JPH06278634A - Rear-wheel steering device of vehicle - Google Patents

Abstract

PURPOSE:To obtain a rear wheel steering device provided with an absolute steering angle detecting means and a relative steering angle detecting means, and an inexpensive rear wheel steering angle detecting means which can correctly detect the actual steering angle of the rear wheels in an early stage. CONSTITUTION:A rear wheel steering device is provided with a steering mechanism SM connected to the rear wheels RW, a driving means S1 to drive and control this steering mechanism SM, an absolute steering angle detecting means S2 to detect the absolute steering angled where the rear wheels RW are actually steered by the driving means S1, a relative steering angle detecting means S3 to detect the relative change of the steering angle of the rear wheels RW, a reference steering angle setting means S4 to set the detected results of the absolute steering angle detecting means S2 as the reference steering angle, and a control means S5 which controls the driving means S1 according to the detected results of the relative steering angle detecting means S3 based on the reference steering angle and adjusts the position of the rear wheels RW. When the steering angle of the rear wheels RW reaches the value within the specified range whose center is at the neutral position by adjusting the control means S5, the reference steering angle setting means S4 re-sets the detected results of the absolute steering angle detecting means S2 as the reference steering angle.

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 system for a vehicle, in which the steering mechanism for the rear wheels is driven and controlled by driving means such as an electric motor.

[0002]

2. Description of the Related Art Conventionally, there has been known a rear wheel steering device for improving steering performance of a vehicle by steering not only front wheels but also rear wheels of the vehicle.
According to Japanese Patent No. 3769, the steering control of the rear wheels is performed by an open control that does not perform feedback, and the steering angle of the front wheels or the rear wheels is determined by the control angle accumulation that is generally a problem in the open control. A four-wheel steering system for a vehicle is disclosed which controls to eliminate the error when the steering wheel is "0", that is, when the steering is not actively performed.

In the steering apparatus described in the above publication, in the description of the embodiment, the actual measurement signal E indicating the actual rear wheel steering angle θr output from the rear wheel steering angle sensor 29 is the comparator 32.
Is input to the comparator 32 and the steering angle “0” detection unit 3 is input to the comparator 32.
It is described that the operation signal G output from 3 is input. Further, the turning angle “0” detection unit 33 outputs the operation signal G when the front wheel turning angle signal D is input and the front wheel turning angle θf indicated by the signal D is “0”. Comparator 3
2 operates when this operation signal G is input, compares the comparison reference value corresponding to the preset rear wheel turning angle “0” with the actually measured rear wheel turning angle θr indicated by the actually measured signal E, and It is described that a correction signal (pulse signal) H corresponding to the deviation amount is output to the driver 31 of the pulse motor 14.

[0004]

Unlike the above-mentioned open-control rear-wheel steering system, in the rear-wheel steering system that requires feedback control, the detection accuracy of the rear-wheel steering angle sensor is
High accuracy is required in all areas of the steering angle. As described above, in order to secure high accuracy over the entire range of the steering angle, an absolute steering angle sensor that can directly detect the steering angle is necessary, but the absolute steering angle sensor generally has a large detection resolution,
Further, since it is analog processing, it is easily affected by noise, and since all of these problems must be solved, it becomes expensive. On the other hand, the relative steering angle sensor that detects the change in the steering angle of the rear wheels can detect the relative steering angle amount with high accuracy,
Although inexpensive, it is not possible to detect the absolute value of the steering angle.

Therefore, the present invention has an absolute steering angle detecting means for detecting the absolute value of the steering angle of the rear wheels and a relative steering angle detecting means for detecting a change in the relative steering angle. It is an object of the present invention to provide a rear wheel steering device equipped with an inexpensive rear wheel steering angle detecting means capable of detecting a steering angle.

[0006]

In order to achieve the above object, the present invention has a steering mechanism SM connected to rear wheels RW and a drive control of the steering mechanism SM, as shown in the outline of the configuration in FIG. The driving means S1 is provided. Further, an absolute steering angle detecting means S2 for detecting an absolute value of a steering angle at which the rear wheel RW is actually steered by the driving means S1, and a relative steering angle detecting means for detecting a relative steering angle change of the steering angle of the rear wheel RW. S3
And a reference steering angle setting means S4 for setting the detection result of the absolute steering angle detection means S2 as a reference steering angle, and a drive means S based on the reference steering angle and according to the detection result of the relative steering angle detection means S3.
1 and controls the position of the rear wheel RW. When the steering angle of the rear wheels RW reaches a value within a predetermined range centered on the neutral position by the adjustment of the control means S5, the reference steering angle setting means S4 uses the detection result of the absolute steering angle detection means S2 as a reference. The steering angle is reset.

In the above-mentioned vehicle rear wheel steering system, when the absolute steering angle detecting means S2 detects that the rear wheels RW have reached the neutral position, the reference steering angle setting means S4 controls the absolute steering angle detecting means S2. The detection result may be reset as the reference steering angle.

Further, according to the present invention, the absolute steering angle detecting means S2 for detecting the absolute value of the steering angle at which the rear wheel RW is actually steered by the drive means S1 and the relative steering angle change of the steering angle of the rear wheel RW are detected. The relative steering angle detecting means S3 for detecting, the reference steering angle setting means S4 for setting the detection result of the absolute steering angle detecting means S2 as the reference steering angle, and the detection result of the relative steering angle detecting means S3 based on the reference steering angle. The drive means S1 is controlled in accordance with the rear wheel RW.
When the absolute steering angle detecting means S2 detects that the rear wheel RW has reached the neutral position, the reference steering angle setting means S4 detects the absolute steering angle detecting means S2. You may comprise so that a result may be reset as a reference steering angle.

