JP3703937B2 - Vehicle steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steering apparatus capable of automatically steering a vehicle.
[0002]
[Prior art]
In recent years, a command signal is generated by a control device based on a guidance signal sent from a road, a detection signal of the road and surrounding conditions, and the vehicle is automatically steered by a steering force generated by an actuator for generating a steering force based on the command signal. Development of a steering device is underway.
[0003]
During such automatic steering, in addition to the steering force generated by the steering force generating actuator, a steering force may be applied to the vehicle due to disturbances such as unevenness and crosswinds on the road.
[0004]
Therefore, the value of the yaw rate, lateral acceleration, etc. of the vehicle corresponding to the change in the steering angle of the vehicle is detected, and the steering force generating actuator is controlled according to the detected value, so that the influence of the additional steering force due to the disturbance is reduced. I was compensated.
[0005]
Further, in such a steering apparatus, it is desired that the driver can switch from the automatic steering mode to the normal steering mode in which the steering force is generated in order to cope with an emergency situation or the like.
[0006]
Therefore, a means for obtaining a deviation between the command rudder angle corresponding to the command signal to the actuator and the actual rudder angle is provided, and when the deviation is equal to or greater than a set value, it is determined that the driver is against automatic steering, It is considered to switch from the automatic steering mode to the normal steering mode.
[0007]
[Problems to be solved by the invention]
In the prior art, the influence of the additional steering force due to disturbance is compensated according to the value corresponding to the change in the steering angle of the vehicle. In other words, after the rudder angle has actually changed, the additional steering force is offset. Therefore, there is a problem that compensation is delayed and the behavior of the vehicle becomes unstable due to disturbance.
[0008]
Further, when the driver actually changes the rudder angle against the steering force generated by the steering force generating actuator, the driver requires a large amount of labor and time. Therefore, there is a problem that it is impossible to deal with an emergency situation promptly.
[0009]
Further, it has not been possible to determine whether the steering force applied other than the steering force generated by the steering force generating actuator is the additional steering force due to disturbance or the additional steering force due to the driver. Therefore, there is a problem that the additional steering force due to the disturbance is erroneously determined as the steering force by the driver, and the automatic steering mode can be erroneously switched to the normal steering mode.
[0010]
Further, on a road surface having a small friction coefficient such as a frozen road surface, the vehicle behavior cannot be controlled if steering is performed in the same manner as a normal road surface. Therefore, it is difficult to perform automatic steering. However, the conventional technology cannot cope with a situation where the friction coefficient of the road surface becomes small during automatic steering.
[0011]
In addition, the fail-safe function for a case where the operation of the actuator for generating the steering assist force is accidentally locked during automatic steering is not sufficient.
[0012]
It is an object of the present invention to provide a vehicle steering apparatus that can solve the above-described problems.
[0013]
[Means for Solving the Problems]
A vehicle steering device according to the present invention includes a steering force generating actuator that generates a steering force based on a signal from a control device in an automatic steering mode, a steering shaft that transmits the steering force to a wheel, and the steering force generating actuator. Means for obtaining a torque transmitted from the steering shaft based on the additional steering force as a value corresponding to the steering force applied to the vehicle from the outside in addition to the steering force generated by the vehicle. The steering force generation actuator is controlled so as to generate a canceling steering force.
When a steering force is applied to the vehicle from the outside, the torque transmitted by the steering shaft changes before the actual steering angle changes. Therefore, the torque transmitted by the steering shaft is obtained as a value corresponding to the steering force applied to the vehicle from the outside, and the steering force generation actuator is controlled so as to cancel the obtained additional steering force. Before the steering angle actually changes due to the additional steering force, the influence of the additional steering force can be compensated.
[0014]
In the present invention, the steering mode can be switched between the automatic steering mode and a normal steering mode in which a steering force generated by a driver is transmitted to the wheels via the steering shaft. In the automatic steering mode, the steering force is switched. Means are provided for determining whether an additional steering force other than the steering force generated by the generating actuator is applied by the driver or externally applied to the vehicle, and the additional steering force is applied by the driver, and It is preferable to provide means for switching from the automatic steering mode to the normal steering mode when the torque corresponding to the additional steering force is equal to or greater than the set value.
According to this configuration, it is possible to switch to the normal steering mode without changing the actual steering angle only by the driver adding a steering force during automatic steering. Thereby, it is possible to quickly switch from the automatic steering mode to the normal steering mode in an emergency situation or the like.
Moreover, since it is determined whether the steering force applied during the automatic steering is applied by the driver or externally applied to the vehicle based on disturbances such as unevenness and crosswinds on the traveling road, the vehicle is externally applied. The added steering force can prevent erroneous switching from the automatic steering mode to the normal steering mode.
[0015]
In the present invention, a steering force is externally applied to the vehicle in the same direction as the steering force generated by the steering force generation actuator, and the absolute value of the torque corresponding to the additional steering force is greater than or equal to a set value. Sometimes it is preferable to provide means for switching from automatic steering mode to normal steering mode.
When the friction coefficient of the road surface decreases, the steering resistance acting on the wheels decreases, so that the steering force is applied to the vehicle from the outside in the same direction as the steering force generated by the steering force generating actuator. Therefore, by switching from the automatic steering mode to the normal steering mode when the absolute value of the torque corresponding to the additional steering force is greater than or equal to the set value, the automatic steering can be canceled when the road surface friction coefficient is small.
[0016]
The steering device according to the present invention releases the lock when the operation of the steering assist force generating actuator and the steering assist force generating actuator are locked, and generates an output of the steering force generating actuator. And a means for increasing the amount corresponding to the steering assist force by the actuator.
Thus, the vehicle can be steered even when the operation of the steering assist force generating actuator is locked. In addition, since the steering force generating actuator can compensate for the lack of steering assisting force due to the steering assisting force generating actuator, the steering performance can be maintained.
