JP6003712B2 - Small mobile body with caster type rear wheels - Google Patents

Description

  The present invention relates to a structure of a small mobile body such as personal mobility or micro mobility, and more particularly to a rear wheel support device and a suspension structure of such a small mobile body.

  In recent years, as a means of moving alone at low speeds for single passengers in areas that are far from walking, such as shopping, commuting, and attending school in areas around the city and where public transportation such as buses is inconvenient, it is more mobile than conventional small vehicles such as bicycles.・ Development and research of a small-sized mobile body having a loading capability and a new concept collectively called “ultra-small mobility” (Non-patent Document 1), which is more compact than a conventional automobile, has been promoted. The performance and equipment required for such a new concept of a small mobile body is generally not limited to sidewalks and bicycle paths. It is good to use, has excellent environmental performance, and has equipment that is not spoiled by hills and rain (equipped with a power unit with sufficient output, shield and roof). Also, from the standpoint of reducing storage space and alleviating parking problems in the city, the mobile body can be folded or downsized when not riding, and can be carried around the city like a carry bag. Furthermore, the usability of the moving body is increased.

  Thus, in the structure of the small mobile body of the new concept collectively referred to as “ultra-small mobility” as described above, the structure is as compact as possible, and at the same time, sufficient mobility and traveling stability capable of traveling on the roadway, It must be structurally stable and comfortable to ride. Therefore, for example, various configurations (patent documents 1 and 2) found in conventional small mobile bodies such as an electric wheelchair, a senior car, a bicycle, an electric motorcycle, a moped motorcycle, an inverted control vehicle, and an electric skateboard. It is necessary to develop a new configuration that cannot be seen.

JP 2002-166709 A JP 2010-18173 A

“Guidelines for the introduction of ultra-compact mobility: To realize a new social life through the development and utilization of new mobility” June 2012 Ministry of Land, Infrastructure, Transport and Tourism

  In the above-mentioned ultra-compact mobility, as described above, it is possible to travel on a road such as a general road, and it is assumed that the traveling performance is higher than that of a small mobile body such as a conventional bicycle. It is required to have higher running stability and structural stability than a small mobile body such as the above. For example, when considering the structure of the rear wheel of a vehicle, it is conceivable to use a caster that can freely change direction as a wheel so that the weight can be reduced and simplified as much as possible. In that case, if it is a conventional small mobile body, for example, a spring structure (Patent Document 1) that applies a restoring force in a direction in which the caster is directed in the straight traveling direction is employed in order to improve the straight traveling performance of the mobile body. However, in the case of ultra-small mobility, it is desirable that the caster has a higher turning performance, that is, a turning ability corresponding to various traveling states or movement states. In addition, in the case of ultra-compact mobility, it is assumed that the vehicle travels at a high speed or for a long time compared to a conventional small mobile body, so it is robust and comfortable to withstand the vibration load input from the unevenness of the road surface during traveling. When a structure with sufficient vibration damping action for a comfortable ride is required, energy saving and downsizing structure, or a foldable or portable structure is considered. It is necessary to consider the ease of this. Therefore, it is difficult to sufficiently satisfy the above requirements with a foldable configuration (such as Patent Document 2) found in a conventional bicycle.

  Thus, one object of the present invention is to have a turning performance and a light weight that can be employed in a new type of small mobile body that can travel on a roadway collectively called “ultra-small mobility” as described above. It is to provide a rear wheel structure with a simple configuration.

  Another object of the present invention is to provide sufficient rigidity and vibration buffering action in consideration of light weight and ease of folding operation that can be adopted in the new type of small mobile body as described above. It is to provide a vehicle suspension structure.

