Steering gear

Abstract

To provide a steering system that can shorten the time required in the process of installing the steering system onto a vehicle. [Solution] The steering device has a reaction force unit that includes a reaction force motor that applies torque to a steering shaft to which a steering wheel can be connected, and a reaction force ECU that controls the drive of the reaction force motor. The reaction force ECU is configured to perform a reference position learning process that learns a reference value θns for the reaction force of the steering shaft, and an input process that inputs a factory command Fcmd from an external factory device in the process of mounting the reaction force unit to the vehicle. The reference position learning process assumes that the drive process of the reaction force motor is performed so that the steering angular velocity ωs of the steering shaft becomes a first velocity V1 and the reference value θns for the reaction force is learned. If a factory command Fcmd is input through the input process, the drive process is performed so that the speed becomes a second velocity V2 which is greater than the first velocity V1 and the reference value θns for the reaction force is learned.

Description

Technical Field

[0001] The present invention relates to a steering device.

Background Art

[0002] For example, Patent Document 1 describes a steering device mounted on a vehicle, including a reaction force motor that generates a steering reaction force on a steering shaft and a reaction force control unit that controls the operation of the reaction force motor. The reaction force control unit performs a midpoint learning calculation for calculating the midpoint of the vehicle's steering angle by performing a "lock-to-lock operation" (hereinafter referred to as such), that is, after operating the steering wheel to the first operating end through the control of the reaction force motor and then performing a reverse operation to the second operating end.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the vehicle manufacturing process, there is a desire to shorten the overall time related to the manufacturing process when passing through the process of mounting a steering device or the like on the vehicle. On the other hand, for example, when performing the above midpoint learning calculation in the process of mounting the steering device on the vehicle, it takes time due to the "lock-to-lock operation", so a corresponding amount of time is required in the process of mounting the steering device on the vehicle.

Means for Solving the Problems

[0005] A steering device capable of solving the above problems has a reaction force unit that includes a reaction force motor connected to a steering shaft to which a steering member can be connected in order to apply torque to the steering shaft, and a reaction force control unit that controls the drive of the reaction force motor. The reaction force control unit is configured to perform a reference position learning process in which a reference position of the steering shaft is learned by rotating the steering shaft in a first or second direction through the drive of the reaction force motor, and an input process in which a specific signal generated through the use of an external device prepared separately from the reaction force unit is input in the process of mounting the reaction force unit to the vehicle. The reference position learning process is based on the premise that the reference position is learned by performing a drive process to drive the reaction force motor so that the rotational angular velocity of the steering shaft becomes a first speed, and when the specific signal is input through the input process, the reference position is learned by performing the drive process so that the rotational angular velocity of the steering shaft becomes a second speed which is greater than the first speed, instead of the first speed.

[0006] According to the steering system described above, when no specific signal is input through the input process, the reference position learning process drives the reaction motor so that the rotational angular velocity of the steering shaft becomes the first speed. On the other hand, when a specific signal is input through the input process, the reference position learning process drives the reaction motor so that the rotational angular velocity of the steering shaft becomes the second speed. For example, if the situation in which a specific signal is input is the process of mounting the reaction unit onto the vehicle, the time required for the reference position learning process can be shortened compared to the situation in which no specific signal is input. Therefore, the time required in the process of mounting the reaction unit onto the vehicle can be shortened. Consequently, the time required in the process of mounting the steering system onto the vehicle can be shortened.

[0007] In the steering device described above, the drive process includes a selection process for selecting a first speed and a second speed. When the specific signal is input in the input process, the drive process is executed using the second speed selected by the selection process. When the specific signal is not input in the input process, the drive process is executed using the first speed selected by the selection process.

[0008] According to the steering device described above, a configuration can be achieved in which the rotational angular velocity of the reaction motor is changed without requiring processes such as physically rewriting the contents of the reference position learning process program in the process of mounting the steering device onto the vehicle or in other processes.

[0009] In the steering device described above, the drive process includes a rotational angular velocity feedback process that calculates a target rotation angle of the steering shaft by controlling the actual rotational angular velocity of the steering shaft to a target rotational angular velocity through feedback control, and a rotational angle feedback process that calculates a torque command value for driving the reaction motor by controlling the actual rotation angle of the steering shaft to the target rotation angle through feedback control. The selection process includes a process in which, while the target rotational angular velocity is set as the first speed, if the specific signal is input through the input process, the second speed is set as the target rotational angular velocity instead of the first speed.

[0010] According to the steering system described above, the reference position can be learned using a controllably stable method that is less susceptible to external disturbances through feedback control. In the steering device described above, the drive process includes a rotation angle feedback process that calculates a torque command value for driving the reaction motor by controlling the actual rotation angle of the steering shaft to a target rotation angle through feedback control, and a rotation angular velocity feedback process that calculates a compensation amount to compensate for the torque command value by controlling the actual rotation angular velocity of the steering shaft to a target rotation angular velocity through feedback control. The selection process includes a process in which, while the target rotation angular velocity is set as the first speed, if the specific signal is input through the input process, the second speed is set as the target rotation angular velocity instead of the first speed.

[0011] According to the steering system described above, the reference position can be learned using a controllably stable method that is less susceptible to external disturbances through feedback control. In the steering system described above, the external equipment is manufactured for the process of mounting the reaction force unit onto the vehicle.

[0012] According to the steering device described above, it is possible to suppress the occurrence of a situation in which the reference position is learned through the drive process of the reaction motor at the second speed, except in the process of mounting the reaction force unit onto the vehicle.

[0013] In the steering device described above, during the process of mounting the reaction force unit onto the vehicle, the steering member is detached from the steering shaft, and the drive process is performed with the steering member detached from the steering shaft when the rotational angular velocity of the steering shaft is set to the second speed.

[0014] According to the steering system described above, the limitations on increasing the rotational speed of the steering shaft when considering the effect of inertial forces acting on the steering shaft can be relaxed.

[0015] In the above-described steering apparatus, the steering apparatus includes a stopper having a first regulating end that regulates rotation of the steering shaft in the first direction and a second regulating end that regulates rotation of the steering shaft in the second direction. The drive processing includes driving the reaction motor so that the steering shaft abuts against the first regulating end, and then driving the reaction motor so that the steering shaft abuts against the second regulating end.

[0016] According to the above-described steering apparatus, even when the reference position is learned by the "lock-to-lock operation", the time required in the process for mounting the steering apparatus on the vehicle can be shortened.

Effects of the Invention

[0017] According to the present invention, the time required in the process at the vehicle assembly factory can be shortened.

Brief Description of the Drawings

[0018] [Figure 1] It is a diagram showing the configuration of a steer-by-wire type steering apparatus according to the first embodiment. [Figure 2] It is a block diagram showing the electrical configuration of the steering control apparatus of FIG. 1. [Figure 3] It is a diagram for explaining the state transition of the CPU in the reaction force ECU of FIG. 2. [Figure 4] It is a diagram for explaining the state transition related to the setting mode of FIG. 3. [Figure 5] It is a diagram for explaining the work related to the reaction force unit in the factory process. [Figure 6] It is a block diagram showing the functions of the reaction force ECU of FIG. 2. [Figure 7] It is a flowchart for explaining the processing procedure of the reference position learning process, which is the work related to the reaction force unit of FIG. 4. [Figure 8] (a) and (b) are graphs showing a part of the change over time of the rotational angular velocity accompanying the execution of the reference position learning process. [Figure 9]It is a block diagram showing the functions of the reaction force ECU according to the second embodiment.

Mode for Carrying Out the Invention

[0019] <First Embodiment> Hereinafter, a first embodiment of the present invention will be described. As shown in FIG. 1, the steering device 2 is, for example, a steer-by-wire type vehicle steering device. The steering device 2 includes a reaction force unit 4 and a steering unit 6. The reaction force unit 4 is steered by a driver via a vehicle steering wheel 3 which is an operation member. The steering unit 6 steers the left and right steering wheels 5 of the vehicle according to the steering input to the reaction force unit 4 by the driver. In the steering device 2, for example, the power transmission path between the reaction force unit 4 and the steering unit 6 is mechanically separated at all times. The power transmission path between a reaction force actuator 12 described later and a steering actuator 31 described later is mechanically separated at all times.

[0020] The reaction force unit 4 includes a steering shaft 11 and a reaction force actuator 12. The steering wheel 3 is connected to the steering shaft 11. The steering shaft 11 is rotatable in the left-right direction through the steering operation of the driver or the operation of the reaction force actuator 12. In the present embodiment, the right rotation direction of the steering shaft 11 is taken as the first direction, and the left rotation direction of the steering shaft 11 is taken as the second direction.

