JP2016068894A - Front fork - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a front fork which easily applies a pre-load to a bearing even if a pair of outer tubes, an upper bracket, an under bracket, and a steering shaft are integrally formed.SOLUTION: A front fork includes: a pair of outer tubes 1; an upper bracket 3 and an under bracket 4 connecting the pair of outer tubes 1; and a steering shaft 5 erecting on the under bracket 4 and rotatably supported by a head tube b1 through a bearing 7. The pair of outer tubes 1, the upper bracket 3, and the under bracket 4, and the steering shaft 5 are integrally formed in the front fork. The front fork includes: a connection member 6 connecting the upper bracket 3 with the steering shaft 5; and a spacer 9 which is provided at an outer periphery of the steering shaft 5 protruding from the head tube b1, contacts with the bearing 7 at one end, and may expand and contract.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a front fork.

  2. Description of the Related Art Conventionally, a front fork that suspends a front wheel of a straddle-type vehicle such as a two-wheeled vehicle or a three-wheeled vehicle includes a leg portion that supports the front wheel and a steering shaft that is rotatably supported by a head pipe via a bearing. The bearing receives a radial load and a thrust load, and the front fork rotates smoothly around the axis of the steering shaft by the operation of the steering wheel to change the direction of the front wheels. (For example, Patent Documents 1 and 2)

JP 2011-201468 A JP 2012-116283 A

  Here, for example, the front fork disclosed in Japanese Patent Application Laid-Open No. 11-91671 is provided with a fork pipe that serves as left and right leg portions that support the front wheel from both sides, and is set to a double-supported type. The front fork further includes a top bridge that connects the upper ends of the left and right fork pipes, and a steering stem that connects the middle part. The center portion of the top bridge and the steering stem is a steering shaft (stem pipe). It is connected.

  The upper end portion of the steering shaft is a male screw portion. The top bridge has a stem pipe mounting hole with a diameter larger than that of the steering shaft. A collar with a collar is fitted in the gap between the steering shaft and the stem pipe mounting hole, and the collar is attached to the stem pipe. It is supported by the bottom of the annular recess around the hole. Further, front fork mounting holes are formed at both ends of the top bridge so that the fork pipe can be fixed by split tightening.

  According to the above configuration, even after the steering shaft and the fork pipe are fixed to the steering stem, the steering shaft is inserted into the head pipe, the top bridge is covered from above the fork pipe and the steering shaft, and the fork pipe is attached to the front fork mounting hole. The steering shaft can be inserted into the stem pipe mounting hole. After inserting the collar with collar into the stem pipe mounting hole and fastening the cap nut to the male thread part of the steering shaft, the top bridge is pushed to the steering pipe side, so the bearing attached to the inner periphery of the head pipe Presumed to be given preload.

  However, the pair of leg portions of the front fork both include a telescopic cylinder member made of an outer tube and an inner tube, and both the outer tubes (a pair of outer tubes) of the pair of leg portions are connected to an upper bracket and an under bracket. In the case where the center portion of the upper bracket and the under bracket is connected by a steering shaft (for example, Japanese Patent Application Laid-Open No. 2008-281050), the front fork is reduced in weight, torsional rigidity and design flexibility are improved. When a pair of outer tubes, an upper bracket, an under bracket and a steering shaft are integrally formed for the purpose of the above, there are the following problems.

  That is, according to the above configuration, the distance between the upper bracket and the under bracket does not change, and the position of the steering shaft with respect to the upper bracket and the under bracket cannot be changed. For this reason, it is difficult to apply a preload to the bearing by moving the upper bracket or the steering shaft with respect to the under bracket and applying a preload to the bearing.

  Accordingly, an object of the present invention is to provide a front fork that can easily preload a bearing even when a pair of outer tubes, an upper bracket, an under bracket, and a steering shaft are integrally formed.

  According to the first aspect of the present invention for solving the above-mentioned problem, a spacer that can be expanded and contracted is provided on the outer periphery of the steering shaft protruding from the head pipe, and one end of the spacer is brought into contact with the bearing. For this reason, even if a pair of outer tube, upper bracket, under bracket and steering shaft are integrally formed, if the spacer is extended, a load in the thrust direction can be applied to the bearing in advance.

