. 1522 c: second sensing unit

152. 152 c: first strain sensor

153. 153 c: second strain sensor

160: integrated circuit chip

170: temperature sensor

180: reference strain sensor

210: reflow element

211: first opening

212: second opening

220: positioning element

A: angle of inclination

OD 1: first outer joint angle

ID 1: first inner joint angle

OD 2: second outer joint angle

ID 2: second inner joint angle

OLT: external tangent line

OPJ: external contact

OPT: point of tangency

F1, F2: force

G1: first trench

G2: second trench

S3: plane surface

H1: first recess

H2: second recess

T1, T2: upper surface of

B1, B2: lower surface

X1, X2, X3: axial direction

L: axial line

N1: normal vector of the first tangent plane

N2: normal vector of the second tangent plane

N3: normal vector of third tangent plane

O1: a first hole

O2: second hole

R1: a first column body

R2: second post body

W1: first supporting wall

W2: second support wall

U1: first inner wall surface

U2: first inner wall surface

I1: first outer wall surface

I2: second outer wall surface

SC1 first tangent plane

SC2 second section

SC 3: third section of cut

XV: longitudinal axial direction

XT: transverse axial direction

P1: first point of symmetry

P2: second point of symmetry

P3: third point of symmetry

Detailed Description

Fig. 1A is a schematic perspective view of a ball screw according to an embodiment of the present invention. FIG. 1B is an enlarged schematic view of the ball screw of FIG. 1A. Fig. 1C and 1D are schematic views illustrating the mounting of the reflow element and the balls in fig. 1B. FIG. 1E is an oblique view of the nut of FIG. 1B.

Referring to fig. 1A and 1B, the ball screw 100 of the present invention includes a screw 110, two nuts 120, a pipe 130, a plurality of balls 140, and a tilt detector 150. The screw 110 is, for example, a metal rod shaped to extend in the axial direction X1 of the axis L, and the screw 100 has a first groove G1 on the outer surface thereof. In detail, the first groove G1 is recessed in the external thread of the screw 110, and the first groove G1 extends to both ends of the screw 110.

Referring to fig. 1C and 1D, the two nuts 120 are rotatably sleeved on the screw 110, and the tilt detector 150 is disposed between the two nuts 120. The inner surface of each nut 120 has a second groove G2. In detail, each of the second grooves G2 is, for example, spirally recessed in the internal thread of the nut 120. Each of the second grooves G2 corresponds to the first groove G1 at intervals, and the first groove G1 and the two corresponding second grooves G2 form the duct 130. Referring to fig. 1B and 1C, the reflow element 210 is disposed in the two nuts 120 and has a first opening 211 and a second opening 212.

A plurality of balls 140 are disposed in the conduit 130 between the nuts 120 and the screw 110. When the two nuts 120 and the screw 110 rotate relatively, each ball 140 is adapted to roll relatively between the first groove G1 and each second groove G2, and enter the backflow element 210 through the first opening 211 (or the second opening 212), and then leave the backflow element 210 through the second opening 212 (or the first opening 211), so as to achieve circulation of the plurality of balls 140. Therefore, the two screw caps 120 can synchronously move linearly along the axial direction X1 of the screw 110 by rolling of the plurality of balls 140 in the duct 130.

Fig. 2A is an exploded view of a nut and tilt detector of the ball screw of fig. 1A. Fig. 2B is an enlarged schematic view of the tilt detector and a first cut plane SC1 of fig. 2A. Fig. 2C is an enlarged view of the tilt detector of fig. 2B rotated 180 degrees in the axial direction X1. FIG. 2D is an enlarged view of the tilt detector of FIG. 2B and another third cut SC 3. Fig. 2E is an enlarged schematic view of the tilt detector of fig. 2B and another second cut SC2 surface.

Referring to fig. 1B, fig. 2A, fig. 2B and fig. 2C, an inclination detector 150 is disposed between the two nuts 120 and is used for detecting an inclination angle a (see fig. 1E) of each nut 120 relative to the axial direction X1 of the screw 110. In the present embodiment, after the positioning element 220 penetrates through the positioning hole of the tilt detector 150, the positioning element 220 is inserted into the corresponding positioning holes 121 of the two nuts 120, respectively, so that the tilt detector 150 is disposed between the two nuts 120, as shown in fig. 2A.

