Transport cart

Abstract

To increase a maximum loading capacity by reducing shaking of a vehicle body while always grounding mecanum wheels during traveling on an undulated road surface.SOLUTION: A transportation truck 10 equipped with mecanum wheels 3 and enabling loading of an article on a plane of a load-carrying platform comprises: a support mechanism 6 for supporting rotary shafts 31 of the mecanum wheels 3 so as to be vertically movable while maintaining the state of being parallel to the plane of the load-carrying platform; a first spring 7 disposed between a vehicle body 2 and the support mechanism 6 and fixed to only one of the vehicle body 2 and the support mechanism 6; and a second spring 8 connected at one end to the vehicle body 2 and at the other end to the support mechanism 6. A spring constant of the first spring 7 is larger than that of the second spring 8. The spring constant of the second spring 8 is set such that the first spring 7 is held between the vehicle body 2 and the support mechanism 6 to support the vehicle body 2 in a state where no article is loaded on the load-carrying platform on a horizontal and flat road surface.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a carrier cart that travels using mecanum wheels.

Background Art

[0002] Patent Document 1 and Non-Patent Documents 1 to 3 disclose vehicles equipped with four mecanum wheels as traveling wheels. The mecanum wheel includes a wheel body and a plurality of barrel-shaped rollers rotatably attached to the outer periphery of the wheel body. Each roller is supported by the wheel body so as to be rotatable about a rotation axis inclined with respect to the rotation axis of the wheel body. By using such a mecanum wheel as a wheel, the vehicle can travel in all directions on the road surface while keeping the direction of the vehicle body fixed in the front-rear direction.

[0003] The vehicle disclosed in Non-Patent Document 1 has a suspension mechanism including a linear guide and a spring that support the rotation axis of the mecanum wheel in a state where it can only move in the vertical direction. The suspension mechanism of the vehicle disclosed in Non-Patent Document 2 is a multi-link type suspension including a spring. And the suspension mechanism of the vehicle disclosed in Non-Patent Document 3 is a trailing arm type suspension including a spring.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

[0006] Vehicles that use Mecanum wheels as their driving wheels cannot perform the function of moving in all directions on the road surface while keeping the vehicle's front-to-rear orientation fixed (hereinafter abbreviated as "omnidirectional movement function") unless all Mecanum wheels are always in contact with the road surface. Therefore, in vehicles that run using Mecanum wheels, it is necessary to use springs with a small spring constant in the suspension mechanism in order to ensure that all Mecanum wheels are reliably in contact with the road surface, even on uneven surfaces.

[0007] However, using springs with a low spring constant in the suspension mechanism results in increased body sway during starting, stopping, and acceleration / deceleration. In particular, in the case of transport carts that carry cargo on top, the center of gravity rises when cargo is loaded, causing the vehicle to tilt significantly when starting or stopping, increasing the risk of tipping over. Furthermore, when using springs with a low spring constant in the suspension mechanism, the weight of the loaded goods causes the springs to compress completely when the load is large, preventing the suspension mechanism from absorbing shocks from the road surface when traveling on uneven roads, thus limiting the maximum load capacity of the transport cart.

[0008] Therefore, the present invention aims to provide a transport trolley that can increase the maximum load capacity while keeping the Mecanum wheels in contact with the ground at all times while traveling on uneven road surfaces, thereby reducing the swaying of the vehicle body. [Means for solving the problem]

[0009] The transport trolley according to the present invention is equipped with Mecanum wheels as wheels for travel and is capable of loading goods on a flat surface of a loading platform, and comprises a support mechanism that supports the rotation axis of the Mecanum wheels so as to be movable in the vertical direction while maintaining a state parallel to the flat surface of the loading platform, a first spring disposed between the vehicle body and the support mechanism and fixed to only one of the vehicle body or the support mechanism, and a second spring having one end connected to the vehicle body and the other end connected to the support mechanism, wherein the spring constant of the first spring is greater than the spring constant of the second spring, and the spring constant of the second spring is set such that, when the loading platform is not loaded with any goods on a horizontal and flat road surface, the first spring is sandwiched between the vehicle body and the support mechanism to support the vehicle body.

