trolley

Abstract

To achieve both improved turning performance and improved load transferability. [Solution] The bogie body 2 of the bogie 1 is configured to be roughly U-shaped in a plan view, and a four-wheel steering mechanism 20 that steers the front casters 6a, 6b and rear casters 8a, 8b located at the four corners of the bogie body 2 in response to the rotation of a connecting bar 4 for connecting to an automated guided vehicle 80 serving as a towing vehicle is positioned so as not to enter at least the inner region of the bogie body 2. As a result, when transferring a load L between the automated guided vehicle 82 and the bogie 1, the automated guided vehicle 82 can enter the inner region of the bogie body 2, making the transfer of the load L easy and reliable. Furthermore, the inclusion of the four-wheel steering mechanism 20 improves turning ability when being towed by the automated guided vehicle 80.

Description

[Technical Field]

[0001] The present invention relates to a bogie to be towed by a towing vehicle. [Background technology]

[0002] Japanese Patent Publication No. 2014-83941 (Patent Document 1) describes a bogie that is towed by a self-propelled towing vehicle and that includes a bogie body that is approximately rectangular in plan view and can be used to place cargo, a pair of left and right front wheels and a pair of left and right rear wheels located at the four corners of the bogie body, and a four-wheel steering mechanism that can steer the pair of left and right front wheels and the pair of left and right rear wheels. Here, the four-wheel steering mechanism comprises: a front wheel support member that has a longitudinal direction and is arranged on the bogie body so as to be rotatable around a central position in the longitudinal direction as a center of rotation, and that supports a pair of left and right front wheels at both longitudinal ends; a rear wheel support member that has a longitudinal direction and is arranged on the bogie body so as to be rotatable around a central position in the longitudinal direction as a center of rotation, and that supports a pair of left and right rear wheels at both longitudinal ends; a link member that has one end rotatably connected to the front wheel support member at a position to the right of the center of rotation of the front wheel support member, and has the other end rotatably connected to the rear wheel support member at a position to the left of the center of rotation of the rear wheel support member; and a connecting member that is connected to the front wheel support member so as to transmit the tractive force of the towing vehicle to the front wheel support member.

[0003] The bogie described in the above publication can steer the four steering wheels in conjunction with the turning of the towing vehicle, thereby improving turning ability and enabling smooth turning. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-83941 Summary of the Invention [Problem to be solved by the invention]

[0005] To facilitate the transfer of a load from a self-propelled guided vehicle (e.g., an automated guided vehicle) loaded with a load to the bogie body, or from the bogie body to the self-propelled guided vehicle, a bogie body having a U-shape in plan view is sometimes employed to allow the self-propelled guided vehicle to enter the inside of the bogie body. Even with a bogie having a U-shape in plan view, there is a demand for improved maneuverability and smoother turning, as with conventional bogies having a generally rectangular bogie body in plan view. However, if the four-wheel steering mechanism described in the above publication is directly adopted in a bogie having a U-shaped bogie body in plan view, part of the four-wheel steering mechanism, particularly the link member, would be located in the inner region of the U, reducing the ease of transferring the load.

[0006] The present invention has been made in consideration of the above, and aims to provide a technology that contributes to achieving both improved maneuverability and improved ease of transferring cargo in a bogie having a bogie body that is U-shaped in a plan view. [Means for solving the problem]

[0007] The bogie of the present invention employs the following means to achieve the above-mentioned object.

[0008] A bogie according to a first aspect of the present invention is configured to be towed by a towing vehicle. The bogie includes a bogie body, first and second front steering wheels, first and second rear steering wheels, a coupling section, and a four-wheel steering mechanism. The bogie body has an upper surface on which a load can be loaded. The bogie body has a generally U-shape in plan view, having a first portion, a second portion, and a third portion. The first portion has a longitudinal direction. The second portion extends generally parallel to the first portion at a position separated by a predetermined distance from the first portion in a direction intersecting the extension direction of the first portion. The third portion extends in a direction intersecting the extension direction of the first and second portions and connects the first and second portions. The first and second front steering wheels have first and second front pivot axes extending in a direction perpendicular to the upper surface. The first and second front steerable wheels are supported by the bogie body so as to be rotatable about first and second front pivot axes. The first and second rear steerable wheels have first and second rear pivot axes extending in a direction perpendicular to the top surface. The first and second rear steerable wheels are supported by the bogie body so as to be rotatable about the first and second rear pivot axes. The coupling unit has a first pivot axis perpendicular to the top surface of the bogie body. The first pivot axis passes through a center position between the first and second front steerable wheels. The coupling unit is supported by the bogie body so as to be rotatable about the first pivot axis along an imaginary plane parallel to the top surface of the bogie body. The coupling unit is connectable to a towing vehicle. The four-wheel steering mechanism is mechanically connected to the first and second front steering wheels, the first and second rear steering wheels, and the coupling portion so as to be able to steer the first and second front steering wheels and the first and second rear steering wheels. The four-wheel steering mechanism is positioned so as not to intrude into at least the inner region surrounded by the first, second, and third portions. Here, "rotation" in the present invention is typically defined as an angular change about an axis, and preferably includes swinging (reciprocating rotation within a certain angle range) and full rotation (rotation) about the axis.

[0009] According to the first aspect of the present invention, the dolly has a dolly body that is generally U-shaped in plan view, allowing a self-propelled guided vehicle (SPG) for transferring a load to the dolly body to enter the inner region of the U-shape, i.e., the inner region surrounded by the first, second, and third portions. This allows for easy and reliable transfer of a load between the SPG and the dolly. Furthermore, the dolly has a four-wheel steering mechanism, which improves maneuverability when towed by a towing vehicle. Furthermore, the four-wheel steering mechanism is positioned so as not to enter at least the inner region surrounded by the first, second, and third portions, and therefore does not impede the entry of the SPG during the transfer of a load between the dolly and the dolly.

[0010] A bogie according to a second aspect of the present invention is the bogie according to the first aspect of the present invention, wherein the four-wheel steering mechanism includes a front steering link arm, a rear steering link arm, and a transmission mechanism. The front steering link arm is pivotally connected to the coupling portion and each of the first and second front steering wheels to turn the first and second front steering wheels based on pivotal movement of the coupling portion. The rear steering link arm is pivotally connected to each of the first and second rear steering wheels to turn the first and second rear steering wheels. The transmission mechanism mechanically connects the coupling portion and the rear steering link arm to turn the first and second rear steering wheels in a direction opposite to the turning direction of the first and second front steering wheels based on pivotal movement of the coupling portion. The front steering link arm, rear steering link arm, and transmission mechanism are arranged so as not to intrude into at least the inner region.

[0011] According to the second aspect of the present invention, a four-wheel steering mechanism can be easily realized.

[0012] A bogie according to a third aspect of the present invention is the bogie according to the second aspect of the present invention, wherein the first front steering wheel is disposed at one end of the first section in the direction of extension. The second front steering wheel is disposed in an intersection region between the first section and the third section. The first rear steering wheel is disposed at one end of the second section in the direction of extension. The second rear steering wheel is disposed in an intersection region between the second section and the third section. The coupling portion is supported on the first section so as to be rotatable about a first rotation axis. The front steering link arm is disposed so as to extend along the first section. The rear steering link arm is disposed so as to extend along the second section. The transmission mechanism has a first link arm and a connecting link arm. The first link arm has an elongated shape having a first end and a second end and is disposed so as to extend along the first section. Furthermore, the first end of the first link arm is rotatably connected to the coupling portion so as to move along the first section based on the rotational movement of the coupling portion. The connecting link arm has an elongated shape with a third end and a fourth end and is positioned to extend along the third portion. The third end of the connecting link arm is pivotally connected directly or indirectly to the second end, and the fourth end is pivotally connected directly or indirectly to the rear steering link arm. The connecting link arm converts movement of the first link arm along the first portion into movement along the third portion and converts movement along the third portion into movement of the rear steering link arm along the second portion.

[0013] According to the third invention, the first link arm, which is linked to the operation of the connecting part, is arranged to extend along the first part, and the connecting link arm, which can convert and transmit the movement of the first link arm along the first part into movement along the second part of the rear steering arm, is simply arranged to extend along the third part.This makes it possible to easily realize a configuration in which the four-wheel steering mechanism does not intrude into at least the inner area surrounded by the first, second, and third parts.

[0014] A bogie according to a fourth aspect of the present invention is the bogie according to the third aspect of the present invention, wherein the transmission mechanism further includes a second link arm, a pivoting portion, and first and second pivoting levers. The second link arm has an elongated shape with a fifth end and a sixth end, and is disposed so as to extend along the second portion. The fifth end of the second link arm is pivotally connected to the pivoting portion. The pivoting portion has a second pivot axis perpendicular to the upper surface of the bogie body. The second pivot axis passes through a center position between the first and second rear steering wheels. The pivoting portion is supported by the second portion so as to be pivotable about the second pivot axis along an imaginary plane parallel to the upper surface of the bogie body. The first pivoting lever has a first connection portion pivotally connected to the second end, a second connection portion pivotally connected to the third end, and a third pivot axis. The first pivoting lever is supported by the third portion so as to be pivotable about the third pivot axis. The first rotating lever converts the movement of the first link arm along the first portion into the movement of the connecting link arm along the third portion. The first connecting portion, the second connecting portion, and the third rotating axis are arranged in a positional relationship where a first imaginary line connecting the first connecting portion and the third rotating axis intersects with a second imaginary line connecting the second connecting portion and the third rotating axis. The second rotating lever has a third connecting portion rotatably connected to the fourth end, a fourth connecting portion rotatably connected to the sixth end, and a fourth rotating axis. The second rotating lever is supported on the third portion so as to be rotatable about the fourth rotating axis. The second rotating lever converts the movement of the connecting link arm along the third portion into the movement of the second link arm along the second portion. The third connection portion, the fourth connection portion, and the fourth rotation axis are disposed in a positional relationship where a third imaginary line connecting the third connection portion and the fourth rotation axis intersects with a fourth imaginary line connecting the fourth connection portion and the fourth rotation axis. The rear steering link arm is rotatably connected to the rotation portion.

[0015] According to the fourth aspect of the present invention, the first link arm and the connecting link arm are connected via the first rotating lever, and the connecting link arm and the rear steering arm are connected via the second rotating lever, the second link arm, and the rotating part, which increases the degree of freedom in arranging the transmission mechanism. This makes it possible to easily layout the transmission mechanism even in a limited space, and reliably realizes a configuration in which the four-wheel steering mechanism does not intrude into at least the inner area surrounded by the first, second, and third parts.

[0016] A bogie according to a fifth aspect of the present invention is the bogie according to the third aspect of the present invention, wherein the transmission mechanism further includes a second link arm and a pivoting unit. The second link arm has an elongated shape having a fifth end and a sixth end, and is disposed so as to extend along the second portion. The fifth end of the second link arm is pivotally connected to the pivoting unit. The pivoting unit has a second pivot axis perpendicular to the upper surface of the bogie body. The second pivot axis passes through a center position between the first and second rear steering wheels. The pivoting unit is supported by the second portion so as to be pivotable about the second pivot axis along an imaginary plane parallel to the upper surface of the bogie body. The connecting link arm has a fifth pivot axis disposed between the third and fourth ends. The connecting link arm has a third end pivotally connected to the second end and a fourth end pivotally connected to the sixth end, and is supported by the third portion so as to be pivotable about the fifth pivot axis. The connecting link arm converts movement of the first link arm along the first portion into movement of the second link arm along the second portion. The rear steering link arm is pivotally connected to the pivot portion.

[0017] According to the fifth aspect of the present invention, the connecting link arm is supported on the third part so as to be rotatable around the fifth rotation axis, the first and second link arms are directly connected to the connecting link arm, and the second link arm and the rear steering arm are connected via a rotating part, thereby preventing an increase in the number of parts constituting the transmission mechanism.

