Electrically assisted cart

Abstract

This electrically assisted cart comprises: a vehicle frame (10) that constitutes a vehicle body; wheels (2) provided to the sides of the vehicle frame (10); an electrical motor (31) that drives the wheels (2); a battery (33) that stores power to be supplied to the electrical motor (31); a handle (25) operated by an operator; and a detection device (37) that detects an operation load on the handle (25). The battery (33) is mounted to the vehicle frame (10) in front of an axle (3) of the wheels (2). The handle (25) extends from the front of the vehicle frame (10) to the front upper side of the vehicle body above the battery (33). The detection device (37) is disposed at a joining part (28) between the vehicle frame (10) and the handle (25).

Description

Electric Assist Cart

[0001] The present invention relates to an electrically assisted cart.

[0002] Conventionally, among carts towed by people or the like, there are electric assist carts equipped with an electric assist function to reduce the burden of towing (see, for example, Patent Document 1). The electric assist cart includes a loading platform, wheels on the left and right sides of the loading platform, a handle pipe on the front of the loading platform, and an assist unit that applies an assist force to the rotation of the wheels. The assist unit includes an electric motor, a battery, and a control unit.

[0003] Since electric assist carts are required to carry heavy cargo, the batteries must have sufficient capacity and can be quite heavy. In Patent Document 1, the battery is located in front of the loading platform and behind the gripping portion of the handle pipe (or the portion that engages with the towing vehicle) in order to improve the maneuverability of the electric assist cart.

[0004] On the other hand, there is a demand for vehicles to be able to carry more cargo. This requires a vehicle body structure that can support the weight of the cargo and a battery capacity that is sufficient to continuously output a high load. To address this issue, there is a demand not only for an improved vehicle body rigidity but also for a configuration that can efficiently provide drive assistance by suppressing false detections and reductions in accuracy of traction force sensors (detection devices that detect operating loads).

[0005] Japanese Patent Application Publication No. 2018-052366

[0006] In response to the above-mentioned problems, the present invention aims to provide an electric assisted cart that can be constructed with a body configuration that ensures body rigidity and maneuverability against the weight of cargo and batteries, while maintaining the detection accuracy of a detection device that detects operating load.

[0007] The electrically assisted cart of the present invention comprises a frame (10) that constitutes the vehicle body, a pair of wheels (2) provided on the sides of the frame (10), an electric motor (31) that drives the wheels (2), a battery (33) that stores electricity to be supplied to the electric motor (31), a handle (25) operated by the operator, and a detection device (37) that detects the operating load on the handle (25), and in this electrically assisted cart (1) that provides driving assistance using the electric motor (31) in accordance with the detection value of the detection device (37), the battery (33) is mounted on the frame (10) forward of the axle (3) of the wheel (2), the handle (25) extends from the front of the frame (10) forward and upward of the vehicle body beyond the battery (33), and the detection device (37) is located at the joint (28) between the frame (10) and the handle (25).

[0008] According to the electrically assisted cart of the present invention, it is possible to construct a body configuration that ensures body rigidity and maneuverability against the weight of cargo and batteries, while maintaining the detection accuracy of the detection device that detects the operating load.

[0009] FIG. 1 is a left side view of an electric assisted cart according to an embodiment; FIG. 2 is a top view of the electric assisted cart; FIG. 3 is a front view of the electric assisted cart; FIG. 4 is a perspective view of the electric assisted cart, showing the configuration of the vehicle frame; FIG. 5 is a perspective view of the electric assisted cart, showing a state in which a battery and the like are mounted on the vehicle frame; FIG. 6 is a perspective view showing an enlarged view of a joint between a subframe of the vehicle frame and a handle pipe; FIG. 7 is a left side view corresponding to FIG. 1 , showing the arrangement of the joint and the operating load; and FIG. 8 is a block diagram showing a control unit of the electric assisted cart.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, unless otherwise specified, the directions of front, rear, left, right, etc. are the same as those of the vehicle described below. In addition, in the drawings used in the following description, an arrow FR indicating the front of the vehicle, an arrow LH indicating the left of the vehicle, an arrow UP indicating the top of the vehicle, and a line CL indicating the center of the left and right of the vehicle body are shown in appropriate locations. In the following description, unless otherwise specified, it is assumed that the vehicle body is in a pre-travel state (stopped state) with the loading platform 5 horizontal.

