JP2003335248A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To take countermeasures for failsafe when breakage or the like occurs in an electric steering motor in a steer-by-wire system wherein a part of a steering transmission system is constituted of an electrical path by releasing mechanical coupling between a steering member and a roller wheel, and to solve the problem that the steering member is heavy in operability when manual steering is established by merely performing the mechanical coupling between the steering member and the roller wheel at the time of fail. <P>SOLUTION: At a normal time, an actuator 20 for emergency puts idling a ring gear 18 as a third element of a planetary gearing mechanism 6, and a steer-by-wire state is generated. When an actuator 12 for steering goes in failure, the actuator 20 for emergency is put in operation as a source to generate a steering assist force. The actuator 20 for emergency rotates the ring gear 18 via a drive transmitting gear 19, and the steering assist force for sliding a steering shaft 7 is obtained. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering system that steers steered wheels based on an operation of a steering member.

[0002]

2. Description of the Related Art In recent years, a so-called steer-by-wire system in which a mechanical connection between a steering member such as a steering wheel and a steered wheel is released and a part of a steering transmission system is constituted by an electric path. The vehicle steering system is provided. For example, in the device disclosed in JP-A-1-233170,
An encoder provided on the steering shaft detects the steering position of the steering wheel, and the yaw rate gyro detects the traveling direction of the vehicle. Then, the steered wheels are steered so that the deviation between the traveling change instruction value based on the detected steering position and the actual traveling direction change amount based on the detection result of the yaw rate gyro becomes zero.

[0003]

However, in this type of steer-by-wire system, it is important to take a fail-safe measure against, for example, disconnection of an electric motor as an actuator for steering. Therefore, it is conceivable to achieve mechanical connection between the steering member and the steered wheels to function as a manual steering when a failure occurs, but there is a problem that the operation of the steering member becomes heavy.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle steering system capable of achieving good steering even when a failure occurs.

[0005]

In order to achieve the above object, the invention according to claim 1 is provided with a differential transmission mechanism interposed in the steering transmission system from the steering member to the steered wheels,
This differential transmission mechanism includes a first element connected to the steering member, a second element connected to the steered wheels, and a third element associating the first and second elements, and a steering actuator for steering the steered wheels. And an emergency actuator that is driveably transmitted to the third element of the differential transmission mechanism and idles the third element during normal operation, and responds to an operation of the steering member from the emergency actuator when an abnormality occurs in the steering actuator. And a control unit for generating a steering assist force.

In the present invention, the third element is normally set to be free so that it can function as a so-called steer-by-wire system in which the mechanical connection between the steering member and the steered wheels is released. Further, when an abnormality occurs in the steering actuator, the steering assist force can be obtained by using the emergency actuator, and good steering can be achieved. The invention according to claim 2 is provided with a differential transmission mechanism interposed in a steering transmission system from the steering member to the steered wheels, and the differential transmission mechanism is a first element connected to the steering member,
A steering actuator for steering the steered wheels, a second element connected to the steered wheels, and a third element for associating the first and second elements with each other, and an actuator for applying a steering reaction force to the steering member. A force actuator, a first clutch interposed between the first element and the reaction force actuator, and a second clutch interposed between any one of the second element and the third element and the reaction force actuator. A clutch and a control unit for disconnecting the first clutch and connecting the second clutch when the steering actuator is in an abnormal state, and for generating a steering assist force from the reaction force actuator according to the operation of the steering member. It is a feature.

In the present invention, the so-called steer-by-wire, in which the mechanical connection between the steering member and the steered wheels is released by connecting the first clutch and disconnecting the second clutch during normal operation It is possible to apply the operation reaction force to the steering member by means of the reaction force actuator while functioning as the above system. Further, when an abnormality occurs in the steering actuator, the first clutch is disengaged and the second clutch is connected, and the steering is performed from the reaction force actuator via the second or third element of the differential transmission mechanism. Good steering can be achieved by generating a steering assist force according to the operation of the member.

According to a third aspect of the present invention, in the first or second aspect, the invention further comprises a driven body which is driven by rotation of the third element of the differential transmission mechanism in normal times. In the present invention, it is possible to drive the driven body by taking out the driving force using the rotation of the third element that normally idles. Further, the driven body can be configured to include at least one of a blower, a fluid pressure pump, and an alternator. With this configuration, when the blower is driven, for example, it is possible to cool various actuators, ECUs and the like by blowing air from the blower.
Furthermore, for example, a water cooling pump as a fluid pressure pump may be driven. Furthermore, an alternator or the like may be driven to generate power.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment 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 steering device 1 for a vehicle (hereinafter, also simply referred to as steering device 1) includes a first steering shaft 3 that is integrally rotatably connected to a steering member 2 such as a steering wheel, and the like. To allow the differential rotation between the first and second steering shafts 3 and 5, and the second steering shaft 5 that is provided coaxially with the first steering shaft 3 and that is connected to the steering mechanism 4 such as a rack and pinion mechanism. And a planetary gear mechanism 6 as a differential transmission mechanism.