Specifically, the tilt detector 150 includes a force-receiving element 151, at least one first strain sensor 152, and at least one second strain sensor 153. The force-receiving element 151 includes a ring structure 157, a first sensing unit 1511 and a second sensing unit 1522. In this embodiment, the ring structure 157 is composed of two separate

semi-ring structures

157a,157 b. The first sensing unit 1511 includes at least one first cavity H1 and at least one first post R1 and the second sensing unit 1522 includes at least one second cavity H2 and at least one second post R2. Referring to fig. 2B and 2C, a normal vector N1 on the first tangential plane SC1 where the ring structure 157 is located is parallel to the axial direction X1 and the first tangential plane SC1 intersects the axis L of the axial direction X1 at a first intersection point. The ring structure 157 is a point-symmetric structure having the first intersection point as a first symmetric point. The point-symmetric structure referred to in the present invention means that there is another partial structure corresponding to any one partial structure of the ring-shaped structure 157. If any partial structure is rotated 180 degrees relative to the first symmetry point P1 after the first tangent plane SC1, it will be overlapped with the other corresponding partial structure, as shown in fig. 2B. In addition, the ring structure 157 has two parallel planes S3, and each plane S3 is in contact with each nut 120. Further, the two parallel planes S3 of the point-symmetric ring structure 157 can respectively urge the two nuts 120 to generate pre-pressure between each ball 140 and the corresponding first groove G1 and second groove G2, and prevent each nut 120 from tilting in the axial direction X1 relative to the screw 110 (see fig. 1E). More specifically, the ring structure 157 is designed to be point-symmetric and two parallel planes S3, so that the force-receiving element 151 can accurately measure the pre-pressure when each nut 120 is not tilted. In addition, the design of the ring structure 157 with point symmetry and the design of the two parallel planes S3 also enable the force-receiving element 151 to accurately measure the inclination angle when the nut 120 is inclined.

In addition, the at least one first strain sensor 152 and the at least one second strain sensor 153 are disposed in the ring structure 157 in a point symmetry manner. In the present embodiment, the number of the first strain sensor 152 and the second strain sensor 153 is, for example, one, and the first strain sensor 152 and the second strain sensor 153 are disposed in the ring structure 157 in a point symmetry manner. However, the present invention does not limit the number of the first strain sensors 152 and the second strain sensors 153. In other embodiments, there may be multiple pairs of sensors disposed on the ring structure 157, and each pair of sensors may include the first strain sensor 152 and the second strain sensor 153 disposed in point symmetry in the ring structure 157. The first strain sensor 152 and the second strain sensor 153 disposed in the ring structure 157 in point symmetry enable the force-receiving element 151 to be in a point-symmetric structure, so that the force-receiving element 151 can accurately measure the pre-pressure or the tilt angle of the nut. To illustrate the first strain sensor 152 and the second strain sensor 153 in point symmetry in more detail, referring to fig. 2E, a section where the first strain sensor 152 and the second strain sensor 153 are located may be defined as a second section SC2, wherein a normal vector N2 of the second section SC2 is parallel to the axial direction X1 of the screw 110. A second intersection of the second tangent plane SC2 and the axis L of the axial direction X1 may be defined as a second point of symmetry P2. The first strain sensor 152 and the second strain sensor 153 are disposed on the force-receiving element 151 in point symmetry, which means that the first strain sensor 152 is overlapped with the corresponding second strain sensor 153 after rotating 180 degrees relative to the second symmetry point P2 on the second tangent plane SC 2.

According to embodiments of the present invention, the force-bearing element 151 may have various types. For example, the force-bearing element 151 may comprise a one-piece ring structure integrally formed therewith, or a two-piece ring structure formed from two separate elements. The shape of the ring-shaped structure may also be a point-symmetric polygon, such as a square or a regular hexagon. Further, in other embodiments, when the shape of the ring-shaped structure is not a point-symmetric polygon, the shape of the ring-shaped structure may also be an equilateral polygon, such as a regular triangle or an equilateral pentagon, etc. In order to accurately measure the pre-pressure or the tilt angle of the nut, at least one strain sensor is disposed on each side of the ring structure (the normal vector of the side is perpendicular to the X1 axis). More specifically, when the two nuts are not tilted, the absolute difference between one electrical signal generated by one strain sensor located on one side of the outer side of the ring structure and the other electrical signal generated by the other strain sensor located on the other side of the outer side of the ring structure is smaller than a predetermined value. In contrast, when the two nuts are tilted, an absolute difference between an electrical signal generated by one strain sensor located on one side of the outer side surface of the ring structure and another electrical signal generated by another strain sensor located on the other side of the outer side surface of the ring structure is greater than a predetermined value. As shown in fig. 2A, fig. 2B and fig. 3A, the force-receiving element 151 includes a two-piece ring structure 157 formed by two independent elements 157a and 157B and two sensing units (a first sensing unit 1511 and a second sensing unit 1522). The first sensing unit 1511 and the second sensing unit 1522 are disposed in the ring structure 157 in a point symmetry manner. In addition, the flexural rigidities (flexural rigidity) of the first sensing unit 1511 and the second sensing unit 1522 are respectively smaller than the flexural rigidity of the ring structure 157. More specifically, the flexural rigidity (the product of the young's modulus of the first sensing unit 1511 and the moment of inertia of the first sensing unit 1511) of the first sensing unit 1511 with the plane in which a longitudinal axis XV and a transverse axis XT are located as a bending plane (bending plane) is smaller than the flexural rigidity (the product of the young's modulus of the ring-shaped structure 157 and the moment of inertia of the ring-shaped structure 157) of the ring-shaped structure 157 with the plane in which an axial direction X1 and another axial direction X2 are located as a bending plane. Similarly, the flexural rigidity of the second sensing unit 1522 with respect to the plane in which the longitudinal axis and the transverse axis are located as the bending plane is smaller than the flexural rigidity of the annular structure 157 with respect to the plane in which the axial direction X1 and the other axial direction X2 are located as the bending plane.

