Motor system and power-assisted vehicle

Abstract

To provide a motor system capable of appropriately assisting output to a first motor and a second motor.SOLUTION: A motor system assists the drive of a man-power drive vehicle that includes a first wheel, a second wheel, and an input unit to which an input and an output for driving the second wheel are input. The motor system includes: a first motor that drives the first wheel; a second motor that drives the second wheel; and a motor control device that adjusts the outputs by the first motor and the second motor. The motor control device decides the assist output by the motor system based on the levels of the input and output, and distributes the assist output to the first motor and second motor based on a first load applied to the first wheel, and a second load applied to the second wheel.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a motor system and an electric assist vehicle.

Background Art

[0002] In recent years, efforts have been made to promote the Sustainable Development Goals (the 2030 Agenda for Sustainable Development, adopted at the United Nations Summit on September 25, 2015 (Heisei 27), hereinafter referred to as "SDGs"). Along with this, technologies aiming to reduce waste and defective products are known in order to ensure sustainable production and consumption patterns.

[0003] Conventionally, an electric assist bicycle equipped with a front wheel motor that drives the front wheel and a rear wheel motor that drives the rear wheel is known. And Patent Document 1 discloses a technique for distributing a predetermined assist output to the front wheel motor and the rear wheel motor in such an electric assist bicycle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the assist output is distributed to the front wheel motor and the rear wheel motor at a simple ratio, there is a problem that slip occurs in the front wheel or the rear wheel, and the driving force of the electric assist bicycle decreases.

[0006] Therefore, an object of the present invention is to provide a motor system capable of appropriately distributing an assist output to a first motor and a second motor.

Means for Solving the Problems

[0007] In order to achieve the above object, the present invention provides a motor system for assisting the drive of a human-powered vehicle including a first wheel, a second wheel, and an input unit to which a human power output for driving the second wheel is input. The motor system includes a first motor for driving the first wheel, a second motor for driving the second wheel, and a motor control device for adjusting the outputs of the first motor and the second motor. The motor control device determines the assist output of the motor system based on the magnitude of the human power output, and distributes the assist output to the first motor and the second motor based on a first load applied to the first wheel and a second load applied to the second wheel.

Effects of the Invention

[0008] According to the present invention, a motor system capable of appropriately distributing the assist output to the first motor and the second motor can be obtained. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0010] [Configuration of Electric Assist Bicycle 1] FIG. 1 is a side view of an electric assist bicycle 1 according to the present embodiment. FIG. 2 is a block diagram of a motor system 100 according to the present embodiment. Hereinafter, on the premise that the electric assist bicycle 1 is placed on a horizontal plane, the direction orthogonal to the placement surface is referred to as the "vertical direction", the direction including the traveling direction of the electric assist bicycle 1 is referred to as the "front-rear direction", and the direction orthogonal to the vertical direction and the front-rear direction is referred to as the "left-right direction".

[0011] The electric assist bicycle 1 is an example of an electric assist vehicle that assists the force (hereinafter referred to as "pedaling force") applied to the pedals 23L and 23R of a user (hereinafter simply referred to as "user") riding on the electric assist bicycle 1 with an electric motor to rotate the front wheel 7F and the rear wheel 7B (that is, to run the electric assist bicycle 1). As shown in FIGS. 1 and 2, the electric assist bicycle 1 includes a main body 2 and a motor system 100. The main body 2 is an example of a human-powered vehicle.

[0012] The main body 2 is a bicycle whose driving force is assisted by the motor system 100. The main body 2 may be an existing bicycle diverted, or may be newly designed to mount the motor system 100. As shown in FIG. 1, the main body 2 mainly includes a frame 3, a front fork 4, a saddle 5, a handlebar 6, a front wheel 7F and a rear wheel 7B (hereinafter, these may be collectively referred to as "wheel 7"), a steering column 8, a pedaling force transmission mechanism 20, and a brake mechanism 30.

[0013] The frame 3 is a member that supports the components (4 to 8, 20, 30) of the main body 2. The frame 3 is composed of, for example, steel, aluminum alloy, chrome molybdenum steel, carbon (carbon fiber reinforced plastic), or a combination thereof. The frame 3 mainly includes, for example, a top tube 11, a down tube 12, a seat tube 13, a head tube 14, a seat stay 15, a chain stay 16, and a bottom bracket shell 17.

[0014] The top tube 11 has its front end connected to the head tube 14 and its rear end connected to the upper end of the seat tube 13, and extends generally in the front-rear direction. The down tube 12 has its front end connected to the head tube 14 and its rear end connected to the bottom bracket shell 17, and extends obliquely rearward and downward. The seat tube 13 has its upper end connected to the rear end of the top tube 11 and its lower end connected to the bottom bracket shell 17, and extends obliquely forward and downward. The seat tube 13 supports the saddle 5 so as to be able to move up and down at its upper end.

