Overhead transport vehicle

Abstract

To provide an overhead transport vehicle capable of suppressing erroneous detection of abnormality.SOLUTION: The ceiling transport vehicle 1 includes the holding unit 7 that holds the article 200, the lift drive unit 6 that raises and lowers the holding unit 7, the monitoring sensors 10 that are provided in the lift drive unit 6, monitor below the lift drive unit 6, and are capable of changing the monitoring range A, and the transport vehicle controller 8 that controls the monitoring range A of the monitoring sensors 10. The transport vehicle controller 8 makes the third monitoring range A1, which is the monitoring range A of the monitoring sensors 10 in the switching period including the timing at which the presence or absence of the article 200 held by the holding unit 7 is switched, wider than the first monitoring range A2, which is the monitoring range A of the monitoring sensors 10 when the holding unit 7 is holding the article 200, and the second monitoring range A3, which is the monitoring range A of the monitoring sensors 10 when the holding unit 7 is not holding the article 200.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] One aspect of the present invention relates to an overhead transport vehicle. [Background technology]

[0002] Patent Document 1 describes an overhead transport vehicle that includes a holding unit that holds an article, a lifting drive unit that raises and lowers the holding unit, and a lateral transfer mechanism that moves the lifting drive unit laterally relative to the main body. In the overhead transport vehicle described in Patent Document 1, a monitoring sensor that monitors the area below the lifting drive unit is provided in the lifting drive unit, and a controller changes the monitoring range of the monitoring sensor according to tilt information related to the tilt of the lifting drive unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2023 / 281781 Summary of the Invention [Problem to be solved by the invention]

[0004] In an overhead transport vehicle, when loading and unloading an item, the load on the holding unit changes depending on the weight of the item at the timing when the holding unit switches between holding an item and not holding an item (hereinafter also referred to as "switching timing"), which may cause the tilt of the lifting and lowering drive unit to change. In this case, with an overhead transport vehicle such as the one described above, it is not easy to change the monitoring range of the monitoring sensor precisely to the switching timing. For example, even if the switching timing is normal, the change in the tilt of the lifting and lowering drive unit due to the switching between holding an item and not holding an item may cause the monitored object (such as the reflector of the holding unit) to fall outside the monitoring range. As a result, there is a risk that the monitoring sensor may erroneously detect an abnormality (such as shaking of the holding unit).

[0005] An object of one aspect of the present invention is to provide an overhead transport vehicle that can suppress erroneous detection of abnormalities. [Means for solving the problem]

[0006] (1) An overhead transport vehicle according to one aspect of the present invention comprises a holding unit that is capable of being raised and lowered and that holds an item, a lifting drive unit that raises and lowers the holding unit, a monitoring sensor that is mounted on the lifting drive unit and monitors below the lifting drive unit and is capable of changing its monitoring range, and a controller that controls the monitoring range of the monitoring sensor, wherein the controller sets a third monitoring range, which is the monitoring range of the monitoring sensor during a switching period that includes the timing when the holding unit switches between holding an item and not holding an item, wider than a first monitoring range, which is the monitoring range of the monitoring sensor when the holding unit is holding an item, and a second monitoring range, which is the monitoring range of the monitoring sensor when the holding unit is not holding an item.

[0007] In this overhead transport vehicle, when loading and unloading items, the monitoring range during the switching period can be made wider than the monitoring range when the holding unit is holding and not holding an item. This makes it possible to prevent the monitoring sensor from detecting an abnormality when the monitoring target falls outside the monitoring range due to a change in the tilt of the lifting drive unit caused by switching between holding and not holding an item at the switching timing, even when the operation is normal. In other words, it is possible to prevent erroneous detection of an abnormality during the switching period.

[0008] (2) In the overhead transport vehicle described in (1) above, the third monitoring range may be a range that combines the first monitoring range and the second monitoring range. In this case, both the first monitoring range and the second monitoring range can be used as the monitoring range during the switching period, so that the monitoring sensor can maintain the monitoring range necessary for abnormality detection even during the switching period, while suppressing erroneous detection of abnormalities.

[0009] (3) Another aspect of the present invention provides a ceiling transport vehicle comprising: a holding unit that is capable of being raised and lowered and that holds an item; a lifting drive unit that raises and lowers the holding unit; a sensor that is provided in the lifting drive unit and that emits directional detection light toward a predetermined position below and detects reflected light of the detection light; a controller that determines a timeout when the reflected light is not detected by the sensor within a set time; and an adjustment unit that adjusts the direction of irradiation of the sensor's detection light, and the controller sets a third set time, which is a set time during a switching period that includes a timing when the holding unit switches between holding an item and not holding an item, to be longer than a first set time, which is a set time when the holding unit is holding an item, and a second set time, which is a set time when the holding unit is not holding an item.

