JPH08163701A - Electric vehicle - Google Patents

Abstract

PURPOSE: To provide a comfortable ride, to efficiently drive a motor and to eliminate the driving noise of the motor at the time of starting by driving the motor at a high PWM frequency when a traveling speed is smaller than a predetermined speed and at a low PWM frequency when the traveling speed is larger than the predetermined speed. CONSTITUTION: When the traveling speed detected by a traveling speed detector 2 is smaller than a speed V previously stored in a microcomputer 12 and a motor current value detected by a load detector 16 is smaller than a predetermined motor current value A, the motor M is driven by a high PWM frequency. Then, when the traveling speed is larger hen the speed V and the motor current value is smaller than the value A, the motor is driven at the small PWM frequency. Thereafter, when the current value exceeds the predetermined value A despite the traveling speed during traveling, the motor M is controlled by further lower frequency, and hence it can efficiently cope with the load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric vehicle such as an electric wheelchair or an electric vehicle that is driven by a motor.

[0002]

2. Description of the Related Art Conventionally, a PWM used in this type of electric vehicle
For the control signal, for example, a PWM frequency is set to an arbitrary value between 300 hertz and 1 kilohertz, and operation is performed at the PWM frequency. Then, the duty at the frequency is set to 50% or 25% to change the energization voltage to the motor to change the motor rotation speed.

However, when the PWM frequency is a low frequency, for example, around 50 hertz, as shown in FIG. 7A, the power supply loss is small but the frequency becomes large, so that cogging is likely to occur and uneven rotation of the motor occurs. This causes a problem that vibration increases during driving and riding comfort deteriorates. Further, at a high frequency, for example, near 5 kHz, as shown in FIG. 7 (B), there is a loss at the rising delay at ON and the falling delay at OFF (the portion between the broken lines), The higher the frequency,
Although the riding comfort is good, there is a problem that the loss increases as the frequency increases, and the motor does not rotate efficiently.

For this reason, conventionally, in this type of electric vehicle, PWM control has been performed by setting the frequency at which the ride comfort is reasonably good and the loss is reasonably low to an arbitrary value. In other words, there is a slight problem in loss and ride comfort, and since the drive is performed at a frequency that considers loss and ride comfort, that is, a frequency between 300 hertz and 1 kilohertz, the motor drive sound is heard at low speeds, which is very annoying. Was offering an electric car.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a quiet electric vehicle which is comfortable to ride on, can drive a motor efficiently, and has no driving noise of the motor when starting.

[0006]

According to the present invention, there is provided an electric vehicle main body which drives a motor for traveling, a motor drive circuit for PWM controlling the motor, and a traveling speed detector for detecting the traveling speed of the electric vehicle main body. When the traveling speed detected by the traveling speed detector is smaller than a predetermined speed V that is set in advance, the motor is driven at a high PWM frequency, and when the traveling speed is higher than the predetermined speed V, a small PWM frequency F
And a control circuit for driving the motor.

Further, a load detection circuit for detecting the motor load is provided, and the control circuit switches the PWM frequency F to a frequency f lower than F when the load is a predetermined load Z or more. To do.

Furthermore, an electric vehicle main body that drives a motor to run, and a motor drive circuit that PWM-controls the motor,
A traveling speed detector for detecting a traveling speed of the electric vehicle main body, a load detecting circuit for detecting the motor load, a traveling speed detected by the traveling speed detector is smaller than a predetermined speed V, and When the detected value of the load detection circuit is smaller than a predetermined load Z, a motor is driven at a high PWM frequency, and when the traveling speed is smaller than V and the load is larger than Z, the traveling speed is When the load is larger than V and the load is smaller than Z, the motor is driven at a low PWM frequency F, and when the traveling speed is larger than V and the load is larger than Z,
The motor is driven at a PWM frequency f smaller than the PWM frequency F.

The load detection circuit is a current detector for detecting the motor current.

