Adaptive front steering system of vehicle

0001The present invention relates to an adaptive front steering system of a vehicle, and more specifically, an adaptive that can ensure the convenience of steering and the safety of driving by changing the steering gear ratio according to the traveling condition of the vehicle.. Regarding the front steering system.

0002Generally, a power steering device that provides steering force of a vehicle is designed to use hydraulic pressure so that the operating force of the steering wheel can be lightly and smoothly steered quickly.

0003Such a power steering device can be selected regardless of the operating force of the steering gear ratio, as well as being able to steer with a small force, and absorbs the impact due to the unevenness of the road surface to prevent transmission to the steering wheel. It also plays a role.

0004In addition, the motor is driven by the ECU according to the operating conditions of the vehicle detected by the vehicle speed sensor and steering torque sensor to give a light and peaceful steering feeling at low speeds, and a heavy steering feeling at high speeds. Many electric steering devices such as EHPS (Electro-hydraulic Power Steering) or MDPS (Motor Driven Power Steering) that provide optimum steering conditions for the driver by providing directional stability are applied. ing.

0005Recently, by integrating the MDPS system and the AFS (Active Front Steering) system, a system that further optimizes the steering conditions provided to the driver has been applied.

0006Normally, the AFS system is a system that changes the steering gear ratio for each vehicle speed to reduce the amount of operation of the steering wheel parked and stopped so that the optimum steering gear ratio can be obtained at high speed.

0007For example, an active front wheel steering type AFS system can add or attenuate not only the steering angle by the driver but also the steering angle by the actuator, and at low speeds, the steering ratio is lowered to reduce the steering response. In addition, the driver will be able to operate stably even at high speeds so that the steering ratio can be increased at high speeds.

0008Due to the drive characteristics, such an AFS system includes actuators such as motors and reduction gears that generate further steering inputs in addition to the driver's steering input, and AFS ECUs that control these to change the steering output. And so on.

0009In addition, the AFS system is applied to mass-produced vehicles and its commercial value is recognized, but due to the high option cost of the vehicle, it is applied only to premium vehicles.

0010This is because the system is complicated, the number of parts is large, and the material cost is high.

0011Therefore, in order to widely apply the AFS system, it is required to develop a replenishment type AFS system that simplifies the system, reduces the number of parts, and reduces the material cost.

0012The techniques behind the present invention are disclosed in Patent Document 1, Patent Document 2, and Patent Document 3.

<p num="0013"><patcit num="1"><text>Japanese Publication No. 2008-273327</text></patcit><patcit num="2"><text>Japanese Publication Patent No. 2003-63423</text></patcit><patcit num="3"><text>US Registered Patent No. 7,306,535</text></patcit></p>

<p num="0014"> The present invention has been devised in consideration of such a point. By applying a hollow motor on the steering column shaft, in a motor that rotates together with the upper shaft, the steering gear is determined by the rotation direction and the amount of rotation of the shaft. By realizing a new type of AFS system with variable ratio, it is possible to simplify the overall system and provide a replenishable adaptive front steering system that can reduce the number of parts and material costs. There is a purpose.</p>

<p num="0015"> The vehicle adaptive front steering system provided by the present invention has the following features.</p><p num="0016"> The adaptive front steering system is arranged coaxially with an upper shaft connected to a steering wheel, a lower shaft acting as an output shaft, and a steering column shaft, and is connected between the upper shaft and the lower shaft. It is a structure that includes a hollow motor and the like.</p><p num="0017"> In such an adaptive front steering system, the motor housing of the hollow motor is connected to the upper shaft side and the motor shaft is connected to the lower shaft side, and the shaft of the hollow motor that rotates together with the upper shaft. The steering gear ratio can be changed according to the direction of rotation and the amount of rotation.</p><p num="0018"> Here, the motor housing of the hollow motor and the upper shaft can be connected via an upper planetary gear device.</p><p num="0019"> At this time, the upper planetary gear device is engaged with the sun gear mounted on the upper shaft, the ring gear mounted on the housing adapter of the motor housing, and the sun gear and the ring gear. It can consist of multiple planetary gears that are transmitted.</p><p num="0020"> Further, the motor shaft and the lower shaft of the hollow motor can be connected via a lower planetary gear device.</p><p num="0021"> At this time, the lower planetary gear device is engaged with the sun gear mounted on the lower shaft, the ring gear mounted on the shaft adapter of the motor shaft, and the sun gear and the ring gear. It can consist of multiple planetary gears that are transmitted.</p><p num="0022"> The adaptive front steering system is installed on the upper shaft and a lock unit that binds the upper shaft side and the lower shaft side in the event of a failure of the MDPS (Motor Driven Power Steering) system, and has a steering angle. And TAS (Torque &amp; Angle sensor), which transmits steering torque information to the ECU, can be further included.</p>

