JP2957603B2 - Front wheel steering angle correction device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-wheel steering device capable of obtaining stable steering characteristics by correcting and turning a front wheel.

(Prior Art) In the conventional rear wheel steering device shown in FIG. 7, a handle shaft 1a fixed to a handle 1 is connected to a side of a front wheel steering device 2 via an engagement between a pinion and a rack (not shown). It is connected to rods 3 and 4.

When the handle 1 is turned, the handle shaft 1a rotates together with the handle 1, and this turning force is applied to the front wheel steering device 2.
Is transmitted to the side rods 3 and 4 via the engagement between the rack and the pinion.

Then, the side rods 3, 4 move in either the left or right direction in the drawing, and steer the front wheels 7, 8 via the knuckle arms 5, 6 connected to the side rods 3, 4.

Further, separately from the front wheel steering device 2, a rear wheel steering device 9 is provided.
The rear wheel steering device 9 includes a motor 10 and
A shaft driver 11 linked to the motor 10 and an encoder 12 and an electromagnetic brake 13 directly connected to the motor 10 are main components. An output shaft (not shown) of the motor 10 is linked to a shaft (not shown) of the shaft driver 11, and side rods 1 are provided at both ends of the shaft.
4 and 15 are connected.

When the motor 10 rotates, the rotational force is transmitted to the side rods 14 and 15 via the shaft driver 11. The side rods 14 and 15 move in the left or right direction in the drawing, and the side rods 14 and 15 move.
Rear wheels 18, 19 via knuckle arms 16, 17 connected to
Steer together.

The electric steering device 9 has the motor 10 and the electromagnetic brake 13 connected to the controller 20. The controller 20 includes a vehicle speed sensor 33, a front wheel steering angle sensor 2a provided on the front wheel side rod 4, and an encoder. 12 are connected.

When the steering wheel 1 is turned and the front wheels 7 and 8 are steered, the actual steering angle of the front wheels is detected by the front wheel steering angle sensor 2a, and the actual vehicle speed is detected by the vehicle speed sensor 33. The signal is input to the controller 20.

Then, the motor 10 rotates according to the input signal.
In addition, the rotation of the motor 10 and the encoder 12 detect the actual rotation amount of the motor 10, and the output signal is fed back to the controller 20 to perform feedback control of the rear wheel steering angle.

In other words, in this rear wheel steering device, the rear wheels 18 and 19 are connected together to a single electric steering device 9 in which a motor 10 is linked, and the motor is controlled by a controller 20.
The turning force of 10 is transmitted to the rear wheels 18 and 19 to control the turning of the rear wheels 18 and 19.

The turning angles of the rear wheels 18, 19 are controlled by the front wheel turning angle and the vehicle speed.

FIG. 8 shows a state in which the steering angle ratio k of the front and rear wheels is controlled to increase with the vehicle speed.

As is apparent from FIG. 8, in this conventional device, when the vehicle speed increases, the front-rear wheel turning ratio k also increases, and the rear wheels turn from the steering angle given at the speed before the vehicle speed increases. Further, steering is performed in the same direction as the steering direction of the front wheels.

When the vehicle speed decreases, the front and rear wheel steering ratio k also decreases,
The rear wheels are further steered in a direction opposite to the steering direction of the front wheels from a steering angle given at a speed before the vehicle speed decreases.

(Problem to be Solved by the Invention) In the conventional device as described above, when the vehicle speed increases from a state where the vehicle is turning at a certain constant speed, the rear wheels rotate at a speed given at a speed before the vehicle speed increases. Steering is further performed from the steering angle in the same direction as the steering direction of the front wheels.

For this reason, the turning radius becomes large, and a so-called strong understeer state occurs.

Also, when the vehicle speed decreases from a state where the vehicle is turning at a certain speed, the turning angle of the rear wheels at the speed before the vehicle speed decreases further turns in the direction opposite to the steering direction of the front wheels. Done.

For this reason, the turning radius is reduced, and a state of so-called strong oversteer is obtained.

The conventional device cannot prevent the turning radius from increasing or decreasing due to the vehicle speed.

 As a result, the steering became unstable and dangerous.

An object of the present invention is to provide a front wheel turning angle correction device that can prevent strong understeer and strong oversteer even when the vehicle speed changes.

