Steering system

Abstract

To provide a steering system excellent in steering performance and running stability.SOLUTION: A steer-by-wire steering system mounted on a vehicle includes: an input device cantilevered on the vehicle and into which force is input by a driver of the vehicle; a detection device configured to detect the magnitude of force or torque acting on the input device; a motor configured to control a turning angle of a wheel of the vehicle; and a control device configured to control the motor such that the turning angle corresponding to the detection result by the detection device is obtained.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a steering system. [Background technology]

[0002] Steer-by-wire steering systems mounted on vehicles are known (see, for example, Patent Document 1). In the steer-by-wire system, the wheels are steered by a motor based on the steering angle of the steering wheel, without mechanically connecting the steering wheel and the wheels. In this system, the steering angle ratio, which is the ratio of the steering angle of the wheels to the steering angle, can be set arbitrarily. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-068518 A Summary of the Invention [Problem to be solved by the invention]

[0004] By setting the steering angle ratio high, steering becomes possible without changing the grip of the steering wheel, improving maneuverability. However, if the steering angle ratio is too high, a small change in the steering angle may cause a large change in the turning angle, which may result in a decrease in driving stability.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a steering system that is excellent in steerability and driving stability. [Means for solving the problem]

[0006] The above object can be achieved by a steer-by-wire steering system mounted on a vehicle, the steering system comprising: an input device supported on one side by the vehicle and to which a force is input by a driver of the vehicle; a detection device that detects the magnitude of the force or torque acting on the input device; a motor that controls the steering angle of wheels of the vehicle; and a control device that controls the motor so that the steering angle corresponds to the detection result of the detection device.

[0007] The input device may include an elastic member that elastically supports the input device between the vehicle, the input device being supported on the vehicle so as to be movable within a predetermined range, an elastic reaction force of the elastic member corresponding to the position of the input device within the predetermined range being input, and the detection device may detect a force or torque acting between a portion of the input device where the driver's force is input and a portion of the input device where the elastic reaction force is input.

[0008] The input device may further include a damping member for damping the moving speed of the input device.

[0009] 4. The steering system according to claim 1, further comprising an operation unit that outputs a command to said control device to maintain said steering angle regardless of said detection result.

[0010] The apparatus may further include an alarm device that issues a predetermined alarm when the detection result exceeds an upper limit value. Effect of the Invention

[0011] According to the present invention, a steering system having excellent steerability and driving stability can be provided. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic configuration diagram of a steering system 1. [Diagram 2] FIG. 2 is an example of a map that defines the target steering angle. [Diagram 3] 3A and 3B are explanatory diagrams of the input device. [Figure 4]4A and 4B are explanatory diagrams of an input device according to a first modified example. [Diagram 5] FIG. 5A is an explanatory diagram of an input device according to a second modified example, and FIG. 5B is an explanatory diagram of an input device according to a third modified example. [Figure 6] FIG. 6A is an explanatory diagram of a modified steering wheel, and FIG. 6B is a modified map that defines a target steering angle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [Outline of steering system configuration] FIG. 1 is a schematic diagram of a steering system 1. The steering system 1 is a steer-by-wire type steering system mounted on a vehicle. The steering system 1 includes an input device 10, a detection device 30, a control device 50, a motor control device 70, a motor 72, a transmission device 74, wheels 76, and a steering angle detection device 78. Although described in detail later, a force is input to the input device 10 by an operation of a driver. The detection device 30 detects the magnitude of the force input to the input device 10. The control device 50 calculates a target steering angle of the wheels 76 according to the detection result of the detection device 30. The motor control device 70 controls the driving torque of the motor 72 according to the target steering angle. The control device 50 and the motor control device 70 each include a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The driving torque of the motor 72 is transmitted to the wheels 76 via the transmission device 74. The steering angle of the wheels 76 is controlled to the target steering angle. The transmission device 74 decelerates the rotation of the motor 72 to linearly move the rack shaft, thereby steering the wheels 76 via the tie rods. The steering angle detection device 78 detects the actual steering angle of the wheels 76 and outputs a detection signal to the control device 50.

[0014] FIG. 2 is an example of a map that specifies the target steering angle. The horizontal axis indicates the force detected by the detection device 30, and the vertical axis indicates the target steering angle. The control device 50 calculates the target steering angle by referring to this map. Although details will be described later, when the direction of the force detected by the detection device 30 is counterclockwise, the target steering angle is calculated as a positive value. When the target steering angle is positive, the wheels 76 are controlled to be steered in the counterclockwise direction. When the direction of the force detected by the detection device 30 is clockwise, the target steering angle is calculated as a negative value. When the target steering angle is negative, the wheels 76 are controlled to be steered in the clockwise direction. As shown in FIG. 2, the larger the force detected by the detection device 30, the larger the target steering angle is calculated to be. The target steering angle may be calculated by an arithmetic expression that uses the force detected by the detection device 30 as an argument.