[0017]
The steering wheel side and the wheel side of the steering shaft are elastically rotatable relative to each other according to the torque transmitted by the steering shaft, and have a value corresponding to the rotation angle of the steering shaft on the steering wheel side. There is provided means for obtaining a series, and means for obtaining a value corresponding to the rotation angle on the wheel side of the steering shaft in time series, and the change in the rotation angle on the steering wheel side of the steering shaft is When it precedes the change of the rotation angle, it judges that the additional steering force is added by the driver, and when the change of the rotation angle on the wheel side of the steering shaft precedes the change of the rotation angle on the steering wheel side, It is preferable to determine that the additional steering force is applied to the vehicle from the outside.
When the change in torque is based on the steering force applied by the driver, the change in the rotation angle on the steering wheel side of the steering shaft precedes the change in the rotation angle on the wheel side. When the change in torque is based on the steering force applied to the vehicle from the outside, the change in the rotation angle on the wheel side of the steering shaft precedes the change in the rotation angle on the steering wheel side. This makes it possible to reliably determine whether the additional steering force is applied by the driver or externally applied to the vehicle.
[0018]
The steering force generating actuator is a brushless motor having a rotor that rotates concentrically with the steering shaft, a stator that surrounds the rotor, and a detector for detecting the rotation angle of the rotor, and detecting the rotation angle of the rotor A value corresponding to the rotation angle of the steering shaft on the steering wheel side is obtained in time series, and a second detector of the rotation angle of the steering shaft on the wheel side with respect to the steering force generating actuator is provided, A value corresponding to the rotation angle on the wheel side of the steering shaft is obtained in time series by the second detector, the rotation angle of the steering shaft obtained by the detector of the rotation angle of the rotor, and the second detection. From the steering shaft rotation angle required by the Preferably, the torque transmitted is determined.
According to this configuration, since the rotor of the brushless motor that generates the steering force in the automatic steering mode rotates concentrically with the steering shaft, the structure is compact. In addition, since a value corresponding to a change in the rotation angle of the steering shaft on the steering wheel side can be obtained in a time series by the rotation angle detector of the rotor, a dedicated detector is not necessary. Further, since the torque corresponding to the additional steering force is obtained from the detector of the rotation angle of the rotor and the output of the second detector, a dedicated torque sensor is not required.
[0019]
The steering device according to the present invention includes a hydraulic actuator for generating a steering assist force, a pump for supplying pressure oil to the hydraulic actuator, a motor for driving the pump, and a rotational speed of the motor for driving the pump. Means for setting the steering assist speed when necessary, and setting the standby speed when steering assist is not required, and when the rotational speed of the pump drive motor increases from the standby speed to the steering assist speed in the normal steering mode, It is preferable that the steering assist force can be generated by the steering force generating actuator only for a certain period from the start of acceleration.
As a result, when the pump drive motor is set to a standby speed when steering assistance is not required to save energy, the pump is steered by the pump during the start-up period until the pump drive motor increases from the standby speed to the steering assist speed. Even if a sufficient amount of pressure oil cannot be supplied to the auxiliary force generating hydraulic actuator, a sufficient steering assist force can be applied. Thereby, the steering feeling in the normal steering mode can be improved.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
A rack and pinion type steering device 1 shown in FIG. 1 transmits a steering force generated by a driver from a steering wheel H to a wheel W via a steering shaft. Further, a steering force generated by a brushless motor 50 described later is transmitted to the wheels W via the steering shaft.
[0022]
The steering shaft includes an input shaft 2 connected to the steering wheel H and an output shaft 4 connected to the input shaft 2 via a torsion bar 3. The torsion bar 3 is connected to the input shaft 2 via a pin 5 and is connected to the output shaft 4 via a serration 6. A pinion 7 is formed on the output shaft 4, and a wheel W is connected to each end of the rack 8 that meshes with the pinion 7. The input shaft 2 is supported by the motor housing 10 c via a sleeve 2 a and a bearing 9 integrated on the outer periphery, and is supported by the output shaft 4 via a bush 11. The output shaft 4 is supported by the rack housing 10 b via bearings 12 and 13. The rack housing 10b and the motor housing 10c are integrated via a valve housing 10a.
[0023]
The input shaft 2 is rotated by a steering torque based on the steering force. The rotation of the input shaft 2 is transmitted to the pinion 7 via the torsion bar 3 and the output shaft 4. The rack 8 moves in the axial direction by the rotation of the pinion 7. The wheels are steered by the movement of the rack 8. At this time, the input shaft 2 on the steering wheel side and the output shaft 4 on the wheel W side of the steering shaft are elastically rotated relative to the coaxial center by the torsion bar 3 being elastically twisted according to the steering torque. To do.
[0024]
Oil seals 14 and 15 are provided between the input / output shafts 2 and 4 and the valve housing 10a. A support yoke 16 that supports the rack 8 is provided, and the support yoke 16 is pressed against the rack 8 by the elasticity of the spring 17.
[0025]
A hydraulic cylinder (hydraulic actuator) 18 that generates a steering assist force is provided. The hydraulic cylinder 18 includes a cylinder tube constituted by the rack housing 10 b and a piston 20 integrated with the rack 8, and includes a first oil chamber 21 and a second oil chamber 22 partitioned by the piston 20. Have.
[0026]
Each of the oil chambers 21 and 22 is connected to a rotary hydraulic control valve 23 that operates based on a steering force. The control valve 23 controls the hydraulic pressure of the pressure oil supplied from the pump 37 to the hydraulic cylinder 18 to generate a steering assist force.
[0027]
That is, the control valve 23 includes a cylindrical first valve member 24 and a second valve member 25 inserted into the first valve member 24 so as to be relatively rotatable coaxially. The first valve member 24 is inserted into the valve housing 10a so as to be relatively rotatable, and is attached to the output shaft 4 via a pin 26 so as to be able to rotate together. The second valve member 25 is integrally formed on the outer periphery of the input shaft 2, and thus rotates together with the input shaft 2. Thereby, the 1st valve member 24 and the 2nd valve member 25 rotate relatively elastically, when the torsion bar 3 twists according to the steering torque transmitted by the said steering shaft. The hydraulic pressure of the pressure oil supplied from the pump 37 to the hydraulic cylinder 18 is controlled according to the relative rotation amount.
