JP2012061885A - Power-assisted truck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power-assisted truck in which frictional resistance of a canister wheel is reduced and which can be started smoothly.SOLUTION: The power-assisted truck 1 in which power is assisted with an electric motor as a worker pushes the truck, includes the canister wheel 4 steered to head for the advancing direction by frictional resistance, right and left drive wheels 5 with power applied thereto with the electric motor, and is configured such that assuming a center line bisecting an area on a carrier 3 as a carrier front-back direction center line Oy, assuming a distance between the carrier front-and back direction center line Oy and a wheel rotary axis of the right and left drive wheels 5 during advancing as a drive wheel base L1, and assuming a distance between the carrier front-back direction center line Oy and a wheel rotary axis O4 of the caster wheel 4 as a caster wheel base L2, the drive wheel base L1 is set to be smaller than the caster wheel base L2.

Description

  The present invention relates to an electric assist cart in which power is assisted by an electric motor as it is pushed by an operator.

  Generally, when a heavy load is placed on a cart used in a factory or the like, an operator needs to push the cart with a large force at the start of transportation, which is a heavy labor.

  As countermeasures, for example, Patent Documents 1 and 2 propose an electric assist cart that detects the force of an operator who pushes the cart and is provided with auxiliary power according to human power by an electric motor.

  In the conventional electric assist cart, two left and right drive wheels and two left and right caster wheels are attached to the lower part of the cart panel, and the load is supported by the four wheels.

  In this type of electric assist cart, power is applied to the drive wheels by an electric motor, and the caster wheels are steered so as to face the traveling direction by frictional resistance.

JP 2006-290319 A JP 2007-176195 A

  However, in such a conventional electric assist cart, when a heavy load is placed, the frictional resistance of the caster wheel increases when the caster wheel is steered so as to face the traveling direction when starting, There was a problem that it was difficult to start smoothly.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an electric assist cart that can reduce the frictional resistance of caster wheels and perform a smooth start.

  The present invention is an electric assist cart whose power is assisted by an electric motor as it is pushed by an operator, and is steered so as to face a traveling direction by a frictional resistance and a body frame on which a loading platform can be installed. It has caster wheels and left and right drive wheels that are powered by an electric motor, and the center line that bisects the area on the loading platform in the front-rear direction is defined as the loading platform front-rear direction center line. If the distance between the line and the wheel rotation axis of the left and right drive wheels is the drive wheel base, and the distance between the center line in the longitudinal direction of the loading platform and the wheel rotation axis of the caster wheel is the caster wheel base, the drive wheel base is smaller than the caster wheel base. It was supposed to be set.

  According to the present invention, since the wheel rotation shafts of the left and right drive wheels are arranged closer to the wheel rotation shafts of the caster wheels with respect to the center axis in the longitudinal direction of the loading platform, the share of the load applied to the caster wheels is reduced. By suppressing the frictional resistance of the caster wheels that are steered so as to face the traveling direction, the power required for starting is reduced, and it becomes possible to smoothly transport heavy objects.

The perspective view of the electrically assisted trolley | bogie which shows embodiment of this invention. The side view of an electric assist cart. The top view of an electric assist cart similarly. The front view of an electric assist cart. The chart which similarly shows an experimental result.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  The electric assist cart 1 shown in FIGS. 1 and 2 is used for transporting heavy objects, for example, in a factory. When the electric assist cart 1 is pushed by an operator and moves, auxiliary power is applied by an electric motor (not shown).

  The electric assist cart 1 includes a body frame 2 provided as a main body thereof, a cargo bed 3 provided on the body frame 2, caster wheels 4 of casters 40 provided at a front portion of the body frame 2, and left and right sides of the body frame 2. The left and right drive wheels 5 provided at the side portions and the operation handle 8 provided at the rear of the cargo bed 3 are provided.

  A rear frame 11 is coupled to the vehicle body frame 2, and an operation handle 8 is supported on the rear frame 11.

  The electric assist cart 1 includes left and right electric motors (not shown) that respectively drive the left and right drive wheels 5, and a controller (not shown) that controls electric power supplied from a battery (not shown) to the left and right electric motors. ), The controller controls the outputs of the left and right electric motors according to the operation force of the operator pushing the operation handle 8, and power is applied to the left and right drive wheels 5.

  The electric assist cart 1 includes a front-rear direction torque sensor 9 that detects torque around the horizontal axis generated in the operation handle 8 as an operation force detection unit that detects the magnitude and direction of the force with which the operator pushes the operation handle 8, and an operation handle. And a turning direction torque sensor 10 that detects torque around the vertical axis.

