JP7283238B2 - steering system - Google Patents

Description

The present invention relates to a steering system for steering wheels.

For example, in an automobile equipped with a steer-by-wire steering system, a steering shaft to which a steering wheel is connected is mechanically separated from a steering shaft that performs reciprocating linear motion for steering wheels (steerable wheels). A steering angle of the steering wheel, that is, a rotation angle of the steering shaft is detected by a rotation sensor, and the steering shaft is linearly moved according to the detection result. Linear motion of the steered shaft is realized by a rack and pinion mechanism and a steered motor of the steering system.

The steering angle of the wheels corresponds to the rotation angle of the pinion of the rack and pinion mechanism. In order to set the steering angle of the wheels to a predetermined value, the control unit of the steering system transmits a command signal corresponding to the detection result of the rotation sensor to the steering motor. The steering motor rotates the pinion about a rotation angle corresponding to the command signal. As a result, the automobile travels along the desired travel locus. Patent document 1 discloses a steering system using steer-by-wire.

JP 2006-315595 A

Conventional steering systems have the following problems. That is, when the automobile turns, the steering motor rotates based on the rotation angle of the steering shaft, but the steering angle of the wheels obtained by the rotation of the steering motor is different from the actual steering angle of the wheels. Sometimes. As a result, a difference occurs between the target travel trajectory intended by the driver and the actual travel trajectory of the vehicle. In other words, even if the driver tries to turn the car in a desired direction by turning the steering wheel, the car does not actually follow the operation, and the driver needs to turn the steering wheel further. This becomes more conspicuous as the turning acceleration of the automobile increases.

One of the causes of the difference between the target travel trajectory and the actual travel trajectory of the vehicle is the wheel bearing device (also called a hub unit) to which the wheels are attached. A wheel bearing device has an inner shaft member to which a wheel is attached, an outer ring member attached to a knuckle on the vehicle body side, and a plurality of rolling elements interposed between the inner shaft member and the outer ring member. Since the wheel bearing device is not a completely rigid body, and the inner shaft member is slightly inclined with respect to the outer ring member when the automobile turns, the above-described difference in trajectory occurs.

Accordingly, an object of the present disclosure is to reduce the difference between the target travel trajectory and the actual travel trajectory of the vehicle in a steering system.

A steering system of the present disclosure includes a rack and pinion mechanism having a rack and a pinion, a steering motor that rotates the pinion, a steering shaft that reciprocates linearly by power transmitted from the pinion to the rack, and the steering A wheel bearing device for mounting a wheel in order to steer the wheel based on the reciprocating linear motion of a shaft, and determining an operation amount of the steering motor and giving a command signal corresponding to the operation amount to the steering motor. A control unit and a sensor device having a sensor head provided in the wheel bearing device,
The wheel bearing device includes an inner shaft member to which the wheel is attached, an outer ring member attached to a vehicle body, and a plurality of rolling elements interposed between the inner shaft member and the outer ring member,
The sensor device has the sensor head that is attached to the outer ring member and detects a part of the inner shaft member. find the parameter for the slope of the line,
The control unit obtains a corrected rotation angle of the pinion based on the parameter, adds the corrected rotation angle to a target rotation angle of the pinion by the steering motor, and operates the steering motor. Determine quantity.

According to the steering system, even if the inner shaft member is tilted with respect to the outer ring member in the wheel bearing device due to the turning of the vehicle, the sensor device obtains the parameter related to the tilt. The control unit obtains the corrected rotation angle of the pinion based on the parameter, adds the corrected rotation angle to the target rotation angle of the pinion by the steering motor, and determines the operation amount of the steering motor. When the operation amount of the steering motor is determined, a command signal corresponding to the operation amount is given to the steering motor. Therefore, it is possible to reduce the difference between the target travel trajectory and the actual trajectory of the automobile due to the inclination of the inner shaft member in the wheel bearing device.