[0010] In this overhead transport vehicle, when loading and unloading an item, the set time for determining the timeout during the switching period can be set longer than the set time for determining the timeout when the holding unit is holding an item and when it is not holding an item. This makes it possible to prevent the sensor from detecting an abnormality when the monitoring target moves out of the monitoring range due to a change in the tilt of the lifting drive unit at the switching timing, even when the situation is normal. In other words, it is possible to prevent erroneous detection of an abnormality.

[0011] (4) The ceiling transport vehicle described in any one of (1) to (3) above may include a lateral transfer mechanism that moves the lifting drive unit laterally relative to the main body. When the lateral transfer mechanism moves the lifting drive unit laterally to load or unload an item, the lifting drive unit may tilt due to its own weight, and the tilt may change depending on whether or not there is an item being held. According to one aspect of the present invention, even in such cases, the above-mentioned operational effect of suppressing erroneous detection of an abnormality is achieved.

[0012] (5) In the overhead transport vehicle described in any one of (1) to (4) above, the holding unit has a positioning unit that is movable up and down relative to the base unit of the holding unit and that contacts the top surface of the article, a detectable object that is integrally provided with the positioning unit, and a detector that is provided on the base unit and that detects the position of the detectable object to detect the relative height position of the positioning unit from its initial position with respect to the base unit, and the controller may determine, when the holding unit is holding an article, a period from when the detection result of the detector recognizes that the positioning unit has risen to when the detection result of the detector recognizes that the positioning unit has returned to its initial position as the switching period during unloading, and may determine, when the holding unit is not holding an article, a period from when the detection result of the detector recognizes that the positioning unit has risen from its initial position to when the detection result of the detector recognizes that the positioning unit has descended as the switching period during loading. In this case, the positioning unit, the detectable object, and the detector can be used to acquire the switching time during unloading and the switching period during loading. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide an overhead transport vehicle that can suppress erroneous detection of abnormalities. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a side view showing the ceiling transport vehicle of the first embodiment. [Figure 2] FIG. 2 is a front view showing the ceiling transport vehicle of FIG. [Figure 3] Fig. 3(a) is an enlarged side view of a part of the ceiling transport vehicle of Fig. 1. Fig. 3(b) is a cross-sectional view showing the area enclosed by the dashed line in Fig. 3(a). [Figure 4] Fig. 4(a) is a schematic front view showing a first monitoring range of the monitoring sensor of Fig. 2. Fig. 4(b) is a schematic front view showing a second monitoring range of the monitoring sensor of Fig. 2. Fig. 4(c) is a schematic front view showing a third monitoring range of the monitoring sensor of Fig. 2. [Figure 5]Fig. 5(a) is a side view illustrating a switching period when unloading the overhead transport vehicle of Fig. 1. Fig. 5(b) is a side view illustrating a continuation of Fig. 5(a). Fig. 5(c) is a side view illustrating a continuation of Fig. 5(b). Fig. 5(d) is a side view illustrating a continuation of Fig. 5(c). Fig. 5(e) is a side view illustrating a continuation of Fig. 5(d). [Figure 6] Fig. 6(a) is a side view illustrating a switching period during loading in the overhead transport vehicle of Fig. 1. Fig. 6(b) is a side view illustrating a continuation of Fig. 6(a). Fig. 6(c) is a side view illustrating a continuation of Fig. 6(b). Fig. 6(d) is a side view illustrating a continuation of Fig. 6(c). Fig. 6(e) is a side view illustrating a continuation of Fig. 6(d). [Figure 7] FIG. 7 is a side view showing the ceiling transport vehicle system according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, the embodiments will be described in detail with reference to the drawings. The same or equivalent elements are designated by the same reference numerals, and redundant explanations will be omitted.

[0016] [First embodiment] As shown in FIG. 1 , an overhead transport vehicle 1 of the first embodiment travels along a track 20 laid near the ceiling of a clean room where semiconductor devices are manufactured. The track 20 forms the travel path of the overhead transport vehicle 1. The overhead transport vehicle 1 transports an item 200 such as a FOUP (Front Opening Unified Pod) that houses multiple semiconductor wafers, and transfers the item 200 to a load port 300 or the like provided in a processing device that performs various processes on the semiconductor wafers. Hereinafter, the terms "upper" and "lower" correspond to the vertical direction, the terms "front" and "rear" correspond to the front-to-rear direction in the traveling direction of the overhead transport vehicle 1, and the terms "left" and "right" correspond to the left-to-right direction of the overhead transport vehicle 1.