  The controller controls the left and right electric motors to generate power corresponding to the torque values detected by the front-rear direction torque sensor 9 and the turning direction torque sensor 10 to move the electric assist cart 1 forward or backward, A driving force for turning and bending is applied.

  A front frame 12 is coupled to the vehicle body frame 2, and a caster 40 is supported on the front frame 12.

  As shown in FIG. 2, the caster 40 includes a caster wheel 4 that is in rolling contact with a road surface, a wheel shaft 41 that rotatably supports the caster wheel 4, an arm 42 that supports the wheel shaft 41, and a base end of the arm 42. And a pivot bracket 43 that supports the pivotable portion about a horizontal axis. The pivot bracket 43 is pivotally supported about a pivot axis T4 (see FIG. 3).

  The caster 40 is swung by the frictional resistance of the caster wheel 4 as the swing axis T4 of the swing bracket 43 and the wheel shaft 41 are offset in the horizontal direction and the electric assist cart 1 moves in either the front, rear, left or right direction. The bracket 43 is rotated to turn, and the caster wheel 4 is steered so as to face the traveling direction.

  A damper rubber 44 (see FIG. 3) is interposed between the arm 42 and the turning bracket 43, and the vertical vibrations of the caster wheels 4 due to road surface irregularities and the like are reduced and absorbed, and the vibrations are transmitted to the vehicle body frame 2. It can be suppressed.

  The left and right drive wheels 5 are supported by the vehicle body frame 2 via a suspension device 20 to be described later so that the vertical vibrations of the drive wheels 5 due to road surface irregularities and the like are reduced and absorbed, and the vibrations are transmitted to the vehicle body frame 2. Can be suppressed.

  A lifting device 80 is provided between the body frame 2 and the loading platform 3. The lifting device 80 lifts and lowers the loading platform 3 by an electric lifting cylinder (not shown). For example, when a heavy object is placed on the loading platform 3 and the caster 40 and the suspension device 20 sink, the lifting device 80 raises the loading platform 3 and adjusts the height of the loading platform 3 with respect to the road surface to be substantially constant. Yes.

  FIG. 3A is a plan view of the electric assist cart 1 as viewed from above, and FIG. 3B is a plan view of the electric assist cart 1 as viewed from below.

  The loading platform 3 is provided so as to cover substantially the entire area above the body frame 2, the casters 40, and the left and right drive wheels 5. A load is directly placed on the loading platform 3. In addition, a roller conveyor (not shown) may be installed on the vehicle body frame 2 instead of the cargo bed 3, and the luggage may be placed via the roller conveyor.

  In FIG. 3 (a), the left and right center line Ox of the loading platform is a straight line that bisects the area on the loading platform 3 in the left and right direction, and the center line Oy in the longitudinal direction of the loading platform is the area in the front and rear direction. A straight line that bisects. A vertical line passing through the intersection (center point on the loading platform 3) of the loading platform lateral center line Ox and the loading platform longitudinal center line Oy is defined as a loading platform center line Oz.

  The electric assist cart 1 is provided with a single caster wheel 4 on the center line Ox in the left-right direction of the loading platform.

  The present invention is not limited to this, and the left and right (two) caster wheels may be provided on the electric assist cart 1. In this case, the turning shafts of the left and right caster wheels are arranged so as to be equidistant in the left-right direction from the loading platform left-right direction center line Ox.

  As shown in FIG. 3B, roller wheels 6 are provided side by side with the drive wheels 5 in the left-right direction. The left and right roller wheels 6 are provided side by side inside the left and right drive wheels 5.

  3A and 3B, a drive wheel shaft installation surface S extending in the left-right direction is set, and the wheel rotation shafts of the left and right drive wheels 5 and the left and right roller wheels 6 (on the drive wheel shaft installation surface S ( Wheel center axes) are arranged respectively. The drive wheel shaft installation surface S is a vertical surface that is orthogonal to the loading platform lateral direction center line Ox and extends parallel to the loading platform longitudinal direction center line Oy.

  The drive wheel shaft installation surface S is arranged behind the center line Oy in the longitudinal direction of the loading platform. The wheel rotation axis O4 of the caster wheel 4 is disposed in front of the center line Oy in the longitudinal direction of the loading platform.

  In the plan view of FIGS. 3A and 3B, the wheel rotation axis O4 of the caster wheel 4 is positioned behind the turning axis T4 and extends in the left-right direction (parallel to the turning axis T4). The distance of the wheel rotation axis (drive wheel shaft installation surface S) of the left and right drive wheels 5 with respect to the direction center line Oy is defined as a drive wheel base L1, and the caster wheel base of the wheel rotation axis O4 of the caster wheel 4 with respect to the loading center longitudinal direction center line Oy. Let L2.

