Substrate transport system and substrate positioning method

Abstract

To provide a substrate transfer system and a substrate positioning method that can correct overruns quickly and accurately, prevent time loss associated with substrate positioning, and improve productivity.SOLUTION: When an elapsed time from a time when the head of a board is detected by a first sensor reaches a deceleration start delay time GT, the transfer speed of the board is reduced to the stop speed (ST6), and the transfer of the board is stopped (ST8) when the head of the board transferred at the stop speed is detected by a second sensor. When the head of the board is detected by a third sensor after the transfer of the board is stopped, a transfer conveyor is operated such that the head of the board approaches the target stop position, and the board is retracted (ST12), and a new deceleration start delay time GT is set by subtracting a time required for the head of the board to advance to the overrun detection position beyond the target stop position from a deceleration start delay time GT (ST14).SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a substrate transport system and a substrate positioning method for transporting a substrate and positioning it at a predetermined target stopping position. [Background technology]

[0002] In a component mounting device, such as a component mounting device used in a component mounting line that mounts components on a board, a board is transported by a transport conveyor and positioned at a predetermined work position in order to perform work on the board. When the transport conveyor receives a board from the upstream side, it initially transports the board at a high speed, and then decelerates the transport speed after a certain time has elapsed since the front end of the board reaches a preset deceleration start reference position, and stops transporting when the front end of the board reaches a target stop position. In this case, if the board overruns beyond the target stop position, it is necessary to operate the transport conveyor to move the board back so that the front end of the board approaches the target stop position. Since overruns lead to time loss, they must be avoided as much as possible. Conventionally, when an overrun occurs, the time from when the front end of the board reaches the deceleration start reference position to when deceleration starts (deceleration start delay time) is shortened so that deceleration starts early (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-157960 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above conventional component mounting device, the time width of the deceleration start delay time that is shortened when the board overruns is fixed, and the changed deceleration start delay time does not necessarily become the optimal value. This causes problems such as the time width of the deceleration start delay time being too small, causing the overrun to continue afterwards, or the time width being too large, causing the overrun to be corrected but taking too long to reach the target stop position, resulting in reduced productivity.

[0005] Therefore, an object of the present invention is to provide a substrate transport system and a substrate positioning method that can quickly and accurately correct overrun even if it occurs, thereby preventing time loss associated with substrate positioning and improving productivity. [Means for solving the problem]

[0006] The substrate transport system of the present invention is a substrate transport system that transports a substrate and positions it at a predetermined target stop position, and includes a transport conveyor that transports the substrate, a first sensor that detects a state in which a leading portion of the substrate transported by the transport conveyor has reached a deceleration start reference position set upstream of the target stop position, a second sensor that detects a state in which the leading portion of the substrate transported by the transport conveyor has reached a stop operation start position set slightly upstream of the target stop position, a third sensor that detects a state in which the leading portion of the substrate transported by the transport conveyor has reached an overrun detection position set slightly downstream of the target stop position, and a detection signal that indicates a time elapsed from when it is detected that the leading portion of the substrate transported by the transport conveyor has reached the deceleration start reference position reaches a preset deceleration start delay time. an operation control unit that decelerates the transport speed of the substrate by the transport conveyor to a preset stopping speed when a state in which the leading portion of the substrate has reached the stop operation start position is detected, thereafter stops transport of the substrate by the transport conveyor when a state in which the leading portion of the substrate has reached the stop operation start position is detected, and after transport of the substrate by the transport conveyor is stopped, operates the transport conveyor to retract the substrate so that the leading portion of the substrate approaches the target stop position when a state in which the leading portion of the substrate has reached the overrun detection position is detected; and a delay time changing unit that, when a state in which the leading portion of the substrate has reached the overrun detection position is detected, subtracts from the deceleration start delay time an overrun time required for the leading portion of the substrate to proceed from the target stop position to the overrun detection position from the deceleration start delay time to set a new deceleration start delay time.

