Patent Description:
The rotational positioning device generally has an input shaft into which a driving force such as a motor is input and an output shaft on which a rotational table for loading a machining work and the like of a machine tool is mounted. An angle detector such as an encoder is installed to the input shaft or output shaft, and the angle detector detects an angle change amount due to rotation of the rotational table. The rotational positioning device controls a driver and a motor based on the detected angle change amount to rotate and position the rotational table at a target angle position.

Patent Literature <NUM> discloses a roller turret cam index device. The roller turret cam index device includes a roller gear and a roller gear cam that are meshed with each other. The roller gear and the roller gear cam are rotatably provided around two rotation axial lines that three-dimensionally cross. In this roller turret cam index device, an encoder, which is a rotation angle detector, is fixed to the housing by an adapter. The input shaft of the encoder is connected to the roller gear shaft of the roller gear by a coupling so as not to be relatively rotatable to the roller gear shaft. Thereby, the encoder detects the rotation of the roller gear shaft. The value detected by the encoder represents the rotation stop position of the roller gear, that is, the index position.

Patent Literature <NUM> discloses a rotational table device. The rotational table device includes: a circular table on which a work is loaded; a rotational shaft for supporting the rotary table; a frame for rotatably supporting the rotational shaft; and a motor accommodated between the frame and the rotational shaft. When the motor is driven, the circular table, together with the rotational shaft, rotates about the rotational shaft axial line, with respect to the frame, and the angle position of the circular table is determined. The rotational shaft is composed of two shaft members. Both the shaft members are combined in a state in which their axial lines are aligned, and are connected by a screw member. There is an annular space between the frame and the rotational shaft, and the space is provided with a motor, a thrust bearing, a radial bearing, and a rotation detector. The rotation detector includes an encoder for detecting a rotation amount of the rotational shaft and an object to be detected by the encoder. The encoder provided on the frame detects the object to be detected separately provided on one of the shaft members of the rotational shaft. Thus, based on the detection signal from the encoder, the rotation amount of the rotational shaft is detected.

Patent Literature <NUM> discloses a machine tool including a processing head which can be positioned along three translation axes which are directed so as to be diagonal to one another, a slewing gear which can slew around a horizontal pivot, a work-piece positioning device which is rotatable around a rotation axis directed perpendicularly to the horizontal pivot, and a measurement frame, which is additionally provided on the slewing gear, can slew together with the slewing gear, and has constituents of a first position measuring system measuring a spatial position of the processing head and constituents of a second position measuring system measuring a spatial position of the work-piece positioning device.

Patent Literature <NUM> discloses a code wheel for a rotary encoder including, in a central portion, a hole into which a rotary shaft of a rotary member is fitted and a code portion including a radial code pattern in a circumferential edge portion.

Patent Literature <NUM> discloses a measuring arrangement calibrated for determining rotational positions of a rotary device that has a first part and a second part which can be rotated relative to the first part about a rotational axis.

Patent Literature <NUM> discloses an electron-beam recording device including a scale having graduations formed to indicate the rotational angular position of a turntable, and at least three read heads arranged at predetermined relative angles on a circumference on the center of rotation of the turntable, for individually reading the graduations to generate read signals.

Patent Literature <NUM> discloses an encoder system including a signal processing circuit including a first position data detection circuit that detects first position data representing positional displacement in rotation of an input shaft, a second position data detection circuit that detects second position data representing positional displacement in rotation of an output shaft, a position data combination circuit that combines the first and second position data to generate combined position data representing the number of rotations of the input shaft and the positional displacement within one rotation of the input shaft, and a position data comparing and collating circuit that compares and collates the first and second position data. Patent Literature <NUM> discloses a wheel bearing device with a rotation detector for use in an automotive vehicle of a type equipped with an anti-lock brake system.

