JP5862113B2 - Vehicle steering control apparatus and steering control method - Google Patents

Description

  The present invention steers a steered wheel to a target steered angle according to the operation of the steered wheel via a steered motor in a state where the torque transmission path between the steered wheel and the steered wheel is mechanically separated. The present invention relates to a vehicle steering control device and a steering control method.

  Conventionally, with the torque transmission path between the steered wheel (steering wheel) and the steered wheel mechanically separated, the steered wheel is moved to the target steered angle according to the operation of the steered wheel via the steered motor. There is a steering control device for turning. Such a steering control device generally forms a system (SBW system) referred to as steer-by-wire (SBW: Steer By Wire, which may be described as “SBW” in the following description). For example, it is described in Patent Document 1.

  The steering control device described in Patent Literature 1 is a clutch that is interposed between a steered wheel and a steered wheel when a state in which the temperature of the steered motor exceeds a preset threshold temperature continues for a preset predetermined time. Is switched from the open state to the fastened state, and the torque transmission path is mechanically coupled. For example, this occurs when a high load is applied to the steering motor and the steering motor is overheated, such as when steering at a large steering angle is repeated.

JP 2003-252227 A

However, in the steering control device described in Patent Document 1, when the steered motor is overheated, the clutch in the opened state is switched to the engaged state to mechanically connect the torque transmission path, and the drive control of the steered motor is stopped. Therefore, there is a possibility that a problem that the steering torque borne by the driver increases may occur.
The present invention has been made paying attention to the above problems, and suppresses an increase in steering torque borne by the driver even when the torque transmission path is mechanically coupled when the steering motor is overheated. It is an object of the present invention to provide a steering control device and a steering control method for a vehicle.

In order to solve the above-described problem, according to one aspect of the present invention, it is determined whether or not the temperature of a turning motor that outputs a turning torque for turning a turning wheel exceeds a preset temperature. And if it determines with the temperature of a steering motor exceeding the preset temperature, a clutch of an open state will be switched to a fastening state, and a torque transmission path will be connected mechanically. In addition to this, the drive control of the steering motor that controls the steering torque to the target turning angle corresponding to the operation of the steered wheels is continued.
Further, when the clutch in the released state is switched to the engaged state, the turning torque is corrected to be reduced from that in the normal state, and the drive control of the turning motor and the output of the turning torque are continued. In addition to this, it is a torque that compensates for the reduction correction of the steering torque, and calculates a steering assist torque that acts in the same direction as the operation direction so as to assist the operation of the steered wheels. Further, the calculated steering assist torque is output by the reaction force motor.

According to the present invention, when the steering motor is overheated, the steering motor is controlled in order to continue the drive control of the steering motor even after the clutch in the opened state is switched to the engaged state and the torque transmission path is mechanically coupled. It is possible to suppress the load on the steering operation by the driver.
As a result, when the steering motor is overheated, an increase in steering torque borne by the driver can be suppressed even if the clutch in the released state is switched to the engaged state and the torque transmission path is mechanically coupled.

1 is a diagram illustrating a schematic configuration of a vehicle including a steering control device according to a first embodiment of the present invention. It is a block diagram which shows schematic structure of the steering control apparatus of 1st embodiment of this invention. It is a flowchart which shows the process which the steering control apparatus of 1st embodiment of this invention performs. It is a flowchart which shows the process which the steering control apparatus of the modification of this invention performs.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
(Constitution)
FIG. 1 is a diagram illustrating a schematic configuration of a vehicle including a steering control device 1 according to the present embodiment. FIG. 2 is a block diagram showing a schematic configuration of the steering control device 1 of the present embodiment.
The vehicle provided with the steering control device 1 of the present embodiment is a vehicle to which the SBW system is applied.
Here, in the SBW system, the driving direction of the steered wheel is controlled by driving the steered motor in accordance with the operation of the steered wheel that the driver of the vehicle steers, thereby changing the traveling direction of the vehicle. . The drive control of the steered motor is achieved by switching the clutch interposed between the steered wheels and the steered wheels to the open state, which is the normal state, and mechanically separating the torque transmission path between the steered wheels and the steered wheels. Perform in the state.

For example, when an abnormality occurs in a part of the SBW system, such as disconnection, the clutch is switched to the engaged state and the torque transmission path is mechanically connected, so that the driver can move the steering wheel. Steering of the steered wheels is continued using the applied force.
As shown in FIGS. 1 and 2, the steering control device 1 of the present embodiment includes a steered motor 2, a steered motor control unit 4, a clutch 6, a reaction force motor 8, and a reaction force motor control unit. 10 is provided.

The steered motor 2 is a motor that is driven according to the steered motor drive current output by the steered motor control unit 4 and has a steerable motor output shaft 12 that can rotate. The steered motor 2 outputs a steered torque for turning steered wheels by being driven according to the steered motor drive current.
A gear (not shown) is provided on the distal end side of the steered motor output shaft 12, and this gear meshes with the rack gear 14.

The steered motor 2 is provided with a steered motor angle sensor 16.
The steered motor angle sensor 16 detects the rotation angle (steering angle) of the steered motor 2, and this detected rotational angle (in the following description, may be described as “steering motor rotational angle”). The included information signal is output to the reaction force motor control unit 10 via the steered motor control unit 4.
The rack gear 14 has a rack shaft 18 that is displaced in the vehicle width direction in accordance with the rotation of the steered motor output shaft 12.

Both ends of the rack shaft 18 are connected to the steered wheels 24 via tie rods 20 and knuckle arms 22, respectively. A tire axial force sensor 26 is provided between the rack shaft 18 and the tie rod 20.
The tire axial force sensor 26 detects an axial force that acts in the axial direction (vehicle width direction) of the rack shaft 18, and this detected axial force (may be described as “tire axial force” in the following description). Is output to the reaction force motor control unit 10.

  The steered wheels 24 are front wheels (left and right front wheels) of the vehicle. When the rack shaft 18 is displaced in the vehicle width direction according to the rotation of the steered motor output shaft 12, the steered wheels 24 are steered via the tie rods 20 and the knuckle arms 22. Change the direction of travel of the vehicle. In the present embodiment, a case where the steered wheels 24 are formed of left and right front wheels will be described. Accordingly, in FIG. 1, the steered wheel 24 formed with the left front wheel is denoted as steered wheel 24L, and the steered wheel 24 formed with the right front wheel is denoted as steered wheel 24R.

The steered motor control unit 4 inputs and outputs information signals through the reaction force motor control unit 10 and a communication line 28 such as a CAN (Controller Area Network).
The steered motor control unit 4 includes a steered position servo control unit 30.
The steered position servo control unit 30 calculates a steered motor drive current for driving the steered motor 2, and outputs the calculated steered motor drive current to the steered motor 2.

