JP3034400B2 - Vehicle rear wheel steering system - Google Patents

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 apparatus for driving a rear wheel steering mechanism 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 which improves the steering performance of a vehicle by steering the rear wheel in addition to the front wheel steering of the vehicle.
Japanese Patent No. 3769 discloses that the steering control of the rear wheels is performed by open control without performing feedback, and the steering angle of the front wheels or the rear wheels is controlled by the steering angle of the front wheels or the rear wheels with respect to accumulation of a control error which is generally a problem in the case of open control. A four-wheel steering device for a vehicle that controls so as to eliminate the error when "0", that is, when active steering is not performed is disclosed.

In the steering apparatus described in the publication, an actual measurement signal E indicating an actually measured rear wheel turning angle θr output from a rear wheel turning angle sensor 29 in the description of the embodiment is compared with a comparator 32.
The comparator 32 includes a steering angle “0” detection unit 3
3 indicates that the operation signal G output from the input terminal 3 is input. The steering angle “0” detector 33 receives the front wheel steering angle signal D, and outputs the operation signal G when the front wheel steering angle θf indicated by the signal D is “0”. Comparator 3
2 operates upon input of the operation signal G, compares a comparison reference value corresponding to a preset rear wheel turning angle “0” with the measured rear wheel turning angle θr indicated by the 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 open control rear wheel steering device described above, in a rear wheel steering device requiring feedback control, the detection accuracy of the rear wheel steering angle sensor is as follows.
High accuracy is required in all areas of the steering angle. As described above, in order to ensure high accuracy over the entire steering angle range, an absolute steering angle sensor that can directly detect the steering angle is required, but the absolute steering angle sensor generally has a large detection resolution,
In addition, since analog processing is liable to be affected by noise, all of these problems must be solved, which is expensive. On the other hand, a relative steering angle sensor that detects a change in the steering angle of the rear wheels can detect the relative steering angle amount with high accuracy,
Although inexpensive, the absolute value of the steering angle cannot be detected.

Accordingly, the present invention has an absolute steering angle detecting means for detecting the absolute value of the steering angle of the rear wheel 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 including 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 provides a steering mechanism SM connected to a rear wheel RW and a drive control of the steering mechanism SM as shown in FIG. A 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
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 driving means S based on the reference steering angle and the detection result of the relative steering angle detection means S3.
1 to control the rear wheel RW around the neutral position of the rear wheel RW.
Control means S5 for adjusting the steering angle . When the steering angle of the rear wheel 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. It is configured to reset the steering angle.

In the above rear wheel steering device for a vehicle, 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. It is preferable that the detection result is reset as the reference steering angle.

The present invention also relates to 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 change of the steering angle of the rear wheel RW. 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 a reference steering angle, and the detection result of the relative steering angle detecting means S3 based on the reference steering angle. The driving means S1 is accordingly controlled to control the rear wheel RW
Control means S5 for adjusting the steering angle of the rear wheel RW around the neutral position. 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 The absolute steering angle detecting means S2 is determined by S4.
May be reset as the reference steering angle.

[0009]