The steering mechanism 4 includes a steering shaft 7 extending in the left-right direction of the vehicle, a knuckle arm 10 that is connected to both ends of the steering shaft 7 via tie rods 8 and supports steering wheels 9. Equipped with. The steered shaft 7 is supported by a housing 11 and is slidable in the axial direction, and a steering actuator 12 composed of an electric motor is coaxially incorporated in the middle thereof. The drive rotation of the steering actuator 12 is converted into sliding of the steered shaft 7 by a motion conversion mechanism such as a ball screw mechanism, and the steered wheels 9 are steered by the sliding of the steered shaft 7.

A feature of the present embodiment is that the steering device 1 is normally operated by a steering device in which a mechanical connection is cut off at an intermediate portion of a steering transmission system A from the steering member 2 to the steered wheels 9. An emergency actuator, which functions as a by-wire system and achieves a mechanical connection between the steering member 2 and the steered wheels 9 when a failure occurs in the steering actuator 12, and which will be described later with respect to the planetary gear mechanism 6. 20 is used to generate a steering assist force to function as a power steering at the time of failure.

A rack gear 7a is formed on a part of the steered shaft 7, and the second steering shaft 5 is formed on the rack gear 7a.
A pinion gear 13 that is provided at the end of the and that rotates integrally with the second steering shaft 5 is meshed. As will be described later, when the second steering shaft 5 is rotationally driven according to the operation of the steering member 2 when the steering actuator 12 fails, the rotation of the second steering shaft 5 is rotated by the pinion gear 13 and the rack gear 7a. It is converted into sliding of the rudder shaft 7, and the turning of the steered wheels 9 is achieved.

The first steering shaft 3 is provided with a reaction force actuator 14 for applying an operation reaction force to the steering member 2, which is composed of, for example, a three-phase brushless motor. The casing of the reaction force actuator 14 is fixed at an appropriate position on the vehicle body. The planetary gear mechanism 6 is rotatably held by a sun gear 15 as an input-side first element, which is integrally rotatably connected to an end portion of the first steering shaft 3, as a first element, and is rotatably held by a carrier 16 at an output side. It includes a plurality of planet gears 17 as a second element that meshes with and a ring gear 18 that has inner teeth 18a that mesh with each planet gear 17 on the inner circumference.

The ring gear 18 forms, for example, a worm wheel by forming external teeth 18b. The external teeth 18b are drivingly connected to an emergency actuator 20 composed of an electric motor via a drive transmission gear 19 composed of, for example, a worm. Emergency actuator 2 during normal operation
0 idles the ring gear 18 (specifically,
Since the sun gear 15 and the carrier 16 can freely rotate relative to each other without restraining each other), the steering apparatus 1 functions as a steer-by-wire system. Further, when the steering actuator 12 has a failure such as a wire breakage, the emergency actuator 20 rotationally drives the ring gear 18 via the drive transmission gear 19 to slide the steered shaft 7 from the emergency actuator 20. I try to get the assist power of.

The steering actuator 12, the reaction force actuator 14, and the emergency actuator 20 are controlled by a control unit 21 including a microprocessor and the like. On the first steering shaft 3, a steering angle sensor 22 as a steering position sensor for detecting a steering angle (steering position) by the steering member 2, and a torque sensor 23 for detecting a steering torque input from the steering member 2. Is provided. These steering angle sensor 22 and torque sensor 23
The detection signal from is input to the control unit 21.

Further, the steering shaft 7 has a steering position sensor 2 for detecting the steering position in relation to the axial position of the steering shaft 7.
4 is provided, and a detection signal from the steered position sensor 24 is also input to the control unit 21. Further, a detection signal from the vehicle speed sensor 25 for detecting the vehicle speed is input to the control unit 21. The control unit 21 drives the steering actuator 12, the reaction force actuator 14, and the emergency actuator 20 based on the input signals from the sensors, respectively.
Control signals are output to 6, 27 and 28.