(Means for Solving the Problems) The present invention provides a handle, a handle shaft swingably connected to the handle, a pinion fixed to the handle shaft,
A rack that meshes with the pinion and has front wheels linked to both ends thereof, a drive mechanism that moves the handle shaft parallel to the rack, a vehicle speed sensor that detects the vehicle speed, and a front wheel steering angle sensor that detects the steering angle of the front wheels. A steering wheel rotation angle sensor for detecting a steering wheel rotation angle, a front wheel steering angle target value calculated according to the vehicle speed and the steering wheel rotation angle, and a signal obtained by comparing the target value with the front wheel steering angle. When the vehicle speed changes in a state where the steering wheel is stopped at a predetermined rotation angle, a signal corresponding to the vehicle speed is output from the controller, while the drive mechanism moves the handle shaft, The rack which meshes with the pinion of the handle shaft is moved in the axial direction by the movement of the handle shaft.

(Operation of the Present Invention) In the present invention, the vehicle speed is detected by a vehicle speed sensor.
Generally, it is known that the turning radius of a vehicle with strong understeer increases as the vehicle speed increases.

It is also known that the turning radius of a vehicle having strong oversteer decreases as the vehicle speed increases.

Therefore, the controller determines the front wheel turning angle target value according to the detected vehicle speed and the steering wheel rotation angle.

Then, a corrected output signal obtained by comparing the front wheel turning angle target value with the front wheel turning angle is output from the controller to the front wheel turning angle correcting mechanism, so that the front wheels are corrected and turned.

(Effect of the Present Invention) Since the front wheels can be corrected and steered according to the vehicle speed, strong understeer and strong oversteer can be prevented, and the stability is improved.

Further, according to the present invention, the handle shaft is moved in parallel by the drive mechanism, and the pinion fixed to the handle shaft is moved integrally with the rack, so that the pinion does not rotate. If the pinion does not rotate in this way, the handle associated with this pinion does not rotate. Therefore, even if the front wheels are corrected and steered, the steering characteristics felt by the driver can be kept constant. Therefore,
A stable steering feeling can be given to the driver.

(Embodiment of the Present Invention) In the apparatus of the first embodiment of the present invention shown in FIG. 1, a handle shaft 1a is linked to a handle 1, and a universal joint 28 is provided in the middle thereof. Further, a pinion 21 is provided at the tip of the universal joint 28.

The tip of the handle shaft 1a and the pinion 21 are inserted into the gear case 30, and the pinion 21 is engaged with the rack 22 provided in the gear case 30. The rotation of the pinion 21 is converted into the horizontal movement of the rack 22.

The gear case 30 is provided with a bearing 29,
The handle shaft 1a is rotatably held by the bearing 29.

The rack 22 which moves in the horizontal direction has side rods 3 and 4 linked to both ends thereof. Knuckle arms 5 and 6 are linked to the sides 3 and 4, and front wheels 7 and 8 are fixed to the knuckle arms 5 and 6. And rack
When the wheel 22 is moved horizontally as described above, the front wheels 7, 8 are steered left and right.

The gear case 30 is provided slidably in the horizontal direction with respect to the rack 22. And this gear case 30
Motor 26 via lever 23, worm 24, worm 25
Is connected to the motor shaft 27. The motor 26 is connected to the controller P, and rotates the motor shaft 27 according to the front wheel turning output signal I _Mr sent from the controller P.

When the motor shaft 27 of the motor 26 rotates, the worm wheel 24 rotates via the worm 25. Worm wheel
24 has a lever 23 at a point B offset from its center A.
Is mounted, and the rotational movement of the worm wheel 24 is converted into the horizontal movement of the lever 23. And this lever
Due to the horizontal movement of 23, the gear case 30 moves horizontally as a whole in the horizontal direction in the figure.

When the gear case 30 moves in the left-right direction in the figure due to the rotation of the motor shaft 27 of the motor 26, the handle shaft 1a rotatably supported by a bearing 29 provided on the gear case 30 also moves. At this time, the handle shaft 1a bends around the universal joint 28 as a fulcrum, and the pinion 21 moves in the left-right direction.

In addition, lever 23, worm wheel 24, worm 25,
The motor 26, the bearing 29 and the gear case 30 constitute the drive mechanism of the present invention.

