Electric vehicle

Abstract

An electric wheel chair 1 comprises: a vehicle body 2a; casters 2c and main wheels 2b; a drive wheel 14c disposed between the casters 2c and the main wheels 2b; a pair of motors 15; a current detecting unit 36 that detects the motor current; a sensor 8 that detects an inclination angle of the vehicle body 2a; a first operating unit 10 that has a grip 20 which can move in the front-back direction of the vehicle body 2a, and a potentiometer 21 that detects the displacement amount of the grip 20 in the front-back direction; and a control device 18 that controls the pair of motors 15. The control device 18 comprises a processing unit 38 that executes: a first comparison process 38c for comparing the motor current and a current threshold Ith that is the motor current in a low-load state; a second comparison process 38d for comparing an inclination angle θ and an angle threshold θth; and a first switching process 38e for switching the control mode of the motors 15 from a normal mode to a stop mode on the basis of the comparison result of the first comparison process 38c and the comparison result of the second comparison process 38d.

Description

Electric vehicles

[0001] The present invention relates to an electric vehicle.

[0002] Patent Document 1 discloses an electric wheelchair. This electric wheelchair includes an operating force detection unit, a motor for propelling the vehicle, and a control circuit. The operating force detection unit includes a grip protruding from the rear of the vehicle and a potentiometer. When the grip is moved forward or backward from a neutral position by the operator's operation, the output of the potentiometer changes in accordance with the displacement. The output of the potentiometer is provided to a control circuit. The control circuit obtains the displacement of the grip based on the output of the potentiometer. When the grip is displaced forward by the operator's operation, the control circuit controls the motor to move the vehicle forward, and when the grip is displaced backward, the control circuit controls the motor to move the vehicle backward.

[0003] Japanese Patent Application Publication No. 10-336803

[0004] In recent years, as methods for providing care support to elderly people and others have diversified, it has become conceivable to attach a motor, drive wheels, control circuit, etc. to a manual wheelchair and use it as an electric wheelchair. For example, the present inventor has proposed an electric wheelchair configured by attaching a drive mechanism having a motor and drive wheels to a wheelchair without a motor (e.g., PCT / JP2021 / 040594). This electric wheelchair has a wheelchair unit with front and rear wheels, the drive mechanism, and an operating unit for operating the drive mechanism. The electric wheelchair moves by placing the drive wheels of the drive mechanism in contact with the road surface and powered by the motor. As with the conventional example described above, the operating unit of the electric wheelchair has a grip that can be moved in the forward and backward directions and a detection unit that detects the amount of forward and backward displacement of the grip. The motor of the drive mechanism is controlled according to the amount of displacement.

[0005] When a wheelchair goes over a step ahead of its direction of travel, the wheelchair needs to be operated by an operator pushing it from behind. For example, when a wheelchair goes up a step ahead of its direction of travel, the operator performs the following step-over operation. The operator pushes with their feet against the tipping bar attached to the lower rear of the wheelchair and pulls the grip. This causes the wheelchair to tilt upward at the front, and the front wheels are lifted upward with the rear wheels as the fulcrum. The operator then causes the lifted front wheels to go over the step. After that, the operator lifts the grip upward, which causes the rear wheels to go up with the front wheels as the fulcrum, and the rear wheels go over the step. In this way, the wheelchair goes over the step by operating the operator. The step-over operation performed by the operator is also called tipping.

[0006] When an electric wheelchair having the drive mechanism (drive wheels) and operating unit described above is operated to climb over a step, the operator pulls or lifts the grip to lift the front or rear wheels upward. At this time, the operator may unintentionally displace the grip in the forward or backward direction. Furthermore, when climbing over a step, the drive wheels may also be lifted along with the front or rear wheels, causing fluctuations in the load on the motor.

[0007] When going over a step, unintentional grip operation by the operator or fluctuations in motor load can cause unexpected motor output. Such unexpected motor output must be suppressed. The above problem is not limited to electric wheelchairs, but occurs in any electric vehicle that has drive wheels in addition to the front and rear wheels and that travels by detecting the operating force applied by the operator using a grip.

[0008] An electric vehicle according to an embodiment of the present disclosure includes a vehicle body, front and rear wheels provided on the vehicle body, drive wheels disposed between the front and rear wheels, a pair of motors for driving the drive wheels, a current detection unit for detecting a motor current flowing through the motor, a sensor for detecting a tilt angle in a longitudinal direction of the vehicle body, a grip movable in a longitudinal direction of the vehicle body, and a first operation unit having an operation detection unit for detecting a displacement of the grip in the longitudinal direction, and a control device for controlling the motor. The control device includes a processing unit that executes a first comparison process that compares the motor current with a current threshold that is a motor current in a low-load state, a second comparison process that compares the tilt angle with a predetermined angle threshold, and a first switching process that switches a control mode of the motor from a normal mode in which the motor is controlled in accordance with the displacement to a stop mode in which the motor is stopped, based on a comparison result of the first comparison process and a comparison result of the second comparison process.

[0009] According to the present disclosure, it is possible to suppress motor output that is unexpected by the operator when climbing over a step.

[0010] FIG. 1 is a perspective view of an electric wheelchair according to an embodiment. FIG. 2 is a view of a drive unit disposed on the right side of the vehicle body, as viewed from the center in the left-right direction of the vehicle body. FIG. 3 is an enlarged view of the vicinity of the upper end of the right support pipe. FIG. 4 is a cross-sectional view of a first operating unit. FIG. 5 is a block diagram showing an example of a configuration for controlling the operation of a motor in an electric wheelchair. FIG. 6 is a diagram showing a manner in which an operator operates the electric wheelchair. FIG. 7 is a block diagram showing an example of processing functions possessed by a processing unit of a control device. FIG. 8 is a flowchart showing an example of mode switching processing executed by the processing unit. FIG. 9 is a diagram showing an example of changes in the tilt angle of an electric wheelchair and changes in motor current over time when climbing over a step. FIG. 10 is a diagram showing the electric wheelchair in which the operator is operating step 1. FIG. 11 is a diagram showing an example of changes in the tilt angle of an electric wheelchair and changes in motor current over time when traveling uphill.

