WO2014092304A1

WO2014092304A1 - Driving apparatus

Info

Publication number: WO2014092304A1
Application number: PCT/KR2013/008280
Authority: WO
Inventors: Seung-Jin Kim
Original assignee: Samsung Techwin Co., Ltd
Priority date: 2012-12-12
Filing date: 2013-09-13
Publication date: 2014-06-19
Also published as: KR20140076351A

Abstract

A driving apparatus includes a base, at least one driven wheel coupled to the base and having a restricted vertical movement with respect to the base, a driving wheel arranged to be capable of vertically moving with respect to the base in order to pass through a virtual plane on which the driven wheel is placed, and an elastic member elastically pressing the driving wheel downwardly with respect to the base.

Description

DRIVING APPARATUS

Exemplary embodiments relate to a driving apparatus.

Mobile robots for automatically transferring goods, such as industrial waste, documents, medicine/reagents, etc., are used in a variety of industrial fields. A mobile robot is generally equipped with a plurality of wheels, and some of the wheels may be connected to a driving portion to drive the mobile robot.

A load loaded on the mobile robot may vary according to the type or amount of goods loaded thereon. As a live load varies, the amount of a load supported by each wheel varies as well.

A support load of a driving wheel connected to a driving portion varies according to the amount of the live load. When the amount of the live load is large, a lateral force is applied to the driving wheel and thus a driving system may have an operational defect or may be damaged.

One or more exemplary embodiments provide a driving apparatus in which the amount of a support load of a driving wheel may be maintained constant regardless of a change in the amount of a load that is loaded.

According to an aspect of an exemplary embodiment, there is provided a driving apparatus includes a base, at least one driven wheel coupled to the base and having a restricted vertical movement with respect to the base, a driving wheel arranged to be capable of vertically moving with respect to the base in order to pass through a virtual plane on which the driven wheel is placed, and an elastic member elastically pressing the driving wheel downwardly with respect to the base.

According to one or more embodiments, the amount of a load applied to a driving wheel may be maintained constant even when the amount of a load that is loaded varies.

FIG. 1 is a perspective view schematically illustrating a driving apparatus according to an exemplary embodiment.

FIG. 2 is an exploded perspective view schematically illustrating the driving apparatus of FIG. 1.

FIG. 3A is a side view schematically illustrating a state in which the driving apparatus of FIG. 1 does not rest on the ground.

FIG. 3B is a side view schematically illustrating a state in which the driving apparatus of FIG. 1 rests on the ground.

FIG. 4 is a cross-sectional view schematically illustrating a modified example of the driving apparatus of FIG. 1.

FIG. 5 illustrates a part of the structure of the driving apparatus of FIG. 4.

FIG. 6 is a cross-sectional view schematically illustrating another modified example of the driving apparatus of FIG. 1.

FIG. 7 is a cross-sectional view schematically illustrating a driving apparatus according to another exemplary embodiment.

FIGS. 8A to 8C schematically illustrate various structures of a driving portion of a driving apparatus, according to exemplary embodiments.

FIGS. 9A to 9B schematically illustrates another exemplary embodiment.

The base may include a guide extending vertically, a vertical movement of the driving wheel is guided by the guide, a support is arranged at an end portion of the guide to be capable of elevating with respect to the guide, and the elastic member is arranged between the support and the driving wheel to elastically press the driving wheel downwardly.

The elastic member may include an elastic pressing force adjustment unit that adjusts an elastic force pressing the driving wheel.

The base may include a guide extending vertically, a vertical movement of the driving wheel may be guided by the guide, a support may be arranged at an end portion of the guide to be capable of elevating with respect to the guide, and the elastic member may be arranged between the support and the driving wheel to elastically press the driving wheel downwardly.

The elastic pressing force adjustment unit may include an elevating apparatus that forcibly elevates the support vertically.

The driving apparatus may further include a load cell measuring the weight of an object loaded on an upper surface of the base and a control unit controlling the elevating apparatus of the elastic pressing force adjustment unit according to the weight of an object that is measured by the load cell.

The support may be screw-coupled to the guide to be capable of elevating with respect to the guide, and the elastic pressing force adjustment unit may rotate the guide to forcibly elevate the support.

The driving apparatus may further include a vertical movement guide that is coupled to the base and guides an elevation of the support to restrict rotation of the support.