[0007] The substrate positioning method of the present invention is a substrate positioning method for transporting a substrate by a transport conveyor and positioning it at a predetermined target stop position, comprising the steps of: decelerating a substrate transport speed by the transport conveyor to a preset stop speed when an elapsed time from when a leading end of the substrate transported by the transport conveyor reaches a deceleration start reference position set upstream of the target stop position reaches a preset deceleration start delay time; and delaying a substrate transport speed by the transport conveyor to a preset stop speed when a leading end of the substrate transported by the transport conveyor at the stop speed reaches a stop operation start position set slightly upstream of the target stop position. the overrun processing step of operating the transport conveyor to move the substrate back so that the leading portion of the substrate approaches the target stop position when the leading portion of the substrate reaches an overrun detection position set slightly downstream of the target stop position after the transport of the substrate by the transport conveyor has been stopped; and the deceleration start delay time changing step of subtracting from the deceleration start delay time the overrun time required for the leading portion of the substrate to proceed from the target stop position to the overrun detection position when the leading portion of the substrate reaches the previous overrun detection position to set a new deceleration start delay time. Effect of the Invention

[0008] According to the present invention, even if an overrun occurs, it can be quickly and accurately corrected, and time loss due to positioning of the substrate can be prevented, thereby improving productivity. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view of a main part of a component mounting apparatus equipped with a board transport system according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a plan view of a main part of a component mounting device according to an embodiment of the present invention; [Diagram 3] FIG. 2 is a block diagram showing a control system of the component mounting device according to the embodiment of the present invention. [Figure 4]FIG. 2A is a plan view of a board transport mechanism provided in a component mounting device according to an embodiment of the present invention; [Diagram 5] 1 is a graph showing a profile of a board conveying speed versus time when board positioning control is performed by a component mounting device according to an embodiment of the present invention; [Figure 6] 5A, 5B, 5C, and 5D are diagrams showing changes in the position of a board when board positioning control is performed by a component mounting device according to an embodiment of the present invention. [Figure 7] A flowchart showing the flow of positioning control of a board by a component mounting device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, the structure of a component mounting device 1 as an example of a component mounting device will be described with reference to Figures 1 and 2. In Figures 1 and 2, the component mounting device 1 is a device that mounts components BH on a board KB, and includes a base 11, a board transport mechanism 12, a plurality of part feeders 13, a head moving mechanism 14, a mounting head 15, a component recognition camera 16, and a control device 17.

[0011] 1 and 2, substrate transport mechanism 12 extends in the left-right direction (X-axis direction) in the center of base 11, and supports and transports both ends of substrate KB from below using transport conveyor 21 having a pair of transport belts 21a arranged opposite each other in the front-rear direction (Y-axis direction). Substrate transport mechanism 12 receives substrate KB sent from the upstream side, transports it to the center of base 11, and positions it at a predetermined working position. That is, in this embodiment, substrate transport mechanism 12 serves as a substrate positioning unit that positions substrate KB at the working position.

[0012] 1 and 2, multiple part feeders 13 are attached to a feeder base 11F provided in front of the board transport mechanism 12 as seen by an operator OP, lined up in the X-axis direction. Each part feeder 13 supplies components BH to be mounted on a board KB to a component supply port 13K provided at the end on the board transport mechanism 12 side.

[0013] 1 and 2, the head moving mechanism 14 includes a fixed beam 14A fixed to the base 11 and extending in the Y-axis direction, and a moving beam 14B whose one end is supported by the fixed beam 14A and extends in the X-axis direction. The mounting head 15 is provided on the moving beam 14B. The moving beam 14B moves in the Y-axis direction on the fixed beam 14A, and the mounting head 15 moves in the X-axis direction on the moving beam 14B. The mounting head 15 can freely move in a horizontal plane (XY plane) above the base 11 by the movement of the moving beam 14B in the Y-axis direction and the movement of the mounting head 15 itself in the X-axis direction.

[0014] 1, the mounting head 15 is equipped with a number of nozzles 15N extending downward. Each nozzle 15N is driven by a nozzle driver 15A provided within the mounting head 15 to move up and down relative to the mounting head 15 and rotate about the Z axis. Vacuum pressure can be supplied to each nozzle 15N through a valve unit 15B provided in the mounting head 15, thereby generating a suction force at the bottom end of each nozzle 15N.

