Automated guided vehicle

Abstract

To provide an unmanned conveyance truck capable of reducing vibration and noise during traveling.SOLUTION: An unmanned conveyance truck 1 includes a truck main body 2 elongated in the fore-and-aft direction, a pair of right and left drive wheels 3, 3 arranged in an intermediate part in the fore-and-aft direction of the truck main body 2 with an interval s1 in the lateral direction orthogonal to the fore-and-aft direction, a pair of right and left front driven wheels 5, 5 provided on the front side of the drive wheels 3, 3 of the truck main body 2, and a single rear driven wheel 6 provided on the rear side of the drive wheels 3, 3 of the truck main body 2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an automated guided vehicle. [Background technology]

[0002] For example, in mail-order warehouses, supply chain logistics centers, airport baggage systems, and multi-product manufacturing facilities, conveyor systems equipped with large-scale crossbelt sorters or slat conveyors have traditionally been widely used. To accommodate e-commerce and other trends that involve a diverse range of products and orders from multiple locations, facility layout changes are becoming commonplace, making it difficult for fixed conveyor systems to keep up. To provide as much flexibility as possible, automated guided vehicles (AGVs) are increasingly being used in warehouses and logistics centers as the running parts of sorting robots, which load items at loading points, transport them to unloading points, and then unload them at unloading points. In such applications, AGVs move in one direction, but by starting, accelerating, and turning as quickly as possible, they can reduce the takt time required to transport workpieces per unit of time. The unmanned transport vehicle disclosed in the following Patent Document 1 (hereinafter also referred to as the "prior art") comprises a vehicle body (carriage body) that is elongated in the fore-and-aft direction, a pair of drive wheels arranged at a distance in the left-right direction perpendicular to the fore-and-aft direction at the midpoint of the cart body in the fore-and-aft direction, a pair of left and right front driven wheels provided in front of the drive wheels, and a pair of left and right rear driven wheels provided behind the drive wheels.

[0003] In addition, a vehicle is also known in which a pair of fixed caster driven wheels, which are provided on the left and right sides of the middle of the fore-and-aft direction of the bogie body, and drive steering wheels are provided in front of and behind the driven wheels (see, for example, Figure 3 of Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-286337 [Patent Document 2] Patent No. 5481994 Summary of the Invention [Problem to be solved by the invention]

[0005] One method for shortening the transport time of transported goods in mail-order warehouses, supply chain logistics centers, airport baggage systems, and multi-product manufacturing facilities is to increase the travel speed of automated guided vehicles. However, the conventional automated guided vehicles described above have a problem in that increasing their travel speed increases vibration and noise while traveling. This is because the floors on which such automated guided vehicles travel are not necessarily flat; rather, the floor is often uneven, and even if the four or six wheels are aligned, some wheels will inevitably float. When traveling in this condition, for example, the wheel alignment line of the two inner, front and rear drive wheels of the four wheels acts as an axis. During travel (especially during acceleration), the left and right driven wheels, which lightly contact the road surface, alternately float off the road surface. This shifts the center of gravity of the triangle formed by the remaining three driven wheels that are in contact with the road surface, or the center of gravity of the triangle formed by one driven wheel and a drive wheel, which is thought to cause the automated guided vehicle to become unstable.

[0006] The present invention has been made to solve the above-mentioned problems, and has an object to provide an unmanned transport vehicle that can reduce vibration and noise while traveling. [Means for solving the problem]