In the rear wheel steering device having the above-mentioned structure, the driving mechanism S1 controls the driving of the steering mechanism SM. On the other hand, the absolute steering angle detecting 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 wheel RW is detected by the relative steering angle detecting means S3. Further, the detection result of the absolute steering angle detecting means S2 is set as the reference steering angle in the reference steering angle setting means S4. The drive device S1 by the control unit S5 in accordance with a detection result of and relative steering angle detecting device S3 on the basis of the reference steering angle is controlled, around the neutral position of the rear wheels RW
Thus, the steering angle of the rear wheel RW is adjusted. This allows the rear wheel RW
When the steering angle reaches a value within a predetermined range around the neutral position, the reference steering angle setting means S4 resets the detection result of the absolute steering angle detection means S2 as the reference steering angle. If 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 further uses 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 device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a 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 accordance with the turning operation of the steering wheel 19. Front wheel steering mechanism 1
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
A second front wheel steering angle sensor 20 is attached to the steering shaft on which the steering wheel 9 is mounted.
Are 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 is steered according to the rotation of a motor 12.
A magnetic pole sensor 18 that detects the rotation angle of the motor 12 is provided at an end of the motor 12. Further, a rear wheel steering angle sensor 21 is provided on a rack shaft 25 serving as a rear wheel steering shaft, and thereby the actual steering angles of the rear wheels 15, 16 are detected. 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 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 a first vehicle speed sensor 22, a second vehicle speed sensor 23, and a 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 the housing 38 of the rear wheel steering mechanism 11, and the magnetic pole sensor 18, the motor housing 40 of the motor 12 and the 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 in FIG. 2 as viewed from the back, a rack shaft 25 is provided at right angles to the traveling direction of the vehicle. It is connected to a 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 cope without changing the housing 38 by exchanging the tubes 39. 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. Then, the rack guide cover 32 is fixed to the housing 38 in a state where the rack guide 31 is urged in the rack 26 direction, whereby the rack 26 is pressed to the pinion 27 side. The pinion 27 is connected to the gear 2 as shown in FIG.
9 is fixed by shrink fit (press-fitting), and the relative rotation is prevented by the pin 37.

As shown in FIG. 4, the rear wheel steering angle sensor 21 has a built-in potentiometer and is provided in parallel with the surface of the gear 29. The pin 54 is connected to the shaft 54 via the lever 33.
The pin 34 is fitted in a hole 35 formed in the gear 29. Thus, 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 of the rear wheels.

As shown in FIG. 3, a pinion 30 is provided at an end of a motor shaft 41 of the motor 12, and a gear 29 meshes with the pinion 30 to form a hypoid gear. The hypoid gear transmits the rotation of the motor shaft 41 of the motor 12 as the rotation of the gear 29. However, 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. Is set so that the reverse efficiency becomes zero. In addition, pinion 3
The 0 and the gear 29 constitute an HRH (high ratio hypoid) gear so as to increase the reduction ratio. The gear ratio is
The number of poles is determined by the number of poles of the motor 12, the resolution of the steering angle, and the like.

As shown in FIG. 5, a motor shaft 41 of the motor 12 is rotatably supported in a motor housing 40. A four-pole magnet 42 is fixed around the motor shaft 41. The motor housing 40 has a magnet 42
, A core 43 is fixed, and a motor winding 44 is wound around the core 43. As is clear from FIG. 6 showing the AA cross section in FIG. 5, the core 43 is formed with twelve protrusions 43a extending in the center direction, and the motor winding 44 is wound around the protrusions 43a. You. As shown in FIG. 7, when the motor winding 44 is viewed from the magnetic pole sensor 18 side, the windings 44a and 44d, 44b and 44b are connected.
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 mounted here. A substrate 49 of the magnetic pole sensor 18 is fixed to an open end of the motor housing 40 by a holder 47 (shown in FIG. 9), and a cover 48 is provided at this open end. On the other hand, the motor 12
A rotor 52 is fixed to an end of the motor shaft 41, and the rotor 52 is provided with a magnet 51. The magnet 51 is formed in a four-pole disc shape as shown in FIG. As shown in FIG. 9, on the substrate 49, three Hall ICs 50 are arranged with a shift of 60 degrees. Outputs of these three Hall ICs 50 are transmitted to magnetic pole sensor signals HA, HB, HC in an electronic control unit 9 described later.
Used as

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

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

The electronic control unit 9 has a microprocessor 1 as 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, 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 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
8 are HA, HB, HC, and the output of the rear wheel steering angle sensor 21 is θr.