[0015] 1 and 2, the component recognition camera 16 is provided in an area between the board transport mechanism 12 and the part feeder 13 of the base 11. The component recognition camera 16 has an imaging optical axis facing upward, and images, from below, the component BH that the mounting head 15 has picked up by adsorbing it to the nozzle 15N.

[0016] In Fig. 3, the control device 17 controls the operation of each unit of the component mounting device 1. Specifically, the control device 17 operates the board transport mechanism 12 to transport the board KB and position it at the work position, and operates each part feeder 13 to supply the component BH to the component supply port 13K. The control device 17 also operates the head moving mechanism 14 to move the mounting head 15 in a horizontal plane. The control device 17 also operates the nozzle driving unit 15A to raise and lower and rotate each nozzle 15N, and operates the valve unit 15B to generate a suction force at the lower end of each nozzle 15N. The control device 17 also causes the component recognition camera 16 to capture the component BH that the mounting head 15 has picked up by the nozzle 15N and adsorbed thereto, and recognizes the component BH.

[0017] 3, control device 17 includes memory unit 17a and operation control unit 17b. Memory unit 17a stores a component mounting program that defines the procedure for executing the component mounting work, as well as various data such as the type and size of components BH to be mounted on board KB. Operation control unit 17b operates each unit of component mounting device 1 in a predetermined order based on the component mounting program stored in memory unit 17a, and mounts components BH at each target mounting coordinate set on board KB.

[0018] When the component mounting device 1 configured as described above performs a component mounting operation of mounting components BH on the board KB, the board transport mechanism 12 first receives the board KB sent from the upstream side, transports it, and positions it at the work position. The positioning of the board KB to the work position by the board transport mechanism 12 will be described in detail later.

[0019] When the board KB is positioned at the work position, the head movement mechanism 14 moves the mounting head 15 to above the part feeder 13. When the mounting head 15 moves to above the part feeder 13, it picks up the components BH supplied by the part feeder 13 by suctioning them onto each of the multiple nozzles 15N.

[0020] After the mounting head 15 picks up the component BH, the head moving mechanism 14 moves the mounting head 15 so that the component BH picked up by the mounting head 15 passes above the component recognition camera 16. The component recognition camera 16 captures an image of the component BH as it passes above, and the control device 17 recognizes the component BH based on the image captured by the component recognition camera 16.

[0021] Once the control device 17 recognizes the component BH, the head movement mechanism 14 moves the mounting head 15 to above the board KB, and the mounting head 15 places the picked-up component BH at the target mounting coordinates set on the board KB. When the mounting head 15 places the component BH at the target mounting coordinates, a position correction is made based on the recognition result of the component BH.

[0022] This series of operations of mounting head 15 is repeated until all of the components BH to be mounted on board KB are mounted, at which point board transport mechanism 12 transports board KB downstream of component mounting device 1. This completes the component mounting operation for one board KB.

[0023] Next, the positioning control of the substrate KB to the working position by the substrate transport mechanism 12 will be described. First, the configuration of the substrate transport mechanism 12 will be described with reference to Figures 4(a) and (b). In Figures 4(a) and (b), the substrate transport mechanism 12 includes a transport conveyor 21 including the pair of transport belts 21a described above, as well as a plurality of sensors (a first sensor 31, a second sensor 32, and a third sensor 33).

[0024] 4(a) and (b), the transport conveyor 21 has two transport belts 21a each wound around a drive pulley 41 and two driven pulleys 42. When the drive pulley 41 is driven by a conveyor drive motor 43, the pair of transport belts 21a travel in the same direction, supporting both ends of the substrate KB from below and transporting it in the X-axis direction.

[0025] 4(a) and (b), a work position where the mounting head 15 performs component mounting work is set on the transport path of the board KB formed by the transport conveyor 21. A target stop position M is set at a position corresponding to the leading end of the board KB positioned at the work position.

