JP4411999B2 - Vehicle steering system - Google Patents

Description

  The present invention relates to a vehicle steering apparatus.

  2. Description of the Related Art Conventionally, there is a steering device including a gear ratio variable system that varies a transmission ratio (gear ratio) of a steering wheel with respect to a steering angle (steering angle) of a steering wheel according to a vehicle state (see, for example, Patent Document 1).

  Such a steering apparatus includes, for example, a gear ratio variable actuator having a differential mechanism (such as a planetary gear mechanism or a harmonic drive) provided on a steering shaft and a motor that drives the differential mechanism. The transmission ratio of the steered wheel with respect to the steering angle is varied by increasing (or decelerating) the rotation of the steering shaft accompanying the steering operation with the variable gear ratio actuator.

  That is, as shown in FIGS. 5 and 6, the steering angle (ACT angle θta) of the steered wheel based on the operation of the gear ratio variable actuator is added to the steered angle (steer turning angle θts) based on the steering operation. Thus, the transmission ratio of the steered wheel with respect to the steering angle θs is varied.

Specifically, when the steering angle of the actual steered wheel relative to the steering angle θs, that is, the tire angle (pinion angle) θt is increased, the ACT angle θta in the same direction as the steering angle θts is added (FIG. 5). For example, when the tire angle θt is made smaller than the steering angle θs, the ACT angle θta opposite to the steering angle θts is added (see FIG. 6). Further, by changing the ACT angle θta to be added according to the vehicle state in this way, good steering characteristics can be obtained.
JP 2002-240734 A

  By the way, conventionally, the gear ratio variable system as described above locks the gear ratio variable actuator (motor or differential mechanism as a driving source) at the end of control such as when the ignition is turned off, and sets the ACT angle θta at that time to the EEPROM. It memorize | stores in non-volatile memories. When restarting, the gear ratio variable control is started with the ACT angle θta read from the EEPROM as an initial value.

  However, such a conventional gear ratio variable system is used when the ACT angle θta cannot be written to the EEPROM at the end of the control due to a failure or when the power supply is interrupted immediately after the initialization of the EEPROM at the start-up. Cannot reproduce the ACT angle θta at the time of restart, that is, the ACT angle becomes invalid. Therefore, the gear ratio variable control cannot be started, and the gear ratio variable actuator remains locked, and the steering feeling is changed. In such a case, there is a problem that even if no failure has occurred in the system itself, it cannot be restored unless it is initialized at a service factory such as a dealer.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle steering apparatus capable of quickly starting gear ratio variable control even when the ACT angle is invalid. .

In order to solve the above-mentioned problem, the invention according to claim 1 adds the second rudder angle of the steered wheel based on motor drive to the first rudder angle of the steered wheel based on the steering angle of the steering wheel. Accordingly, a transmission ratio variable device that varies the transmission ratio of the steering wheel with respect to the steering angle of the steering wheel, a control unit that controls the transmission ratio variable device, and a storage unit that stores the second steering angle at the end of the control The control means is a vehicle steering device that starts control to vary the transmission ratio using the stored second steering angle as an initial value, and detects the first steering angle. 1 detection means and estimation means for estimating an absolute angle of the steered wheel based on a vehicle state quantity used for vehicle control, wherein the control means has an invalid stored second steering angle. In the case, the estimated operation And summarized in that starts control for varying the transmission ratio of the second steering angle as an initial value to be calculated based on the absolute angle and the first steering angle of the wheels.

  According to the above configuration, even when the stored second steering angle becomes invalid, the second steering angle can be calculated from the estimated absolute angle of the steered wheels, and the calculated Control for varying the transmission ratio can be started with the second steering angle as an initial value. As a result, the deviation between the steering angle and the absolute angle of the steered wheels, which is caused by locking the transmission ratio variable device, and the accompanying uncomfortable feeling in steering operation can be quickly eliminated. In addition, since it is not necessary to move the vehicle to a service factory such as a dealer and perform initialization, the convenience can be greatly improved.