[0011] Fig. 1 is a left side view of an electric assisted cart 1 according to an embodiment, Fig. 2 is a top view of the electric assisted cart 1, and Fig. 3 is a front view of the electric assisted cart 1. Fig. 4 is a perspective view of the electric assisted cart 1, illustrating the configuration of the frame 10. Fig. 5 is a perspective view of the electric assisted cart 1, illustrating the state in which a battery 33 and other components are mounted on the frame 10. Line G in the figure indicates the horizontal ground. The electric assisted cart 1 shown in each figure is in a state in which the fore-and-aft direction of the body (frame 10, described below) is horizontal. When the electric assisted cart 1 is actually stopped, the fore-and-aft direction of the body is tilted downward toward the front with respect to the ground G, and the ground-contact portion of the front lower part of the frame 10 is in contact with the ground.

[0012] 1 to 5, the electrically assisted cart 1 comprises a loading platform 5, a frame 10 that supports the loading platform 5 and constitutes the vehicle body, a pair of left and right wheels 2 that are provided on the left and right sides of the loading platform 5 and supported by the frame 10, a pair of left and right handle pipes 26 that are connected to the frame 10 and into which the operating load of the operator is input, a pair of left and right electric motors 31 that drive the left and right wheels 2 individually, a battery 33 that stores power to be supplied to the left and right electric motors 31, and a pair of left and right traction force sensors 37 (see FIG. 6) that detect the operating load on the left and right handle pipes 26.

[0013] The electrically assisted cart 1 provides driving assistance by driving the left and right electric motors 31 in accordance with the detection values ​​of the left and right traction force sensors 37. An assist unit 30 including the left and right electric motors 31 assists the rotation of the left and right wheels 2. The left and right electric motors 31 are, for example, in-wheel motors disposed within the hubs 2a of the left and right wheels 2. The assist unit 30 includes a control unit 35 (see FIG. 8 ) that controls the supply of power from a battery 33 to the left and right electric motors 31.

[0014] Each electric motor 31 is, for example, a direct current (DC) motor, and is driven by power supplied from the control unit 35. The battery 33 is, for example, a secondary battery such as a lithium ion battery, and can be repeatedly charged while mounted on the vehicle or removed from the vehicle body.

[0015] FIG. 8 is a block diagram showing a schematic configuration of the control unit 35. Referring to FIG. 8, the control unit 35 includes a CPU (Central Processing Unit) 35a, a memory 35b, an input unit 35c, and an output unit 35d. The CPU 35a executes programs stored in the memory 35b and controls the operation of the assist unit 30 (driving the left and right electric motors 31). The memory 35b is realized by, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory). The input unit 35c receives detection signals output from various sensors. The output unit 35d outputs command signals to motor drivers and other controlled objects.

[0016] The left and right wheels 2 are connected to the drive shafts of the electric motors 31 on the same left and right sides, and rotate in the forward direction in response to the forward rotation of the electric motors 31. For example, a one-way clutch (not shown) is provided between the electric motors 31 and the wheels 2. When the electric motors 31 rotate forward relative to the wheels 2, the one-way clutch transmits forward rotation torque from the electric motors 31 to the wheels 2. When the rear wheels 4 rotate forward relative to the electric motors 31, the one-way clutch spins freely without transmitting torque from the rear wheels 4 to the electric motors 31.

[0017] The tractive force sensor 37 detects the operating load, including the tractive force, input to the handle pipe 26 and outputs the detected load to the control unit 35. The control unit 35 outputs an electric signal corresponding to the magnitude of the tractive force to the motor driver. The motor driver supplies power from the battery 33 to the electric motor 31 in response to the electric signal from the control unit 35. As a result, the electric motor 31 is driven in accordance with the tractive force detected by the tractive force sensor 37, and provides an assist force to the rotation of the wheels 2.

[0018] <Loading Platform 5> Referring to Figures 1 to 5, the loading platform 5 is a platform for loading cargo or the like. In this embodiment, the loading platform 5 is configured by supporting a flat bottom plate (plate) 6 on the bottom of the vehicle body. Although the loading platform 5 in Figures 2 and 5 shows a single large bottom plate 6, it may be divided into a plurality of unit bottom plates in the fore-and-aft direction of the vehicle, and these unit bottom plates may be arranged in a front-to-rear direction to form the bottom plate 6. The loading platform 5 is formed in the shape of a flat plate, but depending on the type of object to be loaded, it may have irregularities or may have openings such as a lattice pattern.

[0019] The loading platform 5 includes a cargo loading section 7 for loading cargo, and a battery mounting section 8 disposed in front of the cargo loading section 7 and for mounting a battery 33. The cargo loading section 7 has a plurality of floor frames 15 of the vehicle frame 10 disposed below the bottom plate 6. The battery mounting section 8 has a plurality of battery floor frames 16 of the vehicle frame 10 disposed below the bottom plate 6.

