JP2006271189A - Gear motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gear motor in which an establishment of a mechanical origin of gear motor can be quickly performed. <P>SOLUTION: A motor encoder 6 is mounted to a motor shaft 2a of a gear motor 1, and original position is detected by its Z-phase signal. On an output shaft 4 of a reducer 3 is mounted an absolute value encoder 7 with such an accuracy that it is possible to recognize the number of revolutions of the motor shaft, and its absolute rotation positions are detected. At the time when the first Z-phase signal along with the rotation of the motor shaft 2a during starting or the like, mechanical origin where both the motor shaft 2a and the output shaft 4 are positioned at the point of origin can be determined, based on absolute rotation positions of a reducer output shaft 4 obtained from the absolute value encoder 7. A time required to determine the mechanical origin can be shorter than usual, and extra rotating operations can be avoided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a geared motor, and more particularly to a geared motor that can quickly and accurately detect the mechanical starting point of the output shaft of a reduction gear when starting the motor.

  A geared motor configured to output the output rotation of a motor through a speed reducer with high transmission accuracy is used in a drive portion that requires high positioning accuracy in an industrial robot, a machine tool, or the like. As shown in FIG. 11, the geared motor 101 is connected to the motor main body 102, the speed reducer 103 coaxially connected to the motor shaft 102 a of the motor main body 102, and the output side of the speed reducer 103 coaxially. Output shaft 104. As the speed reducer 103, for example, a wave gear speed reducer is used.

  In the geared motor 101, in order to perform positioning and the like with high accuracy, it is necessary to control the rotation angle of the output shaft 104 of the speed reducer 103 with high accuracy. For this purpose, a motor encoder 106 is attached to the motor shaft 102a, and an origin sensor 107 is attached to the output shaft 104.

  In the signal processing circuit 108, the output shaft 104 has a desired rotation angle based on the A, B and Z phase signals obtained from the motor encoder 106 and the origin signal S of one pulse per revolution obtained from the origin sensor 107. A command is issued to the motor driver 109 so that The motor driver 109 rotates the motor shaft 102a according to the received command.

  Here, in the geared motor 101, the rotational angle position is controlled based on the mechanical starting point of the output shaft 104. Therefore, at the time of starting or the like, it is necessary to return the output shaft 104 to the mechanical starting point (origin position).

  However, the conventional geared motor has a problem that it takes a lot of time for such a return to origin operation. That is, as shown in FIG. 12, in the origin return operation of the output shaft 104, the motor shaft 102a is rotated until the origin signal is output from the origin sensor 107 attached to the output shaft 104 (first operation). The motor shaft 102a is reversely rotated to return the output shaft 104 to the rotation angle position immediately before the origin signal is output (second operation), the motor shaft 102a is rotated forward again, and the first after the origin signal is output. It is necessary to stop at the rotational position where the Z-phase signal is output (third operation).

  In such an operation, it is necessary to rotate the motor shaft 102a by the rotation angle corresponding to the reduction gear ratio of the reduction gear at the maximum. For example, when the reduction ratio is 1:50, it is necessary to rotate the motor shaft 102a by 50 rotations, that is, 18000 degrees (50 × 360 degrees), which takes time.

  An object of the present invention is to propose a geared motor capable of quickly and accurately performing an operation of establishing a mechanical starting point.

  In order to solve the above-described problems, the present invention provides a motor with a gear having a configuration in which a speed reducer is connected to a motor shaft, and a motor encoder that outputs A, B, and Z phase signals as the motor shaft rotates. An output-side absolute value encoder for detecting the absolute rotational position of the output shaft of the speed reducer, and a drive for obtaining a mechanical starting point of the motor shaft and the output shaft based on detection values of the motor encoder and the output-side encoder A control circuit, wherein the absolute value encoder has a precision capable of detecting a rotation angle of the output shaft per one rotation of the motor shaft.

  Here, the drive control circuit calculates the mechanical starting point based on the absolute rotation position obtained from the output-side absolute value encoder at the time of generation of the first Z-phase signal obtained from the motor encoder at the time of starting the motor. It is characterized by doing.

  In the present invention, the absolute rotational position of the reduction gear output shaft is detected by the absolute value encoder. Therefore, based on the absolute rotational position of the reducer output shaft at the time when the first Z-phase signal generated along with the rotation of the motor shaft at the time of starting the motor is obtained, the motor shaft and the output shaft are both located at the origin. The starting point can be obtained. In other words, the mechanical starting point can be obtained by simply rotating the motor shaft by 360 degrees at the maximum (just by rotating it once). Therefore, the time required for obtaining the mechanical starting point can be shortened compared to the conventional case, and an extra rotational operation is required. Can be avoided.

