JP4802758B2 - Steering reaction force control device - Google Patents

Description

  The present invention relates to a steering reaction force control device that generates a reaction force torque in response to an operation of a steering wheel operated by a driver to steer a vehicle.

Conventionally, a steering device for a steering-by-wire vehicle includes a steering reaction force control device that applies a reaction force torque to an operation of a steering wheel. This steering reaction force control device acts to return the steering handle to the neutral position, that is, to the steering operation position where the turning angle of the steered wheels becomes zero, and increases as the amount of steering operation from the neutral position increases. It is configured to generate a steering reaction force, and provides a steering feeling in which a steering handle and a steered wheel are mechanically connected.
This steering reaction force control device uses a method of generating a mechanical reaction force torque using an elastic restoring force such as a spring, and generates an electric reaction torque electrically by operating an electric actuator such as an electric motor. There are known a method of combining the both, and a method combining both of them.

For example, in Patent Document 1, a mechanical reaction force generator that mechanically generates a reaction torque on a steering handle by an elastic restoring force of a spring, and an electric reaction force that generates a reaction force torque by an electric motor. A generator. In the mechanical reaction force generator, the generated torque linearly depends on the steering angle of the steering wheel. For this reason, the desired reaction force torque is obtained by compensating the reaction force torque generated by the mechanical reaction force generation device by the electric reaction force generation device.
Further, in Patent Document 2, an electric motor that generates a reaction torque on the steering shaft, a spring that generates a reaction torque on the steering shaft by elastic force, and a stopper that restricts the function of the spring are provided. Generates a reaction torque only by an electric motor, and when a motor abnormality is detected, the stopper is removed and a reaction torque generated by the elasticity of the spring is applied to the steering shaft.
Further, in Patent Document 3, a reaction force torque larger than a predetermined steering torque is generated by a mechanical reaction force generation device, and an electric motor is driven in a direction to reduce the mechanical reaction force torque. The reaction torque of is obtained.
JP-A-10-71957 JP-A-2005-47338 JP 2001-58575 A

  In a mechanical reaction force torque generator using a spring or the like, the reaction force characteristic (reaction torque generated with respect to the steering angle) is fixed, and the reaction force depends on the vehicle speed and the road surface condition (road friction coefficient, etc.). The characteristics cannot be varied. Therefore, in Patent Document 1 or Patent Document 3, by compensating the mechanical reaction force torque with the torque generated by the electric motor, the reaction force torque according to the state of the vehicle can be applied to the steering wheel. A steering feeling can be obtained.

However, the conventional apparatus has a problem that the power consumption of the electric motor is increased.
In general, the target reaction force torque to be applied to the steering wheel is calculated based on vehicle state data such as vehicle speed, road surface reaction force, and steering angle. When the reaction force torque is generated by the spring (mechanical reaction force generator) and the electric motor (electric reaction force generator), the sum of the reaction force torque by the spring and the drive torque of the electric motor is the target. It is conceivable to control the electric motor so as to obtain a reaction torque.

For example, when the target reaction force characteristic (target reaction force torque characteristic with respect to the steering angle θ) as shown in FIG. 3A is derived from the state of the vehicle, the reaction force torque by the spring alone is not sufficient for the target reaction force torque. Therefore, the shortage is compensated by the driving torque of the electric motor. In FIG. 3, (b) represents the reaction torque characteristics of the spring, and (c) represents the torque compensated by the electric motor in this case.
In addition, when the target reaction force characteristic as shown in FIG. 4A is derived from the state of the vehicle, the reaction force torque by the spring is slightly larger than the target reaction force torque, so that the excess is the amount of the spring. The electric motor is driven in a direction to reduce the reaction torque.

  However, the target reaction force characteristic may be set to a considerably small value depending on the vehicle state. For example, during traveling on a low μ road (a road surface with a low friction coefficient), a target reaction force characteristic as shown in FIG. 6A is set. In such a case, as shown in FIG. 6C, the compensation component of the electric motor for reducing the spring reaction force torque is increased, and as a result, the power consumption is also increased. There is also a problem of heat generation of the electric motor.

  The present invention has been made to cope with the above-described problem, and an object thereof is to reduce power consumption by reducing a compensation component of an electric actuator such as an electric motor.