The roller turret cam index device of Patent Literature <NUM> has the encoder externally installed. This increases the size of the roller turret cam index device by the volume of the encoder and further leads to higher cost. The device of Patent Literature <NUM> has such problems. In addition, the encoder externally installed generates an offset between the rotation axial line of the encoder input shaft and the rotation axial line of the roller gear shaft, during assembly in connecting the encoder input shaft and the roller gear shaft. The offset is also called a center deviation. The influence of the assembly error caused by this center deviation generates an error in angle change amount, of the roller gear, detected by the encoder. The influence further generates an error in the target angle position of the roller gear. The device of Patent Literature <NUM> also has such problems. Furthermore, although the roller gear is generally hollow, the encoder externally installed structurally blocks one of the hollow openings. This does not allow the roller gear to pass the cables, hydraulic parts, and the like through the hollow. The device of Patent Literature <NUM> also has such a problem.

A rotational table device of Patent Literature <NUM> has a rotational shaft composed of two shaft members. Both the shaft members are combined with their axial line aligned. However, as in Cited Document <NUM>, a center deviation is generated during assembly in combining the two shaft members. In addition, a center deviation is generated during assembly in separately providing an object to be detected on one of the shaft members of the rotational shaft. The influence of the assembly errors caused by these center deviations generates an error in the angle change amount, of the rotational shaft, detected by the rotation detector. The influence further generates an error in the target angle position of the rotational shaft. The device of Patent Literature <NUM> has such problems. Further, the raceway surface of the bearing is separately provided on the rotational shaft. The assembly error during assembly in separately providing the raceway surface generates an error in the angle change amount, of the rotational shaft, detected by the rotation detector. The influence further generates an error in the target angle position of the rotational shaft. The device of Patent Literature <NUM> also has such problems.

Therefore, an object of the present invention is to solve the above-mentioned problems to provide a rotational positioning device capable of positioning a rotational angle at a target angle position with high precision.

According to one aspect of the present invention is a rotational positioning device as defined by independent claim <NUM>.

According to a specific example of the present invention, the rotational positioning device is configured such that the graduated scale is integrally formed with the rotational member in a radial direction with respect to the rotational member axial line or a direction parallel to the rotational member axial line.

According to a specific example of the present invention, the rotational positioning device is configured such that at least one seat is provided in the housing, and each of the at least one sensor is installed in a corresponding seat of each sensor so as to define a position of each sensor and a gap between each sensor and the scale marks.

According to a specific example of the present invention, the rotational positioning device is configured such that the at least one seat is provided in the housing via a sensor flange.

According to a specific example of the present invention, the rotational positioning device is configured such that a rotational member hole for passing at least a part of the rotational member is provided in the sensor flange, and a central axis line of the rotational member hole is aligned with the rotational member axial line.

According to a specific example of the present invention, the rotational positioning device is configured such that the at least one seat is two or more seats provided along the circumferential direction of the rotational member, the two or more seats are provided such that distances from the rotational member axial line are the same and distances between adjacent seats are the same, the at least one sensor is two or more sensors, and each of the two or more sensors is installed in any one of the two or more seats.

According to a specific example of the present invention, the rotational positioning device further includes a bearing for supporting rotation of the rotational member with respect to the housing, wherein a raceway surface of the bearing is integrally formed with the rotational member.

According to a specific example of the present invention, the rotational positioning device is configured such that the graduated scale is integrally formed with a part of the rotational member accommodated in the housing.

According to a specific example of the present invention, the rotational positioning device is configured such that the rotational member is an output shaft, a rotational table is provided at an end part of the output shaft, and the graduated scale is integrally formed with a part of the output shaft, the part being adjacent to the rotational table.

According to a specific example of the present invention, the rotational positioning device, having the rotational member that is an input shaft, further includes an output shaft rotatable about an output shaft axial line, the output shaft having a transmission mechanism installed along a circumferential direction of the output shaft, wherein the input shaft comes into contact with the transmission mechanism, and thereby the output shaft can rotate with rotation of the input shaft.

According to the present invention, the rotational positioning device can detect the angle change amount of the rotational member with high precision, and can further position the rotational member at the target angle position with high precision.

Oher objects, features, and advantages of the present invention will become apparent from the following description of the embodiments of the present invention taken in conjunction with the accompanying drawings.

