JP3317689B2 - Rotation angle detection mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for converting a rotary motion composed of a combination of a ball screw and a nut into a linear motion, that is, a rotary mechanism that realizes precise positioning of the linear motion of the nut by controlling the rotation of the ball screw. In a mechanism for converting motion into linear motion, a mechanism for detecting a point at which the nut reaches a screw end point such as a start point and an end point of a stroke, and particularly, a mechanism for detecting a position of the nut in a ball screw which cannot be seen due to a closed mechanism. It relates to a mechanism for setting or detecting, that is, setting an arbitrary point at a start point, an end point, and an intermediate point, or electrically detecting the position.

[0002]

2. Description of the Related Art In a relative motion caused by rotation of a ball screw and a nut, for example, when a rotating shaft is a screw, the ball screw and the nut must be closed to confirm that the nut passes through a set position on the shaft. When setting and detecting the starting point and ending point of a stroke or an arbitrary position within the range, the positioning is set by a dog and a limit switch. By the way, in the relative motion due to the rotation of the ball screw and the nut, for example, when the rotating shaft is a screw, in order to confirm that the nut passes through a set position on the shaft, it is recognized by a rotation counter incorporating a gear reducer. Alternatively, as electrical means, a rotation angle within one rotation can be detected using a rotation angle sensor such as a rotary encoder or a resolver. If a multi-rotation potentiometer is used in addition to the latter means, measurement can be made in the rotatable range. However, this means has a problem of lack of durability due to wear caused by friction between the electric slider and the resistance wire.
Therefore, a non-contact electrical device using magnetism or light is used. However, since the rotation angle is detected within one rotation, in the case of multiple rotations, the memory function of the digital counter circuit must be used together. However, when the memory function of the digital counter circuit is used in combination, if the power is cut off, the memory is lost and cannot be detected. Further, under conditions where electricity cannot be used, the rotation angle must be visually observed, and at this time, it cannot be confirmed.

[0003]

SUMMARY OF THE INVENTION According to the present invention, in a positioning mechanism including a ball screw and a nut existing in a closed mechanism, setting and detection of a start point and an end point of a stroke of the nut, or an arbitrary position within the range, are performed. An object of the present invention is to provide a mechanism realized by a rotating shaft and its attached device by directly utilizing the rotation of the shaft of a ball screw, and to achieve an effect equivalent to that of a conventionally required positioning setting by a dog and a limit switch.

[0004]

The ball screw makes multiple rotations. One gear is coaxially joined to the rotation axis of the screw.
Then, when a spur gear having a different number of teeth than the number of teeth of this gear is engaged and transmitted, the spur gears reverse in the opposite direction at almost the same speed. However, since the number of teeth differs by one, a slight rotation difference occurs between the two. The concept of observation confirmation and non-contact electrical detection is established by utilizing the principle that the slight shift of the mating gear is integrated in multiple rotations in one rotation of the detection symmetry axis and the rotation speed can be confirmed from that angle. I do. To realize this, basically, the number of teeth of the second gear attached to the detector needs to be equal to or more than the number of shaft rotations (for example, N rotations) in the controllable range of the detection target shaft. The gears meshing with each other can be either spur gears or internal gears. For the first gear to be detected, select a gear that is one tooth different from the second gear, or if the combination is such that the ratio of the number of teeth of the first gear to the second gear is N ± 1: N, mechanically possible It is.

When it is desired to detect not only the end point but also an arbitrary set point within the control range, it is possible to shift the mark on the base of the second gear or on the base of the same axis by rotational movement from the reference point. When setting is required, it becomes possible by making a multiplex structure. In order to realize electrical specific contact, a magnet is mounted on the first gear or the same base of the detection target shaft, and a second gear or the same base is mounted on the first gear or the same base of the detection target shaft by magnetic induction when the magnet approaches. A magnetic inductor is provided, and a magnetic sensor for detecting that the magnetic flux becomes strong when they are aligned on a straight line is fixed and electrically detected, and the magnet is a light that is an optical transmitter. A method of detecting light consisting of an optical element and an optical sensor by replacing the magnetic inductor with a slit and the detecting part with an optical sensor, and applying this method to the former detecting part in parallel with the emission of laser light and the same light receiving element By arranging and replacing the optical element of the first gear with a light reflecting mirror, a method using laser light is established. The phenomenon at this time is that the laser beam from the fixed base passes through the slit that moves in synchronization with the second gear, hits the reflector on the first gear, and reaches the light receiving element again through the slit. This is made possible by a method of detecting when the slit and the laser beam are on the same line.

