JPH10271607A - Brake control equipment of electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and effectively prevent overcharge of a battery, by driving each brake means under the distribution ratio obtained by a brake force distribu tion deciding means, and applying deceleration which is obtained by a decelera tion operating means to a vehicle. SOLUTION: Mechanical brake force is applied to a rotation system of a wheel 4 by driving a brake actuator 7 by using a mechanical brake means of a controller 3, when brake operation is detected with a brake switch 5. Regenerative brake force is electrically applied to the wheel 4 by setting regenerative mode to a motor 2 and generating regenerative brake force on the motor 2 by using an electrical brake means of the controller 3. Distribution ratio of the mechanical brake force and the regenerative brake force is decided in accordance with the maximum cell voltage of a battery 1. Deceleration which is obtained in accordance with the number of revolutions of the motor 2 is applied to a vehicle, by driving the electrical brake means and the mechanical brake means, in order to totally obtain the brake force under the distribution ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric vehicle powered by an electric motor driven by a battery, and more particularly to applying a regenerative braking and a mechanical braking in accordance with a charging voltage of the battery to apply a braking force. The present invention relates to a braking control device for an electric vehicle as described above.

[0002]

2. Related Art Recently, electric motors (motors) driven by batteries such as Li-ion batteries mounted on vehicles.
2. Description of the Related Art An electric vehicle powered by a power source has attracted attention. Also, in this type of electric vehicle, when the motor is not driven by the battery, conversely, the rotational force of the wheels is applied to the motor to become a load, and a braking force is generated. At this time, the battery is charged using regenerative energy generated in the electric motor. An electric braking technique using such an electric motor is called regenerative braking, and is effective in recovering kinetic energy of a vehicle.

[0003] Incidentally, overcharging of a battery is a factor that causes significant deterioration of the battery characteristics. Therefore, when the battery is fully charged, it is desirable to avoid charging the battery using energy obtained by regenerative braking by the electric motor as much as possible. Therefore, for example, Japanese Patent Application Laid-Open No. 5-252606 discloses that when a battery is almost fully charged at the time of a brake operation, regenerative energy generated in the motor is generated and consumed inside the motor, thereby suppressing charging of the battery. However, it is disclosed that a necessary regenerative braking force is obtained. However, in this case, a new thermal problem occurs, and the configuration of the control system is inevitably complicated.

On the other hand, JP-A-5-284607 discloses that the amount of energy that can be recovered by regenerative braking changes according to the state of deterioration of the battery. It is disclosed that a braking force indicated by the brake operation amount is obtained by using the brake operation amount together with mechanical braking such as a hydraulic pressure driven in accordance with the above-mentioned brake operation.

[0005]

A battery mounted on an electric vehicle is usually realized as an assembled battery in which a plurality of battery cells are connected in series. The electrical characteristics of a plurality of battery cells constituting such an assembled battery (battery) are not always uniform, and usually, not only potential variations due to manufacturing errors, but also charging due to the usage environment (ambient temperature). Variations in the discharge characteristics are also likely to occur. Therefore, even if the overcharge is prevented by controlling the regenerative braking while monitoring the state of charge of the battery based on, for example, the voltage between terminals and the amount of discharge current, only specific battery cells are overcharged. There is a fear.

[0006] Incidentally, when a specific battery cell is overcharged and its charge / discharge characteristics deteriorate, the effect spreads to other battery cells constituting the assembled battery in a chain fashion, and the charge / discharge characteristics of the whole battery deteriorate significantly. I do. If the detection level of the fully charged state of the battery is set low in order to prevent such a problem, the regenerative braking can be applied only when the battery charging energy has been consumed to some extent, and the regenerative braking condition is greatly limited. Will be. Then, the effect of recovering the kinetic energy of the vehicle by the regenerative braking is weakened, and the battery cannot be charged efficiently using the kinetic energy of the vehicle. In addition, it is difficult to obtain a smooth braking effect by regenerative braking peculiar to the electric vehicle.

On the other hand, in an electric vehicle, regenerative braking (regenerative braking) corresponding to engine braking is performed not only at the time of a brake operation as disclosed in the above-mentioned publications, but also when the accelerator operation is stopped (throttle OFF). Is considered to be effective in efficiently collecting the kinetic energy of the vehicle, reducing the brake operation and improving the driving feeling.