[0015] The head tube 14 is connected to the front ends of the top tube 11 and the down tube 12, and extends obliquely forward and downward. And a steering column 8 of the front fork 4 is rotatably inserted into the head tube 14. The steering column 8 supports the handlebar 6 at its upper end. The front fork 4 extends obliquely forward and downward from the head tube 14, and rotatably supports the front wheel 7F at its lower end. Thus, when the handlebar 6 is operated by the user, the direction of the front wheel 7F (that is, the traveling direction of the electric assist bicycle 1) changes. That is, the front wheel 7F is a steerable wheel whose steering angle θ1 can be changed (in other words, steered) by the handlebar 6, and is an example of the first wheel.

[0016] The seat stay 15 has its front end connected to the seat tube 13 and extends obliquely rearward and downward. The chain stay 16 has its front end connected to the bottom bracket shell 17 and extends generally rearward. And the rear wheel 7B is rotatably supported at the connection portion (that is, the rear end) of the seat stay 15 and the chain stay 16.

[0017] The pedaling force transmission mechanism 20 is a mechanism that transmits the pedaling force (human power output PH) of a user sitting on the saddle 5 to the rear wheel 7B. The pedaling force transmission mechanism 20 mainly includes, for example, a crankshaft 21, a pair of crank arms 22L and 22R, a pair of pedals 23L and 23R, a drive gear 24, a driven gear 25, and a chain 26. The pedaling force transmission mechanism 20 (more specifically, a pair of pedals 23L and 23R) is an example of an input part to which the human power output PH for driving the rear wheel 7B is input. Further, the rear wheel 7B is a drive wheel that is driven by the pedaling force transmitted by the pedaling force transmission mechanism 20, and is an example of the second wheel.

[0018] The crankshaft 21 extends in the left - right direction and is rotatably supported by the bottom bracket shell 17. One ends of the crank arms 22L and 22R are connected to both ends of the crankshaft 21 and extend in a direction orthogonal to the crankshaft 21. Further, pedals 23L and 23R are rotatably attached to the other ends of the crank arms 22L and 22R. The drive gear 24 is attached to the crankshaft 21 and rotates integrally with the crankshaft 21. The driven gear 25 is attached to the rear wheel 7B and rotates integrally with the rear wheel 7B. The chain 26 is wound around the drive gear 24 and the driven gear 25.

[0019] When a user sitting on the saddle 5 steps on the pedals 23L and 23R, the crankshaft 21 rotates together with the drive gear 24 by the pedaling force transmitted by the crank arms 22L and 22R. The rotation of the drive gear 24 is transmitted to the driven gear 25 through the chain 26. The driven gear 25 shifts the rotation of the drive gear 24 transmitted through the chain 26 according to the gear ratio of the drive gear 24 and the driven gear 25 and rotates the rear wheel 7B. Note that the pedaling force transmission mechanism 20 may include a plurality of driven gears that rotate integrally with the rear wheel 7B and a derailleur that switches the driven gear around which the chain 26 is wound from among the plurality of driven gears.

[0020] The braking mechanism 30 is a mechanism that brakes the electric assist bicycle 1 according to the operation of the user. The braking mechanism 30 mainly includes, for example, a pair of brake levers 31L and 31R, a front brake 32, and a rear brake 33.

[0021] The brake levers 31L and 31R are attached to the handle 6. The brake lever 31L is operated by the user's left hand, and the brake lever 31R is operated by the user's right hand. The front brake 32 clamps the rim of the front wheel 7F and brakes the front wheel 7F in response to the operation of the brake lever 31R. The rear brake 33 clamps the rim of the rear wheel 7B and brakes the rear wheel 7B in response to the operation of the brake lever 31L. Note that the front brake 32 and the rear brake 33 may clamp a disk that rotates integrally with the wheel 7 instead of clamping the rim of the wheel 7.

[0022] [Configuration of the motor system 100] As shown in FIGS. 1 and 2, the motor system 100 mainly includes, for example, a front wheel motor 102F and a rear wheel motor 102B (hereinafter, these may be collectively referred to as "wheel motors 102") and a motor control device 103. The motor system 100 is a system that controls the driving of the front wheel motor 102F and the rear wheel motor 102B using the electric power stored in the battery 101 (power source). The front wheel motor 102F is an example of a first motor, and the rear wheel motor 102B is an example of a second motor.

[0023] The battery 101 stores electric power for operating the wheel motors 102 and the motor control device 103. The battery 101 may store, for example, the electric power supplied from a commercial power source with a cable (not shown) attached, or may store the regenerative electric power generated by the wheel motors 102. Further, the battery 101 is detachably attached to the upper surface of the down tube 12, for example, as shown in FIG. 1. However, the battery 101 is not limited to being installed at the position shown in FIG. 1 and can be installed at any position of the main body 2.

[0024] The in-wheel motor 102 is an electric motor driven by the electric power supplied from the battery 101 through the motor control device 103. Also, the in-wheel motor 102 is driven according to the control of the motor control device 103. The front-wheel motor 102F is attached to the hub of the front wheel 7F, for example, as shown in FIG. 1, and rotates the front wheel 7F. Similarly, the rear-wheel motor 102B is attached to the hub of the rear wheel 7B, for example, and rotates the rear wheel 7B.

