JP2004058745A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device for a vehicle capable of simply giving the neutral position of the steering wheel with respect to the transmission ratio variable actuator in the steering device for the vehicles which interposes the transmission ratio variable unit driven by a motor varying the transmission ratio in the middle of a steering transmission system directly connecting the steering wheel and the wheel steering shaft. <P>SOLUTION: Middle point finding is performed automatically and simply by detecting the motor torque generated at the winding tightening end or the winding loosing end of a current supply cable for supplying the power to the motor held in power spring state, investigating the rotation end of a motor and returning the motor by only a predetermined amount (for example, half of whole rotation area) from the rotation limit and rotating it. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vehicle steering system.
[0002]
[Prior art]
2. Description of the Related Art In a steering device of a vehicle, mainly an automobile, a steering shaft is rotated by a rotation operation of a steering wheel, and the direction of a steered wheel is changed via a steering mechanism connected to the steering shaft at a fixed gear ratio. The steering mechanism is often provided with a hydraulic or electric steering force assisting device, a so-called power steering device, so that the force required for rotating the steering wheel is small.
[0003]
By the way, when a large operation of the steering wheel such as garage parking, parallel parking, and shifting of the width is required, the operation force of the steering wheel can be small (light turning), and the direction of the steered wheel can be increased with a small amount of steering wheel operation. If it can be changed, it will be convenient because it will be easier to handle. To achieve this, a variable transmission ratio unit (such as a gear unit) is provided in the middle of the steering transmission system that connects the steering wheel and the steered wheels (wheel steering shafts). A type of steering device has been proposed.
[0004]
More specifically, in a steering device of a vehicle, particularly a steering device for an automobile, in recent years, as one part of further enhancement of the function, an operation angle of a steering wheel (steering wheel operation angle) and a wheel steering angle are set in a 1: 1 ratio. There has been developed a so-called variable steering angle conversion ratio mechanism in which a conversion ratio (steering angle conversion ratio) of a steering wheel operating angle to a wheel steering angle is made variable according to a driving state of a vehicle without being fixed. As the driving state of the vehicle, for example, a vehicle speed (vehicle speed) can be exemplified. In high-speed driving, the steering angle conversion ratio is reduced so that the steering angle does not increase rapidly with an increase in the steering wheel operation angle. Then, high-speed running can be stabilized. On the other hand, when driving at low speeds, conversely, by increasing the steering angle conversion ratio, it is possible to reduce the number of rotations of the steering wheel required to turn the steering wheel to the full, and to increase the steering angle such as garage parking, parallel parking, or width shifting. The driving operation can be performed very easily.
[0005]
As a mechanism for varying the steering angle conversion ratio, for example, as disclosed in Japanese Patent Application Laid-Open No. H11-334604, a steering wheel shaft and a wheel steering shaft are directly connected by a gear type transmission unit having a variable gear ratio. There is a type, but this configuration has a disadvantage that the gear ratio changing mechanism of the gear type transmission unit is complicated. Therefore, a type in which the handle shaft and the wheel steering shaft are separated and the wheel steering shaft is rotationally driven by an actuator such as a motor has been proposed in, for example, Japanese Patent Application Laid-Open No. H11-334628. Specifically, based on a steering wheel operation angle detected by the angle detection unit and a steering angle conversion ratio determined according to the vehicle driving state, a finally required wheel steering angle is calculated by computer processing, and the calculated angle is calculated. The wheel steering shaft mechanically separated from the handle shaft is rotationally driven by an actuator (motor) so that the obtained wheel steering angle is obtained.
[0006]
By the way, in such a steering device in which the handle shaft and the wheel steering shaft are separated from each other and an actuator such as a variable transmission ratio motor is interposed therebetween, if an abnormality occurs in the control unit due to runaway of the CPU or the like, the handle shaft and the wheel steering wheel are disconnected. It may not be known at which position the steering shaft has relatively stopped. In this case, work such as straightening the steered wheels of the vehicle at a repair shop or the like, adjusting the winding holding state of the power supply cable to the neutral position, and then adjusting the steering wheel to neutral to restore the original normal relative positional relationship. It had to be done manually.
[0007]
Further, in a vehicle assembling process, when a steering device (steering assembly) incorporating the above-described transmission ratio variable unit is mounted on a vehicle body, when the steering assembly is delivered in advance, the power supply cable is wound and held in a neutral state. The rotation of the power supply cable is prevented (fixed) by a fixing pin, and the steering assembly is mounted on the vehicle body in a neutral state of the steering (an actuator with a variable transmission ratio is fastened to a steering shaft (handle shaft), a harness is connected / fixed, etc.), After that, the mounting is completed by removing the fixing pin.
[0008]
[Problems to be solved by the invention]
However, when the neutral position of the handle is lost due to an abnormality in the control unit or the like as described above, the operator adjusts the winding holding state of the power supply cable to the neutral position, further adjusts the handle to neutral, and returns to the initial normal state. Restoring to a neutral state is troublesome and time-consuming.
In addition, when the steering assembly is installed at the factory, the steering neutral state is maintained by the fixed pin, and the pin is removed after mounting. If the fixed pin comes off for any reason, the neutral state of the steering cannot be understood, and the mounting (assembly) ) Failure occurs. Also, the fixing pins are required only for assembly, resulting in an increase in the number of parts. When the steering assembly is replaced or reassembled at a facility outside the factory such as a dealer, the fixing pin may not be provided, and there is a problem that the neutralization is not easy.
