JP3096124B2 - Vehicle rear wheel steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering device provided with an electric motor for performing a phase inversion control of a steering ratio of a rear wheel at the time of turning, and more particularly to a rear wheel steering control system. It relates to improved detection. Here, the steering ratio θ
_S is the ratio of the front wheel steering angle theta _F for the steering angle theta _R of the rear wheels (=
θ _R / θ _F ).

[0002]

2. Description of the Related Art In general, a rear wheel steering device of a vehicle is designed to steer rear wheels so as to have a predetermined rear wheel steering angle corresponding to a front wheel steering angle. Conventionally, proportional control is performed according to a predetermined steering ratio set according to the vehicle speed or the like. This is a so-called vehicle speed sensitive rear wheel steering device.

In such a rear-wheel steering system, in order to secure the directional stability of the vehicle, the steering ratio is controlled so as to be positive, that is, in the same phase in a middle to high speed range of the vehicle speed. However, since this control is based on the proportional control as described above, the rear wheels are turned to the same phase at the same time as the start of steering, so that sufficient turning performance cannot be obtained. There was a point.

To solve this problem, for example, Japanese Patent Application Laid-Open No. 57-44568 and Japanese Patent Application Laid-Open No.
No. 5 proposes a phase inversion type rear wheel steering device. This means that the yaw rate of the vehicle can be detected, the rear wheels are steered to the opposite phase to the front wheels immediately after the front wheel steering is started, and then steered to the same phase according to the occurrence of the yaw rate. This is called "phase inversion control by yaw rate feedback", and it is possible to achieve both turning performance and directional stability.

[0005] As described above, in the phase inversion control based on the yaw rate feedback, it is extremely important to perform a control operation in which the steering ratio switches from the opposite phase to the same phase in a short time immediately after the start of the front wheel steering. Therefore, in a phase inversion type steering device, it is going to be proposed to employ a high-speed electric motor in order to switch the steering ratio from the opposite phase to the same phase in a short time.

[0006]

A motor for controlling the steering ratio of a rear wheel steering system has a large effect on the behavior of a vehicle, and therefore, it has been conventionally used to detect a failure state of the motor. And whether or not it failed is usually
It is detected by monitoring the output from the turning ratio sensor. The steering ratio sensor has a low response and the timing of detecting occurrence of a failure tends to be delayed, but in a conventional rear wheel steering device that does not perform phase inversion control of the steering ratio, a motor for controlling the steering ratio is used. Since the response speed itself is slow, no problem occurs.

That is, in FIG. 1, the zone I is the steering ratio θ.
Zone II is a safety area determined according to _S and vehicle speed.
Is a danger zone. With high speed of the motor to the wheel operation apparatus after phase inversion type, before the failure of the detection of the failure of the control system of the motor is made, the steering ratio theta _S would readily migrate into danger zone II. That is, when a high-speed motor is used for the phase inversion type rear wheel operating device, the failure cannot be dealt with unless the failure detection is performed at an extremely high speed. Therefore, the present invention has been made in order to improve such disadvantages of the prior art, and an object of the present invention is to provide a phase inversion type steering device in which a steering ratio is controlled by a motor. The present invention proposes a rear wheel steering device that can detect a control system failure at high speed.

[0008]

