JP3480998B2 - Vehicle with electric motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a driving system driven by human power and a driving system driven by an electric motor in parallel, and controls the driving force driven by the electric motor in response to changes in driving force driven by human power (hereinafter referred to as pedaling force). The present invention relates to a vehicle with an electric motor.

[0002]

2. Description of the Related Art It is known to detect a pedaling force and control a driving force of an electric motor, that is, a motor assist amount in accordance with the magnitude of the pedaling force (Japanese Utility Model Laid-Open No. 56-76590, JP-A-2-74491). ). That is, when the burden of human power is large, the driving force of the electric motor is also increased to reduce the load of human power.

It is also considered to determine the assist amount of the motor based on the pedal effort and the vehicle speed. Here, the assist amount of the motor is calculated by a constant cycle, and the obtained result is used as the target assist amount to control the motor.

[0004]

[Problems of the prior art] In this case, when the pedaling force suddenly changes, the target assist amount also greatly changes.
For example, when the pedaling force suddenly increases, the target assist amount also rapidly increases, so that the motor current also rapidly increases and a large impact is applied to the drive system. As a result, the riding comfort becomes poor. In addition, since the motor rotation speed is low especially at the time of starting the vehicle, when the target assist amount becomes large, the motor current becomes excessive and the battery consumption is accelerated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and prevents a sudden change in the assist amount of a motor at the time of a sudden change in pedaling force and reduces the impact on the drive system to improve the riding comfort. It is also an object of the present invention to provide a vehicle with an electric motor that can prevent excessive motor current from flowing and prevent battery consumption.

[0006]

According to the present invention, an object of the present invention is to provide a vehicle with an electric motor in which a human power drive system and an electric drive system are provided in parallel and the output of the electric drive system is controlled in response to a change in the driving force due to human power. In the above, the human power driving force detection means, the travel control means for calculating the target assist amount of the motor for each constant cycle based on the detected human power driving force, and controlling the motor assist amount to the target assist amount, Achieved by a vehicle with an electric motor, characterized by further comprising auxiliary force limiting means for gradually increasing or decreasing the target assist amount at each of the constant cycles while limiting the amount of change in the target assist amount obtained before and after within a certain range. To be done.

[0007]

1 is a side view of an embodiment of the present invention, FIG. 2 is a power system diagram thereof, and FIG. 3 is a block diagram showing the function of its controller.

[0008]

[Vehicle Configuration] First, the overall configuration of the vehicle body will be described with reference to FIGS. In FIG. 1, reference numeral 10 denotes a main frame, a down tube 14 extending obliquely downward and rearward from the head pipe 12, and a pair of left and right chain stays 16 extending rearward from a lower end of the down tube 14 (only one is shown).
A seat tube 18 and a pair of left and right auxiliary stays 20 (only one of which is shown) that stand upright from the lower portion of the down tube 14, a seat tube 18 and an auxiliary stay 2
A pair of left and right back stays 22 (only one of which is shown) are connected to the rear end of the chain stay 16 at the upper end of 0.

A front fork 24 is rotatably held on the head pipe 12, and a front wheel 26 is attached to the lower end and a bar handle 28 is attached to the upper end. Seat tube 18
A seat post 30 is inserted from above and fixed so that its height can be adjusted, and a saddle 32 is attached to the upper end thereof.

Reference numeral 34 denotes a power unit, which is a unit in which a bottom bracket case (hereinafter referred to as a BB case) 36 and a permanent magnet type DC electric motor 38 are integrated. The BB case 36 is a bracket 40,
It is fixed to the lower rear part of the down tube 14 by 42. A crankshaft 44 is inserted through the BB case 36 of the power unit 34, and cranks 46 are fixed to both ends thereof. Crank pedals 48, 48 are attached to the crank 46.

The power unit 34 is internally provided with gears, sprockets and the like (not shown) for transmitting the rotation of the crankshaft 44 to the chain 52 via the crankshaft side one-way clutch 50 (FIG. 2). A planetary gear mechanism is interposed between the crankshaft 44 and the chain 52.

In this planetary gear mechanism, pedaling force is input from the planetary gear and pedaling force is output from the ring gear to the chain 52. Then, the pedaling force F is detected by detecting the torque applied to the central sun gear by the pedaling force detection mechanism 54 including a potentiometer. The rotation of the motor 38 is transmitted to the chain 52 via the planetary roller reducer 56 and the motor-side one-way clutch 57.