According to a second aspect of the present invention, there is provided a determination unit that determines whether or not the vehicle is in a straight traveling state based on a vehicle state quantity used for vehicle control, and the estimation unit is determined to be in the straight traveling state . In this case, the gist is to estimate the absolute angle of the steered wheel as zero.

  According to the above configuration, since the second steering angle is calculated by estimating the absolute angle of the steered wheels as zero, the calculation load is extremely small. Therefore, it is possible to calculate the second steering angle without incurring an increase in arithmetic processing and, consequently, an increase in cost. Note that the determination of the straight-ahead state by the determination unit can be easily realized by using various vehicle state quantities used in normal vehicle control, for example. Therefore, the second steering angle can be calculated at low cost without adding a new configuration for estimating the absolute angle of the steered wheels.

  According to a third aspect of the present invention, there is provided a second detection means for detecting a steering torque, and a correction means for correcting the estimated absolute angle of the steered wheel based on the detected steering torque. The gist.

  According to the above configuration, since the estimated absolute angle of the steered wheel is corrected based on the steering torque, it is possible to start control for varying the transmission ratio based on the more accurate second steering angle. .

The gist of the invention described in claim 4 is that it comprises a notification means for notifying that a return process for starting the control until the transmission ratio is varied is started.
According to the above configuration, even if there is a deviation between the steering angle and the tire angle due to locking of the transmission ratio variable device, it is notified that the return process is in progress. Can alleviate anxiety. In addition, since it is possible to notify the passenger of the completion of the return process before the control for changing the transmission ratio is started, even when the steering feeling changes due to the start of the control. , The feeling of discomfort at that time can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the steering apparatus for vehicles which can start gear ratio variable control rapidly also when ACT angle is invalid can be provided.

Hereinafter, an embodiment in which the present invention is embodied in a vehicle steering apparatus (steering apparatus) provided with a variable gear ratio steering system will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a steering apparatus 1 according to the present embodiment. As shown in the figure, a steering shaft 3 to which a steering wheel (steering) 2 is fixed is connected to a rack 5 via a rack and pinion mechanism 4. It is converted into a reciprocating linear motion of the rack 5 by the and pinion mechanism 4. Then, the traveling direction of the vehicle is changed by changing the angle of the steered wheels 8, that is, the tire angle θt by the reciprocating linear motion of the rack 5 (see FIG. 5).

  Further, the steering device 1 of the present embodiment includes a gear ratio variable actuator 13 that varies the transmission ratio (gear ratio) of the steered wheels 8 with respect to the steering angle θs, and an ECU 14 that controls the operation of the gear ratio variable actuator 13. Yes. In the present embodiment, the gear ratio variable actuator 13 constitutes a transmission ratio variable device.

  In the present embodiment, the gear ratio variable actuator 13 is provided on the steering shaft 3. Specifically, the steering shaft 3 includes a first shaft 15 to which the steering 2 is coupled and a second shaft 16 coupled to the rack and pinion mechanism 4, and the variable gear ratio actuator 13 includes the first shaft 15 and A differential mechanism 21 that couples the second shaft 16 and a motor 22 that drives the differential mechanism 21 are provided.

  The motor 22 rotates forward and backward by being controlled by the ECU 14. The differential mechanism 21 transmits the rotation of the first shaft 15 to the second shaft 16 and decelerates the rotation of the motor 22 to transmit it to the second shaft 16. That is, the gear ratio variable actuator 13 adds the rotation driven by the motor to the rotation of the first shaft 15 accompanying the steering operation input to the differential mechanism 21 and transmits the rotation to the second shaft 16, so that the rack and pinion The rotation of the steering shaft 3 input to the mechanism 4 is increased (or decelerated). In this case, “addition” is defined to include not only addition but also subtraction, and so on.

