Overhead conveyance vehicle

Abstract

[Problem] To provide an overhead conveyance vehicle that suppresses vibration and shaking of an article. [Solution] An overhead conveyance vehicle 1 that travels along a ceiling track while holding an article (a container 100) is provided with: a travel part that travels along the ceiling track; a body part 4 that moves along the ceiling track together with the travel part; a elevating body 20 that is suspended from the body part 4 and can move up and down with respect to the body part 4; a holding part 21 that is fixed to the lower part of the elevating body 20 and holds the article (the container 100); and a variable rigidity mechanism 40 that can switch between a first rigidity state, in which the rigidity between the body part 4 and the holding part 21 is at a first rigidity, and a second rigidity state, in which the rigidity is at a second rigidity higher than the first rigidity. The variable rigidity mechanism 40 switches between the first rigidity state and the second rigidity state according to the traveling state of the overhead conveyance vehicle 1.

Description

Ceiling transport vehicle

[0001] The present invention relates to an overhead transport vehicle.

[0002] An overhead transport vehicle that travels along an overhead track while holding an item has been disclosed (see, for example, Patent Document 1). When transporting an item to a destination, this overhead transport vehicle travels along the overhead track while holding the item, and transports it to a predetermined transfer position. The overhead transport vehicle then performs transfer operations such as moving the item sideways or lowering it at the transfer position, thereby transferring the item to the destination.

[0003] Japanese Patent Application Laid-Open No. 2006-8354

[0004] In an overhead transport vehicle, it is important to suppress vibration and shaking of the articles being held in order to improve the transporting capacity and transfer capacity.

[0005] An object of the present invention is to provide an overhead transport vehicle that suppresses vibration and shaking of articles.

[0006] An overhead transport vehicle according to one aspect of the present invention is a ceiling transport vehicle that runs along a ceiling track while holding an item, and is equipped with a running section that runs along the ceiling track, a main body that moves along the ceiling track together with the running section, a lifting body that is suspended from the main body and can be raised and lowered relative to the main body, a holding section that is fixed to the lower part of the lifting body and holds the item, and a variable stiffness mechanism that can switch between a first stiffness state in which the stiffness between the main body and the holding section is a first stiffness, and a second stiffness state in which the stiffness is a second stiffness higher than the first stiffness, and the variable stiffness mechanism switches between the first stiffness state and the second stiffness state depending on the running state of the ceiling transport vehicle.

[0007] In an aspect of the present invention, the rigidity between the main body and the holding part changes depending on the running state of the overhead transport vehicle, including when the vehicle is stopped, thereby preventing vibrations from being transmitted to items and making the items less likely to shake, and thereby suppressing vibration and shaking of items depending on the state of the overhead transport vehicle.

[0008] According to the above-described aspect of the overhead transport vehicle, the variable stiffness mechanism may be switched to the first stiffness state when the speed of the overhead transport vehicle is equal to or greater than a first speed, and may be switched to the second stiffness state when the speed of the overhead transport vehicle is equal to or less than a second speed that is slower than the first speed, or when the overhead transport vehicle is stopped. With this configuration, it is possible to effectively suppress vibrations to the articles during travel and shaking of the articles during transfer.

[0009] In the overhead transport vehicle according to the above aspect, the rigidity between the main body and the holder may be either or both of a connection rigidity, which is the rigidity between the main body and the lifting body, and a holding rigidity, which is the rigidity between the lifting body and the article, when the holder is holding the article. With this configuration, vibration to the article during travel and shaking of the article during transfer can be effectively suppressed.

[0010] According to the above-described aspect of the overhead transport vehicle, the variable stiffness mechanism may include an elastic body provided between the main body and the upper part of the lifting body, the main body may include an elevation drive unit that can adjust the compression amount of the elastic body by adjusting the position of the lifting body, and the elevation drive unit may change the coupling stiffness by changing the compression amount of the elastic body. With this configuration, it is possible to effectively suppress vibrations to the articles during travel and shaking of the articles during transfer.

[0011] According to the ceiling transport vehicle of the above aspect, the variable stiffness mechanism includes a support part provided at the lower part of the lifting body and moving up and down in response to the lifting and lowering operation of the lifting body, a pressing part provided at the lower part of the support part and pressing downward on the article held by the holding part, and an elastic body provided between the support part and the pressing part, and the main body includes a lifting drive part that adjusts the compression amount of the elastic body by adjusting the position of the lifting body, and the lifting drive part may change the holding stiffness by changing the compression amount of the elastic body. With this configuration, it is possible to effectively suppress vibration to the article during travel and shaking of the article during transfer.

[0012] According to the ceiling transport vehicle of the above aspect, the variable stiffness mechanism includes a receiving member provided on an upper part of the lifting body, a first elastic body provided between the receiving member and the upper part of the lifting body, a support portion provided on a lower part of the lifting body, a connecting member connecting the receiving member and the support portion, a pressing portion provided on a lower part of the support portion and pressing downward against an article held by the holding portion, and a second elastic body provided between the support portion and the pressing portion, the main body includes an elevation drive portion that adjusts the position of the lifting body while keeping the receiving member in contact with the main body to adjust the compression amounts of the first elastic body and the second elastic body, the greater the compression amounts of the first elastic body and the second elastic body, the higher the connection stiffness and holding stiffness, and in the first stiffness state, the compression amounts of the first elastic body and the second elastic body may be controlled to a first compression amount, and in the second stiffness state, the compression amounts of the first elastic body and the second elastic body may be controlled to a second compression amount greater than the first compression amount. This configuration can more effectively suppress vibration to the article during travel and swaying of the article during transfer.

[0013] According to the above aspect of the overhead transport vehicle, the main body may include a lateral movement mechanism that moves the lifting body laterally in the traveling direction, and the lateral movement mechanism may move the lifting body laterally when the main body is in the second rigid state. With this configuration, it is possible to suppress shaking of the article during transfer.

[0014] FIG. 1 is a diagram conceptually showing an overhead transport vehicle according to the present embodiment; FIG. 2 is a diagram schematically showing lateral transfer of an overhead transport vehicle according to the present embodiment; FIG. 3 is a diagram showing the initial state of the overhead transport vehicle according to the present embodiment; FIG. 4 is a diagram showing a state in which the overhead transport vehicle according to the present embodiment is holding a container; FIG. 5 is a diagram showing an example of a storage state according to the present embodiment; FIG. 6 is a diagram explaining a vibration suppression state according to the present embodiment; FIG. 7 is a diagram explaining a swing suppression state according to the present embodiment; FIG. 8 is a diagram explaining an example of the flow of operation of the overhead transport vehicle 1 according to the present embodiment; FIG. 9 is a diagram showing a first modified example of a variable stiffness mechanism according to the present embodiment; FIG. 10 is a diagram showing a second modified example of a variable stiffness mechanism according to the present embodiment.