  Next, the drive control circuit according to the present invention reverses the motor shaft at a first speed and a first operation for rotating the motor shaft at a first speed until the first Z-phase signal is output. A second operation for returning to the angular position immediately before the Z-phase signal is output, and a third operation for stopping the motor shaft when the Z-phase signal is output by rotating the motor shaft forward at a third speed. Is performed to return the motor shaft to the mechanical starting point.

  Here, in a geared motor, even if the motor shaft (reducer input shaft) is fixed due to backlash or twist, it rotates by a small angle when a load torque is applied to the output shaft of the decelerator. The output-side absolute value encoder has a predetermined detection error, and a value obtained by adding a small angle thereto is an error that is expected when the number of rotations N of the motor shaft is determined. Therefore, when determining the number of rotations of the motor shaft from the detection position of the output-side absolute value encoder attached to the output shaft, the number of rotations of the motor shaft cannot be obtained accurately unless the error is taken into consideration. That is, when the number of rotations of the motor shaft is calculated by dividing the detected value of the output side absolute value encoder by the rotation angle of the output shaft per rotation of the motor shaft, before and after the switching point of the number of rotations of the motor shaft In this case, the calculated number of rotations of the motor shaft may be different from the actual number of rotations of the motor shaft due to the influence of errors.

  Therefore, in the present invention, a non-determination zone larger than the above error is assumed in the rotation angle range of the output shaft including the switching point of the number of rotations of the motor shaft, and in the rotation angle range of the output shaft other than the rotation angle range, The number of rotations of the motor shaft can be calculated without being affected by an error so that a Z-phase signal is generated every rotation of the motor shaft.

That is, in the present invention, the rotation angle of the output shaft per rotation of the motor shaft is θ, the number of rotations of the motor shaft is N, and Δ is a value larger than an error included in the detected value of the output-side absolute value encoder. Then, the rotational position P of the output shaft at the time when the Z-phase signal is generated is predetermined so as to be within the following range.
θ (N−1) + Δ ≦ P ≦ θN−Δ

In this case, the drive control circuit obtains the number of rotations N of the motor shaft using the relationship and the detection angle of the output-side absolute value encoder, and when the number of rotations N and the Z-phase signal are generated. Using the rotation angle p of the motor shaft and the gear ratio R of the speed reducer, the position Px of the output shaft can be calculated as follows.
Px = (N × 360 ° + p) / R

  In the present invention, when the speed reducer is coaxially connected to the tip of the motor shaft and the motor encoder is disposed at the rear end of the motor shaft, the motor shaft is coaxially connected from the output shaft. The absolute encoder on the output side can be arranged at the rear end of the rotating shaft that extends through the rear end of the rotary shaft. Of course, the output-side absolute value encoder can be arranged at the tip of the output shaft.

  Next, the geared motor of the present invention detects the absolute rotational position of the output shaft of the reduction gear connected to the input absolute encoder and the motor shaft for detecting the absolute rotational position of the motor shaft. Output side absolute value encoder, and a drive control circuit for obtaining a mechanical starting point of the motor shaft and the output shaft based on detection values of the input side absolute value encoder and the output side absolute value encoder, and the output The side absolute value encoder is characterized by having an accuracy capable of detecting a rotation angle of the output shaft per one rotation of the motor shaft.

  Even in this case, when the number of rotations of the motor shaft is determined from the detection position of the output-side absolute value encoder attached to the output shaft, the number of rotations of the motor shaft cannot be obtained accurately unless the above-described error is taken into consideration.

Therefore, in the drive control circuit of the present invention, the rotation angle of the output shaft per rotation of the motor shaft is θ, the number of rotations of the motor shaft is N, and Δ is an error included in the detection value of the absolute encoder on the output side. Assuming that the value is larger, the rotation start point is determined as follows according to the detection position Pa of the output-side absolute value encoder and the detection position p of the input-side absolute value encoder at the start of rotation of the motor shaft. The number of rotations Na of the motor shaft is calculated.
(1) In the case of θ (N−1) + Δ ≦ Pa ≦ θN−Δ, the actual number of rotations Na of the motor shaft is determined as N.
(2) In the case of θ (N−1) ≦ Pa <θ (N−1) + Δ If p <pn, the number of rotations Na is N,
If p> pn, the number of rotations Na is set to (N-1).
However, pn is a predetermined value.
(3) In the case of θN−Δ <Pa ≦ θN If p> pn, the number of rotations Na is N,
If p <pn, the number of rotations Na is set to (N + 1).

