JP3399226B2 - Electric power steering device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering system in which steering force is assisted by the output of an electric motor.

[0002]

2. Description of the Related Art Generally, in an electric power steering apparatus, a torque sensor for detecting a steering torque is attached to an input shaft to which a steering wheel is fixed, and a motor is driven according to a torque detection value of the torque sensor. The steering assist torque is generated according to the steering force to assist the steering torque.

In such an electric power steering system, since the steering assist torque generated in the electric motor is controlled based on various detection signals such as the torque detection value of the torque sensor, the detection values of these sensors are abnormal. In such a state, the electric motor cannot be accurately controlled. Therefore, the abnormality of these sensors is monitored, and when the abnormality is detected, the device is stopped.

[0004]

However, in the above-mentioned conventional electric power steering apparatus, when the various sensors have an abnormality, the control apparatus immediately stops the current supply to the electric motor. For example, when an abnormality occurs in the torque sensor while steering the steering wheel to the vicinity of the stationary lock with the assistance of the steering assist torque of the electric power steering device, the assist of the steering assist torque is used. The current supply to the electric motor is stopped to stop it, but at this time, the steering assist torque by the electric motor suddenly disappears, so this is applied to the steering shaft by the return force of the elastic deformation of the steering system, such as the twisting force of the tire. The force to return to the neutral position acts and the steering wheel returns to the neutral position. Utoshi, there is a problem that the burden on the driver is applied.

Therefore, the present invention has been made in view of the above-mentioned unsolved problems of the prior art, and is intended to return the steering wheel to the neutral state which occurs when the electric motor is stopped during the assist by the electric power steering. It is an object of the present invention to provide an electric power steering device that can suppress the force that occurs.

[0006]

In order to achieve the above object, an electric power steering apparatus according to claim 1 of the present invention comprises an electric motor connected to a steering system of a vehicle to generate steering assist torque, and the steering system. In the electric power steering apparatus, the steering assist torque is detected by the steering torque detecting means for detecting the steering torque of the electric motor and the electric motor driving means for driving the electric motor based on the steering torque detected by the steering torque detecting means. When the electric motor is stopped during the generation, a short-circuiting means for short-circuiting the terminals of the electric motor for a predetermined time is provided , and the short-circuiting means applies a return force of the twist of the steering system.
A return force estimating means for estimating the return force, and the return force is equal to or more than a predetermined value.
When it is above, the terminals are short-circuited .

According to the first aspect of the present invention, the electric motor driving means drives and controls the electric motor based on the steering torque of the steering system detected by the steering torque detecting means to generate the steering assist torque in the steering system. For example, when the electric motor is stopped due to a failure of the steering torque detecting means, the terminals of the electric motor are short-circuited for a predetermined time by the short-circuiting means. by this,
The return force of the twist of the steering system due to steering acts on the electric motor,
The electric motor is in the regenerative braking state and the return force is suppressed. this
At this time, the steering system of the steering system estimated by the return force estimation means
When the return force of the twist is more than a predetermined value, the end of the motor
The child is short-circuited. Therefore, if the return force is large,
That is, the steering wheel connected to the steering system receives
The return force is suppressed only when the influence of the return force is large.

[0008]

[0009]

Further, in the electric power steering apparatus according to a second aspect of the present invention, the short-circuiting means includes a rotation-state detecting means for detecting a rotation state of the electric motor, and after the terminals of the electric motor are short-circuited, the rotation-state detecting means is provided. It is characterized in that the terminals are short-circuited until it is detected that the rotation of the electric motor has stopped.

According to the second aspect of the present invention, by short-circuiting the terminals of the electric motor, the electric motor is rotationally driven by the twisting return force of the steering system. The rotational state detecting means detects the rotational state of the electric motor. , The terminals of the electric motor are short-circuited until it is detected that the rotation of the electric motor has stopped, and the short-circuit is terminated when the return force no longer acts on the electric motor.

Further, in the electric power steering apparatus according to a third aspect of the present invention, the rotation state detecting means has a voltage detecting resistor connected in series with the electric motor, and the potential difference between both ends of the voltage detecting resistor is also provided. In addition, it is characterized in that the rotation state of the electric motor is detected.