[0021] The steering shaft 11 has a torsion bar 41a, an input shaft 41b, and an output shaft 41c. The input shaft 41b is a part of the steering shaft 11 to which the steering wheel 3 is connected. The output shaft 41c is a part of the steering shaft 11 to which the reaction force actuator 12 is connected. The torsion bar 41a connects the input shaft 41b and the output shaft 41c to each other.

[0022] The first end 11a of the steering shaft 11 has a stopper 11c. The first end 11a is the tip of the output shaft 41c and is the end opposite to the second end 11b of the steering shaft 11 to which the steering wheel 3 is connected. The second end 11b is the tip of the input shaft 41b. The stopper 11c defines the rotation range of the steering shaft 11. Thus, the rotation range of the steering wheel 3, which rotates integrally with the steering shaft 11, is defined by the stopper 11c. For example, the steering shaft 11 can rotate within a rotation range between a right rotation limit position 3a and a left rotation limit position 3b. In this embodiment, the right rotation limit position 3a is an example of a first restricting end that restricts rotation of the steering shaft 11 in a first direction. The left rotation limit position 3b is an example of a second restricting end that restricts rotation of the steering shaft 11 in a second direction.

[0023] The reaction force actuator 12 includes a reaction force motor 13, a steering reduction mechanism 14, and a reaction force ECU 50. The reaction force motor 13 is a motor that applies torque to the steering shaft 11. Hereinafter, the torque applied by the reaction force motor 13 to the steering shaft 11 will be referred to as the reaction force motor torque. The reaction force motor torque includes the steering reaction force, which is a force that opposes the driver's steering as a steering force. The reaction force motor 13 is connected to the output shaft 41c via a steering reduction mechanism 14, which consists of, for example, a worm and wheel. The reaction force motor 13 is, for example, a three-phase brushless motor. The reaction force ECU 50 is electrically connected to the reaction force motor 13. The reaction force ECU 50 mainly controls the driving of the reaction force motor 13. The reaction force ECU 50 is, for example, composed of electronic components mounted on a circuit board. In this embodiment, the reaction force ECU 50 is an example of a reaction force control unit. For example, the reaction force ECU 50 is integrated with the reaction force motor 13, forming a so-called electromechanical integrated MCU.

[0024] The steering unit 6 comprises a pinion shaft 21, a steering shaft 22, a rack housing 23, and a steering actuator 31. The pinion shaft 21 and the steering shaft 22 are connected at a predetermined intersection angle. The rack and pinion mechanism 24 is formed by meshing the pinion teeth 21a formed on the pinion shaft 21 with the rack teeth 22a formed on the steering shaft 22. In other words, the pinion shaft 21 corresponds to a rotation axis having a pinion angle θp that can be converted to a steering angle θi, which is the steering position of the steering wheel 5. The rack housing 23 houses the rack and pinion mechanism 24. The first end of the pinion shaft 21 is connected to the steering shaft 22 while housed inside the rack housing 23. The second end of the pinion shaft 21, opposite to the first end, protrudes from the rack housing 23. Both ends of the steering shaft 22 protrude from both axial ends of the rack housing 23. Tie rods 26 are connected to both ends of the steering shaft 22 via rack ends 25, which are ball joints. The ends of the tie rods 26 are connected to knuckles to which the left and right steering wheels 5 are assembled.

[0025] The steering actuator 31 includes a steering motor 32, a transmission mechanism 33, a conversion mechanism 34, and a steering ECU 60. The steering motor 32 applies a steering force to the steering shaft 22 to steer the steering wheel 5 via the transmission mechanism 33 and the conversion mechanism 34. The steering motor 32 transmits rotation to the conversion mechanism 34 via the transmission mechanism 33, which is for example a belt transmission mechanism. The transmission mechanism 33 converts the rotation of the steering motor 32 into reciprocating motion of the steering shaft 22 via the conversion mechanism 34, which is for example a ball screw mechanism. The steering motor 32 is, for example, a three-phase brushless motor. The steering ECU 60 is electrically connected to the steering motor 32. The steering ECU 60 mainly controls the driving of the steering motor 32. The steering ECU 60 is, for example, composed of electronic components mounted on a circuit board. In this embodiment, the steering ECU 60 is an example of a steering control unit. For example, the steering ECU 60 is integrated with the steering motor 32, forming a so-called mechatronic integrated MCU.

[0026] In the steering system 2 configured in this way, motor torque is applied as steering force from the steering actuator 31 to the steering shaft 22 in response to steering input by the driver, thereby changing the steering angle θi of the steering wheel 5. At this time, a steering reaction force is applied to the steering wheel 3 from the reaction force actuator 12, which opposes the driver's steering input. As a result, in the steering system 2, the steering torque Th required to steer the steering wheel 3 is changed by the steering reaction force, which is the reaction force motor torque applied from the reaction force actuator 12. In other words, the driver can feel the steering wheel 3.

[0027] The reason for providing the pinion shaft 21 is to support the steering shaft 22 together with the pinion shaft 21 inside the rack housing 23. The steering shaft 22 is supported so as to be movable along its axial direction by the support mechanism provided in the steering device 2, and is also pressed toward the pinion shaft 21. As a result, the steering shaft 22 is supported inside the rack housing 23. However, other support mechanisms may be provided to support the steering shaft 22 in the rack housing 23 without using the pinion shaft 21.

[0028] <Electrical configuration of the steering control system> As shown in Figure 1, the reaction force ECU 50 and the steering ECU 60 constitute the steering control device 1, which controls the steering device 2.

[0029] The steering control device 1 is equipped with a connection section 90. The connection section 90 is, for example, a connector having multiple connection terminals. The connection section 90 includes a reaction force side connection section 90a provided in correspondence with the reaction force ECU 50 and a steering side connection section 90b provided in correspondence with the steering ECU 60. The connection section 90 is configured to be connectable to various sensors, a power supply system 46, and a vehicle network 8. The steering control device 1 receives detection results from various sensors, power from the power supply system 46, and data from the vehicle network 8 via the connection section 90.

[0030] Various sensors include, for example, a torque sensor 41, a reaction motor rotation angle sensor 42, a steering motor rotation angle sensor 43, and a vehicle speed sensor 44. The torque sensor 41 is located on the steering shaft 11 between the steering wheel 3 and the steering reduction mechanism 14. The torque sensor 41 detects the steering torque Th, which is a value indicating the torque applied to the steering shaft 11 by the driver's steering input. The steering torque Th is detected in relation to the twisting of the torsion bar 41a located in the middle of the steering shaft 11, between the steering wheel 3 and the steering reduction mechanism 14. The reaction motor rotation angle sensor 42 is located on the reaction motor 13. The reaction motor rotation angle sensor 42 detects the rotation angle θa, which is the angle of the rotation axis of the reaction motor 13, within a range of 360 degrees. The steering motor rotation angle sensor 43 is located on the steering motor 32. The steering motor rotation angle sensor 43 detects the rotation angle θb, which is the angle of the rotation axis of the steering motor 32, within a range of 360 degrees. The vehicle speed sensor 44 detects the vehicle speed V, which is the vehicle's travel speed. The vehicle speed V is acquired by each vehicle device, including the steering control device 1, via the vehicle network 8.

[0031] A power supply system 46 is connected to the steering control device 1. The power supply system 46 includes a battery 47. The battery 47 is a secondary battery mounted on the vehicle and serves as the power source for the reaction motor 13 and the steering motor 32 to operate. The battery 47 also serves as the power source for the steering control device 1, namely the reaction ECU 50 and the steering ECU 60 to operate.

[0032] Between the steering control device 1 and the battery 47, there is a vehicle start switch 48 (indicated as "SW" in Figure 1), such as an ignition switch. The start switch 48 is located in the middle of the power supply line L2, which branches off from power supply line L1, one of the two power supply lines L1 and L2 that connect the steering control device 1 and the battery 47. The start switch 48 is operated when activating various functions to enable the vehicle to operate by activating the vehicle's drive source, such as the engine. The continuity of power supply line L2 is turned on and off through the operation of the start switch 48. For example, power supply line L1 is basically always on, but the continuity of power supply line L1 is indirectly turned on and off as a function of the steering control device 1 depending on the operating state of the steering control device 1.

[0033] The steering control device 1 is connected to the vehicle control device 7 via the vehicle network 8. The vehicle control device 7 is installed separately from the steering control device 1 in the vehicle on which the steering device 2 is mounted. The vehicle control device 7 controls systems that control the drive system related to the vehicle's movement, systems that control the brake system related to the vehicle's braking, and so on.