Embodiments according to the present invention will be described with reference to drawings. However, the present invention is not limited to those embodiments.

First, with reference to <FIG>, the rotational positioning device <NUM> is to be described according to some embodiments of the present invention. <FIG> show cross-sectional views of the rotational positioning device <NUM>. The rotational positioning device <NUM> includes: a housing <NUM>; a rotational member <NUM> rotatable about a rotational member axial line <NUM>; and at least one sensor <NUM>, installed in the housing <NUM>, serving as an angle detector. In <FIG>, although the rotational member <NUM> is entirely accommodated in the housing <NUM>, at least a part of the rotational member <NUM> may be accommodated in the housing <NUM>. A graduated scale <NUM> having a plurality of scale marks is integrally formed with the rotational member <NUM> along the circumferential direction of the rotational member <NUM>.

As shown in <FIG>, the scale marks of the graduated scale <NUM> may be formed integrally with the rotational member <NUM> in the radial direction with respect to the rotational member axial line <NUM> along the circumferential direction of the rotational member <NUM>. Alternatively, as shown in <FIG>, the scale marks of the graduated scale <NUM> may be integrally formed with the rotational member <NUM> in a direction parallel to the rotational member axial line <NUM>. The scale marks may be formed integrally with the rotational member <NUM> in a gear shape, or may be a linearly engraved rotational member <NUM>. Further, the scale marks are not limited to ones that can be visually recognized, and any scale marks may be used as long as they allow the sensor <NUM> to read a predetermined positional interval on the graduated scale <NUM> as an interval for one scale mark. The graduated scale <NUM> may be integrally formed with the rotational member <NUM> along the circumferential direction of any part of the rotational member <NUM>. For example, the graduated scale <NUM> may be formed on a lower part of the rotational member <NUM> as shown in <FIG> and <FIG>, or may be formed on an upper part of the rotational member <NUM> as shown in <FIG>. Further, the graduated scale <NUM> may be formed on a part of the rotational member <NUM> inside the housing <NUM> as shown in <FIG> and <FIG>, or may be formed in a part of the rotational member <NUM> outside the housing <NUM> as shown in <FIG>.

When the rotational member <NUM> is an output shaft in the rotational positioning device <NUM>, a rotational table <NUM> is provided at the end part of the rotational member <NUM> serving as the output shaft, as shown in <FIG>. When the rotational member <NUM> rotates about the rotational member axial line <NUM>, the rotational table <NUM> rotates accordingly. As shown in <FIG> and <FIG>, the graduated scale <NUM> may be integrally formed with a part of the rotational member <NUM>, serving as an output shaft, accommodated in the housing <NUM>. The graduated scale <NUM> may be formed on the lower part of the rotational member <NUM>, or may be formed on the upper part of the rotational member <NUM>. Thus, integrally forming the graduated scale <NUM> on the rotational member <NUM> serving as the output shaft allows detecting the angle change amount of the rotational table <NUM> with high precision. Then, this allows positioning the rotational table <NUM> at the target angle position with high precision. As shown in <FIG>, the rotational member <NUM> may be provided with a transmission mechanism <NUM>. Via the transmission mechanism <NUM>, driving force from an input shaft may be transmitted to rotate the rotational member <NUM> serving as the output shaft. Further, the rotational member <NUM> may be configured without any transmission mechanism <NUM>. With such a configuration, a driving device such as a motor may be directly connected to the rotational member <NUM> to rotate the rotational member <NUM>.

The graduated scale <NUM> may be integrally formed with a part of the rotational member <NUM>, serving as an output shaft, adjacent to the rotational table <NUM>. For example, as shown in <FIG>, the graduated scale <NUM> may be integrally formed with a part of the rotational member <NUM>, serving as an output shaft, between the housing <NUM> and the rotational table <NUM>. Thus, forming the graduated scale <NUM> integrally with the rotational member <NUM>, serving as an output shaft, so as to be adjacent to the rotational table <NUM> allows detecting the angle change amount of the rotational table <NUM> with further high precision. Then, this allows positioning the rotational table <NUM> at the target angle position with high precision.

