Vehicle Adapted to Freely Travel Three-Dimensionally and Up Vertical Walls by Magnetic Force and Wheel for the Vehicle

The present invention relates to vehicles adapted to freely travel in three-dimensional spaces with use of a magnetic force. The present invention also relates to wheels for such vehicles.

Various vehicles of the type mentioned have been proposed which have a pair of wheels at each of the front and rear portions of the vehicle body. Each of the wheels includes a permanent magnet interposed between two or three disks of magnetically permeable material. However, since the permeable disk is in direct contact with the running surface, the surfaces on which such a vehicle is capable of travelling are limited. For example in translation from horizontal wall to vertical wall, the disk becomes attracted to both the walls, failing to leave the horizontal wall and bringing the vehicle to a halt. Further because the permeable disks and the magnet are left exposed during use, the vehicle can not be free from the buildup of ferromagnetic particles of dirt or rust during travel.

An object of the present invention is to solve these problems of the prior art.

More specifically, an object of the invention is to provide a vehicle adapted to travel through pipes without being blocked by obstacles of various configurations such as a vertical wall extending from a horizontal surface.

Another object of the invention is to provide a vehicle which can be free from the buildup of ferromagnetic particles of dirt or rust during travel within pipes.

To fulfill these objects, the present invention provides a vehicle adapted to freely travel three-dimensionally and comprising a vehicle body, and at least one wheel provided at the vehicle body, the wheel comprising an outer wheel member having an annular peripheral wall, an inner wheel member including a portion of magnetically permeable material having an outside diameter smaller than the inside diameter of the outer wheel member and rollable on the inner peripheral surface of the outer wheel member, and a magnet provided in the inner wheel member and having magnetic poles in contact with the permeable portion.

The invention further provides a vehicle adapted to freely travel three-dimensionally and comprising a vehicle body, at least one wheel provided at the vehicle body, and a drive assembly mounted on the vehicle body for driving at least one of the wheels, the wheel comprising an outer wheel member having an annular peripheral wall, an arm rotatably mounted on the central portion of the outer wheel member and having a portion of magnetically permeable material radially extending to a position close to the inner peripheral surface of the outer wheel member, a magnet mounted on the arm with its poles in contact therewith, and an arm rotating portion for rotating the arm through a desired angle independent of the outer wheel's rotation.

According to the embodiment of the invention, each of the wheels attached to the vehicle body comprises an outer wheel member having an annular peripheral wall, an inner wheel member having a portion of magnetically permeable material and a magnet provided in the inner wheel member, so that the magnetic force of the magnet acts on the running surface through the inner wheel member and through the outer wheel member. The vehicle is therefore adapted to travel reliably along vertical surfaces, ceiling, inclined surfaces and the like while being prevented from slipping or falling by the magnetic force of attraction. Especially for translation between two surfaces of different inclinations as between a horizontal wall and a vertical wall, the inner wheel member, which is rollable on the inner peripheral surface of the outer wheel member, first moves from one surface to the other by moving along on the inner peripheral surface of the outer wheel member, which is halted in contact with the two surfaces, thereby permitting the outer wheel member to move along with ease. Consequently, the vehicle is capable of travelling freely of the surface of complex obstacles in a three-dimensional space.

In the case where the outer wheel member has an annular peripheral wall and two side walls closing the respective opposite ends of the peripheral wall to enclose the inner wheel member therein, the inner wheel member can be free from magnetic dust or particles.

According to another embodiment of the invention, the wheel attached to the vehicle body comprises an outer wheel member, an arm rotatably mounted on the central portion of the outer wheel member and having a portion of magnetically permeable material radially extending to a position close to the inner peripheral surface of the outer wheel member, and a magnet mounted on the arm. The arm can therefore be freely oriented toward the running surface magnetically to hold the wheel to the running surface. This enables the vehicle to travel reliably on surfaces of any inclination. The wheel is further provided with an arm rotating portion for rotating the arm through a desired angle. When the wheel comes into contact with a stepped portion, the arm is driven through about 90 degrees and held to the stepped portion, and the outer wheel member is driven in this state, whereby the wheel is caused to climb the stepped portion.