According to the third aspect of the present invention, the voltage detecting resistor is connected in series with the electric motor, and the rotating state of the electric motor is detected based on the potential difference across the voltage detecting resistor. For example, it is determined that the rotation of the electric motor has stopped when the potential difference across the voltage detecting resistor is substantially zero.

[0014]

As described above, according to the first aspect of the present invention.
According to the electric power steering device, when the electric motor is stopped while the steering assist torque is being generated, the twisting return force of the steering system due to steering is applied to the steering wheel connected to the steering system via the steering system. It works, but when the motor is stopped, the terminals of the motor are short-circuited for a predetermined time.Therefore, the return force of the twist acts on the motor to put it in a regenerative braking state, and the return force can be suppressed. The return force acting on the steering wheel can be suppressed.

At this time, when the twisting return force of the steering system estimated by the return force estimating means is equal to or more than a predetermined value,
Since the terminals of the electric motor are short-circuited, the return force can be suppressed only when the influence of the return force on the steering wheel is large, and the return force can be suppressed only when necessary.

According to the electric power steering apparatus of the second aspect , when the terminals of the electric motor are short-circuited, the short-circuited state is maintained until it is detected that the rotation of the electric motor has stopped. While the electric motor is affected by the twisting return force of the steering system, the return force can be reliably suppressed.

Further, according to the electric power steering apparatus of the third aspect , since the voltage detecting resistor is provided in series with the electric motor, the rotation state of the electric motor can be easily detected by detecting the potential difference across the voltage detecting resistor. Can be detected.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. In the figure, 1 is a steering shaft, and this steering shaft 1 is connected through a universal joint 2 to an upper shaft 1a and a lower shaft 1b.
It consists of and. A steering wheel 3 is fixed to the upper end of the upper shaft 1a, and a pinion shaft 5 is connected to the lower end of the lower shaft 1b via a universal joint 4.
The pinion provided at the lower end of the steering gear box 6
The inner side of the rack meshes with the rack of the rack shaft 7. The steering wheel 3, the steering shaft 1, the universal joints 2, 4, the pinion shaft 5, and the rack shaft 7 constitute a steering system.

The pinion shaft 5 is connected to a rotating shaft 9a of an electric motor 9 via a reduction gear mechanism 8. The reduction gear mechanism 8 includes a drive gear 8b and a driven gear 8c that mesh with each other in a casing 8a.
c is fixed to the pinion shaft 5, and the drive gear 8b is fixed to the rotating shaft 9a. The electric motor 9
For example, the electromagnetic clutch 9b is composed of a DC servo motor.
And the rotational force of the reduction gear mechanism 8 via the rotation shaft 9a.
Is transmitted to.

Further, the steering shaft 1 is provided with a steering torque sensor 10 as a steering torque detecting means for detecting a steering torque applied to the steering wheel 3 and transmitted to the steering shaft 1. The steering torque sensor 10 is composed of, for example, a main potentiometer and a sub potentiometer (not shown) having the same operation configuration, converts the steering torque into the torsional angular displacement of the torsion bar provided on the upper shaft 1a, and the torsional angle is converted. The ball screw member converts the displacement into a linear motion, and the ball screw member moves the lever connected to the sliding contact of the potentiometer to change the resistance value output from the sliding contact. .
Then, when the driver steers the steering wheel 3, steering torque detection signals T _M and T composed of analog voltages corresponding to the magnitude and direction of the twist generated in the steering shaft 1 detected by each potentiometer.
Output _S. For example, as shown in FIG. 2, when the steering wheel 3 is in the non-steering state and in the neutral state, a predetermined neutral voltage V ₀ is applied to the steering torque detection signals T _M , T.
_{When the} steering wheel 3 is turned to the right, the neutral voltage V _{0 is} output according to the steering torque at that time.
When the voltage that increases more is turned to the left, a voltage that decreases from the neutral voltage V ₀ is output according to the steering torque at that time.

Reference numeral 11 denotes a vehicle speed detection sensor for detecting a vehicle speed, which detects the number of rotations of the output shaft of the transmission and outputs a vehicle speed detection signal V consisting of a pulse signal having a cycle corresponding to this.