Further, the output shaft position Px can be calculated as follows using the rotation number Na thus determined, the detection position p of the input-side absolute value encoder, and the gear ratio R of the reduction gear. it can.
Px = (Na × 360 ° + p) / R

  Instead of calculating the number of rotations Na in this way, it is determined whether or not the detection position Pa of the output-side absolute value encoder at the time of starting the rotation of the motor shaft is within the range of (1) above. In this case, the actual number of rotations Na of the motor shaft is determined to be N, and if it is out of the range, after the motor shaft is rotated to a position where the detection position Pa is within the range, The number of rotations Na of the motor shaft may be determined to be N.

  Here, when the speed reducer is coaxially connected to the tip of the motor shaft and the input side absolute value encoder is arranged at the rear end of the motor shaft, the motor shaft is connected to the output shaft. The output-side absolute value encoder can be arranged at the rear end portion of the rotating shaft that extends in the coaxial state and extends to the rear end side. Of course, the output-side absolute value encoder can be arranged at the tip of the output shaft.

  In the geared motor of the present invention, the absolute rotational angle position of the output shaft of the reduction gear is detected. Therefore, the mechanical starting point of the output shaft can be obtained based on the origin position of the motor shaft. Therefore, compared with the conventional case where the mechanical starting point is established by actually detecting the origin positions of both axes, the mechanical starting point can be quickly obtained, and unnecessary rotating operation can be omitted. Further, since the number of rotations of the motor shaft is calculated in consideration of the error included in the detection value of the output side absolute value encoder, the mechanical starting point can be obtained with high accuracy.

  Next, in the geared motor of the present invention, the absolute rotation angle positions of both the output shaft and the motor shaft of the speed reducer are detected, so that the rotational operation for obtaining the mechanical starting point of these shafts is unnecessary. There is an advantage of becoming. Further, since the number of rotations of the motor shaft is calculated in consideration of the error included in the detection value of the output side absolute value encoder, the mechanical starting point can be obtained with high accuracy.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram showing a geared motor to which the present invention is applied. The geared motor 1 includes a motor main body 2, a wave gear reducer 3 coaxially connected to a motor shaft 2a extending from the tip of the motor main body 2, and a wave gear reducer 3 coaxially connected to the tip of the wave gear reducer 3. And an output shaft 4.

  The wave gear reducer 3 is, for example, a cup-type wave gear reducer, and is fitted into an annular rigid internal gear, a cup-type flexible external gear disposed on the inside thereof, and the inside thereof. And an elliptical wave generator (not shown), and by rotating the wave generator, the meshing position of the flexible external gear with respect to the rigid internal gear moves in the circumferential direction. A relative rotation corresponding to the difference in the number of teeth between the internal teeth and the external teeth occurs. Usually, the rigid internal gear is fixed, and the cup-type flexible external gear is rotated at a reduced speed, and is rotated at a reduced speed from the output shaft 4 connected to the thick boss formed on the bottom of the cup. Is output. Of course, the present invention can be similarly applied to a type other than a wave gear reducer, such as a planetary gear reducer or a cyclo reducer (registered trademark).

  A rotating shaft 5 that rotates integrally with the output shaft 4 is coaxially connected to the output shaft 4. The rotating shaft 5 passes through the wave gear reducer 3 and the motor shaft 2a in a concentric state, extends to the rear end side, and protrudes rearward from the rear end opening of the motor shaft 2a.

  A motor encoder 6 is attached to the rear end portion of the motor shaft 2a. As the motor shaft 2a rotates, the motor encoder 6 outputs A-phase and B-phase signals having a phase difference of 90 degrees, and a Z-phase signal indicating the origin position is output for one pulse every rotation. The An output-side absolute value encoder 7 is attached to the rear end portion of the rotary shaft 5 that rotates integrally with the output shaft 4. The output-side absolute value encoder 7 can detect the absolute rotation angle position within one rotation of the output shaft 4.