[0009]
It is an object of the present invention to provide a vehicle steering device that can easily provide a reference position such as a neutral position in a relative relationship between a variable transmission ratio actuator and a steering wheel.
[0010]
Means for Solving the Problems and Effects of the Invention
The present invention interposes a variable transmission ratio unit driven by a motor that varies the transmission ratio in the middle of a steering transmission system that directly connects a steering wheel and a wheel steering shaft, and controls the transmission ratio in accordance with the situation of the vehicle. In a vehicle steering system having a transmission ratio control unit,
A cable holder in which the motor is fixed to a handle shaft that rotates integrally with the steering handle, and a power supply cable that supplies power to the motor is formed integrally with the handle shaft at a free end extending from a fixed portion of the motor. The part is spirally wound to generate an elastic force in the relaxing direction, and is held so as to be reduced in outer diameter by being tightened according to the rotation of the steering handle or to be relaxed to increase in outer diameter. Cable holding device,
When operating the motor in the allowable holding range of the power supply cable and rotating the steering handle, a motor torque detection device that detects an increase in motor torque at a winding end or a relaxed end of the power supply cable,
An end exploring device for exploring a winding end or a loose end of the power supply cable by the motor torque indicating a predetermined increase value,
A reference position recognition device that recognizes a reference position of a relative relationship between the handle axis and the steering axis based on the end search;
It is characterized by including.
[0011]
Here, in addition to the above-described cable holding device, the motor torque detecting device, and the end detecting device for detecting the tightened end or the relaxed end of the power supply cable by indicating that the motor torque has a predetermined increase value, A handle neutral recognition device that rotates the motor by a predetermined amount so as to return the steering handle to the neutral position side from the tightened end or the relaxed end.
[0012]
With this configuration, for example, after rotating the motor of the transmission ratio variable unit in the winding direction and detecting a predetermined motor torque (detecting the end of the winding end or the loose end), the motor is preset in the opposite direction. By rotating and stopping the motor by the specified amount, the device automatically finds the neutral point, so that it is possible to easily and quickly set and recover the neutral position of the steering wheel after an abnormality has occurred in the control unit. Work efficiency is improved and maintainability is improved. In addition, even when the steering assembly is mounted on the vehicle body at the factory, the neutral point can be easily given as described above, and the fixing pin can be omitted, so that troubles such as the detachment of the fixing pin can be avoided. In addition, the number of parts can be reduced by eliminating the fixing pin, and the centering can be easily performed at the time of replacement or reassembly at a repair shop away from the dealer's factory.
When the motor of the transmission ratio changing actuator rotates the handle shaft (steering wheel) to the tightened end or the relaxed end of the power supply cable in a state where the steered wheels are straightened, the maximum allowable rotation amount of the handle is, for example, about 5 turns. In this case, after detecting the end at which the motor torque is generated, the motor is reversely rotated about 2.5 times to find the neutral position.
However, the present invention is not limited to the search for the neutral point. For example, in a state where the steered wheels are fully cut, the motor is rotated to the side corresponding to the steering direction, and if the rotation end is detected at the tightened end or the relaxed end, the position becomes the steering wheel and the steering shaft. Becomes a relatively corresponding reference position (steering limit position or motor rotation limit position), so that it does not always return to the neutral side and rotate (reverse rotation) after detecting the rotation end. In this sense, it is not indispensable that the return rotation of about half of the total rotation allowable range after the detection of the motor rotation limit by the motor torque is performed. This is a unique requirement when finding a neutral position.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows an example of the overall configuration of a vehicle steering device (steering control system) to which the present invention is applied (in the present embodiment, “vehicle” is an automobile, The application object of the present invention is not limited to this. The vehicle steering control system 1 has a configuration in which a handle shaft 3 directly connected to a steering handle 2 and a wheel steering shaft 8 are mechanically separated. The wheel steering shaft 8 is driven to rotate by a motor 6 as an actuator. The tip of the wheel steering shaft 8 extends into the steering gear box 9, and the pinion 10, which rotates together with the wheel steering shaft 8, reciprocates the rack bar 11 in the axial direction, thereby changing the steering angle of the wheels 13, 13. . In the vehicle steering control system 1 of the present embodiment, a power steering system in which the reciprocating motion of the rack bar 11 is assisted by a well-known hydraulic, electric or electro-hydraulic power assist mechanism 12 is employed. I have.
[0014]
The handle shaft angle position φ (hereinafter, handle shaft angle position φ) is detected by a handle shaft angle detection unit 101 including a known angle detection unit such as a rotary encoder. On the other hand, the angular position θ of the wheel steering shaft 8 is detected by a steering shaft angle detection unit 103 also including an angle detection unit such as a rotary encoder. In the present embodiment, a vehicle speed detection unit (vehicle speed sensor) 102 that detects a vehicle speed V is provided as a driving state detection unit that detects the driving state of the vehicle. The vehicle speed detection unit 102 includes, for example, a rotation detection unit (for example, a rotary encoder or a tachogenerator) that detects the rotation of the wheel 13. Then, the steering control unit 100 determines a target angle position θ ′ (hereinafter, referred to as a target steering angle position θ ′) of the wheel steering shaft 8 based on the detected handle shaft angle position φ and the vehicle speed V. The operation of the motor 6 is controlled via the motor driver 18 so that the angle position θ of the wheel steering shaft 8 approaches the target steering angle position θ ′.
