JP2000355281A - Steering device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation type steering device for vehicle having a small space for detecting torque and a reduced cost of parts for the detection. SOLUTION: This steering device for vehicle is constituted in such a way that a steering mechanism 1 changing the direction of a wheel 10 is not mechanically connected with a steering wheel 2, steering angle of the steering wheel 2 and steering torque applied on the steering wheel 2 are determined, and a first electric motor 5 incorporated in the steering mechanism 1 is driven and controlled in accordance with the determined steering angle and steering torque to increase, decrease, and control the steering angle. It is provided with a second electric motor 3 connected with a shaft 30 of the steering wheel 2, a detection means 3b detecting a counter electromotive voltage of the second electric motor 3 or a current flowing in the second electric motor 3, and a means 4 computing steering torque based on the counter electromotive voltage or current detected by the detection means 3b, the steering angle, moment of inertia of the steering wheel 2, and moment of inertia of the second electric motor 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering mechanism for changing the direction of a wheel, which is not mechanically connected to a steering wheel, and determines a steering angle of the steering wheel and a steering torque applied to the steering wheel. The present invention relates to a vehicle steering system that controls the drive of an electric motor of a steering mechanism to increase or decrease a steering angle.

[0002]

2. Description of the Related Art Steering of a vehicle is performed by operating a steering means disposed inside a vehicle compartment, for example, a steering wheel (steering wheel).
Is transmitted to a steering mechanism disposed outside the vehicle compartment for steering of a steering wheel (generally, a front wheel). In recent years, hydraulic cylinders,
An actuator for steering assist such as an electric motor is arranged, and the actuator is driven based on a detection result of an operating force applied to a steering wheel for steering,
2. Description of the Related Art A vehicle steering device (power steering device) configured to assist the operation of a steering mechanism according to the rotation of a steering wheel and to reduce the labor burden on a driver for steering has been widely used.

However, in such a conventional steering apparatus for a vehicle, a mechanical connection between a steering wheel, which is a steering means, and a steering mechanism is required, and the position of the steering wheel in the vehicle interior is limited. However, there is a problem that the steering wheel is limited to a position where it can be connected to the steering mechanism outside the vehicle compartment. Further, even when the steering wheel is provided so as to be connectable, a complicated structure is required to realize the connection. The connection structure is required, which is a factor that hinders weight reduction of the vehicle and simplification of the assembly process.

[0004] For example, Japanese Utility Model Publication No. 2-29017 discloses a vehicle steering system which is a linkless power steering system for solving such a problem. In this vehicle steering device, a steering wheel is mechanically separated from a steering mechanism, and a steering actuator is provided in the middle of the steering mechanism in the same manner as a steering assist actuator in a conventional vehicle steering device. An electric motor is arranged, and the electric motor is driven based on the detection result of the operation direction and the operation amount of the steering wheel, thereby performing steering according to the operation of the steering wheel. .

[0005] The vehicle steering apparatus of the separated type configured as described above increases the degree of freedom in arranging the steering wheel.
In addition to the above-mentioned objectives such as reducing the weight of the vehicle, realization of new steering means such as levers and pedals instead of the steering wheel, detection of guidance signs on the road surface, reception of satellite information, etc. It is useful for the future development of automobile technology such as realization.

[0006]

In the vehicle steering apparatus as described above, a conventional torque sensor using a torsion bar is considered as a means for detecting the steering torque. The sensor is expensive, and there is a problem that the degree of freedom in design is limited due to restrictions on size, installation position, and the like. The present invention has been made in view of the above-described circumstances, and has as its object to provide a separated type vehicle steering device in which a space for detecting torque is small, and the cost of parts for that is low. I do.

[0007]

According to a first aspect of the present invention, there is provided a steering apparatus for a vehicle, wherein a steering mechanism for changing the direction of a wheel is not mechanically connected to the steering wheel, and a steering angle of the steering wheel and a steering torque applied to the steering wheel are determined. A vehicle steering device for controlling the drive of a first electric motor of the steering mechanism in accordance with the determined steering angle and steering torque to increase or decrease the steering angle; An electric motor, detection means for detecting a back electromotive voltage of the second electric motor or a current flowing in the second electric motor, and a back electromotive voltage or current detected by the detection means, the steering angle, and the steering wheel. Means for calculating the steering torque based on the moment of inertia of the second electric motor and the moment of inertia of the second electric motor.

