JP3572801B2 - Electric power steering device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering apparatus that assists a steering force with an output of an electric motor.
[0002]
[Prior art]
Generally, in an electric power steering device, a torque sensor that detects a steering torque is attached to an input shaft to which a steering wheel is fixed, and a motor is driven in accordance with a torque detection value of the torque sensor to reduce a steering force. A corresponding steering assist torque is generated to assist the steering force.
[0003]
In such an electric power steering device, the control device controls the steering assist torque generated by the electric motor based on various detection signals such as a torque detection value of a torque sensor. Therefore, when an abnormality occurs in various sensors such as a torque sensor or the control device itself, accurate control of the electric motor cannot be performed. Is detected, the device is stopped.
[0004]
[Problems to be solved by the invention]
In the above-described conventional electric power steering device, when any abnormality occurs in the device such as various sensors or a control device, the current supply to the electric motor is immediately stopped. Therefore, for example, when an abnormality occurs in the control device or various sensors in a state where the steering wheel is being steered to the vicinity of the stationary lock with the assist by the steering assist torque in the electric power steering device, the electric motor is not controlled. The current supply is stopped to stop the assist by the steering assist torque.However, at this time, the steering assist torque by the electric motor suddenly disappears. Therefore, there is a problem that a force is applied to return the steering wheel to the neutral position, the steering wheel attempts to return to the neutral position, and a burden is imposed on the driver.
[0005]
In view of the above, the present invention has been made in view of the above-mentioned conventional unsolved problem, and has been made to reduce the force for returning the steering wheel to a neutral state, which is generated when the electric motor is stopped during assist by the electric power steering. It is an object of the present invention to provide an electric power steering device capable of suppressing the electric power steering.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an electric power steering apparatus according to claim 1 of the present invention includes an electric motor that is connected to a steering system of a vehicle and generates a steering assist torque, and a steering torque detection that detects a steering torque of the steering system. And an electric motor driving means for driving the electric motor in accordance with the steering torque detected by the steering torque detecting means, wherein the electric motor and the electric motor drive control means are cut off. Means, a first short-circuit means for short-circuiting the terminals of the electric motor for a predetermined time together with the operation of the cut-off means, and an electromotive force generated when the electric motor is brought into a regenerative braking state by the short-circuit in the first short-circuit means. And a second short-circuit means for short-circuiting the terminals of the electric motor for a predetermined time.
[0007]
According to the first aspect of the present invention, the electric motor is driven by the electric motor driving means in accordance with the steering torque of the steering system of the vehicle, and the electric motor generates a steering assist torque for the steering system, thereby facilitating the steering operation of the driver. Done in When the motor is stopped, for example, when an abnormality occurs in the motor driving means, the breaking means controls the motor and the motor driving means to be in a cutoff state, and the first short-circuit means causes the terminal of the motor to be stopped. Short circuit. At this time, if the torsional return force due to the elastic deformation of the steering system or the like is large, the electric motor is in a regenerative braking state and an electromotive force is generated, whereby the second short-circuit means is operated, and for example, the torsional return force If the short circuit is performed until it can be considered that the influence of the steering wheel can no longer be received, the return force of the torsion is reliably suppressed by the regenerative braking of the electric motor.
[0008]
Conversely, when the return force of the torsion is small, the electromotive force generated by the motor is small, so that the second short-circuit means does not operate, and the short-circuit of the motor occurs when the short-circuit of the first short-circuit means is released. Be released. Accordingly, if the terminals of the electric motor 9 are short-circuited by the first short-circuit means for a time sufficient for the second short-circuit means to operate, the return force of the torsion is small and the second short-circuit means operates. When it is determined that the motor is not to be operated, the short circuit of the motor is released, and the motor is prevented from becoming a load due to steering in the short circuit state.
[0009]
According to the electric power steering apparatus of the second aspect, the second short-circuit means is constituted by a self-holding relay, and a coil portion thereof is inserted between the first short-circuit means and the electric motor. The second short-circuit means operates according to the electromotive force that excites the coil when the first short-circuit means is in an operating state.