[0015]
A lock mechanism 19 is provided between the handle shaft 3 and the wheel steering shaft 8 so that the lock mechanism 19 can be switched between a locked state in which the two are integrally rotatably locked and an unlocked state in which the lock connection is released. Have been. In the locked state, the rotation angle of the handle shaft 3 is transmitted to the wheel steering shaft 8 without being converted (that is, the steering angle conversion ratio is 1: 1), and manual steering becomes possible. The switching of the lock mechanism 19 to the locked state is performed by a command from the steering control unit 100 when an abnormality occurs.
[0016]
FIG. 2 shows a configuration example of a drive unit unit of the wheel steering shaft 8 by the motor 6 in a state of being attached to an automobile. In the drive unit 14, when the handle shaft 3 is rotated by operating the handle 2 (FIG. 1), the motor case 33 rotates integrally with the motor 6 mounted inside the handle. In the present embodiment, the handle shaft 3 is connected to the input shaft 20 via a universal joint 319, and the input shaft 20 is connected to the first coupling member 22 via bolts 21, 21. The pin 31 is integrated with the first coupling member 22. On the other hand, the pin 31 is fitted and engaged in a sleeve 32a extending rearward from the center of one plate surface of the second coupling member 32. On the other hand, the cylindrical motor case 33 is integrated with the other plate surface side of the second coupling member 32. Reference numeral 44 denotes a cover made of rubber or resin, which rotates integrally with the handle shaft 3. Reference numeral 46 denotes a case for housing the drive unit 14 integrated with the cockpit panel 48, and reference numeral 45 denotes a seal ring for sealing between the cover 44 and the case 46.
[0017]
The stator portion 23 of the motor 6 including the coils 35 is integrally assembled inside the motor case 33. A motor output shaft 36 is rotatably mounted inside the stator portion 23 via a bearing 41. An armature 34 made of a permanent magnet is integrated with the outer peripheral surface of the motor output shaft 36, and coils 35, 35 are arranged so as to sandwich the armature 34. A power supply terminal 50 is taken out of the coils 35, 35 so as to be continuous with the rear end surface of the motor case 33, and power is supplied to the coils 35, 35 by the power supply cable 42 at the power supply terminal 50.
[0018]
As described later, in the present embodiment, the motor 6 is a brushless motor, and the power supply cable 42 is configured as a band-shaped collective cable in which elementary wires that individually supply power to the coils 35 of each phase of the brushless motor are assembled. ing. A cable case 43 having a hub 43a is provided adjacent to the rear end of the motor case 33, and the power supply cable 42 is housed therein in a form wound around the hub 43a in a spiral manner. . The end of the power supply cable 42 opposite to the end connected to the power supply terminal 50 is fixed to the hub 43 a of the cable case 43. When the handle shaft 3 rotates in the forward or reverse direction together with the motor case 33 and the power supply terminal 50, the power supply cable 42 in the cable case 43 winds or extends around the hub 43a, thereby causing the motor case 33 to rotate. Plays a role in absorbing the rotation of This will be described in more detail later.
[0019]
The rotation of the motor output shaft 36 is transmitted to the wheel steering shaft 8 after being reduced at a predetermined ratio (for example, 1/50) via the reduction mechanism 7. In this embodiment, the speed reduction mechanism 7 is constituted by a well-known harmonic drive speed reducer. That is, an elliptical bearing 37 with an inner race is integrated with the motor output shaft 36, and a deformable thin external gear 38 is fitted on the outside thereof. Outside the external gear 38, internal gears 39 and 139 in which the wheel steering shaft 8 is integrated via a coupling 40 are engaged. When the motor output shaft 36 rotates, the difference in the number of teeth between the external gear 38 and the internal gears 39 and 139 is set to n, and the number of teeth of the internal gear 39 is set to N. Rotation is transmitted. The internal gears 39 and 139 include an internal gear 39 and an internal gear 139 that are coaxially arranged. The internal gear 39 is fixed to the motor case 33 and rotates integrally with the motor case 33, while the internal gear 139 is a motor. It is not fixed to the case 33 and is rotatable relative to the motor case 33. In the present embodiment, the input shaft 20, the motor output shaft 36, and the wheel steering shaft 8 of the handle shaft 3 are coaxially arranged on the internal gears 39, 139 in order to measure compactness.
[0020]
Next, the lock mechanism 19 includes a lock member 51 fixed to a lock base portion (the motor case 33 in the present embodiment) which cannot rotate relative to the handle shaft 3, and a relative rotation with respect to the wheel steering shaft 8. And a lock receiving member 52 provided on an impossible lock receiving base portion (in this embodiment, the motor output shaft 36 side). As shown in FIG. 3, the lock member 51 can move forward and backward between a lock position engaged with a lock receiving portion 53 formed on the lock receiving member 52 and an unlock position retracted from the lock receiving portion 53. Is provided. In the present embodiment, a plurality of lock receiving portions 53 are formed at predetermined intervals in a circumferential direction of a lock receiving member 52 that rotates integrally with the wheel steering shaft 8, and a lock portion 51 a provided at the tip of the lock member 51 is provided. In accordance with the rotation angle phase of the wheel steering shaft 8, any one of the plurality of lock receiving portions 53 is selectively engaged. The handle shaft 3 is non-rotatably connected to the motor case 33 (in this embodiment, by the coupling 22 and the pin). When the lock member 51 and the lock receiving member 52 are engaged and locked, the motor output shaft 36 cannot rotate relative to the motor case 33. Since the internal gear 39 of the internal gears 39 and 139 of the speed reduction mechanism 7 is fixed to the motor case 33, the rotation of the handle shaft 3 in the order of the internal gear 39, the external gear 38, and the internal gear 139 causes wheel steering. It will be transmitted directly to the shaft 8.
