JPS61193970A - Rear-wheel steering control device for vehicles - Google Patents

Abstract

PURPOSE:To make a variation in each rear-wheel steering angle performable so smoothly, by making the selection between two steering control modes of rear wheels of a car so as to perform it at a time when the desired steering angle ratios in each steering control mode are accorded with each other. CONSTITUTION:A rear-wheel steering control device is provided with a rear- wheel steering mechanism 30 consisting of an actuator 31 and a longitudinal- form turning member 32. This rear-wheel steering mechanism 30 turns round with a turning fulcrum 32a as a acriterion according to a displacement position of a rod 31a of the actuator 31 in relation to each steering angle of both front wheels 10 by the turning member 32, controlling each steering angle of both rear wheels 20. And, the rear-wheel steering control device is provided with a speed sensor 40, a displacement sensor 50, the waveform shaper 70 connected to an operating switch 60 and the speed sensor 40, and the flip-flop 80 connected to the operating switch 60.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vehicle steering control device, and more particularly to a vehicle rear wheel steering control device for controlling the steering angle of the rear wheels of a vehicle.

[Prior art]

Conventionally, in this type of rear wheel steering control device for a vehicle, for example, as disclosed in Japanese Patent Laid-Open No. 59-81269, a fixed mode that is independent of the vehicle's traveling speed is changed to a mode that changes depending on the traveling speed of the vehicle. The rear wheel steering control mode is switched to the automatic mode when the traveling speed of the vehicle exceeds a set traveling speed.

[Problem that the invention seeks to solve]

However, in such a configuration, if the steering wheel of the vehicle is operated, the steering angle of the rear wheels is instantaneously controlled in a direction contrary to the driver's intention when switching from fixed mode to automatic mode. There is a risk of impairing vehicle handling stability. In contrast, as disclosed in Japanese Patent Application Laid-Open No. 59-81270, the fixed mode is switched to automatic mode when the steering wheel is in the neutral position, or as disclosed in Japanese Patent Application Laid-Open No. 59-81271. As disclosed in the official gazette, there are some systems that switch from fixed mode to automatic mode when the vehicle speed exceeds the set speed and the steering wheel is in the neutral position, but in either case, If the fixed mode is switched to the automatic mode during a steering operation of the steering wheel, a problem similar to that described above occurs.

In order to cope with such a problem, the present invention provides a rear wheel for a vehicle in which switching between two steering control modes for the rear wheels of the vehicle is performed when target steering angle ratios in each steering control mode match. The present invention aims to provide a steering control device.

[Means for solving problems]

In order to solve this problem, the structural feature of the present invention is as illustrated in FIG.
and a steering angle ratio detecting means 2 which detects the actual steering angle ratio of the rear wheels to the front wheels and generates a steering angle ratio detection signal; a first steering angle ratio pattern in which the target steering angle ratio is set to be negative in a first traveling speed region lower than a predetermined value of the traveling speed and reversed to positive in a second traveling speed region higher than the predetermined value; a setting means 3 configured to set a second steering angle ratio pattern in which the second target steering angle ratio is determined in relation to the first traveling speed region; target steering angle ratio determining means 4 for determining the first and/or second target steering angle ratios based on the first and/or second set steering angle ratio patterns; an operating means 5 which is operated to generate an operating signal when making a selection, generates the first determined target steering angle ratio as a first output signal when the operating signal is not generated, and responds to generation of the operating signal; an output signal generating means 6 which generates the second determined target steering angle ratio as a second output signal; and a difference between the value of the first (or second) output signal and the value of the steering angle ratio detection signal. In the rear wheel steering control device, the second set steering angle ratio pattern in the setting means 3 sets the second target steering angle ratio to the first traveling speed region. is made to be larger than the first target steering angle ratio at least on the low speed side thereof and to match the first target steering angle ratio at a value equal to or less than the predetermined value, and in response to the operation signal. holding signal generating means 8 for generating a holding signal and extinguishing the holding signal when the value of the second output signal matches the value of the first output signal; and output signal generating means responsive to generation of the holding signal. 6 to the steering control means 7, and in response to disappearance of the holding signal, only the first output signal is allowed to be applied from the output signal generating means 6 to the steering control means 7. The reason is that the provision permitting means 9 is provided.