[0007] The automated guided vehicle according to the present invention comprises a carriage body elongated in the front-rear direction. The carriage body comprises a pair of left and right drive wheels arranged at an intermediate portion of the carriage body in the front-rear direction with a gap therebetween in the left-right direction perpendicular to the front-rear direction, a pair of left and right front driven wheels provided in front of the drive wheels of the carriage body, and a single rear driven wheel provided behind the drive wheel of the carriage body. The carriage body comprises a pair of left and right first frames arranged at an intermediate portion of the carriage body in the front-rear direction with a gap therebetween in the left-right direction, , transportationThe vehicle comprises a top plate on which a carrying section for loading and unloading goods is installed, and a second frame supporting the top plate. The first frame has a flat central section that holds the drive wheels, an arm section that extends downward from the front end of the central section and is swingably connected to the second frame, and a support section provided at the rear end of the central section. A spring that biases the drive wheels toward a running surface is compressed and installed between the support section and the second frame, and the front driven wheels and the rear driven wheels are attached to the underside of the second frame at a distance in the front-to-rear direction.

[0008] In the present invention, If a line passing through the center of the bogie body in the left-right direction and extending in the front-rear direction is defined as a center line, the rear driven wheels may be disposed offset to the left or right from the center line. In this case, the amount of offset of the rear driven wheels from the center line may be set within a range of 1 / 2 to 1 / 3 of the distance from the center line to the drive wheels, and within a range in which the rear driven wheels are positioned inside the front driven wheels in the left-right direction. [Effects of the Invention]

[0009] According to the present invention, by providing a pair of front driven wheels on the left and right in front of the drive wheels and a single rear driven wheel behind the drive wheels, the three driven wheels are always in contact with the running surface while the unmanned traveling vehicle is traveling, which allows the posture of the unmanned traveling vehicle to be kept stable and, as a result, vibrations and noise while traveling can be reduced. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic side view of an automated guided vehicle according to a first embodiment. [Figure 2] 1 is a schematic plan view of an automated guided vehicle according to a first embodiment. [Figure 3] FIG. 10 is a schematic plan view of an automated guided vehicle according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described with reference to the drawings. Common or corresponding elements in each drawing are designated by the same reference numerals, and descriptions thereof will be simplified or omitted. In each drawing, illustration of some components may be omitted for convenience of drawing.

[0012] Embodiment 1 Fig. 1 is a side view that schematically shows an automated guided vehicle 1 according to embodiment 1. Fig. 2 is a plan view that schematically shows the automated guided vehicle 1 according to embodiment 1. The automated guided vehicle 1 is an automatically driven vehicle that is automatically driven by a computer (not shown).

[0013] The automated guided vehicle 1 comprises a vehicle body 2 made of metal (for example, aluminum or stainless steel) that is elongated in one direction. In the following, the longitudinal direction of the vehicle body 2 is referred to as the front-rear direction, the height direction of the vehicle body 2 as the up-down direction, and the width direction of the vehicle body 2 that is perpendicular to the front-rear and up-down directions as the left-right direction. The traveling direction of the vehicle body 2, indicated by the arrow in the drawing, is referred to as the forward direction.

[0014] The bogie body 2 includes a pair of left and right first frames 21 and a second frame 22. Each first frame 21 has a flat central portion 21a that holds drive wheels 3, which will be described later. A substantially vertical arm portion 21b is integrally formed at the front end of the central portion 21a. A lower portion of the arm portion 21b is swingably connected to an arm connecting portion 22a that branches off from the second frame 22 via a connecting shaft 21c that extends in the left-right direction. A support portion 21d that is in an inverted L shape in a side view and supports a spring 7, which will be described later, is integrally formed at the rear end of the central portion 21a. The spring 7, which will be described later, is compressed between the support portion 21d and the second frame 22. Front driven wheels 5, 5 and a rear driven wheel 6, which will be described later, are attached to the underside of the second frame 22. A plurality of (four in this embodiment) support portions 23 are vertically disposed on the upper surface of the second frame 22, and a top plate 24 is supported by these support portions 23.

[0015] Although not shown, a belt conveyor serving as a carrying section for the sorting robot is installed on the top plate 24. As the belt conveyor, a known type capable of loading transported items at a loading location and unloading transported items at an unloading location can be used, and therefore further explanation will be omitted.

