JP2012131421A - Steering structure of motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering device that can change a turning central position of a handle without changing a forming position of a through-hole in a head pipe.SOLUTION: In the steering structure, an upper bracket 8 and an under bracket 9 which couple a front fork member 5 are rotatably supported to a head pipe 10 in which an upper boss 11 and an under boss 12 are formed using a stem shaft line 10A extending vertically as a shaft center. The steering structure includes: a base shaft 20 being inserted between the upper boss 11 and the lower boss 12; rotation stop parts 300 and 400 which are provided in the part exposed from the head pipe 10 and prevent the base shaft 20 from rotating around the stem shaft line 10A; an upper side eccentric shaft 40 which is provided at an upper end of the base shaft 20, and supports an upper bracket 8 rotatably around the steering shaft line 4A which carries out eccentricity to the stem shaft line 10A; and a lower side eccentric shaft 30 which is provided at a lower end of the base shaft 20, and supports a lower bracket 9 rotatably around the steering shaft line 4A.

Description

  According to the present invention, an upper bracket and an under bracket for connecting a pair of left and right front fork members are rotatably supported with respect to a head pipe portion in which a through-hole penetrating vertically is formed with a stem axis extending vertically. The present invention relates to a steering structure for a motorcycle.

  Conventionally, in a motorcycle, a steering shaft is rotatably supported by a head pipe portion of a main frame. A through-hole penetrating vertically is formed in the head pipe portion, and a steering shaft is inserted into the through-hole. A front fork and a handle are fixed to the steering shaft via a bracket, and the front wheel turns left and right by the operation of the handle.

  For example, in the case of racing, the caster angle may be changed according to the rider's preference. The caster angle means the inclination angle of the front fork. The caster angle is changed by changing the mounting angle of the steering shaft with respect to the head pipe portion. A motorcycle that can change the caster angle is disclosed in Patent Documents 1 and 2.

JP-A-8-127380 Japanese Patent Laid-Open No. 11-301562

  For example, in the case of racing, it is desired to change the turning center position of the steering wheel according to the driver's preference in order to change the steering sensitivity and the like. In the conventional steering structure, the turning center position of the steering wheel is on the axis of the steering shaft. For this reason, in order to change the turning center position of the handle, it is necessary to change the formation position of the through hole for supporting the steering shaft in the head pipe portion. In this case, it is necessary to design the head pipe portion according to the preference of the driver, and the head pipe portion of the same standard cannot be used. As a result, the cost of the motorcycle is increased.

  Therefore, the present invention provides a steering device that can change the turning center position of the handle without changing the formation position of the through hole in the head pipe portion.

  According to the present invention, an upper bracket and an under bracket for connecting a pair of left and right front fork members are rotatably supported with respect to a head pipe portion in which a through-hole penetrating vertically is formed with a stem axis extending vertically. In the steering structure of a motorcycle, the base shaft inserted into the through hole and the portion exposed from the head pipe portion are prevented from rotating around the stem axis line. An anti-rotation portion, an upper eccentric shaft portion provided at an upper end portion of the base shaft and supporting an upper bracket so as to be rotatable around a steering axis eccentric with respect to the stem axis line, and provided at a lower end portion of the base shaft And a lower eccentric shaft portion that rotatably supports the under bracket around the steering axis. To provide a steering structure of a motorcycle.

(A) Preferably, one of the upper eccentric shaft portion and the lower eccentric shaft portion is formed integrally with the base shaft, and the other of the upper eccentric shaft portion and the lower eccentric shaft portion is the base shaft. The steering structure includes a fixing mechanism that fixes the other eccentric shaft portion and the base shaft.

(B) Preferably, the lower eccentric shaft portion is formed integrally with the base shaft, and the upper eccentric shaft portion is formed detachably with respect to the base shaft.

(C) Preferably, the fixing mechanism includes a positioning portion that prevents the other eccentric shaft portion from being fixed away from the steering axis.

(D) Preferably, the fixing mechanism includes a bolt for fastening the other eccentric shaft portion to the base shaft, a positioning pin formed on one of the other eccentric shaft portion and the base shaft, and the other eccentric shaft portion. And a pin hole that engages with the positioning pin formed on the other of the base shafts.

