JP5679865B2 - Transport cart - Google Patents

Description

  The present invention relates to a transport carriage capable of transporting a loaded load.

  In general, in a factory or the like, in order to transport a heavy load, a transport cart that can be moved while the load is mounted is used.

  Japanese Patent Application Laid-Open No. H10-228667 discloses a transport cart in which a suspension mechanism such as a coil spring is provided on a caster that supports a cargo bed. In this transport cart, the vertical movement that occurs when the road surface is stepped is absorbed by the suspension mechanism, and the vibration from the road surface is suppressed from being transmitted to the load mounted on the cargo bed.

JP-A-11-59111

  However, in the transport cart described in Patent Document 1, when traveling with a load exceeding the design maximum load capacity, the weight of the load still acts even if the suspension mechanism has stroked. There is a risk that an excessive load is applied to the suspension mechanism and the wheels.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to prevent a load exceeding a maximum load amount from being loaded on a transport cart.

  The present invention is a transport carriage comprising a vehicle body frame on which a load can be placed via a loading platform, a wheel that supports the vehicle body frame, and a suspension device that suspends the wheel on the vehicle body frame. The apparatus includes a shock absorber that attenuates the vertical movement of the vehicle body frame relative to the wheel. The shock absorber includes a cylinder in which a magnetorheological fluid whose viscosity is changed by the action of a magnetic field is sealed, and the vehicle body frame relative to the wheel. Vertical movement is transmitted through a piston rod, and a piston that slides in the cylinder, a magnetic field generator that applies a magnetic field in the cylinder, and a magnetic field in the cylinder that changes according to the position of the piston are detected. A magnetic field detection unit configured to detect the magnetic field at the position of the piston when a load exceeding a maximum load amount is mounted on the cargo bed. And outputting a signal when it detects a condition.

  In the present invention, the body frame moves up and down with respect to the wheels according to the weight of the load mounted on the loading platform. In response to the vertical movement of the vehicle body frame, the piston slides in the cylinder in the shock absorber. A magnetorheological fluid is sealed in the cylinder, and a magnetic field from the magnetic field generating unit acts on the cylinder. The state of this magnetic field changes according to the position of the sliding piston.

  The magnetic field detection unit that detects the magnetic field in the cylinder outputs a signal when detecting the state of the magnetic field at the position of the piston when a load exceeding the maximum load amount is mounted on the loading platform. By using the signal from the magnetic field detection unit, an alarm can be issued to the operator when a load exceeding the maximum load is loaded on the loading platform. Therefore, it is possible to prevent a load exceeding the maximum load from being loaded on the transport cart.

It is a perspective view of the conveyance trolley concerning a 1st embodiment of the present invention. It is a side view in FIG. It is a front view in FIG. It is sectional drawing of the displacement dependence damper in the conveyance trolley | bogie which concerns on the 1st Embodiment of this invention. It is sectional drawing of the displacement dependence damper in the conveyance trolley | bogie which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the displacement dependence damper in the conveyance trolley | bogie which concerns on the 3rd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
Hereinafter, with reference to FIG. 1 to FIG. 4, a transport cart 100 according to a first embodiment of the present invention will be described.

  First, the overall configuration of the transport cart 100 will be described with reference to FIGS. 1 to 3.

  The transport cart 100 is used for transporting heavy objects, for example, in a factory. The transport cart 100 travels with the driving force applied by the operator being assisted by the assist force generated by the rotation of the electric motor 15 described later.

  The transport carriage 100 includes a vehicle body frame 1, a cargo bed 3 provided on the vehicle body frame 1 on which a load can be placed, an operation handle 5 as an operation unit capable of inputting driving force from two left and right positions of the vehicle body frame 1, A pair of drive wheels 11 provided at intervals on the left and right sides of the body frame 1 and a pair of universal wheels 12 mounted on the body frame 1 and provided behind the drive wheels 11 are provided. The drive wheel 11 is a front wheel of the transport cart 100, and the universal wheel 12 is a rear wheel of the transport cart 100. These drive wheel 11 and universal wheel 12 correspond to wheels.