[0028]
That is, as shown in FIG. 2, a plurality of recesses along the axial direction are formed at equal intervals in the circumferential direction on the inner periphery of the first valve member 24 and the outer periphery of the second valve member 25. The first valve member-side recess is composed of a right steering recess 27 and a left steering recess 28 that are located at equal intervals in the circumferential direction. The concave portion on the second valve member side is composed of a pressure oil supply concave portion 29 and a pressure oil discharge concave portion 30 that are located at equal intervals in the circumferential direction. The right steering recesses 27 and the left steering recesses 28 are alternately arranged in the circumferential direction, and the pressure oil supply recesses 29 and the pressure oil discharge recesses 30 are alternately arranged in the circumferential direction.
[0029]
Each of the right steering recesses 27 communicates with the first oil chamber 21 of the hydraulic cylinder 18 from the first flow path 31 formed in the first valve member 24 and the first port 32 formed in the valve housing 10a.
[0030]
Each left steering recess 28 communicates with the second oil chamber 22 of the hydraulic cylinder 18 from the second flow path 33 formed in the first valve member 24 and the second port 34 formed in the valve housing 10a.
[0031]
Each pressure oil supply recess 29 communicates with the pump 37 via a third flow path 35 formed in the first valve member 24 and an inlet port 36 formed in the valve housing 10a.
[0032]
Each pressure oil discharge recess 30 includes a first discharge path 38 formed in the second valve member 25, a passage 47 between the inner and outer periphery of the input shaft 2 and the torsion bar 3, and a discharge port 40 formed in the valve housing 10a. To the tank 41.
[0033]
As a result, the oil chambers 21 and 22 of the hydraulic cylinder 18 and the pump 37 are connected via the inter-valve oil passage 42 formed between the inner and outer peripheries of the first valve member 24 and the second valve member 25. . The pump 37 is driven by a motor 64, and can be constituted by, for example, a vane pump or a gear pump that discharges pressure oil at a flow rate corresponding to the rotational speed of the pump driving motor 64. In the inter-valve oil passage 42, between the first valve member side concave portion and the second valve member side concave portion, throttle portions A, B, C, D whose opening degree changes due to relative rotation of both valve members 24, 25, and Is done. The hydraulic pressure acting on the hydraulic cylinder 18 is controlled by changing the opening degree of each throttle part A, B, C, D according to the steering torque. FIG. 3 shows the hydraulic circuit.
[0034]
FIG. 2 shows the relative positions of the valve members 24 and 25 in the straight steering position where steering is not performed. In this state, the pressure oil supply recesses 29 and the pressure oil discharge recesses 30 The opening degree of the throttle portions A, B, C, and D is constant.
[0035]
When the vehicle is steered to the right from the straight steering position, each right steering recess 27 and each pressure oil supply recess 29 according to the relative amount of rotation of both valve members 24 and 25 due to torsion of the torsion bar 3 according to the steering torque. Between the left steering recess 28 and each pressure oil discharge recess 30, and the left steering recess 28 and each pressure oil supply The opening degree of the throttle part C between the concave part 29 and the opening degree of the throttle part D between each right steering concave part 27 and each pressure oil discharging concave part 30 become small. As a result, pressure oil corresponding to the steering torque is supplied from the pump 37 to the first oil chamber 21, the oil is recirculated from the second oil chamber 22 to the tank 41, and the steering assist force to the right of the vehicle is applied to the rack 8. Works.
[0036]
When steering from the straight steering position to the left, the apertures of the throttles A, B, C, and D change in the opposite direction to the steering to the right, so that the steering assist force to the left of the vehicle is applied to the rack 8 Works.
[0037]
In order to detect whether or not the hydraulic cylinder 18 is operating, a sensor 44 that detects the movement of the rack 8 that constitutes the piston rod of the hydraulic cylinder 18 is provided. The sensor 44 can be constituted by a potentiometer, for example.
[0038]
When the operation of the hydraulic cylinder 18 is inadvertently locked, an electromagnetic on-off valve 43 for releasing the lock is connected to the control device 61. The electromagnetic on-off valve 43 normally closes the communication path between the first oil chamber 21 and the second oil chamber 22 of the hydraulic cylinder 18, and an excitation current is supplied from the control device 61 to the solenoid 43 a when locked, as will be described later. By being applied, both the oil chambers 21 and 22 are communicated with each other.
[0039]
As shown in FIG. 1, a three-phase brushless motor 50 is provided as an actuator for generating a steering force. The brushless motor 50 includes a rotor 51 attached to the input shaft 2 so as to rotate concentrically with the input shaft 2 via the sleeve 2a, and a stator attached to the motor housing 10c so as to surround the rotor 51. 52 and a detector for detecting the rotation angle of the rotor 51. The detector includes a first resolver 53 having a rotor 53a integrated with the input shaft 2 via a sleeve 2a and a stator 53b attached to the motor housing 10c. The control valve 23 is disposed closer to the wheel W than the brushless motor 50.
[0040]
A second resolver 65 that detects the rotation angle of the steering shaft is provided on the wheel W side of the control valve 23. The second resolver 65 has a rotor 65a integrated with the output shaft 4 and a stator 65b attached to the rack housing 10b.
[0041]
The coil of the stator 52 of the brushless motor 50 and the stator 53 b of the first resolver 53 are connected to the control device 61. The control device 61 is connected to a mode changeover switch 62, an input device 63, the pump driving motor 64, a stator 65 b of the second resolver 65, and a vehicle speed sensor 70.
[0042]
By operating the mode switch 62, the vehicle steering mode can be switched between the automatic steering mode and the normal steering mode. In the automatic steering mode, the brushless motor 50 generates a steering force based on a command signal from the control device 61, and in the normal steering mode, the driver generates a steering force.
