WO2009139059A1

WO2009139059A1 - Conveyance apparatus and work moving distance output method

Info

Publication number: WO2009139059A1
Application number: PCT/JP2008/058933
Authority: WO
Inventors: 繁中島; 邦明飯泉; 信久前田; 泉中島
Original assignee: 有明スチールセンター株式会社
Priority date: 2008-05-15
Filing date: 2008-05-15
Publication date: 2009-11-19
Also published as: JPWO2009139059A1

Abstract

A moving distance of a work is outputted by arithmetic processing of software without detecting the rotation of conveyers. A conveyance apparatus has the conveyers (10, 20) which form a conveyance line, drive motors (11, 21) which individually drive the respective conveyers (10, 20), motor rotation speed setting means (12, 22) which set the rotation speeds of the drive motors (11, 21), and a control means (30) which controls the rotation speeds of the drive motors (11, 21) to set the line speeds of the conveyers (10, 20) and outputs movement pulses corresponding to the unit moving distance (L) of the work (W) on the basis of the operation of the drive motors (11, 21).

Description

Conveying device, work movement distance output method

The present invention relates to a transport device that transports a workpiece, and a work movement distance output method for outputting a travel distance of a workpiece transported by the transport device.

In automatic coating, various processing treatments or production lines, a conveying device for conveying workpieces along the line is used. In general, this conveyor is a conveyor that connects a plurality of conveyor rollers in parallel with a line on which workpieces are arranged with a chain or belt, and rotates a sprocket or pulley for driving the chain or belt with a motor. Is used.

In such a transport device, in order to perform processing such as automatic painting and various processing while transporting, the movement distance of the workpiece being transported is grasped at any time and output to the control device of the processing unit. In the conventional conveying device, a metal blade is attached to the roller shaft of the conveying roller, the rotation of the blade is detected by a proximity sensor, and a movement pulse for grasping the moving distance of the workpiece is output.

However, in such a movement distance output method, when the conveyor is driven by a chain or the like to form a long-distance conveyance line, pulsation may occur in the rotation of the conveyance roller. May not be able to grasp. Also, in principle, high resolution cannot be obtained with such a method. For this reason, an encoder is attached to the shaft of the transport roller, and a moving pulse is output with a high-speed pulse from the encoder. (For example, see Patent Document 1 below).

JP 2006-273497 A

A conveyor line of a transport device may have a plurality of transport conveyors that perform different processes formed on a single line. Even on a single line, the shape and feed system of a roller suitable for processing in each process It may be adopted. In such a case, it is necessary to control the line speed by grasping the operation state for each of the different types of conveyors. For this purpose, a method of attaching a blade to the shaft of the transport roller and detecting rotation by a proximity sensor, or a method of mounting an encoder to the shaft of the transport roller, and a plurality of rotation detection devices that are optimal for each processing step and the incidental for reading them. The device must be installed. For this reason, there is a problem that the construction of the equipment is costly and uneconomical, and the design of the conveyor body is often forced to change in order to install the rotation detection device.

As mentioned above, when the pulsation of the conveyor occurs, when it is desired to obtain a high-resolution travel distance output, or when detecting reverse rotation, it can be solved by using an encoder as described above. Since it is a pulse, there is a problem that an auxiliary device capable of receiving this becomes expensive, and there is a problem that the wiring length is restricted due to the influence of signal attenuation. Furthermore, since the encoder itself is a precision device, a misalignment of the roller shaft that occurs when a load is placed on the transport roller may cause a failure in which the encoder shaft is damaged due to a radial load. If the encoder breaks down, it may take several weeks to deliver the replacement product, or the replacement product is not available and a new model may be selected to modify the mounting parts or auxiliary equipment. Take the risk of stopping for a long time.

Further, in the above-described conventional technology, since the movement pulse is obtained from the rotation cycle, multiplication of the circumference ratio is included when the movement pulse is converted into the movement distance even if any method is adopted. There is a problem that the processing program in the subsequent process becomes complicated by that amount.