At this time, since the handle shaft 1a is not rotating, the rack 22 is pushed right and left by the pinion 21, and corrects and steers the front wheels 7, 8 to be connected via the side rods 3, 4.

Wherein the handle shaft 1a, to detect the rotation angle of the steering wheel 1, is arranged a handle rotation angle sensor 31 for outputting a steering wheel rotation angle signal theta _S.

Further, in the vicinity of the side rods 3 and 4 detects the front wheel turning angle are arranged a front wheel turning angle sensor 32 which outputs a front wheel steering angle signal theta _f.

Further, in this device, a vehicle speed sensor 33 that detects a vehicle speed and outputs a vehicle speed signal V is arranged.

The steering wheel rotation angle sensor 31, the front wheel turning angle sensor 32, and the vehicle speed sensor 33 are each connected to the controller P.

The controller P, and determines the rear wheel steering angle target value _r according to the front wheel turning angle signal theta _f and the vehicle speed signal V sent from the front wheel turning angle sensor 32 and vehicle speed sensor 33, further rotary thereafter A steering angle target value _r and a rear wheel turning angle signal θ described later.
_{and r} to determine the output signal I _Mr. A rear wheel steering device 9 provided at the rear of the vehicle includes a motor 34 and a reduction gear.
35, pinion 36, rack 37, side rods 38, 39
Is the main element.

The motor shaft 40 of the motor 34 is provided with a pinion 36 at its tip via a reduction gear 35.

This pinion 36 meshes with the rack 37 and the motor shaft 40
Is converted into horizontal motion.

This rack 37 is connected to the rear wheels via side rods 38 and 39.
It is connected to 41 and 42.

That is, when the rear wheel steering output signal I _Mr is input from the controller P to the rear wheel steering device 9, the motor shaft 40 of the motor 34
Rotates.

When the motor shaft 40 of the motor 34 rotates, the rotational force is
The speed is reduced via the reduction gear 35, and the pinion 36 is rotated.

The rotational movement of the pinion 36 is converted into horizontal movement by a rack 37, and the rear wheel 4 is moved through side rods 38 and 39.
Steer 1 and 42.

Then, in the vicinity of the side rods 38 and 39, to detect the steering angle of the rear wheels, and a wheel steering angle sensor 43 after outputting a rear wheel steering angle signal theta _r provided.

The rear wheel turning angle sensor 43 is connected to the controller P.

The controller P, is compared with the wheel steering angle signal theta _r and the rear wheel steering angle target value _r was detected in the rear wheel steering angle sensor 43, calculates whether the rear wheel is controlled to the target as the rear rotary The steering output signal I _Mr is determined and output to the rear wheel steering device 9 to steer the rear wheels so that the target steering angle is obtained.

The rear wheel turning angle target value _r is determined by the following equation (1).

_r = kθ _f (1) Here, θ _f is a front wheel turning angle signal, and k is a front and rear wheel turning ratio, as shown in FIG.

Then, the rear wheel turning output signal I _Mr is determined by the following equation (2).

In _{I Mr = l r Δθ r +} m r · dΔθ r / dt + n r ∫Δθ r dt ... (2) _{where, l r, m r, n} r is a constant, [Delta] [theta] _r is rotary rear and the rear wheel steering angle target value _r which is the difference between the steering angle signal θ _r.

The first term l _r Δθ _r is a term that outputs a current proportional to the deviation. When the deviation between the target value and the actual steering angle is large, a large current proportional to the deviation is output, If they match, the current is zero.

The second term, m _r · dΔθ _r / dt, is a term that outputs a current proportional to the differential value of the deviation, and is used to compensate for a delay due to the rotor inertia of the motor.

The third term, n _r ∫Δθ _r dt, is a term that outputs a current proportional to the integral value of the deviation, and is used to cancel a stationary deviation caused by an external force or friction.

The rear wheel turning angle output signal calculated in this way is output to the rear wheel turning device, and controls the turning of the rear wheels as described above.

Next, the steering angle control of the front wheels performed by the controller P will be described in detail.

The front wheel turning angle target value _f is determined by the following equation (3).

_f + θ _s / r + ′ _f (3) where r is a steering wheel steering ratio and ' _f is a front wheel correction steering angle target value.

The front wheel correction steering angle target value ' _f is a rear wheel turning angle target value.
_The same value as _r is adopted.