That is, according to the first aspect of the present invention, there is provided a first gear 3 rotating around a rotation shaft 1 to be detected, and a first rotation gear 2 meshing with the first gear 3. And a second gear 4 that rotates about the center of the first gear 3 and the second gear 4.
1) A pair N (where N is an integer) is provided with a mark 5 near the tooth portion of the first gear 3 and a mark 6 near the tooth portion of the second gear 4 respectively. A point coincident on a straight line connecting the rotating shaft 1 and the rotating shaft 2 is set as a starting point, and the first gear 3 rotates with the rotation of the rotating shaft 1 to be detected from the starting point, and the second gear 4 rotates accordingly. When you do two landmarks 5
In addition, on the principle that the mark 6 coincides again on the straight line, the observation point 7 for observing the coincidence of the two marks 5 and 6 is moved to the second point on the line connecting the rotation axis 1 and the rotation axis 2.
N is provided on the gear 4 and a reference point 8 is provided near the tooth portion of the second gear 4 so that the mark 6 can be set to a position displaced from the reference point 8 by an arbitrary rotation angle.
This is a rotation angle detection mechanism that is equal to or less than N rotations of the rotation axis of the rotation stroke.

In the above, two marks 5 and 6
Start point from a point where the first gear 3 coincides on a straight line connecting the rotation axis 1 and the rotation axis 2 because the first gear 3 rotates with the rotation of the detection target rotation axis 1 from the start point. Then, the second gear 4 rotates with this, and when the least common multiple of the number of teeth is M, the first gear 3 and the second gear 4
When M / (N ± 1) rotation and M / N rotation are performed, respectively, the two marks 5 and 6 coincide again on a straight line.

According to the second aspect of the present invention, the mark 5 of the first gear 3 is provided.
2. A means for detecting a rotation angle equal to or less than N rotations of a rotation axis of an N rotation stroke in the means of claim 1, wherein a mark is formed from a magnet, a mark 6 of the second gear 4 is formed from a magnetic inductor, and an observation point 7 is formed from a magnetic sensor. Mechanism.

According to the third aspect of the present invention, the mark 5 of the first gear 3 is provided.
Is a light transmitter, the mark 6 of the second gear 4 is slit, and the observation point 7
2. The device according to claim 1, wherein the light receiving sensor is formed from a light receiving sensor.
Means for detecting a rotation angle equal to or smaller than N rotations of the rotation shaft of N rotation strokes in the means.

According to the fourth aspect of the present invention, the laser emission port and the laser light receiving sensor are arranged in parallel at the observation point 7, and the second gear 4
The mark 6 of the first gear 3 is used as a reflector, and the mark 5 of the first gear 3 is used as a reflector, and a means for electrically detecting that the laser reflected light reaches the light receiving sensor is provided. This is a rotation angle detection mechanism that is equal to or less than N rotations of the rotation axis of the rotation stroke.

According to a fifth aspect of the present invention, in the means of any one of the first to fourth aspects, the rotation angle of the rotation shaft 1 to be detected is smaller than the rotation angle at the time of N rotation which is a measurable rotation angle. When detection at the rotation angle during rotation is required, L = −
In the case of 1, the rotational position on the second gear 4 rotated by k / N in the direction opposite to the rotational direction from the reference point 8 on the second gear 4 (the same direction as the rotational direction when L = + 1) is marked. 6 is a rotation angle detecting mechanism for a rotation shaft of N rotation strokes or less than N rotations, characterized in that the rotation angle detection mechanism 6 is provided.

According to a sixth aspect of the present invention, in the means of any one of the second to fifth aspects, the first gear 3 and the mark 5 joined to the rotating shaft 1 to be detected are magnetized, light-transmitted or laser-emitted. A magnetic inductor, a slit or a slot corresponding to the mark 5 is provided on a second gear 4 meshing with the first gear 3 or on a rotating base provided coaxially with the rotating shaft 2 of the second gear. A plurality of marks 6 of one kind selected from a laser light receiving sensor are provided, and the marks 6 are stacked in a multiplex manner. is there.

