JPH06205508A - Method and apparatu for regulating speed of motor operated vehicle - Google Patents

Abstract

PURPOSE:To prevent an unstable phenomenon such as floating of front wheels when a motor operated vehicle is abruptly accelerated. CONSTITUTION:Calculating means 5 for calculating a standard duty ratio Dp corresponding to a manipulated variable theta by using the manipulated variable thetaof an accelerator operating member output from an accelerator sensor 3 and standard duty ratio characteristics stored in memory means 4 is provided. Further, detecting means 8 for detecting an operating direction of the member, detecting means 9 for detecting an operating speed of the member, and real duty ratio calculating means 10 for calculating a real duty radio Rpc of a value smaller than the ratio Dp when abrupt acceleration of the member is detected by the means 8, 9 are provided. The ratio Dpc is applied to a control circuit 7 to so control that the duty ratio of the driving current of the motor 1 is equal to the ratio Dpc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed of an electric vehicle for adjusting the rotational speed of an electric motor for driving an electric vehicle such as an electric motorcycle or an electric vehicle according to an operation amount of an accelerator operating member such as an accelerator grip or an accelerator pedal. The present invention relates to a method of adjustment and a device used to carry out the method.

[0002]

2. Description of the Related Art In an electric vehicle, the duty ratio of the drive current of the pulse waveform supplied to the electric motor is changed according to the operation amount of an accelerator operating member such as an accelerator grip or an accelerator pedal operated to adjust the speed of the vehicle. The rotation speed of the electric motor is adjusted by changing.

In this specification, the duty ratio of the drive current means the ratio of the ON period (ON duty ratio) to the period of one cycle of the drive current of the pulse waveform which is ON / OFF controlled. That is, assuming that the waveform of the drive current is as shown in FIG. 9, the duty ratio D is D = {Ton / (Ton + Toff
)} × 100 [%].

Generally, a speed adjusting device of this type includes a drive circuit having a switch means for turning on and off a drive current of an electric motor for driving a vehicle, an accelerator sensor for detecting an operation amount of an accelerator operating member, and a drive current for the electric motor. A drive current detecting means for detecting, a calculating means for calculating the duty ratio of the drive current corresponding to the detected operation amount of the accelerator operation member, and a drive circuit for supplying the drive current having the calculated duty ratio to the electric motor. And a control circuit for controlling the switch means.

Recently, a microcomputer has been used as a calculation means for calculating the duty ratio corresponding to the operation amount of the accelerator operation member. In this case, the memory of the microcomputer stores a standard duty ratio characteristic which gives a relationship between the operation amount θ of the accelerator operating member and the standard duty ratio Dp in the form of a map or a table.
The microcomputer samples the detection output of the accelerator sensor at regular intervals, and executes the routine shown in FIG. 10 every time it samples to calculate the duty ratio of the drive current. In the routine of FIG. 10, first, the detected value θ of the accelerator sensor is read, and the detected value θ of the accelerator sensor is read.
And the standard duty ratio characteristic stored in the memory, the standard duty ratio Dp corresponding to the operation amount θ of the accelerator operation member is calculated by the interpolation method, and the calculated standard duty ratio Dp is controlled as the actual duty ratio Dpc. Give to the circuit. The control circuit controls ON / OFF of the switch means of the drive circuit so that the duty ratio of the drive current supplied to the electric motor becomes equal to the actual duty ratio Dpc.

Various standard duty ratio characteristics that give a relationship between the operation amount θ of the accelerator operating member and the standard duty ratio Dp are conceivable depending on the application of the electric vehicle. In the following description, as shown in FIG. A characteristic in which the duty ratio Dp linearly changes with respect to the manipulated variable θ while the value of θ changes from θ1 to θ2 is defined as a standard duty ratio characteristic. In this case, as the operation amount θ of the accelerator operating member increases, the drive current of the electric motor increases and the rotation speed of the electric motor increases.

According to the conventional method, the transient response when the accelerator operation member is rapidly accelerated, that is, when the position (accelerator position) of the accelerator operation member is rapidly changed from the stop position to the full speed position. The characteristics are as shown in FIG. In FIG. 6, A shows the time change of the accelerator position, and B shows the time change of the duty ratio (= Dp) of the drive current.