Other objects, features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings.

FIG. 1 is a side elevation in vertical section showing a train of vehicles embodying the invention during travel within a pipe;

FIG. 2 is a sectional view schematically showing an example of a wheel which is usable for the vehicles shown in FIG. 1;

FIG. 2A is a sectional view schematically showing another example a of vehicle different from the vehicle shown in FIG. 2 in having no driving;

FIGS. 3a-3e disclose the wheel of FIG. 2 in transition from movement on a horizontal wall to movement on a vertical wall;

FIG. 4 is a sectional view schematically showing another example of a vehicle which is usable for the vehicles of FIG. 1;

FIGS. 5a-5e and FIGS. 6a-6b disclose the wheel of FIG. 4 in transition from movement on a horizontal wall to movement on a vertical wall;

FIGS. 7a-7c disclose a vehicle in transition movement on a stepped horizontal wall;

FIG. 8 is a sectional view showing the wheel of the vehicle of FIG. 7;

FIG. 9 is a diagram showing the angular resolution of the vehicle sensor;

FIG. 10 is a diagram of the scanning of the sensor to detect obstacles and openings within a pipe and

FIGS. 11a-11e are graphs plotting distance and time of sensor data under different pipe conditions.

FIG. 1 shows a vehicle 1A, 1B and 1C of the invention which are connected together and adapted to freely travel three-dimensionally while the train of vehicles is traveling in a pipe A. Each of these vehicles has a body 10, and a pair of wheels 20 at each of the front and rear portions of the vehicle body 10. The vehicle 1A is further provided within its body 10 with a drive assembly 11 (shown in FIG. 2), steering assembly 12, battery unit 13, surface detector 14, device 15 and computer 16. The device 15 can comprise a gyro device and/or a tilt sensor. The vehicle 1B has a battery unit 13 for supplying power to the vehicle 1A. The vehicle 1C has mounted in its body a surface detector 14 which is usable when the train advances reversely, and is adapted to carry thereon various working devices needed. Flexible drive and steering cables 18 extend from the drive assembly 11 and the steering assembly 12 of the vehicle 1A for driving and steering the wheels 20 of these connected vehicles. Alternately, for some applications a single large vehicle may be used instead of the train of vehicles shown in FIG. 1.

