JPH01262267A - Rear wheel steering device of vehicle - Google Patents

Abstract

PURPOSE:To enable the steering according to the driving condition by varying the operation speed of a motor according to the car speed or the operation speed of the handle steering angle to change the responsiveness of the rear wheel steering. CONSTITUTION:A rear wheel steering mechanism B has a reducing mechanism 21 having a gear train, a clutch 22 and a brake mechanism 23 in the linkage mechanism of a relay rod 12 and a servo motor 20. The signals from a handle steering angle sensor 30, a speed sensor 31, and an encoder 32 detecting the rotating position of the servo motor 20 are input to a control unit U, which calculates a target rear wheel steering angle to steer the rear wheels through the servo motor. The operation of the servo motor is regularly monitored by the encoder 32, and the rear wheels are steered under feedback control.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rear wheel steering device for a vehicle that steers the rear wheels.

(Prior Art) Some vehicles have so-called four-wheel steering (4WS) in which both the front wheels and the rear wheels are steered.

In this four-wheel steering, the steering mechanism for the rear wheels is
There is the pirate type in which the front wheel steering mechanism and the rear wheel steering mechanism are mechanically connected, and the type in which the rear wheel steering mechanism is equipped with an electromagnetic drive means such as an electric motor, as seen in Japanese Utility Model Publication No. 62-25275. It is roughly divided into an electric type in which the rear wheels are steered by the driving force of this driving means in conjunction with each other. In this electromagnetic type, it has also been proposed to interpose a speed reduction mechanism between the drive means and the rear wheel steering mechanism in order to minimize the size of the drive means (1983). -2527
(See Publication No. 7).

By the way, in the case of an electrically controlled type steering wheel in which the rear wheels are steered by a motor, the problem is how to determine the operating characteristics such as the operating speed and the generated torque. Of course, in order to improve responsiveness and steer the rear wheels reliably against strong external forces acting on the rear wheels, it is necessary to operate the motor at its maximum capacity, that is, to maximize the operating speed and the maximum generated torque. It is sufficient to use it in such a condition.

However, in this case, the power consumption of the motor becomes large, and it is not preferable in terms of ensuring the durability of the motor.

Therefore, an object of the present invention is to minimize the power consumption of the motor as a drive source for steering the rear wheels, ensure durability, and exhibit the required operating characteristics of -F. To provide a rear wheel steering device for light rain.

(Means and operations for solving the problems) In order to achieve the above-mentioned object, the present invention basically has the following configuration. That is, as shown in the block diagram in FIG. 13, there is a rear wheel steering mechanism for steering the rear wheels, and a drive that is linked to the rear wheel steering mechanism and displaces the rear wheel steering mechanism. The motor is configured to include a motor as a source, a driving state detecting means for detecting a driving state of the vehicle, and an operating characteristic changing means for changing the operating characteristics of the motor according to the driving state of the vehicle.

In this way, in the present invention, it is possible to
) It is possible to obtain sufficient operating characteristics, that is, operating speed and generated torque. Further, since there is no need to unnecessarily increase the operating speed or increase the generated torque, reduction in power consumption and durability of the motor are ensured.

The operating characteristics of a motor basically include operating speed and generated torque. As for the operating speed, responsiveness is especially required when the vehicle speed is high or when the steering wheel is operated slowly, so the operating speed of the motor is set to be faster in such cases. range (2nd or 3rd term).

On the other hand, in vehicles, a battery is usually used as a power source for a motor. However, the voltage generated by this battery varies considerably depending on discharge and the usage status of other electrical equipment, so if the motor is controlled with the same amount of control, it will be affected by fluctuations in battery voltage. The expected operating characteristics will not be obtained. Therefore, by changing the operating characteristics from 1000 to 2000 depending on the battery voltage, the expected operating characteristics of the motor can be obtained (Claim 4).
.

(Example) Examples of the present invention will be described below based on the attached drawings.

In Figure 1, IR is the right front wheel, +L is the left [) IR wheel, 2R is the right rear wheel, 2L is the left rear wheel, and the left and right front wheels are IR.
, II, are linked by a front wheel steering mechanism A, and the left and right rear wheels 2R12L are linked by a rear wheel steering mechanism 13.