[0018] A sixth aspect of the present invention is the bogie of the third aspect, wherein the transmission mechanism further includes first and second pivot levers. The first pivot lever has a first connection portion pivotally connected to the second end, a second connection portion pivotally connected to the third end, and a third pivot axis. The first pivot lever is supported by the third portion so as to be pivotable about the third pivot axis. The first pivot lever converts movement of the first link arm along the first portion into movement of the connecting link arm along the third portion. The first connection portion, the second connection portion, and the third pivot axis are arranged in a positional relationship such that a first imaginary line connecting the first connection portion and the third pivot axis intersects with a second imaginary line connecting the second connection portion and the third pivot axis. The second pivot lever has a fifth connection portion pivotally connected to the fourth end, a sixth connection portion pivotally connected to the rear steering link arm, and a sixth pivot axis. The second pivot lever is engaged with the second rear steering wheel so as to be pivotable about the sixth pivot axis. The second pivot lever converts movement of the connection link arm along the third portion into movement of the rear steering link arm along the second portion. The fifth connection portion, the sixth connection portion, and the sixth pivot axis are positioned such that a fifth imaginary line connecting the fifth connection portion and the sixth pivot axis intersects with a sixth imaginary line connecting the sixth connection portion and the sixth pivot axis. The sixth pivot axis is coaxial with the second rear pivot axis. Here, the mode of "engaging with the second rear steering wheel" in the present invention preferably includes a mode in which the second pivot lever is directly engaged with the second rear steering wheel, as well as a mode in which the second pivot lever is indirectly engaged with the second rear steering wheel.

[0019] According to the sixth aspect of the present invention, the movement along the first part of the first link arm is converted into movement along the third part of the connecting link arm via the first pivoting lever, and the movement along the third part of the connecting link arm causes the second pivoting lever to rotate the second rear steering wheel, and the rotation of the second rear steering wheel causes the rear steering arm to rotate the first rear steering wheel.This allows the transmission mechanism to be configured simply, while reliably achieving coordinated rotation of the first and second rear steering wheels.

[0020] The bogie of the seventh invention is a bogie of any one of the second to sixth inventions, wherein the front steering link arm is connected to the first and second front steering wheels so as to rotate the first and second front steering wheels in the same direction as the rotation direction of the connecting part.

[0021] According to the seventh aspect of the present invention, the turning direction of the first and second front steered wheels can be made to correspond to the rotation direction of the connecting portion.

[0022] A bogie according to an eighth aspect of the present invention is the bogie according to the seventh aspect of the present invention, wherein the front steering link arm is connected to the coupling portion on the opposite side of the first pivot axis from the side where the second section is disposed, and the front steering link arm is connected to the first and second front steering wheels on the opposite side of the first and second pivot axes from the side where the second section is disposed.

[0023] According to the eighth aspect of the present invention, it is possible to easily realize a configuration in which the turning direction of the first and second front steered wheels corresponds to the rotation direction of the connecting portion.

[0024] A bogie according to a ninth aspect of the present invention is the bogie according to any one of the second to eighth aspects of the present invention, wherein the first and second front steering wheels and the front steering link are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism, and the first and second rear steering wheels and the rear steering link are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism.

[0025] According to the ninth aspect of the present invention, when the bogie turns, it is possible to ensure an appropriate difference in rotation angle between the inner steered wheel and the outer steered wheel, thereby stabilizing the turning behavior of the bogie. [Effects of the Invention]

[0026] According to the present invention, in a truck having a truck body that is U-shaped in plan view, it is possible to achieve both improved turning performance and improved ease of transferring loads. [Brief explanation of the drawings]

[0027] [Figure 1] 1A and 1B are two-sided views showing a state in which the carriage 1 of the first embodiment is towed by an automatic guided vehicle 80. FIG. [Figure 2] 1A and 1B are three-view diagrams showing the outline of the configuration of a carriage 1 of a first embodiment. [Figure 3] FIG. 2 is a bottom view of the carriage 1 of the first embodiment as seen from the back side. [Figure 4] 4 is a view seen from the direction of arrow W in FIG. 3. [Figure 5] FIG. 2 is a perspective view showing the outline of the configuration of a four-wheel steering mechanism 20. [Figure 6] 1 is a perspective view showing a state immediately before an automated guided vehicle 82 loaded with a load L enters inside the carriage 1 of the first embodiment. [Figure 7] 10 is a plan view showing a state immediately before an automated guided vehicle 82 loaded with a load L enters inside the carriage 1 of the first embodiment. [Figure 8] 10 is a perspective view showing a state in which an automated guided vehicle 82 loaded with a load L has completed entering inside the carriage 1 of the first embodiment. FIG. [Figure 9] 10 is a plan view showing a state in which an automated guided vehicle 82 loaded with a load L has completed entering inside the carriage 1 of the first embodiment. [Figure 10] 10 is a perspective view showing a state in which the automatic guided vehicle 82 has completed transferring the load L onto the carriage 1 of the first embodiment. FIG. [Figure 11] 10 is a plan view showing a state in which the automatic guided vehicle 82 has completed transferring the load L onto the carriage 1 of the first embodiment. FIG. [Figure 12] FIG. 10 is a bottom view of a modified example of a carriage 1A as seen from the rear side. [Figure 13] FIG. 10 is a bottom view of a modified example of a carriage 1B seen from the rear side. [Figure 14] FIG. 10 is a bottom view of a modified example of a carriage 1C seen from the rear side. [Figure 15] FIG. 10 is a bottom view of a modified example of a carriage 1D seen from the rear side. [Figure 16] FIG. 10 is a bottom view of a modified carriage 1E seen from the rear side. [Figure 17] FIG. 10 is a bottom view of the modified bogie 1F seen from the back side. [Figure 18] FIG. 10 is a bottom view of the carriage 100 of the second embodiment as seen from the back side. [Figure 19] FIG. 10 is a bottom view of a modified carriage 100A as seen from the rear side. [Figure 20] FIG. 10 is a bottom view of a modified carriage 100B seen from the rear side. [Figure 21] FIG. 10 is a bottom view of a modified carriage 100C seen from the rear side. [Figure 22] FIG. 10 is a bottom view of a modified carriage 100D seen from the rear side. [Figure 23] FIG. 11 is a bottom view of the carriage 200 of the third embodiment as seen from the back side. [Figure 24] FIG. 10 is a perspective view showing the outline of the configuration of a four-wheel steering mechanism 20 in a bogie 200 according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0028] Next, the best mode for carrying out the present invention will be described using examples. [Example]

[0029] As shown in Fig. 1, the dolly 1 according to the first embodiment is configured as a towed vehicle that travels while being towed by an automatic guided vehicle 80, and is also configured to be able to transfer a load L between the dolly 1 and another automatic guided vehicle 82, as shown in Figs. 5 to 10. As shown in Figs. 1 and 2, the dolly 1 includes a dolly body 2 that is substantially U-shaped in a plan view, a connecting bar 4 that is rotatably supported on the dolly body 2, a pair of front casters 6a, 6b and a pair of rear casters 8a, 8b that are rotatably supported on the dolly body 2, and a four-wheel steering mechanism 20 that is mechanically connected to the pair of front casters 6a, 6b and the pair of rear casters 8a, 8b. For ease of explanation, the front side in the towing direction of the carriage 1 when the automated guided vehicle 80 travels forward in a straight line will be defined as the "front side," "forward," or "forward direction" of the carriage body 2, the rear side will be defined as the "rear side," "rear," or "rear direction," and the left and right directions in the towing direction of the carriage 1 when the automated guided vehicle 80 travels forward in a straight line will be defined as the "left and right direction" or "vehicle width direction" of the carriage body 2. The automated guided vehicle 80 is an example of an embodiment corresponding to the "towing vehicle" of the present invention.

[0030] As shown in FIG. 2 , the bogie body 2 is composed of a front portion 10, a rear portion 12, and a connecting portion 14, and has an upper surface 2a on which a load L can be placed. The front portion 10 extends in the vehicle width direction. The rear portion 12 extends in the vehicle width direction at a position a predetermined distance away from the front portion. The connecting portion 14 extends in a direction perpendicular to the front portion 10 and the rear portion 12, and connects the front portion 10 and the rear portion 12. The front portion 10, the rear portion 12, and the connecting portion 14 are examples of an embodiment corresponding to the "first portion," "second portion," and "third portion" of the present invention, respectively.

[0031] As shown in FIG. 3 , the connecting bar 4 has a rotation axis Pa1 and is supported by the front section 10 so as to be rotatable (swingable) in the left-right direction about the rotation axis Pa1 along an imaginary plane parallel to the top surface 2a (a plane parallel to the plane of FIG. 3 ). The rotation axis Pa1 is located at the center of the extension direction of the front section 10. In other words, the connecting bar 4 can be said to be located at the center of the extension direction of the front section 10 so as to be rotatable (swingable) in the left-right direction. The connecting bar 4 also has an elongated hole 4a. The elongated hole 4a is located forward of the rotation axis Pa1 and extends in the longitudinal direction of the connecting bar 4. The connecting bar 4 is an example of a configuration that corresponds to a "connecting portion" in the present invention. The rotation axis Pa1 is also an example of a configuration that corresponds to a "first rotation axis" in the present invention.

[0032] As shown in Figures 2 and 3, the pair of front casters 6a, 6b are arranged on the front section 10. More specifically, the front caster 6a has a pivot axis Sa1 and is supported on the right end of the front section 10 so as to be rotatable around the pivot axis Sa1. The front caster 6b has a pivot axis Sa2 and is supported on the left end of the front section 10 (the intersection region of the front section 10 and the connecting section 14) so ​​as to be rotatable around the pivot axis Sa2. The front casters 6a, 6b are examples of an embodiment corresponding to the "first front steering wheel" and the "second front steering wheel" of the present invention, respectively.

[0033] As shown in Figures 2 and 3, the pair of rear casters 8a, 8b are disposed on the rear section 12. More specifically, the rear caster 8a has a pivot axis Sa3 and is supported on the right end of the rear section 12 so as to be rotatable about the pivot axis Sa3. The rear caster 8b has a pivot axis Sa4 and is supported on the left end of the rear section 12 (the intersection region of the rear section 12 and the connecting section 14) so ​​as to be rotatable about the pivot axis Sa4. The rear casters 8a, 8b are examples of an embodiment corresponding to the "first rear steering wheel" and the "second rear steering wheel" of the present invention, respectively.

[0034] 3 to 5, the four-wheel steering mechanism 20 is composed of a front steering link arm 22, a rear steering link arm 24, a first link arm 26, a first rotating lever 28, a connecting link arm 30, a second rotating lever 32, a second link arm 34, and a rotating bar 36. As shown in FIG. 4, the four-wheel steering mechanism 20 is disposed between the bogie body 2 and the pair of front casters 6a, 6b and the pair of rear casters 8a, 8b. The first link arm 26, the first rotating lever 28, the connecting link arm 30, the second rotating lever 32, the second link arm 34, and the rotating bar 36 correspond to the "transmission mechanism" in the present invention, and the rotating bar 36 is an example of a configuration that corresponds to the "rotating unit" in the present invention.

[0035] As shown in Figures 3 and 5, the front steering link arm 22 has an elongated shape and is disposed so as to extend along the front section 10. The front steering link arm 22 has a connection pin 22a approximately in the center in the longitudinal direction, and swivel brackets 40, 42 are rotatably connected to both longitudinal ends of the front steering link arm 22. The connection pin 22a is disposed in the center position in the longitudinal direction of the front steering link arm 22 and protrudes perpendicularly from the front steering link arm 22. The swivel brackets 40, 42 have a U-shape in plan view, having a pair of arms and a bottom portion connecting the pair of arms, and are rotatably connected to both longitudinal ends of the front steering link arm 22. More specifically, the swivel brackets 40, 42 are arranged overlapping the front steering link arm 22 so that the extending direction of their bottoms aligns with the extending direction of the front steering link arm 22. Of the intersection angles where the pair of arms and the bottoms intersect, the intersection angle located on the outer side in the vehicle width direction (the right side for the swivel bracket 40 and the left side for the swivel bracket 42) is rotatably connected to the front steering link arm 22. The front steering link arm 22 configured in this manner has the connecting pin 22a engaged with the elongated hole 4a of the connecting bar 4 and is engaged with the front casters 6a, 6b via the swivel brackets 40, 42. At this time, the rotation axes Sa1, Sa2 of the front casters 6a, 6b are arranged in the inner region of the U-shape of the swivel brackets 40, 42. That is, the connection portion 40a between the front steering link arm 22 and the swivel bracket 40 is disposed on the outer side (right side) in the vehicle width direction with respect to the pivot axis Sa1, and the connection portion 42a between the front steering link arm 22 and the swivel bracket 42 is disposed on the outer side (left side) in the vehicle width direction with respect to the pivot axis Sa2. In other words, it can be said that the front steering link arm 22 and the pair of front casters 6a, 6b are connected in an arrangement that satisfies the geometric conditions of the Ackermann mechanism.