[Effect]

By configuring the present invention in this manner, when the vehicle is caused to make a small turn in its first travel speed range, the operating means 5 generates an operation signal, and the output signal generating means 6 detects the travel speed. The first steering angle ratio determined by the target steering angle ratio determining means 4 in cooperation with the means 1 and the setting means 3.
and (or second) target steering angle ratio to the first and (or second) target steering angle ratio.
), the holding signal generating means 8 generates a holding signal in response to the operation signal, and the steering control means 7
receives the second output signal under the control of the application permitting means 9 responsive to the holding signal, and reduces the difference between the value of the second output signal and the value of the steering angle ratio detection signal. While the rear wheels are being steered, the value of the first output signal and the second output signal generated from the output signal generating means 6 together with the second output signal increase the traveling speed of the vehicle. If they match, the holding signal generating means 8 eliminates the holding signal, and in response, the steering control means 7 receives the first output signal under the control of the application permitting means 9 and outputs the first output signal. Since the rear wheels are steered so as to reduce the difference between the value and the value of the steering angle ratio detection signal, the rear wheel steering control is changed from the rear wheel steering control based on the second steering angle ratio pattern to the rear wheel steering control based on the first steering angle ratio pattern. The switching to is performed only when the first and second target steering angle ratios match each other. Therefore, the change in the rear wheel steering angle before and after the above-mentioned switching occurs smoothly without being affected by the operation of the steering wheel of the vehicle, and as a result, the steering stability of the vehicle is ensured. obtain.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.
The figure shows an example in which the rear wheel steering control device according to the present invention is applied to a four-wheeled vehicle. This rear wheel steering control device has a rear wheel steering mechanism 30, and this rear wheel steering mechanism 30 includes:
It is composed of an actuator 31 fixed to a part of the vehicle body and a longitudinal rotating member 32. The actuator 31 has a rod 31a that extends so as to be displaceable, and the rod 31a is connected to a rotation fulcrum 32a of the rotation member 32 at its tip.

The rotation member 32 is connected to the tie rod 10a of the left front wheel 10 via a link rod 33 at its rotation fulcrum 32b, and the rotation point 32C of this rotation member 32 is connected to the left rear wheel via a link rod 34. It is connected to a tie rod 20a of the ring 20. Therefore, in the rear wheel steering mechanism 30, the rotating member 32 rotates about the rotation fulcrum 32a according to the amount of displacement of the rod 31a of the actuator 31 in relation to the steering angles of both front axles io, io. Controls the steering angle of the rear wheels 20.20. In such a case, the distance between the rotation fulcrum 32a and the rotation point 32b of the rotation member 32 and the distance between the rotation fulcrum 32a and the rotation point 32c are (steering angle of the rear wheels 20)/(steering angle of the front wheels 10). ), hit the steering angle ratio K to the actuator 31
It is set to uniquely correspond to the amount of displacement of the rod 31a. In addition, in Fig. 2, the symbol 10A indicates both front axles 1.
A front wheel steering mechanism for controlling a steering angle of 0°10 is shown.

The rear wheel steering control device also includes a speed sensor 40, a displacement sensor 50, an operation switch 60, a waveform shaper 70 connected to the speed sensor 40, and a flip-flop 80 connected to the operation switch 60. A speed sensor 40 detects the traveling speed U of the vehicle and generates a series of speed pulses at a frequency proportional to this. The displacement sensor 50 detects the actuator 3 corresponding to the actual amount of rotation of the rotation member 32.
The actual displacement amount of the first rod is detected and generated as a displacement detection signal. In such a case, the actual rotation amount of the rotation member 32 corresponds to the actual steering angle ratio K.

The operation switch 60 is a self-resetting normally open type, and when it is temporarily closed, it generates the power supply voltage +Vb from the DC power source as an operation signal. The waveform shaper 70 sequentially shapes the waveform of each speed pulse from the speed sensor 40 and generates a shaped pulse. Flip-flop 80 is set in response to an operation signal from operation switch 60, and generates a low level signal from its output terminal Q and a high level signal from its output terminal Q. Also, flip-flop 80
is reset in response to a high level signal from an AND gate 110, which will be described later, to generate a high level signal from the output terminal Q and a low level signal from the output terminal Q.