[0034] Furthermore, the reaction force side connection part 90a is configured to be connectable to an external factory device 71. The reaction force ECU 50 is configured to receive a specific signal, a factory command Fcmd, from the external factory device 71 via the reaction force side connection part 90a. The factory command Fcmd includes, for example, information for the reaction force ECU 50 to determine whether the power is on or off. For example, the external factory device 71 is a device intended to be used only by factory workers in a vehicle assembly plant, that is, in a plant where the process of mounting the steering device 2 onto a vehicle is carried out. In other words, the factory command Fcmd is information that allows recognition that the process is within a vehicle assembly plant. The external factory device 71 is an external device that generates a factory command Fcmd based on operations by a factory worker and outputs the factory command Fcmd to the reaction force ECU 50. The external factory device 71 is, for example, a portable terminal having input buttons and a monitor. In this case, the factory worker can output the factory command Fcmd to the reaction force ECU 50 by connecting the factory external device 71 to the reaction force side connection part 90a and operating the input buttons while referring to the monitor. The factory external device 71 may also be implemented as software on a computer. In this case, the factory worker can output the factory command Fcmd to the reaction force ECU 50 by connecting the computer to the reaction force side connection part 90a and operating the computer while referring to the computer's monitor.

[0035] <Functions of the steering control system> As shown in Figure 2, the reaction force ECU 50 controls the drive of the reaction force motor 13 in order to control the reaction force motor torque, which is the control amount of the reaction force motor 13 that is the object to be controlled. The steering ECU 60 controls the drive of the steering motor 32 in order to control the steering force, which is the control amount of the steering motor 32 that is the object to be controlled. The reaction force ECU 50 and the steering ECU 60 mutually send and receive information via a local network 49, such as serial communication.

[0036] The reaction force ECU 50 includes a central processing unit (hereinafter referred to as "CPU") 50a and memory 50b. The reaction force ECU 50 performs various processes by having the CPU 50a execute a program stored in memory 50b at predetermined calculation cycles. The steering ECU 60 includes a central processing unit (hereinafter referred to as "CPU") 60a and memory 60b. The steering ECU 60 performs various processes by having the CPU 60a execute a program stored in memory 60b at predetermined calculation cycles. The CPUs 50a, 60a and memories 50b, 60b constitute a microcomputer, which is a processing circuit. Memories 50b, 60b include computer-readable media such as RAM (Random Access Memory) and ROM (Read Only Memory). However, the implementation of various processes by software is just one example. The processing circuits of the reaction force ECU 50 and steering ECU 60 may be configured to implement at least some of the processes by hardware circuits such as logic circuits.

[0037] The CPU 50a in the reaction force ECU 50 receives steering torque Th, vehicle speed V, rotation angle θa, and steering information St as input. The steering information St is information obtained from the steering ECU 60 via the local network 49. The steering information St includes, for example, the pinion angle θp and the steering motor current Ib described later. Based on the steering torque Th, vehicle speed V, rotation angle θa, and steering information St, the CPU 50a calculates a drive control signal MSs to the reaction force inverter 51 for controlling the reaction force motor torque. The reaction force inverter 51 is a drive circuit that converts the DC voltage of the battery 47 into an AC voltage and applies it to the reaction force motor 13. At this time, the CPU 50a refers to the reaction force motor current Ia(iu1,iv1,iw1) flowing through the reaction force motor 13. The reaction force motor current Ia(iu1,iv1,iw1) is quantified as the voltage drop across the shunt resistors provided on each leg of the reaction force inverter 51. As a result, the CPU 50a controls the drive of the reaction motor 13 so that reaction motor torque is generated.

[0038] The CPU 50a converts the rotation angle θa into an integrated angle from the reaction force reference value θns stored in memory 50b. The integrated angle is a value converted within a range exceeding 360° by counting the number of rotations of the reaction force motor 13 from the reaction force reference value θns. The reaction force reference value θns is, for example, a value that indicates the straight-ahead state, which is the steering state of the steering wheel 3 when the vehicle is moving straight. In other words, the reaction force reference value θns is a value that indicates the steering neutral position, which is the rotational position of the steering shaft 11 in the straight-ahead state, and is a value that corresponds to the midpoint value θc of the steering shaft 11. In this embodiment, the reaction force reference value θns is an example of a reference position of the steering shaft 11. The CPU 50a calculates the steering angle θs, which is the rotation angle of the steering shaft 11, by multiplying the converted integrated angle by a conversion coefficient based on the rotational speed ratio of the steering deceleration mechanism 14. The CPU 50a calculates the steering angle θs as an absolute angle with respect to the steering neutral position, i.e., the reference value θns for reaction force. The steering angle θs thus obtained is used when calculating the drive control signal MSs. The steering information Ss used by the CPU 50a, including the steering angle θs, is output to the steering ECU 60 via the local network 49.

[0039] The CPU 60a in the steering ECU 60 receives vehicle speed V, rotation angle θb, and steering information Ss as input. The steering information Ss is information obtained from the reaction force ECU 50 via the local network 49. Based on the vehicle speed V, rotation angle θb, and steering information Ss, the CPU 60a calculates a drive control signal MSt for the steering inverter 61 to control the steering force. The steering inverter 61 is a drive circuit that converts the DC voltage of the battery 47 into an AC voltage and applies it to the steering motor 32. At this time, the CPU 60a refers to the steering motor current Ib(iu2,iv2,iw2) flowing through the steering motor 32. The steering motor current Ib(iu2,iv2,iw2) is quantified as the voltage drop across the shunt resistors provided on each leg of the steering inverter 61. As a result, the CPU 60a controls the drive of the steering motor 32 so that motor torque, which becomes the steering force, is generated.

[0040] The CPU 60a converts the rotation angle θb into an integrated angle from the steering reference value θnt stored in memory 60b. The integrated angle is a value converted within a range exceeding 360° by counting the number of rotations of the steering motor 32 from the steering reference value θnt. The steering reference value θnt is a value that indicates the straight-ahead state, which is the steering state of the steering shaft 22 when the vehicle is moving straight. The CPU 60a calculates the pinion angle θp by multiplying the converted integrated angle by a conversion coefficient based on the rotational speed ratio of the transmission mechanism 33, the lead of the conversion mechanism 34, and the rotational speed ratio of the rack and pinion mechanism 24. The CPU 60a calculates the pinion angle θp, which is the actual rotation angle of the pinion shaft 21, as an absolute angle with respect to the rack neutral position, i.e., the steering reference value θnt. The pinion angle θp thus obtained is used when calculating the drive control signal MSt. Steering information St used by the CPU 60a, such as the pinion angle θp, is output to the reaction force ECU 50 via the local network 49.

[0041] <Regarding CPU state transitions in the reaction force ECU> Figures 3 and 4 show the state transitions of CPU 50a after it is powered on. In the following explanation, one set from power-on to power-off may be referred to as one trip.

[0042] As shown in Figures 3 and 4, when the power is off, the CPU 50a determines to turn on the power by receiving the IG signal Sg (step 100). The IG signal Sg is input to the CPU 50a when the start switch 48 is turned on. The IG signal Sg is also input to the CPU 50a by using the factory external device 71. In this case, the factory external device 71 outputs a factory command Fcmd to the CPU 50a, which is information that allows the CPU 50a to recognize that it is the IG signal Sg.

[0043] After determining that the power is on (step 100), the CPU 50a performs an initial check process (step 102). The initial check process includes checking whether the CPU 50a and memory 50b can operate normally, and checking the operation of the reaction force unit 4. The initial check process includes reading various information from memory 50b and other processes to enable the execution of processes for operating the reaction force unit 4. In the initial check process, the various information that the CPU 50a reads from memory 50b includes the reaction force reference value θns.

[0044] Next, after the initial check process in step 102 is completed, the CPU 50a determines whether or not the reaction force reference value θns has been written to memory 50b (step 104). In step 104, if the CPU 50a was able to read the reaction force reference value θns during the initial check process, it determines that the reaction force reference value θns has been written to memory 50b. If the CPU 50a was unable to read the reaction force reference value θns during the initial check process, it determines that the reaction force reference value θns has not been written to memory 50b.

[0045] The information writable to memory 50b includes volatile information, which is lost and initialized when the power supply to the reaction force ECU 50, particularly memory 50b, is interrupted, and non-volatile information, which is retained even when the power supply to memory 50b is interrupted. The reaction force reference value θns corresponds to volatile information. Therefore, the content of the reaction force reference value θns is lost when the power supply to the reaction force ECU 50, particularly memory 50b, is interrupted. This situation can occur due to the removal and reinstallation of the battery 47 connected to the steering control device 1. In other words, when the battery 47 is removed from the vehicle, power cannot be supplied from both power supply lines L1 and L2, resulting in an interruption of the power supply to memory 50b. After the power supply is interrupted, the reaction force reference value θns is not written to memory 50b as an initial value. In this case, the CPU 50a cannot read the reaction force reference value θns from memory 50b.