[0025] The motor control device 103 controls the driving of the in-wheel motor 102 by the electric power supplied from the battery 101. The motor control device 103 is attached to the back side of the saddle 5 (more specifically, the back surface of the seat post that supports the saddle 5), for example, as shown in FIG. 1. However, the motor control device 103 is not limited to being installed at the position shown in FIG. 1 and can be installed at any position of the main body 2. Also, as shown in FIG. 2, the motor control device 103 is composed of, for example, a distribution board 104, a first board 105F, and a second board 105B.

[0026] The distribution board 104 determines the assist output PA that the entire motor system 100 can output based on the human power output PH input to the pedaling force transmission mechanism 20. Also, the distribution board 104 distributes the assist output PA to the first output P1 and the second output P2 and notifies the first board 105F and the second board 105B. Further, the distribution board 104 determines the regenerative braking forces of the front-wheel motor 102F and the rear-wheel motor 102B and notifies the first board 105F and the second board 105B.

[0027] The first board 105F drives the front-wheel motor 102F with the first output P1 distributed by the distribution board 104. That is, the first board 105F supplies the electric power corresponding to the first output P1 from the battery 101 to the front-wheel motor 102F. Also, the first board 105F generates the regenerative braking force notified from the distribution board 104 in the front-wheel motor 102F to brake the front wheel 7F. Further, the first board 105F charges the battery 101 with the regenerative electric power generated by the front-wheel motor 102F.

[0028] The second substrate 105B drives the rear-wheel motor 102B with the second output P2 distributed by the distribution substrate 104. That is, the second substrate 105B supplies the power corresponding to the second output P2 from the battery 101 to the rear-wheel motor 102B. Also, the second substrate 105B generates the regenerative braking force notified from the distribution substrate 104 in the rear-wheel motor 102B to brake the rear wheel 7B. Further, the second substrate 105B charges the battery 101 with the regenerative power generated by the rear-wheel motor 102B.

[0029] Also, the first substrate 105F and the second substrate 105B may generate a regenerative braking force in the front-wheel motor 102F and the rear-wheel motor 102B in response to the operation of the brake levers 31L and 31R. More specifically, the first substrate 105F generates a regenerative braking force of a magnitude corresponding to the operation amount of the brake lever 31R in the front-wheel motor 102F. The second substrate 105B generates a regenerative braking force of a magnitude corresponding to the operation amount of the brake lever 31L in the rear-wheel motor 102B. Also, the operation amounts of the brake levers 31L and 31R may be detected by a sensor (not shown).

[0030] As an example, the distribution substrate 104, the first substrate 105F, and the second substrate 105B include a CPU and a memory. And each substrate (104, 105F, 105B) executes each process described later by the CPU executing the program stored in the memory. As another example, each substrate (104, 105F, 105B) may be realized by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0031] The distribution board 104, the first board 105F, the second board 105B, and the various sensors (110, 111, 112, 113, 114F, 114B, 115F, 115B) are communicably connected, for example, through CAN (Controller Area Network). Then, when both the first board 105F and the second board 105B are operating normally, the distribution board 104 executes the motor control process shown in FIG. 3. On the other hand, when an abnormality occurs in one of the first board 105F and the second board 105B, the distribution board 104 notifies only the other of the first board 105F and the second board 105B of the output or the regenerative braking force.

[0032] The torque sensor 110 detects the input torque T0 [Nm] input to the pedal force transmission mechanism 20 (crank arms 22L, 22R), and outputs a torque signal indicating the detected input torque T0 to the motor control device 103. The cadence sensor 111 detects the input rotation speed N0 [rpm] of the crank arms 22L, 22R, and outputs a cadence signal indicating the detected input rotation speed N0 to the motor control device 103.

[0033] The vehicle speed sensor 112 detects the vehicle speed V0 [km / h] of the electric assist bicycle 1, and outputs a vehicle speed signal indicating the detected vehicle speed V0 to the motor control device 103. The steering angle sensor 113 detects the steering angle θ1 [dgree] of the front wheel 7F with respect to the forward direction of the electric assist bicycle 1, and outputs a steering angle signal indicating the detected steering angle θ1 to the motor control device 103.

[0034] The load sensor 114F detects the first load W1 [kg] applied to the front wheel 7F, and outputs a load signal indicating the detected first load W1 to the motor control device 103. The load sensor 114B detects the second load W2 [kg] applied to the rear wheel 7B, and outputs a load signal indicating the detected second load W2 to the motor control device 103. The load sensors 114F and 114B may include, for example, the loads W1G and W2G acting in the vertical direction on the wheel 7 and the inclination angle θ2 of the mounting surface of the electric assist bicycle 1 with respect to the horizontal direction. Then, the load sensors 114F and 114B output the first load W1 (= W1G × cos θ2) and the second load W2 (= W2G × cos θ2) orthogonal to the mounting surface.

[0035] As an example, when there is a load in the front basket of the electric assist bicycle 1, the first load W1 > the second load W2. As another example, when the electric assist bicycle 1 is going uphill, the first load W1 < the second load W2. However, the magnitude relationship between the first load W1 and the second load W2 is affected by the complex action of various factors.

