JPH0438269A - Steering system for vehicle - Google Patents

Abstract

PURPOSE:To make a speed transmission ration adjustable with a motor small in output by making a turning angle of the motor so as to be driven and controlled on the basis of the detected value of a speed sensor when the steering angle detected value is less than the value equivalent to the specified steering angle. CONSTITUTION:In a power steering system provided with a power assist mechanism, a second input shaft 12 being connected to a first input shaft 11 by a torsion bar 13 and an output shaft 14 are coupled together by a speed transmission mechanism which consists of a countershaft 15, an angular speed ratio variable gear train A and a speed-up gear train B transmitting its speed to the output shaft 14. A worm gear 33 is rotated and driven by an electric motor 34, through which a speed transmission ratio between these input-output shafts 12, 14 is made variable. The motor 34 is controlled by a controller 53 on the basis of a speed sensor 52 when the detected value of a steering angle sensor 51 is less than the value equivalent to the specified steering angle.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vehicle steering system in which the rotational transmission ratio, that is, the ratio of the wheel turning angle to the steering angle of the steering link wheel, is variable. For example, when the vehicle is stopped or running at a slow speed, by increasing the rotation transmission ratio, the steering angle of the steering wheel required to turn the wheels significantly for parking etc. is reduced, making the steering link wheel easier to operate. The present invention relates to a vehicle steering system that can improve steering stability by reducing the rotational transmission ratio during high-speed driving.

[Prior Art] An example of a conventional vehicle steering device with a variable rotational transmission ratio is disclosed in Japanese Patent Laid-Open No. 17180/1983 or Japanese Patent Laid-Open No. 12/1983.
It is disclosed in the No. 2071 publication.

In these technologies, an input shaft connected to a steering wheel and an output shaft connected to a steering mechanism are linked by a planetary gear device. , JP-A-61-1.220
In the technique described in Japanese Patent No. 71, a carrier of a planetary gear is rotated by a motor, thereby making the rotation transmission ratio variable.

In other words, in this method, the rotation angle of the motor is added to the steering angle of the steering wheel, and the output shaft is rotated in proportion to this combined rotation angle.In order to obtain a large rotational transmission ratio, the rotation speed of the motor must be increased. to rise. For this reason, a high output motor is used.

By the way, it is generally desirable that the rotational transmission ratio be adjusted to a large value at low speeds and a small value at high speeds.

In particular, it is desirable that the maximum rotational transmission ratio be achieved when the steering wheel is turned significantly during a so-called swerve, in which the direction of the wheels is changed while the vehicle is stopped.

Therefore, the present applicant has proposed a steering device in which the rotational transmission ratio is mechanically variable according to the steering angle of the steering wheel. This structure is disclosed in Japanese Patent Application Laid-Open No. 2-14971. This device connects the input shaft and output shaft with an elliptical gear,
When the steering wheel is in the neutral position, a small rotational transmission ratio is obtained, and as the steering wheel rotates thereafter, a larger rotational transmission ratio is obtained. In this device, one of the elliptical gears is caused to revolve by a motor, so that the rotation transmission ratio can be corrected depending on the vehicle speed.

[Problems to be Solved by the Invention] According to this method, when the steering wheel is turned significantly such as when stationary or driving at low speed, a relatively small rotation angle of the steering wheel is sufficient due to the action of the elliptical gear and the speed increasing gear. In addition, the rotation angle of the steering wheel can be further reduced by the revolution of the motor, and when driving at medium or high speeds where the rotation angle of the steering wheel is small, the steering rotation transmission ratio can be appropriately set by the revolution of the motor according to the vehicle speed.

However, in a region where the steering wheel rotation angle is large when the steering wheel is stationary, the rotation transmission ratio increases as the steering rotation angle increases, which increases the load on the motor and requires a correspondingly large output. Ru. On the other hand, at medium and high speeds, which is the other operating range of the motor, the steering operation is generally not performed as quickly, and the force required for turning is lighter than when the steering is stationary. Therefore, when driving at medium or high speeds, the motor only requires a small output. In other words, on the one hand, a large output is required, and on the other hand, a motor is required to have very different characteristics that require only a small output.

Therefore, the present invention aims to realize a steering device that can reduce the output of the motor.