[0009]

In the rear wheel steering system of the vehicle having the above structure, the drive mechanism S1 drives and controls the steering mechanism SM. On the other hand, the absolute steering angle detection means S2 detects the absolute value of the steering angle when the rear wheel RW is actually steered, and
A relative steering angle change of the steering angle of the rear wheels RW is detected by the relative steering angle detection means S3. Further, the reference rudder angle setting means S4 sets the detection result of the absolute rudder angle detection means S2 as the reference rudder angle. Then, the drive means S1 is controlled by the control means S5 based on the reference steering angle and according to the detection result of the relative steering angle detection means S3, and the position of the rear wheel RW is adjusted.
As a result, when the steering angle of the rear wheels RW reaches a value within a predetermined range centered on the neutral position, the reference steering angle setting means S
4, the detection result of the absolute steering angle detecting means S2 is reset as the reference steering angle. When the absolute steering angle detecting means S2 detects that the rear wheels RW have reached the neutral position, the reference steering angle setting means S4 further resets the detection result of the absolute steering angle detecting means S2 as the reference steering angle. It may be set.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rear wheel steering system for a vehicle according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a vehicle equipped with a rear wheel steering device.
The front wheels 3 and 14 are steered by the front wheel steering mechanism 10 in response to a turning operation of a steering wheel 19. Front wheel steering mechanism 1
No. 0 is provided with a first front wheel steering angle sensor 17 for detecting the amount of movement of the rack, and the steering wheel 1
The second front wheel rudder angle sensor 20 is attached to the steering shaft to which 9 is attached.
Is provided, and the steering amount of the front wheels is detected by these sensors. As the first front wheel steering angle sensor 17, for example, a linear sensor such as a potentiometer is used.
As the front wheel steering angle sensor 20, a steering sensor such as a rotary encoder that emits a pulse when rotating is used.

A rear wheel steering mechanism 11 is connected to the rear wheels 15 and 16 and steered according to the rotation of a motor 12.
A magnetic pole sensor 18 for detecting the rotation angle of the motor 12 is provided at the end of the motor 12. Further, a rear wheel steering angle sensor 21 is provided on a rack shaft 25 which is a rear wheel steering shaft, and the actual steering angles of the rear wheels 15 and 16 are detected by this. The rear wheel steering angle sensor 21 may be built in the rear wheel steering mechanism 11. Further, the speed of the vehicle is detected. 2
A system first vehicle speed sensor 22, a second vehicle speed sensor 23, and a yaw rate sensor 24 for measuring the yaw rate of the vehicle are provided. The motor 12 is configured to be controlled by a signal from the electronic control unit 9. That is,
The electronic control unit 9 includes a first front wheel steering angle sensor 17, a second front wheel steering angle sensor 20, a magnetic pole sensor 18, and a rear wheel steering angle sensor 2.
1, sensor outputs of the first vehicle speed sensor 22, the second vehicle speed sensor 23, and the yaw rate sensor 24 are supplied, and the rotation amount of the motor 12 is set according to these outputs.
Is supplied with a control signal.

The rear wheel steering angle sensor 21 of this embodiment is built in the rear wheel steering mechanism 11 as shown in FIG. A cover 36 is fixed to a housing 38 of the rear wheel steering mechanism 11, and a magnetic pole sensor 18, a motor housing 40 of the motor 12 and a rear wheel steering angle sensor 21 are integrally provided on the cover 36. As is apparent from FIG. 3, which is a partial cross-sectional view of the rear wheel steering mechanism 11 shown in FIG. 2, the rack shaft 25 is provided at right angles to the traveling direction of the vehicle, and both end portions of the rack shaft 25 are It is connected to the knuckle arm of the rear wheel via a ball joint 53. Both ends of the rack shaft 25 are protected by boots 28. A tube 39 is fitted to the right end of the housing 38 in the figure. When the rack shafts 25 having different lengths are provided, it is possible to deal with them by changing the tube 39 without changing the housing 38. A rack 26 is formed on the rack shaft 25, and the rack 26 meshes with a pinion 27 extending in the front-rear direction of the vehicle. The rack guide cover 32 is fixed to the housing 38 while the rack guide 31 is biased toward the rack 26, whereby the rack 26 is pressed toward the pinion 27. In addition, the pinion 27, as shown in FIG.
It is fixed to 9 by shrink fit (press fit), and the relative rotation is blocked by the pin 37.

As shown in FIG. 4, the rear wheel steering angle sensor 21 has a built-in potentiometer and is provided parallel to the surface of the gear 29. A pin 34 is attached to the shaft 54 via a lever 33.
Is provided, and this pin 34 is fitted into a hole 35 formed in the gear 29. As a result, when the gear 29 rotates, the shaft 54 also rotates, and the rotation angle of the shaft 54 is detected by the rear wheel steering angle sensor 21. On the other hand, the rotation angle of the shaft 54, that is, the rotation amount of the gear 29 is proportional to the lateral movement amount of the rack shaft 25. Thus, the rear wheel steering angle sensor 21 detects the steering angle amount of the rear wheels.

As shown in FIG. 3, a pinion 30 is provided at the tip of a motor shaft 41 of the motor 12, and a gear 29 meshes with the pinion 30 to form a hypoid gear. This hypoid gear transmits the rotation of the motor shaft 41 of the motor 12 as the rotation of the gear 29, but when a rotational force is applied to the gear 29 from the rack shaft 25 (FIG. 4) side, the motor shaft 41 of the motor 12 does not rotate. Thus, the reverse efficiency is set to zero. Also, pinion 3
The 0 and the gear 29 constitute an HRH (high ratio hypoid) gear so as to have a large reduction ratio. The gear ratio is
Since it is determined by the number of poles of the motor 12, the resolution of the steering angle, etc., it varies depending on the vehicle, but in this embodiment it is set to 67: 1.