Reference numeral 12 denotes a control device as an electric motor driving means for controlling the driving of the electric motor 9, which is a power source 1 such as a battery.
Connected to 3. As shown in FIG. 3, the control device 12 includes steering torque detection signals T _M and T _S from the steering torque sensor 10, a vehicle speed detection signal V from the vehicle speed sensor 11, and a voltage detection circuit 14 described later. Voltage detection signals v _{1 to} v ₄ are supplied. Then, the control device 12
Based on these input signals, a motor control signal Z _M that specifies the rotation direction of the electric motor 9 and its drive amount, an abnormal stop control signal Z _E that controls the electric motor 9 when an abnormality occurs, and a clutch control signal Z that controls the electromagnetic clutch 9b. _C and power 13
Control signal Z for controlling the supply or cutoff of the power supply from
_The control circuit 20 for outputting _R and the motor control signal Z _M
And the abnormal stop control signal Z _E are supplied, and the motor drive circuit 30 that drives and controls the electric motor 9 based on them and the power supply control signal Z _R are supplied. Based on this, the power supply from the power supply 13 to the motor drive circuit 30 is supplied. And a cut-off circuit 61 for controlling the supply or cut-off.

The control circuit 20 includes an A / D converter 2
1 _M , 21 _S , 22 and 23, and a microcomputer 24. This microcomputer 24
Is an input interface circuit 24a and an output interface circuit 24b, an arithmetic processing unit 24c, and a storage unit 2.
4d and at least the input interface circuit 24
The steering torque detection signals T _M and T _{S of the} steering torque sensor 10 are supplied to a via the A / D converters 21 _M and 21 _S , respectively, and the vehicle speed detection signal V of the vehicle speed sensor 11 is supplied to A / D. It is supplied via the converter 22. Further, the voltage detection signals v _{1 to} v ₄ from the voltage detection circuit 14 are converted into digital signals by the A / D converter 23 and supplied. Then, the output interface circuit 24b directly outputs a motor control signal Z _{M for} controlling the drive of the electric motor 9 formed according to the steering assist torque and an abnormal stop control signal Z _E for abnormally stopping the electric motor 9, and also the electromagnetic clutch. The clutch control signal Z _C to 9b and the power supply control signal Z _R to the cutoff circuit 61 are directly output.

Then, the arithmetic processing unit 24c controls the steering.
Steering torque detection signal T from the torque sensor 10_M, T_S
, Vehicle speed detection signal V from the vehicle speed sensor 11, and voltage detection
Voltage detection signal v from the circuit 14₁~ V_FourA /
D converter 21_M, 21_SSteering wheel via
Ku T_MAnd T_S, Vehicle speed detection value V, voltage detection value v₁~ V _Four
As the steering torque T_MIs above the preset value Tα
At some time, the vehicle speed detection value V and the steering torque T_MBased on
To generate a predetermined steering assist torque in the electric motor 9.
Target current value I₀Set the rotation direction and
Drive amount and rotation direction for controlling the drive of the electric motor 9
Control signal Z for identifying_MIs output.

Further, the arithmetic processing unit 24c is provided with the steering wheel.
Steering torque T from the torque sensor 10 _MAnd T_SBased on
Whether or not they match, or if they are detected
The value indicates that the steering torque sensor 10 is broken or short-circuited.
The steering torque is
The abnormality of the sensor 10 is detected. And drive the electric motor 9
During dynamic control, that is, assisting the steering system
When an abnormality of the steering torque sensor 10 is detected,
Short-circuits the terminals of the motor 9 and detects the voltage.
Voltage detection value v from path 14₁~ V_FourBased on
It detects whether the motor 9 is rotating and the motor 9 stops rotating.
Then, the short circuit of the electric motor 9 is stopped. Also, the electromagnetic class
Of the electric motor 9 and the reduction gear mechanism 8 by operating the switch 9b.
The electric motor to the reduction gear mechanism 8 with the mechanical connection cut off.
The transmission of the rotational force of 9 is stopped.

Further, in the arithmetic processing unit 24c, when the steering torque T _M is less than the predetermined set value Tα, the electric motor 9
The electric motor 9 is not driven, as it is not necessary to generate the steering assist torque.