The driving apparatus may further include a load cell measuring the weight of an object loaded on an upper surface of the base and a control unit controlling an elevating apparatus of an elastic pressing force adjustment unit according to the weight of an object that is measured by the load cell.

The driving apparatus may further include a load cell that measures the weight of an object loaded on an upper surface of the base.

The elastic member may include an elastic pressing force adjustment unit that adjusts an elastic force pressing the driving wheel, the driving apparatus further including a control unit that controls the elastic pressing force adjustment unit according to the weight of an object that is measured by the load cell.

The driving portion may include a motor and a reduction gear connected to the motor, and the driving wheel may be connected directly to the reduction gear.

The driving portion may include a motor, a driving pulley coupled to the motor, a driven pulley coupled to the driving wheel, and a belt coupling the driving pulley and the driven pulley.

The base and the driving wheel may be connected to each other, the driving apparatus further including another elastic member that elastically supports a downward movement of the driving wheel.

The elastic member that elastically presses the driving wheel downwardly may have a greater modulus of elasticity than the another elastic member that elastically supports a downward movement of the driving wheel.

The driving apparatus may further comprise an arm which is hinge-connected to the base, and the driving wheel is coupled to the arm.

Hereinafter, one or more embodiments will be described in detail with reference to accompanying drawings. Also, in drawings, same reference numerals denote same elements to avoid repetition.

FIG. 1 is a perspective view schematically illustrating a driving apparatus 1 according to an exemplary embodiment. FIG. 2 is an exploded perspective view schematically illustrating the driving apparatus 1 of FIG. 1.

Referring to FIGS. 1 and 2, the driving apparatus 1 according to the present embodiment includes a base 100, a driven wheel 110, a driving wheel 200, a driving portion 220, an elastic member, a loading frame 300, and a load cell 400.

The base 100 is a portion where the driven wheel 110, the driving wheel 200, the driving portion 220, the elastic member, the loading frame 300, and the load cell 400 are mounted and may be formed of a material having a sufficient rigidity, for example, a metal material, so as to stably support the above elements. A plurality of guides 120 may be arranged on an upper surface of the base 100 to extend upwardly.

The driven wheel 110 is provided in a plural number under the base 100 to be driven to rotate according to a movement of the driving apparatus 1. The driven wheel 110 is coupled to the base 100 by means of a support frame 115. The support frame 115 is rotatably coupled to the base 100 so that the driven wheel 110 may change its direction. In other words, the driven wheel 110 and the support frame 115 may function as a sort of a caster. The vertical movement of the driven wheel 110 may be restricted by the base 100 to support the weight of the driving apparatus 1 and a load loaded thereon.

The driving wheel 200 may be arranged to be capable of moving up and down with respect to the base 100 and may be connected to the driving portion 220 to generate a driving force of the driving apparatus 1. In the present embodiment, the driving wheel 200 is coupled to the driving portion 220 that can be moved up and down with respect to the base 100 and thus the driving wheel 200 may be moved up and down with respect to the base 100. The driving wheel 200 moves up and down while passing through a virtual plane on which the driven wheels 110 are positioned.

The driving wheel 200 may be located in the middle of the driven wheels 110. When the driving wheel 200 is located in the middle of the driven wheels 110, the driving wheel 200 may be less affected by uneven distribution of a load or inclination of the base 100.

The driving portion 220 generates a driving force and transfers the generated driving force to the driving wheel 200. The driving portion 220 may include a motor and a reduction gear. The driving wheel 200 includes a coupling portion 230 that is coupled to the guides 120 provided on an upper surface of the base 100 so that the driving wheel 200 may move up and down with respect to the base 100. In the driving apparatus 1 according to the present embodiment, as illustrated in FIG. 2, the guides 120 are inserted in holes formed in the coupling portion 230 so as to be coupled to the base 100. Accordingly, the driving portion 220 is guided by the guides 120 to be moved up and down.

The elastic member elastically presses the driving wheel 200 downwardly with respect to the base 100. In the present embodiment, the elastic member is a coil spring 130 and is inserted around each of the guides 120 to be arranged above the driving portion 220. A spring support portion 122 is provided at an upper end portion of a main body 121 of each guide 120 to prevent the coil spring 130 from escaping. Accordingly, as the coil spring 130 elastically presses the driving portion 220 downwardly, an elastic pressure may be applied to the driving wheel 200 that is coupled to the driving portion 220.

