JP2003137115A - Car power system - Google Patents

Abstract

(57) [Summary] To provide a power supply system for an automobile equipped with an electric power steering device, which does not impair the followability of the steering wheel at the time of emergency steering due to a decrease in battery voltage or the like. An alternator is directly connected to a drive power supply of the electric power steering device, and a switch is provided between the alternator and a battery. Switching control of the switch is performed based on predetermined information by switch drive control means. Is achieved by doing

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply system for an automobile equipped with an electric power steering device for applying a steering assist force by a motor to a steering system, and particularly when the steering wheel is urgently steered due to a decrease in battery voltage or the like. The present invention relates to a power supply system for an automobile that does not impair the followability of.

[0002]

2. Description of the Related Art An electric power steering system for energizing an automobile steering system with an auxiliary load by a rotational force of a motor uses a transmission mechanism such as a gear or a belt to transmit a driving force of the motor through a speed reducer to a steering shaft or a rack shaft. It is designed to energize the auxiliary load. Such a conventional electric power steering device performs feedback control of the motor current in order to accurately generate the assist torque (steering assist torque). The feedback control is for adjusting the motor applied voltage so that the difference between the current control value and the motor current detection value is small. The adjustment of the motor applied voltage is generally performed by PWM (pulse width modulation) control duty. It is done by adjusting the tee ratio.

Now, a general structure of the electric power steering apparatus will be described with reference to FIG.
The shaft 2 is connected to a tie rod 6 of a steering wheel via a reduction gear 3, universal joints 4a and 4b, and a pinion rack mechanism 5. The shaft 2 is provided with a torque sensor 10 for detecting the steering torque of the steering wheel 1, and a motor 20 for assisting the steering force of the steering wheel 1 is coupled to the shaft 2 via a clutch 21 and a reduction gear 3. Has been done. The control unit 30 for controlling the power steering device includes a battery 14 and an ignition key 1
Power is supplied via 1 and the control unit 30
Calculates the steering assist command value I of the assist command based on the steering torque T detected by the torque sensor 10 and the vehicle speed V detected by the vehicle speed sensor 12, and based on the calculated steering assist command value I. The current supplied to the motor 20 is controlled. The clutch 21 is turned on by the control unit 30 /
It is turned off, and is turned on (coupled) in a normal operating state. The clutch 21 is turned off (disengaged) when the control unit 30 determines that the power steering device is out of order and when the ignition key 11 turns off the power of the battery 14.

The control unit 30 is mainly a CP
Although it is composed of U, a general function executed by a program inside the CPU is shown in FIG.

For example, the phase compensator 31 does not represent a phase compensator as an independent hardware but a phase compensating function executed by the CPU. To explain the function and operation of the control unit 30, the steering torque T detected and input by the torque sensor 10 is phase-compensated by the phase compensator 31 in order to enhance the stability of the steering system.
The phase-compensated steering torque TA is input to the steering assist command value calculator 32. The vehicle speed V detected by the vehicle speed sensor 12 is also input to the steering assist command value calculator 32. The steering assist command value calculator 32 determines the steering assist command value I, which is the control target value of the current supplied to the motor 20, based on the input steering torque TA and vehicle speed V, and the steering assist command value calculator 32 stores it. Is provided with a memory 33. The memory 33 stores the steering assist command value I corresponding to the steering torque with the vehicle speed V as a parameter, and the steering assist command value calculator 32
Is used to calculate the steering assist command value I. The steering assist command value I is input to the subtractor 30A and a feed-forward differential compensator 34 for increasing the response speed.
, The deviation (Ii) of the subtractor 30A is input to the proportional calculator 35, and its proportional output is input to the adder 30B and also to the integral calculator 36 for improving the characteristics of the feedback system. To be done. The outputs of the differential compensator 34 and the integral compensator 36 are also added and input to the adder 30B, and the current control value E that is the addition result of the adder 30B is input to the motor drive circuit 37 as a motor drive signal. The motor current value i of the motor 20 is detected by the motor current detection circuit 38, and the motor current value i is input to the subtractor 30A and fed back.