[0046] Next, if the CPU 50a determines that the reference value θns for the reaction force has been written to memory 50b (step 104: YES) since it was able to read the reference value θns for the reaction force, it proceeds to step 106 to set the normal control mode Mn. In step 106, the CPU 50a sets the control mode flag Fm, which is stored in a predetermined area of ​​memory 50b, to "0". The normal control mode Mn is information that defines how the reaction force motor 13 is driven, and it defines that the reaction force motor 13 is driven so that steering reaction force is generated as reaction force motor torque in an environment in which the vehicle is expected to be used by a driver. The drive control of the reaction force motor 13 while the normal control mode Mn is set will be described later.

[0047] On the other hand, if the CPU 50a determines that the reference value θns for reaction force has not been written to memory 50b because it could not read the reference value θns for reaction force (step 104: NO), it proceeds to step 108 to set the setting mode Mf. In step 108, the CPU 50a sets the control mode flag Fm, which is stored in a predetermined area of ​​memory 50b, to "1". The setting mode Mf is information that defines how to drive the reaction force motor 13, and it defines that the reaction force motor 13 should be driven so that a reaction force motor torque is generated in order to learn the reference value θns for reaction force in an environment where the vehicle is not expected to be used by a driver. The drive control of the reaction force motor 13 while the setting mode Mf is being set will be described later.

[0048] After proceeding to step 106 or step 108, the CPU 50a determines that the power is off because the IG signal Sg is no longer input (step 110). The input of the IG signal Sg to the CPU 50a is stopped when the start switch 48 is turned off. The input of the IG signal Sg to the CPU 50a can also be stopped by using the factory external device 71. In this case, the factory external device 71 stops the input of the factory command Fcmd to the CPU 50a, which is information that allows the CPU 50a to recognize that the IG signal Sg is present.

[0049] Next, if the CPU 50a determines that the power should be turned off (step 110), it executes a shutdown process (step 112). In step 112, the CPU 50a writes various information to the memory 50b. In this case, the CPU 50a erases the contents of the control mode flag Fm and the learning mode flag Fl (described later) in order to initialize the control mode flag Fm that was set during the trip. After that, the CPU 50a stops its operation, thereby stopping the operation of the reaction force ECU 50.

[0050] <Regarding state transitions related to setting modes> As shown in Figure 4, during the setting of setting mode Mf, the CPU 50a determines whether or not there is no input of the factory command Fcmd via the factory external device 71 (step 200). In step 200, the CPU 50a determines whether or not it determined to turn on the power in step 100 triggered by the input of the factory command Fcmd.

[0051] Next, if no factory command Fcmd is input (step 200: YES), the CPU 50a performs a reference position learning process (step 202) to learn the reference value θns for the reaction force through the control of the reaction force motor 13. In step 202, during the reference position learning process, the CPU 50a controls the drive of the reaction force motor 13 so that its rotational speed becomes the first speed V1. The reference position learning process is a process that learns the reference value θns for the reaction force, which is the reference position of the steering shaft 11, by performing a lock-to-lock operation that rotates the steering shaft 11 in a first direction and a second direction through the drive of the reaction force motor 13. The reference position learning process will be described later.

[0052] On the other hand, if the factory command Fcmd is entered (step 200: NO), CPU 50a proceeds to step 204 to set the factory learning mode Mfa. In step 204, CPU 50a sets the learning mode flag Fl in memory 50b to "1". Note that the learning mode flag Fl is initially set to "0". In other words, if CPU 50a determines that step 200: YES, the learning mode flag Fl is "0".

[0053] Next, the CPU 50a performs a reference position learning process (step 206) to learn a reference value θns for the reaction force by controlling the reaction force motor 13. In step 206, the CPU 50a controls the drive of the reaction force motor 13 so that the rotational speed of the reaction force motor 13 becomes the second speed V2, in relation to the reference position learning process performed in step 202. In this embodiment, the second speed V2 is a speed greater than the first speed V1. In other words, during the reference position learning process, the CPU 50a drives the control of the reaction force motor 13 so that the rotational speed of the reaction force motor 13 becomes the second speed V2 instead of the first speed V1. In this embodiment, the process in step 200 is an example of an input process that inputs a specific signal generated through the use of an external device. Also, the processes in steps 202 and 206 are examples of selection processes that select between the first speed V1 and the second speed V2.

[0054] <Regarding work related to reaction units in factory processes> Figure 5 shows the reaction force unit 4 in the process of mounting it onto a vehicle within the vehicle assembly plant. Since the process of mounting the reaction force unit 4 onto a vehicle is one of the vehicle assembly processes performed within the vehicle assembly plant, in the following explanation, the process of mounting the reaction force unit 4 onto a vehicle may be referred to as the "vehicle assembly plant process." For example, as shown by the dashed line in Figure 5, the steering unit 6 is not prepared in the vehicle assembly plant process, that is, the steering wheels 5 of the vehicle are not prepared. Also, in the vehicle assembly plant process, the steering wheel 3 is detached from the steering shaft 11. In this case, since it is before mounting onto the vehicle, the start switch 48, etc., is not prepared, and the reaction force ECU 50 is not connected to the vehicle network 8. However, the battery 47 is connected to the reaction force unit 4 via the reaction force side connection part 90a. Also, the factory external equipment 71 is connected to the reaction force unit 4 via the reaction force side connection part 90a.

[0055] In the vehicle assembly plant process, factory workers connect an external factory device 71 to the reaction force unit 4. By operating the external factory device 71, the factory worker causes the external factory device 71 to output a factory command Fcmd to the reaction force ECU 50. As a result, in the vehicle assembly plant process, even if a start switch 48 or the like is not available, the CPU 50a can perform the power-on determination (step 100) shown in Figure 3 through the input of the factory command Fcmd. The CPU 50a can then perform various processes such as steps 102, 104, 204, and 206. During the reference position learning process (step 206) that can be performed in this case, it is assumed that the factory worker will not touch the reaction force unit 4, i.e., the steering wheel 3, since the steering wheel 3 is detached from the steering shaft 11.

[0056] Furthermore, the reference position learning process (step 206) is expected to be performed not only in the vehicle assembly plant process, but also after the vehicle assembly plant process, for example, at a dealer's vehicle maintenance factory after the vehicle has been shipped to the market. Since the vehicle maintenance factory process targets vehicles that have already been equipped with the steering system 2, various vehicle parts are prepared, including the reaction force unit 4 to which the steering wheel 3 is connected, the steering unit 6 to which the steering wheels 5 are connected, and so on. In other words, the battery 47 and the start switch 48 are prepared in the vehicle maintenance factory process, and the reaction force ECU 50 is also connected to the vehicle network 8. As a result, in the vehicle maintenance factory process, the CPU 50a can perform the power-on determination (step 100) shown in Figure 3 by turning on the start switch 48, since the start switch 48 is prepared. The CPU 50a can then perform various processes such as steps 102, 104, 200, 204, and 206. In the reference position learning process (step 206) that can be performed in this case, since the steering wheel 3 is connected to the steering shaft 11, it is assumed that a factory worker will touch the reaction force unit 4, i.e., the steering wheel 3.

[0057] <About the function of the reaction force ECU> Figure 6 shows some of the processes performed by the reaction force ECU 50. The processes shown in Figure 6 are a part of the processes that are realized when the CPU 50a executes a program stored in memory 50b, and are described for each type of process that is realized. More specifically, the reaction force ECU 50 has a first control unit 510, a second control unit 520, a control mode flag storage unit 530, and a second switch 540.

[0058] The first control unit 510 is the part that controls the drive of the reaction motor 13 in the drive method defined during the setting of the normal control mode Mn. The first control unit 510 generates a steering reaction force corresponding to the steering torque Th through the drive control of the reaction motor 13. The first control unit 510 has a target steering reaction force calculation unit 511, an axial force calculation unit 512, and a subtractor 513.

[0059] The target steering reaction force calculation unit 511 calculates the target steering reaction force T1* based on, for example, the steering torque Th. The target steering reaction force T1* is the target value of the steering reaction force to be generated through the reaction force motor 13. The target steering reaction force calculation unit 511 calculates a larger absolute value of the target steering reaction force T1* the larger the absolute value of the steering torque Th is. The target steering reaction force calculation unit 511 may also make the target steering reaction force T1* variable according to the value of the vehicle speed V.