  The drive wheel base L1 is set smaller than the caster wheel base L2 at a predetermined ratio. By setting the drive wheel base L1 and the caster wheel base L2 at an appropriate ratio, it is possible to reduce both the frictional resistance of the caster wheel 4 and to prevent the wheelie from rising when the vehicle starts.

  The table shown in FIG. 5 is necessary at the time of starting based on the frictional resistance of the caster wheel 4 by changing the ratio of the drive wheel base L1 and the caster wheel base L2 when loading the assumed maximum weight on the loading platform 3. The experimental results of measuring the power and stability at start-up that can suppress the generation of wheelies are shown.

  3 (a) and 3 (b), the distance between the wheel rotation shaft (drive wheel shaft installation surface S) of the left and right drive wheels 5 and the wheel rotation shaft O4 of the caster wheel 4 at the time of forward movement is the wheel base L1 + L2. And By setting the ratio of the drive wheel base L1 to less than 50% with respect to the wheel base L1 + L2, the load ratio applied to the caster wheel 4 increases too much, so the frictional resistance of the caster wheel 4 increases and the power required at the time of starting. It turns out that becomes excessive.

  By setting the ratio of the drive wheel base L1 of the drive wheel shaft installation surface S to the wheel base L1 + L2 to 20% or less, the load ratio applied to the caster wheel 4 is excessively reduced, so that the frictional resistance of the caster wheel 4 is reduced. It can be seen that it becomes difficult to prevent the wheelie from rising when the caster wheel 4 is lifted, and the startability is deteriorated.

  From the table of FIG. 5, by reducing the ratio of the drive wheel base L1 of the drive wheel shaft installation surface S to the wheel base L1 + L2 to less than 50%, it is possible to sufficiently reduce the power required at the start and to generate the wheelie. It can be seen that the stability at the time of starting is sufficiently secured. Moreover, it turns out that the said outstanding characteristic is acquired by making this ratio into 20 to 30%.

  The drive wheel 5 includes a wheel 5c that is rotatably supported via a wheel shaft 5b, and a rubber tire 5a that is attached to the outer periphery of the wheel 5c, and the tire 5a is brought into rolling contact with the road surface. The inside of the tire 5a is filled with air or a rubber material, and a contact portion with respect to the road surface is elastically deformed into a flat shape by a load applied thereto, and a load of, for example, 50 kg or less is supported.

  Since the outer diameter of the drive wheel 5 is larger than that of the roller wheel 6, the ability to get over the road surface step is enhanced, and the contact portion of the tire 5a with respect to the road surface is elastically deformed, so that sufficient traction is obtained.

  The roller wheel 6 includes a hard resin roller 6a, and the annular roller 6a is brought into rolling contact with the road surface. In the roller wheel 6, the contact portion with respect to the road surface of the roller 6a is not greatly elastically deformed, and can support a load of 200 to 900 kg, for example.

  The roller wheel 6 has a higher contact portion with respect to the road surface than the drive wheel 5 and has a large load resistance.

  The roller wheel 6 includes a hard resin roller 6a, and the annular roller 6a is brought into rolling contact with the road surface. In the roller wheel 6, the contact portion with respect to the road surface of the roller 6a is not greatly elastically deformed, and can support a load of 200 to 900 kg, for example.

  4A is a front view of the electric assist cart 1 as viewed from the front, and FIG. 4B is a front view of the electric assist cart 1 as viewed from the rear.

  The suspension device 20 is provided with left and right subframes 21 that respectively support the left and right drive wheels 5 and the roller wheels 6.

  Both end portions of the wheel shaft 5 b of the drive wheel 5 are supported by the subframe 21.

  The roller wheel 6 has an outer diameter (wheel diameter) smaller than that of the drive wheel 5, a wheel shaft (not shown) supported by the bracket 7, and the bracket 7 is coupled to the lower portion of the subframe 21.

  In the electric assist cart 1, the drive wheel 5 and the roller wheel 6 are provided side by side in the left-right direction, so that a sufficient load resistance can be obtained by the roller wheel 3 and the load is supported by the roller wheel 6. Since the load resistance required for the drive wheel 5 is reduced, the drive wheel 5 can elastically deform the contact portion with respect to the road surface to obtain sufficient traction, and the heavy object can be smoothly transported.

  The suspension device 20 includes four suspension arms 22 that are provided on the vehicle body frame 2 so as to support the left and right subframes 21 so that the left and right subframes 21 can be moved up and down, and a spring that is provided between the vehicle body frame 2 and the left and right subframes And a damper 23.