[0015] The present invention will be described below through embodiments, but the following embodiments do not limit the scope of the invention. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention. In the drawings, identical or similar parts may be designated by the same reference numerals, and redundant explanations may be omitted. Furthermore, the shapes and sizes of elements in the drawings may be exaggerated for clarity, and may differ in shape and size from the actual product.

[0016] In the drawings, directions in the drawings may be explained using an XYZ coordinate system. In the XYZ coordinate system, a plane parallel to the horizontal plane is the XY plane. One direction in this XY plane is referred to as the X direction, and the direction perpendicular to the X direction is referred to as the Y direction. Furthermore, the direction perpendicular to the XY plane is referred to as the Z direction. The X, Y, and Z directions will be explained assuming that the direction indicated by the arrow in the drawing is the + direction, and the direction opposite to the arrow is the - direction.

[0017] 1 is a conceptual diagram of an overhead transport vehicle according to this embodiment, showing the overhead transport vehicle 1 according to this embodiment as viewed from the -Y direction side.

[0018] The ceiling transport vehicle 1 travels along a ceiling track R that is set higher than the floor surface, such as the ceiling of a clean room, and transports the container 100 in a suspended state within the storage space AS. The ceiling transport vehicle 1 is used to transport the container 100, for example, between a processing device and a container storage device, or between two processing devices. The X direction in FIG. 1 is the traveling direction of the ceiling transport vehicle 1. The Z direction in FIG. 1 is the vertical direction of the ceiling transport vehicle 1.

[0019] The ceiling transport vehicle 1 is used to transport containers 100, for example, between a processing device and a container storage device, or between two processing devices. The processing device is, for example, a film forming device, a coater / developer, an exposure device, an etching device, etc., and performs various processes in the process of manufacturing devices (e.g., semiconductor devices). The container storage device is, for example, disposed on a transport path for transporting the containers 100 and temporarily stores the containers 100. The container storage device is, for example, disposed near the ceiling. The container 100 stores, for example, wafers or reticles used in the manufacture of semiconductor devices. The container 100 is, for example, a FOUP (Front Opening Unified Pod), a SMIF pod, or a reticle pod whose interior can be purged. The container 100 is an example of an "article" in the present invention.

[0020] The ceiling transport vehicle 1 includes, for example, a running section 2, a connecting section 3a, a support section 3b, a main body section 4, covers 5a and 5b, a lifting section 6, and a control device 9.

[0021] The traveling unit 2 includes wheels 2a and a traveling drive unit 2b. The wheels 2a are arranged in contact with the ceiling track R and are driven to rotate by the driving force of the traveling drive unit 2b. The traveling drive unit 2b generates the driving force for traveling the overhead transport vehicle 1. The traveling drive unit 2b has a traveling motor such as a linear motor or a rotary motor. The traveling drive unit 2b also has a rotary encoder or a linear encoder. The traveling drive unit 2b controls the linear motor or the rotary motor based on the detection results such as the number of rotations of the wheels 2a detected by the rotary encoder or the linear encoder, and adjusts the speed or stopping position of the overhead transport vehicle 1.

[0022] The connecting portion 3 a connects the traveling drive unit 2 b and the support portion 3 b. For example, one end of the connecting portion 3 a is connected to the traveling drive unit 2 b, and the other end is connected to the support portion 3 b. The support portion 3 b is disposed along a horizontal plane and supports the main body portion 4.

[0023] The main body 4 is connected to the travel drive unit 2b via the connecting unit 3a, and moves along the ceiling track together with the travel unit 2. The main body 4 includes, for example, a lifting device 7 and a lateral feed mechanism 8. The lifting device 7 includes a lifting drive unit 11 and a hanging member 12.

[0024] The lifting device 7 lowers or raises the lifting unit 6 at a predetermined speed and maintains the lifting unit 6 at a target height. The lifting unit 6 is suspended from the main body 4 by a plurality of suspension members 12. The lifting drive unit 11 is, for example, a hoist, and lowers the lifting unit 6 by unwinding the plurality of suspension members 12. The lifting drive unit 11 also raises the lifting unit 6 by winding up the plurality of suspension members 12.

[0025] For example, the lifting drive unit 11 includes one or more rotating bodies 110 and a lifting motor 120. The rotating body 110 is, for example, a cylindrical drum having a winding surface for the hanging members 12 on its outer periphery. The lifting motor 120 is an electric motor that rotates the rotating body 110 to wind and unwind (unwind) the multiple hanging members 12. Note that the lifting drive unit 11 may include rollers such as pulleys that support the multiple hanging members 12. When the lifting unit 6 is suspended using the hanging members 12, the lifting drive unit 11 only needs to have a configuration for winding and unwinding the hanging members 12, and does not necessarily have to include the rotating body 110 and the lifting motor 120.

[0026] One end of the hanging member 12 is connected to the lifting drive unit 11, and the other end is connected to the lifting unit 6. The hanging member 12 is, for example, a belt. In this embodiment, the lifting unit 6 is suspended from the main body 4 by, for example, three or four hanging members 12. However, the number of hanging members 12 is not particularly limited, and any number may be used as long as there is more than one. For example, a conductive member such as a cable is provided inside the hanging member 12, and power is supplied from the main body 4 to the lifting unit 6 via this conductive member.

[0027] The lateral feeding mechanism 8 performs a lateral feeding operation to lateralize the lifting drive unit 11 in the left-right direction relative to the traveling direction of the main body unit 4. The traveling direction of the main body unit 4 is the direction in which the overhead transport vehicle 1 travels along the ceiling track R by the traveling unit 2, i.e., the X direction. The left-right direction is the direction perpendicular to the traveling direction, i.e., the Y direction. This left-right direction is the direction in which the lateral feeding mechanism 8 lateralizes the lifting drive unit 11, and will be referred to as the lateral feeding direction D hereinafter.

[0028] The lateral ejection mechanism 8 includes, for example, a base portion 13 and one or more slide portions 14. The lateral ejection mechanism 8 illustrated in Figures 1 and 2 has two slide portions 14. One slide portion 14 is referred to as a "first slide portion 14A," and the other slide portion 14 is referred to as a "second slide portion 14B."

[0029] The base portion 13 is attached below the connecting portion 3 a. The base portion 13 is attached to, for example, the support portion 3 b. The base portion 13 is, for example, a plate-shaped member. The base portion 13 is arranged so that the plane of the base portion 13 is parallel to the horizontal direction.

[0030] The first slide portion 14A is disposed on the underside of the base portion 13. The first slide portion 14A is, for example, a plate-shaped member, and is disposed so that its plane is parallel to the plane of the base portion 13 in the Z direction. The first slide portion 14A has, for example, the same shape as the base portion 13. The first slide portion 14A is movable in a lateral direction relative to the base portion 13.