[0043]
For example, a sign signal transmitted from a transmitter provided on a traveling road or a guard rail, an alarm signal for notifying a collision risk transmitted from a transmitter provided in another vehicle, An induction signal such as a travel line detection signal is input. When the guidance signal is input from the input device 63 in the automatic steering mode, the control device 61 eliminates the deviation between the target steering angle required for steering the vehicle according to the guidance signal and the actual output steering angle. A command signal is output. The brushless motor 50 is driven by the command signal. The steering force generated by the brushless motor 50 is transmitted to the wheels W through the steering shaft, similarly to the steering force generated by the driver in the normal steering mode.
[0044]
Further, the control device 61, as the value corresponding to the steering force added in addition to the steering force generated by the brushless motor 50 during the automatic steering, the torque transmitted by the steering shaft based on the additional steering force, It is obtained from the outputs of the first resolver 53 and the second resolver 65.
[0045]
That is, the input shaft 2 and the output shaft 4 elastically rotate relative to the coaxial center by the torsion bar 3 being elastically twisted according to the steering torque. Therefore, the difference between the rotation angle of the input shaft 2 detected by the first resolver 53 and the rotation angle of the output shaft 4 detected by the second resolver 65 corresponds to the torque transmitted by the steering shaft.
[0046]
FIG. 4 (1) shows the relationship between the output of the first resolver 53 and the rotation angle of the input shaft 2. The control device 61 stores the output Eao of the first resolver 53 when the torque transmitted by the steering shaft is zero and the steering angle is zero as the reference output at the reference position P of the input shaft 2. The control device 61 obtains the rotation angle of the rotor 51 and the rotation angle of the steering shaft on the steering wheel H side in time series from the difference between the actual output of the first resolver 53 and the reference output Eao.
[0047]
FIG. 4B shows the relationship between the output of the second resolver 65 and the rotation angle of the output shaft 4. The control device 61 stores the output Ebo of the second resolver 65 when the torque transmitted by the steering shaft is zero and the steering angle is zero as the reference output at the reference position P of the output shaft 4. The control device 61 obtains the rotation angle on the wheel W side of the steering shaft in time series from the difference between the actual output of the second resolver 65 and the reference output Ebo.
[0048]
Since the outputs of the resolvers 53 and 65 are sinusoidal waveforms, the rotation angle may be different even if the outputs are the same. Therefore, the reference output Eao of the first resolver 53 is different from the reference output Ebo of the second resolver 65. As a result, by comparing the outputs of the resolvers 53 and 65 with each other, the rotation angle can be obtained accurately, and a dedicated detector for obtaining the reference position P is not required, so the cost can be reduced. That is, when the output of the first resolver 53 is the reference output Eao and the output of the second resolver 64 is the reference output Ebo, the rotor 51 and the steering shaft are in the reference position and the rotation angle is zero. .
[0049]
In order to cope with the case where the rotation angle of the steering shaft exceeds one cycle of the sine waveform of the output of each resolver 53, 65, the control device 61 performs a pulse every one cycle of the sine waveform of the output of each resolver 53, 65. A signal is generated, and for each pulse, the rotation angle of the steering shaft for one cycle of the sine waveform is added to the rotation angle obtained from the difference between the actual output of each resolver 53, 65 and the reference output Ebo.
[0050]
FIG. 5 is a block diagram showing a control system in the automatic steering mode configured as described above. In the control device 61, the deviation between the target steering angle θq of the vehicle and the actual output steering angle θo and the transfer function C1 A target torque Tq is calculated. The actual output steering angle θo corresponds to the rotation angle on the wheel W side of the steering shaft. The target torque Tq is a value corresponding to the vehicle speed detected by the vehicle speed sensor 70. The transfer function C1 can be obtained by experiments from the relationship between the deviation between the target steering angle θq and the output steering angle θo and the torque necessary to compensate for the deviation.
A target motor drive current Iq is calculated from a torque obtained by adding a compensation torque Tc described later to a deviation between the target torque Tq and the total torque T transmitted by the steering shaft, and a transfer function C2. The transfer function C2 can be C2 = 1 / (Kt × s), where Kt is the torque constant of the brushless motor 50 and s is the Laplace operator.
The motor applied power Eq is calculated from the deviation between the target motor drive current Iq and the actual drive current Ia of the brushless motor 50 and the transfer function C3. The transfer function C3 can be C3 = K1 + K2 / (τ × s) where K1 is a current control proportional gain, K2 is a current control integral gain, τ is a current control integral time constant, and the Laplace operator is s.
The motor applied power Eq is applied to the brushless motor 50 via the normally closed contact 49.
The drive current Ia of the brushless motor 50 is obtained from the deviation between the motor applied power Eq and the motor output power Ea and the transfer function C4. The transfer function C4 can be obtained by C4 = 1 / (L × s + R) where L is the inductance of the brushless motor 50, R is the internal resistance of the brushless motor 50, and the Laplace operator is s. The motor output power Ea is obtained from the output shaft rotational speed of the brushless motor 50, that is, the rotational angular velocity ωi on the steering wheel H side of the steering shaft, and the transfer function C5. The transfer function C5 corresponds to the induced voltage constant of the brushless motor 50.
The output torque Ta of the brushless motor 50 is obtained from the drive current Ia and the transfer function C6. The transfer function C6 corresponds to the torque constant of the brushless motor 50.
From the sum of the output torque Ta of the brushless motor 50 and the steering torque Th applied by the driver and the transfer function C7, the output shaft rotational speed of the brushless motor 50, that is, the rotational angular velocity of the steering shaft on the steering wheel H side. ωi is obtained. The transfer function C7 is obtained by C7 = 1 / (Ii × s + Ci) where Ii is the inertia on the input shaft 2 side of the steering device, Ci is the viscous resistance on the input shaft 2 side, and s is the Laplace operator. it can.