Here, the steered motor drive current controls the steered torque described above, calculates a target steered angle target steered angle according to the operation of the steered wheels, and steers according to the calculated target steered angle. This is a current for driving and controlling the rudder motor 2.
The calculation of the turning motor drive current is performed by calculating a turning motor current command output by the reaction force motor control unit 10 and a command value (hereinafter referred to as a turning motor actual current) energizing the turning motor 2. In the description, it may be described as “steering motor current command It”. Specifically, the steering motor current command is corrected using the steering motor current command It, and the steering motor drive current is calculated.

  Further, the steered position servo control unit 30 measures the steered motor current command It, and estimates the temperature Tt of the steered motor 2 based on the measured steered motor current command It. Then, an information signal including the estimated temperature Tt of the steered motor 2 is output to the reaction force motor control unit 10. This is because overheating of the motors (the steered motor 2 and the reaction force motor 8) is often caused by resistance heat generation due to current application.

The steered motor current command It is measured, for example, by incorporating a substrate temperature sensor (not shown) in the steered motor 2 and using the incorporated substrate temperature sensor.
Here, as a method for estimating the temperature Tt of the steered motor 2 based on the steered motor current command It, for example, in a large current region, the steered motor current command It is obtained using the measured actual current value. . Specifically, the measured actual current value is compared with the current threshold value stored in advance, and when the measured actual current value is larger than the current threshold value, the measured actual current value is converted into the steering motor. Adopted as current command It.

  On the other hand, in the small current region, the steered motor current command It is estimated based on the rotational speed of the steered motor 2 using the motor NT characteristic that defines the relationship between the rotational speed of the steered motor 2 and the torque. Specifically, the measured current value is not adopted as the steering motor current command It, and the current value estimated based on the rotation speed of the steering motor 2 using the motor NT characteristic is used as the steering motor current command. It is adopted as It.

Then, the temperature Tt of the steered motor 2 is estimated using the steered motor current command It adopted as described above.
The clutch 6 is interposed between the steering wheel 32 (steering wheel) operated by the driver and the steered wheel 24, and is brought into an open state or an engaged state according to a clutch driving current output from the reaction force motor control unit 10. Switch. Note that the clutch 6 is in an open state in a normal state.

  Here, when the state of the clutch 6 is switched to the released state, the torque transmission path between the steered wheels 32 and the steered wheels 24 is mechanically separated, and the steering operation of the steered wheels 32 is not transmitted to the steered wheels 24. And On the other hand, when the state of the clutch 6 is switched to the engaged state, the torque transmission path between the steering wheel 32 and the steered wheel 24 is mechanically coupled, and the steering operation of the steered wheel 32 is transmitted to the steered wheel 24. And

A steering angle sensor 34, a steering torque sensor 36, a reaction force motor 8, and a reaction force motor angle sensor 38 are disposed between the steering wheel 32 and the clutch 6.
For example, the steering angle sensor 34 is provided in a steering column that rotatably supports the steering wheel 32.
Further, the steering angle sensor 34 detects a current steering angle that is a current rotation angle (steering operation amount) of the steering wheel 32. Then, the steering angle sensor 34 outputs an information signal including the detected current steering angle of the steering wheel 32 to the reaction force motor control unit 10. In the following description, the current steering angle may be described as “current steering angle θ”.

Here, recent vehicles often include a sensor that can detect the steering angle of the steered wheels 32 as a standard. For this reason, in this embodiment, the case where the sensor which can detect the steering angle of the steering wheel 32 which is an existing sensor in the vehicle is used as the steering angle sensor 34 will be described.
Similar to the steering angle sensor 34, the steering torque sensor 36 is provided, for example, in a steering column that rotatably supports the steering wheel 32.

The steering torque sensor 36 detects a steering torque that is a torque applied by the driver to the steered wheels 32. Then, the steering torque sensor 36 outputs an information signal including the detected steering torque to the reaction force motor control unit 10. In the following description, the steering torque may be described as “torque sensor value Vts”.
The reaction force motor 8 and the reaction force motor angle sensor 38 will be described later.

  The clutch 6 has a pair of clutch plates 40 that are separated from each other in the opened state and mesh with each other in the engaged state. In FIG. 1 and the following description, of the pair of clutch plates 40, the clutch plate 40 disposed on the steering wheel 32 side is referred to as a “steering wheel side clutch plate 40a”, and the clutch plate disposed on the steered wheel 24 side. 40 is referred to as a “steered wheel side clutch plate 40b”.

The steering wheel side clutch plate 40 a is attached to the steering shaft 42 that rotates together with the steering wheel 32, and rotates together with the steering shaft 42.
The steered wheel side clutch plate 40 b is attached to one end of the pinion shaft 44 and rotates together with the pinion shaft 44.
The other end of the pinion shaft 44 is disposed in the pinion 46. The pinion 46 incorporates a pinion gear (not shown) that meshes with the rack gear 14.

The pinion gear rotates together with the pinion shaft 44. That is, the pinion gear rotates together with the steered wheel side clutch plate 40 b via the pinion shaft 44.
The pinion 46 is provided with a pinion angle sensor 48.
The pinion angle sensor 48 detects the rotation angle of the pinion gear, and outputs an information signal including the detected rotation angle (may be described as “pinion rotation angle” in the following description) to the reaction force motor control unit 10. Output to.

  The reaction force motor 8 is a motor that is driven in accordance with a reaction force motor drive current output from the reaction force motor control unit 10, and rotates a steering shaft 42 that rotates together with the steering wheel 32 to apply a steering reaction force to the steering wheel 32. Can be output. Here, the steering reaction force output from the reaction force motor 8 to the steering wheel 32 switches the clutch 6 to the released state, and mechanically separates the torque transmission path between the steering wheel 32 and the steered wheel 24. In this state, calculation is performed according to the tire axial force acting on the steered wheels 24 and the steering state of the steered wheels 32. Thereby, an appropriate steering reaction force is transmitted to the driver who steers the steered wheels 32. That is, the steering reaction force output from the reaction force motor 8 to the steered wheels 32 is a reaction force acting in a direction opposite to the operation direction in which the driver steers the steered wheels 32.

The reaction force motor angle sensor 38 is a sensor provided in the reaction force motor 8.
The reaction force motor angle sensor 38 detects the rotation angle (steering angle) of the reaction force motor 8 and may describe this detected rotation angle (hereinafter referred to as “reaction force motor rotation angle”). ) Is output to the reaction force motor control unit 10.
The reaction force motor control unit 10 inputs and outputs information signals via the steering motor control unit 4 and the communication line 28. In addition, the reaction force motor control unit 10 receives input of information signals output from the vehicle speed sensor 50 and the engine controller 52 via the communication line 28.

