Linear motor transport system and operation method thereof

Abstract

This linear motor transport system 100 comprises a carrier 10 to which a linear scale 14 and a reference mark 16 are fixed, a linear motor 12 that moves the carrier 10 along a route D, a plurality of sensors 18 arranged along the route D, and a control device 20. When the linear motor 12 is controlled such that the carrier 10 is moved as an initial process, the control device 20 identifies the position of the carrier 10 not on the basis of a reference-mark 14-related output produced by a sensor 18 that has not detected the linear scale 16 among the plurality of sensors 18, but rather on the basis of a reference-mark 14-related output produced by a sensor 18 that has detected the linear scale 16.

Description

[Technical Field]

[0001] The present invention relates to a linear motor transport system and an operation method thereof. [Background technology]

[0002] A conventional linear motor conveyance system is known as a conveyance system for conveying articles, in which a carrier is driven by a linear motor and the carrier conveys the articles. The linear motor conveyance system includes a carrier that holds the articles to be conveyed, a linear motor mover attached to the carrier, a linear motor stator including a plurality of electromagnets (coil units) arranged along a path, and a control device that controls the supply of current to the plurality of electromagnets to move the carrier along the path, and conveys the articles held by the carrier as the mover moves along the path.

[0003] While conventional conveyors move objects in the same direction at a constant speed, linear motor transport systems can individually control the movement of multiple carriers that hold objects. They also allow for flexible control, such as stopping carriers precisely where needed, changing speed, or moving only one carrier in the opposite direction. Furthermore, because linear motor transport systems are driven by linear motors, they are cleaner than transport systems that use other drive methods because they do not generate dust or other particles.

[0004] For this reason, linear motor transport systems have a wide range of applications, such as inter-process transport and processing lines where precision processing is performed on the transport path.

[0005] In a linear motor conveyance system, in order to control the position of the mover, it is necessary to continuously grasp the position of the mover relative to the stator. Conventionally, a linear motor conveyance system has been proposed in which the position of the mover is detected by reading a linear scale provided on the stator side with a sensor provided on the mover side (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-219296 Summary of the Invention [Problem to be solved by the invention]

[0007] In conventional linear motor conveyance systems such as that described in Patent Document 1, a sensor is provided on the mover side, so wiring that outputs the detection results of the sensor needs to be drawn out from the mover side, which restricts the movable range of the mover.

[0008] The present invention has been made in light of these circumstances, and one exemplary purpose of an embodiment of the present invention is to provide a linear motor transport system with improved commercial value. [Means for solving the problem]

[0009] In order to solve the above problems, a linear motor conveyance system according to one aspect of the present invention includes a carrier having a linear scale and a reference mark fixed thereto, a linear motor that moves the carrier along a predetermined path, a plurality of sensors arranged along the path, and a control device. When the control unit controls the linear motor to move the carrier as an initial process, it identifies the position of the carrier based on the output of the sensor that detects the linear scale, not on the output of the sensor that does not detect the linear scale, which is related to the reference mark.

[0010] Another aspect of the present invention is a method for operating a linear motor transport system including a carrier having a linear scale and a reference mark fixed thereto, and a linear motor that moves the carrier along a predetermined path, the method including moving the carrier as an initial process, and identifying a position of the carrier based on an output related to the reference mark from a sensor that detects the linear scale, but not based on an output related to the reference mark from a sensor that does not detect the linear scale, among a plurality of sensors.

[0011] Any combination of the above components, or mutual substitution of the components or expressions of the present invention between methods, devices, systems, etc., are also valid aspects of the present invention. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a linear motor conveyance system with increased commercial value. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a plan view of a linear motor conveyance system according to an embodiment. [Figure 2] 2 is a side view showing the carrier and its periphery in FIG. 1. FIG. [Figure 3] 2 is a timing chart showing outputs from a sensor when the carrier in FIG. 1 is moved as an initial process. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described below based on preferred embodiments with reference to the drawings. The embodiments are illustrative and do not limit the invention, and all features and combinations described in the embodiments are not necessarily essential to the invention. The same or equivalent components, parts, and processes shown in each drawing are designated by the same reference numerals, and redundant descriptions will be omitted where appropriate.