The storage device 24d stores processing programs and the like necessary for the arithmetic processing in the arithmetic processing device 24c, and also sequentially stores the arithmetic results and the like of the arithmetic processing device 24c.

On the other hand, as shown in FIG. 4, the motor drive circuit 30 includes a gate drive circuit 31 to which a motor control signal Z _M and an abnormal stop control signal Z _E output from the control circuit 20 are supplied, and a bridge circuit. 36 and.

The bridge circuit 36 is, for example, an N-chamber.
Transistors such as field-junction FETs (field effect transistors)
Two transistors with each transistor connected in series
Tr ₁And Tr₂, Tr₃And Tr_FourAre connected in parallel
Is formed. And the transistor Tr₁And T
r₃Is connected to the power source 13 via the cutoff circuit 61.
And Tr₂And Tr_FourWhen the connection point of is grounded
, Tr₁And Tr₂Connection point with and Tr₃And Tr_FourWith
The electric motor 9 is connected between the connection points. In addition, fly
Wheel diode D₁~ D_FourAnd connected in series with this
Voltage detection resistor R₁~ R_FourAnd each transistor T
r₁~ Tr_FourAnd are connected in parallel.

The cutoff circuit 61 is composed of, for example, a relay switch having a normally open contact and controls ON / OFF of the power supply of the power supply 13 to the bridge circuit 36, and is based on abnormality monitoring by the control circuit 20. Power control signal Z
_The power is supplied to the bridge circuit 36 when an abnormality occurs.

The gate drive circuit 31 is, for example,
For example, a pulse width modulation circuit, a logic circuit, etc.
Motor control signal Z from computer 24_MSpecified by
Bridge rotation based on the rotation direction and drive amount of the electric motor 9
Each transistor Tr on path 36 ₁~ Tr_FourSupply voltage to
Control of the drive current to the electric motor 9 by
If, for example, the current direction is specified as right,
To the transistor Tr₂And Tr₃To the gate terminal of
The power supply of the power supply 13 is cut off by supplying pressure.
It is supplied to the bridge circuit 36 via the circuit 61 and
Dista Tr₃, Electric motor 9, transistor Tr₂In the direction of
An electric current flows and the electric motor 9 rotates forward, that is, rotates to the right.
It

On the contrary, when the current direction is designated as left
To the transistor Tr₁And Tr _FourTo the gate terminal of
By supplying pressure, the power supply from the power supply 13
The transistor Tr is supplied to the bridge circuit 36.₁， Den
Motivation 9, Transistor Tr_FourCurrent flows in the direction of
The motive 9 rotates in the reverse direction, that is, rotates counterclockwise. And this
At this time, according to the drive amount specified by the gate drive circuit 31,
For example, a PWM (Pulse Width Modulation) signal
And the transistor Tr based on this PWM signal₁or
Is Tr₃By supplying voltage to the gate terminal of
Control the amount of current flowing through the electric motor 9, and
Control signal Z_MIt is the drive amount specified in the direction specified by
It is designed to drive.

Then, the voltage detection circuit 14 performs processing such as amplification and noise removal of the voltage generated at both ends of the voltage detection resistors R _{1 to} R ₄ , and the voltage detection signal v
_It is output to the control circuit 20 as _{1 to} v ₄ .

Next, the operation of the above embodiment will be described with reference to the flowchart of FIG. 5 showing the processing procedure of the steering assist force control processing in the arithmetic processing unit 24c. The process shown in FIG. 5 is executed as a timer interrupt process for each predetermined time (for example, 50 msec) for a predetermined main program (not shown).

In the arithmetic processing unit 24c, first, the steering torques T _M and T _S from the steering torque sensor 10 are read (step S1), and based on this, the steering torques T _M and T _S have substantially the same value. there, or if it is greater than the value which can be taken the steering torque T _M and T _S during normal, or by less whether such, the steering torque T _M and T _S is the disconnection or short circuit in the steering torque sensor 10 The steering torque T may be a value that is considered to be occurring.
An abnormality monitoring process of the steering torque sensor 10 is performed based on _M and T _S (step S2).

