JP2021113027A - Power steering device and vehicle - Google Patents

Abstract

To provide a power steering device and a vehicle capable of improving safety during lane keep assist.SOLUTION: A power steering device comprises an actuator that applies an assist force to a steering shaft to assist a vehicle in maintaining and traveling in a lane, a determination unit that determines whether or not a driver is touching a steering wheel to which the steering shaft is attached, and a control unit that controls the actuator so as to adjust the assist force based on the determination result of the determination unit.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to power steering devices and vehicles.

Conventionally, Lane Keeping Assistant System (LKAS) has been known, which assists steering to maintain the vicinity of the center of the lane when the vehicle travels on the road and reduces the driving burden on the driver. ..

For example, Patent Document 1 discloses a power steering device including an actuator that applies an assist force to the steering shaft at the time of lane keep assist.

In this type of power steering device, the assist force is applied to the steering shaft at the time of lane keep assist, so that the driver can drive the vehicle without touching the steering wheel.

JP-A-2009-274688

By the way, at the time of lane keep assist, there is no difference in the magnitude of the assist force applied to the steering shaft between the case where the driver is touching the steering wheel and the case where the driver is not touching the steering wheel.

As a result, when the driver does not touch the steering wheel, the steering wheel is more likely to rotate than when the driver touches the steering wheel, and as a result, the steering wheel may rotate too much. Therefore, it can be said that there is room for improvement from the viewpoint of improving safety during lane keep assist.

An object of the present disclosure is to provide a power steering device and a vehicle capable of improving safety during lane keep assist.

In order to achieve the above object, the power steering device in the present disclosure is
An actuator that applies an assisting force to the steering shaft to assist the vehicle in maintaining the lane and running.
A determination unit for determining whether or not the driver is touching the steering wheel to which the steering shaft is attached, and a determination unit.
A control unit that controls the actuator so as to adjust the assist force based on the determination result of the determination unit.
To be equipped.

The vehicle in the present disclosure includes the power steering device.

According to the power steering device of the present disclosure, safety can be improved at the time of lane keep assist.

FIG. 1 is a diagram schematically showing a configuration of a vehicle provided with a power steering device according to an embodiment of the present disclosure. FIG. 2 is a functional block diagram of the vehicle ECU. FIG. 3A is a diagram showing the relationship between the steering speed of the steering wheel and the motor assist force. FIG. 3B is a diagram showing the relationship between the steering speed of the steering wheel and the motor assist force. FIG. 4 is a flowchart showing an example of a method for adjusting the motor assist force.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
FIG. 1 is a diagram schematically showing a configuration of a vehicle V including the power steering device 3 according to the embodiment of the present disclosure. In the following specification, it is assumed that the vehicle V is a large vehicle V such as a bus or a truck, but the present disclosure is not limited to the large vehicle V.

The vehicle V has a power steering device 3 as an assist unit. Steering assistance is realized by generating a motor assist force by the motor and a hydraulic assist force by the flood control with respect to the steering force generated by the driver of the vehicle V steering the steering wheel 1 provided on the vehicle V. Further, the vehicle V generates a motor assist force and a hydraulic assist force in response to the steering of the steering wheel 1 and the control of the lane keep assist (LKAS) for keeping the vehicle V in the lane and traveling. , Realize steering assistance.

<Vehicle V configuration>
As shown in FIG. 1, the vehicle V includes a steering wheel 1, a steering shaft 2, a power steering device 3, and a vehicle ECU 10 (Electronic Control Unit).

One end of the steering shaft 2 is connected to the steering wheel 1, and the other end is connected to the input shaft of the power cylinder portion 34 of the power steering device 3 via the stub shaft 4. The steering shaft 2 transmits the steering torque applied to the steering wheel 1 to the power cylinder unit 34.

The power steering device 3 includes a torque sensor 31, an electric motor 32, a power cylinder unit 34, and a pump unit 35.

