Automated guided vehicles

Abstract

The present invention provides an automated guided vehicle (AGV) equipped with a lifting device for loading and raising / lowering loads, which can travel stably even with uneven load distribution. [Solution] An automated guided vehicle (AGV) that can travel in the front-rear direction, comprising: a body frame; left and right drive wheels provided spaced apart in the vehicle width direction of the body frame; a drive source for driving the left and right drive wheels; a lift base supported on the body frame so as to be rotatable along an axis in the vehicle width direction; a swing arm having left and right branch arms, each having its base ends fixed to the left and right ends of the lift base, with its intermediate portion extending in either the front-rear direction or the other, and its rear ends connected at a position a certain distance away from the left and right drive wheels; a driven wheel provided at the connection portion of the left and right branch arms; and a lifting device including the lift base for lifting and lowering loads.

Description

Technical Field

[0001] The present invention relates to an automated guided vehicle (AGV).

Background Art

[0002] In recent years, in factories and logistics sites, automated guided vehicles that can automatically move materials without human intervention for transporting goods have been used. For example, Patent Document 1 discloses an automated guided vehicle in which caster wheels are provided at the four corners of the front, rear, left, and right of a cart for loading, and drive wheels are provided at the central part of the cart. Further, Patent Document 2 discloses an automated guided vehicle in which caster wheels are provided at the four corners of the front, rear, left, and right of a frame equipped with a lifting mechanism for loading and lifting, and steerable drive wheels are provided at two locations before and after the central part of the frame.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In both of the above Patent Documents 1 and 2, driven wheels are provided at the four corners of the front, rear, left, and right of the cart (frame), and drive wheels are provided at the central part of the cart (frame). Therefore, when a load is placed on the cart or the lifting device, and if the load is placed in an uneven load state at this time, when the transport vehicle is driven, an excessive weight is applied to any of the driven wheels, and there is a problem that the running becomes unstable. In other words, when excessive weight is applied to a driven wheel, the driven wheel diagonally opposite it may lift off the ground or come close to lifting, resulting in insufficient contact between the driven wheel and the running surface, causing unstable movement. This problem becomes even more significant in transport vehicles equipped with a lifting device for loading loads, depending on the height of the load placed on the lifting device, leading to even more unstable movement.

[0005] This invention has been made in view of the circumstances described above, and the problem that this invention aims to solve is to provide an automated guided vehicle (AGV) equipped with a lifting device for placing and raising a load, which can travel stably even with uneven load distribution. [Means for solving the problem]

[0006] To solve the above problems, the present invention employs the following means. In other words, the automated guided vehicle of the present invention is an automated guided vehicle that can travel in the front-rear direction and comprises a vehicle frame, left and right drive wheels provided spaced apart in the vehicle width direction of the vehicle frame, a drive source for driving the left and right drive wheels, a lift base supported on the vehicle frame so as to be rotatable along an axis in the vehicle width direction, a swing arm having left and right branch arms, each having its base ends fixed to the left and right ends of the lift base, with its intermediate portion extending in either the front-rear direction or the other, and its rear ends connected at a position a certain distance away from the left and right drive wheels, a driven wheel provided at the connection point of the left and right branch arms, and a lifting device that includes the lift base and lifts and lowers a load on it.

[0007] In one aspect of the present invention, the connecting portion is provided with a caster frame that is rotatable at the center in the vehicle width direction and has an axis extending in the front-rear direction, and a pair of driven wheels are provided at each of the outer ends in the vehicle width direction of the caster frame, which are located inward in the vehicle width direction from the left and right drive wheels.

[0008] Furthermore, in another aspect of the present invention, the left and right branch arms of the swing arm are each formed in an arch shape, rising upward from one end in the front-rear direction and then descending toward the other end. Below these branch arms are the left and right drive sources, which drive the left and right drive wheels, respectively.

[0009] In another aspect of the present invention, the left and right drive wheels are provided on the outer side of the vehicle body frame in the width direction. [Effects of the Invention]

[0010] According to the present invention, an automated guided vehicle equipped with a lifting device can be made to travel stably even with uneven load distribution. [Brief explanation of the drawing]

[0011] [Figure 1] This is a plan view showing the basic configuration of an automated guided vehicle (AGV) as one embodiment of the present invention. [Figure 2] This is a cross-sectional view of the automated guided vehicle along line AA in Figure 1. [Figure 3] This is a front view showing the basic configuration of the automated guided vehicle. [Figure 4] Figure 3 is a plan view of the automated guided vehicle from line BB. [Figure 5] This is a side view showing the basic configuration of the automated guided vehicle. [Modes for carrying out the invention]

[0012] An embodiment of the present invention will be described below with reference to the attached drawings.