[0011] First, the details of the embodiments will be described. [Outline of the Embodiments] (1) An electric vehicle according to the embodiments includes a vehicle body, front and rear wheels provided on the vehicle body, drive wheels disposed between the front and rear wheels, a pair of motors for driving the drive wheels, a current detection unit for detecting a motor current flowing through the motor, a sensor for detecting a tilt angle in the longitudinal direction of the vehicle body, a grip movable in the longitudinal direction of the vehicle body, and a first operation unit having an operation detection unit for detecting a displacement of the grip in the longitudinal direction, and a control device for controlling the motor. The control device includes a processing unit that executes a first comparison process for comparing the motor current with a current threshold value that is a motor current in a low-load state, a second comparison process for comparing the tilt angle with a predetermined angle threshold value, and a first switching process for switching a control mode of the motor from a normal mode in which the motor is controlled in accordance with the displacement amount to a stop mode in which the motor is stopped, based on a comparison result of the first comparison process and a comparison result of the second comparison process.

[0012] In the above configuration, the drive wheels are disposed between the front and rear wheels. Therefore, when the operator of the electric vehicle grips the grip and performs a step-over maneuver with the electric vehicle, causing the vehicle body to tilt around the rear wheels as a fulcrum, the drive wheels lift and the motor enters a low-load state. Furthermore, with the above configuration, the second comparison process can determine whether the vehicle body is tilted to a certain degree in the fore-and-aft direction. Furthermore, in the first comparison process, the current threshold value compared with the motor current is the motor current in a low-load state, so it is possible to determine whether the motor is in a low-load state. In other words, it is possible to determine whether the operator is performing a step-over maneuver with the electric vehicle based on the comparison results of the first and second comparison processes. As a result, when the operator performs a step-over maneuver with the electric vehicle, the motor control mode can be switched from normal mode to stop mode, thereby suppressing unexpected motor output during step-over maneuvers.

[0013] (2) The current threshold value is preferably the motor current when the drive wheels are spinning freely. In this case, the current threshold value can be reliably set to the motor current in a low load state.

[0014] (3) In the electric vehicle, when the first comparison process obtains a comparison result that the motor current is equal to or less than the current threshold value and the second comparison process obtains a comparison result that the tilt angle is equal to or greater than the angle threshold value, it is preferable that the first switching process switches the motor control mode from the normal mode to the stop mode. This makes it possible to switch the motor control mode from the normal mode to the stop mode when an operator is performing an operation to travel over a step with the electric vehicle.

[0015] (4) In the above electric vehicle, if the first comparison process obtains a comparison result that the motor current is equal to or less than the current threshold value and the second comparison process obtains a comparison result that the tilt angle is equal to or greater than the angle threshold value for a predetermined period of time, it is preferable that the first switching process switches the control mode of the motor from the normal mode to the stop mode. In this case, if the motor current is momentarily equal to or less than the current threshold value even though a step-over-step operation is not being performed, switching to the stop mode can be suppressed, thereby improving the accuracy of determining whether a step-over-step operation is being performed.

[0016] (5) In the above electric vehicle, if the electric vehicle further includes a second operation unit that accepts an operation by an operator, the processing unit may further execute a second switching process to switch the motor control mode from the stop mode to the normal mode when the operation is accepted by the second operation unit and the processing unit determines that the tilt angle is smaller than the angle threshold. In this case, the motor control mode is switched from the stop mode to the normal mode by accepting an operation by the operator, thereby preventing the operator from unintentionally switching from the stop mode to the normal mode. As a result, the stop mode can be maintained until the step-over-step operation is completely completed.

[0017] (6) In the electric vehicle described above, when the grip is located at a predetermined reference position set within the movable range of the grip in the normal mode, the processing unit may control the motor to stop the vehicle body. Furthermore, when the processing unit determines that the grip is located at the reference position and the tilt angle is smaller than the angle threshold, the processing unit may execute a second switching process to switch the control mode of the motor from the stop mode to the normal mode. This also prevents the operator from unintentionally switching from the stop mode to the normal mode. As a result, the stop mode can be maintained until the step-over-step operation is completely completed.

[0018] (7) In the electric vehicle, the vehicle body, the front wheels, and the rear wheels may form a wheelchair.

[0019] [Details of the embodiment] A preferred embodiment will be described below with reference to the drawings. [Overall configuration] Figure 1 is a perspective view of an electric wheelchair according to an embodiment. This electric wheelchair 1 has a function of assisting the operator by driving the drive wheels of the electric wheelchair 1 when pushed from behind by the operator.

[0020] The electric wheelchair 1 comprises a wheelchair section 2, a drive mechanism 4, a control box 6, a pair of first operating units 10, and a second operating unit 12. The wheelchair section 2 is a typical wheelchair and comprises a vehicle body 2a mainly composed of a frame made of metal pipes or the like, a pair of main wheels 2b, and a pair of casters 2c. The pair of casters 2c are provided on both the left and right sides of the vehicle body 2a. The pair of main wheels 2b are also provided on both the left and right sides of the vehicle body 2a. The pair of main wheels 2b are provided behind the pair of casters 2c. Therefore, the pair of main wheels 2b are rear wheels. The pair of casters 2c are front wheels. The vehicle body 2a has a seat section 2a1 on which a passenger sits and a backrest section 2a2. The electric wheelchair 1 is configured by attaching the drive mechanism 4, the control box 6, the pair of first operating units 10, and the second operating unit 12 to the wheelchair section 2 that can be used as a wheelchair.

[0021] In the following description, the direction in which the rider faces when riding in the electric wheelchair 1 (the direction in which the backrest 2a2 faces forward) is referred to as the forward direction, and the opposite direction is referred to as the rearward direction. Therefore, the rider rides facing the front of the electric wheelchair 1. Also, the direction facing left from the rider's perspective is referred to as the leftward direction, and the direction facing right from the rider's perspective is referred to as the rightward direction.

[0022] The drive mechanism 4 includes a pair of drive units 14. The pair of drive units 14 are fixed to the left and right sides of the vehicle body 2a. The pair of drive units 14 are arranged on the vehicle inward side of the pair of main wheels 2b. Each of the pair of left and right drive units 14 includes a base plate 14a, an arm 14b, a drive wheel 14c, a motor 15, and a tipping bar 13.

[0023] Figure 2 is a view of the drive unit 14, which is located on the right side of the vehicle body 2a, as seen from the center in the left-right direction of the vehicle body 2a. Referring to Figures 1 and 2, the base plate 14a is fixed to the frame of the vehicle body 2a. This allows the drive unit 14 to be attached to the wheelchair section 2. The tipping bar 13 is provided at the rear end of the base plate 14a. The tipping bar 13 is a member that is stepped on by the foot of an operator operating the electric wheelchair 1 from behind to climb over a step. When the operator steps on the tipping bar 13, the caster 2c is lifted upward with the main wheel 2b as a fulcrum.