The loading frame 300 is coupled to the upper side of the base 100 and transfers the weight of an object loaded thereon to the base 100. A coupling portion 401 of the loading frame 300 may be located directly on the base 100 above the driven wheel 110 so that a loading load may be directly transferred to the driven wheel 110 via a leg portion 310.

The load cell 400 may be arranged on each leg portion 310 of the loading frame 300 to measure the weight of a load loaded on the loading frame 300. However, the position of the load cell 400 is not limited thereto, and the load cell 400 may be provided at various positions, for example, at the upper surface of the loading frame 300, only when the load cell 400 may measure the weight of a load loaded on the loading frame 300.

The driving apparatus 1 of the present embodiment may include a control unit (not shown). The control unit may include a microprocessor to control the driving portion 220, for example, by receiving a control command from the outside, thereby controlling a movement of the driving apparatus 1.

FIG. 3A is a side view schematically illustrating a state in which the driving apparatus 1 of FIG. 1 does not rest on the ground. Referring to FIG. 3A, when the driving apparatus 1 of the present embodiment is separated from the ground, the driving wheel 200 protrudes downwardly by an elastic force applied by the coil spring 130 to the driving portion 220. In other words, the driving wheel 200 is located under a virtual plane L1 on which the driven wheels 110 are placed.

FIG. 3B is a side view schematically illustrating a state in which the driving apparatus 1 of FIG. 1 rests on a ground surface G. Referring to FIG. 3B, when the driving apparatus 1 of the present embodiment contacts the ground surface G, the driving wheel 200 receives a reaction force from the ground surface G. Thus, the coil spring 130 that has elastically pressed the driving wheel 200 downwardly is contracted and then the driving portion 220 and the driving wheel 200 are moved upward altogether. The amount of the weight of the driving apparatus 1 may be greater than the elastic force of the coil spring 130 so that the driving wheel 200 and the driven wheel 110 may simultaneously contact the ground surface G.

When the driving apparatus 1 of the present embodiment is placed on the ground surface G and a load is loaded on the loading frame 300, the load is transferred to the ground surface G via only the driven wheel 110, not via the driving wheel 200. Since the positions of the base 100 and the guide 120 are not changed even when the load on the loading frame 300 increases, the length of the coil spring 130 is not changed.

According to the driving apparatus 1 of the present embodiment, even when the load loaded on the loading frame 300 varies, a force of the driving wheel 200 pressing the ground surface G may be maintained constant as a pressing force of the coil spring 130. Thus, an application of an excessive load to the driving wheel 200 due to a loaded load may be effectively prevented. When the driving wheel 200 assumes an excessive load, an excessive vertical load is applied to a connection portion between the driving portion 220 and the driving wheel 200 , for example, a shaft (not shown), so that a rotational resistance increases or the shaft may be damaged. According to the driving apparatus 1 of the present embodiment, since a load applied to the driving wheel 200 may be maintained constant regardless of the loading load, the above problem may be effectively solved.

The driving apparatus 1 of the present embodiment may be modified to further include an elastic pressing force adjustment unit to adjust an elastic pressing force applied to the driving wheel 200.

FIG. 4 is a cross-sectional view schematically illustrating a modified example of the driving apparatus 1 of FIG. 1 including an elastic pressing force adjustment unit. Referring to FIG. 4, a screw thread is formed on an outer circumferential surface of a guide 125, and a spring support 126 is screw-coupled to the guide 125. In other words, when the spring support 126 is rotated, the spring support 126 may be elevated in a lengthwise direction of the guide 125.

In the embodiment of FIG. 4, an elevating apparatus capable of forcibly elevating the spring support 126 may be provided as the elastic pressing force adjustment unit. The elevating apparatus may include a motor 510, a reduction gear 520, and a driving gear 530. The driving gear 530 is coupled to the spring support 126 so as to transfer a rotational force to the spring support 126. Thus, as the driving gear 530 rotates in one direction or the other around a rotational axis A1, the spring support 126 moves up or down.

FIG. 5 illustrates a part of the structure of the elevating apparatus of FIG. 4 in which the spring support 126 and the driving gear 530 are gear-coupled to each other. Referring to FIG. 5, when the driving gear 530 is rotated by the motor 510, the spring support 126 that is gear-coupled to the driving gear 530 is rotated. Since the spring support 126 is screw-coupled to the guide 125 as described above, the spring support 126 may elevate up and down in the lengthwise direction of the guide 125 as the spring support 126 is rotated forward or backward.

