JPH1132404A - Travel motion control equipment for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a regenerative brake force as required according to situation. SOLUTION: A regenerative brake force RB corresponding to a vehicle speed is determined (S2), with an accelerator and a brake pedal off (S10), a real deceleration is calculated (S16) from a gravity sensor, and if the real deceleration is within a target range (S18, S20), then RB is supplied (S22) as it is to a system controller. If the real deceleration exceeds (S18) the upper limit value of the target range, then RB is reduced (S24) by Δ RB. If this RB is smaller than 0, then S26 sets RB to zero (S28). If RB is larger than 0 (S26), then S22 is executed by RB as it is, an the step is returned to S10. If the real deceleration is smaller than the lower limit value of the target range (S20), then RB is increased just by ΔRB (S30). If this RB is larger than the maximum value MAX (S32), then RB is made to MAX (S34) and if the real deceleration is smaller (S32) than MAX, then S22 is executed with RB as it is, and the step returns to S10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a travel control device for an electric vehicle, and more particularly, to a device for effectively utilizing a regenerative brake.

[0002]

2. Description of the Related Art In general, in an internal combustion engine vehicle, an engine brake operates unless an accelerator pedal and a brake pedal are depressed during traveling. Even in an electric vehicle driven by a motor, it is necessary to apply a brake corresponding to an engine brake in order to make driving feeling similar to that of an internal combustion engine vehicle. Therefore, for example, Japanese Patent Application Laid-Open No. 6-15331
Japanese Patent Laid-Open No. 2 discloses that a constant value regenerative brake is applied when the accelerator is not depressed.

[0003] Also, Japanese Patent Application Laid-Open No. H6-70406 discloses that
The driver sets the drive range to "D", "2",
An electric vehicle that can be selected as "1" is disclosed in which a regenerative brake is actuated in a state where the accelerator is not depressed as described above, but the value of the regenerative brake is changed according to a drive range. I have.

[0004]

However, Japanese Patent Application Laid-Open No.
According to the technique disclosed in JP-A-53312, when the traveling road is a flat ground, a braking force equivalent to an appropriate engine brake can be obtained. However, since the regenerative braking force is constant, when the traveling road is on an uphill, the vehicle is decelerated more than necessary. On a downhill, the vehicle may not only decelerate than expected, but may be accelerated. In particular, when the vehicle is accelerated on a downhill, the driver depresses the brake pedal to apply the friction brake. Therefore, energy that would otherwise be recovered by use of the regenerative brake is converted to heat and consumed.

In the technique disclosed in Japanese Patent Application Laid-Open No. H6-70406,
Since the regenerative braking force is changed by switching the drive range, changing the drive range to a low-speed position such as “1” may make it unnecessary to depress the brake pedal. However, the driver has to change the drive range, and the operation is troublesome. Further, even if the drive range is changed, a regenerative braking force corresponding to a desired engine brake is not always obtained, and in some cases, the brake pedal must be depressed.

An object of the present invention is to provide a travel control device for an electric vehicle that can generate a required regenerative braking force according to a situation.

[0007]

In order to achieve the above object, according to the present invention, a predetermined regenerative braking force equivalent to an engine brake is applied when an accelerator pedal and a brake pedal are off. An electric deceleration detecting means for detecting an actual deceleration of the electric vehicle caused by the regenerative braking force, and the regenerative braking force so that the detected actual deceleration coincides with a target deceleration. Control means for increasing or decreasing the number.

[0008] The predetermined regenerative braking force is determined, for example, based on the speed of the electric vehicle when both pedals are not depressed. The actual deceleration (actual deceleration) caused by the application of the predetermined regenerative braking force is detected by the actual deceleration detecting means. As the actual deceleration detecting means, for example, at least one of a rotational speed detector of a motor of the electric vehicle, a wheel speed detector of the electric vehicle, and a gravity sensor of the electric vehicle, as described in claim 2 One can be used.

The control means controls the regenerative braking force so that the detected actual deceleration matches the target deceleration. The target deceleration can be a predetermined constant value or can be determined based on the vehicle speed when both pedals are not depressed. As a technique for matching the target deceleration, for example, the regenerative braking force is increased or decreased by a predetermined amount, the actual deceleration is detected again, and it is determined whether or not the actual deceleration matches the target deceleration. If not,
Again, a so-called feedback technique can be used that increases or decreases the regenerative braking force by a predetermined amount.