[0024] The arm 14b is provided on the vehicle interior side of the base plate 14a. The arm 14b is fixed to the base plate 14a so as to be swingable up and down. The arm 14b can swing within a predetermined angular range. A motor 15 and a drive wheel 14c are provided at the tip of the arm 14b. The arm 14b supports the drive wheel 14c so as to be able to rotate freely. The arm 14b elastically biases the drive wheel 14c downward. As a result, the arm 14b presses the drive wheel 14c against the road surface to bring it into contact with the road surface.

[0025] The motor 15 is an in-wheel motor and is provided inside the drive wheel 14c. A rotor (not shown) of the motor 15 can rotate integrally with the drive wheel 14c. A stator (not shown) of the motor 15 is fixed to the arm 14b. This allows the motor 15 to rotate and drive the drive wheel 14c. The motor 15 is connected to a battery, a control device, etc. in the control box 6 via a cable (not shown). The cable is inserted into the arm 14b and connects the motor 15 to the control box 6.

[0026] The drive wheels 14c are supported by the arms 14b so as to be rotatable about a rotation axis C1 (FIG. 2) parallel to the left-right direction. The drive wheels 14c are driven to rotate by the motors 15 while in contact with the road surface. The pair of left and right motors 15 drive the pair of left and right drive wheels 14c, causing the wheelchair section 2 (vehicle body 2a) to move.

[0027] As shown in Figure 2, the drive wheel 14c is disposed between the caster 2c and the main wheel 2b. More specifically, the position of the rotation axis C1 in the front-to-rear direction is between the rotation axis C2 of the caster 2c and the rotation axis C3 of the main wheel 2b. Therefore, the ground contact position t1 of the drive wheel 14c on the road surface R is located between the ground contact position t2 of the caster 2c and the ground contact position t3 of the main wheel 2b. The ground contact position t1 of the drive wheel 14c may be located in the range from the ground contact position t2 to the ground contact position t3. In other words, the position of the rotation axis C1 in the front-to-rear direction may be located in the range from the position of the rotation axis C2 to the position of the rotation axis C3.

[0028] As shown in FIG. 1 , the vehicle body 2a has a pair of left and right support pipes 2a3. The pair of support pipes 2a3 support the backrest 2a2. A pair of protrusions 2a4 is provided at the upper ends of the pair of support pipes 2a3. The pair of protrusions 2a4 protrude rearward from the backrest 2a2. The pair of protrusions 2a4 are pipes with openings at their rear ends. The second operating unit 12 is provided on the right protrusion 2a4.

[0029] 3 is an enlarged view of the vicinity of the upper end of the right support pipe 2a3. The second operating unit 12 has an operating switch 12a. The operating switch 12a is a switch for receiving operations by the operator. A pair of first operating units 10 are provided on the pair of protrusions 2a4. Therefore, the pair of first operating units 10 are disposed above the left and right sides of the backrest 2a2. The first operating units 10 have grips 20.

[0030] FIG. 4 is a cross-sectional view of the first operating unit 10. As shown in FIG. 4(a), the first operating unit 10 has a potentiometer 21 in addition to the grip 20. The grip 20 is attached to the tip of the protrusion 2a4 on the left side of the vehicle. The grip 20 has a tubular portion 20a and a bottom portion 20b. The bottom portion 20b closes the rear opening of the tubular portion 20a. The tubular portion 20a is attached to the outer periphery of the protrusion 2a4. The tubular portion 20a can move while sliding on the outer periphery of the protrusion 2a4. Therefore, the grip 20 can move along the axial direction of the protrusion 2a4. The protrusion 2a4 extends in the front-rear direction. Therefore, the grip 20 can move in the front-rear direction relative to the vehicle body 2a.

[0031] The potentiometer 21 is a sensor (operation detection unit) for detecting the amount of displacement of the grip 20 in the fore-and-aft direction. The potentiometer 21 is provided inside the protrusion 2a4. The potentiometer 21 includes a main body 21a and a rod 21b. The main body 21a is fixed to the protrusion 2a4. The rod 21b extends rearward from the main body 21a. The rod 21b passes through the inside of the tubular portion 20a and the protrusion 2a4. The rod 21b is movable axially relative to the main body 21a. The potentiometer 21 detects and outputs the amount of axial displacement of the rod 21b. A tip 21b1 of the rod 21b is fixed to the bottom 20b. Therefore, the rod 21b moves in the fore-and-aft direction integrally with the grip 20. This allows the potentiometer 21 to detect the amount of fore-and-aft displacement of the grip 20 relative to the vehicle body 2a. The potentiometer 21 is connected to a control device (to be described later) in the control box 6. The output of the potentiometer 21 is given to the control device.

[0032] In addition to the potentiometer 21, the protruding portion 2a4 is provided therein with a sleeve 22, a front bushing 23, a rear bushing 24, and a spring 25. The sleeve 22 is a cylindrical member that is inserted into and fixed to the inner circumferential surface of the protruding portion 2a4. The front bushing 23, the rear bushing 24, and the spring 25 are disposed on the inner circumferential side of the sleeve 22.

[0033] The front bushing 23 has a cylindrical portion 23a and a bottom portion 23b. The cylindrical portion 23a is inserted into and fixed to the inner circumferential surface 22a of the sleeve 22. The bottom portion 23b is provided at the front opening of the cylindrical portion 23a. The bottom portion 23b has a central hole 23b1. The rod 21b is inserted through the central hole 23b1. The rear bushing 24 has a cylindrical portion 24a and a bottom portion 24b. The cylindrical portion 24a is inserted into and fixed to the inner circumferential surface 22a of the sleeve 22. The bottom portion 24b is provided at the rear opening of the cylindrical portion 24a. The bottom portion 24b has a central hole 24b1. The rod 21b is inserted through the central hole 24b1.

[0034] The spring 25 is disposed between the front bushing 23 and the rear bushing 24. Thus, the rod 21b passes through the front bushing 23, the rear bushing 24, and the spring 25. A front retainer 26a, a front retaining ring 27a, a rear retainer 26b, and a rear retaining ring 27b are provided on the rod 21b. The front retaining ring 27a is provided on the front side of the spring 25. The front retaining ring 27a is fixed to the rod 21b. The front retaining ring 27a is fitted into a circumferential groove provided in the rod 21b. Thus, the front retaining ring 27a can move integrally with the rod 21b in the axial direction. The rear retaining ring 27b is provided on the rear side of the spring 25. The rear retaining ring 27b is also fixed to the rod 21b. The rear retaining ring 27b is fitted into a circumferential groove provided in the rod 21b. Thus, the rear retaining ring 27b can move integrally with the rod 21b in the axial direction. That is, the front retaining ring 27a and the rear retaining ring 27b are fixed to the rod 21b at a fixed distance in the axial direction.

