Electric vehicle

Abstract

To provide an electric vehicle which can keep high traction on driving wheels without fail and does not roughen a road surface.SOLUTION: An electric vehicle 1 includes: a pair of right and left main frames 31 extending in a front-back direction of the electric vehicle 1; a pair of right and left driven wheels 5 arranged below upper surfaces 31t of the pair of main frames 31 and arranged so as to sandwich the pair of main frames 31 from right and left sides; and a pair of right and left driving wheels 6 arranged below the upper surfaces 31t of the pair of main frames 31 and arranged so as to sandwich the pair of main frames 31 from the right and left sides.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] An embodiment according to the present invention relates to an electric vehicle. [Background technology]

[0002] There is known an electric farm transport vehicle that includes a carrier for carrying harvested crops, a plurality of wheels for supporting the carrier so that the carrier can run, a motor for generating power, and a power transmission mechanism for transmitting the power of the motor to the wheels. The plurality of wheels include a pair of driven wheels and a pair of drive wheels driven by the power of the motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-42616 Summary of the Invention [Problem to be solved by the invention]

[0004] Electric vehicles used in farm fields are required to have high drivability on rough roads such as soft ground, hard ground, and uneven ground. To achieve such drivability, high traction must be maintained on the drive wheels. Electric vehicles used in farm fields are also required to have driving performance that does not damage the road surface. In other words, electric vehicles used in farm fields are required to reliably maintain high traction on the drive wheels while not damaging the road surface.

[0005] Therefore, an object of the present invention is to provide an electric vehicle that can reliably maintain high traction on the drive wheels while preventing damage to the road surface. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, an electric vehicle according to an embodiment of the present invention includes a pair of left and right main frames extending in the fore-and-aft direction of the vehicle, a pair of left and right driven wheels arranged below the respective upper surfaces of the pair of main frames and arranged to sandwich the pair of main frames from the left and right, and a pair of left and right drive wheels arranged below the respective upper surfaces of the pair of main frames and arranged to sandwich the pair of main frames from the left and right. Effect of the Invention

[0007] According to the present invention, it is possible to provide an electric vehicle that can reliably maintain high traction on the drive wheels while preventing damage to the road surface. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view of an electric vehicle according to an embodiment of the present invention; [Diagram 2] 1 is a plan view of an electric vehicle according to an embodiment of the present invention; [Diagram 3] 1 is a side view of an electric vehicle according to an embodiment of the present invention. [Figure 4] 1 is a front view of an electric vehicle according to an embodiment of the present invention; [Diagram 5] FIG. 2 is a rear view of the electric vehicle according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An electric vehicle according to the present invention will now be described with reference to Figures 1 to 5. In the drawings, the same or corresponding components are denoted by the same reference numerals.

[0010] FIG. 1 is a perspective view of an electric vehicle according to an embodiment of the present invention.

[0011] FIG. 2 is a plan view of the electric vehicle according to the embodiment of the present invention.

[0012] FIG. 3 is a side view of the electric vehicle according to the embodiment of the present invention.

[0013] FIG. 4 is a front view of the electric vehicle according to the embodiment of the present invention.

[0014] FIG. 5 is a rear view of the electric vehicle according to the embodiment of the present invention.

[0015] For ease of explanation, the solid arrow F shown in Fig. 2 indicates the forward or forward direction of the electric vehicle 1 according to this embodiment, and the solid arrow B shown in Fig. 2 indicates the rearward or backward direction of the electric vehicle 1 according to this embodiment. Furthermore, the solid arrow L shown in Fig. 2 indicates the leftward direction of the electric vehicle 1 according to this embodiment, and the solid arrow R shown in Fig. 2 indicates the rightward direction of the electric vehicle 1 according to this embodiment.

[0016] The electric vehicle 1 has driven wheels 5 as front wheels and driving wheels 6 as rear wheels.

[0017] The electric vehicle 1 can also be operated with the direction of travel reversed. That is, the electric vehicle 1 may be equipped with driving wheels 6 as the front wheels and driven wheels 5 as the rear wheels. In this case, the front, rear, left and right directions of the electric vehicle 1 are reversed.

[0018] As shown in Fig. 1, an electric vehicle 1 according to this embodiment includes a frame 7 as a chassis, and a plurality of wheels 8 that support the frame 7 so that the vehicle can run. The plurality of wheels 8 include a pair of left and right driven wheels 5 and a pair of left and right drive wheels 6.

[0019] The electric vehicle 1 also includes a pair of left and right first suspension devices 11 that support each of the pair of driven wheels 5 in a steerable manner, a steering device 12 that electrically steers the pair of driven wheels 5, a pair of left and right second suspension devices 15 that support each of the pair of drive wheels 6, a pair of left and right electric motors 16 that output the drive force of each of the pair of drive wheels 6, and a pair of left and right transmission devices 17 that transmit the drive force of each of the pair of electric motors 16 to each of the pair of drive wheels 6.

[0020] Furthermore, the electric vehicle 1 includes a first storage box 21, a first control device 22 housed in the first storage box 21 and controlling each of the pair of electric motors 16, a second storage box 25, a second control device 26 housed in the second storage box 25 and controlling the steering device 12, and a plurality of batteries 28 capable of supplying power to the electric motors 16, the steering device 12, the first control device 22, and the second control device 26.

[0021] The electric vehicle 1 also includes an input device that can be operated to move forward, backward, turn left, and turn right. The input device may be, for example, a combination of a steering wheel, an accelerator, and a shift lever, or may be a joystick that can be operated by tilting a lever.

