JP3059012B2 - Steering gear - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering system.

[0002]

2. Description of the Related Art Generally, in a four-wheeled vehicle, the rotational motion of a steering wheel is converted into a linear motion by a rack and pinion, and the direction of the front wheels is changed by pushing and pulling a knuckle arm or the like, thereby performing a so-called steering operation. There is also known a power steering that facilitates a steering operation by using hydraulic or electric power. Further, a vehicle speed response type steering ratio variable device and a steering angle response type steering ratio variable device are known as means for achieving both the maneuverability and the steering stability of a vehicle. The steering gear ratio (steering ratio) is (steering wheel angle ÷ actual steering angle)
Assuming that the steering gear ratio (steering ratio) is Z, the actual steering angle is calculated by (steering wheel angle ÷ Z).

[0003] A vehicle speed response type steering ratio variable device has been proposed in, for example, Japanese Patent Application Laid-Open No. 58-224852. According to this publication, this device measures the vehicle speed, and according to the vehicle speed, a wheel steering angle (actual steering angle). ), The steering ratio of the steering wheel angle to the steering wheel angle is varied. By increasing the steering ratio at higher speeds, it is possible to achieve both low-speed steering and high-speed stability.

The steering angle response type steering ratio variable device changes the steering ratio in accordance with the magnitude of the steering wheel rotation angle. For example, the steering ratio is reduced as the steering wheel rotation angle increases, thereby reducing the steering speed. It is said that it is possible to achieve both rotation and high-speed stability.

[0005]

The movement that occurs when the vehicle turns is called yawing, and the angular velocity around an axis perpendicular to the vehicle body (generally called the Z-axis) is called yaw rate. It turns out that the way of yaw rate is different.

[0006] On the other hand, the vehicle speed response type steering ratio variable device depends on only the vehicle speed to change the steering ratio (steering gear ratio), and cannot respond to the change in the yaw rate of the vehicle. Therefore, in the vehicle-speed responsive steering ratio variable device, it is necessary for the driver to empirically predict the yaw rate and perform steering, and the steering operation becomes complicated.

[0007] The steering angle variable steering ratio variable device is good at high speeds, but at other low speeds, the steering ratio becomes too large and requires a large steering wheel rotation, thereby increasing driver fatigue. Furthermore, since the change in the steering ratio (steering gear ratio) depends only on the steering angle, it is not possible to cope with the change in the yaw rate of the vehicle, and the driver must empirically predict the yaw rate and steer. And the steering operation becomes complicated. Therefore, an object of the present invention is to provide a steering device that can reduce the burden on the driver.

[0008]

In order to achieve the above object, the present invention provides a control unit for a steering device, which determines a steering gear ratio in a high-speed region based on an upwardly convex constant yaw rate gain curve, and A central control device for determining a steering gear ratio in a low-speed region based on a constant lateral G gain constant curve.

Further, the central control device sets the steering gear ratio in the extremely low speed region in the low speed region to a constant ratio that reaches the maximum actual steering angle at the maximum normal steering angle, and sets the steering gear ratio in the other low speed regions to the lateral G ratio. It is even better if it is determined based on a constant gain curve.

[0010]

The control unit which receives the operation angle signal of the steering rotation shaft and the vehicle speed signal of the vehicle speed sensor receives either the constant yaw rate gain, the constant lateral G gain, or the constant reaching the maximum actual steering angle at the normal steering angle according to the vehicle speed. The steering wheel ratio is calculated on the basis of the steering gear ratio, and the wheels are steered based on the control command from the control unit.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals.
FIG. 1 is a side view of a grip-type steering device of the present invention. The grip-type steering device 1 has a gripping rod 3, a U ring 4, a pivot shaft 5, a grip absolute angle detecting mechanism 6, a torque on a steering rotation shaft 2. The sensor 7, the reaction force generating motor 8, and the grip rotation angle detecting mechanism 9 are arranged in series.