  The resolution of the output-side absolute value encoder 7 is set to a value that can detect the rotation speed of the output shaft 4. In this example, the rotation angle of the output shaft 4 per rotation of the motor shaft is set to the same value. For example, when the reduction ratio of the wave gear reducer 3 is 1:50, the resolution is set to 360 degrees / 50 = 7.2 degrees. From this absolute value encoder 7, an absolute position signal 7S indicating the absolute rotational position of the output shaft 4 is output.

  Detection signals from the motor encoder 6 and the output-side absolute value encoder 7 are respectively supplied to the drive control circuit 8. The drive control circuit 8 issues a position command to the motor driver 9 based on these detection signals. The motor driver 9 drives the motor body 2 so that the output shaft 4 is at a target rotational angle position corresponding to the position command.

  FIG. 2A is an operation explanatory view showing an operation of establishing a mechanical starting point when the geared motor 1 is started. When the power is turned on, the geared motor 1 drives the motor 2 via the motor driver 9 to return the motor shaft 2a to the origin position. That is, the motor shaft 2a is returned to the rotational position (origin position) where the Z-phase signal is first obtained from the motor encoder. This origin return operation is performed, for example, by rotating the motor shaft 2a at the first speed (first operation) until the first Z-phase signal is output, and then reversing the motor shaft 2a at the second speed. Return to the angular position immediately before the Z-phase signal is output (second operation), and then rotate the motor shaft 2a forward at the third speed again and stop the motor shaft 2a when the Z-phase signal is output. The operation procedure is (third operation). The third speed is extremely slow compared to the first speed.

  Here, when the first Z-phase signal is output, the absolute rotational angle position of the output shaft 4 obtained from the output-side absolute value encoder 7 is read. Since the rotation angle of the output shaft 4 per rotation of the motor shaft is known, the origin position of the output shaft 4 can be obtained from the absolute rotation position. For example, when the detected absolute rotational position is 72 degrees, the time point when the Z-phase signal is obtained by returning the motor shaft 2a by 10 rotations is the origin position of the output shaft 4.

  As described above, in this example, the mechanical starting points at which the motor shaft 2 a and the output shaft 4 are returned to the origin positions are obtained by using the output-side absolute value encoder 7 attached to the output shaft 4. Therefore, the operation of returning the output shaft 4 to the origin position becomes unnecessary, and accordingly, the time required for establishing the mechanical starting point can be shortened, and an extra rotation operation can be omitted. As shown in FIG. 2B, it is also possible to obtain the mechanical starting point by performing only the third operation.

  For example, when a galvano mirror is attached to the output shaft 4 and the galvano mirror is reciprocally rotated at a predetermined swing angle, conventionally, an end limit sensor has to be mounted on the output shaft 4. If the present invention is applied, it is not necessary to mount an end limit sensor, so there is an advantage that the apparatus can be configured compactly.

  As shown in FIG. 3, the absolute value encoder 7 can be attached to the tip of the output shaft 4.

  Here, in the drive control circuit 8 of this example, the number of rotations of the motor shaft 2a is calculated as follows. In general, in a geared motor, a reduction gear output shaft rotates by a small angle even when the motor shaft (input shaft to the reduction gear) is fixed due to the occurrence of backlash and twist. As a result, the number of rotations of the motor shaft may not be determined from only the detection value of the absolute value encoder (two-pole encoder) attached to the output shaft. That is, in a predetermined rotation angle range of the output shaft including the switching point of the number of rotations of the motor shaft, the number of rotations of the motor shaft cannot be determined only from the detection value of the absolute value encoder attached to the output shaft.

  That is, the geared motor 1 rotates by a small angle when load torque is applied to the output shaft 4 of the speed reducer 3 even when the motor shaft 2a (speed reducer input shaft) is fixed due to backlash or twist. The absolute value encoder 7 on the output side has a predetermined detection error, and a value obtained by adding a small angle to this becomes an error Δ that is expected when the number of rotations N of the motor shaft is determined. Therefore, when determining the number of rotations N of the motor shaft 2a from the detection position of the output-side absolute value encoder 7 attached to the output shaft, the number of rotations N of the motor shaft cannot be obtained accurately unless the error is taken into consideration. In other words, when the number of rotations N of the motor shaft 2a is calculated by dividing the detected value of the output-side absolute value encoder 7 by the rotation angle θ of the output shaft per rotation of the motor shaft, the rotation of the motor shaft 2a Before and after the switching point of the number of times, the calculated number of rotations N of the motor shaft may be different from the actual number of rotations of the motor shaft 2a due to the influence of errors.

