Conveying device

Abstract

To provide a conveyance device capable of suppressing a decrease in efficiency of conveyance of a conveyance object by a travel cart.SOLUTION: A conveyance device comprises a travel cart, a mast, an elevation part, and a control part. The travel cart is provided with a plurality of drive units each having wheels, a motor driving the wheels, and a slip detection part detecting a wheel slip. The control part stops the travel cart (S4) when at least two slip detection parts among the plurality of slip detection parts detect a slip of a predetermined quantity or more (S2: YES), at least in a state in which the travel cart is accelerated.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a conveying device that conveys conveyed articles. [Background Art]

[0002] Conventionally, in automated warehouses, articles are conveyed by stacker cranes. It is known that slippage occurs on the wheels of the traveling carriage in stacker cranes (see, for example, Patent Document 1). [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2008-254912 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] Here, for example, when control is performed to stop the traveling carriage when slippage occurs on either the front wheels or the rear wheels of the traveling carriage, there has been a problem that the conveying efficiency of conveyed articles by the traveling carriage decreases.

[0005] An object of an aspect of the present disclosure is to provide a conveying device capable of suppressing a decrease in the conveying efficiency of conveyed articles by a traveling carriage. [Means for Solving the Problem]

[0006] To solve the above problems, a transport device according to one aspect of the present disclosure comprises a transport trolley that travels along a track, a mast erected on the transport trolley, a lifting unit that holds the transported object and moves up and down along the mast, and a control unit. The transport trolley is provided with a plurality of drive units, each having wheels that roll on the track, motors that drive the wheels, and slip detection units that detect slippage of the wheels. The control unit stops the transport trolley when, at least when the transport trolley is accelerating, two or more of the slip detection units detect slippage exceeding a predetermined amount. [Effects of the Invention]

[0007] According to one aspect of this disclosure, it is possible to suppress a decrease in the efficiency of transporting goods by a mobile trolley. [Brief explanation of the drawing]

[0008] [Figure 1] This is a front view of a stacker crane according to an embodiment of the present disclosure. [Figure 2] This is a block diagram showing the electrical configuration of a stacker crane according to an embodiment. [Figure 3] This is a block diagram showing the electrical configuration of the driving control unit according to the embodiment. [Figure 4] This flowchart shows an example of the slip detection process flow by the control device according to the embodiment. [Figure 5] This flowchart shows an example of the flow of sensor abnormality detection processing by the driving control unit according to the embodiment. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described below with reference to Figures 1 to 5.

[0010] [Outline configuration of a stacker crane] Figure 1 is a front view of stacker crane 1. Stacker crane 1 is an example of a conveying device used in automated warehouses and the like for transporting goods. As shown in Figure 1, stacker crane 1 comprises a traveling carriage 10, a pair of masts 11, a lifting section 12, and a transfer device 13.

[0011] For the sake of explanation, the vertical and horizontal directions of the stacker crane 1 are defined as shown by the arrows in Figure 1. Furthermore, the front of Figure 1 is defined as the right side of the stacker crane 1, and the back of Figure 1 is defined as the left side of the stacker crane 1. The vertical direction of the stacker crane 1 corresponds to the direction in which the lifting unit 12 moves up and down. The horizontal direction of the stacker crane 1 corresponds to the direction in which the traveling carriage 10 moves.

[0012] The trolley 10 travels along the track in the direction of travel, i.e., in the forward and backward direction. The track is formed by the running rail R1. The trolley 10 has a first wheel 21a and a second wheel 21b. The trolley 10 travels on the running rail R1 by the rotation of the first wheel 21a and the second wheel 21b. The first wheel 21a and the second wheel 21b are examples of wheels that roll on the track.

[0013] The first wheel 21a is located on the front side of the trolley 10. The second wheel 21b is located on the rear side of the trolley 10. The first wheel 21a is driven by the first traction motor 28a. The second wheel 21b is driven by the second traction motor 28b. The first traction motor 28a and the second traction motor 28b are examples of motors that drive wheels.

[0014] A pair of masts 11 are erected on top of the running bogie 10. Each mast 11 is spaced apart in the front-rear direction and extends vertically. Each mast 11 is formed from a vertically elongated hollow member.