The present invention is an example of a problem to deal with such a problem. In other words, when a single line is formed by a plurality of conveyors having different roller shapes and feeding methods, it is not necessary to detect the rotation of the conveyor rollers in the individual conveyors, which affects the design of the conveyor body economically. Without being able to output the movement distance of the workpiece without the use of expensive incidental equipment that receives high-speed pulses when the pulsation of the conveyor occurs, when high resolution is desired, or when reverse rotation is detected, Also, it is possible to grasp the moving distance of the workpiece with high accuracy without being restricted by installation such as wiring length, and to continue without failure due to misalignment of the roller shaft that occurs when a load is placed on the transport roller. That it can perform general conveyance, that the calculation processing for obtaining the moving distance can be simplified, and the subsequent processing program can be simplified, There is an object of the present invention.

In order to achieve such an object, the transfer device and the workpiece movement distance output method according to the present invention include at least the configurations according to the following independent claims.
[Claim 1] A plurality of conveyors forming a conveyor line, driving motors for individually driving the conveyors, motor rotation speed setting means for setting the rotation speeds of the driving motors, and driving motors Control means for setting the line speed of each conveyor and controlling the number of rotations, and outputting a movement pulse according to the unit movement distance of the workpiece based on the operation of the drive motor, the control means, A clock pulse generating means for generating a clock pulse with a fixed period; a driving motor operating means for outputting a stop / start signal for the driving motor in synchronization with the fixed period of the clock pulse; and when the driving motor is in operation Clock pulse accumulating means for accumulating the clock pulses, the set line speed and the accumulated pulse accumulated by the clock pulse accumulating means. A moving distance calculating means for calculating a moving distance of a work moved by the conveyor, and a moving pulse transmitting means for transmitting a moving pulse every time the moving distance reaches a unit distance. Conveying device to do.

[Claim 3] A work movement distance output method in a conveying apparatus comprising a plurality of conveying conveyors forming a conveying line and a driving motor for individually driving each conveying conveyor, wherein the number of rotations of the driving motor is determined. A line speed setting step for controlling and setting the line speed of each conveyor, a clock pulse generating step for generating a fixed period clock pulse, and a stop / start of the driving motor in synchronization with the fixed period of the clock pulse. A driving motor actuating step for outputting a signal, a clock pulse accumulating step for accumulating the clock pulses when the driving motor is actuated, and the set line speed and the cumulative number of clock pulses accumulated, A moving distance calculating step for calculating a moving distance of the workpiece moved by the conveyor. Workpiece movement distance output method to be.

According to the present invention, when a single transfer line is formed by a plurality of transfer conveyors having different roller shapes and feeding methods, the movement distance of the workpiece is output by software calculation processing without detecting the rotation of the individual transfer conveyors. Therefore, the movement distance of the workpiece can be output economically and without affecting the design of the conveyor body. In addition, when pulsation of the conveyor occurs, when high resolution is desired, or when reverse rotation is detected, there is no need to use expensive incidental equipment that receives high-speed pulses, and there are no installation restrictions such as wiring length. It is possible to grasp the movement distance of the workpiece with high accuracy. In addition, continuous conveyance can be performed without failure due to misalignment of the roller shaft that occurs when a load is placed on the conveyance roller. The calculation process for obtaining the movement distance can be simplified, and the subsequent processing program can be simplified.

It is explanatory drawing which showed the whole structure of the conveying apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows the control function of the control means in the conveying apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows operation | movement of the control means in the conveying apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which showed the specific control processing flow for performing the movement pulse transmission of the control means in the conveying apparatus which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing the overall configuration of a transport apparatus according to an embodiment of the present invention. The transport apparatus according to the embodiment of the present invention includes a plurality of

transport conveyors

10 and 20 that form a transport line for transporting workpieces W, drive

motors

11 and 21 that individually drive the

transport conveyors

10 and 20, Motor rotational speed setting means 12 and 22 for setting the rotational speeds of the

driving motors

11 and 21 and the rotational speeds of the

respective driving motors

11 and 21 are set to set the line speeds of the

respective conveyors

10 and 20 and drive them. The control means 30 which outputs the movement pulse according to the unit movement distance of the workpiece | work W based on the operation | movement of the

motors

12 and 22 for operation is provided. In the illustrated example, one conveyance line is formed by two

conveyors

10 and 20, but the present invention is not limited to this, and one conveyance line is formed by three or more conveyors. And a plurality of transport lines formed by a plurality of transport conveyors in parallel.

The

conveyance conveyors

10 and 20 include cases where different forms of rollers and feeding methods are employed. In the example shown in the figure, a single conveying roller 10 is connected to a large-diameter conveying roller 10A arranged in parallel by an endless transmission means 10B such as a chain, and is driven by a driving motor 11 via a sprocket 10C. One transport roller 20 is rotatably driven by a drive motor 21 while supporting an endless transport band 20B having a support bar 20A rotatably at both ends.

