Electric vehicles and electric assist devices for vehicles

Abstract

An electric wheelchair (1) comprises: a vehicle body (2) having casters (2c) and main wheels (2b); a bracket (18) fixed to the vehicle body (2); an arm (20) supported so as to be swingable in the vertical direction by the bracket (18); a drive wheel (14) provided to the leading end section (21a) of the arm (20); an actuator (16) for driving the drive wheel (14); and an elastic member (58) which is provided between the bracket (18) and the arm (20) and biases the arm (20) in the downward direction.

Description

Technical Field

[0001] The present invention relates to an electric vehicle and an electric assist device for a vehicle.

Background Art

[0002] Patent Document 1 discloses an electric assist device used for a wheelchair. This electric assist device includes a main body portion including a battery, an electric motor, and drive wheels, and a mounting bar. The electric motor drives the drive wheels. The mounting bar is a member for mounting the main body portion on the wheelchair body. The position of the main body portion mounted on the vehicle body via the mounting bar can be switched to either a standby position or a driving position. In the standby position, the drive wheels are in a state of being lifted from the road surface. In the driving position, the drive wheels are in a state of being grounded on the road surface. By driving the drive wheels in the driving position, the electric assist device assists the wheelchair in traveling.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A wheelchair equipped with the above conventional electric assist device travels with the main body portion fixed in the driving position. Therefore, impacts and vibrations from the road surface are directly transmitted to the main body portion via the drive wheels. Such impacts and vibrations may cause malfunctions of peripheral devices such as an electric motor mounted on the main body portion and devices for driving the drive wheels.

[0005] Therefore, it is conceivable to mount the main body portion so as to be vertically movable to buffer vibrations from the drive wheels. However, in this case, the drive wheels will be pressed against the road surface only by the weight of the vehicle itself, and sufficient contact pressure on the drive wheels may not be secured, potentially reducing traction and hindering stable driving. [Means for solving the problem]

[0006] (1) The electric vehicle according to this embodiment comprises a vehicle body having wheels, a bracket fixed to the vehicle body, an arm supported by the bracket so as to be able to swing up and down, a drive wheel provided at the tip of the arm, an actuator for driving the drive wheel, and an elastic member provided between the bracket and the arm for biasing the arm downward.

[0007] (7) Another embodiment, viewed from another perspective, is an electric assist device for a vehicle that is mounted on a vehicle. This electric assist device for a vehicle comprises a bracket fixed to the vehicle, an arm provided on the bracket so as to be able to swing up and down, a drive wheel provided at the tip of the arm, an actuator that drives the drive wheel, and an elastic member provided between the bracket and the arm that biases the arm downward. [Effects of the Invention]

[0008] According to this disclosure, it is possible to increase the contact pressure of the drive wheels while damping vibrations from the drive wheels. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a perspective view of an electric wheelchair according to an embodiment. [Figure 2] Figure 2 shows the main components of an electric wheelchair as viewed from the rear. [Figure 3] Figure 3 is an enlarged view of the main part of Figure 1. [Figure 4] Figure 4 is an enlarged perspective view showing the bracket and arm of the drive unit. [Figure 5] Figure 5 is a cross-sectional view of the bracket and arm. [Figure 6A] Figure 6A shows the relationship between the drive wheel and the main wheel when the arm body is in the lower swing position. [Figure 6B] Figure 6B shows the relationship between the drive wheels and the main wheels when the vehicle body is positioned on the road surface. [Figure 7A] Figure 7A shows the force acting on the arm when the brakes are applied to the drive wheels of an electric wheelchair, where the straight line passing through the pivot point of the arm and the rotation point of the drive wheel is not parallel to the road surface. [Figure 7B] Figure 7B shows the force acting on the arm when the brakes are applied to the drive wheels of the electric wheelchair of this embodiment while it is in motion. [Figure 8] Figure 8 shows a bracket for a drive unit according to another embodiment. [Modes for carrying out the invention]

[0010] First, the details of the embodiment will be listed and explained. [Summary of the Embodiment] (1) The electric vehicle according to this embodiment comprises a vehicle body having wheels, a bracket fixed to the vehicle body, an arm supported by the bracket so as to be able to swing up and down, a drive wheel provided at the tip of the arm, an actuator for driving the drive wheel, and an elastic member provided between the bracket and the arm for biasing the arm downward.

