JP2010188770A - Steering angle ratio variable control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the operation performance of a vehicle in a steering angle ratio variable control device capable of variably setting a steering gear ratio which is the ratio of the turning amount of a steered wheel to the operation amount of a steering means. <P>SOLUTION: In the control device 20, a basic steering gear ratio is set based on a vehicle speed V detected by a vehicle speed sensor 15, a gear ratio correction coefficient is also set based on steering holding force H detected by a pressure sensor 14, and a steering gear ratio is set by multiplying the set basic steering gear ratio by the gear ratio correction coefficient. Even when travelling at low speed on a road surface having a low friction coefficient, such a steering that prevents a driver from feeling a sense of incongruity can be achieved. Thus, the operation performance of the vehicle can be improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a steering angle ratio variable control device capable of variably setting a steering gear ratio which is a ratio of a steered wheel turning amount to an operation amount of a steering means.

  The mechanical connection between the steering wheel and the steering mechanism for steering the steered wheels is eliminated, and the steering wheel operating direction and operation amount are detected. There has been proposed a vehicular steering apparatus that applies a driving force from an actuator.

In the vehicle steering apparatus having such a configuration, since the steering wheel and the steering mechanism are not mechanically connected, the steering gear ratio, which is the ratio of the steered wheel steered amount to the steered wheel manipulated variable, is For example, it can be variably set according to the vehicle speed.
In this case, the steering gear ratio is set small when traveling at high speed, and the steering gear ratio is set large when traveling at low speed. Thus, it is possible to suppress the vehicle's wobbling during high-speed traveling, and to reduce the troublesome steering operation during, for example, entering a garage or width-shifting during extremely low-speed traveling.

JP-A-9-142330 JP 2001-114120 A

  However, if the steering gear ratio is variably set only according to the vehicle speed, the steering gear ratio is large at low speeds, whether or not the vehicle is traveling on a road surface with a low coefficient of friction (low μ road) such as a snowy road. Is set. For this reason, the road surface reaction force is small on snowy roads, etc., so that the steering wheel is more than intended for the driver's subtle steering operation more than the usual μ road surface, in other words, more than the driver intended. The vehicle is steered greatly, and as a result, the driver may feel uncomfortable.

  Accordingly, an object of the present invention is to provide a steering angle ratio variable control device capable of improving the driving performance of a vehicle.

  The invention according to claim 1 for achieving the above object is a steering angle ratio variable control device capable of variably setting a steering gear ratio which is a ratio of a steered wheel steered amount with respect to an steered wheel manipulated variable. Gripping force detection means for detecting the gripping force of an operator who grips and operates the means, vehicle speed detection means for detecting the vehicle speed of the vehicle on which the steering angle ratio variable control means is mounted, and detection by the gripping force detection means And a control means for setting a steering gear ratio on the basis of the gripping force and the vehicle speed detected by the vehicle speed detection means.

According to this configuration, the steering gear ratio is variably set according to the vehicle speed and the steering gripping force. As a result, it is possible to perform steering so as not to cause an uncomfortable feeling even on a snowy road.
That is, since the steering force is light on the low μ road, the strength with which the driver grips the steering and the surface pressure that is pushed by the palm are reduced. At this time, by setting the steer ratio to slow, the front wheel turning angle with respect to steering is reduced, and the driver's intention is taken up.

  According to such a steering angle ratio variable control device, it is possible to improve the driving performance of the vehicle.

It is a conceptual diagram for demonstrating the structure of the steering angle ratio variable control apparatus which concerns on one Embodiment of this invention. It is a graph which shows the relationship between a vehicle speed and a basic steering gear ratio. It is a flowchart which shows the flow which determines the gear ratio correction coefficient K.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram for explaining a configuration of a steering angle ratio variable control device according to an embodiment of the present invention. In this steering angle ratio variable control device, the steering actuator 2 driven by the rotation operation of the steering wheel (steering means) 1 is operated by the steering gear 3 to steer the front left and right wheels 4 (steering wheels). Therefore, steering is achieved without mechanically connecting the steering wheel 1 and the steering gear 3. In this case, a steering mechanism is constituted by the steering actuator 2, the steering gear 3, and the like.