[0026] 4(a) and (b), a deceleration start reference position E0 is set upstream of target stop position M, and a stop operation start position E1 is set slightly upstream of target stop position M. In addition, an overrun detection position E2 is set slightly downstream of target stop position M. The distance from the stop operation start position E1 to target stop position M (set stop distance) is D, and the distance from target stop position M to overrun detection position E2 (overrun detection distance) is L (FIG. 4(a)).

[0027] 4(a) and (b), the first sensor 31 is provided at a position to detect when the leading edge of the board KB being transported by the transport conveyor 21 has reached the deceleration start reference position E0. The second sensor 32 is provided at a position to detect when the leading edge of the board KB being transported by the transport conveyor 21 has reached the stop operation start position E1. The third sensor 33 is provided at a position to detect when the leading edge of the board KB being transported by the transport conveyor 21 has reached the overrun detection position E2.

[0028] The first sensor 31, the second sensor 32 and the third sensor 33 are all transmission type optical sensors, and detect when the leading edge of the board KB transported by the transport conveyor 21 blocks the detection light of each sensor, thereby detecting that the leading edge of the board KB has reached the position of the detection light of that sensor. The detection information of each of the first sensor 31, the second sensor 32 and the third sensor 33 is input to the control device 17 (FIG. 3).

[0029] In FIG. 3, the control device 17 includes the above-mentioned storage unit 17a and operation control unit 17b, as well as a delay time setting unit 17c, a timer 17d, and a delay time changing unit 17e. The delay time setting unit 17c sets a deceleration start delay time. Here, the "deceleration start delay time" refers to the time from when the leading end of the board KB being transported by the transport conveyor 21 reaches the deceleration start reference position E0 (the leading end of the board KB is detected by the first sensor 31) until the transport conveyor 21 starts to decelerate the transport speed of the board KB. The initial value of the delay time setting unit 17c is stored in the storage unit 17a, and the delay time setting unit 17c reads out the initial value from the storage unit 17a and sets it as the deceleration start delay time at the start of the component mounting operation. Thereafter, when the deceleration start delay time is changed by the delay time changing unit 17e described later, the changed value is read out and set as the deceleration start delay time.

[0030] When the first sensor 31 detects that the leading edge of the board KB being transported by the transport conveyor 21 has reached the deceleration start reference position E0, the timer 17d measures the elapsed time from the point of detection. Then, when the elapsed time reaches the deceleration start delay time set by the delay time setting unit 17c, the timer 17d outputs information to that effect to the operation control unit 17b.

[0031] When the third sensor 33 detects that the leading edge of the board KB being transported by the transport conveyor 21 has passed the target stop position M and reached the overrun detection position E2 (i.e., when an overrun has occurred), the delay time changing unit 17e sets (changes) the deceleration start delay time set at that time to a new value. Specifically, when an overrun has occurred, the delay time changing unit 17e subtracts the time it takes for the leading edge of the board KB to move from the target stop position M to the overrun detection position E2 (referred to as "overrun time ΔT") from the deceleration start delay time set at that time to set a new deceleration start delay time.

[0032] In this embodiment, substrate transport mechanism 12 and memory unit 17a, operation control unit 17b, delay time setting unit 17c, timer 17d and delay time changing unit 17e of control device 17 constitute substrate transport system 50 which transports substrate KB and positions it at a predetermined target stop position M (FIG. 3). FIG. 5 shows the transport speed V of substrate KB over time (as a profile with respect to time T) as substrate transport system 50 transports substrate KB by transport conveyor 21 until the leading edge of substrate KB reaches target stop position M as a trigger to stop transport of substrate KB.

[0033] 5, when the substrate KB is sent from the upstream side, transportation of the substrate KB begins (arrow A shown in FIG. 6(a)), and the transport speed V of the substrate KB is accelerated until it reaches a predetermined normal transport speed VJ. Then, when the transport speed V of the substrate KB reaches the normal transport speed VJ (time T1 at which acceleration is completed shown in FIG. 5), the transport speed V is thereafter maintained at a constant speed of the normal transport speed VJ.

