JP7808415B2 - production line - Google Patents

Description

The present invention relates to a production line.

For example, in an automobile body assembly and welding line, shell parts such as door panels are individually manufactured on the shell assembly line, and each shell part manufactured on the shell assembly line is then supplied to the main assembly and welding line, where the body-in-white is assembled and welded (see, for example, Patent Document 1).

Patent Document 2 also describes the use of a common AGV (automated guided vehicle) to transport workpieces on the main body assembly line and between the assembly lines, with the aim of reducing equipment costs through standardization of transport equipment.

Japanese Patent Application Laid-Open No. 2000-272560 Japanese Patent Application Laid-Open No. 2019-14006

Meanwhile, on a manufacturing line like the one described above, multiple processes are carried out, and workers in charge of each process may perform specified tasks on the workpieces while moving alongside them as they move along the line. In this case, the workpieces on the line are transported at a predetermined speed so that they fit within a predetermined takt time (the standard work time per process, which refers to the work time common to all processes on the line to which that process belongs; the same applies below). In other words, the speed at which the AGV transports the workpieces (= the movement speed of the AGV) is controlled to a predetermined value so that the time it takes for a worker to perform specified tasks on the workpieces while moving alongside them, and then return to the start position after completing the tasks, is less than the takt time. On the other hand, from the perspective of minimizing worker waiting time, it is desirable to control the movement speed of the AGV to a constant value so that the time required for the series of operations described above is as close to the takt time as possible.

Here, if the change in takt time is made on the order of less than one minute (for example, a few seconds to a few tens of seconds), it becomes necessary to change the AGV's movement speed on the order of ¹⁰ m/min, or in some cases 10 ^m /min. Changing the movement speed on the same order of magnitude requires an expensive AGV, leading to a rise in equipment costs. Furthermore, if a single AGV is to be used for both on-line workpiece transport and inter-line transport, as described above, an AGV with a wide settable speed range and a changeable speed unit that is very small compared to the speed range is required, leading to a further rise in equipment costs.

In light of the above, the technical problem to be solved in this specification is to provide a manufacturing line that can flexibly respond to fluctuations in takt time while suppressing increases in equipment costs.

The above-mentioned problem is solved by the production line of the present invention. Specifically, this production line includes a work line for transporting workpieces while performing predetermined operations on the workpieces, and an AGV capable of moving along the work line while holding the workpieces. The production line further includes a speed setting unit that can set the movement speed of the AGV in stages in predetermined speed increments, and is characterized by the fact that the speed setting unit can vary the movement speed up and down by detecting multiple detectable objects arranged on the work line as the AGV moves.

In this way, in the present invention, when the AGV's movement speed is set in stages in predetermined speed units, the AGV's movement speed can be increased or decreased by utilizing a function that allows the AGV to change its movement speed when it detects an object. This makes it possible to set the AGV's movement speed (average movement speed) while moving along the work line in units smaller than the speed units that the AGV can originally set. This allows the average movement speed to be fine-tuned according to the takt time, even with a general-purpose, inexpensive AGV, making it possible to avoid rising equipment costs while minimizing worker waiting time and flexibly responding to changes in takt time.

Furthermore, in the production line according to the present invention, the speed setting unit may be capable of alternately switching the movement speed between a first movement speed and a second movement speed that is greater than the first movement speed by one speed unit, depending on the cumulative number of detected objects.

In this way, by varying the movement speed up or down based on the cumulative number of detected objects by the AGV, the average movement speed of the AGV can be easily fine-tuned without having to perform complex settings such as changing the type or placement of the detected objects. Furthermore, by alternately raising and lowering the movement speed by speed units, the average movement speed can be fine-tuned efficiently. Therefore, this configuration makes it possible to flexibly respond to takt time more easily and at lower cost.

Furthermore, when the movement speed is varied up or down by a speed unit, in the production line of the present invention, the speed setting unit may adjust the ratio of the set time of the second movement speed to the set time of the first movement speed.

In this way, by adjusting the ratio of the set times for the first and second movement speeds, which differ by a speed unit, the average movement speed of the AGV can be accurately set. In other words, the ratio of the set times for the first and second movement speeds while the AGV is moving on the work line determines the magnitude of the average movement speed as the ratio between the first movement speed and the second movement speed, so by setting the average movement speed in this way, it is possible to more easily and accurately fine-tune the average movement speed.

In this case, in the production line according to the present invention, the speed setting unit may be able to set the movement speed so that the time periods of the first movement speed and the second movement speed are evenly distributed in time series.