  In the invention described in claim 2, the spacer includes an inner cylinder and an outer cylinder that is screwed onto the outer periphery of the inner cylinder. For this reason, the spacer can be easily expanded and contracted, and the spacer can be easily maintained in an arbitrarily extended state.

  In invention of Claim 3, the rotation stopper which prevents co-rotation of an inner cylinder and an outer cylinder is provided. For this reason, since the spacer can be expanded and contracted by gripping and rotating one of the inner cylinder and the outer cylinder with a tool or the like, the operation of expanding and contracting the spacer is easy.

  In the invention described in claim 4, a nut is provided which is screwed onto the outer periphery of the inner cylinder. For this reason, since the outer cylinder can be prevented from loosening, it can be maintained in a state in which a preload is applied to the bearing.

  In the invention according to claim 5, bearings are provided at both ends of the head pipe in the axial direction, an annular outer race press-fitted inside the head pipe, and an annular inner race through which the steering shaft is inserted. A race and a plurality of steel balls held between the outer race and the inner race are provided. The spacer comes into contact with the inner race of the bearing on the upper bracket side, and the inner race of the bearing on the under bracket side comes into contact with the under bracket. For this reason, when the spacer is extended, a load in the thrust direction is applied to both the upper and lower bearings, and a preload is applied to them.

  According to the front fork of the present invention, even when the pair of outer tubes, the upper bracket, the under bracket and the steering shaft are integrally formed, the bearing can be easily preloaded.

It is the semi-sectional view which showed typically the longitudinal cross-section of the principal part of the front fork which concerns on one embodiment of this invention. It is the front view which showed typically the attachment state of the front fork which concerns on one embodiment of this invention. It is the front view which showed the vehicle body side member assembly of the front fork which concerns on one embodiment of this invention. It is the perspective view which decomposed | disassembled and showed the vehicle body side member assembly and connection member of the front fork which concern on one embodiment of this invention. (A) is the enlarged plan view which showed the XX part of the vehicle body side member assembly of the front fork which concerns on one embodiment of this invention. (B) is the enlarged plan view which showed the state which attached the fixed side clamp | tightening part to (a). (C) is the enlarged plan view which showed the process of attaching a drive side clamping part to (b). It is the perspective view which expanded and showed the spacer of the front fork which concerns on one embodiment of this invention. It is the longitudinal cross-sectional view which showed typically the modification of the connection member of the front fork which concerns on one embodiment of this invention. It is the anti-cross-sectional view which showed typically the longitudinal cross-section of the modification of the bearing of the front fork which concerns on one embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. The same reference numerals given throughout the several drawings indicate the same or corresponding parts.

  As shown in FIG. 1, a front fork F according to an embodiment of the present invention connects a pair of outer tubes 1, 1 and the pair of outer tubes 1, 1, and extends in the axial direction of the outer tube 1. An upper bracket 3 and an under bracket 4 provided side by side, and a steering shaft that stands upright on the under bracket 4 and extends toward the upper bracket 3 and is rotatably supported by the head pipe b1 via bearings 7 and 8 5, and the pair of outer tubes 1, 1, the upper bracket 3, the under bracket 4, and the steering shaft 5 are integrally formed, and the upper bracket 3 and the steering shaft 5 are connected to each other. Member 6 and the stearin projecting from the head pipe b1 One end is provided on the outer periphery of the shaft 5 abuts on the bearing 7, and a stretchable spacer 9.

  Hereinafter, in detail, the front fork F according to the present embodiment suspends the front wheel W of the bicycle as shown in FIG. In the following explanation, when the front fork F attached to the bicycle body B is viewed from the front side of the bicycle, the top is “up”, the bottom is “down”, the front is “front”, and the back is “rear”. To do.