[0011] According to the above configuration, since there is an elastic member that biases the vertically swingable arm downward, the drive wheel can be pressed against the road surface while the wheel is in contact with the ground. As a result, vibrations from the drive wheel can be dampened while the contact pressure of the drive wheel on the road surface can be increased.

[0012] (2) Here, when the electric vehicle is traveling in the direction from the rotation center of the drive wheel to the swing center of the arm, if the drive wheel is braked, a force that pulls the tip of the arm in the direction opposite to the traveling direction may act on the tip of the arm by the drive wheel. When such a force pulled by the drive wheel acts on the arm, a force in the direction of rotating the arm upward may occur in the arm. When such a force occurs, it will reduce the ground contact pressure of the drive wheel and vertical vibration may occur in the drive wheel.

[0013] On the contrary, in this embodiment, it is configured such that a straight line passing through the swing center of the arm and the rotation center of the drive wheel when the wheel and the drive wheel are in contact with the road surface is parallel to the road surface. Thereby, even if a force pulled by the drive wheel acts on the arm, it is possible to suppress the generation of a force in the direction of rotating the arm upward. As a result, it is possible to suppress a decrease in the ground contact pressure of the drive wheel and vertical vibration generated in the drive wheel.

[0014] (3) Further, in the above electric vehicle, a low-friction member interposed between the bracket and the arm may be further provided. In this case, even if a simple configuration such as sandwiching the arm and the bracket with a fastening member such as a bolt and a nut is adopted, the frictional force between the arm and the bracket can be appropriately reduced, and the arm can be provided so as to be swingable with respect to the bracket. Further, by sandwiching the arm and the bracket while interposing a low-friction member, an appropriate frictional force can be imparted between the arm and the bracket, and even if a force in the direction of rotating the arm upward occurs, that force can be suppressed. Also, the vibration generated in the arm and the drive wheel can be suppressed by the frictional force between the arm and the bracket.

[0015] (4) In the above electric vehicle, the bracket has a support member including a support shaft that supports the arm swingably, and it is preferable that the low-friction member includes a low-friction washer provided on the outer peripheral side of the support shaft and interposed between the arm and the support member.

[0016] (5) Further, in the above electric vehicle, the arm has a protrusion protruding along the longitudinal direction of the arm on the base end portion side of the arm, and the bracket may have an upper wall portion provided above the protrusion and contacted by the protrusion due to the swing of the arm, and a lower wall portion provided below the protrusion and contacted by the protrusion due to the swing of the arm. In this case, the swing range of the protrusion can be restricted by the upper wall portion and the lower wall portion. Thereby, the swing range of the arm can be restricted. As a result, it is possible to suppress the arm from swinging beyond the necessary range.

[0017] (6) In the above electric vehicle, the vehicle body may include a wheelchair.

[0018] (7) Further, from another viewpoint, the present embodiment is an electric assist device for a vehicle mounted on a vehicle. This electric assist device for a vehicle includes a bracket fixed to the vehicle, an arm provided swingably in the vertical direction on the bracket, a drive wheel provided at the tip of the arm, an actuator that drives the drive wheel, and an elastic member provided between the bracket and the arm and biasing the arm downward.

[0019] According to the above configuration, since there is an elastic member that biases the arm downward, the bracket can be fixed to the vehicle body so that the drive wheel is pressed against the road surface in a state where the wheels of the vehicle are grounded. Thereby, the drive wheel is pressed against the road surface by the elastic member. As a result, it is possible to increase the ground contact pressure of the drive wheel while buffering the vibration from the drive wheel.

[0020] (8) In the above-described electric assist device for a vehicle, the bracket comprises a main body on which the arm is provided, and a fixing part for fixing the main body at a predetermined height position on the vehicle. Preferably, the predetermined height position is a position in which the straight line passing through the pivot center of the arm and the rotation center of the drive wheel of the vehicle to which the electric assist device for a vehicle is attached, when the wheel and the drive wheel of the vehicle are in contact with the road surface, is parallel to the road surface. In this case, it is possible to reduce the contact pressure on the drive wheels and suppress vertical vibrations that occur in the drive wheels.