  The steering actuator 2 can be constituted by an electric motor such as a known brushless motor. The steering gear 3 has a motion conversion mechanism (such as a ball screw mechanism) that converts the rotational motion of the output shaft of the steering actuator 2 into a linear motion in the axial direction (vehicle width direction) of the steering rod 5. The movement of the steering rod 5 is transmitted to the knuckle arm 7 via the tie rod 6, causing the knuckle arm 7 to rotate. Thereby, steering of the wheel 4 supported by the knuckle arm 7 is achieved.

  The steering wheel 1 is connected to a rotating shaft 8 that is rotatably supported with respect to the vehicle body. A reaction force actuator 9 for applying a steering reaction force to the steering wheel 1 is attached to the rotating shaft 8. Specifically, the reaction force actuator 9 can be configured by an electric motor such as a brushless motor having an output shaft integrated with the rotary shaft 8. An elastic member 10 made of a spiral spring or the like is coupled to the end of the rotating shaft 8 on the opposite side of the steering wheel 1 from the vehicle body. The elastic member 10 returns the steering wheel 1 to the straight steering position by the elastic force when the reaction force actuator 9 is not applying torque to the steering wheel 1.

In order to detect an operation input value of the steering wheel 1, an angle sensor 11 for detecting an operation angle δh corresponding to the rotation angle of the rotary shaft 8 is provided. The rotating shaft 8 is provided with a torque sensor 12 for detecting an operation torque T applied to the steering wheel 1. On the other hand, as an output value sensor for detecting the output value of the steering actuator 2, a turning angle sensor 13 for detecting the turning angle δ of the wheel 4 is provided. The steered angle sensor 13 can be configured by a potentiometer or the like that detects the operation amount of the steering rod 5 by the steering actuator 2. Further, in order to detect the steering gripping force H of the driver (operator), the steering wheel 1 is provided with a pressure sensor (gripping force detection means) 14.
Note that the steering gripping force H mainly means a gripping force of the steering wheel 1, but this gripping force includes a force (surface pressure) that pushes the steering wheel 1 with the palm of the hand.

The angle sensor 11, the torque sensor 12, the turning angle sensor 13, and the pressure sensor 14 are connected to a steering system control device (hereinafter referred to as “control device” as appropriate) 20 including a computer. The control device 20 is further connected to a vehicle speed sensor (vehicle speed detection means) 15 that detects the vehicle speed V.
Based on the operation torque T detected by the torque sensor 12 and the operation angle δh detected by the angle sensor 11, the control device 20 performs an appropriate reaction in the direction opposite to the operation direction of the steering wheel 1 via the drive circuit 21. The reaction force actuator 9 is controlled so as to generate a force.

Further, the control device 20 controls the steering actuator 2 via the drive circuit 22. More specifically, for example, the control device 20 sets the basic steering gear ratio P based on the vehicle speed V detected by the vehicle speed sensor 15 and the gear based on the steering gripping force H detected by the pressure sensor 14. By setting the ratio correction coefficient K and multiplying the set basic steering gear ratio P and the gear ratio correction coefficient K, the steering gear ratio K · which is the ratio of the turning amount of the wheel 4 to the operation amount of the steering wheel 1 Set P. Then, a target turning angle δ ^* is obtained by multiplying the set steering gear ratio K · P by the operation angle δh, and the steering actuator 2 is feedback-controlled based on the target turning angle δ ^* .

  The basic steering gear ratio P is set according to a graph as shown in FIG. 2, for example. That is, when the vehicle speed V is low, the basic steering gear ratio P is set to be large, and when the vehicle speed V is high, the basic steering gear ratio P is set to be small. In this example, the basic steering gear ratio P corresponds to the increase in the vehicle speed V. Therefore, the linearity is set so as to be monotonously smaller. In other words, the steering characteristic is quick at low speed and slow at high speed.

FIG. 3 is a flowchart showing a flow of determining the gear ratio correction coefficient K.
The steering gripping force H is detected by the pressure sensor 14 (step S1), and it is determined whether or not the steering gripping force H is small (step S2). As a premise, it is assumed that the control device 20 determines that the vehicle speed is a low vehicle speed equal to or lower than a predetermined value (for example, 5 km / h or lower).
When the steering gripping force H is small (YES in step S2), it is estimated that the road friction coefficient μ is low, and the gear ratio correction coefficient K is made small, that is, the steering characteristic is set to slow (step S3). On the other hand, when the steering gripping force H is large (NO in step S2), it is estimated that the road friction coefficient μ is high (not low), and the gear ratio correction coefficient K is large, that is, the steering characteristic is set to quick. (Step S4). Incidentally, step S4 also means that in this example, the steering characteristic is made normal according to the vehicle speed.

