JPH1035526A - Rear wheel steering wheel turning controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always and certainly detect the reference position of a rear wheel shaft, by writing the output of a rear wheel turning angle sensor in a memory in the case that rear wheel steering wheel turning is judged whether or not it is in a stable condition, and judged that it is in the stable condition. SOLUTION: A CPU 33 outputs its control signal to a rear wheel actuator 40 through an output interface circuit 34 on the basis of the outputs of a rear wheel turning angle sensor 51 and a neutral sensor 52. Also, at this time, it is judged whether or nor a vehicle speed is slower than a predetermined speed, and if it is YES, a counter value is increased by one only after the lapse of predetermined time after the counter value is increased in a previous process, and next, it is judged whether or not the output (rear wheel turning angle value) of a rear wheel turning angle sensor 51 is changed, and also it is judged whether or not the counter value exceeds a predetermined threshold value. Then, in the case that the rear wheel turning angle is not changed and the counter value exceeds the predetermined threshold value, the output of the rear wheel turning angle sensor 51 is written as the present rear wheel turning angle value in an EEPROM 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering control device for controlling the steering of a rear wheel.

[0002]

2. Description of the Related Art Conventionally, a front wheel steering angle is detected while a vehicle is running,
A rear-wheel steering control device that determines a target rear-wheel steering angle in accordance with the detected front-wheel steering angle and controls the rear wheels to be steered to the target rear-wheel steering angle is known.

In order to control the turning of the rear wheels while the vehicle is running, the rear wheels are driven by a rear-wheel steering actuator as initial processing after the ignition is turned on, and are moved in the left-right direction of the vehicle to turn the rear wheels. It is necessary to detect the reference position of the rear wheel shaft to be steered.

In the conventional rear-wheel steering control device, when the ignition is turned off, the output (rear-wheel steering) of a rear-wheel steering angle sensor (a sensor for detecting the rotation angle of a motor that is a driving source of a rear-wheel steering actuator) at the time of ignition-off. Angle value) is stored in the memory. Thereafter, when the ignition is turned on, the rear wheel steering angle value stored in the memory is read. Based on the read rear wheel steering angle value, the motor is driven in the middle direction of the rear wheel shaft stroke. As the motor rotates, the rear wheel shaft is shifted in the axial direction. The position of the rear wheel shaft at the time when the output of the mid-stroke sensor is inverted is detected as the "reference position" of the rear wheel shaft.
These processes are executed in the initial check process after the ignition is turned on.

[0005]

However, the above-described conventional rear wheel steering control device has the following problems.

In the conventional rear-wheel steering control device, the output (rear-wheel steering angle value) of the rear-wheel steering angle sensor when the ignition is turned off is stored in a memory. In this case, the rear wheel steering angle value stored in the memory and the actual rear wheel steering angle value may be shifted to the opposite side with respect to the reference position of the rear wheel shaft for the reason described later. For example, it is assumed that the rear wheel steering angle value stored in the memory is + 1.0 °, while the actual rear wheel steering angle value is −1.0 °. In such a case, the conventional rear wheel steering control device is configured to detect an operation abnormality by a mechanical guard.

The cause of the difference between the rear wheel steering angle value stored in the memory and the actual rear wheel steering angle value is as follows.
(1) The time for writing the rear wheel steering angle value to the memory is limited to a very short time when the ignition is turned off;
(2) By mistakenly detecting when the ignition is off, the rear wheel steering angle value is written into the memory at an incorrect timing; and (3) By the external force applied to the vehicle after the ignition is turned off, the actual rear wheel steering angle value is calculated. Fluctuates.

[0008] In the conventional rear wheel turning control device, the detection at the time of ignition off is performed based on the A / D value of the battery voltage. Therefore, as shown in FIG. 11, the A / D value of the battery voltage is set to a predetermined threshold value (for example, 1/2).
It was necessary to write the rear wheel steering angle value to the memory within a very short period (t ₂ -t ₁ ) from the time when the voltage became lower than V _dd ) to the time when the voltage was reduced to the minimum voltage for operating the microcomputer. On the other hand, EE
The PROM requires sufficient time to write the same value to a plurality of addresses in order to increase data reliability. Therefore, when the rear wheel steering angle value is written to the EEPROM in a very short time, there is a possibility that the reliability of the data may be reduced.

Further, as shown in FIG. 12, when the A / D value of the battery voltage suddenly drops due to some load, the conventional rear wheel steering control device erroneously detects that the ignition is off. There was a risk of doing. For this reason,
The conventional rear wheel steering control device may write the rear wheel steering angle value into the memory at an incorrect timing.

Further, when the actual rear wheel steering angle value fluctuates due to external force applied to the vehicle after the ignition is turned off, a deviation between the rear wheel steering angle value stored in the memory and the actual rear wheel steering angle value occurs. Was likely to occur. For example, the case where the ignition is turned off after stopping the vehicle on the slope corresponds to this case.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a rear wheel steering control device capable of always accurately detecting a reference position of a rear wheel shaft under various circumstances. With the goal.

[0012]

A rear wheel steering control device according to the present invention detects a rear wheel steering angle and outputs a detection signal indicating the rear wheel steering angle, and a rear wheel steering angle sensor. A memory for storing an output of the steering angle sensor, a determining means for determining whether or not the rear wheel steering is in a stable state; and a determining means for determining whether or not the rear wheel steering is in a stable state, the rear wheel steering angle. A writing unit for writing the output of the sensor to the memory, thereby achieving the above object.