[0060] The axial force calculation unit 512 calculates the axial force acting on the steering shaft 22 through the steering wheel 5 based on, for example, at least one of the values ​​of the pinion angle θp and the steering motor current Ib of the steering motor 32. The axial force calculation unit 512 then calculates a torque conversion value (i.e., steering reaction force corresponding to the axial force) T2* by converting the calculated axial force into torque. The axial force calculation unit 512 may make the torque conversion value T2* variable according to the vehicle speed V.

[0061] The subtractor 513 calculates the steering reaction force command value T3* by subtracting the torque conversion value T2* calculated by the axial force calculation unit 512 from the target steering reaction force T1* calculated by the target steering reaction force calculation unit 511.

[0062] The second control unit 520 controls the driving of the reaction force motor 13 using the driving method defined during the setting of the setting mode Mf. The second control unit 520 also executes processing related to the reference position learning process. The second control unit 520 includes a flag setting unit 521, a target steering angle calculation unit 522, and a steering angle feedback control unit 523. Furthermore, the second control unit 520 can be connected to external factory equipment 71 via the reaction force side connection unit 90a.

[0063] The flag setting unit 521 sets the learning mode flag Fl based on whether or not the factory command Fcmd is input. This corresponds to the process in step 204 shown in Figure 4. The flag setting unit 521 outputs the learning mode flag Fl to the target steering angle calculation unit 522.

[0064] The target steering angle calculation unit 522 calculates the target steering angle θs* of the reaction motor 13 in a manner corresponding to the learning mode flag Fl obtained through the flag setting unit 521. The target steering angle calculation unit 522 includes a steering angular velocity calculation unit 524, a first target steering angular velocity storage unit 525, a second target steering angular velocity storage unit 526, a first switch 527, and a steering angular velocity feedback control unit 528.

[0065] The steering angular velocity calculation unit 524 calculates the steering angular velocity ωs by performing a differential operation with respect to the steering angle θs. The steering angular velocity calculation unit 524 outputs the steering angular velocity ωs to the steering angular velocity feedback control unit 528.

[0066] The first target steering angular velocity storage unit 525 calculates the first target steering angular velocity ωs1*, which is a control variable for setting the rotational speed of the reaction motor 13 to the first speed V1, and outputs the first target steering angular velocity ωs1* to the first switch 527. The second target steering angular velocity storage unit 526 calculates the second target steering angular velocity ωs2*, which is a control variable for setting the rotational speed of the reaction motor 13 to the second speed V2, and outputs the second target steering angular velocity ωs2* to the first switch 527. The first target steering angular velocity storage unit 525 and the second target steering angular velocity storage unit 526 are, for example, storage areas of memory 50b. Assuming that the second speed V2 is greater than the first speed V1, the value of the second target steering angular velocity ωs2* will be greater than the value of the first target steering angular velocity ωs1*.

[0067] The first switch 527 outputs a target steering angular velocity ωs*, which is either the first target steering angular velocity ωs1* or the second target steering angular velocity ωs2*, to the steering angular velocity feedback control unit 528 based on the learning mode flag Fl obtained through the flag setting unit 521. If the learning mode flag Fl is "0", i.e., the initial value, the first switch 527 outputs the target steering angular velocity ωs* which is the first target steering angular velocity ωs1* obtained through the first target steering angular velocity storage unit 525. If the learning mode flag Fl is "1", i.e., not the initial value, the first switch 527 outputs the target steering angular velocity ωs* which is the second target steering angular velocity ωs2* obtained through the second target steering angular velocity storage unit 526.

[0068] The steering angular velocity feedback control unit 528 calculates the target steering angle θs* through feedback control of the steering angular velocity ωs obtained through the steering angular velocity calculation unit 524, so as to make it follow the target steering angular velocity ωs* obtained through the first switch 527. The steering angular velocity feedback control unit 528 outputs the target steering angle θs* to the steering angle feedback control unit 523.

[0069] The steering angle feedback control unit 523 calculates the reaction force motor torque command value T4* through feedback control of the steering angle θs in order to make the steering angle θs follow the target steering angle θs* obtained through the steering angular velocity feedback control unit 528. The steering angle feedback control unit 523 outputs the reaction force motor torque command value T4* to the second switch 540.

[0070] The control mode flag storage unit 530 is, for example, the memory area of ​​memory 50b that stores the control mode flag Fm set in steps 106 and 108 shown in Figure 3. In other words, the control mode flag storage unit 530 stores "0" for the control mode flag Fm when the normal control mode Mn is set, and stores "1" for the control mode flag Fm when the setting mode Mf is set.

[0071] The second switch 540 selects a reaction motor torque command value T5* from either the steering reaction force command value T3* or the reaction motor torque command value T4* based on the control mode flag Fm obtained through the control mode flag storage unit 530. If the control mode flag Fm is "0", i.e., the initial value, the second switch 540 selects the reaction motor torque command value T5* which is the steering reaction force command value T3* obtained through the first control unit 510. If the control mode flag Fm is "1", i.e., not the initial value, the second switch 540 selects the reaction motor torque command value T5* which is the reaction motor torque command value T4* obtained through the second control unit 520. Then, the second switch 540 calculates a drive control signal MSs based on the selected reaction motor torque command value T5* and outputs the drive control signal MSs to the reaction force inverter 51.

[0072] The second control unit 520 calculates the reaction motor torque command value T4* by inputting the steering angle θs, which is the rotation angle of the steering shaft 11. However, the rotation angle θa of the reaction motor 13 may be used instead of the steering angle θs. This is because the only difference between the steering angle θs and the rotation angle θa is whether or not the coefficient of the steering reduction mechanism 14 is multiplied, and from the perspective of indicating the current rotational position of the steering shaft 11, the technical significance of the steering angle θs and the rotation angle θa is the same.

[0073] In this embodiment, the processing performed by the second control unit 520 is an example of a drive process. The processing performed by the first switch 527 is an example of a selection process. The processing performed by the steering angle feedback control unit 523 is an example of a rotation angle feedback process. The processing performed by the steering angular velocity feedback control unit 528 is an example of a rotation angular velocity feedback process.

[0074] <Regarding the processing procedure for reference position learning> Figure 7 shows the processing procedure for the reference position learning process for calculating the reference value θns for reaction force, which is performed by the CPU 50a during the setting mode Mf. When the learning mode flag Fl is "0", the CPU 50a performs the reference position learning process so that the steering angular velocity ωs of the steering shaft 11 becomes the first velocity V1. When the learning mode flag Fl is "1", the CPU 50a performs the reference position learning process so that the steering angular velocity ωs of the steering shaft 11 becomes the second velocity V2.

[0075] More specifically, in the reference position learning process, the CPU 50a moves the steering shaft 11 to the right, which is one of the first directions (left or right), at a first speed V1 or a second speed V2 through the drive control of the reaction force motor 13 by the second control unit 520 (step 302). In step 302, the CPU 50a calculates a drive control signal MSs to automatically move the steering shaft 11 to the right.

[0076] Next, the CPU 50a determines whether the steering shaft 11 has reached the rightward rotation limit position 3a (step 304). In step 304, the CPU 50a monitors, for example, the reaction force motor current Ia, the steering torque Th, and the steering angular velocity ωs.

[0077] The CPU 50a determines that the steering shaft 11 has reached the rightward rotation limit position 3a when all of the following four contact conditions (A1) to (A4) are met. (A1) The absolute value of Ia ≥ Ith "Ith" is the current threshold. The current threshold Ith is set based on the perspective of detecting the increase in the current of the reaction motor 13 due to the increase in the load on the reaction motor 13 after the steering shaft 11 has reached the rightward rotation limit position 3a.

[0078] (A2) The absolute value of Th ≤ Tth "Tth" is a torque threshold value, which is set based on the ability to detect when the steering shaft 11 is not being operated by the driver or operator.

[0079] (A3) Absolute value of ωs ≤ ωsth However, "ωth" is the steering angular velocity threshold, and is set based on the perspective of detecting when the steering wheel 3 is not being operated by the driver or operator.

[0080] (A4) t≧tth However, "t" is the time during which the three conditions A1 to A3 are met. "tth" is a time threshold, which is set based on the consideration of preventing an incorrect determination that the steering shaft 11 has reached the rightward rotation limit position 3a when, for example, the three conditions A1 to A3 are met instantaneously.