  The vehicle body frame 1 is a frame in which square pipe materials are combined. The body frame 1 is supported by the drive wheels 11 and the universal wheels 12. The vehicle body frame 1 includes a flat surface portion 1a on which a load is mounted via a loading platform 3, a lower projecting portion 1b projecting from a lower portion of the flat surface portion 1a, and a standing portion standing on an upper rear end of the flat surface portion 1a. And a mounting portion 1c.

  The loading platform 3 is a flat plate with an edge provided so as to cover the upper portion of the plane portion 1 a in the body frame 1. A load is directly mounted on the loading platform 3. The loading platform 3 may be a flat plate without an edge. Further, instead of the cargo bed 3, a roller conveyor may be installed on the vehicle body frame 1, and the luggage may be mounted via the roller conveyor.

  As shown in FIG. 2, an elevating device 2 is provided between the body frame 1 and the loading platform 3. The lifting device 2 lifts and lowers the loading platform 3 with respect to the vehicle body frame 1 by an electric lifting cylinder (not shown). For example, when a heavy article is mounted on the loading platform 3 and the vehicle body frame 1 sinks with respect to the drive wheels 11 and the free wheels 12 by a suspension device 20 described later, the lifting device 2 raises the loading platform 3 and the loading platform with respect to the road surface. It is possible to adjust the height of 3 to be constant.

  The operation handle 5 is an inverted U-shaped handle that is pressed by an operator. The left and right ends of the operation handle 5 are connected to the standing portion 1 c in the vehicle body frame 1. As a result, the driving force input by the operator operating the operation handle 5 is transmitted to the vehicle body frame 1.

  The drive wheel 11 is a small wheel provided so as not to be steered in the front-rear direction of the body frame 1. A pair of drive wheels 11 are provided in the vicinity of the front end of the body frame 1. The drive wheels 11 are fixed to the lower projecting portion 1b of the body frame 1 so as to be movable up and down.

  The universal wheel 12 is a small wheel that always faces in the traveling direction when traveling. The universal wheel 12 is turned by the frictional resistance with the road surface and is steered so as to face the traveling direction. The universal wheel 12 is fixed to the lower projecting portion 1b of the body frame 1 so as to be movable up and down.

  The transport carriage 100 includes four subframes 4 that can move up and down with respect to the body frame 1, and a suspension device 20 that suspends the drive wheels 11 and the universal wheels 12 through the subframe 4 on the body frame 1. .

  Four subframes 4 are provided corresponding to the respective wheels of the pair of drive wheels 11 and the pair of universal wheels 12. Two subframes 4 are arranged on the left and right sides of the body frame 1. A drive wheel 11 or a universal wheel 12 is rotatably fixed to the lower surface of each subframe 4.

  The suspension device 20 includes four suspension arms 22 that support the left and right subframes 4 on the body frame 1 so that the left and right subframes 4 can move up and down, and a spring damper 23 provided between the body frame 1 and the left and right subframes 4.

  Four suspension arms 22 are provided for each subframe 4. Each suspension arm 22 is connected to the body frame 1 and the left and right subframes 4 so as to be rotatable about a horizontal axis, and the suspension arms 22 are parallel links that support the subframe 4 so that the subframe 4 can move in parallel with the body frame 1. Configure the mechanism.

  Thereby, even if the sub-frame 4 moves up and down with respect to the vehicle body frame 1, the posture of the sub-frame 4 does not change, and the positional relationship (alignment) between the drive wheels 11 and the free wheels 12 is kept constant. Therefore, even if the subframe 4 moves up and down, one of the drive wheel 11 and the free wheel 12 is suppressed from floating from the road surface.

  The spring damper 23 absorbs and reduces the vertical vibrations of the drive wheels 11 and the free wheels 12 due to road surface irregularities and the like, and suppresses vibrations from the road surface being transmitted to the vehicle body frame 1. The spring damper 23 expands and contracts as the subframe 4 moves up and down. When the vehicle body frame 1 sinks due to the weight of the load mounted on the loading platform 3, the spring damper 23 strokes in a direction in which the overall length becomes shorter.

  The spring damper 23 is a non-linear spring 25 that elastically supports the vertical movement of the vehicle body frame 1 with respect to the driving wheel 11 and the universal wheel 12 and a shock absorber that attenuates the vertical movement of the vehicle body frame 1 with respect to the driving wheel 11 and the universal wheel 12. Displacement-dependent damper 40. The displacement-dependent damper 40 will be described in detail later with reference to FIG.