(E) Preferably, the anti-rotation portion includes a pinching portion for pinching a protrusion formed on the head pipe portion from both sides in the vehicle width direction.

(F) Preferably, the anti-rotation portion includes a contact portion that contacts the protrusion disposed in the clamping portion, and an adjustment mechanism that adjusts a position where the corresponding contact portion contacts the protrusion. .

  The present invention can change the turning center position of the handle without changing the formation position of the through hole in the head pipe portion.

1 is an overall perspective view of a motorcycle viewed from the upper left rear. It is the perspective view which looked at the steering structure from the upper left rear. It is the perspective view which looked at the steering structure from the upper right front. It is a sectional side view which shows a steering structure. 3 is a bottom view of a base shaft 20 and a lower eccentric shaft portion 30. FIG. 3 is a side view of a base shaft 20 and a lower eccentric shaft portion 30. FIG. 3 is a top view of a base shaft 20 and a lower eccentric shaft portion 30. FIG. 4 is a bottom view of an upper eccentric shaft portion 40. FIG. 4 is a side view of an upper eccentric shaft portion 40. FIG. 4 is a top view of an upper eccentric shaft portion 40. FIG.

(Configuration of this embodiment)
FIG. 1 is an overall perspective view of the motorcycle 1 as viewed from the upper left rear. In FIG. 1, a motorcycle 1 includes a main frame 2, a swing arm 3, a handle 4, a pair of left and right front fork members 5, a front wheel 6, and a rear wheel 7. The front wheel 6 is supported by a pair of left and right front fork members 5. The rear wheel 7 is supported by the swing arm 3. The swing arm 3 is swingably supported with respect to the main frame 2. A steering structure 100 is disposed in the front part of the motorcycle 1.

  FIG. 2 is a perspective view of the steering structure 100 as viewed from the upper left rear. In FIG. 2, the main frame 2 includes a head pipe portion 10 and a pair of left and right side frames 19 extending rearward from the head pipe portion 10.

  FIG. 3 is a perspective view of the steering structure 100 as viewed from the upper right front. In FIG. 3, the pair of left and right front fork members 5 are connected by an upper bracket 8 and an under bracket 9. The upper bracket 8 is disposed above the head pipe portion 10, and the under bracket 9 is disposed below the head pipe portion 10. In the steering structure 100, the upper bracket 8 and the under bracket 9 are rotatably supported with respect to the head pipe portion 10.

  FIG. 4 is a side sectional view showing the steering structure 100. In FIG. 4, the head pipe portion 10 is hollow and has an upper wall 10a and a lower wall 10b. An upper boss portion 11 is formed on the upper wall 10a, and a lower boss portion 12 is formed on the lower wall 10b. The head pipe portion 10 is provided with a stem axis 10 </ b> A that extends vertically. Center axes of the upper boss portion 11 and the lower boss portion 12 are formed on the stem axis 10A. For this reason, a through-hole having the stem axis 10 </ b> A as an axis is formed in the head pipe eve 10 by the inner surface of the upper boss portion 11 and the inner surface of the lower boss portion 12.

  The steering structure 100 includes a stem 200. The stem 200 includes a base shaft 20, a lower eccentric shaft portion 30, and an upper eccentric shaft portion 40. The lower eccentric shaft portion 40 is provided at the lower end portion of the base shaft 20, and the upper eccentric shaft portion 40 is provided at the upper end portion of the base shaft 20. The base shaft 20 and the lower eccentric shaft portion 30 are integrally formed. The upper eccentric shaft portion 40 is detachably attached to the base shaft 20.

  The stem 200 will be described in more detail with reference to FIGS. 5 to 7 show the base shaft 20 and the lower eccentric shaft portion 30. FIG. 5 is a bottom view of the base shaft 20 and the lower eccentric shaft portion 30. FIG. 6 is a side view of the base shaft 20 and the lower eccentric shaft portion 30. FIG. 7 is a top view of the base shaft 20 and the lower eccentric shaft portion 30. 8 to 10 show the upper eccentric shaft portion 40. FIG. 8 is a bottom view of the upper eccentric shaft portion 40. FIG. 9 is a side view of the upper eccentric shaft portion 40. FIG. 10 is a top view of the upper eccentric shaft portion 40.