Reference numeral 58 denotes a rear wheel, which is attached to a rear end of the chain stay 16, that is, a connecting portion between the chain stay 16 and the back stay 22. Here, the hub of the rear wheel 58 is a free wheel 60, and the chain 52 drives the rear wheel 58 only in the forward direction. In FIG. 1, reference numeral 62 denotes a rechargeable battery such as a lead battery, and the seat tube 18
And the auxiliary stay 20 are mounted in a vertically long battery case 64 arranged vertically from above.

A rotation sensor 66 for detecting the rotation speed of a sprocket (not shown) around which the chain 52 is wound is attached to the BB case 36. The rotation sensor 66 also serves as vehicle speed detecting means for detecting the vehicle speed S.
Reference numeral 68 denotes a control unit, which is mounted below the front portion of the down tube 14. The control unit 68 and the power unit 34 are covered with a cover 70.

A pedaling force detection mechanism 5 including a potentiometer
The pedaling force F detected in 4 and the vehicle speed S detected by the vehicle speed sensor 66 are input to the control unit 68, and the control unit 68 controls the motor current based on the pedaling force F and the vehicle speed S to output the motor output, that is, the motor torque. Generate T _M.

The control unit 68 is constructed as shown in FIG. The motor 38 and the battery 62 form a closed circuit together with the switching circuit 72, and this closed circuit serves as the main circuit 74. The switching circuit 72 is composed of, for example, a MOS-FET. A flyhole diode 76 is connected in parallel to the motor 38, and a shunt 78 for current detection is used.
Are attached to the main circuit 74.

Reference numeral 80 denotes a CPU, which outputs a command value i for the output (torque) T _M of the motor 38 based on the pedaling force F and the vehicle speed S.
Is output. That is, the command value i is output so that the output (torque) T _M of the motor 38 is periodically increased / decreased in synchronization with the periodic increase / decrease of the pedal effort F. Further, when the vehicle speed S becomes constant, the motor output T _M may be limited to limit the vehicle speed S.

Reference numeral 82 denotes a gate circuit, which outputs a gate signal g for driving the switching circuit 72 in response to a command value i supplied from the CPU 80 in which the duty ratio changes. That is, when increasing the motor output T _M , the value of (ON time) / (OFF time + ON time) (referred to as duty) of the command value i is increased.

The gate signal g output by the gate circuit 82 based on the command value i is sent to the switching elements of the switching circuit 72 to selectively turn on / off each switching element.

In FIG. 3, reference numeral 84 is a main key switch. When the main switch 84 is turned on, the CPU 8
0 turns on the main relay 86 interposed in the main circuit 74, and also supplies the power supply unit 88, the auxiliary device control unit 90, and the gate circuit 8
2. All other parts of the control unit 68 are activated. The power supply unit 88 steps down the voltage of the battery 62 for traveling by using, for example, a switching regulator to generate the power supply voltage of the CPU 80, the drive voltage of the auxiliary device 92, and the like.

A small-capacity battery (not shown) different from the battery 62 is connected to the power source 88, and the voltage of the battery 62 is reduced by a switching regulator to charge the small-capacity battery. Is also good. The auxiliary device 92 includes lamps and meters, which are driven by the electric power of the power supply part 88 in accordance with a command from the auxiliary device control part 90.

[0022]

[Functions of CPU] Next, the functions of the CPU 80 will be described with reference to FIG.
13 is used for the explanation. The CPU 80 has various functions operated by software. This function is roughly classified into the following four, as shown in FIG. That is, the running / stop control function 100, the stop processing function 102, the system protection function 104, and the failure diagnosis function 106. The system protection function 104 and the failure diagnosis function 106 can be repeated at appropriate timing during other processing of the CPU 80, for example, about 10
It is processed every msec. Figure 4 shows the run / stop control function 1
00 is a flowchart showing the outline of the operation of the system 00, and FIG. 5 is a flowchart showing the outline of the operation of the system protection function 104 and the failure diagnosis function 106.

[0023]

[Running / Stopping Control] The running / stopping control function 100 performs various operations from start to stop determination based on turning on of the main key switch 84, for example, 10 msec.
Repeat each time. The contents of the function 100 will be described below by function.