  That is, the gear ratio variable actuator 13 is controlled by the ECU 14 to add the steering angle (ACT angle θta) of the steered wheels based on the motor drive to the steered angle (steer turning angle θts) of the steered wheels 8 based on the steering operation. Thus, the gear ratio of the steered wheels 8 with respect to the steering angle θs is varied (see FIGS. 5 and 6). In the present embodiment, the steer turning angle θts constitutes the first steering angle, and the ACT angle θta constitutes the second steering angle.

  The ECU 14 includes a CPU 25 and a drive circuit 26. The CPU 25 outputs a motor drive signal to the drive circuit 26 by executing the control program stored in the memory 27. The drive circuit 26 supplies drive power to the motor 22 based on the motor drive signal input from the CPU 25. The motor 22 of the present embodiment is a brushless motor, and the drive circuit 26 supplies three-phase (U, V, W) drive power based on the input motor drive signal.

  That is, the ECU 14 controls the operation of the variable gear ratio actuator 13 by controlling the rotation of the motor 22 through the supply of driving power to the motor 22. Then, by changing the steering angle of the steered wheel based on the motor drive, that is, the ACT angle θta, the gear ratio of the steered wheel 8 with respect to the steering angle θs is varied (gear ratio variable control). In the present embodiment, the CPU 25 constitutes a control unit, a first detection unit, an estimation unit, a determination unit, a second detection unit, and a correction unit.

  More specifically, the steering angle sensor 31 and the wheel speed sensor 33 are connected to the ECU 14, and the CPU 25 detects the steering angle θs and the vehicle speed V based on signals input from these sensors. Further, the CPU 25 detects the steer turning angle θts by multiplying the detected steering angle θs by the gear ratio of the rack and pinion mechanism 4.

  The ECU 14 is connected to a rotation angle sensor 34 that detects the rotation of the motor 22, and the rotation angle sensor 34 outputs a pulse signal Pm to the ECU 14 in accordance with the rotation of the motor 22. The CPU 25 detects the rotational direction and rotational position of the motor 22 based on the pulse signal Pm input from the rotational angle sensor 34, and calculates the ACT angle θta based on the rotational direction and rotational position. When the ignition is turned off (when the IG is turned off), the CPU 25 stores the ACT angle θta at the time of turning off the IG in the memory 27, more specifically, the EEPROM 27a as a storage means.

  The CPU 25 determines an ACT target angle as a control target based on the detected steering angle θs (steer turning angle θts) and the vehicle speed V. The relationship between the steering angle θs and the vehicle speed V and the ACT target angle is obtained in advance by experiments, simulations, etc., and is stored in the memory 27 in the form of a three-dimensional map. The CPU 25 is based on this three-dimensional map. Then, the ACT target angle corresponding to the detected steering angle θs and the vehicle speed V is determined. Then, the CPU 25 outputs a motor drive signal to the drive circuit 26 so that the ACT angle θta follows the ACT target angle. The ACT angle θta is changed by rotating the motor 22 forward and backward based on the drive power supplied from the drive circuit 26.

Next, a start process of the gear ratio variable control in the steering device of the present embodiment will be described.
When the ignition is turned on, that is, when the ignition is started, the CPU 25 first reads out the ACT angle θta stored in the EEPROM 27a. Then, the gear ratio variable control is started with the value as the ACT angle θta at the time of activation, that is, the initial value.

  However, as described above, at startup, the ACT angle θta stored in the EEPROM 27a may be invalid, that is, the ACT angle may be invalid. In such a case, also in the steering device 1 of the present embodiment, the locked state of the gear ratio variable actuator 13 is not released from the viewpoint of fail-safe. That is, the gear ratio variable control is not started until the ACT angle θta is recognized.

  In this embodiment, when the gear ratio variable control cannot be started because the ACT angle is invalid as described above, the CPU 25 determines the tire angle (the absolute angle of the steered wheels 8 based on the vehicle state quantity detected by various sensors). Pinion angle) θt is estimated, and ACT angle θta is calculated based on the estimated tire angle θt and steer turning angle θts. Then, the CPU 25 starts the gear ratio variable control using the calculated ACT angle θta as an initial value.