[0022] The electric vehicle 1 has a substantially symmetrical structure. Therefore, with regard to the devices, mounted equipment, wheels, and other components provided in pairs on the left and right sides, only the components on the left side will be described, and descriptions of the components on the right side will be omitted.

[0023] The frame 7 includes a pair of left and right main frames 31 extending in the fore-and-aft direction of the electric vehicle 1, a plurality of sub-frames 32 extending in the left-right direction of the electric vehicle 1 and connecting the pair of main frames 31, and a pair of left and right lateral extension frames 33 that sandwich the pair of main frames 31 from the left and right of the electric vehicle 1.

[0024] The frame 7 also includes a pair of main frames 31, a plurality of sub-frames 32, and an appropriate reinforcing frame 35 arranged below the pair of lateral extension frames 33 to reinforce the frame 7, as well as a plurality of gussets 38 arranged at the connection points of the various frames 31, 32, 33, and 35.

[0025] The frame 7 functions as a loading platform for the electric vehicle 1. In other words, the upper surface 7t of the frame 7 functions as a loading surface for carrying cargo on the electric vehicle 1. The upper surface 7t of the frame 7 may be inclined within a range suitable for loading cargo, and is preferably substantially horizontal.

[0026] The upper surface 7t of the frame 7 is a plane including the upper surfaces 31t of the pair of main frames 31 and the upper surfaces 33t of the pair of side extension frames 33. In other words, the upper surfaces 31t of the pair of main frames 31 and the upper surfaces 33t of the pair of side extension frames 33 are aligned on the same plane, that is, on the upper surface 7t of the frame 7. The upper surfaces 32t of the multiple sub-frames 32 may be aligned on the upper surface 7t of the frame 7 or may be located below the upper surface 7t of the frame 7.

[0027] The frame 7 supports the steering device 12, the first suspension device 11, the second suspension device 15, the first storage box 21, the second storage box 25, and the plurality of batteries 28 in a suspending manner. All components of the electric vehicle 1 supported by the frame 7 are disposed at a position lower than the upper surface 7t of the frame 7. In other words, all components of the electric vehicle 1 are disposed at a position lower than the upper surfaces 31t of the pair of main frames 31 and the upper surfaces 33t of the pair of side extension frames 33. This brings the position of the center of gravity of the electric vehicle 1 closer to the road surface on which the driven wheels 5 and the driving wheels 6 are in contact with the ground, that is, the center of gravity of the electric vehicle 1 is lowered. The lower the position of the center of gravity, the more stable the running of the electric vehicle 1 is.

[0028] The pair of main frames 31 are disposed in the left-right center of the frame 7 so as to penetrate the frame 7 in the front-rear direction. The pair of main frames 31 may be straight or curved, but are preferably mirror-symmetric with respect to a plane that bisects the frame 7 into the left and right sides of the electric vehicle 1 as the mirror plane. The mirror-symmetric main frames 31 are excellent in rigidity of the frame 7 and in left-right balance of the frame 7. The straight-line main frames 31 have a shorter total length than the curved main frames 31, and are excellent in reducing the weight of the frame 7.

[0029] Each main frame 31 may be a one-piece molded product, or may be a joined body in which a plurality of members are joined together. The one-piece molded main frame 31 has no joints and is therefore lighter than the joined body main frame 31. Reducing the weight of the main frame 31, which is relatively heavy among the components of the electric vehicle 1, enables the electric vehicle 1 to run on road surfaces such as farm fields without damaging them.

[0030] The frame 7 supports the steering system 12 , the first suspension system 11 , the second suspension system 15 , the first storage box 21 , the second storage box 25 , and the plurality of batteries 28 , all of which are supported by the main frame 31 .

[0031] One end 31f of the main frame 31 in the front-rear direction is the front end 31f of the main frame 31, which is closer to the pair of driven wheels 5 and farther from the pair of drive wheels 6. The front end 31f of the main frame 31 protrudes further in a direction away from the pair of drive wheels 6 than the pair of driven wheels 5. In other words, the main frame 31 has a length that protrudes forward beyond the axles 41 of the driven wheels 5 in the front-rear direction of the electric vehicle 1, a so-called front overhang. The front overhang of the main frame 31 is also the front overhang of the frame 7.

[0032] The other end 31b of the main frame 31 in the front-rear direction is the rear end 31b of the main frame 31, which is far from the pair of driven wheels 5 and close to the pair of driving wheels 6. The rear end 31b of the main frame 31 protrudes further from the pair of driving wheels 6 in a direction away from the pair of driven wheels 5. In other words, the main frame 31 has a length that protrudes rearward beyond the axles 42 of the driving wheels 6 in the front-rear direction of the electric vehicle 1, a so-called rear overhang. The rear overhang of the main frame 31 is also the rear overhang of the frame 7.

[0033] Making the rear overhang of the frame 7 larger than the front overhang increases the weight of the electric vehicle 1 shared by the drive wheels 6. This increase in the load shared by the drive wheels 6 effectively improves the traction of the drive wheels 6. The improvement in traction of the drive wheels 6 prevents the drive wheels 6 from spinning on rough roads such as farm fields.

[0034] The main frame 31 has an upper surface 31t that is positioned higher than the top of the steering gear 12, the top of the first suspension gear 11, the top of the second suspension gear 15, the upper surface 32t of the first storage box 21, the upper surface 25t of the second storage box 25, and the upper surfaces 28t of the multiple batteries 28, and supports the steering gear 12, the first suspension gear 11, the second suspension gear 15, the first storage box 21, the second storage box 25, and the multiple batteries 28.

