JP2007283958A - Suspension device for automated guided vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quicken operation by adjusting spring strength by using cargo load and to simplify assembling and reduce the size of a device itself by making a structure simple. <P>SOLUTION: This suspension device for an automated guided vehicle comprises a pair of suspension arms 11 which are vertically swingably mounted to a vehicle body frame 2 and to which drive wheels 7 with electric motors 6 are mounted; a pair of connection rods 12 swingably connected to free end parts of the both suspension arms 11; a pair of spring units 13 fitted to the both connection rods 12 and having compression springs 13c, 13d; and a connection bar 14 having both ends which are vertically movably fitted to upper end parts of the connection rods 12 while coming-off of the both ends is prevented and are supported by the both spring units 13, displaced downwardly by receiving load of a table 4 or load of both the table 4 and cargo, and compressing the compression springs 13c, 13d of the both spring units 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is used for a self-propelled automatic guided vehicle used in a printing factory that prints newspapers and magazines, a factory that manufactures and processes various items, and a warehouse that stores materials and products. In particular, it has a table for loading a load, a plurality of casters, and a pair of motor-equipped drive wheels that can move up and down with respect to the body frame, and the pair of drive wheels are pressed against the floor surface by a spring force. The present invention relates to an improvement of a suspension device for an automatic guided vehicle that is driven on a floor surface.

  Generally, in a printing factory such as a newspaper or a magazine, a new web in a paper vault is carried into a paper feeding unit of a printing rotary press using a self-propelled automatic guided vehicle.

Conventionally, this type of automatic guided vehicle is disposed on the upper surface side of a body frame covered with a cover body, and is disposed on a table on which a web for printing is supported and placed in a horizontal posture, and on both front and rear positions of the body frame. A plurality of casters, and a pair of motor-equipped drive wheels that are disposed on both sides of the center portion of the vehicle body frame and can rotate forward and backward independently of each other, and so-called magnetic induction It is done by the method.
In other words, the automatic guided vehicle is configured to automatically travel along the magnetic tape affixed to the floor surface in the printing factory or the magnetic tape embedded in the floor while receiving control from the control device installed on the ground. By controlling the rotation direction and the number of rotations of the left and right drive wheels that are in contact with the floor surface, it is possible to perform straight traveling (forward and backward), curved traveling, spin turn, and the like.

By the way, since the automatic guided vehicle calculates the travel distance based on the rotational speed of the driving wheel and confirms the position of the automatic guided vehicle, it is necessary to always drive the ground while the driving wheel is in contact with the floor surface. .
The automatic guided vehicle is supported on the floor surface by four casters and two drive wheels. When the paper is loaded on the table, the paper is loaded on the table. The load applied to the drive wheels is completely different from when there is no load.

Therefore, in the conventional automatic guided vehicle, the driving wheel is attached to the vehicle body frame so as to be movable up and down, and a suspension device is provided between the vehicle body frame and the driving wheel, and the driving wheel is always mounted by the spring force of the suspension device. It pushes on the floor.
In addition, the suspension device has a repulsive force of a spring that pushes the driving wheel against the floor surface rather than the weight of the vehicle body when the winding wheel slips on the floor surface when the winding paper is loaded and cannot run. Is configured so that the strength of the spring can be automatically adjusted so that some casters do not rise above the floor surface (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3). .

  Therefore, the automatic guided vehicle has excellent advantages such that the automatic driving vehicle can be driven in a stable posture by optimizing the pressing force of the driving wheel against the floor surface according to the loaded weight by the suspension device. It is.

However, since the suspension device provided in the conventional automatic guided vehicle adjusts the strength of the spring using a motor, a gear transmission mechanism, a screw shaft, etc., the operation is relatively slow, and the strength of the spring is large. There was a problem that it took time to adjust the height. However, since the amount of compression of the spring must be controlled by a sensor for driving the motor, there is a problem that it takes more time for alignment and assembly.
In addition, the conventional suspension device uses a motor, a gear transmission mechanism, a screw shaft, etc. to adjust the strength of the spring, so that the structure becomes extremely complicated and the assembly becomes complicated and the cost increases. There has been a problem that the size of the apparatus itself is increased.
Japanese Patent Laid-Open No. 2002-220048 Japanese Patent No. 3162656 Japanese Patent No. 3313408

  The present invention has been made in view of such problems, and its purpose is to make it possible to adjust the spring strength by using the load of the load to speed up the operation and simplify the structure. It is an object of the present invention to provide a suspension device for an automatic guided vehicle that can simplify assembly, reduce costs, reduce the size of the device itself, and the like.