When it is determined that there is no abnormality in the steering torque sensor 10 as a result of the abnormality monitoring processing (step S3), the steering torque T _M which is the detection value of the main potentiometer from the steering torque sensor 10 is set. Based on this, normal steering assist force control is performed. That is, the steering torque T _M
Is determined to be equal to or greater than the predetermined value Tα, it is determined whether or not it is necessary to generate the steering assist torque by the electric motor 9 in the steering system (step S4). For example, when the driver does not perform the steering operation such as when the vehicle is traveling straight ahead, the steering torque T _M is smaller than the predetermined value Tα, so that the steering torque is not generated on the steering shaft 1 and the steering assist torque is not generated. As it is not necessary to generate the electromagnetic clutch 9b, the clutch control signal Z _C for maintaining the electromagnetic clutch 9b in the off state is output (step S5), and the electric motor 9 is not driven.

Further, when the driver steers, for example, when the vehicle makes a turn from a straight traveling state, the steering torque T _M becomes larger than a predetermined value Tα (step S4). , A clutch control signal Z _C for controlling the electromagnetic clutch 9b to an ON state in which the rotational force of the electric motor 9 can be transmitted to the reduction gear mechanism 8 (step S
6) Based on the vehicle speed detection value V from the vehicle speed sensor 11 and the steering torque T _M , for example, the correspondence between the vehicle speed, the steering torque, and the target current value, which are set in advance and stored in a predetermined storage area, is shown. A target current value I ₀ for generating a steering assist torque in the electric motor 9 according to the steering torque T _M and the vehicle speed detection value V is set based on the control map or the like, and stored in a predetermined storage area ( Step S7).

Then, based on the steering torque T _M , the electric motor 9
Of the target current value I ₀ is specified (step S8).
And a motor control signal Z _M designating the rotation direction to the gate drive circuit 31 (step S9).

For example, when the steering wheel 3 is steered to the right, the steering torque T _M has a voltage value larger than the neutral voltage V ₀ because the steering torque is steered to the right. Based on this, the control circuit 20 recognizes that the vehicle has been steered to the right, sets the target current value I ₀ based on the vehicle speed detection value V and the steering torque T _M , for example, based on a preset control map, etc. The motor control signal Z _M for designating to drive in the direction by the drive amount of the electric motor 9 according to the target current value I ₀ is formed and output.

In response to this, in the gate drive circuit 31, the transistors Tr ₂ and Tr ₃ are turned on and the transistor T is turned on.
The r ₁ and Tr ₄ are controlled to the off state, whereby the power supply from the power source 13 flows in the direction of the transistor Tr ₃ , the electric motor 9 and the transistor Tr ₄ to rotate the electric motor 9 to the right and the rotational force of the electric motor 9 is increased. By being transmitted to the steering system via the reduction gear mechanism 8, the driver can easily operate the steering wheel 3 to the right.

On the contrary, when the driver steers to the left, the steering torque T _M has a voltage value smaller than the neutral voltage V _0. Therefore, the control circuit 20 recognizes that the steering wheel has been steered to the left and rotates. The direction is left and the motor control signal Z _M is output. As a result, the transistors Tr ₂ and Tr ₃ are controlled to be in the off state, the transistors Tr ₁ and Tr ₄ are controlled to be in the on state, and the voltage supplied from the power source 13 is set to the transistor T.
Since the electric current flows in the direction of r ₁ , the electric motor 9, and the transistor Tr ₄ , the electric motor 9 rotates counterclockwise, and the driver can easily operate the steering wheel 3 to the left.

Then, in the abnormality monitoring process (step S2), while the abnormality of the steering torque sensor 10 is not detected, the above process is repeated to generate the steering assist torque according to the steering torque T _M and the vehicle speed detection value V. This facilitates the driver's steering operation.

From this state, for example, when an abnormality such as a short circuit occurs in the steering torque sensor 10, the value of either the steering torque T _M or T _S is a value other than the originally possible value, for example, the value. Since the values are close to zero and the two do not match, the arithmetic processing unit 24c recognizes that the steering torque sensor 10 has an abnormality (steps S1 to S1).
S3). Therefore, the drive control of the electric motor 9 based on the steering torque T _M is not performed, and the abnormal stop process shown in FIG. 6 (step S
Execute 10).