  More specifically, in the present embodiment, the ECU 14 includes the steering angle sensor 31, the wheel speed sensor 33, and the rotation angle sensor 34, as well as a torque sensor 35, a yaw rate sensor 36, and an acceleration sensor for detecting steering torque. 37 is connected. Then, the CPU 25 further calculates the left and right wheel speeds Vtl, Vtr, the steering speed ωs, the steering torque τ, the yaw rate Ry, and the lateral acceleration (lateral G) Fs as vehicle state quantities based on signals input from these sensors. To detect. Then, the CPU 25 performs a straight traveling state determination process for determining whether or not the vehicle is in a straight traveling state based on the detected vehicle state quantities.

Specifically, the CPU 25
-Running (eg V> 30 km / h),
The difference in wheel speed between the two steered wheels 8 is small (for example, | Vtl−Vtr | <1 Km / hr);
-The integrated amount of the steering angle θs during the straight traveling state determination process is small (for example, | integrated amount | <3 deg),
The steering speed ωs is low (eg, | ωs | <5 deg / sec),
The yaw rate Ry is small (eg, | Ry | <1 deg / sec);
The lateral acceleration Fs is small (eg, | Fs | <0.005 Nm),
The steering torque τ is small (eg | τ | <0.5 Nm),
Each of the above condition determinations is repeated for a predetermined time (for example, 1 second), and during that time, if each of the above conditions is continuously satisfied, it is determined that the vehicle is in a straight traveling state. When the CPU 25 determines that the vehicle is in the straight traveling state in the straight traveling state determination process, the CPU 25 estimates that the tire angle θt = 0.

  Here, as shown in FIG. 6, the tire angle θt is the sum of the steering angle θts and the ACT angle θta, and the ACT angle θta is the tire angle θt−the steering angle θts. Therefore, if the tire angle θt in the straight traveling state is set to zero, an ACT angle θta that cancels the steering turning angle θts corresponding to the steering angle θs exists as shown in FIG.

  In the present embodiment, the CPU 25 calculates the ACT angle θta by subtracting the steering turning angle θts from the estimated tire angle θt when it is determined that the vehicle is in the straight traveling state in the straight traveling state determination process. That is, the ACT angle θta is calculated by the equation of ACT angle θta = 0−steer steering angle θts. When the ACT angle θta is calculated, the CPU 25 unlocks the gear ratio variable actuator 13 and starts the gear ratio variable control using the calculated ACT angle θta as an initial value.

  In the present embodiment, the ECU 14 is connected with a warning lamp 38 for notifying the vehicle occupant that the process for starting the gear ratio variable control is started, that is, that the return process is being performed. The warning lamp 38 is turned on from the start of the straight traveling state determination process until the gear ratio variable control is started. When the gear ratio variable control is started, the warning lamp 38 is turned off to notify the passenger of the completion of the return process.

Next, the processing of the CPU at the start will be described with reference to the flowchart of FIG.
At startup, the CPU 25 first determines whether or not the ACT angle is invalid (step 101). If the CPU 25 determines that the ACT angle is invalid (step 101: YES), the CPU 25 starts the return processing shown in steps 102 to 107 below. If the ACT angle θta is recognized normally (step 101: NO), the CPU 25 starts the gear ratio variable control without executing steps 102 to 107 (step 108).

  When the return process is started, the CPU 25 turns on the warning lamp 38 (step 102), and starts a straight traveling state determination process (step 103). Then, the processing of step 102 to step 104 is repeated until it is determined in step 104 that the vehicle is in a straight traveling state (step 104: YES).

  If it is determined in step 104 that the vehicle is in a straight traveling state, the CPU 25 estimates that the tire angle θt = 0 (step 105), and the ACT angle θta based on the estimated tire angle θt (θt = 0). Is calculated (step 106). Then, the warning lamp 38 is turned off (step 107), and the gear ratio variable control is started (step 108).

