JP2001233227A - Steering device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized and light weight steering device for a vehicle at a low cost, with a simple control system and a small number of part items, capable of performing a traffic lane deviation preventing mechanism surely without causing interference problems with steering by a driver, without a special steering angle control mechanism. SOLUTION: A power steering hydraulic setting part 1 mainly performs a vehicle speed sensing type power steering controlling for setting an assisting force for a steering force corresponding to a vehicle speed. The set assisting force is corrected in correspondence to signals from a power steering hydraulic correction part 2, and a hydraulic pressure generation electric motor 6 is controlled to drive based on the corrected assisting force to vary a discharge pressure of a hydraulic generation pump 7. The power steering hydraulic correction part 2 calculates a target steering wheel angle from a front road shape (a curve information). An actual steering wheel angle obtained from a steering wheel angle sensor 5 is compared to the target steering wheel angle to set a correction factor to reduce and/or increase the assisting force.

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 for assisting a vehicle to safely enter a curve on a road ahead.

[0002]

2. Description of the Related Art In recent years, in order to improve the safety of vehicles,
2. Description of the Related Art A comprehensive driving assistance system (ADA; Active Drive Assist system) has been developed that actively supports the driving operation of a driver. This ADA system estimates various possibilities such as a collision with a preceding vehicle, a contact with an obstacle, a lane departure, and the like from the traveling environment information of the vehicle and a traveling state of the own vehicle, and is predicted to be unable to maintain safety. In this case, notification and other control are performed to the driver.

As a device for obtaining the traveling environment information of the vehicle, a laser radar device and the like have been conventionally known, but recently, an image of a landscape or an object in front of the vehicle captured by a plurality of cameras mounted on the vehicle. It has become possible to process information to three-dimensionally recognize roads and traffic environments with sufficient accuracy and time for practical use.

[0004] As for the lane departure prevention function, which is one of the functions of the ADA system, various steering controls are performed when it is determined that the vehicle deviates from the lane under the current driving conditions (vehicle speed, steering wheel angle, etc.). Steering devices have been proposed. For example, Japanese Patent Application Laid-Open No. 9-66853 discloses that in a hydraulic power steering vehicle, power assist is provided by applying a bias to a hydraulic control valve with a bias motor based on a target steering angle required to reach a set target point. There is disclosed a technique of changing the direction in the left-right direction or increasing the steering to avoid the danger of lane change.

[0005]

However, in the above prior art, an oil pump for hydraulic power steering using an engine as a driving source and an electric bias motor for correcting an assist force with respect to a steering force are required, and a control system is also required. An independent system for controlling the oil pump and a system for controlling the bias motor are required, and the number of parts is large, the steering device becomes large, and there is a problem that it is disadvantageous in weight and cost.

The present invention has been made in view of the above circumstances, and does not require a special steering angle control mechanism, has a simple control system, has a small number of parts, is small and light, and is inexpensive. It is an object of the present invention to provide a vehicle steering system that can reliably exhibit a lane departure prevention function without causing an interference problem.

[0007]

According to a first aspect of the present invention, there is provided a vehicle steering system comprising: a front road shape recognition unit for detecting a road shape ahead; and a vehicle speed detection unit for detecting a vehicle speed. Actual steering wheel angle detecting means for detecting an actual steering wheel angle; target steering wheel angle calculating means for calculating a target steering wheel angle based on the front road shape, the vehicle speed, and the actual steering wheel angle; Assist force setting means for setting an assist force with respect to a steering force according to a state; assist force correcting means for comparing the actual handle angle with the target handle angle to correct the assist force; and the assist force setting means. An electric motor for generating hydraulic pressure based on a signal from the motor, a pump for generating hydraulic pressure using the electric motor for generating hydraulic pressure as a drive source, and Characterized in that a hydraulic power steering apparatus that operates by the generated hydraulic pressure of the pump.

In the vehicle steering system according to the first aspect, first, a road shape ahead of the vehicle is detected by the road shape recognizing means.
The vehicle speed is detected by the vehicle speed detecting means, and the actual steering wheel angle is detected by the actual steering wheel angle detecting means. The target steering wheel angle calculating means calculates a target steering wheel angle based on the shape of the road ahead, the vehicle speed, and the actual steering wheel angle. Then, the assist force for the steering force is set by the assist force setting means according to the running state of the vehicle. This assist force is corrected and set by comparing the actual steering wheel angle with the target steering wheel angle by the assist force correcting means. In this manner, the hydraulic pressure generating electric motor is driven and controlled based on the signal from the assist force setting means,
The hydraulic pressure generating pump generates a hydraulic pressure using the hydraulic pressure generating electric motor as a drive source, and the generated hydraulic pressure operates the power steering device.