Preferably, the sensor head has two sensors arranged side by side along the axial direction of the outer ring member and each detecting a distance to a part of the inner shaft member in a non-contact manner,
The sensor device obtains the parameter based on the distance between the two sensors in the axial direction and the distance detected by the two sensors.
With this configuration, it is possible to obtain a parameter relating to the inclination of the center line of the inner shaft member with respect to the outer ring member.

According to the steering system of the present disclosure, it is possible to reduce the difference between the target travel trajectory and the actual travel trajectory of the automobile due to the inclination of the inner shaft member in the wheel bearing device.

It is an explanatory view showing a schematic structure of an example of a steering system. 1 is a cross-sectional view of a wheel bearing device; FIG. FIG. 4 is a schematic diagram showing the behavior of the wheel bearing device when the automobile turns, and is a top view of the wheel bearing device. It is an explanatory view of a part of a sensor device and a bearing device for wheels. It is a figure explaining a means to detect distance by a sensor head.

FIG. 1 is an explanatory diagram showing a schematic configuration of an example of a steering system. A steering system 10 shown in FIG. 1 includes a rack and pinion mechanism 11 , a steering motor 14 , a steering shaft 15 , a wheel bearing device 16 , a control unit 17 and a sensor device 18 . The steering system 10 further includes a steering shaft 26 to which a steering wheel 25 operated by the driver is connected, and a rotation sensor 27 that detects the rotation angle of the steering shaft 26 .

The steering system 10 of the present disclosure is a so-called steer-by-wire device. In other words, the steering shaft 26 and the steered shaft 15 that reciprocates linearly to steer the wheels 7 (steered wheels 7) are mechanically separated. The steering angle of the steering wheel 25 operated by the driver matches the rotation angle of the steering shaft, and the rotation sensor 27 detects the rotation angle. The steering motor 14 linearly moves the steering shaft 15 via the rack and pinion mechanism 11 according to the detection result.

A rotation sensor 27 detects the rotation angle of the steering shaft 26 and transmits a detection signal to the control unit 17 . The control unit 17 determines the amount of operation of the steering motor 14 and gives the steering motor 14 a command signal corresponding to the amount of operation. The control unit 17 determines the operation amount of the steering motor 14 based on the rotation angle of the steering shaft 26, that is, the detection signal of the rotation sensor 27, as well as the corrected rotation angle of the pinion 13, which will be described later.

A rack and pinion mechanism 11 has a rack 12 and a pinion 13 . By rotating the pinion 13 in the first direction and the second direction around the central axis of the pinion 13 , the rack 12 linearly moves in one and the other longitudinal direction of the rack 12 . The longitudinal direction of the rack 12 and the longitudinal direction of the steered shaft 15 are aligned, and the rack 12 is provided on a part of the steered shaft 15 . The steering shaft 15 is a member elongated in the lateral direction of the automobile.

The steering motor 14 rotates the pinion 13 via the reduction gear 14a. The amount of movement for the rotation of the steering motor 14 is determined by the control unit 17 . In other words, the steering motor 14 rotates in the normal and reverse directions by an amount of operation corresponding to the command signal from the control unit 17 . The forward rotation of the steering motor 14 causes the pinion 13 to rotate in the first direction, and the reverse rotation of the steering motor 14 causes the pinion 13 to rotate in the second direction.

The steered shaft 15 is linearly reciprocated by power transmitted from the pinion 13 to the rack 12 . Wheel bearing devices 16 are connected to both ends of the steered shaft 15 via tie rods 28, respectively. When the steered shaft 15 linearly moves in one direction along its longitudinal direction, the wheel 7 attached to the wheel bearing device 16 generates a steered angle for turning to the right. When the steered shaft 15 linearly moves in the other direction along the longitudinal direction, a steered angle for left turning is generated in the wheels 7 attached to the wheel bearing device 16 .

The wheel bearing device 16 is a component to which the wheel 7 is attached, and is also called a hub unit. The wheel bearing device 16 steers the wheels 7 based on the reciprocating linear motion of the steering shaft 15 . FIG. 2 is a cross-sectional view of the wheel bearing device 16. As shown in FIG. The wheel bearing device 16 includes an inner shaft member 21 to which the wheel 7 is attached, an outer ring member 22 attached to a knuckle 29 on the vehicle body side, and a plurality of rolling elements 23 interposed between the inner shaft member 21 and the outer ring member 22. and The rolling elements 23 of the present disclosure are balls.

