Power-assisted vehicle

Abstract

To improve turning performance of a vehicle without using a differential gear.SOLUTION: A power-assisted vehicle (1) comprises: a first electric motor (11) that outputs torque for a first rear wheel; a second electric motor (21) that outputs torque for a second rear wheel; a sensing part (a steering sensor (32) or an inclination sensor (35)) for sensing a vehicle-turning value representing turning of the vehicle; and a control device that calculates target torque of the first electric motor (11) and target torque of the second electric motor (21), on the basis of reference assist torque calculated on the basis of tread force acting on pedals (6L and 6R) and a correction value corresponding to the vehicle-turning value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electrically assisted vehicle. [Background technology]

[0002] Patent Document 1 below discloses a three-wheeled electrically assisted vehicle. In this vehicle, an electric motor is disposed on each of the left and right rear wheels. A differential mechanism is disposed between the left and right rear wheels, and the torque of the crankshaft is transmitted to the left and right rear wheels via a chain and the differential mechanism. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-235679 A Summary of the Invention [Problem to be solved by the invention]

[0004] If the torque transmitted to the left and right rear wheels is always the same, it is difficult to achieve smooth turning. The electrically power-assisted vehicle disclosed in Patent Document 1 has a complex structure due to the inclusion of a differential mechanism, which is undesirable from the viewpoint of cost. [Means for solving the problem]

[0005] (1) The electrically assisted vehicle proposed in this disclosure may include front wheels, a steering wheel for steering the front wheels, a first rear wheel that is one of a right rear wheel and a left rear wheel, a second rear wheel that is the other of the right rear wheel and the left rear wheel, a crankshaft to which a pedal is attached, a torque transmission path for transmitting the torque of the crankshaft to at least one of the first rear wheel and the second rear wheel, a first electric motor that outputs torque for the first rear wheel, a second electric motor that outputs torque for the second rear wheel, a detection unit for detecting a vehicle turning value that represents the turning of the vehicle, and a control device that calculates a target torque of the first electric motor and a target torque of the second electric motor based on a reference assist torque calculated based on a pedal force acting on the pedal and a correction amount according to the vehicle turning value. This can improve the turning performance of the vehicle without using a differential mechanism.

[0006] (2) In the electrically assisted vehicle of (1), in a turn in which the first rear wheel becomes an inside wheel and the second rear wheel becomes an outside wheel, the control device may calculate a correction amount corresponding to the vehicle turning value so as to reduce a target torque of the first rear wheel. In a turn in which the first rear wheel becomes an outside wheel and the second rear wheel becomes an inside wheel, the control device may calculate a correction amount corresponding to the vehicle turning value so as to reduce a target torque of the second rear wheel.

[0007] (3) In the electrically assisted vehicle of (1) or (2), in a turn in which the first rear wheel becomes an inside wheel and the second rear wheel becomes an outside wheel, the control device may calculate a correction amount corresponding to the vehicle turning value so that a target torque of the second rear wheel increases. In a turn in which the first rear wheel becomes an outside wheel and the second rear wheel becomes an inside wheel, the control device may calculate a correction amount corresponding to the vehicle turning value so that a target torque of the first rear wheel increases.

[0008] (4) The electrically assisted vehicle of any one of (1) to (3) may have a torque transmission path that includes a reduction mechanism and transmits the torque of the crankshaft and the torque of the first electric motor to the first rear wheel via the reduction mechanism. The torque of the second electric motor may be transmitted to the second rear wheel without passing through the reduction mechanism.

[0009] (5) In the electrically assisted vehicle of (4), the control device may calculate a target torque of the second electric motor based on the standard assist torque, the correction amount corresponding to the vehicle turning value, and the reduction ratio of the reduction mechanism.

[0010] (6) In the electrically assisted vehicle of (4) or (5) above, the torque transmitted from the second electric motor to the second rear wheel may be greater than the torque transmitted from the first electric motor to the first rear wheel.

[0011] (7) In the electrically assisted vehicle of any one of (4) to (6) above, the control device may calculate a target torque of the second electric motor based on a torque of the crankshaft.

[0012] (8) In any one of the electrically assisted vehicles described above in (1) to (7), the vehicle turning value may be a roll angle of the vehicle.

[0013] (9) In any one of the electrically assisted vehicles (1) to (8) described above, the vehicle turning value may be a rotation angle of a steering shaft.

[0014] (10) In any one of the electrically assisted vehicles described in (1) to (9), the control device may correct the reference assist torque based on the vehicle turning value and the vehicle speed.

[0015] (11) In the electrically assisted vehicle of (10) above, the control device may calculate the correction amount so that the target torque decreases as the vehicle speed increases.

[0016] (12) In any of the electrically assisted vehicles of (1) to (11), the control device may include a first slip detection unit that detects slip of the first rear wheel and a second slip detection unit that detects slip of the second rear wheel, and may calculate a target torque for the first rear wheel and a target torque for the second rear wheel based on the slip detection result. [Brief description of the drawings]

[0017] [Figure 1] 1 is a side view showing an example of an electrically assisted vehicle proposed in the present disclosure. [Diagram 2] FIG. 2 is a plan view showing some of the components of the electrically assisted vehicle. [Diagram 3] FIG. 1 is a block diagram showing components of an electrically assisted bicycle. [Figure 4] FIG. 2 is a functional block diagram showing an example of functions of a control device. [Diagram 5] FIG. 4 is a diagram illustrating an example of a map stored in a storage device. [Figure 6A] FIG. 4 is a diagram illustrating an example of a map stored in a storage device. [Figure 6B] FIG. 4 is a diagram illustrating an example of a map stored in a storage device. [Figure 7] FIG. 4 is a diagram illustrating an example of a map stored in a storage device. [Figure 8A] FIG. 4 is a flow chart showing an example of a control process executed in the control process. [Figure 8B] FIG. 4 is a flow chart showing an example of a control process executed in the control process. [Figure 9] FIG. 11 is a functional block diagram showing another example of functions of the control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [1. Overall composition] An example of an embodiment of a steering control system for a two-wheeled vehicle proposed in this disclosure will be described below. Fig. 1 is a side view of an electrically assisted vehicle 1 which is an example of the embodiment. Fig. 2 is a plan view showing some of the components of the electrically assisted vehicle 1. In the following description, the electrically assisted vehicle 1 may also be simply referred to as a vehicle.

[0019] 1 and 2, the electrically power assisted vehicle 1 is, for example, a three-wheeled vehicle having a front wheel 2 and two rear wheels (more specifically, a left rear wheel 3L and a right rear wheel 3R). Without being limited to this, the electrically power assisted vehicle 1 may be a three-wheeled vehicle having two front wheels and one rear wheel. Furthermore, the electrically power assisted vehicle 1 may be a four-wheeled vehicle having two wheels on the front and two wheels on the rear, or a vehicle having four or more wheels.

[0020] As shown in Figs. 1 and 2, the electrically power assisted vehicle 1 has a steering handle 4 and a main frame 5 extending in the front-rear direction. The steering handle 4 has a steering shaft 4a extending in the up-down direction. The main frame 5 has a head pipe 5a at its front end. The steering shaft 4a is supported at the upper end of the head pipe 5a and can rotate in the circumferential direction of the steering shaft 4a relative to the head pipe 5a. In addition, a front fork 4b is attached to the lower end of the steering shaft 4a, and a front wheel 2 is attached to the front fork 4b. The front fork 4b can rotate in the circumferential direction of the steering shaft 4a in response to the rotation of the steering shaft 4a.

[0021] As shown in Fig. 1, the electrically assisted vehicle 1 has a seat tube 5b extending vertically behind a head pipe 5a. A saddle 9 is fixed to the upper end of the seat tube 5b. The electrically assisted vehicle 1 also has a crankshaft 6 supported by a main frame 5 (for example, the lower end of the seat tube 5b). Left and right pedals 6L and 6R are attached to the crankshaft 6. The shape of the main frame 5 is not limited to the example shown in Fig. 1, and may be modified as appropriate.

[0022] As shown in FIG. 1, the electrically assisted vehicle 1 may have a front basket 8F in front of the steering handle 4. The front basket 8F may be attached to the steering shaft 4a and the front fork 4b. The electrically assisted vehicle 1 may have a child seat instead of the front basket 8F. Also, as shown in FIG. 1, the electrically assisted vehicle 1 may have a rear basket 8B behind the saddle 9. As shown in FIG. 2, the rear basket 8B may be located between the left rear wheel 3L and the right rear wheel 3R. The rear basket 8B may be attached to a rear frame 15, which will be described later.

[0023] As shown in Fig. 2, the electrically power assisted vehicle 1 may have a rear frame 15 extending in the left-right direction behind the main frame 5 or at the rear end of the main frame 5. An axle 16 of the left rear wheel 3L may be fixed to the left end of the rear frame 15, and an axle 17 (see Fig. 1) of the right rear wheel 3R may be fixed to the left end of the rear frame 15. The left and right ends of the rear frame 15 can move in the roll direction of the electrically power assisted vehicle 1 (the circumferential direction centered on an axis along the front-rear direction of the vehicle body) relative to the main frame 5. This makes it possible to keep the main frame 5 in a vertical position when the left rear wheel 3L or the right rear wheel 3R goes up a step.

[0024] As shown in FIG. 2, the electrically assisted vehicle 1 has a first reduction gear mechanism 7. The first reduction gear mechanism 7 includes, for example, a ring-shaped chain 7a, and a front chain wheel 7b and a rear chain wheel 7c (see FIG. 2) engaged with the chain 7a. The front chain wheel 7b is fixed to the crankshaft 6 so as to rotate integrally with the crankshaft 6, and the rear chain wheel 7c is fixed to an axle 16 (see FIG. 2) of the left rear wheel 3L so as to rotate integrally with the axle 16. The front chain wheel 7b and the rear chain wheel 7c may include a sprocket that meshes with the chain 7a, and a one-way clutch that transmits only the torque for rotating the left rear wheel 3L forward to downstream components (for example, the chain 7a or the axle 16).