[0081] Next, if the CPU 50a determines that the steering shaft 11 has not reached the right rotation limit position 3a (step 304: NO), it repeatedly executes the processes in steps 302 and 304. On the other hand, if the CPU 50a determines that the steering shaft 11 has reached the right rotation limit position 3a (step 304: YES), it temporarily stores the right limit position θrl (step 306). In step 306, the CPU 50a temporarily stores the rotation angle θa of the reaction motor 13 at the time it determines that the steering shaft 11 has reached the right rotation limit position 3a as the right limit position θrl in memory 50b.

[0082] Next, the CPU 50a moves the steering shaft 11 to the left at a first speed V1 or a second speed V2 through the drive control of the reaction force motor 13 by the second control unit 520 (step 308). In step 308, the CPU 50a calculates a drive control signal MSs to automatically move the steering shaft 11 to the left.

[0083] Next, the CPU 50a determines whether the steering shaft 11 has reached the left rotation limit position 3b (step 310). In step 310, the CPU 50a monitors, for example, the reaction force motor current Ia, the steering torque Th, and the steering angular velocity ωs, similar to the process in step 304. The CPU 50a then determines that the steering shaft 11 has reached the left rotation limit position 3b when all of the above four conditions (A1) to (A4) are met.

[0084] Next, if the CPU 50a determines that the steering shaft 11 has not reached the left rotation limit position 3b (step 310: NO), it repeatedly executes the processes of steps 308 and 310. On the other hand, if the CPU 50a determines that the steering shaft 11 has reached the left rotation limit position 3b (step 310: YES), it temporarily stores the left limit position θll (step 312). In step 312, the CPU 50a temporarily stores the rotation angle θa of the reaction motor 13 at the time it determined that the left rotation limit position 3b had been reached as the right limit position θrl in memory 50b.

[0085] Next, CPU 50a calculates the midpoint value θc (step 314). In step 314, CPU 50a calculates the midpoint value θc as a value corresponding to half the sum of the right limit position θrl, which was temporarily stored in step 306, and the left limit position θll, which was temporarily stored in step 312. This is also done by adding a value corresponding to half the difference between the right limit position θrl and the left limit position θll to the left limit position θll. The absolute value of the difference between the midpoint value θc and the right limit position θrl is equal to the absolute value of the difference between the midpoint value θc and the left limit position θll.

[0086] Next, the CPU 50a determines the validity of the midpoint value θc (step 316). In step 316, the CPU 50a determines whether the midpoint value θc obtained in step 314 is within a predetermined range. The CPU 60a includes a process to determine whether the midpoint value θc is greater than the lower threshold θcth1 and less than the upper threshold θcth2. For example, the lower threshold θcth1 and the upper threshold θcth2 are set to values ​​within a range obtained by taking tolerances into account, assuming that the rotation angle θa of the reaction force motor 13 is the design value of the steering shaft 11.

[0087] Next, if the CPU 50a determines that the midpoint value θc is not valid (step 316: NO), it repeatedly executes the processes from step 302 onward. On the other hand, if the CPU 50a determines that the midpoint value θc is valid (step 316: YES), it sets the midpoint value θc as the reaction force reference value θns (step 318), terminates the process, and moves on to other processes. In step 318, the CPU 50a writes the value of the midpoint value θc to the memory 50b as the reaction force reference value θns. The reaction force reference value θns thus obtained is a value that indicates the neutral position of the steering shaft 11.

[0088] Next, the CPU 50a moves the steering shaft 11 until it reaches the midpoint value θc through drive control of the reaction force motor 13 by the second control unit 520 (step 320). In step 320, the CPU 50a calculates the reaction force motor torque command value T4* through feedback control of the steering angle θs in order to make the steering angle θs follow the target steering angle θs* which is the midpoint value θc. As a result, after the processing to store the reference value θns for the reaction force in the memory 50b is completed, the steering shaft 11 can be adjusted to the neutral position.

[0089] Conditions (A2) and (A3) may be omitted if the learning mode flag Fl is "1", i.e., in factory learning mode Mfa. This is because, as shown in Figure 5, during the process of mounting the reaction force unit 4 onto the vehicle, it is assumed that factory workers will not touch the reaction force unit 4 because the steering wheel 3 has been detached from the steering shaft 11.

[0090] <Operation and Effects of This Embodiment> Figures 8(a) and 8(b) are graphs showing the changes in steering angle θs and steering angular velocity ωs during the period from the start of the reference position learning process until the steering shaft 11 moves to the rightward rotation limit position 3a (steps 302 and 304). Note that steering angular velocity ωs is synonymous with the rotational speed of the steering shaft 11.

[0091] In the reference position learning process performed at the vehicle maintenance factory ("Post-shipment learning" in Figure 8), the maximum target steering angular velocity ωs* is set to the first target steering angular velocity ωs1*. For example, as shown by the solid line in Figure 8(b), from the moment the steering shaft 11 begins to move to the rightward rotation limit position 3a (time T0), the steering angular velocity ωs of the steering shaft 11 gradually increases toward the first target steering angular velocity ωs1*. Eventually, the steering angular velocity ωs of the steering shaft 11 reaches the first target steering angular velocity ωs1*, i.e., the first velocity V1 (time T11). After that, the steering angular velocity ωs of the steering shaft 11 is maintained at the first velocity V1. This is because the absolute value of the target steering angular velocity ωs* is maintained at the first target steering angular velocity ωs1*. Furthermore, when the absolute value of the steering angle θs of the steering shaft 11 reaches the rightward rotation limit position 3a (time T12), the movement of the steering shaft 11 stops, and the steering angular velocity ωs of the steering shaft 11 becomes "0".

[0092] In contrast, as shown by the solid line in Figure 8(a), for example, the absolute value of the steering angle θs gradually increases toward the rightward rotation limit position 3a. More specifically, the absolute value of the steering angle θs increases curvilinearly until the steering angular velocity ωs reaches the first velocity V1 (time T11). After time T11, the absolute value of the steering angle θs increases such that the slope, which is the rate of change of the steering angle θs per unit time, is maintained at a constant slope T. After that, the absolute value of the steering angle θs coincides with the rightward rotation limit position 3a. In this state, conditions (A1) to (A4) are met, and the CPU 50a stores the rightward limit position θrl in memory 50b.

[0093] On the other hand, in the reference position learning process performed at the vehicle assembly plant (referred to as "Factory Learning" in Figure 8), the maximum target steering angular velocity ωs* is set to the second target steering angular velocity ωs2*. For example, as shown by the dashed line in Figure 8(b), from the moment the steering shaft 11 begins to move to the rightward rotation limit position 3a (time T0), the steering angular velocity ωs of the steering shaft 11 gradually increases toward the second target steering angular velocity ωs2*. Eventually, the steering angular velocity ωs of the steering shaft 11 reaches the second target steering angular velocity ωs2*, i.e., the second velocity V2 (time T21). After that, the steering angular velocity ωs of the steering shaft 11 is maintained at the second velocity V2. This is because the absolute value of the target steering angular velocity ωs* is maintained at the second target steering angular velocity ωs2*. Furthermore, when the absolute value of the steering angle θs of the steering shaft 11 reaches the rightward rotation limit position 3a (time T22), the movement of the steering shaft 11 stops, and the steering angular velocity ωs of the steering shaft 11 becomes "0".

[0094] In contrast, as shown by the dashed line in Figure 8(a), for example, the absolute value of the steering angle θs gradually increases toward the rightward rotation limit position 3a. More specifically, the absolute value of the steering angle θs increases curvilinearly until the steering angular velocity ωs reaches the second velocity V2 (time T21). After time T21, the absolute value of the steering angle θs increases such that the slope, which is the rate of change of the steering angle θs per unit time, is maintained at a constant slope Tα. After that, the absolute value of the steering angle θs coincides with the rightward rotation limit position 3a. In this state, conditions (A1) to (A4) are met, and the CPU 50a stores the rightward limit position θrl in memory 50b.

[0095] Therefore, in the reference position learning process performed at the vehicle assembly plant, the steering shaft 11 reaches the rightward rotation limit position 3a faster compared to the reference position learning process performed at the vehicle maintenance plant. In other words, in the reference position learning process performed at the vehicle assembly plant, the time required for the steering shaft 11 to move to the rightward rotation limit position 3a is shorter compared to the reference position learning process performed at the vehicle maintenance plant (T12 > T22 in Figure 8(a)). This is also true for the time required for the steering shaft 11 to move from the rightward rotation limit position 3a to the leftward rotation limit position 3b, and further, for the time required for the steering shaft 11 to move from the leftward rotation limit position 3b to the midpoint value θc. Therefore, the time required for the entire reference position learning process can be shortened at the vehicle assembly plant compared to the vehicle maintenance plant. Consequently, even if the steering shaft 11 is rotated in the first or second direction to learn the reaction force reference value θns, the time required for the process at the vehicle assembly plant, i.e., the process for mounting the reaction force unit 4 onto the vehicle, can be shortened.

