JP3075011B2 - Braking system for electric vehicles with continuously variable transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric vehicle in which a continuously variable transmission is incorporated between wheels and a driving electric motor, and more particularly to a technique for improving characteristics during braking.

[0002]

2. Description of the Related Art In the case of an electric vehicle, a method is used in which a regenerative torque is generated in a driving electric motor during vehicle braking, and a braking force of the vehicle is obtained by the regenerative torque. An example of this technique is disclosed in Japanese Patent Application Laid-Open No. Sho 59-209004. In this technique, the operation amount of a braking operation member such as a brake pedal is detected, and the electric motor is controlled so that a larger regenerative torque is obtained as the operation amount increases. As a result, a larger regenerative torque is generated as the operation amount is larger, so that a larger braking force can be obtained. In order to operate the electric motor under efficient conditions in various running states, it is effective to incorporate a continuously variable transmission between the electric motor and the wheels. That is, while the vehicle is running at a low speed, the speed ratio is increased to rotate the motor at a relatively high speed relative to the vehicle speed. I will drop it. In this case, the electric motor can always operate efficiently regardless of the vehicle speed.

In the case of an electric vehicle incorporating a continuously variable transmission,
The gear ratio must be maximized when the vehicle stops. Here, the gear ratio is the value obtained by dividing the input shaft rotation speed by the output shaft rotation speed.If this is the maximum, the motor output torque is amplified to the maximum and transmitted to the wheels, and the vehicle starts immediately. it can.

[0004]

An electric vehicle with a continuously variable transmission employs a conventional technique, that is, a technique of increasing a regenerative torque generated in an electric motor in accordance with an operation amount of a braking operation member such as a brake pedal. In application, as the vehicle speed decreases due to braking and the gear ratio increases, the braking torque generated on the wheels increases. The braking torque acting on the wheels is a value obtained by multiplying the regenerative torque generated by the motor by the speed ratio.The speed ratio increases with a decrease in the vehicle speed, so the braking torque also increases with a decrease in the vehicle speed. . For this reason, according to the conventional technique, even if the operation amount of the braking operation member such as the brake pedal is fixed, the braking torque increases during braking, and the vehicle is suddenly decelerated. That is, according to the conventional technique, the brake feeling is deteriorated. The present invention aims to improve the brake feeling of an electric vehicle with a continuously variable transmission.

[0005]

In order to solve the above problems, the present invention has created a braking device for an electric vehicle with a continuously variable transmission having the following structure. This braking device is a braking device for an electric vehicle in which a continuously variable transmission 4 is incorporated between a wheel 2 and an electric motor 6, as schematically shown in FIG. A speed ratio control device 10 that increases the speed ratio of the continuously variable transmission 4 with a decrease in vehicle speed during braking and sets the maximum speed ratio when the vehicle stops even if it is slow;
A torque control device 12 that reduces the regenerative torque of the electric motor 6 as the vehicle speed decreases during braking (corresponding to claim 1).

Here, it is preferable that the increasing tendency of the speed ratio and the decreasing tendency of the regenerative torque with respect to the decrease of the vehicle speed are set so that the braking torque obtained by multiplying the speed ratio by the regenerative torque becomes substantially constant. (Corresponds to item 2). Further, an operation amount detecting means for a braking operation member such as a brake pedal is added, and as the operation amount increases, the regenerative torque of the motor is increased so that the braking torque obtained by multiplying the speed ratio by the regenerative torque increases. Is preferably controlled (corresponding to claim 3).

Further, when the gear ratio control device controls the gear ratio, the larger the operation amount of the braking operation member such as the brake pedal, the more the vehicle speed starts to increase from the higher speed, and the higher the vehicle speed. To reach the maximum speed ratio (corresponding to claim 4). That is, the speed ratio increase start vehicle speed and the maximum speed ratio realizing vehicle speed are made higher as the operating member is operated larger.

