JPH10311365A - Steering wheel damping device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To effectively reduce the vibration of a steering wheel irrespective of an enlargement of a cross section of a frame material of a steering wheel or a dynamic damper. SOLUTION: The vibration damping device for a steering wheel includes a piezoelectric conversion element disposed in close contact with a surface of a frame material of the steering wheel, and a control means for controlling a distortion amount of the piezoelectric conversion element. In the piezoelectric transducer, internal stress is generated in a direction that restricts distortion caused by elastic vibration generated in the piezoelectric transducer. According to this, by controlling the voltage applied to the piezoelectric conversion element by the control means, it is possible to generate a stress in the piezoelectric conversion element in a direction that restricts deformation during vibration. Therefore, the apparent rigidity of the frame material is increased, and the elastic vibration of the frame material is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a vibration damping device for a steering wheel.

[0002]

2. Description of the Related Art In order to reduce unpleasant vibration generated on a steering wheel during running or idling, it is general to increase the rigidity of a frame member. This is to reduce the vibration by increasing the eigenvalue.
Another method is to attach a dynamic damper to lower the frequency response near the eigenvalue.

[0003]

However, the method of increasing the rigidity of the frame material involves increasing the weight mainly due to the increase in the cross section of the frame material, and also reduces the ability to protect the occupant in the event of a collision. There are inconveniences. Moreover, it is difficult to secure ideal rigidity in order to secure a space for installing various devices and switches in the center of the steering wheel. On the other hand, in the method using the dynamic damper, a relatively large installation space is required, and an increase in weight due to the mass member is inevitable. In addition, there is an inconvenience that the damping ability is reduced due to the aging of the spring member.

[0004]

SUMMARY OF THE INVENTION In order to solve such a problem and provide a steering wheel damping device capable of effectively suppressing vibration, the present invention provides a steering wheel damping device. A piezoelectric conversion element disposed in close contact with the surface of the frame material of the steering wheel, and control means for controlling the amount of distortion of the piezoelectric conversion element, wherein distortion caused by elastic vibration generated in the frame material is reduced. The internal stress in the restraining direction is generated in the piezoelectric transducer. According to this, by controlling the applied voltage to the piezoelectric conversion element by the control means,
Stress in a direction that restricts deformation during vibration can be generated in the piezoelectric conversion element. Therefore, the apparent rigidity of the frame material is increased, and the elastic vibration of the frame material is suppressed.

The piezoelectric transducers include PZT (zirconate titanate), PLZT (lanthanum zirconate titanate), and PMN (magnesium niobium lead oxide).
PVDF (polyvinylidene fluoride) and the like are used.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below based on embodiments shown in the accompanying drawings.

FIG. 1 shows a steering wheel frame to which the present invention is applied. The steering wheel frame includes a base plate 1 connected to a steering shaft (not shown), a pair of vertical spokes 3 a extending vertically from a lower end of the base plate 1 to support the rim 2, and left and right sides of the base plate 1. And a pair of horizontal spokes 3b extending laterally from the portion. An airbag assembly (not shown) is mounted on the front side of the base plate 1. In each of the base plate 1 and the spokes 3a and 3b,
A plurality of piezoelectric modules 4 which are vibration damping devices according to the present invention are closely arranged.

The piezoelectric module 4 generates a voltage corresponding to the distortion and generates a distortion corresponding to the applied voltage. As shown in FIG. 2, a rectangular flat piezoelectric conversion element made of PZT or the like is used. 5, a pair of copper electrodes 6 provided on both front and back surfaces of the piezoelectric transducer 5, and a pair of copper electrodes 6
And a cover 8 made of epoxy resin, which is integrated by thermocompression so as to cover the piezoelectric transducer 5, the copper electrode 6, and the control circuit 7.
As shown in FIG. 3, a Ni-containing conductive sheet 9 is provided between the piezoelectric transducer 5 and the electrode 6, and a cover 8 is provided.
Are provided with a polyimide film 10 on both sides.