In addition, the reaction force motor control unit 10 drives and controls the reaction force motor 8 based on information signals received via the communication line 28 and information signals received from various sensors.
The vehicle speed sensor 50 is, for example, a known vehicle speed sensor, detects the vehicle speed of the vehicle, and outputs an information signal including the detected vehicle speed to the reaction force motor control unit 10.
The engine controller 52 (engine ECU) outputs an information signal including the state of the engine (not shown) (engine drive or engine stop) to the reaction force motor control unit 10.

In addition, the reaction force motor control unit 10 includes a command calculation unit 54, a reaction force servo control unit 56, and a clutch control unit 58.
The command calculation unit 54 outputs the vehicle speed sensor 50, the steering angle sensor 34, the engine controller 52, the steering torque sensor 36, the reaction force motor angle sensor 38, the pinion angle sensor 48, the tire axial force sensor 26, and the turning motor angle sensor 16. Received information signal input.
In addition, the command calculation unit 54 calculates a reaction force motor current command based on various information signals received. Then, the command calculation unit 54 outputs the calculated reaction force motor current command to the reaction force servo control unit 56.

In addition, the command calculation unit 54 calculates a steering motor current command based on the various information signals received. Then, the command calculation unit 54 outputs the calculated turning motor current command to the turning position servo control unit 30.
Further, the command calculation unit 54 calculates a clutch current command based on various information signals received. Then, the command calculation unit 54 outputs the calculated clutch current command to the clutch control unit 58.

Hereinafter, calculation of various current commands performed by the command calculation unit 54 will be described.
(Calculation of reaction force motor current command)
The reaction force motor current command is calculated, for example, by multiplying the turning motor rotation angle θt by a preset reaction force motor gain Gh based on information signals output from the vehicle speed sensor 50 and the turning motor angle sensor 16. Do.
Here, the reaction force motor gain Gh is set in advance using a reaction force motor gain map. The reaction motor gain map is a map that depends on the vehicle speed, and is formed in advance and stored in the command calculation unit 54.
That is, when the reaction force motor current command is defined as “Ih ′”, the reaction force motor current command Ih ′ is calculated by the following equation (1).
Ih ′ = θt × Gh (1)

(Calculation of steering motor current command)
The calculation of the steering motor current command is performed, for example, by multiplying the current steering angle θ by a preset steering motor gain Gt based on information signals output from the vehicle speed sensor 50 and the steering angle sensor 34.
Here, the steering motor gain Gt is set in advance using a steering motor gain map. The steered motor gain map is a map that depends on the vehicle speed, and is formed in advance and stored in the command calculation unit 54.
That is, when the steering motor current command is defined as “It ′”, the steering motor current command It ′ is calculated by the following equation (2).
It ′ = θ × Gt (2)

(Calculation of clutch current command)
The calculation of the clutch current command is performed using, for example, the temperature Tt of the steered motor 2 estimated by the steered motor control unit 4 and the clutch engagement temperature St1.
Specifically, first, the temperature Tt of the steered motor 2 estimated by the steered motor control unit 4 and the clutch engagement temperature St1 are compared with the clutch 6 switched to the released state, It is determined whether or not the temperature Tt exceeds the clutch engagement temperature St1.

Here, the clutch engagement temperature St1 is a temperature that is a preset temperature difference lower than a use limit temperature at which it is difficult to normally use the steered motor 2 (normal state, normal control). It is stored in the command calculation unit 54.
In addition, said use limit temperature is set using the rating preset to the steering motor 2, "JIS C 4003" etc., for example.

In the present embodiment, as an example, a case will be described in which the clutch engagement temperature St1 is set to a temperature that is 10 [° C.] lower than the use limit temperature of the steered motor 2. That is, in the present embodiment, as an example, a case where the preset temperature difference is set to “10 [° C.]” will be described.
When it is determined that the temperature Tt of the steered motor 2 exceeds the clutch engagement temperature St1, a command signal for switching the clutch 6 in the released state (normal state) to the engaged state is calculated, and the calculated command signal is Use current command.
The command calculation unit 54 also calculates a command signal for switching the engaged clutch 6 to the released state in accordance with the temperature Tt of the steered motor 2.

The reaction force servo control unit 56 outputs a reaction force motor drive current for driving the reaction force motor 8 to the reaction force motor 8.
Further, the reaction force servo control unit 56 may describe the value of the current (reaction force motor actual current) that is actually energized to the reaction force motor 8 (in the following description, “reaction force motor current value Ih”). Measure).
Here, the calculation of the reaction force motor drive current is performed based on the turning motor current command output from the command calculation unit 54 and the reaction force motor current value It. Specifically, the reaction force motor current command is corrected using the reaction force motor current value Ih, and the reaction force motor drive current is calculated.

Further, the reaction force servo control unit 56 estimates the temperature Th of the reaction force motor 8 based on the measured reaction force motor current value Ih. The estimation of the temperature Th of the reaction force motor 8 is performed in the same procedure as the estimation of the temperature Tt of the turning motor 2 performed by the turning position servo control unit 30, for example.
Based on the clutch current command output from the command calculation unit 54, the clutch control unit 58 calculates a current required for switching the clutch 6 in the released state to the engaged state as a clutch drive current. Then, the calculated clutch drive current is output to the clutch 6.

Hereinafter, an example of an operation performed by the steering control device 1 of the present embodiment will be described with reference to FIGS. 1 and 2 and FIG. 3.
FIG. 3 is a flowchart showing processing performed by the steering control device 1 of the present embodiment.
The flowchart shown in FIG. 3 starts from a state where the driver of the vehicle has started the engine (engine ON) (“START” shown in FIG. 3). When the engine is started, an information signal including the engine driving state is output from the engine controller 52 to the reaction force motor control unit 10. Then, the command calculation unit 54 that receives the input of the information signal including the engine driving state operates the steering control device 1. Note that when the steering control device 1 is operated, the clutch 6 is opened (normal state), and the torque transmission path between the steered wheels 32 and the steered wheels 24 is mechanically separated.

  When the steering control device 1 is operated, the steered position servo control unit 30 estimates the temperature Tt of the steered motor 2, and the reaction force servo control unit 56 estimates the temperature Th of the reaction force motor 8 (shown in step S100 " Tt, Th estimation "). Then, the turning position servo control unit 30 outputs an information signal including the estimated temperature Tt to the command calculation unit 54, and the reaction force servo control unit 56 outputs an information signal including the estimated temperature Th to the command calculation unit 54. Output. When the temperature Tt and the temperature Th are estimated in step S100, the process performed by the steering control device 1 proceeds to step S102.