In addition, a feedback technique is used in which the regenerative braking force is increased or decreased not by a predetermined amount but by the difference between the target deceleration and the actual deceleration, and the actual deceleration is detected again. Can also. Further, the target deceleration may not have a fixed value but have a predetermined allowable range.

According to a third aspect of the present invention, there is provided an electric vehicle in which a predetermined regenerative braking force equivalent to an engine brake is applied in a state where an accelerator pedal and a brake pedal are turned off. Gradient detecting means for detecting, and when the gradient of the road surface detected by the gradient detecting means is a downward gradient, the regenerative braking force is increased in accordance with the downward gradient, and the detected gradient of the road surface is determined to be an upward gradient. And control means for reducing the regenerative braking force in accordance with the upward gradient.

According to the third aspect of the invention, similarly to the first aspect of the invention, a predetermined regenerative braking force acts on the electric vehicle when both pedals are off. Then, the gradient of the road surface in the traveling direction of the electric vehicle is detected by the gradient detecting means. This gradient detecting means may be, for example, a tilt sensor provided in the electric vehicle as described in the fourth aspect of the present invention. When the gradient of the road surface detected by the gradient detecting means is a downward gradient, with a constant regenerative braking force,
Electric vehicles may be accelerated. Therefore, the control means increases the regenerative braking force. Further, when the detected gradient of the road surface is an upward gradient, the electric vehicle may be decelerated too much with a constant regenerative braking force. Therefore, the control means reduces the regenerative braking force to reduce the deceleration of the electric vehicle.

As a technique for increasing or decreasing the regenerative braking force based on the gradient of the road surface, for example, there is a technique of increasing or decreasing the regenerative braking force by a value obtained by multiplying the gradient detected by the gradient detecting means by an appropriate coefficient, and continuing. . Alternatively, there is one in which the regenerative braking force is continuously increased or decreased by a predetermined value.

According to a fifth aspect of the present invention, in the travel control device for an electric vehicle according to the first or third aspect, the increased / decreased regenerative braking force is output within a predetermined allowable range.

According to the fifth aspect of the invention, the regenerative braking force is:
Although it increases or decreases from a predetermined regenerative braking force, it changes only within a predetermined allowable range.

According to a sixth aspect of the present invention, there is provided an electric vehicle in which a predetermined regenerative braking force equivalent to engine braking is applied in a state where an accelerator pedal and a brake pedal are off, wherein the regenerative braking force is applied to the electric vehicle. It has means for changing according to the vehicle speed.

According to the sixth aspect of the present invention, a predetermined regenerative braking force acts on the electric vehicle when both pedals are off. The predetermined regenerative braking force is not a constant value irrespective of the vehicle speed, but is determined, for example, according to the vehicle speed when both pedals are off. For example, as the vehicle speed increases, the predetermined regenerative braking force also increases. Generally, the engine braking force of an internal combustion engine vehicle is also determined by the vehicle speed when both pedals are turned off. Therefore, a driving feeling close to that of an internal combustion engine automobile can be obtained.

According to a seventh aspect of the present invention, in the travel control device for an electric vehicle according to the first, third or sixth aspect, the electric vehicle has a shift range, and the predetermined regenerative braking force is controlled by the shift range. It is set according to.

According to the present invention, when the shift range is a high speed range, the predetermined regenerative braking force is the smallest, and when the shift range is a medium speed range, the predetermined regenerative braking force is intermediate. In the low speed range, the predetermined regenerative braking force is the largest. Therefore, a driving feeling close to that of an internal combustion engine automobile can be obtained.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electric vehicle according to this embodiment is
As shown in FIG. 4, a pair of front wheels 2, 2 and a pair of rear wheels 4,
4 is a four-wheeled vehicle. The rear wheels 4, 4 are motor 6,
6 are driven wheels. Also, front wheels 2, 2
Are driven wheels that are not driven. The motors 6, 6 are supplied with electric power from a chargeable battery 8 controlled by a power control unit, for example, an inverter 10. With this controlled power, the motor 6,
6 is controlled. The inverter 10 includes a motor 6,
The battery 8 is charged by electric power generated by the regenerative braking of No. 6.

The inverter 10 is controlled by a system controller 11. System controller 1
1 is configured by a microcomputer, for example. The system controller 11 supplies a signal for controlling the driving state of the motors 6 to the inverter 10 according to the accelerator signal. The accelerator signal is generated by the accelerator opening sensor 13 by operating the accelerator pedal 12. The system controller 11 outputs a signal for controlling the state of the regenerative brake to the inverter 1 according to a regenerative brake command signal from a brake controller 14 described later.
Supply 0. Further, the system controller 11 supplies a brake controller 14 with a regenerative brake feedback signal notifying the state of the regenerative brake.