[0015] [Input device] 3A and 3B are explanatory diagrams of the input device 10. FIG. 3A is a top view of the input device 10. FIG. 3B is a cross-sectional view taken along line AA of FIG. 3A. The input device 10 is provided on the dashboard of a vehicle. The input device 10 is supported on the vehicle side in a cantilever manner. The input device 10 includes a shaft portion 11, a handle 12, and a stopper portion 16. The base end of the shaft portion 11 is supported on the vehicle. The shaft portion 11 is supported on the vehicle so as to be rotatable around the central axis of the shaft portion 11. The shaft portion 11 is made of, for example, metal. The handle 12 is fixed to the tip of the shaft portion 11. The handle 12 is wheel-shaped, but is not limited to this. The handle 12 is made of, for example, metal. A force is input to the handle 12 by the driver, as will be described in detail later. The shaft portion 11 is provided with a protrusion 13 protruding from its outer circumferential surface. The protrusion 13 is provided extending from the base end side of the shaft portion 11 along the axial direction.

[0016] The detection device 30 is attached between the handle 12 and the protrusion 13 of the shaft portion 11. The detection device 30 detects the force acting on the shaft portion 11. The detection device 30 converts an electrical signal output by a detection unit such as a strain gauge into a force, the electrical signal changing depending on the magnitude of the force acting on the shaft portion 11.

[0017] The stopper portion 16 is fixed to the vehicle so as to surround the periphery of the base end of the shaft portion 11. The stopper portion 16 is made of, for example, metal. The stopper portion 16 is annular. A notch 17 is formed in the stopper portion 16. The notch 17 holds the protrusion 13 of the shaft portion 11. This makes the shaft portion 11 unrotatable relative to the vehicle. Therefore, the steering angle of the handle 12 is approximately zero. Note that the shaft portion 11 is not limited to being completely unrotatable. For example, there may be a gap between the notch 17 and the protrusion 13, and the shaft portion 11 may be rotatable by the amount of this gap.

[0018] The driver inputs a force to rotate the steering wheel 12. Here, the base end of the shaft portion 11 is prevented from rotating by the stopper portion 16 as described above. Therefore, a torsional force acts on the shaft portion 11. The detection device 30 detects the magnitude of the torsional force acting on the shaft portion 11. As described above, the control device 50 calculates the target steering angle to be a larger value as the force detected by the detection device 30 is larger. In this manner, the steering angle of the wheels 76 is controlled to the target steering angle.

[0019] As described above, the driver can control the steering angle of the wheels 76 by inputting a force to the steering wheel 12, which has a zero steering angle. Therefore, the driver does not need to change his / her grip to turn the steering wheel 12 as in the case of a steering wheel. In this way, the steering performance is improved. In addition, the steering angle of the wheels 76 is controlled by the magnitude of the force input by the driver to the steering wheel 12. For this reason, the steering angle of the wheels 76 is prevented from fluctuating greatly. In this way, the driving stability is improved.

[0020] [Modifications of input device] Next, modified examples of the input device will be described. Figures 4A and 4B are explanatory diagrams of an input device 10a of a first modified example. Figure 4A corresponds to Figure 3A. Figure 4B corresponds to Figure 3B. Note that the same components are given the same reference numerals, and duplicated explanations will be omitted.

[0021] The notch 17a of the stopper portion 16a of the input device 10a is formed larger in the circumferential direction than the above-mentioned notch 17. Therefore, the handle 12 can rotate within a predetermined range where the protrusion 13 does not come into contact with the notch 17a. When the protrusion 13 comes into contact with the notch 17a, further rotation of the handle 12 is restricted.

[0022] The protrusion 13 of the shaft portion 11 is elastically supported between the vehicle and the springs 20a and 20b. One end of the spring 20a is attached to the vehicle. The other end of the spring 20a is attached to the protrusion 13. One end of the spring 20b is attached to the vehicle. The other end of the spring 20b is attached to the protrusion 13. The protrusion 13 is supported by the springs 20a and 20b so as to be sandwiched in a direction intersecting the axial direction of the shaft portion 11. The springs 20a and 20b are attached at positions that do not interfere with the stopper portion 16a. The springs 20a and 20b are each a coil spring. The elastic reaction force of the spring 20a and the elastic reaction force of the spring 20b act on the protrusion 13. When the elastic reaction force of the spring 20a and the elastic reaction force of the spring 20b are in balance, the protrusion 13 is located at the center of the rotatable range defined by the notch portion 17a. The springs 20a and 20b are an example of an elastic member. The elastic member is not limited to a coil spring, and may be a plate spring.

