JP4722959B2 - Rear wheel toe angle variable vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit deterioration of control stability when one of a right and a left variable rear wheel toe angle control device fails in a variable rear wheel toe angle vehicle. <P>SOLUTION: An automobile V provided with the variable rear wheel toe angle control devices 10L, 10R provided on a right and a left rear wheel 5R, 5L respectively and variably controlling toe angle of a rear wheel 5, is provided with stroke sensors 16L, 16R provided on the right and the left rear wheel respectively and detecting toe angle &theta; of the corresponding rear wheel 5, and a maximum vehicle speed setting part 53 setting an upper limit value of allowable vehicle speed as the maximum vehicle speed V<SB>max</SB>. The maximum vehicle speed setting part 53 sets the maximum vehicle speed V<SB>max</SB>lower as toe out amount of the rear wheel 5 is larger if at least one of rear wheels 5 becomes uncontrollable under a toe-out condition, and sets the maximum vehicle speed V<SB>max</SB>to the same value as the maximum vehicle speed V<SB>max</SB>corresponding to the maximum toe-out amount if the stroke sensor 16 fails. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a rear wheel toe angle variable vehicle including a pair of rear wheel toe angle variable control devices that independently change the toe angles of left and right rear wheels, and in particular, the rear wheel toe angle variable control device becomes uncontrollable. The present invention relates to a control technique for ensuring steering stability in the case of accidents.

  In a four-wheeled vehicle, generally, a toe angle is set on the front wheels to ensure steering stability, and the left and right front wheels are steered when changing the traveling direction. In recent years, it is possible to control the toe angle of the rear wheels in order to increase the stability during braking and responsiveness during acceleration, or to prevent oblique running during high-speed turning and improve turning performance during low-speed turning. An automobile equipped with a variable toe angle control device has been developed.

  As such a toe angle variable control device, the left and right rear wheels are each provided with an electric actuator that linearly displaces the lateral link in the suspension device that supports the rear wheel or the connecting portion of the trailing link to the vehicle body, and these are driven to extend and contract. Is known so that the toe angles of the left and right wheels can be variably controlled individually (see Patent Document 1).

By the way, when the electric actuator is configured with a feed screw mechanism, if the rear wheel toe angle control device becomes uncontrollable due to a failure, the actuator is fixed in that state by the self-locking function of the screw, and the rear wheel toe angle is controlled. become unable. Therefore, for example, as a rear wheel toe angle control method when abnormality occurs in one of the left and right independent control type toe angle variable control devices, the left and right rear wheels are made symmetrical with respect to the actuator on the side where no failure has occurred. A method for toe control has been proposed by the present applicant as Japanese Patent Application No. 2006-228552.
Japanese Patent Laid-Open No. 9-30438

  However, if one of the rear wheels becomes toe-out and the toe control becomes impossible, the vehicle not only shows an oversteer tendency when turning, but also decreases the straight-line stability against disturbances such as crosswinds. In particular, as the motion characteristics of the vehicle, the stability decreases as the toe-out amount increases, and the stability tends to decrease as the vehicle speed increases even at the same toe-out amount. Therefore, when the rear wheels are in a toe-out state and cannot be controlled during high-speed running, the stability of the vehicle may be significantly reduced.

  The present invention has been made in view of such a background, and provides a rear wheel toe angle variable vehicle that can suppress deterioration in steering stability when one of the left and right rear wheel toe angle variable control devices breaks down. With the goal.

In order to solve the above problems, the present invention is a rear wheel toe angle variable vehicle provided with a rear wheel toe angle variable control device that is provided for each of the left and right rear wheels and variably controls the toe angle of the corresponding rear wheel. Te, provided respectively left and right rear wheels, comprising: a toe angle detecting means for detecting the toe angles of the rear wheels corresponding, the maximum vehicle speed setting means for setting an upper limit value of the acceptable speed as the maximum vehicle speed, the highest The vehicle speed setting means sets the maximum vehicle speed lower than the normal maximum vehicle speed when at least one rear wheel becomes uncontrollable in a toe-out state , and detects the left and right rear wheels detected by the toe angle detection means. The maximum vehicle speed is set to be lower as the total value of the toe-out angles is larger .

In the rear wheel toe angle variable vehicle having the above configuration, when one of the toe angles of the left and right rear wheels detected by the toe angle detecting means is on the toe out side and the other is on the toe in side, The maximum vehicle speed may be set lower as the value obtained by subtracting the toe-in angle increases .