[0025] As shown in Fig. 2, the electrically power assisted vehicle 1 has a first electric motor 11 that outputs torque to assist the driving of the left rear wheel 3L, a first battery 12, and a second reduction mechanism 13. The second reduction mechanism 13 includes, for example, a first gear 13a attached to the output shaft of the first electric motor 11 and a second gear 13b attached to the crankshaft 6. The second gear 13b may include a one-way clutch that transmits only the torque for rotating the crankshaft 6 forward to the crankshaft 6. In addition, the positions of the first electric motor 11 and the first battery 12 are not limited to the examples shown in Figs. 1 and 2, and may be changed as appropriate.

[0026] Fig. 3 is a block diagram showing components of the electrically assisted vehicle 1. In Fig. 3, thick solid lines represent the transmission of power, and thin solid lines represent signals and currents. As shown in Fig. 3, the electrically assisted vehicle 1 may have a torque sensor 31, a steering sensor 32, a vehicle speed sensor 33, a left rear wheel sensor 34L, a right rear wheel sensor 34R, and an inclination sensor 35 in addition to the first electric motor 11 and the first battery 12 shown in Fig. 2.

[0027] The torque sensor 31 is a sensor for detecting the pedaling force applied by the rider to the pedals 6L, 6R. The torque sensor 31 outputs a signal corresponding to the torque (hereinafter also referred to as pedaling torque) generated in the crankshaft 6, for example. The torque sensor 31 may be a magnetostrictive sensor provided on the crankshaft 6, or may be another type of sensor.

[0028] The steering sensor 32 is a sensor that detects the rotation angle (the rotation angle in the circumferential direction of the steering shaft 4a) of the steering handle 4 (see FIG. 1). In the example shown in FIG. 1, the steering sensor 32 is fixed to a support base 32c attached to the main frame 5, and is disposed behind the steering shaft 4a.

[0029] As shown in FIG. 1, a first gear 32a may be fixed to the steering shaft 4a. The steering sensor 32 may have a detection shaft extending in the same direction as the steering shaft 4a (the vertical direction in FIG. 2), and a second gear 32b may be fixed to this detection shaft. The first and second gears 32a, 32b may be aligned in the front-rear direction, and the teeth of these gears 32a, 32b may directly mesh with each other. When the steering shaft 4a rotates, the detection shaft of the steering sensor 32 rotates at an angle according to the gear ratio of the gears 32a, 32b. This allows the steering sensor 32 to detect the rotation angle of the steering shaft 4a in the circumferential direction. That is, the steering sensor 32 can detect the rotation angle of the steering handle 4.

[0030] The vehicle speed sensor 33 detects the speed (vehicle speed) in the traveling direction (for example, forward) of the electrically assisted vehicle 1. The vehicle speed sensor 33 may be a magnetic rotation sensor. The vehicle speed sensor 33 outputs a pulse signal, for example, when a magnet attached to a part of the outer periphery of the front wheel 2 reaches the sensor body.

[0031] When the vehicle speed sensor 33 is a magnetic rotation sensor attached to a wheel, the wheel sensor 33 is preferably provided on a wheel (a driven wheel) on which the torque from the electric motor does not act. In this embodiment, the vehicle speed sensor 33 is attached to the front wheel 2.

[0032] The left rear wheel sensor 34L detects the rotation speed of the left rear wheel 3L. The right rear wheel sensor 34R detects the rotation speed of the right rear wheel 3R. The left rear wheel sensor 34L and the right rear wheel sensor 34R may be magnetic rotation sensors, similar to the vehicle speed sensor 33. The left rear wheel sensor 34L may output a pulse signal, for example, when a magnet attached to the left rear wheel 3L reaches the sensor body. The right rear wheel sensor 34R outputs a pulse signal, for example, when a magnet attached to the right rear wheel 3R reaches the sensor body.

[0033] The tilt sensor 35 detects the roll angle of the body of the electrically assisted vehicle 1. The roll angle of the body is an angle in the circumferential direction centered on an axis along the front-rear direction of the body, and is the tilt angle of the body to the left or right. The tilt sensor 35 may be, for example, an inertial measurement unit (IMU) attached to the main frame 5 or the like.

[0034] The control device 100 includes a calculation device such as a CPU (Central Processing Unit) and a storage device 100M that stores programs and maps for executing calculation processing in the calculation device. The storage device 100M may be a storage medium such as a RAM (Random Access Memory) or a ROM (Read Only Memory).

[0035] The first battery 12 supplies power to the first electric motor drive device 14. The first battery 12 may supply power to a device or component (for example, the control device 100) different from the first electric motor drive device 14. When the driver pedals the pedals 6L, 6R, the control device 100 calculates a reference torque (hereinafter also referred to as a reference assist torque) based on, for example, the vehicle speed of the electrically power assisted vehicle 1 and the pedaling force detected based on the output of the torque sensor 31. Then, the control device 100 calculates a first target torque, which is a target value of the torque output by the first electric motor 11, based on this reference assist torque, and outputs a command value corresponding to this first target torque to the first electric motor drive device 14. The first electric motor drive device 14 receives power from the first battery 12 and supplies power corresponding to the first target torque determined by the control device 100 to the first electric motor 11.

[0036] As shown in FIG. 3, the electrically assisted vehicle 1 has a first torque transmission path 41. The first torque transmission path 41 transmits the torque (pedaling torque) of the crankshaft 6 generated by the rider stepping on the pedals 6L, 6R and the torque output by the first electric motor 11 to the left rear wheel 3L (an example of the first rear wheel). The first torque transmission path 41 has the first reduction gear mechanism 7 (more specifically, the front chain wheel 7b, the chain 7a, and the rear chain wheel 7c) and the axle 16 to which the left rear wheel 3L is attached as a transmission path for transmitting the pedaling torque to the left rear wheel 3L. The front chain wheel 7b, the chain 7a, the rear chain wheel 7c, and the axle 16 are arranged in this order from the upstream of the transmission path. The first electric motor 11 and the crankshaft 6 are arranged upstream of the first reduction gear mechanism 7.

[0037] As shown in FIG. 3, the first torque transmission path 41 has the second reduction gear mechanism 13 (first gear 13a and second gear 13b) in addition to the first reduction gear mechanism 7 and the axle 16 as a transmission path for transmitting the torque of the first electric motor 11 to the left rear wheel 3L. Both the pedaling torque and the torque of the first electric motor 11 are transmitted to the left rear wheel 3L by the first torque transmission path 41. This makes it possible to reduce the pedaling force on the pedals 6L and 6R required for the driver to obtain the vehicle speed of the electrically assisted vehicle 1 desired by the driver. The second reduction gear mechanism 13 is disposed between the first electric motor 11 and the crankshaft 6. The second reduction gear mechanism 13 is disposed upstream of the crankshaft 6, and the first electric motor 11 is disposed upstream of the second reduction gear mechanism 13.

[0038] As shown in FIG. 2, the electrically power-assisted vehicle 1 has a second electric motor 21 that outputs torque for rotating the right rear wheel 3R forward, a second battery 22, and a second electric motor drive device 23. The second battery 22 supplies power to the second electric motor drive device 23. The second battery 22 may supply power to a device or component other than the second electric motor drive device 23. When the driver pedals the pedals 6L, 6R, the control device 100 calculates a second target torque, which is a target value of the torque output by the second electric motor 21, as described later, and outputs a command value corresponding to this second target torque to the second electric motor drive device 23. The second electric motor drive device 23 receives power from the second battery 22 and supplies power corresponding to the second target torque calculated by the control device 100 to the second electric motor 21.

[0039] In the example shown in FIG. 2, the second battery 22 and the second electric motor drive device 23 are disposed rearward of the first battery 12. The second battery 22 and the second electric motor drive device 23 may be disposed rearward of the crankshaft 6. In addition, in the example shown in FIG. 2, the second battery 22 and the second electric motor drive device 23 are disposed between the left rear wheel 3L and the right rear wheel 3R. The second battery 22 and the second electric motor drive device 23 may be disposed below the rear basket 8B. The second battery 22 and the second electric motor drive device 23 may be supported by the rear frame 15.

[0040] The second electric motor drive device 23 may be built into the motor housing that accommodates the second electric motor 21. In this way, the number of wires in the electrically assisted vehicle 1 can be reduced. As will be described later, in the example shown in FIG. 2, the second electric motor 21 is accommodated in the right rear wheel 3R, and the right rear wheel 3R functions as a motor housing. The second electric motor drive device 23 may be accommodated in the right rear wheel 3R together with the second electric motor 21.

[0041] As yet another example, the power to the second electric motor 21 and the second electric motor drive device 23 may be supplied by the first battery 12, instead of the second battery 22. In this case, the power-assisted vehicle 1 does not need to have the second battery 22.

[0042] As shown in Fig. 3, the electrically power assisted vehicle 1 has a second torque transmission path 42 that transmits the torque output by the second electric motor 21 to the right rear wheel 3R (an example of the second rear wheel). The electrically power assisted vehicle 1 can transmit the pedaling torque applied to the pedals 6L, 6R by the driver and the torque output by the first electric motor 11 to one of the rear wheels, the left rear wheel 3L, via the first torque transmission path 41, and can transmit the torque output by the second electric motor 21 to the other rear wheel, the right rear wheel 3R, via the second torque transmission path 42. This makes it possible to drive both the left rear wheel 3L and the right rear wheel 3R, thereby improving the straight-line running performance of the electrically power assisted vehicle 1.

[0043] The torque of the second electric motor 21 may be transmitted to the right rear wheel 3R without passing through the first reduction gear mechanism 7 and the second reduction gear mechanism 13 included in the first torque transmission path 41. As shown in FIG. 2, the second electric motor 21 may be disposed on the right rear wheel 3R. The second electric motor 21 may be an in-wheel motor built into the right rear wheel 3R. In this manner, the structure of the electrically assisted vehicle 1 can be simplified. The second electric motor 21 may have a stator 21a having an iron core and a coil, which is located on the inner periphery of the right rear wheel 3R and fixed to the axle 17 (see FIG. 1) of the right rear wheel 3R, and a rotor 21b which is a magnet or a magnetic body, which is located on the outer periphery of the right rear wheel 3R and rotates in the circumferential direction of the axle 17 of the right rear wheel 3R.

