JPH08313298A - Apparatus and method for detecting origin position - Google Patents

Abstract

PURPOSE: To detect an origin by the simplest constitution of a pair of dogs and an origin sensor which eliminates a special construction even when an operating range of a rotary shaft exceeds 360 deg.. CONSTITUTION: The rotation of a driving source for diving a rotary shaft of a robot or the like is transmitted to the rotary shaft via a mechanism of a fractional acceleration/deceleration ratio. The rotary shaft is rotated in a CW direction or CCW direction in accordance with states of a dog and a sensor for detecting the presence/absence of the dog (steps S1-S4). When a positional relation between the dog and the sensor becomes equal (step S7), the rotary shaft is rotated in the CCW direction, and with the utilization of the fact that a count of pulses of an encoder fitted to the driving source becomes different by a controlling point of view, an origin can be detected at every rotational angular position even when a rotating range of the rotary shaft exceeds 360 deg. (steps S10-S13).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an origin position detecting device for a rotary shaft of a robot or the like, and more particularly to a shaft that rotates more than one revolution and a detecting method therefor.

[0002]

2. Description of the Related Art The structure of a conventional rotary shaft is roughly classified into the following two types. (1) When the drive source and the rotary shaft have the same axis, the rotation of the motor serving as the drive source is directly transmitted to the rotary shaft via a speed reducer or the like.

FIG. 10 shows a rotary shaft in the case where the drive source and the rotary shaft have the same axis as a conventional example. (2) When the drive source and the rotary shaft have different axes, the rotation of the motor serving as the drive source is transmitted to the rotary shaft via a pair of belts and pulleys, a pair of gears, or the like. Figure 11
Fig. 3 shows a rotary shaft in the case where the drive source and the rotary shaft have different axes as a conventional example.

[0004]

As described above, the conventional examples of the origin position detecting device for the rotary shaft in the above-mentioned two configurations are as follows: (1) When the drive source and the rotary shaft have the same axis 1). The method of detecting the dog attached to the origin sensor with the origin sensor The method of determining only by ON / OFF depending on the presence / absence of the dog in the origin sensor is the most general and simple origin position detection device, and is advantageous in terms of cost and space. . However, when the rotation shaft rotates one or more times, there is a portion where the positional relationship between the origin sensor and the dog is the same. Therefore, in this method, the operating range of the rotating shaft is less than one rotation (360 °).

2). Method of detecting with a delay dog attached to the rotary shaft A dog is provided which is rotated by following a certain angle delay with respect to the rotation of the rotary shaft. As a result, even if the operating range of the rotary shaft is one rotation (360 °) or more, the operating range of the dog is less than one rotation (360 °). There is a method of detecting this dog by an origin sensor. However, this method has many methods such as Japanese Patent Laid-Open No. 62-282892, but all of them have problems such as a complicated dog structure and a large space.

3). Method of Providing Absolute Position Detecting Means of Rotation Angle on Rotating Shaft There is a method of mounting an absolute position detecting encoder or the like on the rotating shaft. By detecting the absolute position of the rotation axis and the rotation angle from the reference position, the rotation operation range can be one rotation (36
It is possible to detect the origin position in the case of 0 ° or more. However, in this case, the configuration of the signal processing circuit for detecting the rotation angle becomes complicated. Also, many detection means such as sensors must be arranged. Further, there are many technical and cost problems such as the need for an expensive encoder for absolute position detection.

(2) When the drive source and the rotary shaft have different axial cores, in this case, the rotary shaft side is moved by means such as making the number of teeth of the pulley on the drive side larger than the number of teeth of the pulley on the rotary shaft. A mechanism for increasing the speed is provided so that the drive shaft does not rotate once but the rotating shaft rotates one or more rotations. By providing a general origin detection mechanism that detects the dog attached to the rotary shaft on the drive side with the origin sensor, it becomes possible to detect the origin position of the rotary shaft operating range of one rotation (360 °) or more. .

However, in this case, there is a precision problem that backlash occurs in the speed increasing mechanism on the drive shaft side and the rotating shaft side, and an error in origin detection due to the speed increase is increased by the speed increasing ratio. . Furthermore, there is a problem that the space of the entire rotary shaft mechanism becomes large due to the different shaft cores.

Therefore, the problem to be solved by the present invention is that even when the operating range of the rotary shaft exceeds 360 °,
Origin detection is performed by the simplest pair of dog and origin sensor configuration that does not require a special structure.