[0008]

According to the braking device shown in FIG. 1A, while the vehicle is being braked, the gear ratio increases as the vehicle speed decreases as shown in FIG. 1B. As shown in (C), the regenerative torque of the motor 6 is reduced. For this reason, the increasing tendency of the speed ratio is canceled by the decreasing tendency of the regenerative torque, and a sudden increase in the braking torque during braking is suppressed. Therefore, a good brake feeling can be obtained. Here, if the value obtained by multiplying the gear ratio by the regenerative torque is kept constant, the braking torque generated on the wheels is kept constant as shown in FIG. Get better.

Further, when the braking torque obtained by multiplying the transmission ratio by the regenerative torque increases in accordance with the operation amount of a braking operation member such as a brake pedal, a larger braking torque is obtained as the operator desires sudden braking. By being
The braking feeling becomes very natural. Further, if the speed ratio increase starting vehicle speed and the maximum speed ratio realizing vehicle speed are higher as the operation amount of the braking operation member is larger, a larger braking torque can be obtained from an earlier stage as the operator desires abrupt braking. become. Therefore, the brake feeling is further improved, the regenerative efficiency of the motor is improved, and further, it is possible to prevent the gear ratio from returning to the maximum gear ratio when the vehicle is stopped.

[0010]

Next, an embodiment of the present invention will be described. FIG. 2 shows a system configuration of the electric vehicle of this embodiment. In the figure, reference numeral 6 denotes an electric motor that functions as a driving motor during power running and generates regenerative energy during braking to contribute to braking. For example, a three-phase induction motor can be used. The motor 6 is rotated by receiving power supply from the battery 8, and at the time of braking, obtains regenerative energy to charge the battery 8.

Reference numeral 4 in the figure denotes a continuously variable transmission, for example, a toroidal type continuously variable transmission is suitably used. The continuously variable transmission 4 is incorporated between the electric motor 6 and the wheels 2.
The continuously variable transmission 4 is capable of continuously adjusting the speed ratio (the value obtained by dividing the input shaft rotation speed, ie, the motor rotation speed, by the output shaft rotation speed, ie, the wheel rotation speed). Continuously variable transmission 4
Is controlled by the gear ratio control device 10, and the driving torque or the regenerative torque of the electric motor 6 is controlled by the torque control device 12.

In FIG. 1, reference numeral 14 denotes a motor speed sensor 14, which uses an encoder attached to the motor 6. A vehicle speed sensor 16 detects the rotation speed of the wheel shaft. Reference numeral 18 denotes an accelerator opening sensor that detects an amount of depression of an accelerator pedal. A brake switch 20 is turned on when a braking operation member such as a brake pedal is operated. 22 is a sensor for detecting the operation amount of the braking operation member, such as the amount of depression of the brake pedal,
In this case, a sensor that detects the hydraulic pressure of a hydraulic brake described later is used.

The electric vehicle also incorporates a mechanical braking device. When a brake pedal 28 is depressed, a cylinder 26 operates to actuate a hydraulic mechanical brake 24 to brake the rotation of the wheels 2. Here, the oil pressure in the oil passage between the cylinder 26 and the brake 24 changes according to the amount of depression of the brake pedal 28. The oil pressure sensor 22 detects the operation amount of the braking operation member by detecting the oil pressure.

The gear ratio control device 10 comprises a computer and an actuator controlled by the computer, and the actuator increases or decreases the gear ratio. The torque control device includes a switching element such as a thyristor incorporated between the battery 8 and the motor 6, a firing angle control circuit thereof, a computer, and the like. The gear ratio control device 10 and the torque control device 12 include the sensors 14 to 22.
Is input.

The gear ratio control device 10 controls the gear ratio of the continuously variable transmission 4 in accordance with the procedure shown in FIG. In FIG.
Step S22 is for determining whether or not braking is being performed.
On / off of the brake switch 20 is determined. When it is on, that is, during braking, the processing after step S24 is executed, and during non-braking, processing after step S30 is executed.

During braking, the hydraulic pressure sensor 2 is determined in step S24.
2 is input. Thus, the operation amount of the braking operation member is detected. Next, at step S26, the vehicle speed sensor 16
To detect the current vehicle speed. After the above processing, the target gear ratio is calculated in step S28. In step S28,
The map shown in FIG. 5A is used.