As the elevating apparatus elevates the spring support 126, the interval between the spring support 126 and the coupling portion 230 of the driving portion 220 varies and thus the length of the coil spring 130 arranged therebetween varies accordingly. Since an elastic force increases as the amount of compression of the coil spring 130 increases, in order to increase a force of the driving wheel 200 pressing the ground surface G, the spring support 126 descends in a direction to decrease the length of the coil spring 130. Reversely, in order to decrease the force of the driving wheel 200 pressing the ground surface G, the motor 510 is controlled to allow the spring support 126 to ascend.

The elevation of the spring support 126 to adjust an elastic pressing force applied to the driving wheel 200 may be controlled according to a user's control command or automatically controlled by the control unit using information about a loading load obtained from the load cell 400.

The elastic pressing force adjustment unit may be modified into various different forms.

FIG. 6 is a cross-sectional view schematically illustrating another modified example of the driving apparatus 1 of FIG. 1 including another elastic pressing force adjustment unit. Referring to FIG. 6, the elastic pressing force adjustment unit of the present embodiment may include a screw gear 127 and a motor 511. In other words, a spring support 128 is screw-coupled to the screw gear 127 to be elevated according to the rotation of the screw gear 127 and the motor 511 rotates the screw gear 127. The spring support 128 is slidably coupled to a vertical movement guide 129 so as not to be rotated by the rotation of the screw gear 127. A reduction gear 521 may be arranged between the motor 511 and the screw gear 127 to transfer a sufficient torque.

FIG. 7 is a cross-sectional view schematically illustrating a driving apparatus 2 according to another exemplary embodiment. Referring to FIG. 7, the driving apparatus 2 according to the present embodiment includes a base 101, the driven wheel 110, the driving wheel 200, the driving portion 220, a first elastic member131, and a second elastic member 132.

The base 101 supports the driven wheel 110, the driving wheel 200, the driving portion 220, the first elastic member131, and the second elastic member 132. A space for loading goods may be provided on an upper side of the base 101. In the present embodiment, the base 101 may include an upper side portion 1012 and a lower side portion 1011. A support 1013 and a guide 1014 may be arranged between the upper side portion 1012 and the lower side portion 1011. The support 1013 may be arranged directly above the driven wheel 110 so as to transfer a load placed on the upper side portion 1012 directly to the driven wheel 110. The guide 1014 is arranged inside the base 101 to be coupled to the coupling portion 230 of the driving portion 220. In the present embodiment, since both upper and lower ends of the guide 1014 are coupled to the base 101, the guide 1014 may stably maintain a firmly fixed position even when the shock from the driving wheel 200 is transferred.

The driving portion 220 is slidably coupled to the guide 1014 to be capable of relatively elevating with respect to the base 101. The driving portion 220 may include a drive source such as a motor to drive the driving wheel 200.

The driving wheel 200 receives a rotational force from the driving portion 220 and drives the driving apparatus 2 while pushing the ground surface G in a radial direction as it rotates.

The first elastic member 131 is arranged between the coupling portion 230 of the driving portion 220 and the upper side portion 1012 of the base 101 and elastically presses the driving portion 220 downwardly. The first elastic member 131 may be formed of a coil spring to be inserted around the guide 1014.

The second elastic member 132 is arranged between the coupling portion 230 of the driving portion 220 and the lower side portion 1011 of the base 101 and elastically supports the driving portion 220 upwardly. The second elastic member 132 may be formed of a coil spring that is inserted around the guide 1014. The modulus of elasticity of the second elastic member 132 is smaller than that of the first elastic member 131 so that the second elastic member 132 has an elastic force that is smaller than the first elastic member 131. Thus, although the second elastic member 132 upwardly elastically supports the driving portion 220, the driving portion 220 receives a downward elastic pressing force so as to maintain a close contact with the ground surface G.

In the driving apparatus 2 of the present embodiment, since the loading load is not transferred to the driving wheel 200, the driving wheel 200 may maintain a close contact with the ground surface G with a constant force regardless of the loading load. Thus, the same effect of the driving apparatus 1 of FIG. 1 may be obtained. In addition, since the second elastic member 132 upwardly elastically supports the driving wheel 200, serving as a suspension, shock absorbing performance of the driving apparatus 2 may be further improved.