[0044] [2. Functions of the control device] FIG. 4 is a functional block diagram showing an example of functions of the control device 100. As shown in FIG. 4, the control device 100 may have, as functions, a reference assist torque calculation section 110, a first target torque calculation section 120, a correction amount calculation section 130, a slip detection section 140, a rear wheel assist torque calculation section 150, a rear wheel pedaling torque calculation section 160, and a second target torque calculation section 170. The correction amount calculation section 130 may have a first correction amount calculation section 131 and a second correction amount calculation section 132. The slip detection section 140 may have a first slip detection section 141 and a second slip detection section 142. These functions may be realized by the control device 100 executing a program stored in the storage device 100M (see FIG. 3). In addition, the control device 100 may have functions different from the functions shown in FIG. 4, or may not have all of the functions shown in FIG. 4.

[0045] [2-1. Function to calculate target torque of first electric motor] First, there will be described a function for calculating a first target torque, which is a target value of the torque output by the first electric motor 11. This function may be realized by a reference assist torque calculation unit 110, a first target torque calculation unit 120, a correction amount calculation unit 130 (a first correction amount calculation unit 131), and a slip detection unit 140 (a first slip detection unit 141 and a second slip detection unit 142).

[0046] The reference assist torque calculation unit 110 calculates the reference assist torque based on the pedaling force acting on the pedals 6L and 6R. The reference assist torque calculation unit 110 calculates the reference assist torque based on the pedaling torque detected by the torque sensor 31 (see FIG. 3) and the vehicle speed detected by the vehicle speed sensor 33 (see FIG. 3). For example, the reference assist torque calculation unit 110 calculates an assist ratio, which is the ratio of the reference assist torque to the pedaling torque, based on the vehicle speed detected by the vehicle speed sensor 33, and calculates the reference assist torque by multiplying the pedaling torque detected by the torque sensor 31 by this assist ratio. Here, the reference assist torque calculation unit 110 may calculate the reference assist torque based on a map stored in the storage device 100M. Alternatively, the reference assist torque calculation unit 110 may calculate the reference assist torque based on a predetermined calculation formula.

[0047] FIG. 5 is a diagram showing an example of a map stored in the storage device 100M. The map shown in FIG. 5 shows the relationship between the vehicle speed and the assist ratio. In the map shown in FIG. 5, when the vehicle speed is in the low speed range (for example, when the vehicle speed is 10 km / h or less), the assist ratio is the largest value (for example, 2). When the vehicle speed is in the medium speed range (when the vehicle speed exceeds 10 km / h), the assist ratio decreases as the vehicle speed increases. When the vehicle speed is in the high speed range (for example, when the vehicle speed is 24 km / h or more), the assist ratio becomes the smallest (for example, 0). This makes it possible to increase the reference assist torque when the vehicle speed is in the low speed range, and to decrease the reference assist torque when the vehicle speed is in the high speed range.

[0048] The first target torque calculation unit 120 calculates a first target torque, which is a target torque for the first electric motor 11, based on a reference assist torque calculated based on a pedaling torque representing the pedaling force acting on the pedals 6L and 6R, and a correction amount according to a vehicle turning value representing the turning of the vehicle. Here, the vehicle turning value may be the rotation angle of the steering wheel 4 detected by the steering sensor 32 (see FIG. 3) or may be the roll angle of the vehicle body detected by the tilt sensor 35 (see FIG. 3).

[0049] 4, the first target torque calculation unit 120 calculates the first target torque based on the reference assist torque calculated by the reference assist torque calculation unit 110 and a correction amount calculated by a first correction amount calculation unit 131 described later. The first target torque calculation unit 120 calculates the first target torque, for example, by multiplying the reference assist torque by the correction amount calculated by the first correction amount calculation unit 131. In this case, the correction amount may be a value greater than 0.

[0050] The first correction amount calculation unit 131 calculates a correction amount for the reference assist torque (a correction amount for calculating a first target torque) based on, for example, a roll angle of the vehicle body, which is a vehicle turning value, or a rotation angle of the steering wheel 4. The first correction amount calculation unit 131 may calculate the correction amount for the reference assist torque based on a map stored in the storage device 100M. In addition, the first correction amount calculation unit 131 may calculate the correction amount for the reference assist torque based on a predetermined calculation formula.

[0051] 6A is a diagram showing an example of a map stored in the storage device 100M. In the map shown in FIG. 6A, the vertical axis indicates the correction amount, and the horizontal axis indicates the vehicle turning value. A positive value on the horizontal axis indicates the turning of the vehicle to the right, and a negative value on the horizontal axis indicates the turning of the vehicle to the left rear. The first correction amount calculation unit 131 may refer to the map shown in FIG. 6A and calculate a correction amount according to the vehicle turning value (for example, the rotation angle of the steering wheel 4 detected by the steering sensor 32, or the roll angle of the vehicle body detected by the inclination sensor 35).

[0052] The map shown in FIG. 6A is designed so that the correction amount is small when the vehicle turning value is smaller than 0. Therefore, when the steering wheel 4 is turned leftward and the vehicle is turning leftward, the correction amount calculated by the first correction amount calculation unit 131 is small. When the vehicle is turning with the left rear wheel 3L as the inside wheel and the right rear wheel 3R as the outside wheel, the first correction amount calculation unit 131 calculates a correction amount according to the vehicle turning value so that the target torque (first target torque) of the first electric motor 11 that outputs torque to the left rear wheel 3L is reduced. Under the condition that the pedaling torque and the vehicle speed are constant, the first correction amount calculation unit 131 calculates the correction amount so that the first target torque during left turning is smaller than the first target torque during straight driving. In this way, the rotation speed of the left rear wheel 3L can be reduced relative to the rotation speed of the right rear wheel 3R, and the vehicle can be turned leftward smoothly.

[0053] 6A is designed so that the correction amount decreases as the vehicle turning value decreases within a range where the vehicle turning value is smaller than 0 (in the example of FIG. 6A, within a range of -Xb or more and -Xa or less). Therefore, the first correction amount calculation unit 131 calculates the correction amount so that the first target torque decreases as the vehicle turning value increases in the negative direction (as the turning radius of the left rear wheel 3L relative to the turning radius of the right rear wheel 3R decreases). In this way, when the steering wheel 4 is turned significantly to the left, the rotation speed of the left rear wheel 3L can be significantly reduced relative to the rotation speed of the right rear wheel 3R, making it possible to smoothly turn the vehicle to the left.

[0054] Moreover, the map shown in FIG. 6A is designed so that the correction amount increases as the vehicle turning value increases within a range where the vehicle turning value is greater than 0 (a range of +Xa or more and +Xb or less in the example of FIG. 6A). When the steering wheel 4 is turned to the right and the vehicle is turning to the right, the correction amount calculated by the first correction amount calculation unit 131 increases. When the vehicle is turning with the left rear wheel 3L as the outer wheel and the right rear wheel 3R as the inner wheel, the first correction amount calculation unit 131 calculates a correction amount according to the vehicle turning value so that the target torque (first target torque) of the first electric motor 11 that outputs torque to the left rear wheel 3L increases when the vehicle is turning with the left rear wheel 3L as the outer wheel and the right rear wheel 3R as the inner wheel. Under the condition that the pedaling torque and the vehicle speed are constant, the first correction amount calculation unit 131 calculates the correction amount so that the first target torque when turning to the right is greater than the first target torque when traveling straight. In this way, the rotation speed of the left rear wheel 3L can be increased relative to the rotation speed of the right rear wheel 3R, enabling the vehicle to turn smoothly to the right.

[0055] 6A is designed so that the correction amount is constant when the vehicle turning value exceeds +Xb. This makes it possible to prevent the correction amount calculated by the first correction amount calculation unit 131 from increasing excessively when the steering wheel 4 is turned significantly to the right. This makes it possible to prevent the target torque (first target torque) of the first electric motor 11 from increasing excessively.

[0056] The map shown in Fig. 6A is designed so that the correction amount is constant when the vehicle turning value is within a range including 0 (within a range of -Xa or more and +Xa or less in the example of Fig. 6A). The correction amount in this range (the correction amount when the vehicle turning value is 0) may be, for example, "1".

[0057] The first correction amount calculation unit 131 may calculate a correction amount for the reference assist torque based on the vehicle speed detected by the vehicle speed sensor 33. The first correction amount calculation unit 131 may calculate a correction amount for the reference assist torque by multiplying the correction amount calculated based on the vehicle turning value by the correction amount calculated based on the vehicle speed. In this case, the first target torque calculation unit 120 may calculate the first target torque by correcting the reference assist torque calculated by the reference assist torque calculation unit 110 with a correction amount based on the vehicle turning value and the vehicle speed (by correcting based on the vehicle turning value and the vehicle speed). The first target torque calculation unit 120 may correct the reference assist torque by multiplying the reference assist torque by a correction amount based on the vehicle turning value and the vehicle speed.

[0058] FIG. 6B is a diagram showing an example of a map stored in the storage device 100M. In the map shown in FIG. 6B, the vertical axis represents the correction amount, and the horizontal axis represents the vehicle speed. The first correction amount calculation unit 131 may refer to the map shown in FIG. 6B and calculate a correction amount corresponding to the vehicle speed detected by the vehicle speed sensor 33.

[0059] In the map shown in FIG. 6B, the correction amount when the vehicle speed is in the low speed range is designed to be larger than the correction amount when the vehicle speed is in the medium speed range or the high speed range. In FIG. 6B, the high speed range is a vehicle speed range where the vehicle speed is greater than Xd. The low speed range is a vehicle speed range where the vehicle speed is less than Xc (Xc < Xd). The medium speed range is a vehicle speed range that is larger than the low speed range and lower than the high speed range, and in the example shown in FIG. 6B, it is a vehicle speed range of Xc or more and Xd or less.

