Motor system

Abstract

We provide a motor system with improved assist accuracy. [Solution] The motor system is a system for assisting the driving of a human-powered vehicle, which includes a first wheel, a second wheel, and an input unit to which human power output for driving the second wheel is input, and comprises a first motor and a second motor, a first reduction gear that reduces the rotation of the first motor and transmits it to the first wheel, a second reduction gear that reduces the rotation of the second motor and transmits it to the second wheel, and a motor control device that adjusts 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 human power output, distributes the assist output to the first output and the second output, corrects the first output based on the first reduction efficiency of the first reduction gear, generates the corrected first output in the first motor, corrects the second output based on the second reduction efficiency of the second reduction gear, generates the corrected second output in the second motor.

Description

Technical Field

[0001] The present invention relates to a motor system.

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 (Year 27 of Heisei), 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, technologies for adjusting the power of each of a first motor for assisting the rotation of a front wheel and a second motor for assisting the rotation of a rear wheel based on human driving force are known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the rotation of the motor is decelerated by a speed reducer and transmitted to the wheel, the actual output transmitted to the wheel is smaller than the target output due to the mechanical loss of the speed reducer. Therefore, the technology of Patent Document 1 that does not consider the deceleration efficiency of the speed reducer has a problem of low assist accuracy.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a motor system with improved assist accuracy.

Means for Solving the Problems

[0007] To achieve the above objective, the present invention provides a motor system for assisting the driving of a human-powered vehicle comprising a first wheel, a second wheel, and an input unit to which human power output for driving the second wheel is input, wherein the motor system comprises a first motor and a second motor, a first reduction gear that reduces the rotation of the first motor and transmits it to the first wheel, a second reduction gear that reduces the rotation of the second motor and transmits it to the second wheel, and a motor control device that adjusts the outputs of the first motor and the second motor, wherein the motor control device determines the assist output of the motor system based on the human power output, distributes the assist output to a first output and a second output, corrects the first output based on the first reduction efficiency of the first reduction gear, generates the corrected first output in the first motor, corrects the second output based on the second reduction efficiency of the second reduction gear, and generates the corrected second output in the second motor. [Effects of the Invention]

[0008] According to the present invention, a motor system with improved assist accuracy can be obtained. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side view of an electric assist bicycle according to this embodiment. [Figure 2] This is a block diagram of the motor system according to this embodiment. [Figure 3] This is a flowchart of the motor control process. [Figure 4] This figure shows an example of the relationship between vehicle speed and assist ratio. [Figure 5] This is an example of a deceleration efficiency map. [Modes for carrying out the invention]

[0010] [Configuration of Electric Assist Bicycle 1] Figure 1 is a side view of the electric assist bicycle 1 according to this embodiment. Figure 2 is a block diagram of the motor system 100 according to this embodiment. Hereinafter, assuming that the electric assist bicycle 1 is placed on a horizontal surface, the direction perpendicular to the mounting surface will be referred to as the "up and down direction", the direction including the direction of travel of the electric assist bicycle 1 will be referred to as the "front and back direction", and the direction perpendicular to the up and down direction and the front and back direction will be referred to as the "left and right direction".

[0011] The electric assist bicycle 1 is an example of an electric assist vehicle that uses an electric motor to assist the force applied by the user (hereinafter simply referred to as "user") to pedal 23L and 23R, thereby rotating the front wheel 7F and rear wheel 7B (i.e., driving the electric assist bicycle 1). As shown in Figures 1 and 2, the electric assist bicycle 1 consists of 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 propulsion is assisted by the motor system 100. The main body 2 may be an existing bicycle that has been repurposed, or it may be newly designed to accommodate the motor system 100. As shown in Figure 1, the main body 2 mainly comprises a frame 3, a front fork 4, a saddle 5, handlebars 6, a front wheel 7F and a rear wheel 7B (hereinafter, these may be collectively referred to as "wheels 7"), a steering column 8, a pedaling force transmission mechanism 20, and a brake mechanism 30.