  In order to achieve the above object, a feature of the present invention is a steering reaction force control device that applies a reaction torque according to an operation of a steering wheel operated by a driver to steer a vehicle. And a mechanical reaction force torque applying means for applying a mechanical reaction force torque to the operation of the steering handle, and an electric torque for applying a predetermined torque to the operation of the steering handle by operating an electric actuator. Providing means; target reaction force torque calculating means for calculating a target reaction force torque to be generated in response to the operation of the steering wheel in accordance with the state of the vehicle; and the mechanical reaction with respect to the calculated target reaction force torque. Electric actuator control for controlling the output of the electric actuator of the electric torque applying means so as to compensate for the excess and deficiency of the mechanical reaction force torque applied by the force torque applying means. And a transmission path of the mechanical reaction force torque generated by the mechanical reaction force torque applying means to the steering handle, and a state in which the mechanical reaction torque can be transmitted to the steering handle and a state in which the mechanical reaction torque cannot be transmitted. When the calculated target reaction torque is less than a predetermined value, the mechanical reaction torque is transmitted to the steering wheel by the reaction force transmission switching unit. And switching control means for making it impossible.

  According to the present invention configured as described above, a mechanical reaction force torque applying means and an electric torque applying means are provided, and the mechanical reaction force is applied to the target reaction force torque calculated by the target reaction force torque calculation means. The electric actuator control means controls the output of the electric actuator of the electric torque applying means so as to compensate for the excess and deficiency of the mechanical reaction force torque applied by the torque applying means. This target reaction force torque is calculated according to the state of the vehicle. For example, it is calculated by acquiring at least one vehicle state data of the reaction force input to the steering mechanism from the vehicle speed, the steering angle, and the road surface.

  When the target reaction torque calculated by the target reaction torque calculation means is less than or equal to a predetermined value, the switching control means operates the reaction force transmission cutoff switching means to transfer the mechanical reaction force torque to the steering handle. Block the transmission path. That is, when the target reaction force torque is equal to or less than the predetermined value, the mechanical reaction force torque is not applied to the steering handle, and only the electric torque applying means is used to apply the reaction force torque equivalent to the target reaction force torque. .

When the target reaction force torque is smaller than the mechanical reaction force torque applied by the mechanical reaction force torque applying means, it is necessary to operate the electric actuator in a direction to reduce the reaction force torque. In this case, in a case where the target reaction force is much smaller than the mechanical reaction force torque, a large electric actuator output is required.
Therefore, in the present invention, in such a case, the output of the electric actuator is generated by interrupting the transmission path of the mechanical reaction torque to the steering handle and applying the reaction force to the steering handle only by the electric actuator. Can be suppressed.
As a result, the power consumption of the electric actuator can be reduced. In addition, heat generation of the electric actuator can be suppressed.

  Another feature of the present invention is that the switching control means has the mechanical reaction force torque when the target reaction force torque is approximately half or less of the mechanical reaction force torque generated by the mechanical reaction force torque application means. The purpose is to cut off the transmission path of force torque to the steering wheel.

According to this, the transmission path of the mechanical reaction force torque to the steering handle can be appropriately blocked. In other words, when the target reaction torque is smaller than half of the mechanical reaction torque, the electric actuator is operated with the mechanical reaction torque cut off rather than operating the electric actuator in a direction to reduce the mechanical reaction torque. The power consumption of the electric actuator can be reduced by applying the reaction force torque only.
Therefore, in the present invention, when the target reaction force torque is approximately half or less of the mechanical reaction force torque, the desired reaction force torque can be obtained with a small amount of electric power by cutting off the transmission path of the mechanical reaction force torque to the steering handle. Can be applied to the steering wheel.

  Hereinafter, a steering reaction force control apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows the system configuration of a steering device for a steering-by-wire vehicle equipped with a steering reaction force control device.

This steering device includes a steering handle 11 that is turned by a driver to steer left and right front wheels FW1 and FW2 as steered wheels. The steering handle 11 is fixed to the upper end of the steering input shaft 12, and a steering reaction force applying device 20 is connected to the lower end of the steering input shaft 12.
As will be described later, the steering reaction force applying device 20 applies a predetermined reaction force according to the turning operation state of the driver's steering handle 11, and includes an electric torque applying unit 21, a clutch unit 22, It is comprised from the mechanical reaction force torque provision part 23. FIG.