  The front fork F includes a pair of legs LL and LR that support the front wheel W from both sides, a vehicle body side bracket BU that connects the legs LL and LR, a steering shaft 5 that is attached to the vehicle body side bracket BU, A wheel-side bracket BL that is attached to the both leg portions LL and LR and connects the leg portions LL and LR to the axle of the front wheel W is provided. The vehicle body side bracket BU includes the upper bracket 3 and the under bracket 4 described above, and a handle H is fixed to the upper bracket 3. Further, the steering shaft 5 attached to the vehicle body side bracket BU is rotatably supported by a head pipe b1 of the vehicle body frame which is a skeleton of the vehicle body B via a pair of upper and lower bearings 7 and 8 (FIG. 1). For this reason, the front fork F rotates around the axis of the steering shaft 5 by the operation of the handle H, and the direction of the front wheel W can be changed. Note that the front fork F according to the present invention may be used other than a bicycle, and may be used for a motorcycle or a tricycle.

  Subsequently, the pair of leg portions LL and LR are both a telescopic cylindrical member T composed of the outer tube 1 and the inner tube 2 and a suspension spring provided in the cylindrical member T and elastically supporting the vehicle body B. (Not shown) and a damper (not shown) that is also provided in the cylindrical member T and generates a damping force. In the tubular member T, a vehicle body side bracket BU is attached to the outer tube 1, and a wheel side bracket BL is attached to the inner tube 2. For this reason, when an impact due to road surface unevenness is input to the front wheel W, the inner tube 2 enters and exits the outer tube 1 and the front fork F expands and contracts. Since the suspension spring and the damper (not shown) expand and contract with the expansion and contraction of the front fork F, the impact due to the road surface unevenness is absorbed by the suspension spring, and the expansion and contraction motion of the suspension spring accompanying the impact absorption can be suppressed by the damper.

  In addition, in each leg part LL, LR, the structure accommodated in the cylinder member T is not the above-mentioned limit, It can change arbitrarily. For example, the same configuration may be accommodated in both cylindrical members T, and the configuration accommodated in the cylindrical member T is changed between one leg LL and the other leg LR, and the one leg LL and the other leg LL are changed. The function of the leg LR may be separated.

  Subsequently, the vehicle body side bracket BU connecting the both leg portions LL and LR includes the upper bracket 3 and the under bracket 4 as described above. As shown in FIG. 3, the upper bracket 3 connects both the outer tubes 1 and 1 of the paired leg portions LL and LR, that is, the upper ends of the pair of outer tubes 1 and 1. The other under bracket 4 is provided on the lower side of the upper bracket 3 and connects the axially central portions of the pair of outer tubes 1 and 1. A steering shaft 5 is attached to the under bracket 4.

  The steering shaft 5 is a central portion of the pair of outer tubes 1, 1 and is provided substantially parallel to the outer tubes 1, 1 and extends from the under bracket 4 toward the upper bracket 3. As shown in FIG. 4, the upper bracket 3 is formed with a semicircular recess 3 a that forms a gap between the upper bracket 3 and the steering shaft 5 so that the upper bracket 3 and the steering shaft 5 do not come into direct contact with each other. It has become. The size of the recess 3 a is set to a size that allows the head pipe b 1 to be inserted between the upper bracket 3 and the steering shaft 5. The upper bracket 3 and the steering shaft 5 are connected by a connecting member 6 after the steering shaft 5 is inserted into the head pipe b 1 and a spacer 9 is attached to the outer periphery of the steering shaft 5.

  In the present embodiment, the pair of outer tubes 1, 1, the upper bracket 3, the under bracket 4 and the steering shaft 5 are integrally formed as one collective part. Hereinafter, one assembly part formed by integrally forming the pair of outer tubes 1, 1, the upper bracket 3, the under bracket 4 and the steering shaft 5 is referred to as a vehicle body side member assembly A <b> 1. In the present invention, the term “integral formation” means that the members constituting the vehicle body side member assembly A1 are simultaneously joined and molded to form one vehicle body side member assembly A1. In other words, after forming each member constituting the vehicle body side member assembly A1, when integrated by mechanical joining such as rivets, screws or press-fitting, welding, adhesion or welding, etc., the integrated formation of the present invention Not included.