Although the motor connected to the electronic control unit 9 is represented by 12 in the above-described mechanism, the motor 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
Power is supplied from the IGA and the IGA. The motor driver 5 supplies 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 configured as shown in FIG. 12, and is controlled by the phase switching signal group L1 and the pulse width modulation signal PWM1. 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 output from the output side as they are via the abnormal current limiting circuit 88. The gate drive circuit G11 is a circuit that drives the transistors TA11, TB11, and TC11 of the power MOSFET on and off. The gate drive circuit G11 also performs boosting, applies a boosted voltage to the gates of the transistors TA11, TB11, and TC11, and outputs the boosted voltage as a boosted voltage value RV1. Transistors TA11, TB
The high voltage obtained from the power supply terminal PIGA via the pattern fuse PH, the choke coil TC and the resistor Rs is supplied to each of the three-phase terminals U and TC11 of the motor M.
V and W are connected so as to be supplied. The transistors TA11, TB11, TC11, TA21, TB
A Zener diode is inserted between the gate and the source of TC21 and TC21 to protect the power MOSFET. That is, the power supply voltage is 20 V for some reason.
When the voltage exceeds the threshold voltage, the voltage between the gate and the source of the power MOSFET exceeds 20 V, and the power MOSFET is destroyed. To prevent this, a Zener diode is provided.

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

The voltage PIGM1 and the gate drive circuit G
When the difference from the boosted voltage value RV1 of 11 drops to about 2V,
MOSFET transistors TA11, TB11, TC
11, TA21, TB21, and TC21 may increase on-resistance and cause abnormal heat generation. Therefore, the voltage PIG
When the difference between M1 and the boosted voltage value RV1 becomes equal to or smaller than a predetermined value, all the transistors TA11, TB11, TC11,
TA21, TB21 and TC21 may be turned off. The transistors TA21, TB21, TC2
Since a large current flows through one source, it is desirable that the ground of the weak electric circuit portion such as the microprocessor be a wiring of a different system from these grounds.

A current detection circuit 86 is connected to both ends of the resistor Rs, and detects a current value flowing through the resistor Rs.
The current detection circuit 86 detects that the current flowing through the resistor Rs is 18 A
At this time, it is determined that an overcurrent has occurred, an overcurrent signal is output as the output signal MOC1, and an overcurrent signal is supplied to the pulse width modulation signal synthesizing circuit 89 to limit the operation on the low side. When the current flowing through the resistor Rs is equal to or greater than 25 A, the current detection circuit 86 determines that the current is abnormal, and outputs the output signal
And outputs an abnormal current signal. When an abnormal current occurs, an abnormal current signal is given to the abnormal current limiting circuit 88,
Apply restrictions on the high side and low side. In this case, all the transistors TA11, TB11, TC1
1, TA21, TB21, and TC21 may be turned off for a certain period of time after the detection of the abnormal current. This fixed time may be set to be 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 value of the current value is output from the peak hold circuit 101 as a peak signal MI1. This peak hold circuit 101 is reset at the timing when the reset signal DR1 switches.

Next, the rotation operation of the motor M will be described with reference to FIG. Magnetic pole sensor signals HA, HB, HC
The motor M is rotated by setting the pattern of the phase switching signal as shown in Table 1 in accordance with the state of. Clockwise rotation (CW) is set to right turn, and counterclockwise rotation (CCW) is set to left turn. 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). This state corresponds to the state of the range A shown in FIG. 10. As is clear from the relative rotational position of the magnet 51 with respect to the three Hall ICs, the magnetic pole sensor signals HA and HC become high level (H). I have. The direction of the winding current changes from the U phase to the V phase, and the magnet 51 rotates clockwise as the motor M rotates. When the magnet 51 rotates about 30 degrees, the magnetic pole sensor signal HA switches from a high level to a 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 state proceeds from the left state to the right state in FIG. 10, and the motor M rotates continuously. Thus,
In order to apply clockwise rotation (CW) or counterclockwise rotation (CCW) to the motor M, the pattern of the phase switching signal may be switched in accordance with the upper or lower order of Table 1.

