JP3156340B2 - Regenerative braking 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 regenerative braking device that converts kinetic energy into electric energy by a driving motor and returns the electric energy to the battery during braking in an electric vehicle that runs on a battery and is driven by a driving motor.

[0002]

2. Description of the Related Art In recent years, electric vehicles have been used for some applications because of their quietness and no exhaust gas. This electric vehicle can perform braking by converting kinetic energy into electric energy at the time of braking, unlike a conventional vehicle that runs using an internal combustion engine as a drive source. The electric braking includes regenerative braking and power generation braking. and so on. The regenerative braking converts the kinetic energy of the vehicle into electric energy and then returns it to the battery. The regenerative braking converts the kinetic energy of the vehicle into electric energy and then dissipates it to a resistor to radiate heat as heat energy. A device for performing such two electric braking operations is disclosed in Japanese Utility Model Application Laid-Open No. 61-13501 filed by the present applicant.

In the above-described regenerative braking, when the battery to be charged is almost fully charged, that is, when the battery cannot be charged any more, regenerative power cannot be returned to the battery, so that sufficient braking force cannot be obtained. For this reason, when the battery is fully charged, the above-described dynamic braking is performed, and the current generated by the drive motor is caused to flow through the discharging resistor for consumption.

[0004]

As described above, since the conventional regenerative braking system for an electric vehicle is constructed as described above, it is necessary to newly provide a discharge resistor, which causes an increase in weight and cost. there were.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and a regenerative braking device for an electric vehicle that consumes power that cannot be regenerated when a battery is almost fully charged without providing a new discharge resistor. The purpose is to provide.

[0006]

In order to achieve the above object, a regenerative braking device for an electric vehicle according to the present invention comprises : a charge amount detecting means for detecting that a battery is substantially fully charged ; and a, the input voltage control means for decreasing the drive motor input voltage when the charge state is detected.

[0007]

According to the present invention, the input voltage of the driving motor is controlled to be lower than usual when the battery is almost fully charged. As a result, the current flowing through the drive motor increases, and the copper loss increases. The drive motor generates heat due to the copper loss, and power is consumed .

[0008]

FIG. 1 is a diagram showing the structure of the present invention. At the time of braking control of the electric vehicle, the charge amount detection means 2 detects the charge amount of the battery 1 and sends this detection signal to the input voltage control means 3 when the charge amount is equal to or more than a predetermined value. Input voltage control means 3
By controlling the voltage input to the drive motor 4,
The drive motor 4 controls the amount of current generated during braking control. Further, a temperature detecting means 5 for detecting the temperatures of the drive motor 4 and the input voltage control means 3 is provided, and when the temperature of these devices exceeds a predetermined value, a cooling means for radiating heat generated by regenerative braking. 6 are provided.

A preferred embodiment of the regenerative braking device for an electric vehicle according to the present invention will be described below. FIG. 2 shows the configuration of the present embodiment. When the electric vehicle is driven by the drive motor 11, the electric power from the battery 12 is subjected to frequency conversion and voltage conversion by the inverter 13 and supplied to the drive motor 1. At this time, the control device 14 controls the inverter 13 according to the operation amount of the accelerator 15 operated by the driver, and controls the rotation speed and output of the drive motor 11. Further, the temperatures of the drive motor 11 and the inverter 13 are detected by the temperature sensors 16 and 17, and when the detected temperature exceeds a predetermined temperature, the control device 14 operates the pumps 18 and 19 to supply the cooling water to the radiator 20. , 21. Further, the cooling fans 22 and 23 for sending cooling air to the radiators 20 and 21 are operated to promote heat radiation of the radiators 20 and 21. This cooling pump 1
The control of 8, 19 and the cooling fans 22, 23 will be described later.

When the driver applies braking, the control device 14 controls the frequency of the inverter according to the operation amount of the brake 24 to perform regenerative braking. The electric power generated by the regenerative braking is returned to the battery 12 and charged.

A feature of the present invention is that the voltage applied to the drive motor 11 is controlled in accordance with the amount of charge of the battery during braking. That is, the voltage applied to the drive motor 11 is reduced when the battery 12 is almost fully charged and the power generated by the regenerative braking cannot be returned. Due to the decrease in the voltage, the current flowing through the stator winding of the drive motor 11 and the like increases, and the copper loss increases. This is generated as heat, and eventually a part of the kinetic energy of the electric vehicle main body is converted to heat energy to perform braking.

For this reason, in the present embodiment, the control device 14 constantly monitors the charge amount of the battery 12 by, for example, detecting a terminal voltage, and determines whether or not regenerative power can be returned to the battery 12 during braking. to decide. Based on this determination, the control device 14 controls the inverter 13 as described above, and returns the generated power to the battery or consumes a part of it as heat to obtain a braking force.

In the present embodiment, in order to radiate the heat generated by the above-described process, the capacity of the cooling pumps 18 and 19 and the cooling fans 22 and 23 is set so as to be adjustable. Have been. In other words, when the power generated during braking cannot be returned to the battery, a part of this power is consumed by heat generation. However, since the amount of heat generated cannot be sufficiently dissipated by the conventional cooling capacity, the cooling capacity is set to be further increased. I have.

Next, control of the regenerative braking device as described above will be described with reference to a flowchart shown in FIG. First, it is determined whether a brake operation has been performed (step S10).
1) If performed, a braking force according to the brake operation amount is calculated (step S102). Further, it is determined whether the battery terminal voltage V _B is lower than a predetermined voltage value V _B0 (step S103). If the terminal voltage V _B is lower than the predetermined value V _B0 , regenerative braking control (step S104) is performed. This predetermined value V
_B0 is a voltage for determining that the battery 12 is almost fully charged. Regarding this regenerative braking control, FIG.
This will be described with reference to FIG. First, drive motor 1
1 of the rotation speed N is determined whether or not more than the predetermined value N _B (step S201). If the rotational speed N is equal to or less than the predetermined value N _B controlling the applied voltage V _M of the drive motor 111 in accordance with the following equation (1) (step S202).