The electric torque applying unit 21 is composed of an electric motor with a built-in speed reduction mechanism, and applies a predetermined rotational torque to the steering input shaft by driving the electric motor. Hereinafter, the electric torque applying unit 21 is referred to as a reaction force motor 21.
The clutch unit 22 is an electromagnetic clutch that switches a connection state (connected / not connected) between the steering input shaft 12 and the mechanical reaction force torque applying unit 23, and the steering input shaft 12 is energized by energizing an electromagnetic coil provided therein. By switching the connection state between the mechanical reaction force torque applying unit 23 and the mechanical reaction force torque applying unit 23, the reaction force torque generated in the mechanical reaction force torque applying unit 23 is transmitted to the steering input shaft 12 side and is not transmitted. Switch.

  The mechanical reaction force torque applying portion 23 applies a mechanical reaction force torque to the turning operation of the steering handle 11 when the clutch portion 22 is in a connected state, and can be rotated in the casing 23a. A screw shaft 23b that is provided and connected to a secondary side shaft (a shaft that is connected / disconnected to the steering input shaft) of the clutch portion 22, and a nut that meshes with the screw shaft 23b and moves forward and backward in the axial direction by the rotation of the screw shaft 23b. 23c, a hook-like spring pressing piece 23d fixed around the nut 23c, spring receivers 23e and 23f provided on the upper and lower surfaces of the casing 23a, and provided between the spring receiver 23e and the spring pressing piece 23d. An upper coil spring 23g1 and a lower coil spring 23g2 provided between the spring receiver 23f and the spring pressing piece 23d are provided. Hereinafter, when the upper coil spring 23g1 and the lower coil spring 23g2 are not distinguished, they are simply referred to as springs 23g.

  In the mechanical reaction force torque applying portion 23, when the clutch portion 22 is in the connected state, the rotational operation torque of the steering handle 11 is transmitted to the screw shaft 23b, the screw shaft 23b rotates, and the nut 23c moves upward or downward. Move to. For example, when the steering handle 11 is rotated in the left steering direction from the neutral position, the nut 23c moves upward to compress the upper coil spring 23g1, and the steering handle 11 returns to the neutral position by the elastic restoring force due to the compression. Reaction force torque is applied. On the contrary, when the steering handle 11 is rotated in the right steering direction from the neutral position, the nut 23c moves downward to compress the lower coil spring 23g2, and the steering handle 11 returns to the neutral position by the elastic restoring force by the compression. The reaction torque to be applied is applied. As shown in FIG. 3B, the reaction torque is determined according to the steering angle θ that is an angle from the neutral position. The larger the absolute value of the steering angle θ, the stronger the spring 23g is compressed and the larger the value is. Become.

  The reaction torque applied to the steering handle 11 from the mechanical reaction torque applying portion 23 acts only when the clutch portion 22 is in the connected state, and when the clutch portion 22 is in the disconnected state, the steering input shaft 12 does not work because the rotation of 12 is not transmitted to the screw shaft 23b.

On the other hand, the steering device includes an electric motor 24 incorporating a speed reduction mechanism as an actuator for turning the left and right front wheels FW1 and FW2. Hereinafter, this electric motor 24 is referred to as a steering motor 24.
The output of the steering motor 24 is transmitted to the left and right front wheels FW1, FW2 via the steering output shaft 25, the pinion gear 26, and the rack bar 27. Therefore, when the steering motor 24 rotates, the rotational force is transmitted to the pinion gear 26 via the steering output shaft 25, and the rack bar 27 is displaced in the axial direction by the rotation of the pinion gear 26. The left and right front wheels FW1 and FW2 are steered to the left and right by the 27 axial displacement.

  Next, the electronic control unit 40 that controls the operation of the steering reaction force applying device 20 and the steering motor 24 will be described. The electronic control unit 40 connects a steering angle sensor 31, a steering torque sensor 32, a turning angle sensor 33, a turning torque sensor 34, and a vehicle speed sensor 35.

