JP2007283954A - Steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To satisfy both the suppression of an external turbulence input of a steering system from a road surface, and the improvement of a steering feeling. <P>SOLUTION: A steering wheel 3 which is operated by a driver for steering and a front wheel as a rudder wheel are connected through a rack 7a and a pinion 6. A steering damper 13 is connected with a rack shaft 7. When the steering intention of the driver is sensed based on an output value of a steering torque sensor 16 or a steering angle sensor 15, the damping force of the steering damper 13 is reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a steering device for a vehicle or the like.

In order to suppress torque disturbance that is input to the steering system from the road surface via wheels, a vehicle steering device includes a damper (hereinafter referred to as a steering damper) in a transmission path that connects a steering wheel (operator) and a steered wheel. ) Are arranged (see, for example, Patent Document 1). The technique of Patent Document 1 controls the damping force of the steering damper according to the vehicle speed in a steering device for a motorcycle.
In addition, the electric power steering device that assists the steering with the steering motor includes damper correction means that electrically performs damper correction corresponding to the damping force with respect to the control amount of the steering motor, instead of the mechanical steering damper. There is something.
JP 2005-219617 A

However, in a conventional steering device with a steering damper, the steering feeling may deteriorate due to the steering force being felt heavy or dull due to the action of the damping force of the steering damper.
Similarly, in an electric power steering apparatus equipped with a damper correction means, the steering feeling is deteriorated because the steering is felt heavy or dull by performing damper correction on the control amount of the steering motor. May invite.
Therefore, the present invention provides a steering device that can suppress torque disturbance input from the road surface without deteriorating the steering feeling.

The steering device according to the present invention employs the following means in order to solve the above problems.
The invention according to claim 1 connects an operator (for example, a steering wheel 3 in an embodiment to be described later) operated by a driver for steering and a steered wheel (for example, a front wheel 9 in an embodiment to be described later). A damper (for example, a steering damper 13 in an embodiment to be described later) disposed in a transmission path, and a damper reducing unit (for example, in an embodiment to be described later) that weakens the damping force of the damper when a driver's steering intention is detected. ECU 20).
With this configuration, when the driver's steering intention is not detected (that is, when the vehicle is traveling straight), the damper is normally operated, so that torque disturbance is input from the road surface to the steering system. Can be suppressed. On the other hand, when the driver's intention to steer is detected (that is, when the vehicle is turning), the damper reduction means weakens the damping force of the damper, so that the steering feeling can be improved.

According to a second aspect of the present invention, there is provided a steering motor for assisting steering (for example, a steering motor 10 in an embodiment to be described later), damper correcting means for performing damper correction on a control amount of the steering motor, and driver steering. A steering device comprising: a damper correction reducing means (for example, a switching means 43 in an embodiment described later) for reducing a correction amount of the damper correcting means when a will is detected.
With this configuration, when the driver's steering intention is not detected (that is, when the vehicle is traveling straight), the correction amount by the damper correction means is controlled to a normal value, so that the road surface changes to the steering system. Input of torque disturbance can be suppressed. On the other hand, when the driver's intention to steer is detected (that is, when the vehicle is turning), the damper correction reducing means reduces the correction amount of the damper correcting means, so that the steering feeling can be improved. .

  According to the first aspect of the present invention, when the driver's steering intention is not detected, it is possible to suppress the input of torque disturbance from the road surface to the operator, and when the driver's steering intention is detected. The damping force of the damper can be weakened to improve the steering feeling.

  According to the second aspect of the present invention, when the driver's steering intention is not detected, the torque disturbance can be prevented from being input from the road surface to the operator, and when the driver's steering intention is detected. The steering feel can be improved by reducing the correction amount of the damper correction means.

  Embodiments of a steering apparatus according to the present invention will be described below with reference to the drawings of FIGS. In addition, each Example described below is an aspect of an electric power steering device for a four-wheeled vehicle.