Means for Solving the Problems and

In order to achieve the above object, a rear wheel steering device according to the present invention uses a multi-phase excitation pattern for variably controlling a steering ratio of a rear wheel to a steering angle of a front wheel in at least two directions. A step motor whose rotation direction is controlled, drive control means for controlling the step motor based on predetermined input information to perform phase inversion control of the rear wheel, and phase inversion control of the rear wheel To
A first logical operation circuit for performing a logical operation for performing
Output to output the calculation result of
A first logical operation control unit having a circuit;
A monitor circuit for monitoring an output from one logical operation circuit;
An input circuit for inputting a monitor result from the monitor circuit
Perform the same logical operation as the first logical operation circuit,
The logical operation result and the monitor result input by the input circuit are
By collating, the step mode with respect to the target turning ratio is obtained.
A second logical operation circuit for determining consistency in the driving direction of the motor.
And a second logical operation control unit having
A logical operation circuit that stores the excitation pattern in the monitor circuit;
And the second logical operation circuit outputs the first logical operation circuit.
Calculates the excitation pattern by performing the same logical operation as the path
And the excitation path monitored by the monitor circuit.
The turn is compared with the excitation pattern calculated by itself.
Thus, the step mode with respect to the target turning ratio is
The consistency of the driving direction of the motor is determined. The determination of the consistency of the driving direction of the step motor with respect to the target steering ratio can be performed at a high speed in principle. Therefore, even if a high-speed step motor is used, the motor is stopped early. Fail-safe measures.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a rear wheel steering device of the present invention is applied to a so-called "four-wheel steering device" of a vehicle will be described in detail with reference to the accompanying drawings. The rear wheel steering device of this embodiment has the following features. : As a mechanical mechanism, -1: in order to change the steering ratio theta _S in accordance with the vehicle speed,
A high-speed stepping motor is used for the variable steering ratio mechanism. -2: A hydraulic power cylinder for steering the rear wheel has a spring for forcibly returning the rear wheel to the neutral position at the time of a failure. -3: A hydraulic release circuit is provided so that the rear wheel can be easily returned to the neutral position during a failure. -4: an orifice for reducing the release amount of oil in the release circuit per unit time so that the rear wheel is not returned to the neutral position in a short time when a failure occurs. : Two motors are used for the control of the motor, and the functions of the motors are divided such that the CPU on the master side actually controls the motors and the CPU on the slave side detects a failure. This is to reduce the burden imposed on the slave CPU and reduce the cost of the slave CPU. : The slave-side CPU detects a failure in the steering-ratio control system at a high speed. -1: The target steering ratio (TG) performed by the master CPU
The same calculation as θ _S ) is performed, and the calculation result is compared with the calculation result on the master side. If there is a mismatch, the drive current to the motor is stopped. -2: The target rotation direction from the current steering angle to the target steering angle is compared with the actual motor rotation direction obtained from the phase between the phases of the exciting current supplied to the motor. Stop the drive current to the motor. The phase between the phases of the excitation current monitors the actual current flowing through each excitation coil of the motor. : If a failure is detected, the motor is forcibly stopped and the hydraulic pressure supplied to the power cylinder is released. The instability of the body behavior, which may be caused by the delay of the rear wheel returning to the neutral position due to the orifice in the release circuit, is due to the simultaneous execution of the forced stop of the motor and the release of the hydraulic pressure. Will be resolved.

<Mechanical Configuration of Four-Wheel Steering Apparatus> FIG. 2 shows a configuration of a four-wheel steering system according to an embodiment. As shown,
The rear wheel steering device 10 is mechanically connected via a transmission shaft 52 to a front wheel steering mechanism 14 that steers the front wheel 12, and interlocks with the front wheel steering by the front wheel steering mechanism 14 to operate the rear wheel 1.
6 and wheel steering mechanism 18 after the turning to be the target steering angle TGshita _R of a predetermined rear wheel in accordance with the front wheel steering angle theta _F inputted from the front wheel steering mechanism 14, in the rear wheel steering mechanism 18 and provided, steering-angle-ratio adjusting mechanism 20 for setting and changing the steering angle ratio theta _S, expressed as a ratio of rear wheel steering angle theta _R for the front wheel steering angle theta _F, controls the steering-angle-ratio adjusting mechanism 20 And a control unit 22. The control unit 22 includes a vehicle speed V from the vehicle speed sensor 24 and a front wheel steering angle sensor 26.
(Provided on the steering shaft), the front wheel steering angle θ _F , the steering ratio θ _S from the steering ratio sensor 28, and the yaw rate か ら from the yaw rate sensor 25 are input.

As described later, in the present steering system, the rear wheels are steered by hydraulic force. The source of the hydraulic pressure is the pump 29 in FIG. The pump 29 sends the oil retained in the oil tank 19 to the hydraulic release circuit 31 via the pipe 90. The release circuit 31 is a circuit for releasing the hydraulic pressure in the steering device 18 so that the rear wheel is forcibly brought to the neutral position when a failure occurs. Also, 91
Is a return pipe from the steering mechanism 18.