  In the present embodiment, the vehicle body side member assembly A1 is formed by casting in which a material is heated and poured into a mold and then cooled and solidified into a target shape. Therefore, the pair of outer tubes 1, 1, upper bracket 3, under bracket 4, and steering shaft 5 can be easily integrally formed, and the vehicle body side member assembly A 1 can be easily formed. However, the method of integral formation is limited to casting. Absent.

  In the present embodiment, since the material of the vehicle body side member assembly A1 is CFRP (carbon-fiber-reinforced plastic), the vehicle body side member assembly A1 has both high strength and lightness. However, the material of the vehicle body side member assembly A1 can be arbitrarily changed. If each member constituting the vehicle body side member assembly A1 can be integrally formed, other types of plastic such as GFRP (glass fiber reinforced plastic), or aluminum It may be a metal such as.

  As described above, in the present embodiment, the pair of outer tubes 1, 1, the upper bracket 3 and the under bracket 4 are integrally formed, and the connection between the pair of outer tubes 1, 1 and the upper bracket 3, The connection between the pair of outer tubes 1 and 1 and the under bracket 4 is realized without using bolts. When the connection is performed by bolt connection, in order to secure the strength of the portion, measures such as increasing the thickness are required, which increases the weight. However, according to the configuration, the front fork F is reduced in weight. Is possible.

  Furthermore, according to the said structure, since a pair of outer tubes 1 and 1, the upper bracket 3, and the under bracket 4 are integrally formed, the connection part of the outer tube 1 and the upper bracket 3, and the outer tube 1 and the under bracket 4 The torsional rigidity of the connecting portion can be improved. In addition, according to the said structure, a design is not restrict | limited at each said connection part, The design freedom degree of the said part can be improved.

  Subsequently, the connecting member 6 that connects the upper bracket 3 and the steering shaft 5 is formed separately from the vehicle body side member assembly A1, that is, the pair of outer tubes 1, 1, the upper bracket 3, the under bracket 4, and the steering shaft. 5 is a member that is not integrally formed with 5. The connecting member 6 includes a pair of half-ring-shaped tightening portions 60 and 61 that sandwich the steering shaft 5 from both sides in the radial direction, and a bolt 62 that causes the tightening portions 60 and 61 to approach each other. In the present embodiment, the pair of tightening portions 60 and 61 are made of metal such as aluminum (including an aluminum alloy), but the material of the tightening portions 60 and 61 can be arbitrarily changed.

  One tightening portion 60 is inserted into the recess 3 a of the upper bracket 3 and fixed to the upper bracket 3 with a bolt 63. The other tightening portion 61 is fixed to the upper bracket 3 via the one tightening portion 60 and is not directly fixed to the upper bracket 3. Hereinafter, in order to distinguish between these tightening portions 60 and 61, the tightening portion directly fixed to the upper bracket 3 is not directly fixed to the fixed-side tightening portion 60 and the upper bracket 3, but via the fixed-side tightening portion 60. The tightening portion fixed to the upper bracket 3 is referred to as a driving side tightening portion 61.

  As shown in FIG. 5A, in the present embodiment, the upper bracket 3 is provided with a plurality of stays 3b extending from the edge of the recess 3a toward the recess 3a. Each stay 3b is formed with a bolt insertion hole 3c penetrating in the vertical direction. As shown in FIG. 5 (b), the fixed-side tightening portion 60 formed in a half-ring shape has a plurality of bolt insertion holes 60a penetrating in the vertical direction, and drive-side tightening portions disposed at both ends. A screw hole 60 b that opens toward 61 is formed. When the fixed side tightening portion 60 is inserted into the recess 3a, the bolt insertion hole 60a of the fixed side tightening portion 60 and the bolt insertion hole 3c of the stay 3b face each other vertically. Then, a bolt 63 is inserted from the bolt insertion hole 60a of the fixed-side tightening portion 60 toward the bolt insertion hole 3c of the stay 3b, and a nut (not shown) is inserted into the screw portion of the bolt 63 protruding below the stay 3b. ) Can be fixed to the upper bracket 3.