  The non-linear spring 25 is a coil spring that supports the load received by the subframe 4 by the spring force and expands and contracts as the subframe 4 moves up and down. The nonlinear spring 25 is formed such that a plurality of coil springs having different pitches are formed in series, and the spring constant changes in a plurality of stages. As a result, the spring constant of the nonlinear spring 25 increases in accordance with the stroke amount in the direction in which the vehicle body frame 1 sinks.

  Specifically, the non-linear spring 25 is formed by connecting three coil springs having different spring constants in series, and the spring constant changes in three stages. The change of the spring constant in the nonlinear spring 25 may be any number of steps as long as it changes in a plurality of steps.

  Thereby, the spring constant of the non-linear spring 25 increases stepwise as the weight of the load mounted on the loading platform 3 increases. Therefore, the reaction force of the nonlinear spring 25 increases as the weight of the load mounted on the loading platform 3 increases. That is, the nonlinear spring 25 gradually changes to a hard characteristic according to the weight of the load mounted on the loading platform 3.

  In addition to this, the non-linear spring 25 may change its spring constant according to the stroke amount by changing the number of turns or by forming the material wire in a taper shape whose thickness is not constant. .

  The suspension device 20 is not limited to the above-described configuration, and may have another configuration as long as the posture of the subframe 4 with respect to the vehicle body frame 1 is maintained. For example, instead of the nonlinear spring 25, a linear spring that is formed at a constant pitch and does not change the spring constant may be used.

  The transport carriage 100 is detected by a torque sensor 6 as a pair of torque detectors that detect driving torque acting on each of the two left and right portions of the vehicle body frame 1 when the operation handle 5 is pressed, and the torque sensor 6 detects the transport cart 100. The controller 30 that calculates the assist force to be applied to each drive wheel 11 according to the drive torque and the pair of electric motors 15 that apply the assist force calculated by the controller 30 to each drive wheel 11 is provided.

  The torque sensor 6 is electrically connected to the controller 30 and outputs an electrical signal corresponding to the detected driving torque to the controller 30. The torque sensor 6 is connected to the operation handle 5 and the vehicle body frame 1 and is twisted by the driving force input from the operation unit and transmits the driving force to the vehicle body frame 1, and the torsion bar is twisted. And a potentiometer (not shown) that outputs an electrical signal corresponding to the torsion bar, and detects the driving torque based on the torsion bar torsion. By changing the torsion bar provided in the torque sensor 6, it is also possible to change the operation feeling by the operator according to the loaded load of the carriage without changing other members.

  The electric motor 15 is electrically connected to the controller 30 and rotates according to an electrical signal input from the controller 30. As shown in FIG. 3, the electric motor 15 is disposed inside the drive wheel 11 and applies assist force to the drive wheel 11. The left and right electric motors 15 are provided coaxially with each other, and are arranged in series between the pair of drive wheels 11. The electric motor 15 includes a transmission 16 that decelerates the rotation and transmits it to the drive wheels 11.

  The controller 30 is mounted on the vehicle body frame 1 together with a power supply device and other electronic devices. The controller 30 controls the transport carriage 100 and includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and I / O interface (input / output interface). Consists of a microcomputer. The RAM stores data in the processing of the CPU, the ROM stores a control program of the CPU in advance, and the I / O interface is used for input / output of information with the connected device. Control of the transport carriage 100 is realized by operating a CPU, a RAM, and the like according to a program stored in the ROM.

  The controller 30 controls the left and right electric motors 15 to generate assist forces according to the drive torque detected by the left and right torque sensors 6 to move the transport carriage 100 forward or backward, and to advance, turn, or bend. Give assist power.

  Next, the displacement-dependent damper 40 will be described with reference to FIG.

  The displacement dependent damper 40 is a damper whose damping coefficient can be changed by using a magnetorheological fluid whose viscosity changes due to the action of a magnetic field. The displacement-dependent damper 40 is formed such that its damping coefficient changes proportionally according to the stroke amount. The damping coefficient of the displacement-dependent damper 40 increases in accordance with the stroke amount in the direction in which the vehicle body frame 1 sinks.