[0021] (9) In the above-mentioned electric assist device for a vehicle, the bracket may include a main body portion on which the arm is provided, and a fixing portion that allows the height position of the main body portion in the vehicle to be adjusted. In this case, the height position of the main body can be adjusted so that when the wheels of the vehicle to which the vehicle electric assist device is attached, and the drive wheels, are in contact with the road surface, the straight line passing through the pivot center of the arm and the rotation center of the drive wheels is parallel to the road surface. As a result, the contact pressure on the drive wheels can be reduced, and vertical vibrations occurring in the drive wheels can be suppressed.

[0022] [Details of the embodiment] Preferred embodiments will be described below with reference to the drawings. [Regarding the overall structure] Figure 1 is a perspective view of an electric wheelchair according to an embodiment. Figure 2 is a diagram showing the main parts of the electric wheelchair as viewed from the rear. This electric wheelchair 1 has a function to drive the drive wheels of the electric wheelchair 1 when pushed from behind by the operator, thereby assisting the operator.

[0023] The electric wheelchair 1 is an electric vehicle equipped with a vehicle body 2 and an electric assist device 4 for the vehicle. The vehicle body 2 is a typical wheelchair, comprising a frame 2a mainly composed of metal pipes, a pair of main wheels 2b, and a pair of casters 2c. The frame 2a comprises a pair of rear tubes 2a1, a pair of front tubes 2a2, a pair of upper tubes 2a3, and a pair of lower tubes 2a4.

[0024] The pair of rear tubes 2a1 extend in the vertical direction. The pair of rear tubes 2a1 are arranged parallel to each other with a constant distance between them in the left-right direction. A pair of lower tubes 2a4 are connected to the lower ends of a pair of rear tubes 2a1. A pair of upper tubes 2a3 are connected to a pair of rear tubes 2a1. The portion of the pair of rear tubes 2a1 to which the pair of upper tubes 2a3 are connected is above the lower end. The pair of upper tubes 2a3 and the pair of lower tubes 2a4 extend in the front-to-back direction. The pair of upper tubes 2a3 and the pair of lower tubes 2a4 are arranged approximately parallel to each other with a constant distance between them in the left-to-right direction. The portion of the pair of lower tubes 2a4 behind the rear tube 2a1 is the tipping bar 2t. The tipping bar 2t is a component that is stepped on by the operator's foot. When the operator steps on the tipping bar 2t, the caster 2c is lifted upward with the main wheel 2b as the pivot point.

[0025] The pair of front tubes 2a2 extend vertically. The pair of front tubes 2a2 connects the ends of the pair of upper tubes 2a3 and the ends of the pair of lower tubes 2a4. Therefore, the pair of front tubes 2a2 is shorter than the pair of rear tubes 2a1.

[0026] A pair of casters 2c are mounted at the lower end of the front tube 2a2. A pair of main wheels 2b are mounted at the lower end of the rear tube 2a1. A pair of main wheels 2b are located behind a pair of casters 2c. The pair of main wheels 2b are the rear wheels. The pair of casters 2c are the front wheels. The vehicle body 2 further comprises a seat portion 2d on which the passenger sits and a backrest portion 2e. The seat portion 2d is fixed to a pair of upper tubes 2a3. The backrest portion 2e is fixed to a pair of rear tubes 2a1. The electric wheelchair 1 consists of a vehicle body 2 that can be used as a wheelchair, to which a vehicle-mounted electric assist device 4 is attached.

[0027] In the following explanation, the direction in which the passenger faces forward when they are seated in the electric wheelchair 1 (the direction in which the backrest 2e faces forward) is referred to as the forward direction, and the opposite direction is referred to as the rear direction. Therefore, the passenger will be seated facing forward in the electric wheelchair 1. Also, the direction to the left from the passenger's perspective is referred to as the left direction, and the direction to the right from the passenger's perspective is referred to as the right direction.

[0028] The vehicle electric assist device 4 includes a pair of drive units 8 and a pair of operating units 10. As shown in Figure 1, a pair of protrusions 2a5 are provided at the upper ends of the pair of rear tubes 2a1. The pair of protrusions 2a5 extend further rearward than the backrest portion 2e. The pair of operating parts 10 are provided on the pair of protruding parts 2a5. Therefore, the pair of operating parts 10 are positioned on the left and right upper sides of the backrest part 2e. Each of the pair of operating parts 10 has a grip 12. The grip 12 is movable in the front-rear direction relative to the protrusion 2a5. The operating unit 10 further includes a potentiometer (not shown). The potentiometer detects the displacement of the grip 12 in the front-rear direction. The operating unit 10 provides an output indicating the displacement of the grip 12 to the control device (described later).