[0010]

[Means for Solving the Problems] and

As a structure for solving the problems of the present invention, claim 1 is a device for detecting the origin position of a rotary shaft having an operation range of one rotation or more, for driving the rotary shaft. Detecting the origin at all positions within the operating range by the first pulse and the second pulse generated by the drive source, the dog on the rotation axis and the sensor for detecting the presence or absence of the dog. Is an origin position detecting device.

A second aspect of the present invention is the origin position detecting device according to the first aspect, wherein the acceleration / deceleration ratio of the drive source and the rotary shaft is a fraction. Accordingly, if the rotation direction is different and the dog position is the same, the origin position can be detected by capturing the positional relationship with the reference second pulse.

A third aspect of the present invention is the origin position detecting device according to the first aspect, wherein the dog is fixed at an arbitrary position of the rotary shaft. In this case, the dog is an origin position detection device that rotates integrally with the rotation shaft.

According to a fourth aspect of the present invention, there is provided means for counting the first pulse and means for comparing the counted value with a preset reference value while the rotary shaft rotates in a predetermined range. The origin position detecting device according to claim 1.

According to a fifth aspect of the present invention, the reference value is the first value from when the dog starts rotating right or left from a predetermined position to when the second pulse is first detected. 5. The origin position detecting device according to claim 4, wherein the count values are the left and right count values of the pulse. As a result, it was possible to specifically express that the angles formed were different even if the dog positions were the same.

According to a sixth aspect of the present invention, the second pulse is first detected after the dog starts rotating right or left from a predetermined position while the rotation shaft rotates in a predetermined range. The origin position detecting device according to claim 4, characterized in that This allowed the conditions for comparison with the reference value to be the same.

A seventh aspect of the present invention is the origin position detecting apparatus according to the fourth aspect, wherein the first pulse is a pulse emitted by the drive source with a predetermined resolution as the drive source rotates. This made it possible to obtain the most basic signal for detecting the origin position.

According to an eighth aspect of the present invention, the origin position detecting device according to the fourth aspect is characterized in that the second pulse is a pulse generated by the drive source every one rotation. This makes it possible to obtain a signal that serves as a reference for rotation, even if the rotation shaft does not have a special configuration for grasping the rotation angle.

As another configuration for solving the same problem, a ninth aspect of the present invention is a device for detecting the origin position of a rotary shaft having an operation range of one rotation or more, which drives the rotary shaft. The first pulse and the second pulse generated by the driving source for
The origin position detecting method is characterized in that the origin is detected at all positions within the operating range by the pulse of, the dog on the rotation axis, and the sensor for detecting the presence or absence of the dog.

A tenth aspect of the present invention is the origin position detecting method according to the ninth aspect, wherein the acceleration / deceleration ratio of the drive source and the rotary shaft is a fraction. Accordingly, if the rotation direction is different and the dog position is the same, the origin position can be detected by capturing the positional relationship with the reference second pulse.

The eleventh aspect of the present invention is the origin position detecting method according to the ninth aspect, wherein the dog is fixed at an arbitrary position of the rotary shaft. In this case, the dog is an origin position detection device that rotates integrally with the rotation shaft.

According to a twelfth aspect of the present invention, the first pulse is counted while the rotating shaft rotates in a predetermined range, and the counted value is compared with a preset reference value. 9 is the origin position detection method.

According to a thirteenth aspect of the present invention, the reference value is the first value from when the dog starts rotating right or left from a predetermined position to when the second pulse is first detected.
13. The origin position detection method according to claim 12, wherein the count values are the left and right count values of the pulse. As a result, it was possible to specifically express that the angles formed were different even if the dog positions were the same.

According to a fourteenth aspect of the present invention, the second pulse is first detected after the dog starts rotating right or left from a predetermined position while the rotation shaft rotates in a predetermined range. 13. The origin position detecting method according to claim 12, characterized in that This allowed the conditions for comparison with the reference value to be the same.

According to a fifteenth aspect of the present invention, the origin position detecting method according to the twelfth aspect is characterized in that the first pulse is a pulse emitted by the drive source with a predetermined resolution in accordance with the rotation. This made it possible to obtain the most basic signal for detecting the origin position.

According to a sixteenth aspect of the present invention, the origin position detecting method according to the twelfth aspect is characterized in that the second pulse is a pulse generated by the drive source every one rotation. This makes it possible to obtain a signal that serves as a reference for rotation, even if the rotation shaft does not have a special configuration for grasping the rotation angle.

