Vibration-isolating device for steering wheel of traveling working vehicle with wheel steering mechanism

A vibration-isolating device for a steering wheel of a travelling working vehicle equipped with a wheel steering mechanism includes a first steering shaft (32) that transmits rotational displacement, the first steering shaft being operatively connected to the steering wheel (7); a second steering shaft (33) that transmits rotational displacement, the second steering shaft being operatively connected to the wheel steering mechanism (P, 23); and a vibration-isolating connecting mechanism (31) that operatively connects the first steering shaft (32) and the second steering shaft (33) to each other so that rotational displacement can be transmitted. When the angles of rotational displacement of the first steering shaft (32) and the second steering shaft (33) are within ranges of rotation angles for linearly driving the vehicle, rotational displacement cannot be transmitted between the first steering shaft (32) and the second steering shaft (33).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vibration-isolating device for a steering wheel of a traveling working vehicle equipped with a wheel steering mechanism.

2. Description of the Related Art

A device disclosed in JP 2007-237786A (paragraph [0023], FIGS. 2 to 4) in which a steering post is supported on the top surface of a transmission case via rubber vibration isolators, and a steering shaft connected to a steering wheel is supported within the steering post, is known as a steering wheel vibration-isolating device of a working vehicle of this type.

In this conventional device, only the steering post supported on the transmission case is supported in a vibration-isolating manner, so that vibration transmitted from a wheel steering mechanism to the steering wheel through the steering shaft cannot be blocked, and there is a problem in that vibration of the steering wheel cannot be suppressed.

Moreover, a structure disclosed in JP 8-207784A, in which a steering shaft connected to a steering wheel is supported within a steering post via a cylindrical rubber provided in an upper portion of the steering post and upper and lower rubber bushes holding a bearing inside thereof, is known as a structure for supporting a steering shaft.

Also in this conventional structure, the steering shaft is supported in a vibration-isolating manner only with respect to the steering post, so that vibration transmitted from a wheel steering mechanism to the steering wheel through the steering shaft cannot be blocked, and so there is the problem in that vibration of the steering wheel cannot be suppressed.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a steering wheel vibration-isolating device of a working vehicle that is capable of effectively suppressing vibration transmitted to a steering wheel through a steering shaft.

In order to achieve this object, a vibration-isolating device for a steering wheel according to the present invention, of a traveling working vehicle equipped with a wheel steering mechanism, includes a first steering shaft that transmits rotational displacement, the first steering shaft being operatively connected to the steering wheel; a second steering shaft that transmits rotational displacement, the second steering shaft being operatively connected to the wheel steering mechanism; and a vibration-isolating connecting mechanism that operatively connects the first steering shaft and the second steering shaft to each other so that rotational displacement can be transmitted. The vibration-isolating connecting mechanism has the following functions: when the angles of rotational displacement of the first and second steering shafts are within ranges of rotation angles for linearly driving the vehicle, rotational displacement cannot be transmitted between the first steering shaft and the second steering shaft, and when the angles of rotational displacement of the first and second steering shafts are beyond the ranges of rotation angles for linearly driving the vehicle, rotational displacement can be transmitted between the first steering shaft and the second steering shaft.

When the angles of rotational displacement of the first and second steering shafts are within the ranges of rotation angles for linearly driving the vehicle, that is, when the first and second steering shafts are in a linear drive position, the first steering shaft and the second steering shaft are not interlocked with each other. Accordingly, vibration transmitted from the wheel steering mechanism to the second steering shaft is not transmitted to the first steering shaft. Thus, vibration is not transmitted to the steering wheel.

When the angles of rotational displacement of the first and second steering shafts are beyond the ranges of rotation angles for linearly driving the vehicle, that is, when the first and second steering shafts are in a turn position, the first steering shaft and the second steering shaft are interlocked with each other. However, the steering shafts are interlocked via the vibration-isolating connecting mechanism, so that the transmission of vibration from the second steering shaft to the first steering shaft is suppressed. Accordingly, the transmission of vibration to the steering wheel is blocked or sufficiently suppressed.

With the above-described vibration-isolating device for a steering wheel according to the present invention, the transmission of vibration from the wheel steering mechanism to the steering wheel can be suppressed or blocked, and comfortable maneuverability can be achieved.