[Table 1]

As shown in FIG. 13, the microprocessor 1 includes a target steering angle calculator 60, a motor servo controller 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 calculator 60 calculates a 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 and 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 set as the vehicle speed V, or the maximum value of the two vehicle speed values may be set as the vehicle speed V. Thus, by detecting the vehicle speed by two systems, it is possible to detect an abnormality of 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.
The calculation is performed based on the output values θf1 and θf2 of the reference numerals 7 and 20. In this case, the first front wheel steering angle sensor 17
A potentiometer is used as a potentiometer, but 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, although the steering angle amount can be accurately detected, the initial steering angle amount cannot be detected. Therefore, the absolute value of the output of the second front wheel steering angle sensor 20 is determined by the first front wheel steering angle sensor 17, and after the absolute value is determined, the output of the second front wheel steering angle sensor 20 is used as the steering angle θs.

FIG. 14 is a control block diagram of the motor servo control section 61. The differentiation section 90 differentiates the target steering angle value AGLA to obtain a differentiation value SAGLA. 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 / sec).
c) In the following cases, the differential gain becomes 0, and the differential value SAGL
When the absolute value of A is 12 (deg / sec) or more, the differential gain is set to 4. When the absolute value of the differential value SAGLA is 4 to 12 (deg / sec), the differential gain is set to 0 to 4. Value.

On the other hand, a potentiometer is usually used as the rear wheel steering angle sensor 21, but the potentiometer has a rough accuracy, and the magnetic pole sensor 18 can accurately detect the steering angle amount, but cannot detect the initial steering angle amount. 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 as the absolute steering angle detecting means, and after the absolute value is obtained, the output change of the magnetic pole sensor 18 as the relative steering angle detecting means is obtained. Is used to determine the rotation angle of the motor M, that is, the relative steering angle value θm. That is, the output signal of the motor M is supplied to the actual steering angle value calculation unit 100 having the rear wheel steering angle counter,
Here, the rotation angle θm of the motor M is obtained as a 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 that has been AD-converted based on the output signal of the rear wheel steering angle sensor 21 is used as an actual steering angle value calculation unit 1.
00 is supplied as a reference value.

The rear wheel steering angle sensor 21 has an output characteristic shown in FIG. 21, and is set so that an output voltage corresponding to the absolute steering angle value θr falls within a range surrounded by a 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 within a range of ± 1 deg.
An error of up to 45 deg is allowed. Thus, the absolute steering angle value θr and the rotation angle θm of the relative steering angle value are determined, and based on these, the actual steering angle value RAGL is determined 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
Is subtracted from the actual steering angle value RAGL to obtain a steering angle deviation ΔAGL. The steering angle deviation ΔAGL is processed via the deviation steering angle dead zone providing unit 93. Deviation steering angle dead zone giving section 9
3 indicates that the absolute value of the steering angle deviation ΔAGL is a predetermined value E2PMAX.
In the following case, the steering angle deviation value ETH2 is processed as 0, and the control is stopped when the value of the steering angle deviation ΔAGL is small. The obtained steering angle deviation value ETH2
Is sent to the proportional section 96 and the differentiating section 94. The proportional unit 96 integrates the steering angle deviation value ETH2 by a predetermined proportional gain,
Obtain the proportional term PAGELA. The differentiator 94 differentiates the steering angle deviation value ETH2 to obtain a 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 unit 95, and a differential term DAGLA is obtained. Then, the proportional term PAGELA and the derivative term DAGLA are added by the adder 97, and the steering angle value H
The PID is obtained.

The steering angle value HPID is subjected to a steering angle limit by a deviation steering angle limiter 98. The deviation rudder angle limiter 98 is
The control amount ANG is set in proportion to the steering angle value HPID, and the control amount ANG is not less than 1.5 deg or -1.5 d
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 converter 99 and supplied to the motor driver 5. The motor driver 5 rotates the motor M according to the pulse width modulation signal, and thereby the motor M is servo-controlled.
The steering angle deviation is controlled by PD. Among them, the differential gain of the differential term is changed according to the differential value of the target steering angle value. The differential gain is 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.
Incidentally, an integral term may be added to the PD control. Further, since the rotation angle θm of the motor M also changes due to 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 connected to the magnetic pole sensor signal HA,
Used for inputting HB and HC. Magnetic pole sensor signal H
A and HB are inputted to an exclusive OR circuit EXOR1, and the magnetic pole sensor signal HC and the exclusive OR circuit E are inputted.
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 of FIG. 13 executes a magnetic pole sensor signal edge interrupt routine shown in FIG. here,
Each time there is an interrupt, the number of rotations 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 state of the input terminals of the magnetic pole sensor signals HA, HB, HC is read and stored as the current value. .
Next, in 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
Reference numeral 8 denotes a configuration in which any one of the magnetic pole sensor signals HA, HB, and HC sequentially changes. Therefore, the polarity of any one of the magnetic pole sensor signals HA, HB, and HC should have changed from the previous value and the current value.