In step S102, the command calculation unit 54 compares the temperature Tt of the steered motor 2 with the clutch engagement temperature St1, and determines whether or not the temperature Tt of the steered motor 2 exceeds the clutch engagement temperature St1 (step S102). "Tt>St1?" Here, the process of step S102 is performed with the clutch 6 in the released state (normal state).
If it is determined in step S102 that the temperature Tt is equal to or higher than the clutch engagement temperature St1 ("No" shown in the figure), the processing performed by the steering control device 1 proceeds to step S104.

On the other hand, if it is determined in step S102 that the temperature Tt exceeds the clutch engagement temperature St1 ("Yes" shown in the figure), the processing performed by the steering control device 1 proceeds to step S106.
In step S104, both the steered motor control unit 4 and the reaction force motor control unit 10 perform normal control ("normal control" shown in step S104). Here, the normal control means that the steering motor 2 is driven on the basis of the operation of the steering wheel 32 and the reaction force motor is used to transmit an appropriate steering reaction force to the driver who steers the steering wheel 32. 8 is a drive control. Further, the control at the normal time is performed in a state where the clutch 6 is maintained in the released state.

In step S104, when the steered motor control unit 4 and the reaction force motor control unit 10 perform normal control, the process performed by the steering control device 1 returns to the process of step S100 ("RETURN" shown in FIG. 3). )).
In step S106, the command calculation unit 54 calculates a clutch current command for switching the clutch 6 in the released state to the engaged state, and calculates a value Ic ′ of the clutch drive current as “0” (“clutch engagement: Ic shown in step S106). '= 0'). Thereby, the clutch 6 in the released state is switched to the engaged state, and the torque transmission path between the steered wheel 32 and the steered wheel 24 is mechanically coupled. In step S106, when the released clutch 6 is switched to the engaged state, the process performed by the steering control device 1 proceeds to step S108.

Therefore, in step S106, when the clutch control unit 58 determines that the temperature Tt of the steered motor 2 exceeds the clutch engagement temperature St1, a process of switching the released clutch 6 to the engagement state is performed.
In step S108, the command calculation unit 54 determines the steering motor current command at the time of high temperature (when the steering motor 2 is overheated, the same applies to the following description) (in the following description, “high-temperature steering motor current command It_k ′”). May be written).

Here, the high-temperature steering motor current command It_k ′ is calculated by the following equation (3).
It_k ′ = Vts × Gt1−It1 ′ (3)
In the above formula (3), the steering motor gain at a high temperature is indicated as a high temperature steering motor gain Gt1. The high-temperature steering motor gain Gt1 is set in advance using a high-temperature steering motor gain map and is stored in the command calculation unit 54. Note that the high-temperature steering motor gain map is a map that depends on the vehicle speed, and is formed in advance and stored in the command calculation unit 54.

  Moreover, in said Formula (3), the electric current value used for the calculation of the high temperature turning motor electric current command It_k 'is shown as a turning motor subtraction electric current value It1'. Note that the turning motor subtraction current value It1 ′ is set to 10 [A] in advance, for example, when the current supplied to the turning motor 2 is 60 [A] in the normal control (see step S104). And stored in the command calculation unit 54.

That is, in step S108, the high-temperature steering motor current command It_k ′ is calculated as the steering motor current command It ′ (“It ′ = It_k ′ = Vts × Gt1−It1 ′” shown in step S108). In step S108, when the high-temperature steering motor current command It_k ′ is calculated, the processing performed by the steering control device 1 proceeds to step S110.
Therefore, in step S108, when the clutch control unit 58 switches the clutch 6 in the released state to the engaged state, the steered motor control unit 4 performs processing for continuing the drive control of the steered motor 2.

In addition, in step S108, when the clutch control unit 58 switches the clutch 6 in the released state to the engaged state, the steered motor control unit 4 performs a process of correcting the steered torque to be lower than that in the normal state.
In step S110, the command calculation unit 54 calculates a reaction force motor current command at high temperature (in the following description, it may be described as “high temperature reaction force motor current command Ih_k ′”).

Here, the high-temperature reaction force motor current command Ih_k ′ is calculated according to the following procedure.
First, the steered motor subtraction torque TRt1 ′ is calculated by the following equation (4). Note that the steered motor subtraction torque TRt1 ′ is a value obtained by subtracting, for example, torque for suppressing overheating of the steered motor 2 from torque output by the steered motor 2 in normal control. The steered motor subtraction torque TRt1 ′ is a torque converted to the steering angle of the steered wheels 32.
TRt1 ′ = It1 ′ × TTt (4)
In the above formula (4), the steering motor torque constant, which is a preset torque constant, is indicated as “TTt”.

Next, a high-temperature reaction force motor current command Ih_k ′, which is a reaction force motor current command Ih ′ for causing the reaction force motor 8 to generate a torque equivalent to the turning motor subtraction torque TRt1 ′, is expressed by the following equation (5). Calculate using.
Ih_k ′ = TRt1 ′ / TTh (5)
In the above equation (5), a reaction force motor torque constant, which is a preset torque constant, is indicated as “TTh”.

  Here, the sign (+, −) of the high temperature reaction force motor current command Ih_k ′ is set in the same direction as the sign (+, −) of the high temperature turning motor current command It_k ′. This is because the torque generated by the reaction force motor 8 is used as torque (steering assist torque) for assisting (assisting) the steering operation of the steered wheels 32. The steering assist torque is torque that acts in the same direction as the operation direction so as to assist the driver in operating the steered wheels 32.

  That is, in step S110, a high-temperature reaction force motor current command Ih_k ′ is calculated as the reaction force motor current command Ih ′ (“TRt1 ′ = It1 ′ × TTt”, “Ih ′ = Ih_k ′ = TRt1 ′ shown in step S110). / TTh "). Thereby, in step S110, the process of outputting the steering assist torque for assisting the operation of the steered wheels 32 with the reaction force motor 8 in a state where the clutch 6 in the released state is switched to the engaged state. When the high-temperature reaction force motor current command Ih_k ′ is calculated in step S110, the process performed by the steering control device 1 proceeds to step S112.

Accordingly, in step S110, when the clutch control unit 58 switches the clutch 6 in the released state to the engaged state, the reaction force motor control unit 10 outputs the steering assist torque that assists the operation of the steered wheels 32 by the reaction force motor 8. To do.
In addition, in step S110, a process of calculating the steering assist torque that assists the operation of the steerable wheels 32 as a torque having the same or substantially the same magnitude as the turning torque that is corrected to be decreased from the normal state is performed.

In step S112, the command calculation unit 54 compares the temperature Tt of the steered motor 2 with the stop threshold temperature St of the steered motor 2, and determines whether the temperature Tt of the steered motor 2 exceeds the stop threshold temperature St. Is determined ("Tt>St?" Shown in step S112).
Here, the stop threshold temperature St of the steered motor 2 is a temperature lower than a use limit temperature at which the steered motor 2 is difficult to drive normally, and is a temperature higher than the clutch engagement temperature St1. It is set and stored in the command calculation unit 54.