As shown in FIG. 5, the motor shaft 41 of the motor 12 is rotatably supported in the motor housing 40. A four-pole magnet 42 is fixed around the motor shaft 41. Further, the motor housing 40 includes a magnet 42.
A core 43 is fixed so as to face the core 43, and a motor winding 44 is wound around the core 43. As is apparent from FIG. 6 showing the AA cross section of FIG. 5, twelve protrusions 43a extending in the central direction are formed in the core 43, and the motor winding 44 is wound around the protrusion 43a. It The motor windings 44 are connected by windings 44a and 44d and 44b and 44b as shown in FIG. 7 in which the motor winding 44 is viewed from the magnetic pole sensor 18 side.
One ends of e, 44c and 44f are connected to terminals U, V and W, respectively. Windings 44a, 44b, 44c, winding 4
The other ends of 4d, 44e, and 44f are electrically connected. The motor winding 44 is connected to a wire harness 46 via a terminal 45 for each system.

One end of the motor housing 40 is an open end, and the magnetic pole sensor 18 is attached thereto. The substrate 49 of the magnetic pole sensor 18 is fixed to the open end of the motor housing 40 by the holder 47 (shown in FIG. 9), and the cover 48 is provided at the open end. On the other hand, the motor 12
A rotor 52 is fixed to the end of the motor shaft 41 of the above, and a magnet 51 is provided on the rotor 52. The magnet 51 is formed in a disc shape with four poles, as shown in FIG. As shown in FIG. 9, three Hall ICs 50 are arranged on the substrate 49, each being shifted by 60 degrees. The outputs of these three Hall ICs 50 are output to the magnetic pole sensor signals HA, HB, HC in the electronic control unit 9 described later.
Used as.

That is, when the motor shaft 41 rotates, as shown in FIG.
Hall IC as shown in "Rotating state of magnet 51"
The magnet 51 rotates relatively to (HA, HB, HC in the drawing), and the three magnetic pole sensor signals HA, HB, HC that are the three outputs of the magnetic pole sensor 18 are at the high level (H) as shown in the drawing.
And low level (L). FIG. 10 shows a motor 12
Shows the state of rotating clockwise (CW). When the motor 12 rotates counterclockwise (CCW), the magnetic pole sensor signals HA, HB, HC of the magnetic pole sensor 18 are switched in the direction from the right to the left in the figure. When the winding current of the motor winding 44 is switched in synchronization with the switching of the magnetic pole sensor signals HA, HB and HC, the motor 12 rotates. The direction of the winding current when the motor 12 shown in FIG. 10 rotates will be described later.

FIG. 11 shows the configuration of the electronic control unit 9. The electronic control unit 9 is connected to a vehicle-mounted battery 59. That is, the battery 59 is connected to the motor driver 5 via the fuse and the power supply terminal PIGA, and is also connected to the motor driver 5 and the constant voltage regulator 55 via the fuse, the ignition switch IGSW, and the power supply terminal IGA. The constant voltage regulator 55 outputs a constant voltage Vcc1.

The electronic control unit 9 has a microprocessor 1 which is a control means, and the microprocessor 1 is operated by a constant voltage Vcc1. The above-described first front wheel steering angle sensor 17, second front wheel steering angle sensor 20, and first vehicle speed sensor 2
2, the outputs of the second vehicle speed sensor 23, the yaw rate sensor 24, the magnetic pole sensor 18, and the rear wheel steering angle sensor 21 are input to the microprocessor 1 via the interface 57. Here, the output of the first front wheel steering angle sensor 17 is set to θf.
1, the output of the second front wheel steering angle sensor 20 is θf2, the output of the first vehicle speed sensor 22 is V1, the output of the second vehicle speed sensor 23 is V2, the output of the yaw rate sensor 24 is γ, the magnetic pole sensor 1
The three output signals of 8 are HA, HB, HC, and the output of the rear wheel steering angle sensor 21 is θr.

The motor connected to the electronic control unit 9 is represented by 12 in the above-mentioned mechanism, but is represented by M in the circuit diagrams after FIG. The terminals U, V, W of each phase of the motor M are connected to the motor driver 5 of the electronic control unit 9. Power supply terminal P for motor driver 5
Electric power is supplied from IGA and IGA. Then, the motor driver 5 is provided with a phase switching signal group L1 (L1 is a phase switching signal LA) which is a signal output from the microprocessor 1.
11, LB11, LC11, LA21, LB21, LC
21) and pulse width modulation (Pulse Width)
Modulation) signal PWM1 is input.

The motor driver 5 is constructed as shown in FIG. 12, and is controlled by the phase switching signal group L1 and the pulse width modulation signal PWM1 described above. The phase switching signals LA11, LB11, LC11 for controlling the high side are input to the gate drive circuit G11 via the abnormal current limiting circuit 88. Normally, these input signals are directly output from the output side via the abnormal current limiting circuit 88. The gate drive circuit G11 is a circuit for on / off driving the transistors TA11, TB11, TC11 of the power MOSFET. The gate drive circuit G11 also performs boosting, supplies the boosted voltage to the gates of the transistors TA11, TB11, TC11, and outputs the boosted voltage as a boosted voltage value RV1. Transistors TA11, TB
11 and TC11, high voltage obtained from the power supply terminal PIGA via the pattern fuse PH, the choke coil TC, and the resistor Rs is the three-phase terminals U of the motor M, respectively.
It is connected so as to be supplied to V and W. The transistors TA11, TB11, TC11, TA21, TB
A Zener diode is inserted between the gate and the source of the TC21 and TC21, and is used for protection of the power MOSFET. That is, the power supply voltage is 20V for some reason
When the voltage exceeds the threshold voltage, the gate-source voltage of the power MOSFET exceeds 20 V and the power MOSFET is destroyed, so a Zener diode is provided to prevent this.

