KR20050006915A - System for supplying energy for electronic power steering in electric vehicle and method for the same - Google Patents

Abstract

PURPOSE: An energy supply system for electronic power steering of an electric vehicle and a method thereof are provided to improve the performance of the vehicle, to enhance reliability, to reduce weight of an electric wire by reducing the thickness of the electric wire, to lighten the vehicle through weight reduction of a DC/DC converter, and to reduce the cost. CONSTITUTION: An energy supply system for electronic power steering of an electric vehicle has a motor(22) for power steering and an inverter(21) for power steering to drive the electronic power steering, to receive energy from a driving battery or a fuel cell stack(23) and supply the energy to the inverter for power steering at normal times. The energy supply system has switching elements(31) to enable a controller installed to the electric vehicle to receive a fault signal and to change a flow of energy to an auxiliary battery(24) and to supply the energy to the electronic power steering to move the electric vehicle when the driving battery or the fuel cell stack fails.

Description

Energy supply system for electric power steering of electric vehicle {SYSTEM FOR SUPPLYING ENERGY FOR ELECTRONIC POWER STEERING IN ELECTRIC VEHICLE AND METHOD FOR THE SAME}

The present invention relates to an electric power steering energy supply system method for an electric vehicle, and more particularly, to improve performance and reliability of an electric vehicle, reduce the thickness of the electric wire, and reduce the weight of the electric wire, and a DC / DC converter. The present invention relates to a method for reducing the weight of a DC / DC converter by reducing the capacity of the vehicle, thereby reducing the weight of the vehicle, and reducing the cost of the vehicle.

Unlike ordinary internal combustion engine vehicles, vehicles powered by electric energy and fuel cells are forced to step down voltages of several hundred volts of battery packs or hundreds of volts of fuel cell stacks to 12 volts for the vehicle's electrical load voltage to charge auxiliary batteries. In order to charge the secondary battery, a DC / DC converter is used.

For example, a specific electric vehicle currently uses a DC / DC converter having a capacity of 1.6 Kw, and the capacity of the DC / DC converter continues to increase due to the increase in the electric driving system due to the characteristics of the vehicle. In particular, the load that is increasing the capacity of the DC / DC converter is a 1.2Kw electric power steering, which consumes the energy of the auxiliary battery at all times when driving the vehicle.

As described above, the problems caused by the 1.2 Kw electric power steering, which occupies a large part of the DC / DC converter capacity, are as follows.

First, a large amount of current of about 100 A flows in the electronic power steering, and when the line impedance between the DC / DC converter and the connected line (wire) between the electronic power steering is RL, the DC / DC converter uses the electronic power. In proportion to the current I flowing to the power steering, a voltage drop of IX RL occurs.

Even if the resistance of the line impedance is 0.01 Ω, a line voltage drop of 100 X 0.01 = 1 V is generated, and the loss due to the line voltage drop is I 2 X RL, resulting in an energy loss of 100 watts. If the thickness of the wire is increased in order to reduce the loss as described above, the purchase cost of the wire increases, and the weight of the wire increases and the performance of the vehicle decreases.

If the efficiency of the current DC / DC converter is about 90%, it is 180w to supply 1.6Kw of energy to the DC / DC converter, and 1.78Kw of energy is supplied from the driving battery or fuel cell stack of the vehicle. A degree of loss is occurring in the DC / DC converter. In addition, the increase in the capacity of the DC / DC converter is increasing the price and weight of the DC / DC converter.

In addition, since the DC / DC converter charges 12V with the auxiliary battery and supplies it to the electronic power steering of the vehicle, the auxiliary battery life due to frequent charging and discharging of the auxiliary battery is reduced. In addition, if the charging and discharging efficiency of the auxiliary battery is 90%, the energy supplied to the power steering of 1.2Kw requires the above-described line voltage drop of 100w + 1.33Kw = 1.43kw.

As described above, when the auxiliary battery supplies energy to the electronic power steering, there are problems such as an increase in the weight of the wire, an increase in the price of the DC / DC converter, and a decrease in energy efficiency due to the sequential energy movement of the energy storage device. The energy supply of the electronic power steering system is supplied from the driving battery or fuel cell stack to the DC / DC converter, from the DC / DC converter to the auxiliary battery, and from the auxiliary battery to the power steering. Due to a problem in the system, a fault occurs in the driving battery or the fuel cell stack 11, and the vehicle becomes inoperable and the auxiliary battery 13 is not supplied to the DC / DC converter 12 of the vehicle. The energy remaining in the battery 13 supplies the power steering with energy for a while We are using the system as shown in Fig. 1 in order to be able to drive to the location.

The present invention has been made to solve the above problems, the performance and reliability of the vehicle is increased, the weight of the wire is reduced by reducing the thickness of the wire, DC / DC converter by reducing the capacity of the DC / DC converter The purpose of the present invention is to provide an energy supply system for electric power steering of an electric vehicle, in which a weight reduction of the vehicle is made lighter and a cost reduction is achieved.