[0013]

Embodiments of the present invention will be described with reference to the drawings. In FIG. 1, a coaxial first gear 3 is joined to a rotary shaft 1 of a ball screw. The mark 5 is provided on the vicinity of the tooth portion of the first gear 3 or on a base having substantially the same radius as the first gear 3. The mark 5 is, for example, a magnet piece. Further, a second gear 4 meshing with the first gear 3 is provided. In FIG. 1, the second gear 4 meshes with the first gear 3 with internal teeth. The mark 6 is provided on the second gear 4 or a base on the rotating shaft 2 of the second gear 4 having a radius substantially equal to that of the second gear 4. The mark 6 is, for example, a small piece of steel as a magnetic inductor. An observation point 7 is arranged in the vicinity of the engagement of the two first gears 3 and the second gear 4, that is, on the line connecting the rotating shaft 2 and the rotating shaft 1 so that the marks 5 and 6 are opposed to each other in a straight line. It is provided outside the mark 6.
The observation point 7 is an example in which a magnetic sensor, such as a Hall element or a magnetic IC, is fixed as a detector. Further, a reference point 8 is provided near the tooth portion of the second gear 4. FIG.
Is a diagram schematically showing these.

FIG. 2 is a diagram schematically showing an example in which the second gear of FIG. 1 is an external spur gear. 1 and 2
, The ratio of the number of teeth of the first gear 3 to the number of teeth of the second gear 4 is (N−1) to N, respectively. When the rotation shaft 1 of the first gear 3 is a screw of a ball screw, and when the movable range of the ball screw is N rotations of the rotation shaft 1, the number of teeth of each of the two first gears 3 and the second gear 4 Is set based on this condition. To the last, (N-1): N is a ratio, so the gear module and the number of teeth of each can be set arbitrarily.

FIG. 3 shows that when the first gear 3 of FIG. 2 makes one rotation, the rotation of the second gear 4 is 360 degrees × (1 / N) than one rotation.
This indicates that a rotation delay angle α has occurred.

FIG. 4 shows the case where the rotation angle of the first gear 3 within N rotations is set, for example, when it is desired to set k rotations (where k ≦ N), the rotation direction is opposite to the rotation direction, that is, the rotation of the second gear 4 In the direction opposite to the direction 10, a mark 6, for example, a magnetic inductor, is provided at a position of 360 degrees × (k / N), that is, a reverse rotation angle θ
Set. By doing so, the N of the first gear 3
The rotation angle within the rotation can be detected. K does not necessarily have to be an integer.

The position of the nut in the ball screw is set at the end point (stroke end) of the rotating shaft 1, and at this time, the mark 5 of the first gear 3 and the mark 6 of the second gear 4 are used as observation points 7 serving as reference points. When it is desired to detect a signal at an arbitrary position between the start point and the end point, the position of the mark 6 which is a magnetic inductor is reset according to a calculation formula of reverse rotation angle θ = 360 degrees × k / N as shown in FIG. I just need.

In order to enable setting and detection of two or more points in this application, a plurality of coaxial bases are provided on the second gear 4, and a plurality of magnetic inductors 6 provided on the bases are marked. The magnetic sensors on the detection side have a multi-layer structure by being installed in multiple layers so that their rotation orbits do not coincide with each other. At this time, the magnet serving as the mark 5 placed on the first gear 3 has a height capable of supplying a magnetic force to each layer, whereby each rotation angle set for each layer is magnetically detected and output as an electric signal. Thus, the rotation angles at two or more points can be detected. FIG. 5 shows a schematic diagram in which marks 6 are provided in two stages. In this case, the magnet pieces 5a and 5b, which are the two marks 5, are provided on the first gear 3 so as to be vertically overlapped, and the two magnetic marks 6 having different heights are provided on the second gear 4. An inductor 6a and a magnetic inductor 6b are provided. These magnetic inductors 6 a and 6 b are provided so as to be able to arbitrarily change the positions of the magnetic inductors 6 a and 6 b according to the rotation angle detected on the second gear 4. Note that a reference point 8 is provided on the second gear 4. On the second gear 4, a support frame 11 on which the magnetic sensors 7a and 7b are positioned on a straight line when the marks 5 and 6 come to the closest positions due to the rotation of the two gears is located on the side of the second gear 4. It is erected from the department.

[0019]

As described above, by adopting the mechanism of the present invention, the ball screw housed in the case, which cannot be seen from the outside, rotates, and the nut screwed to the ball screw shaft is straightened. In the moving mechanism, the position of the nut, which cannot be seen, can be accurately confirmed by monitoring the moving position of an element outside the case which is directly connected to the nut. Conventionally, for the electrical detection of the start point, end point (stroke end), or any setting and position within the control range, the setting of a projection called a dock and a limit switch between a linearly moving mechanism element and its corresponding detector Was possible with the installation. However, when the position of the nut was closed from the outside, it could not be confirmed. For example, in a transmission mechanism in which the movement of the nut is linked to other control systems and hydraulic systems and the final output shaft is not directly related to the position of the nut, it is required to confirm the position of the nut by rotating the ball screw. However, confirmation was not easy, and in such a case, the ball screw and the nut were sometimes damaged. One of the causes of the damage was that the shaft was rotated with excessive torque because the detection was ambiguous even at the end of the stroke, and the guide surfaces of both the shaft and the nut, balls and the like were damaged. In the present invention, this can be easily prevented. Further, in the present invention,
In order to enable confirmation of stroke end, setting of arbitrary rotation angle, and electrical detection of these on the input shaft side of the ball screw,
Conventionally, the detection device is attached to the element on the output shaft side that moves linearly. However, since this is performed on the input shaft side, the mechanical design on the output shaft side is simplified, and the work space is expanded.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating an embodiment of the present invention.