The principle of the sensor <NUM> is not particularly limited as long as the sensor can read the scale marks of the graduated scale <NUM>. Examples of the sensor <NUM> include an optical sensor, a magnetic sensor, a coil, and the like. For example, when an optical sensor is installed as the sensor <NUM>, in order to change the light reflection state and transmission state, a linearly engraved part on the rotational member <NUM> may be integrally formed with the rotational member <NUM> to form scale marks. When a magnetic sensor is installed as the sensor <NUM>, in order to change the magnetic poles, a part configured in a gear shape on the rotational member <NUM> may be integrally formed with the rotational member <NUM> to form scale marks. The sensor <NUM> then reads a graduated scale <NUM> having a plurality of scale marks integrally formed with the rotational member <NUM> along the circumferential direction of the rotational member <NUM>. Thereby, the angle change amount due to rotation of the rotational member <NUM> is detected based on the plurality of scale marks. Thus, integrally forming the graduated scale <NUM> on the rotational member <NUM>: can reduce the influence of the center deviation due to the graduated scale <NUM>; allows the rotational positioning device <NUM> to detect the angle change amount of the rotational member <NUM> with high precision; and then allows the rotational member <NUM> to be positioned at a target angle position with high precision. In addition, this can make the rotational positioning device <NUM> compact, reduce the number of parts thereof, and reduce the cost thereof.

The housing <NUM> is provided with at least one seat <NUM> for installing at least one sensor <NUM>. When two or more seats <NUM> are provided in the housing <NUM>, the respective seats <NUM> are provided along the circumferential direction of the rotational member <NUM>. Here, the respective seats <NUM> are also provided so as to be equal in the distance from the rotational member axial line <NUM> of the rotational member <NUM>, and to be equal in the distance to adjacent seat(s) <NUM>. Each of the sensors <NUM> is installed in any of two or more seats <NUM>. Not all the seats <NUM> need to have the sensors <NUM> installed thereon, and there may be a configuration in which only some of the seats <NUM>, as an option, have the sensors <NUM> installed thereon. Each sensor <NUM> is installed in its corresponding seat <NUM> to define the position of each sensor <NUM> with respect to the rotational member <NUM> and to define a gap <NUM> (P) between each sensor <NUM> and the scale marks of the graduated scale <NUM>. The seat <NUM> guarantees a gap <NUM> (P) and determines the distance of each sensor <NUM> from the rotational member axial line <NUM> of the rotational member <NUM>. Thus, installing two or more sensors <NUM> determines the distance between two adjacent sensors <NUM>, and guarantees the position (Q) for each sensor <NUM> to read the scale marks of the graduated scale <NUM>. As a result, the sensor <NUM> and the graduated scale <NUM> are positioned with respect to the rotational member axial line <NUM> of the rotational member <NUM>. This allows the rotational positioning device <NUM> to detect the angle change amount of the rotational member <NUM> with high precision; this then allows the rotational member <NUM> to be positioned at a target angle position with high precision.

The rotational positioning device <NUM> may further include a bearing <NUM> for supporting the rotation, of the rotational member <NUM>, with respect to the housing <NUM>. The raceway surface <NUM> of the bearing <NUM> may be integrally formed with the rotational member <NUM> as shown in <FIG>. As result, the sensor <NUM>, the graduated scale <NUM>, and the bearing <NUM> are positioned with respect to the rotational member axial line <NUM> of the rotational member <NUM>. This allows the rotational positioning device <NUM> to detect the angle change amount of the rotational member <NUM> with high precision; this then allows the rotational member <NUM> to be positioned at a target angle position with high precision. Further, as shown in <FIG>, the central axis line of the inner diameter (D1) of the housing <NUM> part corresponding to the raceway surface <NUM> is aligned with the rotational member axial line <NUM> of the rotational member <NUM>. In <FIG>, although the radial bearing 111a, the first thrust bearing 111b, and the second thrust bearing 111c are provided as the bearing <NUM>, the configuration of the bearing is not limited thereto. Any configuration is allowed as long as the raceway surface <NUM> of the bearing <NUM> is integrally formed with the rotational member <NUM>.