However, even when the regenerative brake corresponding to the engine brake is applied when the accelerator is turned off, if the regenerative braking is controlled in consideration of the variation of the battery cells as described above, a necessary braking force may be required depending on the state of charge of the battery. May not be obtained. In this case, as shown in the above-mentioned publication, it is conceivable to supplement the insufficient braking force by using mechanical braking such as hydraulic pressure in combination.
To operate the mechanical braking means, a separate brake operation is required. That is, since the expected braking force (deceleration effect) cannot be obtained even when the foot is released from the accelerator pedal, it is necessary to operate the brake again to activate the mechanical braking means. This leads to a feeling of discomfort as well as a feeling of uneasiness in driving, and also increases the frequency of brake operation.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention to make it possible to charge a battery efficiently during braking while simplifying and effectively preventing overcharging of the battery. Another object of the present invention is to provide a braking control device for an electric vehicle, which can surely obtain a braking force without a sense of incongruity in accordance with a driving operation, and can sufficiently enhance the driving feeling.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an electric vehicle equipped with a battery mounted on a vehicle and an electric motor driven by the battery, wherein the electric motor has a regenerative braking force. And electrical braking means for applying a braking force to the vehicle by generating the braking force, mechanical braking means for applying a mechanical braking force to the rotating system of the vehicle, and control means for controlling each of these braking means. A throttle operation detecting means for detecting a throttle operation of the vehicle, a brake operation detecting means for detecting a brake operation on the vehicle, and a running state detection for detecting a running state of the vehicle. Means, deceleration calculating means for calculating a deceleration required for the vehicle based on each of these detection results, and a state of charge of the battery, for example. Charging state detecting means for detecting as a maximum terminal voltage in a plurality of battery cells constituting a battery; and the electric state according to a charging state of the battery detected by the charging state detecting means, for example, a maximum terminal voltage of the battery cell. A braking force distribution ratio determining means for determining a distribution ratio between the braking force applied by the braking means and the braking force applied by the mechanical braking means; By driving each of the braking means, the deceleration obtained by the deceleration calculating means is given to the vehicle.

That is, for example, a maximum terminal voltage of the battery cell is obtained as an index indicating the state of charge of the battery, and a distribution ratio between the regenerative braking force and the mechanical braking force is set according to the maximum cell voltage. Then, the deceleration obtained according to the driving operation or the running state of the vehicle is distributed to the electric braking means and the mechanical braking means in accordance with the above-mentioned distribution ratio, and each braking means is driven, whereby the required deceleration (control) is performed. The kinetic energy of the vehicle is recovered in accordance with the state of charge of the battery while the power is maintained, and the battery is efficiently charged.

Incidentally, the mechanical braking means shown here is opposed to electric braking by regenerative braking using an electric motor, and is mechanically using a link mechanism or a vehicle using a fluid such as hydraulic pressure. It is a general term for a brake mechanism that directly applies a braking force to a rotating system, for example, an axle or a wheel.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an electric vehicle braking control apparatus according to an embodiment of the present invention. FIG. 1 is a diagram showing a schematic control system of an electric vehicle. In the figure, reference numeral 1 denotes a Li-ion battery or Ni-H mounted on a vehicle.
It is a battery composed of a battery or the like, and is generally realized as an assembled battery in which a plurality of battery cells are connected in series to obtain a required inter-terminal voltage. The motor (electric motor) 2 is operated by receiving electric power (charging energy) from the battery 1, and its driving force (rotational speed) is controlled by the controller 3. The motor 2 drives the wheels 4 to rotate, and the electric vehicle travels.

The controller 3 detects a driving operation state detected by the brake switch 5 and the throttle sensor 6, and further detects a traveling state of the electric vehicle from the rotation speed of the motor 2. Further, the controller 3 monitors each terminal voltage (cell voltage) of a plurality of battery cells constituting the battery 1. Controller 3
Controls the driving (powering or regeneration) of the motor 2 in accordance with the detection results, and, when a brake operation is detected by the brake switch 5, for example, drives the brake actuator 7 to drive the wheel 4 or the wheel 4 to apply a braking force to a rotating system such as an axle for driving the rotation of the motor 4 (mechanical braking means). An electric braking force is applied to the wheels 4 (electric braking means).