  According to the present invention, one of the above problems is a moving body including a front wheel and a caster-type rear wheel, and supports the caster-type rear wheel so as to be rotatable in the yaw direction of the moving body. And a rear wheel rotation control means for controlling the ease of rotation of the rear wheel in the yaw direction around the rotation axis of the rear wheel based on the amount of motion of the movable body. The In such a configuration, the “moving body” is typically a new type of small moving body capable of traveling on a roadway collectively referred to as “ultra-small mobility” as described above. It may be a moving body equipped with a seat having a front wheel and a rear wheel, a seat that can sit more relaxedly, a roof that prevents rain and wind, a front shield, and the like. The “motion state quantity” may be any physical quantity that represents the motion state of the moving body, and may be the moving speed, acceleration / deceleration, and turning amount (steering angle, turning radius, etc.) of the moving body. “Ease of rotation of the rear wheel in the yaw direction” means that the rear wheel of the moving object subject to the present invention is a caster-type wheel, and can freely rotate in the yaw direction of the moving object by an arbitrary external force. It has a movable structure, and represents the degree or magnitude of the amount of rotation of the rear wheel in the direction of rotation relative to the degree or magnitude of the external force. “Easy to perform” is small or large indicates that the amount of change in the amount of rotation of the rear wheel in response to a certain amount of external force is small or large.

  According to the above configuration, if necessary, the degree of restraint of the movement of the caster-type rear wheel in the yaw direction is adjusted in consideration of the motion state of the moving body, thereby providing a simple caster-type wheel. However, it is possible to give the moving body desired traveling stability and turning performance in accordance with the motion state of the moving body. In addition, as an aspect that gives such running stability and turning performance, specifically, for example, when the moving speed of the moving body is high, the opportunity for external force to swing the rear wheel in the yaw direction increases, while running stability Therefore, it is preferable that the rear wheel is difficult to rotate in the yaw direction. Therefore, when the moving speed of the moving body is large, the rotation of the rear wheel in the yaw direction is smaller than when the moving speed is small. The ease of movement may be reduced. On the other hand, during the turning of the moving body, the direction of the rear wheels preferably changes smoothly following the turning direction required for the moving body, so the target turning amount of the moving body is large. At this time, the ease of rotation of the rear wheels in the yaw direction may be increased as compared to when the target turning amount is small.

  In the above configuration, the control of the ease of rotation of the rear wheel in the yaw direction may be specifically performed using, for example, an elastic force. Typically, when the yaw force is not applied to the rear wheel, the rear wheel is configured so that the rolling direction of the rear wheel coincides with the front-rear direction of the moving body. The body is provided with an elastic force applying means for applying an elastic force in a direction in which the direction of the rear wheel coincides with the front-rear direction of the moving body, and the elastic force changes the rolling direction of the rear wheel of the moving body. It may be used as a restoring force in a direction that matches the front-rear direction. In that case, as the magnitude of the elastic force is larger, the ease of rotation of the rear wheel in the yaw direction is reduced.

  According to another aspect of the present invention, another object of the present invention is a moving body as described above, wherein a first arm that holds a front wheel in a rollable manner at one end, One end of the arm is pivotally attached to the first arm in the vicinity of the end opposite to the front wheel side of the arm, and has a support that supports the rear wheel at the other end. One end is connected to the second arm and the front wheel side end of the first arm, the other end is connected to the rear wheel side end of the second arm, and the front wheel side of the first arm This is achieved by a moving body including a linear member that can be elastically expanded and contracted at least partially in the longitudinal direction between the end of the second arm and the end of the second arm on the rear wheel side.

  According to the above configuration, to put it briefly, the first arm that holds the front wheel, the second arm that holds the rear wheel, the front wheel side end of the first arm, and the rear wheel side of the second arm A triangle is formed by a linear member such as a wire member with a spring that connects between the end portions of the two. Then, by providing the linear member with an elastically expandable portion such as a spring, the length of the linear member elastically expands and contracts with respect to the vertical vibration of the moving body, and the first arm A structure that exhibits an elastic buffering action, that is, a suspension structure, is formed in such a manner that the angle at the pivot point between the first arm and the second arm changes. Further, the movable body can be folded by rotating the first arm and the second arm around the pivot point so that the first arm and the second arm substantially overlap each other. The elastic force of the linear member becomes an auxiliary force for the folding operation, and the operation for storing the moving body when not in use is facilitated. That is, according to the above configuration, the direction of the spring force of the suspension structure is aligned with the displacement direction of the first arm and the second arm in the folding operation. This is advantageous in that