[0021]
In the present embodiment, the lock receiving member 52 is attached to the outer peripheral surface of one end of the motor output shaft 36, and each lock receiving portion 53 is formed in a concave shape cut in the radial direction from the outer peripheral surface of the lock receiving member 52. Have been. As shown in FIG. 2, the lock member 51 is attached to a rotation base 300 provided in the motor case 33 so as to be rotatable around an axis substantially parallel to the wheel steering shaft 8, and has a rear end 55 a coupled thereto. Have been. Further, an elastic member 54 is provided for elastically returning the lock member 51 to the original position when the bias of the solenoid 55 is released. By the operation of urging and releasing the urging of the solenoid 55, the lock formed at the distal end of the lock member 51 via the convex portion 55a provided at the distal end of the solenoid 55a and the groove formed at one end 51b of the lock member 51. The portion 51a approaches / separates from the lock receiving member 52 for the lock / unlock described above.
[0022]
FIG. 4 is a block diagram illustrating an example of an electrical configuration of the steering control unit 100. The main components of the steering control unit 100 are two microcomputers 110 and 120. The main microcomputer 110 has a main CPU 111, a ROM 112 storing a control program, a main CPU-side RAM 113 serving as a work area for the CPU 111, and an input / output interface 114. The sub microcomputer 120 has a sub CPU 121, a ROM 122 storing a control program, a sub CPU RAM 123 serving as a work area of the sub CPU 121, and an input / output interface 124. It is the main microcomputer 110 that directly controls the operation of the motor 6 (actuator) that drives the wheel steering shaft 8, and the sub-microcomputer 120 performs data processing required for operation control of the motor 6, such as calculation of necessary parameters. In parallel with 110, the result of the data processing is communicated with the main microcomputer 110 to monitor and confirm whether the operation of the main microcomputer 110 is normal and to supplement the information as necessary. It performs the function of an auxiliary control unit. In the present embodiment, data communication between the main microcomputer 110 and the sub-microcomputer 120 is performed by communication between the input / output interfaces 114 and 124. Note that the microcomputers 110 and 120 receive the power supply voltage Vcc (for example, +5 V) from a stabilizing power supply (not shown) even after the operation of the vehicle is completed (that is, after the ignition is turned off), and the RAMs 113 and 123 or the EEPROM (described later). ) 115 is stored.
[0023]
Outputs of the handle shaft angle detection unit 101, the vehicle speed detection unit 102, and the steering shaft angle detection unit 103 are distributed and input to input / output interfaces 114 and 124 of the main microcomputer 110 and the sub microcomputer 120, respectively. In this embodiment, each of the detection units is constituted by a rotary encoder, and the count signal from the encoder is directly input to the digital data ports of the input / output interfaces 114 and 124 via a Schmitt trigger unit (not shown). A solenoid 55, which is a driving unit of the lock mechanism 19, is connected to the input / output interface 114 of the main microcomputer 110 via a solenoid driver 56. The microcomputer may be the main microcomputer 110 only, and the sub-microcomputer 120 may be omitted.
[0024]
The motor 6 is constituted by a brushless motor, in this embodiment a three-phase brushless motor, and the rotation speed is adjusted by PWM control. The motor driver 18 is connected to a vehicle-mounted battery 57 serving as a power supply for the motor 6. The voltage (power supply voltage) Vs of the battery 57 received by the motor driver 18 changes as needed (for example, 9 to 14 V) depending on the state of loads distributed to various parts of the vehicle and the power generation state of the alternator. In the present embodiment, such a fluctuating battery voltage Vs is directly used as a motor power supply voltage without passing through a stabilized power supply circuit. Since the steering control unit 100 controls the motor 6 on the premise of using the power supply voltage Vs that fluctuates in a considerable width as described above, a measurement unit for the power supply voltage Vs is provided. In the present embodiment, a branch path for voltage measurement is drawn from a current supply path to the motor 6 (immediately before the driver 18), and a voltage measurement signal is extracted through voltage dividing resistors 60 provided therein. The voltage measurement signal is smoothed by a capacitor 61 and then input to an input port with an A / D conversion function (hereinafter, referred to as an A / D port) of input / output interfaces 114 and 124 via a voltage follower 62.
[0025]
In addition, a current detection unit is provided on a power supply path to the motor 6 to monitor the power supply state of the motor 6 such as occurrence of overcurrent. Specifically, the voltage difference between both ends of the shunt resistor (current detection resistor) 58 provided on the path is measured by the current sensor 70, and a measurement signal of the current Is based on the voltage difference between both ends is supplied to the input / output interfaces 114 and 124. Input to the A / D port. The current sensor 70 also functions as a motor torque detecting device that detects the torque of the motor 6, and as the load (torque) of the motor increases, the motor current increases. As a result, the increase value (peak, etc.) of the motor torque is detected. Can be detected. Note that, other than the shunt resistor, a probe that detects a current based on an electromagnetic principle, such as a Hall element or a current detection coil, may be used.
[0026]
Returning to FIG. 4, the following memory areas are formed in the RAMs 113 and 123 of the microcomputers 110 and 120, respectively.
(1) Vehicle speed measurement value memory: The current vehicle speed measurement value from the vehicle speed sensor 102 is stored.
{Circle over (2)} Handle axis angle position (φ) counter memory: counts a count signal from the rotary encoder constituting the handle axis angle position detection unit 101 and stores the count value indicating the handle axis angle position φ. Note that a rotary encoder capable of identifying the rotation direction is used. In the case of forward rotation, the counter is incremented, and in the case of reverse rotation, the counter is decremented.