[0036] The motor rotation sensor 115F detects the motor rotation speed N1 (= the rotation speed of the front wheel 7F) [rpm] of the front wheel motor 102F, and outputs a rotation speed signal indicating the detected motor rotation speed N1 to the motor control device 103. The motor rotation sensor 115B detects the motor rotation speed N2 (= the rotation speed of the rear wheel 7B) [rpm] of the rear wheel motor 102B, and outputs a rotation speed signal indicating the detected motor rotation speed N2 to the motor control device 103.

[0037] The various sensors (110 to 115B) can adopt any well-known form of sensors. The vehicle speed sensor 112 may detect the vehicle speed V0 of the electric assist bicycle 1 based on, for example, a position signal received from a GPS (Global Positioning Satellite).

[0038] [Motor Control Processing] FIG. 3 is a flowchart of motor control processing. FIG. 4 is a diagram showing an example of the relationship between vehicle speed and assist ratio. FIG. 5 is a diagram showing an example of a motor efficiency map. The motor control processing is processing for controlling the outputs of the front wheel motor 102F and the rear wheel motor 102B, respectively. The motor control device 103 repeatedly executes the motor control processing shown in FIG. 3 at a predetermined time interval, for example, during the period when the power supply of the motor system 100 is turned on (more specifically, when the assist switch is turned on).

[0039] First, the distribution board 104 compares the vehicle speed V0 detected by the vehicle speed sensor 112 with a predetermined second threshold value (S11). The second threshold value may be set, for example, to the assist upper limit speed (e.g., 24 km / h), or may be set to a speed higher than the assist upper limit speed (e.g., 40 km / h).

[0040] Next, when the distribution board 104 determines that the vehicle speed V0 is less than the second threshold value (S11: Yes), it determines the assist output PA [W] based on the input torque T0 detected by the torque sensor 110, the input rotation speed N0 detected by the cadence sensor 111, and the vehicle speed V0 detected by the vehicle speed sensor 112 (S12). First, the distribution board 104 calculates the input output PH based on the following formula 0. Further, the distribution board 104 identifies the assist ratio corresponding to the vehicle speed V0 of the electric assist bicycle 1 based on the relationship shown in FIG. 4. Furthermore, the distribution board 104 multiplies the input output PH by the assist ratio (that is, based on the magnitude of the input output PH) to determine the assist output PA.<## PH = 2πr × T0 × N0 / 60 ··· (Formula 0)

[0041] r is the length of the crank arms 22L and 22R (the rotation radius of the pedals 23L and 23R). The input output PH is the pedaling force input to the pedaling force transmission mechanism 20 by the user of the electric assist bicycle 1. The assist output PA is the output of the motor system 100 (more specifically, the total output of the front wheel motor 102F and the rear wheel motor 102B).

[0042] The greater the human power output PH, the greater the assist output PA. Also, the higher the vehicle speed V0, the smaller the assist output PA. More specifically, when the vehicle speed V is less than 10 [km / h], the assist ratio is 2 (i.e., the assist output PA is twice the human power output PH). When the vehicle speed V0 is between 10 and 24 [km / h], the assist ratio gradually decreases as the vehicle speed V0 increases. When the vehicle speed V0 is equal to or higher than the assist upper limit value (24 [km / h]), the assist ratio (i.e., the assist output PA) becomes 0.

[0043] Next, the distribution board 104 distributes the assist output PA to the first output P1 [W] and the second output P2 [W] based on the first load W1 detected by the load sensor 114F and the second load W2 detected by the load sensor 114B (S13). The first output P1 is the output of the front-wheel motor 102F that assists in driving the front wheel 7F. The second output P2 is the output of the rear-wheel motor 102B that assists in driving the rear wheel 7B. The distribution board 104 distributes the assist output PA so as to satisfy, for example, the following formula 1 and the following formula 2. P1:(PH + P2)=W1:W2 ···(Formula 1) PA = P1 + P2 ···(Formula 2)

[0044] Note that as long as the first output P1 and the second output P2 are determined based on the first load W1 and the second load W2, they do not necessarily have to strictly satisfy the above formula 1. For example, it is sufficient if P1 > (PH + P2) when W1 > W2, P1 = (PH + P2) when W1 = W2, and P1 < (PH + P2) when W1 < W2.

[0045] Next, the distribution board 104 compares the vehicle speed V0 detected by the vehicle speed sensor 112 with a predetermined first threshold value (S14). The first threshold value is set to a value that can be evaluated as immediately after the electric assist bicycle 1 starts running (for example, 5 [km / h]). That is, in step S14, the distribution board 104 determines whether the electric assist bicycle 1 has just started running.

[0046] Next, when it is determined that the vehicle speed V0 is less than the first threshold value (i.e., immediately after the electric assist bicycle 1 starts running) (S14: Yes), the distribution board 104 compares the steering angle θ1 detected by the steering angle sensor 113 with a predetermined threshold angle (S15). The threshold angle is set to a value (for example, ±5°) that can evaluate that the electric assist bicycle 1 is moving straight forward. That is, in step S15, the distribution board 104 determines whether the electric assist bicycle 1 is moving straight forward.