The determining means includes means for determining whether or not the output of the rear wheel steering angle sensor has changed, and time measuring means for measuring an elapsed time. If the output of the angle sensor does not change and the elapsed time measured by the timing means exceeds a predetermined threshold, it may be determined that the rear wheel turning is in a stable state.

[0014] Further, another rear wheel steering control device of the present invention includes:
A rear wheel steering angle sensor that detects a rear wheel steering angle and outputs a detection signal indicating the rear wheel steering angle, and detects a position of a midpoint of a stroke of the rear wheel shaft, and detects a position of a midpoint of the stroke. A stroke midpoint sensor that outputs a detection signal indicating the following, a memory that stores the output of the rear wheel steering angle sensor, reading means that reads the output of the rear wheel steering angle sensor stored in the memory, Moving means for moving the rear wheel shaft in the direction of the midpoint of the stroke according to the output of the rear wheel steering angle sensor; and whether the stroke midpoint sensor has output a detection signal indicating the position of the midpoint. First determining means for determining whether or not the output of the rear wheel steering angle sensor at the time when the stroke midpoint sensor outputs a detection signal indicating the position of the midpoint is equal to a predetermined initial value. Second determining means for determining, and determination by the second determining means Depending on the fruit, and a correcting means for correcting the relationship between the output of the rear wheel steering angle value and the rear wheel steering angle sensor, thereby the objective described above being achieved.

[0015] Further, another rear wheel steering control device of the present invention includes:
A neutral sensor for detecting a neutral point of a rear wheel steering angle, and a first for steering the rear wheel in one direction based on an output of the neutral sensor.
When the neutral point is detected by the neutral sensor during turning by the turning means and the first turning means, the rear wheel is turned in a direction opposite to the turning direction by the first turning means. Second
Turning means, and neutral point detecting means for setting a rear wheel steering angle when the neutral point is detected by the neutral sensor during turning by the second turning means as a neutral point of a rear wheel steering angle. Thus, the above object is achieved.

The operation will be described below.

According to the rear wheel steering control device of the present invention, when it is determined that the rear wheel steering is in a stable state, the output of the rear wheel steering angle sensor is written into the memory. Therefore, the vehicle is less susceptible to the external force applied to the vehicle after the ignition is turned off.
As a result, it is possible to prevent the occurrence of a deviation between the rear wheel steering angle value stored in the memory and the actual rear wheel steering angle value.

Further, according to the rear wheel steering control device of the present invention, it is possible to correct the relationship between the rear wheel steering angle value and the output of the rear wheel steering angle sensor when the ignition is turned on. As a result, it is possible to eliminate the deviation between the rear wheel steering angle value stored in the memory and the actual rear wheel steering angle value.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a rear wheel steering control device 1 according to the present invention. The rear wheel steering control device 1 includes an electronic control device (EC
U) 30 and a rear wheel actuator 40.

The battery 30 and the vehicle speed sensor 21 are connected to the ECU 30. The battery 10 is connected to the ECU 30 via an ignition switch 11, and supplies power to the ECU 30 via a connection line (not shown). The connection between the battery 10 and the ECU 30 by a connection line (not shown) can be switched between disconnection and connection by a command from a CPU 33 described later. The vehicle speed sensor 21 detects the vehicle speed and outputs a detection signal indicating the vehicle speed to the ECU 30.

The ECU 30 outputs a control signal for controlling the rear wheel actuator 40 to the rear wheel actuator 40 based on the output from each sensor.

The rear wheel actuator 40 moves the rear wheel shaft 43 in the axial direction based on a control signal output from the ECU 30. At both ends of the rear wheel shaft 43, tie rods 44a, 44b and knuckle arms 45a,
The left and right rear wheels RW1, RW2 are connected to each other via 45b. The left and right rear wheels RW1, RW2 are steered according to the axial displacement of the rear wheel shaft 43.

The rear wheel actuator 40 includes the electric motor 4
1, a steering gear box 42, and a rear wheel shaft 43.

The direction and amount of rotation of the rotating shaft of the electric motor 41 are electrically controlled by a control signal output from the ECU 30. The electric motor 41 is, for example, a three-phase brushless motor. The rotation axis of the electric motor 41 is
The steering gear box 42 is connected to a rear wheel shaft 43 via a speed reduction mechanism (not shown). The rear wheel shaft 43 is supported so as to be displaceable in the axial direction, and is displaced in the axial direction according to the rotation of the electric motor 41.

The electric motor 41 includes a rear wheel steering angle sensor 51.
Is attached. The rear wheel steering angle sensor 51 detects the rotation angle of the output shaft of the electric motor 41 and outputs a detection signal indicating the rear wheel steering angle to the ECU 30. The detection signal includes, for example, an output A, an output B, and an output C. The rear wheel steering angle value is represented by a combination of the output A to the output C of the rear wheel steering angle sensor 51.

A mid-stroke sensor (neutral sensor) 52 is attached to the rear wheel shaft 43. The stroke midpoint sensor 52 detects the position of the midpoint of the stroke of the rear wheel shaft 43 (the neutral point of the rear wheel steering angle) and indicates the position of the midpoint of the stroke (the neutral point of the rear wheel steering angle). A detection signal is output to the ECU 30. The detection signal is at a high level when, for example, the rear wheel shaft 43 is on the right side of the position of the middle point of the stroke (reference position), and when the rear wheel shaft 43 is on the left side of the position of the middle point of the stroke (reference position). Is low level.