1 is a block diagram schematically showing the configuration of an energy supply system for electronic power steering of an electric vehicle according to the related art.

Figure 2 is a block diagram schematically showing the configuration of an energy supply system for electronic power steering of an electric vehicle according to the present invention.

Figure 3 is a schematic flow chart showing sequentially the energy supply method for electronic power steering of the electric vehicle according to the present invention.

<Description of the symbols for the main parts of the drawings>

21. Power Steering Inverter

22. Power Steering Motor

23. Drive battery or fuel cell stack

24. Spare battery

25. Electric load

26. DC / DC Converter

31. Switching element

In order to achieve the above object, the electric power steering energy supply system of an electric vehicle of the present invention is an electric power steering energy supply system of an electric vehicle driven by electric energy and a fuel cell, wherein the electric power steering is driven. The power steering motor and the power steering inverter are provided so that energy is supplied from the driving battery or the fuel cell stack at all times and supplied to the power steering inverter, and when the driving battery or the fuel cell stack is defective, the electric vehicle is installed in the electric vehicle. The controller is provided with a switching element for receiving a defect signal to change the blur of energy to the auxiliary battery to supply energy to the electronic power steering, characterized in that for moving the electric vehicle.

In order to achieve the above object, the electric power steering energy supply method of an electric vehicle of the present invention is an energy supply method for electric power steering of an electric vehicle driven by electric energy and a fuel cell, wherein (a) the vehicle travels. Determining whether a defect has occurred in the driving battery or the fuel cell stack; (b) if it is determined in step (a) that a defect occurs in the drive battery or the fuel cell stack, using a power source of the electronic power steering as a secondary battery; (c) moving the vehicle to a safe place to stop it.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 2 is a block diagram schematically showing the configuration of the energy supply system for electronic power steering of the electric vehicle according to the present invention.

Referring to the drawings, in the electric power steering energy supply system of an electric vehicle according to the present invention, the electric power steering motor 21 and the power steering inverter for driving the electric power steering of the electric vehicle driven by electric energy and fuel cells 22 is provided. Accordingly, energy is always supplied from the driving battery or the fuel cell stack 23 and supplied to the power steering inverter 22.

In the electric power steering energy supply system of the electric vehicle according to the present invention, when the driving battery or the fuel cell stack 23 is defective, a controller installed in the electric vehicle receives a defect signal and supplies energy to the auxiliary battery 24. A relay or switching element 31 is provided to change the blur of to supply energy to the electronic power steering. That is, the electric vehicle is moved by receiving energy from the auxiliary battery 24 only in an emergency.

The power steering inverter 22 includes a variable voltage variable frequency (VVVF) inverter capable of controlling output voltage and output frequency.

In addition, the vehicle of the electric vehicle is provided with a DC / DC converter 26 for charging the auxiliary battery 24 to step down the voltage of the fuel cell stack 23 to 12V corresponding to the voltage of the vehicle electric load 25. .

The energy supply method for the electronic power steering of the electric vehicle according to the present invention using the energy supply system for the electronic power steering of the electric vehicle according to the present invention having the configuration as described above is as follows.

3 is a schematic flowchart showing sequentially an energy supply method for electronic power steering of an electric vehicle according to the present invention.

Referring again to the drawings, the electric power steering energy supply method for an electric vehicle according to the present invention first determines whether a defect occurs in the driving battery or the fuel cell stack 23 when the vehicle of the electric vehicle is running. (Steps 110,120)

If it is determined in step 120 that a defect occurs in the driving battery or fuel cell stack 23, that is, in an emergency, the power source of the electronic power steering is used as the auxiliary battery 24 (step 130).

The vehicle is then moved to a safe place to stop (step 140).

On the other hand, when it is determined that a defect does not occur in the driving battery or the fuel cell stack 23 in step 120, that is, when the vehicle is normally driven or at all times, the power source of the electronic power steering is used as the driving battery or the fuel cell stack 23. And continues to drive the vehicle (steps 210 and 220).

As described above, the electric power steering is driven by a three-phase power steering motor 21 and an inverter 22. The inverter 22 uses a VVVF type inverter capable of controlling the output voltage and the output frequency. . Therefore, during driving of the vehicle, that is, at all times, energy is supplied from the driving battery or the fuel cell stack 23 to supply the energy to the electronic power steering inverter 22.

On the other hand, the energy is supplied from the auxiliary battery 24 only in an emergency. In an emergency, the vehicle cannot be driven due to a defect of the driving battery or the fuel cell stack 23. In this case, the main purpose is to use the power steering for a short time to move the vehicle to a safe area. The auxiliary battery 24 may be briefly used to move the vehicle to a safe area.

The electronic power steering system using the auxiliary battery 24 only in an emergency and using the driving battery or fuel cell stack 23 at all times is an electronic system using only the auxiliary battery 13 (see FIG. 1) as a power source. Compared to the power steering system, there are the following differences.