In one of preferred embodiments of the vibration-isolating connecting mechanism, at least one engage member connected to one of the first and second steering shafts, at least one opposite engage member connected to the other one of the first and second steering shafts, and a vibration-isolating rubber member disposed between the engage member and the opposite engage member are provided. When the angles of rotational displacement of the first and second steering shaft are within the ranges of rotation angles for linearly driving the vehicle, at least one of the engage member and the opposite engage member is not in contact with the vibration-isolating rubber member. When the angles of rotational displacement of the first and second steering shafts are beyond the ranges of rotation angles for linearly driving the vehicle, the engage member and the opposite engage member are in contact with the vibration-isolating rubber member.

In one of specific examples of such a preferred vibration-isolating connecting mechanism, the engage member and the opposite engage member are projections projecting from one of the steering shafts toward the other one of the steering shafts, and the vibration-isolating rubber member has openings that receive the projections therein. More preferably, the engage member is formed as a connecting pin, the opposite engage member is formed as an opposite connecting pin, the openings of the vibration-isolating rubber member are formed as a fitting hole fitting to the connecting pin or an opposite fitting hole fitting to the opposite connecting pin, the hole diameter of the fitting hole is the same as the pin diameter of the connecting pin, and the hole diameter of the opposite fitting hole is larger than the pin diameter of the opposite connecting pin. According to such a specific example, connecting pins and a vibration-isolating body that are engaged with each other are utilized in order to operatively connect the first steering shaft and the second steering shaft to each other. Furthermore, a part of the fitting holes of the vibration-isolating body fitting to the connecting pins is formed to have a larger diameter than the diameter of the connecting pins. Thus, as long as the angles of rotational displacement of the first and second steering shafts are within the ranges of rotation angles for linearly driving the vehicle, one of the first and second steering shafts is engaged with (connected to) the vibration-isolating body, and the other one of the first and second steering shafts is disengaged from the vibration-isolating body. When the steering wheel is in a linear drive position, the connecting pin of the other one of the first and second steering shafts is clear of the fitting hole, so that the transmission of vibration from the wheel steering mechanism to the first steering shaft is blocked at that clearance. When the steering wheel is operated into a turn position, the connecting pin is brought into contact with the fitting hole to operatively connect the first steering shaft and the second steering shaft to each other. However, the transmission of vibration from the wheel steering mechanism to the first steering shaft is weakened by the vibration-isolating body.

In the linear drive position, a driver tends to easily feel vibration because the driver often just puts the hands on the steering wheel rather than operating the steering wheel. According to the present invention, the first steering shaft and the second steering shaft are not in mechanical contact with each other in this linear drive position, so that vibration is seldom transmitted, and the driver is thus less likely to feel vibration even though the driver often puts the hands on the steering wheel.

In one of specific examples of such a preferred vibration-isolating connecting mechanism, the engage member is an accepting member connected to one of the steering shafts, the opposite engage member is a non-circular member connected to the other one of the steering shafts and accommodated in an internal space defined by a circumferential wall of the accepting member, and the vibration-isolating rubber member has a shape that is interposed in a space between the circumferential wall of the accepting member and the non-circular member in a radial direction. In this specific example, when the steering wheel is in the linear drive position, a clearance is created between the non-circular member and the vibration-isolating rubber member, so that vibration from the wheel steering mechanism to the first steering shaft is blocked at that clearance. When the steering wheel is operated into the turn position, the non-circular member and the vibration-isolating rubber member are brought into contact with each other to interlock the first steering shaft and the second steering shaft with each other. However, the transmission of vibration from the wheel steering mechanism to the first steering shaft is weakened by the vibration-isolating rubber member.

Other features and advantages of the present invention will become apparent from the following description of embodiments by means of the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Here, the working vehicle will be described as a tractor. As shown inFIG. 1, the tractor includes, on the front side of a traveling body3equipped with front and rear wheels1and2, an engine4, an engine hood5covering the engine4, a steering post cover6disposed in a rear portion of the engine hood5, a steering wheel7disposed above the steering post6, and a front loader device FL supported by brackets11vertically extended from both lateral sides of the engine hood5, right and left rear wheel fenders8disposed on the rear side of the traveling body3, a driver's seat9disposed between the right and left rear wheel fenders8, and a mission case10disposed under the driver's seat9.

Now a structure for supporting the front loader device FL will be described. As shown inFIG. 1, lateral side faces of engine supporting frames12disposed on the right side and the left side are connected to lateral side faces of a front end portion of a main frame13extended forwardly from the mission case10on the rear side with first supporting brackets15in a posture oriented in a fore-and-aft direction.