[0016] In this embodiment, the automated guided vehicle 1 is configured to have five running wheels. Specifically, a pair of steering-mechanism-equipped drive wheels (hereinafter referred to as "drive wheels") 3, 3 are provided in the front-rear middle of the vehicle body 2, which are arranged symmetrically with respect to a center line C1 extending in the front-rear direction. The steering mechanism may be, for example, fixed so that the rotation axes of the left and right drive wheels 3, 3 are perpendicular to the center line C1, and the left and right drive wheels 3, 3 may have different rotation speeds or change rotation directions. Therefore, illustration and description of the steering mechanism are omitted. The drive wheels 3, 3 are independently driven to rotate in a forward direction (clockwise in FIG. 1 ) or a reverse direction (counterclockwise in FIG. 1 ) by drive means 4, 4. The drive means 4, 4 are composed of motors such as servo motors. By rotating the drive wheels 3, 3 in opposite directions by the drive means 4, 4, the automated guided vehicle 1 can rotate (turn) around the center Cp between the drive wheels 3, 3. The spacing s1 between the drive wheels 3,3 is set so that the drive wheels 3,3 are located inside the rotation locus of the outer edge of the automated guided vehicle 1 when the automated guided vehicle 1 is rotated. By locating the drive wheels 3,3 in the middle in the front-to-rear direction, the first frame 21 supporting the drive means 4,4 and drive wheels 3,3, which are heavy objects, is located close to the center of rotation, and the weight of the entire frame of the automated guided vehicle 1 is distributed almost evenly between the front and rear, so the moment during rotation can be made as small as possible, and as a result, the braking performance of the automated guided vehicle 1 during rotation can be improved. Furthermore, by rotating both drive wheels 3,3 in the forward direction in synchronization, the automated guided vehicle 1 can be moved straight forward.

[0017] A pair of front driven wheels 5, 5 are provided in front of the drive wheels 3, 3 of the carriage body 2, and are arranged symmetrically about the center line C1 with a spacing s2 smaller than the spacing s1 between the drive wheels 3, 3. The spacing s2 between the front driven wheels 5, 5 is set so as not to step on an indicator affixed to the traveling surface Sr (e.g., the floor of a mail-order warehouse or a supply chain logistics center). Specifically, the spacing s2 is set to a range of 1 / 2 to 1 / 3 of the spacing s1 between the drive wheels 3, 3. Like swivel casters, the front driven wheels 5, 5 are supported by arms that support the wheels and can rotate freely 360 degrees around a rotation axis attached to the main frame of the automated guided vehicle 1. Therefore, when the drive wheels 3, 3 are rotated in opposite directions to rotate (pivot) the automated guided vehicle 1 around the center Cp between the drive wheels 3, 3, the front driven wheels 5, 5 are rotated in the direction of the arms following the rotation, helping the entire carriage to pivot.

[0018] A single rear driven wheel 6 is provided on the rear side of the drive wheels 3, 3, and is located on the center line C1. The distance d1 between the center line C2 extending in the left-right direction of the cart body 2 and the front driven wheels 5, 5 is set equal to the distance d2 between the center line C2 and the rear driven wheel 6. That is, the front driven wheels 5, 5 and the rear driven wheel 6 are arranged to form an isosceles triangle. The front driven wheels 5, 5 and the rear driven wheel 6 are each formed, for example, by a swivel caster. Like the front driven wheels 5, 5, the rear driven wheel 6 is also supported by an arm supporting an axle that supports the wheel, with the part attached to the main body frame of the automated guided vehicle 1 as the rotation axis, and is pivoted 360 degrees. Therefore, when the drive wheels 3, 3 are rotated in opposite directions to rotate the automated guided vehicle 1 around the center Cp between the drive wheels 3, 3, the rear driven wheel 6 is moved in the direction of the arm following the rotation, helping the entire cart to turn.