On the other hand, the phase switching signals LA21, LB21, LC21 for controlling the low side are connected to the gate drive circuit G21 via the pulse width modulation signal synthesis circuit 89 and the abnormal current limiting circuit 88. The pulse width modulation signal synthesis circuit 89 includes phase switching signals LA21, LB21, LC.
21 is a circuit for combining 21 with the pulse width modulation signal PWM1. The gate drive circuit G21 is a circuit for driving the transistors TA21, TB21, TC21 of the MOSFET on and off, and these transistors TA21, T21.
B21 and TC21 are three-phase terminals U, V, and
It is arranged so that W and the ground of the battery 59 are connected. Transistors TA11, TB11, TC1
Protective diodes D3 to D8 are connected to 1, TA21, TB21, and TC21, respectively. The voltage supplied to the transistors TA11, TB11, TC11 is
At the same time, it is output as the voltage PIGM1.

This voltage PIGM1 and the gate drive circuit G
When the difference from the boosted voltage value RV1 of 11 decreases to about 2V,
MOSFET transistors TA11, TB11, TC
On resistance of 11, TA21, TB21, TC21 may increase, and abnormal heat generation may occur. Therefore, the voltage PIG
When the difference between M1 and the boosted voltage value RV1 is less than or equal to a predetermined value, all the transistors TA11, TB11, TC11,
It is preferable to turn off TA21, TB21, TC21. Incidentally, the transistors TA21, TB21, TC2
Since a large current flows through the source of No. 1, it is desirable that the ground of the weak electric circuit section of the microprocessor or the like be a wiring of a system different from these grounds.

A current detection circuit 86 is connected to both ends of the resistor Rs, and the value of the current flowing through the resistor Rs is detected.
The current detection circuit 86 has a current value of 18 A flowing through the resistor Rs.
In the above case, it is determined that the current is an overcurrent, the overcurrent signal is output as the output signal MOC1, the overcurrent signal is supplied to the pulse width modulation signal synthesis circuit 89, and the limitation is applied on the low side. Further, the current detection circuit 86 determines that the current value flowing through the resistor Rs is an abnormal current when the current value is 25 A or more, and the output signal MS1
Outputs an abnormal current signal. When an abnormal current occurs, an abnormal current signal is given to the abnormal current limiting circuit 88,
Place restrictions on the high and low sides. In this case, all transistors TA11, TB11, TC1
1, TA21, TB21, TC21 may be turned off for a certain period of time after the abnormal current is detected. This fixed time may be set within the safe operation area of the FET with respect to the expected maximum current. The current value detected by the current detection circuit 86 is given to the peak hold circuit 101, and the peak hold circuit 101 outputs the peak value of the current value as the peak signal MI1. The peak hold circuit 101 is reset at the timing when the reset signal DR1 switches.

Next, the rotating operation of the motor M will be described with reference to FIG. Magnetic pole sensor signals HA, HB, HC
The motor M rotates by setting the pattern of the phase switching signal as shown in Table 1 according to the state of. The clockwise rotation (CW) is set to right cut, and the counterclockwise rotation (CCW) is set to left cut. First, the order of clockwise rotation 1 in Table 1
The magnetic pole sensor signal is (HA, HB, HC) =
In the case of (H, L, H), the phase switching signal is (LA11,
LB11, LC11, LA21, LB21, LC21)
= (H, L, L, L, H, L) is output. This state corresponds to the state of the range A in FIG. 10, and the magnetic pole sensor signals HA and HC are at the high level (H), as is clear from the relative rotational positional relationship of the magnet 51 with respect to the three Hall ICs. There is. The direction of the winding current changes from the U phase to the V phase, and the magnet 51 rotates clockwise in the drawing as the motor M rotates. When the magnet 51 rotates about 30 degrees, the magnetic pole sensor signal HA switches from high level to low level.
In response to this, the phase switching signal becomes (LA11, LB11, LC
11, LA21, LB21, LC21) = (L, L,
H, L, H, L), the motor M further rotates 30 degrees, and the magnetic pole sensor signal HB becomes high level. In this way, the motor M continuously rotates from the state on the left side in FIG. 10 to the state on the right side. Therefore,
In order to give the clockwise rotation (CW) or the counterclockwise rotation (CCW) to the motor M, the pattern of the phase switching signal may be switched according to the order of the upper stage or the lower stage of Table 1.

[Table 1]

As shown in FIG. 13, the microprocessor 1 includes a target steering angle calculation unit 60, a motor servo control unit 61,
It has a phase switching control unit 62, a magnetic pole sensor abnormality determination unit 63, an open control unit 64, and a switch SW1. The target steering angle calculation unit 60 obtains the target steering angle value AGLA from the yaw rate value γ, the vehicle speed V and the steering angle θs. Although not shown in FIG. 13, the vehicle speed V is determined by the first and second vehicle speed sensors 22, 2
3 is calculated based on the output values V1 and V2. At this time, the average of the two vehicle speed values may be the vehicle speed V, or the maximum value of the two vehicle speed values may be the vehicle speed V. By detecting the vehicle speed in two systems in this way, it is possible to detect an abnormality in the vehicle speed sensor. Although not shown in FIG. 13, the front wheel steering angle θs is determined by the first and second front wheel steering angle sensors 1 and 2.
It is calculated based on the output values θf1 and θf2 of 7 and 20. In this case, normally, the first front wheel steering angle sensor 17
Although a potentiometer is used as the potentiometer, the accuracy of the potentiometer is rough. On the other hand, if a rotary encoder is used as the second front wheel steering angle sensor 20, the amount of steering angle can be detected accurately, but the amount of initial steering angle cannot be detected. Therefore, the first front wheel steering angle sensor 17 determines the absolute value of the output of the second front wheel steering angle sensor 20, and after determining the absolute value, the output of the second front wheel steering angle sensor 20 is set as the steering angle θs.