[0026]

【Example】

(Embodiment 1) An embodiment of the present invention will be described in detail below with reference to FIGS.

First, the structure of the apparatus will be described with reference to FIGS.

FIG. 1 is a sectional view of the center of a main part of a rotary shaft at the tip of a robot according to an embodiment of the present invention.

FIG. 2 is a view taken along the line XX in FIG. 1 as an embodiment of the present invention.

In FIGS. 1 and 2, a rotary shaft 1 is a shaft for mounting a robot hand, for example, and is fixed to a spacer 2, a large pulley 3 and a flange 9, and a bearing incorporated in a main body arm 4. It is rotatably supported by 5. The rotation of the drive motor 6 is transmitted to the large pulley 3 via the small pulley 7 and the timing belt 8 to rotate the rotating shaft 1. The flange 9 is provided with a vertical hole (not shown) for fixing the inverted U-shaped stopper pin 14, and a groove is radially formed from the hole.
The ball 15 is incorporated in the slot 16a of the block 16 so as to be free to move (move while rolling inside the slot 16a) within a certain rotation angle range with respect to the rotating shaft 1. In addition, on the upper part of the block 16, the stopper pin 1
A nib groove 16b is provided so as not to interfere with the block 16 when the 4 rotates. The niger groove 16b is connected at a portion where the position overlaps with the slotted groove 16a. The dog 10 and the stopper pin 14 are the flange 9
Is fixed to and rotates integrally with the rotary shaft 1. Block 16
, The stopper pin 14 moves between the nig groove 16b,
It is attached to the tooth flange 11 fixed to the main body arm 4 so that the ball 15 assembled in the slot 16a abuts on the ball. Origin sensor 1
Reference numeral 3 is attached to a flange 11 fixed to the body arm 4 via a bracket 12. That is, when the drive motor 6 rotates, the rotation shaft 1 rotates by an angle (θ) reduced by the tooth number ratio of the small pulley 7 and the large pulley 3, and the dog 10 also rotates by the same angle (θ). The origin sensor 13 is fixed and is attached at a position where the operation of the dog 10 can be detected.

As a premise of this embodiment, the positional relationship in the rotation direction between the origin sensor 13 and the dog 10 at the origin position is shown in FIG.
The state is shown in. And rotary shaft 1 (dog 10 is the same)
The rotation angle range of is the origin position (θ = 0
°), and the stopper pin 14, the ball 15, the block 16, the slotted groove 1 so that the rotation range is ± (180 ° + α).
The structure is such that the operation can be mechanically limited by the 6a and the relief groove 16b. However, α is an overrun angle which is a small angle of α = 2 ° to 10 °. Further, the dog 10 has a semicircular shape occupying a range of 180 ° as shown in FIG.

Next, referring to FIGS. 3 to 8, the rotation axis 1 is θ = ±.
The operations of the dog 10 and the origin sensor 13 when rotated in the range of (180 ° + α) will be described.

FIG. 3 is an operation explanatory view as one embodiment of the present invention (rotation angle θ of the rotary shaft 1 = − (180 ° +
position of α)).

FIG. 4 is an explanatory view of the operation as one embodiment of the present invention (position of the rotation angle θ of the rotary shaft 1 = −180 °).

FIG. 5 is an explanatory view of the operation as one embodiment of the present invention (position of the rotation angle θ of the rotary shaft 1 = 0 °: origin position).

FIG. 6 is an explanatory view of the operation as one embodiment of the present invention (position of the rotation angle θ of the rotary shaft 1 = + 180 °).

FIG. 7 is a diagram for explaining the operation as one embodiment of the present invention (the rotation angle θ of the rotary shaft 1 = + (180 ° +
position of α)). In addition, as shown in FIG. 5, the rotation of θ is + (plus) in the CW direction and − (minus) in the CCW direction.

FIG. 8 is a diagram showing the relationship between the rotation angle of the rotary shaft 1 and the operation of the origin sensor 13 as one embodiment of the present invention.