[0024]

[Start Determination / Start Torque Sliding Function] First, the start determination function 110 will be described. This function 110 has a constant pedaling force F (start determination pedaling force reference value F ₀ , for example, 3
When it becomes 0 kg or more, it is considered that the intention of the start has been shown, and the running control state is entered via the start torque slide control function 120 described below.

Even when the start determination function 110 indicates the intention to start, the start torque slide control 120 displays the result of the start determination when the vehicle speed S remains 0 for a certain period (for example, 3 seconds) from that point. It is something to cancel. For example, there is a case where a pedaling force is applied while applying a brake so as not to start. At this time, the motor 38
When is driven in the same manner as during normal traveling, a large current continues to flow through the motor 38, accelerating the consumption of the battery 62 and adding a heavy load to the drive system. Therefore, the start is interrupted after a certain period of time.

When the vehicle is stopped with a constant pedaling force applied, for example, when the front wheel is in contact with a wall and a load is applied to the pedal, the motor current flows or stops at regular intervals. It is not preferable to repeat the above operation. Therefore, in this embodiment, a constant value for determining the start (start determination pedal force reference value F ₀ ) is increased by a constant amount α each time the start determination operation is performed.

FIG. 6 is a flow chart of the operation. In the present embodiment, when the main key switch is turned on while the vehicle is stopped or running only by human power, the start waiting mode is automatically set, so that the start waiting mode is determined in step 110A. This start waiting mode determination step 110A is for determining whether or not the current mode is the start waiting mode. In the start waiting mode, if the pedaling force F is greater than or equal to the reference value F ₀ , it is determined that there is a will to start (step 110).
B).

If F ≧ F _{0, the} motor assist is started and the mode is set to the soft start mode (step 110D). Next, the start torque slide control 120
to go into. In this control 120, the timer is first activated (step 120A). If the mode is not the start waiting mode, it is already running, so this start judgment 1
10 and the start torque slide control 120 are bypassed, and the next process, the soft start 130, is entered.

Then, it is checked whether or not the vehicle speed S is 0 (step 120B), and if S = 0, then it is checked whether or not the timer measurement time t reaches a constant value t ₀ (for example, 3 seconds) (step 120C). ). If S ≠ 0, it is determined that the vehicle is actually running, and F ₀ is not changed (step 12
0D) End the start determination function.

If t has reached t ₀ , the reference value F _{0 is set} to F
_It is increased to ₀ + α (step 120D), and the motor assist is controlled to be stopped (step 102). Then, the process returns to the start waiting (step 110A) again. If t has not reached t ₀ , the process returns to the determination of whether the vehicle speed S is 0 (step 120B). If the pedaling force F is still applied and F ≧ F ₀ + α, it is determined that there is a will to start (step 110B), and motor assist is started (step 110D). Repeat this operation n times F
If <F ₀ + nα, motor assist is not performed (step 110B).

[0031]

[Soft start] If the assist amount according to the calculation result (hereinafter referred to as the target assist amount) is suddenly given when the motor assist starts, an inrush current flows to the motor and the impact becomes large. Therefore, a soft start function 130 for smoothly increasing the assist amount actually given as a command value (hereinafter referred to as the actual assist amount) is provided. That is, 10% of the actual assist amount every fixed time (for example, 0.015 seconds)
Is added to the actual assist amount, and when the target assist amount is reached, the mode is set to the traveling mode and the process proceeds to the traveling control 140.

[0032]

[Travel control] The traveling control means 140 in normal traveling is
The optimum target assist amount is calculated in consideration of the vehicle speed S, the pedaling force F, the power supply voltage, the motor current, etc., and the assist amount is updated every fixed time (for example, 0.01 seconds). At that time, the amount of change from the previous assist amount is limited to obtain a smooth assist feeling. That is, as shown in FIG. 4, auxiliary force limiting means (step 140A) is provided.

FIG. 7 is a flow chart of the operation of the assisting force limiting means 140A, and FIG. 8 is a diagram showing an example of the change of the assisting force with time. In this embodiment, since the motor current is PWM controlled, the motor current is represented by its duty D%, and the constant period τ
The change of the target duty D (equivalent to the target assist amount, duty is equivalent to the assist amount in the following description) calculated every (0.01 seconds) is prevented from exceeding a fixed value (for example, 10%). It is a thing.