Next, a driving apparatus according to another exemplary embodiment is provided.

FIGS. 9A to 9B schematically illustrates another exemplary embodiment. Specifically, FIG. 9A illustrates the driving apparatus when it does not rest on the ground and FIG. 9B illustrates the driving apparatus when it rest on the ground.

Referring to FIGS. 9A and 9B, the driving apparatus 3 of this exemplary embodiment also has a base 100, a driven wheel 110, a driving wheel 200, a driving portion 2201, an elastic member 2204, a loading frame 300 as the driving apparatus of FIG. 1. The base 100, the driven wheel 110 and the loading frame 300 of this embodiment are substantially the same as the driving apparatus of FIG. 1. Therefore, detail explanation of the elements is not repeated, and elements which is not described in the driving apparatus 1 of FIG. 1 are mainly explained in the below.

The driving wheel 200 is connected to the driving portion 2201 and rotated by the driving portion 2201. Though driving shaft is not shown in FIG. 9A, the driving wheel 200 are connected to the driving portion 2201 by the driving shaft. That is, the driving portion 2201forcibly rotates the driving shaft and driving shaft and the driving wheel 200 are rotates together.

The driving portion 2201 may comprises a motor to rotate the driving wheel 200. The driving portion 2201 is connected the base 100 and movable relatively to the base 100 in vertical direction. For the driving portion 2201 to move in up and down direction, the driving portion 2201 is hinge connected to the base 100. Specifically, the driving portion 2201 is fixedly connected to an arm 2203 which is rotatable connected to the base. As the arm 2203 rotates around a hinge connection portion 2205, the driving portion 2201 and the driving wheel connected thereto may move up and down direction and may protrude through the virtual plane upon which the driven wheels 110 are disposed.

The elastic member 2204 is disposed between the rod 2203 and the base 100 and elastically pushes the rod 2203 downwardly. The elastic member 2204 may be a coil spring and may further comprise a damper.

As shown in FIG. 9B, when the driving apparatus are rested on the ground, the driving wheel 200 and driving portion 2201 move up and the driving wheel 200 is positioned on the virtual plane L1. Thus, the driving wheel 2201 and the driven wheels 110 in all are positioned on the ground G. When the driving wheel 2201 is in contact with the ground the elastic member 2204 is contracted and exerts elastic force to the driving wheel 200. Since the driven wheels 110 supports the base 100, the contraction amount of the elastic member 2204 remains unchanged by the amount of load on the loading frame 300 as long as the load is heavy enough to push the driving wheel 200 up to the virtual plane L1. As the driving wheel 200 is pushed downwardly by the elastic member 2204 with a same force, the driving shaft is not exposed to excessive non-axial load even when a heavy load is loaded on the loading frame 300. As a result, malfunctions or damages of the driving shaft may be effectively reduced. In addition, moving mechanism for the driving wheel 200 becomes simple and thus, manufacturing cost may be reduced. Also, elastic force of the elastic member 2204 may be effectively delivered by leverage effect.

Although the driving wheel 200 is positioned inside the driven wheels 110 in the above embodiment, the location of the driving wheel 200 is not limited thereto. For instance, the driven wheels 110 are positioned inside and the driving wheel 200 may be positioned outside of the driven wheels 110.

The present exemplary embodiment is not limited to the above descriptions and a variety of modifications may be embodied. For example, although a coil spring is used as the elastic member in the above description, a leaf spring or a constant force spring may be used as the elastic member. In particular, when a constant force spring is used as the elastic member, even when the height of the base 100 is differently designed, the driving wheel 200 may press the ground surface G with a constant force.

Also, although the driving wheel 200 is described above to be arranged between the driven wheels 110, the driving wheel 200 may be provided outside the driven wheels 110. However, for uniform distribution of a load, the driving wheel 200 may be arranged between the driven wheels 110.

The driving portion 220 may have a variety of structures to transfer a driving force to the driving wheel 200. FIGS. 8A to 8C schematically illustrate various structures of the driving portion 220 according to exemplary embodiments. Referring to FIG. 8A, the driving portion 220 includes a motor 221 and a reduction gear 223 that are coupled to the driving wheel 200 in which the driving wheel 200 is directly coupled to the reduction gear 223. The motor 221 and the reduction gear 223 may be provided for each driving wheel 200 so as to allow the driving wheel 200 to be driven independently. Thus, the movement direction of the driving apparatus 2 may be controlled in a differential steering mechanism.