Further, the load detection circuit is an inclination sensor for detecting an inclination angle of the electric vehicle main body.

Further, the load detection circuit is a weight sensor for detecting a load weight applied to the electric vehicle main body.

The high PWM frequency is approximately 15 kHz or higher and the low PWM frequency is lower than 15 kHz.

[0013]

According to the structure of claim 1 of the present invention, this electric vehicle runs by driving the motor at a high PWM frequency at low speed. Then, when the traveling speed detector detects the predetermined speed V or higher, the control circuit switches to the low PWM frequency F to drive the motor.

According to the second aspect of the invention, the predetermined load Z is set in advance when a heavy load such as heavy load or uphill is applied, and when the value becomes equal to or more than Z,
Switch to the PWM frequency f with low loss.

Further, according to the structure of claim 3, when the value of the load is smaller than the predetermined speed V and the value of the load is smaller than the predetermined value A, the motor is driven at a high PWM frequency, and the speed is smaller and larger than the predetermined speed V. When a load is applied, that is, when Z is exceeded, when the load is greater than the predetermined speed V and the predetermined load Z
When it is smaller than P, the motor is driven at the PWM frequency F, and when it is larger than the predetermined speed V and larger than the predetermined load Z, the PWM frequency is switched to f and P with less loss is generated.
Drive the motor at WM frequency.

The load detection circuit detects the value of current flowing through the motor, the inclination angle of the electric vehicle body, or the loaded weight of the electric vehicle body.

Further, the high PWM frequency is about 15 kHz or higher, and the low PWM frequency is lower than 15 kHz.
M control is performed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. 1 to 4 by taking an electric tricycle as an example. In the present embodiment, an electric tricycle has been taken as an example, but the present invention is not limited to electric tricycles, but relates to electric cars in general, and to all PWM-controlled electric cars.

Reference numeral 1 is a main body of an electric three-wheeled vehicle. A drive wheel 2 rotated by a motor M described later is provided at the rear of the main body 1, and one front wheel (not shown) is provided at the front. The front wheels are connected by a handle shaft 3, and a bar handle 4 is provided above the handle shaft 3. By moving the bar handle 4 to the left and right, the front wheels can be moved to the left and right, and steering can be performed.

Reference numeral 5 denotes a floor portion provided between the drive wheels 2 and the front wheels, on which a user puts his / her foot when the user gets on the floor. The floor portion 5 is a frame extending in the front-rear direction (not shown). (Not shown) is fixed on the outer periphery of which is made of resin.

Reference numeral 6 denotes a cover at the rear of the floor 5 for accommodating a battery, a motor, a speed reduction mechanism, and the like.
A chair 7 on which a user rides is provided above.

Reference numeral 8 denotes an accelerator lever that rotates horizontally about one point, and is biased by a spring so as to always return to the front side.

Reference numeral 9 is a display panel provided with a display section for displaying the remaining amount of the battery and the like, and a switch for switching between forward and backward movement and traveling speed.

Next, the control circuit will be described with reference to FIG.

Reference numeral 10 is a battery such as a lead storage battery, and two batteries 12 having a voltage of 12 V are connected in series.
Further, 11 is a constant voltage circuit for stepping down the voltage from the battery 10 and outputting it to the microcomputer 12. The battery M drives the motor M.

Reference numeral 13 is a power switch provided on the display panel 9, and when the power switch 13 is turned on, the microcomputer
A signal is input to 12.

Reference numeral 14 is an accelerator volume whose resistance value changes in association with the movement of the accelerator lever 8. A signal from the accelerator volume 14 is input to the microcomputer 12 as an electric signal.

Reference numeral 15 is a forward / backward switch for switching the traveling direction back and forth. The forward / backward switch 15 causes the motor M to rotate in the forward and reverse directions by the FET in the motor drive circuit 18, which will be described later.

Reference numeral 16 is a load detection circuit for detecting a load applied to the electric tricycle body 1. In the present embodiment, this is used as a current detector to detect the motor M current and the microcomputer 12
I am trying to capture the current value.