In this abnormal stop processing, for example, based on the target current value I ₀ held when the steering assist force control processing was executed last time, it is determined whether or not the electric motor 9 is currently assisting the steering system. It is determined (step S11), and if the previous target current value I ₀ is substantially zero, it is determined that the assist is not being performed, and the process directly proceeds to step S19 described later. Then, when the previous target current value I ₀ is not substantially zero, it is determined that the vehicle is assisting, and whether the vehicle speed detection value V is V ≧ Vα, that is, the vehicle is traveling. It is determined whether there is any (step S12).

When the vehicle is not traveling (step S12), the steering wheel 3 is operated in the stopped state, that is, the steering wheel is in the stationary state.
When the electric motor 9 is stopped in this state, it is determined that the steering wheel 3 may be affected by the returning force due to elastic deformation of the steering system.

If the vehicle is traveling, it is then determined whether or not the previous target current value I ₀ is equal to or greater than the predetermined set value Iα (step S13). The predetermined set value Iα is, for example, 30 when the maximum current value that can be set as the target current value I ₀ is the maximum target current value I _0MAX.
A value of about% is set. This is the maximum target current value I _0M
If the value is about 30% or less of _AX , the motor 9
It is a value that is set assuming that the steering wheel 3 is not affected by the twisting return force even when is stopped.

Therefore, it is determined whether or not the previous target current value I ₀ is 30% or more of the maximum target current value I _0MAX , that is, whether or not the steering assist torque by the electric motor 9 is large.
The previous target current value I ₀ is 30% of the maximum target current value I _0MAX
In the above case, when the electric motor 9 is stopped in this state, it is determined that the steering wheel 3 is affected by the return force of the elastic deformation of the steering system.

When the electric motor 9 is stopped, steering is performed.
The influence of the return force of the elastic deformation of the system on the steering wheel
If it is determined that the mobile phone 3 will receive (step S12,
Step S13), a finger for short-circuiting the terminals of the electric motor 9
Abnormal stop control signal Z _EIs transmitted (step S
14). For example, the transistor Tr₁And Tr₃Turn on
State, Tr₂And Tr_FourOff (or transistor
Ta Tr₂And Tr_FourIs on. Transistor Tr₁Over
And Tr₃To turn off).

Then, only the transistor Tr ₁ or Tr ₃ is turned on (or the transistor Tr ₂ or Tr ₄ ).
The abnormal stop control signal Z _E for instructing the release of the short circuit is transmitted (step S15). Then, the voltage detection values v _{1 to} v ₄ from the voltage detection circuit 14 are read (step S1
6) It is determined whether or not the rotation of the electric motor 9 is stopped by determining whether or not the potential difference across the voltage detection resistors R _{1 to} R ₄ is less than or equal to a predetermined value (step S1).
7).

When the rotation of the electric motor 9 is stopped, the abnormal stop control signal Z _E for turning off each of the transistors Tr _{1 to} Tr ₄ is output and the electromagnetic clutch 9 is output.
The control signal Z _C for turning off b is output (step S
18) Then, for example, the driver is notified of the abnormality of the steering torque sensor 10 and the power supply control signal Z _R for shutting off the power supply to the bridge circuit 36 is output to the shutoff circuit 61. A predetermined process at the time of abnormality such as not executing is executed (step S19), and the process ends.

Then, when it is not considered that the electric motor 9 is stopped, the short circuit instruction is given again (step S1).
4), then instructs the short releasing (step S15), and based on the voltage detection value v ₁ to v ₄ at this time, to determine whether the electric motor 9 is stopped (step S16, S17),
This operation is repeated until it is considered that the electric motor 9 has stopped.

Here, the processing of steps S12 and S13 corresponds to the returning force estimating means, the processing of step S14 corresponds to the short-circuiting means, and the processing of step S17 corresponds to the rotational state detecting means.