That is, the first term of the expression (3) indicates the front wheel turning angle given by the front wheel turning device, and the second term shows the front wheel turning angle given by the front wheel turning angle correction device. It will be.

Then, in the controller P, the front wheel steering angle target value
_f is compared with the front wheel turning angle signal theta _f sent from the front wheel turning angle sensor, and determines the front wheel turning output signal I _Mf.

The front wheel steering output signal I _Mf is given by the following equation (4).

_{I Mf = l f Δθ f +} m f · dΔθ f / dt + n f ∫Δθ f dt ... (4) _{where, l f, m f, n} f is a constant, [Delta] [theta] _f is the front wheel steering angle target value _r and the previous rotary which is the difference between the steering angle signal θ _r.

The first term l _f Δθ _f is a term that outputs a current proportional to the deviation. When the deviation between the target value and the actual steering angle is large, a large current proportional to the deviation is output. If they match, the current is zero.

The second term, m _f · dΔθ _f / dt, is a term that outputs a current proportional to the differential value of the deviation, and is used to compensate for a delay due to the rotor inertia of the motor.

The third term, n _f ∫Δθ _f dt, is a term that outputs a current proportional to the integral value of the deviation, and is used to cancel a stationary deviation caused by an external force or friction.

The front wheel turning angle output signal calculated in this way is output to the front wheel turning device, and controls the turning of the front wheels as described above.

 Now, there is a state where the vehicle is making a steady circular turn at a constant speed.

When the vehicle speed increases from this state, the rear wheel steering output signal I _Mr is _sent from the controller P from the current rear wheel steering angle so that the front wheels are further steered in the direction in which the front wheels are currently steered. Is output. In response to the signal I _Mr , the rear wheel steering device steers the rear wheels.

By turning the rear wheels, the steady side slip angle of the vehicle becomes zero.

At this time, the controller P outputs to the front wheel turning angle correction device a front wheel turning output signal I _Mf that corrects and turns the front wheel in the same direction as the rear wheel by turning the rear wheel. The front wheel turning angle correction device receives the signal I _Mf and _turns the front wheels.

As described above, since the front wheels are corrected and steered in the same direction as the angle at which the rear wheels are steered, it is possible to prevent strong understeer caused by the steering of the rear wheels.

Also, when the vehicle speed decreases from a state of steady circular turning at a constant speed, the rear wheels are steered in a direction opposite to the direction in which the front wheels are currently steered from the current steering angle of the rear wheels. , A rear wheel steering output signal I _Mr is output from the controller P.

In response to the signal I _Mr , the rear wheel steering device steers the rear wheels.

By turning the rear wheels, the steady side slip angle of the vehicle becomes zero.

At this time, the controller P outputs a front wheel turning output signal I _Mf that corrects and turns the rear wheel in the same direction as the rear wheel by turning the rear wheel to the front wheel turning angle correction.

The front wheel turning angle correction device receives the signal I _Mf and _turns the front wheels.

As described above, since the front wheels are corrected and steered in the same direction as the angle at which the rear wheels are steered, it is possible to prevent understeer generated by steering the rear wheels.

As described above, in the device according to the embodiment of the present invention, the steering characteristics can be kept constant while the vehicle slip angle is set to 0, so that the steering stability is improved.

Further, when the correction steering is performed in this manner, the universal joint of the handle 1a of the front wheel steering device is bent, and the handle 1 itself does not rotate or move, so that the steering characteristic felt by the driver can be kept constant. .

In this way, in fact, since the influence of the rear wheel turning of the steering characteristic is kept constant by the correction turning of the front wheel, the driver does not experience the turning of the rear wheel nor the correction turning of the front wheel, so it is as if It can be driven with the feeling of driving a 2WS car that does not steer the rear wheels.

 Next, another embodiment of the present invention is shown in FIGS.

In the second embodiment shown in FIG. 2, a hypoid gear is used instead of the worm 25 and the worm wheel 24 of the first embodiment.
44 and 45 are used. Other configurations are the same as those in the first embodiment, and the same components are denoted by the same reference numerals.

In the third embodiment shown in FIG. 3, single gears 46 and 47 are used instead of the worm 25 and the worm wheel 24.