[Means for Solving the Problem] The above means includes an input shaft connected to a steering wheel of a vehicle, an output shaft connected to a steering mechanism that changes the wheel direction with respect to the vehicle direction, and the input shaft and the output shaft. a rotation transmission mechanism that cooperates to enable rotation transmission between the input shaft and the rotation transmission mechanism; and a rotation transmission mechanism that rotates a part of the rotation transmission mechanism to vary the ratio of the rotation angle of the input shaft to the rotation angle of the output shaft that rotates in accordance with the rotation angle. a steering angle sensor that detects the steering angle from the neutral position of the steering wheel; a speed sensor that detects the running speed of the vehicle; Sometimes, the problem is solved by a vehicle steering system having a motor control means for driving and controlling the rotation angle of the motor based on the value detected by the speed sensor.

[Operation] Now, in the steering device having the above structure, the motor is driven only when the steering angle of the steering link wheel is equal to or less than a predetermined angle.

When the steering angle is below a predetermined value, that is, near the neutral position, the force required to change the direction of the wheels is in a low range, and the load torque applied to the motor is small. For this reason, a motor with a low output will suffice.

Since the rotation transmission ratio can be changed within this range, for example, the steering angle of the steering wheel required to change the direction of the wheels by 30 degrees can be set to 30 degrees at low speeds and 60 degrees at high speeds. Therefore, even if the motor stops rotating when the steering angle exceeds a predetermined angle, the steering angle of the steering wheel required to steer the wheels to the permissible limit can be reduced at low speeds and increased at high speeds. can. In this way, according to the steering system of the present invention, a variable rotation transmission ratio type steering system can be realized using a motor with a small output.

[Effects of the Invention] According to the present invention, the rotation transmission ratio can be made variable using a motor with a small output. When the steering angle becomes large, the motor is stopped, but if the vehicle is traveling at high speed, the steering is not large, so there is no problem even if the motor is stopped. When the vehicle is stopped or running at a slow speed, the motor is stopped after the vehicle is steered by a predetermined angle, but before that, the rotational transmission ratio has been adjusted to a large value near the neutral position. , when the steering wheel is steered by a predetermined angle, it is already wide (because the wheel direction has changed, the steering angle of the steering wheel required to move the wheel from the right limit position to the left limit position, for example, decreases; Vehicle handling is significantly improved.

[Example] Hereinafter, an example embodying the present invention will be described with reference to the drawings.

First, the structure of the steering gear box used in this embodiment will be explained with reference to FIGS. 2 and 3.

Fig. 2 shows an example in which the present invention is applied to a power steering system of a two-pinion type for use in a vehicle equipped with a known power assist mechanism consisting of a hydraulic pump P, a rotary valve type control valve V, a power cylinder C, a reservoir R, etc. In this device, a first intrahuman shaft 11 connected to a steering wheel 10 is arranged coaxially with the first inner shaft 11 and rotatable relative thereto within a predetermined range (within the range of torsion of the torsion bar 13). A second intrahuman shaft 12 provided therein is connected by a torsion bar 13. In addition, the first intrapersonal axis 11 and the second intrapersonal axis 1
An output shaft 14 is disposed coaxially and rotatably relative to the output shaft 2 . A pinion 16 is integrally provided on the output shaft 14, and the rack par 17, which also serves as the piston rod of the power cylinder C, is moved in the axial direction by the pinion 16. The wheels W are steered by a rudder mechanism.

The second human power shaft 12 and the output shaft 14 are linked so that rotation can be transmitted by a rotation transmission mechanism described below. This rotation transmission mechanism consists of an intermediate shaft 15 that is parallel to input/output shafts 12 and 14 and fixed to a carrier 31 (described later), and a variable angular velocity ratio gear that converts the rotation of the input shaft 12 into rotation about the intermediate shaft 15. It has a gear train A and a speed increasing gear train B that transmits rotation about the intermediate shaft 15 to the output shaft 14.

As shown in FIGS. 2 and 3, the variable angular velocity ratio gear train A is composed of a pair of non-circular gears, that is, elliptical gears 21 and 22 whose rotation center is the focal point. is mounted on the second intrapersonal shaft 12 so as to be integrally rotatable, and the other elliptical gear 22 is mounted on the intermediate shaft 15 so as to be rotatable. In this variable angular velocity ratio gear train A, the elliptical gear 21.
22 or Fig. 3, the second
The elliptical gear 2 is
The angular velocity ratio of the elliptical gear 22 to 1 is increased.