(3) Steering angle conversion ratio (α) calculated value memory: The steering angle conversion ratio α calculated based on the measured vehicle speed is stored.
(4) Target steering shaft angle position (θ ′) calculation value memory: a target value of the steering shaft angle position calculated by, for example, φ × α from the current value of the handle shaft angle position φ and the steering angle conversion ratio α; That is, the value of the target steering shaft angle position θ ′ is stored.
(5) Steering shaft angle position (θ) counter memory: counts a count signal from a rotary encoder forming the steering shaft angle detection unit 103, and stores the count value indicating the steering shaft angle position θ. The steering shaft angle detection unit 103 is configured as an increment type rotary encoder capable of identifying the rotation direction, and increments the above counter if the rotation direction of the wheel steering shaft 8 is positive, and decrements the counter if it is reverse. .
(6) Δθ calculated value memory: Stores a calculated value of Δθ (≡θ'-θ) between the target steering axis angle position θ 'and the current steering axis angle position θ.
(7) Power supply voltage (Vs) measured value memory: Stores the measured value of the power supply voltage Vs of the motor 6.
(8) Duty ratio (η) determined value memory: The duty ratio η determined based on Δθ and the power supply voltage Vs for energizing the motor 6 with PWM is stored.
(9) Current (Is) measured value: The measured value of the current Is by the current sensor 70 is stored.
Further, in this example, for searching (recognizing) the neutral position of the steering wheel, a rotation that defines a return rotation amount from a rotation end (a winding end or a loose end of the power supply cable) of the motor 6 to a neutral side, which will be described later. Neutralizing rotation angle for presetting and storing an angle setting value (for example, if the allowable rotation limit of the steering wheel is about 5 rotations, the return rotation setting value of the neutral position is stored as about 2.5 rotations). A memory is provided.
[0027]
The input / output interface 114 of the main microcomputer 110 is provided with an EEPROM 115 as a second storage unit for storing the angular position of the wheel steering shaft 8 at the end of the operation (that is, when the ignition is turned off), that is, the end angular position. Have been. The EEPROM 115 (PROM) can only read data by the main CPU 111 at the first operating voltage (+5 V) at which the main CPU 111 reads / writes data from / to the main CPU RAM 112. By setting a second operating voltage different from the voltage (+5 V) (a voltage higher than the first operating voltage is employed in this embodiment: for example, +7 V), data can be written by the main CPU 111. Therefore, even if the main CPU 111 runs away, the contents will not be rewritten by mistake. The second operating voltage is generated by a booster circuit (not shown) interposed between the EEPROM 115 and the input / output interface 114.
[0028]
Hereinafter, the operation of the vehicle steering control system 1 will be described.
FIG. 8 shows the flow of the processing of the main routine of the control program by the main microcomputer 110. S1 is an initialization process, in which the end angle position (described later) of the wheel steering shaft 8 written in the EEPROM 115 in the end process when the ignition switch was turned OFF last time is read out, and the end angle position is determined at the start of the process. The point is to set as the initial angular position of the wheel steering shaft 8. Specifically, a counter value indicating the end angle position is set in the above-mentioned steering shaft angle position counter memory. Note that a data write completion flag to the EEPROM 115 described later is cleared at this time.
[0029]
When the initialization process is completed, the process proceeds to S2, where the steering control process is performed. The steering control process is repeatedly executed at a constant period (for example, several hundred μs) in order to equalize the parameter sampling intervals. The details will be described with reference to FIG. In S201, the current measured value of the vehicle speed V is read, and then, in S202, the handle shaft angular position φ is read. In S203, a steering angle conversion ratio α for converting the steering shaft angle position φ into the target steering angle position θ ′ of the steering shaft 8 is determined from the calculated value of the vehicle speed V. Different values are set for the steering angle conversion ratio α according to the vehicle speed V. Specifically, as shown in FIG. 6, when the vehicle speed V is higher than a certain value, the steering angle conversion ratio α is set to a small value, and when the vehicle speed V is lower than a certain value, the steering angle conversion ratio α is set to a large value. Is done. In the present embodiment, a table 130 for setting the steering angle conversion ratio α corresponding to various vehicle speeds V is stored in the ROM 112 (122) as shown in FIG. The steering angle conversion ratio α corresponding to the vehicle speed V is calculated by an interpolation method. In the present embodiment, the vehicle speed V is used as the information indicating the driving state of the vehicle. However, in addition to this, the lateral pressure received by the vehicle, the inclination angle of the road surface, and the like are used as information indicating the driving state of the vehicle. And it is possible to set the steering angle conversion ratio α to a specific value according to the detected value. It is also possible to determine the basic value of the steering angle conversion ratio α in accordance with the vehicle speed V, and to use the basic value as needed based on information other than the vehicle speed as described above.
[0030]
In S204, the target steering shaft angle position θ ′ is calculated by multiplying the detected steering shaft angle position φ by the determined steering angle conversion ratio α. Then, in S205, the current steering shaft angle position θ is read. In S206, a difference Δθ (= θ′−θ) between the current steering axis angle position θ obtained from the steering axis angle position counter and the target steering axis angle position θ ′ is calculated. Further, in S207, the current measured value of the power supply voltage Vs is read.
