JPH08127352A - Power steering system for vehicle - Google Patents

Abstract

PURPOSE: To reduce a cost as a system total unit, to accurately control assist force by preventing easily receiving of an influence by fluctuation of battery voltage, and to attain energy saving by suppressing waste energy consumption in a booster circuit. CONSTITUTION: A motor drive current I is checked, 101, and when it is 11 or more, boosted voltage Vout is set to V2 (V2=100V), 102. When the motor drive current I is 11 or less, whether elapsed or not a prescribed time Δt or more, after the motor drive current I is decreased to 11 or less, is checked, 103. When the current I is decreased to 11 or less for the prescribed time Δt or more continued, the boosted voltage Vout is lowered down to Vin 104.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention adjusts a current supplied from an in-vehicle battery to a motor on the basis of a vehicle speed detected by a vehicle speed sensor and a steering wheel steering angle detected by a steering angle sensor to assist steering wheel steering. The present invention relates to a vehicle power steering system that controls force.

[0002]

2. Description of the Related Art Conventionally, as this type of power steering system, a motor drive power steering system (MDPS) having a basic configuration shown in FIG.
There is. In the figure, 1 is an in-vehicle battery, 2 is an alternator, 3 is an engine, 4 is a vehicle speed sensor, 5 is a steering angle sensor, 6 is a power steering unit, 7 is an electric motor drive pump, 8 is an ignition switch, and 9 is a signal controller. 10 is a power controller.

In this MDPS, the vehicle speed detected by the vehicle speed sensor 4 and the steering wheel steering angle detected by the steering angle sensor 5 are
It is given to the signal controller 9. The signal controller 9 generates an electric motor drive signal based on the vehicle speed and the steering wheel steering angle from the vehicle speed sensor 4 and the steering angle sensor 5, and supplies the generated electric motor drive signal to the power controller 10. The power controller 10 adjusts the current supplied from the vehicle-mounted battery 1 to the electric motor drive pump 7 according to the electric motor drive signal from the signal controller 9.

As a result, the hydraulic pressure to the power steering unit 6 is controlled, and when steering in the low speed traveling range, the assist force is increased to lighten the steering force, and when steering in the medium to high speed traveling region, the steering force is decreased to the contrary. The assist force at the time of steering the steering wheel is controlled so as to make the steering wheel heavier.

[0005]

However, this M
In the DPS, the in-vehicle battery 1 is connected to the electric motor drive pump 7.
It is assumed that the battery voltage (DC12V) is directly applied. That is, as the motor 7-1 used in the electric motor drive pump 7, a DC 12V specification motor is used. For this reason, a large current is passed through the motor 7-1 to obtain a large torque.
There is a problem that the thickening of the wiring used is inevitable and the cost of the entire system increases.

The battery voltage of the vehicle-mounted battery 1 is
It depends on the size of the load. The motor 7-1 is affected by the fluctuation of the battery voltage, and as a result, the assist force at the time of steering the steering wheel fluctuates. That is, the battery voltage is as low as 12V, and this low battery voltage is directly applied to the motor 7-1.
The generated torque of the motor 7-1 greatly fluctuates even with a slight voltage fluctuation, which causes a problem that the assist force during steering of the steering wheel is not accurately controlled.

In the above description, an automobile using an internal combustion engine as a prime mover is taken as an example, but an electric automobile (E
The same problem occurs when it is used in V vehicles. In an EV vehicle, the main voltage supply source is only the battery, and its voltage fluctuation is large. Also, in the above, MDPS
However, the same problem occurs in a FEPS (Full Electric Power Steering System) in which the assist force is controlled by directly driving the motor without using hydraulic pressure.

The present invention has been made to solve such a problem, and an object of the present invention is to reduce the size of a motor and the wiring used, thereby reducing the cost of the entire system. In addition, the power steering for a vehicle is capable of controlling the assist force with high accuracy because it is not easily affected by the fluctuation of the battery voltage, and can save energy by suppressing unnecessary energy consumption in the booster circuit. To provide a system.