[0010]
According to the second aspect of the present invention, when the first short-circuit means is operated to short-circuit the terminals of the motor, the coil portion forming the second short-circuit means is brought into a regenerative braking state of the motor. Excited. At this time, when the electromotive force generated by the motor is large, the coil section is excited to operate the second short-circuit means to short-circuit the terminals of the motor, and when the electromotive force is small, the second short-circuit is performed. Since the means does not operate, the operation of the second short-circuit means is controlled in accordance with the magnitude of the torsional return force of the steering system.
[0011]
【The invention's effect】
As described above, according to the electric power steering apparatus of the first aspect of the present invention, when stopping the motor, the terminals of the motor are short-circuited for a predetermined time by the first short-circuiting means. When the electromotive force generated in the regenerative braking state is large, that is, when the torsional return force of the steering system is large, the second short-circuiting means is operated to continuously short-circuit between the terminals of the motor. When the torsional return force of the steering system is large, the electric motor is in a regenerative braking state and the torsional return force can be suppressed. When the torsional return force is small, the short circuit of the first short-circuit means can be prevented. Since the short circuit between the terminals of the motor is released at the end of the operation, it is possible to prevent the motor from operating as a load by operating the motor with the motor shorted at an earlier stage. , It can be easily performed steering operation.
[0012]
Further, according to the electric power steering apparatus of the second aspect, when the first short-circuit means is operated to short-circuit the terminals of the electric motor, the coil portion forming the second short-circuit means is excited. Therefore, the operation of the second short-circuit means can be easily controlled according to the magnitude of the torsional return force of the steering system.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. In the figure, reference numeral 1 denotes a steering shaft, which is composed of an upper shaft 1a and a lower shaft 1b connected via a universal joint 2. A steering wheel 3 is fixed to an upper end of the upper shaft 1a, and a pinion shaft 5 is connected to a lower end of the lower shaft 1b via a universal joint 4, and a pinion provided at a lower end of the pinion shaft 5 is provided. Are engaged with the rack of the rack shaft 7 inside the steering gear box 6. 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.
[0014]
The pinion shaft 5 is connected to a rotation shaft 9 a of a motor 9 via a reduction gear mechanism 8. The reduction gear mechanism 8 includes a driving gear 8b and a driven gear 8c that mesh with each other in a casing 8a. The driven gear 8c is fixed to the pinion shaft 5, and the driving gear 8b is fixed to the rotating shaft 9a. I have. The motor 9 is composed of, for example, a DC servomotor, and its rotational force is transmitted to the reduction gear mechanism 8 via an electromagnetic clutch 9b and a rotating shaft 9a.
[0015]
Further, the steering shaft 1 is provided with a steering torque sensor 10 as 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 includes, for example, a main potentiometer and a sub potentiometer (not shown) having the same operation configuration, and converts the steering torque into a torsional angular displacement of a torsion bar provided on the upper shaft 1a. The displacement is converted into linear motion by a ball screw member, the lever connected to the sliding contact of the potentiometer is moved by the ball screw member, and the resistance value output from the sliding contact is varied. . When the driver steers the steering wheel 3, a steering torque detection signal T composed of an analog voltage corresponding to the magnitude and direction of the twist generated in the steering shaft 1 detected by each potentiometer. _M , T _S For example, when the steering wheel 3 is in a non-steering state and in a neutral state, a predetermined neutral voltage is applied to the steering torque detection signal T. _M , T _S When the steering wheel 3 is turned to the right, a voltage that increases from the neutral voltage according to the steering torque at that time is output, and when the steering wheel 3 is turned to the left, a voltage that decreases from the neutral voltage is output according to the steering torque at that time. It has become.
[0016]
Reference numeral 11 denotes a vehicle speed detection sensor for detecting a vehicle speed, for example, detecting a rotation speed of an output shaft of a transmission and outputting a vehicle speed detection signal V including a pulse signal having a cycle corresponding to the rotation speed.