[0031]
The motor 6 rotationally drives the wheel steering shaft 8 so that the difference Δθ between the target steering shaft angle position θ ′ and the current steering shaft angle position θ decreases. When Δθ is large, the rotation speed of the motor 6 is increased, and when Δθ is small, the motor 6 is rotated so that the steering shaft angle position θ can quickly and smoothly approach the target steering shaft angle position θ ′. The rotation speed of the motor. Basically, proportional control is performed using Δθ as a parameter. However, in order to suppress overshoot and hunting and stabilize the control, it is desirable to perform well-known PID control in consideration of the differentiation or integration of Δθ. .
[0032]
The motor 6 is under PWM control as described above, and the rotation speed is adjusted by changing the duty ratio η. If the power supply voltage Vs is constant, the rotation speed can be almost uniquely adjusted by the duty ratio. However, in the present embodiment, the power supply voltage Vs is not constant as described above. Therefore, the duty ratio η is determined in consideration of the power supply voltage Vs (S208). For example, as shown in FIG. 7, a two-dimensional duty ratio conversion table 131 for providing a duty ratio η corresponding to each combination of various power supply voltages Vs and Δθ is stored in the ROM 112 (122), and the power supply voltage Vs And the value of the duty ratio η corresponding to the calculated value of Δθ can be read and used. Note that the rotation speed of the motor 6 also varies depending on the load. In this case, the state of the motor load can be estimated based on the measured value of the motor current Is by the current sensor 70, and the duty ratio η can be corrected and used.
[0033]
The processing up to this point is executed in parallel by both the main microcomputer 110 and the sub microcomputer 120 in FIG. For example, whether the operation of the main microcomputer 110 is normal or not is determined by transferring the calculation result of each parameter stored in the RAM 113 of the main microcomputer 110 to the sub-microcomputer 120 at any time. By performing the collation, it is possible to monitor whether or not an abnormality has occurred. On the other hand, the main microcomputer 110 generates a PWM signal based on the determined duty ratio η. Then, the motor 6 is subjected to PWM control by outputting the PWM signal to the motor driver 18 with reference to a signal from a rotary encoder constituting the steering shaft angle detection unit 103.
[0034]
Returning to FIG. 8, in S3, it is confirmed whether or not the ignition switch is turned off. If the ignition switch is turned off, the end processing of S4 is performed. That is, when the ignition switch is turned off, it means that the operation of the vehicle has been completed. Therefore, the main microcomputer 110 reads out the end angle position of the wheel steering shaft 8 stored in the steering shaft angle position counter. This is stored in the EEPROM 115, and the data write completion flag provided in the RAM 113 is set, thus ending the processing.
[0035]
As conceptually shown in FIG. 10, a power supply cable (spiral cable) 42 is a flexible (elastic) band-shaped harness covered with a resin insulating material, and includes a three-port harness for supplying electricity to the motor 6, for example. The phase conductors are encapsulated insulated from one another, and control signal lines can also be incorporated. One end of the power supply cable is fixed to a rotary tightening member (hub 43 a) of the cable case 43, and the other end is fixed to a harness fixing portion on the vehicle body B side. To). A fixed outer case 43b of the case 43 is fixed to the vehicle body B side, and a rotary tightening member (a tightening shaft) 43a is rotatably held inside the outer case 43b in the fixed state. Of the cable 42 expands (expands) in the loosened state (relaxed state), and the rotation of the tightening member 43a (in other words, the rotation of the steering shaft 3 and the housing (motor case 33)). Rotation).
[0036]
FIG. 10B shows a winding end of the power supply cable 42 (a rotatable area of the motor 6 and, for example, a right end of the rotatable area of the steering handle 2), and FIG. Left end). Now, the wheel steering shaft 8 is fixed at the straight traveling position (neutral position) of the wheel 13, and the motor case 8 (housing) is free from the steering shaft 8. In other words, when the lock member 52 of FIG. 3 constituting the mechanical lock mechanism at the time of abnormality is released to the unlock position by the operation of the solenoid 55 and the lock is released, the handle 2, the handle shaft 3, and the motor case ( The housing 33 is in a state where it can rotate freely. The winding member 43a of the power supply cable 42 is in a state where it can rotate integrally with the handle 2 and the like.
[0037]
Here, when the motor 6 is driven to rotate, the wheels 13 (tires) and the wheel steering shafts 8 (output shafts) are stopped at the neutral position, so that the rotation of the motor 6 causes a reaction to the motor case 33 and the tightening member 43 a of the cable 42. And the handle 2 and the like rotate integrally. With this rotation, when the power supply cable 42 reaches the winding end as shown in FIG. 10B, the motor torque (also referred to as motor current) increases as shown in FIG. . On the other hand, even when the power supply cable 42 reaches the loosened end as shown in FIG. 10C, the outer periphery of the cable 42 is pressed against the inner peripheral surface of the fixed outer case, losing any further places. As shown, the motor torque increases at the loosening end as well as at the winding end. Then, the rotatable range between the left and right ends, which is the point at which the motor torque rises, is the entire allowable rotation angle θ0 of the motor 6 (and thus the handle 2). Roughly speaking, if it is further rotated back (reverse rotation) by θ0 / 2 from the right end or the left end, the neutral position of the steering wheel 2 can be found.
[0038]
FIGS. 12 (A) to 12 (C) show that the housing (motor case 33) is at an arbitrary position with respect to the neutral wheel steering shaft 8 (output shaft), FIG. 3 conceptually shows the rotation of. The spiral case (fixed outer case 43b) is fixed to the vehicle body, and the base end of the harness (power supply cable 42) is also fixed to the vehicle body. As shown in (B), the actuator (motor 6) is rotated so that the housing rotates in the spiral winding direction, and when the torque reaches a specified torque (upper limit torque in the spiral winding direction), the driving of the motor 6 is stopped. Next, as shown in (C), the motor 6 is rotationally driven in the reverse direction (winding loosening direction) by a specified number of rotations (for example, 2.5 rotations) and stopped. In response to the driving of the motor 6, the free handle 2 first rotates in one direction, and then reverses by, for example, 2.5 rotations to recognize the neutral position (completion of the neutral setting).