[0036] As shown in Figures 3 and 5, the rear steering link arm 24 has an elongated shape and is disposed so as to extend along the rear section 12. The rear steering link arm 24 has a connection pin 24a approximately in the center in the longitudinal direction, and swivel brackets 44, 46 are rotatably connected to both ends in the longitudinal direction. The connection pin 24a is disposed in the center position in the longitudinal direction of the rear steering link arm 24 and protrudes perpendicularly from the rear steering link arm 24. The swivel brackets 44, 46 have a U-shape in plan view, having a pair of arms and a bottom portion connecting the pair of arms, and are rotatably connected to both ends in the longitudinal direction of the rear steering link arm 24. More specifically, the swivel brackets 44, 46 are positioned overlapping the rear steering link arm 24 so that the extending direction of their bottoms aligns with the extending direction of the rear steering link arm 24. Of the intersection angles where the pair of arms and the bottoms intersect, the intersection angle positioned on the inner side in the vehicle width direction (the left side in the swivel bracket 44 and the right side in the swivel bracket 46) is rotatably connected to the rear steering link arm 24. In the rear steering link arm 24 configured in this manner, the connecting pin 24a is engaged with the elongated hole 36a (described later) of the pivot bar 36, and is also engaged with the rear casters 8a, 8b via the swivel brackets 44, 46. At this time, the pivot axes Sa3, Sa4 of the rear casters 8a, 8b are positioned in the inner region of the U-shape of the swivel brackets 44, 46. That is, the connection portion 44a between the rear steering link arm 24 and the swivel bracket 44 is disposed on the inner side (left side) in the vehicle width direction with respect to the pivot axis Sa3, and the connection portion 46a between the rear steering link arm 24 and the swivel bracket 46 is disposed on the inner side (right side) in the vehicle width direction with respect to the pivot axis Sa4. In other words, it can be said that the rear steering link arm 24 and the pair of rear casters 8a, 8b are connected in an arrangement that satisfies the geometric conditions of the Ackermann mechanism.

[0037] As shown in FIGS. 3 and 5 , the first link arm 26 has an elongated shape and is disposed so as to extend along the front section 10. One end of the first link arm 26 is pivotally connected to the connecting bar 4. In other words, the first link arm 26 is disposed so as to extend from the connecting bar 4 toward the connecting section 14. A connection portion 27 between the one end of the first link arm 26 and the connecting bar 4 is disposed on the opposite side of the rotation axis Pa1 from the side on which the elongated hole 4a (connection pin 22a) is disposed. In other words, the elongated hole 4a (connection pin 22a), the rotation axis Pa1, and the connection portion 27 are disposed in this order from the front side of the front section 10 (the front side in the longitudinal direction of the connecting bar 4). The other end of the first link arm 26 is pivotally connected to a first rotating lever 28. One end of the first link arm 26 is an example of an embodiment that corresponds to a "first end" in the present invention, and the other end of the first link arm 26 is an example of an embodiment that corresponds to a "second end" in the present invention.

[0038] As shown in FIGS. 3 and 5 , the first rotating lever 28 has a generally V-shaped planar shape and includes a first arm and a second arm that intersects with the first arm. The first rotating lever 28 has a rotation axis Pa2 in the intersecting region between the first arm and the second arm, and is supported by the connecting portion 14 so as to be rotatable about the rotation axis Pa2. The first arm of the first rotating lever 28 has a connection portion 28a to which the other end of the first link arm 26 is rotatably connected, and the second arm of the first rotating lever 28 has a connection portion 28b to which one end of the connecting link arm 30 is rotatably connected. In other words, the connection portions 28a, 28b, and the rotation axis Pa2 are positioned such that an imaginary line VL1 connecting the connection portion 28a and the rotation axis Pa2 intersects with an imaginary line VL2 connecting the connection portion 28b and the rotation axis Pa2. The first rotating lever 28 is supported by the coupling portion 14 in such a manner that the connection portion 28b is disposed on the opposite side of the rotation axis Pa2 from the side on which the connection portion 27 is disposed (on the outer side (left side) in the vehicle width direction). The connection portion 28a corresponds to the "first connection portion" in the present invention, and the connection portion 28b is an example of an embodiment corresponding to the "second connection portion" in the present invention. The imaginary straight lines VL1 and VL2 correspond to the "first imaginary straight line" and the "second imaginary straight line" in the present invention, respectively, and the rotation axis Pa2 is an example of an embodiment corresponding to the "third rotation axis" in the present invention.

[0039] As shown in FIGS. 3 and 5 , the connecting link arm 30 has an elongated shape and is disposed so as to extend along the connecting portion 14. One end of the connecting link arm 30 is rotatably connected to the second piece (connecting portion 28b) of the first rotating lever 28. In other words, the connecting link arm 30 is disposed so as to extend from the first rotating lever 28 toward the intersection region between the connecting portion 14 and the rear portion 12. The other end of the connecting link arm 30 is rotatably connected to the second rotating lever 32. One end of the connecting link arm 30 corresponds to the "third end" in the present invention, and the other end of the connecting link arm 30 corresponds to the "fourth end" in the present invention, which are examples of an embodiment.

[0040] 3 and 5, the second rotating lever 32 has basically the same configuration as the first rotating lever 28 and is generally V-shaped in plan view, having a first arm and a second arm that can intersect with the first arm. The second rotating lever 32 has a rotation axis Pa3 in the intersecting region between the first arm and the second arm, and is supported by the connecting portion 14 so as to be rotatable about the rotation axis Pa3. The first arm of the second rotating lever 32 has a connection portion 32a to which the other end of the connecting link arm 30 is rotatably connected, and the second arm of the second rotating lever 32 has a connection portion 32b to which one end of the second link arm 34 is rotatably connected. In other words, the connecting portions 32a, 32b, and the rotation axis Pa3 are disposed in a positional relationship in which an imaginary line VL3 connecting the connecting portions 32a and the rotation axis Pa3 intersects with an imaginary line VL4 connecting the connecting portions 32b and the rotation axis Pa3. The second rotating lever 32 is supported by the coupling portion 14 in such a manner that the connecting portion 32a is disposed on the inner side (right side) in the vehicle width direction with respect to the rotation axis Pa3. The connecting portion 32a corresponds to the "third connecting portion" of the present invention, and the connecting portion 32b is an example of an embodiment corresponding to the "fourth connecting portion" of the present invention. The imaginary lines VL3 and VL4 correspond to the "third imaginary line" and the "fourth imaginary line," respectively, and the rotation axis Pa3 is an example of an embodiment corresponding to the "fourth rotation axis" of the present invention.

[0041] As shown in FIGS. 3 and 5 , the second link arm 34 has an elongated shape and is disposed so as to extend along the rear section 12. One end of the second link arm 34 is rotatably connected to the second piece (connection portion 32b) of the second pivot lever 32, and the other end of the second link arm 34 is rotatably connected to the pivot bar 36. In other words, the second link arm 34 is disposed so as to extend from the second pivot lever 32 along the rear section 12. A connection portion 37 between the other end of the second link arm 34 and the pivot bar 36 is disposed forward of a pivot axis Pa4 (described later) of the pivot bar 36 and forward of a long hole 36a (described later) of the pivot bar 36. In other words, the connection portion 37, the long hole 36a (connection pin 24a), and the pivot axis Pa4 are disposed in this order from the front side of the rear section 12 (the front side in the longitudinal direction of the pivot bar 36). One end of the second link arm 34 is an example of an embodiment that corresponds to the "sixth end" of the present invention, and the other end of the second link arm 34 is an example of an embodiment that corresponds to the "fifth end" of the present invention.

[0042] As shown in FIGS. 3 and 5 , the rotating bar 36 has a rotation axis Pa4 and is supported by the rear section 12 so as to be rotatable (swingable) in the left-right direction about the rotation axis Pa4 along an imaginary plane parallel to the top surface 2a (a plane parallel to the paper surface of FIG. 3 ). The rotation axis Pa4 is disposed at a central position in the extension direction of the rear section 12. In other words, the rotating bar 36 can be said to be rotatable (swingable) in the left-right direction and disposed at a central position in the extension direction of the rear section 12. The rotating bar 36 also has an elongated hole 36a. The elongated hole 36a is disposed on the front side of the rotation axis Pa4 and extends in the longitudinal direction of the rotating bar 36. The rotation axis Pa4 is an example of an embodiment corresponding to a “second rotation axis” in the present invention.

[0043] The four-wheel steering mechanism 20 configured in this manner can be said to be disposed within the bogie body 2 when the bogie body 2 is viewed from above, as shown in Fig. 3. In other words, the four-wheel steering mechanism 20 can be said to be disposed so as not to intrude into at least the inner region 70 of the bogie body 2 (the inner region surrounded by the front portion 10, the rear portion, and the connecting portion 14).

[0044] Furthermore, the four-wheel steering mechanism 20 is configured to connect the first link arm 26 and the connecting link arm 30 via the first rotating lever 28, and to connect the connecting link arm 30 and the rear steering link arm 24 via the second rotating lever 32, the second link arm 34, and the rotating bar 36, thereby improving the degree of freedom in arranging the four-wheel steering mechanism 20 on the bogie body 2. This allows for easy layout even within a limited space, and ensures that the four-wheel steering mechanism 20 does not intrude into at least the inner region 70.

[0045] Next, the operation of the bogie 1 configured in this manner will be described, in particular the operation when transferring the load L to and from the automatic guided vehicle 82, and the operation of the bogie 1 accompanying the left and right turning travel of the automatic guided vehicle 80 as a towing vehicle. First, the operation when transferring the load L to and from the automatic guided vehicle 82 will be described, and then the steering operation of the bogie 1 accompanying the left and right turning travel of the automatic guided vehicle 80 will be described.

[0046] <Transfer of load L> When transferring the load L from the automatic guided vehicle 82 to the carriage 1, the automatic guided vehicle 82 carrying the load L is caused to enter the inner area 70 of the carriage 1, as shown in Figures 6 to 9. Here, the load L is loaded on the automatic guided vehicle 82 with its bottom surface higher than the upper surface 2a of the carriage body 2.

[0047] 8 and 9, when the automatic guided vehicle 82 has entered the inner area 70 to a position where the load L can be placed on the upper surface 2a of the carriage body 2, the automatic guided vehicle 82 is stopped, and the position of the load L is lowered until the bottom surface of the load L abuts against the upper surface 2a of the carriage body 2 at that position. This changes the placement location of the load L from the automatic guided vehicle 82 to the carriage 1 (upper surface 2a of the carriage body 2). Thereafter, as shown in FIGS. 10 and 11, the automatic guided vehicle 82 is caused to exit the inner area 70, thereby completing the transfer of the load L from the automatic guided vehicle 82 to the carriage 1.

[0048] On the other hand, when transferring the load L from the dolly 1 to the automatic guided vehicle 82, the procedure can be reversed from the above. That is, the automatic guided vehicle 82 is caused to enter the inner region 70 of the dolly 1 loaded with the load L, and the automatic guided vehicle 82 is stopped at a position where the automatic guided vehicle 82 can place the load L. At that position, the platform of the automatic guided vehicle 82 is raised until the bottom surface of the load L is separated from the upper surface 2a of the dolly main body 2. As a result, the placement location of the load L is changed from the dolly 1 (the upper surface 2a of the dolly main body 2) to the automatic guided vehicle 82. Thereafter, the automatic guided vehicle 82 loaded with the load L is caused to exit the inner region 70, thereby completing the transfer of the load L from the dolly 1 to the automatic guided vehicle 82.

[0049] In this way, when transferring the load L between the automated guided vehicle 82 and the carriage 1, the automated guided vehicle 82 is caused to enter the inner region 70 of the carriage 1, so that the work of transferring the load L to the carriage body 2 can be carried out easily and reliably. Furthermore, since the four-wheel steering mechanism 20 is positioned so as not to enter at least the inner region 70, the entry of the automated guided vehicle 82 is not impeded during the work of transferring the load L to and from the carriage 1.