[0008]

In the conventional adjusting device,
As shown in FIG. 6, when the accelerator operation member is suddenly accelerated, the duty ratio of the drive current is immediately adjusted to the standard duty ratio Dp corresponding to the operation amount, so that the motor is controlled with good responsiveness. However, because the output of the electric motor rises sharply when the accelerator operation member is suddenly accelerated, depending on the weight balance of the vehicle and the condition of the road surface,
There has been a problem that an unstable running state occurs such that the front wheels of the vehicle are lifted.

An object of the present invention is to provide a speed adjusting method for an electric vehicle and a method therefor, which eliminates the risk of unstable running of the vehicle when a sudden acceleration operation of the accelerator operating member is performed and improves the safety. It is to provide a speed adjusting device used for carrying out.

[0010]

The invention described in claim 1 is operated to adjust the duty ratio of the drive current and the vehicle speed when the drive current of the electric motor for driving the vehicle is pulse width modulated. A standard duty ratio characteristic that gives a relationship between the operation amount θ of the accelerator operating member is stored in the storage means, the operation amount θ is sampled at regular intervals, and the sampled operation amount θ and the standard duty ratio are sampled. A standard duty ratio Dp corresponding to the manipulated variable θ sampled from the ratio characteristic is calculated, and a new actual duty ratio Dp of the drive current is calculated based on the calculated standard duty ratio Dp.
The present invention relates to a speed adjusting method for adjusting the speed of an electric vehicle by determining c and changing the drive current of the electric motor according to the operation amount θ by pulse-width modulating the driving current with the actual duty ratio Dpc.

In the method of the present invention, when a sudden acceleration operation of the accelerator operation member is detected, a duty having a value smaller than the standard duty ratio Dp calculated based on the sampled operation amount θ by a predetermined ratio. The ratio is set to a new actual duty ratio Dpc.

According to a second aspect of the present invention, as shown in FIG. 1, a drive circuit 2 having a switch means for turning on and off a drive current of an electric motor 1 for driving a vehicle, and for adjusting a speed of the vehicle. An accelerator sensor 3 for detecting the operation amount of the accelerator operation member that is operated, and a standard duty that stores the relationship between the operation amount θ of the accelerator operation member and the standard duty ratio Dp of the drive current corresponding to the operation amount θ. Ratio characteristic storage means 4, standard duty ratio calculation means 5 for calculating the standard duty ratio Dp corresponding to the operation amount of the accelerator operation member obtained by sampling the output of the accelerator sensor using the standard duty ratio characteristic, and standard duty ratio The actual duty ratio determining means 6 for determining the actual duty ratio Dpc of the drive current based on the ratio, and the pulse width modulation of the drive current with the actual duty ratio Dpc. Those related to speed control device for an electric vehicle and a control circuit 7 for controlling the switching means of the driving circuit 2 in.

According to the present invention, the actual duty ratio determining means 6 detects the operating direction of the accelerator operating member, and the operating speed information for detecting a variable including the operating speed information of the accelerator operating member. The operation amount θ sampled when it is detected by the detection means 9, the operation direction detection means and the operation speed information detection means that the accelerator operation member is operated at an operation speed exceeding the size set on the speed increasing side. Standard duty ratio Dp calculated based on
The actual duty ratio calculation means 10 for obtaining a new duty ratio Dpc having a value smaller than the predetermined duty ratio by a predetermined ratio.

The operation direction detecting means can be constituted by, for example, means for comparing the newly calculated standard duty ratio Dp with the actual duty ratio Dpc already given to the control circuit.

The operation direction detecting means can also be constituted by means for comparing the current sampling value with the previous sampling value every time the output of the accelerator sensor is sampled.

In the operation speed information detecting means, for example,
The difference between the newly calculated standard duty ratio Dp and the actual duty ratio Dpc already given to the control circuit is calculated as the variable.

In the operation speed information detecting means, the operation amount θt of the accelerator operation member sampled this time,
A difference from the previously sampled manipulated variable θt-1 may be calculated as the variable.