[0039]
FIG. 13 shows a flow of such a neutral position setting (automatic midpointing) process. For example, when the originally set neutral position (relative reference position between the wheel steering shaft and the steering wheel) is not known due to a failure of a control unit such as a CPU or the like, and this automatic midpointing processing is performed as repair, P1 , The tire (wheel 13) is adjusted to the straight traveling position (neutral). On the other hand, when a steering unit including the motor 6 and the like is mounted on the vehicle body as a part assembly in a factory assembly, the housing (motor case 33) is mounted on the vehicle body in Q1 with the rotation phase of the housing (motor case 33) set to an arbitrary state (that is, fixed). There is no pin and it is fastened to the handle shaft 3 at an arbitrary rotation phase. Further, in Q2, the tire (wheel 13) is adjusted to the straight traveling position.
[0040]
Then, starting of the motor 6 is started from the next step R1, and the motor 6 that is the variable transmission ratio actuator is driven to rotate in the direction of winding (right end) of the power supply cable 42, for example. In the process of driving the motor, R2 detects the motor torque and determines whether or not the torque has exceeded a specified maximum value (threshold value) Tmax. Here, as for the torque of the motor 6, the CPU 111 or the like refers to the current value temporarily stored in the RAM 113 or the like to determine whether the value of the current sensor 70 in FIG. The comparison is determined.
[0041]
If it is detected in R2 that the motor torque has exceeded the predetermined value (see also FIG. 11), it is determined that the power supply cable 42 has reached the winding end as shown in FIG. , The driving of the motor is stopped, and the motor 6 is reversed and returned to the loosening direction (relaxation direction) of the power supply cable 42, for example, the left end side by a predetermined rotation amount (for example, 2.5 rotations). The motor 6 may be reversed immediately after reaching the right end or the like without intervening the stop mode.
[0042]
If the motor 6 is stopped after performing the return rotation of half of the motor rotation range in R3, the neutral point of the handle 2 can be found (set). When the motor 6 is rotated back by a predetermined amount, the CPU 111 or the like samples (refers to) the motor rotation amount by a motor rotation amount sensor such as a rotary encoder attached to the motor 6, and when the rotation amount reaches a predetermined rotation amount. The motor 6 may be stopped. The operator may finely adjust the handle position at R4 to set the final neutral position. Further, when the neutral position is determined, the mechanical lock can be turned on as necessary at R5 (the operation of the solenoid 55 in FIG. 3 is released to move the lock member 51 from the unlock position to the lock position).
[0043]
Note that the rotation limit angle position of the steering wheel due to the setting state (winding end or loosening end) of the power supply cable 42 is set outside the steering limit angle. (Rotation torque increase at the end or the loosening end). That is, when the steering wheel is fully turned in a normal state, the power supply cable does not reach the winding end or the loosening end, and the steering rack (not shown) with the power supply cable 42 having some clearance is provided. End hits the stopper, which is the steering limit. Therefore, assuming that the steering rotation speed at the steering limit at a transmission ratio of 1: 1 is, for example, two and a half rotations to the right or left, if the rotation of the steering wheel is stopped by the power cable 42, the steering wheel is relatively smaller than the steering limit angle. You should only go beyond (outside the steering limit). If, for example, two and a half turns back from there, the handle stops at a position slightly off neutral. In a production process or the like, if the operator slightly returns this to the neutral position by hand and completes the operation, a highly accurate midpoint can be set. R4 in FIG. 13 also assumes this.
[0044]
From a different point of view, the rotation amount of the motor 6 can be adjusted so as to eliminate such correction work by the operator. In other words, the return rotation amount of the motor 6 is corrected by increasing the water amount by an angle difference between the tightened end or loosened end of the power supply cable 42 detected by the increase in the torque of the motor 6 and the steering limit (the state in which the steering rack contacts the stopper). Set. For example, if the angle difference is Δθ, and if the total rotation allowable angle in both the left and right directions is set to θ0 by the setting (resistance) of the power supply cable 42, the rotation amount (rotation angle) of the return rotation of the motor 6 is ( By setting (θ0 / 2) + Δθ, it is possible to execute more accurate setting of the neutral position (middle point setting).
[0045]
The motor 6 is rotated toward the loose end of the power supply cable 42 at R1 in FIG. 13, and when the motor torque is increased at R2, the motor 6 is returned to a predetermined amount in the winding direction of the power supply cable 42 at R3. Thus, the neutral position can be found. It does not matter in which direction the motor 6 is rotated first if the torque is significantly increased by the power supply cable 42 in either direction. However, if the motor torque increases in the peak direction in the winding direction, but the motor torque does not increase in the peak direction in the loosening direction (relaxation direction) and it is difficult to define the rotation end of the motor 6, the winding limit is set. It is essential to detect the rotation end.