The steering angle sensor 31 is assembled to the steering input shaft 12, detects the rotation angle from the neutral position of the steering handle 11, and outputs the steering angle θ as an operation input value. The steering torque sensor 32 is also assembled with the steering input shaft 12, detects the torque input to the steering handle 11, and outputs it as the steering torque T1.
The turning angle sensor 33 is assembled to the turning output shaft 25, detects the rotation angle from the neutral position of the turning output shaft 25, and corresponds to the actual turning angle δ (the turning angle of the left and right front wheels FW1, FW2). ). The turning torque sensor 34 is also assembled to the turning output shaft 25, detects torque acting on the turning output shaft 25, and outputs it as turning torque T2. The steering torque sensor 34 detects a road surface reaction force, that is, a force input to the rack bar 27 from the road surface such as a self-aligning torque. Therefore, a load sensor that detects the axial load acting on the rack bar 27 may be provided instead of the steering torque sensor 34.
The vehicle speed sensor 35 detects the vehicle speed of the vehicle and outputs it as the vehicle speed V.
Here, regarding the steering angle θ and the actual turning angle δ, the neutral position is “0”, the left rotation angle is represented by a positive value, and the right rotation angle is represented by a negative value.

The electronic control unit 40 includes a microcomputer including a CPU, a ROM, a RAM, and the like as main components. By executing various programs including the reaction force control program shown in FIG. Each operation of the motor 24 is controlled. On the output side of the electronic control unit 40, a drive circuit 41 that drives the reaction force motor 21 of the steering reaction force applying device 20, a drive circuit 42 that drives the clutch unit 22, and a drive circuit 43 that drives the steering motor 24. Are connected to each other. In the drive circuit 41, a current detector 41a for detecting the drive current flowing in the reaction force motor 21 is provided, and in the drive circuit 43, a current detector 43a for detecting the drive current flowing in the steering motor 24 is provided. It has been.
The drive current detected by the current detectors 41 a and 43 a is fed back to the electronic control unit 40 in order to control the drive of both the motors 21 and 24.

  Next, a reaction force control routine executed by the electronic control unit 40 will be described. FIG. 2 shows a reaction force control routine, which is stored in the ROM of the electronic control unit 40 as a control program. This reaction force control routine starts when an unillustrated ignition switch is turned on by the driver, and is repeatedly executed at a predetermined short cycle.

When this control routine is started, first, at step S10, the steering angle θ detected by the steering angle sensor 31, the vehicle speed V detected by the vehicle speed sensor 35, the steering torque T1 detected by the steering torque sensor 32, and the steering. The turning torque T2 detected by the torque sensor 34 is input.
Subsequently, in step S11, a target reaction force torque value T * (hereinafter referred to as target reaction force torque T *) is calculated based on the input steering angle θ, vehicle speed V, and steering torque T2. In the present embodiment, the target reaction force characteristic map MP relating the target reaction force torque T * to the steering angle θ as shown in FIG. 7 is electronically controlled by the number corresponding to the combination of the vehicle speed V and the turning torque T2. It is stored as data in the storage circuit of the unit 40. Then, an optimum target reaction force characteristic map MP is extracted based on the vehicle speed V representing the vehicle state and the turning torque T2. This target reaction force characteristic is set so that the target reaction force torque T * increases in proportion to the vehicle speed V and the road surface reaction force or in an exponentially proportional manner.
Therefore, the target reaction force torque T * with respect to the current steering angle θ is obtained from the target reaction force characteristic map MP.
The calculation of the target reaction force torque T * is not limited to the configuration obtained from such a map MP, and may be obtained by calculation from a function f (θ, V, T2) or the like, for example.

Subsequently, in step S12, the target reaction force torque T * at the current steering angle θ is a mechanical reaction force torque value Tspr (hereinafter referred to as a spring reaction torque) generated by the mechanical reaction force torque applying unit 23 at the steering angle θ. It is determined whether or not it is larger than a value (Tspr / 2 + k) obtained by adding a predetermined value k to a half value of the force torque Tspr.
The spring reaction force torque Tspr is determined according to the steering angle θ as shown in the spring reaction force characteristic of FIG. The electronic control unit 40 stores this spring reaction force characteristic in the ROM, and calculates the spring reaction force torque Tspr from the steering angle θ.
The predetermined value k is set and stored in advance in consideration of the temporal plastic deformation of the spring 23g, and is a small value with respect to the spring reaction force torque Tspr.