If it is determined in step S112 that the temperature Tt is equal to or higher than the stop threshold temperature St ("No" shown in the figure), the processing performed by the steering control device 1 proceeds to step S114.
On the other hand, if it is determined in step S112 that the temperature Tt exceeds the stop threshold temperature St (“Yes” shown in the figure), the processing performed by the steering control device 1 proceeds to step S116.

Note that the processing performed in step S114 will be described later.
In step S116, the command calculation unit 54 sets the high-temperature steering motor current command It_k ′ used as the steering motor current command It ′ to “0” (“It ′ = It_k ′ = 0” shown in step S116). Although not specifically shown, drive control of the reaction force motor 8 is continued. In step S116, when the high-temperature steering motor current command It_k ′ is set to “0”, the processing performed by the steering control device 1 proceeds to step S118.

In step S118, the command calculation unit 54 compares the temperature Th of the reaction force motor 8 with the stop threshold temperature Sh of the reaction force motor 8, and determines whether or not the temperature Th of the reaction force motor 8 exceeds the stop threshold temperature Sh. (“Th> Sh?” Shown in step S118).
Here, the stop threshold temperature Sh of the reaction force motor 8 is a temperature lower than the use limit temperature at which the reaction force motor 8 is difficult to drive normally, and is preset and stored in the command calculation unit 54. deep.

If it is determined in step S118 that the temperature Th is equal to or higher than the stop threshold temperature Sh ("No" shown in the figure), the processing performed by the steering control device 1 proceeds to step S120.
On the other hand, if it is determined in step S118 that the temperature Th exceeds the stop threshold temperature Sh (“Yes” shown in the figure), the processing performed by the steering control device 1 proceeds to step S122.

In step S122, the command calculation unit 54 sets the high-temperature reaction force motor current command Ih_k ′ used as the reaction force motor current command Ih ′ to “0” (“Ih ′ = Ih_k ′ = 0” shown in step S122). If the high-temperature reaction force motor current command Ih_k ′ is set to “0” in step S122, the process performed by the steering control device 1 proceeds to step S130.
In step S114, as in step S118, the command calculation unit 54 compares the temperature Th of the reaction force motor 8 with the stop threshold temperature Sh of the reaction force motor 8, and the temperature Th of the reaction force motor 8 sets the stop threshold temperature Sh. It is determined whether or not it exceeds (“Th> Sh?” Shown in step S114).

If it is determined in step S114 that the temperature Th is equal to or higher than the stop threshold temperature Sh ("No" shown in the figure), the processing performed by the steering control device 1 proceeds to step S120.
On the other hand, if it is determined in step S114 that the temperature Th exceeds the stop threshold temperature Sh ("Yes" shown in the figure), the processing performed by the steering control device 1 proceeds to step S124.

Note that the processing performed in step S120 will be described later.
In step S124, as in step S122, the command calculation unit 54 sets the high-temperature reaction force motor current command Ih_k ′ used as the reaction force motor current command Ih ′ to “0” (“Ih ′ = Ih_k ′ shown in step S124). = 0 "). If the high-temperature reaction force motor current command Ih_k ′ is set to “0” in step S124, the process performed by the steering control device 1 proceeds to step S126.

In step S126, the command calculation unit 54 calculates the high-temperature steering motor current command It_k ′ used as the steering motor current command It ′ by the following equation (6).
It_k ′ = Vts × Gt1 (6)
That is, in step S126, unlike step S108 described above, the high-temperature steering motor current command It_k ′ is calculated without using the steering motor subtraction current value It1 ′ (“It ′ = It_k ′ = Vts shown in step S108). × Gt1 ”). When the high-temperature steering motor current command It_k ′ is calculated in step S126, the processing performed by the steering control device 1 proceeds to step S120.

In step S120, the command calculation unit 54 compares the temperature Tt of the steered motor 2 with the stop threshold temperature St of the steered motor 2, and determines whether the temperature Tt of the steered motor 2 exceeds the stop threshold temperature St. ("Tt>St?" Shown in step S120).
If it is determined in step S120 that the temperature Tt is equal to or higher than the stop threshold temperature St ("No" shown in the figure), the processing performed by the steering control device 1 proceeds to step S130.

On the other hand, if it is determined in step S120 that the temperature Tt exceeds the stop threshold temperature St (“Yes” shown in the figure), the processing performed by the steering control device 1 proceeds to step S128.
In step S128, the command calculation unit 54 sets the high-temperature steering motor current command It_k ′ used as the steering motor current command It ′ to “0” (“It ′ = It_k ′ = 0” shown in step S128). In step S128, when the high-temperature steering motor current command It_k ′ is set to “0”, the processing performed by the steering control device 1 proceeds to step S130.

  In step S130, the command calculation unit 54 compares the temperature Tt of the steered motor 2 with the control return threshold temperature St2 of the steered motor 2, and the temperature Th of the reaction force motor 8 and the control return threshold of the reaction force motor 8 are compared. The temperature Sh1 is compared. Then, it is determined whether or not the temperature Tt of the steered motor 2 exceeds the control return threshold temperature St2, and whether or not the temperature Th of the reaction force motor 8 exceeds the control return threshold temperature Sh1 (“Tt shown in step S130”). > St2? And Th> Sh1? ").

  Here, the control return threshold temperature St2 of the steered motor 2 is a temperature lower than the above-described clutch engagement temperature St1, and is preset and stored in the command calculation unit 54. Further, the control return threshold temperature Sh1 of the reaction force motor 8 is lower than the stop threshold temperature Sh described above, and is set in advance and stored in the command calculation unit 54. The reason why the control return threshold temperature St2 is set to a temperature lower than the clutch engagement temperature St1 and the reason why the control return threshold temperature Sh1 is set to a temperature lower than the stop threshold temperature Sh are both to have hysteresis.

  If it is determined in step S130 that the temperature Tt is equal to or lower than the control return threshold temperature St2 and the temperature Th is the control return threshold temperature Sh1 ("No" shown in the drawing), the process performed by the steering control device 1 is as follows. The process proceeds to S104. As a result, the clutch 6 in the engaged state is switched to the disengaged state, and the steering motor control unit 4 and the reaction force motor control unit 10 are controlled at the normal time, so that the process performed by the steering control device 1 is performed at the normal time. Return to control at.

  On the other hand, if it is determined in step S130 that two conditions are satisfied (“Yes” shown in the drawing), the processing performed by the steering control device 1 returns to the processing in step S100 (“RETURN” shown in FIG. 3). )). Here, the “two conditions” determined in step S130 are that the temperature Tt exceeds the control return threshold temperature St2 and that the temperature Th exceeds the control return threshold temperature Sh1.