  The displacement-dependent damper 40 includes a cylinder 41 in which a magnetorheological fluid is sealed, and a piston 43 that slides in the cylinder 41 by transmitting the vertical movement of the vehicle body frame 1 with respect to the drive wheel 11 and the universal wheel 12 via a piston rod 44. An electromagnet 45 serving as a magnetic field generating unit that applies a magnetic field in the cylinder 41 and a magnetic sensor 47 serving as a magnetic field detecting unit that detects a magnetic field in the cylinder 41 that changes according to the position of the piston 43 are provided. The displacement dependent damper 40 is interposed between the vehicle body frame 1 and the sub frame 4 via the upper end of the piston rod 44 and the lower end of the cylinder 41.

  The cylinder 41 includes a cylindrical portion 41a formed in a cylindrical shape having openings at both ends, and a head member 41b and a bottom member 41c that close the openings at both ends of the cylindrical portion 41a.

  A magnetorheological fluid is sealed in the cylinder 41. This magnetorheological fluid changes its apparent viscosity by the action of a magnetic field, and is a liquid in which fine particles having ferromagnetism are dispersed in a liquid such as oil. The viscosity of the magnetorheological fluid changes according to the strength of the applied magnetic field, and returns to its original state when the magnetic field is no longer affected.

  The cylinder 41 is made of a nonmagnetic material. Accordingly, the magnetorheological fluid sealed in the cylinder 41 is prevented from being attracted to the inner peripheral surface of the cylinder 41 by being magnetized.

  The piston 43 is formed in a columnar shape whose outer diameter is smaller than the inner diameter of the cylinder 41. That is, the piston 43 is formed between the inner periphery of the cylinder 41 with an annular interval through which the magnetorheological fluid can pass.

  The piston 43 slides in the cylinder 41 in the axial direction in accordance with the vertical movement of the vehicle body frame 1. When the piston 43 slides in the cylinder 41, the magnetorheological fluid passes through the interval between the piston 43 and the cylinder 41. The displacement dependent damper 40 generates a damping force by the annular space between the piston 43 and the cylinder acting as an orifice.

  The piston 43 is formed of a nonmagnetic material. Thereby, the magnetic field of the electromagnet 45 does not act directly on the piston 43, and the magnetorheological fluid sealed in the cylinder 41 is not attracted to the piston 43 by being magnetized.

  The piston rod 44 is formed coaxially with the piston 43. One end of the piston rod 44 is slidably supported by the bottom member 41c. The other end of the piston rod 44 passes through a hole 41d formed in the head member 41b, is slidably supported by the head member 41b, and extends to the outside of the cylinder 41.

  In this manner, the piston rod 44 is slidably supported by the head member 41b and the bottom member 41c, so that even if there is an annular interval between the outer periphery of the piston 43 and the cylinder 41, the cylinder 41 can slide in the axial direction without shifting in the radial direction.

  The electromagnet 45 is provided in the piston 43 and slides integrally with the piston 43 in the cylinder 41. The electromagnet 45 is wound coaxially with the piston 43 and is connected to an external power supply device (not shown) via a wiring (not shown) passing through the piston rod 44. The electromagnet 45 adjusts the strength of the generated magnetic field by adjusting the current value of the power supplied from the power supply device.

  When the weight of the load mounted on the loading platform 3 is increased, the vehicle body frame 1 sinks with respect to the drive wheel 11 and the universal wheel 12 and the piston rod 44 moves in a direction to enter the cylinder 41. At this time, the current value of the electromagnet 45 is adjusted so that the magnetic field becomes stronger as the piston rod 44 enters the cylinder 41.

  Therefore, as the piston 43 descends, the magnetic field of the electromagnet 45 becomes stronger, and the apparent viscosity of the magnetorheological fluid near the piston 43 increases. Accordingly, the damping coefficient of the displacement-dependent damper 40 increases as the piston rod 44 enters the cylinder 41.

  As a result, the damping coefficient of the displacement-dependent damper 40 increases proportionally as the weight of the load mounted on the loading platform 3 increases. Therefore, the displacement dependent damper 40 is adjusted so that the damping force increases as the weight of the load mounted on the loading platform 3 increases.

