Steering device

A steering device comprises a steering shaft to which a steering wheel is attached, a steering column for housing and supporting the steering shaft so as to be rotatable, a tilt unit for tilting the steering column and the steering shaft, a main bracket fixed to a vehicle side bracket and a pressure applying member provided between the main bracket and the steering column for applying a pressure in one direction to the steering column.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. §119 to Japanese Patent Application 2004-187747, filed on Jun. 25, 2004, the entire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a steering device whose rigidity is improved.

BACKGROUND

A steering device mounted to a vehicle, such as an automobile, generally includes a steering shaft, which is supported by a steering column. Specifically, the steering shaft is connected at one end thereof to a steering wheel, and also connected at the other end thereof to a tire by means of an intermediate shaft or the like. In this circumstance, vibrations caused by rotations on an engine or a rough or bumpy load surface has been transmitted to the steering wheel by means of the steering shaft. To reduce the vibrations transmitted to the steering wheel as possible, the rigidity of the steering column has been enhanced.

A known steering device, disclosed in JP 2002-193110A, employs an electric tilt steering system and includes an electric tilt unit for tilting the steering column in a vertical direction, the steering column being connected to, for example, the vehicle steering wheel.

Such steering device further includes a column tube, the column tube being supported at a column tilting point so as to be tilted thereabout. Thus, when a driver operates a switch for adjusting the steering device, an angle of the steering column is adjusted by means of the electric tilt unit.

When the steering column is tilted, the column tube is slid in a vertical direction in a manner where a roughly triangular protruded shape of a sliding member of the column tube slides on a roughly triangular recessed shape of a contact portion (pressure pad) of the column tube. The contact portion is fastened to a housing, which is attached to the steering column, by means of a bolt so as to apply a pressure constantly to the column tube in a horizontal direction. Thus, by means of the bolt applying a pressure to the column tube, vibrations in a vertical direction or a horizontal direction of the steering column can be reduced.

In this configuration, even when a load is applied to the steering wheel in a vertical direction or a horizontal direction, vibrations in a vertical direction or a horizontal direction on the steering column can be reduced; as a result, rigidity of the steering column can be enhanced.

Specifically, according to the known steering device, when the pressure is applied in a right direction, because the pressure is also applied to the column tilting point, at which the steering column is tilted, or applied to the tilt unit, the vibrations on the steering column cannot be reduced adequately, as a result, the vibrations transmitted to the steering wheel cannot be reduced. Further, in this circumstance, load fluctuation may be easily generated, and rotations of the motor may become uneven, as a result, a level of the noise may be increased.

Further, because the column tube is fitted to the housing at the tilt unit side by means of a nut, and also fit to the housing at the contacting portion by the sliding member, when a large pressure is applied to the column tube at the steering wheel side in a vertical direction, the column tube may be disengaged from the sliding member so that the column tube may become unstable. Consequently, a rotational moment is applied to the fitting portion of the column tube at the tilt unit side; as a result, it becomes difficult to secure rigidity of the steering column.

Thus, a need exist for the steering device to improve rigidity of the steering column in order to reduce vibrations from transmitting to the steering wheel.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a steering device comprises a steering shaft to which a steering wheel is attached, a steering column for housing and supporting the steering shaft so as to be rotatable, a tilt unit for tilting the steering column and the steering shaft, a main bracket fixed to a vehicle side bracket and a pressure applying member provided between the main bracket and the steering column for applying a pressure in one direction to the steering column.

DETAILED DESCRIPTION

An embodiment of the present invention will be explained in accordance with drawings attached hereto. A steering device in the embodiment is mounted to a vehicle such as an automobile. Specifically, the steering device, employing an electric tilt steering system, includes an electric tilt unit for tilting a steering column in a vertical direction, the steering column being provided at a lower end of a vehicle steering wheel.

A configuration of the steering device in this embodiment will be explained in accordance withFIG. 1,FIG. 2A andFIG. 2B.FIG. 1illustrates a side view of the steering device,FIG. 2A illustrates a cross section of the steering device inFIG. 1along a I-I line andFIG. 2B illustrates a cross section of the steering device inFIG. 1along a II-II line.

As shown inFIG. 1, the steering device according to the present embodiment further includes a steering shaft2to which a steering wheel1is attached, a steering column3for housing and supporting the steering shaft2so as to be rotatable and a tilt unit20for tilting the steering column3together with the steering shaft2.