The control of the turning ratio variable mechanism 20 by the control unit 22 is performed in the middle vehicle speed or high vehicle speed range.
When the front wheel 12 is steered from a steering angle of zero, the steering ratio θ _S is negative immediately after the start of the front wheel steering, and thereafter, the steering ratio θ _S
The phase inversion control is performed so as to make positive. FIG. 3 is a perspective view showing the rear wheel steering mechanism 18.
FIG. 4 shows the turning ratio variable mechanism 20 in the rear wheel turning mechanism 18 in detail in the direction V-V in FIG.

As shown in FIG. 3, the rear wheel steering mechanism 18 includes:
The variable steering ratio mechanism 20, hydraulic switching valve 32, rear wheel steering rod 34, displacement transmission mechanism 36, and hydraulic power cylinder 38 are provided. The turning ratio variable mechanism 20 includes an output rod 40, a bevel gear 42, a swing shaft member 44,
A pendulum arm 46 and a connecting rod 48 are provided, and these members are accommodated in a case 50 as shown in FIG.

The output rod 40 is supported slidably casing 50 in the axial L ₃ directions, by stroke displacement to the axis L ₃ direction, the rear wheel steering rod 34 through the displacement transmitting mechanism 36 that It is displaced in the axial direction (vehicle width direction), whereby the rear wheels connected to both ends of the rear wheel steering rod 34 are steered. Bevel gear 42 is rotatably supported by the case 50 around the axis L ₃ and the coaxial axes L ₁ of the output rod 40. Then, the pinion 52a of the rear end of the transfer shaft 52 to the bevel gear 42 meshing is adapted to rotate about the axis L ₁ along with the rotation by the steering of the steering wheel 30. In other words, the front wheel steering angle θ _F is changed from the front wheel steering mechanism 14 via the transmission shaft 52 to the rear wheel steering mechanism 1.
8 will be input.

The oscillating shaft member 44 has an axis L ₂ that can take a position (position shown) coaxial with the axis L ₃ of the output rod 40, and is fixed to the oscillating gear 54. The oscillating gear 54 meshes with a worm 58 that is rotated by the drive of a servomotor 56 controlled by the control unit 22, and rotates around an axis perpendicular to the paper plane that intersects with the axis L ₂ , thereby oscillating. The shaft member 44 is also rotated at the same time. That is, as will be apparent from the detailed description later, the servo motor 56 can variably set the steering ratio depending on the rotational angle position. Pendulum arm 46
Is connected to the swing shaft member 44 so as to swing around the axis L ₂ of the swing shaft member 44, and the axis L ₄ of the pendulum arm 46 swings with the rotation axis of the swing shaft member 44. so as to pass through the intersection of the axis L ₂ of the shaft member 44, pivot shaft member 44
The connection position to is determined.

The connecting rod 48 has an axis L ₅ balanced with the axis L _{3 of the} output rod 40, and is connected to the output rod 40, the bevel gear 42 and the pendulum arm 46. The connection to the output rod 40
Be done by the end screwed to one end of the connecting rod 48 fixed to the lever 40a, the connection to the bevel gear 42 is formed on the bevel gear 42 at a point from the axis L ₁ of the bevel gear 42 of the distance γ The other end of the connecting rod 48 is inserted through the insertion hole 42a, and the connection to the pendulum arm 46 is performed by a ball joint member 60 provided at the end of the connecting rod 48 so as to be rotatable in all directions.
The pendulum arm 46 is inserted through the insertion hole 60a. Therefore, the connecting rod 48 is fixed with respect to the output rod 40 but the bevel gear 42
For slidable in the axial L ₅ direction (i.e. the axis L ₃ direction), slidable (the direction perpendicular to the axis L ₃ in the state shown) the axis L ₄ direction relative to the pendulum arm 46 It is. Incidentally, the axis L ₄ of the pendulum arm 46, the inclination by the rotation of the pivot shaft member 44 in the cross direction of the axis L _3, but the pendulum arm 46 is able to slide in the inclined direction, in this case comprises a sliding component orthogonal the direction of the axis L ₃ even, and, since挾角change in the axis L ₄ and the axis which L ₅ is absorbed by the rotation action of the ball joint member 60, connecting the pendulum arm 46 the rod 48 component in the orthogonal direction of the axis L ₃ of the force transmitted to the is absorbed in the connection point, thereby enabling relative movement of said direction.