Reference numeral 17 is a frequency switching circuit for switching the PWM frequency for driving the motor M. The frequency switching circuit 17 is 1
The signal from the microcomputer 12 set in three stages of 00 hertz, 500 hertz and 15 kilohertz is switched to each frequency according to the condition to drive the motor.

Reference numeral 18 is a PWM from the frequency switching circuit 17.
A motor drive circuit that performs duty control based on a signal of the accelerator volume 14 based on a frequency, and the motor drive circuit 18 determines the rotation speed of the motor M by turning on and off an FET (not shown). .

Reference numeral 19 is an electromagnetic brake for stopping and fixing the rotation of the motor M. The electromagnetic brake 19 is designed so that a signal from the microcomputer 12 is input to the electromagnetic brake drive circuit 19 to operate the electromagnetic brake 20. . This electromagnetic brake 20
Is operating when the vehicle stops at zero traveling speed or when it reaches a critical speed.

Reference numeral 21 is a traveling speed detector that detects the traveling speed of the main body 1 and inputs a signal to the microcomputer 12. The traveling speed detector 21 is an encoder that detects the rotational speed of the wheels and the motor M. ing.

Next, the frequency for PWM control will be described with reference to FIG.

The waveform shown in FIG. 2 (A) is a PWM frequency with a frequency of 15 kilohertz, and there is a delay in the rising portion, the falling portion, and the portion indicated by the arrow between the broken lines in the figure when ON. This portion becomes a loss of electric power when driving the motor.

The waveform shown in FIG. 2B has a frequency of 500.
At the PWM frequency of hertz, the rising and falling portions of the arrow surrounded by the broken line are losses as in the case of FIG. At 500 hertz, the loss is less than at 15 kilohertz described above, and generally, the lower the PWM frequency, the smaller the loss.

The waveform shown in FIG. 2C has a frequency of 100.
At Hertz PWM frequency, there is little loss in this case.

When PWM control is performed at these frequencies,
Motor M depends on how long it is turned on in one cycle
The rotation speed of is determined. For example, in the case of 50% PWM control, only 50% of the rising portion of the frequency of the motor M
Will be turned on.

Next, switching of the PWM frequency will be described with reference to FIG.

While the electric tricycle body 1 is traveling, the traveling speed detector 21 constantly detects the traveling speed and compares it with the speed V stored in advance in the microcomputer 12 (S1). In the present invention, the speed V is set to 4 km / h. Then, when the traveling speed is less than 4 kilometers per hour, the motor current detector, that is, the motor current value detected by the load detection circuit 16, and a predetermined microcomputer.
The motor current value A stored in the 12 memories is compared (S2). That is, the motor current value is detected as a load, and the predetermined load Z is compared with the actual load. In this embodiment, this current value A is 20A. When the current value of the motor M is smaller than A, the motor M is driven at the PWM frequency of 15 kHz, which is a high frequency (S3). 15
When driving at kilohertz, when the traveling speed is V or less, that is, when the vehicle is moving at a low speed, and when the motor current value is A or less, that is, when the load is small, such as not climbing up and not carrying heavy luggage. It is detecting. At this time, the reason why the PWM frequency is controlled at 15 kHz is that the use of a frequency inaudible to the human ear to reduce the motor noise eliminates annoying noise and enables quiet running. Further, when 15 kilohertz is used, the loss is large, but since it is used only at a low speed of 4 kilometers per hour or less, the absolute current value is small, so that there is no particular problem with the loss. The reason why the high frequency is used even if the frequency is inaudible to the human ear is that the low frequency is likely to cause cogging and is not suitable for control.

Next, when the motor current value is A or less at a speed of 4 kilometers or more (S4), the vehicle travels at a frequency smaller than 15 kilohertz, that is, at a frequency with less loss because the speed increases (S5). In this embodiment, the control is performed using 500 Hertz.