The steering device further includes a first fixing and mounting portion M1and a second fixing and mounting portion M2at which the steering column3is fixed to the vehicle. The first fixing and mounting portion M1is fixed to a vehicle side bracket4so as to form a column fixing point at which the steering column3is fixed to the vehicle. On the other hand, the second fixing and mounting portion M2is also fixed to the vehicle side bracket4so as to form a column tilting point at which the steering column3can be tilted relative to the vehicle about a supporting point S (column tilting point).

The steering column3includes a housing5, which serves as a case of the steering column3, and a column tube6, which is inserted in the housing5in an axial direction thereof. Further, the steering shaft2is inserted in the column tube6.

The housing5is connected to a pair of arm members7by means of links L1, L2and L3, which serve as interlocking members. Thus, the housing5is rotatably supported by the arm members7at a pivot P1(column fixing point) so as to rotate thereabout.

The tilt unit20includes the links L1, L2and L3on the steering column3in order to adjust the tilt position of the steering wheel1by use of a drive from the tilt motor23.

The links L1, L2and L3includes a first link L1, a second link L2and a third link L3. Specifically, the first link L1is rotatably supported by the vehicle side bracket4by means of the pivot P1, the second link L2is rotatably supported by the housing5of the steering column3by means of a pivot P2, which serves as a connecting member, and the third link L3is formed integrally with the housing5. Further, the first link L1is connected to the second link L2by means of a pivot P3serving as a connecting member, the second link L2is connected to the tilt holder21by means of a pivot P4serving as a connecting member, and the third link L3is connected to the tilt slider22by means of a pivot P5serving as a connecting member. Further, the tilt unit20is comprised of the tilt holder21, which is connected to the vehicle side bracket4by means of the first link L1and the second link L2, and the tilt slider22, which is connected to the steering column3.

The tilt holder21includes a driving member such as the tilt motor23and gears such as a worm gear, a wheel gear and a tilt worm (not shown). Specifically, when the tilt motor23is driven, a rotation of the tilt motor23transmitted to the worm gear, and this rotation further transmitted to the wheel gear, which meshes with the worm gear. Furthermore, the tilt worm is rotated integrally with the wheel gear; as a result, the rotation of the tilt worm is transmitted to the tilt slider22.

An actuation of the tilt unit20for adjusting the position of the steering column3will be explained. The tilt unit20is actuated, for example, when a driver operates a switch on an instrument panel. Specifically, when the driver wants to tilt the steering column3in an upward direction, the tilt slider22is moved so as to slide in a direction where the pivot P4is distanced from the pivot P5in order to tilt the steering column3in an upward direction relative to the supporting point S.

On the other hand, when the driver wants to tilt the steering column3in a downward direction, the tilt slider22is moved so as to slide in a direction where the pivot P4comes close the pivot P5in order to tilt the steering column3in a downward direction relative to the supporting point S. The tilt unit20can be actuated automatically by use of a sensor which is provided on a vehicle seat for detecting that the seat has been seated by the driver.

Further, as shown inFIG. 2A andFIG. 2B, a rigidity improving structure10is provided at the steering column3, which is fixed to the vehicle side bracket4by use of bolts16through a main bracket13, which faces the steering column3and includes a pair of rigid brackets14aand14b. The main bracket13is provided so as not to rotate relative to the vehicle side bracket4when the steering column3is tilted.

The pair of rigid brackets14aand14bis provided integrally with the main bracket13at a lower portion thereof by means of a welding in a manner where these rigid brackets14aand14bare extending in a lower direction. Specifically, as shown inFIG. 2AandFIG. 2B, the steering column3is supported so as to be sandwiched between the rigid brackets14aand14b, which are formed integrally with the main bracket13. Further, as shown inFIG. 2A, a plate spring11a(pressure applying member) is provided between the rigid bracket14aand the housing5so as to be fixed to the rigid bracket14aby means of a bolt12(fixing member), and a plate spring11b(pressure applying member) is provided between the rigid bracket14band the housing5so as to be fixed to the rigid bracket14bby means of a bolt12(fixing member). Furthermore, as shown inFIG. 2B, a plate spring11c(pressure applying member) is provided between the rigid bracket14aand the housing5so as to be fixed to the rigid bracket14aby means of a bolt12(fixing member), and a plate spring11d(pressure applying member) is provided between the rigid bracket14band the housing5so as to be fixed to the rigid bracket14bby means of a bolt12(fixing member). The plate springs11aand11care applying pressures to a flat surface15aof the housing5, and the plate springs11band11dare applying pressures to a flat surface15bof the housing5.