By setting the regenerative mode for the motor 2, the regenerative energy generated in the motor 2 by receiving the rotational force from the wheels 4, which is the kinetic energy of the vehicle, is controlled by the battery 3 under the control of the controller 3. And the battery 1 is charged. However, the charging of the battery 1 with the regenerative energy is managed by regenerative braking control described later based on the result of monitoring the terminal voltages of the plurality of battery cells constituting the battery 1 described above.

The controller 3 detects not only the operation of depressing the brake pedal by the brake switch 5 but also the amount of braking operation corresponding to the depressing force by, for example, a pressure sensor incorporated in the brake pedal. The throttle sensor 6 detects not only the depression operation of the accelerator pedal but also the acceleration operation amount corresponding to the depression amount.

In the electric vehicle according to this embodiment, for example, the brake actuator 7 shown in FIG.
The electronic control negative pressure booster mechanism configured as shown in FIG. This electronic control negative pressure booster mechanism is realized by using a brake booster 10 used as a brake booster, and basically applies an oil pressure to a wheel cylinder by controlling the operation of a master cylinder. It has a function of applying a mechanical braking force to the wheel 4.

Briefly describing this electronically controlled negative pressure booster mechanism, the booster 10 includes a push rod 11 for controlling the operation of the master cylinder and an operating rod 12 connected to a brake pedal. Further, inside the booster 10, a diaphragm 13 is provided.
A negative pressure chamber 15, an atmosphere chamber 16, and a control pressure chamber 17, which are defined by the bellows 14, are provided.

When the brake pedal is depressed, the booster mechanism opens the atmosphere chamber 16 by moving the operating rod 12 against the first return spring 12a. The push rod 11 is driven against the second return spring 11a by the pressure difference between the atmospheric chamber 16 and the negative pressure chamber 15, thereby operating the master cylinder. When the brake pedal is not depressed, the atmosphere chamber 16 is communicated with the control pressure chamber 17 by the operating rod 12 which is returned by the first return spring 12a. In this state, the push rod 11 is moved to the second return spring 11 in accordance with the pressure difference between the control pressure applied to the control pressure chamber 17 and the negative pressure chamber 15.
a to actuate the master cylinder.

In particular, in this electronically controlled negative pressure booster mechanism, a first solenoid valve 18 provided between the control pressure chamber 17 and the atmosphere, and between the control chamber 17 and the negative pressure chamber 15 are provided. The pressure in the control chamber 17 is electronically adjusted by selectively controlling the driving of the second solenoid valve 19, whereby the master cylinder is driven independently of the operation of the brake pedal, thereby controlling the wheels 4. Mechanical braking force.

The adjustment of the magnitude of the mechanical braking force by electronic control of the first and second solenoid valves 18 and 19 is performed by changing the duty ratio when the control pressure is intermittently introduced into the control pressure chamber 17. It is performed by making it variable. Specifically, the hydraulic pressure obtained via the master cylinder is the required braking force (deceleration)
The feedback control of the operation of the solenoid valves 18 and 19 may be performed so that the target pressure for obtaining the target pressure is obtained.

As described above, the electric vehicle according to this embodiment has an electronically controlled negative pressure booster mechanism (mechanical braking means) capable of applying a mechanical braking force independently of the depression operation of the brake pedal. The feature of the brake control device is that, as shown in FIG.
The terminal voltages (cell voltages) of a plurality of battery cells constituting the battery 1 are monitored, and regenerative braking by the motor 2 (electric braking means) according to the maximum voltage among these cell voltages.
And the distribution ratio of the braking force by the mechanical braking force (mechanical braking means) by the booster mechanism is variably set.

That is, when applying a braking force determined according to the driving operation or running state of the electric vehicle, the distribution ratio between the regenerative braking force by the electric braking means and the mechanical braking force by the mechanical braking means is determined. It is determined according to the maximum cell voltage of the battery 1, and the regenerative braking force by driving the electric braking means and the driving of the mechanical braking means so that the braking force can be obtained in total under this distribution ratio. And the mechanical braking force of each of them is controlled.