[0010] This invention makes it possible to keep the Mecanum wheels in contact with the ground at all times while driving on uneven road surfaces, while reducing body sway and increasing the maximum load capacity.

[0011] In one embodiment of the transport trolley according to the present invention, the support mechanism may support the rotation axis of the Mecanum wheel on both sides of the Mecanum wheel.

[0012] In this configuration, since the rotation axis of the Mecanum wheel is supported on both sides of the Mecanum wheel, the support members are less prone to deformation than in a cantilevered system, and therefore the maximum load capacity can be increased compared to a cantilevered system.

[0013] In one embodiment of the transport trolley according to the present invention, the support mechanism may be a swing arm that can swing in a direction perpendicular to the rotation axis of the Mecanum wheel.

[0014] In one embodiment of the transport trolley according to the present invention, the first spring may be positioned above the rotation axis of the Mecanum wheel, with the first spring supporting the vehicle body.

[0015] According to this aspect, the load supported by the first spring does not affect the bending rigidity of the swing arm, and it is possible to reduce the rigidity of the swing arm, so that the swing arm can be lightened.

[0016] In one aspect of the transport cart according to the present invention, the first spring may be a rubber spring.

[0017] According to this aspect, due to the characteristics of rubber, it is possible to absorb the running vibration peculiar to the mecanum wheel. Also, compared with a metal spring, a rubber spring is inexpensive and the processing cost for attaching it to the vehicle body etc. is small, so the cost can be reduced.

[0018] In one aspect of the transport cart according to the present invention, the second spring may be a gas spring.

Effects of the Invention

[0019] The present invention can reduce the sway of the vehicle body and increase the maximum load capacity while always grounding the mecanum wheels during traveling on a road surface with undulations.

Brief Description of the Drawings

[0020] [Figure 1] It is a perspective view of the transport cart of the embodiment of the present disclosure. [Figure 2] It is a side view showing the state where the transport cart of the present embodiment is parked on a horizontal and flat road surface. [Figure 3] It is a side view showing the state where the swing arm is separated from the first spring during the transport cart of the present embodiment traveling on a road surface with undulations.

Modes for Carrying Out the Invention

[0021] The transport trolley 10 of this embodiment will be described below with reference to Figures 1 to 3. Figure 1 is a perspective view of the transport trolley 10. However, the loading platform 1, which will be described later, is omitted from Figure 1. As shown in Figure 1, the transport trolley 10 includes a trolley frame 2 that is roughly rectangular in shape as part of the vehicle body. The trolley frame 2 includes two side members 21 that extend in the front-rear direction on both the left and right sides of the transport trolley 10, and two cross members 22 that extend in the vehicle width direction and connect the side members 21 on both the left and right sides. One cross member 22 is located on the front and one on the rear side of the transport trolley 10. Furthermore, the trolley frame 2 includes an arm mounting plate 23. One arm mounting plate 23 is located on both the left and right sides of the transport trolley 10 and is fixed to the underside of the central part in the front-rear direction of the side members 21.

[0022] The transport cart 10 is equipped with four Mecanum wheels 3 for driving. One Mecanum wheel 3 is positioned on the right front, right rear, left front, and left rear of the transport cart 10. Each Mecanum wheel 3 consists of a wheel body and a number of barrel-shaped rollers rotatably mounted on the outer circumference of the wheel body. Each roller is supported by the wheel body so as to be able to rotate around a rotation axis that is inclined with respect to the rotation axis of the wheel body. However, in Figures 1 to 3, the barrel-shaped rollers are omitted and the Mecanum wheels 3 are simplified to cylindrical shapes.

[0023] The transport cart 10 is equipped with four electric motors 4 as a power source to rotate the Mecanum wheels 3. Each of the four electric motors 4 is connected to the rotation axis 31 of the Mecanum wheels 3. By individually controlling the rotation direction and rotation speed of the four electric motors 4, the transport cart 10 can travel in all directions on the road surface while keeping the front-to-rear orientation of the vehicle fixed. The transport cart 10 is equipped with a rectangular waterproof case 5. The control devices for the four electric motors 4 are built into the waterproof case 5.