FIG. 2 shows the configuration of the ECU 30. ECU
Reference numeral 30 denotes an analog / digital converter (A / D converter) 31, an input interface circuit 32, and a CPU 3
3, an output interface circuit 34, a ROM 35,
An EEPROM 36 is provided.

The power supply voltage is supplied from the battery 10 to the A / D converter 31 when the ignition switch 11 is on. The A / D converter 31 converts an analog value of the power supply voltage into a digital value.

The outputs of the sensors 21, 51 and 52 are transmitted to the CPU 33 via the input interface circuit 32.

The CPU 33 executes various control programs in accordance with the outputs of the sensors, and controls the rear wheel actuator 40
To generate a control signal for controlling. The control signal is transmitted to the rear wheel actuator 4 via the output interface circuit 34.
Output to 0.

The ROM 35 is used to store various control programs to be executed by the CPU 33. The EEPROM 36 is used to store rear wheel steering angle values.

FIG. 3 shows the processing procedure of the program P1 for writing the value of the detection signal (rear wheel steering angle value) output from the rear wheel steering angle sensor 51 into the EEPROM 36. The program P1 is stored in the ROM 35. The program P1 is executed by the CPU 33 after the ignition is turned off.

Hereinafter, the program P will be described with reference to FIG.
The first processing procedure will be described.

[0035] In step S301, the vehicle speed whether or not a predetermined velocity v ₀ less is determined. The vehicle speed is detected by a vehicle speed sensor 21. The predetermined speed v ₀ is set in advance to a sufficiently small value. In the following step S301a, the counter value C is initialized to “0”.

In step S302, it is determined whether a predetermined time (for example, 5 milliseconds) has elapsed since the counter value C was incremented in the previous processing. If “Yes” in the step S302, the counter value C
Is incremented by one (step S30).
3). If "No" in the step S302, the counter value C is not incremented, and the step S302
Is repeatedly executed. Here, the counter value C
Is stored, for example, as an external variable of the program P1.

In step S304, the rear wheel steering angle sensor 5
It is determined whether the output of No. 1 (the rear wheel steering angle value) has changed.

[0038] In step S305, the counter value C is whether exceeds a predetermined threshold value C ₀ is determined.

The rear wheel without steering angle value is changed, and when the counter value C exceeds a predetermined threshold value C _0, the process proceeds to step S306.

In step S306, the rear wheel steering angle sensor 5
EEPROM3 output of 1 as a wheel steering angle value θ _r after the current
6 is written. Thereafter, the connection between the battery 10 and the ECU 30 by a connection line (not shown) is disconnected, and the ECU 3
The power supply to 0 is cut off.

On the other hand, if it is determined in step S304 that the rear wheel steering angle value has changed, the process proceeds to step S307. In step S307, the count value C
Is initialized to “0”, and then, in step S308, the counter value R is incremented by one. As a result, if the counter value R is larger than the predetermined threshold value R ₀ , the warning lamp is turned on (Steps S309 and S310). Lighting of such a warning lamp is an example of an operation based on diagnosis (self-diagnosis function).

When the counter value C is decremented from a certain value, and the rear wheel steering angle value does not change and the counter value C becomes zero, the output of the rear wheel steering angle sensor 51 is reduced. it may be written in EEPROM36 as wheel steering angle value θ _r after the current.

FIGS. 4 (a) to 4 (e) show a time change of the vehicle speed, a time change of the counter value C, and the rear wheel steering angle sensor 51.
, The output (output A or output B or output C), the stroke (or rear wheel steering angle) of the rear wheel shaft 43 and the rear wheel steering angle write inhibit signal. An example is shown below.

The predetermined speed v ₀ is a speed v (4W) that defines the lower limit value of the control range (4WS control range) of the four-wheel steering vehicle.
S) is preset so as to be smaller than that of FIG.
(A)).

When the vehicle speed becomes lower than the predetermined speed v ₀ ,
The counter value C is incremented from the initial value “0” (FIG. 4B). When the counter value C exceeds a predetermined threshold value C _0, the rear wheel steering angle write inhibit signal is changed from high level to low level (Fig. 4 (e)). When the rear wheel steering angle write inhibit signal is at a high level, writing to the memory of the current rear wheel steering angle value theta _r is prohibited. When the rear wheel steering angle write inhibit signal is at a low level, writing into the memory of the current rear wheel steering angle value theta _r is allowed. Therefore, the rear wheel steering angle write inhibit signal changes from high level to low level, defines the timing of writing the wheel steering angle value theta _r after the current in the memory.

When the stroke of the rear wheel shaft 43 (or the rear wheel steering angle) changes, the output (output A or output B or output C) of the rear wheel steering angle sensor 51 also changes in accordance with the change (FIG. 9). 4 (d) and FIG. 4 (c)). Each of the outputs A to C of the rear wheel steering angle sensor 51 is either a high level or a low level. The combination of the output A~ output C of the rear wheel steering angle sensor 51 represents the wheel steering angle value theta _r after the current. For example, when (output A, output B, output C) = (L, H, H), θ _r = 0 °
Represents Here, H indicates a high level, and L
Indicates a low level.