FIG. 14 is a control block diagram of the motor servo control unit 61. The differentiating unit 90 differentiates the target rudder angle value AGLA to obtain the differential value SAGLA, and the differential gain setting unit 91 sets the target rudder angle. Differential value SAGLA
The differential gain YTDIFGAIN is obtained based on the absolute value of. The absolute value of the differential value SAGLA is 4 (deg / se
c) In the following cases, the differential gain is 0 and the differential value SAGL
The differential gain is set to 4 when the absolute value of A is 12 (deg / sec) or more, and the differential gain is 0 to 4 when the absolute value of the differential value SAGLA is 4 to 12 (deg / sec). It becomes a value.

On the other hand, a potentiometer is normally used as the rear wheel steering angle sensor 21, but the potentiometer has a rough precision, and the magnetic pole sensor 18 can detect the steering angle amount with high accuracy, but the initial steering angle amount can be detected. Can not. Therefore, the absolute value of the steering angle of the rear wheels 15, 16 is obtained by the rear wheel steering angle sensor 21 which is the absolute steering angle detecting means, and after the absolute value is obtained, the output change of the magnetic pole sensor 18 which is the relative steering angle detecting means. From this, the rotation angle of the motor M, that is, the relative steering angle value θm is determined. That is, the output signal of the motor M is supplied to the actual steering angle value calculation unit 100 having a rear wheel steering angle counter,
Here, the rotation angle θm of the motor M is obtained as the count value θc of the rear wheel steering angle counter that is incremented or decremented according to the output pulse signal of the magnetic pole sensor 18. Further, the absolute steering angle value θr which is AD-converted based on the output signal of the rear wheel steering angle sensor 21 is the actual steering angle value calculation unit 1
00 as a reference value.

The rear wheel steering angle sensor 21 has the output characteristics shown in FIG. 21, and is set so that the output voltage corresponding to the absolute steering angle value θr falls within the range surrounded by the broken line in FIG. In this embodiment, the output is 2.5 V at the 0 deg position (neutral position), and the error is limited to a maximum of ± 0.25 deg in the range of ± 1 deg, but ± 0..0 in the vicinity of the maximum steering angle (± 5 deg).
An error of 45 deg is allowed. Thus, the absolute steering angle value θr and the rotation angle θm of the relative steering angle value are calculated, and the actual steering angle value RAGL is calculated based on these and supplied to the subtraction unit 92. The neutral correction control of the rear wheel steering angle by these sensors will be described later.

In the subtracting section 92, the target steering angle value AGLA
The actual steering angle value RAGL is subtracted from this to obtain the steering angle deviation ΔAGL. This steering angle deviation ΔAGL is processed via the deviation steering angle dead zone imparting section 93. Deviation steering angle dead zone applying unit 9
3, the absolute value of the steering angle deviation ΔAGL is a predetermined value E2PMAX.
In the following cases, the steering angle deviation value ETH2 is set to 0, and when the value of the steering angle deviation ΔAGL is small, the control is stopped. Obtained steering angle deviation value ETH2
Is sent to the proportional section 96 and the differentiating section 94. The proportional portion 96 integrates the steering angle deviation value ETH2 by a predetermined proportional gain,
Obtain the proportional term PAGELA. Further, the differentiating unit 94 differentiates the steering angle deviation value ETH2 to obtain the steering angle deviation differential value SETH2. The steering angle deviation differential value SETH2 and the above-described differential gain YTDIFGAIN are integrated by the integrating section 95, and the differential term DAGLA is obtained. Then, the proportional term PAGLA and the differential term DAGLA are added by the adder 97, and the steering angle value H
The PID is obtained.

The steering angle value HPID is limited by the deviation steering angle limiter 98. The deviation steering angle limiter 98 is
The control amount ANG is set in proportion to the steering angle value HPID, and the control amount ANG is 1.5 deg or more or -1.5d.
It is set so as not to be less than or equal to eg. The control amount ANG is converted into a pulse width modulation signal by the pulse width modulation conversion unit 99 and supplied to the motor driver 5. The motor driver 5 rotates the motor M according to the pulse width modulation signal, and the motor M is servo-controlled by this.
Further, the steering angle deviation is PD-controlled. Among these, the differential gain of the differential term is changed according to the differential value of the target steering angle value. The differential gain becomes 0 when the differential value of the target steering angle value is small, and the control in this case is performed only by the proportional term.
An integral term may be added to the PD control. Further, since the rotation angle θm of the motor M changes depending on the fluctuation of the power supply voltage, the battery voltage may be measured and the control amount ANG may be corrected according to the battery voltage.

As shown in FIG. 15, the interrupt terminal and the normal input terminal of the microprocessor 1 are the magnetic pole sensor signal HA,
It is used for inputting HB and HC. Magnetic pole sensor signal H
A and HB are input to the exclusive OR circuit EXOR1, and the magnetic pole sensor signal HC and the exclusive OR circuit E are input.
The output signal of XOR1 is an exclusive OR circuit EXO
It is connected to input to R2. Thus, if any one of the magnetic pole sensor signals HA, HB, HC changes, the output of the exclusive OR circuit EXOR2 changes.