[0031] The second slide portion 14B is disposed on the underside of the first slide portion 14A. The second slide portion 14B is, for example, a plate-shaped member disposed such that its plane is parallel to the plane of the base portion 13 and the plane of the first slide portion 14A in the Z direction. The second slide portion 14B has, for example, the same shape as the first slide portion 14A. An elevation drive unit 11 is provided on the underside of the second slide portion 14B. The second slide portion 14B is movable in the lateral extension direction relative to the first slide portion 14A. The lateral extension mechanism 8 has, for example, a drive unit (not shown), such as an electric motor, and uses the driving force from this drive unit to lateralize the first slide portion 14A in the lateral extension direction D relative to the base portion 13, and also lateralize the second slide portion 14B in the same lateral extension direction D relative to the first slide portion 14A in conjunction with the lateral extension of the first slide portion 14A. The lateral extension mechanism 8 may have any configuration that can extend the lift drive unit 11 in the lateral extension direction D, and may employ a configuration other than the base unit 13 and one or more slide units 14 .

[0032] A cover 5a is provided on the -X side of the main body 4, and a cover 5b is provided on the +X side. The covers 5a and 5b are each fixed to the support 3b and extend from the support 3b in the -Z direction. The pair of covers 5a and 5b form a space in which the container 100 is accommodated, i.e., an accommodation space AS.

[0033] The lifting unit 6 includes a lifting platform 20, a holding unit 21, and a variable stiffness mechanism 40. The lifting platform 20 is an example of a lifting body. The lifting body is not limited to the lifting platform 20, and may be any lifting body that can be raised and lowered relative to the main body 4.

[0034] The other ends of the multiple hanging members 12 are fixed to the lifting platform 20. The lifting platform 20 is, for example, a plate-like member, and is suspended by the multiple hanging members 12 so that its plane is parallel to the horizontal plane. However, in this embodiment, the shape of the lifting platform 20 is not particularly limited.

[0035] The holding unit 21 is fixed to the underside of the lifting platform 20. The holding unit 21 holds the container 100. For example, the holding unit 21 holds the container 100 by gripping the flange 100A of the container 100, thereby suspending and holding the container 100. The method by which the holding unit 21 grips the container 100 is not particularly limited, and the holding unit 21 may grip the container 100 from above or by pinching it from the left and right. The holding unit 21 is, for example, a chuck having multiple claws 21a that can move horizontally. The holding unit 21 moves the claws 21a below the flange 100A by a driving force such as a motor. The lifting drive unit 11 then winds up the hanging member 12, causing the holding unit 21 to rise, thereby holding the container 100 in a suspended state.

[0036] The variable stiffness mechanism 40 is capable of switching between a first stiffness state in which the stiffness between the main body 4 and the holding unit 21 is a first stiffness and a second stiffness state in which the stiffness is a second stiffness higher than the first stiffness when the holding unit 21 is holding the container 100 in the storage space AS. The variable stiffness mechanism 40 has a first variable stiffness mechanism 22 and a second variable stiffness mechanism 23. In the variable stiffness mechanism shown in FIG. 1 , the stiffness between the main body 4 and the holding unit 21 refers to both the connection stiffness Ru between the main body 4 and the lifting platform 20 and the holding stiffness Rd between the lifting platform 20 and the flange 100A of the container 100.

[0037] The first variable stiffness mechanism 22 has a mechanism that can adjust the connection stiffness Ru between the main body 4 and the lifting platform 20 when the holding part 21 is holding the container 100. The first variable stiffness mechanism 22 is provided, for example, on the upper surface side of the lifting platform 20. The first variable stiffness mechanism 22 includes, for example, a receiving member 30 and a first elastic body 31.

[0038] The receiving member 30 is provided on the upper part of the lifting platform 20. The upper surface of the receiving member 30 supports the lower surface of the lifting drive unit 11. Specifically, when the ceiling transport vehicle 1 stores the container 100 in the storage space AS, the upper surface of the receiving member 30 comes into contact with the lower surface of the lifting drive unit 11. The receiving member 30 is, for example, a plate-shaped member, and is arranged so that its flat surfaces (upper and lower surfaces) are parallel to a horizontal plane.

[0039] The first elastic body 31 is provided between the lower surface of the receiving member 30 and the upper surface of the lifting platform 20. The first elastic body 31 includes, for example, one or more of a gel material, a rubber material, and a compression spring. The upper end of the first elastic body 31 contacts the receiving member 30, and the lower end contacts the upper surface of the lifting platform 20.

[0040] The second variable stiffness mechanism 23 has a mechanism that can adjust the holding stiffness Rd between the lifting platform 20 and the flange 100A of the container 100 when the holder 21 is holding the container 100. The second variable stiffness mechanism 23 includes, for example, a support portion 51, a pressing portion 52, a connecting member 53, and a second elastic body 54.

[0041] The support portion 51 is provided at the bottom of the lift platform 20. The support portion 51 is disposed so that its plane is parallel to the horizontal plane.

[0042] The pressing portion 52 is provided below the support portion 51 and presses downward the container 100 held by the holding portion 21. The pressing portion 52 is a member that fits into a recess 100B formed in a flange 100A of the container 100 held by the holding portion 21, for example, to position the holding portion 21 relative to the container 100.

[0043] The connecting member 53 connects the receiving member 30 and the support portion 51. The connecting member 53 is, for example, a member extending in the vertical direction, with one end fixed to the receiving member 30 and the other end fixed to the support portion 51. The connecting member 53 is movable in the vertical direction relative to the lift platform 20. Therefore, the support portion 51 is also movable in the vertical direction relative to the lift platform 20. For example, when the receiving member 30 moves downward, the connecting member 53 also moves downward. Therefore, the support portion 51 fixed to the other end of the connecting member 53 also moves downward relative to the lift platform 20.

[0044] The second elastic body 54 is provided between the support portion 51 and the pressing portion 52. That is, one end of the second elastic body 54 is connected to the support portion 51, and the other end is connected to the pressing portion 52. The second elastic body 54 biases the pressing portion 52 downward. The second elastic body 54 includes, for example, one or more of a gel material, a rubber material, and a compression spring.

[0045] The control device 9 may include a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) and a non-volatile or volatile semiconductor memory (e.g., RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), or EEPROM (Electrically Erasable Programmable Read Only Memory)). For example, the control device 9 may be a microcontroller such as an MCU.

[0046] The control device 9 controls various operations of the ceiling transport vehicle 1. The control device 9 controls the travel drive unit 2b to control the travel of the ceiling transport vehicle 1. The control device 9 controls the lateral feeding operation of the lateral feeding mechanism 8 by controlling a drive unit (e.g., an electric motor) provided in the lateral feeding mechanism 8.

[0047] The control device 9 controls the lifting drive unit 11. For example, the control device 9 controls the rotation of the lifting motor 120 to control the winding and unwinding (lowering) of the hanging member 12. In other words, the control device 9 can control the position of the lifting unit 6 in the Z direction (hereinafter referred to as the "position of the lifting unit 6") by controlling the rotation of the lifting motor 120. FIG. 2 is a diagram schematically showing lateral transfer of the ceiling transport vehicle according to this embodiment. Lateral transfer refers to transferring the container 100 to a predetermined position by unwinding the hanging member 12 after a lateral transfer operation. The ceiling transport vehicle 1, for example, travels to a predetermined position on the ceiling track R (hereinafter referred to as the "transport position") with the container 100 stored in the storage space AS, and performs lateral transfer at the transport position.