[0029] The pair of drive units 8 are fixed to the left and right sides of the frame 2a. The pair of drive units 8 are positioned on the inward side of the pair of main wheels 2b. Each pair of drive units 8 comprises a drive wheel 14 and an actuator 16. The actuator 16 drives the drive wheel 14. The actuator 16 is an in-wheel motor and is located inside the drive wheel 14. The drive unit 8 will be described in detail later.

[0030] The vehicle electric assist device 4 further includes a control box (not shown) that houses a battery and control devices for controlling each part. The battery stores power supplied to the pair of drive units 8 (actuators 16) and other parts. The control device has the function of controlling a pair of actuators 16 based on the outputs provided by a pair of operating units 10. As described above, the outputs of the pair of operating units 10 indicate the amount of displacement of a pair of grips 12. The control device controls a pair of actuators 16 based on the displacement of the pair of grips 12 so that the relative position between the grips 12 and the frame 2a (vehicle body 2) is maintained. The control device can drive the drive wheels 14 using the actuator 16, thereby accelerating or maintaining the speed of the vehicle body 2. Furthermore, the control device can decelerate the vehicle body 2 by applying brakes to the drive wheels 14 using regenerative braking or short-circuit braking, etc., by having the actuator 16 perform these actions.

[0031] For example, when the operator pushes the grip 12 forward, the grip 12 is displaced forward. The control device moves the vehicle body 2 forward based on the output of the pair of operating units 10 to return the grip 12 to its original position. Conversely, when the operator pulls the grip 12 backward, the grip 12 is displaced backward. The control device moves the vehicle body 2 backward to return the grip 12 to its original position. In this way, the control device adjusts the amount of movement of the actuator 16 in response to the push and pull of the grip 12 by the operator. Through this, the control device controls the pair of actuators 16 so that the relative position between the grip 12 and the vehicle body 2 is maintained.

[0032] [Regarding the configuration of the drive unit] Figure 3 is an enlarged view of the main part of Figure 1. In Figure 3, the main wheel 2b on the right and the drive wheel 14 and actuator 16 on the left are omitted for ease of understanding. The drive unit 8 further comprises a bracket 18 and an arm 20. Bracket 18 is a plate-shaped component. Bracket 18 is fixed to the lower tube 2a4 and the rear tube 2a1. The arm 20 is supported by the bracket 18 so as to be able to swing up and down. The arm 20 has an arm body 21 and a projection 22 integrally provided on the arm body 21. A notch 21a1 is provided at the tip 21a of the arm body 21. The axle 14a extending from the drive wheel 14 is fixed to the notch 21a1. As a result, the drive wheel 14 and the actuator 16 are mounted on the tip portion 21a of the arm body 21. Therefore, when the arm body 21 swings vertically, the drive wheel 14 and actuator 16 move vertically.

[0033] The rotor (not shown) of the actuator 16 is capable of rotating integrally with the drive wheel 14. The stator (not shown) of the actuator 16 is fixed to the arm 20. As a result, the actuator 16 rotates the drive wheel 14.

[0034] Figure 4 is an enlarged perspective view showing the bracket 18 and arm 20 of the drive unit 8. Figure 4 shows the bracket 18 and arm 20 of the left drive unit 8. The left and right drive units 8 have the same configuration. Therefore, this section will describe the left drive unit 8.

[0035] The bracket 18 has a main body portion 24 and a fixing portion 26. An arm 20 is provided on the main body portion 24. The fixing part 26 is provided on the upper side of the main body part 24. The fixing part 26 fixes the main body part 24 at a predetermined height position on the vehicle body 2. The fixing portion 26 includes a front fixing portion 28 and a rear fixing portion 30. The front fixing portion 28 has a rectangular plate-shaped portion 28a connected to the main body portion 24 and a semi-cylindrical member 28b. One end of the semi-cylindrical member 28b is inserted into a slit 28c provided in the plate-shaped portion 28a and fixed to the plate-shaped portion 28a. The other end of the semi-cylindrical member 28b is fixed to the plate-shaped portion 28a by a bolt 28d. A lower tube 2a4 passes between the plate-shaped portion 28a and the semi-cylindrical member 28b (see Figure 3). The lower tube 2a4 is sandwiched between the plate-shaped portion 28a and the semi-cylindrical member 28b. As a result, the front fixing portion 28 is fixed to the lower tube 2a4.