The rigidity improving structure10of the steering device according to this embodiment will be further explained in accordance withFIG. 3AandFIG. 3B.FIG. 3Aillustrates an enlarged side view indicating the rigidity improving structure10shown inFIG. 1, andFIG. 3Billustrates an exploded perspective view of the rigidity improving structure10shown inFIG. 3A.

A structure on the left side of the rigidity improving structure is shown inFIG. 3A, however, the same structure can be applied to the right side of the rigidity improving structure10. As shown inFIG. 3A, the plate spring11ais fixed to a right portion of the rigid bracket14aby means of the bolt12, and the plate spring11cis fixed to a left portion of the rigid bracket14aby means of the bolt12. In the same manner, as shown inFIG. 3B, the plate spring11bis fixed to a right portion of the rigid bracket14bby means of the bolt12, and the plate spring11dis fixed to a left portion of the rigid bracket14bby means of the bolt12.

As mentioned above, the main bracket13, which is integrally formed with the rigid brackets14aand14b, is screwed to the vehicle side bracket4at flange portions13aof the main bracket13by means of the bolts16as shown inFIG. 2.

Using such rigidity improving structure10, a characteristic frequency of the steering device can be enhanced. Specifically, the characteristic frequency means a frequency based on a resonance generated by the steering device, and the characteristic frequency of the steering device may be affected by weight or rigidity of the steering device. More specifically, when weight or rigidity is changed, the characteristic frequency of the steering device is also changed. Generally, when the rigidity of the steering device of the steering device is increased while the weight of the steering device is not changed, the characteristic frequency is increased, and when the rigidity of the steering device is decreased while the weight of the steering device is not changed, the characteristic frequency is decreased.

A graph inFIG. 4indicates differences between the characteristic frequency with the rigidity improving structure10and the characteristic frequency without the rigidity improving structure10. The characteristic frequency is measured by detecting an output frequency on the steering wheel1, which is transmitted from the front side of the steering shaft2. A dashed line inFIG. 4indicates the characteristic frequency with the rigidity improving structure10(FIG. 1), and the solid line inFIG. 4indicates the characteristic frequency with the rigidity improving structure10. More specifically, a horizontal axis indicates a frequency, and a vertical axis indicates a vibration transmitting ratio (output frequency/input frequency).

As shown inFIG. 4, when the rigidity improving structure10is used, the characteristic frequency on the steering column3can be enhanced. Specifically, because the steering wheel1is connected to the tire through the steering shaft2(FIG. 1) and an intermediate shaft (not shown), vibrations from an engine (not shown), which is driven, or vibrations from the tire, the vibrations being caused by roughness of a road surface while the vehicle is running, are transmitted to the steering wheel1. Thus, it is preferable that the steering device includes a structure by which the steering wheel1is not vibrated sympathetically with the vibrations from the tire or the engine. The above rigidity improving structure10provided at the steering device can reduce vibrations on the steering wheel1, the vibrations being generated sympathetically with the vibrations from the tire or the engine by enhancing the characteristic frequency of the steering device. Thus, the vibrations on the steering wheel1can be reduced, as a result, vibrations that are transmitted to the driver can be reduced.