<FIG> relate to the rotational positioning device <NUM> of the embodiment shown in <FIG>, in which the rotational member102 is used as an output shaft, and a rotational table <NUM> is provided at an end part of the rotational member <NUM> serving as an output shaft. The graduated scale <NUM> has a plurality of scale marks at substantially equal intervals. The graduated scale <NUM> are formed integrally with the rotational member <NUM> in the radial direction with respect to the rotational member axial line <NUM> along the circumferential direction of the rotational member <NUM>. Further, the rotational positioning device <NUM> may further include a second rotational member <NUM> rotatable about a second rotational member axial line <NUM>. In the rotational positioning device <NUM> of <FIG>, there is employed a roller gear cam mechanism having a rotational member <NUM> serving as an output shaft and a second rotational member <NUM> serving as an input shaft. Here, the second rotational member <NUM> is a cam that has a screw-shaped cam rib and is rotatable about the second rotational member axial line <NUM>. The rotational member <NUM> is rotatable about the rotational member axial line <NUM> orthogonal to the second rotational member axial line <NUM>. A plurality of bearings included in the transmission mechanism <NUM> are arranged on the rotational member <NUM> along the circumferential direction thereof. A motor <NUM> is connected to the second rotational member <NUM>. The motor <NUM> is driven to rotate the second rotational member <NUM> about the second rotational member axial line <NUM>. This transmits the input torque of the cam to the rotational member <NUM> via the plurality of bearings included in the transmission mechanism <NUM>, and rotates the rotational member <NUM> about the rotational member axial line <NUM>. Each of the plurality of bearings included in the transmission mechanism <NUM> may be in a rolling contact with the cam rib of the second rotational member <NUM>, or may be a roller follower or a cam follower. Further, the plurality of bearings included in the transmission mechanism <NUM> each include a shaft member, an outer ring part rotatable along the outer peripheral surface of the shaft member, and the like. Further, each of the plurality of bearings may be a bearing with rolling contact including rollers and the like between the shaft member and the outer ring part, or may be a bearing with sliding contact not including rollers and the like. In this case, the shaft member may be directly fitted to the rotational member <NUM>.

In <FIG>, although the second rotational member <NUM> serving as the input shaft is a drum-shaped cam, it may be a cylindrical cam (barrel cam) or a globoidal cam. Further, the second rotational member <NUM> serving as the input shaft and the rotational member <NUM> serving as the output shaft are in a circumscribed positional relationship. However, depending on the shape of the cam of the second rotational member <NUM> serving as the input shaft, the one rotational member may be in an inscribed positional relationship to the other rotational member. Further, the roller gear cam mechanism is employed in the rotational positioning device <NUM> of <FIG>. However, any mechanism is allowed as long as it can transmit the input torque of the second rotational member <NUM> to the rotational member <NUM> via the transmission mechanism <NUM>. For example, a barrel cam mechanism may be employed, or a gear mechanism may be employed.

