JPH06315207A - Brake system for electric automobile equipped with variable speed drive - Google Patents

Abstract

PURPOSE:To enhance brake feeling by assembling a variable speed drive between a wheel and a motor and providing a controller for increasing the speed change ratio as the vehicle speed decreases during brake operation up to a maximum speed change ratio at the time of stoppage of the vehicle, and a torque controller for decreasing the regenerative torque of the motor as the vehicle speed decreases. CONSTITUTION:Speed change ratio of a variable speed drive 4 is controlled by a speed change ratio controller 10 and the drive torque or the regenerative torque of a motor 6 is controlled by a torque controller 12. The speed change ratio controller 10 comprises a computor and an actuator being controlled by the computor to increase/decrease the speed change ratio. The torque controller 12 comprises a switching element, e.g. a thyristor, assembled between a battery 8 and the motor 6, a firing angle controller therefor, a computor, etc. The speed change controller 10 and the torque controller 12 receive signals from sensors 14-22. This constitution improves brake feeling and energy efficiency.

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 a wheel and an electric motor for driving, 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 when the vehicle is braked, and the braking force of the vehicle is obtained by the regenerative torque. An example of this technique is disclosed in Japanese Patent Laid-Open No. 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 the larger the operation amount is, the larger the regenerative torque is obtained. As a result, a larger regenerative torque is generated as the operation amount is larger, and a larger braking force is obtained. In order to make the electric motor work 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 at a low speed, the gear ratio is increased to rotate the motor at a relatively high speed relative to the vehicle speed, and when the vehicle speed is high, the gear ratio is decreased to reduce the motor rotation speed relative to the vehicle speed. Drop it. In this way, the electric motor can always work efficiently regardless of the vehicle speed.

In the case of an electric vehicle incorporating a continuously variable transmission,
It is necessary to maximize the gear ratio when the vehicle is stopped. Here, the gear ratio is the value obtained by dividing the input shaft speed by the output shaft speed.When this is the maximum value, the motor output torque is amplified to the maximum and transmitted to the wheels, and the vehicle starts immediately. it can.

[0004]

A conventional technique, namely, a technique of increasing a regenerative torque generated in an electric motor according to an operation amount of a braking operation member such as a brake pedal is applied to an electric vehicle with a continuously variable transmission. When applied, the braking torque generated on the wheels increases as the vehicle speed decreases due to braking and the gear ratio increases. The braking torque acting on the wheels is a value obtained by multiplying the regenerative torque generated in the motor by the gear ratio.Since the gear ratio increases as the vehicle speed decreases, the braking torque also increases as the vehicle speed decreases. . Therefore, according to the conventional technique, even if the amount of operation of the braking operation member such as the brake pedal is constant, 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 is intended 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 configuration. 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 the concept is schematically shown in FIG. 1 (A). A gear ratio control device 10 that increases the gear ratio of the continuously variable transmission 4 as the vehicle speed decreases during braking, and sets the maximum gear ratio when the vehicle is stopped even at a slow speed.
During braking, a torque control device 12 that reduces the regenerative torque of the electric motor 6 as the vehicle speed decreases (corresponding to claim 1).

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

Further, when the gear ratio control device controls the gear ratio, as the operation amount of the braking operation member such as the brake pedal is larger, the gear ratio starts to increase from the faster vehicle speed and the faster vehicle speed. It is preferable that the maximum gear ratio is reached by (corresponding to claim 4). That is, the vehicle speed at which the gear ratio increase starts and the vehicle speed at which the maximum gear ratio is achieved become faster as the operating member is operated more.

[0008]

According to the braking device shown in FIG. 1 (A), while the vehicle is being braked, the gear ratio increases as the vehicle speed decreases as shown in FIG. 1 (B), while the braking ratio shown in FIG. As shown in (C), the regenerative torque of the motor 6 is reduced. Therefore, the increasing tendency of the gear 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. If the value obtained by multiplying the gear ratio by the regenerative torque is kept constant, the braking torque generated at the wheels will be kept constant as shown in Fig. 1 (D), and the brake feeling will be extremely high. Get better.

