JP2004042829A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device for a vehicle, achieving a smaller size even when using a plurality of actuators. <P>SOLUTION: A first electric motor 4 for giving operating reaction to a steering member 2 is connected to a sun gear 15 as a first element for a differential transmission mechanism 5 and a second electric motor 20 for varying a steering ratio (or assisting steering) is connected to a ring gear 18 as a third element for the differential transmission mechanism 5. The plurality of electric motors 4, 20 are coordinated with the differential transmission mechanism 5 to achieve a smaller size. The first electric motor 4 is arranged coaxially with a first steering shaft 3 to achieve a further smaller size. Operating torque on the steering member 2 is detected depending on a current variation ΔI of the first electric motor 4 and the controlled voltage of the first electric motor 4 is regulated corresponding thereto. No need exists for a separate torque sensor. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vehicle steering device that steers steered wheels based on an operation of a steering member.
[0002]
[Prior art]
A variable steering ratio mechanism [VGRS (Variable Gear Ratio System)] for varying the ratio of the steering amount of the steered wheels according to the steering amount of a steering member such as a steering wheel, and an electric motor for variable steering ratio control. There have been provided various types of vehicle steering devices provided with (for example, see Japanese Patent Application Laid-Open No. 5-77751). In this case, an electric motor for generating the steering assist force and an electric motor for the above-described variable steering ratio control are provided.
[0003]
On the other hand, in recent years, a so-called steer-by-wire system (also referred to simply as SBW), in which a mechanical connection between a steering member and a steered wheel is released and a part of a steering transmission system is constituted by an electric path. A steering device for a vehicle is provided. In this case, an electric motor for steering and an electric motor for reaction force for applying an operation reaction force to the steering member are provided. In addition, when the steering ratio variable function is added, a high-output electric motor is required as an electric motor for steering, and the control thereof becomes complicated.
[0004]
[Problems to be solved by the invention]
When a plurality of electric motors are provided as in these vehicle steering devices, there is a problem that the size is increased.
The present invention has been made in view of the above problems, and has as its object to provide a vehicular steering device that can achieve downsizing in a vehicular steering device having a plurality of actuators (electric motors).
[0005]
Means for Solving the Problems and Effects of the Invention
In order to achieve the above object, the invention according to claim 1 provides a steering member, a first element connected to the steering member, a second element connected to the steered wheels, and a third element that associates the first and second elements. , A first actuator for applying an operation reaction force to the steering member, and a first actuator for applying an operation reaction force to the steering member, and a drive transmission capable of being connected to the third element. A second actuator for changing a steering ratio, which is a ratio of a steered amount of the steered wheel to a steered amount of the steered member, or an operation for detecting an operation angle of the steered member; An angle detection unit, and a control unit that drives and controls the first actuator based on a detected operation angle detected by the operation angle detection unit and / or a state quantity related to torque applied to the steering member. It is an butterfly.
[0006]
In the present invention, the first element and the third element of the differential transmission mechanism are driven by the first and second actuators, respectively, and the first actuator applies an operation reaction force to the steering member, while the second actuator applies the operation reaction force to the steering member. By rotating the differential transmission mechanism differentially, the steering ratio between the rotation amount of the steering member and the steering amount of the steered wheels is set to a required value, or a steering assist force for assisting the steering of the steered wheels is generated. Can be done. Moreover, by associating the first and second actuators with the corresponding elements of the differential transmission mechanism, it is possible to reduce the size of the vehicle steering system as a whole.
[0007]
According to a second aspect of the present invention, in the first aspect, the first actuator includes an electric motor disposed coaxially with a support shaft of a steering member, and the control unit controls a control voltage of the electric motor by controlling the electric motor. It is characterized in that it is adjusted according to the amount of change in current. In the present invention, further miniaturization can be achieved by arranging the electric motor coaxially with the support shaft of the steering member. In addition, since the operation torque applied to the steering member can be detected according to the amount of change in the current of the electric motor, the structure can be significantly simplified as compared with the case where a separate torque sensor is provided.
[0008]
According to a third aspect of the present invention, in the first or second aspect, the first actuator is an electric motor including a rotor directly connected coaxially with a support shaft of a steering member, and a stator disposed around the rotor. It is characterized by including. Such a layout of the rotor and the stator saves space and contributes to an improvement in the efficiency of the electric motor.