(Operation)
Next, an example of the operation performed by the steering control device 1 of the present embodiment will be described with reference to FIGS. 1 to 3.
As described above, when the steering control device 1 is operated, the temperature Tt of the steered motor 2 and the temperature Th of the reaction motor 8 are estimated, and the steered motor is switched in a state in which the clutch 6 is switched to the opened state. It is determined whether or not the second temperature Tt exceeds the clutch engagement temperature St1.
When it is determined that the temperature Tt of the steered motor 2 exceeds the clutch engagement temperature St1, it is determined that the steered motor 2 is overheated, the clutch 6 in the opened state is switched to the engaged state, and the steered wheels 32 are switched. And the steered wheel 24 are mechanically coupled.

After switching the clutch 6 in the disengaged state to the engaged state, the high temperature turning motor current command It_k ′ is calculated, and the drive control of the turning motor 2 is continued. In addition, the high-temperature reaction force motor current command Ih_k ′ is calculated, and the torque generated by the reaction force motor 8 is used as a steering assist torque for assisting the steering operation of the steered wheels 32.
That is, in the steering control device 1 of the present embodiment, it is determined that the steered motor 2 is overheated, the clutch 6 in the released state is switched to the engaged state, and the steered wheels 32 and the steered wheels 24 are mechanically coupled. Even after this, the drive control of the steered motor 2 is continued.

For this reason, it becomes possible to suppress that the steered motor 2 becomes a load with respect to the steering operation, and even if the torque transmission path is mechanically coupled when the steered motor 2 is overheated, the steering torque borne by the driver is reduced. The increase can be suppressed.
Further, in the steering control device 1 of the present embodiment, it is determined that the steered motor 2 is overheated, the clutch 6 in the released state is switched to the engaged state, and the steered wheels 32 and the steered wheels 24 are mechanically coupled. Even so, the steering operation is assisted by the steering assist torque generated by the reaction force motor 8.

Therefore, in order to suppress overheating of the steered motor 2, even if the torque output from the steered motor 2 is subtracted in normal control, this subtraction is compensated by the steering assist torque output from the reaction force motor 8. It becomes possible to do. Thereby, even if the torque transmission path is mechanically coupled when the steering motor 2 is overheated, it is possible to suppress an increase in steering torque borne by the driver.
If it is determined that the temperature Tt of the steered motor 2 exceeds the stop threshold temperature St while the drive control of the steered motor 2 is continued with the clutch 6 in the released state switched to the engaged state, The drive control of the rudder motor 2 is stopped.

Similarly, it is determined that the temperature Th of the reaction force motor 8 exceeds the stop threshold temperature Sh while the drive control of the reaction force motor 8 is continued with the clutch 6 in the released state switched to the engaged state. Then, the drive control of the reaction force motor 8 is stopped.
When it is determined that the temperature Tt is equal to or lower than the control return threshold temperature St2 and the temperature Th is the control return threshold temperature Sh1, the engaged clutch 6 is switched to the released state. In addition to this, the driving states of the steering motor 2 and the reaction force motor 8 are the driving states in the normal time of the SBW system.

  Note that, as described above, the steering control method implemented by the operation of the steering control device 1 of the present embodiment determines whether or not the temperature Tt of the steered motor 2 exceeds the preset clutch engagement temperature St1. A rudder motor temperature determination step is included. Further, in the steering control method of the present embodiment, when it is determined in the steered motor temperature determination step that the temperature Tt exceeds the clutch engagement temperature St1, the clutch control step for switching to the engagement state when the clutch 6 is in the released state is performed. Have. In addition to this, the steering control method of the present embodiment has a steering motor control step for continuing the drive control of the steering motor 2 even after the clutch 6 in the released state is switched to the engaged state in the clutch control step.

In addition, the steering control method implemented by the operation of the steering control device 1 of the present embodiment is such that the operation direction is assisted so as to assist the operation of the steered wheels 32 when the clutch 6 in the released state is switched to the engaged state in the clutch control step. A reaction force motor control step for outputting the steering assist torque acting in the same direction by the reaction force motor 8.
Thus, the turning position servo control unit 30 and the command calculation unit 54 correspond to the turning motor temperature determination unit.
Similarly, step S102 corresponds to a steered motor temperature determination step. Step S106 corresponds to a clutch control step. Step S108 corresponds to a steered motor control step. Step S110 corresponds to a reaction force motor control step.

(Effects of the first embodiment)
(1) When the clutch control unit 58 determines that the steering position servo control unit 30 and the command calculation unit 54 (steering motor temperature determination unit) determine that the temperature Tt of the steering motor 2 exceeds the clutch engagement temperature St1. When the clutch 6 is in the released state, the clutch 6 is switched to the engaged state. In addition to this, the steered motor control unit 4 continues the drive control of the steered motor 2 even after the clutch control unit 58 switches the opened clutch 6 to the engaged state.

For this reason, even after the temperature Tt of the steering motor 2 exceeds the clutch engagement temperature St1, the clutch 6 in the released state is switched to the engagement state and the torque transmission path is mechanically coupled. Drive control can be continued.
As a result, even if the torque transmission path is mechanically coupled when the steered motor 2 is overheated, it is possible to suppress the steered motor 2 from becoming a load on the steering operation, and the steering torque borne by the driver is reduced. The increase can be suppressed.

Further, since the torque transmission path is mechanically coupled when the steered motor 2 is overheated, the temperature Tt of the steered motor 2 rises and the drive control is stopped as compared with the case where the torque transmission path is mechanically separated. It is possible to extend the time that elapses until it is necessary to do so.
This makes it possible to extend the time that elapses until the steered motor 2 becomes a load for the steering operation, compared with the case where the torque transmission path is mechanically separated, and the steering torque borne by the driver is reduced. It is possible to extend the time during which the increase can be suppressed.

(2) When the steered motor control unit 4 switches the clutch 6 in the released state to the engaged state by the clutch control unit 58, the steered torque is corrected to be smaller than that in the normal state.
For this reason, it is possible to suppress an increase in the temperature Tt of the steered motor 2 as compared with a case where the steered torque is not corrected to be reduced from the normal state.
As a result, it is possible to extend the time that elapses until the temperature Tt of the steered motor 2 increases and the drive control needs to be stopped, and elapses until the steered motor 2 becomes a load for the steering operation. It becomes possible to extend the time to do. Thereby, it becomes possible to extend the time which can suppress the increase in the steering torque which a driver | operator bears.

(3) When the reaction force motor control unit 10 switches the clutch 6 with the clutch control unit 58 to the disengaged state to the engaged state, the steering assist torque that acts in the same direction as the operation direction so as to assist the operation of the steering wheel 32 is applied. , And output from the reaction force motor 8. In addition to this, the steering assist torque is set to a torque having the same or substantially the same magnitude as the turning torque that has been corrected to decrease from the normal state.