FIG. 5A is a diagram in which the horizontal axis is the vehicle speed, the oil pressure is a parameter, and the target gear ratio is the vertical axis. The hydraulic pressure is converted into a unit obtained by dividing the amount of depression of the brake pedal by the entire stroke, and is 0%, 25%, 50% in FIG.
%, 75% and 100% cases are shown. Actually, the intermediate hydraulic pressure is also mapped.

In the figure, a100 indicates the relationship between the vehicle speed and the target gear ratio when the vehicle is depressed by 100%. Similarly, when a75 is 75%, a50 is 50%, a25
Is 25%, and a0 shows the relationship between the vehicle speed and the target gear ratio during coasting. Since the vehicle speed decreases during braking, the phenomenon proceeds from right to left, and the speed ratio increases as the vehicle speed decreases. In the figure, V1 indicates the vehicle speed at which the gear ratio starts increasing, and the higher the brake pedal is depressed, the higher the speed. That is, V1-100>V1-75>
V1-50>V1-25> V1-0. The V2 shows the vehicle speed when the gear ratio reaches a maximum speed ratio gamma _MAX, and has a fast enough when the brake pedal is depressed strongly. That is, V2-100>
V2-75>V2-50>V2-25> V2-0.

If the regenerative torque of the motor 6 is constant,
The larger the gear ratio, the greater the braking torque. According to the relationship shown in FIG. 5A, as the brake pedal is depressed more strongly, a larger braking torque is obtained from an earlier stage. This is a natural relationship, and a natural brake feeling can be obtained.

On the other hand, during power running, the steps after step S30 in FIG. 4 are executed, and the target gear ratio is determined based on the depression amount of the accelerator pedal and the vehicle speed. The gear ratio control device 10 operates the actuator to adjust the gear ratio of the continuously variable transmission 4 to the target gear ratio determined in steps S28 and S34 (step S36).

The torque control device controls the torque of the electric motor 6 in accordance with the procedure shown in FIG. Step S2
Is for determining whether or not braking is being performed. Step S22
Works equally well with. During braking, the steps after step S4 are executed.
In step S4, a value corresponding to the amount of depression of the brake pedal is input, and in step S6, the vehicle speed is input. Thereafter, the target regenerative torque is calculated in step S8.

In step S8, the map shown in FIG. 5B is used. In FIG. 5B, the vehicle speed is plotted on the horizontal axis, the amount of depression of the brake pedal is used as a parameter, and the target regenerative torque is plotted on the vertical axis. In the figure, the subscript 100 is 75, 50, 25 when the brake pedal is depressed 100%.
Indicates that the vehicle is depressed by 75, 50, and 25%, respectively, and 0 indicates that the vehicle is coasting. During braking, the vehicle speed decreases and the phenomenon proceeds from right to left. That is, the regenerative torque is reduced as the vehicle speed decreases. Here, the vehicle speed at which the regenerative torque starts decreasing is set equal to the vehicle speed at which the speed ratio starts increasing. The vehicle speed at which the reduction of the regenerative torque ends is set equal to the maximum speed ratio realizing vehicle speed.

In this manner, the speed ratio increasing during braking is compensated by the regenerative torque decreasing during braking, and the control torque during braking does not increase rapidly. Thus, according to the present embodiment, rapid deceleration during braking is prevented, and a good brake feeling is obtained.

In this embodiment, the maps shown in FIGS. 5A and 5B are determined so that the braking torque obtained by multiplying the speed ratio by the regenerative torque is substantially constant. Also, as shown in FIG. 5C, the relationship is set such that the greater the braking pedal is, the greater the braking torque is. Unless the amount of depression of the brake pedal is changed, the braking torque does not change during braking, so that the brake feeling is extremely good. Also, the more the brake pedal is depressed (generally, the larger the operation member for braking is operated), the larger the braking torque is obtained, so that the brake feeling is natural.