[0046]
In addition to the search for the neutral position, as shown in an automatic reference position setting routine shown in FIG. 14, in a state where the steering shaft and the steering wheel are separated, the tire (wheel 13) is fully cut to one limit in U1. stop. In this state, in U2, the motor 6 that is a variable transmission ratio actuator is driven toward the rotation limit (for example, the winding end of the power supply cable 42) of the power supply cable 42 corresponding to the direction in which the handle is fully turned, When the motor torque reaches the specified maximum value in U3, the motor 6 is stopped in U4. Then, the reference position of the steering wheel corresponding to the steering limit of the wheel 13 can be found. In U5, the fine adjustment of the reference position can be performed, and in U6, the mechanical lock can be applied in that state as needed to hold the reference position.
[0047]
Even in this case, the winding of the power supply cable 42 that generates the motor torque described above, in order to correct the angle difference when the motor 6 rotates to the end of the winding or loosening of the power supply cable 42 beyond the steering limit of the wheel 13. Alternatively, if the motor 6 is rotated to the winding loose end and then the motor 6 is returned and stopped by the angular difference between the steering limit and the winding or loosening end of the power supply cable 42 (for the overshoot), A more accurate reference position search can be performed.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing the overall configuration of a vehicle steering control system according to the present invention.
FIG. 2 is a longitudinal sectional view showing one embodiment of a drive unit.
FIG. 3 is a sectional view taken along line AA of FIG. 2;
FIG. 4 is a block diagram showing an example of an electrical configuration of a vehicle steering control system according to the present invention.
FIG. 5 is a schematic diagram of a table for giving a relationship between a steering angle conversion ratio and a vehicle speed.
FIG. 6 is a schematic diagram showing an example of a pattern for changing a steering angle conversion ratio according to a vehicle speed.
FIG. 7 is a schematic diagram of a two-dimensional table for determining a duty ratio based on a motor power supply voltage and an angle deviation Δθ.
FIG. 8 is a flowchart showing an example of a main routine of computer processing in the vehicle steering control system of the present invention.
FIG. 9 is a flowchart illustrating an example of details of a steering control process of FIG. 8;
FIG. 10 is a simplified diagram conceptually showing a structure of a power supply cable and a winding end and a loosening end thereof.
FIG. 11 is a graph illustrating an increase in motor torque at a winding end and a loosening end of the power supply cable.
FIG. 12 is an explanatory diagram showing a concept of setting a neutral position.
FIG. 13 is a flowchart illustrating an example of a process of setting a neutral position (automatic midpointing).
FIG. 14 is a flowchart illustrating an example of a reference position setting process other than the process of setting a middle point.
[Explanation of symbols]
3 Handle shaft 6 Motor (actuator)
8 Wheel steering shaft 42 Power supply cable 70 Current sensor (motor torque detector)
Reference Signs List 100 Steering control unit 101 Handle shaft angle detecting unit 103 Steering shaft angle detecting unit 111 Main CPU
115 EEPROM (second storage unit)
113 Main CPU RAM
121 Sub CPU
123 RAM for secondary CPU (first storage unit)

Claims (4)

Transmission ratio control that interposes a transmission ratio variable unit driven by a motor that varies the transmission ratio in the middle of a steering transmission system that directly connects a steering wheel and a wheel steering shaft, and controls the transmission ratio according to the situation of the vehicle. In a vehicle steering device having a portion,
A cable holder in which the motor is fixed to a handle shaft that rotates integrally with the steering handle, and a power supply cable that supplies power to the motor is formed integrally with the handle shaft at a free end extending from a fixed portion of the motor. The part is spirally wound to generate an elastic force in the relaxing direction, and is held so as to be reduced in outer diameter by being tightened according to the rotation of the steering handle or to be relaxed to increase in outer diameter. Cable holding device,
When operating the motor in the allowable holding range of the power supply cable and rotating the steering handle, a motor torque detection device that detects an increase in motor torque at a winding end or a relaxed end of the power supply cable,
An end exploring device for exploring a winding end or a loose end of the power supply cable by the motor torque indicating a predetermined increase value,
A reference position recognition device that recognizes a reference position of a relative relationship between the handle axis and the steering axis based on the end search;
A steering device for a vehicle, comprising: Transmission ratio control that interposes a transmission ratio variable unit driven by a motor that varies the transmission ratio in the middle of a steering transmission system that directly connects a steering wheel and a wheel steering shaft, and controls the transmission ratio according to the situation of the vehicle. In a vehicle steering device having a portion,
A cable holder in which the motor is fixed to a handle shaft that rotates integrally with the steering handle, and a power supply cable that supplies power to the motor is formed integrally with the handle shaft at a free end extending from a fixed portion of the motor. The part is spirally wound to generate an elastic force in the relaxing direction, and is held so as to be reduced in outer diameter by being tightened according to the rotation of the steering handle or to be relaxed to increase in outer diameter. Cable holding device,
When operating the motor in the allowable holding range of the power supply cable and rotating the steering handle, a motor torque detection device that detects an increase in motor torque at a winding end or a relaxed end of the power supply cable,
An end exploring device for exploring a winding end or a loose end of the power supply cable by the motor torque indicating a predetermined increase value,
A handle neutral recognition device that rotates the motor by a predetermined amount so as to return the steering handle to the neutral position side from a winding end or a loose end of the power supply cable;
A steering device for a vehicle, comprising: 3. The vehicle steering system according to claim 1, wherein the motor is rotated in a winding direction to detect a predetermined motor torque, and then the motor is rotated in a reverse direction by a predetermined amount and then stopped. The said handle | steering-wheel axis | shaft and the said wheel steering axis | shaft are coaxially located, The winding axis | shaft which winds or loosens the said mo-cable and the output shaft of the said motor are further coaxially arrange | positioned between them. The vehicle steering system according to any one of claims 1 to 4.

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