A vehicle steering apparatus according to the present invention according to claim 2 is a vehicle steering apparatus according to claim 1,
The assist force correcting means compares the absolute value of the actual steering wheel angle with the absolute value of the target steering wheel angle, and if the absolute steering wheel angle is larger than the absolute value of the target steering wheel angle, While the assist force is corrected to be lower, the correction is made to increase the assist force when the absolute value of the actual handle angle is smaller than the absolute value of the target handle angle.

That is, if the absolute value of the actual steering wheel angle is larger than the absolute value of the target steering wheel angle and it is determined that the steering wheel is turned too much, the assisting force correcting means reduces the assisting force to reduce the steering force. If it is determined that the steering wheel feels heavier than usual and the absolute value of the actual steering wheel angle is smaller than the absolute value of the target steering wheel angle and the steering wheel is not turned, the assist force is increased to make the steering force lighter than usual.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 relate to an embodiment of the present invention. FIG. 1 is a functional block diagram showing the overall configuration of a vehicle steering system, FIG. 2 is a simplified explanatory diagram of the operation of a hydraulic system, and FIG. FIG. 4 is a characteristic diagram illustrating the correction, and FIG. 4 is a flowchart of the hydraulic pressure correction control in the power steering hydraulic pressure correction unit.

As shown in FIG. 1, in a vehicle steering system according to the present invention, a power steering oil pressure setting unit 1 as an assist force setting unit and a power steering oil pressure correction unit 2 as an assist force correction unit are used as control systems. The output signal from the power steering oil pressure correction unit 2 is configured to be input to the power steering oil pressure setting unit 1.

The power steering oil pressure setting unit 1 is connected to a vehicle speed sensor 3 as vehicle speed detecting means, and the power steering oil pressure correction unit 2 is connected to a vehicle speed sensor 3.
And front road shape recognition unit 4 as front road shape recognition means
And a steering wheel angle sensor 5 as an actual steering wheel angle detecting means, an output signal from the power steering hydraulic pressure setting unit 1 is output to a hydraulic pressure generating electric motor 6, and the hydraulic pressure generating electric motor 6 is drive-controlled. It is supposed to.

The power steering oil pressure setting unit 1 includes:
Based on a vehicle speed-sensitive power steering control that sets an assist force with respect to a steering force according to the vehicle speed, the set assist force is further corrected in accordance with a signal from the power steering oil pressure corrector 2, and the corrected assist force is corrected. , And mainly comprises an assist oil pressure setting section 1a, an assist oil pressure change section 1b, a target current setting section 1c, and a current control section 1d.

The assist hydraulic pressure setting section 1a selects a map of characteristics (correspondence map of assist force and steering torque) corresponding to the current vehicle speed from a plurality of maps of assist force characteristics set in advance. is there.

The assist hydraulic pressure changing section 1b changes and sets the selected map based on a signal input from the power steering hydraulic pressure correcting section 2. In the present embodiment, as will be described later, correction is performed by multiplying a correction coefficient input from the power steering oil pressure correction unit 2 by the assist force of the map.

The target current setting section 1c is required to generate the assist force corrected by the assist oil pressure change section 1b with reference to the characteristic diagram of the hydraulic pressure generating electric motor 6 obtained and set in advance through experiments and the like. Set the appropriate current as the target current.

The current control section 1d includes a target current setting section 1
The drive of the hydraulic pressure generating electric motor 6 is controlled by the target current set in c.

The power steering oil pressure correction unit 2 includes:
A target steering wheel angle is calculated from the road shape ahead (curve information) according to a flowchart of hydraulic pressure correction control described later, and the target steering wheel angle and the current steering wheel angle (actual steering wheel angle) obtained from the steering wheel angle sensor 5 are calculated. This is for setting a correction coefficient for the assist force by comparison, and is mainly composed of a target steering wheel angle setting unit 2a, a steering wheel angle comparison unit 2b, and a control characteristic change instruction unit 2c.

The target steering wheel angle setting unit 2a calculates a target steering wheel angle based on the following formula (1) based on the vehicle speed V from the vehicle speed sensor 3 and the curve radius ρ of the front road from the front road shape recognition unit 4, for example. Calculate the angle θHT.