As described above, the magnetic pole sensor signals HA, HB,
When there is a change in any one of the HCs, the magnetic pole sensor abnormality determination unit 63 shown in FIG. 13 executes the magnetic pole sensor signal edge interrupt routine shown in FIG. here,
Each time there is an interrupt, the number of revolutions of the motor M is calculated, and then the state of the magnetic pole sensor signal is determined and stored as the current value. That is, first, in step 201, the current value stored so far is updated as the previous value, and in step 202, the states of the input terminals of the magnetic pole sensor signals HA, HB, HC are read and stored as the current value. .
Next, at step 203, the previous predicted value is read from the map shown in Table 2. As will be described later, the magnetic pole sensor 1
8 is configured such that any one of the magnetic pole sensor signals HA, HB, and HC changes in order. Therefore, the polarity of any one of the magnetic pole sensor signals HA, HB, and HC should change with respect to the previous value and the current value.

[Table 2]

All the possible states for the current value are stored in the previous predicted value of the map of Table 2. Specifically, when the current value is (HA, HB, HC) = (L, L, H), the previous prediction value is (H, L, H) or (L,
H, H). In step 204 of FIG. 16, the previous predicted value and the actual previous value are compared. Magnetic pole sensor 18
If is working properly, the previous predicted value and the previous value should match. Therefore, if the previous predicted value and the previous value match, the magnetic pole sensor abnormality flag Fab is determined in step 205.
n is cleared (0). If the previous predicted value does not match the previous value, the magnetic pole sensor abnormality flag Fabn is set (1) in step 206, and this magnetic pole sensor signal edge interrupt routine ends. Thus, in the subsequent processing, if the magnetic pole sensor abnormality flag Fabn is 1, it is determined that the magnetic pole sensor 18 has an abnormality, and if the magnetic pole sensor abnormality flag Fabn is cleared, the following description will be given. The phase switching signal pattern is set according to the routine of 17.

The phase switching control unit 62 of FIG. 13 performs the processing as shown in FIG. First, in step 210, it is determined whether or not the magnetic pole sensor abnormality flag Fabn is 0, and if it is set (if 1), the following processing is not performed. That is, when an abnormality is detected in the magnetic pole sensor 18, the phase switching control routine is not executed. When the magnetic pole sensor abnormality flag Fabn is not set, the routine proceeds to step 211, where it is judged whether or not there is an edge interrupt of the magnetic pole sensor signal. If there is an interruption, in steps 212 to 214, the value CW is set in the direction flag DI if the clockwise rotation should be performed, and the direction flag DI is set if the counterclockwise rotation should be performed. The value CCW is set. The direction of rotation can be determined by whether the steering angle value HPID is positive or negative.
If HPID> 0, the direction flag DI = CCW is set,
If HPID <0, the direction flag DI = CW is set.

Next, at step 215, the phase switching signal pattern is set based on the map of Table 3 below. The phase switching signal is a 6-bit signal, and each bit takes a high level "H" or a low level "L" and is defined as shown in Table 4 below. In step 215, the next phase switching signal pattern is set based on the state of the phase switching signal pattern and the direction flag DI that have been output so far. For example,
The current value is (LA11, LB11, LC11, LA21,
LB21, LC21) = (H, L, L, L, H, L) and if DI = CW (clockwise rotation), the next value is (H, L, L, L, L, H). ) Is set. The set phase switching signal pattern is calculated as a phase switching signal group L1 in the microprocessor 1. If the control cycle is fast, this phase switching control routine may be performed within the magnetic pole sensor signal edge interrupt routine. When the steering angle value HPID becomes zero when the direction flag is set, the phase switching is set to the stop mode and (L
A11, LB11, LC11, LA21, LB21, L
C21) = (L, L, L, L, L, L).

[Table 3]

[Table 4]

In the open controller 64 of FIG. 13,
Processing is performed as shown in FIG. First, step 220
At, it is determined whether or not the magnetic pole sensor abnormality flag Fabn is 1, and if it is 0, the following processing is not performed. That is, when the magnetic pole sensor 18 is normal, the open control routine is not executed. Therefore, the switch S depending on the determination result of the magnetic pole sensor abnormality determination unit 63 of FIG.
When W1 is switched and the state is normal, the phase switching control unit 62 functions and the above-mentioned phase switching control routine is executed, and when abnormal, it is switched to the open control unit 64 side and the open control routine is executed. In this open control routine, the open control execution flag Fop and the timer T are used. When the predetermined time is set in the timer T, the timer T is gradually decremented after that, and becomes 0 after the predetermined time. The open control execution flag Fop is set to 0 in the initial state.

At step 221, the state of the open control executing flag Fop is judged, and if the open control executing flag Fop is 0, then at step 222, the timer T is set to a predetermined time (for example, 1 second). To be done. Then, until the timer T becomes 0 or less, step 224
At, the motor brake pattern is set to the phase switching signal pattern. The motor brake pattern is (LA1
1, LB11, LC11, LA21, LB21, LC2
1) = (L, L, L, H, H, H), (LA12, LB
12, LC12, LA22, LB22, LC22) =
(L, L, L, H, H, H). When the predetermined time has elapsed, in step 225, the open control execution flag Fop is set (1). Since the timer T is 0 or less in this state, the next phase switching signal pattern is set from the map shown in Table 5 in step 227.
Next, at step 228, the timer T is set again. In step 226, step 227 is executed only when the timer T is 0 or less, so step 227 is executed every predetermined time set in timer T.