[0050] <Steering operation of bogie 1> When the automated guided vehicle 80, which is towing the bogie 1 via the connecting bar 4, turns left or right, the bogie 1 also turns left or right while traveling in response. Here, the bogie 1 has a four-wheel steering mechanism 20, which improves the turning ability when being towed by the automated guided vehicle 80. That is, for example, when the automated guided vehicle 80 turns right, the connecting bar 4 turns rightward about the rotation axis Pa1 (clockwise when the bogie 1 is viewed from the direction of the top surface 2a, counterclockwise in FIG. 3). This causes the front steering link arm 22 to move (swing) rightward (rightward when the bogie 1 is viewed from the direction of the top surface 2a, leftward in FIG. 3) along the front portion 10. Here, the front steering link arm 22 is engaged with the elongated hole 4a of the connecting bar 4 via the connecting pin 22a, so that it can move (swing) smoothly along the front portion 10.

[0051] In response to the movement (swing) of the front steering link arm 22 to the right (to the right when the trolley 1 is viewed from the direction of the top surface 2a, left in Figure 3), the pair of front casters 6a, 6b rotate to the right (clockwise when the trolley 1 is viewed from the direction of the top surface 2a, counterclockwise in Figure 3) via the swivel brackets 40, 42.

[0052] On the other hand, when the connecting bar 4 rotates rightward (clockwise when the bogie 1 is viewed from the direction of the top surface 2a, counterclockwise in FIG. 3 ) about the rotation axis Pa1, the first link arm 26 moves (swings) leftward (leftward when the bogie 1 is viewed from the direction of the top surface 2a, rightward in FIG. 3 ) along the front portion 10. The movement (swing) of the first link arm 26 to the left (leftward when the bogie 1 is viewed from the direction of the top surface 2a, rightward in FIG. 3 ) is converted into movement (swing) of the second link arm 34 to the left along the rear portion 12 (leftward when the bogie 1 is viewed from the direction of the top surface 2a, rightward in FIG. 3 ) and transmitted via the first rotating lever 28, the connecting link arm 30, and the second rotating lever 32.

[0053] Then, due to the movement (swing) of the second link arm 34 to the left (left when the bogie 1 is viewed from the direction of the top surface 2a, right in FIG. 3), the turning bar 36 turns to the left (counterclockwise when the bogie 1 is viewed from the direction of the top surface 2a, clockwise in FIG. 3) about the turning axis Pa4. Accordingly, the rear steering link arm 24 moves (swings) to the left (left when the bogie 1 is viewed from the direction of the top surface 2a, right in FIG. 3) along the rear portion 12. Here, the rear steering link arm 24 is engaged with the elongated hole 36a of the turning bar 36 via the connecting pin 24a, and therefore can move (swing) smoothly along the rear portion 12.

[0054] In response to movement (swing) of the rear steering link arm 24 to the left (left when viewing the trolley 1 from the direction of the top surface 2a, right in Figure 3), the pair of rear casters 8a, 8b rotate to the left (counterclockwise when viewing the trolley 1 from the direction of the top surface 2a, clockwise in Figure 3) via the swivel brackets 44, 46.

[0055] In this way, when the unmanned guided vehicle 80 turns to the right, the pair of front casters 6a, 6b turn to the right (clockwise when the cart 1 is viewed from the direction of the top surface 2a, counterclockwise in Figure 3), and the pair of rear casters 8a, 8b turn to the left (counterclockwise when the cart 1 is viewed from the direction of the top surface 2a, clockwise in Figure 3), thereby improving the maneuverability of the cart 1.

[0056] On the other hand, for example, when the unmanned guided vehicle 80 turns to the left, the various parts of the four-wheel steering mechanism 20 (front steering link arm 22, rear steering link arm 24, first link arm 26, first pivoting lever 28, connecting link arm 30, second pivoting lever 32, second link arm 34, pivoting bar 36) rotate or move (swing) in the opposite direction to when the unmanned guided vehicle 80 turns to the right, causing the pair of front casters 6a, 6b to rotate to the left (counterclockwise when the cart 1 is viewed from the direction of the top surface 2a, clockwise in Figure 3), and the pair of rear casters 8a, 8b to rotate to the right (clockwise when the cart 1 is viewed from the direction of the top surface 2a, counterclockwise in Figure 3), thereby improving the maneuverability of the cart 1.

[0057] Here, the front steering link arm 22 and the pair of front casters 6a, 6b, and the rear steering link arm 24 and the pair of rear casters 8a, 8b are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism, so that an appropriate difference in rotation angle can be ensured between the inside front casters 6a, 6b and rear casters 8a, 8b and the outside front casters 6a, 6b and rear casters 8a, 8b when the bogie 1 turns. This stabilizes the turning behavior of the bogie 1.

[0058] In the first embodiment, the long hole 4a (connection pin 22a), the pivot axis Pa1, and the connection portion 27 between the first link arm 26 and the connecting bar 4 are arranged in this order from the front side in the longitudinal direction of the connecting bar 4, but this is not limiting. For example, as shown in a modified bogie 1A illustrated in Fig. 12, the pivot axis Pa1, the long hole 4a (connection pin 22a), and the connection portion 27 may be arranged in this order from the front side in the longitudinal direction of the connecting bar 4, or as shown in a modified bogie 1B illustrated in Fig. 13, the long hole 4a (connection pin 22a), the connection portion 27, and the pivot axis Pa1 may be arranged in this order from the front side in the longitudinal direction of the connecting bar 4.

[0059] 12, the bogie 1A has the same configuration as the bogie 1 of the first embodiment except that the arrangement of the rotation axis Pa1, the elongated hole 4a (connection pin 22a), and the connection portion 27 has been changed compared to the bogie 1 of the first embodiment, and that the connection position between the front steering link arm 22 and the swivel brackets 40, 42 has been changed accordingly. Therefore, to avoid redundant explanation, the same components of the bogie 1A of the modified example as those of the bogie 1 of the first embodiment described above will be assigned the same reference numerals, and illustrations and detailed explanations thereof will be omitted.

[0060] In the bogie 1A, in order to make the rotation direction of the connecting bar 4 and the rotation direction of the pair of front casters 6a, 6b the same, as shown in Figure 12, the front steering link arm 22 and the swivel brackets 40, 42 are positioned so that the extension direction of the bottom of the swivel brackets 40, 42 and the extension direction of the front steering link arm 22 are parallel, and the front steering link arm 22 is rotatably connected to the arm portion of the pair of arms of the swivel brackets 40, 42 that is positioned on the inner side in the vehicle width direction (the left side for the swivel bracket 40 and the right side for the swivel bracket 42).

[0061] Even with this type of bogie 1A, the automated guided vehicle 82 can enter the inner region 70 of the bogie 1A, making it possible to easily and reliably transfer the load L onto the bogie body 2, and because the four-wheel steering mechanism 20 is positioned so as not to enter at least the inner region 70, the entry of the automated guided vehicle 82 is not impeded during the operation of transferring the load L to and from the bogie 1A. Furthermore, as the automated guided vehicle 80 turns, the pair of front casters 6a, 6b can be turned in the same direction as the rotation direction of the connecting bar 4, while the pair of rear casters 8a, 8b can be turned in the opposite direction to the pair of front casters 6a, 6b, thereby improving the turning ability of the bogie 1A. Furthermore, because the front steering link arm 22 and the pair of front casters 6a, 6b, and the rear steering link arm 24 and the pair of rear casters 8a, 8b are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism, when the bogie 1A turns, it is possible to ensure an appropriate difference in rotation angle between the inside front casters 6a, 6b and rear casters 8a, 8b and the outside front casters 6a, 6b and rear casters 8a, 8b. This makes it possible to stabilize the turning behavior of the bogie 1A.

[0062] 13, the bogie 1B has the same configuration as the bogie 1 of the first embodiment except that the arrangement of the rotation axis Pa1, the elongated hole 4a (connection pin 22a), and the connection portion 27 has been changed compared to the bogie 1 of the first embodiment, and that the connection position between the rear steering link arm 24 and the swivel brackets 44, 46 has been changed accordingly. Therefore, in order to avoid redundant explanation, the same reference numerals are used for the components of the bogie 1B of the modified example that are the same as those of the bogie 1 of the first embodiment described above, and illustrations and detailed explanations thereof will be omitted.

[0063] In the bogie 1B, in order to make the rotation direction of the connecting bar 4 and the rotation direction of the pair of front casters 6a, 6b the same, as shown in Figure 13, the rear steering link arm 24 and the swivel brackets 44, 46 are positioned so that the extension direction of the bottom of the swivel brackets 44, 46 and the extension direction of the rear steering link arm 24 are parallel, and the rear steering link arm 24 is rotatably connected to the arm portion of the pair of arms of the swivel brackets 44, 46 that is positioned on the outer side in the vehicle width direction (the right side of the swivel bracket 44 and the left side of the swivel bracket 46).

[0064] With such a bogie 1B, the automated guided vehicle 82 can also enter the inner region 70 of the bogie 1B, making it possible to easily and reliably transfer the load L onto the bogie body 2, and since the four-wheel steering mechanism 20 is positioned so as not to enter at least the inner region 70, the entry of the automated guided vehicle 82 is not impeded during the operation of handing over the load L to and from the bogie 1B. Furthermore, as the automated guided vehicle 80 turns, the pair of front casters 6a, 6b can be turned in the same direction as the rotation direction of the connecting bar 4, while the pair of rear casters 8a, 8b can be turned in the opposite direction to the pair of front casters 6a, 6b, thereby improving the turning ability of the bogie 1B. Furthermore, because the front steering link arm 22 and the pair of front casters 6a, 6b, and the rear steering link arm 24 and the pair of rear casters 8a, 8b are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism, when the bogie 1B turns, it is possible to ensure an appropriate difference in rotation angle between the inside front casters 6a, 6b and rear casters 8a, 8b and the outside front casters 6a, 6b and rear casters 8a, 8b. This makes it possible to stabilize the turning behavior of the bogie 1B.

[0065] In the first embodiment, the connecting portion 37 between the other end of the second link arm 34 and the rotating bar 36, the elongated hole 36a (connection pin 24a), and the rotation axis Pa4 are arranged in this order from the front side in the longitudinal direction of the rotating bar 36, but this is not limiting. For example, as shown in a modified bogie 1C illustrated in Fig. 14, the connecting portion 37, the rotation axis Pa4, and the elongated hole 36a (connection pin 24a) may be arranged in this order from the front side in the longitudinal direction of the rotating bar 36, or as shown in a modified bogie 1D illustrated in Fig. 15, the rotation axis Pa4, the connecting portion 37, and the elongated hole 36a (connection pin 24a) may be arranged in this order from the front side in the longitudinal direction of the rotating bar 36.

[0066] 14, the bogie 1C has the same configuration as the bogie 1 of the first embodiment except that the arrangement of the rotation axis Pa4, the elongated hole 36a (connection pin 24a), and the connection portion 37 has been changed compared to the bogie 1 of the first embodiment, and that the connection position between the rear steering link arm 24 and the swivel brackets 44, 46 has been changed accordingly. Therefore, in order to avoid redundant explanation, the same components of the bogie 1C of the modified example as those of the bogie 1 of the first embodiment described above will be assigned the same reference numerals, and illustrations and detailed explanations thereof will be omitted.

[0067] In the bogie 1C, in order to make the rotation direction of the swivel bar 36 and the rotation direction of the pair of rear casters 8a, 8b the same, as shown in Figure 14, the rear steering link arm 24 and the swivel brackets 44, 46 are positioned so that the extension direction of the bottom of the swivel brackets 44, 46 is parallel to the extension direction of the rear steering link arm 24, and the rear steering link arm 24 is rotatably connected to the arm portion of the pair of arms of the swivel brackets 44, 46 that is positioned on the outer side in the vehicle width direction (the right side of the swivel bracket 44 and the left side of the swivel bracket 46).