According to a fourth aspect of the present invention, in the first aspect, a planetary transmission mechanism is interposed between the steering member and the first element, and the first actuator is provided coaxially with one element of the planetary transmission mechanism. It is characterized by including an electric motor. In the case of a planetary transmission mechanism, for example, the backlash is smaller than that of a worm gear mechanism or the like, and the control of the reaction force on the steering member via the first actuator is easy.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle steering system according to an embodiment of the present invention. Referring to FIG. 1, a vehicle steering system 1 includes a first steering shaft 3 as a support shaft of a steering member 2 that is integrally rotatably connected to a steering member 2 such as a steering wheel, and a first steering shaft 3. A second steering shaft 6 connected coaxially to the first steering shaft 3 via a first electric motor 4 as a first actuator for reaction force and a differential transmission mechanism 5 to the first steering shaft 3; And a steering mechanism 7 such as a rack and pinion mechanism connected to the second steering shaft 6.
[0010]
The steering mechanism 7 includes a steering shaft 8 that extends in the left-right direction of the vehicle, and a knuckle arm 11 that is coupled to both ends of the steering shaft 8 via tie rods 9 and supports a steered wheel 10. The steered shaft 8 is supported by the housing 12 and is slidable in the axial direction. Steering of the steered wheels 10 is achieved by sliding of the steered shaft 8.
A rack gear 8a is formed on a part of the steered shaft 8, and a pinion gear 13 provided at an end of the second steering shaft 6 and integrally rotating with the second steering shaft 6 is formed on the rack gear 8a. Are engaged. When the second steering shaft 6 is rotationally driven in accordance with the operation of the steering member 2, the rotation of the second steering shaft 6 is converted into sliding of the steered shaft 8 by the pinion gear 13 and the rack gear 8a. Steering of the steering wheel 10 is achieved.
[0011]
The first electric motor 4 functions to give an operation reaction force to the steering member 2. The first electric motor 4 has a housing 4a rotatably supported via a bearing 14 on a fixed member such as a vehicle body or a steering column, and a rotating shaft 4b. The housing 4a is connected to the first steering shaft 3 so as to be integrally rotatable. The rotation shaft 4b is integrated with a sun gear 15 as a first element (sun member) on the input side of the differential transmission mechanism 5, which is arranged coaxially with the first steering shaft 3 and the second steering shaft 6. It is rotatably connected.
[0012]
The differential transmission mechanism 5 is a mechanism for allowing the differential rotation between the first and second steering shafts 3 and 6, and includes, for example, a planetary gear mechanism as a planetary transmission mechanism as illustrated.
The differential transmission mechanism 6 includes a plurality of planet gears 17 as second elements (planet members) that are rotatably held by the above-described sun gear 15 on the input side and the carrier 16 on the output side and mesh with the sun gear 15. And a ring gear 18 serving as a ring member having an inner tooth 18a meshing with each planetary gear 17 on the inner periphery.
[0013]
The ring gear 18 forms, for example, a worm wheel by forming external teeth 18b on the outer periphery. The external teeth 18b are drivingly connected to a second electric motor 20 as a second actuator for varying the steering ratio via a drive transmission gear 19 made of, for example, a worm. Although not shown, the casing of the second electric motor 20 is fixed at an appropriate position on the vehicle body.
The first electric motor 4 and the second electric motor 20 are controlled by a control unit C including a microprocessor and the like.
[0014]
The first steering shaft 3 is provided with a steering angle sensor 21 as a steering position sensor for detecting a steering angle (steering position) of the steering member 2. A detection signal from the steering angle sensor 21 is input to the control unit C.
Further, the steered shaft 8 is provided with a steered position sensor 22 for detecting a steered position in relation to the axial position of the steered shaft 8, and also controls a detection signal from the steered position sensor 22. The data is input to the unit C. Further, a detection signal from a vehicle speed sensor 23 for detecting a vehicle speed is input to the control unit C.
[0015]
The control unit C outputs a control signal to drive circuits 24 and 25 as drive units for driving the first electric motor 4 and the second electric motor 20, respectively, based on the input signals from the sensors. I do.
For example, a steering ratio between the rotation amount of the steering member 2 and the steering amount of the steered wheels 9 is set according to the traveling state of the vehicle, for example, the vehicle speed, and the set steering ratio and the operation amount of the steering member 2 are set. Based on this, a voltage command value of the second electric motor 20 for varying the steering ratio is set, and a control signal corresponding to the voltage command value is given to the drive circuit 25 to drive and control the second electric motor 20. .
[0016]
On the other hand, a signal relating to the current value I flowing through the first electric motor 4 for reaction force is further supplied to the control unit C via the line 26 from the first electric motor 4 itself.