[0048] When the holder 21 holds the container 100 in the storage space AS, the control device 9 controls the rotation of the lift motor 120 to change the position of the lift unit 6, thereby operating the first variable stiffness mechanism 22 and the second variable stiffness mechanism 23. This allows the control device 9 to adjust both the coupling stiffness Ru and the holding stiffness Rd. In other words, when the holder 21 holds the container 100 and the upper surface of the receiving member 30 is in contact with the lower surface of the lift drive unit 11, the control device 9 can adjust both the coupling stiffness Ru and the holding stiffness Rd by adjusting the position of the lift unit 6.

[0049] The control device 9 changes both the coupling stiffness Ru and the holding stiffness Rd depending on the traveling state of the ceiling transport vehicle 1. The traveling state includes, for example, at least one of the following: the start of traveling of the ceiling transport vehicle 1 storing the container 100; a state in which the speed of the ceiling transport vehicle 1 is equal to or greater than a first threshold (hereinafter referred to as the "first traveling state"); the start of a stopping operation of the ceiling transport vehicle 1 storing the container 100; a state in which the speed of the ceiling transport vehicle 1 is less than a second threshold (hereinafter referred to as the "second traveling state"); and a state in which the ceiling transport vehicle 1 is stopped (hereinafter referred to as the "stopped state"). Note that the second threshold is smaller than the first threshold to create hysteresis, but may be the same value as the first threshold.

[0050] The second traveling state may be a state in which the ceiling transport vehicle 1 traveling along the ceiling track R while holding the container 100 decelerates to stop, and the speed of the decelerating ceiling transport vehicle 1 becomes less than a second threshold value that is slower than the first threshold value. The second traveling state may not include the state from when the ceiling transport vehicle 1 starts traveling until the speed of the ceiling transport vehicle 1 becomes equal to or greater than the second threshold value, or may include this state.

[0051] The control device 9 may, for example, determine whether the current running state of the ceiling transport vehicle 1 is the first running state or the second running state. The control device 9 may, for example, determine whether the current running state of the ceiling transport vehicle 1 is the first running state or the second running state by directly measuring the speed of the ceiling transport vehicle 1 using a speed sensor or the like. The control device 9 may, for example, indirectly acquire the speed of the ceiling transport vehicle 1 by measuring values ​​such as the number of rotations of the travel drive unit 2b and the voltage supplied to the travel drive unit 2b, and determine whether the current running state of the ceiling transport vehicle 1 is the first running state or the second running state.

[0052] In addition, a section in which the overhead transport vehicle 1 travels at a speed equal to or greater than a first threshold (hereinafter referred to as the "first section"), a section in which the overhead transport vehicle 1 travels at a speed less than a second threshold (hereinafter referred to as the "second section"), and a section in which the overhead transport vehicle 1 stops (hereinafter referred to as the "third section") are set in advance. The control device 9 may determine whether the overhead transport vehicle 1 is currently in the first running state or the second running state by determining whether the overhead transport vehicle 1 is currently in the first, second, or third section. However, in this embodiment, it is sufficient to directly or indirectly determine whether the overhead transport vehicle 1 is currently in the first or second running state, and the method of determination is not particularly limited. In addition, the control device 9 may determine whether the overhead transport vehicle 1 is currently stopped based on the sensor result of the speed sensor, the rotation speed of the travel drive unit 2b, the voltage supplied to the travel drive unit 2b, and the like. Alternatively, the control device 9 may determine that the overhead transport vehicle 1 is currently stopped when it detects that the overhead transport vehicle 1 is currently in the third section.

[0053] The control device 9 controls the position of the lifting unit 6 so that, for example, both the connection stiffness Ru determined by the first variable stiffness mechanism 22 and the holding stiffness Rd determined by the second variable stiffness mechanism 23 are higher in the second traveling state or when the ceiling transport vehicle 1 is stopped than in the first traveling state. For example, when the traveling state of the ceiling transport vehicle 1 is the first traveling state, the control device 9 controls the connection stiffness Ru to the first connection stiffness Ru1 and the holding stiffness Rd to the first holding stiffness Rd1 by setting the position of the lifting unit 6 to a first position P1 (see, for example, FIG. 6 ). The state in which the connection stiffness Ru is controlled to the first connection stiffness Ru1 and the holding stiffness Rd is controlled to the first holding stiffness Rd1 may be referred to as a "vibration suppression state." The vibration suppression state is a state in which vibration of the container 100 is suppressed during traveling. The vibration suppression state is an example of a first stiffness state.

[0054] When the ceiling transport vehicle 1 is in the second traveling state or is stopped, the position of the lifting unit 6 is set to a second position P2 (see, for example, FIG. 7 ) higher than the first position P1, thereby setting the connection stiffness Ru to a second connection stiffness Ru2 higher than the first connection stiffness Ru1 and setting the holding stiffness Rd to a second holding stiffness Rd2 higher than the first holding stiffness Rd1. The state in which the connection stiffness Ru is controlled to the second connection stiffness Ru2 and the holding stiffness Rd is controlled to the second holding stiffness Rd2 is sometimes referred to as the "sway-suppressed state." The sway-suppressed state is a state in which swaying of the container 100 is suppressed. Note that when the lifting unit 6 is at the first position P1 and the second position P2, the upper surface of the receiving member 30 contacts the lower surface of the lifting drive unit 11. The sway-suppressed state is an example of the second stiffness state.

[0055] The holding operation of the ceiling transport vehicle 1 will be described below. Fig. 3 shows the ceiling transport vehicle 1 in a state where it is not holding a container 100 (hereinafter referred to as the "initial state"). In the initial state shown in Fig. 3, the holding unit 21 is not holding a container 100, and the upper surface of the receiving member 30 is not in contact with the lower surface of the lifting drive unit 11. Fig. 4 shows the state where the ceiling transport vehicle 1 is holding a container 100.

[0056] When the ceiling transport vehicle 1 is in its initial state, the lifting drive unit 11, under the control of the control device 9, pays out the hanging member 12 to lower the lifting unit 6. As the lifting unit 6 lowers, as shown in Figure 4, the pressing unit 52 fits into the recess 100B of the flange 100A, and the pressing unit 52 rises relative to the holding unit 21, which is lowering due to its own weight. When the pressing unit 52 rises relatively to a predetermined position, the holding unit 21 is determined to have reached the holding position, and the lifting drive unit 11 stops the lowering of the lifting unit 6.

[0057] When the descent of the lifting unit 6 stops, the holding unit 21 holds the container 100 by moving the claws 21a below the flange 100A based on instructions from the control unit 9. Once the holding unit 21 holds the container 100, the lifting drive unit 11, under control of the control unit 9, lifts the lifting unit 6 by winding up the multiple hanging members 12. The container 100 is accommodated in the accommodation space AS. Hereinafter, the state in which the container 100 is accommodated in the accommodation space AS may be referred to as the "accommodated state."