When the speed ratio during braking and the regenerative torque are controlled as shown in FIGS. 5A and 5B, the motor speed during braking changes as shown in FIG. 5D. Again, the phenomenon proceeds from right to left. In the figure, d1 is a characteristic when no transmission is provided. On the other hand, d100 to d0 show the case according to this embodiment. As shown by the arrow d2, according to this embodiment, the motor speed during braking is kept high.

FIG. 5E shows the motor efficiency.
The line e90 shows the motor rotation speed and the regenerative torque at which 90% efficiency can be obtained.
% And 80% are shown.

According to the present embodiment, as described with reference to FIG. 5D, it can be seen that the motor speed during braking is kept high, so that it can be used under conditions of good regenerative efficiency. As described above, according to the present embodiment, regenerative energy can be obtained with high efficiency, and the battery can be charged efficiently.

[0028]

According to the present invention, there is provided an electric vehicle in which a continuously variable transmission is incorporated between an electric motor and wheels so that the motor can be efficiently used. Since the regenerative torque is reduced, the braking torque is maintained at a substantially good level during the control, and a good brake feeling is obtained. In particular, if the product of the increasing tendency of the speed ratio and the decreasing tendency of the regenerative torque is set to be constant, the braking torque will be constant unless the operation amount of the braking operation member such as the brake pedal is changed, Extremely good brake feeling. Furthermore, if a larger braking torque is obtained as the operation amount of the braking operation member is larger, a natural brake feeling can be obtained.

If the speed ratio increase start vehicle speed and the maximum speed ratio realizing vehicle speed are set to be higher as the operation amount is larger, a larger braking torque is generated from an earlier stage as the operator desires a stronger braking action. Thus, a very desirable brake feeling can be obtained. At the same time, the regeneration efficiency can be increased. As described above, according to the present invention, it is possible to realize an electric vehicle having good brake feeling and high energy efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram conceptually illustrating the present invention.

FIG. 2 is a system diagram of an embodiment.

FIG. 3 is a diagram showing a torque braking procedure.

FIG. 4 is a diagram showing a procedure for braking a gear ratio.

FIG. 5 is a characteristic diagram of a gear ratio, a regenerative torque, etc.

[Explanation of symbols]

 2 Wheel 4 Continuously variable transmission 6 Electric motor 10 Gear ratio control device 12 Torque control device

Claims (4)

(57) [Claims] 1. A braking device for an electric vehicle in which a continuously variable transmission is incorporated between wheels and an electric motor, wherein during braking, a speed ratio of the continuously variable transmission is increased with a decrease in vehicle speed; A gear ratio control device that sets the maximum gear ratio when the vehicle is stopped at the latest, and a torque control device that reduces the regenerative torque of the electric motor as the vehicle speed decreases during braking. A braking device for an electric vehicle with a continuously variable transmission. 2. The braking device for an electric vehicle with a continuously variable transmission according to claim 1, wherein the tendency of the speed ratio to increase with decreasing vehicle speed and the tendency of decreasing regenerative torque with decreasing vehicle speed are determined by multiplying the speed ratio and the regenerative torque. A braking device for an electric vehicle with a continuously variable transmission, wherein the obtained braking torque is set so as to be maintained substantially constant. 3. The braking device for an electric vehicle with a continuously variable transmission according to claim 1, wherein the electric vehicle further includes an operation amount detecting means for a braking operation member, and the speed ratio and the regeneration during braking. A braking device for an electric vehicle with a continuously variable transmission, wherein a value obtained by multiplying the torque is substantially maintained at a larger braking torque as the operation amount detected by the operation amount detecting means is larger. 4. A braking device for an electric vehicle in which a continuously variable transmission is incorporated between wheels and an electric motor, and an operation amount detecting means of a braking operation member is incorporated. As the operation amount detected by the amount detection means is larger, the vehicle speed at the start of the increase of the gear ratio is increased and the vehicle speed reaching the maximum gear ratio is also increased. A braking device for an electric vehicle with a continuously variable transmission, comprising a speed ratio control device for increasing a speed ratio.