More specifically, the first side of the torque sensor 7
A bracket 11 is mounted with a plurality of hexagon socket head bolts 12, and a grip absolute angle detection mechanism 6 is mounted on the first bracket 11 with an elongated cross-shaped small screw 13, and a first shaft 7 a of the torque sensor 7 and a grip absolute angle detection are performed. The pivot shaft 5 is inserted in common with the mechanism 6, the U ring 4 is attached to the other end of the pivot shaft 5, the flat washer 14 and the nut 15
It is fixed at. The pivot shaft 5 and the U ring 4 are spline-coupled, and the relative mounting angle can be changed. The pivot shaft 5 is fastened to the first shaft 7a of the torque sensor 7 by a set screw 16 and a key 17. Set screw 16
Is screwed by a driver or the like through a notch (not shown) opened in the first bracket 11.

A sub bracket 18 is attached to the reaction force generating motor 8 to which the grip rotation angle detecting mechanism 9 is attached in advance with a plurality of hexagon socket head bolts 19, and the sub bracket 18 and the second bracket 21 are separated from each other. It is also fastened to the other side of the torque sensor 7 with a hexagon socket head cap screw 22. At this time, the motor shaft 8a is fitted to the second shaft 7b of the torque sensor 7.

FIG. 2 is a view taken in the direction of the arrow 2 in FIG. 1. The mounting seat 23 formed on the first bracket 11 is joined and fixed to, for example, the inner surface of the front door 25 by bolts 24. The same applies to the second bracket 21.

In FIG. 1, the grip absolute angle detecting mechanism 6 is a rotary variable resistor, a potentiometer, and a brush rotating together with the pivot shaft 5 slides on a fixed-side resistive element to output voltage. Is an analog instrument that converts the absolute angle of the grip bar 3 into an electric signal.

The torque sensor 7 measures a relative torque difference between the pivot shaft 5 and the motor shaft 8a, and includes a piezoelectric element and a strain gauge therein, and converts a distortion amount into a current or a voltage.

The reaction force generating motor 8 applies a predetermined rotational reaction force, that is, a response force to the grip bar 3, and is appropriately decelerated by a built-in speed reducer. The grip rotation angle detection mechanism 9 is a rotary encoder, that is, a mechanism that converts a rotation angle into an electric signal, and is, for example, a magnetic encoder.
It is a digital instrument that converts the rotation angle into the number of pulses.

FIG. 3 is a perspective view showing an example of use of the grip-type steering device of the present invention. The driver M grips the grip bar 3 of the grip-type steering device 1 with the right hand, and points to the left or right as indicated by arrows. Turn and steer. In the figure, 27 is a sheet, 28 is an instrument panel, and 29 is a rearview mirror.

FIG. 4 is a system diagram of the grip-type steering device according to the present invention. When the driver turns the grip bar 3 to the left or right, the grip rotation angle detecting mechanism 9 immediately transmits the rotation angle and direction signal to the electronic device. The control unit 30 (hereinafter referred to as “ECU3
0 "). The ECU 30 calculates the rotational reaction force in the arithmetic unit and outputs the motor 8 via the motor drive unit 31.
To give a rotational reaction force to the grip bar 3. The torque sensor 7 detects a difference between the torque applied to the first axis and the torque applied to the second axis (see FIG. 1), and sends this signal to the ECU 30 via the strain amplifier 32. The ECU 30 controls the motor 8 so that the torque difference becomes a predetermined value.

FIG. 5 is a calculation flow chart relating to the CPU (central control unit) of FIG. 4. In ST01 (step 1; the same applies hereinafter), the stick operation angle θ signal from the encoder and the vehicle speed V signal from the vehicle speed sensor are converted. Read. In this embodiment,
ST02 and ST03 discriminating steps are provided to classify the vehicle speed V into high speed, low speed, and extremely low speed. If the vehicle speed V is equal to or higher than the low / high speed switching speed Vh, the process proceeds to ST04. If it is equal to or less than the speed Vm, go to ST05,
If it is less than Vm, the process branches selectively to ST06.