[0017] Thus, the connection between the connecting rod 48 and the pendulum arm 46 in the steering-angle-ratio adjusting mechanism 20, so have been made so as to be moved relative to each other in the direction perpendicular to the axis L _3, pendulum arm 46 The locus of the connecting point between the pendulum arm 46 and the connecting rod 48 when is rotated is the axis L
A circular locus or an elliptical locus on the outer peripheral surface of the cylinder having a radius γ centered at ₃ .

FIG. 5 shows a case where the axis L ₂ of the swinging shaft member 8 is inclined by θ with respect to the axis L ₃ of the output rod 40 (ie,
Is a diagram to uninhabitable a state of displacement of the output rod 40 of the axis L ₄ of the pendulum arm 46 when tilted θ with respect to the orthogonal direction of the axis L _3). As apparent from the figure, even pendulum arm 46 swings to the left or right direction, the displacement of the connecting point between the connecting rod 48 and the pendulum arm 46 being equal the swing amount, respectively the axis L ₃ direction S
Output rod 40 and the connecting rod 48 each also displacement of the output rod 4 from being fixedly connected to the shaft line L ₃ direction S
Becomes

As described above, the output rod 40 shown in FIG.
Are equal to each other if the swing amount of the pendulum arm 46 is equal. However, the displacement amount S itself is the same as the steering amount of the steering wheel, and the rotation amount of the bevel gear 42 accompanying this is the same. However, it changes depending on the magnitude of θ. Accordingly, the steering ratio theta _S is the setting and changing of the amount of inclination theta of the pivot shaft 46 by the operation control of the servo motor 56 can be set and changed. Further, the swing shaft member 44 can be tilted not only counterclockwise as described above but also clockwise,
At this time, the output rod 4 against the rotation of the bevel gear 42
The moving direction of 0 is opposite to the above case. As a result, it is possible to steer the steering wheel or steer the rear wheels in the same or opposite phases with respect to the front wheels. Variable steering ratio mechanism 2
The steering ratio θ _S set and changed by 0 is detected based on the inclination θ of the swing shaft member 44 by the steering ratio sensor 28 attached to the swing shaft member 44 as shown in FIG. It has become so.

Next, the turning ratio of the rear wheel turning mechanism 18 is determined.
Parts other than the change mechanism 20 will be described. First, the above oil
The pressure switching valve 32 includes a valve housing 62 and the housing
The output rod relative to the housing 62
40 axis L₃ Axis L parallel to ₆ Displaceable in the direction
And a spool 64 accommodated therein. Spool 5
2 is an output rod 40 and a rear through a displacement transmission mechanism 36.
It is displaced by the wheel steering rod 34. This sp
To the hydraulic power cylinder 38 due to the displacement of the
The supply of pressure is controlled, ie the valve housing shown
When it is displaced rightward from the neutral position with respect to
-Hydraulic pressure is supplied to the right oil chamber 66 of the cylinder 38,
To the left oil chamber 68 of the hydraulic power cylinder 38
A chamber is supplied.

The rear wheel steering rod 34 is connected to the chamber rod 4
0 extending in the axial L ₃ parallel to the vehicle width direction, and tie rods (not shown) displaced in that direction, which steers the rear wheels coupled to the left and right ends via a knuckle arm,
The displacement is performed by the hydraulic pressure of the hydraulic power cylinder 38. The rear wheel steering rod 34 is provided with a centering spring 70. If the hydraulic system of the hydraulic power cylinder 38 is lost due to damage or failure of the hydraulic system of the hydraulic switching valve 32 or the hydraulic power cylinder 38, or damage or failure of the mechanical system of the rear wheel steering device 10, the hydraulic system When the system is released to the drain and the hydraulic pressure in the hydraulic power cylinder 38 is lost, the rear wheel steering rod 34 is positioned by the centering spring 70 at a neutral position, that is, at a position where the rear wheel is not steered and is in a straight running state. In addition, it is configured to achieve a so-called fail-safe.

The hydraulic power cylinder 38 is for displacing the rear wheel steering rod 34 in the vehicle width direction by an oil compression force, and a piston 72 is directly fixed to the rear wheel steering rod 34. Left and right oil chambers 68, 6
6 are provided.
The seal members 74 and 76 are fixed to a housing 78 of the hydraulic power cylinder 38 and are slidable with the rear wheel steering rod 34.

