JP2000016312A - Electric steering angle control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote the miniaturization of an electric motor and an electric motor drive circuit. SOLUTION: A power supply circuit 32 for normal control in which an electric motor 20 is driven in forward/reverse directions to control the steering angle, and a power supply circuit 33 for abnormal condition in which the current to return the steering angle to the neutral position is supplied to the electric motor when an abnormality is detected in the system, are connected to a common electric motor in parallel, and when an abnormality is detected, the power supply circuit for normal control is shut off, and the power supply circuit for abnormal condition is connected. The steering drive in a normal condition and the neutral position returning drive in an abnormal condition can be effected by a single electric motor, and the steering angle can surely be returned to the neutral position. In particular, by providing a current limit means, the current capacity of the power supply circuit for abnormal condition can be reduced, and the increase in size of the device constitution by providing this circuit can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric steering angle control device for generating a steering force of a wheel by an electric motor.

[0002]

2. Description of the Related Art There have been proposed various techniques relating to front and rear wheel steering devices which attempt to improve the dynamic characteristics of a vehicle by turning the rear wheels in accordance with the front wheel steering angle (Japanese Patent Application Laid-Open No. Hei 9 (1999)).
-58515 and the like). Such a front-rear wheel steering device generally incorporates a fail-safe device that automatically returns the steering angle to a neutral position (straight running state) when the steering angle sensor is abnormal (or when the engine is stopped). .

As this fail-safe device, there is known a fail-safe device provided with a neutral position return spring for forcibly returning a steering rod to a neutral steering angle position when normal steering angle control cannot be continued. (Japanese Patent Laid-Open No. 8-301131)
No., etc.).

[0004]

However, according to this conventional device, even if the steering angle sensor fails and the neutral position cannot be specified, the neutral position can be reliably restored to the neutral position and the straight running state can be maintained. Since the resilient force of the neutral position return spring having the force described above is constantly acting on the steering rod, the electric motor that provides the steering angle can steer against the resilient force of the return spring in addition to the road surface resistance. Output must be able to be generated. Therefore, miniaturization of the electric motor and the electric motor drive circuit has been hindered.

[0005] Two main and auxiliary driving devices and a clutch for selectively connecting both driving devices to the steering device are provided, and when the main driving device fails, the auxiliary driving device returns the rear wheel steering angle to the neutral position. In this case, the steering angle sensor must always be able to specify the neutral position, and the auxiliary angle sensor that operates only at the time of abnormality has been proposed. Since a drive must be provided,
The size of the entire device cannot be reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems imposed on the prior art, and a main object of the present invention is to reduce the size of an electric motor and an electric motor drive circuit. The present invention provides an electric steering angle control device configured as described above.

[0007]

In order to achieve the above object, the present invention provides a normal control power supply circuit 32 for controlling the steering angle by driving the electric motor 20 forward or reverse.
When a system abnormality is detected, an abnormality power supply circuit 33 for supplying a current for returning the steering angle to the neutral position to the electric motor is connected in parallel to a common electric motor, and when a system abnormality is detected, the normal control power supply circuit is connected. And a power supply circuit for abnormal situations is connected. According to this, the normal steering drive and the neutral position return drive at the time of abnormality can be performed by a single electric motor, and can be reliably returned to the neutral position. In particular, by providing the current limiting means, the current capacity of the power supply circuit for abnormal situations can be reduced, so that the increase in the size of the device configuration due to the provision of the circuit can be suppressed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to an embodiment shown in the accompanying drawings.

FIG. 1 shows the entire driving section of an electric rear wheel steering apparatus according to the present invention. In FIG.
A slide shaft 1 connected to a knuckle arm of a rear wheel via a tie rod (not shown) is supported by a casing 3 via a slide bearing 2 so as to be slidable in the axial direction.

At a central portion in the axial direction of the slide shaft 1, a radial protrusion is provided to engage with the slide shaft 1 and a pair of guide rods 4 extending in parallel with a rotation shaft described later in order to prevent the slide shaft 1 from rotating. A part 5 is formed (see FIG. 2).
As shown in FIGS. 3 and 4, displacement of the protrusion 5 in the axial end direction is restricted by a ring member 6 laser-welded to the slide shaft 1 and a resin bearing 7. Clutch blocks 8a and 8b adapted to be rotatable in a predetermined angle range are fitted respectively.