  Preferably, the length of the linear member extending between the front wheel end of the first arm and the rear wheel end of the second arm is In particular, the direction of the rotation axis of the rear wheel is variable between a direction substantially parallel to the vertical direction of the moving body and a direction inclined at a predetermined angle from the direction. It's okay. As will be described later in the section of the embodiment, when the direction of the rotation axis of the rear wheel is inclined from a direction substantially parallel to the vertical direction of the movable body, the rolling direction of the rear wheel is changed to the longitudinal direction of the movable body. A matching action is also obtained. In addition, since the height of the moving body is changed depending on the length of the linear member and the running stability can be controlled, the length of the linear member can be changed based on the amount of motion of the moving body. In particular, when the moving speed of the moving body is large, when the linear member is extended, the height of the moving body is lowered and the running stability is increased as compared to when the moving speed is low. It will be.

  In general, according to the present invention described above, in a small moving body having a caster type rear wheel, it is possible to stabilize the yaw direction of the rear wheel without significantly increasing the weight. As compared with the conventional small mobile body, higher turning performance, that is, turning ability corresponding to various traveling states or motion states can be obtained. Further, as will be described in detail in the section of the embodiment described later, a mechanism for controlling the ease of rotation around the rotation axis of the caster type rear wheel can be achieved relatively easily. In addition, the present invention can be advantageously applied to a mobile body generally called “ultra-small mobility” that can travel on a roadway without complicating the configuration of the mobile body so much. Furthermore, according to the structure in which the first arm and the second arm pivotally attached to each other are connected by a linear member that can be elastically expanded and contracted at least partially, the suspension mechanism and the moving body that are indispensable for stable running are provided. Thus, it is possible to avoid the significant increase in the number of parts of the moving body and the complexity of the structure.

  Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the present invention.

1A and 1B are a schematic perspective view and a side view of a moving body to which the present invention is applied. FIG. 1C is a schematic side view of a state in which the moving body is folded. FIG. 1D is a view similar to FIG. 1B in a state where the connecting wire of the moving body is extended to reduce the height. FIGS. 2A and 2B are schematic side views of the moving body to which the present invention is applied and the folded state, respectively, equipped with a winding mechanism for the connecting wire. 2C and 2D are schematic views of the internal configuration of the winding device for the connecting wire of the moving body, FIG. 2C is a state in which the wire is held, and FIG. This is a state in which a winding / unwinding operation is performed. FIG. 2E is a diagram schematically showing the meshing of the gear in FIG. FIG. 2F schematically shows the arrangement of gears when the winding and unwinding operations of the wire 13a for controlling the vertical displacement of the front shield are executed in the connecting wire winding device. It is a figure. FIGS. 3A and 3B are examples of a structure that provides a restoring force for aligning the direction of the rear wheel with the front-rear direction of the moving body in the yaw direction in the caster-type rear wheel of the moving body. It is a typical side view of the rear wheel vicinity which shows. FIG. 4 (A) shows the control of the restoring force for adjusting the direction of the rear wheel in the yaw direction to the front-rear direction of the moving body (in the rear wheel of the moving body according to the present invention). FIG. 6 is a schematic side view of the vicinity of a rear wheel showing a configuration for performing control of ease of rotation. FIGS. 4B and 4C are views of the configuration of FIG. 4A viewed from the bottom, FIG. 4B is a state where the restoring force is set small, and FIG. 4C is the restoring force. This is a large setting. The upper stage is a state in which the rolling direction of the rear wheel is aligned with the front-rear direction of the moving body, and the lower stage is a state in which the rear wheel is rotated around the rotation axis. FIGS. 2D and 2C are schematic side views of the vicinity of the rear wheel showing another embodiment of the control of the restoring force of the rear wheel. FIG. 5 is a block diagram showing a control configuration for controlling the ease of rotation of the rear wheels based on the vehicle motion state according to the present invention. FIG. 6 is a schematic side view of the vicinity of the rear wheel for explaining the case where the control of the ease of rotation of the rear wheel according to the present invention is executed by changing the direction of the rotation axis of the rear wheel.