With reference to FIG. 2, each wheel 20 comprises an outer wheel member 21 having an annular peripheral wall 22 and side walls 23 covering opposite sides of the wall 22, an inner wheel member 25 of magnetically permeable material having an outside diameter smaller than the inside diameter of the outer wheel member 21 and rollable on the inner peripheral surface of the outer wheel member 21, and a magnet 27 fitted in the inner wheel member 25 with their poles in contact therewith. The peripheral wall 22 and the side walls 23 of the outer wheel member can be made of a metal, rubber, synthetic resin or composite material of such substances having rigidity capable of bearing the load of the vehicle body and the magnetic forces. The outer wheel member has a disk 24 formed in its central portion with an opening for the magnet 27 to extend therethrough and covering the opening of the wheel member 21. The disk 24 is flexible so as to shift its opening radially. It is desired that the peripheral wall 22 contain magnetic particles, which are preferably arranged into a multiplicity of columns radially of the outer wheel member, whereby the lines of magnetic force from the magnet 27 can be effectively directed toward the running surface. Alternately, outer wheel member 21 can be a metal shell. By using a metal shell the outer wheel member 21 can be made very rigid and strong. As will be clear from the later discussion of FIG. 3, a rigid outer wheel member 21 is desirable to avoid deformations of outer wheel member 21 during transitions from a horizontal wall to a vertical wall or the like. The metal shell can be coated with softer materials, such as rubber, to increase traction and to avoid damaging the surface on which outer wheel member 21 is rolling. Additionally, the peripheral wall 22 can be made of magnetic steel, iron, or other magnetically permeable material to assist in transmitting the magnetic field from inner wheel member 25 to surface A. In this particular embodiment it is desirable to make side walls 23 out of a non-magnetic metal to reduce unwanted magnetic flux leakage. The non-magnetic metal side walls 23 may be welded or otherwise attached to the magnetic metal peripheral wall 22 to form the metal shell for outer wheel member 21. The inner wheel member 25 of the present embodiment has a pair of bowl-shaped disks of soft iron spaced apart from each other. Alternatively, the inner wheel member 25 can have a pair of solid disks. Whether bowl-shaped or solid, the outer circumference of inner wheel member 25 can be shaped to match the curvature of the pipe. The inner wheel member 25 can be made of other magnetically permeable material. The magnet 27 is in the form of a bar and is fixedly provided between the pair of soft iron disks of the inner wheel member 25, with the N and S poles in contact with the disks. Although the magnet used in the present embodiment is a permanent magnet for lightness, an electromagnet is alternatively usable if the weight and power poses no substantial problem. The same is true of the other embodiments to be described below. Since the wheel of FIG. 2 has steering and driving functions, the wheel is provided with the mechanisms to be described below for performing these functions. An annular bevel gear 28 is fixedly mounted around the central portion of the magnet 27 and coupled to the drive assembly 11 and the steering assembly 12. FIG. 2 partly shows the drive assembly 11 and the steering assembly 12. The drive assembly 11 comprises a flexible drive shaft 110, a gear 111 supported by the vehicle body and rotatable by the drive shaft, drive bellows 112 connected at one end thereof to the gear, and a bevel gear 113 connected to the other end of the bellows and meshing with the bevel gear 28 on the magnet 27. The steering assembly 12 comprises a flexible steering shaft 120, a gear 121 supported by the vehicle body and rotatable by the steering shaft, steering bellows 122 connected at one end thereof to the gear, and a pair of bearings 123 connected to the other end of the steering bellows and rotatably supporting the magnet 27 inside. The steering gear 121 and the steering bellows 122 have a central hollow portion for the drive bellows 112 to extend therethrough coaxially. The pair of bearings 123 are disposed on the respective opposite sides of the bevel gears 113 and 28. Disposed between the gear 121 and the pair of bearings 123 is a coiled compression spring 125 surrounding the steering bellows 122 for supporting the load of the vehicle body. In the wheel 20, the rotation of the drive shaft 110 is transmitted to the gear 28 to rotate the magnet 27 and the inner wheel member 25. The rotation of the wheel member 25 rotates the outer wheel member 21 to advance the vehicle body. Rotation of the outer wheel member 21 tends to sweep unwanted magnetic debris, such as rust particles, away from the magnetic field of the inner wheel member 25. Once away from the strong magnetic field, the debris will fall or can be easily brushed off. Further, the rotation of the steering shaft 120 is transmitted to the magnet 27 via the bearings 123, rotating the magnet 27, inner wheel member 25 and outer wheel member 21 about an axis peripendicular to the running surface for steering. The drive bellows 112 and the steering bellows 122 are metal bellows, which are free to stretch or contract axially thereof to absorb irregularities in the running surface but are rigid in the direction around the axis for the transmission of torque. These bellows can be replaced by various means which are so constructed as to produce the same effect. For example, the drive shaft can be provided with a universal joint and a telescopic expansion joint at an intermediate portion thereof.

In the case where the wheel 20 need not have the driving function, the gear 111 and driven bellows 112 can be dispensed with since there is no need to connect the wheel to the drive shaft 110. Further if the wheel 20 need not have the steering function, as shown in FIG. 2A, a shock absorber 126 and a coiled compression spring 125 can be provided for supporting the bearings 123 supporting the magnet 27, with the bevel gears 113, 28, the steering bellows 122, etc. dispensed with.