[0060] Also, the map shown in FIG. 6B is designed such that when the vehicle speed is in the medium speed range, the correction amount decreases as the vehicle speed increases. For this reason, when the vehicle speed is in the medium speed range, the first correction amount calculation unit 131 calculates a correction amount for the reference assist torque such that the correction amount decreases as the vehicle speed increases. By doing so, the first target torque calculated (corrected) by the first target torque calculation unit 120 can be reduced as the vehicle speed increases.

[0061] The correction amount for the first target torque may be a value to be added to or subtracted from the reference assist torque, rather than a value to be multiplied by the reference assist torque. This correction amount may also be calculated by the first correction amount calculation unit 131 so that the first target torque when turning right is greater than the first target torque when traveling straight.

[0062] The slip detection unit 140 detects slip of the left rear wheel 3L and the right rear wheel 3R. The first slip detection unit 141 detects slip of the left rear wheel 3L, and the second slip detection unit 142 detects slip of the left rear wheel 3L. The first slip detection unit 141 determines whether or not slip is occurring in the left rear wheel 3L based on, for example, the vehicle speed detected by the vehicle speed sensor 33, a vehicle turning value indicating the turning of the vehicle (for example, the roll angle of the vehicle body or the rotation angle of the steering wheel 4), and the rotation speed of the left rear wheel 3L detected by the left rear wheel sensor 34L.

[0063] The slip detection unit 140 calculates an ideal rotation speed of the left rear wheel 3L according to the vehicle speed and the vehicle turning value, for example, based on the vehicle speed detected by the vehicle speed sensor 33 and the vehicle turning value. Here, the ideal rotation speed of the left rear wheel 3L is a rotation speed determined by the vehicle speed detected by the vehicle speed sensor 33, the dimensions of the vehicle body (for example, the distance between the axle of the front wheel 2 and the axle of the rear wheels 3L and 3R, the distance between the left and right rear wheels 3L and 3R), and the turning radius of the vehicle represented by the vehicle turning value, when the left rear wheel 3L is not slipping. The ideal rotation speed of the left rear wheel 3L may be calculated based on the vehicle speed detected by the vehicle speed sensor 33 and the vehicle turning value, using a calculation formula (a calculation formula prestored in the storage device 100M) that uses these as parameters.

[0064] The slip detection unit 140 determines that the left rear wheel 3L is slipping when the slip amount of the left rear wheel 3L represented by the difference between the ideal rotation speed calculated as above and the rotation speed of the left rear wheel 3L actually detected by the left rear wheel sensor 34L (for example, a value obtained by subtracting the rotation speed calculated based on the vehicle speed and the vehicle turning value from the rotation speed of the left rear wheel 3L detected by the left rear wheel sensor 34L) exceeds a threshold value. The slip amount may be the ratio of the rotation speed obtained by the above-mentioned calculation to the rotation speed of the left rear wheel 3L actually detected by the left rear wheel sensor 34L.

[0065] Similar to the first slip detection unit 141, the second slip detection unit 142 determines whether or not the right rear wheel 3R is slipping based on the vehicle speed detected by the vehicle speed sensor 33, the vehicle turning value, and the rotation speed of the right rear wheel 3R detected by the right rear wheel sensor 34R. Similar to the first slip detection unit 141, the second slip detection unit 142 calculates the ideal rotation speed of the right rear wheel 3R according to the vehicle speed and the vehicle turning value. The ideal rotation speed of the right rear wheel 3R is a rotation speed determined by the vehicle speed detected by the vehicle speed sensor 33, the dimensions of the vehicle body (for example, the distance between the axle of the front wheels and the axle of the rear wheels 3L and 3R, the distance between the left and right rear wheels 3L and 3R), and the turning radius of the vehicle represented by the vehicle turning value when the right rear wheel 3R is not slipping. If the amount of slip of the right rear wheel 3R, represented by the difference between this rotation speed and the actual rotation speed of the right rear wheel 3R detected by the right rear wheel sensor 34R, exceeds a threshold value, it may be determined that the right rear wheel 3R is slipping.

[0066] The first target torque calculation unit 120 may calculate (correct) a first target torque, which is a target torque for the left rear wheel 3L, based on the result of slip detection by the slip detection unit 140. The first target torque calculation unit 120 may calculate the first target torque, for example, so that the first target torque when it is determined by the first slip detection unit 141 that slip is occurring in the left rear wheel 3L is smaller than the first target torque when it is determined that no slip is occurring in the left rear wheel 3L. In this way, when slip is occurring in the left rear wheel 3L, the rotation speed of the left rear wheel 3L can be reduced to promote elimination of the slip.

[0067] [2-2. Function for calculating target torque of second electric motor] Next, there will be described a function for calculating a second target torque, which is a target value of the torque output by the second electric motor 21. This function may be realized by a reference assist torque calculation section 110, a rear wheel assist torque calculation section 150, a second target torque calculation section 170, a correction amount calculation section 130 (a second correction amount calculation section 132), and a slip detection section 140 (a first slip detection section 141 and a second slip detection section 142).

[0068] The second target torque calculation unit 170 calculates a second target torque, which is a target torque for the second electric motor 21, based on, for example, a reference assist torque, and the reduction ratio of the first reduction gear mechanism 7 and the reduction ratio of the second reduction gear mechanism 13. In the example shown in Fig. 4, a rear wheel assist torque calculation unit 150, which will be described later, calculates a rear wheel assist torque based on the reference assist torque, the reduction ratio of the first reduction gear mechanism 7, and the reduction ratio of the second reduction gear mechanism 13. Then, the second target torque calculation unit 170 calculates the second target torque based on this rear wheel assist torque and the rear wheel pedaling torque calculated by a rear wheel pedaling torque calculation unit 160, which will be described later.

[0069] The rear wheel assist torque calculation unit 150 calculates the rear wheel assist torque. The rear wheel assist torque is the torque that the first electric motor 11 applies to the left rear wheel 3L. The rear wheel assist torque calculation unit 150 calculates the rear wheel assist torque based on the reference assist torque, the reduction ratio of the first reduction gear mechanism 7, and the reduction ratio of the second reduction gear mechanism 13. The rear wheel assist torque calculation unit 150 calculates the rear wheel assist torque, for example, by multiplying the reference assist torque by the reduction ratio of the first reduction gear mechanism 7 and the reduction ratio of the second reduction gear mechanism 13.

[0070] The rear wheel pedaling torque calculation unit 160 calculates the torque (rear wheel pedaling torque) applied to the left rear wheel 3L by the pedaling force on the pedals 6L, 6R. The rear wheel pedaling torque calculation unit 160 calculates the rear wheel pedaling torque based on the pedaling torque detected by the torque sensor 31 and the reduction ratio of the first reduction mechanism 7. The rear wheel pedaling torque calculation unit 160 calculates the rear wheel pedaling torque, for example, by multiplying the pedaling torque detected by the torque sensor 31 by the reduction ratio of the first reduction mechanism 7. As described above, the second reduction mechanism 13 is disposed in the first torque transmission path 41 between the crankshaft 6 to which the pedals 6L, 6R are attached and the first electric motor 11. For this reason, the rear wheel pedaling torque calculation unit 160 may calculate the rear wheel pedaling torque without using the reduction ratio of the second reduction mechanism 13.

[0071] The second target torque calculation unit 170 may calculate the target torque of the second electric motor 21 based on the reference assist torque and a correction amount according to a vehicle turning value (for example, a roll angle of the vehicle body or a rotation angle of the steering wheel 4). In the example shown in Fig. 4, the second target torque calculation unit 170 calculates the second target torque based on the rear wheel assist torque calculated by the rear wheel assist torque calculation unit 150 described above and a correction amount calculated by the second correction amount calculation unit 132 described below. The second target torque calculation unit 170 calculates the second target torque, for example, by multiplying the rear wheel assist torque by the correction amount calculated by the second correction amount calculation unit 132.

[0072] The second correction amount calculation unit 132 may calculate a correction amount for the rear wheel assist torque (a correction amount for calculating the second target torque) based on the vehicle turning value, similarly to the first correction amount calculation unit 131. The second correction amount calculation unit 132 may calculate the correction amount for the rear wheel assist torque based on a map stored in the storage device 100M. In addition, the second correction amount calculation unit 132 may calculate the correction amount for the rear wheel assist torque based on a predetermined calculation formula.

[0073] Fig. 7 is a diagram showing an example of a map stored in the storage device 100M. In the map shown in Fig. 7, similar to Fig. 6A, the vertical axis indicates the correction amount, and the horizontal axis indicates the vehicle turning value. A positive value on the horizontal axis indicates a turning of the vehicle to the right, and a negative value on the horizontal axis indicates a turning of the vehicle to the left. The second correction amount calculation unit 132 may refer to the map shown in Fig. 7 and calculate a correction amount according to the vehicle turning value (for example, the rotation angle of the steering wheel 4 detected by the steering sensor 32, or the roll angle of the vehicle body detected by the inclination sensor 35).

[0074] The map shown in FIG. 7 is designed so that the correction amount is small when the vehicle turning value is larger than 0, in contrast to the map in FIG. 6A. Therefore, when the steering wheel 4 is turned to the right and the vehicle is turning to the right, the correction amount calculated by the second correction amount calculation unit 132 is small. When the vehicle is turning with the right rear wheel 3R as the inside wheel, the correction amount according to the vehicle turning value is calculated so that the target torque (second target torque) of the second electric motor 21 that outputs torque to the right rear wheel 3R is reduced. The second correction amount calculation unit 132 calculates the correction amount so that the second target torque during right turning is smaller than the second target torque during straight running under the condition that the pedaling torque and the vehicle speed are constant. In this way, the rotation speed of the right rear wheel 3R can be reduced relative to the rotation speed of the left rear wheel 3L, and the vehicle can be turned smoothly to the right.