[0015] The upper ends of a pair of masts 11 are connected by an upper frame 14. The upper frame 14 has guide rollers 15. The guide rollers 15 are guided by a guide rail R2 fixed to the ceiling (not shown). The upper frame 14 is configured to be movable in the front-rear direction while being guided by the guide rail R2.

[0016] The lifting section 12 is supported by a pair of masts 11 and moves up and down along the masts 11. The lifting section 12 is suspended and supported by four wires 20 wound around a rotating body 23. One lifting motor 22 is provided at the front of the traveling carriage 10. The lifting section 12 moves up and down along the masts 11 as the lifting motor 22 drives the rotating body 23 to rotate in forward and reverse directions, causing the wires 20 to be wound up or unwound. Note that two lifting motors 22 may be provided, one at the front and one at the rear of the traveling carriage 10.

[0017] The transfer device 13 is supported by the lifting section 12. The transfer device 13 has a fork mechanism (not shown) for holding the transported object M. The transfer device 13 places the transported object M at a predetermined transfer position in a storage section (not shown) by extending and retracting the fork mechanism.

[0018] The trolley 10 is equipped with a lifting sensor 26. The lifting sensor 26 detects the vertical position of the lifting unit 12. The lifting sensor 26 detects the vertical position of the lifting unit 12 by emitting laser light in the vertical direction toward a reflector 26a located on the lower surface of the lifting unit 12 and receiving the light reflected by the reflector 26a, thereby detecting the distance to the lifting unit 12. Although a laser-type distance sensor is used for the lifting sensor 26, it is not limited to this, and a barcode-type distance meter may also be used.

[0019] Further, the traveling carriage 10 is provided with a traveling sensor 29. The traveling sensor 29 is an example of a position detection unit that detects the position of the traveling carriage 10 along the track. The traveling sensor 29 emits laser light along the longitudinal direction of the traveling rail R1 toward a reflector 29a disposed at one end of the traveling rail R1, and receives light reflected by the reflector 29a, thereby detecting the distance to the reflector 29a and thus detecting the position of the traveling carriage 10.

[0020] [Electrical Configuration of Stacker Crane] Next, the electrical configuration of the stacker crane 1 will be described with reference to FIG. 2. FIG. 2 is a block diagram showing the electrical configuration of the stacker crane 1. As shown in FIG. 2, the stacker crane 1 further includes a first notification unit 24, a second notification unit 25, a first encoder 27a, a second encoder 27b, and a control device 30.

[0021] The first notification unit 24 is a portion for notifying a user that slip has occurred in the first wheel 21a when slip of the first wheel 21a is detected by the first slip detection unit 34. The first notification unit 24 is configured to include, for example, a speaker that outputs audio and a display that displays an error code or the like.

[0022] The second notification unit 25 is a portion for notifying a user that slip has occurred in the second wheel 21b when slip of the second wheel 21b is detected by the second slip detection unit 35. The second notification unit 25 is configured to include, for example, a speaker that outputs audio and a display that displays an error code or the like.

[0023] The first encoder 27a is, for example, a rotary encoder disposed near the first traveling motor 28a and configured to detect the rotation speed of the first traveling motor 28a. The first encoder 27a outputs a signal corresponding to the rotation speed of the first traveling motor 28a to the first slip detection unit 34.

[0024] The second encoder 27b is, for example, a rotary encoder positioned near the second travel motor 28b and detects the rotational speed of the second travel motor 28b. The second encoder 27b outputs a signal corresponding to the rotational speed of the second travel motor 28b to the second slip detection unit 35.

[0025] The control device 30 includes a travel control unit 31, a lifting control unit 32, a transfer control unit 33, a first slip detection unit 34, and a second slip detection unit 35, and controls the operation of each part of the stacker crane 1.

[0026] The travel control unit 31 is an example of a control unit that controls the travel operation of the travel carriage 10. Based on the detection results of the travel sensor 29, the travel control unit 31 controls the drive of the first travel motor 28a and the second travel motor 28b, thereby controlling the travel operation of the travel carriage 10.

[0027] The lifting control unit 32 controls the lifting operation of the lifting unit 12 by controlling the drive of the lifting motor 22 based on the detection result of the lifting sensor 26, thereby moving the transfer device 13 to a desired stopping position in the vertical direction.