[0035] The multiple sub-frames 32 extend in the left-right direction of the electric vehicle 1. The multiple sub-frames 32 include, for example, a sub-frame 32 spanning across front ends 31f of the pair of main frames 31, a sub-frame 32 spanning across rear ends 31b, and a sub-frame 32 spanning across an intermediate portion of the main frame 31 between the front ends 31f and the rear ends 31b in the front-rear direction.

[0036] The pair of driven wheels 5 are disposed below the respective upper surfaces 31t of the pair of main frames 31, and disposed so as to sandwich the main frame 31 from the left and right in a plan view (FIG. 2) of the electric vehicle 1. The tops of the respective driven wheels 5 are disposed below the respective upper surfaces 31t of the pair of main frames 31.

[0037] Each of the driven wheels 5 has an axle 41. For ease of explanation, the axle 41 of the driven wheels 5 is referred to as the front wheel axle 41. In addition, the width dimension obtained by adding the tread width of the pair of driven wheels 5 to the tire width of one of the driven wheels 5 is referred to as the outermost edge width of the pair of driven wheels 5.

[0038] The pair of drive wheels 6 are disposed below the respective upper surfaces 31t of the pair of main frames 31, and disposed so as to sandwich the pair of main frames 31 from the left and right in a plan view (FIG. 2) of the electric vehicle 1. The tops of the respective drive wheels 6 are disposed below the respective upper surfaces 31t of the pair of main frames 31.

[0039] Each driving wheel 6 has an axle 42. For ease of explanation, the axle 42 of the driving wheels 6 is referred to as the rear wheel axle 42. In addition, the width dimension obtained by adding the tread width of the pair of driving wheels 6 to the tire width of one driving wheel 6 is referred to as the outermost edge width of the pair of driving wheels 6.

[0040] The main frame 31, which is sandwiched between the pair of drive wheels 6 and the pair of driven wheels 5, is disposed toward the center in the width direction of the electric vehicle 1, specifically, in the center of the electric vehicle 1. Therefore, the left and right balance of the electric vehicle 1 is easily balanced, and therefore the shared load of the left and right drive wheels 6 is also easily balanced. The balance of the shared load of the left and right drive wheels 6 effectively acts to stabilize the traction of the left and right drive wheels 6. Stable traction of the left and right drive wheels 6 prevents the drive wheels 6 from spinning on rough roads such as farm fields. Furthermore, if the traction of the left and right drive wheels 6 is stabilized on rough roads such as farm fields, the electric vehicle 1 can run stably without damaging the road surface.

[0041] In the width direction of the electric vehicle 1, the pair of side extension frames 33 are provided inside the larger of the outermost edge width of the pair of driven wheels 5 and the outermost edge width of the pair of driving wheels 6. In the width direction of the electric vehicle 1, the pair of side extension frames 33 are more preferably provided inside the smaller of the outermost edge width of the pair of driven wheels 5 and the outermost edge width of the pair of driving wheels 6. Therefore, the electric vehicle 1 is likely to avoid contact between surrounding obstacles and the frame 7 including the side extension frames 33 both during driving and turning. In addition, the pair of side extension frames 33 are located inside the driving trajectories of the left and right driven wheels 5 and the left and right driving wheels 6, so that the size of the frame 7 as a cargo bed in the width direction is expanded without restricting the driving performance and turning performance of the electric vehicle 1.

[0042] The pair of side extension frames 33 has a center of gravity Gsf that is located between the front wheel axle 41 and the rear wheel axle 42 in the front-rear direction of the electric vehicle 1, close to the rear wheel axle 42 and far from the front wheel axle 41. In other words, the center of gravity of the frame 7 including the side extension frames 33 is close to the rear wheel axle 42 and far from the front wheel axle 41. Therefore, the load shared by the driving wheels 6 is greater than the load shared by the driven wheels 5. This increase in the load shared by the driving wheels 6 effectively improves the traction of the driving wheels 6. The improvement in traction of the driving wheels 6 prevents the driving wheels 6 from spinning on rough roads such as farm fields.

[0043] In addition, in a plan view of the electric vehicle 1 (FIG. 2), the side extension frame 33 has a first portion 45 arranged so as to be sandwiched between the driven wheels 5 and the driving wheels 6, and a second portion 46 arranged so as to be sandwiched between the main frame 31 and the driving wheels 6. In a plan view of the electric vehicle 1 (FIG. 2), the pair of side extension frames 33 avoid the upper part of the pair of driven wheels 5 and the upper part of the pair of driving wheels 6. By doing so, even if the driven wheels 5 and the driving wheels 6 swing significantly in the vertical direction of the electric vehicle 1, that is, even if the frame 7 sinks deeply, the electric vehicle 1 can prevent contact between the frame 7 and the driven wheels 5 and between the frame 7 and the driving wheels 6. In other words, the electric vehicle 1 can keep the ground clearance of the frame 7 as a cargo bed low. The frame 7 with a low ground clearance can contribute to lowering the center of gravity of the electric vehicle 1.

[0044] The first section 45 has a pair of front and rear extension frames 51 that protrude to either the left or right from the pair of main frames 31 so as to expand the width of the frame 7, and an outer edge frame 52 that is bridged between the protruding ends of the pair of extension frames 51 and extends in the fore-aft direction of the electric vehicle 1. The pair of extension frames 51 are spaced apart in the fore-aft direction of the electric vehicle 1, are parallel to each other, and extend perpendicular to the main frames 31. The outer edge frame 52 extends parallel to the main frames 31 and is perpendicular to the pair of extension frames 51.