The

driving motors

11 and 21 may be any motors that can obtain the driving torque of the

conveyors

10 and 20, and for example, AC motors such as an induction motor and a synchronous motor can be used. The motor rotation speed setting means 12 and 22 are provided corresponding to the

respective drive motors

11 and 21, and individually set the rotation speeds of the

drive motors

11 and 21 for driving the

conveyors

10 and 20 having different forms. To get any line speed.

Since the material and line load of the work supporting part may be different for each of the

conveyors

10 and 20, the degree of wear of the components of the

conveyors

10 and 20 varies, and the line speed varies at a constant motor rotation speed. There is a case. In order to cope with this, the

conveyors

10 and 20 corresponding to the respective processing steps are driven by

individual drive motors

11 and 21, and the number of rotations of the

drive motors

11 and 21 is controlled to be uniform and arbitrary. Trying to get a line speed of. When the

drive motors

11 and 21 are AC motors, inverters that generate variable power supply frequencies can be used as the motor rotation speed setting means 12 and 22. The line speed can be accurately controlled by employing an inverter having a vector control function that operates by correcting slippage of the

drive motors

11 and 21 due to the load and heat of the

conveyors

10 and 20.

The control means 30 controls the number of rotations of the

drive motors

11 and 21 to set the line speed of each conveyor, and moves pulses corresponding to the unit travel distance of the workpiece W based on the operation of the

drive motors

11 and 21. Pw is output. The output movement pulse Pw is input to, for example, a coating processing unit of an automatic coating apparatus, a processing unit of an automatic processing apparatus, or the like, and processing control according to the movement distance of the workpiece is executed.

Specifically, the control means 30 can be composed of a PLC (programmable logic controller) that drives the motor speed setting means (inverters) 12 and 22, and has a fixed period as a control function as shown in FIG. Clock pulse generating means 30A for generating a clock pulse, driving motor operating means 30B for outputting a stop / start signal of the driving

motors

11 and 21 in synchronization with a fixed cycle of the clock pulses, and driving

motors

11 and 21 The moving distance of the workpiece W moved by the

conveyors

10 and 20 is determined by the clock pulse accumulating means 30C for accumulating the clock pulses during the operation, and the set line speed and the accumulated pulse number accumulated by the clock pulse accumulating means 30C. The moving distance calculating means 30D for calculating and the moving pulse Pw every time the moving distance reaches the unit distance The moving pulse transmitting means 30E for transmitting.

The operation of the control means 30 having the above-described control function (workpiece movement distance output method) will be described with reference to FIG. As shown in FIG. 3A, the clock pulse generating means 30A (clock pulse generating step) generates a clock pulse having a fixed period (for example, one period t _s = 10 ms). For this, for example, a fixed clock that is standardly installed in the PLC can be used. After setting the line speed of the conveyors 10 and 20 (line speed setting step), the control means 30 executes a control operation based on a fixed-cycle clock pulse generated by the clock pulse generating means 30A.

The drive motor actuating means 30B (drive motor actuating step) includes a drive motor 11, in order to obtain a signal for starting and stopping the

transport conveyors

10, 20 and an arbitrary line speed v of the

transport conveyors

10, 20. 21 The set values of the individual rotational speeds are output to the motor rotational speed setting means 12 and 22. In order to start and stop the

conveyors

10 and 20, start / stop signals S1 and S2 of the

drive motors

11 and 21 are output. The signals S1 and S2 generate clock pulses as shown in FIG. The signal is output in synchronization with a fixed cycle of the clock pulse generated by the means 30A.

When the drive motor actuating means 30B outputs the start signal S1, each of the

drive motors

11 and 21 is controlled to the rotational speed set by the motor rotational speed setting means 12 and 22 by gradually increasing the rotational speed. In this case, the time t _a taken during acceleration startup, so that the time (twice in the illustrated example) even multiple of one clock period in the fixed period as described above, have set the acceleration degree (FIG. 3 (c )reference). Further, when the drive motor operating means 30B outputs the stop signal S2, each of the

drive motors

11 and 21 is gradually stopped from the rotational speed set by the motor rotational speed setting means 12 and 22 and stopped. At this time, the degree of deceleration is set so that the time t _d required for deceleration stop is also a time that is an even multiple of one clock cycle in the above-described fixed cycle (twice in the illustrated example) (FIG. 3 (c)). )reference).