Next, the steering wheel vibration-isolating device will be described. As shown inFIGS. 1 to 3, a power steering unit P is placed within the engine hood5, and a pitman arm23for steering a driving system having the front and rear wheels1and2is pivotably supported at the lower end position of a case27housing the power steering unit P, whereby a wheel steering mechanism is constructed.

A steering post24is provided above the power steering unit P and fixedly attached to a console box joined to the engine hood5, and a first steering shaft32is supported by the steering post24. The steering wheel7is attached to the upper end position of the first steering shaft32projecting to the outside of the console box.

Next, a structure for supporting the steering post24in a vibration-isolating manner with the case27housing the power steering unit P will be described. As shown inFIGS. 2 and 3, a flange-like receiving plate portion28is fixedly attached to the upper end position of the case27, and a flanged portion24A is provided at the lower end position of the steering post24. A connecting member29is interposed between the receiving plate portion28and the flanged portion24A to connect the receiving plate portion28and the flanged portion24A to each other. Accordingly, the steering post24is supported by the case27housing the power steering unit P.

As shown inFIGS. 3 and 4, the connecting member29has a flat top face portion29A that is connected to and that receives the flanged portion24A, skirts293B drooped downwardly from both end positions of the flat top face portion29A, and flat bottom face portions29C formed at the lower end position of the right and left skirts293.

As shown inFIGS. 2 and 3, rubber vibration isolators30are disposed between the right and left flat bottom face portions29C and the receiving plate portion28disposed at the upper end position of the case27, and the connecting member29is supported via the rubber vibration isolators30. Thus, vibration from the power steering unit P is no longer easily transmitted to the steering post24.

The connecting member29will be described in detail. As shown inFIGS. 3 and 4, the flat top face portion29A has a square shape, and the skirts29B having the same width as the flat top face portion29A extend downwardly from the flat top face portion29A. The lower end of the skirts293B is bent horizontally to form the flat bottom face portions29C, and the right and left flat bottom face portions29C have a narrower width than the lower end width of the skirts29B as shown inFIG. 4. The positions of the flat bottom face portions29C are shifted from each other in the depth direction in such a manner that the flat bottom face portions29C are point symmetric with respect to the axial center of the first steering shaft32and such that the left flat bottom face portion29C is positioned on the back side inFIG. 4and the right flat bottom face portion29C is positioned on the front side.

As shown inFIGS. 3 and 4, a pair of right and left rubber vibration isolators30are disposed between the flat bottom face portions29C and the receiving plate portion28. The rubber vibration isolators30are respectively mounted to the right and left flat bottom face portions29C. As is the case with the flat bottom face portions29C, the positions of the rubber vibration isolators30are shifted from each other in the depth direction, and the rubber vibration isolators30are point symmetric with respect to the axial center of the first steering shaft32. Accordingly, the two rubber vibration isolators30support the connecting member29in a vibration-isolating manner by being positioned in point-symmetric positions with respect to the axial center of the first steering shaft32.

As shown inFIGS. 3 and 4, each of the flat bottom face portions29C has a plate-like portion29cextending downwardly from one of the side edges thereof in the depth direction ofFIG. 3. The plate-like portions29care vertically suspended along the rubber vibration isolators30and extend to a position close to the top surface of the receiving plate portion28supporting the rubber vibration isolators30. With such a configuration, when the rubber vibration isolators30shrink under a compression force, the shrinking of the rubber vibration isolators30is regulated by the plate-like portions29cmaking contact with the receiving plate portion28.

Next, a vibration-isolating connecting mechanism31that cuts off the transmission of vibration through a steering shaft will be described. As shown inFIGS. 2 and 3, the first steering shaft32connected to the steering wheel7is housed within the steering post24, and a second steering shaft33juts out from the case27housing the power steering unit P. The vibration-isolating connecting mechanism31is interposed between the first steering shaft32and the second steering shaft33, and thus the transmission of vibration from the power steering unit P to the steering wheel7is suppressed.

As shown inFIGS. 2 and 3, the vibration-isolating connecting mechanism31includes a coupling portion32A secured to the lower end of the first steering shaft32, a first connecting member34having a relay shaft34A jutting out therefrom and being capable of engaging with and rotating integrally with the coupling portion32A, a rubber vibration isolator35disposed under the first connecting member34and serving as the vibration-isolating body that supports the first connecting member34in a vibration-isolating manner, and a second connecting member36that receives the rubber vibration isolator35from below and transmits a rotational operating force, the second connecting member36being provided with a coupling material36A into which the second steering shaft33vertically extended from the power steering unit P is fitted.