[0018]

As described above, by detecting the operating direction of the accelerator operating member and the variable including the information of the operating speed, when the rapid acceleration operation of the accelerator operating member is detected, the duty ratio Dpc of the drive current is changed. If the correction calculation is performed to make the duty ratio smaller than the standard duty ratio Dp, the rate of increase in the output of the electric motor when the accelerator operating member is rapidly accelerated can be suppressed to a low level, so that the accelerator operating member is rapidly accelerated. It is possible to prevent the front wheels of the vehicle from being lifted when the vehicle is on, and it is possible to improve the safety of the electric vehicle.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 schematically shows the hardware construction of an embodiment of the present invention. The electric motor 3 of this embodiment is a three-phase brushless electric motor. The drive circuit 2 includes, for example, a known switch circuit in which six switch means (FET or transistor) capable of on / off control are connected in a three-phase bridge, and the output of the battery 11 is the power supply circuit 12 and the drive circuit 2. Through the three-phase armature winding 1u of the motor 1
~ 1w.

Each switch means of the drive circuit 2 is on / off controlled with a predetermined duty ratio by a control signal given from the control circuit 7, whereby the drive current of the electric motor 1 is P.
The rotation speed of the electric motor is adjusted by WM control. Since the method of supplying the drive current to the three-phase brushless motor is well known, its detailed description is omitted.

The accelerator sensor 3 detects an operation amount (angle or movement distance) θ of an accelerator operation member such as an accelerator grip or an accelerator pedal, and outputs an electric signal corresponding to the operation amount θ. As the accelerator sensor, for example, a potentiometer provided so that the mover works in conjunction with the accelerator operating member can be used.

An analog output of the accelerator sensor 3 is given to a predetermined input port of a microcomputer 14 through an analog / digital converter (A / D converter) 13. Further, in order to detect the drive current Id supplied to the electric motor 1 through the drive circuit 2, a current detection resistor 15 having a sufficiently small resistance value is connected between the drive circuit 2 and the ground, and the voltage across the resistor 15 ( The drive current detection signal) is converted into a digital signal by the drive current detection circuit 16 and given to the microcomputer 14 and the control circuit 7.

The microcomputer 14 samples the output of the accelerator sensor 3 (output of the A / D converter 13) every predetermined sampling time δt, and executes a predetermined program every time the output of the accelerator sensor 3 is sampled. Then, the actual duty ratio Dpc is determined for the operation amount θ of the accelerator operating member detected by the accelerator sensor 3. When it is detected that the drive current Id exceeds the limit value Ids, the actual duty ratio Dpc is corrected so that the drive current Id is suppressed to the limit value Ids or less.

The control circuit 7 controls the switching means of the drive circuit 2 so that the duty ratio of the drive current (pulse waveform) of the electric motor 1 becomes equal to the actual duty ratio Dpc determined by the microcomputer. Control circuit 7
In addition, when it is detected that the drive current Id exceeds a permissible limit value set higher than the limit value Ids, the switching means of the drive circuit 2 is cut off to perform a protective operation for limiting the drive current. It has become. The power supply voltage of the microcomputer 14 and the control circuit 7 is given from the power supply circuit 12.

The microcomputer 14 is provided with a ROM and a RAM as storage means, and a standard duty ratio characteristic giving a relationship between the standard duty ratio Dp and the operation amount θ of the accelerator operating member as shown in FIG. It is stored in ROM in the form. With this ROM,
The standard duty ratio characteristic storage means 4 of FIG. 1 is configured.

The microcomputer 14 samples the output of the accelerator sensor 3 at a constant sampling time δt, and executes a predetermined routine according to a program stored in the ROM every time the output of the accelerator sensor 3 is sampled. Thus, the standard duty ratio calculation means 5 and the actual duty ratio determination means 6 shown in FIG. 1 are realized.
An example of a flowchart showing an algorithm of a routine that is executed each time the output of the accelerator sensor is sampled is shown in FIG.

When the routine shown in FIG. 3 is started at a certain sampling time, first, the operation amount θ detected by the accelerator sensor 3 is read, and the standard duty ratio corresponding to the operation amount close to the detected operation amount θ is obtained. The value is read from the map or table stored in the standard duty ratio characteristic storage means, and the standard duty ratio Dp corresponding to the detected operation amount θ is calculated by the interpolation method. By the process of this calculation, the standard duty ratio calculation means 5 of FIG. 1 is realized.