As described above, the flexural rigidities of the first sensing unit 1511 and the second sensing unit 1522 are respectively smaller than the flexural rigidity of the ring structure 157 along the axial direction, so that the ring structure 157 can apply a proper pre-pressure to the two nuts 120, and the first strain sensor 152 and the second strain sensor 153 can have a better measurement sensitivity when measuring the strain of the stressed element 151. For example, the first sensing unit 1511 includes a first cavity H1 and a first cylinder R1 disposed outside the ring structure 157. The first cavity H1 has a plurality of inner surfaces including an upper surface T1, a lower surface B1, a left surface and a right surface. Two ends of the first pillar R1 are connected to the upper surface T1 and the lower surface B1 of the first cavity H1, respectively. Similarly, the second sensing unit 1522 includes a second cavity H2 and a second cylinder R2 disposed at the other side of the outer ring of the ring structure 157. The second cavity H2 has a plurality of inner surfaces including an upper surface T2, a lower surface B2, a left surface and a right surface. Two ends of the second pillar R2 are connected to the upper surface T2 and the lower surface B2 of the second cavity H2, respectively. In this embodiment, the flexural rigidity of the first sensing unit 1511 is less than that of the ring structure 157 and the flexural rigidity of the second sensing unit 1522 is less than that of the ring structure 157. Therefore, when the two nuts 120 apply forces F1 and F2 to the force-receiving element 151, the first sensing unit 1511 generates a large lateral displacement (lateral deflection). In other words, the displacement of the first cylinder R1 of the first sensing unit 1511 or the second cylinder R2 of the second sensing unit 1522 in the axial direction XT is greater than the displacement of the ring structure 157 in the axial direction X2 (or the axial direction X3). This allows the tilt detector 150 to have better sensitivity when measuring the tilt angle or pre-stress of the two nuts.

In addition, the first strain sensor 152 is disposed on the first cylinder R1 of the first sensing unit 1511 for sensing the strain amount of the first cylinder R1 and the second strain sensor 153 is disposed on the second cylinder R2 of the second sensing unit 1522 for sensing the strain amount of the second cylinder R2. In addition, the first sensing unit 1511 and the second sensing unit 1522 disposed in the ring structure 157 in a point symmetry manner can make the force-receiving element 151 a point symmetry structure, so that the force-receiving element 151 can accurately measure the pre-pressure or the tilt angle of the nut when receiving the forces F1 and F2 of the two nuts 120.

To describe the first sensing unit 1511 and the second sensing unit 1522 in more detail, refer to fig. 2D. The section where the first sensing unit 1511 and the second sensing unit 1522 are located can be defined as a third section SC3, and a normal vector N3 of the third section SC3 is parallel to the axial direction X1. The intersection of the third tangent plane SC3 and the axis L along the axial direction X1 may be defined as a third point of symmetry P3. In the embodiment, the first sensing unit 1511 and the second sensing unit 1522 are disposed in the ring structure 157 in a point-symmetric manner, respectively, means that after the first cylinder R1 and the first cavity H1 of the first sensing unit 1511 rotate 180 degrees on the third section SC3 relative to the third symmetric point P3, the first cylinder R1 and the first cavity H1 are respectively overlapped with the second cylinder R2 and the second cavity H2 of the second sensing unit 1522.

Fig. 3A and 3B are schematic diagrams illustrating the bearing forces F1 and F2 of the tilt detector of fig. 1B. According to an embodiment of the present invention, the first pillar R1 may be further designed. Specifically, as shown in fig. 3A and 3B, the first cylinder R1 of the present embodiment may be provided with a first hole O1. The first hole O1 can be a through hole (through hole) penetrating through the first cylinder R1 or a blind hole (blind via) in the first cylinder R1. The first hole O1 allows the first post R1 to form two opposite first supporting walls W1. The first cylinder R1 is provided with a first hole O1 to reduce the rigidity of the first cylinder R1 in the axial direction X1 of the screw 110, thereby reducing the flexural rigidity of the first sensing unit 1511 and improving the measurement sensitivity of the first strain sensor 152.