  The magnetic sensors 47 are sensors having Hall elements that detect magnetism, and a pair of magnetic sensors 47 are provided on the outer periphery of the cylinder 41 so as to face each other. The magnetic sensor 47 is not limited to a sensor having a Hall element, and may have any configuration as long as the sensor is switched and outputs a signal when the detected magnetic strength exceeds a predetermined threshold. . Further, the number of the magnetic sensors 47 is not limited to a pair, and may be any number.

  The magnetic sensor 47 is attached to the outer periphery of the cylinder 41 corresponding to the position of the piston 43 when the piston rod 44 enters the cylinder 41 most. In the magnetic sensor 47, since the electromagnet 45 approaches as the body frame 1 sinks and the piston 43 slides, the magnetic field acting from the electromagnet 45 becomes stronger. The magnetic sensor 47 outputs a signal when the strength of the acting magnetic field exceeds a predetermined threshold value set in advance.

  This predetermined threshold value is a value determined by detecting in advance the strength of the magnetic field corresponding to the position of the piston 43 when the maximum load amount is loaded on the loading platform 3.

  Therefore, by issuing a warning from an alarm device (not shown) using the signal output from the magnetic sensor 47, the operator is notified that the weight of the load loaded on the cargo bed 3 exceeds the maximum load amount. be able to. Therefore, it is possible to prevent a load exceeding the maximum load from being loaded on the loading platform 3. Further, it is possible to prevent an excessive load from being applied to the suspension device 20, the drive wheel 11, the free wheel 12 and the like due to the weight of the load mounted on the loading platform 3.

  Further, by using the magnetic sensor 47, it is possible to detect in a non-contact manner that a load exceeding the maximum load amount is loaded on the loading platform 3, unlike the case of using another contact type sensor such as a limit switch. Therefore, wear or damage caused by contact can be prevented.

  In addition, since the driving force of the transport cart 100 is assisted by the output of the electric motor 15, the transport cart 100 is heavier than a normal manual cart, and the weight of the load that can be mounted on the load platform 3 is also large. Therefore, in the transport cart 100, the effect by detecting that the load exceeding the maximum load capacity is loaded on the load platform 3 by using the displacement dependent damper 40 is remarkable as compared with the normal manual cart.

  According to the above embodiment, there exist the effects shown below.

  The body frame 1 moves up and down with respect to the drive wheels 11 and the universal wheels 12 according to the weight of the load mounted on the loading platform 3. In response to the vertical movement of the vehicle body frame 1, the piston 43 slides in the cylinder 41 in the displacement-dependent damper 40. A magnetorheological fluid is sealed in the cylinder 41, and a magnetic field from the electromagnet 45 is acting. The state of this magnetic field changes according to the position of the sliding piston 43.

  The magnetic sensor 47 that detects the magnetic field in the cylinder 41 outputs a signal when detecting the state of the magnetic field at the position of the piston 43 when a load exceeding the maximum load amount is mounted on the loading platform 3. By using a signal from the magnetic sensor 47, when a load exceeding the maximum load amount is loaded on the loading platform 3, an alarm device can issue an alarm to the worker. Therefore, it is possible to prevent a load exceeding the maximum load from being loaded on the loading platform 3.

(Second Embodiment)
Hereinafter, with reference to FIG. 5, a displacement-dependent damper 240 used in the electric assist cart according to the second embodiment of the present invention will be described. In each embodiment described below, the same reference numerals are given to the same components as those in the above-described embodiment, and a duplicate description will be omitted as appropriate.

  The second embodiment is different from the above-described embodiment in that a displacement-dependent damper 240 is used as a shock absorber. This displacement-dependent damper 240 is different from the displacement-dependent damper 40 in the first embodiment in that a magnet 245 as a magnetic field generation unit is attached to the cylinder 41 and a magnetic sensor 47 is provided in the piston 43.

  The cylinder 41 has a flat portion 42 formed thinner on the outer periphery of the cylindrical portion 41a than the other portions of the cylinder 41.

  The flat portion 42 is formed in a concave shape at two locations on the outer periphery of the cylinder 41 at intervals of 180 degrees. The plane part 42 is formed as a plane parallel to the tangential direction of the cylinder 41. By forming the flat portion 42, the magnet 245 to be attached can be formed in a flat shape, and the processing cost of the magnet 245 can be reduced.