[0034] When the first sensor 31 detects that the leading edge of the substrate KB being transported at the normal transport speed VJ has reached the deceleration start reference position E0 (FIG. 6(a); substrate detection time T2 shown in FIG. 5), the operation control unit 17b uses the timer 17d to measure the elapsed time from the point in time when the leading edge of the substrate KB was detected by the first sensor 31. Then, when the elapsed time measured by the timer 17d reaches the set deceleration start delay time GT (FIG. 5) (deceleration start time T3 shown in FIG. 5), the transport speed V is decelerated to a preset stop speed VT.

[0035] The deceleration of the transport speed V of the board KB by the transport conveyor 21 continues until the transport speed V reaches the stop speed VT (deceleration end time T4 shown in FIG. 5), after which the board KB is transported at the constant speed of the stop speed VT. Then, when the second sensor 32 detects that the leading edge of the board KB being transported by the transport conveyor 21 at the stop speed VT has reached the stop operation start position E1 (FIG. 6(b), stop operation start time T5 shown in FIG. 5), the operation control unit 17b stops the transport of the board KB by the transport conveyor 21. This causes the board KB to stop at a position past the stop operation start position E1 (ideally at the target stop position M).

[0036] Here, if the deceleration start delay time GT is set to an appropriate value for the weight of the board KB and the slippage state on the transport belt 21a, the board KB will stop without the leading edge of the board KB overrunning (without the leading edge of the board KB reaching the overrun detection position E2). However, if the deceleration start delay time GT is longer than the appropriate value, the board KB may overrun, and in this case the leading edge of the board KB will reach the overrun detection position E2 and be detected by the third sensor 33 (FIG. 6(c)). In this state where an overrun has occurred, the board KB is significantly displaced from the working position, so the operation control unit 17b operates the transport conveyor 21 to move the board KB backward so that the leading edge of the board KB approaches the target stop position M (FIG. 6(d), arrow B shown in the figure).

[0037] In this retreat operation of the substrate KB, it is sufficient that the leading edge of the substrate KB is positioned upstream of the overrun detection position E2 (toward the target stop position M). Therefore, the movement amount of the substrate KB when the substrate KB retreats may be simply defined as the distance from the target stop position M to the overrun detection position E2 (overrun detection distance L).

[0038] In this way, when the time elapsed since the first sensor 31 detects that the leading end of the board KB being transported by the transport conveyor 21 has reached the deceleration start reference position E0 reaches the predetermined deceleration start delay time GT (when the time elapsed measured by the timer 17d reaches the deceleration start delay time GT), the operation control unit 17b decelerates the transport speed V of the board KB by the transport conveyor 21 to the predetermined stop speed VT, and then, when the second sensor 32 detects that the leading end of the board KB has reached the stop operation start position E1, the operation control unit 17b stops the transport of the board KB by the transport conveyor 21. Furthermore, after stopping the transport of the board KB by the transport conveyor 21, when the third sensor 33 detects that the leading end of the board KB has reached the overrun detection position, the operation control unit 17b operates the transport conveyor 21 to move the board KB backward so that the leading end of the board KB approaches the target stop position M.

[0039] Furthermore, as described above, when an overrun of the substrate KB occurs, the delay time change unit 17e subtracts the time required for the leading edge of the substrate KB to move from the target stop position M to the overrun detection position E2 (overrun time ΔT) from the current deceleration start delay time GT to set a new deceleration start delay time GT. Specifically, the overrun time ΔT is calculated by using the overrun detection distance L and the stop speed VT as its approximate value, and calculating ΔT=L / VT. Alternatively, when the time required from when the second sensor 32 detects the leading edge of the substrate KB until when the third sensor 33 detects the leading edge of the substrate KB (stop time) is MT, the stop time MT, the set stop distance D, and the stop speed VT may be used to calculate ΔT=MT-D / VT.

[0040] Next, the transfer procedure (substrate positioning method) of the substrate KB by the substrate transfer system 50 based on the time profile of the transfer speed V of the substrate KB shown in Fig. 5 described above will be described with reference to the flowchart shown in Fig. 7. The substrate transfer system 50 starts positioning the substrate KB to the work position when the component mounting device 1 starts the component mounting operation. To do this, first, a deceleration start delay time GT is set (step ST1). Specifically, the operation control unit 17b reads out an initial value of the deceleration start delay time GT from the memory unit 17a, and sets the read initial value as the deceleration start delay time GT.