[0035] The front retainer 26a, the rear retainer 26b, and the spring 25 are disposed between the front snap ring 27a and the rear snap ring 27b. The front retainer 26a and the rear retainer 26b are annular members that are passed through by the rod 21b. The front retainer 26a and the rear retainer 26b hold the front and rear end faces of the spring 25. The front retainer 26a is interposed between the front bushing 23 and the front end face of the spring 25. The rear retainer 26b is interposed between the rear bushing 24 and the rear end face of the spring 25.

[0036] 4A shows the case where the grip 20 is in the neutral position. The grip 20 is in the neutral position when it is not being held by the operator or when the operator is not inputting an operating force. When the grip 20 is in the neutral position, the spring 25 urges the front retainer 26a toward the front bushing 23. The spring 25 also urges the rear retainer 26b toward the rear bushing 24. At this time, the front retainer 26a abuts against the cylindrical portion 23a of the front bushing 23. The rear retainer 26b abuts against the cylindrical portion 24a of the rear bushing 24. In other words, when the grip 20 is in the neutral position, the distance between the front retainer 26a and the rear retainer 26b is shorter than the free length of the spring 25.

[0037] FIG. 4B shows the case where the grip 20 moves forward from the neutral position. When the grip 20 moves forward from the neutral position, the rod 21b also moves forward. This changes the output of the potentiometer 21. When the grip 20 and rod 21b move forward from the neutral position, the spring 25 is pressed forward by the rear retainer 26b and rear snap ring 27b. As a result, the rear retainer 26b moves away from the rear bushing 24. When the grip 20 moves further forward, the front snap ring 27a abuts against the bottom 23b of the front bushing 23, as shown in FIG. 4B. As a result, the front snap ring 27a and the front bushing 23 restrict the forward movement of the rod 21b.

[0038] FIG. 4C shows the case where the grip 20 has moved rearward from the neutral position. When the grip 20 moves rearward from the neutral position, the rod 21b also moves rearward. This changes the output of the potentiometer 21. When the grip 20 and rod 21b move rearward from the neutral position, the spring 25 is pressed rearward by the front retainer 26a and the front snap ring 27a. As a result, the front retainer 26a moves away from the front bushing 23. When the grip 20 moves further rearward, the rear snap ring 27b abuts against the bottom 24b of the rear bushing 24, as shown in FIG. 4C. As a result, the rear snap ring 27b and the rear bushing 24 restrict the rearward movement of the rod 21b.

[0039] With the above-described configuration, the grip 20 can be elastically moved in the front-to-rear direction around the neutral position by the spring 25. Furthermore, the range of movement of the grip 20 and the rod 21b in the front-to-rear direction is limited by the front bushing 23, the rear bushing 24, the front retaining ring 27a, and the rear retaining ring 27b.

[0040] 1 and 2, the control box 6 is fixed to the frame portion on the lower right side of the seat portion 2a1. The control box 6 houses a battery, a control device for controlling each part, and the like.

[0041] Fig. 5 is a block diagram showing an example of a configuration for controlling the operation of the motor in the electric wheelchair 1. As shown in Fig. 5, the electric wheelchair 1 further includes a sensor 8, a battery 16, and a control device 18. The sensor 8, the battery 16, and the control device 18 are housed in a control box 6.

[0042] The sensor 8 is fixed to the vehicle body 2a (inside the control box 6). The sensor 8 is, for example, an IMU (Inertial Measurement Unit). The sensor 8 in this embodiment includes at least a three-axis acceleration sensor. The sensor 8 is connected to the control device 18. The output of the sensor 8 is provided to the control device 18. The control device 18 determines the tilt angle of the vehicle body 2a in the longitudinal direction based on the output of the sensor 8. In other words, the sensor 8 functions as a sensor for detecting the tilt angle of the vehicle body 2a in the longitudinal direction.

[0043] The battery 16 supplies power to the pair of motors 15 and each component that requires operating power. The control device 18 controls the drive mechanism 4 (the pair of motors 15) by providing command values ​​to the drive mechanism 4, thereby controlling the speed of the vehicle body 2 a.

[0044] The drive mechanism 4, which includes a pair of motors 15, has a pair of drive circuits 34. Each of the pair of motors 15 includes a motor body 15a and a rotation detector 15b. The motor body 15a includes the main components of the motor, such as a rotor and a stator. The rotation detector 15b is, for example, a Hall sensor provided on the motor body 15a. The rotation detector 15b detects the rotation state of the rotor of the motor body 15a. The rotation detector 15b is connected to the drive circuit 34 and the control device 18. The output of the rotation detector 15b is provided to the drive circuit 34 and the control device 18.

[0045] The pair of drive circuits 34 are, for example, inverters. The pair of drive circuits 34 may be housed in the control box 6, or may be provided on the base plate 14a or the arm 14b. The pair of drive circuits 34 are connected to the control device 18, the battery 16, and the pair of motors 15. The pair of drive circuits 34 provide power from the battery 16 to the pair of motors 15. The pair of drive circuits 34 have the function of providing drive power to the pair of motors 15 based on a speed command value provided by the control device 18 and the output of the rotation detector 15b, and controlling the motors 15 to rotate at the speed indicated by the speed command value.

[0046] The pair of drive circuits 34 and the pair of motors 15 (motor bodies 15a) are connected by a pair of power lines 34a. A pair of current detectors 36 are provided on the pair of power lines 34a. The pair of current detectors 36 are current sensors that detect the current flowing through the pair of power lines 34a. In other words, the pair of current detectors 36 detect the motor current flowing through the pair of motors 15. The pair of current detectors 36 are connected to the control device 18. The outputs of the pair of current detectors 36 are provided to the control device 18.

[0047] The pair of first operating unit 10 and second operating unit 12 are also connected to the control device 18. As described above, the output of the first operating unit 10 (of the potentiometer 21) and the output of the second operating unit 12 are provided to the control device 18.

[0048] The control device 18 is configured by a computer or the like that includes a processing unit 38 consisting of a processor or the like, and a storage unit 40 consisting of a memory, a hard disk, or the like. The storage unit 40 stores computer programs and necessary information to be executed by the processing unit 38. The processing unit 38 executes computer programs stored in a computer-readable, non-transitory recording medium such as the storage unit 40, thereby realizing the various processing functions of the control device 18.