  Therefore, in this example, as shown in FIG. 4, non-determination zones A1 and A3 larger than the above error are assumed in the rotation angle range of the output shaft 4 including the switching point of the number of rotations of the motor shaft 2a. In the rotation angle range A2 (determination zone) of the output shaft 4 other than the angle range, it is determined in advance so that a Z-phase signal is generated every rotation of the motor shaft, and the number of rotations N of the motor shaft 2a is set without being affected by errors. It can be calculated.

That is, if the rotation angle of the output shaft 4 per rotation of the motor shaft is θ, the number of rotations of the motor shaft is N, and Δ is a value larger than the error included in the detection value of the output side absolute value encoder 7, the Z-phase signal is The rotation position Pa of the output shaft 4 at the time of occurrence is predetermined so as to be within the following range.
θ (N−1) + Δ ≦ Pa ≦ θN−Δ

Therefore, the drive control circuit 8 can determine the number of rotations N of the motor shaft 2a from the detection value Pa of the output side absolute value encoder 7 without being affected by the error. Further, the position Px of the output shaft 4 is calculated as follows using the calculated number N of rotations, the rotation angle p of the motor shaft 2a when the Z-phase signal is generated, and the gear ratio R of the speed reducer. Can do.
Px = (N × 360 ° + p) / R

(Embodiment 2)
Next, FIG. 5 is a schematic configuration diagram showing another example of a geared motor to which the present invention is applied. Since the basic configuration of the geared motor 1A shown in this figure is the same as in FIG. 1, the corresponding parts are denoted by the same reference numerals, and description thereof is omitted.

  The motor with gear 1A of this example is different in that the input-side absolute value encoder 10 is attached to the motor shaft 2a. When the absolute value encoders 7 and 10 are arranged on both the shafts 2a and 4, when the power is turned on, the absolute rotation angle positions (signals 10S) of the respective shafts 2a and 4 obtained from the two absolute value encoders 7 and 10 are supplied. 7S), the mechanical starting point is immediately obtained. Therefore, a rotating operation for establishing a mechanical starting point at the time of starting or the like is not necessary.

  Here, also in the case of this example, when the number of rotations of the motor shaft 2a is determined from the detection position of the output-side absolute value encoder 7 attached to the output shaft 4, the motor shaft 2a can be accurately determined unless the aforementioned error is taken into consideration. The number of rotations cannot be determined.

Therefore, in the drive control circuit 8 of this example, the rotation angle of the output shaft 4 per rotation of the motor shaft is θ, the number of rotations of the motor shaft 2 a is N, and Δ is an error included in the detection angle of the output-side absolute value encoder 7. If the value is larger than that, the rotation start is performed as follows according to the detection position Pa of the output-side absolute value encoder 7 and the detection position p of the input-side absolute value encoder 10 at the start of rotation of the motor shaft 2a. The number of rotations Na of the motor shaft 2a at the time is calculated.
(1) In the case of θ (N−1) + Δ ≦ Pa ≦ θN−Δ, the actual number of rotations Na of the motor shaft is determined as N.
(2) In the case of θ (N−1) ≦ Pa <θ (N−1) + Δ If p <pn, the number of rotations Na is N,
If p> pn, the number of rotations Na is set to (N-1).
However, pn is a predetermined value as will be described later.
(3) In the case of θN−Δ <Pa ≦ θN If p> pn, the number of rotations Na is N,
If p <pn, the number of rotations Na is set to (N + 1).

Then, the position Px of the output shaft 4 is calculated as follows using the rotation number Na thus determined, the detection position p of the input-side absolute value encoder 10 and the gear ratio R of the reduction gear. The main drive is started.
Px = (Na × 360 ° + p) / R

  The determination method will be specifically described with reference to FIG. Since the output-side absolute value encoder 7 includes an error as described above, the detected value increases or decreases by an amount corresponding to the error centering on the detected value when there is no error indicated by the solid line L1 in FIG. Therefore, the detected value Pa varies within the range of dotted lines L2 and L3 drawn above and below the solid line L1.

  For this reason, the number of rotations N calculated from the detected value Pa of the output-side absolute value encoder 7 may not coincide with the actual number of rotations Na of the motor shaft 2a. That is, in the region indicated by the oblique line B1 in FIG. 4, the number of rotations of the motor shaft 2a is calculated to be one less (N-1). On the contrary, in the region indicated by the oblique line B3, it is calculated that the number of rotations is (N + 1) more. In other areas, the actual number of rotations can be calculated.