[0015] Fig. 1 is a plan view showing a schematic configuration of a linear motor conveyance system 100 according to an embodiment. Fig. 2 is a side view showing a carrier 10 of the linear motor conveyance system 100 and its surroundings.

[0016] The linear motor conveying system 100 includes a carrier 10 for holding an article to be conveyed, a linear motor 12 for driving the carrier 10, a reference mark 14 and a linear scale 16 fixed to the carrier 10, a plurality of sensors 18 arranged along a path P along which the carrier 10 can move, and a control device 20 for overall control of the linear motor conveying system 100. Each of the plurality of sensors is connected to the control device 20 by wire. Note that for ease of understanding, the number of carriers 10 is set to one, but this is not limited thereto, and typically a plurality of carriers 10 are provided.

[0017] The linear motor 12 includes a stator 22 and a mover 24 attached to the carrier 10 .

[0018] In this embodiment, the stator 22 is formed in a rectangular shape that is long in the direction D in a plan view. The stator 22 includes a plurality of electromagnets (coil units) 26 that are aligned in the direction D. Only some of the electromagnets 26 are shown in FIG. 1 as an example. Current can be supplied individually to the plurality of electromagnets 26 from a power source 34. The arrangement of the plurality of electromagnets 26 defines a path P. Although not particularly limited, in this embodiment, the path P is linear.

[0019] The mover 24 is attached to the lower surface of the carrier 10 so as to face the electromagnet 26 from above and below. The mover 24 includes a magnet. The mover 24 moves along a path P due to the interaction between the magnetic field generated by the electromagnet 26 and the magnetic field of the magnet of the mover 24.

[0020] The stator 22 may be provided with a linear guide that guides the movement of the mover 24 or the carrier 10. Alternatively, the mover 24 may be magnetically levitated above the stator 22 without providing a linear guide.

[0021] In this example, the reference mark 14 is provided on the lower surface of the carrier 10. The reference mark 14 may also be provided on the linear scale 16. The reference mark 14 is not particularly limited, but may be a magnet if the sensor 18 is magnetic, or may be marked glass or steel tape if the sensor is optical.

[0022] The position of the reference mark 14 on the carrier 10 in the D direction (hereinafter simply referred to as the position of the reference mark 14) preferably coincides with the reference position of the carrier 10 in the D direction (hereinafter simply referred to as the reference position of the carrier 10). The reference position is a reference position for the carrier 10 in the D direction, and is typically the center position of the carrier 10 in the D direction. When the position of the reference mark 14 coincides with the reference position of the carrier 10, the position of the reference mark 14 becomes the position of the carrier 10.

[0023] The reference mark 14 may be provided at any position on the carrier 10, but the relative position of the reference mark 14 with respect to the reference position must be known. If the position of the reference mark 14 does not match the reference position of the carrier 10, the position of the carrier 10 can be determined by taking into account the absolute position of the reference mark 14 and the distance in the D direction between the reference position and the reference mark 14.

[0024] In the following, for the sake of simplicity, it is assumed that the position of the reference mark 14 coincides with the reference position of the carrier.

[0025] In this example, the linear scale 16 is fixed to the underside of the carrier 10 in the same manner as the reference mark 14. The linear scale 16 is not particularly limited, but may be a magnetic scale if the sensor 18 is magnetic, or may be a graduated glass scale or steel tape if the sensor is optical. The linear scale 16 is provided on the carrier 10 so that the center of the linear scale 16 in the D direction coincides with the reference position of the carrier 10, although this is not a limitation.

[0026] The linear scale 16 has an effective area 16a and two ineffective areas 16b adjacent to both ends of the effective area 16a in direction D. The effective area 16a is an area where the sensor 18 can read the scale, and the ineffective areas 16b are areas where the sensor 18 cannot read the scale.

[0027] The sensor 18 includes a mark detection unit 28 configured to be able to detect the reference mark 14, and a scale detection unit 29 configured to be able to detect the linear scale 16. In this embodiment, the sensor 18 is arranged so that, in a plan view, the mark detection unit 28 is located on the movement path of the reference mark 14, and the scale detection unit 29 is located on the movement path of the linear scale 16.