The control unit C calculates a current change amount ΔI of the first electric motor 4 from a signal related to the current value I from the line 26. Since the current change amount ΔI is proportional to the steering torque applied to the steering member 2, the control unit C calculates a voltage command value (control voltage) V of the first electric motor 4 using the following equation. .
[0017]
V = K · ΔI + C
Here, K is a gain, and C is a voltage addition amount according to the driving situation, and is set according to, for example, a vehicle speed detected by the vehicle speed sensor 23, a steering angle detected by the steering angle sensor 21, and the like.
The first electric motor 4 controlled by the control voltage V applies a desired reaction torque to the steering member 2.
[0018]
According to the present embodiment, the first electric motor 4 for applying an operation reaction force to the steering member 2 is connected to the sun gear 15 as the first element of the differential transmission mechanism 5, while the steering ratio variable. By connecting the second electric motor 20 to the ring gear 18 as the third element of the differential transmission mechanism 5, each electric motor 4, 20 can be associated with the corresponding element 15, 18 of the differential transmission mechanism 5, respectively. Thus, the overall size of the vehicle steering system 1 can be reduced.
[0019]
In addition, by arranging the first electric motor 4 for reaction force on the same axis as the first steering shaft 3 serving as a support shaft of the steering member 2, further downsizing can be achieved.
In addition, since the operation torque to the steering member 2 can be detected according to the current change amount ΔI of the first electric motor 4, the structure can be significantly simplified as compared with the case where a separate torque sensor is provided. it can.
In the present embodiment, the second electric motor 20 functions as an electric motor for varying the steering ratio. However, the present invention is not limited to this, and the second electric motor 20 functions as an electric motor for assisting steering. In this case, the second electric motor 20 applies a steering assist force to the steered shaft 8 via the differential transmission mechanism 5, the second steering shaft 6, the pinion gear 13, and the rack gear 8a. .
[0020]
Next, FIG. 2 shows another embodiment of the present invention. Referring to FIG. 2, the present embodiment is different from the embodiment of FIG. 1 in that the embodiment of FIG. Although the first steering shaft 3 is directly driven by the first electric motor 4, in the present embodiment, the first electric motor 26 as a reaction force actuator is connected to the first steering shaft 3 via the planetary transmission mechanism 27. The point is that the steering shaft 3 is driven.
[0021]
The planetary transmission mechanism 27 is composed of, for example, a planetary gear mechanism. The planetary transmission mechanism 27 includes a sun gear 28 that is rotationally driven by a first electric motor 26, and a plurality of planetary gears 30 that are rotatably supported by a carrier 29 that is integrally rotatable with the first steering shaft 3. , A non-rotatable ring gear 31. The first electric motor 26 has a rotating shaft 26a supported by a housing fixed to a fixed member such as a vehicle body or a steering column. The rotating shaft 26a coaxially connects the sun gear 28 so as to be integrally rotatable. I do.
[0022]
When the first electric motor 26 drives the sun gear 28 to rotate, the planetary gear 30 revolves while rotating, and the carrier 29 rotates. As a result, an operation reaction force is applied to the steering member 2 from the first electric motor 26 via the planetary transmission mechanism 27. Reference numeral 32 denotes a torque sensor for detecting an operation torque applied to the steering member 2, and a signal from the torque sensor 32 is input to the control unit C. The control unit C controls the first electric motor 26 via the drive circuit 24 in accordance with a signal from the torque sensor 32 and the like. The other configuration is the same as that of the embodiment of FIG.
[0023]
According to the present embodiment, torque transmission loss is small and control is easy, as compared with a case where an operation reaction force is applied via, for example, a worm gear mechanism.
In the embodiment of FIG. 2, an example is shown in which the first electric motor 26 drives the sun gear 28 to rotate, but the present invention is not limited to this, and the ring gear 31 may be driven to rotate.
1 and 2, the second electric motor 20 drives, for example, the ring gear 18 as one element of the differential transmission mechanism 5 via the drive transmission gear 19. Any element of the mechanism 5 may be configured to be driven by a direct drive method.
[0024]
For example, with reference to FIG. 3 which is a schematic diagram, a differential transmission mechanism 5 including a planetary transmission mechanism such as a planetary gear mechanism and a second transmission mechanism are provided in a housing 33 fixed to a fixing member such as a vehicle body or a steering column. A second electric motor 34 as an actuator is accommodated.
A carrier 16 that rotatably supports a planetary gear 17 of the differential transmission mechanism 5 is connected to the first steering shaft 3 so as to be integrally rotatable. Further, the sun gear 15 of the differential transmission mechanism 5 is connected to the second steering shaft 6 so as to be integrally rotatable.