Next, during running, regardless of the running speed, if the current value exceeds A, it is determined that the load is large, such as an uphill road or a heavy load is placed (S2) (S2).
4), the motor is controlled at the frequency f lower than the frequency F (S6). In this embodiment, 100 hertz is used. In this case, since the frequency f has less loss than the frequency F, it is possible to efficiently cope with the load.

In this embodiment, when a large load is applied, the driving force is emphasized rather than the control sound of the motor. Therefore, at any speed, the frequency is set to f when the current value exceeds a certain level. However, when the control sound is emphasized and controlled, regardless of the load, that is, the current value,
15 kHz at speeds below V, frequency F at speeds above V per hour
The travel control can be performed with.

Next, the second embodiment will be described with reference to FIG.

In this embodiment, the structure and control circuit of the electric three-wheeled vehicle are the same as those in the first embodiment, so the description thereof will be omitted and only the flow chart of the different parts will be described.

While the electric tricycle body 1 is traveling, the traveling speed detector 21 constantly detects the traveling speed and compares it with the speed V stored in advance in the microcomputer 12 (S1). In the present invention, the speed V is set to 4 km / h. When the traveling speed is less than 4 kilometers per hour, the motor current detection circuit, that is, the load detection circuit 16
The motor current value detected by is compared with the motor current value A stored in the memory of the predetermined microcomputer 12 (S2). That is, the motor current value is detected as a load, and the predetermined load Z is compared with the actual load. In this embodiment, this current value is 20A. If the current value of the motor M is smaller than A, the motor M is driven at a PWM frequency of 15 kHz (S3). When driving at 15 kilohertz, when the traveling speed is V or less, that is, at a low speed such as when starting, and the motor current value is A or less, that is, when the load is small such as not climbing up and not carrying heavy luggage. Is being detected. At this time, PW of 15 kHz
The reason for controlling with the M frequency is that by using a frequency that cannot be heard by the human ear to reduce the motor noise, there is no harsh sound and the vehicle can run quietly. Further, when 15 kilohertz is used, the loss is large, but since it is used only at a low speed of 4 kilometers per hour or less, the absolute current value is small, so that there is no particular problem with the loss. In this embodiment, 15 kHz is used as the PWM frequency, but it is sufficient if the frequency is inaudible to the human ear, and is approximately 15
There is no problem if it is above kilohertz. However, in this embodiment, since the loss of the PWM frequency is also taken into consideration, the lowest value of the frequency that cannot be heard by the human ear is used.

Next, when the motor current value is equal to or less than A at a speed of 4 kilometers or more (S4), the vehicle travels at a frequency smaller than 15 kilohertz, that is, at a frequency with less loss because the speed increases (S5). In this embodiment, the control is performed using 500 Hertz.

Next, when the motor current value is A or more at a speed of 4 kilometers or more, control is performed at 100 hertz having a frequency lower than 500 hertz (S6). This is 500
This is because 100 Hertz has less loss than Hertz, and the driving efficiency is improved when a load is applied.

If the motor current value is A or more at a speed of 4 kilometers or less, the motor is driven at 500 hertz.

As described above, the microcomputer 12 stores in advance the three stages of frequencies of 15 kHz, 500 Hz and 100 Hz, and when the motor current value exceeds A during normal traveling, the motor current value is less than A. Also, by controlling the motor M at a frequency lowered by one step, it is possible to efficiently control at a frequency suitable for the traveling speed.

In the present embodiment, the PWM frequency is controlled in three stages, but it may be divided into finer parts and analog control may be performed according to the traveling speed and the load.

Next, a case where the motor current detection circuit is replaced with an inclination sensor as a circuit for detecting the load and the load during traveling is detected by the inclination will be described.

Reference numeral 22 denotes an inclination sensor provided on the electric tricycle body 1 for detecting an inclination angle. The inclination sensor 22 has a pendulum 24 attached to a rotary shaft of a volume 23 so that the inclination angle is changed and the volume 23 is changed. The resistance value of is changed, and the tilt angle can be converted into an electric signal for detection.