Here, in the hatched area B1, the detection value p of the input-side absolute value encoder 10 is small,
On the contrary, in the hatched area B3, the value is close to the maximum value pm. Therefore, in this example, in the area A1 including the oblique line B1, that is, in the case of (2) above, when the detected value p of the input-side absolute value encoder 10 is smaller than the predetermined value pn, the motor shaft 2a The number of rotations Na is determined to be N. Otherwise, the number of rotations is reduced by one (N-1) to prevent erroneous detection of the number of rotations. Similarly, in the region A3 including the oblique line B3, that is, in the case of (3) above, conversely, if the detected value p of the input-side absolute value encoder 10 is larger than a predetermined value pn, the motor shaft 2a The number of rotations Na is determined to be N. Otherwise, the number of rotations is increased by one (N + 1), thereby preventing erroneous detection of the number of rotations due to an error. In the area A2 between them, that is, in the case of the above (1), there is no possibility of erroneous detection due to an error, so the number of rotations is determined as N as it is.

  As the value pn, generally, a value that is half of the maximum value pm of the detection value p can be adopted. In the cases (2) and (3), it is also possible to adopt different values as the value of pn serving as a discrimination criterion.

  Next, the calculation control of the number of rotations can be performed with reference to a correspondence table created in advance as shown in FIG. 6, for example. The correspondence table is an area determination table assigned in advance to each position of the output shaft 4. As shown in FIG. 7, the odd-numbered areas correspond to the rotation angle range of the output shaft 4 including the switching point of the rotation number of the motor shaft 2a, and these areas are non-determination zones larger than the above error. This corresponds to the cases (2) and (3) above. The even-numbered area is a determination zone and corresponds to the case (1) above.

  FIG. 8 shows a flow of calculation control of the number of rotations performed with reference to the correspondence table. In the determination zone, the value obtained by dividing the corresponding area number by “2” is the number of rotations (steps ST1 → ST2, 3 → ST4 → ST5). If it is in the non-determination zone, the detected value p of the input side absolute value encoder 10 is referred to. If the value is larger than pm / 2, the value obtained by subtracting “1” from the area number is “2”. The value obtained by dividing is used as the number of rotations (steps ST1 → ST2, 3 → ST4 → ST6, 7 → ST8). On the other hand, when the detected value p is smaller than pm / 2, the value obtained by dividing the value obtained by adding “1” to the area number by “2” is used as the number of rotations (steps ST1 → ST2, 3 → S4 → ST6, 7 → ST9).

  Here, when the detected value Pa of the output-side absolute value encoder 7 at the time of starting rotation of the motor shaft 2a is in the non-determination zone, the motor shaft 2a is rotated and the detected value Pa becomes a value in the determination zone. The drive control may be performed as described above.

Next, when calculating the number of rotations Na as described above, the angle reproducibility of the output-side absolute value encoder 7 is ± 360 / (R × 4) [°, where R is the gear ratio of the speed reducer 3. ]is necessary. However, if the following method is adopted, the rotation number Na can be accurately calculated even when the angle reproducibility of the output-side absolute value encoder 7 is half the value, that is, ± 360 / (R × 2) [°]. .
The meaning of each symbol in the following description is as follows.
Ri: Resolution of input-side absolute value encoder 10 Ro: Resolution of output-side absolute value encoder 7 Air: Actual absolute value of input-side absolute value encoder 10 (0 to (Ri-1))
Ait: Temporary absolute value of input-side absolute value encoder 10 (0 to (Ri-1))
Ao: absolute value of the output-side absolute value encoder 7 (0 to (Ro-1))
Rg: Reduction gear reduction ratio Na: Actual number of rotations (0 to (Rg-1))
Nt: Temporary number of rotations (0 to (Rg-1))

  This will be described with reference to FIGS. 9 and 10. First, in the geared motor 1A, the temporary absolute value Ait of the input-side absolute value encoder 10 with respect to the absolute value Ao of the output-side absolute value encoder 7 at a known temperature, torque, and speed is measured. Thereafter, a temporary rotation number Nt is assigned to each absolute value of the output-side absolute value encoder 7 (step ST11 in FIG. 10).