If any one of the outputs A to C of the rear wheel steering angle sensor 51 changes, the counter value C becomes "1".
It is initialized to 0 "(FIGS. 4B and 4C).
Therefore, if any one of the outputs A to C of the rear wheel steering angle sensor 51 changes before the counter value C exceeds the predetermined threshold value C ₀ , the rear wheel steering angle write inhibit signal becomes It is maintained at a high level (FIG. 4E).

As described above, the rear wheel steering control device 1 of the present invention
According to the above, when the vehicle speed becomes sufficiently low, the counter value C is incremented from the initial value. Without rear wheel steering angle value varies, the counter value C exceeds a predetermined threshold value C _0, the rear wheel steering control system 1 judges that "rear rotary steering is stable state", when the determination Is written into the memory. Thus, the writing of the rear wheel steering angle value into the memory is started before the ignition is turned off. As a result, the time allowed for writing to the memory can be made longer as compared with the conventional writing of the rear wheel steering angle value to the memory.

The rear wheel turning control device 1 may determine that "the rear wheel turning is in a stable state" when the vehicle speed is constant. Alternatively, the rear wheel steering control device 1
Regardless of the vehicle speed, when the counter value C without rear wheel steering angle value varies exceeds a predetermined threshold value C ₀ "rear rotary steering is stable state" may be determined as.

As described above, the rear wheel steering control device 1 of the present invention
According to this, when the rear wheel turning is in a stable state, the rear wheel steering angle value is written in the memory, and therefore, it is hardly affected by an external force applied to the vehicle after the ignition is turned off.
Thus, it is possible to prevent a deviation between the rear wheel steering angle value stored in the memory and the actual rear wheel steering angle value. For example, even when the vehicle is stopped on a slope and the ignition is turned off, it is possible to prevent a deviation between the rear wheel steering angle value stored in the memory and the actual rear wheel steering angle value from occurring. It becomes possible.

Further, according to the rear wheel turning control device 1 of the present invention, the timing of writing the rear wheel steering angle value into the memory is not limited to when the ignition is turned off. This means that EEP
The reliability of the rear wheel steering angle value stored in the ROM 36 is improved.

FIG. 5 shows the processing procedure of a program P1 'for writing the value of the detection signal (rear wheel steering angle value) output from the rear wheel steering angle sensor 52 into the EEPROM 36. Program P1 'is a further improvement of program P1. The program P1 'is the same as the program P1 except that steps S311 and S312 are inserted. Therefore, the same steps are denoted by the same reference numerals and description thereof will be omitted.

[0053] At step S311, the wheel steering angle value theta _r ^m after the previous is read from EEPROM 36. Step S
In 312, the last rear wheel steering angle value read from the EEPROM 36 theta _r and ^m absolute value of the difference between the wheel steering angle value theta _r after the current ^{_{(| θ r m -θ r |}} ) is a predetermined threshold It is determined whether the value is equal to or more than the value θ _r0 . If the result of the determination in step S312 is “Yes”, the process proceeds to step S306,
Wheel steering angle value θ _r after the current is written to the EEPROM36. If the result of the determination in step S312 is "No", the processing is terminated without wheel steering angle value theta _r after the current is written in the EEPROM 36.

As described above, the improved program P1 '
In, when the difference between the data stored in the memory and the data to be written to the memory from now on is smaller than a predetermined threshold value, the data is not written to the memory. This can prevent data from being written to the memory every time the vehicle stops. As a result, the number of times of writing data to the memory can be reduced.

FIG. 6 shows a processing procedure of the program P2 for correcting the reference position of the rear wheel shaft 43 when the ignition is turned on, prior to the rear wheel steering control during running of the vehicle. The program P2 is stored in the ROM 35.
The program P2 is executed by the CPU 33 every predetermined time.

Hereinafter, the program P will be described with reference to FIG.
The processing procedure 2 will be described.

In step S601, it is determined whether or not the ignition switch 11 has changed from the off state to the on state. This is because the program P2 is a part of the initial check process executed immediately after the ignition is turned on.

[0058] In step S602, the rear wheel steering angle value θ _r is read from EEPROM36.

[0059] At step S603, drives the rear wheel actuator 40 to the midpoint direction of the stroke on the basis of the wheel steering angle value theta _r after read.

In step S604, it is determined whether the output of the mid-stroke sensor 52 has changed as the rear wheel actuator 40 is driven. If the output of the mid-stroke sensor 52 has changed, the process proceeds to step S
Proceed to 605.

In step S605, it is determined whether or not the output pattern of the rear wheel steering angle sensor 51 at the time when the output of the stroke midpoint sensor 52 changes matches the initial value pattern. Here, the output pattern of the rear wheel steering angle sensor 51 is a combination of each value of the output A to the output C of the rear wheel steering angle sensor 51, and the initial value pattern is the rear wheel corresponding to the rear wheel steering angle of 0 °. It refers to the output pattern of the steering angle sensor 51. For example, the initial value pattern is (output A, output B, output C)
= (L, H, H). Here, H indicates a high level, and L indicates a low level.

If the output pattern of the rear wheel steering angle sensor 51 obtained in step S605 matches the initial value pattern, the process ends.