As shown in FIG. 2, the speed-increasing gear train B is composed of a pair of large and small circular gears 23 and 24.
is formed integrally with the elliptical gear 22 and rotatably assembled on the intermediate shaft 15, and the small diameter gear 24 is formed integrally with the output shaft 14 and rotates integrally with the output shaft 14. In this speed increasing gear train B, the rotation of the large diameter gear 23 is increased by a predetermined amount (determined by the diameters of both gears 23 and 24) and is transmitted to the small diameter gear 24.

Further, in this embodiment, the intermediate shaft 15 or the carrier 31
The carrier 31 rotates (revolutions) around the axes of the first internal shaft 11, the second input shaft 12, and the output shaft 14 in the housing 30, and integrally rotates the sector gear 32. It has a worm gear 33 that engages with the gear 32, and is rotated within a range until it comes into contact with the housing 30 (see FIG. 3). The worm gear 33 is rotatably assembled to the housing 30 and is connected to an electric motor 34 that can rotate in forward and reverse directions.
It is designed to be rotationally driven by. Note that the electric motor 34 has a configuration in which the current direction and the current value are controlled by the controller 53.
3 receives signals from a steering angle sensor 51 and a speed sensor 52.

In the gearbox configured as described above, when the steering wheel 10 is rotated, the first blade shaft 1
The first and second inner shafts 12 rotate, and the rotation is transmitted to the output shaft 14 via the variable angular velocity ratio gear train A and the speed increasing gear train B, and the rack par 17 is moved in the axial direction in accordance with the rotation of the output shaft 14. The wheels W are steered via the steering mechanism. In addition, at this time, the first human blade shaft 11 and the second blade shaft
A slight relative rotation occurs between the input shafts 12 and the control valve V operates, assisting the power cylinder C or the rack par 17 to move in the axial direction.

In this embodiment, since the invention is applied to a power steering device, the steering wheel 10 and the second input shaft 12
A small relative rotation occurs in between.

However, this difference is small and substantially the second input shaft 1
2 rotates following the steering of the steering wheel IO. Further, when the present invention is applied to manual steering, relative rotation due to twisting of the torsion bar does not occur.

In the above transmission system, since the variable angular velocity ratio gear train A is configured to increase the angular velocity ratio of the elliptical gear 22 to the elliptical gear 21 in accordance with the amount of rotation of the second inner shaft 12 from the neutral position, the steering When the amount of rotational operation of the wheel IO from the neutral position is small (when operating near the neutral position), the angular velocity ratio of the elliptical gear 22 to the elliptical gear 21 is set to a small value. Therefore, even if the rotation of the second inner shaft 12 transmitted via the variable angular velocity ratio gear train A is increased by a predetermined amount by the speed increasing gear train B, the amount of rotation of the output shaft 14 is the same as the amount of rotational operation of the steering wheel IO. The values are approximately equal and not very large, and driving stability is improved. In the graph shown by the solid line in FIG. 6, this appears as a characteristic in which the wheel turning angle changes gradually in a range where the value of the steering angle θ□ is small.

By the way, as the amount of rotational operation of the steering wheel 10 from the neutral position increases, the angular velocity ratio of the elliptical gear 22 to the elliptical gear 21 increases accordingly, and due to the synergistic effect with the speed increasing gear train B, the amount of rotation of the output shaft 14 increases. becomes larger, improving operability. This means that the solid line in Figure 6 is the steering angle θ.
This appears as a characteristic that increases rapidly as □ increases.

Next, the operation of the controller 53 and the motor 34 controlled thereby will be explained with reference to FIG.

FIG. 1 is a diagram showing a processing procedure executed by the controller 53, and this processing is repeatedly executed at very short predetermined time intervals.

In step 102, the signal from the speed sensor 52 is input and the vehicle speed V is determined manually. Step 103 is the steering angle sensor 5
1 signal is input and the steering angle θ8 is input. Step 10
4, the absolute value of the input steering angle θ8 is the predetermined steering angle θHMA.
It is compared with the absolute value of X.