  In order to achieve the above object, a first aspect of the present invention includes a table disposed on an upper surface side of a vehicle body frame for loading a load, and a plurality of casters disposed at both front and rear positions of the vehicle body frame. A pair of motor-equipped drive wheels that are disposed on both sides of the vehicle body frame and are movable up and down with respect to the vehicle body frame. The drive wheels are pressed against the floor surface by a spring force. A suspension device for an automated guided vehicle that is driven to travel, wherein the suspension device is swingably attached to a vehicle body frame in a vertical direction, and a pair of suspension arms to which drive wheels with an electric motor are attached, and both suspensions A pair of vertical connecting rods that are swingably connected to the free end of the arm, and a compression that is attached to both connecting rods and generates spring force when compressed A pair of spring units having a pair of screws, and both ends are fitted to the upper and lower ends of the connecting rods so that they can be moved up and down and supported by the spring units. It is composed of a connecting bar that receives the load of both and displaces downward to compress the compression springs of both spring units, and the connecting bar is subjected to table load or both table load and load, and the connecting bar is displaced downward. In this case, a spring force is generated in both spring units, and both drive wheels are pressed against the floor side via the suspension arms by the spring force.

  The invention according to claim 2 of the present invention has a small spring constant in which both spring units generate a small spring force when no load is loaded on the table and lightly push the driving wheel to the floor surface via the suspension arm. An auxiliary compression spring and a main compression spring having a larger spring constant than the auxiliary compression spring that generates a large spring force when loading the table and strongly presses the driving wheel against the floor via the suspension arm. It is characterized by having.

  According to a third aspect of the present invention, the upper limit position regulation for regulating the upper limit positions of the suspension arm and the drive wheel by contacting the free end portions of both the connecting rods or both suspension arms with the upper limit position stopper provided on the body frame. The present invention is characterized in that a bolt and a lower limit position regulating bolt that abuts a lower limit position stopper provided on the vehicle body frame and regulates the lower limit position of the suspension arm and the drive wheel are provided.

A suspension system for an automatic guided vehicle according to the present invention includes a pair of suspension arms to which driving wheels with an electric motor are attached, a pair of connection rods connected to both suspension arms, and a pair of spring units attached to both connection rods. And a connecting bar that is supported by the two spring units and receives the load of the table on which the load is supported and placed, or receives both the load of the table and the load and is displaced downward to compress the compression springs of the two spring units. When the load of the table or both the table and the load is applied to the connecting bar and the connecting bar is displaced downward, the spring force is generated in both spring units, and the two driving wheels are caused to move to the suspension arms by the spring force. It is comprised so that it may be pressed to a floor surface side through, respectively.
That is, since the suspension device of the present invention adjusts the strength of the compression spring of the spring unit via the connection bar using the load of the load, when the load of the load is applied to the connection bar, The compression spring is immediately compressed and the strength of the compression spring is adjusted, so that the operation becomes extremely fast as compared with a conventional suspension device using a motor, a screw shaft or the like. However, since the pressing force of the drive wheels against the floor surface is automatically changed according to the weight of the load to be loaded, the automatic guided vehicle can be driven in a stable state (posture).
In the suspension device of the present invention, the two spring units each include an auxiliary compression spring having a small spring constant and a main compression spring having a large spring constant. A small auxiliary compression spring acts to lightly push the drive wheel to the floor, and when loading a table, the main compression spring with a large spring constant acts to push the drive wheel to the floor Since it is configured, the automatic guided vehicle can travel reliably and satisfactorily in a stable state (attitude).
Furthermore, the suspension device of the present invention is composed of a pair of suspension arms, a pair of connecting rods, a pair of spring units, and a single connecting bar. Compared with the suspension device, the structure becomes extremely simple, and the assembly can be simplified, the cost can be reduced, the device itself can be downsized, and the maintenance can be simplified. However, the upper limit position and lower limit position of the suspension arm and drive wheel are restricted by the upper limit position restriction bolt and the lower limit position restriction bolt provided at the free end of the connecting rod or suspension arm. The structure can be further simplified as compared with a conventional suspension device that restricts the upper limit position and the lower limit position of a wheel or the like.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 to 3 show an automatic guided vehicle 1 provided with a suspension device 8 according to an embodiment of the present invention. The automatic guided vehicle 1 includes, for example, a paper feeding unit and a paper of a printing press in a newspaper printing factory. The paper automatically travels along the transport path of the winding paper P (load) for printing with the storage, loads the new winding paper P in the paper storage, and transports it to the paper feed section of the printing press. It is configured to automatically run on the floor in the printing factory by a magnetic induction method.