FIG. 2 is a flow chart for explaining the steering control process executed by the control unit 21. Referring to FIG. 2, the control unit 21 monitors whether the steering actuator 12 is operating normally (step S1). When no abnormality has occurred in the steering actuator 12, the control unit 21 keeps the emergency actuator 20 free (step S2), and adjusts the rotation amount of the steering member 2 according to, for example, the traveling state of the vehicle. Set the ratio (transmission ratio, gear ratio) to the turning amount of the steered wheels 9 [VGR
(Variable Gear Ratio) function], the voltage command value of the steering actuator 12 is set based on the set transmission ratio and the operation amount of the steering member 2, and the control signal corresponding to the voltage command value is set to the drive circuit 28. To control the drive of the steering actuator 12 (step S3). As a result, the steering actuator 12 outputs a torque for sliding the steered shaft 7 in a direction corresponding to the operating direction of the steering member 2, which is good according to the running condition of the vehicle and the operating mode of the steering member 2. Steering is achieved. In addition, not necessarily VG
It is not necessary to set the R function.

In this way, when an abnormality occurs in the steering actuator 12 while the steering actuator 12 is being driven and controlled, the control section 21 outputs a control signal to the drive circuit 27, and the emergency actuator which has been idling until then. The drive control of 20 is started (step S4). As a result, mechanical coupling is achieved between the steering member 2 and the steering mechanism 4 via the planetary gear mechanism 6, and the detection results of the steering angle sensor 22, the torque sensor 23, and the vehicle speed sensor 25 are obtained. The driving force of the emergency actuator 20 generated according to the detection result or the like can be transmitted to the steering mechanism 4 via the ring gear 18, the carrier 16 and the second steering shaft 5 to achieve appropriate steering assistance.

As described above, in the present embodiment, the normal functioning as a steer-by-wire system is performed, and the VGR function is exerted if necessary. When a failure occurs in the steering actuator 12, the steering member 2 and the steering mechanism 4 are mechanically coupled via the planetary gear mechanism 6, while the ring gear 18 as the third element of the planetary gear mechanism 6 is used as an emergency actuator. The steering assist force can be obtained by driving with 20. As a result, even when a failure occurs, the steering member 2 can be operated with a light operating force, and good steering can be achieved.

When a failure occurs in the steering actuator 12, a PWM control signal corresponding to the operation angle of the steering member 2 is created, and this PWM control signal is used as the emergency actuator 2.
0 into the drive circuit 27, and the emergency actuator 2
An appropriate steering assist force may be generated from zero. In the above embodiment, the sun gear 15 is connected to the steering member 2 and the carrier 16 supporting the planetary gear 17 is connected to the steered wheels 9, but the present invention is not limited to this, and the first element connected to the steering member 2 is And the second element connected to the steered wheels 9 are the sun gear 15, the carrier 16 and the ring gear 18.
Any two of them may be selected, and the remaining gear may be used as a third element, and the emergency actuator 20 may be connected to the third element so as to be capable of driving transmission.

Next, FIG. 3 shows another embodiment of the present invention. Referring to FIG. 3, the present embodiment is different from the embodiment of FIG. 1 in the following. That is, the first steering shaft 3 connected to the sun gear 15, which is the first element of the planetary gear mechanism 6, and the reaction force actuator 14 for applying an operation reaction force to the steering member 2 can be connected and separated from each other. The first clutch 31 is interposed. Further, a second clutch 32 that can be connected and disengaged is interposed between the reaction force actuator 14 and the drive transmission gear 19. The first and second clutches 31 and 32 are controlled so that they are alternatively brought into a connected state.

The normal reaction force actuator 14 is connected to the first steering shaft 3 and applies an operation reaction force to the steering member 2. Further, when the steering actuator 12 is out of order, the reaction force actuator 14, which is a source of the steering assist force, is connected to the drive transmission gear 19, and the reaction force actuator 14 is connected.
The driving force generated by the drive transmission gear 19 and the ring gear 1
The steering assist force for sliding the steered shaft 7 is provided to the second steering shaft 5 via the carrier 8 and the carrier 16.

The control unit 21 controls the steering actuator 12, the reaction force actuator 14, the first and second clutches 31 and 32 based on the input signals from the sensors.
Drive circuits 26, 28, 29 for respectively driving the
The control signal is output to 30. Next, FIG.
4 is a flowchart for explaining a steering control process executed by the control unit. Referring to FIG. 4, the control unit 2
1 monitors whether the steering actuator 12 is operating normally (step T1).