The integral value of the output shaft rotational speed ωi of the brushless motor 50 becomes the rotational angle θi on the steering wheel H side of the steering shaft.
The total torque T transmitted by the steering shaft is obtained from the deviation between the rotation angle θi on the steering wheel H side of the steering shaft and the rotation angle θo on the wheel W side and the transfer function C8. The transfer function C8 corresponds to the torsion spring constant of the torsion bar 3.
From the total torque T transmitted by the steering shaft and the transfer function C9, the output torque Tv of the hydraulic cylinder 18 for generating steering assist force is obtained. The transfer function C9 is obtained from the hydraulic control characteristics of the pressure oil supplied to the hydraulic cylinder 18 by the control valve 23.
From the sum of the output torque Tv of the hydraulic cylinder 18 and the disturbance torque Td corresponding to the steering force applied to the vehicle from the outside, and the transfer function C10, the rotational angular velocity ωo on the wheel W side of the steering shaft is obtained. The transfer function C10 is obtained by C7 = 1 / (Io × s + Co), where Io is the inertia on the output shaft 4 side of the steering device, Co is the viscous resistance on the output shaft 4 side, and s is the Laplace operator. it can.
The integral value of the rotational angular velocity ωo on the wheel W side of the steering shaft becomes the rotational angle θo on the wheel W side of the steering shaft.
[0051]
The flowchart of FIG. 6 shows a steering mode switching control procedure by the control device 61.
[0052]
The control device 61 first determines whether or not the current time is in the automatic steering mode (step 1). In the automatic steering mode, automatic steering is performed by driving the brushless motor 50 (step 2).
[0053]
At the time of the automatic steering, it is determined whether the additional steering force other than the steering force generated by the brushless motor 50 is applied by the driver or a disturbance externally applied to the vehicle (step 3). If the additional steering force is a disturbance, the automatic steering is continued.
That is, when the change in the rotation angle on the steering wheel H side of the steering shaft precedes the change in the rotation angle on the wheel W side, it is determined that the additional steering force is applied by the driver. On the other hand, when the change in the rotation angle on the wheel W side of the steering shaft precedes the change in the rotation angle on the steering wheel H side, it is determined that the additional steering force is applied to the vehicle from the outside. In the present embodiment, the deviation between the rotational angular velocity ωi on the steering wheel H side of the steering shaft and the rotational angular velocity ωo on the wheel W side is obtained, and the rotational angular velocity on the steering wheel H side is determined in the determination unit 61a of the control device 61. If ωi is larger than the rotational angular velocity ωo on the wheel W side, it is judged that it was added by the driver. If the rotational angular velocity ωo on the wheel W side is larger than the rotational angular velocity ωi on the steering wheel H side, it is added from the outside. Judge that
[0054]
When the additional steering force is applied by the driver (No in Step 3), the determination unit 61a determines whether or not the torque Th corresponding to the additional steering force is equal to or greater than the set value T1 (Step 4).
That is, the total torque T transmitted by the steering shaft is obtained from the difference between the rotation angle of the steering shaft obtained by the first resolver 53 and the rotation angle of the steering shaft obtained by the second resolver 65, and the total torque is obtained. By subtracting the torque due to the steering force generated by the brushless motor 50 from T, the torque Th corresponding to the additional steering force is obtained. The torque due to the steering force generated by the brushless motor 50 is obtained from the value of the drive current Ia of the brushless motor 50.
[0055]
When the torque Th corresponding to the additional steering force of the driver is greater than or equal to the set value T1, an open signal is output to the normally closed contact 49. As a result, the power applied to the brushless motor 50 is cut off, the automatic steering mode is canceled, and the normal steering mode is switched (step 5). The set value T1 can be determined based on the steering force generated by the driver when indicating the intention of steering.
[0056]
When the torque Th corresponding to the additional steering force of the driver is less than the set value T1, automatic steering is continued.
[0057]
In step 3, when the additional steering force is externally applied to the vehicle due to disturbance, the determination unit 61a determines whether or not the additional steering force is in the same direction as the steering force generated by the brushless motor 50. (Step 6).
That is, when the total torque transmitted by the steering shaft is smaller than the torque due to the steering force generated by the brushless motor 50, it is determined that the directions of both steering forces are the same direction.
[0058]
In step 6, when the direction of the steering force generated by the brushless motor 50 is the same as the direction of the additional steering force, the determination unit 61a sets the absolute value of the disturbance torque Td corresponding to the additional steering force as a set value. It is determined whether or not T2 or more (step 7).
[0059]
When the absolute value of the disturbance torque Td is equal to or greater than the set value T2, an alarm signal is issued (step 8), after which an open signal is output to the normally closed contact 49, the automatic steering mode is canceled, and the normal steering mode is entered. Switch (step 5). An alarm device (not shown) such as a buzzer or a lamp that issues an alarm to the driver by the alarm signal is activated. Before switching from the automatic steering mode to the normal steering mode, the steering force is generated in the brushless motor 50 so that the steering angle of the wheel W is not temporarily changed, so that the vehicle is stabilized. Also good.
[0060]
In step 6, when the direction of the steering force generated by the brushless motor 50 and the direction of the additional steering force are not the same direction, in step 7, when the absolute value of the disturbance torque Td is less than the set value T2, the disturbance torque Td The brushless motor 50 is controlled so as to generate a steering force that cancels out the above, and the influence of disturbance is compensated (step 9).
That is, the compensation torque Tc for canceling the disturbance torque Td is calculated, and the compensation torque Tc is added to the target torque Tq, so that the brushless motor 50 is generated so as to generate a steering force that cancels the additional steering force. Control. An arithmetic expression for obtaining the compensation torque Tc from the disturbance torque Td can be obtained in advance by experiments.
[0061]
In both the normal steering mode and the automatic steering mode, the control device 61 instructs the rotational speed of the pump drive motor 64 to be the steering assist speed when the steering assist is necessary and to set the standby speed when the steering assist is not necessary. Output a signal.