  By storing these pieces of information in the nonvolatile memory of the drive control circuit 8, for each absolute value Ao of the output-side absolute value encoder 7, a temporary absolute value Ait of one input-side absolute value encoder 10 and One provisional rotation number Nt can be obtained. However, the actual absolute value Air of the input-side absolute value encoder 10 with respect to the absolute value Ao of the output-side absolute value encoder 7 varies depending on operating conditions such as temperature, torque, and speed, and the invariance is not related.

  Therefore, after reading the absolute value Ait corresponding to the absolute value Ao and the number of rotations Nt from the nonvolatile memory (step ST12 in FIG. 10), the absolute value Ait and Ri / 2 are compared (step ST13 in FIG. 10). When the absolute value Ait is smaller than Ri / 2, (Ait + Ri / 2) is compared with the actual absolute value Air (step ST14 in FIG. 10). When the value of (Ait + Ri / 2) is equal to or less than the absolute value Air, the number of rotations Na is set to (Nt−1) (step ST15 in FIG. 10). Otherwise, the number of rotations Na is set to Nt (step ST16 in FIG. 10).

  On the other hand, if the absolute value Ait is greater than or equal to Ri / 2, the value of (Ait−Ri / 2) is compared with the absolute value Air (step ST17 in FIG. 10). When the value of (Ait−Ri / 2) is equal to or less than the absolute value Air, the rotation number Na is set to Nt (step ST18 in FIG. 10). Otherwise, the rotation number Na is set to (Nt + 1) (step ST19 in FIG. 10).

By doing so, the actual absolute value Air of the input-side absolute value encoder 10 with respect to the absolute value Ao of the output-side absolute value encoder 7 is obtained from the temporary absolute value Ait.
± ((Ri / 2)-(Ri / (Ro / Rg)))
Even if it changes only, it is possible to accurately calculate the actual number of rotations Na.

It is a schematic block diagram of the geared motor which concerns on Embodiment 1 to which this invention is applied. It is operation | movement explanatory drawing which shows the operation | movement which calculates | requires the mechanical starting point in the motor with a gear of FIG. It is operation | movement explanatory drawing which shows the operation | movement which calculates | requires the mechanical starting point in the motor with a gear of FIG. It is a schematic block diagram which shows another structural example of a motor with a gear. It is explanatory drawing which shows the method for calculating the rotation frequency of a motor shaft. It is a schematic block diagram which shows the structural example of the motor with a gear which concerns on Embodiment 2 to which this invention is applied. It is explanatory drawing which shows the area determination for calculating the frequency | count of rotation of the motor shaft in the motor with a gear of FIG. It is explanatory drawing which shows the method for calculating the rotation frequency of the motor shaft in the motor with a gear of FIG. It is explanatory drawing which shows the calculation flow of the rotation frequency of the motor shaft in the motor with a gear of FIG. It is explanatory drawing which shows another method for calculating the rotation frequency of the motor shaft in the motor with a gear of FIG. It is explanatory drawing which shows the calculation flow of the method for calculating the rotation frequency of the motor shaft of FIG. It is a schematic block diagram of the conventional geared motor. It is operation | movement explanatory drawing which shows the establishment operation | movement of the mechanical starting point of the conventional motor with a gear.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor with gear 2 Motor body 2a Motor shaft 3 Wave gear reducer 4 Output shaft 6 Motor encoder 7, 10 Absolute value encoder 8 Drive control circuit 9 Motor driver

Claims (13)