Therefore, in order to suppress overheating of the steered motor 2, even if the torque output from the steered motor 2 is subtracted during normal control, this subtraction is compensated by the steering assist torque generated by the reaction force motor 8. It becomes possible to do.
As a result, even if the torque transmission path is mechanically coupled when the turning motor 2 is overheated, it is possible to suppress overheating of the turning motor 2 and to suppress an increase in steering torque borne by the driver. .

In addition to this, the steering assist torque is set to a torque having the same or substantially the same magnitude as the turning torque that has been corrected to decrease from the normal state.
As a result, even if the torque transmission path is mechanically coupled when the steered motor 2 is overheated, overheating of the steered motor 2 is suppressed, and a change in steering torque borne by the driver is reduced. An increase in the steering torque to be borne can be suppressed.

(4) The clutch engagement temperature St1 is set to a temperature that is lower than the preset use limit temperature for the steered motor 2 by a preset temperature difference.
For this reason, even if the temperature Tt of the steered motor 2 rises when the steered motor 2 is overheated, the torque transmission path can be mechanically coupled with a margin of temperature difference before reaching the use limit temperature. It becomes possible.
As a result, it is possible to reduce the possibility that the increased temperature Tt of the steered motor 2 reaches the use limit temperature when the steered motor 2 is overheated, and the temperature Tt of the steered motor 2 is increased to drive control. It is possible to extend the time that elapses until it is necessary to stop the operation.

(5) In the steering control method of the present embodiment, when it is determined in the steered motor temperature determining step that the temperature Tt of the steered motor 2 exceeds the clutch engagement temperature St1, the clutch 6 is in an open state in the clutch control step. Switch to the engaged state. In addition, after the clutch 6 in the released state is switched to the engaged state in the clutch control step, the drive control of the steered motor 2 is continued in the steered motor control step.

For this reason, even when the clutch T in the disengaged state is switched to the engaged state and the torque transmission path is mechanically coupled in a state where the temperature Tt of the steered motor 2 exceeds the clutch engagement temperature St1, the steering motor 2 Drive control can be continued.
As a result, even if the torque transmission path is mechanically coupled when the steered motor 2 is overheated, it is possible to suppress the steered motor 2 from becoming a load on the steering operation, and the steering torque borne by the driver is reduced. The increase can be suppressed.

In addition to this, it is possible to extend the time that elapses until the temperature Tt of the steered motor 2 rises and the drive control needs to be stopped, as compared with the case where the torque transmission path is mechanically separated. It becomes.
This makes it possible to extend the time that elapses until the steered motor 2 becomes a load for the steering operation, compared with the case where the torque transmission path is mechanically separated, and the steering torque borne by the driver is reduced. It is possible to extend the time during which the increase can be suppressed.

(6) In the steering control method of the present embodiment, when the clutch 6 in the released state is switched to the engaged state in the clutch control step, the steering assist torque for assisting the operation of the steered wheels 32 is applied to the reaction force in the reaction force motor control step. Output by motor 8.
Therefore, in order to suppress overheating of the steered motor 2, even if the torque output from the steered motor 2 is subtracted during normal control, this subtraction is compensated by the steering assist torque generated by the reaction force motor 8. It becomes possible to do.
As a result, even if the torque transmission path is mechanically coupled when the turning motor 2 is overheated, it is possible to suppress overheating of the turning motor 2 and to suppress an increase in steering torque borne by the driver. .

(Modification)
(1) In the steering control device 1 of the present embodiment, the reaction force motor control unit 10 outputs the steering assist torque by the reaction force motor 8 when the clutch control unit 58 switches the clutch 6 in the released state to the engaged state. However, the present invention is not limited to this. That is, the reaction force motor control unit 10 may perform a process of stopping the reaction force motor 8 when the clutch control unit 58 in the released state is switched to the engaged state.

In this case, the steering control device 1 performs the processing shown in FIG. FIG. 4 is a flowchart illustrating processing performed by the steering control device 1 according to the modification of the present embodiment.
The flowchart shown in FIG. 4 starts from a state where the driver of the vehicle has started the engine (engine ON) (“START” shown in FIG. 4), and proceeds to the process of step S200. In the following description, descriptions of processes similar to those described with reference to FIG. 3 may be omitted.

Since the process of step S200 is the same as the process of step S100 described above, the description thereof is omitted.
In step S202, the command calculation unit 54 compares the temperature Tt of the steered motor 2 and the clutch engagement temperature St1, and determines whether or not the temperature Tt of the steered motor 2 exceeds the clutch engagement temperature St1 (step S202). "Tt>St1?" Here, the process of step S202 is performed with the clutch 6 in the released state (normal state). If it is determined in step S202 that the temperature Tt is equal to or higher than the clutch engagement temperature St1 ("No" shown in the figure), the processing performed by the steering control device 1 proceeds to step S204.

On the other hand, if it is determined in step S202 that the temperature Tt exceeds the clutch engagement temperature St1 ("Yes" shown in the figure), the processing performed by the steering control device 1 proceeds to step S206.
The process of step S204 is the same as the process of step S104 described above, and the process of step S206 is the same as the process of step S106 described above.

In step S208, the command calculation unit 54 calculates a high-temperature steering motor current command It_k ′ using the following equation (7).
It_k ′ = Vts × Gt1 (7)
That is, in step S208, the high-temperature steering motor current command It_k ′ is calculated as the steering motor current command It ′ (“It ′ = It_k ′ = Vts × Gt1” shown in step S208). When the high-temperature steering motor current command It_k ′ is calculated in step S208, the process performed by the steering control device 1 proceeds to step S210.

In step S210, the command calculation unit 54 sets the high-temperature reaction force motor current command Ih_k ′ used as the reaction force motor current command Ih ′ to “0” (“Ih ′ = Ih_k ′ = 0” shown in step S210). In step S210, when the high-temperature reaction force motor current command Ih_k ′ is set to “0”, the processing performed by the steering control device 1 proceeds to step S212.
In step S212, the command calculation unit 54 compares the temperature Tt of the steered motor 2 with the stop threshold temperature St of the steered motor 2, and determines whether or not the temperature Tt of the steered motor 2 exceeds the stop threshold temperature St. ("Tt>St?" Shown in step S212).

If it is determined in step S212 that the temperature Tt exceeds the stop threshold temperature St (“Yes” shown in the figure), the processing performed by the steering control device 1 proceeds to step S214.
On the other hand, if it is determined in step S212 that the temperature Tt is equal to or higher than the stop threshold temperature St ("No" shown in the figure), the processing performed by the steering control device 1 proceeds to step S216.