That is, if the total torque T transmitted by the steering shaft is equal to or greater than a preset value according to the necessity of steering, the control device 61 instructs the rotation speed of the pump drive motor 64 to be the steering assist speed. Is output. The steering assist speed is a speed set in advance so that the flow rate of the pressure oil sent from the pump 37 becomes a flow rate necessary for steering assist. The steering assist speed changes according to the vehicle speed detected by the vehicle speed sensor 70. That is, the steering assist speed is determined so that the steering assist force is increased at low vehicle speeds to improve the turning performance of the vehicle, and the steering assist force is decreased at high vehicle speeds to improve the running stability of the vehicle.
If the total torque T transmitted by the steering shaft is less than the set value, the determination unit 61a outputs an instruction signal for setting the rotational speed of the pump drive motor 64 to the standby speed. The standby speed is a preset speed smaller than the steering assist speed, and is zero in the present embodiment, but may be a value larger than zero. Thereby, energy saving can be achieved.
[0062]
In the normal steering mode, when the rotational speed of the pump drive motor 64 increases from the standby speed to the steering assist speed, a drive command signal is output to the brushless motor 50 for a certain period from the start of the speed increase. Thereby, the brushless motor 50 generates a steering assist force. The magnitude of the steering assist force generated by the brushless motor 50 is set such that the pump driving motor 64 can secure the steering assist force generated at the steering assist speed. What is necessary is just to set so that the steering feeling of a driver can be improved for the fixed period from the said acceleration start which generates the steering assist force in the brushless motor 50. FIG.
[0063]
In both the automatic steering mode and the normal steering mode, the control device 61 operates the steering assist force generating hydraulic cylinder 18 by the signal from the sensor 44 when the drive current Ia is applied to the brushless motor 50. It is determined whether or not. When the operation of the hydraulic cylinder 18 is locked, the control device 61 outputs a lock release signal. Thereby, the solenoid 43a of the electromagnetic on-off valve 43 is excited, the first oil chamber 21 and the second oil chamber 22 of the hydraulic cylinder 18 are communicated, and the lock is released. When the lock is released, the control device 61 outputs a signal for increasing the output of the brushless motor 50 by the amount of the steering assist force by the hydraulic cylinder 18.
[0064]
In the above configuration, when a steering force is applied to the vehicle from the outside, the torque transmitted by the steering shaft changes before the actual steering angle changes. Therefore, the torque transmitted by the steering shaft as a value corresponding to the steering force applied to the vehicle from the outside is obtained, and the brushless motor 50 is controlled so as to cancel the obtained additional steering force. The influence of the additional steering force can be compensated before the steering angle actually changes due to the force. Thereby, the influence of disturbance can be compensated quickly and reliably, and the behavior of the vehicle can be stabilized.
[0065]
Further, according to the above configuration, when the driver applies a steering force during automatic steering, it is possible to switch to the normal steering mode without changing the actual steering angle. Thereby, it is possible to quickly switch from the automatic steering mode to the normal steering mode in an emergency situation or the like. In addition, since it is determined whether the steering force applied during the automatic steering is applied by the driver or externally applied to the vehicle, it is possible to erroneously switch from the automatic steering mode to the normal steering mode due to disturbance. Can be prevented.
[0066]
In the above configuration, additional steering is performed without using a dedicated torque sensor by obtaining the rotation angle on the steering wheel H side and the rotation angle on the wheel W side of the steering shaft that elastically rotates relative to the transmission torque. The torque corresponding to the force can be obtained easily and quickly. When the change in torque is based on the steering force applied by the driver, the change in the rotation angle on the steering wheel H side of the steering shaft precedes the change in the rotation angle on the wheel W side. When the change in the torque is based on the steering force applied to the vehicle from the outside, the change in the rotation angle on the wheel W side of the steering shaft precedes the change in the rotation angle on the steering wheel H side. This makes it possible to reliably determine whether the additional steering force is applied by the driver or externally applied to the vehicle.
[0067]
In the above configuration, it is determined whether or not a steering force is applied to the vehicle from the outside in the same direction as the steering force generated by the brushless motor 50. Thereby, it can be determined whether or not the steering resistance acting on the wheels has decreased due to the decrease in the friction coefficient of the road surface. By switching from the automatic steering mode to the normal steering mode when the absolute value of the disturbance torque Td corresponding to the additional steering force is equal to or greater than the set value T2, the automatic steering can be canceled when the road surface friction coefficient is small.
[0068]
Further, when the steering assist force generating hydraulic cylinder 18 is locked, the lock is released, so that the vehicle can be steered and the fail-safe function can be improved. Further, since the output of the brushless motor 50 is increased by the steering assist force by the hydraulic cylinder 18, the steering performance can be maintained.
[0069]
Since the rotor 51 of the brushless motor 50 that generates a steering force in the automatic steering mode rotates concentrically with the steering shaft, the response to the control by the control device 61 is quick, and the structure becomes compact and simple. In addition, since the first resolver 53 of the brushless motor 50 can obtain the value corresponding to the change in the rotation angle of the steering shaft on the steering wheel H side in time series, a dedicated detector is not required. Further, since the torque corresponding to the additional steering force is obtained from the outputs of the first resolver 53 and the second resolver 65, a dedicated torque sensor becomes unnecessary. Thereby, the structure can be made simple and compact, and the manufacturing cost can be reduced. In addition, the output of the resolvers 53 and 65 can be adjusted simply by rotating the rotors 53a and 65a with respect to the stators 53b and 65b.
[0070]
Further, in the above configuration, when the pump driving motor 64 is set to a standby speed when steering assistance is unnecessary and energy saving is intended, in the rising period until the pump driving motor 64 increases from the standby speed to the steering assist speed, Even if a sufficient amount of pressure oil cannot be supplied to the hydraulic cylinder 18 for generating the steering assist force by the pump 37, the steering assist force can be applied by the brushless motor 50. Thereby, the steering feeling at the time of normal steering can be improved.