[0058] FIG. 5 illustrates an example of a storage state according to this embodiment. In the storage state, the upper surface of the receiving member 30 contacts the lower surface of the lift drive unit 11. When the upper surface of the receiving member 30 contacts the lower surface of the lift drive unit 11, the first variable stiffness mechanism 22 operates to increase the coupling stiffness Ru between the main body 4 and the lift platform 20. Specifically, when the upper surface of the receiving member 30 is pressed against the lower surface of the lift drive unit 11, the first elastic body 31 is compressed, generating an elastic force in the vertical direction corresponding to the amount of compression. In other words, when the lift unit 6 is pressed against the lift drive unit 11 (main body 4), the first elastic body 31 is compressed, generating an elastic force in the vertical direction corresponding to the amount of compression. The first elastic body 31 urges the receiving member 30 upward and the lift platform 20 downward by this elastic force. The compression amount of the first elastic body 31 may be, for example, the length of the first elastic body 31 that is changed when the upper surface of the receiving member 30 is pressed against the lower surface of the lifting drive unit 11.

[0059] In this way, when the first elastic body 31 sandwiched between the lift drive unit 11 and the lift platform 20 is compressed, an elastic force corresponding to the amount of compression is generated, thereby increasing the connection rigidity Ru between the lift drive unit 11 and the lift platform 20. Note that the greater the amount of compression of the first elastic body 31, the higher the connection rigidity Ru. Note that the compression amount of the first elastic body 31 varies depending on the distance L between the lift drive unit 11 and the lift platform 20. In other words, as the lift platform 20 moves upward and the distance L between the lift drive unit 11 and the lift platform 20 becomes shorter, the compression amount of the first elastic body 31 increases. Therefore, by changing the distance L between the lift drive unit 11 and the lift platform 20, the ceiling transport vehicle 1 can change the compression amount of the first elastic body 31, and as a result, the connection rigidity Ru.

[0060] When the upper surface of the receiving member 30 is pressed against the lower surface of the lifting drive unit 11 and the first elastic body 31 is compressed, the lifting platform 20 moves upward. That is, when the first elastic body 31 is compressed, the second variable stiffness mechanism 23 is activated and the pressing part 52 is displaced upward relative to the support part 51. As a result, the second elastic body 54 is compressed, and the holding stiffness Rd between the lifting platform 20 and the flange 100A of the container 100 increases. Specifically, an elastic force in the vertical direction corresponding to the compression amount of the second elastic body 54 is generated. The second elastic body 54 presses the pressing part 52 against the flange 100A with an elastic force corresponding to the compression amount of the second elastic body 54.

[0061] In this way, when the second elastic body 54 sandwiched between the lifting platform 20 and the container 100 is compressed, an elastic force corresponding to the amount of compression is generated, pressing the pressing portion 52 against the flange 100A. This increases the holding rigidity Rd between the lifting platform 20 and the flange 100A of the container 100. Note that the greater the amount of compression of the second elastic body 54, the higher the holding rigidity Rd.

[0062] The compression amount of the second elastic body 54 varies depending on the distance between the support portion 51 and the pressing portion 52. In the example shown in Fig. 5, the distance between the support portion 51 and the pressing portion 52 varies depending on the distance L between the lift drive unit 11 and the lift platform 20. Therefore, the compression amount of the second elastic body 54, like the compression amount of the first elastic body 31, varies depending on the distance L between the lift drive unit 11 and the lift platform 20. In other words, pressing the lift unit 6 against the lift drive unit 11 (main body 4) compresses not only the first elastic body 31 but also the second elastic body 54.

[0063] As the lift platform 20 moves upward and the distance L between the lift drive unit 11 and the lift platform 20 becomes shorter, the compression amount of the second elastic body 54 increases. Therefore, the ceiling transport vehicle 1 can change the compression amount of the second elastic body 54 by changing the distance L between the lift drive unit 11 and the lift platform 20, thereby changing the holding rigidity Rd. In the configuration illustrated in FIG. 5 , changing the distance L between the lift drive unit 11 and the lift platform 20 is equivalent to changing the pressing force F, which is the force pressing the lift unit 6 against the lift drive unit 11 (main body 4). Therefore, the ceiling transport vehicle 1 can change the compression amount of the first elastic body 31 and the compression amount of the second elastic body 54 by changing the pressing force F, thereby changing the connection rigidity Ru and the holding rigidity Rd.

[0064] A method for controlling the connection stiffness Ru and the holding stiffness Rd will be described below. Fig. 6 is a diagram illustrating the connection stiffness Ru and the holding stiffness Rd in the vibration suppression state. Fig. 7 is a diagram illustrating the connection stiffness Ru and the holding stiffness Rd in the sway suppression state.

[0065] When the container 100 is in the storage state, and the speed of the ceiling transport vehicle is in the first traveling state where the speed of the ceiling transport vehicle is equal to or greater than the first threshold, the control device 9 places the ceiling transport vehicle 1 in the vibration suppression state by controlling the pressing force F to a first pressing force F1, as illustrated in FIG. 6 . Specifically, when the traveling state is the first traveling state, the control device 9 controls the position of the lifting unit 6 to a first position P1, thereby pressing the upper surface of the receiving member 30 against the lower surface of the lifting drive unit 11 with the first pressing force F1. The distance L between the lifting drive unit 11 and the lifting platform 20 in the vibration suppression state is referred to as the "first distance L1." In the vibration suppression state, the compression amount of the first elastic body 31 is the first compression amount, and the compression amount of the second elastic body 54 is the first compression amount. Therefore, the connection stiffness Ru becomes the first connection stiffness Ru1 corresponding to the first compression amount, and the holding stiffness Rd becomes the first holding stiffness Rd1 corresponding to the first compression amount.

[0066] When the container 100 is in the storage state, in the second traveling state where the speed of the ceiling transport vehicle 1 is less than a second threshold value that is slower than the first threshold value, the control device 9 controls the pressing force F to a second pressing force F2 to put the ceiling transport vehicle 1 into a vibration suppression state. The second pressing force F2 is greater than the first pressing force F1.

[0067] Specifically, when the ceiling transport vehicle 1 is in the second traveling state, the control device 9 controls the distance between the lifting drive unit 11 and the lifting platform 20 to a second distance L2 that is narrower than the first distance L1 by gradually changing the position of the lifting unit 6 to a second position P2 that is higher than the first position P1. The vibration suppression state shown in Fig. 7 is a state in which the position of the lifting unit 6 is raised from the first position P1 to the second position P2 by retracting the multiple hanging members 12 by a predetermined amount from the vibration suppression state shown in Fig. 6.