A configuration example of the motor drive circuit 37 will be described with reference to FIG. 7. The motor drive circuit 37 is based on the current control value E from the adder 30B and is based on the field effect transistor (FE).
T) An FET gate drive circuit 371 that drives each gate of FET1 to FET4, an H bridge circuit that includes FET1 to FET4, and a boosting power supply 372 that drives the high side of FET1 and FET2. FET1 and FET2 are turned on / off by a PWM (pulse width modulation) signal having a duty ratio D1 determined based on the current control value E.
When turned off, the magnitude of the current Ir that actually flows through the motor is controlled. FET3 and FET4 have a duty ratio D
In the region where 1 is small, the duty ratio D2 defined by a predetermined linear function equation (D2 = a · D1 + b with a and b as constants)
Is driven by the PWM signal of, and in a region where the duty ratio D1 is large, it is turned on / off according to the rotation direction of the motor determined by the sign of the PWM signal. For example, when the FET3 is in the conductive state, the current is FET1, the motor 20, the F
A current flows in the positive direction through the motor 20 through the ET3 and the resistor R1. When the FET 4 is in the conductive state, the current flows through the FET 2, the motor 20, the FET 4, and the resistor R2, and the negative current flows through the motor 20. Therefore, the current control value E from the adder 30B is also a PWM output. The motor current detection circuit 38 detects the magnitude of the positive current based on the voltage drop across the resistor R1 and the magnitude of the negative current based on the voltage drop across the resistor R2. The motor current value i detected by the motor current detection circuit 38 is input to the subtractor 30A and fed back.

[0007]

An important specification required for the steering performance in the above control device is the followability of the steering assist device. That is, it is important to consider how fast the steering can be steered without feeling discomfort, assuming steering during emergency avoidance. In the case of electric power steering, the performance of the motor is dominant in the followability.

The power supply voltage of the motor is usually a voltage (14.5 to 12.0) supplied from an alternator or a battery.
V) and the size of the motor is also limited by mechanical specifications, so that the followability that can be realized in the design of the motor is limited. On the other hand, when followability becomes a problem, assist (current) is also required.

As shown in FIG. 1, a conventional automobile power supply system supplies electricity to an electric power steering device (EPS) and other loads (lamps, air conditioners, etc.) while charging a battery with power generated by an alternator. is doing.

However, many electric components in the automobile have a heavy load such as a headlight and an air conditioner, and recently, a very heavy load such as an electric power steering device has come out.

For this reason, if the vehicle is suddenly steered with the headlights, the air conditioner, etc. turned on, the battery will be in a high load state and the voltage of the battery will drop. As a result, the followability of the motor shifts from A (in the case of 14.5V) to B (in the case of 12.0V) and decreases as shown in FIG. 8, and there is a problem that the required followability cannot be obtained. .

Further, when the steering wheel is steered steeply to avoid danger, the steering torque increases. Therefore, it is necessary to generate an assist torque. When the motor is driven beyond the capacity limit of the motor, FIG. As shown in, the motor current value suddenly changes, and as a result, the steering torque changes in an impulse manner. That is, when the steer steering is performed at time t1 in FIG. 9, the motor angular velocity ω increases as shown in FIG. 9A, whereas the motor current i is as shown in FIG. Decrease sharply. At the same time, the steering torque T sharply increases after time t1 as shown in FIG. 7C, the natural vibration of the system is excited, and the phenomenon shown by A in FIG. 7C gives the driver a feeling of strangeness.

Therefore, it is necessary to ensure that the current supplied to the motor of the electric power steering apparatus is not insufficient so that stable steering assist can be performed.

The present invention has been made under the circumstances as described above, and an object of the present invention is to supply a power supply system for an automobile capable of supplying sufficient electric power to a motor of an electric power steering apparatus. .