[0009]

In order to achieve such an object, the first invention (the invention according to claim 1) is the vehicle power steering system described above, wherein a current supply passage to a motor is provided. a booster circuit provided to boost the battery voltage from the vehicle battery, while applied to the motor as a boosted voltage V _{ou t,} monitors the load of the motor, when the load exceeds a predetermined value I1, the boosted voltage V _out Is to raise. According to a second invention (an invention according to claim 2), in the above-described vehicle power steering system, a booster circuit is provided on the way of a current supply path to the motor to boost the battery voltage from the vehicle battery
While applying the boosted voltage V _out to the motor, the load of the motor is monitored, and when the load becomes equal to or more than a predetermined value I1, the boosted voltage V _out is increased and continues for a predetermined time Δt or more to be equal to or less than the predetermined value I1. When it becomes, the boosted voltage V _out is lowered. A third invention (an invention according to claim 3) is a vehicle power steering system as described above, wherein a booster circuit is provided on the way of a current supply path to the motor to boost the battery voltage from the vehicle-mounted battery.
While applying the boosted voltage V _out to the motor, the load of the motor is monitored and the boosted voltage V _out is changed according to the load.

[0010]

Therefore, according to the present invention, in the first invention,
When the load on the motor becomes equal to or greater than the predetermined value I1, the boost voltage V _out applied to the motor increases. For example, when the current flowing through the motor becomes a predetermined value I1 or more, the boost voltage V _out is 12 V (minimum value: battery voltage) to 100 V.
Rises to the highest value. . In the second invention, when the load of the motor exceeds a predetermined value I1, then it increases the boosted voltage V _out, when it becomes less than the predetermined value I1 continues a predetermined time Δt above, the boosted voltage V _out drops. For example, when the current flowing through the motor becomes a predetermined value I1 or more, the boosted voltage V
_out is 12V (minimum value: battery voltage) to 100V
When the voltage rises to the (maximum value) and continues to fall below the predetermined value I1 for a predetermined time Δt or longer, the boosted voltage V _out drops from 100V to 12V. In the third invention, the boosted voltage V _out changes according to the load on the motor. For example, according to the current flowing through the motor, the boosted voltage V increases as the current increases.
_{As out} increases and current decreases, boosted voltage V _out
Descends.

[0011]

EXAMPLES The present invention will now be described in detail based on examples. FIG. 2 is an electric circuit diagram showing a main part of the MDPS showing an embodiment of the present invention. In the figure, 4 is a vehicle speed sensor, 5 is a steering angle sensor, 7-1 'is a motor of an electric motor drive pump, 11 is a microcomputer, 12 is a booster circuit, 13 is a drive circuit, Tr1 is a power transistor, D1 to D4. Is a diode, and R1 to R4 are resistors.

The booster circuit 12 is provided on the way of the current supply path from the vehicle battery to the motor 7-1 '.
That is, the battery voltage V _in (DC1
2V) application point P1 and voltage application point P to the motor 7-1 '
It is provided between the capacitor C1 and C2, the coil C1, the coil L1, the diode D5, the switching transistor Tr2, and the oscillation circuit 12-1.

The microcomputer 11 has terminals A to K.
And a divided voltage V due to the resistors R1 and R2 at the terminal A.
a is applied to the terminal E, and the divided voltage Vb generated by the resistors R3 and R4 is applied to the terminal E. The microcomputer 11
The battery voltage V _in that is applied from the divided voltage Va to the point P1
Is detected, the boosted voltage V generated at the point P2 from the divided voltage Vb
_{When out} is detected and the battery voltage V _in drops by a set value or more, the boosted voltage V _out is lowered or set to V _in . In this case, a warning lamp (not shown) is turned on to give a warning to the driver.

The steering angle of the steering wheel detected by the steering angle sensor 5 is applied to the terminal I, and the vehicle speed detected by the vehicle speed sensor 4 is applied to the terminal K. The microcomputer 11 generates an electric motor drive signal based on the vehicle speed and the steering wheel steering angle from the vehicle speed sensor 4 and the steering angle sensor 5, and outputs the generated electric motor drive signal from the terminal F to the drive circuit 13.
Output to.

Information about the temperature of the transistor Tr2 is given to the terminal C, and information about the current flowing through the transistor Tr2 is given to the terminal D. Information about the temperature of the transistor Tr1 is given to the terminal G, and information about the current flowing through the transistor Tr1 (current flowing through the motor 7-1 ') is given to the terminal H. Information regarding the number of rotations of the motor 7-1 'is given to the terminal J.

Further, the microcomputer 11 outputs a duty ratio instruction value from the terminal B to the oscillation circuit 12-1 of the booster circuit 12. The duty ratio instruction value determines the duty ratio of the pulse wave output from the oscillation circuit 12-1 to the transistor Tr2. In addition,
In this embodiment, the oscillation frequency of the oscillation circuit 12-1 is 2
It is set to 0 kHz.