[0075] 7 is designed so that the correction amount decreases as the vehicle turning value increases within a range where the vehicle turning value is greater than 0 (a range of Xa or more and Xb or less in the example of FIG. 7). The second correction amount calculation unit 132 calculates the correction amount so that the second target torque decreases as the vehicle turning value increases in the positive direction (as the turning radius of the right rear wheel 3R relative to the turning radius of the left rear wheel 3L decreases). In this way, when the steering wheel 4 is turned significantly to the right, the rotation speed of the right rear wheel 3R can be significantly reduced relative to the rotation speed of the left rear wheel 3L, enabling the vehicle to turn smoothly to the right.

[0076] Moreover, the map shown in FIG. 7 is designed so that the correction amount increases as the vehicle turning value decreases (increases in the negative direction) within a range where the vehicle turning value is smaller than 0 (in the range of -Xa or more and -Xb or less in the example of FIG. 7). Therefore, when the steering wheel 4 is turned leftward and the vehicle is turning leftward, the correction amount calculated by the second correction amount calculation unit 132 increases. When the vehicle is turning with the left rear wheel 3L as the inside wheel and the right rear wheel 3R as the outside wheel, the second correction amount calculation unit 132 calculates a correction amount according to the vehicle turning value so that the target torque (second target torque) of the second electric motor 21 that outputs torque to the right rear wheel 3R increases. The second correction amount calculation unit 132 calculates a correction amount so that the second target torque during left turning is larger than the second target torque during straight driving under the condition that the pedaling torque and the vehicle speed are constant. By doing so, when the vehicle is turning left, the rotation speed of the right rear wheel 3R can be increased relative to the rotation speed of the left rear wheel 3L, improving the turning performance of the vehicle to the left.

[0077] 7 is designed to keep the correction amount constant when the vehicle turning value falls below -Xb. This makes it possible to prevent the correction amount calculated by the second correction amount calculation unit 132 from increasing excessively when the steering wheel 4 is turned significantly to the left. This makes it possible to prevent the target torque (second target torque) of the second electric motor 21 from increasing excessively.

[0078] 6A, the map shown in Fig. 7 is designed so that the correction amount is constant when the vehicle turning value is within a range including 0 (in the example of Fig. 7, within a range of -Xa or more and +Xa or less). The correction amount in this range (the correction amount when the vehicle turning value is 0) may be, for example, "1".

[0079] The second correction amount calculation unit 132 may calculate a correction amount for the rear wheel assist torque based on the vehicle speed detected by the vehicle speed sensor 33, similarly to the first correction amount calculation unit 131. More specifically, the second correction amount calculation unit 132 may calculate a correction amount for the rear wheel assist torque by multiplying a correction amount calculated based on the vehicle turning value by a correction amount calculated based on the vehicle speed. In this case, the second target torque calculation unit 170 may calculate the second target torque by correcting the rear wheel assist torque calculated by the rear wheel assist torque calculation unit 150 with a correction amount based on the vehicle turning value and the vehicle speed. More specifically, the second target torque calculation unit 170 may correct the reference assist torque by multiplying the reference assist torque by a correction amount based on the vehicle turning value and the vehicle speed.

[0080] The second correction amount calculation unit 132 may, for example, refer to the map shown in FIG. 6B to calculate the correction amount according to the vehicle speed detected by the vehicle speed sensor 33. As described above, the map shown in FIG. 6B is designed so that the correction amount decreases as the vehicle speed increases when the vehicle speed is in the medium speed range. For this reason, the second correction amount calculation unit 132 calculates the correction amount for the reference assist torque so that the second target torque decreases as the vehicle speed increases when the vehicle speed is in the medium speed range. In this way, the second target torque calculated (corrected) by the second target torque calculation unit 170 can be reduced in accordance with an increase in the vehicle speed.

[0081] The correction amount for the second target torque may be a value to be added to or subtracted from the reference assist torque, rather than a value to be multiplied by the reference assist torque. This correction amount may also be calculated by the second correction amount calculation unit 132 so that the second target torque when turning left is larger than the second target torque when traveling straight.

[0082] The second target torque calculation unit 170 may calculate the second target torque based on the reference assist torque, the correction amount (correction amount according to the vehicle turning value, etc.) calculated by the second correction amount calculation unit 132, and the reduction ratios included in the first torque transmission path 41 (the reduction ratio of the first reduction mechanism 7 and the reduction ratio of the second reduction mechanism 13). In the example shown in FIG. 4, the rear wheel assist torque calculation unit 150 calculates the rear wheel assist torque based on the reference assist torque, the reduction ratio of the first reduction mechanism 7, and the reduction ratio of the second reduction mechanism 13, as described above. Then, the second target torque calculation unit 170 calculates the second target torque by correcting the calculated rear wheel assist torque with the correction amount calculated by the second correction amount calculation unit 132.

[0083] The second target torque calculation unit 170 may calculate the target torque of the second electric motor 21 based on the torque (pedaling torque) of the crankshaft 6. In the example shown in FIG. 4, the rear wheel pedaling torque calculation unit 160 calculates the rear wheel pedaling torque based on the pedaling torque detected by the torque sensor 31 and the reduction ratio of the first reduction gear mechanism 7, as described above. Then, the second target torque calculation unit 170 calculates the second target torque based on the rear wheel pedaling torque calculated by the rear wheel pedaling torque calculation unit 160 and the rear wheel assist torque calculated by the rear wheel assist torque calculation unit 150. The second target torque calculation unit 170 calculates the second target torque, for example, by adding the rear wheel pedaling torque to the rear wheel assist torque.

[0084] In this way, the rear wheel pedaling torque is added to the second target torque calculated by the second target torque calculation unit 170, while the rear wheel pedaling torque is not added to the first target torque calculated by the first target torque calculation unit 120. Therefore, when the vehicle is traveling straight (when the vehicle turning value is 0), the second target torque becomes larger than the first target torque. That is, the torque transmitted from the second electric motor 21 to the right rear wheel 3R becomes larger than the torque transmitted from the first electric motor 11 to the left rear wheel 3L. This makes it possible to make the torque transmitted only from the second electric motor 21 to the right rear wheel 3R closer to the torque transmitted from the pedals 6L, 6R and the first electric motor 11 to the left rear wheel 3L, thereby improving the straight-line running performance of the electrically power-assisted vehicle 1.

[0085] The second target torque calculation unit 170 may calculate the second target torque, which is the target torque for the right rear wheel 3R, based on the result of slip detection by the slip detection unit 140, similarly to the first target torque calculation unit 120. For example, the second target torque calculation unit 170 may calculate the second target torque so that the second target torque when it is determined by the second slip detection unit 142 that slip is occurring in the right rear wheel 3R is smaller than the second target torque when it is determined that no slip is occurring in the right rear wheel 3R. In this way, when slip is occurring in the right rear wheel 3R, the rotation speed of the right rear wheel 3R can be reduced to promote elimination of the slip.

[0086] [2-3. Comparison of torque transmitted to the left and right rear wheels] When TT1 is the first target torque calculated by the first target torque calculation unit 120, TB1 is the reference assist torque calculated by the reference assist torque calculation unit 110, TP1 is the pedaling torque detected by the torque sensor 31, A1 is the correction amount calculated by the first correction amount calculation unit 131, Ga is the reduction ratio of the first reduction mechanism 7, and Gb is the reduction ratio of the second reduction mechanism 13, and when no slip occurs in the left rear wheel 3L and the right rear wheel 3R, the torque TR1 transmitted to the left rear wheel 3L can be expressed, for example, by the following equation 1.

[0087] TR1 = TP1 x Ga + TT1 x Ga x Gb =TP1×Ga+TB1×A1×Ga×Gb...Formula 1

[0088] Furthermore, if TT2 is the second target torque calculated by the second target torque calculation unit 170, TB2 is the rear wheel assist torque calculated by the rear wheel assist torque calculation unit 150, TP2 is the rear wheel pedaling torque calculated by the rear wheel pedaling torque calculation unit 160, and A2 is the correction amount calculated by the second correction amount calculation unit 132, then the torque TR2 transmitted to the right rear wheel 3R can be expressed, for example, by the following equation 2.

[0089] TR2=TT2 =TP2+TB2×A2 =TP1×Ga+TB1×A2×Ga×Gb...Formula 2

[0090] When the vehicle is traveling straight, the vehicle turning value is 0, and there is no slippage in the left rear wheel 3L and the right rear wheel 3R, the correction amount A1 calculated by the first correction amount calculation unit 131 and the correction amount A2 calculated by the second correction amount calculation unit 132 may be the same. In this case, the torque to the left rear wheel 3L calculated by the above formula 1 is the same as the torque to the right rear wheel 3R calculated by the above formula 2. In this way, when the vehicle is traveling straight and there is no slippage, the torques transmitted to the left rear wheel 3L and the right rear wheel 3R can be made to match. This makes it possible to make the torque output to the left rear wheel 3L and the torque output to the right rear wheel 3R match or approximate each other, thereby improving the straight-line performance of the electrically assisted vehicle 1.

[0091] [3. Flowchart] 8A and 8B are flow charts showing an example of a control process executed by the control device 100. The control device 100 may repeatedly execute the control processes shown in FIG. 8A and FIG. 8B. As described later, in the process of FIG. 8A, a first target torque, which is a torque to the left rear wheel 3L, is calculated, and in the process of FIG. 8B, a second target torque, which is a torque to the right rear wheel 3R, is calculated. The processes executed by the control device 100 are not limited to the examples shown in FIG. 8A and FIG. 8B. For example, not all of the processes shown in FIG. 8A and FIG. 8B may be executed, or processes different from the processes shown in FIG. 8A and FIG. 8B may be executed. In addition, the processes shown in FIG. 8A and FIG. 8B may be executed in an order different from the order shown in the figures.