[0013] Frame 3 is a component that supports the main body 2's components (4-8, 20, 30). Frame 3 is made of, for example, steel, aluminum alloy, chromium-molybdenum steel, carbon (carbon fiber reinforced plastic), or a combination thereof. Frame 3 mainly consists of, 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 is connected at its front end to the head tube 14 and at its rear end to the upper end of the seat tube 13, and extends generally in the front-to-back direction. The down tube 12 is connected at its front end to the head tube 14 and at its rear end to the bottom bracket shell 17, and extends diagonally downward and backward. The seat tube 13 is connected at its upper end to the rear end of the top tube 11 and at its lower end to the bottom bracket shell 17, and extends diagonally downward and forward. The seat tube 13 supports the saddle 5 at its upper end so that it can be raised and lowered.

[0015] The head tube 14 is connected to the front ends of the top tube 11 and the down tube 12 and extends diagonally forward and downward. The steering column 8 of the front fork 4 is rotatably inserted through the head tube 14. The steering column 8 supports the handlebars 6 at its upper end. The front fork 4 extends diagonally forward and downward from the head tube 14 and rotatably supports the front wheel 7F at its lower end. As a result, the direction of the front wheel 7F (i.e., the direction of travel of the electric assist bicycle 1) changes when the handlebars 6 are operated by the user. In other words, the front wheel 7F is a steering wheel whose steering angle can be changed (in other words, steerable) by the handlebars 6, and is an example of a first wheel.

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

[0017] The pedaling force transmission mechanism 20 is a mechanism that transmits the pedaling force (human power torque TH) 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 driving 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 torque TH (human power output PH) for driving the rear wheel 7B is input. Further, the rear wheel 7B is a driving 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 driving 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 looped around the driving 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 driving gear 24 by the pedaling force transmitted by the crank arms 22L and 22R. The rotation of the driving gear 24 is transmitted to the driven gear 25 through the chain 26. The driven gear 25 shifts the rotation of the driving gear 24 transmitted through the chain 26 according to the gear ratio of the driving 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 looped 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"), a front wheel reducer 108F and a rear wheel reducer 108B (hereinafter, these may be collectively referred to as "reducer 108"), 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).

[0023] The front wheel motor 102F is an example of the first motor, the rear wheel motor 102B is an example of the second motor, the front wheel reducer 108F is an example of the first reducer, and the rear wheel reducer 108B is an example of the second reducer. However, the rear wheel motor 102B may be the first motor, the front wheel motor 102F may be the second motor, the rear wheel reducer 108B may be the first reducer, and the front wheel reducer 108F may be the second reducer.

[0024] Battery 101 stores power to operate the wheel motor 102 and the motor control device 103. Battery 101 may store power supplied from a commercial power source via a cable (not shown), or it may store regenerative power generated by the wheel motor 102. Battery 101 is detachably attached to the upper surface of the down tube 12, for example, as shown in Figure 1. However, battery 101 is not limited to being installed in the position shown in Figure 1, but can be installed at any position on the main body 2.

[0025] The wheel motor 102 is an electric motor driven by power supplied from the battery 101 via the motor control device 103. The wheel motor 102 is driven according to the control of the motor control device 103. The front wheel motor 102F is mounted on the hub of the front wheel 7F, for example, as shown in Figure 1, and rotates the front wheel 7F. Similarly, the rear wheel motor 102B is mounted on the hub of the rear wheel 7B, for example, and rotates the rear wheel 7B.

[0026] The reduction gear 108 reduces the rotation of the wheel motor 102 and transmits it to the wheel 7. The reduction gear 108 is installed between the output shaft of the wheel motor 102 and the hub of the wheel 7. The reduction gear 108 is, for example, a planetary gear reduction gear. However, the configuration of the reduction gear 108 is not particularly limited and may be a worm type, a gear train type, etc. The front wheel reduction gear 108F is, for example, housed and integrated in the housing of the front wheel motor 102F. The rear wheel reduction gear 108B is, for example, housed and integrated in the housing of the rear wheel motor 102B.