[Example 1]
First, a first embodiment of a steering apparatus according to the present invention will be described with reference to the drawings of FIGS.
As shown in FIG. 1, the electric power steering apparatus includes a manual steering force generation mechanism 1, and the manual steering force generation mechanism 1 includes a steering shaft 4 integrally coupled to a steering wheel (operator) 3. It is connected to a pinion 6 of a rack and pinion mechanism via a connecting shaft 5 having a joint. The pinion 6 meshes with the rack teeth 7a of the rack shaft 7 that can reciprocate in the vehicle width direction, and left and right front wheels 9, 9 as steered wheels are linked to both ends of the rack shaft 7 via tie rods 8, 8. Has been. With this configuration, a normal rack and pinion type steering operation can be performed when the steering wheel 3 is steered, and the direction of the vehicle can be changed by turning the front wheels 9 and 9. The rack shaft 7 and the tie rods 8 and 8 constitute a steering mechanism.

  A steering motor 10 that supplies an auxiliary steering force for reducing the steering force generated by the manual steering force generation mechanism 1 is disposed coaxially with the rack shaft 7. That is, in this electric power steering apparatus, the steering motor 10 assists steering. The output of the steering motor 10 is converted into thrust through the ball screw mechanism 12 and is applied to the rack shaft 7.

  The steering shaft 4 is provided with a steering angle sensor (steering angle detection means) 15 for detecting the steering angle of the steering shaft 4, and a steering gear box (not shown) that houses the rack and pinion mechanism (6, 7a). ) Is provided with a steering torque sensor (steering torque detecting means) 16 for detecting the steering torque acting on the pinion 6. Further, a yaw rate sensor (yaw rate detecting means) 18 for detecting the yaw rate of the vehicle and a vehicle speed sensor (vehicle speed detecting means) 19 for detecting the vehicle speed are attached to appropriate positions of the vehicle body.

  The steering angle sensor 15 is an electrical signal corresponding to the detected steering angle, the steering torque sensor 16 is an electrical signal corresponding to the detected steering torque, the yaw rate sensor 18 is an electrical signal corresponding to the detected yaw rate, and the vehicle speed sensor 19 is Electrical signals corresponding to the detected vehicle speed are output to the control device (ECU) 20 respectively.

  The ECU 20 determines a target current to be supplied to the steering motor 10 based on a control signal obtained by processing input signals from these sensors 16, 18, and 19, and supplies the steering motor 10 via the drive circuit 21. The output torque of the steering motor 10 is controlled, and the auxiliary steering force (assist amount) in the steering operation is controlled.

More specifically, the ECU 20 calculates a base current corresponding to the steering torque and the vehicle speed based on the output signals of the steering torque sensor 16 and the vehicle speed sensor 19. Usually, the base current increases as the steering torque increases, and the base current decreases as the vehicle speed increases.
Further, the ECU 20 calculates a yaw rate reaction force correction current based on the output signal of the yaw rate sensor 18. The yaw rate reaction force correction current is a reaction force component that generates torque in a direction that cancels the yaw rate when the yaw rate is generated, for example, when the vehicle is turning. Normally, the yaw rate reaction force correction current is set to increase as the yaw rate increases.
Then, the ECU 20 determines the target current of the steering motor 10 by subtracting the yaw rate reaction force correction current from the base current.

The rack shaft 7 is connected to a steering damper (damper) 13 for suppressing torque disturbance input from the road surface through the front wheels 9 to the steering system. That is, the steering damper 13 is disposed on a transmission path that connects the steering wheel 3 and the front wheel 9. The steering damper 13 includes an electronically controlled damping force variable damper that can adjust the damping force based on an electric signal.
The configuration of the electronically controlled damping force variable damper is not particularly limited. For example, the cylinder is defined as two oil chambers by a piston sliding in the cylinder, and an oil passage connecting these two oil chambers is formed. A throttle valve may be provided in the middle, and the damping force may be adjusted by controlling the opening of the throttle valve. In this case, the rack shaft 7 is connected to the piston. Further, instead of the throttle valve, a magnetic fluid circulation part is provided in which a magnetic fluid is sealed in a region in the middle of the oil passage, and the magnetic fluid flows. A coil is provided outside the magnetic fluid circulation part, and a current flowing through the coil is provided. It is also possible to adjust the strength of the magnetic field generated by the coil by controlling the pressure, thereby controlling the viscosity of the magnetic fluid and adjusting the damping force.