<p num="0023"> The adaptive front steering system provided by the present invention has the following advantages.</p><p num="0024"> First, by installing the motor coaxially with the steering column shaft, the number of parts is reduced compared to the existing worm shaft and worm wheel structure AFS and belt structure AFS, and the motor housing rotates with the upper shaft. Since the rotation angle of the output shaft is directly determined, the system can be simplified, such as eliminating the need for complicated gear devices, and the AFS system can be designed compactly, such as by reducing the number of parts and reducing material costs. It is advantageous for the configuration of.</p><p num="0025"> Second, the rotation of the motor housing can cause the wires connected to the housing to become entangled, but planetary gears are used in each of the vertical directions of the motor to design the motor so that it can only rotate within ± 90 °. This can solve the problem of wire entanglement.</p>

0026<figref num="1">It is a schematic sectional drawing which shows the adaptive front steering system by one Example of this invention.</figref><figref num="2">It is a perspective view which shows the upper planetary gear device of the adaptive front steering system by one Embodiment of this invention.</figref><figref num="3">It is a perspective view which shows the lower planetary gear device of the adaptive front steering system by one Embodiment of this invention.</figref>

0027Hereinafter, the present invention will be described in detail with reference to the attached drawings.

0028FIG. 1 is a schematic cross-sectional view showing an adaptive front steering system according to an embodiment of the present invention, and FIGS. 2 and 3 are upper planets of an adaptive front steering system according to an embodiment of the present invention. It is a perspective view which shows the gear device and the lower planetary gear device.

0029As shown in FIGS. 1 to 3, the adaptive front steering system steers a vehicle equipped with an electric power steering device (MDPS) by changing the steering gear ratio according to a driving situation. It is a replenishment type model with improved convenience and running stability.

0030For example, the adaptive front steering system uses a hollow motor on the steering column shaft, but the motor housing is connected to the upper shaft side, and the motor shaft is connected to the lower shaft side. And the lower shaft are not mechanically connected and can move relative to each other.

0031Specifically, unlike the existing AFS method of adjusting the rotation angle using planetary gears, harmonic gears, worms and worm wheels, the adaptive front steering system provided by the present invention rotates together with the upper shaft. This is a system in which the steering gear ratio is changed according to the direction in which the shaft rotates and the amount of rotation in the hollow motor.

0032To that end, the adaptive front steering system includes an upper shaft 10 that is connected to a steering wheel (not shown).

0033Such an upper shaft 10 is arranged in a coaxial structure with the steering column shaft (not shown), and is connected to the steering column shaft side by a flange fastening structure (not shown), a coupler (not shown), or the like. It operates in the same way as the operating speed and angle of the steering wheel operated by the driver.

0034At this time, in order to grasp the steering intention of the driver, a TAS23 is installed on the upper shaft 10 in a coaxial structure, and information on the steering angle and steering torque is transmitted from the TAS23 to the ECU.

0035The adaptive front steering system also includes a lower shaft 11 that acts as the final output shaft for steering wheel operation.

0036The lower shaft 11 is arranged coaxially with the upper shaft 10 and is supported by a structure connected to the lower planetary gear device 20 side, which will be described later.

0037The power output from such a lower shaft 11 can be transmitted to the gearbox (not shown) side.

0038Further, the adaptive front steering system includes a hollow motor 12 which is arranged coaxially with the steering column shaft and is connected between the upper shaft 10 side and the lower shaft 11 side.