In this vehicle steering system, the steering mechanism for changing the direction of the wheels is not mechanically connected to the steering wheel, but determines the steering angle of the steering wheel and the steering torque applied to the steering wheel, and determines the steering angle according to the determined steering angle and steering torque. Then, the first electric motor of the steering mechanism is drive-controlled to increase or decrease the steering angle. A second electric motor is connected to the shaft of the steering wheel, and the detecting means detects a back electromotive voltage of the second electric motor or a current flowing through the second electric motor. The calculating means calculates the steering torque based on the back electromotive voltage or current detected by the detecting means, the steering angle, the inertia moment of the steering wheel, and the inertia moment of the second electric motor. As a result, it is possible to realize a separation type vehicle steering device in which the space for detecting the torque is small and the cost of parts for the detection is low.

A second aspect of the present invention is directed to a vehicle steering system, wherein the second electric motor is a reaction motor that applies a force to the steering wheel in a direction opposite to the operation direction.

In this vehicle steering system, the second electric motor is a reaction motor that applies a force to the steering wheel in a direction opposite to the operation direction, so that a space for detecting torque is not required. Therefore, it is possible to realize a separation type vehicle steering device with a low component cost.

In the steering apparatus for a vehicle according to a third aspect of the present invention, the steering mechanism for changing the direction of the wheels is not mechanically connected to the steering wheel, and the steering angle of the steering wheel and the steering torque applied to the steering wheel are determined. In a vehicle steering system for controlling the driving of a first electric motor of the steering mechanism in accordance with a steering torque to increase or decrease a steering angle, a second electric motor connected to a shaft of the steering wheel is provided.
An electric motor, and detection means for detecting a back electromotive voltage of the second electric motor or a current flowing through the second electric motor,
Means for calculating the steering torque based on the back electromotive voltage or current detected by the detection means, the moment of inertia of the steering wheel, and the moment of inertia of the second electric motor.

In this vehicle steering system, the steering mechanism for changing the direction of the wheels is not mechanically connected to the steering wheel, but determines the steering angle of the steering wheel and the steering torque applied to the steering wheel. Then, the first electric motor of the steering mechanism is drive-controlled to increase or decrease the steering angle. A second electric motor is connected to the shaft of the steering wheel, and the detecting means detects a back electromotive voltage of the second electric motor or a current flowing through the second electric motor. The calculating means calculates the steering torque based on the back electromotive voltage or current detected by the detecting means, the inertia moment of the steering wheel, and the inertia moment of the second electric motor. As a result, it is possible to realize a separation type vehicle steering device in which the space for detecting the torque is small and the cost of parts for the detection is low.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing an embodiment. FIG. 1A is a principle diagram showing a principle structure of a vehicle steering system according to the present invention.
The vehicle steering system is connected to a steering wheel 2 (steering wheel), and a reaction motor 3 (second electric motor) that applies a force to the steering wheel 2 in a direction opposite to the operation direction; A detector 34 (detection means) for detecting an electromotive voltage or a current flowing through the reaction motor 3 and a rotary encoder 33 for detecting a steering angle of the steering wheel 2 are provided.

The vehicle steering system also includes a detector 34.
And the detected back electromotive voltage or current and the rotary encoder 33
Is provided with a steering controller 4a (means for calculating) which calculates and detects the steering torque applied to the steering wheel 2 based on the detected steering angle, the moment of inertia of the steering wheel 2 and the moment of inertia of the reaction motor 3. The steering control unit 4a also performs a reaction force control that applies a force in a direction opposite to the operation direction to the steering wheel 2 by the reaction force motor 3 based on the steering torque calculated and detected. FIG.
(B) is a speed increasing gear for increasing the rotation speed of the reaction force motor 3 between the steering wheel 2 and the reaction force motor 3 of the vehicle steering apparatus having the principle configuration shown in FIG. FIG. 7 is a principle diagram showing a principle configuration in a case where 7 is provided.