In the embodiment, the front wheel steering mechanism A includes a pair of left and right knuckle arms 3R13L and a tie rod 4R14L, and a relay rod 5 that connects the pair of left and right tie rods 4R14L. A steering mechanism C is linked to this front wheel steering mechanism A, and the steering mechanism C is of a rack and pinion type in this embodiment, and a pinion 6, which is a component thereof, is connected to a handlebar 8 via a shaft 7. connected. As a result, when the handle 8 is operated to the right, the relay rod 5 is displaced to the left in FIG. 1, and the knuckle arm 3R53
1 is steered clockwise in the figure by an amount corresponding to the operational displacement i of the handle 8, that is, the steering angle, about the rotation centers 3R' and 3L'. Similarly, when you turn the handle 8 to the left, depending on the amount of displacement of this operation,
The left and right front wheels IR and IL will be steered to the left.

Similarly to the heavy wheel steering mechanism A, the rear wheel steering mechanism B also includes a pair of left and right knuckle arms l0R1101, tie rods l]R, Il[, and the tie rods 111(, +
It has a relay rod 12 that connects l+-, and a neutral holding means 13 is attached to this relay rod 12. As shown in FIG. 3, the neutral holding means 1:3 has a casing 15 fixed to the middle rest 14, and a pair of spring receivers +6a, 16b are loosely fitted in the casing 15, and these springs A compression spring]7 is disposed between the receivers 6a and 16b. The relay rod 12 extends through the casing 15, and the relay rod 12 is formed with a pair of flanges 12a and 12b spaced apart from each other.
2a and I2b are configured to receive the spring receivers 16a and 16b, and the relay rod 12 is always urged in the neutral direction by the compression spring 17. Of course compression spring 1
7 is said to have enough spring force to overcome side forces during cornering.

The rear wheel steering mechanism B is linked to a servo motor 20 as a drive source for steering the rear wheels 2R121.

More specifically, the relay rod 12 and the servo motor 20
A reduction mechanism 21 including, in order from the relay rod 12 side, a gear train 21a and a ball screw 21b,
A clutch 22 and a brake mechanism 23 are interposed.

As a result, the clutch 22 causes the servo motor 2 to
The brake mechanism 23 is configured to be able to mechanically disconnect the link between the rear wheel steering mechanism B and the rear wheel steering mechanism B, and the brake mechanism 23 can grip the output shaft of the rear wheel motor 20 to lock the rotation of the output shaft. ing.

With the above configuration, when the clutch 22 is in the connected state, the relay rod 12 is displaced to the left or right in FIG. It is steered clockwise or counterclockwise in the figure by an amount corresponding to the amount of rotation of the servo motor 20 about the rotation centers 10R' and IOL'. On the other hand, the clutch 2
When the rear wheel 2R121- is in the disconnected state, the rear wheel 2R121- is forcibly returned to the neutral position by the neutral holding means 13, and is held at this neutral position. In other words, when the clutch 22 is disengaged, the front wheel lR11+-
This is a so-called 2WS small mountain where only one wheel is steered.

Here, the rear wheel steering control is vehicle speed sensitive, and an example of changing the steering ratio according to the vehicle speed is as shown in FIG. 3. When the control characteristics shown in FIG. 3 are applied, the rear wheel steering angle relative to the steering wheel steering angle changes in the same phase direction as the vehicle speed increases. This situation is shown in FIG. In order to carry out such control, signals are basically input to the control unit U from a steering wheel angle sensor 30, a vehicle speed sensor 31, and an encoder 32 that detects the rotational position of the motor 20 (noted by L). The control unit U calculates a target rear wheel steering angle based on the steering wheel steering angle and the heavy speed, and outputs a control signal corresponding to the required rear wheel steering amount to the servo motor 2o. The encoder 32 constantly monitors whether or not the servo motor 2o is operating properly, that is, under feedback control, the rear wheel 2R1
2I- steering is performed.