[0027] The motor control device 103 controls the drive of the wheel motor 102 using power supplied from the battery 101. The motor control device 103 is mounted on the underside of the saddle 5 (more specifically, on the back of the seat post supporting the saddle 5), for example, as shown in Figure 1. However, the motor control device 103 is not limited to being installed in the position shown in Figure 1, and can be installed at any position on the main body 2.

[0028] Furthermore, as shown in Figure 2, the motor control device 103 is composed of, for example, a distribution board 104, a front wheel board 105F, and a rear wheel board 105B. However, the configuration of the motor control device 103 is not limited to the example in Figure 2, and the functions of the distribution board 104, the front wheel board 105F, and the rear wheel board 105B may be integrated onto a single board. Also, the division of roles of the distribution board 104, the front wheel board 105F, and the rear wheel board 105B is not limited to the following example.

[0029] The distribution board 104 determines the assist output PA [W] that the entire motor system 100 can output based on the human power output PH [W] input to the pedal force transmission mechanism 20. The distribution board 104 also distributes the assist output PA to the front wheel output PF (first output) [W] and the rear wheel output PB (second output) [W]. Furthermore, the distribution board 104 corrects the front wheel output PF based on the deceleration efficiency R1 (first deceleration efficiency) of the front wheel reducer 108F and notifies the front wheel board 105F of the corrected front wheel output PF' [W]. Similarly, the distribution board 104 corrects the rear wheel output PB based on the deceleration efficiency R2 (second deceleration efficiency) of the rear wheel reducer 108B and notifies the rear wheel board 105B of the corrected rear wheel output PB' [W].

[0030] The front wheel board 105F generates the corrected front wheel output PF' notified by the distribution board 104 to the front wheel motor 102F. That is, the front wheel board 105F supplies power corresponding to the corrected front wheel output PF' from the battery 101 to the front wheel motor 102F. The rear wheel board 105B generates the corrected rear wheel output PB' notified by the distribution board 104 to the rear wheel motor 102B. That is, the rear wheel board 105B supplies power corresponding to the corrected rear wheel output PB' from the battery 101 to the rear wheel motor 102B.

[0031] As an example, the distribution board 104, the front wheel board 105F, and the rear wheel board 105B each include a CPU and memory. Each board (104, 105F, 105B) then performs the processes described later by having the CPU execute a program stored in memory. As another example, each board (104, 105F, 105B) may be implemented by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). Furthermore, the distribution board 104, the front wheel board 105F, and the rear wheel board 105B are connected to each other so as to be able to communicate bidirectionally, for example, via a CAN (Controller Area Network).

[0032] Furthermore, the motor system 100 according to this embodiment further includes rotation speed sensors 106F and 106B, and temperature sensors 107F and 107B. However, the rotation speed sensors 106F and 106B and the temperature sensors 107F and 107B may be external components connected to the motor system 100. In addition, the motor system 100 is connected to a torque sensor 110, a cadence sensor 111, and a vehicle speed sensor 112.

[0033] The rotation speed sensor 106F detects the front wheel rotation speed NF [rpm] of the front wheel motor 102F and outputs a rotation speed signal indicating the detected front wheel rotation speed NF to the distribution board 104. The rotation speed sensor 106B detects the rear wheel rotation speed NB [rpm] of the rear wheel motor 102B and outputs a rotation speed signal indicating the detected rear wheel rotation speed NB to the distribution board 104.

[0034] The temperature sensor 107F detects the front wheel motor temperature tF [°C] of the front wheel motor 102F (for example, the housing, coil, and circuit board of the front wheel motor 102F) and outputs a temperature signal indicating the detected front wheel motor temperature tF to the distribution board 104. The temperature sensor 107B detects the rear wheel motor temperature tB [°C] of the rear wheel motor 102B (for example, the housing, coil, and circuit board of the rear wheel motor 102B) and outputs a temperature signal indicating the detected rear wheel motor temperature tB to the distribution board 104.