After the standard duty ratio Dp is calculated, the duty ratio Dp is compared with the actual duty ratio Dpc (stored in the RAM) currently given to the control circuit 7, and Dp is larger than Dpc. When it is large (when the accelerator operation member is operated to the speed increasing side), the difference δ between Dp and Dpc
Calculate D. This δD corresponds to the increment of the duty ratio (acceleration increment) required during the minute time δt from the previous sampling time to the current sampling time, and the operation amount θ of the accelerator operating member at the time of δt.
It corresponds to the increase of. If δD / δt is calculated here, information on the operating speed of the accelerator operating member can be obtained. However, in this example, δt is constant, so δD
Information on the operating speed of the accelerator operating member can be obtained from the information itself. By the process of calculating this δD, the operation speed information detecting means 9 of FIG. 1 is realized.

After calculating the acceleration increment δD of the duty ratio, δD is compared with the set value δDs of the acceleration increment to obtain δD.
Is larger than δDs, that is, when the operation speed of the accelerator operating member during acceleration operation exceeds the set speed, a duty ratio of a value smaller than the newly calculated standard duty ratio Dp is newly added. A new calculated actual duty ratio Dpc.
Store pc in RAM. This correction calculation can be performed by various methods, and an appropriate method may be selected according to the characteristics of the electric motor, the application of the vehicle, etc. In this embodiment, the current Dpc plus δD / n is used. It is a new Dpc. Here, n is set to an appropriate value larger than 1. The actual duty ratio Dpc is stored at a predetermined address in the RAM.

The standard duty ratio Dp corresponding to the manipulated variable of the accelerator operating member because the accelerator operating member has not been operated or the deceleration side has been operated between the last sampling time and the current sampling time.
Is equal to or less than the actual duty ratio Dpc currently given to the control circuit (when Dp ≦ Dpc is satisfied), the newly calculated standard duty ratio Dp is set as the new actual duty ratio Dpc. Even when it is detected that the operation (acceleration operation) to the acceleration side is performed, if the acceleration increment δD of the duty ratio is equal to or less than the set value δDs (the operation speed of the accelerator operating member is higher than the set speed). If it is lower), the newly calculated standard duty ratio Dp is directly used as the new actual duty ratio Dpc.

After determining the actual duty ratio Dpc based on the operation amount of the accelerator operating member as described above, the detected value of the drive current Id is read, and the drive current Id and the limit value I are read.
Compare with ds. As a result, the drive current Id becomes less than the limit value Ids.
In the following cases, the determined actual duty ratio Dpc is left as it is and the process returns to the main routine to wait for the next sampling. When the detected drive current Id exceeds the limit value Ids, a predetermined coefficient α is added to the actual duty ratio Dpc newly determined according to the output of the accelerator sensor so that the drive current is equal to or less than the limit value. Multiply (<1),
Alternatively, the actual duty ratio Dpc is corrected to a small value by subtracting a predetermined value from the newly determined Dpc.

As described above, the new actual duty ratio D
By the process of determining pc, the actual duty ratio calculation means 10 of FIG. 1 is realized.

According to the above embodiment, the transient response characteristics when the accelerator operating member is suddenly operated from the stop position to the full speed position (when the rapid acceleration operation is performed) are as shown in FIG. 7, for example. In FIG. 7, the polygonal line A shows the change over time in the accelerator position, and the curve A shows the transient response of the actual duty ratio Dpc in the case of the above embodiment. The polygonal line B indicates that the standard duty ratio Dp of FIG.
It shows a response of the actual duty ratio at the time of sudden acceleration when the standard duty ratio Dp obtained according to the characteristic against the manipulated variable θ is directly used as the actual duty ratio Dpc. As is clear from this figure, according to the present invention, when the accelerator operating member is rapidly accelerated, the actual duty ratio is made smaller than the standard duty ratio at each time.
It is possible to prevent the output of the electric motor from becoming excessive, prevent an unstable state such as lifting of the front wheels of the vehicle, and improve safety.

In the above embodiment, information on the operating direction and operating speed of the accelerator operating member is obtained from the actual duty ratio Dpc given to the control circuit and the newly calculated standard duty ratio Dp. Information on the operating direction and operating speed of the accelerator operating member may be obtained from the output of the sensor 3. A flowchart corresponding to FIG. 3 in this case is shown in FIG.

In the example of FIG. 4, the output of the accelerator sensor sampled this time is θt, the output of the accelerator sensor sampled last time is θt-1, and θt and θt-1
The operation direction of the accelerator sensor is detected by comparing with. Further, the difference Δθ between θt and θt-1 is calculated, and the operation speed of the accelerator sensor is detected from this Δθ. Since δθ is the amount of change in the accelerator sensor operation amount θ that occurs during the sampling time δt, the operation speed of the accelerator sensor can be obtained by calculating δθ / δt. Here, since δt is constant, Information on operation speed can be obtained. Compare this δθ with the set value δθs,
When it is detected that δθ is larger than δθs, a correction calculation for making the actual duty ratio smaller than the standard duty ratio is performed. The other points are similar to those of the embodiment of FIG.