The vehicle thus constructed travels in the following manner, for example, for translation from horizontal wall to vertical wall. FIG. 3 shows one of the wheels 20 of the vehicle during travel. First as seen in FIG. 3 (a), the wheel 20 moves along from right to left in the drawing while rolling on the horizontal wall. In the wheel 20, the inner wheel member 25 is driven to roll along inside the outer wheel member 21 to thereby advance the outer wheel member 21. Upon coming into contact with the vertical wall as shown in FIG. 3 (b), the outer wheel member 21 is used to advance horizontally, permitting the inner wheel member 25 to ascend the inner peripheral surface of the outer wheel member (see FIG. 3 (c)). When the inner wheel member 25 continues its rotation after ascending the inner peripheral surface of the outer wheel member 21 to the position shown in FIG. 3 (d), the outer wheel member 21 starts to advance upward along the vertical wall (see FIG. 3 (e)). In translation from vertical wall to horizontal wall as shown in FIG. 1 or in ascending or descending a curved surface, the inner wheel member 25 moves along such a running surface, allowing the outer wheel member 21 to move along together with the member 25. In this way, the wheel 20 is capable of traveling along walls in a three-dimensional space freely.

Next, the diameter ratio between the outer wheel member 21 and the inner wheel member 25 of the wheel 20 will be described. For the transition from the state of FIG. 3 (b) to the state of FIG. 3 (c), the inner wheel member 25 needs to ascend the inner surface of the outer wheel member from the position most proximate to the horizontal wall, i.e., from the lowermost portion of the inner surface of the outer wheel member, against a magnetic force Fv acting toward the horizontal wall. In this case, the greater the difference in diameter between the outer wheel member 21 and the inner wheel member 25, the smaller is the height the inner wheel member 25 ascends per revolution thereof and therefore the smaller is the force needed for the member 25 to ascend the inner surface. However, when the diameter difference between the two wheel members is excessively large, the magnetic force Fh acting on the vertical wall is likely to be insufficient in an intermediate state like the state shown in FIG. 3 (c). Especially, if the magnetic force is insufficient in translation from vertical wall to ceiling or like horizontal wall, the vehicle is likely to fall. On the other hand, if the two wheel members are closer in diameter, the greater is the force required of the inner wheel member for ascending the inner surface of the outer wheel member, but greater is the magnetic force available in the intermediate state. Accordingly, the diameter ratio between the outer wheel member and the inner wheel member must be so determined as to meet both the requirements in respect of the ease with which the inner wheel member moves along the outer wheel member's inner surface against the magnetic force Fv and the magnitude of force holding the wheel to the running surface. It is desired that the difference between the inner and outer wheel members be as great as possible insofar as a sufficient holding force is available. In determining the diameter difference, consideration is given to the coefficient of friction between the two wheel members, mode of translation between running surface portions, weight of the inner wheel member including the magnet, weight of the vehicle, etc.

Even in the case where the wheel 20 is not coupled to the driven shaft like the wheels of the vehicle 1B, the wheel is held to the wall in the same manner as described above and differs only in that the inner wheel member is moved as by the traction of the preceding vehicle.

The vehicle 1A shown in FIG. 1 is equipped with the surface detector 14, device 15 and computer 16 to be described below.

The surface detector 14 comprises a projector for emitting light forwardly of the vehicle, a position sensor for detecting the position of a reflecting surface from the light emitted by the projector and reflected from the surface to produce a surface position signal, and means for rotating the projector and the position sensor about an axis in parallel to the direction of advance of the vehicle body. Preferably the projector is a semiconductor laser for projecting a beam. The position sensor can be a semiconductor position sensor or like known device capable of detecting the position of reflecting surfaces from the reflected light. The rotating means rotates the projector and the position sensor about the above-mentioned axis to thereby scan the inner surface of the contemplated pipe with the light from the projector and obtain surface position signals for the entire inner surface.

An important quality of the sensor is its angular resolution. When the vehicles approach an opening in the pipe wall, such as a tee joint, the sensor will see only a small gap in the pipe wall. The size of this gap depends on how far the vehicles is from the opening. In FIG. 9, the required angular resolution is shown. If the minimum feature, F, to be measured is 5 mm at a distance, L, of 200 mm, about 0.5 degree resolution, B, is required.

The sensor scans the pipe wall ahead of the vehicles. By moving the laser and photodetector together, the sensor is made to scan a circle, preferably concentric with the circumference of the pipe. Alternatively, the scanning could be accomplished by moving the focusing optics with the laser and sensor stationary. If anything intruded in the pipe space (A in FIG. 10) it would show up as an unusually close distance on the sensor. Also any openings in the pipe (B) would be seen as a longer or infinite distance. The sensor processing module receives these distance-versus-time (the time represents the angular position of the sensor) data and processes them to determine whether the pipe is clear, whether there is an obstacle in the pipe, or whether a junction has been reached (and if so, what type of junction).