[0096] <Effects of this embodiment> According to the embodiment described above, the following further effects can be obtained. (1-1) The reference position learning process selects either the first speed V1 or the second speed V2 depending on whether or not the factory command Fcmd is input. For example, in the process at the vehicle assembly plant, it becomes unnecessary to implement the drive process for the reaction motor 13 using the second speed V2 and then reprogram (rewrite the program) to drive the reaction motor 13 using the first speed V1 when the vehicle is shipped to the market. Therefore, it is possible to realize a configuration in which the steering angular velocity ωs of the steering shaft 11 can be changed between the vehicle assembly plant and the vehicle maintenance plant without requiring a process of physically rewriting the contents of the program stored in memory 50b, such as reprogramming.

[0097] (1-2) The steering angle feedback control unit 523 and the steering angular velocity feedback control unit 528 perform feedback control to drive the reaction force motor 13 at the first speed V1 or the second speed V2, thereby executing the reference position learning process. Therefore, due to the effect of feedback control, the reference value θns for the reaction force can be learned in a control-stable manner that is less susceptible to disturbances.

[0098] (1-3) The reference position learning process executes the drive process of the reaction motor 13 at the second speed V2 only when a factory command Fcmd generated from an external factory device 71 manufactured for processes in a vehicle assembly plant is input. Therefore, it is possible to suppress the occurrence of a situation in which the reference value θns for the reaction force is learned through the drive process of the reaction motor 13 at the second speed V2 in processes other than those in a vehicle assembly plant, for example, in a vehicle maintenance plant.

[0099] (1-4) For example, when the steering wheel 3 is attached to the steering shaft 11, the absolute value of the inertial force acting on the steering wheel 3, i.e., the steering shaft 11, is larger than when the steering wheel 3 is detached from the steering shaft 11. In this case, the impact on the steering shaft 11 and the stopper 11c is greater when the steering shaft 11 reaches the rightward rotation limit position 3a or the leftward rotation limit position 3b. Also, the mechanical load at the start of rotation of the steering shaft 11 is greater. Therefore, when the steering wheel 3 is attached, it becomes necessary to limit the increase in the rotational speed of the steering shaft 11 from the viewpoint of protecting the reaction force unit 4 from the effects of the inertial force. In contrast, if the situation in which the rotational speed of the steering shaft 11 is increased is considered to be when the steering wheel 3 is detached, it becomes unnecessary to consider the effects of the inertial force. This is effective in relaxing the limitations when increasing the rotational speed of the steering shaft 11.

[0100] <Second Embodiment> The second embodiment will now be described with reference to the drawings. This embodiment differs from the first embodiment in the configuration of the second control unit 520. For this reason, the same reference numerals are used for components and processes as in the first embodiment, and their descriptions are omitted. In this embodiment, the processes performed by the second control unit 520 are an example of drive processes. The processes performed by the first switch 527 are an example of selection processes. The processes performed by the steering angle feedback control unit 523 are an example of rotation angle feedback processes. The processes performed by the steering angular velocity feedback control unit 528 are an example of rotation angular velocity feedback processes.

[0101] As shown in Figure 9, the second control unit 520 has, in addition to the configuration of the second control unit 520 of the first embodiment, a target steering angle calculation unit 551, a multiplier 552, and a compensation amount calculation unit 553.

[0102] The target steering angle calculation unit 551 calculates the target steering angle θs*. In step 302 of Figure 7, the target steering angle calculation unit 551 sets the target steering angle θs* to a value that exceeds the rotational angle position corresponding to the rotation limit position 3a to the right of the stopper 11c. In step 308 of Figure 7, the target steering angle calculation unit 551 sets the target steering angle θs* to a value that exceeds the rotational angle position corresponding to the rotation limit position 3b to the left of the stopper 11c. In step 320 of Figure 7, the target steering angle calculation unit 551 sets the target steering angle θs* to a value that corresponds to the value of the midpoint value θc. The target steering angle calculation unit 551 outputs the target steering angle θs* to the steering angle feedback control unit 523.

[0103] The steering angular velocity feedback control unit 528 of the compensation amount calculation unit 553 calculates the compensation amount gain G through feedback control of the steering angular velocity ωs in order to make the steering angular velocity ωs follow the target steering angular velocity ωs*. The steering angular velocity feedback control unit 528 outputs the compensation amount gain G to the multiplier 552.

[0104] The steering angle feedback control unit 523 calculates the reaction force motor torque command value T4*(2) through feedback control of the steering angle θs in order to make the steering angle θs follow the target steering angle θs* obtained through the target steering angle calculation unit 551. The steering angle feedback control unit 523 outputs the reaction force motor torque command value T4*(2) to the multiplier 552.

[0105] The multiplier 552 multiplies the reaction force motor torque command value T4*(2) obtained through the steering angle feedback control unit 523 by the compensation amount gain G obtained through the steering angular velocity feedback control unit 528. This allows the multiplier 552 to calculate the reaction force motor torque command value T4* corresponding to the target steering angular velocity ωs*. The multiplier 552 outputs the reaction force motor torque command value T4* to the second switch 540. In this embodiment, the compensation amount gain G is an example of a compensation amount that compensates for the torque command value.

[0106] According to this embodiment, the same functions and effects as those of the first embodiment are achieved. <Other Embodiments> Each of the above embodiments may be modified as follows. Furthermore, the following other embodiments can be combined with each other to the extent that they do not conflict with the technical standards.

[0107] In each of the above embodiments, the factory external device 71 may be a device that outputs the factory command Fcmd via wireless communication. In this case, the reaction force side connection part 90a only needs to have the function of communicating wirelessly with the factory external device 71. In other words, the reaction force side connection part 90a may be configured to be connectable to the factory external device 71 via wireless communication.

[0108] In each of the above embodiments, the factory command Fcmd only needs to be information that allows the CPU 50a to recognize that it is a process in a vehicle assembly plant, and does not need to be information that allows the CPU 50a to recognize that it is an IG signal Sg. In this case, in step 100 executed in a process in a vehicle assembly plant, the CPU 50a may determine to turn on the power based on the input of a signal equivalent to the IG signal Sg from a factory facility other than the factory command Fcmd.

[0109] In each of the embodiments described above, the process in step 110 may be a process that determines the power is turned off when an IG off signal is input. For example, the IG off signal may be a signal that is input to the CPU 50a when the start switch 48 is turned off. In other embodiments described herein, the factory external device 71 may be configured to output a factory command Fcmd to the CPU 50a, which is information that allows the CPU 50a to recognize that an IG off signal has been received.

[0110] In each of the above embodiments, it is not essential that the following requirements (B1) to (B4) are met in the process at the vehicle assembly plant. (B1) The steering unit 6 is not provided.

[0111] (B2) The steering wheel 3 is detached from the steering shaft 11. (B3) The start switch 48, etc., is not provided. (B4) The reaction force ECU 50 is not connected to the vehicle network 8.

[0112] Furthermore, in other embodiments described herein, work in the vehicle assembly plant process may be performed in any situation where at least one of the requirements (B1) to (B4) above is not considered, for example, when the steering wheel 3 is mounted on the steering shaft 11. In contrast, in the vehicle maintenance plant process, work in the vehicle maintenance plant process may be performed in any situation where at least one of the requirements (B1) to (B4) above is selected, for example, when the steering wheel 3 is detached from the steering shaft 11.

[0113] In each of the embodiments described above, it is assumed that factory workers perform the reference position learning process in a vehicle assembly plant or a vehicle maintenance plant. However, it is also possible to assume that the reference position learning process is performed at a location other than a vehicle maintenance plant after the vehicle has been shipped to the market. For example, it is possible to assume that the reference position learning process is performed at the time of the first power-on, such as when the vehicle owner (driver) replaces the battery 47 at a location other than a vehicle maintenance plant. In this case, since the vehicle is equipped with the steering device 2, as in the vehicle maintenance plant process, it is sufficient to perform the reference position learning process at the first speed V1 (step 202). In addition, if it is assumed that the reference position learning process is performed at a location other than a vehicle maintenance plant, as in the other embodiments described herein, from the viewpoint of the safety of the vehicle owner (driver), it is possible to perform the reference position learning process at a speed smaller than the first speed V1. In this case, at the vehicle maintenance plant, depending on the connection status of the external maintenance equipment that is intended to be used only at the vehicle maintenance plant, it is sufficient to perform the reference position learning process at a speed smaller than the first speed V1 or at the first speed V1. Furthermore, when the reference position learning process is performed outside of a vehicle maintenance factory after the vehicle has been shipped to the market, if neither the factory external equipment 71 nor the maintenance external equipment is connected, the reference position learning process should be performed at a speed lower than the first speed V1.