[Basic Operation of Boosting Circuit 12] Boosting Circuit 12
Of the coil L by switching the transistor Tr2 by the pulse wave from the oscillation circuit 12-1.
This is because the accumulation and release of energy are repeated at 1 and a high voltage at the time of release appears on the cathode side of the diode D5.

That is, when the transistor Tr2 is turned on, a current flows through the coil L1, and when the transistor Tr2 is turned off, the current flowing through the coil L1 is cut off. When the current flowing through the coil L1 is cut off, a high voltage is generated on the cathode side of the diode D5 so as to prevent a change in magnetic flux due to the cutoff of the current. By repeating this, a high voltage is repeatedly generated on the cathode side of the diode D5,
It is smoothed by the capacitor C2, and the point P is set as the boost voltage V _out.
Occurs in 2.

The boosted voltage V _out generated by the booster circuit 12 depends on the duty ratio instruction value output from the terminal B of the microcomputer 11, and if the duty ratio instruction value is large, the boosted voltage V _out becomes high and the duty ratio is increased. If the ratio instruction value is small, the boosted voltage V _out becomes low. That is, if the on-duty of the pulse wave output from the oscillation circuit 12-1 to the transistor Tr2 is large, the boosted voltage V _out is high, and conversely, if the on-duty is small, the boosted voltage V _out is low.

In this embodiment, the maximum value of the boosted voltage V _out is 100 V, so that the motor 7-1 'has a maximum value of 1.
Not a 2V specification motor, but a 100V specification motor (D
C brush motor) is used. That is, in the present embodiment, as the motor 7-1 ', a high voltage specification motor capable of obtaining a large torque with a small current is used.

As a result, the size of the motor 7-1 'is reduced and the wiring used is made thinner to reduce the cost of the entire system. The boosted voltage V _out is 100
By setting to V, it is possible to use a low-cost element used in home appliances. In addition, in this embodiment,
Variations of the boosted voltage V _out relative to the variation of the battery voltage V _in is small, as less susceptible to fluctuations in the battery voltage V _in, can be controlled accurately assist force.

The booster circuit 12 has high power and low loss as the transistor Tr2 due to recent technological innovation.
Since a low-cost transistor can be obtained, it can be manufactured at low cost. That is, even if the booster circuit 12 is used,
The cost increase is absorbed by the cost reduction due to the downsizing of the motor 7-1 ', the thinning of the wiring used, and the like, and the cost of the entire system is reduced.

Further, in the present embodiment, the oscillation frequency of the oscillation circuit 12-1 is set to 20 kHz, but the coil L1 can be made smaller by further raising the oscillation frequency. As a result, compactness can be promoted and cost can be reduced. The upper limit of the oscillation frequency of the oscillation circuit 12-1 is restricted in consideration of the switching speed of the transistor Tr2, and the oscillation frequency can be increased by using a high-speed transistor Tr2.

Further, in this embodiment, the oscillator circuit 12-1 is provided in the booster circuit 12, but the oscillator circuit 12-1 is used.
Is omitted, and a pulse wave whose duty ratio is adjusted is output from the terminal B of the microcomputer 11,
This pulse wave may be directly applied to the transistor Tr2.

[Operation of Microcomputer 11] Next, the operation of the microcomputer 11 will be described with its functions. Microcomputer 11
Is a current (motor drive current) I flowing through the motor 7-1 '.
When is increased, the boosted voltage V _out is increased, and when decreased, the boosted voltage V _out is decreased. That is, when the load on the motor 7-1 ′ is small, that is, when a large assist force is not required, in order to avoid unnecessary energy consumption in the booster circuit 12, the booster operation in the booster circuit 12 is suppressed and the boosted voltage V lower _out . On the other hand, when the load on the motor 7-1 'increases, that is, when a large assist force is required, the boost voltage V _out is increased.

The characteristic processing operation of the microcomputer 11 will be described with reference to the flowchart shown in FIG. The microcomputer 11 checks the motor driving current I which is input through the terminal H (step 101), if the motor driving current I is set value I1 or more, the boosted voltage V _out predetermined value V2 (the embodiment Then V
2 = 100V) (step 102).