  Note that the insertion direction of the bolt 63 can be arbitrarily changed. Although not shown, a screw hole may be formed in the stay 3b, and the bolt 63 may be screwed into the screw hole to eliminate the nut. In this case, a metal cylinder member in which a screw groove is formed on the inner periphery may be integrated with the stay 3b by insert molding, and the bolt 63 may be screwed into the cylinder member. The integral formation of the present invention is a concept including the case where a metal member or the like is integrated as the vehicle body side member assembly A1 by insert molding as described above. Further, when the screw hole for screwing the bolt 63 is formed in the fixed-side tightening portion 60, as described above, the fixed-side tightening portion 60 is made of metal. Even if the screw holes are directly formed, the strength does not become insufficient.

  Next, as shown in FIG. 5C, the drive side tightening portion 61 is formed with bolt insertion holes 61 a that open toward the fixed side tightening portion 60 at both ends thereof. When both end portions of the driving side tightening portion 61 are opposed to both end portions of the fixed side tightening portion 60, the screw hole 60b of the fixed side tightening portion 60 and the bolt insertion hole 61a of the driving side tightening portion 61 are formed. It is designed to face in the front-rear direction. Then, when the bolt 62 is inserted into the bolt insertion hole 61a and the screw portion of the bolt 62 is screwed into the screw hole 60b, the driving side tightening portion 61 is fixed to the fixed side tightening portion 60, and these are used for the steering shaft. 5 can be tightened.

  Thus, in this Embodiment, a bolt coupling part can be concentrated on the connection member 6 part. For this reason, compared with the case where a bolt coupling | bond part is disperse | distributed, the part which requires intensity | strength can be decreased and the front fork F can be reduced in weight even when it is a case where bolt coupling | bonding is utilized. Further, in the present embodiment, although not shown, an attachment hole for fixing the handle H is formed in the fixed-side tightening portion 60 so that the handle H can be fixed by bolt connection.

  Next, as shown in FIG. 1, the pair of upper and lower bearings 7 and 8 that rotatably support the steering shaft 5 are both ball bearings. The upper bearing 7 is held between an annular outer race 70 press-fitted inside the head pipe b1, an annular inner race 71 into which the steering shaft 5 is press-fitted inward, and the outer race 70 and the inner race 71. A plurality of steel balls 72 to be provided. Similarly to the upper bearing 7, the other lower bearing 8 includes an annular outer race 80 that is press-fitted inside the head pipe b 1, an annular inner race 81 that the steering shaft 5 is press-fitted inside, and an outer A plurality of steel balls 82 held between the race 80 and the inner race 81 are provided.

  The upper end portion and the lower end portion of the head pipe b1 are formed with enlarged diameter portions b10 and b11 whose inner circumference is larger than the inner circumference of other portions, and the enlarged diameter portions b10 and b11 and the other portions. Steps b12 and b13 are respectively formed at the boundary. The upper bearing 7 is press-fitted until the outer race 70 comes into contact with the upper step b12 from above the head pipe b1 to the inside of the upper diameter enlarged portion b10. The races 71 are assembled so as to overlap in this order. The other lower bearing 8 is press-fit until the outer race 80 comes into contact with the lower step b13 from below the head pipe b1 to the lower enlarged portion b11. The steel ball 82 and the inner race 81 are assembled so as to overlap in this order.

  In addition, an expandable and contractable spacer 9 is provided between the upper bearing 7 and the connecting member 6. The spacer 9 is formed in a cylindrical shape and disposed on the outer periphery of the steering shaft 5, and includes an inner cylinder 90 and an outer cylinder 91 that is screwed onto the outer periphery of the inner cylinder 90. The spacer 9 is disposed with the inner cylinder 90 on the upper side and the outer cylinder 91 on the lower side. As shown in FIG. 6, an engagement portion 91 a having a two-sided width such as a hexagonal column shape is provided on the outer periphery of the outer cylinder 91 so that a tool or the like can be hooked. Further, a rotation stopper 92 is provided between the inner cylinder 9 and the fixed-side tightening portion 60 to prevent relative rotation in the circumferential direction between the inner cylinder 90 and the connecting member 6.