DESCRIPTION OF SYMBOLS 1 ... Moving body 2 ... Front shield 2a ... Fairing part 3 ... Front wheel 4 ... Front wheel drive part 5 ... Main frame (1st arm)
6, 8, 11 ... pivot 7 ... swing arm (second arm)
DESCRIPTION OF SYMBOLS 9 ... Seat surface 10 ... Back support 12 ... Spring 13, 13a ... Wire 14 ... Rear wheel 14a ... Rear-wheel axle 15 ... Wire winding device 16 ... Pulley 22 ... Motor with reduction gears 24, 26, 26a ... Gear 25 ... Wire Winding shafts 27, 28 ... meshing teeth 29 ... spring 30 ... winding shaft end 31 ... pressing device 41 ... caster housing 42 ... rear wheel yaw direction rotating shaft 43 ... torsion bar 45 ... torsion spring 50 ... coil spring 51 ... Actuators

  The present invention will now be described in detail with reference to a few preferred embodiments with reference to the accompanying drawings. In the figure, the same reference numerals indicate the same parts.

Structure of mobile body The small mobile body to which the present invention is applied is a mobile body generally referred to as “personal mobility”, “ultra-small mobility”, etc. And a small mobile body equipped with a power unit, a suspension unit, a front shield and the like having an intermediate configuration of the conventional automobile. Referring to FIGS. 1A and 1B, the basic configuration of such a small movable body 1 is that a left and right front wheel 3 and a front wheel drive unit 4 that electrically drives these front wheels can be pivoted by a pivot 6. A main frame (first arm) 5 that is held on the rear side and a rear wheel 14 is supported at one end, and the other end is pivotally connected to an upper portion of the main frame 5 by a pivot 8 And a swing arm (second arm) 7. On the upper surface of the front wheel drive unit 4, a fairing unit 2 a having a front shield 2 slidable in the vertical direction may be provided in a state inclined slightly rearward from the vertical direction. A seat composed of a seating surface 9 and a backrest 10 may be provided above the pivot point 8 with the swing arm 7. The seat surface 9 and the backrest 10 may be pivotable relative to each other about the pivot 11. Further, the lower end of the main frame 5 and the lower end of the swing arm 7 are connected by a connecting wire 13 including an elastically extendable spring 12, and the main frame 5, the swing arm 7 and the wire 13 form a substantially triangular shape. Thus, a trailing type suspension structure is formed. That is, when the main frame 5 and the swing arm 7 receive a load from above, the spring 12 of the connecting wire 13 extends to balance the load. Then, vibration from the road surface received by the main frame 5 and the swing arm 7 or vibration due to other factors is absorbed by expansion and contraction of the spring 12 of the connecting wire 13. The driving of the moving body is performed by electrically driving the front wheels, and the turning of the moving body may be performed, for example, by giving a rotational speed difference between the left and right front wheels. Thus, the above moving body can travel like an electric bicycle with a suspension while the driver is sitting on a chair.

  Furthermore, a feature of the structure of the moving body 1 is that it can be folded when the moving body is not used. As shown in FIG. 1C, when the movable body 1 is folded, the front shield 2 is slid down and substantially superimposed on the fairing portion 2a, The seat surface 9 and the backrest 10 are pivoted by a pivot 11 and folded substantially parallel to the main frame 5, and the swing arm 7 is pivoted by a pivot 8 and folded substantially parallel to the main frame 5. Further, the main frame 5 is pivoted around the pivot 6 in a substantially vertical direction with respect to the front wheel drive unit 4. The connecting wire 13 may be bent when the swing arm 7 overlaps the main frame 5. And when it is folded and downsized as shown in FIG. 1 (C), the moving body is pulled by the user like a carry bag with the rear wheel (which is a free wheel without power) as a rotating wheel. Can be carried. Or you may make it move following a user's walk by driving the front wheel 3 which has motive power. Thus, according to the above-described features, unlike a conventional small mobile body such as a bicycle, the power device, the suspension device, the front shield, and the like are equipped. Since downsizing can be easily achieved, it is expected that advantages such as bringing to public transportation such as trains and buses, reducing storage space, and mitigating bicycle parking problems will be expected. In addition, in order to hold | maintain a use state (expanded state) and a folding state, the locking mechanism for hold | maintaining each part stably by arbitrary forms may be provided suitably.