The rear wheels 4, 4 have hydraulic brakes 15, 15
, And hydraulic brakes 16, 16 are also provided on the front wheels 2, 2. These hydraulic brakes 15, 15, 1
6 and 16 are ABS (anti-lock brake system)
With the hydraulic pressure supplied by the hydro unit 17, the front wheels 2,
2 and the rear wheels 4, 4 are respectively braked.

The hydro unit 17 receives a control oil pressure generated by the master cylinder 20 by operating the brake pedal 18 via a control valve unit 22. The control valve unit 22 receives the control signal from the brake controller 14 and controls the ABS hydro unit 22.

The brake controller 14 is constituted by, for example, a microcomputer, controls the control valve unit 22 in accordance with the detection output of the pressure sensor 26, and controls the braking states of the hydraulic brakes 15, 15, 16, 16.
The pressure sensor 26 is provided in an oil passage between the master cylinder 20 and the control valve unit 22, and is connected to the brake pedal 18.
The pressure change generated by the operation is detected.

A control signal from an ABS ECU (electronic control unit for an antilock brake system) 24
The braking state of the hydraulic brakes 15, 15, 16, 16 is also controlled by being supplied to the hydro unit 17. As the control signal, a wheel speed detector, for example, a speed signal of an electric vehicle detected by front wheel speed sensors 28, 28 is used.

In addition, a gravity sensor 30 is provided near the center of gravity of the body of the electric vehicle. The gravity sensor 30 supplies signals indicating acceleration and deceleration of the electric vehicle to the brake controller 14. The brake controller 14 includes an accelerator pedal 12 and a brake pedal 18.
Supplies a regenerative brake command signal to the system controller 11 so that the inverter 10 generates a regenerative braking force corresponding to the engine brake of the internal combustion engine vehicle in an off state, that is, in a state where both pedals are not depressed. . In a state where a regenerative braking force corresponding to the engine brake is generated, a regenerative brake command signal for controlling the regenerative braking force is supplied to the system controller 11 based on the output of the gravity sensor 30.

Hereinafter, a program for the brake controller 14 to perform the above control will be described with reference to FIGS. First, as shown in FIG. 1, an initial value RB0 of the regenerative brake amount is set in a variable RB of the regenerative brake amount included in the regenerative brake command signal supplied to the system controller 11 (step S2).

The initial value RB0 is determined, for example, as shown in FIG. First, the vehicle speed V of the electric vehicle is calculated (step S4). This vehicle speed is determined by the front wheel speed sensor 28,
It is determined based on the output of the motor 28 or the output of a rotation speed detector (not shown) built in the motor 6.

Then, the vehicle speed V is input to a look-up table prepared in advance in the brake controller 14, and RB0 corresponding to the input vehicle speed is read from the look-up table (step S6). The relationship between the vehicle speed and the initial value RB0 of the regenerative braking amount is stored in a look-up table. As shown in FIG. 3, the relationship between the vehicle speed and RB0 is such that as the vehicle speed V increases, R
B0 is determined to be large. In particular, in the type in which the electric vehicle can switch the drive range, the RBO is the smallest in the “D” range with the largest gear ratio, and the RB0 is the smallest in the “1” range with the smallest gear ratio.
Is large, and the gear ratio is in the “2” range, which is halfway between the two ranges, and RB0 is an intermediate value between RB0 in both ranges. This is to obtain a driving feeling similar to that of an internal combustion engine automobile.

The RB0 determined in this way is output (step S8), and is set to the variable RB of the regenerative braking amount in step S2. Note that 0 can be used as the initial value RB0.

Next, it is determined whether the accelerator pedal 12 and the brake pedal 18 are fully closed, that is, in the off state, in other words, whether both the pedals 12 and 14 are depressed (step S10). If at least one of the pedals is depressed, it is not necessary to generate a regenerative braking force equivalent to the engine brake, so the variable RB of the regenerative braking amount is set to 0 (step S12), and this variable RB0 is supplied to the system controller 11. (Step S14), Step S2
Again.