The microcomputer 90 has a central processing unit 92 (hereinafter referred to as CPLI) connected to each other via a data bus 91.
92'), read-only memory 93 (hereinafter referred to as ROM93), random access memory 9
4 (hereinafter referred to as RAM 94), each input port 95, 9
6 and each output port 97.98.99, C
The PU 92 repeatedly executes a computer program previously stored in the ROM 93 in cooperation with the waveform shaper 70 and the flip-flop 80 according to the flowchart shown in FIG.
00 and both analog switches 120 and 140 are performed. Note that the input port 95 is connected to the waveform shaper 70, and the input port 96 is connected to the output terminal Q of the flip-flop 80.

The comparator 100 compares first and second output signals respectively generated from the output ports 98 and 99 as described later, and generates a low level signal when the level of the first output signal is lower than the level of the second output signal. Then, when the levels of the output signals match, a high level signal is generated. AND gate 110 generates a high level signal in response to each high level signal from output terminal Q of comparator 100 and flip-flop 80, and generates a high level signal in response to a low level signal from at least one of comparator 100 and output terminal Q of flip-flop 80. Generates a low level signal in response.

The analog switch 120 receives a high level signal (or low level signal) from the output terminal Q of the flip-flop 80.
In response to this, the first output signal is opened (or opened) to allow (or block) the first output signal generated from the output port 97 as described below to be applied to the drive circuit 150 . analog switch 14
0 is closed (or opened) under the inverting action of the inverter 130 in response to the low level signal (or high level signal) from the output terminal Q of the flip-flop 80, and is output from the output port 99 to the drive circuit 150. Allowing (or blocking) the second output signal of the signal. Drive circuit 150
generates a drive signal that reduces the difference between the level of the first output signal from the analog switch 120 (or the level of the second output signal from the analog switch 140) and the level of the displacement detection signal from the displacement sensor 50. and is applied to the actuator 31.

In this embodiment configured as described above, if the vehicle is running at low speed without operating the operation switch 60,
While the CPU 92 is executing the computer program according to the flowchart of FIG.
The running speed U of the vehicle is calculated based on the number of shaped pulses received through the pulse generator. Then, the CPU 92 performs step 1.
At step 61, the target steering angle ratio is calculated to be 1 according to the calculated traveling speed U from the steering angle ratio pattern A (see FIG. 3) which represents the relationship between the target steering angle ratio and the traveling speed U of 1, and step 162
, the calculated traveling speed U is calculated from the steering angle ratio pattern B (see FIG. 3) that expresses the relationship between the target steering angle ratio and the traveling speed U of 2.
Accordingly, 2 is calculated as the target steering angle ratio.

In such a case, each of the steering angle ratio patterns A and B is stored in the ROM 94 in advance, and in the steering angle ratio pattern ^, the target steering angle ratio is 1, and the travel speed u is equal to the predetermined travel speed u.
It becomes negative at o, becomes zero at uwuO, and u>u
It is set to be positive at o. Furthermore, in the steering angle ratio pattern B, the target steering angle ratio is set so that 2 becomes zero when U≦uo. However, 2 for each target steering angle ratio Kl is (target steering angle of rear wheel 20)/(front wheel 1
The steering angle ratio pattern A (or B) is selected based on the non-operation (or operation) of the operation switch 60.

After that, since the operation switch 60 is not operated at this stage, the CPU 92 receives the high level signal from the output terminal Q of the flip-flop 80 through the input port 96 and the data bus 91 in step 163, and outputs "NO", and in step 164, the calculated target steering angle ratio is set to 1 and generated from the output port 97 as the first output signal. Then, the analog step 120 applies the first output signal from the output port 97 to the drive circuit 150 in a closed state based on the high level signal from the output terminal Q of the flip-flop 80. Next, the drive circuit 150 generates a drive signal that reduces the difference between the level of the displacement detection signal from the displacement sensor 50 and the level of the first output signal from the analog switch 120, and in response to this, the actuator 31 rod 3
The rotating member 32 is rotated so that the actual displacement amount of 1a matches the value of the drive signal. As a result, the rear wheel 20
The actual steering angle is controlled so that it matches the target steering angle. Note that at this stage, since u<uo, K1<0.

In such a state, for example, when an operation signal is generated by temporarily closing the operation switch 60 in order to turn the vehicle with a small turning radius, the flip-flop 80
generates a low level signal from its output terminal Q, and also generates a high level signal from its output terminal Q, and the CPU
92 receives the low level signal from the output terminal Q of the flip-flop 80 through the input port 96 and the data bus 91 in step 21163 and determines it as rYESJ, and in step 165 sets 1 to the calculation target steering angle ratio. A first output signal is generated from the output port 98, and in step 166, the calculated target steering angle ratio of 2 is generated from the output port 99 as a second output signal.