Also, referring to FIG. 8B, the driving portion 220, including the motor 221 and the reduction gear 223, may transfer a driving force to the driving wheel 200 via a belt and a pulley. In other words, a drive pulley 225 is connected directly to the motor 221 and the reduction gear 223, and a driven pulley 215 coupled to the driving wheel 200 is connected to the drive pulley 225 via a belt 226. Thus, a driving force generated by the motor 221 may be transferred to the driving wheel 200. The belt 226 connecting the drive pulley 225 and the driven pulley 215 may be a timing belt.

Also, referring to FIG. 8C, in the driving portion 220, the motor 221 and the driving wheel 200 may be connected to each other via the

pulleys

225 and 215 and the belt 226, without an additional reduction gear. As such, even without the reduction gear 223, the driving force of the motor 221 may be effectively transferred to the driving wheel 200 by controlling the output of the motor 221 and the rotation ratio of the

pulleys

225 and 215.

According to an aspect of an exemplary embodiment, there is provided a driving apparatus.

Claims

A driving apparatus comprising:

a base;

at least one driven wheel coupled to the base and having a restricted vertical movement with respect to the base;

a driving wheel arranged to be capable of vertically moving with respect to the base in order to pass through a virtual plane on which the driven wheel is placed; and

an elastic member elastically pressing the driving wheel downwardly with respect to the base.
The driving apparatus of claim 1, wherein the base comprises a guide extending vertically, a vertical movement of the driving wheel is guided by the guide, a support is arranged at an end portion of the guide to be capable of elevating with respect to the guide, and the elastic member is arranged between the support and the driving wheel to elastically press the driving wheel downwardly.
The driving apparatus of claim 1, wherein the elastic member comprises an elastic pressing force adjustment unit that adjusts an elastic force pressing the driving wheel.
The driving apparatus of claim 3, wherein the base comprises a guide extending vertically, a vertical movement of the driving wheel is guided by the guide, a support is arranged at an end portion of the guide to be capable of elevating with respect to the guide, and the elastic member is arranged between the support and the driving wheel to elastically press the driving wheel downwardly.
The driving apparatus of claim 4, wherein the elastic pressing force adjustment unit comprises an elevating apparatus that forcibly elevates the support vertically.
The driving apparatus of claim 5, further comprising:

a load cell measuring the weight of an object loaded on an upper surface of the base; and

a control unit controlling the elevating apparatus of the elastic pressing force adjustment unit according to the weight of an object that is measured by the load cell.
The driving apparatus of claim 4, wherein the support is screw-coupled to the guide to be capable of elevating with respect to the guide, and the elastic pressing force adjustment unit rotates the guide to forcibly elevate the support.
The driving apparatus of claim 7, further comprising a vertical movement guide that is coupled to the base and guides an elevation of the support to restrict rotation of the support.
The driving apparatus of claim 7, further comprising:

a load cell measuring the weight of an object loaded on an upper surface of the base; and

a control unit controlling an elevating apparatus of an elastic pressing force adjustment unit according to the weight of an object that is measured by the load cell.
The driving apparatus of claim 1, further comprising a load cell that measures the weight of an object loaded on an upper surface of the base.
The driving apparatus of claim 10, wherein the elastic member comprises an elastic pressing force adjustment unit that adjusts an elastic force pressing the driving wheel, the driving apparatus further comprising a control unit that controls the elastic pressing force adjustment unit according to the weight of an object that is measured by the load cell.
The driving apparatus of claim 1, wherein the driving portion comprises a motor and a reduction gear connected to the motor, and the driving wheel is connected directly to the reduction gear.
The driving apparatus of claim 1, wherein the driving portion comprises:

a motor;

a driving pulley coupled to the motor;

a driven pulley coupled to the driving wheel; and

a belt coupling the driving pulley and the driven pulley.
The driving apparatus of claim 1, wherein the base and the driving wheel are connected to each other, the driving apparatus further comprising another elastic member that elastically supports a downward movement of the driving wheel.
The driving apparatus of claim 14, wherein the elastic member that elastically presses the driving wheel downwardly has a greater modulus of elasticity than the another elastic member that elastically supports a downward movement of the driving wheel.
The driving apparatus of claim 1, further comprising an arm which is hinge-connected to the base, wherein the driving wheel is coupled to the arm.