[0092] 8A, first, the reference assist torque calculation unit 110 calculates a reference assist torque based on the pedaling torque detected by the torque sensor 31 and the vehicle speed detected by the vehicle speed sensor 33 (step S101). The reference assist torque calculation unit 110 calculates a torque ratio according to the vehicle speed based on, for example, the map shown in FIG. 6A, and calculates the reference assist torque by multiplying the pedaling torque by this torque ratio.

[0093] Next, the correction amount calculation unit 130 (first correction amount calculation unit 131) calculates a correction amount for the reference assist torque calculated in step S101 based on a vehicle turning value (for example, the rotation angle of the steering wheel 4 detected by the steering sensor 32, or the roll angle of the vehicle body detected by the inclination sensor 35) (step S102). In step S102, the first correction amount calculation unit 131 calculates a correction amount according to the vehicle turning value based on, for example, the map shown in FIG. 6A.

[0094] In step S102, the first correction amount calculation unit 131 calculates a correction amount so as to reduce the first target torque when, for example, the vehicle is turning to the left (when the vehicle is turning with the left rear wheel 3L as the inside wheel and the right rear wheel 3R as the outside wheel), and calculates a correction amount so as to increase the first target torque when the vehicle is turning to the right (when the vehicle is turning with the left rear wheel 3L as the outside wheel and the right rear wheel 3R as the inside wheel).

[0095] In step S102, the first correction amount calculation unit 131 may calculate a correction amount of the reference assist torque calculated in step S101 based on the vehicle speed detected by the vehicle speed sensor 33. In step S102, the first correction amount calculation unit 131 may calculate a correction amount according to the vehicle speed based on, for example, the map shown in FIG. 6B so that the correction amount decreases as the vehicle speed increases.

[0096] Next, the first target torque calculation unit 120 calculates the first target torque based on the reference assist torque calculated in step S101 and the correction amount calculated in step S102 (step S103). In step S103, the first target torque calculation unit 120 calculates the first target torque, for example, by multiplying the reference assist torque by the correction amount.

[0097] Next, the slip detection unit 140 (first slip detection unit 141) determines whether or not slipping is occurring on the left rear wheel 3L (step S104). In step S104, the first slip detection unit 141 calculates the rotation speed of the left rear wheel 3L based on the vehicle speed and the vehicle turning value, for example, and compares this with the rotation speed of the left rear wheel 3L detected by the left rear wheel sensor 34L to determine whether or not slipping is occurring on the left rear wheel 3L.

[0098] When it is determined that the left rear wheel 3L is slipping (Y in step S104), the first target torque calculation unit 120 reduces the first target torque calculated in step S103 (step S105), for example. In step S105, the first target torque calculation unit 120 may calculate the first target torque so that the first target torque is reduced with an increase in the amount of slip of the left rear wheel 3L (the difference between the rotation speed of the left rear wheel 3L detected by the left rear wheel sensor 34L and the rotation speed calculated based on the vehicle speed and the vehicle turning value). Moreover, after determining whether or not the left rear wheel 3L is slipping, the first target torque calculation unit 120 may directly calculate the first target torque based on the determination result, the reference assist torque calculated in step S101, and the correction amount calculated in step S102.

[0099] Next, the control device 100 controls the first electric motor 11 based on the first target torque calculated in step S103 or step S105 (step S106). In step S106, the control device 100 instructs the first electric motor drive device 14 (see FIG. 3) to output the first target torque. The first electric motor drive device 14 supplies power corresponding to the first target torque to the first electric motor 11. As a result, torque corresponding to the first target torque calculated in step S103 or step S105 is output from the first electric motor 11 to the left rear wheel 3L.

[0100] 8B, the rear wheel assist torque calculation unit 150 calculates the rear wheel assist torque, which is the torque applied by the first electric motor 11 to the left rear wheel 3L, based on the reference assist torque calculated in step S101, the gear ratio of the first reduction gear mechanism 7 (the front chain wheel 7b, the chain 7a, and the rear chain wheel 7c) shown in FIG. 2, and the gear ratio of the second reduction gear mechanism 13 (the first gear 13a and the second gear 13b) (step S201). In step S201, the rear wheel assist torque calculation unit 150 calculates the rear wheel assist torque, for example, by multiplying the reference assist torque by the gear ratio of the first reduction gear mechanism 7 and the gear ratio of the second reduction gear mechanism 13.

[0101] Next, the correction amount calculation unit 130 (second correction amount calculation unit 132) calculates the correction amount of the rear wheel assist torque calculated in step S201 based on the vehicle turning value (for example, the rotation angle of the steering wheel 4 detected by the steering sensor 32, or the roll angle of the vehicle body detected by the inclination sensor 35) (step S202). In step S202, the second correction amount calculation unit 132 calculates the correction amount according to the vehicle turning value based on, for example, the map shown in FIG.

[0102] In step S202, the second correction amount calculation unit 132 calculates a correction amount so that the second target torque decreases when the vehicle is turning to the right (when the right rear wheel 3R is the inside wheel and the left rear wheel 3L is the outside wheel), and calculates a correction amount so that the second target torque increases when the vehicle is turning to the left (when the right rear wheel 3R is the outside wheel and the left rear wheel 3L is the inside wheel).

[0103] In step S202, the second correction amount calculation unit 132 may calculate a correction amount of the assist torque calculated in step S201 based on the vehicle speed detected by the vehicle speed sensor 33. In step S202, the second correction amount calculation unit 132 may calculate a correction amount according to the vehicle speed based on, for example, the map shown in Fig. 6B so that the correction amount decreases as the vehicle speed increases.

[0104] Next, the rear wheel pedaling torque calculation unit 160 calculates the rear wheel pedaling torque, which is the torque applied to the left rear wheel 3L by the pedaling force applied to the pedals 6L, 6R, based on the pedaling torque detected by the torque sensor 31 and the gear ratio of the first reduction gear mechanism 7 shown in Fig. 2 (step S203). In step S203, the rear wheel pedaling torque calculation unit 160 calculates the rear wheel pedaling torque, for example, by multiplying the pedaling torque by the gear ratio of the first reduction gear mechanism 7.

[0105] Next, the second target torque calculation unit 170 calculates a second target torque based on the rear wheel assist torque calculated in step S201, the correction amount calculated in step S202, and the rear wheel pedaling torque calculated in step S203 (step S204). In step S204, the second target torque calculation unit 170 calculates the second target torque, for example, by multiplying the rear wheel assist torque calculated by the rear wheel assist torque calculation unit 150 by the correction amount calculated by the second correction amount calculation unit 132, and adding the result to the rear wheel pedaling torque calculated by the rear wheel pedaling torque calculation unit 160.

[0106] Next, the slip detection unit 140 (second slip detection unit 142) determines whether or not slipping is occurring in the right rear wheel 3R (step S205). In step S205, the second slip detection unit 142 determines whether or not slipping is occurring in the right rear wheel 3R by, for example, comparing the rotation speed of the right rear wheel 3R calculated based on the vehicle speed and the vehicle turning value with the rotation speed of the right rear wheel 3R detected by the right rear wheel sensor 34R.

[0107] When it is determined that the right rear wheel 3R is slipping (Y in step S205), the second target torque calculation unit 170 reduces the second target torque calculated in step S204 (step S206), for example. In step S206, the second target torque calculation unit 170 may calculate the second target torque so that the second target torque is reduced with an increase in the amount of slip of the right rear wheel 3R (the difference between the rotation speed of the right rear wheel 3R detected by the right rear wheel sensor 34R and the rotation speed calculated based on the vehicle speed and the vehicle turning value). After determining whether or not the right rear wheel 3R is slipping, the second target torque calculation unit 170 may directly calculate the second target torque based on the determination result, the rear wheel assist torque calculated in step S201, the correction amount calculated in step S202, and the pedaling torque calculated in step S204.

[0108] Finally, the control device 100 controls the second electric motor 21 based on the second target torque calculated in step S204 or step S206 (step S207). In step S207, the control device 100 instructs the second electric motor drive device 23 (see FIG. 3) to output the second target torque. The second electric motor drive device 23 supplies power corresponding to the second target torque to the second electric motor 21. As a result, torque corresponding to the second target torque calculated in step S204 or step S207 is output from the second electric motor 21 to the right rear wheel 3R.

[0109] As described above, it is possible to drive both the left rear wheel 3L and the right rear wheel 3R by calculating the first target torque, which is the target torque of the first electric motor 11, and the second target torque, which is the target torque of the second electric motor 21, and outputting torque from both the first electric motor 11 and the second electric motor 21. Furthermore, as described above, when the vehicle is traveling straight and there is no slippage in the left rear wheel 3L and the right rear wheel 3R, the straight-line running performance of the electrically power-assisted vehicle 1 can be improved by making the torques transmitted to the left rear wheel 3L and the right rear wheel 3R equal or approximate each other.

[0110] [4. Modifications] The present invention is not limited to the above-described embodiment, and various modifications may be made. For example, in the embodiment, the first torque transmission path 41 including the first reduction gear mechanism 7 including the front chain wheel 7b, the chain 7a, and the rear chain wheel 7c shown in FIG. 2 transmits the torque of the crankshaft 6 and the torque output by the first electric motor 11 to the left rear wheel 3L. However, the present invention is not limited to this, and the first torque transmission path 41 may transmit the torque of the crankshaft 6 and the torque output by the first electric motor 11 to the right rear wheel 3R. In this case, the second torque transmission path 42 may transmit the torque output by the second electric motor 21 to the left rear wheel 3L. In this way, both the left rear wheel 3L and the right rear wheel 3R can be driven, improving the straight-line running performance of the vehicle.