[0035] The torque sensor 110 detects the human-powered torque TH [Nm] input to the pedaling force transmission mechanism 20 (crank arms 22L, 22R) and outputs a torque signal indicating the detected human-powered torque TH to the motor control device 103. The cadence sensor 111 detects the human-powered rotation speed NH [rpm] of the crank arms 22L, 22R and outputs a cadence signal indicating the detected human-powered rotation speed NH to the motor control device 103. The vehicle speed sensor 112 detects the vehicle speed V [km / h] of the electric assist bicycle 1 and outputs a vehicle speed signal indicating the detected vehicle speed V to the motor control device 103.

[0036] The various sensors (106F, 106B, 107F, 107B, 110-112) can be any known form of sensor. Furthermore, the various sensors (106F, 106B, 107F, 107B, 110-112) can be attached to any position on the electric assist bicycle 1. The vehicle speed sensor 112 may, for example, detect the vehicle speed V of the electric assist bicycle 1 based on a position signal received from a GPS (Global Positioning Satellite).

[0037] [Motor control processing] Figure 3 is a flowchart of the motor control process. Figure 4 is a diagram showing an example of the relationship between vehicle speed and assist ratio. Figure 5 is an example of a deceleration efficiency map. The motor control process is the process of adjusting the output of the front wheel motor 102F and the rear wheel motor 102B, respectively. The motor control device 103 repeatedly executes the motor control process shown in Figure 3 at predetermined time intervals, for example, during the period when the motor system 100 is powered ON (more specifically, when the assist switch is ON).

[0038] First, the distribution board 104 acquires the detected values ​​from various sensors (106F, 106B, 107F, 107B, 110-112) (S11). In this embodiment, the distribution board 104 acquires, for example, the front wheel rotation speed NF detected by the rotation speed sensor 106F, the rear wheel rotation speed NB detected by the rotation speed sensor 106B, the front wheel motor temperature tF detected by the temperature sensor 107F, the rear wheel motor temperature tB detected by the temperature sensor 107B, the human-powered torque TH detected by the torque sensor 110, the human-powered rotation speed NH detected by the cadence sensor 111, and the vehicle speed V detected by the vehicle speed sensor 112.

[0039] Next, the distribution board 104 determines (estimates) the assist output PA and deceleration efficiencies RF and RB based on the detection results of various sensors (106F, 106B, 107F, 107B, 110-112) (S12).

[0040] The distribution board 104 determines the human power output PH by substituting, for example, the human power torque TH and the human power rotation speed NH into the following equation 1. The human power output PH is the output input to the pedaling force transmission mechanism 20 by the user of the electric assist bicycle 1. r is the length of the crank arms 22L and 22R (the turning radius of the pedals 23L and 23R). PH=2πr×TH×NH / 60 (Formula 1)

[0041] Furthermore, the distribution board 104 identifies the assist ratio corresponding to the vehicle speed V of the electric assist bicycle 1 based on the relationship shown in Figure 4. In addition, the distribution board 104 determines the assist output PA by multiplying the human power output PH by the assist ratio (i.e., based on the magnitude of the human power output PH). The assist output PA is the output generated by the motor system 100.

[0042] As shown in Figure 4, the greater the human power output PH, the greater the assist output PA. Also, the faster the vehicle speed V, the smaller the assist output PA becomes. 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), and between 10 and 24 km / h, the assist ratio gradually decreases as the vehicle speed V increases, and when the vehicle speed V is above the assist limit (24 km / h), the assist ratio (i.e., the assist output PA) becomes 0.