[0024] Figure 2 is a side view showing the transport cart 10 stopped on a horizontal and flat surface. As shown in Figure 2, a flat platform 1 is fixed on the cart frame 2. A flat surface 11 is formed on the upper side of the platform 1, and the transport cart 10 can carry goods loaded on the flat surface 11 of the platform 1 and travel on it. The transport cart 10 can be used, for example, to transport automobile parts within an automobile factory. The transport cart 10 can also be used, for example, as a cart to carry and transport a work robot performing work within an automobile factory.

[0025] The transport trolley 10 is equipped with a trailing arm type suspension mechanism consisting of a swing arm 6, a first spring 7, and a second spring 8. Figure 3 is a side view showing the state in which the swing arm 6 is separated from the first spring 7 while the transport trolley 10 is traveling on an uneven road surface.

[0026] As shown in Figures 1 to 3, the swing arm 6 is a support mechanism that rotatably supports the rotation axis 31 of the Mecanum wheel 3 on both sides of the Mecanum wheel 3. The swing arm 6 is mounted on the arm mounting plate 23 so that it can swing in a direction perpendicular to the rotation axis 31 of the Mecanum wheel 3. The swing arm 6 can swing vertically around the swing axis 61 supported by the arm mounting plate 23 as the center of rotation. Because the swing arm 6 is mounted on the arm mounting plate 23 in this way, the swing arm 6 can move the rotation axis 31 of the Mecanum wheel 3 vertically while maintaining a state parallel to the plane 11 of the cargo bed 1. The swing arm 6 has a flat upper surface 62. The swing arm 6 is mounted on the arm mounting plate 23 so that the upper surface 62 is positioned below the side member 21.

[0027] The first spring 7 is a rubber spring with a roughly rectangular shape. The first spring 7 is positioned between the side member 21 and the swing arm 6 and is fixed to the side member 21. Depending on the swing angle of the swing arm 6, the first spring 7 may contact the upper surface 62 of the swing arm 6 as shown in Figure 2, or it may be separated from the upper surface 62 of the swing arm 6 as shown in Figure 3. The first spring 7 is positioned above the rotation axis 31 of the Mecanum wheel 3 in the state where the first spring 7 is in contact with the swing arm 6 and supporting the vehicle body, as shown in Figure 2.

[0028] The second spring 8 is a gas spring with one end connected to the side member 21 and the other end connected to the swing arm 6. The spring constant of the second spring 8 is set to a smaller value than the spring constant of the first spring 7. The spring constant of the second spring 8 is set so that, as shown in Figure 2, the first spring 7 contacts the upper surface 62 of the swing arm 6 when the cargo bed 1 is not loaded with any goods on a horizontal and flat road surface.

[0029] As the spring constants of the first spring 7 and the second spring 8 are set in this manner, when the transport trolley 10 is stationary or traveling on a flat road surface, the second spring 8 compresses under the load of the vehicle body, and the first spring 7, which has a higher spring constant than the second spring 8, supports the vehicle body. In other words, as shown in Figure 2, the first spring 7 contacts the upper surface 62 of the swing arm 6, and the first spring 7 is sandwiched between the side member 21 and the swing arm 6, supporting the vehicle body. In this state, with the first spring 7 supporting the vehicle body, the amount of deformation of the rubber first spring 7 is small relative to the magnitude of the applied load, so even when the weight of the load is large, the vehicle body does not tilt excessively during starting, stopping, or acceleration / deceleration, and the swaying of the vehicle body can be reduced.

[0030] Furthermore, when the transport trolley 10 travels on an uneven road surface, an upward load may be applied to the Mecanum wheel 3 from the road surface when the Mecanum wheel 3 crosses over a raised section of the road surface. When an upward load is applied to the Mecanum wheel 3 from the road surface in this way, the first spring 7, which is sandwiched between the side member 21 and the swing arm 6, compresses, absorbing the impact of the Mecanum wheel 3 being pushed up from the road surface.