[0068] With this type of bogie 1C, the automated guided vehicle 82 can also enter the inner region 70 of the bogie 1C, making it possible to easily and reliably transfer the load L onto the bogie body 2, and since the four-wheel steering mechanism 20 is positioned so as not to enter at least the inner region 70, the entry of the automated guided vehicle 82 is not impeded during the operation of transferring the load L to and from the bogie 1C. Furthermore, as the automated guided vehicle 80 turns, the pair of front casters 6a, 6b can be turned in the same direction as the rotation direction of the connecting bar 4, while the pair of rear casters 8a, 8b can be turned in the opposite direction to the pair of front casters 6a, 6b, thereby improving the turning ability of the bogie 1C. Furthermore, because the front steering link arm 22 and the pair of front casters 6a, 6b, and the rear steering link arm 24 and the pair of rear casters 8a, 8b are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism, when the bogie 1C turns, it is possible to ensure an appropriate difference in rotation angle between the inside front casters 6a, 6b and rear casters 8a, 8b and the outside front casters 6a, 6b and rear casters 8a, 8b. This makes it possible to stabilize the turning behavior of the bogie 1C.

[0069] 15, the bogie 1D has the same configuration as the bogie 1 of the first embodiment, except that the positions of the rotation axis Pa4, the elongated hole 36a (connection pin 24a), and the connection portion 37 are changed compared to the bogie 1 of the first embodiment. Therefore, in order to avoid redundant explanation, the same components of the modified bogie 1B as those of the bogie 1 of the first embodiment described above are denoted by the same reference numerals, and illustrations and detailed explanations thereof will be omitted.

[0070] Even with this type of bogie 1D, the automated guided vehicle 82 can enter the inner region 70 of the bogie 1D, making it possible to easily and reliably transfer the load L onto the bogie body 2, and since the four-wheel steering mechanism 20 is positioned so as not to enter at least the inner region 70, the entry of the automated guided vehicle 82 is not impeded during the operation of handing over the load L to and from the bogie 1D. Furthermore, as the automated guided vehicle 80 turns, the pair of front casters 6a, 6b can be turned in the same direction as the rotation direction of the connecting bar 4, while the pair of rear casters 8a, 8b can be turned in the opposite direction to the pair of front casters 6a, 6b, thereby improving the turning ability of the bogie 1D. Furthermore, because the front steering link arm 22 and the pair of front casters 6a, 6b, and the rear steering link arm 24 and the pair of rear casters 8a, 8b are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism, when the bogie 1D turns, it is possible to ensure an appropriate difference in rotation angle between the inside front casters 6a, 6b and rear casters 8a, 8b and the outside front casters 6a, 6b and rear casters 8a, 8b. This makes it possible to stabilize the turning behavior of the bogie 1D.

[0071] In the first embodiment and the above-described modified examples, one front steering link arm 22 is rotatably supported on the connecting bar 4, and the swivel brackets 40, 42 are rotatably connected to both ends of the single front steering link arm 22. However, this is not limiting. For example, as shown in a modified bogie 1E illustrated in FIG. 16 , one end of each of two front steering link arms 21, 23 may be rotatably supported on the connecting bar 4, and the swivel brackets 40, 42 may be rotatably connected to the other ends of the front steering link arms 21, 23. In this case, unlike the bogies 1, 1A, 1B, 1C, and 1D of the first embodiment and the above-described modified examples, it is not necessary to provide the connecting bar 4 with an elongated hole 4a. In other words, the connecting pins 21a, 23a of the front steering link arms 21, 23 may be rotatably connected to the connecting bar 4 without using the elongated hole 4a.

[0072] The bogie 1E can also achieve the same effects as those achieved by the bogies 1, 1A, 1B, 1C, and 1D of the first embodiment and the above-described modified examples.

[0073] In the first embodiment and the above-described modified examples, the movement of the connecting link arm 30 is transmitted to the swivel brackets 44, 46 via the second rotating lever 32, the second link arm 34, the rotating bar 36, and the rear steering link arm 24, but the present invention is not limited to this. For example, as shown in a modified bogie 1F illustrated in FIG. 17 , the second rotating lever 32 and the second link arm 34 may be eliminated, and the connecting link arm 30 may be rotatably connected to the swivel bracket 460 via the connection portion 31, thereby transmitting the movement of the connecting link arm 30 directly to the swivel bracket 460 and transmitting the swivel movement of the swivel bracket 460 to the swivel bracket 44 via the rear steering link arm 24. The swivel bracket 460 has the connection portion 31 to which the other end of the connecting link arm 30 is rotatably connected, and a connection portion 460a to which one end of the rear steering link arm 24 is rotatably connected. In other words, the connecting portion 31, the connecting portion 460a, and the pivot axis Sa4 are disposed in a positional relationship such that an imaginary line VL5 connecting the connecting portion 31 and the pivot axis Sa4 intersects with an imaginary line VL6 connecting the connecting portion 460a and the pivot axis Sa4. The connecting portion 31 is disposed on the outer (left) arm of the pair of arms of the swivel bracket 460 in the vehicle width direction. Note that, when the rear steering link arm 24 and the swivel brackets 44, 460 are disposed so that the extending direction of the rear steering link arm 24 and the extending direction of the bottoms of the swivel brackets 44, 460 are parallel, the rear steering link arm 24 is rotatably connected via the connecting portion 460a to the intersecting corner of the pair of arms and the bottoms of the swivel brackets 44, 460 that is disposed on the inner side in the vehicle width direction (the left side of the swivel bracket 44, and the right side of the swivel bracket 460). The connection portion 31 is a feature that corresponds to a "fifth connection portion" of the present invention, and the connection portion 460a is an example of a feature that corresponds to a "sixth connection portion" of the present invention.

[0074] The bogie 1F can also achieve the same effects as those achieved by the bogies 1, 1A, 1B, 1C, and 1D of the first embodiment and the above-described modified examples. [Example]

[0075] Next, a bogie 100 of a second embodiment will be described. Fig. 18 is a configuration diagram showing an outline of the configuration of the bogie 100 of the second embodiment. The bogie 100 of the second embodiment has the same configuration as the bogie 1 of the first embodiment except that, compared to the bogie 1 of the first embodiment, the connection relationship between the rear steering link arm 24 and the swivel brackets 44, 46 is changed, and the first rotating lever 28 and the second rotating lever 32 are deleted, and the first link arm 26 and the second link arm 34 are directly connected to the connecting link arm 130. Therefore, in order to avoid redundant explanation, the same reference numerals are used to designate the components of the bogie 100 of the second embodiment that correspond to the components of the bogie 1 of the first embodiment, and detailed explanations thereof will be omitted.

[0076] 18, in a state in which the rear steering link arm 24 and the swivel brackets 44, 46 are positioned so that the extension direction of the rear steering link arm 24 is parallel to the extension direction of the bottoms of the swivel brackets 44, 46, the rear steering link arm 24 is rotatably connected to one of the pair of arms of the swivel brackets 44, 46 that is positioned on the outer side in the vehicle width direction (the right side of the swivel bracket 44 and the left side of the swivel bracket 46). This allows the rotation direction of the rotating bar 36 and the rotation direction of the pair of rear casters 8a, 8b to be the same.

[0077] As shown in FIG. 18 , the connecting link arm 130 has an elongated shape and is disposed so as to extend along the connecting portion 14. The connecting link arm 130 has a rotation axis 130a at approximately the center in the longitudinal direction thereof and is supported by the connecting portion 14 so as to be rotatable around the rotation axis 130a. One end of the connecting link arm 130 is rotatably connected to the other end of the first link arm 26 via a connecting portion 130b, and the other end of the connecting link arm 130 is rotatably connected to one end of the second link arm 34 via a connecting portion 130c. The rotation axis 130a is an example of an embodiment corresponding to the “fifth rotation axis” of this invention.

[0078] In the bogie 100 of the second embodiment configured in this manner, the direction of movement of the first link arm 26 along the front portion 10 is reversed by the connecting link arm 130 and transmitted to the second link arm 34. That is, the second link arm 34 moves along the rear portion 12 in the opposite direction to the direction of movement of the first link arm 26. As a result, as the automated guided vehicle 80 turns, the pair of front casters 6a, 6b can be rotated in the same direction as the rotation direction of the connecting bar 4, while the pair of rear casters 8a, 8b can be rotated in the opposite direction to the pair of front casters 6a, 6b. As a result, the turning performance of the bogie 100 can be improved. Since the front steering link arm 22 and the pair of front casters 6a, 6b, and the rear steering link arm 24 and the pair of rear casters 8a, 8b are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism, similar to the bogie 1 of Example 1, it is possible to ensure an appropriate difference in rotation angle between the inside front casters 6a, 6b and rear casters 8a, 8b and the outside front casters 6a, 6b and rear casters 8a, 8b when the bogie 100 turns. This makes it possible to stabilize the turning behavior of the bogie 100. Naturally, the unmanned transport vehicle 82 can enter the inner area 70 of the trolley 100, so the transfer of the load L onto the trolley body 2 can be carried out easily and reliably, and since the four-wheel steering mechanism 20 is positioned so as not to enter at least the inner area 70, the entry of the unmanned transport vehicle 82 is not obstructed during the transfer of the load L between the trolley 100 and the unmanned transport vehicle 82.

[0079] In the second embodiment, the long hole 4a (connection pin 22a), the pivot axis Pa1, and the connection portion 27 between the first link arm 26 and the connecting bar 4 are arranged in this order from the front side in the longitudinal direction of the connecting bar 4, but this is not limiting. For example, as shown in a modified bogie 100A illustrated in Fig. 19, the pivot axis Pa1, the long hole 4a (connection pin 22a), and the connection portion 27 may be arranged in this order from the front side in the longitudinal direction of the connecting bar 4, or as shown in a modified bogie 100B illustrated in Fig. 20, the long hole 4a (connection pin 22a), the connection portion 27, and the pivot axis Pa1 may be arranged in this order from the front side in the longitudinal direction of the connecting bar 4.

[0080] 19, the bogie 100A has the same configuration as the bogie 100 of the second embodiment except that the arrangement of the rotation axis Pa1, the elongated hole 4a (connection pin 22a), and the connection portion 27 has been changed relative to the bogie 100 of the second embodiment, and that the connection position between the front steering link arm 22 and the swivel brackets 40, 42 has been changed accordingly. Therefore, in order to avoid redundant explanation, the same components of the bogie 100A of the modified example as those of the bogie 100 of the second embodiment described above will be assigned the same reference numerals, and illustrations and detailed explanations thereof will be omitted.

[0081] In the bogie 100A, in order to make the rotation direction of the connecting bar 4 and the rotation direction of the pair of front casters 6a, 6b the same, as shown in Figure 19, the front steering link arm 22 and the swivel brackets 40, 42 are positioned so that the extension direction of the bottom of the swivel brackets 40, 42 and the extension direction of the front steering link arm 22 are parallel, and the front steering link arm 22 is rotatably connected to the arm portion of the pair of arms of the swivel brackets 40, 42 that is positioned on the inner side in the vehicle width direction (the left side of the swivel bracket 40 and the right side of the swivel bracket 42).

[0082] In this type of bogie 100A, the automated guided vehicle 82 can also enter the inner region 70 of the bogie 100A, so the work of transferring the load L to the bogie body 2 can be carried out easily and reliably, and since the four-wheel steering mechanism 20 is positioned so as not to enter at least the inner region 70, the entry of the automated guided vehicle 82 is not hindered during the work of transferring the load L to and from the bogie 100A. Furthermore, as the automated guided vehicle 80 turns, the pair of front casters 6a, 6b can be turned in the same direction as the rotation direction of the connecting bar 4, while the pair of rear casters 8a, 8b can be turned in the opposite direction to the pair of front casters 6a, 6b, so the turning ability of the bogie 100A can be improved. Furthermore, because the front steering link arm 22 and the pair of front casters 6a, 6b, and the rear steering link arm 24 and the pair of rear casters 8a, 8b are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism, when the bogie 100A turns, it is possible to ensure an appropriate difference in rotation angle between the inside front casters 6a, 6b and rear casters 8a, 8b and the outside front casters 6a, 6b and rear casters 8a, 8b. This makes it possible to stabilize the turning behavior of the bogie 100A.

[0083] 20, the bogie 100B has the same configuration as the bogie 100 of the second embodiment except that the arrangement of the rotation axis Pa1, the elongated hole 4a (connection pin 22a), and the connection portion 27 has been changed relative to the bogie 100 of the second embodiment, and that the connection position between the rear steering link arm 24 and the swivel brackets 44, 46 has been changed accordingly. Therefore, in order to avoid redundant explanation, the same components of the modified bogie 100B as those of the bogie 100 of the second embodiment described above will be assigned the same reference numerals, and illustrations and detailed explanations thereof will be omitted.