Regarding the control circuit, the load detection circuit of the above-described embodiment is replaced with an inclination sensor, a predetermined load Z, that is, a predetermined inclination angle is predetermined, and when the load is exceeded, a predetermined load Z or more is applied. Determine that Then, it is applied to the first and second embodiments, and the PWM frequency is switched when the predetermined tilt angle is exceeded. In the case of the present embodiment, it is most desirable that the inclination angle is about 7 degrees.

Next, the case where the load detection circuit is replaced with a weight sensor and the load during traveling is detected by the loaded weight will be described.

This weight sensor is provided in the lower part of the chair 7,
It is suitable to be provided near the drive wheel 2 or the front wheel.

The weight sensor has a weight of about 100 kilograms when it is provided on the lower portion of the chair 7, and has a weight of about 85 kilograms when it is provided on the drive wheels 2 or the front wheels.
It is appropriate to set the predetermined load Z to about 5 kilograms.

This embodiment is also applied to the above-mentioned first or second embodiment, and the PWM frequency is switched when a predetermined weight is exceeded.

As described above, when the traveling speed is lower than the predetermined speed or 4 kilometers per hour, the motor is driven at a PWM frequency of 15 kHz or higher, which is a high PWM frequency. If it becomes larger than kilometers, a predetermined small predetermined value of less than 15 kilohertz which is a low PWM frequency 5
Since the PWM frequency of the motor is switched at 00 Hertz,
When there is little mechanical noise at low speeds, the vehicle operates at a frequency that is inaudible to the human ear, so it can run very quietly. Further, when the speed exceeds 4 kilometers per hour, the vehicle travels at a frequency with little loss, so that the driving efficiency is good.

Further, when the load is equal to or more than the predetermined load Z, the PWM
Since the frequency is switched to a low frequency of 100 Hertz, it is possible to drive the motor efficiently without loss.
You can drive smoothly.

Further, the traveling speed is a predetermined speed of 4
When the load is smaller than a kilometer and the load is smaller than a predetermined load Z, which is a high PWM frequency, 1
When the motor is driven at a PWM frequency of 5 kilohertz and the traveling speed is less than 4 kilometers per hour and the load is greater than Z, and when the traveling speed is greater than 4 kilometers per hour and the load is less than Z, PWM frequency 5 lower than 15 kHz, which is a low PWM frequency
The motor is driven at 00 hertz, and when the traveling speed is higher than 4 kilometers per hour and the load is higher than a predetermined value, the motor is driven at a low frequency of 100 hertz, so that there is no jarring sound when starting and it is quiet. You can drive to. Further, when the traveling speed becomes faster, the vehicle travels at a frequency with less loss, so that the driving efficiency is improved. Further, since the frequency is switched according to the magnitude of the load, it is only necessary to switch the predetermined frequency, and the frequency can be easily switched according to the running state.

In the above-described embodiment, the PWM frequency is set to 15
The frequency is set to 3 levels of kilohertz, 500 hertz and 100 hertz, but it is sufficient if the frequency is inaudible at low speed operation, and the PWM frequency when the speed becomes fast is efficient from 50 hertz which does not cause cogging. It may be set within 1 kilohertz and is not particularly limited to this value.

Although the predetermined traveling speed is set to 4 km / h, this value may be set to 2 km / h or 3 km / h.

[0064]

According to the present invention, when the traveling speed is lower than the predetermined speed V, the motor is driven at a high PWM frequency, and when the traveling speed is higher than the predetermined speed V, the low PWM frequency is low. The PWM frequency of the motor is switched to the value F, and when the mechanical sound at low speed is small, the vehicle operates at a frequency that is inaudible to the human ear, so that the vehicle can run very quietly. Also, the predetermined speed V
When the value exceeds, the vehicle runs at a frequency with less loss, resulting in good driving efficiency.