In step S214, the command calculation unit 54 sets the high-temperature steering motor current command It_k ′ used as the steering motor current command It ′ to “0” (“It ′ = It_k ′ = 0” shown in step S214). In step S214, when the high-temperature steering motor current command It_k ′ is set to “0”, the processing performed by the steering control device 1 proceeds to step S216.
In step S216, the command calculation unit 54 compares the temperature Tt of the steered motor 2 with the control return threshold temperature St2 of the steered motor 2, and the temperature Th of the reaction force motor 8 and the control return threshold of the reaction force motor 8 are compared. The temperature Sh1 is compared. Then, it is determined whether or not the temperature Tt of the steered motor 2 exceeds the control return threshold temperature St2, and whether or not the temperature Th of the reaction force motor 8 exceeds the control return threshold temperature Sh1 (“Tt shown in step S216”). > St2? And Th> Sh1? ").

If it is determined in step S216 that the temperature Tt is equal to or lower than the control return threshold temperature St2 and the temperature Th is the control return threshold temperature Sh1 ("No" shown in the drawing), the process performed by the steering control device 1 is as follows. The process proceeds to S204.
On the other hand, if it is determined in step S216 that two conditions are satisfied (“Yes” shown in the drawing), the processing performed by the steering control device 1 returns to the processing in step S200 (“RETURN” shown in FIG. 4). )). Here, the “two conditions” determined in step S216 are that the temperature Tt exceeds the control return threshold temperature St2 and that the temperature Th exceeds the control return threshold temperature Sh1.

(2) In the steering control device 1 of the present embodiment, the steering assist torque is set to the same or substantially the same magnitude as that of the turning torque that is corrected to be decreased from the normal state. However, the present invention is not limited to this. Absent. In other words, the steering assist torque output from the reaction force motor 8 by the reaction force motor control unit 10 may be a torque that is not the same as or substantially the same as the magnitude of the turning torque that is corrected to be decreased from the normal state. .

Even in this case, in order to suppress overheating of the steered motor 2, even if the torque output from the steered motor 2 is subtracted in the normal control, this subtraction is generated by the reaction force motor 8. It becomes possible to make up with auxiliary torque.
As a result, even if the torque transmission path is mechanically coupled when the turning motor 2 is overheated, it is possible to suppress overheating of the turning motor 2 and to suppress an increase in steering torque borne by the driver. .

(3) In the steering control device 1 of the present embodiment, the temperature Tt of the steered motor 2 is estimated, but the present invention is not limited to this. That is, for example, a temperature sensor may be installed inside the steered motor 2 and the temperature Tt of the steered motor 2 may be detected by the installed temperature sensor.
Similarly, a temperature sensor may be installed inside the reaction force motor 8, and the temperature Th of the reaction force motor 8 may be detected by the installed temperature sensor.

DESCRIPTION OF SYMBOLS 1 Steering control apparatus 2 Steering motor 4 Steering motor control part 6 Clutch 8 Reaction force motor 10 Reaction force motor control part 12 Steering motor output shaft 14 Rack gear 16 Steering motor angle sensor 18 Rack shaft 20 Tie rod 22 Knuckle arm 24 Rolling Steering wheel 26 Tire axial force sensor 28 Communication line 30 Steering position servo control unit 32 Steering wheel 34 Steering angle sensor 36 Steering torque sensor 38 Reaction force motor angle sensor 40 Clutch plate 42 Steering shaft 44 Pinion shaft 46 Pinion 48 Pinion angle sensor 50 Vehicle speed Sensor 52 Engine controller 54 Command calculation unit 56 Reaction force servo control unit 58 Clutch control unit

Claims (4)

A steered motor that outputs steered torque for steered steered wheels;
A steered motor control unit that calculates a target steered angle according to the operation of the steered wheel and drives and controls the steered motor according to the target steered angle;
A clutch capable of switching between an open state in which a torque transmission path between the steered wheel and the steered wheel is mechanically separated and a fastening state in which the torque transmission path is mechanically coupled;
A steered motor temperature determining unit that determines whether the temperature of the steered motor exceeds a preset temperature; and
When the steering motor temperature determination unit determines that the temperature of the steering motor exceeds the preset temperature, a clutch control unit that switches to an engaged state when the clutch is in an open state;
A reaction force motor that outputs a reaction force acting in a direction opposite to the operation direction for steering the steered wheel, or a steering assist torque that acts in the same direction as the operation direction;
A reaction force motor control unit that drives and controls the reaction force motor ,
The steering motor control unit, when the clutch control unit Ru switches the clutch in an open state to the engaged state, the steering torque reduction correction to than the normal state of the drive control and the steering torque of the steering motor Continue output ,
The reaction force motor control unit calculates the steering assist torque that compensates for the decrease correction amount of the turning torque when the clutch control unit switches the released clutch to the engaged state, and calculates the calculated steering assist torque. steering control apparatus for a vehicle characterized that you output in the reaction force motor. The steering assist torque, Ri torque der before Symbol decreased little corrected size the same or substantially the same size of the steering torque,
The decrease corrected the turning torque is steering control apparatus for a vehicle according to claim 1 wherein the torque der Rukoto obtained by subtracting the subtraction torque set in advance from the turning torque of the normal state. Temperature said preset the steering control of the vehicle according to claim 1 or claim 2, characterized in that said the temperature difference lower preset temperature than use limit temperature which is preset in the turning motor apparatus. A steered motor temperature determining step for determining whether or not the temperature of the steered motor that outputs the steered torque for turning the steered wheels exceeds a preset temperature;
When it is determined that the temperature of the steered motor exceeds the preset temperature in the steered motor temperature determining step, an open state that mechanically separates a torque transmission path between the steered wheel and the steered wheel; A clutch control step of switching to an engaged state when a clutch that can be switched is in an open state, and an engaged state in which the torque transmission path is mechanically coupled;
Even after the clutch in the released state is switched to the engaged state in the clutch control step, the target turning angle corresponding to the operation of the steered wheel is calculated, and the drive control of the steering motor corresponding to the target turning angle is performed. A steering motor control step to be continued;
A reaction force motor control step for driving and controlling a reaction force acting in a direction opposite to the operation direction for steering the steered wheel or a steering assist torque acting in the same direction as the operation direction. Yes, and
In the steered motor control step, when the clutch in the opened state is switched to the engaged state in the clutch control step, the steered torque is corrected to be reduced from the normal state, and the drive control of the steered motor and the output of the steered torque are performed. Continue
In the reaction force motor control step, when the clutch that has been released in the clutch control step is switched to the engaged state, the steering assist torque that compensates for the reduction correction of the steering torque is calculated, and the calculated steering assist torque Is output by the reaction force motor .

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