[0020] The axle 3 of the wheels 2 is disposed rearward of the center 7c of the cargo loading section 7 in the longitudinal direction. The battery 33 is mounted on the battery mounting section 8 forward of the axle 3 of the wheels 2. Line C3 in the figure indicates the central axis (shaft center) of the axle 3. By mounting the battery 33 forward of the axle 3, the weight of the battery 33 generates a moment that rotates the frame 10 and the handle pipe 26 downward toward the front about the axle 3. As a result, when the vehicle is unloaded, the bed 5 and the handle pipe 26 tilt downward toward the front, and even when loaded with cargo, the bed 5 and the handle pipe 26 are likely to tilt downward toward the front. This makes it easier to meet the prerequisites for performing assist control, facilitating the design of assist control.

[0021] <Frame 10> Referring to Figures 1 to 5, the frame 10 is formed by, for example, joining multiple types of steel materials together by welding or the like. The frame 10 includes a pair of left and right main frames 11 extending in the front-rear direction along the left and right side edges of the cargo bed 5, and a pair of left and right sub-frames 12 extending in the front-rear direction and spaced apart vertically above each of the left and right main frames 11. A plurality of gusset frames 13 inclined relative to the up-down direction in side view are installed between the main frames 11 and the sub-frames 12 on the same left and right sides. The plurality of gusset frames 13, together with the main frames 11 and the sub-frames 12, form a truss structure.

[0022] Front end portions 12a of the left and right sub-frames 12 extend further forward than front end portions 11a of the left and right main frames 11. At each of the left and right sides of the vehicle frame 10, the front end portions 12a of the sub-frames 12 and the front end portions 11a of the main frame 11 are connected to the upper and lower ends, respectively, of lower portions 26b of handle pipes 26 that are inclined upward toward the front. Rear end hanging portions 12b that bend downward are connected to the rear ends of the left and right sub-frames 12. The lower ends of the rear end hanging portions 12b are joined to the rear end of the main frame 11.

[0023] In the embodiment, the main frame 11 and the handle pipe 26 are formed from a single steel pipe, but they may be separate members joined together by welding or the like. The handle pipe 26 is divided into an upper portion 26a and a lower portion 26b at the height of the subframe 12, and these upper portion 26a and lower portion 26b are formed from a single steel pipe, but they may be separate members joined together by welding or the like. The upper portion 26a of the handle pipe 26 and the subframe 12 may be formed from a single, continuous steel pipe. The lower portion 26b of the handle pipe 26 can also be considered to be part of the vehicle frame 10. The handle pipe 26 extends forward and upward from the front of the vehicle frame 10, reaching a position forward and upward of the battery 33.

[0024] The vehicle frame 10 includes a pair of left and right vertical frames 14 extending upward from the front portions of the left and right main frames 11. The left and right vertical frames 14 are joined at their upper ends to the front-to-rear intermediate portions of the subframes 12 on the same left and right sides. On both the left and right sides of the front portion of the vehicle frame 10, a region R1 is formed that is triangular in side view and is surrounded by the vertical frames 14, the front portions of the subframes 12, and the lower portions 26b of the handle pipes 26. A battery mounting section 8 is located between the left and right regions R1. Most of the battery 33 mounted on the battery mounting section 8, except for the lower front portion of the battery 33, is located within the region R1 in side view.

[0025] A plurality of (five) floor frames 15 extend in the vehicle width direction between the left and right main frames 11 and connect the left and right main frames 11. A plurality of (four) battery floor frames 16 are arranged in the vehicle width direction in front of the foremost floor frame 15.

[0026] The battery floor frame 16 extends in the front-to-rear direction, and its rear end is joined by welding to the outer peripheral surface of the frontmost floor frame 15. In this embodiment, the battery floor frame 16 is offset upward relative to the floor frame 15 in order to increase the weld bead length at the rear end of the battery floor frame 16. The battery floor frame 16 is disposed at a height that overlaps with the floor frame 15 in the vertical direction, but the battery floor frame 16 and the floor frame 15 may also be disposed with an offset in the vertical direction such that they do not overlap each other.

[0027] The pair of battery floor frames 16 on the outer sides in the vehicle width direction are inclined in plan view so that the front ends are positioned more inward in the vehicle width direction. The trapezoidal area between the pair of battery floor frames 16 on the outer sides in the vehicle width direction in plan view becomes the battery mounting section 8 of the cargo bed 5.