The outer ring member 22 has a cylindrical outer ring main body portion 31 and a fixing flange portion 32 extending radially outward from the outer ring main body portion 31 . An outer ring raceway surface 33 is formed on each of the axial one side and the other side of the inner circumference of the outer ring main body portion 31 . A flange portion 32 is attached to the knuckle 29 . Thereby, the wheel bearing device 16 including the outer ring member 22 is fixed to the vehicle body of the automobile.

The inner shaft member 21 has a shaft-like hub axle 34 (also referred to as an inner axle) and an inner ring 35 fixed to the other side of the hub axle 34 in the axial direction. The hub shaft 34 has a shaft body portion 36 provided radially inward of the outer ring member 22 and a flange portion 37 . The shaft body portion 36 is a portion elongated in the axial direction. The flange portion 37 is a portion that extends radially outward from one axial side of the shaft body portion 36 . A bolt hole 38 is formed in the flange portion 37 . The wheel 7 is fixed to the flange portion 37 by bolts 39 attached to the bolt holes 38 . The inner ring 35 is an annular member, and is externally fitted and fixed to a portion 36 a of the shaft body portion 36 on the other side in the axial direction.

A shaft raceway surface 40 is formed on the outer peripheral side of the shaft body portion 36 , and an inner ring raceway surface 41 is formed on the outer peripheral surface of the inner ring 35 . A plurality of rolling elements 23 are provided between the outer ring raceway surface 33 on one side in the axial direction and the shaft raceway surface 40 . A plurality of rolling elements 23 are provided between the outer ring raceway surface 33 and the inner ring raceway surface 41 on the other side in the axial direction. In each row, a plurality of rolling elements 23 are held by retainers 24 .

As described above, the inner shaft member 21 rotates about the center line C0 with respect to the outer ring member 22 . In the present disclosure, the centerline C0 of the wheel bearing device 16 and the centerline C2 of the outer ring member 22 are aligned. As will be described later (see FIG. 3), when the automobile turns, the center line C1 of the inner shaft member 21 is slightly different from the center line C2 of the outer ring member 22 because the wheel bearing device 16 is not a completely rigid body. tilt.

FIG. 3 is a schematic diagram showing the behavior of the wheel bearing device 16 when the automobile turns, and is a top view of the wheel bearing device 16. As shown in FIG. As described above, the wheel bearing device 16 has a plurality of rolling elements 23 interposed between the inner shaft member 21 and the outer ring member 22 . The outer ring member 22 is a fixed member that is fixed to the vehicle body side of the automobile. The inner shaft member 21 has wheels 7 attached thereto and is supported by the outer ring member 22 via rolling elements 23 .

When the automobile turns, the wheel bearing device 16 to which the wheel 7 is attached rotates about a predetermined angle (θ1) about the center line P of the strut (not shown) extending in the vertical direction. As a result, the direction of the center line C2 of the outer ring member 22 changes. In FIG. 3, the dashed line indicates the center line C2 of the outer ring member 22 when the automobile goes straight (before turning), and the dashed line indicates the center line C2 of the outer ring member 22 when the automobile turns to the right. . The calculated steering angle of the wheels 7 when the vehicle is turning is θ1 with reference to the case where the vehicle is traveling straight.

Here, when the automobile turns, as described above, the direction of the center line C2 of the outer ring member 22 changes, but the wheels 7 go straight in the direction of rotation and try to rotate. Therefore, the center line C1 of the inner shaft member 21 is slightly inclined with respect to the center line C2 of the outer ring member 22 . In FIG. 3, the calculated direction of rotation of the wheel 7 perpendicular to the centerline C2 (indicated by a dashed line) is indicated by arrow R1. The direction of the arrow R1 is an imaginary state in which the wheel bearing device 16 is a rigid body and the center line C1 of the inner shaft member 21 is not inclined with respect to the center line C2 of the outer ring member 22. FIG. On the other hand, since the center line C1 of the inner shaft member 21 is actually inclined with respect to the center line C2 of the outer ring member 22, the rotation direction of the wheel 7 due to the inclination is indicated by an arrow R2. In particular, the higher the turning acceleration of the automobile, the greater the inclination of the center line C1 with respect to the center line C2. In FIG. 3, the inclination angle of the center line C1 of the inner shaft member 21 with respect to the center line C2 of the outer ring member 22 is "Q".