The torque sensor 31 is provided on the steering shaft 2. The torque sensor 31 detects an input torque (steering torque) applied to the steering shaft 2 when the steering wheel 1 is steered by the driver.

The vehicle ECU 10 is a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory), a RAM (Random Access Memory), a backup RAM (or a non-volatile memory), an interface, and the like. Is an electronic control circuit having the above as a main component. The CPU realizes various functions (described later) by executing instructions (routines) stored in the ROM.

The vehicle ECU 10 acquires the input torque from the torque sensor 31. The EEPROM stores an indicated value map in which the input torque and the indicated value are associated with each other. The vehicle ECU 10 outputs an indicated value corresponding to the input torque to the electric motor 32 based on the indicated value map.

The electric motor 32 is connected to the steering shaft 2 and rotates at a rotational speed according to a value indicated by the vehicle ECU 10 to generate a rotational driving force (motor assist force). As a result, the motor assist force is transmitted to the input shaft of the power cylinder unit 34. The electric motor 32 functions as a motor assist unit.

The pump unit 35 controls the flow rate of the hydraulic oil supplied from the reservoir tank (not shown) to the power cylinder unit 34 under the control of the vehicle ECU 10.

The power cylinder unit 34 and the pump unit 35 function as a hydraulic assist unit that generates a hydraulic assist force, which is a hydraulic assist force. As a result, the hydraulic assist force is transmitted to the steering wheel 6 of the vehicle V via the link mechanism 5. The actuator according to the present disclosure includes an electric motor 32 that functions as a motor assist unit, and a power cylinder unit 34 and a pump unit 35 that function as a hydraulic assist unit.

As described above, the motor assist force and the hydraulic assist force are transmitted to the steering wheel 6 of the vehicle V. As a result, the steering wheel 6 rotates.

By the way, in the lane keep assist (LKAS), since the assist force is applied to the steering shaft 2, the driver can drive the vehicle without touching the steering wheel 1. However, there is no difference in the magnitude of the assist force between the case where the driver touches the steering wheel 1 and the case where the driver does not touch the steering wheel 1. As a result, when the driver does not touch the steering wheel 1, the steering shaft 2 to which the assist force is applied is more likely to rotate than when the driver touches the steering wheel 1, and as a result, the steering shaft 2 may rotate too much. There is. Therefore, it can be said that there is room for improvement from the viewpoint of improving safety.

Therefore, the vehicle ECU 10 according to the present embodiment has a function for improving safety.

Hereinafter, the details of the vehicle ECU 10 will be described. As shown in FIG. 2, the vehicle ECU 10 has functions as an acquisition unit 101, a determination unit 102, and a control unit 103.

Further, the power steering device 3 according to the present embodiment includes a known detection unit (not shown) capable of detecting whether or not the driver is touching the steering wheel 1 (presence or absence of contact). For example, the detection unit may be a capacitance type touch sensor that can detect the presence or absence of contact based on the capacitance formed between the driver's hand and the steering wheel 1. Further, the detection unit may detect the presence or absence of contact based on the difference in the magnitude of the steering torque generated by the power steering device 3. Further, the detection unit may be an in-vehicle camera that captures an image of the steering wheel 1.

The storage unit (for example, EEPROM) stores a map showing an instruction value output from the vehicle ECU 10 to the electric motor 32 at the time of lane keep assist. The map has a map A that is referenced when the driver is not touching the steering wheel 1 and a map B that is referenced when the driver is touching the steering wheel 1.

Further, the power steering device 3 according to the present embodiment includes a known detection unit (not shown) capable of detecting the steering speed of the steering wheel 1. The storage unit (for example, EEPROM) also stores a predetermined target value Na (see FIG. 3A) and a target value Nb (see FIG. 3B) of the steering speed of the steering wheel 1. The target value Na may be the same as the target value Nb, may be smaller than the target value Nb, or may be larger than the target value Nb.