0039The hollow motor 12 is composed of a motor housing 13 and a motor shaft 14, and is connected to the upper shaft 10 side and the lower shaft 11 side, respectively, with the motor housing 13 facing upward and the motor shaft 14 facing downward.

0040For example, the motor housing 13 can be connected to the upper shaft 10 side via the upper planetary gear device 15 by using a disk-shaped housing adapter 17 formed on the rear surface portion.

0041Further, the motor shaft 14 can be connected to the lower shaft 11 side via the lower planetary gear device 20 by using a disk-shaped shaft adapter 21 connected to the tip portion thereof by the coupler 24.

0042Such a hollow motor 12 is electrically connected to the ECU and is supplied with power from the ECU to rotate.

0043Since the motor shaft 14 of such a hollow motor 12 is not mechanically fixed to the upper shaft 10 side, it can be rotated only by the current adjusted by the ECU regardless of the rotation of the upper shaft 10.

0044Further, the adaptive front steering system is located above and below the hollow motor 12, and two planetary gear devices that mediate power between the hollow motor 12 side and the upper shaft 10 and the lower shaft 11, that is, the upper planetary gear. Includes device 15 and lower planetary gear device 20.

0045In such a planetary gear device, since the ring gear is fixed and the gear ratio is fixed, the variable steering angle is not affected.

0046Specifically, the planetary gear device is a motor housing connected to the upper shaft 10 side, unlike the role of the planetary gear device (variable steering gear ratio) in an AFS system using an existing planetary gear device. It reduces the rotation angle of 13 and keeps the rotation gear ratio of the upper shaft 10 and the lower shaft 11 at 1: 1 in the event of a system failure.

0047The adaptive front steering system also includes an upper planetary gear device 15 that mediates power between the upper shaft 10 side and the hollow motor 12 side.

0048The upper planetary gear device 15 includes a combination of a sun gear 16a, a ring gear 18a, and a plurality of planetary gears 19a.

0049The sun gear 16a is mounted on the upper shaft 10 in a coaxial structure and can rotate together. The ring gear 18a is concentrically arranged on the outer shell of the sun gear 16a and is supported on the steering column (not shown) side. The planetary gear 19a can be fixedly installed in a structure, and the planetary gear 19a is arranged within a distance between the central sun gear 16a and the outer ring gear 18a, and can rotate and idle at the same time by meshing transmission with these.

0050The planetary gears 19a consist of four gears arranged at regular intervals, and each planetary gear 19a is freely extended to each gear shaft 25 vertically extended from the upper surface of the housing adapter 17 formed in the motor housing 13. It can be supported by a rotatable structure.

0051As a result, when the upper shaft 10 rotates by the driver operating the steering wheel, the sun gear 16a rotates, and at the same time, each planet gear 19a rotates with respect to the fixed ring gear 18a, and at the same time, the sun gear It spins around, and eventually the entire motor housing 13 including the housing adapter 17 to which the planetary gear 19a belongs can rotate about the upper shaft axis as the central axis.

0052That is, when the upper shaft 10 rotates, the rotation is transmitted to the upper planetary gear device 15 and the motor housing 13 also rotates.

0053At this time, the rotation angle of the motor housing 13 is smaller than that of the upper shaft 10 due to the gear ratio of the upper planetary gear device 15.

0054For example, if the gear ratio of the upper planetary gear device 15 is 1: 4, when the steering wheel rotates 360 °, the motor housing 13 rotates 90 °, and by adjusting the gear ratio in this way, the steering wheel locks. -The motor housing 13 can rotate about 180 ° even when to-lock (LOCK TO LOCK).

0055With this angle of rotation, it is possible to solve the problem that the power supply line and signal line that must be connected to the hollow motor side are entangled by the rotation of the motor housing 13.

0056The adaptive front steering system also includes a lower planetary gear device 20 that mediates power between the lower shaft 11 side and the hollow motor 12 side.

0057Such a lower planetary gear device 20 is composed of a combination of a sun gear 16b, a ring gear 18b, and a plurality of planetary gears 19b, similarly to the upper planetary gear device 15.