In the examples shown in FIGS. 3 and 4, the actual duty ratio Dpc corresponding to the operation amount θ of the accelerator operating member is determined and then the detected value of the drive current Id is read, but at other times. For example, the detected value of the drive current Id may be read before the calculation of the standard duty ratio Dp.

In the present invention, the process of comparing the drive current Id with the limit value Ids and correcting the duty ratio so as to limit the drive current to the limit value or less is not always necessary. For example, the motor is protected from overcurrent. In the case where a fuse is provided for this purpose, or when the overcurrent is detected as in the above embodiment, the control circuit 7 turns off the switch means of the drive circuit to perform the protective operation. Can omit the above process for limiting the drive current.

In the above embodiment, when it is detected that a sudden acceleration operation of the accelerator sensor is detected, a value obtained by multiplying the acceleration increment δD of the duty ratio by a coefficient 1 / n (n> 1), Actual duty ratio D already given to the control circuit
Although a new actual duty ratio Dpc is calculated by adding it to pc, the standard duty ratio Dp is also small by multiplying the newly calculated standard duty ratio Dp by a predetermined correction coefficient K (<1). Actual duty ratio Dpc
(= KDp) may be obtained.

Further, an appropriate transient response characteristic with respect to the elapsed time t of the duty ratio during acceleration is obtained as shown by the polygonal line A in FIG. 8 and calculated from the standard duty ratio Dp vs. manipulated variable θ characteristic shown in FIG. When it is detected that the standard duty ratio Dp is larger than the duty ratio obtained from the transient response characteristic of the polygonal line a, it is determined that the acceleration operation is rapidly performed, and the appropriate transient response characteristic during acceleration (Fig. The actual duty ratio Dpc may be set so as to follow the polygonal line 8).

That is, in the transient response characteristic during acceleration of the polygonal line a shown in FIG. 8, when the actual duty ratio at a certain time is Dpc ', a constant time δt from that time
The proper actual duty ratio at the time when (sampling time) has elapsed is Dpc '+ δDp. Here, δDp is an appropriate acceleration duty ratio increment during the δt time.
Standard duty ratio Dp newly calculated from the sampling value of the output of the accelerator sensor and the standard duty ratio characteristic
Is compared with the above Dpc ′ + δDp, and Dp> D between them.
When the relation of pc '+ δDp is established, it is determined that the rapid acceleration operation is performed, and control is performed so that Dpc' + δDp becomes the new actual duty ratio Dpc. The control can be made to follow. In FIG. 8, the polygonal line B indicates that at each time.
2 shows the response characteristic at the time of acceleration when the standard duty ratio obtained by the standard duty ratio characteristic of is the actual duty ratio Dpc.

In the above embodiment, the case where the three-phase brushless electric motor is used is taken as an example, but the present invention can be applied to the case where another electric motor such as an electric motor with a DC brush is used.

[0042]

As described above, according to the present invention, when the operation direction of the accelerator operating member and the variable including information on the operating speed are detected, and when the rapid acceleration operation of the accelerator operating member is detected, Since the correction calculation for making the duty ratio Dpc of the drive current smaller than the standard duty ratio Dp is performed, the rate of increase in the output of the electric motor when the accelerator operating member is suddenly accelerated is suppressed to be low. There is an advantage that the front wheels of the vehicle can be prevented from being lifted up when the vehicle is suddenly accelerated, and the safety of the electric vehicle can be improved. According to the present invention, the operation feeling of the vehicle is
Since the driving feeling of the vehicle driven by the internal combustion engine is approximated, a driver accustomed to the vehicle driven by the internal combustion engine can drive the electric vehicle without feeling discomfort.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a speed adjusting device according to the present invention.

FIG. 2 is a block diagram showing a configuration of hardware used in an embodiment of the present invention.

FIG. 3 is a flowchart showing a method of determining an actual duty ratio in the embodiment of the present invention.

FIG. 4 is a flowchart showing a method of determining an actual duty ratio in another embodiment of the present invention.