[0025]
The second electric motor 34 is disposed coaxially with the first and second steering shafts 3 and 6, and a rotor 34 a that rotates integrally with the ring gear 18, takes in the periphery of the rotor 34 a, and is supported by the housing 33. And a stator coil 34b.
According to the present embodiment, since the second electric motor 34 is disposed coaxially with the differential transmission mechanism 5, space can be saved, and the torque from the second electric motor 34 can be efficiently transmitted. Can be transmitted.
[0026]
4A, 4B, and 4C each show another embodiment of the present invention. Each embodiment shows an example in which a speed reduction mechanism R is provided between the second electric motor 20 and the ring gear 18 of the differential transmission mechanism 5.
In the embodiment of FIG. 4A, as the reduction mechanism R, a driven gear 35 composed of a spur gear that is rotationally driven by the second electric motor 20 and a spur gear that meshes with the drive gear 35 and rotates integrally with the ring gear 18. And a gear 36.
[0027]
In the embodiment shown in FIG. 4B, as the reduction mechanism R, a driven gear 37 composed of a bevel gear rotationally driven by the second electric motor 20 and a driven gear composed of a bevel gear that meshes with the drive gear 37 and rotates integrally with the ring gear 18 are used. A cross shaft gear mechanism having a gear 38 is used. Instead of the cross shaft gear mechanism, a staggered shaft gear mechanism such as a hypoid gear mechanism can be used.
In the embodiment of FIG. 4C, as the reduction mechanism R, a drive pulley 39 that is rotationally driven by the second electric motor 20, and the drive pulley 39 and the drive gear transmitted through the endless transmission band 40 are integrated with the ring gear 18. A belt pulley mechanism including a rotating driven pulley 41 is used.
[0028]
In each of the embodiments shown in FIGS. 4A to 4C, a large reduction ratio can be ensured with a simple mechanism, and a high transmission efficiency can be realized with little play.
Note that the present invention is not limited to the above embodiments, and various changes can be made within the scope of the claims of the present invention.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle steering system according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a schematic configuration of a vehicle steering system according to another embodiment of the present invention.
FIG. 3 is a schematic diagram showing a schematic configuration of a main part of a vehicle steering system according to still another embodiment of the present invention.
FIGS. 4A, 4B and 4C are schematic diagrams each showing a schematic configuration of a main part of a vehicle steering system according to still another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vehicle steering apparatus 2 Steering member 3 First steering axis (support axis of steering member)
4 First electric motor (first actuator)
Reference Signs List 5 Differential transmission mechanism 6 Second steering shaft 7 Steering mechanism 8 Steering shaft 8a Rack gear 10 Steered wheel A Steering transmission system 13 Pinion gear 15 Sun gear (first element)
16 Career (2nd element)
17 planetary gear (second element)
18 Ring gear (third element)
18a Internal teeth 18b External teeth 19 Drive transmission gear 20 Second electric motor (second actuator)
C control section 21 steering angle sensor 22 steering position sensor 23 vehicle speed sensor 26 first electric motor (first actuator)
27 planetary transmission mechanism 28 sun gear 29 carrier 30 planetary gear 31 ring gear 32 torque sensor 34 second electric motor (second actuator)
34a rotor 34b stator coil (stator)

Claims (4)

A differential transmission mechanism including a steering member, a first element connected to the steering member, a second element connected to the steered wheels, and a third element that associates the first and second elements;
A first actuator coupled to the steering member and the first element so as to be able to transmit a drive, and for applying an operation reaction force to the steering member;
A second actuator that is connected to the third element so as to be able to transmit drive, and that changes a steering ratio, which is a ratio of a steering amount of a steered wheel to a steering amount of a steering member, or assists steering of the steered wheel;
Operation angle detection means for detecting an operation angle of the steering member;
A control unit for driving and controlling the first actuator based on a detected operation angle detected by the operation angle detection means and / or a state quantity related to a torque applied to the steering member. Steering gear. 2. The control device according to claim 1, wherein the first actuator includes an electric motor arranged coaxially with a support shaft of the steering member, and the control unit adjusts a control voltage of the electric motor according to a change amount of a current of the electric motor. A steering device for a vehicle, comprising: The vehicle according to claim 1 or 2, wherein the first actuator includes an electric motor including a rotor directly connected coaxially to a support shaft of a steering member, and a stator disposed around the rotor. Steering gear. The planetary transmission mechanism is interposed between the steering member and the first element, and the first actuator includes an electric motor provided coaxially with one element of the planetary transmission mechanism. Vehicle steering system.

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