That is, referring to FIG. 7, first, the target duty D _{N of} this time and the target duty D _N-1 of the previous time before the time τ are stored (step 140B), and if the duty D is increasing (step 140C). ), The duty D _N-1 is increased by 10% to be D ₁ (step 140D). Since D _N <D ₁ if the target duty D _N is an increase of 10% or less relative to the previous target duty D _N-1 (step 140E), at the D ₂ = D _N a (step 140E) The D ₂ The motor output is controlled as the target duty (step 140G). Then, D ₂ is set as the previous target duty D _N-1 (step 140
H) Return to step 140B.

If D _N is greater than or equal to D _{1 in} step 140E, it means that the target duty has increased by 10% or more, and D ₂ = D ₁ is set (step 140I),
This D ₂ is controlled as the target duty (step 1
40G).

If the target duty is decreasing (step 140C), the previous target duty D _N-1 is reduced by 10% to D ₁ (step 140J). And D _N
If> D ₁ (step 140K), the decrease width is within 10%, so _DN is set to the target duty D ₂ (step 14K).
0L), and if D _N ≦ D _{1, the} decrease range is 10% or more,
Let D ₁ be the target duty D ₂ (step 140
M).

The above operation is shown by the solid line A in FIG. The virtual line B shows the change of the duty D when the control by the auxiliary force limiting means 140A is not performed. As described above, by using the means 140A, the increase and decrease of the motor current can be smoothed, the riding comfort can be improved, and the impact applied to the drive system can be reduced. Further, especially when the motor speed is low at the time of starting, the excessive current is limited, and the consumption of the battery 62 is prevented. Note that this traveling control limits the motor assist rate at high speeds. For example, a map that defines the assist rate for the vehicle speed S and the pedaling force F may be set in advance to have a small assist rate at high speed.

[0038]

[Stop determination control] In this embodiment, the intention to stop is determined by using the pedaling force F and the vehicle speed S without using the brake switch. FIG. 9 is a flow chart of this determination operation.

First, when the vehicle speed S is 0 (step 150
A) If the pedaling force F is less than a constant value F ₁ (for example, 12 kg, which corresponds to about 2 kg · m in torque) (step 150
B), start the stop determination timer and continue the integration if the timer is already integrating (step 150).
C, 150D). The integrated value t of this timer is a constant value t _0.
When (for example, 1 second) is reached (step 150E), a stop process for setting the motor output to 0 is started (step 1
02).

When F <F ₁ is not satisfied (step 150
B) and F are F ₂ (F ₂ is larger than F ₁ , for example, 30
If the variation width ΔF of the pedaling force F is equal to or less than a constant value ΔF ₀ (for example, 12 kg) (step 150H), another timer is started and the integration is continued as it is if the timer is already integrating. (Steps 150I, J), the integrated time t ₁ is a constant value t
_{If 10} (for example, 2 seconds) continues, it is determined that there is a will to stop (step 150K). When the vehicle speed S is other than 0 (step 150
A) or when the above conditions are not met, the timer is reset (step 150L) and the process returns to step 110. At this time, the mode is maintained as it is.

When it is determined that the vehicle has the intention to stop as described above, the stop process (step 102) is started, the motor output is gradually reduced, and the mode is set to the start waiting mode to prepare for the next running. That is, it waits for the pedaling force F to be input again. In addition, pedaling force F, vehicle speed S
When there is no input signal from outside such as, it enters energy saving mode. For example, the gate circuit 82, the main relay 86, the power supply unit 88, and the like are powered off, and the CPU 80 also stops operating except for the function of detecting the presence or absence of an external input.

[0042]

[System Protection] Next, the system protection function 104 will be described. As shown in FIG. 5, this function includes a battery overvoltage check function 160, a battery low voltage check function 170, a low power consumption mode determination function 180, and the like.

The battery overvoltage check 160 protects the system when the battery is replaced with a high voltage battery by remodeling. That is, the main key switch 84 (FIG. 3)
When is turned on, it is checked whether or not the battery voltage is above a certain value, and if it is above a certain value, the control is stopped to restrict traveling and the energy saving mode is entered. By doing so, it is possible to reliably prevent traveling while charging. Even if the battery voltage returns to normal in this state, it is desirable to improve safety by preventing the vehicle from traveling unless the main key switch 84 is once turned off.