Here, the predetermined steering angle θHMAX is set so that the force required to steer the direction of the wheels is within a relatively small range at a steering angle smaller than the predetermined steering angle θHMAX. When the determination in step 104 is YES, that is, while the steering angle is near the neutral position,
Read out the angle ratio K. Here, the angle ratio is determined in step 105.
As shown in the figure, it is mapped as a function of the vehicle speed V and stored in advance in the controller 53.

In step 105, the vehicle speed input in step 102 ~
The map is searched according to the value of , and the angle ratio K at the relevant speed is searched.

In step 106, the rotation angle θ of the motor 34 is calculated by multiplying the steering angle θ□ input in step 103 by the angle ratio K retrieved in step 105. and step 1
At step 07, the controller 53 outputs a drive signal to the motor 34 to set the rotation angle of the motor 34 to θ. Step 1
In step 08, the rotation angle of the motor calculated in step 106 is set to θ. shall be. And the above processing is lθ, 1≦1θHMA
It is executed repeatedly for X.

When 1θ)+1>oHMAX l, step 106 is skipped and θMB is substituted for the rotation angle θ of the motor 34 instead. Here θ. ]θH1>1θHMAX is the value of θ at the stage immediately before it becomes l. That is, θ141〉θ)IMAX
1, the rotation angle of the motor 34 is fixed to the angle at that time.

Note that in order to maintain the rotation angle of the motor 34 at a constant value, it is sufficient to simply stop energizing the motor 34. As is clear from FIG. 3, since the carrier 31 is connected to the motor 34 via a worm gear, even if a force that causes the carrier 31 to revolve acts, the motor 34 will not be rotated due to friction. be.

Next, the operation carried out by the process shown in Fig. 1 is explained in Fig. 4.5.6.
This will be explained with reference to the figures.

FIG. 4 shows the rotation angle θ of the motor 34 at low speed and high speed, with the horizontal axis representing the steering angle θH of the steering wheel. Here, when the speed is low, the angle ratio K is positive, as shown in step 105 in FIG. 1, and when the speed is high, it is negative.

FIG. 5 schematically shows the influence caused by the rotation of the motor 34, and FIG. 5(a) shows a state in which both the input shaft 12 and the pressure shaft 15 are in the neutral position, and the motor 34 is in the neutral position. It shows.

FIG. 5(b-2) shows a case where the vehicle is running at high speed and the angle ratio K is negative, and the rotation of the motor 34 with respect to the rotation angle θH of the input shaft 12 (assumed to be positive in the counterclockwise direction). A case is shown in which the positions of the carrier 31 and the intermediate shaft 15 rotate in the same direction due to the angle θM. The rotation angle on the intermediate shaft 15 side at this time is indicated by α.

FIG. 5(c-2) shows a case where the vehicle is at medium speed and the angle ratio is K or zero. The rotation angle on the intermediate shaft 15 side at this time is represented by β.

FIG. 5(d-2) shows a case where the vehicle is at low speed and the angle ratio K is positive, and the motor 34 rotates the carrier 31 or the intermediate shaft 15 in the opposite direction with respect to the rotation direction of the input shaft 12. . The rotation angle on the intermediate shaft 15 side at this time is indicated by γ.

As is clear from the above, if the angle ratio is positive, the carrier 31
If the input shaft 12 is negative, the drive current of the motor 34 is controlled to rotate in the same direction. In this case, as is clear from the illustration, α<β<γ. That is, the angle ratio K is changed depending on the vehicle speed, so that the lower the vehicle speed, the thicker the intermediate shaft 15 or the output shaft 14 (rotates,
It is understood that the rotation angle of the output shaft 14 becomes smaller as the speed increases.

In Fig. 6, the horizontal axis represents the steering angle (i.e., the rotation angle of the input shaft 12).
, the vertical axis shows the steering angle of the wheels, and the steering angle θ
8 is the predetermined steering angle θHMA! It is understood that the wheels are steered significantly at low speeds within the following range. Note that b-2 in Figure 6. The points indicated by c-2 and cl-2 are (
This corresponds to the states b-2), (c-2), and (d-2).