In step S10, both pedals 12,
If it is determined that both of the pedals 18 have not been stepped on, the current deceleration of the electric vehicle, that is, the actual deceleration, is calculated based on the output of the gravity sensor 30 (step S16). Gravity sensor 30
In practice, it is only necessary to input the output of the gravity sensor 30. When the actual deceleration is calculated from the outputs of the front wheel speed sensors 28, 28 or the rotation speed of the motor 6 without using the gravity sensor 30, for example, the output of the front wheel speed sensors 28, 28 or the motor 6 The value obtained when the rotation speed is input is stored, and the difference between the output of the front wheel speed sensors 28, 28 or the rotation speed of the motor 6 input this time is obtained, and the difference is multiplied by an appropriate coefficient.

It is determined whether the actual deceleration thus calculated is higher than the upper limit of the target range (step S1).
8). The upper limit of this target range is determined by multiplying a predetermined constant target deceleration by a coefficient slightly larger than 1, for example. If the actual deceleration is below the upper limit of the target range, it is determined whether the actual deceleration is below the lower limit of the target range. (Step S20). The lower limit of the target range is determined by multiplying the target deceleration by a coefficient slightly smaller than 1, for example.
If the actual deceleration is higher than the lower limit of the target range, the regenerative braking amount variable RB is supplied to the system controller 11 as it is (step S22). Therefore, when the actual deceleration is within the target range, the variable RB of the regenerative braking amount is output without being modified. This is to prevent the regenerative braking amount from frequently changing due to a slight change in the actual deceleration. That is, a dead zone is provided for the target deceleration.

Although the target deceleration is set to a constant value, for example, the relationship between the vehicle speed and the target deceleration is stored in a look-up table, and the vehicle speed is set in the same manner as in the determination of the initial value RB0 of the regenerative braking amount. The target deceleration according to the vehicle speed may be obtained by inputting the data into a look-up table. The target range upper limit and lower limit were obtained by multiplying the target deceleration by a coefficient, respectively, but the target range upper limit and lower limit were determined by adding and subtracting an appropriate deviation value to and from the target deceleration. You may.

If it is determined in step S18 that the actual deceleration is higher than the upper limit of the target range, it is considered that, for example, the electric vehicle is climbing a slope and the regenerative braking amount is too large. Therefore, to reduce the amount of regenerative braking,
The variable RB of the regenerative braking amount is reduced by a predetermined value ΔRB (step S24). Instead of decreasing RB by ΔRB which is a predetermined value, RB may be decreased by the difference between actual deceleration and target deceleration.

Next, it is determined whether the reduced RB is smaller than 0 (step S26). If RB is smaller than 0, the regenerative braking force cannot be obtained even if the RB is output as it is, and conversely, the motors 2 and 2 are driven.
Is set to 0 (step S28), step S22 is executed, and the RB set to 0 is output. If it is determined in step S26 that RB is not smaller than 0, step S22 is directly executed and the RB corrected in step S24 is output. Then, step S10 is executed again.

If the actual deceleration is higher than the upper limit of the target range, steps S10, S16, S18, S24, S2
6. The loop of S28 and S22 is executed, and the RB is corrected several times so that the actual deceleration falls within the target range. As a result, when the actual deceleration falls within the target range, step S10,
The loop of S16, S18, S20, S22 is executed,
The actual deceleration within the target range is maintained. If either of the pedals 12, 18 is depressed while any of the loops is being executed, steps S10 to S12, S14 are executed.
Is executed, and the regenerative braking force is set to 0.

If it is determined in step S20 that the actual deceleration is lower than the lower limit of the target range, it is considered that the electric vehicle is traveling down a slope, for example, and the regenerative braking amount is insufficient. Therefore, the variable RB of the regenerative braking amount is increased by a predetermined amount ΔRB (step S3).
0). Note that RB may be increased by a value corresponding to the difference between the actual deceleration and the target deceleration.

Then, the increased RB is the maximum value M
It is determined whether it is larger than AX (step S32). This maximum value MAX may be the maximum regenerative braking amount that the motors 2 and 2 can output. Or battery 8
It can be set to a value determined from the viewpoint of preventing heat generation and deterioration. In the case of an electric vehicle whose drive range can be changed, a different MAX may be set for each range. Of course, every time the range is changed to "D", "2", "1", MAX is set to be small. by this,
Driving can be performed with a feeling similar to the driving feeling of an internal combustion engine automobile.

If the actual deceleration is larger than MAX, the variable RB of the regenerative braking force is set to MAX (step S3).
4) Then, step S22 is executed, and the RB set to MAX is output. As a result, a regenerative braking force greater than MAX is not output. The actual deceleration is M
If it is not larger than AX, step S22 is executed, and the RB at that time is output as it is.