As described above, when workers in charge of each process on a production line work while moving with their workpieces, they can intuitively grasp the progress of the work they are currently performing from their own position. However, if, for example, the time period when the relatively faster second movement speed is used is concentrated in the latter half of the process, the relationship between the worker's position and the actual progress of the work will differ from the previous relationship, making it difficult to grasp the progress of the work in the same intuitive manner as before. In contrast, by allowing the first and second movement speeds to be alternated so that the time periods of the first and second movement speeds are evenly distributed chronologically, it is possible to avoid situations where one movement speed is biased toward another. This allows workers to grasp their own progress (position) in the same intuitive manner as before. This makes it possible to flexibly respond to takt time while maintaining worker productivity.

Furthermore, in the production line according to the present invention, multiple detection objects may be arranged at equal intervals on the work line.

In this way, by arranging multiple detectable objects at equal intervals, it is easy to determine the time it takes to move at a constant speed (= interval between detectable objects / moving speed). As a result, the average moving speed can be calculated instantly and accurately based on the moving speed fluctuation history, making it possible to more easily and accurately fine-tune the average moving speed of the AGV.

Furthermore, in the production line according to the present invention, the AGV may be a path-guided AGV that can move along guides on the work line, and the speed setting unit may be able to change the movement speed up or down when it detects multiple guides as detection targets arranged intermittently along the work line.

In this way, a route-guided AGV that can move along a guide is a general-purpose AGV and can be obtained inexpensively. Furthermore, if a guide is used as the object to be detected, the guide can be used as the object to be detected using the functions that route-guided AGVs normally have. Therefore, it is possible to build a production line with the above configuration inexpensively.

As described above, the present invention makes it possible to provide a manufacturing line that can flexibly respond to fluctuations in takt time while suppressing increases in equipment costs.

1 is a plan view of a main part of a manufacturing line according to an embodiment of the present invention; 2 is a graph showing an example of a history of speeds set by the speed setting unit shown in FIG. 1 for the AGV. 10 is a graph showing another example of the speed history set by the speed setting unit shown in FIG. 1 .

The following describes the details of a production line according to one embodiment of the present invention, with reference to the accompanying drawings.

Figure 1 shows a plan view of a production line 10 according to this embodiment. As shown in Figure 1, this production line 10 mainly comprises a work line 12 for performing predetermined operations on a workpiece 11, an AGV 13 that can move along the work line 12 while holding the workpiece 11, and a speed setting unit 14 that can set the speed of the AGV 13.

The work line 12 has work areas A (A1, A2...An) for carrying out multiple processes S (S1, S2...Sn). Each work area A is staffed with a worker W (W1, W2...Wn) in charge of each process S. In this embodiment, the work 11 carried into each work area A by the AGV 13 moves along the flow direction X of the work line 12, and the worker W for each process S performs predetermined tasks on the work 11 while moving along the work line 12 together with the work 11.

In this embodiment, the work area A of each process S has dimensions equal to the flow direction X of the work line 12.

In this embodiment, the AGV 13 is a route-guided AGV that is capable of moving along guides (first guides 15) that are continuously arranged on the work line 12. In this embodiment, as shown in FIG. 1, the first guides 15 are continuously arranged along the work line 12. The first guides 15 are arranged so as to pass through all work areas A (A1, A2...An) on the work line 12. The AGV 13 detects the first guides 15 with a sensor (not shown), and is capable of moving on the first guides 15 in the direction in which the first guides 15 extend.

Furthermore, second inductors 16, which are inductors for setting the speed, are arranged intermittently along the first inductors 15 on the work line 12. These multiple second inductors 16 correspond to the detection objects according to the present invention. In this embodiment, a predetermined number (10 in FIG. 1) of second inductors 16 are arranged per process S. Furthermore, these multiple second inductors 16 are arranged at equal intervals in the flow direction X. The AGV 13 detects the second inductors 16 using a sensor (not shown) and transmits the detection information to the speed setting unit 14.

From a cost perspective, magnetic materials such as magnetic tape are preferred for the first and second inductors 15, 16, but this is not a limitation. Induction methods (inductors) using non-magnetic media, such as optical reflection or magnetic induction, may also be used.

The speed setting unit 14 can set the movement speed V of the AGV 13 according to a preset takt time T. When the work area A of each process S has equal dimensions in the flow direction X as described above, the movement speed V of the AGV 13 is set to an appropriate value so that the time from time t1 when the work 11 being transported by the AGV 13 begins to be carried into the work area A to time t2 when the work 11 begins to be carried out of the work area A (passage time t2 - t1 through the work area A) is less than the takt time T and is as close to the takt time T as possible.