  According to the above configuration, since the inner cylinder 90 is prevented from rotating by the connecting member 6 and the inner cylinder 90 and the outer cylinder 91 are prevented from rotating together, the outer cylinder 91 is rotated by hooking a tool or the like on the engaging portion 91a. Then, the inner cylinder 90 moves in and out of the outer cylinder 91 by the feed screw, and the axial length of the spacer 9 changes. When the axial length of the spacer 9 is increased, that is, when the spacer 9 is extended, the inner cylinder 90 is pressed against the connecting member 6 and the outer cylinder 91 is pressed against the inner race 71 of the upper bearing 7. For this reason, a thrust load is applied to the upper and lower bearings 7 and 8 in advance. That is, according to the above configuration, even if the pair of outer tubes 1, 1, upper bracket 3, under bracket 4 and steering shaft 5 are integrally formed, preload can be easily applied to the bearings 7, 8. 8, the steering shaft 5 can be stably supported.

  Further, a nut 93 (FIG. 1) is screwed onto the outer periphery of the inner cylinder 90 in the upper side of the outer cylinder 91 and in series with the outer cylinder 91. For this reason, it becomes a double nut, and it can prevent that the outer cylinder 91 loosens by vibration etc. and preload is not applied to the bearings 7 and 8.

  Next, a method for assembling the front fork F to the vehicle body B according to the present embodiment will be described.

  In the pre-processing step of the assembly work, the inner tube 2, the damper (not shown), the suspension spring (not shown), the wheel side bracket BL, etc. are attached to the vehicle body side member assembly A1, and the connecting member 6 in the front fork F Assemble components other than the spacer 9. Hereinafter, in the front fork F, a member excluding the connecting member 6 and the spacer 9 is referred to as a front fork assembly.

  In the first step of the assembling work, the steering shaft 5 of the front fork assembly is inserted from the lower side of the head pipe b1 into the head pipe b1 with the upper and lower bearings 7 and 8 attached inside, and the upper side from the head pipe b1. A spacer 9 is attached to the outer periphery of the steering shaft 5 protruding to

  In the subsequent second stroke, the fixed side tightening portion 60 is fixed to the upper bracket 3 with the bolt 63, and then the driving side tightening portion 61 is covered on the rear side of the steering shaft 5, and both ends thereof are fixed side tightening portions. It is made to oppose the both ends of 60. Then, the bolt 62 is screwed into the screw hole 60b from the rear side of the driving side tightening portion 61 through the bolt insertion hole 61a. As a result, the connecting member 6 can be fixed to the upper bracket 3, and the steering shaft 5 can be fixed to the upper bracket 3 by tightening the steering shaft 5 with the fixed side tightening portion 60 and the driving side tightening portion 61.

  In the subsequent third step, a tool or the like is hooked on the engaging portion 91a of the outer cylinder 91 of the spacer 9 to rotate the outer cylinder 91, and the spacer 9 is extended. When the outer cylinder 91 is tightened on the upper surface of the upper bearing 7, a preload is applied to the upper and lower bearings 7 and 8. Subsequently, the nut 93 is tightened on the upper surface of the outer cylinder 91 to prevent the outer cylinder 91 from loosening.

  On the other hand, when the front fork F is removed from the vehicle body B and the front fork F is tuned or repaired, the connecting member 6 and the spacer 9 are removed from the front fork F and the steering shaft is removed from the head pipe b1. When 5 is pulled down, it can be handled in the state of a front fork assembly. As described above, the front fork F according to the present embodiment is a bicycle front fork used for a bicycle, and is small and lightweight. For this reason, even if a pair of leg part LL, LR cannot be isolate | separated, the handling as a front fork assembly is easy.

  Next, the effect of the front fork F according to the present embodiment will be described.

  In the present embodiment, the connecting member 6 includes a half-ring-shaped fixed side fastening portion 60 and a drive side fastening portion 61 (a pair of fastening portions) that sandwich the steering shaft 5 from both sides in the radial direction. Then, the fixed side tightening portion (one tightening portion) 60 is inserted into the recess 3 a and fixed to the upper bracket 3. Further, the drive side tightening portion (the other tightening portion) 61 is fixed to the upper bracket 3 via the fixed side tightening portion 60.