The clock pulse accumulating means 30C (clock pulse accumulating step) counts clock pulses with a fixed period by the start signal S1 of the driving motor operating means 30B, and accumulates the number of pulses when the driving

motors

11 and 21 are operated.

The moving distance calculating means 30D (moving distance calculating step) calculates the moving distance L of the workpiece W by the following equation (1) from the set line speed v and the accumulated pulse number n accumulated by the clock pulse accumulating means 30C. .

At this time, in a more specific embodiment of the movement distance calculation means 30D, the cumulative pulse number n is obtained by halving the cumulative pulse number accumulated at the time of acceleration start or deceleration stop, and this cumulative pulse number n The moving distance L is calculated from the equation (1) by At this time, since the time t _a taken for acceleration start is set to one clock period even multiple of time, number of pulses accumulated by the time t _a has become a number divisible always 2, the cumulative total The pulse number n is always a natural number. In the example shown in FIG. 3 (c), the time t _a at the time of acceleration starting since the set to twice the clock period at a fixed period, the two pulses which are accumulated from the starting as a pulse, is accumulated thereafter 1 is added to the number of pulses to be obtained to obtain the cumulative pulse number n in the equation (1).

As an easy-to-understand example, if it is necessary to obtain a cumulative set number of pulses of 2 pulses (ie, L1 = 2t _S · v) at a constant set line speed v to obtain the unit feed distance L1, the start signal S1 is output. , The moving distance of the unit feed distance L1 at the third pulse of the fixed period clock pulse, and thereafter the moving distance of L2 = 2 × L1, L3 = 3 × L1,..., Ln = n × L1 every time two pulses are accumulated. become. That is, in the example shown in the figure, a fixed-period clock pulse is accumulated after the start signal S1 is output, and the accumulated pulse number n obtained by subtracting 1 from the accumulated pulse number is substituted into equation (1) for movement. The distance L is calculated.

Then, set to twice the one clock period in the fixed period of time t _d during deceleration stop when the stop signal S2 as shown in FIG. 3 (b) is output in synchronism with the clock pulses of a fixed period Therefore, the accumulated pulse number n obtained by adding 1 to the accumulated pulse number (a value obtained by subtracting 1 for the acceleration start from the actually counted pulse number) until the stop signal S2 is output is expressed by the equation ( By substituting in 1), the moving distance L until the stop can be calculated.

In such a movement distance calculation means 30D, the acceleration / deceleration gradient of the

transfer conveyors

10 and 20 can be made a straight line, and the movement distance can be calculated in consideration of a decrease in the line speed during acceleration / deceleration. The movement distance can be grasped.

As shown in FIG. 3E, the movement pulse transmission means 30E outputs a movement pulse Pw every time the movement distance L reaches a set unit feed distance n × L1 (n = 1, 2, 3,...). To do. In the illustrated example, on the basis of the profile of the line speed shown in FIG. 3 (b), the fixed period 2 pulse at the time t _a taken for acceleration starting from the translation to the start signal S1 output pulse of fixed period clock pulse When the third pulse is accumulated, a movement pulse Pw1 corresponding to the unit feed distance L1 is output, and thereafter, movement pulses Pw2, Pw3,... Are output each time two fixed-period clock pulses are accumulated. Then, after the stop signal S2 is output, the subsequent two fixed-cycle clock pulses are converted into one pulse. Therefore, when the converted one pulse is added and two pulses are accumulated from the previous movement pulse output, that is, the previous movement. When the third fixed-cycle clock pulse is accumulated from the pulse output, the last movement pulse Pwe is output. In the example shown in the figure, the unit feed distance L1 is set to a multiple (2t _S · v) of the clock pulse cycle, but the unit feed distance L1 itself is set to an arbitrary value regardless of the clock pulse cycle. can do. In this case, the calculated movement distance L and the set unit feed distance n × L1 are compared for each program scan, and the movement pulse Pw is output when the movement distance L reaches n × L1.

FIG. 4 is an explanatory diagram showing a specific control processing flow for performing the movement pulse transmission of the control means 30. In order to execute the illustrated flow, it is necessary that the scan time of all the processing programs is smaller than ½ of the fixed period of the clock pulse.