(1) Relationship between Rotation Angle of Rotating Shaft 1 (Dog 10) and Operating State of Origin Sensor 13 The origin sensor 13 turns on when the dog 10 is detected and turns off when it is not detected. When the rotary shaft 1 rotates in the CW direction from the origin position (θ = 0 °) and rotates in the direction of Fig. 5 → Fig. 6 → Fig. 7, and vice versa, it rotates in the CCW direction as shown in Fig. 5 → Fig. 4 → Fig. 3. FIG. 8 shows an ON / OFF state of the origin sensor 13 at the time of performing. That is, the range in which the origin sensor 13 is ON is: θ = −180 ° to − (180 ° + α) (area of) θ = 0 ° to + 180 ° (area of) The range of OFF is: θ = 0 ° to −180 ° (area of) θ = + 180 ° to + (180 ° + α) (area of), simply by turning on and off the origin sensor 13. If the position of the rotary shaft 1 is to be detected only by itself, the areas of and in FIG. 8 cannot be distinguished from each other. Therefore, the following origin detection is performed.

(2) Point of Origin Detection As shown in FIG. 8, the pulse from the encoder of the drive motor 6 is emitted with a predetermined resolution. The C-phase pulse is emitted once when the drive motor 6 makes one rotation. If the ratio of the number of teeth of the small pulley 7 and the large pulley 3 is set as a fractional value (for example, when the small pulley 7 makes one rotation, the large pulley 3 makes 3/4 rotation, etc.)
As described above, the position of θ = + 180 ° and the position of θ = −180 ° can be discriminated. That is, when the respective positions of θ = ± 180 ° are considered, the dog 10 and the origin sensor 13 have the same positional relationship (see FIGS. 4 and 6). However, by setting the reduction ratio as a fraction, the dog 10 is rotated in the CCW direction at the position of θ = + 180 °, and the number of pulses 21 output by the encoder of the drive motor 6 until the first C-phase pulse is output is similar to When the dog 10 is rotated in the CCW direction at the position of θ = −180 °, the number of pulses output by the encoder of the drive motor 6 until the first C-phase pulse is output 22
The number of pulses in is different. The positional relationship between the C-phase pulse of the drive motor 6, the pulse of the encoder, and the dog 10 (rotating shaft 1) is always constant. Therefore, if the number of pulses 21 and the number of pulses 22 are compared, the origin can be detected within the range of the rotation angle θ of the rotary shaft 1 = ± (180 ° + α).

(3) Origin Detection Method As described above, the point in this embodiment is how to discriminate the areas of and from FIG.

Therefore, when the dog 10 (rotating shaft 1) detects the origin from within the area of or, the dog 10 (rotating shaft 1) is rotated in the order of →, → to move to either one of the areas. . On the other hand, the origin detection from the or area is the simplest means for moving to the origin position (when the origin sensor 13 is ON, it rotates in the CCW direction, when it is OFF, it rotates in the CW direction, and the origin sensor 13 turns ON / O.
When the FF is switched, the position is corrected and the set origin position is reached. ).

In the following, the dog 10 (rotary shaft 1) is →
A method of moving to → will be described with reference to FIGS. 8 and 9. It should be noted that since the general method described above is used for the movement from the areas and to the origin position, the description thereof will be omitted.

FIG. 9 is a flow chart showing the flow of processing as an embodiment of the present invention.

Here, the number of pulses output by the encoder before the drive motor 6 makes one revolution or more and two revolutions or less (for example, about 1.5 revolutions) is defined as the number of search pulses.

Before starting the processing, it is first confirmed whether or not the dog 10 is at the origin position (step S1).
If it is at the origin position, the origin sensor 13 is ON, so the rotation direction of the dog 10 (rotation shaft 1) is set to the CW direction (step S2). On the other hand, if it is not at the origin position, the origin sensor 13 is OFF, so the rotation direction of the dog 10 (rotation axis 1) is CC.
The direction is W (step S3). In step S4, rotation starts in each direction, and the origin sensor 13
The presence / absence of a change in the ON / OFF state of is monitored (step S5). If the ON / OFF state of the origin sensor 13 does not change even if the rotation of the drive motor 6 is continued until the number of search pulses described above (step S6), the process proceeds to the movement processing to the origin position (step S14). On the other hand, in step S5, if the ON / OFF state of the origin sensor 13 is changed before the drive motor 6 is rotated up to the number of search pulses, the ON / OFF state of the origin sensor 13 is confirmed (step S7). When the origin sensor 13 is OFF, the dog 10 (rotating shaft 1) is rotated in the opposite direction (step S8). Step S7
In the case where the origin sensor 13 is ON, the pulse counter output from the encoder of the drive motor 6 is reset to 0 (step S9), and the dog 10 (rotary shaft 1) is rotated to C
The rotation in the CW direction is started (step S10). CC
It is monitored that the C-phase pulse of the drive motor 6 is first generated after the rotation in the W direction is started (step S1).
1) The value of the pulse counter output by the encoder of the drive motor 6 when the C-phase pulse is generated is compared with the above-mentioned pulse number 21 or pulse number 22 (step S12). If the result is equal to the number of pulses 21, the process proceeds to the movement to the origin position (step S14). On the other hand, if the number of pulses is equal to 22, the dog 10 (rotating shaft 1) is rotated in the CW direction by the number corresponding to the number of search pulses (step S13), and processing for moving to the origin position (step S1) is performed.
Proceed to 4).