[0017]
Reference numeral 12 denotes a control device serving as a motor driving unit for controlling the driving of the motor 9 and is connected to a power supply 13 such as a battery. As shown in FIG. 2, the control device 12 includes a steering torque detection signal T from the steering torque sensor 10. _M , T _S And a vehicle speed detection signal V from the vehicle speed sensor 11 are supplied. Then, the control device 12 generates a motor control signal Z for designating the rotation direction and the driving amount of the motor 9 based on these input signals. _M , A clutch control signal Z for controlling the electromagnetic clutch 9b _C And a power control signal Z for controlling the supply or cutoff of the power supply from the power supply 13 _R And a control circuit 20 for outputting the motor control signal Z. _M And a motor drive circuit 30 for driving and controlling the motor 9 based on the power supply control signal Z. _R Is supplied, and a shutoff circuit 61 that supplies or shuts off a power supply from the power supply 13 to the motor drive circuit 30 based on the power supply 13; _E And a failure monitoring circuit 65 that stops the motor 9 by performing a predetermined process when the input is input.
[0018]
The control circuit 20 includes an A / D converter 21 _M , 21 _S , 22 and a microcomputer 24.
The microcomputer 24 has at least an input interface circuit 24a and an output interface circuit 24b, an arithmetic processing unit 24c, and a storage device 24d. The input interface circuit 24a has a steering torque detection signal T _M , T _S Are the A / D converters 21 respectively. _M , 21 _S , And a vehicle speed detection signal V of the vehicle speed sensor 11 is supplied via an A / D converter 22. Further, a motor control signal Z for driving and controlling the motor 9 is formed from the output interface circuit 24b in accordance with the steering assist torque. _M Is output directly, and the clutch control signal Z to the electromagnetic clutch 9b is output. _C And a power control signal Z to the shutoff circuit 61 _R Is output directly.
[0019]
The arithmetic processing unit 24c outputs a steering torque detection signal T from the steering torque sensor 10. _M , T _S And a vehicle speed detection signal V from the vehicle speed sensor 11 _M , 21 _S And the steering torque T via _M And T _S , The vehicle speed detection value V, and the steering torque T _M Is greater than or equal to a predetermined set value Tα, the vehicle speed detection value V and the steering torque T _M , A target current value I for causing the motor 9 to generate a predetermined steering assist torque. ₀ And a rotation direction, and a motor control signal Z for specifying a drive amount and a rotation direction for controlling the drive of the motor 9 based on these. _M Is output.
[0020]
Further, the arithmetic processing unit 24c is, for example, a steering torque T from the steering torque sensor 10. _M And T _S The abnormality detection of various sensors such as the steering torque sensor 10 is performed based on whether or not these two values match, or whether the detected value is not a value indicating that the steering torque sensor 10 is disconnected or short-circuited. When an abnormality is detected, a predetermined process at the time of abnormality is executed.
[0021]
In the arithmetic processing unit 24c, the steering torque T _M Is smaller than the predetermined set value Tα, it is not necessary to generate the steering assist torque by the motor 9, and the motor 9 is not driven.
[0022]
Further, the arithmetic processing unit 24c has a watchdog timer, performs a predetermined abnormality handling process based on the watchdog pulse from the watchdog timer, and outputs the watchdog pulse to the abnormality detection signal Z. _E Is output to the failure monitoring circuit 65.
[0023]
The storage device 24d stores processing programs and the like necessary for the arithmetic processing in the arithmetic processing device 24c, and sequentially stores the calculation results of the arithmetic processing device 24c.
[0024]
On the other hand, as shown in FIG. 3, the motor drive circuit 30 outputs a motor control signal Z output from the control circuit 20. _M , And a bridge circuit 36. The bridge circuit 36 includes, for example, two transistors Tr in which transistors such as N-channel junction FETs (field effect transistors) are connected in series, respectively. ₁ And Tr ₂ , Tr ₃ And Tr ₄ Are connected in parallel. And the transistor Tr ₁ And Tr ₃ Is connected to the power supply 13 via the cutoff circuit 61, and Tr ₂ And Tr ₄ Is grounded, and Tr ₁ And Tr ₂ Connection point and Tr ₃ And Tr ₄ The motor 9 is connected via a failure monitoring circuit 65 that cuts off between the motor 9 and the bridge circuit 36.