[0068] In the vibration suppression state, the compression amounts of the first elastic body 31 and the second elastic body 54 are each a second compression amount (>first compression amount) that is greater than the first compression amount. Therefore, the connection stiffness Ru becomes a second connection stiffness Ru2 corresponding to the second compression amount, and the second connection stiffness Ru2 in the vibration suppression state is higher than the first connection stiffness Ru1 in the vibration suppression state. Furthermore, the holding stiffness Rd becomes a second holding stiffness Rd2 corresponding to the second compression amount, and the second holding stiffness Rd2 in the vibration suppression state is higher than the first holding stiffness Rd1 in the vibration suppression state.

[0069] As described above, in the first traveling state, the state of the ceiling transport vehicle 1 is switched to the vibration suppression state, and in the second traveling state, the state of the ceiling transport vehicle 1 is switched to the sway suppression state. Specifically, in the first traveling state, the ceiling transport vehicle 1 travels with the position of the lifting unit 6 lowered from the second position P2 to the first position P1 so that the pressing force F becomes a first pressing force F1 that is weaker than the second pressing force F2 ( FIG. 6 ). Also, in the second traveling state, the ceiling transport vehicle 1 travels or stops with the position of the lifting unit 6 raised from the first position P1 to the second position P2 so that the pressing force F becomes a second pressing force F2 that is stronger than the first pressing force F1. For example, when switching from the vibration suppression state to the sway suppression state, the pressing force F is changed stepwise from the first pressing force F1 to the second pressing force F2. In other words, switching from the vibration suppression state to the sway suppression state or switching from the sway suppression state to the vibration suppression state may be performed stepwise rather than discontinuously.

[0070] The following describes the vibration and shaking of the container 100 held by the ceiling transport vehicle 1. When the ceiling transport vehicle 1 is traveling along the ceiling track R with the container 100 stored in the storage space AS, the vibration of the ceiling transport vehicle 1 may be transmitted to the container 100, causing the container 100 to vibrate. For example, when the ceiling transport vehicle 1 travels, the wheels 2a rolling on the ceiling track R may be subjected to an impact at the joint (connection) of the ceiling track R. For example, if there is a step at the joint of the ceiling track R, some impact may be applied to the wheels 2a when the ceiling transport vehicle 1 travels over the step. When an impact is applied to the wheels 2a, the impact causes vibration throughout the entire ceiling transport vehicle 1, which may then be applied to the container 100. For this reason, it is desirable to suppress this vibration as much as possible.

[0071] When the ceiling transport vehicle 1 performs a transfer operation, such as moving the container 100 laterally or lowering it, at a transfer position on the ceiling track R, the ceiling transport vehicle 1 stops at that transfer position before starting the transfer operation. Here, during the transfer operation, the container 100 may be significantly shaking in the traveling direction or sideways. If the transfer operation to the load port is started while the container 100 is significantly shaking, the container 100 may run onto the carrier guide on the load port. Therefore, it is possible to wait at the transfer position without starting the transfer operation until the shaking of the container 100 stops, but in that case, the transfer time will be longer and the transport capacity will be reduced. Therefore, during the transfer operation, it is desirable to minimize the shaking of the container 100.

[0072] Consider a case where the coupling stiffness Ru and the holding stiffness Rd are maintained constant regardless of the traveling state by controlling the pressing force F to be constant. For example, to suppress shaking of the container 100 during transfer operations, the pressing force F is increased to maintain the coupling stiffness Ru and the holding stiffness Rd at a high level. In this case, shaking of the container 100 during transfer operations can be suppressed, but vibration of the container 100 during traveling cannot be suppressed and increases. Specifically, if the coupling stiffness Ru and the holding stiffness Rd are high, they are easily transmitted from the main body 4 to the container 100 via the lifting unit 6. In other words, if the coupling stiffness Ru and the holding stiffness Rd are set high to suppress shaking of the container 100 during transfer operations, vibration of the container 100 during traveling cannot be suppressed. On the other hand, if the coupling stiffness Ru and the holding stiffness Rd are set low to suppress vibration of the container 100 during traveling, shaking of the container 100 during transfer operations cannot be suppressed.

[0073] In this way, if the connection stiffness Ru and the holding stiffness Rd are always maintained constant regardless of the traveling state, only one of the vibration of the container 100 during traveling and the shaking of the container 100 during transfer operations can be suppressed.

[0074] In one example configuration of this embodiment, the ceiling transport vehicle 1 does not always keep the pressing force F constant, but instead changes the pressing force F depending on the traveling state of the ceiling transport vehicle 1. In other words, the ceiling transport vehicle 1 changes the coupling stiffness Ru and the holding stiffness Rd depending on the traveling state of the ceiling transport vehicle 1. For example, when traveling in the first traveling state, the ceiling transport vehicle 1 sets the pressing force F to a first pressing force F1, thereby lowering the coupling stiffness Ru and the holding stiffness Rd and establishing a vibration-suppressed state in which vibrations due to the above-mentioned impact are less likely to be transmitted to the container 100. On the other hand, when a stopping operation is initiated or traveling is stopped, the ceiling transport vehicle 1 sets the pressing force F to a second pressing force F2, which is higher than the first pressing force F1, thereby increasing the coupling stiffness Ru and the holding stiffness Rd and establishing a vibration-suppressed state in which shaking of the container 100 is suppressed. This effectively suppresses both vibration of the container 100 during traveling and shaking of the container 100 during transfer operations.

[0075] An example of the flow of operation of the ceiling transport vehicle 1 according to this embodiment is described below. FIG. 8 is a diagram illustrating an example of the flow of operation of the ceiling transport vehicle 1 according to this embodiment. First, the ceiling transport vehicle 1 travels along the ceiling track R without holding a container 100 and stops at a predetermined position on the ceiling track R (step S101). At the predetermined position on the ceiling track R, the ceiling transport vehicle 1 lowers the lifting unit 6 to a specified position using the lifting drive unit 11 (step S102). The pressing unit 52 engages with the recess 100B of the flange 100A, and the holding unit 21 reaches the holding position. When the holding unit 21 reaches the holding position, the lowering of the lifting unit 6 stops, and the holding unit 21 holds the container 100 (step S103). When the holding unit 21 holds the container 100, the ceiling transport vehicle 1 raises the lifting unit 6 (step S104).

[0076] Here, when the ceiling transport vehicle 1 stores the container 100 in the storage space AS, the pressing force F is set to a first pressing force F1, thereby setting the connection stiffness Ru to a first connection stiffness Ru1 and the holding stiffness Rd to a first holding stiffness Rd1. That is, when the container 100 is stored in the storage space AS, the control device 9 controls the ceiling transport vehicle 1 to a vibration suppression state by setting the pressing force F to the first pressing force F1 (step S105). The first connection stiffness Ru1 and the first holding stiffness Rd1 are adjusted, for example, so that the vibration of the container 100 during travel is within an allowable range.

[0077] The overhead transport vehicle 1 travels on the overhead track R toward the transfer position while maintaining the pressing force F at the first pressing force F1 (step S106). As the overhead transport vehicle 1 approaches the transfer position, the control device 9 gradually reduces the speed of the overhead transport vehicle 1 to stop it at the transfer position (step S107). Then, when the speed of the overhead transport vehicle 1 becomes equal to or less than the second threshold, the control device 9 changes the pressing force F from the first pressing force F1 to the second pressing force F2.