  If “YES” is determined in step S12, that is, the target reaction torque T * is larger than a value obtained by adding a predetermined value k to a half value of the spring reaction torque Tspr (T *> Tspr / 2 + k). If it is determined, next, in step S13, the setting state of the flag F is confirmed, and it is determined whether or not F = 0. This flag F represents the connection / disconnection state of the clutch part 22, and if F = 0, it represents a connection state, and if F = 1, it represents a non-connection state. The flag F is set to F = 0 when this control routine is started.

In the confirmation of the flag F in step S13, if it is determined that F = 0, the process proceeds to the next step S15, and the clutch unit 22 is brought into a connected state. In this case, since the flag F has already been set to F = 0, the engaged state of the clutch portion 22 is continued.
On the other hand, in the confirmation of the flag F in step S13, if it is determined that F = 1, the flag F is set to F = 0 in step S14, the process proceeds to step S15, and the clutch unit 22 is disconnected. Switch from state to connected state. In this case, the electronic control unit 40 outputs a switching control signal to the drive circuit 42 to bring the clutch unit 22 into a connected state.
Accordingly, the spring reaction force torque generated by the mechanical reaction force torque applying unit 23 is transmitted to the steering handle 11 via the steering input shaft 12.

Subsequently, the process proceeds to step S16, and the output torque of the reaction force motor 21 is calculated. In step S16, the output torque of the reaction force motor 21 is set to a value obtained by subtracting the spring reaction force torque Tspr from the target reaction force torque T *.
That is, since the clutch portion 22 is in the connected state, the difference between the target reaction force torque T * and the spring reaction force torque Tspr is set as the target output torque of the reaction force motor 21.

For example, when a target reaction force characteristic map as shown in FIG. 3A is extracted according to the vehicle state, the reaction force torque is obtained only by the spring reaction force torque generated by the mechanical reaction force torque application unit 23. Therefore, the output torque of the reaction force motor 21 is calculated so as to compensate for the shortage (see FIGS. 3B and 3C).
As shown in FIG. 4, when the target reaction force characteristic is smaller than the spring reaction force characteristic, the spring reaction force torque generated in the mechanical reaction force torque applying unit 23 is reduced in accordance with the difference. The output torque of the reaction force motor 21 is calculated.

  Subsequently, the process proceeds to step S17, and a control command corresponding to the calculated output torque (target motor torque) is output to the drive circuit 41. The drive circuit 41 forms an inverter circuit with switching elements (not shown), and controls the duty ratio of the switching elements by PWM control in accordance with a control command value from the electronic control unit 40 to be applied to the reaction force motor 21. Adjust. The electronic control unit 40 inputs the current value flowing from the drive circuit 41 to the reaction force motor 21 from the current detector 41 a and also inputs the steering torque T <b> 1 from the steering torque sensor 32, and the target motor torque is input to the reaction force motor 21. The feedback control is performed so that the drive current corresponding to. By the driving control of the reaction force motor 21, the steering reaction force applying device 20 applies a reaction force corresponding to the target reaction force torque T * to the steering handle 11 via the steering input shaft 12.

  On the other hand, the determination in step S12 is “NO”, that is, it is determined that the target reaction force torque T * is equal to or less than a value obtained by adding a predetermined value k to a half value of the spring reaction force torque Tspr (T * ≦ Tspr / 2 + k). If so, in step S23, the target reaction force torque T * is now less than the value obtained by subtracting the predetermined value k from the half value of the spring reaction force torque Tspr (Tspr / 2−k). Determine whether.

  For example, when traveling on a low μ road, as shown in FIG. 5, the target reaction force characteristic map MP set to be considerably smaller than the spring reaction force characteristic is selected. In such a case, T * <Tspr / 2−k, and the determination in step S23 is “YES”. In this case, the process proceeds to step S18. In step S18, the state of the flag F is confirmed. If F = 1, the process proceeds to step S21, and the clutch portion 22 is kept in the disconnected state.