Following step S22, step S10
The following is executed again. Therefore, if the actual deceleration is smaller than the lower limit of the target range, steps S10, S16, S1
The loop of 8, S20, S30, S32, and S22 is repeated, and when the actual deceleration falls within the target range, step S1 is executed.
The loop of 0, S16, S18, S20, S22 is executed, and the actual deceleration is maintained within the target range. Of course, if the accelerator pedal or the brake pedal is depressed during this process, steps S10 to S12 and S14 are executed, and the regenerative braking force becomes zero.

As described above, the variable RB of the regenerative braking amount
Can be modified only in a predetermined allowable range, for example, in the range of 0 to MAX, so that the vehicle can be driven with the same feeling as an internal combustion engine vehicle.

In the above embodiment, the actual deceleration of the electric vehicle was obtained from the output of the gravity sensor 30, the output of the front wheel speed sensor 28, or the rotation speed of the motors 2, 2. However, an inclination sensor (not shown) may be provided on the electric vehicle to detect the gradient of the electric vehicle traveling on a traveling road, and the regenerative braking amount may be controlled according to the detected value. .

The processing performed by the brake controller 14 in that case will be described with reference to the flowchart shown in FIG. As in the flow chart of FIG.
10, S12 and S14 are executed. If it is determined in step S10 that both pedals 12 and 18 are not depressed, the value θ of the inclination sensor is acquired (step S3).
4). The value θ of the inclination sensor is, for example, a positive value proportional to the inclination angle in the case of an upward gradient, and a negative value proportional to the inclination angle in the case of a downward gradient.

Next, the value of the tilt sensor is judged whether the range of the allowable tilt angle range - [theta] ₀ and + theta ₀ a predetermined (step S36). The permissible tilt angle range is defined as an angle range in which the electric vehicle can be regarded as traveling on flat ground, for example. When it is determined that the inclination angle falls within the allowable inclination angle range, RB is output (step S38). At this time, RB0 determined in step S2 is output as RB.

If it is determined in step S36 that the inclination angle θ is not within the range of the allowable inclination angle range −θ ₀ and + θ ₀ , the inclination angle θ is multiplied by a predetermined coefficient α,
The change amount ΔRB of the regenerative brake is calculated (step S
40). Then, from the regenerative brake amount RB at that time, Δ
RB is subtracted (step S42). When the value of ΔRB is positive (in the case of an upward slope), the value of RB decreases and ΔRB
Is negative (in the case of a downward slope), the value of RB increases.

Next, it is determined whether RB is smaller than 0 (step S44). If it is determined that RB is smaller than 0, RB is set to 0 (step S46), and step S46 is performed.
38 is executed, and an RB that is 0 is output. Also, R
If B is greater than 0, it is determined whether the RB is greater than the maximum value MAX (step S48). RB is MA
If it is larger than X, RB is set to MAX (step S5).
0) Then, step S38 is executed, and the RB set to MAX is output. The value of MAX can be set variously as described in the above embodiment.

When step S38 is executed, step S10 is executed next, and step S34 and subsequent steps are executed unless one of both pedals is depressed. Therefore, as long as the value of the inclination sensor does not change, the regenerative braking force continues to increase or decrease by αθ.

In the above two embodiments, after setting an initial value determined according to the vehicle speed in the RB, the RB is corrected based on the output of the gravity sensor 30 or the like or the inclination sensor.
It is also possible to keep the initial value corresponding to the vehicle speed in the RB without any correction. Further, it is also possible to determine an initial value corresponding to the vehicle speed using the drive range as a parameter, set this initial value as RB, and maintain the RB without correction.

[0050]

As described above, according to the first aspect of the present invention, the regenerative braking force is not a predetermined constant value but a constant regenerative braking force such that the actual deceleration matches the target deceleration. Since the actual deceleration corresponding to the target deceleration can be obtained even when the travel path of the electric vehicle is, for example, a slope, the vehicle is easy to drive. In particular, when traveling downhill, when only a certain amount of regenerative braking force is applied, it is easy to accelerate, the frequency of applying the friction brake by pressing the brake pedal increases, and the energy recovery efficiency decreases However, according to the first aspect of the present invention, since the actual deceleration matches the target deceleration even on a downhill, there is almost no need to apply a friction brake, and the energy recovery efficiency can be improved. Also, even when the vehicle is traveling on an uphill, the regenerative braking force does not become too large, and the frequency of depressing the accelerator pedal is reduced, so that the power consumption of the battery can be improved. This actual deceleration can be obtained from one of various things as described in claim 2.