In the steering system 10 of the present disclosure (see FIG. 1), when the vehicle turns, the steering motor 14 rotates based on the rotation angle of the steering shaft 26 (the steering angle of the steering wheel 25). However, due to the inclination (inclination angle Q) occurring in the wheel bearing device 16, the steering angle θ1 of the wheels 7 caused by the rotation of the steering motor 14 and the actual steering angle θ2 of the wheels 7 are different. may differ. As a result, a difference occurs between the target travel trajectory intended by the driver and the actual travel trajectory of the vehicle. Therefore, in the steering system 10 of the present disclosure, control is performed to reduce this difference. The control will be explained later.

FIG. 4 is an explanatory diagram of part of the sensor device 18 and the wheel bearing device 16. As shown in FIG. The sensor device 18 has a sensor head 19 provided on the wheel bearing device 16 . The sensor device 18 further has a calculator 45 (see FIG. 1) that processes the signal output by the sensor head 19 . The control unit 17 may have the functions of the calculator 45 . As shown in FIG. 4, the sensor head 19 is attached to the outer ring member 22 . The sensor head 19 detects part of the inner shaft member 21 .

In the present disclosure (see FIGS. 2 and 4), the sensor head 19 is mounted on the inner side of the vehicle (the other side in the axial direction) opposite to the outer side of the vehicle (one side in the axial direction) to which the wheel 7 is attached in the wheel bearing device 16. is provided in In the present disclosure, the target member 44 attached to the inner ring 35 is targeted for detection. Since the target member 44 is fixed to the inner ring 35 , the inclination angle of the inner shaft member 21 having the inner ring 35 with respect to the outer ring member 22 matches the inclination angle of the target member 44 . Therefore, a parameter relating to the inclination of the target member 44 is determined by the sensor device 18 .

The sensor head 19 has two sensors 20a and 20b. The two sensors 20 a and 20 b face the target member 44 and are arranged side by side along the axial direction of the outer ring member 22 . Various forms can be adopted as the sensors 20a and 20b. Each of the two sensors 20a and 20b detects the distance from the inner shaft member 21 to the target member 44 in a non-contact manner.

FIG. 5 is a diagram for explaining means for detecting the distance by the sensor head 19. As shown in FIG. The distance to the part of the target member 44 detected by the first sensor 20a is "Z1", and the distance to the other part of the target member 44 detected by the second sensor 20b is "Z2". . A calculator 45 of the sensor device 18 calculates a parameter related to the inclination of the target member 44, that is, the center line C1 of the inner shaft member 21 with respect to the outer ring member 22, based on the signals from the sensor head 19 (two sensors 20a and 20b). A parameter relating to the slope of is calculated.

In the present disclosure, the parameter is the inclination angle Q between the centerline C2 of the outer ring member 22 and the centerline C1 of the inner shaft member 21 . Based on the distances Z1 and Z2 and the distance d between the two sensors 20a and 20b in the axial direction, the computing unit 45 obtains the tilt angle Q [rad] as the parameter from the following equation (1).

Q=atan{(Z1−Z2)/d}π×180 Equation (1)

Note that the parameter may be other than the tilt angle Q. The parameters may be the distances Z1 and Z2, or values correlated with the tilt angle Q (for example, having a linear relationship).

[Regarding the processing performed by the control unit 17]
The control executed by the control unit 17 to reduce the difference between the target travel trajectory intended by the driver and the actual trajectory of the vehicle will be described.