[0023] The driver rotates the steering wheel 12 against the elastic reaction force of the springs 20a and 20b. The elastic reaction force of the springs 20a and 20b acts on the shaft portion 11 according to the rotational position of the steering wheel 12. As a result, a torsional force acts between the steering wheel 12 and the protrusion 13 of the shaft portion 11. The detection device 30 is provided between the steering wheel 12 and the protrusion 13 of the shaft portion 11. Therefore, the detection device 30 can detect the force acting between the part of the input device 10 to which the force of the driver is input and the part of the input device 12 to which the elastic reaction force is input. Therefore, the detection device 30 can detect the torsional force acting on the shaft portion 11. Even when the steering wheel 12 is located within the rotatable range, the steering angle of the wheels 76 is controlled based on the magnitude of the force detected by the detection device 30.

[0024] For example, it is conceivable to provide a sensor that detects the rotational position of the steering wheel 12, and control the steering angle of the wheels 76 based on the detection result of this sensor. However, providing the above sensor in addition to the detection device 30 may increase the number of parts and the cost. In addition, the structure and control may become complicated. In this embodiment, the detection device 30 can be used to control the steering angle of the wheels 76 even when the steering wheel 12 is located within the rotatable range. This makes it possible to prevent the occurrence of the above problems.

[0025] For example, right turns, left turns, and lane changes, which require a small steering angle of the wheels 76, are performed by rotating the steering wheel 12 within its rotatable range. A U-turn, which requires a large steering angle of the wheels 76, is performed based on the magnitude of the force input to the steering wheel 12 with the rotation of the steering wheel 12 restricted. In this way, the operability of the steering wheel 12 is improved.

[0026] When the rotation of the steering wheel 12 is restricted, a torsional force acts on the shaft 11 due to the elastic reaction force of the springs 20a and 20b at the position where the rotation of the steering wheel 12 is restricted and the force applied to the steering wheel 12 by the driver. The detection device 30 detects the magnitude of this force, and the steering angle of the wheels 76 is controlled based on the detection result of the detection device 30.

[0027] The springs 20a and 20b are attached to the protrusion 13, but are not limited to this. For example, the springs 20a and 20b may be attached to a portion between the detection device 30 and the base end of the shaft portion 11.

[0028] FIG. 5A is an explanatory diagram of an input device 10b of a second modified example. A protrusion 14 is provided between the detection device 30 of the shaft portion 11a and the handle 12. The protrusion 14 protrudes from the outer circumferential surface of the shaft portion 11a. The protrusion 14 extends along the axial direction of the shaft portion 11a. The shaft portion 11a is supported by dampers 22a and 22b. One end of the damper 22a is attached to the vehicle. The other end of the damper 22a is attached to the protrusion 14. One end of the damper 22b is attached to the vehicle. The other end of the damper 22b is attached to the protrusion 14. The protrusion 14 is supported by the dampers 22a and 22b so as to be sandwiched in a direction intersecting the axial direction of the shaft portion 11a. Each of the dampers 22a and 22b exerts a reaction force on the shaft portion 11 according to the rotation speed of the shaft portion 11a. This damps the rotation speed of the shaft portion 11a. The dampers 22a and 22b are an example of a damping member.

[0029] The dampers 22a and 22b can suppress rattling of the handlebars 12 at a position where the elastic reaction force of the spring 20a and the elastic reaction force of the spring 20b are balanced, thereby improving operability. The dampers 22a and 22b also suppress the rotation speed of the handlebars 12. This can suppress a delay in the steering response of the wheels 76 in response to an excessively fast rotation speed of the handlebars 12.

[0030] 5B is an explanatory diagram of an input device 10c according to a third modified example. In the input device 10c, the dampers 22a and 22b are attached to the protrusion 13. In this modified example as well, it is possible to suppress rattling of the handle 12 at a position where the elastic reaction force of the spring 20a and the elastic reaction force of the spring 20b are balanced.

[0031] When the driver turns the steering wheel 12, the elastic reaction force of the springs 20a and 20b and the reaction force of the dampers 22a and 22b act on the shaft portion 11. For this reason, for example, when the driver tries to turn the steering wheel 12 with a large force, a large twisting force can be applied to the shaft portion 11 even if the steering wheel 12 is within the rotatable range. As a result, when the driver inputs a large force to the steering wheel 12 in an emergency, for example, the corresponding force is detected by the detection device 30. Therefore, the wheels 76 can be steered significantly in a short period of time, improving safety.