On the other hand, if it is determined in step S18 that F = 0, the flag F is set to F = 1 in step S19, the process proceeds to step S21, and the clutch unit 22 is changed from the connected state to the disconnected state. Switch. In this case, the electronic control unit 40 outputs a switching control signal to the drive circuit 42 to place the clutch unit 22 in a disconnected state.
Therefore, the spring reaction force torque generated by the mechanical reaction force torque applying unit 23 is not transmitted to the steering handle 11.

  Further, when the determination in step S23 is “NO”, that is, it is determined that the target reaction force torque T * is equal to or greater than a value obtained by subtracting the predetermined value k from the half value of the spring reaction force torque Tspr (T * ≧ Tspr / 2-k), next, the setting state of the flag F is confirmed in step S20. If the flag F is F = 1, the process proceeds to step S21 to continue the disengaged state of the clutch portion 22. If the flag F is F = 0, the process proceeds to step S15 to keep the clutch unit 22 engaged.

  That is, when “NO” is determined in step S23, the operation of the clutch portion 22 is not switched. Therefore, a region where (Tspr / 2−k) ≦ T * ≦ (Tspr / 2 + k) is a dead zone where the switching operation of the clutch unit 22 is not performed.

If the clutch part 22 is set to a non-engaged state by step S21, a process will be advanced to step S22 and the output torque of the motor 21 for reaction force will be calculated. In step S22, the output torque of the reaction force motor 21 is set to the same value as the target reaction force torque T *.
That is, since the clutch portion 22 is in the non-connected state, the spring reaction force torque generated in the mechanical reaction force torque applying portion 23 is not transmitted to the steering handle 11, and therefore the output torque of the reaction force motor 21 is set to the target reaction force. It is set to the same value as the torque T *.

Subsequently, the process proceeds to step S17, where a control command corresponding to the calculated output torque (target motor torque) is output to the drive circuit 41. In step S17, the reaction force motor 21 is drive-controlled as described above, and the target reaction force torque T * is applied to the steering handle 11 via the steering input shaft 12.
Such a reaction force control routine is repeatedly executed at a predetermined short cycle, and based on a target reaction force characteristic and a spring reaction force characteristic corresponding to the vehicle state, switching of the clutch portion 22 and output control of the reaction force motor 21 are performed. Is done.

Here, the principle of reducing the power consumption of the reaction force motor 21 by switching the coupling of the clutch portion 22 will be described.
As described above, when the determination in step S23 is “YES”, that is, it is determined that the target reaction force torque T * is less than the value obtained by subtracting the predetermined value k from the half value of the spring reaction force torque Tspr (T * <Tspr / 2-k), the clutch portion 22 is disengaged (S21), and the reaction force torque of only the reaction force motor 21 is applied to the steering handle 11 (S22).
In step S23, the predetermined value k is set to a very small value with respect to the spring reaction force torque. Therefore, it is determined whether or not the target reaction force torque T * is smaller than about half of the spring reaction force torque Tspr. Judgment.

  When traveling on a low μ road, as shown in FIG. 5A, a target reaction force characteristic map set to be considerably smaller than the spring reaction force characteristic may be selected. In such a case, the target reaction force torque T * is set to a value smaller than ½ of the spring reaction force torque Tspr. At this time, in this embodiment, the output torque required for the reaction force motor 21 to bring the clutch portion 22 into a non-connected state is equal to the target reaction force torque T * as shown in FIG. Same value and small output.

On the other hand, when the clutch portion 22 is not provided, the reaction force motor 21 needs to be driven in a direction to reduce the spring reaction force torque Tspr generated in the mechanical reaction force torque applying portion 23, as shown in FIG. The smaller the target reaction torque T *, the larger the motor compensation torque is required.
That is, as can be seen by comparing the motor compensation torque in FIG. 6C and the motor output torque in FIG. 5C, the target reaction force torque T * is less than ½ of the spring reaction force torque Tspr. In this case, it can be understood that the output of the reaction force motor 21 can be smaller if the transmission path of the spring reaction force torque generated by the mechanical reaction force torque applying unit 23 to the steering handle 11 is cut off.