[0025]
The shutoff circuit 61 is configured by, 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. A power supply control signal based on abnormality monitoring by the control circuit 20. Z _R The power supply to the bridge circuit 36 is cut off when an abnormality occurs.
[0026]
The gate drive circuit 31 includes, for example, a pulse width modulation circuit, a logic circuit, and the like. _M Each transistor Tr of the bridge circuit 36 is based on the rotation direction and the driving amount of the motor 9 specified by ₁ ~ Tr ₄ Is supplied to the motor 9 to control the supply of the drive current to the motor 9. If the failure monitoring circuit 65 is in a connected state between the motor 9 and the bridge circuit 36, for example, Is specified as the transistor Tr ₂ And Tr ₃ Of the power supply 13 is supplied to the bridge circuit 36 via the cutoff circuit 61 and the transistor Tr ₃ , Motor 9, transistor Tr ₂ , And the motor 9 rotates forward, that is, clockwise.
[0027]
Conversely, if the current direction is specified as left, the transistor Tr ₁ And Tr ₄ The power supply from the power supply 13 is supplied to the bridge circuit 36 by supplying a voltage to the gate terminal of the transistor Tr. ₁ , Motor 9, transistor Tr ₄ , And the motor 9 rotates in the reverse direction, that is, rotates to the left. At this time, the gate drive circuit 31 forms, for example, a PWM (Pulse Width Modulation) signal in accordance with the designated drive amount, and the transistor Tr is generated based on the PWM signal. ₁ Or Tr ₃ By supplying a voltage to the gate terminal of the motor 9, the amount of current flowing through the motor 9 is controlled, and the motor 9 is controlled by the motor control signal Z. _M Is driven in the direction specified by the driving amount specified.
[0028]
As shown in FIG. 3, the failure monitoring circuit 65 outputs an abnormality detection signal Z from the arithmetic processing unit 24c of the control circuit 20. _E Detector 65a for inputting a signal R, and a relay R operated and controlled by the failure detector 65a ₁ ~ R ₃ And a motor stop control circuit 65b having the following.
[0029]
And the relay R ₁ Is the coil part L ₁ Is connected to the power supply 13 and the other end is connected to the failure detector 65a. ₁ Is one terminal of the motor 9 and the transistor Tr of the bridge circuit 36, for example. ₃ And Tr ₄ Is connected between the connection points. And the coil part L ₁ Is excited, the connection between the bridge circuit 36 and one terminal of the motor 9 is established. Also, relay R ₂ Is a self-holding relay, and one of the coil portions L ₂₁ Is connected to the power supply 13, and the other end is connected to the failure detector 65a. Also, the other coil portion L ₂₂ Are interposed between terminals of the motor 9. And the contact portion S ₂ Is composed of a movable contact a and fixed contacts b and c. The movable contact a is connected to one terminal of the motor 9 and the coil portion L. ₂₂ The fixed contact b is opened, and the fixed contact c is connected to the other terminal of the motor 9 and the coil L. ₂₂ Connected between. And the coil part L ₂₂ Is excited, the movable contact a and the fixed contact c are connected, and the relay R ₂ , The terminals of the motor 9 are short-circuited, and the coil portion L ₂₁ Is excited, the movable contact a and the fixed contact c are cut off and the relay R ₂ The short circuit between the terminals of the motor 9 due to this is released. At this time, the coil portion L ₂₂ Is excited and once the movable contact a and the fixed contact c are connected, the coil portion L ₂₂ This connection state is maintained even when the excitation of the ₂₁ When the is excited, the movable contact a and the fixed contact c are cut off.
[0030]
And relay R ₃ Is the coil part L ₃ Is connected to the power supply, the other end is connected to the failure detector 65a, and its contact S ₃ Is one terminal of the motor 9 and the coil portion L ₂₂ And is interposed between them. And the coil part L ₃ Is excited, the terminals of the motor 9 are short-circuited.