FIG. 2 is a diagram schematically illustrating another embodiment of the present invention.

FIG. 3 is a diagram schematically illustrating the principle of the present invention.

FIG. 4 is a diagram schematically illustrating another principle of the present invention.

FIG. 5 is a perspective view showing an embodiment in which the present invention is applied to a ball screw.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotation axis 2 Rotation axis 3 1st gear 4 2nd gear 5 Mark 6 Mark 7 Observation point 8 Reference point 9 Rotation direction 10 Rotation direction 11 Support frame 12 Ball screw rotation axis α Delay angle θ Reverse rotation angle

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01B 21/22 G01B 7/30 G01B 5/24

Claims (6)

(57) [Claims] 1. A first gear 3 that rotates about a rotation shaft 1 to be detected and a second gear 4 that meshes with the first gear 3 and rotates about a rotation shaft 2. The first gear 3 and the second gear 3
The ratio of the number of teeth of each tooth of the gear 4 is (N + L) to N (where N is an integer and L is ± 1), and a mark 5 and a tooth portion of the second gear 4 are provided near the tooth portion of the first gear 3. Marks 6 are provided on the vicinity, respectively, and two marks 5 and a point where the marks 6 coincide on a straight line connecting the rotation axis 1 and the rotation axis 2 are set as a starting point, and from the starting point, the rotation of the rotation axis 1 to be detected is performed. Rotate the first gear 3,
In principle, when the second gear 4 rotates, the two marks 5 and 6 coincide again on a straight line.
An observation point 7 for observing that the two marks 5 and 6 have matched with each other is a second gear 4 on a line connecting the rotation shaft 1 and the rotation shaft 2.
And a reference point 8 is provided near the tooth portion of the second gear 4,
A rotation angle detecting mechanism for a rotation axis of N rotation strokes or less of N rotation strokes, wherein the mark 6 can be set to a position displaced from the reference point 8 by an arbitrary rotation angle. 2. The mark 5 of the first gear 3 is a magnet, the second gear 4
2. The rotation angle detecting mechanism according to claim 1, wherein the mark is formed by a magnetic inductor and the observation point is formed by a magnetic sensor. 3. The N rotation stroke of claim 1, wherein the mark 5 of the first gear 3 is formed by an optical transmitter, the mark 6 of the second gear 4 is formed by a slit, and the observation point 7 is formed by a light receiving sensor. A rotation angle detection mechanism that is equal to or less than N rotations of the rotation shaft. 4. A laser emitting port and a laser light receiving sensor are arranged in parallel at an observation point 7, a mark 6 of the second gear 4 is a slit, a mark 5 of the first gear 3 is a reflector, and the laser reflected light is received. 2. The rotation angle detecting mechanism according to claim 1, further comprising means for electrically detecting arrival at the sensor. 5. The mechanism according to claim 1, wherein the rotation angle of the rotation shaft 1 to be detected is smaller than the rotation angle at the time of N rotation, which is the measurable rotation angle, at the time of k rotation. When L = -1 from the reference point 8 on the second gear 4 in the direction opposite to the rotation direction,
In the case of = + 1, a mark 6 is provided at the rotational position on the second gear 4 which has been rotated k / N in the same direction as the rotational direction. mechanism. 6. The mechanism according to claim 2, wherein the first gear 3 joined to the rotating shaft 1 to be detected and the mark 5 are provided with any one of a magnet, an optical transmitter or a laser emitting port. And a magnetic gear, a slit or a laser receiving sensor corresponding to the mark 5 on a second gear 4 meshing with the first gear 3 or on a rotating base provided coaxially with the rotating shaft 2 of the second gear. A plurality of marks 6 of one kind are arranged, and the marks 6 are stacked in multiple layers.
A plurality of rotation angle detection mechanisms of N rotations or less of the rotation axis of the rotation stroke.