According to the present embodiment, following effects can be obtained.(1) According to the embodiment, the plate spring11a(pressure applying member) is provided between the rigid bracket14aand the housing5so as to be fixed to the rigid bracket14aby means of the bolt12(fixing member), and the plate spring11b(pressure applying member) is provided between the rigid bracket14band the housing5so as to be fixed to the rigid bracket14bby means of the bolt12(fixing member). Furthermore, the plate spring11c(pressure applying member) is provided between the rigid bracket14aand the housing5so as to be fixed to the rigid bracket14aby means of the bolt12(fixing member), and the plate spring11d(pressure applying member) is provided between the rigid bracket14band the housing5so as to be fixed to the rigid bracket14bby means of the bolt12(fixing member). The plate springs11aand11care applying pressures to the flat surface15aof the housing5, and the plate springs11band11dare applying pressures to the flat surface15bof the housing5. Thus, rigidity of the steering column3in a horizontal direction inFIG. 2can be enhanced, and further rigidity of the steering column3in a vertical direction inFIG. 2can also be enhanced together with the enhancement of the rigidity in a horizontal direction. Thus, rigidity of the steering column3can be enhanced in order to reduce the vibrations transmitting to the steering wheel1.(2) According to the embodiment, the plate springs11a,11b,11cand11dare fixed to the rigid brackets14aand14bby means of the bolts12. With such a simple structure, the pressures can be preferably applied to the flat surfaces15aand15b, which are formed on each side of the housing5.(3) According to the embodiment, the above rigidity improving structure10provided at the steering device can reduce the vibrations on the steering wheel1, the vibrations being generated sympathetically with the vibrations from the tire or the engine by enhancing the characteristic frequency of the steering device. Thus, the vibrations on the steering wheel can be reduced, as a result, vibrations that are transmitted to the driver can be reduced.(4) According to the embodiment, the plate springs11a,11b,11cand11dare provided between the housing5of the steering column3and the rigid brackets14aand14b. Thus, because the steering column3is pressed in the vicinity of the steering shaft2, to which the vibrations are transmitted, rigidity of the steering column3can be preferably enhanced without applying a pressure being more than requires.

An embodiment according to the present invention is not limited to the above configurations. The embodiment can be modified as follow.

According to the embodiment, the four pressure applying members are applied to the rigid brackets14aand14b, specifically, two pressure applying members are fixed to the rigid bracket14a, which is provided on the left side of the steering column inFIG. 2AandFIG. 2B, and the other two pressure applying members are fixed to the rigid bracket14b, which is provided on the right side of the steering column inFIG. 2AandFIG. 2B. However, at least one pressure applying member may be provided between the rigid bracket14aor the rigid bracket14band the housing5and the housing5. In other words, a configuration and a number of the pressure applying member may be vary, specifically, two pressure applying member may be provided on the rigid brackets14a(left) and the rigid bracket14b(right) so as to be in a pair, or the two pressure applying member may be provided only on the rigid brackets14aor only on the rigid bracket14b.

According to the embodiment, the plate spring11a(pressure applying member) is provided to the rigid bracket14a, and the plate spring11b(pressure applying member) is provided to the rigid bracket14b. The plate spring11aand the plate spring11bare provided in pairs. In addition, the plate spring11c(pressure applying member) is provided to the rigid bracket14aand the plate spring11d(pressure applying member) is provided to the rigid bracket14b. The plate spring11cand he plate spring11care provided in pairs. The plate springs11aand11care applying pressures to the flat surface15a, and the plate springs11band11dare applying pressures to the flat surface15b. However, the positions of the plate springs11a,11b,11cand11dmay be changed.

Between the flat surface portion15aof the housing5and each of the plate springs11aand11c, and between the flat surface portion15bof the housing5and each of the plate springs11aand11c, a coating such as a grease can be applied in order to make the steering column3to be tilted smoothly in a vertical direction.

According to the embodiment, the tilt unit20is actuated electrically, however, the tilt unit20may be actuated manually.

According to the embodiment, instead of the tilt unit20, the steering device may includes a telescopic unit, which can adjust the column tube6in a longitudinal direction of the vehicle along an axial line of the column tube6.

According to the embodiment, the plate springs11aand11care fixed to the rigid bracket14aby means of the bolt12, which serves as a fixing member, and the plate springs11band11dare fixed to the rigid bracket14bby means of the bolt12, which serves as a fixing member. However, the structure may be modified as follow. For example, sliding members31, which contact to the housing5, and coil springs32, which serve as pressure applying members, may be attached to the rigid brackets14aand14b. A configuration on the rigid bracket14b, in this modified embodiment, will be explained with reference toFIG. 5. Because the same configuration can be applied to the rigid bracket14a, an explanation for the configuration on the rigid bracket14awill be skipped. The sliding member31is attached to the rigid bracket14bby means of a coil spring32and a load adjusting screw34(screw member) so as to be able to adjust a load applied to the rigid bracket14b. Further, a spacer33is welded integrally with the rigid bracket14bin order provide enough length thereto, into which the load adjusting screw34is screwed.

Thus, the coil spring32applies a load, which is adjusted by the load adjusting screw34provided at the rigid bracket14b, to the steering column3, as a result, rigidity of the steering column3in a horizontal direction inFIG. 5can be enhanced. After the load adjusting screw34is screwed in the rigid bracket14bso as to adjust a load of the coil spring32, the load adjusting screw34is maintained by means of a fixing screw35.