Therefore, in this embodiment, it is determined whether or not the target reaction force torque T * is smaller than about half of the spring reaction force torque Tspr, and the connection state of the clutch portion 22 is controlled to be switched based on the determination result. ing.
As a result, the power consumption of the reaction force motor 21 can be reduced. Therefore, the electric load of the on-vehicle battery (not shown) can be reduced to stabilize the power supply system. Further, the heat generation of the reaction force motor 21 can be suppressed.

In general, not only a steering device but also many electric control systems are connected to a vehicle-mounted battery. In such a power supply system, each electric control system extracts the necessary power from the in-vehicle battery as needed. However, when the operation of each electric control system overlaps, a large current is instantaneously drawn from the in-vehicle battery. As a result, the battery voltage may decrease and the operation of the electric control system may become unstable.
In response to such a problem, in the present embodiment, the load of the on-vehicle battery is reduced by reducing the power consumption of the reaction force motor 21 to prevent such a problem.

Next, the steering control executed by the electronic control unit 40 will be described.
The electronic control unit 40 inputs the steering angle θ corresponding to the turning operation of the steering handle 11 from the steering angle sensor 31, and calculates the turning angle δ corresponding to the input steering angle θ. Then, the left and right front wheels FW1, FW2 are steered so as to coincide with the steered angle δ. That is, the electronic control unit 40 detects and inputs the drive current value flowing from the drive circuit 43 to the steering motor 24 by the current detector 43a, and inputs the actual turning angle detected by the turning angle sensor 33. To do. Then, the electronic control unit 40 feedback-controls the drive circuit 43 so that an appropriate drive current flows through the steering motor 24 so that the left and right front wheels FW1, FW2 are steered to the steered angle δ.
By the drive control by the electronic control unit 40, the rotation of the steering motor 24 is transmitted to the pinion gear 26 via the steering output shaft 25, and the rack bar 27 is displaced in the axial direction by the pinion gear 26. Due to the displacement of the rack bar 27 in the axial direction, the left and right front wheels FW1, FW2 are steered to a turning angle δ corresponding to the steering angle θ.

  According to the steering device of the present embodiment described above, the steering reaction force applying device 20 including the reaction force motor 21, the clutch portion 22, and the mechanical reaction force torque applying portion 23, and the steering reaction force applying device. When the target reaction force torque T * set in accordance with the vehicle state is smaller than approximately half of the spring reaction force torque Tspr (Tspr-k), the clutch unit 22 is turned off. Since the control is switched to the connected state and the reaction force torque is applied to the steering handle 11 only by the reaction force motor 21, the power consumption of the reaction force motor 21 can be suppressed. As a result, it is possible to prevent the voltage drop of the in-vehicle battery and stabilize the operation of various electric control systems. Further, the heat generation of the reaction force motor 21 can be suppressed.

  In addition, since a predetermined value k is added to the spring reaction force torque and compared with the target reaction force torque, it is possible to cope with the temporal plastic deformation of the spring. Furthermore, since the region where (Tspr / 2−k) ≦ T * ≦ (Tspr / 2 + k) is a dead zone in which the switching operation of the clutch portion 22 is not performed, the target reaction force torque T * is equal to the spring reaction force torque Tspr. Even when the change is increased or decreased with a value of ½ as a boundary, the clutch portion is not switched more than necessary, and the stable and proper operation of the clutch portion 22 can be maintained.

  Further, since the reaction force torque is applied to the steering handle 11 using the spring restoring force by the mechanical reaction force torque applying unit 23, it is good even at extremely low speed steering or at a minute steering near the neutral position. A steering feeling can be obtained. In other words, in the case of a configuration in which reaction force torque is applied only with an electric motor, high accuracy sensors and control processing are required to create a good steering feeling during extremely low speed steering or minute steering near the neutral position. Although it was substantially difficult, in this embodiment, the steering feeling can be improved by combining the mechanical reaction force torque applying portion 23 and the reaction force motor 21.

As mentioned above, although the vehicle steering apparatus of this embodiment was demonstrated, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the objective of this invention.
For example, in the present embodiment, the predetermined value k is added to the spring reaction torque in consideration of the time-dependent plastic deformation of the spring, but a configuration in which the predetermined value k is not used may be used.
In addition, the structure of the mechanical reaction force torque applying unit 23 is not limited to the coil spring, and various structures can be employed.
Furthermore, a configuration may be employed in which hysteresis is provided in the target reaction force characteristic and the target reaction force characteristic in which the target reaction force torque is set according to not only the steering angle but also the steering direction is used.