When the load is equal to or more than the predetermined load Z, the PWM
Since the frequency is switched to f lower than F, the vehicle can travel efficiently without loss.

Further, when the traveling speed is smaller than the predetermined V and the load is smaller than the predetermined predetermined load Z, the motor is driven at a high PWM frequency so that the traveling speed is smaller than V and the load is small. When it is larger than Z, when the traveling speed is larger than V and the load is smaller than Z, the motor is driven at a low PWM frequency F, the traveling speed is larger than V, and the load is larger than a predetermined value Z. When it is large, the motor is driven at a low frequency f, so that there is no jarring sound when starting and it is possible to run quietly. In addition, since the vehicle travels at a frequency with little loss during traveling, driving efficiency is improved. Further, since the frequency is switched according to the magnitude of the load, it is only necessary to switch the predetermined frequency, and the frequency can be easily switched according to the running state.

Further, since the motor is controlled at a high PWM frequency of about 15 kHz or more, it is inaudible, and it can run quietly at low speed, and PW less than 15 kHz at high speed.
Since the motor is controlled by the M frequency, there is no loss and the vehicle can run efficiently.

[Brief description of drawings]

FIG. 1 is a flowchart showing a first embodiment of the present invention.

FIG. 2 is a diagram showing waveforms of different PWM frequencies.

FIG. 3 is a control circuit diagram of the same.

FIG. 4 is an overall perspective view of the electric vehicle main body.

FIG. 5 is a flowchart showing a second embodiment of the present invention.

FIG. 6 is a side view of a tilt sensor showing a third embodiment of the present invention.

FIG. 7 is a diagram showing waveforms of different PWM frequencies according to the related art.

[Explanation of symbols]

 M Motor 1 Electric vehicle main body 18 Motor drive circuit 21 Travel speed detector 12 Control circuit 16 Load detection circuit 22 Tilt sensor

Claims (7)

[Claims] 1. An electric vehicle main body that drives by driving a motor, a motor drive circuit that PWM-controls the motor, and a traveling speed detector that detects the traveling speed of the electric vehicle main body.
When the traveling speed detected by the traveling speed detector is smaller than a predetermined predetermined speed V, the motor is driven at a high PWM frequency, and when the traveling speed is larger than the predetermined speed V, a low frequency PWM frequency F is used. An electric vehicle including a control circuit for driving a motor. 2. A load detection circuit for detecting the motor load is provided, and the control circuit is configured to set a predetermined load Z.
In the above case, the electric vehicle according to claim 1, wherein the PWM frequency F is switched to a frequency f lower than F. 3. An electric vehicle main body that drives by driving a motor, a motor drive circuit that PWM-controls the motor, and a traveling speed detector that detects a traveling speed of the electric vehicle main body.
A load detection circuit for detecting the motor load and a traveling speed detected by the traveling speed detector are smaller than a predetermined speed V, and a detection value of the load detection circuit is smaller than a predetermined load Z. When it is small, the motor is driven with a high PWM frequency, and the traveling speed is V
Is smaller than Z and the load is larger than Z, and the traveling speed is larger than V and the load is smaller than Z,
The motor is driven at a low PWM frequency, and the traveling speed is V
, And the load is larger than Z, the P
An electric vehicle that drives a motor at a PWM frequency f that is smaller than the WM frequency F. 4. The electric vehicle according to claim 2, wherein the load detection circuit is a current detector that detects the motor current. 5. The electric vehicle according to claim 2, wherein the load detection circuit is an inclination sensor that detects an inclination angle of the electric vehicle main body. 6. The electric vehicle according to claim 2, wherein the load detection circuit is a weight sensor for detecting a loaded weight of the electric vehicle main body. 7. The electric vehicle according to claim 2, wherein the high PWM frequency is approximately 15 kilohertz or more and the low PWM frequency is less than 15 kilohertz.