[0047] Next, when it is determined that the steering angle θ1 is less than the threshold angle (i.e., the electric assist bicycle 1 is moving straight forward) (S15: Yes), the distribution board 104 increases the first output P1 determined in step S13 and decreases the second output P2 (S16). More specifically, the distribution board 104 increases the first output P1 by a predetermined width α (i.e., P1 + α) or a predetermined magnification β (i.e., P1 × β). Note that α is a number greater than 0, and β is a number greater than 1. Also, α and β may be predetermined fixed values or variable values that increase as the steering angle θ1 becomes smaller. Furthermore, the distribution board 104 decreases the second output P2 by the amount by which the first output P1 is increased so as to satisfy the above formula 2.

[0048] Also, when it is determined that the steering angle θ1 is greater than or equal to the threshold angle (i.e., the electric assist bicycle 1 is not moving straight forward) (S15: No), the distribution board 104 decreases the first output P1 determined in step S13 (S17). For example, the distribution board 104 may decrease the first output P1 as the steering angle θ1 increases. Also, in step S17, the distribution board 104 may increase the second output P2 by the amount by which the first output P1 is decreased, or may not change the second output P2.

[0049] Hereinafter, the first output P1 after executing steps S16 and S17 is denoted as "first output P1'", and the second output P2 after executing steps S16 and S17 is denoted as "second output P2'". Similarly, for the first output P1 and the second output P2 after executing step S18 described later, they are also denoted as "first output P1'" and "second output P2'".

[0050] Furthermore, when the distribution board 104 determines that the vehicle speed V0 is equal to or higher than the first threshold value (that is, not immediately after the electric assist bicycle 1 starts running) (S14: No), based on the motor characteristic map shown in FIG. 5, the total torque of the first torque T1 when driving the front wheel motor 102F with the first output P1 and the second torque T2 when driving the rear wheel motor 102B with the second output P2 is redistributed to the front wheel motor 102F and the rear wheel motor 102B so that the energy efficiency is maximized (S18).

[0051] First, the distribution board 104 substitutes the first output P1 and the second output P2 determined in step S13 and the motor rotation speeds N1 and N2 detected by the motor rotation sensors 115F and 115B into the following formulas 3 and 4 to calculate the first torque T1 and the second torque T2. Here, R is the radius of the wheel 7. T1 = 60 × P1 / (2πR × N1) ···(Formula 3) T2 = 60 × P2 / (2πR × N2) ···(Formula 4)

[0052] Next, the distribution board 104 identifies a first efficiency E1 corresponding to the combination of the first torque T1 and the motor speed N1, and a second efficiency E2 corresponding to the combination of the second torque T2 and the motor speed N2 in the motor efficiency map shown in FIG. 5. In FIG. 5, it is assumed that N1 = N2, but N1 ≠ N2 may also be possible. Then, the distribution board 104 fixes the motor speeds N1 and N2, and determines the first torque T1' and the second torque T2' such that the sum of the first efficiency E1' and the second efficiency E2' is maximized. Note that the first efficiency E1' is the energy efficiency corresponding to the combination of the first torque T1' and the motor speed N1. Also, the second efficiency E2' is the energy efficiency corresponding to the combination of the second torque T2' and the motor speed N2.

[0053] Here, the first torque T1 and the second torque T2 before correction, and the first torque T1' and the second torque T2' after correction satisfy the relationship of the following Equation 5. That is, the distribution board 104 redistributes the total torque to the front-wheel motor 102F and the rear-wheel motor 102B so that the energy efficiency is maximized without changing the total torque of the front-wheel motor 102F and the rear-wheel motor 102B. Also, if the distribution board 104 substitutes the first torque T1' and the second torque T2' after correction into T1 and T2 in Equation 3 and Equation 4, the first output P1' and the second output P2' after correction can be identified. T1 + T2 = T1' + T2' ···(Equation 5)

[0054] The motor efficiency map shown in FIG. 5 shows that the energy efficiency is higher toward the inside of the figure. Note that the specific shape of the motor efficiency map varies depending on the specifications of the front-wheel motor 102F and the rear-wheel motor 102B. In the example of FIG. 5, the first torque T1 is decreased to be the first torque T1' after correction, and the second torque T2 is increased to be the second torque T2' after correction. However, in which direction the first torque T1 and the second torque T2 are corrected (increased or decreased) varies depending on the combination of the first torque T1, the second torque T2, and the motor speeds N1 and N2.

[0055] Next, the distribution board 104 notifies the first output P1' to the first board 105F and notifies the second output P2' to the second board 105B. Then, the first board 105F drives the front-wheel motor 102F with the first output P1' distributed by the distribution board 104 (that is, supplies the power corresponding to the first output P1' from the battery 101 to the front-wheel motor 102F). Also, the second board 105B drives the rear-wheel motor 102B with the second output P2' distributed by the distribution board 104 (that is, supplies the power corresponding to the second output P2' from the battery 101 to the rear-wheel motor 102B) (S19).