[0028] When the mark detection unit 28 detects the reference mark 14, that is, when the reference mark 14 passes directly above the mark detection unit 28, it outputs a pulse signal of a predetermined intensity or greater to the control device 20. The pulse width of the pulse signal is preferably approximately the same as the resolution of the mark detection unit 28, but may be longer. The control device 20, as will be described in detail later, determines whether the reference mark 14 is located directly above the mark detection unit 28 based on the signal output by the mark detection unit 28.

[0029] The scale detection unit 29 reads the scale provided on the linear scale 16 that moves above the scale detection unit 29, and outputs one pulse signal to the control device 20 every time the linear scale 16 and therefore the carrier 10 move R [μm] (R is the resolution of the scale detection unit 29). In other words, the scale detection unit 29 outputs a number of pulse signals corresponding to the movement distance of the linear scale 16 and therefore the carrier 10. The control device 20 counts the pulse signals output by the scale detection unit 29 to identify (detect) the position of the carrier 10 in the D direction or the amount of change in position. Note that the following describes the case where the position is identified.

[0030] Although the multiple sensors 18 are not particularly limited, they are arranged at equal intervals in this example. Specifically, they are arranged at intervals S. The multiple sensors 18 are particularly arranged so that the interval S between the sensors 18 and the length of the effective area 16a of the linear scale 16 (hereinafter referred to as the "effective area length") Le satisfy the relationship "interval S < effective area length Le." In this case, no matter where the carrier 10 is located on the path P, the effective area 16a of the linear scale 16 is located in the detection area of ​​one of the sensors 18 (i.e., directly above the sensor 18), so the position of the carrier 10 can be identified. It is assumed that the positions of each of the multiple sensors 18 are known.

[0031] The control device 20 includes a position specifying unit 30 and a linear motor control unit 32 that controls the linear motor 12 to move the carrier 10 .

[0032] The linear motor control unit 32 controls the supply of current from the power source 34 to each electromagnet 26 while feeding back position information of the carrier 10 identified by the position identification unit 30 as described below, thereby moving the carrier 10 to the desired position.

[0033] The position determination unit 30 determines the position of the carrier 10 based on the output of the sensor 18 .

[0034] Linear motor conveyance systems are stopped and started regularly or irregularly. For example, in some factories, for safety reasons, they are stopped when work hours end and started when work hours begin. Also, for example, if a linear motor conveyance system is used on each of multiple processing lines, the number of processing lines in operation may increase or decrease as the number of product orders increases or decreases, and therefore the linear motor conveyance system may be stopped and started accordingly.

[0035] When a linear motor transport system stops, specifically when the power to its control device is turned off, the carrier position information held by the control device is lost. While it is conceivable that the control device could retain the position information, there is no guarantee that the carrier will not move while the linear motor transport system is stopped. Therefore, when the linear motor transport system is started, the position must be identified.

[0036] Therefore, in the linear motor conveying system 100, as an initial process immediately after startup, the linear motor control unit 32 moves the carrier 10 and determines the position of the carrier 10 by having one of the sensors 18 detect the reference mark 14.

[0037] When a signal of a threshold intensity or greater (hereinafter also referred to as a high level) is output from the mark detection unit 28 of any one of the multiple sensors 18_1 to 18_N (N is an integer of 2 or greater, and in the examples of FIGS. 1 to 3, N is 3 or greater), specifically when a high-level signal is output from the first detection unit 28 of sensor 18_i, for example, the position identification unit 30 identifies that the reference mark 14, and therefore the carrier 10, is located directly above that sensor 18_i. The position identification unit 30 determines that the sensor 18_i that detected the reference mark 14 is the sensor that serves as the reference for identifying the absolute position of the carrier 10 (hereinafter referred to as the "reference sensor").

[0038] The position specifying unit 30 counts the pulse signals output from the scale detecting unit 29 of the reference sensor as the carrier 10 moves, with the count being "0" when the reference mark 14 is located directly above the reference sensor.