When the movement pulse transmission flow starts, first, a transmission unit feed distance X [mm] is set (P1 = X: Step S01). Then, a specified value (for example, 10 [ms]) of one fixed period clock pulse is substituted into the variable P2, and the initial value P1 (= X) is substituted into the variable P3 of the next transmission distance, thereby setting the variable of the set line speed. A set value v [mm / min] is substituted for P4 (step S02: line speed setting step).

Next, it is confirmed whether proper initial settings have been made (whether P2 ≦ 60000) or whether the setting line speed setting has been changed (step S03). If this confirmation is “NO”, the variable P2, If P3 and P4 have been reset (step S02) and appropriate initial settings have been made and there is no change in the set line speed v (step S03: “YES”), the process proceeds to the next step.

Then, it is confirmed whether or not there is a request for operation of the

conveyors

10 and 20 for each scan of the program (step S04), and if there is (step S04: “YES”), when clock pulses with a fixed period are counted At the same time (step S05: “YES”), the above-described start signal S1 is output, and the conveyor is maintained in the subsequent scan (step S06). The start signal S1 is always output in synchronization with a fixed-cycle clock pulse (step S05: “NO”). When there is no conveyor operation request in each program scan (step S04: “NO”), the fixed cycle clock pulses are counted (step S07: “YES”), and the stop signal S2 described above is output, and thereafter In this scan, the conveyor OFF is maintained (step S08). The stop signal S2 is also always output in synchronization with a fixed-cycle clock pulse (step S07: “NO”).

Next, it is confirmed that the

transfer conveyors

10 and 20 are ON (step S09). If the conveyor is ON (step S09: “YES”), the conveyor ON time after the start signal S1 is output is counted and the conveyor OFF time. Is reset (step S10), and the accumulated conveyor ON time is not performed until the counted conveyor ON time becomes 1/2 or more of the set conveyor acceleration time (step S11: “NO”). When the conveyor acceleration time is ½ or more (step S11: “YES”), the pulse accumulation is performed together with the fixed-cycle clock pulse count (step S12: “YES”) (P2 = P2 + 10), and L [mm ] = P4 × P2 / 60000 to calculate the movement distance L (step S13).

On the other hand, if the conveyor OFF is confirmed after the stop signal is output (S08) (step S09: “NO”), the conveyor ON time is reset and the conveyor OFF time after the stop signal S2 is output is counted ( Step S14) When the counted conveyor OFF time is less than ½ of the set conveyor deceleration time (Step S15: “YES”), together with a fixed cycle clock pulse count (Step S12: “YES”), pulse accumulation (P2 = P2 + 10) and the movement distance L is calculated as L [mm] = P4 × P2 / 60000 (step S13). When the conveyor OFF time becomes ½ or more of the conveyor deceleration time (step S15: “NO”), pulse accumulation is not performed (step S15: “NO”).

The processing from step S09 to step S15 is a specific processing flow for calculating the moving distance L of the work by reducing the cumulative number of pulses accumulated at the time of acceleration start or deceleration stop to 1/2. It is possible to calculate an accurate movement distance L taking into account a decrease in line speed during acceleration / deceleration.

Then, when the calculated moving distance L becomes equal to or longer than the next transmission distance P3, a movement pulse Pw is output (movement pulse ON), and the next transmission distance P3 is updated with P3 = P3 + P1 (step S17). When the calculated movement distance L is less than the next transmission distance P3 (step S16: “NO”), the movement pulse is turned OFF (step S18) in the scan of that time. After that, the next program scan starts from step S03.

The movement pulse transmission flow of FIG. 4 will be described with specific examples. Setting the line speed v = 21000mm / min, when a clock pulse one period _t s = 10 ms, the distance which the workpiece is moved between the 1 period _{t s} becomes _{v · t s = 21000 × 10} /60000 = 3.5mm. A set unit feeding distance X = 10 mm, (see FIG. 3) when the time t _a taken during acceleration start is to be set to twice the clock pulse 1 period t _s, the start signal S1 is output The clock pulse of the first fixed period is set to no count, the accumulation is started from the next pulse, the movement distance L = 3.5 × 3 ≧ 10 is judged at the third pulse, and the unit movement distance L1 = 10 mm is judged to have moved. Then, the movement pulse Pw1 is output. After that, every time a pulse is accumulated, L = 3.5 × 6 ≧ 2 × 10 when the number of accumulated pulses is n = 6, and L = 3.5 × 9 ≧ 3 × 10 when n = 9. A moving pulse is output.