[0028] The transfer control unit 33 controls the transfer operation of the transfer device 13 by controlling the fork mechanism. In this way, the control device 30 controls the travel operation of the traveling trolley 10, the lifting operation of the lifting unit 12, and the transfer operation of the transfer device 13 to load the transported object M into the storage unit or load the transported object M out of the storage unit.

[0029] The first slip detection unit 34 detects slippage of the first wheel 21a based on the rotational speed of the first travel motor 28a detected by the first encoder 27a and the amount of change in the position of the travel carriage 10 in the direction of travel detected by the travel sensor 29.

[0030] The second slip detection unit 35 detects slippage of the second wheel 21b based on the rotational speed of the second travel motor 28b detected by the second encoder 27b and the amount of change in the position of the travel carriage 10 in the direction of travel detected by the travel sensor 29.

[0031] The first wheel 21a, the first notification unit 24, the first encoder 27a, the first running motor 28a, and the first slip detection unit 34 constitute the first drive unit 41. The second wheel 21b, the second notification unit 25, the second encoder 27b, the second running motor 28b, and the second slip detection unit 35 constitute the second drive unit 42. The first wheel 21a of the first drive unit 41 and the second wheel 21b of the second drive unit 42 are positioned at different locations in the direction of travel of the trolley 10.

[0032] [Electrical configuration of the drive control unit] Next, the electrical configuration of the driving control unit 31 will be explained in detail with reference to Figure 3. Figure 3 is a block diagram showing the electrical configuration of the driving control unit 31. As shown in Figure 3, the driving control unit 31 includes a synchronous control unit 36, a first servo amplifier 37, and a second servo amplifier 38.

[0033] The synchronous control unit 36 ​​receives an abnormal signal from the first slip detection unit 34 indicating that slip has occurred on the first wheel 21a, and an abnormal signal from the second slip detection unit 35 indicating that slip has occurred on the second wheel 21b.

[0034] Furthermore, the synchronization control unit 36 ​​determines the travel pattern of the traveling trolley 10 based on the position of the traveling trolley 10 in the direction of travel detected by the travel sensor 29 and the distance between it and the target stopping position. Travel patterns include acceleration, constant speed, and deceleration.

[0035] The synchronous control unit 36 ​​transmits a driving speed command information to the first servo amplifier 37, which commands a target driving speed according to the driving pattern. The first servo amplifier 37 operates the first driving motor 28a based on the difference between the driving speed obtained from the change in driving position per unit time detected by the driving sensor 29 and the target driving speed from the synchronous control unit 36.

[0036] The first servo amplifier 37 determines a torque command value such that the difference between the above-mentioned travel speed and the target travel speed becomes zero, and controls the rotation of the first travel motor 28a by supplying a current corresponding to that torque command value to the first travel motor 28a.

[0037] The first servo amplifier 37 provides the determined torque command value to the second servo amplifier 38. Based on the torque command value from the first servo amplifier 37, the second servo amplifier 38 controls the rotation of the second drive motor 28b by supplying a current corresponding to that torque command value to the second drive motor 28b.

[0038] [Flow of slip detection processing by the control device] Next, the flow of the slip detection process by the control device 30 will be explained with reference to Figure 4. Figure 4 is a flowchart showing an example of the flow of the slip detection process by the control device 30.

[0039] In the flowchart shown in Figure 4, first, the first slip detection unit 34 of the control device 30 determines whether or not it has detected a slip of the first wheel 21a exceeding a predetermined amount (S1). In step S1, the first slip detection unit 34 performs a threshold determination to determine whether or not the difference between the travel distance of the trolley 10, calculated based on the rotational speed of the first trolley motor 28a detected by the first encoder 27a, and the amount of change in the position of the trolley 10 in the direction of travel, detected by the travel sensor 29, is greater than or equal to a predetermined threshold.

[0040] The first slip detection unit 34 determines that a predetermined amount or more of slip has occurred in the first wheel 21a if the difference between the calculated travel distance of the traveling carriage 10 and the amount of change in the position of the traveling carriage 10 in the direction of travel is greater than or equal to a predetermined threshold.