[0063] Table 1, when the output pattern of the wheel steering angle sensor 51 after being obtained matches the initial value pattern in step S605, the output pattern of the rear wheel steering angle value theta _r and the rear wheel steering angle sensor 51 Shows the relationship between Table 1
For example, it is stored in the ROM 35 in advance.

[0064]

[Table 1]

If the output pattern of the rear wheel steering angle sensor 51 obtained in step S605 does not match the initial value pattern, the process proceeds to step S606.

[0066] At step S606, the correcting the relationship between the output pattern of the rear wheel steering angle value theta _r and the rear wheel steering angle sensor 51. Such correction is achieved by regarding the output pattern of the rear wheel steering angle sensor 51 obtained in step S605 as an initial value pattern. For example, the output pattern of the rear wheel steering angle sensor 51 obtained in step S605 is (output A, output B, output C) = (H, H, L)
In this case, this output pattern is associated with the rear wheel steering angle value of 0 ° as an initialization pattern.

[0067] Table 2 shows the corrected relationship between the output pattern of the rear wheel steering angle value theta _r and the rear wheel steering angle sensor 51. Table 2 is stored in the ROM 35 in advance, for example. Table 2
Relative wheel steering angle value theta _r row after the table 1 corresponds to shifted by 2 column worth a line in the output pattern of Table 1 in the right direction.

[0068]

[Table 2]

[0069] The relationship between the output pattern of the wheel steering angle value theta _r after the above-described rear wheel steering angle sensor 51 corrected, for example, the rear wheel steering angle value from -0.9 ° + 0.9 ° Done within a range. The range is one of the output patterns of the rear wheel steering angle sensor 51.
This is because it corresponds to a cycle. In order to realize such correction, a table showing the corrected relationship is obtained by setting the rear wheel steering angle value to-
What is necessary is just to prepare in the range of 0.9 to +0.9 degrees. Thus, the reference position of the rear wheel shaft 43 can be corrected.

The above-described correction is performed when the rear wheel steering angle value is-
A range smaller than 0.9 ° or a rear wheel steering angle value of +0.
It can also be performed in a range larger than 9 °. However, this range is a rear wheel steering angle range corresponding to one rotation of the electric motor 41. In any case, it is necessary to design such that the characteristic (hysteresis) of the stroke midpoint sensor 52 falls within the range.

[0071] Further, in the example described above, an example was described of correcting the relationship between the output pattern of the rear wheel steering angle value theta _r and the rear wheel steering angle sensor 51. Rear and the rear wheel steering angle value θ _r wheel steering angle sensor 5
Instead of correcting the relationship between the first output pattern and the first output pattern, the relationship between the stroke value and the output pattern of the rear wheel steering angle sensor 51 may be corrected. In this case, R
Table 3 shows an example of a table to be stored in the OM 35.

[0072]

[Table 3]

As described above, the rear wheel steering control device 1 of the present invention
Thus, the relationship between the rear wheel steering angle value and the output pattern of the rear wheel steering angle sensor 51 can be corrected when the ignition is turned on. As a result, it is possible to eliminate the deviation between the rear wheel steering angle value stored in the memory and the actual rear wheel steering angle value.

FIG. 7 schematically shows the structure of the stroke midpoint sensor 52. The stroke midpoint sensor 52 is
1 and a Hall element 62. The magnet 61 has an S pole and an N pole, and is attached to the rear wheel shaft 43. The rear wheel shaft 43 is supported so as to be able to stroke left and right. Hall element 62 is fixed to the vehicle. The output of the Hall element 62 is supplied to the ECU 30 as the output of the mid-stroke sensor 52.

FIG. 8 is a graph showing the output characteristic of the stroke midpoint sensor 52. The mid-stroke sensor 52 outputs a high-level signal when the rear wheel shaft 43 is on the right side of the reference position.
Is at the left side of the reference position, a low-level signal is output. In the present specification, the position where the signal output from the stroke midpoint sensor 52 changes from the high level to the low level is referred to as the “reference position” of the rear wheel shaft 43.

Table 4 shows the output characteristics of the stroke midpoint sensor 52 in a table format. The mid-stroke sensor 52 outputs a signal (high level or low level) having an undefined level when the rear wheel shaft 43 is positioned near the reference position. The stroke midpoint sensor 52 outputs a signal having a fixed level (high level) when the Hall element 62 is malfunctioning or when the harness connector for connecting the stroke midpoint sensor 52 to the ECU 30 is defective. Level or low level).

[0077]

[Table 4]

Alternatively, a mid-stroke sensor having characteristics opposite to those shown in FIG. 8 and Table 4 may be used.

FIG. 9 shows an outline of the processing of the program P3 for detecting the reference position of the rear wheel shaft 43 when the ignition is turned on, prior to the rear wheel steering control when the vehicle is running. The program P3 is stored in the ROM 35.
The program P3 is executed by the CPU 33 every predetermined time.

Hereinafter, the program P will be described with reference to FIG.
Process 3 (reference position detection process) will be described.

When the rear wheel turning control is normal, when the vehicle speed falls below a certain value, the turning control of the rear wheels is prohibited, and the rear wheel shaft 43 is returned to the reference position. Therefore, when the ignition is on, in most cases, the rear wheel shaft 4
3 is considered to be at the reference position.