Regarding the structure of the suspension structure of the moving body As described above, the suspension structure of the moving body according to the present invention is elastically provided at the end of the main frame 5 and the swing arm 7 which are pivotally attached to each other on the side opposite to the pivot point. It is formed by connecting with a wire 13 including a spring 12 that can be expanded and contracted. In such a configuration, the length of the wire 13 may be changeable under an arbitrary condition, for example, by the setting of the driver or based on the traveling state of the moving body. For example, as shown in FIG. 1 (D), when the wire 13 is extended, the height of the moving body is lowered, thereby improving the lateral G resistance in the curve traveling by lowering the center of gravity and / or the effect of extending the wheel base. The running stability during high speed running can be improved.

  In addition, regarding the suspension structure of the moving body of the present invention, a winding (unwinding) device for the wire 13 is provided in the moving body 1 for the purpose of adjusting the length of the wire 13 and storing it when folded. It may be. Referring to FIG. 2, for example, the winding device 15 for the wire 13 is specifically attached to the front wheel drive unit 4, and when the moving body is used, as shown in FIG. 13 is adjusted to an appropriate length (the moving state of the moving body, for example, the length of unwinding may be adjusted based on the moving speed), and when the moving body is stored, FIG. As shown in B), the wire 13 may be accommodated in the winding device 15.

  As one structure for achieving the operation of the winding device 15, for example, as illustrated in FIGS. 2C and 2D, a configuration using a motor 22 with a speed reducer may be employed. In the case of the illustrated example, more specifically, in the housing of the winding device 15, the motor 22 with a speed reducer in which a gear 24 (such as a spur gear) is mounted on the rotary shaft 23, and the wire 13 is rotated. And a wire winding shaft 25 for winding and unwinding the wire. The winding shaft 25 has a gear 26 selectively engaged with the gear 24 and a meshing tooth (dog clutch) 27 meshed with a meshing tooth (dog clutch) 28 fixed to the housing of the winding device 15. And a spring 29 that is biased in a direction to release the engagement between the gear 24 and the gear 26 is disposed between the meshing tooth 28 and the end 30 of the winding shaft 25. A pressing device 31 that selectively displaces the winding shaft 25 in the direction in which the gear 24 and the gear 26 are engaged is disposed adjacent to the end 30 of the winding shaft 25.

  In the operation of the winding device 15, first, when the length of the wire 13 is held at a certain length, as shown in FIG. 2C, the pressing device 31 and the motor 22. Accordingly, the engagement of the gear 24 and the gear 26 is released by the action of the spring 29, and the winding shaft 25 is displaced so that the meshing tooth 27 is engaged with the meshing tooth 28. It is made to the state. In this state, the wire 13 is unwound and held at a predetermined length. On the other hand, when the length of the wire 13 is adjusted or when the wire 13 is wound, the pressing device 31 is energized, and as a result, as shown in FIG. The portion 30 is pressed and displaced against the action of the spring 29, the engagement between the meshing tooth 27 and the meshing tooth 28 is released, and as shown in FIG. Engagement with the gear 26 is achieved. In this state, when the motor 22 is energized, the rotation of the rotating shaft 23 and the gear 24 causes the gear 26 and the winding shaft 25 to rotate, until the wire 13 reaches a predetermined length. Winding or unwinding of the wire 13 is executed. In particular, when the moving body is folded, the wire 13 may be wound as much as possible. When the unwound length of the wire 13 reaches a desired length, the urging of the pressing device 31 and the motor 22 is stopped, and the winding shaft 25 is again displaced by the action of the spring 29. The engagement teeth 27 and the engagement teeth 28 are engaged, and the length of the wire 13 is maintained.