[0028] Between the upper ends of the left and right vertical frames 14, there is provided a cargo bed upper cross frame 17 that connects the left and right subframes 12. In a front-to-rear intermediate portion in a range forward of the vertical frames 14 and rearward of the front ends 12a of the subframes 12, there are provided a battery cross frame 18 that connects the left and right subframes 12, and a plurality (two) battery suspension frames 19 that hang down from the battery cross frame 18 and are joined to the front ends of at least some of the plurality of battery floor frames 16 (in this embodiment, the pair of battery floor frames 16 on the outer sides in the vehicle width direction). In this embodiment, only the rear ends of the pair of battery floor frames 16 on the inner sides in the vehicle width direction are joined to another component (the floor frame 15), but a structure in which the plurality of battery floor frames 16 are connected to each other at their front ends or at the front-to-rear intermediate portion may also be used.

[0029] The battery 33 mounted on the battery mounting section 8 has a rectangular parallelepiped shape with its width, depth, and height aligned with the left-right direction (vehicle width direction), the front-rear direction, and the up-down direction of the vehicle. Plates (partition walls) 8a are provided on the left and right side surfaces, front and rear surfaces, and top and bottom surfaces of the battery mounting section 8 (the bottom surface is a bottom plate 6), respectively, to conceal the battery 33 and protect it from external disturbances. For convenience of illustration, the plates 8a on the top and front surfaces of the battery mounting section 8 are omitted from FIG. 5. Referring to FIG. 3, for example, the battery 33 may be offset to one side, left or right, on the battery mounting section 8, so that a control unit 35U constituting the control section 35 may also be mounted thereon.

[0030] 1 to 5, the left and right wheels 2 each include a wheel having a hub 2a, spokes 2b, and a rim 2c, and a tire 2d mounted on the outer periphery of the rim 2c. The center of the hub 2a is supported by an axle 3 that runs along the vehicle width direction. The axle 3 is located rearward of the front-rear center 7c of the cargo loading section 7 of the bed 5 and above the top surface of the bed 5 (above the main frame 11).

[0031] Support frames 21 are arranged on the outer sides of the left and right main frames 11 in the vehicle width direction, extending in the front-rear direction on the outer sides of the wheels 2 in the vehicle width direction. The front and rear ends of the support frames 21 are bent inward in the vehicle width direction and joined to the front and rear ends of the main frames 11 by welding or the like. Inner and outer shaft support plates 11c, 21c that protrude upward are provided at the middle front and rear parts of each of the main frames 11 and the support frames 21. Both ends of the axle 3 are supported at both ends by these inner and outer shaft support plates 11c, 21c.

[0032] It is also possible to have a configuration in which the support frame 21 and the outer shaft support plate 21c are not provided, and the inner end of the axle 3 in the vehicle width direction is cantilevered by the main frame 11 and the inner shaft support plate 11c.

[0033] 1 to 5, the left and right handle pipes 26 extend obliquely from the front end 11a of the main frame 11 toward the upper front in a side view. The left and right handle pipes 26 are gently curved in a side view so as to approach horizontal as they extend toward the upper front. The handle pipes 26 integrally have an upper portion 26a located above the subframe 12 and a lower portion 26b located below the subframe 12. In this embodiment, the pipe length of the upper portion 26a is longer than the pipe length of the lower portion 26b. At the front end of the handle pipe 26, the pipe length direction is approximately horizontal in a side view.

[0034] The left and right handle pipes 26 are gently curved inward in the vehicle width direction in plan view in a range rearward of joints 28 with the left and right sub-frames 12 and forward of the front ends 11a of the left and right main frames 11. The front ends of the left and right sub-frames 12 are also gently curved in plan view so as to overlap with the curvature of the left and right handle pipes 26. The left and right handle pipes 26 reach their front ends while narrowing the space between them in the vehicle width direction in plan view. The front ends of the left and right handle pipes 26 are curved inward in the vehicle width direction from near the front ends in plan view.

[0035] A linear grip portion 27 is formed between the front ends of the left and right handle pipes 26 and extends along the vehicle width direction. The left and right handle pipes 26 and the grip portion 27 are formed, for example, as a single continuous piece. The left and right handle pipes 26 and the grip portion 27 are integrally configured as a U-shaped handle frame 25 that opens rearward in a plan view. The grip portion 27 is provided with a locking portion 27a for locking the electric assist cart 1 to a hook of a towing vehicle.