The control unit 17 obtains the corrected rotation angle of the pinion 13 based on the parameter (inclination angle Q). The corrected rotation angle of the pinion 13 is the angle by which the pinion 13 is additionally rotated as the vehicle turns. The relationship between the parameter (inclination angle Q) and the corrected rotation angle of the pinion 13 is set in advance, and the set information is stored in the control unit 17 . The relationship between the parameter (inclination angle Q) and the corrected rotation angle of the pinion 13 is set as a previously obtained function, for example.

Therefore, when the parameter (inclination angle Q) is obtained, the corrected rotation angle is uniquely obtained. In the present disclosure, the rotation angle of pinion 13 and the steering angle of wheels 7 are in a linear relationship. Therefore, the rotation angle of the pinion 13 for additionally giving the wheel 7 a steering angle corresponding to the value of the inclination angle Q is the corrected rotation angle. Note that the corrected rotation angle may have a negative value as well as a positive value.

When the corrected rotation angle is obtained, the control unit 17 adds the corrected rotation angle to the target rotation angle of the pinion 13 by the steering motor 14 (hereinafter referred to as the "target rotation angle"). The amount of movement of the rudder motor 14 is determined. The target rotation angle is the rotation angle of the pinion 13 determined based on the rotation angle of the steering shaft 26 detected by the rotation sensor 27 (hereinafter referred to as "sensor detection angle").

In the present disclosure, the relationship between the sensor detection angle and the target rotation angle is set in advance, and the set information is stored in the control unit 17 . The relationship between the sensor detection angle and the target rotation angle is set, for example, as a previously obtained function. Therefore, when the sensor detection angle is obtained, the target rotation angle is uniquely obtained. The target rotation angle may be obtained by using one or both of the steering speed and the vehicle speed in addition to the sensor detection angle.

When the control unit 17 obtains the target rotation angle based on the corrected rotation angle of the pinion 13 and the angle detected by the sensor, the control unit 17 adds the corrected rotation angle to the target rotation angle. The control unit 17 performs control to rotate the pinion 13 about the angle obtained by the addition. That is, the control unit 17 determines the operation amount of the steering motor 14 required to rotate the pinion 13 by the angle obtained by adding the corrected rotation angle to the target rotation angle. The control unit 17 generates a command signal corresponding to the determined operation amount of the steering motor 14 . The command signal is output from the control unit 17 to the steering motor 14 . The steering motor 14 operates based on the command signal to steer the wheels 7 . As a result, the wheels 7 are steered with the tilt of the inner shaft member 21 in the wheel bearing device 16 taken into consideration for the steering angle of the wheels 7 based on the sensor detection angle.

[Regarding the steering system 10 of the present disclosure]
As described above, the steering system 10 of the present disclosure (see FIG. 1) includes the rack and pinion mechanism 11 having the rack 12 and the pinion 13, the steering motor 14 that rotates the pinion 13, and the transmission from the pinion 13 to the rack 12. A steered shaft 15 that performs reciprocating linear motion by the power generated by the steering shaft 15 and a wheel bearing device 16 to which the wheels 7 are attached in order to steer the wheels 7 based on the reciprocating linear motion of the steered shaft 15 . Furthermore, the steering system 10 comprises a control unit 17 and a sensor device 18 .

The sensor device 18 has a sensor head 19 attached to the outer ring member 22 and having a part of the inner shaft member 21 as a detection target. Based on the signal from the sensor head 19 , the sensor device 18 obtains a parameter regarding the inclination of the center line C<b>1 of the inner shaft member 21 with respect to the outer ring member 22 .

The control unit 17 determines the corrected rotation angle of the pinion 13 based on the parameters. Further, the control unit 17 adds the corrected rotation angle to the target rotation angle (target rotation angle) of the pinion 13 by the steering motor 14 to determine the operation amount of the steering motor 14 . After determining the operation amount of the steering motor 14, the control unit 17 gives the steering motor 14 a command signal corresponding to the operation amount.