[0013] In Figures 1-4, the automated guided vehicle 1 comprises a body frame 2, left and right drive wheels 3a and 3b, drive sources (motors) 4a and 4b, a lift base 5, a swing arm 6, left and right driven wheels 7a and 7b, and a lifting device 8.

[0014] The automated guided vehicle 1 can travel in the direction of arrow F and the opposite direction of arrow B, which is the direction of arrow B. For the sake of explanation here, arrow F is regarded as the front and arrow B as the rear. Also, this automated guided vehicle 1 can change its traveling direction by varying the rotational speeds of the left and right drive wheels 3a and 3b. This automated guided vehicle 1 is configured such that its traveling state, the vertical movement of the lifting device 8, etc. are controlled by wireless commands from the outside.

[0015] As shown in FIGS. 1 and 4, the vehicle body frame 2 has a configuration including a front wall portion 21 and left and right side wall portions 22a and 22b extending rearward from the front wall portion 21. On the outside of the side wall portions 22a and 22b, the left and right drive wheels 3a and 3b are respectively rotatably attached. Inside the side wall portions 22a and 22b, traveling drive sources (motors) 4a and 4b for rotationally driving the drive wheels 3a and 3b are provided. The traveling drive sources (motors) 4a and 4b are respectively arranged so as to be close to the left and right drive wheels 3a and 3b. The front wall portion 21 is provided with left and right driven wheels 7a and 7b configured as casters.

[0016] On the side wall portions 22a and 22b of the vehicle body frame 2, a shaft body 23 is rotatably supported between the central portions in the front-rear direction thereof. A lift base portion 5 is provided on the shaft body 23, and the lift base portion 5 is rotatable about the rotation axis X0 of the shaft body 23.

[0017] As shown in FIG. 2, the lift base portion 5 is a structure including a main wall portion 24 rising upward from the shaft body 23 and a horizontal wall portion 25 extending rearward from the lower end of the main wall portion 24. On the rear surface of the main wall portion 24, two guide convex portions 26 and 26 are provided spaced apart left and right.

[0018] As shown in FIGS. 1 and 4, the base end portions of the swing arms 6 are fixed to the left and right end portions of the lift base portion 5. The swing arms 6 are configured such that their intermediate portions extend in either one of the front-rear directions. The swing arm 6 includes left and right branch arms 41a and 41b, and connecting rods 42a and 42b provided across the rear ends of the left and right branch arms 41a and 41b. The connecting rods 42a and 42b are arranged at a certain distance apart at the rear ends of the left and right branch arms 41a and 41b, and the quadrilateral part formed by the connecting rods 42a and 42b and the left and right branch arms 41a and 41b constitutes the connecting portion 43 of the left and right branch arms 41a and 41b.

[0019] As shown in FIGS. 1, 4, and 5, at the center in the vehicle width direction of the connecting rods 42a and 42b, a shaft body 44 is provided in the longitudinal direction of the vehicle body frame 2 across between these connecting rods 42a and 42b. A caster frame 45 is supported rotatably about the rotation axis X1 of the shaft body 44 on the shaft body 44. A pair of left and right driven wheels 46a and 46b configured as casters are provided at the outer ends in the vehicle width direction of the caster frame 45 respectively. In this case, the left and right driven wheels 46a and 46b are located inward in the vehicle width direction from the left and right drive wheels 3a and 3b.

[0020] The swing arm 6 configured as described above is rotatable in a vertical plane about the shaft body 44 together with the lift base portion 5. The left and right branch arms 41a and 41b of the swing arm 6 are each formed in an arch shape that rises upward from one end provided with the connecting rods 42a and 42b in the longitudinal direction and descends toward the other end provided with the lift base portion 5, and left and right traveling drive sources (motors) 4a and 4b for driving the left and right drive wheels 3a and 3b respectively are provided below these branch arms 41a and 41b.