[0036] <Traction Force Sensor 37> Fig. 6 is an enlarged perspective view of the joint 28 between the subframe 12 and the handle pipe 26, and Fig. 7 is a side view corresponding to Fig. 1 showing the arrangement of the joint 28 and the operating load. Referring to Figs. 6 and 7, the traction force sensor 37 in this embodiment is, for example, a pair of upper and lower strain sensors 37a, 37b, and is disposed at the joint 28 between the subframe 12 and the handle pipe 26. The joint 28 includes a predetermined range forward and above the front end 12a of the subframe 12 (for example, a range within a predetermined distance L1 (for example, 150 mm) along the axis C26 from an intersection P1 between the axis C12 of the subframe 12 and the axis C26 of the handle pipe 26). In a side view of the vehicle body, the traction force sensor 37 is disposed on a straight line T1 connecting the axis of the front end (grip portion 27) of the handle pipe 26 and the axis C3 of the axle 3 of the wheel 2.

[0037] Because the handle pipe 26 acts as a cantilever beam forward of the front end 12a of the subframe 12, deflection increases forward of the joint 28. For this reason, by locating the traction force sensor 37 forward of the joint 28, the detected value of the operating load increases and detection accuracy improves. In this embodiment, at the joint 28 between the handle pipe 26 and the subframe 12, the strain sensors 37a, 37b are installed inside the pipe or on a shaft coupling provided in that area so that the strain sensors 37a, 37b are not exposed to the outside.

[0038] The strain sensors 37a, 37b are provided, for example, on the upper and lower surfaces of the handle pipe 26, respectively. When using the electrically assisted cart 1, the tractive force sensor 37 is zeroed after loading cargo or the like. The zero point is set (calibrated) when loading cargo or the like as follows: First, cargo is loaded onto the bed 5 with the front of the vehicle frame 10 in a state where it is on the ground (with the handle pipe 26 tilted downward at the front). At this time, no operating load is input to the handle pipe 26, and the electric motor 31 is in an assist-off state.

[0039] After loading cargo, the handle pipe 26 is lifted from a state in which the front of the frame 10 is on the ground, making the loading platform 5 horizontal and putting the electrically assisted cart 1 in a position where it can be towed (traveled). At this time, due to the load from the center of gravity of the cargo acting on the front-rear center 7c, which is located forward of the axle 3, in the cargo loading section 7 of the loading platform 5, and the load from the battery 33 acting on the battery mounting section 8, when the handle pipe 26 is lifted, a large bending load is generated at the branch point of the handle pipe 26 from the frame 10 (the base of the upper part 26a of the handle pipe 26, and the joint 28 with the subframe 12).

[0040] After lifting the handle pipe 26 and bringing the loading platform 5 to a standstill, the zero point of the tractive force sensor 37 is taken using a switch or the like provided on the grip portion 27. At this time, the value at which the detected value of the tractive force sensor 37 stands still is taken as the zero point. Specifically, the point at which the difference (difference between compression and tension) between the detected values ​​of the strain sensors 37a and 37b attached to the top and bottom surfaces of the handle pipe 26 is maximized is taken as the reference point. This setting reduces variations in the initial load detection value due to the cargo loading condition.

[0041] When the detected value of the tractive force sensor 37 changes relative to a set reference value (zero point) (i.e., when a pushing or pulling force acts on the handle pipe 26 in the longitudinal direction of the vehicle), the control unit 35 drives the electric motor 31 in response to the change, thereby assisting the cart in traveling. The amount of assistance is determined by outputting in proportion to the operating load or in response to the total load at the time the reference value was obtained (i.e., if the cargo is light, the output is reduced to conserve battery power).

[0042] When a traction force sensor 37 is installed on each of the left and right handle pipes 26, the left and right electric motors 31 may be driven differentially in accordance with the difference between the detected values ​​of the left and right traction force sensors 37. When differential control is used, large detection errors make it difficult to steer as intended. In contrast, by mounting the sensor at the base of the upper part 26a of the handle pipe 26, it is possible to detect deflection in a region where deformation is relatively large, thereby relatively reducing noise and suppressing detection errors.

[0043] The strain sensor is inexpensive and requires less signal processing because it directly converts the deflection of the handle pipe 26 into resistance (electrical signal). As a result, the configuration can be made smaller.

[0044] As described above, the electric assisted cart 1 in the above embodiment comprises a loading platform 5, a frame 10 that supports the loading platform 5 and constitutes the vehicle body, a pair of wheels 2 that are provided on the sides of the loading platform 5 and supported by the frame 10, a handle pipe 26 that is connected to the frame 10 and operated by the driver, an electric motor 31 that drives the wheels 2, a battery 33 that stores electricity to be supplied to the electric motor 31, and a traction force sensor 37 that detects the operating load on the handle pipe 26, and in the electric assisted cart 1 that provides driving assistance using the electric motor 31 in accordance with the detection value of the traction force sensor 37, the battery 33 is mounted on the frame 10 forward of the axle 3 of the wheel 2, the handle pipe 26 extends from the front of the frame 10 upward and in front of the vehicle body beyond the battery 33, and the traction force sensor 37 is located at the joint 28 between the frame 10 and the handle pipe 26.