Here, the AGV 13 is configured to be able to set the travel speed V in stages using a predetermined speed unit Vu. In this case, the travel speed V of the AGV 13 can be set within a range of multiples of the speed unit Vu, which is set to a predetermined magnitude in advance. Therefore, the speed setting unit 14 first sets the travel speed V within the above-mentioned settable range so that one work area A can be passed through in the same time as the takt time T. Then, if it is not possible to set a travel speed V that can pass through one work area A in the same time as the takt time T, the first travel speed V1 is set to a value obtained by adding the lower limit speed Vm of the AGV 13 to the largest multiple of the speed unit Vu so that one work area A can be passed through in a time slightly longer than the takt time T. Then, the second travel speed V2 is set to a value that is larger than the first travel speed V1 by the speed unit Vu.

Then, the ratio of the time period of the first moving speed V1 to the time period of the second moving speed V2 is set so that the transit time t2-t1 through one work area A is shorter than the takt time T and as close to the takt time T as possible. For example, in this embodiment, where multiple second guides 16 are arranged at ten equally spaced locations per work area A (see FIG. 1), and the moving speed V to be set is the intermediate value between the first moving speed V1 and the second moving speed V2, the speed history for each moving speed V1 and V2 is set so that there are five time periods for the first moving speed V1 and five time periods for the second moving speed V2, as shown in FIG. 2. As a result, the average moving speed VA, which is the moving speed of the AGV 13 while it is moving along the work line 12, is set to a value outside the range obtained by adding a multiple of the speed unit Vu to the lower limit speed Vm. Specifically, the average moving speed VA is set to the average value (V1 + V2)/2 of the first moving speed V1 and the second moving speed V2.

In addition, in this embodiment, the speed setting unit 14 can alternately switch the movement speed V between a first movement speed V1 and a second movement speed V2 depending on the cumulative number of detections of the second lead-in devices 16. In this embodiment, if the cumulative number of detections of the second lead-in devices 16 in one work area A is odd, the movement speed V of the AGV 13 can be switched to the first movement speed V1, and if the cumulative number of detections of the second lead-in devices 16 is even, the movement speed V of the AGV 13 can be switched to the second movement speed V2.

In addition, in order to make it easier for the worker W to intuitively grasp the progress of the work, the speed history of each movement speed V1, V2 may be set so that each movement speed V1, V2 is evenly distributed over time. Figure 2 shows an example in which the movement speed V of the AGV 13 is varied up and down so that five time periods of the first movement speed V1 alternate with five time periods of the second movement speed V2.

In any case, the movement speed V of the AGV 13 is set within an appropriate range, taking into account that the worker W works on the workpiece 11 while moving. As an example, the movement speed V is set to 0.5 m/min or more and 3.0 m/min or less.

The effects of the present invention will be explained below mainly based on Tables 1 and 2. Tables 1 and 2 show verification results when the flow direction dimension of the work area A (the moving distance of one process S of the AGV 13) is 2.5 m and the speed unit Vu of the AGV 13 is 0.15 m/min.

First, consider the stoppage time of the AGV 13 when moving through each work area A on the work line 12 at a constant movement speed V, as in the conventional case. As shown in Table 1, when the takt time T is changed in increments of 0.05 minutes (3 seconds), the speed setting unit of the conventionally configured AGV 13 sets the movement speed V in steps at a predetermined speed unit Vu (here, 0.15 m/min) as a constant speed while passing through work area A. Therefore, for example, if the takt time T is 2.4 minutes, the stoppage time of the AGV 13 can be kept to around 1 second by setting the movement speed V to 1.05 m/min. However, if the takt time T is shortened by 0.05 minutes from 2.4 minutes (if the takt time T is set to 2.35 minutes), the movement speed V of the AGV 13 must be increased by the speed unit Vu, resulting in a significant increase in stoppage time.

In contrast, in the production line 10 according to this embodiment, the AGV 13's movement speed V is fluctuated up and down by utilizing a function that allows the AGV 13 to change the movement speed V when it detects the second inductor 16 as the detection target (see Figure 2). This allows the movement speed V (average movement speed VA) of the AGV 13 while it moves along the work line 12 to be set in units smaller than the speed unit Vu that the AGV 13 can originally set (in this embodiment, a value 0.1 times Vu). For example, as shown in Table 2, if the takt time T is reduced by 0.05 minutes from 2.4 minutes to 2.35 minutes, the downtime of the AGV 13 can be significantly reduced by setting the average movement speed VA to 1.065 m/min. In this way, with the production line 10 according to this embodiment, even if a general-purpose, inexpensive AGV is used for the AGV 13, the average movement speed VA can be fine-tuned according to the takt time T, making it possible to avoid a rise in equipment costs while minimizing waiting time for workers W and flexibly responding to changes in the takt time T.