[0032] [Handle modification] FIG. 6A is an explanatory diagram of a steering wheel 12a of a modified example. A switch 12b is provided on the outer periphery of the steering wheel 12a. The switch 12b can be pressed by the driver. The switch 12b is electrically connected to the control device 50a. While the switch 12b is pressed down, the switch 12b outputs a command to the control device 50a to maintain the steering angle regardless of the detection result of the detection device 30. The control device 50a that receives the command sets the current steering angle of the wheels 76 to the target steering angle. Therefore, while the switch 12b is pressed down, the steering angle of the wheels 76 is maintained. As a result, the steering angle of the wheels 76 is maintained by pressing the switch 12b without the driver having to continuously input a force to the steering wheel 12a. In this way, operability is improved. The switch 12b is not limited to being provided on the steering wheel 12a. For example, the switch 12b may be provided at the driver's feet. The switch 12b is an example of an operating unit.

[0033] A vibration actuator 12c is provided in the steering wheel 12a. The vibration actuator 12c is electrically connected to the control device 50a. When the force detected by the detection device 30 exceeds an upper limit value, the control device 50a drives the vibration actuator 12c to vibrate the steering wheel 12a. This allows the driver to recognize that excessive force is being applied to the steering wheel 12a. This prevents the driver from unnecessarily applying excessive force to the steering wheel 12a. In this way, operability is improved. The vibration actuator 12c is an example of an alarm unit.

[0034] The notification unit is not limited to the vibration actuator 12c. For example, the notification unit may be a display that displays an image, a speaker that outputs sound, or a light that outputs light. For example, a warning image may be displayed on a dashboard display. A warning sound may be output from a speaker of the vehicle or a speaker of the car navigation system. A predetermined warning light may be turned on.

[0035] [Variation of calculation of target steering angle] FIG. 6B is a modified example of a map that defines a target steering angle. FIG. 6B corresponds to FIG. 2. In FIG. 6B, a target steering angle is defined according to a vehicle speed. Specifically, a target steering angle is defined for each of low-speed driving, medium-speed driving, and high-speed driving. The control device 50 acquires the vehicle speed from a vehicle speed sensor, and calculates a target steering angle by referring to the map of FIG. 6B. According to this map, the target steering angle is calculated to be smaller as the vehicle speed increases. This improves safety during high-speed driving while ensuring steerability during low-speed driving, for example. The target steering angle may be calculated by an arithmetic expression that uses the force detected by the detection device 30 and the vehicle speed as arguments.

[0036] In the above embodiment and modified example, the detection device 30 detects the magnitude of the force input to the input device 10, but it may detect the magnitude of the torque input to the input device 10. In this case as well, the target steering angle calculated is larger as the torque increases.

[0037] In the above embodiment and modified example, an input device 10 including a joystick 12 that allows the driver to input a force to rotate the joystick has been described. However, the input device is not limited to this. For example, the input device may be a joystick that allows a force to be input in the left-right direction. In this case, the joystick may be supported by the vehicle so that it cannot slide or tilt. The driver inputs a force in the left-right direction to the joystick. This causes a bending force to act on the joystick. The detection device detects this bending force.

[0038] The joystick may be supported by the vehicle so as to be slidable or tiltable within a predetermined range in the left-right direction. In this case, the joystick may be elastically supported between the vehicle and the joystick by an elastic member. A damper may be provided to attenuate the sliding speed or tilting speed of the joystick. The joystick may be provided with the above-mentioned switch 12b and vibration actuator 12c.

[0039] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0040] 1 Steering system 10, 10a, 10b, 10c Input device 11 Shaft 12, 12a Handle 12b Switch (operation part) 12c Vibration actuator (alarm unit) 13, 14 Convex part 16, 16a Stopper part 17, 17a Notch 20a, 20b Spring (elastic member) 22a, 22b Damper (damping member) 30 Detection Device 50, 50a Detection device 72 Motor 76 Wheels

Claims

1. A steer-by-wire steering system mounted on a vehicle, an input device supported by a cantilever on the vehicle and to which a force is input by a driver of the vehicle; A detection device for detecting a magnitude of a force or torque acting on the input device; A motor for controlling a steering angle of the wheels of the vehicle; a control device that controls the motor so that the steering angle corresponds to a detection result of the detection device; and Equipped with a steering system.

2. an elastic member that elastically supports the input device between the input device and the vehicle; the input device is supported by the vehicle so as to be movable within a predetermined range, and an elastic reaction force of the elastic member is input according to a position of the input device within the predetermined range; The steering system according to claim 1 , wherein the detection device detects a force or a torque acting between a portion of the input device to which the force of the driver is input and a portion of the input device to which the elastic reaction force is input.

3. The steering system according to claim 2 , further comprising a damping member for damping a moving speed of the input device.

4. 4. The steering system according to claim 1, further comprising an operation unit that outputs a command to the control device to maintain the steering angle regardless of the detection result.

5. 4. The steering system according to claim 1, further comprising an alarm device that issues a predetermined alarm when the detection result exceeds an upper limit value.

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