[0084] In the bogie 100B, in order to make the rotation direction of the connecting bar 4 and the rotation direction of the pair of front casters 6a, 6b the same, as shown in Figure 20, the rear steering link arm 24 and the swivel brackets 44, 46 are positioned so that the extension direction of the bottom of the swivel brackets 44, 46 and the extension direction of the rear steering link arm 24 are parallel, and the rear steering link arm 24 is rotatably connected to the intersection corner where the pair of arms and bottoms of the swivel brackets 44, 46 intersect, which is located on the inner side in the vehicle width direction (the left side of the swivel bracket 44 and the right side of the swivel bracket 46).

[0085] In such a bogie 100B, the automated guided vehicle 82 can also enter the inner region 70 of the bogie 100B, so that the work of transferring the load L to the bogie body 2 can be carried out easily and reliably, and since the four-wheel steering mechanism 20 is positioned so as not to enter at least the inner region 70, the entry of the automated guided vehicle 82 is not impeded during the work of transferring the load L to and from the bogie 100B. Furthermore, as the automated guided vehicle 80 turns, the pair of front casters 6a, 6b can be turned in the same direction as the rotation direction of the connecting bar 4, while the pair of rear casters 8a, 8b can be turned in the opposite direction to the pair of front casters 6a, 6b, so that the turning ability of the bogie 100B can be improved. Furthermore, because the front steering link arm 22 and the pair of front casters 6a, 6b, and the rear steering link arm 24 and the pair of rear casters 8a, 8b are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism, when the bogie 100B turns, it is possible to ensure an appropriate difference in rotation angle between the inside front casters 6a, 6b and rear casters 8a, 8b and the outside front casters 6a, 6b and rear casters 8a, 8b. This makes it possible to stabilize the turning behavior of the bogie 100B.

[0086] In the second embodiment, the connecting portion 37 between the other end of the second link arm 34 and the rotating bar 36, the elongated hole 36a (connection pin 24a), and the rotation axis Pa4 are arranged in this order from the front side in the longitudinal direction of the rotating bar 36, but this is not limiting. For example, as shown in a modified bogie 100C illustrated in Fig. 21, the connecting portion 37, the rotation axis Pa4, and the elongated hole 36a (connection pin 24a) may be arranged in this order from the front side in the longitudinal direction of the rotating bar 36, or as shown in a modified bogie 100D illustrated in Fig. 22, the rotation axis Pa4, the connecting portion 37, and the elongated hole 36a (connection pin 24a) may be arranged in this order from the front side in the longitudinal direction of the rotating bar 36.

[0087] 21, the bogie 100C has the same configuration as the bogie 100 of the second embodiment except that the arrangement of the rotation axis Pa4, the elongated hole 36a (connection pin 24a), and the connection portion 37 has been changed relative to the bogie 100 of the second embodiment, and that the connection position between the rear steering link arm 24 and the swivel brackets 44, 46 has been changed accordingly. Therefore, in order to avoid redundant explanation, the same components of the bogie 100C of the modified example as those of the bogie 100 of the second embodiment described above will be assigned the same reference numerals, and illustrations and detailed explanations thereof will be omitted.

[0088] In the bogie 100C, in order to make the rotation direction of the swivel bar 36 and the rotation direction of the pair of rear casters 8a, 8b the same, as shown in Figure 21, the rear steering link arm 24 and the swivel brackets 44, 46 are positioned so that the extension direction of the bottom of the swivel brackets 44, 46 is parallel to the extension direction of the rear steering link arm 24.When this is done, the rear steering link arm 24 is rotatably connected to the intersection corner where the pair of arms and bottoms of the swivel brackets 44, 46 intersect, which is located on the inner side in the vehicle width direction (the left side for the swivel bracket 44 and the right side for the swivel bracket 46).

[0089] In such a bogie 100C, the automated guided vehicle 82 can also enter the inner region 70 of the bogie 100C, so that the work of transferring the load L to the bogie body 2 can be carried out easily and reliably, and since the four-wheel steering mechanism 20 is positioned so as not to enter at least the inner region 70, the entry of the automated guided vehicle 82 is not impeded during the work of transferring the load L to and from the bogie 100C. Furthermore, as the automated guided vehicle 80 turns, the pair of front casters 6a, 6b can be turned in the same direction as the rotation direction of the connecting bar 4, while the pair of rear casters 8a, 8b can be turned in the opposite direction to the pair of front casters 6a, 6b, so that the turning ability of the bogie 100C can be improved. Furthermore, because the front steering link arm 22 and the pair of front casters 6a, 6b, and the rear steering link arm 24 and the pair of rear casters 8a, 8b are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism, when the bogie 100C turns, it is possible to ensure an appropriate difference in rotation angle between the inside front casters 6a, 6b and rear casters 8a, 8b and the outside front casters 6a, 6b and rear casters 8a, 8b. This makes it possible to stabilize the turning behavior of the bogie 100C.

[0090] 22, the bogie 100D has the same configuration as the bogie 100 of the second embodiment, except that the arrangements of the rotation axis Pa4, the elongated holes 36a (connection pins 24a), and the connection portions 37 are changed compared to the bogie 100 of the second embodiment. Therefore, in order to avoid redundant explanation, the same components of the modified bogie 100B as those of the bogie 100 of the second embodiment described above are denoted by the same reference numerals, and illustrations and detailed explanations thereof will be omitted.

[0091] In such a bogie 100D, the automated guided vehicle 82 can also enter the inner region 70 of the bogie 100D, so that the work of transferring the load L onto the bogie body 2 can be carried out easily and reliably, and since the four-wheel steering mechanism 20 is positioned so as not to enter at least the inner region 70, the entry of the automated guided vehicle 82 is not impeded during the work of transferring the load L to and from the bogie 100D. Furthermore, as the automated guided vehicle 80 turns, the pair of front casters 6a, 6b can be turned in the same direction as the rotation direction of the connecting bar 4, while the pair of rear casters 8a, 8b can be turned in the opposite direction to the pair of front casters 6a, 6b, so that the turning ability of the bogie 100D can be improved. Furthermore, because the front steering link arm 22 and the pair of front casters 6a, 6b, and the rear steering link arm 24 and the pair of rear casters 8a, 8b are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism, when the bogie 100D turns, it is possible to ensure an appropriate difference in rotation angle between the inside front casters 6a, 6b and rear casters 8a, 8b and the outside front casters 6a, 6b and rear casters 8a, 8b. This makes it possible to stabilize the turning behavior of the bogie 100D. [Example]

[0092] Next, a bogie 200 of a third embodiment will be described. FIG. 23 is a configuration diagram showing an outline of the configuration of the bogie 200 of the third embodiment. The bogie 200 of the third embodiment has the same configuration as the bogie 1 of the first embodiment except that, compared to the bogie 1 of the first embodiment, the pair of front casters 6a, 6b and the pair of rear casters 8a, 8b are changed to a pair of front steering wheels 206a, 206b and a pair of rear steering wheels 208a, 208b, and accordingly, the swivel brackets 40, 42, 44, 46 are changed to steering knuckles 240, 242, 244, 246, and the front steering link arm 22 is changed to front steering link arms 221, 223. Therefore, in order to avoid redundant explanation, the components of the bogie 200 of the third embodiment that correspond to the components of the bogie 1 of the first embodiment are denoted by the same reference numerals, and detailed explanations thereof will be omitted. The front steering wheels 206a, 206b correspond to the "first front steering wheel" and the "second front steering wheel" in the present invention, respectively, and the rear steering wheels 208a, 208b are an example of an embodiment corresponding to the "first rear steering wheel" and the "second rear steering wheel" in the present invention, respectively.

[0093] 23, the connecting bar 4 has a rotation axis Pa1 and is supported by the front section 10 so as to be rotatable (swingable) in the left-right direction about the rotation axis Pa1. The rotation axis Pa1 is disposed at the center in the extension direction of the front section 10. In other words, the connecting bar 4 can be said to be disposed at the center in the extension direction of the front section 10 so as to be rotatable (swingable) in the left-right direction.

[0094] 23, the pair of front steering wheels 206a, 206b and the pair of rear steering wheels 208a, 208b are rotatably supported by steering knuckles 240, 244 and steering knuckles 244, 246, respectively. The steering knuckles 240, 244 and the steering knuckles 244, 246 have turning axes Sa1, Sa2 and turning axes Sa3, Sa4, respectively, and support the pair of front steering wheels 206a, 206b and the pair of rear steering wheels 208a, 208b on the bogie body 2 so that the pair of front steering wheels 206a, 206b and the pair of rear steering wheels 208a, 208b can turn around the turning axes Sa1, Sa2 and the turning axes Sa3, Sa4. As shown in FIGS. 23 and 24, the steering knuckles 240, 244 and the steering knuckles 244, 246 are respectively integrated with knuckle arms 241, 243 and knuckle arms 245, 247.

[0095] As shown in Figure 23, the knuckle arms 241, 243 extend rearward at an incline approaching each other. Connection portions 240a, 242a are disposed at the tips of the knuckle arms 241, 243, respectively, and one end of the front steering link arms 221, 223 is rotatably connected to the knuckle arms 241, 243 via the connection portions 240a, 242a. In other words, the front steering link arms 221, 223 and the pair of front steering wheels 206a, 206b are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism. The other ends of the front steering link arms 221, 223 are rotatably connected to the connecting bar 4 via the connection portions 221a, 223a. Here, connection portion 27 between one end of first link arm 26 and connecting bar 4 is disposed on the opposite side of connection portions 221a, 223a from the side on which rotation axis Pa1 is disposed. In other words, it can be said that the rotation axis Pa1, connection portions 221a, 223a, and connection portion 27 are disposed in this order from the front side of front section 10 (the front side in the longitudinal direction of connecting bar 4). The other end of first link arm 26 is rotatably connected to first rotating lever 28.

[0096] 23, the knuckle arms 245, 247 extend forward at an inclination that brings them closer to each other. Connection portions 244a, 246a are disposed at the tips of the knuckle arms 245, 247, respectively, and both ends of the rear steering link arm 24 are rotatably connected to the knuckle arms 245, 247 at the connection portions 244a, 246a. In other words, it can be said that the rear steering link arm 24 and the pair of rear steering wheels 208a, 208b are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism.

[0097] The bogie 200 of the third embodiment also has the same effect as the bogie 1 of the first embodiment, that is, since the automated guided vehicle 82 can enter the inner region 70 of the bogie 200, the work of transferring the load L to the bogie body 2 can be easily and reliably performed, and since the four-wheel steering mechanism 20 is arranged so as not to enter at least the inner region 70, the entry of the automated guided vehicle 82 is not obstructed during the work of transferring the load L to and from the bogie 200. Furthermore, as the automated guided vehicle 80 turns, the pair of front steering wheels 206a, 206b can be turned in the same direction as the rotation direction of the connecting bar 4, while the pair of rear steering wheels 208a, 208b can be turned in the opposite direction to the pair of front steering wheels 206a, 206b, so the turning performance of the bogie 200 can be improved. Furthermore, because the front steering link arms 221, 223 and the pair of front steering wheels 206a, 206b, and the rear steering link arm 24 and the pair of rear steering wheels 208a, 208b are connected in an arrangement that satisfies the geometric conditions of the Ackermann mechanism, it is possible to ensure an appropriate difference in rotation angle between the inside front steering wheels 206a, 206b and rear steering wheels 208a, 208b and the outside front steering wheels 206a, 206b and rear steering wheels 208a, 208b when the bogie 200 turns. This makes it possible to stabilize the turning behavior of the bogie 200.

[0098] In the third embodiment, the rotation axis Pa1, the connection portions 221a, 223a, and the connection portion 27 are arranged in this order from the front side in the longitudinal direction of the connecting bar 4, but this is not limiting. When changing the arrangement order of the rotation axis Pa1, the connection portions 221a, 223a, and the connection portion 27, the extension direction of the knuckle arms 241, 243 can be appropriately changed to connect the front steering link arms 221, 223 and the pair of front steering wheels 206a, 206b in an arrangement that satisfies the geometric conditions of the Ackermann mechanism.