The displacement transmission mechanism 36 includes an output rod 34
, The spool 64 and the rear wheel steering rod 34 are engaged with each other, the displacement of the output rod 40 causes the spool 64 to be displaced in a predetermined direction, and the rear wheel steering rod generated by the displacement of the spool 64. 3
4 is configured to be operated in a direction to displace the spool 64 in a direction opposite to the above direction.

That is, the displacement transmitting mechanism 36 is constituted by a cross lever composed of a vertical lever and a horizontal lever.
One end A of the vertical lever is connected to the output rod 40, the other end B is connected to the rear wheel steering rod 34, one end of the horizontal lever is connected to the case of the rear wheel steering device 10 which is fixed in an oblique body, and the other end D is connected to the spool 64.
Is engaged. The engagement ends A, B, and D are respectively provided with an output rod 40, a rear wheel steering rod 34, and a spool 64.
Are engaged with each other so as to be axially immovable and movably and rotatably in other directions, and the engagement end C is rotatably and non-movably engaged by a ball joint. ing.

[0025] By the output rod 40 strokes displaced in the axial L ₃ directions, allowed displace the rear wheel steering rod 34 through the displacement transmitting mechanism 36 in the axial direction, thereby, the both ends of the rear-wheel steering rod 34 Although the rear wheel (not shown) connected to the steering unit is steered, the operation principle of the steering amount transmission is not directly related to the present invention, and this is described in Japanese Patent Application Laid-Open No. 1-273772. Since it is described in detail, its detailed description is omitted. As described in detail above, the rear wheel steering device 10 according to the present embodiment controls the variable turning ratio mechanism 20 provided in the rear wheel turning mechanism 18 mechanically connected to the front wheel turning mechanism 14. As a result, the phase inversion control is performed, so that when the front wheels 12 have the zero steering angle, the rear wheels 14 can be mechanically and reliably maintained at the zero steering angle.

<Hydraulic Circuit> A hydraulic circuit for the rear wheel steering mechanism 18 will be described with reference to FIGS. As described above, in this steering system, the rear wheels are steered by hydraulic pressure. If the hydraulic system of the hydraulic switching valve 32 or the hydraulic power cylinder 38 is damaged or malfunctions and the hydraulic pressure in the hydraulic power cylinder 38 is lost, or the mechanical or electrical system of the rear wheel steering device 10 is damaged or malfunctions. ,
The centering spring 70 positions the rear wheel steering rod 34 at the neutral position when the hydraulic system is released to the drain and the hydraulic pressure in the hydraulic power cylinder 38 is lost accordingly. In FIG. 2, the hydraulic release circuit 31 interposed between the pump 29 and the steering mechanism 18 includes a spring 7
This is a circuit for releasing the hydraulic pressure in the steering device 18 in order to activate the zero.

FIG. 6 shows a detailed configuration of the release circuit 31. This circuit 31 has first and second two release passages 81 and 82 that connect a pipe 90 as a high-pressure passage and a pipe 91 as a low-pressure passage. Both release passage 8
1 and 82 are arranged in parallel with each other to form a first release passage 8.
The first release passage 82 is located closer to the pump 29 to form a release passage on the pump side, and the second release passage 82 is located closer to the control valve 16 to form a release passage on the power cylinder side.

An electromagnetic opening / closing valve 83 and an electromagnetic switching valve 85 are connected to the first release passage 81 and the second release passage 82, respectively. A throttle 84 is connected to the second release passage 82. The on-off valve 85 provided between the second release passage 82 and the pipe 90 is a three-port two-position switching valve. The on-off valve 83 is a signal RL from the control unit 22.
₁ is controlled to open and close. That is, RL ₁ = 1: closed RL ₁ = 0: open. The switching valve 85 receives a signal RL from the control unit 22.
_{2 is} controlled. That is, when RL ₂ = 0,
The pipe 90 is divided between the pump 29 (first release passage 81) side and the hydraulic pressure switching valve 32 (second release passage 82) side, and the pipe 90 on the valve 32 side communicates with the second release passage 82. On the other hand, when RL ₂ = 1,
The pipe 90 communicates with the pump 29 (first release passage 81) side and the hydraulic pressure switching valve 32 (second release passage 82) side, and disconnects the second release passage 82.
FIG. 7 shows an equivalent circuit in a state where RL ₁ = 0 and RL ₂ = 0.
FIG. 8 shows an equivalent circuit in a state where RL ₁ = 1 and RL ₂ = 1. The circuit diagram of the control unit of FIG. 9 and FIG.
As will be apparent from the flow chart of the control procedure 2, the signals (RL ₁ , RL ₂ ) are generated from a signal FAIL representing a fail state recognized by the control unit.