As shown inFIGS. 3 and 5, flanged portions34B and36B are provided on the surfaces of the first connecting member34and the second connecting member36that make contact with the rubber vibration isolator35, and four connecting pins34aand36ajut out from the flanged portions34B and36B toward each other. On the other hand, the rubber vibration isolator35has the shape of a considerably thick flat plate, and fitting holes35A and35B passing through the rubber vibration isolator35in the axial direction are formed at eight circumferential positions in the rubber vibration isolator35.

As shown inFIG. 5, the hole diameters of the fitting holes35A and35B and the pin diameters of the connecting pins34aand36aare sized as described below. That is to say, regarding the fitting holes35A and35B, the fitting holes35A having a large diameter and the fitting holes35B having a small diameter are formed alternately, and the hole diameter of the small-diameter fitting holes35B is the same as the pin diameter of the connecting pins34aextended from the first connecting member34. On the other hand, the hole diameter of the large-diameter fitting holes35A is larger than the pin diameter of the connecting pins36aextended from the second connecting member36.

With a configuration as described above, when the angle of rotational displacement of each of the first steering shaft32and the second steering shaft33is within a range of rotation angles for linearly driving the vehicle, that is, in a state where the steering wheel7is operated in a linear drive position, the connecting pins36aextended from the second connecting member36fit in the large-diameter fitting holes35A without having contact with the inner circumferential surface of the large-diameter fitting holes35A. Therefore, vibration from the second steering shaft33is not transmitted to the first steering shaft32or is suppressed.

As the steering wheel7is rotated from the above-described state, the angles of rotational displacement of the first steering shaft32and the second steering shaft33exceed the ranges of rotation angles for linearly driving the vehicle. During this operation, the connecting pins34aextended from the first connecting member34drive the rubber vibration isolator35to rotate, and due to the rotation of the rubber vibration isolator35, the large-diameter fitting holes35A come into contact with the connecting pins36aand apply a rotational operating force on the second connecting member36. That is to say, the connecting members34and36are interlocked with each other via the rubber vibration isolator35, so that vibration from the power steering unit P is suppressed from being transmitted to the steering wheel7by the rubber vibration isolator35absorbing the vibration. As a result, whether the steering wheel7is in the linear drive position or in a turn position, the propagation of vibration is suppressed, and the driver can have a comfortable steering feeling.

Second Embodiment

Here, a vibration-isolating device in which the vibration-isolating connecting mechanism37has a different form from that of the first embodiment will be described. As shown inFIG. 6, the receiving plate portion28is provided on the top surface of the case27housing the power steering unit P, and the connecting member29is attached above the receiving plate portion28via the rubber vibration isolators30as in the first embodiment. The connecting member29includes the flat top face portion29A, the right and left skirts29B, and the right and left flat bottom face portions29C.

As shown inFIG. 6, each of the flat bottom face portions29C has the plate-like portion29cextending downwardly from one of the side edges thereof in the depth direction ofFIG. 4. The plate-like portions29care vertically suspended along the rubber vibration isolators30and extend to a position close to the top surface of the receiving plate portion28supporting the rubber vibration isolators30. With such a configuration, when the rubber vibration isolators30shrink under a compression force, the shrinking of the rubber vibration isolators30is regulated by the plate-like portions29cmaking contact with the receiving plate portion28.

Now the vibration-isolating connecting mechanism37for the steering shafts will be described. As shown inFIG. 6, the flat top face portion29A of the connecting member29has a hole vertically passing through the flat top face portion29A, a supporting boss42in a vertical posture is mounted in a state where the supporting boss42is fitted within the hole, and the supporting boss42extends upwardly from the hole.

An upper relay shaft45interlocking the first steering shaft32equipped with the steering wheel7with the second steering shaft33projecting from the case27housing the power steering unit P is inserted in the supporting boss42. A shaft retaining ring45ais mounted at a middle position between the upper and lower end lines of the upper relay shaft45and determines the position of the upper relay shaft45, which is inserted in the supporting boss42, in the vertical direction. A needle bearing is mounted within the supporting boss42, thereby rotatably supporting the upper relay shaft45.