  In FIG. 6, the base shaft 20 is a multi-stage columnar member extending along the central axis 20A. The base shaft 20 has a lower end portion 21, an intermediate portion 22, and an upper end portion 23. The outer diameters of the upper end portion 21 and the lower end portion 23 are equal, and the outer diameter of the intermediate portion 22 is smaller than the outer diameters of the upper end portion 21 and the lower end portion 23. Further, a lightening hole 27 is formed in the upper end portion 21, and a lightening hole 28 is formed in the intermediate portion 22.

  In FIG. 6, the lower eccentric shaft portion 30 includes a lower eccentric shaft 31, a stopper portion 32, and a clamping portion 33. The lower eccentric shaft 31 is a columnar member that extends downward along the central axis 31A. The central axis 31 </ b> A of the lower eccentric shaft 31 is eccentric with respect to the central axis 20 </ b> M of the base shaft 20. The stopper portion 32 is a plate-like member that spreads outside the upper boss portion 11 in a plane perpendicular to the central axis 31A. The stopper portion 32 connects the lower eccentric shaft 31 and the lower end portion 23 of the base shaft 20. The clamping part 33 is formed integrally with the stopper part 32. The structure of the clamping part 33 is mentioned later.

  In FIG. 9, the upper eccentric shaft portion 40 includes an upper eccentric shaft 41, a stopper portion 42, and an insertion portion 43. The upper eccentric shaft 41 is a columnar member extending upward along the central axis 41A. When the upper eccentric shaft portion 40 is fixed to the base shaft 20, the central axis 41 </ b> A of the upper eccentric shaft 41 is eccentric with respect to the central axis 20 </ b> M of the base shaft 20. The stopper portion 42 is a plate-like member that spreads outside the lower boss portion 12 in a plane perpendicular to the central axis 41A. The insertion portion 43 is a columnar member that extends downward along the central axis 43A. When the upper eccentric shaft portion 40 is fixed to the base shaft 20, the center axis 43 </ b> A coincides with the center axis 20 </ b> M of the base shaft 20.

  A fixing mechanism for fixing the upper eccentric shaft portion 40 to the base shaft 20 and a positioning portion for positioning the upper eccentric shaft portion 40 with respect to the base shaft 20 will be described with reference to FIGS. 4 and 5 to 10.

  As shown in FIGS. 5 and 6, a hole 24 that opens upward is formed in the upper end 23 of the base shaft 20. When the upper eccentric shaft portion 40 is attached to the base shaft 20, the insertion portion 43 of the upper eccentric shaft portion 40 is inserted into the hole portion 24. For this reason, the hole portion 24 is formed so that the inner surface of the hole portion 24 substantially coincides with the outer surface of the insertion portion 43 of the upper eccentric shaft portion 40. A bolt hole 25 is formed in the upper end portion 23 from the lower surface of the hole portion 24 downward. A female screw is formed in the bolt hole 25, and the bolt hole 25 meshes with a bolt 70 shown in FIG. As shown in FIGS. 8, 9, and 10, a through hole 44 is formed in the insertion portion 43 and the stopper portion 42. When the insertion portion 43 is inserted into the hole 24, the upper eccentric shaft portion 40 is fixed to the base shaft 20 by inserting the bolt 70 into the through hole 44 and fastening the bolt 70. In other words, the fixing mechanism includes at least the bolt hole 25 formed in the base shaft 20, the through hole 44 formed in the insertion portion 43 and the stopper portion 42, and the bolt 70.