[0071]
7 and 8 show a first modification of the present invention. The difference from the above embodiment is that a torque sensor 107 is provided between the brushless motor 50 and the control valve 23 instead of the second resolver 65.
[0072]
The torque sensor 107 is connected to the first and second detection coils 133 and 134 held by the valve housing 10a and the first valve member 24 of the control valve 23 via a connecting member 140 so as to be able to rotate together. A first detection ring 136 made of a magnetic material and a second detection ring 137 made of a magnetic material connected to the input shaft 2 so as to be able to rotate together.
The one end surface of the first detection ring 136 and the one end surface of the second detection ring 137 are arranged so as to face each other, and teeth 136a and 137a are respectively provided on the opposing end surfaces of the detection rings 136 and 137 along the circumferential direction. A plurality are provided.
The other end side of the second detection ring 137 is a small-diameter portion 137b having a smaller outer diameter than the one end side.
The first detection coil 133 is disposed so as to cover the space between the first detection ring 136 and the second detection ring 137, and the second detection coil 134 is disposed so as to cover the second detection ring 137. , 134 are connected to a signal processing circuit 141 formed on a substrate attached to the valve housing 10a. In the signal processing circuit 141, the first detection coil 133 is connected to the oscillator 146 via the resistor 145, the second detection coil 134 is connected to the oscillator 146 via the resistor 147, and each detection coil 133, 134 is differentially connected. The amplifier circuit 148 is connected.
As a result, when the torsion bar 3 is twisted by the torque transmitted by the steering shaft and the two detection rings 136 and 137 rotate relative to each other elastically, the opposing areas of the teeth 136a and 137a of the detection rings 136 and 137 change. Due to the change in area, the magnetic resistance to the magnetic flux generated by the first detection coil 133 between the teeth 136a and 137a changes. Therefore, the output of the first detection coil 133 changes according to the change, and corresponds to the output. The transmitted torque is detected. The torque detection signal is input to the control device 61.
The second detection coil 134 faces the small diameter portion 137 b of the second detection ring 137. The outer diameter of the small-diameter portion 137b is set so that the magnetic resistance with respect to the magnetic flux generated by the second detection coil 134 and the magnetic resistance with respect to the magnetic flux generated by the first detection coil 133 are equal in a state where the steering resistance is not acting. ing. As a result, the output fluctuation of the first detection coil 133 due to the temperature fluctuation is equal to the output fluctuation of the second detection coil 134 due to the temperature fluctuation, so that it is canceled out by the differential amplifier circuit 148, and the fluctuation of the detected value of the steering torque due to the temperature. Compensated.
Further, in place of the oil seal 14 between the input shaft 2 and the valve housing 10a in the above embodiment, the oil seal 114 is provided between the connecting member 140 and the input shaft 2, and between the connecting member 140 and the valve housing 10a. Is placed.
Others are the same as in the above embodiment, and the same parts are denoted by the same reference numerals.
[0073]
According to the first modification, torque transmitted by the steering shaft is obtained by the torque sensor 107 as a value corresponding to the steering force applied in addition to the steering force generated by the brushless motor 50 during automatic steering. The torque detected by the torque sensor 107 corresponds to the rotation angle on the wheel W side of the steering shaft. The control device 61 obtains the torque detected by the torque sensor 107 in time series. When the change in the rotation angle on the steering wheel H side of the steering shaft required by the first resolver 53 precedes the change in torque detected by the torque sensor 107, the control device 61 adds the additional steering force by the driver. Judge that it was done. On the other hand, when the change in torque detected by the torque sensor 107 precedes the change in the rotation angle on the steering wheel H side, it is determined that the additional steering force is applied to the vehicle from the outside. It can be determined by comparing the rotational angular speed and the torque change speed which of the rotational angle change and the torque change precedes.
[0074]
9 and 10 show a second modification of the present invention. The difference from the first modification is that the steering assist force is applied using a steering assist motor 180 instead of the hydraulic cylinder 18. Therefore, the motor 180 is driven based on the signal from the control device 61 so that the steering assist force according to the torque detected by the torque sensor 107 and the vehicle speed detected by the vehicle speed sensor 70 can be applied, and the output of the motor 180 Is transmitted to the rack 8 via the ball screw mechanism 190.
That is, the motor 180 is provided so as to cover the rack 8 protruding from the rack housing 10b, a motor housing 180a attached to the rack housing 10b, a stator 180b fixed to the inner periphery of the motor housing 180a, The motor housing 180a has a cylindrical rotor 180e rotatably supported through bearings 180c and 180d, and the rack 8 is surrounded by the rotor 180e. The ball screw mechanism 190 has a male screw 190a integrally formed on the outer periphery of the rack 8, and a ball nut 190b screwed to the male screw 190a via a ball. The ball nut 190 is coupled to the rotor 180e so as to be able to rotate together. The control device 61 applies a driving current corresponding to the torque transmitted by the steering shaft and the vehicle speed, thereby driving the motor 180, and the rotational force of the rotor 180e is converted into an axial force via the ball nut 190b, the ball, and the male screw 190a. It is converted and transmitted to the rack 8 as a steering assist force. The output torque of the motor 180 is obtained from the control characteristic of the drive current of the motor 180 by the control device 61.
The driving current of the motor 180 is applied from the control device 61 via the relay circuit 181. The relay circuit 181 includes a relay switch that cuts off the power supply to the motor 180 when the rotation of the motor 180 is locked while a drive current is applied to the motor 180. The relay circuit 181 can be the same as the conventional one. When the power supply to the motor 180 is interrupted, the lock of the motor 180 is released. When the power supply to the motor 180 is cut off, the control device 61 outputs a signal for increasing the output of the brushless motor 50 by the steering assist force by the motor 180.
Others are the same as those of the first modification, and the same parts are denoted by the same reference numerals.