The basic control system described above has a dual configuration for fail-safe purposes. That is, a front wheel steering angle sensor 34 is added to the steering wheel steering angle sensor 30, a second vehicle speed sensor 35 is added to the vehicle speed sensor 31,
For the encoder 32, the relay rod is better than the clutch 22! A rear wheel steering angle sensor 36 is added to detect the mechanical displacement of the member on the second side, and rear wheel steering is performed only when both corresponding sensors of these sensors 30 to 36 detect the same value. It's like that.

That is, in the sensors 30 to 36, for example, the first
The vehicle speed detected by the vehicle speed sensor 31 and the second medium speed sensor:
If the vehicle speed is different from the vehicle speed detected at 35, it means that a failure has occurred, and the rear wheels 2R121, .

Further, in order to detect various failures, on/off signals from switches 37 to 40 are manually input to the control unit U, and alternator 1. A signal indicating the presence or absence of power generation is manually inputted from the terminal 41. Here, the switch 37
is a neutral clutch switch, switch 38 is an inhibitor switch, switch 39 is a brake switch,
Switch 40 is an engine switch. Here, in a heavy vehicle equipped with a manual transmission, the neutral switch 37 outputs an off signal when the shift position of the manual transmission is neutral or when the clutch pedal is depressed, and otherwise outputs an on signal. It looks like this. In a heavy vehicle equipped with an automatic transmission, the inhibitor switch 38 outputs an on signal when the range is in neutral (N) or parking (P), and outputs an off signal when the range is in the driving range. It has become. The three brake switches output an ON signal when the brake pedal is depressed, and the engine switch 40 outputs an ON signal when the engine is in operation.

The control system shown in FIG. 5 is shown in a block diagram. That is, the microprocessor 50 has a dual structure of I and II, and the microprocessor 50 receives signals from the vehicle speed sensor 31, 35, switches 37 to 40, the alternator, and the terminal 4I via the buffer 51. The signals from the sensors 30, 34, and 36 are input manually through the A/D converter 52, and the encoder 32
A signal from the computer is inputted via the interface 53. On the other hand, the signals generated in the microprocessor 50 are sent to the servo motor 29 via a drive circuit 54 and to the motor brake 2 via a brake drive circuit 55.
3 or to the clutch 22 via the clutch drive circuit 56. This rear wheel steering control is started on the condition that the signal from the alternator 1, terminal 41 becomes high (Hl). still,
In the same figure, reference numeral 57 is a battery, 58 is an ignition key switch, and 59 is a relay. When some kind of failure occurs in the four-wheel steering control system, the relay drive circuit 60 operates to stop the power supply to the coil 61. As a result, the B contact of the relay 59 is closed and the warning lamp 62 is turned on.

Next, failures and their treatment will be explained.Here, a treatment corresponding to the location where the failure occurs is taken, and there are two modes of treatment as follows.

Position A (control during first fail mode) Rear wheel 2R22
This is a case where control of L and determination of its position are still possible. That is, when it is possible to return to neutral by the dryer 20, the motor 20 is used to return to neutral. Specifically, the contents of this procedure are as follows: ■ After the warning lamp 62 lights up, ■ The rear wheels 2R12L are returned to the neutral position by the drive of the servo motor 20; ■ After that, the motor brakes 2; The agreement will be concluded.

Process 'ξ state, B (This is the state when the control of the 11-' rear wheel 2R12I- with the 72 fail motor II and the 16 judgment becomes impossible.The contents of this procedure are as follows. .

■: After the warning clamp 62 lights up, ■The clutch 22 is turned off, and the connection between the servo mower 20 and the rear wheel steering mechanism [3 is cut off, ■The neutral holding means 1
After waiting for the rear wheels 2I7.2[6 to return to the neutral position by the spring force of 3, the clutch 22 is connected.

Preferably, after cutting Kuratu T-22,
The Kura rake 23 is now fastened. This temporarily prevents the rear wheel 2 from running out of control.
F<, 21. , will be physically relocated. After that, the supply of power to the motor 20 is cut off.

Next, the operating characteristics of the motor 20 and changes in the operating time will be explained.