[0078] When the pressing force F is changed from the first pressing force F1 to the second pressing force F2, the compression amount of the first elastic body 31 and the compression amount of the second elastic body 54 both increase, so that the connection stiffness Ru becomes a second connection stiffness Ru2 that is greater than the first connection stiffness Ru1, and the holding stiffness Rd becomes a second holding stiffness Rd2 that is greater than the first holding stiffness Rd1. That is, when the speed of the ceiling transport vehicle 1 becomes equal to or less than the second threshold, the control device 9 changes the pressing force F to the second pressing force F2, thereby transitioning the ceiling transport vehicle 1 from the vibration suppression state to the sway suppression state (step S108). The second connection stiffness Ru2 and the second holding stiffness Rd2 are adjusted, for example, so that the sway of the container 100 is within an allowable range.

[0079] When the ceiling transport vehicle 1 stops at the transport position (step S109), the lateral delivery mechanism 8 moves the lifting platform 20 sideways (step S110). Here, the pressing force F is maintained at the second pressing force F2 even when the ceiling transport vehicle 1 stops at the transport position. Therefore, the lateral delivery mechanism 8 moves the lifting platform 20 sideways while the connection stiffness Ru is maintained at the second connection stiffness Ru2 and the holding stiffness Rd is maintained at the second holding stiffness Rd2. In other words, the lateral delivery mechanism 8 moves the lifting platform 20 sideways when the ceiling transport vehicle 1 is in the vibration suppression state. This effectively suppresses vibration of the container 100 during lateral delivery.

[0080] The ceiling transport vehicle 1 does not have to transition to the vibration suppression state in step S105 of Fig. 8. For example, in step S106, the control device 9 may transition the ceiling transport vehicle 1 to the vibration suppression state by changing the pressing force F to the first pressing force F1 when the speed of the ceiling transport vehicle 1 becomes equal to or greater than the first threshold. In this case, the control device 9 may control the ceiling transport vehicle 1 to the vibration suppression state when the lifting unit 6 is raised to store the container 100 in the storage space AS in step S105. Then, the ceiling transport vehicle 1 may start traveling while remaining in the vibration suppression state in step S106, and transition the ceiling transport vehicle 1 from the vibration suppression state to the vibration suppression state by changing the pressing force F to the first pressing force F1 when the speed of the ceiling transport vehicle 1 becomes equal to or greater than the first threshold.

[0081] Furthermore, the variable stiffness mechanism 40 in the above-described embodiment includes the first variable stiffness mechanism 22 and the second variable stiffness mechanism 23, but is not limited to this. The variable stiffness mechanism 40 may include, for example, either the first variable stiffness mechanism 22 or the second variable stiffness mechanism 23. Fig. 9 is a diagram showing a first modified example of the variable stiffness mechanism 40. The variable stiffness mechanism 40 of the first modified example shown in Fig. 9 is the first variable stiffness mechanism 22.

[0082] In the first modified example, the rigidity between the main body 4 and the holding part 21 is the connection rigidity Ru. In the ceiling transport vehicle 1 of the first modified example, when the holding part 21 is holding a container 100, the connection rigidity Ru, which is the rigidity between the lifting drive part 11 and the lifting platform 20, is changed depending on the running state of the ceiling transport vehicle 1, including when it is stopped. In the vibration suppression state of the first modified example, the connection rigidity Ru is the first connection rigidity Ru1. In the sway suppression state of the first modified example, the connection rigidity Ru is the second connection rigidity Ru2. Even in the first modified example, it is possible to effectively suppress both the vibration of the container 100 during running and the sway of the container 100 during transfer operations.

[0083] Fig. 10 is a diagram showing a second modified example of the variable stiffness mechanism 40. The variable stiffness mechanism 40 of the second modified example shown in Fig. 10 is the second variable stiffness mechanism 23. Note that the second variable stiffness mechanism 23 of the second modified example further includes a receiving member 30, as an example.

[0084] In the second modified example, the rigidity between the main body 4 and the holding part 21 is the holding rigidity Rd. In the ceiling transport vehicle 1 of the second modified example, when the holding part 21 is holding the container 100, the holding rigidity Rd, which is the rigidity between the lifting platform 20 and the container 100, is changed depending on the running state of the ceiling transport vehicle 1, including when it is stopped. In the vibration suppression state of the second modified example, the holding rigidity Rd is the first holding rigidity Rd1. In the shaking suppression state of the second modified example, the holding rigidity Rd is the second holding rigidity Rd2. Even in the second modified example, it is possible to effectively suppress both the vibration of the container 100 during running and the shaking of the container 100 during transfer operations.

[0085] In this way, in the ceiling transport vehicle 1 of this embodiment, when the holding unit 21 is holding the container 100, either or both of the connection stiffness Ru and the holding stiffness Rd are changed depending on the traveling state, including the stopping state, of the ceiling transport vehicle 1. With this configuration, both vibration and shaking can be effectively suppressed.

[0086] The first variable stiffness mechanism 22 and the second variable stiffness mechanism 23 may be independently controllable. For example, a first motor for operating the first variable stiffness mechanism 22 and a second motor for operating the second variable stiffness mechanism 23 may be provided, and the control device 9 may operate the first motor to change the coupling stiffness Ru and control the second motor to change the holding stiffness Rd.