  As shown in FIG. 7, the base shaft 20 is formed with a pin 26 that protrudes upward from the lower surface of the hole 24. The center axis of the pin 26 is eccentric with respect to the center axis of the bolt hole 25. On the other hand, as shown in FIG. 8, the upper eccentric shaft portion 40 is provided with a pin hole 45 formed upward from the lower surface of the insertion portion 43. The center axis of the pin hole 45 is eccentric with respect to the center axis of the through hole 44. The positional relationship between the central axis of the pin 26 and the central axis of the bolt hole 25 is equal to the positional relationship between the central axis of the pin hole 45 and the central axis of the through hole 44. 7 is a top view and FIG. 8 is a bottom view. Therefore, in FIGS. 7 and 8, the position of the pin 26 with respect to the bolt hole 25 is opposite to the position of the pin hole 45 with respect to the through hole 44. It has become. For this reason, the pin 26 is inserted into the pin hole 45 when the insertion part 43 is inserted into the hole 24. Further, by inserting the bolt 70 into the through hole 44 and fastening the bolt 70, the upper eccentric shaft portion 40 is fixed to the base shaft 20, and the upper eccentric shaft portion 40 is centered with respect to the base shaft 20. Positioned around 20A. That is, the fixing mechanism includes the pin 26 and the pin hole 45 as a positioning portion.

  Referring to FIG. 4 again, a support structure for supporting the stem 200 with respect to the head pipe portion 10 and an assembling method for assembling the stem 200 with respect to the head pipe portion 10 will be described. The base shaft 20 is inserted into the upper boss portion 11 and the lower boss portion 12 of the head pipe portion 10. A spacer 13 is press-fitted between the outer surface of the upper end portion 21 of the base shaft 20 and the inner surface of the upper boss portion 11. A spacer 14 is press-fitted between the outer surface of the lower end portion 22 of the base shaft 20 and the inner surface of the lower boss portion 12. The spacers 13 and 14 fill a gap between the inner surface of the upper boss portion 11 and the inner surface of the lower boss portion 12 and the outer surface of the base shaft 20. For this reason, the base shaft 20 is supported by the head pipe portion 10. In the present embodiment, the spacer 13 and the spacer 14 are ball bearings. In a state where the base shaft 20 is supported by the head pipe portion 10, the center axis 20 </ b> A of the base shaft 20 coincides with the stem axis 10 </ b> A set in the head pipe portion 10. Further, the upper eccentric shaft portion 40 is fixed to the base shaft 20 by a bolt 70.

  The assembly method includes the following steps. First, the outer race of the spacer 13 is press-fitted into the upper boss portion 11. Further, the outer race of the spacer 14 is press-fitted into the lower boss portion 12. A ball is fitted into the outer race of the spacer 14. On the other hand, the inner race of the spacer 14 is press-fitted into the lower end portion 21 of the base shaft 20. Next, the base shaft 20 with the inner race is inserted into the through hole of the head pipe portion 10 from below, the upper end portion 23 is disposed in the outer race of the spacer 14, and the lower end portion 21 is in the outer race of the spacer 13. Be placed. The inner race fixed to the base shaft 20 closes the outer race and the ball fixed to the lower boss portion 12. Next, the ball is fitted into the outer race fixed to the upper boss portion 11. On the other hand, a presser nut 71 is fitted into the insertion portion 43 of the upper eccentric shaft portion 40 and an inner race of the spacer 13 is press-fitted. Next, the insertion portion 43 having the holding nut 71 and the inner race is inserted into the upper boss portion 11 of the head pipe portion 10 from above. As a result, the inner race fixed to the insertion portion 43 closes the outer race and the ball fixed to the upper boss portion 11. Next, the upper eccentric shaft portion 40 is fastened to the base shaft 20 by the bolt 70. Here, the holding nut 71 is positioned between the inner race of the spacer 13 and the lower surface of the stopper portion 42 of the upper eccentric shaft portion 40. For this reason, by fastening the bolt 70, the inner race is pressed against the outer race in the spacer 13, and the inner race is pressed against the outer race in the spacer 14. As a result, the spacers 13 and 14 and the holding nut 71 are completely sandwiched between the stopper portion 42 of the upper eccentric shaft portion 40 and the stopper portion 32 of the lower eccentric shaft portion 30. In this way, the assembly of the stem 200 and the assembly of the stem 200 to the head pipe portion 10 are completed at the same time.