  In this electric power steering device, in order to achieve both suppression of torque disturbance input from the road surface and improvement of steering feeling, the driver is willing to steer and turns the vehicle (in other words, the front wheels 9), the damping force of the steering damper 13 is weakened, and ideally, the damping force is reduced to zero so as to improve the steering feeling. When the vehicle is traveling straight (in other words, when the front wheel 9 is not steered), the damping force of the steering damper 13 is increased to sufficiently apply the damper, and the torque disturbance input from the road surface is sufficiently attenuated. Let

Next, steering damper control in this embodiment will be described with reference to the flowchart of FIG.
The steering damper control routine shown in the flowchart of FIG. 2 is repeatedly executed by the ECU 20 at regular intervals.
First, in step S101, it is determined whether or not the vehicle is traveling straight. The method for determining whether or not the vehicle is traveling straight is, for example, when the steering torque detected by the torque sensor 16 is a predetermined value or less, or when the steering angle detected by the steering angle sensor 15 is a predetermined value or less. In addition, it can be determined that the vehicle is traveling straight. Alternatively, when both of these two conditions are satisfied, it may be determined that the vehicle is traveling straight.

If the determination result in step S101 is “YES” (straight-running state), the process proceeds to step S102, where the control of the steering damper 13 is turned on, and the control for greatly applying the damping force is executed.
As a result, when the vehicle is traveling straight, in other words, when the driver is not willing to steer, the damping action by the steering damper 13 can be sufficiently applied, and disturbance from the road surface is input to the steering system. Therefore, it is possible to make it difficult to transmit disturbance to the steering wheel 3.

If the determination result in step S101 is “NO” (turning state), the process proceeds to step S103, where the control of the steering damper 13 is turned off, and the damping force is made zero or minimal.
As a result, when the vehicle is turning, in other words, when the driver is willing to steer, the damping action by the steering damper 13 can be zero or minimized, and as a result, the steering feeling is improved. In other words, when the damping force of the steering damper 13 is large when the vehicle is turning, the steering feeling is deteriorated, for example, the steering feels heavy due to the damping force. Nothing happens.
In this embodiment, the ECU 20 executes the processes of steps S101 to S103, thereby realizing a damper reducing means.

[Example 2]
Next, a second embodiment of the steering apparatus according to the present invention will be described with reference to the drawing of FIG.
The electric power steering apparatus of the first embodiment described above is configured to provide a mechanical steering damper 13 on the rack shaft 7 to apply a damping force to the steering system, but the electric power steering apparatus of the second embodiment is Instead of providing the steering damper 13, the control amount of the steering motor 10 is electrically corrected (damper correction) corresponding to the damping force.
The overall configuration of the electric power steering apparatus according to the second embodiment is obtained by omitting the steering damper 13 from the electric power steering apparatus according to the first embodiment.

A method for determining a target current to be supplied to the steering motor 10 which is a characteristic part of the electric power steering apparatus according to the second embodiment will be described.
The ECU 20 calculates a base current (control amount) Ib corresponding to the steering torque and the vehicle speed based on the output signals of the steering torque sensor 16 and the vehicle speed sensor 19, and outputs signals of the steering angle sensor 15, the yaw rate sensor 18, and the vehicle speed sensor 19. The correction current Ia corresponding to the yaw rate, vehicle speed, and steering angular velocity is calculated based on the above, and the target current of the steering motor 10 is determined by subtracting the correction current Ia from the base current Ib.

The calculation method of the base current Ib is the same as in the first embodiment, and the base current Ib increases as the steering torque increases, and the base current Ib decreases as the vehicle speed increases.
A method of calculating the correction current Ia will be described with reference to the block diagram of FIG. In the second embodiment, the correction current Ia is calculated by adding the damper correction current Id and the yaw rate reaction force correction current Iy.

  The damper correction current Id is based on the steering angular velocity ω calculated by time differentiation of the steering angle detected by the steering angle sensor 15 with reference to the first correction current table 41 and the vehicle speed detected by the vehicle speed sensor 19. Calculated. The first correction current table 41 is a table in which the steering angular speed ω set for each vehicle speed V is used as an address. The damper correction current Id increases as the steering angular speed ω increases, and the damper correction current Id increases as the vehicle speed V increases. It is set to be large. Instead of calculating the steering angular velocity ω by differentiating the steering angle detected by the steering angle sensor 15 with respect to time, a steering angular velocity sensor may be provided on the steering shaft 4 and the steering angular velocity ω may be directly detected by the steering angular velocity sensor. Is possible. The damper correction current Id corresponds to the damping force of the steering damper 13 in the first embodiment. In the second embodiment, the ECU 20 executes a process of calculating the damper correction current Id with reference to the first correction current table 41. Thus, a damper correction unit is realized.