When no abnormality has occurred in the steering actuator 12, the control unit 21 causes the first clutch 31 to operate.
Is connected and the second clutch 32 is disengaged (step T2). Therefore, the reaction force actuator 14
Has a normal function of applying an operation reaction force to the steering member 2.
On the other hand, the ring gear 18 which is the third element of the planetary gear mechanism 6
The steering device 1 functions as a steer-by-wire system in which the mechanical connection between the steering member 2 and the steering mechanism 4 is released by the idling of the steering device 2.

Then, for example, a ratio (transmission ratio, gear ratio) between the rotation amount of the steering member 2 and the turning amount of the steered wheels 9 is set in accordance with the running condition of the vehicle [VGR (Variable Gear Ratio)].
Function], the voltage command value of the steering actuator 12 is set based on the set transmission ratio and the operation amount of the steering member 2, and a control signal corresponding to the voltage command value is given to the drive circuit 28 to perform steering. The driving actuator 12 is controlled (step T3). As a result, the steering actuator 12 outputs a torque for sliding the steered shaft 7 in a direction corresponding to the operating direction of the steering member 2, which is good according to the running condition of the vehicle and the operating mode of the steering member 2. Steering is achieved. In addition, the reaction force actuator 14 is operated by the steering member 2
It has a normal function of giving an operation reaction force to. It is not always necessary to set the VGR function.

Thus, when an abnormality occurs in the steering actuator 12 while the steering actuator 12 is being driven and controlled, the control section 21 outputs a control signal to the drive circuits 29 and 30 to disengage the first clutch 31. Then, the second clutch 32 is connected (step T4). Then, the reaction force actuator 14 is drive-controlled so that the reaction force actuator 14 functions as a source of the steering assist force (step T5).

As a result, mechanical coupling between the steering member 2 and the steering mechanism 4 via the planetary gear mechanism 6 is achieved, and the detection results of the steering angle sensor 22, the torque sensor 23 and the vehicle speed are obtained. To transmit the driving force of the reaction force actuator 14 generated according to the detection result of the sensor 25 or the like to the steering mechanism 4 via the ring gear 18, the carrier 16 and the second steering shaft 5 to achieve appropriate steering assistance. You can As described above, in the present embodiment, the system operates normally as a steer-by-wire system and, if necessary, exhibits the VGR function. When a failure occurs in the steering actuator 12, the steering member 2 and the steering mechanism 4 are mechanically coupled via the planetary gear mechanism 6, while the ring gear 1 as the third element of the planetary gear mechanism 6 is connected.
8 can be driven by the reaction force actuator 14 as the source of the steering assist force to obtain the steering assist force. As a result, even when a failure occurs, the steering member 2 can be operated with a light operating force, and good steering can be achieved.

When a failure occurs in the steering actuator 12, a PWM control signal corresponding to the operation angle of the steering member 2 is created, and this PWM control signal is used as the reaction force actuator 1.
4 into the drive circuit 26, and the reaction force actuator 1
It is also possible to generate an appropriate steering assist force from No. 4. Although the sun gear 15 is connected to the steering member 2 and the carrier 16 supporting the planetary gear 17 is connected to the steered wheels 9 in the embodiment of FIG. 3, the present invention is not limited to this, and the first element connected to the steering member 2 is And, as the second element connected to the steered wheels 9, any two of the sun gear 15, the carrier 16 and the ring gear 18 are selected, and the remaining gear is used as the third element, and the second clutch 32 is provided to the third element. The reaction force actuator 14 may be connected so as to be capable of driving transmission.

Further, in the embodiment of FIG. 3, the second cllar 32 is interposed between the ring gear 18, which is the third element of the planetary gear mechanism 6, and the reaction force actuator 14,
Although the steering assist force of the reaction force actuator 14 is transmitted via the ring gear 18 when the steering actuator 12 fails, the invention is not limited to this. For example, as shown in FIG. 5, the second steering shaft 5 connected to the second element of the planetary gear mechanism 6
And the second actuator 3 between the reaction force actuator 14 and
2 may be interposed to transmit the steering assist force of the reaction force actuator 14 via the second steering shaft 5 when the steering actuator 12 fails. The carrier 16, which is the second element of the planetary gear mechanism, and the reaction force actuator 14
A second clutch may be interposed between and.

In each of the above-described embodiments, the planetary gear mechanism 6 in the normal state has a third element, for example, a ring gear 18 in order to prevent the reaction force actuator 14 and the steering actuator 12 from interfering with each other. The torque is passed through and the ring gear 18 is idling. By the rotation of the ring gear 18 as the third element generated for the torque distribution in this way, for example, as the driven body,
The blower 33 as shown in FIG. 6A, the fluid pressure pump 34 as shown in FIG. 6B, and the alternator 35 as shown in FIG. 6C may be driven.