  The upper bracket 8 and the under bracket 9 are supported by the stem 200 as follows. A lower collar 53 is fitted in a through hole 9 a formed in the under bracket 9. Two bearings 51 and 52 are arranged inside the lower collar 53. The lower eccentric shaft 31 of the lower eccentric shaft portion 30 is disposed inside the two bearings 51 and 52. In this way, the under bracket 9 is rotatably supported by the lower eccentric shaft 31 of the lower eccentric shaft portion 30. On the other hand, an upper collar 63 is fitted in a through hole 8 a formed in the upper bracket 8. Two bearings 61 and 62 are arranged inside the upper collar 63. The upper eccentric shaft 41 of the upper eccentric shaft portion 40 is disposed inside the two bearings 61 and 62. In this way, the upper bracket 8 is rotatably supported by the upper eccentric shaft 41 of the upper eccentric shaft portion 40.

  The central axis 31A of the lower eccentric shaft 31 of the lower eccentric shaft portion 30 and the central axis 41A of the upper eccentric shaft 41 of the upper eccentric shaft portion 40 coincide. The central axis 31A and the central axis 41A constitute a steering axis 4A in the motorcycle 1. By operating the handle 4 fixed to the upper bracket 8, the front wheel 6 supported by the two front fork members 5 turns around the steering axis 4A.

  In FIG. 2, the steering structure 100 includes a lower anti-rotation portion 300 and an upper anti-rotation portion 400 that prevent the stem 200 from rotating around the stem axis 10 </ b> A.

  In FIG. 2, the lower detent portion 300 includes a clamping portion 33 that sandwiches the protrusion 15 formed on the head pipe portion 10 from both sides in the vehicle width direction. The clamping part 33 is provided in the lower eccentric shaft part 30 as described above.

  As shown in FIG. 4, the protrusion 15 is formed behind and below the lower boss portion 12. The protrusion 15 is formed on the head pipe portion 10 as a handle stopper for limiting the turning range of the handle 4 in the conventional steering structure. In the conventional steering structure, the motorcycle 1 is configured so that the steering axis 4A coincides with the stem axis 10A, and a part of the front fork member 5 or the under bracket 9 can come into contact with the protrusion 15 as a handle stopper. Designed.

  In FIG. 5, the clamping part 33 is provided with two protrusions 33a extending in the radial direction of the central axis 31A. Each protrusion 33a is formed with a bolt hole 33b in which a female screw is formed.

  In FIG. 2, the contact bolt 72 is inserted in the bolt hole 33b of each protrusion 33a. The contact bolt 72 consists only of a screw shaft. The position of the contact bolt 72 in the bolt hole 33b can be adjusted by operating the contact bolt 72 with a screw driver. For this reason, the abutting bolt 72 can abut on the protrusion 15 disposed in the clamping portion 33. The male screw formed in the bolt hole 33 b and the contact bolt 72 constitutes an adjustment mechanism that adjusts the position where the contact bolt 72 contacts the protrusion 15. Therefore, the steering structure 100 includes the clamping unit 33 and the adjustment mechanism.

  In FIG. 2, the upper detent portion 400 includes a connecting bracket 73 that connects the stopper portion 42 of the upper eccentric shaft portion 40 and the upper wall 10 a of the head pipe portion 10. The connecting bracket 73 has a U shape and has four insertion holes 73a for inserting bolts. The connection bracket 73 is fixed to the upper wall 10a by two bolts and is fixed to the stopper portion 42 by two bolts.

  In FIG. 8, the stopper part 42 has two bolt holes 42a. The bolt hole 42a penetrates the stopper part 42 up and down. The inner surface of the bolt hole 42a is formed as a female screw.

(Operation and effect of this embodiment)
This embodiment has the following operations and effects.

  The present embodiment includes a base shaft 20, anti-rotation portions 300 and 400, an upper eccentric shaft portion 40, and a lower eccentric shaft portion 30. The central axis 41A of the upper eccentric shaft 41 and the central axis 31A of the lower eccentric shaft 31 coincide with each other, and the central axis 41A and the central axis 31A are eccentric with respect to the central axis 20A of the base shaft 20. When the base shaft 20, the upper eccentric shaft portion 40, and the lower eccentric shaft portion 30 are attached to the head pipe portion 10, the central axis 20A coincides with the stem axis 10A, and the central axis 41A and the central axis 31A are the steering axis 4A. Matches. That is, the position of the steering axis 4A is different from the position of the stem axis 10A. In addition, the rotation of the base shaft 20 around the stem axis 10 </ b> A is restricted by the rotation preventing portions 300 and 400. For this reason, this embodiment can change the turning center position (steering axis 4A) of the handle 4 without changing the formation position of the through hole (upper boss part 11 and lower boss part 12) in the head pipe part 10.