V _M = k ₁ · V _B · N / N _B (1) At this time, k ₁ is a predetermined coefficient indicating the relationship between the battery terminal voltage V _B and the motor applied voltage V _M. Further, when the drive motor rotation speed N exceeds a predetermined value N _B controlling the applied voltage V _M of the drive motor 11 in accordance with the following equation (2) (step S203).

[0016] shows the relationship between _{V M = k 1 · V B} ... (2) above regenerative braking of the drive motor applied voltage V _M and the rotational speed N by the chain line in FIG.

Next, when the battery terminal voltage V _B is equal to or higher than the predetermined value V _B0 in step S103, it is determined that the generated power cannot be returned to the battery 12, and a part of the generated power is used for the drive motor. Braking is performed as heat generated by resistance such as copper loss (step S105). The heating braking control is shown in FIG. 4 (B) and FIG. 5, the rotational speed N of the drive motor when a predetermined value or less N _B, in accordance with the following equation (3), controls the drive voltage applied to the motor V _M ( Step S2
12).

V _M = k ₂ · V _B · N / N _B (3) When the drive motor speed N exceeds a predetermined value N _B ,
Controlling the drive voltage applied to the motor V _M according to the following equation (4).

[0019] shows the relationship between _{V M = k 2 · V B} ... (4) above such heat generation during braking of the drive motor applied voltage V _M and the rotational speed N in solid lines in FIG. The coefficient k ₂ is a coefficient k ₁ value smaller than the above-mentioned (k ₂ <k _1), the applied voltage V _M is reduced from the time of regenerative braking.

That is, by selecting these coefficients in accordance with the charge amount of the battery 12, it is possible to obtain a braking force which is not greatly affected by the charge amount of the battery.

If it is determined in step S101 (FIG. 3) that the brake operation has not been performed, the necessary driving force is calculated (step S106). Then, the process proceeds to the driving force control (step S107), and the control is performed according to the flowchart shown in FIG.
As described above, when the rotational speed N of the drive motor is equal to or less than a predetermined value N _B according to the equation (5), if it exceeds a predetermined value N _B performs control in accordance with Equation (6) (step S222, step S223) .

[0022] After setting the motor voltage V _M by _{V M = k 3 · V B} · N / N B ... (5) V M = k 3 · V B ... (6) or step S104, S105, S107, drive An operation for obtaining the torque required for braking is performed (step S108).

When the calculation relating to the drive control or the braking control of the drive motor 11 is completed, the drive motor 11
And the like, related to cooling control. First, the drive motor 11 and the inverter 13 are detected by the temperature sensors 16 and 17.
Is compared with a _first predetermined value t _{1. If} the temperature t exceeds the predetermined value t ₁ , the cooling pumps 18 and 19 and the cooling fan 2
2 and 23 are operated (step S111). At this time, the output P _{P of the} pumps 18 and 19 and the output P _{F of the} fans 22 and 23
Are operated at P _P1 and P _F1 respectively (step S111).
If the temperature t of the drive motor 1 is lower than the first predetermined value t ₁ (step S109), the cooling pump 18
The operation of the cooling fan 19 and the cooling fans 22 and 23 is not performed (step S112).

The temperature t of the drive motor 11 further rises to a second predetermined temperature t higher than the first predetermined temperature t _1.
If it exceeds ₂ (step S113), the cooling pump 18,
19 and the outputs of the cooling fans 22 and 23 are P _P2 and P
_F2 (P _P1 <P _P2 , P _F1 <P _F2 ) (step S
114), increase the cooling capacity. Since a part of the electric power generated by the drive motor 11 is generated and consumed as described above, the amount of heat generated by the drive motor 11 and the like becomes larger than usual. In the present embodiment, a cooling system capable of obtaining a two-stage cooling capacity is provided as described above.

As described above, the cooling pumps 18, 19
The first predetermined temperature t ₁ and the second predetermined temperature t ₂ for switching the start of the operation of the cooling fans 22 and 23 and their abilities are set similarly for the drive motor 11 and the inverter 13. As described, the drive motor 1
It is, of course, possible to set different settings for 1 and the inverter 13.

[0026]

As is evident from the foregoing description fever, even when the not be regenerated battery is almost fully charged der Ri power in the present invention, to increase the current flowing to the driving motor or the like, thereby the resistance of the copper loss Power consumption. For this reason, a remarkable decrease in the braking force does not occur. Further, since it is not necessary to newly add a discharge resistor for the power consumption, there is no increase in cost and weight.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of the present invention.

FIG. 2 is a view showing a preferred embodiment of a regenerative braking device for an electric vehicle according to the present invention.

FIG. 3 is a flowchart for explaining control of the apparatus of the present embodiment.

FIG. 4 is a flowchart for explaining the control of the apparatus according to the present embodiment, and particularly for controlling the voltage applied to the drive motor.

FIG. 5 is a diagram illustrating a relationship between the number of rotations of a drive motor and an applied voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Drive motor 12 Battery 13 Inverter 14 Control device 16, 17 Temperature sensor 20, 21 Radiator 22, 23 Cooling fan

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60L 7/22 B60L 3/00

Claims (1)

(57) [Claims] 1. A regenerative braking system for an electric vehicle and a control device for controlling the drive motor and the battery and the drive motor, and a charge amount detection means for detecting that the battery is fully charged substantially, the generally Regenerative braking for an electric vehicle , comprising : input voltage control means for reducing the input voltage of the drive motor when a fully charged state is detected .