[0045] The second section 46 has a sub-extension frame 55 that protrudes from the pair of main frames 31 to either the left or right so as to extend the width of the frame 7, and a sub-peripheral frame 56 that spans between the middle part of the extension frame 51 on the rear side of the first section 45 and the protruding end of the sub-extension frame 55 and extends in the front-rear direction of the electric vehicle 1. The sub-extension frame 55 is parallel to the extension frame 51 of the first section 45, is disposed closer to the drive wheels 6 than the extension frame 51 on the rear side of the first section 45, and extends perpendicular to the main frame 31. In a plan view of the electric vehicle 1 (FIG. 2), the sub-extension frame 55 has a protruding end closer to the main frame 31 than the drive wheels 6, and an extension line of the sub-extension frame 55 crosses the drive wheels 6. The sub-peripheral frame 56 extends parallel to the main frame 31 and is perpendicular to the extension frame 51 and the sub-extension frame 55.

[0046] The side extension frame 33 having the first portion 45 and the second portion 46 extends the function as a cargo bed of the main frame 31 disposed toward the center of the frame 7. In addition, the second portion 46 extends the function as a cargo bed of the frame 7 to the area sandwiched between the driving wheels 6 and the main frame 31, which is insufficient to be extended by the first portion 45 alone, and moves the center of gravity Gsf of the side extension frame 33 closer to the driving wheels 6, thereby increasing the load shared by the driving wheels 6 and effectively improving the traction of the driving wheels 6.

[0047] In addition, the second portion 46 may be disposed so as to be sandwiched between the main frame 31 and the driven wheel 5.

[0048] Each gusset 38 is provided at each of the butt joints of elongated members such as the main frame 31, the sub-frame 32, the side extension frame 33, and the reinforcing frame 35, and connects multiple members that meet at the butt joints.

[0049] At least one of the pair of main frames 31 and the pair of side extension frames 33 may be provided with a fixing device 62 capable of fixing an auxiliary platform 61 arranged on the upper surfaces 31t, 33t thereof. The auxiliary platform 61 may be a flat plate as a loading platform, or may be a platform for loading a work machine. In the electric vehicle 1, the auxiliary platform 61 suitable for various applications, such as fruit harvesting and transporting harvested fruit, is loaded onto the frame 7 and fixed with the fixing device 62. In this way, the electric vehicle 1 can provide flexible and suitable convenience according to various applications. The lowering of the center of gravity of the electric vehicle 1 and the suppression of the ground height of the upper surface 7t of the frame 7 resulting from this lowering of the center of gravity improve the convenience of the electric vehicle 1 even when the auxiliary platform 61 is loaded. The auxiliary platform 61 may overlap above the driven wheels 5 and the driving wheels 6. Such an auxiliary platform 61 enhances the function of the electric vehicle 1 as a loading platform.

[0050] The first suspension device 11 is fixed to the frame 7 so as to be suspended from the main frame 31 via a driven wheel support frame 71 provided at the front end of the main frame 31. The first suspension device 11 supports the driven wheels 5, i.e., the front wheels, so as to be swingable in the vertical direction of the electric vehicle 1. The first suspension device 11 includes a first swing arm 72 supported by the driven wheel support frame 71 around a swing axis extending in the front-rear direction of the electric vehicle 1 so as to be able to swing the driven wheels 5 in the vertical direction of the electric vehicle 1, and a first damper 73 bridged between the first swing arm 72 and the driven wheel support frame 71 to cushion the swing of the first swing arm 72.

[0051] In a plan view (FIG. 2) of the electric vehicle 1, the steering device 12 is disposed between the front end portions 31f of the pair of main frames 31. The steering device 12 is fixed to the frame 7 so as to be suspended from the main frame 31 via the driven wheel support frame 71 together with the first suspension device 11. The steering device 12 includes a second electric motor 75 that converts the electric power stored in the multiple batteries 28 to output the steering force of the driven wheels 5 as steered wheels, and a pair of tie rods 76 that distribute and transmit the steering force of the second electric motor 75 to each of the pair of driven wheels 5. The steering device 12 applies a steering angle to the driven wheels 5 by pushing and pulling the pair of tie rods 76 to the left and right by the steering force generated by the second electric motor 75.

[0052] The second suspension device 15 integrally supports the drive wheels 6, the electric motor 16, and the transmission device 17. The second suspension device 15 supports the drive wheels 6, i.e., the rear wheels, so as to be swingable in the vertical direction of the electric vehicle 1. The second suspension device 15 is fixed to the frame 7 so as to be suspended from the main frame 31 via a drive wheel support frame 81 that is provided rearward of the center of the main frame 31 and extends in the left-right direction of the main frame 31. The drive wheel support frame 81 is located directly below a pair of extension frames 51 closer to the drive wheels 6, i.e., a pair of rear extension frames 51, and extends in the left-right direction of the electric vehicle 1 in parallel therewith. The frame 7 includes a pair of left and right drive wheel support reinforcement frames 82 that extend in the vertical direction of the electric vehicle 1 and are bridged between the drive wheel support frame 81 and each of the extension frames 51. The drive wheel support frame 81 and a pair of extension frames 51, which are integrated into a pair of drive wheel support reinforcement frames 82, firmly support the second suspension device 15, which collectively oscillates the drive wheels 6, the electric motor 16, and the transmission device 17.

[0053] The second suspension device 15 includes a second swing arm 83 that is supported by the drive wheel support frame 81 around a swing axis extending in the left-right direction of the electric vehicle 1 and that can swing the drive wheel 6 in the up-down direction of the electric vehicle 1, and a second damper 85 that is spanned between the second swing arm 83 and the second portion 46 of the lateral extension frame 33 and that cushions the swing of the second swing arm 83.