[0045] This configuration enables assisting the driving of the wheels 2 by detecting the load acting on the joint 28 between the vehicle body (frame 10) and the handle pipe 26. In the case of a cart that assists driving by detecting the load acting on the handle pipe 26, the detection of tractive force is also related to the load of the cargo. For example, if a heavy battery 33 is placed on the axle 3, the load distribution on the vehicle body under static cargo load conditions varies significantly depending on the cargo loading condition (center of gravity position). In other words, the assist strength and output characteristics change each time cargo is loaded on the vehicle body. On the other hand, by placing the battery 33 forward, the center of gravity position is offset forward in an unladen state. This relatively reduces the change in load distribution due to cargo, enabling stable sensing. Furthermore, by placing the tractive force sensor 37 at the joint 28 between the handle pipe 26, which extends forward and upward, and the frame 10, a torque depending on the length of the handle pipe 26 acts on the joint 28. This allows a relatively large load to be detected, thereby relatively reducing the influence of noise due to cargo or external disturbances.

[0046] Referring to Figure 7, the battery 33 is disposed at the front end of the frame 10, which shifts the center of gravity of the vehicle forward. As a result, when the rider grips and lifts the handle pipe 26, an upward force F1 is applied to the grip portion 27 (and the joint portion 28). On the other hand, when the rider pushes the handle pipe 26 forward, a forward force F2 is applied to the grip portion 27 (and the joint portion 28). Therefore, the resultant force F3 of the force lifting the handle pipe 26 and the force pushing the handle pipe 26 acts in a direction along the handle pipe 26 extending forward and upward. Therefore, the operating load during cart operation can be converted into a pure pulling load and detected, and the operating load during cart operation can be accurately detected by a simple tractive force sensor 37.

[0047] In the above-mentioned electric assisted cart 1, the vehicle frame 10 comprises a main frame 11 extending longitudinally along the loading platform 5, and a sub-frame 12 extending longitudinally above the main frame 11, the sub-frame 12 extending forward more than the main frame 11, and the handle pipe 26 is joined to the front end 12a of the main frame 11 and the sub-frame 12 and extends diagonally forward and upward.

[0048] According to this configuration, the handle pipe 26 is joined to the front end portion 12a of the main frame 11 and the sub-frame 12 and extends diagonally forward and upward, which has the following effects: When the rider lifts the handle pipe 26, a force F1 is applied, which generates a bending load at the joint 28 of the handle pipe 26 and the sub-frame 12. Furthermore, when the rider applies a horizontal force F2 to the handle pipe 26, a resultant force F3 of the horizontal force and the force lifting the handle pipe 26 acts along the handle pipe 26. Therefore, the operating load can be converted into a pure tensile load and detected.

[0049] In the above-mentioned electric assisted cart 1, the traction force sensors 37 are strain sensors 37a, 37b, which are arranged at the joint 28 between the subframe 12 and the handle pipe 26, and the joint 28 includes a predetermined range forward and above the front end 12a of the subframe 12.

[0050] According to this configuration, by arranging the strain sensors 37a, 37b in a range forward and above the front end 12a of the subframe 12 at the joint 28 between the subframe 12 and the handle pipe 26, it becomes easier to detect the load applied to the handle pipe 26. Because the handle pipe 26 acts as a cantilever forward of the front end 12a of the subframe 12, deflection is greater on the front side of the joint 28. Therefore, by arranging the strain sensors 37a, 37b on the front side of the joint 28, the detected value of the operating load becomes larger and the system becomes relatively more resistant to noise input. Therefore, this configuration is particularly effective when the operating environment is uneven, and it can suppress sudden acceleration and deceleration of the electric motor 31.

[0051] In the above-described electrically assisted cart 1, the joint 28 and the traction force sensor 37 are arranged on a straight line T1 connecting the front end of the handle pipe 26 and the axle 3 of the wheel 2 when viewed from the side of the vehicle body.

[0052] According to this configuration, the joint 28 and the traction force sensor 37 are disposed on the straight line T1 connecting the front end of the handle pipe 26 and the axle 3 of the wheel 2, which has the following effect: Since the front end of the handle pipe 26 rotates around the axle 3, a bending load is likely to occur at the joint 28 on the straight line T1 connecting the front end of the handle pipe 26 and the axle 3. By disposing the traction force sensor 37 at this joint 28, the detected value of the operating load increases, enabling the operating load to be detected with high accuracy.

