JP2800586B2 - Brake device for electric vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake device for an electric vehicle having a regenerative brake and a mechanical brake.

[0002]

2. Description of the Related Art As a conventional electric vehicle equipped with a regenerative brake and a mechanical brake, for example, "NISSAN"
FEV "Nissan Motor Co., Ltd. issued". In electric vehicles as described above,
At the time of braking, the deceleration / braking energy is recovered to the battery by causing the drive motor to generate regenerative power, and the required braking force is obtained by using a mechanical brake such as a hydraulic brake device.

[0003]

However, in the above-described conventional electric vehicle brake system, the regenerative brake is influenced by the braking force depending on the state of charge of the battery. That is, when the battery is almost fully charged, the current flowing to the battery is small, and the regenerative braking is not so effective. In such a case, the load on the mechanical brake is increased. Since an electric vehicle has a heavy battery and is inherently heavy in weight, the capacity of a mechanical brake tends to be insufficient. In particular, when the battery voltage is high when the battery is fully charged as described above and the regenerative power generation itself is suppressed, the regenerative braking is hardly effective,
Since the driver tries to obtain the braking force and further increases the load on the mechanical brake, there is a problem that the rotor may generate heat and fade.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art as described above, and it is possible to effectively use regenerative energy, improve the fade resistance of a mechanical brake, and improve the brake performance as a whole. It is an object of the present invention to provide a brake device for an electric vehicle that can improve the performance.

[0005]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as described in the claims. That is, according to the first aspect of the present invention, a configuration is used in which the vehicle is driven by converting the electric power of the battery into a driving force by a motor during driving, and the kinetic energy of the vehicle is converted into regenerative power by the motor during deceleration and braking. In an electric vehicle having a configuration for regenerating to the battery and a configuration for converting the kinetic energy to frictional energy with a mechanical brake provided near a wheel of the vehicle to perform braking, a brake operation amount of the mechanical brake is provided. Brake operation amount detection means, voltage detection means for detecting the battery voltage, forced cooling means for forcibly cooling the mechanical brake, and the motor in accordance with the brake operation amount and the battery voltage. Of the regenerative power generated by the regenerative cooling means is supplied to the forced cooling means, and the supplied · The operation amount and the battery voltage is provided and a control means for controlling to higher number supplied. The above-mentioned brake operation amount detecting means corresponds to, for example, the depression amount sensor 21 of the brake pedal in the embodiment shown in FIG. 1 described later, the voltage detecting means also corresponds to the battery voltmeter 20, and the forced cooling means also applies forced cooling. The control means corresponds to the fans 15, 16, 17, and 18, and the control means also corresponds to the control device 13 and the switching element 19.

Further, in the invention according to claim 2,
The brake device for an electric vehicle according to claim 1,
A capacitor is connected to a regenerative energy supply line to the forced cooling means, a momentary large power generated by sudden braking or the like is temporarily stored in the capacitor, and the power is supplied to the forced cooling means with a time delay. Make up. The above-mentioned capacitor corresponds to, for example, the capacitor 23 in the embodiment of FIG.

[0007]

As described above, in the first aspect of the present invention, the forced cooling means for forcibly cooling the mechanical brake is provided, and the forced cooling means is driven by a part of the regenerative electric power obtained during regeneration. is there. And by increasing the regenerative power to the forced cooling means as the brake operation amount and the battery voltage are higher, the regenerative brake operates even when the battery is fully charged, reducing the load on the mechanical brake, Further, the mechanical brake is forcibly cooled by utilizing the regenerative energy to improve the fade resistance of the mechanical brake.

Further, in the invention according to claim 2,
By providing a capacitor that stores regenerative power, storing large power generated during sudden braking in the capacitor and supplying it to the forced cooling means with a time delay, the large power generated during short braking can be efficiently used. It is intended to be used.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram of an electric system and a hydraulic system according to an embodiment of the present invention. In FIG. 1, 1, 2, 3
And 4 are wheels of the vehicle, 5, 6, 7 and 8 are rotors of hydraulic disc brakes provided on each wheel, 9
Is a transmission, 10 is a motor for driving the vehicle, 1
1 is a differential gear, 12 is a battery, 13 is a control device, 14 is a brake pedal, 15, 16, 17 and 18 are forced cooling fans, 19 is a switch element, 20
Is a battery voltmeter, 21 is a brake pedal depression amount sensor, and 22 is a hydraulic path.

FIG. 2 is a flowchart showing a control procedure during braking in the embodiment of FIG. Less than,
The operation of the embodiment of FIG. 1 will be described based on FIG. First,
The voltage V of the battery 12 is detected by the battery voltmeter 20. Next, the brake pedal 1 is detected by the depression amount sensor 21.
4 is detected. The depression amount B corresponds to the operation amount of the brake. The brake pedal 14 is mechanically connected to a disc brake via a hydraulic device (not shown) and a hydraulic path 22 so that a vehicle braking function can be realized without fear of failure. Next, the signals of the battery voltage V and the depression amount B are input to the control device 13. The controller 13 sets the battery voltage V within a range not exceeding the maximum charging amount determined from the battery voltage V at that time.
And the amount of current f charged to the battery based on
(B, V) is defined. The charge current amount f (B, V) has, for example, characteristics as shown in FIG. 3, and the higher the battery voltage V, the smaller the charge current amount f (B, V). In addition,
FIG. 3A shows the characteristics when the battery voltage is low.
(B) shows the characteristics when the battery voltage is large. Next, the control device 13 sets the fan current g (B, B,
V). The fan current amount g (B, V) has, for example, a characteristic as shown in FIG. 3. The fan current amount g (B, V) increases as the battery voltage V increases and the depression amount B increases.
(B, V) increases.