If the motor drive current I is I1 or less in step 101, it is determined whether or not the state where the motor drive current I is I1 or less continues for a predetermined time Δt or more, that is, the motor drive current I1 continues for a predetermined time Δt or more. It is checked whether I1 or less (step 103). If it is not less than I1 continuously for Δt time or more, the process proceeds to step 102. If the voltage is continuously reduced to I1 or less for Δt time or more, the boosted voltage V _out is decreased to V _in (step 104).

Needless to say, the adjustment of the boosted voltage V _out depends on the duty ratio instruction value output from the terminal B, and the boosting operation in the booster circuit 12 is performed by reducing the duty ratio instruction value. Is suppressed, the boosted voltage V _out is reduced, and energy consumption in the booster circuit 12 is suppressed. When the duty ratio instruction value is 0,
The boosting operation in the booster circuit 12 is stopped, and the boosted voltage V _out becomes the battery voltage V _in (minimum value).

FIG. 3A illustrates a change state of the motor drive current I, and FIG. 3B illustrates a change state of the boosted voltage V _out . During the period from time t ₀ to time t ₁ , steering is not performed and the motor drive current I is I1 or less. Therefore, the boosted voltage V _out is set to V _in . With the start of steering, the motor drive current I increases and becomes I1 or more (time t ₁ ), and the boosted voltage V _out is increased to V2 (100 V).

With the completion of steering, the motor drive current I decreases and the motor drive current I becomes less than I1 (time t ₂ ).
When the state of I1 or less continues for a predetermined time Δt or more (time t ₂ '), the boosted voltage V _out is dropped to V _in . That is, even if the motor drive current I becomes less than or equal to I1, the boosted voltage V _out maintains V2 during Δt time. As a result, when re-steering at an early timing immediately after the end of steering, it is possible to prevent a feeling of strangeness in steering and to improve steering feeling.

When the motor drive current I is re-steered and becomes I1 or more (time t ₃ ), the boosted voltage V _out is increased to V 2 as in the case of time t ₁ . As the steering ends, the motor drive current I decreases and the motor drive current I
When it is less than 1 (time t ₄ ), and is re-steered before Δt time elapses from that time, that is, the motor drive current I is increased from time t ₄ to time t ₄ ′ when Δt time elapses. When it becomes I1 or more, the boosted voltage V _out does not decrease and V2 is maintained.

With the completion of steering, the motor drive current I decreases and the motor drive current I becomes I1 or less (time t ₅ ).
When the state of I1 or less continues for a predetermined time Δt or more (time t ₅ ′), the boosted voltage V _out is dropped to V _in . As described above, according to this embodiment, the motor drive current I is Δ
If I1 or more continues for t hours or more, the boosted voltage V
_Out is dropped to become V _in , wasteful energy consumption in the booster circuit 12 is suppressed, and energy can be saved.

In this embodiment, the load of the motor 7-1 'is monitored by the motor drive current I, but it may be monitored by the rotation speed of the motor 7-1'. Also, various parameters for monitoring the load can be considered. Further, in this embodiment, when the motor driving current I becomes I1 below, but the boosted voltage V _out and to be lowered into V _in, it is needless to say not intended to be limited to the V _in.

Further, the criterion for lowering (increasing) the boosted voltage V _out does not have to be I1, and a plurality of criterion are provided to gradually decrease (increase) the boosted voltage V _out.
You may allow it. Further, according to the motor drive current I, as the motor drive current I increases, the boosted voltage V
_{It is also possible} to increase _out and decrease the boosted voltage V _out as the motor drive current I decreases. Further, in this embodiment, the coil L1 is used as the booster circuit 12, but a booster circuit using a transformer may be used.
That is, the booster circuit is not limited to this method, and may be any booster circuit that can arbitrarily set the boosted voltage.

Although the DC brush motor is used as the motor 7-1 'in this embodiment, a DC brushless motor may be used instead of the DC brush motor.
FIG. 4 shows an electric circuit diagram of a main part of the MDPS when the DC brushless motor is used. In this case, the brushless motor driver circuit 13 'is provided and the power transistor Tr
₁₁ through the transistor circuit 14 consisting to Tr ₁₆ and the diode D6～D11, "to adjust the current supplied to. Motor 7-1" motor 7-1 as by using a DC brushless motor, a brush replacement (e.g., During continuous operation of the motor, once / 2000 to 3000 km) is unnecessary, long-term stability is ensured, and durability is improved.