ΘHT = (1 + A · V ² ) · (L / ρ) · G (1) where L is a wheelbase, A is a stability factor which is a steer characteristic inherent to the vehicle, and G is a steering gear ratio. It is.

The handle angle comparator 2b calculates the absolute value of the target handle angle θHT and the absolute value of the actual handle angle θH obtained by the handle angle sensor 5, and calculates the actual handle angle from the absolute value of the target handle angle θHT. deviation Δθ of the absolute value of θH (=
| ΘHT | − | θH |), and the control characteristic change instructing unit 2
output to c.

The control characteristic change instructing unit 2c sets a correction coefficient of the assist force with reference to a map previously set by an experiment or the like according to the deviation Δθ from the steering wheel angle comparing unit 2b. The power is output to the assist hydraulic pressure changing unit 1b of the power steering hydraulic pressure setting unit 1.

For example, as shown in FIG. 3, when the road ahead has a right curve as shown in FIG. 3 (a), the power steering hydraulic pressure setting unit 1 usually uses the assist hydraulic pressure setting unit 1a according to the vehicle speed according to the vehicle speed. When the deviation Δθ is 0), 1 is set as the assist force correction coefficient, and an assist force having characteristics as shown in FIG. 3B is set.

Here, when the deviation .DELTA..theta. Is inputted as a positive value from the steering wheel angle comparing section 2b of the power steering oil pressure correcting section 2, that is, when | .theta.H | <| .theta.HT | In the section 2c, a value larger than 1 is set as a correction coefficient of the assist force, and is output to the assist oil pressure change section 1b of the power steering oil pressure setting section 1. Then, the assist hydraulic pressure changing unit 1b multiplies the normal assist force characteristic by this correction coefficient, and corrects the assist force so that the assist force becomes larger than normal (FIG. 3C).

That is, if | θH | <| θHT |, and it is determined that the steering wheel is not short on the curve ahead, the assist force is made larger than usual and the steering force is made lighter than usual. Urge the driver to steer further.

On the other hand, when a negative value of the deviation Δθ is input from the steering wheel angle comparison unit 2b of the power steering oil pressure correction unit 2, that is, when | θH |> | θHT | In the instructing unit 2c, a value smaller than 1 and larger than 0 is set as a correction coefficient of the assist force, and is output to the assist oil pressure changing unit 1b of the power steering oil pressure setting unit 1. Then, the assist hydraulic pressure changing unit 1b multiplies the normal assist force characteristic by this correction coefficient, and corrects the assist force so that the assist force is smaller than normal (see FIG. 3).
(D)).

That is, if | θH |> | θHT |, and it is determined that the steering wheel is turned too far against the curve ahead, the assist force is made smaller than usual and the steering force is made heavier than usual. And prompt the driver to return the steering wheel.

In the present embodiment, the front road shape recognizing section 4 extracts a front road from image data in front of the vehicle using a white line or the like, recognizes the road shape three-dimensionally, and determines the bending direction, Detects information such as the radius of a curve.
It is composed of CD cameras 4a, 4a and a road shape detector 4b ahead.

The pair of CCD cameras 4a, 4a are attached at a fixed interval in front of the ceiling in the vehicle compartment, stereoscopically image an object in front of the vehicle from different viewpoints, and output an image signal to the front road shape detecting section 4b. .

The front road shape detection section 4b divides the imaged scenery given by the image signals from the pair of CCD cameras 4a, 4a into small areas, and performs stereo image processing of the object for each of the small areas to perform three-dimensional processing. , And obtain image data of the distance distribution of the three-dimensional coordinates of each object. Then, white lines, guardrails, curbs, etc. are extracted from the image data of this distance distribution, these are approximated by polygonal lines, and the area surrounded by the left and right polygonal lines is determined as the own lane, and the horizontal component of the data of this own lane is determined. , A road curve is detected by a vertical component, and a road component is detected three-dimensionally from a near side to a distant side.

The electric motor 6 for generating oil pressure, which is driven and controlled by the power steering oil pressure setting unit 1, serves as a driving source of a pump 7 for generating oil pressure. Is varied.

The hydraulic pressure generated by the hydraulic pressure generating pump 7 is introduced into a power cylinder 9 integrated with a steering gear box 8.
0 are respectively extended and connected to knuckle arms (not shown) of the left and right wheels 11.

Next, the hydraulic system of the vehicle steering system will be described.
This will be described with reference to FIG.