Therefore, for example, stationary
When an abnormality occurs in the steering torque sensor 10 while
In the arithmetic processing unit 24c, the steering torque sensor 10
Steering torque T from_M, T_SBased on steering torque sensor
When 10 abnormalities are detected, the vehicle is stopped and assisted.
The short-circuit instruction
I do. In response to this, the gate drive circuit 31
Register Tr₁~ Tr _FourFor example, a transistor
Tr₁And Tr₃ON state, transistor Tr₂as well as
Tr_FourControl to the off state. This makes the bridge
In the circuit 36, the transistor Tr₁, Electric motor 9, transition
Star Tr₃To form a closed circuit. At this time,
Since the current supply to the motive 9 is cut off, the elastic change of the steering system
Depending on the shape, the return that tries to rotate the electric motor 9 in the opposite direction
The force works, which causes the electric motor 9 to operate as a generator.
Then, the regenerative braking state is set. Therefore, the elastic deformation of the steering system
Since the return force due to
Return force due to elastic deformation of the steering system transmitted to the wheel 3
Is suppressed, and sudden reverse rotation with respect to the steering wheel 3
No force acts in the direction.

Then, the potential difference between both ends of the voltage detecting resistors R _{1 to} R ₄ when the transistor Tr ₁ is turned off in the state where the terminals of the electric motor 9 are short-circuited is detected, and the electric motor 9 is rotated based on the detected potential difference. To determine if has stopped. Then, when each potential difference becomes zero, it is assumed that the rotation of the electric motor 9 due to the return force of the elastic deformation of the steering system is stopped, and all the transistors Tr _{1 to} Tr ₄ are controlled to the off state,
The electromagnetic clutch 9b is controlled to the off state to stop the assist by the electric motor 9.

Similarly, the vehicle shifts to gentle turning.
When an abnormality is detected in the steering torque sensor 10 when
If the steering wheel 3 is gently steered,
If the steering assist torque by the electric motor 9 is small,
Flow value I₀Is the maximum target current value I _0MAXIf less than 30% of
Is the steering system, even if the electric motor 9 is stopped in this state.
It was judged that the effect of the elastic deformation return force was small, and
All transistors Tr ₁~ Tr_FourControl to the off state,
The electromagnetic clutch 9b is controlled to the off state. By this
The current supply to the electric motor 9 is cut off,
Since the return force due to sexual deformation is small, the steering wheel
The rule 3 is not suddenly rotated in the opposite direction.

Further, when an abnormality of the steering torque sensor 10 is detected, for example, when the vehicle suddenly shifts to a turning drive, the steering wheel 3 is steered greatly, so that the torque generated in the steering system is The steering assist torque by the electric motor 9 is large. Therefore, the target current value I
_{Since 0} becomes larger than the maximum target current value I _0MAX , it is judged that the return force of the elastic deformation of the steering system has a large effect, and the electric motor 9 is short-circuited to return the elastic deformation of the steering system as described above. The force causes the electric motor 9 to operate as a generator to bring the electric motor 9 into a regenerative braking state. by this,
The return force of elastic deformation is suppressed, and the steering wheel 3
It is possible to avoid sudden rotation in the opposite direction.

FIG. 7 shows a change in the angle of the steering wheel 3 when the electric motor 9 is stopped during assist, and FIG. 7 (a) shows a conventional case in which the terminals of the electric motor 9 are not short-circuited. The stopping method, FIG. 7B, shows an angle changing state by the stopping method of the present invention in which the terminals of the electric motor 9 are short-circuited.

As shown in FIG. 7B, from the state where the steering assist torque is being generated, the electric motor 9 is stopped at time t, and when the steering assist torque becomes zero, the terminals of the electric motor 9 are short-circuited. Since the electric motor 9 is in the regenerative braking state, a braking torque acts on the steering system. Compared with FIG.
It can be seen that the steering wheel 3 gently returns to the neutral state.

Further, in the above embodiment, the voltage detecting resistors R _{1 to} R ₄ are provided to detect the terminal voltage of the electric motor 9. Therefore, the electric voltage of the electric motor 9 can be easily detected from the terminal voltage. The rotation state can be detected, and the terminals are short-circuited until the voltage between the terminals becomes substantially zero, that is, until the rotation of the electric motor 9 is stopped. A short circuit will occur until it is no longer affected by the return force. For example, by releasing the short circuit state while the return force is being generated, it is possible to ensure that the return force is transmitted to the steering wheel 3 and suddenly rotated. Can be avoided.