[0053] In the above-mentioned electric assisted cart 1, the loading platform 5 comprises a battery mounting section 8 on which the battery 33 is mounted and a cargo loading section 7 on which cargo is loaded, the battery mounting section 8 being arranged in front of the cargo loading section 7, and the axle 3 of the wheel 2 being arranged behind the center 7c of the cargo loading section 7 in the fore-and-aft direction.

[0054] According to this configuration, the battery mounting section 8 is disposed in front of the cargo loading section 7, and the axle 3 is disposed behind the longitudinal center 7c of the cargo loading section 7, which has the following effect: The center of gravity of cargo loaded on the cargo loading section 7 tends to be concentrated at the longitudinal center 7c of the cargo loading section 7. Therefore, by disposing the axle 3 behind the longitudinal center 7c of the cargo loading section 7, coupled with the battery 33 being disposed on the front side of the loading platform 5, the center of gravity of the entire cart tends to be located forward of the axle 3. Therefore, whether the cart is empty or loaded with cargo, a downward force is applied to the handle pipe 26, and therefore the operating load on the handle pipe 26 is always in the same direction, allowing for stable detection of the operating load.

[0055] In the above-mentioned electric assisted cart 1, the vehicle frame 10 has a vertical frame 14 that extends upward from the front of the main frame 11 and is joined to the middle part of the front and rear of the subframe 12, and when viewed from the side of the vehicle body, at least a part of the battery 33 is arranged in an area R1 surrounded by the vertical frame 14, the subframe 12 and the handle pipe 26.

[0056] According to this configuration, the battery 33 is disposed in the region R1 surrounded by the vertical frames 14, the subframe 12, and the handle pipe 26 in a side view of the vehicle body, so that the battery 33 is disposed on the front side of the loading platform 5. This offsets the center of gravity in an unladen state forward, making it possible to relatively reduce changes in load distribution due to the weight of cargo, and enabling stable sensing. By disposing the battery 33 in the triangular region R1 surrounded by the vertical frames 14, the subframe 12, and the diagonal handle pipe 26 in a side view of the vehicle body, the load of the battery 33, which is a heavy object, can be supported by the truss structure. Because the main frame 11, which is disposed below, is shorter forward than the subframe 12, a large space can be secured for the operator's feet.

[0057] In the above-mentioned electric assisted cart 1, the subframe 12 extends further forward in the vehicle body than the main frame 11, the vertical frame 14 extends upward from the main frame 11 and is connected to the mid-front / rear portion of the subframe 12, and the battery 33 is positioned in a region R1 forward of the vertical frame 14 and rearward of the joint 28 between the subframe 12 and the handle pipe 26.

[0058] According to this configuration, the battery 33 is positioned between the vertical frame 14 extending upward from the main frame 11 and the joint 28 of the subframe 12 and the handle pipe 26, so that the vertical frame 14 can distribute and support the load of the battery 33 between the main frame 11 and the subframe 12.

[0059] In the above-mentioned electric assisted cart 1, the vehicle frame 10 comprises a pair of left and right main frames 11 and sub-frames 12, and in the cargo loading section 7 of the loading platform (5), a floor frame 15 extending in the vehicle width direction and connecting the left and right main frames 11 together, and in the battery mounting section 8 of the loading platform (5), a battery floor frame 16 extending forward from the front end of the floor frame 15, a pair of left and right vertical frames 14 extending upward from the front parts of the left and right main frames 11 and joined to the front and rear middle parts of the left and right sub-frames 12, a battery cross frame 18 connecting the left and right sub-frames 12 together in a range forward of the vertical frames 14 and rearward of the front ends of the sub-frames 12, and a battery suspension frame 19 hanging down from the battery cross frame 18 and connected to the battery floor frame 16.

[0060] According to this configuration, the battery mounting section 8 is formed in a box shape and includes the battery floor frame 16, the battery cross frame 18, and the battery suspension frame 19, which provides the following effects: The battery 33 is firmly supported by overhanging it in front of the cargo bed 5, and the center of gravity of the vehicle is shifted forward, making it easier to balance the center of gravity when cargo is loaded. The weight of the battery 33 supported by the battery floor frame 16 is supported by the battery suspension frame 19 and is distributed to the left and right sub-frames 12 by the battery cross frame 18. Furthermore, the battery floor frame 16 is not connected to the handle pipe 26, so the battery weight is not directly input to the handle pipe 26. This reduces the impact of the battery weight on the sensor installation section.