The operation of the rear wheel actuator 40 when the rear wheel steering control is normal will be described below. First, the rear wheel actuator 40 drives the rear wheel shaft 43 rightward at a high speed by 0.3 ° (FIG. 9).
Next, the rear wheel actuator 40 drives the rear wheel shaft 43 at a high speed to the left by 0.3 ° (FIG. 9).
Here, “0.3 °” corresponds to the hysteresis of the Hall element 62. Therefore, when the rear wheel shaft 43 is at the reference position when the ignition is turned on, the output of the stroke midpoint sensor 52 changes from low level to high level by driving the rear wheel shaft 43 as shown in FIG. By driving the rear wheel shaft 43 as shown in FIG. 9, the output of the mid-stroke sensor 52 changes from high level to low level. As a result, the reference position of the rear wheel shaft 43 is detected. In addition, "at high speed" means "at high speed to the extent that no abnormal noise is generated".

Next, the operation of the rear wheel actuator 40 when the rear wheel steering control is abnormal will be described.

When the rear wheel shaft 43 is stopped on the left side of the reference position at the time of the previous ignition off, the rear wheel actuator 40 sets the rear wheel shaft 43 to 0.3 °.
After the high-speed driving to the right by the amount, the motor is further driven to the right at a low speed until the output of the stroke midpoint sensor 52 changes from the low level to the high level (and in FIG. 9). Next, the rear wheel actuator 40 drives the rear wheel shaft 43 at a high speed to the left by 0.3 ° (FIG. 9).
of). Thus, the reference position of the rear wheel shaft 43 is detected. Note that “at low speed” means “at a low speed that does not significantly affect the vehicle behavior”.

When the rear wheel shaft 43 is stopped on the right side of the reference position at the time of the previous ignition off, the rear wheel actuator 40 adjusts the rear wheel shaft 43 by 0.3 °.
After the high-speed driving to the left by the amount, the motor is further driven to the left at a low speed until the output of the stroke midpoint sensor 52 changes from the high level to the low level (and in FIG. 9). Thus, the reference position of the rear wheel shaft 43 is detected.

Next, the operation of the rear wheel actuator 40 when the hall element 62 is out of order or when the harness connector is defective will be described.

When the output of the stroke midpoint sensor 52 is fixed at a low level, the rear wheel actuator 4
0 drives the rear wheel shaft 43 at a high speed to the right by 0.3 °, and then drives the rear wheel at a further low speed to the right until the rear wheel is further steered by 1.6 ° (see FIGS. 9 and '). ). If the rear wheel is further steered by 1.6 ° without the output of the stroke midpoint sensor 52 changing from the low level to the high level, the ECU 30 determines that the operation is abnormal due to a failure of the sensor or the like. Turn on the warning lamp.

When the output of the stroke midpoint sensor 52 is fixed at a high level, the rear wheel actuator 4
0 drives the rear wheel shaft 43 to the left at a high speed of 0.3 °, and then drives the rear wheel further to the left at a low speed until the rear wheel is further steered by 1.6 ° (FIGS. 9 and 9). ). If the rear wheel is further turned by 1.6 ° without changing the output of the stroke midpoint sensor 52 from the high level to the low level, the ECU 30 determines that the operation is abnormal due to a failure of the sensor or the like. Turn on the warning lamp.

As described above, when the output of the stroke midpoint sensor 52 is fixed at the low level or the high level, the malfunction is detected by the software guard before the malfunction is detected by the mechanical guard. Can be detected. As a result, the detection of the operation abnormality is multiplexed, and the safety is improved.

FIG. 10 is a flowchart showing the procedure of the processing of the program P3 (reference position detection processing). FIG.
0 is designed to be applicable to all cases described with reference to FIG.

In step S1001, it is determined whether or not the ignition switch 11 has changed from the off state to the on state. This is because the program P3 is a part of the initial check process executed immediately after the ignition is turned on.

In step S1002, it is determined whether the vehicle speed is higher than a predetermined speed _VL . If it is determined that the vehicle speed is higher than the predetermined speed _VL , the process proceeds to step S1003. Thus, when the vehicle speed is the predetermined speed V
_{The reason} why the reference position detection process is performed when the value is larger than _L is that it is difficult to drive the rear wheel actuator 40 when the vehicle speed is low. Meanwhile, although not shown in FIG. 10, when the vehicle speed is greater than the predetermined speed V _H, the overall initial check processing is aborted. Therefore, the reference position detection processing is actually executed when the vehicle speed is in the range of _{VL to VH} (about 10 to 30 km / h in the present embodiment).

In step S1003, it is determined whether the output of the stroke midpoint sensor 52 is at a low level (Lo). If the determination in step S1003 is “Yes”, the ECU 30 outputs a “right turning command (high speed)” to the rear wheel actuator 40 (step S100).
4). "Right steering command (high speed)" refers to the left and right rear wheels RW1,
The electric motor 41 is steered so that the RW2 is steered rightward at high speed.
Is a command to control the rotation of. On the other hand, step S100
If the determination of No. 3 is “No”, the ECU 30 outputs a “left steering command (high speed)” to the rear wheel actuator 40 (step S1013). The “left steering command (high speed)” is a command for controlling the rotation of the electric motor 41 so that the left and right rear wheels RW1 and RW2 are steered to the left at high speed. Here, "high-speed" means "high-speed so that abnormal noise does not occur".