  For example, when the connecting member 6 is of a tightening type and includes a tightening portion formed in an arc shape and a bolt that narrows the joint gap of the tightening portion, the tightening portion is fixed to the upper bracket 3. If the gap is narrowed after that, the tightening portion is deformed, and a load is applied to the connecting portion between the tightening portion and the upper bracket 3. However, according to the above configuration, the driving side tightening portion 61 is brought close to the fixed side tightening portion 60 that is directly fixed to the upper bracket 3, and the steering shaft 5 can be tightened with these. Therefore, when the steering shaft 5 is tightened by the connecting member 6, it is possible to suppress a load from being applied to the connecting portion (portion connected by the bolt 63) between the connecting member 6 and the upper bracket 3.

  The configuration of the connecting member 6 is not limited to the above, and can be arbitrarily changed. For example, it may be changed as shown in FIG. A connecting member 6A shown in FIG. 7 is fixed to the upper bracket 3 and encloses an annular guide 64 surrounding the recess 3a, and an annular tightening portion through which the steering shaft 5 is inserted and screwed into the inner periphery of the guide 64. 65. The tightening portion 65 includes a wedge portion 65a that is inserted into the gap between the upper bracket 3 and the steering shaft 5 and has a tapered outer periphery. According to the above configuration, when the tightening portion 65 is rotated and moved downward, the wedge portion 65 a is pushed into the gap between the upper bracket 3 and the steering shaft 5, and the steering shaft 5 is tightened by the tightening portion 65. . Also in this case, when the steering shaft 5 is tightened by the connecting member 6A, it is possible to suppress a load from being applied to the connecting portion between the connecting member 6A and the upper bracket 3.

  In the present embodiment, the upper bracket 3 is formed with a recess 3 a that forms a gap between the upper bracket 3 and the steering shaft 5.

  According to the above configuration, even if the pair of outer tubes 1, 1, the upper bracket 3, the under bracket 4, and the steering shaft 5 are integrally formed, steering is performed using the gap formed between the upper bracket 3 and the steering shaft 5. Since the shaft 5 can be inserted into the head pipe b1, the assembly of the front fork F to the vehicle body B can be easily realized.

  In the present embodiment, the bearings 7 and 8 are provided at the upper end and the lower end (both ends in the axial direction) of the head pipe b1, and are annular outer races that are press-fitted inside the head pipe b1. 70, 80, annular inner races 71, 81 through which the steering shaft 5 is inserted, and a plurality of steel balls 72, 82 held between the outer races 70, 80 and the inner races 71, 81. With. The spacer 9 comes into contact with the inner race 71 of the bearing 7 on the upper side (upper bracket 3 side), and the inner race 82 of the bearing 8 on the lower side (under bracket 4 side) comes into contact with the under bracket 4.

  According to the said structure, when the spacer 9 is extended, the load of a thrust direction will be applied to both the upper and lower bearings 7 and 8, and preload will be given to these. In the present embodiment, the spacer 9 is sandwiched between the connecting member 6 and the upper bearing 7, but this is not restrictive. For example, depending on the configuration of the spacer 9 or the configuration of the connecting member 6, the spacer 6 may be sandwiched between the upper bracket 3 and the upper bearing 7, or may be sandwiched between the under bracket 4 and the lower bearing 8. May be.

  Further, in the present embodiment, the steering shaft 5 is press-fitted inside the inner races 71 and 81, whereby a radial load is applied to the bearings 7 and 8 in advance. However, as shown in FIG. 8, a wedge K may be inserted between the inner races 71 and 81 and the steering shaft 5 to obtain the above-mentioned effect.

  Further, as described above, in the present embodiment, the upper and lower bearings 7 and 8 are both ball bearings. However, if a radial load and a thrust load are received, the configuration of the bearings 7 and 8 is as follows. Can be arbitrarily changed individually.

  In the present embodiment, the front fork F includes a nut 93 that is screwed onto the outer periphery of the inner cylinder 90.

  According to the above-described configuration, the outer cylinder 91 can be prevented from loosening by using a double nut, so that the bearings 7 and 8 can be maintained in a preloaded state. Depending on the configuration of the spacer 9, the nut 93 may be eliminated.