Further, each of the first supporting walls W1 includes a first outer wall surface I1 and a first inner wall surface U1. The first exterior wall I1 defines a first exterior engagement angle OD1 with the upper interior surface T1 of the first cavity H1 or the lower interior surface B1 of the first cavity H1. The first inner wall surface U1 defines an inner engagement angle ID1 with the upper inner surface T1 of the first pocket H1 or the lower inner surface B1 of the first pocket H1. The first outside engagement angle OD1 and the first inside engagement angle ID1 may have different designs according to different design requirements. For example, the first outer engagement angle OD1 may be an acute angle and the first inner engagement angle ID1 may be an obtuse angle. At this time, since the first inner joint angle ID1 of the first pillar R1 is greater than the first outer joint angle OD1, it can be ensured that each first supporting wall W1 of the first pillar R1 is bent (or buckled) from the first inner wall surface U1 toward the first outer wall surface I1 when the first pillar R1 is subjected to various forces F1 and F2.

Similarly, the same design as that of the second column R2 can be adopted to ensure that each of the second supporting walls W2 of the second column R2 bends (or buckles) from the second inner wall surface U2 to the second outer wall surface I2 under the action of the forces F1 and F2 of the second column R2.

For better definition of the first outer engagement angle OD1, please refer to fig. 2B and fig. 3A. FIG. 3A is a cross-sectional view of the first pillar R1, the upper surface T1 of the first cavity H1 and the lower surface B1 of the first cavity H1, the normal vector of the cross-section being parallel to the axial direction X3. In this section, the upper surface T1 of the first cavity H1 and the first outer wall surface I1 are connected to the outer contact OPJ. The outer tangent line OLT passes through the outer point OPJ and is tangent to the first outer wall face I1 at an outer tangent point OPT. The first outer engagement angle OD1 may be defined as the angle between the outer tangent OLT and the upper surface T1 of the first cavity H1. Similarly, the second outer engagement angle OD2 may also be defined in the same manner.

In addition, as shown in the sectional view of FIG. 3A, the upper surface T1 of the first cavity H1 is connected to the inner joint IPJ (not shown) of the first inner wall surface U1. An internal tangent ILT (not shown) passes through the internal point IPJ and is tangent to the first inner wall surface U1 at an internal point IPT. The first inner and outer engagement angle ID1 may be defined as the angle between the inner tangent ILT and the upper surface T1 of the first cavity H1. Similarly, the second inside engagement angle ID2 may also be defined in the same manner. The design that each first supporting wall W1 of the first pillar R1 and each second supporting wall W2 of the second pillar R2 are bent from the inner wall surface to the outer wall surface allows the first strain sensor 152 and the second strain sensor 153 to measure correct electrical signals, so that an integrated circuit chip (ASIC chip) can calculate a correct pre-pressure value. In the present embodiment, since the first outer engagement angle OD1 is an acute angle and the first inner engagement angle ID1 is an obtuse angle, when the first cylinder R1 receives forces F1 and F2, each first supporting wall W1 of the first cylinder R1 bends from the first inner wall surface U1 toward the first outer wall surface I1. Similarly, since the second outer engagement angle OD2 is acute and the second inner engagement angle ID2 is obtuse, when the second column R2 receives forces F1 and F2, the second support walls W2 of the second column R2 are also bent from the second inner wall surface U2 toward the second outer wall surface I2. In another embodiment, the first outer engagement angle is larger than the first inner engagement angle and the second outer engagement angle is larger than the second outer engagement angle, so as to ensure that each of the first support wall W1 of the first column R1 and the second support wall W2 of the second column R2 bends from the outer wall surface toward the inner wall surface under the action of the forces F1 and F2 applied to the first column R1 and the second column R2.

The first strain sensor 152 may be disposed on the first outer wall I1 or the first inner wall U1 of the first cylinder R1 of the first sensing unit 1511. Meanwhile, the second strain sensor 153 may be disposed on the second outer wall surface I2 or the second inner wall surface U2 of the second column R2 of the second sensing unit 1522. The first outer wall surface I1 or the first inner wall surface U1 is a high strain area of the first pillar R1 when bearing the forces F1 and F2. Similarly, the second outer wall surface I2 or the second inner wall surface U2 is a high strain region of the second column R2 when receiving the forces F1 and F2. Since the first strain sensor 152 and the second strain sensor 153 are both disposed in the high strain region, the first strain sensor 152 can sensitively sense the first strain value of the first pillar R1 to generate a first electrical signal, and the second strain sensor 153 can sensitively sense the second strain value of the second pillar R2 to generate a second electrical signal. By comparing the difference between the first electrical signal and the second electrical signal, it can be determined whether the two nuts 120 abutting on the two parallel planes S3 of the force-receiving component 151 are tilted with respect to the screw 110.