As shown inFIGS. 7 and 8, at a lower end portion of the upper relay shaft45, an accepting member45A constituting the vibration-isolating connecting mechanism37is formed integrally therewith, and a mounting space in which a rubber vibration isolator46is to be mounted is formed inside the circumferential wall of the accepting member45A. The mounting space has approximately fan-shaped spaces formed respectively at three positions in the circumferential direction and having a certain width in the circumferential direction, and the rubber vibration isolator46can be accommodated in those spaces so that the rubber vibration isolator46is not allowed to rotate more than a slight rotation angle.

On the other hand, as shown inFIGS. 7 and 8, a lower relay shaft47is disposed under the accepting member45A, and a non-circular member47A having a Y-shape when viewed in the axial direction is formed on the upper end of the lower relay shaft47. Three side portions47aoutwardly-extending in the Y-shape of the non-circular member47A can respectively enter into and engage with approximately fan-shaped recessed portions of the accepting member45A. When the angles of rotational displacement of the first steering shaft32and the second steering shaft33are within the ranges of rotation angles for linearly driving the vehicle, that is, in a state where the steering wheel7is operated in the linear drive position, a clearance is formed between the side portions47aof the non-circular member47A with the rubber vibration isolator46and the recessed portions of the accepting member45A. When the angles of rotational displacement of the first steering shaft32and the second steering shaft33are beyond the ranges of rotation angles for linearly driving the vehicle, that is, in a state where the steering wheel7is operated to turn the vehicle, the three side portions47acovered by the rubber vibration isolator46are brought into contact with one of the side walls of the respective recessed portions of the accepting member45A, and thus the first steering shaft32and the second steering shaft33are rotated integrally.

As shown inFIG. 6, under the lower relay shaft47, the second steering shaft33is extended upwardly from the case27housing the power steering unit P, and a coupling material48extending between a lower end portion of the lower relay shaft47and an upper end portion of the second steering shaft33is provided.

An annular recessed groove33ais formed near the upper end of the second steering shaft33, and an engaging ball body48amounted inside the coupling material48engages with the annular recessed groove33a. A plate spring material48bis mounted on the outer circumferential surface of the coupling material48and biases the engaging ball body48ain an inward direction to engage the ball body48awith the annular recessed groove33a.

With such a configuration, the engaging ball body48aengages with the annular recessed groove33a, and the engaged state is maintained by the plate spring material48b, as shown inFIG. 6. Accordingly, the coupling material48is maintained in an engaged state while extending between the lower end portion of the lower relay shaft47and the upper end portion of the second steering shaft33. The coupling material48and the lower relay shaft47are formed integrally so as to rotate integrally with each other, and the coupling material48and the second steering shaft33are spline-fitted. Thus, a steering wheel operating force is transmitted from the lower relay shaft47to the second steering shaft33via the coupling material48.

Other Embodiments

(1) An embodiment may also be employed in which, inFIGS. 3 and 5, the large-diameter fitting holes35A and the small-diameter fitting holes35B are formed so that the hole diameter of the large-diameter fitting holes35A is the same as the diameter of the connecting pins36aextended from the second connecting member36and the hole diameter of the small-diameter fitting holes35B is larger than the diameter of the connecting pins34aextended from the first connecting member34, and a clearance is created between the small-diameter fitting holes35B and the connecting pins34aextended from the first connecting member34.

(2) In the configuration shown inFIGS. 3 and 5and in the embodiment described in the foregoing paragraph (1), it is also possible that the fitting holes35A and the fitting holes35B all have the same hole diameter, and the external diameter of the connecting pins34aextended from the first connecting member34or the external diameter of the connecting pins36aextended from the second connecting member36is set to a slightly smaller diameter.

(3) In the embodiment shown inFIGS. 3 and 5and in the embodiments described in the foregoing paragraphs (1) and (2), it is also possible that a clearance is created between a part (e.g., two) of the four connecting pins34aextended from the first connecting member34and the corresponding fitting holes35B, and no clearance is created between the rest of the connecting pins34aextended from the first connecting member34and all of the connecting pins36aextended from the second connecting member36and the corresponding fitting holes35A and35B.

(4) In the embodiment shown inFIGS. 3 and 5and in the embodiments described in the foregoing paragraphs (1) and (2), it is also possible that a clearance is created between a part (e.g., two) of the four connecting pins36aextended from the second connecting member36and the corresponding fitting holes35A, and no clearance is created between the rest of the connecting pins36aextended from the second connecting member36and all of the connecting pins34aextended from the first connecting member34and the corresponding fitting holes35A and35B.

(5) A soft resin or a sponge or the like can be used instead of the rubber vibration isolator35.