In this embodiment, MDPS has been described as an example, but it can be applied to FEPS in the same manner. In addition, the type of vehicle prime mover (internal combustion engine, EV
Car ... etc) and battery voltage (12V, 24
It is possible to apply to all vehicles in the same way regardless of the magnitude of V ... Etc). In addition, MD for EV cars
When PS is used, it is conceivable to step down a high voltage as a vehicle drive motor power source and apply the voltage to an electric motor drive pump. At this time, the same technical idea is applied to the step-down circuit to save energy. Is possible.

[0037]

As is apparent from the above description, according to the present invention, the battery voltage is boosted and the boosted voltage V _out.
As it is applied to the motor, a large torque can be obtained with a small current, and high voltage specifications (for example, 100V specifications)
As a result, the cost of the entire system can be reduced by downsizing the motor and thinning the wiring used. Further, the boosted voltage V
It is possible to accurately control the assist force on the assumption that the fluctuation of _out is small and is hardly affected by the fluctuation of the battery voltage. Further, in the first aspect of the invention, when the load of the motor becomes equal to or higher than the predetermined value I1, the boost voltage V _out applied to the motor increases, and in the second aspect of the invention, the load of the motor becomes equal to or higher than the predetermined value I1. In this case, the boosted voltage V _out rises, and when the boosted voltage V _out continues to fall below the predetermined value I1 for a predetermined time Δt or longer, the boosted voltage V _out drops, and in the third invention, the boosted voltage V _out depends on the load of the motor. Changes and the load of the motor is small, that is, when a large assisting force is not required, the boosted voltage V _{out is set} to be low, and wasteful energy consumption in the booster circuit can be suppressed to save energy. .

[Brief description of drawings]

FIG. 1 is a flow chart showing a characteristic processing operation of the microcomputer in FIG.

FIG. 2 is an electric circuit diagram showing a main part of an MDPS showing an embodiment of the present invention.

FIG. 3 is a diagram illustrating a change state of a motor drive current I and a change state of a boost voltage V _out .

FIG. 4 is an electric circuit diagram showing a main part of the MDPS when a DC brushless motor is used instead of the DC brush motor.

FIG. 5 is a diagram showing a basic configuration of a conventional MDPS.

[Explanation of Codes] 1 ... In-vehicle battery, 4 ... Vehicle speed sensor, 5 ... Rudder angle sensor,
7-1 '... Motor of electric motor drive pump, 11 ... Microcomputer, 12 ... Booster circuit, 13 ... Drive circuit, Tr1, Tr2 ... Transistor, L1 ... Coil, 1
2-1 ... Oscillation circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B62D 113: 00

Claims (3)

[Claims] 1. A vehicle for controlling an assist force during steering of a steering wheel by adjusting a current supplied from a vehicle battery to a motor based on a vehicle speed detected by a vehicle speed sensor and a steering wheel steering angle detected by a steering angle sensor. In the power steering system, provided on the way of a current supply path to the motor, for boosting a battery voltage from the vehicle-mounted battery, a boosted voltage V
a booster circuit for applying to said motor as _out, monitors the load of the motor, and wherein that the when the load exceeds a predetermined value I1, with the boosted voltage raising means for raising the boosted voltage V _out Power steering system for vehicles. 2. A vehicle for controlling an assist force during steering of a steering wheel by adjusting a current supplied from a vehicle battery to a motor based on a vehicle speed detected by a vehicle speed sensor and a steering wheel steering angle detected by a steering angle sensor. In the power steering system, provided on the way of a current supply path to the motor, for boosting a battery voltage from the vehicle-mounted battery, a boosted voltage V
a booster circuit applied to the motor as _out , a load of the motor is monitored, and a booster voltage raising means for raising the boosted voltage V _out when the load of the motor is over a predetermined value I1. A power steering system for a vehicle, comprising: boosted voltage drop means for monitoring the boosted voltage V _out when the load continues to fall below a predetermined value I1 for a predetermined time Δt or longer. 3. A vehicle for controlling an assist force during steering of a steering wheel by adjusting a current supplied from a vehicle battery to a motor based on a vehicle speed detected by a vehicle speed sensor and a steering wheel steering angle detected by a steering angle sensor. In the power steering system, provided on the way of a current supply path to the motor, for boosting a battery voltage from the vehicle-mounted battery, a boosted voltage V
_A power steering system for a vehicle, comprising: a booster circuit applied to the motor as _out, and boosted voltage varying means for monitoring a load of the motor and changing the boosted voltage V _out according to the load. .