[0017] The ceiling transport vehicle 1 includes a frame unit (main body) 2, a traveling unit 3, a lateral unit (lateral transfer mechanism) 4, a theta unit 5, an elevation drive unit (elevation drive unit) 6, a holding unit 7, and a transport vehicle controller (controller) 8. The frame unit 2 has a center frame 15, a front frame 16, and a rear frame 17. The front frame 16 extends downward from the front end of the center frame 15. The rear frame 17 extends downward from the rear end of the center frame 15.

[0018] The traveling unit 3 is disposed above the center frame 15. The traveling unit 3 travels along the track 20 by, for example, receiving a contactless supply of power from a high-frequency current line laid along the track 20. The lateral unit 4 is disposed below the center frame 15. The lateral unit 4 moves the theta unit 5, the lifting drive unit 6, and the holding unit 7 laterally relative to the frame unit 2. The theta unit 5 is disposed below the lateral unit 4. The theta unit 5 rotates the lifting drive unit 6 and the holding unit 7 within a horizontal plane. The side is the side in the traveling direction of the overhead transport vehicle 1 (the horizontal direction perpendicular to the traveling direction), and is also referred to as the lateral direction.

[0019] The lifting drive unit 6 is disposed below the theta unit 5. The lifting drive unit 6 raises and lowers the holding unit 7 by reeling in and out a plurality of belts B connected to the holding unit 7. The holding unit 7 is disposed below the lifting drive unit 6. The holding unit 7 is provided so that it can be raised and lowered by the lifting drive unit 6. The holding unit 7 has a pair of grippers 12 that can be opened and closed in the horizontal direction. The holding unit 7 holds the flange 201 of the article 200 with the pair of grippers 12.

[0020] The transport vehicle controller 8 is disposed on the center frame 15. The transport vehicle controller 8 is an electronic control unit configured with a CPU (Central Processing Unit), a ROM (Read only memory), a RAM (Random access memory), etc. The transport vehicle controller 8 controls each part of the overhead transport vehicle 1. The transport vehicle controller 8 may be configured with multiple electronic control units. The transport vehicle controller 8 may be disposed on the front frame 16, etc.

[0021] The overhead transport vehicle 1 configured as described above operates, for example, as follows when transferring an article 200 from a load port 300 to the overhead transport vehicle 1. First, the overhead transport vehicle 1 not holding the article 200 stops at a predetermined position near the load port 300. In a transfer (so-called lateral transfer) when the position of the frame unit 2 of the overhead transport vehicle 1 at the stopped position is laterally separated from the load port 300, the lateral unit 4 moves the theta unit 5, lift drive unit 6, and holding unit 7 laterally to a predetermined position corresponding to the load port 300. The lift drive unit 6 lowers the holding unit 7, and the flange 201 of the article 200 placed on the load port 300 is held by the holding unit 7. On the other hand, in transfers where the position of the frame unit 2 of the overhead transport vehicle 1 at the stopped position is not laterally separated from the load port 300 (so-called direct downward transfers), the lifting drive unit 6 lowers the holding unit 7, and the flange 201 of the article 200 placed on the load port 300 is held by the holding unit 7. Next, the lifting drive unit 6 raises the holding unit 7 to the upper end, and the article 200 is placed between the front frame 16 and the rear frame 17. Thereafter, the overhead transport vehicle 1 holding the article 200 starts traveling.

[0022] Furthermore, when transferring the article 200 from the ceiling transport vehicle 1 to the load port 300, the ceiling transport vehicle 1 operates, for example, as follows. First, the ceiling transport vehicle 1 holding the article 200 stops at a predetermined position around the load port 300. In lateral transfer, the lateral unit 4 moves the theta unit 5, the lift drive unit 6, and the holding unit 7 laterally to a predetermined position corresponding to the load port 300. The lift drive unit 6 lowers the holding unit 7, placing the article 200 on the load port 300, and releasing the holding of the flange 201 by the holding unit 7. On the other hand, in direct downward transfer, the lift drive unit 6 lowers the holding unit 7, placing the article 200 on the load port 300, and releasing the holding of the flange 201 by the holding unit 7. Next, the lift drive unit 6 raises the holding unit 7 to the upper end. After that, the ceiling transport vehicle 1, which is not holding the article 200, starts traveling.