In addition, in this embodiment, the speed setting unit 14 can alternately switch the movement speed V between a first movement speed V1 and a second movement speed V2 that is greater than the first movement speed V1 by a speed unit Vu, depending on the cumulative number of detections of the second inductor 16. This makes it possible to set the average movement speed VA of the AGV 13 to a desired value with minimal fluctuations in the movement speed V. This makes it difficult for the worker W to notice fluctuations in the movement speed V, ensuring the same level of workability as before.

In addition, in this embodiment, as shown in FIG. 2, the movement speed V is switched so that the time periods of the first movement speed V1 and the second movement speed V2 are evenly distributed in chronological order, which prevents the time periods of one movement speed (e.g., the second movement speed V2) from being concentrated in the first or second half of process S. This allows worker W to grasp his or her own progress (position) in the same way as before. This makes it possible to flexibly respond to the takt time T while maintaining worker W's workability.

The above describes one embodiment of the present invention, but the production line according to the present invention can also have configurations other than those described above, as long as they do not deviate from the spirit of the invention.

Figure 3 shows a graph related to the speed history of an AGV according to another embodiment of the present invention. In this embodiment, the speed setting unit 14 is capable of setting the speed history of the AGV 13 in a manner different from the speed history shown in Figure 2. More specifically, if the average movement speed VA of the AGV 13 to be set according to the takt time T is closer to the first movement speed V1 than to the second movement speed V2, as shown in Figure 3, the speed history of each movement speed V1, V2 is set so that the time period of the first movement speed V1 is longer than the time period of the second movement speed V2. In this illustrated example, the movement history of each movement speed V1, V2 is set so that the ratio of the time period of the first movement speed V1 to the time period of the second movement speed V2 is 7:3.

In this embodiment, too, from the perspective of making it easier for worker W to intuitively grasp the progress of work, the speed history of each movement speed V1, V2 is set so that each movement speed V1, V2 is evenly distributed over time. As shown in Figure 3, if the time period of the second movement speed V2 is shorter than the time period of the first movement speed V1, it is desirable to fluctuate the movement speed V of the AGV 13 up and down so that the time period of the first movement speed V1 and the time period of the second movement speed V2 alternate in a 2:1 ratio, as shown, for example.

Of course, the speed history shown in Figures 2 and 3 is merely an example. The speed setting unit 14 can set any speed history for the movement speed V, as long as it is possible to fluctuate the movement speed V up and down and set the movement speed V (average movement speed VA) of the AGV 13 while it is moving along the work line 12 in units smaller than the speed unit Vu that the AGV 13 originally has.

In addition, while the above embodiment illustrates the application of a route-guided AGV as the AGV 13, this is of course not limited to this. For example, an AGV that does not require an inductor 15 (16), such as an autonomous mobile type, may also be applied. In this case, it is essential that a detection object for setting the speed be placed on the work line 12. Of course, if there is space available for installation other than the floor surface on the work line 12, such as the side of the work line 12, the detection object may be placed on a surface other than the floor surface (such as the ceiling surface).

10 Manufacturing line 11 Work 12 Work line 13 AGV
14 Speed setting unit 15 First lead 16 Second lead A Work area S Process T Takt time V Movement speed V1 First movement speed V2 Second movement speed VA Average movement speed Vm Lower limit speed Vu Speed unit W Worker X Conveyance direction

Claims (2)

a work line for carrying out a predetermined operation on the work while transporting the work;
an AGV capable of moving on the work line while holding the workpiece,
a speed setting unit that can set the movement speed of the AGV in stages in predetermined speed units;
A manufacturing line characterized in that the speed setting unit varies the movement speed of the AGV up and down by detecting multiple objects arranged on the work line as the AGV moves, thereby making it possible to adjust the average movement speed of the AGV while it is moving on the work line to be smaller than the specified speed unit that can be set by the speed setting unit . The manufacturing line described in claim 1, wherein the speed setting unit alternately switches the movement speed between a first movement speed and a second movement speed that is greater than the first movement speed by the speed unit, depending on the cumulative number of detections of the detection target object.