In FIG. 6A, the blower 33 is driven via the drive transmission gear 36 and the bevel gear mechanism 37 that mesh with the outer teeth 18b of the ring gear 18 of the planetary gear mechanism 6. In the fluid pressure pump 34 of FIG. 6 (b), the rotor 38, which is provided coaxially with the drive transmission gear 36 so as to be integrally rotatable, is rotationally driven in the fixed casing 39, whereby the fluid sucked from the suction side path 40 is removed. Discharge is performed through the discharge side path 41. The fluid pressure pump 34 may be a water cooling pump.

In the alternator 35 of FIG. 6 (c), the rotor coil 42, which is coaxially rotatable with the drive transmission gear 36 and is integrally rotatable, is rotationally driven in the stator coil 43, and the alternating current induced thereby is rectified by a rectifier circuit. The voltage is converted into direct current through 44 and the vehicle battery 45 is charged. In FIG. 6A, a blower 33 as a driven body
May be directly driven without the drive transmission gear 36 and the bevel gear mechanism 37. In addition, the fluid pressure pump 34 of FIG.
Alternatively, the alternator 35 in FIG. 6C may be directly driven by the ring gear 18 without the drive transmission gear 36.

Besides, the present invention is not limited to the above-mentioned respective embodiments, and various modifications can be made within the scope of the claims of the present invention.

[Brief description of 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 flowchart showing the flow of steering control of the vehicle steering system of FIG.

FIG. 3 is a schematic diagram showing a schematic configuration of a vehicle steering system according to another embodiment of the present invention.

4 is a flowchart showing a flow of steering control of the vehicle steering system of FIG.

FIG. 5 is a schematic diagram showing a schematic configuration of a vehicle steering system according to still another embodiment of the present invention.

6 (a), (b) and (c) are schematic views respectively showing a main part of a vehicle steering system according to still another embodiment of the present invention.

[Explanation of symbols]

1 Vehicle steering system 2 Steering member 3 First steering shaft 4 Steering mechanism 5 Second steering shaft 6 Planetary gear mechanism (differential transmission mechanism) 7 Steering axis 7a rack gear 9 steered wheels 12 Steering actuator 13 pinion gear 14 Reaction force actuator 15 Sun Gear (first element) 16 career 17 Planetary gear (second element) 18 Ring gear (3rd element) 18a internal teeth 18b external teeth 19 Drive transmission gear 20 Emergency actuator 21 Control unit 22 Steering angle sensor 23 Torque sensor 24 Steering position sensor 25 vehicle speed sensor 26-30 drive circuit 31 First clutch 32 Second clutch 33 Blower (driven body) 34 Fluid pressure pump (driven body) 35 Alternator (driven body)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Azuma             3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka               Koyo Seiko Co., Ltd. (72) Inventor Ryohei Hayama             3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka               Koyo Seiko Co., Ltd. (72) Inventor Naotake Kanda             3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka               Koyo Seiko Co., Ltd. (72) Inventor Shingo Maeda             3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka               Koyo Seiko Co., Ltd. (72) Inventor Masayuki Ueno             3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka               Koyo Seiko Co., Ltd. F-term (reference) 3D033 CA04 CA05 CA13 CA16 CA17                       CA18 CA21

Claims (3)

[Claims] 1. A differential transmission mechanism interposed in a steering transmission system from a steering member to steered wheels, the differential transmission mechanism including 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 is included, and further, a steering actuator for steering the steered wheels and a third element of the differential transmission mechanism are driveably connected to the third element, and the third element is normally provided. A vehicle steering system, comprising: an emergency actuator that idles the vehicle; and a control unit that generates a steering assist force according to the operation of the steering member from the emergency actuator when an abnormality occurs in the steering actuator. 2. A differential transmission mechanism interposed in a steering transmission system from the steering member to the steered wheels, the differential transmission mechanism including a first element connected to the steering member, a second element connected to the steered wheels, and A steering actuator for steering the steered wheels, a reaction force actuator for applying a steering reaction force to the steering member, and a third element for associating the first and second elements are provided. First intervening between force actuator
Clutch, a second clutch interposed between any one of the second element and the third element and the reaction force actuator, and the first clutch is disengaged when the steering actuator is abnormal and the second clutch And a control unit for connecting a steering wheel and generating a steering assist force from the reaction force actuator according to the operation of the steering member. 3. The vehicle steering system according to claim 1, further comprising a driven body which is driven by rotation of a third element of the differential transmission mechanism during normal operation.