Further, the rigidity improving structure10and the pressure applying member may be modified as follow. For example, sliding members41, which contact to the housing5, and adjusting screws44, which serve as pressure applying members, may be attached to the rigid brackets14aand14b. A configuration on the rigid bracket14b, in this modified embodiment, will be explained with reference toFIG. 6. Because the same configuration can be applied to the rigid bracket14a, an explanation for the configuration on the rigid bracket14awill be skipped.

The sliding member41is attached to the rigid bracket14bby means of the adjusting screw44so as to be able to adjust a torque or a load applied to the rigid bracket14b. Further, a spacer43is welded integrally with the rigid bracket14bin order provide enough length thereto, into which the adjusting screw44is screwed. By adjusting the position of the adjusting screw44, to which the sliding member41is press fit, the pressure applied to the steering column3can be adjusted. Thus, rigidity of the steering column3in a horizontal direction inFIG. 6can be enhanced. After the load adjusting screw44is screwed in the rigid bracket14b, the load adjusting screw44is maintained by means of a fixing screw45. Same effects can be obtained in these modified embodiments shown inFIG. 4andFIG. 5.

According to the embodiment, the pressure applying members are fixed to the rigid brackets14aand14b, which are formed integrally with the main bracket, the main bracket13being fixed to the vehicle side bracket4. The position of the pressure applying members may be changed to any place between the column tilting point (supporting point S) and the steering wheel1. For example, when the steering column3is fixed at a lower end thereof, and a column tilting point in this configuration is positioned nearer to the steering wheel1than the column tilting point in the embodiment, same effect as in the embodiment can be obtained. Thus, vibrations on the steering column3can be reduced preferably.

According to the embodiment, the pressure applying member is provided between the rigid bracket14aor14band the housing5. However, the pressure applying member may be provided between the main bracket13and the steering column3(except a portion at which the housing5is attached). In this configuration, same effects as in the embodiment can be obtained.

According to the embodiment, the steering column3includes the rigidity improving structure10, the main bracket13, and the rigid brackets14aand14b, however, the rigidity improving structure10may be formed integrally with, for example, the vehicle side bracket4. In this configuration, the rigidity improving structure10may include a supporting member facing the steering column and supporting the steering column so as to be sandwiched between the rigid brackets14aand14b, and a pressure applying member, which is provided between the supporting member and the steering column so as to apply a pressure to the steering column in one direction.

According to the present invention, the pressure applying member provided between the main bracket and the steering column for applying a pressure to the steering column in one direction, in other words, for applying a pressure to the steering column from the main bracket. Thus, rigidity of the steering column in a horizontal direction can be enhanced, and rigidity of the steering column in a vertical direction also be enhanced together with the enhancement of the rigidity in a horizontal direction. Thus, rigidity of the steering column can be enhanced, as a result, the vibrations transmitting to the steering wheel can be reduced.

According to the present invention, the pressure applying member is provided between the column tilting point and the steering wheel. Thus, because the pressure applying member is provided at a portion where the vibrations are transmitted, the vibrations on the steering column can be reduced preferably.

According to the present invention, the plate spring serving as the pressure applying member is fixed to the rigid bracket by means of the screwing member. Thus, with such a simple structure, the pressure can be preferably applied to the side surface of the steering column.

According to the present invention, a level of the load applied to the steering column by the sliding member can be adjustable by means of the coil spring and the screw member. Thus, the level of the load applied to the side of the steering column from the rigid bracket side can be adjusted.

According to the present invention, a level of the load applied to the steering column by the sliding member can be adjustable by means of the adjusting screw, which is serving as a pressure applying member. Thus, the level of the load applied to the side of the steering column from the rigid bracket side can be adjusted.

According to the present invention, the steering device comprises the steering shaft to which the steering wheel is attached, the steering column for housing and supporting the steering shaft so as to be rotatable, the tilt unit for tilting the steering column and the steering shaft, the supporting member sandwiching the steering column in order to support it and the pressure applying member provided between the supporting member and the steering column for applying a pressure in one direction to the steering column. Thus, rigidity of the steering column in a horizontal direction can be enhanced, and rigidity of the steering column in a vertical direction also be enhanced together with the enhancement of the rigidity in a horizontal direction. Thus, rigidity of the steering column can be enhanced, as a result, the vibrations transmitting to the steering wheel can be reduced.