In the wheel toe angle variable vehicle after the above-described configuration, before Symbol maximum vehicle speed setting means, before Symbol toe angle detecting means if a failure is set to the same as the maximum vehicle speed corresponding to the maximum toe-out angle the maximum vehicle speed Configure as follows.

  According to the present invention, when at least one of the left and right rear wheel toe angle variable control devices becomes uncontrollable in the toe-out state, the maximum vehicle speed is set to be lower than that in the normal state, so that high-speed traveling with poor steering stability is achieved. Can be suppressed. In addition, as the toe-out amount of the rear wheel increases, the maximum vehicle speed is set lower, thereby ensuring the predetermined steering stability and ensuring the vehicle performance as free as possible even after a failure occurs. Become.

  Also, if at least one of the left and right rear wheel toe angle variable control devices becomes uncontrollable in the toe-out state, the maximum vehicle speed is set lower as the toe-out amount of the rear wheel is larger, and the toe angle detection means fails. By setting the maximum vehicle speed equal to the maximum vehicle speed corresponding to the maximum toe-out amount, it is possible to ensure predetermined steering stability even if the toe angle at the time of the failure is unknown.

<< Configuration of Embodiment >>
<Overall configuration of automobile>
Hereinafter, an embodiment of a rear wheel toe angle variable vehicle according to the present invention will be described in detail with reference to the drawings. In the description, for the wheels and the members arranged therewith, that is, tires, electric actuators, etc., suffixes L or R indicating left and right are attached to the numerals, respectively, for example, left rear wheel 5L, right rear For example, the rear wheel 5 or the rear wheels 5L and 5R are collectively referred to as the wheel 5R.

  FIG. 1 is a schematic configuration diagram of an automobile V including left and right rear wheel toe angle variable control devices 10L and 10R according to the embodiment. The vehicle V includes front wheels 3L and 3R fitted with tires 2L and 2R, and rear wheels 5L and 5R fitted with tires 4L and 4R. The front wheels 3L and 3R and the rear wheels 5L and 5R are It is suspended from the vehicle body 1 by left and right front suspensions 6L, 6R and rear suspensions 7L, 7R.

  The vehicle V also includes a front wheel steering device 9 that directly steers the front wheels 3 via a rack and pinion mechanism by steering the steering wheel 8, and left and right electric actuators provided for the left and right rear suspensions 7L and 7R. Left and right rear wheel toe angle variable control devices 10L and 10R for individually changing the toe angles of the rear wheels 5L and 5R by extending and retracting 11L and 11R are provided. Although detailed illustration is omitted, the electric actuator 11 includes a housing connected to the vehicle body 1 side, a motor housed in the housing, a speed reducer, a feed screw mechanism using trapezoidal screws, and a female screw member of the feed screw mechanism. In addition, it is composed of an output rod or the like connected to the rear wheel 5 side, and linearly expands and contracts by converting the rotational motion of the motor into thrust motion by a feed screw mechanism. The feed screw mechanism has a self-locking function depending on the relationship between the lead angle and the friction angle of the screw, and has a structure that does not reverse-differentiate even if there is an input from the output rod side.

  In addition to an ECU (Electronic Control Unit) 12 that controls various systems and a vehicle speed sensor 13, the vehicle V is provided with various sensors (not shown). Provided for control. The ECU 12 includes a microcomputer, a ROM, a RAM, peripheral circuits, input / output interfaces, various drivers, and the like, and is connected to each sensor 13 and an MCU (Motor Control Unit) 14 described later via a communication line. Yes. The ECU 12 calculates the target toe angle of the rear wheels 5 based on the detection results of the sensors 13 and the like, calculates the stroke amount of each electric actuator 11, and outputs a drive control signal to the MCU 14, thereby The toe control of the wheels 5L and 5R is performed separately on the left and right.

  The ECU 12 regulates the maximum speed of the automobile V by controlling the fuel injection device 15 provided in the engine E based on the detection results of the sensors 13 and the like. The maximum speed is normally 180 km / h, for example, but is variably set by the ECU 12 as an allowable upper limit of the vehicle speed according to the state of the vehicle V.

  The MCU 14 includes a microcomputer, ROM, RAM, peripheral circuits, input / output interfaces, various drivers, and the like. The MCU 14 drives and controls the electric actuator 11 based on the drive control signal output from the ECU 12, Detection of a failure of the electric actuators 11L and 11R based on the detection value of the current sensor flowing in the electric actuator 11 and the detection value of the stroke sensor 16 installed in the left and right electric actuators 11 and the detection value of the current detection means Including failure detection means. When the failure of the electric actuator 11 is detected, the MCU 14 outputs an actuator failure signal to the ECU 12. When the detection signal of the stroke sensor 16 cannot be received or when the detection signal exceeds the detectable range, the MCU 14 sends the sensor failure signal to the ECU 12. Output to.