Fig. 4A is an exploded view of a nut and a tilt detector of a ball screw according to another embodiment of the present invention. Fig. 4B is an enlarged view of the tilt detector of fig. 4A. Referring to fig. 4A and 4B, the tilt detector 150c of the present embodiment includes a force-receiving element 151c, a first strain sensor 152c, a second strain sensor 153c, and two

sensing units

1511c, 1522 c. The two

sensing units

1511c, 1522c are disposed at two outer sides of the ring structure 157c in a point-symmetric manner, respectively. The tilt detector 150c of the present embodiment has substantially the same structure as the tilt detector 150 of fig. 2A. The difference between the two embodiments is that the force-bearing element 151c of the tilt detector 150c comprises an integrally formed ring-shaped structure 157 c.

Referring to fig. 1B and 1E and fig. 3A and 3B, a method for sensing the inclination angle of each nut 120 by the inclination detector 150 of the ball screw 100 will be described.

In the present embodiment, an integrated circuit chip 160 is further included, which is, for example, disposed in the low strain region (e.g., the lower surface B1 of the first cavity H1) of the tilt detector 150 and transmits the electrical signal by wireless transmission. In other embodiments, the ASIC chip is disposed outside the ball screw and transmits electrical signals through a conductive wire, for example. When the two nuts 120 respectively press the force-receiving member 151, two opposite forces F1 and F2 respectively act on the two parallel planes S3. The two forces F1 and F2 simultaneously cause the two columns (the first column R1 and the second column R2) of the force-receiving element 151 to generate strain, wherein the first strain sensor 152 disposed on the first column R1 measures the strain amount of the first column R1 to generate a first electrical signal, and the second strain sensor 153 measures the strain amount of the second column R2 to generate a second electrical signal.

The difference between the first electrical signal and the second electrical signal is then calculated by the integrated circuit chip 160. If the integrated circuit chip 160 determines that the absolute value of the difference is greater than the predetermined value, that is, the first electrical signal is greater than the second electrical signal or the second electrical signal is greater than the first electrical signal, it indicates that the strains of the two columns R1 and R2 in the stressed element 151 are different. This means that the two nuts 120 are not pressed parallel to the planes S3 but inclined to the axial direction X1, resulting in uneven force applied to the force-receiving element 151. At this point, the ic chip 160 generates a notification signal indicating that the two nuts are tilted, thereby notifying the user that the ball screw must be serviced. When the ic chip 160 determines that the absolute value of the difference is smaller than the predetermined value, this indicates that the strain amounts of the two columns R1 and R2 in the force-receiving element 151 are close to each other. This means that the two nuts 120 are not tilted and are pressed against the planes S3, so that the forces exerted by the force-receiving elements 151 are equalized. At this time, the ic chip 160 records the first electrical signal and the second electrical signal for calculating the pre-pressure applied to the ball 140 by the tilt sensor 150.

Further, referring to fig. 2B, fig. 3A and fig. 3B, the ball screw 100 further includes two temperature sensors 170 and two reference strain sensors 180. The two temperature sensors 170 are respectively disposed in the first cavity H1 of the first sensing unit 1511 and the second cavity H2 of the second sensing unit 1522. The two reference strain sensors 180 are also disposed in the first cavity H1 of the first sensing unit 1511 and the second cavity H2 of the second sensing unit 1522, respectively. In detail, the reference strain sensor 180 and the temperature sensor 170 are disposed on the upper surface T1 or the lower surface B1 of the first cavity H1. Another reference strain sensor 180 and another temperature sensor 170 are disposed on the upper surface T2 or the lower surface B2 of the second cavity H2. The upper surface T1 or the lower surface B1 of the first cavity H1 and the upper surface T2 or the lower surface B2 of the second cavity H2 are low strain regions in the force-receiving element 151. The two temperature sensors 170 are disposed in the low strain region, so that the value measured by the temperature sensors 170 is prevented from being interfered by external forces F1 and F2, and the temperature in the ball screw can be accurately measured. The two reference strain sensors 180 are respectively disposed in the low strain regions, so that the measured values of the reference strain sensors 180 are prevented from being interfered by external forces F1 and F2, and the strain caused only by temperature changes can be accurately measured.