[0075]
In addition, this invention is not limited to the said embodiment and modification. For example, a torque sensor that detects torque transmitted by the steering shaft may be provided between the steering wheel and the steering force generation actuator. In this case, the torque transmitted by the steering shaft based on the additional steering force can be directly obtained without subtracting the torque generated by the actuator from the total torque transmitted by the steering shaft as described above.
[0076]
【The invention's effect】
According to the present invention, in a steering device that can automatically steer a vehicle, the influence of disturbance can be compensated quickly and reliably, the behavior of the vehicle can be stabilized, and the automatic steering is canceled on a frozen road surface or the like having a small friction coefficient. The behavior can be prevented from becoming uncontrollable, and the fail-safe function can be improved when the operation of the actuator for generating steering assist force is accidentally locked.If an emergency situation occurs in the automatic steering mode, the influence of disturbance can be reduced. It is possible to quickly switch to the normal steering mode according to the driver's intention without receiving it, and it is possible to reduce the cost by making the structure compact and simple.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a vehicle steering apparatus according to an embodiment of the present invention.
2 is a sectional view taken along line II-II in FIG.
FIG. 3 is a hydraulic circuit diagram of a vehicle steering apparatus according to an embodiment of the present invention.
FIGS. 4A and 4B are views showing the relationship between the output of the first resolver and the relationship between the outputs of the second resolver with respect to the rotation angle of the steering shaft of the steering apparatus for a vehicle according to the embodiment of the present invention. FIGS.
FIG. 5 is a block diagram showing a control system according to the embodiment of the present invention.
FIG. 6 is a flowchart showing a control procedure of the vehicle steering apparatus according to the embodiment of the present invention.
FIG. 7 is a cross-sectional view of a vehicle steering apparatus according to a first modification of the present invention.
FIG. 8 is an output processing circuit diagram of a torque sensor of a steering apparatus for a vehicle according to a first modification of the present invention.
FIG. 9 is a diagram illustrating the configuration of a steering apparatus for a vehicle according to a second modification of the present invention.
FIG. 10 is a sectional view of a steering apparatus for a vehicle according to a second modification of the present invention.
[Explanation of symbols]
2 Input shaft
4 Output shaft
18 Hydraulic cylinder (actuator for generating steering assist force)
23 Control valve
37 pump
50 Brushless motor (steering force generating actuator)
51 rotor
52 Stator
53 First resolver
61 Controller
64 Pump drive motor
65 Second resolver
107 Torque sensor
180 motor
H Steering wheel
W wheel

Claims (7)

A steering force generating actuator for generating a steering force based on a signal from the control device in the automatic steering mode;
A steering shaft that transmits the steering force to the wheels;
Means for obtaining a torque transmitted by the steering shaft based on the additional steering force as a value corresponding to a steering force externally applied to the vehicle other than the steering force generated by the steering force generation actuator ;
In the automatic steering mode, there is provided means for determining whether an additional steering force other than the steering force generated by the steering force generating actuator is applied by the driver or externally applied to the vehicle ,
A vehicle steering apparatus in which a steering force generating actuator is controlled so as to generate a steering force that cancels an additional steering force applied from the outside to the vehicle corresponding to the obtained torque . The steering mode can be switched between the automatic steering mode and the normal steering mode in which the steering force generated by the driver is transmitted to the wheels via the steering shaft ,
Additional steering force of that is added by the driver, and, according to when the torque corresponding to the additional steering force is equal to or greater than a set value, to claim 1 where the means for switching from the automatic steering mode to the normal steering mode is provided Vehicle steering device. When the steering force is applied from the outside to the vehicle in the same direction as the steering force generated by the steering force generating actuator, and the absolute value of the torque corresponding to the added steering force is equal to or greater than the set value, automatic steering is performed. The vehicle steering apparatus according to claim 2, further comprising means for switching from the mode to the normal steering mode. An actuator for generating steering assist force;
And a means for releasing the lock when the operation of the actuator for generating steering assist force is locked and increasing the output of the actuator for generating steering assist force by an amount corresponding to the steering assist force by the actuator for generating steering assist force. Item 4. The vehicle steering device according to Item 2 or 3. The steering wheel side and the wheel side of the steering shaft are elastically rotatable relative to the torque transmitted by the steering shaft,
Means for obtaining a value corresponding to the rotation angle of the steering shaft on the steering wheel side in time series;
Means for obtaining a value corresponding to the rotation angle on the wheel side of the steering shaft in time series,
When the change in the rotation angle on the steering wheel side of the steering shaft precedes the change in the rotation angle on the wheel side, it is determined that the additional steering force is applied by the driver, and the rotation of the steering shaft on the wheel side is determined. change corners, when preceding a change in the rotational angle at the steering wheel side, the steering apparatus for a vehicle according to any one of claims 2-4 to determine that the additional steering force is added from the outside to the vehicle . The steering force generating actuator is a brushless motor having a rotor that rotates concentrically with the steering shaft, a stator that surrounds the rotor, and a detector for the rotation angle of the rotor,
A value corresponding to the rotation angle on the steering wheel side of the steering shaft is obtained in time series by the rotation angle detector of the rotor,
A second detector of the rotation angle of the steering shaft on the wheel side relative to the steering force generating actuator is provided;
A value corresponding to the rotation angle on the wheel side of the steering shaft is obtained in time series by the second detector,
The torque transmitted by the steering shaft is obtained from the difference between the rotation angle of the steering shaft determined by the detector of the rotation angle of the rotor and the rotation angle of the steering shaft determined by the second detector. steering apparatus for a vehicle according to any one of 5. A hydraulic actuator for generating steering assist force;
A pump for supplying pressure oil to the hydraulic actuator;
A motor that drives the pump;
Means for setting the rotational speed of the pump drive motor to a steering assist speed when steering assistance is required, and a standby speed when steering assistance is not required,
In the normal steering mode, when the rotational speed of the motor for driving the pump increases from the standby speed to the steering assist speed, the steering assist force can be generated by the steering force generating actuator for a certain period from the start of the acceleration. steering apparatus for a vehicle according to any one of claims 2-6.

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