[0031]
Therefore, the coil portion L ₃ Is excited, and the terminals of the motor 9 are short-circuited. When the short-circuit causes the motor 9 to be in a regenerative braking state, an electromotive force generated in the motor 9 causes the coil portion L ₂₂ Is excited, which causes the relay R ₂ The movable contact a and the fixed contact c are controlled to be connected.
[0032]
And each coil part L ₁ , L ₂₁ , L ₃ Is excited by the failure detector 65a. ₁ , L ₂₁ To make the bridge circuit 36 and the motor 9 connected to each other, ₂ Is controlled so as not to cause a short circuit between the terminals of the motor 9 by the control circuit 20. _E Is input, the coil portion L ₁ Of the bridge circuit 36 and the motor 9 to stop the excitation of ₃ Is energized for a predetermined time and relay R ₃ To short-circuit the terminals of the motor 9 for a predetermined time. Further, the abnormality detection signal Z _E After a predetermined time has passed since the ₂ Coil part L ₂₁ And the movable contact a and the fixed contact c are controlled to be cut off.
[0033]
Here, the relay R ₁ Corresponds to the shut-off means, and the relay R ₂ Corresponds to the first short-circuit means, and the relay R ₃ Corresponds to the second short-circuit means.
Next, the operation of the above embodiment will be described based on a time chart shown in FIG.
[0034]
In the failure detector 65a, when activated, the relay R ₁ Coil part L ₁ To control the bridge circuit 36 and the motor 9 to a connected state. Also, relay R ₂ Coil part L ₂₁ To extinguish the movable contact a and the fixed contact c so that the terminals of the motor 9 are not short-circuited.
[0035]
At this time, the relay R ₃ Are not excited, so that the terminals of the motor 9 are not short-circuited.
In the arithmetic processing unit 24c, the steering torque T, which is the detection value of the main potentiometer from the steering torque sensor 10, is used. _M Based on the vehicle speed detection value V from the vehicle speed sensor 11, the steering assist force control is performed. That is, the steering torque T _M Is determined to be greater than or equal to a predetermined value Tα to determine whether it is necessary to generate a steering assist torque by the motor 9 in the steering system. For example, when the vehicle is running straight, When no operation is performed, the steering torque T _M Is smaller than the predetermined value Tα, it is determined that no steering torque is generated on the steering shaft 1 and no steering assist torque needs to be generated. _C Is turned off and the motor 9 is not driven.
[0036]
When the driver performs steering, for example, when the vehicle shifts from a state in which the vehicle is traveling straight, the steering torque T _M Is larger than the predetermined value Tα, so that the clutch control signal Z for controlling the electromagnetic clutch 9b to an on state capable of transmitting the torque of the motor 9 to the reduction gear mechanism 8 is set. _C And the detected vehicle speed V from the vehicle speed sensor 11 and the steering torque T _M For example, based on a control map or the like indicating the correspondence between the vehicle speed, the steering torque, and the target current value, which is set in advance and stored in a predetermined storage area, the steering torque T _M Current value I for causing the motor 9 to generate a steering assist torque corresponding to the vehicle speed detection value V ₀ Set. And the steering torque T _M The rotation direction of the motor 9 is specified based on the target current value I ₀ Motor control signal Z for specifying the rotation direction _M To the gate drive circuit 31.
[0037]
For example, when the steering wheel 3 is steered to the right, the steering torque T _M Has turned to the neutral voltage V ₀ It becomes a voltage value larger than. Based on this, the control circuit 20 recognizes that the vehicle has been steered to the right, and detects the vehicle speed detection value V and the steering torque T. _M And the target current value I based on a preset control map or the like. ₀ And set the target current value I to the right. ₀ Motor control signal Z designating to drive by the drive amount of motor 9 according to _M Is formed and output.
[0038]
In response to this, the gate drive circuit 31 outputs the transistor Tr ₂ , Tr ₃ In the ON state, the transistor Tr ₁ And Tr ₄ Is turned off. At this time, since the failure monitoring circuit 65 controls the bridge circuit 36 and the motor 9 to be connected, the power supply from the power supply 13 is ₃ , Motor 9, transistor Tr ₄ , The motor 9 rotates clockwise, and the torque of the motor 9 is transmitted to the steering system via the reduction gear mechanism 8, so that the driver can easily operate the steering wheel 3 in the right direction. be able to.