The method for sensing and calibrating the first strain sensor 152 and the second strain sensor 153 by the temperature sensor 170 and the reference strain sensor 180 is described below. The temperature sensor 170 is used for measuring the temperature in the first cavity H1 (or the second cavity H2) disposed in the force-receiving component 151. During operation of the ball screw, the temperature in the first cavity H1 and the second cavity H2 changes. The reference strain sensor 180 is disposed on the lower surface B1 of the first cavity H1, which is a low strain area in the force-receiving member 151. Therefore, the reference strain sensor 180 only senses the strain caused by the temperature change to the force receiving element 151, and does not sense the strain caused by the forces F1 and F2 to the force receiving element 151. Further, the strain amount sensed by the first strain sensor 152 is caused by the temperature change and the forces F1 and F2. The first electrical signal sensor measured by the first strain sensor 152 and the reference electrical signal measured by the corresponding reference strain sensor 180 are corrected by the quartz bridge strain gauge circuit, so as to eliminate the influence of the temperature change on the strain amount of the stressed element 151, and further accurately calculate the forces F1 and F2 applied by the two nuts to the two planes S3 of the tilt sensor 150.

In summary, the ball screw of the present invention can be used to detect the tilting degree of the nut and the magnitude of the pre-pressure applied to the balls. When the inclination degree of the screw cap is within an acceptable range, the invention can sense the pre-pressure of the ball screw and the change of the pre-pressure. The annular structure in the stress element of the inclination detector is a point-symmetric structure, and two planes of the annular structure are parallel to the contact surfaces of the nuts at two sides, so that the nuts are not easy to incline and the ball screw can be prevented from being worn. Therefore, the invention can improve the reliability and the service life of the ball screw. In addition, because the annular structure in the stress element is a point-symmetric structure and two planes in contact with the nut are parallel to each other, the stress element can stably and accurately sense the force from the nut, so that the accurate sensing of the pre-pressure of the ball screw is realized. The columns of the invention also have inner joint angles and outer joint angles with different angles, so that the support walls of the columns can be ensured to be bent from the outer wall surface to the inner wall surface or from the inner wall surface to the outer wall surface under various stress conditions, and the sensing sensitivity and the sensing accuracy of each strain sensor are improved. Furthermore, the ball screw of the present invention further has a temperature sensor and a reference strain sensor disposed in the low stress region, which can directly measure the temperature variation of the ball screw, thereby avoiding the temperature variation from affecting the measurement accuracy of the pre-pressure, and achieving a ball screw with a combined function of nut tilt sensing capability and pre-pressure measurement capability.

Although the present invention has been described with reference to the above embodiments, it should be understood that the invention is not limited thereto, and that various changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A ball screw, comprising:

a screw rod having a first groove on its outer surface

Two nuts having second grooves on the inner surface

The screw rod extends along the axial direction of the axis, and the two screw caps are sleeved on the screw rod so as to enable the two screw caps to move along the axial direction;

a duct constituted by the first groove and the corresponding second groove,

a plurality of balls disposed in the conduit; and

the inclination detector is arranged between the two nuts and is used for detecting the inclination angles of the two nuts, and the inclination detector comprises:

a force-receiving element, comprising:

the normal vector on a first tangent plane of the at least one annular structure is parallel to the axial direction, and the first tangent plane and the axial line are intersected at a first intersection point;

at least one first strain sensor; and

at least one second strain sensor for measuring a strain in the sample,

wherein the two planes are parallel to each other and are respectively contacted with the two nuts, the at least one annular structure is a point-symmetric structure taking the first intersection point as a first symmetric point,

wherein a normal vector on a second tangent plane of the at least one first strain sensor and the at least one second strain sensor is parallel to the axial direction, the second tangent plane intersects the axis at a second intersection point, the at least one first strain sensor and the at least one second strain sensor are disposed on the at least one annular structure in point symmetry with the second intersection point as a second symmetry point,

wherein, the force-bearing element further comprises at least one first sensing unit and at least one second sensing unit, wherein a normal vector on a third section where the at least one first sensing unit and the at least one second sensing unit are located is parallel to the axial direction, the third section intersects with the axis at a third intersection point, the at least one first sensing unit and the at least one second sensing unit are disposed in the at least one annular structure point-symmetrically with the third intersection point as a third symmetry point, the at least one first sensing unit further comprises at least one first recess and at least one first cylinder, the at least one second sensing unit further comprises at least one second recess and at least one second cylinder, two ends of the at least one first cylinder are respectively connected with the upper surface and the lower surface of the at least one first recess, two ends of the at least one second cylinder are respectively connected with the upper surface and the lower surface of the at least one second recess, the at least one first cavity and the at least one second cavity are disposed in the at least one ring structure point-symmetrically at the third point of symmetry, the at least one first post and the at least one second post are disposed in the at least one ring structure point-symmetrically at the third point of symmetry, wherein the at least one first strain sensor is disposed on the at least one first post and the at least one second strain sensor is disposed on the at least one second post.

2. The ball screw of claim 1, wherein the two planes respectively urge the two nuts to generate pre-stress between the plurality of balls and the corresponding first and second grooves.