[0039] The position specifying unit 30 specifies the distance of the carrier 10 from the reference sensor, i.e., the relative position of the carrier 10 with respect to the reference sensor, based on the count value of the pulse signal output from the scale detection unit 29 of the reference sensor. The position specifying unit 30 specifies the position of the carrier 10 by adding the specified relative position to the position of the reference sensor.

[0040] When the carrier 10 moves a certain distance, the effective area 16a of the linear scale 16 moves out of the detection range (i.e., directly above) of the scale detection unit 29 of the reference sensor. When this happens, the position of the carrier 10 cannot be determined based on the output of the reference sensor. Therefore, before the effective area 16a of the linear scale 16 moves out of the detection range of the reference sensor, it is necessary to use a sensor 18 adjacent to the reference sensor, whose effective area 16a of the linear scale 16 is within its detection range (i.e., directly above), as the new reference sensor. In other words, it is necessary to switch the reference sensor.

[0041] Specifically, for example, when the sensor 18_i is the reference sensor, if the carrier 10 moves to the right side of the paper in the direction D and the relative position of the carrier 10 with respect to the sensor 18_i (count value of the pulse signal) reaches a predetermined value, the position specifying unit 30 designates the adjacent sensor 18_i+1 as the new reference sensor. Therefore, although the position specifying unit 30 previously specified the absolute position of the carrier 10 by specifying the relative position of the carrier 10 with respect to the sensor 18_i, after switching the reference sensor, the position specifying unit 30 specifies the absolute position of the carrier 10 by specifying the relative position of the carrier 10 with respect to the sensor 18_i+1. In other words, the position of the carrier 10 is specified by adding the relative position of the carrier 10 with respect to the sensor 18_i+1 to the position of the sensor 18_i+1.

[0042] As described above, the position specifying unit 30 repeatedly continues to specify the position of the carrier 10 while switching the reference sensor as the carrier 10 moves.

[0043] Generally, the sensor 18 is assumed to be used in a state in which the scale detection unit 29 is always detecting the linear scale 16. After careful consideration, the inventors of the present invention have recognized that when the scale detection unit 29 is not detecting the linear scale 16, the output of the mark detection unit 28 becomes indefinite, and a high-level signal is output even though the reference mark 14 has not actually been detected. Therefore, when determining a reference sensor based on the detection result of the reference mark 14 in the initial processing, if the output from the mark detection unit 28 is used without selection, there is a risk that the reference sensor will be determined incorrectly, and the position of the carrier 10 will be identified incorrectly. This will be described in detail with reference to FIG. 3.

[0044] FIG. 3 is a time chart showing the output from the sensor 18 when the carrier 10 is moved as an initial process.

[0045] At time t0, power supply to each sensor 18 begins. At time t1, current supply to the electromagnet 26 begins. In this example, the carrier 10 moves to the right due to the current supply to the electromagnet 26. At time t2, the right end of the effective area 16a of the linear scale 16 reaches directly above the scale detection unit 29 of the sensor 18_1. At time t3, the reference mark 14 reaches directly above the mark detection unit 28 of the sensor 18_1. At time t4, the right end of the effective area 16a of the linear scale 16 reaches directly above the scale detection unit 29 of the sensor 18_2. In other words, the effective area 16a of the linear scale 16 positions the linear scale 16 directly above the scale detection units 29 of both the sensor 18_1 and the sensor 18_2. At time t5, the linear scale 16 reaches a position to the right of the sensor 18_1. In other words, the linear scale 16 is no longer directly above the sensor 18_1. At time t6, the reference mark 14 reaches directly above the mark detection portion 28 of the sensor 18_2.

[0046] From time t0 to time t4, the effective area 16a of the linear scale 16 is not directly above the scale detection unit 29 of the sensor 18_2, and therefore the scale detection unit 28 does not detect the linear scale 16. Therefore, the output of the mark detection unit 28 of the sensor 18_2 from time t0 to time t4 is indefinite, and in this example, it outputs high-level signals and low-level signals even though the reference mark 14 is not positioned directly above the mark detection unit 28 of the sensor 18_2. If the output of the mark detection unit 28 of the sensor 18_2 from time t0 to time t4 is used to determine the reference sensor, there is a risk that the position of the carrier 10 will be erroneously identified.