[0099] In the third embodiment, the connecting portion 37, the elongated hole 36a (connection pin 24a), and the rotation axis Pa4 are arranged in this order from the front side in the longitudinal direction of the rotating bar 36, but this is not limiting. When the arrangement order of the connecting portion 37, the elongated hole 36a (connection pin 24a), and the rotation axis Pa4 is changed, the extending direction of the knuckle arms 245, 247 can be appropriately changed to connect the rear steering link arm 24 and the pair of rear steering wheels 208a, 208b in an arrangement that satisfies the geometric conditions of the Ackermann mechanism.

[0100] The present embodiment shows an example of a mode for carrying out the present invention, and therefore the present invention is not limited to the configuration of the present embodiment.

[0101] <Additional Notes> In view of the above-mentioned gist of the invention, the bogie according to the present invention can be configured in the following aspects. (Aspect 1) "A dolly towed by a towing vehicle, a carriage body that is substantially U-shaped in plan view, having a first portion that has an upper surface on which a load can be placed and that has a longitudinal direction, a second portion that extends substantially parallel to the first portion at a position separated by a predetermined distance from the first portion in a direction that intersects with the extension direction of the first portion, and a third portion that extends in a direction that intersects with the extension direction of the first and second portions and connects the first and second portions; first and second front steering wheels having first and second front pivot axes extending in a direction perpendicular to the upper surface and supported on the bogie body so as to be rotatable about the first and second front pivot axes; first and second rear steering wheels having first and second rear pivot axes extending in a direction perpendicular to the upper surface and supported on the bogie body so as to be rotatable about the first and second rear pivot axes; a coupling section that has a first rotation axis that is perpendicular to the upper surface and passes through a center position between the first and second front steering wheels, the coupling section being supported by the bogie body so as to be rotatable about the first rotation axis along an imaginary plane that is parallel to the upper surface, and that is connectable to the towing vehicle; a four-wheel steering mechanism that is mechanically connected to the first and second front steering wheels, the first and second rear steering wheels, and the coupling portion so as to be able to steer the first and second front steering wheels and the first and second rear steering wheels, and that is positioned so as not to intrude into at least an inner region surrounded by the first, second, and third portions; A trolley equipped with (Aspect 2) "The four-wheel steering mechanism is a front steering link arm rotatably connected to the connecting portion, the first front steering wheel, and the second front steering wheel so as to be able to turn the first and second front steering wheels based on the rotational movement of the connecting portion; a rear steering link arm rotatably connected to each of the first and second rear steering wheels so as to allow the first and second rear steering wheels to turn; a transmission mechanism that mechanically connects the connecting portion and the rear steering link arm so as to turn the first and second rear steering wheels in a direction opposite to the turning direction of the first and second front steering wheels based on the rotational movement of the connecting portion; It has The front steering link arm, the rear steering link arm, and the transmission mechanism are arranged so as not to intrude into at least the inner region. The dolly according to aspect 1. (Aspect 3) "The first front steering wheel is disposed at one end of the first portion in the extending direction, the second front steering wheel is disposed in an intersection region between the first portion and the third portion; The first rear steering wheel is disposed at one end of the second portion in an extending direction, the second rear steering wheel is disposed in an intersection region between the second portion and the third portion, the connecting portion is supported by the first portion so as to be rotatable around the first rotation axis, the front steering link arm is positioned to extend along the first portion; the rear steering link arm is positioned to extend along the second portion; The transmission mechanism includes: a first link arm having an elongated shape with a first end and a second end and disposed to extend along the first portion; a connecting link arm having an elongated shape with a third end and a fourth end and disposed to extend along the third portion; It has the first link arm has a first end pivotally connected to the connecting portion so as to move along the first portion in response to the pivotal movement of the connecting portion; The connecting link arm has a third end pivotally connected directly or indirectly to the second end to convert movement of the first link arm along the first portion into movement along the third portion, and a fourth end pivotally connected directly or indirectly to the rear steering link arm to convert movement along the third portion into movement of the rear steering link arm along the second portion. The dolly according to aspect 2. (Aspect 4) "The transmission mechanism is a second link arm having an elongated shape with a fifth end and a sixth end and disposed to extend along the second portion; a rotation unit having a second rotation axis that is perpendicular to the upper surface and passes through a center position between the first and second rear steering wheels; First and second pivot levers; and the second link arm has the fifth end rotatably connected to the rotating portion, the rotating portion is supported by the second portion so as to be rotatable about the second rotation axis along an imaginary plane parallel to the upper surface, the first pivot lever has a first connection portion pivotally connected to the second end portion, a second connection portion pivotally connected to the third end portion, and a third pivot axis, and is supported by the third portion pivotally about the third pivot axis to convert movement of the first link arm along the first portion into movement of the connecting link arm along the third portion; the first connection portion, the second connection portion, and the third rotation axis are disposed in a positional relationship in which a first imaginary line connecting the first connection portion and the third rotation axis intersects with a second imaginary line connecting the second connection portion and the third rotation axis, the second pivot lever has a third connection portion pivotally connected to the fourth end portion, a fourth connection portion pivotally connected to the sixth end portion, and a fourth pivot axis, and is supported by the third portion pivotally about the fourth pivot axis to convert movement of the connecting link arm along the third portion into movement of the second link arm along the second portion; the third connection portion, the fourth connection portion, and the fourth rotation axis are disposed in a positional relationship in which a third imaginary line connecting the third connection portion and the fourth rotation axis intersects with a fourth imaginary line connecting the fourth connection portion and the fourth rotation axis, The rear steering link arm is pivotally connected to the pivot portion. The cart according to the third aspect. (Aspect 5) "The transmission mechanism is a second link arm having an elongated shape with a fifth end and a sixth end and disposed to extend along the second portion; a rotation unit having a second rotation axis that is perpendicular to the upper surface and passes through a center position between the first and second rear steering wheels; and the second link arm has the fifth end rotatably connected to the rotating portion, the rotating portion is supported by the second portion so as to be rotatable about the second rotation axis along an imaginary plane parallel to the upper surface, the connecting link arm has a fifth pivot axis disposed between the third end and the fourth end, the third end being pivotally connected to the second end and the fourth end being pivotally connected to the sixth end, and the connecting link arm being supported on the third portion so as to be pivotable about the fifth pivot axis, to convert movement of the first link arm along the first portion into movement of the second link arm along the second portion; The rear steering link arm is pivotally connected to the pivot portion. The cart according to the third aspect. (Aspect 6) "The transmission mechanism further includes first and second rotary levers, the first pivot lever has a first connection portion pivotally connected to the second end portion, a second connection portion pivotally connected to the third end portion, and a third pivot axis, and is supported by the third portion pivotally about the third pivot axis to convert movement of the first link arm along the first portion into movement of the connecting link arm along the third portion; the first connection portion, the second connection portion, and the third rotation axis are disposed in a positional relationship in which a first imaginary line connecting the first connection portion and the third rotation axis intersects with a second imaginary line connecting the second connection portion and the third rotation axis, the second pivot lever has a fifth connection portion pivotally connected to the fourth end portion, a sixth connection portion pivotally connected to the rear steering link arm, and a sixth pivot axis, and is pivotally engaged with the second rear steering wheel about the sixth pivot axis to convert movement of the connection link arm along the third portion into movement of the rear steering link arm along the second portion; the fifth connection portion, the sixth connection portion, and the sixth rotation axis are disposed in a positional relationship in which a fifth imaginary line connecting the fifth connection portion and the sixth rotation axis intersects with a sixth imaginary line connecting the sixth connection portion and the sixth rotation axis, The sixth pivot axis is disposed coaxially with the second rear pivot axis. The cart according to the third aspect. (Aspect 7) The front steering link arm is connected to the first and second front steering wheels so as to turn the first and second front steering wheels in the same direction as the rotation direction of the connecting portion. The dolly according to any one of Aspects 2 to 6. (Aspect 8) The front steering link arm is connected to the coupling portion on the side opposite to the side where the second portion is disposed with respect to the first rotation axis, and is connected to the first and second front steering wheels on the side opposite to the side where the second portion is disposed with respect to the first and second front pivot axes. The cart according to aspect 7. (Aspect 9) "The first and second front steering wheels and the front steering link arm are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism, The first and second rear steering wheels and the rear steering link arm are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism. The dolly according to any one of Aspects 2 to 8. [Explanation of symbols]

[0102] 1. Cart (cart) 1A Dolly (Dolly) 1B Cart (Cart) 1C Cart (Cart) 1D dolly (trolley) 1E Dolly (Dolly) 1F Trolley (trolley) 2. Cart body (car body) 2a Top surface (Top surface) 4 Connecting bar (connecting part) 4a long hole 6a Front caster (first front steering wheel) 6b Front caster (second front steering wheel) 8a Rear caster (first rear steering wheel) 8b Rear caster (second rear steering wheel) 10 Front part (1st part) 12 Rear part (second part) 14 Connecting part (3rd part) 20 Four-wheel steering mechanism (four-wheel steering mechanism) 21 Front steering link arm (front steering link arm) 21a connecting pin 22 Front steering link arm (front steering link arm) 22a connecting pin 23 Front steering link arm (front steering link arm) 23a connecting pin 24 Rear steering link arm (rear steering link arm) 24a connecting pin 26 First link arm (transmission mechanism, first link arm) 27 Connection 28 First rotating lever (transmission mechanism, first rotating lever) 28a Connection part (first connection part) 28b Connection part (second connection part) 30 Connecting link arm (transmission mechanism, connecting link arm) 31 Connection part (5th connection part) 32 Second rotating lever (transmission mechanism, second rotating lever) 32a Connection part (third connection part) 32b Connection part (fourth connection part) 34 Second link arm (transmission mechanism, second link arm) 36 Rotating bar (transmission mechanism, rotating part) 36a long hole 37 Connection 40 Swivel bracket 40a connection 42 Swivel bracket 42a Connection 44 Swivel bracket 44a Connection 46 Swivel bracket 46a Connection 70 Inner area 80 Automated Guided Vehicle (Tow Truck) 82 Automated Guided Vehicle 100 carts (carts) 100A dolly (dolly) 100B dolly (dolly) 100C dolly (dolly) 100D dolly (dolly) 130 Connecting link arm (transmission mechanism, connecting link arm) 130a Pivot axis (fifth pivot axis) 130b Connection 130c connection 200 carts (carts) 206a Front steering wheel (first front steering wheel) 206b Front steering wheel (2nd front steering wheel) 208a Rear steering wheel (first rear steering wheel) 208b Rear steering wheel (second rear steering wheel) 221 Front steering link arm (Front steering link arm) 221a Connection 223 Front steering link arm (Front steering link arm) 223a Connection 240 Steering knuckle 240a connection 241 Knuckle Arm 242 Steering knuckle 242a Connection 243 Knuckle Arm 244 Steering knuckle 245 Knuckle Arm 246 Steering knuckle 247 Knuckle Arm 460 Swivel bracket 460a Connection part (6th connection part) L Load (load) Pa1 Rotation axis (first rotation axis) Pa2 rotation axis (3rd rotation axis) Pa3 rotation axis (4th rotation axis) Pa4 Rotation axis (second rotation axis) Sa1 Swivel axis (first front swivel axis) Sa2 Swivel axis (second front swivel axis) Sa3 Swivel axis (first rear swivel axis) Sa4 Swivel axis (2nd rear swivel axis, 6th rotation axis) VL1 Virtual line (first virtual line) VL2 Virtual line (second virtual line) VL3 Virtual line (third virtual line) VL4 Virtual line (4th virtual line) VL5 Virtual Line (5th Virtual Line) VL6 Virtual Line (6th Virtual Line)

Claims

1. A dolly towed by a towing vehicle, a carriage body having a generally U-shape in plan view, the carriage body having a first portion having an upper surface on which a load can be placed and a longitudinal direction, a second portion extending generally parallel to the first portion at a position spaced a predetermined distance from the first portion in a direction intersecting the extension direction of the first portion, and a third portion extending in a direction intersecting the extension direction of the first and second portions and connecting the first and second portions; first and second front steering wheels having first and second front pivot axes extending in a direction perpendicular to the upper surface and supported on the bogie body so as to be rotatable about the first and second front pivot axes; first and second rear steering wheels having first and second rear pivot axes extending in a direction perpendicular to the upper surface and supported on the bogie body so as to be rotatable about the first and second rear pivot axes; a coupling section that has a first rotation axis that is perpendicular to the upper surface and passes through a center position between the first and second front steering wheels, the coupling section being supported by the bogie body so as to be rotatable about the first rotation axis along an imaginary plane that is parallel to the upper surface, and that is connectable to the towing vehicle; a four-wheel steering mechanism that is mechanically connected to the first and second front steering wheels, the first and second rear steering wheels, and the coupling portion so as to be able to steer the first and second front steering wheels and the first and second rear steering wheels, and that is positioned so as not to intrude into at least an inner region surrounded by the first, second, and third portions; Equipped with The four-wheel steering mechanism includes: a front steering link arm rotatably connected to the connecting portion, the first front steering wheel, and the second front steering wheel so as to be able to turn the first and second front steering wheels based on the rotational movement of the connecting portion; a rear steering link arm pivotally connected to each of the first and second rear steering wheels so as to allow the first and second rear steering wheels to turn; a transmission mechanism that mechanically connects the connecting portion and the rear steering link arm so as to turn the first and second rear steering wheels in a direction opposite to the turning direction of the first and second front steering wheels based on the rotational movement of the connecting portion; It has the front steering link arm is connected to the connecting portion on the side opposite to the side on which the second portion is disposed with respect to the first rotation axis so as to turn the first and second front steered wheels in the same direction as the rotation direction of the connecting portion, and is connected to the first and second front steered wheels on the side opposite to the side on which the second portion is disposed with respect to the first and second front pivot axes, The front steering link arm, the rear steering link arm, and the transmission mechanism are arranged so as not to intrude into at least the inner region. Cart.