The piezoelectric module 4 configured as described above
Is actually bent into a predetermined shape so that it can be in close contact with the outer peripheral surface when actually mounted on the spokes 3a and 3b.
First, as shown in an enlarged view in FIG. 4, the vertical spokes 3a extending from the lower end of the base plate 1 are curved in an arc shape along the outer peripheral surface of the round bar-shaped spokes 3a, and the longitudinal direction is the vertical spokes. 3a is arranged along the axial direction. On the other hand, in the horizontal spokes 3b extending from the left and right sides of the base plate 1, the center line of the piezoelectric module 4 is bent so as to draw a spiral as shown in FIG. 4 are arranged so that the center line is oblique.

The piezoelectric module 4 arranged on the base plate 1 remains the flat plate shown in FIG. 2, and as shown in an enlarged manner in FIGS. 6 and 7, the piezoelectric module 4 is provided on the surface opposite to the connecting surface of the spokes 3a and 3b. It is provided in a unimorph shape. Note that the piezoelectric module 4 may be provided in a bimorph shape on both the front and back surfaces of the base plate 1.

The control circuit 7 is a resonance analog circuit set to have a frequency characteristic corresponding to the resonance frequency of the portion where the piezoelectric module 4 is provided. More specifically, the control circuit 7 is connected in parallel with each other as shown in FIG. The resistor R and the coil L are connected in series with each other, or the resistor R and the coil L are connected in parallel with the capacitor C as shown in FIG. is there.

Next, the operation principle of the device of the present invention will be described.

[0013] When vibration is transmitted from the steering shaft to the steering wheel, vertical vibration and oscillating vibration are generated in the steering wheel. At this time, the vertical spokes 3a mainly generate bending vibration, and the horizontal spokes 3b mainly generate torsional vibration. Then, with the vibration of the spokes 3a and 3b in the vertical and horizontal directions, bending vibration is generated in the portion of the base plate 1 where the spokes 3a and 3b are connected.

When vibrations occur in the base plate 1 and the spokes 3a and 3b in this manner, a distortion is generated in the piezoelectric conversion element 5 of the piezoelectric module 4 closely disposed to the base plate 1 and the spokes 3a and 3b. A voltage that changes periodically is input from the conversion element 5 to the control circuit 7. When the base plate 1 and the spokes 3a and 3b start oscillating at the resonance frequency, the control circuit 7 having a frequency characteristic corresponding to the resonance frequency acts to suppress the distortion of the piezoelectric conversion element 5, and the base plate 1 and the spokes 3a and 3b.
A vibration damping force is applied to 3b.

For example, the vertical spokes 3a that bend and vibrate,
As shown in FIG. 10, when trying to bend, a compressive stress is generated in the piezoelectric conversion element 5 of the piezoelectric module 4a on the tension side as shown by an arrow, and the piezoelectric conversion element 5 of the piezoelectric module 4b on the compression side is indicated by an arrow. As shown, tensile stress occurs. Thereby, the bending of the vertical spokes 3a is suppressed. When the spoke 3a bends in the opposite direction, the piezoelectric module 4
Tensile and compressive stresses opposite to those described above are generated at a and 4b, respectively, to suppress the bending of the vertical spokes 3a.

When torsional vibration occurs in the lateral spokes 3b, as in the case of the bending vibration of the vertical spokes 3a, the stress in the direction of restricting the expansion / contraction strain generated on the outer peripheral surface due to the torsional vibration of the lateral spokes 3b is generated by the piezoelectric transducer. 5, the torsional distortion of the lateral spokes 3b is suppressed, and the torsional vibration of the lateral spokes 3b is suppressed.

On the other hand, as shown by an arrow A in FIG. 6, the vertical spokes 3a generate bending vibration in a direction substantially perpendicular to the base plate 1, and the base plate 1 portion to which the vertical spokes 3a are connected tends to deform. However, a moment indicated by an arrow B in FIG. 6 is generated by the internal stress of the piezoelectric conversion element 5 in the piezoelectric module 4 provided here, and the deformation of the base plate 1 is suppressed. On the other hand, FIG.
As indicated by an arrow A in the figure, when the portion of the base plate 1 to which the horizontal spokes 3b are coupled is to be deformed by the torsional vibration of the horizontal spokes 3b, the internal stress of the piezoelectric conversion element 5 of the piezoelectric module 4 causes the arrow in FIG. The moment indicated by B is generated, and the deformation is suppressed.