3. The ball screw of claim 1, further comprising an integrated circuit chip, wherein the at least one first strain sensor generates a first electrical signal and the at least one second strain sensor generates a second electrical signal when the force-receiving element is strained, the integrated circuit chip calculating a difference between the first electrical signal and the second electrical signal.

4. The ball screw of claim 3, wherein the integrated circuit chip generates a notification signal when the integrated circuit chip determines that the absolute value of the difference is greater than a predetermined value.

5. The ball screw of claim 3, wherein the IC chip records the first electrical signal and the second electrical signal when the IC chip determines that the absolute value of the difference is less than a predetermined value.

6. The ball screw of claim 1, wherein the flexural rigidity of the at least one first sensing unit and the flexural rigidity of the at least one second sensing unit are respectively less than the flexural rigidity of the at least one ring structure, and wherein the at least one first strain sensor is disposed in a high strain region of the first sensing unit.

7. The ball screw according to claim 1, wherein the at least one first cylinder further comprises a first hole formed therein to form two first support walls for reducing the rigidity of the at least one first cylinder in the axial direction, and the at least one second cylinder further comprises a second hole formed therein to form two second support walls for reducing the rigidity of the at least one second cylinder in the axial direction.

8. The ball screw according to claim 7, wherein the two first supporting walls respectively comprise at least one first outer wall surface and at least one first inner wall surface, the at least one first outer wall surface and the upper surface of the at least one first cavity or the lower surface of the at least one first cavity define a first outer engagement angle, the at least one first inner wall surface and the upper surface of the at least one first cavity or the lower surface of the at least one first cavity define a first inner engagement angle, and the first inner engagement angle is smaller than the first outer engagement angle.

9. The ball screw according to claim 7, wherein the two first supporting walls respectively comprise at least one first outer wall surface and at least one first inner wall surface, the at least one first outer wall surface and the upper surface of the at least one first cavity or the lower surface of the at least one first cavity define a first outer engagement angle, the at least one first inner wall surface and the upper surface of the at least one first cavity or the lower surface of the at least one first cavity define a first inner engagement angle, and the first inner engagement angle is larger than the first outer engagement angle.

10. The ball screw of claim 1, further comprising at least one temperature sensor and at least one reference strain sensor disposed in the low strain region of the first sensing unit.

11. The ball screw of claim 10, wherein the at least one first strain sensor is disposed on the at least one first post, the at least one reference strain sensor and the at least one temperature sensor are disposed on the upper surface of the at least one first cavity or the lower surface of the at least one first cavity.

12. A ball screw, comprising:

a screw rod having a first groove on its outer surface

Two nuts having second grooves on the inner surface

a duct constituted by the first groove and the corresponding second groove,

a plurality of balls disposed in the conduit; and

a force-receiving element, comprising: the normal vector on a first tangent plane of the at least one annular structure is parallel to the axial direction, and the first tangent plane and the axial line are intersected at a first intersection point;

at least one first strain sensor;

at least one second strain sensor;

at least one reference strain sensor;

at least one temperature sensor;

wherein the two planes are parallel to each other and are respectively in contact with the two nuts, the at least one annular structure is a point-symmetric structure taking the first intersection point as a first symmetric point, the at least one first strain sensor and the at least one second strain sensor are arranged in a high strain region of the stressed element, the at least one reference strain sensor and the at least one temperature sensor are arranged in a low strain region of the stressed element,

wherein, the force-bearing element further comprises at least one first sensing unit and at least one second sensing unit, wherein a normal vector on a third section where the at least one first sensing unit and the at least one second sensing unit are located is parallel to the axial direction, the third section intersects with the axis at a third intersection point, the at least one first sensing unit and the at least one second sensing unit are point-symmetrically arranged in the at least one annular structure with the third intersection point as a third symmetry point, the flexural rigidity of the at least one first sensing unit and the flexural rigidity of the at least one second sensing unit are respectively smaller than the flexural rigidity of the at least one annular structure, wherein the at least one first strain sensor is arranged in a high strain area of the first sensing unit, wherein the at least one first sensing unit further comprises at least one first recess and at least one first column, the at least one second sensing unit further includes at least one second cavity and at least one second post, two ends of the at least one first post are respectively connected to the upper surface and the lower surface of the at least one first cavity, two ends of the at least one second post are respectively connected to the upper surface and the lower surface of the at least one second cavity, the at least one first cavity and the at least one second cavity are disposed in the at least one annular structure in a point-symmetric manner with respect to the third point of symmetry, the at least one first post and the at least one second post are disposed in the at least one annular structure in a point-symmetric manner with respect to the third point of symmetry, wherein the at least one first strain sensor is disposed on the at least one first post, and the at least one second strain sensor is disposed on the at least one second post,

the normal vector on a second tangent plane where the at least one first strain sensor and the at least one second strain sensor are located is parallel to the axial direction, the second tangent plane intersects with the axis at a second intersection point, and the at least one first strain sensor and the at least one second strain sensor are arranged on the at least one annular structure in a point-symmetric manner by taking the second intersection point as a second symmetric point.