When the steering angle θ, (or the predetermined steering angle θl (MAX) or more, the motor 34 is fixed at that position, so when it is steered further, it can be considered that the influence of the rotation of the motor 34 has been removed. Fifth In the figure (b-1,), (cl), (
d-1) are respectively (b-2L (c-2L (d-2
), and the respective states are shown in b-1.) in Fig. 6. c-1,d
- Corresponds to the point shown in 1. There, the vehicle is in a low speed state θ
) After the IMAI steering results in the state shown in Figure 6 d-2, when further steering is performed, the subsequent curve (characteristic curve between the steering angle θ8 and the wheel turning angle) is as shown in the figure (1-1 onwards). It becomes equal to the curve.Similarly, when the vehicle is at high speed, θH□
8 After being steered to the state shown in Figure 6 b-2,
When the vehicle is further steered, the subsequent curve becomes equal to the curve after b-i shown in the drawing.

In other words, if the vehicle is at low speed, the positional relationship of the elliptical gears will achieve a large rotational transmission ratio while the vehicle is being steered to oHMAX, so even if the motor 34 is stopped afterwards, the rotational transmission ratio will not be maintained in the entire steering range. This results in a higher rotational transmission ratio than at high speeds.

Therefore, even if the motor 34 is rotated only near the neutral position, the steering angle of the steering wheel required to steer the wheels to the maximum is θ1 at low speeds, but θ2 at high speeds. It can be seen that both maneuverability at low speeds and steering stability at high speeds are achieved satisfactorily.

In the case of this embodiment, the rotation angle of the motor 34 is at most K.
MAX *θHMAX. Here, KMAX is the maximum value among the angle ratios mapped in advance.

Therefore, further rotation of the motor 34 can be prohibited.

Therefore, even if an abnormality occurs in the motor and its rotation becomes uncontrollable, the motor will be regulated by the rotation inhibiting member and will be prevented from running out of control, preventing a situation where it becomes impossible to operate. Ru.

As explained above, in this embodiment, a rotation transmission mechanism is provided between the input shaft and the output shaft in which the rotation transmission ratio increases as the input shaft is rotated from the neutral position, and the force required to rotate the wheels is small. Drives the motor only near the neutral position. Motors with low power can be used for this purpose.

When the steering angle increases, the motor is stopped, but while the motor is being driven, the motor is set to a state where a large rotational transmission ratio is obtained at low speeds and a small rotational transmission ratio at high speeds. Even if the steering wheel is stopped, it is possible to obtain a large rotational transmission ratio at low speeds and a small rotational transmission ratio at high speeds in the entire steering range.

[Brief explanation of the drawing]

FIG. 1 shows the motor 3 implemented by the controller 53.
4 is a diagram showing the control procedure of step 4, FIG. 2 is a diagram showing the overall configuration of the carrier box used in the present invention, and FIG. 3 is a diagram showing the control procedure of FIG.
■A cross-sectional view taken along the line, FIG. 4 is a characteristic line diagram showing the relationship between the steering wheel steering angle θ and the rotation angle of the motor 34, FIG. 5 is a diagram explaining the operation of the embodiment, and FIG. 6 is a steering wheel FIG. 3 is a characteristic line diagram of the steering angle of the vehicle and the turning angle of the wheels. Steering wheel 2nd input shaft output shaft intermediate shaft rack bar (steering mechanism) Oval gear (non-circular gear) Circular gear motor Rudder angle sensor Speed sensor controller Rudder angle comparison processing A Variable angular velocity ratio gear train B Speed-up gear train W- Wheel diagram 1

Claims (1)

[Scope of Claims] An input shaft connected to a steering wheel of a vehicle; an output shaft connected to a steering mechanism that changes the direction of the wheels with respect to the vehicle direction; rotation transmission between the input shaft and the output shaft. a rotation transmission mechanism that cooperates; a motor that imparts rotation to a portion of the rotation transmission mechanism to vary the ratio of the rotation angle of the input shaft to the rotation angle of the output shaft that rotates following the rotation transmission mechanism; and the steering wheel. a steering angle sensor that detects a steering angle from a neutral position of a wheel; a speed sensor that detects a running speed of a vehicle; A vehicle steering device comprising: a motor control means for driving and controlling the rotation angle of the motor based on a value detected by the motor.