[Table 2]

In the previous predicted value of the map in Table 2, all possible states for the current value are stored. Specifically, when the current value is (HA, HB, HC) = (L, L, H), the previous predicted value is (H, L, H) or (L, L, H).
H, H). In step 204 in FIG. 16, the previous predicted value is compared with the actual previous value. Magnetic pole sensor 18
If is functioning properly, the previous predicted value should match the previous value. Therefore, if the previous predicted value matches the previous value, at step 205, the magnetic pole sensor abnormality flag Fab
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 the 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 is abnormal, and if the magnetic pole sensor abnormality flag Fabn is cleared, the following description will be given. A phase switching signal pattern is set according to the routine of S17.

The phase switching control section 62 shown in FIG. 13 performs processing as shown in FIG. First, in step 210, it is determined whether or not the magnetic pole sensor abnormality flag Fabn is 0. If this flag 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. If the magnetic pole sensor abnormality flag Fabn has not been set, the routine proceeds to step 211, where it is determined whether or not the above-described edge interrupt of the magnetic pole sensor signal has occurred. If there is an interrupt, in steps 212 to 214, the value CW is set in the direction flag DI if rotation in the clockwise direction is to be performed, and the value is set in the direction flag DI if rotation in the counterclockwise direction is to be performed. The value CCW is set. The rotation direction can be determined based on whether the aforementioned steering angle value HPID is positive or negative,
If HPID> 0, the direction flag DI = CCW, and
If HPID <0, the direction flag DI = CW.

Next, at step 215, a phase switching signal pattern is set based on the map shown in 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 phase switching signal pattern output so far and the state of the direction flag DI. For example,
The current values are (LA11, LB11, LC11, LA21,
If (LB21, LC21) = (H, L, L, L, H, L) and DI = CW (clockwise rotation), the next value is (H, L, L, L, L, H). ) Is set. The set phase switching signal pattern is calculated in the microprocessor 1 as a phase switching signal group L1. If the control cycle is early, this phase switching control routine may be performed in the above-described magnetic pole sensor signal edge interrupt routine. If 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 control unit 64 shown in FIG.
The processing is performed as shown in FIG. First, step 220
In the above, it is determined whether the magnetic pole sensor abnormality flag Fabn is 1 or not, 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, according to the determination result of the magnetic pole sensor abnormality determination unit 63 in FIG.
When W1 is switched, the phase switching control unit 62 functions and the above-described phase switching control routine is executed in a normal state, and is switched to the open control unit 64 side in an abnormal state to execute the open control routine. In the open control routine, the open control execution flag Fop and the timer T are used. When a predetermined time is set in the timer T, the timer T is gradually decremented thereafter and becomes 0 after the predetermined time. The open control execution flag Fop is set to 0 in the initial state.

In step 221, the state of the open control execution flag Fop is determined. If the open control execution flag Fop is 0, then in step 222, the timer T is set to a predetermined time (for example, 1 second). Is done. Step 224 until the timer T becomes 0 or less.
, The motor brake pattern is set in 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). In this state, since the timer T is 0 or less, the next phase switching signal pattern is set at step 227 from the map shown in Table 5.
Next, in step 228, the timer T is set again. In step 226, step 227 is executed only when the timer T is equal to or less than 0, so that step 227 is executed every predetermined time set in the 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, if 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, L, H). The map shown in Table 5 is set so that when the absolute steering angle value θr is negative, the map rotates to the right, and when the absolute steering angle value θr is positive, the map rotates to the left. In either case, 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 is less than 1, 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 vehicle returns to neutral.