ST04 relates to a steering gear ratio function Zh called a "constant yaw rate gain line", and the arithmetic expression is given by "Equation 1". As a result, the manner in which the yaw rate is output with respect to the operation angle does not differ depending on the vehicle speed, eliminating the need for the driver to perform the steering operation in a predictable manner, thereby ensuring stable driving performance and reducing the burden on the driver. .

[0022]

(Equation 1)

ST05 relates to a steering gear ratio function Zm called "lateral G gain constant line", and the arithmetic expression is given by "Equation 2". As a result, agility in a low-speed range where steering responsiveness of the vehicle is required is secured, and the amount of operation of the driver is reduced.

[0024]

(Equation 2)

ST06 sets a steering gear ratio to a steering gear ratio function Zl called "maximum actual steering angle achievement ratio", and the stick angle at which the driver can easily and normally turn the stick angle is set as a normal operation angle. In this case, the normal operation maximum angle {the front wheel maximum actual steering angle} is calculated. As a result, the actual steering angle is prevented from being maximized with a small operation angle, and the maximum actual steering angle can be realized with the maximum value of the operation angle, so that maneuverability of the vehicle at extremely low speed can be secured.

FIG. 6 is a graph showing an example of the relationship between the vehicle speed and the steering gear ratio according to the present invention, wherein the x-axis is the vehicle speed and the y-axis is the steering gear ratio Z. That is, in a high-speed region equal to or higher than Vh, the steering gear ratio Z is determined by the “yaw rate gain constant line” which is a curve that is upwardly convex, and Vm−Vh
In a low-speed region between the two, the steering gear ratio Z is determined by the “lateral G gain constant line” which is a downwardly convex curve, and 0-
In the extremely low speed range of Vm, the steering gear ratio Z is "the maximum actual steering angle achievement ratio". When the x coordinate is near Vm and Vh, adjacent curves are connected by a smooth line to prevent the value of the read steering gear ratio Z from becoming extremely discontinuous.

After the above processing, returning to FIG.
In step 8, the steering wheel angle θ is divided by the steering gear ratio Z to obtain a front wheel actual steering angle command value αf1. Next, a vehicle response tuning filter process is performed in ST09 to determine a front wheel actual steering angle command value αf (ST10). This may cause the responsiveness of the vehicle to become too sensitive in the extremely low / low speed range as shown in FIG. Therefore, the yaw rate rise is suppressed by passing through a tuning filter so that the driver does not feel uncomfortable.

The control signal via the front wheel gear box control routine of ST11 is a PWM (pulse width
The signal is converted into a pulse signal by a modulation) generator 33, and is turned via a PWM interface unit 34 and motor drive units 35 and 36.
The wheel 38 is driven to steer the wheels 39 and 40.

The absolute grip angle detection mechanism (potentiometer) 6 is a grip rotation angle detection mechanism (encoder).
As in the case of 9, the rotation angle from the neutral position of the grip bar 3 is monitored, and at the same time, the absolute angle of the grip is detected to determine the neutral position when the system is started up. It is also provided as a backup for the angle detection mechanism 9. For example, the ECU 30 compares the digital signal of the grip rotation angle detecting mechanism 9 with the analog signal of the potentiometer 6 and determines that the accuracy of each device is good if the difference between them is equal to or less than a certain value.

Next, the reason for selecting each curve in FIG. 6 will be described. Basically, by keeping the yaw rate gain constant, the way the yaw rate appears with respect to the operating angle does not differ depending on the vehicle speed, eliminating the need for the driver to perform the steering operation as expected, ensuring stable driving performance. As a result, the burden on the driver is reduced. However, in the low speed range, the lateral G gain is kept constant, and the start-up of the vehicle, that is, the agility is emphasized. Then, in the extremely low speed range such as garage with so-called stationary steering, it is necessary to reach the maximum actual steering angle at the normal operation maximum angle, so the maximum actual steering angle achievement ratio is selected, and a steering ratio less than this is necessary. And not.