  The lower eccentric shaft portion 30 is formed integrally with the base shaft 20, and the upper eccentric shaft portion 40 is formed so as to be detachable from the base shaft 20. In addition, the present embodiment includes a fixing mechanism (bolt hole 25, through hole 44, and bolt 70) that fixes the upper eccentric shaft portion 40 and the base shaft 20. Therefore, in the present embodiment, the base shaft 20, the upper eccentric shaft portion 40, and the lower side can be attached to the head pipe portion 10 while the base shaft 20, the upper eccentric shaft portion 40, and the lower eccentric shaft portion 30 are detachable. Compared with the case where the eccentric shaft portion 30 is formed individually, an increase in the number of parts and a decrease in strength can be suppressed.

  In particular, of the two eccentric shaft portions, the lower eccentric shaft portion 30 close to the road surface is formed integrally with the base shaft 20. The load that the motorcycle 1 receives from the road surface during traveling is transmitted from the front wheels 6 and the front fork member 5 to the head pipe portion 10 via the under bracket 9 rather than the upper bracket 8. That is, a larger load is applied to the connecting portion between the lower eccentric shaft portion 30 and the base shaft 20 than to the connecting portion between the upper eccentric shaft portion 40 and the base shaft 20. For this reason, this embodiment can obtain the rigidity of the part to which a load is applied relatively easily by integration.

  The fixing mechanism includes positioning portions (pins 26 and pin holes 45). For this reason, the present embodiment can prevent the upper eccentric shaft portion 40 configured to be detachable from being displaced with respect to the base shaft 20.

  In particular, the positioning portion includes a pin 26 and a pin hole 45. For this reason, this embodiment can position the upper eccentric shaft portion 40 with respect to the base shaft 20 with a simple configuration.

  The lower detent portion 300 includes a pinching portion 33 for pinching the protrusion 15 formed on the head pipe portion 10 from both sides in the vehicle width direction. For this reason, this embodiment can simplify the shape of the head pipe part 10 required for rotation prevention.

  The lower detent portion 300 includes an abutting bolt 72 and an adjusting mechanism that adjusts the position of the abutting bolt (a male screw formed on the bolt hole 33b and the abutting bolt 72). For this reason, even when the processing accuracy of the head pipe portion 10 is low, it is possible to realize the detent of the base shaft 20 at a desired position.

(Modification)
The present embodiment can employ the following modified configuration.

  In order to make the stem 200 detachable with respect to the head pipe portion 10, it is sufficient that at least one of the upper eccentric shaft portion 40 and the lower eccentric shaft portion 30 is detachable with respect to the base shaft 20. In the present embodiment, the base shaft 20 and the lower eccentric shaft portion 30 are integrated, and the upper eccentric shaft portion 40 is detachable from the base shaft 20. Instead, the base shaft 20 and the upper eccentric shaft portion 40 may be integrated, and the lower eccentric shaft portion 30 may be detachable from the base shaft 20.

  The present embodiment includes the lower anti-rotation portion 300 and the upper anti-rotation portion 400, but it is sufficient that at least one anti-rotation portion is provided.

  A combination of one protrusion and a sandwiching portion having the other recess can be employed between the head pipe portion 10 and the stem 200 as the rotation preventing portion. In the present embodiment, a protrusion is formed on the head pipe portion 10, and a clamping portion 33 is formed on the upper eccentric shaft portion 40. Instead of this, a clamping portion may be formed in the head pipe portion 10 and a protrusion may be formed in the upper eccentric shaft portion 40.

  The spacers 13 and 14 that support the base shaft 20 in the upper boss portion 10 and the lower boss portion 20 of the head pipe portion 10 are not limited to bearings. Moreover, you may design the outer diameter of the base shaft 20 so that it may become equal to the internal diameter of the upper boss | hub part 10 and the lower boss | hub part 20, instead of providing a spacer.