Then, the analog switch 140 switches the flip-flop 8
The second output signal from the output port 99 is closed by the inverting action of the inverter 130 in response to the low level signal from the output terminal Q. At this time, since Kl<K2=0, the output of the comparator 100 is a low level signal, and the analog switch 12
0 is open. Thus, the drive circuit 150 generates a drive signal that reduces the difference between the level of the displacement detection signal from the displacement sensor 50 and the level of the second output signal from the analog switch 140, and in response to this, the drive circuit 150 By rotating the rotating member 31 in the same manner as described above, the actual steering angle of the rear wheels 20 is changed to the target steering angle (i.e., K1
= 0). This allows the vehicle to make small turns smoothly.

After that, due to an increase in the traveling speed U of the vehicle, the calculated target steering angle ratio in step 161 is changed to 1 in step 162.
When the calculated target steering angle ratio equals 2, the comparator 100 generates a high level signal, and the AND gate 1
1O generates a high level signal, flip-flop 80
is reset to produce a high level signal and a low level signal from each output terminal Q and Q. Then, in the same manner as described above, the analog switch 140 is opened and the analog switch 120 is closed at the same time, allowing the first output signal to be applied from the output port 97 to the drive circuit 150.

In other words, when the calculated target steering angle ratio 1 matches the calculated target steering angle ratio 2 at u=uo, the analog switch 1
40 is opened to cut off the application of the second output signal from the output port 99 to the drive circuit 150 and the analog switch 12
Since the first output signal is allowed to be applied from the output port 97 to the drive circuit 150 by closing 0, the value of the drive signal from the drive circuit 150 changes smoothly without becoming discontinuous. Control of the steering angle of the rear wheels 20 to the target value by the rear wheel steering mechanism 30 is performed smoothly regardless of the continuous operation of the front wheel steering mechanism 10A. This means that
Steering angle ratio pattern B to steering angle ratio pattern A of the rear wheels 20
This means that steering control at the time of switching to is always performed smoothly without impairing the steering stability of the vehicle.

In addition, in the above embodiment, the steering angle ratio pattern B is
Although an example has been described in which 2=0 at ≦uo, the present invention is not limited to this. For example, as shown by the broken line in FIG. 5, instead of the steering angle ratio pattern ct-ti and the steering angle ratio pattern B, It may be adopted and implemented. In such case,
In steering angle ratio pattern C, the target steering angle ratio of 3 (corresponding to the target steering angle ratio of 2) corresponds to the ultra-low speed range of the vehicle (i.e., the area below the ultra-low speed ul (<uo)). It becomes positive at , becomes zero at u=u l, and u>u
Immediately after l is established, it becomes negative and matches 1. Therefore, from steering angle ratio pattern C to steering angle ratio pattern A
Not only is the rear wheel steering control performed smoothly as in the previous embodiment, but also when there is an obstacle near the rear wheels 20, when u < ul. , under the operation of the operation switch 30, the rear wheel 20
As a result, the vehicle can be smoothly run at very low speed while preventing the rear wheels 20 from coming into contact with the obstacle.

Furthermore, in the embodiment described above, the steering angle ratio pattern B was stored in the microcomputer 90 in advance.
Instead of this, a potentiometer may be employed, and the target steering angle ratio of the steering angle ratio pattern B may be changed to 1, but is not limited to zero, and may be arbitrarily set using the potentiometer according to preference.

Further, in implementing the present invention, steering angle ratio pattern A
is not limited to a single steering angle ratio pattern, but is composed of a plurality of steering angle ratio patterns that are partially or totally parallel to each other, and each of these steering angle ratio patterns is selected according to preference with an appropriate selection switch. It may be implemented as follows.