[0019] The two drive wheels 3, 3 are each biased toward the running surface Sr by a coil spring 7. The first frame 21 on which the wheels are pivoted and the spring (coil spring) 7 located at the rear serve two purposes: to press the drive wheels 3, 3 against the ground during acceleration, and to bias the drive wheels 3, 3 to accommodate ground irregularities. However, the spring constants of the springs 7 for each purpose are different, and the role of biasing the drive wheels 3, 3 to accommodate ground irregularities becomes dominant. As a result, during acceleration, the springs 7 sink, causing the bogie body 2 to tilt backward, resulting in a significant shift in the center of gravity. A plate-shaped stopper 8 is provided on the upper surface of the center portion 21a of the first frame 21, with a predetermined gap Sp between it and the second frame 22. The gap Sp can be set appropriately taking into account the stroke length of the spring 7 and other factors. When the spring 7 displaces (compresses) by a distance corresponding to the gap Sp, the stopper 8 contacts the underside of the second frame 22, restricting further displacement (compression) of the spring 7, i.e., restricting the relative downward movement of the drive wheels 3, 3. In this case, the stopper 8 may be formed of a rubber material (e.g., nitrile rubber) with a higher damping coefficient than the spring 7. After the stopper 8 contacts the second frame 22, the displacement of the spring 7 follows the damping coefficient of the stopper 8. Therefore, when the spring 7 displaces significantly and rebounds, the rubber stopper 8 absorbs the recoil. As a result, the same effect as a shock absorber that prevents spring recoil by the resistance of oil flowing through an orifice can be achieved at a low cost. The location of the stopper 8 is not limited to the central portion 21a of the first frame 21. It may also be located on the underside of the second frame 22 facing the central portion 21a. The shape of the stopper 8 is not particularly limited as long as it can limit the relative movement of the drive wheels 3, 3, and may be a block or pillar shape.

[0020] According to this embodiment, while the automated guided vehicle 1 is traveling, particularly during acceleration when the front driven wheels 5, 5 lightly contact the running surface Sr, the front driven wheels 5, 5 and the rear driven wheels 6 always contact the running surface Sr. That is, since the three driven wheels 5, 5, 6 always contact the running surface Sr while traveling, the left and right front driven wheels 5, 5 do not alternately lift off the running surface Sr as in the conventional example. Therefore, the posture of the automated guided vehicle 1 can be maintained stable, thereby reducing vibration and noise during traveling. Furthermore, a single rear driven wheel 6 is positioned behind the drive wheels 3, 3 of the vehicle body 2, with the distance d1 between the center line C2 extending in the left-right direction of the vehicle body 2 and the front driven wheels 5, 5 and the distance d2 between the center line C2 and the rear driven wheel 6 being set equal. As a result, the rear driven wheel 6, which is positioned quite far behind the drive wheels 3, 3, uses a moment corresponding to that distance to prevent the drive wheel 3 from sinking the spring 7 on the rear side of the first frame 21 during acceleration, causing a large shift in the center of gravity of the cart body 2. This allows the automatic guided vehicle 1 to accelerate without any vibration.

[0021] Here, we consider a comparative example, which differs from the present embodiment in that the arrangement of the front and rear driven wheels is reversed. In this comparative example, a single front driven wheel is provided in front of the drive wheels, and a pair of left and right rear driven wheels are provided behind the drive wheels. According to this comparative example, as in the present embodiment, the three driven wheels are always in contact with the running surface during travel, so the driven wheels do not lift off the running surface, reducing vibration and noise during travel. However, it was confirmed that the automated guided vehicle overshoots the designated stopping position when decelerating and stopping. Furthermore, because the front driven wheels stop in a state where they are misaligned in the left-right direction, i.e., the 360-degree swinging arm supporting the rotation axis of the front driven wheels is facing away from the direction of travel, the left-right misalignment of the front driven wheels must be corrected when travel resumes.