In the above embodiment, the passive control by the analog circuit built in the piezoelectric module 4 has been described. As shown in FIG. 11, the vibration of the frame material 11 such as the base plate 1 and the spokes 3a and 3b is detected by the acceleration sensor. 12 and the acceleration sensor 12
Is processed by the control circuit 13 to determine the vibration frequency and the vibration amplitude of the frame material 11, and the voltage for generating the vibrating force in the direction to cancel the vibration of the frame material 11 is determined by the battery
It is also possible to use an active control in which the voltage is applied to the piezoelectric conversion element 5 from the amplifier 4 through the amplifier 15. According to this, the frequency of the voltage applied to the piezoelectric conversion element 5 can be freely adjusted in accordance with the vibration frequency and the vibration amplitude of the frame member 11, so that it is possible to suppress vibration over a wide range, and it is difficult with the conventional method. It is also possible to cut off low-frequency regions.

Since the vibration of the frame member 11 is not only detected by the acceleration sensor 12, the piezoelectric transducer 5 itself has a function of outputting a voltage corresponding to the amount of distortion.
The applied voltage may be controlled so as to cancel the output.

Further, in this active control, the apparent spring constant of the frame member 11 can be freely changed by changing the voltage applied to the piezoelectric transducer 5. Thus, when the voltage applied to the piezoelectric transducer is controlled in accordance with the signal from the vehicle collision sensor, the shock when the occupant's body collides with the steering wheel at the time of the collision is reduced, and the obstacle to the body is reduced. Can be reduced.

[0021]

As described above, according to the present invention, the apparent rigidity of the frame material is increased by controlling the amount of distortion of the piezoelectric transducer by the control means to restrain the elastic deformation of the frame material. Elastic vibration can be effectively suppressed. Since the piezoelectric transducer can generate a large strain stress even with a small size and has high durability, it has a great effect in solving problems in weight, durability and installation space. In addition, the apparent rigidity of the frame material can be adjusted by the control means, and the apparent rigidity of the frame material can be increased or decreased as necessary, so that the ability to protect the occupant in the event of a collision can be increased.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a frame of a steering wheel to which the present invention is applied.

FIG. 2 is a perspective view showing a piezoelectric module as a vibration damping device according to the present invention.

FIG. 3 is a sectional view of the piezoelectric module shown in FIG. 2;

FIG. 4 is an enlarged perspective view of a main part of the vertical spoke shown in FIG. 1;

FIG. 5 is an enlarged perspective view of a main part of the lateral spoke shown in FIG. 1;

FIG. 6 is an enlarged perspective view of a main part of a connecting portion between the vertical spokes and the base plate shown in FIG. 1;

FIG. 7 is an enlarged perspective view of a main part of a connecting portion between the lateral spokes and the base plate shown in FIG. 1;

FIG. 8 is a circuit diagram showing a configuration example of a control circuit shown in FIG. 2;

9 is a circuit diagram showing another configuration example of the control circuit shown in FIG. 2;

FIG. 10 is an essential part cross-sectional view for explaining the principle of damping vertical spokes.

FIG. 11 is a block diagram showing a configuration example of a control unit when an external voltage is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base plate 2 Rim 3a Vertical spoke 3b Horizontal spoke 4 Piezoelectric module 5 Piezoelectric conversion element 6 Copper electrode 7 Control circuit 8 Coating body 9 Conductive sheet 10 Polyimide film 11 Frame material 12 Acceleration sensor 13 Control circuit 14 Battery 15 Amplifier

Claims (1)

[Claims] A piezoelectric transducer disposed in close contact with a surface of a frame material of a steering wheel; and control means for controlling an amount of distortion of the piezoelectric transducer. A vibration damping device for a steering wheel, wherein an internal stress in a direction for restraining the resulting distortion is generated in the piezoelectric transducer.