The two clutch blocks 8a and 8b have a substantially cylindrical shape, and a large-diameter portion 9 is provided on the protruding portion 5 side at the center of the slide shaft.
Is formed on the side remote from the protruding portion 5, and a convex portion 10 having a rectangular cross section whose top surface is placed on a circumferential surface slightly smaller than the inner diameter of the concave portion of the slide block described later divides the circumference equally. A plurality of small-diameter portions 11 are formed between the large-diameter portion 9 and the convex portion 10, that is, at the center in the axial direction. These clutch blocks 8a and 8b are elastically biased in one direction by a torsion spring 12 wound between the inner peripheral surface of the large diameter portion 9 and the outer peripheral surface of the slide shaft 1. I have.

Large diameter portion 9 of both clutch blocks 8a and 8b
Has a pair of arms 13 projecting in the radial direction.
As shown in FIG. 5, the ends of these arms 13 project into guide grooves 14 having a crank shape on one side from the center formed symmetrically on the inner surface of the casing 3. The arm 13 has a rocker arm 16 that is oscillated by electromagnetic actuators 15a and 15b that perform linear motion.
The free ends of the electromagnetic actuators 15a and 15b are in contact with the free ends of the electromagnetic actuators 15a and 15b, respectively.
The clutch blocks 8a and 8b can be rotated by a predetermined angle by transmitting the signals to the arm 13 via the 16b.

Screws 1 having opposite threads from the center in the axial direction
7a and 17b are cut off, and a rotating shaft 18 extending parallel to the slide shaft 1 is supported by the casing 3 so as to be rotatable and non-displaceable in the axial direction. The rotation shaft 18 is driven forward and reverse by an electric motor 20 via a reduction gear mechanism 19.

A pair of slide blocks 21a and 21b are screwed into the screw portions 17a and 17b of the rotating shaft 18 at symmetrical positions from the axial center. These slide blocks 21a and 21b are integrally formed with a clutch block engaging hole 23 having a plurality of concave portions 22 which can be engaged with the convex portions 10 of the clutch blocks 8a and 8b fitted on the slide shaft 1. ing. In addition, these slide blocks 2
The reference numerals 1a and 21b engage with the guide rods 4 that prevent the slide shaft 1 from rotating, and secure the concentric accuracy of the clutch block engagement hole 23 with the slide shaft 1.

A concave portion 22 formed on the inner peripheral surface of the clutch block engaging hole 23 formed on the slide blocks 21a and 21b corresponds to the convex portion 10 on the outer peripheral surface of the clutch blocks 8a and 8b. 12, only the urging force is acting, ie, the electromagnetic actuator 15a
When the thrust 15b is not acting on the rocker arms 16a and 16b, the phase angle is determined so that the projection 10 and the recess 22 are aligned with each other.

The end faces of the slide blocks 21a and 21b abut against a stopper 24 formed on the casing 3 with a thickness equal to the axial dimension of the protrusion 5 provided at the axial center of the slide shaft 1. The movement range is determined by the dimension L between the inner surfaces in the axial direction of the casing 3 so that the casing 3 can move from the position by a distance corresponding to the maximum stroke of the slide shaft 1 corresponding to the maximum steering angle of the rear wheel.

Next, the operation of the apparatus of the present invention will be described with reference to FIG.
The description will be made on the assumption that the slide shaft 1 is moved leftward from the steering angle neutral position shown in FIG.

Although not shown in FIG. 1, the two clutch blocks 8a and 8b are individually driven to rotate by individual electromagnetic actuators 15a and 15b. Actuator 15
a, only the left clutch block 8a is actuated against the biasing force of the torsion spring 12 so that the guide groove 1
4 between the circumferential portions 14a. Then, the convex portion 10 of the left clutch block 8a and the left slide block 21
A phase shift occurs between the concave portion 22 and the convex portion 10 on the outer peripheral surface of the left clutch block, and the convex portion 10 adjacent to the concave portion 22 on the inner peripheral surface of the left slide block is aligned on the same straight line in the axial direction. .

When the electric motor 20 starts rotating forward in this state, the two slide blocks 21 screwed to the rotary shaft 18 are rotated.
The a.21b moves in a direction away from each other by the action of the reverse screw. Then, the left slide block 21a interferes with the protrusion 10 of the left clutch block 8a, and the left slide block 2
The leftward axial force acting on 1a is applied to the left clutch block 8a.
Through the slide shaft 1.

On the other hand, the convex portion 10 of the right clutch block 8b
And the concave portion 22 of the right slide block 21b are aligned with each other, so that movement of the right slide block 21b in the axial end direction (rightward movement) has no effect on the right clutch block 8b. The arm 13 of the right clutch block 8b is engaged with an inward axial portion 14b of the guide groove. Thus, the slide shaft 1 moves to the left.