When the pipe is clear, the plot of distance vs. time for a pipe slightly larger than the vehicle's cross section will be more or less a constant, as shown in FIG. 11 (a). When the vehicle's cross-section is much less than the pipe, we get a curve, FIG. 11 (b), in which the distance is more or less constant for the portion of the pipe closest to the vehicles then rises smoothly and drops back smoothly to the constant value. An obstacle in the pipe, such as a wrench, results in a distance discontinuity in the normal distance curve, followed by a short constant value, followed by a discontinuity back to the normal distance curve, as in FIG. 11 (c). A pipe junction results in a loss of data for a period of time because the return is lost while the beam falls into the branch pipe, resulting in a break in the distance-vs.-time curve, as in FIG. 11 (d). An ell junction, unlike a tee, results in a loss of signal on one side of the pipe with a increased signal on the opposite side, as in FIG. 11 (e).

Besides the surface detector 14 utilizing light as described above, also usable are those utilizing various means such as ultrasonic waves or microwaves.

As the device 15 various kinds of gyros and/or tilt sensors can be used. The gyro can be one of various known means such as ring laser gyro, turned dry gyro, single-degree-of-freedom floated rate integrating gyro and the like. The tilt sensor can be one or more of the various known types such as the pendulum potentiometer, magnetoresistive tilt sensor, and the like. The device 15 detects the position of the vehicle within pipes to produce a vehicle orientation signal. The computer 16 detects the position of the vehicle and the configuration of surfaces such as bent inner surfaces of pipes and obstacles ahead of the vehicle from the vehicle position signal and the surface position signal from the surface detector 14. The computer 16 then feeds signals for controlling the direction of travel and speed for the travel of the vehicle based on the result to the drive assembly 11, which in turn controls the speed and steering based on the signals. In the case where changes in the surface configurations inside pipes are limited to specific patterns, it is possible to store the patterns of surface configurations which can be present within pipes and to identify a particular surface configuration from the corresponding pattern selected from among the stored patterns with reference to the surface configuration data provided by the surface position signal. Surface configurations can then be identified with greater ease more promptly with use of a simplified device. It is further possible for the computer 16 to store a piping map prepared in advance and for the vehicle to determine its course from the vehicle position signal and surface position signal with reference to the stored map.

Alternatively, the travel of the vehicle is controllable according to a program prepared for the computer, or by remote control or various other methods.

FIG. 4 shows another example of a wheel useful for the vehicle shown in FIG. 1. The illustrated wheel 40 comprises an outer wheel member 41 having an annular peripheral wall 42 and side walls 43 covering opposite sides of the wall 42, an inner wheel member 45 of magnetically permeable material having an outside diameter smaller than the inside diameter of the outer wheel member 41 and rollable on the inner peripheral surface of the outer wheel member 41, and a magnet 47 fitted in the inner wheel member 45 with their poles in contact therewith. The drive shaft 110 of a drive assembly 11 is connected to the inner side wall 43 of the outer wheel member 41. The peripheral wall 42 and the side walls 43 of the outer wheel member can be made of a metal (which is preferably nonmagnetic), rubber, synthetic resin or composite material of such substances having rigidity capable of bearing the load of the vehicle body. The inner wheel member 45 of the present embodiment has a pair of soft iron disks which are spaced apart from each other. The inner wheel member 45 can be made of other magnetically permeable material. The magnet 47 is fixedly provided between the pair of soft iron disks, with the N and S poles in contact with the respective disks.