[0041] After setting the deceleration start delay time GT, when the board KB is sent from the upstream side, the conveyor drive motor 43 is operated to start transport of the board KB by the transport conveyor 21 (step ST2). Then, the system enters a state of waiting for the first sensor 31 to detect the leading edge of the board KB (step ST3). When the first sensor 31 detects the leading edge of the board KB (FIG. 6(a)), the timer 17d measures the elapsed time from that point (step ST4), and the system enters a waiting state until the elapsed time reaches the set deceleration start delay time GT (step ST5).

[0042] When the elapsed time reaches the deceleration start delay time GT, the transport speed V is decelerated from the normal transport speed VJ to the stop speed VT (deceleration process of step ST6), and the process enters a state of waiting for detection of the leading edge of the substrate KB by the second sensor 32 (step ST7). Then, when the second sensor 32 detects the leading edge of the substrate KB (FIG. 6(b)), the operation of the transport conveyor 21 is stopped, and the transport operation of the substrate KB is stopped (stop process of step ST8).

[0043] When the conveying operation of the board KB by the conveyor 21 is stopped, the timer 17d starts measuring time (step ST9). Then, the timer 17d judges whether the leading edge of the board KB is detected by the third sensor 33 (step ST10) until a predetermined time (overrun detection time) has elapsed (step ST11). If the leading edge of the board KB is not detected by the third sensor 33 during that time, it is determined that the board KB has not overrun, and the positioning operation of the board KB is terminated. On the other hand, if the leading edge of the board KB is detected by the third sensor 33 before the overrun detection time has elapsed (FIG. 6(c)), the conveyor drive motor 43 of the conveyor 21 is rotated in the opposite direction, and the conveyor 21 is operated to move the board KB backward so that the leading edge of the board KB approaches the target stop position M (overrun processing step of step ST12, FIG. 6(d)).

[0044] After the substrate KB is moved backward in step ST12, the overrun time ΔT is calculated as described above (step ST13). Then, after the overrun time ΔT is calculated, the calculated overrun time ΔT is subtracted from the deceleration start delay time GT (GT=GT-ΔT) to set a new deceleration start delay time GT (deceleration start delay time changing step ST14), and the positioning operation of the substrate KB is terminated.

[0045] As described above, in the substrate transport system 50 of this embodiment and the substrate positioning method using the same, when it is detected that the leading edge of the substrate KB has exceeded the target stop position M and reached the overrun detection position E2, the timing to start decelerating the transport speed V of the substrate KB is accelerated to prevent the substrate KB from overrunning, and the time width for accelerating the timing to start deceleration is set to the time (overrun time ΔT) required for the leading edge of the substrate KB to move from the target stop position M to the overrun detection position E2. Therefore, even if an overrun occurs, it can be corrected quickly and accurately, and the time loss associated with the positioning of the substrate KB can be prevented, thereby improving productivity.

[0046] Although the embodiment of the present invention has been described so far, the present invention is not limited to the above, and various modifications are possible. For example, in the above embodiment, the movement amount of the board KB to be moved back when the board KB overruns beyond the target stop position M is simply set to the overrun detection distance L between the target stop position M and the overrun detection position E2, but the board KB may be moved back by a distance obtained by accurately measuring the overrun distance by which the leading end of the board KB overruns the target stop position M. Also, in the above embodiment, an example is shown in which the board transport system 50 and the method for positioning the board KB according to the present invention are applied to the component mounting device 1, but the present invention can be similarly applied to other component mounting devices (for example, a screen printing device, an inspection device, etc.). [Industrial Applicability]

[0047] To provide a substrate transport system and a substrate positioning method capable of quickly and accurately correcting an overrun even if it occurs, preventing time loss associated with substrate positioning, and improving productivity. [Explanation of symbols]