[0054] The swing shaft of the second swing arm 83 overlaps with the drive wheel support frame 81 in a plan view of the electric vehicle 1. That is, the swing shaft of the second swing arm 83 is located between the front wheel axle 41 and the rear wheel axle 42 in the front-rear direction of the electric vehicle 1, and is close to the rear wheel axle 42 and far from the front wheel axle 41. The second swing arm 83 houses the transmission device 17. In the width direction of the electric vehicle 1, the second swing arm 83 supports the drive wheel 6 on a side closer to the main frame 31 than the drive wheel 6, and supports the electric motor 16 on a side farther from the main frame 31 than the electric motor 16. In other words, the second suspension device 15 supports the drive wheel 6 on the lateral outer side of the electric vehicle 1 and supports the electric motor 16 on the lateral inner side of the electric vehicle 1, centered around the second swing arm 83.

[0055] In the front-rear direction of the electric vehicle 1, the electric motor 16 is between the axle 42 of the driving wheel 6 and the axle 41 of the driven wheel 5, close to the axle 42 of the driving wheel 6, and far from the axle 41 of the driven wheel 5. In addition, in the front-rear direction of the electric vehicle 1, the electric motor 16 is between the swing shaft of the second swing arm 83 and the axle 42 of the driving wheel 6, close to the swing shaft of the second swing arm 83, and far from the axle 42 of the driving wheel 6. In other words, the electric motor 16 is disposed near the base of the second swing arm 83, and the driving wheel 6 is disposed near the protruding end of the second swing arm 83.

[0056] The electric motor 16 has an output shaft 16o that outputs the driving force of the drive wheels 6. The output shaft 16o of the electric motor 16 and the axle 42 of the drive wheels 6 are parallel to each other. The electric motor 16 is disposed inside the second swing arm 83 in the width direction of the electric vehicle 1 and is fixed to the second swing arm 83. The electric motor 16 has a cylindrical outer tube that extends toward the center of the electric vehicle 1 in the width direction of the electric vehicle 1. The left and right second suspension devices 15 can be close to each other in the width direction of the electric vehicle 1 to the extent that the outer tubes of the left and right electric motors 16 do not overlap each other. In other words, the minimum value of the tread width of the left and right drive wheels 6 depends on the size of the left and right electric motors 16.

[0057] The transmission device 17 is housed in the corresponding second swing arm 83. The transmission device 17 is a reducer, and transmits the driving force from the output shaft 16o of the electric motor 16 to the rear wheel axle 42 after reducing the speed.

[0058] In the front-rear direction of the electric vehicle 1, the centers of gravity Gbatt of the batteries 28 are arranged to sandwich the imaginary line VL1 passing through the axles 42 of the drive wheels 6. In other words, the centers of gravity Gbatt of the front battery 28F and the centers of gravity Gbatt of the rear battery 28B are arranged to sandwich the imaginary line VL1 passing through the axles 42 of the drive wheels 6. In general, the battery 28 is a relatively heavy mounted device among all the components of the electric vehicle 1. By arranging the centers of gravity Gbatt of the batteries 28, which are heavy in this way, to sandwich the imaginary line VL1 passing through the axles 42 of the drive wheels 6, the weight of the batteries 28 effectively acts to improve the traction of the drive wheels 6. The improvement in traction of the drive wheels 6 prevents the drive wheels 6 from spinning on rough roads such as farm fields.

[0059] In the front-rear direction of the electric vehicle 1, the centers of gravity Gbatt of the batteries 28 are arranged to sandwich the imaginary line VL2 passing through the output shaft 16o of the electric motor 16. In other words, the centers of gravity Gbatt of the front battery 28F and the rear battery 28B are arranged to sandwich the imaginary line VL2 passing through the output shaft 16o of the electric motor 16. In general, the electric motor 16 is a relatively heavy mounted device among all the components of the electric vehicle 1, similar to the battery 28. By arranging the center of gravity Gbatt of the battery 28, which is the heaviest among all the components of the electric vehicle 1, to sandwich the imaginary line VL2 passing through the output shaft 16o of the electric motor 16, which is also heavy, the weight of the batteries 28 and the weight of the electric motor 16 effectively act in combination with the improvement of the traction of the drive wheels 6. The improvement of the traction of the drive wheels 6 prevents the drive wheels 6 from spinning on rough roads such as farm fields.

[0060] In other words, the multiple batteries 28 are biased closer to the driving wheels 6 than to the driven wheels 5 in the front-rear direction of the electric vehicle 1 .

[0061] Each battery 28 is, for example, a 12-volt lead-acid battery. The plurality of batteries 28 includes at least two batteries 28 electrically connected in series. Here, the battery 28 disposed between the driven wheels 5 as the front wheels and the driving wheels 6 as the rear wheels is referred to as the front battery 28F, and the battery 28 disposed closer to the rear end portion 31b of the main frame 31 than the front battery 28F is referred to as the rear battery 28B.

[0062] In a plan view of the electric vehicle 1 (FIG. 2), the front battery 28F is disposed so as to be sandwiched in the center of the pair of main frames 31. The front battery 28F is fixed to the frame 7 so as to be suspended from the main frames 31 via a front battery support frame 91.

[0063] In a plan view of the electric vehicle 1 (FIG. 2), the rear battery 28B is arranged so as to be sandwiched between the rear end portions 31b of the pair of main frames 31. The rear battery 28B is fixed to the frame 7 so as to be suspended from the main frame 31 via a rear battery support frame 92.