FIG. 5 shows the wheel 40 thus constructed as it moves along from horizontal wall onto vertical wall. With reference to FIG. 5(a), the wheel 40 has its outer wheel member 41 driven to move along from right to left in the drawing while rolling on the horizontal wall. Although the inner wheel member 45, as positioned close to the horizontal wall, is subjected to a large force Fv acting toward the horizontal wall, a force Fh acting toward the vertical wall occurs when the wheel member approaches the vertical wall. Subsequently, the outer wheel member 41 comes into contact with the vertical wall. The inner wheel member 45 is positioned closer to the horizontal wall by a distance corresponding to its weight and the greater force of attraction to the closer horizontal wall as shown in FIG. 5 (b), and the force Fh acting toward the vertical wall is slightly smaller than the force Fv acting toward the horizontal wall. In this state, the drive force of the vehicle is applied to the wheel 40, which in turn moves away from the horizontal wall in the following manner. Suppose the front wheel (wheel 40 illustrated) of the vehicle, which is drivable by both the front and rear wheels, is in contact with the vertical wall. The drive force of the rear wheel acts to advance the vehicle body forward, strongly pressing the front wheel against the vertical wall. Under this action, the front when rotated by a drive force moves away from the horizontal wall. Alternatively, if the illustrated wheel 40 is the rear wheel this wheel moves away from the horizontal wall by the traction of the front wheel already ascending the vertical wall. When the outer wheel member is in contact with the vertical wall in any case, the inner wheel member 45 has been moved slightly toward the vertical wall with a larger distance from the horizontal wall than previously. Consequently, the force Fv acting toward the horizontal wall is smaller than previously, such that the force required for moving the outer wheel member from the horizontal wall can be correspondingly smaller. With increasing amount of ascent of the outer wheel member after leaving the horizontal wall, the force Fv acting toward the horizontal wall decreases. The force Fv toward the horizontal wall then becomes equal to the force Fh toward the vertical wall as shown in FIG. 5 (c). When the amount of ascent further increases thereafter, the force Fv toward the horizontal wall becomes smaller than the force Fh toward the vertical wall. This slightly moves the inner wheel member 45 further toward the vertical wall as seen in FIG. 5 (d) with a further increase in the force Fh toward the vertical wall. In this way, the inner wheel member moves toward the vertical wall with an increase in the force Fh as the amount of ascent increases, with the result that the inner wheel member 45 is brought to the position most proximate to the vertical wall by being pulled by the force Fh as shown in FIG. 5 (e). Consequently, a large holding force Fh acts on the vertical wall, permitting the vehicle to ascend the vertical wall reliably. In translation from vertical wall to horizontal wall as shown in FIG. 1 or in ascending or descending a curved surface, the travel of the outer wheel member 43 along such a running surface allows the inner wheel member 45 to move along together with the member 43. Thus, the wheel 40 is capable of traveling along walls in a three-dimensional space freely.

Next, the diameter ratio between the outer wheel member 43 and the inner wheel member 45 will be described. FIG. 6 (a) shows the case wherein the difference between the diameters of the outer and inner wheel members 42 and 45 is great, and FIG. 6 (b) shows the case where the difference is small. FIGS. 6 (a) and (b) both show the outer wheel member in contact with a vertical wall after traveling along a horizontal wall. As already described with reference to FIG. 5, the inner wheel member 45 is positioned closer to the horizontal wall by a distance corresponding to the weight thereof and the greater force of attraction of the horizontal wall than the position where the inner wheel member is at equal distances from the two walls. If the difference in diameter between the outer and inner wheel members 42 and 45 is excessively great, during transition from one wall to the other the inner wheel member 45 will be positioned away from both the horizontal and vertical walls in an intermediate state as shown in FIG. 6 (a). The forces toward the horizontal wall and the vertical wall are then small, failing to hold the vehicle to the running surface properly. Especially, if the holding force is insufficient in translation from ceiling or like horizontal wall to vertical wall, the vehicle is likely to fall. These forces act basically similarly also in translation from vertical wall to horizontal wall and in translation between walls which are different in inclination, although gravity will act in a different mode. Conversely, a larger outer wheel diameter will help remove magnetic debris by carrying it further away from the magnetic inner wheels. FIG. 6 (b) shows that when the inner and outer wheel members are closer in diameter then the inner wheel member 45 will stay closer to the walls, as can be seen in FIG. 6. Accordingly, the diameter ratio between the outer wheel member and the inner wheel member must be so determined as to meet both the requirements in respect of the ease with which the outer wheel member removes magnetic particle matter and the magnitude of holding force on the running surface. It is desired that the difference between the two wheel members be as great as possible insofar as a sufficient holding force is available. In determining the diameter difference, consideration is given to the coefficient of friction between the wheel and the running surface, mode of translation between running surface portions, weight of the inner wheel member including the magnet, weight of the vehicle body, etc.