According to the steering system 10 having the above configuration, even if the inner shaft member 21 is tilted with respect to the outer ring member 22 in the wheel bearing device 16 due to turning of the vehicle, the sensor device 18 obtains a parameter related to the tilt. be done. The control unit 17 determines the corrected rotation angle of the pinion 13 based on the parameters. The corrected rotation angle is added to the target rotation angle (target rotation angle) of the pinion 13 by the steering motor 14 to determine the operation amount of the steering motor 14 . When the operation amount of the steering motor 14 is determined, a command signal corresponding to the operation amount is given to the steering motor 14 .

As a result, the wheels 7 are steered with the tilt of the inner shaft member 21 in the wheel bearing device 16 taken into consideration for the steering angle of the wheels 7 based on the sensor detection angle. As a result, it is possible to reduce the difference between the target travel trajectory and the actual travel trajectory of the vehicle caused by the inclination of the inner shaft member 21 of the wheel bearing device 16 .

In the steering system 10 of the present disclosure, the sensor head 19 has two sensors 20a, 20b (see FIGS. 4 and 5). The sensors 20a and 20b are arranged side by side along the axial direction of the outer ring member 22, and detect the distance to the target member 44, which is a part of the inner shaft member 21, in a non-contact manner. Then, the sensor device 18 detects the distance d between the two sensors 20a and 20b in the axial direction and the distances Z1 and Z2 detected by the two sensors 20a and 20b. A parameter relating to the inclination of the center line C1 of is obtained.

[About others]
In the above embodiment, the steering angle of the steering wheel 25 operated by the driver is detected by the rotation sensor 27 as the rotation angle of the steering shaft 26 . A case has been described where the control unit 17 determines the operation amount of the steering motor 14 using the detection result (and also using the corrected rotation angle).
The steering system 10 of the present disclosure can also be applied to automobiles in which automatic driving is performed without being based on the driver's operation as described above. In the case of an automatic driving car, for example, the control unit 17 acquires map information, GPS information, and information from an on-vehicle sensor such as an on-vehicle camera, and based on the information, the pinion 13 is targeted by the steering motor 14. A rotation angle (target rotation angle) is determined by calculation or the like. Then, the amount of operation of the steering motor 14 is determined by adding the corrected rotation angle obtained by the above process to the determined target rotation angle.

The embodiments disclosed this time are illustrative in all respects and are not restrictive. The scope of rights of the present invention is not limited to the above-described embodiments, but includes all modifications within the scope of equivalents to the configurations described in the scope of claims.

7: Wheel 10: Steering system 11: Rack and pinion mechanism 12: Rack 13: Pinion 14: Steering motor 15: Steering shaft 16: Wheel bearing device 17: Control unit 18: Sensor device 19: Sensor head 20a: First sensor 20b: second sensor 21: inner shaft member 22: outer ring member 23: rolling element d: interval dimension Z1, Z2: distance

Claims (2)

A rack and pinion mechanism having a rack and a pinion, a steering motor that rotates the pinion, a steering shaft that performs reciprocating linear motion by power transmitted from the pinion to the rack, and a reciprocating linear motion of the steering shaft. a wheel bearing device for mounting the wheel in order to steer the wheel; a control unit that determines an operation amount of the steering motor and gives a command signal corresponding to the operation amount to the steering motor; a sensor device having a sensor head provided in the bearing device,
The wheel bearing device includes an inner shaft member to which the wheel is attached, an outer ring member attached to a vehicle body, and a plurality of rolling elements interposed between the inner shaft member and the outer ring member,
The sensor device has the sensor head that is attached to the outer ring member and detects a part of the inner shaft member. find the parameter for the slope of the line,
The control unit obtains a corrected rotation angle of the pinion based on the parameter, adds the corrected rotation angle to a target rotation angle of the pinion by the steering motor, and operates the steering motor. determine the amount,
steering system. The sensor head has two sensors that are arranged side by side along the axial direction of the outer ring member and detect a distance to a part of the inner shaft member in a non-contact manner,
The sensor device obtains the parameter based on the distance between the two sensors in the axial direction and the distance detected by the two sensors.
A steering system according to claim 1 .

Images