Further, when the braking torque obtained by multiplying the gear ratio by the regenerative torque becomes large in accordance with the operation amount of the braking operation member such as the brake pedal, a large braking torque is obtained as when the operator desires a sudden braking. By being
The braking feeling is very natural. Further, if the vehicle speed at which the gear ratio increase starts and the vehicle speed at which the maximum gear ratio is achieved 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 a sudden braking. become. Therefore, the brake feeling is further improved, the regeneration efficiency of the motor is improved, and it is possible to prevent the gear ratio from returning to the maximum gear ratio even when the vehicle is stopped.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment embodying the present invention will be described. FIG. 2 shows the system configuration of the electric vehicle of this embodiment. Reference numeral 6 in the figure is an electric motor that functions as a drive motor during power running and that generates regenerative energy during braking and contributes to braking. For example, a three-phase induction motor can be used. The motor 6 is supplied with electric power from the battery 8 to rotate, while regenerative energy is obtained during braking to charge the battery 8.

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

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

A mechanical braking device is also incorporated in this electric vehicle. When the brake pedal 28 is depressed, the cylinder 26 operates to activate the hydraulic mechanical brake 24 to brake the rotation of the wheels 2. Here, the hydraulic pressure in the oil passage between the cylinder 26 and the brake 24 changes according to the depression amount of the brake pedal 28. The oil pressure sensor 22 detects an 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 is composed of a switching element such as a thyristor incorporated between the battery 8 and the motor 6, its ignition angle control circuit, a computer, and the like. The gear ratio control device 10 and the torque control device 12 include the sensors 14 to 22.
Signal is input.

The gear ratio control device 10 controls the gear ratio of the continuously variable transmission 4 according to the procedure of FIG. In FIG.
Step S22 is to determine whether or not braking is in progress,
The on / off state 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, the processing after step S30 is executed.

During braking, the hydraulic pressure sensor 2 is operated at step S24.
Input 2 signal. Thereby, the operation amount of the braking operation member is detected. Next, in step S26, the vehicle speed sensor 16
The current vehicle speed is detected by. After the above processing, the target gear ratio is calculated in step S28. In step S28,
The map of FIG. 5 (A) is used.

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

In the figure, a100 indicates the relationship between the vehicle speed and the target gear ratio when the vehicle is fully depressed. Similarly thereafter, when a75 is 75%, a50 is 50%, a25
Indicates a relationship between the vehicle speed and the target gear ratio during coasting at 25%, and a0. Since the vehicle speed decreases during braking, the phenomenon progresses from right to left, and the gear ratio increases as the vehicle speed decreases. In the figure, V1 indicates the vehicle speed at which the gear ratio starts to increase, and the higher the brake pedal is depressed, the higher the vehicle speed. That is, V1-100>V1-75>
The relationship is V1-50>V1-25> V1-0. Further, V2 indicates the vehicle speed when the gear ratio reaches the maximum gear ratio γ _MAX , and becomes higher as the brake pedal is strongly depressed. That is, V2-100>
They are in a relationship of V2-75>V2-50>V2-25> V2-0.

When the regenerative torque of the motor 6 is constant,
The larger the gear ratio is, the larger the braking torque can be obtained. According to the relationship shown in FIG. 5 (A), the stronger the brake pedal is depressed, the larger the braking torque can be obtained from an earlier stage. This is a natural relationship and will give a natural brake feeling.

On the other hand, during power running, step S30 and subsequent steps in FIG. 4 are executed, and the target gear ratio is determined by 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 processing procedure of FIG. Step S2
Is for determining whether or not braking is being performed, and step S22
Works the same as. During braking, steps S4 and after are executed,
In step S4, a value corresponding to the brake pedal depression amount is input, and in step S6, the vehicle speed is input. After that, 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. The subscript 100 in the figure is 75, 50, 25 when the brake pedal is fully depressed.
Indicates 75, 50, and 25% of depression, and 0 indicates coasting. The vehicle speed decreases during braking, and the phenomenon progresses from right to left. That is, the regenerative torque decreases as the vehicle speed decreases. Here, the reduction start vehicle speed of the regenerative torque is made equal to the increase start vehicle speed of the gear ratio. The vehicle speed at which the reduction of the regenerative torque is finished is made equal to the maximum speed ratio achieved vehicle speed.