Hereinafter, the principle of the vehicle steering system having such a configuration will be described. As shown in FIG. 1B, when the speed increasing gear 7 is provided, the gear ratio of the speed increasing gear 7 is n: 1, the steering angle of the steering wheel 2 is θ _h , and the rotation angle of the reaction motor 3 is Assuming θ _m , θ _m = n · θ _h (1) Further, the torque applied to the gear of the speed increasing gear 7 on the steering wheel 2 side is T _x , the torque applied to the gear of the speed increasing gear 7 on the reaction motor 3 side. Is _Ty , _Tx = n · _Ty (2)

Here, the torque (steering torque) applied to the steering wheel 2 is T, the torque applied to the reaction motor 3 is T _m , the known moment of inertia of the steering wheel 2 is I _h , and the known reaction motor 3 is the moment of inertia I _m of the viscous drag coefficient C _h from the steering wheel 2 until the speed increasing gear 7 is known, the viscosity resistance coefficient from the speed increasing gear 7 is known up to the reaction motor 3 When C _{m, T x = T-I h ·} θ h "-C h · θ h '(3) T y = T m + I m · θ m" + C m · θ m' (4) ( where, θ '= dθ / dt θ ″ = d ² θ / dt ² )

[0017] (3), (4) by substituting expression (2) _{below, T-I h · θ h} "-C h · θ h '= nT m + nI m · θ
_m ″ + nC _m · θ _m ′ From equation (1), T−I _h · θ _h ″ −C _h · θ _h ′ = nT _m + nI _m · n
_{· Θ h "+ nC m ·} n · θ h ' to _{organize, T-nT m = I h} · θ h" + C h · θ h' + n 2 I m · θ h "+ n 2 C m · θ h '= ^{_{(I h + n 2 I m}} ) θ h "+ (C h + n 2 C m) θ h '(5)

I) There is no reaction force of the reaction motor (T _m =
0) Neglecting viscous resistance component, (from 5), from the ^{_{T = (I h + n 2}} I m) θ h "θ h = θ m / n, T = ((I h + n 2 I m) / n) θ _m ″ (6)

[0019] The counter electromotive voltage constant of the reaction force motor 3 and K _e, the counter electromotive voltage V = K _e · of the reaction motor 3 at this time
θ _m ′. Therefore, θ _m ′ = V / K _e ∴θ _m ″ = V ′ / K _e (where V ′ = dV / d
t) Therefore, (from _{6), T = (I h + n} 2 I m) · V '/ (n · K e) (7) next, the reaction motor 3 that the detector 34 detects the counter electromotive voltage V , from the moment of inertia I _m moment of inertia I _h and the reaction motor 3 of the steering wheel 2 can obtain a torque T applied to the steering wheel 2. That is, instead of the reaction motor 3, the case of using the electric motor is not a reaction motor, the counter electromotive voltage V of the electric motor, from the moment of inertia I _h and of the electric motor inertia moment I _m of the steering wheel 2, a steering The torque T applied to the wheel 2 can be obtained.

Here, considering the viscous resistance component, (5)
The equation and _{θ h = θ m / n,} T = (I h + n 2 I m) θ m "/ n + (C h + n 2 C m) θ m '/ n (8) θ m' = V / K 'from _{/ K e, T = (I} h + n 2 I m) V' e and _{θ m "= V / nK e} + (C h + n 2 C m) V / nK e (9)

Ii) There is a reaction force of the reaction force motor (T _m ≠ 0)
If the torque T _m applied to the reaction motor 3, can be determined by detecting the current i flowing through the reaction motor 3, when the torque constant of the reaction force motor 3 and _{K t, T m = i ·} K
_t . Therefore, when the reaction motor 3 is operated, if the flowing current i is detected, the values obtained in (6) to (6) are obtained in i).
By adding nT _m to each equation of (9), the torque T applied to the steering wheel 2 can be obtained.

For example, in equation (8), nT_mT = (I_h+ N^TwoI_m) Θ_m″ / N + (C_h+ N^TwoC_m) Θ_m'/ N + nT_m = (I_h+ N^TwoI_m) Ω_m'/ N + (C_h+ N^TwoC_m) Ω_m/ N + nT_m (10) (However, ω_m= Θ_m'= Rotational speed of reaction motor 3_m'= Dω_m/ Dt) and the stearin detected by the rotary encoder 33
Steering angle θ of wheel 2 _h(Or the rotation angle of the reaction motor 3
Degree θ_m), Flows to the reaction force motor 3 detected by the detector 34
Current i, moment of inertia I of steering wheel 2_h
And the inertia moment I of the reaction motor 3_mMore reaction mode
Due to viscous drag
Torque T applied to the steering wheel 2
You.

FIG. 2 is a block diagram showing a main configuration of an embodiment of a vehicle steering system according to the present invention. The vehicle steering system includes a steering mechanism 1 for causing a pair of steering wheels 10, 10 arranged on the left and right sides of a vehicle body (not shown) to perform a steering operation, and a steering mechanism 1 which is mechanically separated from the steering mechanism 1. The steering wheel 2 includes a steering wheel 2 as a steering means, a reaction force actuator 3 (second electric motor) for applying a reaction force to the steering wheel 2, and a steering control unit 4 using a microprocessor. In accordance with the operation of the steering control unit 4 in accordance with the operation described above, the steering motor 5 (first electric motor) arranged in the middle of the steering mechanism 1 is driven to operate the steering mechanism 1.