The form of such braking control will be described with reference to FIG. 3. This processing is started by the controller 3 sequentially taking in data detected by various sensors (step S1). This data is taken in not only by the rotation speed of the motor 2 and the terminal voltages (cell voltages) of a plurality of battery cells constituting the battery 1, but also by throttle information (accelerator operation amount) obtained from the throttle sensor 6, This is performed by detecting brake information (brake operation amount) obtained from the brake switch 5.

After the information on the running state and the driving operation of the vehicle is taken in, it is then determined whether the throttle is off according to the throttle information, that is, whether or not the accelerator operation is off [step S2]. ]. When the acceleration operation is performed by depressing the accelerator pedal, the throttle is not naturally off, and in this case, the motor 2 is controlled in power running according to the throttle information (throttle opening) [Step S].
3]. In other words, according to the accelerator operation amount indicating the driver's acceleration intention, the information is obtained as information on the throttle opening, etc.
By driving the motor 2 with the charging energy of the battery 1, a required rotational force (rotational speed) is obtained. In this case, the braking control from step S1 is repeatedly executed again.

On the other hand, when the throttle is off, the distribution of the braking force is calculated according to the terminal voltage (cell voltage) of the battery cell in the battery 1 detected as described above (step S4). Specifically, as shown in FIG. 4, first, each terminal voltage (cell voltage) of a plurality of battery cells constituting the battery 1 is detected [Step S2
1], and detects the maximum cell voltage therein [Step S2]
2]. Then, the detected maximum cell voltage is compared with a preset control voltage (charge inhibition voltage) Vmax [Step S2
3] If the maximum cell voltage has reached the control voltage,
Obtain a determination result of regenerative braking prohibition [Step S2
4]. That is, when one of the plurality of battery cells constituting the battery 1 has reached the control voltage, it is determined that further charging is inappropriate and a determination result of regenerative braking inhibition is obtained.

On the other hand, if the maximum cell voltage has not reached the control voltage, a determination result of regenerative braking permission is obtained [Step S25]. In particular, when the determination result of the regenerative braking permission is obtained, the distribution ratio between the regenerative braking and the mechanical braking is determined according to the maximum cell voltage [Step S2.
6]. That is, the distribution ratio of the braking force that defines in what proportion the regenerative braking force obtained by the regenerative braking by the motor 2 and the mechanical braking force obtained by driving the negative pressure booster mechanism are applied. And the battery 1
Is determined according to the maximum cell voltage.

This distribution ratio is given as table data predetermined according to the cell voltage, for example, as shown in FIG. Therefore, by referring to this table according to the cell voltage, the distribution ratio of the braking force according to the cell voltage at that time can be obtained. Incidentally, when the cell voltage is lower than the predetermined voltage V1, the distribution ratio is set such that the regenerative brake becomes 100% and the mechanical brake becomes 0%, and the cell voltage is higher than the predetermined voltage V2. In this case, the regenerative brake is 0% and the mechanical brake is 100%
Is determined as the distribution ratio. Further, when the cell voltage is in the range of the voltages V1 and V2, the distribution ratio to the regenerative brake monotonously decreases as the cell voltage increases, and the distribution ratio is determined as a distribution ratio that compensates for the shortfall caused by the mechanical brake. Can be

When the cell voltage exceeds the voltage V2, the distribution ratio to the regenerative brake is set to 0%. Therefore, the above-described steps S23 and S24 for omitting the regenerative brake operation prohibition determination processing are omitted. May be.
If the distribution ratio between regenerative braking and mechanical braking is determined according to the cell voltage (charged state) of the battery 1 as described above, then, as shown in FIG. ) Is calculated [Step S
5]. The calculation of the deceleration is basically performed in accordance with operation information such as an accelerator operation and a brake operation detected in step S1 described above. In particular, accelerator off is detected from accelerator operation information obtained by the throttle sensor 6, and a deceleration (braking force) corresponding to, for example, an engine braking force is calculated according to the rotation speed of the motor 2 at that time.

Incidentally, the engine brake is a braking action that is generated by a rotational force applied to the internal combustion engine from the wheels when the accelerator is turned off in an automobile powered by the internal combustion engine. Therefore, in an electric vehicle having no internal combustion engine, no engine braking force is generated. Therefore, in this embodiment, in order to generate a braking force corresponding to the engine braking force when the accelerator is off,
As described above, the deceleration (braking force) required at that time is calculated according to the rotation speed of the motor 2.