13. The ball screw of claim 12, wherein the two planes respectively urge the two nuts to create a pre-stress between the plurality of balls and the corresponding first and second grooves.

14. The ball screw of claim 12, further comprising an integrated circuit chip, wherein the at least one first strain sensor generates a first electrical signal and the at least one second strain sensor generates a second electrical signal when the force-receiving element is strained, the integrated circuit chip calculating a difference between the first electrical signal and the second electrical signal.

15. The ball screw of claim 14, wherein the integrated circuit chip generates a notification signal when the integrated circuit chip determines that the absolute value of the difference is greater than a predetermined value.

16. The ball screw of claim 14, wherein the integrated circuit chip records the first electrical signal and the second electrical signal when the integrated circuit chip determines that the absolute value of the difference is less than a predetermined value.

17. A ball screw, comprising:

a screw rod having a first groove on its outer surface

Two nuts having second grooves on the inner surface

a duct constituted by the first groove and the corresponding second groove,

a plurality of balls disposed in the conduit; and

a force-receiving element, comprising:

at least one annular structure with two planes, wherein a normal vector on a first tangent plane of the at least one annular structure is parallel to the axial direction, and the first tangent plane and the axial line are intersected at a first intersection point;

at least one first sensing unit comprising:

at least one first cavity;

at least one first column;

at least one first hole;

at least one second sensing unit comprising:

at least one second cavity;

at least one second post;

at least one second hole;

at least one first strain sensor;

at least one second strain sensor;

at least one reference strain sensor; and

at least one temperature sensor is arranged on the base,

wherein a normal vector on a third tangent plane of the at least one first sensing unit and the at least one second sensing unit is parallel to the axial direction, the third tangent plane intersects with the axis at a third intersection point, the two planes are parallel to each other and are respectively in contact with the two nuts, the at least one annular structure is a point-symmetric structure taking the first intersection point as a first symmetric point, the at least one first sensing unit and the at least one second sensing unit are arranged in the at least one annular structure in a point-symmetric manner taking the third intersection point as a third symmetric point, the flexural rigidity of the at least one first sensing unit and the flexural rigidity of the at least one second sensing unit are respectively smaller than that of the stressed element, and two ends of the at least one first column are respectively connected with the upper surface and the lower surface of the at least one first recess, the at least one first hole is disposed in the at least one first column to form two first support walls, each of the first support walls includes at least one outer wall surface and at least one inner wall surface, the at least one outer wall surface and the upper surface of the at least one first recess or the lower surface of the at least one first recess define an outer joint angle, the at least one inner wall surface and the upper surface of the at least one first recess or the lower surface of the at least one first recess define an inner joint angle, the inner joint angle is greater than the outer joint angle, the at least one reference strain sensor and the at least one temperature sensor are disposed on the upper surface of the at least one first recess or the lower surface of the at least one first recess,

wherein the at least one first strain sensor is disposed on the at least one first post and the at least one second strain sensor is disposed on the at least one second post,

the normal vector on a second tangent plane where the at least one first strain sensor and the at least one second strain sensor are located is parallel to the axial direction, the second tangent plane intersects with the axis at a second intersection point, and the at least one first strain sensor and the at least one second strain sensor are arranged on the at least one annular structure in a point symmetry manner by taking the second intersection point as a second symmetry point.

18. The ball screw according to claim 17, wherein the at least one first cavity and the at least one second cavity are disposed point-symmetrically in the at least one ring structure with the third intersection point as a third symmetry point, the at least one first column and the at least one second column are disposed point-symmetrically in the at least one ring structure with the third intersection point as a third symmetry point, two ends of the at least one first column are connected to the upper surface and the lower surface of the first cavity, respectively, and two ends of the at least one second column are connected to the upper surface and the lower surface of the at least one second cavity, respectively.

19. The ball screw of claim 17, wherein the two planes respectively urge the two nuts to generate pre-stress between the balls and the corresponding first and second grooves.

20. The ball screw of claim 17, further comprising an integrated circuit chip, wherein the at least one first strain sensor generates a first electrical signal and the at least one second strain sensor generates a second electrical signal when the force-receiving element is strained, the integrated circuit chip calculating a difference between the first electrical signal and the second electrical signal.

21. The ball screw of claim 20, wherein the integrated circuit chip generates a notification signal when the integrated circuit chip determines that the absolute value of the difference is greater than a predetermined value.

22. The ball screw of claim 20, wherein the integrated circuit chip records the first electrical signal and the second electrical signal when the integrated circuit chip determines that the absolute value of the difference is less than a predetermined value.