  Therefore, the steering gear ratio K · P, which is set by multiplying the basic steering gear ratio P and the gear ratio correction coefficient K, is relatively slow when the steering wheel 1 is traveling at a low vehicle speed (including when the vehicle is stationary) below a predetermined value. Is set smaller (step S3). As a result, the amount of steering of the wheels 4 is suppressed, and the problem of being steered more than intended by the driver on a low μ road such as a snowy road is solved.

  The flowchart of FIG. 2 is repeatedly executed according to a predetermined short control cycle. For this reason, for example, when the driver starts to steer the steering wheel 1 that was gripping weakly from the middle, the change of the gripping force H is immediately reflected in the control (NO in step S2), and the steering wheel 1 is steered. The characteristic is set to quick (step S4), and the steering can be performed with the intent of the driver. On the other hand, when the driver starts to steer the steering wheel 1 that has been squeezed with a strong grip, the change in the gripping force H is immediately reflected in the control (YES in step S2). The steering characteristic is set to slow (step S3), and accurate steering can be performed taking into account the driver's intention. Although not shown in the flowchart, even when the vehicle speed is no longer lower than the predetermined speed, the change in the vehicle speed is immediately reflected in the control, and the steering characteristics are set according to the vehicle speed.

  By the way, when entering the garage, when shifting the width, the vehicle speed is slow at extremely low speed, and the driver grips the steering wheel 1, so the steering gear ratio K / P is set large, and the front wheel turning angle can be adjusted without changing the wheel. Can be secured.

In the present invention, the steering wheel and the steering mechanism are not mechanically connected to each other, but are not only mechanically connected to the vehicle steering apparatus using the steer-by-wire as described in Patent Documents 1 and 2 described above. The present invention can also be applied to an apparatus as described in JP-A-2001-260924.
Further, the steering gear ratio may be set according to the gripping force H. For example, the steering gear ratio may be set so that the steering characteristics become slower as the gripping force H detected via the pressure sensor 14 is smaller at a low vehicle speed below a predetermined value.
In addition, the predetermined value at a low vehicle speed equal to or lower than the predetermined value is 5 km / h, but may be 10 km / h, for example.

  Further, by reversing the relationship between the gripping force H and the steering characteristic, the steering characteristic becomes slow when the gripping force H is strong, that is, matches the driving feeling of each person. Such steering characteristics may be used. By the way, the characteristics can be switched by providing a switch for switching characteristics in the driver's seat so that the driver can be operated appropriately.

1 Steering wheel (steering means)
2 Steering actuator 3 Steering gear 4 Wheel 5 Steering rod 6 Tie rod 7 Knuckle arm 8 Rotating shaft 9 Reaction force actuator 10 Elastic member 11 Angle sensor 12 Torque sensor 13 Steering angle sensor 14 Pressure sensor (gripping force detection means)
15 Vehicle speed sensor (vehicle speed detection means)
20 Steering system control device (control means)
21 Reaction Force Actuator Drive Circuit 22 Steering Actuator Drive Circuit

Claims (2)

In the steering angle ratio variable control device that can variably set the steering gear ratio, which is the ratio of the steering amount of the steered wheels to the operation amount of the steering means,
Gripping force detection means for detecting the gripping force of an operator who grips and operates the steering means;
Vehicle speed detection means for detecting the vehicle speed of the vehicle on which the steering angle ratio variable control device is mounted;
A steering angle ratio variable control device comprising: a control unit that sets a steering gear ratio based on a gripping force detected by the gripping force detection unit and a vehicle speed detected by the vehicle speed detection unit. The control means includes
When the detection result of the vehicle speed detection means is a low vehicle speed below a predetermined value and the gripping force detected by the gripping force detection means is small (S2 → Yes), the steering gear ratio is set small (S3). The steering angle ratio variable control device according to claim 1, wherein the steering characteristic is slow.

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