First, the thickness of the line can be reduced. That is, since the driving battery or the fuel cell stack 23 is used as a power source for the electronic power steering driving, a very high voltage is used compared to the voltage of the auxiliary battery 24. Therefore, since the amount of current flowing to the wire at the same output is reduced, the weight of the vehicle can be reduced since the thinner wire of the wire sent from the driving battery or fuel cell stack to the power steering inverter 22 can be used as compared to the conventional system. .

In addition, since the power of the auxiliary battery 24 is instantaneously used only in an emergency, the thickness of the wire from the auxiliary battery 24 to the electronic power steering is thicker than the electric power steering system using the power of the auxiliary battery 24 at all times. It is possible to design a smaller.

In addition, due to the reduction of the blurring current, the power loss due to the drop in the voltage drop of the wire is reduced. For example, a particular electric vehicle uses a voltage of 312V, which reduces the current flowing to 1/26 compared to a system using 12V.

Therefore, the voltage drop on the wire is 0.01 X 100/26 = 0.04 V. As a result, the power dissipation at the wire is 0.15 watts, a significant improvement over conventional 100 watt losses.

In addition, the price of the DC / DC converter decreases due to the capacity reduction of the DC / DC converter 26, the weight is reduced, and power loss is reduced. That is, since the capacity of the DC / DC converter 26 can be designed except for the load of the electronic power steering, the capacity reduction of the DC / DC converter 26 and the resulting price reduction of the DC / DC converter 26 and Weight reduction can be obtained and power losses due to reduced capacity of the DC / DC converter 26 at the same efficiency.

In addition, power loss due to a decrease in the frequency of use of the auxiliary battery is reduced, and the life of the auxiliary battery is extended. That is, in the case of the electronic power steering using energy of the auxiliary battery as shown in FIG. 1, the life of the auxiliary battery should be shortened and the charging and discharging efficiency of the auxiliary battery should be considered due to the frequent use of the auxiliary battery. In the case of a system directly supplied with energy, power loss due to the increase of the life of the auxiliary battery 24 and the charge / discharge efficiency need not be considered.

As described above, the drive battery or fuel cell stack 23 is always used using the system as shown in FIG. 2, and when the drive battery or fuel cell stack 23 is defective, the controller in the vehicle receives this signal. As shown in FIG. 2, the blur of energy is supplied to the auxiliary battery 24 by using a relay or another switching element 31 to supply energy to the electronic power steering.

In addition, since the electronic power steering inverter 22 is a VVVF type inverter, the output voltage and frequency are varied regardless of the voltage input to the electronic power steering inverter 22 to supply power of a desired voltage and frequency to the three-phase power steering. Input to the motor 21 is possible.

Therefore, adding only one relay or switching element 31 can achieve all the effects as mentioned above.

As described above, the method for supplying energy for electric power steering of an electric vehicle according to the present invention has the following effects.

The power supply of the electronic power steering increases the power loss of the vehicle by a complex system that moves three times from the driving battery and fuel cell stack to the DC / DC converter, from the DC / DC converter to the auxiliary battery, and from the auxiliary battery to the electronic power steering. And the system can be simplified by applying the proposed system to increase the cause of failure caused by the complexity of the energy storage system that moves energy over three times, thereby improving the performance of the vehicle and the reliability of the vehicle.

And because the thickness of the wire can be reduced, the weight of the wire is reduced, and the weight of the DC / DC converter by weight reduction of the DC / DC converter can reduce the weight of the vehicle.

In addition, the DC / DC converter's capacity can be reduced and wire weight can be reduced, resulting in cost savings.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

Claims (4)

In the energy supply system for electronic power steering of an electric vehicle driven by electric energy and fuel cells, A power steering motor and a power steering inverter are provided to drive the electronic power steering, and constantly receives energy from a driving battery or a fuel cell stack and supplies the power steering inverter to the power steering inverter. In the case of a drive battery or fuel cell stack failure, a controller installed in the electric vehicle receives a defect signal and changes a blur of energy to an auxiliary battery to supply energy to the electronic power steering, thereby moving the electric vehicle. An energy supply system for electric power steering of an electric vehicle, characterized in that for making. The method of claim 1, The power steering inverter is an electronic power steering energy supply system for an electric vehicle, characterized in that the VVVF inverter capable of controlling the output voltage and output frequency. In the energy supply method for electronic power steering of an electric vehicle driven by electric energy and fuel cells, (a) determining whether a defect occurs in the driving battery or the fuel cell stack when the vehicle is running; (b) if it is determined in step (a) that a defect occurs in the drive battery or the fuel cell stack, using a power source of the electronic power steering as a secondary battery; (c) moving the vehicle to a safe place to stop the electric power steering method for electric power steering of an electric vehicle. The method of claim 3, If it is determined in step (a) that no defect has occurred in the driving battery or the fuel cell stack, the electric power steering of the electric vehicle is characterized by using the power source of the electronic power steering as the driving battery or fuel cell stack. Energy supply method.