[0056] Next, the distribution board 104 executes slip control processing (S20). The slip control processing is a process of further correcting the first output P1' and the second output P2' in order to prevent slip (more specifically, wheel spin) of each of the front wheels 7F and the rear wheels 7B. Details of the slip control processing will be described later with reference to FIG. 6.

[0057] On the other hand, when the distribution board 104 determines that the vehicle speed V0 is equal to or higher than the second threshold (S11: No), based on the first load W1 detected by the load sensor 114F and the second load W2 detected by the load sensor 114B, the distribution board 104 determines the regenerative braking forces B1 and B2 of the front-wheel motor 102F and the rear-wheel motor 102B respectively (S21). That is, the larger the first load W1, the larger the regenerative braking force B1 of the front-wheel motor 102F, and the larger the second load W2, the larger the regenerative braking force B2 of the rear-wheel motor 102B. More specifically, the distribution board 104 may match the ratio of the first load W1 and the second load W2 with the ratio of the regenerative braking forces B1 and B2. Further, the larger the difference between the vehicle speed V0 and the second threshold, the larger the absolute values of the regenerative braking forces B1 and B2 may be made.

[0058] Then, the distribution board 104 notifies the determined regenerative braking force B1 to the first board 105F and notifies the determined regenerative braking force B2 to the second board 105B. Also, the first board 105F brakes the front wheel 7F by generating the regenerative braking force B1 notified from the distribution board 104 in the front wheel motor 102F. Similarly, the second board 105B brakes the rear wheel 7B by generating the regenerative braking force B2 notified from the distribution board 104 in the rear wheel motor 102B. Further, the first board 105F and the second board 105B charge the battery 101 with the regenerative power generated by the front wheel motor 102F and the rear wheel motor 102B.

[0059] [Slip control process] FIG. 6 is a flowchart of the slip control process. First, the distribution board 104 determines whether or not the front wheel 7F rotationally driven by the front wheel motor 102F driven by the first output P1' is slipping (S31). The distribution board 104 calculates, for example, the slip ratio S by substituting the wheel speed V1 (= 2π × R × N1) of the front wheel 7F specified from the motor rotation speed N1 detected by the motor rotation sensor 115F and the vehicle speed V0 detected by the vehicle speed sensor 112 into the following Equation 6. Then, the distribution board 104 may determine that the front wheel 7F is slipping when the slip ratio S is equal to or greater than a threshold value (for example, 0.2), and determine that the front wheel 7F is not slipping when the slip ratio S is less than the threshold value. S = (V1 - V0) / V1 ···(Equation 6)

[0060] Next, when the distribution board 104 determines that the front wheel 7F is slipping (S31: Yes), it decreases the first output P1' (S32). The distribution board 104 decreases the first output P1' by a predetermined width γ (that is, P1' + γ) or a predetermined magnification δ (that is, P1' × δ). Note that γ is a number less than 0, and δ is a number less than 1. Note that γ and δ may be predetermined fixed values or variable values that increase as the difference between the wheel speed V1 and the vehicle speed V0 increases.

[0061] Next, the distribution board 104 determines whether the rear wheel 7B driven by the rear wheel motor 102B driven by the second output P2' is slipping (S33). The distribution board 104 may compare, for example, in the same manner as in step S31, the wheel speed V2 (= 2π × R × N2) of the rear wheel 7B specified from the motor rotation speed N2 detected by the motor rotation sensor 115B with the vehicle speed V0 detected by the vehicle speed sensor 112.

[0062] And when the distribution board 104 determines that the rear wheel 7B is slipping (S33: Yes), it decreases the second output P2' (S34). The method of decreasing the second output P2' may be the same as in step S32. On the other hand, when the distribution board 104 determines that the rear wheel 7B is not slipping (S33: No), it increases the second output P2' (S35). Note that the first output P1' decreased in step S32 and the second output P2' increased in step S35 need to satisfy the relationship of Equation 2.

[0063] On the other hand, when the distribution board 104 determines that the front wheel 7F is not slipping (S31: No), it determines whether the rear wheel 7B driven by the rear wheel motor 102B driven by the second output P2' is slipping (S36). And when the distribution board 104 determines that the rear wheel 7B is slipping (S36: Yes), it decreases the second output P2' (S37) and increases the first output P1' (S38). The process of step S36 may be the same as that of step S33, the process of step S37 may be the same as that of step S32, and the process of step S38 may be the same as that of step S35.

[0064] That is, when one of the front wheel 7F and the rear wheel 7B is slipping and the other is not slipping (S31: Yes & S33: No / S31: No & S36: Yes), the distribution board 104 decreases one of the first output P1' and the second output P2' (the output on the slipping side) (S32 / S37) and increases the other of the first output P1' and the second output P2' (the output on the non-slipping side) (S35 / S38).