[0039]
Conversely, when the driver steers to the left, the steering torque T _M Is the neutral voltage V ₀ The control circuit 20 recognizes that steering has been performed to the left since the voltage value is smaller than the motor control signal Z. _M Is output. Thereby, the transistor Tr ₂ , Tr ₃ Is off, the transistor Tr ₁ And Tr ₄ Is turned on, and the supply voltage from the power supply 13 ₁ , Motor 9, transistor Tr ₄ , The motor 9 rotates to the left, and the driver can easily operate the steering wheel 3 to the left.
[0040]
These processes are repeated to obtain the steering torque T. _M And a steering assist torque corresponding to the vehicle speed detection value V is generated to facilitate the driver's steering operation.
The arithmetic processing unit 24c detects abnormality of each sensor. For example, in the case of the steering torque sensor 10, the steering torque T _M , T _S Based on the steering torque T _M And T _S Are substantially equal to each other, or the steering torque T _M And T _S Depends on whether the steering torque T is larger or smaller than the value that _M And T _S Is not a value that is considered to have a disconnection or a short circuit in the steering torque sensor 10 or the like. _M , T _S The abnormality monitoring process of the steering torque sensor 10 is performed based on When it is determined that the steering torque sensor 10 is abnormal as a result of the abnormality monitoring processing, predetermined processing such as notifying the driver of an abnormality is performed.
[0041]
Then, from this state, for example, as shown in FIG. 4, when an abnormality occurs in the arithmetic processing unit 24c and the watchdog timer is activated to output a watchdog pulse, the watchdog pulse is output to the abnormality detection signal Z. _E Is input to the failure detector 65a (at time t). ₁ ).
[0042]
In response to this, the failure detector 65a receives the excitation coil L ₁ To the excitation coil L ₃ To start excitation. Thereby, the relay R ₁ Is cut off, the connection between the bridge circuit 36 and the motor 9 is cut off, and the relay R ₃ Is connected and the relay R ₃ , Coil part L ₂₂ , The motor 9 is formed, and the terminals of the motor 9 are short-circuited.
[0043]
At this time, in a state where the steering wheel 1 is largely steered, that is, when the steering assist torque by the motor 9 is large, the steering assist torque by the motor 9 suddenly disappears. Acts on the motor 9, and the motor 9 enters a regenerative braking state.
[0044]
As a result, an electromotive force is generated in the motor 9, and the motor 9, the relay R ₃ , Coil part L ₂₂ Current flows through the closed circuit consisting of At this time, when the electromotive force is large, that is, when the return force of the torsion due to the elastic deformation of the steering system is large such as when the steering is largely steered, the coil portion L ₂₂ The current flowing through is large. Therefore, the coil portion L is generated by the electromotive force of the motor 9. ₂₂ The current flowing through the contact point S ₂ Exceeds the operable current value (time t ₂ ), Contact S ₂ Is activated, the movable contact a and the fixed contact c are connected, and the motor 9, the relay R ₂ Is formed, and the terminals of the motor 9 are short-circuited.
[0045]
Then, at the failure detector 65a, the time t ₁ With coil part L ₃ When a predetermined time has elapsed since the excitation of ₃ Then, the excitation is stopped. This predetermined time is determined by the coil unit L ₃ Relay R with the excitation of ₃ Is activated and the terminals of the motor 9 are short-circuited, the electromotive force of the motor 9 is ₂ When the coil portion L is at a value at which ₂₂ Is excited by the electromotive force, and the contact portion S ₂ Is a time required to operate, for example, about 0.5 to 1 second.