[0021] As shown in FIG. 2, the lifting device 8 includes the lift base portion 5, and includes a lift lifting portion 61, a screw shaft 62, and a drive mechanism 63 for rotationally driving the screw shaft 62. The lift lifting portion 61 includes a top plate 64 on which a load is placed, a lifting plate 65 provided so as to extend downward from the lower surface of the top plate 64, an engagement concave portion 66 provided on the lifting plate 65 and engaged with the guide convex portion 26, and a female screw member 67 provided on the lifting plate 65 and screwed with the screw shaft 62.

[0022] The guide projection 26 and the engaging recess 66 restrict movement of the lifting plate 65 to only the vertical direction, while constraining movement in the forward, backward, left, and right directions (configured as a so-called linear guide).

[0023] As shown in Figure 2, the screw shaft 62 is provided so as to protrude upward from the horizontal wall portion 25 of the lift foundation 5. This screw shaft 62 is rotationally driven by a drive mechanism 63 provided on the horizontal wall portion 25. The drive mechanism 63 comprises a motor 81, a sprocket wheel 82 provided on the rotation axis of the motor 81, a sprocket wheel 83 provided on the lower end of the screw shaft 62, and a chain 84 wound between the sprocket wheels 82 and 83.

[0024] Furthermore, the drive mechanism 63 is not limited to a combination of a sprocket wheel 83 and a chain 84 wound between sprocket wheels 82 and 83, but may also use gears, a combination of a timing belt and pulley, etc.

[0025] When the motor 81 is driven to rotate the screw shaft 62 under this configuration, the female screw member 67 moves up and down, causing the lifting plate 65 and the top plate 64 to move up and down. At this time, the lifting section 61 is only able to move up and down because the engaging recess 66 is guided by the guide projection 26.

[0026] In the above configuration, the optimal load ratio for achieving stable running on these wheels is determined by the dimensional ratio of the distance L1 from the left and right drive wheels 3a and 3b to the rotation axis X0 of the axle body 23, the distance L2 from the left and right driven wheels 7a and 7b to the rotation axis X0 of the axle body 23, and the distance L3 from the left and right driven wheels 46a and 46b to the rotation axis X0 of the axle body 23. This load ratio is set to a state where stable operation is possible even without a load.

[0027] Furthermore, in the above configuration, the screw shaft 62 of the lifting device 8 is located at the center in the width direction of the automated guided vehicle 1 and at the center in the front-rear direction of the top plate 64. In addition, this screw shaft 62 is located on the rotation axis X2 of the left and right drive wheels 3a and 3b, and the rotation axis X0 of the lift base 5 and swing arm 6 is located in front of the rotation axis X2.

[0028] Next, the operation of the automated guided vehicle 1, which has the above configuration, will be explained. When the automated guided vehicle 1 is driven, the drive sources (motors) 4a and 4b are driven by external instructions to rotate the left and right drive wheels 3a and 3b, causing the vehicle to move. In this case, the vehicle is steered freely by the speed difference between the left and right drive wheels 3a and 3b.

[0029] For example, after stopping under the load, the automated guided vehicle 1 activates the lifting device 8, raises the top plate 64, and places the load on the top plate 64. In this configuration, the lifting plate 65 supporting the top plate 64 is provided with an engaging recess 66, which is guided only upward by the guide projection 26 while its movement in the front, back, left, and right directions is restricted.

[0030] In this state, the load can be transported to the desired location as needed. In this case, stable operation is possible if the load on the top plate 64 is placed so that the load is evenly distributed across the entire surface of the top plate 64, but there are cases where the load is unevenly distributed. In this automated guided vehicle 1, stable operation is possible even if the load is unevenly distributed.

[0031] In other words, if there is an uneven load in the way the load is stacked, the lift base 5 rotates around the rotation axis X0 of the shaft 23, and the caster frame 45 rotates around the rotation axis X1 of the shaft 44. By doing so, the left and right drive wheels 3a and 3b, and the left and right driven wheels 46a and 46b, make contact with the running surface while maintaining an appropriate frictional force, preventing excessive load from being applied to a particular wheel and causing the wheel on the opposite side to lift off the ground or come close to lifting off the ground, thereby ensuring that the automated guided vehicle 1 runs in a stable state.