[0031] In contrast, immediately after the Mecanum wheel 3 crosses a raised section of the road surface, or when the Mecanum wheel 3 enters a depression in the road surface, the second spring 8 swings the swing arm 6 downwards, as shown in Figure 3, pressing the Mecanum wheel 3 against the road surface. In this state, the swing arm 6 is separated from the first spring 7. Because the second spring 8 presses the Mecanum wheel 3 against the road surface in accordance with the unevenness of the road surface, the transport trolley 10 can always keep all of its Mecanum wheels 3 in contact with the ground, even when traveling on uneven road surfaces. Therefore, the transport trolley 10 can travel on uneven road surfaces without compromising its omnidirectional mobility function by ensuring that the driving force of all Mecanum wheels 3 is maintained.

[0032] Furthermore, even when traveling on uneven surfaces, the swing arm 6 only separates from the first spring 7 for a brief moment. Due to the weight of the vehicle and its load, the swing arm 6 quickly returns to contact with the first spring 7, so the vehicle is supported by the first spring 7 for most of the time while traveling. In this way, even when traveling on uneven surfaces, the transport cart 10 maintains support for the vehicle body by the first spring 7, which has a high spring constant, except for very short periods of time. Therefore, even when the weight of the goods loaded on the cargo bed 1 is large, the swaying of the vehicle body can be reduced. In addition, by supporting the vehicle body with the first spring 7, which has a high spring constant, even when traveling with a heavy load, the deformation of the first spring 7 is small and the vehicle body does not easily tilt. This reduces the risk of tipping over during starting, stopping, and acceleration / deceleration, and ensures driving stability. Therefore, the transport cart 10 can have a larger maximum load capacity compared to a transport cart equipped only with springs with low spring constants in its suspension mechanism.

[0033] Furthermore, the transport trolley 10 can also reduce the running vibrations characteristic of Mecanum wheels. Mecanum wheels 3 generate vibrations with a small amplitude characteristic of Mecanum wheels while in motion. However, the rubber first spring 7, due to the properties of rubber, can absorb the vibrations characteristic of Mecanum wheels so that they are not transmitted to the vehicle body. Therefore, by using the rubber first spring 7, the transport trolley 10 can reduce the vibrations of the vehicle body while in motion. Moreover, the rubber first spring 7 is less expensive than a metal spring, and the processing costs for attaching it to the vehicle body are also lower compared to a metal spring, so the cost of the transport trolley 10 can be reduced by using the rubber first spring 7.

[0034] Furthermore, in the transport trolley 10, the swing arm 6 supports the rotation axis 31 of the Mecanum wheel 3 on both sides of the Mecanum wheel 3, making it less prone to deformation compared to a cantilevered swing arm, even when the weight of the load is increased. Therefore, the transport trolley 10 can increase its maximum load capacity compared to when a cantilevered swing arm is used in the suspension mechanism. Note that if the swing arm 6 deforms, the rotation axis 31 of the Mecanum wheel 3 will not be parallel to the plane 11 of the loading platform 1, and the Mecanum wheel 3 will make contact with the road surface at an angle, which can easily cause unexpected vibrations and problems such as being unable to drive in a straight line.

[0035] Furthermore, as already mentioned, the first spring 7 is positioned above the rotation axis 31 of the Mecanum wheel 3, in a state where it contacts the swing arm 6 and supports the vehicle body, as shown in Figure 2. By positioning the first spring 7 in this way, the load received from the first spring 7 no longer affects the bending rigidity of the swing arm 6. Therefore, it becomes possible to reduce the rigidity of the swing arm 6 to the load received from the second spring 8, and the swing arm 6 can be made lighter by changing its shape, such as thinning the wall or hollowing it out.