FIG. 5 is a diagram showing an example of a relationship between a standard duty ratio of a drive current of an electric motor and an operation amount of an accelerator operation member.

FIG. 6 is a diagram showing a transient response characteristic at the time of rapid acceleration when a conventional speed adjusting device is used.

FIG. 7 is a diagram showing a transient response characteristic at the time of sudden acceleration in the example of the present invention.

FIG. 8 is a diagram showing a transient response characteristic at the time of sudden acceleration in another embodiment of the present invention.

FIG. 9 is a waveform diagram for explaining the duty ratio of the drive current of the electric motor.

FIG. 10 is a flowchart showing a method of determining an actual duty ratio in a conventional speed adjusting device.

[Explanation of symbols]

 1 Motor 2 Drive Circuit 3 Accelerator Sensor 4 Standard Duty Ratio Characteristic Storage Means 5 Standard Duty Ratio Calculation Means 6 Actual Duty Ratio Determining Means 7 Control Circuit 8 Operating Direction Detection Means 9 Operating Speed Information Detecting Means 10 Actual Duty Ratio Computing Means

Claims (6)

[Claims] 1. A relationship between a duty ratio of a driving current of a motor for driving a vehicle when the pulse current is modulated and an operation amount θ of an accelerator operating member operated to adjust a speed of the vehicle. Is stored in advance, the operation amount θ is sampled at regular intervals, and a standard corresponding to the operation amount θ sampled from the sampled operation amount θ and the standard duty ratio characteristic is stored. The duty ratio Dp is calculated, a new actual duty ratio Dpc of the drive current is determined based on the calculated standard duty ratio Dp, and the drive current is pulse-width modulated with the actual duty ratio Dpc to drive the electric motor. In a speed adjusting method for adjusting the speed of an electric vehicle by changing an electric current according to an operation amount θ, when a rapid acceleration operation of the accelerator operating member is detected. Speed control method for an electric vehicle, characterized in that the duty ratio of a new actual duty ratio of the predetermined ratio by a value smaller than the standard duty ratio Dp which is calculated based on the operation amount θ sampled. 2. A drive circuit having switch means for turning on and off a drive current of an electric motor for driving a vehicle, and an accelerator sensor for detecting an operation amount of an accelerator operation member operated for adjusting a speed of the vehicle. The standard duty ratio characteristic storage means for storing the relationship between the operation amount θ of the accelerator operation member and the standard duty ratio Dp of the drive current corresponding to the operation amount θ, and the output of the accelerator sensor were sampled and obtained. Standard duty ratio calculating means for calculating the standard duty ratio Dp corresponding to the operation amount of the accelerator operation member using the standard duty ratio characteristic, and the actual duty ratio D of the drive current based on the standard duty ratio.
A speed adjusting device for an electric vehicle, comprising: an actual duty ratio determining means for determining pc; and a control circuit for controlling a switching means of the drive circuit so as to pulse-width modulate the drive current with the actual duty ratio Dpc, The actual duty ratio determination means is an operation direction detection means for detecting an operation direction of the accelerator operation member, an operation speed information detection means for detecting a variable including information on an operation speed of the accelerator operation member, and the operation direction detection means. When it is detected by the means and the operation speed information detecting means that the accelerator operation member is operated at an operation speed exceeding the size set on the speed increasing side, it is calculated based on the sampled operation amount θ. The actual duty ratio calculator for obtaining a new duty ratio Dpc which is a value smaller than the standard duty ratio Dp by a predetermined ratio. A speed adjusting device for an electric vehicle, comprising: a step. 3. The operation direction detecting means comprises means for comparing the newly calculated standard duty ratio Dp with the actual duty ratio Dpc already given to the control circuit. 2. The speed control device for an electric vehicle according to 2. 4. The operation direction detecting means comprises means for comparing a current sampling value with a previous sampling value each time the output of the accelerator sensor is sampled. Electric vehicle speed control device. 5. The operation speed information detecting means calculates the difference between the newly calculated standard duty ratio Dp and the actual duty ratio Dpc already given to the control circuit as the variable. 5. The speed adjustment device for an electric vehicle according to any one of 4 above. 6. The operation speed information detecting means calculates the difference between the operation amount θt of the accelerator operation member sampled this time and the operation amount θt−1 sampled last time as the variable amount. 5. The speed adjustment device for an electric vehicle according to any one of 4 above.