[0032] In this case, the left and right driven wheels 7a and 7b are less susceptible to the effects of uneven loads due to the relationship between the front-to-rear center position of the top plate 64, i.e., the position where the screw shaft 62 is located, and the position of the rotation axis X0 of the lift base 5 and swing arm 6, and are always in contact with the running surface with appropriate frictional force. Thus, the automated guided vehicle 1 can travel stably because each wheel makes contact with the running surface with appropriate frictional force.

[0033] Furthermore, in order to achieve stable driving against uneven loads during vehicle operation, for example, one could consider arranging the left and right wheels on a single axle and placing a third wheel behind (or in front of) these left and right wheels to provide three-point support. This three-point support prevents any of the wheels from lifting off the ground in the event of an uneven load.

[0034] In this regard, the automated guided vehicle 1 has its left and right drive wheels 3a and 3b positioned outward in the vehicle width direction of the vehicle frame 2, and furthermore, the left and right driven wheels 46a and 46b are positioned behind the left and right drive wheels 3a and 3b, and inward in the vehicle width direction from the left and right drive wheels 3a and 3b, so that an effect close to a pseudo three-point support is obtained, enabling stable driving.

[0035] Furthermore, this effect is not limited to cases where the load is unevenly distributed; the same effect can be obtained even when there are irregularities on the running surface, thus enabling stable driving. Furthermore, since the automated guided vehicle 1 can run stably even when unloaded, it can run stably in both unloaded and unevenly loaded conditions.

[0036] Furthermore, when an automated guided vehicle (AGV) is to slide under a box pallet or the like to place a load, it is desirable to keep the vehicle height as low as possible. In this regard, the AGV 1 has branch arms 41a and 41b of the swing arm 6 formed in an arch shape, and the drive sources (motors) 4a and 4b for travel are located below them. Therefore, the vehicle height in the section where the drive sources (motors) 4a and 4b are installed can be kept low, thus meeting the requirement for a low vehicle height.

[0037] In the above embodiment, the left and right driven wheels 46a and 46b, located behind the left and right drive wheels 3a and 3b, are supported by the swing arm 6, and the swing arm 6 is supported by the rotation axis X1 of the shaft body 44. However, in addition to this configuration, depending on the characteristics of the load, the left and right driven wheels 7a and 7b, located in front of the vehicle frame 2, may also be supported by the swing arm 6 and configured to be rotatable. [Explanation of Symbols]

[0038] 1. Automated Guided Vehicle (AGV) 2. Vehicle frame 3a, 3b driving wheels 4a, 4b Drive source (motor) for propulsion 5. Lift foundation 6. Swingarm 7a, 7b Driven wheel 8. Lifting device 23 Axis 41a, 41b Branch arms 44 Axis 45 Caster Frame 46a, 46b Driven wheel 61 Lift Lifting Section 63 Drive mechanism

Claims

1. An unmanned transport vehicle that can move freely in the forward and backward directions, The vehicle frame and The left and right drive wheels are provided spaced apart in the vehicle width direction of the vehicle body frame, A drive source for driving the left and right drive wheels, A lift base is supported on the vehicle frame so as to be rotatable along the axis in the vehicle width direction, A swing arm comprising left and right branch arms, each having its base end fixed to the left and right ends of the lift base, with its intermediate portion extending in either the front or rear direction, and its rear end connected at a position a certain distance away from the left and right drive wheels, A driven wheel is provided at the connecting portion of the left and right branch arms, The lifting device includes the aforementioned lift base and is used to lift and lower a load, An automated guided vehicle equipped with [a specific feature].

2. The connecting portion is provided with a caster frame that is rotatable on an axis extending in the front-rear direction, located at the center in the vehicle width direction. The unmanned transport vehicle according to claim 1, wherein a pair of driven wheels is provided at each of the outer ends of the caster frame in the vehicle width direction, the driven wheels being located inward in the vehicle width direction from the left and right drive wheels.

3. The left and right branch arms of the swing arm are each formed in an arch shape, rising upward from one end in the front-rear direction and then descending toward the other end. The unmanned transport vehicle according to claim 1 or 2, wherein the left and right drive sources for driving the left and right drive wheels are provided below these branch arms.

4. The unmanned transport vehicle according to claim 1 or 2, wherein the left and right drive wheels are provided on the outer side of the vehicle body frame in the width direction.

Images