The damper correction current Id is input to the switching unit 43. The switching means 43 is a means for switching the output value of the damper correction current Id based on the straight traveling determination signal, and makes the vehicle go straight without the driver's intention to steer (in other words, the front wheels 9 are not steered). Is determined, the damper correction current Id calculated with reference to the first correction current table 41 is output as the damper correction current Id, and the driver is willing to steer and turns the vehicle (in other words, the front wheels 9), the damper correction current Id is output as zero. In this embodiment, a damper correction reducing means is realized by the switching means 43.
Note that the method for determining whether or not the vehicle is traveling straight is the same as in the first embodiment. For example, when the steering torque detected by the torque sensor 16 is equal to or less than a predetermined value, or detected by the steering angle sensor 15. When the steering angle is less than or equal to a predetermined value, it is determined that the vehicle is in a straight traveling state, or it is determined that the vehicle is in a straight traveling state when both conditions are satisfied.

The yaw rate reaction force correction current Iy is calculated with reference to the second correction current table 42 based on the yaw rate γ detected by the yaw rate sensor 18 and the vehicle speed V detected by the vehicle speed sensor 19. The second correction current table 42 is a table whose address is the yaw rate γ set for each vehicle speed V. The yaw rate reaction force correction current Iy increases as the yaw rate γ increases, and the yaw rate reaction force correction current increases as the vehicle speed V increases. Iy is set to be large. In the second embodiment, the yaw rate γ is a vehicle behavior parameter, and the yaw rate reaction force correction current Iy can be said to be a reaction force component set according to the vehicle behavior.
The ECU 20 adds a damper correction current Id output from the switching unit 43 and the yaw rate reaction force correction current Iy, and performs a limiter process 44 for limiting the added value so as not to exceed a preset maximum value and minimum value. The correction current Ia is obtained.

According to the electric power steering apparatus configured as described above, the switching means 43 is calculated with reference to the first correction current table 41 when the vehicle is traveling straight ahead, in other words, when the driver does not intend to steer. Since the damper correction current Id is output as the damper correction current Id, the damper correction with respect to the base current Ib is sufficiently performed, and disturbance from the road surface can be prevented from being input to the steering system, and the steering wheel 3 is disturbed. Can be difficult to convey.
On the other hand, when the vehicle is turning, in other words, when the driver is willing to steer, the switching means 43 outputs zero as the damper correction current Id, so that the damper correction amount for the base current Ib is set to zero. As a result, the steering feeling is improved. That is, if the damper correction amount with respect to the base current Ib is large when the vehicle is turning, the steering feeling is deteriorated, for example, the steering feels heavy, but this does not occur in this electric power steering apparatus.
Therefore, in this electric power steering device, it is possible to achieve both suppression of torque disturbance input from the road surface and improvement of steering feeling.

[Other Examples]
The present invention is not limited to the embodiment described above.
For example, in the first embodiment described above, the present invention has been described as being applied to an electric power steering apparatus. However, the present invention can also be applied to a hydraulic power steering apparatus.
In the first embodiment described above, the steering damper 13 is cooperatively controlled by the ECU 20 of the electric power steering device. However, a steering damper control device for controlling the steering damper 13 is provided separately from the ECU 20 of the electric power steering device. You may comprise so that a control signal may be communicated between the control apparatus for steering dampers, and ECU20.

It is a schematic block diagram in Example 1 of the steering device which concerns on this invention. 3 is a flowchart illustrating an example of steering damper control in the steering device according to the first embodiment. It is a block diagram which shows the correction | amendment electric current calculation process in Example 2 of the steering device which concerns on this invention.

Explanation of symbols

3 Steering wheel (operator)
9 Front wheels (steering wheels)
10 Steering motor 13 Steering damper (damper)
20 ECU (Damper reduction means)
43 Switching means (damper correction reducing means)

Claims (2)

A damper disposed on a transmission path that connects an operator operated by a driver for steering and a steered wheel;
Damper reducing means for weakening the damping force of the damper when detecting the steering intention of the driver;
A steering apparatus comprising: A steering motor for assisting steering;
Damper correction means for performing damper correction on the control amount of the steering motor;
A damper correction reducing means for reducing a correction amount of the damper correction means when detecting the steering intention of the driver;
A steering apparatus comprising:

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