  By the way, in the moving body of the present invention, as described above, when the moving body is expanded and folded, the front shield is also moved in the vertical direction. May be achieved. Specifically, for example, first, as shown in FIGS. 2A and 2B, a wire between the lower end of the front shield 2 and the winding device 15 is interposed via a pulley 16. Connected at 13a. The upward movement of the front shield is achieved by winding the wire 13a through the pulley 16 by the winding device 15, and the downward movement of the front shield is performed by winding the wire 13a from the winding device 15. Achieved by putting out. Note that winding and unwinding of the wire 13a may be performed in the same manner as the winding and unwinding of the wire 13. The rotation of the gear that rotates integrally with a winding shaft (not shown) for winding and unwinding the wire 13a may be achieved using the motor 22. In this case, as illustrated in FIG. 2F, a gear 26a for winding and unwinding the wire 13a is disposed on the circumference of the gear 24 attached to the rotating shaft 23 of the motor 22. According to such a configuration, it is not necessary to separately provide a motor for winding / unwinding the wire 13 and a motor for winding / unwinding the wire 13a, which is advantageous in terms of weight saving and space saving. is there.

Rear wheel support structure As already described, the driving and turning of the moving body of the present invention is performed by rotationally driving the left and right front wheels differentially using an in-wheel motor or the like. In order to enable a small turning of the body, caster type wheels that can swing or rotate in the yaw direction of the moving body with respect to the swing arm 7 may be employed. However, in the case of a caster-type rear wheel that can rotate in the yaw direction, if the speed of the moving body increases, the swinging tends to occur due to factors such as vibration, so that the running stability decreases, and a phenomenon such as spin Can occur. Therefore, in order to improve running stability, as illustrated in FIG. 3, the rotation direction of the rear wheel 14 is aligned with the front-rear direction of the movable body on the rotation shaft 42 of the rear wheel 14. A spring mechanism that provides a restoring force may be provided. Specifically, as the spring mechanism, for example, as illustrated in FIG. 3A, the rear wheel 14 is supported by a U-shaped caster housing 41 so as to be able to roll around the axle 14a. In the configuration in which 41 is rotatably supported on a rotation shaft 42 fixed to the swing arm 7, the rotation shaft 42 is configured by a rotary bearing and a hollow bolt, and a torsion is formed in the hollow hole of the rotation shaft 42. The bar 43 is penetrated. The torsion bar 43 has an L shape, and one end thereof is fixedly coupled to the caster housing 41 and the other end is fixedly coupled to a fixing portion 44 fixed to the swing arm 7. In such a configuration, when the rear wheel 14 and the caster housing 41 are rotated in the yaw direction, the torsion bar 43 is twisted, thereby generating an elastic restoring force in a direction to eliminate the twist. It will be. Further, as another aspect of the spring mechanism described above, instead of the torsion bar 43 penetrating the rotation shaft 42, the spring mechanism is wound around the rotation shaft 42 as shown in FIG. Alternatively, a torsion spring 45 that is fixed to the fixed portion 46 and the other end is fixed to the caster housing 41 may be used.

  By the way, in the case of the mobile body of the present invention, the motion state such as the speed and the turning amount changes variously as compared with a mobile body (such as a handcart) having a conventional caster type wheel. Therefore, it is preferable that the ease of rotation of the rear wheel (in the yaw direction) is appropriately controlled according to the motion state such as the speed of the moving body and the turning amount. The control of the ease of rotation of the rear wheel is performed by adjusting the magnitude of the elastic restoring force acting in the direction in which the rolling direction of the rear wheel 14 is aligned with the front-rear direction of the moving body. Achievable. Thus, in the mobile body of the present invention, the magnitude of the elastic restoring force acting on the rear wheel 14 is controlled so as to control the ease of rotation of the caster-type rear wheel. May be adjusted based on the amount of motion state.