In this way, the gear ratio that increases during braking is compensated by the regenerative torque that decreases during braking, and the control torque during braking does not rise sharply. In this way, according to this embodiment, it is possible to prevent a sudden deceleration during braking and to obtain a good brake feeling.

In the case of this embodiment, the maps of FIGS. 5A and 5B are determined so that the braking torque obtained by multiplying the gear ratio by the regenerative torque becomes substantially constant. Further, as shown in FIG. 5 (C), the braking torque is set to have a larger value as the brake pedal is strongly depressed. As long as the amount of depression of the brake pedal is not changed, the braking torque does not change during braking, so the brake feeling is extremely good. Further, the stronger the brake pedal is depressed (generally, the larger the operating member for braking is operated), the larger the braking torque is obtained, so that the brake feeling is natural.

When the gear ratio and the regenerative torque during braking are controlled as shown in FIGS. 5 (A) and 5 (B), the motor rotational speed during braking changes as shown in FIG. 5 (D). In this case also, the phenomenon progresses from right to left. In the figure, d1 is the characteristic when the transmission is not provided. On the other hand, d100 to d0 indicate the case according to this embodiment. As shown by the arrow d2, according to this embodiment, the motor rotational speed during braking is kept high.

FIG. 5 (E) shows the motor efficiency.
The line e90 shows the motor speed and regenerative torque at which 90% efficiency is obtained, and e85 and e80 are 85 respectively.
%, 80% efficiency is obtained.

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

[0028]

According to the present invention, in an electric vehicle in which a continuously variable transmission is incorporated between an electric motor and wheels to enable efficient use of the motor, the gear ratio is increased during braking while the vehicle speed decreases. Since the regenerative torque is reduced, the braking torque is maintained at a substantially good level during control, and a good brake feeling is obtained. In particular, when the increasing ratio of the gear ratio and the decreasing tendency of the regenerative torque are set such that the product of both is constant, the braking torque becomes constant unless the operation amount of the braking operation member such as the brake pedal is changed, The brake feel is extremely good. Furthermore, when a larger braking torque is obtained as the operation amount of the braking operation member is larger, a natural brake feeling is obtained.

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

[Brief description of drawings]

FIG. 1 is a diagram conceptually showing 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 braking procedure of a gear ratio.

[Figure 5] Characteristic diagram of gear ratio, regenerative torque, etc.

[Explanation of symbols] 2 wheels 4 continuously variable transmission 6 electric motor 10 gear ratio control device 12 torque control device

Claims (4)

[Claims] 1. A braking device for an electric vehicle in which a continuously variable transmission is incorporated between a wheel and an electric motor, wherein a gear ratio of the continuously variable transmission is increased with a decrease in vehicle speed during braking. The vehicle is characterized by including a gear ratio control device that sets a 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. Braking device for electric vehicles with continuously variable transmission. 2. The braking system for an electric vehicle with a continuously variable transmission according to claim 1, wherein the increasing ratio of the gear ratio with respect to a decrease in vehicle speed and the decreasing tendency of the regenerative torque with respect to a decrease in vehicle speed are multiplied by the gear 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 an operation amount detecting means for a braking operation member is added to the electric vehicle, and the gear ratio and the regeneration are provided 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 a wheel and an electric motor, and an operation amount detection means of a braking operation member is incorporated, the operation being performed during braking. The larger the operation amount detected by the amount detecting means, the higher the vehicle speed at the start of the increase of the gear ratio and the higher the vehicle speed at which the maximum gear ratio is reached. A braking device for an electric vehicle with a continuously variable transmission, comprising a gear ratio control device for increasing a gear ratio.