[0023] As shown in Figures 1 and 2, the ceiling transport vehicle 1 is equipped with a monitoring sensor 10 and a reflector 11. The monitoring sensor 10 is provided on the lifting drive unit 6. The monitoring sensor 10 monitors the area below the lifting drive unit 6. The monitoring sensor 10 is a sensor that can change the monitoring range A. The monitoring sensor 10 is a vibration detection sensor for detecting vibration of the holding unit 7. The monitoring sensor 10 is not particularly limited, but is, for example, a laser range finder. The monitoring range A is a vibration detection range in which vibration of the holding unit 7 can be detected. The monitoring range A is a range in which the detection result is valid.

[0024] The monitoring sensor 10 emits light (such as laser light) so as to scan horizontally downward within a monitoring range A. If the monitoring range A can be set and input, the monitoring sensor 10 changes the monitoring range A by changing this input. The monitoring sensor 10 emits light toward a reflector 11 below, and detects the returning light when the laser light is reflected by the reflector 11. The monitoring sensor 10 is connected to the transport vehicle controller 8.

[0025] The reflector 11 is provided on the holding unit 7. As an example, the reflector 11 is provided in the center of the upper part of the holding unit 7. The reflector 11 is disposed with its reflective surface facing upward, and reflects light from above upward. The reflector 11 is disposed directly below the monitoring sensor 10 when the lifting drive unit 6 is in a horizontal position. The reflector 11 is the object to be monitored by the monitoring sensor 10. There are no particular limitations on the reflector 11, and various reflectors can be used.

[0026] In the ceiling transport vehicle 1, when the holding unit 7 is not shaking, the monitoring sensor 10 receives the returning light from the reflector 11, thereby detecting that the holding unit 7 is not shaking. On the other hand, in the ceiling transport vehicle 1, when the holding unit 7 is shaking, the light from the monitoring sensor 10 is not projected onto the reflector 11, and the monitoring sensor 10 does not receive the reflected light from the reflector 11. This allows the monitoring sensor 10 to detect that the holding unit 7 is shaking (abnormal). The shaking of the holding unit 7 corresponds to the motion (swing) of a pendulum with the lift drive unit 6 as the fulcrum and the belt B as the arm.

[0027] As shown in FIGS. 3(a) and 3(b), the holding unit 7 further includes a center cone (positioning portion) 108, a dog (detectable object) 110, and a detection portion 120. FIG. 3(b) is a cross-sectional view of the area enclosed by the dashed line frame H in FIG. 3(a). The center cone 108, the dog 110, and the detection portion 120 are supported by a support member 62 provided on a base portion 61 of the holding unit 7. A guide 63 is fixed to the support member 62. The guide 63 is a cylindrical member extending vertically. A rod 64 is inserted into the guide 63. A flange 65 capable of abutting against the upper end surface of the guide 63 is provided on the upper end of the rod 64.

[0028] The center cone 108 is a member that contacts the upper surface of the article 200. The center cone 108 is a downwardly convex mountain-shaped member. The center cone 108 fits into a recess 291a formed in the flange 201 to position the holding unit 7 relative to the article 200. The center cone 108 is attached to the lower end of the rod 64. A coil spring 66 is arranged between the center cone 108 and the guide 63. The coil spring 66 biases the center cone 108 downward relative to the support member 62. With the above configuration, the center cone 108 is provided so as to be able to move up and down relative to the base part 61 of the holding unit, with an initial position being a position where the flange 65 at the upper end of the rod 64 abuts against the upper end surface of the guide 63.

[0029] The dog 110 includes a first light-shielding plate 111 and a second light-shielding plate 112. The first light-shielding plate 111 and the second light-shielding plate 112 are disposed at different positions in the up-down direction. The dog 110 is fixed to the flange 65 of the rod 64. As a result, the dog 110 is provided integrally with the center cone 108 via the rod 64, and can move up and down in conjunction with the relative up-and-down movement of the center cone 108 with respect to the holding unit 7.

[0030] The detection unit 120 includes a first photointerrupter 121 and a second photointerrupter 122. The first photointerrupter 121 and the second photointerrupter 122 are attached to the support member 62. The first photointerrupter 121 and the second photointerrupter 122 can detect the positions of the first light-shielding plate 111 and the second light-shielding plate 112, respectively (i.e., the ON / OFF of the output from each light-receiving portion of the first photointerrupter 121 and the second photointerrupter 122). The detection unit 120 detects the relative rise of the center cone 108 from its initial position with respect to the base portion 61 of the lifting drive unit 6 by detecting each position of the first light-shielding plate 111 and the second light-shielding plate 112.