  The magnet 245 is a permanent magnet attached to the outer periphery of the cylinder 41 corresponding to the position of the piston 43 when the piston rod 44 enters the cylinder 41 most. The magnet 245 is formed in a shape corresponding to the flat portion 42 and is attached to the flat portion 42. Since the flat portion 42 is formed thinner than the other portions of the cylinder 41, it does not prevent the magnetic field of the magnet 245 from acting on the magnetorheological fluid enclosed in the cylinder 41.

  Since the magnet 245 is a permanent magnet, no electric power is required to generate a magnetic field. Therefore, as compared with the first embodiment using the electromagnet 45, the structure can be simplified as much as the power supply device for supplying power to the electromagnet 45 is unnecessary, and the cost can be reduced.

  A pair of magnets 245 are provided so as to face each other. One magnet 245 has an N pole on the side in contact with the flat portion 42 of the cylinder 41, and the other magnet 245 has an S pole on the side in contact with the flat portion 42 of the cylinder 41. As a result, a linear magnetic field is generated between the pair of opposed magnets 245, and the magnetic field can be applied to the magnetorheological fluid in the cylinder 41.

  When the weight of the load mounted on the loading platform 3 is increased, the vehicle body frame 1 sinks with respect to the drive wheel 11 and the universal wheel 12 and the piston rod 44 moves in a direction to enter the cylinder 41. Therefore, the piston 43 approaches the magnet 245, and the influence of the magnetic field by the magnet 245 on the magnetorheological fluid passing through the interval between the piston 43 and the cylinder 41 increases.

  Therefore, according to the stroke of the piston rod 44 in the direction of entering the cylinder 41, the apparent viscosity of the magnetorheological fluid increases. Accordingly, the damping coefficient of the displacement-dependent damper 40 increases as the piston rod 44 enters the cylinder 41.

  As a result, the damping coefficient of the displacement-dependent damper 40 increases proportionally as the weight of the load mounted on the loading platform 3 increases. Therefore, the displacement dependent damper 40 is adjusted so that the damping force increases as the weight of the load mounted on the loading platform 3 increases.

  The magnetic sensor 47 is connected to an external alarm device via a wiring (not shown) that is embedded in the piston 43 and passes through the piston rod 44. The magnetic sensor 47 may be connected via the controller 30 instead of being directly connected to the alarm device.

  The magnetic sensor 47 is provided so as to slide integrally with the piston 43 in the cylinder 41. Since the magnet 245 approaches the magnetic sensor 47 as the body frame 1 sinks and the piston 43 slides, the magnetic field applied from the magnet 245 becomes stronger. As in the first embodiment, the magnetic sensor 47 outputs a signal when the strength of the acting magnetic field exceeds a predetermined threshold value set in advance.

  Similarly to the first embodiment, this predetermined threshold is also obtained by detecting in advance the strength of the magnetic field corresponding to the position of the piston 43 when the maximum load amount is loaded on the loading platform 3. The value to be determined.

  Therefore, by issuing an alarm from the alarm device using the signal from the magnetic sensor 47, it is possible to notify the operator that the weight of the load mounted on the loading platform 3 exceeds the maximum load amount.

  As described above, according to the second embodiment, similarly to the first embodiment, it is possible to prevent a load exceeding the maximum load amount from being loaded on the loading platform 3. Therefore, it is possible to prevent an excessive load from being applied to the suspension device 20, the drive wheel 11, the free wheel 12, and the like due to the weight of the load mounted on the loading platform 3.

(Third embodiment)
Hereinafter, with reference to FIG. 6, a displacement-dependent damper 340 used in the electric assist cart according to the third embodiment of the present invention will be described.

  The third embodiment is different from the above-described embodiment in that a displacement-dependent damper 340 is used as a shock absorber. This displacement-dependent damper 340 is different from the displacement-dependent damper 240 in the second embodiment in that the magnetic sensor 47 is attached to the cylinder 41.

  The magnetic sensor 47 is attached to the bottom member 41 c in the cylinder 41. Thereby, unlike the second embodiment, since it is not necessary to pass the wiring of the magnetic sensor 47 through the piston rod 44, the processing cost can be reduced.