  That is, as shown in FIGS. 1 to 3, the automatic guided vehicle 1 includes a vehicle body frame 2 made of a mold material, a plate material, and the like, a cover body 3 that covers the front, rear, left and right side surfaces, and the upper surface of the vehicle body frame 2, and a vehicle body frame. 2, a table 4 that supports and places the web P in a horizontal position, four casters 5 that are pivotably attached to both front and rear positions of the body frame 2 and are grounded to the floor surface, and a body frame A pair of drive wheels 7 with a pair of electric motors 6 (motors with a reduction gear) that are arranged opposite to each other on both sides of the central portion 2 and can rotate forward and backward independently of each other; A suspension device 8 provided between the drive wheels 7, a driving battery 9 provided on the vehicle body frame 2, a control panel (not shown) provided on the vehicle body frame 2, and a pickup coil provided on the vehicle body frame 2 A servo amplifier, a reactor (both not shown), etc., and a control device installed on the ground along a magnetic tape (not shown) affixed to the floor surface in a printing factory or a magnetic tape embedded in the floor surface ( It is configured to automatically run while receiving control from (not shown).

  The automatic guided vehicle 1 is supported on a floor surface by casters 5 disposed at four corners of a body frame 2 and is movably supported on a floor surface, and a pair of drive wheels 7 disposed at a central portion of the body frame 2. Thus, the vehicle is driven to travel on the floor surface, and the pair of drive wheels 7 travels straight forward (forward or backward) by simultaneously rotating forward or backward at the same rotational speed, and both drive wheels. By making a difference in the rotational speed of 7, it is possible to travel in a curved line, and further, a spin turn can be performed by rotating one drive wheel 7 forward and rotating the other drive wheel 7 in reverse. It can be done.

  The table 4 of the automatic guided vehicle 1 is supported by a pair of guide rails 10 provided in a vertical posture at the front end portion and the rear end portion of the vehicle body frame 2 as shown in FIG. The load of the table 4 itself and the load of the web P loaded on the table 4 can be hung on the connection bar 14 of the suspension device 8.

  The suspension device 8 according to the embodiment of the present invention automatically adjusts the pressing force of the driving wheels 7 to the floor surface according to the weight of the web P (load) and optimizes the automatic guided vehicle 1. This is for traveling in a stable posture (a posture in which all casters 5 are in contact with the floor surface), and the strength of the spring is adjusted using the weight of the load.

  That is, as shown in FIGS. 1 to 4, the suspension device 8 is attached to the vehicle body frame 2 so as to be swingable in the vertical direction, a pair of suspension arms 11 to which drive wheels 7 with an electric motor 6 are attached, and both suspensions. A pair of vertical connecting rods 12 that are swingably connected to the free end of the arm 11 and compression springs 13c and 13d that are attached to both connecting rods 12 and generate a spring force when compressed. A pair of spring units 13 and both ends are fitted to the upper ends of the connecting rods 12 so that they can be moved up and down and supported by the spring units 13. The connecting bar 14 receives both loads of the web P and is displaced downward to compress the compression springs 13c and 13d of the two spring units 13. When the load of the table 4 or the load of both the table 4 and the web P is applied and the connecting bar 14 is displaced downward, a spring force is generated in the spring units 13 and the drive wheels 7 are caused by the spring force. It is configured to be pressed against the floor surface via the suspension arm 11.

Specifically, both the suspension arms 11 are formed in a substantially inverted U shape on the side surfaces, and the base end side of the suspension arms 11 is freely rotatable via a support shaft 16 on a bracket 15 provided on the body frame 2. It is attached, and the free end side thereof moves up and down with respect to the body frame 2 around the support shaft 16. Drive wheels 7 with an electric motor 6 are attached to intermediate portions of the suspension arms 11 via brackets 17, respectively.
One suspension arm 11 is attached to the vehicle body frame 2 on the rear side of the drive wheel 7 so as to be swingable in the vertical direction, and the other suspension arm 11 is vertically mounted on the vehicle body frame 2 on the front side of the drive wheel 7. It is attached so that it can swing in the direction.