[0111] In this case, the first correction amount calculation unit 131 may calculate a correction amount for the reference assist torque based on, for example, the map shown in FIG. 7 so that the target torque (first target torque) of the first electric motor 11 that outputs torque to the right rear wheel 3R increases when the vehicle is turning leftward (when the vehicle is turning with the right rear wheel 3R as the outside wheel). Furthermore, the second correction amount calculation unit 132 may calculate a correction amount for the rear wheel assist torque based on, for example, the map shown in FIG. 6A so that the target torque (second target torque) of the second electric motor 21 that outputs torque to the left rear wheel 3L increases when the vehicle is turning rightward (when the vehicle is turning with the left rear wheel 3L as the outside wheel). In this way, the vehicle can be turned smoothly in a structure in which the torque of the crankshaft 6 and the torque of the first electric motor 11 are transmitted to the right rear wheel 3R and the torque of the second electric motor 21 is transmitted to the left rear wheel 3L.

[0112] Also, in the embodiment, an example has been described in which, when the vehicle is turning with the left rear wheel 3L as the inside wheel, the first correction amount calculation unit 131 calculates the correction amount so as to reduce the first target torque, which is the target torque of the first electric motor 11 that outputs torque to the left rear wheel 3L, and, when the vehicle is turning with the right rear wheel 3R as the inside wheel, the second correction amount calculation unit 132 calculates the correction amount so as to reduce the second target torque, which is the target torque of the second electric motor 21 that outputs torque to the right rear wheel 3R. Here, when the vehicle is turning with the left rear wheel 3L as the inside wheel, the first correction amount calculation unit 131 may calculate the correction amount so that the first target torque becomes "0" (so that the first electric motor 11 does not output torque) or so that the first target torque becomes negative (so that the first electric motor 11 outputs torque that rotates the left rear wheel 3L backward). Similarly, when the vehicle is turning with the right rear wheel 3R as the inside wheel, the second correction amount calculation unit 132 may calculate the correction amount so that the second target torque becomes "0" (so that the second electric motor 21 does not calculate torque), or may calculate the correction amount so that the second target torque becomes negative (so that the second electric motor 21 outputs torque that rotates the right rear wheel 3R backward). Doing so may allow the vehicle to turn more smoothly.

[0113] In the above-described embodiment, the second target torque is calculated based on the torque (rear wheel pedaling torque) applied to the left rear wheel 3L by the pedaling force on the pedals 6L, 6R, and thus the difference in torque transmitted to the left and right rear wheels 3L, 3R when the vehicle is traveling straight is substantially eliminated. However, the rear wheel pedaling torque does not have to be used to calculate the second target torque. The second target torque calculation unit 170 may calculate the second target torque based on the rear wheel assist torque and the correction amount calculated by the second correction amount calculation unit 132. The second target torque calculation unit 170 may also calculate the second target torque based on the reference assist torque and the correction amount.

[0114] In the embodiment, the first correction amount calculation unit 131 calculates the correction amount of the first target torque to be output to the left rear wheel 3L based on the map stored in the storage device 100M, and the second correction amount calculation unit 132 calculates the correction amount of the second target torque to be output to the right rear wheel 3R based on the map stored in the storage device 100M. However, the present invention is not limited to this. The control device 100 may calculate ideal rotation speeds of the left and right rear wheels 3L and the right rear wheel 3R based on the vehicle speed detected by the vehicle speed sensor 33 and the vehicle turning value, and compare the ideal rotation speeds with the actual rotation speeds detected by the left rear wheel sensor 34L and the right rear wheel sensor 34R to calculate the first target torque to be output to the left rear wheel 3L and the second target torque to be output to the right rear wheel 3R. The control device 100 may calculate a first target torque to be output to the left rear wheel 3L and a second target torque to be output to the right rear wheel 3R so that the rotational speeds of the left rear wheel 3L and the right rear wheel 3R match ideal rotational speeds (the rotational speeds of the left rear wheel 3L and the right rear wheel 3R determined by the vehicle speed, the dimensions of the vehicle body, and the vehicle turning radius represented by the vehicle turning value when the left rear wheel 3L and the right rear wheel 3R are not slipping).

[0115] Fig. 9 is a functional block diagram showing another example of the functions of the control device 100. As shown in Fig. 9, the control device 100 may have, as functions, a correction amount calculation unit 210, a first target torque calculation unit 220, and a second target torque calculation unit 230 in addition to the reference assist torque calculation unit 110 described in the embodiment. The correction amount calculation unit 210 may have a first correction amount calculation unit 211 and a second correction amount calculation unit 212. These functions may be realized by the control device 100 executing a program stored in the storage device 100M.

[0116] The first correction amount calculation unit 211 calculates an ideal rotation speed of the left rear wheel 3L (the rotation speed of the left rear wheel 3L determined by the vehicle speed, the dimensions of the vehicle body, and the turning radius of the vehicle represented by the vehicle turning value when the left rear wheel 3L is not slipping) based on, for example, the vehicle speed detected by the vehicle speed sensor 33 and the vehicle turning value (for example, the rotation angle of the steering wheel 4 detected by the steering sensor 32, or the roll angle of the vehicle body detected by the inclination sensor 35), and calculates the speed difference between this and the rotation speed detected by the left rear wheel sensor 34L. Then, based on this speed difference, it calculates a correction amount of the first target torque to be output to the left rear wheel 3L. Similarly, the second correction amount calculation unit 212 calculates an ideal rotation speed of the right rear wheel 3R (the rotation speed of the right rear wheel 3R determined by the vehicle speed, the dimensions of the vehicle body, and the turning radius of the vehicle represented by the vehicle turning value when the right rear wheel 3R is not slipping) based on the vehicle speed detected by the vehicle speed sensor 33 and the vehicle turning value, and calculates the speed difference between this and the rotation speed detected by the right rear wheel sensor 34R. Then, based on this speed difference, the second correction amount calculation unit 212 calculates the correction amount of the second target torque to be output to the right rear wheel 3R.

[0117] The first correction amount calculation unit 211 may calculate a positive value as the correction amount when the rotation speed detected by the left rear wheel sensor 34L is lower than the rotation speed calculated based on the vehicle speed and the vehicle turning value for the left rear wheel 3L, and may calculate a negative value as the correction amount when the rotation speed detected by the left rear wheel sensor 34L is higher than the rotation speed calculated based on the vehicle speed and the vehicle turning value for the left rear wheel 3L. Similarly, the second correction amount calculation unit 212 may calculate a positive value as the correction amount when the rotation speed detected by the right rear wheel sensor 34R is lower than the rotation speed calculated based on the vehicle speed and the vehicle turning value for the right rear wheel 3R, and may calculate a negative value as the correction amount when the rotation speed detected by the right rear wheel sensor 34R is higher than the rotation speed calculated based on the vehicle speed and the vehicle turning value for the right rear wheel 3R.

[0118] The correction amount (absolute value of the correction amount) calculated by the first correction amount calculation unit 211 may increase with an increase in the speed difference calculated for the left rear wheel 3L. Similarly, the correction amount (absolute value of the correction amount) calculated by the second correction amount calculation unit 212 may increase with an increase in the speed difference calculated for the right rear wheel 3R.

[0119] The first target torque calculation unit 220 calculates a first target torque to be output to the left rear wheel 3L based on the reference assist torque calculated by the reference assist torque calculation unit 110 based on the pedaling torque and the vehicle speed, and the correction amount calculated by the first correction amount calculation unit 211. The first target torque calculation unit 220 calculates the first target torque, for example, by adding the correction amount to the reference assist torque. Similarly, the second target torque calculation unit 230 calculates a second target torque to be output to the right rear wheel 3R, based on the reference assist torque and the correction amount calculated by the second correction amount calculation unit 212. The second target torque calculation unit 230 calculates the second target torque, for example, by adding the correction amount to the reference assist torque.

[0120] As described above, the first target torque and the second target torque may be calculated so that the rotation speeds of the left rear wheel 3L and the right rear wheel 3R match the ideal rotation speeds of the left rear wheel 3L and the right rear wheel 3R, which are determined by the vehicle speed, the dimensions of the vehicle body, and the vehicle turning value. The first target torque and the second target torque calculated in this manner may then be output to the left rear wheel 3L and the right rear wheel 3R. This also improves the straight-line running performance and turning performance of the vehicle.

[0121] [5. Summary] (1-1) As described above, the electrically power assisted vehicle 1 may have the front wheel 2, a first rear wheel (e.g., the left rear wheel 3L) which is one of the right rear wheel 3R and the left rear wheel 3L, a second rear wheel (e.g., the right rear wheel 3R) which is the other of the right rear wheel 3R and the left rear wheel 3L, a crankshaft 6 to which the pedals 6L, 6R are attached, a first electric motor 11, and a second electric motor 21. The electrically power assisted vehicle 1 may also have a first torque transmission path 41 which transmits the torque of the crankshaft 6 generated by depressing the pedals 6L, 6R and the torque output by the first electric motor 11 only to the first rear wheel of the first rear wheel and the second rear wheel, and a second torque transmission path 42 which is a mechanism which transmits the torque output by the second electric motor 21 only to the second rear wheel of the first rear wheel and the second rear wheel. This allows both the left rear wheel 3L and the right rear wheel 3R to be driven without using a differential mechanism, thereby improving the straight-line running performance of the vehicle while keeping costs down.

[0122] (1-2) The first torque transmission path 41 may also include the first reduction gear mechanism 7 (the front chain wheel 7b, the chain 7a, and the rear chain wheel 7c). The first electric motor 11 and the crankshaft 6 may be disposed upstream of the first reduction gear mechanism 7.

[0123] (1-3) The second electric motor 21 may be disposed on the second rear wheel. The second electric motor 21 may be, for example, an in-wheel motor built into the second rear wheel. In this way, the structure of the electrically power assisted vehicle 1 can be simplified.