The battery low voltage check function 170 protects the battery from over discharge when the battery voltage drops extremely. Here, the battery voltage recovers and rises when the control is stopped and the discharge current is cut off even if the battery voltage extremely drops during traveling.
For this reason, control becomes possible again, but over-discharge of the battery progresses and battery consumption increases. So the main key switch 8
Immediately after turning on 4, voltage check is performed under no load condition,
When it is less than the set value, it is desirable to prohibit the subsequent control and issue a warning.

The battery low voltage check function 170 may be performed as shown in FIG. That is, the battery voltage V
_{B is set} to two threshold values V _th1 and V _th2 (V _th1 <V
_th2 ) (steps 170A, 170B), V
_{If th1} or less, the LED is continuously turned on and the timer is started (step 170C). Then, the timer is set to a fixed time t
_{When 20} (for example, 5 seconds) is added up (step 170D),
All controls are stopped (step 192).

If V _B is between V _th1 and V _th2 (steps 170A and 170B), the LED is blinked to call attention (step 170F). If V _B is V _th2 or more, there is no problem with the battery voltage, so another control is performed (step 170G).

As described above, when the voltage V _B is equal to or lower than V _{th1, the} control is not stopped immediately, but if the LED is continuously turned on by the timer and the control is stopped after a certain time, the vehicle is prevented from stopping suddenly. You can For example, when the vehicle starts at an intersection or the like, the voltage may drop and the LED may start to light up before the crossing ends. However, even in such a case, it is possible to drive as it is within the timer set time t ₂₀ and cross the intersection. It will be possible.

The low power consumption mode discriminating function 180 discriminates the above-mentioned energy saving mode, and is in a stopped state (S
= 0) and the input signal of the vehicle speed S is not continuously for a fixed time (for example, 5 minutes), the energy saving mode is set. In this mode, the gate circuit 82, the main relay 86, etc. are powered off as described above, and the CPU 80 also stops operating.

The fault diagnosis function 106 detects various abnormalities, and if there is an abnormality, the abnormal battery voltage is detected (step 16).
0, 170) and issues a warning (step 190),
The control is stopped (step 192). In step 192 of this control stop, the main relay 86 is turned off, and the CPU
80 also leaves the warning process and the low power consumption mode determination function and stops other operations. FIG. 11 is an operation flow chart showing an abnormality detection function of the vehicle speed sensor 66 as an example of the failure diagnosis function 106, and FIG. 12 is an operation explanatory view thereof.

The abnormality detection of the vehicle speed sensor 66 is determined because the output of the vehicle speed sensor 66 is not present before and after starting. That is, when this operation starts (step 10
6A), if the output of the vehicle speed sensor 66 (vehicle speed S) is 0 (step 106B), the fluctuation width ΔF of the pedal effort F is detected (step 106C). As shown in FIG. 12, the fluctuation width ΔF is obtained by the difference ΔF _n = F _{n + 1} −F _n between the pedaling forces F _n and F _{n + 1} detected at every constant time τ ₁ . This time τ ₁ is set to 0.5 seconds, for example.

ΔF _n is compared with a constant value ΔF ₀ (step 106D), and if ΔF _n ≧ ΔF _{0, a} timer is started (step 106E), and when the integrated value t ₃ reaches a constant value t ₃₀ , the vehicle speed sensor 66 is informed. There is an abnormality (Step 1
06G). That is, a warning is issued and the timer is reset. Then, the control is stopped (step 192). If the vehicle speed S ≠ 0 before the integrated value t _{3 of the} timer reaches t ₃₀ (step 106B) or ΔF <ΔF ₀ (step 106D), the timer is reset as no abnormality (step 106I), etc. Control (step 10)
6J).

Thus, even if the vehicle speed S is 0, the pedal effort F
When the fluctuation width ΔF of the vehicle speed sensor 66 exceeds a certain value, it is determined that the vehicle speed sensor 66 is abnormal. Therefore, even if the vehicle speed sensor 66 is disconnected or its output disappears, the abnormality can be detected. As described above, if the failure diagnosis 106 is terminated and there is no abnormality, the control returns to other normal control (step 194, FIG. 5).