In step S1005, it is determined whether or not the output of the stroke midpoint sensor 52 is at a high level (Hi). Before the left and right rear wheels RW1, RW2 steer by 0.3 °, when the output of the stroke midpoint sensor 52 changes from low level (Lo) to high level (Hi),
The process proceeds to step S1006 (step S1005
And step S1008).

In step S1006, the ECU 30
A “left steering command (high speed)” is output to the rear wheel actuator 40. Thereafter, when the output of the stroke midpoint sensor 52 changes from the high level (Hi) to the low level (Lo), a “stop command” (a command to stop the rotation of the electric motor 41) is output in step S1020. The processing ends (step S1007). Thus, the reference position of the rear wheel shaft 43 is detected.

Before the output of the stroke midpoint sensor 52 changes from low level (Lo) to high level (Hi),
When the left and right rear wheels RW1, RW2 are turned by 0.3 °,
The process proceeds to step S1009 (step S1005
And step S1008).

In step S1009, the ECU 30
A “right steering command (low speed)” is output to the rear wheel actuator 40. “Right turn command (low speed)” refers to the left and right rear wheels RW
1. Commands for controlling the rotation of the electric motor 41 so as to steer the RW2 rightward at a low speed. Here, "low speed"
What is "Slow enough to not significantly affect vehicle behavior"
It means.

Before the left and right rear wheels RW1, RW2 steer by 1.6 °, when the output of the stroke midpoint sensor 52 changes from low level (Lo) to high level (Hi),
The process proceeds to step S1006 (step S1010
And step S1011). On the other hand, if the left and right rear wheels RW1 and RW2 are turned by 1.6 ° before the output of the stroke midpoint sensor 52 changes from the low level (Lo) to the high level (Hi), "stop" is performed in step S1021. Command (a command to stop the rotation of the electric motor 41), and the process proceeds to step S1012 (step S101).
0 and step S1011).

In step S1012, the warning lamp is turned on. Lighting of such a warning lamp is an example of an operation based on diagnosis (self-diagnosis function). In this way, the warning of the operation abnormality is notified to the driver.

Steps S1014 to S1019
Are the same as the operations in steps S1005 to S1012, and the description is omitted here.

As described above, the rear wheel turning control device 1 of the present invention controls the rear wheel shaft 4 during the initial check process.
3 to the left and right strokes,
Then, the position at which the output level changes is detected, and thereafter the operation is performed with the detected position as a reference position. Such a reference position detection process does not require storing the rear wheel steering angle value in the memory when the ignition is turned off. Therefore,
An error does not occur due to a difference between the rear wheel steering angle value stored in the memory and the actual rear wheel steering angle value. As a result, the reference position of the rear wheel shaft 43 can always be detected accurately.

When the rear wheel shaft 43 is stopped at the reference position, the reference position detection process can be performed by moving the rear wheel shaft 43 right and left at a high speed. Therefore, in most cases, the reference position detection processing can be completed in a short time. Even when the rear wheel shaft 43 is stopped at a position other than the reference position, the reference position detection processing can be completed in a relatively short time.

Furthermore, even when the output from the mid-stroke sensor 52 is a fixed value due to a failure of the Hall element 62 or a defective harness connector, etc., the operation abnormality is not detected by the mechanical guard. In addition, an abnormal operation can be detected by software guard. As a result, the detection of the operation abnormality is multiplexed, and the safety is improved.

The reference position detecting process shown in FIGS. 9 and 10 can be executed in step S603 shown in FIG.

When the rear wheel steering angle is in a stable state,
The neutral point of the rear wheel steering angle may be corrected by storing the rear wheel steering angle value in the memory and turning the rear wheel based on the rear wheel steering angle value stored in the memory. Such an embodiment can be expressed as follows.

(1) A relative steering angle sensor for detecting a relative steering angle of a rear wheel from a predetermined point, a neutral sensor for detecting a neutral point of a rear wheel steering angle, an output of the relative steering angle sensor and the neutral An absolute steering angle calculating means for calculating a steering angle from a neutral point of the rear wheel based on an output of the sensor, a memory for storing a calculation result of the absolute steering angle calculating means, and a rear wheel steering state in a stable state. Stable state determining means for determining whether or not there is, and storing the calculation result of the absolute steering angle calculating means in the memory when the rear wheel turning state is determined to be stable by the stable state determining means. Means, first turning means for turning the rear wheel in the direction of the neutral point based on the absolute steering angle stored in the memory at a predetermined timing, and the neutral turning during the turning by the first turning means. When the neutral point is detected by the sensor, The second steering means for steering the rear wheel in the direction opposite to the steering direction, and the output of the relative steering angle sensor when the neutral point is detected by the neutral sensor during steering by the second steering means. A rear wheel steering control device comprising a neutral point and a neutral point correcting means for correcting the neutral point.

In the rear wheel turning control device according to the embodiment (1), the vehicle is turned at a first speed from a start of turning by the first turning means and the second turning means to a predetermined turning angle. ,
After the predetermined steering angle has been turned, a turning speed control means for turning at a second speed lower than the first speed may be provided.

Further, in the rear wheel turning control apparatus according to the embodiment (1), when the turning by the first turning means reaches a predetermined steering angle, a failure judging means for judging that the neutral sensor system is faulty. May be provided.

In this embodiment, the steering speed control means may be further provided. In this case, it is preferable that the predetermined steering angle referred to by the failure determination means is a steering angle larger than the predetermined steering angle referred to by the turning speed control means.