[0015]

SUMMARY OF THE INVENTION The present invention relates to a power supply system for an automobile equipped with an electric power steering device, in which the followability of the steering wheel during emergency steering is not impaired, especially due to a decrease in battery voltage or the like. The above object of the present invention is to provide a power supply system for an automobile equipped with an electric power steering device that applies a steering assist force by a motor to a steering system, and to directly connect an alternator and a drive power supply of the electric power steering device. A switch is provided between the alternator and the battery, and the switch drive control means controls the switching of the switch based on predetermined information.

Another object of the present invention is to provide an alternator and a drive power source for the electric power steering device in a power supply system of an automobile equipped with an electric power steering device for applying a steering assist force by a motor to a steering system. And a first switch is provided between the alternator and the battery, and a second switch is provided between the battery and the load, and the switch drive control means operates both switches based on predetermined information. This can be achieved more effectively by interlocking the opening / closing control of the switch.

Further, the predetermined information used for controlling the switch can be more effectively achieved by including at least the sudden steering state signal output from the electric power steering device.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is to supply stable electric power to a motor of an electric power steering device of an automobile equipped with an electric power steering device for applying a steering assist force by a motor to a steering system. Thus, the present invention relates to a power supply system for an automobile, in which stable steering assist can be obtained even when a sudden steering operation is performed when a high load other than the electric power steering is applied while the engine speed is decreasing.

A power supply system for an automobile according to the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a conventional automobile power supply system, in which the electric power generated by an alternator (alternating current generator) 101 by the rotation of an engine is stored in a battery 102 and is connected to the output side of the battery 102. Electric power is supplied to the electric power steering device (EPS) 103, a load 104 such as a headlight and an air conditioner.

In the conventional power supply system having such a structure, the load 10 is limited because the capacity of the battery is limited.
When a large amount of electric power is consumed in 4, for example, when using the air conditioner, headlights, rear defogger, etc. at the same time, the electric power supplied to the EPS is small, so a large amount of electric current is required, such as during sudden steering. When it is necessary, normal assistance cannot be obtained, and there is a drawback that the driver feels something strange (a feeling of being caught, a feeling of being caught, etc.).

FIG. 2 is a diagram showing a first embodiment of a vehicle power supply system according to the present invention, in which the electric power generated by the alternator 101 is directly supplied to the EPS 103 and the battery 102 via the switch SW1. Is also supplied to the battery 102 so that the battery 102 is charged. Further, electric power is supplied to the load 104 connected to the output side of the battery 102 to operate the air conditioner or the like.

The basic idea of the present invention is as follows. That is, the electric power generated by the alternator 101 is
Power is supplied to both the EPS 103 and the battery 102, but when the EPS 103 temporarily needs a large amount of power (for example, during steer steering), the power supply to the battery 102 is temporarily stopped and all the power is supplied to the EPS side. To stabilize the operation of the EPS.

However, when the load 104 consumes almost no electric power and the battery 102 is in a fully charged state, the current flowing from the alternator 101 to the battery 102 is small, and thus even if the motor of the EPS 103 consumes a large current. It is not necessary to turn off the switch SW1.

From the above, the conditions for turning off SW1 are summarized as follows: Unconditionally turned off during sudden steering, otherwise: When the EPS103 motor consumes a large current (high torque generation) And when the amount of power generation in the alternator 101 is small (the engine speed is low) or the battery voltage is low (a large amount of power is required on the load side).

The switch SW1 is normally closed (O
In the N state), the switch SW1 is controlled so that the switch SW1 is temporarily turned off only when the above conditions are met, and is returned to the ON state when the condition is canceled.

Even if the OFF condition is not released, the switch SW1 may be controlled so as to be forcibly turned ON after a predetermined time has passed from the viewpoint of battery protection (preventing overdischarge). Good.