Both the connecting rods 12 are composed of a vertical shaft portion 12 b having a male screw 12 a at the upper end portion and a yoke portion 12 c provided at the lower end portion of the shaft portion 12 b, and the yoke portion 12 c is the free end of the suspension arm 11. By being rotatably attached to the portion via a connecting shaft 18, the suspension arm 11 is swingably connected to the free end portion of the suspension arm 11. The both connecting rods 12 are held in a vertical posture by fitting both end portions of the connecting bar 14 to both shaft portions 12b.
Further, as shown in FIG. 4, both the connecting rods 12 are respectively formed with female screw holes 12 d on the upper surface of the shaft portion 12 b, and bolt insertion holes 3 a formed in the cover body 3 on the upper surface side of the automatic guided vehicle 1. The manual operation bolt 19 is inserted into the shaft portion 12b and the lower end portion of the manual operation bolt 19 is screwed into the female screw hole 12d, and the manual operation bolt 19 is brought into contact with the cover body 3 on the upper surface. Is rotated upward in a direction to be screwed into the shaft portion 12b, thereby being lifted upward by a predetermined amount. By lifting both connecting rods 12, both suspension arms 11 swing upward and both drive wheels 7 are lifted from the floor surface, so that the automatic guided vehicle 1 can be moved by hand.
Further, both connecting rods 12 are provided on the body frame 2 and upper limit position regulating bolts 21 that abut upper limit position stoppers 20 provided on the body frame 2 to regulate the upper limit positions of the suspension arm 11 and the drive wheels 7. Lower limit position restricting bolts 23 that contact the lower limit position stopper 22 and restrict the lower limit position of the suspension arm 11 and the drive wheel 7 are provided.

The upper limit position restricting bolt 21 and the lower limit position restricting bolt 23 are screwed to a support plate 25 in a horizontal posture fixed to the upper surface of the yoke portion 12c of the connecting rod 12 by a bolt 24 so as to be adjustable in height. The upper end position of the suspension arm 11 and the drive wheel 7 is regulated by bringing the head of the bolt 21 into contact with the upper limit position stopper 20 provided on the vehicle body frame 2, and the lower end of the shaft portion of the lower limit position regulating bolt 23 is restricted. The lower limit position of the suspension arm 11 and the drive wheel 7 can be regulated by contacting the lower limit position stopper 22 provided on the vehicle body frame 2.
The upper limit position regulating bolt 21 lifts the connecting rod 12 with the manual operation bolt 19 and swings the suspension arm 11 upward to lift the drive wheel 7 from the floor surface. This is to prevent rocking.
Further, the lower limit position regulating bolt 23 prevents the suspension arm 11 from further swinging downward when the driving wheel 7 falls into a depression on the floor surface and the suspension arm 11 swings downward when the automatic guided vehicle 1 travels. It is for doing so.

The two spring units 13 urge the free end portion of the suspension arm 11 downward by the spring force generated by the compression to press the driving wheel 7 toward the floor surface, and between the driving wheel 7 and the floor surface. A double cylinder fitted in the shaft portion 12b of the connecting rod 12 in a loosely fitted state as shown in FIG. 4 so as to obtain a necessary frictional force for running the automatic guided vehicle 1. A spring receiving cup 13a having a structure, and a spring receiving ring 13b that is fitted in the inner cylindrical portion 13a ′ of the spring receiving cup 13a in a loosely fitted state and can be brought into contact with the upper end of the outer cylindrical portion 13a ″ of the spring receiving cup 13a; The auxiliary compression spring 13c having a small spring constant is inserted between the inner cylindrical portion 13a ′ and the outer cylindrical portion 13a ″ of the spring receiving cup 13a and interposed between the bottom portion of the spring receiving cup 13a and the spring receiving ring 13b. And spring receiver And a main compression spring 13d having a spring constant larger than that of the auxiliary compression spring 13c. The main compression spring 13d is interposed between the coupling bar 12 and the end of the connection bar 14 fitted to the shaft portion 12b of the connection rod 12. When the web P is not stacked, the auxiliary compression spring 13c is compressed by receiving the load of the table 4 and the connecting bar 14 to generate a small spring force, and the stack 4 is loaded with the web P. In some cases, both the auxiliary compression spring 13c and the main compression spring 13d are compressed under the load of the table 4, the connecting bar 14, and the web P, and a large spring force is generated.
Note that the repulsive force of the auxiliary compression spring 13c and the main compression spring 13d used in the two spring units 13 is unmanned between the drive wheel 7 and the floor surface regardless of whether the paper roll P is loaded or not. Necessary frictional force for traveling the transport vehicle 1 is obtained, and all the casters 5 are grounded to the floor so that the automatic guided vehicle 1 can travel in a stable posture.
When the main compression spring 13d is compressed, the auxiliary compression spring 13c is also compressed. However, since the spring receiving ring 13b contacts the upper end of the outer cylindrical portion 13a ″ of the spring receiving cup 13a, the auxiliary compression spring 13c is It is not compressed more than necessary.