The acquisition unit 101 acquires a detection result (detection signal or imaging data) from the detection unit.

The determination unit 102 determines whether or not the driver is touching the steering wheel 1 from the detection result of the detection unit.

<When the driver is not touching the steering wheel 1>
When the driver does not touch the steering wheel 1 during lane keep assist, the control unit 103 controls the motor assist unit so as to adjust the motor assist force with reference to the map A. As a result, the command value shown in the map A is output from the vehicle ECU 10 to the electric motor 32.

The control unit 103 also controls the motor assist unit so as to reduce the motor assist force when the steering speed of the steering wheel 1 is equal to or higher than the target value Na.

FIG. 3A is a diagram showing the relationship between the steering speed of the steering wheel 1 and the motor assist force. The horizontal axis of FIG. 3A shows the steering speed (m / s), and the vertical axis shows the motor assist force (Nm).

When the command value shown in the map A is output from the vehicle ECU 10 to the electric motor 32, the motor assist force suddenly rises as shown in FIG. 3A, so that the steering speed of the steering wheel 1 reaches the target value Na. Is fast. The motor assist force drops sharply after the steering speed reaches the target value Na. As a result, the motor assist force applied to the steering shaft 2 becomes relatively small. Therefore, it is possible to prevent the steering wheel 1 from rotating too much even when the driver does not touch the steering wheel 1 during the lane keep assist.

<When the driver is touching the steering wheel 1>
On the other hand, when the driver touches the steering wheel 1 during lane keep assist, the control unit 103 controls the motor assist unit so as to adjust the motor assist force with reference to the map B. As a result, the command value shown in the map B is output from the vehicle ECU 10 to the electric motor 32.

The control unit 103 also controls the motor assist unit so as to reduce the motor assist force when the steering speed of the steering wheel 1 is equal to or higher than the target value Nb.

FIG. 3B is a diagram showing the relationship between the steering speed of the steering wheel 1 and the motor assist force. The horizontal axis of FIG. 3B shows the steering speed (m / s), and the vertical axis shows the motor assist force (Nm).

When the command value shown in the map B is output from the vehicle ECU 10 to the electric motor 32, the motor assist force rises relatively slowly as shown in FIG. 3B, so that the steering speed of the steering wheel 1 is the target value Nb. Is slow to reach. The motor assist force gradually decreases after the steering speed reaches the target value Nb. As a result, when the driver touches the steering wheel 1 during lane keep assist, a frictional force acting in the direction opposite to the rotation direction of the steering wheel 1 acts, so that the steering wheel 1 does not rotate too much.

Next, a method of adjusting the motor assist force during lane keep assist will be described with reference to FIG. FIG. 4 is a flowchart showing an example of a method for adjusting the motor assist force. This flow starts at a predetermined time interval at the time of lane keep assist. Further, here, it is assumed that the vehicle ECU 10 executes the functions of the acquisition unit 101, the determination unit 102, and the control unit 103.

First, in step S100, the vehicle ECU 10 acquires a detection result from the detection unit.

Next, in step S110, the vehicle ECU 10 determines whether or not the driver is touching the steering wheel 1 based on the detection result of the detection unit. If the driver has not touched the steering wheel 1 (step S110: NO), the process proceeds to step S120. When the driver is touching the steering wheel 1 (step S110: YES), the process proceeds to step S150.

In step S120, the vehicle ECU 10 controls the motor assist unit with reference to the map A.

Next, in step S130, the vehicle ECU 10 determines whether or not the steering speed of the steering wheel 1 is equal to or higher than the target value Na. When the steering speed is equal to or higher than the target value Na (step S130: YES), the process proceeds to step S140. If the steering speed is less than the target value Na (step S130: NO), the process returns to before step S120.

Next, in step S140, the vehicle ECU 10 controls the motor assist unit so as to reduce the motor assist force with reference to the map A. After that, the process shown in FIG. 4 ends.