  In the present embodiment, the lower collar 53 and the upper collar 63 are both concentric colors. In the concentric collar, the center of the inner peripheral surface of the collar coincides with the center of the outer peripheral surface of the collar. Here, the lower collar 53 is formed with an inner peripheral surface that contacts the bearings 51 and 52 that support the under bearing 9 and an outer peripheral surface that contacts the inner peripheral surface of the under bracket 9. Similarly, the upper collar 63 has an inner peripheral surface and an outer peripheral surface. For the lower collar 53 and the upper collar 63, it is possible to adopt an eccentric color instead of a concentric collar. In the eccentric collar, the center of the inner peripheral surface of the collar is eccentric with respect to the center of the outer peripheral surface of the collar. In this case, the position of the front fork member 5 is changed in the horizontal plane with respect to the base shaft 20. For this reason, the position of the front wheel 6 can be adjusted in the front-rear direction with respect to the main frame 2.

1 Motorcycle 4 Handle 4A Steering axis 5 Front fork member 8 Upper bracket 9 Under bracket 10 Head pipe part 10A Stem axis 11 Upper boss part (through hole)
12 Lower boss (through hole)
15 Protrusion 20 Base shaft 25 Bolt hole 25 (fixing mechanism)
30 Lower eccentric shaft 31 Lower eccentric shaft 31A Center axis (steering axis)
33b Bolt hole (adjustment mechanism)
33 Clamping portion 40 Upper eccentric shaft portion 41 Upper eccentric shaft 41A Center axis (steering axis)
44 Through hole 44 (fixing mechanism)
70 bolts (fixing mechanism)
72 Contact bolt (contact part, adjustment mechanism)
100 Steering structure 300 Lower detent section 400 Upper detent section

Claims (7)

A motorcycle in which an upper bracket and an under bracket for connecting a pair of left and right front fork members are rotatably supported with respect to a head pipe portion in which a through-hole penetrating vertically is formed with a stem axis extending vertically as a center. In the steering structure,
A base shaft inserted through the through hole;
A detent portion provided in a portion exposed from the head pipe portion, and preventing the base shaft inserted through the through hole from rotating around the stem axis line,
An upper eccentric shaft portion that is provided at an upper end portion of the base shaft and supports the upper bracket so as to be rotatable around a steering axis that is eccentric with respect to the stem axis;
A steering structure for a motorcycle, comprising: a lower eccentric shaft portion provided at a lower end portion of the base shaft and supporting an under bracket so as to be rotatable around the steering axis. One of the upper eccentric shaft portion and the lower eccentric shaft portion is formed integrally with the base shaft,
The other of the upper eccentric shaft portion and the lower eccentric shaft portion is detachably formed with respect to the base shaft,
The steering structure includes a fixing mechanism that fixes the other eccentric shaft portion and the base shaft.
The steering structure for a motorcycle according to claim 1. The lower eccentric shaft portion is formed integrally with the base shaft,
The steering structure for a motorcycle according to claim 2, wherein the upper eccentric shaft portion is detachable from the base shaft.   4. The motorcycle steering structure according to claim 2, wherein the fixing mechanism includes a positioning portion that prevents the other eccentric shaft portion from being fixed off the steering axis. 5.   The fixing mechanism includes a bolt that fastens the other eccentric shaft portion to the base shaft, a positioning pin formed on one of the other eccentric shaft portion and the base shaft, and the other eccentric shaft portion and the other of the base shaft. The motorcycle steering structure according to claim 4, further comprising: a pin hole that engages with the formed positioning pin.   2. The motorcycle steering structure according to claim 1, wherein the anti-rotation portion includes a sandwiching portion that sandwiches a protrusion formed on the head pipe portion from both sides in the vehicle width direction.   The said rotation stop part is provided with the contact part which contact | abuts to the said protrusion arrange | positioned in the said clamping part, and the adjustment mechanism which adjusts the position where the said contact part contact | abuts to the said protrusion. Motorcycle steering structure.

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