[0031] As shown in Figures 4(a), 4(b), and 4(c), the transport vehicle controller 8 controls the monitoring range A of the monitoring sensor 10. The transport vehicle controller 8 defines the monitoring range A of the monitoring sensor 10 when the holding unit 7 is holding an item 200 (hereinafter also referred to as the "item holding period") as a first monitoring range A1. The transport vehicle controller 8 defines the monitoring range A of the monitoring sensor 10 when the holding unit 7 is not holding an item 200 (hereinafter also referred to as the "non-item holding period") as a second monitoring range A2. The transport vehicle controller 8 sets a third monitoring range A3, which is the monitoring range A of the monitoring sensor 10 during the switching period, to be wider than the first monitoring range A1 and the second monitoring range A2. The switching period includes the timing when the presence or absence of the item 200 held by the holding unit 7 is switched by placing the item 200 held by the holding unit 7 on the load port 300 or by the holding unit 7 holding the item 200 placed on the load port 300.

[0032] The first monitoring range A1 and the second monitoring range A2 are ranges of the same area. The second monitoring range A2 is a range obtained by shifting the first monitoring range A1 laterally. The third monitoring range A3 is a range that combines the first monitoring range A1 and the second monitoring range A2. The third monitoring range A3 is larger than the first monitoring range A1 and larger than the second monitoring range A2.

[0033] The transport vehicle controller 8 recognizes the holding period, non-holding period, and switching period based on the detection result of the detection unit 120 (i.e., the relative height position of the center cone 108 with respect to the base part 61 of the lifting drive unit 6). An example will be described below.

[0034] For example, as shown in Figure 5(a), when unloading an article 200 onto a load port 300, the holding unit 7 holding the article 200 descends. At this time, the center cone 108 fits into the recess 291a of the flange 201 and is pushed upward by a certain amount by the flange 201. The light receiving part of the first photointerrupter 121 is in the OFF state, and the light receiving part of the second photointerrupter 122 is in the ON state. Based on this, the transport vehicle controller 8 recognizes that the holding unit 7 is holding the article 200 (article holding period).

[0035] As shown in FIG. 5(b), the holding unit 7 holding the article 200 continues to descend, and the article 200 is placed on the load port 300. In this state, as shown in FIG. 5(c), the holding unit 7 descends further, and the center cone 108 is pushed further upward by the weight of the holding unit 7 itself. As a result, the light receiving portion of the first photointerrupter 121 switches from an OFF state to an ON state, and the light receiving portion of the second photointerrupter 122 switches from an ON state to an OFF state. Based on this, the transport vehicle controller 8 recognizes that the center cone 108 has risen. In addition, the transport vehicle controller 8 recognizes that the holding unit 7 has reached a holding position where the pair of grippers 12 can advance and retreat from the underside of the flange 201 by opening and closing the pair of grippers 12.

[0036] As shown in FIG. 5(d), the holding unit 7 stops descending and the pair of grippers 12 opens. As shown in FIG. 5(e), the holding unit 7 that is not holding the item 200 rises. As a result, the light receiving elements of both the first photointerrupter 121 and the second photointerrupter 122 are turned ON. Based on this, the transport vehicle controller 8 recognizes that the center cone 108 has returned to its initial position and that the holding unit 7 is not holding the item 200 (item non-holding period). When unloading such an item 200, the transport vehicle controller 8 recognizes the period from when it recognizes the rise of the center cone 108 to when it recognizes that the center cone 108 has returned to its initial position as the switching period during unloading.

[0037] 6(a), when loading an article 200 from the load port 300, the holding unit 7 not holding the article 200 descends. At this time, the center cone 108 is located at the initial position, and the light receiving parts of both the first photointerrupter 121 and the second photointerrupter 122 are in the ON state. Based on this, the transport vehicle controller 8 recognizes that the holding unit 7 is not holding the article 200 (non-article holding period).

[0038] 6(b), the holding unit 7 descends, and the center cone 108 fits into the recess 291a of the flange 201, and the weight of the holding unit 7 itself acts on the center cone 108, pushing it relatively upward. At this time, the light receiving portion of the first photointerrupter 121 is in the ON state, and the light receiving portion of the second photointerrupter 122 is in the OFF state. Based on this, the transport vehicle controller 8 recognizes that the center cone 108 has risen from its initial position and reached the holding position of the holding unit 7.