[0036] The rear fixing portion 30 has a protruding portion 30a that protrudes inward from the edge of the main body portion 24, and a column portion 30b that extends upward from the tip of the protruding portion 30a. The upper surface of the protruding portion 30a is in contact with the lower tube 2a4 (see Figure 3). A notch 30b1 is provided at the tip of the column portion 30b. The threaded portion 3a protruding from the hub 3 of the main wheel 2b, which is fixed to the rear tube 2a1, is fixed to the notch 30b1 (see Figure 3). The column portion 30b is sandwiched between the hub 3 and the nut 3b that screws onto the threaded portion 3a. In this way, the rear fixing portion 30 is fixed to the rear tube 2a1. The fixing part 26 is fixed to the lower tube 2a4 and the rear tube 2a1. In this way, the fixing part 26 fixes the main body part 24 to the frame 2a.

[0037] As shown in Figure 4, the arm body 21 of the arm 20 provided on the main body 24 swings around the central axis C1. In other words, the central axis C1 is the pivot point of the arm body 21. Figure 5 is a cross-sectional view of the bracket 18 and the arm 20. Figure 5 shows a cross-section along the vertical direction including the central axis C1.

[0038] As shown in Figure 5, the bracket 18 further includes a support member 34. The support member 34 is a member that pivotably supports the arm 20. The support member 34 comprises a support shaft 36, a spacer 38, a washer 44, and a nut 42. The support member 34 is fixed to a support hole 24a provided in the main body 24. The support hole 24a is a hole centered on the central axis C1. The support shaft 36 has a shaft portion 36a, a head portion 36b, and a threaded portion 36c. The head portion 36b is provided at one end of the shaft portion 36a. The threaded portion 36c is provided at the other end of the shaft portion 36a. A nut 42 is screwed onto the threaded portion 36c.

[0039] The support member 34 is constructed by arranging the arm 20, a spacer 38, and a washer 44 on the outer circumference of the support shaft 36. Furthermore, a pair of low-friction washers 40 are incorporated into the support member 34. The pair of low-friction washers 40 are positioned on both sides of the arm 20. On the outer circumference of the support shaft 36, a washer 44, a low-friction washer 40, an arm 20, another low-friction washer 40, a spacer 38, and the main body 24 are arranged in order from the head 36b toward the threaded portion 36c.

[0040] The washer 44 is a component that prevents the individual components from falling off the support shaft 36. The spacer 38 is a cylindrical member. The shaft portion 36a is inserted into the inner circumference of the spacer 38. The spacer 38 is a member that ensures the distance between the main body portion 24 and the arm 20. A hole 21b1 is provided at the base end 21b of the arm body 21. The shaft portion 36a is inserted into the hole 21b1. A sliding bearing 46 is interposed between the hole 21b1 and the shaft portion 36a. The pair of low-friction washers 40 are washers with low coefficients of friction on both their surface and back. The low-friction washer 40 is interposed between the arm 20 and the spacer 38, and between the arm 20 and the washer 44. Examples of low-friction washers 40 include ordinary washers coated with a low-friction material such as fluororesin on both the front and back surfaces, or washers made of a low-friction material. Furthermore, spring washers and corrugated washers can also be used as low-friction washers 40. Spring washers and corrugated washers can moderately reduce the coefficient of friction by reducing the contact area between themselves and the member they are in contact with.

[0041] The washer 44, low-friction washer 40, arm 20, low-friction washer 40, spacer 38, and main body 24 are fastened between the head 36b and the nut 42. In other words, the arm 20, the main body 24, and other components are held together by the fastening members, the support shaft 36 and the nut 42.

[0042] Since the arm 20 is positioned between a pair of low-friction washers 40, the frictional force between the arm 20 and the support member 34 can be moderately reduced. In other words, even if a simple configuration is adopted, such as in this embodiment, in which the arm 20 and the main body 24 are clamped together by a fastening member, the frictional force between the arm 20 and the support member 34 can be reduced to a reasonable degree, and the arm 20 can be pivotably mounted relative to the support member 34 (bracket 18).