In step 227, the next value is set according to the current phase switching signal pattern and the result of comparison between the absolute steering angle value θr output from the rear wheel steering angle sensor 21 and the predetermined value A1. A1 is set to a value close to zero (for example, 0.5 degrees). For example, the current phase switching signal pattern is (LA1
1, LB11, LC11, LA21, LB21, LC2
1) = (H, L, L, L, H, L) and when the absolute steering angle value θr is −1 deg, the next phase switching signal pattern is (H, L, L, L, L, H). The map in Table 5 is set to rotate right when the absolute steering angle value θr is negative, and to rotate left when the absolute steering angle value θr is positive. In any case, the absolute value of the rear wheel steering angle acts so as to approach zero. The absolute value of the rear wheel steering angle is a predetermined value A
When it becomes 1 or less, the phase switching signal pattern becomes (L, L, L,
L, L, L), and the motor 12 stops. Therefore,
In the open control routine, the phase switching signal pattern is controlled so that the rear wheel steering angle becomes zero and the neutral return is performed.

[Table 5]

FIG. 19 shows the processing for the neutral correction control of the rear wheel steering angle. When the ignition switch (not shown) is turned on and the microprocessor 1 is reset, first, at step 301, the rear wheel steering angle sensor is detected. 21 output signal is A
The D-converted absolute steering angle value θr of the rear wheels is read, and it is determined in step 302 whether or not the temporary setting completion flag is set (1). If the temporary setting completion flag is not set, the temporary setting process is performed in step 303. That is, the absolute steering angle value θr is used as it is as the initial value of the rear wheel steering angle counter. After that, the temporary setting completion flag is set in step 304, and the process proceeds to step 305 as in the case where it is determined in step 302 that the temporary setting completion flag is set.

At step 305, it is judged if the neutral correction completion flag is set or not. If not, the routine proceeds to step 306. Here, if the absolute steering angle value θr of the rear wheel steering angle sensor 21 is within ± 1 deg, the process proceeds to step 307, and after the absolute steering angle value θr is set to the rear wheel steering angle counter value θc, at step 308. The neutral correction completion flag is set, and the process proceeds to step 309. If the rear wheel steering angle is out of the range of ± 1 deg, the process directly proceeds to step 309 as in the case where the neutral correction completion flag is not set. Note that the condition of step 306 is | θr
It is also possible that | <1 deg and | θc | <1 deg. According to this, due to the abnormality of the rear wheel steering angle sensor 21, | θr | <1
Even if the erroneous determination of deg is made, it is possible to prevent the rear wheel position from being largely displaced.

In step 309, it is determined whether or not the neutral re-correction completion flag is set, and if not set, it is determined in step 310 whether or not the neutral re-correction condition is satisfied. That is, it is determined whether or not the output voltage of 2.5 V at the neutral position (point 0) in FIG. 21 is crossed. As the determination condition at this time, | θc | <1deg may be added as an AND condition as in step 306 described above. If this neutral recorrection condition is satisfied, the absolute steering angle value θ is determined in step 311.
After r is set to the value θc of the rear wheel steering angle counter, step 3
At 12, the neutral recorrection completion flag is set. After the neutral re-correction completion flag is set in steps 309 and 312, or when the neutral re-correction condition is not satisfied in step 310, the process is continued in step 313.
Then, the rear wheel steering control is performed as described above. In this control, the value θc of the rear wheel steering angle counter is set according to the rotation angle θm of the relative steering angle value, and based on this, the actual steering angle value RAG
L is obtained, and rear wheel steering control is performed.

The neutral correction control in steps 305 to 308 may be omitted and the neutral recorrection control in steps 309 to 312 may be performed immediately after the provisional setting is completed.
However, in the case where the vehicle continuously travels on a curve after turning on the ignition switch, it takes a long time to reach the neutral position (point 0). Therefore, early steering angle adjustment can be performed without omitting the neutral correction control. It is desirable to do.

As described above, in the present embodiment, the rear wheel steering angle sensor 21 is required to have high accuracy (for example, ± 0.25 deg) near neutral as shown in FIG. 21, but the absolute steering angle value is large. Since there is no problem even if the accuracy is low in the region, the rear wheel steering angle sensor 21 can be formed at low cost and the adjustment can be easily performed. Further, after neutral correction, it is controlled by the magnetic pole sensor 18 which is a relative steering angle detecting means,
Even if a failure such as a wire breakage or a short circuit occurs, a sudden rear wheel steering operation is not performed.

FIG. 20 shows another embodiment of the present invention. When the neutral correction is performed after the steps 301 to 303 of FIG. 19 are processed and the temporary setting completion flag is set, the absolute steering angle value If the error is large, the rear wheel steering angle changes abruptly. Therefore, in order to prevent this, the steering angle is gradually adjusted. That is, step 304 in FIG.
And step 309 are processed as shown in FIG. In step 306, the absolute steering angle value θr of the rear wheels is ± 1d
If it is determined to be within the predetermined range of eg, the difference ΔE between the rear wheel steering angle counter value θc and the absolute steering angle value θr is calculated in step 317, and then the neutral correction is completed in step 318. Flag is set.

Then, the routine proceeds to steps 319 to 324, and if the difference ΔE is positive, at step 320 the value θc of the rear wheel steering angle counter is decremented (-1) and
In step 321, the difference ΔE is decremented. On the other hand, if the difference ΔE is determined to be negative in step 322, the value θc of the rear wheel steering angle counter is incremented (+1) in step 323, and the difference ΔE is calculated in step 324.
E is incremented. After being processed in this way, the process proceeds to steps 309 to 312 in FIG. 19 and the neutral recorrection control described above is performed.

[0047]

Since the present invention is constructed as described above, it has the following effects. That is, in the vehicle rear wheel steering system of the present invention, the detection result of the absolute steering angle detection means is set as the reference steering angle, and the drive means is set based on the reference steering angle and according to the detection result of the relative steering angle detection means. Control the position of the rear wheels, and when the steering angle of the rear wheels reaches a value within a predetermined range centered on the neutral position, reset the detection result of the absolute steering angle detection means as the reference steering angle. Since the rear wheel steering angle sensor can be formed at low cost and can be easily adjusted, an inexpensive rear wheel steering device can be provided. Further, for example, even when the absolute steering angle detecting means fails, the relative steering angle detecting means controls the steering, so that a sudden rear wheel steering operation can be avoided.