[0041] The first slip detection unit 34 performs the threshold determination every time the first running motor 28a rotates a predetermined number of times, for example, two times. Here, L1 [mm] is the distance traveled by the running trolley 10 based on two rotations of the first running motor 28a. For example, the first slip detection unit 34 determines that a predetermined amount or more of slip has occurred in the first wheel 21a when the difference between the distance traveled by the running trolley 10 L1 [mm] and the amount of change in the position of the running trolley 10 in the direction of travel detected by the running sensor 29 is 0.4 × L1 [mm] or more.

[0042] This makes it possible to detect the occurrence of slippage exceeding a predetermined amount in the first wheel 21a at an early stage. Furthermore, by appropriately setting the threshold for the threshold determination described above, it becomes possible to detect the occurrence of slippage exceeding a predetermined amount in the first wheel 21a even more quickly.

[0043] If the first slip detection unit 34 has not detected a predetermined amount of slip in the first wheel 21a (S1: NO), it repeats step S1. On the other hand, if the first slip detection unit 34 has detected a predetermined amount of slip in the first wheel 21a (S1: YES), it determines whether or not the second slip detection unit 35 has detected a predetermined amount of slip in the second wheel 21b (S2).

[0044] In step S2, the second slip detection unit 35 performs a threshold determination to determine whether the difference between the travel distance of the traveling carriage 10, calculated based on the rotational speed of the second traveling motor 28b detected by the second encoder 27b, and the amount of change in the position of the traveling carriage 10 in the direction of travel, detected by the traveling sensor 29, is greater than or equal to a predetermined threshold.

[0045] The second slip detection unit 35 determines that a predetermined amount or more of slip has occurred in the second wheel 21b if the difference between the calculated travel distance of the traveling carriage 10 and the amount of change in the position of the traveling carriage 10 in the direction of travel is greater than or equal to a predetermined threshold.

[0046] The second slip detection unit 35 performs the threshold determination every time the second travel motor 28b rotates a predetermined number of times, for example, two times. Here, L2 [mm] is the distance traveled by the trolley 10 based on two rotations of the second travel motor 28b. For example, the second slip detection unit 35 determines that a predetermined amount or more of slip has occurred in the second wheel 21b when the difference between the distance traveled by the trolley 10 L2 [mm] and the amount of change in the position of the trolley 10 in the direction of travel detected by the travel sensor 29 is 0.4 × L2 [mm] or more.

[0047] This makes it possible to detect the occurrence of slippage exceeding a predetermined amount in the second wheel 21b at an early stage. Furthermore, by appropriately setting the threshold for the threshold determination described above, it becomes possible to detect the occurrence of slippage exceeding a predetermined amount in the second wheel 21b even more quickly.

[0048] If the second slip detection unit 35 does not detect a slip of the second wheel 21b exceeding a predetermined amount (S2: NO), the process returns to step S1. On the other hand, if the driving control unit 31 detects a slip of the second wheel 21b exceeding a predetermined amount (S2: YES), it controls the first servo amplifier 37 to stop the rotation of the first driving motor 28a (S3).

[0049] After step S3, the driving control unit 31 controls the second servo amplifier 38 to stop the rotation of the second driving motor 28b (S4). As a result, the driving trolley 10 stops. With this, the slip detection process by the driving control unit 31 shown in Figure 4 is completed.

[0050] In this manner, the traction control unit 31 will stop the traction vehicle 10 if, at least while the traction vehicle 10 is accelerating, all slip detection units, namely the first slip detection unit 34 and the second slip detection unit 35, detect a slip amount or more.

[0051] [Flowchart of sensor anomaly detection processing by the driving control unit] Next, the flow of the sensor abnormality detection process by the driving control unit 31 will be explained with reference to Figure 5. Figure 5 is a flowchart showing an example of the flow of the sensor abnormality detection process by the driving control unit 31. In this embodiment, the sensor abnormality detection process shown in Figure 5 is executed, for example, at predetermined intervals.

[0052] In the flowchart shown in Figure 5, first, the traction control unit 31 determines whether or not the traction vehicle 10 is in motion (S11). In step S11, the traction control unit 31 determines whether or not the traction vehicle 10 is in motion based on the detection of the rotation of the first traction motor 28a and the second traction motor 28b by the first encoder 27a and the second encoder 27b.