[0039] As shown in FIG. 6(c), the holding unit 7 stops descending and closes the pair of grippers 12. The holding unit 7 rises, and the pair of grippers 12, which have advanced below the flange 201, rise until they abut against the lower surface of the flange 201. As a result, the center cone 108 relatively descends a certain amount and stops. As shown in FIG. 6(d), when the pair of grippers 12 abut against the lower surface of the flange 201, the output from the light receiving portion of the first photointerrupter 121 switches from the ON state to the OFF state, and the output from the light receiving portion of the second photointerrupter 122 switches from the OFF state to the ON state.

[0040] As a result, the transport vehicle controller 8 recognizes the descent of the center cone 108 and recognizes that the holding unit 7 is holding the item 200 (item holding period). When loading such an item 200, the transport vehicle controller 8 recognizes the period from when the center cone 108 is recognized as rising from its initial position to when the center cone 108 is recognized as falling as the switching period during loading. Then, as shown in FIG. 6(e), the holding unit 7 holding the item 200 rises until it reaches a predetermined position.

[0041] Incidentally, when unloading and loading the article 200, for example, at the switching timing, the load of the article 200 on the holding unit 7 may be removed or added, causing a change in the inclination of the lifting drive unit 6, and even though the operation is normal, the reflector 11 may move out of the monitoring range A, causing the monitoring sensor 10 to erroneously detect an abnormality. In this regard, with the ceiling transport vehicle 1, when unloading and loading the article 200, the third monitoring range A3 during the switching period can be made wider than the first monitoring range A1 during the article holding period and the second monitoring range A2 during the article non-holding period.

[0042] This prevents the monitoring sensor 10 from erroneously detecting an abnormality due to the reflector 11 moving out of the monitoring range A. In other words, it is possible to prevent erroneous detection of an abnormality during the switching period. Furthermore, even when a change in the inclination of the lifting drive unit 6 (monitoring sensor 10) cannot be clearly detected when transferring the article 200, and when it cannot be clearly determined whether or not the article 200 is under load, it is possible to prevent erroneous detection by the monitoring sensor 10.

[0043] In the ceiling transport vehicle 1, the third monitoring range A3 is the combined range of the first monitoring range A1 and the second monitoring range A2. In this case, during the switching period, both the first monitoring range A1 and the second monitoring range A2 can be set as the monitoring range A, so that the monitoring sensor 10 can maintain the monitoring range A necessary for abnormality detection even during the switching period, while suppressing erroneous detection of abnormalities.

[0044] The overhead transport vehicle 1 is equipped with a lateral unit 4 that moves the lifting drive unit 6 laterally relative to the frame unit 2. When the lateral unit 4 moves the lifting drive unit 6 laterally to load or unload an item, the lifting drive unit 6 may tilt due to its own weight, and this tilt may change depending on whether or not there is an item 200 being held. Even in such cases, the overhead transport vehicle 1 achieves the above-mentioned advantageous effect of suppressing false detection of an abnormality.

[0045] In the overhead transport vehicle 1, the holding unit 7 includes a center cone 108 that is movable up and down relative to the base 61 and contacts the top surface of the article 200, a dog 110 that is integrally formed with the center cone 108, and a detection unit 120 that is attached to the base 61 and detects the position of the dog 110 to detect the relative height position of the center cone 108 from its initial position. When the holding unit 7 is holding an article 200, the transport vehicle controller 8 determines the switching period for unloading as the period from when the center cone 108 is recognized as rising to when the center cone 108 is recognized as returning to its initial position. When the holding unit 7 is not holding an article 200, the transport vehicle controller 8 determines the switching period for loading as the period from when the center cone 108 is recognized as rising from its initial position to when the center cone 108 is recognized as descending. In this case, the center cone 108, the dog 110, and the detection unit 120 can be used to acquire the switching time for unloading and the switching period for loading.

[0046] [Second embodiment] Next, a second embodiment will be described, focusing on the differences from the first embodiment.

[0047] As shown in Figure 7, the ceiling transport vehicle 301 of the second embodiment differs from the first embodiment in that it is equipped with a light emitting and receiving sensor 210 instead of the monitoring sensor 10 (see Figure 1), further equipped with an actuator 215, and equipped with a transport vehicle controller (controller) 208 instead of the transport vehicle controller 8 (see Figure 1).