The deceleration corresponding to the engine braking force is given, for example, as table data indicating the deceleration previously determined according to the rotation speed of the motor 2 as shown in FIG. Therefore, the calculation of the deceleration is executed by, for example, referring to the table according to the rotation speed of the motor 2 at that time and obtaining the rotation speed indicated by the rotation speed.

When the braking force (deceleration) equivalent to the engine brake for operating when the accelerator is turned off is obtained as described above, the brake switch 5
It is determined whether or not is off [Step S6]. That is, it is determined whether not only the accelerator-off operation but also the aggressive braking operation is performed by depressing the brake pedal. When the brake switch 5 is off, the above-described deceleration is determined according to the rotation speed of the motor 2 and the distribution ratio of the braking force determined according to the cell voltage of the battery 1 as described above. The regenerative braking force and the mechanical braking force required to obtain the deceleration are calculated respectively (step S7). The calculation of these braking forces is based on the deceleration (required braking force), the distribution ratio indicated by the solid line in FIG. 5 set for regenerative braking, and the diagram set for mechanical braking. 5 is performed by multiplying the distribution ratios indicated by broken lines in FIG.

The electric regenerative braking control is executed by controlling the regenerative braking by the motor 2 in accordance with the respective braking forces thus obtained [Step S8], and at the same time, the operation of the negative pressure booster mechanism is controlled. By doing so, mechanical automatic brake control is executed [Step S9].
These braking forces act comprehensively on the vehicle, so that a braking force corresponding to the engine brake obtained as described above is applied.

Therefore, for the vehicle, when the accelerator is turned off, it is obtained according to the running speed at that time (the number of revolutions of the motor 2) regardless of the state of charge of the battery 1.
A braking force corresponding to the engine brake is stably and reliably applied. Therefore, the driver can feel a highly natural deceleration effect accompanying the stoppage of the operation of the accelerator pedal. In addition, at this time, if the battery 1 has a charge margin, the kinetic energy of the vehicle is recovered by the regenerative brake driven under the distribution ratio set as described above, and the battery 1 is charged. However, when the cell voltage of the battery 1 has reached the above-described control voltage V2, the distribution ratio of the braking force to the regenerative braking is set to 0%. Does not charge the battery 1. Therefore, overcharging of the battery 1 is effectively prevented.

On the other hand, if the ON state of the brake switch 5 is detected by the above-described determination processing in step S6, the deceleration required by the brake operation is calculated according to the brake operation amount [step S10]. That is, in this case, since the positive braking is instructed by the depressing operation of the brake pedal, the positive deceleration (braking force) required by the driver by the depressing operation of the brake pedal, Calculate according to the amount of depression. As described above, the deceleration associated with the brake operation is calculated by detecting the depression amount (depression pressure) of the brake pedal using a pressure sensor incorporated in the brake pedal, and calculating the deceleration corresponding to the depression force. It is executed by obtaining from such table data.

Thereafter, according to the braking force distribution ratio determined according to the cell voltage of the battery 1 as described above, the motor 2 is regenerated and driven basically in the same manner as the processing shown in step S7. The regenerative braking force to be applied and the mechanical braking force applied using the negative pressure booster mechanism are calculated [Step S11]. However, since the regenerative braking force obtained by regeneratively driving the motor 2 has a limit, for example, first, the regenerative braking force by the motor 2 is calculated according to the distribution ratio of the braking force to the regenerative braking, and this regenerative braking force is described above. By subtracting from the deceleration (braking force) determined according to the depression force of the brake pedal, the braking force applied by the mechanical braking means is calculated. According to the braking force (deceleration) calculated in this way, the regenerative braking of the motor 2 is controlled, and the operation of the negative pressure booster mechanism is controlled.
The cooperative regenerative braking control using both the electric braking by the regenerative braking and the mechanical braking using the negative pressure booster mechanism is executed [Step S12].

Specifically, the regenerative braking control of the motor 2 is performed so that the regenerative braking force calculated as described above is obtained.
At the same time, from the braking force required according to the brake depression force,
The braking force obtained by the regenerative braking may be subtracted, and the braking force obtained by the subtraction may be used as a control target value of the electronically controlled negative pressure booster mechanism to feedback-control the operation of the booster mechanism. That is, as shown in FIG. 7, since there is a limit to the braking force obtained by regenerative braking, the braking force that is insufficient with respect to the braking force (total braking force) determined according to the brake pedal force is reduced by mechanical braking. It is sufficient to execute the cooperative regenerative brake control by applying the power as power.