[0049] [Processing performed by the processing unit] Figure 6 is a diagram showing how an operator operates the electric wheelchair 1. An operator A of the electric wheelchair 1 holds the grips 20 of the pair of first operating units 10 with each hand and operates the electric wheelchair 1 by pushing the electric wheelchair 1 from behind. At this time, the pair of grips 20 move relatively in the front-to-rear direction with respect to the vehicle body 2a. The pair of first operating units 10 provide outputs corresponding to the movement of the pair of grips 20 to the control device 18. The control device 18 generates speed command values ​​based on the outputs provided by the pair of first operating units 10 and provides the speed command values ​​to the pair of drive circuits 34.

[0050] The output from the pair of first operating units 10 indicates the amount of longitudinal displacement of the pair of grips 20 relative to the vehicle body 2a. The control device 18 calculates the amount of longitudinal displacement of each of the pair of grips 20 based on the output from the pair of first operating units 10. Note that this amount of displacement is the distance between a reference position (e.g., a neutral position) preset within the movable range of the grips 20 and the current position of the grips 20. When the reference position and the current position coincide in the longitudinal direction, the amount of displacement is zero. The control device 18 discretely acquires the amount of displacement of the grips 20 over time and stores the information in the memory unit 40.

[0051] When the operator A grips and operates the first operating unit 10 and the second operating unit 12, the control device 18 controls the drive mechanism 4 so that the movement of the vehicle body 2a in response to the amount of displacement simulates mechanical impedance characteristics. That is, the control device 18 controls the drive mechanism 4 so that the distance H between the grip 20 and the vehicle body 2a is constant while reproducing a movement in which the grip 20 and the vehicle body 2a are connected by a virtual spring 42 and a virtual damper 44, as shown in FIG.

[0052] Controlling the drive mechanism 4 so that the distance H between the grip 20 and the vehicle body 2a remains constant includes controlling the amount of displacement to be zero or a predetermined set value. As a result, the control device 18 controls the drive mechanism 4 to move the vehicle body 2a forward according to the amount of displacement of the grip 20. For example, when the operator A moves forward and presses the grip 20 forward, the control device 18 controls the drive mechanism 4 to move the vehicle body 2a forward. Conversely, when the operator A moves backward and pulls the grip 20 rearward, the control device 18 controls the drive mechanism 4 to move the vehicle body 2a backward. Furthermore, when the position of the grip 20 is in the reference position (neutral position), the control device 18 controls the drive mechanism 4 to stop the vehicle body 2a.

[0053] FIG. 7 is a block diagram showing an example of processing functions of the processing unit 38 of the control device 18. The processing unit 38 has the functions of executing a motor control process 38a, a filter process 38b, a first comparison process 38c, a second comparison process 38d, a first switching process 38e, and a second switching process 38f. As described above, the motor control process 38a controls the drive mechanism 4 (the pair of motors 15) to move the vehicle body 2a in accordance with the displacement amount of the grip 20. The filter process 38b is a process performed on the output of the sensor 8. The processing unit 38 performs the filter process 38b on the output of the sensor 8 to obtain an estimated value of the tilt angle in the fore-and-aft direction of the vehicle body 2a. The processing unit 38 treats the obtained estimated value as the tilt angle. The filter process 38b is, for example, a Kalman filter process. The tilt angle obtained by the processing unit 38 is an angle with respect to the horizontal direction. The tilt angle θ is set to 0 degrees when the electric wheelchair 1 is located on a horizontal road surface. Therefore, the tilt angle θ indicates the tilt angle relative to the electric wheelchair 1 positioned on a horizontal road surface.

[0054] The first comparison process 38c is a process of comparing the motor current I flowing through the pair of motors 15 with a current threshold Ith. The motor current I is determined by the control device 18 based on the outputs of the pair of current detection units 36. The current threshold Ith is set to the motor current I when the pair of motors 15 are in a low-load state, such as when the drive wheels 14c are spinning. For example, the load from the road surface acting on the drive wheels 14c is gradually reduced, and the motor current I is measured until the drive wheels 14c start spinning. The motor current I at which it is clearly determined that the motors 15 are in a low-load state is set as the current threshold Ith. By using the current threshold Ith in the first comparison process 38c, the processing unit 38 can determine whether the pair of motors 15 are in a low-load state.

[0055] The second comparison process 38d is a process for comparing the tilt angle θ of the vehicle body 2a in the longitudinal direction with a predetermined angle threshold θth. As described above, the tilt angle θ is obtained by performing the filter process 38b on the output of the sensor 8. The angle threshold θth is set to a value at which it can be determined that the vehicle body 2a is tilted due to the operator's operation to climb over a step. More specifically, the tilt angle θ of the vehicle body 2a when the operator performs the operation to climb over the lowest step that is too high for the operator to push the electric wheelchair over is set to the angle threshold θth.

[0056] The first switching process 38e is a process for switching the control mode of the pair of motors 15 from the normal mode to the stop mode based on the comparison results of the first comparison process 38c and the comparison results of the second comparison process 38d. The normal mode is a mode for executing the motor control process 38a. In other words, the normal mode is a mode for controlling the pair of motors 15 so as to advance the vehicle body 2a in accordance with the amount of displacement of the grip 20. The stop mode is a mode for stopping the pair of motors 15. In the stop mode, the processing unit 38 controls the pair of motors 15 so that power is not supplied to them. Therefore, in the stop mode, the pair of motors 15 are stopped and do not output torque for driving the drive wheels 14c.

[0057] The second switching process 38f is a process for switching the control mode of the pair of motors 15 from the stop mode to the normal mode. The processing unit 38 executes the second switching process 38f when the second operating unit 12 accepts an operation by the operator and determines that the tilt angle θ is smaller than the angle threshold value θth.

[0058] As described above, the processing unit 38 of the control device 18 executes a switching process for switching the control mode of the pair of motors 15 between the normal mode and the stop mode.

[0059] [Regarding the Mode Switching Process] Figure 8 is a flowchart showing an example of the mode switching process executed by the processing unit 38. The processing unit 38 constantly executes the mode switching process. In the mode switching process, the processing unit 38 first sets the counter value C of a counter functionally included in the processing unit 38 to 0 (step S1 in Figure 8). Next, the processing unit 38 switches the control mode of the pair of motors 15 to the normal mode (step S2 in Figure 8). This causes the processing unit 38 to execute the motor control process 38a (Figure 7).