[0087] The above-described embodiments disclose the following configurations: <Configuration 1> An overhead transport vehicle 1 that travels along an overhead track R while holding an article (container 100), comprising: a travel unit 2 that travels along the overhead track R; a main body unit 4 that moves along the ceiling track R together with the travel unit 2; a lifting platform 20 that is suspended from the main body unit 4 and is capable of raising and lowering relative to the main body unit 4; a holding unit 21 that is fixed to the bottom of the lifting platform 20 and holds the article (container 100); and a variable stiffness mechanism 40 that is switchable between a first stiffness state (vibration suppression state) in which the stiffness between the main body unit 4 and the holding unit 21 is a first stiffness, and a second stiffness state in which the stiffness is a second stiffness higher than the first stiffness, wherein the variable stiffness mechanism 40 switches between the first stiffness state (vibration suppression state) and the second stiffness state (swing suppression state) depending on the traveling state of the overhead transport vehicle 1. <Configuration 2> The ceiling transport vehicle 1 according to Configuration 1, wherein the variable stiffness mechanism 40 switches to a first stiffness state (vibration suppression state) when the speed of the ceiling transport vehicle 1 is a first speed or higher, and switches to a second stiffness state (sway suppression state) when the speed of the ceiling transport vehicle 1 is a second speed or lower that is slower than the first speed, or when the ceiling transport vehicle is stopped. <Configuration 3> The ceiling transport vehicle 1 according to Configuration 1 or 2, wherein the stiffness is one or both of a connection stiffness Ru that is the stiffness between the main body 4 and the lifting platform 20, and a holding stiffness Rd that is the stiffness between the lifting platform 20 and the article (container 100) when the holding part 21 is holding the article (container 100). <Configuration 4> A ceiling transport vehicle 1 of any of configurations 1 to 3, wherein the variable stiffness mechanism 40 comprises an elastic body (first elastic body 31) provided between the main body 4 and the upper part of the lifting platform 20, the main body 4 comprises a lifting drive unit 11 that can adjust the amount of compression of the elastic body by adjusting the position of the lifting platform 20, and the lifting drive unit 11 changes the coupling stiffness Ru by changing the amount of compression of the elastic body.<Configuration 5> The variable stiffness mechanism 40 comprises: a support section 51 provided at the bottom of the lifting platform 20 and moving up and down in response to the lifting and lowering operation of the lifting platform 20; a pressing section 52 provided at the bottom of the support section and pressing downward the item (container 100) held by the holding section 21; and an elastic body (second elastic body 54) provided between the support section and the pressing section; and the main body section 4 comprises a lifting and lowering drive section 11 that adjusts the compression amount of the elastic body by adjusting the position of the lifting platform 20, and the lifting and lowering drive section 11 changes the holding stiffness Rd by changing the compression amount of the elastic body, an overhead transport vehicle 1 of any of configurations 1 to 3. <Configuration 6> The variable stiffness mechanism 40 comprises: a receiving member 30 provided on the upper part of the lifting platform 20; a first elastic body 31 provided between the receiving member 30 and the upper part of the lifting platform 20; a support section 51 provided on the lower part of the lifting platform 20; a connecting member 53 connecting the receiving member and the support section; a pressing section 52 provided on the lower part of the support section and pressing downward the article (container 100) held by the holding section 21; and a second elastic body 54 provided between the support section and the pressing section; and the main body section 4 comprises an elevation drive section 11 that adjusts the compression amounts of the first elastic body 31 and the second elastic body 54 by adjusting the position of the lifting platform 20 with the receiving member in contact with the main body section 4; and the coupling stiffness Ru and the holding stiffness Rd become higher as the compression amounts of the first elastic body 31 and the second elastic body 54 become larger, The ceiling transport vehicle 1 of any of configurations 1 to 3, wherein in the first rigidity state (vibration suppression state), the compression amounts of the first elastic body 31 and the second elastic body 54 are controlled to a first compression amount, and in the second rigidity state, the compression amounts of the first elastic body 31 and the second elastic body 54 are controlled to a second compression amount that is larger than the first compression amount. <Configuration 7> The ceiling transport vehicle 1 of any of configurations 1 to 6, wherein the main body 4 is provided with a lateral movement mechanism 8 that moves the lifting platform 20 laterally in the traveling direction, and the lateral movement mechanism 8 moves the lifting platform 20 laterally when in the second rigidity state.

[0088] One or more of the requirements described in the above-described embodiments may be omitted. Furthermore, the requirements described in the above-described embodiments may be combined as appropriate. Furthermore, the execution order of each procedure shown in this embodiment can be realized in any order as long as the results of a previous procedure are not used in a subsequent procedure. Furthermore, even if the operations in the above-described embodiments are described using terms such as "first," "next," and "subsequently" for convenience, it is not necessary to perform the operations in this order. Furthermore, to the extent permitted by law, the disclosures of Japanese Patent Application No. 2023-093147 and all documents cited in the above-described embodiments are incorporated herein by reference.

[0089] DESCRIPTION OF SYMBOLS 1 Ceiling transport vehicle 4 Main body 6 Lifting unit 11 Lifting drive unit 20 Lifting platform 21 Holding unit 22 First variable stiffness mechanism 23 Second variable stiffness mechanism

Claims

1. A ceiling transport vehicle that runs along a ceiling track while holding an item, comprising: a running section that runs along the ceiling track; a main body section that moves along the ceiling track together with the running section; a lifting body that is suspended from the main body section and can be raised and lowered relative to the main body section; a holding section that is fixed to the lower part of the lifting body and holds the item; and a variable stiffness mechanism that can switch between a first stiffness state in which the stiffness between the main body section and the holding section is a first stiffness, and a second stiffness state in which the stiffness is a second stiffness higher than the first stiffness, wherein the variable stiffness mechanism switches between the first stiffness state and the second stiffness state depending on the running state of the ceiling transport vehicle.

2. The ceiling transport vehicle described in claim 1, wherein the variable stiffness mechanism switches to the first stiffness state when the speed of the ceiling transport vehicle is a first speed or higher, and switches to the second stiffness state when the speed of the ceiling transport vehicle is a second speed or lower that is slower than the first speed or when the ceiling transport vehicle is stopped.

3. The ceiling transport vehicle according to claim 1 or 2, wherein the rigidity is either or both of a connection rigidity, which is the rigidity between the main body and the lifting body when the holding part is holding the item, and a holding rigidity, which is the rigidity between the lifting body and the item.

4. A ceiling transport vehicle as described in claim 3, wherein the variable stiffness mechanism includes an elastic body provided between the main body and an upper part of the lifting body, the main body includes a lifting drive unit capable of adjusting the amount of compression of the elastic body by adjusting the position of the lifting body, and the lifting drive unit changes the connecting stiffness by changing the amount of compression of the elastic body.

5. The variable stiffness mechanism comprises: a support section provided at the bottom of the lifting body and moving in an up and down direction in response to the lifting and lowering movement of the lifting body; a pressing section provided at the bottom of the support section and pressing downwardly against the item held by the holding section; and an elastic body provided between the support section and the pressing section; and the main body section comprises a lifting and lowering drive section which adjusts the amount of compression of the elastic body by adjusting the position of the lifting body, and the lifting and lowering drive section changes the holding stiffness by changing the amount of compression of the elastic body.A ceiling transport vehicle as described in claim 3.

6. The ceiling transport vehicle according to claim 3, wherein the variable stiffness mechanism comprises: a receiving member provided on an upper part of the lifting body; a first elastic body provided between the receiving member and the upper part of the lifting body; a support part provided on a lower part of the lifting body; a connecting member connecting the receiving member and the support part; a pressing part provided on the lower part of the support part and pressing downwardly the item held by the holding part; and a second elastic body provided between the support part and the pressing part; and the main body part comprises an elevation drive part that adjusts the compression amount of the first elastic body and the second elastic body by adjusting the position of the lifting body with the receiving member in contact with the main body part, and the larger the compression amount of the first elastic body and the second elastic body, the higher the connection stiffness and the holding stiffness become, and in the first stiffness state, the compression amount of the first elastic body and the second elastic body is controlled to a first compression amount, and in the second stiffness state, the compression amount of the first elastic body and the second elastic body is controlled to a second compression amount larger than the first compression amount.

7. The ceiling transport vehicle according to claim 1, wherein the main body is provided with a lateral movement mechanism that moves the lifting body laterally in the direction of travel, and the lateral movement mechanism moves the lifting body laterally when in the second rigidity state.