[0043] The distribution board 104 estimates the deceleration efficiency RF and RB based on the deceleration efficiency map in Figure 5, for example. The distribution board 104 estimates the value corresponding to the front wheel rotation speed NF and the front wheel motor temperature tF from the values ​​R11 to R55 set in Figure 5 as the deceleration efficiency RF. Similarly, the distribution board 104 estimates the value corresponding to the rear wheel rotation speed NB and the rear wheel motor temperature tB from the values ​​R11 to R55 set in Figure 5 as the deceleration efficiency RB.

[0044] The reduction efficiencies RF and RB refer to the ratio (0 to 1) of the output (torque) of the reduction gear 108 to the output (torque) of the wheel motor 102. In other words, the reduction efficiencies RF and RB are complements of the mechanical losses of the reduction gear 108. That is, when power equivalent to the front wheel output PF is supplied to the front wheel motor 102F, the actual output transmitted to the front wheel 7F is PF × RF. Similarly, when power equivalent to the rear wheel output PB is supplied to the rear wheel motor 102B, the actual output transmitted to the rear wheel 7B is PB × RB.

[0045] Figure 4 is a table (two-dimensional array) that holds the reduction efficiencies R11 to R55 of the gearbox 108, corresponding to the rotational speeds N1 to N5 and motor temperatures t1 to t5 of the wheel motor 102. In other words, the distribution board 104 according to this embodiment estimates the reduction efficiencies RF and RB based on the combination of rotational speed and motor temperature of the wheel motor 102.

[0046] Furthermore, assuming the motor temperature t is the same (e.g., t1), the greater the rotational speed N1~N5, the smaller the deceleration efficiency R11~R15 (R11>R12>R13>R14>R15). Also, assuming the rotational speed N is the same (e.g., N1), the greater the motor temperature t1~t5, the smaller the deceleration efficiency R11~R51 (R11>R21>R31>R41>R51). The specific values ​​of the deceleration efficiency map have been determined in advance through experiments and simulations.

[0047] However, the method for estimating the deceleration efficiencies RF and RB is not limited to the example in Figure 4. As another example, the distribution board 104 may estimate the deceleration efficiencies RF and RB based on the rotational speed N of the wheel motor 102, the motor temperature t of the wheel motor 102, and the output torque T of the wheel motor 102. That is, the deceleration efficiency map may be a three-dimensional array that holds the deceleration efficiency R corresponding to the rotational speed N of the wheel motor 102, the motor temperature t of the wheel motor 102, and the output torque T of the wheel motor 102. Note that, assuming the rotational speed N and motor temperature t are the same, the larger the output torque T, the smaller the deceleration efficiency. The output torque T of the wheel motor 102 may be detected by a torque sensor provided on the wheel motor 102, or it may be calculated using equations 10 and 11 described later.

[0048] Furthermore, among the parameters used to estimate the deceleration efficiency RF and RB, at least one of the following can be omitted: the rotational speed N of the wheel motor 102, the motor temperature t of the wheel motor 102, and the output torque T of the wheel motor 102. In other words, the distribution board 104 only needs to estimate the deceleration efficiency RF and RB based on at least one of the rotational speed N of the wheel motor 102, the motor temperature t of the wheel motor 102, and the output torque T of the wheel motor 102. As yet another example, the distribution board 104 may also estimate the deceleration efficiency RF and RB based on the ratio of the output (torque) of the wheel 7 to the output (torque) of the wheel motor 102.

[0049] Next, the distribution board 104 distributes the assist output PA to the front wheel output PF and the rear wheel output PB (S13). As an example, the distribution board 104 may adjust the distribution ratio of the assist output PA to the front wheel output PF and the rear wheel output PB based on the relative magnitudes of the deceleration efficiencies RF and RB, as shown in Equations 2 and 3. More specifically, the distribution board 104 may distribute the assist output PA to the front wheel output PF and the rear wheel output PB in the ratio of the deceleration efficiencies RF and RB. That is, the distribution board 104 should increase the distribution ratio to the front wheel output PF as the deceleration efficiency RF is greater, and increase the distribution ratio to the rear wheel output PB as the deceleration efficiency RB is greater. PF:PB = RF:RB ... (Equation 2) PF + PB = PA ... (Equation 3)