[0064] The frame 7 supports the front battery 28F, which is one of the multiple batteries 28 and is disposed between the drive wheels 6 and the driven wheels 5, so that it can be attached and detached by moving it to either the left or right of the electric vehicle 1 (solid line arrow α in FIG. 2), and supports the rear battery 28B (other battery), one of the multiple batteries 28, so that it can be attached and detached by moving it closer to or away from the imaginary line VL1 passing through the axle 42 of the drive wheels 6 (solid line arrow β in FIG. 2). In other words, the front battery support frame 91 supports the front battery 28F so that it can be attached and detached by moving it to either the left or right of the electric vehicle 1. The rear battery support frame 92 supports the rear battery 28B so that it can be attached and detached by moving it closer to or away from the imaginary line VL1 passing through the axle 42 of the drive wheels 6.

[0065] Such a structure for attaching and detaching the battery 28 significantly improves the ease of attaching, detaching, and replacing the battery 28 of the electric vehicle 1. In addition, because the structure for attaching and detaching the battery 28 of the electric vehicle 1 includes a plurality of batteries 28 with different attachment and detachment directions, it is possible to easily prevent confusion over the mounting locations of the batteries 28, whether the mounting locations of the plurality of batteries 28 are limited and are handled separately, or the mounting locations of the plurality of batteries 28 are changed from time to time.

[0066] Setting the height Hbatt of the battery 28, which is relatively heavy among all the components of the electric vehicle 1, low contributes to the electric vehicle 1. However, if the height Hbatt of the battery 28 is too low, the battery 28 may come into contact with the road surface and be damaged when the electric vehicle 1 is driven on an uneven road surface such as a farm field. On the other hand, the running performance of the electric vehicle 1 depends on the diameters of the driven wheels 5 and the driving wheels 6. Therefore, the height Hbatt of the bottom surface 28b of each battery 28 above the ground is set to be higher than one-third the diameter of the driving wheels 6. By doing so, the running performance of the electric vehicle 1 is improved, and the center of gravity of the electric vehicle 1 can be lowered, that is, the running can be stabilized, within a range where damage to the battery 28 can be avoided.

[0067] The first control device 22 is housed in the first storage box 21 and controls the multiple electric motors 16 .

[0068] In a plan view (FIG. 2) of the electric vehicle 1, the first storage box 21 that houses the first control device 22 is arranged so as to overlap any one of the plurality of batteries 28 and the plurality of electric motors 16. The first storage box 21 is sandwiched between a pair of main frames 31 and arranged below the upper surfaces 31t of the pair of main frames 31. In the front-rear direction of the electric vehicle 1, the first storage box 21 is arranged between the axles 41 of the pair of driven wheels 5 and the axles 42 of the pair of driving wheels 6, close to the axles 42 of the pair of driving wheels 6 and far from the axles 41 of the pair of driven wheels 5. In addition, in the front-rear direction of the electric vehicle 1, the first storage box 21 is arranged so as to straddle an imaginary line VL1 that passes through the axles 42 of the pair of driving wheels 6.

[0069] By arranging the first storage box 21 near the battery 28, the length of the power cable connected from the multiple batteries 28 to the multiple electric motors 16 via the first storage box 21 can be easily shortened. In general, a power cable has a small wire number, a large wire diameter, and a weight per unit length that is heavier than a signal line. The shorter the cable length of such a power cable, the more it contributes to reducing the weight of the electric vehicle 1. In addition, by stacking the first storage box 21 on the battery 28, the electric vehicle 1 can easily prevent contact between the first storage box 21 and surrounding obstacles, and can reliably protect the first control device 22 housed in the first storage box 21. Furthermore, by sandwiching the first storage box 21 between a pair of main frames 31, the electric vehicle 1 can easily prevent contact between the first storage box 21 and surrounding obstacles, and contact between the first storage box 21 and luggage loaded on the frame 7 as a loading platform, and can reliably protect the first control device 22 housed in the first storage box 21. Furthermore, by arranging the first storage box 21 near the battery 28, the weight of the electric vehicle 1 shared by the drive wheels 6 is further increased. This increase in the load shared by the drive wheels 6 effectively improves the traction of the drive wheels 6. The improvement in traction of the drive wheels 6 prevents the drive wheels 6 from spinning on rough roads such as farm fields.

[0070] The second control device 26 is housed in the second storage box 25 and controls the second electric motor 75 .

[0071] In a plan view (FIG. 2) of the electric vehicle 1, the second storage box 25 that houses the second control device 26 is arranged so as to overlap at least one of the plurality of batteries 28 and the plurality of electric motors 16. The second storage box 25 is sandwiched between a pair of main frames 31 and arranged below the upper surfaces 31t of the pair of main frames 31. In the front-rear direction of the electric vehicle 1, the second storage box 25 is arranged between the axles 41 of the pair of driven wheels 5 and the axles 42 of the pair of driving wheels 6, close to the axles 42 of the pair of driving wheels 6, and far from the axles 41 of the pair of driven wheels 5. The second storage box 25 is closer to the axles 41 of the pair of driven wheels 5 than the first storage box 21, and is arranged in front of the first storage box 21. The second storage box 25 is arranged almost directly above the front battery 28F.

[0072] By arranging the second storage box 25 in front of the first storage box 21, the length of the power cable connected from the plurality of batteries 28 to the second electric motor 75 via the second storage box 25 can be easily shortened. In addition, by stacking the second storage box 25 on the battery 28, the electric vehicle 1 can easily prevent contact between the second storage box 25 and surrounding obstacles, and can reliably protect the second control device 26 housed in the second storage box 25. Furthermore, by sandwiching the second storage box 25 between the pair of main frames 31, the electric vehicle 1 can easily prevent contact between the second storage box 25 and surrounding obstacles, and contact between the second storage box 25 and luggage loaded on the frame 7 as a cargo bed, and can reliably protect the second control device 26 housed in the second storage box 25. In addition, by arranging the second storage box 25 near the battery 28, the weight of the electric vehicle 1 shared by the drive wheels 6 is further increased. This increase in the shared load of the drive wheels 6 effectively works to improve the traction of the drive wheels 6. Improving the traction of the drive wheels 6 prevents the drive wheels 6 from spinning on rough roads such as farm fields.