As described above, during braking, the motor 10 is used as a generator, and f (B, V) + g
(B, V), and f (B, V) + g (B,
The current V) is regenerated through the control device 13. Then, in the control device 13, the fan current is g (B,
V), for example, the duty of the switch 19 is controlled. As a result, a current of f (B, V) flows through the battery 12, and g (B, V) flows through the forced cooling fans 15 to 18.
V) flows. In the above control, the battery 1
If 2 is near full charge, the battery voltage is high,
Therefore, the charging current amount f (B, V) decreases, and the fan current amount g (B, V) increases. Therefore, the forced cooling fan is driven by a large current to improve the cooling capacity and effectively prevent fade of the mechanical brake.Also, the amount of regenerative power generated does not decrease as a whole, so the regenerative brake can also be used effectively. I can do it. The battery 12
Is discharged, the battery voltage is low, the charging current amount f (B, V) is large, and the battery 12 is rapidly charged. In this case, the energy of the regenerative power generation is mainly used for the charging current, and the amount of fan current g
(B, V) becomes smaller.

FIG. 4 shows another embodiment of the present invention. In FIG. 4, 23 is a large-capacity capacitor,
In addition, the same reference numerals as those in FIG. Unlike electric trains and the like, braking in an electric vehicle often involves sudden braking frequently. For this reason, the forced cooling fans 15 to 18 only use the electric power regenerated in a short time during the braking period.
When the is driven, the cooling is stopped after the sudden braking is released, so that the cooling of the brake may be insufficient. In addition, since there is a limit to the energy that can be absorbed by the forced cooling fans 15 to 18, the instantaneous large power may be discarded. In the embodiment of FIG. 4, in order to solve the above problem, a capacitor 23 connected in parallel with the forced cooling fans 15 to 18 is provided. The capacitor 23 can also absorb short-time large electric power generated at the time of sudden braking or the like. In FIG. 4, when the switch element 19 is turned on by a command from the control device 13, the capacitor 23 is simultaneously supplied with power to the forced cooling fans 15 to 18.
To store power. Then, after that, when the brake is released and the switch element 19 is also turned off, the capacitor 23 and the forced cooling fans 15 to 18 become a closed circuit, and current flows from the capacitor 23 according to the impedance of the forced cooling fans 15 to 18. Flow, forced cooling fan 15
~ 18 operate continuously to maintain cooling.

FIG. 5 is a characteristic diagram showing the above state.
(A) shows the power consumption of the forced cooling fan, and (b) shows the regenerative power generation characteristics. In FIG. 5A, the solid line a is shown in FIG.
In the embodiment, the amount of power consumed by the forced cooling fan, the dashed line b indicates the amount of regenerative power generated for a short time by sudden braking, and the broken line c indicates the amount of power that can be consumed by the forced cooling fan in the absence of the capacitor 23.

[0014]

As described above, in the first aspect of the present invention, the forced cooling means for forcibly cooling the mechanical brake is provided, and the forced cooling means is driven by a part of the regenerative electric power obtained during regeneration. The regenerative power is supplied to the forced cooling means as the brake operation amount and the battery voltage are higher, so that the regenerative brake operates even when the battery is fully charged, reducing the load on the mechanical brake. By reducing the pressure and forcibly cooling the mechanical brake using the regenerative energy, the effect of improving the fade resistance of the mechanical brake can be obtained. In the invention according to claim 2,
In addition to the above effects, by providing a capacitor for storing regenerative power, storing large power generated at the time of sudden braking in the capacitor and supplying it to the forced cooling means with a time delay, The effect that the large electric power which is sometimes generated in a short time can be efficiently used can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electric system and a hydraulic system according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure in the embodiment of FIG.

FIG. 3 shows a charging current amount f (B, V) in the embodiment of FIG.
FIG. 7 is a characteristic diagram of the fan current amount g (B, V).

FIG. 4 is another embodiment of the present invention, and is a block circuit diagram of an electric system and a hydraulic system.

FIG. 5 is a characteristic diagram of power consumption and regenerative power generation of a forced cooling fan in the embodiment of FIG. 4;

[Explanation of symbols]

1, 2, 3, 4 ... wheels of the vehicle 5, 6, 7, 8 ... rotor of hydraulic disc brake provided on each wheel 9 ... transmission 10 ... motor for driving the vehicle 11 ... differential gear 12 ... battery 13 ... control Device 14: Brake pedal 15, 16, 17, 18 ... Forced cooling fan 19 ... Switch element 20 ... Battery voltmeter 21 ... Brake pedal depression amount sensor 22 ... Hydraulic path 23 ... Capacitor

Claims (2)

(57) [Claims] 1. A configuration in which electric power of a battery is converted into driving force by a motor during driving to drive the vehicle, and a configuration in which kinetic energy of the vehicle is converted into regenerative power by the motor and regenerated to the battery during deceleration and braking. Wherein the kinetic energy is converted into frictional energy by a mechanical brake provided near a wheel of the vehicle to perform braking, and the brake operation amount is detected by detecting a brake operation amount of the mechanical brake. Means, voltage detection means for detecting the voltage of the battery, forced cooling means for forcibly cooling the mechanical brake, and controlling the amount of regenerative power generated by the motor in accordance with the brake operation amount and the battery voltage. And supplying a part of the obtained regenerative energy to the forcible cooling means. A braking device for an electric vehicle, comprising: control means for controlling so as to supply as much as possible. 2. A brake device for an electric vehicle according to claim 1, wherein a capacitor is connected to a regenerative energy supply line to said forced cooling means, and momentary large electric power generated by sudden braking or the like is temporarily stored in said capacitor. A brake device for an electric vehicle, wherein the power is stored and supplied to the forced cooling means with a time delay.