The hydraulic pressure generating pump 7 is driven by a belt by a hydraulic pressure generating electric motor 6 and discharges hydraulic oil. The discharged hydraulic oil is supplied to a hydraulic pressure generating electric motor 6 by a flow control valve 12. An appropriate amount is controlled in accordance with the number of revolutions of the motor 6 and supplied to the control valve 14 via the hose A13.

When the steering wheel 15 is steered, the control valve 14 connected to the pinion shaft 16 operates to form a flow path of hydraulic oil according to the steering direction, and the hydraulic oil passes through the pipe A17 or B18. Is supplied to the working chamber A or the working chamber B of the power cylinder 9. The hydraulic oil that has entered one of the working chambers acts on the rack piston 19 to generate a right or left axial force on the rack shaft 20 to assist and reduce the steering force.

Thus, the movement of the rack piston 19 causes the hydraulic oil in the other working chamber to be pushed back, and the pipe A17
Alternatively, the oil is returned to the oil reservoir 22 via the pipe B18, the control valve 14, and the hose B21.

In the vehicle steering system configured as described above, first, the assist oil pressure setting unit 1a of the power steering oil pressure setting unit 1 determines the current vehicle speed from a plurality of assist force characteristic maps set in advance. Select the corresponding property map. This characteristic map is corrected by multiplying the assist force by a correction coefficient input from the power steering hydraulic pressure correction unit 2 in the assist hydraulic pressure change unit 1b.

Next, the target current setting section 1c refers to the characteristic diagram of the hydraulic pressure generating electric motor 6 obtained and set in advance through experiments or the like to generate the assist force corrected by the assist hydraulic pressure changing section 1b. The required current is set as a target current, and the current control unit 1d drives and controls the hydraulic pressure generating electric motor 6 with the target current set by the target current setting unit 1c.

When the hydraulic pressure generating electric motor 6 is driven by the target current, oil is discharged from the hydraulic pressure generating pump 7 into the steering gear box 8 with a hydraulic pressure corresponding to the target current, and an assist force with respect to the steering force is generated. Occurs.

As shown in the flow chart of FIG. 4, the hydraulic pressure correction control by the power steering hydraulic pressure correction unit 2 first includes a step (hereinafter abbreviated as “S”) 101 in which the front road shape recognition unit 4 outputs the front road shape. The curve information (curve direction, curve radius) of the vehicle speed sensor 3 is read in S102.
Read the vehicle speed from.

Then, the program proceeds to S103, in which the target steering wheel angle setting section 2a calculates the target steering wheel angle by the above equation (1), and proceeds to S104 to read the actual steering wheel angle from the steering wheel angle sensor 5, and then proceeds to S105. The steering angle deviation is calculated by the steering wheel angle comparison unit 2b.

Then, the process proceeds to S106, in which the control characteristic change instructing unit 2c refers to a map set in advance by experiments or the like in accordance with the deviation of the steering wheel angle calculated in S105, and calculates a correction coefficient of the assist force. Set. This correction coefficient is set to a value larger than 1 when the deviation of the steering wheel angle is a positive value, and set to a value smaller than 1 and larger than 0 when the deviation of the steering wheel angle is a negative value. When the deviation of the steering wheel angle is 0, 1 is set as the assist force correction coefficient.

Then, the process proceeds to S107 and proceeds to S106.
Is output to the assist hydraulic pressure changing unit 1b of the power steering hydraulic pressure setting unit 1, and the routine exits.

In this way, when the steering angle comparison unit 2b of the power steering oil pressure correction unit 2 determines that the steering angle deviation is a positive value and the steering wheel is not enough for the curve ahead, Control characteristic change instructing unit 2c
By multiplying the normal characteristic map by the correction coefficient of the assist force larger than 1 from the above, the assist force becomes larger than usual and the steering force becomes lighter than usual, and the driver is urged to perform further steering.

On the other hand, when the steering angle comparison unit 2b of the power steering oil pressure correction unit 2 receives a negative steering angle deviation and determines that the steering wheel is turned too far against the curve ahead, 1 from the control characteristic change instructing unit 2c
By multiplying the normal characteristic map by a correction coefficient of an assist force smaller than 0, the assist force becomes smaller than usual and the steering force becomes heavier than usual, and the driver is urged to steer in the direction of returning the steering wheel.