Accordingly, in this case, the kinetic energy of the vehicle that can be recovered by the battery 1 is obtained as the regenerative energy of the motor 2, and the regenerative braking force is applied to the vehicle while charging the battery 1 using the regenerative energy. As a sum of the mechanical braking force and the mechanical braking force, an appropriate braking force according to the amount of depression of the brake pedal is applied. Note that the regenerative braking force (deceleration) shown in the region where the pedal effort is substantially zero (0) in FIG. 7 indicates a braking force applied to the vehicle when the accelerator is turned off, which corresponds to the engine braking force. I have.

According to the braking control executed as described above, the distribution ratio between the braking force by the regenerative brake and the braking force by the mechanical brake is determined based on the terminal voltages of the plurality of battery cells constituting the battery 1. As long as regenerative braking is possible, regenerative braking by the motor 2 is applied to recover kinetic energy of the vehicle and charge the battery 1. When the cell voltage of the battery 1 is sufficiently high, regenerative braking itself is prohibited by setting the distribution ratio of regenerative braking to 0%, and charging of the battery 1 by regenerative energy is prohibited to prevent overcharging. It is something to prevent. Therefore, according to the device of this embodiment, the battery 1 can be efficiently charged by the kinetic energy of the vehicle while the overcharging of the battery 1 is reliably prohibited, and the energy recovery efficiency is sufficiently high. can do.

Therefore, even when the battery characteristics (charge / discharge characteristics) of a plurality of battery cells constituting the battery 1 vary, the charging of the battery 1 is controlled by focusing on the battery cell having the worst condition. So you can
It is possible to effectively prevent the overall battery performance of the battery 1 from deteriorating. In particular, it is possible to effectively prevent a situation where only a specific battery cell is overcharged.

When the vehicle is braked in accordance with the operation when the accelerator is turned off or the brake pedal is operated, while the regenerative brake by the motor 2 is operated under the above-described conditions, the regenerative brake alone is insufficient. Since the braking force is applied by the mechanical braking means by the operation of the negative pressure booster mechanism, a necessary braking force according to the above operation can be reliably applied. As a result, it is possible to apply an appropriate braking force to the vehicle regardless of the state of charge of the battery 1.

In particular, even when the accelerator is off without any brake operation, a braking force corresponding to the engine braking force according to the running state at that time can be appropriately applied. In addition, when the battery 1 has a charge margin, the battery 1 can be charged while the kinetic energy of the vehicle is actively collected by the operation of the regenerative brake.

Further, a braking force according to the driving operation of the vehicle is applied irrespective of the state of charge of the battery 1.
The driver can operate the accelerator and the brake without paying special attention to the state of charge of the battery 1 without monitoring the state of charge of the battery 1.
In particular, simply by stopping the accelerator operation, a braking force corresponding to the engine brake works according to the running state (running speed) at that time, and the braking effect (deceleration action) can be captured as a driving feeling. Driving with a sense of security and without discomfort can be performed.

By the way, if the braking force corresponding to the engine brake is not applied when the accelerator operation is stopped,
The number of brake operations for speed adjustment increases, and the driver feels uncomfortable differently from driving an automobile equipped with an internal combustion engine. On the other hand, if only the regenerative braking is applied when the accelerator operation is stopped, there are cases where the regenerative braking functions effectively depending on the state of charge of the battery 1 and cases where the regenerative braking does not work. There is a possibility that a feeling may be generated and a situation in which the brake is operated in a hurry may occur. In this regard, according to the above-described braking control according to the present invention, a braking force similar to that in the case of an automobile equipped with an internal combustion engine, that is, a braking force corresponding to an engine braking force is applied with the stop of the accelerator operation. Therefore, a safe driving operation without a sense of incongruity can be performed, and the drivability of the electric vehicle can be improved.