[0043] As shown in Figures 4 and 5, the projection 22 of the arm 20 is provided on the base end 21b side of the arm body 21. The projection 22 has a radial portion 50 and a longitudinal portion 52. The radial portion 50 protrudes from the side surface 21c of the arm body 21. The radial portion 50 extends along the radial direction perpendicular to the central axis C1. The radial portion 50 also extends from the base end 21b in a direction intersecting the longitudinal direction of the arm body 21. The longitudinal portion 52 extends from the side surface 50a of the radial portion 50. The longitudinal portion 52 extends in the direction opposite to the direction in which the arm body 21 extends. The longitudinal portion 52 extends approximately parallel to the longitudinal direction of the arm body 21.

[0044] As shown in Figure 4, the bracket 18 has a bent portion 54 that protrudes inward along the side edge of the main body portion 24. The bent portion 54 has a recess 55. The recess 55 is formed by cutting out the edge of the bent portion 54. The recess 55 has an upper wall portion 55a and a lower wall portion 55b. The upper wall portion 55a and the lower wall portion 55b face each other.

[0045] The longitudinal portion 52 is inserted into the recess 55. Therefore, the upper wall portion 55a is located above the longitudinal portion 52. The lower wall portion 55b is located below the longitudinal portion 52. Furthermore, the longitudinal portion 52 (projection 22) is provided integrally with the arm body 21. Therefore, the longitudinal portion 52 swings along with the swinging of the arm body 21. When the arm body 21 swings downward by a predetermined angle, the longitudinal portion 52 swings upward and comes into contact with the upper wall portion 55a. In this case, further upward swinging of the longitudinal portion 52 is restricted. Furthermore, when the arm body 21 swings upward by a predetermined angle, the longitudinal portion 52 swings downward and comes into contact with the lower wall portion 55b. In this case, further downward swinging of the longitudinal portion 52 is restricted.

[0046] Therefore, the swing range of the longitudinal portion 52 (projection 22) is limited by the upper wall portion 55a and the lower wall portion 55b. This limits the swing range of the arm 20 (arm body 21). As a result, it is possible to suppress the arm body 21 from swinging beyond the required range.

[0047] In other words, the range of motion of the arm body 21 is limited to the range from the position where the longitudinal portion 52 and the upper wall portion 55a of the arm body 21 come into contact with each other to the position where the longitudinal portion 52 and the lower wall portion 55b of the arm body 21 come into contact with each other. In the following explanation, the position of the arm body 21 where the longitudinal portion 52 and the upper wall portion 55a abut is referred to as the lower swing position, and the position of the arm body 21 where the longitudinal portion 52 and the lower wall portion 55b abut is referred to as the upper swing position.

[0048] As shown in Figure 4, the drive unit 8 further includes an elastic member 58. The elastic member 58 is provided between the bracket 18 and the arm 20. The elastic member 58 biases the arm 20 (arm body 21) downward. The elastic member 58 is, for example, a tension coil spring.

[0049] An L-shaped spring attachment portion 24b is provided at the rear end of the main body portion 24. Furthermore, a spring bolt 60 is provided on the radial portion 50 of the projection 22. The spring bolt 60 is inserted into the hole 50b of the radial portion 50 (see Figure 5). The spring bolt 60 tightens the radial portion 50 by screwing it into a nut 62. In this way, the spring bolt 60 is fixed to the radial portion 50.

[0050] One end of the elastic member 58 is hooked onto the spring attachment portion 24b. The other end of the elastic member 58 is hooked onto the groove portion 60a at the tip of the spring attachment bolt 60. With the longitudinal portion 52 in contact with the upper wall portion 55a, the elastic member 58 applies a tensile force between the spring attachment portion 24b and the spring attachment bolt 60. Therefore, when no force is acting to swing the arm body 21 upward, the position of the arm body 21 is the downward swing position. When the arm body 21 is in the lower swing position, the elastic member 58 applies a tensile force between the spring attachment portion 24b and the spring attachment bolt 60. Therefore, when the position of the arm body 21 is between the lower swing position and the upper swing position, the elastic member 58 biases the arm 20 (arm body 21) downward.