[0114] In each of the above embodiments, the steering angular velocity feedback control unit 528 may include a change amount guard processing unit that performs change amount guard processing to limit the change in the difference between the steering angular velocity ωs and the target steering angular velocity ωs* to a certain amount. This suppresses large rotations of the steering shaft 11 when the steering shaft 11 rotates. In this case, during the reference position learning process, the steering angular velocity ωs can be increased at a constant slope during the period from when movement to the rightward rotation limit position 3a begins until the first velocity V1 or second velocity V2 is reached (T0 to T11 shown in Figure 8).

[0115] In each of the above embodiments, the processing procedure for the reference position learning process is not limited to the procedure shown in Figure 7 and can be changed as appropriate. For example, the processing order of steps 302 to 306 may be changed so that it is executed after the processing of steps 308 to 312. In addition, it is sufficient to include either the set of processing steps 302 to 306 or the set of processing steps 308 to 312. Therefore, the CPU 50a will temporarily store either the right limit position θrl or the left limit position θll. In this case, the processing in step 314 may be a process that calculates the midpoint value θc by subtracting the design value of half the rotation range of the steering wheel 3 from either the temporarily stored right limit position θrl or the left limit position θll.

[0116] In each of the above embodiments, it is not essential to include the process of step 320 of the reference position learning process shown in Figure 7, i.e., the process of adjusting the steering shaft 11 to the neutral position. For example, if the process of step 320 is omitted, the reference position learning process may be a process of rotating the steering shaft 11 to the right limit position θrl or the left limit position θll. In other words, the reference position learning process may include a process after the process of step 318 to ensure that the position of the steering shaft 11 reaches a predetermined position.

[0117] In the second embodiment described above, the second control unit 520 does not necessarily have to include a multiplier 552. For example, if the multiplier 552 is omitted, the steering angular velocity feedback control unit 528 may be configured to calculate a compensation component to make the steering angular velocity ωs follow the target steering angular velocity ωs* instead of calculating a compensation gain G. The second control unit 520 may also include an adder that calculates the reaction force motor torque command value T4*(2) by adding the compensation component, instead of the multiplier 552. Alternatively, the second control unit 520 may include filtering instead of the multiplier 552. In this case, the steering angular velocity feedback control unit 528 may be configured to calculate a filter constant that defines the characteristics of the filtering process, instead of calculating a compensation gain G. The filtering in the other embodiments described herein may be, for example, an LPF that suppresses fluctuations in the reaction force motor torque command value T4* obtained through the steering angle feedback control unit 523. In this case, the characteristic of the filtering is the cutoff frequency of the LPF, etc.

[0118] In each of the above embodiments, the process of step 104 shown in Figure 3 may be a process of determining from the contents of memory 50b whether or not it is the first power-up after battery replacement and setting the setting mode Mf.

[0119] In each of the above embodiments, the displacement of the steering wheel 3, i.e., the steering shaft 11, is not limited to the amount calculated based on the integration of the rotation angle θa. For example, it may be the detected value of a steering angle sensor that directly detects the rotation angle of the steering shaft 11. The steering angle sensor may be provided, for example, between the steering wheel 3 and the torque sensor 41 on the steering shaft 11.

[0120] In each of the above embodiments, the steering member operated by the driver to steer the vehicle is not limited to the steering wheel 3. For example, it may be a joystick. In each of the above embodiments, the reaction motor 13 mechanically connected to the steering wheel 3 is not limited to a three-phase brushless motor. For example, it may be a brushed DC motor.

[0121] In each of the above embodiments, it is not essential to include the steering deceleration mechanism 14. In each of the above embodiments, the steering unit 6 transmits the rotation of the steering motor 32 to the conversion mechanism 34 via the transmission mechanism 33. However, the steering unit 6 is not limited to this, and for example, it may be configured to transmit the rotation of the steering motor 32 to the conversion mechanism 34 via a gear mechanism. Alternatively, the steering unit 6 may be configured so that the steering motor 32 directly rotates the conversion mechanism 34. Furthermore, the steering unit 6 may be configured to include a second rack and pinion mechanism, and the steering unit 6 may be configured so that the rotation of the steering motor 32 is converted into reciprocating motion of the steering shaft 22 by the second rack and pinion mechanism.

[0122] In each of the above embodiments, the steering unit 6 is not limited to a configuration in which the right steering wheel 5 and the left steering wheel 5 are linked. In other words, it may be a configuration in which the right steering wheel 5 and the left steering wheel 5 can be controlled independently.

[0123] • In each of the above embodiments, the steering device 2 has a linkless structure in which the reaction force unit 4 and the steering unit 6 are mechanically separated at all times. However, it is not limited to this, and for example, the reaction force unit 4 and the steering unit 6 may be mechanically separated by a clutch. [Explanation of Symbols]

[0124] 2… Steering gear 3…Steering wheel (steering component) 4…Reaction unit 11… Steering shaft 11c... Stopper (first regulated end, second regulated end) 13… Reaction motor 50…Reaction Force ECU (Reaction Force Control Unit) 71…External equipment for factory (external equipment) 520...Second processing unit 523... Steering Angle Hoodback Control Unit 527...First switch 528... Steering angular velocity feedback control unit

Claims

1. A steering device for a vehicle having a reaction force unit including a reaction force motor connected to a steering shaft to apply torque to the steering shaft to which a steering member can be connected, and a reaction force control unit that controls the driving of the reaction force motor, The reaction force control unit, A reference position learning process is performed to learn the reference position of the steering shaft by rotating the steering shaft in a first or second direction through the drive of the reaction force motor, The process for mounting the reaction unit onto the vehicle is configured to include an input process that inputs a specific signal generated through the use of an external device prepared separately from the reaction unit, The aforementioned reference position learning process is, Assuming that the reference position is learned by performing a drive process to drive the reaction motor so that the rotational angular velocity of the steering shaft becomes a first velocity, A steering device that learns the reference position by executing the drive process such that, when the specific signal is input through the input process, the rotational angular velocity of the steering shaft becomes a second speed which is greater than the first speed, instead of the first speed.

2. The drive process includes a selection process for selecting the first speed and the second speed, When the specific signal is input in the input process, the drive process is executed at the second speed selected by the selection process. The steering device according to claim 1, wherein if the specific signal is not input in the input processing, the drive processing is performed at the first speed selected by the selection processing.

3. The aforementioned drive process is A rotational angular velocity feedback process calculates the target rotation angle of the steering shaft by controlling the actual rotational angular velocity of the steering shaft to a target rotational angular velocity through feedback control. The system includes a rotation angle feedback process that calculates a torque command value for driving the reaction motor by controlling the actual rotation angle of the steering shaft to the target rotation angle through feedback control, The steering device according to claim 2, wherein the selection process includes, while the target rotational angular velocity is set as the first speed, if the specific signal is input through the input process, the process of setting the second speed as the target rotational angular velocity instead of the first speed.

4. The aforementioned drive process is A rotation angle feedback process calculates a torque command value for driving the reaction force motor by controlling the actual rotation angle of the steering shaft to a target rotation angle through feedback control. The system includes a rotational angular velocity feedback process that calculates a compensation amount to compensate for the torque command value by controlling the actual rotational angular velocity of the steering shaft to a target rotational angular velocity through feedback control, The steering device according to claim 2, wherein the selection process includes, while the target rotational angular velocity is set as the first speed, if the specific signal is input through the input process, the process of setting the second speed as the target rotational angular velocity instead of the first speed.

5. The steering device according to claim 1, wherein the external equipment is equipment manufactured for the process of mounting the reaction force unit onto the vehicle.

6. In the process of mounting the reaction force unit onto the vehicle, the steering member is detached from the steering shaft. The steering device according to claim 1, wherein the drive process is performed when the rotational angular velocity of the steering shaft is set to the second speed, and the steering member is detached from the steering shaft.

7. The steering device has a stopper having a first restricting end that restricts the rotation of the steering shaft in the first direction and a second restricting end that restricts the rotation of the steering shaft in the second direction. The steering device according to claim 1, wherein the drive process includes driving the reaction motor so that the steering shaft contacts the first restricting end, and then driving the reaction motor so that the steering shaft contacts the second restricting end.

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