[0046]
And the coil part L ₃ At the time t ₃ Is stopped at this point, the relay R ₃ Is cut off and the relay R ₃ The short circuit between the terminals of the motor 9 is released, but at time t ₂ With relay R ₂ Is activated, the relay R ₂ As a result, the terminals of the motor 9 are kept in a short-circuit state. Then, at the failure detector 65a, the time t ₁ Time t after a predetermined time has passed since ₄ And the coil part L ₂₁ Of the movable contact a for a predetermined time during which the movable contact a is operable, and the movable contact a and the fixed contact c are controlled to be in a cut-off state. ₂ The short circuit between the terminals of the motor 9 due to the above is released. Thereby, the relay R is connected between the terminals of the motor 9. ₂ And R ₃ Are not short-circuited.
[0047]
Here, the coil portion L ₂₁ Time t to excite ₄ Is determined for about 0.3 to 0.5 seconds because the time required for the steering wheel 3 to receive the torsional return force due to the elastic deformation of the steering system is about 0.3 to 0.5 seconds. Is set so that the steering wheel 3 is gradually returned to the neutral position, for example, about 1 second.
[0048]
Therefore, an abnormality occurs in the arithmetic processing unit 24c and the relay R ₁ When the current supply to the motor 9 is interrupted, the terminals of the motor 9 are short-circuited, so that the return force of torsion due to the elastic deformation of the steering system acts on the motor 9 and the motor 9 is brought into a regenerative braking state. To suppress the torsional return force. Therefore, the return force of the torsion transmitted to the steering wheel 3 can be suppressed, and the steering wheel 3 is moved to the point in time t when the terminals of the motor 9 are short-circuited. ₁ From time t ₄ , The steering state gradually shifts to the neutral state.
[0049]
On the other hand, when the steering wheel 3 is not being steered or is not largely steered at the time when an abnormality occurs in the arithmetic processing device 24c, the torsional force of the tire, the elastic deformation of the steering system, etc. Since the return force of the twist is small, the time t ₁ With relay R ₃ Is activated, and even if the terminals of the motor 9 are short-circuited, the electromotive force generated by the motor 9 is small. Therefore, the coil portion L ₂₂ Current flowing through the contact S ₂ Does not work.
[0050]
Therefore, the failure detector 65a outputs the time t ₁ With coil part L ₃ At a time t after a predetermined time has elapsed since the start of excitation ₃ With coil part L ₃ At this point, the short circuit of the motor 9 is released.
[0051]
Therefore, for example, when a steering operation is performed by shifting to a turning state immediately after an abnormality occurs in the arithmetic processing unit 24c during straight running and the current supply to the motor 9 is cut off, the torsional return force is obtained. Is small, the time t at which the torsional return force is considered to be small ₃ As a result, the short circuit between the terminals of the motor 9 is released, so that it is possible to prevent the steering of the steering wheel 3 from becoming heavy due to the motor 9 becoming a load.
[0052]
Therefore, when an abnormality occurs in the arithmetic processing unit 24c, that is, when the motor 9 cannot be driven and controlled in accordance with the steering torque of the steering system, two closed circuits are connected between the terminals of the motor 9. To form a short circuit in two stages. ₃ When the electromotive force of the motor 9 is large, that is, when the torsional return force of the steering system is large, the relay R ₂ Is operated to short-circuit until the steering wheel 3 is no longer affected by the torsional return force, so that the influence of the torsional return force of the steering system on the steering wheel 3 can be reliably reduced.
[0053]
When the return force of the steering system torsion is small, the relay R ₂ When the driver performs steering immediately after an abnormality has occurred in the arithmetic processing unit 24c, the short-circuit between the terminals of the motor 9 is prevented by the relay because the torsional return force of the motor 9 is small. R ₃ Is released at the time when is released, so that the motor 9 does not become a load and the steering operation can be easily performed.
[0054]
Further, in the above embodiment, only when the return force of the torsion is large, short-circuiting is performed until the steering wheel is no longer affected by this return force, so that short-circuiting between the terminals of the motor 9 can be effectively performed. It is possible to minimize the load on the motor 9 due to the short circuit.
[0055]
Further, in the above-described embodiment, since the stop control of the motor 9 is performed by providing a plurality of relays and controlling the operation thereof, it is possible to output an appropriate control signal when an abnormality occurs in the control circuit 20. Even if it is not possible, it is possible to avoid the influence of the return force of the torsion due to the elastic deformation of the steering system.