  Specifically, as a mechanism for adjusting the elastic force acting on the rear wheel 14 based on the amount of motion state, for example, as illustrated in FIG. 4A, the rear wheel 14 is attached to the caster housing 41 on the axle. The caster housing 41 is supported so as to be able to roll around the pivot member 14 a, and the caster housing 41 is rotatably supported with respect to the rotating shaft 42 attached to the swing arm 7. In addition, a spring mechanism capable of adjusting the elastic force is attached. More specifically, with reference to the figure, the coil spring 50 is attached so that the pin 54 provided on the front side of the caster housing 41 is pulled forward with respect to the swing arm 7. The front end of the coil spring 50 is locked to an operating shaft 52 of an actuator 51 fixedly attached to the swing arm 7 via a pin 53, and the position of the operating shaft 52 in the front-rear direction of the moving body. By this, the magnitude of the elastic force of the coil spring 50 that pulls the caster housing 41 forward is changed. In the operation of this configuration, during straight traveling at a certain speed, the actuator 51 positions the operating shaft 52 as illustrated in FIG. 4B, so that an external force is applied to the rear wheel. In such a case, a certain amount of elastic force acts so that the direction of the rear wheel is aligned with the front-rear direction of the moving body, and as shown in the lower part of FIG. The rear wheels are allowed to swing within the range where the two are balanced.

  From this state, when the speed of the moving body increases, as illustrated in FIG. 4C, the actuator 51 pulls the operating shaft 52 forward, and thereby the coil spring 50 is extended. The elastic force acts to align the direction of the rear wheel in the front-rear direction of the moving body, thereby reducing the degree of rotation of the rear wheel as shown in the lower part of FIG. The ease of rotation of the rear wheels will be reduced. The pull-in amount of the operating shaft 52 of the actuator 51 may be increased as the speed increases, and thereby the ease of turning the rear wheel may be reduced as the speed increases. On the other hand, since the direction of the rear wheels preferably changes following the turning direction of the moving body when the moving body turns, the actuator 51 projects the operating shaft 52 rearward than when traveling straight ahead. It's okay. In this case, since the coil spring 50 is contracted, the elastic restoring force acting on the rear wheel is reduced, and the change in the direction of the rear wheel is more easily permitted. The protruding amount of the operating shaft 52 of the actuator 51 may be increased as the required turning amount is increased, thereby increasing the ease of rotation of the rear wheels.

  Further, as another aspect of the mechanism for adjusting the elastic force acting on the rear wheel 14 based on the amount of motion state as described above, the expansion and contraction of the coil spring 50 is exemplified in FIG. As shown in FIG. 4 (E), the push / pull cable 56 may be used, or a link mechanism including a bell crank 57 and a rod 58 may be used.

  The control of the elastic force (coil spring expansion / contraction control) in the mechanism for adjusting the elastic force acting on the rear wheel 14 based on the amount of motion state is performed following the speed control and turning control of the moving body. It's okay. In short, referring to the control block diagram of FIG. 5, first, the driver makes a desired speed or acceleration / deceleration and a desired turning amount (the rudder of the moving body) with respect to the control system input device 100 such as a joystick. When the angle is input, a target speed, a target acceleration / deceleration and / or a target turning amount corresponding to the driver's input is transmitted from the control system input device to the front wheel differential drive control device 101. The differential drive control device 101 calculates the rotation amount (target torque) of the differential motor from the target speed or the target acceleration / deceleration, and also determines the left / right difference between the turning radius of the moving body and the rotation amount of the differential motor from the target turning amount. , The motor rotation amount command corresponding to these control target values is transmitted to the front wheel drive motor inverter 102, and the power corresponding to the control command is transmitted from the front wheel drive motor inverter 102 to the front wheel drive motor 4. Supplied. Further, in the differential drive control device 101, a rotation allowable angle in the yaw direction of the rear wheel corresponding to the speed is determined from the target speed and the target turning amount, and an actuator corresponding to the rotation allowable angle. A control command representing the driving amount 51 (the amount of expansion and contraction of the coil spring) is given to the rear wheel rotation control inverter 103. Then, electric power corresponding to the control command is supplied from the rear wheel rotation control inverter 103 to the actuator 51, and the displacement of the operating shaft 52 is executed by the actuator 51, thereby adjusting the length of the coil spring 50.