[0048] The light emitting and receiving sensor 210 is a sensor provided in the lifting and lowering drive unit 6. The light emitting and receiving sensor 210 emits directional detection light (such as laser light) toward a point downward and detects the reflected light of the detection light. The light emitting and receiving sensor 210 here emits the detection light toward the reflecting plate 11 below. The light emitting and receiving sensor 210 is connected to the transport vehicle controller 208. The reflecting plate 11 reflects the detection light from above upward, and is located directly below the light emitting and receiving sensor 210 when the lifting and lowering drive unit 6 is in a horizontal position.

[0049] The actuator 215 adjusts the irradiation direction (direction) of the detection light emitted by the light emitting and receiving sensor 210. The actuator 215 can freely change the angle of the light emitting and receiving sensor 210 relative to the elevation drive unit 6. The actuator 215 is provided in the elevation drive unit 6. The actuator 215 constitutes an adjustment unit. By driving the actuator 215, the irradiation direction of the detection light of the light emitting and receiving sensor 210 is changed so that it moves along the lateral direction. Here, the actuator 215 can change the irradiation direction of the detection light of the light emitting and receiving sensor 210 among a first direction, a second direction, and a third direction which are different from each other. The first direction, the second direction, and the third direction have angles with the horizontal direction that decrease in this order. The actuator 215 is not particularly limited, and various known actuators can be used.

[0050] During an item non-holding period, the guided vehicle controller 208 changes the irradiation direction of the detection light of the light emitting and receiving sensor 210 to a first direction so that the detection light of the light emitting and receiving sensor 210 is irradiated toward the reflector 11. During a switching period, the guided vehicle controller 208 changes the irradiation direction of the detection light of the light emitting and receiving sensor 210 to a second direction so that the detection light of the light emitting and receiving sensor 210 is irradiated toward the reflector 11. During an item holding period, the guided vehicle controller 208 changes the irradiation direction of the detection light of the light emitting and receiving sensor 210 to a third direction so that the detection light of the light emitting and receiving sensor 210 is irradiated toward the reflector 11.

[0051] The guided vehicle controller 208 performs a timeout determination when reflected light is not detected by the light emitting / receiving sensor 210 within a set time. For example, the timeout determination is a determination that a state in which reflected light is not detected by the light emitting / receiving sensor 210 within a set time is a "timeout" and that there is a possibility that an abnormality such as shaking of the holding unit 7 (item 200) has occurred. The guided vehicle controller 208 sets the third set time, which is the set time for timeout determination during the switching period, longer than both the first set time, which is the set time for timeout determination during the item holding period, and the second set time, which is the set time for timeout determination during the item non-holding period. The first set time and the second set time may be equal to each other or may be different from each other. Other functions of the guided vehicle controller 208 are the same as those of the guided vehicle controller 8 (see FIG. 1). The guided vehicle controller 208 constitutes a determination unit.

[0052] As described above, it is possible to suppress erroneous detection of an abnormality in the ceiling transport vehicle 301 as well. Furthermore, in the ceiling transport vehicle 301, when unloading and loading the article 200, the third set time, which is the set time for determining timeout during the switching period, can be made longer than the first set time and the second set time, which are the set times for determining timeout during the article holding period and the article non-holding period. This makes it possible to suppress, for example, a situation where, at the switching timing, even in normal operation, the reflector 11 moves out of the monitoring range due to the influence of a change in the tilt of the lift drive unit 6 caused by switching between holding an article and not holding an article, causing the light emitting and receiving sensor 210 to detect an abnormality. In other words, it is possible to suppress erroneous detection of an abnormality.

[0053] [Variations] Although the embodiments have been described above, one aspect of the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the invention.

[0054] In the above embodiment, the item 200 is not particularly limited, and may be any object that can be transported by the ceiling transport vehicle 1. In the above embodiment and the above modified example, the transport vehicle controller 8 is provided as a controller, but instead of or in addition to this, one or more controllers other than the transport vehicle controller 8 may be provided. In the above embodiment and the above modified example, the item 200 is transferred between the load port 300, but the item 200 may also be transferred between other placement sections such as shelves.

[0055] In the above embodiment and modified example, the center cone 108, the dog 110, and the detector 120 are used to obtain the item holding period, the item non-holding period, and the switching period, but this is not limited to this. Various known methods and configurations may be used to obtain the item holding period, the item non-holding period, and the switching period. In the above embodiment and modified example, the switching period is not particularly limited as long as it is a period that includes the timing when the holding unit 7 switches between holding and not holding the item 200.