When the slide shaft 1 starts moving to the left and the arm 13 of the left clutch block 8a engages with the outward axial portion 14c of the guide groove, the left clutch block 8a cannot rotate. Even when the power supply to the left electromagnetic actuator 15a is stopped at that point and the rocker arm 16a is returned by the biasing spring, the engagement between the left clutch block 8a and the left slide block 21a is maintained.

By setting the lead angles of the screws 17a and 17b of the rotary shaft 1 to be smaller than the friction angle, the steering angle at the time when the electric motor 20 is stopped can be maintained.

When the electric motor 20 is rotated in the reverse direction, the two slide blocks 21a and 21b move in the
That is, since the slide shaft 1 moves toward the center, the left slide block 21a and the radial protrusion 5 formed at the axial center of the slide shaft 1 engage with the slide shaft 1
Moves to the right to return to the neutral position. Also at this time, since the convex portion 10 of the right clutch block 8b and the concave portion 22 of the right slide block 21b are in alignment, any movement toward the center of the right slide block 21b (leftward movement) will cause Has no effect.

If the left electromagnetic actuator 15a is already demagnetized when the arm 13 of the left clutch block 8a is aligned with the circumferential portion 14a of the guide groove 14 at the neutral position,
The left clutch block 8a is rotated by the action of the torsion spring 12, so that the projection 10 of the left clutch block 8a and the recess 22 of the left slide block 21a are aligned, and the connection between the left slide block 21a and the slide shaft 1 is established. Cut off.
In this neutral position, both slide blocks 21a and 21b
However, since the radial projection 5 of the slide shaft 1 is sandwiched at the same time as the stopper 24 of the casing 3 is also sandwiched, the steering angle can be adjusted with high precision and high rigidity in cooperation with the frictional angle action of the screw. The neutral position is maintained. In this state, the arms 13 of the left and right clutch blocks 8a and 8b
Is located at the shoulder of the circumferential portion 14a of the guide groove, so that both slide blocks 21a and 2
Even if 1b moves, the neutral state of the slide shaft 1 is maintained.

When the slide shaft 1 is moved rightward beyond the neutral position, the electromagnetic actuator 15b
Is excited, and the electric motor 20 is rotated forward.
Then, contrary to the above, only the right clutch block 8b rotates, and the axial force to the right of the right slide block 21b is transmitted to the slide shaft 1 via the right clutch block 8b. At this time, since the left clutch block 8a and the left slide block 21a are not engaged, the leftward movement of the left slide block 21a has no effect on the slide shaft 1.

In this manner, by selectively exciting the two electromagnetic actuators 15a and 15b and simultaneously selecting the rotation direction of the electric motor 20, the rotation is determined by which of the two electromagnetic actuators 15a and 15b is excited. When the direction of the rudder is determined and the electric motor 20 rotates forward, the steering angle increases, and when the electric motor 20 rotates reversely, it always returns to the neutral position.
Therefore, it is not necessary to determine the turning direction in the neutral return control.
When the slide block 21 returns to the neutral position,
Since the a.21b abuts against the stopper 24 of the casing 3 and the protrusion 5 of the slide shaft 1 and cannot move any further, it is sufficient to interrupt the current to the electric motor 20 by detecting the overload, and also to detect the neutral position. Not required.

This device includes a first sensor 25 for detecting the left and right movement of the slide shaft 1 and two slide blocks 21a.
A second sensor 26 for detecting the relative contact / separation movement of 21b is provided, and an abnormality can be determined based on these outputs.

The two sensors 25 and 26 are arms 27 and 28 fixed to the rotation shaft of a rotation detector such as a potentiometer.
Is connected to the slide shaft 1 and one slide block 2
It is connected to the pins 29 and 30 implanted in 1a, and detects the axial movement of the slide shaft 1 and one slide block 21a by converting it into a rotation angle (see FIG. 6).

When the clutch means is connected, that is, when the slide blocks 21a and 21b and the slide shaft 1 are integrated with each other, it is determined whether or not only one side is fixed. This can be done without any problem, but if the other clutch means is connected to increase the steering angle to the other, the clutch means on both sides will be in a connected state, and the slide shaft 1 will not be able to move. It can be done by monitoring. If both are stuck, the steering angle cannot be increased to either the left or right. Therefore, it can be determined by monitoring the current or the steering angle value of the electric motor 20 when turning to either one.