The present invention is not limited to the above embodiment. In the embodiment, the mechanical braking force is applied by using the electronically controlled negative pressure booster mechanism. However, the ABS (anti-skid braking system) has a similar braking force control function. Therefore, it is possible to provide a mechanical braking force by using this function. Further, not only the maximum cell voltage of the plurality of battery cells constituting the battery 1 but also the average cell voltage may be obtained to determine whether regenerative braking can be performed. Alternatively, the remaining charge capacity of the battery may be obtained by integrating the amount of discharge current from the battery. In this case, the distribution ratio between regenerative braking and mechanical braking may be determined according to the remaining charge capacity of the battery. Further, the state of charge of the battery can be easily determined from the terminal voltage of the battery. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0046]

As described above, according to the present invention, there is provided an electric vehicle including a battery mounted on a vehicle and an electric motor driven by the battery, wherein the electric motor generates a regenerative braking force. A braking control device comprising: electric braking means for applying a braking force to the vehicle; mechanical braking means for applying a mechanical braking force to a rotating system of the vehicle; and control means for controlling each of these braking means. A deceleration calculating means for calculating a deceleration required for the vehicle in accordance with a throttle operation, a brake operation, and a traveling state of the vehicle; and a charge state of the battery, for example, a terminal voltage of a plurality of battery cells constituting the battery. State detecting means for detecting the regenerative braking by the electric braking means in accordance with the state of charge of the battery, and the mechanical braking means That has become one that determines the distribution ratio of the mechanical braking. Then, the regenerative braking force and the mechanical braking force are determined according to the distribution ratio, and an appropriate deceleration is given according to the driving operation of the vehicle, the traveling speed, and the like.

Therefore, according to the present invention, the rate of regenerative braking and the rate of mechanical braking are controlled in accordance with the state of charge of the battery, so that overcharging of the battery can be effectively prevented and the state of charge of the battery can be reduced. It is possible to reliably obtain the braking force according to the driving operation without being concerned. Therefore, it is possible to perform a safe driving operation without a sense of incongruity while effectively recovering the kinetic energy of the vehicle, and consequently it is possible to reduce the number of braking operations. As a result, advantages such as drastic improvement in drivability of the electric vehicle can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a control system in an electric vehicle according to the present invention.

FIG. 2 is a diagram showing a schematic configuration of an electronically controlled negative pressure booster mechanism incorporated in the electric vehicle according to the present invention.

FIG. 3 is an exemplary view showing an example of a processing procedure of braking control in the electric vehicle according to one embodiment of the present invention.

FIG. 4 is a diagram showing a procedure for determining whether or not regenerative braking control can be executed based on the voltage of a battery cell constituting a battery.

FIG. 5 is a diagram illustrating a relationship between distribution ratios (distribution ratios) between regenerative brakes and mechanical brakes that are changed and set according to a state of charge (cell voltage) of a battery.

FIG. 6 is a diagram showing a relationship between a motor speed and a deceleration (braking force) corresponding to an engine braking force.

FIG. 7 is a diagram showing the concept of cooperative regenerative braking control using both regenerative braking by a motor and mechanical braking by mechanical braking means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery 2 Motor (motor) 3 Controller 5 Brake switch 6 Throttle sensor 7 Brake actuator 10 Booster 15 Negative pressure chamber 16 Atmospheric chamber 17 Control pressure chamber 18 First solenoid valve 19 Second solenoid valve

Claims (2)

[Claims] 1. An electric vehicle comprising a battery mounted on a vehicle and an electric motor driven by the battery, wherein the electric motor generates a regenerative braking force to apply a braking force to the vehicle. And mechanical braking means for applying a mechanical braking force to the rotation system of the vehicle, and control means for controlling each of these braking means, wherein the control means controls the throttle operation of the vehicle. Throttle operation detecting means for detecting, brake operation detecting means for detecting a brake operation on the vehicle, running state detecting means for detecting a running state of the vehicle, and a reduction required for the vehicle based on each detection result. Deceleration calculating means for calculating a speed; charge state detecting means for detecting a state of charge of the battery; Brake control apparatus for an electric vehicle characterized by comprising a braking force distribution ratio determining means for determining a distribution ratio of the braking force applied by the braking force and the mechanical braking means for applying the electric braking means. 2. The brake control device for an electric vehicle according to claim 1, wherein the charge state detection means detects a charge state of the battery from a maximum terminal voltage between a plurality of battery cells constituting the battery.