Failure diagnosis function 106 of this vehicle speed sensor 66
A can be configured as shown in the functional block diagram of FIG. That is, the vehicle speed S detected by the vehicle speed detecting means including the vehicle speed sensor 66 is S = 0 by the vehicle speed determining means 200.
It is determined whether or not. Reference numeral 202 denotes a fluctuation range detecting means of the pedal effort F. The fluctuation range ΔF obtained here is input to the fluctuation range comparison means 204 when the vehicle speed S is 0, and here, a constant value ΔF _0.
Is compared with ΔF> ΔF ₀ and the timer start signal T
Output _s .

Reference numeral 206 denotes a timer, which is set by the timer start signal T _s and starts counting time. The timer 206 outputs an abnormality determination signal I when the integrated value reaches a certain time t ₃₀ . The abnormality determination signal I is stored in the buffer memory 208, while at the same time causing the warning means 210 to generate a warning and causing the stop processing means 212 to perform control stop processing. Also, the timer 206 is reset.

In this embodiment, auxiliary force limiting means 140A
Then, the target assist amount calculated by the pedaling force F or the pedaling force F and the vehicle speed S is represented by a duty, and the variation amount in each constant cycle is limited to ± 10% or less. Not limited to. For example, the amount of change in the target assist amount may be limited to within a certain ratio of the motor drive torque, or the amount of change in duty or torque may be set within a range determined numerically.

[0056]

As described above, the invention of claim 1 is provided with the assisting force limiting means for limiting the variation amount of the target assist amount obtained corresponding to the human driving force within a certain range within a certain range. Therefore, the assist amount of the motor changes smoothly even if the human-powered driving force drastically changes. Therefore, the mechanical impact applied to the drive system is reduced, and the riding comfort is improved. Further, since the motor current does not become excessive when starting, it is possible to prevent battery consumption.

Here, the target assist amount may be determined not only by the human power but also by the vehicle speed (claim 2). In this case, it is possible to prevent the vehicle speed from becoming excessive by limiting the assist amount at the time of high speed, and it is possible to reduce the energy consumption of the battery.

[Brief description of drawings]

FIG. 1 is a side view of a bicycle with a motor according to an embodiment of the present invention.

[Fig. 2] Power system diagram

FIG. 3 is a functional block diagram of a controller

[Figure 4] Flow chart for running and stopping

[Fig. 5] Operation flow chart for system protection and fault diagnosis

FIG. 6 is an operation flow chart of start torque slide control.

FIG. 7 is an operation flow chart of the auxiliary force limiting function.

FIG. 8 is a diagram showing an example of the change over time of the assisting force.

FIG. 9 is an operation flowchart of stop determination control.

FIG. 10 is an operation flow chart of the battery low voltage check function.

FIG. 11 is an operation flowchart of a vehicle speed sensor failure diagnosis.

FIG. 12: Flow chart of the operation

FIG. 13 is a functional block diagram of the same.

[Explanation of symbols]

38 motor 44 crankshaft 54 Pedal force sensor as means for detecting human driving force 66 Vehicle speed sensor as vehicle speed detecting means 80 CPU 140 Travel control means 140A Auxiliary force limiting means F Treading force as human power S vehicle speed

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoichiro Miyata 2500 Shinkai, Iwata, Shizuoka Prefecture Yamaha Motor Co., Ltd. (72) Inventor, Yasuo Suganuma 2500 Shinkai, Iwata, Shizuoka Yamaha Motor Co., Ltd. (56) References JP-A-2-74491 (JP, A) JP-A-4-321482 (JP, A) JP-A-4-358987 (JP, A) JP-A-56-17775 (JP, A) Actual development Sho-56 -76590 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B62M 23/02 B60L 15/28 B62K 11/00

Claims (2)

(57) [Claims] 1. A vehicle with an electric motor, wherein a human-powered drive system and an electric drive system are provided in parallel, and the output of the electric drive system is controlled in response to changes in the drive force due to human power. Travel control means for calculating the target assist amount of the motor for each constant cycle based on the detected human-powered driving force and controlling the motor assist amount to this target assist amount, and the change of the target assist amount obtained before and after the constant period. A vehicle with an electric motor, comprising: auxiliary force limiting means for gradually increasing or decreasing the target assist amount for each of the constant cycles while limiting the amount within a certain range. 2. The vehicle with an electric motor according to claim 1, further comprising a vehicle speed detection means, wherein the travel control means calculates a target assist amount based on the vehicle speed and the human-powered driving force.