[0051] Figure 6A shows the relationship between the drive wheel 14 and the main wheel 2b when the arm body 21 is in the lower swing position. As shown in Figure 6A, when the main wheels 2b and drive wheels 14 of the vehicle body 2 are not in contact with the road surface R, no force from the road surface R acts on the arm body 21. Therefore, the position of the arm body 21 becomes the downward swinging position. When the arm body 21 is in the downward swing position, the lowest point of the drive wheel 14 is lower than the lowest point of the main wheel 2b.

[0052] Figure 6B shows the relationship between the drive wheels 14 and the main wheels 2b when the vehicle body 2 is positioned on the road surface R. In this case, the caster 2c, main wheel 2b, and drive wheel 14 are in contact with the road surface R. Therefore, the position of the arm body 21 is between the lower swing position and the upper swing position. At this time, the elastic member 58 biases the vertically swingable arm body 21 downwards, so that the drive wheel 14 is pressed against the road surface R by the tensile force of the elastic member 58. As a result, it is possible to increase the contact pressure of the drive wheel 14 while dampening the vibrations transmitted from the drive wheel 14 to the vehicle body 2.

[0053] Furthermore, in this embodiment, the straight line L is configured to be parallel to the road surface R when the caster 2c, main wheel 2b, and drive wheel 14 are in contact with the road surface R. The straight line L is a straight line that passes through the central axis C1, which is the pivot center of the arm body 21, and the rotation center C2 of the drive wheel 14.

[0054] In this embodiment, "the straight line L is parallel to the road surface R" includes not only the case where the straight line L is parallel to the road surface R, but also the case where the straight line L is approximately parallel to the road surface R. "The straight line L is parallel to the road surface R" means that the acute angle θ of the angle formed by the straight line along the road surface R and the straight line L is 0 degrees or more and 8 degrees or less. In this embodiment, the position of the arm body 21 where the straight line L is approximately parallel to the road surface R is included between the lower swing position and the upper swing position.

[0055] Here, we will explain the case where the brakes are applied to the drive wheels when an electric wheelchair, whose straight line L is not parallel to the road surface R, is moving forward. Figure 7A shows the force acting on the arm when the brakes are applied to the drive wheels 114 while an electric wheelchair, whose straight line L is not parallel to the road surface R, is in motion. Figure 7A shows the case where the electric wheelchair is moving in the direction from the rotation center C2 of the drive wheel 114 toward the central axis C1 of the arm 120 (forward movement). In this case, since the drive wheels 114 are braked (regenerative braking or short-circuit braking), a force F1 acts on the tip portion 120A of the arm 120, pulling it in the opposite direction to the direction of travel due to the drive wheels 114. At this time, since the straight line L is not parallel to the road surface R, a force F2 may be generated on the arm 120 in a direction that causes the arm 120 to rotate upward. When such a force F2 is applied to the arm 120, it reduces the contact pressure on the drive wheel 114, and can also cause vertical vibrations in the drive wheel 114.

[0056] Figure 7B shows the force acting on the arm when the brakes are applied to the drive wheels of the electric wheelchair of this embodiment while it is in motion. As shown in Figure 7B, when the straight line L is parallel to the road surface R, even if a force is applied to the arm 20 by the drive wheel 14, it is possible to suppress the generation of a force that rotates the arm 20 upward. As a result, the contact pressure of the drive wheel 14 can be reduced, and vertical vibrations occurring in the drive wheel can be suppressed.

[0057] Furthermore, in this embodiment, by clamping the arm 20 and the support member 34 (bracket 18) with a low-friction washer 40 in between, an appropriate frictional force can be applied between the arm 20 and the support member 34, and even if a force is generated in the direction that rotates the arm 20 upward, that force can be suppressed. In addition, the frictional force between the arm 20 and the support member 34 can suppress vibrations generated in the arm 20 and the drive wheel 14.

[0058] [Regarding other embodiments] Figure 8 shows the bracket 18 of the drive unit 8 according to another embodiment. This embodiment differs from the above embodiment in that the notch 30b1 provided in the column portion 30b is longer in the height direction, and the slit 28c and bolt holes 28b1 are arranged in multiple rows along the height direction.

[0059] The fixing portion 26 of this embodiment has the above configuration, which allows the height position of the main body portion 24 on the vehicle body 2 to be adjusted. Therefore, the height position of the main body 24 can be adjusted so that the straight line L is parallel to the road surface. As a result, the contact pressure of the drive wheels 14 can be reduced, and vertical vibrations occurring in the drive wheels 14 can be suppressed.