  By the way, the configuration for applying the restoring force as described above to the caster type rear wheel can also be achieved by inclining the rotation axis of the rear wheel from the vertical direction to the front of the moving body as shown in FIG. That is, as shown in the drawing, when the axis Y of the rotation axis of the rear wheel is tilted from the vertical direction V, the intersection of the axis Y and the road surface moves forward from the ground contact point of the wheel, and thereby the ground contact point of the wheel. In this case, a rearward force acts, which becomes a restoring force of the rear wheel. Since the magnitude of the restoring force depends on the trail amount D between the intersection of the axis Y and the road surface and the contact point of the wheel, the trail amount D may be adjusted to obtain a desired restoring force. Adjustment of the direction of the rotation axis of the rear wheel, that is, the trail amount D is achieved by adjusting the narrow angle between the main frame 5 and the swing arm 7 by adjusting the length of the wire 13 (FIG. 1 (D)). According to this configuration, an unexpected swinging motion of the rear wheel due to a disturbance lateral force or the like is suppressed, and it is possible to maintain straight running performance, which is advantageous. In addition, the structure which inclines the rotational axis of a rear wheel may be used together with the structure which gives a restoring force with the spring illustrated in FIG.

  Thus, according to the above-described series of configurations of the present invention, the rear wheel is a caster type small moving body, and does not significantly increase the weight, and has a simple structure and various running states or motion states. Maintenance or improvement of running stability corresponding to the above is achieved.

  Although the above description has been made in relation to the embodiment of the present invention, many modifications and changes can be easily made by those skilled in the art, and the present invention is limited to the embodiment exemplified above. It will be apparent that the invention is not limited and applies to various devices without departing from the inventive concept.

Claims (6)

A mobile body comprising a front wheel and rear wheel casters formula, a support for supporting rotatably the rear wheel of the caster type in the yaw direction of the movable body, its orientation with respect to the rear wheel wherein An elastic force applying means for applying an elastic force so as to coincide with the longitudinal direction of the moving body, an actuator for increasing or decreasing the elastic force of the elastic force applying means, and when the moving speed of the moving body is high, the moving speed is low. A moving body having rear wheel rotation control means for controlling the actuator so that the ease of rotation of the rear wheel in the yaw direction is reduced .   2. The movable body according to claim 1, wherein when the target turning amount of the moving body is large, it is easier to rotate the rear wheel in the yaw direction than when the target turning amount is small. The moving body is increased.   The moving body according to claim 1, wherein a first arm that holds the front wheel in a rollable manner at one end, and a vicinity of an end of the first arm opposite to the front wheel A second arm having one end pivotally attached to the first arm and having the support body supporting the rear wheel at the other end; and the first arm One end is connected to the end portion on the front wheel side, and the other end is connected to the end portion on the rear wheel side of the second arm, and the end on the front wheel side of the first arm And a linear member that can be elastically expanded and contracted at least partially in the longitudinal direction between the first arm and the end of the second arm on the rear wheel side.   The movable body according to claim 3, wherein the linear member extends between the end of the first arm on the front wheel side and the end of the second arm on the rear wheel side. A movable body having a variable length, and a direction of the rotation axis of the rear wheel being variable between a direction substantially parallel to the vertical direction of the movable body and a direction inclined at a predetermined angle from the direction. .   5. The moving body according to claim 3, wherein the length of the linear member is changeable based on a motion state amount of the moving body.   6. The moving body according to claim 5, wherein when the moving speed of the moving body is high, the linear member is elongated as compared to when the moving speed is low.

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