JP2000016322A - Rear wheel steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten the retaining rigidity for the neutral position even in case of abnormality or the like without any increase in size of the device by providing an axial position regulating means disposed on a casing where a movable part engages during the non-connecting state of a clutch means. SOLUTION: The inner surface of a casing 3 is provided with a guide wall 47 where the upper end face of a pin 44 is brought into sliding contact, and when a slide shaft 1 starts to move, the upper end face of the pin 44 is brought into the lower surface of the guide wall 47 to keep the projecting state of the pin 44 without pressing force of an electromagnetic actuator 45. In the neutral position, the electromagnetic actuator 45 is demagnetized to put the pin 44 in the state of separating from a slide block 41 (clutch non-connection), whereby the upper end part of the pin 44 rushes into a hole 48 provided in the casing 3 to regulate the position of the pin 44. Thus, even if an electrically-driven motor 20 is driven in error to move the slide block 41, the axial movement of the slide shaft 1 is mechanically inhibited.

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, and more particularly, to a rear wheel steering device provided with a neutral position holding means when an abnormality occurs.

[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 make it possible to set the neutral position at the time of abnormality or the like without increasing the size of the apparatus. It is an object of the present invention to provide a rear wheel steering device that can increase the holding rigidity.

[0007]

In order to achieve the above object, according to the present invention, an axial force is applied to a slide shaft supported by a casing so as to be movable in an axial direction and connected to a rear wheel. In a rear wheel steering device that controls a wheel steering angle, a slide block that moves by being driven by an actuator on an axis parallel to a slide axis, and a slide axis that selects connection or non-connection between the slide axis and the slide block. The clutch means has a movable portion on its side, and axial position defining means provided on the casing so that the movable portion is engaged when the clutch means is not connected. According to this, no extra force is applied during normal steering, so that less power is required for steering, and in the neutral position, external forces such as lateral forces applied to the wheels are applied to the casing. I can take it. In addition, since the slide shaft and the slide block are disconnected from each other at the neutral position, even if the slide block malfunctions, it does not affect the neutral holding.

[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. A clutch block 8a serving as a movable portion of a clutch means that is rotatable in a predetermined angle range.
8b 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.

The concave portion 22 formed on the inner peripheral surface of the clutch block engaging hole 23 forming the fixing portion of the clutch means formed on the slide blocks 21a and 21b is formed with the convex portion 10 on the outer peripheral surface of the clutch blocks 8a and 8b. In the state where only the urging force of the torsion spring 12 is acting, that is, when the thrust of the electromagnetic actuators 15a and 15b is not acting on the rocker arms 16a and 16b, the convex portion 10 and the concave portion 22 The phase angle is determined so as to match.

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 projection 10 of the left clutch block 8a, that is, the clutch is engaged, and the leftward axial force acting on the left slide block 21a is applied to the slide shaft 1 via the left clutch block 8a.
It is transmitted to.

On the other hand, the convex portion 10 of the right clutch block 8b
Is aligned with the recess 22 of the right slide block 21b,
That is, since the clutch is not connected, the movement (rightward movement) of the right slide block 21b in the axial end direction has no effect on the right clutch block 8b. The arm 13 of the right clutch block 8b is provided with the inward axial portion 1 of the guide groove.
4b. 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 an aligned state (clutch is not connected),
Movement of the right slide block 21b toward the center (leftward movement) has no effect on the right clutch block 8b.

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 (see FIG. 5), which defines the axial position of the left and right clutch blocks 8a and 8b. Even if 21b 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.

FIG. 7 shows another embodiment of the clutch means. Note that the same reference numerals are given to portions corresponding to the first embodiment, and description thereof will be omitted. In the present embodiment, the coil spring 3 is turned in a direction (in a state shown in FIG. 7) in which the relationship with each of the slide blocks 21 a and 21 b non-rotatably screwed to the rotary shaft 18 having the reverse screws 17 a and 17 b cut is cut.
A pair of pins 32a and 32b elastically urged at 1 are provided in the center of the slide shaft 1 as movable portions of the clutch means. These pins 32a and 32b normally cut off the connection with the corresponding slide blocks 21a and 21b (clutch is not connected), but the electromagnetic actuator 15a
・ When pushed out by 15b, each slide block 21a
-The leading ends of the slide blocks 21a and 21b are inserted into the holes 33a and 33b provided in the 21b, and the slide blocks 21a and 21b are individually connected to the slide shaft 1 (clutch connection).

In this structure, when one of the two electromagnetic actuators 15a and 15b (for example, the left side) is excited, the tip of the corresponding left pin 32a is slid leftward as shown in FIG. It is made to protrude into the hole 33a of the block 21a. When the electric motor 20 starts rotating forward in this state, the two slide blocks 21a and 21b screwed to the screws 17a and 17b of the rotating shaft 18 move in directions to be separated from each other by the action of reverse screws. Then, the slide shaft 1 is moved to the left slide block 21 via the left pin 32a.
a, both slide blocks 21a.
It moves to the left with the separation movement of 21b.

On the other hand, since the right electromagnetic actuator 15b is demagnetized, the right pin 32b is
b does not enter the hole 33b, and the rightward movement of the right slide block 21b has no effect.

On the inner surface of the casing 3, a guide wall 34 corresponding to the guide groove 14 of the first embodiment is provided.
When the slide shaft 1 starts to move leftward, the upper end surface of the left pin 32a contacts the lower stage of the guide wall 34, and the projected state of the left pin 32a is maintained regardless of the pressing force of the left electromagnetic actuator 15a.