According to the third aspect of the present invention, when the electric vehicle is traveling on a down slope, the regenerative braking force increases, so that the frequency with which the brake pedal is depressed is reduced, and the energy recovery efficiency is improved. When the electric vehicle is traveling uphill, the regenerative braking is reduced, so that the frequency of pressing the accelerator pedal is reduced, and the power consumption of the battery can be reduced.
As in the fourth aspect of the present invention, an inclination sensor can be used for detecting the inclination.

According to the fifth aspect of the present invention, the regenerative braking force can be changed between an upper limit value and a lower limit value of a predetermined allowable range. do not do. Since an internal combustion engine vehicle has a certain limit in the engine braking force, it can be driven with the same feeling as an internal combustion engine vehicle.

According to the present invention, the regenerative braking force acting on the electric vehicle when both pedals are off is:
It is not a constant value irrespective of the vehicle speed, but is determined, for example, according to the vehicle speed when both pedals are turned off. Therefore, for example, if the vehicle speed is high, the predetermined regenerative braking force also increases. Generally, the engine braking force of an internal combustion engine vehicle is also determined by the vehicle speed when both pedals are turned off. Therefore, a driving feeling close to that of an internal combustion engine automobile can be obtained.

According to the present invention, when the shift range is a high speed range, the predetermined regenerative braking force is the smallest, and when the shift range is a medium speed range, the predetermined regenerative braking force is intermediate. In the low-speed range, the predetermined regenerative braking force is the largest, so that a driving feeling close to that of an internal combustion engine vehicle can be obtained.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a part of a program executed by a brake controller of an embodiment of an electric vehicle traveling control device according to the present invention.

FIG. 2 is a diagram showing another portion of the program executed by the brake controller of the embodiment.

FIG. 3 is a diagram showing a relationship between a vehicle speed and an initial value of regenerative energy in the embodiment.

FIG. 4 is a block diagram of the embodiment.

FIG. 5 is a flowchart showing a program executed by a brake controller of another embodiment of the travel control device for an electric vehicle according to the present invention.

[Explanation of symbols]

 2 front wheel 4 rear wheel 6 motor 8 battery 10 inverter 12 accelerator pedal 14 brake controller (control means) 18 brake pedal 30 gravity sensor (actual deceleration detecting means)

Claims (7)

[Claims] 1. An electric vehicle in which a predetermined regenerative braking force equivalent to engine braking is applied when an accelerator pedal and a brake pedal are off, wherein an actual deceleration of the electric vehicle caused by the regenerative braking force is detected. A travel control device for an electric vehicle, comprising: an actual deceleration detecting unit that performs the operation; and a control unit that increases and decreases the regenerative braking force so that the detected actual deceleration matches the target deceleration. 2. The traveling control device for an electric vehicle according to claim 1, wherein the actual deceleration is a rotation speed detector of a motor of the electric vehicle, a wheel speed detector of the electric vehicle, and a gravity sensor of the electric vehicle. A travel control device for an electric vehicle obtained by at least one of the following. 3. An electric vehicle in which a predetermined regenerative braking force equivalent to engine braking is applied when an accelerator pedal and a brake pedal are off, a gradient detecting means for detecting a gradient of a road surface in a traveling direction of the electric vehicle. When the gradient of the road surface detected by the gradient detecting means is a downward gradient, the regenerative braking force is increased in accordance with the downward gradient, and when the detected gradient of the road surface is an upward gradient, Control means for decreasing the regenerative braking force according to the following. 4. The travel control device for an electric vehicle according to claim 3, wherein the gradient detecting means is a tilt sensor provided in the electric vehicle. 5. The travel control device for an electric vehicle according to claim 1, wherein the increased / decreased regenerative braking force is output within a predetermined allowable range. 6. An electric vehicle in which a predetermined regenerative braking force equivalent to an engine brake is applied when an accelerator pedal and a brake pedal are off, wherein the regenerative braking force is changed according to a vehicle speed of the electric vehicle. Running control device for an electric vehicle having the means. 7. The travel control device for an electric vehicle according to claim 1, wherein the electric vehicle has a shift range, and the predetermined regenerative braking force is set according to the shift range. Travel control device for electric vehicles.