(Other Embodiments) (1) In FIG. 2, the dog 10 has a semicircular shape having a range of 180 °, but if the dog angle is 90 °, for example, the rotating shaft 1 Rotation range of θ = + 90 ° +
It can be α to − (270 ° + α). That is, if the dog angle is β, the rotation angle θ is θ = +
(Β + α) to − (360 ° −β + α), or by reversing the origin sensor ON and OFF, θ = + (360 ° −β +
There is a relationship of α) to − (β + α), which can be set in any angle range.

(2) In FIG. 1, a pair of pulleys is used to obtain a fractional reduction ratio. Therefore, the drive source and the rotary shaft have different axes, but if a fractional speed reducer is used, the drive source and the rotary shaft can be made to have the same axis.

(3) Not only deceleration but also a case where a fraction speedup mechanism is provided is applicable.

(4) In FIG. 1, one pair of pulleys is
You may change to a transmission mechanism, such as a pair of gears and a pair of rollers.

(5) In FIG. 8, the values of the pulse number 21 and the pulse number 22 are different, and the origin sensor is ON / OFF.
Other configurations may be used as long as the position of and the position of the C-phase pulse of the drive motor are different. That is, the acceleration / deceleration ratio does not have to be a fraction.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus. <Effects of the Embodiment> (1) By using the reduction ratio as a fraction and grasping the positional relationship with the C-phase pulse of the drive motor 6 serving as a reference, the dog 1
The position of 0 (rotary axis 1) at θ = + 180 ° and θ = −180
It became possible to determine the position of °. (2) When the dog 10 (rotating shaft 1) detects the origin from within the area of or, rotate it to →, →
By always moving to either of the areas, the processing of origin detection and the processing of moving to the origin position could be simply divided. (3) The number of search pulses is equal to or more than 1 rotation of the drive motor 6 2
By setting the number of pulses output by the encoder before the rotation is performed (for example, about 1.5 rotations), it is possible to prevent the drive motor 6 from rotating longer than necessary and longer than the C-phase pulse interval. (4) If the dog 10 is at the origin position, the rotation direction of the dog 10 (rotating shaft 1) is the CW direction, and if not at the origin position, the rotation direction of the dog 10 (rotating shaft 1) is the CCW direction. It was possible to prevent the drive motor 6 from moving the dog 10 (rotating shaft 1) out of the rotation range in detecting the origin from any position. (5) Except when the state of the origin sensor 13 does not change even if the dog 10 (rotating shaft 1) is rotated by the number of search pulses, the position of the dog 10 is set to the position shown in FIG. The state of FIG. 6 (that is, θ = ± 180 °
By moving to each position) and unifying
The subsequent processing could be performed by one processing flow without dividing the case. (6) Reset the counter of the pulse output by the encoder to 0, rotate the dog 10 (rotary shaft 1), and set the number of pulses of the encoder until the C-phase pulse is first output to 21 and 22 pulses. By comparison, by utilizing the fact that the positional relationship between the pulse of the C phase of the drive motor 6 and the pulse of the encoder and the dog 10 (rotating shaft 1) is always constant by a simple method, θ = ± 180 ° The position could be detected.

[0053]

As described above, according to the present invention,
Even when the operating range of the rotary shaft exceeds 360 °, the origin can be detected by the simplest pair of dog and origin sensor configuration that does not require a special structure. Further, both the acceleration and deceleration mechanisms are possible, and the invention can be applied to a wide range of acceleration and deceleration ratios.

[0054]

[Brief description of drawings]

FIG. 1 is a central sectional view of a main part of a rotary shaft at a tip of a robot as an embodiment of the present invention.

FIG. 2 is a view on arrow XX in FIG. 1 as one embodiment of the present invention.