[0060] After switching the operating mode to the normal mode, the processing unit 38 proceeds to step S3 and executes a first comparison process 38c (FIG. 7). More specifically, the processing unit 38 compares the motor current I flowing through the pair of motors 15 with a current threshold Ith and determines whether the motor current I is equal to or less than the current threshold Ith (step S3 in FIG. 8). In step S3, if the processing unit 38 determines that the motor current I of at least one of the pair of motors 15 is equal to or less than the current threshold Ith, the processing unit 38 proceeds to step S4. In step S4, the processing unit 38 executes a second comparison process 38d (FIG. 7). More specifically, the processing unit 38 determines whether the tilt angle θ is equal to or greater than the angle threshold θth (step S4 in FIG. 8).

[0061] If it is determined in step S4 that the tilt angle θ is equal to or greater than the angle threshold θth, the processing unit 38 proceeds to step S5, where it determines whether the counter value C is greater than the threshold Cth (step S5 in FIG. 8). If it is determined in step S5 that the counter value C is greater than the threshold Cth, the processing unit 38 switches the control mode of the pair of motors 15 to the stop mode (step S6 in FIG. 8).

[0062] Here, the counter value C is a value that is counted up when the determination results of both steps S3 and S4 are positive. That is, the counter value C is a value that indicates the elapsed period during which the determination results of steps S3 and S4 are positive. The threshold value Cth is a value for determining whether the state during which the determination results of steps S3 and S4 are positive has continued for a predetermined period.

[0063] If it is determined in step S5 that the counter value C is not greater than the threshold value Cth (is equal to or less than the threshold value Cth), the processing unit 38 proceeds to step S8, increments the counter value C by 1, and returns to step S3. Therefore, if the determination results of steps S3 and S4 remain positive, the processing unit 38 repeats steps S3, S4, S5, and S8. If the determination results of steps S3 and S4 remain positive for a predetermined period determined by the threshold value Cth, the processing unit 38 proceeds to step S6, where it switches the control mode of the pair of motors 15 to the stop mode.

[0064] If the processing unit 38 determines in step S3 that the motor current I is not equal to or less than the current threshold value Ith (greater than the current threshold value Ith), the processing unit 38 proceeds to step S7, sets the counter value C to 0, and returns to step S3. If the processing unit 38 determines in step S4 that the tilt angle θ is not equal to or less than the angle threshold value θth (greater than the angle threshold value θth), the processing unit 38 proceeds to step S7, sets the counter value C to 0, and returns to step S3. Therefore, even if the determination results in steps S3 and S4 remain positive for a certain period of time, if at least one of the determination results in steps S3 and S4 becomes negative, the processing unit 38 sets the counter value C to 0 (step S7 in FIG. 8 ) and maintains the normal mode.

[0065] In this embodiment, if the comparison result in step S3 indicates that the current of the pair of motors 15 is equal to or less than the current threshold value Ith, and the comparison result in step S4 indicates that the tilt angle θ is equal to or greater than the angle threshold value θth, the processing unit 38 switches the control mode of the pair of motors 15 to the stop mode. That is, the processing unit 38 executes a first switching process 38e (FIG. 7) in step S6.

[0066] When the control mode of the pair of motors 15 is switched from the normal mode to the stop mode in step S6, the processing unit 38 proceeds to step S9, where it determines whether or not an operation by the operator has been accepted by the second operation unit 12 (step S9 in FIG. 8 ). If it is determined in step S9 that an operation by the operator has been accepted by the second operation unit 12, the processing unit 38 proceeds to step S10. In step S10, the processing unit 38 determines whether or not the tilt angle θ is smaller than the angle threshold value θth (step S10 in FIG. 8 ).

[0067] If it is determined in step S10 that the tilt angle θ is smaller than the angle threshold value θth, the processing unit 38 returns to step S1, sets the counter value C to 0 (step S1 in FIG. 8), and switches the control mode from the stop mode to the normal mode (step S2 in FIG. 8). In other words, if the processing unit 38 determines that the second operation unit 12 accepts an operation by the operator and that the tilt angle θ is smaller than the angle threshold value θth, the processing unit 38 executes the second switching process 38f (FIG. 7).

[0068] [Regarding Control Mode Switching During Step-Going Operation] FIG. 9 is a diagram showing an example of the change over time in the tilt angle θ of the electric wheelchair 1 and the change over time in the motor current I during step-going operation. The upper part of FIG. 9 shows the state of the electric wheelchair 1. The middle part of FIG. 9 shows the change over time in the tilt angle θ. The lower part of FIG. 9 shows the change over time in the motor current I. Although FIG. 9 shows the motor current I of one of the pair of motors 15, it is assumed here that the motor current I of both motors 15 is approximately the same. Note that with respect to the motor current I in the lower part, when the sign of the motor current I is positive, the pair of motors 15 rotates to move the vehicle body 2a forward, and when the sign of the motor current I is negative, the pair of motors 15 rotates to move the vehicle body 2a backward. In other words, the sign attached to the motor current I in FIG. 9 indicates the rotation direction of the motor 15. Therefore, in the following description, when the motor current I and the current threshold Ith are compared as values, the absolute value of the motor current I and the absolute value of the current threshold Ith are compared.

[0069] The step-climbing operation is an operation that the operator A performs on the electric wheelchair 1. Figure 9 shows the step-climbing operation in stages. The step-climbing operation includes four steps 1 to 4. In step 1, the operator A pushes down with his / her foot on the tipping bar 13 of the electric wheelchair 1, which is stopped on a level road surface, and pulls the grip 20 toward him / her. In step 2, the operator A continues the operation of step 1 and lifts the caster 2c upward, using the main wheel 2b as a fulcrum. In step 3, the operator A moves the lifted caster 2c onto the step D, and further lifts the grip 20 upward, thereby lifting the main wheel 2b upward. In step 4, the operator A moves the lifted main wheel 2b onto the step D. The step-climbing operation is performed on the electric wheelchair 1 through these four steps 1 to 4.

[0070] In FIG. 9 , before time T1, the electric wheelchair 1 is shown stopped on a level road surface. In this case, the tilt angle θ is 0 degrees. The motor current I is also 0. In FIG. 9 , step 1 is operated from time T1 to time T3. FIG. 10 shows the electric wheelchair 1 in which operator A is operating step 1. As shown in FIG. 10 , in step 1, operator A pulls the grip 20 toward himself (in the direction of the arrow). This causes the grip 20 to move backward. The control device 18 of the electric wheelchair 1 controls the drive mechanism 4 to move the vehicle body 2a backward in accordance with the amount of displacement of the grip 20. However, operator A is stepping on the tipping bar 13. This prevents the electric wheelchair 1 from moving backward. Therefore, the electric wheelchair 1 remains stopped without moving backward.