[0048] 17b Operation control section 17e Delay time change section 21 Transport Conveyor 31 First Sensor 32 Second Sensor 33 The third sensor 50 Substrate transport system M Target stop position GT deceleration start delay time ΔT Overrun Time E0 Deceleration start reference position E1 Stop operation start position E2 Overrun detection position VT stop speed L Overrun detection distance D Set Stop Distance KB board

Claims

1. A substrate transport system that transports a substrate and positions it at a predetermined target stopping position, A transport conveyor that transports the substrate; a first sensor that detects a state in which a leading end of the substrate transported by the transport conveyor reaches a deceleration start reference position that is set upstream of the target stop position; a second sensor that detects a state in which a leading end of the substrate conveyed by the transport conveyor has reached a stop operation start position set slightly upstream of the target stop position; a third sensor that detects a state in which a leading end of the board transported by the transport conveyor reaches an overrun detection position set slightly downstream of the target stop position; an operation control unit that decelerates the transport speed of the substrate by the transport conveyor to a preset stop speed when a time elapsed since it is detected that the leading end of the substrate transported by the transport conveyor has reached the deceleration start reference position reaches a preset deceleration start delay time, and then stops transport of the substrate by the transport conveyor when it is detected that the leading end of the substrate has reached the stop operation start position, and after the transport of the substrate by the transport conveyor is stopped, operates the transport conveyor to move the substrate back so that the leading end of the substrate approaches the target stop position when it is detected that the leading end of the substrate has reached the overrun detection position; a delay time changing unit that, when it is detected that a state in which the leading end of the substrate has reached the overrun detection position, subtracts an overrun time required for the leading end of the substrate to proceed from the target stop position to the overrun detection position from the deceleration start delay time to set a new deceleration start delay time; A substrate transfer system comprising:

2. 2. The substrate transport system according to claim 1, wherein the overrun detection distance from the target stop position to the overrun detection position is L, and the stop speed is VT, and the overrun time .DELTA.T is calculated by .DELTA.T=L / VT.

3. 2. The substrate transport system of claim 1, wherein a set stopping distance, which is a distance from the stopping operation start position to the target stopping position, is D, the stopping speed is VT, and a stopping time, which is a time required from when the second sensor detects the leading edge of the substrate to when the third sensor detects the leading edge of the substrate, is MT, and the overrun time ΔT is calculated by ΔT = MT - D / VT.

4. A substrate positioning method for transporting a substrate by a transport conveyor and positioning the substrate at a predetermined target stopping position, comprising the steps of: a deceleration process for decelerating a transport speed of the substrate by the transport conveyor to a preset stop speed when an elapsed time from when a leading end of the substrate transported by the transport conveyor reaches a deceleration start reference position set upstream of the target stop position reaches a preset deceleration start delay time; a stopping step of stopping the transport of the substrate by the transport conveyor when a leading end of the substrate transported by the transport conveyor at the stopping speed reaches a stopping operation start position set slightly upstream of the target stopping position; an overrun processing step of, when a leading edge of the substrate reaches an overrun detection position set slightly downstream of the target stop position after the substrate is stopped from being transported by the transport conveyor, operating the transport conveyor to move the substrate back so that the leading edge of the substrate approaches the target stop position; a deceleration start delay time changing step of, when the leading end of the substrate reaches a previous overrun detection position, subtracting an overrun time required for the leading end of the substrate to move from the target stop position to the overrun detection position from the deceleration start delay time to set a new deceleration start delay time; A substrate positioning method comprising:

5. 5. The substrate positioning method according to claim 4, wherein, when an overrun detection distance from said target stop position to said overrun detection position is L and said stop speed is VT, said overrun time .DELTA.T is calculated by .DELTA.T=L / VT.

6. 5. The substrate positioning method of claim 4, wherein a set stopping distance which is a distance from the stopping operation start position to the target stopping position is D, the stopping speed is VT, and a stopping time which is a time required from when a leading edge of the substrate reaches the stopping operation start position until when the leading edge of the substrate reaches the overrun detection position is MT, and the overrun time ΔT is calculated by ΔT=MT-D / VT.

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