First, the motor 20 has characteristics as shown in FIG.
Basically, as the operating speed increases, the generated torque decreases. The shaded area shown in FIG. 7 is the usage range (ability range) of Chi-Yu 20. Such a motor 20 can have appropriate characteristics within the range of use mentioned above by changing at least one or both of the pulse duration and the number of pulses using a so-called WM (pulse modulation method). Become. Of course, by changing both the pulse duration and the number of pulses, the characteristic lines a and V in Figure 7 can be set arbitrarily, and an example of this arbitrarily set characteristic line is shown by the β line. . Therefore, in the following explanation, only the case where the number of pulses is changed will be explained, but it goes without saying that the number of pulses may also be changed.

The basic operating characteristics of the motor 20 are set using vehicle speed and steering angle (heavy wheel steering angle) as parameters during the pulse, as shown in FIG. When the operating characteristic, for example, the β line in Figure 7, is selected based on this map, the operating speed is determined by the magnitude of the external load at that time, and as a result, the generated torque is determined (Section 7 IXI A
(see point). In this way, the pulse mode is determined using the vehicle speed and the steering wheel angle as parameters when the vehicle speed is the motor 20.
This is because the steering angle is the main factor related to the operating speed, that is, the response, and the steering angle is the main factor in resisting the torque generated by the motor 20, that is, the external force acting on the rear wheel 2R121-. Of course, this basic pulse PV! is set so as to reduce power consumption as much as possible.

The above-mentioned basic pulse P■ is changed, that is, corrected, depending on the running state of the gods of Φ. In the example, the parameters for this detection include: vehicle speed, steering wheel operation speed (obtained by differentiating the steering angle), battery voltage, and target rear wheel steering f (+e T and actual rear wheel steering angle). deviation from the steering angle θR (output value of the sensor 36), ■External force tire reaction force), ■ Operation amount of the relay rod 12 (neutral holding means 1
There are a total of six types of spring force of the compression spring in No. 3, and in the example, the above-mentioned θR).

The above correction terms are as follows:
The larger the value, the larger the correction term. A typical example of a map for setting this correction term is shown in FIG.

On the other hand, regarding the battery voltage (2) above, the smaller the voltage value, the larger the correction term becomes. When each correction term of 0) to ■ is shown by C5 to C6, the pulse that is finally output to the motor 20 is 1-) W = )'■X (1+C! +C2...
It is calculated using the formula 10CG). Of course, the PW in the sixth term of the above equation is in the basic pulse, and the left term is in the final pulse after correction.

Regarding the tire reaction force mentioned in (1) above, the following will explain the tire reaction force with reference to Fig. 1-). First, assuming that the point of contact of the rear wheel 2R with the road surface is 0, the moment of the external force around the steering center (+oL'') of the rear wheel 2R is proportional to the distance between the steering center 101.' and the point of contact O. It will be proportional.

On the other hand, the external force input from the tires to the relay rod 12 is related to the magnitude of the distance 1 between the relay rod 12 and the steering center 101,'. -■- The flooding changes depending on the vehicle speed, and L changes depending on the rear wheel steering angle. Therefore, depending on the vehicle speed and the steering wheel angle (resulting in the rear wheel steering angle), the rear wheel
The load force acting on R, that is, the tire reaction force, may be released.

More specifically, the flood is calculated in advance based on the vehicle speed), and the external force applied to the ground contact point 0 is calculated based on the vehicle speed and steering angle (lateral G x load). Furthermore, 1
．． The load force applied to the relay rod 12 is finally obtained by the ratio of

Next, control for changing the operating characteristics of the motor 20 described above will be explained with reference to the flowchart shown in FIG. In the following explanation, P indicates a step.

First, after the system is initialized at PI, signals from each sensor (including battery voltage) are input manually at P2.

In P3, the target steering angle θT of the rear wheels is determined by comparing the vehicle speed and the steering wheel steering angle (Ii?N transverse steering available steering angle) with the steering ratio characteristics shown in Fig. 4 (Fig. 5). In addition, at P4, the basic PW during the pulse is determined based on the vehicle speed and the steering angle (map in FIG. 8).