[0022] In contrast, according to this embodiment, when the automated guided vehicle 1 decelerates and stops, the force acting on the front side of the automated guided vehicle 1 can be received by the two front driven wheels 5, 5. In this case, the front driven wheels 5, which are swivel casters, do not sink, and the moment acting on the front side by the stopping power is received by the two front driven wheels while the center of gravity does not move forward much. This allows the stopping power to be applied effectively without lurching. In the case of a single front driven wheel, no bending force is applied to the arm supporting the rotating shaft of the wheel that touches the wheel, so the automated guided vehicle 1 can remain facing the direction of travel. Therefore, the automated guided vehicle 1 can be stopped at the specified stopping position. Moreover, because the arm supporting the rotating shaft of the front driven wheels 5, 5 does not shift left or right from the direction of travel, there is no need to correct the left or right positional deviation of the front driven wheels 5, 5 when resuming travel.

[0023] Furthermore, according to this embodiment, even if a force is applied to the outer drive wheel 3 when the unmanned transport vehicle 1 turns, the displacement of the spring 7 that biases the drive wheel 3 is suppressed by the stopper 8, so that the tilt of the unmanned transport vehicle 1 can be suppressed.

[0024] Embodiment 2 FIG. 3 is a schematic plan view of an automated guided vehicle 10 according to a second embodiment. In this embodiment, the rear driven wheels 6 are offset to the left or right (left side in FIG. 3) from the center line C1. In this case, the offset amount Ao of the rear driven wheels 6 from the center line C1 is set within a range of ½ to ⅓ of the distance d3 from the center line C1 to the drive wheels 3, and within a range in which the rear driven wheels 6 are positioned inside the front driven wheels 5 in the left-right direction. In this embodiment, as in the first embodiment, the three driven wheels 5, 5, 6 always contact the running surface Sr while the automated guided vehicle 10 is traveling. However, compared to this embodiment, the automated guided vehicle 1 in which the rear driven wheels 6 are positioned on the center line C1 as in the first embodiment has a more stable posture during traveling, which allows for greater reduction in vibration and noise during traveling and provides better braking performance during deceleration. [Explanation of symbols]

[0025] 1,10 unmanned guided vehicle, 2 vehicle body, 3 driving wheel, 5 front driven wheel, 6 rear driven wheel, 7 spring, 8 stopper, Sr running surface

Claims

1. An unmanned transport vehicle having a carriage body that is long in the front-rear direction, A pair of left and right drive wheels arranged at an intermediate portion of the carriage body in the front-rear direction at an interval in the left-right direction perpendicular to the front-rear direction; A pair of left and right front driven wheels provided in front of the drive wheels of the bogie body; a single rear driven wheel provided on the rear side of the drive wheel of the bogie body; Equipped with the carriage body includes a pair of left and right first frames arranged at a longitudinal intermediate portion with a gap in the left-right direction, a top plate on which a carrying section for loading and unloading transported objects is installed, and a second frame supporting the top plate; the first frame has a flat central portion that holds the drive wheels, an arm portion that extends downward from a front end of the central portion and is swingably connected to the second frame, and a support portion that is provided at a rear end of the central portion, a spring is compressed and disposed between the support portion and the second frame to bias the drive wheel toward a traveling surface; The unmanned transport vehicle has the front driven wheels and the rear driven wheels attached to the underside of the second frame at a distance in the front-rear direction.

2. 2. The automated guided vehicle according to claim 1, wherein the rear driven wheels are arranged offset to the left or right from the center line, where the center line is a line passing through the center of the vehicle body in the left-right direction and extending in the front-rear direction.

3. 3. The automated guided vehicle according to claim 2, wherein an offset amount of the rear driven wheels from the center line is set within a range of 1 / 2 to 1 / 3 of the distance from the center line to the drive wheels, and within a range in which the rear driven wheels are positioned inside in the left-right direction of the front driven wheels.

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