  In this embodiment, the vehicle steering device has been described. Among them, the steering reaction force applying device 20, the steering angle sensor 31, the steering torque sensor 32, the steering torque sensor 34, the vehicle speed sensor 35, and the electronic control unit 40 are described. The drive circuits 41 and 42 constitute a steering reaction force control device.

  The mechanical reaction force torque applying section 23 in the present embodiment corresponds to the mechanical reaction force torque applying means of the present invention, and the electric torque applying section 21 (reaction force motor) in the present embodiment is the electric power of the present invention. The processing of steps S10 and S11 (processing of the electronic control unit 40) in the reaction force control routine of the present embodiment corresponds to the target reaction force torque calculation device of the present invention. The processing of steps S16, S17, and S22 (processing of the electronic control unit 40) in the force control routine corresponds to the electric actuator control means of the present invention, and the clutch portion 22 of the present embodiment serves as the reaction force transmission cutoff switching means of the present invention. Correspondingly, the processing of steps S12, S13, S14, S15, S23, S18, S19, S20, S21 in the reaction force control routine of this embodiment (electronic control). Processing unit 40) corresponds to the switching control means of the present invention.

It is a schematic block diagram of the steering apparatus of the vehicle provided with the steering reaction force control apparatus. It is a flowchart showing a reaction force control routine. It is explanatory drawing showing a target reaction force characteristic, a spring reaction force characteristic, and a motor compensation torque (at the time of clutch part connection). It is explanatory drawing showing a target reaction force characteristic, a spring reaction force characteristic, and a motor compensation torque (at the time of clutch part connection). It is explanatory drawing showing a target reaction force characteristic, a spring reaction force characteristic, and a motor output torque (at the time of a clutch part non-connecting). It is explanatory drawing showing a target reaction force characteristic, a spring reaction force characteristic, and a motor compensation torque (when a clutch part is not provided). It is explanatory drawing showing the map for calculating a target reaction force torque.

Explanation of symbols

FW1, FW2 ... front wheels, 11 ... steering handle, 12 ... steering input shaft, 20 ... steering reaction force applying device, 21 ... electric torque applying portion (reaction force motor), 22 ... clutch portion, 23 ... mechanical reaction force Torque imparting section, 23b ... screw shaft, 23c ... nut, 23d ... spring pushing piece, 23g1, 23g2 ... coil spring, 31 ... steering angle sensor, 32 ... steering torque sensor, 33 ... steering angle sensor, 34 ... steering torque sensor 35 ... Vehicle speed sensor, 40 ... Electronic control unit, 41, 42, 43 ... Drive circuit.

Claims (2)

In a steering reaction force control device that applies a reaction torque according to an operation of a steering wheel operated by a driver to steer a vehicle,
Mechanical reaction force torque applying means for applying mechanical reaction force torque to the operation of the steering handle;
An electric torque applying means for operating the electric actuator to apply a predetermined torque to the operation of the steering handle;
Target reaction force torque calculating means for calculating a target reaction force torque to be generated in response to the operation of the steering wheel according to the state of the vehicle;
Electricity for controlling the output of the electric actuator of the electrical torque applying means so as to compensate for the excess or deficiency of the mechanical reaction force torque applied by the mechanical reaction force torque applying means with respect to the calculated target reaction torque. An actuator control means;
The mechanical reaction force torque generated by the mechanical reaction force torque applying means is provided in a transmission path to the steering handle, and the mechanical reaction force torque can be transmitted to the steering handle. Reaction force transmission cutoff switching means for switching,
When the calculated target reaction force torque is less than or equal to a predetermined value, the reaction force transmission cut-off switching means includes switching control means for making the mechanical reaction force torque impossible to transmit to the steering handle. A steering reaction force control device. The switching control means transmits the mechanical reaction force torque to the steering handle when the target reaction torque is approximately half or less of the mechanical reaction torque generated by the mechanical reaction torque applying means. The steering reaction force control device according to claim 1, wherein the steering reaction force control device is cut off.

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