After this, in P5 to P7, prerequisite calculations for obtaining the correction term are performed. That is, in P5, the actual steering angle θR is subtracted from the target rear wheel steering angle θT, thereby obtaining the steering angle (deviation) necessary to achieve the OT.
is calculated. Further, in P6, the steering angle is differentiated to obtain the operating speed. Then, at P7, the tire reaction force is determined as described above.

In P8, the data manually generated in P2 and 1]5
A total of six types of correction terms C1 to C5 described above are determined according to the values obtained in ~[)7. After this, at P9,
The final pulse PW is determined by the basic pulse pulse PW and each complementary +'F- term C1 to C6. After this, P.I.
At 0, the motor 20 is driven to realize the target rear wheel turning angle θT with the pulse 1] (1) in the pulse determined at P9. Then, at pH, feedback control using the output of the sensor 36 that detects the actual steering angle of the rear wheels 2R121 causes the motor 2 to
0 does not reach the predetermined target speed (more reliable realization of the target operating speed).

(Effects of the Invention) As is clear from the above description, according to the present invention, the rear wheels can be appropriately steered while reducing the power consumption of the motor and ensuring durability.

In particular, by changing the operating speed of the motor in accordance with the vehicle speed or the operating speed of the steering wheel steering angle, the responsiveness of rear wheel steering can be sufficiently satisfied.

Furthermore, by changing the torque generated by the motor according to the battery voltage, the motor can be operated with the expected operating characteristics regardless of battery voltage fluctuations, and the rear wheels can be steered with the expected movement. .

[Brief explanation of the drawing]

FIG. 1 is an overall system diagram showing one embodiment of the present invention. Figure 2 is a configuration diagram of the rear wheel steering mechanism. FIG. 3 is an enlarged sectional view of the neutral holding means. FIG. 4 is a control characteristic diagram of a vehicle speed sensitive type which is an example of rear wheel steering. FIG. 5 is a characteristic diagram showing changes in rear wheel steering angle according to vehicle speed. FIG. 6 is a block diagram of a control system according to the embodiment. FIG. 7 is a diagram showing the characteristics of the motor and its range of use. FIG. 8 is a diagram showing a map for obtaining the basic operating characteristics of a motor. FIGS. 9 and 10 are diagrams showing a master knob for obtaining a supplementary IE term used to change the operating characteristics of the motor according to the running condition of the vehicle. FIG. 11 is an enlarged plan view showing the vicinity of the connection between the rear wheel and the relay rod. FIG. 12 is a flowchart showing a control example of the present invention. FIG. 13 is a block diagram showing the configuration of the present invention. l: Front wheel 2: Rear wheel 20: Servo motor 30.34: Sensor (handle steering angle) 31.35: Sensor (vehicle speed) 57: Battery U: Control unit B: Rear wheel steering mechanism Fig. 2 Fig. 3 Fig. 5 Figure 9 Figure 1 o Diagram meter
Babut no spittoon Figure 11 Figure 12

Claims (4)

[Claims] (1) a rear wheel steering mechanism for steering the rear wheels; a motor that is linked to the rear wheel steering mechanism and serves as a drive source for displacing the rear wheel steering mechanism; and detecting the running state of the vehicle. A rear wheel steering device for a vehicle, comprising: a running state detection means; and an operating characteristic changing means for changing the operating characteristics of the motor according to the running state of the vehicle. (2) In claim 1, the driving state detecting means detects vehicle speed, and the operating characteristic changing means changes the operating speed of the motor when the vehicle speed is high compared to when the vehicle speed is low. Something that makes it faster. (3) In claim 1, the driving state detecting means detects the operating speed of the steering wheel, and the operating characteristic changing means detects the operating speed of the steering wheel when it is fast compared to when it is slow. and the operating speed of the motor is increased. (4) In claim 1, the running state detecting means detects the voltage of a battery as a power source for the motor, and the operating characteristic changing means detects when the voltage of the battery is low. The torque generated by the motor is made larger than when the torque is large.