[0073] The electric vehicle 1 moves straight forward or backward by making the outputs of the left and right electric motors 16 substantially the same, i.e., making the torques of the left and right drive wheels 6 the same, and by making the steering angle of the pair of driven wheels 5 zero degrees with the output of the second electric motor 75, i.e., by aligning the front wheel axle 41 with the left and right direction of the electric vehicle 1. The electric vehicle 1 also turns left or right by making the outputs of the left and right electric motors 16 different, i.e., making the torques of the left and right drive wheels 6 different, and by applying a steering angle to the pair of driven wheels 5 with the output of the second electric motor 75 according to the difference in the outputs of the left and right electric motors 16. The forward movement, backward movement, left turn, and right turn of the electric vehicle 1 are controlled by the first control device 22 and the second control device 26 based on the operation signal output by the input device.

[0074] As described above, the electric vehicle 1 according to this embodiment includes a pair of left and right main frames 31 extending in the front-rear direction of the electric vehicle 1, a pair of left and right driven wheels 5 arranged below the respective upper surfaces 31t of the pair of main frames 31 and arranged to sandwich the pair of main frames 31 from the left and right, and a pair of left and right drive wheels 6 arranged below the respective upper surfaces 31t of the pair of main frames 31 and arranged to sandwich the pair of main frames 31 from the left and right. Therefore, the left and right balance of the electric vehicle 1 is easily balanced, and the shared load of the left and right drive wheels 6 is also easily balanced. The balance of the shared load of the left and right drive wheels 6 effectively acts to stabilize the traction of the left and right drive wheels 6. The stability of the traction of the left and right drive wheels 6 prevents the drive wheels 6 from spinning on a rough road such as a farm field. Therefore, the electric vehicle 1 can easily achieve both high drivability and driving performance that does not damage the road surface.

[0075] Moreover, the electric vehicle 1 according to this embodiment includes a main frame 31 having one end 31f that protrudes beyond the pair of driven wheels 5 in a direction away from the pair of drive wheels 6. Therefore, the electric vehicle 1 can easily expand its function as a cargo bed by making the front overhang of the frame 7 larger than the rear overhang.

[0076] Furthermore, the electric vehicle 1 according to this embodiment includes a main frame 31 having another end 31b that protrudes beyond the pair of driving wheels 6 in a direction away from the pair of driven wheels 5. Therefore, by making the rear overhang of the frame 7 larger than the front overhang, the electric vehicle 1 increases the load shared by the driving wheels 6, improving the traction of the driving wheels 6, and easily expands its function as a cargo bed.

[0077] The electric vehicle 1 according to this embodiment includes a pair of electric motors 16 each outputting a driving force for a pair of driving wheels 6, a first control device 22 controlling the pair of electric motors 16, and a first storage box 21 arranged to overlap at least one of the plurality of batteries 28 and the plurality of electric motors 16 and to accommodate the first control device 22. The first storage box 21 is sandwiched between the pair of main frames 31 and arranged below the upper surfaces 31t of the pair of main frames 31, and is arranged between the axles 41 of the pair of driven wheels 5 and the axles 41 of the pair of driving wheels 6 in the front-rear direction of the electric vehicle 1, close to the axles 42 of the pair of driving wheels 6 and far from the axles 41 of the pair of driven wheels 5. Therefore, in the electric vehicle 1, the power cables connecting the plurality of batteries 28 to the plurality of electric motors 16 are shortened, and the weight of the electric vehicle 1 is reduced. The reduction in weight of the electric vehicle 1 improves the running performance on rough roads. Moreover, the electric vehicle 1 easily prevents contact between the first storage box 21 and surrounding obstacles, and reliably protects the first control device 22 housed in the first storage box 21. Furthermore, the electric vehicle 1 concentrates the weight of the components in the vicinity of the multiple batteries 28, thereby increasing the load shared by the drive wheels 6 and achieving both a lighter total weight and high traction for the drive wheels 6.

[0078] Furthermore, the electric vehicle 1 according to this embodiment includes a pair of left and right side extension frames 33 that are provided to sandwich the pair of main frames 31 from the left and right on the inside of the larger of the outermost edge width of the pair of driven wheels 5 and the outermost edge width of the pair of driving wheels 6, and have a center of gravity Gsf that is located between the axles 41 of the pair of driven wheels 5 and the axles 42 of the pair of driving wheels 6 in the front-rear direction of the electric vehicle 1, close to the axles 42 of the pair of driving wheels 6, and far from the axles 41 of the pair of driven wheels 5. The pair of side extension frames 33 increase the load shared by the driving wheels 6, and effectively act to improve the traction of the driving wheels 6. The improvement in traction of the driving wheels 6 prevents the driving wheels 6 from spinning on rough roads such as farm fields, and improves the running performance of the electric vehicle 1.

[0079] Moreover, the electric vehicle 1 according to this embodiment includes a pair of left and right side extension frames 33, each having a second portion 46 disposed so as to be sandwiched between the pair of main frames 31 and the pair of driven wheels 5. Therefore, in the electric vehicle 1, the function of the frame 7 as a cargo bed is extended to the region sandwiched between the driving wheels 6 and the main frames 31, which is insufficient to be extended by the first portion 45 alone, and the center of gravity Gsf of the side extension frames 33 is brought closer to the driving wheels 6, thereby increasing the load shared by the driving wheels 6 and improving the traction of the driving wheels 6.