  Each suspension arm 22 has both ends connected to the body frame 2 and the left and right subframes 21 so as to be rotatable about a horizontal axis, and a parallel link that supports the subframe 21 so that the subframe 21 can be translated relative to the body frame 2. Configure the mechanism.

  Based on the above configuration, even if the subframe 21 moves up and down with respect to the vehicle body frame 2, the posture of the subframe 21 does not change, and the positional relationship (alignment) between the drive wheels 5 and the roller wheels 6 is kept constant. Thereby, even if the sub-frame 21 moves up and down, one of the drive wheel 5 and the roller wheel 6 is suppressed from floating from the road surface.

  The suspension device 20 is not limited to this, and may have another structure as long as the posture of the sub frame 21 with respect to the vehicle body frame 2 is maintained.

  The spring damper 23 includes a coil spring 23a and a damper 23b, and expands and contracts as the subframe 21 moves up and down.

  The coil spring 23a supports the load received by the subframe 21 by the spring force, and expands and contracts as the subframe 21 moves up and down.

  As the damper 23b expands and contracts, the hydraulic oil filled therein flows through a damping valve (not shown), and generates a damping force that suppresses vibration of the subframe 21.

  As described above, in the present embodiment, the electric assist cart 1 whose power is assisted by the electric motor as it is pushed by the operator, the vehicle body frame 2 on which the loading platform 3 can be installed, and the friction resistance. A caster wheel 4 that is steered so as to face the traveling direction, and left and right drive wheels 5 that are powered by an electric motor, and a center line that bisects the area on the loading platform 3 in the longitudinal direction is a longitudinal direction of the loading platform. The center line Oy is the distance between the front / rear direction center line Oy and the wheel rotation shafts of the left and right drive wheels 5 at the time of forward movement, and the distance between the front / rear direction center line Oy and the wheel rotation axis O4 of the caster wheels 4 is The distance between the caster wheel base L2 and the caster wheel base L2 is set smaller than the caster wheel base L2.

  Based on the above configuration, when the electric assist cart 1 is pushed by an operator and the caster wheel 4 is steered so as to face the traveling direction by its frictional resistance, auxiliary power is applied to the left and right drive wheels 5 by the electric motor. As a result, the labor of the operator is reduced.

  The electric assist cart 1 is supported by the load being shared by the caster wheel 4, the drive wheel 5, and the roller wheel 6, thereby obtaining a sufficient load resistance.

  Since the wheel rotation axis of the left and right drive wheels 5 is arranged closer to the wheel rotation axis of the caster wheel 4 with respect to the loading platform longitudinal center line Oy, the share of the load applied to the caster wheel 4 is reduced. The rolling frictional resistance of the caster wheel 4 steered so as to face the direction is suppressed, the power required at the time of starting is reduced, and a heavy object can be transported smoothly.

  In the present embodiment, the distance between the wheel rotation axis of the drive wheel 5 and the wheel rotation axis O4 of the caster wheel 4 is the wheel base L1 + L2, and the ratio of the drive wheel base L1 of the left and right drive wheels 5 to the wheel base L1 + L2 is 50%. It was set as the structure made into less than.

  Based on the above configuration, the ratio of the drive wheel base L1 of the drive wheel shaft installation surface S to the wheel base L1 + L2 is less than 50%, thereby sufficiently reducing the power required for starting and suppressing the generation of wheelies. It is possible to ensure sufficient startability.

  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.

1 Electric assist cart
2 Body frame
3 loading platform 4 caster wheels
5 drive wheels
6 Roller wheels 40 Casters

Claims (2)

An electric assist cart whose power is assisted by an electric motor as it is pushed by an operator,
A body frame that allows the loading platform to be installed;
Caster wheels that are steered to face the direction of travel by frictional resistance;
Left and right drive wheels powered by the electric motor,
A center line that bisects the area on the loading platform in the front-rear direction is a center line in the front-rear direction of the loading platform,
When moving forward, the distance between the center line in the longitudinal direction of the loading platform and the wheel rotation axis of the left and right drive wheels is defined as a drive wheel base, and the distance between the center line in the longitudinal direction of the loading platform and the wheel rotation axis of the caster wheel is defined as a caster wheel base. Then, the drive wheel base is set to be smaller than the caster wheel base.   The distance between the wheel rotation shaft of the drive wheel and the wheel rotation shaft of the caster wheel is a wheel base, and the ratio of the drive wheel base of the left and right drive wheels to the wheel base is less than 50%. The electric assist cart described in 1.

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