At least one seat <NUM> may be provided in the housing <NUM> via a sensor flange <NUM> shown in <FIG>. In other words, the sensor <NUM> is installed in the housing <NUM> via the seat <NUM> provided in the sensor flange <NUM>. <FIG> shows the shape of the sensor <NUM> to be installed on the seat <NUM> of the sensor flange <NUM>. The sensor flange <NUM> is provided with a rotational member hole <NUM> for passing at least a part of the rotational member <NUM>. As shown in <FIG>, the central axis line <NUM> of the rotational member hole <NUM> is aligned with the rotational member axial line <NUM> of the rotational member <NUM>. The central axis line of the inner diameter (D2) of the housing <NUM> part corresponding to the sensor flange <NUM> is also aligned with the rotational member axial line <NUM> of the rotational member <NUM>, as shown in <FIG>. As a result, the central axis line of the inner diameter (D2) is also aligned with the central axis line <NUM> of the rotational member hole <NUM>. Thus, installing the sensor <NUM> in the housing <NUM> via the sensor flange <NUM> causes the sensor flange <NUM> to determine the position of the sensor <NUM>. This facilitates adjusting the position of the sensor <NUM> even after assembling the rotational positioning device <NUM>. There is an installation surface of the sensor flange <NUM> for installing the sensor flange <NUM> on the housing <NUM>. The sensor flange <NUM> defines the distance (A) from this installation surface to the sensor <NUM> installed on the sensor flange <NUM>, and guarantees a gap <NUM> (P). Further, the sensor flange <NUM> defines the distance (B) of the seat <NUM> from the central axis line <NUM> of the rotational member hole <NUM>. The sensor flange <NUM> also defines the position (C) of the seat <NUM> in the circumferential direction of the rotational member hole <NUM>. Thereby, the sensor flange <NUM> guarantees the position (Q) in which the sensor <NUM> reads the scale marks of the graduated scale <NUM>. Further, the sensor flange <NUM> may be provided with a cable hole <NUM>. Then, a cable may be connected to the sensor <NUM> via the cable hole <NUM> to receive a signal, detected by the sensor <NUM>, regarding the angle change amount due to rotation of the rotational member <NUM>.

As shown in <FIG> and <FIG>, the housing <NUM> may be provided with a seal flange <NUM>. Then, the sensor flange <NUM> and the seal flange <NUM> may provide a sensor and cable installation space <NUM> therebetween. A seal <NUM> may be provided between the rotational member <NUM> and the sensor flange <NUM> to prevent the lubricant from entering the sensor and cable installation space <NUM>. Alternatively, the seal <NUM> may be provided between the rotational member <NUM> and the seal flange <NUM> to isolate the sensor and cable installation space <NUM> from the external space.

<FIG> relate to the rotational positioning device <NUM> of the embodiment shown in <FIG>, and are substantially the same as those of <FIG>. However, the different point is, as shown in <FIG>, that a graduated scale <NUM>, having a plurality of scale marks at substantially equal intervals, is formed integrally with the rotational member <NUM> in a direction parallel to the rotational member axial line <NUM> along the circumferential direction of the rotational member <NUM>. Further, according to the formed graduated scale <NUM>, the shape of the sensor flange <NUM> is changed as shown in <FIG>, and the shape of the sensor <NUM> is changed as shown in <FIG>.

The rotational positioning device <NUM> may be capable of detecting the angle change amount due to the rotation of the rotational table <NUM> for loading the machining works and the like of the machine tool. Therefore, the graduated scale <NUM> may be integrally formed with the second rotational member <NUM> serving as the input shaft shown in <FIG> and <FIG>. In this case, as shown in <FIG>, the rotational positioning device <NUM> includes: a housing <NUM>; a second rotational member <NUM> rotatable about a second rotational member axial line <NUM>; and at least one sensor <NUM> serving as an angle detector installed in the housing <NUM>. A graduated scale <NUM> having a plurality of scale marks is integrally formed with the second rotational member <NUM> along the circumferential direction of the second rotational member <NUM>. As shown in <FIG>, the scale marks of the graduated scale <NUM> may be formed integrally with the second rotational member <NUM> in the radial direction with respect to the second rotational member axial line <NUM> along the circumferential direction of the second rotational member <NUM>. Alternatively, as shown in <FIG>, the scale marks may be integrally formed with the second rotational member <NUM> in a direction parallel to the second rotational member axial line <NUM>. The rotational positioning device <NUM> further includes a rotational member <NUM> serving as an output shaft rotatable about a rotational member axial line <NUM>. A transmission mechanism <NUM> is installed on the rotational member <NUM>, serving as an output shaft, along the circumferential direction of the rotational member <NUM>. Then, the second rotational member <NUM>, serving as the input shaft, is in contact with the transmission mechanism <NUM>. Therefore, as the second rotational member <NUM> rotates, the rotational member <NUM> serving as the output shaft can rotate. Note that, in this case, the rotational member <NUM> does not necessarily need a graduated scale <NUM> formed thereon, and both the rotational member <NUM> and the second rotational member <NUM> may have the graduated scales <NUM> formed thereon.