<Structure of Control Unit> FIG.
FIG. 2 is a block diagram showing a detailed configuration of a computer 22. Shown in the figure
As described above, the unit 22 has a thread with the master CPU 100.
CPU101. Control procedure described later (FIG. 12)
As can be understood from FIG.
6 is actually driven. These CPUs 100 and 101
Are signals from various sensors (yaw rate signal ψ, front wheel rotation)
Steering angle θ_F , Vehicle speed V, steering ratio θ_S ) To enter
Each has an input port. This is the slave CPU1
01 is also the yaw rate signal ψ, the front wheel turning angle θ_F , Vehicle speed V,
Steering ratio θ_S To control the motor 56
The same operation as the master CPU 100
To do that. Excitation signal for driving motor 56
Are four of A, A /, B and B /. These excitation signals
Are the respective excitation phase coils A, A /, B, B /
Is output to For convenience, the excitation signal from the master CPU is
A_M , A /_M , B_M , B /_M And slave C
The excitation signal from PU 101 is A_S , A /_S , B_S,
B /_S And Here, “/” added to the signal name is
Means the inversion of the signal. Thus, the output of the master CPU
A from power port_M , A /_M , B_M , B /_M But
A is output from the output port of the slave CPU 101.
_S , A /_S, B_S , B /_S Is output. Excitation signal
Issue A_M And A_S , A /_M And A / _S , B_M And B_S
 , B /_M And B /_S Each set has four AND games
Are input to each of the clients 102. In other words, A_M And A
_S , A /_M And A /_S , B_M And B_S , B /_M 
And B /_S In both sets, the logical values are both "1".
Only when the excitation phase coil driver is
A current flows through 103. Electric current flowing through each coil
Are monitored by the monitor circuit 104, respectively.
Issue A_R , A /_R , B_R , B /_R As each of
It is input to the interrupt input port 105 of the CPU.

FIGS. 10 and 11 show the phase relationship among the excitation signal signals A _R , A / _R , _BR , and B / _R for rotating the motor 56 in the counterclockwise direction CCW or clockwise direction CW, respectively. Show. That is, the signals _AR , A / _R , _BR
, B / _R is input to each interrupt input port 105 of each CPU as a rising signal, each CPU processes the input as an interrupt input. As will be described later, each CPU can monitor the actual rotation direction of the motor 56 if each signal stores the time change at the time of rising each signal.

According to the timing charts of FIGS. 10 and 11, if the monitoring signals A _R and A / _R are inputted earlier than the signals B _R and B / _R , the motor 5
6 can be estimated to be rotating in the CCW, and if input late, it can be estimated to be rotating in the CW. Since the monitor signals _AR , A / _R , _BR , and B / _R monitor the current flowing through the motor coil, C
Not only when the PU goes out of control, but also when the driver circuit 103 is short-circuited or opened, or when the coil is short-circuited or disconnected, they are recognized as failures because they occur as rotational direction mismatch.

It should be noted that detecting runaway of the motor based on the direction of rotation can be performed at a very high speed. If the motor of this embodiment is a stepping motor having about 3000 steps, in principle, the failure state can be recognized only by the stepping of the motor in the opposite direction by one or two steps. Such high-speed recognition of motor failure is necessary for the first time with the advent of a phase-reversal type steering ratio control type rear wheel steering device as in this embodiment.

The logic of failure detection has been described above.
The fail-safe logic will be described. In this embodiment, when a failure is detected, the drive current to the motor 56 is stopped, and at the same time, the hydraulic pressure supplied to the power cylinder is released. In this embodiment, the fail state: above the rotational direction of mismatch,: discrepancies between calculation result of the target steering ratio TGshita _S in each CPU,: various disconnection or the like which is detected at the sensor, defined as the failure You.