As is well known, the steering mechanism 1 includes both ends of a steering shaft 11 that extends in the left-right direction of the vehicle body and slides in the axial direction, and knuckle arms 12 that support the wheels 10, 10.
12 are connected by separate tie rods 13, 13, respectively.
The tie rods 13 and 1 are moved by sliding the steering shaft 11 in both directions.
The knuckle arms 12, 12 are pushed and pulled via 3 to steer the wheels 10, 10 to the left and right. This steering is performed by the steering motor 5, which is coaxially formed in the middle of the steering shaft 11. The rotation is converted into sliding of the steering shaft 11 by an appropriate motion conversion mechanism.

The rotation around the axis of the steering shaft 11 is restricted by rotation restricting means (not shown) interposed between the steering shaft 11 and the steering shaft housing 14. And the steering (steering of the steering wheels 10, 10) according to the rotation of the steering motor 5 is performed. The steering angles of the wheels 10, 10 steered in this manner are determined by a relative sliding position between the steering shaft housing 14 on one side of the steering motor 5 and the steering shaft 11 as a medium.
The output of the steering angle sensor 16 is supplied to the steering control unit 4 together with the output of the rotary encoder 15 for detecting the rotational position of the steering motor 5.

The reaction force actuator 3 for applying a reaction force to the steering wheel 2 is an electric motor (for example, a three-phase brushless motor), and its casing is fixed to an appropriate portion of a vehicle body (not shown) in relation to the rotating shaft 30. It is attached. The steering wheel 2 is coaxially fixed to a protruding end on one side of the rotating shaft 30.

The reaction force actuator 3 has a drive circuit 3a corresponding to a reaction force instruction torque signal given from the steering control unit 4.
When the steering wheel 2 is mounted on one end of the rotating shaft 30, a force (reaction force) in a direction opposite to the operation direction is applied to the steering wheel 2 attached to one end of the rotating shaft 30. Therefore, it is necessary to apply a steering torque against the reaction force generated by the reaction force actuator 3 to the rotation operation of the steering wheel 2. Thus, the steering wheel 2
Is calculated and detected by the steering control unit 4 based on the current flowing through the reaction force actuator 3,
It is used for adjusting the reaction force generated by the reaction force actuator 3. The current sensor 3 b detects a current flowing from the drive circuit 3 a to the reaction force actuator 3 and supplies the detected current to the steering control unit 4.

The operation amount (steering angle) of the steering wheel 2 is detected including the operation direction by a rotary encoder 33 attached to the reaction force actuator 3, and these detection results are given to the steering control unit 4. Have been. Further, the steering control unit 4 is provided with a detection result of a vehicle speed sensor 6 for detecting a running speed of the vehicle. The output of the steering control unit 4 is provided to the reaction force actuator 3 and the steering motor 5 via respective drive circuits 3a and 5a. The reaction force actuator 3 and the steering motor 5 Are performed in response to the instruction signals of the above.

The steering control unit 4 includes the steering wheel 2
Is determined, a reaction force control for generating a reaction force instruction torque signal to the reaction force actuator 3 in order to generate a reaction force, and a steering angle of the steering wheel 2 detected by the rotary encoder 33; As described above, the steering applied to the steering wheel 2 by the current flowing through the reaction force actuator 3 (reaction force motor) detected by the current sensor 3b, the moment of inertia of the steering wheel 2, and the moment of inertia of the reaction force actuator 3 Calculate and detect torque.

The steering control unit 4 recognizes an operation angle including an operation direction of the steering wheel 2 based on an input from the rotary encoder 33 and recognizes an operation angle based on an input from a steering angle sensor 16 attached to the steering mechanism 1. The steering angle deviation from the actual steering angle is calculated, and the steering angle deviation is corrected to be large or small according to the vehicle speed given as an input from the vehicle speed sensor 6 and the steering torque calculated and detected. A steering angle is obtained, and a steering control operation for driving the steering motor 5 is performed until the target steering angle is obtained. At this time, an input from the rotary encoder 15 is used as a feedback signal for checking whether or not the steering motor 5 has reached a desired rotational position.