FIG. 3 shows an example of the drive control method of the switch SW1. The sudden steering state signal or the motor current i (FIG. 6) 105 output from the EPS 103 and other information such as the engine speed or the battery voltage. 1
06 is taken into the switch drive control means 107 and compared with a limit value (reference value) provided in the switch drive control means 107, and when the above condition is satisfied, the contact of the switch SW1 is opened (OFF). Control to Also, a timer (not shown) provided in the switch drive control means 107 may be used to forcefully return to the ON state when the OFF state exceeds a predetermined time.

Whether or not the steering wheel is being steered is determined by the differential value of the torque input or the value of the motor angular acceleration in the EPS controller, and the switch is driven by the port signal (ON / OFF signal) or serial communication. Informed to the control means.

Examples of the switch include a relay and the like.

When the switch SW1 is turned off, all the power generated by the alternator 101 is supplied to the EPS 103, so that stable assist can be obtained.

The switch SW1 is turned off mainly at the time of sudden steering. At this time, even if the battery voltage drops because electricity does not flow to the battery 102,
Since this is only the moment of sudden steering, the time for which the switch is open can be made very short, so that there is almost no effect on other electric components (load) due to the battery voltage drop.

FIG. 4 is a diagram showing a second embodiment of the power supply system for an automobile according to the present invention, in which a load 104 and a load A (for example, an engine, a light, etc.) 104a that needs to be constantly supplied with electricity are momentarily supplied. Load B (eg, power window, air conditioner, etc.) 104 that does not hinder even if the power is turned off
b, a switch SW2 is provided between the battery 102 and the load B104b, and a switch SW1 and a switch SW are provided.
2 is interlocked, and drive control is performed under the above conditions.

By doing so, the switch is turned off.
It is possible to reduce the consumption of the battery 102 during the FF.

[0035]

According to the present invention, when an abrupt steering operation is performed when a high load other than the electric power steering device is applied in a state where the engine speed is reduced, only the electric power steering device changes from the alternator. Since electricity is supplied, the voltage drop of the motor can be prevented, and normal steering assist can be performed.

[Brief description of drawings]

FIG. 1 is a diagram showing a conventional vehicle power supply system.

FIG. 2 is a diagram showing a first embodiment of a power supply system for an automobile according to the present invention.

FIG. 3 is a diagram illustrating an example of a switch drive control method.

FIG. 4 is a diagram showing a second embodiment of the power supply system for an automobile according to the present invention.

FIG. 5 is a block diagram showing an example of an electric power steering device.

FIG. 6 is a block diagram showing a general internal configuration of a control unit.

FIG. 7 is a connection diagram showing an example of a motor drive circuit.

FIG. 8 is a diagram for explaining a decrease in motor performance limit due to a decrease in power supply voltage.

FIG. 9 is a diagram for explaining a conventional operation example in the case of performing a quick steering operation.

[Explanation of symbols]

101 Alternator 102 battery 103 Electric power steering system (EPS) 104 load 107 switch drive control means

Claims (3)

[Claims] 1. In a power supply system of an automobile equipped with an electric power steering device for applying a steering assist force by a motor to a steering system, an alternator is directly connected to a drive power supply of the electric power steering device, and the alternator is also provided. A power supply system for an automobile, characterized in that a switch is provided between the battery and the battery, and the switch drive control means controls the opening and closing of the switch based on predetermined information. 2. A power supply system for an automobile equipped with an electric power steering device for applying a steering assist force by a motor to a steering system, wherein an alternator is directly connected to a drive power supply of the electric power steering device, and the alternator is also connected. A first switch is provided between the battery and the battery, and a second switch is provided between the battery and the load, and the switch drive control means interlocks the open / close control of both switches based on predetermined information. Car power supply system characterized by being carried out. 3. The power supply system for a vehicle according to claim 1, wherein the predetermined information includes at least a rapid steering state signal output from the electric power steering device.