FIG. 3 is an operation explanatory diagram as one embodiment of the present invention (position of rotation angle θ of rotary shaft 1 = − (180 ° + α)).

FIG. 4 is an operation explanatory diagram as one embodiment of the present invention (position of rotation angle θ of rotary shaft 1 = −180 °).

FIG. 5 is an operation explanatory diagram as one embodiment of the present invention (position of rotation angle θ of the rotary shaft 1 = 0 °: origin position).

FIG. 6 is an operation explanatory view as one embodiment of the present invention (position of rotation angle θ of rotation shaft 1 = + 180 °).

FIG. 7 is an operation explanatory diagram as one embodiment of the present invention (position of rotation angle θ of rotation shaft 1 = + (180 ° + α)).

FIG. 8 is a diagram showing the relationship between the rotation angle of the rotary shaft 1 and the operation of the origin sensor 13 as one embodiment of the present invention.

FIG. 9 is a flowchart showing a flow of processing as an embodiment of the present invention.

FIG. 10 is a diagram showing a rotary shaft in the case where the drive source and the rotary shaft have the same shaft center as a conventional example.

FIG. 11 is a diagram showing a rotating shaft in the case where the drive source and the rotating shaft of the rotating shaft are different from each other as a conventional example.

[Explanation of symbols]

 1 rotary shaft 2 spacer 3 large pulley 4 main body arm 5 bearing 6 drive motor (with encoder) 7 small pulley 8 belt 9 flange 10 dog 11 tooth flange 12 bracket 13 origin sensor 14 stopper pin 15 ball 16 block 16a long hole shape Groove 16b Nige groove 21 pulse number 22 pulse number

Claims (16)

[Claims] 1. A device for detecting an origin position of a rotary shaft having an operation range of one rotation or more, wherein a first pulse and a second pulse emitted from a drive source for driving the rotary shaft, and An origin position detecting device, characterized in that the origin is detected at all positions within the operating range by a dog for detecting the presence or absence of the dog on the rotation axis. 2. The acceleration / deceleration ratio of the drive source and the rotary shaft is
The origin position detection device according to claim 1, wherein the origin position detection device is a fractional number. 3. The origin position detecting device according to claim 1, wherein the dog is fixed at an arbitrary position of the rotary shaft. 4. A means for counting the first pulse while the rotating shaft rotates in a predetermined range, and means for comparing the counted value with a preset reference value. The origin position detecting device according to claim 1. 5. The reference value is a value of the first pulse from when the dog starts rotating right or left from a predetermined position to when the second pulse is first detected. The origin position detecting device according to claim 4, wherein the count values are left and right respectively. 6. The rotation shaft rotates within a predetermined range from when the dog starts rotating right or left from a predetermined position to when the second pulse is first detected. The origin position detecting device according to claim 4, wherein 7. The origin position detecting apparatus according to claim 4, wherein the first pulse is a pulse emitted by the drive source with a predetermined resolution as the drive source rotates. 8. The origin position detecting device according to claim 4, wherein the second pulse is a pulse generated by the drive source for each rotation. 9. An apparatus for detecting an origin position of a rotary shaft having an operation range of one rotation or more, wherein a first pulse and a second pulse emitted from a drive source for driving the rotary shaft, An origin position detecting method, characterized in that the origin is detected at all positions within the operating range by a dog for detecting the presence or absence of the dog on the rotation axis. 10. The origin position detecting method according to claim 9, wherein the acceleration / deceleration ratio of the drive source and the rotary shaft is a fraction. 11. The origin position detecting method according to claim 9, wherein the dog is fixed at an arbitrary position of the rotation shaft. 12. The method according to claim 9, wherein the first pulse is counted while the rotating shaft is rotating in a predetermined range, and the counted value is compared with a preset reference value. Origin position detection method. 13. The reference value is a value of the first pulse from when the dog starts rotating right or left from a predetermined position to when the second pulse is first detected. 13. The origin position detecting method according to claim 12, wherein the count values are for each of the left and right sides. 14. While the rotation shaft rotates within a predetermined range, from when the dog starts rotating right or left from a predetermined position to when the second pulse is first detected. 13. The origin position detecting method according to claim 12, wherein 15. The origin position detecting method according to claim 12, wherein the first pulse is a pulse emitted by the drive source with a predetermined resolution as the drive source rotates. 16. The origin position detecting method according to claim 12, wherein the second pulse is a pulse generated by the drive source for each rotation.