As described above, according to the embodiment of the present invention, the hydraulic pressure generating pump 7 for generating the assisting force for the steering force is driven by the hydraulic pressure generating electric motor 6, and the hydraulic pressure generating electric motor 6 is normally used. The power steering control is corrected by the control of the lane departure prevention function and the drive is controlled, so that it is possible to achieve both the power steering function and the lane departure prevention function with one power source that assists the steering force it can. For this reason, it is possible to configure a steering device with a simple control system, a small number of components, a small size, a light weight, and a low cost without providing a special steering angle control mechanism.
In addition, since the lane departure prevention function is achieved by increasing or decreasing the assist force more than usual, the problem of interference with steering by the driver does not occur.

In this embodiment, the shape of the road ahead is
Although an example has been described in which recognition is performed based on stereo images obtained from the pair of CCD cameras 4a, 4a, detection may be performed based on another method, for example, road information obtained from a navigation device. Further, the power steering oil pressure setting unit 1 is based on the vehicle speed sensitive control, but may be another engine speed sensitive control or a combination thereof.

[0049]

As described above, according to the first aspect of the present invention, the shape of the road ahead, the vehicle speed, and the actual steering wheel angle are detected, and the target steering wheel angle is calculated based on these to calculate the actual steering wheel angle. The steering wheel angle and the target steering wheel angle are compared with each other to correct the assist force with respect to the steering force set according to the traveling state of the vehicle, and the hydraulic pressure serving as the drive source of the hydraulic pressure generating pump is adjusted to the corrected assist force. Since the generation electric motor is driven and controlled, there is no need to provide a special steering angle control mechanism, a simple control system, a small number of parts, small size, light weight, low cost, and the problem of interference with driver steering. The lane departure prevention function can be reliably exhibited without any occurrence.

In this case, as in the second aspect of the present invention,
The absolute value of the actual steering wheel angle is compared with the absolute value of the target steering wheel angle, and if the absolute steering wheel angle is larger than the absolute steering wheel angle, the assist force is corrected to be lower while the actual steering wheel angle is corrected. If the absolute value of the steering wheel angle is smaller than the absolute value of the target steering wheel angle, the assist force is corrected to be increased, and if it is determined that the steering wheel is turned too much, the assist force is reduced to reduce the steering force. Makes the driver feel heavier than usual, but if it is determined that the driver will not turn the steering wheel, the assist force can be increased to make the driver feel the steering force lighter than usual,
There is no problem of interference with steering by the driver.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing the overall configuration of a vehicle steering system.

FIG. 2 is a simplified explanatory diagram of the operation of the hydraulic system.

FIG. 3 is a characteristic diagram illustrating correction of an assist force.

FIG. 4 is a flowchart of hydraulic pressure correction control in a power steering hydraulic pressure correction unit.

[Explanation of symbols]

Reference Signs List 1 power steering oil pressure setting unit (assisting force setting means) 2 power steering oil pressure correcting unit (assisting force correcting means) 3 vehicle speed sensor (vehicle speed detecting means) 4 forward road shape recognition unit (forward road shape recognition means) 5 steering wheel angle sensor ( Actual steering wheel angle detecting means) 6 Electric motor for generating hydraulic pressure 7 Pump for generating hydraulic pressure 8 Steering gear box 9 Power cylinder 15 Handle

Claims (2)

[Claims] 1. A front road shape recognizing means for detecting a shape of a road ahead, a vehicle speed detecting means for detecting a vehicle speed, an actual steering wheel angle detecting means for detecting an actual steering angle, Target steering wheel angle calculating means for calculating a target steering wheel angle based on the actual steering wheel angle; assist force setting means for setting an assist force with respect to a steering force according to a traveling state of the vehicle; Assist force correction means for correcting the assist force by comparing with the target steering wheel angle, an electric motor for generating hydraulic pressure for controlling drive based on a signal from the assist force setting means, and driving the electric motor for generating hydraulic pressure A hydraulic pressure generating pump that generates a hydraulic pressure as a source, and a hydraulic power steering device that operates by the hydraulic pressure generated by the hydraulic pressure generating pump. A steering device for a vehicle, comprising: 2. The assist force correcting means compares the absolute value of the actual steering wheel angle with the absolute value of the target steering wheel angle, and determines the absolute value of the actual steering wheel angle as the absolute value of the target steering wheel angle. If the absolute value of the actual steering wheel angle is smaller than the absolute value of the target steering wheel angle, the assisting force is corrected to be increased while the assisting force is corrected to be lower when the steering angle is larger. The vehicle steering device according to claim 1.