[0110]

According to the rear wheel steering control device of the present invention, when it is determined that the rear wheel steering is in a stable state, the output of the rear wheel steering angle sensor is written into the memory. Therefore, the vehicle is less susceptible to the external force applied to the vehicle after the ignition is turned off. As a result, it is possible to prevent the occurrence of a deviation between the rear wheel steering angle value stored in the memory and the actual rear wheel steering angle value.

Further, according to the rear wheel steering control device of the present invention, the relationship between the rear wheel steering angle value and the output of the rear wheel steering angle sensor can be corrected when the ignition is turned on. As a result, it is possible to eliminate the deviation between the rear wheel steering angle value stored in the memory and the actual rear wheel steering angle value.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a rear wheel steering control device 1 of the present invention.

FIG. 2 is a diagram showing a configuration of an electronic control unit (ECU) 30 included in the rear wheel turning control device 1.

FIG. 3 is a flowchart showing a processing procedure of a program P1 for writing a value of a detection signal (rear wheel steering angle value) output from a rear wheel steering angle sensor 52 into an EEPROM 36;

FIG. 4A is a diagram showing a temporal change of a vehicle speed, and FIG.
Is a diagram showing a temporal change in the counter value C, (c) is a diagram showing a temporal change in the output (output A or output B or output C) of the rear wheel steering angle sensor 51, and (d) is a diagram showing the rear wheel. Shaft 4
3 is a diagram showing a temporal change of a stroke 3 (or a rear wheel steering angle), and FIG. 7E is a diagram showing a temporal change of a rear wheel steering angle write inhibit signal.

FIG. 5 is a flowchart showing a processing procedure of a program P1 ′ for writing a value of a detection signal (rear wheel steering angle value) output from a rear wheel steering angle sensor 52 to an EEPROM 36;

FIG. 6 is a flowchart showing a processing procedure of a program P2 for correcting a reference position of a rear wheel shaft 43 when an ignition is turned on, prior to a rear wheel steering control when the vehicle is running.

FIG. 7 is a diagram schematically showing a structure of a stroke midpoint sensor 52;

FIG. 8 is a graph showing output characteristics of a stroke midpoint sensor 52;

FIG. 9 is a diagram showing an outline of processing of a program P3 for detecting a reference position of a rear wheel shaft 43 when an ignition is turned on, prior to rear wheel steering control during vehicle running.

FIG. 10 is a flowchart showing a processing procedure of a program P3.

FIG. 11 is a diagram for describing writing of a rear wheel steering angle in a conventional rear wheel steering control device.

FIG. 12 is a diagram for describing writing of a rear wheel steering angle in a conventional rear wheel steering control device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 rear wheel steering control device 10 battery 11 ignition switch 21 vehicle speed sensor 30 electronic control device (ECU) 41 electric motor 42 steering gear box 43 rear wheel shafts 44a, 44b tie rods 45a, 45b knuckle arm 51 rear wheel steering angle sensor 52 during stroke Point sensors RW1, RW2 Left and right rear wheels

Claims (4)

[Claims] 1. A rear wheel steering angle sensor for detecting a rear wheel steering angle and outputting a detection signal indicating the rear wheel steering angle; a memory storing an output of the rear wheel steering angle sensor; Determination means for determining whether or not the vehicle is in a stable state; and writing means for writing the output of the rear wheel steering angle sensor to the memory when the rear wheel steering is determined to be in a stable state. Rear wheel steering control device. 2. The determining means comprises: means for determining whether or not the output of the rear wheel steering angle sensor has changed; and time measuring means for measuring an elapsed time. If the output of the wheel steering angle sensor does not change and the elapsed time measured by the timing means exceeds a predetermined threshold, it is determined that the rear wheel turning is in a stable state. 2. The rear wheel steering control device according to 1. 3. A rear-wheel steering angle sensor for detecting a rear-wheel steering angle and outputting a detection signal indicating the rear-wheel steering angle; A stroke midpoint sensor that outputs a detection signal indicating the position of the midpoint of the stroke, a memory that stores the output of the rear wheel steering angle sensor, and a reading unit that reads the output of the rear wheel steering angle sensor stored in the memory. Moving means for moving the rear wheel shaft in the direction of the midpoint of the stroke in accordance with the read output of the rear wheel steering angle sensor; and detecting that the stroke midpoint sensor indicates the position of the midpoint. First determining means for determining whether or not a signal has been output; and an output of the rear wheel steering angle sensor when the stroke midpoint sensor outputs a detection signal indicating the position of the midpoint coincides with a predetermined initial value. Second determining means for determining whether or not to perform Depending on the determination result by the constant unit, rear wheel steering control system that includes a correcting means for correcting the relationship between the output of the rear wheel steering angle value and the rear wheel steering angle sensor. 4. A neutral sensor for detecting a neutral point of a rear wheel steering angle, first steering means for steering a rear wheel in one direction based on an output of the neutral sensor, and first steering. When the neutral point is detected by the neutral sensor during turning by the means, second turning means for turning the rear wheel in a direction opposite to the turning direction by the first turning means; A rear wheel steering control device comprising: a neutral point detecting means for setting a rear wheel steering angle to a neutral point of a rear wheel steering angle when a neutral point is detected by the neutral sensor during turning by the steering means.