When the electric motor 20 is started to rotate in the reverse direction, the two slide blocks 21a and 21b move in a direction approaching each other, and accordingly, the slide shaft 1 moves rightward toward the neutral position.

To move the slide shaft 1 to the right from the neutral position, the right electromagnetic actuator 15b is excited and the right pin 32b is turned into the hole 33b of the right slide block 21b.
I just need to rush.

In the neutral position, the two electromagnetic actuators 15a and 15b are both demagnetized and the left and right pins 32a and 32b are demagnetized.
b is disengaged from the slide blocks 21a and 21b shown in FIG.
The shoulders of the guide wall 34 interfere with the upper ends of the pins 32a and 32b, and the positions of the pins 32a and 32b are defined. Thus, even if the electric motor 20 is erroneously driven and the two slide blocks 21a and 21b move, the axial movement of the slide shaft 1 is mechanically prohibited.

The two slide blocks 21a and 21b sandwich the radial projection 5 of the slide shaft 1 and also sandwich the stopper 24 of the casing 3 at the same time, so that the steering angle neutral position is more firmly held. The points are the same as in the first embodiment. Further, the determination of the failure in which the clutch means is stuck and the connection becomes impossible can also be performed based on the steering situation as in the first embodiment.

FIG. 9 shows still another embodiment of the present invention. The slide block 41 in FIG. 9 is non-rotatably screwed to the rotary shaft 18 having a single thread 42 cut over the entire length in the axial direction, and moves left and right by driving the electric motor 20 forward and reverse. It is supposed to.

A pin 44 resiliently urged by a coil spring 43 in a direction of disconnecting the connection with the slide block 41 (the state shown in FIG. 9) is provided inside the center of the slide shaft 1 as a movable portion of the clutch means. Have been. The pin 44 normally disconnects the connection with the slide block 41 (clutch is not connected), but when pushed out by the electromagnetic actuator 45, the tip of the pin 44 enters the hole 46 provided in the slide block 41 (see FIG. 10). (Shown state), the slide block 41 is connected to the slide shaft 1 (clutch connection).

In this structure, the electromagnetic actuator 4
When the electric motor 20 is started to rotate in either the forward or reverse direction in a state where the slide block 41 is connected to the slide shaft 1 via the pin 44 by exciting the slide block 1, the screw 42 of the rotary shaft 18 cannot rotate. The screwed slide block 41 is moved in the left or right direction by a screw action. Then, the slide shaft 1 moves together with the slide block 41.

On the inner surface of the casing 3, there is provided a guide wall 47 to which the upper end surface of the pin 44 can slide.
Starts moving, the upper end surface of the pin 44 contacts the lower surface of the guide wall 47, and the projected state of the pin 44 is maintained regardless of the pressing force of the electromagnetic actuator 45.

When the electric motor 20 is started to rotate in the reverse direction, the slide block 41 moves in the opposite direction, and the slide shaft 1 also moves in the opposite direction.

At the neutral position, the electromagnetic actuator 45 is demagnetized to bring the pin 44 out of the slide block 41 shown in FIG.
The upper end of the pin 44 protrudes into the hole 48 provided in the casing 3, and the position of the pin 44 is defined. Thereby, even if the electric motor 20 is erroneously driven and the slide block 41 moves, the slide shaft 1
Is mechanically prohibited.

The movable portion of the clutch means is not limited to the pin 44 protruding into the hole 46 of the slide block 41 as described above. For example, the movable portion of the clutch means may be a forked bifurcated shape that sandwiches both ends of the slide block 41 in the axial direction. .

[0047]

As described above, according to the present invention, when the steering angle is in the neutral position, the slide shaft is mechanically connected to the casing, so that an external force such as a lateral force applied to the wheels is applied to the casing. It will be accepted. Therefore, no extra force is applied during normal steering, so that the output of the steering motor can be reduced, and the rigidity for holding the neutral position can be increased without increasing the size of the rear wheel steering device. A great effect is obtained above. In addition, since the slide shaft and the slide block are not connected at the neutral position, even if the slide block malfunctions, it does not affect the neutral holding and the direction selection clutch. Since the failure of the means can be determined from the steering condition, there is no need to provide a sensor for monitoring the operation of the electromagnetic actuator, so that the simplification of the failure detection means and high reliability can be achieved at a high level.

[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 sectional view of a main part showing a second embodiment relating to the clutch means.

FIG. 8 is a cross-sectional view of a main part showing a connected state of the clutch means shown in FIG. 7;

FIG. 9 is a conceptual structural view showing an alternative unconnected state of the clutch means.

FIG. 10 is a conceptual structural view showing a connected state of the clutch means shown in FIG. 9;

[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 Rotation shaft 19 Reduction gear mechanism 20 Electric motor 21a / 21b Slide block 22 Concave 23 Engagement hole 24 Stopper 25 First sensor 26 Second sensor 27/28 Arm 29/30 Pin 31 Coil spring 32a・ 32b pin 33a ・ 33b hole 34 guide wall 41 slide block 42 screw 43 coil spring 44 pin 45 electromagnetic actuator 46 hole 47 guide wall 48 hole

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Kunio Shirakawa, Inventor Kunio Wako, 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. 3D034 CA10 CC09 CD13 CE05

Claims (1)

[Claims] 1. A rear wheel steering device which is supported by a casing so as to be movable in an axial direction, and controls a rear wheel steering angle by applying an axial force to a slide shaft connected to a rear wheel. A slide block that is driven by an actuator on a parallel axis and moves, clutch means provided with a movable portion on the slide shaft side to select connection or non-connection between the slide shaft and the slide block, A rear wheel steering device, comprising: an axial position defining means provided on the casing so that the movable portion is engaged when the clutch means is not connected.