In FIG. 9, when these fail states are recognized, the master CPU 100 issues a fail signal FAIL
_M , the slave CPU 101 outputs a failure signal FAIL
_S is output to the AND gate 109. That is, when either the fail signal FAIL _M or the fail signal FAIL _S becomes “1”, RL ₁ and RL ₂ become “0”, the driver 103 is turned off, and the solenoids 83 and 85 are turned off.
Turns off. As described above, when the solenoids 83 and 85 are turned off, the release circuit 31 operates to form a release passage as shown in FIG.

By explaining the control procedures shown in FIGS. 12 and 13, the master CPU 100 and the slave CPU
The control operation in 101 will be described. FIG. 12 is a flowchart of a main routine of a control procedure of each of the master CPU 100 and the slave CPU 101.
7 is a processing procedure of an interrupt signal performed in each of the master CPU 100 and the slave CPU 101.

First, in step S2 of FIG.
Each CPU receives a yaw rate signal from an input port 108.
ψ, front wheel steering angle θ_F , Vehicle speed V, steering ratio θ_S , FG
And a disconnection signal of each sensor. here,
The FG signal is output according to the rotation of the step motor 56.
This is a rotation position signal where
This signal is generated as a fixed number of pulses. Step S
In step 4, it is checked whether any of the disconnection signals is "1".
Bell. If any disconnection signal is “1”, the 4WS
As a failure of the stem, the excitation signal
Issue A_M , A / _M , B_M , B /_M And A_S , A /
_S , B_S , B /_S To “0” to excite the motor
Cut off magnetic current. The power supplied to the power cylinder 38 is also
In order to release the oil pressure, the FAIL signal is
Set to “1”.

It is confirmed in step S4 that there is no disconnection.
If so, the process proceeds to step S10. In step S10,
Each CPU has the target turning ratio TGθ_S The above sensor signal
Signal (yaw rate signal ψ, front wheel turning angle θ_F , Vehicle speed V, rolling
Rudder ratio θ_S ). In step S12
And each CPU calculates the calculated target turning ratio TGθ._SThe other
To the other CPU through the bus 110 (FIG. 9) and
In step S14, the target steering ratio TGθ from the other side_S Receiving
I can. In step S16, the target turning ratio T calculated by itself is calculated.
Gθ_S Is the target steering ratio TGθ calculated by the other_S And match
I do. If the collation is obtained, the target turning ratio T is determined in step S20.
Gθ_S From the excitation signal (A_M , A / _M , B_M , B
/_M Or A_S , A /_S , B_S , B /_S )
Is calculated and output to the motor 56 in step S22.

On the other hand, in step S18, each CPU
Calculated target turning ratio TGθ_S If there is no match between
Proceed to steps S6 and S8 to turn off the excitation signal.
And generates a fail signal to the power cylinder 38
Release hydraulic pressure. Each CPU is powered by a motor coil.
Flow monitor signal A_R , A /_R , B _R , B /_R To
The input as the interrupt signal has been described above. these
When the signal is input to each CPU, each CPU
The interrupt processing routine shown in FIG. Immediately
In step S30, an input as an interrupt signal is made.
Monitor signal A_R , A /_R , B_R , B /_R 
Read and store the current logical value of. Step S32
Now, the monitor signal read last time and the monitor
The actual rotation direction of the motor 56 is calculated from the comparison with the motor signal.
I do. Then, in step S34, the target turning ratio TGθ
_S Motor is targeted based on the comparison between
Determine if it is rotating in the direction. If they do not match,
In step S36, the excitation signal is turned off, and
In S38, a fail signal is generated to release the hydraulic pressure. Hide
Process the monitor signal to interrupt the actual rotation of the motor.
Estimating the direction makes motor runaway extremely fast
Can be detected.

FIG. 14 is a timing chart of the operation when the occurrence of a failure is detected in the process of performing the "phase inversion control". Since the steering device of this embodiment detects a motor failure at a high speed, it is possible to shift to the fail-safe operation before the steering ratio greatly touches the opposite phase side. Then, the fail-safe operation is to cut the motor and detect the hydraulic pressure at the same time as the detection of the failure, so that the rear wheel is displaced from the neutral position while the hydraulic pressure remains in the power cylinder, as is apparent from FIG. The time spent in the state is shortened. Incidentally, FG signal from the motor 56 between each CPU and other CPU, and outputs the excitation signal from the output port 106, the synchronization with the timing when outputting the target steering ratio TGshita _S to the other CPU use.