[0050] As another example, the distribution board 104 may set the front wheel output PF and the rear wheel output PB to the same value (=PA / 2). As yet another example, the distribution board 104 may distribute the assist output PA such that the front wheel output PF and the sum of the rear wheel output PB and the human power output PH are the same (i.e., the outputs of the front wheel 7F and the rear wheel 7B are the same), as shown in equations 4 and 5. PF=PB+PH (Formula 4) PF + PB = PA ... (Equation 5)

[0051] Next, the distribution board 104 corrects the front wheel output PF based on the deceleration efficiency RF and corrects the rear wheel output PB based on the deceleration efficiency RB (S14). The distribution board 104 can calculate the corrected front wheel output PF' by dividing the front wheel output PF by the deceleration efficiency RF, for example, as shown in equation 6. Similarly, the distribution board 104 can calculate the corrected rear wheel output PB' by dividing the rear wheel output PB by the deceleration efficiency RB, for example, as shown in equation 7. The distribution board 104 then notifies the front wheel board 105F of the corrected front wheel output PF' and front wheel rotation speed NF, and notifies the rear wheel board 105B of the corrected rear wheel output PB' and rear wheel rotation speed NB. PF' = PF / RF ... (Equation 6) PB'=PB / RB (Formula 7)

[0052] However, the specific method for correcting the front wheel output PF and rear wheel output PB is not limited to the examples described above. As another example, the distribution board 104 may further multiply equations 6 and 7 by a coefficient α (0 ≤ α < 1). The coefficient α is a margin that ensures the sum of the actual outputs of the front wheel 7F and rear wheel 7B does not exceed the assist output PA. As yet another example, the distribution board 104 may use equations 8 and 9 to calculate the corrected front wheel output PF' and the corrected rear wheel output PB'. That is, the distribution board 104 should correct the front wheel output PF such that the corrected front wheel output PF' becomes smaller as the deceleration efficiency RF increases, and correct the rear wheel output PB such that the corrected rear wheel output PB' becomes smaller as the deceleration efficiency RB increases. PF' = PF + PF(1 - RF) ... (Equation 8) PB' = PB + PB(1 - RB) ... (Equation 9)

[0053] Next, the front wheel board 105F drives the front wheel motor 102F to output the corrected front wheel output PF' (S15). More specifically, the front wheel board 105F calculates the front wheel torque TF [Nm] by substituting the corrected front wheel output PF' and the front wheel rotation speed NF into equation 10, and torque-controls the front wheel motor 102F to generate the calculated front wheel torque TF. Similarly, the rear wheel board 105B drives the rear wheel motor 102B to output the corrected rear wheel output PB' (S15). More specifically, the rear wheel board 105B calculates the rear wheel torque TB [Nm] by substituting the corrected rear wheel output PB' and the rear wheel rotation speed NB into equation 11, and torque-controls the rear wheel motor 102B to generate the calculated rear wheel torque TB. TF = PF' / {(NF × 2π) / 60} ... (Equation 10) TB=PB' / {(NB×2π) / 60} (Equation 11)

[0054] As a result, the front wheel 7F is driven by the front wheel torque TF, and the rear wheel 7B is driven by the human power torque TH + rear wheel torque TB. As a result, the electric assist bicycle 1 moves. Note that the human power torque TH, front wheel torque TF, rear wheel torque TB, deceleration efficiency RF, RB, and vehicle speed V are values ​​that change with each control cycle (each time the motor control process is executed).

[0055] [Effects of the Embodiment] According to the above embodiment, by correcting the front wheel output PF and rear wheel output PB considering the reduction efficiency RF and RB of the reducer 108, the sum of the actual outputs of the front wheel 7F and rear wheel 7B can be brought closer to the assist output PA compared to Patent Document 1, which does not consider the reduction efficiency RF and RB. This makes it possible to obtain a motor system 100 with improved assist accuracy.