Further, when it is detected that the rear wheels have reached the neutral position, the reference steering angle setting means resets the detection result of the absolute steering angle detecting means as the reference steering angle. In the above, the accuracy of the neutral correction control can be further improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a front view of a rear wheel steering mechanism used in an embodiment of the present invention.

3 is a partial cross-sectional view of the rear wheel steering mechanism of FIG.

4 is a cross-sectional view of the rear wheel steering mechanism of FIG.

FIG. 5 is a sectional view of a motor used in an embodiment of the present invention.

FIG. 6 is a sectional view of a motor used in an embodiment of the present invention.

FIG. 7 is an explanatory view of windings of the motor shown in FIGS.

FIG. 8 is a front view of a magnet used in an embodiment of the present invention.

FIG. 9 is a front view of the substrate of the magnetic pole sensor used in the embodiment of the present invention.

FIG. 10 is an operation explanatory view of the electric motor according to the embodiment of the present invention.

FIG. 11 is a circuit configuration diagram of an electronic control device used in an embodiment of the present invention.

12 is a circuit configuration diagram of a driver of the electronic control device of FIG.

13 is a functional block diagram of a microprocessor of the electronic control device of FIG.

14 is a functional block diagram of a motor servo control unit of the microprocessor of FIG.

15 is a circuit configuration diagram of a magnetic pole sensor input circuit of the electronic control device of FIG.

FIG. 16 is a flowchart of a magnetic pole sensor signal edge interrupt according to an embodiment of the present invention.

FIG. 17 is a flowchart of phase switching control according to an embodiment of the present invention.

FIG. 18 is a flowchart of open control according to an embodiment of the present invention.

FIG. 19 is a flowchart of the rear wheel steering angle neutral correction control according to the embodiment of the present invention.

FIG. 20 is a flowchart showing a part of the neutral correction control of the rear wheel steering angle in another embodiment of the present invention.

FIG. 21 is a graph showing the output characteristic of the rear wheel steering angle sensor in the embodiment of the present invention.

FIG. 22 is a block diagram showing an outline of the configuration of the present invention.

[Explanation of symbols]

1 Microprocessor 5 Motor driver 9 Electronic control device 12 Motor (electric motor) 17,20 1st, 2nd front wheel steering angle sensor 18 Magnetic pole sensor (rotation sensor) 21 Rear wheel steering angle sensor 22,23 1st, 2nd vehicle speed Sensor 55 Constant voltage regulator 57 Interface 59 Battery 60 Target rudder angle calculation unit 61 Motor servo control unit 62 Phase switching control unit 63 Magnetic pole sensor abnormality determination unit 64 Open control unit 86 Current detection circuit 88 Abnormal current limiting circuit 89 Pulse width modulation signal synthesis Circuit 90, 94 Differentiating part 91 Differential gain setting part 92 Subtracting part 93 Deviation steering angle dead zone imparting part 95 Accumulating part 96 Proportional part 97 Addition part 98 Deviation steering angle limiter 99 Pulse width modulation converting part 100 Actual steering angle value calculating part 101 Peak Hold circuit AGLA Target rudder angle value HA, HB, HC Magnetic pole Capacitors signal L1 phase switching signal group LA11, LB11, LC11, LA21, LB21,
LC21 Phase switching signal M Motor PWM1 Pulse width modulation signal U, V, W
Terminal V Vehicle speed γ Yaw rate value θs Steering angle

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location B62D 137: 00 (72) Inventor Kazutaka Tamura 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Tadashi Matsumoto, 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor, Hidemori Tsuka, 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation

Claims (3)

[Claims] 1. A rear wheel steering system for a vehicle, wherein a steering mechanism connected to a rear wheel of the vehicle is driven and controlled by a drive means.
An absolute steering angle detecting means for detecting an absolute value of a steering angle at which the rear wheel is actually steered by the drive means, and a relative steering angle detecting means for detecting a relative steering angle change of the steering angle of the rear wheel,
The reference steering angle setting means for setting the detection result of the absolute steering angle detection means as the reference steering angle, and the drive means for controlling the drive means based on the reference steering angle and according to the detection result of the relative steering angle detection means. Control means for adjusting the position of the wheels, and when the steering angle of the rear wheels reaches a value within a predetermined range centered on the neutral position by the adjustment of the control means, the reference steering angle setting means A rear-wheel steering system for a vehicle, wherein the detection result of the absolute steering angle detection means is reset as the reference steering angle. 2. When the absolute steering angle detection means detects that the rear wheels have reached the neutral position,
2. The rear wheel steering system according to claim 1, wherein the reference steering angle setting means resets the detection result of the absolute steering angle detection means as the reference steering angle. 3. A rear wheel steering system for a vehicle, wherein a steering mechanism connected to a rear wheel of the vehicle is driven and controlled by a drive means.
An absolute steering angle detecting means for detecting an absolute value of a steering angle at which the rear wheel is actually steered by the drive means, and a relative steering angle detecting means for detecting a relative steering angle change of the steering angle of the rear wheel,
The reference steering angle setting means for setting the detection result of the absolute steering angle detection means as the reference steering angle, and the drive means for controlling the drive means based on the reference steering angle and according to the detection result of the relative steering angle detection means. Control means for adjusting the position of the wheels, and when it is detected that the rear wheels have reached the neutral position in the absolute steering angle detection means, the reference steering angle setting means of the absolute steering angle detection means A rear wheel steering system for a vehicle, wherein a detection result is reset as the reference steering angle.