[0071] At this time, the caster 2c, main wheel 2b, and drive wheel 14c are in contact with the road surface R. As the drive wheel 14c is in contact with the road surface R, a load acts on the motor 15. Meanwhile, the control device 18 controls the drive mechanism 4 to move the vehicle body 2a backward. Therefore, in FIG. 9, the motor current I increases negatively between time T1 and time T3. The motor current I reaches the current threshold Ith (-Ith) at time T2, and then continues to increase negatively.

[0072] 9, the tilt angle θ is maintained at 0 degrees from time T1 to time T3. Therefore, the control device 18 maintains the control mode of the pair of motors 15 in the normal mode from time T1 to time T3 (steps S2 and S4 in FIG. 8).

[0073] In Figure 9, the operation of step 2 is performed between time T3 and time T6. In step 2, the operation of step 1 is continued, and the caster 2c is lifted upward with the main wheel 2b as the fulcrum. Therefore, the tilt angle θ gradually increases. The tilt angle θ reaches the angle threshold θth at time T4, and then exceeds the angle threshold θth.

[0074] Furthermore, the drive wheel 14c is disposed between the caster 2c and the main wheel 2b. Therefore, the drive wheel 14c is gradually lifted upward along with the caster 2c. The drive wheel 14c is elastically biased downward by the swingable arm 14b. Therefore, when the caster 2c is lifted upward, the drive wheel 14c follows the road surface within the swing range of the arm 14b, maintaining contact with the ground. When the caster 2c is lifted beyond the swing range of the arm 14b, the drive wheel 14c enters a spinning state. As the drive wheel 14c is gradually lifted upward, the load acting on the motor 15 gradually decreases. Therefore, in FIG. 9 , the motor current I gradually decreases (approaches zero) between times T3 and T6 while the control device 18 maintains control of the motor 15 (control to move the vehicle body 2a backward). The motor current I reaches the current threshold Ith (-Ith) at time T5 and then continues to decrease.

[0075] At time T5, the motor current I becomes equal to or less than the current threshold Ith, and the tilt angle θ becomes equal to or greater than the angle threshold θth. Therefore, the determination results of both steps S3 and S4 in Fig. 8 are affirmative. In Fig. 9, the determination results of both steps S3 and S4 in Fig. 8 are affirmative from time T5 to time T6.

[0076] Here, the period between time T5 and time T6 is assumed to be a predetermined period determined by the threshold value Cth (FIG. 8). In this case, when time T6 is reached, the control device 18 switches the control mode of the pair of motors 15 from the normal mode to the stop mode (steps S5 and S6 in FIG. 8). Therefore, no power is supplied to the pair of motors 15. Therefore, the motor current I becomes zero after time T6.

[0077] In Figure 9, the operation of step S3 is performed between time T6 and time T7. In step S3, caster 2c climbs onto step D, and then main wheel 2b is lifted upward. Therefore, the tilt angle θ is maintained at a high value until caster 2c climbs onto step D. Thereafter, as main wheel 2b is lifted upward, tilt angle θ decreases. At time T7, tilt angle θ becomes 0.

[0078] 9, the operation of step S4 is performed after time T7. In step S4, the raised main wheels 2b climb up onto the step D. Thus, the electric wheelchair 1 climbs over the step D, and the step climbing operation is completed.

[0079] In this embodiment, the drive wheels 14c are disposed between the casters 2c (front wheels) and the main wheels 2b (rear wheels). Therefore, when the operator A grips the grips 20 and performs a step-climbing maneuver with the electric wheelchair 1, causing the vehicle body 2a to tilt around the main wheels 2b, the drive wheels 14c are lifted, placing the pair of motors 15 in a low-load state. Furthermore, according to this embodiment, the second comparison process 38d ( FIG. 7 ) can determine whether the vehicle body 2a is tilted to a certain degree in the fore-and-aft direction. Furthermore, in the first comparison process 38c, the current threshold Ith compared with the motor current I is the motor current I in the low-load state, so it can be determined whether the pair of motors 15 are in a low-load state. In other words, the first comparison process 38c and the second comparison process 38d can determine whether the operator is performing a step-climbing maneuver with the electric wheelchair 1. As a result, when the operator operates the electric wheelchair 1 to climb over a step, the control mode of the pair of motors 15 can be configured to switch from normal mode to stop mode, thereby suppressing the motor output when climbing over a step.

[0080] This makes it possible to prevent the occurrence of unexpected motor output by operator A, even if the operator unintentionally operates the grip 20 or there is a fluctuation in the load on the motor 15 when climbing over a step.

[0081] In addition, in this embodiment, when the motor current I is equal to or less than the current threshold Ith and the tilt angle θ is equal to or greater than the angle threshold θth for a predetermined period of time, the control mode of the pair of motors 15 is switched from the normal mode to the stop mode. This makes it possible to suppress switching to the stop mode when the motor current I is equal to or less than the current threshold Ith momentarily and the motor current is equal to or less than the current threshold while no step-crossing operation is being performed, thereby improving the accuracy of determining whether or not a step-crossing operation is being performed.

[0082] Fig. 11 is a diagram showing an example of the change over time in the tilt angle θ of the electric wheelchair 1 and the change over time in the motor current I when the electric wheelchair 1 travels uphill. In Fig. 11, the electric wheelchair 1 starts moving forward and begins to climb the uphill road between time T11 and time T14. Therefore, the tilt angle θ increases between time T11 and time T14. The motor current I also gradually increases.

[0083] Here, suppose that at time T12, the tilt angle θ reaches the angle threshold θth, and then at time T13, the motor current I reaches the current threshold Ith. In this case, between time T12 and time T13, the motor current I is equal to or less than the current threshold Ith, and the tilt angle θ is equal to or greater than the angle threshold θth. However, the drive wheels 14c of the electric wheelchair 1 traveling uphill are not lifted upward. Therefore, the load acting on the motor 15 does not decrease. Therefore, the motor current I quickly increases and exceeds the current threshold Ith. Thus, even when the electric wheelchair 1 travels uphill, there is a risk that the motor current I may momentarily fall below the current threshold Ith, and the motor current may also fall below the current threshold Ith.