[0061] The present invention is not limited to the above-described embodiment. The configurations in the above-described embodiment are merely examples of the present invention, and various modifications are possible without departing from the spirit of the present invention, such as replacing the components of the embodiment with well-known components.

[0062] DESCRIPTION OF SYMBOLS 1 Electrically assisted cart 2 Wheel 3 Axle 5 Loading platform 7 Cargo loading section 7c Center in the fore-and-aft direction 8 Battery mounting section 10 Frame 11 Main frame 11a Front end 12 Subframe 12a Front end 14 Vertical frame 15 Floor frame 16 Battery floor frame 18 Battery cross frame 19 Battery suspension frame 25 Handle frame (handle) 26 Handle pipe 27 Grip (front end) 28 Joint 31 Electric motor 33 Battery 37 Traction force sensor (detection device) 37a, 37b Strain sensor L1 Range R1 Area T1 Straight line

Claims

1. An electrically assisted cart (1) comprising: a frame (10) that constitutes a vehicle body; a pair of wheels (2) provided on the sides of the frame (10); an electric motor (31) that drives the wheels (2); a battery (33) that stores electricity to be supplied to the electric motor (31); a handle (25) operated by a driver; and a detection device (37) that detects the operating load on the handle (25), wherein the electric motor (31) provides driving assistance in accordance with the detection value of the detection device (37); wherein the battery (33) is mounted on the frame (10) forward of the axle (3) of the wheels (2); the handle (25) extends from the front of the frame (10) forward and upward of the vehicle body beyond the battery (33); and the detection device (37) is located at the joint (28) between the frame (10) and the handle (25).

2. An electrically assisted cart as described in claim 1, wherein the vehicle frame (10) supports a loading platform (5) and comprises a main frame (11) extending longitudinally along the loading platform (5), and a sub-frame (12) extending longitudinally above the main frame (11), the sub-frame (12) extending forward of the main frame (11), and the handle (25) is joined to the front end (12a) of the main frame (11) and the sub-frame (12) and extends diagonally forward and upward.

3. An electric assist cart as described in claim 2, wherein the detection device (37) is a strain sensor (37a, 37b) and is arranged at a joint (28) between the subframe (12) and the handle (25), and the joint (28) includes a predetermined range (L1) forward and above the front end (12a) of the subframe (12).

4. An electric assist cart as described in claim 3, wherein the joint (28) and the detection device (37) are arranged on a straight line (T1) connecting the front end of the handle (25) and the axle (3) of the wheel (2) when viewed from the side of the vehicle body.

5. An electric assist cart as described in claim 1, wherein the vehicle frame (10) supports a loading platform (5), the loading platform (5) comprises a battery mounting section (8) for mounting the battery (33) and a cargo loading section (7) for loading cargo, the battery mounting section (8) is arranged in front of the cargo loading section (7), and the axles (3) of the wheels (2) are arranged rearward of the center (7c) in the fore-and-aft direction of the cargo loading section (7).

6. An electrically assisted cart as described in claim 2, wherein the vehicle frame (10) comprises a vertical frame (14) extending upward from the front of the main frame (11) and joined to the mid-front / rear part of the sub-frame (12), and at least a part of the battery (33) is arranged in an area (R1) surrounded by the vertical frame (14), the sub-frame (12) and the handle (25) when viewed from the side of the vehicle body.

7. The electrically assisted cart according to claim 6, wherein the subframe (12) extends further forward than the main frame (11), the vertical frame (14) extends upward from the main frame (11) and is connected to the midpoint between the front and rear of the subframe (12), and the battery (33) is disposed in front of the vertical frame (14) in a region (R1) rearward of a joint (28) between the subframe (12) and the handle (25).

8. The vehicle frame (10) supports the loading platform (5), and includes a pair of left and right main frames (11) extending longitudinally along the loading platform (5), a pair of left and right sub-frames (12) extending longitudinally above the left and right main frames (11), a floor frame (15) extending in the vehicle width direction and connecting the left and right main frames (11) in the cargo loading section (7) of the loading platform (5), a battery floor frame (16) extending forward from the front end of the floor frame (15) in the battery mounting section (8) of the loading platform (5), a pair of left and right vertical frames (14) extending upward from the front of the left and right main frames (11) and joined to the front and rear intermediate portions of the left and right sub-frames (12), respectively, 8. The electric assist cart according to claim 1, further comprising: a battery cross frame (18) that connects the left and right subframes (12) together in a range forward of the left and right vertical frames (14) and rearward of the front ends of the left and right subframes (12); and a battery suspension frame (19) that hangs down from the battery cross frame (18) and is connected to the battery floor frame (16).

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