[Table 5]

FIG. 19 shows the process of neutral correction control of the rear wheel steering angle. When an ignition switch (not shown) is turned on and the microprocessor 1 is reset, first, at step 301, a rear wheel steering angle sensor is set. 21 output signal is A
The D-converted absolute steering angle value θr of the rear wheel is read, and it is determined in step 302 whether the temporary set completion flag is set (1). If the temporary setting completion flag has not been set, a 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. Thereafter, the temporary set 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 set completion flag is set.

In step 305, it is determined whether or not the neutral correction completion flag is set. If not, the process 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 the absolute steering angle value θr is set to the value θc of the rear wheel steering angle counter. The neutral correction completion flag is set, and the routine 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. The condition of step 306 is | θr
| <1 deg and | θc | <1 deg. According to this, when the rear wheel steering angle sensor 21 is abnormal, | θr | <1
Even if the deg is incorrectly determined, it is possible to prevent the rear wheel position from being largely shifted.

In step 309, it is determined whether the neutral re-correction completion flag is set. If not, it is determined in step 310 whether the neutral re-correction condition is satisfied. That is, it is determined whether the output voltage has crossed the output voltage of 2.5 V at the neutral position (point 0) in FIG. As a determination condition at this time, | θc | <1 deg may be added as an AND condition as in step 306 described above. If the neutral re-correction 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, a neutral re-correction 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 proceeds to step 313.
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 re-correction control in steps 309 to 312 may be performed immediately after the provisional setting is completed.
However, when the vehicle is running continuously on a curve after the ignition switch is turned on, the time required to reach the neutral position (point 0) becomes longer, so that the early steering angle adjustment can be performed without omitting the neutral correction control. It is desirable to do.

As described above, in this 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 adjustment can be easily performed. Further, after the neutral correction, since the control is performed by the magnetic pole sensor 18 as the relative steering angle detecting means,
Even when a failure such as disconnection or short circuit occurs, no sudden rear wheel steering operation is performed.

FIG. 20 shows another embodiment of the present invention. When neutral correction is performed after steps 301 to 303 of FIG. 19 are set and the temporary setting completion flag is set, the difference between the absolute steering angle and the absolute steering angle is calculated. If the error is large, the rear wheel steering angle changes abruptly. To prevent this, the steering angle is gradually adjusted. That is, step 304 in FIG.
The processing is performed as shown in FIG. In step 306, the absolute steering angle value θr of the rear wheel is ± 1d
If it is determined that the difference is within the predetermined range of eg, the difference .DELTA.E between the value .theta.c of the rear wheel steering angle counter and the absolute steering angle .theta.r is calculated in step 317, and then the neutral correction is completed in step 318. The flag is set.

Then, the process proceeds to steps 319 to 324. If the difference ΔE is positive, the value θc of the rear wheel steering angle counter is decremented (−1) in step 320, 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 determined in step 324.
E is incremented. After such processing, the process proceeds to steps 309 to 312 in FIG. 19, and the above-described neutral re-correction control is performed.

[0047]

Since the present invention is configured as described above, the following effects can be obtained. That is, in the rear wheel steering device of the vehicle of the present invention, the detection result of the absolute steering angle detecting means is set as the reference steering angle, and the driving means is set based on the reference steering angle and in accordance with the detection result of the relative steering angle detecting means. To adjust the steering angle of the rear wheel around the neutral position of the rear wheel, and when the steering angle of the rear wheel reaches a value within a predetermined range around the neutral position, the detection result of the absolute steering angle detecting means Is set as the reference steering angle, and the rear wheel steering angle sensor can be formed at low cost and can be easily adjusted, so that an inexpensive rear wheel steering device can be provided. . Also, for example, even when the absolute steering angle detecting means fails, the relative steering angle detecting means is controlled, so that a sudden rear wheel steering operation can be avoided.

Further, when it is detected that the rear wheel has 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 accuracy of the neutral correction control can be further improved.