Even in the case where the outer wheel member 43 is not connected to the drive shaft, the wheel is held positioned on the wall surface in the same manner as above while the inner wheel member moves along; the only difference is that the outer wheel member 43 moves along as by being pulled by the preceding vehicle.

FIG. 7 shows another embodiment of vehicle and the state thereof during travel. The vehicle 1D has a body 60 and a pair of wheels 70 provided at each of its front and rear portions. The vehicle body 60 has the same construction as the vehicle body 10 shown in FIG. 1 and is further provided with the arm drive assembly to be described below. The vehicle body 60 can be shaped variously like the vehicles 1B and 1C in FIG. 1 and can be connected to another one. With reference to FIG. 8, the wheel 70 comprises an outer wheel member 71 having an annular peripheral wall 72 and side walls 73 covering the respective sides of the wall, an arm 75 made of a magnetically permeable material, rotatably mounted on the central portion of the outer wheel member 71 and extending almost to the inner periphery of the outer wheel member 71, and a magnet 77 mounted on the arm. The peripheral wall 72 and the side walls 73 of the outer wheel member can be made of a metal (which is preferably nonmagnetic), rubber, synthetic resin or composite material of such substances which has rigidity capable of bearing the load of the vehicle body. The drive assembly 11 has a drive shaft 110 connected to the inner side wall 73 of the outer wheel member 71. The drive shaft 110 is in the form of a tube having an arm rotating shaft 76 extending therethrough for rotating the arm 75 through a desired angle. The arm rotating shaft 76 is connected to the arm drive assembly of the vehicle body 60. The arm 75 of the present embodiment has a pair of soft iron rods which are spaced apart from each other. Other magnetically permeable material is usable for the arm 75. The magnet 77 is fixedly provided between the pair of soft iron rods of the arm 75 with its N and S poles in contact with the respective rods.

The vehicle 1D operates in the following manner. For travel on a flat or continuously curved surface, the arm 75 is so supported as to freely rotate about its shaft axis. This causes a magnetic force acting between the arm 75 and the running surface to orient the outer end of the arm toward the running surface to produce magnetic attraction between the surface and the arm 75. Accordingly, even if the running surface is vertical, horizontal like a ceiling surface, or inclined, the attraction prevents the vehicle body from sliding or falling. When the running surface has a stepped portion, the outer wheel member 71 comes into contact with the stepped portion to stop the vehicle body as seen in FIG. 7 (a). In this case, the arm rotating shaft 76 is rotated forward through about 90 degrees by the arm drive assembly 19 (see FIG. 7(b)) , whereby the outer end of the arm 75 is oriented toward the stepped portion to produce magnetic attraction between the arm and the stepped portion. When driven in this state, the outer wheel member 71 rotates in contact with the stepped portion, causing the vehicle body 60 to climb the stepped portion as seen in FIG. 7(c). Although FIG. 7 shows the front wheel in contact with the stepped portion, the rear wheel also behaves similarly. A forward drive force, when continuously acting on the wheel which is out of contact with the stepped portion, permits the vehicle to climb the stepped portion with greater ease. In such a case, it is desirable to release the arm from the arm rotating shaft after the outer wheel member has rotated through an angle (for example, of 15 to 20 degrees) to render the arm free to rotate.

Although a clearance is provided between the arm outer end and the outer wheel member according to the embodiment of FIG. 7, a roller may be mounted on the arm end for rolling contact with the outer wheel member.

The vehicle of the present invention is free to travel on walls of magnetic material as described above. This renders the vehicle usable in various places, for example, within pipes, gas, petroleum, water and like tanks, hulls and hazardous regions for travel and for working with the devices mounted on the vehicle.

The present invention is not limited to the foregoing embodiments but can be modified variously without departing from the scope of the invention as defined in the appended claims.