[0056] In the above embodiment, the third monitoring range A3 is the combined range of the first monitoring range A1 and the second monitoring range A2, but is not limited to this. For example, the third monitoring range A3 may be a range that is significantly larger than the combined range of the first monitoring range A1 and the second monitoring range A2. In this case, an abnormality is not actually detected during the switching period, and only an abnormality can be detected while the article 200 is being held by the holding unit 7 and is being raised or lowered.

[0057] In the second embodiment, the light emitting and receiving sensor 210 is used as a sensor, but the present invention is not limited to this, and other known sensors such as a photoelectric sensor may be used instead of the light emitting and receiving sensor 210. In the second embodiment, the actuator 215 is used, but the present invention is not limited to this, and other motors may be used instead of the actuator 215.

[0058] The third set time, which is the set time for determining the timeout in the second embodiment, may be set to be longer than the expected switching period. In this case, an abnormality is not actually determined during the switching period, and only an abnormality can be detected during the lifting operation while the article 200 is held by the holding unit 7.

[0059] The components in the above-described embodiments and modifications are not limited to the materials and shapes described above, and various materials and shapes can be applied. The components in the above-described embodiments and modifications can be applied as desired to the components in other embodiments and modifications. Some of the components in the above-described embodiments and modifications can be omitted as appropriate without departing from the spirit of one aspect of the present invention. [Explanation of symbols]

[0060] 1,301...ceiling transport vehicle, 4...lateral unit (lateral transfer mechanism), 6...lifting drive unit (lifting drive part), 7...holding unit, 8...transport vehicle controller (controller), 10...monitoring sensor, 61...base part, 108...center cone (positioning part), 110...dog (detectable object), 120...detection part, 200...item, 208...transport vehicle controller (judgment part), 210...light emitting and receiving sensor (sensor), 215...actuator (adjustment part), A...monitoring range, A1...first monitoring range, A2...second monitoring range, A3...third monitoring range.

Claims

1. a holding unit that is provided so as to be able to rise and fall and that holds an article; an elevation drive unit that raises and lowers the holding unit; a monitoring sensor provided in the lifting / lowering drive unit, monitoring a position below the lifting / lowering drive unit and capable of changing a monitoring range; a controller for controlling the monitoring range of the monitoring sensor; The controller A ceiling transport vehicle in which a third monitoring range, which is the monitoring range of the monitoring sensor during a switching period including the timing when the holding unit switches between holding and not holding the item, is wider than a first monitoring range, which is the monitoring range of the monitoring sensor when the holding unit is holding the item, and a second monitoring range, which is the monitoring range of the monitoring sensor when the holding unit is not holding the item.

2. The ceiling transport vehicle according to claim 1 , wherein the third monitoring range is a range that is a combination of the first monitoring range and the second monitoring range.

3. a holding unit that is provided so as to be able to rise and fall and that holds an article; an elevation drive unit that raises and lowers the holding unit; a sensor provided in the lifting / lowering drive unit, which irradiates directional detection light toward a predetermined position below and detects reflected light of the detection light; a controller that determines a timeout when the reflected light is not detected by the sensor within a set time; an adjustment unit that adjusts the irradiation direction of the detection light of the sensor, The controller A ceiling transport vehicle in which a third set time, which is the set time during a switching period including the timing when the holding unit switches between holding and not holding the item, is set longer than a first set time, which is the set time when the holding unit is holding the item, and a second set time, which is the set time when the holding unit is not holding the item.

4. The ceiling transport vehicle according to claim 1 or 3, further comprising a lateral transfer mechanism that moves the lifting drive unit laterally relative to the main body unit.

5. The holding unit is a positioning unit that is provided so as to be movable up and down relative to a base unit of the holding unit and that comes into contact with an upper surface of the article; a detection object provided integrally with the positioning portion; a detection unit that is provided on the base unit and detects a position of the detection object to thereby detect a relative rise of the positioning unit from an initial position with respect to the base unit, The controller In a state where the holding unit is holding the article, the period from when the positioning unit is recognized as rising by the detection result of the detection unit until when the positioning unit is recognized as returning to its initial position by the detection result of the detection unit is defined as the switching period during unloading; A ceiling transport vehicle as described in claim 1 or 3, wherein the switching period during loading is the period from when the detection result of the detection unit recognizes the positioning unit's rise from its initial position to when the detection result of the detection unit recognizes the positioning unit's descent when the holding unit is not holding the item.

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