A motor encoder that outputs A, B and Z phase signals as the motor shaft rotates;
An absolute encoder on the output side for detecting the absolute rotational position of the output shaft of the speed reducer connected to the motor shaft;
A drive control circuit for obtaining a mechanical starting point of the motor shaft and the output shaft based on detection values of the motor encoder and the output absolute value encoder;
The geared motor, wherein the output-side absolute value encoder has an accuracy capable of detecting a rotation angle of the output shaft per one rotation of the motor shaft. In claim 1,
The drive control circuit calculates the mechanical start point based on a detection angle of the output-side absolute value encoder at the time of generation of the first Z-phase signal obtained from the motor encoder after the start of rotation of the motor shaft. A geared motor. In claim 2,
The drive control circuit performs a first operation of rotating the motor shaft forward at a first speed until the first Z-phase signal is output, and reverses the motor shaft at a second speed to generate a Z-phase signal. A home return operation including a second operation for returning to the angular position immediately before the output and a third operation for rotating the motor shaft forward at a third speed and stopping the motor shaft when a Z-phase signal is output. A geared motor, wherein the motor shaft is returned to the mechanical starting point. In claim 2,
When the rotation angle of the output shaft per one rotation of the motor shaft is θ, the number of rotations of the motor shaft is N, and Δ is a value larger than an error included in the detection value of the output-side absolute value encoder, the Z-phase signal The geared motor is characterized in that the rotation position P of the output shaft at the time of occurrence of the occurrence of the rotation is predetermined so as to be within the following range.
θ (N−1) + Δ ≦ P ≦ θN−Δ In claim 4,
The drive control circuit obtains the number of rotations N of the motor shaft from the detection angle of the output-side absolute value encoder,
Using the rotation number N, the rotation angle p of the motor shaft at the time when the Z-phase signal is generated, and the gear ratio R of the speed reducer, the position Px of the output shaft is calculated as follows. Features a geared motor.
Px = (N × 360 ° + p) / R In any one of claims 1 to 5,
The speed reducer is connected coaxially to the tip of the motor shaft,
The motor encoder is arranged at the rear end of the motor shaft;
The geared motor, wherein the output-side absolute value encoder is disposed at a rear end portion of a rotary shaft that extends coaxially from the output shaft to the rear end side. In any one of claims 1 to 5,
The speed reducer is connected coaxially to the tip of the motor shaft,
The motor encoder is arranged at the rear end of the motor shaft;
A geared motor, characterized in that the output-side absolute value encoder is arranged at the tip of the output shaft. An absolute encoder on the input side for detecting the absolute rotational position of the motor shaft;
An absolute encoder on the output side for detecting the absolute rotational position of the output shaft of the speed reducer connected to the motor shaft;
A drive control circuit for obtaining a mechanical starting point of the motor shaft and the output shaft based on detection values of the input-side absolute value encoder and the output-side absolute value encoder;
The geared motor, wherein the output-side absolute value encoder has an accuracy capable of detecting a rotation angle of the output shaft per one rotation of the motor shaft. In claim 8,
In the drive control circuit,
When the rotation angle of the output shaft per one rotation of the motor shaft is θ, the number of rotations of the motor shaft is N, and Δ is a value larger than an error included in the detection value of the output-side absolute value encoder,
Depending on the detection position Pa of the output-side absolute value encoder at the start of rotation of the motor shaft and the detection position p of the input-side absolute value encoder, the rotation of the motor shaft at the start of rotation is as follows. A geared motor characterized by calculating the number of times Na.
(1) In the case of θ (N−1) + Δ ≦ Pa ≦ θN−Δ, the actual number of rotations Na of the motor shaft is determined as N.
(2) In the case of θ (N−1) ≦ Pa <θ (N−1) + Δ If p <pn, the number of rotations Na is N,
If p> pn, the number of rotations Na is set to (N-1).
However, pn is a predetermined value.
(3) In the case of θN−Δ <Pa ≦ θN If p> pn, the number of rotations Na is N,
If p <pn, the number of rotations Na is set to (N + 1). In claim 9,
The drive control circuit uses the rotation number Na obtained as described above, the detection position p of the input-side absolute value encoder, and the gear ratio R of the speed reducer as follows, and outputs the position Px of the output shaft as follows. A geared motor characterized by calculating
Px = (Na × 360 ° + p) / R In claim 7,
In the drive control circuit,
When the rotation angle of the output shaft per one rotation of the motor shaft is θ, the number of rotations of the motor shaft is N, and Δ is a value larger than the error included in the detection value of the output-side absolute value encoder, Determining whether or not the detection position Pa of the output-side absolute encoder at the start of rotation is within the following range;
θ (N−1) + Δ ≦ Pa ≦ θN−Δ
If it is within the range, the actual number of rotations Na of the motor shaft is determined to be N,
In the case of out of the range, the actual number of rotations Na of the motor shaft is determined to be N after the motor shaft is rotated to a position where the detection position Pa is within the range. . In any one of claims 8 to 11,
The speed reducer is connected coaxially to the tip of the motor shaft,
The input side absolute value encoder is arranged at the rear end of the motor shaft,
The geared motor, wherein the output-side absolute value encoder is disposed at a rear end portion of a rotary shaft that extends coaxially from the output shaft to the rear end side. In any one of claims 8 to 11,
The speed reducer is connected coaxially to the tip of the motor shaft,
The input side absolute value encoder is arranged at the rear end of the motor shaft,
A geared motor, characterized in that the output-side absolute value encoder is arranged at the tip of the output shaft.

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