[0065] Then, the distribution board 104 repeatedly executes the processes of steps S31 to S38 until it is determined that neither the front wheel 7F nor the rear wheel 7B is slipping (S36: No). Further, the distribution board 104 notifies the first board 105F of the first output P1' corrected (increased or decreased) in steps S32, S34, S35, S37, and S38, and notifies the second board 105B of the second output P2'. Furthermore, the first board 105F drives the front wheel motor 102F with the first output P1' newly notified from the distribution board 104, and the second board 105B drives the rear wheel motor 102B with the second output P2' newly notified from the distribution board 104.

[0066] In the motor control process shown in FIG. 3, some or all of steps S14 to S18, S20, and S21 can be omitted. For example, steps S14 to S17 can be omitted, step S18 can be omitted, step S20 can be omitted, or steps S11 & S21 can be omitted. Also, the execution order of each step of the motor control process may be changed without departing from the gist of the present invention.

[0067] [Operation and Effect of Embodiment] According to the above embodiment, since the assist output PA is distributed to the first output P1 and the second output P2 in the ratio of the first load W1 and the second load W2, the wheel 7 with a larger load is rotationally driven with a larger torque, and the wheel 7 with a smaller load is rotationally driven with a smaller torque. As a result, it is possible to prevent one of the front wheel 7F and the rear wheel 7B from slipping and wasting the assist output PA. In this way, since the assist output PA can be appropriately distributed to the front wheel motor 102F and the rear wheel motor 102B, energy loss can be suppressed and the running stability of the electric assist bicycle 1 can be improved.

[0068] Also, in the slip control process according to the above embodiment, by correcting (fine-tuning) the first output P1' and the second output P2' within the range where the wheel 7 does not slip, the slip of the wheel 7 can be more appropriately prevented. As a result, the energy loss due to slip is further reduced. When steps S16 to S18 are omitted, in the slip control process, the first output P1 and the second output P2 determined in step S13 are corrected (fine-tuned).

[0069] Also, in the slip control process according to the above embodiment, by increasing one of the first output P1' and the second output P2' by the amount by which the other is decreased, the assist output PA can be distributed to the front wheel motor 102F and the rear wheel motor 102B without waste.

[0070] Also, according to the above embodiment, by increasing the output of the front wheel motor 102F immediately after the electric assist bicycle 1 starts running (S16), the traction force immediately after the start of running increases, so the electric assist bicycle 1 can be smoothly accelerated. On the other hand, if the output of the front wheel motor 102F is increased when the steering angle θ1 is large, the electric assist bicycle 1 may run in an unintended direction. Therefore, in such a case, conversely, by decreasing the output of the front wheel motor 102F (S17), the running stability of the electric assist bicycle 1 can be maintained.

[0071] Also, according to the above embodiment, by determining the regenerative braking forces B1 and B2 generated when the vehicle speed V0 is equal to or higher than the second threshold value based on the loads W1 and W2, the electric assist bicycle 1 can be stably decelerated.

[0072] Furthermore, according to the above embodiment, by separating the distribution board 104 that implements the function of determining the output P1, P2 and the regenerative braking forces B1, B2, the first board 105F that controls the front wheel motor 102F, and the second board 105B that controls the rear wheel motor 102B, even if an abnormality occurs in one of the first board 105F and the second board 105B, the assist of the electric assist bicycle 1 can be continued with the remaining board.

[0073] [Modification Example] FIG. 7 is a block diagram of a motor system 100' according to a modification example. Note that detailed description of the common points with the above embodiment is omitted, and the description will focus on the differences. The motor control device 103' according to the modification example is different from the above embodiment in the configuration of the distribution board 104. More specifically, the motor control device 103' is different from the above embodiment in that the distribution board 104 is omitted and the first board 105F' and the second board 105B' have a distribution function.

[0074] The distribution function is the function implemented on the distribution board 104 according to the above embodiment. That is, in the motor control device 103' according to the modification example, the distribution function is redundantly implemented (i.e., duplicated) on the first board 105F' and the second board 105B'.

[0075] When the distribution function of the first board 105F' is valid (operating normally), the motor control device 103' distributes the assist output PA by the first board 105F' to control the front wheel motor 102F and notifies the second board 105B' of the second output P2. At this time, the second board 105B' suspends the distribution function and controls the rear wheel motor 102B with the second output P2 notified from the first board 105F'. On the other hand, when the distribution function of the first board 105F' is invalid (an abnormality has occurred), the motor control device 103' distributes the assist output PA by the second board 105B' to control the rear wheel motor 102B and notifies the first board 105F' of the first output P1. At this time, the first board 105F' controls the front wheel motor 102F with the first output P1 notified from the second board 105B'.

[0076] According to the modified example, by redundantly implementing the distribution function on the first substrate 105F' and the second substrate 105B', the redundancy of the motor control device 103' is improved. As a result, even if a trouble occurs, the possibility of continuing the assist of the electric assist bicycle 1 by the motor system 100' is improved.

[0077] Note that the specific configurations of the motor control devices 103 and 103' are not limited to the examples in FIGS. 2 and 7. As another example, the functions of the motor control device may be integrated on one substrate.