0058The sun gear 16b is mounted on the lower shaft 11 in a coaxial structure and can rotate together. The ring gear 18b is concentrically arranged on the outer shell of the sun gear 16b and is supported on the steering column (not shown) side. The planetary gear 19b can be fixedly installed in a structure, and the planetary gear 19b is arranged within a distance between the central sun gear 16b and the outer ring gear 18b, and can rotate and idle at the same time by meshing transmission with these.

0059The planetary gears 19b consist of four gears arranged at regular intervals, and each planetary gear 19b is a gear shaft vertically extended from the bottom surface of a shaft adapter 21 connected via a motor shaft 14 and a coupler 24. Can be supported by a freely rotatable structure at 25.

0060As a result, when the motor shaft 14 of the hollow motor 12 rotates under the control of the ECU, each planetary gear 19b in the shaft adapter 21 of the motor shaft 14 rotates and idles with respect to the fixed ring gear 18b. When the sun gear 16b rotates in association with the rotation and idling of the planetary gear 19b, power is output by the lower shaft 11 that rotates together with the sun gear 16b, and steering is performed.

0061At this time, the steering gear ratio can be changed according to the rotation direction and the amount of rotation of the motor shaft 14.

0062Further, the adaptive front steering system includes a lock unit 22 that serves to bind the upper shaft 10 side and the lower shaft 11 side in the event of a failure of the MDPS (Motor Driven Power Steering) system.

0063The lock unit 22 is a type that uses a solenoid valve, is installed on one side of the front surface (bottom surface) of the motor housing 13, and operates in a manner of selectively binding to the shaft adapter 21 side.

0064The solenoid valve type lock unit can be applied with almost the same structure and method as the solenoid valve type lock unit adopted in a general AFC system.

0065For example, when the lock unit 22 is activated, the plunger 26 of the solenoid valve is inserted and fastened into a hole (not shown) or a groove (not shown) formed in the shaft adapter 21 to be fastened to the motor housing 13 side and the motor shaft. It can be tied to the shaft adapter 21 side to which 14 belongs.

0066That is, when the MDPS system fails, the upper shaft 10 and the lower shaft 11 are not mechanically fixed, so that the lower shaft 11 does not move even if the upper shaft 10 rotates.

0067Therefore, a lock unit 22 using a solenoid valve is required.

0068Normally, the motor housing 13 and the shaft adapter 21 on the lower planetary gear device side are connected to such a lock unit 22 when the engine is off or in a failure mode.

0069Without the lower planetary gear device 20, for example, even if the steering wheel is turned 360 °, the lower shaft 11 rotates 90 °, so that the minimum turning radius becomes very large.

0070To compensate for this, a lower planetary gear device 20 can be placed between the motor shaft 14 and the lower shaft 11 to maintain an overall steering gear ratio of 1: 1 even in the event of an MDPS failure.

0071Although the role of planetary gears in a general AFS system is a means for varying the steering gear ratio, the upper planetary gear device 15 provided in the present invention serves to reduce the angle of rotation of the motor housing 13 and lower. The planetary gear device 20 serves to adjust the overall steering gear ratio to 1: 1 in the event of an MDPS failure.

0072Therefore, when the driver operates the steering wheel, the operating force at this time is output to the upper shaft 10 the upper planetary gear device 15 the hollow motor 12 the lower planetary gear device 20 the lower shaft 11, and the steering is performed. At the same time, the steering gear ratio is changed by the amount of rotation of the motor shaft 14 due to the operation of the hollow motor 12 according to the traveling condition of the vehicle, so that the convenience of steering and the stability of traveling are ensured.

0073In the present invention, by applying an AFS system equipped with a hollow motor and a two-row planetary gear device, parts are reduced as compared with an AFS system using an existing planetary gear device, which is advantageous in terms of cost and packaging. ..

007410 Upper shaft 11 Lower shaft 12 Hollow motor 13 Motor housing 14 Motor shaft 15 Upper planetary gear device 16a, 16b solar gear 17 Housing adapter 18a, 18b ring gear 19a, 19b planetary gear 20 Lower planetary gear device 21 shaft adapter 22 Lock unit 23 TAS (Torque &amp; Angle sensor) 24 coupler 25 gear shaft 26 Plunger