2. the first front steering wheel is disposed at one end of the first portion in an extension direction, the second front steering wheel is disposed in an intersection region between the first portion and the third portion; the first rear steering wheel is disposed at one end of the second portion in an extending direction, the second rear steering wheel is disposed in an intersection region between the second portion and the third portion; the connecting portion is supported by the first portion so as to be rotatable about the first rotation axis, the front steering link arm is positioned to extend along the first portion; the rear steering link arm is positioned to extend along the second portion; The transmission mechanism includes: a first link arm having an elongated shape with a first end and a second end and disposed to extend along the first portion; a connecting link arm having an elongated shape with a third end and a fourth end and disposed to extend along the third portion; It has the first link arm has a first end pivotally connected to the connecting portion so as to move along the first portion in response to pivotal movement of the connecting portion; The connecting link arm has a third end pivotally connected directly or indirectly to the second end to convert movement of the first link arm along the first portion into movement along the third portion, and a fourth end pivotally connected directly or indirectly to the rear steering link arm to convert movement along the third portion into movement of the rear steering link arm along the second portion. The carriage according to claim 1 .

3. The transmission mechanism includes: a second link arm having an elongated shape with a fifth end and a sixth end and disposed to extend along the second portion; a rotation unit having a second rotation axis that is perpendicular to the upper surface and passes through a center position between the first and second rear steering wheels; First and second pivot levers; and the second link arm has the fifth end rotatably connected to the rotating portion, the rotating portion is supported by the second portion so as to be rotatable about the second rotation axis along an imaginary plane parallel to the upper surface, the first pivot lever has a first connection portion pivotally connected to the second end portion, a second connection portion pivotally connected to the third end portion, and a third pivot axis, and is supported by the third portion pivotally about the third pivot axis to convert movement of the first link arm along the first portion into movement of the connecting link arm along the third portion; the first connection portion, the second connection portion, and the third rotation axis are disposed in a positional relationship in which a first imaginary line connecting the first connection portion and the third rotation axis intersects with a second imaginary line connecting the second connection portion and the third rotation axis, the second pivot lever has a third connection portion pivotally connected to the fourth end portion, a fourth connection portion pivotally connected to the sixth end portion, and a fourth pivot axis, and is supported by the third portion pivotally about the fourth pivot axis to convert movement of the connecting link arm along the third portion into movement of the second link arm along the second portion; the third connection portion, the fourth connection portion, and the fourth rotation axis are disposed in a positional relationship in which a third imaginary line connecting the third connection portion and the fourth rotation axis intersects with a fourth imaginary line connecting the fourth connection portion and the fourth rotation axis, The rear steering link arm is pivotally connected to the pivot portion. The carriage according to claim 2.

4. A bogie towed by a towing vehicle, a carriage body having a generally U-shape in plan view, the carriage body having a first portion having an upper surface on which a load can be placed and a longitudinal direction, a second portion extending generally parallel to the first portion at a position spaced a predetermined distance from the first portion in a direction intersecting the extension direction of the first portion, and a third portion extending in a direction intersecting the extension direction of the first and second portions and connecting the first and second portions; first and second front steering wheels having first and second front pivot axes extending in a direction perpendicular to the upper surface and supported on the bogie body so as to be rotatable about the first and second front pivot axes; first and second rear steering wheels having first and second rear pivot axes extending in a direction perpendicular to the upper surface and supported on the bogie body so as to be rotatable about the first and second rear pivot axes; a coupling section that has a first rotation axis that is perpendicular to the upper surface and passes through a center position between the first and second front steering wheels, the coupling section being supported by the bogie body so as to be rotatable about the first rotation axis along an imaginary plane that is parallel to the upper surface, and that is connectable to the towing vehicle; a four-wheel steering mechanism that is mechanically connected to the first and second front steering wheels, the first and second rear steering wheels, and the coupling portion so as to be able to steer the first and second front steering wheels and the first and second rear steering wheels, and that is positioned so as not to intrude into at least an inner region surrounded by the first, second, and third portions; Equipped with The four-wheel steering mechanism includes: a front steering link arm rotatably connected to the connecting portion, the first front steering wheel, and the second front steering wheel so as to be able to turn the first and second front steering wheels based on the rotational movement of the connecting portion; a rear steering link arm pivotally connected to each of the first and second rear steering wheels so as to allow the first and second rear steering wheels to turn; a transmission mechanism that mechanically connects the connecting portion and the rear steering link arm so as to turn the first and second rear steering wheels in a direction opposite to the turning direction of the first and second front steering wheels based on the rotational movement of the connecting portion; It has the first front steering wheel is disposed at one end of the first portion in an extension direction, the second front steering wheel is disposed in an intersection region between the first portion and the third portion; the first rear steering wheel is disposed at one end of the second portion in an extending direction, the second rear steering wheel is disposed in an intersection region between the second portion and the third portion; the connecting portion is supported by the first portion so as to be rotatable about the first rotation axis, the front steering link arm is positioned to extend along the first portion; the rear steering link arm is positioned to extend along the second portion; The transmission mechanism includes: a first link arm having an elongated shape with a first end and a second end and disposed to extend along the first portion; a connecting link arm having an elongated shape with a third end and a fourth end and disposed to extend along the third portion; a second link arm having an elongated shape with a fifth end and a sixth end and disposed to extend along the second portion; a rotation unit having a second rotation axis that is perpendicular to the upper surface and passes through a center position between the first and second rear steering wheels; It has the first link arm has a first end pivotally connected to the connecting portion so as to move along the first portion in response to pivotal movement of the connecting portion; the second link arm has the fifth end rotatably connected to the rotating portion, the rotating portion is supported by the second portion so as to be rotatable about the second rotation axis along an imaginary plane parallel to the upper surface, the connecting link arm has a fifth pivot axis disposed between the third end and the fourth end, the third end being pivotally connected to the second end and the fourth end being pivotally connected to the sixth end, and the connecting link arm being supported by the third portion so as to be pivotable about the fifth pivot axis, to convert movement of the first link arm along the first portion into movement of the second link arm along the second portion; the rear steering link arm is rotatably connected to the rotating portion, The front steering link arm, the rear steering link arm, and the transmission mechanism are arranged so as not to intrude into at least the inner region. Cart.

5. A bogie towed by a towing vehicle, a carriage body having a generally U-shape in plan view, the carriage body having a first portion having an upper surface on which a load can be placed and a longitudinal direction, a second portion extending generally parallel to the first portion at a position spaced a predetermined distance from the first portion in a direction intersecting the extension direction of the first portion, and a third portion extending in a direction intersecting the extension direction of the first and second portions and connecting the first and second portions; first and second front steering wheels having first and second front pivot axes extending in a direction perpendicular to the upper surface and supported on the bogie body so as to be rotatable about the first and second front pivot axes; first and second rear steering wheels having first and second rear pivot axes extending in a direction perpendicular to the upper surface and supported on the bogie body so as to be rotatable about the first and second rear pivot axes; a coupling section that has a first rotation axis that is perpendicular to the upper surface and passes through a center position between the first and second front steering wheels, the coupling section being supported by the bogie body so as to be rotatable about the first rotation axis along an imaginary plane that is parallel to the upper surface, and that is connectable to the towing vehicle; a four-wheel steering mechanism that is mechanically connected to the first and second front steering wheels, the first and second rear steering wheels, and the coupling portion so as to be able to steer the first and second front steering wheels and the first and second rear steering wheels, and that is positioned so as not to intrude into at least an inner region surrounded by the first, second, and third portions; Equipped with The four-wheel steering mechanism includes: a front steering link arm rotatably connected to the connecting portion, the first front steering wheel, and the second front steering wheel so as to be able to turn the first and second front steering wheels based on the rotational movement of the connecting portion; a rear steering link arm pivotally connected to each of the first and second rear steering wheels so as to allow the first and second rear steering wheels to turn; a transmission mechanism that mechanically connects the connecting portion and the rear steering link arm so as to turn the first and second rear steering wheels in a direction opposite to the turning direction of the first and second front steering wheels based on the rotational movement of the connecting portion; It has the first front steering wheel is disposed at one end of the first portion in an extension direction, the second front steering wheel is disposed in an intersection region between the first portion and the third portion; the first rear steering wheel is disposed at one end of the second portion in an extending direction, the second rear steering wheel is disposed in an intersection region between the second portion and the third portion; the connecting portion is supported by the first portion so as to be rotatable about the first rotation axis, the front steering link arm is positioned to extend along the first portion; the rear steering link arm is positioned to extend along the second portion; The transmission mechanism includes: a first link arm having an elongated shape with a first end and a second end and disposed to extend along the first portion; a connecting link arm having an elongated shape with a third end and a fourth end and disposed to extend along the third portion; First and second pivot levers; It has the first link arm has a first end pivotally connected to the connecting portion so as to move along the first portion in response to pivotal movement of the connecting portion; the first pivot lever has a first connection portion pivotally connected to the second end portion, a second connection portion pivotally connected to the third end portion, and a third pivot axis, and is supported by the third portion pivotally about the third pivot axis to convert movement of the first link arm along the first portion into movement of the connecting link arm along the third portion; the first connection portion, the second connection portion, and the third rotation axis are disposed in a positional relationship in which a first imaginary line connecting the first connection portion and the third rotation axis intersects with a second imaginary line connecting the second connection portion and the third rotation axis, the second pivot lever has a fifth connection portion pivotally connected to the fourth end portion, a sixth connection portion pivotally connected to the rear steering link arm, and a sixth pivot axis, and is pivotally engaged with the second rear steering wheel about the sixth pivot axis to convert movement of the connection link arm along the third portion into movement of the rear steering link arm along the second portion; the fifth connection portion, the sixth connection portion, and the sixth rotation axis are disposed in a positional relationship in which a fifth imaginary line connecting the fifth connection portion and the sixth rotation axis intersects with a sixth imaginary line connecting the sixth connection portion and the sixth rotation axis, The sixth rotation axis is disposed coaxially with the second rear rotation axis, The front steering link arm, the rear steering link arm, and the transmission mechanism are arranged so as not to intrude into at least the inner region. Cart.

6. The front steering link arm is connected to the first and second front steering wheels so as to turn the first and second front steering wheels in the same direction as the rotation direction of the connecting portion.

6. The bogie according to claim 4 or 5.

7. The front steering link arm is connected to the coupling portion on a side opposite to the side on which the second portion is disposed with respect to the first rotation axis, and is connected to the first and second front steering wheels on a side opposite to the side on which the second portion is disposed with respect to the first and second front pivot axes. The truck according to claim 6.

8. the first and second front steering wheels and the front steering link arm are connected in an arrangement that satisfies the geometric conditions of an Ackermann mechanism, The first and second rear steering wheels and the rear steering link arm are connected in a configuration that satisfies the geometric conditions of the Ackermann mechanism. A bogie according to any one of claims 1 to 5.

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