FIG. 7 is a diagram showing another embodiment of FIG. 5, in which the calculation flow (ST02 to ST06) of FIG. 5 is replaced with a map ST02A. The map of ST02A is a chart or graph showing the relationship between the vehicle speed and the steering gear ratio, and the steering gear ratio is determined by giving the vehicle speed.

FIG. 8 is a graph showing the relationship between the vehicle speed and the steering gear ratio according to the present invention, and FIG. 6 shows an example of the relationship between the vehicle speed and the steering gear ratio according to the present invention. A relationship graph of the vehicle speed-steering gear ratio is selected according to the lateral G and the yaw rate.

Although the present invention has been described using a grip-type steering device in this embodiment, the present invention is not limited to this, and the present invention may be applied to a steering device using a normal steering wheel.

[0034]

As described above, according to the present invention, the control unit to which the operation angle signal of the steering rotation shaft and the vehicle speed signal such as the vehicle speed sensor are input, is provided with either the constant yaw rate gain or the constant lateral G gain according to the vehicle speed. The steering gear ratio is calculated based on the steering wheel, and the wheels are steered based on a control command from the control unit, so that steering stability is secured at high speeds, and the vehicle starts up at low speeds, The agility is improved, and the burden on the driver can be reduced.

If the maximum actual steering angle is achieved in the extremely low frequency range at the normal operation maximum angle, the so-called stationary steering becomes easy. As described above, according to the present invention, the driver can easily steer the vehicle at all vehicle speeds without being conscious of the vehicle motion.

[Brief description of the drawings]

FIG. 1 is a side view of a grip-type steering device of the present invention.

FIG. 2 is a view taken in the direction of arrow 2 in FIG. 1;

FIG. 3 is a perspective view showing an example of use of the grip-type steering device of the present invention.

FIG. 4 is a system diagram of a grip-type steering device of the present invention.

FIG. 5 is a flowchart showing the operation of the CPU (central control unit) shown in FIG. 4;

FIG. 6 is a graph showing an example of the relationship between vehicle speed and steering gear ratio according to the present invention.

FIG. 7 is a view showing another embodiment of FIG. 5;

FIG. 8 is a graph showing a relationship between a vehicle speed and a steering gear ratio according to the present invention.

[Description of Signs] 1 ... Steering device, 2 ... Steering rotating shaft, 3 ... Grip bar portion, 30 ... Control unit, Z ... Steering gear ratio, V
… Vehicle speed, θ… Stick operation angle.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B62D 125: 00 137: 00 (56) References JP-A-62-46768 (JP, A) JP-A-61-193969 (JP, A) JP-A-4-283168 (JP, A) JP-A-62-46774 (JP, A) JP-A-62-178474 (JP, A) JP-A-61-238570 (JP, A) JP-A-62 -46770 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6/00

Claims (2)

(57) [Claims] An operation angle signal of a steering rotary shaft and a vehicle speed signal of a vehicle speed sensor are input to a control unit, which calculates a steering gear ratio, and based on a control command from the control unit, turns a wheel. In the steering apparatus, the control unit determines a steering gear ratio in a high-speed region based on an upwardly convex constant yaw rate gain curve when the x axis is a vehicle speed and the y axis is a steering gear ratio. A steering device comprising a central control device for determining a steering gear ratio in a low speed region based on a constant lateral G gain constant curve. 2. The central control device sets a steering gear ratio in an extremely low speed region in a low speed region to a constant ratio that reaches a maximum actual steering angle at a normal steering maximum angle, and sets the steering gear ratios in other low speed regions to the same. 2. The steering apparatus according to claim 1, wherein the steering apparatus is determined based on a constant lateral G gain curve.