  When the body frame 1 sinks and the piston 43 slides, the piston 43 affects the magnetic field in the cylinder 41 generated by the magnet 245, and the state of the magnetic field detected by the magnetic sensor 47 changes.

  The magnetic sensor 47 outputs a signal when the state of the magnetic field applied from the magnet 245 changes as the body frame 1 sinks and the piston 43 slides, and the applied magnetic field becomes a predetermined state. .

  This predetermined threshold value is a value determined by detecting in advance the state of the magnetic field corresponding to the position of the piston 43 when the maximum load amount is loaded on the loading platform 3.

  Therefore, by issuing an alarm from the alarm device using a signal from the magnetic sensor 47, it is possible to notify the operator that the weight of the load mounted on the loading platform 3 exceeds the maximum load amount.

  As described above, according to the third embodiment, similarly to the first and second embodiments, it is possible to prevent a load exceeding the maximum load amount from being loaded on the loading platform 3. Therefore, it is possible to prevent an excessive load from being applied to the suspension device 20, the drive wheel 11, the free wheel 12, and the like due to the weight of the load mounted on the loading platform 3.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The conveyance trolley | bogie which concerns on this invention can be utilized as a trolley | bogie for conveying a load.

DESCRIPTION OF SYMBOLS 100 Carriage 1 Body frame 3 Loading platform 5 Operation handle 6 Torque sensor 11 Driving wheel 12 Free wheel 15 Electric motor 20 Suspension device 25 Non-linear spring 30 Controller 40 Displacement dependent damper 41 Cylinder 43 Piston 45 Electromagnet 47 Magnetic sensor 240 Displacement dependent damper 245 Magnet 340 Displacement-dependent damper

Claims (7)

A body frame on which luggage can be placed via a loading platform;
Wheels for supporting the body frame;
A suspension vehicle that suspends the wheel on the vehicle body frame,
The suspension device includes a shock absorber that attenuates the vertical movement of the body frame with respect to the wheel,
The shock absorber is
A cylinder in which a magnetorheological fluid whose viscosity is changed by the action of a magnetic field is enclosed;
A vertical movement of the body frame relative to the wheel is transmitted via a piston rod, and a piston sliding in the cylinder;
A magnetic field generator for applying a magnetic field in the cylinder;
A magnetic field detection unit for detecting a magnetic field in the cylinder that changes according to the position of the piston,
The said magnetic field detection part outputs a signal, when detecting the state of the magnetic field in the position of the said piston when the load exceeding the maximum loading amount is mounted in the said loading platform, The conveyance cart characterized by the above-mentioned. The piston is provided with an interval through which the magnetorheological fluid can pass between the inner periphery of the cylinder,
2. The transport cart according to claim 1, wherein the shock absorber generates a damping force when the magnetorheological fluid passes through an interval between the piston and the cylinder.   The magnetic field detection unit outputs a signal when the magnetic field acting from the magnetism generating unit becomes stronger as the body frame sinks and the piston slides, and the strength of the acting magnetic field exceeds a predetermined threshold value. The conveyance cart according to claim 1 or 2, wherein The magnetic field generator is an electromagnet that slides integrally with the piston in the cylinder,
The said magnetic field detection part is attached to the said cylinder corresponding to the position of the said piston when the said piston rod approachs most in the said cylinder, The conveyance trolley of Claim 3 characterized by the above-mentioned. The magnetic field generator is a permanent magnet attached to the cylinder corresponding to the position of the piston when the piston rod enters the cylinder most.
The said magnetic field detection part is provided so that it may slide integrally with the said piston within the said cylinder, The conveyance trolley | bogie of Claim 3 characterized by the above-mentioned.   The magnetic field detecting unit changes the state of the magnetic field applied from the magnetism generating unit in response to the body frame sinking and the piston sliding, and signals when the applied magnetic field is in a predetermined state. The conveyance cart according to claim 1 or 2, wherein the carriage is output. The magnetic field generator is a permanent magnet attached to the cylinder corresponding to the position of the piston when the piston rod enters the cylinder most.
The transport cart according to claim 6, wherein the magnetic field detection unit is attached to the cylinder.

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