Further, in the embodiment described above, an example was described in which the rear wheel steering mechanism 30, the displacement sensor 50, and the drive circuit 50 were used to control the steering of the rear wheels 20, but instead of this,
A hydraulic cylinder provided on the axle between the rear wheels 20.20, an electro-hydraulic servo mechanism connected to this hydraulic cylinder, a differential amplifier connected to this electro-hydraulic servo mechanism, a front wheel steering angle sensor, and a rear wheel steering angle sensor. Recruit, step 164
(or 165), the target rear wheel steering angle of the rear wheels 20 is determined by multiplying the target steering angle ratio by 1 by the detection result of the front wheel steering angle sensor for the steering angle of the front wheels 10.@1 Target rear wheel steering angle In step 166, the target steering angle ratio is multiplied by 2 by the detection result of the front wheel steering angle sensor in the same manner as described above to obtain a target rear wheel steering angle of the rear wheels 20, and a second target rear wheel steering angle is determined. generated as a signal, and the differential amplifier generates the first
The difference between the value of the (or second) target rear wheel steering angle signal and the detection result of the rear wheel steering angle sensor for the rear wheel 20 is differentially amplified, and the electro-hydraulic servo mechanism The hydraulic cylinder is hydraulically driven according to the dynamic amplification result, and then the rear wheel 2
Even if the steering is controlled so that each steering angle of 0.20 is set to the target value, substantially the same effect as in the embodiment described above can be achieved. The electro-hydraulic servo mechanism includes a torque motor that rotates according to the differential amplification result of the differential amplifier, and a conversion mechanism that converts the rotation of the torque motor into linear motion.
The conversion mechanism has a switching valve that selectively switches between three positions depending on the linear momentum of the conversion mechanism, and depending on the switching position of the switching valve, pressure oil from the hydraulic source is transferred to one of the two chambers of the hydraulic cylinder (or (on the other hand) or cut off from the same hydraulic cylinder.

[Brief explanation of the drawing]

FIG. 1 is a diagram corresponding to the configuration of the invention described in the claims, FIG. 2 is an overall configuration diagram showing one embodiment of the present invention, and FIG. 3 is the relationship between the target steering angle ratio and the vehicle running speed. 4 is a flow chart showing the operation of the microcomputer shown in FIG. 2, and FIG. 5 is a pattern diagram showing a modification of the pattern shown in FIG. 3. Explanation of symbols 10... Front wheel, 20... Rear wheel, 30... Rear wheel steering mechanism, 40... Vehicle speed sensor, 50... Displacement sensor,
60... Operation switch, 80... Flip-flop, 90... Microcomputer, 100... Comparator, 110... AND gate, 120, 140
...Analog switch, 130...Inverter. Applicant Toyota Motor Corporation Representative Patent Attorney Teru Hase - 14g1 Figure 3 Figure 5JE

Claims (1)

[Claims] A running speed detection means detects the running speed of the vehicle and generates a running speed detection signal; a steering angle ratio detection means detects the actual steering angle ratio of the rear wheels to the front wheels and generates a steering angle ratio detection signal; Of the first and second target steering angle ratios for the front wheels of the vehicle, the first target steering angle ratio is set to be negative in a first traveling speed region lower than a predetermined value of the traveling speed, and a second traveling speed region higher than the predetermined value. The first steering angle ratio pattern determined to be positively reversed and the second target steering angle ratio are
a setting means configured to set a second steering angle ratio pattern determined in relation to the traveling speed region; and the first and/or second set steering angle ratio in relation to the value of the traveling speed detection signal. a target steering angle ratio determining means for determining the first and/or second target steering angle ratio based on a pattern; and an operating means that is operated to generate an operation signal when selecting the second determined target steering angle ratio. , generates the first determined target steering angle ratio as a first output signal when the operation signal is not generated, and outputs the second determined target steering angle ratio as a second output signal in response to generation of the operation signal.
output signal generating means for generating an output signal; and
a rear wheel steering control device comprising: a steering control means for controlling the steering of the rear wheels so as to reduce a difference between the value of the output signal (or second) and the value of the steering angle ratio detection signal; A second set steering angle ratio pattern makes the second target steering angle ratio larger than the first target steering angle ratio at least on the low speed side in the first traveling speed region, and sets the second target steering angle ratio to a value equal to or less than the predetermined value. 1 target steering angle ratio, and generates a hold signal in response to the operation signal, and outputs the hold signal when the value of the second output signal matches the value of the first output signal. holding signal generating means for extinguishing the hold signal;
Only allowing the second output signal to be applied from the output signal generating means to the steering control means in response to generation of the holding signal, and controlling the steering from the output signal generating means in response to disappearance of the holding signal. A rear wheel steering control device for a vehicle, comprising: an application permitting means for permitting only application of the first output signal to the means.