[0084] In this embodiment, even in this case, switching to the stop mode can be suppressed, thereby improving the accuracy of determining whether or not a step-over-step operation is being performed. Note that the predetermined period determined by the threshold value Cth is set to a period longer than the period during which the motor current I momentarily becomes equal to or less than the current threshold value Ith when the electric wheelchair 1 travels uphill.

[0085] Returning to FIG. 9 , after time T7, the electric wheelchair 1 stops in a horizontal position. At this time, the tilt angle θ is 0 degrees, which is smaller than the angle threshold θth. When the operator A operates the operation switch 12a of the second operation unit 12, the control device 18 determines that the operation of the second operation unit 12 by the operator A has been accepted (step S9 in FIG. 8 ), and also determines that the tilt angle θ is smaller than the angle threshold θth (step S10 in FIG. 8 ). Therefore, the control device 18 switches the control mode of the pair of motors 15 from the stop mode to the normal mode (step S2 in FIG. 8 ).

[0086] In this way, the control device 18 switches the control mode of the pair of motors 15 from the stop mode to the normal mode by accepting an operation by the operator A, thereby preventing the operator A from switching from the stop mode to the normal mode unintentionally. As a result, the stop mode can be maintained until the operation of climbing over the step is completely completed.

[0087] In this embodiment, when the tilt angle θ is smaller than the angle threshold θth, the control device 18 switches the control mode of the pair of motors 15 from the stop mode to the normal mode upon receiving an operation from the operator A via the second operating unit 12. However, instead of receiving an operation from the second operating unit 12, the control mode of the pair of motors 15 may be switched from the stop mode to the normal mode by the operator A releasing his / her hands from the grips 20 and returning the grips 20 to the reference position (neutral position). In this case, too, receiving an operation from the operator A can prevent the operator A from unintentionally switching from the stop mode to the normal mode. As a result, the stop mode can be maintained until the step-over-step operation is completely completed. Furthermore, since the grips 20 are moved to the reference position, the electric wheelchair 1 does not start traveling when the stop mode is switched to the normal mode.

[0088] [Others] The embodiments disclosed herein are illustrative in all respects and are not limiting. In the above embodiment, the control mode of the pair of motors 15 is switched from the normal mode to the stop mode when the motor current I is equal to or less than the current threshold Ith and the tilt angle θ is equal to or greater than the angle threshold θth for a predetermined period of time. However, the control mode of the pair of motors 15 may be switched from the normal mode to the stop mode without waiting for the predetermined period of time when the motor current I is determined to be equal to or less than the current threshold Ith and the tilt angle θ is determined to be equal to or greater than the angle threshold θth. Even in this case, it is possible to prevent the occurrence of motor output unexpected by the operator when climbing over a step.

[0089] In the above embodiment, the case of an electric wheelchair 1 is illustrated, but the present invention can also be applied to electric vehicles other than wheelchairs, such as carts and wagons, which are provided with an electric drive mechanism. The scope of the present invention is not limited to the above embodiment, and includes all modifications within the scope of equivalents to the configurations described in the claims.

[0090] DESCRIPTION OF SYMBOLS 1 Electric wheelchair 2 Wheelchair section 2a Vehicle body 2a1 Seat section 2a2 Backrest section 2a3 Support pipe 2a4 Protrusion section 2b Main wheel 2c Caster 4 Drive mechanism 6 Control box 8 Sensor 10 First operation section 12 Second operation section 12a Operation switch 13 Tipping bar 14 Drive unit 14a Base plate 14b Arm 14c Drive wheel 15 Motor 15a Motor body 15b Rotation detector 16 Battery 18 Control device 20 Grip 20a Cylindrical section 20b Bottom section 21 Potentiometer 21a Main body section 21b Rod 21b1 Tip section 22 Sleeve 22a Inner peripheral surface 23 Front bush 23a Cylindrical section 23b Bottom section 23b1 Center hole 24 Rear bushing 24a Cylindrical portion 24b Bottom portion 24b1 Central hole 25 Spring 26a Front retainer 26b Rear retainer 27a Front snap ring 27b Rear snap ring 34 Drive circuit 34a Power line 36 Current detection unit 38 Processing unit 38a Motor control processing 38b Filter processing 38c First comparison processing 38d Second comparison processing 38e First switching processing 38f Second switching processing 40 Memory unit 42 Spring 44 Damper A Operator C Counter value C1 Rotation axis C2 Rotation axis C3 Rotation axis Cth Threshold value D Step H Distance I Motor current Ith Current threshold value R Road surface θ Inclination angle θth Angle threshold value

Claims

1. A vehicle body, Front and rear wheels provided on the vehicle body; A drive wheel disposed between the front wheels and the rear wheels; A pair of motors for driving the drive wheels; a current detection unit that detects a motor current flowing through the motor; a sensor for detecting a tilt angle of the vehicle body in the front-rear direction; A first operation unit having a grip that is movable in a front-rear direction of the vehicle body and an operation detection unit that detects a displacement amount of the grip in the front-rear direction; an operation switch that accepts an operation of the electric vehicle by an operator; A control device for controlling the motor; Equipped with The control device includes: a first comparison process for comparing the motor current with a current threshold value that is a motor current in a low load state; a second comparison process for comparing the tilt angle with a predetermined angle threshold; a processing unit that executes a first switching process of switching a control mode of the motor from a normal mode in which the motor is controlled in accordance with the displacement amount to a stop mode in which the motor is stopped, based on a comparison result of the first comparison process and a comparison result of the second comparison process; When the processing unit determines that the operation is accepted by the operation switch and that the tilt angle is smaller than the angle threshold value, the processing unit further executes a second switching process of switching the control mode of the motor from the stop mode to the normal mode. Electric vehicle.

2. The current threshold is the motor current when the drive wheels spin. The electric vehicle according to claim 1 .

3. When a comparison result that the motor current is equal to or less than the current threshold value is obtained by the first comparison process and a comparison result that the tilt angle is equal to or more than the angle threshold value is obtained by the second comparison process, In the first switching process, the control mode of the motor is switched from the normal mode to the stop mode. The electric vehicle according to claim 1 or 2.

4. When a state in which the first comparison process obtains a comparison result that the motor current is equal to or less than the current threshold value and a state in which the second comparison process obtains a comparison result that the tilt angle is equal to or more than the angle threshold value continues for a predetermined period of time, In the first switching process, the control mode of the motor is switched from the normal mode to the stop mode. The electric vehicle according to claim 1 or 2.

5. (delete)

6. (delete)

7. The vehicle body, the front wheels, and the rear wheels constitute a wheelchair. The electric vehicle according to any one of claims 1 to 4.