[0047] 3, the effective area 16a of the linear scale 16 is not directly above the scale detection unit 29 of the sensor 18_3, and therefore the scale detection unit 28 does not detect the linear scale 16. Therefore, the output of the mark detection unit 28 of the sensor 18_3 at each time in FIG. 3 is indefinite, and in this example, it outputs a high-level signal and a low-level signal even though the reference mark 14 is not located directly above the mark detection unit 28 of the sensor 18_3. If the output of the sensor 18_3 at each time in FIG. 3 is used to determine the reference sensor, there is a risk that the position of the carrier 10 will be erroneously identified.

[0048] Furthermore, until time t2, the effective area 16a of the linear scale 16 is not directly above the scale detection unit 29 of the sensor 18_1, and therefore the scale detection unit 29 does not detect the linear scale 16. Therefore, the output of the mark detection unit 28 of the sensor 18_1 is indefinite until time t2, and in this example, it continues to output a high-level signal until time t2, even though the reference mark 14 is not located directly above the sensor 18_2. At time t2, the effective area 16a of the linear scale 16 is located directly above the scale detection unit 29 of the sensor 18_1, and therefore the scale detection unit 29 correctly outputs a low-level signal. In other words, even though the reference mark 14 is not located directly above the mark detection unit 28 of the sensor 18_1 at time t2, the output of the mark detection unit 28 changes. If the output of the sensor 18_1 at time t2 is used to determine the reference sensor, the position of the carrier 10 may be erroneously identified.

[0049] At time t3, the effective area 16a of the linear scale 16 is directly above the scale detection unit 28 of sensor 18_1, and therefore, the scale detection unit 28 detects the linear scale 16. Therefore, the output of the mark detection unit 28 of sensor 18_1 at time t3 is an output resulting from the actual detection of the reference mark 14. As described above, in this embodiment, the multiple (all) sensors 18 are equally spaced at intervals S (interval S<effective area length Le), but a different configuration is also conceivable. That is, it is conceivable that some of the multiple sensors 18 are arranged such that the interval between adjacent sensors 18 is equal to or greater than the effective area length Le. In this case, if the output is adopted when the effective area 16a of the linear scale 16 is directly above only one sensor 18, as at time t3, there is a risk that the output of the mark detection unit 28 resulting from the effective area 16a of the linear scale 16 moving away from directly above the scale detection unit 29 (i.e., the output becomes undefined) will be adopted.

[0050] Therefore, the position specifying unit 30 of this embodiment specifies the position of the carrier 10 based not on the output from the mark detection unit 28 of the sensor 18 whose scale detection unit 29 does not detect the linear scale 16 among the multiple sensors 18, but on the output from the mark detection unit 28 of the sensor 18 whose scale detection unit 29 detects the linear scale 16. In particular, the position specifying unit 30 specifies the position of the carrier 10 based on the output from the mark detection unit 28 of the sensor 18 that is located ahead of the two adjacent sensors 18 in the movement direction of the carrier 10 after the scale detection units 29 of the two adjacent sensors 18 among the multiple sensors simultaneously detect the linear scale 16. This makes it possible to avoid erroneous detection of the reference mark 14 and therefore erroneous determination of the position of the carrier 10.

[0051] For example, in the illustrated example, the position determination unit 30 determines the position of the carrier 10 based on the output (i.e., the output at time t6) from the mark detection unit 28 of the sensor 18_2, which is located in front (to the right) of the two adjacent sensors 18_1, 18_2 in the direction of movement of the carrier 10, after the scale detection units 29 of the two adjacent sensors 18_1, 18_2 among the multiple sensors 18 simultaneously detect the linear scale 16.

[0052] Two adjacent sensors 18 simultaneously detecting the linear scale 16 may be two sensors whose timing of changing the count number based on the pulse signals output by their scale detection units 29 in accordance with the movement distance of the linear scale 16 coincides a predetermined number of times.