Further, in the above embodiment, when the electric motor 9 is stopped, the steering system is elastically deformed based on whether the vehicle is stopped or the previous target current value I ₀ is equal to or greater than the predetermined value Iα. The magnitude of the return force is estimated, and the return force needs to be suppressed because the short circuit between the terminals of the electric motor 9 is performed only when the return force is large and the influence on the steering wheel 3 is predicted to be large. The short circuit is performed only at a certain time, the return force can be efficiently suppressed, and the processing efficiency can be improved.

In the above embodiment, the control circuit 20
Although the description has been given of the case where the above is configured by a microcomputer, the present invention is not limited to this, and it is also possible to configure by combining electronic circuits such as an adder and an integration calculator.

Further, in the above embodiment, the case where the bipolar transistor is used as the switching element of the bridge circuit has been described, but the present invention is not limited to this, and a field effect transistor or the like can be applied.

In the above embodiment, the case where the motor is driven by the bridge circuit has been described, but the present invention is not limited to this. For example, a drive circuit is formed by a bidirectional contact relay or the like, and the motor is drive-controlled by this. It is also possible to do so.

Further, in the above embodiment, the case where the voltage detecting resistor is provided in series with the flywheel diode has been described, but the present invention is not limited to this, and for example, as shown in FIG. 8, transistors Tr ₁ and Tr _{2 are provided.} A shunt resistor for voltage detection is provided between the connection point of or the connection point of the transistors Tr ₃ and Tr ₄ and the electric motor 9, and the stop of the rotation of the electric motor 9 is detected by detecting the potential difference between the both ends. It is also possible to do so.

In the above embodiment, the case where the steering torque sensor composed of the main potentiometer and the sub potentiometer is applied has been described, but the present invention is not limited to this, and the steering torque sensor composed of one potentiometer. It is also possible to apply.

Further, in the above embodiment, the case where the steering assist force control process is stopped when an abnormality occurs in the steering torque sensor has been described. However, the present invention is not limited to this. The steering assist force control process may be stopped even when the steering assist torque corresponding to the torque actually generated in the steering shaft 1 cannot be calculated.

[Brief description of drawings]

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

FIG. 2 is an output characteristic diagram of a steering torque sensor applicable to the present invention.

FIG. 3 is a block diagram showing an example of a control device according to the present invention.

4 is a block diagram showing an example of a motor drive circuit 30 of FIG.

FIG. 5 is a flowchart showing an example of a processing procedure of steering assist force control processing of the arithmetic processing unit.

FIG. 6 is a flowchart illustrating an example of a processing procedure of abnormal stop processing.

FIG. 7 is an explanatory diagram for explaining the operation of the present invention.

FIG. 8 is a block diagram showing another example of the motor drive circuit 30.

[Explanation of symbols]

3 the steering wheel 9 motor 9b electromagnetic clutch 10 a steering torque sensor 11 vehicle speed sensor 12 the controller 13 supply 14 voltage detection circuit 20 control circuit 30 motor drive circuit 31 a gate drive circuit 36 bridge circuit D ₁ to D ₄ flywheel diode Tr ₁ to Tr ₄ transistors R _{1 to} R ₄ Voltage detection resistor

Claims (3)

(57) [Claims] 1. A motor connected to a steering system of a vehicle to generate steering assist torque, steering torque detecting means for detecting steering torque of the steering system, and steering torque detected by the steering torque detecting means. the electric power steering system and a motor driving means for driving the electric motor, wherein when stopping the motor steering assist torque during development, with a short-circuiting means for short-circuiting between the terminals of the electric motor a predetermined time, the The short-circuit means estimates the twisting return force of the steering system.
A return force estimating means, and the return force is equal to or more than a predetermined value.
The electric power steering device is characterized in that the terminals are short-circuited when the electric power steering device is turned on. 2. The short-circuit means includes a rotation state detection means for detecting a rotation state of the electric motor, and after the terminals of the electric motor are short-circuited, the rotation state detection means detects that the rotation of the electric motor has stopped. until claim 1 Symbol mounting of the electric power steering apparatus is characterized in that so as to short-circuit between the terminals. 3. The rotating state detecting means has a voltage detecting resistor connected in series with the electric motor, and detects the rotating state of the electric motor based on a potential difference between both ends of the voltage detecting resistor. The electric power steering apparatus according to claim 2 , characterized in that.