[0124] (1-4) Furthermore, the electrically power assisted vehicle 1 may have a control device 100 that controls the first electric motor 11 and the second electric motor 21. The first torque transmission path 41 may include a first reduction gear mechanism 7 (the front chain wheel 7b, the chain 7a, and the rear chain wheel 7c). The first electric motor 11 and the crankshaft 6 may be disposed upstream of the first reduction gear mechanism 7. The second electric motor 21 may be disposed on the second rear wheel. The control device 100 may calculate a second target torque, which is a target torque for the second electric motor 21, based on a reference assist torque calculated based on the pedaling forces acting on the pedals 6L, 6R and the reduction ratio of the first reduction gear mechanism 7. The control device 100 (second target torque calculation unit 170) may calculate the second target torque based on, for example, a reference assist torque calculated based on the pedaling force acting on the pedals 6L, 6R, the reduction ratio of the first reduction mechanism 7, the reduction ratio of the second reduction mechanism 13 (first gear 13a and second gear 13b), and the pedaling torque detected by the torque sensor 31.

[0125] (2-1) The electrically power-assisted vehicle 1 may have front wheels 2, a steering wheel 4 for steering the front wheels 2, a first rear wheel (e.g., the left rear wheel 3L) which is one of the right rear wheel 3R and the left rear wheel 3L, a second rear wheel (e.g., the right rear wheel 3R) which is the other of the right rear wheel 3R and the left rear wheel 3L, and a crankshaft 6 to which pedals 6L, 6R are attached. The electrically power-assisted vehicle 1 may have a first torque transmission path 41 for transmitting the torque of the crankshaft 6 to at least one of the first rear wheel and the second rear wheel, a first electric motor 11 which outputs torque for the first rear wheel, a second electric motor 21 which outputs torque for the second rear wheel, and a detection unit for detecting a vehicle turning value representing turning of the vehicle (e.g., a steering sensor 32 which detects the rotation angle of the steering wheel 4, or an inclination sensor 35 which detects the roll angle of the vehicle body). The electrically power assisted vehicle 1 may have a control device 100 that calculates a first target torque, which is a target torque for the first electric motor 11, and a second target torque, which is a target torque for the second electric motor 21, based on a reference assist torque calculated based on the pedaling force acting on the pedals 6L, 6R and a correction amount according to a vehicle turning value. This makes it possible to improve the turning performance of the vehicle without using a differential mechanism.

[0126] (2-2) In addition, in a turn in which the first rear wheel becomes the inside wheel and the second rear wheel becomes the outside wheel, the control device 100 may calculate a correction amount corresponding to the vehicle turning value so as to reduce the target torque of the first rear wheel. In addition, in a turn in which the first rear wheel becomes the outside wheel and the second rear wheel becomes the inside wheel, the control device 100 may calculate a correction amount corresponding to the vehicle turning value so as to reduce the target torque of the second rear wheel.

[0127] (2-3) In addition, in a turn in which the first rear wheel becomes the inside wheel and the second rear wheel becomes the outside wheel, the control device 100 may calculate a correction amount corresponding to the vehicle turning value so that the target torque of the second rear wheel increases. In addition, in a turn in which the first rear wheel becomes the outside wheel and the second rear wheel becomes the inside wheel, the control device 100 may calculate a correction amount corresponding to the vehicle turning value so that the target torque of the first rear wheel increases.

[0128] (2-4) Furthermore, the electrically assisted vehicle 1 may have a first torque transmission path 41 that includes a first reduction gear mechanism 7 and transmits the torque of the crankshaft 6 and the torque of the first electric motor 11 to the first rear wheel via the first reduction gear mechanism 7. The torque of the second electric motor 21 may be transmitted to the second rear wheel without passing through the first reduction gear mechanism 7.

[0129] (2-5) Furthermore, the control device 100 may calculate a second target torque, which is a target torque for the second electric motor 21, based on the reference assist torque, a correction amount according to the vehicle turning value, and the reduction ratio of the first reduction gear mechanism 7.

[0130] (2-6) Furthermore, the torque transmitted from the second electric motor 21 to the second rear wheel may be greater than the torque transmitted from the first electric motor 11 to the first rear wheel.

[0131] (2-7) Furthermore, the control device 100 may calculate a second target torque, which is a target torque for the second electric motor 21, based on the torque (pedaling torque) of the crankshaft 6. For example, the control device 100 may calculate a rear wheel assist torque based on a reference assist torque, a correction amount according to the vehicle turning value, and the reduction ratio of the first reduction gear mechanism 7 and the second reduction gear mechanism 13, and may calculate the second target torque by adding to the rear wheel pedaling torque calculated based on the pedaling torque and the reduction ratio of the first reduction gear mechanism 7.

[0132] (2-8) The vehicle turning value may also be the roll angle of the vehicle.

[0133] (2-9) The vehicle turning value may be the rotation angle of the steering shaft.

[0134] (2-10) Moreover, the control device 100 may correct the reference assist torque based on the vehicle turning value and the vehicle speed.

[0135] (2-11) Furthermore, the control device 100 may calculate a correction amount so that the target torque decreases as the vehicle speed increases. The control device 100 may calculate a correction amount for the reference assist torque so that the first target torque decreases as the vehicle speed increases. The control device 100 may calculate a correction amount for the rear wheel assist torque so that the second target torque decreases as the vehicle speed increases.

[0136] (2-12) Furthermore, the control device 100 may include a first slip detection unit 141 that detects slip of the first rear wheel and a second slip detection unit 142 that detects slip of the second rear wheel, and may calculate a first target torque that is a target torque for the first rear wheel and a second target torque that is a target torque for the second rear wheel based on the slip detection result. [Explanation of symbols]

[0137] 1 Electrically assisted vehicle, 2 Front wheel, 3L Left rear wheel, 3R Right rear wheel, 4 Steering handle, 4a Steering shaft, 4b Front fork, 5 Main frame, 5a Head pipe, 5b Seat tube, 6 Crankshaft, 6L, 6R Pedals, 7 First reduction mechanism, 7a Chain, 7b Front chain wheel, 7c Rear chain wheel, 8F Front basket, 8B Rear basket, 9 Saddle, 11 First electric motor, 12 First battery, 13 Second reduction mechanism, 13a First gear, 13b Second gear, 14 First electric motor drive device, 15 Rear frame, 16, 17 Axle, 21 Second electric motor, 21a Stator, 21b Rotor, 22 Second battery, 23 Second electric motor drive device, 31 Torque sensor, 32 Steering sensor, 32a First gear, 32b Second gear, 32c Support, 33 Vehicle speed sensor, 34L left rear wheel sensor, 34R right rear wheel sensor, 35 tilt sensor, 41 first torque transmission path, 42 second torque transmission path, 100 control device, 100M storage device, 110 reference assist torque calculation unit, 120, 220 first target torque calculation unit, 130, 210 correction amount calculation unit, 131, 211 first correction amount calculation unit, 132, 212 second correction amount calculation unit, 140 slip detection unit, 141 first slip detection unit, 142 second slip detection unit, 150 rear wheel assist torque calculation unit, 160 rear wheel pedaling torque calculation unit, 170, 230 second target torque calculation unit.

Claims

1. The front wheel and A steering handle for steering the front wheels; a first rear wheel to which the power is transmitted, the first rear wheel being one of a right rear wheel and a left rear wheel; a second rear wheel which is the other of the right rear wheel and the left rear wheel; A crankshaft to which the pedals are attached; a torque transmission path for transmitting torque of the crankshaft to at least one of the first rear wheel and the second rear wheel; a first electric motor outputting torque for the first rear wheel; a second electric motor outputting torque for the second rear wheel; A detection unit for detecting a vehicle turning value representing a turning of the vehicle; a control device that calculates a target torque of the first electric motor and a target torque of the second electric motor based on a reference assist torque calculated based on a depression force acting on the pedal and a correction amount corresponding to the vehicle turning value; An electrically assisted vehicle having the above-mentioned features.

2. When the first rear wheel becomes an inside wheel and the second rear wheel becomes an outside wheel, the control device calculates a correction amount according to the vehicle turning value so as to reduce a target torque of the first rear wheel; When the first rear wheel becomes an outer wheel and the second rear wheel becomes an inner wheel, the control device calculates a correction amount according to the vehicle turning value so that a target torque of the second rear wheel is reduced. An electrically assisted vehicle according to claim 1.

3. When the first rear wheel becomes an inside wheel and the second rear wheel becomes an outside wheel, the control device calculates a correction amount according to the vehicle turning value so that a target torque of the second rear wheel is increased, When the first rear wheel becomes an outer wheel and the second rear wheel becomes an inner wheel, the control device calculates a correction amount according to the vehicle turning value so that a target torque of the first rear wheel is increased.

3. An electrically assisted vehicle according to claim 1 or 2.

4. a torque transmission path including a reduction mechanism for transmitting the torque of the crankshaft and the torque of the first electric motor to the first rear wheel via the reduction mechanism; The torque of the second electric motor is transmitted to the second rear wheel without passing through the reduction mechanism. An electrically assisted vehicle according to claim 1.

5. The control device calculates a target torque of the second electric motor based on the reference assist torque, the correction amount corresponding to the vehicle turning value, and a reduction ratio of the reduction mechanism. An electrically assisted vehicle according to claim 4.

6. The torque transmitted from the second electric motor to the second rear wheel is greater than the torque transmitted from the first electric motor to the first rear wheel. An electrically assisted vehicle according to claim 4.

7. The control device calculates a target torque of the second electric motor based on the torque of the crankshaft. An electrically assisted vehicle according to claim 4.

8. The vehicle turning value is the roll angle of the vehicle. An electrically assisted vehicle according to claim 1.

9. The vehicle turning value is a rotation angle of a steering shaft. An electrically assisted vehicle according to claim 1.

10. The control device corrects the reference assist torque based on the vehicle turning value and the vehicle speed. An electrically assisted vehicle according to claim 1.

11. The control device calculates the correction amount so that the target torque decreases as the vehicle speed increases. An electrically assisted vehicle according to claim 10.

12. The control device includes a first slip detection unit that detects slip of the first rear wheel and a second slip detection unit that detects slip of the second rear wheel, and calculates a target torque for the first rear wheel and a target torque for the second rear wheel based on a result of the slip detection. An electrically assisted vehicle according to claim 1.

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