[0078] [Other Modified Examples] The electric assist vehicles to which the motor systems 100 and 100' can be applied are not limited to the electric assist bicycle 1. As another example, the electric assist vehicles to which the motor systems 100 and 100' can be applied may have a plurality of front wheels 7F and / or rear wheels 7B, or may be provided with a pair of left and right wheels instead of the front wheels 7F and the rear wheels 7B.

[0079] The embodiments of the present invention have been described above. Note that the present invention is not limited to the above-described embodiments and includes various modified examples. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of this embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of this embodiment. Furthermore, for a part of the configuration of this embodiment, addition, deletion, and replacement with other configurations are possible.

Explanation of Reference Numerals

[0080] 1... Electric assist bicycle, 2... Body, 3... Frame, 4... Front fork, 5... Saddle, 6... Handlebar, 7B... Rear wheel, 7F... Front wheel, 8... Steering column, 11... Top tube, 12... Down tube, 13... Seat tube, 14... Head tube, 15... Seat stay, 16... Chain stay, 17... Bottom bracket shell, 20... Pedal force transmission mechanism, 21... Crankshaft, 22L, 22R... Crank arms, 23L, 23R... Pedals, 24... Driving gear, 25... Driven gear, 26... Chain, 30... Brake mechanism, 31L, 31R... Brake levers, 32... Front brake, 33... Rear brake, 100, 100’... Motor system, 101... Battery, 102B... Rear wheel motor, 102F... Front wheel motor, 103, 103’... Motor control device, 104... Distribution board, 105B, 105B’... Second board, 105F, 105F’... First board, 110... Torque sensor, 111... Cadence sensor, 112... Vehicle speed sensor, 113... Steering angle sensor, 114B, 114F... Load sensor, 115B, 114F... Motor rotation sensor

Claims

1. In a motor system for assisting the drive of a human-powered vehicle including a first wheel, a second wheel, and an input section to which a human power output for driving the second wheel is input, a first motor for driving the first wheel, a second motor for driving the second wheel, and a motor control device for adjusting the outputs of the first motor and the second motor, wherein the motor control device determines an assist output of the motor system based on the magnitude of the human power output, and distributes the assist output to the first motor and the second motor based on a first load applied to the first wheel and a second load applied to the second wheel. A motor system characterized by the above.

2. In the motor system according to Claim 1, when the human power output is PH, the assist output is PA, the first load is W1, the second load is W2, the first output of the first motor is P1, and the second output of the second motor is P2, the motor control device distributes the assist output to the first output and the second output so as to satisfy Expression 1 and Expression 2. A motor system characterized by the above. P1:(PH + P2)=W1:W2...(Expression 1) PA = P1 + P2...(Expression 2)

3. In the motor system according to Claim 2, the motor control device decreases the first output when the first wheel slips, and decreases the second output when the second wheel slips. A motor system characterized by the above.

4. In the motor system according to Claim 3, when one of the first wheel and the second wheel slips and the other does not slip, the motor control device decreases one of the first output and the second output and increases the other of the first output and the second output. A motor system characterized by the above.

5. In the motor system according to Claim 2, the first wheel is a steerable front wheel, the second wheel is a rear wheel, and the motor control device increases the first output and decreases the second output while the speed of the human-powered vehicle is less than a first threshold value. A motor system characterized by the above.

6. In the motor system according to Claim 5, the motor control device decreases the first output when the steering angle of the first wheel is greater than or equal to a threshold angle while the speed of the human-powered vehicle is less than the first threshold value. A motor system characterized by the above.

7. In the motor system according to claim 2, the motor control device redistributes the total torque of the first torque when driving the first motor with the first output and the second torque when driving the second motor with the second output to the first motor and the second motor so that the energy efficiency is maximized based on a predetermined motor characteristic map. A motor system characterized by that.

8. In the motor system according to claim 1, when the speed of the human-powered vehicle is equal to or higher than a second threshold value, the motor control device generates a regenerative braking force for the first motor and the second motor based on the first load and the second load. A motor system characterized by that.

9. In the motor system according to claim 8, the motor control device increases the regenerative braking force as the difference between the speed of the human-powered vehicle and the second threshold value increases. A motor system characterized by that.

10. In the motor system according to claim 1, the motor control device, a distribution board that distributes the assist output to a first output and a second output, a first board that drives the first motor with the first output distributed by the distribution board, A motor system characterized by including a second board that drives the second motor with the second output distributed by the distribution board.

11. In the motor system according to claim 1, the motor control device, has a distribution function that distributes the assist output to a first output and a second output, a first board that drives the first motor with the first output distributed by the distribution function, including a second board that has the distribution function and drives the second motor with the second output distributed by the distribution function, when the distribution function of the first board is valid, the assist output is distributed by the first board, A motor system characterized in that when the distribution function of the first board is invalid, the assist output is distributed by the second board.

12. A first wheel, a second wheel, an input unit to which a human power output for driving the second wheel is input, An electric assist vehicle comprising the motor system according to claim 1 that assists in driving the first wheel and the second wheel.

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