[0060] 〔others〕 The embodiments disclosed herein are illustrative in all respects and not restrictive. In the above embodiment, a case in which a tension coil spring is used as the elastic member 58 is illustrated, but instead of a tension coil spring, an annular rubber or the like may be used.

[0061] Furthermore, in the above embodiment, an example was given in which the position of the arm body 21 where the straight line L is substantially parallel to the road surface R is included between the lower swing position and the upper swing position. However, the lower swing position and the upper swing position may be included within the range of the position of the arm body 21 where the straight line L is substantially parallel to the road surface R. In this case, the range of motion of the arm body 21 can be limited to the range in which the straight line L is approximately parallel to the road surface R.

[0062] In the above embodiment, a vehicle body 2 having front and rear wheels (caster 2c and main wheel 2b) was illustrated, but the vehicle body 2 may also be configured to have at least one of the front and rear wheels. Furthermore, in the above embodiment, an example was given in which a vehicle body 2, which is a general wheelchair, is fitted with a vehicle electric assist device 4. However, the vehicle body 2 may be a trolley, wagon, or the like, in addition to a wheelchair. The scope of the present invention is not limited to the embodiments described above, and includes all modifications within the scope of equivalence to the configurations described in the claims. [Explanation of Symbols]

[0063] 2. Vehicle body 4. Electric assist devices for vehicles 14 drive wheels 16 Actuators 18 brackets 20 Arms 21a Tip 21b Proximal end 22 protrusions 24 Main body 26 Fixed part 34 Support Member 36 Support shaft 40 Low-friction washers (low-friction components) 55a Upper wall section 55b Lower wall part 58 Elastic members

Claims

1. A vehicle body having wheels, A bracket fixed to the vehicle body, An arm supported by the bracket so as to be able to swing vertically, A drive wheel provided at the tip of the aforementioned arm, An actuator that drives the aforementioned drive wheel, The system includes an elastic member provided between the bracket and the arm, which biases the arm downward, The arm has a projection that protrudes along the longitudinal direction of the arm from the base end side of the arm, The bracket has an upper wall portion provided above the projection and against which the projection abuts when the arm swings, and a lower wall portion provided below the projection and against which the projection abuts when the arm swings. Electric vehicle.

2. When the wheel and the drive wheel are in contact with the road surface, the straight line passing through the pivot point of the arm and the rotation point of the drive wheel is parallel to the road surface. The electric vehicle according to claim 1.

3. The bracket and the arm are further provided with a low-friction member interposed between them. The electric vehicle according to claim 2.

4. The bracket has a support member including a support shaft that pivotably supports the arm, The electric vehicle according to claim 3, wherein the low-friction member is provided on the outer circumference of the support shaft and includes a low-friction washer interposed between the arm and the support member.

5. The vehicle body includes a wheelchair. The electric vehicle according to claim 1.

6. An electric assist device for vehicles that is installed on a vehicle, A bracket fixed to the aforementioned vehicle, An arm is provided on the bracket so as to be able to swing vertically, A drive wheel provided at the tip of the aforementioned arm, An actuator that drives the aforementioned drive wheel, The system includes an elastic member provided between the bracket and the arm, which biases the arm downward, The arm has a projection that protrudes along the longitudinal direction of the arm from the base end side of the arm, The bracket has an upper wall portion provided above the projection and against which the projection abuts when the arm swings, and a lower wall portion provided below the projection and against which the projection abuts when the arm swings. Electric assist device for vehicles.

7. The aforementioned bracket is The main body portion on which the aforementioned arm is provided, The vehicle includes a fixing part for fixing the main body at a predetermined height position, The aforementioned predetermined height position is The position in which the straight line passing through the pivot point of the arm and the rotation point of the drive wheel of the vehicle, to which the vehicle electric assist device is attached, is parallel to the road surface when the wheel and the drive wheel of the vehicle are in contact with the road surface. The electric assist device for a vehicle according to claim 6.

8. The aforementioned bracket is The main body portion on which the aforementioned arm is provided, The vehicle comprises a fixing part that allows adjustment of the height position of the main body. The electric assist device for a vehicle according to claim 6.

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