  Stroke sensors 16L and 16R as toe angle detection means detect the stroke amount of each output rod by detecting the positions of magnets arranged close to each other from the differential transformer. When the detection signal of the stroke sensor 16 is fed back to the MCU 14, the electric actuator 11 expands and contracts by the stroke amount calculated by the ECU 12, and changes the left and right rear wheels 5L and 5R to a desired toe angle.

  According to the vehicle V configured as described above, the left and right electric actuators 11L and 11R are simultaneously symmetrically displaced to freely control toe-in / to-out of the left and right rear wheels 5L and 5R under appropriate conditions. In addition, if one of the left and right electric actuators 11L and 11R is extended and the other is contracted, the left and right rear wheels 5L and 5R can be steered left and right. For example, the vehicle V changes the rear wheel 5 to toe-out during acceleration, the rear wheel 5 to to-in during braking, and the rear wheel 5 during high-speed turning, based on the vehicle motion state grasped by various sensors in order to improve steering stability. The wheel 5 is in phase with the front wheel rudder angle, and the rear wheel 5 is toe-changed (turned) in phase opposite to the front wheel rudder angle during low-speed turning.

<Functional configuration of rear wheel toe angle variable control device>
FIG. 2 is a schematic block diagram of the left and right rear wheel toe angle variable control device 10. As shown in the figure, the ECU 12 mounted on the vehicle V includes an input interface 51, a failure determination unit 52, a maximum vehicle speed setting unit 53, and an output interface 54 as components.

The input interface 51 receives a vehicle speed signal detected by the vehicle speed sensor 13, detection signals of the left and right stroke sensors 16L and 16R output by the MCU 14, an actuator failure signal, and a sensor failure signal. The failure determination unit 52 determines the operating state of the rear wheel toe angle control device 10 based on various signals input from the MCU 14. Maximum vehicle speed setting unit 53 sets the maximum vehicle speed V _max, based on the determination result of the fault determination unit 52 and the vehicle speed signal. When the set maximum vehicle speed signal is output to the fuel injection device 15 via the output interface 54, the amount of fuel injected by the fuel injection device 15 is controlled, and the vehicle speed of the automobile V is regulated.

<< Effects of Embodiment >>
Next, the operation of this embodiment will be described. FIG. 3 is a flowchart showing a maximum vehicle speed setting procedure by the rear wheel toe angle variable vehicle V according to the embodiment. When the vehicle V receives an actuator failure signal or a sensor failure signal from the MCU 14 while traveling, the vehicle V performs the maximum rear wheel vehicle speed setting process shown in FIG.

  First, the ECU 12 determines in the failure determination unit 52 whether or not the rear wheel toe angle is uncontrollable (step 1). In this determination, when an actuator failure signal for either the left or right actuator 11 or a sensor failure signal for the left or right stroke sensor 16 is input from the MCU 14, the rear wheel toe angle control is not possible ( Only if none of these signals is input, it is determined that the rear wheel toe angle control is possible (No). Therefore, it is not determined No in this embodiment. However, although not shown here, it is also possible to determine that control is possible even when any fault signal is input by the fault tolerant design.

  On the other hand, when it is determined in step 1 that the rear wheel toe angle control is impossible (Yes), the failure determination unit 52 determines whether or not the cause of the control failure is a failure of the stroke sensor 16 (step 2). In this determination, when a sensor failure signal is input for one of the left and right stroke sensors 16 or both, it is determined that the stroke sensor has failed (Yes), and when none of these signals is input, the stroke sensor It is determined that there is no failure (No).

  If it is determined in step 2 that there is no stroke sensor failure (No), the failure determination unit 52 obtains the toe angle θ of the rear wheel 5 that has become uncontrollable from the detection result of the stroke sensor 16 input via the MCU 14. (Step 4). On the other hand, if it is determined in step 2 that the stroke sensor has failed (Yes), the failure determination unit 52 determines the toe angle θ of the rear wheel 5 that has become uncontrollable as the maximum toe-out angle that can be taken due to the structure of the electric actuator 11. Assume (step 3).