[0080] Furthermore, the electric vehicle 1 according to this embodiment includes a pair of left and right side extension frames 33 that avoid the pair of driven wheels 5 and the pair of drive wheels 6 in a plan view ( FIG. 2 ) of the electric vehicle 1. Therefore, the electric vehicle 1 can keep the ground clearance of the frame 7 serving as a cargo bed low. The frame 7 with a low ground clearance can contribute to lowering the center of gravity of the electric vehicle 1.

[0081] Moreover, the electric vehicle 1 according to this embodiment includes a pair of main frames 31 and a pair of side extension frames 33, each having upper surfaces 31t, 33t that are arranged on the same plane. Therefore, the position of the center of gravity of the electric vehicle 1 is closer to the road surface on which the driven wheels 5 and the driving wheels 6 are in contact with the ground, that is, the center of gravity of the electric vehicle 1 is lowered. The lower the position of the center of gravity, the more stable the running of the electric vehicle 1 is.

[0082] Furthermore, the electric vehicle 1 according to this embodiment includes a fastener 62 that is provided on at least one of the pair of main frames 31 and the pair of lateral extension frames 33 and is capable of fixing an auxiliary stand 61 arranged on their upper surfaces 31t, 33t. The lowering of the center of gravity of the electric vehicle 1 and the associated reduction in the ground clearance of the upper surface 7t of the frame 7 improve the convenience of the electric vehicle 1 even when the auxiliary stand 61 is loaded.

[0083] As described above, the electric vehicle 1 according to the embodiment of the present invention can reliably maintain high traction on the drive wheels 6 while preventing the road surface from becoming rough.

[0084] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0085] 1...electric vehicle, 5...driven wheel, 6...driving wheel, 7...frame, 7t...upper surface, 8...wheel, 11...first suspension device, 12...steering device, 15...second suspension device, 16...electric motor, 16o...output shaft, 17...transmission device, 21...first storage box, 21...first storage box, 22...first control device, 25...second storage box, 25t...upper surface, 26...second control device, 28...battery, 28F...front battery, 28B...rear battery, 28t...upper surface, 28b...bottom surface, 31...main frame, 31t...upper surface, 31f...one end, front end, 31b...other end, rear end, 32...sub-frame, 32t...upper surface, 33...side extension frame, 33t...upper surface, 35...reinforcement frame, 38...gusset, 41...driven wheel axle, front wheel axle, 42...driven wheel axle, rear wheel axle, 45...first part, 46...second part, 51...extension frame, 52...outer edge frame, 55...sub-extension frame, 56...sub-outer edge frame, 61...auxiliary base, 62...fixing device, 71...driven wheel support frame, 72...first swing arm, 73...first damper, 75...second electric motor, 76...tie rod, 81...driven wheel support frame, 82...driven wheel support reinforcement frame, 83...second swing arm, 85...second damper, 91...front battery support frame, 92...rear battery support frame.

Claims

1. A pair of left and right main frames extending in a front-rear direction of the vehicle; A pair of left and right driven wheels that are disposed below the upper surfaces of the pair of main frames and that are disposed so as to sandwich the pair of main frames from the left and right; an electric vehicle comprising: a pair of left and right drive wheels disposed below the respective upper surfaces of the pair of main frames and disposed so as to sandwich the pair of main frames from the left and right.

2. The electric vehicle according to claim 1 , wherein one end of the main frame in the front-rear direction protrudes beyond the pair of driven wheels in a direction away from the pair of drive wheels.

3. 3. The electric vehicle according to claim 1, wherein the other end of the main frame in the front-rear direction protrudes beyond the pair of drive wheels in a direction away from the pair of driven wheels.

4. A pair of electric motors each outputting a driving force for the pair of drive wheels; A control device for controlling the pair of electric motors; a storage box that is arranged to overlap at least one of the plurality of batteries and the plurality of electric motors and that stores the control device, 3. The electric vehicle according to claim 1 or 2, wherein the storage box is sandwiched between the pair of main frames, disposed below an upper surface of each of the pair of main frames, and disposed between the axles of the pair of driven wheels and the axles of the pair of driving wheels in the fore-and-aft direction, close to the axles of the pair of driving wheels and far from the axles of the pair of driven wheels.

5. 3. The electric vehicle according to claim 1 or 2, further comprising a pair of left and right lateral extension frames arranged to sandwich the pair of main frames from the left and right on the inside of the larger of an outermost edge width of the pair of driven wheels and an outermost edge width of the pair of drive wheels, and having a center of gravity located between the axles of the pair of driven wheels and the axles of the pair of drive wheels in the front-rear direction, close to the axles of the pair of drive wheels, and far from the axles of the pair of driven wheels.

6. The electric vehicle according to claim 5 , wherein each of the side extension frames has a portion disposed so as to be sandwiched between the main frame and the driven wheels.

7. The electric vehicle according to claim 5 , wherein the pair of lateral extension frames avoid the pair of driven wheels and the pair of driving wheels in a plan view of the vehicle.

8. The electric vehicle according to claim 5 , wherein an upper surface of each of the pair of main frames and an upper surface of each of the pair of side extension frames are disposed in the same plane.

9. The electric vehicle according to claim 8 , wherein at least one of the pair of main frames and the pair of side extension frames includes a fastener capable of fastening an auxiliary base disposed on the upper surface thereof.

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