In the second and third embodiments shown in FIGS.
The rotational force of the motor shaft 40 of the motor 26 is converted into a rotational movement about the point A as the center of the worm wheel 24. The rotational movement of the worm wheel 24 is converted into a horizontal movement of the gear case 30 via the lever 23. And this gear case
As in the first embodiment, the pinion 21 and the rack 22 are moved by the horizontal movement of 30 and the corrected steering is performed.

Next, in the fourth embodiment shown in FIG. 4, the worm wheel 49 meshing with the worm 48 is formed into a sector shape. The worm wheel 49 is rotated around point A.

Then, point A and point B offset from point A
Lever 50 connected to this worm wheel 49 with a point
Has a long hole at a connection point C with the gear case 30.

Now, when the motor shaft 27 of the motor 26 rotates, this rotational force is converted via the worm 48 into a circular motion of the worm wheel 49 about the point A as the center of rotation.

Then, the circular motion of the worm wheel 49 is converted into the horizontal motion of the gear case 30 in the elongated hole at the point C.

The pinion is moved by the horizontal movement of the gear case 30.
The fact that the rack 22 moves and the correction steering is performed
This is the same as the first embodiment.

The fifth embodiment shown in FIG. 5 uses hypoid gears 51 and 52 instead of the worm 48 and the worm wheel 49 of the fourth embodiment shown in FIG.

 Other structures are the same as those of the mechanism shown in FIG.

The front wheel turning angle correcting mechanism shown in FIG. 6 uses single-row gears 53 and 54 instead of the worm 48 and the worm wheel 49 of the front wheel turning angle correcting mechanism shown in FIG.

 Other structures are the same as those of the mechanism shown in FIG.

In the apparatus of this embodiment, in a vehicle that steers rear wheels, the front wheels are steered by the same angle in the same direction as the rear wheels. However, in order to set the control characteristics of the vehicle that are easy to steer and safe, it is natural that any direction and any angle correction steering may be performed.

That is, even in a vehicle that does not steer the rear wheels, it is possible to set easy-to-steer and safe steering characteristics in accordance with various steering characteristics of the vehicle such as understeer, oversteer, and reversesteer. .

[Brief description of the drawings]

1 to 6 show an apparatus according to an embodiment of the present invention.
1 is an overall view showing the configuration of each function, FIG. 2 is a view showing a front wheel turning angle correcting mechanism using a hypoid gear, and FIG. 3 is a front wheel turning angle correcting mechanism using a single-row gear. FIG. 4 is a diagram showing a front wheel turning angle correcting mechanism using a worm gear, FIG. 5 is a diagram showing a front wheel turning angle correcting mechanism using a hypoid gear, and FIG. 6 is a front wheel turning using a single-row gear. FIGS. 7 and 8 show a steering angle correction mechanism, and FIGS. 7 and 8 show a conventional device.
FIG. 7 is an overall view showing the configuration of each function, and FIG. 8 is a graph showing the relationship between the vehicle speed V and the front / rear wheel turning ratio k. Handle …… 1, handle shaft …… 1a, pinion …… 21,
Front wheels 7, 8, Racks 22, Motor 26, Vehicle speed sensor 33, Front wheel steering angle sensor 32, Steering wheel rotation angle sensor 31, Controller P

Continuation of the front page (56) References JP-A-63-28763 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B62D 5/04 B62D 6/00

Claims (1)

(57) [Claims] 1. A handle, a handle shaft swingably connected to the handle, a pinion fixed to the handle shaft, a rack meshing with the pinion and linking front wheels to both ends thereof, and a handle shaft parallel to the rack. A drive mechanism for moving, a vehicle speed sensor for detecting a vehicle speed, a front wheel steering angle sensor for detecting a steering angle of a front wheel, a steering wheel rotation angle sensor for detecting a steering wheel rotation angle, and according to a vehicle speed and a steering wheel rotation angle. A controller for calculating a front wheel steering angle target value, and outputting a signal obtained by comparing the target value to the front wheel steering angle to the drive mechanism, with the steering wheel stopped at a predetermined rotation angle. When the vehicle speed changes, a signal corresponding to the vehicle speed is output from the controller, and the drive mechanism moves the handle shaft. Front wheel steering angle correction device rack meshing with the pinion, characterized in that it has a configuration that moves in the axial direction.