[0056]
In the above embodiment, the case where the control circuit 20 is configured by a microcomputer has been described. However, the present invention is not limited to this, and the control circuit 20 may be configured by combining electronic circuits such as an adder and an integration calculator.
[0057]
Further, in the above embodiment, the case where a bipolar transistor is used as the switching element of the bridge circuit has been described. However, the present invention is not limited to this, and a field effect transistor or the like can be applied. Similarly, a switching element such as a transistor can be applied instead of the relay of the failure monitoring circuit.
[0058]
In the above embodiment, the case where the motor is driven by the bridge circuit has been described. However, 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 drive of the motor is thereby controlled. It is also possible.
[0059]
Further, in the above-described embodiment, the case where the steering torque sensor including the main potentiometer and the sub potentiometer is applied is described. However, the present invention is not limited to this, and the steering torque sensor including one potentiometer is applied. It is also possible.
[0060]
Further, in the above-described embodiment, the case where the abnormality of the control circuit 24 is detected by the watchdog timer has been described. However, the present invention is not limited to this. For example, the state of power supply to the control circuit 24, the content of data communication, etc. It is also possible to detect an abnormality of the control circuit 24 based on the above. In short, it is only necessary to detect that the control circuit 24 is not outputting a normal control signal. Further, when an abnormality of various sensors such as a torque sensor is detected, an abnormality detection signal Z is output. _E Is output to the failure detector 65a, even if the motor 9 is stopped due to some abnormality, the steering wheel 3 can be stopped without being affected by the return force of the twisting of the steering system accompanying the steering. In addition, the present invention can be applied to a case where the motor 9 is stopped, for example, during steering assist by the motor 9 irrespective of the occurrence of an abnormality.
[0061]
Further, in the above embodiment, the relay R ₂ The short circuit between the terminals of the motor 9 due to the ₁ Has been described as being opened after a predetermined time has elapsed since the operation of the motor 9. However, for example, it is assumed that the electromotive force generated due to the regenerative braking of the motor 9 is detected, and that the rotation of the motor 9 due to the torsional return force is stopped. When the relay R ₂ It is also possible to open a short circuit caused by the above.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.
FIG. 2 is a block diagram illustrating an example of a control device according to the present invention.
FIG. 3 is a block diagram illustrating an example of a motor drive circuit 30 and a failure monitoring circuit 65 of FIG. 2;
FIG. 4 is a timing chart for explaining the operation of the present invention.
[Explanation of symbols]
3 Steering wheel
9 Motor
9b Electromagnetic clutch
10 Steering torque sensor
11 Vehicle speed sensor
12 Control device
13 Power supply
14 Voltage detection circuit
20 Control circuit
30 Motor drive circuit
31 Gate drive circuit
36 Bridge circuit
65 Failure monitoring circuit
65a Failure detector
65b Motor stop control circuit
Tr ₁ ~ Tr ₄ Transistor

Claims (2)

An electric motor that is connected to a steering system of a vehicle and generates steering assist torque; a steering torque detecting unit that detects a steering torque of the steering system; and an electric motor that drives the electric motor according to the steering torque detected by the steering torque detecting unit. An electric power steering apparatus comprising: a driving unit; and a first disconnecting unit that disconnects the electric motor from the electric motor driving control unit, and a first terminal that short-circuits the terminals of the electric motor for a predetermined time together with the operation of the first disconnecting unit. A short-circuiting means, and a second short-circuiting means that operates in response to an electromotive force generated when the electric motor is brought into a regenerative braking state by a short-circuit in the first short-circuiting means, and short-circuits between terminals of the electric motor for a predetermined time; An electric power steering device comprising: The second short-circuit means is constituted by a self-holding relay, and a coil portion thereof is interposed between the first short-circuit means and the electric motor, and the second short-circuit means is connected to the first short-circuit means. 2. The electric power steering apparatus according to claim 1, wherein the apparatus operates according to the electromotive force that excites the coil when the element is activated.

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