As described above, according to the present embodiment, the following features can be obtained.
(1) When the CPU 25 determines that the ACT angle is invalid, the CPU 25 executes a straight traveling state determination process for determining whether or not the vehicle is in a straight traveling state. If it is determined that the vehicle is traveling straight, the tire angle θt = 0 is estimated, and the ACT angle θta is calculated based on the estimated tire angle θt (θt = 0). Then, the gear ratio variable control is started with the ACT angle θta calculated by the calculation as an initial value.

  As a result, the ACT angle θta is read at startup because the ACT angle θta cannot be written to the EEPROM at the end of control due to a failure or the power supply is interrupted immediately after initialization of the EEPROM at startup. Even if this is not possible, the gear ratio variable control can be started immediately. As a result, the deviation between the steering angle θs and the tire angle θt caused by locking the variable gear ratio actuator 13 and the accompanying discomfort in the steering operation can be quickly eliminated. In addition, since it is not necessary to move the vehicle to a service factory such as a dealer and perform initialization, the convenience can be greatly improved.

  (2) The CPU 25 detects the vehicle speed V, the steering angle θs, the left and right wheel speeds Vtl, Vtr, the steering speed ωs, the steering torque τ, the yaw rate Ry, and the lateral acceleration (lateral G) detected by various sensors connected to the ECU 14. ) A straight running state determination process is performed based on Fs. That is, by performing the straight traveling state determination process based on the vehicle state amount used for vehicle control, it is possible to determine the straight traveling state of the vehicle without adding a new configuration. Therefore, the tire angle θt (θt = 0) can be estimated without causing an increase in cost.

  (3) The CPU 25 turns on the warning lamp 38 from the start of the straight traveling state determination process until the gear ratio variable control is started. With such a configuration, when the gear ratio variable actuator 13 is locked and a deviation occurs between the steering angle θs and the tire angle θt (for example, a constant steering angle despite being in a straight traveling state). Even if θs is generated or the like (see FIG. 2), it is notified that the return process is being performed, so that the passenger's anxiety can be alleviated. Furthermore, before the gear ratio variable control is started, the completion of the return process is notified to the passenger by turning off the warning lamp 38. Therefore, even when the steering feeling changes due to the start of the gear ratio variable control, The uncomfortable feeling at that time can be relieved.

In addition, you may change each said embodiment as follows.
In the present embodiment, when the CPU 25 determines that the vehicle is in the straight traveling state by the straight traveling state determination process, it is assumed that the tire angle θt = 0. However, the present invention is not limited to this, and the tire angle θt may be estimated as the maximum angle when the steering 2 is operated to the steering end (lock-to-lock end position). Alternatively, the tire angle θt may be directly measured.

  In the present embodiment, the CPU 25 determines the vehicle speed V, the left and right wheel speeds Vtl, Vtr, the steering angle θs, the steering speed ωs, the steering torque τ, the yaw rate Ry, and the lateral acceleration (lateral G) Fs in the straight traveling state determination process. Used as vehicle state quantity. However, the present invention is not limited to this, and parameters used as vehicle state quantities in the straight traveling state determination process, such as performing straight traveling state determination based on the vehicle speed V, the left and right wheel speeds Vtl, Vtr, the steering angle θs, and the steering speed ωs, and combinations thereof May be set arbitrarily. Moreover, you may set the threshold value in each condition determination arbitrarily. The steering torque τ is used as the vehicle state quantity when the electric power steering device (EPS), the yaw rate Ry and the lateral acceleration (lateral G) Fs are provided with the side slip prevention device (ESP). More accurate determination can be performed without inviting.

  In the present embodiment, the gear ratio variable control is started immediately after calculating the ACT angle θta in step 106. However, the present invention is not limited to this, for example, the gear ratio variable control is not started until the vehicle speed is equal to or lower than the predetermined speed by the vehicle speed determination, or the gear ratio variable control is not started at the time of restart after running, that is, until the next trip, etc. The condition determination may be performed as a premise for starting the gear ratio variable control.