[0053] If the travel control unit 31 does not detect the rotation of the first travel motor 28a and the second travel motor 28b using the first encoder 27a and the second encoder 27b, it determines that the travel trolley 10 is not in motion (S11: NO) and returns to step S11.

[0054] On the other hand, when the travel control unit 31 detects the rotation of the first travel motor 28a and the second travel motor 28b using the first encoder 27a and the second encoder 27b, it determines that the travel carriage 10 is in motion (S11: YES), and determines whether the position of the travel carriage 10 detected by the travel sensor 29 has changed (S12).

[0055] If the position of the trolley 10 detected by the trolley sensor 29 changes (S12: YES), the trolley control unit 31 determines that the trolley sensor 29 is operating normally and returns to step S11.

[0056] On the other hand, if the position of the trolley 10 detected by the trolley sensor 29 does not change (S12: NO), the trolley control unit 31 determines that an abnormality has occurred in the trolley sensor 29 (S13), stops the rotation of the first trolley motor 28a and the second trolley motor 28b, and stops the trolley 10 (S14). With this, the sensor abnormality detection process shown in Figure 5 is completed.

[0057] In the stacker crane 1 of this embodiment described above, the travel control unit 31 stops the traveling carriage 10 only when all of the slip detection units of the first slip detection unit 34 and the second slip detection unit 35 detect a slip of a predetermined amount or more (S2:YES) (S4).

[0058] In the stacker crane 1, since the mast 11 is erected on the traveling carriage 10, it tends to tilt in the direction of travel during acceleration. This makes the wheels on the front side of the traveling carriage 10 more prone to slipping, while the rear wheels in the direction of travel are less prone to slipping due to the larger load on them.

[0059] When transporting objects M by a stacker crane 1 having such a structure, even if slippage occurs on either the first wheel 21a or the second wheel 21b, the trolley 10 can still move using the other wheel. This prevents the trolley 10 from stopping unnecessarily, thereby suppressing a decrease in the transport efficiency of the objects M by the stacker crane 1.

[0060] Furthermore, the first wheel 21a, which is the wheel of the first drive unit 41, is positioned at the front of the traveling carriage 10, and the second wheel 21b, which is the wheel of the second drive unit 42, is positioned at the rear of the traveling carriage 10. By positioning the first wheel 21a and the second wheel 21b at different positions in the direction of travel of the traveling carriage 10 in this way, it is possible to suppress the tilting of the stacker crane 1, on which the mast 11 is erected, in the direction of travel during acceleration.

[0061] Furthermore, in the sensor abnormality detection process shown in Figure 5, the driving control unit 31 determines that an abnormality such as a malfunction has occurred in the driving sensor 29 (S13), and stops the driving trolley 10 (S14).

[0062] If a malfunction occurs in the driving sensor 29, the driving speed, which is determined from the change in driving position per unit time detected by the driving sensor 29, will no longer change. In this case, the first servo amplifier 37 will supply excessive current to the first driving motor 28a in an attempt to bring the above driving speed closer to the target driving speed, causing the rotation speed of the first driving motor 28a to become too high, and the driving trolley 10 to accelerate excessively.

[0063] Therefore, in this embodiment, the travel control unit 31 stops the travel trolley 10 when it determines that an abnormality has occurred in the travel sensor 29, thereby preventing the travel trolley 10 from accelerating excessively. This ensures safety when transporting the transported object M by the stacker crane 1.

[0064] [Other embodiments] In the embodiment described above, the trolley 10 is provided with two drive units, a first drive unit 41 and a second drive unit 42. However, it is not limited to this, and for example, four drive units may be provided. In this case, the trolley 10 may be stopped if all of the slip detection units of the four drive units detect a slip of a predetermined amount or more in each wheel. Alternatively, for example, the trolley 10 may be stopped if the slip detection units of two or more of the four drive units detect a slip of a predetermined amount or more in each wheel.

[0065] Furthermore, in the above-described embodiment, a laser-type distance sensor, the running sensor 29, is used as the position detection unit for detecting the position of the running trolley 10 along the track, but the invention is not limited to this. For example, a barcode-type distance meter, which has a barcode extending along the track and a reading unit positioned on the running trolley 10 to read the barcode, may be used as the position detection unit.