[0056] Furthermore, according to the above embodiment, the accuracy of estimating the deceleration efficiency RF and RB is improved by estimating the deceleration efficiency RF and RB based on at least one of the rotational speed, motor temperature, and output torque of the wheel motor 102. As a result, the assist accuracy of the motor system 100 is further improved.

[0057] Furthermore, according to the above embodiment, the assist accuracy of the motor system 100 is further improved by biasing the output of the front wheel motor 102F and the rear wheel motor 102B towards the side with higher deceleration efficiency RF and RB.

[0058] [Other variations] The electric vehicles to which the motor system 100 can be applied are not limited to the electric assist bicycle 1. As another example, the electric vehicles to which the motor system 100 can be applied may have multiple front wheels 7F and / or rear wheels 7B, or may have a pair of wheels on the left and right sides instead of front wheels 7F and rear wheels 7B. As yet another example, the electric vehicles to which the motor system 100 can be applied are not limited to those that rotate the wheels 7 by assisting the user's pedaling force with the wheel motor 102, but may also be those that run solely on the propulsion force of the wheel motor 102 (e.g., kick scooters, certain small mopeds). Furthermore, the motor system 100 can be applied not only to electric vehicles but also to any device driven by an electric motor (e.g., radiator fans, power windows, electric oil pumps, etc.).

[0059] Embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the described configurations. Furthermore, it is possible to replace some of the configurations of this embodiment with those of other embodiments, and it is also possible to add configurations from other embodiments to the configuration of this embodiment. Moreover, it is possible to add, delete, or replace some of the configurations of this embodiment with those of other embodiments. [Explanation of symbols]

[0060] 1...Electric assist bicycle, 2...Main body, 3...Frame, 4...Front fork, 5...Saddle, 6...Handlebars, 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...Pedaling force transmission mechanism, 21...Crank axle, 22L,22R...Crank arm, 23L,23R...Pedal, 24...Drive gear, 25...Driven gear, 26...C Chain, 30...Brake mechanism, 31L, 31R...Brake lever, 32...Front brake, 33...Rear brake, 100...Motor system, 101...Battery, 102B...Rear wheel motor, 102F...Front wheel motor, 103...Motor control device, 104...Distribution board, 105B...Rear wheel board, 105F...Front wheel board, 106F, 106B...Rotation speed sensor, 107F, 107B...Temperature sensor, 108F...Front wheel reducer, 108B...Rear wheel reducer, 110...Torque sensor, 111...Cadence sensor, 112...Vehicle speed sensor

Claims

1. In a motor system that assists the driving of a human-powered vehicle comprising a first wheel, a second wheel, and an input unit to which human power output for driving the second wheel is input, First motor and second motor, A first reduction gear that reduces the rotation of the first motor and transmits it to the first wheel, A second reduction gear that reduces the rotation of the second motor and transmits it to the second wheel, The system includes a motor control device that adjusts the outputs of the first motor and the second motor, The motor control device is Based on the aforementioned human power output, the assist output of the motor system is determined. The assist output is distributed to the first output and the second output. Based on the first reduction efficiency of the first reduction gear, the first output is corrected, and the corrected first output is generated by the first motor. A motor system characterized by correcting the second output based on the second reduction efficiency of the second reduction gear, and generating the corrected second output in the second motor.

2. In the motor system according to claim 1, The motor control device is The first deceleration efficiency is estimated based on at least one of the rotational speed of the first motor, the temperature of the first motor, and the output torque of the first motor. A motor system characterized by estimating the second reduction efficiency based on at least one of the rotational speed of the second motor, the temperature of the second motor, and the output torque of the second motor.

3. In the motor system according to claim 2, The motor control device is characterized by distributing the assist output to the first output and the second output in the ratio of the first reduction efficiency and the second reduction efficiency.

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