Thus integrally forming the graduated scale <NUM> on the input shaft can reduce the size of the rotational positioning device <NUM>. Further, when the angle transmission precision between the input shaft and the output shaft is good, installing an angle detector on the input shaft allows a lower precision than installing an angle detector on the output shaft. For example, when the reduction ratio between the input shaft and the output shaft is <NUM> and the target positioning precision of the output shaft is <NUM> bits (<NUM>°/<NUM><NUM>), installing an angle detector on the output shaft directly needs <NUM>-bit precision. On the other hand, installing the angle detector on the input shaft can lower the precision by <NUM> bits (<NUM> = <NUM><NUM>), that is, <NUM> bits can achieve the same precision, and this can reduce the cost.

<FIG> each show an enlarged view of the inside of the rotational positioning device <NUM> according to the embodiment shown in <FIG>. The size of the rotational positioning device <NUM> is changed according to the application. However, regardless of the size, the rotational positioning device <NUM> just has a graduated scale <NUM> formed integrally with the rotational member <NUM>, and a sensor <NUM> installed along the circumferential direction of the rotational member <NUM>, in the same manner as the above described. This allows creating a rotational positioning device <NUM> that is not limited in size.

<FIG> shows an example of positioning precision with respect to a command position when there is no center deviation between the rotational member <NUM> and the graduated scale <NUM>. <FIG> shows an example of positioning precision with respect to the command position when there is a center deviation between the rotational member <NUM> and the graduated scale <NUM>. These examples are specific examples showing that integrally forming the graduated scale <NUM> on the rotational member <NUM> has improved the positioning precision. The positioning precision is based on the command position, which is the target angle position of the rotational member <NUM> serving as an output shaft. Specifically, the positioning precision has improved by about <NUM> arcsec, from a maximum of about <NUM> arcsec to a maximum of about <NUM> arcsec.

<FIG> is a cross-sectional view of a rotational positioning device <NUM> having: a graduated scale <NUM> integrally formed with a part of the rotational member <NUM> accommodated in a housing <NUM>; and a sensor <NUM> installed in a sensor and cable installation space <NUM> in the housing <NUM>. <FIG> shows a rotational positioning device when an angle detector is externally attached. In the rotational positioning device of <FIG>, an external encoder <NUM> serving as an angle detector is fixed to a housing via an installation base <NUM>. The external encoder <NUM> has a fitting shaft <NUM> connected to an output shaft via an encoder collar <NUM> and an extension flange <NUM>. On the other hand, in the rotational positioning device <NUM> of <FIG>, the sensor <NUM> is installed and the graduated scale <NUM> is formed, in the space which is a dead space in the conventional configuration. This can make the rotational positioning device <NUM> more compact than the conventional one, reduce the number of parts, and reduce the cost.

The rotational positioning device <NUM> may employ the angle detector that is an angle detector with a self-calibration function as disclosed in Patent Literature <NUM> to <NUM>. One angle detector with a self-calibration function as shown in <FIG>, due to its configuration, has a plurality of sensors <NUM> arranged along the circumferential direction of the rotational member <NUM>. Each of the plurality of sensors <NUM> reads a graduated scale <NUM> having a plurality of scale marks integrally formed with the rotational member <NUM> in the radial direction with respect to the rotational member axial line <NUM> along the circumferential direction of the rotational member <NUM>. Thereby, the angle change amount due to rotation of the rotational member <NUM> is detected based on the plurality of scale marks. <FIG> shows the positioning precision for scale mark numbers calculated from the angle change amount detected by each of the plurality of sensors <NUM>. Based on the angle change amount detected by each of the plurality of sensors <NUM>, there is calculated a calibration curve that eliminates the angle error shown in <FIG>. Then, the angle error based on this calibration curve is subtracted from the angle change amount of one representative sensor <NUM>, so that there can be calculated the true angle change amount due to the rotation of the rotational table <NUM>. Thus, employing the angle detector with a self-calibration function allows detecting the angle change amount of the rotational table <NUM> with high precision. Then, this allows positioning the rotational table <NUM> at the target angle position with high precision. Note that although the number of sensors is eight in <FIG>, the number may be two or more.