The state in which the clutch means cannot be connected is determined when both are not connected, because the slide shaft 1 does not move even if the slide blocks 21a and 21b move, so that when either one is turned, This can be performed by comparing the outputs of the first and second sensors 25 and 26. When only one of them is not connected, the steering angle to the other increases but the steering angle to one does not increase, so that the outputs of the first and second sensors 25 and 26 when the vehicle is steered to the right and left. It can be determined by comparing. At this time, as described above, since each arm 13 of both the left and right clutch blocks 8a and 8b is located at the shoulder of the circumferential portion 14a of the guide groove, the clutch means is not connected and the two slide blocks 21a and 2a are not connected.
Even if 1b is opened, the neutral state of the slide shaft 1 is maintained.

In this manner, a failure in which the clutch means is stuck and becomes unreachable can be determined from the steering condition without adding a sensor for monitoring the movement of the electromagnetic actuator. Simplification can be achieved.

As shown in FIG. 7, an electric motor 20 for applying an axial force to the slide shaft 1 is provided with a motor for normal use such as a bridge connection of an FET in order to switch the rotation direction by a signal from an electronic control unit 31. A current is supplied via the drive circuit 32. Further, an abnormal-state motor drive circuit 33 to which a current is supplied only at the time of an abnormality is connected to the brush terminal of the motor 20 in parallel with the normal-time motor drive circuit 32.

Each of the normal-time motor drive circuit 32 and the abnormal-time motor drive circuit 33 is provided with a relay contact (which may be a non-contact relay using an FET or the like) operated by an abnormality detection signal from the abnormality detection circuit 34a. The motor drive circuit 32 for normal operation is shut off and the motor drive circuit 33 for abnormal operation is connected when an abnormality occurs. The normally open contact 35a is connected to the normal motor drive circuit 32, the normally closed contact 35b is connected to the abnormal motor drive circuit 33, and the relay drive signal from the abnormality detection circuit 34 is normal. It is output only when an error occurs, and is not output when an error occurs. Thus, the above-described effect can be obtained even when the electronic control unit 31 fails.

The abnormal-time motor drive circuit 33 is provided with a current limiting circuit 36.
Is limited to the minimum necessary to return the steering angle to the neutral position while traveling on a dry road surface. This is because, in the event of an abnormality, it is necessary to return the steering angle gently to avoid a sudden change in the vehicle behavior, and to reduce the current capacity so that the wires can be made thinner and the circuit elements and contacts can be made smaller.

If the normal and abnormal brushes are separately provided, the steering angle control becomes impossible due to the abnormal motor drive circuit 32 and the brush wear. Can also be returned to the neutral position.

[0036]

As described above, according to the present invention, it is possible to reliably return to the neutral position by using the drive motor for normal steering, so that fail-safe reliability can be achieved without increasing the size of the device configuration. A great effect can be exerted in order to further increase.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing the device of the present invention with a part cut away.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is an enlarged sectional view of a main part.

FIG. 4 is a sectional view taken along the line IV-IV in FIG.

FIG. 5 is a sectional view taken along the line VV in FIG. 4;

FIG. 6 is a partial view taken along line VI-VI in FIG. 2;

FIG. 7 is a conceptual motor drive circuit diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slide shaft 2 Slide bearing 3 Casing 4 Guide rod 5 Projection part 6 Ring member 7 Resin bearing 8a / 8b Clutch block 9 Large diameter part 10 Convex part 11 Small diameter part 12 Torsion spring 13 Arm 14 Guide groove 15a / 15b Electromagnetic actuator 16a / 16b Rocker arm 17a / 17b Screw 18 Rotating shaft 19 Reduction gear mechanism 20 Electric motor 21a / 21b Slide block 22 Recess 23 Engagement hole 24 Stopper 25 First sensor 26 Second sensor 27/28 Arm 29/30 Pin 31 Electronic control unit 32 Motor drive circuit for normal operation 33 Motor drive circuit for abnormal operation 34 Abnormality detection circuit 35a / 35b contacts 36 Current limiting circuit

Continuation of the front page (72) Inventor Norio Kakizaki 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (Reference) 3D033 CA03 CA05 CA18 CA20 CA24 CA31 3D034 CA10 CC09 CD13 CD18 CE05 CE13 5H209 AA10 BB08 CC01 DD02 GG13 HH10 HH14 JJ01 5H303 AA13 BB14 CC03 DD01 KK35

Claims (2)

[Claims] 1. A power supply circuit for normal control for controlling a steering angle by driving an electric motor forward / reversely, and an abnormality supply for supplying a current to the electric motor for returning the steering angle to a neutral position when a system abnormality is detected. And a power supply circuit connected in parallel to a common electric motor, and when a system abnormality is detected, the power supply circuit for normal control is shut off and the power supply circuit for abnormality is connected to the electric steering angle control device. . 2. The electric steering angle control device according to claim 1, wherein the abnormal-time power supply circuit includes current limiting means.