According to such an embodiment, when high resolution is desired, the clock pulse cycle is shortened, and when the resolution may be coarse, the clock pulse cycle is lengthened and the scan time is increased to perform arithmetic processing. The load can be reduced. Further, the transmission unit feed distance X for obtaining the movement pulse can be arbitrarily set.

As an example of applying the transport apparatus according to such an embodiment to a transport line of an automatic coating apparatus, one transport conveyor 10 is a roller conveyor for coating, and the other transport conveyor 20 is a slat conveyor for drying. To. At this time, when it is desired to detect the position of the workpiece W with a high resolution of about 100 mm so that the paint is not wasted during painting, the transmission unit feed distance X is set to 100 mm. On the other hand, since it is only necessary to know the rough position of the workpiece at the time of drying, a low resolution of about 1000 mm may be used in order to reduce the calculation load of the control means 50. In this case, the transmission unit feed distance X is set to 1000 mm. To do.

As a specific example of such an embodiment, an inverter having a vector control function, which is operated by correcting motor slip due to load or heat, is adopted as the motor rotation speed setting means 12, 22. Control the speed. Further, an inexpensive PLC for FA is used as the control means 30, the inverter is driven by this PLC, and the above-described control flow is executed using a fixed clock that is standardly mounted on the PLC as a fixed-period clock pulse. According to this, the position of the workpiece on the transfer conveyor line can be detected properly by electronically generating movement pulses with no accumulated error, without using any conventional proximity sensor or encoder. It becomes possible to do.

According to this, an arbitrary unit feed distance movement pulse can be obtained by the program software at an arbitrarily set line speed, and it is possible to eliminate restrictions on installation of the apparatus for installing the rotation detection apparatus. . This can reduce the time and cost of equipment design, condition selection, and maintenance, avoid false detections due to conveyor pulsation and hardware failure, and can construct various processing lines with high reliability and high availability.

Claims

Controls the rotation speed of each drive motor, a plurality of transfer conveyors forming a transfer line, a drive motor for individually driving each transfer conveyor, a motor rotation speed setting means for setting the rotation speed of each drive motor And a control means for setting a line speed of each conveyor and outputting a movement pulse corresponding to a unit movement distance of the workpiece based on the operation of the driving motor,
The control means includes
Clock pulse generating means for generating a fixed-period clock pulse;
Driving motor operating means for outputting a stop / start signal of the driving motor in synchronization with a fixed period of the clock pulse;
Clock pulse accumulating means for accumulating the clock pulse when the driving motor is operated;
A moving distance calculating means for calculating a moving distance of a work moved by the conveyor, based on the set line speed and the accumulated pulse number accumulated by the clock pulse accumulating means;
A transport apparatus comprising: a travel pulse transmitting means for transmitting a travel pulse each time the travel distance reaches a unit distance.
The drive motor actuating means performs acceleration start and deceleration stop from the line speed in an even multiple of one clock cycle in the clock pulse,
The transport apparatus according to claim 1, wherein the moving distance calculating unit calculates a moving distance of the work by reducing a cumulative pulse number accumulated at the time of the acceleration start or the deceleration stop to ½.
It is a work movement distance output method in a transfer device comprising a plurality of transfer conveyors forming a transfer line and a drive motor for individually driving each transfer conveyor,
A line speed setting step for setting the line speed of each conveyor by controlling the number of rotations of the drive motor;
A clock pulse generating step for generating a fixed-period clock pulse;
A driving motor operating step of outputting a stop / start signal of the driving motor in synchronization with a fixed period of the clock pulse;
A clock pulse accumulating step of accumulating the clock pulses when the driving motor is operated;
A moving distance calculating step of calculating a moving distance of a work moved by the conveyor by the set line speed and the cumulative number of clock pulses accumulated;
A workpiece movement distance output method characterized by comprising:
The driving motor operating step performs acceleration start and deceleration stop from the line speed in an even multiple of one clock cycle in the clock pulse,
4. The workpiece movement distance according to claim 3, wherein the movement distance calculation step calculates the workpiece movement distance by halving a cumulative pulse number accumulated at the time of the acceleration start or the deceleration stop. 5. output method.