  Here, when only one of the left and right actuators 11 fails and it is determined that the toe angle control is impossible, the toe angle θ of the rear wheel 5 that has become uncontrollable is not controllable, for example, as shown in FIG. The angle θ with respect to the axle X of the right rear wheel 5R. On the other hand, when it is determined that the toe angle control is impossible due to the failure of both the left and right actuators 11, the toe angle θ of the rear wheel 5 that has become uncontrollable becomes uncontrollable as shown in FIG. 5, for example. The sum angle of the angle θR with respect to the axle X of the right rear wheel 5R and the angle θL with respect to the axle X of the left rear wheel 5L that has become uncontrollable. As shown in FIG. 5, when both the left and right rear wheels 5 are on the toe-out side, both angles are added, but when one of the rear wheels 5 is on the toe-in side, the angle is subtracted. This is because, for example, if the left and right rear wheels 5 are cut by the same angle on the toe-in side and the toe-out side, respectively, the influence on the steering stability of the vehicle is small even at high speeds.

Next, the ECU 12 determines in the maximum vehicle speed setting unit 53 whether or not the toe angle θ acquired in step 3 or step 4 is on the toe-out side (step 5). When the toe angle θ of the rear wheel 5 that has become uncontrollable is on the toe-in side (No), the above procedure is repeated. On the other hand, when the toe angle θ of the rear wheel 5 that has become uncontrollable is on the toe-out side (Yes), the allowable speed obtained by searching the map shown in FIG. 6 is set as the maximum vehicle speed V _max (step 6). This map is set so that the highest speed V _max becomes lower as the toe out magnitude is large, the maximum value is the maximum speed V _max equal 180 km / h in the normal. Then, ECU 12 is a maximum vehicle speed signal indicative of the maximum vehicle speed _{V max} set output toward the fuel injection device 15 (step 7), and the procedure ends.

Thus, when at least one of the wheel toe angle variable control system 10 after the left and right become uncontrollable at toe-out state, the maximum vehicle speed V _max is set lower than normal, poor driveability high-speed running is suppressed, as the toe out magnitude of the rear wheels 5 is larger, by the maximum vehicle speed V _max is set low, with a predetermined steering stability is ensured, undergo minimal restrictions even after failure However, it is possible to continue traveling while ensuring a predetermined traveling performance. Also, when the stroke sensor 16 has failed, by setting the maximum vehicle speed V _max equal to the maximum vehicle speed V _max corresponding to the maximum toe out magnitude, even unknown toe angle at failure, predetermined Steering stability is ensured.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. Accordingly, the present invention can be changed as appropriate without departing from the spirit of the present invention.

Schematic configuration diagram of an automobile equipped with a left and right rear wheel toe angle variable control device Block diagram of left and right rear wheel toe angle variable control device Flow chart showing maximum vehicle speed setting procedure A plan view showing a state where the right rear wheel is out of control Plan view showing a state in which the left and right rear wheels are out of control A map to find the allowable vehicle speed from the toe-out amount

Explanation of symbols

V Car 1 Car body 5 Rear wheel 10 Rear wheel toe angle variable control device 11 Electric actuator 12 ECU
13 Vehicle speed sensor 14 MCU
15 Fuel Injection Device 16 Stroke Sensor (Toe Angle Detection Means)
52 Failure determination part 53 Maximum vehicle speed setting part

Claims (3)

A rear wheel toe angle variable vehicle provided with a rear wheel toe angle variable control device that is provided for each of the left and right rear wheels and variably controls a toe angle of a corresponding rear wheel,
A toe angle detecting means provided for each of the left and right rear wheels, for detecting the toe angle of the corresponding rear wheel;
And a maximum vehicle speed setting means for setting an upper limit value of the acceptable speed as the maximum vehicle speed,
The maximum vehicle speed setting means sets the maximum vehicle speed lower than the normal maximum vehicle speed when at least one rear wheel becomes uncontrollable in a toe-out state , and detects the left and right rear positions detected by the toe angle detection means. The rear wheel toe angle variable vehicle, wherein the maximum vehicle speed is set lower as the total value of the wheel toe-out angles is larger . The maximum vehicle speed setting means subtracts the other toe-in angle from one toe-out angle when one of the toe angles of the left and right rear wheels detected by the toe-angle detecting means is on the toe-out side and the other is on the toe-in side. The rear wheel toe angle variable vehicle according to claim 1, wherein the maximum vehicle speed is set lower as the calculated value is larger. Before Symbol maximum vehicle speed setting means, if the previous SL toe angle detection means fails, and sets the same as the maximum vehicle speed corresponding to the maximum toe-out angle the maximum vehicle speed, in claim 1 or claim 2 The rear wheel toe angle variable vehicle described .

Images