[0036] <Supplement to the embodiment> The transport trolley of the present invention is not limited to the above-described form and can be implemented in various forms within the scope of the gist of the present invention. For example, the thickness, area, and mounting position of the first spring may be changed according to the weight of the load and the position of the center of gravity of the transport trolley. The first spring may not be fixed to the vehicle body but may be fixed to the swing arm. Also, depending on the characteristics of the transport trolley's running vibration, vibration-absorbing rubber may be used as the material for the first spring. Furthermore, a coil spring may be used for the second spring as long as the stroke amount and the ground pressure of the Mecanum wheel can be secured. In addition, as long as the rotation axis of the Mecanum wheel can move vertically while maintaining a state parallel to the horizontal reference of the transport trolley, the suspension mechanism may be a type other than the trailing arm type, such as the linear guide type disclosed in Non-Patent Document 1 or the multi-link type disclosed in Non-Patent Document 2.

[0037] [Structure of the invention] [Configuration 1] A transport cart equipped with Mecanum wheels for driving, capable of loading goods onto a flat platform, A support mechanism that supports the rotation axis of the Mecanum wheel so that it can move vertically while maintaining a state parallel to the plane of the loading platform, A first spring is positioned between the vehicle body and the support mechanism and is fixed to either the vehicle body or the support mechanism, A second spring, one end of which is connected to the vehicle body and the other end of which is connected to the support mechanism, is provided. The spring constant of the first spring is greater than the spring constant of the second spring. A transport trolley characterized in that the spring constant of the second spring is set such that the first spring is sandwiched between the vehicle body and the support mechanism to support the vehicle body when the trolley is on a horizontal and flat road surface with no goods loaded on the trolley bed. [Configuration 2] A transport trolley as described in Configuration 1, A transport trolley characterized in that the support mechanism supports the rotation axis of the Mecanum wheel on both sides of the Mecanum wheel. [Configuration 3] A transport trolley as described in configuration 1 or 2, A transport trolley characterized in that the support mechanism is a swing arm that can swing in a direction perpendicular to the rotation axis of the Mecanum wheel. [Structure 4] A transport trolley as described in any one of items 1 to 3, A transport trolley characterized in that, when the first spring supports the vehicle body, the first spring is positioned above the rotation axis of the Mecanum wheel. [Composition 5] A transport trolley as described in any one of items 1 to 4, A transport trolley characterized in that the first spring is made of rubber. [Composition 6] A transport trolley as described in any one of items 1 to 5, A transport trolley characterized in that the second spring is a gas spring. [Explanation of Symbols]

[0038] 1. Loading platform, 2. Trolley frame, 3. Mecanum wheel, 4. Electric motor, 5. Waterproof case, 6. Swing arm, 7. First spring, 8. Second spring, 10. Transport trolley, 11. Flat surface, 21. Side member, 22. Cross member, 23. Arm mounting plate, 31. Rotating shaft, 61. Swing shaft, 62. Top surface.

Claims

1. A transport cart equipped with Mecanum wheels for driving, capable of loading goods onto a flat platform, A support mechanism that supports the rotation axis of the Mecanum wheel so that it can move vertically while maintaining a state parallel to the plane of the loading platform, A first spring is positioned between the vehicle body and the support mechanism and fixed to only one of the vehicle body or the support mechanism, A second spring, one end of which is connected to the vehicle body and the other end of which is connected to the support mechanism, is provided. The spring constant of the first spring is greater than the spring constant of the second spring. A transport trolley characterized in that the spring constant of the second spring is set such that the first spring is sandwiched between the vehicle body and the support mechanism to support the vehicle body when the trolley is on a horizontal and flat road surface with no goods loaded on the trolley bed.

2. A transport trolley according to claim 1, A transport trolley characterized in that the support mechanism supports the rotation axis of the Mecanum wheel on both sides of the Mecanum wheel.

3. A transport trolley according to claim 1 or 2, A transport trolley characterized in that the support mechanism is a swing arm that can swing in a direction perpendicular to the rotation axis of the Mecanum wheel.

4. A transport trolley according to claim 3, A transport trolley characterized in that, when the first spring supports the vehicle body, the first spring is positioned above the rotation axis of the Mecanum wheel.

5. A transport trolley according to claim 4, A transport trolley characterized in that the first spring is made of rubber.

6. A transport trolley according to claim 5, A transport trolley characterized in that the second spring is a gas spring.

Images