[0066] Alternatively, a magnetic force detection type distance meter may be used as a position detection unit, which has a magnet section in which north poles and south poles are arranged alternately at predetermined intervals along the track, and which detects the position of the trolley 10 on the track based on the detection of changes in the magnetic force of the magnet section. Furthermore, a distance meter having a scale placed on the running rail R1 and an encoder placed on the trolley 10 to detect the scale may also be used as a position detection unit.

[0067] Furthermore, in the above-described embodiment, the travel control unit 31 stops the travel carriage 10 when all slip detection units detect a predetermined amount of slip or more while the travel carriage 10 is accelerating, but it is not limited to this. The travel control unit 31 may, for example, stop the travel carriage 10 when all slip detection units detect a predetermined amount of slip or more while the travel carriage 10 is traveling at a constant speed or when the travel carriage 10 is decelerating.

[0068] Furthermore, in the embodiment described above, the first slip detection unit 34 detects slippage of the first wheel 21a based on the rotational speed of the first travel motor 28a detected by the first encoder 27a and the amount of change in the position of the travel carriage 10 in the direction of travel detected by the travel sensor 29, but is not limited to this. For example, the first slip detection unit 34 may detect slippage of the first wheel 21a by determining whether the difference between the travel distance of the travel carriage 10 calculated based on the torque command value from the first servo amplifier 37 and the amount of change in the position of the travel carriage 10 in the direction of travel detected by the travel sensor 29 is greater than or equal to a predetermined value.

[0069] Furthermore, in the above-described embodiment, the trolley 10 is stopped if the position of the trolley 10 in the direction of travel, as detected by the travel sensor 29, does not change while the trolley 10 is traveling. However, the embodiment is not limited to this. For example, a torque sensor that detects the torque applied to the second wheel 21b may be provided, and the trolley 10 may be stopped if the torque detected by the torque sensor is above a predetermined threshold. This prevents the second travel motor 28b from overheating due to excessive rotation.

[0070] Furthermore, in the above-described embodiment, the first servo amplifier 37 performs torque control to determine the torque command value so that the difference between the running speed and the target running speed becomes zero, but it is not limited to this. The first servo amplifier 37 may also perform proportional-integral control, which performs proportional control and integral control based on the difference between the running speed and the target running speed.

[0071] 〔summary〕 A transport device according to Embodiment 1 of the present disclosure comprises a trolley that travels along a track, a mast erected on the trolley, a lifting unit that holds the transported object and moves up and down along the mast, and a control unit. The trolley is provided with a plurality of drive units, each having wheels that roll on the track, motors that drive the wheels, and slip detection units that detect the slip of the wheels. The control unit stops the trolley when, at least when the trolley is accelerating, two or more of the slip detection units detect a predetermined amount of slip or more.

[0072] According to the above configuration, by providing multiple wheels, even if slippage occurs in one wheel, the remaining wheels allow the vehicle to continue moving, and the vehicle is stopped only when slippage is detected in two or more wheels. This reduces the frequency of the vehicle stopping and suppresses the decrease in the efficiency of transporting goods by the transport device.

[0073] In the transport device according to Embodiment 2 of the present disclosure, in Embodiment 1, the control unit may stop the traveling trolley if, at least when the traveling trolley is accelerating, all of the slip detection units detect a slip of a predetermined amount or more.

[0074] With the above configuration, the trolley is stopped only when slippage is detected in all of the wheels, thereby minimizing the frequency of the trolley stopping and further suppressing the decrease in the efficiency of transporting materials by the transport device.

[0075] The transport device according to embodiment 3 of the present disclosure further comprises a position detection unit for detecting the position of the traveling trolley along the track, in embodiment 1 or 2 described above. The slip detection unit may detect the slip based on the rotational speed of the motor and the amount of change in the position detected by the position detection unit.

[0076] With the above configuration, the slip detection unit can detect slippage based on the motor's rotation speed and the change in position detected by the position detection unit, allowing the trolley to be stopped at a desired timing.