The operation of the vehicle steering system having such a configuration will be described below with reference to the flowchart of FIG. First, the steering control unit 4 controls the current sensor 3b.
To read by detecting the current i flowing through the reaction motor 3 (S2), the nT _m storing determined by _{n · i · K t (S4} ). Next, the steering control unit 4 determines the steering angle θ of the steering wheel 2 detected by the rotary encoder 33.
_h (or the rotation angle θ _m of the reaction force motor 3), the rotation speed ω _m of the reaction force motor 3 is calculated and detected, and read (S6).
It is stored as the rotation speed ω _m (N) of the current sampling cycle (S8). Next, the steering control unit 4 calculates a difference between the rotation speed ω _m (N) of the current sampling cycle and the rotation speed ω _m (N−1) detected and stored in the previous sampling cycle, and calculates Δω _m (S10).

Next, the steering control unit 4 divides Δω _m by the sampling period Δt to obtain and store the rotational acceleration ω _m ′ of the reaction force motor 3 (S12). Next, the steering control unit 4 compares the stored nT _m (S4) and the rotational acceleration ω _m ′ (S12) of the reaction motor 3 with the equation (10) T = (I _h + n ² _Im ) ω _{m '/ n + (C h +} n 2 C m) are substituted into _{ω m / n + nT m (} 10), the torque T applied to the steering wheel 2
(Steering torque) is calculated (S14). Next, the steering control unit 4 determines the rotation speed ω _m (N) of the current sampling cycle.
Is the rotation speed ω _m (N-1) of the previous sampling cycle.
And returns (S16).

When an electric motor other than the reaction motor is used in place of the reaction motor 3, a back electromotive voltage V of the electric motor and an inertia moment I _{h of the} steering wheel 2 are obtained.
And from the moment of inertia I _m of the electric motor, (9) by calculating the equation, it is possible to obtain a torque T applied to the steering wheel 2.

[0034]

According to the vehicle steering system according to the first and third aspects of the present invention, the space for detecting the torque is small,
Therefore, it is possible to realize a separation type vehicle steering device with a low component cost.

According to the vehicle steering system of the second invention,
A space for detecting the torque is not required, and a separate type vehicle steering device with a low component cost can be realized.

[Brief description of the drawings]

FIG. 1 is a principle diagram showing the principle structure of a vehicle steering system according to the present invention.

FIG. 2 is a block diagram showing a main configuration of an embodiment of the vehicle steering system according to the present invention.

FIG. 3 is a flowchart showing the operation of the vehicle steering system according to the present invention.

[Explanation of symbols]

Reference Signs List 1 steering mechanism 2 steering wheel (steering wheel) 3 reaction force motor (reaction force actuator, second electric motor) 3a, 5a drive circuit 3b current sensor (detection means) 4, 4a steering control unit (calculation means) 5 steering Motor (first electric motor) 7 Speed-up gear 30 Rotation shaft (steering wheel shaft) 33 Rotary encoder 34 Detector (detection means)

Claims (3)

[Claims] A steering mechanism for changing the direction of a wheel is not mechanically connected to a steering wheel, but determines a steering angle of the steering wheel and a steering torque applied to the steering wheel, and according to the determined steering angle and steering torque,
Controlling the drive of a first electric motor of the steering mechanism;
A steering apparatus for a vehicle for controlling a steering angle to increase or decrease, comprising: a second electric motor connected to a shaft of the steering wheel;
Detecting means for detecting the back electromotive voltage of the electric motor or the current flowing in the second electric motor, the back electromotive voltage or current detected by the detecting means, the steering angle, the moment of inertia of the steering wheel, and the second Means for calculating the steering torque based on the moment of inertia of the electric motor. 2. The vehicle steering system according to claim 1, wherein the second electric motor is a reaction motor that applies a force to the steering wheel in a direction opposite to an operation direction thereof. 3. A steering mechanism for changing a direction of a wheel is not mechanically connected to the steering wheel, and determines a steering angle of the steering wheel and a steering torque applied to the steering wheel, and according to the determined steering angle and steering torque,
Controlling the drive of a first electric motor of the steering mechanism;
A steering apparatus for a vehicle for controlling a steering angle to increase or decrease, comprising: a second electric motor connected to a shaft of the steering wheel;
Detecting means for detecting the back electromotive voltage of the electric motor or the current flowing through the second electric motor, the back electromotive voltage or current detected by the detecting means, the moment of inertia of the steering wheel, and the inertia of the second electric motor. Means for calculating the steering torque based on the moment.