[Brief description of the 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 one embodiment of the present invention.

FIG. 3 is a partial sectional view of the rear wheel steering mechanism shown in FIG. 2;

FIG. 4 is a sectional view of the rear wheel steering mechanism shown in FIG. 2;

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

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

FIG. 7 is an explanatory diagram of windings of the motor of FIGS.

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

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

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

FIG. 11 is a circuit configuration diagram of an electronic control unit used in one 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 in FIG.

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

FIG. 15 is a circuit configuration diagram of a magnetic pole sensor input circuit of the electronic control device of FIG. 11;

FIG. 16 is a flowchart of a magnetic pole sensor signal edge interrupt in one embodiment of the present invention.

FIG. 17 is a flowchart of a phase switching control in one embodiment of the present invention.

FIG. 18 is a flowchart of open control in one embodiment of the present invention.

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

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

FIG. 21 is a graph showing output characteristics of a rear wheel steering angle sensor according to one embodiment of the present invention.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Microprocessor 5 Motor driver 9 Electronic control unit 12 Motor (electric motor) 17, 20 First and second front wheel steering angle sensor 18 Magnetic pole sensor (rotation sensor) 21 Rear wheel steering angle sensor 22, 23 First and second vehicle speed Sensor 55 Constant voltage regulator 57 Interface 59 Battery 60 Target steering 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 limit circuit 89 Pulse width modulation signal synthesis Circuits 90, 94 Differentiating section 91 Differential gain setting section 92 Subtracting section 93 Deviation steering angle dead zone providing section 95 Integration section 96 Proportion section 97 Addition section 98 Deviation steering angle limiter 99 Pulse width modulation conversion section 100 Actual steering angle value calculation section 101 Peak Hold circuit AGLA Target steering 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

Continued on front page (72) Inventor Kazutaka Tamura 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Tadashi Matsumoto 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Hidemori Tsuka 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (56) References JP-A-4-135979 (JP, A) JP-A-4-362473 (JP, A) JP-A-4 -252912 (JP, A) JP-A-2-95980 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6/00 B62D 7/14

Claims (3)

(57) [Claims] 1. A rear wheel steering device for a vehicle, wherein a steering mechanism connected to a rear wheel of the vehicle is drive-controlled by a driving unit.
An absolute steering angle detection unit that detects an absolute value of a steering angle at which the rear wheel is actually steered by the driving unit; a relative steering angle detection unit that detects a relative steering angle change of the steering angle of the rear wheel;
A reference steering angle setting unit that sets a detection result of the absolute steering angle detection unit as a reference steering angle; and controls the driving unit based on the reference steering angle and according to a detection result of the relative steering angle detection unit. Steering the rear wheel around the neutral position of the wheel
And control means for adjusting the angular, when the steering angle of the rear wheel by adjusting the control means has reached a value within a predetermined range centered on the neutral position, the said reference steering angle setting means absolute steering A rear wheel steering device for a vehicle, wherein a detection result of an angle detecting means is reset as the reference steering angle. 2. When the absolute steering angle detecting means detects that the rear wheel has reached the neutral position,
2. The rear wheel steering device according to claim 1, wherein the reference steering angle setting unit resets a detection result of the absolute steering angle detection unit as the reference steering angle. 3. A rear wheel steering apparatus for a vehicle, wherein a driving mechanism controls a steering mechanism connected to rear wheels of the vehicle.
An absolute steering angle detection unit that detects an absolute value of a steering angle at which the rear wheel is actually steered by the driving unit; a relative steering angle detection unit that detects a relative steering angle change of the steering angle of the rear wheel;
A reference steering angle setting unit that sets a detection result of the absolute steering angle detection unit as a reference steering angle; and controls the driving unit based on the reference steering angle and according to a detection result of the relative steering angle detection unit. Steering the rear wheel around the neutral position of the wheel
Control means for adjusting the angle , and when the absolute steering angle detection means detects that the rear wheel has reached the neutral position, the reference steering angle setting means detects the absolute steering angle detection result. Is set again as the reference steering angle.