[0077] In the transport device according to embodiment 4 of the present disclosure, in embodiment 3, the slip detection unit may perform a threshold determination to determine whether the difference between the travel distance of the transport trolley calculated based on the rotation speed of the motor and the amount of change in position detected by the position detection unit is greater than or equal to a predetermined threshold, and if the difference is greater than or equal to the threshold, it may determine that a slip of a predetermined amount or more has occurred.

[0078] With the configuration described above, by appropriately setting the threshold for threshold determination, the occurrence of wheel slippage can be detected quickly.

[0079] In the transport device according to aspect 5 of the present disclosure, in any of aspects 1 to 4 above, the plurality of drive units include a first drive unit and a second drive unit. The wheels of the first drive unit and the wheels of the second drive unit may be arranged at different positions on the traveling carriage in the traveling direction of the traveling carriage.

[0080] According to the above configuration, by arranging the wheels of the first drive unit and the wheels of the second drive unit at different positions in the direction of travel of the trolley, it is possible to suppress the tilting of the conveying device in the direction of travel during acceleration, and to effectively suppress a decrease in the conveying efficiency of the conveyed goods.

[0081] In the transport device according to embodiment 6 of the present disclosure, in any of embodiments 1 to 5, the control unit may determine that an abnormality has occurred in the position detection unit if the position detected by the position detection unit does not change when the traveling trolley is traveling due to the rotation of the motor of the drive unit, and stop the traveling trolley.

[0082] According to the above configuration, the control unit stops the trolley if it determines that an abnormality has occurred in the position detection unit. This prevents the trolley from accelerating excessively, thereby improving the safety of the transport device.

[0083] In the transport device according to embodiment 7 of the present disclosure, in embodiment 3, the slip detection unit may perform the threshold determination each time the motor rotates a predetermined number of times.

[0084] With the above configuration, by performing a threshold check each time the motor rotates a predetermined number of times, the occurrence of slippage in each wheel can be detected at an early stage.

[0085] In the transport device according to aspect 8 of the present disclosure, in any of aspects 1 to 7 above, the drive unit may have a notification unit that notifies the outside when the slip detection unit detects slip of a predetermined amount or more.

[0086] According to the above configuration, each of the multiple drive units is equipped with a notification unit, and each notification unit provides notification corresponding to the wheel in which slippage has occurred. This allows the user to identify, for example, the wheels in which slippage has occurred and take appropriate action.

[0087] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of Symbols]

[0088] 1. Stacker crane 10. Running bogie 11 Mast 12 Lifting section 13 Transfer equipment 21a 1st wheel 21b 2nd wheel 22 Lifting motor 24 First News Department 25. Second News Department 26. Sensor for lifting / lowering 27a First Encoder 27b Second encoder 28a First motor for travel 28b Second motor for travel 29. Driving sensors 30 Control device 31. Driving control unit 32 Lifting control unit 33 Transfer control unit 34 First slip detection unit 35 Second slip detection unit 41 First drive unit 42 Second drive unit

Claims

1. A trolley that travels along the track, A mast erected on the aforementioned traction vehicle, A lifting section that holds the conveyed object and moves up and down along the mast, Control unit and Equipped with, The aforementioned trolley is provided with a plurality of drive units, each having wheels that roll on the track, a motor that drives the wheels, and a slip detection unit that detects the slippage of the wheels. The control unit, A transport device characterized in that, when the transport trolley is accelerated, if two or more of the slip detection units detect a predetermined amount of slip or more, the transport trolley is stopped.

2. The control unit, The transport device according to claim 1, characterized in that, when the transport trolley is accelerated, all of the slip detection units detect a slip of a predetermined amount or more, the transport trolley is stopped.

3. The system further includes a position detection unit for detecting the position of the trolley along the aforementioned track, The conveying device according to claim 1 or 2, characterized in that the slip detection unit detects the slip based on the rotational speed of the motor and the amount of change in position detected by the position detection unit.

4. The conveying device according to claim 3, wherein the slip detection unit performs a threshold determination to determine whether the difference between the travel distance of the traveling trolley calculated based on the rotation speed of the motor and the amount of change in position detected by the position detection unit is greater than or equal to a predetermined threshold, and determines that a slip of a predetermined amount or more has occurred when the difference is greater than or equal to the threshold.

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