The connecting bar 14 is fixed to the lower surface side of the table 4 that moves up and down in a horizontal posture that is inclined in the front-rear direction of the automatic guided vehicle 1, and both ends thereof are at the upper ends of the shaft portions 12 b of both connecting rods 12. Each of the spring units 13 is fitted into the two spring units 13 so as to be movable up and down while being prevented from coming off. Therefore, the connecting bar 14 receives the load of the table 4 or both the load of the table 4 and the web P supported and placed on the table 4. When receiving only the load of the table 4, the connecting bar 14 is slightly lower downward. Displacement compresses only the auxiliary compression spring 13c of the two spring units 13, and when receiving both loads of the table 4 and the web P, the main compression spring 13d of the two spring units 13 is displaced downward as described above. And the auxiliary compression spring 13c are both compressed. As a result, a spring force is generated in both spring units 13, and both drive wheels 7 are pressed against the floor surface via the suspension arms 11 by the spring force.
Further, both end portions of the connecting bar 14 are prevented from coming off from the shaft portion 12b of the connecting rod 12 by a split nut 26 screwed to the upper end portion of the shaft portion 12b of the connecting rod 12, so that the compressed spring units 13 It is biased upward by a spring force and is in contact with the lower surface of the split nut 26.
The connecting bar 14 is fixed to the lower surface side of the table 4 in a horizontal posture inclined in the front-rear direction of the automatic guided vehicle 1 because the central part of the connecting bar 14 is the central part of the table 4 and the central part of the vehicle body frame 2. This is because the automatic guided vehicle 1 is balanced in accordance with the above.

  Thus, in the automatic guided vehicle 1 provided with the suspension device 8 described above, the connection bar 14 receives only the load of the table 4 and slightly lowers when the paper 4 is not stacked on the table 4 when the paper P is not stacked. Only the auxiliary compression spring 13c of the two spring units 13 is compressed by being displaced by an amount. As a result, a small spring force is generated in both spring units 13, and both drive wheels 7 are lightly pressed to the floor surface via the suspension arms 11 by the small spring force.

When the automatic guided vehicle 1 is not loaded, the automatic guided vehicle 1 can be propelled even if the friction force acting between the drive wheel 7 and the floor surface is small. The automatic guided vehicle 1 can be reliably traveled only by lightly pressing the floor surface.
Further, when the automatic guided vehicle 1 is not loaded, both the drive wheels 7 are pressed lightly toward the floor by the both spring units 13, so that the drive wheels 7 are pressed toward the floor more than the weight of the automatic guided vehicle 1. The repulsive force of the spring is not exceeded, and all casters 5 are in contact with the floor surface, and the automatic guided vehicle 1 can be driven in a stable posture.

  On the other hand, when the web 4 is stacked on the table 4, the connecting bar 14 is greatly displaced downward by receiving the load of the table 4 and the load of the web P loaded on the table 4, and the main compression springs of the two spring units 13. 13d and the auxiliary compression spring 13c are compressed. As a result, a large spring force is generated in both spring units 13, and both drive wheels 7 are strongly pressed to the floor surface via the suspension arms 11 by the large spring force. As a result, even if the automatic guided vehicle 1 is loaded with a heavy web P, the drive wheels 7 do not slip with respect to the floor surface, and the automatic guided vehicle 1 can be reliably run. At this time, both drive wheels 7 are receiving a strong upward reaction force from the floor, but the sum of the weight of the automatic guided vehicle 1 and the weight of the web P is more than the reaction force acting on the drive wheels 7. Since it is large, the transport cart does not float and all casters 5 are in contact with the floor. Therefore, the automatic guided vehicle 1 travels in a stable posture.