<Modifications> The present invention can be variously modified without departing from the spirit thereof. For example, in the above embodiment,
Although the two CPUs have substantially the same function, the cost of the slave CPU can be reduced by reducing the load on the slave CPU. To reduce this load, 2
There are two approaches. First, the slave CPU 1
01, in the same manner as the master CPU 100, the monitor signal was input to perform the calculation in the rotation direction. However, this calculation is left to the master CPU, and the calculation result in the rotation direction is changed from the master to the bus line 110. You may.

FIG. 15 shows one proposal as such a modification. In the figure, only the master CPU 100 sends an excitation signal to the motor 56 via the driver 200. The excitation signal is supplied to the monitor circuit 201 on the way.
Is monitored by the master CPU 10
0 is input to the interrupt circuit of the slave CPU. The slave CPU 101 calculates the target turning ratio TGθ calculated by itself.
_The compatibility between _S and the monitor signal is examined. If there is no problem, the ENABLE signal is set to “1”, and if there is a problem, it is set to “0”. In the driver circuit 200, ENA
Only when the BLE signal is “1” is the excitation signal
6 to be sent.

[0042]

As described above, according to the present invention,
The determination of the consistency of the driving direction of the step motor with respect to the target turning ratio can be performed at a high speed in principle. Therefore, even if a high-speed step motor is used, the motor stop or the like can be performed early. Fail-safe measures can be taken.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a phenomenon that occurs according to the related art.

FIG. 2 is a diagram illustrating an overall configuration of a four-wheel steering system according to a preferred embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of a main part of the rear wheel steering device according to the embodiment illustrated in FIG. 1;

FIG. 4 is a view for explaining a configuration of a main part of the variable steering ratio mechanism of the embodiment shown in FIG. 1;

FIG. 5 is a view for explaining the operation principle of the turning ratio variable mechanism of FIG. 4;

FIG. 6 is a diagram illustrating a configuration of a hydraulic release circuit in FIG. 2;

FIG. 7

FIG. 8 is a view for explaining the operation of the hydraulic release circuit of FIG. 6;

FIG. 9 is a diagram showing a circuit configuration of the control unit in FIG. 2;

FIG. 10

FIG. 11 is a timing chart illustrating logic for detecting the rotation direction of the motor.

FIG.

FIG. 13 is a flowchart showing a control procedure of each CPU of the control unit.

FIG. 14 is a timing chart for explaining the effect of simultaneously stopping the motor and releasing the hydraulic pressure when a failure occurs in the embodiment.

FIG. 15 is a diagram showing a modification of FIG. 2;

[Explanation of symbols]

 Reference Signs List 18 rear wheel turning mechanism, 20 turning ratio variable mechanism, 22 control unit, 31 hydraulic release circuit, 56 step motor, 83 opening / closing valve, 85 switching valve, 100 master CPU, 101 slave CPU

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-271074 (JP, A) JP-A-2-24272 (JP, A) JP-A-3-217374 (JP, A) JP-A-3-217374 27976 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B62D 6/00 B62D 7/14

Claims (1)

(57) [Claims] 1. A step motor in which the rotation direction is controlled by a multi-phase excitation pattern for variably controlling a steering ratio of a rear wheel with respect to a steering angle of a front wheel in at least two directions, and a phase inversion control of a rear wheel. Drive control means for performing control for driving the step motor based on predetermined input information, and for performing phase inversion control of rear wheels.
First logical operation circuit for performing the logical operation of
And an output circuit for outputting the
A first logical operation control unit, and a monitor circuit for monitoring an output from the first logical operation circuit.
And input for inputting the monitoring result from the monitoring circuit
And the same logical operation as that of the first logical operation circuit is performed.
The result of the logical operation and the monitor connection input by the input circuit.
By comparing the result with the target steering ratio,
Logic operation for determining the consistency of the drive direction of the stepper motor
A second logical operation control unit having a first path and a second path, wherein the first logical operation circuit is provided with the excitation path to the monitor circuit.
And outputting a turn, wherein the second logical operation circuit is the same as the first logical operation circuit.
A logic operation is performed to calculate the excitation pattern,
The excitation pattern monitored by the monitor circuit
And the excitation pattern calculated by itself.
By this, the stepping motor with respect to the target steering ratio
A rear wheel steering device for a vehicle, which determines consistency of a driving direction .