In step S150, the vehicle ECU 10 controls the motor assist unit with reference to the map B.

In step S160, the vehicle ECU 10 determines whether or not the steering speed of the steering wheel 1 is equal to or greater than the target value Nb. When the steering speed is equal to or higher than the target value Nb (step S160: YES), the process proceeds to step S170. If the steering speed is less than the target value Nb (step S160: NO), the process returns to before step S150.

In step S170, the vehicle ECU 10 refers to the map B and controls the motor assist unit so as to reduce the motor assist force. After that, the process shown in FIG. 4 ends.

In the power steering device 3 according to the above embodiment, a motor assist portion that applies a motor assist force for assisting the vehicle V to maintain the lane and travel is attached to the steering shaft 2, and the steering shaft 2 is attached. A determination unit 102 that determines whether or not the driver is touching the steering wheel 1 and a control unit 103 that controls the motor assist unit so as to adjust the motor assist force based on the determination result of the determination unit 102. Be prepared.

With the above configuration, when the driver is not touching the steering wheel 1 at the time of lane keep assist, it is possible to prevent the steering wheel 1 from rotating excessively by adjusting the motor assist force. As a result, safety can be improved during lane keep assist.

In addition, the above embodiments are merely examples of embodiment of the present disclosure, and the technical scope of the present disclosure should not be construed in a limited manner by these. .. That is, the present disclosure can be implemented in various forms without departing from its gist or its main features.

In the above embodiment, when the driver does not touch the steering wheel 1 during lane keep assist, the motor assist unit is controlled with reference to the map A, and when the driver touches the steering wheel 1, the map is used. The motor assist unit is controlled with reference to B. However, this disclosure is not limited to this. For example, a plurality of maps may be created according to the magnitude of the gripping force (torque) when the driver is touching the steering wheel 1, and the motor assist unit may be controlled by referring to these maps. Further, when creating a plurality of maps, the minimum torque is the gripping force (torque) between the gripping force (minimum torque) when the driver is not touching the steering wheel 1 and the large gripping force (maximum torque). The map created in the case of the above and the map created in the case of the maximum torque may be complemented.

Further, in the above embodiment, for example, when the driver does not touch the steering wheel 1 at the time of lane keep assist, when adjusting the motor assist force, the command value shown in the map A is sent from the vehicle ECU 10 to the electric motor. It is output to 32. However, this disclosure is not limited to this. For example, the indicated value calculated based on a predetermined calculation formula may be output from the vehicle ECU 10 to the electric motor 32.

Further, in the above embodiment, the present disclosure is applied to an actuator including both a motor assist unit and a hydraulic assist unit, but the present disclosure may be applied to an actuator including one of the motor assist units.

The present disclosure is suitably used for a vehicle provided with a power steering device 3 that is required to improve safety at the time of lane keep assist.

1 Steering wheel 2 Steering shaft 3 Power steering device 4 Stub shaft 5 Link mechanism 6 Steering wheel 10 Vehicle ECU
31 Torque sensor 32 Electric motor 34 Power cylinder part 35 Pump unit 101 Acquisition part 102 Judgment part 103 Control part

Claims (4)

An actuator that applies an assisting force to the steering shaft to assist the vehicle in maintaining the lane and running.
A determination unit for determining whether or not the driver is touching the steering wheel to which the steering shaft is attached, and a determination unit.
A control unit that controls the actuator so as to adjust the assist force based on the determination result of the determination unit.
To prepare
Power steering device. The control unit controls the actuator so as to reduce the assist force when the steering speed of the steering wheel is equal to or higher than a predetermined target value.
The power steering device according to claim 1. The actuator includes a motor assist unit that generates the assist force by a motor and a hydraulic assist unit that generates the assist force by a flood control.
The control unit controls the motor assist unit so as to adjust the assist force.
The power steering device according to claim 1 or 2. A vehicle comprising the power steering device according to any one of claims 1 to 3.

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