  In the present embodiment, the front fork F includes a rotation stopper 92 that prevents the inner cylinder 90 and the outer cylinder 91 from rotating together.

  According to the above configuration, the spacer 9 can be expanded and contracted by gripping and rotating one of the inner cylinder 90 and the outer cylinder 91 with a tool or the like, and therefore the operation of expanding and contracting the spacer 9 is easy. However, the rotation stopper 92 may be eliminated.

  Further, in the present embodiment, the rotation stopper 92 prevents relative rotation in the circumferential direction between the inner cylinder 90 and the connecting member 6, and prevents the inner cylinder 90 and the outer cylinder 91 from rotating together. However, the method for preventing the inner cylinder 90 and the outer cylinder 91 from rotating together can be arbitrarily changed.

  In the present embodiment, the spacer 9 includes an inner cylinder 90 and an outer cylinder 91 that is screwed onto the outer periphery of the inner cylinder 90.

  According to the above configuration, the spacer 9 can be easily expanded and contracted, and the spacer 9 can be easily maintained in an arbitrarily extended state. The configuration of the spacer 9 is not limited to the above and can be arbitrarily changed.

  In the present embodiment, the front fork F connects the pair of outer tubes 1, 1 and the pair of outer tubes 1, 1, and the upper bracket 3 provided side by side in the axial direction of the outer tube 1 and The pair of outer brackets 4 includes an under bracket 4 and a steering shaft 5 that stands on the under bracket 4 and extends toward the upper bracket 3 and is rotatably supported on the head pipe b1 via a bearing 7. The tubes 1, 1, the upper bracket 3, the under bracket 4, and the steering shaft 5 are integrally formed, a connecting member 6 that connects the upper bracket 3 and the steering shaft 5, and protrudes from the head pipe b 1. On the outer periphery of the steering shaft 5 Vignetting one end abuts on the bearing 7, and a stretchable spacer 9.

  According to the above configuration, the pair of outer tubes 1, 1, the upper bracket 3, the under bracket 4 and the steering shaft 5 are integrally formed for the purpose of reducing the weight of the front fork F, improving torsional rigidity, and improving design flexibility. Even in such a case, if the spacer 9 is extended, a load in the thrust direction can be applied to the bearings 7 and 8. Therefore, a preload can be easily applied to the bearings 7 and 8.

  Although the preferred embodiments of the present invention have been described in detail above, modifications, changes and modifications can be made without departing from the scope of the claims.

F Front fork 1 Outer tube 3 Upper bracket 4 Under bracket 5 Steering shaft 6 Connecting member 7, 8 Bearing 9 Spacer 90 Inner cylinder 91 Outer cylinder 92 Non-rotating 93 Nut

Claims (5)

A pair of outer tubes;
Connecting the pair of outer tubes, an upper bracket and an under bracket provided side by side in the axial direction of the outer tube;
A steering shaft which stands upright on the under bracket and extends toward the upper bracket, and is rotatably supported by a head pipe via a bearing;
The pair of outer tubes, the upper bracket, the under bracket and the steering shaft are integrally formed,
A connecting member that connects the upper bracket and the steering shaft;
A front fork provided on the outer periphery of the steering shaft that protrudes from the head pipe and having an end that abuts on the bearing and can be expanded and contracted. The spacer is
An inner cylinder,
The front fork according to claim 1, further comprising an outer cylinder that is screwed onto an outer periphery of the inner cylinder. The front fork according to claim 2, further comprising a rotation stopper that prevents the inner cylinder and the outer cylinder from rotating together. The front fork according to claim 2, further comprising a nut screwed onto an outer periphery of the inner cylinder. The bearings are provided at both ends of the head pipe in the axial direction, an annular outer race that is press-fitted inside the head pipe, an annular inner race through which the steering shaft is inserted, and A plurality of steel balls held between the outer race and the inner race,
The spacer contacts the inner race of the bearing on the upper bracket side;
The front fork according to any one of claims 1 to 4, wherein the inner race of the bearing on the under bracket side abuts on the under bracket.

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