  In the present embodiment, the warning lamp 38 is provided as a notification means. However, a notification may be made using a display of a car navigation system, an in-vehicle TV, or the like, or a notification may be made by voice.

  In the present embodiment, when it is determined that the vehicle is in the straight traveling state, the tire angle θt = 0 is estimated in step 105, and in the next step 106, based on the estimated tire angle θt (θt = 0). The ACT angle θta was calculated (see FIG. 3). However, the present invention is not limited to this, and as shown in FIG. 4, when the tire angle θt = 0 is estimated in step 205, the tire angle θt is further corrected based on the steering torque τ (step 205a). The ACT angle θta may be calculated based on the tire angle θt. With such a configuration, a more accurate ACT angle θta can be calculated.

  The correction calculation of the tire angle θt based on the steering torque τ is easily performed by, for example, storing the relationship between the steering torque τ and the vehicle speed V and the tire angle θt in the form of a map in the memory 27 and referring to the map. It is feasible. Further, steps (step 201 to step 208) other than step 205a in FIG. 4 are the same as the steps (steps 101 to 108) of this embodiment shown in FIG.

  In the present embodiment, the variable gear ratio actuator 13 is provided on the steering shaft 3, but may be embodied as a rack type variable gear ratio actuator provided on the rack 5.

The schematic block diagram of the steering device of this embodiment. Explanatory drawing which shows the relationship between the tire angle and ACT angle in gear ratio variable control. The flowchart which shows the process of CPU at the time of a start. The flowchart which shows the process of CPU at the time of the start of another example. Explanatory drawing of gear ratio variable control. Explanatory drawing of gear ratio variable control.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 2 ... Steering wheel (steering), 8 ... Steering wheel, 13 ... Variable gear ratio actuator, 14 ... ECU, 22 ... Motor, 25 ... CPU, 31 ... Steering angle sensor, 33 ... Wheel speed sensor, 34 ... rotation angle sensor, 35 ... torque sensor, 36 ... yaw rate sensor, 37 ... acceleration sensor, θs ... steering angle, θt ... tire angle (pinion angle), θts ... steer steering angle (first steering angle), θta ... ACT angle (second steering angle), V: vehicle speed, Vtl, Vtr: wheel speed, ωs: steering speed, τ: steering torque, Ry: yaw rate, Fs: lateral acceleration (lateral G).

Claims (4)

Transmission that varies the transmission ratio of the steering wheel with respect to the steering angle of the steering wheel by adding the second steering angle of the steering wheel based on the motor drive to the first steering angle of the steering wheel based on the steering angle of the steering wheel A variable ratio device, control means for controlling the variable transmission ratio device, and storage means for storing the second steering angle at the end of the control, wherein the control means stores the stored second steering angle. Is a vehicle steering device that starts control to vary the transmission ratio with an initial value as an initial value,
First detection means for detecting the first steering angle;
An estimation means for estimating an absolute angle of the steered wheel based on a vehicle state quantity used for vehicle control ;
When the stored second steering angle is invalid, the control means initially sets a second steering angle calculated based on the estimated absolute angle of the steered wheel and the first steering angle. A vehicle steering apparatus characterized by starting control for varying the transmission ratio as a value. The vehicle steering apparatus according to claim 1,
A determination means for determining whether or not the vehicle is in a straight traveling state based on a vehicle state quantity used for vehicle control ;
The estimation device estimates the absolute angle of the steered wheels to be zero when it is determined that the vehicle is in the straight traveling state. In the vehicle steering device according to claim 1 or 2,
Second detection means for detecting steering torque;
A vehicle steering apparatus comprising: correction means for correcting the estimated absolute angle of the steered wheel based on the detected steering torque. In the vehicle steering device according to claim 1,
A vehicle steering apparatus comprising: a notification means for notifying that a return process for starting the control until the transmission ratio is varied is started.

Images