In the suspension device 8 of the automatic guided vehicle 1 described above, the strength of the compression springs 13c and 13d of the spring unit 13 is adjusted via the connecting bar 14 using the load of the web P. When the load of the web P is applied to the connecting bar 14, the compression springs 13c and 13d are immediately compressed, and the strength of the compression springs 13c and 13d is appropriately adjusted. The operation is faster than the conventional suspension device 8 used.
The suspension device 8 is composed of a pair of suspension arms 11, a pair of connecting rods 12, a pair of spring units 13, and a single connecting bar 14. Therefore, a motor, a screw shaft, or the like is used. Compared to the conventional suspension device 8, the structure is extremely simple, and the assembly can be simplified, the cost can be reduced, the device itself can be downsized, and the maintenance can be simplified.

  In the above embodiment, the upper limit position restricting bolt 21 and the lower limit position restricting bolt 23 are provided on the connecting rod 12. However, in the other embodiments, the free end of the suspension arm 11 is provided. You may make it provide the upper limit position control bolt 21 and the lower limit position control bolt 23 in a part.

It is a partially cutaway side view of the automatic guided vehicle provided with the suspension device according to the embodiment of the present invention. It is a partially cutaway plan view of the automatic guided vehicle. It is a longitudinal front view of the automatic guided vehicle. It is a vertical front view of the principal part of a suspension apparatus.

Explanation of symbols

  1 is an automated guided vehicle, 2 is a body frame, 4 is a table, 5 is a caster, 6 is an electric motor, 7 is a drive wheel, 8 is a suspension device, 11 is a suspension arm, 12 is a connecting rod, 13 is a spring unit, and 13c is An auxiliary compression spring, 13d is a main compression spring, and 14 is a connecting bar.

Claims (3)

  A table (4) disposed on the upper surface side of the body frame (2) for loading a load, a plurality of casters (5) disposed at both front and rear positions of the body frame (2), and the body frame (2) And a drive wheel (7) with a pair of electric motors (6) which are disposed on both sides of the center portion and are movable up and down with respect to the vehicle body frame (2). The drive wheel (7) is floored by a spring force. A suspension device (8) of an automatic guided vehicle (1) that is pressed against a surface to drive on a floor surface, and the suspension device (8) swings up and down on a vehicle body frame (2). A pair of suspension arms (11) to which a drive wheel (7) with an electric motor (6) is attached, and a pair of vertical postures swingably connected to the free ends of both suspension arms (11). Connecting rod (12) and both A pair of spring units (13) having compression springs (13c) and (13d) that are attached to the connecting rod (12) and generate a spring force when compressed, and both ends of the connecting rods (12) It is fitted to the two spring units (8) so that it can be moved up and down while being prevented from coming off at the upper end of the lower part, and receives the load on the table (4) or both the table (4) and the load. And a connection bar (14) that compresses the compression springs (13c) and (13d) of both spring units (8), and the connection bar (14) has a load of the table (4) or the table (4). When both loads of the load are applied and the connecting bar (14) is displaced downward, a spring force is generated in the two spring units (8), and the two driving wheels (7) are moved to the suspension arms (by the spring force). 11) through the floor Automatic guided vehicle suspension system, characterized by being configured to be pressed against each to.   Both spring units (8) generate a small spring force when no load is loaded on the table (4) and lightly push the drive wheels (7) against the floor surface via the suspension arm (11). A small auxiliary compression spring (13c) and an auxiliary force that generates a large spring force when loading on the table (4) and strongly pushes the drive wheel (7) to the floor surface via the suspension arm (11). The suspension device for an automatic guided vehicle according to claim 1, further comprising a main compression spring (13d) having a larger spring constant than the compression spring (13c).   The free ends of both the connecting rods (12) or both suspension arms (11) abut against the upper limit position stopper (20) provided on the vehicle body frame (2), so that the suspension arms (11) and the drive wheels (7) The lower limit position of the suspension arm (11) and the drive wheel (7) is regulated by contacting the upper limit position regulating bolt (21) for regulating the upper limit position and the lower limit position stopper (22) provided on the vehicle body frame (2). The suspension device for an automatic guided vehicle according to claim 1, further comprising a lower limit position regulating bolt (23).

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