Further, another angle detector with a self-calibration function as shown in <FIG> has, due to its configuration, a plurality of sensors <NUM> arranged along the circumferential direction of the rotational member <NUM>. Each of the plurality of sensors <NUM> reads a graduated scale <NUM> having a plurality of scale marks integrally formed with the rotational member <NUM> in the direction parallel to the rotational member axial line <NUM> along the circumferential direction of the rotational member <NUM>. Thereby, the angle change amount due to rotation of the rotational member <NUM> is detected based on the plurality of scale marks. The angle detector with a self-calibration function as shown in <FIG> can also obtain the same result as in <FIG> and <FIG>. Note that although the number of sensors is five in <FIG>, the number may be two or more.

<FIG> shows an example of a positioning control method using a rotational positioning device <NUM> in which a graduated scale <NUM> is formed integrally with a rotational member <NUM> serving as an output shaft. <FIG> shows an example of a positioning control method using a rotational positioning device <NUM> in which a graduated scale <NUM> is integrally formed with a second rotational member <NUM> serving as an input shaft. In the rotational positioning device <NUM>, when the input shaft rotates as shown by an arrow, the rotational angle of the input shaft is transmitted, the output shaft rotates as shown by an arrow, and a rotational table <NUM> also rotates accordingly. A sensor <NUM> serving as an angle detector detects the angle change amount due to the rotation of the output shaft or the input shaft based on a plurality of scale marks of the graduated scale <NUM>. The angle change amount is communicated to a controller or driver <NUM> for driving a motor <NUM> as a reference angle for positioning the rotational table <NUM>. The controller or driver <NUM> controls the motor <NUM> according to the difference between the target angle position and the reference angle, and positions the rotational table <NUM> at the target angle position with high precision.

Claim 1:
A rotational positioning device(<NUM>), comprising:
a housing (<NUM>) ;
a rotational member (<NUM>) rotatable about a rotational member axial line (<NUM>), at least a part of the rotational member (<NUM>) being accommodated in the housing (<NUM>); and
at least one sensor (<NUM>) installed in the housing,
wherein in order to rotate the rotational member (<NUM>), a motor is connected to the rotational member (<NUM>), or the rotational member (<NUM>) has a transmission mechanism (<NUM>) installed along a circumferential direction of the rotational member (<NUM>), driving force being transmitted to the rotational member (<NUM>) via the transmission mechanism (<NUM>); and
wherein a graduated scale (<NUM>) having a plurality of scale marks is integrally formed with the rotational member (<NUM>) along a circumferential direction of the rotational member (<NUM>), the at least one sensor (<NUM>) detects an angle change amount due to rotation of the rotational member (<NUM>) based on the plurality of scale marks, and the rotational member (<NUM>) is to be positioned at a target angle position based on the angle change amount,
characterized in that the rotational positioning device (<NUM>) further comprises a sensor flange (<NUM>) installed in the housing (<NUM>), a circular rotational member hole (<NUM>) being provided in the sensor flange (<NUM>), the at least one sensor (<NUM>) installed on the sensor flange (<NUM>);
wherein at least a portion of the rotational member (<NUM>) is housed within the rotational member hole (<NUM>), whereby a central axis line (<NUM>) of the rotational member hole (<NUM>) is aligned with the rotational member axial line (<NUM>) such that a position of the at least one sensor (<NUM>) to the graduated scale (<NUM>) is determined; and
wherein a first seal (<NUM>) is provided between the sensor flange (<NUM>) and the rotational member (<NUM>) to prevent a lubricant from entering a space (<NUM>) where the at least one sensor (<NUM>) is installed.