[0053] The predetermined number of times is preferably a plurality of times. In this case, it can be said that two adjacent sensors 18 reliably detect the linear scale 16 simultaneously. The predetermined number of times may be, for example, six times. In this case, for example, the six times when the count number based on the detection of the linear scale 16 by sensor 18_1 switches from 12 to 13, 13 to 14, 14 to 15, 15 to 16, 16 to 17, and 17 to 18 coincide with the six times when the count number based on the detection of the linear scale 16 by sensor 18_2 switches from 0 to 1, 1 to 2, 2 to 3, 3 to 4, 4 to 5, and 5 to 6, so it is determined that sensors 18_1 and 18_2 detect the linear scale 16 simultaneously.

[0054] Next, the effects of the embodiment will be described. According to the present embodiment, the position of the carrier 10 can be detected by the sensor 18 provided on the stator 22 side, so there is no need to provide a sensor on the carrier 10 to detect the position of the carrier 10. Therefore, there is no need to install a battery on the carrier 10 or to draw wires from the carrier 10.

[0055] Furthermore, according to this embodiment, the position of the carrier 10 is determined not based on the output of the mark detection unit 28 of a sensor 18 whose scale detection unit 29 does not detect the linear scale 16, but based on the output of the mark detection unit 28 of a sensor 18 whose scale detection unit 29 detects the linear scale 16. This makes it possible to avoid erroneous detection of the reference mark 14, and to determine the position of the reference mark 14 and therefore the carrier 10.

[0056] Furthermore, according to this embodiment, after the scale detection units 29 of two adjacent sensors 18 among the plurality of sensors simultaneously detect the linear scale 16, the position of the carrier 10 is identified based on the output of the mark detection unit 28 of the sensor 18 that is located ahead of the two sensors 18 in the movement direction of the carrier 10. This makes it possible to more reliably avoid erroneous detection of the reference mark 14, and thereby identify the position of the reference mark 14 and therefore the carrier 10.

[0057] The present invention has been described above based on an embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each treatment process, and that such modifications are also within the scope of the present invention. Modifications will be described below.

[0058] Any combination of the above-described embodiments and modifications is also useful as an embodiment of the present invention. A new embodiment resulting from the combination has the combined effects of the combined embodiments and modifications. [Industrial Applicability]

[0059] The present invention relates to a linear motor transport system and an operation method thereof. [Explanation of symbols]

[0060] 10 carrier, 12 linear motor, 14 reference mark, 16 linear scale, 18 sensor, 20 control device, 100 linear motor conveying system.

Claims

1. a carrier to which a linear scale and reference mark are fixed; a linear motor that moves the carrier along a predetermined path; a plurality of sensors arranged along the path; a control device; Equipped with A linear motor conveying system in which, when the control device controls the linear motor to move the carrier as an initial process, the control device determines the position of the carrier based on the output regarding the reference mark from a sensor of the multiple sensors that is detecting the linear scale, rather than based on the output regarding the reference mark from a sensor that is not detecting the linear scale.

2. The linear motor conveying system of claim 1, wherein the output regarding the reference mark used to identify the position of the carrier is the output regarding the reference mark by the sensor located in front of the movement direction of the carrier, after two adjacent sensors among the plurality of sensors simultaneously detect the linear scale.

3. The linear motor conveying system according to claim 2, wherein the two adjacent sensors simultaneously detecting the linear scale are two sensors whose timing of changing the count number based on the pulse signal output in accordance with the moving distance of the linear scale coincides a predetermined number of times.

4. 4. The linear motor conveying system according to claim 3, wherein the predetermined number of times is a plurality of times.

5. A method for operating a linear motor conveyance system including a carrier to which a linear scale and a reference mark are fixed, a linear motor that moves the carrier along a predetermined path, and a plurality of sensors arranged along the path, the method comprising: moving the carrier as an initial process; Identifying the position of the carrier based on an output regarding the reference mark from a sensor that detects the linear scale, but not based on an output regarding the reference mark from a sensor that does not detect the linear scale among the plurality of sensors; A method for operating a linear motor transport system including:

Images